The synthesis of soft and machinable, yet orderly porous materials has long been considered unfeasible. This is the case since in nature ordered porosities can be found in long-range extended crystalline networks, which are generally rigid and brittle, while softness and processability commonly originate from network defects and disorder in amorphous materials.
Researchers from Japan and Spain now report to have found a way to unite these properties once considered irreconcilable, paving the way for ultralight and flexible materials, which could find application in energy storage devices, building insulation and aerospace technology.
The very basis for the synthesis of this intriguing material are its small scale building blocks — so called metal-organic polyhedra (MOP) consisting of metal ions and ligands (see figure on the right). The
soluble, stable, permanently porous MOPs used by the researches consist of rhodium ions, oxygen and the so-called H2bdc-C12 ligand.
To achieve the coordination of the MOPs the researchers deployed a cross- linker molecule called 1,4-bis(imidazol-1-ylmethyl)benzene (for short: bix). The addition of this cross-linker resulted in the formation of coordination polymer particles (CPP) via a mechanism consisting of nucleation, elongation and cross-linking (see figure below). Remarkably, it was shown that an exact control of the resulting CPP size was possible through the adjustment of the deployed reaction conditions (e.g. amount of cross-linker added, rate of cross-linker addition). Moreover, the researchers found that the addition of excess bix followed by heating induces the formation of supramolecular colloidal gels (SCG). This means that, the intrinsic porosity of the MOPs was successfully integrated into two different large-scale amorphous geometries.
Through supercritical drying of the resulting SCGs with supercritical CO2, supramolecular aerogels (SAG) were obtained. These aerogels were found to exhibit a hierarchical macro-porous structure built up from fused polymer particles, while the intrinsic porosity of the MOP monomers was retained throughout the entire processing sequence. Consequently, aerogels possessing both micro and macro pores were synthesized (see figure below), leading to extraordinary adsorption properties of the final material (superior to blank MOPs and CPPs).
By fabricating two different macroscopic amorphous materials from monomeric MOPs (CPP and SCG/SAG), the authors found a way to better understand the process of synthesizing macroscopic shapes from molecular building blocks. On the basis of their remarkable findings, they assume that through further research on this topic, this “relationship between molecular scale geometries and resulting macroscopic shapes“ can be further investigated and eventually understood entirely, leading to groundbreaking advances “towards the development of soft matter that is both permanently porous and amenable to materials processing”.
More details: Carne-Sanchez et al. “Self-assembly of metal–organic polyhedra into supramolecular polymers with intrinsic microporosity ” Nature Communications Volume 9, https://www.nature.com/articles/s41467-018-04834-0
Read more at: https://phys.org/news/2018-07-stable-aerogels.html
With both global oil consumption and environmental awareness steadily increasing, both economical as well as environmental aspects require an efficient, reliable, and cheap method to remove spilled oil from water. Selective oil absorption is an auspicious technique for this purpose since it is low cost, generally achieves high absorption capacities and offers the opportunity to recycle the working material. Yet, commercial absorption materials still suffer from several shortcomings (e.g. poor oil water selectivity, complicated fabricating process), which is why further advances in material engineering are required in order to obtain applicable oil absorbents.
With the aim of finding an efficient, environmental compatible and economical sorbent material, researchers from the Dalian Polytechnic University (China) have now successfully synthesized a low-cost, organic aerogel based on corn straw and filter paper, which exhibits good performance as an oil sorbent from aqueous media.
The outstanding feature of the synthesized aerogel material is that it originates from corn straw, which is generally considered as a waste product and thus nowadays is still being burned, positively contributing to global greenhouse gas emissions. However, its abundance, low-cost and biodegradability make it an potent raw material for large scale applications. Its main disadvantage — the inherent brittleness of materials originating from it — was overcome by the addition of filter paper pieces to the precursor material leading to the required flexibility of the final aerogel material.
For the preparation of the aerogels, the corn straw was first ground then washed with sodium hydroxide before hydrochloric acid was added. Subsequent filtration and drying led to corn straw particles (P-CS), which were then dispersed in water together with small pieces of commercial filter paper via vigorous stirring. Thereafter, the dispersion was frozen at -25 °C for 12 hours before freeze drying at -55 °C for 36 hours. The final step of the production process, which is shown in the figure below, was the hydrophobization of the corn straw aerogel (A-CS) through chemical vapor deposition of methyltrimethoxysilane (MTMS).
Analysis of the final freeze-dried aerogel structures unveiled that the material exhibited a porous 3D-structure and a good thermal stability up to 250 °C. Dependent on the solids content and the P-CS:filter paper ratio densities ranging from 14 to 58 mg/cm3 were attained, while porosities between 96 and 99 % were achieved. Water contact angle measurements showed a successful hydrophobization, with measured contact angles reaching values up to 152°.
Investigation of the selectivity and absorptivity for a range of different solvents showed that while water absorptivities were below 1 g/g for the hydrophobized corn straw aerogels (MTA-CS), absoprtivities of organic solvents such as oil or DMF were in the range of 40 g/g. Hence selectivities towards organic solvents were extremely high. Moreover, the MTA-CS did not only absorb the organic phase with a high selectivity, but also in a rapid fashion, leading to fast oil removal from aqueous solutions (see figure below).
With the novel low cost absorbent material synthesized by the Chinese research team disadvantages of conventional oil absorption were overcome, which might pave the way for the widespread utilization of biodegradable oil sorbents originating from corn straw. Certainly, it will be interesting to see whether novel bio-based oil absorbing materials can outperform their synthetic counterparts (e.g. poly(melamine- formaldehyde), polyurethane and polystyren) in the future.
More details: Yuan Li et al. “Preparation of corn straw based spongy aerogel for spillage oil capture” Korean Journal of Chemical Engineering May 2018, Volume 35, Issue 5, pp 1119–1127, https://link.springer.com/article/10.1007/s11814-018-0010-3
Read more at: http://www.chemengonline.com/inexpensive-renewable-aerogel-shows-promise-handling-oil-spills/?printmode=1
The search for alternative energy sources and novel means of (decentralized) power generation have become one of the central modern research topics. Due to their high efficiency and robustness fuel cells are considered to be an integral part in the envisaged future energy supply. Yet, conventional designs still require platinum-based catalysts to promote the oxygen reduction reaction (ORR). This has become a major obstacle in fuel cell technology, prohibiting their cost-efficient and widespread application. In light of this problem, the search for alternative catalyst materials has become a key aspect in fuel cell research.
Recent findings revealed that activated carbon (AC) is one such auspicious material for the catalysis of the ORR, which could replace conventional platinum (Pt) catalysts. Yet, AC exhibits significant shortfalls regarding its electrical conductivity as well as the number of active catalytic sites. Moreover, its application in fuel cells requires extremely large mass loadings to achieve decent performance.
To overcome these limitations, researchers from the Northwestern Polytechnical University, Xi’an (China) have suggested the production of AC-graphene hybrid aerogels as ORR catalyst materials.
The composite aerogel materials were produced via the process schematically shown in the figure below, which includes the addition of AC to a graphene oxide dispersion, followed by hydrogel formation via hydrothermal processing and freeze drying.
Characterization of the synthesized samples showed that through the addition of graphene to the aerogel matrix, the aerogel hybrids exhibited lower densities than pure AC (0.050-0.096 g/cm3), larger specific surface areas (500-750 m2/g) and a meso-porous structure consisting of more micro and meso pores than common activated carbon (see figure below).
Owing to these superior morphological characteristics, the aerogel samples outperformed conventional AC in terms of the ORR catalytic performance (e.g. larger onset potential, limiting current density and exchange current density), which was shown in the course of multiple electrochemical measurements. These superior properties were validated by initial experiments in a electrolytic testing device, in which the AC-graphene aerogel electrode outperformed its plain AC counterpart at 20 times smaller mass loadings.
The authors conclude that the enhanced ORR performance at lower mass loadings can be attributed to the larger surface area and more micro-porous structure of AC-graphene aerogels when compared to pure AC. Since the suggested synthesis route can be scaled-up easily and does not include any expensive techniques or precursors, they see great potential in their new composite material, as it offers a cheap and scalable alternative for applications requiring light weight ORR catalysts (e.g. fuel cells or metal air batteries). Moreover, further enhancements in the hybrid’s electrochemical properties might be attained through doping the aerogel matrix with other atoms (e.g. N, S, P).
With fuel cells being one auspicious alternative to conventional power sources, technical progress in this field is required to reach a more sustainable future. Amongst others, this study shows that due to the extraordinary properties aerogel based materials offer they can help us to reach present or future political and societal milestones.
More details: Yang Yang and Honglong Chang “Multi-scale porous graphene/activated carbon aerogel enables lightweight carbonaceous catalysts for oxygen reduction reaction” Mater. Res. Vol. 33 No. 9 May 14 2018, https://doi.org/10.1557/jmr.2017.372
Both economical as well as environmental considerations demand for high-performance building insulation materials to reduce global energy requirements for space heating and cooling. At the same time, devastating events like the Grenfell Tower fire, which broke out in 2017 in West London causing 72 deaths, highlight that besides low thermal conductivities, insulation materials must be fire retardant and robust even under extreme conditions.
Targeting this, researchers from the University of Science and Technology of China Hefei have now successfully manufactured a composite aerogel material which excels in both these categories. The novel phenol-formaldehyde-resin (PFR)/SiO2 aerogel which is composed of a three-dimensional, interpenetrating binary network structure, exhibits lower heat conductivities than conventional insulation materials and possesses outstanding fire retardant properties as well as great structural stability when being subjected to high temperature flames.
Synthesis of the gel matrix consisting of an inorganic SiO2 network and a polymeric PFR network (see Figure on the right) was achieved via the so called chitosan templated method. First, the precursors TEOS, acetic acid, and phenol were solubilized in an ethanol water mixture, which was then added to an aqueous chitosan solution, before adding formaldehyde. Thereafter, the resulting mixture was hydrothermally treated at 160 °C for 10 hours resulting in the hydrogel samples. Lastly, the hydrogels were solvent exchanged with acetone before being supercritically dried with CO2, resulting in the final composite aerogel.
To assess the impact of SiO2 contents on the final aerogel properties, samples of different SiO2/PFR ratios were produced. Characterization of the different aerogels showed that densities increase with increasing SiO2 content, but remain below 75 g/cm3 even for 80 % SiO2 (PSi-80). Additionally, both the strength and the elastic modules were found to increase with SiO2 content, while all aerogel samples could be compressed by more then 60 % without significant structural collapse occurring.
In terms of the samples’ thermal stability aerogels of high inorganic contents exhibited superior properties during cone calorimetry evaluation (lower thermal degradation and lower heat release rate), highlighting the positive impact of SiO2.
For the PSi-70 sample, exhibiting a great mechanical and thermal stability, a minimum thermal conductivity of 24 W/Km was obtained at low temperature and low relative humidity (T=-12 °C, RH<10 %). Remarkably, decent thermal conductivities (<45 W/Km) were also obtained at increased temperatures and high relative humidities (T=22 °C, RH>75 %), greatly outperforming commercial insulation materials such as EPS or mineral wool.
To test the aerogels’ flame resistance, slabs of the composite aerogel were subjected to a propane/butane flame (see Figure below, a), which generates a flame temperature of approx. 1300 °C. Astonishingly, the PSi aerogel retained its monolithic structure even after 30 minutes of flame exposure (see Figure below, g and h). Moreover, while only the white SiO2 network was left on the directly exposed front side, the sample maintained its structural features on the backside to great extents. This was attributed to the fact that the low thermal conductivity of the aerogel prevented a stark increase in temperature on the backside (see Figure below, c-e), despite the large temperatures (>1300 °C) on the sample frontside. As the backside temperature was below 310 °C even after 30 minutes of flame exposure (see Figure below, f), the authors concluded that the employment of the composite aerogel insulation guarantees the prevention of the collapse of reinforced concrete structures, which is reported to occur above 350 °C. Similar flame resistance testing of commercial PF foam and a PFR/attapulgite composite aerogel resulted in larger backside temperatures (>400 °C) and sample disintegration, underlining the outstanding characteristics of the investigated PSi aerogels.
In summary, the authors conclude that their novel aerogel is a promising candidate for next-generation insulation materials, as it unites great mechanical stability and fire retardant properties with outstanding characteristics in terms of thermal insulation. While certain challenges regarding economic scalability and rentability are still to be overcome, phenolic-silica aerogels surely seem very auspicious from a technical perspective alone.
More details: Zhi-Long Yu et al. “Fire-Retardant and Thermally Insulating Phenolic-Silica Aerogels” Angew. Chem. Int. Ed. 2018, 57, 4538 –4542, https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201711717
Read more at: https://www.advancedsciencenews.com/fire-retardant-binary-network-aerogel/
Extraction and impregnation techniques employing supercritical CO2 as the working fluid can be considered as the non plus ultra in their fields, due to the extraordinary properties s.c. CO2 offers (e.g. high solubility, good miscibility, bio-compatibility, non-flammability, etc.). Especially in the field of aerogel synthesis supercritical drying techniques present the most favorable characteristics, yielding superior materials possessing large surface areas and porosities.
Yet, one major drawback of these processes are the high pressures needed during operation, necessitating expensive equipment (e.g. high pressure pumps) as well as extensive amounts of compression work, consequently entailing relatively high energy and plant costs.
To overcome this limitation of supercritical impregnation, extraction and drying techniques a team of scientists from the University of Birmingham (UK) have now suggested a novel cost-efficient plant setup
To achieve a plant setup not requiring any pumping or compression equipment, the authors suggest a relatively straight-forward approach — cooling down the pressure vessel (to 253 K/ -20 °C) prior to its filling with CO2. This simple preparation step led to the fact, that CO2 stored at ambient temperature, entered the vessel voluntarily when the inlet valve was being opened, due to the natural pressure gradient arising from the temperature difference (see figure below: 1a → 1b). As soon as the desired amount of CO2 was located inside the autoclave, it was sealed and subsequently heated to the desired final temperature, entailing an increase in system pressure and hence the obtainment of a supercritical fluid inside the vessel (see figure below: 1b → 3).
Consequently, a process not requiring any external pressurization equipment to pump CO2 into the setup or obtain the desired operating pressure was devised successfully.
To estimate the required final temperature and amount of CO2 inside the autoclave, which both have to be selected correctly for the process to work safely and properly, thermodynamic calculations based on a suitable equation of state (EOS) were conducted. Due to its suitability for supercritical fluids, the authors selected the Soave-Redlich-Kwong EOS for this purpose.
For the mapping and setting of both crucial parameters during operation, the setup was equipped with a temperature regulating unit and a high-resolution hanging scale attached to the autoclave.
Using the proposed setup, the authors were able to successfully dry monolithic LA gellan gum gels, impregnate freeze-dried gel structures with Vitamin E and extract caffeine from green coffee beans and black tea leaves. Furthermore, their economical analysis unveiled that the associated plant costs were reduced by a factor of 3 and 5, when compared to conventional batch and semicontinuous drying modes respectively, while the predicted energy costs were more than 30 % lower than for batch drying and 72 % lower than for semicontinuous drying.
Therefore, the authors concluded that their new plant setup is an auspicious alternative to conventional drying, impregnation and extraction configurations due to its flexibility and the lower investment and operation costs associated to it.
While these arguments may be true for small scale lab or tabletop configurations, for which the costs of the process periphery are relatively high and a broad applicability might be desired, it is dubious whether the same is true for larger, specialized configurations, for which the majority of costs generally stem from the autoclave. Especially the batch type mode of operation of the suggested technique can be considered as an exclusion criteria for industrial-scale plants, since it leads to dramatically longer processing times, vastly reducing the plant throughput.
A last concern of the novel process is its robustness and safeness, as small errors during operation (e.g. overfilling the autoclave or exceeding the desired temperature) can have devastating effects, turning the setup into a hazardous system. Since it will require a great deal of work to devise a fail-save plant, it is doubtful whether drying units deploying the suggested technique will ever be sold commercially.
More details: Cassanelli et al. “Design of a Cost-Reduced Flexible Plant for Supercritical Fluid-Assisted Applications” Chem. Eng. Technol. 2018, 41, No. 00, 1–11. https://doi.org/10.1002/ceat.201700487
Due to their outstanding mechanical properties, such as high flexibility and rigidity, graphene aerogels are considered a promising type of aerogel for multiple applications. Recent studies found that by accurately tailoring the three-dimensional alignment of the graphene sheets inside the aerogel, these properties can be further enhanced. Simulations even predicted graphene structures exhibiting only 4.6 % the density of steel but 10 times its strength. Therefore, the ordered alignment of graphene sheets has has become a crucial part in graphene aerogel synthesis.
Because of its cheapness, scalability and environmental compatibility, freeze casting has been shown to be an efficient way to achieve the desired alignment of graphene-oxide (GO) sheets in a frozen monolith. This is the case, since GO sheets are rejected from the ice crystal upon freezing, which means that by determining the freezing direction, the alignment of the resulting GO scaffold can be tailored, as the sheets are “trapped” in between the resulting ice crystals. Through deploying various different directional freezing techniques, multiple GO-alignments (e.g. micro-honeycomb or ordered lamellar structures) have already been achieved.
Motivated by these findings, researchers from the Institute for Basic Science and the National Institute of Science and Technology in Ulsan (Korea) have managed to synthesize vertically and radially align graphene aerogels, resembling the structure of a micro-turbine.
The stated aerogels were manufactured by freeze casting an aqueous GO dispersion in a tailor-made setup in which two perpendicular temperature gradients (one in radial and one in axial direction) could be generated. With this setup, the researchers aimed at a simultaneous axial and radial alignment of the GO-sheets inside the frozen dispersion, resulting in a turbine-like GO scaffold, as shown in the figure below.
Initial tests conducted in this bi-directional freezing (BDF) setup unveiled that interactions between water and the GO sheets (e.g. H-bonding) influenced the ice crystal growth, thereby entailing undesired final crystal shapes and sizes, which is why several additives (e.g. ethanol, cellulose and chitosan) were successfully employed to reduce these unwanted interactions.
Following the freeze-casting procedure in the presence of these additives, the resulting monoliths were freeze-dried and reduced chemically using hydrazine vapor, yielding dry and reduced graphene aerogel structures.
The characterization of the obtained graphene aerogel monoliths showed that a highly ordered structure with the desired features (e.g. increasing lamellae channel widths towards the outer edges of the monolith) were obtained, which can be seen in the figure below. Furthermore, the aerogels exhibited a density of 6.9 g/cm3 and a specific surface area of 45.9 m2/g.
To highlight the superiority of the novel ordered structure, the mechanical properties and absorptivities of the BDF aerogel were compared to those of aerogels of an unordered and a honeycomb pore structure. Apart from its outstanding rigidity, being able to carry ∼10 000 times its own weight without deformation, the “turbine” aerogel exhibited neither a substantial loss in strength nor visible plastic deformation upon multiple successive compression cycles. Even after 1000 compression cycles at 50 % strain, the BDF aerogels exhibited a deformation as little as 8 %, while the unordered and honeycomb structures exhibited similar or larger values after just 15 cycles. This was attributed to the fact that the blades of the turbine-like structure did not brake or dislocate when being strained.
To assess the absorptivity of the different samples, the maximum uptake of different liquid organic compounds (e.g. ethanol, IPA, acetone, pump oil, etc.) from an aqueous solution was investigated. Not only did the BDF aerogel outdo its counterparts in terms of the absorption capacity, but it also exhibited an extraordinary cycling stability when repeatedly removing the solvent from the aerogel pores via combustion subsequent to absorption (see figure below).
These outstanding findings once more highlight the unique features graphene aerogels offer and reveal that enhancements in their characteristic properties are readily attainable. Hence, further substantial advancements in the field of graphene aerogels are only a matter of time, making these materials one of the more auspicious candidates for future groundbreaking innovations. Certainly, the aerogel community will be captivated by this remarkable material for many years to come.
More details: Wang et al. “Freeze-Casting Produces a Graphene Oxide Aerogel with a Radial and Centrosymmetric Structure” ACS Nano, March 2018. https://doi.org/10.1021/acsnano.8b01747
Back in November 2016, the US based insulation firm Armacell has established a joint venture with the Silica Aerogel specialist JIOS Aerogel Ltd. (Korea), to develop and manufacture aerogel blankets.
Recently, the first fruits of this partnership were reaped as Armacell has released the ArmaGel HT insulation blanket, a flexible and versatile blanket equipped with aerogel particles. The novelty of this type of aerogel blanket is that, in contrast to conventional commercial manufacturing techniques, Armacell has developed a new type of process during which aerogel particles are injected mechanically into an existing blanket structure, instead of synthesizing aerogel matrices in situ. This does not only reduce processing times vastly (down to just two hours), but also increases the process scalability and efficiency as well as the freedom in design. Hence, Armacell promises a more economical and tailored solution for its customers.
In addition to its flexibility, the ArmaGel HT insulation blanket is thin and light-weight, allowing for easy handling, cheap transportation as well as simple assembly and replacement, which decreases machine down times and labor costs. Furthermore, the absence of any substantial dust formation upon machining allows for a simple and straight forward cutting of the blankets into tailored shapes. Therefore, it is an ideal material for thermal and sound insulation of “pipes, vessels and ducts (including elbows, fittings, flanges etc.) in offshore, industrial (typically oil and gas) and process equipment” for applications up to 650 °C.
Due to the absence of any toxic constituents, the aerogel blankets are environmentally safe and can be disposed on landfills, while their hydrophobicity and breathability significantly diminishes the risk of corrosion under insulation.
Most importantly, ArmaGel HT blankets exhibit great thermal and acoustic insulation properties, their thermal conductivities being comparable to those of commercially available aerogel blankets manufactured by their direct competitor Aspen Aerogels (USA), which can be seen in the figure below. Therefore, the market entry of Armacell could intensify the competition in the aerogel blanket market, which is currently being dominated by Aspen aerogels (especially in the US).
Although insulation blankets are just one of many applications for aerogel materials, they have certainly been one of the most widely used aerogel products so far. Hence, it’s good news that new competitors are entering the market to revive competition and accelerate innovation cycles, making the manufactured goods accessible for a large consumer base. We are confident that such developments will further motivate research and entrepreneurship in the versatile field of aerogel materials and therefore propel aerogels to common everyday materials.
Read more at:
https://corporate.armacell.com/en/armagel/
https://insulatenetwork.com/armagel
Edits:
* The thermal conductivity curve for ArmaGel HT have been updated according to the latest product TDS.
In search for a straight-forward and economical drying technique for aerogel materials, removing the main obstacle for the wide-spread application of aerogel materials — their tremendous costs — researchers from the University of Newcastle have been inspired by the way dragonflies and damselflies dry their lightweight and porous wings under ambient conditions.
In the course of their research the scientist stumbled upon the fact, that dragonflies dry their highly porous wings — which make up only 2 % of their entire bodyweight despite their large size — in a matter of a handful of hours (sometimes even as little as one hour) during their final metamorphosis into the adult. They hypothesized that this rapid but at the same time gentle drying process of the aerogel-like wings at ambient conditions can be attributed to the involvement of just one simple chemical compound — bicarbonate.
The formation of sodium chloride (NaCl) and CO2 from sodium bicarbonate, which takes place upon the addition of trimethylchlorosilane (TMCS), was found to be a straight forward technique to produce CO2 inside an aqueous porous medium, with the formed gas preventing pore collapse in the course of successive ambient pressure drying (APD), mimicking this process (supposedly) occurring in nature. As schematically shown in the figure on the right, this means that CO2 formed in situ works as a stabilizer
Schematic of novel APD drying technique deploying sodium bicarbonate and TMCS. of the gel pores, acting against the capillary pressure arising when the solvent is removed from the gel network via APD.
The suggested drying technique was tested using silica gels synthesized from tetraethoxysilane, which were placed into a sodium bicarbonate solution for 24 h after aging. Before drying the gels at ambient pressure (60 °C), small quantities of TMCS were poured upon them to initiate the CO2-forming reaction and hence prevent pore collapse. To further enhance the aerogel properties by removing the by-product NaCl from the gel pores an additional washing step was added to the procedure either after or during the drying step.
The resulting aerogels were found to exhibit similar properties as samples prepared via supercritical CO2 drying, exhibiting bulk densities as low as 0.06 g/cm3, porosities exceeding 98 % and specific surface areas of up to 700 m2/g, highlighting the great suitability of this drying technique for the manufacturing of silica aerogels. Further testing showed that the same process can also be applied to dawsonite (NaAlCO3(OH)2) aerogels synthesized with aluminum sec-butoxide and therefore is not limited to silica aerogels.
Certainly, the most outstanding characteristics of the suggested aerogel synthesis route are its simplicity, cost-efficiency, scalability and wide applicability, making it a strong alternative to conventional drying techniques. Especially its ultra low material cost, estimated at $4 per kilogram of aerogel, and the absence of any specialized or hazardous processing conditions (such as elevated temperatures or pressures and toxic materials) could propel the presented approach to market maturity and hence make aerogel materials accessible for commercial sectors, such as the building or clothing industry.
More details: Han et al. “Bioinspired Synthesis of Monolithic and Layered Aerogels” Advances Materials. https://doi.org/10.1002/adma.201706294
Read more at:
http://www.millenniumpost.in/world/dragonfly-wings-inspire-new-generation-of-aerogels-296492 https://phys.org/news/2018-04-world-oldest-insect-aerogels.html
Quantum dot-sensitized solar cells (QDSCs) are the third generation of solar cells, using quantum dots as the absorbing photovoltaic material, which allow for larger theoretical efficiencies than conventional silica based cells.
In addition to the major problems of this cell type — insufficient light absorption and electron hole recombination on the QD-electrolyte interface — which have been addressed in recent years yielding efficiencies up to 11 %, one great obstacle standing in the way of their large scale implementation is electrolyte loss due to evaporation. To avoid this undesired leakage of electrolyte entailing inferior cell performance, solid electrolyte carrier membranes have been introduced. Generally, synthetic polymer membranes have been deployed for this purpose. However, in light of environmental aspects, requiring a shift towards bio-compatible and renewable components, bio-based membranes are a logical replacement for their synthetic counterparts.
With the aim of devising biocompatible QDSC carrier membranes, scientists from the Aalto University in Finland have tested bio-based aerogel materials in QDSC cells, consisting of a CdS-sensitized photo-anode, a Pt counter electrode and a polysulfide redox electrolyte (see figure below).
To investigate the effect of different biopolymers, aerogels consisting of bacterial cellulose (BC), cellulose nanofibers (CNF), chitin nanofibers (ChNF) and TEMPO-oxidized CNF (TOCNF) were synthesized via gelation, solvent exchange and freeze-drying. Apart from their different fibrillar structures, the polymers exhibited a variety of different functional groups and surface charges, facilitating an investigation of the impact of these properties on cell performance.
Subsequent to gel drying, the aerogel samples were soaked with the polysulfide electrolyte, yielding free standing, flexible and stable structures in all four cases, allowing for easy sample handling and cell assembly.
The resulting membrane equipped QDSCs were then tested under irradiation of one sun (=1000 W/m2) to compare their performance to that of a reference cell filled with the untapped liquid electrolyte. All samples exhibited a similar photocurrent-voltage behavior, which can be seen in the figure on the right. Furthermore, the obtained values for the internal charge transfer resistance were comparable for all five cell type, suggesting that the membranes did not interfere with the internal charge transfer. Lastly, it was determined that neither membrane type had any detrimental effects on the polysulfide redox reaction, despite the difference surface charges of the deployed polymers.
In light of these findings, the authors concluded that cellulose and chitin based aerogels are suitable materials for organic electrolyte carrier membranes in QDSCs, since the performance of all aerogel-equipped samples was on par with that of the membrane-free reference cell. Out of the four different precursor materials, the researchers see the greatest promise in BC aerogels, due to its cost-efficient production technique via microbial fermentation and the resulting high purity of the biopolymer, guaranteeing a cheap and straight-forward production of BC aerogel membranes.
Certainly, the presented study can only be considered as an initial foray into the field of bio-based aerogel electrolyte carrier membranes. Future work will have to investigate the performance of such materials in more elaborate QDSC architectures to assess their potential for large scale implementation. Still, this pioneering work encourages endeavors aiming at the application of aerogel materials in photovoltaics. In case further work on this topic will underpin these findings, aerogels surely have the potential to become integral building blocks of next generation solar cells.
More details: Borghei et al. “Biobased aerogels with different surface charge as electrolyte carrier membranes in quantum dot-sensitized solar cell” Cellulose, 2018. https://doi.org/10.1007/s10570-018-1807-2
The Association of Advanced Porous Materials (Advapor) is to offer a € 3000 award to the “best” PhD completed in the field of Advanced Porous Materials. Defense must occur before June 2019.
The decision will be made by the steering team of the Advapor association and “best” will be judged on both technical merit and potential impact within our growing industry.
The award is designed to support the winning candidate in the presentation & publication of their work.
The award will be announced at the 2018 Aerogel Seminar in Hamburg.
Any candidate wishing to apply for this award must submit a concise summary of their work to info@advapor.org by the 31st July 2018.
Summary should include:
The Aerogel Seminar will take place at the Technical University Hamburg 24-16 /9 /2018.
Join now at our Website www.Advapor.org & help determine the future of Advanced Porous Materials.
The Aerogel Seminar 2018 date is fast approaching. To get a gist of what’s in store, click the video from a previous aerogel conference organized in Hamburg (2014)
Cotton is widely considered as a promising precursor material for aerogels due to its biodegradability, abundance, and non-toxicity. Furthermore, it is a low cost and renewable resource, making it an auspicious material for the addressing of environmental problems. Therefore, numerous studies have reported the utilization of cotton aerogels as superabsorbents for various different applications (e.g. cleaning up of oil spills or water purification).
Based on recent developments, allowing for the production of modified hydrophobic cotton aerogels, researchers from the South China University of Technology Guangzhou have come up with a new ingenious field of application — the trapping of methane bubbles, released by underground sea sediments, from water.
This application is of a special interest as methane is a very potent greenhouse gas, being responsible for approximately one fifth of the atmospheric greenhouse effect. Since aquatic system such as lakes, rivers or oceans are considered to be major sources of methane, releasing trapped gases to the atmosphere via bubbles, the capturing and safe storage of methane bubbles originating from marine environments could mitigate the negative impacts of climate change substantially.
In order to explore this idea, the research team from the South China University of Technology synthesized cotton aerogels (CAs) of varying cotton concentrations via freeze-drying. To ensure the hydrophobicity of the aerogels, the CAs were thereafter silanized with methyltrimethoxysilane, using a thermal chemical vapor deposition method. This resulted in stable monolithic cotton aerogels, which showed promising methane absorption characteristics under both static and dynamic conditions.
By submerging the different hydrophobic cotton aerogels (HCAs) in artificial seawater and exposing them to gaseous methane, it was found that the static absorption capacity increased with decreasing cotton concentration (i.e. larger porosity) and increasing submergence depth. Furthermore, the assessment of the dynamic absorptivity of the samples via compression/recovery cycles revealed that the process exhibits an outstanding repeatability, as the samples retained their absorption capacity to large extents.
With the aim of investigating a continuous strategy to safely transport methane above sea level, a pipe connecting the HCAs to the water surface was attached to the aerogel monoliths. This approach, which is schematically shown in the figure below, led to a steady and controlled transport of methane to the surface, as the bubbles trapped within the aerogel travelled through the pipe due to the existing pressure difference, resulting in an immediate recovery of the aerogel absorption capacity.
Certainly, the reduction of methane emissions from lakes and oceans could have a substantial positive impact on the world-wide greenhouse gas emissions. Therefore, the novel findings motivate a further investigation of the climate change mitigation potential of the deployment of (aerogel-based) methane bubble absorbents in aquatic systems.
The hydrophobic aerogels investigated in this study are not only captivating because of their excellent methane absorptivity, but also exhibit outstanding properties in terms of bio-compatibility and non-toxicity, paving the way for large scale deployment even in fragile eco-systems.
If further positive results in this field can be achieved, the trapping of methane from seawater could even become an economical process, with the captured methane being sold to compensate for the required investment and operational costs.
More details: Nan Li et al. “A Low-cost, Sustainable and Environmentally Sound Cellulose Absorbent with High Efficiency for Collecting Methane Bubbles from Seawater” ACS Sustainable Chem. Eng. https://pubsdc3.acs.org/doi/pdf/10.1021/acssuschemeng.8b00146
Despite their intriguing characteristics (e.g. ultralow density, high porosity & electrical conductivity), the application of carbon aerogels is generally limited by their poor mechanical strength and brittleness. Researchers from the Zhejiang University (China) were now able to manufacture highly flexible, binary carbon aerogels (bCAs) consisting of graphene and multi-walled carbon nanotubes (MWNTs), which can resist compressive and tensile stresses. These novel bCAs were successfully used as strain sensors to detect complex three dimensional movements.
The novel aerogels were fabricated by creating an aqueous solution equipped of graphene oxide and MWNTs which was then given shape by additive 3D-printing. Thereafter, the structures were freeze-dried before being chemically or thermally reduced.
Owing to their hierarchical assembly, which is schematically shown in the figure below, the novel bCAs exhibit an extraordinary stretching stability over a wide range of conditions (e.g. temperatures from 93-773 K). Furthermore, they exhibit a noteworthy fatigue resistance, being able to retain their structural shape to great extents for at least 100 cycles at 200 % tensile strain.
Another key characteristic of the bCAs is their change in resistance in tension (gentle increase) and compression (steep increase). Exploiting this feature, the researchers equipped the joints of a snake-like robot with bCAs to be able to sense the robot’s movements and configurations. As shown in the figure below, a sensor array consisting of three bCAs was sufficient to map the continuously changing configurations and hence accurately identify the robot’s movements.
The authors identify other potential applications of the bCAs in wearable electronic devices, lightweight mechanical devices and fields of application requiring robustness and reliability in the most extreme conditions (e.g. aerospace engineering). Furthermore, the researchers are confident that their assembly method can be deployed for the fabrication of other highly stretchable aerogel materials.
More details: Fan Guo et al. “Highly stretchable carbon aerogels.” Nature Communications. https://www.nature.com/articles/s41467-018-03268-y
Read more: https://phys.org/news/2018-03-rubbery-carbon-aerogels-greatly-applications.html
The German chemical company BASF Polyurethanes GmbH has won the German Design Award for its Excellent Product Design in the category Building and Elements. The jury selected the aerogel insulation material SLENTITE® due to its unique combination of properties, facilitating space-saving insulation concepts which open up entirely new creative possibilities to architects and designers.
The novel aerogel material, consisting of 90 % air, allows for the reduction of insulation thicknesses by 50 %, when compared to standard insulation materials. Besides its outstanding thermal insulation properties, it is the first solid, breathable aerogel panel produced from polyurethane. Furthermore, it is easily machined without excessive dust generation, allowing for tailored shapes & sizes and direct application on walls or facades.
Consequently, the SLENTITE® thermal insulation panels eclipse any commercial insulation material while fulfilling all demands placed on modern building materials.
Its honoring by the German Design Award jury could spark the interest of potential customers and competitors, stimulating the aerogel insulation material market.
Read more:
http://www.german-design-award.com/en/the-winners/gallery/detail/17074-slentite.html
https://www.basf.com/en/company/news-and-media/news-releases/2018/02/p-18-120.html
https://www.bi-medien.de/artikel-24501-bm-extrem-schlanke-daemmplatte-von-basf.bi
Recently, we have reported on the potential of aerogel sorbents for CO2 capture and storage (CCS). Despite their favorable properties, the deployed amine functionalized aerogels (AMAs) were found to require optimization to allow for their successful economical implementation. Increasing the activity and capacity of solid sorbents while decreasing their cost, is therefore an issue which is currently under investigation. Researchers from the US and Sri Lanka now report to have found an efficient, cheap and environmentally benign solid CO2 sorbent: KOH-activated carbon chitin aerogels.
The novel sorbent material was synthesized from commercial chitin powder from shrimp shells, which was dispersed in a sodium-urea-water solution. Repeated freezing/thawing cycles of this solution resulted in the formation of a stable hydrogel, which subsequently was freeze-dried to obtain a chitin aerogel. Thereafter, carbonization of the aerogel was achieved by heating the sample to 800 °C under nitrogen atmosphere. In the last step, the aerogel was again heated to 850 °C (under N2 atmosphere) in the presence of potassium hydroxide (KOH) to obtain the activated carbon aerogel. Consequently, the inexpensive manufacturing technique, which does not require any costly or toxic chemicals, and the abundance of the precursor materials facilitate the cheap production of chitin-based CO2 sorbents.
The final activated carbon aerogels were found to exhibit large specific surface areas (> 500 m2/g), more than 35 times larger than that of their parent chitin aerogels. Additionally, the micro pore volume, which is an important parameter for CO2 capture, increased by the factor of 95 between the chitin aerogel and the carbonized and KOH-activated sample. These two factors explain why the obtained CO2 sorptivity value of 0.48 mmol/g (1 atm, 0 °C), obtained for the chitin aerogel, could be vastly increased to 5.02 mmol/g by further processing (i.e. carbonization and activation). As shown in the figure below, similar increase in sample sorptivity was also measured at room temperature (0.28 mmol/g and 3.44 mmol/g, respectively). This means that the morphological changes taking place inside the aerogel structure during carbonization and activation have a significant impact on the final sorbent properties.
The authors conclude that they have found an environmentally benign and very inexpensive way of manufacturing highly active chitin-based sorbents for CO2 capture. Additionally, the sorbents are synthesized from a biopolymer, making the final material biodegradable and non-toxic.
More details: Dassanayake, R.S., Gunathilake, C., Abidi, N. et al.; Activated carbon derived from chitin aerogels: preparation and CO2 adsorption, Cellulose (2018). https://doi.org/10.1007/s10570-018-1660-3
Fragility and brittleness have always been flaws of delicate three-dimensional aerogel structures. Especially when exposed to harsh conditions (e.g. in aerospace applications), their frailty has limited the broad application of aerogels in such fields. A Chinese team of researchers from the Beijing Jiaotong University has now attended to this matter. By equipping a ZrO2–SiO2 aerogel with Polycrystalline ZrO2 fibers (ZrO2f), aerogels possessing high thermal and mechanical resilience have been devised. Astonishingly, these monolithic aerogels do not only excel in terms of stability, but also show low bulk densities and thermal conductivities.
The idea of adding a fibrous agent to the aerogel matrix is that, when dispersed evenly throughout the matrix, the fibers act as an additional mechanical backbone. This means that the fibers hinder fracturing and irreversible deformation through fiber-bridging and crack-deflection (see Figure below) when the monolithic structure is being strained. Furthermore, due to the even dispersion of the fibers in the aerogel matrix, the contribution of heat conduction through the fibers is minimized and hence the overall heat conductivity increases only marginally upon addition of the fibrous ZrO2.
In summary, these effects lead to highly insulating aerogels possessing compressive strengths 3-10 times higher than previously reported. Therefore, applications in very demanding environments are facilitated, which might prove to be significant in aerospace engineering and other fields in which stable and highly insulating materials are essential.
More details: Xianbo Hou, Rubing Zhang and Daining Fang; An ultralight silica-modified ZrO2–SiO2 aerogel composite with ultra-low thermal conductivity and enhanced mechanical strength, Scripta Materialia Volume 143, 15 January 2018, Pages 113-116. http://doi.org/10.1016/j.scriptamat.2017.09.028
Researchers from the Kyoto University (Japan) successfully synthesized transparent, machinable, scalable, super-compressible, highly elastic and super-insulating polyvinylpolymethylsiloxane aerogels and xerogels. Remarkably, the study reports that these outstanding features were present not only in aerogels produced using supercritical drying, but in those produced using ambient pressure drying, too.
The sample preparation was achieved by mixing vinylmethyldimethoxysilane (VMDMS) or vinylmethyldiethoxysilane (VMDES) with 1-5 % of di-tert-butyl peroxide (DTBP), to initiate the radical polymerization at 120 °C, yielding a transparent viscous liquid mainly containing polyvinylmethyldimethoxysilane (PVMDMS) or polyvinylmethyldiethoxysilane (PVMDES). Thereafter, BzOH, H2O and tetramethylammonium hydroxide (TMAOH) were added to the liquid and the mixture was heated to 80 °C for one hour to obtain transparent and flexible gels. Prior to solvent exchange with isopropanol (IPA), the gels were aged between four or five days at 80-100 °C. Removal of the liquid was subsequently accomplished in three different ways (see Figure below): (1) supercritical drying with CO2; (2) solvent exchange into n-hexane followed by drying at ambient pressure; (3) direct drying from IPA at ambient pressure.
It was established that key to the intriguing properties of the dried aerogels and xerogels are their homogeneous porous nanostructure, composed of flexible hydrocarbon chains chemically cross-linked with polymethylsiloxanes. Notably, this type of nanostructure structure exhibited low densities (0.16-0.22 g/cm3) and heat conductivities (15.0-15.4 mW/m K), as well as high specific surface areas (900-1000 m2/g), good transparency (>80 % light transmittance), and extraordinary flexibility (see attached video). Additionally, the flexible network structures allowed for a recovery of the evaporation-induced gel shrinkage through a “spring-back” effect (see Figure below), making the supercritical drying step dispensable.
In summary, these findings imply that an ultra-low cost pathway to manufacture aerogels by ambient pressure drying while still preserving extraordinary properties required for applications as superinsulators has been established. This means that one of the main obstacles for the broad application of aerogels — their high manufacturing costs — has been overcome, which might pave the way for their large scale deployment.
More details: Zu et al.; Transparent, Superflexible Doubly Cross-Linked Polyvinylpolymethylsiloxane Aerogel Superinsulators via Ambient Pressure Drying , ACS Nano, January 8, 2018. https://doi.org/10.1021/acsnano.7b07117
Video of aerogel bending test: Click Here
The search for active yet economical water purification strategies is in full swing as increasing industrial activity results in sharp surges in wastewater production, and the ever-growing global population increases demand for clean drinking water.
Commonly, separated, sophisticated absorption processes are deployed to remove either organic or inorganic contaminants from sewage water due to their high efficiency and moderate cost. However, it remains a challenge to devise robust, efficient and economical absorbents for the wide range of trace elements occurring in wastewater. Ideally, novel absorption materials should be able to remove inorganic compounds such as dyes or heavy metals and also be active against harmful viral or bacterial pathogens.
In pursuit of such a material, researchers from Jinan University (China) have synthesized an aerogel structure exhibiting extraordinary dye and heavy metal absorbing properties, by using graphene oxide (GO) and a type of abundant mineral called montmorillonite (MMT). The desired anti-pathogenic activity was realized through equipping the aerogel matrix with a common anti-bacterial agent, resulting in absorbents displaying excellent antibacterial activity against Gram-positive and Gram-negative bacteria.
The aerogel material exhibiting these intriguing properties was manufactured through mixing GO powder, ascorbic acid, and a MMT solution, then inducing gelation through heat treatment at 95 °C. After aging of the hydrogel in a PVA solution for two days, the gel was then freeze dried at -55 °C, resulting in a monolithic aerogel structure, which is shown in the Figure below.
Absorption experiments showed that the aerogel absorbents were not only able to remove more than 95 % of methyl orange and methylene blue dyes from aqueous solutions, but also exhibited great properties for the removal of heavy metals from water (e.g. >90 % removal efficiency for chromium ion removal). This activity was found to be stable over numerous absorption/desorption cycles, with sample regeneration being achieved by vigorous shaking. Furthermore, the addition of antibacterial dodecyl dimethyl benzyl ammonium chloride (1227) to the initial precursor solution was found to provide the aerogel with antibacterial activity, which was shown using E. coli and S. aureus bacteria cultures, each losing over 90 % of their cell viability in the presence of the GO-MMT-1227 aerogel material.
Due to these extraordinary findings, the researchers are confident that they have found an efficient, versatile, recyclable, and robust absorbent material, which has the potential to revolutionize water purification. If economical large scale manufacturing and long term stability can be achieved, the novel material might indeed replace state-of-the-art sorbents in wastewater treatment systems.
More details: Yunyun Zhang et al.; The utilization of a three-dimensional reduced graphene oxide and montmorillonite composite aerogel as a multifunctional agent for wastewater treatment, RSC Adv., 2018,8, 4239-4248. https://doi.org/10.1039/C7RA13103H
The enhancing effects of polyaniline (PANi) coatings on ion and electron conductivity are well known (see also here), which is why researchers from the Sun Yat-sen University (China) devised PANi-coated activated carbon/sulfur aerogels (ACA-500-S) in order to improve the electrochemical properties of the un-coated composite. By synthesizing this novel electrode material, the research team hopes to address drawbacks of Li-S batteries (e.g. low ionic conductivity, dissolution of polysulfides in electrolytes).
Carbon/sulfur composite aerogels were produced by heat-melting state-of-the-art activated carbon aerogels (ACA-500) in the presence of elemental sulfur. As shown in the Figure below, the PANi coating was subsequently applied by in-situ chemical oxidative polymerization at low temperatures, yielding the final ACA-500-S@PANi electrode material. Investigation of the sample morphology via FESEM and TEM revealed that the manufacturing technique led to a homogeneous distribution of sulfur and PANi on the aerogel surface. Because of the even dispersion of the active agents on the aerogel matrix, enhanced electrochemical performance was expected from the ACA-500-S@PANi composite.
This expectation was confirmed in ensuing experiments, which compared the specific capacity, capacity discharge, and capacity retention of the ACA-500-S and ACA-500-S@PANi materials. It was shown that the latter material outperformed the carbon/sulfur aerogel in all regards, which was attributed to the synergistic effect of the carbon aerogel matrix and the PANi coating on ion and electron conductivity as well as electrode stability. More specifically, the researchers discovered that the ACA-500-S@PANi structure presented high reversible capacities at low (at 0.2 C: 1208 mAh g−1) and high (at 3.0 C: 542 mAh g−1) discharge rates. Furthermore, long term cycling at 1.0 C demonstrated that it exhibits a notable initial discharge capacity of 926 mAh g-1 and outstanding capacity retention of over 65 % at a low capacity decay rate of 0.48 ‰ per cycle.
Because of these findings, the researchers are confident that the novel aerogel composite will be able to boost the performance of lithium-sulfur batteries, meeting the increasing demand for batteries exhibiting a high energy density and long life span at low cost.
More details: Tang et al.; Polyaniline-Coated Activated Carbon Aerogel/Sulfur Composite for High- performance Lithium-Sulfur Battery, Nanoscale Research Letters 2017. https://doi.org/10.1186/s11671-017-2372-6
Although we might not recognize it, electronic sensors have developed into essential components in our everyday life. They provide our smartphones with necessary information, guarantee safe travels in our cars and ensure that our homes are adequately air conditioned. With increasing automatization in the industrial and private sector (e.g. internet of things, smart home, autonomous driving, etc.), the importance of those tiny helpers for our prosperity, well-being and safety will only increase. Therefore, it will be essential to develop more efficient, powerful and complex sensors, which are able to process information in a reliable fashion.
Researchers from the Linköping University (Sweden), were now able to manufacture a type of thermoelectric aerogel, which is able to simultaneously sense pressure and temperature. Moreover, the pressure and temperature signals are decoupled, allowing for a reliable synchronous measuring of both parameters.
The dual-parameter PNG aerogels sensors were synthesized from a mixture of poly3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS), nano-fibrillated cellulose (NFC) and glycidoxypropyl trimethoxysilane (GOPS). This precursor selection led to an elastic, yet robust thermoelectric PNG aerogel, being able to sense pressure changes (NFC & GOPS) and temperature variations (PEDOT:PSS). Post-treatment in dimethylsulfoxide (DMSO) vapor not only increased the pressure sensitivity of the aerogel, but also resulted in a decoupling of the temperature and pressure signal by changing the internal charge carrier transport through the material.
Testing of the aerogel composite in an experimental setup, schematically depicted below, showed that pressure and temperature gradient could be obtained from two independent parameters of the current-voltage curve. The pressure signal is indicated by the slope, whereas the y-intercept denotes the temperature gradient across the aerogel (see also Figure below).
These revolutionary findings could pave the way for further research on multi parameter sensing aerogels, facilitating innovations which rely on powerful sensors. The Swedish research team already anticipates the utilization of their novel dual scale PNG aerogel in e-skin applications.
More details: Han et al.; Thermoelectric Polymer Aerogels for Pressure–Temperature Sensing Applications, Advanced Functional Materials, Volume 27, Issue 44 November 24, 2017. https://doi.org/10.1002/adfm.201703549,
Annually, the Swiss Federal Office of Energy awards the Watt d’Or Award to people, companies and organizations that “develop the energy technologies for the future, bring innovative products onto the market and set new standards for practical solutions that unite energy and environment awareness with comfort requirements, aesthetics and economic interests”.
This year, a prototypical aerogel-insulated apartment building, devised by the Zurich-based architectural office Dietrich Schwarz has been awarded the Watt d’Or in the category Buildings and Space.
With new challenges in terms of energy efficiency and space requirements arising, architects are faced with a fundamental conflict — providing highly effective insulation at constant or even slimmer wall thicknesses. The only escape from this dilemma are advancements in insulation materials, yielding scalable structures of extremely low thermal conductivity.
Aerogels are one type of material promising exactly those required characteristics and therefore are generally considered to possess great merit for the future building insulation market.
Due to these intriguing insulating properties of aerogels, the architects of Dietrich Schwarz (Switzerland) have selected aerogel-equipped wood elements to insulate the exterior facade of their latest award-winning project in Zurich (see image above). Thereby, the building floor space was maximized without jeopardizing energetic requirements placed on modern architecture. Additionally, vacuum-insulated windows, phase-change materials in the facades reducing the required cooling and heating demands, rooftop PV panels and a thermal heat pump complete the holistic approach to reduce the energy intensity of modern housing.
Another eye-catching, futuristic feature of the apartment block are its convex oriels, providing sound insulation from the noisy street. Through these elements regular room ventilation via opened windows can be achieved without experiencing excessive noise pollution.
In light of the abundance of novel architectural elements, providing a high level of comfort at vastly reduced energetic footprint, found in this building concept, the selection of the jury of the Swiss Federal Office of Energy does not come as a surprise.
If building concepts such as the one by Dietrich Schwarz will prove their worth, it will only be a matter of time until aerogel-based insulation materials will become a market standard.
Read more at:
https://www.tagesanzeiger.ch/zuerich/stadt/zuercher-architekten-ueberzeugen-mit-ultraduenner-daemmung/story/21704599
https://www.baublatt.ch/verschiedenes/watt-dor-2018-ein-intelligentes-licht-fuer-tier-und-mensch
Finding non-cytotoxic carrier materials that ensure a controlled release of an active hydrophobic drug over a long period of time is considered to be the “holy grail” in wound dressing applications. A team of researchers from Brazil and the USA report to have found a material that combines all of those desired characteristics.
The novel silica-polymer hybrid (SPH) aerogels, synthesized from silica nanoparticles, polyvinyl alcohol (PVA), polyacrylic acid (PAA), and water, were manufactured via freeze-drying and subsequent thermal treatment (see Figure below). While the freeze-drying ensured a complete removal of water, the ensuing thermal treatment at 160 °C facilitated the cross-linking between PVA and PAA, guaranteeing aerogel stability in aqueous media.
Experiments conducted with dexamethasone (DEX), an agent used for the treatment of skin diseases, allergies, and rheumatic problems, showed that the SPH aerogels exhibit high drug encapsulation efficiencies, taking up around 75 % of DEX from an ethanol/water mixture within 24 hours. This feature was ascribed to the trapping of DEX molecules within the mesoporous silica nanoparticles.
The release rate of DEX from the aerogels was investigated by placing the loaded samples into a stirred phosphate buffered saline (PBS) solution at 37 °C and measuring the progression of the DEX concentration with time. These measurements showed that after an initial rapid discharge of DEX, the release rate leveled off, so that even after two months a steady drug discharge was obtained. This slow and prolonged release of DEX molecules was attributed to the polymer pore structure, limiting the mass transfer from the drug encapsulation site (silica nanoparticles) to the solution. Supporting this finding were results for SPH aerogels of a different constitution, which showed that a change in PVA:PAA ratio, yielding morphological modifications of the polymer pore network, leads to a significant change in drug release behavior.
In order to assess the biocompatibility and cytotoxicity of the synthesized material, the cell viability of vero cells and L929 fibroblasts was investigated in the presence of the SPH aerogels. This line of experiment showed that there is virtually no decrease in cell viability for either cell type after 72 hours, regardless of precursor selection.
The authors see potential applications of SPH aerogels in the treatment of skin burns or melanoma, which require wound dressing over extended periods of time. Furthermore, they see potential in tailoring the aerogel structures (e.g. with antibodies) to further extend their potential biological and medical applications.
More details: Follmann et al.; Multifunctional Hybrid Aerogels: Hyperbranched Polymer- Trapped Mesoporous Silica Nanoparticles for Sustained and Prolonged Drug Release, Nanoscale, December 2017. http://doi.org/10.1039/C7NR08464A
Coal fired power plants will play a substantial role in energy production for the majority of industrialized nations until at least the middle of this century. This is an issue since the large-scale combustion of carbon-based resources is a major contributor to the rising atmospheric CO2 levels. In order to achieve the ambitious multilateral goals to lessen the detrimental effects of global warming by stabilizing the global CO2 levels outlined in the Paris Agreement, the greenhouse gas emissions from coal fired power plants will need to be reduced drastically.
One way to achieve this reduction in emitted greenhouse gases without abandoning coal-based power production is the capturing and sequestration of emitted CO2 (see graphic below). This can be done by retro-fitting existing power plants with carbon capture and storage (CCS) units, which remove carbon dioxide from flue gas, before storing it in a designated location. Most commonly, temperature-swing adsorption (TSA) processes, utilizing aqueous amine solutions as sorbents, are proposed for CO2 capturing. However, the regeneration of the amine solution results in an energy penalty which drastically reduces the thermal efficiency of the power plant. Therefore, alternative sorbents requiring less energy for regeneration are under investigation.
In a joint effort, a project team consisting of Aspen Aerogels, the University of Akron, ADA-ES, and Longtail Consulting have synthesized and tested solid amine functionalized aerogels (AFA) in a bench scale fluidized bed reactor, in order to assess their potential for future application in CCS.
It was found that the AFAs synthesized by Aspen Aerogels showed promising CO2 adsorption behavior and good stability over numerous adsorption-desorption cycles. On top of that, the novel solid sorbents possess significantly lower heats of reaction with CO2 than commonly deployed liquid and solid sorbents. In a subsequent step, the AFAs were coated at the University of Akron, yielding pellets possessing a good cyclic stability in the presence of SO2. The novel AFA pellets were then tested in a bench scale fluidized bed reactor to determine their physical properties (e.g. fluidizing gas velocities, void fraction, etc.) in such a reactor setup.
Based on those findings, Longtail Consulting modeled the hydrodynamic and heat transfer properties of the solid aerogel sorbent in the fluidized bed reactor and finalized the process requirements. Subsequently, a techno-economic analysis (TEA) of the entire CO2 capturing unit (assuming 90 % capturing efficiency) fitted to a coal fired, supercritical steam cycle power plant producing 550 MWe was performed. Despite offering a promising behavior from a technological perspective, the TEA revealed that utilizing novel AFA sorbents results in approx. 20 % higher levelized electricity costs. This finding was mainly attributed to the fact that the attrition of the material during fluidization was unknown, yielding high variable costs for the selected scenario. Additionally, a relatively high apparent particle density inside the fluidized be reactor led to a massive pressure drop, causing a surge in auxiliary electricity input.
In light of these findings, the project team concluded that further testing under practical conditions and simultaneous optimization of the AFAs will be essential to make solid sorbents an economical alternative to state-of-the-art aqueous amines.
As the need for creative solutions to reduce greenhouse gas emissions is only increasing, it is promising to see that the vast potential of aerogels is being explored to address climate change. Whether or not solid sorbents can be successfully utilized in TSA in an economically reasonable way may prove to be one of the key factors determining the success of CCS.
Full Report: https://doi.org/10.2172/1349123
Read more at: https://www.osti.gov/scitech/biblio/1349123
Because of their unique characteristics, graphene aerogels are attractive materials for a wide range of applications. However, due to their micro-fibrous structure, strength and resilience, which are both desired properties, are generally considered to be mutually exclusive. By employing a bidirectional freeze-drying technique, researchers from the Zhejiang University (China) have successfully manufactured monolithic graphene aerogels uniting both properties.
In order to achieve those exceptional characteristics, the micro-scale architecture of the aerogels was based on the structure of a thalia dealbata stem, which is able to provide sufficient strength to support the plants leaves and blossoms while enduring powerful external forces (e.g. strong winds). The mimicking of this special three-dimensional lamellar structure consisting of bridged layers (see Figure above), yielded aerogel structures exhibiting strength and resilience simultaneously (see Figure below).
When compared to a graphene aerogel exhibiting a random structure, the biomimetic aerogel showed a significant superiority in recovery behavior after being strained. Furthermore, the authors found that the aerogel architecture and hence the mechanical properties of the graphene structures can be further optimized by tuning the precursor composition.
The fabrication of such firm and robust structures could be play a pivotal role in establishing graphene aerogels in sensing applications. Additionally, the manufacturing technique reported by the authors can potentially be extended to other materials in order to obtain tailored micro-architectures.
More details: Miao Yang et al.; Biomimetic Architectured Graphene Aerogel with Exceptional Strength and Resilience, ACS Nano, 2017, 11 (7), pp 6817–6824. https://doi.org/10.1021/acsnano.7b01815
Read more at: https://www.forbes.com/sites/samlemonick/2017/07/31/plant-inspires-super-strong-aerogel/#2b9b35b96415
The Hamburg based startup Aerogelex has received the ETPN (European Technology Platform for Nanomedicine) Award 2017 for Best Nanomedicine Product/Deal at the Bio-Europe 2017. The awards committee was impressed by Aerogelex’s biopolymer aerogels for wound dressing, pharmaceutical, and life science applications.
Aerogelex’s goal is to facilitate the implementation of aerogels in cosmetic, food, pharmaceutical, and thermal applications by transferring their wealth of knowledge about aerogels and aerogel manufacturing to partners who see value in the performance aerogels can offer. Aerogelex will partner with companies and research groups to solve the materials and processing challenges associated with bringing aerogels and aerogel-based materials to market.
Aerogelex is currently open to partnership with individuals and companies who looking to establish a foothold in biopolymer aerogels, or who are interested in using supercritical drying in their manufacturing process. Businesses that partner with Aerogelex will get access to an aerogel production plant where aerogel prototypes can be manufactured and optimized. After a successful pilot phase, partnering companies will learn how to manufacture aerogels on a large scale in order to establish their own expertise.
To get a glimpse of the technological opportunities that supercritical drying and biopolymer aerogels offer, curious minds can purchase the first official product from Aerogelex on BuyAerogel.com. The ”AeroEggs” up for sale are unique aerogels made from hard-boiled eggs that reveal the endless possibilities that aerogels can offer.
Full video of Nanomedicine Award ceremony with presentation from Aerogelex founder Dr. Raman Subrahmanyam: https://www.youtube.com/watch?v=P6JXJBrQVfY&list=PLjyB2R13BJCv4XVHoxm1TsZL_VkZiELDk
Increasing atmospheric CO2 levels and dwindling fossil fuel resources have motivated the search for sustainable and renewable sources of energy. Hydrogen is considered to be an environmentally friendly alternative to common fossil fuels, as it does not emit environmentally harmful greenhouse gases upon combustion. Therefore, the quest for an efficient and sustainable way of generating hydrogen on a large scale is in full swing.
Supercritical water gasification (SCWG) of biomass is one such renewable hydrogen production technique that is currently being investigated. Due to the unique properties of supercritical water (e.g. high diffusivity, miscibility with gases) the process promises high energy conversion efficiencies. However, a suitable catalyst for the reaction, ensuring high H2 yields while suppressing coke and tar formation, has remained elusive. Researchers from the University of Western Ontario (Canada) have recently synthesized a Ru-Ni-Al2O3 catalyst which has shown promise for the SCWG process.
Synthesis of the catalyst required the formation of a clear solution which was achieved by mixing the aluminum support in isopropanol at 75 °C followed by the addition of nitric acid. Thereafter, the metallic precursors (nickel nitrate and ruthenium acetylacetonate) were added to the sol to initiate the aging process. After completion of the gel formation, the liquids contained in the porous structure were extracted via low temperature supercritical drying with CO2. In a last step the samples were calcined and reduced at 600 °C to obtain the ready-to-use aerogel catalysts (see Figure below).
The Ru-Ni-Al2O3 aerogel, synthesized via this process, exhibited a higher specific surface area and pore volume when compared to impregnated or xerogel Ru-Ni-Al2O3 catalysts. These superior structural features significantly enhanced the hydrogen yields during SCWG, due to the increase in available active surface area. Furthermore, the porous aerogel morphology was also shown to decrease unwanted coke formation on the catalyst surface. A comparison of Ni-Al2O3 and Ru-Ni-Al2O3 aerogel catalysts revealed that the promoting nature of ruthenium (Ru) leads to superior catalytic activities for the bimetallic composite. Additionally, the utilization of Ru further decreased coke formation during the gasification reaction.
In order to assess the cyclic stability of the aerogel structures Ni-Al2O3 and Ru-Ni-Al2O3 catalysts were employed in three consecutive SCWG reactions. Both structures showed signs of deactivation (e.g. decrease in surface area), however, even during the third experimental run a decent catalytic activity was observed for both structures. For example, the recycled Ru-Ni-Al2O3 aerogel exhibited only slightly smaller hydrogen yields than the fresh Ru-Ni-Al2O3 xerogel and the fresh impregnated Ni-Al2O3 catalysts.
Although numerous projects aiming at the development of renewable energy generation processes are in progress, we are still a long way from a fully formed strategy to replace fossil fuels globally. Therefore, technical advancements paving the way to a more sustainable future are essential. This study has shown that aerogels could play an integral role in propelling alternative processes such as supercritical water gasification to market maturity.
More details: Md. Zakir Hossain, Muhammad B.I. Chowdhury, Anil Kumar Jhawar, Paul A. Charpentier; Supercritical water gasification of glucose using bimetallic aerogel Ru-Ni-Al2O3 catalyst for H2 production, Biomass and Bioenergy Volume 107, December 2017, Pages 39-51. https://doi.org/10.1016/j.biombioe.2017.09.010
As demand for oil increases, so does its extraction and, consequently, the frequency of production-related accidents. This necessitated advancements in oil separation and absorption techniques to make sure that environmental disasters can be prevented.
An efficient way to remove oil and solvents from contaminated waters are absorbents, which directly remove the oil in the deployed surroundings. Additionally, they facilitate the possibility of recycling the absorbed oil after recollection. However, common absorbing materials utilized for the cleaning of oil spills are known to have a low environmental compatibility.
In light of these facts, researchers from the National University of Singapore have synthesized novel environmentally benign cotton-cellulose aerogels which exhibit promising oil absorption characteristics. The monolithic pure cotton (PC) and cellulose-cotton (CC) aerogels were manufactured using a freeze-drying technique. In order to ensure hydrophobicity of the materials (see figure on the right), the aerogels were silanized using methyltrimethoxysilane. Thereafter, the absorption capacity of the aerogels was investigated for different solvents (e.g. dichloromethane, motor oil, ethanol).
The synthesized PC and CC aerogels were able to absorb all utilized solvents to large extents with loading capacities of up to 100 g/g being measured. Additionally it was discovered that absorption capacities increase with solvent density. In order to analyze the recyclability of the aerogels, two different recycling techniques were investigated. These experiments revealed that distillation cycling guarantees a superior sustaining of the absorbing performance when compared to squeeze cycling.
The intriguing findings of the authors once again highlight that aerogels can be applied in areas reaching beyond the field of insulation.
More details: Hanlin Cheng et. al; Cotton aerogels and cotton-cellulose aerogels from environmental waste for oil spillage cleanup, Materials & Design Volume 130, 15 September 2017, Pages 452-458. https://doi.org/10.1016/j.matdes.2017.05.082
Although monolithic aerogels of numerous types and forms have been produced using a broad palette of techniques, it remains a challenge to accurately tailor the micro- and macrostructure of the resulting three-dimensional structures. Recently, researchers from Kansas State University (USA) have presented a 3D-printing freeze drying technique promising just that.
The so-called 3D freeze assembling printing (3DFAP) technique facilitates the fabrication of monolithic aerogels of various macrostructures (see figure on the right). Using this process, the team of researchers was able to produce silver nanowire aerogels (SNWA), that have ultra-low density (1.3 mg/cm3) and high electrical conductivity (0.24 S/cm), while also exhibiting outstanding mechanical features such as good compressive resistance and tunable Poisson ratios (even negative). Experiments investigating the effect of mechanical stress on material resistance revealed outstanding cyclic stability. Furthermore, the different structures were found to exhibit extremely high mechanical resilience, even under tensile stress.
In light of these promising results, the authors conclude that through facilitating the manipulation of the aerogel macrostructure, the novel production technique offers the possibility to manufacture three-dimensional aerogel structures for applications in the fields of sensing, energy storage or catalysis. They are also convinced that the 3DFAP technique can be applied to produce other 3D nanomaterial architectures.
More details: Pengli Yan et. al; 3D Printing Hierarchical Silver Nanowire Aerogel with Highly Compressive Resilience and Tensile Elongation through Tunable Poisson’s Ratio, Small Volume 13, Issue 38 October 11, 2017. http://onlinelibrary.wiley.com/doi/10.1002/smll.201701756/abstract
Read more at: http://www.advancedsciencenews.com/3d-printing-tunable-poisson-ratio-metallic-aerogels/
Owing to their unique characteristics, graphene aerogels are considered promising materials for a wide range of applications in fields such as energy storage, catalysis, and sensing. A research team from the Tsinghua University (China) has successfully demonstrated that another item can be added to this impressive list — adsorption and pre-concentration of air pollutants. Hierarchical porous graphene aerogels (HPGAs) synthesized via self-assembly, freeze drying and subsequent calcination have been shown to possess outstanding characteristics for extracting chemical warfare agents (CWAs) from ambient air.
The researchers found that the graphene aerogels, composed of a porous three-dimensional pore network (see Figure above), exhibited a good thermal and mechanical stability. Adsorption experiments with sarin, a highly toxic nerve agent, showed that the HPGAs display outstanding adsorption/desorption behavior in a wide range of operation conditions (e.g. desorption temperature, relative humidity). Furthermore, repeated cycling of the graphene aerogels did not result in a drop in adsorption efficiency or a change in material morphology, underlining the high resilience of HPGAs.
Given those intriguing results, the authors hypothesize that graphene aerogels could be efficient materials for the removal of other hazardous gases from air and hence might prove to be a promising alternative in cases of industrial accidents or terrorist attacks.
More details: Qiang Han, Liu Yang, Qionglin Liang and Mingyu Ding; Three-dimensional hierarchical porous graphene aerogel for efficient adsorption and preconcentration of chemical warfare agents, Carbon Volume122, October 2017, pages 556-563. https://doi.org/10.1016/j.carbon.2017.05.031
Aerogels, long familiar only to researchers and pioneers, are now making their way into consumer products. One such example is the newly introduced Life-PocketTM by the Norwegian company Helly Hansen.
It is rumored that when the Canadian Skiing Team was asked which improvements they hoped for in skiing apparel, they explicitly demanded for an insulated smartphone chest pocket, which facilitates a longer battery lifetime. With the aim of making the pro-skiers innermost wish a reality, the team at Helly Hansen found a partner which had a solution at hand — PrimaLoft (USA), a company focused on insulation for outerwear, gloves and footwear.
Using “Primaloft Aerogel Gold” insulating material, the designers at Helly Hansen have created a pocket which protects the battery of cell phones even in the most extreme weather conditions (-28.0 °C / -18.4 ℉). This high performance insulation composite (CLO ratings: 1.29-2.00) is a pressure resistant material encapsulated in a waterproof membrane that can be used for insulating pockets, shoes and gloves.
Since the aerogel is only located on the outside of the jacket, body warmth is utilized to maintain a certain temperature inside the chest pocket and hence prevent temperature-related performance decrease of smartphone batteries. According to the company, jackets equipped with the Life-PocketTM and the Life-Pocket+TM keep phones two or three times warmer than regular ski jackets, respectively.
Initial hands-on tests of the product showed a significant increase in battery life, demonstrating that the aerogel-insulated pocket delivers on its promise (more details).
It will be interesting to see whether the unique characteristics of aerogel materials begin to attract a broader interest from product designers.
Read more at: https://www.hellyhansen.com/news/the-life-pocket-saving-battery-life-in-cold-environments/
Read more at: https://www.airfreshing.com/news-helly-hansen-life-pocket
Read more at: https://gearjunkie.com/aerogel-helly-hansen-lifepocket-powder-suit
Read more at: https://gearjunkie.com/primaloft-gold-aerogel-insulation
Supercapacitors are generally viewed as promising energy storage alternatives for future mobile applications, due to their immense energy and power density. Researchers from the Jiangsu University (China) have now been able to greatly improve electrochemical characteristics of graphene/polyaniline aerogels, which are considered a promising material for super capacitor electrodes, by doping them with nitrogen.
The resulting 3D nitrogen-graphene/polyaniline (N-GE/PANI) foams exhibited a rough and wrinkled surface area on which the PANI spheres were incorporated (see Figure).
Furthermore, it was found that the combination of N-GE and PANI resulted in superior specific capacitance, when compared to the individual materials. This finding was ascribed to the synergetic effect of combining a conductive polymer ensuring a large pseudocapacitance of the electrode and a highly porous nitrogen-doped carbon matrix which provides a high conductivity and rigidity. Another line of experiment, analyzing the cycling stability of the novel electrode material found that after 5000 cycles the specific capacitance of the electrode was largely retained (95.9 %), indicating the suitability of the foam composite for long-term operation.
Given these promising results, the authors conclude that the extraordinary characteristics of the synthesized electrode make it an auspicious candidate for applications in supercapacitors.
More details: Jun Zhu, Lirong Kong, Xiaoping Shen, Quanrun Chen, Zhenyuan Ji, Jiheng Wang, Keqiang Xu, Guoxing Zhu; Three-dimensional N-doped graphene/polyaniline composite foam for high performance supercapacitors, Applied Surface Science Volume 428, 15 January 2018, Pages 348-355. https://doi.org/10.1016/j.apsusc.2017.09.148
Researchers from the Swiss Federal Laboratories for Materials Science and Technology (Empa) have discovered that the insulating properties of state-of-the-art insulating bricks can be significantly enhanced by replacing the filling material with silica aerogel granules.
Commercially available insulating bricks (shown in the figure below), which unite structural and insulating functions in one component, are composed of a rigid clay or concrete shell in which the cavities are filled with an insulating material (e.g. mineral wool, PU foam). While their simplicity makes these monoliths, in theory, an ideal building material, their inferior insulating performance compared to a layered approach (i.e. layering different materials for structural and insulating purposes on top of each other), has limited the application of insulating bricks in the building sector.
However, simulations and measurements showed that by replacing the filling material with silica aerogel the thermal conductivity of the insulating brick can be significantly reduced (> 30 %), yielding a higher insulating performance for a given brick thickness. Accordingly, this facilitates the construction of thinner insulating walls, which is crucial in locations where space-saving architecture is required (e.g. dense urban locations).
Due to the cost of aerogels, the “Aerobrick” is not an economically viable solution today. Nonetheless, the authors conclude that the projected future drop in aerogel prices will potentially transform aerogel-filled insulating bricks into a strong alternative to layered insulating techniques in the near future.
More details: Jannis Wernery, Avner Ben-Ishai, Bruno Binder, Samuel Brunner; Aerobrick – An aerogel-filled insulating brick, Energy Procedia Volume 134, October 2017, Pages 490–498 https://doi.org/10.1016/j.egypro.2017.09.607
In an interdisciplinary study entitled “Spirited Skies Project” researchers of the School of Creative Arts and Humanities (Charles Darwin University, Australia), the AMC Metropolitan College (Greece) and the University of Science and Technology (China) have explored the idea of manufacturing aerogel-based dome structures for goedesic and lunar habitats.
After highlighting aerogel characteristics relevant for applications in architecture such as their insulating, optical and acoustic properties, the authors present examples of aerogel composites used in architecture like the glazed skylight of the Eli and Edythe Broad Art Museum (Lansing, USA).
Although the cost of aerogel materials currently limits their application to selected signature projects, the writers conclude that the rising demand for passive building design combined with dropping aerogel prices will soon facilitate the utilization of such composites in the building sector on a large scale.
Driven by these developments, the authors envisage the possibility of dome-like structures consisting of facades filled with translucent aerogels (see Figure 2 below). This design would allow structures that are naturally lit and highly insulated.
More details: Michaloudis I, Skouloudi M, Bok C, Jingyan Q (2017) Spirited Skies Project: Silica Aerogel Domes for the Habitat of the Future. Adv Automob Eng 6: 166. doi: 10.4172/2167-7670.1000166 https://www.omicsonline.org/peer-reviewed/spirited-skies-project-silica-aerogel-domes-for-the-habitat-of-the-future-94152.html
Researchers from the SASTRA University (India) have successfully produced biodiesel from crude Hevea brasiliensis oil (CHBO) using an enzymatic transesterification process.
The major advantage of this process over the commonly deployed chemical transesterification process is that both the energy and post-treatment requirements are reduced significantly. This is because enzymatic transesterification neither requires high reaction temperatures nor basic or acid catalysts. Instead, an enzyme (here: lipase) active at temperatures slightly above ambient temperature, immobilized on a support material (here: silica aerogel), catalyzes the transesterfication reaction.
The researchers obtained fatty acid methyl ester (FAME) yields comparable to those reported for chemical transesterification (>90 %) at 30 °C when using lipase immobilized on silica aerogels. Furthermore, it was found that the enzymes largely retained their activity even after ten cycles. A characterization of the fuel synthesized from the rubber seeds showed that the fuel properties were compatible with ASTM Biodiesel (D 6751a) and European Biodiesel Standards (EN 14214).
Hence, the authors concluded that the enzymatic transesterfication of CHBO offers a more environmental compatible and economical approach to biodiesel synthesis when compared to the state of the art chemical transesterfication processes.
More details: A.Arumugam, D.Thulasidharan & Gautham B.Jegadeesan; Process optimization of biodiesel production from Hevea brasiliensis oil using lipase immobilized on spherical silica aerogel, Renewable Energy Volume 116, Part A, February 2018, Pages 755-761 https://doi.org/10.1016/j.renene.2017.10.021
A team of researchers from the Fuzhou University (China) has accomplished to synthesized self-supporting carbon nitride (CN) aerogels through an aqueous sol-gel process followed by freeze drying (see Figure).
The resulting aerogels, which were manufactured without the need for strong acids or cross-linking agents, exhibit electrical conductivity and high specific surface areas. In theory, these reported material characteristics are ideal preconditions for the utilization of the novel aerogels as photocatalysts.
To demonstrate the aerogels’ photocatalytic activity, the authors measured hydrogen evolution rates of several CN-based materials immersed in an irradiated water/triethanolamine (TEOA) solution and found that for the analyzed settings, the water splitting reaction was accelerated by almost one order of magnitude in the presence of the CN aerogel, when compared to bulk CN. Moreover, it was found that the aerogel catalysts exhibit good cycling stability, ensuring a good long-term reactivity of the material.
Apart from their application in solar-to-chemical energy conversion, the authors also see great potential for the CN aerogels in fields such as separation and sensing.
More details: Honghui Ou et al. Carbon Nitride Aerogels for the Photoredox Conversion of Water, Angewandte Chemie (2017). DOI: 10.1002/ange.201705926. http://onlinelibrary.wiley.com/doi/10.1002/anie.201705926/abstract
Read more at: https://www.analytik-news.de/Presse/2017/480.html
Researchers of the University of Tehran (Iran) have attempted to boost the insulating behavior of two different acrylic resins by incorporating silica aerogels. Both resins were produced using methyl methacrylate, 2-ethylhexyl acrylate and acrylic acid monomers, but one resin additionally contained named acrylamide (AAm).
Unsurprisingly, the thermal properties of the resins were improved by the addition of silica aerogel. However, the mechanical properties (e.g. hardness and pull-off strength), which are a key factor for the application of resins as coating films, were shown to deteriorate in the presence of silica aerogels for the resin without AAm. In contrast to that, the resin containing AAm exhibited outstanding mechanical features, which was related to the formation of hydrogen bonds between the aerogel and the acrylamide monomers, ensuring a more homogeneous dispersion of aerogel particles in the resin (see SEM image on the right). The authors therefore concluded that the acrylic resin modified with acrylamide and silica aerogel particles can be used as an insulating roof coating to reduce the thermal losses in buildings.
It will be interesting to witness whether further developments in this field will transform aerogel containing paints to an integral part of energy efficient infrastructure.
More details: Karami et al. Improvement of thermal properties of pigmented acrylic resin using silica aerogel, Journal of Applied Polymer Science (2017). DOI: 10.1002/app.45640 http://onlinelibrary.wiley.com/doi/10.1002/app.45640/full
IDTechEx has released an extensive report on the global aerogel market, discussing present day as well as future developments in the field.
It not only covers market analyses and forecasts, but also gives an elaborate introduction to aerogel properties and manufacturing techniques. Moreover, aerogel products and their applications are summarized and SWOT analyses for the different material types are presented. Last but not least, the report also features profiles of key aerogel manufacturers.
The authors of the 123-page report claim to have issued “the most comprehensive and authoritative view of the global aerogel market”, based on the company’s “interview-based primary research”.
While not all chapters might be of a particular interest to all readers, the broad approach of this report certainly offers the opportunity for both researchers and entrepreneurs to dive into the field of aerogels.
Report sample pages: IDTechEx_Samplepages_Aerogels20172027TechnologiesMarketsandPlayers
An initial determination of the US International Trade Commission (ITC) has found two Asian aerogel manufacturers guilty of infringing on several of Aspen Aerogel’s patents.
The ruling came more than a year after the complaint by Aspen Aerogels (filed in May 2016), asserting Nano Tech Co. (South Korea) and Guangdog Alison High-Tech Co. (China) are importing patented insulants into the US. The motions of both companies, stating the invalidity of the Aspen Aerogels patent claims, have been rejected by Judge McNamara. A final ruling on the matter is expected in January 2018.
With Aspen Aerogel announcing to spend almost 4 % of their projected annual revenue on expenses associated with patent enforcement in their financial outlook for 2017, it becomes clear the significance this matter has for the company. The outcome of the investigation will therefore be decisive for the future strategy of the company in terms of protection of their intellectual property.
Read more at: https://www.printedelectronicsworld.com/articles/12910/initial-results-emerge-from-the-aspen-aerogel-patent-infringement-case
Researchers from the Lawrence Livermore National Laboratory (California, USA) have recently manufactured monolithic aerogels consisting of silver nanowires (AgNW). The newly devised production technique, consisting of freeze-casting and sintering, facilitates tunable aerogel properties (e.g. bulk densities, pore structure, and conductivity). Due to its electrical conductivity, applications for the new material range from fuel cells to medical devices.
Although the discovered aerogel structures are of an outstanding quality, the researchers are already aiming at enhancing the material features.The researchers hope to further increase the electrical conductivity by reducing the average pore size and nanowire diameter, while at the same time increasing the length of the nanowires. Of course this prospect only boosts the likelihood of finding silver nanowire aerogels in future applications.
More details: Fang Qian et al. Ultralight Conductive Silver Nanowire Aerogels, Nano Letters (2017). DOI: 10.1021/acs.nanolett.7b02790
Read more at: https://phys.org/news/2017-10-ultralight-silver-nanowire-aerogel-boon.html
CO2 adsorption isotherms at 1 atm and 0 °C (a) and 1 atm and 25 °C (b) for chitin aerogels (1), carbonized chitin aerogels (2) and KOH-activated chitin aerogels
Image of “Aerobrick” — Insulating brick with silica aerogel granule filling.
