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.

Died water droplets on top of hydrophobic cotton cellulose aerogel

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.

Different aerogel geometries produced using the 3DFAP production technique

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.

Morphological structure images of hierarchical porous graphene aerogel (HPGA) at different magnifications.

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-Pocket^TM  by the Norwegian company Helly Hansen.

Helly Hansen Life-Pocket

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-Pocket^TM  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).

SEM images of (a, b) N-GE and (c, d) N-GE/PANI electrode composites. The insets in (c) and (d) are a photo of the 3D N-GE/PANI monolith and an SEM image of PANI nanospheres, respectively

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.

Image of “Aerobrick” — Insulating brick with silica aerogel granule filling.

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).

Figure 1: Exterior view of 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.

Figure 2: a) Exterior view of lunar glass domes “Spirited skies”. b) Lunar glass dome’s interior view.

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. 

Figure: Hevea brasiliensis seeds.

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).

a) Fabrication strategy of CN aerogel. b) Images of colloidal solutions of CN nanoparticles, CN hydrogel and CN aerogel.

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

SEM image of (a) pure silica aerogel,
(b) resin without AAm monomer & 5 wt % aerogel)
and (c) resin with AAm monomer & 5 wt % aerogel).

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

Read more at: http://www.farbeundlack.de/Wissenschaft-Technik/Rohstoffe/Lackbindemittel/Verbessert-Silica-Aerogel-die-thermischen-Eigenschaften-von-Acrylharz