Tag Archives: aerogels

Frozen smoke from Union College (New York state)

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I’m always a sucker for a good metaphor or analogy and this February 3, 2014 news item on ScienceDaily nicely fit the bill,

One day, Union College’s [New York state] Aerogel Team’s novel way of making “frozen smoke” could improve some of our favorite machines, including cars.

“When you hold aerogel it feels like nothing — like frozen smoke. It’s about 95 to 97 percent air,” said Ann Anderson, professor of mechanical engineering. “Nano-porous, solid and very low density, aerogel is made by removing solvents from a wet-gel. It’s used for many purposes, like thermal insulation (on the Mars Rover), in windows or in extreme-weather clothing and sensors.”

It seems the researchers have developed a new technique for fabricating aerogel which they are wanting to commercialize (from a Feb. 2014 [?] news release originally published as an article in the Union College Magazine’s Fall 2013 issue),

Together with Brad Bruno, Mary Carroll and others, Anderson is studying the feasibility of commercializing their aerogel fabrication process. A time and money-saver, it could appeal to industries already using aerogel made in other ways.

During rapid supercritical extraction (RSCE), chemicals gel together (like Jell-O) in a hot press; the resulting wet-gel is dried by removing solvents (the wet part). The remaining aerogel (dried gel), is created in hours, rather than the days or weeks alternative methods take.

RSCE, Anderson said, is also approximately seven times cheaper, requiring one hour of labor for every 8 hours the other methods need.

A good place for such a process, and Union aerogel, is the automotive industry.

“Our 3-way catalytic aerogels promote chemical reactions that convert the three major pollutants in automotive exhaust – unburned hydrocarbons, nitrogen oxides and carbon monoxide – into less harmful water, nitrogen and carbon dioxide,” Anderson said. “Because aerogels have very high surface areas and good thermal properties, we think they could replace precious metals, like platinum, used in current catalytic converters.”

Indeed, the surface area of one 0.5-gram bit of aerogel equals 250 square meters.

“That’s a lot of surface area for gases to come in contact with, facilitating very efficient pollution mitigation,” Anderson said.

I have mentioned aerogel before in several postings including this Aug. 20, 2012 posting titled: Solid smoke; a new generation of aerogels.

Bacterial cellulose could suck up pollutants from oil spills

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Who doesn’t love a cellulose story, especially when it could involve cleaning up oil spills? The Feb. 26, 2013 news item on phys.org titled, Airy but thirsty: Ultralight, flexible, fire-resistant carbon nanotube aerogels from bacterial cellulose, highlights some work being done in China,

They can absorb vast amounts of oil or organic compounds, yet they are nearly as light as air: highly porous solids made of a three-dimensional network of carbon nanotubes. In the journal Angewandte Chemie, Chinese scientists have now introduced a simple technique for the production of these ultralight, flexible, fire-resistant aerogels. Their method begins with bacterial cellulose as an inexpensive starting material. Their fibrous lightweights can “suck” organic contaminants from polluted water and could possibly be used as pressure sensors.

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The researchers [led by Shu-Hong Yu at the Hefei National Laboratory for Physical Sciences at Micrscale (HFNL), Univeristy of Science and Technology of China] trimmed off small pieces of the tangled cellulose nanofibers. These were freeze-dried and then pyrolyzed at 1300 °C under argon. This converts the cellulose into graphitic carbon. The density decreases but the network structure remains intact. The result is a black, ultralight, mechanically stable aerogel. Because it is porous and highly hydrophobic, it can adsorb organic solvents and oils—up to 106 to 312 times its own weight. It draws oil out of an oil/water mixture with high efficiency and selectivity, leaving behind pure water. This makes the new aerogel an ideal candidate for cleaning up oil spills or sucking up nonpolar industrial pollutants. The absorbed substances can easily be removed from the gel through distillation or combustion, allowing the gel to be used again.

There’s more about the work and its possible applications at physorg.com or, if you have access behind the paywall, here’s a citation and a link to the research article,

Ultralight, Flexible, and Fire-Resistant Carbon Nanofiber Aerogels from Bacterial Cellulose by Zhen-Yu Wu, Chao Li, Dr. Hai-Wei Liang, Prof. Dr. Jia-Fu Chen, Prof. Dr. Shu-Hong Yu. Angewandte Chemie International Edition, Volume 52, Issue 10, pages 2925–2929, March 4, 2013.

Here’s an image which illustrates the aerogels’ ability to suck up an organic solvent and explains some of the excitement,

Thirsty fibers: The aerogels described in the title can be fabricated in large scale by using a low-cost biomass, bacterial cellulose, as a precursor, which can be produced at industrial level in a microbial fermentation process. The carbon nanofiber aerogels (black pieces in picture) exhibit superior absorption capacity for organic solvents (red solution) and high potential for pressure sensing. [downloaded from http://onlinelibrary.wiley.com/doi/10.1002/anie.201209676/abstract;jsessionid=3EFB4241C0083135A6E657808F5410E5.d03t04]

Thirsty fibers: The aerogels described in the title can be fabricated in large scale by using a low-cost biomass, bacterial cellulose, as a precursor, which can be produced at industrial level in a microbial fermentation process. The carbon nanofiber aerogels (black pieces in picture) exhibit superior absorption capacity for organic solvents (red solution) and high potential for pressure sensing. [downloaded from http://onlinelibrary.wiley.com/doi/10.1002/anie.201209676/abstract;jsessionid=3EFB4241C0083135A6E657808F5410E5.d03t04]

Solid smoke; a new generation of aerogels

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The latest American Chemical Society (244th) meeting (Fall 2012, Aug. 19 – 23, 2012) includes a presentation on one of my favourite topics ‘solid smoke’ or aerogel, as it’s called more commonly.

From the Aug. 19, 2012 news item on Nanowerk (Note: I have removed a reference to a video on previous generations of aerogels that the folks at Nanowerk found and included with this news item),

A major improvement in the world’s lightest solid material and best solid insulating material, described here today, may put more of this space-age wonder into insulated clothing, refrigerators with thinner walls that hold more food, building insulation and other products.

The report, on development of a new flexible “aerogel” — stuff so light it has been called “solid smoke” — was part of the 244th National Meeting & Exposition of the American Chemical Society, the world’s largest scientific society. …

Mary Ann B. Meador, Ph.D., explained that traditional aerogels, developed decades ago and made from silica, found in beach sand, are brittle, and break and crumble easily. Scientists have improved the strength of aerogels over the years, and Meador described one of these muscled-up materials developed with colleagues at the NASA Glenn Research Center in Cleveland, Ohio.

The Aug. 19, 2012 news release from the American Chemical Society, which originated the news item, describes this new generation of aerogels’ strength and potential applications,

“The new aerogels are up to 500 times stronger than their silica counterparts,” Meador said. “A thick piece actually can support the weight of a car. And they can be produced in a thin form, a film so flexible that a wide variety of commercial and industrial uses are possible.”

Flexible aerogels, for instance, could be used in a new genre of super-insulating clothing that keeps people warm in the cold with less bulk than traditional “thermal” garments. Tents and sleeping bags would have the same advantages. Home refrigerator and freezer walls insulated with other forms of the material would shrink in thickness, increasing storage capacity. Meador said that the aerogel is 5-10 times more efficient than existing insulation, with a quarter-inch-thick sheet providing as much insulation as 3 inches of fiberglass. And there could be multiple applications in thin-but-high-efficiency insulation for buildings, pipes, water heater tanks and other devices.

NASA envisions one use in an advanced re-entry system for spacecraft returning to Earth from the International Space Station, and perhaps other missions. Re-entry vehicles need a heat shield that keeps them from burning up due to frictional heating from Earth’s atmosphere. Those shields can be bulky and heavy. So NASA is exploring use of a heat shield made from flexible aerogel that inflates like a balloon when spacecraft enter the atmosphere.

Meador said the material also could be used to insulate spacesuits. However, it likely would not be good for firefighting clothing products, which require protection beyond the 575 degrees Fahrenheit limits of the aerogel.

The scientists also offered a brief explanation of how these new aerogels are made (from the ACS news release),

Scientists produced the stronger new aerogels in two ways. One involved making changes in the innermost architecture of traditional silica aerogels. They used a polymer, a plastic-like material, to reinforce the networks of silica that extend throughout an aerogel’s structure. Another involved making aerogels from polyimide, an incredibly strong and heat-resistant polymer, or plastic-like material, and then inserting brace-like cross-links to add further strength to the structure.

My last mention of ‘solid smoke’ was in my Mar.27, 2012 posting about the 243rd meeting of the American Chemical Society held in Spring 2012.

Nanocellulose at the American Chemical Society’s 243rd annual meeting

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Nanocellulose seems to be one of the major topics at the ACS’s (Americal Chemical Society) 243rd annual meeting themed Chemistry of Life  in San Diego, California, March 25-29, 2012. From the March 25, 2012 news item on Nanowerk,

… almost two dozen reports in the symposium titled, “Cellulose-Based Biomimetic and Biomedical Materials,” that focused on the use of specially processed cellulose in the design and engineering of materials modeled after biological systems. Cellulose consists of long chains of the sugar glucose linked together into a polymer, a natural plastic–like material. Cellulose gives wood its remarkable strength and is the main component of plant stems, leaves and roots. Traditionally, cellulose’s main commercial uses have been in producing paper and textiles –– cotton being a pure form of cellulose. But development of a highly processed form of cellulose, termed nanocellulose, has expanded those applications and sparked intense scientific research. Nanocellulose consists of the fibrils of nanoscale diameters so small that 50,000 would fit across the width of the period at the end of this sentence.

“We are in the middle of a Golden Age, in which a clearer understanding of the forms and functions of cellulose architectures in biological systems is promoting the evolution of advanced materials,” said Harry Brumer, Ph.D., of Michael Smith Laboratories, University of British Columbia, Vancouver. He was a co-organizer of the symposium with J. Vincent Edwards, Ph.D., a research chemist with the Agricultural Research Service, U.S. Department of Agriculture in New Orleans, Louisiana. “This session on cellulose-based biomimetic and biomedical materials is really very timely due to the sustained and growing interest in the use of cellulose, particularly nanoscale cellulose, in biomaterials.”

One of the presenters has a very charming way of describing the nanocellulose product his team is working on (from the news item),

Olli Ikkala, Ph.D., [Aalto University, Finland] described the new buoyant material, engineered to mimic the water strider’s long, thin feet and made from an “aerogel” composed of the tiny nano-fibrils from the cellulose in plants. Aerogels are so light that some of them are denoted as “solid smoke. [emphasis mine]” The nanocellulose aerogels also have remarkable mechanical properties and are flexible.

There were some 20 presentations in this symposium held under the auspices of the ACS annual meeting. Here’s a few of the presentations (some of these folks have been featured on this blog previously), from the news item,

Native cellulose nanofibers: From biomimetic nanocomposites to functionalized gel spun fibers and functional aerogels Olli Ikkala, Professor, PhD, Aalto University, P.O. Box 5100, Espoo, Finland, FIN-02015, Finland , 358-9-470 23154, olli.ikkala@aalto.fi Native cellulose nanofibers and whiskers attract interest even beyond the traditional cellulose community due to their mechanical properties, availability and sustainability. We describe biomimetic nanocomposites with aligned self-assemblies combining nanocellulose with nanoclays, polymers, block copolymer, or graphene, allowing exciting mechanical properties. Functional ductile and even flexible aerogels are presented, combining superhydrophobicity, superoleophobicity, oil-spill absorption, photocatalytics, optically switchable water absorption, sensing, and antimicrobial properties. Finally mechanically excellent fibers are gel-spun and functionalized for electric, magnetic, optical and drug-release properties.

Evaluation of skin tissue repair materials from bacterial cellulose Lina Fu, Miss, Huazhong University of Science & Technology, College of Life Science & Technology, 1037 Luoyu Road, Wuhan, Hubei, 430074, China , 86-18971560696, runa0325@gmail.com Bacterial cellulose (BC) has been reported as the materials in the tissue engineering fields, such as skin, bone, vascular and cartilage tissue engineering. Exploitation of the skin substitutes and modern wound dressing materials by using BC has attracted much attention. A skin tissue repair materials based on BC have been biosynthesized by Gluconacetobacter xylinus. The nano-composites of BC and chitosan form a cohesive gel structure, and the cell toxicity of the composite is excellent. Unlike other groups, which showed more inflammatory behavior, the inflammatory cells of the BC group were mainly polymorph-nuclear and showed few lymphocytes. The BC skin tissue repair material has an obviously curative effect in promoting the healing of epithelial tissue and reducing inflammation. With its superior mechanical properties, and the excellent biocompatibility, these skin tissue repair materials based on BC have great promise and potential for wound healing and very high clinical value.

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New materials from nanocrystalline cellulose Mark MacLachlan [mentioned in my Nov. 18, 2010 posting], University of British Columbia, Department of Chemistry, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada , 604-822-3070, mmaclach@chem.ubc.ca Nanocrystalline cellulose (NCC) is available from the acid-catalyzed degradation of cellulosic materials. NCC is composed of cylindrical crystallites with diameters of ca. 5-10 nm and large aspect ratios. This form of cellulose has intriguing properties, including its ability to form a chiral nematic structure. By using the chiral nematic organization of NCC as a template, we have been able to create highly porous silica films and carbon films with chiral nematic organization.1,2 These materials are iridescent and their structures mimic the shells of jewel beetles. In this paper, I will describe our recent efforts to use NCC to create new materials with interesting optical properties.

Factors influencing chiral nematic pitch and texture of cellulose nanocrystal films Derek G Gray, McGill University, Department of Chemistry, Pulp and Paper Building, 3420 University Street, Montreal, QC, H3A 2A7, Canada , 1-514-398-6182, derek.gray@mcgill.ca Appropriately stabilized cellulose nanocrystal (NCC) suspensions in water form chiral nematic liquid crystalline phases above some critical concentration. In the absence of added electrolye, the chiral nematic pitch of such suspensions is longer than that of visible light. Films prepared by evaporation from the suspensions also often display the characteristic fingerprint patterns characteristic of long-pitch chiral nematic phases, but the pitch values can be shifted into the visible range by adding small quantities of electrolyte to the evaporating suspension. The factors that control the final pitch have been the subject of some confusion. While still not well understood, it is clear that at high nanocrystal concentrations and in solid films, the pitch is not simply a reversible function of nanocrystal concentration. We examine some of the factors that control the pitch and liquid crystal texture during the drying of chiral nematic NCC films.

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Bioprinting of 3D porous nanocellulose scaffolds for tissue engineering and organ regeneration Paul Gatenholm, Professor, [mentioned in my March 19, 2012 posting] Wallenberg Wood Science Center, Chalmers, Department of Chemical and Biological Engineering, Kemigarden 4, Goteborg, V. Gotaland, SE41296, Sweden , 46317723407, paul.gatenholm@chalmers.se Nanocellulose is a promising biocompatible hydrogel like nano-biomaterial with potential uses in tissue engineering and regenerative medicine. Biomaterial scaffolds for tissue engineering require precise control of porosity, pore size, and pore interconnectivity. Control of scaffold architecture is crucial to promote cell migration, cell attachment, cell proliferation and cell differentiation. 3D macroporous nanocellulose scaffolds, produced by unique biofabrication process using porogens incorporated in the cultivation step, have shown ability to attract smooth muscle cells, endothelial cells, chondrocytes of various origins, urethral cells and osteoprogenitor cells. We have developed bioprinter which is able to produce 3D porous nanocellulose scaffolds with large size and unique architecture. Surface modifications have been applied to enhance cell adhesion and cell differentiation. In this study we have focused on use of 3D porous Nanocellulose scaffolds for stem cell differentiation into osteogenic and chondral lineages.