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Demonstration of the flexibility of cellulose–silica composite aerogel. Credit: J. Cai et al.; Angewandte Chemie.

This sounds like the type of breakthrough aerogel fans have yearning for.

A newly published paper in Angewandte Chemie reports on an Asian group’s success at using cellulose fibers as a scaffold/template for a resultant silica aerogel that delivers a product that has great mechanical strength and flexibility, while retaining a large surface area and semitransparency.

Aerogel has been something of a tease for many years. It has incredible insulating abilities, but the one enormous problem for silica aerogel is that it is frustratingly brittle and difficult to work into practical applications. Some developers have found limited success via hybridization techniques with support materials such as polyurethane, polystyrene or even nanofibrillar bacterial cellulose and microfibrillated cellulose gel.

However, with support from the Japan Society for the Promotion of Science’s Foreign Researcher Fund of Japan and the National Basic Research Program of China, researchers at Wuhan University, China, and University of Tokyo, took a different cellulose-based route. They already knew that they could exploit “cellulose II” crystallinity  (dissolution and then regeneration/reassembly of fibrils) to form aerogels with good mechanical strength, light transmittance and high porosity — characteristics that they suspected would make it an effective substrate for silica aerogel.

In brief, the group, led by Lina Zhang, impregnated a sample of nanoporous cellulose gel (with its interconnected nanofibrillar network) with a silica precursor, tetraethyl orthosilicate. According to the paper, “The resulting composite gels were dried with supercritical CO₂ to give cellulose–silica aerogels with low density, moderate light transmittance, a large surface area, high mechanical integrity and excellent heat insulation.”

They then went one step farther and used calcination to remove the cellulose matrix, leaving a silica-only aerogel. The key point here is that this silica aerogel’s structure is much different than pure silica aerogel. In the latter, primary silica nanoparticles form and then randomly coagulate resulting in an isotropic 3D network. “In contrast,” again quoting from the paper, the authors say, “the formation of silica nanoparticles in the cellulose gel seems to cause their deposition onto the cellulose fibrils. As a result, removal of cellulose by calcination results in the nanofibrillar silica network.”

The group compared a variety of aerogels, including silica-only and cellulose-only aerogels; cellulose-silica composites, with varying levels of silica; and cellulose-templated silica aerogel.

What they found at the macroscopic level is that the composite aerogels didn’t inherit the fragility of the silica, but instead seem to inherit the flexibility and strength of the cellulose network (see knotted sample of one of the composites, above).

While the tensile modulus and strength of the cellulose–silica aerogel were less than pure cellulose aerogel, “the compression modulus of the composite (7.9MPa) is more than two orders of magnitude higher than that of silica aerogel, and about 50 times higher than that of the aerogel prepared from bacterial cellulose.”

Because of the cellulose content, the composite aerogels break down when used above 300°C. However, below that temperature, the cellulose-silica aerogel retained strong heat insulating properties. Thermal conductivity of the prepared samples ranged from 0.025 W m^-1 K^-1 to 0.045 W m^-1 K^-1.

These numbers compare favorably with polystyrene foam (0.030 W m^-1 K^-1), however, the researchers note that the ability of the cellulose–silica aerogels to perform up to 300°C give it a leg up on insulation materials made of polymer that soften and breakdown at similar temperatures.

“Thus,” according to the authors,”the cellulose–silica composite is potentially useful as heat insulating material with high mechanical stability, together with processability to form sheets, fibers, or beads. … [They] retained the mechanical strength and flexibility, large surface area, semitransparency, and low thermal conductivity of the cellulose aerogels. The ease of preparation and wide tuneability of composition/properties with this method are expected to form the basis for the development of various advanced nano-porous materials.”

The paper, ”Cellulose-silica nanocomposite aerogels by in situ formation of silica in cellulose gel,” (doi:10.1002/ange.201105730) is written by Jie Cai, Shilin Liu, Jiao Feng, Satoshi Kimura, Masahisa Wada, Shigenori Kuga, and Lina Zhang.

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Clarke with Champion Supersuit: Credit Clarke and Hanesbrand

Following up on the post from last week about Hanesbrands/Element 21’s Champion aerogel jacket that was used in Jamie Clarke’s successful ascent of Mt. Everest, an AP story indicates that the superinsulating Supersuit jacket may be in stores soon, and that Aspen Aerogel – the source of the insulation in the jacket – business is growing well enough that it plans to double the size of one of its facilities.

From the AP:

Champion parent Hanesbrands and Element 21, a Toronto company that licensed the aerogel technology, have spent two years and $2 million to solve those problems. If they succeed, they might have a competitor to insulators such as Thinsulate and Primaloft.

[. . . ]

The company wants to push aerogel into even more mainstream applications, including mass-market Champion gear set to be sold at Target and other stores sometime next year. Hanes spokesman Matt Hall said any Champion item developed containing aerogel would be “significantly under $100.”

The story goes on to note that Aspen has outgrown a fairly new $30 million, 150,000 square foot plant in East Providence, R.I.:

Aspen, based in Northborough, Mass., lowered costs by opening up to new industrial markets, making its manufacturing more efficient by improving chemistry and lowering costs for its raw material. It has also expanded manufacturing, opening a plant in Rhode Island in 2008. It now plans to double the plant’s size.

 

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GreenTech reported that some aerogel companies are offering thin blankets that serve as replacements for traditional fiberglass, foam or cellulose insulation. It’s still more expensive upfront but the costs have fallen to the point that it can make sense in certain cases, particularly masonry or curved walls. The video posted above shows aerogel insulation over bent tubing.

Aerogels are made by removing the liquid from gels, resulting in a material that is more than 90 percent air. The porous structure of the nanomaterial makes it difficult for heat to pass through. As a result, aerogels make very good and light-weight insulators.

Aspen Aerogels says that its aerogel blankets have two to four times the insulating value per inch compared to fiberglass or foam. It’s also relatively easy to work with, allows water vapor to pass through and is fire resistant.

Material company Cabot has also developed its Nanogel insulator for buildings. Another company, ThermaBlok, has had its insulation used in demonstration houses built during last year’s Solar Decathlon home competition.

Contractors have started using the material on superinsulated homes that are sealed from the outside, both over masonry and under shingles. On wood frame homes, thin strips of aerogel can be applied to studs to prevent what’s called thermal bridging, where heat escapes through the walls’ framing.

Aspen provides this chart for for the R-value-philes (Spaceloft being Aspen’s brand name for their building insulation aerogel):

Read more about aerogel:

Aerogel markets report available

Aerogel-based -40°C hydration system to be licensed

Solar Decathlon entries make use of aerogel

Aeroclay research at Case Western

NASA’s aerogel grid captures amino acid in space

Cabot”s Nanogel aerogel insulation selected for 50 km of subsea pipelines

Artistic aerogel light demonstrations

Aerogel used in classic car remake

Aerogel’s potential to mop up oil spills

Aerogel has potential as tunable waveplate

Universe’s largest catcher’s mitt?

Birdair demonstrates aerogel membrane roofing systems

Nanotube aerogel sheets - better than real muscle?

Introduction to aerogel video

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Credit: Yanko Design

Not in actual production, but Yanko Design is trying to stretch the possibilities with a new type of all-terrain vehicle for forest fire fighters to do recon and actual fire suppression:

To create a homogenous directive towards survivability AMATOYA incorporates state-of-the-art clear aerogel laminated insulation in the windows and bodywork, a dedicated auxiliary water supply to operate a highly efficient, intelligent temperature controlled spray down system, military grade sacrificial thermo ceramic intumescent paints, and a mechanically injected large displacement diesel engine specifically engineered for the unique conditions experienced on the fire ground.

Hat tip to AutoBlog.

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Team Germany's window louvers with integrated thin-film CIGS cells. (Credit: Stefano Paltera/DOE Solar Decathlon)

Team Germany!

Team Germany won first place in the 2009 Solar Decathlon by applying photovoltaics to every available surface. I had been rooting for Virginia Tech for their use of aerogel as insulation that allowed natural light to shine through, but it only ranked 13 out of 20 competitors.

Team Germany’s Cube House was considered the most technologically advanced.

On the roof: a 11.1 kW photovoltaic system of 40 monocrystalline silicon panels. On the sides: 250 thin-film panels that look like glossy clapboards. The thin films used copper-indium-gallium-diselenide layers.

The combination system was expected to produce 200 percent of the energy needed by the house. The thin film panels, while less efficient than conventional silicon, were projected to perform better in cloudy weather than silicon.

Team Germany got its proof on the competition’s fifth day when skies turned slate gray and a cold rain splattered the solar village. By late afternoon, as federal commuters started streaming home and electricity demand throughout the city began climbing, the Team Germany house was producing 12.68 kW and consuming 12.33 kW, for a net export of .35 kW. Net production also occurred on two other rainy days.

Team Illinois’ house finished a close second, emphasizing energy efficiency over power production.

“Team Germany built a gingerbread house packed with solar panels,” said Richard King, DOE Solar Decathlon director. “In the rain, the thin-film panels were making electricity. It made the difference.”

Each team actually was graded on 10 criteria:

• Architecture
• Market Viability
• Engineering
• Lighting Design
• Communications
• Comfort Zone
• Hot Water
• Appliances
• Home Entertainment
• Net Metering

Team Germany was the only team to score a perfect 150 points out of a possible 150 in the net metering category, for having produced more electricity over the entire two-week testing period than it consumed. The DOE gave the Net Metering the highest weight in the contest, and each of the other categories received 75-100 possible points each.

The University of Minnesota entry was winner in the Engineering category and ranked 5th overall.

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