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The clay–polymer layer-by-layer process (a) and an illustration of the quadlayer nano brick wall structure of PEI (blue), PAA (green), PEI and MMT clay (red). Credit: M.A. Priolo, et al; Nano Letters.

It’s easy to imagine that the makers of food products have a wish list for packaging that, besides the obvious need to be inexpensive and easy to use, 1) indicates freshness; 2) is antimicrobial; 3) is microwaveable; 4) is transparent; and 5) creates a strong barrier to air.

I don’t know how the progress is going on #1 and #2, but a group of researchers from Texas A&M University seem to have a good handle on addressing wishes #3, 4 and 5. In two papers (one about a year old and one more recent), a nanocomposites team led by Jaime Grunlan, a TAMU mechanical engineering professor who did his Ph.D. work in materials science, reports on work it has been doing with applying layers of a special clay to polymer film to create highly effective gas barriers.

In the first paper, published in early 2010 Applied Materials & Interfaces (doi:10.102.1021/am900820k), Grunlan’s group reported on a transparent and super air-tight “brick and mortar”-like nanostructure construction method, based on water processing. This construction is accomplished via a layer-by-layer assembly method of depositing alternating thin films of sodium montmorillonite clay and branched polyethylenimine onto a 179 µm substrate of poly(ethylene terephthalate). After putting 70 of these PEI-MMT bilayers together on the PET substrate (resulting in a film thickness of 231 nanometers), the permeability to oxygen becomes 0.002 X 10^-6 cc/(m² day atm), the lowest permeability ever reported for a polymer-clay composite.

The researchers attributed the lack of permeability of the brick wall nanostructure to “alternate adsorption of polymeric mortar and highly oriented, exfoliated clay platelets.” Essentially, oxygen or other gas molecules have to travel such a “tortuous” bricks-and-mortar path through the film that they seldom succeed in getting through.

They also predicted that films made in this way, because of their high level of transparency and ability to be a gas barrier, “would be good candidates for a variety of flexible electronics, food and pharmaceutical packaging.”

The interest in this type of superbarrier film performance to food and pharmaceuticals seems pretty obvious, but the interest to the electronics industry is rooted in the development of flexible devices (think flexible organic LEDs) for which other thin film materials, such as SiO_x, Al₂O₃ and EVOH are problematic because of cracking or expensive fabrication processes.

TEM cross-sectional image of film with five quadlayers. Credit: M.A. Priolo; Nano Letters.

In the most recent paper, published in Nano Letters (doi:10:1021:nl103047k) the TAMU group reports they have been able to create an even thinner superbarrier, composed of only 12 polymer and four clay layers (51 nanometers), that are far less permeable than SiO_x and Al₂O₃.

Actually, in this new work, they have added one more component — poly(acrylic acid) — and alternated the layering sequence in an approach that produces a “quadlayer” of PEI-clay-PAA-clay. When put on a PET substrate, four of these quad layers are enough to better the performance of SiO_x and EVOH, and that even five layers have an average light transmission of 95 percent across the visible light spectrum.

The researchers note that, “When combined with ambient processing from water, high transparency and flexibility, these quadlayer coatings are among the best barrier films of any type ever reported.” Another feature is that, unlike metalized plastics, food wrapped in these films can be heated in a microwave oven.

Comparison of PET versus polymer—clay thin film. Credit: M.A. Priolo.

There is one weakness, however, to these films: Their performance lessens as humidity increases. They have learned that some of this can be offset through thermal cross-linking in the PEI and PAA layers. Nevertheless, they report that the humid oxygen transmission rate of the quadlayer film is much less than for untreated PET. Where humidity performance is a concern, the group suggests that quadlayer assemblies could be deposited directly onto a film, such as poly(chlorotrifluoroethylene) that is known to have high moisture barrier properties.

Grunlan recently did a presentation on this work at a meeting of the American Chemical Society, and in an ACS news release he puts his group’s work in perspective, noting “Others have added clay to polymer to reduce (gas) permeability, but they are thousands of times more permeable than our film. We have the most organized structure — a nano-brick wall — which is the source of this exceptional barrier. This is truly the most oxygen impermeable film in existence.”

His group also notes that because the new film is about 70 percent clay and contains a small amount of polymer, it is more eco-friendly than current plastics and may be able to replace some foil packaging.

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Schematic showing the architecture of the sensor developed at Princeton. Credit Stephen Y. Chou; Princeton.

Check ‘em out:

Princeton engineers make breakthrough in ultrasensitive Raman-based sensor

Princeton researchers have invented an extremely sensitive sensor that opens up new ways to detect a wide range of substances, from tell-tale signs of cancer to hidden explosives. The sensor, which is the most sensitive of its kind to date, relies on a completely new architecture and fabrication technique developed by the Princeton researchers. It’s operation is based on surface-enhanced Raman scattering.

New tricks from old polymers

Organic solar cells, light-emitting diodes, and thin-film transistors could be enhanced by polymers that mimic the properties of traditional inorganic semiconductors.

DOE and HUD launch energy efficiency loan program

“PowerSaver “loans, backed by the Federal Housing Administration, will be available from 18 lenders in certain regions of the country to provide homeowners up to $25,000 to make energy-efficient improvements, including door and window replacement. The two-year pilot program was just kicked off by the Department of Housing and Urban Development and the Department of Energy.

Chicago’s Willis Tower to become a vertical solar farm

The iconic Willis Tower (formally the Sears Tower) is set to become a massive solar electric plant with the installation of a pilot solar electric glass project. They will replace the windows on the south side of the 56th floor with a new type of photovoltaic glass developed by Pythagoras Solar which preserves daylighting and views while reducing heat gain and producing the same energy as a conventional solar panel. The project could grow to 2 MW in size.

Less is more: Researchers pinpoint graphene’s varying conductivity level

Researchers at North Carolina State University have found one of the first roadblocks to utilizing graphene for fast electronic devices, by showing that its conductivity decreases significantly when more than one layer is present. With the help of the high performance computers at Oak Ridge National Lab, the NC State team discovered both good and bad news about graphene: With a single layer of graphene, the mobility — and therefore conductivity — shown by the researchers’ simulations turned out to be much higher than they had originally thought; the bad news is that the mobility of electrons in bilayer graphene is roughly an order of magnitude lower than in a single graphene sheet.

Jell-O device detects organ failure

Using only aluminum foil, gelatin, a 12-cent LED light, and a few other inexpensive materials, researchers have developed a sensor that can detect pancreatitis quickly and easily. About the size of a matchbox, the sensor relies on a two-step process to diagnose the disease, a sudden inflammation of the pancreas that can lead to severe stomach pain, nausea, fever, shock and, in some cases, death.

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Marra

The ACerS Glass and Optical Materials Division is holding its annual meeting May 15-19 in Savannah, Ga., and I just learned that nuclear energy materials expert John Marra has agreed to do a special and timely presentation about Japan’s nuclear power accident at the conference dinner May 17. Marra, the chief research officer of the Savannah River National Lab, has tentatively titled his talk, “Beyond Fukushima: Advanced materials to enable enhanced nuclear power systems.”

I am really looking forward to this because, as far as I know, it will be the first semi-public presentation by a federal lab official in which there is an attempt to sum-up some of the engineering lessons from the Fukushima/TEPCO situation.

The context of this, of course, is that rising fuel prices and increased concerns about greenhouse gas emissions had many scientists and policy makers looking toward nuclear power (and new generations of nuclear reactors) as a way to offset fossil fuels. In reaction to the Fukushima situation, some nations and some members of the science and technology community now want to take a second look at future plans for growing nuclear power systems.

In an abstract on his presentation, Marra says:

On March 11, 2011 an earthquake centered near Japan and the resultant tsunami caused significant damage to several reactors at the Fukushima Daiichi nuclear plant causing many to question the long-term future of nuclear power. As Japan and the international community begin to look at the lessons-learned from the Fukushima accident, advanced materials that eliminate or reduce the consequences of severe accidents will find increased application in advanced nuclear power systems.

Ceramic and glass materials, which have long played a very important role in the commercial nuclear industry, offer some significant advantages under accident conditions. This presentation will review the sequence of events that led to the Fukushima Daiichi accident and discuss the critical role that ceramic and glass materials play throughout the nuclear fuel cycle, and the critical material advancements required to enable the “nuclear renaissance” in light of the recent events.

The conference dinner runs 7-10 p.m. on May 17, and I expect Marra will begin his talk around 8:30 p.m.

I plan on running an interview with Marra, a past president of ACerS, for the August issue of the Bulletin, but I highly recommend that anyone interested in advanced glass science and technology (including optical materials, optical devices, coatings, sensors, solar energy materials, glass–ceramics, and structures and properties) considere coming to the GOMD meeting.

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Getting a sneak preview of the displays at the soon-to-be dedicated Inamori Kyocera Museum of Fine Ceramics are Kate Wilkins and Susan Kowalczyk. Credit: Alfred Univ.

Recently I’ve covered a few stories related to exhibitions on technical ceramics (e.g., here and here), but these have been about exhibits that are part of much larger ceramic and glass art museums. But, today’s story is about a museum fully dedicated to the science and engineering aspects of ceramics.

Alfred University representatives have announced that they will be holding an official dedication ceremony May 10 for the Inamori Kyocera Museum of Fine Ceramics, in Alfred, N.Y., that will serve as the main showcase for ceramic research and technologies.

Inamori

(First, some semantics housekeeping: Some international ceramists, especially the Japanese, use the term “Fine Ceramics” as interchangeable with “High Tech Ceramics.” Obviously, this gets confusing because many North American and Europeans also use the term “Fine China” to refer to a high quality of ceramic dinnerware. But, the “Fine Ceramics” reference in the museum’s title is made in deference to the namesake, Kazuo Inamori, founder and chairman emeritus of Kyocera Corp. — one of the world’s largest manufacturers of high-tech ceramics — and a long-time supporter of Alfred’s programs.)

The dedication ceremony will be at 12:30 p.m. on May 10, in Binns-Merrill Hall on the AU campus.  The event is open to the public, and Inamori, himself, will be on hand for the dedication.

In an AU news release, the university’s president, Charles M. Edmondson, says the school is very honored to have Inamori at the event. “Dr. Inamori has been a valued friend to the University and in particular to our School of Engineering, so we are delighted he will be here as we dedicate this museum in his honor,” notes Edmondson.

Edmonson goes on to say that the museum “will play an important role in educating young people about the vital role of ceramics in the future economy — in areas ranging from information technology to medical devices, diagnostic systems, industrial equipment, renewable energy and environmental preservation.”

On the morning of the dedication, AU is holding a special symposium, ”Ceramics: Past, Present and Future,” organized in Inamori’s honor. The symposium will start at 9 a.m. on May 10 in the Nevins Theater located in the Powell Campus Center, and is open to the public, free of charge. (If you are planning to attend, AU asks that you email Marlene Wightman, director of continuing education, at Wightman@alfred.edu or to call her at 607-871-2425.

Inamori is expected to speak as part of the symposium. He will be joined by ACerS President Marina Pascucci, a 1977 AU alumna and president of CeraNova in Marlborough, Mass.; Terry Michalske (’75), director of the Savannah River National Lab; and Gary Messing (’73), head of the materials science and engineering department at Pennsylvania State University. Also among the speakers is Linda Jones, associate vice president and head of the New York State College of Ceramics at Alfred University, who is an ACerS Fellow and a member of its board of directors.

The museum will offer information on ceramic materials and applications, including historical developments, technical breakthroughs and examples of how ceramics have become ubiquitous as enabling technology in everything from electronics to more specialized applications like fuel cells, solar panels and biomedical implants.

AU is also opening the Discovery Lab next to the Inamori Museum. School officials say the lab will be AU’s center for outreach activities involving students (and their teachers) from kindergarten through 12th grade. University faculty members are developing educational programming, including demonstrations and hand-on activities.

Doreen Edwards, dean of the school of engineering, says she anticipates visitors will include specialists and scientists. “People who are involved in the manufacture of ceramics and related technologies will find this of interest, but there is also plenty to draw the general public,” she says.

The artistic side of ceramics is not totally left out of the picture. The university notes that its Schein-Joseph Museum of Ceramics has an extensive collection of ceramic art and is located adjacent to the new museum in Binns-Merrill Hall. “This is an absolute reflection of the College of Ceramics that joins both the School of Art & Design and the Inamori School of Engineering,” says AU’s Linda Jones. “From the inception of the College, it was recognized that creativity and technical understanding are essential to address the challenges of our time.”

AU recalls that Inamori’s relationship with Alfred University dates back to the 1980s. The school awarded him an honorary Doctor of Science degree in 1988, recognizing his leadership in the field of advanced ceramic materials.  He created Alfred University’s Inamori Scholarships, which assist deserving students studying art or engineering.

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