Hydroxyl terminated MXene Ti3C2 with monolayers of hydrazine molecules between the MXene layers. Credit: Vadym Mochalin, Drexel University.
The cover story of the April issue of the ACerS Bulletin described the interesting family of carbides and nitrides known as the MAX phases. Their name refers to their composition, where M is a transition metal, A is an ‘A’ group element from the periodic table (specifically the subset of elements 13-16), and X is carbon or nitrogen. Investigators discovered the materials about 40 years ago, and research on these materials really picked up in the mid-1990s. As the article details, the layered-structure MAX phases have properties typical of metals, as well as properties typical of ceramics.
The locus of activity on the resurgent research on the MAX phases is Drexel University in the laboratories of Yury Gogotsi and Michel Barsoum (and extends now to Texas A&M in Barsoum protégé Miladin Radovic’s group).
In 2004, when they were about 10 years into their work on the MAX phases, graphene was “discovered” by a British and Russian team of physicists, setting off a flood of research on two-dimensional materials. The Drexel team thought they, too, might be able to make 2D materials from the MAX phases by selectively removing the ‘A’ constituent. They named these compounds MXenes as a reference to their M and X constituents and structural similarity to graphene.
Like graphene, the materials have good electrical properties and can be intercalated. If the layers can be made thin enough, a host of interesting applications opens up, such as lithium-ion battery electrodes and electrochemical capacitors (supercapacitors). In a new paper in Nature Communications, they report new work on several titanium carbide compounds-Ti3C2, Ti3CN, and TiNbC-that were synthesized by selectively removing aluminum from the corresponding MAX phases.
Computer simulations indicated it might be possible to store a large amount of charge by delaminating (or exfoliating) the MXene layers, but large-scale delamination had been elusive, according to a university press release. Recently, the Drexel team successfully delaminated MXene layers by intercalating with organic molecules. Gogotsi, an author on the paper, explains in an email, “Intercalation reactions, like the one shown [in the image], establish MXenes as full-fledged members of the growing family of 2D materials.”
They were able to make paper like MXene by filtering flakes from the solution. The “paper” is reportedly flexible and electrically conductive. According to the press release, “Critically, this work demonstrates that such material can be synthesized on a large scale.”
Even more, the lithium-ion storage capacity of the paper like MXene was four times that of typical MXene at, according to the abstract, extremely high charging rates. Results also show that the 2D material’s charge-discharge cycle performs better than graphite, which is the material now used for lithium-ion battery anodes.
Gogotsi says in the press release, “By demonstrating chemical intercalation of organic molecules between MXene layers, we have substantially altered properties of MXenes. By separating MXene sheets via intercalation, we produced excellent materials for electrodes of batteries and electrochemical capacitors. “
The team also thinks that 2D MXenes made by intercalation delamination may be used in composites, sensors, catalysis, and other applications.
If you read this blog often, you may notice a few similarities between Power Practical’s PowerPot thermoelectric power generation devices, and a new solid oxide few cell gadget being offered by a Berkeley National Lab startup company, Point Source Power (PSP).
The applications in mind for both of these power generation systems are generally the same: Can simple, small power generation methods be brought to underdeveloped parts of the world that may lack an electric grid but could benefit greatly from consumer electronics, such as cell phones and LED lighting? According to a story on the Berkeley Lab website, there are about 2.5 billion people that live without grid.
The guts of what PSP is calling its VOTO product is a “groundbreaking metal-supported solid oxide fuel cell (M-SOFC) technology,” that is described as tolerant of all organic fuel types. The point of this is that it can be used in parts of the world that rely on wood, charcoal or even cow dung for heating and cooking purposes.
Essentially, the VOTO has two parts. It has a detachable handle that stores the power from the mini fuel cell. (The part of the handle that detaches contains an LED for lighting and also can be used for recharging purposes.) The handle is attached to the small fuel cell mechanism that actually requires several fuel cell cards (see schematic). As mentioned above, this is actually M-SOFC technology, and these fuel cards are primarily stainless steel, rather than ceramic. PSP calls this system “Votosynthesis.”
The business plan for both Power Practical and PSP causes a little confusion (and numerous troll comments). Both want to make their products available at low cost to the developing and underdeveloped world. But, to accomplish that, they also have to market them to customers in the developed world who might see them as great tools for outdoor enthusiasts, campers, emergencies, etc.
PSP’s CEO Craig Jacobson says in another short YouTube video that consumers in America will have to pay more for the VOTO, but the company intends to use the proceeds from those sales to support sales and distribution in poorer parts regions of the globe. Kenya is said to be the where PSP will first attempt to market VOTO. The handle will sell for about $17 and the replaceable fuel cell cards for $7. The latter is expected to last for three to four months of regular use.
Berkeley Lab says that before helping launching PSP in 2008, Jacobson helped develop the VOTO system while at the institution. The lab reports
Jacobson co-invented the fuel cell in his 13 years as a materials scientist at Berkeley Lab. Working with Steve Visco and Lutgard DeJonghe, both still affiliated with the Lab, their breakthrough was in finding a way to replace most of the ceramics in the fuel cell with stainless steel, a far cheaper and more durable material. “Ceramics are typically brittle and relatively expensive to process and assemble into systems,” Jacobson said. “We got rid of 90 percent of the ceramics, keeping only a very thin functional layer, about half the thickness of human hair, to serve as the electrolyte.”
Jacobson goes on to say, “Fuel cells have been around for over 50 years—they work great. There are only three problems with fuel cells: cost, cost and cost. Our philosophy is, let’s get rid of those costs and make a fuel cell that can run on anything that burns.”
Despite its apparent simplicity, Berkeley Lab says the VOTO ultimately required the licensing of 130 patents.
Although the VOTO isn’t quite as powerful as a PowerPot (~500mA maximum at 5V versus 1A max at 5V), the PowerPot is more expensive (about $125 for the basic 5W pot).
Chemical engineering researchers have identified a new mechanism to convert natural gas into energy up to 70 times faster, while effectively capturing the greenhouse gas carbon dioxide. “This could make power generation from natural gas both cleaner and more efficient,” says Fanxing Li, coauthor of a paper on the research and an assistant professor of chemical and biomolecular engineering at North Carolina State University. At issue is a process called chemical looping, in which a solid, oxygen-laden material—called an “oxygen carrier”—is put in contact with natural gas. The oxygen atoms in the oxygen carrier interact with the natural gas, causing combustion that produces energy. Previous state-of-the-art oxygen carriers were made from a composite of inert ceramic material and metal oxides. But Li’s team has developed a new type of oxygen carrier that include a “mixed ionic-electronic conductor,” which effectively shuttles oxygen atoms into the natural gas very efficiently—making the chemical looping combustion process as much as 70 times faster. This mixed conductor material is held in a nanoscale matrix with an iron oxide. The oxide serves as a source of oxygen for the mixed conductor to shuttle out into the natural gas. In addition to energy, the combustion process produces water vapor and CO2. By condensing out the water vapor, researchers are able to create a stream of concentrated CO2 to be captured for sequestration.
Over 20 million people in Europe suffer from osteoarthritis, which can lead to extensive damage to the knee and hip cartilage. Stem cells offer a promising way forward but a key challenge has been to design a ’smart material’ that is biologically effective for cartilage tissue regeneration. Now researchers have identified a blend of naturally occurring fibers such as cellulose and silk that makes progress towards affordable and effective cell-based therapy for cartilage repair a step closer. The EPSRC-funded study, published in Biomacromolecules and undertaken by University of Bristol (UK) researchers, explored the feasibility of using natural fibers such as silk and cellulose as stem cell scaffolds—the matrix to which stem cells can cling to as they grow. Both cellulose and silk are commonly used in textiles but the researchers demonstrated an unexpected use for the two natural polymers when mixed with stem cells. The team treated blends of silk and cellulose for use as a tiny scaffold that allows adult connective tissue stem cells to form into preliminary form of chondrocytes—the cells that make healthy tissue cartilage - and secrete extracellular matrix similar to natural cartilage. Wael Kafienah, lead author from the University’s School of Cellular and Molecular Medicine, says, “We were surprised with this finding, the blend seems to provide complex chemical and mechanical cues that induce stem cell differentiation into preliminary form of chondrocytes without need for biochemical induction using expensive soluble differentiation factors. This new blend can cut the cost for health providers and makes progress towards effective cell-based therapy for cartilage repair a step closer.”
Researchers from Ulsan National Institute of Science and Technology (UNIST) demonstrated high-performance polymer solar cells (PSCs) with power conversion efficiency (PCE) of 8.92 percent, which are the highest values reported to date for plasmonic PSCs using metal nanoparticles (NPs). Compared to silicon-based devices, PSCs are lightweight (which is important for small autonomous sensors), solution processability (potentially disposable), inexpensive to fabricate (sometimes using printed electronics), flexible, and customizable on the molecular level, and they have lower potential for negative environmental impact. Polymer solar cells have attracted a lot of interest due to these many advantages. Although these many advantages, PSCs currently suffer from a lack of enough efficiency for large scale applications and stability problems but their promise of extremely cheap production and eventually high efficiency values has led them to be one of the most popular fields in solar cell research. The research team employed the surface plasmon resonance effect via multi-positional silica-coated silver NPs to increase light absorption.
Preterm infants appear to mature better if they are shielded from most wavelengths of visible light, from violet to orange. But it has been a challenge to develop a controllable light filter for preterm incubators that can switch between blocking out all light—for sleeping—and all but red light to allows medical staff and parents to check up on the kids when they’re awake. Now, in a paper accepted for publication in Applied Physics Letters, researchers describe a proof-of-concept mirror that switches between reflective and red-transparent states when a small voltage is applied. The research team had previously identified a magnesium-iridium reflective thin film that transforms into a red-transparent state when it incorporates protons. Providing those protons in a way that is practical for preterm incubators, however, was the challenge. The typical method—using dilute hydrogen gas—is unacceptable in a hospital setting. So the team created a stack of thin films that includes both an ion storage layer and the magnesium-iridium layer: a voltage drives protons from the ion storage layer to the magnesium-iridium layer, transforming it into its red-transparent state. Reversing the voltage transforms it back into a reflective mirror. The researchers report that the device still allows some undesirable light wavelengths through, but a force of just 5 volts changes the device’s state in as little as 10 seconds. The researchers are now looking at other materials to improve color filtering and switching speed.
Simpleware, a company set up to commercialize EPSRC-supported research at the University of Exeter, has won The Queen’s Award for Enterprise in the International Trade Category. Founded in 2003 by Philippe Young, the company’s pioneering software converts 3D image data into high-quality computer models used for engineering design and simulation. The technology has been applied across a host of disciplines and industries—from mobile phones to car engines; asphalt damage to back pain, contact lenses to hearing aids. The software is underpinned by patented techniques developed and improved with the aid of EPSRC funding to produce a previously unattainable level of realism in 3D simulations. Since 2008, Simpleware’s exports have seen an overseas sales growth of 690 percent. The company’s global export markets include the United States, Germany, Japan, France, China, Australia, Canada and other EU countries. Strong re-selling networks are also being established in India, Taiwan, and Singapore. The majority of sales are to blue-chip companies, research institutes and universities world-wide, including NASA and the Naval Research Laboratory. Young says, “The ability to generate robust and accurate numerical models from various sources of image data has started a revolution in the world of multi-physics simulation.
University of Illinois researchers have developed a new way to produce highly uniform nanocrystals used for both fundamental and applied nanotechnology projects. “We have developed a unique approach for the synthesis of highly uniform icosahedral nanoparticles made of platinum,” explains Hong Yang, a professor of chemical and biomolecular engineering and a faculty affiliate at the Center for Nanoscale Science and Technology at Illinois. “This is important both in fundamental studies-nanoscience and nanotechnology-and in applied sciences such as high performance fuel cell catalysts. Yang’s research group focuses on the synthesis and understanding structure-property relationship of nanostructured materials for applications in energy, catalysis, and biotechnology. “Although polyhedral nanostructures, such as a cube, tetrahedron, octahedron, cuboctahedron, and even icosahedron, have been synthesized for several noble metals, uniform Pt icosahedra do not form readily and are rarely made,” states Wei Zhou, a visiting scholar with Yang’s research group. An icosahedron crystal is a polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. According to Yang, icosahedral shaped crystals can improve the catalytic activity in oxygen reduction reaction partly because of the surface strain. “The key reaction step to improve the activity of oxygen electrode catalysts in the hydrogen fuel cell is to optimize the bond strength between Pt and absorbed oxygen-containing intermediate species,” Yang says. “This allows the rapid production of water and let the intermediate react and leave the surface quickly so the catalyst site can be used again.”
A team led by Professor Keon Jae Lee from the Department of Materials Science and Engineering at KAIST has developed in vivo silicon-based flexible large-scale integrated circuits (LSI) for biomedical wireless communication. Silicon-based semiconductors have played significant roles in signal processing, nerve stimulation, memory storage, and wireless communication in implantable electronics. However, the rigid and bulky LSI chips have limited uses in in vivo devices due to incongruent contact with the curvilinear surfaces of human organs. Although several research teams have fabricated flexible integrated circuits (ICs, tens of interconnected transistors) on plastics, their inaccurate nanoscale alignment on plastics has restricted the demonstration of flexible nanotransistors and their large-scale interconnection for in vivo LSI applications such as main process unit, high-density memory and wireless communication. Professor Keon Jae Lee’s team fabricated radio frequency integrated circuits interconnected with thousand nanotransistors on silicon wafer by state-of-the-art CMOS process, and then they removed the entire bottom substrate except top 100 nm active circuit layer by wet chemical etching.
Video of REO hydrophobic surfaces in action. Credit: MIT News Office; YouTube.
I meant to write about this topic several months ago when the editors of Nature Materials published a remarkable paper about a relatively simple method to make a hydrophobic, which, in this case, are made from ceramic materials. The thrust of the paper was that rugged ceramic materials could be made to be intrinsically hydrophobic through the use of rare-earth oxides. The paper was written by a research group at MIT led by Kripa K. Varasani and I was again reminded of the topic last week when MIT Technology Review published a related story.
The pursuit of hydrophobicity has entailed everything from the studying of lotus leaves to the creation of fairly exotic coatings and films. In this case, however, the thrust of the investigators work was relatively straightforward: They wondered if the tendency of ceramics to be hydrophilic (e.g., with certain metal oxides, such as alumina, water gets bound when its oxygen atoms share electrons with the aluminum atoms, and, in turn, the oxygens in the ceramic share their electrons with hydrogen in the water) could be reversed by interfering with the hydrogen bonding and therefore prevent the ceramic from accepting electrons from water.
The investigators insight, according to the paper, is that rare-earth oxides, which have unfilled 4f orbitals, but these orbitals “are shielded from interactions with the surrounding environment by the full octet of electrons in the 5s2p6 outer shell.” The introduction of rare earths into the ceramic composition, then, might prevent the bonding and render the material hydrophobic.
Led by Varanasi, a materials scientist, the group tested their idea by making simple ceramic disks from powders composed of pure rare earth oxides (REOs) of 13 elements in the lanthanides series—from cerium oxide to lutetium oxide. The fourteenth, promethium oxide, was purposely skipped over because it is radioactive.
They gave a mirror finish to the disks by polishing in order to minimize roughness and texture effects, and then put them to several tests. Sure enough, the worked! The authors write, “As hypothesized, all the REOs are hydrophobic: water contact angels range between 100° and 115°. Also, the polar component of the surface free energy for all REOs was found to be negligible. Moreover, there is minimal variance in the wetting properties over the entire series.”
Moving closer to application-related properties, the group tested the disks with steam condensation, water droplet impingement, high-temperatures, and abrasion wear. These tests “demonstrated dropwise condensation, complete water droplet bounce-off [see video, above], and sustained hydrophobicity after high-temperature exposure and abrasion.”
Of course, demonstrating that some ceramics could be intrinsically hydrophobic was quite an accomplishment*, but Varanasi’s groups goal also had a practical side. They say, for example, that hydrophobic ceramics could play an important role by improving the efficiency of steam-based energy generation. In a separate Nature article about this research, Varanasi tells the publication that a problem with current generators is that steam condenses into water on the rotating blades of the turbine and causes the loss of energy. He says the efficiency loss from this effect could be as great as 30 percent. Likewise, with wind turbines, accumulated water can freeze on turbine blades, again creating efficiency losses and, perhaps, catastrophic failure. He says that in both examples, a superhydrophobic surface composed of the REOs could make an enormous difference.
As ceramists and other materials scientists and engineers know, there are many reliable methods for applying ceramics surfaces that could be employed to add hydrophobic surface to substrates, although the researchers caution that the effects of materials geometries and mismatches of coefficients of thermal expansion would have to be considered.
But, overall, using the REOs to achieve hydrophobic surfaces isn’t all that difficult, and, not surprisingly, Nature reports, “Varanasi is now working with energy and technology companies partnered with the MIT Energy Initiative, which co-funded his work, to test the ceramics in real-world applications.”
* Nature reports that credit for noticing the hydrophobicity of ceria may go to a research group led by Chin Li Cheung, working at the University of Nebraska-Lincoln’s Department of Chemistry and Nebraska Center for Materials and Nanosciences, that was focused on other topics and didn’t pursue the hydrophobic properties further.
Corning Inc. announced that its board of directors has approved a capital expenditure plan of approximately $250 million to increase manufacturing capacity of the company’s diesel emissions control products. The majority of the investment will increase capacity at the Erwin diesel facility near Corning, which manufactures large ceramic substrates and filters for heavy-duty diesel engine, truck, construction, and agricultural equipment manufacturers worldwide. “Important heavy-duty regulations in China and Europe, as well as for non-road vehicles, take effect over the next two years which could double demand for our products by 2017,” says Mark Beck, executive vice president, Corning Environmental Technologies & Life Sciences Business Group. Corning’s diesel plant in Erwin began manufacturing large substrates in 2004 and now also produces particulate filters for heavy-duty applications. The company has already completed two facility expansions to accommodate global market growth. Corning said spending on the $250 million project will occur over a three-year period and will not change the company’s previous capital spending forecasts for 2013 and 2014. The latest project is expected to be operational in 2015 and to create an additional 250 new full-time positions if market demand grows as expected.
Infab Refractories Inc. is a descendant of Eastern Refractories Co, which opened a branch office in Lewiston on Holland Street in the 1940s. The Lewiston satellite was located strategically with a rail siding, for delivery of the refractory firebricks needed to service the boilers of various power plants, paper mills and manufacturing plants. The company was sold to a national contractor in the late ’90s and was soon re-sold, becoming employee owned in 2004. David Collins, the principle owner of Infab Refractories, is the grandson of the first regional manager of Eastern Refractories, Ted Collins. Infab Refractories has expanded its client base through the manufacture of custom-made, removable insulation blankets and various other high-temperature products under the direction of owner Jean (John) Bergeron and former owner Dick Marston at their current location on the corner of Whipple and Summer streets in Lewiston.
Minerals Technologies Inc. (reported net income of $18.8 million, or $0.53 per share for the first quarter 2013, compared with $18.0 million, or $0.51 per share in the first quarter of 2012, a 4-percent increase. “We began 2013 with solid operating performance, which generated a record in profit for both Minerals Technologies and our Specialty Minerals segment,” says Joseph C. Muscari, executive chair. “During the quarter we saw organic growth from new satellites ramping up in Asia, and we also announced three new commercial agreements for our FulFill technology, two in North America and one in South America.” The company’s worldwide sales declined 2 percent to $251.3 million from $257.1 million in the first quarter of 2012. Foreign exchange had an unfavorable impact of 1 percentage point of this decline, and two fewer days in the quarter affected sales by an additional 2 percentage points. Operating income was $27.1 million, a 1-percent increase over the $27.0 million recorded in the prior year’s first quarter.
(Washington Post) Fiber cement, a century-old material, has become popular in recent decades as a cheaper, more durable alternative to wood siding. It used to be reinforced with asbestos until the 1980s, when that hazardous substance was eliminated from its manufacture. Now the material is typically made with cement, sand, wood fibers and additives. In recent years, designs made from the mixture have expanded from wood-grained boards to paneling resembling brick, stone and stucco, and contemporary furnishings. “We use it on about 90 to 95 percent of our remodeling and addition projects,” says Bill Millholland, executive vice president of Case Design and Remodeling of Bethesda. “I can’t think of much we are doing that is not fiber cement. It looks like real wood siding, but it doesn’t decay, and it’s fire-resistant.” James Hardie Industries is the largest producer of the material in the country, and its HardiePlank siding “has become the Kleenex of fiber cement,” Millholland says.
(Tanzania Daily News) Tanzania’s total cement production is expected to more than double over the next two years, thanks to the new entrants, which expect to amplify competition. The current four firms that produce Twiga, Simba, Rhino and Tembo brands have a combined installed annual capacity of 3.75 million [metric] tons and output is expected to reach 8.65 million tons per year in 2015. The new producers are Dangote Cement, Lake Cement, and Lee Building Material plus the existing firms’ expansion expected to boost production by 4.9 million tons per annum. Tanzania Securities’ CEO, Moremi Marwa, says the firms are taking advantages of increased cement demand pushed by construction activities that grew at an annual average rate of eight per cent over the past five years. “We expect local demand to grow at over 10 per cent if infrastructure investments are sustained at the current levels and the economic momentum remains as projected,” Marwa says. The demand, currently standing at four million tons, has been growing at a compound annual growth rate of 10 per cent over the past five years to 2012. “We note that Tanzania is currently a net importer of cement, importing about 500,000 tons per annum or 12 per cent of the total consumption,” the CEO says in a cement analysis report. He adds, “We estimate that current sector utilization of the installed capacity is 90 per cent, offering minimal room for upside unless the projected new capacity is added.”
XG Sciences Inc. announced today that it has launched a new generation of anode materials for lithium-ion batteries with four times the capacity of conventional anodes. The new anode material is produced through proprietary manufacturing processes and uses the company’s xGnP graphene nanoplatelets to stabilize silicon particles in a nano-engineered composite structure. The material displays dramatically improved charge storage capacity with good cycle life and high efficiencies. “We are pleased to announce the immediate availability of this new high-capacity anode product,” says Rob Privette, vice president of energy markets. “Our new silicon-graphene anode material, when used in combination with our existing xGnP graphene products as conductive additives, provides significantly higher energy storage than conventional battery materials. This is great news for applications like smartphones, tablet computers, stationary power and vehicle electrification that use rechargeable lithium-ion batteries. We are working with battery makers to translate this exciting new material into batteries with longer run-time, faster charging and smaller sizes than today’s batteries.” Privette says that the exact performance of the new anode materials will depend on the specific battery formulations used by the cell manufacturer, noting that XGS has demonstrated capacity of 1500 mAh/g with low irreversible capacity loss and stable cycling performance in life tests.
3M announced that two of its recent technologies have received prestigious honors from the Edison Awards, a program conducted by the non-profit organization Edison Universe, which is dedicated to fostering future innovators. The company’s 3M LED Advanced Light received a Gold Edison Award in the Lighting category while the 3M Molecular Detection System earned a Silver Edison Award within the Diagnostic/Analytic Systems category. Nominees were judged by a panel of more than 3,000 leading business executives including previous winners, academics, and leaders in the fields of product development, design, engineering, science and medicine. The evaluation criteria used for this comprehensive, peer-reviewed process emphasized themes of concept, value, delivery and impact. The 3M LED Advanced Light—the company’s first-ever bulb—couldn’t be more appropriate for an innovation award named after Thomas Edison. The 3M LED Advanced Light provides an option that’s just as bright as a traditional bulb, and with its special Light Guide Technology, it shines in all directions. Developed with 3M multilayer optical film, adhesives and heat management technologies, the stylish bulb provides long-term cost savings but doesn’t compromise on energy efficiency.