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.
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.
By this time next year, Europe will be enforcing a tough, new standard on exhaust emissions from trucks and busses. Starting in September 2014, all new passenger and many lighter-weight commercial vehicles in regions covered by the European Commission’s rules will be required to have “Euro 6″-certified engines, and, in response, vehicle manufacturers and various research groups have been accelerating their filtration R&D. Switzerland’s Empa is of the institutions focusing on this issue, and researchers there say they are excited about some unconventional restructuring of the main filter components—typically ceramic substrates—that they say will enable manufacturers to meet pollution goals.
Heretofore, the standard diesel emissions filter is an extruded honeycomb-structure ceramic (e.g., cordierite) substrate that has a light coating of a catalytic material, such as platinum or palladium, which allows it to convert NOx and CO in the exhaust and capture soot. The honeycomb monolith substrate can withstand the stresses of temperature cycling during normal use and also during “regenerative” cycles when collected particulates (soot) are removed.
The conventional approach to engineering these filters is to allow exhaust gasses to pass through relative easily while providing maximum exposure to the surfaces bearing the catalyst. Turbulence was a thing to be avoided.
However, one research group at Empa, its Internal Combustion Engines Laboratory, says there is a downside to the honeycomb monolith: The flow of the exhaust gasses is distributed unevenly. Most of the exhaust gasses pass through the center section of the filter, creating a high-temperature zone and leaving much of the outer regions of the honeycomb relatively unused. To compensate for the unused regions, Empa says the honeycomb filters have to be relatively long (besides adding general manufacturing costs, the extra length also means the use of extra expensive catalytic material).
Empa claims that the impetus for rethinking the filter design was the viewing of a diesel filter whose central section had partially melted (see photo). The researchers’ novel idea, which began to emerge a few years ago, was to embrace the turbulence of the exhaust and put it to use to distribute the gasses more evenly.
But, a rugged ceramic substrate to support the catalyst would still be needed, and the Internal Combustion Engines Lab turned to researchers in Empa’s High-Performance Ceramics Laboratory. Instead of relying on the straight-through openings of a honeycomb, the ceramics group began to tinker with a special catalyst-coated ceramic foam, which they subsequently named Foamcat. The structure of the foam would encourage the turbulence needed to more evenly distribute the exhaust through the filter.
To filter engineers, the Empa approach probably raises several questions, especially in regard to the mechanical strength of a ceramic foam and to the negative effects of the turbulence, i.e., loss of engine performance due to back pressures from the exhaust. In response, a news release from the institute says
[S]cientists succeeded in increasing the mechanical strength of the material many times over. Currently the research team is working to optimize the structure of the ceramic—the foam substrate has a greater air resistance than the monolith that results in a slight comparative increase in fuel consumption. Using sophisticated computer simulation techniques, the Empa team has developed foam structures which reduce the air resistance without affecting the necessary turbulence.
According to Empa, the bottom-line benefit is that the surface area of the Foamcat substrate is much more efficiently used than with a honeycomb monolith. It claims that the efficiency is improved so much that the Foamcat filter can match the performance of a honeycomb filter at half the length and only requires one third of the expensive catalysts.
Whether vehicle manufacturers ultimately embrace the ceramic foam design remains to be seen. The problem of the expense of noble metal catalysts is vexing to manufacturers and other groups have been trying to find substitutes such as acicular mullite.
Nevertheless, Empa says it has been partnering for over a year with catalyst-maker Umicore and diesel engine manufacturer Fiat Powertrain Technologies to do field tests with a Foamcat filters. It also says that Swiss electrical utility IWB has been testing a vehicle fitted with the Foamcat filter for 18 months.
The stakes are high. According to a document (pdf) on the Euro 6 standards prepared by Cummins, all NOx emissions will have to be 75 percent less and particulate matter will have to be 66-95 percent less than current “Euro 5″ limits.
Looking forward to GOMD—Phillips to speak at honorary symposium; Varshneya reprises glass short course
James C. Phillips, who will speak at GOMD a symposium in his honor, discusses the idea of “big data” in this YouTube video, “Six Impossible Things.” Credit: YouTube.
Have you ever met a verb?
This is how I think of people who are all action. They have a great deal of energy, seem to be always in motion, and their enormous intellectual curiosity generates new ideas at a dizzying pace. Because they move so fast, their intellectual wakes cut a wide swath.
Allow me to highlight three of the “verbs” that will be at the Glass and Optical Materials Division Annual Meeting that will take place in conjunction with PACRIM 10, June 2-7. They are James Charles Phillips, Arun Varshneya, and John Mauro.
Phillips (Verb #1) will be honored in the aptly named, “James C. Phillips Honorary Symposium.” The symposium’s eight sessions span the entire five days of the conference’s technical program! Phillips, who celebrated his 80th birthday in March, is a condensed matter physicist by training, but his influence appears to be boundless.
The symposium organizer, Corning researcher John Mauro (Verb #2) says of Phillips, “Every decade since he began working, he has made huge contributions to science.”
Phillips is credited with developing semiconductor pseudopotential theory in the 1950s, which provided the basis for more than 30,000 published articles on the electronic structure of materials. In the 1960s, he dove into understanding superconductivity tunneling mechanisms. According to a Wikipedia biography, his microscopic theory of superconductive tunneling usurped the prevailing theory of the time, which had been proposed by the late Nobel-laureate, John Bardeen.
Phillips earned BS and MS degrees in mathematics and physics from the University of Chicago, and his PhD in algebraic topology. In the 1970s, the full weight of that education and research backgrounds led to the development of the topological constraint theory of glasses, in particular, as it applies to the optimization of glassy networks.
And, this is the point of intersection among the three “verbs” of this story. While Arun Varshneya (Verb #3) was a professor at Alfred University, he introduced Mauro—who was then an undergraduate student in glass science—to Phillips’ papers on topological constraint theory. The ideas resonated with Mauro, and he developed them further in his PhD work. At Corning Inc., Mauro used topological constraint theory to engineer Gorilla Glass 3, as explained in an earlier post.
“Jim works at the intersection of physics and glass,” Mauro says. “Not many of us work in both fields. He is interested not only in knowing the science of glass, but also in applying it to glass, including industrial glass.”
However, Mauro notes, “Jim’s work as a condensed matter physicist has so much influence in traditional fields and others,” as his work in the 1980s and 1990s gives witness. In the 1980s, he made significant contributions to theory of high temperature superconductors, and in the 1990s, he contributed new discoveries about disordered networks to the field.
In a 2011 lecture on “big data” posted on YouTube, Phillips quips, “One of the things physicists worry about is that there is nothing left to do.” Phillips is proof to the contrary. As the 21st century unfolds, he is applying his considerable intellectual talents and experience to detecting and fighting cancer. The new research involves taking theories used to optimize glass design and applying them to protein design. Phillips will provide the details himself in his talk, “Curing cancer using engineered viruses,” on Wednesday afternoon (June 5) at 2:00 p.m.
Varshneya, now professor emeritus of glass science at Alfred University, will be teaching a short course at GOMD: “Fundamentals of Glass Science.” He traditionally teaches this course at GOMD and usually to a full-capacity crowd.
It is not possible to separate Varshneya-the-glassman from Varshneya-the-teacher. Varshneya says he knew he would be a teacher from a young age. “I loved teaching ever since I was an 8th grader back in India,” where he tutored some of his classmates in the basics of math and science. “I knew then that I wanted to be a teacher some day,” he writes in an email.
As a teacher, he says his primary objective is to motivate his students to learn more, starting with the basics. The short course is designed for professionals working in other scientific or engineering disciplines and builds on their knowledge and experience, like “dendrites attempting to develop lots of branches,” he says. This year, he says, he plans to incorporate more examples from everyday life to demonstrate glass science principles and practices.
I’ve sat in on Varshneya’s course. He is a verb.
Thermo-Calc Software AB announced the release of Thermo-Calc 3.0, which constitutes the third generation of its popular computational thermodynamics software. Thermo-Calc is a powerful software package used to perform thermodynamic and phase diagram calculations for multi-component systems of practical importance. Calculations are based on thermodynamic databases produced using the CALPHAD method. Databases are available for Steels, Ti-, Al-, Mg-, Ni-alloys, multi-component oxides and many other materials. ”Our main ambitions for this new version of Thermo-Calc have been to unify the two earlier versions of Thermo-Calc (i.e. Thermo-Calc Classic and Thermo-Calc Windows) into one application, and to create a framework that is suitable for future extension with additional modules and functionality that will integrate more closely with our other software tools such as DICTRA and TC-PRISMA,” says Anders Engström, CEO of Thermo-Calc Software AB.
When Ghrepower, a Shanghai-based manufacturer of small and medium-size wind turbines, decided to set up a subsidiary in Swansea, Wales, in 2011 to tap into the British wind turbine market, it did not realize how much of an impact it would make on the local community. One thing of great help to Ghrepower was the GO Wales Work Placements scheme, created to help Welsh graduates find work. Graduates participating in the scheme work at companies located in Wales for between six to 10 weeks, during which time the Welsh government contributes up to 100 pounds. When the placement period ends, the employers can offer the workers long-term jobs if they wish to. “We expanded overseas because the wind turbine market in China is restricted by China’s immature smart grid system, which is the infrastructure essential for delivering energy generated from wind farms to people’s homes,” Deng says. “As our products are manufactured in China, we have certain cost advantages. For example, a crucial material for the wind turbines battery is a magnet, which in turn relies on rare earth materials. As China produces rare earths, we have a cost advantage,” he says. At the same time, Deng points out that some of its extra functions single it out from its competitors. For example, the wind turbines’ propeller blades can change shape in response to the amount of wind available. “This technology is common for large scale wind turbines, but quite rare for small and medium-scale turbines, and makes us unique.
Cabot Corp. completed an expansion project at its fumed silica facility in Barry, Wales. Production capacity at the site has been increased by 25 percent. The expansion is part of a three-year plan started in 2011 to increase Cabot’s global fumed metal oxide capacity by 35-40 percent. This expansion project is an extension of Cabot’s long-term relationship with Dow Corning. Furthermore, the increased production capacity supports Cabot’s growth in the rising global silicones market. This market is poised to grow at 6-9 percent per year over the coming decade. Through the expansion project, Cabot can now use a wider range of silane raw materials to make a broader portfolio of products to meet silicones and other market needs. Cabot and Dow Corning have worked closely together in Barry since 1991, when Cabot built its fumed silica facility adjacent to Dow Corning’s silicone monomer plant. As part of a highly interdependent and collaborative “fence-line” relationship, Dow Corning provides Cabot with silanes that are converted to fumed silica for Dow Corning’s compounded silicones applications, as well as for other customers and applications including electronics, adhesives, and composites.
Orbite Aluminae Inc. and Veolia Environmental Services signed an exclusive worldwide collaborative agreement for the treatment and recycling of red mud generated by industrial alumina production using the Bayer process. The terms of the partnership include the construction of the first plant to treat red mud using Orbite’s patented process. Red mud often remains stored in situ, which increases the risk of accidental spills. To meet this environmental and complex challenge facing the aluminum industry, Orbite and Veolia Environmental Services endeavour to bring the solution to treat the red mud stockpiled around the world in an economically and socially sustainable manner. These technologies allow for the extraction of smelter-grade alumina and high-purity alumina, as well as other products such as rare earths and rare metals, from various feedstocks including aluminous clay and bauxite, all without producing red mud. Veolia Environmental Services is the only worldwide integrated operator covering the entire value chain of waste management (collection, sanitation, treatment and recovery).
Sacmi has recently added to its long list of innovations for the sanitaryware sector with the introduction of a new brand, Reco2. The machine technical specifications allow for very considerable savings, minimization of energy consumption and reduction of polluting emissions. Sacmi’s system solutions which provide pre-drying stations enabling the energy consumption of the production line to be further reduced while, at the same time, improving health and safety in the workplace. With Sacmi’s plants customers can count on a reduction in production cycle times of 40%, in storage space requirements of 30% and in total energy costs of the complete pre-drying and drying process of up to 50%. Furthermore, the presence in glazing booths of innovative dry filters provides for the elimination of waste water and, therefore, treatment costs.
PPG Industries has launched the PPG Glass Education Center, a comprehensive website to help architects, specifiers, students, and construction industry professionals learn more about designing, specifying and building with glass. Divided into three sections—glass topics, glass FAQs and glossary—the PPG Glass Education Center features a compelling mix of videos, colorful illustrations and educational features that address issues such as preventing thermal glass breakage, specifying IGUs, how low-e glass works, and how heat-treated glass differs from heat-strengthened glass. The Glass Education Center is not designed as a promotional or marketing tool. The site’s existing content is based on the most frequently asked questions PPG fields on its website, during sales calls and through its call center, and new educational material will be added continually. In addition to hosting five short videos (3 to 6 minutes each), the Glass Education Center contains an extensive glossary of industry terms and nearly two dozen frequently asked questions covering low-e glass, glass safety issues and more. Six more videos will be added to the site before July, along with content driven by architects’ questions and input.