You are browsing the archives of NIST.

Daniel Shechtman’s diffraction pattern was tenfold: turning the picture a tenth of a full circle (36 degrees) results in the same pattern. Credit: Shechtman; Royal Swedish Academy of Sciences.

Daniel Shechtman, while working at NIST alongside other luminaries, such as John Cahn, set the physics and materials science world atwitter (even before Twitter!) in 1984 when Physical Review Letters (doi:10.1103/PhysRevLett.53.1951) published a paper by him, Cahn, Denis Gratias and Ilan Blech reporting the discovery of a material that had a unique diffraction pattern (above) suggestive of a crystalline structure but apparently lacked a regularly ordered and repeating three-dimensional pattern.

The discovery reported was duly attributed to Shechtman. In 1982, he stumbled upon the phenomenon while studying an aluminum-mangnese alloy. The unexpected appearance of ten major dots in each concentric circle in the material’s diffraction pattern initially baffled Shechtman and others because it was unknown in crystallographic guides and seemed to violate the basic rules of crystallography. He followed up the initial data with other experiments that indicated the material had a five-fold symmetry, a characteristic that was thought to be impossible.

Cahn et al.’s contribution to Shechtman’s work was primarily to confirm his findings and conclusions about the existence of what came to be known as quasicrystals.

What Shechtman had discovered, in essence, in the Al-Mn alloy is that the five-fold symmetry creates an aperiodic regular “pattern” or “quasiperiodic” structure. Perhaps the easiest way to wrap one’s thinking around an regular aperiodicity is to look at the work, coincidentally done just several years before Shechtman’s discovery, by mathematicians, such as Roger Penrose, who created special mosaics with a limited number of tiles, a limitation that provides the appearance of some pattern similarities, while creating patterns that never actually repeat (see example, below). A Fibonacci sequence is another familiar example of regular aperiodicity.

Pentagonal aperiodic tiling by Roger Penrose using only two sizes of tiles. Identifying the vertices as atomic positions generates a quasiperiodic structure. Credit: R. Penrose; Royal Swedish Academy of Sciences.

The work of Penrose and others eventually provided Shechtman (and others who joined the investigation of quasicrystals) an explanation of how the material might actually be structured.

Shechtman’s assertions made him an outcast for a few years, but his dogged pursuit of an explanation of his findings eventually put him ahead of other researchers who, as it turns out, had observed similar patterns and data but had too-hastily dismissed the diffractions as being the result of twinned or intermingled crystals.

Background material provided by the Royal Swedish Academy of Sciences reports that hundreds of different types of quasicrystals have now been synthesized and that at least one natural mineral has been found to have that structure. Here is what the Academy says about the uses of quasicrystals:

When trying out different blends of metal, a Swedish company managed to create [a] steel with many surprisingly good characteristics. Analyses of its atomic structure showed that it consists of two different phases: hard steel quasicrystals embedded in a softer kind of steel. The quasicrystals function as a kind of armor. This steel is now used in products such as razor blades and thin needles made specifically for eye surgery.

Despite being very hard, quasicrystals can fracture easily, like glass. Due to their unique atomic structure, they are also bad conductors of heat and electricity, and have non-stick surfaces. Their poor thermal transport properties may make them useful as so-called thermoelectric materials … Today, scientists also experiment with quasicrystals in surface coatings for frying pans, in components for energy-saving light-emitting diodes, and for heat insulation in engines, among other things.

Here’s a great 2010 interview with Shechtman, who now works at Technion:

Share

NIST Extends Response Period for Comments on Proposed New Advanced Manufacturing Program

To accommodate additional interested parties, the National Institute of Standards and Technology (NIST) today announced a 30-day extension on a request seeking public comment on the proposed new Advanced Manufacturing Technology Consortia program. The comment period now ends 11:59 p.m., Eastern Time, on Thursday, Oct. 20, 2011. The Request For Information asks interested parties to answer 23 questions about eligibility for consortia membership, selection criteria for research funds, best practices for maximizing small business participation or disseminating results, and a number of other topics. Comments will be accepted by email only to AMtechRFC@nist.gov. All comments will be made publicly available.

DOE and Israel Announce $3.1 Million in Cooperative Clean Energy Projects

The U.S. Department of Energy (DOE) today highlighted a milestone in U.S.-Israel cooperation on clean energy technology. DOE and the Ministry of National Infrastructures of Israel (MNI) have selected four projects in California, Pennsylvania, and Washington to receive $3.1 million under the 2011 Binational Industrial Research and Development (BIRD) Energy program. Each of the cooperative projects includes a U.S. and Israeli partner and addresses energy challenges and opportunities of interest to both countries, while focusing on commercializing clean energy technologies that improve our economic competitiveness, create jobs, and support innovative companies. The selected projects will leverage private sector cost-share for a total project value of $8.46 million.

GE, Nissan Sign R&D Agreement to Fast Track Broader Adoption of Electric Cars

GE and Nissan have signed a two-year research collaboration to speed up the development of a reliable, robust smart charging infrastructure to fuel mass market adoption of electric cars like the Nissan LEAF and have identified two key focus areas for the research efforts. The first relates to the integration of electric vehicles with homes and buildings. The second looks at electric vehicle charging dynamics and the future impact on the grid once millions of electric cars are on the road.

Copper nanowire organization method could mean cheaper substitute for ITO films

Duke University chemist Ben Wiley and his graduate student have developed a technique to organise copper atoms to form long, thin, non-clumped nanowires. The nanowires are then transformed into transparent, conductive films and coated onto glass or plastic for applications in displays on mobile phones, e-readers and iPads. They could also be utilized to build foldable electronics and improved solar cells, according to new research.

 The research shows that the copper nanowire films have the same properties as those currently used in electronic devices and solar cells, but are less expensive to manufacture.

Development of Sensor Device Using High-transparency Organic Piezoelectric Film

Murata Manufacturing Co., Ltd. has developed a sensor device using high-transparency organic piezoelectric film. This film has the following characteristics: (1) high piezoelectric output constant*1; (2) high transparency (light beam transmittance of 98% or higher [according to the internal haze measurement]); and (3) free from pyroelectric effect*2. As smartphones, tablet computers, and portable game devices become more widespread, there is a growing demand for a new human/machine interface. Conventional piezoelectric films are usually subject to a pyroelectric effect, which is a disadvantage because they cannot detect bending and twisting vibrations separately from changes in temperature. Murata has developed a high-transparency piezoelectric film free from pyroelectric effect through joint research with Kansai University and Mitsui Chemicals Inc.

Share

NexTech’s 10 µm MCO coating on SS441 substrate 900°C, 200 hours, air. Credit: NexTech.

Here’s what we are hearing:

PPG to increase global production capacity for precipitated silica

PPG Industries announced that it is increasing its global precipitated silica production capacity by more than 18,000 tons per year in response to growing global demand. The capacity expansion includes projects at PPG’s Lake Charles, La., and Delfzijl, Netherlands, manufacturing locations. PPG pioneered the development of synthetic precipitated silica, becoming one of the first manufacturers to bring them to market in the 1930s. Today, PPG’s silica products business is a global leader in the manufacture of precipitated silica for tire, battery separator, carrier, coatings, industrial rubber, footwear and silicone end-use applications. The business also makes TESLIN substrate, a microporous sheet material used for card, specialty print, in-mold graphic, tag and label use, as well as technology-focused applications such as e-Passports and RFID cards and labels.

Altair board appoints H. Frank Gibbard president and CEO; Stephen B. Huang to be vice president and CFO

Gibbard has more than 30 years of experience in battery and fuel cell businesses, having served as vice president for research, Development and advanced engineering at Duracell and as CEO of the fuel cell company H Power Corp. At H Power he led a $104 million IPO that resulted in a NASDAQ listing in 2000. He holds a Ph.D. in physical chemistry from the MIT and is a frequent speaker at technical and business conferences on electrochemical energy storage. Huang is a seasoned financial executive with 18 years of experience with U.S. companies, ranging from controller to CFO. He is fluent in Mandarin Chinese and experienced in the financial management of joint US-Chinese companies. His experience in setting up and managing operations in China is particularly valuable for Altair’s expansion in global markets.

Mettler Toledo issues new white paper on transfer of weighing data for process control

Mettler Toledo is pleased to issue a new white paper that provides points to consider when defining operating boundaries, and data objectives for transfer of weighing process data to PLC, MES or ERP systems. Efficient transfer of weighing process data to higher level PLC, MES or ERP systems makes manufacturing processes more efficient and more transparent. It can result in more accurate or faster filling and control processes. Increased transparency can improve asset use, reduce operating costs, and make complying with certification standards or industrial regulations easier. But identifying and implementing the most effective system for data transfer and integration can be challenging.

NexTech Materials demonstrates stainless steel protective coatings for 40,000+ hours of operation in SOFCs

A critical challenge in the commercialization of solid oxide fuel cells is the selection and manufacture of components that will last for thousands of hours, but at an economical cost. NexTech Materials Ltd. has performed accelerated stability tests that predict a service life of over 40,000 hours at 750°C for low cost ferritic steel (AL 441 HP) interconnect components protected by its manganese-cobalt spinel. coatings. This achievement represents a critical milestone for intermediate temperature solid oxide fuel cells. To date, SOFC system lifetime has been limited by the metal component oxidation. As demonstrated by NexTech, MCO protective coatings reduce the oxidation rate of ferritic steels by a factor of twenty or more.

Momentive To Expand Specialty Quartz Plant in Geesthacht, Germany

Momentive Performance Materials Inc.’s Quartz & Ceramics is expanding its specialty quartz production facility in Geesthacht, Germany. The $14 million expansion project t will enable Momentive to meet increasing global demand for its high-purity specialty fused quartz crucibles, used by the photovoltaic industry to produce solar wafers and the semiconductor industry in the production of computer chips. The company manufactures a variety of specialty products that are essential to the photovoltaic wafer and semiconductor microchip production, including fused quartz crucibles used to “grow” silicon ingots, large-diameter fused quartz tubing, rods, and solid ingot in which silicon wafers are processed to make microchips.

Share

Mechanism for the occurrence of ZTE. NTEM and PTET denote negative thermal expansion caused by magnetic ordering and positive thermal expansion caused by temperature, respectively, and a_M and a_T are the corresponding lattice parameters. Δa_M and Δa_T are the changes in the lattice parameter caused by magnetic ordering and temperature, respectively. In the temperature range between T₁ and T₂ where Δa_M + Δa_T = 0, the ZTE behavior occurs. Credit: Song et al.; Advanced Materials.

Specialized materials that do not change their volume with alteration of temperature may now be easier to produce, thanks to work by a multinational team of scientists into the mechanism of such behavior in antiperovskite manganese nitrides.

Every child learns in school that materials expand or contract with changes in temperature. There are only a few special materials that barely or do not alter their volume in response to temperature, and this normally only occurs over a relatively narrow temperature window. This property is called zero thermal expansion. But such materials are in great demand for both precision engineering of sensitive bulk systems and as components for nanodevices. For example, the gyroscopes used in spacecraft must maintain the same functionality independent of the temperature at which they operate.

The most common way to control thermal expansion is by combining materials with different thermal expansion behavior, however, this method leads to local stresses and strains that often enhance material fatigue and thus shorten component lifetime. Zero thermal expansion in a single, uncombined material is only known in a few cases, one of which is a class of materials called antiperovskite manganese nitrides.

Now, Xiaoyan Song at Beijing University of Technology (China) and coworkers from as far afield as NIST, University of Jena (Germany), the Chinese Academy of Sciences and the National Institute for Materials Science (Japan), have worked together on these antiperovskite manganese nitrides to discover how the effect occurs and thus to extend it beyond the normal temperature ranges for these materials.

The scientists found that the thermal expansion behavior of the antiperovskite manganese nitrides can be controlled by altering the lattice site occupancy of the manganese within the solid-state structure, i.e., each compound has a fixed number of available sites that can be occupied by manganese and some of these sites may be left unoccupied while the whole structure is still retained. Such alteration affects the magnetic ordering in the material which in turn influences the behavior of the material with respect to temperature.

The scientists achieved a much larger than usual range of temperatures over which zero thermal expansion occurs in antiperovskite manganese nitrides; three to four times greater than previously reported.

Professor Song believes that their mechanism for altering the zero thermal expansion behavior is a universal one that could be applied to other types of material also. This result should enable materials scientists to provide engineers and nanoscientists with new and varied building blocks for the most critical of applications.

Editor’s note: Carol Stanier is a writer for Materials Views.

Share

Rice University researchers, Robert Vajtai, Enrique Barrera and Yao Zhao created a conductive cable from iodine-doped nanotubes capable of carrying household current. Credit: Jeff Fitlow/Rice University

Showing how something works is more effective than telling how it works. With the assistance of a fluorescent lightbulb, Rice University researchers demonstrated successful substitution of standard copper wiring with a carbon nanotube cable.

Using double-walled CNTs spun into a cable several centimeters long, a recent Rice PhD, Yao Zhao, constructed a rig that allowed him to run electricity through a CNT cable to a fluorescent lightbulb. The lightbulb was left “on” for several days without interruption and without any sign of degradation in the CNT cable. Zhao is in Enrique Barrera’s research group. CTT recently interviewed Barrara as part of the MSE football series.

The cable was constructed of billions of double-wall CNTs and fabricated by collaborators at Tsinghua University in China. The cables were doped with iodine to increase their conductivity, and Zhao found they could be tied together without losing conductivity.

In a Rice press release, Barrera says the cables have the potential to be just as effective as metal wiring, at about 1/6 the weight. He also said that the chemical processes used to make lab-scale cables will become part of a larger process that starts with raw materials and produces a steady stream of nanocable. The next step for the team is “to make longer, thicker cables that carry higher current while keeping the wire ligtweight.”

The work was published in the Nature journal, Scientific Reports.

Meanwhile, NIST has been studying the reliability of CNTs for electronic devices with the goal of developing measurement and techniques to test fabrication quality and reliability.

Recession and clumping, in gold electrodes after NIST researchers applied 1.7 volts of electricity to the carbon nanotube wiring for an hour. NIST reliability tests may help determine whether nanotubes can replace copper wiring in next-generation electronics.Credit: M. Strus; NIST

Possibly relevant to the Rice work, NIST researchers have been studying failure in CNT networks, where electrons physically jump from one CNT to another, and found that failure seemed to happen between nanotubes, which is the point of greatest resistance. In a press release, NIST postdoctoral researcher, Mark Strus said that by monitoring the initial starting resistance and stages of degradation, it was possible to predict whether the resistance would degrade gradually or sporadically. Gradual degradation is preferred because it allows for operational limits to be set for devices. NIST has developed some electrical stress tests “that link initial resistance to degradation rate, predictability of failure and total device lifetime. The test can be used to screen for proper fabrication and reliability of nanotube networks.”

Also from NIST, a study of CNT interconnects between gold electrodes found that the CNTs carried very high current densities for awhile, but degraded under constant current. By about 40 hours, the edges of the metal electrodes receded and clumped, leading to device failure. Further NIST research is focusing on the intersections between CNT and metals, as well as between different CNTs. In th press release Strus said, “The common link is that we really need to study the interfaces.”

Share