Now, an international research team including chemist Scott Auerbach at the University of Massachusetts Amherst has developed a new molecular-level probe to track how various components in a mixture absorb microwave energy to different extents. Results of their experiments conducted at the Institute Laue-Langevin, Grenoble, France, are reported in a recent issue of Physics Review Letters.
The research team also includes chemical engineer W. Curtis Conner, Jr. and chemistry graduate student Julian Santander, both of UMass Amherst, with others at the University of Lyon and the University of Edinburgh.
With the new tool, based on quasi-elastic neutron scattering, researchers can for the first time measure the effective temperature of components in a mixture to determine which part is hot and which is not. This technique has the potential to determine exactly how microwave heating speeds up chemical and material syntheses. “With this breakthrough, we’ve converted microwave heating from a mysterious tool to a well-understood and predictable method for promoting and speeding up materials synthesis,” Auerbach says.
Most people using a microwave oven know that it warms unevenly and foods must be stirred before eating. This is because fat, proteins, water and minerals such as calcium in milk all absorb energy at different rates, Auerbach explains. The same is true for compounds and synthetic materials in laboratory experiments. But microwaves are widely used because they’re faster, more efficient and promote the chemical changes needed in modern materials science, while conventional heating does not, he adds.
“What we’ve done is to develop a technique for probing a material synthesis activated with microwaves. We blast the system with microwaves and neutrons at the same time. The neutrons act as the probe, bouncing off the system to tell us what’s going on with the temperature inside. It’s like a microscopic thermometer stuck into the system, giving a different temperature reading for each component in the mixture,” Auerbach says.
In experiments, Auerbach and coworkers applied this new method to understand microwave heating of zeolites, which are materials with molecule-sized pores. At present, zeolites are used as catalysts for refining petroleum to high-octane gasoline. They also show promise for refining biomass into biofuels. Auerbach refers to the zeolite as “a hotel for molecules” such as benzene and methanol, which can rotate and vibrate in each room, or bounce from room to room. “We found from the neutron scattering that microwaves cause the molecules to rotate like mad, and bounce from room to room, but they do not vibrate much.”
An expert in computer simulations of microwave-heated zeolites, Auerbach says by using such simulations, “It’s almost as if we can shrink down to the size of an atom to watch this motion, figure out where the microwave energy is going and why it is so efficiently promoting the chemistry. It’s a new kind of thermometer to use for the guest molecules.”
He and colleagues did not get perfect agreement between laboratory experiments and computer simulations, he notes, but for broad characterization of zeolite host temperature, effective guest translational (“room to room”) and spinning temperature, their results provide “very good agreement on the extent of selective heating.”
Overall, the authors summarize that their work provides “the first unambiguous, microscopic evidence for athermal effects in microwave-driven zeolite-guest materials.” With this advance, Auerbach suggests that microwave heating will be a “hot field for a long time to come.”
Scott Auerbach | Newswise Science News
Matter falling into a black hole at 30 percent of the speed of light
24.09.2018 | Royal Astronomical Society
Scientists solve the golden puzzle of calaverite
24.09.2018 | Moscow Institute of Physics and Technology
The Fraunhofer FEP has been involved in developing processes and equipment for cleaning, sterilization, and surface modification for decades. The CleanHand Network for development of systems and technologies to clean surfaces, materials, and objects was established in May 2018 to bundle the expertise of many partnering organizations. As a partner in the CleanHand Network, Fraunhofer FEP will present the Network and current research topics of the Institute in the field of hygiene and cleaning at the parts2clean trade fair, October 23-25, 2018 in Stuttgart, at the booth of the Fraunhofer Cleaning Technology Alliance (Hall 5, Booth C31).
Test reports and studies on the cleanliness of European motorway rest areas, hotel beds, and outdoor pools increasingly appear in the press, especially during...
The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.
This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.
Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...
Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.
"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...
A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.
Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...
Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.
21.09.2018 | Event News
03.09.2018 | Event News
27.08.2018 | Event News
25.09.2018 | Life Sciences
25.09.2018 | Life Sciences
25.09.2018 | Life Sciences