Researchers report new understanding of ther…

Researchers report new understanding of thermoelectric materials

The promise of thermoelectric materials as a source of clean energy has driven the search for materials that can efficiently produce substantial amounts of power from waste heat.

Researchers reported a major step forward Friday, publishing in Science Advances the discovery of a new explanation for asymmetrical thermoelectric performance, the phenomenon that occurs when a material that is highly efficient in a form which carries a positive charge is far less efficient in the form which carries a negative charge, or vice versa.

Zhifeng Ren, M. D. Anderson Chair Professor of Physics at the University of Houston, director of the Texas Center for Superconductivity at UH and corresponding author on the paper, said they have developed a model to explain the previously unaddressed disparity in performance between the two types of formulations. They then applied the model to predict promising new materials to generate power using waste heat from power plants and other sources.

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Atomic engineering with electric irradiation

Atomic engineering with electric irradiation

Atomic engineering can selectively induce specific dynamics on single atoms followed by combined steps to form large-scale assemblies thereafter. In a new study now published in Science Advances, Cong Su and an international, interdisciplinary team of scientists in the departments of Materials Science, Electronics, Physics, Nanoscience and Optoelectronic technology; first surveyed the single-step dynamics of graphene dopants. They then developed a theory to describe the probabilities of configurational outcomes based on the momentum of a primary knock-on atom post-collision in an experimental setup. Su et al. showed that the predicted branching ratio of configurational transformation agreed well with the single-atom experiments. The results suggest a way to bias single-atom dynamics to an outcome of interest and will pave the road to design and scale-up atomic engineering using electron irradiation.

Controlling the exact atomic structure of materials is an ultimate form of atomic engineering. Atomic manipulation and atom-by-atom assembly can create functional structures that are synthetically difficult to realize by exactly positioning the atomic dopants to modify the properties of carbon nanotubes and graphene. For example, in quantum informatics, nitrogen (N) or phosphorous (P) dopants can be incorporated due to their nonzero nuclear spin. To successfully conduct experimental atomic engineering, scientists must (1) understand how desirable local configurational change can be induced to increase the speed and the success rate of control, and (2) scale up the basic unit processes into feasible structural assemblies containing 1 to 1000 atoms to produce the desired functionality.

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Scientists create new aluminum alloy with fl…

Scientists create new aluminum alloy with flexibility, strength, lightness

Aluminum is one of the most promising materials for aeronautics and automobile industry. Scientists from the National University of Science and Technology (MISIS) found a simple and efficient way of strengthening aluminum-based composite materials. Doping aluminum melt with nickel and lanthanum, scientists managed to create a material combining benefits of both composite materials and standard alloys: flexibility, strength, lightness. The article on the research is published in Materials Letters.

Lighter and faster aircraft and vehicles require lighter materials. One of the most promising materials is aluminum, or rather, aluminum-based composites.

Scientists from NUST MISIS scientific school “Phase Transitions and Development of Non-Ferrous Alloys” created a new strong Al-Ni-La composite for aircraft and automobile industry. Doping elements were added to the aluminum melt, forming special chemical compounds that further formed strong reinforcing structure.

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Adding a carbon atom transforms 2-D semicond…

Adding a carbon atom transforms 2-D semiconducting material

A technique that introduces carbon-hydrogen molecules into a single atomic layer of the semiconducting material tungsten disulfide dramatically changes the electronic properties of the material, according to Penn State researchers at Penn State who say they can create new types of components for energy-efficient photoelectric devices and electronic circuits with this material.

“We have successfully introduced the carbon species into the monolayer of the semiconducting material,” said Fu Zhang, doctoral student in materials science and engineering lead author of a paper published online today in Science Advances.

Prior to doping—adding carbon—the semiconductor, a transition metal dichalcogenide (TMD), was n-type—electron conducting. After substituting carbon atoms for sulfur atoms, the one-atom-thick material developed a bipolar effect, a p-type—hole—branch, and an n-type branch. This resulted in an ambipolar semiconductor.

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Photodoping in 2-D materials for fabrication…

Photodoping in 2-D materials for fabrication of logic devices

National University of Singapore scientists have discovered a method for photoinduced electron doping on molybdenum ditelluride (MoTe2) heterostructures for fabricating next generation logic devices.

Two-dimensional (2-D) transition metal dichalcogenides (TMDs) are promising building blocks for the development of next generation electronic devices. These materials are atomically thin and exhibit unique electrical properties. Researchers are interested to develop n- and p-type field effect transistors (FET) using the 2-D TMDs for building fundamental logic circuit components. These components include p-n junctions and inverters.

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New technique could pave the way for simple …

New technique could pave the way for simple color tuning of LED bulbs

Volkmar Dierolf and an international team demonstrate the possibility of tuning the color of a GaN LED by changing the time sequence at which the operation current is provided to the device.

A new technique―the result of an international collaboration of scientists from Lehigh University, West Chester University, Osaka University and the University of Amsterdam―could pave the way for monolithic integration for simple color tuning of a light bulb, according to Volkmar Dierolf, Distinguished Professor and Chair of Lehigh’s Department of Physics, who worked on the project.

“This work could make it possible to tune between bright white and more comfortable warmer colors in commercial LEDs,” says Dierolf.

The team demonstrated the possibility of color tuning Gallium Nitride (GaN)-based GaN LEDs simply by changing the time sequence at which the operation current is provided to the device. Light-emitting diodes or LEDs are semiconductor devices that emit light when an electric current is passed through it. Notably, the technique is compatible with current LEDs that are at the core of commercial solid state LED lighting.

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Magnetic nanoparticles can ‘burn’ cancer cells

Magnetic hyperthermia is still a highly experimental cancer treatment, but new research shows that the therapy is tunable

Unfortunately, cancer isn’t simply a single disease, and some types, like pancreas, brain or liver tumours, are still difficult to treat with chemotherapy, radiation therapy or surgery, leading to low survival rates for patients. Thankfully, new therapies are emerging, like therapeutic hyperthermia, which heats tumours by firing nanoparticles into tumour cells. In a new study published in EPJ B, Angl Apostolova from the University of Architecture, Civil Engineering and Geodesy in Sofia, Bulgaria and colleagues show that tumour cells’ specific absorption rate of destructive heat depends on the diameter of the nanoparticles and the composition of the magnetic material used to deliver the heat to the tumour.

Magnetic nanoparticles delivered close to the tumour cells are activated using alternating magnetic fields. Hyperthermia therapy is effective if the nanoparticles are absorbed well by the tumour cells but not by cells in healthy tissue. Therefore, its effectiveness depends on the specific absorption rate. Bulgarian scientists have studied several nanoparticles made of an iron oxide material called ferrite, to which are added small quantities of copper, nickel, manganese or cobalt atoms – a method called dopping.

The researchers investigated magnetic hyperthermia based on these particles, both in mice and in cell cultures, for two distinct heating methods. The methods differ in terms of how the heat is generated in the particles: via direct or indirect coupling between the magnetic field and the magnetic moment of the particles.

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