Thermal Transistor Handles Heat at the Nanoscale

By Andrew Myers

You’ve felt the heat before — the smartphone that warms while running a navigation app or the laptop that gets too hot for your lap.

The heat produced by electronic devices does more than annoy users. Heat-induced voids and cracking can cause chips and circuits to fail.

Schematic

Schematic of the experimental thermal transistor. A slice of molybdenum disulfide (MoS2) sits on a piece of silicon dioxide, bathed in a solution of lithium ions. (Sood et al, Nature Communications)

New Insights into Semiconductors for Spintronic Applications from Hard X-Ray Photoemission

“Spintronics” holds promise for new types of devices for information processing and data storage, with ones and zeros being stored in the spin state of electrons as well as their electric charge. Such devices could be faster and more energy efficient than current electronics.

Dilute magnetic semiconductors such as manganese-doped gallium arsenide are a promising material for spintronics, said Slavomir Nemsak, staff researcher at the Lawrence Berkeley National Laboratory and former postdoc in the UC Davis Department of Physics, working with Professor Charles Fadley and Adjunct Professor Claus Schneider. They have ferromagnetic properties but are not themselves metals. They are called “dilute” because the dopant makes up a small amount (a few percent) of the semiconductor material.

Graphene Layered with Magnetic Materials Could Drive Ultrathin Spintronics

Scientists with instrument

UC Davis project scientist Gong Chen (right) and coauthor Andres Schmid of Lawrence Berkeley Lab with the SPLEEM instrument used for imaging magnetic fields inside materials. Photo by Roy Kaltschmidt/LBL.

Tiny swirling textures in the magnetic fields within layered materials could be a key to replacing disk drives and flash memory in computing devices. Physicists at UC Davis and the Lawrence Berkeley National Laboratory are exploring how these patterns form in materials layered with graphene, an ultrathin form of carbon. A paper on the work was published online May 28 in Nature Materials.

Piezomagnetic Material Changes Magnetic Properties When Stretched

Piezoelectric materials, which generate an electric current when compressed or stretched, are familiar and widely used: think of lighters that spark when you press a switch, but also microphones, sensors, motors and all kinds of other devices. Now a group of physicists has found a material with a similar property, but for magnetism. This “piezomagnetic” material changes its magnetic properties when put under mechanical strain.

Magnetic experiment

Top: A piece of BaFe2As2 is stretched while magnetic measurements are taken (the copper wire coil is part of the NMR device). Lower diagram shows atoms in a plane, with black arrows showing how magnetic spins lie in plane and point in opposite directions. Grey arrows show how the magnetic spin of atoms shifts as the material is stretched.

Podcast: A New Book Explores The Glass of Wine

Glass and wine have gone together for thousands of years. A new book, “The Glass of Wine,” delves into the science, history and artistry of this pairing. The book is by Jim Shackelford, distinguished professor emeritus of materials science and engineering in the College of Engineering, and writer and blogger Penelope Shackelford.

Glass scientist Jim Shackelford and blogger Penelope Shackelford are the authors of a new book, “The Glass of Wine” that explores the relationship between the drink and its perfect host. Photo by Daniela Wood.

New Technique Makes Light Metallic Nanofoam

By Becky Oskin

A simple method for manufacturing extremely low-density palladium nanofoams could help advance hydrogen storage technologies, reports a new study from the University of California, Davis.

Palladium nanofoam

UC Davis physicists Dustin Gilbert, Kai Liu and colleagues have come up with a new method to make a nanofoam of palladium. The foamy metal could be used to store hydrogen in vehicles or for other purposes. (Image credit: Dustin Gilbert and Kai Liu, UC Davis)

Industry Supports UC Davis Coffee Research

The Research Center of the Specialty Coffee Association (SCA) is teaming up with the UC Davis Coffee Center to embark on a two-year project to re-evaluate the scientific assumptions, measurement tools, sensory information, and – most importantly – consumer research that forms the foundation of the coffee industry’s fundamental understanding of coffee brewing.

Students in the UC Davis “Design of Coffee” class learn engineering principles from roasting and brewing coffee.

This research is underwritten with funding from Breville, which produces high-end appliances, including coffee and tea equipment.

New Types of Structures for Cage-Like Clathrates

Compounds Could Be Basis For Devices That Turn Waste Heat Into Electricity

Cage-like compounds called clathrates could be used for harvesting waste heat and turning it into electricity. UC Davis chemists just discovered a whole new class of clathrates, potentially opening new ways to make and apply these materials.

Journal cover image

UC Davis chemists discovered a new class of clathrates that break the four-bond rule. The discovery was featured on the cover of the journal Angewandte Chemie (Wiley)

UC Davis’ McClellan Nuclear Reactor, At 27 One of “Newest” in U.S.

By Lisa Howard

On January 20, 1990, when the nuclear reactor at McClellan Air Force Base achieved its first sustained nuclear reaction known as “criticality,” it was the newest reactor in the United States.

Six years later, when the Tennessee Valley Authority launched the Watts Bar Nuclear Generating Station, the nuclear reactor at McClellan was relegated to second newest. McClellan would go on to retain that ranking for another two decades until this past October when the Tennessee Valley Authority launched Watts Bar Unit 2.

Perovskite, Potential Solar Cell Material Unsuited for Real-World Use

By Becky Oskin

Solar cells made from perovskites have sparked great excitement in recent years because the crystalline compounds boast low production costs and high energy efficiencies. Now UC Davis scientists have found that some promising compounds — the hybrid lead halide perovskites — are chemically unstable and may be unsuited for solar cells.

“We have proven these materials are highly unlikely to function on your rooftop for years,” said Alexandra Navrotsky, interdisciplinary professor of ceramic, earth, and environmental materials chemistry at UC Davis and director of the Nanomaterials in the Environment, Agriculture, and Technology (NEAT) organized research unit.