RIVERSIDE, Calif. (www.ucr.edu) – Metals are one of the most widely used materials in the world, serving as one of the elemental building blocks of society and technology. The combination of different elemental metals are what are known as metal alloys, and we use them every day in our cell phones, cars, buildings, cookware, and so on. Materials scientists, engineers, and metallurgists are always seeking ways to improve the materials we use as a society as well as develop materials that drive technology forward.

Typical rough type yellow diamond crystals for jewelry applications. R. Abbaschian et al., Diamond Related Materials, 2005, Vol. 14, No. 11-12, 1916-1919.

Distinguished Professor Reza Abbaschian

Researchers at the High-pressure High-temperature Materials Processing Laboratory (HPHT Lab) at the University of California, Riverside (UCR) are investigating the development and processing of different materials such as nickel-carbon alloys, high-entropy alloys, and diamonds for a wide variety of applications. This research is led by Distinguished Professor Reza Abbaschian, who is also Winston Chung Endowed Professor in Sustainability and Director of the Winston Chung Global Energy Center at UCR. Professor Abbaschian has published more than 250 scientific articles, including eight books. His research has led to the formation of gemstone quality laboratory-made diamonds through Gemesis Diamond Company.

The research carried out at HPHT Lab consists of many different methods for materials development and processing, such as arc-melting electromagnetic levitation for alloy processing and high-pressure machines for diamond synthesis.

In a paper published in Materials Today Communications, researchers at HPHT Lab investigate the phenomenon of liquid phase separation in molten “high-entropy alloys”, which refer to alloys containing many different metals in near-equal parts, which is different from traditional alloy design. Liquid phase separation in metals can be understood as a type of liquid-state separation in molten metal, similar to the separation we see in oil and water. Many solid phases can form during alloy solidification, and depending on the amount of solute material in the system, researchers can tailor alloys for very specific purposes (e.g. steels, nickel-based superalloys for jet engines and  cast irons).  However, if phase separation occurs in the liquid state during casting of an alloy, then the material properties one hopes to achieve are lost due to the heterogeneity of the resulting solid. In collaboration with scientists from Oak Ridge National Laboratory (ORNL), liquid phase separation of molten alloys was recently  observed in-situ through the use of neutron imaging!

Scanning electron microscope image of two frozen metal phases that separated in the liquid. Derimow and Santodonato et al., J. Imaging, 2018, 4,5.

Other interesting research that is being carried out at HPHT Lab consists of the study of graphene growth from molten alloys, continuing the work from a paper published by HPHT Lab titled: Growth of Large-are Graphene Films from Metal-carbon Melts. The current research seeks to minimize the difficulty of graphene synthesis as well as scale the process such that lower melting point alloys can be utilized for large area graphene growth for industrial applications. The benefits to graphene growth from a molten alloy are that the graphene layers are grown on an atomically smooth surface, which leads to higher quality graphene. More information about HPHT Lab can be found at:http://abbaschianlab.engr.ucr.edu.

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