Faculty and Staff
- Hongmin Zhu
- Associate Professor
- Osamu Takeda
- Assistant Professor
- Lu Xin
Thermophysical properties of high temperature melts such as viscosity, density, surface tension and electrical conductivity are very important to study the liquid structure at the atomic level, to design the metallurgical apparatus and to simulate the industrial process. We study the essential behavior of liquid by determining the properties precisely. For instance, the viscometer developed in our laboratory based on the oscillating method is available to measure the viscosity of iron based and nickel based molten alloys, molten semiconductors such as silicon and also molten salts up to 1600℃. The range of the viscosity available is approximately 0.3 to 50 mPa s. The reliability of the measurement is evaluated to be most excellent in the world.
Molten salts have wide electrochemical windows and enable the many reactions involving the formation of reactive metals such as lithium and rare earth metals. Recently, we are developing great innovative project. It’s on the storage and transportation of hydrogen through lithium hydride. In the system, it is necessary to produce metallic lithium electrochemically from the hydroxide (by-product after H2 generated), and the thermodynamics of the electrolytic system and the electrochemical reactions are revealed. As the lithium hydride has large hydrogen storage density, the method is expected to establish the mass transport of hydrogen.
High temperature materials processing serves the safe and efficient waste treatment and recycling process. For instance, the waste treatment of polychlorobiphenyls (PCBs) with a strong toxicity has been desired for long time, but the complete treatment has not been realized because PCBs have very tough chemical structure and there is a risk of the formation of dioxins. We tried the decomposition of PCBs by using basic molten salts such as KOH-K2CO3 and NaOH-Na2CO3 mixtures and achieved the excellent decomposition with high decomposition efficiency more than 99.999%. We are also developing the recycling process for rare earth magnet by using molten fluoride. In general, rare earth magnet scraps are heavily contaminated by oxygen, and they can’t be recycled as it is. We deoxidized the scraps by remelting with fluoride and obtained magnet alloys with low oxygen concentration (under 200 mass-ppm O).