Environment System Engineering

Research

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Environment System Engineering

Overview

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Thermal plasmas have simply been used as a high temperature source. This indicates that thermal plasmas may have more capabilities in material processing, especially production of high-quality and high-performance materials, if thermal plasmas are utilized effectively as chemically reactive gases. Therefore we developed the numerical analysis to investigate non-equilibrium characteristics in thermal plasmas. These results can be utilized for the nano-material synthesis as well as waste treatment using thermal plasmas.

The thermal plasma approach has been applied for many fields, including treatment of harmful waste materials, recovery of useful material from waste, and production of high-quality and high-performance materials, such as synthesis of nanoparticles, deposition of thin films, and plasma spraying. Induction thermal plasmas offer unique advantages including high enthalpy to enhance reaction kinetics, high chemical reactivity, oxidation and reduction atmospheres in accordance with required chemical reactions, and rapid quenching. These advantages increase the advances and demands in plasma chemistry and plasma processing.

Functional nanoparticles of silicide and boride were prepared by induction thermal plasmas. Silicide and rare-earth boride are attractive materials because of their high melting temperature, high electrical conductivity and low work function. Therefore these nanoparticles would be applied for electromagnetic shielding, and solar control windows with interaction with IR and UV light. For the preparation of silicide, Si powder premixed with metal powder (Mo, Ti, Co, Fe, Cr, or Mn) was injected into the plasma. For the preparation of rare-earth boride, premixed powders of rare-earth oxide, B and C were introduced into the thermal plasma. In the thermal plasma, the injected powders were evaporated and reacted with boron. After the evaporation and reaction, the vapor was rapidly cooled after the plasma flame. The nanoparticles were prepared on condition that the vapor was quickly quenched by the water-cooled copper coil. Another purpose is to investigate the condensation mechanism of mixture vapor of feed powders in thermal plasmas. The characteristics of the prepared nanoparticles are affected by the vapor pressure ratio of the constituent materials. Investigation of physical and chemical processes in thermal plasma processing is indispensable for Nanoparticle synthesis.

Application for destruction of hazardous and waste materials by thermal plasmas is developed. Radioactive waste treatment by thermal plasmas is an active research field, therefore plasma treatments of low-level radioactive wastes (LLW) as well as ion-exchange resin are investigated. Moreover, reactive thermal plasma for halogenated hydrocarbon decomposition is developed. For halogenated hydrocarbon decomposition, the stable generation of DC steam plasmas is the important factor for industrial application. Steam plasmas are suitable for halogenated hydrocarbon decomposition because hydrogen and oxygen combine with the liberated halogen and carbon atoms to prevent recombination reactions that result in the reformation of halogenated hydrocarbons.

Staff

Professor Takayuki Watanabe
Assistant Professor Manabu Tanaka

The Main Research Topics

  • Modeling of Reactive Plasma Flows
  • Development of Innovative In-Flight Melting Technology for Energy Conservation
  • Generation of Steam Plasmas under Atmospheric Pressure
  • Waste Treatment by Reactive Plasmas
  • Synthesis of Functional Nanoparticles by Thermal Plasmas
  • Lunar Resources Utilization
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