Thermal Plasma Synthesis Research Articles

Numerical analyses of thermal plasma synthesis of NO and thermal plasma decomposition of CO2.

アルゴン熱プラズマ流中でN2とO2よりNOを生成させる場合, CO2を分解してCOを生成させる場合の2つの反応系について理論計算を行った.計算は, 速度, 温度, 濃度の半径方向の分布を考慮した2次元モデルとそれらの半径方向分布を考慮しない1次元モデルの2つのモデルで行った.その結果, どちらの反応系でも2次元モデルの計算結果は実験値と良い一致がみられた.また, 1次元モデルの計算結果はCO2分解の場合は実験値と比較的良い一致が見られたものの, NO合成の場合ではそれらより低い計算結果を与えた.これは生成物であるNOやCOの分解速度の温度依存性の違いによるためと推測された.また, 得られた軸方向の転化率分布より最適なクエンチングの位置を推定することができた.

Homogeneous nucleation of particles from the vapor phase in thermal plasma synthesis

Particle nucleation and growth are simulated for iron vapor in a thermal plasma reactor with an assumed one-dimensional flow field and decoupled chemistry and aerosol dynamics. Including both evaporation and coagulation terms in the set of cluster-balance rate equations, a sharply defined homogeneous nucleation event is calculated. Following nucleation the vapor phase is rapidly depleted by condensation, and thereafter particle growth occurs purely by Browntan coagulation. The size and number of nucleated particles are found to be affected strongly by the cooling rate and by the initial monomer concentration. An explanation is presented in terms of the response time of the aerosol to changing thermodynamic conditions.

Advanced Powder Feeding Device for Use in Gas/Solid Plasma Synthesis and Processing Applications

ABSTRACTA series of powder feeders, developed during the course of an experimental study involving the synthesis of carbon monoxide from pure carbon and carbon dioxide, have been described in detail. The most efficient and reliable of these powder feeders was capable of continuously producing uniform mixtures of powdered carbon entrained in carbon dioxide gas. This device was also capable of producing a relatively wide range of solid/ gas mixture ratios (from about 0.8 to 3.2 g/l) at carbon dioxide gas flow rates between 75 and 200 1/min. In addition, it was relatively easy to vary and control solid/gas mixture ratios and gas flow rates using this powder feeder. Similar powder feeders may be useful in other thermal plasma synthesis or processing applications as well as in other applications requiring accurately blended mixtures of gases and powdered solids

Thermal plasma synthesis of transition metal nitrides and alloys

Applications of arc plasma processing to high-temperature chemistry of Group V nitrides and Si and Ge alloys are studied. The transition metal nitrides δ-VN, δ-NbN, and δ-TaN are directly synthesized in a dc argon-nitrogen plasma from powders of the metals. A large excess of N2 is required to form stoichiometric δ-VN, while the Nb and Ta can only be synthesized with a substoichiometric N content. In a dc argon plasma the alloys V3Si, VSi2, NbSi2, NbGe2, Cr3Si, and Mo3Si are obtained from powder mixtures of the corresponding elements. The compounds are identified by x-ray diffraction patterns and particle shape and size are studied by electron microscopy.