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Plasma synthesis of nano-sized metallic powders.

机译：等离子体合成纳米级金属粉末。

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摘要

The small dimension(s) of nano-sized materials leads to novel and enhanced mechanical and physical properties that are commercially desirable in many fields. A thermal plasma reactor has been developed for the formation of nanometer sized metal particulates. In the reactor system, a supersonic nozzle and a powder filter were designed and used for fast quenching of the hot gas and collection of the product powder, respectively.; By vaporization of fed coarse powders in the plasma flame, and quench of the metal vapors in the nozzle at the rate of 10{dollar}sp7{dollar} K/sec, nanometric iron and copper powders have been successfully produced, respectively. The powders were collected in the secondary quench and air-tight collection system. The particle size of the product power was 5 {dollar}sim{dollar} 30 nanometers and the particles are spherical, obtained through TEM analysis. The oxidation of nano-sized powder was almost prevented, obtained through XRD analysis, The product recovery was 45 {dollar}sim{dollar} 80%. Both the quench nozzle and the new collection filter worked as designed.; Investigations on the improvement of the product powder recovery were performed. Experimental results have shown that under the conditions such as, 15 {dollar}sim{dollar} 20% of H{dollar}sb2{dollar} used as the secondary plasma gas and a part of carrier gas, up to 30 kW of plasma input power applied and 6 l/min of carrier gas injected, etc., the optimum recovery can be achieved.; Mathematical models were developed to describe the velocity, pressure and temperature fields for the nozzle flow. They show that a high quench rate of hot gas can be obtained through the nozzle. Also, the equations for the nucleation and growth model were formulated to study particle size and size distribution and to understand the condensation process during the flow of plasma gas and metal vapor in the quench nozzle. The results indicate that the particle size of the product powder decreases with an increase in flow velocity and a decrease in gas temperature in the quenching nozzle.
机译：纳米尺寸材料的小尺寸导致新颖和增强的机械和物理性能，这在许多领域是商业上所期望的。已经开发了用于形成纳米尺寸的金属微粒的热等离子体反应器。在反应器系统中，设计了超声波喷嘴和粉末过滤器，分别用于热气体的快速淬火和产物粉末的收集。通过在等离子火焰中蒸发进料的粗粉，并以10 spsp7 {K K / sec的速率淬灭喷嘴中的金属蒸气，分别成功地生产了纳米铁粉和铜粉。粉末在二次淬火和气密收集系统中收集。通过TEM分析获得的产物粉末的粒径为5纳米（30nm），并且该颗粒是球形的。通过X射线衍射分析，几乎可以防止纳米级粉末的氧化。产物的回收率为45％，80％。骤冷喷嘴和新的收集过滤器均按设计工作。对产品粉末回收率的改善进行了研究。实验结果表明，在诸如15 {sim} {dol} 20％的H {dol} sb2 {dol}用作二次等离子气体和一部分载气的条件下，等离子输入高达30 kW施加功率和注入6 l / min的载气等，可以实现最佳回收率。建立了数学模型来描述喷嘴流的速度，压力和温度场。他们表明可以通过喷嘴获得较高的热气淬灭率。此外，制定了成核和生长模型方程，以研究颗粒尺寸和尺寸分布，并了解在淬火喷嘴中等离子气体和金属蒸气流动期间的冷凝过程。结果表明，产物粉末的粒径随着淬火喷嘴中流速的增加和气体温度的降低而减小。

著录项

  • 作者

    Zhu, Wenxian.;

  • 作者单位

    University of Idaho.;

  • 授予单位 University of Idaho.;
  • 学科 Engineering Metallurgy.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 195 p.
  • 总页数 195
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;
  • 关键词

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