高频感应热等离子体具有能量密度大、温度高和冷却速率快等特点，是制备特种粉体的重要手段之一. 本工作介绍了过程所在高频热等离子体制备特种粉体方面的研究进展. 利用热等离子体的高温和快速冷却过程，粗颗粒经等离子体弧高温气化，通过控制冷却速率能得到纳米粉体，利用该方法制备了纳米球形硅、铁、钴和镍等粉体，纳米硅粉可用于锂离子电池负极材料. 具有固定熔点的不规则颗粒在等离子体弧中经熔融形成球形液滴，快速冷却能获得规则致密的球形颗粒，通过等离子体球化制备了高熔点的钨、钼、铌、铬等规则致密的球形粉体. 利用活性氢的瞬时强化还原反应，采用化学气相沉积能制备超细钨、钼、镍和铜等球形金属超细粉体. 活性氧有助于调控颗粒的氧化生长过程，采用金属等的氧化反应可获得多种特殊形貌的氧化物.
High frequency (HF) thermal plasma with high processing temperature (up to 10000 K) in the flame zone and fast quenching rate (105?106 K/s) at the flame tail is one of the most important methods to prepare special powders. In addition, thermal plasma is a powerful tool for synthesizing well-dispersed powders in a continuous and scalable process. In this manuscript, progress on preparation of special powders using HF thermal plasma in our team was introduced. Powders with large size were fed into plasma flame and vaporized to make them vaporation, and ultrafine powders were produced after fast quenching by physical vapor deposition (PVD). Spherical nanopowders of Si, Fe, Co, Ni could be prepared by PVD. Synthesized Si nanopowders display perfect spherical shape with smooth surface and good dispersity, which exhibit super electrochemical performance as anode for Li-ion batteries. Powders with irregular shape fed into plasma flame were melted to form spherical liquid drops and fast quenched to form spherical powders. W, Mo, Nb, Cr, Ni, Ti, V spherical powders could be prepared using HF thermal plasma. Hydrogen plasma with reactive radicals could help to enhance the hydrogen reductive reaction, which could make precursors to be reduced transiently to get metal nanopowders by chemical vapor deposition (CVD). W, Ni and Cu spherical nanopowders could be prepared using CVD. Synthesized W nanopowders with well defined spherical particles exhibit high sintering activity and strengthen the mechanical properties of obtained compacts. Oxygen plasma with reactive radicals can help to tune the growth of oxides in the plasma, and oxides with various morphologies can be produced using oxygen plasma. Al2O3 spherical nanopowders can be prepared and their sintering behavior shows that the aggregates are avoided and the grains are always uniform during sintering, owing to the employment of well dispersed spheres.
[1] He J P, Bai L Y, Jin H C, Yuan F L. Optimization of Tungsten Particles Spheroidization with Different Size in Thermal Plasma Reactor based on Numerical Simulation [J]. Powder Technology, 2016,302: 288-297.
[2] He J P, Bai L Y, Jin H C, Jia Z Y, Hou G L, Yuan F L. Simulation and experimental observation of silicon particles' vaporization in RF thermal plasma reactor for preparing Si nano-powder [J]. Powder Technology, 2017,313:27-35.
[3] 侯果林. 基于等离子体制备的硅基锂电池负极材料及其电化学性能研究 [D]. 北京：中国科学院大学，2016年：42
[4] Hou G L, Cheng B L, Cao Y B, Yao M S, Li B Q, Zhang C, Weng Q H, Wang X, Bando Y S, Golberg D, Yuan F L. Scalable production of 3D plum-pudding-like Si/C spheres: Towards practical application in Li-ion batteries[J]. Nano Energy, 2016, 24: 111-120.
[5] Hou G L, Cheng B L, Ding F, Yao M S, Cao Y B, Hu P, Ma R X, Yuan F L. Well dispersed silicon nanospheres synthesized by RF thermal plasma treatment and their high thermal conductivity and dielectric constant in polymer nanocomposites [J]. RSC Advances. 2015,5:9432-9440.
[6] 张海宝. 高频热等离子体制备纳微球形钨粉的研究 [D]. 北京：中国科学院研究生院，2012年：111-115
[7] Li B Q, Sun Z Q, Jin H C, Hu P, Yuan F L. Fabrication of homogeneous tungsten porous matrix using spherical tungsten powders prepared by thermal plasma spheroidization process[J].Int. Journal of Refractory Metals and Hard Materials [J]. 2016, 59:105–113
[8] 李保强. 热等离子制备的球形钨粉在W-Cu复合材料中的应用研究[D]. 北京：中国科学院大学，2018年：42-45
[9] 闫世凯. 射频等离子体球化二氧化硅粉体的研究[D]. 北京：中国科学院研究生院，2006年：41-43
[10] Li B Q, Sun Z Q, Hou G L, Ding F, Hu P, Yuan F L. The sintering behavior of quasi-spherical tungsten nanopowders [J]. Int. Journal of Refractory Metals and Hard Materials, 2016,56:44-50
[11] Li B Q, Sun Z Q, Hou G L, Hu P, Yuan F L. Fabrication of fine-grained W-Cu composites with high hardness [J]. Journal of Alloys and Compounds, 2018, 766:204-214
[12] 白柳杨. 微细金属镍粉的制备及其在导电浆料中的应用[D]. 北京：中国科学院研究生院，2009年：57-59
[13] Bai L Y, Zhang H B, Jin H C, Yuan F L, Huang S L, Li J L. Radio-Frequency Atmospheric-Pressure Plasma Synthesis of Ultra?ne ZrC Powders [J]. Int. J. Appl. Ceram. Technol. 2012,1–8
[14] Bai L Y, Jin H C, Lu C, Yuan F L, Huang S L, Li J L. RF thermal plasma-assisted metallothermic synthesis of ultrafine ZrB2 powders[J]. Ceramics International. 2015, 41:7312-7317
[15] Hou G L, Cheng B L, Ding F, Yao M S, Hu P, Yuan F L. Synthesis of Uniform alpha-Si3N4 Nanospheres by RF Induction Thermal Plasma and Their Application in High Thermal Conductive Nanocomposites[J]. ACS Applied Materials & Interfaces , 2015,7:2873-2881
[16] Hu P , Yuan F L, Bai L Y，Li J L, Chen Y F. Plasma Synthesis of Large Quantities of Zinc Oxide Nanorods[J]. J.Phys.Chem.C 2007,111:194-200
[17] Zhang H B, Yao M S, Bai L Y, Xiang W C, Huang S L, Li J L, Yuan F L. Synthesis of uniform octahedral tungsten trioxide by RF Induction thermal plasma and its application in gas sensing[J], CrystEngComm, 2013, 15:1432-1438
[18] Sun Z Q, Li, B Q, Hu P, Ding F, Yuan F L. Alumina ceramics with uniform grains prepared from Al2O3 nanospheres[J]. Journal of Alloys and Compounds,2016, 688:933-938
[19] Sun Z Q, Ding F, Fan, J M, Hu P, Yuan F L. The synthesis of alumina membrane with interconnected uniform pores from inactive spheres[J]. Int J Appl Ceram Technol. 2017,14:825-832
