Reactive thermal plasmas: ultrafine particle synthesis and coating deposition
Reactive thermal plasmas: ultrafine particle synthesis and coating deposition
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DOI：
10.1016/s0257-8972(97)00294-6
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发表时间：
1997-12-01
影响因子：
5.4
通讯作者：
Denoirjean, A
中科院分区：
文献类型：
--
作者：
Fauchais, P;Vardelle, A;Denoirjean, A
由直流电弧或射频放电在接近大气压的压力下产生的热等离子体射流的特征在于重物质的高温（在6000和14000 K之间）和等离子体流的高速度（在100和2500 m s（-1）之间）。它们可以用于它们的物理性能，即加速和熔化固体颗粒（直径范围为10 - 100 μ m）以喷涂厚涂层（从0.1毫米到几毫米），或者用于它们的反应性能。当试剂被引入等离子体流中时，它们被转化为处于激发态的高反应性自由基和/或原子。由于边界层等离子体-基底中的陡峭梯度，这些活性物质可以形成具有高沉积速率（类似于100 μ m h（-1））的涂层：该过程称为热等离子体辅助化学气相沉积（PCVD）。在没有基底和使用足够的淬火的情况下，它们也可以形成超细颗粒，其尺寸在淬火过程中很难通过温度控制。这些PCVD工艺可用于在等离子体射流中飞行的固体和熔融颗粒的表面上形成新的化学物质，或者在所产生的飞溅物上和连续的道次之间形成具有分散的硬质相的涂层（反应性等离子体喷涂）。也可以使直径为几微米的反应性颗粒（例如碳和金属）团聚，以在飞行中的颗粒内实现放热反应，并在空气中喷涂碳化物涂层。本文介绍了我们在这方面的知识：（1）等离子体直流和射频炬的主要特性，转移电弧和试剂和/或淬灭气体的注入，（2）反应气体流动注入的模拟问题，靠近衬底的边界层，超微粒合成及PCVD涂层的相应实验结果，（3）等离子体的化学反应，（4）等离子体化学反应，（5）等离子体化学反应，（6）等离子体化学反应，（7）等离子体化学反应，（8）等离子体化学反应，（9）等离子体化学反应，（10）等离子体化学反应，（10）等离子体化学反应，（10）等离子体化学反应，（11）等离子体化学反应，（12）等离子体化学反应，（13）等离子体化学反应，（14）等离子体化学反应，（15）等离子体化学反应，（16）等离子体化学反应，（17）等离子体化学反应，（18）等离子体化学反应，（19）等离子体化学反应，（通过闪蒸和超细颗粒合成的薄膜沉积;和（3）通过喷涂团聚颗粒（在10 - 50 μ m尺寸范围内）实现的反应性等离子喷涂，其中发生自蔓延高温合成，或者通过将反应性气体与等离子射流混合实现。(C)1997年Elsevier Science S.A.
Thermal plasmas jets produced by d.c. arcs or RF discharges at pressures close to atmospheric pressure are characterized by the high temperatures (between 6000 and 14 000 K) of heavy species and high velocities (between 100 and 2500 m s(-1)) of plasma flow. They can be used either for their physical properties, i.e. acceleration and melting of solid particles (in the diameter range 10-100 mu m) to spray thick coatings (from 0.1 mm to a few millimetres), or for their reactive properties. When reagents are introduced in the plasma stream, they are transformed in highly reactive radicals and/or atoms in excited states. These reactive species can form a coating with high deposition rates (similar to 100 mu m h(-1)) due to the steep gradients in the boundary layer plasma-substrate: this process is called thermal plasma-assisted chemical vapour deposition (PCVD). Without substrate and using adequate quenching, they can also form ultrafine particles, the size of which is controlled (with difficulty) by temperature during the quenching process. These PCVD processes can be used to form new chemical species on the surface of solid and molten particles in flight in the plasma jets, or on the resulting splats and between the successive passes to produce coatings with dispersed hard phases (reactive plasma spraying). It is also possible to agglomerate reactive particles (e.g. carbon and metal) a few micrometres in diameter, to achieve exothermic reactions within the particles in flight and spray carbide coatings in air. This paper presents our knowledge in these fields as follows: (1) the main characteristics of plasma d.c. and RF torches, transferred arcs and the injection of reagents and/or quenching gases; (2) the modelling problems of reactive gas flow injection; boundary layer close to the substrate; ultrafine particle synthesis with the corresponding experimental results obtained for PCVD coatings; thin film deposition by flash evaporation and ultrafine particle synthesis; and (3) the reactive plasma spraying achieved either by spraying agglomerated-particles (in the 10-50 mu m size range) where self-propagating high-temperature synthesis occurs, or by mixing a reactive gas with the plasma jet. (C) 1997 Elsevier Science S.A.