Papers by Keyword: Silicon Nitride Coating

Abstract: Silicon nitride coatings were prepared by chemical vapor deposition (CVD) method. The effect of raw precursor materials (SiH4 and NH3) ratio, gas flow amount, reaction temperature, and reaction pressure and deposition time to the microstructure, chemical compositions and crystal structures of the silicon nitride coatings are investigated. The results suggest that when the SiH4 and NH3 are used as the precursors, Ar is used as the protect gas, H2 is used as the carrier gas, the flow amount of SiH4 and NH3 is 200 sccm and 1000 sccm, the reaction pressure is 100 Pa, the reaction temperature is 900 oC and the deposition time is 30 min, the silicon nitride coatings with high deposition rate (~ 85 Å/min), small grain size (~ 0.2 µm) and high density are obtained. XRD results of the obtained silicon nitride coatings suggest their phase structure is amorphous.

Abstract: In magneto-plasma-dynamic (MPD) arcjet generators, plasma is accelerated by electromagnetic body forces. Silicon nitride reactive spraying was carried out using an MPD arcjet generator with crystal silicon rods and nitrogen gas. Because higher-velocity, higher-temperature and higher-density and larger-area plasmas are produced with the MPD arcjet generator than those with conventional thermal plasma torches, nitriding of silicon can be enhanced. A dense and uniform β-Si3N4 coating with 30 μm in thickness was formed after 200 shots at a repetitive frequency of 0.03 Hz with a discharge current of 9 kA and a substrate temperature of 700 °C. The Vickers hardness reached about 1300. Furthermore, silicon carbide and aluminum nitride sprayings were conducted with some spraying systems. All results showed that the MPD arcjet generator had high potentials for spraying.