The effects of substrate rotation on thermal plasma chemical vapor deposition of diamond

Asmann, Marcus; Borges, C. F. M.; Heberlein, J.; Pfender, E.

doi:10.1016/s0257-8972(01)01176-8

Cited by 5 publications

(2 citation statements)

References 16 publications

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“…2 is capable of achieving substrate melting and splat directional solidification for most feedstock material and substrate combinations. Note that the proposed process is similar to, but different from, Thermal Plasma Chemical Vapor Deposition (TPCVD) in which the thermal plasma-heated precursors evaporated, decomposed and reacted in the boundary layer over the substrate or on the substrate to form the films [20,21]. Figure 2 also shows a schematic of splat solidification with substrate melting.…”

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confidence: 99%

Toward the Achievement of Substrate Melting and Controlled Solidification in Thermal Spraying

Zhang

Wei

Zhang

et al. 2007

Plasma Chem Plasma Process

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The substrate is usually kept at a distant location in traditional thermal spraying, and substrate melting, which can improve splat adhesion usually does not happen. By moving the substrate close to the plasma flame and attaching a temperature control device to the backside of the substrate, as well as by additional heating from the molten droplets, substrate melting may occur and directional splat solidification becomes possible. In this proposed design, the substrate temperature is controlled by spray distance, flame temperature and initial substrate temperature. The variations of particle in-flight characteristics and contact interface temperature on spray distance are investigated. Optimal operating conditions are determined.heat transfer coefficient, W m -2 K -1 h i h fus Latent heat of fusion, J kg -1 Ja Jakob number, Ja = c ps (T f -T sub )/h fus k Thermal conductivity, W m -1 K -1 L v Latent heat of vaporization, J kg -1 L m Latent heat of melting, J kg -1 _ m v Mass melting rate, kg s -1 P Pressure, Pa Pr Prandtl number, Pr = m/a _ Q Energy input due to particles, W m -3 r, R Radial coordinate, m Re Reynolds number, Re = qVd/l St Stefan number, St = c pl (T p -T f )/h f t Time, s T Temperature, K T B Splat bottom temperature, K T m Melting temperature, K e u ! Favre average velocity vector, m s -1 u 0 ! Velocity fluctuation, m s -1 V Particle speed, m s -1 V p ! Particle velocity vector, m s -1WeWeber number, We = qV 2 d/r x,y,z Coordinate, m Y i Mass fraction of the i th speciesGreek Symbols a Thermal diffusivity, m 2 s -1 h Coordinate in the circumferential direction D Temperature factor e Emissivity U Viscous dissipation, kg m -3 s -1 l Viscosity, kg m -1 s -1 l t Turbulent viscosity, kg m -1 s -1 m Kinetic viscosity, m 2 s -1 n Flattening ratio q Density, kg m -3 r Surface tension, N m -1 r s Stefan-Boltzmann constant, W m -2 K -4

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confidence: 99%

Toward the Achievement of Substrate Melting and Controlled Solidification in Thermal Spraying

Zhang

Wei

Zhang

et al. 2007

Plasma Chem Plasma Process

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“…The heat transfer [16,28,[30][31][32] between the plasma jet the rotating silica rod has been simulated using a commercial CDF code Fluent © . Figure 9 shows the two-dimensional geometry and boundaries adopted.…”

Section: Heat Transfer Modelmentioning

confidence: 99%

Study of the thermal plasma etching at atmospheric pressure on silica rods

Benocci¹,

Esena²,

Galassi³

et al. 2004

J. Phys. D: Appl. Phys.

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Etching of SiO 2 rods has been obtained with a dc torch with argon as the process gas in an air environment at atmospheric pressure; the high temperature of the plasma jet causes vaporization of the exposed area. The apparatus and torch operative parameters have been set up to obtain a depth etch rate of up to 0.6 mm min −1 corresponding to 0.826 g min −1 .An enthalpy probe has been employed to monitor the plasma conditions before the thermal plasma etching process and from the experimental etch rate a surface rod temperature of T sur = 2057 K has been derived. Etching has been obtained with uniformity over the entire exposed area with peak to peak differences below 1%.The plasma to rod heat transfer has been simulated using a commercial CFD code Fluent © . The model consists of a non-steady two-dimensional simulation for a compressible turbulent fluid, with an adapted grid calculation. Boundary conditions have been set out using the enthalpy probe plasma jet map. In particular for the flow, the continuity equation for chemical species, the species transport equations (Fick's Law), the momentum conservation equations, the energy equation and the turbulent kinetic energy have been solved. In the solid regions the convective energy transfer due to the rotational motion of the rod, the conduction and radiation energies have been considered. The heat transfer between the fluid and the silica walls (continuity temperature between the fluid and the solid) accounts for the energy loss due to surface radiation (q r ) and vaporization (q v ) obtained from experimental data.A rod surface temperature of 2057 K obtained from experimental etch rate data agrees well with the calculated temperature obtained using Fluent © (T sim = 2010 K).

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