Proceedings of the 12th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 9, Issue 7/8
The Laser Chemical Vapour Precipitation ( L-CVP) of Si 3 N 4 powders from mixtures of halogenated... more The Laser Chemical Vapour Precipitation ( L-CVP) of Si 3 N 4 powders from mixtures of halogenated silanes and NH3 has been studied. The reactant gases were mixed at varying position in the laser beam, thus preventing low temperature reactions The Si3N_4 .wa~ collected and separated from the waste product, NH 4 Cl, by electro~tatic preczp~ta~wn. A major problem in utilizing SiHCl 3 and SiCl 4 is their poor absorption of radzatwn from COrlasers. SF6 and SiF 4 have been explored for possible use as an inert sensitizer. Silicon can be prepared from SiH 2 C/ 2 without the use of a sensitizer. The diameter of the Si3N4 particles is typically between 15 nm and 110 nm dependent on the process conditions.
Electron spin resonance spectra have been observed and hyperfine couplings measured for radicals ... more Electron spin resonance spectra have been observed and hyperfine couplings measured for radicals prepared by reaction of aromatic nitro compounds with pentacyanocobaltate(I1). The spectra point to the formation of a coordination complex between the pentacyanocobaltate(II) and the nitro compounds with a strong spin delocalization over transition metal ion and the aromatic nitro ligand.
Abstract Thin films of several first-row transition metals on inert substrates have been subjecte... more Abstract Thin films of several first-row transition metals on inert substrates have been subjected to boronation at moderate temperatures in order to study the equilibrium compositions of metal (M) boride conversion coatings. No crystalline subborides M y B ( y ⪢1) could be obtained under the conditions employed, the lowest boride being crystalline MB (M = Fe, Co, Ni). Extended boronation yielded amorphous species MB x ( x ⪢1, increasing with time), having low diffusion rates for boron. Borided iron samples were oxidized in air at room temperature.
Particle‐precipitation‐aided chemical vapor deposition (PP‐CVD) is a modification of the conventi... more Particle‐precipitation‐aided chemical vapor deposition (PP‐CVD) is a modification of the conventional CVD process, where an aerosol is formed in the gas phase and particles are deposited on a substrate. The driving force for particle deposition is thermophoresis. The synthesis of titanium nitride (TiN) has been studied. TiN is formed on the substrate, as well as in the gas phase. At low temperature differences, only dense microstructures with equiaxed grains are observed; porous coherent layers are found in experiments where larger temperature differences are applied. Additional increase in the temperature difference only leads to loose powder deposits. In principle, the PP‐CVD process is a suitable method for the synthesis of thin porous layers of ceramics.
Kinetics of tungsten low-pressure chemical-vapor deposition using WF6 and SiH4 studied by in situ growth-rate measurements
Journal of Applied Physics, 1993
The kinetics of tungsten low-pressure chemical-vapor deposition (LPCVD) using WF6 and SiH4 have b... more The kinetics of tungsten low-pressure chemical-vapor deposition (LPCVD) using WF6 and SiH4 have been studied in a vertical hot-wall reactor equipped with a microbalance. In situ growth-rate measurements were performed by monitoring the sample weight during tungsten film deposition. The kinetics of the LPCVD process appear to be determined by the ratio of the partial pressures of SiH4 and WF6. At low SiH4/WF6 ratios, i.e., p(SiH4)/p(WF6)≤0.3, the kinetics are first and zeroth order with respect to p(SiH4) and p(WF6), respectively. At higher ratios, i.e., 0.5≤p(SiH4)/p(WF6)≤1.0, the deposition rate is second and minus first order with respect to p(SiH4) and p(WF6), respectively. In both kinetic regimes a zeroth-order dependence on p(H2) was observed. The growth rate does not vary substantially in the temperature range 200–400 °C. Maximum rate values are observed near 300 °C. An attempt has been made to interpret the observed kinetic behavior in terms of a Langmuir–Hinshelwood model. T...
Proceedings of the 12th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 9, Issue 7/8
The Laser Chemical Vapour Precipitation ( L-CVP) of Si 3 N 4 powders from mixtures of halogenated... more The Laser Chemical Vapour Precipitation ( L-CVP) of Si 3 N 4 powders from mixtures of halogenated silanes and NH3 has been studied. The reactant gases were mixed at varying position in the laser beam, thus preventing low temperature reactions The Si3N_4 .wa~ collected and separated from the waste product, NH 4 Cl, by electro~tatic preczp~ta~wn. A major problem in utilizing SiHCl 3 and SiCl 4 is their poor absorption of radzatwn from COrlasers. SF6 and SiF 4 have been explored for possible use as an inert sensitizer. Silicon can be prepared from SiH 2 C/ 2 without the use of a sensitizer. The diameter of the Si3N4 particles is typically between 15 nm and 110 nm dependent on the process conditions.
Electron spin resonance spectra have been observed and hyperfine couplings measured for radicals ... more Electron spin resonance spectra have been observed and hyperfine couplings measured for radicals prepared by reaction of aromatic nitro compounds with pentacyanocobaltate(I1). The spectra point to the formation of a coordination complex between the pentacyanocobaltate(II) and the nitro compounds with a strong spin delocalization over transition metal ion and the aromatic nitro ligand.
Abstract Thin films of several first-row transition metals on inert substrates have been subjecte... more Abstract Thin films of several first-row transition metals on inert substrates have been subjected to boronation at moderate temperatures in order to study the equilibrium compositions of metal (M) boride conversion coatings. No crystalline subborides M y B ( y ⪢1) could be obtained under the conditions employed, the lowest boride being crystalline MB (M = Fe, Co, Ni). Extended boronation yielded amorphous species MB x ( x ⪢1, increasing with time), having low diffusion rates for boron. Borided iron samples were oxidized in air at room temperature.
Particle‐precipitation‐aided chemical vapor deposition (PP‐CVD) is a modification of the conventi... more Particle‐precipitation‐aided chemical vapor deposition (PP‐CVD) is a modification of the conventional CVD process, where an aerosol is formed in the gas phase and particles are deposited on a substrate. The driving force for particle deposition is thermophoresis. The synthesis of titanium nitride (TiN) has been studied. TiN is formed on the substrate, as well as in the gas phase. At low temperature differences, only dense microstructures with equiaxed grains are observed; porous coherent layers are found in experiments where larger temperature differences are applied. Additional increase in the temperature difference only leads to loose powder deposits. In principle, the PP‐CVD process is a suitable method for the synthesis of thin porous layers of ceramics.
Kinetics of tungsten low-pressure chemical-vapor deposition using WF6 and SiH4 studied by in situ growth-rate measurements
Journal of Applied Physics, 1993
The kinetics of tungsten low-pressure chemical-vapor deposition (LPCVD) using WF6 and SiH4 have b... more The kinetics of tungsten low-pressure chemical-vapor deposition (LPCVD) using WF6 and SiH4 have been studied in a vertical hot-wall reactor equipped with a microbalance. In situ growth-rate measurements were performed by monitoring the sample weight during tungsten film deposition. The kinetics of the LPCVD process appear to be determined by the ratio of the partial pressures of SiH4 and WF6. At low SiH4/WF6 ratios, i.e., p(SiH4)/p(WF6)≤0.3, the kinetics are first and zeroth order with respect to p(SiH4) and p(WF6), respectively. At higher ratios, i.e., 0.5≤p(SiH4)/p(WF6)≤1.0, the deposition rate is second and minus first order with respect to p(SiH4) and p(WF6), respectively. In both kinetic regimes a zeroth-order dependence on p(H2) was observed. The growth rate does not vary substantially in the temperature range 200–400 °C. Maximum rate values are observed near 300 °C. An attempt has been made to interpret the observed kinetic behavior in terms of a Langmuir–Hinshelwood model. T...
Uploads
Papers by P. Van Der Put