| 1. |
- Joshi, S. V., et al.
(författare)
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Effect of quenching conditions on particle formation and growth in thermal plasma synthesis of fine powders
- 1990
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Ingår i: Plasma Chemistry and Plasma Processing. - : Kluwer Academic Publishers-Plenum Publishers. ; 10:2, s. 339-358
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Tidskriftsartikel (refereegranskat)abstract
- The vapor-phase synthesis of ultrafine powders in reactive thermal plasma systems is studied. A mathematical model is developed to determine the effect of quenching conditions on the size characteristics of powders produced. The particle nucleation is considered to be due to both condensation of product vapor and surface reaction between adsorbed reactant species. The particle growth is considered to be exclusively due to further condensation of product vapor. Numerical predictions on powder formation are explored through a case study for the synthesis of zinc oxide powders from zinc vapor and oxygen carried in argon gas. The results of the present srudy indicate that the size characteristics of plasma-produced powders can be significantly enhanced by gradual, regulated quenching, as opposed to the rapid quenching conventionally used in the past. The results further indicate that distribution of the quench gas along the reactor provides an effective means to accomplish the much desired control over the powder properties. © 1990 Plenum Publishing Corporation.
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| 2. |
- Joshi, S. V., et al.
(författare)
-
Knudsen effect on plasma-particle mass transfer. I. Formulation and application to self-diffusion
- 1986
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Ingår i: Plasma Chemistry and Plasma Processing. - : Kluwer Academic Publishers-Plenum Publishers. ; 6:3, s. 281-298
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Tidskriftsartikel (refereegranskat)abstract
- The Knudsen effect on mass transfer between a plasma gas and a small particle is investigated. A predictive model is developed by incorporating the Z-potential approach into the jump theory. The predictions of the model are explored through a case study. The results indicate that the Knudsen effect is significant and depends strongly on the particle size and the surface conditions. The plasma and the particle surface temperatures are also found to be determining factors. Under certain conditions, it is observed that the Knudsen effect can enhance the plasma-particle mass transfer, contrary to the predictions of the previous near-isothermal models. © 1986 Plenum Publishing Corporation.
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| 3. |
- Joshi, S. V., et al.
(författare)
-
Particle-gas mass transfer under plasma conditions
- 1986
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Ingår i: International Journal of Heat and Mass Transfer. ; 29:10, s. 1565-1573
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Tidskriftsartikel (refereegranskat)abstract
- A simple analytical method is proposed for particle-gas mass transfer calculations under plasma conditions. This method, called the Z-potential method, fully accounts for the temperature variation of the gas transport properties while permitting use of the convenient isothermal expression Sh = 2.0. The Z-potential approach is also found to be extremely useful in ascertaining the Knudsen discontinuum effect on mass transfer between the plasma gas and a small particle. A predictive model for the Knudsen effect, developed by combining the Z-potential approach with the jump theory, is illustrated in detail by means of a case study on a nitrogen plasma system. © 1986.
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| 4. |
- Joshi, S. V., et al.
(författare)
-
The integral mean diffusivity for particle-gas mass transfer calculations under thermal plasma conditions
- 1985
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Ingår i: Plasma Chemistry and Plasma Processing. - : Kluwer Academic Publishers-Plenum Publishers. ; 5:2, s. 143-161
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Tidskriftsartikel (refereegranskat)abstract
- A new integral mean diffusivity is proposed for the calculation of the mass transfer rate around a small particle immersed in a thermal plasma gas. Analogous to the integral mean thermal conductivity widely used for the corresponding heat transfer calculations, the integral mean diffusivity greatly facilitates the use of the convenient isothermal correlation, Sh=2.0, for the gas-particle mass transfer calculations. The calculation method accounts for both ordinary molecular diffusion and thermal diffusion. The latter has been found to play a significant role under thermal plasma conditions. The use of the integral mean diffusivity is illustrated with an example calculation on an Ar-He plasma system. © 1985 Plenum Publishing Corporation.
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