| 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. |
- Chatterjee, M., et al.
(författare)
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Thermal barrier coatings from sol-gel-derived spray-grade Y2O3-ZrO2 microspheres
- 1993
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Ingår i: Journal of Materials Science. - : Kluwer Academic Publishers. ; 28:10, s. 2803-2807
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Tidskriftsartikel (refereegranskat)abstract
- For the development of ceramic thermal barrier coatings, spray-grade yttria-stabilized zirconia microspheres were prepared by the sol-gel technique. Oxide microspheres were obtained by calcination of the corresponding gel spheres at 1000 °C. Scanning electron microscopic and optical microscopic observations revealed the material thus obtained to have a predominantly spherical morphology and the requisite size distribution (5-50 μm). The dense, calcined microspheres showed good flowability. X-ray diffraction studies indicated the presence of the tetragonal polymorph of ZrO2 as the major phase, in addition to about 14% monoclinic ZrO2. The plasma-sprayed YSZ coatings made from the sol-gel-derived microspheres showed a further decrease in the monoclinic ZrO2 content (6%). The coatings survived 40-50 thermal cycles (30 min at 1200 °C followed by a water quench), indicating good thermal shock resistance. © 1993 Chapman & Hall.
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| 3. |
- Joshi, S. V., et al.
(författare)
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Plasma spraying of an indigenous yttria stabilized zirconia powder prepared by the sol-gel technique
- 1993
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Ingår i: Bulletin of Materials Science. - : Springer India. ; 16:1, s. 19-28
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Tidskriftsartikel (refereegranskat)abstract
- An indigenous sol-gel derived yttria-partially stabilized zirconia (Y-PSZ) powder has been characterized and its suitability for plasma spraying applications evaluated. The powder, determined to have about 5·1% yttria content, predominantly consisted of spherical particles with an average equivalent particle diameter close to 25 μm. Furthermore, it was found that the powder did not contain any particles >50 μm, which is considered the ideal upper size limit for spray-grade ceramic powders in order to ensure complete melting during spraying. The sol-gel produced powder exhibited good flow characteristics and the plasma sprayed coatings developed using this powder were also found to have excellent thermal shock resistance. The corresponding results obtained using an imported Y-PSZ powder are also presented for the purpose of comparison. © 1993 Indian Academy of Sciences.
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