Robert J. De Angelis

Zirconium oxide crystal phase: The role of the pH and time to attain the final pH for precipitation of the hydrous oxide

Precipitated hydrous zirconium oxide can be calcined to produce either a monoclinic or tetragonal product. It has been observed that the time taken to attain the final pH of the solution in contact with the precipitate plays a dominant role in determining the crystal structure of the zirconium oxide after calcination at 500 /sup 0/C. The dependence of crystal structure on the rate of precipitation is observed only in the pH range 7--11. Rapid precipitation in this pH range yields predominately monoclinic zirconia, whereas slow (8 h) precipitation produces the tetragonal phase. At pH of approximately 13.0, only the tetragonal phase is formed from both slowly and rapidly precipitated hydrous oxide. The present results, together with earlier results, show that both the pH of the supernatant liquid and the time taken to attain this pH play dominant roles in determining the crystal structure of zirconia that is formed after calcination of the hydrous oxide. The factors that determine the crystal phase are therefore imparted in a mechanism of precipitation that depends upon the pH, and it is inferred that it is the hydroxyl concentration that is the dominant factor.

Structural studies of Pt-Sn catalysts on high and low surface area alumina supports

For a series of catalysts containing 1 wt. % Pt and Sn∶Pt ratios ranging from ca. 1 to 8, the only crystalline alloy phase detected by XRD was SnPt (1∶1). The XRD intensity of lines for the SnPt (1∶1) alloy phase increase with increasing Sn∶Pt ratios, indicating the presence of unalloyed Pt in the samples containing low tin loadings.

High temperature sulfidation of six alloys

Six ferrous alloys were exposed for 100 h to a gas mixture containing 1 pct hydrogen sulfide and 3 pct steam at a temperature of 650 °C. Their relative resistances to corrosive attack were in the order: plain carbon (worst), Inconel 600, Incoloy 800, 316 stainless, 304 stainless and Armco 18SR (best).

Metallographic and chemical analyses of a plain carbon steel plate after long term service in a coal gasifier

Abstract The steel inner liner of a coal gasifier was examined. This liner had been directly exposed to a coal gasification reaction for 20 years. The microstructure was observed and the chemical composition analyzed as functions of position in the vessel. Evidence of corrosion, embrittlement, and carburization was sought. Although pronounced microstructural variations were observed in this steel liner, the chemical composition was found to be quite uniform.

Application of X-Ray Diffraction Techniques to Study the Sintering of Catalysts

An x-ray diffraction single profile analysis method is presented which allows the calculation of the particle size distribution function (PSD). This method is verified by using it to analyze simulated diffraction profiles from single, duplex, triplex, and normal distributions of particle sizes. This method is employed to study the sintering of a nickel catalyst.

Mechanical properties of a plain carbon steel plate after long term service in a coal gasifier

Abstract The steel inner liner of a coal gasifier was examined. This liner was directly exposed to a coal gasification reaction for 20 years. The mechanical properties were measured as a function of position in the vessel and these are correlated with previously reported variations of microstructure. The initial properties of the steel were estimated and compared to the final measured properties.

Metallographic analysis of a steel plate which failed in service in a coal gasifier

Abstract A material sample containing a portion of the crack that caused failure of the inner shell of a coal gasifier was examined metallographically and compared with a sample of the same material far from the region of failure. Corrosion pitting was observed on the base metal but seemed to have had no catastrophic effect. However, limited observations indicated that corrosion pitting of weld filler metal produced the failure.