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Texture and sinterability of MgO powders
CERAMICS
INTERNATIONAL,
Vol
123
11, n 4, ,985
CERAMICS INTERNATIONAL Vol. I-XI
ABSTRACTSOFPAPERS Vol. I, January/December,
1975
REACTIVITY OF ULTRAFINE-Ti02 POWDERS WITH BaCOj
(ANATASE)
behaviour on heating of MgO derived from a well-oriented natural brucite, agree with the analysis of the initial stages of sintering published by Pampuch and later by Exner, Petzow, and Wellner.
Yoko Suyama and Akio Kato The solid-state reaction between anatase-TiOz powders with various particle-size distributions and BaCO3, was investigated by means of TGA in O2 and in COZ. The reactivity of TiO2 powders increased remarkably as the particle size grew smaller than 0.2 pm. TG curves in CO2 differed from those in OZ. In C02, a high reactivity was observed at around 620% and the reactivity increased as the size of Ti02-particles decreased. The beginning and completion temperatures of the reaction in CO: were higher by about 1OO’C than those in 02. The difference of TG curves between the two atmospheres was interpreted in terms of a layered interface model. The particle-size distribution curve of the BaTiOs powder produced was parallel to that of the starting Ti02 powder.
QUANTITATIVE USE OF GUINIER X-RAY CAMERAS IN SOLID STATE REACTION KINETICS D.E. Clark. G.J. Scott and L.L. Hench Monochromated Guinier-deWolff and Guinier-Lenne x-ray powder cameras and a scanning microdensitometer have been combined into a data system for the study of solid state reaction kinetics. Application of the room-temperature and high temperature cameras to both interface-controlled and diffusion-controlled kinetics is discussed. A graphical analysis method is presented.
WETTING OF BARIUM HEXAFERRITE METALS PHASE RELATIONSHIPS AND HfOz-NdzOs
IN THE SYSTEMS Hf02-Laz03
P. Duran Phase relationships were studied in the systems HfOz-La203 and Hf02-Nd203 at temperatures between 1,300’C to 2,300%. The formation of the pyrochlore structure compounds LazHfzO, (a = 10.779 A) and Nd2Hf20: (a = 10.629 A) was found. Limits were established for the range of the single-phase and two phase regions of the solid solutions based on Hf02, La2Hf20,, Nd2Hf20-, La207 and Nd203. Based on experimental evidence obtained by X-ray diffraction and using precision lattice parameters, phase diagrams for the systems hafnialanthana and hafnia-neodimia are suggested.
TEXTURE AND SINTERABILITY R. Pampuch,
OF MgO POWDERS
Z. Librant and J. Piekarczyk
Characterization of MgO powders obtained by thermal decomposition of spectrally-pure magnesium hydroxide, magnesium-ammonium carbonate, and magnesium oxalate at 350°-1000°C, in terms of the crystallite size, lattice microstrains, and texture. The composition of the systems was checked by X-ray diffraction and IF&spectrography. The behaviour during heating and the final microstructure of sintered ceramic bodies have been shown to be a function of the initial texture of the powders which is due to the different mechanism of decomposition of the particular starting compounds The results, supported by parallel observations of
A. Passerone,
BY MOLTEN
E. Biagini and V. Lorenzelli
The interaction between molten metals and the sintered magnetic oxide BaFelzOls has been studied in order to determine its wettability. Pure copper, silver and silver-zinc alloys, insofar as they are oxygen-active are the metals considered. The pure metals do not wet the ferrite. Introduction of zinc into silver results in a strong interaction between liquid and the ferrite thus giving a marked decrease of the contact angle. Coating the ferrite with an intermediate surface-active metal which forms a solid solution with the molten metal results in complete spreading if the temperature, time of contact and thickness of the deposited metal are adequately controlled.
EFFECT OF GLAZE ON STRENGTH PORCELAIN
OF HIGH-TENSION
M. Haberko and K. Haberko Seventy glazes of different compositions were applied to high alumina porcelain body. Reaction between a glaze and the body was studied. Three types of an intermediate zone were found. Phases crystallizing at the glaze- body contact were determined. In overlying glaze layers cristobalite and quartz grains were observed. No correlation was found between the type and thickness of the intermediate layer and tensile strength of the glazed test samples, but a strong correlation existed between cristobalite and quartz content in a glaze layer and the tensile strength of the glazed test samples.
INTERNATIONAL,
Vol
123
11, n 4, ,985
CERAMICS INTERNATIONAL Vol. I-XI
ABSTRACTSOFPAPERS Vol. I, January/December,
1975
REACTIVITY OF ULTRAFINE-Ti02 POWDERS WITH BaCOj
(ANATASE)
behaviour on heating of MgO derived from a well-oriented natural brucite, agree with the analysis of the initial stages of sintering published by Pampuch and later by Exner, Petzow, and Wellner.
Yoko Suyama and Akio Kato The solid-state reaction between anatase-TiOz powders with various particle-size distributions and BaCO3, was investigated by means of TGA in O2 and in COZ. The reactivity of TiO2 powders increased remarkably as the particle size grew smaller than 0.2 pm. TG curves in CO2 differed from those in OZ. In C02, a high reactivity was observed at around 620% and the reactivity increased as the size of Ti02-particles decreased. The beginning and completion temperatures of the reaction in CO: were higher by about 1OO’C than those in 02. The difference of TG curves between the two atmospheres was interpreted in terms of a layered interface model. The particle-size distribution curve of the BaTiOs powder produced was parallel to that of the starting Ti02 powder.
QUANTITATIVE USE OF GUINIER X-RAY CAMERAS IN SOLID STATE REACTION KINETICS D.E. Clark. G.J. Scott and L.L. Hench Monochromated Guinier-deWolff and Guinier-Lenne x-ray powder cameras and a scanning microdensitometer have been combined into a data system for the study of solid state reaction kinetics. Application of the room-temperature and high temperature cameras to both interface-controlled and diffusion-controlled kinetics is discussed. A graphical analysis method is presented.
WETTING OF BARIUM HEXAFERRITE METALS PHASE RELATIONSHIPS AND HfOz-NdzOs
IN THE SYSTEMS Hf02-Laz03
P. Duran Phase relationships were studied in the systems HfOz-La203 and Hf02-Nd203 at temperatures between 1,300’C to 2,300%. The formation of the pyrochlore structure compounds LazHfzO, (a = 10.779 A) and Nd2Hf20: (a = 10.629 A) was found. Limits were established for the range of the single-phase and two phase regions of the solid solutions based on Hf02, La2Hf20,, Nd2Hf20-, La207 and Nd203. Based on experimental evidence obtained by X-ray diffraction and using precision lattice parameters, phase diagrams for the systems hafnialanthana and hafnia-neodimia are suggested.
TEXTURE AND SINTERABILITY R. Pampuch,
OF MgO POWDERS
Z. Librant and J. Piekarczyk
Characterization of MgO powders obtained by thermal decomposition of spectrally-pure magnesium hydroxide, magnesium-ammonium carbonate, and magnesium oxalate at 350°-1000°C, in terms of the crystallite size, lattice microstrains, and texture. The composition of the systems was checked by X-ray diffraction and IF&spectrography. The behaviour during heating and the final microstructure of sintered ceramic bodies have been shown to be a function of the initial texture of the powders which is due to the different mechanism of decomposition of the particular starting compounds The results, supported by parallel observations of
A. Passerone,
BY MOLTEN
E. Biagini and V. Lorenzelli
The interaction between molten metals and the sintered magnetic oxide BaFelzOls has been studied in order to determine its wettability. Pure copper, silver and silver-zinc alloys, insofar as they are oxygen-active are the metals considered. The pure metals do not wet the ferrite. Introduction of zinc into silver results in a strong interaction between liquid and the ferrite thus giving a marked decrease of the contact angle. Coating the ferrite with an intermediate surface-active metal which forms a solid solution with the molten metal results in complete spreading if the temperature, time of contact and thickness of the deposited metal are adequately controlled.
EFFECT OF GLAZE ON STRENGTH PORCELAIN
OF HIGH-TENSION
M. Haberko and K. Haberko Seventy glazes of different compositions were applied to high alumina porcelain body. Reaction between a glaze and the body was studied. Three types of an intermediate zone were found. Phases crystallizing at the glaze- body contact were determined. In overlying glaze layers cristobalite and quartz grains were observed. No correlation was found between the type and thickness of the intermediate layer and tensile strength of the glazed test samples, but a strong correlation existed between cristobalite and quartz content in a glaze layer and the tensile strength of the glazed test samples.