Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00268.X
N. Hirosaki, A. Okada
The flexural strength of Si{sub 3}N{sub 4} having an as-sintered surface was measured to investigate the effects of the sintering atmosphere on the surface. The as-sintered strength of Si{sub 3}N{sub 4} fires in 0.1 MPa N{sub 2} (pressureless sintering) degraded to 39% of its ground strength as a result of near-surface voids formed by thermal decomposition reactions between Si{sub 3}N{sub 4} and additive oxides. The as-sintered strength of Si{sub 3}N{sub 4} fired at 70 MPa N{sub 2} (gas pressure sintering), however, was shown to retain as much as 76% of its ground strength. This result seems to indicate that high-pressure N{sub 2} gas suppressed the void formation by reducing the decomposition reactions. Gas pressure sintering was effective in avoiding thermal decomposition and in maintaining a higher as-sintered strength.
{"title":"Effects of N sub 2 gas pressure sintering on the surface and strength of Si sub 3 N sub 4","authors":"N. Hirosaki, A. Okada","doi":"10.1111/J.1551-2916.1988.TB00268.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00268.X","url":null,"abstract":"The flexural strength of Si{sub 3}N{sub 4} having an as-sintered surface was measured to investigate the effects of the sintering atmosphere on the surface. The as-sintered strength of Si{sub 3}N{sub 4} fires in 0.1 MPa N{sub 2} (pressureless sintering) degraded to 39% of its ground strength as a result of near-surface voids formed by thermal decomposition reactions between Si{sub 3}N{sub 4} and additive oxides. The as-sintered strength of Si{sub 3}N{sub 4} fired at 70 MPa N{sub 2} (gas pressure sintering), however, was shown to retain as much as 76% of its ground strength. This result seems to indicate that high-pressure N{sub 2} gas suppressed the void formation by reducing the decomposition reactions. Gas pressure sintering was effective in avoiding thermal decomposition and in maintaining a higher as-sintered strength.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78842910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00266.X
J. Sparks, D. Tucker
In an attempt to obtain pure mullite after firing, the spinnability of an alumina-silica gel was examined by hydrolizing an aluminum alkoxide and then an aluminum and silicon alkoxide mixture. The production of pure mullite was successful and the precursor alumina-silica sol was found to be spinnable. The stability of the spun fiber is being studied.
{"title":"Production of mullite by the sol-gel method","authors":"J. Sparks, D. Tucker","doi":"10.1111/J.1551-2916.1988.TB00266.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00266.X","url":null,"abstract":"In an attempt to obtain pure mullite after firing, the spinnability of an alumina-silica gel was examined by hydrolizing an aluminum alkoxide and then an aluminum and silicon alkoxide mixture. The production of pure mullite was successful and the precursor alumina-silica sol was found to be spinnable. The stability of the spun fiber is being studied.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72675273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00254.X
S. Awasthi, J. L. Wood
{"title":"C/C Composite Materials for Aircraft Brakes","authors":"S. Awasthi, J. L. Wood","doi":"10.1111/J.1551-2916.1988.TB00254.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00254.X","url":null,"abstract":"","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90400262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00257.X
S. Mukherjee, J. Cordaro, J. C. Debsikdar
The pore structures and microstructures of silica gel monoliths derived from the polycondensation of tetramethoxysilane (TMOS) in basic pH were characterized after various stages of sintering, using N{sub 2} gas adsorption-desorption, mercury porosimetry, and TEM. Gels dried by supercritical drying, i.e., aerogels and gels dried slowly in air have different pore structures and sinter with contrasting results when heat-treated under identical conditions. The air-dried gels do not sinter to full density and exhibit bloating on heating to high temperatures (1,100{degree}C), whereas under the same condition aerogels sinter to dense, transparent glass without bloating. Transmission electron microscopy shows that the microstructure of gels is composed of 5- to 10-nm primary spherical particles which clustered to form large (100 nm) spherical aggregates loosely bound to each other. In aerogels, two types of porosity exit: macroporosity and ultraporosity.
{"title":"Pore structures and microstructures of silica gel monoliths at different stages of sintering","authors":"S. Mukherjee, J. Cordaro, J. C. Debsikdar","doi":"10.1111/J.1551-2916.1988.TB00257.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00257.X","url":null,"abstract":"The pore structures and microstructures of silica gel monoliths derived from the polycondensation of tetramethoxysilane (TMOS) in basic pH were characterized after various stages of sintering, using N{sub 2} gas adsorption-desorption, mercury porosimetry, and TEM. Gels dried by supercritical drying, i.e., aerogels and gels dried slowly in air have different pore structures and sinter with contrasting results when heat-treated under identical conditions. The air-dried gels do not sinter to full density and exhibit bloating on heating to high temperatures (1,100{degree}C), whereas under the same condition aerogels sinter to dense, transparent glass without bloating. Transmission electron microscopy shows that the microstructure of gels is composed of 5- to 10-nm primary spherical particles which clustered to form large (100 nm) spherical aggregates loosely bound to each other. In aerogels, two types of porosity exit: macroporosity and ultraporosity.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81391795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00260.X
P. Nordine, R. Schiffman
Evaporation of aluminum oxide was studied from 1,800 to 2,327 K by laser-induced fluorescence (LIF) detection of Al atom vapor over sapphire and alumina spheres that were levitated in an argon gas jet and heated with a continuous wave CO{sub 2} laser. Optical properties were determined from apparent specimen temperatures measured with an optical pyrometer and true temperatures deduced from the LIF intensity versus temperature measurements using the known temperature dependence of the Al atom vapor concentration in equilibrium with Al{sub 2}O{sub 3}. The effects of impurities and dissolved oxygen on the high-temperature optical properties of aluminum oxide were discussed.
{"title":"Containerless laser-induced flourescence study of vaporization and optical properties for sapphire and alumina","authors":"P. Nordine, R. Schiffman","doi":"10.1111/J.1551-2916.1988.TB00260.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00260.X","url":null,"abstract":"Evaporation of aluminum oxide was studied from 1,800 to 2,327 K by laser-induced fluorescence (LIF) detection of Al atom vapor over sapphire and alumina spheres that were levitated in an argon gas jet and heated with a continuous wave CO{sub 2} laser. Optical properties were determined from apparent specimen temperatures measured with an optical pyrometer and true temperatures deduced from the LIF intensity versus temperature measurements using the known temperature dependence of the Al atom vapor concentration in equilibrium with Al{sub 2}O{sub 3}. The effects of impurities and dissolved oxygen on the high-temperature optical properties of aluminum oxide were discussed.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83882244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00267.X
F. Kirkbir, H. Komiyama
Submicrometer, highly porous (BET area <320 m{sup 2}/g) TiO{sub 2} powders were synthesized by vapor-phase hydrolysis of titanium tetraisopropoxide, Ti(OPr{sup i}){sub 4}, in a tubular-flow reactor under atmospheric pressure at 443 to 783 K. Particle size increased with increasing inlet Ti(OPr{sup i}){sub 4} concentration and with decreasing inlet H{sub 2}O concentration and temperature. It is suggested that particle formation and growth occurred in a very short residence time in the reactor. Almost all of the Ti(OPr{sup i}){sub 4} could be converted to TiO{sub 2} powder with negligible deposition inside the reactor, indicating the high efficiency of the process.
{"title":"Continuous production of fine TiO sub 2 powders by vapor-phase hydrolysis of titanium tetraisopropoxide","authors":"F. Kirkbir, H. Komiyama","doi":"10.1111/J.1551-2916.1988.TB00267.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00267.X","url":null,"abstract":"Submicrometer, highly porous (BET area <320 m{sup 2}/g) TiO{sub 2} powders were synthesized by vapor-phase hydrolysis of titanium tetraisopropoxide, Ti(OPr{sup i}){sub 4}, in a tubular-flow reactor under atmospheric pressure at 443 to 783 K. Particle size increased with increasing inlet Ti(OPr{sup i}){sub 4} concentration and with decreasing inlet H{sub 2}O concentration and temperature. It is suggested that particle formation and growth occurred in a very short residence time in the reactor. Almost all of the Ti(OPr{sup i}){sub 4} could be converted to TiO{sub 2} powder with negligible deposition inside the reactor, indicating the high efficiency of the process.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79759072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00270.X
T. Umeda, H. Kozuka, S. Sakka
High-{Tc} superconducting oxide fibers were fabricated by the sol-gel method. An aqueous solution of metal acetates was concentrated to form a viscous sol, from which gel fibers were spun. The gel fibers, 5 to 1,000 {mu}m in diameter, were converted to ceramic fibers by heating to 900{degree}C. The fired fibers ({Tc}(onset) of 94 K and {Tc} (end) of 62.2 K) were rough and had porous microstructures.
{"title":"Fabrication of YBa sub 2 Cu sub 3 O sub 7 minus. delta. superconducting fibers by the sol-gel method","authors":"T. Umeda, H. Kozuka, S. Sakka","doi":"10.1111/J.1551-2916.1988.TB00270.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00270.X","url":null,"abstract":"High-{Tc} superconducting oxide fibers were fabricated by the sol-gel method. An aqueous solution of metal acetates was concentrated to form a viscous sol, from which gel fibers were spun. The gel fibers, 5 to 1,000 {mu}m in diameter, were converted to ceramic fibers by heating to 900{degree}C. The fired fibers ({Tc}(onset) of 94 K and {Tc} (end) of 62.2 K) were rough and had porous microstructures.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90218670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00253.X
S. Schneider, David R. Bradley
{"title":"The Standardization of Advanced Ceramics","authors":"S. Schneider, David R. Bradley","doi":"10.1111/J.1551-2916.1988.TB00253.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00253.X","url":null,"abstract":"","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85160551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00271.X
G. E. Peterson, R. P. Stawicki, U. Paek, Princeton Nj T-Erc
To ascertain the practical value of superconducting ceramics in circuits, the resistance of a superconducting strip was compared with a copper strip over the range 0.5 to 20 MHz.
{"title":"Comparison of the low-temperature resistance of high Tc superconductors and copper at 0. 5 to 20 MHz","authors":"G. E. Peterson, R. P. Stawicki, U. Paek, Princeton Nj T-Erc","doi":"10.1111/J.1551-2916.1988.TB00271.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00271.X","url":null,"abstract":"To ascertain the practical value of superconducting ceramics in circuits, the resistance of a superconducting strip was compared with a copper strip over the range 0.5 to 20 MHz.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81193876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1111/J.1551-2916.1988.TB00259.X
Chude Feng, W. Schulze
The synthesized monosized PSN complex precursor powder was produced using the methods of the controlled hydrolysis of Nb(OC{sub 2}H{sub 5}){sub 5} and the growth of scandium and lead carbonates on the as-hydrolyzed Nb{sub 2}O{sub 5} particle surface. Calcining the carbonates to oxides and sintering at different temperatures with various cooling rates produced dense ceramics. The relation between dielectric relaxation character and structural ordering of the sintered PSN ferroelectric ceramics was investigated.
{"title":"Characterization of lead scandium niobate ceramics prepared by precipitation method","authors":"Chude Feng, W. Schulze","doi":"10.1111/J.1551-2916.1988.TB00259.X","DOIUrl":"https://doi.org/10.1111/J.1551-2916.1988.TB00259.X","url":null,"abstract":"The synthesized monosized PSN complex precursor powder was produced using the methods of the controlled hydrolysis of Nb(OC{sub 2}H{sub 5}){sub 5} and the growth of scandium and lead carbonates on the as-hydrolyzed Nb{sub 2}O{sub 5} particle surface. Calcining the carbonates to oxides and sintering at different temperatures with various cooling rates produced dense ceramics. The relation between dielectric relaxation character and structural ordering of the sintered PSN ferroelectric ceramics was investigated.","PeriodicalId":7260,"journal":{"name":"Advanced Ceramic Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79296172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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