Pub Date : 2003-10-01DOI: 10.1179/174327613X13789817049900
A. El-Kheshen
Abstract A series of glass/ceramic composites were prepared from pyrex borosilicate glass with silica. The effects of 15 vol.-% alumina addition on cristobalite formation in this system have been studied. Cristobalite formation in the composites has been found to decrease with addition of alumina, which may be attributed to a strong coupling reaction between Al3+ from alumina and K+ from pyrex borosilicate glass. The resulting glass/ceramic composites containing alumina have low thermal expansion coefficient owing to the presence of a lower amount of cristobalite in the glass matrix. The formation of cristobalite limits the efficiency of the ceramic substrate when used in circuit boards.
{"title":"Effect of alumina addition on properties of glass/ceramic composite","authors":"A. El-Kheshen","doi":"10.1179/174327613X13789817049900","DOIUrl":"https://doi.org/10.1179/174327613X13789817049900","url":null,"abstract":"Abstract A series of glass/ceramic composites were prepared from pyrex borosilicate glass with silica. The effects of 15 vol.-% alumina addition on cristobalite formation in this system have been studied. Cristobalite formation in the composites has been found to decrease with addition of alumina, which may be attributed to a strong coupling reaction between Al3+ from alumina and K+ from pyrex borosilicate glass. The resulting glass/ceramic composites containing alumina have low thermal expansion coefficient owing to the presence of a lower amount of cristobalite in the glass matrix. The formation of cristobalite limits the efficiency of the ceramic substrate when used in circuit boards.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131450728","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 : 2003-10-01DOI: 10.1179/174327613X13789817049865
M. Kakade, S. Ramanathan, P. De
Abstract Lanthanum strontium manganite La0·84Sr0·16MnO3 (LSM)powder was prepared by combustion synthesis, using a concentrated solution of nitrates of lanthanum, strontium, and manganese as oxidiser, and citric acid as fuel. The as formed powder was found to be crystalline LSM consisting of porous agglomerates of fine particles, and exhibited about 7% total weight loss on heating up to 1100 °C. Dispersion conditions for wet grinding of the powder agglomerates calcined at 1100 °C were evaluated from zeta potential and viscositystudies. A maximum zeta potential of - 35 mV was noted at a pH of 11, while pseudoplasticity of the slurry decreased with decreasing solid concentration. Powder with d50 of around 3 μm and free of agglomerates of size greater than 10 μm was formed by wet grinding. Further calci nation of this powder at 1350 °C improved the solids loading in the slurry. The tape cast slurry composition was optimised for minimum content of binder, plasticiser, and water with acceptable pseudoplasticity to form flexible and flat tapes. The dried tapes cut to required sizes were subjected to controlled binder burnout followed by sintering in the range 1350-1450 °C. The sintered flat specimens exhibited densities in the range 65-80% of theoretical, and open porosities in the range 35-20%, with a homogeneous distribution of pore phase in the matrix.
{"title":"Combustion synthesis, powder treatment, dispersion and tape casting of lanthanum strontium manganite","authors":"M. Kakade, S. Ramanathan, P. De","doi":"10.1179/174327613X13789817049865","DOIUrl":"https://doi.org/10.1179/174327613X13789817049865","url":null,"abstract":"Abstract Lanthanum strontium manganite La0·84Sr0·16MnO3 (LSM)powder was prepared by combustion synthesis, using a concentrated solution of nitrates of lanthanum, strontium, and manganese as oxidiser, and citric acid as fuel. The as formed powder was found to be crystalline LSM consisting of porous agglomerates of fine particles, and exhibited about 7% total weight loss on heating up to 1100 °C. Dispersion conditions for wet grinding of the powder agglomerates calcined at 1100 °C were evaluated from zeta potential and viscositystudies. A maximum zeta potential of - 35 mV was noted at a pH of 11, while pseudoplasticity of the slurry decreased with decreasing solid concentration. Powder with d50 of around 3 μm and free of agglomerates of size greater than 10 μm was formed by wet grinding. Further calci nation of this powder at 1350 °C improved the solids loading in the slurry. The tape cast slurry composition was optimised for minimum content of binder, plasticiser, and water with acceptable pseudoplasticity to form flexible and flat tapes. The dried tapes cut to required sizes were subjected to controlled binder burnout followed by sintering in the range 1350-1450 °C. The sintered flat specimens exhibited densities in the range 65-80% of theoretical, and open porosities in the range 35-20%, with a homogeneous distribution of pore phase in the matrix.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128298277","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 : 2003-10-01DOI: 10.1179/096797803225005016
R. A. Rocha, E. Muccillo
Abstract Nanocrystalline gadolinia doped ceria powder was prepared by a combustion synthesis process using polyvinyl alcohol as fuel, with the aim of obtaining nanosized crystallites of this solid solution with high specific surface area. The structures of the polymer gel and the calcined materials were investigated by Fourier transform infrared spectroscopy. Residual carbon content and specific surface area determinations were carried out on calcined powders. Microstructural characterisation was done by X-ray diffractometry and scanning electron microscopy. The results demonstrate that nanocrystalline particles of the solid solution can be prepared with low carbon content and high specific surface area by this one step synthesis technique.
{"title":"Preparation of nanocrystalline gadolinia doped ceria powders by combustion synthesis process","authors":"R. A. Rocha, E. Muccillo","doi":"10.1179/096797803225005016","DOIUrl":"https://doi.org/10.1179/096797803225005016","url":null,"abstract":"Abstract Nanocrystalline gadolinia doped ceria powder was prepared by a combustion synthesis process using polyvinyl alcohol as fuel, with the aim of obtaining nanosized crystallites of this solid solution with high specific surface area. The structures of the polymer gel and the calcined materials were investigated by Fourier transform infrared spectroscopy. Residual carbon content and specific surface area determinations were carried out on calcined powders. Microstructural characterisation was done by X-ray diffractometry and scanning electron microscopy. The results demonstrate that nanocrystalline particles of the solid solution can be prepared with low carbon content and high specific surface area by this one step synthesis technique.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123473743","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 : 2003-10-01DOI: 10.1179/096797803225005043
J. Yohannan, J. Jacob, A. Lonappan, K. T. Mathew
Abstract Microwave dielectric properties and crystal structure of Sr1-xBaxNb2O6 ceramics (x = 0·39, 0·45, 0·50, 0·55, 0·57, 0·60, 0·65) have been investigated. The microwave cavity perturbation technique was employed for the study of dielectric properties. Parameters such as complex permittivity and conductivity of strontium barium niobate ceramics were determined at the S band by measuring changes in the resonant frequencies and Q values of the cavity resulting from the introduction of the sample. The real part of the complex permittivity of all samples shows an increase with frequency, whereas the imaginary part of permittivity decreases as frequency increases. The effects of composition and sintering temperature on crystal structure and microstructure were studied by X-ray powder diffraction and scanning electron microscopy. Most compositions show preferred orientations along the c axis, as is evident from the relatively high intensity of (001) and (002) peaks. The microstructure contains ferroelectric domainlike structures with increasing barium content.
{"title":"Structural and microwave dielectric properties of Sr1-xBaxNb2O6 ceramics at microwave frequencies","authors":"J. Yohannan, J. Jacob, A. Lonappan, K. T. Mathew","doi":"10.1179/096797803225005043","DOIUrl":"https://doi.org/10.1179/096797803225005043","url":null,"abstract":"Abstract Microwave dielectric properties and crystal structure of Sr1-xBaxNb2O6 ceramics (x = 0·39, 0·45, 0·50, 0·55, 0·57, 0·60, 0·65) have been investigated. The microwave cavity perturbation technique was employed for the study of dielectric properties. Parameters such as complex permittivity and conductivity of strontium barium niobate ceramics were determined at the S band by measuring changes in the resonant frequencies and Q values of the cavity resulting from the introduction of the sample. The real part of the complex permittivity of all samples shows an increase with frequency, whereas the imaginary part of permittivity decreases as frequency increases. The effects of composition and sintering temperature on crystal structure and microstructure were studied by X-ray powder diffraction and scanning electron microscopy. Most compositions show preferred orientations along the c axis, as is evident from the relatively high intensity of (001) and (002) peaks. The microstructure contains ferroelectric domainlike structures with increasing barium content.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122732651","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 : 2003-10-01DOI: 10.1179/174327613X13789816719141
S. Papargyri, R. G. Cooke, D. Papargyris, A. Botis, G. Papapolymerou, A. D. Papargyris
Abstract A series of short fibre ceramic composites was produced by mixing, slip casting, and sintering kaolin clay with Al2O3 or mullite fibres at various volume contents. Sintering was conducted in air at various temperatures. The resulting composites were characterised with respect to chemical and mineralogical composition, microstructure, and mechanical properties. Sintering above 1200 °C changed the microstructure of kaolin from a weak point bonded structure to a strong dense glass ceramic structure, and changed δ-Al2O3 to α-Al2O3. The addition of oxide fibres to kaolin clay resulted in the formation of ceramic matrix composites, the properties of which depended on sintering temperature, matrix and fibre structures and relative volumes, the properties of the fibre/matrix interface, and fibre length. A relative increase in strength and toughness with incorporation of fibres is achieved with limited additions of fibres, and mainly in the weak point bonded structures. The application of linear elastic fracture mechanics to the examined ceramic matrix composites is also discussed.
{"title":"Mechanical properties of short oxide fibre-kaolin clay matrix composites","authors":"S. Papargyri, R. G. Cooke, D. Papargyris, A. Botis, G. Papapolymerou, A. D. Papargyris","doi":"10.1179/174327613X13789816719141","DOIUrl":"https://doi.org/10.1179/174327613X13789816719141","url":null,"abstract":"Abstract A series of short fibre ceramic composites was produced by mixing, slip casting, and sintering kaolin clay with Al2O3 or mullite fibres at various volume contents. Sintering was conducted in air at various temperatures. The resulting composites were characterised with respect to chemical and mineralogical composition, microstructure, and mechanical properties. Sintering above 1200 °C changed the microstructure of kaolin from a weak point bonded structure to a strong dense glass ceramic structure, and changed δ-Al2O3 to α-Al2O3. The addition of oxide fibres to kaolin clay resulted in the formation of ceramic matrix composites, the properties of which depended on sintering temperature, matrix and fibre structures and relative volumes, the properties of the fibre/matrix interface, and fibre length. A relative increase in strength and toughness with incorporation of fibres is achieved with limited additions of fibres, and mainly in the weak point bonded structures. The application of linear elastic fracture mechanics to the examined ceramic matrix composites is also discussed.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134236530","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 : 2003-10-01DOI: 10.1179/096797803225005034
C. A. Gutiérrez, R. Moreno
Abstract Optimum dispersing conditions for 43 vol.-% aqueous Al2O3 suspensions have been studied by assessing rheological behaviour as a function of dispersant concentration. A commercial polyelectrolyte was used as dispersant. The particle pair potentials have been calculated by considering the electrostatic and steric contributions. Variations in the steric potential produce significant changes in the shape and level of the potential energy curves and allow the prediction of the stability of suspensions that should coagulate according to the DLVO equation. Colloidal stability and rheological behaviour are correlated with the green and sintered densities of Al2O3 bodies produced by slip casting.
{"title":"Interparticle potentials of aqueous Al2O3 suspensions","authors":"C. A. Gutiérrez, R. Moreno","doi":"10.1179/096797803225005034","DOIUrl":"https://doi.org/10.1179/096797803225005034","url":null,"abstract":"Abstract Optimum dispersing conditions for 43 vol.-% aqueous Al2O3 suspensions have been studied by assessing rheological behaviour as a function of dispersant concentration. A commercial polyelectrolyte was used as dispersant. The particle pair potentials have been calculated by considering the electrostatic and steric contributions. Variations in the steric potential produce significant changes in the shape and level of the potential energy curves and allow the prediction of the stability of suspensions that should coagulate according to the DLVO equation. Colloidal stability and rheological behaviour are correlated with the green and sintered densities of Al2O3 bodies produced by slip casting.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"34 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131660525","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 : 2003-08-01DOI: 10.1179/096797803225004963
Huili Li, Y. Wei
Abstract Samples of interstitial free (IF) steel were heated at 1600 ° C for 90 min in graphite crucibles lined with MgO based castables bonded with microsilica. The total oxygen content (TOC) of the IF steel was determined for castables with various microsilica contents, and inclusions in the steel and refractory were characterised by SEM and EDS. As the microsilica content in the MgO castable increased from 3 to 7 wt-%, the TOC of the IF steel decreased. It is proposed that this is due to the formation of a viscous liquid layer between the molten steel and the refractory. This liquid layer prevents dissolution of oxides from the refractory into the molten steel and so decreases the TOC of IF steel. In addition, the liquid layer may act as an absorber for oxide inclusions in the molten steel.
{"title":"Effect of microsilica in MgO based castables on oxygen content of interstitial free steel","authors":"Huili Li, Y. Wei","doi":"10.1179/096797803225004963","DOIUrl":"https://doi.org/10.1179/096797803225004963","url":null,"abstract":"Abstract Samples of interstitial free (IF) steel were heated at 1600 ° C for 90 min in graphite crucibles lined with MgO based castables bonded with microsilica. The total oxygen content (TOC) of the IF steel was determined for castables with various microsilica contents, and inclusions in the steel and refractory were characterised by SEM and EDS. As the microsilica content in the MgO castable increased from 3 to 7 wt-%, the TOC of the IF steel decreased. It is proposed that this is due to the formation of a viscous liquid layer between the molten steel and the refractory. This liquid layer prevents dissolution of oxides from the refractory into the molten steel and so decreases the TOC of IF steel. In addition, the liquid layer may act as an absorber for oxide inclusions in the molten steel.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130282222","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 : 2003-08-01DOI: 10.1179/096797803225005007
E. Salahi, J. Heinrich
Abstract Aluminium nitride samples were produced by a reaction bonding process using AlN and Al powders with flake-like and equiaxed morphologies as starting materials. Changing the particle sizes and morphologies of the aluminium starting powders led to changes in degree of reaction and microstructure of the resulting reaction bonded aluminium nitride ceramics. At 25 wt-%Al, the degree of reaction showed a maximum, decreasing at higher aluminium concentrations. The degree of reaction was increased by increasing nitrogen gas flowrate or nitriding temperature. It was also found to be increased by reducing the average particle size of the Al starting powder, the green bulk density, or the sample thickness, and also by choosing flakelike morphology. SEM and optical micrographs of reaction bonded aluminium nitride samples revealed the pore structure and morphology of primary and secondary aluminium nitride.
{"title":"Correlation between nitriding process and microstructure of reaction bonded aluminium nitride ceramics","authors":"E. Salahi, J. Heinrich","doi":"10.1179/096797803225005007","DOIUrl":"https://doi.org/10.1179/096797803225005007","url":null,"abstract":"Abstract Aluminium nitride samples were produced by a reaction bonding process using AlN and Al powders with flake-like and equiaxed morphologies as starting materials. Changing the particle sizes and morphologies of the aluminium starting powders led to changes in degree of reaction and microstructure of the resulting reaction bonded aluminium nitride ceramics. At 25 wt-%Al, the degree of reaction showed a maximum, decreasing at higher aluminium concentrations. The degree of reaction was increased by increasing nitrogen gas flowrate or nitriding temperature. It was also found to be increased by reducing the average particle size of the Al starting powder, the green bulk density, or the sample thickness, and also by choosing flakelike morphology. SEM and optical micrographs of reaction bonded aluminium nitride samples revealed the pore structure and morphology of primary and secondary aluminium nitride.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"os-23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127769714","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 : 2003-08-01DOI: 10.1179/096797803225004954
S. El-Hemaly, N. Khalil, L. G. Girgis
Abstract Three aluminous cement compositions containing different proportions of barium aluminate were prepared from mixtures of calcined alumina, Egyptian barite, and limestone, by sintering briquettes at around 1600°C. The sintered bodies were ground to produce a cement powder of suitable fineness in which the predominant phases were found to be barium aluminate and calcium dialuminate. These cements were found to possess satisfactory cementitious behaviour and high refractoriness. Refractory castable compositions, based on the prepared cements and using sintered magnesia as aggregate, were formulated and evaluated for their physical, mechanical, and refractory properties. High strength and low shrinkage characterise the castable shapes in the cured, dried, and fired states. Such barium aluminate containing castables could be used effectively for lining structures subjected to very high temperatures.
{"title":"Refractory castables based on barium aluminate cements","authors":"S. El-Hemaly, N. Khalil, L. G. Girgis","doi":"10.1179/096797803225004954","DOIUrl":"https://doi.org/10.1179/096797803225004954","url":null,"abstract":"Abstract Three aluminous cement compositions containing different proportions of barium aluminate were prepared from mixtures of calcined alumina, Egyptian barite, and limestone, by sintering briquettes at around 1600°C. The sintered bodies were ground to produce a cement powder of suitable fineness in which the predominant phases were found to be barium aluminate and calcium dialuminate. These cements were found to possess satisfactory cementitious behaviour and high refractoriness. Refractory castable compositions, based on the prepared cements and using sintered magnesia as aggregate, were formulated and evaluated for their physical, mechanical, and refractory properties. High strength and low shrinkage characterise the castable shapes in the cured, dried, and fired states. Such barium aluminate containing castables could be used effectively for lining structures subjected to very high temperatures.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121794549","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 : 2003-08-01DOI: 10.1179/096797803225004972
A. Chakraborty, Swagatika Das, Sonali Gupta
Abstract Structural changes on heat treatment of English kaolinite have been studied by a standard X-ray technique. Changes in the lattice parameters, strain values, and crystal sizes of mullite and cristobalite have been calculated using a computer based Rietveld program. The results show two separate stages of mullite formation during the reaction of kaolinite. Changes in the composition of mullite during the course of its formation are discussed.
{"title":"Evidence for two stage mullite formation during thermal decomposition of kaolinite","authors":"A. Chakraborty, Swagatika Das, Sonali Gupta","doi":"10.1179/096797803225004972","DOIUrl":"https://doi.org/10.1179/096797803225004972","url":null,"abstract":"Abstract Structural changes on heat treatment of English kaolinite have been studied by a standard X-ray technique. Changes in the lattice parameters, strain values, and crystal sizes of mullite and cristobalite have been calculated using a computer based Rietveld program. The results show two separate stages of mullite formation during the reaction of kaolinite. Changes in the composition of mullite during the course of its formation are discussed.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"4 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129126665","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：