The development of the microstructure of simple glass-ceramics, of molar compositions 70SiO2·30Li2O and 69SiO2·30Li2O·1P2O5, has been studied by the techniques of transmission electron microscopy, optical microscopy, X-ray powder diffraction and electrical loss measurements. Surface nucleation of lithium disilicate crystals occurred in all samples, and internal nucleation occurred in samples of the first glass treated for 1 h at 450, 475 or 500°C before crystallization at 750°C. Internal nucleation always occurred in samples of the glass containing P2O5 which were crystallized at 750°C, but the grain size of the crystalline product depended strongly on the temperature of the previous lower temperature heat treatment (the “nucleation stage”). The optimum nucleation range was close to 500°C for 1 h heat treatments. The results suggest that glass-in-glass phase separation, which was observed in both glasses, did not promote crystal nucleation directly, but effects due to an influence of phase separation on crystal growth rates are suggested. Possible reasons for the action of P2O5 as a nucleation catalyst are discussed, but firm conclusions cannot be reached on the present evidence.
{"title":"Crystal nucleation in lithium silicate glasses","authors":"H. Harper, P. F. James, P. Mcmillan","doi":"10.1039/DF9705000206","DOIUrl":"https://doi.org/10.1039/DF9705000206","url":null,"abstract":"The development of the microstructure of simple glass-ceramics, of molar compositions 70SiO2·30Li2O and 69SiO2·30Li2O·1P2O5, has been studied by the techniques of transmission electron microscopy, optical microscopy, X-ray powder diffraction and electrical loss measurements. Surface nucleation of lithium disilicate crystals occurred in all samples, and internal nucleation occurred in samples of the first glass treated for 1 h at 450, 475 or 500°C before crystallization at 750°C. Internal nucleation always occurred in samples of the glass containing P2O5 which were crystallized at 750°C, but the grain size of the crystalline product depended strongly on the temperature of the previous lower temperature heat treatment (the “nucleation stage”). The optimum nucleation range was close to 500°C for 1 h heat treatments. The results suggest that glass-in-glass phase separation, which was observed in both glasses, did not promote crystal nucleation directly, but effects due to an influence of phase separation on crystal growth rates are suggested. Possible reasons for the action of P2O5 as a nucleation catalyst are discussed, but firm conclusions cannot be reached on the present evidence.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"85 5 1","pages":"206-213"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86487319","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}
Properties of the heterocyclic polymer prepared by the reaction of naphthalene-1,4,5,8-tetracarboxylic acid with 3,3′-diaminobenzidene are discussed. Light scattering, viscometric and freezing point depression measurements on dilute solutions lead to the conclusion that in strong acids BBB is protonated and takes on a flexible coil conformation in dilute solutions. Viscometric data on concentrated solutions likewise follow the behaviour expected for coiled chains, but exhibit the behaviour expected for entangled chains at unusually low concentrations, and a segmental mobility that decreases rapidly with increasing polymer concentration. These data, together with X-ray diffraction studies on the undiluted polymer, are discussed in terms of short range interactions leading to stacked aggregates in very concentrated solutions and the bulk polymer.
{"title":"Dilute and concentrated solutions of a heterocyclic polymer (BBB)","authors":"G. Berry","doi":"10.1039/DF9704900121","DOIUrl":"https://doi.org/10.1039/DF9704900121","url":null,"abstract":"Properties of the heterocyclic polymer prepared by the reaction of naphthalene-1,4,5,8-tetracarboxylic acid with 3,3′-diaminobenzidene are discussed. Light scattering, viscometric and freezing point depression measurements on dilute solutions lead to the conclusion that in strong acids BBB is protonated and takes on a flexible coil conformation in dilute solutions. Viscometric data on concentrated solutions likewise follow the behaviour expected for coiled chains, but exhibit the behaviour expected for entangled chains at unusually low concentrations, and a segmental mobility that decreases rapidly with increasing polymer concentration. These data, together with X-ray diffraction studies on the undiluted polymer, are discussed in terms of short range interactions leading to stacked aggregates in very concentrated solutions and the bulk polymer.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"62 1","pages":"121-136"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86765047","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}
The capabilities and limitations of the small-angle X-ray scattering technique which have been found for the establishment of the mechanisms of early stages of phase separation in glass systems are examined. This includes the evaluation of the criteria for distinguishing between the mechanisms of initial separation such as nucleation and spinodal decomposition. The application of this technique for directly following nucleation processes is given. The information obtained employing these methods concerning qualitative differences in the early stages of phase separation as functions of composition and temperature of ZrO2-containing phases in two MgO·Al2O3·3SiO2·X ZrO2 glasses are presented. The X-ray scattering results show that precipitation of a ZrO2 phase is not a necessary prelude to the crystallization of the glass.
{"title":"Phase separation in glass and glass-ceramic systems","authors":"G. F. Neilson","doi":"10.1039/DF9705000145","DOIUrl":"https://doi.org/10.1039/DF9705000145","url":null,"abstract":"The capabilities and limitations of the small-angle X-ray scattering technique which have been found for the establishment of the mechanisms of early stages of phase separation in glass systems are examined. This includes the evaluation of the criteria for distinguishing between the mechanisms of initial separation such as nucleation and spinodal decomposition. The application of this technique for directly following nucleation processes is given. The information obtained employing these methods concerning qualitative differences in the early stages of phase separation as functions of composition and temperature of ZrO2-containing phases in two MgO·Al2O3·3SiO2·X ZrO2 glasses are presented. The X-ray scattering results show that precipitation of a ZrO2 phase is not a necessary prelude to the crystallization of the glass.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"11 8","pages":"145-154"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91427895","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}
Modern theory and the experimental method of small angle X-ray scattering (SAXS) permit one to find, without any a priori suppositions and with sufficient accuracy, a series of integral structural characteristics of the sub-micro-inhomogeneous (supra-molecular) structure of glass. The temperature dependence of the principal characteristics gives the possibility of describing the change of a glass structure during its heat treatment with great reliability. For example, the area of the geometrical surface separating two phases has been determined, and the change of the “bidispersive structure” with the heat treatment has been studied; it was thereby proved that the high dispersive structure is a result of the terminal velocity of cooling from high temperatures and that it also has a phase-separation nature (the secondary phase separation).Two methods—SAXS and scattering of visible light—have been used as experimental checks of the theory of spinodal decomposition, taking as an example sodium silicate glass, containing 12.5 % sodium oxide. Disagreement of the experimental results with the theoretical predictions has been found. This fact has been explained by the dependence of the diffusion coefficient and some other parameters upon the concentration which have been disregarded in the approximate variant of the theory. The main SAXS characteristics of the inhomogeneous glass structure have been defined, viz., the mean-square electron density fluctuation, the effective size and area of inhomogeneous regions and the distance between their centres.
{"title":"Small-angle X-ray scattering and scattering of visible light by phase-separated glasses","authors":"N. Andreev, E. A. Porai-Koshits","doi":"10.1039/DF9705000135","DOIUrl":"https://doi.org/10.1039/DF9705000135","url":null,"abstract":"Modern theory and the experimental method of small angle X-ray scattering (SAXS) permit one to find, without any a priori suppositions and with sufficient accuracy, a series of integral structural characteristics of the sub-micro-inhomogeneous (supra-molecular) structure of glass. The temperature dependence of the principal characteristics gives the possibility of describing the change of a glass structure during its heat treatment with great reliability. For example, the area of the geometrical surface separating two phases has been determined, and the change of the “bidispersive structure” with the heat treatment has been studied; it was thereby proved that the high dispersive structure is a result of the terminal velocity of cooling from high temperatures and that it also has a phase-separation nature (the secondary phase separation).Two methods—SAXS and scattering of visible light—have been used as experimental checks of the theory of spinodal decomposition, taking as an example sodium silicate glass, containing 12.5 % sodium oxide. Disagreement of the experimental results with the theoretical predictions has been found. This fact has been explained by the dependence of the diffusion coefficient and some other parameters upon the concentration which have been disregarded in the approximate variant of the theory. The main SAXS characteristics of the inhomogeneous glass structure have been defined, viz., the mean-square electron density fluctuation, the effective size and area of inhomogeneous regions and the distance between their centres.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"241 1","pages":"135-144"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75725111","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}
In order to have information about the conformational energy of polymer chains, the structures of small molecules which have chemical configurations similar to those of polymer chains are studied. The results for polyethylene, poly(vinylchloride), polypropylene, 1,4-polyisoprene, 1,4-polybutadiene, nucleic acid and polypeptides show that the conformations of small model molecules are closely correlated with those of polymer chains.
{"title":"Stable conformations of polymer chains and model compound molecules","authors":"T. Shimanouchi","doi":"10.1039/DF9704900060","DOIUrl":"https://doi.org/10.1039/DF9704900060","url":null,"abstract":"In order to have information about the conformational energy of polymer chains, the structures of small molecules which have chemical configurations similar to those of polymer chains are studied. The results for polyethylene, poly(vinylchloride), polypropylene, 1,4-polyisoprene, 1,4-polybutadiene, nucleic acid and polypeptides show that the conformations of small model molecules are closely correlated with those of polymer chains.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"62 1","pages":"60-69"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83390163","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}
The radius of gyration and the second osmotic virial coefficient of a model chain molecule is calculated numerically with a Monte Carlo procedure. The model is intended to resemble cellulose trinitrate (CTN). The expansion coefficients of stiff chain molecules such as CTN or DNA are near unity at high molecular weights and in good solvents.
{"title":"Radius of gyration of stiff chain molecules as a function of the chain length and the interactions with the solvent","authors":"R. Kirste","doi":"10.1039/DF9704900051","DOIUrl":"https://doi.org/10.1039/DF9704900051","url":null,"abstract":"The radius of gyration and the second osmotic virial coefficient of a model chain molecule is calculated numerically with a Monte Carlo procedure. The model is intended to resemble cellulose trinitrate (CTN). The expansion coefficients of stiff chain molecules such as CTN or DNA are near unity at high molecular weights and in good solvents.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"23 1","pages":"51-59"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75323908","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}
The influence of various heat-treatment on the viscosity, transformation temperature and electric conductivity of some soda-silica glasses in the immiscibility region was investigated. Two distinct temperature regions were found for several glasses. In one of the regions, heat-treatment leads to the “droplet” structure, whereas in the other it leads to the “two-framework” structure. The boundary between these regions was attributed to the boundary line of the spinodal region. A noticeable decrease in the transformation temperature of low-viscosity phase was found for the glass with a discontinuous low-viscosity phase. The uniform tension in droplets was assumed to be the cause of this effect.
{"title":"Properties of phase-separated soda-silica glasses as a means of investigation of their structure","authors":"O. Mazurin, G. Roskova, V. P. Kluyev","doi":"10.1039/DF9705000191","DOIUrl":"https://doi.org/10.1039/DF9705000191","url":null,"abstract":"The influence of various heat-treatment on the viscosity, transformation temperature and electric conductivity of some soda-silica glasses in the immiscibility region was investigated. Two distinct temperature regions were found for several glasses. In one of the regions, heat-treatment leads to the “droplet” structure, whereas in the other it leads to the “two-framework” structure. The boundary between these regions was attributed to the boundary line of the spinodal region. A noticeable decrease in the transformation temperature of low-viscosity phase was found for the glass with a discontinuous low-viscosity phase. The uniform tension in droplets was assumed to be the cause of this effect.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"23 1","pages":"191-199"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82002418","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}
The regions of glass formation and liquid-liquid immiscibility have been determined in the soda-baria-silica system. Immiscibility occurs in the high silica corner of the system, and extends over a continuous region from the BaO—SiO2 to the Na2O—SiO2 limiting binaries. In an extensive region close to the glass-forming boundary and including mostly the barium disilicate field, crystallization occurred by homogeneous nucleation to produce a glass ceramic. Some of these compositions also showed metastable immiscibility. Nucleation, growth and coarsening of the crystals were studied; first, a metastable high-temperature polymorph of barium disilicate appears growing as spherulites, but on prolonged heating a lathe-like structure appears.
{"title":"Immiscibility, nucleation and crystal growth in the soda-baria-silica system","authors":"D. Burnett, R. W. Douglas","doi":"10.1039/DF9705000200","DOIUrl":"https://doi.org/10.1039/DF9705000200","url":null,"abstract":"The regions of glass formation and liquid-liquid immiscibility have been determined in the soda-baria-silica system. Immiscibility occurs in the high silica corner of the system, and extends over a continuous region from the BaO—SiO2 to the Na2O—SiO2 limiting binaries. In an extensive region close to the glass-forming boundary and including mostly the barium disilicate field, crystallization occurred by homogeneous nucleation to produce a glass ceramic. Some of these compositions also showed metastable immiscibility. Nucleation, growth and coarsening of the crystals were studied; first, a metastable high-temperature polymorph of barium disilicate appears growing as spherulites, but on prolonged heating a lathe-like structure appears.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"54 1","pages":"200-205"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82169129","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}
The relationship of the simple segment theory to the Orwoll-Flory theory is examined; this suggests a restatement of the principle of congruence as five postulates. These are tested in turn against the molar volume, thermal expansivity and isothermal compressibility measurements of Diaz Pena and Benitez de Soto on the system n-hexane + n-hexadecane, using the methods of Patterson and Bardin. The molar volume data are analyzed also by a method based on the principle of corresponding states, which includes direct comparison of each solution with a reference n-alkane. The Patterson-Bardin analyses accord with the analyses of the molar volumes, with reservations because of an inconsistency in the thermal expansivity results. The solutions appear to follow the same reduced equation of state as do the n-alkanes, but their equivalent substances depart significantly from the locus of reducing parameters defined by the n-alkanes. The implications of this departure are discussed.
研究了简单分段理论与Orwoll-Flory理论的关系;这暗示了作为五个假设的一致性原则的重述。利用Patterson和Bardin的方法，对Diaz Pena和Benitez de Soto在正己烷+正十六烷体系上的摩尔体积、热膨胀率和等温压缩率进行了测试。摩尔体积数据的分析还采用了一种基于对应态原理的方法，该方法包括将每种溶液与参考正构烷烃进行直接比较。Patterson-Bardin分析结果与摩尔体积分析结果一致，但由于热膨胀率结果不一致而有所保留。溶液似乎遵循与正构烷烃相同的化简状态方程，但它们的等效物质明显偏离正构烷烃所定义的化简参数轨迹。本文讨论了这种偏离的含义。
{"title":"Solutions of n-alkanes: volume-related properties and the principle of congruence","authors":"A. Cruickshank, C. P. Hicks","doi":"10.1039/DF9704900106","DOIUrl":"https://doi.org/10.1039/DF9704900106","url":null,"abstract":"The relationship of the simple segment theory to the Orwoll-Flory theory is examined; this suggests a restatement of the principle of congruence as five postulates. These are tested in turn against the molar volume, thermal expansivity and isothermal compressibility measurements of Diaz Pena and Benitez de Soto on the system n-hexane + n-hexadecane, using the methods of Patterson and Bardin. The molar volume data are analyzed also by a method based on the principle of corresponding states, which includes direct comparison of each solution with a reference n-alkane. The Patterson-Bardin analyses accord with the analyses of the molar volumes, with reservations because of an inconsistency in the thermal expansivity results. The solutions appear to follow the same reduced equation of state as do the n-alkanes, but their equivalent substances depart significantly from the locus of reducing parameters defined by the n-alkanes. The implications of this departure are discussed.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"106 1","pages":"106-114"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87912095","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}
The infra-red absorptivity of vitreous silica has been investigated in the region 100–15 cm–1 at 300 and 100 K. Above 18 cm–1 the absorptivity is independent of temperature and is undoubtedly caused by fundamental vibrations. A theory suggests that the absorptivity divided by the frequency squared should be more closely related to the density of vibrational states than should the direct spectrum. There is a maximum in this function at about 38 cm–1 which is due to the vibrations that can be considered as derived from the transverse acoustic maximum of cristobalite when it is vitrified. There is no evidence of fine structure in the infra-red spectrum, and it seems likely that the greatly increased heat capacity of vitreous silica at low temperatures over that of cristobalite is partly caused by the broadening of the transverse acoustic maximum.
{"title":"Infra-red and Raman spectra of glasses. Part 2.—Far infra-red spectrum of vitreous silica in the range 100–15 cm–1","authors":"P. Wong, E. Whalley","doi":"10.1039/DF9705000094","DOIUrl":"https://doi.org/10.1039/DF9705000094","url":null,"abstract":"The infra-red absorptivity of vitreous silica has been investigated in the region 100–15 cm–1 at 300 and 100 K. Above 18 cm–1 the absorptivity is independent of temperature and is undoubtedly caused by fundamental vibrations. A theory suggests that the absorptivity divided by the frequency squared should be more closely related to the density of vibrational states than should the direct spectrum. There is a maximum in this function at about 38 cm–1 which is due to the vibrations that can be considered as derived from the transverse acoustic maximum of cristobalite when it is vitrified. There is no evidence of fine structure in the infra-red spectrum, and it seems likely that the greatly increased heat capacity of vitreous silica at low temperatures over that of cristobalite is partly caused by the broadening of the transverse acoustic maximum.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"221 1","pages":"94-102"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75898247","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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