Lithium Metasilicate Research Articles

The crystallisation of glasses based on eutectic compositions in the system Li2O-Al2O3-SiO2

Structural transformations have been studied in glasses related in composition to the binary eutectic between lithium metasilicate and β-spodumene. Crystallisation processes and changes in microstructure during the controlled heating of the glasses have been followed using X-ray diffraction, electron microscopy, high temperature microscopy, thermal analysis and electron spin resonance spectroscopy. The influence exerted by titanium dioxide on the phase relationships, crystal growth rates and micromorphology of the polycrystalline products of heat-treatment has been investigated and the findings used as a basis for proposals on the role of TiO2 during nucleation and crystal growth.

Neutron effects in thermally treated glasses

Dielectric measurement and small angle X-ray scattering techniques were used to examine the structure of a binary Li 2O-2SiO 2 glass after exposure to an integrated flux of 10 17 nvt fast neutrons. There is little change in the dielectric properties of the ascast, amorphous glass. However, the results indicate that irradiation accelerates the sequence of crystallization reactions occurring during thermal treatment of the glass. The dissolution rate of lithium metasilicate crystals which appear as a percursor to equilibrium crystallization appears to be enhanced.

Crystallization Behaviour of Three Glass Compositions in the System Li2O—Al2O3—SiO2

Three glass compositions, one corresponding to β-Eucryptite, another corresponding to Lithium Metasilicate and the third corresponding to 1070°C eutectic on the lithium metasilicate-β-eucryptite join in the composition triangle lithium metasilicate-β-spodumene-β-eucryptite of the system Li2O-Al2O3-SiO2 were studied with respect to their crystallization behaviour. The phases crystallizing out after different heat treatment schedules and using different nucleating agents were identified by X-ray diffraction patterns. In all cases, the initial crystallization product was Eucryptite silica-O form. However, in the case of 1070°C eutectic composition the development of lithium metasilicate phase was also noticed after heat treating at 800°C for 5 hours.The first DTA peak due to crystallization was used to distinguish the effects of ZrO2, TiO2 and V2O5 as nucleating agents. With 5% zirconia additions the first crystallization peak temperature was maximum while in the case of 5% V2O5 additions it was minimum. There was, however, no change in the initial crystallization products with and without the nucleating agents.

Effect of a Metastable Precipitate on the Electrical Properties of an Li2,O-SiO2Glass

Glass structural differences in a 17.5 wt% (30 mole %) Li2O-SiO2 glass resulting from thermal treatments in the annealing-transformation range were studied using electron microscopy, X-ray analysis, and dc and ac electrical properties. Metastable, crystalline lithium metasilicate precipitates and subsequently redissolves prior to the appearance of the equilibrium lithium disilicate crystals. The lithium metasilicate gives rise to dielectric loss peaks in the 100 hz to 1 Mhz range which can be rationalized on the basis of the Maxwell-Wagner-Sillars heterogeneous dielectric model.

Nucleation and Crystallization Behaviour of Two Glass Compositions in the System Li2O-Al2O3-SiO2

Two glass compositions in Li2O-Al2O3-SiO2 system, one corresponding to β-Spodumene, and the other corresponding to the eutectic at 1026°C were prepared, and studied with respect to their crystallization behaviour. The phases crystallizing on heat treatment at different temperature schedules and for different nucleating agents were identified by X-ray diffraction patterns. In all cases, the major phase present was Li2O.Al2O3.6SiO2. Besides, lithium metasilicate and lithium orthosilicate were also crystallized. DTA technique was used to distinguish the effects of TiO2, and ZrO2 as nucleating agents.

Infrared Determination of Percent Crystallinity of Lithium Metasilicate and Lithium Disilicate Devitrified from Glass

Infrared Determination of Percent Crystallinity of Lithium Metasilicate and Lithium Disilicate Devitrified from Glass

Cooled glass slide for a vacuum system: A P Rumyantsev, Zavod Labor, 11, 1965, 1420.

The devitrification behaviour and the electrical conductivity of five glasses near the lithium metasilicate composition have been studied using differential thermal analysis. X-ray diffraction and impedance analysis. All the studied glasses devitrify in two steps. The influences of replacing SiO2 by Al2O3and of the LiO2 content on the activation energy of crystal growth and of electrical conductivity have been pointed out.

Glass Formation and Recrystallization in the Lithium Metasilicate Region of the System Li2O–Al2O3–SiO2

The stability of the vitreous state in the lithium metasilicate region of the system Li2O–Al2O3–SiO2 was found to be a function of the concentration of lithia. The higher the lithia content, the less stable was the glass. The devitrification of glasses in this system was studied. In addition to the phases present at or near the liquidus, it was found that the β‐eucryptite–β‐quartz solid solution phase was metastable over most of the region. The Li2O–SiO2, β‐Li2O–Al2O3–4SiO2 solid solution, β‐Li2O–Al2O3–2SiO2 solid solution triple point was estimated to be near 62.5% SiO2, 17% Al2O3, and 20.5% Li2O (by weight). The thermal expansions of bodies in this region were measured and the values obtained are explained in terms of the phases present.

Studies on the Mechanical Strength of the Photosensitive Opal Glass

When a lithium containing photosensitive glass is exposed to ultraviolet light and then subjected to the heat treatment, it changes into a polycrystalline material characterized by its good mechanical properties (S. D. Stookey. Ind. Eng. Chem., 45, 115 (1953)).The purpose of this paper is to present the relation between the mechanical strength and the grain size of the constituent crystallites of the resultant material.Glass specimens (2.5×5×50mm) of the oxide composition SiO2 81, Li2O 12.5, K2O 2.5, Al2O3 4, CeO2 0.03, Au 0.027% (wt.) were exposed to ultraviolet light by placing them at a distance of 10cm from a 500 watt high pressure mercury lamp for 2 to 1000 min. After the exposure they were heated at three steps; first at 510°C for 30 min. to cause formation of gold nuclei, then at 620°C for 60 min. to cause crystallization of lithium metasilicate partially (40%) from the base glass, and finally at 900°C for 60 min. to convert almost the whole of the base glass to polycrystalline materials consisted of lithium disilicate and β-quartz. The grain size of the constituent crystallites of the resultant material was able to be varied from 0.85 to 2.3μ by changing the U. V. exposure time (Ref. M. Tashiro and S. Sakka. J. Ceram. Assoc. Japan, 67, 263 (1959)).Tests for bending strength and Vickers hardness were made with two classes of specimens, one which completed a whole course of the above heat treatments and the other which completed only the first half of the heat treatments, i.e., heated only up to 620°C.The tests have shown that, for the specimens which completed the whole course of the heat treatments, crystallization increases mechanical strength of the specimens, and the relation between the average grain size of the constituent crystallites (d) and the mechanical properties (M) (both of the bending strength and Vickers hardness) is given by the equation, M=const⋅d1/2.For the specimens heated up to 620°C, partial crystallization of the glass phase was found to increase the mechanical strength of the specimens but in somewhat more complex way. This was attributed to the effects of glass phase still remaining in considerable amounts (60%) in the specimens.

Fundamental Studies on the Photosensitive Glass Relation between the Exposure Time and Transparency

An opal type of photosensitive glass, when exposed to ultraviolet light and subsequently heated to about its softening temperature, changes in transparency due to the formation of nonmetallic submicroscopic crystallites within the glass. In this study the transparency change of the glass having the following composition was studied in relation to the exposure time: SiO2 81, Li2O 12.5, K2O 2.5, Al2O3 4, CeO2 0.03, Au 0.027% by weight.Glass specimens of 2mm thick plates were exposed to ultraviolet light by placing the near a 500 watt high pressure mercury lamp at a distance of 10cm for various times ranging from 1 to 1000 min. After exposure all of specimens were heated firstly at 510°C for 30 min. and then at 620°C for 60 min. to cause the formation of gold nuclei and lithium metasilicate crystallites at respective temperatures. The measuremeat of light transmittance in the visible region was made of these specimens with a photoelectric spectrophotometer.It was found that (1) the transparency decreases with increasing exposure time up to 30 min. (due to the formation of metasilicate crystallites); (2) between 30 and 180 min., however, it increases with increasing exposure time; the specimen with the exposure time of 180 min. is almost transparent though its color is deep red; (3) over 180 min. it again decreases with increasing exposure time.The peculiar change in transparency with increasing exposure time was discussed on the basis of the size of lithium metasilicate crystallites within the glass. The increase in transparency with increasing exposure time in the range between 30 and 180 min, was attributed to the decrease of the size of crystallites under a limiting value which is too small for scattering visible light within the glass. The density measurement by a sink-float method was also made to support this conclusion.

Phase Equilibria in the System Lithium Metasilicate–β‐Eucryptite

A phase equilibrium study of the join lithium metasilicate–β–eucryptite in the system Li2O–Al2O3–SiO2 was made by the quench method. The phase diagram was found to be a simple binary with a eutectic at 1070°C and 57% eucryptite. The relationship of these data to the ternary system is discussed.

The System Lithium Metasilicate--Spodumene--Silica

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe System Lithium Metasilicate--Spodumene--SilicaRustum. Roy and E. F. OsbornCite this: J. Am. Chem. Soc. 1949, 71, 6, 2086–2095Publication Date (Print):June 1, 1949Publication History Published online1 May 2002Published inissue 1 June 1949https://doi.org/10.1021/ja01174a053RIGHTS & PERMISSIONSArticle Views505Altmetric-Citations73LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (912 KB) Get e-Alerts Get e-Alerts