Alumina as a Devitrification Inhibitor during Sintering of Borosilicate Glass Powders

Cristobalite is formed when borosilicate glass (Corning Code 7740) is sintered at temperatures ranging from 700^o to 1000^o C. The precipitation kinetics, determined by XRD analysis, exhibit a characteristic incubation period which decreases with increasing sintering temperature, from 60-120 min at 700^oC to 3-5 min at 1000^o C. Activation analysis of precipitation shows an activation energy of 75 kJ/mol, which is close to that for the diffusion of Na+ in borosilicate glass, suggesting mass-transport controlled kinetecs. ^1.,5With added alumina content greater than a critical value, however, the cristobalite formation in the borosilicate glass is completely prevented at the sintering temperatures investigated. The critical alumina content is found to decrease with decreasing alumina particle size but with increasing sintering temperature. The above result, similar to observations previously made in a binary glass mixture containing a low-softening borosilicate glass (BSG) and a high-softening high silica glass (HSG) ³ is attributed to a strong coupling between Al³⁺ from alumina and Na⁺ from borosilicate glass. The coupling reaction causes segregation of Na⁺ in boraosilicate glass to alumina, thus forming a Na⁺-and Al³⁺-rich reaction layer around alumina particles far too rapid for cristobalite formation.     

ESR Study of Devitrification Processes

The radiation-induced ESR centers in glasses with different Ti concentrations were studied to elucidate crystallization processes in the glass. The parameters of the induced ESR absorption associated with the T ₂ center were investigated systematically as a function of heat treatment. The induced T ₂ centers in the glasses containing small concentrations of Ti characteristically decreased in intensity as nucleation began and disappeared completely in devitrified samples. A mechanism is proposed for the destruction of the T ₂ center as nucleation proceeds to crystallization. Supporting X-ray diffraction evidence is given. The systematic decrease in the ESR intensity of this radiation-induced center provides a means of monitoring devitrification processes in glasses.     

Polarization-Dependent Birefringence in Lithium Aluminosilicate Glass

Glass and Ceramics - The formation of polarization-dependent birefringence, apparently due to the formation of nanogratings, in the bulk of lithium silicate and lithium aluminosilicate glasses...     

Sm3+掺杂碱锌硼硅酸盐玻璃析晶过程的微观结构研究

采用HTEM,NMR以及红外光谱技术,研究适宜半导体微晶掺杂的Sm3 掺杂碱硼硅酸盐基础玻璃在热处理过程中,玻璃结构的变化特点.研究结果表明,含Sm3 基础玻璃失透的主要原因在于在热作用下玻璃中[SiO4]4-以及[BO4]4-四面体结构首先分解形成了富硅相以及富硼相,稀土Sm3 则富集到富硼相中,并进一步析出了硼酸钐晶体;通过优化玻璃的组成能够改进基础玻璃的热稳定性.     

锂铝硅玻璃的研究进展

与传统的钠钙硅玻璃和高铝玻璃相比,锂铝硅玻璃具有网络结构致密、弹性模量较高和适宜两步法化学钢化等特点,被视为第三代高强玻璃基板,可用作电子信息产品盖板、航空透明器件以及舰船、特种车辆的观察窗口等。目前,锂铝硅玻璃的研究主要涉及:(1)探究锂铝硅玻璃的“组成-结构-性能”本构关系,为设计优化高性能锂铝硅玻璃提供理论指导和性能预测;(2)改进现有溢流和浮法成型方法和装备,满足大尺寸、多厚度和高尺寸精度锂铝硅玻璃成型需要;(3)研究锂铝硅玻璃的两步法化学增强方法,解决表面压应力和应力层深度同步提升难题,显著提高玻璃强度、硬度和抗跌落性能。本文基于上述三个方面综述了锂铝硅玻璃的国内外研究进展。     

IR Spectroscopy Study of Pre-Crystallization and Its Effect on the Phase Composition of Lithium Aluminosilicate Glass and Glass Ceramic

The effect of pre-heating on the phase composition of lithium aluminosilicate glass and glass ceramic is studied by the IR spectroscopy method. The results obtained provide a deeper insight into the kinetics of phase transformation in heat-treated materials and the temperature regime of crystal nucleation.     

Nucleation and Crystallization of a Lithium Aluminosilicate Glass

An aluminosilicate glass of composition 61SiO₂6Al₂O₃10MgO6ZnO·12Li₂O·5TiO₂ (mol%) has been prepared by a melting process and investigated as far as crystallization is concerned. Glass-ceramic is easily obtained because glass shows a high tendency to crystallize starting from 700°C. The crystalline phases evolve with temperature, showing the aluminosilicates to be the main phase up to 1050°C, followed by metasilicates and silicates, some of which have lower melting points. The titanates of Mg and Zn develop from the phase-separated glass, soon after T _g, and grow to form nucleation centers for the other crystalline phases. The evolution from phase-separated glass to glass-ceramic has been followed by many thermal, diffractometric, spectroscopic, and microscopic techniques.     

陶瓷产品“失透”的研究与实践

通过对陶瓷失透产品特征的分析,阐述了陶瓷产品产生失透的机理,提出了在实际工作中解决失透这一陶瓷产品缺陷的措施。     

Al2O3对电子玻璃高温黏度及析晶性能的影响

研究了不同含量的Al2O3对电子玻璃高温黏度和析晶性能的影响。结果表明,随着氧化铝含量的增加,电子玻璃的高温黏度、成型温度均降低,但析晶黏度减小,与成型的砖尖黏度差值减小,不利于溢流下拉成型。     

Further Studies of the Crystallization of a Lithium Silicate Glass

Rates of crystallization of Li₂O · 2SiO₂, from an Li₂O · 4SiO₂ glass as a function of platinum concentration at 600° and 650° C were determined. At both temperatures a maximum rate was obtained in the region of 0.005% Pt. Calculations of the activation energies for the crystallization process showed that 0.005%, Pt lowered it to less than half its original value of 120 kcal per mole. Electron microscopy of this glass quenched from 1450OC revealed a granular structure 250 A in size which was believed to be due to lithium-rich clusters in the glass, svpporting the concepts of other investigators. In glasses containing 0.025%, an additional phase identified as silica O was found. Explanations for the effectiveness of platinum as a nucleating agent in this glass are offered.     

锂铝硅酸盐玻璃陶瓷抗侵蚀性的研究

列出采用三种独立的方法对锂铝硅酸盐型玻璃陶瓷(OTM-357型材料)抗侵蚀性介质作用的研究数据,表明其结果近似,而且材料的抗化学侵蚀性极高,从而使其应用范围扩大。     

硅酸铝锂组成的玻璃陶瓷强度的提高

根据研究可以得出结论，以硅酸铝锂组成的玻璃陶瓷通过在NaNO3溶液中进行离子交换可以使制品的强度得到提高。该玻璃陶瓷系按照陶瓷生产工艺，利用高浓度悬浮液以泥浆浇注法在多孔模里浇注成型，随后按照规定的热处理制度对坯体进行烧结和冷却。选择了通过离子交换使制品强度得到提高的最佳的温度—时间制度。     

溴化锂吸收式制冷空调在玻璃工业中的应用

分析了利用玻璃工业中的余热资源产生的蒸汽作为溴化锂吸收式制冷空调系统的动力来源如何在满足玻璃工厂各车间空调需求的同时做到节约能源和保护环境.     

A Technology for Accelerated Calcination of Lithium Aluminosilicate Glass Ceramics

The results of a study of the processes of sintering and crystallization of Li-aluminosilicate glass ceramics have shown a route towards saving heat-treatment time (by a factor of 2.5 – 3.0) and power consumption without detriment to the major physicomechanical characteristics of the components produced.     

锂磷酸盐微晶玻璃固体电解质材料研究进展

锂磷酸盐微晶玻璃固体电解质具有合成简单,电化学稳定性高等优点,已经对其进行了大量的研究工作。结合近几年的研究,分别综述了三元、四元和五元3种不同系统的锂磷酸盐微晶玻璃固体电解质所具有的最大电导率。并描述了Nasicon结构的快离子导体和交流阻抗谱在计算电导率上的应用。锂磷酸盐微晶玻璃固体电解质在全固态锂离子电池中将会有更广泛的应用。     

Effect of Temperature on the Structuring and Properties of Glass and Glass Ceramic of Lithium Aluminosilicate Composition

Results of a study of sintering and crystallization of lithium aluminosilicate-based glass ceramic prepared by casting aqueous high-density slips into porous molds are reported. Optimum conditions for the formation of structure and phase composition of the glass ceramic and the development of required properties are established.     

Devitrification behaviour of plasma-sprayed glass coatings

Glass and glass-ceramic coatings on ceramic tiles have been manufactured by plasma-spraying high-performance CAS (in wt%—SiO₂, 60%; Al₂O₃, 15%; CaO, 23%; others, traces) and CZS (in wt%—SiO₂, 50%; CaO, 31%; ZrO₂, 16.5%; Al₂O₃, 2%; others, traces) glass frits. The CZS system has a surface crystallization at about 1050 °C. Such behaviour would not easily allow to obtain a fully crystalline bulk glass-ceramic, but the defectiveness of the plasma-sprayed coating supplies many nucleation sites. Thus, it becomes completely crystalline and well sintered after a 850 °C for 30 min + 1050 °C for 15 min treatment. The CAS frit, designed not to produce significant crystallization, is well sintered after a 850 °C for 30 min + 950 °C for 30 min thermal treatment, but remains too brittle due to its glassy nature. A 1050 °C treatment allows a few pseudowollastonite crystals to form in a glassy matrix; their formation also hinders sintering. Thus, mechanical properties are inferior to heat-treated plasma-sprayed CZS.     

Surface Nucleation and Crystal Orientation in Lithium Silicate Glass Fibers

The effect of inorganic surface treatments on the orientation of lithium disilicate crystals formed in Li₂O·2.75SiO₂ glass fibers was studied. Glass fibers 0.5 mm and 9μ in diameter were subjected to various surface treatments at room temperature and then heated between 550O and 800°C. It was observed that metal salt solutions applied to the fiber surfaces at room temperature decreased the degree of orientation during heating only if the metal entered the glass and formed nucleation sites within the fibers. Orientation could also be decreased by removing lithium from the glass surfaces. Comparison of the crystallization characteristics of untreated and AgNO₃-treated fibers indicated that the crystallization behavior was controlled by either a growth process or a nucleation process, depending on whether the temperature was below or above 625°, respectively.