Swelling of Microporous High-Silica Glasses

The swelling of microporous glasses in water was found to change as a function of the heat–treatment time and temperature required for phase separation in the original borosilicate glass (70SiO₂-23B₂O₃-7Na₂O (wt%)). The swelling appears to be determined primarily by the quantity of silica gel remaining in the micropores, which in turn is determined by the composition of the alkali-borate-rich phase of the phase-separated glass.     

Dielectric Relaxation in High-Silica Borosilicate Glasses

Borosilicate glasses with high silica and varying water content were made by a process similar to that of Vycor. Dielectric relaxation measurements show a de-conduction activation energy equal to that of fused silica, no apparent dependence of the dc conductivity on water content, and an unexpectedly narrow relaxation-time distribution equivalent to a simple RC circuit element. A single relaxation process is observed in all samples regardless of water content and neither the conductivity nor the activation energy are significantly altered by a 50-fold change in water content.     

超薄铝硅玻璃离子交换工艺研究

高强度超薄盖板玻璃是电子信息产品的重要组成部分,化学强化(离子交换)是提升超薄盖板玻璃力学性能的主要技术途径。在离子交换过程中,玻璃易产生应力弛豫等现象,导致化学强化玻璃难以具备较高的表面压应力、较大的应力层深度与较高的维氏硬度。本文采用两步法离子交换工艺,研究了熔盐、离子交换温度与时间等因素对强化后超薄铝硅玻璃应力层分布及维氏硬度等性能的影响。结果表明,本文所研发的两步法离子交换工艺,可以使玻璃兼具较高的表面压应力、较大的应力层深度与较高的表面维氏硬度。离子交换后,铝硅玻璃的表面压应力可达900 MPa以上,应力层深度可达70 μm以上,同时表面维氏硬度达7.2 GPa以上。     

Effect of Nitriding on Electrolysis and Devitrification of High-Silica Glasses

Devitrification occurs near the cathode when reconstructed high-silica glasses and fused quartz undergo electrolysis at 900°C. The crystalline phase is cristobalite and results from a concentration of alkali ions. Subsequent and more superficial crystallization around the alkali-rich spot is caused by interaction of the glass with alkali vapors coming from the central spot. The degree of devitrification increases with the alkali content of the glass. Devitrification at constant alkali level can be reduced in reconstructed glasses by nitriding the porous glass with ammonia at a high temperature before consolidation. Devitrification decreases and viscosity and electrical resistivity increase as the nitriding temperature increases 500° to 1000°C. Nitrided glasses are more resistant to electrolytically induced devitrification than is fused quartz.     

新型硫卤玻璃GeS2-Ga2S3-AgX(X=Cl,Br,I)中的K+-Ag+离子交换

以油酸钾为熔盐,GeS2-Ga2S3-AgX(X=Cl,Br,I)玻璃为基玻璃,在270℃的环境温度下,以氮气作为保护气氛,成功地进行了K -Ag 离子交换。在50GeS2-25Ga2S3-25AgI玻璃中,K 离子的交换深度可达256μm,并对交换深度、离子扩散系数以及离子浓度之间的规律进行了初步研究。通过离子交换研究,为制备硫卤玻璃光波导奠定了基础,并可以进一步拓宽硫卤玻璃的应用前景。     

Preparation of High-Silica Glasses from Colloidal Gels: I, Preparation for Sintering and Properties of Sintered Glasses

A new method for preparing fused silica and high-silica glasses through the sougel process is described. Ordinarily, fused silica is formed by fusion of silica at 1900° to 2000°C. The method described consists of preparation of a porous body by mixing colloidal silica with water, drying, redispersion, molding by casting, followed by gelation, drying, and sintering at 1450° to 1500°C. The sintering is facilitated by addition of 3 to 5 wt% B₂O₃. The process of dispersion-drying-redispersion (so-called "double process") results in formation of a two-mode pore structure which permits drying of cast tubes and rods without breakage. The preparation of the porous bodies, study of pore structure, and properties of resulting glasses are described in Part I, the sintering is considered in Part II, and the mechanism of gel formation is interpreted from infrared spectroscopy studies in Part III.     

Preparation of High-Silica Glasses from Colloidal Gels: II, Sintering

The sintering of dried colloidal SiO₂ gels, whose preparation and properties are reported in Part I, is described. The effects of various sintering parameters were studied and the conditions for achievement of the best optical quality include the use of: a pretreatment of the SiO₂ at ∼925°C, moderate heating rate (∼400°C/h), He+CI₂ atmosphere, 1500° to 1600°C sintering temperature, and 1 to 4 h sintering time. Dynamic sintering kinetic studies (heating rate=400°C/h) show that this SiO₂ sinters to nearly theoretical density by about 1380°C. However, optical transparency is achieved by removal of minor residual porosity at above 1500°C. Isothermal sintering data fit to a model assuming interconnecting cylinders of SiO₂ predict the proper activation energy for the viscosity if initial stages of sintering are considered. Residual porosity in sintered glasses is related to large interstices in the unsintered gel.     

Conductivity Behavior of High-Silica Glasses with Varied Concentrations of Sodium Ions

The low-frequency conductivity of silica glasses containing 5% B₂O₃ and from 0.02 to 6.7% Na₂O is extrapolated to dc values and analyzed in terms of temperature and concentration dependence. The concentration dependence of the conductivity occurs exclusively in the activation enthalpy. This prevents an analysis of the number of ions participating in the conduction in all but one sample for which tracer diffusion data gave a correlation factor of unity in the Nernst-Einstein equation. The concentration dependence of the activation enthalpy was analyzed empirically. The activation enthalpy varies linearly with sodium-sodium separation or jump distance. This result suggests that, at low Na concentrations, the conducting ions execute several separate motions between nonequilibrium sites before reaching the nearest equivalent site. The empirical equation is shown to fit activation energy data for silica glasses containing from 0.06 to 40% Na₂O.     

Preparation of High-Silica Glasses from Colloidal Gels: III, Infrared Spectrophotometric Studies

The gel process for making silica was studied by infrared spectrophotometry of solid samples in various stages of dehydration. Spectra were recorded in the high-frequency overtone region (2500 to 8000 cm^-1) as well as in the region of fundamental absorption (200 to 4000 cm^-1), depending on the nature of the sample. Molecular water was distinguished from silanol groups and the effects of hydrogen bonding were observed. Drying and heat treatment of gels at low temperatures (<150°C) causes a loss of unbonded included water, but significant loss of hydrogen-bonded water occurs only with relatively high-temperature heat treatments (>800°C). Hydration of siloxane groups on pore surfaces and attachment of water molecules by hydrogen bonding to these surface silanol groups is reversible for heat treatments up to 1025°C. At higher temperatures (>1025°C), active sintering takes place, converting the porous structure into a homogeneous silica network. In this process, surface silanol groups become isolated within the silica network, giving rise to vibrational frequencies characteristic of internal -OH groups. Also, at the higher temperatures silanol groups react to form siloxane groups with loss of H₂O. A model is presented for formation of a gel in which hydrogen bonding initiates association of colloidal particles, followed by strengthening through interparticle solid silica precipitation.     

Effect of Cerium on the Ion-Exchange Parameters in Alkali Silicate Glasses

Alkali gallosilicate glasses containing 1–8 mol % CeO₂ after ion-exchange treatment in a NaNO₃ melt at different temperatures are studied. The refractive index distributions in glasses with different cerium oxide contents are obtained, and the profiles of the Na₂O concentration distribution in the samples containing 2 mol % CeO₂ after ion-exchange treatment at temperatures T = 500–550°C are determined. It is revealed that, as the cerium oxide content increases, the interdiffusion coefficient decreases, whereas the refractive index increment increases. The results obtained are analyzed within the framework of the model of dopant segregation, according to which cerium undergoes selective incorporation and concentration displacement into polar microregions of the glass.     

Spectral-Luminescent Properties of Composite Materials Based on Nanoporous High-Silica Glasses Activated with Bismuth and Cerium Ions

Glass Physics and Chemistry - Composite materials based on matrices of high-silica nanoporous glasses activated with bismuth and cerium ions are synthesized. It is found that the samples, depending...     

Infrared Spectroscopy Study of Composite Materials Based on Nanoporous High-Silica Glasses Activated with Silver and Lanthanum Ions

Glass Physics and Chemistry - Composite materials (CMs) activated by silver and lanthanum ions based on high-silica porous glass (PG) matrices have been synthesized. The CMs were studied by IR...     

Method of Fabricating Ceria-Stabilized Tetragonal Zirconia Polycrystals

Most zirconia-based toughened ceramics need specialized processes to achieve their desired properties. In this paper, we report the fabrication of toughened ceria-stabilized tetragonal zirconia polycrystal by conventional processing, i.e., ball milling and cold-pressing followed by sintering. We believe that ball milling works here because a somewhat coarser particle size is actually beneficial in this case. Although the samples were not fully dense (they need not be), a composition of ZrO₂-12 mol% CeO₂ yielded a fracture toughness value of 14.1 MPa·m^1/2. This is comparable to values reported for materials processed by specialized techniques and can be rationalized in terms of R-curve behavior.     

In Situ Measurement of Capacitance: A Method for Fabricating Nanoglass

The capacitance of the Na₂O–SiO₂ glass was measured in situ during heat treatment at various frequencies, 20, 100, 1, 3, 10, and 30 kHz. It was found that the capacitance of the glass abruptly decreases after a certain duration. The glass was quenched at this stage. It was confirmed by the X-ray diffraction and transmission electron microscopy that this decrease of capacitance was associated with the formation of crystallites in the glass matrix. The size of crystallites was observed to be in the range of about 10 nm.     

带有滤光光阑的微透镜阵列制备方法

文章提出了一种采用湿法刻蚀制备含滤光光阑的三明治结构微透镜阵列(MLA)的方法。该方法制备的微透镜阵列透镜一致性好,其上的滤光层能够有效遮挡杂光,极大改善了激光直写光刻系统(LDI)的曝光效果,并且该方法具有制备设备简单、制备成本低、适合大批量制备的特点。     

A New Method of Fabricating NASICON Thin Film

Nasicon thin films of 15 μm thick on YSZ sub-strates were prepared by means of solid state reaction at 1230℃ for 10 hours,Stuctural characteriza-tion of the films were performed by XRD ,SEM and EDX,A new tyype of CO2 gas sensor with Nasicon thin film as solid electrolyte was developed.     

Crack Blunting of High-Silica Glass

The mechanical strength of abraded high-silica glass was measured after immersion in water and silicic acid solution at room temperature and 88°C. The strength increase was observed at 88°C. This phenomenon is usually explained by crack blunting. From an observation of the dissolution rate of a porous glass with a similar composition and a comparison of the strength increase in water and silicic acid, it was concluded that the dissolution and subsequent precipitation of the high–silica glass is the mechanism of the crack blunting.     

Sodium Diffusion in High-Silica Glass

Isotope effect and electrical conductivity measurements were used to investigate the mechanism of Na⁺ diffusion in high-SiO₂ glass. A Haven ratio near unity and comparatively high isotope effect values suggest a quasi-interstitial mechanism for Na⁺ diffusion. At low Na⁺ concentration the Na⁺−Na⁺ separation distance is so large that the Na⁺ jumps become uncorrelated.     

对玻璃材质热稳定性能测试方法的探讨

对玻璃材质热稳定性能测试方法的探讨刘新年，林宝英，付桂臣（西北轻工业学院７１２０３１）ＡＮｅｗＭｅｔｈｏｄｆｏｒＭｅａｓｕｒｉｎｇＴｈｅｒｍａｌＳｈｏｃｋＲｅｓｉｓｔａｎｃｅｏｆＧｌａｓｓｅｓ￥ＬｉｕＸｉｎｎｉａｎ；ＬｉｎＢａｏｙｉｎｇ；ＦｕＧｕｉｃ...     

废弃玻璃水热热压-煅烧法制备泡沫玻璃

泡沫玻璃是一种性能优越的新型环保建筑材料.本文以废弃玻璃和水为原料,利用水热热压-煅烧法制备泡沫玻璃,考查了水热压力、煅烧时间、煅烧温度和升温速率对样品形貌、体积密度及抗压强度等性能的影响,并通过TG-DTG、XRD、SEM等对过程原理进行了分析.结果表明煅烧温度是影响产品质量的主要因素,水热压力、煅烧时间、升温速率对其影响不大.得到的最优条件为:水热压力8.5 MPa、水热温度200℃下反应45 min,以5℃/min的速率加热至800℃煅烧1h,在此条件下制得的泡沫玻璃发泡均匀,密度为0.24 g/cm3左右,抗压强度可达1.6MPa.