Hydration of fly ash cement

It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO₂ generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.     

Formation of the bubble structure in the 26Li<Subscript>2</Subscript>O · 74SiO<Subscript>2</Subscript> glass

The formation of a bubble structure in the glass of composition 26Li₂O · 74SiO₂ is investigated. The stable reproducible characteristics of the bubble structure are obtained, namely, dependences of the number of bubbles on the conditions of glass synthesis, i.e., the synthesis temperature, the synthesis time, and the type of initial reagents. It is shown that the number of bubbles decreases with an increase in the height of the sample (glass melt in the crucible), as well as with an increase in the synthesis temperature at a fixed synthesis time or with an increase in the synthesis time for each specific temperature. The bubble size distribution curves are obtained for all synthesis conditions. The reproducible bubble structure is determined for each layer of the glass sample, which is subsequently used in studying the kinetics of heterogeneous nucleation.     

原料粒度对超白玻璃熔化澄清质量的影响

通过调节不同配合料(石英砂、白云石和石灰石)的粒度,研究了原料粒度对超白浮法玻璃熔化质量的影响。使用高温视像观察装置和玻璃熔化分析软件,观察并分析在颗粒粒度含量不同条件下,超白浮法玻璃熔化澄清过程中配合料的初熔温度和气泡量,以此来表征玻璃的熔化澄清质量。结果表明:随着石英砂粒度的增大,玻璃初熔温度升高;石英砂粒度过大或过小都会影响玻璃澄清质量,在小于0.125 mm细粉含量达12%时,澄清效果最好;随着白云石和石灰石粒度的增大,初熔温度升高;白云石粒度增大或石灰石粒度减小,澄清质量均变差。     

铋掺杂铝硅酸盐玻璃的超宽带近红外发光性质

采用高温熔融法制备了组分为50SiO_2-xAl_2O_3-(50-x)MgO-Bi_2O_3(x=5,10,15,20,摩尔比)的铋掺杂铝硅酸盐玻璃。研究了铋掺杂铝硅酸盐玻璃超宽带近红外发光性质,探讨了玻璃基质的光学碱度对铋离子宽带发光特性的影响。结果表明:在690nm和808nm的激发下,铋掺杂铝硅酸盐玻璃的红外荧光中心分别位于1106nm和1294nm;随光学碱度的增强,铋离子的红外发光强度减弱。并对铋离子超宽带发光的机理进行了探讨,认为其红外发光源于低价的Bi~+和Bi~(2+)。     

Shrinkage of an oxygen bubble rising in a molten glass

The mechanisms controlling the evolution of a bubble surrounded by molten glass are important to understand in order to improve melting in glass furnaces, particularly during a change in composition. In order to provide insight into this phenomenon, the behavior of an isolated bubble rising in molten glass is examined both experimentally and numerically.An experimental procedure developed specifically to observe, in situ, a rising bubble is described. Two soda-lime-silica compositions are tested, with low and high iron content, respectively.The numerical model used to describe bubble shrinkage is based on the results recently proposed in Pigeonneau (2009). A specific mass transfer coefficient is used for oxygen where the oxidation–reduction reaction of iron oxides is taken into account.A comparison between the experimental and numerical results shows the importance of the oxidation–reduction reaction of iron in the mass transfer of oxygen. The shrinkage rate of a pure O₂ bubble is enhanced with reduced molten glass iron content.     

池窑鼓泡对熔制玻璃质量和产量的影响

利用Flutank玻璃熔制过程三维计算机模拟技术,系统研究了鼓泡对熔制玻璃质量、产量的影响.结果表明:鼓泡使窑内熔体温度升高、流速加快,玻璃熔制、均化条件改善,微细气泡澄清条件变差,玻璃单耗降低.对文中选用的浮法窑,鼓泡能提高日产量23%,并维持原有的熔制、均化、冷却条件不变.池窑鼓泡后,日产量增加不会改变可见大气泡(半径小于0.5mm)的排除条件,但影响可见小气泡(半径小于0.25mm)和微细气泡(半径小于0.1mm)的澄清.模拟结果还揭示:鼓泡虽然略微降低出料口截面热均匀性,但不会出现分层现象.鼓泡管间距选择不当会产生有害的"沉降流".     

泡沫玻璃气泡缺陷与解决方案

泡沫玻璃是一种具有均匀气泡结构的玻璃制品,具有隔热、吸声、防潮、防火等特点的轻质高强建筑材料和装饰材料。泡沫玻璃的生产过程中,经常会遇到气泡结构不均或大气泡等气泡缺陷。本文从气泡的产生机理分析入手,针对具体的气泡缺陷种类,分析产生原因,提出解决方案,更好地实现泡沫玻璃的内在和外观质量。     

浅议浮法玻璃气泡问题的分析与解决

在生产实践中,玻璃产品中的气泡问题一直是困扰玻璃生产厂家的一大难题。本文介绍了某玻璃企业玻璃产品出现气泡以后的观察、分析和解决过程,提出气泡的形成、变化、消失、再出现的过程,是气体在玻璃熔体中溶解和扩散的结果,了解各种气体在玻璃熔体中的特性和行为方式,有针对性地确定好玻璃熔化的温度曲线和燃料分配,这对减少玻璃中气泡是很重要的。     

浮法玻璃固定气泡的研究与治理

简述了浮法玻璃中气泡形成的机理和类型,着重对某公司固定气泡形成的位置和原因进行了分析,通过增设池底风机、调整池底风量、更换新矿点、改善对辊破碎方式等措施,可有效解决固定气泡的问题,效果显著。     

Effect of atmosphere control on magnetic properties of CaO-Al2O3-SiO2-Fe3O4 glass ceramics

The influences of atmosphere during processes of melting and heat treatment, heat treatment temperature, Fe₃O₄ content and basicity on the magnetic properties of magnetite-based glass ceramics were investigated. For sample containing 20 % Fe₃O₄ melted in different atmospheres, the highest saturation magnetisation was realized in 20vol% air + 80 vol% Ar, due to the fact that ratio of Fe³⁺ to Fe²⁺ in melt obtained in this atmosphere was close to 2. However, it was found that the coercivity of glass ceramics was not affected by the melting atmosphere. A high sintering temperature led to the decrease of saturation magnetisation and the increase of coercivity. As increasing Fe₃O₄ content, the main crystal phase transformed from CaSiO₃ to CaFe_0.6Al_1.3Si_1.08O₆ and finally to magnetite phase, accompanied by the increase of saturation magnetisation and coercivity. In addition, the increase of basicity caused the decrease of saturation magnetisation and the increase of coercivity.     

Experimental study of bubble formation in a glass-forming liquid doped with cerium oxide

This work aims to study the mechanisms of oxygen bubble formation coming from redox reaction of a polyvalent element incorporated in a glass melt. Borosilicate glass composition is selected for its use as a glass matrix for nuclear waste conditioning. Cerium is selected as a polyvalent element as it may be found in nuclear waste. The chosen material is characterized in terms of physical properties which influence bubble formation and growth. A postmortem optical microscope approach is used to observe bubbles in the investigated material after thermal treatment for varying temperatures (900°C-1100°C) and durations. To support the understanding of oxygen bubble formation, cerium speciation by X-ray absorption near-edge structure (XANES) and bubble gas composition are experimentally evaluated. In this article, we indicate how bubbles are formed in the investigated glass melt system. It is also demonstrated that the mechanisms that govern bubble evolution are fundamentally the same and that the plot's optimum points are strongly influenced by the temperature. These last statements are confirmed by considering some bubble features, such as bubble mean density and bubble mean diameter evolutions, and normalizing the experimental time using a characteristic residence time (t_η) obtaining thereafter a dimensionless time, which is a function of the glass melt properties obtained by the physical characterizations. The impact of temperature and time on bubble formation is described.     

Activity–Composition Relations of Chromium Oxide in Silicate Melts at 1500°C under Strongly Reducing Conditions

The solubility and activity–composition relations of chromium oxide in melts of the systems CaO–CrO _x –SiO₂ and CaO–Al₂O₃–CrO _x –SiO₂ have been determined at 1500°C by equilibrating melts with Pt–Cr alloys at known oxygen pressures. It is shown that the increase in the concentration of divalent chromium ions, as the oxygen pressure and the basicity of melt decrease, results in a dramatic increase in the solubility of chromium oxide in the liquid phase. An increase in the Al₂O₃ content of the melt leads to a decrease in the solubility of chromium oxide over the whole composition range studied. The activity coefficient of CrO has been found to increase with increasing melt basicity and decreasing oxygen pressure whereas the activity coefficient of CrO_1.5 decreases sharply with increasing melt basicity for siliceous melts but levels off at a basicity ratio (wt% CaO/wt% SiO₂) of about 0.7. An increase in the Al₂O₃ content of the melts results in an increase in the activity coefficient of CrO.     

浮法玻璃熔窑内气泡的分布研究

通过对正常运行的浮法熔窑内不同部位玻璃液取样分析,研究了不同部位玻璃液中微小气泡的含量,揭示了气泡在熔窑内消除的主要机理,研究发现熔窑内玻璃液流、温度和芒硝在熔窑不同部位对气泡的分布起到重要的作用。     

GASES IN GLASS*

An apparatus is described for extracting the gas from glass at glass-furnace temperature and determining its composition. Results are given for glasses of various compositions and various melting histories. All ordinary glasses were found to contain appreciable quantities of dissolved (or chemically combined) gas, the amount varying from a few hundredths to a few tenths per cent. Water is frequently the most abundant gas, the content being highest in borosilicate glasses. Carbon dioxide is also usually present, the amount depending on the basicity of the glass. Nitrogen, carbon monoxide, and hydrogen were never found present in appreciable quantities. All oxidized glasses contain some oxygen. Glasses containing arsenic give off a comparatively large volume of oxygen. The effect of this oxygen on fining is discussed. It has been found that remelting a glas has little effect on the gas content. The gas content is greatly influenced by the size of the melt, being the lowest in small experimental melts.     

Influence of lattice modifier on the nonlinear refractive index of tellurite glass

We studied the influence of different lattice modifiers (Nb₂O₅, Bi₂O_3, or TiO₂) on the nonlinear refractive index of a tellurite glass matrix by using the Z-scan technique. Based on the ability of the lattice modifiers to decrease the band-gap energy while simultaneously increasing the linear refractive index of the TeO₂-based glass, we investigated how these modifiers affect the nonlinear refractive indices. All studied glass presented high nonlinearities, and the addition of lattice modifiers made only a small contribution to increasing magnitude. These results could be explained through the observation of the band-gap energy reduction, which is related to the increase in the non-bridging oxygen content with the addition of the lattice modifier. The increase in the refractive index nonlinearity is explained by the optical basicity and the high electronic polarizability of the modifiers ions.     

Compositional Dependence of Absorption Spectra of Ti3+ in Silicate, Borate, and Phosphate Glasses

Absorption spectra of Ti³⁺ were measured for silicate, borate, and phosphate glasses doped with 0.5 mol% Ti₂O₃.The absorption coefficient at the peak wavelength of the ₂T₂→₂E transition of Ti³⁺ is used as a parameter showing the relative content of Ti³⁺ions in glass samples. The effect of glass composition on Ti³⁺/Ti⁴⁺ redox was studied. For multicomponent glasses, a basicity parameter calculated from glass composition is proposed in terms of coulomb force between the cation and the oxygen ion. The value of the absorption coefficient depends on basicity in silicate and borate glasses; however, it is independent of composition in phosphate glasses.     

Solubility of finely dispersed powders of calcium-containing glasses in a water medium. Calcium-silicate glasses

The effect of the composition of calcium-silicate glasses on the behavior of powders with different dispersity (500, 60, and 10 µm) in a water medium is investigated. The acid-base characteristics of the water medium and the concentration of calcium ions in a water solution after soaking glass powders are determined. It is shown that the main parameter determining the mechanism of the glass dissolution in water is their basicity modulus.     

Behavior of Multicomponent Gas Bubbles in Glass Melts

A mathematical model is proposed to study the behavior of multicomponent gas bubbles in glass melts. The effects of the melt temperature on bubble radius, trajectory, and composition were studied as a function of time, both accounting for and disregarding bubble boundary motion. It is shown that accounting for the boundary motion results in shorter refining times, smaller bubbles, and larger concentrations of the gaseous species than if this motion is disregarded. It is also shown that the bubble trajectory is almost a linear function of time and that mass transfer has a very small effect on bubble trajectory and refining times; however, it has a strong influence on the bubble radius, which, in the absence of mass transfeir, increases linearly with the temperature.     

The Effect of the Substrate on the Isomerization of Model Disperse Dyes based on Stilbene

A study of the thermal isomerization of a series of model disperse dyes based on stilbene is described. The results show that the rate of isomerization is influenced by the basicity of the substrate and also by the moisture content. It is suggested that the observed humidity effect is due to an increase in the ease of diffusion of the dye molecules in the substrate.     

Spatial distribution of nucleated bubbles in molten glasses undergoing coalescence and growth

Two‐dimensional spatial distributions and growths of nucleated bubbles during the re‐melting of “float” glass samples are experimentally investigated. To follow the bubble population undergoing coalescence, the temporal behavior of the Voronoï tessellation built by the bubble positions are monitored. During coalescence, the Voronoï cell areas are fitted by a single‐parameter Gamma distribution. Numerical time simulation of population of bubbles undergoing coalescence shows an exponential increase in the parameter associated to the Gamma distribution with the fraction of coalesced bubbles in agreement with experimental observation. An initial density of nuclei is then estimated; direct observation would require an extremely high space resolution. The bubble number density is two orders of magnitude larger on the side which was in contact with tin bath than on the other side in contact with atmosphere. Moreover, bubbles grow faster on tin side. From a thermodynamic and mass transfer models, we prove that tin reduces the glass former liquid which leads to an increase in dissolved sulfur explaining the more abundant bubble population and the enhanced growth rate on tin side.