Ion-Exchange Interaction of Glass-Forming Silicate Melts with Mixed Chloride Melts

The ion-exchange interaction of the sodium aluminosilicate and sodium galliumsilicate melts with a mixture of molten Li, Na, K, Rb, Cs, and Ba chlorides is studied. It is established that two alkaline silicate melts are characterized by negative deviations from the ideal behavior, and silicate melts containing alkaline and alkaline-earth cations are characterized by noticeable positive deviations from the ideal behavior.     

Physical Thermodynamic Model of Alkali and Alkaline-Earth Fluorozirconate Glass-Forming Melts

A physical model for the thermodynamics of glass-forming alkali and alkaline-earth fluorozirconate melts is presented that takes into consideration the strong negative deviation from ideal behavior that is manifested by deep eutectic wells in the phase diagrams and large exothermic heats of mixing. The model is based on chemical equilibria between anionic complexes with six- to eight-fold coordination of zirconium and a simple Temkin model for the free energy of mixing. Calculated phase diagrams and liquidliquid heats of mixing agree well with the experimental data. The model predicts six-fold coordination of zirconium in glass-forming melts, which implies that the fragile nature of fluorozirconate glasses can be explained by a significant increase in the coordination of zirconium when the melt is quenched to the glassy state.     

Interrelation of Diffusion and Thermodynamic Characteristics in Silicate Glass and Glass-Forming Melts

A correlation was established between the character of the concentration dependence of the self-diffusion coefficients and the deviation from ideality for mixed alkali silicate glass and melts and a melt containing alkaline and alkaline-earth cations.     

Calculation of the Viscosity of Glass-Forming Melts: V. Binary Borate Systems

Relationships for calculating the viscosity of boron oxide and binary borate melts in the range 10¹–10¹³ P have been proposed. The temperature dependence of the viscosity is described by the equation log = –3.5 + [/(log T –log ₀ )]^1/n . The parameters of the equation are calculated from the composition by the empirical formulas. The model proposed takes into account the shift of chemical equilibria in a melt. The principle of summation of the fluidities associated with the mobility of different structural units is used in calculating the viscosity over a wide range of component concentrations. The mean error in calculations of the characteristic temperatures is equal to 20 K in the glass transition range and 30–40 K in the range of low viscosities.     

Stimulus Responsive Poly(ferrocenylsilanes): Redox Chemistry of Iron in the Main Chain

Redox chemistry of organometallic poly(ferrocenylsilane) polymers (soluble in organic or aqueous environment) is discussed. Poly(ferrocenyldimethylsilane) (PFDMS) was oxidized in CH₂Cl₂ solution with different oxidants. Oxidation was accomplished with stepwise increasing amounts of ferric chloride (FeCl₃), iodine (I₂) and tris(4-bromophenyl)ammoniumyl hexachloroantimonate ( ). The process was followed by UV–visible spectroscopy. Mixed-valence salts with different Fe(III)/Fe(II) ratios were obtained. The oxidation products were characterized by Mössbauer spectroscopy, which proved to be a very valuable tool to analyze mixed valence ferrocenyl compounds. Mössbauer analysis demonstrated that 100% oxidation could be achieved with TBPA^{· +}. Decamethylferrocene (DMFC) was found to be a suitable reducing agent for the oxidized polymer. The reduction process was monitored by UV–visible spectroscopy. The polymer was characterized by gel permeation chromatography (GPC) following the oxidation/reduction cycle and evidence of some fragmentation of the chains was observed. A water-soluble PFS polycation was successfully oxidized with FeCl₃ for pH values between 4 and 5. Ascorbic acid (vitamin C) was found to completely reduce the oxidized water-soluble polymer.     

Analysis of Regularities in Composition Dependence of the Viscosity for Glass-Forming Oxide Melts: II. Viscosity of Ternary Alkali Aluminosilicate Melts

The data available in the literature on the viscosity of alkali aluminosilicate melts are collected and analyzed using the SciGlass information system. It is established that there are two composition regions in which the composition dependences of the viscosity logarithm at a constant temperature (above 1000°C) are adequately described by linear equations. The largest amount of data is available for the composition region with an alkali oxide concentration exceeding the aluminum oxide concentration ([R ₂O] > [Al₂O₃]). In this region, the viscosity of melts is predominantly affected by two factors, namely, the concentration of alkali oxide uncombined into the alkali aluminate complex and the nature of alkali cations. At a constant concentration of unbound alkali oxide, the replacement of SiO₂ by AlRO₂ is accompanied by a noticeable decrease in the viscosity of lithium aluminosilicate melts, a very weak decrease in the viscosity of sodium aluminosilicate melts, and a considerable increase in the viscosity of potassium aluminosilicate melts. In the second composition region ([R ₂O] < [Al₂O₃]), the replacement of SiO₂ by AlO_1.5 at a constant alkali metal content is attended by a decrease in the viscosity. In this region, the viscosity increases when changing over from Li₂O to K₂O upon complete substitution of one alkali oxide for another. Different variants of structural interpretation of the regularities revealed are discussed.     

Dissolution of Iron in Silicate Melts

The oxidation and dissolution of metallic iron in silicate melts were investigated. The base composition consisted of Idaho soil with quartz and potassium feldspars as primary phases. Iron immersed in melts of unaltered soil and SiO₂-K₂O underwent minimal oxidation at 1400°C. Melts consisting of soil, 10 wt% of added K₂O, and 5-20 wt% of added Fe₂O₃ were capable of dissolving Fe. Progressively greater Fe dissolution occurred with increasing Fe₂O₃ content. A melt containing 20 wt% Fe₂O₃ dissolved 10 wt% Fe within 3 h. Melts containing greater than 10 wt% Fe₂O₃ crystallized almost entirely as magnetite (Fe₃O₄) and augite (Ca(Mg,Fe(2+))(SiO₃)₂). The data obtained also suggest that added Fe₂O₃ contributed to an increased rate of oxygen diffusion in these melts.     

Interaction of Y2O3-Stabilized Cubic ZrO2 with Sodium Silicate and Sodium Aluminosilicate Glass-Forming Melts

The kinetics of interaction of the cubic solid solution 92ZrO₂ · 8Y₂O₃ with sodium silicate and sodium aluminosilicate oxide glass-forming melts is investigated at a temperature of 1100°C. It is found that the stability of cubic -ZrO₂ against dissolution in an oxide melt is determined by the composition of the anionic matrix of the melt and depends on the difference between the acid–base characteristics of oxide systems being in contact. It is demonstrated that this process can be described by the contracting volume equation and is limited by the rate of motion of the reaction interface.     

Chemistry of Uranium in Aluminophosphate Glasses

The U(VI)-U(V)-U(IV) redox equilibria were monitored in two sodium aluminophosphate base compositions at a variety of melt temperatures, imposed oxygen fugacities, and uranium contents. The higher redox states of uranium were quite soluble in the phosphate glasses, whereas U(IV) would readily precipitate from the melts as UO₂. Comparisons of the uranium redox equilibria established in phosphate melts vs those in silicate melts indicated that the coordination sites of the individual uranium species are generally the same in both solvent systems although they differ in detail.     

Redox Equilibrium of Iron in Silicate Glasses

The effect of some additives on the equilibrium of valence forms of iron is investigated. It is demonstrated that tin and carbon more significantly than fluorine reduce iron. The redox potential of the glass matrix affects the equilibrium between difference valence forms of iron much less than additives correcting spectral characteristics of glass.     

镀铬液中铁的测定

根据氨性溶液的特性,向镀液中加入过量的氨水与铁作用生成氢氧化铁沉淀,从而与镀铬液及杂质金属,如:铜、锌、镍等分离。用稀王水溶解氢氧化铁,使铁离子全部氧化为三价而与硫氰酸铵生成深红色的硫氰酸铁配位物,借此进行比色测定。方法简单,准确。     

镀铬溶液中铁的测定

研究了在吐温-80存在下,于pH=2~3的盐酸溶液中,三价铁离子与二安替比林甲烷和碘化钾作用形成棕黄色的三元离子缔合物的显色反应条件。该体系的最大吸收峰为400 nm,表观摩尔吸光系数4ε00=7.5×104L/(m o l.cm),Fe3+质量浓度在0.16~2.8 m g/L范围内符合比尔定律。该法可用于镀铬液中铁的测定。     

碱融分光光度法测定钛铁中二氧化硅

本法采用氢氧化钠在高温炉中对钛铁样品进行熔融,使钛铁中的硅在碱性环境中能完全熔解,熔解后熔块经硝酸酸化处理,其溶液中可溶性硅酸与钼酸铵作用,用硫酸亚铁还原为硅钼蓝,根据硅钼蓝的深浅,以吸光度法测出硅的含量。     

镀铬溶液中铜铁的快速分析

介绍了镀铬溶液中铜、铁杂质的快速分析方法。分别采用二乙基二硫代氨基甲酸钠(DDTC)光度法和水杨酸光度法测定镀铬溶液中铜和铁的质量浓度。实验表明:这两种分析方法操作简单,结果准确,能够满足快速监控镀铬溶液中铜、铁杂质的要求。     

The Influence of Chemical Composition of Silicate Glass-Forming Melts on the Kinetics of Their Interaction with Y2O3-Stabilized Cubic ZrO2

The influence of the chemical composition of sodium silicate, sodium calcium silicate, and sodium aluminosilicate glass-forming melts on the kinetics of their interaction with a 92ZrO₂ · 8Y₂O₃ cubic solid solution is investigated. It is demonstrated that the kinetics and the mechanism of interaction are determined by the degree of dissociation of the anionic matrices of the melts under investigation. In turn, the degree of dissociation depends on the chemical nature and concentration of oxides (modifiers and network-formers) and the temperature. It is found that the process rate can be limited by the diffusion or chemical interaction depending on the reaction conditions.