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.     

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.     

Calculation of Temperature Dependences of the Viscosity and Volume Relaxation Time for Oxide Glass-Forming Melts from Chemical Composition and Dilatometric Glass Transition Temperature

The relaxation parameter K _sthat is equal to the ratio of the viscosity to the Kohlrausch volume relaxation time _s is analyzed. It is shown that this parameter can be evaluated from the temperature T ₁₃(corresponding to a viscosity of 10¹³P) and the glass transition temperature T ₈ ⁺determined from the dilatometric heating curve. The maximum error of the estimate with due regard for experimental errors is equal to ±(0.4–0.5)logK _sfor strong glasses and ±(0.6–0.8)logK _sfor fragile glasses, which, in both cases, corresponds to a change in the relaxation times with a change in the temperature by ±(8–10) K. It is revealed that the viscosity, the Kohlrausch volume relaxation time _s , and the shear modulus Gof glass-forming materials in silicate, borate, and germanate systems satisfy the relationship log( _s G/) 1. The procedure for calculating the temperature dependences of the viscosity and the relaxation times in the glass transition range from the chemical composition and the T ₈ ⁺temperature for glass-forming melts in the above systems is proposed. The root-mean-square deviations between the calculated and experimental temperatures T ₁₁and T ₁₃are equal to ±(6–8) K for all the studied (silicate, borate, germanate, and mixed) oxide glass-forming systems. The proposed relationships can be useful for evaluating the boundaries of the annealing range and changes in the properties and their temperature coefficients upon cooling of glass-forming melts.     

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.     

Temperature Dependence of Interfacial Tension of Polymer Melts

A unique behavior of interfacial tension of polymer melts is that, in an ordinary temperature region of strong segregation, the entropy effect of chain molecules on the composition-gradient term in the free energy at the interface can make the interfacial tension increase with increasing temperature. To confirm this role of the entropy, interfacial tension of polystyrene/poly(dimethylsloxane) was measured as a function of temperature, and was found to increase with increasing temperature. Using temperature dependence of the segment-segment interaction parameter, which was evaluated from experimental coexistence curves, it was shown that the entropy effect was responsible for this positive temperature dependence of the interfacial tension. The experimental result was also discussed on the basis of scaled expressions of interfacial tension as a function of segregation strength covering weak, strong, and very strong segregation regimes.     

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.     

一个新的聚合物熔体粘性模型

本文分析了了聚合物熔体于稳态剪切流动中的粘性特性，进而提出一新的四参数粘性模型η＝ηｆ／｛Ｋ「１＋（ｒ／ｒｆ）＾１－ｎ｝。应用毛细管流变仪，考察了几种热塑性树脂的流动性，并对模型进行了初步的验证。     

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.     

On the Temperature Dependence of the Viscosity of Multicomponent Glasses in the Glass Transition Range

The viscosities of eight optical glasses are measured in the vicinity of the glass transition temperature (450–680°C, 10¹¹–10¹² P). It is demonstrated that the Shishkin and Williams–Landell–Ferry equations are applicable in the temperature range under investigation. The parameters of the fluctuation free volume concept are calculated. The physical meaning of these parameters is discussed.     

Viscosity and Surface Tension of Oxynitride Glass Melts

The viscosities and surface tensions of three MgO-Al₂O₃-Y₂O₃-SiO₂-based oxynitride glass melts were measured. Glass transition temperature, Littleton temperature, and sink-in temperature were obtained, and by using the Vogel-Fulcher-Tammann equation the viscosities were calculated from T _g (820° to 940°C) to 1600°C. The surface tensions were measured by the drop weight and the drop geometry methods and displayed values between about 500 and 600 N.mm⁻¹. These values are about a factor of two higher than the surface tensions of oxide glass melts.     

Negative Pressure Dependence of Viscosity

It is shown that according to the Adam-Gibbs theory of viscosity the sign of the pressure dependence of viscosity is the same as the sign of the relaxational expansion coefficient. Existing data on systems where negative pressure dependence of viscosity has been observed and relaxational expansion coefficient values are available under the same temperature and pressure conditions appear to support this result. It is therefore suggested that the negative pressure dependence of viscosity and the negative relaxational expansion coefficient have a common mechanistic origin and that this result, in turn, supports the Adam-Gibbs model of viscosity.     

Experiments and Model Simulations of the Viscosity and Dilatation of Glass Coatings with Temperature Dependence

Glass coatings on ceramics or metals are microcomposite materials, consisting of granular oxide phases as pigments and small bubbles that are distributed in glass. Knowledge of dilatation and viscosity versus temperature is essential for applications and simulation methods are necessary. However, the significance of the models depends on the specificity of the compositions and microstructure of glass-containing pigments.
In this study, the viscosity and dilatation of glass coatings were characterized by dilatometry and the sessile drop method. The results show how the physical properties vary with the quantity of zircon grains and bubbles. Simulations with calculation methods for bulk glasses show discrepancies with the experiments, which are caused by the presence of zircon grains and bubbles. We provide evidence that improved models can be obtained by adding equations describing the behavior of glasses containing rigid inclusions and bubbles. The resulting methods provide the opportunity to discover new composition areas of glass coatings having predefined combinations of properties.     

聚合物熔体延伸粘度的研究方法

聚合物熔体的延伸粘度是影响聚合物熔体流动特性和成型制品性能的重要因素。本文较为系统地介绍了聚合物熔体延伸粘度的理论和实验研究方法,着重介绍了Cogswell、Gibson、Binding和Berstered等人的理论研究工作,为进一步研究熔体的延伸粘度提供思路。     

若干硫系玻璃黏度变化速率的结构起源探索

用熔融淬冷法制备Ge33 As12 Se55、Ge22 As20 Se58、Ge10 As40 Se50、As40 Se60、Se硫系玻璃,采用流变仪测试样品黏弹状态的黏度,计算各样品黏度的Vogel-Fulcher-Tammann方程和黏度变化速率(即料性).结合拉曼光谱,根据玻璃微观结构对料性的影响规律进行系统分析...     

Correlation between the Width of the Glass Transition Region and the Temperature Dependence of the Viscosity of High-Tg Glasses

A correlation exists between the width of the glass transition region measured using DTA or DSC during heating and the activation enthalpy Δ H _η^* for the shear viscosity of high-Tginorganic glasses. This is demonstrated by the constancy of a dimensionless parameter C = (Δ H _η^*/ R )(1/Tg – 1/Tg'), where Tg and Tg' are temperatures marking the extrapolated onset and finish of the transition region on the DTA or DSC trace. The logarithm of the shear viscosity at Tg, log η (Tg), is also approximately constant for high-Tg glasses. Using the universal values of C and log η (Tg), fairly reliable estimates of shear viscosities from the transition range through the working range can be made from the Tg and Tg' values obtained using DTA or DSC.     

Chemistry of Uranium in Glass-Forming Melts: Redox Interactions of Uranium with Chromium and Iron in Aluminosilicates

The mutual interactions by internal redox reactions of uranium and chromium and uranium and iron in two aluminosilicate glass-forming melts were studied by optical spectrophotometry. Cr(VI) was found to oxidize completely all available U(V) and U(IV) to U(VI), whereas Fe(III) was not a strong enough oxidizing agent to affect the uranium redox states. Cr(II) totally reduced all the U(V) and U(VI) in the system to U(IV); Fe(II) did not reduce any of the uranium redox species. Cr(III) coexisted with U(VI), U(V), and U(IV) in the melts. The degree of mutual interaction was governed not only by the difference in redox potentials between the respective redox couples, but also by the stability of molecular associations between the redox ions within the melt microstructure.     

On Concentration Dependence of Polymer Solution Viscosity

Abstract

In the present article the relation between polymer solution Newtonian viscosity and its concentration is based on the idea that this relation is determined by the macomolecule coil size. This assumption allows, on the one hand, to construct the simple theory of Huggins constant (K _H) and, on the other hand to use viscosimetric data for estimation of the coil size. Therefore the suggested approach seems very productive.     

蔗渣浆低浓黑液多聚物粘度对温度依赖性的关联模型

利用聚合物自由体积理论模拟了蔗渣浆低浓黑液对粘度对温度的依赖性的数学模型，最终得出黑液多聚物粘度与温度的相关式：η=A1exp[B1/(T-T0)]。利用示差扫描量热分析技术（DSC）得出了蔗渣黑液多聚物中连续相与分散相的转变曲线，并获得了表观温度T0的平均值为255K；通过实验数据拟合可回归出蔗渣黑液多聚物在不同浓度时的系数A1和B1值。因此，使用该粘度的数学模型可估算蔗渣低浓（接近40％固含量）黑液多聚物在操作温度范围内（20－100℃）的粘度值。