Gamma-Ray Induced Coloring of Some Phosphate Glasses

The changes in gamma-ray induced optical absorption in phosphate glasses resulting from changes in composition, conditions during melting, and additions of small amounts of some oxides are discussed. A resolution of the induced spectra showed that the observed absorption is due to the superposition of three bands at 2.3, 2.9, and 5.5 e.v. (540, 425, and 225 mü) and to a fourth band whose absorption peak is beyond 6 e.v. The ultraviolet induced absorption increases, whereas the visible absorption decreases in glasses melted under reducing conditions as opposed to those melted under normal conditions in air and on replacement of K⁺ by Na⁺ or Li⁺. A similar effect is produced on replacement of Ba⁺⁺ by Pb++ and on the addition of T1₂O to a CaO-P₂O₅ glass or the addition of As₂O₃ to a CaOP₂O₅, GeO₂ glass. Additions of large amounts of GeO₂ are accompanied by a decrease in the number of nonbridging oxygens and a decrease in the visible induced absorption. Replacement of Ca ⁺⁺ by Ba⁺⁺ ions showed an over-all decrease in the induced absorption. The addition of small amounts of the oxides of germanium, titanium, iron, thallium, niobium, and arsenic showed an appreciable effect in inhibiting the visible induced coloration.     

Role of Cerium in Suppression of Gamma-Ray Induced Coloring of Borate Glasses

The role of cerium in the suppression of gamma-ray induced coloration in glass has been found to depend on the relative concentration of Ce³⁺ to Ce⁴⁺ ions as well as on the total cerium content. In a borate glass having high ultraviolet transmission, it has been found that both Ce³⁺ and Ce⁴⁺ ions are necessary to suppress the optical absorption bands induced in the visible region. The role of cerium can be explained on the basis of a change in its oxidation state as a result of gamma irradiation. It is postulated that the cerous ions, by the reaction Ce³⁺→ Ce⁴⁺+ e , suppress the induced visible band at 2.36 ev (525 mμ), which may result from positive hole centers. High cerous ion concentration results, however, in an induced center (Ce³⁺+ e ) which absorbs in the visible at about 1.9 ev (650 mμ). The presence of Ce⁴⁺ ions near Ce³⁺ prevents the formation of this center possibly by the reaction Ce⁴⁺+ e → Ce³⁺. These induced opposite changes in the oxidation state of cerium tend to maintain a balance in the ratio of Ce³⁺ to Ce⁴⁺ ions in the glass during irradiation, and the suppression of the visible bands depends on this ratio.     

Structural and Optical Properties of Lead-Boro-Tellurrite Glasses Induced by Gamma-Ray

Spectrophotometric studies of lead borotellurite glasses were carried out before and after gamma irradiation exposure. The increasing peak on the TeO₄ bi-pyramidal arrangement and TeO₃₊₁ (or distorted TeO₄) is due to augmentation of irradiation dose which is attributed to an increase in degree of disorder of the amorphous phase. The structures of lead tellurate contain Pb₃TeO₆ consisting of TeO₃ trigonal pyramid connected by PbO₄ tetragonal forming a three-dimensional network. The decrease of glass rigidity is due to irradiation process which is supported by the XRD diffractograms results. The decreasing values of absorption edge indicate that red shift effect occur after irradiation processes. A shift in the optical absorption edge attributed to an increase of the conjugation length. The values of optical band gap, E_opt were calculated and found to be dependent on the glass composition and radiation exposure. Generally, an increase and decrease in Urbach’s energy can be considered as being due to an increase in defects within glass network.     

A Gamma-Ray Induced Absorption Band in Some Lead Borate Glasses

Observations made on some lead borate, lead aluminoborate, and lead boroaluminosilicate glasses have shown that an absorption band is induced at 1.5 e.v. (825 mμ) by gamma irradiation. Experimental evidence indicates that this band is associated with Pb²⁺ ions and boron in the structure of these glasses. On replacing PbO by Tl₂O in a borate glass, two strong bands were observed; one band corresponds to the 1.5 e.v. band induced in lead borate glasses and a completely new band at 1.0 e.v. (1235 mμ). A postulate for the center responsible for the absorption band at 1.5 e.v. is proposed.     

Kinetics of Indentation Cracking in Glass

The propagation of indentation radial cracks in soda—lime silicate glass is measured as a function of time after indentation. Rapid lift-off of the indenter from the specimen surface causes a step-function perturbation in the radial crack mechanical energy release rate, thus providing access to a large range of observable crack velocities in the indentation stress field. Analysis of the data shows distinct threshold, reaction-limited, and transport-limited behavior in the crack velocity responses, in agreement with measurements made using macroscopic crack geometries. Atomistic models of fracture kinetics in reactive environments are fit to the data and are deconvoluted to yield the underlying atomic-scale, bond-rupture parameters. These latter are used to calculate potential functions for activated fracture and predict crack velocity responses as a function of temperature and pressure.     

A Chemical Kinetics Model for Glass Fracture

We utilize a chemical-kinetics-based model to describe the rate of crack extension in vitreous silica as a function of the applied stress and the presence of reactive species. Our approach builds upon previous fracture models that treat the atomic bond rupture process at the crack tip as a stressenhanced hydrolysis reaction. We derive the stress dependence for siloxane hydrolysis from measurements of hydrolysis rates for strained silicate ring structures. The stress dependence determined for siloxane hydrolysis yields an activation volume of 2.0 cm³/mol, which is in good agreement with the stress dependence determined for silicate glass fracture. This result supports previous fracture models that are based on absolute reaction rate theory and predicts an exponential dependence of crack extension rate on applied stress intensity.     

磷酸盐激光玻璃离子交换动力学研究

对Li2O质量分数不同的磷酸盐激光玻璃进行了离子交换实验,并研究了熔盐中K+及Na+在玻璃中的扩散动力学。使用波分散光谱(WDS)技术分析了K+及Na+在玻璃中的扩散深度,并研究了两种离子在玻璃中的离子扩散系数和扩散活化能。实验结果表明,玻璃中Li2O质量分数较高时,K+及Na+在玻璃中的扩散深度较大;混合碱效应导致离子的扩散系数降低。     

Kinetics of Chromium Oxide Transformations in Glass Melting

The kinetics of chromium oxide transformations in glass batch under heating and in glass melt has been studied. The different degrees of transformation of CrO₃ and Cr₂O₃ is demonstrated. The conditions of equilibrium between chromium oxides in the case of their simultaneous presence in glass melt is determined. The conditions of the interaction between chromium and iron oxides in the glass melt are investigated, including the surface layer in which an equilibrium between the colorant oxides can be achieved in accordance with the reaction conditions and the composition of the gaseous atmosphere. The low reaction velocities in the glass melt are due to its high viscosity and low values of diffusion coefficients. __________ Translated from Steklo i Keramika, No. 8, pp. 3 – 5, August, 2005.     

玻璃纤维增强聚丙烯非等温结晶动力学研究

利用差示扫描量热仪结合Avrami方程研究了玻璃纤维（GF）增强聚丙烯（PP）复合体系的非等温结晶动力学,探讨了GF含量及长度对PP结晶行为的影响。通过偏光显微镜观察了复合材料的结晶形态。结果表明,引入GF改变了PP的结晶温度,对其结晶有成核作用,并随着GF含量的增加,PP的半结晶时间（t1/2）呈下降趋势,结晶速率逐渐上升;同时随着GF长度的增加,PP的结晶速率是先增大后减小。PP和PP/GF复合材料的Avrami指数均在2.99～3.40,说明PP的结晶成核机理和生长方式没有改变。     

Kinetics of Leaching of Lead Glass by Ethylenediaminetetraacetic Acid

Treatment of lead glass with a hot basic solution of the sodium salt of ethylenediaminetetraacetic acid (EDTA) was shown to remove lead from the glass surface. A mechanism is proposed whereby lead is removed by a two-step reaction involving hydroxyl ions and EDTA. The rate constant and the overall heat of activation were estimated for this reaction. Potassium and silicon are also removed from the glass surface and show a dependence similar to that of lead removal. Potassium and silicon, however, do not form complexes with EDTA. Thus, it appears that lead removal weakens the silicate structure of the glass surface, allowing the potassium and silicon to be attacked and removed by hydroxyl ions and/or water. Experimental results indicate that the silicon released from the glass surface is in the form of silica.     

Kinetics of Contact Drying of Gel for Glass Production

The optimum regime for drying silicophosphate gel for glass production are selected. The kinetics of drying of gel is investigated.     

Kinetics of Surface-Layer Formation on Simulated Nuclear Waste Glass

Waste glass immersed in water at high temperatures and pressures rapidly develops a surface layer. The growth of this layer was followed semi quantitatively using an optical interference technique. Growth rates were measured as a function of temperature and pressure in distilled water and 1% NaCl solution. Pressures of 25 to 85 × 10³ Pa had no measurable effect at 200°C on glass immersed in water. At a pressure of 25 × 10⁵ Pa the growth rate increased with temperature in both water and salt solution. The rates were described in terms of activation energies (83.4 kj/mol for water and 53.0 for salt solution) with approximately equal rates in both solutions at 240°C. The rates of growth were linear in all cases. The surface layer began to exhibit cracks when its thickness exceeded =2.5 μm and it eventually spalled.     

Non-Isothermal Crystallization Kinetics of a Blast Furnace Slag Glass

The capability of the blast furnace slag to be vitrified was investigated by means of differential thermal analysis (DTA), scanning electron microscopy, and X-ray diffraction (XRD) in samples prepared by melting without the addition of any other ingredients. Differential thermal analysis revealed the presence of two major exothermic peaks. XRD indicates the presence of more than one crystalline phase: gehlenite Ca₂Al₂SiO₇, BaAl₂Si₂O₈, and pyroxene Ca(Mg,Al)(Si,Al)₂O₆. The activation energy of crystallization was estimated on the basis of DTA carried out on particle size 312–500 μm at different heating rates. Analysis of non-isothermal DTA data yielded values of 457.5 KJ/mol and 2.21 for the activation energy of crystallization and the Avrami exponent, respectively. A value for the activation energy corresponding to structural relaxation at temperatures around the glass transition has also been determined for this glass.     

Darkening Kinetics of Photochromic Glass at High Excitation Levels

A conventional copper sensitized photochromic glass was subjected to three excitation intensities, 21 mW/cm², 45 mW/cm², and 108 mW/cm², between 0.3 μm and 0.4 μm. The effect of glass heat treatment as well as excitation intensity on the equilibrium absorption and the darkening rates is described. Results indicated that both the equilibrium absorption and the rate of darkening increase with excitation intensity.     

连续玻纤增强HDPE复合材料的结晶动力学

采用差示扫描量热(DSC)法分析了不同降温速率下高密度聚乙烯(HDPE)和连续玻纤(GF)增强HDPE复合材料的非等温结晶和熔融行为。使用莫志深法对HDPE和HDPE/GF复合材料的非等温结晶动力学进行研究,得出莫氏方程可以描述其非等温结晶动力学过程。并且采用偏光显微镜(POM)观察结晶形态。结果显示:降温速率越大,聚合物结晶峰越宽、聚合物开始结晶时的温度越低、结晶峰温度越低。GF起到异相成核的作用,使得HDPE/GF复合材料的成核速率高于纯HDPE,但由于纤维对晶体生长具有一定的阻碍作用,使其结晶焓较低。通过熔融曲线分析发现,降温速率和GF的加入对HDPE及HDPE/GF复合材料熔融温度和熔融峰温度的影响并不显著。采用莫志深法的研究结果与由动力学参数得出的结论相一致,HDPE/GF复合材料比HDPE更易结晶。POM等温结晶观察结果表明,HDPE/GF复合材料比HDPE的结晶速率更快,这与DSC和莫志深方程结果一致。     

组成对铜离子扩散着色玻璃光谱性能的影响研究

红色玻璃以其鲜艳的色彩备受消费者的青睐。本文以氯化亚铜为主要原料,添加一定量的黏结剂和填充剂,在空气气氛中制备了铜离子扩散红色玻璃。研究发现组成中氯化亚铜、硫酸亚铁、氧化亚锡等对铜离子扩散着色有很大的影响。通过控制氯化亚铜、硫酸亚铁、氧化亚锡等的用量可以制备出应用广泛的红色玻璃。     

Kinetics of Formation of the Porous Structure in Foam Glass

The results of studying the production of foam glass based on container, sheet, and lamp glass cullet and their mixture are described. The possibility of using the parameters obtained from the correlation of the relative density and porosity of the initial and the final state of the material for predicting, control, and kinetic research of pore formation in foam glass is demonstrated. Formulas for processing kinetic data and calculating the thermophysical properties of a batch are proposed.