Elastic Moduli of Glasses at Elevated Temperatures by a Dynamic Method

The elastic constants of thirteen glasses were measured by a dynamic method at elevated temperatures. Both Young's modulus and the shear modulus were determined and from these Pois-son's ratio was calculated as a function of temperature. Fused silica, Vycor-brand glass, and Pyrex-brand glass had positive temperature coefficients of elastic moduli, whereas all the other glasses showed negative coefficients. Poisson's ratio was found to rise with temperature in all thirteen glasses. This is interpreted as an indication of an approach to the liquid state.     

Structural and Luminescence Studies on Barium Sodium Borosilicate Glasses Containing Uranium Oxides

Barium sodium borosilicate glasses containing different amounts of uranium oxides were prepared by conventional melt quench method and investigated for their structural aspects by ²⁹Si and ¹¹B MAS NMR technique combined with steady‐state luminescence and lifetime measurements. Based on MAS NMR studies, it is confirmed that uranium ions act as network modifier up to 15 wt% and beyond which a separate uranium containing phase is formed. From the luminescence studies, it is inferred that uranyl species is in a highly distorted environment. For more than 15 wt% uranium oxide incorporation, weaker U–O–U linkages are formed at the expense stronger U–O–Si/B linkages, as suggested by the excited state lifetime value of the uranyl species as well as red shift in emission peak maximum. For glass samples containing more than 25 wt% uranium oxides, crystalline barium uranium silicate gets phase separated from glass matrix as confirmed by XRD studies.     

STUDY OF PHOTOLUMINESCENCE IN GLASS*

The influence of composition and temperature on the fluorescence of glasses containing uranium and glasses containing cuprous oxide and stannous oxide was investigated. Secondary cations reduce the fluorescence of uranium in the glasses studied, depending to a certain extent on the electrostatic conditions they produce in the glass structure. The intensity of fluorescence as well as the structure of the spectrum diminishes in the order of phosphate, silicate, and borate glasses of equivalent compositions, which shows that fluorescence is favored by increase of oxygen in the glass structure without increasing the interfering secondary cations. Raising the temperature greatly diminishes the intensity of the fluorescence as well as the structure of the spectrum of glasses containing uranium. The fluorescence of the glasses containing cuprous oxide and stannous oxide as activators seems to be favored by increase in lime and increase in silica. These glasses possess appreciable phosphorescence, which appears to be enhanced by increase in silica and decrease in lime. A peculiar property of this type of luminescent glass is a maximum which it exhibits in its fluorescence-temperature relation-ship. There are indications that electrons are set free from the excited centers (copper atoms or small groups of copper atoms), which wander about in the glass structure.     

COLOR FORMATION IN VITREOUS BODIES1

A simple vitreous body of the Parian type was made up and the coloring produced by adding varying amounts of cobalt, chromium, iron, uranium, nickel, and copper oxide was determined. The color was measured by the Hardy recording spectrophotometer, and the resulting curves were analyzed for the three attributes of color. The hue, brilliancy, and saturation were all proportional to the logarithm of the coloring oxide. It was found that the color was mainly due to the particles of the practically undissolved oxide, and not to a colored glass. This makes it possible to color a body for use in reflected light, but not for transmitted light. Some excellent magenta red bodies were produced by reducing the copper oxide, but the results could not be consistently reproduced.     

Hydrothermal synthesis of silicon oxide clad uranium oxide nanowires

A facile method to synthesize silicon oxide clad uranium oxide nanowires is presented. U₃Si₂, used as a precursor, was oxidized to produce uranium oxide nanocrystallites and amorphous silicon oxide under hydrothermal conditions at 300°C and a pressure of 7.8 × 10⁶ Pa. The growth of uranium oxide nanowires was assisted by silicon oxide via assembling the uranium oxide nanocrystallites in an amorphous silicon oxide matrix. The microstructure and composition of silicon oxide clad uranium oxide nanowires were characterized by XRD, SEM, TEM, and EDS. The uranium oxide in the nanowires was determined as UO_2.34 with a fluoride cubic structure.     

Experimental investigation and thermodynamic simulation of the uranium oxide–zirconium oxide–iron oxide system in air

The behavior of melts and the phase composition of crystallization products of six compositions in the uranium oxide-zirconium oxide-iron oxide system in air have been investigated. It has been revealed that crystallized samples containing 20–50 wt % uranium oxide and 25–80 wt % iron oxide (the rest is zirconium oxide) consist of five crystalline phases and involve two types of eutectic structures. The possible factors responsible for this phenomenon have been considered.     

Improved Impact Resistance in Soda-Lime-Silica Glasses Through Zinc Oxide Substitutions

Several soda-lime-silica glasses were melted in which up to 8.52 wt% zinc oxide was substituted for calcium and magnesium oxide. Sonic Young's modulus and Charpy impact resistance measurements were made. The results indicated that an increase of 8.52 wt % zinc oxide reduced the Young's modulus by 9.0% and increased the impact resistance of the soda-lime-silica glass by 4.1% .     

THE EFFECTS OF ADDITIONS OF ZINC OXIDE AND CADMIUM OXIDE ON SIMPLE GLASSES1

The glass consisted of the composition SiO₂ 58%, PbO 22%, and Na₂O 20%. Zinc oxide was introduced in increments of 5% up to a maximum of 20% as a substitute for equivalent parts of Na₂O. Similar substitutions were made with cadmium oxide. The following physical properties were studied: thermal expansions, solubilities in hydrochloric acid, indices of refraction, and annealing conduct. Analyses of the glasses were made. The suitability of these glasses as vitreous enamels is discussed. A vacuum electric furnace for melting and fining glass under reduced pressures is described.     

Characterization of glassy materials for immobilization of radioactive waste with a high iron oxide content

The influence of the content of oxides in the simulated high-level wastes on the phase composition, the structure, and the water resistance of borosilicate-based glassy materials for immobilization is investigated. An increase in the waste oxide content from 45 to 65 wt % leads to an increase in the fraction of the crystalline phase of the magnetite-type spinel from 3–5 to 20–22 vol %. The glassy materials are characterized by a low leaching rate of the main waste components in water. A considerable increase in the leaching rate of sodium ions and, to a lesser extent, aluminum and uranium ions is observed for the glassy materials containing waste oxides at a content of 55 wt % and more due to the depolymerization of the structural glass network. Under the same conditions, the leaching rate of iron does not increase noticeably because of the high resistance of the iron-containing spinel to water.     

URANIUM OXIDE COLORS AND CRYSTALS IN LOW TEMPERATURE GLAZE COMBINATIONS1

A study has been made of the color and crystallization of some uranium, lead, sodium, and boron glazes fired in a pure oxidizing atmosphere, both alone and with the addition of certain inorganic compounds. The colors obtainable are yellow, orange, red, green, brown, and black. By using only uranium oxide and red lead it is possible to produce any shade from light yellow to dark orange or red. About 10% of yellow uranium oxide is required to produce the deepest shade of orange. A study has been made of the crystals found in these glazes and the effect on them of adding clay and certain other compounds, and of increasing the time of firing. It is shown that the volatilization of lead is a very great factor in the preparation of crystalline structures.     

Multilayer coating with self-sealing properties for carbon-carbon composites

This work proposes a simple and low cost method to deposit an effective multilayer protective coating on carbon-carbon composites (C/C). The first layer is made of molybdenum disilicide particles in a barium boron aluminosilicate glass (SABB); the second (external) layer is made of yttrium oxide modified SABB. A study of the reactions between the yttrium oxide and the SABB glass is presented. The coated C/C were submitted to thermal cycling or thermal aging tests up to 1300 °C in air. Weight losses were less than 0.5% in 50 h of thermal cycling and less then 1% in 150 h of thermal aging.     

碱土金属氧化物含量对模拟高放废液玻璃固化体析晶行为的影响

以硼硅酸盐玻璃作为基础玻璃基材,通过熔融法制备了含16%(质量分数)模拟高放废液的玻璃固化体,探究了碱土金属氧化物含量对玻璃固化体析晶行为的影响,以期在保证玻璃固化体性能要求的前提下,通过控制碱土金属氧化物的含量抑制玻璃固化体的析晶倾向。结果显示:碱土金属氧化物(CaO+MgO+BaO)含量在7%~19%(质量分数)时,玻璃固化体析晶上限温度和析晶率随碱土金属氧化物含量的降低而逐渐降低;玻璃网络聚合度的增加能够显著增强玻璃固化体的抗析晶性能,当碱土金属氧化物含量低于11%(质量分数)时玻璃固化体中硫酸盐的溶解度明显下降。基于包容0.7%(质量分数)SO₃的要求,碱土金属氧化物含量适宜组成应控制在11%(质量分数)以上。     

Bonding of Dental Glass to Nickel-Chromium Alloys

Two 80Ni · 20Cr-type alloys, one 99.99% pure and one with 98% purity, formed a multilayer oxide scale with an outer layer of NiO and a single-layer scale with outer portion richer in Cr₂O₃, respectively. An applied K-aluminosilicate glass at 1020°C penetrated the latter oxide scale. Adherence was present at all interfaces due to the existence of chemical equilibrium. Fracture occurred in the multilayer oxide scale and in the glass close to the oxide glass interface, respectively.     

The activity and mechanism of uranium oxide catalysts for the oxidative destruction of volatile organic compounds

Uranium oxide based catalysts have been investigated for the oxidative destruction of volatile organic compounds (VOCs) to carbon oxides and water. The catalysts have been tested for the destruction of a range of organic compounds at space velocities up to 70 000 h⁻¹. Destruction efficiencies greater than 99% can be achieved over the appropriate uranium based catalyst in the temperature range 300–450°C. Volatile organic compounds investigated include benzene, butylacetate, cyclohexanone, toluene, methanol, acetylene, butane, chlorobutane and chlorobenzene. The catalysts are thermally stable, destroy low concentrations and mixtures of VOCs and lifetime studies indicate that deactivation during oxidation of chlorinated VOCs did not occur. A temporal analysis of products (TAPs) reactor is used to investigate the mechanism of oxidation of VOCs by uranium oxide catalysts. Studies indicated that VOCs were oxidised directly to carbon oxides on the catalyst surface. A combination of TAP pulse experiments with oxygen present and absent in the gas phase has indicated that the lattice oxygen from the catalyst is responsible for the total oxidation activity. This has been confirmed by studies using isotopically labelled oxygen which indicates that the catalyst operates by a redox mechanism.     

Electrochemical reduction behavior of U3O8 powder in a LiCl molten salt

The reduction path of the U₃O₈ powder vol-oxidized at 1200 °C has been determined by a series of electrochemical experiments in a 1 wt.% Li₂O/LiCl molten salt. Various reaction intermediates are observed by during electrolysis of U₃O₈. The formation of the metallic uranium is caused from two different reduction paths, a direct reduction of uranium oxide and an electro-lithiothermic reduction. As the uranium oxide is converted to the metallic uranium, the lithium metal is more actively formed in the cathode basket. The reducibility of the rare earth oxides with the U₃O₈ powder has been tested by constant voltage electrolysis. The results suggest the advanced vol-oxidation could lead to the enhancement in the reducibility of the rare earth fission products.     

锂辉石在中性硼硅玻璃中的应用研究

以锂辉石中的Li2O等量替代中性硼硅玻璃(简称5.0医药玻璃)化学组成中的Na2O和B2O3,研究Li2O对工艺性能和节能减排的影响。研究结果表明:Li2O具有较好的助熔效果,可以显著降低玻璃高、低温黏度特征点所对应的温度;当0.20%～0.30%(质量分数)Li2O替代Na2O时,5.0医药玻璃拉管工艺性能达到最好,0.20%Li2O替代B2O3时,其拉管工艺性能最好。因此,锂辉石对中性硼硅玻璃具有显著的节能减排效果,并能显著提高其拉管工艺性能。     

Chemical reactivity of oxide materials with uranium and uranium trichloride

A graphite crucible is used for the manufacturing of uranium ingots in the uranium casting equipment of the electrorefining process. Uranium and uranium alloys are typically induction melted in graphite crucibles under a vacuum condition; however, due to the chemical reactivity of uranium and most alloying elements with carbon, a protective ceramic coating is generally applied to the graphite crucibles. To investigate the most suitable ceramic coating material for application to graphite melting crucibles used for the melting uranium in uranium casting equipment, firstly, a thermodynamic analysis using HSC software was performed to examine the chemical reactivity of ceramic oxide materials with uranium and uranium trichloride, and also, experiments concerning the reactivity of molten uranium in some ceramic coated crucibles were performed at 1,300 °C. From the results, yttria was finally selected as the most suitable ceramic coating material for application to graphite crucibles for melting the uranium.     

Extraction of Uranium from Seawater Using Magnetic Adsorbents

Abstract

A new process for the extraction of uranium from seawater was developed. In the process, uranium adsorption is effected using powdered magnetic adsorbents; the adsorbents are then separated from seawater using magnetic separation technology. This process is superior to a column method using a granulated hydrous titanium oxide adsorber bed in the following ways: (1) a higher rate of adsorption is realized because smaller particles are used in the uranium adsorption; and (2) blocking, which is inevitable in an adsorber bed, is eliminated.

The composite hydrous titanium-iron oxide as a magnetic adsorbent having high uranium adsorption capacity and magnetization can be prepared by adding urea to a mixed solution of titanium sulfate and ferrous sulfate. Adsorption and desorption of uranium and the removal of the adsorbent using a small-scale uranium extraction plant (about 15 m³/d) is reported, and the feasibility of uranium extraction from seawater by this process is demonstrated.     

四水八硼酸钠的发展现状及展望

四水八硼酸钠主要应用于农业方面,此外还是性能优良的防腐剂和杀菌剂。由于该产品中B2O3含量高达67％,较五水硼砂高出43个百分点,具有更为优良的运输和储存性能,应用于高硼硅酸盐玻璃行业具有比五水硼砂更强的优势,在工业领域的应用前景十分广阔。     

EFFECT OF IRON OXIDE ON MELTING OF GLASS*

The addition of small amounts of iron oxide (0.1 to 0.2%) to soda-lime-silica glass batches exerts a profound influence in increasing the output of glassmelting tanks as well as in favoring the production of higher quality glass. The color produced by this addition, moreover, is not objectionable for many uses of the ware. The accelerated melting rate probably is the result of a chemical effect of iron oxide in the batch and a physical property possessed by such glass to absorb radiation from the flames more efficiently. Attempts to measure these effects were made by rioting the melting rate of glasses which contain varying additions of iron oxide and by determining the temperature gradient that exists in glass when it is melted in a miniature tank. The presence of iron oxide aids melting and fining in crucible melts at 1200°C., but no effect was observed at higher temperatures. The measurement of temperature gradients in a pot holding 45 lb. of glass and heated by flames passing over the glass surface showed that the temperature gradient increases with iron oxide content.