Radiation Resistance of Porous Glasses

The sintering and evaporation of porous glasses under exposure to CO₂ laser radiation are investigated. It is demonstrated that the resistance of porous glasses to middle-IR laser radiation depends on the conditions of their preparation. The threshold radiation power densities necessary for sintering porous glasses of different compositions are obtained. The optical breakdown in porous glasses is studied. The resistance to near-IR laser radiation is determined for porous glasses prepared under different conditions.     

Applications of Radiation Effects in Glasses in Low-and High-Level Dosimetry

Two types of dosimetry using special glasses as sensing elements are reviewed. Both systems give an integrated total dose measurement. One system is based on a change in luminescence with dose and covers the range 10 to 10,000 rads. The second system is based on an optical absorption change with dose and covers the range 10⁴ to 10⁷ rads.     

Effect of Radiation on Glasses in Borosilicate and Boron-Lead-Silicate Systems

The effect of an electron flux and gamma radiation on glasses produced in a synthetic glass batch is considered. The origin of the radiation color centers arising in glasses and the disintegration of these centers in thermal and photodecolorization is investigated.     

Formation of Color Centers in Glasses Exposed to Gamma Radiation

Glasses exposed to gamma radiation develop a visible absorption band similar to the F -band developed in alkali halide crystals. The function of cerium in preventing coloration of glass was studied in detail in an ultraviolet-transmitting phosphate base glass in which its characteristic absorption could be measured. When visible absorption was thus prevented, radiation still caused a strong absorption in the ultraviolet which was associated with the electronic structure of cerium. On this basis, transition ions of similar electronic structure were introduced. It was found that iron, manganese, cobalt, nickel, vanadium, copper, and, under certain conditions, some other elements do suppress the formation of the visible absorption band formed in the base glass by radiation while forming more or less prominent bands in other spectral regions. Thus the colorless iron phosphate glass remained colorless under radiation and could be considered to be "protected." Conversely, with cobalt the new band which reached into the visible was relatively intense and stable, suggesting its use to indicate radiation dose.     

Effect of Gamma Radiation on Spectral Transmission of Some Commercial Glasses

An account is given of the effect of gamma radiation on the spectral transmission of certain commercial glasses. Curves are given showing the rate of fading of the coloration produced in these glasses by doses of gamma radiation in the range 10⁴ to 10⁸ rads. The effect on the optical density of some of these glasses by increasing doses of gamma radiation is discussed.     

Radiation Effects on the Physical Properties of Low-Expansion-Coefficient Glasses and Ceramics

The effects of irradiation on the coefficient of thermal expansion (CTE), the density, and the elastic moduli of low-CTE materials such as amorphous SiO₂, ultra-low-expansion glass, β-SiC, Astrositall, and Zerodur were surveyed. It was found that the properties of all of these materials were affected by radiation exposures up to 2 × 10⁹ rd; SiO₂ and SiC were the most radiation-resistant of the materials studied.     

Radiation,Crystallization, and Physical Properties of Cadmium Borate Glasses

Silicon - The melt-quenching method has been used to fabricate Na2B4O7 - CdO glass system. The XRD diffractometer procedure was used to check the status of these samples. Inter-ionic distance (Ri)...     

Nonradiative Energy Losses and Radiation Trapping in Neodymium-Doped Phosphate Laser Glasses

Fluorescence radiation trapping and nonradiative energy losses from the Nd³⁺⁴F_3/2 state are reported for two widely used commercial phosphate laser glasses (LHG-8 and LG-770). The effects of hydroxyl-group, transition-metal (Cu, Fe, V, Co, Ni, Cr, Mn, and Pt), and rare-earth (Dy, Pr, Sm, and Ce) impurities on the ⁴F_3/2 nonradiative decay rate in these glasses are quantified. Nd concentration quenching effects are reported for doping levels ranging from about 0.5 × 10²⁰ to 8.0 × 10²⁰ ions/cm³. The results are analyzed using the Förster–Dexter theory for dipolar energy transfer. Quenching rates for transition-metal ions correlate with the magnitude of spectral overlap for Nd emission (donor) and the metal ion absorption (acceptor). The nonradiative decay rates due to hydroxyl groups follow Förster–Dexter theory except at low Nd-doping levels (≲2 × 10²⁰ ions/cm³) where the quenching rate becomes independent of the Nd concentration. The data suggest a possible correlation of OH sites with Nd ions in this doping region. The effects of radiation trapping on the fluorescence decay are reported as a function of sample size, shape, and doping level. The results agree well with the theory except for samples with small doping-length products; in these cases, multiple internal reflections from the sample surfaces enhance the trapping effect.     

Effects of Radiation and Hydrogen on the Fracture Resistance of Borosilicate Glasses

In this study, short bar fracture toughness samples were used to determine the effects of radiation and hydrogen on the resistance to fracture of vitreous silica and four commercial borosilicate glasses. The results showed that neither exposure to 10¹⁰ rads of γ-radiation nor saturation to a room-temperature-equivalent exposure of 408 atm of hydrogen had an effect on fracture resistance. Nevertheless, when samples were saturated with hydrogen and then exposed to radiation, resistance to fracture increased significantly in some of the glasses. The increase in the resistance to fracture correlated directly with the increase in concentration of hydroxyl and hydride groups created by exposure to radiation and hydrogen. The concentration of these groups differs with glass composition and accounts for the difference in behavior between the types of glass studied.     

Radiation Synthesis of Grafted Polymers for Studying Thermoluminescence Characterization and Its Possible Application as a Dosimeter at Low Doses

Radiation-induced graft copolymerization of binary monomer system acrylic acid/acrylamide (AAc/AAm) (50/50) onto low density polyethylene (LDPE) and polypropylene (PP) films were investigated. Sulfonation was carried out for the prepared graft copolymers using concentrated sulfuric acid (97%) at 60°C for 15 min. The sulfonated grafted films found to have a thermal stability and better hydrophilic character than the grafted ones due to the ionic character resulting from this conversion. The thermoluminescence (TL) characteristics of grafted and sulfonated films were studied with regard to their use as off-line dosimeters in radiotherapy. The structural characterizations were performed by using FTIR, DSC and TGA. The sulfur content was determined by elemental analysis (EA). The TL responses were tested with ⁶⁰Co beam in the dose range 0.1–7 Gy. The dosimetric characterization has yielded a very good reproducibility, and independence of the radiation energy. The TL signal is not influenced by the dose rate and exhibits a very low thermal fading. Moreover, the sensitivity of the samples compares favorably than that of standard TLD-100 dosimeters. Finally, at the same dose the TL response for LDPE-g-P (AAm/AAc) films is higher than that of PP-g-P (AAm/AAc) and the sulfonated grafted films are more sensitive to radiation than the grafted ones.     

利用聚四氟乙烯剂量计进行堆芯γ测量

根据反应堆孔道内环境的特殊性,采用聚四氟乙烯作为制备剂量计的材料,利用铝制吊筒及铝管实现在反应堆孔道活性区范围内,纵向不同点位的γ剂量率测量。     

Investigation of Glasses Using Surface Profiling by Spectrochemical Analysis of Sputter-Induced Radiation: II, Field-Driven Formation and Electrochemical Properties of Protonated Glasses Containing Various Proton Concentrations

The ion-sputtering technique for measuring concentration profiles in glass surfaces provides a method for studying ionic transport in solids. Simultaneous field-driven lithium ion and proton transfer from solutions into, and migration of these ions within, several lithium silicate glasses was investigated quantitatively. This work leads to the new field of protonated glasses which are distinguished by the availability of all sites to both cationic species. Conductivity and mobilities reported as a function of concentration (50°C) do not exhibit the typical features of the mixed-alkali effect. Mechanisms are proposed for ionic transfer across solution-glass interfaces and for migration of ions within protonated glasses. Small proton mobilities at low proton concentrations are explained in terms of specific sites which function as proton traps and are identified by infrared spectroscopy. The condition for stability of boundaries between migrating ions is discussed.     

Oxynitride Glasses

Oxynitride glasses are grain boundary phases within silicon nitride ceramics. The desire to understand their nature led to various investigations on oxynitride glass formation, structure, properties, and crystallization. This paper provides a review of oxynitride glasses and outlines the effect of glass chemistry, including nitrogen contents and cation ratios, on properties such as glass transition temperature, Young's modulus, and viscosity and relates this to structural features within the glass. A short outline of crystallization of oxynitride glasses to form glass–ceramics is presented.     

Arsenate Glasses

Stability regions were determined for a new family of glasses. Arsenic pentoxide (As₂O₅) forms binary glasses with alkali metal oxides (except Li₂O) and the known glass-formers B₂O₃, P₂O₅, GeO₂, and TeO₂. It also forms ternary glasses with Li₂O and a variety of alkaline earth, transition metal, and post-transition metal oxides when gallium oxide (and in some instances indium oxide) is present as a third component.     

Effect of Gamma Radiation on Optical and EPR Absorption Spectra of Phosphate and Fluoride Glasses Containing Lead

The induced optical and EPR absorption spectra of phosphate and fluoride glasses containing lead are investigated. It is revealed that exposure to gamma radiation leads to the formation of radiation-induced defects responsible for the induced absorption band with a maximum at 12500–13500 cm⁻¹ and the EPR signal in the form of an almost symmetric line with a g factor of 1.999 and a linewidth of ≈26 Oe. Analysis of the intensities of the absorption bands and the EPR signals in the spectra of glasses with low terbium, tin, and carbon contents and the study of their thermal bleaching demonstrate that the color centers are electron traps, whereas the paramagnetic centers are hole-trapping centers. Examination of the change in the parameters of the absorption bands in the spectra of glasses with different R ₂O contents (R = Na, K, Rb, Cs) makes it possible to determine the location of the color centers associated with the Pb⁺ ions in the structure. It is established that the glasses under investigation are characterized by the nonlinear absorption of radiation at a wavelength of 1.06 μm. The mechanism of formation of radiation-induced defects is considered. Original Russian Text Copyright ? 2005 by Fizika i Khimiya Stekla, Bocharova, Karapetyan.     

Gamma Radiation Shielding and Mechanical Studies on Highly Dense Lithium Iron Borosilicate Glasses Modified by Zinc Oxide

Silicon - Five glass samples of a new zinc-iron lithiumborosilicate (LBSFZ) with the chemical formula 64.8B2O3–8.5SiO2–1.5Fe2O3 – (25.2 − x)Li2O - x ZnO...     

Tellurite Glasses

The boundaries of regions of glass-forming compositions were determined in binary tellurite systems with alkali, alkaline-earth, and heavy-metal oxides, and in the ternary systems TeO₂-WO₃-Ta₂O₅, TeO₂-WO₃-BaO, TeO₂-WO₃-Bi₂O₃, and TeO₂-WO₃-Tl₂O. On the basis of a structural interpretation of liquid immiscibility in binary oxide systems and of X-ray diffraction investigation of the structure of tellurite glasses, a crystallochemical interpretation of glass formation is proposed, as well as a method for calculating the modifier-poor boundaries of the regions of glass-forming compositions in binary systems. An investigation of the crystallizability, density, optical constants, spectral transmission characteristics, and chemical durability of the tellurite glasses as functions of their chemical compositions has led to the development of a new flint-type optical glass, with n _d= 2.1608 and v = 17.4, possessing a high chemical durability and resistance to devitrification.