Irradiation-induced and postirradiation processes in fluoroaluminate glasses

We have measured the EPR and induced optical absorption spectra of several fluoroaluminate glasses prepared under different redox conditions and containing NH₄HF₂, EuF₃, or Eu₂O₃ additions. Analysis of spectra taken after gamma irradiation to various doses and isothermal bleaching kinetics of individual absorption bands indicates that the color centers responsible for induced absorption in the UV spectral region are hole traps related to either oxygen (45000 and 42000 cm^?1) or fluorine (37500 cm^?1). In the visible range, we have revealed three absorption bands. We assume that the 17400 cm^?1 absorption is due to an electron trap involving Y³⁺. Our data suggest some evidence that paramagnetic hole centers and electronic color centers may be formed in the same events.     

Optical Properties of Gamma-Irradiated Ba(PO3)2-Containing Fluoroaluminate Glasses

Optical absorption and electron paramagnetic resonance measurements were used to assess the nature of the paramagnetic and color centers in gamma-irradiated LiF-containing BaSrCaMgAl₂F₁₄glasses with Ba(PO₃)₂additions. The radiation-induced processes in the glasses containing 1.5 mol % Ba(PO₃)₂are dominated by PO₄ ^2–and PO₃ ^2–centers, which have large capture cross sections. Substitution of 0.8–1.8 mol % oxides has a significant effect on the formation of radiation-induced color centers in the glasses studied.     

Obvious enhancement in electrochemical capacitive properties for poly(3,4-ethylenedioxythiophene) electrodes prepared under optimized conditions

This work investigates the effect of preparation conditions on the supercapacitive performances of the poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes electrodeposited detailedly. These preparation conditions include electrode substrates, electrodeposition modes, parameters, and counter anions. Electrochemical characterizations indicate an evident impact of electrode substrates on the electrochemical behaviors of the PEDOT electrodes prepared. Graphite foils (GF) as the electrode substrate show better electrochemical capacitive properties relative to conductive glasses (CG). This can be ascribed to lower sheet resistance and better adhesion to the PEDOT films for the former. Moreover, SEM and AFM tests indicate that different electrodeposition modes, parameters, and counter anions would result in different morphologies and roughness for the PEDOT electrodes obtained, consequently affecting their supercapacitive performances. Among numerous preparation conditions, the polystyrene sulfonic acid salt-doped PEDOT deposited on GF substrates prepared with potentiostatic mode at 0.9 V shows the best supercapacitive behaviors, delivering the specific capacitance of 108.2 mF cm^?2 at 0.2 mA cm^?2, also exhibiting good rate capability and superior cycle performance (keeping 93.4% of initial capacitance after 10,000 cycles). This work indicates that the supercapacitive properties of PEDOT electrodes can be substantially enhanced by changing their preparation conditions.

     

The titaniummolten glass system: interactions and wetting

Titanium interactions with three molten glasses based on sodium disilicate, with additions of TiO₂ or La₂O₃, are studied under very reducing conditions, and the kinetics of spreading and equilibrium contact angles are determined. Titanium enters the molten glass as Ti³⁺, as shown by EPR spectrometry. Redox reactions occurring at solid—liquid interface and inside bulk glass are studied, and their influence on drop equilibrium is analysed.     

Introduction of color centers in fluorinated sol gel quartz glasses by radiation thermal treatment

Data are presented to show how fluorination influences the optical quality and radiation resistance of quartz glasses fabricated by the sol gel method. It is found that under the action of gamma radiation, mainly E′ centers form in the glasses. The incorporation of fluorine in the xerogel lattice promotes the removal of hydroxyl groups and enhances the radiation optical resistance of the synthesized samples in the red. It is observed that the radiation resistance of the glass is enhanced in the ultraviolet by using irradiation-annealing cycles and this is attributed to a decrease in the concentration of radiation-induced E′ centers. Pis’ma Zh. Tekh. Fiz. 23, 74–79 (December 26, 1997)     

Irradiation induced defects in glasses resulting in the photoionization of polyvalent dopants

The extent of solarization is strongly influenced by many factors such as glass matrix, dopants, or irradiation source. Typical irradiation induced effects are illustrated in a series of glasses doped with a selection of polyvalent ions. Intrinsic and extrinsic defects, consisting of electron and hole centers, are characterized with optical and EPR spectroscopy. Used in combination, both spectroscopic methods allow to detect a wide range of defects. UV-lamp irradiation causes in fluoride-phosphate glasses the photoreduction of Ni²⁺, Pb²⁺ and Ag⁺ while Co²⁺, Ce³⁺, Fe²⁺ and Mn²⁺ are photooxidized. The influence of the glass matrix is evident for Ni²⁺ which is photooxidized in borosilicate, but reduced in fluoride-phosphate glasses. Iron ions also show different redox reactions depending on the glass matrix, as well as on the melting conditions, which will be shown for low alkaline borosilicate glasses doped with iron or tin. Changes in the nature and the rate of defect formation could be observed within the irradiation process of a fluoride-phosphate glass co-doped with Mn²⁺ and Fe²⁺ and during thermal annealing of a lamp irradiated phosphate glass containing Co²⁺. The series Mn²⁺, Fe²⁺, Co²⁺ and Ni²⁺ shows a trend of increased photooxidation with increasing electro-negativity or decreasing mass of the ions.     

Formation of Photosensitive Layers in Alkali Germanate Glasses

The induced optical absorption spectra of 70GeO₂ ⋅ 10Ga₂O₃ ⋅ 20Li₂O glasses are measured. A process is described for producing photosensitive layers on alkali germanate glasses using ion-exchange diffusion from salt melts containing silver nitrate. The effects of the sensitizer (Ce³⁺, Fe³⁺, and Fe²⁺) and preparation, UV irradiation, and heat treatment conditions on the mechanisms of silver reduction in the surface layer of germanate glasses are examined. The results demonstrate that colloidal silver particles can be produced via ion exchange at 350°C in glasses containing 0.1 wt % Fe₂O₃. The particle diameter in a glass prepared under reducing conditions is estimated at 2.5 nm.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 753–761.Original Russian Text Copyright © 2005 by Bocharova.     

Microinhomogeneities in Tellurite Glasses

Two- and three-component TeO₂-based glasses prepared by melting appropriate oxide mixtures, followed by cooling or casting, are characterized by laser ultramicroscopy. The results demonstrate that the glasses contain microinhomogeneities 0.07–0.2 µm in size at a level of 10³ to 10⁶ cm⁻³. Their size and concentration depend on the glass composition and preparation conditions.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 881–885.Original Russian Text Copyright © 2005 by Zorin, Churbanov, Snopatin, Grishin, Petrova, Plotnichenko.     

Nb添加对Ti基非晶合金腐蚀及力学性能的影响

为研究微量添加Nb元素对Ti_(40)Zr_(10)Cu_(34-x)Pd_(14)Sn_2Nb_x(x为原子数分数,x=0、1%、3%、5%)非晶合金的耐腐蚀性能及力学性能的影响,本文利用动态极化曲线,分析了在0.144 mol/L的NaCl溶液及0.2 mol/L的PBS溶液中非晶合金Ti_(40)Zr_(10)Cu_(34-x)Pd_(14)Sn_2Nb_x(x=0、1%、3%、5%)的电化学性能,并通过材料拉伸试验研究了非晶合金块状样品的室温压缩性能.结果表明:在0.144 mol/L的NaCl溶液中,非晶合金样品在阳极区出现了自发钝化的特征,钝化电流密度在10~(-7)～10~(-8) A/cm~2,钝化电流密度随着Nb的添加略有降低,且点蚀电位随Nb原子数分数的增加分别为200、340、400和490 mV,说明微量添加Nb元素能有效提高Ti基非晶合金的耐点蚀能力,即在0.144 mol/L的NaCl溶液中Ti基非晶合金的耐腐蚀性随着Nb含量的增加而增强;在0.2 mol/L的PBS溶液中,因磷酸根离子的缓蚀作用,Nb添加导致的成分变化对非晶合金的腐蚀行为影响不大;此外,添加了原子数分数为1%及3%Nb的非晶合金,其压缩强度及塑性变形能力变化不大,但添加5%Nb的非晶合金因较大体积分数纳米晶的存在导致其室温断裂强度及塑性变形能力有明显下降.     

Relation between carbonation resistance,mix design and exposure of mortar and concrete

When cement with mineral additions is employed, the carbonation resistance of mortar and concrete may be decreased. In this study, mortars containing mineral additions are exposed both to accelerated carbonation (1% and 4% CO₂) and to natural carbonation. Additionally, concrete mixtures produced with different cements, water-to-cement ratios and paste volumes are exposed to natural carbonation. The comparison of the carbonation coefficients determined in the different exposure conditions indicates that mortar and concrete containing slag and microsilica underperform in the accelerated carbonation test compared to field conditions. The carbonation resistance in mortar and concrete is mainly governed by the CO₂ buffer capacity per volume of cement paste. It can be expressed by the ratio between water added during production and the amount of reactive CaO present in the binder (w/CaO_reactive) resulting in a novel parameter to assess carbonation resistance of mortar and concrete containing mineral additions.     

The a.c. conductivity of CuO-containing lead silicate glasses

The a.c. conductivity of copper-free and copper-containing lead silicate glasses of the base composition 80PbO–20SiO₂ (wt %), equivalent to 51.5PbO–48.5SiO₂ (mol %), was measured at different temperatures and frequencies. The ratio Cu²⁺/Cu_total as a function of CuO content in the glasses studied was quantitatively determined by ESR. The results were used to derive the mechanism of conduction in lead silicate glasses. Values of a.c. conductivity, dielectric loss and dielectric constant decreased with the addition of CuO up to 0.25 g/100 g glass and increased with further additions of CuO. This may be due to the gradual decrease in the ratio Cu²⁺/Cu_total (as indicated by ESR) with increasing CuO content, through reduction of some Cu²⁺ ions to Cu⁺ ions, which have higher mobility. The a.c. conductivities agreed with the Anderson and Stuart model and indicated that the conduction mechanism was ionic in character.     

On the origin of near-IR luminescence in Bi-doped materials (I). Generation of low-valence bismuth species by Bi and Bi synproportionation

Creation of bismuth-containing near-infrared (NIR) luminescent centers by synproportionation reaction of Bi³⁺ and Bi⁰ was demonstrated in borate and phosphate glasses. This finding is discussed in the light of low-valence nature of bismuth NIR-luminescent centers. The experimental data is consistent with the hypothesis of univalent Bi⁺ (and, possible, subvalent cluster Bi ions) as a source of NIR luminescence. The dependence of Bi luminescent centers stability on oxoacidity of glass melts was discussed.     

高熵非晶合金耐腐蚀性能研究进展

高熵非晶合金是近年来发展起来的一种新型合金材料,因其兼具高熵合金和非晶合金优异的力学性能、耐腐蚀性能、磁性能等功能特性,引发了众多学者的广泛关注。本文简述了高熵非晶合金的含义与特点,介绍了高熵非晶材料的制备方法及组织与性能;归纳了该类材料的耐蚀机理与耐腐蚀性能的最新研究成果;展望了采用机器学习助力设计高熵非晶合金的新范式,并指出探究工况环境下的腐蚀失效机制、完善高熵非晶合金微观耐蚀机理与优化相关制备工艺是该材料广泛应用的前提条件。针对高熵非晶合金的开发及其耐腐蚀性开展的应用基础研究,将为我国海洋事业的“远洋化、深海化”提供先进的技术支撑和材料保障。     

Postirradiation Behavior of Rare-Earth-Activated Fluoroaluminate Glasses

The induced absorption and electron paramagnetic resonance (EPR) spectra of gamma-irradiated fluoroaluminate glasses activated with Eu³⁺ and Ce³⁺ are studied. The bleaching kinetics in glasses containing 0.001 to 0.1 mol % Eu₂O₃ are analyzed in terms of a capture-volume model. Eu³⁺ is shown to act as a protector ion, suppressing the induced absorption in the fluoroaluminate glasses. The introduction of CeF₃ stabilizes the color centers responsible for the induced absorption in the visible range. The effects of gamma irradiation and subsequent heat treatment on the EPR spectra of the glasses containing Ce, Tb, and Eu are analyzed. The shape of the central resonance (CR line) in the EPR spectra of the heat-treated samples is shown to depend on the nature of the rare-earth-related trapping center. The EPR data are interpreted under the assumption that the paramagnetic species responsible for the main component of the CR line are of a hole nature.     

Raman microprobe investigation of oxygen and carbon dioxide dissolution from bubbles in silicate glasses containing antimony oxide

The effect of addition of antimony oxide and/or sodium nitrate to silicate glass compositions upon the changes in the relative concentrations of oxygen and carbon dioxide in their bubbles from heat treatment was investigated using the Raman microprobe technique. The addition of antimony oxide to these glasses increased the relative rates of oxygen dissolution from their bubbles with respect to glasses containing no refining agents. These increases were closely related to the absolute amounts of Sb³⁺ ions that were present in the glasses. The relative rates were faster for glasses containing antimony oxide than for glasses containing the same molar amounts of arsenic oxide. The higher Sb³⁺/Sb⁵⁺ ratios for glasses containing antimony oxide with respect to the As³⁺/As⁵⁺ ratios for glasses containing arsenic oxide caused the relative rates of oxygen dissolution to be dramatically greater for the former glasses. In contrast to an earlier investigation with silicate glasses containing arsenic oxide, the addition of sodium nitrate to glasses containing antimony oxide using a similar glass preparation did not significantly change their relative rates of oxygen dissolution.     

Evaluation of Measurement Uncertainty in Determination of Lead in Glass Materials by a Standard Complexometric Method

Lead is an important constituent for the preparation of wide variety of glasses like high refractive index optical glasses, radiation shielding glasses, ceramic glazes, enamels, high electrical resistance glasses, glass soldiers and sealants, etc. Determination of exact quantity of lead is therefore very essential to obtain the desired property of different glasses. With a view to meet the necessity, the measurement uncertainty of the results of lead determination in different lead containing glasses have been evaluated. The lead content has been determined complexometrically at pH 4.3 using di-sodium salt of EDTA. The sources of uncertainty of the results of measurement have been identified as contributions from repeatability, standardization of EDTA, volume measurement by volumetric flask, burette, pipette and end point detection. Sources of uncertainty have been identified and combined following the EURACHEM guidelines. The results show that the major sources of uncertainty arise from standardization and end point detection.     

Effect of ZrO<Subscript>2</Subscript> on the alkali resistance and mechanical properties of basalt fibers

We have studied the effect of zirconia additions on the properties of basalt glasses and fibers. The solubility limit of ZrO₂ in basalt glasses is determined to be 7.1 wt %. Fibers produced from modified basalt glass contain both tetragonal and monoclinic zirconia. The highest ZrO₂ concentration in basalt fibers is 3.1 wt %. We have determined the fiber drawing temperature ranges and assessed the tensile strength and alkali resistance of the fibers. With increasing ZrO₂ content, the tensile strength of the fibers (d = 11−12 μm) decreases from 1.8 to 0.6 GPa. The addition of less than 3.1 wt % ZrO₂ increases the alkali resistance of the basalt fibers by 37%. The addition of more than 3.1 wt % ZrO₂ to the glass batch reduces the alkali resistance and tensilestrength of the basalt fibers.     

Effect of secondary heat treatment on the spectroscopic properties of Na<Subscript>2</Subscript>O-Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

We have studied the optical absorption and luminescence spectra of 45Na₂O · xNb₂O₅ · (55 − x)P₂O₅ glasses containing 5, 10, 20, 25, 30, and 35 mol % Nb₂O₅. The results indicate that the absorption band around 26000 cm⁻¹, responsible for the yellow color of the glasses, is due to the [Nb^(5+)--O⁻] center and disappears upon secondary heat treatment. Heat treatment of europium-doped glasses increases the concentration of Eu³⁺ centers in an asymmetric environment, which is accompanied by an increase in luminescence efficiency. The reason for this is that the Eu³⁺ ions are located outside the niobate subsystem of the glass matrix. The europium in the glasses studied acts as a protector ion.     

Study of fluorine losses and spectroscopic properties of Er doped oxyfluoride silicate glasses and glass ceramics

The fluorine losses during synthesis of Er³⁺ doped transparent glasses in the SiO₂–PbO–PbF₂ system were investigated. The final fluorine contents of the glasses were detected by using a fluorine ion selective electrode. The results show that high fluorine losses are occured in the normal preparation processes. With the increase of initial PbF₂ contents or melting time resulted in the increase of the fluorine losses. The thermal and spectroscopic properties of the glasses and the corresponding glass ceramics were investigated through the analysis of the differential scanning calorimetry (DSC), absorption and upconversion luminescence spectra. The effects of fluorine contents show a decrease of the glass transition temperatures (Tg) of the glasses and an enhancement of upconversion intensity of the corresponding glass ceramics.     

Preparation and characterization of binary V2O5-Bi2O3 glasses

Characterization of the binary V₂O₅-Bi₂O₃ glasses prepared by rapidly quenching the melt has been made from the studies of X-ray diffraction, scanning electron microscopy, infrared absorption, differential thermal analysis, electron paramagnetic resonance, chemical analysis, density and electrical properties. Stable glasses are obtained for 95 to 75 mol % V₂O₅ by quenching on a stainless steel substrate, while quenching on a copper substrate extends the glass formation range from 95 to 70 mol % V₂O₅. The V-O bond vibration in the glasses occurs at 1020 cm^–1 and the V^5% ion exists in six-fold coordination as in crystalline V₂O₅. All the glasses appear to be in single phase. The spin concentration in the glasses is found to be independent of temperature. A second heat-treatment at 255° C develops crystalline phase in the glasses. Unlike infrared absorption, electron paramagnetic resonance, density and chemical compositions, the electrical and thermal (DTA) properties are found to be slightly sensitive to the thermal history of preparation of the glasses. The high-temperature (300 to 500 K) conduction in the glasses seems to be due to adiabatic hopping of polarons. The thermopower is observed to be independent of temperature and provides evidence for small polaron formation in the glasses.