Gadolinium doping of vanadate-tellurate glasses and glass ceramics

In order to further elucidate the local structure of ternary xGd₂O₃(100 − x)[0.7TeO₂ · 0.3V₂O₅] glasses with x = 0, 5, 10, 15, 20 mol%, FTIR spectroscopy, XRD diffraction and density measurement were performed. FTIR and density data show that by increasing the gadolinium ions content of the samples the excess of oxygen may be accommodated by the inter-conversion of some [VO₄] into [VO₅] structural units and of [TeO₃] into [TeO₄] units. The composition of the heat-treated glasses was found to consist mainly of the Te₂V₂O₉ crystalline phase. Varying x between 15 and 20 mol% Gd₂O₃ produces structural modification having as result an increase of the glass network polymerization degree. Accordingly, the gadolinium ions play a particular role related to the improvement of the homogeneity of the glasses and in accommodating the glass network with the excess of oxygen.     

Preparation and characterization of magnesium-aluminium-silicate glass ceramics

Synthesis of machinable quality magnesium aluminium silicate (MgO-Al₂O₃-SiO₂) for fabrication of insulators/spacers usable in high voltage applications under high vacuum conditions has been carried out following two different routes i.e. (i) sintering route, and (ii) glass route. A three-stage heating schedule involving calcination, nucleation and crystallization, has been evolved for the preparation of magnesium aluminium silicate (MAS) glass ceramic with MgF₂ as a nucleating agent. The effect of sintering temperature on the density of compacted material was studied. Microstructure and machinability of samples obtained from both routes were investigated. They were also characterized for microhardness. Initial studies on material obtained by glass route reveal that these samples are superior to those obtained from sintered route in respect of their high voltage breakdown strength and outgassing behaviour. Outgassing rate of 10⁻⁹ Torr l·s⁻¹ cm⁻² and breakdown strength of 160 kV/cm were obtained. Different types of spacers, lugs, nuts and bolts have been prepared by direct machining of the indigenously developed glass ceramic.     

氧化铈膜制备及其耐腐蚀性能

采用不同的制备溶液及制备参数在X80钢表面制备出不同的氧化铈膜,并对其耐腐蚀性能进行了研究.利用扫描电镜、能谱仪、XRD、拉曼光谱、接触角测试仪对不同的氧化铈膜腐蚀前后的表面形貌、元素、物相及亲水性进行了分析,利用电化学工作站对不同的氧化铈膜在3.5wt.％NaCl溶液中的开路电位、线性极化电阻、交流阻抗、极化曲线进行...     

Preparation and characterization of cerium oxide templated from activated carbon

The application of carbon templating to the preparation of cerium oxide and cerium–zirconium mixed oxide was investigated. Impregnation of a highly mesoporous activated carbon (Darco KB-B) with aqueous cerium nitrate, followed by calcination to remove the template, afforded nanocrystalline ceria with a surface area of up to 148 m²/g. Ceria-zirconia with surface area of 148 m²/g was similarly prepared. TEM studies on the ceria product revealed the presence of a polycrystalline phase, comprised of irregular aggregates of ceria crystallites of ca. 6.5 nm diameter. Use of activated carbon fibers (ACFs) as templates afforded ceria with a gross morphology resembling that of the fiber template. The lower surface areas (3–59 m²/g) of the resulting ceria reflect the mainly microporous nature of the ACFs; evidently the Ce nitrate solution is largely unable to penetrate the micropores. TEM showed the ceria fibers to be comprised of crystallites possessing a morphology similar to the Darco KB-B templated ceria.     

Preparation and optical characterization of e-beam deposited cerium oxide films

Cerium oxide films, of 0.3–1 μm thickness, were reactively deposited in the oxygen atmosphere onto quartz plates by the PVD method. An electron gun was used as an evaporation source. Films were characterized with the AFM method, Raman spectroscopy and spectrophotometrically. Optical properties of these films were examined for the wavelength range 0.2–2.5 μm. Films were characterized by high transparency, between 0.38 and 2.5 μm. The complex refractive index, n^*=n − jk, was evaluated. The dispersion characteristics for n(λ) and k(λ) were presented. We found that the refractive index strongly depends on the temperature of substrates (300 K ⩽ T_s ⩽ 673 K) during film deposition. Estimated values of the refractive index (at λ = 0.55 μm) were in the range 1.91–2.34.     

Effect of fluoride doping on impedance spectra of barium strontium titanate glass ceramics

A system of barium strontium titanate glass ceramics with different fluoride concentrations were prepared by melt-annealing technique. The effect of fluoride doping on impedance spectra of the barium strontium titanate glass ceramics were investigated. According to the impedance spectroscopy studies, three (low, middle, and high frequency) electrical responses, which corresponds to glass phase, crystal–glass interface and crystal interior were identified. It is shown that with the increase of fluoride concentration, the resistivity of the glass phase passed through a minimum and then increased. In addition, the capacitance of the crystal–glass interface increased and the capacitance of the crystal phase decreased with the increase of the fluoride concentration. Moreover, as a result of ac conductivity calculation and analysis, it is believed that the dc conduction was affected by the glass and crystal–glass interface regions and ac regime was attributed to the crystal phase. Based on the results, a change of the compensation mechanism from electronic to ionic one with variation in fluoride concentration was proposed.     

Studies of radiation defects in cerium,europium and terbium activated oxyfluoride glasses and glass ceramics

Terbium, cerium and europium activated oxyfluoride glasses and glass ceramics have been studied by thermally stimulated luminescence (TSL) and optical absorption techniques after the X-ray irradiation. A creation of colour centres in oxyfluoride glass matrix and TSL peaks depending on the activator type were observed. LaF₃ and rare earth activators were analysed by SEM–EDS.     

Preparation of forsterite-based glass ceramics for LTCC from potassium feldspar

A forsterite-based glass ceramic material has been developed from potassium feldspar for low temperature co-fired ceramics (LTCC). The crystalline phases and microstructure of forsterite-based glass ceramics were investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results show only forsterite was formed in temperature range 900–1,050 °C, and sapphirine was formed in temperature range 1,080–1,100 °C. The glass compact could be well densified at 950 °C, and full densification samples were obtained in temperature range 1,000–1,050 °C. The physical properties including dielectric properties, bending strength and thermal expansion of the specimens were also evaluated. The dielectric constants are in the range 7.00–8.25 and dielectric loss is below 0.01 in the frequency range 1–10 MHz. The specimens obtained in temperature range 950–1,100 °C are of high bending strength (69–106 MPa). The linear coefficient of thermal expansion of the specimen sintered at 1,080 °C is 9.76 × 10^?6 K^?1. All of these qualify the forsterite-based glass ceramic for further investigation as a candidate suitable for applications in LTCC field.     

Pulsed-laser deposition of textured cerium oxide thin films on glass substrates at room temperature

Cerium oxide thin films are deposited on glass by pulsed laser deposition at room temperature and characterized by X-ray diffraction and atomic force microscopy. The effects of ambient gas, rate of deposition and fluence on growth of films have been studied. The films grown in forming gas and with a high rate of deposition are polycrystalline and show preferential orientation along <011> direction with a roughness of ∼ 2 nm. Films prepared in oxygen have low crystallinity.     

Preparation and photoluminescence properties of fluorosilicate glass ceramics containing CeOF: Dy nanocrystals

The Ce³⁺ and Dy³⁺ co-doped oxyfluoride glasses and glass ceramics containing CeOF or CeF₃ nanocrystals have been prepared in the reducing atmosphere. The crystallinity increased significantly with the Ce³⁺ concentration, while the crystal size of nanocrystals is mainly influenced by the annealing temperatures. The glasses and glass ceramics emitted white light, deriving from a combination of the Ce³⁺ blue and the Dy³⁺ yellow light. The emission intensity and CIE chromaticity coordinates of the Ce³⁺ and Dy³⁺ co-doped glasses can be tuned by adjusting the ratio of Ce³⁺/Dy³⁺ concentration or the annealing temperature.     

Interferometric measurement of refractive-index change in photosensitive glass

We report on a technique for determining the change in the refractive index of photosensitive glass. We have demonstrated our interferometer-based technique on fiber preform and bulk glass samples, achieving an optical-path-difference (OPD) repeatability of 0.2 nm. For the bulk glass sample we measured an OPD of 15.2 ? 3.0 nm, corresponding to an index change of 2.1 ? 0.7 x 10(-5). Our technique was found to be insensitive to the effects of photodarkening and material compaction.     

Preparation of graphene oxide and its modification effect on base asphalt

In this paper, graphene oxide (GO) was synthesized by pressurized oxidation method and GO-modified asphalt was prepared by solution melting method. The structure and morphology of GO was characterized by Raman spectra, Fourier Transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM), and the results showed that single-layer or few-layer large size GO was obtained. The chemical structure of the GO-modified asphalt and the SARA (saturates, aromatics, resins and asphaltenes) components were characterized by FTIR and thin-layer chromatography with flame ionization detector (TLC/FID). In addition, the effect of GO on the physical properties of base asphalt was also studied. The results showed that there was no chemical change in the modification process and that GO was physically dispersed in the asphalt. GO has little influence on the penetration, ductility, softening point and penetration index of asphalt, the adhesion and temperature stability of asphalt are not changed much. The addition of GO differs from the adsorption of light components by polymer-modified asphalt, but fundamentally hinders the thermal oxygen conversion between the components and improved the low-temperature crack resistance of modified asphalt.     

Synthesis and conductivity of cerium oxide nanoparticles

Cerium oxide (CeO₂) nanoparticles have been synthesized through composite-hydroxide-mediated approach. The X-ray powder diffraction (XRD) measurement proved that the pure cubic CeO₂ could be obtained at a low temperature region (170-220 °C). The particle size, micrograph morphology and microstructure were investigated by transmission electron microscope (TEM) and environmental scanning electron microscope (ESEM). The conductivity of as-synthesized CeO₂ was measured by a standard four-probe method. The conductivity of CeO₂ increases slightly with the increase of temperature. And the conductivity increases rapidly to 0.02418 s cm^− 1 at 830 °C. The product is a potential material for intermediate temperature solid oxide fuel cells (ITSOFC).     

低温烧结Al2O3-硅酸盐玻璃系玻璃陶瓷的制备和性能研究

采用Al2O3-硅酸盐玻璃复合体系制备低温烧结玻璃陶瓷，通过TG-DTA、XRD、SEM等分析方法对样品进行表征，随着玻璃含量的增加玻璃陶瓷的烧结温度逐渐降低，在玻璃含量约为50％（质量分数）时玻璃陶瓷的热导率达到最大值2．70W/m·K，此时的玻璃陶瓷具有低的烧结温度（800℃）、高的相对密度（≥95％）、低的电容率（8～10）、低的介电损耗（1．5％～0．7％），有望成为LED封装用基板材料。     

Electron-beam modification of the near-surface layers of photosensitive glasses

Electron-beam treatment of photosensitive silicate glasses doped with silver or copper ions leads to the formation of metal nanoparticles in the near-surface layer of a sample. The characteristics of this layer depend on the type of metal ions, pre- and postirradiation heat treatments, charge distribution, and conditions for the removal of electrons from the surface. A certain spatial profile of charge distribution can lead to the formation of lenslike structures with a thickness of 200–400 nm.