Effect of three-stage isothermal annealing on the nucleation process in GeSe2 glasses

We studied the mechanism of crystallization of GeSe₂ bulk glass into the so-called low-temperature GeSe₂ crystalline phase. Initial isothermal annealing at a temperature T₁ below 400 °C and subsequent isothermal crystallization at 440 °C were carried out in a differential scanning calorimeter (DSC). The crystallization time (t_c), defined by the interval from the onset of annealing at 440 °C to the observation of a DSC peak, became shorter with increasing T₁. Nucleation occurs during this initial annealing. Next, T₁ was fixed at 330 °C and specimens were subsequently annealed at T₂<T₁. It was found that t_c increased as T₂ decreased from 330 °C. The nuclei generated at T₁ were reconverted to the glassy state.     

Microstructural development of the isothermal phase transformation during ageing at 250 °C in 2Y-TZP ceramics

The behaviour of isothermal phase transformation, during ageing at 250 °C, in 2Y-TZP and related microstructural development, were investigated. The mode of microstructural development due to isothermal phase transformation was greatly dependent on grain size and the density of the sintered body. Isothermal phase transformation and related microstructural changes began at the specimen surface, near the pores, where the change of strain free energy for a t-m transformation was small and water vapour was easily contacted. The transformed region showed porous microstructures, which appeared due to the formation of cracks upon isothermal transformation.     

Thermally stimulated luminescence studies of BaB4O7 compound

In this paper thermally stimulated luminescence (TSL) studies of BaB₄O₇ compound are reported for the first time. The polycrystalline sample of BaB₄O₇ was prepared by a melting method and the formation of the BaB₄O₇ compound was confirmed by an X-ray diffraction study. The compound has orthorhombic structure at room temperature. The TSL glow curves of BaB₄O₇ compound when heated at a constant heating rate of 4°C/s exhibit two thermoluminescence (TL) glow peaks at 110 and 150°C followed by a shoulder around 210°C. The trapping parameters associated with the prominent glow peak of BaB₄O₇ are reported using isothermal luminescence decay method (ILDM). As a check the trap parameters are also calculated by glow curve shape (Chen's) method after isolating the prominent glow peak by thermal cleaning technique. Our results show a very good agreement between the trapping parameters calculated by the two methods.     

Sn-rich phase coarsening during isothermal annealing for as-soldered Sn–Ag–Cu solder

The effect of Sn-rich coarsening in Sn–Ag–Cu solder joints produced by isothermal annealing was investigated. The isothermal annealing temperatures employed were from 30 to 150 °C for 24 h up to 1,008 h of annealing time. An Infinite Focus Measurement system (IFM®) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) were used for microscopic analysis and elemental analysis, respectively. As the annealing time and temperature increased, a eutectic component Cu, diffused into the Sn-rich phases, coarsening the Sn-rich phases, and the activation energy value for the coarsening was determined to be 41 kJ/mol.     

Influence of a small amount of Al2O3 addition on the transformation of Y2O3-partially stabilized ZrO2 during annealing

Tetragonal-to-monoclinic phase transformations in 2 and 3 mol% Y2O3–ZrO2 ceramics and their composites with 5 vol% Al2O3 during annealing in water and in vacuum at 353–623 K were investigated to explore the effect of a small quantity of Al2O3 addition on the transformation. The dispersion of Al2O3 particles into the ZrO2(Y2O3) matrix was found to be effective to suppress the transformation directly induced by the attack of H2O during annealing in water, even though the amount was as small as 5 vol%. However, the transformation predominantly caused by thermal activation during annealing in vacuum was not affected by the limited amount of Al2O3 addition. The effect of suppression of Al2O3 on the water-induced phase transformation was considered to be realized through the hydroxydation of Al2O3 particles, by which the sample surface was effectively "protected" from further attack of H2O, which accelerated the low-temperature degradation transformation. This revised version was published online in November 2006 with corrections to the Cover Date.     

Tetragonal-to-monoclinic phase transformation during thermal cycling and isothermal ageing in yttria-partially stabilized zirconia

The tetragonal-to-monoclinic (T → M) phase transformation accompanied with thermal cycling has been studied by ionic conductivity, dilatation and X-ray diffraction measurements. With repeating thermal cycling, theM _s point shifts to a higher temperature, the amount of expansion due to T → M transformation increases, and the transformation proceeds from the surface in the specimen interiors. These phenomena are attributed to grain boundary cracking which occurs as a result of the transformation. The time-transformation isotherms at 353 K and at room temperature can be expressed by the Johnson-Mehl equationf=1−exp(−bt ⁿ ), and the samen value of 0.7 was obtained irrespective of grain size and of environment.     

Orientation-controlled phase transformation of Bi2O3 during oxidation of electrodeposited Bi film

High-temperature fluorite structure Bi₂O₃ is a well-known solid electrolyte owing to its high oxygen ion conductivity. In this study, Bi₂O₃ thin film was prepared by the oxidation process of the electrodeposited metallic Bi film. The crystal structures of the oxidized Bi films varied with the applied voltages during the electroplating process. Pure α-Bi₂O₃ was obtained when the oxidation was conducted for the metallic Bi film electrodeposited at −0.1 V. Only β-Bi₂O₃ was observed as a −0.5 V electrodeposited Bi film was oxidized. The crystal structure of Bi₂O₃ obtained by oxidation of metallic Bi film may dominantly be affected by the orientation of as-electrodeposited Bi film. Such kind of process is favorable to the preparation of functional ceramic with specific crystal structure.     

Growth, optical transmission and X-ray photoemission studies of BaB2O4 single crystals

Beta barium borate (-BBO) crystals have been grown by the top seeded solution growth technique (TSSG) using Na₂O as a flux. The crystals exhibited high transparency and the absence of inclusions and found to have sodium contamination in the range 150 to 230 p.p.m. The effect of this contamination on some crystal properties of interest has been investigated. The presence of impurities causes optical absorption below 550 nm in BBO crystals of both and -phases. X-ray photo emission spectroscopy (XPS) measurements performed on these crystals show that sodium gives rise to a measurable shift in the binding energies of the constituent ions. Further, the results show that Na⁺ ions enter into the lattice substitutionally and provide charge trapping sites close to the band edge.     

Stabilization and phase transformation of CuFe2O4 sintered from simulated copper-laden sludge

The feasibility of stabilizing copper-laden sludge by high-temperature CuFe(2)O(4) ferritization process is investigated with different sintering temperature, and the prolonged leaching test. The thermal behavior, structural morphology, phase composition, and phase transformation of the stabilized sludge were investigated by using thermal gravimetry-differential scanning calorimetry, scanning electron microscopy and X-ray diffraction. The leaching behavior of the stabilized sludge under acidic environment was evaluated by modified Toxicity Characteristic Leaching Procedure (TCLP). The results indicated that CuFe(2)O(4) could be effectively formed at around 800°C by the iron oxide precursor with a 3h of short sintering. The transformation was discovered on crystallographic spinel structures: the low-temperature (800-900°C) tetragonal phase (t-CuFe(2)O(4)) and the high-temperature (～ 1000°C) cubic phase (c-CuFe(2)O(4)). At higher temperatures (～ 1100°C), the formation of cuprous ferrite delafossite phase (CuFeO(2)) from the dissociation of CuFe(2)O(4) was also noticed. Both CuFe(2)O(4) spinel and CuFeO(2) delafossite phase have a better intrinsic resistance to acidic environment when compared to that of CuO phase by the modified TCLP test. The sintering strategy designed for copper-laden sludge is proven to be beneficial in stabilizing copper.     

氮化硼薄膜在退火相变中的应力研究

利用射频溅射系统在P型Si（100）衬底上制备氮化硼薄膜。对其进行600～1000℃的常压下N2保护退火。通过傅立叶变换红外谱（FTIR）分析，发现hBN-cBN-hBN的可逆相变。通过不同温度退火后立方相横光学振动模式峰位的移动，计算了氮化硼薄膜中残余应力的变化。发现沉积后退火很好地解决了高立方相氮化硼薄膜应力释放的问题，可提高立方氮化硼薄膜在硅衬底上的粘附性。并且探索性地讨论在退火过程中c-BN成核、生长与薄膜中应力变化的关系。     

Solid state reactions in the Fe2O3-CaCO3-In2O3 system

The kinetics of solid-state reactions of powdered reactants were investigated by X-ray and by differential thermogravimetry in a magnetic field. Measurements revealed mutual diffusion of the Fe³⁺ and In³⁺ ions in the Fe₂O₃-In₂O₃ system heat treated for 3 h at 700 to 1400° C. Diffusion of indium into the Fe₂O₃ lattice caused a shift of the Curie temperature of the antiferromagnetic iron oxide towards lower temperatures. Only Caln₂O₄ was found between CaCO₃ and In₂O₃ up to 1400° C. Also, in the Fe₂O₃-CaCO₃-In₂O₃in system, the reaction started with the mutual diffusion of iron and indium and the forming of CaFe₂O₄. End-products were the magnetic -Ca₄Fe₁₄O₂₅ and CaFe₄O₇, and the non-magnetic CaFe₅O₇, depending on the In³⁺ concentration. Indium stabilized the magnetic calcium-iron oxide structures, shifting their Curie temperatures towards lower values.     

Solid state compatibilities in CaO–CaO.Al2O3–CaSO4–CaF2 system

The determination of the phases assemblages in equilibrium in the CaO–CaO.Al2O3–CaSO4–CaF2 system at 1100°C has been performed. Four assemblages are found and one more is deduced. 3CA.CaSO4 appears in all compatibility tetrahedra in solid state or in melt presence. It is compatible with C3A, C12A7ss, CA, C11A7.CaF2 and the aluminate formed depends on Al2O3 and CaF2 proportion, (cement chemistry abbreviations: C=CaO, A=Al2O3). © 1998 Kluwer Academic Publishers     

Viscosity and surface tension change in BaB2O4 melt by substitution of Al or Ga for B

Abstracts are not published in this journal     

Viscosity and surface tension change in BaB2O4 melt by substitution of Al or Ga for B

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.