Effect of Sulfide Ions on the Anodic Dissolution of Copper in Acetate Media

It is voltammetrically found that a covering film forms on copper in S^2–-ion-containing acetate media. It follows from thermodynamic equilibria, crystallographic parameters, and x-ray spectra of the metal and its compounds that the overall anodic process is composed of two separate processes and yields Cu₂S and Cu₂O. The reaction order in S^2– ions (log i/log C _i)_{E = const}is 0.37. Possible stages of the electrode process are suggested.     

Through-thickness cleavage fracture stress of a Ti-V-N plate steel

Through-thickness cleavage fracture stresses, σ* _f , have been determined for six microstructures of a Ti-V-N plate steel directly by through-thickness four-point bending (4PB) notched specimens. Results showed that σ* _f is higher for ferrite-bainite microstructures than for ferrite-banded pearlite. For an identical finish-rolling temperature (FRT), the plates with a high cooling rate have a higher value of σ* _f than their counterparts with a low cooling rate. Following the same cooling rate, the highest values of σ* _f are obtained for steels finish rolled above A _r3 but below T _NR (nonrecrystallization) and the lowest for steels finish rolled below A _r3, which contain deformed ferrite (DF) with texture components. Cleavage microcracks are observed to initiate at second-phase particle or pearlite-ferrite interface and then to propagate into ferrite matrix. Growing microcracks could be arrested by bainite phase distributed uniformly in ferrite matrix, which contributes to a high value of σ* _f . The low value of σ* _f was attributed to elongated ferrite-deformed ferrite and martensite/austenite (MA) microstructures.     

Fabrication and characterization of SmO_（0.7）F_（0.2）FeAs bulk with a transition temperature of 56.5 K

The superconductivity of iron-based superconductor SmO 0.7 F 0.2 FeAs was investigated. The SmO 0.7 F 0.2 FeAs sample was prepared by the two-step solid-state reaction method. The onset resistivity transition temperature is as high as 56.5 K. X-ray diffraction (XRD) results show that the lattice parameters a and c are 0.39261 and 0.84751 nm, respectively. Furthermore, the global J c was more than 2.3 × 10 5 A/cm 2 at T = 10 K and H = 9 T, which was calculated by the formula of J c = 20ΔM/[a(1-a/(3b))]. The upper critical fields, H c2 ≈ 256 T (T = 0 K), was determined according to the Werthamer-Helfand-Hohenberg formula, indicating that the SmO 0.7 F 0.2 FeAs was a superconductor with a very promising application.     

VUV photoluminescence of (Gd,Zn)PO4:Tb3+ phosphors synthesized by ultrasonic spray pyrolysis

High-quality (Gd_0.955−xZn_0.045)PO₄:xTb³⁺ (0.06≤x≤0.15) green phosphors were synthesized by ultrasonic spray pyrolysis. With an increase of Tb³⁺ content, the emission intensities caused by the ⁵D₄→^{7 F} _J (J = 3, 4, 5, and 6) and ⁵D₃→⁷F_J (J = 4, 5, and 6) transitions of Tb³⁺ increased and decreased, respectively, allowing a purer green emission. The emission intensity of (Gd_0.805Zn_0.045)PO₄:0.15Tb³⁺ at 544 nm was 53.0% stronger than that of (Gd_0.895Zn_0.045)PO₄:0.06Tb³⁺. The emission intensity and the green color purity were remarkably improved by increasing Tb³⁺ content in (Gd_0.955−xZn_0.045)PO₄:xTb³⁺.     

关于焊接接头分区不均匀裂纹体的J积分

用反例证明了分区不均匀介质中J 积分的不守恒性。注意到应力应变分量的间断性,提出了J~*积分以修正J 积分。进而说明了J~*积分的守恒性、物理意义及其能量率表达式的适用性。对用有限元分析分区不均匀介质时,提出了界面单元的概念和构造方法。     

Photoresponse and donor concentration of plasma-sprayed TiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript>-ZnO electrodes

The photoelectrochemical characteristics of plasma-sprayed porous TiO₂, TiO₂-5%ZnO, and TiO₂-10%ZnO electrodes in 0.1 N NaOH solution were studied through a three-electrode cell system. The microstructure, morphology, and composition of the electrodes were analyzed using an electron probe surface roughness analyzer (ERA-8800FE), scanning electron microscopy, and x-ray diffraction. The results indicate that the sprayed electrodes have a porous microstructure, which is affected by the plasma spray parameters and composition of the powders. The TiO₂-ZnO electrodes consist of anatase TiO₂, rutile TiO₂, and Zn₂Ti₃O₈ phase. The photoresponse characteristics of the plasma-sprayed electrodes are comparable to those of single-crystal TiO₂, but the breakdown voltage is close to 0.5 V (versus that of a saturated calomel electrode). The short-circuit photocurrent density (J _SC) increases with a decrease of donor concentration, which was calculated according to the Gartner-Butler model. For the lowest donor concentration of a TiO₂-5%ZnO electrode sprayed under an arc current of 600 A, the short-circuit J _SC is approximately 0.4 mA/cm² higher than that of the TiO₂ electrodes under 30 mW/cm² xenon light irradiation. The J _SC increases linearly with light intensity. The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf, Germany.     

Surface tension and thermodynamic properties of liquid Ag-Bi solutions

With the maximum bubble pressure method, the density and surface tension were measured for five Ag-Bi liquid alloys (X _Bi=0.05, 0.15, 0.25, 0.5, and 0.75), as well as for pure silver. The experiments were performed in the temperature range 544–1443 K. Linear dependences of both density and surface tension versus temperature were observed, and therefore the experimental data were described by linear equations. The density dependence on concentration and temperature was derived using the polynomial method. A similar dependence of surface tension on temperature and concentration is presented. Next, the Gibbs energy of formation of solid Bi₂O₃, as well as activities of Bi in liquid Ag-Bi alloys, were determined by a solid-state electromotive force (emf) technique using the following galvanic cells: Ni, NiO, Pt/O ⁻²/W, Ag _X Bi _(1−X), Bi ₂ O _3(s). The Gibbs energy of formation of solid Bi₂O₃ from pure elements was derived: =−598 148 + 309.27T [J · mol⁻¹] and =−548 008 + 258.94T [J · mol⁻¹]; the temperature and the heat of the α → δ transformation for this solid oxide were calculated as 996 K and 50.14 J · mol⁻¹. Activities of Bi in the liquid alloys were determined in the temperature range from 860–1075 K, for five Ag-Bi alloys (X _Ag=0.2, 0.35, 0.5, 0.65, 0.8), and a Redlich-Kister polynomial expansion was used to describe the thermodynamic properties of the liquid phase. Using Thermo-Calc software, the Ag-Bi phase diagram was calculated. Finally, thermodynamic data were used to predict surface tension behavior in the Ag-Bi binary system.     

Surface tension and thermodynamic properties of liquid Ag-Bi solutions

With the maximum bubble pressure method, the density and surface tension were measured for five Ag-Bi liquid alloys (X _Bi=0.05, 0.15, 0.25, 0.5, and 0.75), as well as for pure silver. The experiments were performed in the temperature range 544–1443 K. Linear dependences of both density and surface tension versus temperature were observed, and therefore the experimental data were described by linear equations. The density dependence on concentration and temperature was derived using the polynomial method. A similar dependence of surface tension on temperature and concentration is presented. Next, the Gibbs energy of formation of solid Bi₂O₃, as well as activities of Bi in liquid Ag-Bi alloys, were determined by a solid-state electromotive force (emf) technique using the following galvanic cells: Ni, NiO, Pt/O ⁻²/W, Ag _X Bi _(1−X), Bi ₂ O _3(s). The Gibbs energy of formation of solid Bi₂O₃ from pure elements was derived: =−598 148 + 309.27T [J · mol⁻¹] and =−548 008 + 258.94T [J · mol⁻¹]; the temperature and the heat of the α → δ transformation for this solid oxide were calculated as 996 K and 50.14 J · mol⁻¹. Activities of Bi in the liquid alloys were determined in the temperature range from 860–1075 K, for five Ag-Bi alloys (X _Ag=0.2, 0.35, 0.5, 0.65, 0.8), and a Redlich-Kister polynomial expansion was used to describe the thermodynamic properties of the liquid phase. Using Thermo-Calc software, the Ag-Bi phase diagram was calculated. Finally, thermodynamic data were used to predict surface tension behavior in the Ag-Bi binary system.     

Thermodynamic and topological instability approaches for forecasting glass-forming ability in the ternary Al–Ni–Y system

A thermodynamic approach to predict bulk glass-forming compositions in binary metallic systems was recently proposed. In this approach, the parameter γ* = ΔH^amor/(ΔH^inter − ΔH^amor) indicates the glass-forming ability (GFA) from the standpoint of the driving force to form different competing phases, and ΔH^amor and ΔH^inter are the enthalpies for glass and intermetallic formation, respectively. Good glass-forming compositions should have a large negative enthalpy for glass formation and a very small difference for intermetallic formation, thus making the glassy phase easily reachable even under low cooling rates. The γ* parameter showed a good correlation with GFA experimental data in the Ni–Nb binary system. In this work, a simple extension of the γ* parameter is applied in the ternary Al–Ni–Y system. The calculated γ* isocontours in the ternary diagram are compared with experimental results of glass formation in that system. Despite some misfitting, the best glass formers are found quite close to the highest γ* values, leading to the conclusion that this thermodynamic approach can be extended to ternary systems, serving as a useful tool for the development of new glass-forming compositions. Finally the thermodynamic approach is compared with the topological instability criteria used to predict the thermal behavior of glassy Al alloys.     

The Influence of Centerline Sigma (σ) Phase on the Through-Thickness Toughness and Tensile Properties of Alloy AL-6XN

The J-integral fracture toughness and tensile behavior of AL-6XN (ATI Properties Inc., Pittsburgh, PA, USA) plate material in the short-transverse (S-T) orientation was studied. The material was tested with respect to the presence or absence of microstructural ‘packets’ of brittle sigma phase (σ-phase) particles within the austenite matrix, located near the centerline of the plate. The J-integral-fracture resistance curve (J-R-curve) qualitatively indicated that the presence of the σ-phase packets is a detriment to the fracture toughness of the material in the S-T orientation. Tensile specimens containing the packets of σ-phase particles exhibited reduced yield and tensile strengths as well as pronounced reduction in ductility compared to specimens nominally free of σ-phase packets. Particle cracking was observed within the σ-phase packets, which lead to premature fracture. This limited the ability of the material to plastically deform and work-harden, thereby accounting for the observed reductions in ductility, toughness, and ultimate tensile strength.