System Nd-Pd-O: Phase diagram and thermodynamic properties of oxides using a solid-state cell with advanced features

An isothermal section of the phase diagram for the system Nd-Pd-O at 1350 K has been established by equilibration of samples representing 13 different compositions and phase identification after quenching by optical and scanning electron microscopy, x-ray diffraction, and energy dispersive analysis of x-rays. The binary oxides PdO and NdO were not stable at 1350 K. Two ternary oxides Nd₄PdO₇ and Nd₂Pd₂O₅ were identified. Solid and liquid alloys, as well as the intermetallics NdPd₃ and NdPd₅, were found to be in equilibrium with Nd₂O₃. Based on the phase relations, three solidstate cells were designed to measure the Gibbs energies of formation of PdO and the two ternary oxides. An advanced version of the solid-state cell incorporating a buffer electrode was used for high-temperature thermodynamic measurements. The function of the buffer electrode, placed between reference and working electrodes, was to absorb the electrochemical flux of the mobile species through the solid electrolyte caused by trace electronic conductivity. The buffer electrode prevented polarization of the measuring electrode and ensured accurate data. Yttria-stabilized zirconia was used as the solid electrolyte and pure oxygen gas at a pressure of 0.1 MP a as the reference electrode. Electromotive force measurements, conducted from 950 to 1425 K, indicated the presence of a third ternary oxide Nd₂PdO₄, stable below 1135 (±10) K. Additional cells were designed to study this compound. The standard Gibbs energy of formation of PdO (†_f G ⁰) was measured from 775 to 1125 Kusing two separate cell designs against the primary reference standard for oxygen chemical potential. Based on the thermodynamic information, chemical potential diagrams for the system Nd-Pd-O were also developed.     

Fatigue Life of Cast Titanium Alloys Under Simulated Denture Framework Displacements

The objective of the study was to evaluate the hypothesis that the mechanical properties and fatigue behavior of removable partial dentures (RPD) made from cast titanium alloys can be improved by alloying with low-cost, low-melting elements such as Cu, Al, and Fe using commercially pure Ti (CP-Ti) and Ti-6Al-4V as controls. RPD specimens in the form of rest-shaped, clasp, rectangular-shaped specimens and round-bar tensile specimens were cast using an experimental Ti-5Al-5Cu alloy, Ti-5Al-1Fe, and Ti-1Fe in an Al₂O₃-based investment with a centrifugal-casting machine. The mechanical properties of the alloys were determined by performing tensile tests under a controlled displacement rate. The fatigue life of the RPD specimens was tested by the three-point bending in an MTS testing machine under a cyclic displacement of 0.5 mm. Fatigue tests were performed at 10 Hz at ambient temperature until the specimens failed into two pieces. The tensile data were statistically analyzed using one-way ANOVA (α = 0.05) and the fatigue life data were analyzed using the Kaplan-Meier survival analysis (α = 0.05). The experimental Ti-5Al-5Cu alloy showed a significantly higher average fatigue life than that of either CP-Ti or Ti-5Al-1Fe alloy (p < 0.05). SEM fractography showed that the fatigue cracks initiated from surface grains, surface pores, or hard particles in surface grains instead of the internal casting pores. Among the alloys tested, the Ti-5Al-5Cu alloy exhibited favorable results in fabricating dental appliances with an excellent fatigue behavior compared with other commercial alloys.     

A diagnostic method based on RVM (return voltage measurement) for condenser bushings with oil–paper insulation systems

The bushing of a transformer is one part of the transformer system, but is as vital as the transformer itself because it forms a part of the main circuit. Deterioration and abnormal condition of the bushing possibly cause its destruction, shortage of the main circuit to the Earth, and fire in the systems, so that diagnosis of the bushings is thus very important. At present, mainly visual inspection from outside of the bushing is carried out. Inspection of the inside condition of the bushing by dissolved gas analysis of the inside oil is done only as sampling for selected bushings because it is difficult due to the sealed construction of the bushings. Therefore, a simple diagnostic method for bushings has been expected for a long time. In Eastern Europe, the RVM (Return Voltage Measurement) method based on scanning the polarization spectra was applied to the oil–paper insulation systems inside the transformer as a diagnostic method. In this paper we investigate theoretically the principle of the RVM method applied to bushings with the same oil–paper insulation systems as the transformer by using the equivalent circuit, and the possibility of using this novel diagnostic method for condenser‐type bushings is demonstrated by a model experiment. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 21–29, 2000     

Synthesis of 2H‐Thiopyrans by Rhodium(II) Acetate‐Catalyzed Reaction of 4‐Amino‐2,5‐dihydro‐3‐thiophenecarbonitriles with α‐Diazocarbonyl Compounds. Part 1

4‐Amino‐2,5‐dihydro‐3‐thiophenecarbonitriles 1 reacted with dimethyl diazomalonate in the presence of rhodium(II) acetate to give regioselectively 4‐cyano‐2H‐thio‐pyrans 2 (C ₂— S insertion), and 5‐cyano‐2H‐thiopyrans (C ₅— S insertion) were not isolated. Similar insertion was also observed in the reaction of 1 with methyl diazoacetoacetate and ethyl diazobenzoylacetate. The starting compounds 1 were synthesized by the reaction of tetrahydro‐4‐oxo‐3‐thiophene‐carbonitrile with morpholine, piperidine, and pyrrolidine in the presence of formic acid in ethanol.     

Thermodynamic Analysis of Deoxidation of Titanium Through the Formation of Rare-Earth Oxyfluorides

In this work, the possibility of the direct removal of oxygen species from metallic Ti through the formation of rare-earth oxyfluorides has been investigated from a thermodynamic viewpoint. The deoxidation limit of β-Ti using rare-earth metals (M: Y, La, Ce, and Nd) as deoxidants was evaluated. It was found that Ti metal with an oxygen concentration of 200 mass ppm or less could be theoretically obtained under the M/MOF/MF₃ equilibrium at 1300 K (1027 °C), which suggested a possibility of reducing the oxygen content in Ti below 500 mass ppm utilizing a fluoride-based molten salt. Furthermore, a new deoxidation process, in which oxygen was removed in the form of MOF compounds using Mg deoxidant, was discussed as well. The obtained results revealed that the oxygen content in β-Ti could be theoretically reduced to a level below 1000 mass ppm using a MF₃-containing molten salt equilibrated with Mg. Rare-earth metals and their alloys are usually produced by the electrolysis in a fluoride-based molten salt; hence, the modern industrial electrolysis techniques can be potentially utilized for deoxidizing Ti scrap.     

Experimental characterization of high-speed impact damage behavior in a three-dimensionally woven SiC/SiC composite

This paper discusses high-speed impact damage in a three-dimensionally woven SiC/SiC composite (3D-CMC). The impact damage was introduced by a steel ball projectile in 3D-CMC plates with and without thermal exposure. The surface and internal damages were observed by optical microscopy and X-ray CT. A crater was observed on the collision surface. The X-ray CT measurement revealed that multiple pyramid-shaped cone cracks were generated beneath the crater when the impact speed was relatively low. At an impact speed exceeding the critical speed, a spall fragment was ejected from the back surface, while no internal damage was observed in the fragment. The spall fracture mode differed between the virgin and the thermally-exposed specimens. This difference is the result of embrittlement of the fiber/matrix interface due to oxidation of the carbon coating layer in the thermally-exposed specimen. In addition, it is found that z-yarns improve impact resistance by constraining delamination.     

Electromagnetic wave radiated from an insulating spacer in gas insulated switchgear with partial discharge detection

As a means of diagnosing partial discharge (PD) signals propagate inside a Gas Insulated Switchgear (GIS), a study for the leakage of electromagnetic waves (EM-waves) emitted from the insulating spacer was implemented. The EM-waves leaking out from the solid insulator have the resonance frequencies depend on the spacing between adjacent bolts in the direction of the flange circumference, because the leakage portion is the equivalent of a slot antenna. In this paper, using an electromagnetic analysis model which has a simulated spacer on a concentrically-shaped GIS tank, the output characteristics of the EM-waves that leaked out from the slit were analyzed under various conditions such as the spacing between adjacent bolts, the width of the spacer, the dielectric constant of the spacer and the form of the flange. Also the actual measurement by the experimental equipment used to simulate the model was implemented for comparison with the analytical results. Consequently, the optimal specifications of the sensor and the measurement method used to achieve highly-sensitive detection for practical use were summarized and proposed as well as evaluating the effectiveness of the electromagnetic analysis model adopted in this paper.     

Effective Dissolution of Platinum by Using Chloride Salts in Recovery Process

Platinum (Pt) is typically recovered by employing dissolution processes in aqueous solutions; however, these processes require a long processing time and considerable quantities of acids with strong oxidants owing to the high chemical stability of Pt. In order to develop an efficient dissolution process, we studied chlorination treatments for Pt prior to dissolution. Chlorination was carried out at 673?K to 873?K (400?°C to 600?°C) using copper(II) chloride (CuCl₂) as a chlorine source. While pure Pt was insoluble in hydrochloric acid (HCl(aq)), the entire Pt component of the treated sample dissolved in HCl(aq) under certain conditions. Therefore, the proposed method can be used as a new, environmental friendly Pt recovery process.     

Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants

Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.