Electrical Conduction in β-Bi2O3 Doped with Sb2O3

Electrical conduction in tetragonal β-Bi₂O₃ doped with Sb₂O₃ was investigated by measuring electrical conductivity, ionic transference number, and Seebeck coefficient. The β-Bi₂O₃ doped with 1 to 10 mol% Sb₂O₃ was stable up to 600°C and showed an oxygen ionic and electronic mixed conduction, where the electron conduction was predominant at low oxygen pressures. The oxygen-ion conductivity showed a maximum at 4 mol% Sb₂O₃, whereas the activation energy for the ionic conduction remained unchanged for 4 to 10 mol% Sb₂O₃-doped specimens. These results were interpreted in terms of the oxygen vacancy concentration and the distortion of the tetragonal structure. The electron conductivity and its oxygen pressure dependence decreased with increasing Sb₂O₃ content. The fact that Sb⁵⁺ is partially reduced by excess electrons in heavily doped β specimens at low oxygen pressures is explained.     

Formation of Lead Zirconate-Lead Titanate Solid Solutions

Formation of the Pb(Zr,Ti)O₃ solid solution in the system PbO-TiO₂-ZrO₂ was studied by chemical analysis and X-ray powder diffrac-tometry. Only PbTiO₃ and Pb(Zr,Ti)O₃ were found as reaction products. The following three elementary reactions seemed to be reasonable for the formation of the Pb(Zr,Ti)O₃ phase: PbO + TiO₂→ PbTiO₃, PbTiO₃+ PbO + ZrO₂→Pb(Zr_1-λTi_λ)O₃, and Pb(Zr_l-λTi_λ)O₃+ PbTiO₃→ Pb(Zr_1-λ'Ti_λ')O₃ (λ<λ').     

Stress-Induced Transformation and Plastic Deformation for Y2O3-Containing Tetragonal Zirconia Polycrystals

Yttria-containing tetragonal zirconia polycrystals with low thermal stability showed plastic deformation with a maximum bending strain of 0.8% due to the stress-induced tetragonal to monoclinic transformation. The strain rate depended on applied stress and temperature. The temperature at which the transformation rate is maximum increases with increasing applied stress. Changes in microstructure and crystallographic structure after plastic deformation were examined by transmission electron microscopy and X-ray analyses. The mechanism of plastic deformation is discussed in relation to the tetragonal to monoclinic transformation.     

Development of Reference Shunt for Short‐Time Alternating High Current Tests and Study of Measuring System

Short‐circuit tests for power circuit breakers and others require alternative short‐time current measurement, from a few kA to over several tens kA. However, the reference measurement system as a national standard or a specified secondary standard instrument to directly perform comparative test as a complete calibration test in high current class has not yet been established globally. The Japan Short‐Circuit Testing Committee (hereinafter referred to as “JSTC”) has therefore developed a shunt resistor that can be used as a standard instrument for high current measurement. Reference system using this shunt resistor is also considered by JSTC. The performance of the newly developed shunt resistor has been checked through several methods, such as resistance measurement, high power current test, high frequency current test, temperature rise test, and interference test. The results of the tests proved satisfactory performance. Resistance of the shunt resistor before and after the tests was invariant and stable. This makes the shunt resistor adequate for a reference in practical use. In addition, evaluation of uncertainty of the whole reference system including this shunt resistor satisfactorily fulfills the requirements of IEC 62475 edition 1.0, 2010.     

Plasma Behavior in a High‐Temperature Noble Gas Plasma Disk‐Shaped MHD Power Generator

R‐θ two‐dimensional numerical simulations have been carried out to clarify the plasma behavior in a high‐temperature noble gas plasma disk‐shaped magnetohydrodynamic (MHD) generator. At low inlet total temperature and high load resistance, the plasma has spiral structure which is similar to the nonuniform structure under the weak noble gas ionization condition in a seed‐plasma MHD generator. As seen in a linear‐shaped Faraday‐type MHD generator, the plasma becomes stable with increase in the inlet total temperature because the coulomb collision of electrons becomes dominant. Even at low inlet total temperature, the ionization instability can be suppressed for low load resistance, because the relatively low electron temperature due to less Joule heating makes the ionization relaxation time longer than plasma residential time.     

Effect of Axial Slit on Metallic Tube for Wireless Power Transfer via Magnetic Resonance Coupling

Wireless power transfer using a metallic tube with an axial slit was attempted to demonstrate the wireless power transfer using magnetic resonance coupling to the diagnostics infrastructure. The transmission efficiency with variable distance was measured using the transmission and receiver resonators in the tube. Besides, the transmission and receiver resonators were, respectively, set outside and inside the tube. These experiments are carried out in the computational study using FDTD method.     

Thermochromism in Reduced Phosphate Glasses

Coloring and bleaching of reduced phosphate glasses in the systems K₂O-B₂O_r Al₂O₃-P₂O₅ and K₂O-Al₂O₃-P₂O₅, containing no silver halide, were studied. The as-cast glasses, which are colorless and transparent, become tinged with red when they are reheated at high temperatures for long times. The bleached specimens (PTC-RP glass) are obtained by heating at >600°C, then quenching. The PTC-RP glasses exhibit coloring phenomena by irradiation of light or by heating above 200°C; the colored glasses are again bleached thermally. Coloring of the glasses by heating is described in this paper in terms of phase change within the colloidal phosphorus formed in the glasses. The apparent activation energy for the thermocoloring is estimated to be ∼15×10⁴ J/mol (35 kcal/mol).     

Cavitation peening to improve the fatigue strength of nitrocarburized steel

Shot peening is a commonly employed technique used to improve the fatigue strength of nitrocarburized components. However, the compound layer of the component can be broken by this technique. Cavitation peening (CP) is an alternative shotless technique, which can increase the fatigue strength of the component without separation of the compound layer. To evaluate the potential of CP as a means for improving fatigue strength, nitrocarburized carbon steel (JIS S50C) has been analyzed in the non‐peened and CP conditions. The fatigue strength of CP specimens was increased by 15% in comparison with that of non‐peened specimens. This increase in the fatigue strength of CP specimen was achieved by the increase in the maximum hardness and compressive residual stress within the diffusion zone.     

Plasma Fluid Flow Behavior and Power Generation Characteristics in a High‐Temperature Inert Gas Plasma Faraday MHD Generator

The plasma fluid flow behavior and power generation characteristics in a Faraday magnetohydrodynamic (MHD) generator using a high‐temperature inert gas (argon) plasma have been examined in a time‐dependent two‐dimensional numerical simulation. The inhomogeneous and unstable plasma at an inlet total temperature of 7000 K results in reductions and fluctuations in the output power. The plasma becomes homogeneous and stable as the inlet total temperature increases to 9000 K. One of the reasons for the suppression of ionization instability may be weakness of the dependency of the electrical conductivity on the electron number density, because the Coulomb collision of electrons becomes dominant during deviation from Saha equilibrium.