Electrical resistivity, oxidation resistivity and hardness of single crystal compounds in the Er–Rh–B system

Single crystals of ternary borides ErRh₃B (cubic,Pm3m), ErRh₃B₂ (monoclinic, C2/m) and ErRh₄B₄ (tetragonal, P4₂/nmc) have been grown from copper solution by slow cooling method. The electrical resistivity, oxidation resistivity and Vickers microhardness were studied. The electrical resistivities at room temperature of the (100) face of ErRh₃B, (001) face of ErRh₃B₂ and (100) face of ErRh₄B₄ are 25.6 μΩ·cm, 50.0 μΩ·cm and 106.8 μΩ·cm, respectively. According to thermogravimetric and differential thermal analyses, the oxidation of ErRh₃B, ErRh₃B₂ and ErRh₄B₄ start at 1030°C, 373°C and 690°C, respectively. The weight gain of the same compounds after heating in air up to 1200°C is 0.7%, 15.44% and 5.4%, respectively. The values of the Vickers microhardness for the (100) face of ErRh₃B, the (100) face of ErRh₃B₂ and the (110) face of ErRh₄B₄ are 4.8–5.0 GPa, 10.4–10.9 GPa and 10.9–11.3 GPa, respectively. The effect of boron content and crystal structure of each compound on the electrical resistivity, oxidation resistivity and Vickers microhardness are discussed.     

The anodic behavior of amorphous Ni-19P alloys in different amorphous states

An amorphous Ni-19P alloy prepared by rapid quenching of white heat melt showed a higher anodic dissolution current density in 1 N HCl in comparison with the same amorphous alloy prepared by rapid quenching of red heat melt. After structural relaxation these two specimens showed the same anodic polarization curve which is located between the polarization curves of as-quenched two specimens. The thermograms of these two as-quenched specimens were different from each other, showing that the difference in the amorphous states is due to the difference in structural relaxation during preparation. The difference in anodic behavior between these two as-quenched specimens seems due to the difference in the amounts of quenched-in defects. The higher current density of the relaxed specimen in comparison with the as-quenched specimen prepared by rapid quenching of the red heat melt has been interpreted in terms of introduction of chemical heterogeneity as a result of rearrangement and regroupings of atoms in the alloy during structural relaxation. The steady state current density was fairly low in the low potential region without showing a difference between two as-quenched specimens and then increased with increasing polarization potential. The difference in the quality of as-quenched alloy specimens seemed to be masked by the formation of phosphorus-covered alloy surfaces during anodic polarization at potentials lower than about 200 mV(SCE), because of a negligibly small dissolution rate constant of phosphorus in comparison with that of nickel.     

放电等离子快速烧结纳米3Y-TZP材

本文采用放电等离子烧结技术（ＳＰＳ）快速烧结结纳米３Ｙ－ＴＺＰ材料,利用ＳＰＳ技术快速烧结,可制备出完整、致密的３Ｙ－ＴＺＰ材料,在烧结温度为１３００℃,保温３ｍｉｎ条件下,相对密度达９８．２％,晶粒仅１００￣１３０ｎｍ,研究发现,材料的密度随烧结温度的变化趋势与一般快速烧结有明显区别;材料的晶粒随烧结温度的提高而长大,但长大幅度小于其他一些烧结方法所得的３Ｙ－ＴＺＰ材料,本研究对这些现象进行了理     

Swelling of poly(glycidyl methacrylate) gel particles by organic solvents

Fine particles of poly(glycidyl methacrylate) (PGMA) were prepared by suspension polymerization and crosslinked via the ring-opening reaction of the epoxide group with formic acid. A fraction of the spherical gel particles averaging about 70°m in diameter was examined under an optical microscope with its swelling behavior in a number of solvents. Equilibrium degrees of swelling were established with accuracy to show that this polymer gel has rather unusual affinities for solvents: (i) It is swollen (and, without the crosslinks, soluble in most cases) in many types of solvents, (ii) it cannot be represented by a single value of solubility parameter, and (iii) it is not swollen at all in water nor in aliphatic alcohols, in spite of the presence of hydroxy groups in the chain.     

A study on the deterioration characteristics of power capacitors with oil-impregnated paper

Power capacitors are highly reliable due to their completely enclosed configuration. They are relatively trouble-free over the long term. However, their dielectric strength can be reduced due to some stresses, including overvoltage application or thermal degradation of the insulation material during long periods of operation; these events can result in dielectric breakdown of capacitors in extreme cases. Since almost all power capacitors with oil-impregnated paper have been operated for more than twenty years, some kind of failure should be expected. To prevent these incipient accidents, it is important to examine the insulation deterioration mechanism and evaluate the degree of deterioration before capacitor breakdown. To establish a diagnostic method of deterioration of the capacitors with oil-impregnated paper, we have conducted thermally and electrically accelerated deterioration tests and investigated the changes of their characteristics. Based on the experimental results we obtained, it can be concluded that the behavior of the oil-dissolved gases can be used as a useful index to diagnose the insulation deterioration of these capacitors.     

Technological progress in high-voltage XLPE power cables in Japan.II

For pt.I see ibid., vol.4, no.5, p.9-16 (1988). Cables designed for particular applications and improved performance are described. The products discussed are: (1) water-impervious cable; (2) composite XLPE/optical fiber cable; (3) 66-kV submarine cable; (4) commercial long-distance 275-kV line; and (5) 500-kV short-distance line. The discussion is confined to the Japanese cable industry     

Impact control of grasping [robot manipulators]

The stabilization effect of collision in impact-controlled manipulator-object systems is discussed. The stability of system behavior is analyzed by the Lyapunov direct method. Some simulation results are shown to confirm the effect. Collision is one of the nonlinear problems where the dynamical structure changes. In industrial fields, the phenomenon is utilized effectively to suppress vibrations, but collision is a difficult problem to treat in the field of control because the methodology is mostly based on linear theory. The nonlinear impact force is modeled as a Hertz-type force with damping. A nonlinear matrix and a quadratic form is defined to examine system stability. As a results, stable control with collision phenomena is obtained