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51.
The electrical conductivity of iron-containing silica glasses was measured from 80 to 350 K. The conductivity data were analyzed based on the hopping conduction theory. The hopping binding energy (Wp ) and disorder energy WD ) were calculated from the activation energy at high and low temperatures. The disorder energy obtained was much lower than reported for FeO-P2 O5 glasses, but similar to that for vandium-containing glasses. 相似文献
52.
Diffusion of cobalt,chromium, and titanium in Ni3Al 总被引:1,自引:0,他引:1
Y. Minamino S. B. Jung T. Yamane K. Hirao 《Metallurgical and Materials Transactions A》1992,23(10):2783-2790
Diffusion studies of cobalt, chromium, and titanium in Ni3Al (γ′) at temperatures between 1298 and 1573 K have been performed using diffusion couples of (Ni-24.2 at. pct Al/Ni-24.4
at. pct Al-2.91 at. pct Co), (Ni-24.2 at. pct Al/Ni-23.1 at. pct Al-2.84 at. pct Cr), and (Ni-24.2 at. pct Al/Ni-20.9 at.
pct Al-3.17 at. pct Ti). The diffusion profiles were measured by an electron probe microanalyzer, and the diffusion coefficients
of cobalt, chromium, and tita-nium in γ′ containing 24.2 at. pct Al were determined from those diffusion profiles by Hall’s
method. The temperature dependencies of their diffusion coefficients (m[su2]/s) are as follows: ~D(Co)
= (4.2 ± 1.2) × 1O-3exp {-325 ± 4 (kJ/mol)/RT} ~D(Cr) = (1.1 ± 0.3) × 10-1 exp {-366 ± 3 (kJ/mol)/RT} and D(Ti)
= (5.6 ± 3.1) × 101 exp {-468 ± 6 (kJ/mol)/RT} The values of activation energy increase in this order: cobalt, chromium, and titanium. These
activation energies are closely related to the substitution behavior of cobalt, chromium, and titanium atoms in the Ll2 lattice sites of γ′; the cobalt atoms occupying the face-centered sites in the Ll2 structure diffuse with the normal activation energy, whereas the titanium atoms oc-cupying the cubic corner sites diffuse
with a larger activation energy that includes the energy due to local disordering caused by the atomic jumps. The chromium
atoms which can occupy both sites diffuse with an activation energy similar to that of cobalt atoms. 相似文献
53.
Toshimi Yamane Masatoshi Yasunaga Keiichi Hirao Shinsuke Yamasaki Keizo Kazama Kosei Yoshida Rikio Takeda Minoru Hiratani 《Journal of Materials Science》1988,23(1):305-310
Repetition numbers of bending of Cu-0.81 wt% Cr, Cu-0.81 wt% Cr-0.14 wt% Sn and Cu-0.26 wt% Cr-0.10 wt% Sn alloys were investigated. After solution treatment, the first two types of copper alloys have a primary chromium phase; this is not so in the last alloy. The primary chromium phase does not influence the repetition numbers of bending of cold-rolled specimens; the repetition numbers of bending of specimens aged at 723 K for 1.8 × 103 sec after cold rolling are higher than those of cold-rolled specimens. The cause of this is considered to be a recovery of work-hardening during ageing. 相似文献
54.
Since the publication of Masters and Johnson's Human Sexual Inadequacy in 1970, sex therapy has become an established, though controversial, new approach to the treatment of sexual disorders. Masters and Johnson adopted the position that any other form of psychotherapy should be avoided or suspended during the two- or three-week period of sex therapy. Helen Kaplan, in considering sex therapy to be a type of psychotherapy, has stressed that the skillful trained psychotherapist uses his awareness of the psychodynamics and unconscious conflicts of the couple in modifying and tailoring the sex therapy program to their individual needs. In the present study, sex therapy, utilizing a second therapist, was introduced into an ongoing psychoanalytic psychotherapy. 相似文献
55.
56.
β-Propiolactone (βPL) was graft-copolymerized onto styrene–divinylbenzene copolymers containing various carboxylates or sulfonates, composed of anions and cations having different electronegativities. In parallel, the mechanism of polymerizations of βPL by relatively neutral catalysts was studied in comparison with the behaviors of graft copolymerizations. In the graft copolymerization onto the trunk polymer containing various carboxylates, a lower electronegativity of countercation favors a higher anionic polymerization activity and the order of rate of polymerization coincides with that of anionic activities of catalysts. On the other hand, in the case of trunk polymer containing sulfonates, a higher electronegativity of countercation favors a cationic polymerization activity, and the order of rate of polymerization coincides with that of cationic activity of catalyst. The order of grafting efficiency at fixed total conversion coincides almost with that of anionic activity. The comparatively higher grafting efficiency in the grafting onto trunk polymer containing carboxylic acid might support an anionic graft copolymerization mechanism by carboxyl anion. The two following mechanisms were proposed for the initiation of the polymerization by the trunk polymer containing sodium sulfonate, in which acrylic acid is transformed from βPL. 相似文献
57.
Noboru Yamazaki Seiichi Nakahama Akira Hirao Juheiji Kawabata Hiromichi Noguchi Yasuzo Uchida 《Polymer Bulletin》1980,2(4):269-274
Summary Catalysis of cationic polyelectrolytes for the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate anion was studied in a buffer solution (pH=9.0). Cross-linked poly (4-vinylpyridinium) salts prepared from 4-vinylpyridine and , -dibromides were used as cationic catalysts. The cross-linked catalysts were found to accelerate markedly the decarboxylation in comparison with the linear water-soluble analogues. Effect of the polymer structure such as the length of (CH2)x linkages between positive charges on the catalytic activity was examined. It was suggested that the acceleration by the cross-linked polymer catalysts would be due to the hydrophobic microenvironment around the catalytic sites. 相似文献
58.
Heishiciro Takahama Hitoshi Kawamura Seizo Kato Hajime Yokosawa 《International Journal of Engineering Science》1979,17(6):735-744
Energy separation performance of a steam-operated vortex tube is experimentally investigated, and some reasonable criteria and expressions to estimate the energy separation performance are also introduced. The performance characteristics defined by the above expressions are the same as those of ideal gas in the high superheated region, and are well expressed independently of the degree of superheat, total mass flow rate and discharge resistance. When steam is in the wet region at the nozzle outlet, the performance considerably decreases because of the energy waste from moisture vaporization. And no energy is separated when the dryness fraction is less than approximately 0.98. Some technical data including the optimum operating conditions are also offered. 相似文献
59.
Mark I. Jones Maria-Cecilia Valecillos Kiyoshi Hirao Yukihiko Yamauchi 《Journal of the European Ceramic Society》2002,22(16):2981-2988
Silicon nitride ceramics have been produced by microwave sintering at 28 GHz with Y2O3, Al2O3 and MgO as sintering additives. The effect of initial β content of the Si3N4 starting powder on the microstructural development has been assessed by scanning electron microscopy (SEM) and quantitative image analysis. Phase transformation behaviour was assessed by X-ray diffraction. Mechanical properties of the sintered bodies were determined through assessment of hardness and fracture toughness. It was found that the samples sintered from powders with lower initial β content developed larger grains than those from higher β content powders, due to fewer nucleation sites during the →β transformation. However, attempts to develop a more bimodal microstructure by using a mixture of the two grades of powder, in an effort to increase both fracture toughness and fracture strength, were unsuccessful. In this case the microstructure was similar to that developed in the materials produced from higher β content powders. The mechanical properties of the sintered bodies were very similar, despite differences in microstructure. This was attributed to the strong bonding between the grains and grain boundary phase resulting in crack paths in all the materials that were predominantly transgranular, with little debonding or crack deflection. Under these circumstances the effect of larger grains is eliminated. 相似文献
60.
Tatsuki Ohji Kiyoshi Hirao Shuzo Kanzaki 《Journal of the American Ceramic Society》1995,78(11):3125-3128
The R -curve behavior was characterized by the Vickers indentation flaw technique, for highly anisotropic silicon nitride, a silicon nitride whose fibrous grains are highly aligned. The measured crack lengths ranged from 30 to 500 μm. The fracture resistance of a conventional self-reinforced silicon nitride was determined for comparison using the same procedures. While in the self-reinforced material several hundred micrometers of crack extension were required to obtain a high fracture toughness, the highly anisotropic material exhibited a high toughness from the beginning of the measured crack length range with little increase in the following range. It is suggested that the toughness of the highly anisotropic material steeply rises in a very short crack extension, which is advantageous in avoiding catastropic fractures. 相似文献