[en] The surface relief of αdouble_prime martensite plates in a polycrystalline Ti-4.74 at. pct Mo alloy was studied by atomic force microscopy (AFM). The orientation of matrix grains was measured by electron backscatter diffraction (EBSD), and measured surface tilt angles were compared with calculation by the crystallographic theory of martensite transformation. The observed maximum tilt angle was close to the predicted value of 7.57 deg. The overall agreement between measured and calculated tilt angles was improved significantly by taking into account not only the inclination of habit plane to the specimen surface, but also the shear direction predicted from the theory. The tile angle may vary with the moving direction of the interface unless the habit plane is perpendicular to the specimen surface. However, this effect was small in this transformation

[en] A scanning transmission electron microscope (STEM)-energy dispersive X-ray (EDX) analysis was made of the Mo concentration at boundaries between degenerate ferrite and austenite in an Fe-0.28mass%C-3mass%Mo alloy isothermally reacted below the bay temperature of the time-temperature-transformation (TTT)-diagram. The measured Mo concentration scattered widely from one boundary to another and varied considerably along the individual boundaries. The enrichment factor of Mo corrected for the sampling volume (beam diameter) to boundary thickness ratio showed an increasing tendency with isothermal holding time and reached as large as 15 when the alloy entered the transformation stasis. The amount of Mo in the boundary is compared with that calculated under the assumption of quasi-steady state diffusion that is used to analyze the solute drag effects on the motion of interphase boundaries

[en] The three-dimensional (3-D) distribution, morphology and nucleation site of intragranular ferrite formed in association with MnS particles were observed by computer-aided reconstruction of images obtained by serial sectioning in an Fe-0.1mass% C-1.5mass% Mn alloy isothermally reacted at 610 and 640 deg. C. 3-D analysis indicated that essentially all the intragranular ferrite precipitates nucleate at inclusions. The 3-D shape of idiomorphic ferrite precipitates was considerably more irregular than would be expected from their shape on polished specimen surfaces. Electron backscattering diffraction analysis showed that ferrite particles nucleated at inclusions were often composed of several grains and subgrains, and most of them were in contact with the surfaces of inclusions. Widmanstaetten ferrite which grew radially from inclusions had a lath rather than a plate shape at the temperature studied

[en] Bi₂Sr₂CaCu₂O_8+X (Bi-2212) high-T_c superconductors (HTS) bulk conductors have been prepared by a new diffusion process for current lead application. The Bi-2212 HTS diffusion layer is synthesized through the reaction between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating with Ag addition. The HTS diffusion layers about 150 μm in thickness are formed around both outside and inside of the hollow cylinders. The Ag added to the coating enhances the diffusion reaction, and precipitates on the surface of the specimen decreasing the contact resistance between the HTS ceramic layer and the current terminal. The Bi-2212 HTS layer consists of thin plate-like grains grown in the diffusion direction. They are mainly composed of grains with a-axis orientation. The transport current is expected to pass longitudinally through the cylinders on the ab planes. The transport current of the hollow cylinder 27/19 mm in outside/inside diameter and 200 mm in length reaches 6000 A at 4.2 K and self-field, which corresponds to the current density of 28,000 A/cm². The total heat load, including the heat leakage conducted through the cylinder between 4 and 40 K, is estimated to be less than 400 mW at 5000 A. Present Bi-2212 HTS conductors seem to be promising as large transport current leads for superconducting magnets

No abstract available

[en] The quality of fossil fuels tends to be evaluated by amounts of CO₂ emissions. For the evaluation of an oil shale from this point, an on-line thermogravimetric-gas chromatographic system was used to measure CO₂ evolution profiles on temperature with a small oil shale sample. This method makes it possible to estimate the amounts of CO₂ evolved from kerogen and carbonates in retorting and those from carbonates in combustion, respectively. These results will be basic data for a novel oil shale retorting process for the control of CO₂ emissions. The profiles for Thai and Colorado oil shales have shown CO₂ mainly evolved by the pyrolysis of kerogen below 550 degree C, and that evolved by the decomposition of carbonates above that temperature. On the other hand, the profile for Condor oil shale showed that most carbonates decomposed below 550 degree C, while only small amounts of carbonates decomposed above this temperature. 14 refs., 2 figs., 3 tabs

[en] Iron mixed-valence complex (n-C₃H₇)₄N[Fe^IIFe^III(dto)₃] (dto=C₂O₂S₂) undergoes a charge transfer phase transition and a ferromagnetic transition at 120 and 7 K, respectively. Recently, we have succeeded in obtaining single crystals and we investigated the magnetic properties. From the analysis of the crystal structure and the magnetic properties for the single crystal, the mechanism of the ferromagnetic ordering and the direction of the ferromagnetic coupled magnetic moment were elucidated

[en] The growth of austenite during continuous heating in plain low-carbon martensite is simulated extending the analytical model by Judd and Paxton to include the carbon diffusion through the matrix. It is assumed that cementite is fully precipitated at an early stage of heating so that austenite is nucleated above the eutectoid temperature either on cementite or away from it, e.g., on prior austenite grain boundary. The austenite grows fast until all cementite particles vanish and thereafter continues to grow at a gradually increasing rate with temperature. Cementite particles remain up to a higher temperature with the increase in heating rate, initial particle size of cementite and the decrease in the number of austenite nuclei. Due to slow carbon diffusivity in austenite, the cementite free of austenite tends to dissolve faster than the cementite on which austenite was nucleated except when the particle size of cementite and/or the number of austenite nuclei is small.

[en] If Fe"I"I"IO_3S_3 or Fe"I"IO_3S_3 can be realized, the mixed valence state of Fe and specific magnetic properties associated with this state can be expected. For this purpose, the authors developed a new assembled-metal complexes A[M"I"IFe"I"I"I(mto)_3], which were cross-linked with monothio oxalate with the site of Fe"I"I"IO_3S_3, and examined their physical properties based on magnetic measurement and "5"7Fe Moessbauer spectroscopy. They performed the complex formation of [Fe"I"I"I(mto)_3]"3"- from K_2(mto) and Fe(NO_3)_3·9H_2O, and further made it react with FeCl_2·4H_2O and (n-C_4H_9)_4NBr to obtain (n-C_4H_9)_4N[Fe"I"IFe"I"I"I(mto)_3]. They checked the magnetic order state and magnetic transition temperature using a SQUID magnetometer, and performed residual magnetization and "5"7Fe Moessbauer spectroscopy. As a result, it was found that the concerted phenomena of spin equilibrium and the valence fluctuation of Fe"I"I-Fe"I"I"I occurred. In addition, from the characteristics of similar synthetic compounds, it was found that the dynamic spin equilibrium in Fe"I"I"IO_3S_3 site played a very important role in the formation of magnetic order. (A.O.)

[en] We have investigated the spin crossover transition of the triazole bridged one dimensional Fe^II complexes, [Fe(4-NH₂trz)₃](o-, m-, p-tos)₂·nH₂O (tosH = toluenesulfonic acid), in order to study the isomerization effect of counter anion on the spin crossover phenomenon by means of ⁵⁷Fe Moessbauer spectroscopy and magnetic susceptibility measurement. In the heating process, the spin transition of the all salts occurs around room temperatures, i.e. those of o-, m-, p-tos salts are 330 K, 319 K and 320 and 350 K, respectively. In the cooling process, the structural isomerization effect of counter anion on the spin crossover phenomenon is more remarkable than that in the heating process. In the case of o-tos salt, the spin transition occurs at 250 K with thermal hysteresis of 80 K. On the other hand, in the case of the m-tos salt, the spin transition occurs abruptly at 319 K with negligible small hysteresis. In the case of the p-tos salt, the spin transition occurs abruptly at 295 K in the cooling process in spite of stepwise spin transitions in the heating process.