Continued from p. 673; No. 8 (1956) Vol. 42 Tetsu-to-Hagane.
In this paper, the apparatus and auxiliary parts for determination of the rapid hydrogen content are described and its roles in operation are also additionally described.

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Molibdenum coatings having a thickness of 5-30μm were chemically deposited on 10×13×0.5mm substrates of nickel, iron, copper and 18-8 stainless steel for 60 minutes, using the following CVD reaction;
2MoCl₅(g)+5H₂(g)→2Mo(s)+10HCl(g)……(1)
The molybdenum coatings on nickel substrates were obtained at 550-750°C and resisted peeling even under a thermal shock of 600-700°C. A diffusion layer 3-10μm thick was observed at the interface between the molybdenum and the nickel substrate. Examination using a micro X-ray diffraction meter showed that the compound MoNi₄ formed in the diffusion layer.
Molybdenum coatings were also deposited on iron substrates at 750-800°C, on copper at 550-650°C, and on 18-8 stainless steel at 550-750°C. The molybdenum coatings on iron and copper were thicker than those on nickl. A diffusion layer was observed between molybdenum and each of the substrates.
The use of nickel-plated iron substrates made it possible to obtain molybdenum coatings on iron substrates at temperatures as low as 550°C.

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Thermodynamic properties of In, Tl, Cd, Zn, Sn or Pb in their amalgams were analyzed by the potentiometric measurements at high temperatures 150 to 200°C. In the cases of Zn, Pb, and Sn amalgams, their activity coefficients increased rapidly with temperature, but those of In, Tl and Cd amalgams decreased gradually. A difference between a normal amalgam potential for an amalgam and a standard electrode potential for a metal, E*, was studied. It was known that the value of E*indicated a deviation from a value calculated by Raoult's law. A temperature dependence of activity, partial molar enthalpy change, and a concentration dependence of temperature coefficient of e. m. f., partial molar entropy change, were discussed in relation to types of amalgam. It was seen that the potential difference between the metal and its saturated amalgam, Es, for In and Tl was zero while -8 to-2mV for Cd, Zn and Sn. Therefore, In and Ti amalgams were considered as a simple mixture of mercury and each of the metals. On the other hand, Zn, Cd, Sn and Pb amalgams were regarded as a complex such as Hg_xM_ywhich was dissolved in a mercury or a simple mixture of mercury and each of the metals.

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A TiC coating method on steels containing various alloying elements and the coating mechanism have been investigated. Steels containing large amount of alloying elements were carburized by a drip feed method. All of the carburized steels were able to be coated with TiC from a bath with 5mol NaCN. A carbon potential of the bath added NaCN was known to be 0.1% by a carburizing test. The effects of alloying elements, Ni, Cr, Mn, and Si, in steels on the coating were also studied. Except a case of 3.0% Si, a good coating was obtained. Electron prove microanalyses (EPMA) revealed that Ni, Cr, and Mn did not diffuse into the coating while a large amount of V was accumulated in it. The mech anism of TiC coating was also investigated. When KF was used instead of K₂TiF₆ for the sourse of F, the TiC coating was obtained. From the study on the effects of the KF addition by using EPMA, it was found that the Ti deposition occured according to a disproportionation reaction. An activation energy for the TiC coating was similar to that of the diffusion of carbon in a 0.9% C steel. This fact may suggest that a rate determining step for the coating is a diffusion of carbon.

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Some small fraction of large grains was observed in the microstructure of sintered ZnFe₂O₄, MnZnFe₂O₄, Fe₃O₄ (in N₂) and MnFe₂O₄ (in air). This structure is sometimes called "duplex structure". As the sintering proceeded, the number of large grains increased to form the continuous structure of large grains, while the size of large grains did not increase remarkably. On the other hand, the duplex structure was not observed in the ferrites with the composition of NiFe₂O₄ and CoFe₂O₄, independent of prefiring and sintering conditions. However, when amounts of Fe₂O₃ were excess in the composition of the ferrites, duplex-like structures were observed. This structure was also formed in the CoFe₂O₄ containing platinum powder (Pt black) known as a redox catalyst. From these results, the duplex structures seem to be formed in such ferrites that are easy to vary their compositions or valencies at high temperatures. In addition, the growth of small grains was very slow during the formation of duplex structure. It was considered that the exaggerate grain growth was generated by the local activation of the stabilized grain boundaries, which was caused by the variation of compositions or valencies during the sintering.

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