巻号一覧
17 巻, 7 号
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牟田 明徳1971 年 17 巻 7 号 p. 285-294
発行日: 1967/04/25
公開日: 2009/12/04
ジャーナル フリーPDF形式でダウンロード (8674K) -
斎藤 安俊1971 年 17 巻 7 号 p. 295-299
発行日: 1967/04/25
公開日: 2009/12/04
ジャーナル フリーThermal decomposition of hydrous oxide and oxycarbonate of thorium has been studied by thermogravimetry (TG), differential thermal analysis (DTA) and Hahn's emanation technique. Hydrous oxide was precipitated from thorium salt solution by the addition of hydroxide ion. TG curves showed that hydrous oxide gradually lost water and did not suffer from a step-by-step dehydration. DTA curves showed an endothermic peak around 150°C followed by a small exothermic peak at 250°-300°C. In emanation curves two prominent peaks were observed, one corresponding to the 150°C peak in DTA, and the other centered at 400°-450°C. The endothermic peak in DTA and two emanation peaks were presumed to be due to the escape of adsorbed or occluded water, and the exothermic peak in DTA due to the crystallization of amorphous hydrous oxide. The hydrous oxide might be not hydroxide nor oxide hydrated but actuated oxide. Hydrous oxycarbonate lost water rapidly to about 200°C on heating, resulting in the formation of ThOCO3⋅H2O, and then followed by less rapid decomposition to the oxide.
In the electron microscope, the oxide particles prepared from hydrous oxide and oxycarbonate were in irregular shape of agglomerates of fine primary particles.抄録全体を表示PDF形式でダウンロード (1754K) -
斎藤 安俊1971 年 17 巻 7 号 p. 300-306
発行日: 1967/04/25
公開日: 2009/05/22
ジャーナル フリーThe Hahn's emanation technique using the escaping tendency of 54.5-second thoron has been applied to the following studies: (1) the effect of calcination temperature on the specific surface area of thorium dioxide prepared from the oxalate, and (2) activation energies for the diffusion of thoron in thorium dioxides prerared from oxalate, hydrous oxide and oxycarbonate by firing at 1050°C. The measured emanation activity was simply assumed to be composed of the recoil fraction and diffusion fraction.
The room-temperature emanation activity, which can be taken as being equal to the recoil fraction and being proportional to the specific surface area, decreased with increasing calcination temperature, and it corresponded well to the decrease in the measured specific surface area and the rate of absorbing water vapor.
From the Arrhenius plots of the diffusion fraction which was obtained by substraction of the roomtemperature emanation activity from the measured activity at each temperature, activation energies for the diffusion of thoron in thorium dioxide were determined. Depending on the temperature and the source of the oxide, different activation energy processes could be attributed to the various diffusion processes.抄録全体を表示PDF形式でダウンロード (589K) -
黒木 英憲, 若林 徹, 徳永 洋一1971 年 17 巻 7 号 p. 307-313
発行日: 1967/04/25
公開日: 2009/12/04
ジャーナル フリーIt has been reported by H. Kuroki and Y. Tokunaga that most of the commercial iron powders represent an abnormal brittleness, mainly grain boundary rupture and partly cleavage, in the density range of 6.8-7.3 g/cc. In the present work some attempts were made to clarify the cause of these brittle ruptures.
It was concluded that the abnormal brittleness is caused by a remarkable grain growth in the density range around 7g/cc. Based on the experimental observations, two different mechanisms of embrittlement are considered.
First, the embrittlement can occur through the enhancement of the ductile-brittle transition temperature caused by grain growth, as was observed in the case of electrolytic and millscale iron powders, which is well known on ferritic steel.
The second mechanism is due to a grain boundary rupture and observed on reduced ore powder. This type of rupture was observed even at high temperatures (>150°C). Although a large number of fine nonmetallic inclusions are contained in reduced ore iron powder, the volume fraction and the notch effect of these inclusions seem to be relatively smaller than those of the residual pores in the sintered iron structure. Therefore, the brittleness of the coarse grain structure of the reduced ore iron powder compact could be of the same character as low temperature brittleness, but abnormally expanded to high temperatures with a largely diffused transition temperature.抄録全体を表示PDF形式でダウンロード (1808K) -
徳永 洋一, 芹野 洋一1971 年 17 巻 7 号 p. 314-319
発行日: 1967/04/25
公開日: 2009/05/22
ジャーナル フリーThe interdiffusion coefficients of the Fe-Ni system were determined in hydrogen atmosphere over the temperature range from 1000°to 1350°C on four couples with different combinations of plate and powder compact. The concentration gradients were measured with an electron probe microanalyser, and the diffusion coefficients were calculated by the Matano analysis. The results showed that the activation energy for the interdiffusion in the couple of Fe/Ni plate varies from 60 to 70 Kcal/mol with the decreasing nickel contents, while it is about 50 Kcal/mol in the couple of Fe/Ni powder compact. This suggests that the diffusibility of both elements are enhanced in the powder side zone of the couple. The enhanced diffusibility is also observed on both couples of Fe plate/Ni powder compact and Fe powder compact/Ni plate.
The Kirkendall marker movement in a couple of powder compact indicates that iron atoms diffuse more rapidly than nickel atoms, and the ratio of the intrinsic diffusion coefficient of iron and nickel is about 2 at 1300°C. Furthermore, there exist a highly porous zone on the iron side and a highly densified zone on the nickel side across the initial interface.抄録全体を表示PDF形式でダウンロード (2902K)
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