巻号一覧
19 巻, 3 号
選択された号の論文の4件中1～4を表示しています
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久野 洋1972 年 19 巻 3 号 p. 85-89
発行日: 1972/08/25
公開日: 2009/05/22
ジャーナル フリーPacking fractions and average contact numbers of random packings of circles have been calculated with the Monte-Carlo method simulation by a computer.
Circles were put into a rectangular container in order. The bottom of the container was taken as x axis and circles were put into the container alongy axis. The circles were assumed to be under a static force field along y axis and directed towards the bottom, and to roll down to dynamically stable positions and settle there.
Obtained results were compared with three dimensional packings of spheres and it was considered that our results on two dimensional packings correspond to those on observed packings of steel balls.
Calculations on the random packings of mixtures of circles of two different sizes and of those with normal size distributions of various standard deviations were performed.抄録全体を表示PDF形式でダウンロード (321K) -
I. Dependence of Oxygen Partial Pressure and Temperature on the Electrical Conductivity and Thermoelectric Power of High Purity Sintered Indium OxideJunichi Hattori, Tomoaki Sasaki, Kenzo Hijikata1972 年 19 巻 3 号 p. 90-98
発行日: 1972/08/25
公開日: 2009/05/22
ジャーナル フリーThe electrical conductivity (ac and dc) and the thermoelectric power of high purity polycrystalline indium oxide prepared from 6-nine indium metal were measured as a function of temperature 300°-600°C and oxygen partial pressure 1.5-760 mmHg (Po2+Pargon: 760 mmHg) under the homogeneous nonstoichiometric phase. The results of thermoelectric power measurements indicated an n-type semiconductor in all these experimental conditions. The ac conductivity was nearly independent on frequency over the range 1-80 KHz from 300°-600°C. The electrical conductivity was well represented by the relation σ ?? PO2-1/4 in nearly intrinsic range at above ca 400°C, and the thermoelectric power had also roughly same -1/4 pressure dependence. Therefore, the predominant defects in oxygen deficient region were presumed any one: a) singly ionized oxygen vacancies, b) doubly ionized indium interstitials, c) coexistence of both a) and b). In spite of using the high purity specimen at lower temperature range, impurity conduction was observed. Thereby, it must be inferred that purity of indium oxide requires at least concentration of impurity below 1014 atom/cm3, so as to obtain exact intrinsic character at lower temperature range.抄録全体を表示PDF形式でダウンロード (474K) -
山本 博司1972 年 19 巻 3 号 p. 99-105
発行日: 1972/08/25
公開日: 2009/05/22
ジャーナル フリーA tungsten filament of incandescent lamp recrystallizes and becomes brittle when the lamp is first lighted. It has been desired to prevent the filament to become brittle. In order to find the desirable process, effects of the dopant added to tungsten oxide on tungsten powder and the washing treatment of doped or undoped tungsten powder were investigated in the present study.
This study revealed the following facts. (1) Dopant rich layers were deposited on the surfaces of tungsten perticles produced through the reduction process of doped tungsten oxide by hydrogen. (2) These dopant rich layers played a role as adhesive and joined primary particles into coalescences. (3) The washing treatment by dilute hydrofluoric acid removed these dopant rich layers, and therefore broke the coalescences into smaller particles. (4) This washing treatment by hydrofluoric acid increased the apparent densitys of both of green compact and sintered body, and increased the ductility of recrystallized filament.
Furthermore, the effects of the doping and the washing treatment on the ductility of recrystallized filament were discussed.抄録全体を表示PDF形式でダウンロード (5781K) -
鈴木 寿, 福家 康矩, 林 宏爾1972 年 19 巻 3 号 p. 106-112
発行日: 1972/08/25
公開日: 2009/12/04
ジャーナル フリーThe restriction effects of the additional VC on the grain growth of WC in WC-Co alloy were in detail investigated in relation to the grain size of starting WC powder, and Co and carbon contents of the alloy. The WC powder was prepared by heating the mixture of W powder (-0.5μ) and carbon black powder at 1000-1300°C for 1.5 hr in hydrogen atmosphere. The grain size of this WC powder was reduced to various sizes by ball-milling. WC-(0-2)%VC-(5-20)%Co alloys with various grain sizes and 'carbon contents were vacuum-sintered mainly at 1400°C for various times.
The results obtained were as follows: (1) The restriction effect was found to be controlled almost by the ratio of VC/Co, and not by the ratio of VC/WC. Even under the same ratio of VC/Co, the effect was affected by the carbon content of the alloy. (2) When the mean grain size of starting WC powder exceeded a certain critical value, the addition of VC more than a definit value resulted in the normal grain growth of WC in VC contained alloys. However, in the case of the mean grain size smaller than the critical value, it resulted in the abnormal grain growth of WC (with fine grain size of WC in the matrix). For instance, in the usual WC powder having grain size larger than -0.3μ, addition of VC more than -5% in the binder checked the abnormal grain growth (mean grain size of WC in the matrix decreased with increasing amount of VC). However, in the fine grained WC powder having mean grain size smaller than -0.2μ, such a restriction method of adding VC was by this time invalid because of the occurrence of the abnormal grain growth, leading to the impossibility of obtaining micro-grained alloys. The above critical grain sizes (0.2-0.3μ) and the critical amount of VC were naturally considered to vary according to size distributions of the starting WC powder, sintering temperatures, Co contents, etc. (3) The three phase region and the compositions of the binder phase in WC-VC-Co alloys were also examined.抄録全体を表示PDF形式でダウンロード (9126K)
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