巻号一覧
78 巻, 8 号
選択された号の論文の6件中1～6を表示しています
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熊倉 浩明, Shujun Ye, Zhaoshim Gao, Yunchao Zhang, 松本 明善, 戸叶 一正2014 年 78 巻 8 号 p. 287-294
発行日: 2014年
公開日: 2014/08/01
ジャーナル フリーMgB2 is expected to operate in helium-free condition to replace the practical metal superconducting wires in liquid helium condition. But the critical current properties for MgB2 wires are lower for large-scale applications at present. Internal Mg diffusion (IMD) method is promising to fabricate high performance MgB2 wires. Recently, we fabricated high Jc thin MgB2 wires by applying IMD method and using 4%C-coated high quality B powder. During the heat treatment most of the B layer was reacted with Mg to form MgB2. Highest Jc of 1100 A/mm2 and 760 A/mm2 were obtained at (4.2 K, 10 T) and (20 K, 5 T), respectively for the wire fabricated with the C-coated B powder. Engineering Jc(Je) was higher than 100 A/mm2 at 4.2 K and 10 T. These values of Jc and Je are higher than those of well-known SiC-added wire. SiC addition brings about Mg2Si precipitates which act as barriers of superconducting currents and decrease Jc, while the wire fabricated with C-coated B powder contains no such precipitates. Among many iron arsenide superconductors, K-doped BaFe2As2(Ba-122) and SrFe2As2(Sr-122) are the most interesting superconductors for high field magnet applications due to their high Bc2 of over 50 T and relatively small anisotropy. We fabricated Ba(Sr)-122 tapes by applying ex situ powder-in-tube(PIT) technique. We found that the uniaxial pressing brings about a dramatic improvement of transport Jc for ex situ PIT processed Ba(Sr)-122 tape when it is properly combined with flat rolling and heat treatment. The pressure was changed between 0.4 GPa to 4 GPa. The increase of uniaxial pressing from 0.4 GPa to 4 GPa significantly enhanced Jc values from 210 A/mm2 to 860 A/mm2 at 4.2 K and 10 T. Microstructure analysis with SEM indicates that the packing density of Ba-122 core pressed under 4 GPa is higher than that of the tape pressed under 0.4 GPa. This suggests that the packing density is one of the most important parameters that influence Jc of ex situ PIT processed Ba-122 superconducting tapes.
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論文
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後 裕介, 岡井 大祐, 山本 厚之, 福嶋 豊, 谷口 善一, 松永 淳2014 年 78 巻 8 号 p. 295-302
発行日: 2014年
公開日: 2014/08/01
ジャーナル フリーThree-point bending tests have been carried out in order to observe the fractures behavior of coated TiN films and to evaluate adhesion strengths at interfaces between the films and substrates. The substrates were hot work tool steel, SKD61, with and without nitriding treatment, which were coated with TiN films by physical vapor deposition (PVD). Two types of specimens were, therefore prepared, one of which consisted of TiN surface layer and the substrate of SKD61 (TiN/SKD61), while in another one nitride layer was formed between them (TiN/Nitride layer/SKD61). Scratch tests were also carried out for comparison. Specimens with 20L mm×6W mm×0.5t mm were cut from the coated specimens including the coated surface as L-W planes for using in bending tests. The specimen was set on the small bending device which had been developed by the authors, and then bent with referring to strain obtained from a strain gauge glued on the specimen. The specimen was set into SEM for observation. The L-W and L-t surfaces of the specimen were observed. Bending deformation and observation on the same areas were intermittently carried out until the substrate was fractured. On the specimen without the diffusion layer, cracks initiated at the surface of the TiN film and penetrated into the film in the perpendicular direction to the interface. The cracks arrested at the interface. Delamination of the TiN film from the substrate did not occur at the interface, but cracks initiated in the interior of the TiN film and propagated parallel to the interface, which caused fragmentation of the TiN film. Adhesion strength between the TiN film and the substrate was higher than the fracture stress of the TiN film.
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吉村 彰大, 松野 泰也2014 年 78 巻 8 号 p. 303-309
発行日: 2014年
公開日: 2014/08/01
ジャーナル フリーThe recovery of gold from secondary sources like electronic wastes has received much attention because of the many industrial applications and high market prices of precious metal. Electrical and electronic equipments (EEEs) account for approximately 10% of annual demand for gold in Japan as well as in the world. Therefore, waste of EEEs (WEEEs) contains much amount of gold, whose grade can be much higher than that of natural ore. Substance flow analysis (SFA) is a useful tool for determining the flow and in-use stock of substances in specific geographic regions. In this work, we estimated the annual consumption and in-use stock of gold for small EEEs, and the amount of gold contained in discarded EEEs during 1984-2012. As a result, the maximum amount of consumption for EEEs production, in-use stock in EEEs and discard in WEEEs were 8.87 t in 2006, 44.5 t in 2005 and 6.90 t in 2008, respectively. Mobile phone accounted for the largest share of the recent consumption and discard of gold, whereas, audio system has accounted for the largest share of the in-use stock for many years. This difference was caused by the average lifetimes and parameters of Weibull distributions for EEEs.
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鈴木 佑輝, 陳 子諒, 不破 章雄2014 年 78 巻 8 号 p. 310-316
発行日: 2014年
公開日: 2014/08/01
ジャーナル フリーBismuth antimony telluride BixSb2−xTe3 thermoelectric thin films were prepared by electrodeposition from alkaline solution adjusted to pH=9.0 in order to inhibit hydrogen from generating. NTA (nitrile-tri-acetic acid: C6H9NO6) was used so as to increase solubility of bismuth in the alkaline solution.
Electrochemical behaviors of Bi(III), Te(IV), Sb(III) and their mixtures were firstly investigated by LSV (linear sweep voltammetry) for elucidation of electrochemical condition of diffusion controlled deposition. Then, BixSb2−xTe3 electrochemical deposition experiments were conducted from the mixed solution under potential of diffusion controlled condition, i.e. −0.7 V, −0.8 V, and −0.9 V, where [Bi]/[Sb] ratio in solution was varied from 0 to 13 while keeping [Bi]+[Sb]=2 mmol/L, [Te]=1.6 mmol/L, [NTA]=0.1 mol/L and 333 K using rubber heater.
Thermoelectric power properties such as semiconductor type, electric conductivity, Seebeck factor and power factor were measured and evaluated for the BixSb2−xTe3.
The experiment results revealed are as follows: (1) BixSb2−xTe3 thin films can be obtained by electrochemical deposition at electric potential (−0.7~−1.0 V) under limiting current density from alkaline solution including NTA, (2) composition of films can be controlled by the mixed solution composition as well as imposed electric potential, (3) the (015) crystalline face orientation becomes stronger when absolute value of imposed potential becomes smaller, and (4) n-type semiconducting thermoelectric thin films can be prepared when x is smaller than 0.6, and p-type thin films can be prepared when x is larger than 0.6.
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石山 新太郎, 馬場 祐治, 藤井 亮, 中村 勝, 今堀 良夫2014 年 78 巻 8 号 p. 317-321
発行日: 2014年
公開日: 2014/08/01
ジャーナル フリーLow temperature synthesis of lithium-nitride compound was conducted on the lithium target for BNCT by N2/H2O mixing gas squirt in the ultra high vacuum chamber, and the following results were derived; (1) Lithium-nitride compound was synthesized on the lithium target under 101.3 Pa N2 gas squirt at room temperature and in the ultra high vacuum chamber under the pressure of 1×10−8 Pa. (2)Remarkable contamination by O and C was observed on the lithium-nitride compound synthesized under the squirt pressure of 13.3~80 Pa/1.33~4.7 Pa N2/H2O mixing gas. (3) No contamination and synthesis of Li-N compound was observed under the squirt pressure of 0.013~0.027 Pa/0~0.005 Pa N2/H2O mixing gas. (4) Contamination by O and C was enhanced with excessive addition of H2O at the pressure of over 1.33 Pa.
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石山 新太郎, 馬場 祐治, 藤井 亮, 中村 勝, 今堀 良夫2014 年 78 巻 8 号 p. 322-325
発行日: 2014年
公開日: 2014/08/01
ジャーナル フリーTo remove high level of contaminants by O and C from Li3N surface for Boron Neutron Capture Therapy target, high temperature thermal desorption was conducted up to 1123 K in ultra high vacuum and the following results were derived; (1) During thermal desorption up to 1023 K, typical three peaks of vacuum pressure disturbance due to vaporization of contaminants were observed in vacuum pressure-temperature curve. (2) Over-layered contaminants having lower melting point than 1023 K on Li3N surface is completely removed by high temperature thermal desorption up to 1123 K in ultra high vacuum. (3) From these desorption results, it is suggested that these contaminants corresponding to these vaporization peaks are H2O and Li compounds having lower melting point than 1023 K, of which LiOH and Li2CO3 were synthesized by decomposition process of Li3N with residual H2O and CO2 in low temperature.
Fig. 2 Fullsize ImageXPS wide–scan spectra for lithium deposited layer bombarded with 1 keV N2+ ions for various fluences. The fluences were: (a) 0 atoms cm−2, (b) 4.2×1015 atoms cm−2, (c) 4.6×1016 atoms cm−2, and (d) 6.3×1017 atoms cm−2.抄録全体を表示PDF形式でダウンロード (1161K)
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