近時,科学技術の進歩にともなって,純粋物質の性質についての知識が非常に重要であることが一般に認められ,また一方,いろいろな実用上の規準物質,あるいは各種製造工業における原料として高純度物質に対する要望が高まり,物質を高純度に精製する種々の方法が開発されてきた.ここで述べる(zone-melting)とは原理的にはFig.1のように長い固体柱の中で比較的幅の狭い溶融帯(以下ゾーンと略記)をその長さの方向に沿って移動させるという操作で,主として固体物質の精製に用いられている.またこの方法は別の利用法として激量物質の濃縮や,あるいは逆に微量物質を主成分中に均一に分布させることなどに用いることができる.
1952年,Pfannによって半導体用の高純度ゲルマニウムの精製に用いられて以来,数多くの人によっての金属,合金,無機化合物など,種々の固体物質への応用が報告され,最近では特に有機化合物の精製にしばしば応用されて成功している.
総括的な成書もすでにPfann¹⁾,Helington²⁾,Schildknecht³⁾らによってあらわされ,その理論的基礎,操作技術上の諸問題,豊富な種々の応用例がまとめられているので,本稿では筆者らの研究室で行なってきた研究をおもに金属キレート類の分離精製法としてのの応用という面に限って述べることにする.

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本研究では1500 K以上の融点をもつ高温融体について、凝固界面近傍における幾何学的原子配置をその場観測することにより、凝固現象における液相構造と固相構造の相関を明らかにすることを目的とした。そのため、レーザー加熱型を用いた高温融体の放射光X線回折実験装置を構築し、円柱試料の凝固界面近傍における構造因子の取得に成功した。

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Crystal growth of Pb_1-xSn_xTe and Hg_1-xCd_xTe of most interesting narrow gap semi-conductors are reviewed. Problems arising in growth of the crystals, especially with an energy gap of about 0.1 eV, are pointed out and various methods are discussed to solve them.
Differences in advantages between growth methods generally used are also shown, containing Bridgeman, Czochoralski, vapor transport, liquid epitaxial and vacuum evaporation growth techniques.

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The purpose of this study is to construct a reduced-order model (ROM) for real-time control to suppress three-dimensional unsteady thermocapillary convection in a thin liquid layer, a simple physical model for single-crystal manufacturing. To manufacture single crystals with high quality and at low cost, it is essential to suppress unsteady thermocapillary convection. If a full order model based on fluid governing equations is used for control to obtain high performance, they involve high computational costs and require significant time. To address this issue, we developed a Galerkin-ROM (G-ROM), constructed using Proper Orthogonal Decomposition (POD). As a results, the velocity fields reconstructed with POD largely matched the original data, but discrepancies were observed in the velocity fields reproduced by the G-ROM. To improve accuracy, closure models with pseudo-viscosity and higher-order mode corrections were introduced. However, as these improvements failed to resolve the issue, combined with insights from our previous research, we concluded that POD bases are unsuitable for constructing ROMs targeting HTW.

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The development of a current leads using YBCO superconducting rods was reviewed. The textured YBCO rods were fabricated by a zone-melt process. A high I_c value of 2,000 A was obtained by the structural control of texturing and pinning centers by Y211 particles. The highly textured structure was realized by the growth conditions of high G/R (G: Temperature Gradient and R: Growth Rate). The fine Y211 particles were obtained by the addition of the Pt powder to reduce a coarsening rate of Y211 in the liquid. The current leads were formed by the development of packaging technique for high mechanical strength and connection with the electrodes. Concerning the mechanical strength, no degradation of I_c performance due to a vibration of 15 G was achieved. Consequently, the current leads with not only high superconducting current but low thermal invasion and Joule heating was realized. It was confirmed that the total heat load could be suppressed to be 0.21 W/pair for 500 A where the high and low temperatures were controlled to be 80 and 20 K, respectively.

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結晶精製の原理を学び,体験を通して理解させることを目的として,学生実験のなかで「帯融溶法による結晶精製」を課題とした。限られた授業時間内に実際に結晶を精製し,その評価を学生自ら行うことは時間の制約上簡単ではない。諸条件を考えて精製する試料としてビスマス,不純物として鉛を選び,帯融溶後の試料の長さ方向に沿った熱起電力を測定することで精製の効果の検出法を確立し,学生実験のユニークな題目とすることができた。

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