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本研究では晶析による複合化技術の発展を支援するためのモデルケースとして,実験的に観測が困難な結晶表面/水溶液界面上のアルカリ金属塩化物水溶液の挙動を分子動力学(MD)法により解析し,溶液中でのクラスター形成機構および粒子形態形成に及ぼす結晶表面特性の影響について検討した.さらに,不均一核生成機構を微視的に解明するため,疎水性物質である高配向熱分解黒鉛(HOPG)基板近傍におけるNaCl水溶液,KCl水溶液の溶質および溶媒の動力学的性質を調べた.イオン径が小さく結晶界面に水分子を引き寄せやすいNa[+]イオンでは,水分子が界面に配向安定化する.一方,イオン径が大きいK+ やRb+イオンでは,界面と水分子との相互作用が小さいため,水分子が界面から脱離しやすくなり結晶成長が進行した.つまり,水分子の選択的な吸着が結晶成長速度に大きく影響することが分かった.また,溶液濃度によって結晶成長形態が異なることが分かり,沿面成長や付着成長などの構造化の違いが明らかとなった.さらに,複合化の汎用性を高める目的で高配向熱分解黒鉛(HOPG)上におけるNaCl,KCl水溶液の構造解析を行った.その結果,KCl水溶液の方が界面近傍にクラスターが生成することが分かった., In this study, as a model case to support the development of composite technologies with crystallization method, the behavior of alkali metal chloride solutions at crystal substrates/solutions interfaces has been investigated through molecular dynamics (MD) simulations. Specifically the effects of crystal surface properties on cluster formation in solution and particle morphogenesis have been studied. In order to clarify heterogeneous nucleation, dynamic properties of both the solute and solvent in NaCl and KCl solutions near the hydrophobic highly-oriented pyrolytic graphite (HOPG) substrate were microscopically examined. Simulation results showed that Na[+] cation in crystal, due to its small size and large local electric fields, strongly interacts with interfacial water molecules. Consequently, water molecules near the interface are stabilized on these salt crystal surfaces with a distinct orientation. On the other hand, since the interaction between water and cations for KCl and RbCl salts is weak at interface, water molecules are easily desorbed from the surface and the crystal growth proceeds. That is, the selective adsorption of water molecules strongly influences the crystal growth rate. The crystal morphology depends on the solution concentration and the differences in structuring of lateral and adhesive growth are revealed. Furthermore, to improve general versatility of conjugation the structural analysis of NaCl and KCl solutions on HOPG substrate has been performed. As a result, compared with the NaCl solution/HOPG, more clusters are generated locally near the interface in the KCl solution/HOPG system., 抄録の「Na[+]」の[+]は上付き

In order to realize producing high-quality materials, a large number of studies have been carried out concerning the solidification/melting process of metals and semiconductor materials in both terrestrial and space environment. The previous studies mainly focused upon the solidification and melting processes themselves. In the real system, however, one cannot neglect effects of molten material convective flow (for example, natural convection, Marangoni convection and so on) upon the solidification process and the resulting quality of the materials. This paper introduces an influence of Marangoni convection on a liquid-solid interfacial shape and thermal convective field in the vicinity of the interface in a liquid layer., 資料番号: AA0048095032

In the Traveling Liquidus-Zone (TLZ) method, it is essential to reduce the two-dimensionality. In order to investigate the way to reduce the two-dimensionality, a two-dimensional TLZ model is introduced. From the two-dimensional model, the two-dimensionality index delta is defined. It is found that the delta is not small enough on the ground in the large sample diameter. The microgravity condition cannot improve sufficiently near the crucible wall. It is found that the GaAs seed can drastically improve the delta., 資料番号: AA0048095021

微小重力下で凸型形状の固液界面を有する半導体結晶が成長する条件を検討するために、数値計算を行った。本研究では、境界適合座標(BFC)法を用いた。支配方程式として、円柱座標系における熱伝導方程式を使用した。安定性を良くするために若干の変換技法を用いた。数値計算の信頼性を評価するために、計算結果を実験結果と比較した。, In order to investigate conditions to grow semiconductor crystals with a convex solid-liquid interface under microgravity, numerical calculation is carried out. In this study, the Boundary Fitted Coordinate (BFC) method is used. The thermal conduction equation in the cylindrical coordinates is used as the governing equation. To get the better numerical stability, several transformation techniques are considered. To evaluate the reliability of numerical results, the calculation results are compared with the experimental results., 資料番号: AA0002208009, レポート番号: NASDA-TMR-990006E

Ice crystal growth in supercooled antifreeze protein solutions is inhibited by their adsorption at the ice/water interface, and this phenomenon is a matter of vital importance for survival of living organisms in subzero environments. Several kinds of proteins with this function are known at the present time and are mainly categorized into two types of proteins: AntiFreeze GlycoProteins (AFGP) with sugar and AntiFreeze Proteins (AFP) without sugar. These interactions are being studied with keen interest as the functional proteins to control ice crystal growth. While these proteins have dramatic consequence for natural biological processes and technological applications, only little is known about the dynamic mechanism of ice growth inhibition. The purpose of this research is to learn the antifreeze mechanism based on the fundamental studies of ice crystal growth. Precise measurements of growth rates of ice crystals in AFGP solutions showed that oscillations are a fundamental feature for the crystal growth controlled by the adsorbed macro molecules such as the AFGP. Since the oscillatory phenomena may be strongly affected by the external turbulence like convection, the microgravity experiments in space will be very important to understand the mechanism of self oscillatory growth. We propose a project of a new space experiment using the ice cell specimen that has been developed by JAXA to carry out the space experiments of the morphological instability of ice crystals in pure supercooled water. Theoretical considerations for ice crystal growth in the AFGP solution were also carried out to explain the relationships between the adsorption states of antifreeze proteins and the growth kinetics., 資料番号: AA0063706001

We are preparing for crystal growth experiments in microgravity using Gradient Heating Furnace (GHF). The one-dimensional Traveling Liquidus-Zone (TLZ) growth model is limited by the radial temperature gradient, convection in a melt and so on. Such factors affecting one-dimensionality are studied experimentally and theoretically. Reaction between the melt and cartridge materials is being investigated for analyzing safety requirements and for designing flight cartridges. Here, achievements in the present preparatory stage are reported., 資料番号: AA0063349016

パラボリックフライトによる微小重力環境下における以下の研究主題を論じた。燃焼合成および化学炉としてのテルミット反応、固液界面の濡れ性、微小振動低減用受動制振システム、CVD(化学蒸着)プロセスにおけるプラズマの挙動、イモリ・メダカの行動、および生体信号の取得と処理。, The following topics were discussed: combustion synthesis and thermite reaction applied as chemical oven, wettability at a solid-liquid interface, passive damping system for reduction of microvibration, the behavior of plasma in CVD (Chemical Vapor Deposition) process, behavior of newt and medaka, and physiological data acquisition and processing., 資料番号: AA0000740000, レポート番号: NASDA-TMR-960023

宇宙空間でのいくつかの科学的および生物学的材料実験が液体(溶融物)固体(容器)界面における濡れ現象を無視したために失敗したことはよく知られている。それゆえ固液界面の濡れ挙動に及ぼす重力効果を解明する必要がある。地上での静的濡れ現象についての値を正確に評価するために多くの試みが行われてきたが、宇宙空間における動的および静的濡れ問題は未解決のままである。本報告では、液柱法により重力効果および動的条件を考慮にいれて固液界面の濡れ性を論じた。パラボリックフライト中の航空機を用いた実験結果を液柱形状および接触角から評価した。この液柱形状をCCDビデオ記録システムにより観察し、デジタル画像処理手法を用いて解析した。, It is well known that some material scientific and biological experiments came out to be a failure due to the neglect of wetting phenomena at the liquid (molten material)-solid (container material) interfaces on space. Thus, it is required to estimate the gravitational effects on the wetting behavior between the liquid-solid interface. Though many attempts had been tried to evaluate precisely the value of the static wetting phenomena on the ground, the dynamical and statical wetting problems on space had remained unsolved. So in this report, the wettability on the liquid-solid interface considering the gravitational effects and the dynamical conditions by liquid bridge method are discussed. The experimental results were evaluated from the liquid bridge shapes and the contact angles using an aircraft in parabolic flight. The liquid bridge shapes were observed by CCD video recording system and analyzed by using the technique of digital image acquisition and processing., 資料番号: AA0000740002, レポート番号: NASDA-TMR-960023

パラボリックフライトによる微小重力環境下における以下の研究主題を論じた。イモリおよびメダカの行動、両生類における動揺病、固液界面の濡れ性、矩形セル内の流体の挙動、材料加工のための静電位置制御システム、および石英容器との濡れ性に及ぼす試料の精製処理効果。, The following topics were discussed: newt and medaka behavior, motion sickness in amphibian, wettability at the solid-liquid interface, fluid behavior in a rectangular cell, electrostatic positioning system for material processing, and effect of refining treatment of sample on the wettability to quartz container., 資料番号: AA0000741000, レポート番号: NASDA-TMR-960024

Surface-tension-driven flow of molten silicon was investigated under microgravity and on earth for liquid bridge configuration. In order to investigate instability structure in a molten silicon bridge, observed were temperature oscillation and its phase relationship using thermocouples, oscillation of a molten silicon bridge surface using phase shift interferometry, oscillation of melt/solid interface position oscillation and so on. Instability structure shows azimuthal wave number m, depending on an aspect ratio of a liquid bridge: Gamma = h(height)/r(radius). Surface-tension-driven-flow shows oxygen partial pressure dependence of an ambient atmosphere. This is due to oxygen partial pressure dependence of temperature coefficient of surface tension., 資料番号: AA0045947018, レポート番号: NAL SP-56

1. Introduction||2. Theory of thermal elastohydrodynamic lubrication||3. Numerical analysis of boundary slips for thermal point EHL contact||4. Experimental study on lubrication with oleophobic coating||5. Conclusions and outlook, 九州工業大学博士学位論文 学位記番号：工博甲第548号 学位授与年月日：令和4年3月25日, 令和3年度