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Article type: Cover
1979 Volume 6 Issue 3-4 Pages
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Published: December 25, 1979
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Article type: Index
1979 Volume 6 Issue 3-4 Pages
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Article type: Index
1979 Volume 6 Issue 3-4 Pages
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ichiro Sunagawa
Article type: Article
1979 Volume 6 Issue 3-4 Pages
35-43
Published: December 25, 1979
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A brief historical review is given of the previous studies on the relation between the form and the structure of crystals, on the equilibrium and growth forms, on the relation between dendritic and bulky crystals, on the malformation of external forms, on the habit variations in relation to environmental conditions, on the surface microtopography of crystal faces, and on the morphological stability. It is emphasized that the problem should be studied in relation to crystal growth mechanisms. Considering that the morphology of crystals has been studied in diversed fields of researches, an interdiciplinal co-operation research group was organized and initiated in 1977 with 3 years project to study and discuss the problem. The group consists of 12 members from diversed research fields, and financially supported by a Grant-in-Aid for Fundamental Research from the Ministry of Education. Morphology of whiskers, metallic ultra fine particles, crystals grown from solution phases, mineral crystals, snow crystals, surface microtopography of crystal faces and liquid-solid interfaces, morphological stability and theory of morphology of crystals have been studied in relation to crystal growth mechanisms and environmental conditions. This issue reports the results of studies and the activity of the group.
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T. Kuroda, T. Irisawa, A. Ookawa
Article type: Article
1979 Volume 6 Issue 3-4 Pages
44-50
Published: December 25, 1979
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When a polyhedral crystal grows from solution in a stable way, the supersaturation is not uniform over its interface (Berg effect). The rate of stable growth of a cubic crystal is determined by numerical calculations, by taking account of three dimensional diffusion field surrounding it and growth kinetics on the interface. It depends on the supersaturation σ_∞ at infinity as well as the crystal size L. Then, the shape stability is discussed. It is shown that a catastrophe occurs first at the center of the face, and the curve of stability limit, σ_∞ versus L, is obtained.
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Toshio Kuroda, Rolf. Lacmam
Article type: Article
1979 Volume 6 Issue 3-4 Pages
51-64
Published: December 25, 1979
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The new interpretation on habits ofice growing from vapour is proposed. The primary habits of ice alternate three times (plates→ - 4℃→ columns → -10℃ → plates→from -20℃ to -35℃ → columns) with decreasing temperature. The theory is based on a viewpoint that the surface of ice just below 0℃ is covered with a quasi liquid layer, whose depth or coverage 〓 decreases with falling temperature, and therefore the growth mechanism of a surface changes also as followings : i) Vapour-Quasi Liquid-Solid-Mechanism (〓>1) , ii) Adhesive Growth on a surface strongly adsorbed by water molecules (0.01<〓<1) and iii) Two Dimensional Nucleation Growth on a singular surface (〓<0.01) . As the change in surface structure as well as growth mechanism depend on surface orientation, the complicated habits change is caused mainly by the combination of growth mechanism of each surface, i.e. {0001} and {101^^-0 }. The first and second transition temperature are expected to be independent on absolute supersaturation Δp as same as experiments. On the other hand the third one is the temperature where the two dimensional nucleation growth of {0001} surface reaches the one of { 101^^-0}, so that it falls with decreasing Δp. The observed marked columnar crystals can be explained only by {0001} account of spherical volume diffusion field near taking surfaces and cylindrical one near {1010} surfaces. For plate like crystals between - 10℃ and -20℃ to -35℃ the surface diffusion from {0001} to {101^^-0} and volume diffusion with cylindrical symmetry near {101^^-0} surfaces are very important.
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Teisaku Kobayashi, Toru Takahashi
Article type: Article
1979 Volume 6 Issue 3-4 Pages
65-74
Published: December 25, 1979
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To explain the orientational relations in c-axes between each component for the polycrystalline snow crystals, such as twin prisms, spatial and radiating dendrites, and combination of bullets, a cubic structure model accompanied by CSL boundaries is proposed at the stage of formation of polycrystalline nucleus. The formation mechanism of stacking fault and cubic structure nucleus is studied by means of two-dimensional nucleation model. It is shown that the condition under which the crystals are divided into twin prisms and polycrystalline crystals (spatial type and radiating type, etc.) depends on the degrees of supercooling and the dimensions of cubic structure.
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Akira Yamashita
Article type: Article
1979 Volume 6 Issue 3-4 Pages
75-85
Published: December 25, 1979
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By using large cloud chambers small snow crystals were grown in free fall from frozen water droplets. When a frozen water droplet grows in a supercooled cloud, 20 facets, {0001}, {101^^-0} and {101^^-0}, appear on its spherical surface at first. Pyramidal faces, {101^^-0}, gradually disappear and it changes to a hexagonal short column with gas enclosures. At temperatures about -15℃ it grows to a double-plate via a solid hexagonal plate. One of two plates of the crystal grows larger than the other and it grows to a hexagonal dendrite. In a larger plate some markings indicating comparatively thick parts are observed ; it is possible to infer a growth history by analyzing such markings. When a plate-like snow crystal grows, the most rapidly growing part extends or pushes out parallel to one of <112^^-0> directions ; the part may be indicated by an edge formed by neighboring two prism faces. This is also applicable to every branch and this occurs because a plate-1ike snow crystals grows by two dimensional nucleation occurring at <(101^^-0) (101^^-0)> edges.
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Ichiro Sunagawa
Article type: Article
1979 Volume 6 Issue 3-4 Pages
86-94
Published: December 25, 1979
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A critical review is given of how the knowledge on the morphology of mineral crystals can be practically used to understand the kinetic processes in natural crystallization. Based on the analysis of R-σ relation in relation to the morphology of crystals, the characteristics of crystal growth taking place in magma are analysed. Dendritic and hopper crystals can appear only when a magma is solidified under extreme conditions, and the most rock-forming crystals grow by layer-by-layer growth mechanisms to form bulky crystals. Significance of internal heterogeneities in these bulky crystals, like lineage structures, growth bandings and sector structures is explained in relation to geological problems. Crystal growth mechanism taking place in hydrothermal metasomatism, contact and regional metamorphisms are analyzed based on the observations of the surface microtopographs of crystals. In hydrothermal metasomatism and contact metamorphism, it is assumed that the original solid rocks are dissolved to form a new low supersaturated solution from which crystals grow by the spiral mechanism. In contrast, crystallization in regional metamorphism is best simulated to the sintering process, in which Oswald ripening occurs extensively. Habit changes of bulky crystals grown in hydrothermal solutions are explained in relation to their growth environments, using calcite and pyrite as examples. Origin of striated faces is put forward as a problem to be solved in future.
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Masao Kitamura, Syoichi Hosoya, Ichiro Sunagawa
Article type: Article
1979 Volume 6 Issue 3-4 Pages
95-101
Published: December 25, 1979
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It is well known that twinned crystals exhibit morphological characteristics which are different from those of the o-existing single crystals. They are summarized in four characteristics; (1) more flattened morphology than single crystals, (2) larger size than single crystals, (3) appearance of faces uncommon for single crystals, and (4) less kind of crystal faces. These characteristics have been accounted for in terms of re-entrant corner effect at twin junctions. The validity of this explanation is critically investigated based on a model of crystals containing imperfections. For real crystals, these morphological characteristics can appear only when crystals grow under low supersaturation and contain more dislocations in the twin boundary than the surface. Morphological characteristics of twinned crystals (examples : quartz twins after Japan Law, spinel twins of diamond, Ge ribbon crystals) are analyzed on the new model.
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Takaki Shichiri
Article type: Article
1979 Volume 6 Issue 3-4 Pages
102-112
Published: December 25, 1979
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The morphology of crystals of II-VI compounds grown from the vapour phases which has been reported so far is summarized. Many of them have the zinc blende and wurtzite structures and show similar morphology. They are classified into the needle, hollow, plate, stubby and dendrite shapes, which are arranged in the tables in relation to their growth conditions. Crystals of different morphologies are shown in the photographs. The growth mechanisms for the crystals of hollow and plate shapes are discussed. The former is related to the growth of spiral, whisker and skeleton, and the latter the slipping of dislocation, the two-dimensional nucleation, the diffusion of molecule on the surface and the whisker growth. The effects of crystal polarity and the structure to the shape are also discussed.
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Ryozi Uyeda
Article type: Article
1979 Volume 6 Issue 3-4 Pages
113-121
Published: December 25, 1979
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Kimoto Published in the Present vo1ume a review article on the same subject. It describes exact results in detail, particularly for each metal. On the other hand, the present paper gives author's ideas, some of which are still speculative, related on the crystal growth in a smoke. Contents are as follows: 1) Macroscopic features of smokes. Factors determining the shape of smokes; Smoke of standard type. 2) Crystal growth of smoke particles. Thechnique of specimen collection for electron microscopy ; General characters of particles in each zone in a smoke; Condensation of metal vapour ; Vapour growth and coalescence growth ; Equillibrium form and growth form. 3) Crystal habits of fcc metals. Classification of habits; Truncation degree and the zone for each habit; Metals of the first and the second group p. 4) Crystal habits of bcc metals. Truncation degree of rhombic dodecahedron; Comparison with theoretical value. 5) Problems of A-15 structure. Two hypotheses; A- 1 5 structure and multiply twined particles; Experimental facts discouraging the second hypothesis (i) and (ii). 6) Metals with phase transformations. Be, Ti, Mn and Fe; Problems in the future.
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Kazuo Kimoto
Article type: Article
1979 Volume 6 Issue 3-4 Pages
122-165
Published: December 25, 1979
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Various experimental results of the studies on fine particles produced by evaporation and subsequent condensation in inert gas at low pressure are reviewed. A brief historical survey is given and experimental arrangements for the production of the particles are described. The structure of the smoke, the qualitative particle size distributions, small particle statistics and the crystallographic aspects of the particles are considered in some detail. Emphasis is laid on the crystal morphology and the related crystal structures of the particles of some 24 elements.
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Ichiro Sunagawa
Article type: Article
1979 Volume 6 Issue 3-4 Pages
166-179
Published: December 25, 1979
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Singnificance and importance of surface microtopography of crystal faces in the studies of crystal growth mechanisms are discussed. Morphology of growth spirals is defined by 1) the degree of polygonization, and 2) the step separations. These are related to α, φ_<ss>,φ_<sf>,φ_<ff>, T, γ, Δμ. The observed morphologies of growth spirals are confronted with the computer simulated spirals, and are analysed in terms of the above factors. The surface microtopographies of crystal faces formed in different phases and environmental conditions are compared and analysed based on the modern theoretical achievements on spiral morphology. The relation between surface microtopography and external morphology of crystals is discussed.
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Hiroshi Komatsu
Article type: Article
1979 Volume 6 Issue 3-4 Pages
180-188
Published: December 25, 1979
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A review of the theory of melt growth and solid-liquid interface was made referring to the kinetic equations. In situ observation of growth and melting processes of salol crystals was attempted using a differential interference microscope and colour videotape recording. Behaviour of thin layers on the basal faces of salol during growth and melt was analysed. Most thin and small crystals (about 50μ in edge length) were dislocation free. Dependence of the effect of reentrant angle on supercooling was found. Micro-topogrphic features were compared among vapour, solution and melt growth.
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Tatau Nishinaga, Kangsa Pak
Article type: Article
1979 Volume 6 Issue 3-4 Pages
189-201
Published: December 25, 1979
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Two typical LPE morphologies have been theoretically and experimentally studied. The one is called wave or terrace which appears on the substrate with a small misorientation from (111) or (100) low index singular plane. The other has a spike shape and is found on the edge of the substrate. Both morphologies are studied by solving 2-dimensional diffusion equation. The former is explained by morphological stability theory in which solid-liquid interface shape has been connected with the 2-dimensional diffusion field. The theory predicts the functional dependency of the wavelength on supersaturation as well as roughly its absolute value. The latter morphology which has been called edge growth is explained to be formed by the diffusion of the solute from the outside of the solution on the nongrowth region adjacent to the growth edge. Several methods to minimize the edge growth have been proposed.
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Ryukiti Hashiguti, Tsutomu Ishibashi, Hisami Yumoto
Article type: Article
1979 Volume 6 Issue 3-4 Pages
202-205
Published: December 25, 1979
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The effects of Bi impurity on the morphology and growth mechanism of (physicial) vapor-deposited Cd crystals were investigated. Scanning electron microscopic observation revealed, for the first time, hexagonal prismatic Cd crystals which were grown on the Bi contaminated pyrex glass tube wall. This kind of morphology does not appear in the case of pure Cd without the impurity Bi. The top of the hexagonal prismatic crystal was usually rounded hemispherically. X-ray microprobe invest.ingation showed that the tip of the crystals contained about 57 wt% Bi. It was concluded that the Cd hexagonal prismatic crystals grow by the mechanism of vapor-liquid-solid with the impurity Bi.
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Article type: Appendix
1979 Volume 6 Issue 3-4 Pages
206-
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Article type: Appendix
1979 Volume 6 Issue 3-4 Pages
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Article type: Appendix
1979 Volume 6 Issue 3-4 Pages
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Article type: Appendix
1979 Volume 6 Issue 3-4 Pages
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Article type: Appendix
1979 Volume 6 Issue 3-4 Pages
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Article type: Appendix
1979 Volume 6 Issue 3-4 Pages
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Article type: Cover
1979 Volume 6 Issue 3-4 Pages
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Article type: Cover
1979 Volume 6 Issue 3-4 Pages
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