Granular Crystals Research Articles

Ramsbeckite from the Hirao mine at Minoo, Osaka, Japan

Ramsbeckite was found as a vein forming mineral in altered shale at the Hirao mine, Minoo, Osaka, Japan. It occurred as aggregates of euhedral granular crystals up to 0.5 mm across, in association with sphalerite, chalcopyrite, smithsonite, aurichalcite, amorphous manganese dioxide, schulenbergite, brochantite, serpierite, limonite and an unidentified mineral. It was emerald green to blue-green in color with a vitreous luster in hand specimen. An EPMA and CHNS/O analyzer gave the empirical formula (Cu9.380Zn5.542Ni0.034Co0.027Fe0.020Mn0.013)Σ15.016[(SO4)3.871(CO3)0.166]Σ4.037(OH)21.958·6.06H2O on the basis of O = 44. The unit cell parameters were a = 16.106 (3), b = 15.568 (2), c = 7.109 (1) A, β = 90.23 (1)°, and Z = 2. The mineral was optically biaxial negative with refractive indices α = 1.676, β = 1.704 and γ = 1.707, and 2VX(calc) = 37.8°. The Vickers microhardness was 162 (144-182) kg/mm2 (10 g load), and the Mohs hardness was 3.5. The measured density was 3.36 g/cm3. It is likely that ramsbeckite at the Hirao mine crystallized from Cu and Zn-bearing fluids.

Micromorphology and classification of Argids and associated gypsiferous Aridisols from central Iran

Gypsiferous Aridisols occupy the largest area within the Iranian Aridisols. Information on the genesis and classification of these soils is rather limited. Objectives of this research were to study the micromorphology of the gypsic, argillic, and calcic horizons, to understand the mode of formation of gypsic horizon in three different landscapes, and to test the criteria of the most recently revised Soil Taxonomy and FAO classification system in selected gypsiferous Aridisols occurring in central Iran. A total of 15 representative pedons occurring on three different landscapes (colluvial fans, plateaus, and alluvial plain) were studied. Evidence of illuviation in the colluvial soils is provided by the increase in the clay content and the fine to total clay ratio in the subsoil and by the well-developed, but considerably disrupted, clay coatings observed in thin sections. In addition to pendants, gypsum occurs as microscopic-sized particles, such as single and radiating fibrous shaped particles, random lenticular and granular crystals, along channels and planar voids with no apparent orientation to the associated surface. Gypsum also occurs as relatively larger interlocking plates. The horizon sequence, together with their chemical and micromorphological properties, reveals that gypsum accumulated in different landscapes has different modes of formation. The coexistence of argillic, calcic, and gypsic horizons in colluvial soils is a peculiar combination, suggesting a multistage pedogenesis in this landscape. Paleo-argillic horizons were likely developed under a moister environment than today. This study has also shown that the most recently revised version of the American Soil Taxonomy and FAO soil classification can reasonably well classify these soils. However, there is still a need to modify the criteria of both classification systems at the lower levels, particularly for the classification of the soils that are polygenetic.

A new class of silica enriched, highly depleted komatiites in the southern Kaapvaal Craton, South Africa

Abstract The 3.33 Ga Commondale Ultramafic Suite, located in the southeastern part of the Kaapvaal Craton, represents a previously unrecognized compositional variant of Archaean komatiites. Textures, compositions and structures of cooling units are unlike komatiite flow successions described in greenstone belts in the Kaapvaal Craton and elsewhere in the world. Olivine phenocrysts are the most magnesian known from any natural magmas with core compositions >Fo96. Both orthopyroxene and olivine are present as spinifex and as granular crystals. Geochemically these are some of the most depleted magmas ever recorded with extreme depletion of Ti (Primitive Mantle normalized Ti 0.9. These lavas could have been derived from multiple fractional melting events in a plume axis source, but given that most komatiites are considered to have formed in plume environments, it seems anomalous that similar compositions have not been described from other Archaean greenstone belts. An alternate mechanism may be that these komatiites formed in an unusual tectonic setting that may have involved water. Such a setting could be subduction-related melting of a depleted mantle wedge.

Nanostructure Evolution of Homogeneous Poly(ethylene‐co‐1‐octene) as a Function of Strain

AbstractPolyolefin elastomers with varying 1‐octene content and different thermal history are studied by wide‐angle X‐ray scattering (WAXS) and small‐angle X‐ray scattering (SAXS) during drawing and after relaxation. The multidimensional chord distribution function (CDF) reveals the nanostructure made from crystallites in the amorphous matrix. Both lamellae and granular crystals are found. Lamellae do not form stacks. The SAXS peak is observed because each lamella is covered by an amorphous layer of well‐defined thickness. Arrangement, rotation, fine chain slip and failure of the domains are directly observed as a function of elongation. During straining and relaxation a well oriented macrolattice with colloidal dimensions but short‐ranging order is formed. Two processes are generating microfibrils, namely (1) arrangement of granular crystallites, and (2) irreversible disruption of lamellae (coarse slip) followed by arrangement of their fragments. The second process stabilizes the colloidal lattice permanently. The higher the comonomer content, the later the irreversible process starts. Quenching from the melt shifts the onset to lower deformation. Deformation of microfibrils is not homogeneous. Instead, there is a limiting long period that cannot be exceeded without disruption. It is related to the position of the maximum in the SAXS pattern (which is almost constant).Long periods in the CDF z(r12, r3) of an ethylene‐octene block copolymer after relaxation from drawing.magnified imageLong periods in the CDF z(r12, r3) of an ethylene‐octene block copolymer after relaxation from drawing.

Ramsbeckite from the Hirao mine at Minoo, Osaka, Japan

Ramsbeckite was found as a vein forming mineral in altered shale at the Hirao mine, Minoo, Osaka, Japan. It occurred as aggregates of euhedral granular crystals up to 0.5 mm across, in association with sphalerite, chalcopyrite, smithsonite, aurichalcite, amorphous manganese dioxide, schulenbergite, brochantite, serpierite, limonite and an unidentified mineral. It was emerald green to blue-green in color with a vitreous luster in hand specimen. An EPMA and CHNS/O analyzer gave the empirical formula (Cu9.380Zn5.542Ni0.034Co0.027Fe0.020Mn0.013)Σ15.016[(SO4)3.871(CO3)0.166]Σ4.037(OH)21.958·6.06H2O on the basis of O = 44. The unit cell parameters were a = 16.106 (3), b = 15.568 (2), c = 7.109 (1) A, β = 90.23 (1)°, and Z = 2. The mineral was optically biaxial negative with refractive indices α = 1.676, β = 1.704 and γ = 1.707, and 2VX(calc) = 37.8°. The Vickers microhardness was 162 (144-182) kg/mm2 (10 g load), and the Mohs hardness was 3.5. The measured density was 3.36 g/cm3. It is likely that ramsbeckite at the Hirao mine crystallized from Cu and Zn-bearing fluids.

Bulk density as method of evaluating reducibility of hard hematite ore in direct reduction process

Massive hematite ore (MHO) is a special high grade iron ore used as lump ore in the process of obtaining direct reduced iron (DRI). The influence of porosity on the reducibility has been investigated using optical and scanning electron microscopes. Hematite is the main component of the samples and occurs as granular crystals (10 μm), microplates (1 μm) and euhedral martite (10-30 μm). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (Å to 1 μm) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (Å to 5 μm) related to euhedral martite crystals are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 18%, whereas unweathered samples have a porosity less than 2·5%. Varajão et al. showed that reducibility is strongly enhanced by porosity and this work shows that reducibility can be indirectly evaluated by bulk density.

Lanmuchangite, a new thallium (Hydrous) Sulphate from Lanmuchang, Guizhou Province, China

Lanmuchangite is a new thallium hydrous sulfate from the oxidation zone hosting rich thallium ore bodies in the Lanmuchang thallium (mercury) ore deposit, Xinren County, Guizhou Province, China. This new mineral is named after the locality where it was discovered. The mineral is associated with melanterite, pickeringite, potassium alum, jarosite, gypsum, arsenic blane, sulphur and some unknown minerals. The aggregates of lanmuchangite range from 2 to 10 mm in size. In general, the aggregates are compact and massive in form and are composed of anhedral granular crystals measuring in size from 40 to 90 μm, but the single crystal grains show distinct boundaries. Parallel columnar aggregates are occasionally seen, which are composed of subhedral to euhedral columnar crystals ranging in size from 15 to 65μm. White, light yellow to white in color, glassy in luster and transparent. Hvmesa = 94 - 124 kg/mm2,Hm =3.1 -3.4, density =2.22 g/cm3. Under the polarization microscope the mineral is colorless and homogeneous, with Nmeas = 1.495. It is easily water-soluble. The average chemical composition is; Tl2O = 33.25, A12O3 =8.07, SO3 =25.19, SiO2 =0.10, K2O=0.35, CaO=0.08, MgO=0.06, FeO=0.04 and H2O =33.46 [the crystal water (H2O) was measured by thermogravimetery (TG ) while the other composition were determined by electron microprobe ], totaling 100.60%. The empirical formula is (Tl1.00K0.03)1.05 (Al1.01 Si0.01Ca0.01 Mg0.01)1.04 [ SO4 ]2.01. 11.88 H2O and the simplified formula is TlAl[SO4]2. 12H2O. The compatibility of lanmuchangite is -0.03 and its value falls within the range of ± 0.020 — ±0.039, so the compatibility is excellent. Its TG curve demonstrated that the crystal water was lost (i. e., dewatering) in stages at 101, 130 and 230°C. At the temperature of 243°C the process of dewatering came to the end and the sum of lost crystal water reaches 33.30 wt%. IR spectroscopic analysis showed that the absorption bands 3374—3147 cm-1 and 1655—1648 cm-1 are due to tensile and bending vibration of crystal water molecules (H2O) whereas those at 1131 cm-1 and 605 cm-1 are attributed to tensile and bending vibration of group [ SO4 ]-2. Lanmuchangite is of the isometric system, with space group = Pa3,a = 12.212(5)A, v = 1821(2)A3, and Z=4. The strongest diffraction lines [d (I, hkl)] from the X-ray power diffraction data are 4.314(100, 220), 2.801(70, 331), 7.03(54, 111), 2.731(35, 420), 6.11(27, 200), 3.524(24, 222), 3.676(22, 311), 3.051(22, 400), 2.350(21, 511), 3.263(20, 321), 2.494(20,422), 1.932(19, 620).

傾斜冷却板を用いたセミソリッドAC4CHアルミニウム合金の連続鋳造

Semisolid casting of aluminum alloy is an advanced casting technology for the foundry industry. The advantages of semisolid casting are ease of casting at low temperature and high fluidity of the semisolid slurry, which have to contain granular, fine and homogeneous crystals. Conventional semisolid slurry processing is performed by electromagnetic stirring or mechanical stirring, both of which involve large equipment and high costs. In this investigation, we developed a simple semisolid process of AC4CH aluminum casting using an inclined cooling plate. Numerous α aluminum granular crystals nucleated on the inclined cooling plate during its flow, and the semisolid slurry ran into an isolated tundish. The crystals then became granular grains in the tundish. The semisolid slurry was cast into a horizontal continuous casting machine. The billet was 60 mm in diameter and 1000 mm in length and the casting speed was between 2 and 4 mm/s. The finest grain size of 50 μm could be obtained by casting at 897 K with a casting speed of 4 mm/s, an angle of 60°, and a length of 160 mm.

セミソリッド連続鋳造で作製された６０７０および７０７５アルミニウム合金のチクソフォーミング特性

To compare the thixoformability between granular crystal structures and dendrite crystal ones of 6070 and 7075 aluminum alloy billets produced by the semisolid and conventional DC continuous casting, the thixoforming test was performed at a constant deformation speed of 4mm/s in an argon atmosphere. The test piece consisting of granular crystals of 6070 alloy reveals that the thixoforming power was less than 1 kN during three quarters of forming process and the maximum power at the final stage was 18kN. In contrast, the test piece consisting of dendrite crystal structure reveals that the power was more than 5 kN at the first stage and as the forming process proceeded, the power increased. The maximum power at the last stage was 35 kN. Granular grains of primary α aluminum coexisting with the liquid phase were possible to move easily into the die cavity, because the liquid phase played an important role of lubricant as the thixoforming was performed to the semisolid slurry. However, when dendrite network was developed throughout the billet, the liquid phase among interdendrites only moved at the first stage. Hence, the deformation resistance increased and the thixoforming power became larger at the later stages. The same results were obtained by the thixoforming of 7075 aluminum alloy.

傾斜冷却板を用いた６０７０および７０７５アルミニウム合金のセミソリッド連続鋳造

Semisolid casting is the most advanced technology for obtaining granular grains in aluminum-alloy cast structures. The conventional semisolid slurry is produced by electromagnetic or mechanical stirring. Both apparatuses that perform these tasks are large and costly. We developed a simple semisolid casting process for 6070 and 7075 aluminum alJoys using an inclined cooling plate. In this process, numerous granular aluminum crystals are nucleated on the inclined cooling plate while flowing downward. The semisolid slurry was held isothermally in the heat-isolating tundish and the granular grains grew inside. The semisolid slurry was then cast into a horizontal continuous casting machine. The resulting billet was 60 mm in diameter and 600 mm in length. For the 6070 aluminum alloy, the casting speed was 3 mm/s. The finest grain size of 56 μm was obtained by casting at 656°C, and by using the inclined cooling plate of 60° and 200 mm.

Epitaxial growth of granular single crystals.

Compaction from a random-loose-packed to a random-close-packed phase is observed when monodisperse granular beds are shaken, but beyond this packing, the system freezes up in a jammed structure. Here we report a technique to grow large hard-sphere granular crystals, with perfect stacking and no defects by means of a "gas phase" epitaxial procedure. We study the growth mechanism and provide evidence that the observed granular crystallization is driven by gravity and energy dissipation.

Stress transmission through three-dimensional ordered granular arrays.

We measure the local contact forces at both the top and bottom boundaries of three-dimensional face-centered-cubic and hexagonal-close-packed granular crystals in response to an external force applied to a small area at the top surface. Depending on the crystal structure, we find markedly different results which can be understood in terms of force balance considerations in the specific geometry of the crystal. Small amounts of disorder are found to create additional structure at both the top and bottom surfaces.

Effect of agglomeration of triacylglycerols on the stabilization of a model cream

This study has been carried out on solidification of a model cream using palm oil as a sole fat source. It was found that the addition of 1-palmitoylglycerol to palm oil promoted the solidification of the model cream while the addition of 1-oleoylglycerol had no such effect. Solid fat content of palm oil in the cream with 1-palmitoylglycerol was found to be lower than those of palm oil and palm oil with 1-oleoylglycerol after cooling from 60 to 5 °C. Crystallization behaviors of bulk palm oil and mixture of 1, 3-dipalmitoyl- 2-oleoyl-glycerol (POP) and 1-palmitoyl-2, 3-dioleoyl-glycerol (POO) were then studied in the presence of monoacylglycerols. Formation of granular crystals was observed for palm oil and POP/POO mixture in the presence of 1-palmitoylglycerol. HPLC of the granular crystals revealed that agglomeration of higher melting point triacylglycerols (TAGs) around 1-palmitolyglycerol took place, which promoted the formation of granular crystals. It was suggested that the agglomeration of higher melting point TAGs around 1-palmitoylglycerol which was preferentially adsorbed at the oil-water interface of oil droplets in the model cream led to destabilization of oil-in-water emulsion and the solidification of the model cream. At the same time, it was suggested that the fatty acid moiety of emulsifiers played an important role in the agglomeration of TAGs and stabilization of o/w emulsions.

Effect of agglomeration of triacylglycerols on the stabilization of a model cream

This study has been carried out on solidification of a model cream using palm oil as a sole fat source. It was found that the addition of 1-palmitoylglycerol to palm oil promoted the solidification of the model cream while the addition of 1-oleoylglycerol had no such effect. Solid fat content of palm oil in the cream with 1-palmitoylglycerol was found to be lower than those of palm oil and palm oil with 1-oleoylglycerol after cooling from 60 to 5 °C. Crystallization behaviors of bulk palm oil and mixture of 1, 3-dipalmitoyl- 2-oleoyl-glycerol (POP) and 1-palmitoyl-2, 3-dioleoyl-glycerol (POO) were then studied in the presence of monoacylglycerols. Formation of granular crystals was observed for palm oil and POP/POO mixture in the presence of 1-palmitoylglycerol. HPLC of the granular crystals revealed that agglomeration of higher melting point triacylglycerols (TAGs) around 1-palmitolyglycerol took place, which promoted the formation of granular crystals. It was suggested that the agglomeration of higher melting point TAGs around 1-palmitoylglycerol which was preferentially adsorbed at the oil-water interface of oil droplets in the model cream led to destabilization of oil-in-water emulsion and the solidification of the model cream. At the same time, it was suggested that the fatty acid moiety of emulsifiers played an important role in the agglomeration of TAGs and stabilization of o/w emulsions.

Microporosity of BIF hosted massive hematite ore, Iron Quadrangle, Brazil

Massive hematite ore (MHO) is a special high-grade iron ore, used as lump ore in the process of obtaining direct reduction iron (DRI). The influence of porosity on the reducibility of MHO from the Capitão do Mato Mine (Iron Quadrangle, Brazil) was investigated using optical and scanning electron microscopes on drill core and open pit samples. Hematite is the main component of the samples and occurs as granular crystals (10 mum), microplates (1 mum) and euhedral martite (10 to 30 mum). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (Å to 1 mum) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (Å to 5 mum) related to euhedral martite crystals, are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 11%, whereas unweathered samples have a porosity less than 2.5%. Reducibility is strongly enhanced by porosity, but inhibited by structure (bedding).

Fabrication of Cubic Gallium Nitride Single Crystal using a K-Ga Melt.

Granular and platelet-shaped gallium nitride (GaN) crystals were prepared at 600-700°C and 4-7MPa of N2 for 24-96h by using a K-Ga melt. The granular crystals with a size of 50-80μm were a mixture of cubic zincblende-type GaN (c-GaN) and hexagonal wurztite-type GaN (h-GaN). The ratio of c-GaN in the mixture increased with decreasing temperature and with decreasing N2 pressure. The platelet crystals obtained were h-GaN and have a size of about 1mm. A colorless transparent grain of GaN with a size of 80μm was characterized by cathodoluminescence (CL) spectroscopy at room temperature. A CL peak with a full width at half maximum of 76meV was observed at 3.209eV which agreed with the near band emission peak position reported for c-GaN thin films.

傾斜冷却板を用いたAZ91Dマグネシウム合金の半溶融鋳造

To obtain an ingot of AZ91D magnesium alloy containing granular primary crystals of magnesium in the cast structure, we performed semisolid casting using an inclined cooling plate. In this casting process, molten metal is flown onto the inclined cooling plate to induce the primary magnesium crystal nucleation on the cooling plate. The molten metal containing the primary magnesium crystals which is flown onto the inclined cooling plate is cast in a preheated mold, where the crystals grow into grains. Factors which affect the cast structures are pouring temperature, the angle of the incline, and the length of the cooling plate. Under optimal conditions, an ingot of fine grains is obtained. Next, under optimal conditions of mold casting, we performed continuous casting along a horizontal direction, and we obtained a billet with a diameter of about 40 mm and a length of about 600 mm. All of the cast structures obtained were composed of fine grains.

Crystallization behavior of 1,3-dipalmitoyl-2-oleoyl-glycerol and 1-palmitoyl-2,3-dioleoyl-glycerol

A model margarine was stored under a temperature fluctuation cycle of 5—20 °C until granular crystals were observed. Using information obtained from the granular crystals, the crystallization behaviors of major triacylglycerols of palm oil, 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1-palmitoyl-2,3-dioleoyl-glycerol (POO), and their mixtures were then investigated. It was shown that in the model margarine, the POP content in the granular crystals was higher than in their surrounding materials, and the X-ray diffraction pattern of the granular crystals revealed that they were the most stable polymorph, β. 99% pure POP, POO, and their mixtures were then stored under the above-mentioned temperature cycle. POP was found to form the unstable polymorph, α, when cooled rapidly from the melt. Within 24 hours transformation into the γ polymorph and then into the β polymorph was observed. POO was shown to transform into the β' polymorph from α. When POP and POO were mixed, the β polymorph did not emerge, instead it was shown that POP and POO were both agglomerated in the mixtures, giving rise to the formation of granular crystals.

Crystallization behavior of 1,3-dipalmitoyl-2-oleoyl-glycerol and 1-palmitoyl-2,3-dioleoyl-glycerol

A model margarine was stored under a temperature fluctuation cycle of 5—20 °C until granular crystals were observed. Using information obtained from the granular crystals, the crystallization behaviors of major triacylglycerols of palm oil, 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1-palmitoyl-2,3-dioleoyl-glycerol (POO), and their mixtures were then investigated. It was shown that in the model margarine, the POP content in the granular crystals was higher than in their surrounding materials, and the X-ray diffraction pattern of the granular crystals revealed that they were the most stable polymorph, β. 99% pure POP, POO, and their mixtures were then stored under the above-mentioned temperature cycle. POP was found to form the unstable polymorph, α, when cooled rapidly from the melt. Within 24 hours transformation into the γ polymorph and then into the β polymorph was observed. POO was shown to transform into the β' polymorph from α. When POP and POO were mixed, the β polymorph did not emerge, instead it was shown that POP and POO were both agglomerated in the mixtures, giving rise to the formation of granular crystals.

Effect of Laser Wavelength for Surface Morphology of Aluminum Nitride Thin Films by Nitrogen Radical-Assisted Pulsed Laser Deposition

AlN thin films were prepared on Si(100) substrates by the nitrogen radical-assisted pulsed laser deposition method at a low substrate temperature (200°C) as a function of the laser wavelength (1064, 532 and 266 nm). At the laser wavelength of 1064 nm, Al-rich AlN films were deposited and granular crystals with a diameter of 50 nm were observed on the film surface. The surface roughness (Ra) was 15 nm. At the laser wavelength of 266 nm, c-axis-oriented AlN thin films with smooth surfaces (Ra=5 nm) were obtained and the atomic ratio of N/Al was stoichiometric. The full width at half maximum (FWHM) value of the diffraction profile in the 2θ/θ scan mode was 0.55°. It was found that the use of an ultraviolet laser was more effective for preparing the c-axis-oriented AlN films with a stoichiometric concentration and smooth surfaces.