• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.167-168
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• 2006

A hyrdrothermal synthesis has been developd to prepare rod-like crystals of copper oxide using copper nitrate trihydrate as a function of synthesis temperature, stirring speed and solution pH value. The properties of the fabricated crystals were studied using scanning electron microscopy, X-ray diffraction and particle size analysis. The morphology of the synthesized CuO was dependent on both the pH value of the solution and the morphology of the seed materials. Synthesized particles have regular morphologies and a uniform size distribution.

• Korean Journal of Metals and Materials
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• v.48 no.9
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• pp.861-866
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• 2010

Tetrapod-shaped ZnO crystals were synthesized through a simple oxidation of metallic Zn powder in air without the presence of any catalysts or substrates. X-ray diffraction data revealed that the ZnO crystals had wurtzite structure. It is supposed that the growth of the tetrapod proceeded in a vapor-solid growth mechanism. As the amount of the source powder increased, the size of the tetrapod decreased. The tip morphology of the tetrapod changed from a needle-like shape to a spherical shape with the oxidation time. ZnO crystals with rod shape were fabricated via the oxidation of Zn and Sn mixture. Sn played an important role in the formation of ZnO crystals with different morphology by affecting the growth mode of ZnO crystals. The cathodoluminescent properties were measured for the samples. The strongest green emission was observed for the rod-shaped ZnO crystals, suggesting that the crystals had the high density of oxygen vacancies.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.560-574
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• 1997

The present study was undertaken to investigate the crystal growth onto human enamel mineral and synthetic hydroxyapatite(HA) seeds in media resembling the enamel fluid composition. Effects of fluoride at high concentrations on the precipitation were also examined in a bench-top crystal growth model adopting a miniaturized reaction column. The Ca, P and F concentrations and pH values of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated during the experimental period, and finally viewed under a scanning electron microscope. Remarkable findings were that 1) both biological and synthetic seeds with the same total surface areas yielded similar amounts of crystal growth, 2) the amount of crystal growth was accelerated in a manner depending on fluoride concentrations in the media, 3) SEM observations disclosed that without the addition of fluoride, precipitation of thin, plate-like OCP crystals became prominent, but by increasing the fluoride concentration(beyond 1ppm F), rod-like crystals having a pointed edge were most frequently observed, without any evidence for precipitation of the plate-like crystals. Furthermore, the dimension of rod-like crystals was increased in proportion to fluoride concentrations, 4) there was no difference in the morphological feature of precipitated mineral phase upon seeding between human enamel seed and synthetic HA seed. The overall results support the view that the seeded crystal growth model is of value to gain insight into the mechanism of enamel crystal growth under fluoride regimens.

• Korean Journal of Materials Research
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• v.29 no.7
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• pp.432-436
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• 2019

Zinc oxide(ZnO) micro/nanocrystals are grown via thermal evaporation of ZnO powder mixed with Mn powder, which is used as a reducing agent. The ZnO/Mn powder mixture produces ZnO micro/nanocrystals with diverse morphologies such as rods, wires, belts, and spherical shapes. Rod-shaped ZnO micro/nanocrystals, which have an average diameter of 360 nm and an average length of about $12{\mu}m$, are fabricated at a temperature as low as $800^{\circ}C$ due to the reducibility of Mn. Wire-and belt-like ZnO micro/nanocrystals with length of $3{\mu}m$ are formed at $900^{\circ}C$ and $1,000^{\circ}C$. When the growth temperature is $1,100^{\circ}C$, spherical shaped ZnO crystals having a diameter of 150 nm are synthesized. X-ray diffraction patterns reveal that ZnO had hexagonal wurtzite crystal structure. A strong ultraviolet emission peak and a weak visible emission band are observed in the cathodoluminescence spectra of the rod- and wire-shaped ZnO crystals, while visible emission is detected for the spherical shaped ZnO crystals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.203-206
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• 2001

The applicability of shaped growth of yttrium orthovanadate was approved by successful growth of rod-like single crystals with the rectangular shape. Nd-doped single crystals with content of $Nd^{3+}$ ions of 1,2,3,5 atomic % in the starting melt were grown by the EFG technique with the size up to $10^{*}10mm$ in section and up to 85 mm in length. For the testing of the multiple growth of the orthovanadates, two and three Nd-and Yb-doped $YVO_{4}$ single crystals were grown by the EFG technique simultaneously up to 110 mm in length.

• Journal of the Korean institute of surface engineering
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• v.49 no.5
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• pp.472-476
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• 2016

The nano-array of the vertically aligned rod-like particles grown on ZnO coated glass-substrates was obtained via hydrothermal process. ZnO thin film coatings were prepared on the glass substrates using a MOD (metallorganic deposition) dip-coating method with zinc chloride dihydrate as starting material and 2-ethylhexanol as solvent. ZnO nanorods were synthesized on the seeded substrates by hydrothermal method at $80^{\circ}C$ using zinc-nitrate hexahydrate as a Zn source and sodium hydroxide as a mineralizer. Under the hydrothermal condition, the rod-like nanocrystals were easily attaching on the already ZnO seeded (coated) glass surface. It has been shown that the hydrothermal synthesis parameters are key factors in the nucleation and growth of ZnO crystallites. By controlling of hydrothermal parameters, the ZnO particulate morphology could be easily tailored. Rod-shaped ZnO arrays on the glass substrates consisted of elongated crystals having 6-fold symmetry were predominantly developed at high Zn precursor concentration in the pH range 7~11.

• Journal of the Korean Chemical Society
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• v.52 no.2
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• pp.164-168
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• 2008

CaWO4 crystals were synthesized by a microemulsion method. Various sizes and shapes of CaWO4 were obtained by changing the molar ratio (w) of H2O to CTAB. At w=5 and 10, oval CaWO4 crystals with length of 100 nm and 500 nm were obtained, respectively. At w=20, rod-like CaWO4 crystal with length of 1 μm was obtained. The sphere CaWO4 crystal with length of about 2~3 μm was obtained at w=30. The CaWO4 crystal morphology changes from oval to sphere via a rod by aggregation with increasing the molar ratio of H2O to CTAB.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.610-615
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• 2001

Over 800 thousand tons per year (TPY) agricultural biowastes, such as sugar cane bagasse, sugarcane leaf, rice straw, rice husk and corn leaf, are produced in Taiwan. These biomasses are the major types of agricultural wastes and are abundantly available. However, these biowastes cause disposal and landfill problems. Ossification ashes of the agricultural biowastes containing 70-95 % amorphous silica would make the utilization system of agricultural biowaste ashes become highly economically and environmentally attractive. Experimentally, high crystallinity (99%$^{+}$) zeolites ZSM-5 and ZSM-48 synthesized from the reaction mixtures containing a silica source from ashes of these biowastes gasification were investigated. Tetrapropylammonium bromide (TPABr) and 1,6-diamino-hexane (C$_{6}$ DN) were used as structure-directing agents in syntheses of ZSM-5 and ZSM-48, respectively. X-ray powder diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX) data indicated that ZSM-5 or ZSM-48 with a high crystallinity can be obtained within 48 hours of crystallization in the high pressure (15-20 atm) autoclave at 393-473 K. The Si/Al ratios of synthetic zeolite products were determined by X-ray fluorescence (XRF) and induced couple plasma/mass spectroscopy (ICP/MS). It was observed that the ZSM-5 crystals a.e composed of hexagonal rod-shaped crystals with typically 8-13 пm in size by SEM. In addition, ZSM-48 crystalline materials are composed of spherical aggregates of needle-shaped or rod-like crystals with typically 2-3 пm in diameter and 6-8 пm in length.h.

• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.463-468
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• 2006

Hydrothermal deposition of hydroxyapatite coatings on two types of $ZrO_2$ substrates (3 mol% $Y_2O_3$-doped and 13 mol% $CeO_2$-doped tetragonal $ZrO_2s$) was studied using aqueous solutions of $Ca(NO_3)_2\;4H_2O$ and $(NH_4)_2HPO_4$ containing EDTA (ethylene diamine tetra acetic acid) disodium salt as a chelating agent for $Ca^{2+}$ ions. For the precipitation of the coatings, the $EDTA-Ca^{2+}$ chelates were decomposed by oxidation with $H_2O_2$ at $90^{\circ}C$. The deposition behavior, morphology, and orientation of the coatings were investigated while varying the solution pH using scanning electron microscopy and X-ray diffractometry. For the two sub-strates, sparse deposition of the coating was obtained at pH 5.5, whereas a uniform deposition was obtained at pH 7.1, 9.8, and 11.4 with a denser microstructure for the higher pH. The coating consisted of thin needle-like or plate-like crystals ($1-2{\mu}m$ length or diameter) at pH 7.1, but fine rod-like crystals ($1-2{\mu}m$ length, $0.1{\mu}m$ diameter) at pH 9.8 and 11.4. The coatings were $1-3{\mu}m$ thick and showed a preferred orientation of the hydroxyapatite crystals with their c axis (i.e., the elongated direction) perpendicular to the substrate surface especially for pH 9.8 and 11.4.

• Journal of the Korean institute of surface engineering
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• v.33 no.5
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• pp.373-380
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• 2000

The flow melting behavior of the electrolytic tinplate during reflow treatment was investigated in terms of morphology and structure of coating layers which were electrodeposited with variation of electrolyte temperature. It was commonly found that the nucleation density of the electrodeposits showed little difference with the electrolyte temperature, and the growth of electrodeposited tin occurred along <100> direction of (002) plane. At low electrolyte temperature, the (002) plane of tin nucleated paralleling to the substrate and grew perpendicularly to the substrate, which rendered porous rod-like deposits. With increasing the temperature, the (002) plane nucleated declining $15^{\circ}$ to the substrate and also grew to the normal <100> direction, which enabled lateral growth of the tin crystals and rendered compact deposits. During reflow treatment, the matte deposit transformed to the reflowed state via transition regions consisted of contraction, island formation, and wetting . The matte deposits formed at low temperature exhibited wide transition regions because of poor thermal transfer between crystals due to their porous nature. While that formed at high temperature transformed very rapidly to the reflowed state by enhanced thermal transfer between the compact crystals.