• Microbiology and Biotechnology Letters
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• v.42 no.3
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• pp.297-301
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• 2014

We examined the effect of ionic liquid on the crystallization efficiency of vancomycin in an increased surface area crystallization with silica gel. The crystallization efficiency was improved by the addition of ionic liquid, [BMIm][$BF_4$]. The addition of ionic liquid (20%, v/v) on the increased surface area crystallization with silica gel dramatically reduced the crystallization time by 6 folds (4 h), compared with the results of the case where the surface area-increasing material and ionic liquid had not been added. In addition, the crystal size of vancomycin was decreased and the crystal quality of vancomycin was improved by increasing the addition of ionic liquid.

• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.20-24
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• 2014

Joule heat is generated by applying an electric filed to a conductive layer located beneath or above the amorphous silicon film, and is used to raise the temperature of the silicon film to crystallization temperature. An electric field was applied to an indium tin oxide (ITO) conductive layer to induce Joule heating in order to carry out the crystallization of amorphous silicon. Polycrystalline silicon was produced within the range of a millisecond. To investigate the kinetics of Joule-heating induced crystallization (JIC) solid phase crystallization was conducted using amorphous silicon films deposited by plasma enhanced chemical vapor deposition and using tube furnace in nitrogen ambient. Microscopic and macroscopic uniformity of crystallinity of JIC poly-Si was measured to have better uniformity compared to that of poly-Si produced by other methods such as metal induced crystallization and Excimer laser crystallization.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.173-179
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• 1999

The effect of the surface activation treatment on the crystallization of the amorphous silicon film was investigated. The amorphous silicon film was deposited on the silica substrate with LPCVD technique. Wet blasting with silica slurry or exposure with Nd:YAG laser beam was applied on the amorphous silicon film before annealing for the crystallization. For the analysis of the crystallinity, XRD, Raman, and SEM were employed. In this investigation, the prior surface activation treatment like silica wet blasting or Nd:YAG laser beam exposure before annealing for the crystallization were found to be effective in the enhancement of the crystallization. It is believed that these treatment lower the activation energy required for the crystallization of the amorphous silicon film.

• Microbiology and Biotechnology Letters
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• v.42 no.3
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• pp.232-237
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• 2014

We investigated the effects of silica gels on the reduction of the crystallization time for the purification of vancomycin. The shortest crystallization time for vancomycin was obtained when silica gel with a pore diameter of $40-60{\AA}$ and with a particle diameter of 230-400 mesh was used as the material. The use of silica gel as a surface area increasing material dramatically reduced the crystallization time four fold (6 h) when compared with the results where the surface area had not been similarly increased. In addition, the crystal size of vancomycin was decreased with the addition of silica gel. This improved crystallization process has a significant effect on the convenience and feasibility of the purification step for vancomycin.

• Fibers and Polymers
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• v.1 no.2
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• pp.76-82
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• 2000

A series of random copolyesters having various compositions were synthesized by bulk copolymerization of bishydroxyethyl terephthalate (BHET) with 1,4-cyclohexane dimethanol (CHDM) or dimethyl isophthalate (DMI). CHDM and DMI content was less than 10 wt%. For the synthesized copolyesters, isothermal crystallization rate, melting behavior, and equilibrium temperature were investigated by calorimetry and by Avrami and Hoffman-Weeks equation. Crystalline lattice and morphology were studied by WAXD and SEM. Regardless of the composition, the value of the Avrami exponent was about 3, which indicates that crystallization mechanism of the copolyester was similar to those of PET homopolymer. Incoporation of CHDM or DMI units in PET backbone decreased the crystallization rate of the copolyesters. Surface free energy of copolyesters was evaluated using the newly proposed equation. The value of surface free energy was about 189$\times$$10^{-6}$/$J^{2}$/$m^{4}$ regardless of comonomer contents. This result is in good agreement with that of PET homopolymer.

• Journal of Adhesion and Interface
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• v.5 no.4
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• pp.17-23
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• 2004

In this study, we prepared the polycarbonates with various molecular weights by melt polymerization and investigated the crystallization by solvent induced crystallization. Effects of the types and compositions of solvents, crystallizing temperatures and molecular weights on crystallinity and melt temperatures of polycarbonates were evaluated by DSC, XRD and SEM. In case of low molecular weight polycarbonates and high crystallization temperature, the crystallinity of the polycarbonate was increased. As the increase of the crystallization temperature and the solution concentration, relatively uniform crystalline structures were obtained. Also, by treating with mixed solvents, the control of desired surface areas and crystallinity could be possible.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.363-367
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• 1999

New glass ceramics were investigated for the application as substrates to be used in hard disk devices. The glass system to precipitate lithium di-silicate was studied so as to optimize the composition to realize very high surface flatness. The addition of small amount of several metal oxides with high valences had very drastic effects on the microstructure, because they played a role of crystallization agents, and consequently it determined surface flatness even after the polishing process. The possible mechanism changes of crystal growth due to the addition of metal oxides were discussed in relation to the final micro-texture development. The glass ceramics with very high surface flatness(Ra=7.1 $\AA$) was obtained by the addition of the mixture of $P-2O_5 \;and \;MoO_3$ as crystallization agents.

• ETRI Journal
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• v.19 no.1
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• pp.26-35
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• 1997

The substrate effects on solid-phase crystallization of amorphous silicon (a-Si) films deposited by low-pressure chemical vapor deposition (LPCVD) using $Si_2H_6$ gas have been extensively investigated. The a-Si films were prepared on various substrates, such as thermally oxidized Si wafer ($SiO_2$/Si), quartz and LPCVD-oxide, and annealed at 600$^{\circ}C$ in an $N_2$ ambient for crystallization. The crystallization behavior was found to be strongly dependent on the substrate even though all the silicon films were deposited in amorphous phase. It was first observed that crystallization in a-Si films deposited on the $SiO_2$/Si starts from the interface between the a-Si and the substrate, so called interface-interface-induced crystallization, while random nucleation process dominates on the other substrates. The different kinetics and mechanism of solid-phase crystallization is attributed to the structural disorderness of a-Si films, which is strongly affected by the surface roughness of the substrates.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.58-63
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• 2010

The glass-ceramics made from the mixture of coal bottom ash, produced from a thermal power plant mixed with $Na_2O$ and $Li_2O$ was fabricated and their crystallization behavior was studied using a non-isothermal analyzing method. The temperature for 50% crystallization was higher than the exothermic peak temperature $T_p$ at DTA curve and the quickest crystallization temperature was much the same as $T_p$ as identified from the relationships of crystallized fraction and crystallization rate with temperature. By using Kissinger equation describing a crystallization behavior, the activation energy (262 kJ/mol), the Avrami constant (1.7) and the frequency ($5.7{\times}10^{16}/s$) for crystallization were calculated from which the nepheline crystal could be expected as showing an 1~2-dimensional surface crystallization behavior mainly with some bulk crystallization tendency at the same time. The actual observation of microstructure using SEM showed the considerable amount of surface crystals of dendrite and the bulk crystals with low fraction, so the prediction by the Kissinger equation was in accord with the crystallization behavior of glass-ceramics fabricated in this study.

• Journal of the Korean institute of surface engineering
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• v.41 no.2
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• pp.48-50
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• 2008

Solid phase crystallization (SPC) of amorphous silicon is usually conducted at around $600^{\circ}C$ since it is used in the application of flat panel display using thermally susceptible glass substrate. In this study we conducted SPC experiments at temperatures higher than $600^{\circ}C$ using silicon wafers. Crystallization rate becomes dramatically rapid at higher temperatures since SPC kinetics is controlled by nucleation with high value of activation energy. We report SPC kinetics of high temperatures compared to that of low temperatures.