• Journal of Biosystems Engineering
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• v.39 no.2
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• pp.122-133
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• 2014

Purpose: This study was to develop an effective process for fabricating biocompatible calcium phosphate powders (CPPs) using horse bones, and to investigate the characteristics of them. Methods: The characteristics of horse bone powders (HBPs) were investigated according to the different osseous tissue types (compact bone and cancellous bone), bone types (spine and tibia), pretreatment methods (cold water, $H_2O_2$, and hot water), sintering time (4, 8 and 12h), and sintering temperature (600, 900, 1100 and $1300^{\circ}C$). In addition, the grinding methods were compared based on the wet grinding (ball mill) and dry grinding (blade grinder) method to make it as powders. Finally, their cytotoxicity and cell viability were checked. Results: Regardless of the types of osseous tissues and bones, HBPs were well fabricated as biocompatible CPPs. It was also found that the pretreatment methods did not influence on the resultants, showing well-fabricated HBPs. Considering the processing time, the hot water method was the most suitable compared to other pretreatment methods. Further, 12h-sintering time was sufficient to remove residual organic compounds. The sintering temperatures greatly affected the properties of bone powders fabricated. The x-ray diffraction (XRD) peak of horse bone sintered at $600^{\circ}C$ was most closed to that of hydroxyapatite (HA). Our bioactivity study demonstrated that the HBPs fabricated by sintering horse bones at $1300^{\circ}C$ showed the best performance in terms of cell viability whereas the HBPs $1100^{\circ}C$ showed the cytotoxicity. Conclusions: Using various types of horse bone tissues, biocompatible CPPs were successfully developed. We conclude that the HBPs may have a great potential as biomaterials for various biological applications including bone tissue engineering.

• Journal of the Korean Society of Radiology
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• v.9 no.3
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• pp.169-174
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• 2015

$LiGd_9(SiO_4)_6O_2:Ce^{3+}$ phosphors were synthesized by solid-state reaction method. The structural characteristic was investigated by X-ray powder diffraction analysis. The emission and excitation spectra of the $Ce^{3+}$ ions doped $LiGd_9(SiO_4)_6O_2$ phosphors were obtained under the UV excitation. The emission spectra of $LiGd_9(SiO_4)_6O_2:Ce^{3+}$ shows the band at 410 nm corresponding to the $^2F_{5/2}$ and $^2F_{7/2}$ states of $Ce^{3+}$. The red shift of $Ce^{3+}$ emission is found as the $Ce^{3+}$ concentration increases, which could be explained by the change in crystal-field symmetry and strength with increasing $Ce^{3+}$ concentration. Fluorescence decay time of $Ce^{3+}$ was about 20 ns. When the concentration of $Ce^{3+}$ increases life time was slightly reduced.

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.604-611
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• 2005

Polyethylene glycol (PEG) 6000-based solid dispersions (SDs), by incorporating various pharmaceutical excipients or microemulsion systems, were prepared using a fusion method, t o compare the dissolution rates and bioavailabilities in rats. The amorphous structure of the drug in SDs was also characterized by powder X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The ketoconazole (KT), as an antifungal agent, was selected as a model drug. The dissolution rate of KT increased when solubilizing excipients were incorporated into the PEG-based SDs. When hydrophilic and lipophilic excipients were combined and incorporated into PEG-based SDs, a remarkable enhancement of the dissolution rate was observed. The PEG-based SDs, incorporating a self microemulsifying drug delivery system (SMEDDS) or microemulsion (ME), were also useful at improving the dissolution rate by forming a microemulsion or dispersible particles within the aqueous medium. However, due to the limited solubilization capacity, these PEG-based SDs showed dissolution rates, below 50% in this study, under sink conditions. The PEG-based SD, with no pharmaceutical excipients incorporated, increased the maximum plasma concentration (C$_{max}$) and area under the plasma concentration curve (AUC$_{0-6h}$) two-fold compared to the drug only. The bioavailability was more pronounced in the cases of solubilizing and microemulsifying PEG-based SDs. The thermograms of the PEG-based SDs showed the characteristic peak of the carrier matrix around 60$^{\circ}C$, without a drug peak, indicating that the drug had changed into an amorphous structure. The diffraction pattern of the pure drug showed the drug to be highly crystalline in nature, as indicated by numerous distinctive peaks. The lack of the numerous distinctive peaks of the drug in the PEG-based SDs demonstrated that a high concentration of the drug molecules was dissolved in the solid-state carrier matrix of the amorphous structure. The utilization of oils, fatty acid and surfactant, or their mixtures, in PEG-based SD could be a useful tool to enhance the dissolution and bioavailability of poorly water-soluble drugs by forming solubilizing and microemulsifying systems when exposed to gastrointestinal fluid.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.108-113
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• 2013

Chalcopyrite material $CuInSe_2$ (CIS) is known to be a very prominent absorber layer for high efficiency thin film solar cells. Current interest in the photovoltaic industry is to identify and develop more suitable materials and processes for the fabrication of efficient and cost-effective solar cells. Various processes have been being tried for making a low cost CIS absorber layer, this study obtained the CIS nanoparticles using commercial powder of 6 mm pieces for low cost CIS absorber layer by high frequency ball milling and cryogenic milling. And the CIS absorber layer was prepared by paste coating using milled-CIS nanoparticles in glove box under inert atmosphere. The chalcopyrite $CuInSe_2$ thin films were successfully made after selenization at the substrate temperature of $550^{\circ}C$ in 30 min, CIS solar cell of Al/ZnO/CdS/CIS/Mo structure prepared under various deposition process such as evaporation, sputtering and chemical vapor deposition respectively. Finally, we achieved CIS nanoparticles solar cell of electric efficient 1.74 % of Voc 29 mV, Jsc 35 $mA/cm^2$ FF 17.2 %. The CIS nanoparticles-based absorber layers were characterized by using EDS, XRD and HRSEM.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.16-21
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• 2001

Optical properties of $Ag_2CdSnSe_4$ and $Ag_2CdSnSe_4:Co^{+2}$ quaternary semiconductor single crystals grown by the chemical transport reaction method were investigated. The analysis of the X - ray powder diffraction measurements showed that these crystals have a wurtzite structure with lattice constants a = 4.357 $\AA$, c = 7.380 $\AA$, for $Ag_2CdSnSe_4$ and a = 4.885 $\AA$, c = 7.374 $\AA$, for $Ag_2CdSnSe_4:CO^{2+}$. The direct band gap at 298K, obtained from the optical absorption measurement, is found to be 1.21 eV for $Ag_2CdSnSe_4$ and 1.02 eV for $Ag_2CdSnSe_4:CO^{2+}$. The shrinkage of the band gap due to Co-doping is observed and is about 190 meV, We observed four absorption bands of $Co^{2+}$ ions in two near infrared regions of optical absorption spectra of $Ag_2CdSnSe_4$:$Co^{+2}$. These absorption bands were assigned as due to electronic transitions between the split energy levels of $Co^{2+}$ ions in $T_d$ crystal field under spin-orbit interactions.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.139-165
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• 1991

The properties of a investment material can be described by the consistency at the slurry state, the setting time, the compressive strength and the thermal expansion during the casting. In this study the effect of the production parameters which are included the ratio of quartz and cristobalite, the content of binder, the water powder ratio and the content and concentration of additives on the properties of the gypsum-bonded investments has been investigated with help of the consistency test, the vicat needle test, the compressive strength test, the thermal expansion test, x-ray diffraction and DTA thermal differential test. The experimental results showed that the constitution of a investment with W/P ratio of 0.34, 30% of gypsum, 0.8% aluminium sulfate, 2% magnesium sulfate, 0.6% sodium phosphate was adapted for the properties of the KDA Spec. No. 13 type I investment. The important experimental results are summarized as follows. 1. The consistency of the investment decreased with increasing amount of aluminium sulfate and decreasing amount of sodium phosphate. An addition of magnesium sulfate up to 2% an increase of the consistency was shown. But 3% magnesium sulfate in investment showed a decrease of consistency. The consistency did not vary significantly with a variation of the content of gypsum and cristobalite and the W/P ratio. 2. Aluminium sulfata and the magnesium sulfate promoted the hardening and the aluminium phoshpate delayed the hardening. The setting time increased with amount of gypsum. The effect of the matrix on the setting time was insignificant. With the W/P ratio of 0.34 the setting time was 14 min. 3. The compressive strength decreased with the amount of aluminium sulfate up to 0.25% and increased with the amount of aluminium sulfate greater than 3%. The compressive strength decreased as decreasing the amount of magnesium sulfate and gypsum and as increasing the W/P ratio. The effect fo the refractory on the compressive strength was also not significant. With the W/P ratio of 0.34 the compressive strength was $34Kg/mm^2$. 4. The 1st thermal expansion was found at the temperature near $250^{\circ}C$ and the steady state or the contraction stage was found at the temperature between $250^{\circ}C$ and $500^{\circ}C$. After this stage the 2nd thermal expansion took place at the temperature near $500^{\circ}C$. The amount of thermal expansion increased with decreasing the content of magnesium sulfate, aluminium sulfate and gypsum and the W/P ratio. And the amount of thermal expansion increased as the content of sodium phosphate ad cristobalite. With the W/P ratio of 0.34 the amount of total expansion was 1.2%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.57-58
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• 2008

PTC thermistor are characterized by an increase in the electrical resistance with temperature. The PTC materials of middle Curie point were produced or that of high Curie point (above $200^{\circ}C$), it was determined that compositional modifications of $Pb^{2+}$ for $Ba^{2+}$ produce change sin the Curie point to higher temperature. PTC ceramic materials with the Curie point above $120^{\circ}C$ were prepared by adding $PbTiO_3$, PbO or $Pb_3O_4$ into $BaTiO_3$. Thereby, adding $Pb^{2+}$ into $BaTiO_3$-based PTC material to improve Tc was studied broadly, however, weal know that PbO was poisonous and prone to volatilize, then to pollute the circumstance and hurt to people, so we should dope other innocuous additives instead of lead to increase Tc of composite PTC material. In order to prepare lead-free $BaTiO_3$-based PTC with middle Curie point, the incorporation on $Bi_{1/2}Na_{1/2}TiO_3$ into $BaTiO_3$-based ceramics was investigated on samples containing 0, 1, 2, 3, 4, and 50mol% of $Bi_{1/2}Na_{1/2}TiO_3$. $Bi_{1/2}Na_{1/2}TiO_3$ was compounded as standby material by conventional solid-state reaction technique. The starting materials were $Bi_{1/2}Na_{1/2}TiO_3$, $BaCO_3$, $TiO_2$ and $Y_2O_3$ powder, and using solid-state reaction method, too. The microstructures of samples were investigated by SEM, DSC, XRD and dielectric properties. Phase composition and lattice parameters were investigated by X-ray diffraction.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.425-430
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• 2015

ZSM-5 crystals grew by hydrothermal synthesis method on the surface of foam type porous silicon carbide ceramics which fabricated by polymer replica method. Oxide layer was developed on the surface of the porous silicon carbide ceramics to induce growth of ZSM-5 from the surface. In this study, hydrothermal synthesis was carried out for 7 h at $150^{\circ}C$ using TEOS, $Al(NO_3){\cdot}9H_2O$ and TPAOH as raw materials in the presence of the porous silicon carbide ceramics. X-ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses were confirmed $1{\sim}3{\mu}m$ sized ZSM-5 crystals have grown on the surface of porous silicon carbide ceramics. BET data shows that small pores about $10{\AA}$ size drastically enhanced and surface area increased from $0.83m^2/g$ to $30.75m^2/g$ after ZSM-5 synthesis on the surface of foam type porous silicon carbide ceramics.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.32-43
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• 1996

A $CdIn_{2}Te_{4}$ single crystal was grown by modified veritical bridgman method. The $CdIn_{2}Te_{4}$ single crystal was evaluated to be tetragonal by the powder method. The $CdIn_{2}Te_{4}$ single crystal was confirmed to be grown with its c axis along the lengthe of the boule by the Laue reflection method. Hall effect of $CdIn_{2}Te_{4}$ single crystal was estimated by van der pauw method from 293 K to 30 K. Hall data of the sample perpendicular to c axis was $n=8.75{\times}10^{23}electrons/m^{3},\;R_{H}=7.14{\times}10^{-5}m^{3}/C,\;{\sigma}=176.40{\omega}^{-1}m^{-1},\;{$\mu}=3.41{\times}10^{-2}m^{2}/V.s$ and the sample parallel to c axis was $n=8.61{\times}10^{23}electrons/m^{3},\;R_{H}=7.26{\times}10^{-5}m^{3}/C,\;{\sigma}=333.38{\omega}^{-1}m^{-1}\;and\;{$\mu}=2.42{\times}10^{-2}m^{2}/V.s$ for room temperature. The value of Hall coefficient on sample perpendicular or parallel to c axis were positive. There $CdIn_{2}Te_{4}$ single crystal was p-type semiconductor.

• Journal of the Korean Magnetics Society
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• v.16 no.2
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• pp.140-143
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• 2006

Single crystalline $CoFe_2O_4$ thin films on (100) MgO substrates were fabricated using a rf magnetron sputtering method. The deposited films were investigated for their crystallization by X-ray diffraction, Rutherford back-scattering spectroscopy and field emission scanning electron microscopy. When a cobalt ferrite film was deposited at the substrate temperature of $600^{\circ}C$, squared grains of about 200 nm were uniformly distributed in the film. However, the grains became irregular and their sizes also varied from 30 to 150 nm when the substrate temperature was $700^{\circ}C$. Hysteresis loops of a film deposited at $600^{\circ}C$ showed that the magnetically easy axis of the film was perpendicular to the substrate surface. Except for the squareness ratio, magnetic properties of the cobalt ferrite films grown by the present rf sputtering method were as good as those of the films prepared by a laser ablation method: The in-plane and perpendicular coercivities were 283 and 6800 Oe, respectively. As the thickness of the deposited film increased twice, the saturation magnetization became double but the coercivity remained unchanged. However, deposition of the Co ferrite films with a higher rf powder decreased the squareness ratio and the perpendicular coercivity of the films.