• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.14-18
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• 2016

A novel $Ce^{3+}$ doped $(Ce_xLu_{1-x})_3MgAl_3SiO_{12}$ phosphor was successfully synthesized by a conventional solid-state reaction. Heat-treatment temperature was controlled from 1250 to $1550^{\circ}C$ for 5 h. XRD and PL properties were analyzed for the optimum heat-treatment condition. Ce doping concentration was varied from 2.0 to 10.0 mol% for the optimum Ce doping concentration. The PL intensity, peak wavelength and FWHM were calculated with the Ce doping concentration, and evaluated for the application to LED packaging. Particle size and morphology were also characterized for synthesized phosphor sample at optimum heat-temperature and Ce doping concentration.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.57-67
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• 2002

The effect of $\beta$-TCP and PHA as additives on initial setting time, compressive strength and surface micro-structure after in vitro test of bone cement in TTCP and DCPA system was investigated. The median particle sizes of TTCP, $\beta$-TCP, DCPA and PHA for bone cement were about 3, 5, 0.9 and 4${\mu}{\textrm}{m}$, respectively. Initial setting time and compressive strength of bone cement with various composition was measured by Vicat test and Universal Testing Machine, and surface morphology and crystalline phases of bone cements were observed and analyzed by SEM and x-ray diffractometer. Initial setting time was not affected by composition but by powder/liquid ratio, and cement with PHA required double amount of solution for paste as much as one without PHA, especially. It was thought that $\beta$-TCP and PHA in bone cements was not related to setting reaction. Thus, the addition of $\beta$-TCP and PHA in bone cements decreased compressive strength and inhabited HAP from being produced on surface in vitro test. In conclusion, it was not expected that $\beta$-TCP and PHA in TTCP-DCPD bone cements enhanced the strength and bioacitivity.

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.145-152
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• 2003

Capacitance of a hybrid capacitor that has characteristics of both electrolyte capacitor and supercapacitor is determined by anode surface covered with oxide layer. In this study, optimal condition processes for anode to fabricate a high voltage hybrid capacitor was investigated. We mixed aluminum powder having mean particle size of $40{\mu}m$ with NaCl powders at weight ratio of 4 : 1 and prepared a disk type electrode after annealing at various temperature. After dissolving NaCl in $50^{\circ}C$ distilled water, heat treatment, eletropolishing, chemical treatment, and the first and the second etching of Al disk were conducted. In each process, capacitances and resistances of the disk measured by ac-impedance analyzer were compared to find its optimum treatment condition. Also, the surface morphology of treated disks were observed and compared by SEM. After the second etching, the Al disk was anodized at 365V to make an anode of hybrid supercapacitor that can be operated at 300V, Capacitance and resistance of the anodized Al disk electrode was compared with those of commercialized conventional aluminum electrolytic capacitor at different frequencies.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.695-700
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• 2014

In the present study, the melting temperature depression of Sn nanoparticles manufactured using the modified evaporation method was investigated. For this purpose, a modified evaporation method with mass productivity was developed. Using the manufacturing process, Sn nanoparticles of 10 nm size was manufactured in benzyl alcohol solution to prevent oxidation. To examine the morphology and size distribution of the nanonoparticles, a transmission electron microscope was used. The melting temperature of the Sn nanoparticles was measured using a Differential scanning calorimetry (DSC) which can calculate the endothermic energy during the phase changing process and an X-ray photoelectron spectroscopy (XPS) used for observing the manufactured Sn nanoparticle compound. The melting temperature of the Sn nanoparticles was observed to be $129^{\circ}C$, which is $44^{\circ}C$ lower than that of the bulk material. Finally, the melting temperature was compared with the Gibbs Thomson and Lai's equations, which can predict the melting temperature according to the particle size. Based on the experimental results, the melting temperature of the Sn nanoparticles was found to match well with those recommended by the Lai's equation.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.3
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• pp.193-203
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• 2005

Highly c-axis oriented nanocrystalline ZnO thin films on silica glass substrates were prepared by spin coating-pyrolysis process with a zinc naphthenate precursor. Only the XRD intensity peak of (002) phase was observed for all samples. With an increase in heat treatment temperature, the peak intensity of (002) phase increases. No significant aggregation of particle was present. From scanning probe microscopy analyses, three-dimensional grain growth, which was thought to be due to inhomogeneous substrate surface and c-axis oriented grain growth of the ZnO phase, was independent on heal-treatment temperature. Highly homogeneous surface of the highly-oriented ZnO film was observed at $800^{\circ}C$. All the films exhibited a high transmittance (above 80%) in visible region except film heat treated at $1000^{\circ}C$, and showed a sharp fundamental absorption edge at about $0.38{\sim}0.40{\mu}m$. The estimated energy band gap for all the films were within the range previously reported for films and single crystal. ZnO films, consisting of densely packed grains with smooth surface morphology were obtained by heat treatment at $600^{\circ}C{\sim}800^{\circ}C$, expected to be ideal for practical application, such as transparent conductive film and optical device.

• Resources Recycling
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• v.19 no.5
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• pp.58-67
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• 2010

Platy silver powders with varied size and thickness were prepared by polyol process with $PdCl_2$ in ethylene glycol and characterized its properties and investigated the effects of reaction time, $NH_4OH$, PVP(poly-vinylpyrrolidone) and $PdCl_2$. The characteristics of the products were verified by scanning electron microscopy(SEM), high resolution transmitted electron microscopy(HR-TEM), X-ray diffraction(XRD) and particle size analyzer(PSA) and image analyzer. Platy silver powder was prepared about $5.5\;{\mu}m$ of size and $0.2\;{\mu}m$ at 120minute. It was found that the size of powders increased by the increasing of $NH_4OH$ and $PdCl_2$ concentrations, and the thickness of powders was decreased by increasing of PVP concentration.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.3
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• pp.157-162
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• 2006

Objective of this research was to evaluate optimal conditions of arsenic adsorption in water by zero-valent iron (ZVI). Batch experiment showed that adsorption of arsenic by ZVI followed a Langmuir isotherm model. The masses of As(V) adsorbed onto ZVI were increased as decreasing pH of the reacting solution (pH 3: 2.05, pH 5: 1.82, pH 7: 1.24, pH 9: 1.03 mg As/g $Fe^0$) and as increasing the temperature ($15^{\circ}C$ : 1.59, $25^{\circ}C$ : 1.81, 35 : $1.93^{\circ}C$ mg As/g $Fe^0$). The SEM and EDS (energy dispersive X-ray spectrometer) analysis of morphology and structure of ZVI before and after reacting with arsenic in water revealed that a relatively smooth and large surface of ZVI was transformed into a coarse and small surface particle after the reaction. The EDS spectra on the chemical composition of ZVI demonstrated that arsenic was incorporated into ZVI by adsorption mechanism. The XRD analysis also identified that the only peak for $Fe^0$ in the ZVI before the reaction and confirmed that $Fe^0$ was transformed into $Fe_2O_3$ and FeOOH, and As into $FeAsO_4{\cdot}2H_2O$.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.3
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• pp.307-326
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• 2004

Statement of problem. The long-term success of implants is the development of a stable direct connection between bone and implant surface, which must be structural and functional. To improve a direct implant fixation to the bone, various strategies have been developed focusing on the surface of materials. Among them, altering the surface properties can modify cellular responses such as cell adhesion, cell motility and bone deposition. Purpose. This study was to evaluate the cellular behaviors on the surface-modified titanium by morphological observation, cellular proliferation and differentiation. Material and methods. Specimens were divided into five groups, depending on their surface treatment: electropolishing(EP) anoclizing(AN), machining(MA), blasting with hydroxyapatite particle(RBM) and electrical discharge machining(EDM). Physicochemical properties and microstructures of the specimens were examined and the responses of osteoblast-like cells were investigated. The microtopography of specimens was observed by scanning electron microscopy(SEM). Surface roughness was measured by a three-dimensional roughness measuring system. The microstructure was analyzed by X-ray diffractometer(XRD) and scanning auger electron microscopy(AES). To evaluate cellular responses to modified titanium surfaces, osteoblasts isolated from neonatal rat were cultured. The cellular morphology and total protein amounts of osteoblast-like cell were taken as the marker for cellular proliferation, while the expression of alkaline phosphatase was used as the early differentiation marker for osteoblast. In addition, the type I collagen production was determined to be a reliable indicator of bone matrix synthesis. Results. 1. Each prepared specimen showed specific microtopography at SEM examination. The RBM group had a rough and irregular pattern with reticulated appearance. The EDM-treated surface had evident cracks and was heterogeneous consisting of broad sheet or plate with smooth edges and clusters of small grains, deep pores or craters. 2. Surface roughness values were, from the lowest to the highest, electropolished group, anodized group, machined group, RBM group and EDM group. 3. All groups showed amorphous structures. Especially anodized group was found to have increased surface oxide thickness and EDM group had titaniumcarbide(TiC) structure. 4. Cells on electropolished, anodized and machined surfaces developed flattened cell shape and cells on RBM appeared spherical and EDM showed both. After 14 days, the cells cultured from all groups were formed to be confluent and exhibited multilayer proliferation, often overlapped or stratified. 5. Total protein amounts were formed to be quite similar among all the group at 48 hours. At 14 days, the electropolished group and the anodized group induced more total protein amount than the RBM group(P<.05). 6. There was no significant difference among five groups for alkaline phosphatase(ALP) activity at 48 hours. The AN group showed significantly higher ALP activity than any other groups at 14 days(P<.05). 7. All the groups showed similar collagen synthesis except the EDM group. The amount of collagen on the electropolished and anodized surfaces were higher than that on the EDM surface(P<.05).

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.299-306
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• 2016

In this study, new hydroxyapatite powder surface composites were investigated for protective effects against ultraviolet rays. Hydroxyapatite (HAp) is biocompatible and does not cause nebula phenomenon on skin. We investigated the surface modification of hydroxyapatite to improve UV block and skin usage. Dimethicone, lauroyl lysine, triethoxycaprylylsilane and silica were used as coating agents for the surface modification of HAp. To prepare the composite complex of the modified surface, the dimethicone, lauroyl lysine and triethoxycaprylylsilane were prepared by a dry process, and silica by a hydrothermal synthesis method. The HAp-silica was chosen as the best composite powder when measuring its sun protection levels. We investigated the characteristics of the surface of HAp-silica by SEM, particle size analyzer and energy dispersive spectrometry (EDS). Additionally, the stability in the formulation, UV block effect, and safety in BB creams were investigated. In conclusion, HAp-silica prepared by the modification of HAp complex surface improved the skin usage and UV block effect by enhancing the white cloudy phenomenon. These results indicate that HAp-silica may be used for UV block cosmetics.

• Journal of the Korean Chemical Society
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• v.45 no.4
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• pp.341-350
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• 2001

Aluminum Hydroxide was employed as a thermal retardent and flame retardent for Chloropolyethylene (CPE) rubbery materials which is the construction material of automotive oil cooler hose. and then cure characteristics, physical properties, thermal resistance and flame retardation of compounded rubber were investigated, and optimum mixing conditions of rubber and flame retarding agent were deduced from the experimental results. CPE rubber material which has excellent properties of chemical corrosion resistance and cold resistance and inexpensive in price was used to prepare rubber specimen. The by-product of ething, produced from the process of surface treatment of aluminum was processed to aluminum hydroxide via crushing and purification, which is characterized by XRD, PSA, SEM and ICP-AES techniques in terms of phase, size, distribution, morphology and components of particles and then mixed to CPE rubber materials in the range of 0~80 phr. Hardness, tensile strength, elongation and thermal properties of compounded rubber specimens were tested. The optimum mixing ratio of rubber to additives to give maximum effect on thermal resistance and flame retardation, within the range of tolerable specification for rubber materials, was determined to be 40 phr. The flame retardation of CPE rubber materials was found to be increased by 5 times at this mixing ratio.