• Journal of Periodontal and Implant Science
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• v.28 no.2
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• pp.235-247
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• 1998

Calcium sulfate has a long history of medical use as an implant material. The biocompatibiliry of the material has been clearly established. Bone ingrowth concomitant with resorption occurs rapidly with efficient conduction of bone from particle to particle. Calcium sulfate also has a potential for functioning as a good bamer membrane. The purpose of this study was to compare the biocompatibility of different types of calcium sulfate grafting materials including an expelimental calcium sulfate compound on periodontal ligament cells in vitro as a preliminary test towards the development of a more convenient and useful form of grafting material which could promote regeneration of periodontal tissue. Human periodontal ligament cells were collected from the premolar teeth extracted for orthodontic treatment. cells were cultured in a.MEM culture medium containing 20% FBS, at $37^{\circ}C$ and 100% humidity, in a 5% CO2 incubator. Cells were cultured into 96 well culture plate $1{\times}104$ cells per well with $\alpha$-MEM and incubated for 24 hours. After discarding the medium, those cells were cultured in $\alpha$-MEM contained with 10% FBS alone (control group), in medcal-grade calcium sulfate(MGCS group), in plaster(plaster group), experimental calcium sulfate paste(CS paste group) for 1, 2, 3 day respectively. And then each group was characterized by examining of the cell counting, MTI assay, collagen synthesis. The results \vere as follows. 1. In the analysis of cell proliferation by cell counting, both medical-grdde calcium sulfate group and plaster group showed no stastically significant difference at day 1, 2, 3 accept for plaster group at day 1 compared to control group, but there was stastically significant difference between CS paste group and all other groups at day 1, 2, 3(P<0.05). 2. In the analysis of cytotoxicity by MIT assay, both medical-grade calcium sJlfate group and plaster group showed no stastically significant difference compared to control group at day 1, 2, 3 but there was stastically significant difference between CS paste group and all other groups at day 1, 2, 3(P<0.OS). 3. In the analysis of collagen synthesis by immunoblotting assay, high level was detected for medical-grade calcium sulfate group and plaster group at day 1, 2, 3 compared to CS paste group. On the basis of these results, medical-grade calcium sulfate and plaster was shown to possess biocompatibility whereas the CS paste had unfavourable outcome. This observation shows a need for modification of the materials contained in calcium sulfate paste.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.104-107
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• 2005

[ $TiN_x$ ] powder have been fabrication by making of reaction between titanium powder and $Si_3N_4$ bowl during a planetary milling. Milling times were maintained for 1 hour, 5 hours, and 10 hours, respectively. The XRD result showed existence of non-stoichiometric compound of $TiN_{0.26}$ after 5 hours milling and coexistence of TiN with $TiN_{0.26}$ after 10 hours milling. Particle size distribution was investigated by particle size analyzer and microstructure was analyzed by FE-SEM. The size of titanium was decreased with increasing the milling time and the mean size of $TiN_x$ after 10 hours milling was increased by 200 nm.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.337-341
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• 2004

Engineering ceramics have superior heat resistance, corrosion resistance, and wear resistance. Consequently, these art significant candidates for hot-section structural components of heat engine and the inner containment of nuclear fusion reactor. Besides, some of them have the ability to heal cracks and great benefit can be anticipated with great benefit the structural engineering field. Especially, law fracture toughness of ceramics supplement with self-healing ability. In the present study, we have been noticed some practically important points for the healing behavior of silicon nitride, alumina, mullite with SiC particle and whisker. The presence of silicon carbide (SiC) in ceramic compound is very important for crack-healing behavior. However, self-healing of SiC has not been investigated well in detail yet. In this study, commercial SiC was selected as sample, which can be anticipated in the excellent crack healing ability. The specimens were produced three-point bending specimen with a critical semi-circular crack of which size that is about $50-700{\mu}m$. Three-point bending test and static fatigue test were performed cracked and healed SiC specimens. A monotonic bending load was applied to cracked specimens by three-point loading at different temperature. The purpose of this paper is to report Strength Properties and Elastic Waves Characteristics of Silicon Carbide with Crack Healing Ability.

• Electrical & Electronic Materials
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• v.10 no.5
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• pp.440-446
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• 1997

This research has been performed for the fabrication of high quality ferrite plastic magnet. The magnetic properties of S $r_{5.9}$F $e_2$ $O_3$ ferrite bonded magnets by injection moulding with a variety of applied magnetic field were investigated. 0.3wt% CaCO3, 0.2wt% $SiO_2$, 0.5wt% $Al_2$ $O_3$and 0.5wt% N $a_2$ $SiO_3$are added in order to improve the magnetic properties of Sr-ferrite plastic magnets during the powder fabrication. For carbon coating on chemical compound specimen, 5wt% polyvinyl alcohol is added, and then calcinated under $N_2$ environment of 12$25^{\circ}C$. The particle size is distributed from 0.9~1.2${\mu}{\textrm}{m}$ which approximates to the single domain. The obtained Sr ferrite powder is well mixed with silane coupling and calcium stearate of 1wt%. Nest, the specimen is pelleted after kneading each of them with polyamidel2 as a binder. When the temperature of injection and mould were 25$0^{\circ}C$ and 8$0^{\circ}C$ respectively at injection pressure of 200kgf/$\textrm{cm}^2$, the degree of orientation was 85.3% under the applied magnetic field of 12kOe. As the results, when the packing density of Sr ferrite powder was 90wt%, the magnetic properties of Sr ferrite bonded magnet were follows : $_{B}$ $H_{c}$=2.41kOe, Br=3.1kG, (BH)$_{max}$=2.21MgOe. Especially, the Sr-ferrite bonded magnet with 10wt% N $d_2$F $e_{14}$B additive were as follows : $_{B}$ $H_{c}$=2.57kOe, Br=3.14kG and (BH)$_{max}$=2.39MGOe.GOe.GOe.GOe.e.

• Resources Recycling
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• v.16 no.2 s.76
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• pp.32-39
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• 2007

The measurement of physicochemical properties of ASR incineration ash has been carried dot and the preparation of light-weight material has also been performed using ASR ash for recycling point of view as building or construction materials. For this aim, chemical composition, particle size distribution, and heavy metal leachability were examined for 2 bottom ashes and 4 fly ashes obtained from the domestic ASR incinerator. In the present work, attempt has been made to prepare the lightweight material using boiler ash as a raw material, which is prepared by forming the mixture of boiler ash, lightweisht filler and inorganic binder and followed by calcination at elevated temperature. As a result, the content of Cu in bottom ash was as high as about 3wt% so that the recovery of Cu from ash was required. The major compound of SDR #5 and Bag filter #6 was found to be $CaCl_2{\cdot}Ca(OH)_2{\cdot}H_2O\;and\;CaCl_2{\cdot}4H_2O$, respectively. It is thought that heavy metal teachability of lightweight material prepared with boiler ash was significantly decreased due to the encapsulation or stabilization of heavy metal compounds.

• Proceedings of KOSOMES biannual meeting
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• 2005.11a
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• pp.159-163
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• 2005

This experimental study was performed to investigate internal flow and unsteady flow characteristics using a model for actual shape of a plate heat exchanger and visualization of flow through the particle image velocimetry. Seven Reynolds numbers were selected by calculation with the height of grooved channel and sectional mean velocity of inlet flow in the experiment, and instantaneous velocity distributions and flow characteristics were experimently investigated. The triangular grooved channel had a compound flow consisting of the flow in lower channel and the groove flow receiving shear stress by the channel flow in the experiment. The sheared mixing layer, in the boundary between the triangular groove and the channel, affected main flow to raise turbulent in the channel.

• Journal of Powder Materials
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• v.9 no.6
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• pp.422-432
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• 2002

Mechanically driven decomposition of intermetallics during mechanical milling(MM 1 was investigated. This process for Fe-Ce and Fe-Sn system was studied using conventional XRD, DSC, magnetization and alternative current susceptibility measurements. Mechanical alloying and milling form products of the following composition (in sequence of increasing Gecontent): $\alpha$(${\alpha}_1$) bcc solid solution, $\alpha$+$\beta$-phase ($Fe_{2-x}Ge$), $\beta$-phase, $\beta$+FeGe(B20), FeGE(B20), FeGe(B20)+$FeGe_2$,$FeGe_2$,$FeGe_2$+Ge, Ge. Incongruently melting intermetallics $Fe_6Ge_5$ and $Fe_2Ge_3$ decompose under milling. $Fe_6Ge_5$ produces mixture of $\hat{a}$-phase and FeGe(B20), $Fe_2Ge_3$ produces mixture of FeGe(B20) and $FeGe_2$ phases. These facts are in good agreement with the model that implies local melting as a mechanism of new phase for-mation during medchanical alloying. Stability of FeGe(B20) phase, which is also incongruently melting compound, is explained as a result of highest density of this phase in Fe-Ge system. Under mechanical milling (MM) in planetary ball mill, FeSn intermetallic decomposes with formation $Fe_5Sn_3$ and $FeSn_2$ phases, which have the biggest density among the phases of Fe-Sn system. If decomposition degree of FeSn is relatively small(<60%), milled powder shows superparamagnetic behavior at room temperature. For this case, magnetization curves can be fitted by superposition of two Langevin functions. particle sizes for ferromagnetic $Fe_5Sn_3$ phase determined from fitting parameters are in good agreement with crystalline sizes determined from XRD data and remiain approximately chageless during MM. The decomposition of FeSn is attributed to the effects of local temperature and local pressure produced by ball collisions.

• Journal of Powder Materials
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• v.23 no.3
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• pp.240-246
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• 2016

In order to improve the high-temperature oxidation stability, sintered 434L stainless steel is studied, focusing on the effect of the addition of metallic oxides to form stable oxide films on the inner particle surface. The green compacts of Fecralloy powder or amorphous silica are added on STS434L and oxidized at $950^{\circ}C$ up to 210 h. The weight change ratio of 434L with amorphous silica is higher than that of 434L mixed with Fecralloy, and the weight increase follows a parabolic law, which implies that the oxide film grows according to oxide diffusion through the densely formed oxide film. In the case of 434L mixed with Fecralloy, the elements in the matrix diffuse through the grain boundaries and form $Al_2O_3$ and Fe-Cr oxides. Stable high temperature corrosion resistance and electrical resistivity are obtained for STS434L mixed with Fecralloy.

• Journal of the Korean Applied Science and Technology
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• v.19 no.1
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• pp.10-18
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• 2002

In this study, it should be mentioned that Lipid-LCG can be prepared with the main compound of hydrogenated lecithin in oil-in water emulsion. The results of its physical property and stability are as follows. First, the best suitable compositions of Lipid-LCG are made from 4.0wt% of the hydrogenated lecithin, 4.0wt% of cetostearyl alcohol as emulsifier and gelling agent, 3.0wt% of butylene glycol and 2.0wt% glycerin as moisturizers, 3.0wt% of cyclomethicone, 3.0wt% of isononyl-isononanoate, 3.0wt% of capric/caprylic triglycerides, 3.0wt% of macadamia oil as emollients. Second, As the optimum conditions to form Lipid-LCG, which figured out 6.0 ${\pm}$ 1.0 for pH level, 32kg/mm, min for hardness to make a .essence to be formed the ternary phase of liquid crystal(multi-lamellar type). Third, as the analytical result of this system, it obtained that particle size is $1{\sim}8{\mu}m$ level, and is certified with it at 400 and 1,000 magnifications by microscope. The stability of Lipid-LCG is very stable on condition of a low temperature ($4^{\circ}C$), a room temperature ($25^{\circ}C$) and a high temperature ($40^{\circ}C$), which is not to be split in for a long time(for 3-month). We produced our own moisturizing essence, which has a good affinity to skin by means of this system.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04b
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• pp.239-244
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• 1999

aluminum sulfate (alum) as a representative retention aid in papermaking processes was added to pulp suspensions, and the aluminum components adsorbed on the pulp were investigated quantitatively by two types of X-ray elementary analyses with regard to simultaneous changes of their surface charges. X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence analysis (XFA) were applied to determine the aluminum components retained in pulp pads up to ca. 10 nm and 100${\mu}$m depth, respectively. In other words, XPS was utilized to analyze the outermost surface layers of the samples, and XFA was available for measurement of their extensive regions. A particle charge detector (PCD) was used to monitor streaming potentials at various pHs of the pulp mixtures under moderate sharing conditions. At pH 4.5 of pulp suspensions containing alum, surface charges of pulp fibers varied from negative to slight negative (approximately neutral) according to adsorption of aluminum components onto the pulp fibers. Subsequently, when a dilute NaOH solution in limited amounts was added to pulp mixtures, both streaming potentials and surface aluminum content of the pulp fibers increased distinctly although little total aluminum retention increased. Further addition of alkali solutions brought drastic decreases of the surface charges and surface aluminum content, while total aluminum content, on the contrary, increased gradually under neutral conditions. These results indicate that residual aluminum ions remained in pulp suspensions are predominantly adsorbed on surfaces of pulp fibers by adequate alkali additions and they must sufficiently cationize the fiber surfaces with increases of somewhat cationic aluminum complexes formed on the surfaces. On the other hand, aluminum components formed in higher pH ranges have nearly no contribution to improvement of charge properties of the pulp fiber surfaces, even though aluminum retention in pulp pads increases. XPS and XFA analyses combined with streaming potential measurement using a PCD suggest close relationships between aluminum content on the pulp fiber surfaces and their charge properties.