• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.578-579
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• 2006

We investigated that the effect of $CaCO_3$ based compound on machinability of two types of PM steels. One is a copper steel which is selected as a general PM steel, and the other is a diffusion alloyed steel selected as a high strength PM steel. It is found that $CaCO_3$ based compound addition improves machinability in drilling of both of the PM steels. Although the compound addition degrades the mechanical properties of PM steels, it is considered that decrease of the properties can be compensated by increasing density.

• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.739-750
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• 1997

Treatment of root perforation elicits special considerations due to its blood-contaminated circumstances. It is known that conventional dental restorative materials are all leaking. Calcium sulfate is the material which react with water to become chemically set. This study, therefore, was performed to develop a new compound containing calcium sulfate and to evaluate its physical and biological characteristics. Three materials were used, IRM, calcium sulfate, calcium sulfate-hydroxyapatite compound. The composition of the calcium sulfate-hydroxyapatite compound was basically 50 % of calcium sulfate and 50 % of hydroxyapatite mixed with guajacol. The materials were mixed in conventional way and underwent four physical test procedures, setting time, solubility test, compressive strength, and marginal leakage test. All materials were evaluated under the scanning electron microscope to examine the marginal sealing ability. Animal experiment was also performed to test the materials' tissue response. Twenty-four dog's premolars were tested with either furcation perforations or apical retro-fillings. From the results, we found that calcium sulfate possess the good marginal sealing ability. However, calcium sulfate creates many voids which is caused by crystal thrusting action when it reacts with water. It seemed that the voids caused disintegration of the material which eventually lead to tissue reaction. By compounding calcium sulfate and hydroxyapatite, we were able to obtain the better physical properties but it showed larger marginal gap between the material and the root surface. Within the six weeks observation period, both IRM and calcium sulfate-hydroxyapatite compound showed good tissue responses in animal experiment. It is concluded that calcium sulfate would be the material of choice in root perforation repair, but the physical property needs to be further improved.

• 열처리공학회지
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• 제15권5호
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• pp.219-227
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• 2002

This study has been performed to investigate the effect of $CO_2$ content on the growth characteristics of the compound layer, porous layer and corrosion characteristics of carbon steels after gaseous nitrocarburizing in $70%-NH_3-CO_2-N_2$ at $580^{\circ}C$ for 2.5 hrs. The results obtained from the experiment were the thickness of the compound and porous layers increased with increasing $CO_2$ contents. At the same fixed gas composition the thickness of the compound and porous layer increased with increasing carbon content of the specimens. X-ray diffraction analysis showed that compound layer was mainly consisted of ${\varepsilon}-Fe_{2-3}(N,C)$ and ${\gamma}^{\prime}-Fe_4N$ as the increased with $CO_2$ contents in atmosphere, compound layer was chiefly consisted of ${\varepsilon}-Fe_{2-3}(N,C)$ phase. With increasing $CO_2$ content and total flow rate in gaseous nitrocarburizing, the amount of ${\varepsilon}-Fe_{2-3}(N,C)$ phase in the compound layer was increased. The current density of passivity decreased with increasing $CO_2$ content due to the development of porous layer at the out most surface of ${\varepsilon}-Fe_{2-3}(N,C)$.

• 융합정보논문지
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• 제12권5호
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• pp.126-132
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• 2022

데크재, 산책로 등 옥외용도로 대부분 사용되고 있는 합성목재(Wood Plastic Compound;WPC)를 실내 용도의 건축용 내장재로 사용하기 위하여, 항균성, 총 휘발성 유기화합물 배출량(TVOC), 난연성 등이 개선된 WPC 패널을 제조하였다. 고밀도 폴리에틸렌(HDPE)과 편백나무 목분(Chamacyparis obtusa wood flour), 항균제 및 난연제 등의 첨가제를 혼합한 후 압출 성형하여 합성목재(Wood Plastic Composite) 컴파운드 펠렛을 제조하였다. 이 WPC 컴파운드 펠렛을 이축압출기를 사용하여 제조한 합성목재 패널(303mm×606mm×10mm)은 우수한 항균 및 항진균 특성을 나타냈다. 또한 패널의 총 휘발성 유기화합물 배출량(TVOC)은 0.062mg/m2·h 였으며, KS F 2271의 난연성 2등급 표준을 달성하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2008년도 추계학술발표대회 및 제15회 신소재 심포지엄
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• pp.28.1-28.1
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• 2008

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 추계학술발표강연 및 논문개요집
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• pp.158-158
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• 1998

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.487-492
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• 2002

The growth kinetics of intermetallic compound layers formed between eutectic Sn-58Bi solder and (Cu, electroless Ni-P/Cu) substrate were investigated at temperature between 70 and 120 C for 1 to 60 days. The layer growth of intermetallic compound in the couple of the Sn-58Bi/Cu and Sn-58Bi/electroless Ni-P system satisfied the parabolic law at given temperature range. As a whole, because the values of time exponent (n) have approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by volume diffusion over the temperature range studied. The apparent activation energies of Cu$_{6}$Sn$_{5}$ and Ni$_3$Sn$_4$ intermetallic compound in the couple of the Sn-58Bi/Cu and Sn-58Bi/electroless Ni-P were 127.9 and 81.6 kJ/mol, respectively.ely.

• 한국재료학회지
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• 제33권3호
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• pp.101-105
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• 2023

A mixture of elemental Co₅₀Si₅₀ powders was subjected to mechanical alloying (MA) at room temperature to prepare a CoSi thermoelectric compound. Consolidation of the Co₅₀Si₅₀ mechanically alloyed powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 800 ℃ and 1,000 ℃ under 50 MPa. We have revealed that a nanocrystalline CoSi thermoelectric compound can be produced from a mixture of elemental Co₅₀Si₅₀ powders by mechanical alloying after 20 hours. The average grain size estimated from a Hall plot of the CoSi intermetallic compound prepared after 40 hours of MA was 65 nm. The degree of shrinkage of the consolidated samples during SPS became significant at about 450 ℃. All of the compact bodies had a high relative density of more than 94 % with a metallic glare on the surface. X-ray diffraction data showed that the SPS compact produced by sintering mechanically alloyed powders for 40-hours up to 800 ℃ consisted of only nanocrystalline CoSi with a grain size of 110 nm.

• 한국재료학회지
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• 제11권12호
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• pp.1063-1067
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• 2001

The effect of the pulse parameters(pulse ratio and frequency) on the characteristics of the nitrided layer in the pulsed plasma nitrified SCM435 Steels was investigated. Material properties of the nitrided layer were analysed by employing optical microscope, scanning electron microscope(SEM), X-ray diffractometer(XRD) and micro-Vickers hardness tester. It was found that both the compound layer thickness and the surface hardness decreased with decreasing of pulse ratios. At high pulse ratio, the compound layer thickness and the surface hardness were rapidly decreased with decreasing frequency compared to lower pulse ratios.

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.111-113
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• 1996

Dielectric properties at microwave frequency region of the five-layered compound $Ba_5Nb_4O_{15}$ prepared by the conventional solid state reaction method were investigated. $Ba_5Nb_4O_{15}$ has excellent microwave dielectric characteristics; ${\varepsilon}_r$=38, Q=7500 at 10 GHz, and ${\tau}_l$=+50 ppm/K. Since this compound has a high dielectric constant, high Q and sufficiently stable characteristics, it is useful for the applications at microwave frequencies.