• 기술사
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• 제20권4호
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• pp.5-11
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• 1987

The experiment was carried out for the purpose of studying the carburization of pure iron ingot and sintered iron powder by solid carbon in the atmosphere of $N_2$ gas. The velocity of carburization was estimated by the diffusion coefficient D calculated by carburization equation. The results obtained were as follows ; 1. The briqueted sample of iron fine powder which made by higher pressure, carburization depth and carbon concentration were increased as much, and pure iron shelved the maximum value. 2, The higher the carburization temperature, carburization depth and carbon concentration were increased, and the melting zone which had 3.0~3.3%C at the interface of carburization was formed at 130$0^{\circ}C$. As the pure iron ingot was carburized, the diffusion coefficient D of carbon were 0.211$\times$$10^{-6}$$\textrm{cm}^2$ㆍsec$^{-1}$ at 120$0^{\circ}C$ and 0.391$\times$$10^{-6}$$\textrm{cm}^2$ㆍsec$^{-1}$ at 130$0^{\circ}C$, respectively. 4. As the sintered iron powder was carburized at the pressure of 4 ton/$\textrm{cm}^2$, the diffusion coefficient of carbon were 0.157$\times$$10^{-6}$$\textrm{cm}^2$ㆍsec$^{-1}$ at 120$0^{\circ}C$ and 0.103$\times$$10^{-5}$$\textrm{cm}^2$ㆍsec$^{-1}$ at 130$0^{\circ}C$, respectively.

• 한국주조공학회지
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• 제8권3호
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• pp.287-295
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• 1988

The experiment was carried out for the purpose of studying the carburization of pure iron ingot and sintered iron powder by solid carbon in the atmosphere of CO gas. The volocity of carburization was estimaed by the diffusion coefficient D calculated by carburization equation. The results obtained were as follow: 1. The higher the carburization temperature, carburization depth and carbon concentration were increased, and the melting zone which had $2.8{\sim}3.4%C$ at the $3{\sim}4mm$ from interface of carburization was formed at $1300^{\circ}C$. 2. The main carburization mechanism of pure iron ingot and the sintered iron powder were proceeded by CO gas up to $1100^{\circ}C$, solid carbon over than $1300^{\circ}C$, respectively. 3. The main carburization mechanism of pure iron ingot at $1200^{\circ}C$ was proceeded by solid carbon, and sintered iron powder was proceeded bs CO gas, however, in case the reaction time, the carburization was proceeded by solid carbon over than 5hrs. 4. The diffusion coefficient D of carbon were $0.559{\times}10^{-6}cm^2.sec^{-1}$ at $1100^{\circ}C$, $0.237{\times}10^{-6}cm^2.sec^{-1}$ at $1200^{\circ}C$, $0.087{\times}10^{-6}cm^2.sec^{-1}$ at $1300^{\circ}C$, in case of pure iron ingot carburized. 5. The diffusion coefficient D of carbon were $0.124\;cm^2.sec^{-1}$ at $1100^{\circ}C$, $0.102\;cm^2.sec^{-1}$ at $1200^{\circ}C$, $0.480\;{\times}10^{-6}cm^2.sec^{-1}$ at $1300^{\circ}C$, in the case of sintered iron carburized at the pressuring $4ton\;/\;cm^2$.

• Mass Spectrometry Letters
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• 제7권4호
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• pp.102-105
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• 2016

This study explored the feasibility of using a carburization technique to enhance the ion intensity of isotopic analysis of ultra-trace levels of uranium using thermal ionization mass spectrometry (TIMS). Prior to fixing uranium samples on TIMS filaments, graphite powder suspended in nitric acid was deposited on rhenium filaments. We observed an enhancement of $^{238}U^+$ intensity by a factor of two when carburization was used, and were able to roughly optimize the amount of graphite powder necessary for carburization. The positive shift in heating current when evaporating filaments upon carburization implies that uranium was chemically altered by carburization, when compared to normal fixation processes. The good agreement between our method and known standards down to an ultra-trace level shows that the proposed technique can be applied to isotopic uranium analysis down to abundances of ~10 pg.

• 한국분말재료학회지
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• 제5권3호
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• pp.178-183
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• 1998

Ultrafine WC-10wt.%Co cemented carbides powders were synthesized by direct carburization. W-Co composite powders and carbon black powders were mixed by wet ball milling and dried. The mixed powders were heated to 800 $^{\circ}C$ with heating rate of 8.2$^{\circ}C$/min and held for various times in flowing $H_2$. For carbon addition of 140%, the carburization was completed by heating at 80$0^{\circ}C$ for 4 hours. The carburization time decreased with increasing amount of carbon and carburization was completed by heating at 800 $^{\circ}C$ for 2 hours with carbon addition of 150%. WC-10 wt%Co cemented carbides powders fabricated by direct carburization have nanoscale WC($\/leqq$100 nm) size.

• 한국세라믹학회지
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• 제45권7호
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• pp.387-394
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• 2008

The Physical property changes of calcined clay by carburization were investigated studied. The carburization mechanism is the penetration of carbon which occurred during incomplete fuel combustion into crevice of clay structure. The experiments for elasticity and freeze-thaw resistance were conducted, and the results can be summarized as follows: Dynamic modulus of elasticity and also freeze-thaw resistance of calcined clay by carburization treatment increased more than 92% after testing 300 cycle, which was more improved than 88% of calcined clay. Therefore, it can decrease the possibility of winter-sowing, which is one the weakness of calcined clay. It is on the basis of the fact that the porosity of calcined clay by carburization treatment is about 12%, which indicates smaller pore spaces comparing with the 14% of porosity of calcined clay and those values were calculated by apparent porosity show and also supported by SEM images. Infrared emissivity of calcined clay by carburization treatment and calcined clay were respectively 0.92 and 0.9l at $80^{\circ}C$. However, those values were 0.91 and 0.88 at $200^{\circ}C$, which means infrared emissivity of calcined clay by carburization treatment shows 3.6% higher than the calcined clay. Moreover, within the wavelength range from 3 to $7\;{\mu}m$, while the calcined clay had low infrared emissivity, the calcined clay by carburization treatment had increased infrared emissivity. It is inferred that it was affected by carbon element that has high infrared absorptivity within this wavelength range.

• 한국분말재료학회지
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• 제24권1호
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• pp.29-33
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• 2017

Titanium carbide (TiC) powders are successfully synthesized by carburization of titanium hydride ($TiH_2$) powders. The $TiH_2$ powders with size lower than $45{\mu}m$ (-325 Mesh) are optimally produced by the hydrogenation process, and are mixed with graphite powder by ball milling. The mixtures are then heat-treated in an Ar atmosphere at $800-1200^{\circ}C$ for carburization to occur. It has been experimentally and thermodynamically determined that the de-hydrogenation, "$TiH_2=Ti+H_2$", and carburization, "Ti + C = TiC", occur simultaneously over the reaction temperature range. The unreacted graphite content (free carbon) in each product is precisely measured by acid dissolution and by the filtering method, and it is possible to conclude that the maximal carbon stoichiometry of $TiC_{0.94}$ is accomplished at $1200^{\circ}C$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.1017-1020
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• 2008

콘크리트구조물에서의 탄산화 현상은 단독 또는 복합적으로 작용하고 사용환경의 조건에 따라 각각 상이한 탄산화 현상을 나타나게 된다. 이에 본 연구에서는 사용연수가 $10{\sim}60$여년이 경과되고 사용환경이 상이한 건축물과 토목구조물에 대하여 탄산화 깊이와 알칼리 농도를 측정하여 열화 정도를 판단하였다. 그 결과 건축물(옥내)은 외기에 노출된 토목구조물 보다 빠르고 해안가에 근접 할수록 열화현상이 심화된 것으로 나타났다. 또한, 공동구 또는 지하터널 보다는 하수암거의 용도로 사용하는 콘크리트구조물에서의 열화현상이 큰 것으로 조사되었다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.642-643
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• 2006

Direct reduction and carburization process was thought one of the best methods to make nano-sized WC powder. The oxide powders were mixed with graphite powder by ball milling in the compositions of WC-5,-10wt%Co. The mixture was heated at the temperatures of $600{\sim}800^{\circ}C$ for 5 hours in Ar. The reaction time of the reduction and carburization was decreased as heating temperatures and cobalt content increased. The mean size of WC/Co composite powders was about 260 nm after the reactions. And the mean size of WC grains in WC/Co composite powders was about 38 nm after the reaction at $800^{\circ}C$ for 5 hours.

• 열처리공학회지
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• 제20권2호
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• pp.65-71
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• 2007

Microstructural changes and hardness variations in STS 304 steel have been investigated during the processes of carbide dispersion (CD) carburization; carburization, austenitization, subzero treatment and tempering. The carbon content of the surface layer increased up to maximum 4.0% after carburization, and the content was homogenized with the value of 2.3% to the $95{\mu}m$ from the surface after austenitization. The carbide appeared during CD carburization process was $Cr_7C_3$ type, which was composed network carbides along the austenite grain boundaries, square type carbides in the interior of the grain and fine nano-sized carbides. The fine nano-sized carbides precipitated at the austenitization stage and possibly subzero treatment stage were coarsened after tempering at $200^{\circ}C$, resulting the hardness decrease. The tempered steel without subzero treatment increased hardness with increasing time due to the continuous precipitation of fine carbides during tempering. The nano-sized carbide appeared square type morphology.

• 한국재료학회지
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• 제23권5호
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• pp.293-298
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• 2013

In this study, an HP-mod. type(KHR-45A), which is used as a heater tube material in the pyrolysis process, was evaluated for its carburizing properties. It was confirmed from the microstructural observation of the tubes that the volume fraction of carbide increased and that the coarsening of Cr-carbide generated as a degree of carburization increased. The depth of the hardened layer, which is similar to the thickness of the carburized region of each specimen, due to carburization is confirmed by measurement of the micro-Vickers hardness of the cross section tube, which thickness is similar to that of the carburized region of each specimen. Two types of chromium carbides were identified from the EBSD (electron back-scattered diffraction) image and the EDS (energy-dispersive spectroscopy) analysis: Cr-rich $M_{23}C_6$ in the outer region and Cr-rich $M_7C_3$ in the inner region of tubes. The EDS analysis revealed a correlation between the ferromagnetic behavior of the tubes and the chromium depletion in the matrix. The chromium depletion in the austenite matrix is the main cause of the magnetization of the carburized tube. The method used currently for the measurement of the carburization of the tubes is confirmed; carburizing evaluation is useful for magnetic flux density measurement. The volume fraction of the carbide increased as the measuring point moved into the carburized side; this was determined from the calculation of the volume fraction in the cross-section image of the tubes. These results are similar to the trends of carburization measurement when those trends were evaluated by measurement of the magnetic flux density.