실리콘 및 탄소 복합 열환원 반응을 이용한 페로실리크롬 합금철의 제조

김종호,정은진,이고기,정우광,유선준,장영철,Kim, Jong Ho,Jung, Eun Jin,Lee, Go-Gi,Jung, Woo-Gwang,Yu, Seon Jun,Chang, Young Chul 한국재료학회 2017 한국재료학회지 Vol.27 No.5

Fe-Si-Cr ferroalloy is predominantly produced by carbothermic reduction. In this study, silicothermic and carbothermic mixed reduction of chromite ore to produce Fe-Si-Cr alloy is suggested. As reductants, silicon and silicon carbide are evaluated by thermochemical calculations, which prove that silicon carbide can be applied as a raw material. Considering the critical temperature of the change from the carbide to the metallic form of chromium, thereduction experiments were carried out. In these high temperature reactions, silicon and silicon carbide act as effective reductants to produce Fe-Si-Cr ferroalloy. However, at temperatures lower than the critical temperature, silicon carbide shows a slow reaction rate for reducing chromite ore. For the proper implementation of a commercial process that uses silicon carbide reductants, the operation temperature should be kept above the critical temperature. Using equilibrium calculations for chromite ore reduction with silicon and silicon carbide, the compositions of reacted metal and slag were successfully predicted. Therefore, the mass balance of the silicothermic and carbothermic mixed reduction of chromite ore can be proposed based on the calculations and the experimental results.

Optimisation study for making aluminium nitride using an improved carbothermal reduction-nitridation process

Moon Soo Kang,Kwang Hee Shin,Dae Woong Kim,Su Jin Kim,Tam Tran,Myong Jun Kim 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.12

In order to obtain a high thermal conductivity, impurities such as oxygen and carbon should be removed from aluminiumnitride (AlN) during its synthesis using a carbothermal reduction-nitridation (CRN) process. In this study, AlN powders wereprepared under various conditions (1550-1750 oC, 0.5-4.0 hrs, nitrogen at 75-399 ml/min) using mixtures of alumina (Al2O3)and carbon black (C) at different molar ratios of 0.28 to 0.40. Residual carbon of the synthesized AlN powder was removedin a decarbonisation step using an electric furnace (600-900 oC, 0.5-4.0 hrs). The synthesis of AlN from alumina-carbon blackmixtures of Al2O3/C molar ratio of 0.31 (5% excess carbon black) at optimum conditions of 1700 oC for 3-4 hrs and airdecarbonisation (annealing) at 750 oC for 2 hrs produced product containing 385 ppm C and 0.62 wt% O2, lower than forcurrent commercial products.

Characterization of nanocrystalline porous SiC powder by electrospinning and carbothermal reduction

Kim, S.J.,Yun, S.M.,Lee, Y.S. Korean Society of Industrial and Engineering Chemi 2010 Journal of industrial and engineering chemistry Vol.16 No.2

Nanocrystalline porous silicon carbide (SiC) powder was prepared from various ratios with SiO<SUB>2</SUB> as silicon source and carbon black as carbon source by electrospinning method and subsequent carbothermal reduction. Their microstructure, thermal stability and porosity of prepared porous silicon carbide (SiC) powder were evaluated as function of Si to C ratios in precursor. 3C/Si could not often maintain the spherical form against oxygen-carbon reaction during calcination owing to relatively low carbon content. On the other hand, the uniformed spherical forms were presented with deep wrinkles in the other prepared samples. They were believed that the wrinkled surfaces were formed by vaporization of carbonaceous gas made from carbon and oxygen. When the carbon ratio to silicon (C/Si) was 5, the β-SiC was observed without remained silica and silicon metal. Further increase in the carbon content in the precursor led to sharp and high intensity of SiC peak. Initial decomposition temperature of prepared sample was increased with decreasing C/Si ratio. We confirmed that whereas 3C/Si and 4C/Si had higher big macropore, 5C/Si and 6C/Si had much large pore volume in the range of mesopore diameter (2-50nm) and small macropore (50-100nm).

Characterization of nanocrystalline porous SiC powder by electrospinning and carbothermal reduction

Sang Jin Kim,Seok-Min Yun,이영석 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.2

Nanocrystalline porous silicon carbide (SiC) powder was prepared from various ratios with SiO2 as silicon source and carbon black as carbon source by electrospinning method and subsequent carbothermal reduction. Their microstructure, thermal stability and porosity of prepared porous silicon carbide (SiC) powder were evaluated as function of Si to C ratios in precursor. 3C/Si could not often maintain the spherical form against oxygen–carbon reaction during calcination owing to relatively low carbon content. On the other hand, the uniformed spherical forms were presented with deep wrinkles in the other prepared samples. They were believed that the wrinkled surfaces were formed by vaporization of carbonaceous gas made from carbon and oxygen. When the carbon ratio to silicon (C/Si) was 5, the b-SiC was observed without remained silica and silicon metal. Further increase in the carbon content in the precursor led to sharp and high intensity of SiC peak. Initial decomposition temperature of prepared sample was increased with decreasing C/Si ratio. We confirmed that whereas 3C/Si and 4C/Si had higher big macropore, 5C/Si and 6C/Si had much large pore volume in the range of mesopore diameter (2–50 nm) and small macropore (50–100 nm).

Synthesis of Titanium Diboride and Composites by Carbothermic Reduction of Titanium Oxide and Boric Oxide

Yoon, Su-Jong,Jha, Animesh The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.4

The formation of titanium diboride ($TiB_2$ ) via the reduction of $TiO_2$ with boric oxide and carbon was studied in a partially reducing atmosphere of argon mixed with 4 vol.%H2. The effect of reaction time, temperature, partial pressure of nitrogen and $TiO_2/B_2_O3$ stoichiometric ratio on the reducibility of oxides has been studied. The phases formed were analysed by using X-ray rowder diffraction and scanning sosctron microscopic techniques. In this paper, we also investigated the presence of $CaC_2$ as a reducing agent on the reducibility of oxide mixtures and on the Ti-B-C-Ca-O phase equilibria. The morphology of $TiB_2$ formed in the presence of $CaC_2$ is compared with the microstructure of $TiB_2$ formed as a consequence of carbothermic reduction. The observed variation in $TiB_2$ crystals formed is also explained.

WC platelet formation via high-energy ball mill

Kim, J.,Kang, S. MPR Pub. Services 2014 International journal of refractory metals & hard Vol.47 No.-

This work investigates the factors affecting the morphology of WC powder. WO<SUB>3</SUB>-C mixtures were prepared by high-energy ball milling and nano-sized WC powder was obtained in the form of platelets with a high aspect ratio (5-20) carbothermally. We observed that the WC powder contains excess (101) plane along with high level of strain during initial heating stage. Further, the temperature for the platelet formation coincides with that for the reduction of (101) peak intensity in the XRD pattern. From this study we found that the presence of excess (101) plane and high strain promoted the formation of platelet WC effectively.

분무건조법에 의해 제조된 Ti-Co-O계 산화물 분말의 고체 탄소에 의한 환원/침탄

이길근,문창민,김병기 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.1

In the present study, the focus is on the analysis of carbothermal reduction of the titanium-cobalt-oxygen based oxide powder by solid carbon for the optimizing synthesis process of ultra fined TiC/Co composite powder. The titanium-cobalt-oxygen based oxide powder was prepared by the combination of the spray drying and desalting processes using the titanium dioxide powder and cobalt nitrate as the raw materials. The titanium-cobalt-oxygen based oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixture during carbothermal reduction were analysed using XRD and TGA. The synthesized titanium-cobalt-oxygen based oxide powder has a mixture of $TiO_2$ and $CoTiO_3$. This oxide powder was transformed to a mixed state of titanium car-bide and cobalt by solid carbon through four steps of carbothermal reduction steps with increasing temperature; reduction of $CoTiO_3$ to $TiO_2$ and Co, reduction of $TiO_2$, to the magneli phase($Ti_nO_{2n-1}$, n>3), reduction of the mag-neli phase($Ti_nO_{2n-1}$, n>3) to the $Ti_nO_{2n-1}$(2$\leq$n$\leq$3) phases, and reduction and carburization of the $Ti_nO_{2n-1}$(2$\leq$n$\leq$3) phases to titanium carbide.

WC/Co 초경 스크랩 산화물의 고체탄소에 의한 환원/침탄

이길근,하국현,Lee Gil-Geun,Ha Gook-Hyun 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.2

In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste $WC-8 wt.\%Co$ hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste $WC-8wt.\%Co$ hardmetal has a mixture of $WO_{3} and CoWO_{4}$. This oxide powder reduced at about $850^{\circ}C$, formed tungsten carbides at about $950^{\circ}C$, and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about $1100^{\circ}C$ by solid carbon under a stream of argon. The WC/Co composite powder synthesized at $1000^{\circ}C$ for 6 hours from oxide powder of waste $WC-8wt.\%Co$ hardmetal has an average particle size of $0.3 {\mu}m$.

Carbothermic Reduction of Oxide Powder Prepared from Titanium Dioxide and Cobalt Nitrate

Lee, Gil-Geun,Ha, Gook-Hyun The Japan Institute of Metals 2006 MATERIALS TRANSACTIONS Vol.47 No.12

<P>The carbothermic reduction of a titanium-cobalt-oxygen-based oxide powder was analyzed to understand the carbothermal reduction step of the spray thermal conversion process for the synthesis of titanium carbide/cobalt composite powder. The starting powder was prepared by the combination of the spray drying and desalting methods using titanium dioxide powder and cobalt nitrate. The synthesized oxide powders were mixed with carbon black, and then these mixtures were heat treated under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixtures during heat treatment were analyzed using XRD and TG-DTA. The synthesized oxide powders have a mixed phase structure of anatase-TiO<SUB>2</SUB> and CoTiO<SUB>3</SUB> phases without regard to the cobalt content. These composite oxide powders were carbothermally reduced to the titanium carbide/cobalt composite powder through four steps with increasing temperature; reduction of CoTiO<SUB>3</SUB>, reduction of anatase-TiO<SUB>2</SUB>, formation of titanium oxycarbide and formation of TiC from titanium oxycarbide. The titanium carbide formability increased with the increasing relative amount of the complex oxide, CoTiO<SUB>3</SUB>, in the titanium-cobalt-oxygen-based oxide powder.</P>

Carbothermal process-derived porous N-doped carbon for flexible energy storage: Influence of carbon surface area and conductivity

Sawant, Sandesh Y.,Cho, Moo Hwan,Kang, Misook,Han, Thi Hiep Elsevier 2019 Chemical engineering journal Vol.378 No.-

<P><B>Abstract</B></P> <P>A simple and scalable method to synthesize N-doped carbon (NC) based on a carbothermal reduction of a ZnO/carbon composite (ZCC) obtained from the decomposition of a zinc aniline nitrate complex is reported. The present study examined the effects of the structural characteristics of NC, such as electrical conductivity and surface area, more precisely without altering the other structural features of NC. A carbothermal reduction of ZCC allowed the production of hierarchically porous NC with a low sheet resistance of 0.432 kΩ □<SUP>−1</SUP> without any post-treatment with Zn nanorods as a valuable byproduct. The resulting NC exhibited ultra-high stability and rate capability, i.e., 100% stability after 200,000 cycles up to 300 A g<SUP>−1</SUP> with a high capacitance of 229 F g<SUP>−1</SUP> at 0.5 A g<SUP>−1</SUP>. The 288% increase in surface area with a similar % contribution from micro and mesopores and similar electrical conductivity increased the electrochemical charge storage capacity of NC by 266%. Similarly, NC materials possessing a similar surface area but a large difference in electrical conductivity resulted in a 1539% difference in charge storage capacity. Enhancement of both the surface area and electrical conductivity improved the capacitance of NC drastically to 4098% higher than the base product. A prototype flexible solid-state supercapacitor fabricated from the obtained NC delivered a very high areal capacitance of 363.6 mF cm<SUP>−2</SUP> (at 0.5 mA cm<SUP>−2</SUP>) with ultra-high stability (82%) even after 70,000 cycles (at 25 mA cm<SUP>−2</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> N-doped carbon (NC) with tunable properties is obtained using carbothermal method. </LI> <LI> Simultaneous production Zn nanotubes results in waste-free approach. </LI> <LI> Charge storage capacity of NC precisely studied against conductivity/surface area. </LI> <LI> High capacitance of 229 F/g with exceptional rate capability is observed for NC. </LI> <LI> Ultra-high stability is retained with flexible prototype solid state device. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>