• 한국분말재료학회지
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• 제25권3호
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• pp.240-245
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• 2018

This study focuses on the fabrication of a WC/Co composite powder from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere for the recycling of WC/Co hardmetal. Mixed powders are manufactured by mechanically milling the oxide powder of WC-13 wt% Co hardmetal scrap and carbon black with varying powder/ball weight ratios. The oxide powder of WC-13 wt% Co hardmetal scrap consists of $WO_3$ and $CoWO_4$. The mixed powder mechanically milled at a lower powder/ball weight ratio (high mechanical milling energy) has a more rapid carbothermal reduction reaction in the formation of WC and Co phases compared with that mechanically milled at a higher powder/ball weight ratio (lower mechanical milling energy). The WC/Co composite powder is fabricated at $900^{\circ}C$ for 6 h from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere. The fabricated WC/Co composite powder has a particle size of approximately $0.25-0.5{\mu}m$.

• 한국분말재료학회지
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• 제16권5호
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• pp.310-315
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• 2009

Ultra-fine TiC/Co composite powder was synthesized by the carbothermal reduction process without wet chemical processing. The starting powder was prepared by milling of titanium dioxide and cobalt oxalate powders followed by subsequent calcination to have a target composition of TiC-15 wt.%Co. The prepared oxide powder was mixed again with carbon black, and this mixture was then heat-treated under flowing argon atmosphere. The changes in the phase, mass and particle size of the mixture during heat treatment were investigated using XRD, TG-DTA and SEM. The synthesized oxide powder after heat treatment at 700$^{\circ}C$ has a mixed phase of TiO$_2$ and CoTiO$_3$ phases. This composite oxide powder was carbothermally reduced to TiC/Co composite powder by the solid carbon. The synthesized TiC/Co composite powder at 1300$^{\circ}C$ for 9 hours has particle size of under about 0.4 $\mu$m.

• 한국세라믹학회지
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• 제31권8호
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• pp.893-901
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• 1994

In this study, AlN powder of fine particle size and of high purity was synthesized by the carbothermal reduction-nitridation of monodisperse, spherical Al(OH)3 which had been prepared by sol-gel method using Al(O-sec-C4H9)3 as the starting material. Depending on the mixing order and kinds of reducing agents, the optimum condition for the preparation of AlN was determined as follows. AlN single-phase was produced by the carbothermal reduction-nitridation of (1) Benzene-washed Al(OH)3 and the reducing agent, carbon, which was mixed in a ball mill: for 5 hours at 140$0^{\circ}C$ under NH3 atmosphere; (2) The mixture prepared by hydrolysis of alkoxide solution into which carbon had been dispersed beforehand: for 5 hours at 135$0^{\circ}C$ ; (3) Al(OH)3 Poly(furfuryl alcohol) composite powder: for 2.5 hours at 135$0^{\circ}C$; (4) The mixture of Al(OH)3 and polyacrylonitrile: for 5 hours at 140$0^{\circ}C$. Addition of CaF2 increased the nitridation rate when carbon or polyacrylonitrile was used as the reducing agent; but it had no effect on the nitridation rate when furfuryl alcohol was used as the reducing agent.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.304-310
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• 1998

Carbothermal reduction has been one of the important processes for the production of ceramic raw materials such as silicon carbide, silicon nitride, boron carbide, etc. The process has also been one of several trials for the recovery of ZnO from ZnO-containing waste. It usually involves two consecutive steps: the evolution of Zn vapor and its oxidation with air. In this study a ZnO-containing raw material is reduced by carbon at $1250^{\circ}C$ and the evolved Zn vapor is oxidized with air, resulting in fine powders of ZnO. computer programs, THERMO and PYROSIM developed by MINTEK, are used to simulate the process thermodynamically and the results are compared with the experimental results. It is shown that the ZnO-containing raw material can be reduced and can form fine ZnO with the yield as high as 98.7% under a proper condition. Based on these results, a process is engineered for the production of ZnO in a rotary kiln at a rate of 3 tons/day. The produced ZnO powders show properties suitable to the usual applications in ceramic industries with a purity of > 95wt% and an average particle size of ∼3${\mu}m$.

• 한국세라믹학회지
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• 제43권9호
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• pp.582-587
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• 2006

Decomposition behavior of $ferro-Si_3N_4$was investigated with varying temperature and holding time in mud components for high temperature refractory applications. Porosities gradually increased with increasing temperature and holding time due to the carbothermal reduction of $Si_3N_4\;and\;SiO_2$. Silicon monoxide (SiO) as a intermediate resulted from evaporation of $Si_3N_4\;and\;SiO_2$ reacted with C sources to generate needle-like ${\beta}-SiC$ and Fe in $Si_3N_4$ acted as a catalyst in order to enhance growth of SiC grain with the preferred orientation. SiC generation yield increased with increasing holding time, all of the $Si_3N_4\;and\;SiO_2$ affected on SiC formation up to 2h. However, SiC generation was only dependent on residual $SiO_2$ over 2h, because the carbothermal reduction reaction of $Si_3N_4$ was no longer possible at that time.

• 한국세라믹학회지
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• 제43권9호
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• pp.552-557
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• 2006

A low temperature processing route for fabricating porous SiC ceramics by carbothermal reduction has been demonstrated. Effects of expandable microsphere content, sintering temperature, filler content, and carbon source on microstructure, porosity, compressive strength, cell size, and cell density were investigated in the processing of porous silicon carbide ceramics using expandable microspheres as a pore former. A higher microsphere content led to a higher porosity and a higher cell density. A higher sintering temperature resulted in a decreased porosity because of an enhanced densification. The addition of inert filler increased the porosity, but decreased the cell density. The compressive strength of the porous ceramics decreased with increasing the porosity. Typical compressive strength of porous SiC ceramics with ${\sim}70%$ porosity was ${\sim}13 MPa$.

• 한국세라믹학회지
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• 제44권6호
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• pp.331-337
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• 2007

High temperature reaction behaviors of various oxide materials (such as bauxite, pyrophyllite, mullite and fused silica powders) used in the refractory materials for tap-hole plugging of blast furnace were investigated with varying temperature in the carbon surrounding. Kinetics of carbothermal reduction of $SiO_2$ for forming SiC with high corrosion resistance were strongly dependent on it's crystalline phase. SiC generation yield increased with increasing catalyst amount in oxide regardless of generated SiO gas amount at temperature of $<1500^{\circ}C$. However, in case of fused silica over $1500^{\circ}C$, SiC generation yield was dominantly influenced by SiO amount without catalyst effect. Bauxite showed the most effective carbothermal reduction reaction, since bauxite have a large amount of catalyst and well-dispersed $SiO_2$ phase in oxide matrix.

• 한국재료학회지
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• 제13권10호
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• pp.677-682
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• 2003

SiC nanowires were synthesized by carbothermal reduction using metal catalysts. Synthesized nanowires had mean diameters of 30∼50 nm and several $\mu\textrm{m}$ length. The kind of catalysts affects form of SiC nanowire because of difference of growth mechanisms. These differences were made by catalyst's physical property and relative activities to the source gas. Ni acted a conventional catalyst of VLS growth mechanism. But, Case of Fe, SiC nanowire was grown by stable VLS growth mechanism without relation of growth conditions. SiC nanowire was grown by two step growth model using Cr catalyst. Conversion ratios to the SiC nanowire were increased with growth conditions. Case of Cr, conversion ratio was about 45% that was higher than other catalyst used. This high conversion ratio was obtained by the addition VS growth to radial direction on the as-grown nanowires.

• 한국재료학회지
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• 제33권12호
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• pp.530-536
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• 2023

The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiO_x materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO₂) was synthesized using TEOS as a starting material for the fabrication of such SiO_x through heating in a reduction atmosphere. SiO_x powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiO_x powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiO_x.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2000년도 추계학술발표강연 및 논문개요집
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• pp.152-152
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• 2000