• 한국분말재료학회지
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• 제10권4호
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• pp.270-274
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• 2003

Recently, the fabrication process of W-Cu nanocomposite powders has been researched to improve the sinterability by mechanochemical process (MCP), which consists of ball milling and hydrogen-reduction with W- and Cu-oxide mixture. However, there are many control variables in this process because the W oxides are hydrogen-reduced via several reduction stages at high temperature over 80$0^{\circ}C$ with susceptive reduction conditions. In this experiment, the W-15 wt%Cu nanocomposite powder was fabricated with the ball-milling and hydrogen-reduction process using W and CuO powder. The microstructure of the fabricated W-Cu nanocomposite powder was homogeneously composed of the fine W particles embedded in the Cu matrix. In the sintering process, the solid state sintering was certainly observed around 85$0^{\circ}C$ at the heating rate of 1$0^{\circ}C$/min. It is considered that the solid state sintering at low temperature range should occur as a result of the sintering of Cu phase between aggregates. The specimen was fully densified over 98% for theoretical density at 120$0^{\circ}C$ for 1 h with the heating rate of 1$0^{\circ}C$/min.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.292-293
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• 2006

$ZnNb_2O_6$ ceramics were sintered under the presence of zinc-borosilicate(ZBS) glass and resultant microwave dielectric properties were investigated with a view to applying the composition to LTCC technology. The addition of 10~30 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. In general, increased addition of ZBS glass increased sinterability but it decreased the dielectric properties significantly due to the formation of an excessive liquid and second phases. The sintered $ZnNb_2O_6$ ceramics at $900^{\circ}C$ with 25 wt% ZBS glass demonstrated 15.8 in dielectric constant(${\varepsilon}_r$), 5,400 in quality factor($Q{\times}f_0$), and $-98\;ppm/^{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_f$).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.313-314
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• 2006

$BiNbO_4$ ceramics were sintered under the presence of zinc-borosilicate(ZBS) glass and resultant microwave dielectric properties were investigated with a view to applying the composition to LTCC technology. The addition of 5~20 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. In general, increased addition of ZBS glass increased sinterability and temperature coefficient of resonant frequency(${\tau}_f$), but it decreased the dielectric constant(${\varepsilon}_r$) and quality factor($Q{\times}f_0$) significantly due to the formation of an excessive liquid. The sintered $BiNbO_4$ ceramics at $900^{\circ}C$ with 15 wt% ZBS glass demonstrated 25 in dielectric constant(${\varepsilon}_r$), 3,700 in quality factor($Q{\times}f_0$), and -32 $ppm/{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_f$).

• 한국결정성장학회지
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• 제29권1호
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• pp.1-5
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• 2019

산화물을 포함한 세라믹 재료의 물성은 소재 치밀도에 크게 영향을 받는다. 따라서 소재 치밀도를 높이기 위한 다양한 노력들이 진행되어왔다. 이중 많이 사용되는 전략으로 재료 소결 시 소결조제를 첨가하는 것이다. 기존의 소결조제는 3차원 구조를 갖는 구형의 분말이었다. 본 연구에서는 차별화 전략으로 세륨산화물의 소결 밀도를 높이기 위해 2차원 층상구조를 갖는 소결조제를 첨가하였다. 실제로 2차원 층상구조의 조결조제에 의해 소결밀도가 증가되는 것을 확인할 수 있었다. 2차원 층상구조 소재로 초나노 두께(~1 nm)를 갖는 $TiO_x$와 $MnO_x$ 나노쉬트가 이용되었다.

• 한국분말재료학회지
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• 제29권5호
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• pp.357-362
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• 2022

The low-temperature sinterability of TiO₂-CuO systems was investigated using a solid solution of SnO₂. Sample powders were prepared through conventional ball milling of mixed raw powders. With the SnO₂ content, the compositions of the samples were Ti_1-xSn_xO₂-CuO(2 wt.%) in the range of x ≤ 0.08. Compared with the samples without SnO₂ addition, the densification was enhanced when the samples were sintered at 900℃. The dominant mass transport mechanism seemed to be grain-boundary diffusion during heat treatment at 900℃, where active grain-boundary diffusion was responsible for the improved densification. The rapid grain growth featured by activated sintering was also obstructed with the addition of SnO₂. This suggested that both CuO as an activator and SnO₂ dopant synergistically reduced the sintering temperature of TiO₂.

• 열처리공학회지
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• 제36권4호
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• pp.206-214
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• 2023

Tungsten carbide has many industrial applications due to its high electrical and thermal conductivity, high melting temperature, high hardness and good chemical stability. Because tungsten carbide is difficult to sinter, it is sintered with nickel or cobalt as a binder and is currently used in nozzles, cutting tools, and molds. Alumina is reported to be a viable binder for tungsten carbide due to its higher oxidation resistance and lower cost than nickel and cobalt. The ultrafine tungsten carbide-graphene-alumina composites were rapidly sintered in a high frequency induction heating active sintering unit. The microstructure and mechanical properties (fracture toughness and hardness) of the composites were investigated and analyzed by Vickers hardness tester and electron microscope. Since the high-frequency induction heating sintering method enables high-speed sintering, ultrafine composites can be prepared by preventing grain growth. In the tungsten carbide-graphene-alumina composites, the grain size of tungsten carbide increased with the amount of alumina participation. The hardness and fracture toughness of the tungsten carbide-5% graphene- x% alumina (x = 0, 5, 10,15) composites were 5.1, 8.6, 8.6, and 8.4 MPa-m^1/2 and 2384, 2168, 2165, and 2102 kg/mm², respectively. The fracture toughness increased without a significant decrease in hardness. Sinterability was improved by adding alumina to tungsten carbide-graphene.

• 한국분말재료학회지
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• 제31권2호
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• pp.146-151
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• 2024

Pure SnO₂ has proven very difficult to densify. This poor densification can be useful for the fabrication of SnO₂ with a porous microstructure, which is used in electronic devices such as gas sensors. Most electronic devices based on SnO₂ have a porous microstructure, with a porosity of > 40%. In pure SnO₂, a high sintering temperature of approximately 1300℃ is required to obtain > 40% porosity. In an attempt to reduce the required sintering temperature, the present study investigated the low-temperature sinterability of a current system. With the addition of TiO₂, the compositions of the samples were Sn_1-xTi_xO₂-CoO(0.3wt%)-CuO(2wt%) in the range of x ≤ 0.04. Compared to the samples without added TiO₂, densification was shown to be improved when the samples were sintered at 950℃. The dominant mass transport mechanism appears to be grain-boundary diffusion during heat treatment at 950℃.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.58-65
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• 2005

The $LaCrO_3$-dispersed Cr alloys for metallic interconnect of solid oxide fuel cell were prepared as a function of $LaCrO_3$ content in the range of 5 to 25 vol.% and were sintered at 1500$^{\circ}C$ under an Ar atmosphere with 5 vol.% $H_2$. The sintering and oxidation behaviors of these alloys were examined. The alloys indicated a good sinterability above 95% relative density at a given sintering condition, and their sintering densities is independent on $LaCrO_3$ content. The $LaCrO_3$ particles of the sintered alloys were concentrated on interfaces of Cr particles, and the size of the Cr particles increased with decreasing $LaCrO_3$ content, which is caused by inhibited grain growth of Cr particle by $LaCrO_3$ particle. The oxidation test showed all $LaCrO_3$-dispersed Cr alloys have good oxidation resistance as compared with pure Cr, which is attributed to presence of $LaCrO_3$ at the interface at which the oxidation reaction occurs rapidly. The Cr alloys with about 15 vol.% $LaCrO_3$ are very resistant to oxidation.

• 한국결정성장학회지
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• 제7권3호
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• pp.481-486
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• 1997

국산 하동고령토로부터 AlSiCa의 주원료인 $Al_2O_3$-SiC계 내화물 원료를 합성하는 데는 성공하였으며, 합성된 $Al_2O_3$-Sic 합성분말의 산화반응을 검토하였다. 공기중에서 산소와 반응시켜 Sic가 $SiO_2$로 산화될 때 필요한 활성화 에너지는 $\Delta$G=74.86 KJ/mol 이었으며, 수소분위기에서 $1500^{\circ}C$ 및 $1600^{\circ}C$에서 상압소성한 결과 vaporization 현상때문에 소결특성이 좋지 않았다. whisker-SiC상태로 합성되는 이 복합체는 AlSiCa의 고온내화벽돌이외의 고온구조용 재료로 응용될 수도 있다.

• 한국세라믹학회지
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• 제55권6호
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• pp.570-575
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• 2018

Hydroxyapatites (HAps) were synthesized using the powdered waste of fishery products, i.e., fish scales and crab shells, as starting materials. HAp was synthesized by a wet-chemistry method followed by calcination at 600 and $800^{\circ}C$. Calcined crabshell powder revealed a single HAp phase and fine powder, while calcined fish-scale powder showed a ${\beta}-TCP$ secondary phase, even at the higher calcination temperature. Dense HAp pellets were obtained from the crab-shell powder by spark plasma sintering at $1000^{\circ}C$ for 10 min under applied pressures of 40 and 80 MPa in a vacuum state, giving sample densities of 2.93 and $3.06g/cm^3$, respectively. The estimated grain size of HAp was $448{\pm}96$ and $283{\pm}59nm$ for applied pressures of 40 and 80 MPa, respectively. In contrast, the HAp obtained using the pressureless sintering technique showed excessive grain growth without further densification.