http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
MgO-Carbon 내화물의 산화반응기구와 TiC첨가에 의한 산화방지 효과
천승호,공현식,전병세,Cheon, Sungho,Kong, Hyunsik,Jun, Byungsei 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.9
The kinetics of oxidation and disappearance of graphite in MgO-C refractories containing TiC were, in the temperature range from 1000 to 1200$^{\circ}C$, investigated to enhance the oxdation resistance of MgO-C refractproes. The air was blown into the furnace at flow rate of 0.2 litters per minute, and then weight decrease was measured with a thermo balance at 30 seconds intervals until the value of weight became unchanged. The value of effective diffusion coefficient (De) for the specimen of MgO-C was 1.39${\times}$10$\^$-4/ ㎡/sec. The diffusion of oxygen through decarburized layer was the rate deforming step in the overall oxidation process under present experimental conditions. The TiC additions enhanced the oxidation resistance of the MgO-C refractories. 마그카본계 내화물의 산화저항성을 증대시키기 위하여 섭씨 100$0^{\circ}C$에서 120$0^{\circ}C$에서 산화기구를 조사하고, TiC를 첨가하여 산화저항성 증가에 대한 효과를 관찰하였다. 산소공급을 위해 공기를 분당 0.2리터의 속도로 흘려주었으며 열천칭으로 무게변화가 없어질 때까지 매 30초 간격마다 무게감소를 측정하였다 본 실험에서 사용된 마그카본계 시편의 산화거동과 관련한 유효확산 계수는 1.39${\times}$$10^{-4}$ $m^2$/sec이다. 이러한 실험조건에서 총체적인 산화공정은 산화된 기공층을 통하여 내부로 향하는 산소의 확산에 의해 지배되는 반응으로 해석할 수 있다. TiC를 첨가한 시편은 마그카본계 내화물의 산화 저항성을 증대시켰다.
Nitrided Pressureless Sintering 공정을 이용한 질화규소 세라믹스의 제조 및 특성
천승호,한인섭,정용희,서두원,이시우,홍기석,우상국,Cheon, Sung-Ho,Han, In-Sub,Chung, Yong-Hee,Seo, Doo-Won,Lee, Shi-Woo,Hong, Kee-Soeg,Woo, Sang-Kuk 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.12
Nitrided Pressureless Sintering(NPS) 공정에 의한 질화규소 세라믹스의 기계적 특성, 미세구조 및 열적 특성을 세 가지조성을 갖는 $Al_{2}O_3,\;Y_{2}O_3$ 소결조제의 변화에 따라 조사하였다. 또한 각 조성에서 금속 실리콘의 첨가량을 0, 5, 10, 15, 그리고 $20wt\%$로 변화를 주어 실리콘의 첨가효과를 조사하였다. $5wt\%\;Al_{2}O_3,\;5wt\%\;Y_{2}O_3$, 그리고 $5wt\%$ Si 조성에서 질화규소 소결체의 치밀화가 진행되었으며, 4점 꺽임강도와 상대밀도는 각각 500 MPa과 $98\%$를 나타내었다. 또한 상온에서 열팽창계수와 열전도도는 각각 $2.89{\times}10^{-6}/^{\circ}C$와 $28W/m^{\circ}C$를 나타내었으며, 20,000회의 열충격 싸이클을 반복한 후, 꺽임강도를 측정한 결과, 초기 500MPa의 강도를 유지하고 있었다. The mechanical properties and microstructure and thermal properties of Nitrided Pressureless Sintering(NPS) silicon nitride ceramics, containing three type of $Al_{2}O_3,\;Y_{2}O_3$ sintering additives, were investigated. Also, we have investigated the effect of silicon metal content changing with 0, 5, 10, 15, and $20wt\%$ Si in each composition. In $5wt\%\;Al_{2}O_3,\;5wt\%\;Y_{2}O_3,\;and\;5wt\%$ Si composition, silicon nitride sintered body was successfully densified to a high density. The average 4-point flexural strength and relative density of these specimens were 500 MPa and 98% respectively. Also, Thermal expansion coefficient and thermal conductivity of specimens at room temperature were $2.89{\times}10^{-6}/^{\circ}C\;and\;28W/m^{\circ}C$, respectively. The flexural strength of sintered specimens after thermal shock test of 20,000 cycles was maintained as-received value of 500 MPa.
입내 분산형 Al<sub>2</sub>O<sub>3</sub>/Ag 나노복합체의 제조와 특성
천승호,한인섭,히데오 아와지,Cheon, Sung-Ho,Han, In-Sub,Awaji, Hideo 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.4
Alumina/silver ($Al_2O_3/Ag$) nanocomposites with Ag content up to 9 vol% were prepared from nanopowder by soaking method using ${\gamma}-Al_2O_3$ of needle type and spark plasma sintering (SPS). The mechanical properties of specimens were investigated three-point flexural strength and toughness as a function of the Ag contents. The maximum flexural strength of the alumina/silver nanocomposite was 850 MPa for the 1 vol% composite, and also higher than monolith alumina as about 800 MPa at 3, 5, and 7 vol% Ag contents. Fracture toughness by single edged V-notch beam (SEVNB) was $4.05MPa{\cdot}m^{1/2}$ for the 3 vol% composite and maintained about $4.00MPa{\cdot}m^{1/2}$ at 5, and 7 vol% Ag content. Microstructure of fracture surface for each fracture specimens was observed. Due to the inhibition effect of alumina grain growth, the average grain size of nanocomposites depends on the content of Ag nano particles. The fracture morphology of nanocomposite with dislocation (sub-grain boundary) by silver nano-particles of second phases in the alumina matrix also showed transgranular fracture-mode compare with intergranular of monolith alumina. Thermal conductivity of specimens at room temperature was about 40 W/mK for the 1 vol% Ag content.
ρ-알루미나결합 알루미나 캐스터블의 용융슬래그에 의한 침식기구
천승호,전병세 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.10
$\rho$-알루미나 결합 진동성형용 알루미나 캐스터블 내화물의 매트릭스부분과 용응 슬래그와의 침식거동을 젭센(Jabsen)이 주장한 이론을 기초로 하고 킹거리(Kingery)가 제안한 반응 기구를 통해 규명하였다. 매트릭스 부분의 초기침식이 분자확산거동에 의하여 지배되며, 아레니우스 관계식과 잘 일치하고 있어 온도의존성 활성화 과정으로 받아들 수 있다. 슬래그와 경계층의 Ca 농도차이가 23.2%로서 경계층을 형성하기 위한 물질이동의 구동력이 되었다. 매트릭스의 침식정도가 뮬라이트 소결체보다 심하지만 킹거리의 침식반응 기구와 잘 일치하고 있어 캐스터블의 수명예측이 가능하다. The Corrosion behavior of the matrix of the $\rho$-alumina bonded alumina vibrated castable was, on the basis of Jabsen's theory, elucidated by use of the Kingery's reaction mechanism. Corrosion of the matrix during induction period was controlled by the molecular diffusion. The temperature dependence of activation process is well established by the Arrhenius plots. The difference of Ca concentration between slag and interface is 23.2%, which causes a driving force of the materials transfer. The extent of the corrosion of the matrix is more deeper than that of the sintered mullite, but the corrosion mechanism can be well employed as the reaction mechanism proposed by the Kingery. The life time of the castable may be well estimated by the corrosion mechanism of Kingery.
천승호,한인섭,히데오 아와지 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.4
Alumina/silver (Al2O3/Ag) nanocomposites with Ag content up to 9 vol% were prepared from nanopowder by soaking method using γ-Al2O3 of needle type and spark plasma sintering (SPS). The mechanical properties of specimens were investigated three-point flexural strength and toughness as a function of the Ag contents. The maximum flexural strength of the alumina/silver nanocomposite was 850MPa for the 1 vol% composite, and also higher than monolith alumina as about 800 MPa at 3, 5, and 7 vol% Ag contents. Fracture toughness by single edged V-notch beam (SEVNB) was 4.05 MPa·m 1/2 for the 3 vol% composite and maintained about 4.00MPa·m 1/2 at 5, and 7 vol% Ag content. Microstructure of fracture surface for each fracture specimens was observed. Due to the inhibition effect of alumina grain growth, the average grain size of nanocomposites depends on the content of Ag nano particles. The fracture morphology of nanocomposite with dislocation (sub-grain boundary) by silver nano-particles of second phases in the alumina matrix also showed transgranular fracture-mode compare with intergranular of monolith alumina. Thermal conductivity of specimens at room temperature was about 40W/mK for the 1 vol% Ag content.