하동카올린으로부터 $\beta$-Sialon의 합성

이홍림,이형직 한국세라믹학회 1984 한국세라믹학회지 Vol.21 No.1

$eta$-Sialon synthesis was investigated via the simultaneous reduction and nitridation of Hadong Pink Kaolin using the graphite as a reducing agent at 135$0^{\circ}C$ under 80% $N_2-20%H_2$ atmosphere. When Hadong Pink Kaolin-graphite-silicon nitride seed(molar ratio ; $SiO_2:C:Si_3N_4$=1;3.5:0.05) mixture was heated at 135$0^{\circ}C$ for as long as 20h in 80%$N_2-20%H_2$ atmosphere a homogeneous $eta$-Sialon$(Si_{3.5}Al_{2.5}O_{2.5}N_{2.5})$ was mainly formed together with a small amount of $\alpha$-$Si_3N_4$.

완도납석으로부터 제조한 $\beta$-Sialon에 대한 SiC의 복합화 효과

이홍림,김신,이형직,Lee, Hong-Lim,Kim, Shin,Lee, Hyung-Jik 한국세라믹학회 1988 한국세라믹학회지 Vol.25 No.3

완도납석과 carbon black 의 혼합물을 135$0^{\circ}C$에서 질소분위기를 사용하여 탄소환원질화법으로 $\beta$-Sialon 분물에 $\beta$-SiC를 제2상으로 넣어서 $Y_2O_3$와 $ZrO_2$를 각 소결조제로 사용하여 175$0^{\circ}C$에서 2시간 동안 상압소결하였다. 10wt %의 $Y_2O_3$를 소결조제로 사용하였을 때에 파괴인성은 3.8MN/m^{3/2}$, 3점꺽임 강도는 470MN/$m^2$ 그리고 경도는 13.7MN/$m^2$로서 좋은 값을 나타내었다. 이와 같은 파괴인성과 꺽임강도의 증가는 균열편향과 균열나눠짐에 의한 것으로 생각된다. $\beta$-Sialon powder was prepared by the reduction-nitridation reaction from the mixture of Wando Pyrophyllite and carbon black at 135$0^{\circ}C$ in $N_2$ atmosphere. $\beta$-SiC powder was added to the prepared $\beta$-Sialon powder to make $\beta$-Sialon-SiC composite. The $\beta$-Sialon-SiC composites were sintered pressurelessly at 175$0^{\circ}C$ for 2h, using $Y_2O_3$ and $ZrO_2$(monoclinic) as sintering aids. Comparatively higher values of the fracture toughness (3.8 MN/㎥/2), M.O.R. (470 MN/$m^2$) and vickers microhardness (13.7 MN/$m^2$) were obtained when 10 wt% $Y_2O_3$ was added as a sintering aid. The improved fracture toughness and M.O.R. are assumed to be the results of crack deflection and crack branching by the second phase SiC particles.

Al-isopropoxide로부터 제조한 AlN 세라믹스의 기계적 성질과 미세구조에 미치는 산화물 첨가제의 영향

이홍림,황해진 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.6

In this study, effects of oxide additives on mechanical properties and microstructure of A1N and A1N polytype ceramics were investigated. Fine A1N powder was synthesized by nitriding alumiuim hydroxide prepared from Al-isopropoxide, at 1350$^{\circ}C$ for 10h in N2 atmosphere. By adding 3w/o Y2O3, 0.56w/o CaO, and 10w/o SiO2 to AlN powder, AlN and AlN polytype ceramics were prepared by hot-pressing under the pressure of 30 MPa at 1800$^{\circ}C$ for 1h. AlN ceramics with no additives formed considerable amount of AlON phase, while AlN ceramics doped with Y2O3 or CaO decreased AlON phase and formed Y-Al or Ca-Al oxide compound. AlN+10w/o SiO2(+3w/o Y2O3) composition produced AlON and AlN polytype compound having 21R as a major phase. Room temperature flexural strength of AlN ceramics with no additive was 246MPa, and room temperature flexural strength and critical temperature difference by thermal shock(ΔTc) of AlN ceramics dooped with Y2O3 or CaO were 532MPa/340$^{\circ}C$ and 423MPa/300$^{\circ}C$, respectively. Y2O3 and CaO used as sintering agent played roles of densification and oxygen removal of AlN ceramics, and affected grain growth/grain morphologies of AlN ceramics.

공침법으로 제조한 $ZrO_2$+3m/o $Y_2O_3$계 분체의 특성(II) : Y-TZP의 기계적 성질 및 미세구조에 미치는 $Al_2O3$와 $Cr_2O_3$의 첨가영향

이홍림,최동근,홍기곤,신현곤 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.4

The effects of Al2O3 and Cr2O3 addition on the mechanical properties and microstructures of Y-TZP ceramics obtained by co-precipitation method of ZrO2+3m/o Y2O3, following pressureless sintering at 150$0^{\circ}C$ for 2h were investigated. The addition of Al2O3 and Cr2O3 improved the Y-TZP sinterability and the Al2O3 addition showed the better effect on Y-TZP sintering than that of the Cr2O3 addition. The density and microstructure had the better effect on the bending strength of specimen more than stressinduced phase transformation (SIPT) of ZrO2 from tetragonal to monoclinic phase. The hardness of the specimens was found to be depend on the relative density and the fracture toughness of Y-TZP was found to rely on the amount of SIPT. The grian size of Cr2O3-doped Y-TZP was observed to be relatively smaller and had a narrower distribution than that of Al2O3-doped Y-TZP. If decomposition reaction of Cr2O3 can be controlled at high temperatures, it is anticipated that the mechanical properties of Y-TZP can be much improved by the Cr2O3 addition.

MgO.$nAl_2O_3$ 스피넬에 대한 증발속도의 측정으로부터 산소의 확산계수의 결정

이홍림,배철훈 한국세라믹학회 1983 한국세라믹학회지 Vol.20 No.2

MgO.$Al_2O_3$ polycrstalline spinel powder was subjected to vaporization over the temperature range of 1150-130$0^{\circ}C$ under H2 atmosphere. Diffusion coefficient of oxygen ion through the spinel were calculated using the measure vaporization rates as follows : D=28.4 exp(-901500/RT) Reference data of the vaporization rates of MgO.$8Al_2O_3$ single crystal spinel were applied to the vaporiza-tion model proposed in this study and were calculated to give the oxygen ion diffusion coefficients over the tempera-ture 1700-195$0^{\circ}C$. The obtained diffusion coefficients are as follows: $D=3.20{\times}106$ exp(-155600/RT)

Poling 강도 변화에 따르는 PZT 세라믹스의 강도와 균열성장 의존성

이홍림,권종오,한봉석 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.8

The dependence of strength, crack growth, fracture mode and degree of domain rearrangement of PZT ceramics on poling strength were studied. The PZT [(Pb0.94Sr0.06)(Zr0.46Ti0.54)O3+Nb(trace)] specimens were poled at 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 kv/mm, and the strength of the specimens was measured by 3 point flexure system. The bending strength of the specimen decreased in different modes according to the bending directions; xz, zx and yz plane direction with x axis of the poling direction in Cartesian coordinate system. The strength differences between the directions increased as the poling strength increased. The fracture mode transferred to intergranular fracture mode from transgranular one as the poling strength increased. The mechanical breakdown occurred when the poling strength higher than 3 kV/mm was applied to the specimen. It was observed that the crack length increased in the normal direction to the poling direction, however, decreased in the parallel direction to the poling direction when the poled PZT specimen was indented by the Vickers indenter. However, the crack produced by indentation continuously was continuously increased little by little after indentation on the specimen. The domain rearrangement occurred as the poling strength increased and the domains were rearranged more effectively when the electric field was continuously increased little by little.

알콕사이드로부터 Mullite분말의 합성 및 그 특성

이홍림,함종근 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.6

A very fine and pure mullite powder of the stoichiometric composition was prepared from aluminium isopropoxide and tetraethylorthosilicate by an alkoxide hydrolysis method using NH4OH as a catalytic agent. The gel powder obtained from the hydrolysis was calcined at 80$0^{\circ}C$ and 125$0^{\circ}C$. The average particle sizes of the powders calcined at 80$0^{\circ}C$ and 125$0^{\circ}C$ were 0.19${\mu}{\textrm}{m}$ and 0.25${\mu}{\textrm}{m}$, respectively. The specific surface areas of the powders calcined at 80$0^{\circ}C$ and 125$0^{\circ}C$ were 114.7$m^2$/g and 20.6$m^2$/g, respectively. The bending strength and fracture toughness of the mullite ceramics sintered at 1$650^{\circ}C$ were 263.1MPa and 2.30MPa.m1/2 respectively.

알루미나 세라믹스의 반복 피로 수명 예측을 위한 응력 모델

이홍림,박성은,한봉석 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.10

Cyclic fatigue experiment was carried out to predict the life time of alumina ceramics. Four kinds of model were suggested to obtain the adequate representative static stress corresponding to the cyclic stress applied to the alumina specimens. Arithmetic mean stress model gives 21.81 of the crack growth exponent, integrated stress model gives 22.15, maximum stress model gives 24.57, and equivalent static stress model gives 24.43. It is considered that the equivalent static stress model is the most reasonable and gives the best adequate crack growth exponents value.

벽돌과 내화벽돌(내화재료)의 발달사

이홍림 한국세라믹학회 2008 세라미스트 Vol.11 No.5

연구발표논문초록 : Si3N4 및 Sic 의 산화반응

이홍림,최태운,김창은 한국화학공학회 1981 춘계총회초록집 Vol.- No.-