종자 입정을 이용한 저전압용 ZnO 바리스터의 제조

강을손,성건용,김종희 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.4

Low-voltage ZnO-based varistors were made by seed grain method at various sintering conditions. Their microstructure and electrical properties were investigated and comlpared with those of the ZnO varistors made by a conventional method at the same sintering condition. During the sintering process, the added seed ZnO grain rapidly grew to be a gaint grain(above 500$\mu\textrm{m}$) provinding easy current path. Therefore the breakdown voltage was lowered as much as the order of 1/10-1/5 in comparison to that of the varistor made by a conventional method. But the grain size of the giant ZnO was little influenced by sintering condition, so the breakdown voltate was also little influenced. The weight loss was decreased by the addition of the seed grain, because the giant grain decreased the evaporation area. Therefore the nonobmic property of the specimen made by seed grain method was little influencedby sintering condition. In this research the low-voltage varistor made by seed grain method showed the least leakage current when sintered at 1150$^{\circ}C$ for zero hour.

$B_4C-SiC$ 복합체의 상압소결거동

김득중,강을손 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.7

The B4C-C system was investigated to gain an understanding of the sintering behaviors of B4C. In order to get sintered density of 97% TD, sintering temperature of 225$0^{\circ}C$ was necessary. Since such a high temperature operation is actually difficult on a commercial basis, our objective was to examine the possibility of decreasing the sintering temperature by adding SiC. The addition of SiC in B4C increases the sintering rate about at 210$0^{\circ}C$ and results in a fine microstructure with more than 98% relative density on 55 wt% B4C-40wt% SiC-5 wt% C composition. The probability of liquid phase sintering was investigated, but the evidences of liquid phase formation were not observed with XRD and TEM observation. It was proposed that the addition of SiC and carbon to B4C reduce interface energy during sintering, which results in enhanced grain-boundary diffusion. Thus, the enhanced grain-boundary diffusion and retarded grain growth by SiC improve densification.

기계적합금법에 의한 $\textrm{TiB}_2$ 분말의 제조 및 Zr과 Ta이 합성에 미치는 영향

황연,강을손,Hwang, Yeon,Kang, Eul-Son 한국재료학회 1999 한국재료학회지 Vol.9 No.8

기계적합금법으로 Ti와 B의 혼합분말로부터 $TiB_2$분말을 제조하였고, Zr과 Ta의 Ti 치환 효과를 조사하였다. (Ti+B)의 혼합분말을 280시간 분쇄하여 $TiB_2$단일상을 얻었고 기계적합금화 도중 비정질상은 관찰되지 않았다. Ti의 일부를 원자반경이 Ti보다 큰 Zr으로 치환한 결과 기계적합금화에 걸리는 시간이 크게 감소한 반면에, 붕화물 생성열이 절대값이 $TiB_2$상보다 작은 Ta로 치환하면 280시간 분쇄하여도 단일상을 형성하지 못하였다. TiB$_2$powders were prepared by mechanical alloying, and the effect of Zr and Ta substitution for Ti was investigated. It was possible to produce titanium diboride phase by mechanical alloying titanium and boron elemental powders for 280 hours. The amorphization reaction, a common process which occurs during mechanical alloying, has not been found. When zirconium of which atomic radius was larger than that of titanium was substituted for Ti, the alloying time was greatly reduced. On the contrary, substitution of tantalum for titanium prolonged the alloying time because of the less negative heat of formation of tantalum diboride than that of titanium diboride.

알루미나의 방탄특성에 대한 입경의 영향

백용기,강을손,정동익,최원봉 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.4

Two kinds of alumina specimens with different grain size (1 and 51 $\mu\textrm{m}$) but same density were prepared by hot-pressing. Fracture strength and fracture toughness of these specimens at low strain rate, sonic velocity, and elastic property were evaluated. Ballistic performance against Cal. 50 AP projectile was characterized by thick-backing method by using A16061-T6 reference block. Mechanical properties measured at low strain rate showed that the specimen with samll grain (SG) were better than specimen with large grain (LG). Fracture strength and fracture toughness of LG specimen were 131 MPa and 3.01 MPa{{{{ SQRT { m} }}, but those of SG specimen were 349 and 4.23, respectively. Sonic velocity and elastic properties of these specimen were similar, but bulk velocity and bulk modulus were different at amount of 4 and 9%. The tendency of ballistic performance was not consistent with the mechnaical properties at low strain rate. The ballistic performance based on quantitative efficiency revealed that the LG specimen (5.13) was ballistically better than the SG specimen (4.00) in spite of their lower mechanical properties.

초기분말의 결정상이 $Al_2O_3$를 소결 조제로한 고온가압 SiC 세라믹스의 기계적 특성에 미치는 영향

정동익,강을손,최원봉,백용기 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.3

Densification behavior, microstructural evolution, and mechanical properties of hot-pressed specimens using $\beta$-SiC and $\alpha$-SiC powder with Al2O3 additive were studied. Beta-SiC powder was fully densified as 205$0^{\circ}C$, but $\alpha$-SiC powder was at 210$0^{\circ}C$. The maximum flexural strength and the fracture toughness of the specimen hot-pressed using $\beta$-SiC powder were 681 MPa and 6.7 MPa{{{{ SQRT {m } }}, and thosevalues of specimen hot-pressed using $\alpha$-SiC powder were 452 MPa and 4.7 MPa{{{{ SQRT {m } }}, respectively. The strength superiority of specimen hot-pressed using $\beta$-SiC powder was due to the finer grain size, and higher density. The higher toughness of specimen hot-pressed using $\beta$-SiC powder than $\alpha$-SiC powder than $\alpha$-SiC powder was due to the crack deflection mechanism arised from the difference of thermal expansion coefficient between $\alpha$ and $\beta$-SiC phases which were co-existed in the sintered body.

ZnO-Bi2O3계의 소결초기단계와 입자성장에 관한 연구

성건용,강을손,김종희 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.4

The sintering behavior and grain growth of ZnO in 99.0mol% ZnO-1.0mol% Bi2O3 which are the basic compositions of ZnO varistor were studied. The microstructrual observation confirmed that the final sintered density was mainly determined at the initial stage of sintering, i.e. grain rearrangement and grain growth which were induced by the penetration of eutectic melts formed at eutectic temperature(74$0^{\circ}C$). But when the liquid penetration was terminated, the grain growth did not promote further densification. Activation energy of the grain growth of ZnO in the system of 99.0mol% ZnO-1.0mol% Bi2O3 was 44.8$\pm$1.8Kcal/mol.

TiB₂ 나노 입자의 연소합성 시 MgO 희석제가 미치는 영향

이병기,이종무,박제형,강을손,백승수,김도경,Lee, Byung-Ki,Lee, Jong-Moo,Park, Je-Hyeong,Kang, Eul-Son,Baek, Seung-Soo,Kim, Do-Kyung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.9

The effect of MgO diluents in combustion synthesis of $TiB_2$ nano particles was investigated. The reaction $TiO_2\;+\;B_2O_3\;+\;xMg\;{\rightarrow}\;TiB_2\;+\;5MgO$ was used to synthesize $TiB_2$ nano particles. The combustion velocity was measured to examine the relation between the reaction temperature and the morphologies of particles. The diluent MgO did not react with the reactants and played a role to decrease combustion temperature. As the MgO diluents contents increased, the particles with the smaller size and the narrower size distribution were synthesized. At the condition of 6 mole of MgO, the combustion wave velocity was about 5 cm/see and the synthesized particles showed the size of 60 nm with narrow size distribution.

철계 액상을 통한 붕화지르코늄의 소결

우상국,한인섭,김흥수,양준환,강을손,김종희 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.3

In the present study the effect of the addition of Fe on the pressureless and hot press sintering behavior was studied under Ar atmosphere. Pressureless sintering was performed 1900~220$0^{\circ}C$ under. Ar atmosphere. The addition of 1 wt% Fe was increased effectively of the sintered density. However it was impossible to obtain high density higher than 90%,. Zr-Fe-B compound in liquid phase was observed from the EDS and WDS analysis. It was considered that sinterability was enhanced due to the mass transfer through Fe based liquid phase formed at the sintering temperature. Hot pressing was performed at 1600~1$700^{\circ}C$ under Ar atmos-phere for 1 hr. It was possible obtain 95% relative density of ZrB2 specimen which is higher density at pressure-less sintering. It could be thought that ZrB2 particles was rearranged through liquid phase by applied pressure during initial stage of sintering.

Fabrication and Properties of Reactively Hot Pressed HfB2-HfC Ultra-High Temperature Ceramics

이승준,성영훈,백승수,강을손,김도경 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.6

HfB2-HfC composites were prepared by reactive hot pressing using Hf and B4C at temperatures of 1800 and 1900oC for 60 min under 32 MPa in an Ar atmosphere. The reaction sequences of the HfB2-HfC composite were studied through series of pressureless heat treatments ranging from 800 to 1600oC. The effect of size reduction of the starting powders on densification was investigated by vibration milling. Fully dense HfB2-HfC composites were obtained by size reduction of the starting powders via vibration milling. The oxidation behaviour of the HfB2-HfC composites at 1500oC in air showed formation of a non-protective HfO2 scale with linear mass gain. Examination of the mechanical properties showed that particle size reduction via vibration milling also led to improved flexural strength, hardness and fracture toughness.

TiB2 나노입장의 연소합성 시 MgO 희석제가 미치는 영향

박제형,김도경,이병기,이종무,강을손,백승수 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.9

The effect of MgO diluent in combustion synthesis of TiB2 nano particles was investigated. The reaction TiO2 + B2O3 + xMg → TiB2 + 5MgOwas used to synthesize TiB2 nano particles. The combustion velocity was measured to examine the relation between the reaction temperature and the morphologies of particles. The diluents MgO did not react with the reactants and played a role to decrease combustion temperature. As the MgO diluents contents increased, the particles with the smaller size and the narrower size distribution were synthesized. At the condition of 6 mole of MgO, the combustion wave velocity was about 5 cm/sec and the synthesized particles showed the size of 60 nm with narrow size distribution.