• Journal of the Korean Ceramic Society
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• v.16 no.1
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• pp.26-30
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• 1979

The microstructures and memory core characteristics of substituted lithium ferrites with addition of $Bi_2O_3$, $V_2O_5$, $Nb_2O_3$, and $P_2O_5$ were investigated. The effects of composite flux on the sintering of the substituted lithium ferrites were also studied. The results show that the addition of $Bi_2O_3$, $V_2O_5$, and $Nb_2O_5$ enhances sintering whereas $Sb_2O_3$ and $P_2O_5$ inhibits it, and that the addition of $Nb_2O_5$ results in uniform grain size while the addition of $Bi_2O_3$ or $V_2O_5$ results in non-uniformity in grain size. When $P_2O_5$ was added with $V_2O_5$ or $Bi_2O_3$, however, it results in uniform grain size and improved memory core properties.

• Journal of the Korean Ceramic Society
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• v.28 no.10
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• pp.751-756
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• 1991

Continuous microstructural changes on heating of hardened paste prepared from primary clinker of CA2 composition was studied. On heating period, several characteristic shrinkages and microstructural changes took place in the specimen due to the dehydration and recrystallization of calcium aluminates without regard to the accelerative shrinkage resulted from sintering. Though micropores formed by dehydration decreased with recrystallization of calcium aluminates, micropores formed by plate-type gibbsite in the hydrates were maintained up to the temperature at which CA2 becomes main phase and had influence to the microstructure of the final clinker.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.691-697
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• 1989

Fine TiO2 and BaTiO3 powders having spherical particles were synthesized by ultrasonic spray pyrolysis of alcoholic solution of metal alkoxide in an electric furnace heated at 400-90$0^{\circ}C$. Microstructure and composition of particles synthesized were observed by TEM and XRD respectively. Spectific surface area of powders synthesized was examined through BET specific surface area measurement. TEM observation revealed that the particle size did not change irrespective of pyrolysis temperature but decreased according to the increase of concentration and spherical particle was consisted of primary particles of about 0.02${\mu}{\textrm}{m}$. As for BaTiO3 powder, the ratio of Ti/Ba was 0.987 by EDX analysis.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.46-52
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• 2004

AlSi-Al$_2$O$_3$ composite layer was prepared by plasma spray on steel substrate. The composite powder for plasma spray was prepared by simple mechanical blending. The wear resistance of the composite layers and matrix aluminum alloy were performed in terms of size distribution of ceramic particles. Friction coefficients of AlSi were decreased with incorporation of $Al_2$O$_3$. The tribological properties of coated layers were affected by the size of incorporated $Al_2$O$_3$ particle. The reinforcement of $Al_2$O$_3$ particle into aluminum alloy matrix decreased the friction coefficient as well as wear loss.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.464-470
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• 1996

Toughening mechanism of boron carbide ceramics by the addition of titanium boride was investigated. Speci-men was prepared by hot pressing of boron carbide with upto 30vol% of titanium boride particulates. Toughness of boron carbide ceramics was increased from 4.7 MPa m1/2 to 6.3 MPa m1/2 with 15 vol% TiB2 addition. But further increase of TiB2 content results in slow decrease of toughness. From microstructure evaluation and crack propagation behavior it is concluded that the major toughening mechanism is crack deflection pheno-mena.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.287-291
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• 2005

Pop-in deformation phenomena in aluminum was studied. Whether a pop-in occurs or not depended on the surface polishing method. Pop-in did not occur in aluminum which was polished mechanically, while it occurred in aluminum which was polished electrically. When pop-in occurred, elastic deformation preceded. Pop-in mechanism based on dislocation activity was suggested. Suggested mechanism was consistent with the result of microstructure analysis by Focused Ion Beam polisher (FIB) and Transmission Electron Microscopy (TEM).

• Journal of the Korean Ceramic Society
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• v.30 no.5
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• pp.347-356
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• 1993

In joining alumina ceramics to metal by using Mo-Mn metallizing process the effects of metallizing thickness, temperature, and the composition of paste on the bond strength and the microstructure of joining interface were investigated. The bond strength variation in the range of metallizing temperature, 1350~155$0^{\circ}C$ was more than 150MPa above 145$0^{\circ}C$ and the optimum metallizing thickness was 30${\mu}{\textrm}{m}$. The optimum contents of Mn in Mo-Mn paste was 5% due to the bond strength decrease with the increase of addition. The effect of SiO2 addition in paste on bond strength was saturated around 200MPa. It was also observed that as the particle size of Mo decreased, the joinning with higher bond strength was shown in spite of low metallizing temperature.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.264-272
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• 1998

The effect of catalytic condition on the properties of SiO2 aerogels has been investigated and then the dri-ed aerogels were partially densified to induce mechanical strength by heat treatment in order to prepare Type-VI silica by Sol-Gel method. Aerogel made by 1-step base process had the highest skeletal density lowest shrinkage and the smallest particle size. But in case of using acid catalyst in both 1st and 2nd step had the lowest skeletal density highest shrinkage and the largest particle size The aerogel synthesized by 1-step base process was most transparent because of its homogeneous microstructure. During heat treatments cracks occurred below 200$^{\circ}C$ for aerogel with the skeletal density lower than 1.9 g/cm3 but the with the higher skeletal density did not cracked up to 800$^{\circ}C$ shrinkage and skeletal density increased as heating temperature increased due to condensation and viscous sintering mechanism.

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.388-392
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• 2001

저압 화학증착법으로 등방성 흑연 기판 위에 탄화규소 증착층을 제조하였다. 반응관 내부의 전체 반응압력(이하 반응압력)을 1.5torr-100torr로 변화시켜 증착층의 미세구조에 미치는 영향을 조사하였다. 120$0^{\circ}C$ 이하에서는 전체 반응압력 변화에 상관없이 일정하게 낮은 증착속도를 보였으며, 미세구조는 round-top 구조를 나타내었다. 125$0^{\circ}C$, 10torr를 기준으로 증착온도와 반응압력이 증가함에 따라 미세구조가 round-top 구조에서 angular, faceted 구조로 변하였으며, 이는 반응압력이 증가함에 따라 증착기구가 표면반응에서 물질전달로 전이하였기 때문이다.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.941-948
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• 1994

An underwater grout on material resistance against segregation in water were studied by water soluble polymer (methyl cellulose and acrylic acid ester and styrene). The mechanical properties of the grout agents were investigated through the observation of the microstructure and application of fracture mechanic. When the soluble polymer MC+AAES added with 0.6 wt% to the underwater grout agents the compressive strength, flexural strength and Young's modulus were about 58 MPa, 10 MPa and 3.2 GPa respectively, and critical stress intensity was about 0.8 MNm-1.5. It can be considered that the strength improvement and fracture toughness increase may be due to the pore decrease and bonding force by material resistance against segregation in water.