• 한국분말재료학회지
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• 제12권1호
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• pp.7-16
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• 2005

Dye-sensitized solar cells(DSSCs) have been under investigation for the past decade due to their attractive features such as high energy conversion efficiency and low production costs. The basis for energy conversion in the injection of electrons from a photoexcited stateof a dye sensitizer into the conduction band of the nanocrystalline $TiO_2$ semiconductor upon absorption of light. It is believed that the DSSC is one of the most promising technologies to solve the significant energy problems. In this article, the development trends and perspective of DSSCs were reviewed.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.585-586
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• 2006

Several chemicals were studied to suppress the damage due to stress corrosion cracking (SCC) of steam generator (SG) tubes in nuclear power plants. The effects on the SCC of the compounds, $TiO_2$, TyzorLA and $CeB_6$, were tested for several types of SG tubing materials. The test with the addition of $TiO_2$ and $CeB_6$ showed an effect in decreasing the SCC for the SG tubing material. However, $CeB_6$ caused some more SCC for Alloy 800. The penetration property into a crevice of the inhibitors was investigated by using Alloy 600 specimens with different gap.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2004년도 International Symposium on Powder Materials and Processing
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• pp.55-55
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• 2004

• 한국재료학회지
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• 제20권3호
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• pp.142-147
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• 2010

Nano-sized $BaNd_2Ti_5O_{14}$ powders were prepared by the spray pyrolysis process. Sucrose used as the organic additive enabled the formation of nano-sized $BaNd_2Ti_5O_{14}$ powders. The powders prepared from the spray solution without sucrose had a spherical shape, dense structure and micron size before and after calcination. However, the precursor powders prepared from the spray solution with sucrose had a large size, and hollow and porous morphology. The precursor powders had an amorphous crystal structure because of the short residence time of the powders inside the hot wall reactor. The complete decomposition of sucrose did not occur inside the hot wall reactor. Therefore, the precursor powders obtained from the spray solution with sucrose of 0.5M had a carbon content of 39.2wt.%. The powders obtained from the spray solution with sucrose of 0.5M had a slightly aggregated structure of nano-sized primary powders of $BaNd_2Ti_5O_{14}$ crystalline phase after calcination at $1000^{\circ}C$. The calcined powders turned into nano-sized $BaNd_2Ti_5O_{14}$ powders after milling. The mean size of the $BaNd_2Ti_5O_{14}$ powders was 125 nm.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2000년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.11-11
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• 2000

Large-size ceramic/metal bulk FGMs have been fabricated on a recently developed and the world's largest Spark Plasma Sintering(SPS) systems, As a part of the development program for practical production processes and machines for FGMs by SPS, the processes, mechanical properties, dimensional size and shape effects, and production machine systems were investigated. In the past, $ZrO_{2}$/TiAI, $ZrO_{2}$/Ni, $Al_{2}O_{3}$/Ti, WC/Co, WC/Co/Steel, A1/P, Polymide, Cu/Polymide, nano-composites, porous and other combinations of bulk FGMs have already been processed using SPS. However, most of the specimen sizes were small, in a range of 20 to 30mm in diameter. Recently disk-shape sintered compacts with diameters of 100 and 150 mm, and thickness of approximately 15 and 17 mm, $ZrO_{2}$(3Y)/ stainless steel FGMs were homogenous consolidated in a shorter sintering time, while maintaining high quality and repeatability by utilizing a temperature gradient sintering method. The SPS heating up and holding time totaled less than one hour. Therefore, the SPS process in expected to find increased use in the fabrication of large-size FGMs as a new industrial processing technology. This paper introduces SPS systems, the processing principles, features and the characteristies of ceramic/metal bulk FGM.

• 한국세라믹학회지
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• 제36권11호
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• pp.1252-1260
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• 1999

The defect chemistry and electrical characteristics of the grain boundaries of semiconducting SrTiO3 ceramics synthesized with wet-chemically surface-coated powders were investigated. The starting powders were separated into groups of 1-10${\mu}{\textrm}{m}$ 10-20${\mu}{\textrm}{m}$ etc by sedimentation and sieving methods. Na+ ions were absorbed on the powder surfaces by wet chemical-treatment method. The width of the grain boundary ranged up to several nm and the intergranular materials was amorphous. The additives coated on the surface of the powders were observed to be present at the grain boundaries of the ceramics. The diffusion depth of the additives into grains was about 30nm for the SrTiO3 ceramics synthesized with 5w/o coated materials, The threshold voltage grain boundary resistance and boundary potential barrier of the ceramics increased from 0.67V/cm 2.27k$\Omega$ and 0.05eV to 80.9V/cm 13.0k$\Omega$ 1.44eV with increasing the amount of the additives from 0 to 5 w/o respectively .

• 한국재료학회:학술대회논문집
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• 한국재료학회 1997년도 한국재료학회 추계학술발표회
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• pp.17-17
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• 1997

• 한국세라믹학회지
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• 제25권3호
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• pp.231-236
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• 1988

$Al_2O_3$ 기지에 미치는 2차상의 영향을 알아보기 위하여 SiC 입자를 5~20vol.% 분산시키고 소결조제로서 $TiO_2$ 또는 RY_2O_3$를 2.5wt.%첨가하여 180$0^{\circ}C$, $N_2$분위기 중에서 90분간 상압소결 하였다. SiC함량이 증가함에 따라 소결체의 밀도는 감소하였지만 기계적 물성은 증가하여 $Y_2O_3$를 소결조제로 첨가한 경우, 꺾임강도는 525MPa, 경도는 17.1GPa,파괴인성은 4.1 MPa.$m^{1/2}$ 정도의 최고값을 나타내었고 반면 $TiO_2$를 소결조제로 첨가한 경우 꺾임강도 285MPa , 경도 12.1GPa 정도의 값을 나타냈다. 그리고 이와 같은 기계적 물성의 증진은 주로 SiC의 복합화에 따른 균열의 편향과 $Al_2O_3$ 의 입자성장억제효과에 의한 것으로 밝혀졌다.

• 한국결정성장학회지
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• 제30권3호
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• pp.103-109
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• 2020

La₂O₃ 첨가량에 따른 결정상 및 미세구조 변화와 유전특성과의 상관관계에 대해 연구하였다. 고상반응법을 이용해 합성된 0.3 mol% TiO₂ 과잉 BaTiO₃ 분말에 대해 La₂O₃ 첨가량을 다르게 첨가하여 1250℃에서 2시간 동안 소결되었다. 상온에서 측정된 XRD는 La₂O₃ 첨가량이 증가함에 따라 lattice parameter가 변화하였고, 정방정비가 감소하였다. 이는 La³⁺가 Ba²⁺ 자리에 치환되어 정방정상의 불안정성을 높여 입방정상으로 상전이 된 것으로 설명할 수 있다. La₂O₃ 첨가량이 증가할 때, 임계입자성장구동력(Δg_c)이 최대 입자성장구동력 (Δg_max)보다 높아져, 입자크기와 밀도가 감소하였다. 유전상수는 La₂O₃가 증가함에 따라 감소하였는데, 이를 결정상 및 미세구조의 변화에 대한 효과로 분석하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 추계학술강연 및 발표대회
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• pp.8-8
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• 2002

TiC core/(Ti,Mo)C rim structure in TiC-$Mo_2C$-Ni base cermet which is generally prepared by sintering below 145$0^{\circ}C$ had been believed to be generated by the solid diffusion of Mo atoms 1 into TiC grains (D. Moskowitz and M.Humenik, 1r.:1966). Afterward, it was clarified that the c core/rim structure is generated by solution/re-precipitation mechanism : (1) $Mo_2C$ grains and s small TiC grains dissolve into the Ni liquid, (2) the dissolved Mo, Ti and C atoms migrate to the s surface of TiC coarse grains, (3) the Mo, Ti and C precipitate on the surface of TiC coarse g grains and form (Ti,Mo)C solid solution rim, and (4) the Ostwald ripening (grain growth by s solution/re-precipitation mechanism) of TiC-core/(Ti,Mo)-rim grains continues, and thus the w width of (Ti,Mo)C rim (at the same time, the grain size) increases with sintering time, etc. ( (H.Suzuki, K.Hayashi and O.Terada: 1973). The TiC-core was found not to disappear even by s sintering at 190$0^{\circ}C$ (ibid.: 1974) Recently, FeSi core/$Fe_2Si_5$-rim structure in Fe-66.7at%Si thermoelectric aIloy was found to also h hardly shrink and disappear by long heating at an appropriate temperature (1999: M.Tajima and K K.hayashD. Then, the authors considered its cause, and clarified experimentaIly that the disappearance of FeSi-core/$Fe_2Ski_5$-rim structure could be attributed to the exhaustion of diffusion-contributable vacancies in core/rim structure (N.Taniguchi and K.Hayashi:2001). At p present, the authors and my coworker are investigating whether the non-disappearance of TiC c core can be explained also from the new hypothesis "Exhaustion of diffusion-contributable v vacancies in corelrim structure".ure".uot;.