• 한국수소및신에너지학회논문집
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• 제18권3호
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• pp.250-255
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• 2007

Hydrogen storage properties of $Ti_{0.32}Cr_{0.43-X}V_{0.25}M_X$($0{\leq}X{\leq}0.1$, M=Fe, Mn, Si) have been investigated. With varing of Mn content, the lattice parameter of the alloy was unchanged and similar to that of $Ti_{0.32}Cr_{0.43}V_{0.25}$ alloy. With increase of Fe, Si content, the lattice parameters of the BCC phases decreased. When the Fe content was 8 at%, the desorption plateau pressure increased to several atmospheres without decrease of the effective hydrogen storage capacity of the alloy. When the Mn content was 8 at%, the effective hydrogen storage capacity showed approximately 2.5 wt% without change in the desorption plateau pressure. With increase of Si content, hysteresis increased and hydrogen storage capacity decreased rapidly. A study was also made on how desorption temperature affected the usable hydrogen of the $Ti_{0.32}Cr_{0.35}V_{0.25}Mn_{0.08}$ alloy. The temperature was varied from 293 to 413 K, and the pressure from 5 to 0.002 MPa. The usable hydrogen of the alloy was 2.7 wt% when absorbed and desorbed at 293 K and 373 K., respectively. The heat of hydride formation of the alloy was approximately -35.5 kJ/mol $H_2$.

• 한국진공학회지
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• 제17권2호
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• pp.117-121
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• 2008

탄소계열의 SiOC 박막은 화학적 증착방법으로 bistrimethylsilylmethane와 산소의 혼합개스를 사용하여 증착하였다. SiOC 박막의 화학적인 특성은 FTIR 분석을 이용하였으며, I-V 측정법을 이용하여 비교하였다. $950\sim1200\;cm^{-1}$ 영역에서 생기는 결합들은 Si-C 결합, Si-O-C 결합과 Si-O 결합으로 이루어졌으며, SiOC 박막의 누설전류는 탄소함량이 증가함에 따라서 증가하였다. 그리고 누설전류는 Si-O-C 결합의 함량과 유사한 경향성을 나타냈다. FTIR 분석에서 디컨벌류션한 데이터는 SiOC 박막이 3가지 특성이 있는 것을 확인할 수 있었으며, 접촉각은 이러한 3가지 유형에 대한 차이점을 보여주었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2008년도 제35회 하계학술대회 초록집
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• pp.121-121
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• 2008

• 한국세라믹학회지
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• 제29권5호
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• pp.347-356
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• 1992

Various kaolin samples with different alumina content were prepared from calcined admixture of kaolin and ammonium sulfate by varying the treatment time in sulfuric acid. Samples were nitridated under N2 or N2-H2 atmosphere with changing the amount of added carbon, the reaction time and temperature. As the alumina content lowered, the size of kaolin particles decreased and the specific surface area increased. XRD analysis indicated that ${\alpha}$-quartz remained by decomposition of halloysite and meta-halloysite. Experimental results of nitridation behavior are summerized as follows; 1) Nitridation under N2 atmosphere. With the increase of C/SiO2 ratio and with the decrease of Al2O3 content, disappearance of XRD pattern peaks of mullite, ${\alpha}$-quartz and ${\alpha}$-Al2O3 were accelerated at 1300$^{\circ}C$. SiC was the main phase in the reaction product of acid-treated kaolin samples nitridated at 1300$^{\circ}C$ for 10 hours regardless of C/SiO2 ratio. But the XRD peak intensities of ${\beta}$-Si3N4, ${\beta}$-sialon and SiC did not show much difference when untreated raw kaolin was fired at the same condition. When the ratio of C/SiO2 was 3.5, ${\beta}$-sialon and ${\beta}$-Si3N4 existed in the reaction product of about 22% alumina containing kaolin sample fired at 1350$^{\circ}C$ for 7 hours. Only ${\beta}$-sialon existed in the same sample fired at 1400$^{\circ}C$ for 10 hours. ${\beta}$-sialon was obtained from all of the acid-treated kaolin samples fired at 1400$^{\circ}C$ for 40 hours, but AlN and SiC remained in the untreated kaolin sample. Z value of the ${\beta}$-sialon obtained from the 22% alumina containing kaolin sample fired at 1400$^{\circ}C$ for 40 hours was about 1.3(XRD) and 1.5(EDS). 2) Nitridation under 80N2+2OH2 mixed gas atmosphere with the C/SiO2 ratio of 1 Mullite was not found, but ${\alpha}$-Si3N4, and ${\beta}$-sialon were present in the reaction product of about 22% alumina containing kaolin sample fired at 1300$^{\circ}C$ for 10 hours. When untreated kaolin sample was nitridated at the same condition, mullite remained. AlN and SiC were not found in the reaction product of about 22% alumina containing kaolin sample fired at 1350$^{\circ}C$ for 5 hours. On the other hand, AlN and SiC remained in the product of untreated kaolin fired at the same condition.

• 한국세라믹학회지
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• 제49권4호
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• pp.325-327
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• 2012

Europium-doped $LaSi_3N_5$ phosphor was synthesized from LaSi/Si/$Si_3N_4/Eu_2O_3$ mixture by nitridation at $1390^{\circ}C$ and additional annealing at $1650^{\circ}C$ for 4 h. The phosphor shows emissions in the green light region with a maximum at 560 nm. With increasing europium content in the general formula $La_{1-z}Eu_zSi_3N_{5-z}O_{1.5z}$ from z = 0.01 to 0.06 there was a maximum emission for z = 0.04 followed by concentration quenching for the highest europium content (z = 0.06).

• The Korean Journal of Ceramics
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• 제1권2호
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• pp.101-105
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• 1995

Electrical discharge machinable $Si_3N_4$ was fabricated with the addtion of 20-60 vol% TiN by gas pressure sintering. Their sinterability, microstructure, mechanical and electrical properties were characterized as a function of the TiN content. The addition of TiN up to 20 vol% increased the flexural strength and fracture toughness as compared with those of the monolithic Si3N4. For the TiN content higher than 40 vol%, the electrical resistivity was lower than $1062\Omega$.cm. The $Si_3N_4$ with the addition of 40 vol% of TiN appears to have the optimum considerable sinterability, mechanical and electrical properties, and machinability. A microstructural analysis showed that the enhanced toughening was due to the crack deflection.

• 한국세라믹학회지
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• 제23권6호
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• pp.59-65
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• 1986

Flexural strength fracture toughness and strengthening mechanisms of cordierite ceramics reinforced by SiC whiskers up to 40vol% were investigated. The specimens were hot pressed at Ar atmosphere. The porosity increased with the SiC whisker content. Flexural strength and single edge notch beam fracture toughness were measured up to 1,000$^{\circ}C$. Extrapolating to zero porosity the reinforced composites exhibited in-creasings in flexural strength and fracture toughness with the SiC whisker content. The composites were strengthened mainly by load transfer crack impediment and partially by crack deflection mechanisms. Impurities played an important role in determining the mechanical properties of the composites.

• 한국세라믹학회지
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• 제35권2호
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• pp.129-136
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• 1998

The effects of MgO on the resistance to corrosion and oxidation of Al2O3-SiC-C refractory have been in-vestigated. The resistance to oxidation was improved as the amount of MgO increased. The resistance to corrosion was enhanced until 2 wt% MgO content but degraded over that content. From the dependence of temperatuer on the oxidation resistance oxidation was suppressed by the microstructural densification caused by spinel formation over 1200~130$0^{\circ}C$and the formation MgO-Al2O3-SiO2 liguid-phase over 130$0^{\circ}C$ The weight loss of specimens containing MgO with various purity at range of 95 to 99% and par-ticle size of -0.045 mm to -0.074 mm was examined. The oxidation resistance was not changed signficantly with the particle size and purity of MgO powders.

• 한국주조공학회지
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• 제30권6호
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• pp.205-209
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• 2010

This study evaluates the influence of strontium addition and holding time on mechanical properties for Al-10.5wt%Si-2wt%Cu secondary die-casting alloy and the measured electrical conductivity of modified alloys. A general improvement in the mechanical properties of the alloy was observed after adding the strontium. Ultimate tensile strength, elongation and electrical conductivity of modified alloys were improved by increasing strontium content and holding time. From these results, the optimal strontium content and holding time were identified on the mechanical properties of Al-10.5wt%Si-2wt%Cu secondary die-casting alloys.

• 한국세라믹학회지
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• 제29권2호
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• pp.127-135
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• 1992

It has been reported that natural petalite showed a low negative thermal coefficient and wide coefficient and wide coexisting region with liquid phase in Li2O-Al2O3-SiO2 system. Therefore, we investigated variation of microstructure and thermal and mechanical properties when the amount of SiO2 content in petalite compound and MgO addition to it compound were changed. As SiO2 content exceeded 80 wt%, crystal phases of $\beta$-cristobalite and $\beta$-spondumene solid solution were formed. Generally, the densification and bending strength were increased by the addition of MgO, but the positive thermal coefficient was found in the case of MgO 10 wt% addition because of second phase and glassy phase.