• Journal of the Korean Ceramic Society
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• v.28 no.10
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• pp.785-792
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• 1991

An investigation of the crack propagation behavior of Al2O3-33Vol.% SiCw at 140$0^{\circ}C$ was conducted with various loading frequencies. Higher crack propagation was observed in lower frequency and higher load ratios. Interface sliding fracture due to glassy phase from the oxidation of SiCw and cavitation along grain boundary of diffusional creep appeared to be the main mechanism of fatigue fracture in slower crack propagation while interface sliding and whisker pull out aided by glassy phase formation played main role of fatigue fracture for higher crack growth condition. The frequency effect on deformation behavior was discussed with a Maxwell model.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.205.2-205.2
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• 2014

The effects of ion beam mixing of a SiC film coated on super alloys (hastelloy X substrates) were studied, aiming at developing highly sustainable materials at above $900^{\circ}C$ in decomposed sulfuric acid gas (SO2/SO3/H2O) channels of a process heat exchanger. The bonding between two dissimilar materials is often problematic, particularly in coating metals with a ceramics protective layer. A strong bonding between SiC and hastelloy X was achieved by mixing the atoms at the interface by an ion-beam: The film was not peeled-off at ${\geq}900^{\circ}C$, confirming excellent adhesion, although the thermal expansion coefficient of hastelloy X is about three times higher than that of SiC. Instead, the SiC film was cracked along the grain boundary of the substrate at above $700^{\circ}C$. At ${\geq}900^{\circ}C$, the film was crystallized forming islands on the substrate so that a considerable part of the substrate surface could be exposed to the corrosive environment. To cover the exposed areas and cracks multiple coating/IBM processes have been developed. An immersion corrosion test in 80% sulfuric acid at $300^{\circ}C$ for 100 h showed that the weight retain rate was gradually increased when increasing the processing time.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.132-136
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• 2007

Oxidation resistance of sintered ${\beta}-FeSi_{2}$ was investigated at intermediate temperature range in air atmosphere. Fully dense and porous bodies of ${\beta}-FeSi_{2}$ samples were fabricated by using the Spark Plasma Sintering (SPS). They were annealed at $900^{\circ}C$ for 5days to obtain ${\beta}-FeSi_{2}$ phase. The bulk samples were oxidized at $800,\;900\;and\;950^{\circ}C$ in air atmosphere. The high temperature oxidation tests reveal that amorphous $SiO_{2}$ layer, similar to Si was formed and grew parabolically on ${\beta}-FeSi_{2}$. Accelerated oxidation is not observed as well as cracks and grain boundary oxidation. Granular ${\varepsilon}-FeSi$ was developed below the oxide layer as a result of oxidation of ${\beta}-FeSi_{2}$. Oxidation resistance of sintered ${\beta}-FeSi_{2}$ was excellent for high-temperature thermoelectric application.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2181-2193
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• 1995

The effective elasticity and conduction of composite materials containing arbitrarily oriented multiple phases has been analyzed using the concept of orientation-dependent average fields and concentration factors. The analysis provided closed form expressions for the effective stiffnesses and conductivities. Under the prescribed boundary conditions, the concentration factors were evaluated by the equivalent inclusion principle, through which the interaction between various phases is approximated by the Mori-Tanaka mean-field approximation. SiC particulate(SiC$_{p}$) reinforce aluminum(Al) matrix composites were fabricated and their elastic constants and electrical conductivities were measured together with a careful study of their microstructure. The measured properties showed a systematic anisotropy and this behavior could be attributed to the preferred orientation of SiC$_{p}$. The theoretical model developed was applied to the computation of the anisotropic properties of these composites. Both two-phase and three-phase composites were considered based on the microstructural information. The SiC$_{p}$ was modeled as an ellipsoid with planar random orientation distribution in the extruded Al/SiC$_{p}$ composites. The effect of extraneous phase such as intermetallic compounds was also investigated.tigated.

• Journal of the Korean Magnetics Society
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• v.12 no.2
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• pp.41-45
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• 2002

The low-field tunnel-type magnetoresistance (MR) properties of sol-gel derived $La_{0.7}Pb_{0.3}MnO_3(LPMO)$ thin film deposited on different substrate have been investigated. Polycrystalline thin films were fabricated by spin-coating on $SiO_2/Si(100)$ substrate and that with yttria-stabilized zirconia (YSZ) buffer layer, while c-axis-oriented thim film was grown on $LaAlO_3(001)$ (LAO) single crystal substrate. The full width half maximum (FWHM) of the rocking curve scan of LPMO/LAO film is $0.32^{\circ}$. Tunnel-type MR ratio is 0.52 % in $LPMO/SiO_2/Si$(100) film and that of $LPMO/YSZ/SiO_2/Si$(100) film is as high as 0.68 %, whereas that of LPMO/LAO(001) film is less than 0.4 % under the applied field of 500 Oe at 300 K. Well-pronounced MR hysteresis was registered with an MR peak in the vicinity of the coercive field. The low-field tunnel-type MR characteristics of thin films deposited on different substrates originates from the behavior of grain boundary properties.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.29-33
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• 2014

The electrochemical characteristics of Al-Si casting alloys (Al-10%Si, Al-9%Si, Al-7%Si) in 3.5% NaCl solution at room temperature was studied using potentiodynamic techniques. The electrochemical values of corrosion potential($E_c$), corrosion current density($I_c$) and corrosion rate(mpy) were examined. The Al-Si alloys had several compounds such as $Mg_2Si$, ${\pi}$-$Al_8Si_6Mg_2Fe$ and $Al_2CuMg$ which could affect corrosion resistance significantly. The potentiodynamic polarization curve exhibited typical active behavior in anodic polarization curve. The major corrosion mechansim for the Al-Si alloys were pitting and grain boundary corrosion. As increasing Si and Cu contents, their corrosion resistance was decreased.

• Resources Recycling
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• v.20 no.5
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• pp.34-39
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• 2011

Metallurgical grade silicon(MG-Si) was melted with Ca at 1500$^{\circ}C$ under Ar atmosphere. The sample was cooled at 10 $^{\circ}C$/min to room temperature and leached in aqua regia. In the present study, the effect of Ca addition and conditions of acid leaching on removal of Fe and P in MG-Si were investigated. CaSi$_2$ phase was formed at the grain boundary of MG-Si melting with Ca. Also FeSi$_2$ phase was precipitated in CaSi$_2$ phase. By the formation of CaSi$_2$ phase, 97% of Fe and 66 % of P were removed from Ca added MG-Si with the particle size of 600~850${\mu}m$ by aqua regia(more than 30%) leaching.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.131-138
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• 1997

Silicon carbide films were chemically vapor deposited onto graphite substrates using MTS(Ch3SiCl3) as a source and Ar or H2 as a diluent gas. The experiments were performed at a fixed condition such as a de-position temperature of 130$0^{\circ}C$, a total pressure of 10 torr, and a flow rate of 100 sccm for each MTS and carrier gas. The purpose of this study is to consider the variation of the growth behavior with the addition of each diluent gas. It is shown that the deposition rate leads to maximum value at 200 sccm addition ir-respective of diluent gases and the deposition rate of Ar addition is faster than that of H2 one. It seems that these characteristics of deposition rate are due to varying interrelationship between boundary layer thick-ness and the concentration of a source with each diluent gas addition, when overall deposition rate is con-trolled by mass transport kinetics. The preferred orientation of (220) plane was maintained for the whole range of Ar addition. However, above 200 sccm addition, especially that of (111) plane was more increased in proportion to H2 addition. Surface morphologies of SiC films were the facet structures under Ar addition, but those were gradually changed from facet to smooth structures with H2 addition. Surface roughness be-came higher in Ar, but it became lower in H2 with increasing the amount of diluent gas.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.571-577
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• 2006

We fabricated thermal evaporated 10 nm-Ni/(poly)Si and 10 nm-Ni/1 nm-Ir/(poly)Si films to investigate the thermal stability of nickel monosilicide at the elevated temperatures by rapid annealing them at the temperatures of $300{\sim}1200^{\circ}C$ for 40 seconds. Silicides for salicide process was formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester is used for sheet resistance. Scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An x-ray diffractometer and an auger depth profile scope were used for phase and composition analysis, respectively. Nickel silicides with iridium on single crystal silicon actives and polycrystalline silicon gates showed low resistance up to $1200^{\circ}C$ and $800^{\circ}C$, respectively, while the conventional nickel monosilicide showed low resistance below $700^{\circ}C$. The grain boundary diffusion and agglomeration of silicides led to lower the NiSi stable temperature with polycrystalline silicon substrates. Our result implies that our newly proposed Ir added NiSi process may widen the thermal process window for nano CMOS process.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.121-121
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• 2000

반도체 산업의 발달에 따라 소자의 보다 빠른 동작 속도와 큰 집적도를 갖은 ULSI 구조를 얻기 위해, 새로운 금속배선 재료가 요구되고 있다. 기존의 금속 배선인 Al 및 Al 합금은 비교적 낮은 비저항과 박막형성의 용이함으로 인하여 현재까지 금속배선 재료로 사용되고 있으나, 고집적화에 따라 RC Time Delay와 Electromigration의 문제점을 들어내었다. 이러한 문제를 해결할 새로운 배선 재료로 Al보다 낮은 비저항을 가지며, electromigration 저항성을 갖는 Cu 금속배선 재료가 활발히 연구되고 있다. 본 실험에서는 (100) Si 웨이퍼를 기판으로 사용하였으며, 각층은 SiO2/Si3N4/EP Cu/Seed Cu/ TaN/SiO2/Si wafer 상태로 증착하였다. 확산방지막으로 TaN을 사용하였고, seed Cu는 sputtering 으로 증착하였으며, seed Cu 만으로 된 박막과 seed Cu + electro plating Cu로 구성된 박막을 제작하였다. 제작 완료된 박막은 N2 분위기에서 20$0^{\circ}C$ 120 min, 45$0^{\circ}C$ 60min 동안 열처리하여 Cu 박막의 조직 변화를 TEM 및 여러 분석방법을 이용하여 분석하였다. Plan-view TEM결과, 45$0^{\circ}C$, 60min 열처리함에 따라 결정립 성장이 일어난 것을 확인 할 수 있었다. 그러나, 성장후에도 twin boundary, stacking fault, dislocation, small defect 등은 여전히 남아 있음이 관찰된다. 그림 1(a)는 as-deposit 상태이며, 그림 1(b)는 45$0^{\circ}C$, 60min 열처리한 plan-view TEM 사진이다.