• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.4
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• pp.308-317
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• 2007

We fabricated thermally-evaporated 10 nm-Ni/(poly)Si and 10 nm-$Ni_{0.5}Co_{0.5}$/(Poly)Si structures to investigate the microstructure of nickel silicides at the elevated temperatures required lot annealing. Silicides underwent rapid annealing at the temperatures of $600{\sim}1100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope and an Auger depth profilescope were employed for the determination of vortical microstructure and thickness. Nickel silicides with cobalt on single crystal silicon actives and polycrystalline silicon gates showed low resistance up to $1100^{\circ}C$ and $900^{\circ}C$, respectively, while the conventional nickle monosilicide showed low resistance below $700^{\circ}C$. Through TEM analysis, we confirmed that a uniform, $10{\sim}15 nm$-thick silicide layer formed on the single-crystal silicon substrate for the Co-alloyed case while a non-uniform, agglomerated layer was observed for the conventional nickel silicide. On the polycrystalline silicon substrate, we confirmed that the conventional nickel silicide showed a unique silicon-silicide mixing at the high silicidation temperature of $1000^{\circ}C$. Auger depth profile analysis also supports the presence of this mixed microstructure. Our result implies that our newly proposed NiCo-alloy composite silicide process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• Korean Journal of Materials Research
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• v.30 no.3
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• pp.149-154
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• 2020

A powder-in-sheath rolling method is applied to the fabrication of a carbon nano tube (CNT) reinforced copper composite. A copper tube with outer diameter of 30 mm and wall thickness of 2 mm is used as sheath material. A mixture of pure copper powder and CNTs with a volume content of 3 % is filled in a tube by tap filling and then processed to an 93.3 % reduction using multi-pass rolling after heating for 0.5 h at 400 ℃. The specimen is then sintered for 1h at 500 ℃. The relative density of the 3 vol%CNT/Cu composite fabricated using powder in sheath rolling is 98 %, while that of the Cu powder compact is 99 %. The microstructure is somewhat heterogeneous in width direction in the composite, but is relatively homogeneous in the Cu powder compact. The hardness distribution is also ununiform in the width direction for the composite. The average hardness of the composites is higher by 8Hv than that of Cu powder compact. The tensile strength of the composite is 280 MPa, which is 20 MPa higher than that of the Cu powder compact. It is concluded that the powder in sheath rolling method is an effective process for fabrication of sound CNT reinforced Cu matrix composites.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.848-849
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• 2006

Bulk metallic glass (BMG) composites combining a $Cu_{54}Ni_6Zr_{22}Ti_{18}$ matrix with brass powders or $Zr_{62}A_{l8}Ni_{13}Cu_{17}$ metallic glass powders were fabricated by spark plasma sintering. The brass powders and Zr-based metallic glass powders added for the enhancement of plasticity are well distributed homogeneously in the Cu-based metallic glass matrix after consolidation. The BMG composites show macroscopic plasticity after yielding, and the plastic strain increased to around 2% without a decrease in strength for the composite material containing 20 vol% Zr-based amorphous powders. The proper combination of strength and plasticity in the BMG composites was obtained by introducing a second phase in the metallic glass matrix.

• Composites Research
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• v.32 no.3
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• pp.141-147
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• 2019

In this study, micro-sized and nano-sized pure aluminum (Al) powders were compressed by unidirectional pressure at room temperature. Although neither type of Al bulk was heated, they had a high relative density and improved mechanical properties. The microstructural analysis showed a difference in the process of densification according to particle size, and the mechanical properties were measured by the Vickers hardness test and the nano indentation test. The Vickers hardness of micro Al and nano Al fabricated in this study was five to eight times that of ordinary Al. The grain refinement effect was considered to be one of the strengthening factors, and the Hall-Petch equation was introduced to analyze the improved hardness caused by grain size reduction. In addition, the effect of particle size and dispersion of aluminum oxide in the bulk were additionally considered. Based on these results, the present study facilitates the examination of the effect of particle size on the mechanical properties of compacted bulk fabricated by the powder metallurgy method and suggests the possible way to improve the mechanical properties of nano-crystalline powders.

• Coupled systems mechanics
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• v.11 no.3
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• pp.267-284
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• 2022

Due to the high usage of ABS in industries, such as aerospace, auto, recreational devices, boat, submarines, etc., the purpose of this project was to find a way to weld this material, which gives advantages, such as affordable, high speed, and good connection quality. In this experimental project, the friction welding method was applied with parameters such as numerical control (NC) machine with two different speeds and three cross-sections, including a flat surface, cone, and step. After the end of the welding process, samples were then applied for both tensile and bending tests of materials, and the results showed that, with increasing the machining velocity Considering of samples, the friction of the surface increased and then caused to increase in the surface temperature. Considering mentioned contents, the melting temperature of composite materials increased. This can give a chance to have a better combination of Nanomaterial to base melted materials. Thus, the result showed that, with increasing the weight percentage (wt %) of Nanomaterials contents, and machining velocity, the mechanical behavior of welded area for all three types of samples were just increased. This enhancement is due to the better melting process on the welded area of different Nano contents; also, the results showed that the shape of the welding area could play a significant role, and by changing the shape, the results also changed drastically.A better shape for the welding process was dedicated to the step surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1278-1282
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• 2004

수열처리법으로 nano-sized $CeO_2$ 입자를 $Al_3O_3$ 입자의 표면에 균일하게 코팅하여 $AL_2O_3/O_2$ composite 연마 입자를 제조하었다. 제조된 $Al_2O_3\CeO_2$ composite 입자의 뭍성을 TEM, XRD, zeta potential analyzer 및 particle size analyzer로 측징하였다. $Al_2O_3/CeO_2$ composite 입자와 구성된 슬러리와 비교 시료로서 $Al_2O_3$와 $CeO_2$ 입자를 혼합한 슬러리를 사용하여 thermal oxide film에 대한 연마특성을 평가하였다. 연마슬러리에 포함된 $A1_2O_3/CeO_2$ composite 입자와 $Al_2O_3$와 $CeO_2$ 혼합입자에서 나노 크기의 세리아 입자가 sub-micron 크기의 알루미나 입자의 표면에 균일하게 코팅되므로서 $Al_2O_3$ 단일 성분의 슬러리에 비해 removal rate(RR)는 106 nm/min, WIWNU는 $8\sim9%$, roughness는 $2.6{\AA}$의 향상된 연마 특성을 나타내었다. 알루미나 입자의 불규칙한 형상 때문에 $Al_2O3/CeO_2$ composite 슬러리와 $Al_2O_3$ 와 $CeO_2$ 혼합슬러리의 연마 특성이 비슷한 수준을 나타내었다.

• Composites Research
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• v.35 no.5
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• pp.328-333
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• 2022

In this study, the fabrication conditions of CFRP rebar were controlled to derive the correlation between flexural strength and pore characteristics. The fabrication conditions of CFRP rebar were adjusted for presence or absence of rib, resin temperature, and curing furnace temperature. Flexural strength and pore characteristics of fabricated CFRP rebar were analyzed. The flexural strength of CFRP rebar was changed depending on the fabrication condition, such as the presence or absence of rib, the resin temperature, and the curing furnace temperature. It was confirmed that the flexural strength of CFRP rebar was significantly lowered when the rib was not wound. As a result of Nano X-ray CT analysis, the max. pore diameter was shown in CFRP rebar prepared at a resin temperature of 60℃. According to optical microscopic analysis, the maximum porosity was 6.89% in No. 1, and the minimum porosity was 2.88% in No. 7. The correlation coefficient between porosity used optical microscopy and flexural strength was -0.64, which was higher than the correlation coefficient between porosity or pore size used Nano X-ray CT and flexural strength.

• Resources Recycling
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• v.19 no.4
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• pp.51-57
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• 2010

As a recycling of Si sludge from Si wafer process, a Si-SiC-CuO-C composite material was synthesized and investigated as an anode material for lithium batteries. The Si sludge consisted of Si, SiC, machine oil, and metallic impurities. The oil and metal impurities was removed by organic washing, magnetic separation, and acid washing. The Si-SiC-CuO-C composite from the recovered Si-SiC mixture was prepared by high-energy mechanical milling. According to the electrochemical tests such as charge-discharge capacity and cycling behavior, it showed the improved cycle performance. The SiC and CuO-related phases were presumed to restrain the volume expansion of the anode and Fe, however, should be removed below 10 ppm prior to synthesis of the composite because it caused the capacity loss of the active material itself.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.43-44
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• 2007

SiO and graphite composite has been prepared by adopting high energy ball milling technique. The anode material shows high initial discharge and charge capacity values of 1138 and 568 mAh/g, respectively. Since the materials formed during initial discharge process the nano silicon/$Li_4SiO_3\;and\;Li_2O$ remains as interdependent, it may be expected that the composite exhibiting higher amount of irreversible capacity$(Li_2O)$ will deliver higher reversible capacity. In this study, pretreatment method of constant current-constant voltage (CC-CV) Provided high coulombic efficiency of SiO/C composite electrode removing the greater part of irreversible capacity.

• Composites Research
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• v.37 no.3
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• pp.186-189
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• 2024

This study compared and evaluated the mechanical properties of carbon fiber reinforced thermoplastic polymer (CFRTP) mixed with nanofillers. After mixing various nanofillers such as Multi-wall carbon nanotube (MWCNT), Silicon oxide, Core shell rubber, and Aramid nanofiber with Polyamide 6 (PA6) resin, this is used as a matrix to create a carbon fiber reinforced composite material (CFRP) was manufactured and its physical properties were measured. Depending on the type and mixing ratio of nanofiller, tensile strength, inter-laminar shear strength (ILSS), and Izod impact strength were measured. In terms of tensile strength and impact strength, the highest values were obtained when mixing core shell rubber, however the ILSS was optimal when mixing less than 1 wt.% of silicon oxide.