• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.7-12
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• 1997

Amorphous $Fe_{50}Zr_{50}$ alloy has been manufactured by mechanical alloying from pure elemental powders of Fe and Zr in conventional ball mill under an Ar atmosphere. Structure and magnetic properties of the amorphous phase were studied by transmission electron microscopy and SQUID magnetometry. Selected area diffraction patterns taken from the mechanically alloyed powders showed two halo rings, indicating coexistence of Fe rich and Zr rich amorphous phases in mechanically alloyed powder. Curie temperature of the Fe rich amorphous phase, measured by Arrot plot, was 195 K. Fe content in the ferromagnetic amorphous phase, estimated from the Curie temperature, was about 65 at%. Spin wave stiffness constant of $Fe_{50} Zr_{50}$ alloys processed for 100 and 200 hrs were 52.2 and 63.8 meV, respectively. The higher spin wave stiffness constant in 200 hrs milled powders may arise from the precipitation of $\alpha$-Fe by partial crystallization of amorphous phase.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.42.1-42.1
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• 2009

오스테나이트 스테인리스강은 우수한 내식성 및 기계적 특성으로 인해 구조용 재료로 널리 사용되고 있다. 표준원전 경수로의 경우 가압기 밀림관소재로 Nb 안정화 오스테나이트 스테인리스강인 type 347 스테인리스강이 사용되고 있다. 그러나 원전배관에서는 운전중 배관내 온도편차에 의한 열응역과 하중변화에 의한 기계적하중에 의해 피로손상을 받는다. 일반적으로 범용 오스테나이트 스테인리스강(AISI 304, 316)의 피로균열 성장거동에 대한 연구결과는 국내외적으로 다수 축적되어 있으나 type 347 탄소, 질소 함량에 따른 기계적 특성 및 피로균열성장 연구는 매우 미비하다. 따라서 본 연구에서는 탄소와 질소의 함량에 따른 기계적거동을 평가하고, 이에 따른 피로균열전파속도를 관찰하여 스테인리스강의 정확한 피로균열전파속도 곡선을 제시하고자 한다. 실험에 사용된 시편은 두께 5mm, 폭 25.4mm CT시편을 사용하였으며, 1mm의 예비균열을 주었다. 그리고 실험온도는 상온과 원전가동온도인 $316^{\circ}C$에서 실시하였으며, 주파수는 10Hz를 주었다. 실험결과 각 함량에 따른 type 347의 미세조직 관찰결과 기지내에 압연방향을 따라 조대한 석출물의 흐름이 관찰되었으며, 크기나 분포가 큰 차이를 보였다. C+N 함량이 낮은 시편은 주로 $0.1\;{\mu}m$ 이하의 미세한 입자들이 오스테나이트 기지조직의 입내와 입계에 고르게 분포되어 있었다. 그러나 C+N 함량이 높은 시편의 경우에는 $0.1\;{\mu}m$ 이하의 미세한 입자들과 함께 국부적으로 $1\sim10\;{\mu}m$의 조대한 입자들이 분포하고 있는 것이 관찰되었다. 그리고 질소의 함량이 높아짐에 따라 인장강도는 증가하였으며, 피로시험결과 고온에서 실험한 피로균열성장률 곡선이 상온보다 높게 나타남을 확인할 수 있었다. 그리고 질소가 적게 첨가되고 탄소의 함량이 많을수록 피로균열성장률은 ASME 곡선보다 낮게 나타났다.

• Polymer(Korea)
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• v.33 no.4
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• pp.364-370
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• 2009

The curing kinetics and mechanical properties of siloxane-diaminodiphenylmethane (ETSO-DDM) on the two kinds of bisphenol (BPH) system which are DGEBA and DGEBF were investigated with the different contents of ETSO. To investigate the curing kinetics of the ETSO-DDM/BPH systems, differential scanning calorimeter (DSC) was used. The mechanical properties of ETSO-DDM/BPH systems were also examined by universal testing machine (UTM), tensile test and flexural test. From experimental results, the activation energies and mechanical properties of ETSO-DDM/BPH were improved with the decrease contents of ETSO. This was due to the high cross-linking density made from short length of ETSO-DDM, resulting in improving the mechanical inter-locking between ETSO-DDM and BPH in these systems.

• Elastomers and Composites
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• v.42 no.1
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• pp.9-19
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• 2007

In this study, SBR (Styrene-butadiene rubber: solid content: 25 wt%) nanocomposites reinforced with carbon/organoclay(C18-MMT) were manufactured by a latex method. The SBR nanocomposites was made with the dual phase fillers. The mixing ratios, i.e. carbon black/C18-MMT, were 50/0, 49/1, 48/2, 47/3, 45/5, 44/6, 40/10. Total filler content of compounds was restricted to 50 phr. Cure characteristics and mechanical properties of SBR nanocomposites with carbon black and C18-MMT were evaluated. The SBR nanocomposites containing 49/1 ratio of carbon black/C18-MMT showed good dispersity and excellent values of ODR torque, tensile strength, modulus and tear energy. It was found that the improvement of the mechanical properties was mainly due to the reinforcing effect, i.e., the improvement of dispersion of silicates in the rubber matrix.

• Elastomers and Composites
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• v.45 no.1
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• pp.2-6
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• 2010

The sizing treatments of PAN-based carbon fiber surfaces were carried out in order to improve the interfacial adhesion in the carbon fibers/nylon6 composite system. The parameter to characterize the wetting performance and surface free energy of the sized fibers were determined by a contact angle method. The mechanical interfacial properties of the composites were investigated using critical stress intensity factor ($K_{IC}$). The cross-section morphologies of sized CFs/nylon6composites were observed by SEM. As the experimental results, it was observed that silane-based sizing treated carbon fibers showed higher surface free energies than other sizing treatments. In particular, the KIC of the sizing-treated carbon fibers reinforced composites showed higher values than those of untreated carbon fibers-reinforced composites. This result indicated that the increase in the surface free energy of the fibers leads to the improvement of the mechanical interfacial properties of carbon fibers/nylon6 composites.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.313-317
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• 2010

최근에는 반도체 공정 기술의 발달로 인하여 프로세서의 성능은 급속도록 발전하였다. 하지만 프로세서에서 소모되는 전력이 급속도록 증가하고, 이에 따라 발생된 높은 온도는 프로세서 신뢰성에 부정적인 영향을 미치고 있다. 그러므로 최근의 프로세서 설계 시 전력, 온도등도 성능과 함께 중요한 고려사항이다. 프로세서의 신뢰성에 치명적인 영향을 미치는 고온현상을 해결하기 위해서 여러 가지 연구가 이루어지고 있다. 대표적으로 방열 판, 냉각 팬 등을 이용한 기계적인 기법과 동적 온도 관리 기법, 연산 이관 기법등을 적용한 구조적인 기법이 활발하게 연구되고 있다. 이러한 기법들의 적용으로 프로세서의 온도를 효과적으로 제어할 수 있게 되었으나 기계적인 냉각 기법은 냉각 효율성이 높지 않다는 단점이 존재하고, 구조적 설계 기법을 통한 냉각기법은 온도를 제어하기 위해 프로세서의 성능을 저하시키는 치명적인 단점이 존재하기 때문에 두 기법 모두 더 많은 연구가 필요하다. 최근의 프로세서 온도 제어 연구의 초점은 부가적인 장치를 통해 프로세서 내에서 발생 된 온도를 제어하는 기계적인 냉각 기법에서 프로세서 내에서 발생하는 온도를 효과적으로 제어하여 프로세서의 신뢰성과 냉각 비용을 절감할 수 있는 구조적 설계 기법으로 이동하고 있다. 본 논문에서는 연구의 초점이 이동하는 원인에 대해 분석하고자 고성능 프로세서에서의 기계적 냉각 기법의 냉각 효율성을 분석하고자 한다. 실험 결과, 온도를 제어하는 데 있어서 매우 높은 비용($1^{\circ}C$ 감소 당 최대 3.58W, 평균 3.36W)이 소모되는 것으로 나타났다. 향후에는 구조적인 설계 기법의 냉각 효율성을 분석하는 실험을 진행하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.80-85
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• 2016

Carbon fiber-reinforced composite materials have been widely used in various industrial fields, but there are limits to increasing their strength and stiffness, because of the short-length fibers that are impregnated in them. In this study, a lab-scale small extruder system was developed with the capability to perform the carbon fiber impregnation and extrusion process in order to evaluate the properties of long-length carbon fiber reinforced thermoplastic composite materials molded by the LFT-D method. Specimens were made with the small extruder to press-mold long-length carbon fiber composite materials and evaluate their material properties. As a result, it was found that the carbon fiber length, press load and carbon fiber contents have a considerable influence on the strength and stiffness. Additional studies on such factors as the mixing screw design and coating of the carbon fiber are needed in order to improve the mechanical properties of carbon fiber composite materials.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1999-2004
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• 2011

This research aims to develop polymer composites which can be used for PEMFC bipolar plate by injection molding process. Considering the moldability and stiffness, we used LCP(Liquid crystal polymer) as base resin. In order to improve electrical conductivity and mechanical properties, we chose carbon black, and both synthetic graphite and expanded graphite. The composites with different recipe are prepared for injection molding of PEMFC bipolar plate and CAE(Computer Aided Engineering) analysis was performed to predict melt flow and fiber orientation We did successfully fabricate the ASTM specimens by injection molding, and measure the electrical conductivity of the samples by using four point probe device. We measured mechanical properties such as flexural strength, flexural modulus and Izod impact strength. Conclusively, the electrical conductivity increased with increasing additive concentration, but both flexural strength and Izod impact strength decreased due to the brittle nature of carbon-based additives.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.179-184
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• 2016

In this work, the influence of milled carbon fiber direction on mechanical properties of milled carbon fibers/carbon blacks/natural rubber compounds was investigated. The compounds were prepared by adding the 6 phr milled carbon fibers (MCFs) and 40 phr carbon blacks (CBs) into the natural rubber. The MCFs were aligned in a parallel and orthogonal direction in the compounds using two-roll-mill machine. Mechanical properties of compounds were studied by tensile characteristics and tearing strength. As a result, the compounds showed higher tensile strength, 100%~300% modulus, and tearing strength than those of using any other compounds due to the aligning MCFs in parallel. Mechanical properties of the compounds reinforced with non-aligned MCFs were inferior to those of others. Consequently, the parallel aligned MCFs in the compounds led to an increase of tensile properties and improvement of tearing strength, resulted from MCFs with the high elastic modulus.

• Korean Journal of Food Science and Technology
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• v.23 no.3
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• pp.336-340
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• 1991

Correlations among instrumental. sensory parameters and overall preference of jelly texture were studied. Instrumental rheological characteristics of the jelly were measured with a rheometer, and sensory and overall score were measured by sensory evaluation. Instrumental maximum force was correlated to sensory hardness and shortness, and sensory springiness and stickiness were correlated to instrumental springiness and adhesiveness force respectively. Also the most significant instrumental parameters with respect to overall preference were cohesiveness and adhesiveness force with their values being 0.93 and 0.89 repectively. Multiple linear regression resulted in a following equation: overall score = 2.70 + 6.25(cohesiveness) - 0.095(adhesiveness force) with a correlation coefficient of 0.94.