• Bulletin of the Korean Chemical Society
• /
• 제23권2호
• /
• pp.315-319
• /
• 2002

Visible surface-assisted desorption/ionization mass spectrometry (SALDI-MS) has been investigated for several small macromolecules deposited on the graphite plate using laser radiation at 532 nm where most of the macromolecules are transparent. The graphite surface functioned well as a photon absorbing material and an energy transfer mediator for visible light. The results show that visible SALDI is a much softer ionization technique than UV-MALDI and FAB-MS in our results with synthetic macromolecules, PPG, PPGMBE and cavitand molecules. For the SALDI of biomolecules, glycerol as a proton source was essential with the graphite plate. As in visible SALDI, the role division of the photon absorbing material and the cationization agent can provide a generality in mass spectrometric analysis of macromolecules compared with MALDI using the dual functional matrix.

• 한국분말재료학회지
• /
• 제7권2호
• /
• pp.71-77
• /
• 2000

A process has been successfully used to manufacture 6061/Graphite composite material and the Graphite particles are distributed uniformly within the Al alloy matrix. The 6061 powders was mixed with natural Graphite particles in a ball milling blender and cold compacted specimens were extruded into rods 15mm in diameter at 450$^{\circ}C$. The results showed that tensile properties of the composites with Graphite content have been reduced. The emergence of fine microstructures appeared to be related to the graphite volume. Heat-treated composites were found to possess good mechanical properties as compared with those of non heated composites. A model was used that the tensile strength of the composites would be estimated from the theoretical calculation and experimental data.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1996년도 제24회 춘계학술대회
• /
• pp.45-54
• /
• 1996

The effect of graphite on the frictional characteristics of Cu-based sintered friction materials was studied by pin-on-disk type wear test. A study has been carried out concerning the optimum concentration of graphite in sintered friction material to obtain the minimum wear rate and low friction coefficient . Friction coefficient and wear rate were increased as increasing the content of graphite in the matrix. In the study the optimum concentration of graphite was 19vol % to get the minimum wear rate and optimal frick'ion coefficient.

• 한국주조공학회지
• /
• 제25권1호
• /
• pp.40-50
• /
• 2005

A series of heavy section ductile cast iron ingots with the cube length of 250mm were systematically investigated as functions of casting parameters of sand casting. Abnormal graphite formation was specially observed with the variation of Si content and Bi or Sb addition. Effects of chilling during casting and adaptation of riserless system were also examined, and proved to be effective for the prevention of both shrinkage and abnormal graphite such as chunky one. The formation of chunky graphite was effectively prevented by low Si content despite the promotion of pearlite matrix structure. The ferritic matrix was encouraged to form by high Si content and chunky graphite formation was effectively suppressed by the addition of Bi and Sb. Bi addition, however, was not good enough to control the microstructure owing to the sensitive cooling rate dependent inoculation behavior and relative low ability of nodulization. Sb addition, on the other hand, was proved to be effective for the microstructural control and enhancement of various mechanical properties such as strength, elongation, and impact energy. It may be suggested that optimized casting parameters should be applied to produce heavy section ductile cast iron with reliability.

• 분석과학
• /
• 제5권4호
• /
• pp.349-358
• /
• 1992

본 연구에서는 흑연로 원자흡수분광법을 이용하여 혈액을 1% Triton X-100을 5배 희석시킨 다음 납 함량을 직접 측정하였다. 혈액내 방해 성분을 제거하기 위하여 매트릭스 변형제를 사용하여 최적의 분석 조건을 조사하였다. 매트릭스 변형제로서 1% $(NH_4)_2HPO_4$와 0.1% $PdCl_2$를 같이 사용하고 700도에서 회화시켰을 때에, 일본 비교 분석 프로그램에 의해 제공된 혈중 납 함량에 대한 정도관리용 표준시료(우혈)의 공인값과 비교적 잘 일치하였다. 이 실험에서 얻은 표준편차는 $31{\mu}gPb/l$에서 $624{\mu}gPb/l$ 범위에서는 1% $(NH_4)_2HPO_4$ 및 1% $(NH_4)_2HPO_4$와 0.1% $PdCl_2$를 매트릭스 변형제로서 사용했을 경우 각각 2.2~6.3%, 3.1~9.1%였다.

• Carbon letters
• /
• 제14권1호
• /
• pp.40-44
• /
• 2013

The bipolar plate is the most important and most costly component of proton exchange membrane fuel cells. The development of a suitable low density bipolar plate is scientifically and technically challenging due to the need to maintain high electrical conductivity and mechanical properties. Here, bipolar plates were developed from different particle sizes of natural and expanded graphite with phenolic resin as a polymeric matrix. It was observed that the particle size of the reinforcement significantly influences the mechanical and electrical properties of a composite bipolar plate. The composite bipolar plate based on expanded graphite gives the desired mechanical and electrical properties as per the US Department of Energy target, with a bulk density of 1.55 $g.cm^{-3}$ as compared to that of ~1.87 $g.cm^{-3}$ for a composite plate based on natural graphite (NG). Although the bulk density of the expanded-graphite-based composite plate is ~20% less than that of the NG-based plate, the I-V performance of the expanded graphite plate is superior to that of the NG plate as a consequence of the higher conductivity. The expanded graphite plate can thus be used as an electromagnetic interference shielding material.

• Carbon letters
• /
• 제17권1호
• /
• pp.33-38
• /
• 2016

In the present study, exfoliated graphite nanoplatelets (xGnP) with different particle sizes were coated onto polyacrylonitrile-based carbon fibers by a direct coating method. The flexural properties, interlaminar shear strength, and the morphology of the xGnP-coated carbon fiber/phenolic matrix composites were investigated in terms of their longitudinal flexural strength and modulus, interlaminar shear strength, and by optical and scanning electron microscopic observations. The results were compared with a phenolic matrix composite counterpart prepared without xGnP. The flexural properties and interlaminar shear strength of the xGnP-coated carbon fiber/phenolic matrix composites were found to be higher than those of the uncoated composite. The flexural and interlaminar shear strengths were affected by the particle size of the xGnP, while the particle size had no significant effect on the flexural modulus. It seems that the interfacial contacts between the xGnP-coated carbon fibers and the phenolic matrix play a role in enhancing the flexural strength as well as the interlaminar shear strength of the composites.

• 한국주조공학회지
• /
• 제17권1호
• /
• pp.93-99
• /
• 1997

A possibility of production of aluminium matrix composites by using the lost foam process was investigated. Silicon carbide particles, graphite particles, and stainless steel wires were used as reinforcement materials. The reinforcement materials were introduced to the polystyrene to form patterns via injection molding process. The results obtained from this experiment can be summarized as follows. In Al/SiCp system, the particles with the radius of $100{\mu}m$ and over were entrapped in the matrix in the case of upward freezing of which solidification direction was opposite to floating direction of the particles. And few particles were entrapped in the matrix in downward freezing. In Al/graphite system, almost no particles were entrapped in the matrix except the area chill attatched. When the thickness of polystyrene slice was 4mm in Al/stainless steel wire system, the floating tendency of fibers was observed to increase as the distance from the ingate was increased.

• Bulletin of the Korean Chemical Society
• /
• 제34권5호
• /
• pp.1435-1440
• /
• 2013

To investigate the influence of the carbon matrix on the electrochemical performance of Si/C composites, four types of Si/C composites were prepared using graphite, petroleum coke, pitch and sucrose as carbon precursors. A ball mill was used to prepare Si/C blends from graphite and petroleum coke, whereas a dispersion technique was used to fabricate Si/C composites where Si was embedded in disordered carbon matrix derived from pitch or sucrose. The Si/pitch-based carbon composite showed superior Si utilization (96% in the first cycle) and excellent cycle retention (70% after 40 cycles), which was attributed to the effective encapsulation of Si and the buffering effect of the surrounding carbon matrix on the silicon particles.

• Composites Research
• /
• 제13권2호
• /
• pp.72-80
• /
• 2000

흑연분말 첨가가 탄소/탄소 복합재료의 물성에 미치는 영향에 대하여 연구하였다. 페놀수지에 흑연분말을 0~30wt.%첨가하여 greenbody(G/B)를 제조하고 이를 $1000^{\circ}C$까지 탄화시켜 탄소/탄소 복합재료를 제조하였다. 굽힘특성은 G/B와 탄소/탄소 복합재료 모두 흑연분말 20wt.% 첨가시 최대치를 보였으며, 그 이상에서는 수지 내의inhomogeneity 증가 때문에 굽힘강도가 감소하였다. 페놀수지만을 경화시킨 경우에는 흑연분말을 20wt.% 첨가한 수지의 굽힘 강도가 첨가하지 않은 수지의 경우보다 낮은 값을 보였으나, 탄화 후에는 혹연분말의 첨가가 탄화수축 감소와 균열경로를 바꾸어 주는 효과를 주어서, 분말을 첨가한 시편의 굽힘 강도가 3배 이상 증가하였다. Mode II ENF 시험결과, G/B와 탄소/탄소 복합재료 모두 20wt.%의 흑연분말 첨가시에 에너지해방율($G_{II}$)이 증가하였으나, 분말의 첨가가 탄소/탄소 복합재료에 더 효과적임을 에너지해방율의 증가치로부터 확인할 수 있었다.