• Carbon letters
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• 제8권1호
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• pp.25-29
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• 2007

The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.50-53
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• 2000

The effect of punching density on the mechanical and thermal properties of nonwoven needle-punched carbon/phenol composite was studied. The carbonized preforms were farmed into composites with phenol resin. The interlaminar shear, tensile and flexural strengths were increased with increasing punching density. However, excessive punching density decreased interlaminar shear and tensile strengths. Erosion rate of carbon/phenol composite was decreased with increasing punching density

• Journal of Forest and Environmental Science
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• 제33권1호
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• pp.39-48
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• 2017

With the growing global concern about climate change, relationship between carbon stock density and tree species has become important for international climate change mitigation programmes. In this study, 150 Quadrats were laid down to assess the diversity, biomass and carbon stocks in each of the forest ranges (Barkot Range, Lachchiwala Range and Thano Range) of Dehra Dun Forest Division in Doon Valley, Western Himalaya, India. Community level carbon stock density was analyzed using Two Way Indicator Species Analysis. Species Richness and Shannon Weiner index was correlated with the carbon stocks of Doon Valley. Positive and weak relationship was found between the carbon stock density and Shannon Weiner Index, and between carbon stock density and Species Richness.

• 한국주조공학회지
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• 제23권2호
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• pp.86-93
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• 2003

It has been a major concern in the foundry that steel castings manufactured by the evaporative pattern casting process encounter the carbon pick-up problem. A carbon rich layer at the evaporative pattern cast surface is a result of interactions between the gaseous products from foamed polystyrene and the molten metal. The carburized layer with a high hardness makes it difficult to machine the casting. In this study, the influence of the density of EPS pattern and coatings on carbon pick-up phenomena of S25C and S45C commercial carbon cast steel were investigated. As the density of EPS pattern is increased, the carbon concentration of decomposed pattern is increased and the thickness of carburized layer at the surface of steel castings is increased. Also as the density of coatings is increased, the permeability of coatings is decreased and the thickness of carburized layer at the surface of steel castings is increased. S25C steel which has lower original carbon content compared to S45C steel exhibited severe carburization.

• Carbon letters
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• 제3권2호
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• pp.85-92
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• 2002

4D carbon fiber preforms were manufactured by weaving method and their carbon fiber volume fractions were 50% and 60%. In order to form carbon matrix on the preform, coal tar pitch was used for matrix precursor and high density carbon/carbon composites were obtained by high densification process. In this process, manufacture of high density composites was more effective according to pressure increasement. When densificating the preform of 60% fiber volume fraction with 900 bar, density of the composites reached at 1.90 $g/cm^3$ after three times processing. Degree of pressure in the densification process controls macro pore but it can not affect micro pore. During the carbonization process, micro pore of the preform were filled fully by once or twice densification processing. But micro pore were not filled easily in the repeating process. Therefore, over three times densification processing is the filling micro pore.

• Journal of Forest and Environmental Science
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• 제34권2호
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• pp.145-152
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• 2018

Quantification of Carbon stock has become in the contest of changing climate and mitigation potential of forests. Two different forest types, Dry Shiwalik Sal Forest and Moist Shiwalik Sal Forest in Barkot and Lachchiwala of Doon Valley, Western Himalaya are selected for the study. Volume equations, destructive sampling and laboratory analysis are done to estimate the carbon stock in different carbon pools like trees, shrubs, herbs and soils. Considerable variations are observed in terms of carbon stocks in different forest types. In Dry Shiwalik Sal Forest, carbon stock density varied between 129.81 and $136.00MgCha^{-1}$ while in Moist Shiwalik Sal Forest, carbon stock density ranged from 222.29 to $271.67MgCha^{-1}$. Tree species like Shorea robusta, Syzigium cumini, Miliusa velutina, Acacia catechu, and Mallotus philippensis had significant role in carbon sequestration. Shorea robusta had contributed highest in carbon stock due to highest density. Total of 2,338,280.165 Mg carbon stock was estimated in all the forest types.

• Carbon letters
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• 제2권3_4호
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• pp.192-201
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• 2001

The Carbon/Carbon composite was prepared from 3D carbon fiber preform and coal tar pitch as matrix precursor. In order to evaluate of ablative characteristics of the composite, liquid rocket system was employed Kerosene and liquid oxygen was used as propellants, operating at a nominal chamber pressure of 330 psi and a nominal mixture ratio (O/F) of 2.0. The results of an experimental evaluation were that high density composite exhibited high, while low density composites showed low erosion resistance. The erosion rate against heat flux was highly depended on the density of the materials. The morphology of eroded fiber showed differently according to collision angle with heat flux on the composite. The granular matrix which derived from carbonization pressure of 900 bar was more resistance to heat flux than well-developed flow type matrix.

• 한국추진공학회지
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• 제10권1호
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• pp.44-53
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• 2006

전산화 단층촬영법을 이용하여 탄소/탄소 목삽입재의 밀도 분포를 평가하였다. 전산화 단층촬영법의 Team hardening, 전기적 잡음 및 산란 X-ray의 영상을 보정하고 신호 대 잡음비를 높여 최적화할 때 측정된 탄소/탄소 복합재료의 밀도는 98.74%의 신뢰도 수준에서 ${\pm}0.01g/cm^3$ 분포를 갖는 것으로 평가되었다. 전산화 단층촬영 결과의 검증은 탄소/탄소 목삽입재를 절단하여 수침법에 의한 밀도 측정과 주사전자현미경 관찰을 통하여 수행되었으며 단층촬영 결과는 수침법에 의한 밀도 분포와 주사전자현미경의 영상과 일치하였다.

• 한국산림과학회지
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• 제112권2호
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• pp.188-194
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• 2023

본 연구는 우리나라의 대나무림에 대한 탄소계정을 위하여 탄소배출계수 중 하나인 목재기본밀도를 도출하기 위하여 수행되어 졌다. 대나무는 전라남도와 경상남도에 주로 분포해 있으며, 계수 도출을 위한 표준목은 솜대, 왕대, 맹종죽 등 3수종별로 각각 101본씩을 선정하여 활용하였다. 목재기본밀도 도출은 KS F 2098 방법을 따랐다. 측정결과, 솜대의 목재기본밀도는 0.83 g/cm³, 왕대는 0.81 g/cm³, 맹종죽은 0.72 g/cm³로 각각 나타났다. 그렇지만, 우리나라는 대나무 분포 면적이 많지 않고, 맹종죽의 경우 일정 지역에 국한되어 생육하고 있다. 따라서 대나무에 적용할 수 있는 목재기본밀도는 하나로 통합하여 0.79 g/cm³로 확정하였다. 그리고 도출된 목재기본밀도에 대한 불확도를 평가한 결과, 1.61%로 낮은 불확도 값을 가져, 본 분석에서의 측정값에 대한 신뢰도를 확인할 수 있었다. 본 연구에서는 이번에 개발한 목재기본밀도와 기존의 바이오매스확장계수, 뿌리함량비 등을 이용하여 대나무 표준목에 대한 탄소저장량을 계산하고, 이를 확장시켜 ha단위까지 계산해 보았다. 이번 연구로 대나무의 재적을 이용하여 목재기본밀도 등 탄소배출계수 적용으로 탄소저장 및 흡수량 계산이 가능하게 되었다. 본 결과가 우리나라 탄소중립 정책 및 산림관리 방향에 도움이 되기를 기대한다.

• Carbon letters
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• 제6권4호
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• pp.234-242
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• 2005

Bending and tensile properties of 2D cross-ply C/C composites with processing heat treatment temperature (HTT) are evaluated. C/C composites used are made from two types of PAN based T700 and M40 carbon fibers with phenolic resin as carbon matrix precursor. Both the types of composites are heat treated at different temperatures (ranging from 750 to $2800^{\circ}C$) and characterized for bending and tensile properties. It is observed that, real density and open porosity increases with HTT, however, bulk density does show remarkable change. The real density and open porosity are higher in case T-700 carbon fiber composites at $2800^{\circ}C$, even though the density of M40 carbon fiber is higher. Bending strength is considerably greater than tensile strength through out the processing HTT due to the different mode of fracture. The bending and tensile strength decreases in both composites on $1000^{\circ}C$ which attributed to decrease in bulk density, thereafter with increase in HTT, bending and tensile strength increases. The maximum strength is in T700 fiber based composites at HTT $1500^{\circ}C$ and in M40 fiber based composites at HTT $2500^{\circ}C$. After attending the maximum value of strength in both types of composite at deflection HTT, after that strength decreases continuously. Decrease in strength is due to the degradation of fiber properties and in-situ fiber damages in the composite. The maximum carbon fiber strength realization in C/C composites is possible at a temperature that is same of fiber HTT. It has been found first time that the bending strength more or less 1.55 times higher in T700 fiber composites and in M40 fiber composites bending strength is 1.2 times higher than that of tensile strength of C/C composites.