• Macromolecular Research
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• 제8권4호
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• pp.192-198
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• 2000

Cure characteristics and physical properties of carbon black-filled natural rubber (NR) compounds depending on the mixing procedure were studied using the compounds with different pre-final mixing (FM-1) stages. Carbon master batch (MB) and first and second remitting (1RM and 2RM) stages were employed as the FM-1 stage. Bound rubber content of the FM compound decreased with increasing the mixing steps. This was due to the decrease of the molecular weight distribution of the polymer by the rubber chain scission during the mixing. The Mooney viscosity decreased with increasing the mixing steps. Cure characteristics of the compounds were found to be different with the mixing procedures. The cure times of the compound became slower by increasing the number of the mixing steps. This was explained by the length of rubber chain, the carbon black network, distribution of the curatives in the compound, and immobilization of the polymeric segments. Modulus and tensile strength of the vulcanizate did not show a specific trend with the mixing procedure. Fatigue life of the vulcanizate increased by increasing the mixing stages.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2071-2078
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• 2024

The precipitation of solutes is a major cause of irradiation hardening and embrittlement limiting the service life of reactor pressure vessel (RPV) steels. Impurities play a significant role in the formation of precipitation in RPV materials. In this study, the effects of carbon on cluster formation and irradiation hardening were investigated in an RPV alloy Fe-1.35Mn-0.75Ni using C and Fe ions irradiation at 290 ℃. Nanoindentation results showed that C ion irradiation led to less hardening below 1.0 dpa, with hardening continuing to increase gradually at higher doses, while it was saturated under Fe ion irradiation. Atom probe tomography revealed a broad size distribution of Ni-Mn clusters under Fe ion irradiation, contrasting a narrower size distribution of small Ni-Mn clusters under C ion irradiation. Further analysis indicated the influence of carbon on the cluster formation, with solute-precipitated defects dominating under C ion irradiation but interstitial clusters dominating under Fe ion irradiation. Simulations suggested that carbon significantly affected solute nucleation, with defect clusters displaying smaller size and higher density as carbon concentration increased. The higher hardening at doses above 1.0 dpa was attributed to a substantial increase in the number density of defect clusters when carbon was present in the matrix.

• Composites Research
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• 제33권4호
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• pp.198-204
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• 2020

본 연구에서는 탄소나노튜브 다발을 포함하는 나노복합재료의 열-기계적 특성을 정량적으로 예측하기 위하여 분자동역학 전산모사와 유한요소 기반 균질화 기법을 적용하였다. 응집된 탄소나노튜브의 수가 증가함에 따라 동일한 탄소나노튜브의 체적분율에도 불구하고, 면내 영률 및 면내 전단계수는 감소하였고, 면내 열팽창계수는 증가함을 확인할 수 있었다. 계면의 두께를 조사하기 위하여 밀도의 반경 방향 분포(Radial density distribution)을 조사하였으며, 계면의 두께는 탄소나노튜브의 수와는 거의 무관함을 확인할 수 있었다. 기지와 계면은 등방성 재료로 가정하였으며, 예측한 계면의 열-기계적 특성에 따르면, 응집된 탄소나노튜브의 수가 증가함에 따라 계면의 영률 및 전단계수는 감소하였으며, 열팽창계수는 반대로 증가하였다. 이를 토대로, 탄소나노튜브 다발을 포함하는 PLA 나노복합재료의 열-기계적 특성 예측을 위한 멀티스케일 균질화 모델을 개발하였다.

• Advances in nano research
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• 제11권6호
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• pp.621-640
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• 2021

Effect of thickness stretching on mechanical behavior of functionally graded (FG) carbon nanotubes reinforced composite (CNTRC) laminated nanoplates resting on elastic foundation is analyzed in this paper using a novel quasi 3D higher-order shear deformation theory. The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Single-walled carbon nanotubes (SWCNTs) are the reinforced elements and are distributed with four power-law functions which are, uniform distribution, V-distribution, O-distribution and X-distribution. To cover various boundary conditions, an analytical solution is developed based on Galerkin method to solve the governing equilibrium equations by considering the nonlocal strain gradient theory. A modified two-dimensional variable Winkler elastic foundation is proposed in this study for the first time. A parametric study is executed to determine the influence of the reinforcement patterns, power-law index, nonlocal parameter, length scale parameter, thickness and aspect ratios, elastic foundation, thermal environments, and various boundary conditions on stresses, displacements, buckling loads and frequencies of the CNTRC laminated nanoplate.

• 한국산업융합학회 논문집
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• 제21권1호
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• pp.29-36
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• 2018

Low pressure casting process for unidirectional carbon fiber reinforced aluminum (UD-CF/Al) composites which is an infiltration route of molten Al into porous UD-CF preform has been a cost-effective way to obtain metal matrix composites (MMCs) but, easy to cause non-uniform fiber distribution as CF clustering. Such clustered CFs have been a problem to decrease the density and thermal conductivity (TC) of composites, due to the existence of pores in the clustered area. To obtain high thermal performance composites for heat-sink application, the relationship between fiber distribution and porosity has to be clearly investigated. In this study, the CF distribution was evaluated with quantification approach by using two-dimensional spatial distribution method as local number 2-dimension (LN2D) analysis. Note that the CFs distribution in composites sensitively changed by sizes of Cu bridging particles between the CFs added in the UD-CF preform fabrication stage, and influenced on only $LN2D_{var}$ values.

• Advances in nano research
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• 제8권2호
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• pp.135-148
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• 2020

The incorporation of carbon nanotubes in a polymer matrix makes it possible to obtain nanocomposite materials with exceptional properties. It's in this scientific background that this work was based. There are several theories that deal with the behavior of plates, in this research based on the Mindlin-Reissner theory that takes into account the transversal shear effect, for analysis of the critical buckling load of a reinforced polymer plate with parabolic distribution of carbon nanotubes. The equations of the model are derived and the critical loads of linear and parabolic distribution of carbon nanotubes are obtained. With different disposition of nanotubes of carbon in the polymer matrix, the effects of different parameters such as the volume fractions, the plate geometric ratios and the number of modes on the critical load buckling are analysed and discussed. The results show that the critical buckling load of parabolic distribution is larger than the linear distribution. This variation is attributed to the concentration of reinforcement (CNTs) at the top and bottom faces for the X-CNT type which make the plate more rigid against buckling.

• 약학회지
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• 제36권3호
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• pp.269-277
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• 1992

The effects of ginseng saponins on the distribution of nerve cells in cerebral cortex of carbon monoxide (CO)-intoxicated mice were studied in the young ($5{\sim}8$ weeks) and aged ($43{\sim}52$ weeks) mice. Mice were exposed to 5000 ppm of CO for 40 minutes (72% HbCO). After that, nerve cells in motor(area 4), somatosensory(area 3) and visual(area 17) area of cerebral cortex was observed. In young mice, the number of nerve cells in each area was significantly decreased on 1st, 7th and 14th day after CO intoxication. In aged mice, that was also decreased after CO intoxication. Especially the number of the nerve cells in motor and somatosensory area was significantly decreased on 1st and 7th day, while that in visual area was decreased only on 1st day. The number of nerve cells in young mice pretreated with ginseng saponins were significantly decreased less on 7th and 14th day than that of untreated mice. The number of nerve cells in each area of normal aged mice was larger than that of normal young mice. The results suggest that CO exposure causes local degeneration or disturbance of nerve cells and delayed neurologic sequelae, while ginseng saponins might play a role of protective action on the nerve cells which were damaged by CO.

• 한국표면공학회지
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• 제52권6호
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• pp.357-363
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• 2019

We investigated a synthesis yield and diameter distribution of single-walled carbon nanotubes (SWNTs) with respect to the growth position in a horizontal chemical vapor deposition (CVD) chamber. Thin films and line-patterned Fe films (0.1 nm thickness) were prepared onto ST-cut quartz substrates as catalyst to compare the growth behavior. The line-patterned samples showed higher growth density and parallel alignment than those of the thin film catalyst samples. In addition, line density of the aligned SWNTs at central region of the chamber was 7.7 tubes/㎛ and increased to 13.9 tubes/㎛ at rear region of the CVD chamber. We expect that the enhanced amount of thermally decomposed feedstock gas may contribute to the growth yield enhancement at the rear region. In addition, the lamina flow in the chamber also contribute to the perfect alignment of the SWNTs based on the value of gas velocity, Reynold number, and Knudsen coefficient we employed.

• Advances in concrete construction
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• 제17권3호
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• pp.127-133
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• 2024

Textile reinforced concrete (TRC) has gained attention as a viable alternative to conventional reinforced concrete due to its improved mechanical properties and design adaptability. Despite significant research into the mechanical properties of TRC, studies regarding the flexural effect of pre-stretching with different numbers of textile reinforcements are currently limited. Therefore, this research focuses on assessing the flexural characteristics of TRC panels with the incorporation of mesh pre-stretching. Additionally, the study compares the flexural behaviour between alkali-resistant (AR) glass fibre TRC and carbon fibre TRC. A three-point bending test was conducted to assess the flexural behaviour of TRC, investigating the impact of the number of textile layers and the application of pre-stretching on flexural strength and post-cracking stiffness. The findings, exhibited by the flexural stress vs. displacement curve, indicate that applying pre-stretching to carbon fibre TRC effectively increases the flexural strength of carbon textiles and enhances post-cracking stiffness. Moreover, the greater the number of carbon textiles, the higher the flexural stress of the specimens, provided the textiles are placed in the tensile zone. Nevertheless, when comparing carbon fibre TRC with AR glass fibre TRC, it is found that the increase in flexural strength is more significant for carbon fibre TRC. Overall, applying pre-stretching to carbon fibre significantly improves the TRC's flexural performance, specifically during the post-cracking stage and in crack distribution. Furthermore, due to the higher elastic modulus and tensile strength of carbon fibre, TRC reinforced with carbon textiles shows greater flexural strength and ductility compared to AR glass fibre TRC.

• 공업화학
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• 제23권3호
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• pp.320-325
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• 2012

$SiO_2/Al_2O_3$ 비가 10.5인 실리카-알루미나(SA), 10인 수소형 모더나이트(HM), 12.5인 탈알루미늄 모더나이트(DM) 등을 이용하여 폐윤활유의 촉매분해를 수행하였다. 촉매의 분해능은 SA > DM > HM 시료 순으로 높았다. SA 시료 상에서 얻어진 분해오일은 휘발유의 탄소수 분포와 가까웠고 반면 DM 시료의 경우에는 경유의 탄소수 분포와 가까웠다. HM시료 상에서 얻어진 분해오일의 탄소수 분포는 휘발유와 경유의 중간 정도였다. 산량은 $SA\;{\approx}\;HM$ > DM 시료 순으로 많았다. 10 A 이하의 균일 세공을 가지는 HM과 DM 시료와는 달리, SA 시료의 세공은 10~50 A 범위의 분포를 나타내었다. 이러한 결과들은 촉매의 산량과 세공 크기가 분해오일의 탄소수 분포와 관계가 있음을 보여준다. 촉매 표면에 탄소 및 불순물의 침적에 의한 표면적 감소는 SA > HM > DM 시료 순으로 컸다.