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다중벽 탄소나노튜브 강화 에폭시 복합재료에 플라즈마 처리가 미치는 영향
유재상(Jaesang Yu),정하나(Hana Jung),김연직(Yonjig Kim),최회길(Hoi Kil Choi),오유나(Yuna Oh) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Plasma treatment methodology is widely used to functionalize the surfaces of nanofillers in order to enhance elastic, thermal and electrical properties of composites. In this study, plasma process of two types was employed for nitrogen doping on the surface of multiwalled carbon nanotube (MWCNT). First, nitrogen doping on MWCNTs was carried out in a horizontal quartz tube using N2 plasma at the powers of 100 W for 10 min. Second, MWCNTs were surface-modified with plasma treatments using nitrogen by nanocular instrument of 50mA for 1hr. The influence of the doping on the structure of CNTs was studied using XPS and Raman spectroscopy. N-doped MWCNT reinforced epoxy composites were fabricated and tested to investigate the effect of functionalized surfaces of MWCNTs. FE-SEM was used to confirm the dispersion and interphase of MWCNTs. In addition, quasi-static tensile tests were performed to examine the effect of various weight contents of MWCNTs, 0 to 1.0 wt%, on determining the bulk elastic composite properties.
Yu, Namhee,Yong, Seunghui,Kim, Hong Kwan,Choi, Yoon‐,La,Jung, Yeonjoo,Kim, Doyeon,Seo, Jihae,Lee, Ye Eun,Baek, Daehyun,Lee, Jinseon,Lee, Seungjae,Lee, Jong Eun,Kim, Jaesang,Kim, Jhingook,Lee, Sa John Wiley and Sons Inc. 2019 MOLECULAR ONCOLOGY Vol.13 No.6
<P>The roles of miRNAs in lung cancer have not yet been explored systematically at the genome scale despite their important regulatory functions. Here, we report an integrative analysis of miRNA and mRNA sequencing data for matched tumor–normal samples from 109 Korean female patients with non‐small‐cell lung adenocarcinoma (LUAD). We produced miRNA sequencing (miRNA‐Seq) and RNA‐Seq data for 48 patients and RNA‐Seq data for 61 additional patients. Subsequent differential expression analysis with stringent criteria yielded 44 miRNAs and 2322 genes. Integrative gene set analysis of the differentially expressed miRNAs and genes using miRNA–target information revealed several regulatory processes related to the cell cycle that were targeted by tumor suppressor miRNAs (TSmiR). We performed colony formation assays in A549 and NCI‐H460 cell lines to test the tumor‐suppressive activity of downregulated miRNAs in cancer and identified 7 novel TSmiRs (miR‐144‐5p, miR‐218‐1‐3p, miR‐223‐3p, miR‐27a‐5p, miR‐30a‐3p, miR‐30c‐2‐3p, miR‐338‐5p). Two miRNAs, miR‐30a‐3p and miR‐30c‐2‐3p, showed differential survival characteristics in the Tumor Cancer Genome Atlas (TCGA) LUAD patient cohort indicating their prognostic value. Finally, we identified a network cluster of miRNAs and target genes that could be responsible for cell cycle regulation. Our study not only provides a dataset of miRNA as well as mRNA sequencing from the matched tumor–normal samples, but also reports several novel TSmiRs that could potentially be developed into prognostic biomarkers or therapeutic RNA drugs.</P>
Estimation of interfacial properties of nanocomposites using an analytical interphase model
Choi, Hoi Kil,Yu, Jaesang,Kim, Eunho,Sup Shin, Eui Elsevier 2018 Composite Structures Vol.184 No.-
<P><B>Abstract</B></P> <P>In this study, an analytical interphase model is proposed to estimate the interfacial properties between a polymer matrix and carbon nanotubes (CNTs). A molecular dynamics (MD) simulation was performed to obtain the interaction energy and the geometrical parameters of the interphase. The CNTs had the different embedded surface area and functional groups. The interfacial shear strength and critical pull out force were estimated by using an analytical interphase model. The interfacial properties estimated by the proposed interphase model matched the results of the pull out test closely. The changes in the interaction energy and inter thickness introduced by the functionalization of CNTs improved the interfacial properties. These results show that the proposed assumptions were effective and the proposed interphase model using a MD simulation was useful for estimating the interfacial properties of nanocomposites.</P>
Nam, Ki-Ho,Yu, Jaesang,You, Nam-Ho,Han, Haksoo,Ku, Bon-Cheol Elsevier 2017 Composites science and technology Vol.149 No.-
<P><B>Abstract</B></P> <P>We report a facile method to enhance mechanical properties of polymer nanocomposites using three-dimensional (3D) network structures of functionalized graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) in a polymer matrix. The GO and MWCNTs were functionalized using Fisher indole and diazonium-salt reactions to produce pyridine (Py) moiety on the GO and MWCNTs. The functionalized GO (Py-RGO) and MWCNT (Py-MWCNT) nanocomposites exhibited hydrogen-bond assisted 3D network structures in a polyimide (PI) matrix. By incorporating 1 wt% of carbon materials (0.9 wt% Py-RGO and 0.1 wt% Py-MWCNTs) in a PI, the tensile strength and modulus of the ternary nanocomposites reached 581 MPa and 31 GPa, respectively, which was an enhancement of 221% and 312% compared with pristine PI. The fracture energy of the PI/Py-RGO/Py-MWCNT nanocomposites improved 200% and approached 29.7 MJ m<SUP>−3</SUP>. The formation of the 3D network structure of the functionalized carbon nanomaterials is considered to significantly affect load transfer of nanofillers in the polymer matrix, and produce high performance polymer nanocomposites.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Carbon nanofiber-reinforced polymeric nanocomposites
Changwoon Jang,John Hutchins,Jaesang Yu 한국탄소학회 2013 Carbon Letters Vol.14 No.4
Five vapor-grown carbon nanofiber (VGCNF) reinforced vinyl ester (VE) nanocomposite configurations were fabricated, imaged, and mechanically tested in order to obtain information on the influence and the interactions of the role of the microstructure at lower length scales on the observed continuum level properties/response. Three independent variables (the nanofiber weight fraction and two types of nanofiber mixing techniques) were chosen to be varied from low, middle, and high values at equally spaced intervals. Multiple mixing techniques were studied to gain insight into the effect of mixing on the VGCNF dispersion within the VE matrix. The point count method was used for both lower length-scale imaging techniques to provide quantitative approximations of the magnitude and the distribution of such lower length-scale features. Finally, an inverse relationship was shown to exist between the stiffness and strength properties of the resulting nanocomposites under uniaxial quasistatic compression loading.
분자동역학 시뮬레이션을 이용한 CNT/에폭시 복합재의 열기계적 거동 예측
최회길 ( Hoikil Choi ),정하나 ( Hana Jung ),유재성 ( Jaesang Yu ),신의섭 ( Euisup Shin ) 한국복합재료학회 2015 Composites research Vol.28 No.5
본 논문에서는 CNT강화 에폭시 복합재의 열기계적 거동을 예측하고 그 경향을 분석하기 위해 분자동역학 시뮬레이션을 이용하여 해석을 수행하였다. 에폭시 내부 CNT의 체적비율을 0~25%까지 총 6개의 모형을 구성하였다. 열적 거동을 보기 위해 300~600 K까지 일정하게 온도를 상승시켰으며, 온도와 비체적 관계를 이용하여 유리전이 온도와 열팽창 계수를 산출하였다. 또한 일정 변형도 하중을 통해 탄성 계수를 산출하여 기계적 거동을 예측하였다. 추가적으로 CNT의 표면처리에 따른 기계적 거동을 분석하였다. 질소 도핑 및 COOH, OH 그룹을 처리한 3개의 모형을 구성하였으며, 각 모형의 탄성 계수 및 경계면 거동에 대한 해석을 수행하였다. 이를 통해 에폭시 내부 CNT의 응집은 열기계적 거동에 교란을 가지고 올 수 있으며, 표면처리는 복합재의 기계적 물성뿐만 아니라 경계면 특성까지도 향상시킬 수 있음을 확인하였다. In this paper, molecular dynamics (MD) simulation was carried to predict thermo-mechanical behaviors for carbon nanotube (CNT) reinforced epoxy composites and to analyze the trends. Total of six models having the volume fractions of CNT from 0 to 25% in epoxy were constructed. To predict thermal behaviors, temperature was increased constantly from 300 to 600 K, and the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) analyzed using the relationship between temperature and specific volume. The elastic moduli that represented to the mechanical behaviors were also predicted by constant strain. Additionally, the effects of functionalization of CNT on mechanical behaviors of composite were analyzed. Models were constructed to represent CNTs functionalized by nitrogen doping and COOH groops, and interfacial behaviors and elastic moduli were analyzed. Results showed that the agglomerations of CNTs in epoxy cause by perturbations of thermo-mechanical behaviors, and the functionalization of CNTs improved the interfacial response as well as mechanical properties.