Effect of Commingled Yarn Type on the Manufacturing of Glass Fiber/Polypropylene Composite Prepreg

Jinwon Cho(조진원),Jaehyeung Park(박재형) 한국고분자학회 2021 폴리머 Vol.45 No.3

본 연구에서는 다른 방식의 커밍글 얀(commingled yarn)과 제직방법을 이용하여 유리섬유와 폴리프로필렌 복합 프리프레그를 제조하고 그 구조 특성과 성질에 대해 살펴보았다. 복합 프레프레그 제조를 위하여 covering 방식과 air textured 방식으로 제조된 두 종류의 커밍글 얀을 이용하여, 평직과 능직으로 직조하였다. 프리프레그 제작 시 커밍글얀 방식과 직조방법에 따라 유리 섬유의 배열이 불규칙적으로 이동됨을 확인하였고, 이는 열가소성 수지인 폴리프로필렌의 높은 점도에 기인한 것이다. 직조된 유리섬유 패턴의 변형은 프리프레그의 기계적 물성에 큰 영향을 미치는 것을 확인하였다. 본 연구에서 확인된 결과들은 향후 하이브리드 섬유를 이용한 프리프레그 개발 시 공정을 설계하는데 도움이 될 것으로 기대된다. Glass fiber/polypropylene (GF/PP) composite prepregs were produced using different types of commingled yarns with different weave patterns. The commingled yarn used in this study was prepared using covering and air textured methods and the prepared commingled yarns were woven into two different weave patterns, plain and twill. The results show the effect of the commingling method and weave pattern on impregnation and alignment of GF in the composite prepregs due to the flow of the highly viscous molten PP resins. The mechanical properties (tensile strength, puncture impact properties, and Izod pendulum impact resistance) of the prepared composite prepregs were also evaluated. The results of this study show that the best tensile and impact resistance properties of composite prepreg is achieved using fabrics with a twill weave pattern made from air textured yarn (ATY) commingled yarns, which ensures the uniformity and alignments of the GF yarns in the composite.

On the Role of Heteronuclear Interactions in Boosting H₂ Production from HCOOH Decomposition on Bimetallic Pd-M Catalysts

Jinwon Cho,Sangheon Lee,Sung Pil Yoon,Jonghee Han,Suk Woo Nam,Kwan-Young Lee,Hyung Chul Ham 한국진공학회 2017 한국진공학회 학술발표회초록집 Vol.2017 No.8

Enhanced Selectivity to H₂ Formation in Decomposition of HCOOH on the Ag₁₉@Pd₆₀ Core-Shell Nanocluster from First-Principles

Cho, Jinwon,Lee, Sangheon,Han, Jonghee,Yoon, Sung Pil,Nam, Suk Woo,Choi, Sun Hee,Hong, Seong-Ahn,Lee, Kwan-Young,Ham, Hyung Chul American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.10

<P> In this study, using spin-polarized density functional theory calculation we examined the origin of enhanced catalytic activity toward H<SUB>2</SUB> production from HCOOH in Ag<SUB>19</SUB>@Pd<SUB>60</SUB> core-shell nanoclusters (a 79-atom truncated octahedral cluster models). First, we find that the Pd monolayer shell on the Ag core can greatly enhance the selectivity to H<SUB>2</SUB> formation via HCOOH decomposition compared to the pure Pd<SUB>79</SUB> cluster by substantially reducing the binding energy of key intermediate HCOO and in turn the barrier for dehydrogenation. This activity enhancement is related to the modification of d states in the Pd monolayer shell by the strong ligand effect between Ag core and Pd shell, rather than the tensile strain effect by Ag core. In particular, the absence of dz<SUP>2</SUP>-r<SUP>2</SUP> density of states near the Fermi level in the Pd monolayer shell (which originated from the substantial charge transfer from Ag to Pd) is the main reason for the increased H<SUB>2</SUB> production from HCOOH decomposition. </P>

개미산 분해 반응에서 수소 생산성 증대를 위한 Pd/Pd₃Fe 합금 촉매: 범밀도 함수 이론 연구

조진원 ( Jinwon Cho ),한종희 ( Jonghee Han ),윤성필 ( Sung Pil Yoon ),남석우 ( Suk Woo Nam ),함형철 ( Hyung Chul Ham ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.2

본 연구에서는 양자 역학 계산 이론 중 하나인 Density Functional Theory (DFT)를 사용하여 Pd/Pd₃Fe 촉매 표면에서 개미산(HCOOH) 분해 반응으로부터 수소를 생산하는 반응 메커니즘을 분석하였다. 기존 연구에 따르면, 단일 원자 촉매 중에서 개미산 분해 반응에 가장 높은 수소 생산성을 기록하는 원자는 Pd 촉매이지만, 부 반응으로 생산되는 CO가 Pd에 독성을 띄우기 때문에 Pd 촉매의 성능을 저하시킨다. 이러한 단점을 극복하고자, Pd를 기반으로 Pd와 Fe를 3:1로 합금하여 Pd₃Fe가 코어(core) 형태로 존재하고 Pd가 표면에 위치한 core-shell Pd/Pd₃Fe 촉매를 설계하여 개미산 분해 반응에 의한 수소 생산 속도를 계산하였다. 순수 Pd촉매 보다 Pd/Pd₃Fe 촉매의 수소 생산 반응의 활성 에너지가 감소 하였다. 그 이유는 Pd와 Fe가 합금화 되면서 Pd₃Fe의 격자 상수가 2.76 A로 줄어 들어 HCOO의 흡착에너지를 0.03 eV 감소시켰고, Fe에서 표면 Pd로 전자가 이동하면서 표면 전자 구조가 변화하여 HCOO의 흡착에너지를 0.29 eV 낮추었기 때문이다. 본 연구에서 제안하는 결과를 바탕으로 추후 개미산으로부터 수소 생산이 더 용이한 새로운 촉매 설계 메커니즘을 제안하고자 한다. Formic acid has been known as one of key sources of hydrogen. Among various monometallic catalysts, hydrogen can be efficiently produced on Pd catalyst. However, the catalytic activity of Pd is gradually reduced by the blocking of active sites by CO, which is formed from the unwanted indirect oxidation of formic acid. One of promising solutions to overcome such issue is the design of alloy catalyst by adding other metal into Pd since alloying effect (such as ligand and strain effect) can increase the chance to mitigate CO poisoning issue. In this study, we have investigated formic acid deposition on the bimetallic Pd/Pd₃Fe core-shell nanocatalyst using DFT (density functional theory) calculation. In comparison to Pd catalyst, the activation energy of formic acid dehydrogenation is greatly reduced on Pd/Pd₃Fe catalyst. In order to understand the importance of alloying effects in catalysis, we decoupled the strain effect from ligand effect. We found that both strain effect and ligand effect reduced the binding energy of HCOO by 0.03 eV and 0.29 eV, respectively, compared to the pure Pd case. Our DFT analysis of electronic structure suggested that such decrease of HCOO binding energy is related to the dramatic reduction of density of state near the fermi level.

Polymeric graphitic carbon nitride nanosheet-coated amorphous carbon supports for enhanced fuel cell electrode performance and stability

Lee, In Hyuk,Cho, Jinwon,Chae, Keun Hwa,Cho, Min Kyung,Jung, Juhae,Cho, Jongin,Lee, Hyun Jin,Ham, Hyung Chul,Kim, Jin Young Elsevier 2018 Applied Catalysis B Vol.237 No.-

<P><B>Abstract</B></P> <P>Carbon blacks, which consist of the assemblies of small graphene clusters having a spherical concentric packing structure, are amorphous and have widely been used as catalyst supports for proton exchange membrane fuel cell (PEMFC) electrodes. However, poor electrochemical corrosion resistance during extended use and repeated cyclic operation of PEMFCs shortens their practical device lifetime; surface defects, such as nanosized disordered domains, have been established as the most influential factors. Herein, we coupled polymeric graphitic carbon nitride (pg-CN) with amorphous carbon black (a-CB) in a core@shell structure to produce an electrochemically efficient and stable electrocatalyst support. Our protocol allowed for the simultaneous optimization of uniformly thin graphitic shell structures for electrochemical corrosion stability and nitrogen-enriched functionalities on the carbon surfaces for electrocatalyst (e.g., platinum) nucleation. The newly prepared a-CB@pg-CNs enhanced the stable fuel cell devices operation and remained invariant even at high potential (1.2–1.7 V). Significantly, when used for constructing the PEMFC electrode, a-CB@pg-CN support-based Pt catalyst electrodes outperformed and exhibited superior stability over state-of-the-art commercial a-CB-based counterparts. Experimental observations and density functional theory (DFT) calculations revealed that the unusual electrocatalytic properties of as-prepared a-CB@pg-CNs originated from an intrinsic chemical and electronic coupling that synergistically reduced electrochemical corrosion kinetics and promoted catalyst–support interactions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polymeric graphitic carbon nitride was coated on amorphous carbon. </LI> <LI> The a-CB@pg-CN supports showed an electrochemical stability. </LI> <LI> Pt has been perfectly deposited on a-CB@pg-CN. </LI> <LI> The Pt/a-CB@pg-CN catalyst enhanced the stable PEM fuel cell devices operation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Selective production of 2,3-butanediol and acetoin by a newly isolated bacterium Klebsiella oxytoca M1.

Cho, Sukhyeong,Kim, Kyung Duk,Ahn, Jae-Hyung,Lee, Jinwon,Kim, Seon-Won,Um, Youngsoon Humana Press 2013 Applied biochemistry and biotechnology Vol.170 No.8

<P>A newly isolated bacterium, designated as Klebsiella oxytoca M1, produced 2,3-butanediol (2,3-BDO) or acetoin selectively as a major product depending on temperature in a defined medium. K. oxytoca M1 produced 2,3-BDO mainly (0.32~0.34 g/g glucose) at 30 C while acetoin was a major product (0.32~0.38 g/g glucose) at 37 C. To investigate factors affecting product profiles according to temperature, the expression level of acetoin reductase (AR) that catalyzes the conversion of acetoin to 2,3-BDO was analyzed using crude protein extracted from K. oxytoca M1 grown at 30 and 37 C. The AR expression at 37 C was 12.8-fold lower than that at 30 C at the stationary phase and reverse transcription PCR (RT-PCR) analysis of the budC (encoding AR) was also in agreement with the AR expression results. When AR was overexpressed using K. oxytoca M1 harboring pUC18CM-budC, 2,3-BDO became a major product at 37 C, indicating that the AR expression level was a key factor determining the major product of K. oxytoca M1 at 37 C. The results in this study demonstrate the feasibility of using K. oxytoca M1 for the production of not only 2,3-BDO but also acetoin as a major product.</P>

Evaluation of Thermal Deformation Model for BGA Packages Using Moire Interferometry

Jinwon Joo,Seungmin Cho 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.2

A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moire inter-ferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moire experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.<br/>

STUDY ON CHARACTERISTICS OF RATED AND UNSTEADY CONDITION OF 5KW CLASS MID-TEMPERATURE METHANE-STEAM REFORMER

Kyungin Cho,Jinwon Yun,Sangseok Yu 한국신재생에너지학회 2017 AFORE Vol.2017 No.11

자동차 실내 IAQ향상을 위한 HVAC 내외기율 범위에 따른 수치 해석적 연구

서진원(Jinwon Seo),최윤호(Yunho Choi),임택규(Taekkyu Lim),조중원(Chungwon Cho),박지용(Jiyong Park),김만회(Manhoe Kim) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11

The air quality inside the cabin of an automobile is closely related to the health of those who spend a lot of time in their vehicles. Automotive indoor air quality can be improved in several ways; the most common and effective of which was to dilute the polluted air with fresh air through the vehicle"s HVAC. In this study, we considered switching between the outside air mode and the recirculation mode of the automotive HVAC, and how that change affected the concentration of pollution within the vehicle. The possible range between the outside air mode and the recirculation mode of the vehicle"s HVAC obtained by this experiment was applied to the CFD analysis. Furthermore, the actual vehicles were infused with gas over time and were compared for the purposes of feasibility review of numerical simulation and concentration trends of experimental data. In the CFD analysis, UDF(user defined function) was applied to our code in order to decipher the range of outside air and recirculation mode of the HVAC. Data generated through the full range between outside air and recirculation mode of the vehicle"s HVAC were analyzed under a variety of conditions which allowed the identification of characteristics which changed indoor air quality source concentration.

Evaluation of Thermal Deformation Model for BGA Packages Using Moire Interferometry

Joo, Jinwon,Cho, Seungmin The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.2

A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moire interferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moire experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.