Copper Shell Networks in Polymer Composites for Efficient Thermal Conduction

Yu, Seunggun,Lee, Jang-Woo,Han, Tae Hee,Park, Cheolmin,Kwon, Youngdon,Hong, Soon Man,Koo, Chong Min American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.22

<P>Thermal management of polymeric composites is a crucial issue to determine the performance and reliability of the devices. Here, we report a straightforward route to prepare polymeric composites with Cu thin film networks. Taking advantage of the fluidity of polymer melt and the ductile properties of Cu films, the polymeric composites were created by the Cu metallization of PS bead and the hot press molding of Cu-plated PS beads. The unique three-dimensional Cu shell-networks in the PS matrix demonstrated isotropic and ideal conductive performance at even extremely low Cu contents. In contrast to the conventional simple melt-mixed Cu beads/PS composites at the same concentration of 23.0 vol %, the PS composites with Cu shell networks indeed revealed 60 times larger thermal conductivity and 8 orders of magnitude larger electrical conductivity. Our strategy offers a straightforward and high-throughput route for the isotropic thermal and electrical conductive composites.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-22/am4030406/production/images/medium/am-2013-030406_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4030406'>ACS Electronic Supporting Info</A></P>

RTA-Treated Carbon Fiber/Copper Core/Shell Hybrid for Thermally Conductive Composites

Yu, Seunggun,Park, Bo-In,Park, Cheolmin,Hong, Soon Man,Han, Tae Hee,Koo, Chong Min American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.10

<P>In this paper, we demonstrate a facile route to produce epoxy/carbon fiber composites providing continuous heat conduction pathway of Cu with a high degree of crystal perfection via electroplating, followed by rapid thermal annealing (RTA) treatment and compression molding. Copper shells on carbon fibers were coated through electroplating method and post-treated via RTA technique to reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated carbon fiber composites with Cu shell of 12.0 vol % prepared via simple compression molding, revealed 18 times larger thermal conductivity (47.2 W m<SUP>–1</SUP> K<SUP>–1</SUP>) in parallel direction and 6 times larger thermal conductivity (3.9 W m<SUP>–1</SUP> K<SUP>–1</SUP>) in perpendicular direction than epoxy/carbon fiber composite. Our novel composites with RTA-treated carbon fiber/Cu core/shell hybrid showed heat conduction behavior of an excellent polymeric composite thermal conductor with continuous heat conduction pathway, comparable to theoretical values obtained from Hatta and Taya model.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-10/am500871b/production/images/medium/am-2014-00871b_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am500871b'>ACS Electronic Supporting Info</A></P>

Interface-engineered Polypropylene Blends for High Voltage Power Cable Insulations

Seunggun Yu(유승건),이대호 한국고분자학회 2020 한국고분자학회 학술대회 연구논문 초록집 Vol.45 No.2

Highly Thermal Conductive Composites with Three-Dimensional Percolative Networks of Cu Shell

Seunggun Yu,Seung Hwan Lee,Jun Pyo Hong,Soon Man Hong,Chong Min Koo 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Triboelectric nanogenerators with transfer-printed arrays of hierarchically dewetted microdroplets

Park, Chanho,Yu, Seunggun,Cho, Suk Man,Song, Giyoung,Lee, Yujeong,Kang, Han Sol,Lee, Seung Won,Eoh, Hongkyu,Park, Cheolmin Elsevier 2018 Nano energy Vol.51 No.-

<P><B>Abstract</B></P> <P>Triboelectric nanogenerators (TENG) is of great interest as an emerging power harvester due to its simple device architecture and high efficiency. Despite development of various surface modification techniques for enhancing the performance of a TENG with a given triboelectric pair of materials, a method capable of being used universally on a variety of surfaces and improving the performance of TENGs with diverse surfaces remains a challenge. Here, we demonstrate a novel transfer-printing technique of hierarchically dewetted polymer droplets on various TENG surfaces for performance enhancement of the TENGs. Our method is based on controlled dewetting of a thin supramolecular assembled film of two end-functionalized polymer blends on a prepatterned poly(dimethyl siloxane) mold, followed by the physical pattern-transfer of arrays of the dewetted droplets consisting of supramolecular assembled nanostructures on a TENG contact surface. The hierarchically dewetted microdroplets comprising soft-etched nanopores efficiently improve the performance of a TENG by more than three times compared to one without the transferred pattern. The pattern-transfer is successfully achieved on various surfaces including not only oxides, plastics, rubbers, and metals, but also fabrics, coins, vegetables, and shells, making our approach a convenient way for enhancing the triboelectric performance of a given TENG.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Transfer printing was used as a versatile tool to enhance contact area of a TENG. </LI> <LI> The performance of a TENG was improved by more than three times with the pattern. </LI> <LI> A variety of surfaces were suitable, including oxides, plastics, rubbers, and metals. </LI> <LI> Transfer printing well occurred on stretchable, bendable, and roughened substrates. </LI> <LI> The printing offers opportunities for broadening the choice of materials for TENGs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Sulfur doped graphene/polystyrene nanocomposites for electromagnetic interference shielding

Shahzad, Faisal,Yu, Seunggun,Kumar, Pradip,Lee, Jang-Woo,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min Elsevier 2015 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.133 No.-

<P><B>Abstract</B></P> <P>In this paper, for the first time, we present a simple and straightforward method to improve not only electrical conductivity and complex permittivity but also electromagnetic interference (EMI) shielding effectiveness of reduced graphene oxide (rGO)/polystyrene (PS) nanocomposites through sulfur doping. Sulfur-doped reduced graphene oxide with thiophene-like structure (2.6at.% S), synthesized through a simple heating process of a mixture of graphene oxide and sulfur powder, revealed almost three times larger electrical conductivity (1095Sm<SUP>−1</SUP>) than undoped rGO (395Sm<SUP>−1</SUP>). The SrGO/PS nanocomposite showed not only 150% larger electrical conductivity and 50% larger complex permittivity, but also improved EMI shielding effectiveness (24.5dB) at a frequency of 18GHz than rGO/PS nanocomposite (21.4dB) at the same loading level of 7.5vol.%. Considering the simplicity and effectiveness of process, sulfur doping of graphene is expected to be used as a versatile method to improve EMI shielding efficiency of graphene/polymer nanocomposites.</P>

Highly Anisotropic Copper Oblate Ellipsoids Incorporated Polymer Composites with Excellent Performance for Broadband Electromagnetic Interference Shielding

Seung Hwan Lee,Seunggun Yu,Faisal Shahzad,Jun Pyo Hong,Chong Min Koo 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Molecularly Engineered Surface Triboelectric Nanogenerator by Self-Assembled Monolayers (METS)

Song, Giyoung,Kim, Younghoon,Yu, Seunggun,Kim, Min-Ook,Park, Sang-Hee,Cho, Suk Man,Velusamy, Dhinesh Babu,Cho, Sung Hwan,Kim, Kang Lib,Kim, Jongbaeg,Kim, Eunkyoung,Park, Cheolmin American Chemical Society 2015 Chemistry of materials Vol.27 No.13

<P>Self-powered energy harvesters utilizing triboelectric effect and electrostatic induction have been widely studied, leading in the materials viewpoint to numerous material pairs for facile charge separation upon repetitive contacts with elaborate topological structures. Here, we present a simple but robust triboelectric platform based on a molecularly engineered surface triboelectric nanogenerator by self-assembled monolayers (METS). Triboelectric surface charge density of a substrate was readily controlled by the variation of end-functional groups of self-assembled monolayers (SAMs). In particular, by employing fluorine terminated SAMs, we are able to develop a METS with the maximum open circuit voltage and short circuit current of 105 V and 27 μA, respectively, under relatively gentle mechanical contacts with the 3N vertical force at 1.25 Hz. The power density of the device was 1.8 W/m<SUP>2</SUP> at the load resistance of 10 MΩ more than 60 times greater than that of an unmodified dielectric/Al device. Moreover, our approach with SAMs was extended to various types of surfaces including fabrics of silk, cotton, and poly(ethylene terephthalate) (PET) and a PET film, and the results of single-friction-surface triboelectric nanogenerators with these materials offers a facile and universal guideline for designing triboelectic materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-13/acs.chemmater.5b01507/production/images/medium/cm-2015-01507p_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b01507'>ACS Electronic Supporting Info</A></P>

Shape-Adaptable 2D Titanium Carbide (MXene) Heater

Park, Tae Hyun,Yu, Seunggun,Koo, Min,Kim, Hyerim,Kim, Eui Hyuk,Park, Jung-Eun,Ok, Byeori,Kim, Byeonggwan,Noh, Sung Hyun,Park, Chanho,Kim, Eunkyoung,Koo, Chong Min,Park, Cheolmin American Chemical Society 2019 ACS NANO Vol.13 No.6

<P>Prior to the advent of the next-generation heater for wearable/on-body electronic devices, various properties are required, including conductivity, transparency, mechanical reliability, and conformability. Expansion to two-dimensional (2D) structure of metallic nanowires based on network- and mesh-type geometries has been widely exploited for realizing these heaters. However, the routes led to many drawbacks such as the low-density cross-bar linking, self-aggregation of wire, and high junction resistance. Although 2D carbon nanomaterials such as graphene and reduced graphene oxide (rGO) have shown their potentials for the purpose, CVD-grown graphene with sufficiently high conductivity was limited due to its poor processability for large-area applications, while rGO fabricated with a complex reduction process involving the use of toxic chemicals suffered from a low electrical conductivity. In this study, we demonstrate a simple and robust process, utilizing electrostatic assembling of negatively charged MXene flakes on a positively treated surface of substrate, for fabricating a metal-like 2D MXene thin film heater (TFH). Our TFH showed a high optical property (>65%), low sheet resistance (215 ?/sq), fast electrothermal response (within dozens of seconds) with an intrinsically high electrical conductivity, and mechanical flexibility (up to 180? bending). Its capability for forming a firm and stable ionic-type interface with a counterpart surface allows us to develop a shape-adaptable and patchable thread heater (TH) that can be shaped on diverse substrates even under harsh conditions of conventional sewing or weaving processes. This work suggests that our shape-adaptable MXene heaters are potentially suitable not only for wearable devices for local heating and defrosting but also for a variety of emerging applications of soft actuators and wearable/flexible healthcare monitoring and thermotherapy.</P> [FIG OMISSION]</BR>

Low percolation 3D Cu and Ag shell network composites for EMI shielding and thermal conduction

Lee, Seung Hwan,Yu, Seunggun,Shahzad, Faisal,Hong, Junpyo,Noh, Seok Jin,Kim, Woo Nyon,Hong, Soon Man,Koo, Chong Min Elsevier 2019 Composites science and technology Vol.182 No.-

<P><B>Abstract</B></P> <P>Metal-coated polymer bead based composites are promising as electromagnetic interference (EMI) shielding and thermally conductive materials because they form a percolation 3D metal shell network at very low filler content. Herein, we fabricated 3D Cu/Ag shell network composites through electroless plating of metal on polymer beads and a simple hot pressing technique. Cu and Ag shells provide a continuous network for electron and heat conduction; thus, yielding excellent EMI shielding effectiveness of 110 dB at a 0.5 mm thickness and a thermal conductivity of 16.1 W m<SUP>−1</SUP>K<SUP>−1</SUP> at only 13 vol % of metal filler. The properties of composites depend on the size of polystyrene (PS) beads and large size metal-coated PS bead composites exhibit higher electrical conductivity, EMI shielding effectiveness, and thermal conductivity than small size bead composites. These results are ascribed to the reduction in the number of contact interfaces between metal-coated beads, which minimizes the interfacial resistance. This study is set to pave the way for designing advanced EMI shielding and thermal conductive materials by a scalable and efficient synthesis approach.</P>