Gold functionalized-graphene oxide-reinforced acrylonitrile butadiene rubber nanocomposites for piezoresistive and piezoelectric applications

Bismark Mensah,Dinesh Kumar,Gi-Bbeum Lee,Joohye Won,Kailash Chandra Gupta,Changwoon Nah 한국탄소학회 2018 Carbon Letters Vol.25 No.-

Gold functionalized graphene oxide (GOAu) nanoparticles were reinforced in acrylonitrilebutadiene rubbers (NBR) via solution and melt mixing methods. The synthesized NBR-GOAu nanocomposites have shown significant improvements in their rate of curing, mechanical strength, thermal stability and electrical properties. The homogeneous dispersion of GOAu nanoparticles in NBR has been considered responsible for the enhanced thermal conductivity, thermal stability, and mechanical properties of NBR nanocomposites. In addition, the NBR-GOAu nanocomposites were able to show a decreasing trend in their dielectric constant (ε´) and electrical resistance on straining within a range of 10–70%. The decreasing trend in ε´ is attributed to the decrease in electrode and interfacial polarization on straining the nanocomposites. The decreasing trend in electrical resistance in the nanocomposites is likely due to the attachment of Au nanoparticles to the surface of GO sheets which act as electrical interconnects. The Au nanoparticles have been proposed to function as ball rollers in-between GO nanosheets to improve their sliding on each other and to improve contacts with neighboring GO nanosheets, especially on straining the nanocomposites. The NBR-GOAu nanocomposites have exhibited piezoelectric gauge factor (GFε´) of ~0.5, and piezo-resistive gauge factor (GFR) of ~0.9 which clearly indicated that GOAu reinforced NBR nanocomposites are potentially useful in fabrication of structural, high temperature responsive, and stretchable strain-sensitive sensors.

Reflectarray Antenna Capable of 1-Bit Switchable W-Band Beamforming Network

Bismark Asamani,Seongmin Pyo 한국전기전자학회 2021 전기전자학회논문지 Vol.25 No.2

This paper presents a new reflectarray antenna capable with 1-bit switchable capability for W-band beamforming network. The proposed antenna has been optimized using two unit-cells with sizes of 1.0 ㎜ and 1.3 ㎜ to form a total number of 193 radiating elements on a square aperture surface of length 30 ㎜. These radiating elements are spaced 0.5 wavelengths apart and fed by a 15 ㏈i pyramidal horn antenna as the feed antenna placed 53 ㎜ away from the aperture center. The proposed reflectarray achieves a realized peak gain of 22.52 ㏈i, a half-power beamwidth of 5.1° in both E- and H-planes at the test frequency of 80 ㎓ and operates over a wide bandwidth from 74 ㎓ to 90 ㎓.

Seismic Retrofitting of a Container Crane using Steel Braces, Supplementary Damping and Isolation Devices

Bismark Kofi Meisuh,Van Bac Nguyen,Gibae Kim,Jungwon Huh 대한토목학회 2021 대한토목학회 학술대회 Vol.2021 No.10

Preparation and properties of graphene-reinforced acrylonitrile-butadiene rubber nanocomposites

Bismark Mensah,나창운,임동권,Dinesh Kumar 한국고분자학회 2015 한국고분자학회 학술대회 연구논문 초록집 Vol.2015 No.4

Comparative Analysis of the Dynamic Behaviors of Steel Pedestrian Bridges with Circular Tubular Girders

Bismark Kofi Meisuh,안진희,허정원,김인태,이동석 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.1

The dynamic behavior of two circular tubular steel pedestrian bridges, namely an end cut-off girder bridge and a concrete-filled girder bridge, were examined in this study. The former is proposed in this study as a solution to the construction problems associated with the latter. The numerical models of the two bridges, which were developed and analyzed using the ABAQUS program, were subjected to pedestrian-induced vibrations and seismic excitations to evaluate the acceleration and stress response of the bridge and bridge girders, respectively. The results demonstrate that the two bridge types exhibit similar serviceability performance under a given dynamic load. Specifically, the acceleration response under pedestrian loading differed marginally between the two by approximately 5%. In contrast, the maximum stress in the end cut-off bridge under the seismic excitations was 45% higher than that in the concrete-filled bridge. However, the stress levels observed in both bridge types were within the seismic performance limit.

층상점토 충전 브롬화 이소부틸-이소프렌 검 나노복합체의 점착거동

맨사비스마르크 ( Bismark Mensah ),김성진 ( Sung Jin Kim ),이대학 ( Dae Hak Lee ),김한길 ( Han Gil Kim ),오종갑 ( Jong Gab Oh ),나창운 ( Chang Woon Nah ) 한국고무학회 2014 엘라스토머 및 콤포지트 Vol.49 No.1

브롬화 이소부틸 이소프렌 (BIIR) 고무의 점착성에 미치는 나노점토(Cloisite 20A)의 영향을 조사하였다. 고무내 나노점토의 분산성은 SEM, TEM, XRD으로 분석하였다. 나노점토 충전 및 미충전 고무의 열적안정성은 TGA로 분석하였으며, 충전고무에서 열적안정성을 보였다. 또한 나노점토를 첨가하면 보강효과에 의해 고무의 강도가 증가하였다. 나노점토 첨가로 계면간 분자확산 정도는 감소할 것으로 판단되었지만, 본 연구에서 관찰된 분자확산에 의해 형성된 계면의 두께는 분자사슬간 엄킴현상을 유발하는데 충분하여 계면점착력이 증가하는 것으로 나타났다. 계면점착력 증가현상은 일정한 이상 (8 phr)의 나노점토가 첨가되었을 때 나타났다. 나노점토 첨가에 따른 표면특성의 변화를 조사하기 위해 접촉각 측정을 하였는데 큰 변화는 관찰되지 않았다. The effect of nanoclay (Cloisite 20A) on the self-adhesion behavior of uncured brominated-isobutylene-isoprene rubber (BIIR) has been studied. The dispersion state of nanoclay into the rubber matrix was examined by SEM, TEM and XRD analysis. The thermal degradation behavior of the filled and unfilled samples was examined by TGA and improvement in the thermal stability of the nanocomposites occurred based on the weight loss (%) measurements. Also, addition of nanoclay enhanced the cohesive strength of the material by reinforcement action thereby reducing the degree of molecular diffusion across the interface of butyl rubber. However, the average depth of penetration of the inter-diffused chains was still adequate to form entanglement on either side of the interface, and thus offered greater resistance to peeling, resulting in high tack strength measurements. The improvement in tack strength was only achieved at critical nanoclay loading above 8 phr. Contact angle measurement was also made to examine the surface characteristics. There was no significant interfacial property change by employing the nanoclay.

원형튜브거더 보행자 강교의 진동 사용성 평가

( Meisuh Bismark Kofi ),( Huh Jungwon ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.1

Pedestrian bridges with circular tubular girders are faced with constructional difficulties. This study proposes a solution that involves using end cut-off girder to overcome the challenges associated with installing bearings on the full circular section girders. The two girder types are incorporated into two separate finite element models of a simple bridge to evaluate the acceleration response of the bridge under pedestrian-induced dynamic load. The results show that introducing the end cut-off did not compromise the serviceability performance of the bridge.

Graphene-reinforced elastomeric nanocomposites: A review

Mensah, Bismark,Gupta, Kailash Chandra,Kim, Hakhyun,Wang, Wonseok,Jeong, Kwang-Un,Nah, Changwoon Elsevier 2018 POLYMER TESTING -LONDON- Vol.68 No.-

<P><B>Abstract</B></P> <P>The development of graphene nanosheets and/or their derivatives (GSDs) has sparkled worldwide overwhelming industrial and academic research interests, due to their unique and potentially useful properties. This review is written to highlight the state of art of GSDs/elastomer nanocomposites and their applications in various fields of technologies. It begins with reviewing the recent progress made in GSDs/elastomer nanocomposites in comparison to elastomer nanocomposites based on carbon nanotubes. The role of GSDs structures, functionalization, type of matrices, and content of fillers on properties of GSDs/elastomer composites has been reviewed systematically. The basic properties of various GSDs/elastomer nanocomposites including; morphology, curing behavior, mechanical properties such as Young's modulus (E), tensile strength (σ<SUB>s</SUB>) and elongation at break (E<SUB>b</SUB>), electrical percolation threshold, and thermal stability have been discussed in details. Finally, an attempt has been made to identify the critical challenges, which still need to be addressed for improving the processing of GSDs/elastomer nanocomposites and to explore their prospects for advanced applications. The article has been concluded by summarizing the key facts of GSDs that play significant role in developing GSDs/elastomer nanocomposites for technological applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This review article covers every aspect of elastomer nanocomposites based on graphenes and graphenes derivatives(GSD). </LI> <LI> Characterization of GSD structure, morphology functionalization, matrix type, and various properties of GSD/elastomer composite have been systematically reviewed. </LI> <LI> Challenges for further improving the processing of GSD/elastomeric nanocomposites and for exploring future advanced applications of elastomer nanocomposites.. </LI> </UL> </P>

Damage Potential of Different Frequency Content Earthquakes on Typical Korean Jumbo Container Crane

Meisuh, Bismark Kofi,Shin, Geunock,Kim, Jongwoo,Huh, Jungwon 대한토목학회 2020 대한토목학회 학술대회 Vol.2020 No.10

Amphipathic Starch with Phosphate and Octenylsuccinate Substituents for Strong Adhesion to Cotton in Warp Sizing

Sarkodie Bismark,Zhifeng Zhu 한국섬유공학회 2018 Fibers and polymers Vol.19 No.9

The objectives of this work were to survey the effect of amphipathic modification of starch on the adhesion to cotton fibers for improving the adhesion of starch to cotton in warp sizing. The amphipathic starch (AS) with oleophilic octenylsuccinate and hydrophilic phosphate substituents was prepared by the phosphorylation with sodium tripolyphosphate (STP) followed by the octenylsuccinylation with 2-octenylsuccinic anhydride (OSA). Two series of AS samples with differential total degrees of substitution (DSt) and substituent ratios of phosphates to octenylsuccinates were evaluated by fourier transform infrared (FTIR) analysis, degree of substitution, adhesion to cotton and surface tension. The adhesion of the starch to fibers was investigated using a legal method (FZ/T 15001-2008). The FTIR spectra revealed that octenylsuccinates and phosphates have been attached to the backbones of the starch. The amphipathic modification of starch with STP and OSA was an effective method to enhance the adhesion of corn starch to cotton. The strong adhesion of the AS to cotton was attributed to the reduced surface tension arisen from oleophilic octenylsuccinate and hydrophilic phosphate substituents and increased steric hindrance of the substituents introduced onto starch. The investigation showed that the improvement in the adhesion of the starch after amphipathic modification could be buttressed by the tensile strength of cotton yarns sized with AS. It was found that the AS was desizable and showed satisfactory desizing efficiency in oxidant desizing. Based on the adhesion, reaction efficiencies, and desizability, the AS with a total DSt of 0.033 and a substituent ratio of DSp0.014/DSo0.032 showed potential for use in warp sizing.