Yeoh Cheow Keat
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Preferred name
Yeoh Cheow Keat
Official Name
Cheow Keat, Yeoh
Alternative Name
Yeoh, C. K.
Yeoh, Cheow Keat
Yeoh, Cheow-Keat
Main Affiliation
Scopus Author ID
16231574200
Researcher ID
EGP-0633-2022

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Effect of zinc oxide suspension on the overall filler content of the PLA/ZnO composites and cPLA/ZnO composites

2023-01-01 , Tan M.A. , Yeoh Cheow Keat , Teh P.L. , Nor Azura Abdul Rahim , Song C.C. , Voon Chun Hong

This work aimed to study the effect of zinc oxide (ZnO) filler suspension on the mechanical, electrical, and thermal properties of polylactic acid (PLA)/ZnO and cPLA/ZnO. Fused deposition modelling, one of the additive manufacturing methods, was used to fabricate the PLA specimen. PLA was used as the main material in this project, and the ZnO suspension was added during the printing process. The speed of the dispenser (low speed = 1,000 rpm, medium speed = 1,400 rpm, and high speed = 1,800 rpm) was the parameter that was varied to control the filler content of the composite. All the samples underwent a tensile test to determine the mechanical properties, followed by the scanning electron microscopy (SEM) test to analyse the fracture surface properties of the tensile test. SEM observations showed the PLA samples' inherent smooth appearance, but the PLA/ZnO composite showed a rougher surface. PLA and cPLA composites showed an enhanced storage modulus but lower loss modulus than the pure samples. Because of the high thermal and electrical conductivity of carbon black and ZnO, cPLA composites had higher electrical and thermal conductivity than PLA composites.

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Microwave welding of thermoplastic using silicon carbide nanowhiskers as susceptor effect of heating duration

2024-06 , Phey Yee Foong , Voon Chun Hong , Lim Bee Ying , Teh Pei Leng , Yeoh Cheow Keat , Mohd Afendi Rojan , Nor Azizah Parmin , Subash Chandra Bose Gopinath , Foo Wah Low , Muhammad Kashif , Nor Azura Abdul Rahman , Sam Sung Ting , Veeradasan Perumal

Microwave welding is becoming more popular than conventional joining methods due to its advantages such as rapid and localised heating as well as applicable to components with complicated geometry. Previously reported susceptor, such as carbonaceous materials and conductive polymers, are toxic and the welding process involving these susceptors is time-consuming. Because of its exceptional microwave absorption and biocompatibility, silicon carbide nanowhiskers (SiCNWs) was employed as the microwave susceptor for microwave welding. Microwave welding in this study comprises of only three simple steps: SiCNWs suspension preparation, SiCNWs application and microwave heating. The weld strength of welded joint was then characterised using tensile test and energy dispersive x-ray spectroscopy equipped scanning electron microscopy (EDS-SEM) to study its mechanical properties and cross-section microstructure. The influence of microwave irradiation time was studied in this study, and it is found that the weld strength rose with the extension of microwave irradiation time, until a maximum weld strength of 1.61 MPa was achieved by 17 s welded joint. The development of SiCNWs reinforced PP nanocomposite welded joint layer is responsible for the enhanced weld strength. Prolonged heating duration may also result in flaws such as void formation at the welded joint, which subsequently lowered the weld strength to 0.60 MPa when the heating duration was extended to 20 s. In sum, a strengthen welded joint can be formed with rapid microwave heating under the proper control of heating duration.

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Comparison study between recovered carbon black and commercial carbon black filled epoxy conductive materials

2024-01-01 , Ooi H.M. , Teh Pei Leng , Yeoh Cheow Keat , Wong W.C. , Yew C.H. , Lim X.Y. , Yeoh K.K. , Nor Azura Abdul Rahim , Voon Chun Hong

Waste tire management and recycling have grown to be significant issues because they bring up a global environmental concern. Thus, turning recycled waste tires into useful products may help tackle the environmental issue. This research aims to study and compare the effect of recycled carbon black (rCB) and commercial carbon black (CB) at certain 15 vol. % of filler loading on the mechanical, thermal, morphology and electrical properties of epoxy/CB composites. For this project, epoxy resin, diethyltoluenediamine (DETDA), recovered carbon black (rCB) and commercial carbon black (CB) graded N330, N550, N660 and N774 were mixed and compared accordingly to the formulation determined. The CB content was dispersed in the epoxy matrix using the mechanical mixing technique. The distribution and dispersion of CB in the epoxy matrix affect the characteristics of the conductive composites. rCB content at 15 vol% was selected at fixed content for comparison purposes due to the optimum value in electrical conductivity results. The flexural strength results followed the sequence of rCB>N774>N660>N550>N330. As for electrical conductivity results, epoxy/N330 exhibited the highest conductivity value, while the others achieved a magnitude of X10-3 due to the highest external surface area of N330. In terms of thermal stability, epoxy/N330 and epoxy/N774 were slightly more stable than epoxy/rCB.

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Microwave welding with SiCNW/PMMA nanocomposite thin films: enhanced joint strength and performance

2025-01 , Phey Yee Foong , Voon Chun Hong , Lim Bee Ying , Foo Wah Low , Teh Pei Leng , Nor Azizah Parmin , Subash Chandra Bose Gopinath , Veeradasan Perumal , Yeoh Cheow Keat , Nor Azura Abdul Rahim

Most previously reported susceptors for microwave welding are in powder form. In this study, a thin-film susceptor was employed due to its uniform heating rate and ease of handling. Silicon carbide nanowhisker (SiCNW) were incorporated into a poly(methyl methacrylate) (PMMA) matrix to create a nanocomposite thin film, which served as the susceptor. The microwave welding process involved three straightforward steps: fabrication of the PMMA/SiCNW nanocomposite thin film, application of the nanocomposite film to the target area, and subsequent microwave heating. Upon cooling, a robust microwave-welded joint was formed. The mechanical properties and microstructure of the welded joints were characterized using single-lap shear tests, three-point bending tests, and scanning electron microscopy. Results demonstrated that the shear strength and elastic modulus of the welded joints were optimized with increased heating time and SiCNW filler loading. This optimization is attributed to the formation of a SiCNW-filled polypropylene (PP) nanocomposite layer of increasing thickness at the welded joint interface. However, the incorporation of SiCNW also constrained the mobility of the PP chains, reducing the joint’s flexibility. Furthermore, the welded joint formed with the PMMA/SiCNW nanocomposite thin-film susceptor exhibited an 18.82% improvement in shear strength compared to joints formed with a powdered SiCNW susceptor. This study not only demonstrates the potential of PMMA/SiCNW nanocomposite thin films as efficient susceptors for microwave welding but also paves the way for developing high-performance polymer-based composite joints with improved mechanical properties for applications in the automotive, aerospace, and construction industries.

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Microwave Welding of Thermoplastic using Silicon Carbide Nanowhiskers as Susceptor: Effect of Heating Duration

2024-06-01 , Foong P.Y. , Voon Chun Hong , Lim Bee Ying , Teh Pei Leng , Yeoh Cheow Keat , Mohd Afendi Rojan , Nor Azizah Parmin , Low F.W. , Subash Chandra Bose Gopinath , Kashif M. , Rahman N.A.A. , Sam Sung Ting , Perumal V.

Microwave welding is becoming more popular than conventional joining methods due to its advantages such as rapid and localised heating as well as applicable to components with complicated geometry. Previously reported susceptor, such as carbonaceous materials and conductive polymers, are toxic and the welding process involving these susceptors is time-consuming. Because of its exceptional microwave absorption and biocompatibility, silicon carbide nanowhiskers (SiCNWs) was employed as the microwave susceptor for microwave welding. Microwave welding in this study comprises of only three simple steps: SiCNWs suspension preparation, SiCNWs application and microwave heating. The weld strength of welded joint was then characterised using tensile test and energy dispersive x-ray spectroscopy equipped scanning electron microscopy (EDS-SEM) to study its mechanical properties and cross-section microstructure. The influence of microwave irradiation time was studied in this study, and it is found that the weld strength rose with the extension of microwave irradiation time, until a maximum weld strength of 1.61 MPa was achieved by 17 s welded joint. The development of SiCNWs reinforced PP nanocomposite welded joint layer is responsible for the enhanced weld strength. Prolonged heating duration may also result in flaws such as void formation at the welded joint, which subsequently lowered the weld strength to 0.60 MPa when the heating duration was extended to 20 s. In sum, a strengthen welded joint can be formed with rapid microwave heating under the proper control of heating duration.

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Dielectric and mechanical properties of PLA-carbon composites

2024-04 , Mathanesh Thangarajan , Yeoh Cheow Keat , Teh Pei Leng , Wee Chun Wong , Chong Hui Yew , Kang Zheng Khor , Nor Azura Abdul Rahim , Voon Chun Hong

This study focuses on the development and characterization of Carbon-based Polylactide (PLA) composites for 3D printer filaments. The aim is to enhance the electrical and mechanical properties of PLA by incorporating recovered carbon black (RCB) in different mesh sizes (500, 1000, 1500, and 2000 mesh). Electrical impedance spectroscopy and dielectric constant measurements were performed to investigate the electrical properties of the composites. Results showed that the addition of RCB increased the dielectric constant, with values ranging from 2.5 to 7.1, indicating improved electrical performance. Scanning electron microscopy (SEM) analysis revealed the dispersion of carbon particles within the composites, enhancing their electrical conductivity. The effect of RCB particle size on electrical properties was also explored, with smaller particle sizes (2000 mesh) resulting in the highest conductivity of 6.2 S/m. Tensile testing demonstrated that the addition of RCB increases the tensile strength of PLA, with values ranging from 28.6 MPa to 47.2 MPa, and the elastic modulus, ranging from 832 MPa to 1.56 GPa, depending on the mesh size. The optimal combination of RCB content and mesh size resulted in a composite with a tensile strength of 43.8 MPa. Overall, this research provides insights into the development of Carbon-based PLA composites with improved electrical and mechanical properties.

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Effect of silicone rubber on the properties of epoxy/recovered carbon black (rCB) conductive materials

2024-04 , Pei Chee Leow , Teh Pei Leng , Yeoh Cheow Keat , Wee Chun Wong , Chong Hooi Yew , Xue Yi Lim , Kai Kheng Yeoh , Nor Azura Abdul Rahim , Voon Chun Hong

The primary focus of this study is to investigate the effect of silicone rubber (SR) content on the mechanical, thermal, electrical conductivity, and morphological properties of epoxy/recovered carbon black (rCB) conductive material. The conductive material is used to produce the electrostatic discharge (ESD) tray for the electronic packaging industry. This study investigated the effect of silicone rubber content (0, 5, 10, 15, and 20 vol.%) on the properties of epoxy/SR/rCB conductive materials, with the rCB content fixed at 15 vol.% for its optimum electrical conductivity. The silicone rubber acts as a toughening agent for epoxy. Through the fracture toughness result, it can be identified that silicone rubber plays a role in improving the toughness properties of the epoxy/SR/rCB conductive material. The optimum results for mechanical properties were recorded at 5 vol.% SR. The addition of SR to the epoxy matrix enhances the electrical properties of the epoxy/SR/rCB conductive material. The effect of thermal aging on epoxy/SR/rCB conductive materials was also studied to determine the properties of the conductive material materials at high temperatures for a long period of time. After thermal aging, the mechanical, thermal, electrical conductivity, and morphological properties of the epoxy/SR/rCB conductive material were slightly reduced.

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A comparative study of microwave welding using multiwalled carbon nanotubes and silicon carbide nanowhiskers as microwave susceptors

2024-10 , Phey Yee Foong , Voon Chun Hong , Lim Bee Ying , Teh Pei Leng , Yeoh Cheow Keat , Mohd Afendi Rojan , Nor Azizah Parmin , Subash Chandra Bose Gopinath , Foo Wah Low , Muhammad Kashif , Nor Azura Abdul Rahman , Sam Sung Ting , Veeradasan Perumal

Recently, microwave welding has arisen as an advanced joining method due to its versatility and rapid heating capabilities. Among others, microwave susceptors play a crucial role in microwave welding, as different classes of microwave susceptors have distinct microwave heating mechanisms. In this work, polypropylene (PP) was utilized as a thermoplastic substrate and two types of microwaves susceptors, namely multiwalled carbon nanotubes (MWCNTs) and silicon carbide nanowhiskers (SiC NWs), were studied for microwave welding. The susceptor was first dispersed in acetone to form susceptor suspension. Next, the susceptor suspension was deposited onto the targeted area on substrate and paired with another bare PP substrate. The paired sample was then exposed to 800 W microwave radiation in a microwave oven. Afterward, the welded joint was evaluated using a tensile test and scanning electron microscopy to determine its joint strength and cross-section microstructure. The results showed that the joint strength increased as the heating duration increased. The welded joint formed using MWCNTs achieved a maximum strength of 2.26 MPa when 10 s was used, while the SiC NWs-formed welded joint achieved a maximum strength of 2.25 MPa at 15 s. This difference in duration in forming a complete welded joint can be attributed to the higher microwave heating rates and thermal conductivity of MWCNTs. However, increasing the heating duration to 20 s caused severe deformation at the welded joint and resulted in low joint strength. Overall, this study highlights the significance of understanding the microwave heating mechanism of different susceptors and provides essential insight into the selection of a microwave susceptor for microwave welding.

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Comparison study: The effect of unmodified and modified graphene nano-platelets (GNP) on the mechanical, thermal, and electrical performance of different types of GNP-filled materials

2021-09-01 , Ka Wei K. , Teh Pei Leng , Yeoh Cheow Keat , Hakimah Osman , Sullivan M. , Voon Chun Hong , Lim Bee Ying , Mohamad Syahmie Mohamad Rasidi

Graphene nano-platelet (GNP) nano-fillers were successfully covalently functionalized with carboxylic and epoxide groups as proven by Fourier-transform infrared spectroscopy. This paper reports the effect of unmodified and modified GNP nano-fillers on the mechanical, thermal, and electrical performance of GNP-filled materials. The results show that the mechanical properties of GNP-filled materials were enhanced with a modified GNP nano-filler. Among the GNP-filled materials, the modified epoxy/NR/GNP compatibilized material shows higher flexural and toughness properties. The modified GNP nano-filler has reduced the thermal stability of the modified compatibilized material. This is because the oxygen-containing groups (C–O–C and –COOH) on the surfaces of modified GNP nano-fillers have lower thermal stability; which accelerates the thermal decomposition of the modified material. Modified compatibilized material shows higher electrical conductivity than the unmodified compatibilized material. X-ray diffraction results proved that d-spacing of modified GNP nano-fillers in modified compatibilized material was shortest when compared to unmodified GNP nano-fillers in unmodified compatibilized material, thus, allowing more electrons to travel at a faster rate through the conductive pathways.

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