Khor Shing Fhan
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Preferred name
Khor Shing Fhan
Official Name
Shing Fhan, Khor
Alternative Name
Khor, S. F.
Fhan, Khor Shing
Shing, Fhan Khor
Khor, Shing F.
Shing Fhan, Khor
Main Affiliation
Scopus Author ID
35242874900
Researcher ID
W-7216-2019

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The Effect of the Amylose/Amylopectin Contents of Starch on Porosity and Dielectric Properties of the Porous Hydroxyapatite/Starch Composites

2020-07-09 , Chong You B. , Cheng Ee Meng , Abu Bakar S. , Nashrul Fazli Mohd Nasir , Eng Swee Kheng , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Khor Shing Fhan

This study aims to determine the effect of the amylose/amylopectin contents of starch on the porosity and dielectric properties of porous hydroxyapatite/starch composites. The porous hydroxyapatite/starch composites were prepared by utilizing the starches (rice, corn and potato starch) via gelatinization and retrogradation process. The complex permittivity of the porous hydroxyapatite/starch composites were evaluated in the frequency range of 12.4-18.0 GHz. The porous composites were exhibited the higher average porosity by using the starch with higher amylopectin content. The highly porous hydroxyapatite/starch composites with higher amylopectin content show the significant fluctuation peaks (at 13.8 and 16.6 GHz) and the higher imaginary part of the complex permittivity (ϵ′′) at higher frequency in the dielectric spectrum, respectively. The real (ϵ′) and imaginary part (ϵ′′) of the complex permittivity of the porous composites could be enhanced by increasing the average porosity and the amylopectin contents.

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Dielectric, Electrical Conductivity, and Thermal Stability Studies of Cellulosic Fibers Reinforced Polylactic Acid Composites

2022-01-01 , Azahari A.N. , Mohd Ridzuan Mohd Jamir , Mohd Shukry Abdul Majid , Maslinda Abu Bakar @ Yahaya , Cheng Ee Meng , Khor Shing Fhan , Rahman M.T.A. , Sulaiman M.H.

In this study, biodegradable polylactic acid (PLA) composites were reinforced with three different natural fibers, were bamboo (BF), sugarcane (SF), and banana pseudostem (BPF) fibers, and prepared at different loadings (10, 20, and 30 wt.%). The solvent casting particulate leaching method was implemented to produce porous composites, and salt was used as the particulate material. The dielectric properties of the PLA/BF, PLA/SF, and PLA/BF composites were studied for different loadings of cellulosic fibers. The composites were observed using scanning electron microscopy (SEM), and the PLA composites with 30 wt.% filler content were analyzed using Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). According to the dielectric tests, all PLA/BF, PLA/SF, and PLA/BPF composites have low dielectric constants and dielectric loss. The PLA/BF composites exhibited the highest dielectric constant, dielectric loss, and electrical conductivity, followed by the PLA/BF and PLA/SF composites. The morphology of the composites showed their porous structure. The FTIR spectra showed the main constituents presented in the composites, and the PLA/BF showed higher thermal stability than the other composites.

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Complex Impedance and Modulus Analysis on Porous and Non-Porous Scaffold Composites Due to Effect of Hydroxyapatite/Starch Proportion

2023-01-01 , Beh C.Y. , Cheng Ee Meng , Tan X.J. , Mohd Nasir N.F. , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Khor Shing Fhan , Lee K.Y. , Che Wan Sharifah Robiah Mohamad

This study aims to investigate the electric responses (complex modulus and complex impedance analysis) of hydroxyapatite/starch bone scaffold as a function of hydroxyapatite/starch proportion and the microstructural features. Hence, the non-porous and porous hydroxyapatite/starch composites were fabricated with various hydroxyapatite/starch proportions (70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 10/90 wt/wt%). Microstructural analysis of the porous hydroxyapatite/starch composites was carried out by using scanning electron microscopy. It shows that the formation of hierarchical porous microstructures with high porosity is more significant at a high starch proportion. The complex modulus and complex impedance analysis were conducted to investigate the electrical conduction mechanism of the hydroxyapatite/starch composites via dielectric spectroscopy within a frequency range from 5 MHz to 12 GHz. The electrical responses of the hydroxyapatite/starch composites are highly dependent on the frequency, material proportion, and microstructures. High starch proportion and highly porous hierarchical microstructures enhance the electrical responses of the hydroxyapatite/starch composite. The material proportion and microstructure features of the hydroxyapatite/starch composites can be indirectly reflected by the simulated electrical parameters of the equivalent electrical circuit models.

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Low frequency dielectric and optical behavior on physicochemical properties of hydroxyapatite/cornstarch composite

2021-10-15 , Beh C.Y. , Cheng Ee Meng , Nashrul Fazli Mohd Nasir , Khor Shing Fhan , Eng S.K. , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Lee K.Y.

An investigation on relationship among the physicochemical, optical and dielectric properties of the hydroxyapatite/cornstarch (HA/Cs) composites with the starch proportion of 30, 40, 50, 60, 70, 80 and 90 wt% is presented in this work. The HA/Cs composites have been characterized via FTIR, XRD, DRS and impedance analyzer. This work depicts that the strong interaction is exhibited between the hydroxyapatite nanoparticles and starch as the starch proportion increases. This increment trend results in the higher crystallinity of the HA/Cs composites. The highly crystallized HA/Cs with hydroxyapatite nucleation center presents low optical properties (diffuse reflectance and optical band gap energy). The HA/Cs composite with 80 wt% starch proportion (H2C8) show higher dielectric properties (dielectric constant, loss factor and conductivity) due to the stronger interfacial interaction and close-packed HA/Cs crystalline structure. The relationship among the physicochemical, optical and dielectric properties of the HA/Cs composite is studied in this work for potential of instrumentation design.

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Microwave dielectric analysis on adhesive disbond in acrylic glass (Poly (Methyl Methacrylate)) at KU-band

2020-10-01 , Cheng Ee Meng , Mohd A.R. , Shahriman Abu Bakar , Zuradzman Mohamad Razlan , You K.Y. , Nashrul Fazli Mohd Nasir , Mohd Shukry Abdul Majid , Khairul S.B. , Mohd Ridzuan Mohd Jamir , Beh C.Y. , Khor Shing Fhan

A microwave dielectric spectroscopy for detecting adhesive disbonds between acrylic glass (aka Poly (methyl methacrylate)) was discussed. The adhesive bond was developed using epoxy resin and acrylate. The level of joint disbond can be quantified using Young Modulus. In this work, the strength of bond is affected by radius of air void within adhesive bond. A high-frequency electromagnetic wave propagated through two joint acrylic glass with acrylate and epoxy adhesive using waveguide adaptor WR90 in conjunction with professional network analyser. This electromagnetic wave is reflected and transmitted at the bond interface due to mismatch impedance at adhesive bond. The output is a dielectric properties that characterizes the bond interface. The increment of Young Modulus leads to increment of dielectric constant and loss factor for epoxy resin and acrylates, respectively.

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Dielectric Properties of Hydrothermally Modified Potato, Corn, and Rice Starch

2022-06-01 , Beh C.Y. , Cheng Ee Meng , Nashrul Fazli Mohd Nasir , Mohd Tarmizi E.Z. , Khor Shing Fhan , Mohd Shukry Abdul Majid , Lee K.Y. , Mohd Ridzuan Mohd Jamir

The effect of starch granule sizes, shapes, composition, and frequency on the dielectric properties (dielectric constant, loss factor, and conductivity) of native and hydrothermally modified starches (potato, corn, and rice starch) are investigated in this work. Dielectric properties are determined from 5 Hz to 5 GHz. The modified starches exhibit lower dielectric properties than the native starches from 5 Hz to 5 GHz due to the disruption of the native polysaccharide’s molecular arrangement. The modified potato starch shows the highest loss factor (208.12 at 50 Hz and 19.95 at 500 Hz) and stable conductivity (~5.33 × 10−7 S/m at 50 Hz and 500 Hz) due to the larger continuous network structure after hydrothermal modification. The rice starch shows the largest difference in dielectric constant (47.30%) and loss factor (71.42%) between the modified form and native form in the frequency range of 5 MHz–5 GHz. This is due to the restriction of dipole motions in the closely packed structure after hydrothermal modification. The findings indicate that the quality of starch modification can be characterized by dielectric properties for assisting starch-based plastic production’s design.

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Fabrication and characterization of three-dimensional porous cornstarch/n-HAp biocomposite scaffold

2020-12-01 , Beh C.Y. , Cheng Ee Meng , Nashrul Fazli Mohd Nasir , Mohd Shukry Abdul Majid , Mohd Roslan M.R. , You K.Y. , Khor Shing Fhan , Mohd Ridzuan Mohd Jamir

The aim of this study is to investigate the morphological, functional group, crystallinity and mechanical properties of a three-dimensional porous cornstarch/n-HAp (nano-hydroxyapatite) biocomposite scaffold. In this study, cornstarch/n-HAp scaffolds were fabricated using the solvent casting and particulate leaching technique. The porous cornstarch/n-HAp composites with various cornstarch contents (30, 40, 50, 60, 70, 80 and 90 wt%) were prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer and compression test. The morphology of the scaffolds possessed macropores (200–600 Î¼m) and micropores (50–100 Î¼m) with a high interconnectivity. The porosity of the porous cornstarch/n-HAp scaffolds varied between 53 and 70% with compressive strength and compressive modulus of 2.03 and 8.27 MPa, respectively. The results suggested that highly porous cornstarch/n-HAp scaffold properties with adequate mechanical properties can be obtained for applications in bone tissue engineering.

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Microwave dielectric analysis on porous hydroxyapatite/starch composites with various ratio of hydroxyapatite to starch

2020-07-09 , You B.C. , Cheng Ee Meng , Shahriman Abu Bakar , Nashrul Fazli Mohd Nasir , Eng Swee Kheng , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Khor Shing Fhan

This study aims to investigate the dielectric response of the porous hydroxyapatite/starch composites by varying the starch proportion in determining the feasibility of the microwave sample characterization technique in bone tissue engineering. The porous hydroxyapatite/starch composites were fabricated by using natural starch (gelatinization and retrogradation) through the solvent casting and particulate leaching technique. The dielectric constant (ϵ′) and loss factor (ϵ″) of the complex permittivity of the porous hydroxyapatite/starch composites were measured in the Ku band frequency of 12.4-18.0 GHz. ϵ′ and ϵ″ of the porous composites increase with frequency. The highly porous composite that due to higher starch proportion exhibit higher ϵ′ and ϵ″, resulting in the significant dielectric responses.

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Morphological and optical properties of porous hydroxyapatite/cornstarch (HAp/Cs) composites

2020-01-01 , Beh C.Y. , Cheng Ee Meng , Nashrul Fazli Mohd Nasir , Mohd Tarmizi E.Z. , Eng S.K. , Mohd Shukry Abdul Majid , Mohd Ridzuan Mohd Jamir , Khor Shing Fhan , Ahmad Saad F.S.

This paper presents the correlation between the morphological characteristics and the diffuse reflectance (optical properties) of the porous hydroxyapatite/cornstarch (HAp/Cs) composites with various starch proportions (30, 40, 50, 60, 70, 80 and 90 wt%). The porous composites were measured via SEM and enhanced by image processing to find the average pore size, strut width, and average surface roughness. The average porosity of the porous composites was measured using liquid displacement method. The diffuse reflectance spectroscopy was implemented to investigate the diffuse reflectance and the corresponding optical band gap energy of the porous composites in the 500e900 nm range. A relationship between morphological characteristics and diffuse reflectance properties were established using Pearson's correlation coefficient. The findings of the study depict that a strong correlation can be noticed between optical band gap energy with porosity, pore sizes and surface roughness of the porous composites. Meanwhile, the strong correlations between the diffuse reflectance spectral gradient with surface roughness can be observed. The moderate correlations can be observed between the diffuse reflectance spectral gradient with pore sizes and strut width of the porous composites.

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Formation of Bio-based Derived Dicalcium Silicate Ceramics via Mechanochemical Treatment: Physical, XRD, SEM and FTIR Analyses

2023-07-01 , Yunus S.N.H. , Khor Shing Fhan , Banjuraizah Johar , Nur Maizatul Shima Adzali , Jakfar N.H. , Cheng Ee Meng , Tarmizi E.Z.M. , Talib Z.A.

Beta-dicalcium silicate plays an important role in modern technology, but its tendency for polymorphic transformation results in the dusting phenomenon, is a major challenge. Therefore, mechanochemical treatment is used to reduce the particle size to retain the stability of the polymorph. In this study, pure dicalcium silicate ceramics of β-monoclinic structure with P 121/c1 space group were synthesized using calcium oxide and silicate powders derived from calcined eggshells and rice husks, respectively. The powders were mixed in a 2:1 molar ratio by mechanochemical treatment and heat-treated in the air at temperatures ranging from 900°C to 1100°C for 2 h. The results reveal that pure beta-dicalcium silicate formed at 1100°C without adding stabilizers. The properties of the pristine and sintered bodies were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). SEM revealed that the grain and pore sizes increase with rising sintering temperatures. FTIR spectra indicate the existence of Si-O bonds in tetrahedrons on all the samples. The sample sintered at 1000°C attains the lowest bulk density (1.2463 g/cm3), whereas the apparent porosity is the highest (62.5%). The reason for this trend is due to the decomposition of carbonate into CO2 gas. The densification onset for the sample sintered at 1100°C as the bulk density rises and grain size achieves 6.06 μm. This study further explains the effect of sintering temperatures on the physical, structural, and morphological properties of Ca2SiO4 which would also be useful for further optimization of its use.-4 SiO4.

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