Ho Li Ngee
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Ho Li Ngee
Official Name
Ho, Li Ngee
Alternative Name
Li Ngee, Ho
Ho, Li Ngee
Ngee, Ho Li
Ho, L. N.
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Scopus Author ID
57219028372
Researcher ID
DDY-6348-2022

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  • Publication
    Cold-pressed fly ash geopolymers: effect of formulation on mechanical and morphological characteristics
    ( 2021)
    Ong Shee-Ween
    ;
    Heah Cheng Yong
    ;
    Lynette Wei Ling Chan
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Ho Li Ngee
    ;
    Liew Yun Ming
    ;
    Ooi Wan-En
    ;
    Ng Yong-Sing
    ;
    Nur Ain Jaya
    This research uses low alkali activator content and cold pressing technique for fly ash-based geopolymers formation under room temperature condition. The geopolymers were prepared using four different parameters: fly ash/alkali activator ratio, sodium hydroxide concentration, sodium silicate/sodium hydroxide ratio and pressing force. The results indicated that the compressive strength (114.2 MPa) and flexural strength (29.9 MPa) of geopolymers maximised at a fly ash/alkali activator ratio of 5.5, a 14 M sodium hydroxide concentration, a sodium silicate/sodium hydroxide ratio of 1.5 and a pressing force of 5 tons (pressing stress of 100.0 MPa and 155.7 MPa for compressive and flexural samples, respectively). The degree of reaction (40.1%) enhanced the structure compactness with minimum porosity. The improved mechanical properties confirmed that a high strength pressed geopolymer could be formed at low alkali activator content without the aid of temperature.
  • Publication
    Effect of sodium aluminate on the fresh and hardened properties of fly ash-based one-part geopolymer
    ( 2021)
    Ooi Wan-En
    ;
    Liew Yun Ming
    ;
    Heah Cheng Yong
    ;
    Ho Li Ngee
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Ong Shee-Ween
    ;
    Andrei Victor Sandu
    The one-part geopolymer binder was synthesis from the mixing of aluminosilicate material with solid alkali activators. The properties of one-part geopolymers vary according to the type and amount of solid alkali activators used. This paper presents the effect of various sodium metasilicate-to-sodium aluminate (NaAlO2/Na2SiO3) ratios on fly ash-based one-part geopolymer. The NaAlO2/Na2SiO3 ratios were set at 1.0 to 3.0. Setting time of fresh one-part geopolymer was examined through Vicat needle apparatus. Mechanical and microstructural properties of developed specimens were analysed after 28 days of curing in ambient condition. The study concluded that an increase in NaAlO2 content delayed the setting time of one-part geopolymer paste. The highest compressive strength was achieved at the NaAlO2/Na2SiO3 ratio of 2.5, which was 33.65 MPa. The microstructural analysis revealed a homogeneous structure at the optimum ratio. While the sodium aluminium silicate hydrate (N-A-S-H) and anorthite phases were detected from the XRD analysis.
  • Publication
    Copper-filled electrically conductive adhesives with enhanced shear strength
    ( 2014)
    Ho Li Ngee
    ;
    Hiroshi Nishikawa
    In this study, the effects of diethyl carbitol (diluent) and tertiary amines on the electrical, mechanical, and rheological properties of the Cu-filled polyurethane-based electrically conductive adhesives (ECAs) were investigated. Significant difference could be observed in the electrical resistivity and shear strength of ECA prepared with different amount of diethyl carbitol. Reduced electrical resistivity was found in ECAs prepared with addition of tertiary amines, but no obvious change was observed in the shear strength of the ECA joint. Rheological property of the ECA paste was investigated in order to understand the correlation of the viscosity of ECA paste and electrical resistivity and shear strength of ECA joint. Results revealed that decrease in viscosity of the ECA paste reduced electrical resistivity and enhanced shear strength of ECA joint. A Cu-filled polyurethane-based ECA with considerably low electrical resistivity at the magnitude order range of 10-3 Ωcm, and significantly high shear strength (above 17 MPa) could be achieved.
  • Publication
    Comparative mechanical and microstructural properties of high calcium fly ash one-part geopolymers activated with Na₂SiO₃-anhydrous and NaAlO₂
    ( 2021)
    Ooi Wan-En
    ;
    Liew Yun Ming
    ;
    Heah Cheng Yong
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Ho Li Ngee
    ;
    Foo Kai Loong
    ;
    Ong Shee-Ween
    ;
    Ng Hui-Teng
    ;
    Ng Yong-Sing
    ;
    Nur Ain Jaya
    ;
    Long-Yuan Li
    This paper investigates the effect of varying solid alkali activators on the fresh and hardened properties and microstructural changes of one-part geopolymers (OPGs). Single and binary solid alkali activators were used to activate high calcium fly ash. The alkali activators were either solely sodium metasilicate (Na₂SiO₃) or a combination of sodium aluminate (NaAlO₂) and sodium metasilicate (Na₂SiO₃). The OPG activated with anhydrous Na₂SiO₃ achieved an excellent 28-day compressive strength of 83.6 MPa while OPG activated with NaAlO₂ and Na₂SiO₃ attained a compressive strength of 45.1 MPa. The Na₂SiO₃-activated OPG demonstrated better fluidity than the OPG activated with NaAlO₂ and Na₂SiO₃ due to the thixotropic behaviour caused by the NaAlO₂. The Na₂SiO₃-activated OPG consisted of sodium-calcium aluminium silicate hydrate ((N,C)-A-S-H) gel phase, while the OPG activated with NaAlO₂ and Na₂SiO₃ comprised of the coexistence of sodium aluminium silicate hydrate (N-A-S-H) and calcium aluminium silicate hydrate (C-A-S-H) gel phases. Regardless of the distinctive properties, the OPGs are adequate for building materials applications.
  • Publication
    Correlation between crystal structure and thermal reaction of TiOâ‚‚ - Graphene Oxide
    ( 2021-04)
    Siti Kartom Kamarudin
    ;
    Muhammad Asri Idris
    ;
    Nur Farhana Diyana Mohd Yunos
    ;
    Banjuraizah Johar
    ;
    Ho Li Ngee
    ;
    Syarifah Norfaezah Sabki
    ;
    Suhaimi Illias
    TiO₂ - Graphene oxide (GO) (GO = 0-1.0wt %) powders were synthesised using sol-gel method and annealed at 500°C. The samples were then characterised using X-ray diffraction (XRD). The additional of GO gave significant influence on the crystal structure of TiO₂. The lattice parameter of TiO₂ were increased with decreasing GO concentration. The unit cell volume of TiO₂-GO annealed in N2 decreased with the oxygen occupancy. In contrary, the TiO₂-GO annealed in O₂ has an increase in O₂ occupancies in the lattice that was nearly proportional to its unit cell volume. A continuous weight loss was recorded by TGA at a temperature range of T= 30 - 1000°C that were associated with H2O, C-H and C-O species. It is concluded that the Ti-O-C and Ti-C bonds were formed for samples annealed in O₂ and N2 respectively. The weight loss of TiO₂-GO annealed in O₂ is lesser than that annealed in N2 for same concentration additional GO into TiO₂.
  • Publication
    Explicating the importance of aeration and pH for Amaranth degradation and electricity generation in a viable hybrid system of photocatalytic fuel cell and electro-Fenton process
    ( 2020-05-15)
    Thor Shen Hui
    ;
    Ho Li Ngee
    ;
    Ong Soon An
    ;
    Noradiba Nordin
    ;
    Ong Yong Por
    ;
    Yap Kea Lee
    Hybrid system of photocatalytic fuel cell (PFC) and electro-Fenton (EF) process emerges as an environmentally sustainable technology for wastewater treatment and energy recovery. The established dual-cell hybrid system can reduce the recombination of electron and hole in photoanode and PFC acts as the power source for EF process. Hence, the optimal conditions for dye degradation synchronized with electricity generation in the dual-cell hybrid system should be determined. The in-situ generation of hydroxyl radicals was the key factor for dye degradation in the system. Hence, the operating parameters such as aeration and initial pH of dye were assessed. Higher decolourization efficiency was attained in aerated PFC (76.6%) and aerated EF process (84.5%). Enhanced power density (1.493 μW cm−2) was achieved in aerated hybrid system through the elevated transfer of electrons from photoanode in PFC to the cathode of EF process. Acidic environment was favoured for the dye degradation in both PFC and EF process. At optimal pH 3, PFC and EF process attained highest colour removal efficiency which were 88.5% and 84.5%, respectively. Consequently, largest power density (2.221 μW cm−2) and maximum current density (0.012 mA cm−2) were achieved in the hybrid system under pH 3 condition in both PFC and EF process.
  • Publication
    Cold-pressed fly ash geopolymers: effect of formulation on mechanical and morphological characteristics
    ( 2021-11-01)
    Ong Shee Ween
    ;
    Heah Cheng Yong
    ;
    Liew Yun Ming
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Chan L.W.L.
    ;
    Ho Li Ngee
    ;
    Ooi Wan-En
    ;
    Nur Ain Jaya
    ;
    Ng Yong-Sing
    This research uses low alkali activator content and cold pressing technique for fly ash-based geopolymers formation under room temperature condition. The geopolymers were prepared using four different parameters: fly ash/alkali activator ratio, sodium hydroxide concentration, sodium silicate/sodium hydroxide ratio and pressing force. The results indicated that the compressive strength (114.2 MPa) and flexural strength (29.9 MPa) of geopolymers maximised at a fly ash/alkali activator ratio of 5.5, a 14 M sodium hydroxide concentration, a sodium silicate/sodium hydroxide ratio of 1.5 and a pressing force of 5 tons (pressing stress of 100.0 MPa and 155.7 MPa for compressive and flexural samples, respectively). The degree of reaction (40.1%) enhanced the structure compactness with minimum porosity. The improved mechanical properties confirmed that a high strength pressed geopolymer could be formed at low alkali activator content without the aid of temperature.
  • Publication
    Towards greener one-part geopolymers through solid sodium activators modification
    ( 2022-12-10)
    Ooi Wan-En
    ;
    Liew Yun Ming
    ;
    Heah Cheng Yong
    ;
    Ho Li Ngee
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Bin Khalid M.S.
    ;
    Foo Kai Loong
    ;
    Ong Shee-Ween
    ;
    Pei Seng T.
    ;
    Hang Yong Jie
    ;
    Khairunnisa Zulkifly
    This paper investigates the influence of various solid activators and their mixing parameters on the physical, mechanical and microstructural characteristics of greener one-part geopolymers (OPG) based on high calcium fly ash. The high calcium fly ash that has rarely been explored was utilised to develop OPG in this study. The anhydrous sodium metasilicate (Na2SiO3) with negative environmental impact propelled the partial replacement of Na2SiO3 with sodium hydroxide (NaOH) and sodium carbonate (Na2CO3). Two sets of high calcium fly ash OPGs were developed: (1) the MH-OPG comprised Na2SiO3 and NaOH; (2) the MC-OPG comprised Na2SiO3 and Na2CO3. The optimal MH-OPG (73 MPa) and MC-OPG (75 MPa) exhibited superior compressive strength, higher than the minimal requirement (>28 MPa) of ASTM C150/C150M-18 for construction binder material. Various solid alkali activators triggered different reaction mechanisms, yielding distinctive reaction products that contributed to strength growth. The sodium calcium aluminosilicate hydrate ((N,C)-A-S-H) gel was developed in MH-OPG, whereas the sodium carbonate hydrate, sodium aluminosilicate hydrate (N-A-S-H) and calcium aluminosilicate hydrate (C-A-S-H) binding phases were developed in the MC-OPG. Although Na2CO3 reduced the water demand, improved the fluidity and setting time, the MC-OPG was more sensitive to the alteration of mixing compositions, suggesting a tougher performance control during field application than the MH-OPG. The total embodied carbon (EC) of MC-OPG was lowered by 15.4% compared to that of MH-OPG. The embodied carbon index (ECI) of MH-OPG and MC-OPG were 81.3% and 84.7% less than that of OPC products. This work suggests that substituting Na2SiO3 with NaOH or Na2CO3 effectively produced a greener construction material without compromising mechanical strength.
  • Publication
    Adopting co-metabolism strategy for optimized biotreatment of ortho-hydroxytoluene and bioelectricity generation in microbial fuel cell: Transformation products and pathways
    ( 2022-10-01)
    Tan S.M.
    ;
    Ong Soon An
    ;
    Ho Li Ngee
    ;
    Wong Y.S.
    ;
    Che Zulzikrami Azner Abidin
    ;
    Teoh T.P.
    ;
    Yap K.L.
    This study investigated the effects of carbon source availability and concentrations, external loads (Rload), and cathode conditions on the overall removal rate of ortho-hydroxytoluene and bioelectricity generation characteristics in anti-gravity flow microbial fuel cell (AGF-MFC) through co-metabolism approach. Sodium acetate outperformed sucrose, glucose and carbamide, and the optimum influent acetate concentration (1000 mg L−1) significantly enhanced the o-hydroxytoluene degradation by 13.41 % (98.71 %), output voltage by 15.14 % (609.25 mV) and power generation by 30.96 % (159.44 mW m−2). The results demonstrated that there were prominent differences in MFC performances under different Rload (p < 0.05). Different external load conditions resulted in varying electron transfer reactions, and thus affecting the removal efficiency and power responses of MFC system. A complete removal of o-hydroxytoluene and highest power density of 173.10 mW m−2, with a Chemical Oxygen Demand (COD) removal of 93.56 % were obtained with the Rload of 230 Ω, where the Rload approaches the cell design point. Hysteresis phenomenon was detected in the dynamic polarization during Rload variations. Moreover, it was observed that the removal efficiency of o-hydroxytoluene was significantly enhanced with aeration rate of 50 mL min−1, and dissolved oxygen concentration of 5.4 mg L−1. Conversely, higher aeration rate (400 mL min−1) had caused a decline of 26 % in power generation, ascribed to the limited active surface area for oxygen reduction reaction. Additionally, the degradation pathway of o-hydroxytoluene was proposed based on the identified intermediates.
  • Publication
    Biotreatment of sulfonated dyestuffs with energy recovery in microbial fuel cell: Influencing parameters, kinetics, degradation pathways, mechanisms, and phytotoxicity assessment
    ( 2021-08-01)
    Tan S.M.
    ;
    Ong Soon An
    ;
    Ho Li Ngee
    ;
    Wong Y.S.
    ;
    Che Zulzikrami Azner Abidin
    ;
    Thung W.E.
    ;
    Teoh T.P.
    Removal of recalcitrant sulfonated dyestuff intermediates from wastewater has been an urgent challenge for environmental technologies. In this regard, the biodegradations of monoazo Methyl Orange (MO) and diazo dyes Reactive Black 5 (RB5) towards wastewater treatment and bioelectricity generation in microbial fuel cell were investigated and compared through the studies on azo dye concentration, aeration, sampling points arrays, and electrode spacings. The degradation of diazo RB5 yielded higher chemical oxygen demand removal, decolourization efficiencies, and power generation over monoazo MO. The decolourization efficiency of RB5 (97.62%) increased with an increase of RB5 concentration (50 mg/L), suggesting that the system has the capability of removing higher RB5 concentration. However, contrary results were obtained with MO due to its toxicity. This study also demonstrated that the decolourization rate of diazo RB5 (0.1533 h-1) was ≈ 53% higher than monoazo MO (0.0727 h-1). The findings revealed that the degradation kinetic was remarkably influenced by the chemical structure of dye, where dye with more electron-withdrawing groups at para position are more susceptible to be reduced. Higher output voltage (568.59 mV) and power generation (108.87 mW/m2) were attained with RB5 due to electron donor availability and electron-shuttling characteristics of RB5 decolourized intermediates. Furthermore, detailed degradation pathways of MO and RB5 were presented based on the UV-vis and GC-MS results. The phytotoxicity assessment via Sorghum bicolor seeds had further verified the reduction in toxicity after the treatment of azo dyes.