29 results on '"Tan Wai Kian"'
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2. Synergy Effect of Plasmonic Field Enhancement and Light Confinement in Mesoporous Titania-Coated Aluminum Nanovoid Photoelectrode.
- Author
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Kawamura G, Hirai D, Yamauchi S, Tan WK, Muto H, and Matsuda A
- Abstract
Photoelectrochemical (PEC) water splitting is a highly demanded technology for the realization of sustainable society. Various types of photoanodes have been developed to achieve high efficiency of PEC water splitting. Plasmonic field enhancement and light confinement effects are often adopted to improve PEC performance. However, their synergistic effects have not been studied. In this work, a mesoporous TiO
2 layer was deposited on an Al plate with a nanovoid array structure, which acts as a photoanode and simultaneously exhibits a light confinement effect and surface plasmon resonance. The solo and synergy effects were investigated through experimental photocurrent measurements and theoretical simulations using the finite-difference time-domain method. The highest improvement in PEC performance was confirmed when the synergy effect occurred.- Published
- 2023
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3. Fabrication and electrochemical properties of electrode composites for oxide-type all-solid-state batteries through electrostatic integrated assembly.
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Hikima K, Sato Y, Yokoi A, Tan WK, Muto H, and Matsuda A
- Abstract
All-solid-state batteries, which use flame-resistant solid electrolytes, are regarded as safer alternatives to conventional lithium-ion batteries for various applications including electric vehicles. Herein, we report the fabrication of cathode composites for oxide-type all-solid-state batteries through an electrostatic assembly method. A polyelectrolyte is used to adjust the surface charge of the matrix particles to positive/negative, and the aggregation resulting from electrostatic interactions is utilized. Composites consisting of cathode active material particles (LiNi
1/3 Mn1/3 Co1/3 O2 (NMC) or LiNi0.5 Mn1.5 O4 (LNMO)), solid electrolyte particles Li1.3 Al0.3 Ti1.7 (PO4 )3 (LATP), and electron conductive one-dimensional carbon nanotubes (CNT) are formed via an electrostatic integrated assembly of colloidal suspensions. Electrostatic integration increases the electronic conductivity by two orders of magnitude in the NMC-LATP-CNT composite (6.5 × 10-3 S cm-1 /3.2 × 10-5 S cm-1 ) and by six orders of magnitude in the LNMO-LATP-CNT composite (6.4 × 10-3 S cm-1 /2.3 × 10-9 S cm-1 ). The dispersion of CNTs in the cathode composite is enhanced, resulting in percolation of e- path even at 1 wt% (approximately 2.5 vol%) CNT. This study indicates that an integrated cathode composite can be fabricated with particles uniformly mixed by electrostatic interaction for oxide-type all-solid-state batteries., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)- Published
- 2023
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4. Characterization of Fungal Foams from Edible Mushrooms Using Different Agricultural Wastes as Substrates for Packaging Material.
- Author
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Majib NM, Sam ST, Yaacob ND, Rohaizad NM, and Tan WK
- Abstract
Agricultural wastes and leaves, which are classified as lignocellulosic biomass, have been used as substrates in the production of fungal foams due to the significant growth of the mushroom industry in recent years. Foam derived from fungi can be utilized in a variety of industrial applications, including the production of packaging materials. Here, white oyster mushrooms ( Pleurotus florida ) and yellow oyster mushrooms ( Pleurotus citrinopileatus ) were cultivated on rice husk, sawdust, sugarcane bagasse, and teak leaves. Fungal foams were produced after 30 days of incubation, which were then analyzed using scanning electron microscopy (SEM), thermal analysis (TGA), and chemical structure using Fourier-transform infrared spectroscopy. Mechanical testing examined the material's hardness, resilience, and springiness, and water absorption tests were used to determine the durability of the fungal foams. Our findings demonstrated that fungal foams made from rice husk and teak leaves in both mycelium species showed better mechanical properties, thermal stability, and minimal water absorption compared to the other substrates, and can thus have great potential as efficient packaging materials.
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- 2023
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5. Degradation of Diazo Congo Red Dye by Using Synthesized Poly-Ferric-Silicate-Sulphate through Co-Polymerization Process.
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Zainudin NF, Sam ST, Wong YS, Ismail H, Walli S, Inoue K, Kawamura G, and Tan WK
- Abstract
The ability of poly-ferric-silicate-sulphate (PFSS) synthesized via a co-polymerization process has been applied for the removal of diazo Congo red dye. A novel degradation pathway of diazo Congo red dye by using PFSS is proposed based on LC-MS analysis. Diazo Congo red dye was successfully removed using synthesized PFSS at lower coagulant dosages and a wider pH range, i.e., 9 mg/L from pH 5 to 7, 11 mg/L at pH 9, and 50 mg/L at pH 11. The azo bond cleavage was verified by the UV-Vis spectra of diazo Congo red-loaded PFSS and FTIR spectra which showed disappearance of the peak at 1584 cm
-1 for -N=N- stretching vibrations. The synchronized results of UV-Vis spectra, FTIR, and the LC-MS analysis in this study confirmed the significance of the Si and Fe bond in PFSS towards the degradation of diazo Congo red dye. The successfully synthesized PFSS coagulant was characterized by FTIR, SEM, TEM, and HRTEM analysis. From this analysis, it was proven that PFSS is a polycrystalline material which is favorable for the coagulation-flocculation process. Based on all these findings, it was established that synthesized PFSS can be employed as a highly efficient polymeric coagulant for the removal of dye from wastewater.- Published
- 2023
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6. A Novel Controlled Fabrication of Hexagonal Boron Nitride Incorporated Composite Granules Using the Electrostatic Integrated Granulation Method.
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Nakazono T, Yokoi A, Tan WK, Kawamura G, Matsuda A, and Muto H
- Abstract
Despite the availability of nano and submicron-sized additive materials, the controlled incorporation and utilization of these additives remain challenging due to their difficult handling ability and agglomeration-prone properties. The formation of composite granules exhibiting unique microstructure with desired additives distribution and good handling ability has been reported using the electrostatic integrated granulation method. This study demonstrates the feasible controlled incorporation of two-dimensional hexagonal boron nitride (hBN) sheets with alumina (Al
2 O3 ) particles, forming Al2 O3 -hBN core-shell composite granules. The sintered artifacts obtained using Al2 O3 -hBN core-shell composite granules exhibited an approximately 28% higher thermal conductivity than those obtained using homogeneously hBN-incorporated Al2 O3 composite granules. The findings from this study would be beneficial for developing microstructurally controlled composite granules with the potential for scalable fabrication via powder-metallurgy inspired methods.- Published
- 2023
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7. Anodic nanoporous WO 3 modified with Bi 2 S 3 quantum dots as a photoanode for photoelectrochemical water splitting.
- Author
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Abouelela MM, Kawamura G, Tan WK, and Matsuda A
- Abstract
Although anodic nanoporous (ANP) WO
3 has gained a lot of attention for photoelectrochemical water splitting (PEC-WS), there is still a lack of efficient WO3 -based photoanodes with sufficient light absorption and good e- /h+ separation and transfer. The decoration of ANP WO3 with narrow bandgap semiconductor quantum dots (QDs) can enhance charge carrier transfer while reducing their recombination, resulting in a high PEC efficiency. In this study, ANP WO3 was synthesized via an anodic oxidation process and then modified with Bi2 S3 QDs via successive ionic layer adsorption and reaction (SILAR) process and examined as a photoanode for PEC-WS under ultraviolet-visible illumination. The ANP WO3 photoanode modified with ten cycles of Bi2 S3 QDs demonstrated the highest current density of 16.28 mA cm-2 at 0.95 V vs RHE, which is approximately 19 times that of pure ANP WO3 (0.85 mA cm-2 ). Furthermore, ANP WO3 /Bi2 S3 QDs (10) photoanode demonstrated the highest photoconversion efficiency of 4.1 % at 0.66 V vs RHE, whereas pure ANP WO3 demonstrated 0.3 % at 0.85 V vs RHE. This can be attributed to the proper number of Bi2 S3 QDs significantly enhancing the visible light absorption, construction of type-II band alignment with WO3, and improved charge separation and migration. The modification of ANP WO3 with nontoxic Bi2 S3 QDs as a prospective metal chalcogenide for enhancing visible light absorption and PEC-WS performance has not yet been investigated. Consequently, this study paves the path for a facile technique of designing effective photoelectrodes for PEC-WS., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)- Published
- 2023
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8. Photoreduction of Cr(VI) in wastewater by anodic nanoporous Nb 2 O 5 formed at high anodizing voltage and electrolyte temperature.
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Alias N, Hussain Z, Tan WK, Kawamura G, Muto H, Matsuda A, and Lockman Z
- Abstract
In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization voltage and electrolyte temperature was studied to find an optimum condition for circular, ordered, and uniform pore formation. The diameter of the pores was found to be larger when the applied voltage was increased from 20 to 80 V. The as-anodized porous film was also observed to comprise of nanocrystallites which formed due to high field-induced crystallization. The nanocrystallites grew into orthorhombic Nb
2 O5 after post-annealing treatment. The Cr(VI) photoreduction property of both the as-anodized and annealed Nb2 O5 samples obtained using an optimized condition (anodization voltage: 60 V, electrolyte temperature: 70 °C) was compared. Interestingly, the as-anodized Nb2 O5 film was found to display better photoreduction of Cr(VI) than annealed Nb2 O5. However, in terms of stability, the annealed Nb2 O5 presented high photocatalytic efficiency for each cycle whereas the as-anodized Nb2 O5 showed degradation in photocatalytic performance when used continually., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)- Published
- 2022
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9. Controlled formation of carbon nanotubes incorporated ceramic composite granules by electrostatic integrated nano-assembly.
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Muto H, Sato Y, Tan WK, Yokoi A, Kawamura G, and Matsuda A
- Abstract
Controlled incorporation of carbon nanotubes (CNT) with alumina (Al
2 O3 ) and zirconia (ZrO2 ) nanoparticles using an electrostatic nano-assembly method for the fabrication of homogeneous CNT-incorporated Al2 O3 -ZrO2 and CNT-incorporated shell-layer Al2 O3 -ZrO2 composite granules is demonstrated. The spark-plasma-sintered CNT-incorporated shell-layer Al2 O3 -ZrO2 artifact exhibited approximately 15 times higher electrical conductivity than a homogeneous CNT-incorporating artifact. This novel composite granule fabrication method using an electrostatic integrated assembly of colloidal nanomaterials would be beneficial for the development of multiscale and multicomponent composite materials.- Published
- 2022
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10. Enhanced photocatalytic and antimicrobial performance of a multifunctional Cu-loaded nanocomposite under UV light: theoretical and experimental study.
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Abd Elkodous M, El-Khawaga AM, Abdel Maksoud MIA, El-Sayyad GS, Alias N, Abdelsalam H, Ibrahim MA, Elsayed MA, Kawamura G, Lockman Z, Tan WK, and Matsuda A
- Subjects
- Anti-Bacterial Agents pharmacology, Catalysis, Light, Potassium Permanganate, Silicon Dioxide, Titanium pharmacology, Ultraviolet Rays, Nanocomposites, Water Pollutants, Chemical
- Abstract
Due to modern industrialization and population growth, access to clean water has become a global challenge. In this study, a metal-semiconductor heterojunction was constructed between Cu NPs and the Co
0.5 Ni0.5 Fe2 O4 /SiO2 /TiO2 composite matrix for the photodegradation of potassium permanganate, hexavalent chromium Cr(VI) and p -nitroaniline (pNA) under UV light. In addition, the electronic and adsorption properties after Cu loading were evaluated using density functional theory (DFT) calculations. Moreover, the antimicrobial properties of the prepared samples toward pathogenic bacteria and unicellular fungi were investigated. Photocatalytic measurements show the outstanding efficiency of the Cu-loaded nanocomposite compared to that of bare Cu NPs and the composite matrix. Degradation efficiencies of 44% after 80 min, 100% after 60 min, and 65% after 90 min were obtained against potassium permanganate, Cr(VI), and pNA, respectively. Similarly, the antimicrobial evaluation showed high ZOI, lower MIC, higher protein leakage amount, and cell lysis of nearly all microbes treated with the Cu-loaded nanocomposite.- Published
- 2022
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11. Nanoporous anodic Nb 2 O 5 with pore-in-pore structure formation and its application for the photoreduction of Cr(VI).
- Author
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Alias N, Hussain Z, Tan WK, Kawamura G, Muto H, Matsuda A, and Lockman Z
- Subjects
- Catalysis, Chromium, Nanopores, Niobium
- Abstract
An anodic film with a nanoporous structure was formed by anodizing niobium at 60 V in fluorinated ethylene glycol (fluoride-EG). After 30 min of anodization, the anodic film exhibited a "pore-in-pore" structure; that is, there were smaller pores growing inside larger pores. The as-anodized film was weakly crystalline and became orthorhombic Nb
2 O5 after heat treatment. The energy band gap of the annealed nanoporous Nb2 O5 film was 2.9 eV. A photocatalytic reduction experiment was performed on Cr(VI) under ultraviolet (UV) radiation by immersing the nanoporous Nb2 O5 photocatalyst in a Cr(VI) solution at pH 2. The reduction process was observed to be very slow; hence, ethylenediaminetetraacetic acid (EDTA) was added as an organic hole scavenger, which resulted in 100% reduction after 45 min of irradiation. The photocatalytic reduction experiment was also performed under visible light, and findings showed that complete reduction achieved after 120 min of visible light exposure., (Copyright © 2021. Published by Elsevier Ltd.)- Published
- 2021
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12. Formation of Dense and High-Aspect-Ratio Iron Oxide Nanowires by Water Vapor-Assisted Thermal Oxidation and Their Cr(VI) Adsorption Properties.
- Author
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Budiman F, Tan WK, Kawamura G, Muto H, Matsuda A, Abdul Razak K, and Lockman Z
- Abstract
Coral-like and nanowire (NW) iron oxide nanostructures were produced at 700 and 800 °C, respectively, through thermal oxidation of iron foils in air- and water vapor-assisted conditions. Water vapor-assisted thermal oxidation at 800 °C for 2 h resulted in the formation of highly crystalline α-Fe
2 O3 NWs with good foil surface coverage, and we propose that their formation was due to a stress-driven surface diffusion mechanism. The Cr(VI) adsorption property of an aqueous solution on α-Fe2 O3 NWs was also evaluated after a contact time of 90 min. The NWs had a removal efficiency of 97% in a 225 mg/L Cr(VI) solution (pH 2, 25 °C). The kinetic characteristic of the adsorption was fitted to a pseudo-second-order kinetic model, and isothermal studies indicated that the α-Fe2 O3 NWs exhibited an adsorption capacity of 66.26 mg/g. We also investigated and postulated a mechanism of the Cr(VI) adsorption in an aqueous solution of α-Fe2 O3 NWs., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)- Published
- 2021
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13. Nanocomposite matrix conjugated with carbon nanomaterials for photocatalytic wastewater treatment.
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Abd Elkodous M, S El-Sayyad G, Abdel Maksoud MIA, Kumar R, Maegawa K, Kawamura G, Tan WK, and Matsuda A
- Abstract
The problem of hazardous wastewater remediation is a complicated issue and a global challenge. Herein, a layered Co
0.5 Ni0.5 Fe2 O4 /SiO2 /TiO2 composite matrix was prepared and incorporated with three carbon nanomaterials having different dimensionalities, carbon dots (C-dots, 0D), single-walled carbon nanotubes (1D), and reduced graphene oxide (2D), in an effort to create effective photocatalytic nanocomposites for chloramine-T removal from water. Microstructural analyses confirmed the formation of nanocomposites and revealed their chemistry and structure. Elemental mapping revealed a uniform distribution of elements throughout the nanocomposite matrix that was free of impurities. The spherical shape of the matrix particles (average diameter ~90 nm) and their conjugation with the carbon nanomaterials were confirmed. Nitrogen adsorption-desorption isotherms revealed that the nanocomposites were mesoporous but also contained macropores. The surface chemical compositions of the nanocomposites were investigated and showed a range of available binding energies. The kinetics of photocatalysis by the system were studied, and the effects of different parameters (such as photocatalyst dose and charge-carrier scavengers) on the efficiency of chloramine-T degradation were also investigated. The nanocomposite loaded with 10% C-dots exhibited high UV-assisted photocatalytic activity for chloramine-T degradation (65% removal efficiency)., (Copyright © 2020 Elsevier B.V. All rights reserved.)- Published
- 2021
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14. Nanomaterial Fabrication through the Modification of Sol-Gel Derived Coatings.
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Tan WK, Muto H, Kawamura G, Lockman Z, and Matsuda A
- Abstract
In materials processing, the sol-gel method is one of the techniques that has enabled large-scale production at low cost in the past few decades. The versatility of the method has been proven as the fabrication of various materials ranging from metallic, inorganic, organic, and hybrid has been reported. In this review, a brief introduction of the sol-gel technique is provided and followed by a discussion of the significance of this method for materials processing and development leading to the creation of novel materials through sol-gel derived coatings. The controlled modification of sol-gel derived coatings and their respective applications are also described. Finally, current development and the outlook of the sol-gel method for the design and fabrication of nanomaterials in various fields are described. The emphasis is on the significant potential of the sol-gel method for the development of new, emerging technologies.
- Published
- 2021
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15. Formation of grassy TiO 2 nanotube thin film by anodisation in peroxide electrolyte for Cr(VI) removal under ultraviolet radiation.
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Taib MAA, Alias N, Jaafar M, Razak KA, Tan WK, Shahbudin IP, Kawamura G, Matsuda A, and Lockman Z
- Abstract
Arrays of TiO
2 nanotubes (TiO2 NTs) with grassy surfaces were observed on titanium foil anodised at 60 V in fluorinated ethylene glycol (EG) with added hydrogen peroxide (H2 O2 ). The grassy surface was generated by the chemical etching and dissolution of the surface of the TiO2 NTs walls, which was accelerated by the temperature increase on the addition of H2 O2 . Upon annealing at 600 °C, the grassy part of the TiO2 NTs was found to consist of mostly anatase TiO2 whereas the bottom part of the anodic oxide comprised a mixture of anatase and rutile TiO2 . The TiO2 NTs were then used to reduce hexavalent chromium (Cr(VI)) under ultraviolet radiation. They exhibited a rather efficient photocatalytic effect, with 100% removal of Cr(VI) after 30 min of irradiation. The fast removal of Cr(VI) was due to the anatase dominance at the grassy part of the TiO2 NTs as well as the higher surface area the structure may have. This work provides a novel insight into the photocatalytic reduction of Cr(VI) on grassy anatase TiO2 NTs.- Published
- 2020
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16. Carbon-dot-loaded Co x Ni 1-x Fe 2 O 4 ; x = 0.9/SiO 2 /TiO 2 nanocomposite with enhanced photocatalytic and antimicrobial potential: An engineered nanocomposite for wastewater treatment.
- Author
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Abd Elkodous M, El-Sayyad GS, Youssry SM, Nada HG, Gobara M, Elsayed MA, El-Khawaga AM, Kawamura G, Tan WK, El-Batal AI, and Matsuda A
- Abstract
Water scarcity is now a serious global issue resulting from population growth, water decrease, and pollution. Traditional wastewater treatment plants are insufficient and cannot meet the basic standards of water quality at reasonable cost or processing time. In this paper we report the preparation, characterization and multiple applications of an efficient photocatalytic nanocomposite (Co
x Ni1-x Fe2 O4 ; x = 0.9/SiO2 /TiO2 /C-dots) synthesized by a layer-by-layer method. Then, the photocatalytic capabilities of the synthesized nanocomposite were extensively-studied against aqueous solutions of chloramine-T trihydrate. In addition, reaction kinetics, degradation mechanism and various parameters affecting the photocatalytic efficiency (nanocomposite dose, chloramine-T initial concentration, and reaction pH) were analyzed in detail. Further, the antimicrobial activities of the prepared nanocomposite were tested and the effect of UV-activation on the antimicrobial abilities of the prepared nanocomposite was analyzed. Finally, a comparison between the antimicrobial abilities of the current nanocomposite and our previously-reported nanocomposite (Cox Ni1-x Fe2 O4 ; x = 0.9/SiO2 /TiO2 ) had been carried out. Our results revealed that the prepared nanocomposite possessed a high degree of crystallinity, confirmed by XRD, while UV-Vis. recorded an absorption peak at 299 nm. In addition, the prepared nanocomposite possessed BET-surface area of (28.29 ± 0.19 m2 /g) with narrow pore size distribution. Moreover, it had semi-spherical morphology, high-purity and an average particle size of (19.0 nm). The photocatalytic degradation efficiency was inversely-proportional to chloramine-T initial concentration and directly proportional to the photocatalyst dose. In addition, basic medium (pH 9) was the best suited for chloramine-T degradation. Moreover, UV-irradiation improved the antimicrobial abilities of the prepared nanocomposite against E. coli, B. cereus, and C. tropicalis after 60 min. The observed antimicrobial abilities (high ZOI, low MIC and more efficient antibiofilm capabilities) were unique compared to our previously-reported nanocomposite. Our work offers significant insights into more efficient water treatment and fosters the ongoing efforts looking at how pollutants degrade the water supply and the disinfection of water-borne pathogenic microorganisms.- Published
- 2020
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17. Magnetically recoverable magnetite-reduced graphene oxide as a demulsifier for surfactant stabilized crude oil-in-water emulsion.
- Author
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Yau XH, Khe CS, Mohamed Saheed MS, Lai CW, You KY, and Tan WK
- Subjects
- Emulsions, Ferrosoferric Oxide chemistry, Graphite chemistry, Hydrogen-Ion Concentration, Oxidation-Reduction, Recycling, Nanocomposites chemistry, Petroleum, Surface-Active Agents chemistry, Wastewater chemistry, Water Purification methods
- Abstract
Oily wastewater, especially water-oil emulsion has become serious environmental issue and received global attention. Chemical demulsifiers are widely used to treat oil-water emulsion, but the toxicity, non-recyclable and non-environmental friendly characteristic of chemical demulsifiers had limited their practical application in oil-water separation. Therefore, it is imperative to develop an efficient, simple, eco-friendly and recyclable demulsifiers for breaking up the emulsions from the oily wastewater. In this study, a magnetic demulsifier, magnetite-reduced graphene oxide (M-rGO) nanocomposites were proposed as a recyclable demulsifier to break up the surfactant stabilized crude oil-in-water (O/W) emulsion. M-rGO nanocomposites were prepared via in situ chemical synthesis by using only one type Fe salt and GO solid as precursor at room temperature. The prepared composites were fully characterized by various techniques. The effect of demulsifier dosage and pH of emulsion on demulsification efficiency (ED) has been studied in detailed. The demulsification mechanism was also proposed in this study. Results showed that M-rGO nanocomposites were able to demulsify crude O/W emulsion. The ED reaches 99.48% when 0.050 wt.% of M-rGO nanocomposites were added to crude O/W emulsion (pH = 4). Besides, M-rGO nanocomposites can be recycled up to 7 cycles without showing a significant change in terms of ED. Thus, M-rGO nanocomposite is a promising demulsifier for surfactant stabilized crude O/W emulsion., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2020
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18. Design of Heat-Conductive hBN-PMMA Composites by Electrostatic Nano-Assembly.
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Yokoi A, Tan WK, Kuroda T, Kawamura G, Matsuda A, and Muto H
- Abstract
Micro/nanoscale design of composite materials enables alteration of their properties for advanced functional materials. One of the biggest challenges in material design is the controlled decoration of composite materials with the desired functional additives. This study reports on and demonstrates the homogeneous decoration of hexagonal boron nitride (hBN) on poly(methylmethacrylate) (PMMA) and vice versa. The formation of the composite materials was conducted via a low environmental load and a low-energy-consuming, electrostatic nano-assembly method which also enabled the efficient usage of nano-sized additives. The hBN/PMMA and PMMA/hBN composites were fabricated in various size combinations that exhibited percolated and layer-oriented structures, respectively. The thermal conductivity behaviors of hBN/PMMA and PMMA/hBN composites that exhibited good microstructure were compared. The results showed that microstructural design of the composites enabled the modification of their heat-conducting property. This novel work demonstrated the feasibility of fabricating heat-conductive PMMA matrix composites with controlled decoration of hBN sheets, which may provide a platform for further development of heat-conductive polymeric materials.
- Published
- 2020
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19. Liquid Phase Synthesis and Morphological Observation of BaTiO₃-CoFe₂O₄ Nanocomposite Films.
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Oura K, Kawamura G, Tan WK, Yamaguchi K, Muto H, and Matsuda A
- Abstract
A novel and inexpensive fabrication method of multiferroic nanocomposite films via liquid-phase formation is demonstrated in this work. Well-aligned anodized TiO₂ nanotube arrays on a Ti substrate were used as the core template. The anodized TiO₂ nanotube arrays were then hydrothermally treated in Ba(OH)₂ aqueous solution to form BaTiO₃ (BTO) nanotube arrays. The average pore diameter and thickness of the BTO nanotube arrays obtained were approximately 50~70 nm and 2~4 μ m, respectively. The BTO nanotube arrays were then dip-coated with CoFe₂O₄ (CFO) sol with the assistance of vaccum impregnation equipment to enable the penetration of CFO sol into the tubular pores of the BTO nanotube arrays. The good distribution of CFO in the BTO nanotube arrays was confirmed by electron microscopy accompanied with elemental analysis. The good crystallinity of CFO and BTO in the nanocomposite was confirmed by X-ray diffraction, and the nanocomposite film exhibited anisotropic ferrimagnetic properties upon an in plane and out-plane applied magnetic field.
- Published
- 2020
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20. Facile Fabrication of Plasmonic Enhanced Noble-Metal-Decorated ZnO Nanowire Arrays for Dye-Sensitized Solar Cells.
- Author
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Tan WK, Muto H, Ito T, Kawamura G, Lockman Z, and Matsuda A
- Abstract
Novel decoration of high aspect ratio zinc oxide nanowires (ZnO NWs) with noble metals such as Ag and Au nanoparticles (NPs) was demonstrated in this work. A facile method of chemical deposition with good controllability, as well as good homogeneity would be a huge advantage towards large scale fabrication. The highlight of this work is the feasibility of multiple component decoration such as a hybrid (co-exist) Ag-Au NPs decorated ZnO NWs formation that could be beneficial towards the development of nanoarchitectured materials with the most desired properties. The local surface plasmon effect (LSPR) of Ag and Au NPs were confirmed using extinction spectra and significant photoelectrochemical conversion efficiency (PCE) enhancement of dye-sensitized solar cells (DSSCs) was achieved. The Ag-NPs and hybrid Ag-Au NPs decorated ZnO NWs marked an impressive 125 and 240% efficiency improvement against pure ZnO NWs. The improved dye light extinction resulted from the LSPR effect that had enabled greater electron generation leading to improved PCE. As the complex design of oxides' nanoarchitectures have reached a point of saturation, this novel method would enable further enhancement in their photoelectrochemical properties through decoration with noble metals via a simple chemical deposition route.
- Published
- 2020
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21. Rapid Nucleation of Reduced Graphene Oxide-Supported Palladium Electrocatalysts for Methanol Oxidation Reaction.
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Ng JC, Tan CY, Ong BH, Matsuda A, Basirun WJ, Tan WK, Singh R, and Yap BK
- Abstract
Small sized electrocatalysts, which can be obtained by rapid nucleation and high supersaturation are imperative for outstanding methanol oxidation reaction (MOR). Conventional microwave synthesis processes of electrocatalysts include ultrasonication, stirring, pH adjustment, and microwave irradiation of the precursor mixture. Ethylene glycol (EG), which serves as a reductant and solvent was added during the ultrasonication or stirring stage. However, this step and pH adjustment resulted in unintended multi-stage gradual nucleation. In this study, the microwave reduction approach was used to induce rapid nucleation and high supersaturation in order to fabricate small-sized reduced graphene oxide-supported palladium (Pd/rGO) electrocatalysts via the delayed addition of EG, elimination of the pH adjustment step, addition of sodium carbonate (Na₂CO₃), prior microwave irradiation of the EG mixed with Na₂CO₃, and addition of room temperature precursor mixture. Besides its role as a second reducing agent, the addition of Na₂CO₃ was primarily intended to generate an alkaline condition, which is essential for the high-performance of electrocatalysts. Moreover, the microwave irradiation of the EG and Na₂CO₃ mixture generated highly reactive free radicals that facilitate rapid nucleation. Meanwhile, the room temperature precursor mixture increased supersaturation. Results showed improved electrochemically active surface area (78.97 m² g
-1 , 23.79% larger), MOR (434.49 mA mg-1 , 37.96% higher) and stability.- Published
- 2019
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22. Micro- and Nano-assembly of Composite Particles by Electrostatic Adsorption.
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Tan WK, Araki Y, Yokoi A, Kawamura G, Matsuda A, and Muto H
- Abstract
This work reports on a novel controlled nanocomposite fabrication technique which is applicable for material design via a micro- and nano-assembly method. The principle is based on the use of electrostatic adsorption of the surface charge-modified particles via layer-by-layer assembly. The polarity and the zeta potential of the surface charge was controlled using polycation and polyanion, while the zeta potential strength was controlled via the number of alternating coating layers which was determined using zeta potential measurement. A systematic study was conducted to demonstrate the feasibility of composite material assembly via electrostatic adsorption using alumina (Al
2 O3 ) and silica (SiO2 ) composite as a study model, which was carried out as a function of surface zeta potential, surface coverage percentage, and processing time. The considerable potential of this technique for composite material design is also further demonstrated with controlled assembly involving different materials in various structural forms such as fiber, whisker, nanosheets, and even irregular-shaped foam-like structured urethane. The composite materials designed using this EA method possess good potentials to be utilized for various applications such as mechanical property control, composite ceramic films formation, selective laser sintering, and rechargeable metal-air battery.- Published
- 2019
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23. Correction to: Controlled Microstructure and Mechanical Properties of Al2O3-Based Nanocarbon Composites Fabricated by Electrostatic Assembly Method.
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Tan WK, Hakiri N, Yokoi A, Kawamura G, Matsuda A, and Muto H
- Abstract
Please note that in the original article [1] the name of the second author, Norio Hakiri, was erroneously ordered; the name was ordered with the given and family names the wrong way around, as 'Hakiri Norio'.
- Published
- 2019
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24. Controlled microstructure and mechanical properties of Al 2 O 3 -based nanocarbon composites fabricated by electrostatic assembly method.
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Tan WK, Hakiri N, Yokoi A, Kawamura G, Matsuda A, and Muto H
- Abstract
This work reports on the microstructure-controlled formation of interconnected carbon-layered Al
2 O3 ceramics using carbon nanoparticles (CNP)-alumina (Al2 O3 ) composite particles. The Al2 O3 micro-particles used in this study were obtained by granulation of nano-sized Al2 O3 nanoparticles with an average diameter of 150 nm. Then, CNP-Al2 O3 composite was fabricated using an electrostatic assembly method using the granulated Al2 O3 and CNP. The decoration of CNP on the surface of granulated Al2 O3 was investigated as a function of primary particle size and coverage percentage using a fixed amount of CNP. Notably, an interconnected layer of carbon particles at the interface of Al2 O3 that resemble the grain boundaries was obtained. The mechanical properties of the samples obtained with different particle size and CNP coverage on Al2 O3 particles were also investigated which presented the possibility to control the mechanical properties through microstructural design of composite ceramic materials.- Published
- 2019
- Full Text
- View/download PDF
25. PMMA-ITO Composite Formation via Electrostatic Assembly Method for Infra-Red Filtering.
- Author
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Tan WK, Yokoi A, Kawamura G, Matsuda A, and Muto H
- Abstract
Formation of functional composite materials with desired properties is important for advanced application development. However, formation of a homogenous composite material via conventional mixing methods still remains a challenge due to agglomeration. Therefore, this work reports and demonstrates the formation of a homogeneous poly(methylmethacrylate) (PMMA)-indium tin oxide (ITO) composite with high visible light transparency (up to 90%) with an excellent shielding effect of infra-red (IR) via a facile electrostatic assembly method. This PMMA-ITO composite with good transparency and an IR shielding effect has good potential to be used in the automobile industry for vehicle windscreens as well as in heat preservation or preventive technology. The IR shielding rate is demonstrated to be controllable by changing the amount of ITO nanoparticles additive. This finding would provide a platform for development of IR optical related polymeric composite materials.
- Published
- 2019
- Full Text
- View/download PDF
26. Multiferroic nanocomposite fabrication via liquid phase using anodic alumina template.
- Author
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Kawamura G, Ohara K, Tan WK, Goto T, Nakamura Y, Inoue M, Muto H, Yamaguchi K, Boccaccini AR, and Matsuda A
- Abstract
We report a novel and inexpensive fabrication process of multiferroic nanocomposite via liquid phase using an anodic alumina template. The sol-gel spin-coating technique was used to coat the template with ferrimagnetic CoFe
2 O4 . By dissolving the template with NaOH aqueous solution, a unique nanotube array structure of CoFe2 O4 was obtained. The CoFe2 O4 nanotube arrays were filled with, and sandwiched in, ferroelectric BaTiO3 layers by a sol-gel spin-coating method to obtain the composite. Its multiferroicity was confirmed by measuring the magnetic and dielectric hysteresis loops.- Published
- 2018
- Full Text
- View/download PDF
27. Anodic Ag/TiO2 nanotube array formation in NaOH/fluoride/ethylene glycol electrolyte as a photoanode for dye-sensitized solar cells.
- Author
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Nyein N, Tan WK, Kawamura G, Matsuda A, and Lockman Z
- Abstract
Self-organized, 23 μm-thick anodic TiO2 nanotube (TNT) arrays were formed in sodium hydroxide/fluoride/ethylene glycol (EG) electrolyte at 60 V for 60 min. The presence of sodium hydroxide (NaOH) in the fluoride/EG electrolyte accelerates the formation of the TiO2 nanotube arrays. The anodic film was then decorated with silver nanoparticles (Ag NPs) by the photodeposition process and used as a photoanode in a rear-side-illuminated dye-sensitized solar cell. The Ag NPs decorated TNT arrays, with the former having diameters of 10-30 nm formed from 0.2 M of Ag-precursor solution and exhibiting the highest photoconversion efficiency (η) of 3.7% and a short-circuit current density of 12.2 mA cm(-2) compared to η = 3% and short-circuit current density of 9.1 mA cm(-2) for a sample without Ag NPs. The increase in η is thought to be due to the surface plasmon resonance and excess electrons from the nanoparticles.
- Published
- 2016
- Full Text
- View/download PDF
28. Ag nanoparticle-deposited TiO2 nanotube arrays for electrodes of Dye-sensitized solar cells.
- Author
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Kawamura G, Ohmi H, Tan WK, Lockman Z, Muto H, and Matsuda A
- Abstract
Abstract: Dye-sensitized solar cells composed of a photoanode of Ag nanoparticle (NP)-deposited TiO2 nanotube (TNT) arrays were fabricated. The TNT arrays were prepared by anodizing Ti films on fluorine-doped tin oxide (FTO)-coated glass substrates. Efficient charge transportation through the ordered nanostructure of TNT arrays should be carried out compared to conventional particulate TiO2 electrodes. However, it has been a big challenge to grow TNT arrays on FTO glass substrates with the lengths needed for sufficient light-harvesting (tens of micrometers). In this work, we deposited Ag nanoparticles (NPs) on the wall of TNT arrays to enhance light-harvesting property. Dye-sensitized solar cells with these Ag NP-deposited TNT arrays yielded a higher power conversion efficiency (2.03 %) than those without Ag NPs (1.39 %)., Pacs Codes: 06.60.Ei Sample preparation, 81.05.Bx Metals, Semimetals, Alloys, 81.07.De Nanotubes.
- Published
- 2015
- Full Text
- View/download PDF
29. Formation of two-dimensional ZnO nanosheets by rapid thermal oxidation in oxygenated environment.
- Author
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Tan WK, Li LC, Razak KA, Kawamura G, Muto H, Matsuda A, and Lockman Z
- Abstract
Crystalline 2-D (dimensional) ZnO nanosheets were formed by rapid thermal oxidation of etched Zn foil in oxygen at 300 degrees C and 400 degrees C. Short oxidation time was varied from 10, 20 and 30 min. The morphologies and optical properties of the ZnO nanosheets evolved with the oxidation temperature and time. At 300 degrees C, ZnO nanosheets with thickness ranging from 32 nm to 80 nm were obtained while at 400 degrees C, the thickness of the nanosheets increased from 88 nm to approximately 200 nm after 10 and 30 min of oxidation, respectively. The surface roughness of the ZnO nanosheets and grain size increased with oxidation time and temperature. Photoluminescence of the oxidized samples shows ultraviolet (UV) and visible emissions indicating good crystallinity of ZnO which was further confirmed by high-resolution transmission electron microscope observation of ZnO wurtzite interplanar spacing. Photocatalytic activity of ZnO was also investigated by using degradation of methyl orange (MO) and all the samples exhibit photocatalytic activity. The sample oxidized at 400 degrees C for 10 min show better MO degradation after 2 h of exposure due to higher surface area and better crystallinity of the ZnO nanosheets obtained.
- Published
- 2014
- Full Text
- View/download PDF
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