Sakdanuphab, Rachsak
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Sakdanuphab, Rachsak
Alternative Name
Sakdanuphab, R.
Sakdanuphab, Rachasak
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rachsak.sa@kmitl.ac.th
67 results
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Item type:Publication, Tuning the thermoelectric performance of flexible copper selenide thin films through sputtering pressure and hybrid microwave annealing(2025-10-10); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Microwave-assisted biosynthesis of silver nanoparticles using two marine microalgal extracts and their antimycobacteriosis activity against bacteria isolated from Betta splendens(2025-12-01); ; ; This study explores the synthesis and antibacterial properties of silver nanoparticles (AgNPs) as a safer, eco-friendly alternative to traditional chemical treatments for bacterial infections. AgNPs were synthesized using aqueous extracts of marine microalgae, Isochrysis galbana and Chaetoceros calcitrans, via conventional and microwave-assisted methods, with the latter accelerating nanoparticle production. Extracts in ethanol, hexane, and acetone were tested, with the ethanolic extract of I. galbana showing the strongest antibacterial effects. The AgNPs exhibited broad-spectrum antibacterial activity against pathogens such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and fish pathogens like Aeromonas veronii. Microwave-assisted synthesis with ethanolic extracts resulted in the highest inhibition, particularly against fish and tuberculosis-related pathogens, including Mycobacterium marinum. Nanoparticle formation was confirmed using various characterization methods, including ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), which revealed crystalline structures. Transmission electron microscopy (TEM) analysis revealed that AgNPs varied in size, with an average diameter of less than 50 nm and all particles being smaller than 100 nm. This research demonstrates the potential of AgNPs as an effective alternative to antibiotics, offering targeted bacterial inhibition while reducing the risk of antibiotic resistance. This makes it a promising approach for treating bacterial infections in ornamental fish. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Dual optimization of ZT and output power in bulk Bi2Te3 through metal-assisted chemical etching(2026-03-01); ; Nguyen, Duc NamThermoelectric materials offer a promising route for sustainable energy harvesting by directly converting waste heat into electricity, enabling compact, solid-state, and environmentally friendly energy solutions. Among them, bismuth telluride (Bi₂Te₃) stands out as the benchmark material for near-room-temperature applications due to its excellent electronic transport properties and commercial maturity. However, achieving high-performance in bulk or thick-film Bi₂Te₃ remains a formidable challenge. Conventional strategies such as doping, alloying, and nanoinclusion, while successful in thin films, often fail to translate effectively to bulk systems due to issues like pore collapse, poor uniformity, and degraded electrical connectivity. These limitations hinder the formation of efficient phonon-scattering architectures without compromising charge transport, resulting in limited improvement in the thermoelectric figure of merit (ZT). In this study, we present a novel and scalable nanoengineering strategy that applies metal-assisted chemical etching (MACE) to fabricate nanoporous surface layers on bulk Bi₂Te₃ for the first time. Unlike conventional nanostructuring techniques, MACE enables the formation of oriented nanostructures via a simple wet-chemical process, offering high tunability, low cost, and compatibility with large-area substrates. To reduce interfacial resistance, nickel was subsequently electrodeposited onto the nanostructured surface, forming a conformal contact layer that improves charge extraction and output performance. By systematically tuning the MACE duration, the optimized nanostructured Bi₂Te₃ sample exhibited a 2.3-fold improvement compared to the pristine bulk sample. Furthermore, due to the increased surface area from the nanoporous architecture, the internal resistance and output power of the nanostructured Bi₂Te₃ devices demonstrated 25-fold and 5.8-fold improvments, respectively, relative to the untreated sample. These remarkable improvements are attributed to the synergistic effect of enhanced phonon scattering within the nanoporous layer and improved charge transport enabled by the conformal nickel coating. This work not only introduces a powerful nanostructuring route for Bi₂Te₃ but also establishes a practical platform for high-performance, thick-film thermoelectric devices. The findings offer deep insight into the structure, property, and performance relationships governing thermoelectric efficiency and pave the way toward the scalable fabrication of next-generation thermoelectric modules for real-world applications such as industrial waste heat recovery and self-powered electronics. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Advanced AlN/SiO2/AlN multilayer coatings for protecting gold-like decorative surfaces: Improved hardness and color stability(2025-12-01); ; This study explores the development of multilayer AlN/SiO<inf>2</inf>/AlN thin film coatings to enhance tarnish resistance, surface hardness, and color stability of gold-coated silver substrates for decorative use. Gold films were deposited via electroplating, followed by multilayer coatings using reactive magnetron sputtering. The SiO<inf>2</inf> thickness was systematically varied while maintaining fixed AlN layers. Optical evaluations using CIE Lab parameters confirmed that the specimen with a 110-min SiO<inf>2</inf> layer exhibited acceptable color difference (ΔE < 5). X-ray photoelectron spectroscopy (XPS) revealed stable Al–N and Si–O bonds with minimal oxidation. Nanoindentation tests showed a significant hardness increase, reaching 7.02 ± 0.62 GPa. After 240 days of ambient exposure, multilayer-coated samples showed no visible discoloration or sulfur-induced degradation, unlike uncoated and electrochemically coated samples. These results confirm that AlN/SiO<inf>2</inf>/AlN multilayers effectively improve the durability and aesthetic stability of gold-like surfaces, offering a promising solution for long-term decorative applications. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Enhancing the anti-tarnish and mechanical properties of gold-coated silver sheets for decorative applications using TiO2 film protection(2024-12-01); ; This study explores an innovative method to enhance the anti-tarnish and mechanical properties of gold-coated silver sheets, targeting decorative applications through the TiO<inf>2</inf> film coatings. The research focuses on gold films with a thickness of approximately 100 nm, and TiO<inf>2</inf> films ranging from 10 to 31 nm. It was observed that the color of the multilayer coatings exhibited significant sensitivity to variations in thickness, indicating that a TiO<inf>2</inf> coating with a thickness around 20 nm could be optimally applied to the gold film, maintaining an acceptable ΔE value. X-ray photoelectron spectroscopy analysis demonstrated the TiO<inf>2</inf> film's potential to inhibit the formation of Ag<inf>2</inf>S on the surface, thereby enhancing tarnish resistance. Furthermore, the application of a 20 nm TiO<inf>2</inf> layer reduced the friction coefficient from 0.28 to 0.24 for gold-coated silver. Durability tests involving 1,000 abrasion cycles revealed that the gold film without TiO<inf>2</inf> protection experienced delamination, with only about 57 % of the coated area remaining intact. In contrast, the samples protected with a TiO<inf>2</inf> layer retained approximately 90 % of the coating, underscoring the effectiveness of TiO<inf>2</inf> in preserving the structural integrity and appearance of the gold-coated silver sheets. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Enhanced hydrophilicity for TiO2 nanotube array by simultaneous nitrogen plasma and thermal annealing treatments(2018-09-05); In this work, highly ordered TiO<inf>2</inf> nanotube (TNTs) array was fabricated by electrochemical anodization technique on titanium sheet. Simultaneous N<inf>2</inf> plasma and thermal annealing process were employed on TNTs using different N<inf>2</inf> gas flow rates at 500°C. As-anodized and N<inf>2</inf> plasma TNTs were characterized for their microstructure, surface elemental composition, and wettability by scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and contact angle measurement, respectively. It was found that N<inf>2</inf> plasma and thermal annealing treatments affect to the change of crystal structure, surface chemistry and wettability of TNTs. The N<inf>2</inf> plasma TNTs exhibits anatase phase with the orientations of (101) and (200). XPS spectra show that the nitrogen atom from plasma was introduced into the surface of TNTs and depends on the N<inf>2</inf> gas flow rates. From contact angle measurement, it can be observed the improvement of wettability (hydrophilicity) of the TNTs due to the N-doped TiO<inf>2</inf> nanotube after N<inf>2</inf> plasma and thermal annealing treatments. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Advances in flexible telluride thin-film thermoelectric generators: Deposition, performance, and module fabrication(2026-04-01); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Enhancing the electrical conductivity and thermoelectric figure of merit of the p-type delafossite CuAlO2 by Ag2O addition(2017-10-01); (CuAlO<inf>2</inf>)<inf>1-x</inf>(Ag<inf>2</inf>O)<inf>x</inf> specimens with 0 ≤ x ≤ 0.06 were prepared through the sintering of mixtures of CuO, Al<inf>2</inf>O<inf>3</inf> and Ag<inf>2</inf>O powders at 1373 K. Hall effect, Seebeck coefficient and electrical conductivity measurements were subsequently employed to assess the electrical transport properties. The electrical conductivity of the as-sintered samples was found to increase with Ag<inf>2</inf>O addition as a result of increases in the carrier density. Over the temperature range of 323–623 K, the transport properties can be attributed to thermally activated transitions from the acceptor state to the valence band. In contrast, the variable range hopping theory is applicable over the temperature range of 623–873 K. Ag<inf>2</inf>O addition evidently reduces the defect binding energy in the electronic structure of the CuAlO<inf>2</inf>. The addition of this compound also obstructs the formation of both a spinel phase and CuO, such that the oxygen off-stoichiometry value and the carrier density are increased with increasing Ag<inf>2</inf>O levels. The presence of Ag metal has the main effect on thermal conductivity below 400 K, while above 400 K increases in the phonon concentration affect the conductivity. The highest value obtained for the figure of merit was 0.0044 at 573 K, from a sample containing 0.2 at.% Ag<inf>2</inf>O. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Optimum sintering temperature for thermoelectric properties of low-cost CuAl0.90Fe0.10O2 material(2016-10-01); Sintering temperature is a key parameter that affects thermoelectric properties. In this study, a suitable temperature to synthesize thermoelectric properties of low-cost delafossite CuAl<inf>0.90</inf>Fe<inf>0.10</inf>O<inf>2</inf> was investigated through the sintering of CuO, Al<inf>2</inf>O<inf>3</inf> and Fe<inf>2</inf>O<inf>3</inf> mixed powder at 1333, 1423 and 1473 K. The optimum sintering temperature is at 1333 K, where the single-phase CuAlO<inf>2</inf> and the highest dimensionless figure of merit of 0.014 at the measured temperature of 873 K were observed. CuAlO<inf>2</inf> with trace amounts of CuO, and CuAl<inf>2</inf>O<inf>4</inf> and CuO were found at the sintering temperature of 1423 and 1473 K, respectively. The highest Seebeck coefficient and thermal conductivity was at the sintering temperature of 1473 K, with the maximum electrical conductivity and power factor at the measured temperature of 873 K of 5.7 Ω<sup>−1</sup> cm<sup>−1</sup> and 9.81 × 10<sup>−5</sup> Wm<sup>−1</sup> K<sup>−2</sup>, respectively. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Simultaneous Seebeck coefficient and electrical conductivity enhancement of GeSbTe films via Sn addition(2022-06-15); ; Sn-added GeSbTe (GST) thin films were deposited using a co-magnetron sputtering technique. The effects of varying the Sn content through a variable Sn target sputtering power and post annealing at 673 K were investigated. The DC power density applied to the GST target was controlled at 50 W, while the power density of the Sn target was increased from 0 W to 40 W. The results demonstrate the coexistence of the fcc-GST, hcp-GST and SnTe phases in the Sn-added GST thin films. The substitution of Sn at the Ge-site increases the crystallization speed and leads to defects and lattice disordered local arrangement in the GST films, causing the Seebeck coefficient to increase. The SnTe phase was created as a result of the high Sn content in the sample due to the over-doping limit of Sn into the GST structure. The presence of SnTe in Sn-doped GST films increased the electrical conductivity. The maximum power factor of 17.0 μW/cmK<sup>2</sup> at 450 K was obtained at an Sn content of 14.7 at%. These results indicated that the thermoelectric properties of Sn-doped GST films were improved via the formation of an appropriate amount of SnTe composite.