Papers by Author: Papot Jaroenapibal

Abstract: Ni-P coatings were prepared on low carbon steel substrates using the pulse electrodeposition method. The influence of the pulse duty cycle on the phosphorus content and hardness of the Ni-P coatings was investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to examine the surface morphology and chemical composition of the Ni-P coating layers. The results showed that an increased pulse duty cycle (20% - 80%) led to a decreased phosphorus content from 17.81 wt.% to 13.71 wt.%. The microhardness values were found to have an inverse relationship with the phosphorus content. The highest hardness of 538.22 ± 12.92 HV_0.1 was obtained from the sample produced with a duty cycle of 80%, which had the lowest P content of 13.71 wt.%.

Abstract: Nickel-Phosphorous/diamond coatings were electrodeposited onto steel substrates using a pulse-stirring method. The electrodeposition process involved a solution containing nickel sulphate, phosphorus acid, and diamond particles, resulting in the co-electrodeposition of 4-8 µm of diamond particles into a Ni-P matrix. To investigate the effects of electrodeposition current density on the properties of the Ni-P/diamond composite coating, scanning electron microscopy (SEM), hardness testing, and electrochemical testing were employed. The research findings revealed that higher current density (0.03 A/cm²) led to a denser diamond particle coating with diamond contents of up to 32.70 vol%. Additionally, the Ni-P/diamond coatings achieved a maximum hardness of 2819 ± 12.55 HV_0.1 when fabricated using the current density of 0.03 A/cm². The "pulse-stirring fabrication" method yields a coating with significantly enhanced wear resistance due to incorporating densely packed diamond particles. The intermittent pulses during the fabrication process are crucial for achieving the desired dispersion and adhesion of the diamond particles, leading to a practical and durable wear-resistant coating.

Abstract: This study aims to synthesize and examine the optical and photoelectrochemical properties of tungsten oxide (WO₃) nanofibers prepared by electrospinning and calcination using different temperatures (500, 700, and 900 °C). The electrospinning solution contained a mixture of polyvinyl alcohol (PVA, 7.5% w/v) and ammonium metatungstate hydrate (AMH, 16.7% w/v). The morphology of WO₃ nanofibers was observed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorbance of calcined WO₃ nanofibers was measured, and the data was used to calculate the optical band gap energy (E_g) through Tauc’s relation. The of calcined WO₃ nanofibers were found to be from 2.85 to 3.08 eV. The minimum value of was obtained from the sample calcined at 900 °C. Linear sweep voltammetry (LSV) was employed in the photocurrent measurements under simulated AM 1.5G at 100 mW/cm² irradiance. The WO₃ nanofiber photoanode calcined at 900 °C exhibited the maximum photoconversion efficiency (PCE) of 1.53%, a twice enhancement in PCE compared with those obtained from WO₃ nanofibers calcined at lower temperatures. This study suggests the potential pathway for the optimal synthesis of high performance nanostructured metal oxide electrodes for photoelectrochemical water splitting.

Abstract: Ni-W-B alloy coating containing amorphous boron particle were fabricated by direct current electrodeposition on low carbon steel substrates. The effect of boron concentration in the plating bath on the surface morphology, the overall boron content in the deposited layers and the hardness of the resulting coating layer were investigated. Scanning electron microscopy (SEM) revealed that the surface morphology of the Ni-W-B coating layer was largely modified by the boron particle loading in the electroplating suspension. Distinct nodular structures were observed in these samples. Energy dispersive X-ray spectroscopy (EDS) spectra suggested that the overall boron content in the coating layer increased with increasing boron particle loading from 1 to 3 g/L. Too high boron particle loading of 10 g/L resulted in lower overall boron content. The highest hardness of 680.86 ± 17.67 Hv was obtained from Ni-W-B/B coating layer fabricated using the boron particle loading of 5 g/L.

Abstract: This work describes the fabrication steps and surface-enhanced Raman scattering (SERS) activities of the cross-linked polyvinyl alcohol (PVA)/Ag nanofibers. The water-insoluble electrospun PVA/Ag nanofibers were achieved by post-electrospinning treatment processes. Physical crosslinking was induced by heat treatments, while chemical crosslinking took place through the reactions with glutaraldehyde (GA). Scanning electron microscopy (SEM) images have shown that cross-linked PVA/Ag nanofibers remained mostly intact after immerging in water for 30 min. The testing of SERS activities was performed on these substrates using the methylene blue (MB) molecules as tested substances. The results have shown that the PVA/Ag nanofibers can be used as SERS substrates for rapid screening of biochemical substances. The Raman enhancement factor (EF) of approximately 10⁴ corresponding to the detection limit of 10^-4 M of MB molecules was achieved.

Abstract: X-ray photoelectron spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) were used to analyse the effect of oxygen plasma treatment on properties of aluminum oxide thin films. The aluminum oxide films were fabricated using a reactive sputtering system. The as-deposited films were treated with oxygen plasma powered by an RF generator. During the plasma treatment, the pressures were set at 1 x 10^-1 to 1x 10^-2 mbar, while the RF supplied powers at 100 W and 200 W. It was observed that lower plasma powers and higher pressures resulted in smoother films. The O/Al ratio of the films were found to decrease with increasing plasma powers and pressures. The thickness and refractive index of the films were significantly affected by the oxygen plasma treatment process, which could be related to the change in films’ packing density and the etching at the surface.

Abstract: In this work, tungsten oxide (WO₃) nanofibers were synthesized using electrospinning technique. Direct current electrophoretic deposition (DC-EPD) was conducted to deposit the nanofibers onto fluorine-doped tin oxide (FTO) electrodes. The photoelectrochemical performance of WO₃ nanostructured electrodes was investigated and compared between the samples containing pristine WO₃ and Ag/WO₃ composite nanofibers. An up-to-6-fold enhancement in photoconversion efficiency (PCE) was obtained from Ag/WO₃ composite nanofiber photoanode.

Abstract: This work demonstrated the improvement of belite cement compressive strength by incorporating nanosilica coated single-walled carbon nanotubes (SWNTs@SiO₂) into the cement paste. The structure and chemical compositions of SWNTs@SiO₂ materials were characterized by transmission electron microscopy and energy dispersive X-ray spectroscopy techniques, respectively. Belite cement composites were prepared by mixing belite cement paste with different loadings of SWNTs@SiO₂ ranging from 0.02 – 0.1 wt%. In order to measure the early strength of cement composites, the samples were aged for 7 days, and then subjected to compression tests. Effects of uncoated SWNTs and silica coated SWNTs loadings on the compressive strength of belite cement composites were studied. Without pre-coating SWNTs with nanosilica, the SWNTs additives led to large decrease in compressive strength of belite cement composite. Improvements in compressive strength of belite cement are shown in samples that incorporated SWNTs@SiO₂ loadings. The coating layer helps enhance bonding strength between reinforced SWNTs and the matrix, as well as promote hydration reactions in the cement paste. The highest increase in the compressive strength of 18.8 % is found in the sample with the minimal SWNTs@SiO₂ loading of 0.02%.

Abstract: This paper demonstrates a technique to synthesize silica-coated single-walled carbon nanotubes (SWNTs@SiO₂) based on sodium dodecyl sulfate (SDS), 3-aminopropyltriethoxysilane (APTES), ammonium hydroxide (NH₄OH) and tetraethyl orthosilicate (TEOS). The coating of silica is done to promote bond strength between SWNTs@SiO₂ and other materials. The anionic surfactant used in the coating process helps create linkages between the silica coupling agent and the SWNTs’ walls without compromising the excellent properties of SWNTs. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDX) were employed to characterize the sizes of SiO₂ particles, the structure of SWNTs@SiO₂, and the elements existed in the materials. The size of SiO₂ particles has shown to be dependent on the amount of TEOS concentration and reaction time. Higher TEOS concentration and longer reaction time led to larger SiO₂ particles. Successful coatings of SiO₂ on SWNTs have been demonstrated. Silica appeared to be uniformly coated on the SWNTs surfaces. The thickness of the coating layer was found to be approximately 3-7 nm.

Abstract: This work reports the impedance analysis and carbon monoxide gas sensing response of tungsten oxide (WO₃) nanofibers with silver (Ag) nanoparticle doping. The Ag-doped WO₃ nanofibers were prepared by an electrospinning technique. The impedance spectroscopic measurements of undoped and Ag-doped WO₃ nanofibers were performed to study the contribution of electrical parameters involved in the electron transport. The impedance modeling obtained from the fitted Nyquist plot shows that the RC components attributed to Ag-WO₃ interface are introduced to the system upon Ag addition. Carbon monoxide (CO) gas detection was carried out by resistance measurement using a DC method. The sensitivity of Ag-doped WO₃ nanofibers is found to be greater than that of the undoped sample. The improved sensitivity is derived from the high interface resistance between Ag and WO₃ grains. The contribution of Ag dopants is conceived to induce electronic structure alteration of the sensor material.