Papers by Author: Somchai Thongtem

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Authors: Titipun Thongtem, Somchai Thongtem
Abstract: Li1-xNi1+xO2 powder was prepared by using tartaric acid as a complexing agent. A 1 : 1 : 2 mole ratio of Li : Ni : tartaric acid was used to form carboxylate precursors which were calcined at 650–800 oC for 14–48 h. TGA of the precursors showed that formation of Li1-xNi1+xO2 initiates at 600 oC and above. By using XRD, Li1-xNi1+xO2 with 650–800 oC calcination was detected. Calculated intensity ratios of I(003)/I(104) and I(006+102)/I(101) showed that the best condition is at 750 oC for 34 h. The crystallite size was estimated using the Scherrer equation. AAS and titration techniques showed that Ni3+/(Ni3+ + Ni2+) and mean oxidation state of nickel are 66.50 wt% and 2.67 respectively. EDX showed that the powder was comprised by Ni and O. The faceted particles are shown by SEM. TEM and electron diffraction showed the results that are in accordance with the above.
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Authors: Titipun Thongtem, Suttasinee Katunyoo, Somchai Thongtem
Abstract: Nano-rod ZnWO4 was solvothermally prepared by the reaction of Zn(CH3COO)2.2H2O with Na2(WO4).2H2O in water at 150-200 oC using the pH of 5.0, 7.0, 9.0 and 12.0 for 24, 48 and 72 h. N-cetyl pyridinium chloride was used as a surfactant. By using XRD, SAED, EDX and TEM, nano-rod ZnWO4 containing Zn, W and O was detected. The pH values can play a role in the length of the nano-rods and their crystallinities. FTIR revealed the presence of Zn-O-W, W-O and Zn-O stretching vibrations of the products. Their photoluminescent (PL) spectra are similar and the wavelengths at the highest intensities were detected over the range of 445-450 nm.
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Authors: Chatdanai Boonruang, Titipun Thongtem, Michael J. McNallan, Somsorn Singkarat, Somchai Thongtem
Abstract: Two γ-TiAl alloys, Ti-47Al-2Nb-2Cr (MJ12) and Ti-47Al-2Nb-2Mn-0.8TiB2 (MJ47), were pressed in C powder to form rods and carburized by directly applying electrical power through them at 274.3 ± 26.4 W, 80 A for MJ12 and at 293.4 ± 16.8 W, 80 A for MJ47 in Ar atmosphere. The alloys were analysed using an x-ray diffractometer (XRD), a scanning electron microscope (SEM) equipped with an energy dispersive x-ray (EDX) analyser and a Rutherford backscattering spectrometer (RBS) incorporated with NUSDAN solfware. Knoop hardness and wear resistance were improved and found to be in accord with the analytical results.
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Authors: Boonyong Punantapong, Somchai Thongtem, M.J. Fagan
Abstract: This paper presents the results of an experimental procedure where a grid is applied to the edge of a specimen and the local crack-tip displacement fields are calculated using finite element technique. Increasingly, the objective of finite element simulations is to predict the response of the mechanics of material failure are related to microstructural process that occur in the materials as a result of the loading conditions. At the same time, The influences of coating thickness, coating stiffness, and assume crack pattern on the stresses concentration between the neighbouring layers of material are evaluated. Consequently, one approach to simulating the response of structures is to explicity model the mechanisms of damage and failure in the material.
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Authors: Boonyong Punantapong, Somchai Thongtem, M.J. Fagan, C. Soorapanth
Abstract: Cartilage and bone are specialized connective tissues composed of roughly the same material: cell embedded in an extracellular matrix, permeated by the network of fibers. Then the properties of cartilage are anisotropic and inhomogeneous structure. At the same time, the structure of cartilage is rather porous allowing fluid to move in and out of the tissue. Thus the properties of cartilage were changed with the fluid content. The objective of this study is to demonstrate that the biomechanical properties of the pericellular matrix vary with depth from the coated cartilage surface, and observed regions of cartilage failure. This objective is achieved by solving problems with the finite element method. The conceptual model was subjected to the boundary conditions of confined compression on porous of cartilage anisotropy. The experimental results were demonstrated that neither the Young’s modulus nor the Poisson’s ratios exhibit the same values when measured along the loading directions. The results were supported an essential functional property of the tissue which the glenoid surface may be susceptible to cartilage degeneration.
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Authors: Somchai Thongtem, Pisith Singjai, Titipun Thongtem, Panumath Saksoangmuang
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Authors: Somchai Thongtem, Pisith Singjai, Titipun Thongtem, Suphaporn Daothong
Abstract: Carbon nanotubes (CNTs) were grown on 304 stainless steel using iron as a catalyst. By using the applied voltages of 4-6 kV, iron wire with 0.5 mm in diameter was sparked for 1, 2, 10 and 100 times to form catalytic dots on the steel substrate. CNTs were subsequently grown in a gas mixture of 10 ml/s Ar and 0.1 ml/s C2H2 at a temperature range 700 - 900 K for 300 s (5 min). The dots and CNTs were characterised using AFM, SEM and TEM to determine their characteristics.
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Authors: Titipun Thongtem, Sulawan Kaowphong, Somchai Thongtem
Abstract: MWO4 (M = Ca, Sr, Ba and Pb) was solvothermally prepared using metallic nitrates and sodium tungstate in 25/5 volume ratios of glycerol/water (SGL) and propylene glycol/water (SPG) at 160 oC for 6 h. XRD revealed the presence of MWO4 single phase with tetragonal scheelite structure. The strong W-O stretching band of WO4 tetrahedrons was detected at 705-875 cm-1. The product images show nano-sized particles in basic SGL and SPG solvents and flower-like particles in SPG solvent with pH of 6.7. Central peaks of the luminescent spectra are 445, 446, 443 and 440 nm, respectively.
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Authors: Titipun Thongtem, Anukorn Phuruangrat, Somchai Thongtem
Abstract: CdS was synthesized by solvothermal reaction of CdCl2.2.5H2O and (NH2)2CS in ammonia solution at 200 oC for 10 h. XRD, TEM and SAED show that the products are nanocrystalline CdS. The phase is 100 % hexagonal (hcp) in pure water, gradually transformed into cubic with the increase of NH3 concentration, and 100 % cubic in 25 % NH3 solution. By using FTIR, no solvents were detected in the products. Raman analysis revealed the presence of 1LO (longitudinal optical) and 2LO phonon peaks at 297.0 and 597.1 cm-1 for CdS (hcp), and 295.9 and 596.9 cm-1 for CdS (cubic), respectively. Strong peaks of the photoluminescent (PL) spectra were detected at 450 nm for hcp, and 519 nm for cubic.
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Authors: Wonchai Promnopas, Titipun Thongtem, Somchai Thongtem
Abstract: Purified cadmium sulfide crystals were successfully synthesized from 1:2 molar ratio of Cd and S powders by a 900 W microwave plasma for 120 min and 140 min. In the present research, XRD and SAED patterns including SEM, TEM, and FIB images were used to indicate phase and morphology of the products, with their Raman peaks at 303 and 605 cm-1. Photoemission was determined to be 537 nm, and direct energy gap (Eg) to be 2.48-2.51 eV.
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