Sakdanuphab, Rachsak

Preferred name

Alternative Name

Sakdanuphab, R.

Sakdanuphab, Rachasak

Main Affiliation

College of Advanced Manufacturing Innovation

rachsak.sa@kmitl.ac.th

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Enhanced hydrophilicity for TiO2 nanotube array by simultaneous nitrogen plasma and thermal annealing treatments
(2018-09-05)
Sattha, Chanawee
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Sakulkalavek, Aparporn
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Sakdanuphab, Rachsak
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.
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Enhancing the electrical conductivity and thermoelectric figure of merit of the p-type delafossite CuAlO2 by Ag2O addition
(2017-10-01)
Pantian, Sarayut
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Sakdanuphab, Rachsak
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Sakulkalavek, Aparporn
(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.
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Optimum sintering temperature for thermoelectric properties of low-cost CuAl0.90Fe0.10O2 material
(2016-10-01)
Siriwongrungson, Vilailuck
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Sakulkalavek, Aparporn
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Sakdanuphab, Rachsak
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−1 cm−1 and 9.81 × 10−5 Wm−1 K−2, respectively.
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The advantages of ga-graded obtained by growth profile modification and Na incorporation on Cu(In,Ga)Se2 solar cells
(2014-01-01)
Sakdanuphab, Rachsak
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Chatraphorn, Sojiphong
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Yoodee, Kajornyod
Cu(In,Ga)Se<inf>2</inf> (CIGS) compound is a p-type semiconductor that has been used as light absorber layer in high efficiency thin film solar cell. The CIGS compound can be adjusted the band gap energy by varying the ratio of [Ga]/([In] +[Ga]) ratio (x). From theoretical and simulation, it was found that band gap grading in CIGS thin films showed the advantages to increase the efficiency of solar cells. Generally, the band gap grading can be done by the growth of non homogeneous x-ratio in depth of CIGS thin films. In this work, we develop two approaches to create band gap grading in CIGS thin films; (1) modifying the growth profile and (2) using Na incorporation in the growth process. The effects of Ga-graded would be revealed and compared with homogeneous CIGS thin films. CIGS thin films were grown on soda-lime glass and Al<inf>2</inf>O<inf>3</inf> coated soda-lime glass substrates by molecular beam deposition method. The growth process was based on 2-stage and 3-stage growth profiles. The as grown films were characterized for their structural property, chemical composition and optical transmission as well as solar cell performance. The Auger electron spectroscopy in depth profiles revealed the variation of x- ratio increasing from the surface toward the back contact in CIGS films with our modified growth profile and Na incorporation. This result indicated Ga-graded in CIGS thin films. The structural property of Gagraded CIGS films showed the (112) preferred orientation of the chalcopyrite structure with a broad asymmetric spectrum related to the inhomogeneous structure. The optical transmission measurements of the Ga-graded CIGS film showed the broad transition near the absorption edge indicating the effect of the band gap grading as a result of the variation in depth of the Ga-content. From I-V measurements, the solar cell efficiencies significantly increase due to the advantages of Ga-graded constitute. © (2014) Trans Tech Publications, Switzerland.
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Figures of merit of low-cost CuAl0.9Fe0.1O2 thermoelectric material prepared at different solid state reaction sintering temperatures
(2015-01-01)
Sakulkalavek, Aparporn
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Thonglamul, Rungnapa
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Sakdanuphab, Rachsak
In this study, we investigated a CuAl<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf> compound prepared at two different sintering temperatures in order to find out the effects of sintering temperature on the compound's figure of merit of thermoelectric properties. The thermoelectric CuAl<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf> compounds were prepared from high purity grade Cu<inf>2</inf>O, Al<inf>2</inf>O<inf>3</inf> and Fe<inf>2</inf>O<inf>3</inf> powders. The mixture of these powders were ground and then pressed with uniaxial pressure into pellets. The pellets obtained were sintered in the air at 1423K and 1473K. X-ray diffraction (XRD) patterns showed a single phase of CuAl<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf> with rhombohedral structure, R3¯m, along with a trace of CuO second phase. Moreover, the XRD peaks of the sample sintered at 1423K indicated that more Fe3+ atoms replaced Al3+ atoms in this sample than they did in the sample sintered at 1473K. The average grain size of the CuAl<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf> compound prepared increased with increasing sintering temperature, whereas its mean pore size and porosity decreased with increasing sintering temperature. The dispersed small pores markedly decreased the thermal conductivity of the compound, while the Fe3+ substitution of Al3+ increased its electrical conductivity. The highest figure of merit (ZT) found was 0.021 at 973K in the CuAl<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf> sample sintered at 1423K. Our findings show that this low-cost material with a reasonable figure of merit is a good candidate for thermoelectric applications at high-temperature.
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Effect of additional laser-sensitive pigment on marking brightness and physical property of polypropylene plastic
(2018-09-01)
Tubwat, Alongkorn
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Sakdanuphab, Rachsak
In this study, laser marking was performed by radiative laser beam having wavelength of 1064 nm onto the surface of polypropylene (PP) specimens with laser-sensitive pigment addition. The different amount of laser-sensitive pigment were added onto the PP plastic in the range from 0 to 4.5 wt%. The effect of laser marking parameters such as laser power, scanning speed and pulse frequency on the contrast between marking pattern and the specimens were investigated. In addition, the physical properties such as tensile strength, elongation at break and heat-resistant of the specimens with laser-sensitive pigment addition were determined. The results showed that the brightness of marking pattern was increased as the amount of pigment was increased due to the high absorption of laser-sensitive pigment in the specimens. The pigment content of 0.6 wt% was achieved for the highest contrast laser marking of PP. For the physical characteristics, PP plastic with laser pigment addition showed the decrease of tensile strength as the laser pigment was increased. However, the laser pigment addition can increase heat-resistance of PP plastic. The optimum laser parameter for maximization of brightness of marking pattern and maintaining the physical property were also found out in this study.
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The effects of O2:N2 gas ratios on structural, optical, electrical properties of TiOxNy thin film deposited by reactive DC magnetron sputtering
(2015-01-01)
Khumtong, Tanakorn
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Sakdanuphab, Rachsak
In this work, titaniumoxynitride (TiO<inf>x</inf>N<inf>y</inf>) thin films were deposited on glass slide substrates by using reactive dc magnetron sputtering technique. The reactive gas ratios between O<inf>2</inf> and N<inf>2</inf> were studied in the range of 15-30% with a constant of Ar gas at 110 sccm and a time of 120 minutes. Microstructure, optical, and electrical properties of TiO<inf>x</inf>N<inf>y</inf> thin films were analysis by using SEM, AFM, GIXRD, UV-VIS spectrophotometer, and 4-point probe measurements. We found that the thickness of the films decreases from 1.0 to 0.8 μm by increasing of O<inf>2</inf> gas ratios. The TiO<inf>x</inf>N<inf>y</inf> thin films have smooth surface related to small nano-grain size. The roughness of the films slightly decreases when O<inf>2</inf> gas ratios increase. From optical transmission spectra, we observed that the transparent of the films increases with different O<inf>2</inf> gas ratio and shifts the band gap from 2.67 to 3.32 eV. The resistivity of the films obviously increases from 3.04 × 10-3Ω-cm to 5.45 Ω-cm depending on O<inf>2</inf> gas ratio. These results indicate the phase changes of the TiO<inf>x</inf>N<inf>y</inf> films from metallic to oxide phases. The XRD spectra show poor crystalline TiN (220) and TiO<inf>2</inf> (021) at 15% of O<inf>2</inf> ratio and then the films become amorphous structure by increasing the O<inf>2</inf> gases. The O<inf>2</inf>:N<inf>2</inf> gas ratios also affects to the different concentration of oxygen and nitrogen into the TiO<inf>x</inf>N<inf>y</inf> thin films that lead to the various structural, optical and electrical properties.
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Achieving thermoelectric improvement through the addition of a small amount of graphene to CuAlO2 synthesized by solid-state reaction
(2018-07-15)
Daichakomphu, Noppanut
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Sakdanuphab, Rachsak
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Harnwunggmoung, Adul
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Pinitsoontorn, Supree
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Sakulkalavek, Aparporn
In this work, delafossite CuAlO<inf>2</inf> powders with graphene (0.00–0.20 wt%) were synthesized by a solid-state reaction method. X-ray diffraction and transmission electron microscope results indicated that graphene was segregated in CuAlO<inf>2</inf> as a split phase, such as composite material. A little addition of graphene content reduces the thermal conductivity and increases the carrier concentration because the graphene generates many point defects and aided carrier-phonon scattering. The CuAlO<inf>2</inf> with graphene content of 0.05 wt% shows the maximum electrical conductivity of 470 S/m at 700 K. In addition, the maximum value for ZT of 0.0045 was recorded at 575 K with the graphene/CuAlO<inf>2</inf> composite (0.05 wt%). Therefore, in brief, this study has highlighted the benefits of combining delafossite CuAlO<inf>2</inf> with a small amount of graphene as a potential route for achieving highly efficient thermoelectric materials.
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Structural, morphological and adhesion properties of coFeB thin films deposited by DC magnetron sputtering
(2013-10-29)
Ibuki, Chuleerat
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Sakdanuphab, Rachasak
In this work the effects of amorphous (glass) and crystalline (Si) substrates on the structural, morphological and adhesion properties of CoFeB thin film deposited by DC Magnetron sputtering were investigated. It was found that the structure of a substrate affects to crystal formation, surface morphology and adhesion of CoFeB thin films. The X-Ray diffraction patterns reveal that as-deposited CoFeB thin film at low sputtering power was amorphous and would become crystal when the power increased. The increase in crystalline structure of CoFeB thin film is attributed to the crystalline substrate and the increase of kinetic energy of sputtering atoms. Atomic Force Microscopy images of CoFeB thin film clearly show that the roughness, grain size, and uniformity correlate to the sputtering power and the structure of substrate. The CoFeB thin film on glass substrate shows a smooth surface and a small grain size whereas the CoFeB thin film on Si substrate shows a rough surface and a slightly increases of grain size. Sticky Tape Test on CoFeB thin film deposited on glass substrate indicates the adhesion failure with a high sputtering power. The results suggest that the crystalline structure of substrate affects to the atomic bonding and the sputtering power affects to intrinsic stress of CoFeB thin film. © (2013) Trans Tech Publications, Switzerland.
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Effect of real working environment/formation of oxide phase on thermoelectric properties of flexible Sb2Te3 films
(2019-09-01)
Somdock, Nuttakrit
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Harnwunggmoung, Adul
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Sakulkalavek, Aparporn
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Sakdanuphab, Rachsak
Flexible Sb<inf>2</inf>Te<inf>3</inf> thin films, for thermoelectric generator applications, were deposited by DC magnetron sputtering. As-deposited films were annealed in air to simulated a realistic operating environment. The oxidation behavior of the films was studied by monitoring their phase change on exposure to air at different temperatures between 50 and 300 °C for annealing times from 1 to 15 h. Oxidation of Sb and Te formed Sb<inf>2</inf>Te<inf>4</inf> and TeO<inf>2</inf> phases when annealing above 100 °C and Sb<inf>2</inf>Te<inf>3</inf> decomposed into oxide phases at an annealing temperature of 250 °C for 15 h. The thermoelectric performance decreased as the content of Sb<inf>2</inf>O<inf>4</inf> and TeO<inf>2</inf> phases increased. These findings show the limitations of Sb<inf>2</inf>Te<inf>3</inf> films operating in air without vacuum or a protective environment. We propose that the kinetic growth of oxide formation on the Sb<inf>2</inf>Te<inf>3</inf> thin films depend on chemical activation energy and oxygen diffusion through the oxide barrier by the variation of annealing temperature and annealing time, respectively.

Sakdanuphab, Rachsak

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