Rudradawong, Chalermpol

Preferred name

Alternative Name

Rudradawong, C.

Main Affiliation

School of Science

chalermpol.ru@kmitl.ac.th

Now showing 1 - 7 of 7

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High temperature electrical and thermal properties of activated bamboo charcoal/C12A7 mayenite composite prepared by carbon diffusion process
(2019-03-15)
Rudradawong, Chalermpol
;
Ruttanapun, Chesta
Activated carbon from bamboo charcoal (BC) was diffused into the C12A7 mayenite compound via carbon diffusion process for synthesizing BC and C12A7 composite (BC/C12A7 composite). The BC/C12A7 composite was fabricated by carbon diffusion at holding time 5, 10 and 20 h for investigating electrical and thermal properties at high temperature. Result of XRD revealed the C12A7 structure and confirmed by Raman spectrum. Obtained energy gap showed at 4.93, 5.26, 5.19 and 5.09 eV at holding times of 0, 5, 10 and 20 h, respectively. Electrical conductivity significantly increased with increasing temperature and increased as a function of increasing holding time. Carrier concentration showed approximately 1.27 × 10 17 , 1.32 × 10 17 and 2.76 × 10 17 cm −3 of 5, 10 and 20 h, respectively. Temperature dependence of thermal conductivity showed as proportion of T −1 due to phonon-phonon scattering of Umklapp process. The thermal conductivity decreased from pristine C12A7 approximately 0.4 W m −1 K −1 in all BC/C12A7 composite samples.
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Reinvestigation thermoelectric properties of CuAlO2
(2014-01-01)
Ruttanapun, Chesta
;
Kosalwat, Wattana
;
Rudradawong, Chalermpol
;
Jindajitawat, Phumin
;
Buranasiri, Prathan
Bulk CuAlO2 delafossite has been synthesized by solid state reaction to reinvestigate the thermoelectric properties. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured in a high temperature range of 300 to 960 K. The result of positive sign of Seebeck coefficient confirms p-type nature of CuAlO2 compund. The results of bulk sample for Seebeck coefficient, the electrical conductivity and thermal conductivity are range of 900 to 300 μV/K, of 0.01 to 2 S/cm, and of 3.5 W/mK to 1.5 W/mK. The maximum ZT value of bulk sample is 0.017 at a 960 K. These results can be concluded that the bulk CuAlO2 by solid state state displays thermoelelctric material.
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Effect of Ga-substitution for Fe sites of delafossite CuFe1-xGaxO2 (X = 0.0, 0.1, 0.3, 0.5) on thermal conductivity
(2016-03-05)
Hongaromkij, Yuttana
;
Rudradawong, Chalermpol
;
Ruttanapun, Chesta
This work aimed to study the effect of the Ga3+-substitution of Fe3+ sites in CuFeO<inf>2</inf> delafossite on its thermal conductivity. CuFe<inf>1-x</inf>Ga<inf>x</inf>O<inf>2</inf> (x = 0, 0.1, 0.3, and 0.5) samples were synthesized and their phase structure and ionic composition were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The thermal conductivity of the samples was measured at a high temperature range of 298-573 K. The XRD results confirmed that the samples were pure phase delafossite with hexagonal structure space group: R3m while the EDX results showed composition atomic percent of Ga 100% of x = 0.1, 93% of x = 0.3 and 90% of x = 0.5 and the XPS results revealed Cu1+ and Cu2+, Fe2+ and Fe3+, and Ga3+ ion states in the structure. The Ga-substitution decreased the thermal conductivity of the samples below that of nondoped CuFeO<inf>2</inf>. The high substitution sample (x = 0.5) exhibited the lowest thermal conductivity, 2.5 W/mK at 573 K. Ga substitution into Fe sites affected the lattice thermal conductivity partly through phonon scattering processes arising from mass difference and lattice strain.
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Method of high active preparation and electrical properties of CuFeO2 delafossite-type
(2014-01-01)
Rudradawong, Chalermpol
;
Wichainchai, Aree
;
Sakulkalavek, Aparporn
;
Hongaromkid, Yuttana
;
Ruttanapun, Chesta
In this paper, the CuFeO<inf>2</inf> compound were prepared by classical solid state reaction (CSSR) and direct powder dissolved solution (DPDS) method from starting material metal oxides and metal powders. Preparation of two methods shows that, direct powder dissolved solution faster recover phases than classical solid state reaction method. The fastest method gets from starting materials Cu and Fe metal powders, the electrical conductivity, Seebeck coefficient, carrier concentration and mobility are 10. 68 S/cm, 244. 59 μV/K, 12. 86×1016 cm-3 and 494. 96 cm2/V. s, respectively. In addition, each CuFeO<inf>2</inf> compounds were investigated on crystal structure and electrical properties. From XRD and SEM results, all samples have a crystal structure delafossitetype (R3m) and a large grain boundary more than 15 μm by electrical conductivity corresponds to grain boundary and lattice parameter: a increases. Within this paper, from above results exhibit that preparation CuFeO<inf>2</inf> from Cu and Fe by direct powder dissolved solution method most appropriate for thermoelectric oxide materials due to high active for preparation else high lattice strain and high power factor are 0. 00052 and 0. 64×10-4 W/mK2, respectively. © (2014) Trans Tech Publications, Switzerland.
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Effect of excess oxygen for CuFeO2.06 delafossite on thermoelectric and optical properties
(2017-12-01)
Rudradawong, Chalermpol
;
Ruttanapun, Chesta
This work presents the role of excess oxygen in CuFeO<inf>2.06</inf> compounds on thermoelectric and optical properties. The CuFeO<inf>2.06</inf> specimens were synthesized by solid state reaction method. X-ray diffraction technique has confirmed the CuFeO<inf>2</inf> structure for the specimens. In particularly, CuFeO<inf>2.06</inf> specimen revealed the structural extension of lattice parameter: a and c. Also, the specimen found increasing excess oxygen of approximately 3% as a resulted enhancement of mixed valence state of Cu+ and Cu2+ ions. XPS showed mixed valence state of the Cu+/Cu2+ ions, and Fe3+ and Fe2+ ions was also found in the CuFeO<inf>2.06</inf> specimen. Mixed valence states contributed the co-existence of hole and electron carriers for conduction. Consequently, electrical conductivity of the CuFeO<inf>2.06</inf> specimen increased up to 23 S/cm at 873 K. Also, increasing Seebeck coefficient was shown to be approximately 302 μV/K at 873 K. The CuFeO<inf>2.06</inf> specimen was found power factor to be approximately 2.1 × 10−4 W/m∙K2 at 873 K. The indirect optical gap of CuFeO<inf>2.06</inf> (2.40 eV) was lower than that of the CuFeO<inf>2</inf> (2.60 eV). Thus, thermoelectric and optical properties were governed by an existence of excess oxygen.
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Combined effects of Mg reducing and Sn doping on the electrical conductivity of polycrystalline Ca12Al14O33 mayenite
(2019-04-01)
Rudradawong, Chalermpol
;
Ruttanapun, Chesta
Polycrystalline Ca<inf>12</inf>Al<inf>14</inf>O<inf>33</inf> was prepared by a solid state reaction method. All samples showed the phase of the Ca<inf>12</inf>Al<inf>14</inf>O<inf>33</inf> by X-ray powder diffraction (XRD). The Mg heat treatment and Sn doping contributions dominated to increase the lattice constant a from 11.909(3) to 12.163(1) Å. Electron excitation energy of all samples were assigned by absorption spectra. The excitation energy between 2.68 and 2.79 eV was found after the Mg heat treatment. Electrical conductivity increased approximately 109 orders of magnitude at room temperature when experiencing Mg heat treatment for 10 h. The highest electrical conductivity obtained from the Ca<inf>12</inf>Al<inf>12.8</inf>Sn<inf>1.2</inf>O<inf>33</inf>/Mg(10) sample was 7.65 S cm− 1 at 573 K. The low activation energy for electrical conductivity was approximately 0.038 eV as a result of the Mg heat treatment. The influence of the Sn doping excellence supported the increase of the electrical conductivity with the Mg heat treatment process.
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Improvement of Thermoelectric Material by Reduction Thermal Conductivity of Sn-doped CuFeO2 Delafossite Compound
(2015-09-02)
Hongaromkij, Y.
;
Rudradawong, C.
;
Wichainchai, A.
;
Ruttanapun, C.
In this work, the polycrystalline CuFe1-xSnxO2 (x = 0.005, 0.01, 0.03) were synthesized by a solid state reaction method with sintering temperature at 1323K for 40 hours. The XRD pattern and TGA results showed the crystal structure of hexagonal delafossite-type structure for space group (166). Thermal conductivity was decreased because the large atomic mass of the Sn substituted to the Fe sites of CuFeO2. This caused phonon scattering by the point defect of the mass difference between Sn atom and Fe atom. The minimal value of the thermal conductivity was 2.1 W/mK at 573K for Sn = 0.03. © 2015

Rudradawong, Chalermpol

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