Vittayakorn, Naratip
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Vittayakorn, Naratip
Alternative Name
Vittayakorn, N.
Vittayakorn, Narathip
Main Affiliation
Email
naratip.vi@kmitl.ac.th
34 results
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Item type:Publication, Titanate Nanosheets/Cellulose Composite Showing Improved Crystallinity and Decreased Water Wettability by Gamma-Irradiation(2025-11-25) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Phase Evolution, Microstructure and Electrical Behavior of (Ba0.97Ca0.03)(Ti0.94-x/2Sn0.06-x/2Wx)O3 Ceramics Synthesized via the Solid-State Combustion Technique(2022-01-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Tailoring charge affinity, dielectric property, and band gap of bacterial cellulose paper by multifunctional Ti2NbO7 nanosheets for improving triboelectric nanogenerator performance(2023-02-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrical conductivity, magnetism, and optical properties of reduced BaCeO 3(2019-03-01); ; Kolodiazhnyi, TarasBaCeO <inf>3</inf> -based perovskites are well-known proton and oxygen ion conductors. For practical applications as electrolytes in solid oxide fuel cells, these compounds must be robust towards reduction of cerium ion. In this work, we explore the effect of reducing atmosphere on the physical properties of undoped and Nb-doped BaCeO <inf>3</inf> . The BaCeO <inf>3</inf> perovskite structure is thermodynamically stable at least up to 1450 <sup>∘</sup> C upon annealing in H <inf>2</inf> -containing atmosphere. Annealing at 1550 <sup>∘</sup> C causes a decomposition of the BaCeO <inf>3</inf> . The higher annealing temperature leads to higher concentration of Ce <sup>3 +</sup> ions and a higher electrical conductivity. With increasing the annealing temperature from 1300 to 1450 <sup>∘</sup> C , the activation energy of conductivity decreases from E <inf>a</inf> = 0.31–0.263 eV. We attribute the electrical conductivity in reduced BaCeO <inf>3</inf> to the activation of the small polaron hopping in agreement with the recent first-principles calculations. However, in contrast to the theoretical predictions, we find no evidence of the Ce <sup>3 +</sup> –Ce <sup>3 +</sup> spin-singlet small bipolarons. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, AC Conductivity and dielectric properties of lepidocrocite-type alkali titanate tunable by interlayer cation and intralayer metal(2020-11-02); The lepidocrocite-type layered alkali titanate AxMyTi2-yO4 has diverse chemical compositions with variation in charge per formula unit x, the interlayer cation A+, and the intralayer metal M. Despite this multivariable nature, the composition dependence of physical properties is not well explored. We report herein the AC conductivity and the complementary dielectric properties of Cs0.7M0.35Ti1.65O4, K0.8M0.4Ti1.6O4 (M = Zn, Ni), and the mixed-interlayer ion Cs0.6K0.1Zn0.35Ti1.65O4. For Cs0.7Zn0.35Ti1.65O4, the total AC conductivity is ~7 × 10-8 to 2 × 10-6 S·cm-1 at 200-350 °C, associating with an activation energy Ea ∼865 meV. Meanwhile, the conductivity of K0.8Zn0.4Ti1.6O4 is higher by 1 order of magnitude at much lower temperature (25-150 °C) and a smaller Ea ∼250 meV. This difference originates from the compositional robustness of the cesium-containing samples, contrasting with the sintering-induced changes in the potassium analogues. For the latter, the loss of the interlayer K+ ion results in (i) generation of carriers due to charge compensation, (ii) reduction of sheet charge density and weakening of electrostatic attraction, and (iii) widening of the interlayer distance, all contributing to a lower Ea in K0.8M0.4Ti1.6O4. The angular frequency dependence of conductivity, dielectric permittivity (up to a colossal value of 109), and dielectric loss follows the universal power law. Our work demonstrates the potential of simple compositional variation for electrical properties tuning, prompting a more in-depth investigation covering a wider range of possible candidates of x, A+, and M in lepidocrocite titanate. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The apparent PTCR effect in layered alkali titanates - A correlation between temperature dependent electrical properties and thermal analyses(2024-12-01); Adsorbed water promotes proton conduction in ceramics at ambient conditions prior to its evaporation, apparently leading to the positive temperature coefficient of resistivity (PTCR) effect. Using surface water-containing Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> (1.8 mol water/mol titanate) as an example, the static conductivity (at 50 °C) of ∼10<sup>−5</sup> S cm<sup>−1</sup> is one thousand times that at 200 °C due to the enhanced proton conduction. At 50–150 °C, the conductivity decreases by 4 orders of magnitude because water evaporation decreases the number of charge carriers. At 150–400 °C, the conduction in water-free Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> is thermal-activated with the apparent activation energy E<inf>a</inf> ∼58–72 kJ mol<sup>−1</sup>, depending on the formalisms. We show clearly that an endothermic DSC peak (water evaporation) in Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> coincides with all eight presentations of AC properties examined. Similar correlations are obtained from the TG/DTG curves in Cs<inf>2</inf>Ti<inf>5</inf>O<inf>11</inf>·H<inf>2</inf>O containing mostly intercalated water. The correlation between thermal analyses and AC properties points out that water molecules essentially contribute to the charge transport at ambient conditions of layered alkali titanates. This scenario might be potentially extended to other humidity-sensitive ceramics. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Structural, optical, and electrical properties of cellulose/titanate nanosheets composite with enhanced protection against gamma irradiation(2023-10-01); ; Charoonsuk, ThitiratTwo-dimensional (2D) materials have emerged as a promising functional filler in nanocomposites due to their unique anisotropy and resilience to harsh conditions. We report herein the use of Ti<inf>0.91</inf>O<inf>2</inf> nanosheets as a protective component against γ-irradiation to cellulose paper. The titanate nanosheets were prepared via a sequence of solid-state synthesis of lepidocrocite-type Cs<inf>0.7</inf>Ti<inf>1.825</inf>O<inf>4</inf>, proton exchange to H<inf>0.7</inf>Ti<inf>1.825</inf>O<inf>4</inf>·H<inf>2</inf>O, and exfoliation with tetrabutylammonium hydroxide. The nanosheets were incorporated into the commercial cellulose filter paper by a simple dip coating up to 0.6 mg cm<sup>−2</sup>, equivalent to 10 wt% TiO<inf>2</inf>. The nanosheets distribution was demonstrated by energy dispersive X-ray (EDX) mapping, synchrotron radiation X-ray tomographic microscopy (SRXTM), and atomic force microscopy (AFM). It is found that γ-irradiation (up to 50 kGy) destroyed the cellulose Iβ crystallinity of uncoated paper, but this is less pronounced in the cellulose/titanate nanosheets composite. This was also confirmed by the lack of a 235 nm-absorption characteristics of irradiation-induced decomposition product(s) in nanosheets-containing papers, which also exhibit UVA shielding property. The coated samples remained white while the uncoated ones were darkened with γ-irradiation. In addition, the nanosheets-coated papers showed dielectric permittivity, loss tangent, and AC conductivity which were invariant of the γ-dose, unlike those from the uncoated ones. Our work demonstrates the use of lead-free Ti<inf>0.91</inf>O<inf>2</inf> nanosheets as a γ-shielding component to slow down/prevent structural, optical, and electrical properties damages in cellulose paper, which could extend to other nature-derived materials. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Phase evolution, microstructure and electrical response of KNNT ceramics with Li+ substitution and doping(2022-01-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Effect of Adsorbed Water and Temperature on the Universal Power Law Behavior of Lepidocrocite-Type Alkali Titanate Ceramics(2021-06-17); The ubiquitous (re)adsorption of atmospheric water by functional ceramics leads to some applications such as humidity sensing; at the same time, this phenomenon complicates the understanding of the nature of original conducting species. We presented herein the effects of adsorbed water on the electrical properties and charge transport of K0.8Zn0.4Ti1.6O4, Cs0.7Zn0.35Ti1.65O4, and Cs0.6K0.1Zn0.35Ti1.65O4 lepidocrocite-type alkali titanate ceramics. A small amount of atmospheric water (0.02-0.33 mol/mol) is merely adsorbed on the external surface but not intercalated into the interlayer space. In temperature scan experiments, water sorption leads to the dielectric permittivity/loss hysteresis loops, where the values upon cooling are unusually larger than those upon heating. In frequency scan experiments, multiple frequency- and temperature-dependent anomalies are detected. The AC conductivity was fitted to the Jonscher universal power law response (σ′AC = σDC + Aωs) from 101 to 106 Hz and 400-25 °C. We observed an uncommon U-shaped A(T) but an inverted U-shaped s(T), regardless of the interlayer ion, charge per formula unit, or pellet density. These plots allow a qualitative description of (i) the apparent activation energy, (ii) the effective dimension of the conduction pathway, and (iii) the charge carrier concentration, all as a function of the temperature under the influence of atmospheric water. Our physical interpretation is potentially applicable to other systems, providing insights into the (unintentional) water-induced conductions and complementing rigorous but time-consuming investigations by controlled humidity experiments. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Alternating current properties of bulk- and nanosheet-graphitic carbon nitride compacts at elevated temperatures(2023-08-23);