KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 65

Some of the metrics are blocked by your
consent settings
Process-structure-property relationships in low-temperature microwave dielectric ceramics: from glass-assisted sintering to cold sintering for 5G/6G devices
(2026-12-01)
Pulphol, Phieraya
;
Tang, Ying
;
Fang, Liang
;
Vittayakorn, Wanwilai
;
Sukkha, Usa
With the rapid advancement of wireless communication from 5G to 6G, a pressing need has emerged for microwave dielectric ceramics with excellent performance at reduced processing temperatures, compatible with low-temperature co-fired ceramic technology. This review traces historical milestones and highlights modern design strategies for achieving optimum dielectric constant, ultra-low dielectric loss, and near-zero temperature coefficient of resonant frequency. Special emphasis is placed on recent advances in low-temperature densification routes, including sintering aids, intrinsically low-sintering-temperature ceramic families, and novel techniques like the cold sintering process. This review provides a critical analysis of the performance trade-offs inherent to each strategy, addressing the persistent challenges in achieving ultra-low loss. Furthermore, we highlight the paradigm shift toward a holistic, multifunctional design imperative for 6G systems. Finally, the transformative potential of cross-disciplinary approaches, particularly AI-assisted discovery, and computational modeling, is discussed as a key enabler for accelerating the design of next-generation, high-performance, and sustainable LTCC-compatible materials.
Some of the metrics are blocked by your
consent settings
The opposing effect of gamma irradiation on proton and sodium ion conduction in Na2Ti3O7 and its defective analog
(2026-10-01)
Maluangnont, Tosapol
;
Chaithaweep, Kanokwan
;
Sangtawesin, Tanagorn
;
Vittayakorn, Naratip
It is known that γ-irradiation of Na<inf>2</inf>Ti<inf>3</inf>O<inf>7</inf> induces Na + ion deintercalation, oxygen-vacancy formation, and proton/water incorporation, yielding the defective phase Na<inf>2- x </inf>H<inf>0.5 x </inf>Ti<inf>3</inf>O<inf>7-0.5 x </inf>(OH)<inf>0.5 x </inf> with multiple charge carriers. Although Na<inf>2</inf>Ti<inf>3</inf>O<inf>7</inf> is a well-studied ion conductor, charge-transport details in its γ-irradiated analogs remain limited. Here, we report their AC conductivity and dielectric properties under a temperature cycle (RT→350 °C→RT). Proton conduction dominates at ambient temperature but diminishes upon heating. This produces a dehydration-driven increase of resistivity known as the apparent Positive Temperature Coefficient of Resistivity (PTCR) effect, consistent with the Heywang model recently applied to water-adsorbing ceramics. Proton conductivity increases with γ-irradiation dose up to 200 kGy, then decreases at 400 kGy due to excessive structural disorder. At high temperatures, Na+ ion conduction prevails and follows Arrhenius behavior, with activation energy decreasing with dose. This discrepancy might be understood considering that Na+ ion conduction is governed primarily by its concentration rather than mobility; excessive doses lower activation energy but deplete Na+ ions and decrease conductivity. Dielectric-loss fitting using Jonscher's universal dielectric response (UDR) indicates that proton-transport pathways are sensitive to thermal history, whereas Na+ ion conduction exhibits low-frequency dispersion (LFD) across all conditions.
Some of the metrics are blocked by your
consent settings
Kinetic analysis of liquid–solid contact electrification: Using adsorption models as mechanistic probes for hybrid EDL behavior
(2026-08-01)
Chaithaweep, Kanokwan
;
Pharino, Utchawadee
;
Pongampai, Satana
;
Sriphan, Saichon
;
Charoonsuk, Thitirat
Liquid–solid interfaces are central to technologies ranging from energy storage to triboelectric nanogenerators (TENGs). Whereas classical electric double layer (EDL) theory describes these interfaces mainly in terms of electrostatic ion adsorption, hybrid EDL concepts suggest that interfacial electron transfer may also contribute importantly to charge generation. However, the hybrid EDL model has so far been discussed primarily at a qualitative level or through complex theoretical and computational treatments, and a simple, experimentally accessible macroscopic kinetic handle that can discriminate, in operando, between adsorption‑dominated and ET‑influenced regimes remains lacking. By analyzing high-resolution charging dynamics over systematically varied H₂SO₄ and HNO₃ concentrations, a clear concentration-dependent kinetic transition is identified. At low ionic strengths, the charging process is described more effectively by pseudo-second-order (PSO) kinetics, consistent with a reaction-influenced interfacial step, whereas at higher concentrations the system becomes pseudo-first-order (PFO) dominated, consistent with transport- and ion-screening-controlled behavior. Although previous studies have provided compelling theoretical and spectroscopic evidence that interfacial electron transfer contributes to liquid–solid contact electrification in TENGs, these mechanisms have rarely been examined through such simple macroscopic kinetic formalisms. In this work, classical adsorption kinetic models are used as operational probes for distinguishing electron-transfer-influenced regimes from ion-transport-dominated regimes at PTFE/liquid interfaces. The PSO-to-PFO crossover reported here is interpreted within the hybrid EDL framework as a kinetic marker of a transition from an electron-transfer-influenced charging regime at low concentration to an ion-transport- and screening-dominated regime at high concentration, thereby demonstrating how adsorption kinetics can serve as a practical diagnostic language for liquid–solid triboelectric systems.
Some of the metrics are blocked by your
consent settings
Composition–structure mapping of fluorine–graphite intercalation compounds
(2026-07-01)
Maluangnont, Tosapol
Fluorine–graphite intercalation compounds (FGICs) have been extensively studied for their enhanced conductivity, yet their reported composition–structure relationships remain scattered. Here, we present an empirical analysis of FGICs focusing on interlayer spacing dᵢ, carbon-to-fluorine ratio C/F, and stage number s, compiling literature data spanning multiple decades. Variations to graphite host (including highly oriented pyrolytic graphite, natural graphite, powder, fiber, mesophase pitch, microbead, and specialized carbon sources) and synthetic methods are also considered. Despite substantial variability in experimental protocols, the data (184 entries) collapse into three regimes across stages 1–4 with C/F ∼0.63–16.7 (71.5−8.6 wt%F). The dᵢ ∼4.4, ∼6.0, and ∼11.4 Å regimes have been interpreted in the literature as corresponding to fluorine nesting, semi-ionic fluorine intercalation, and graphite bi-intercalation structures, respectively. Other smaller subsets are also identified at dᵢ ∼5.5 Å (coexistence of planar sp2 C=C/puckered sp3 C−F), 6.0 Å (covalent C−F), and 7.8 Å (F<inf>2</inf> perpendicular to graphene sheets). This diversity reflects the anisotropic mechanical response of graphite: stiffness along the stacking direction constrains expansion, while in-plane softness accommodates compositional variation. We introduce V<inf>gal</inf> representing the available gallery volume (i.e., at the interlayer space) per carbon atom which does not require assumptions about fluorine size. This descriptor preserves such three regimes, whereas the traditional packing fraction varies widely and may exceed physically meaningful limits. Taken together, this work provides an interpretative classification of FGICs, consolidating insights into fluorine intercalation that are not evident from individual reports while helping place future FGICs within, and potentially extend, the known composition–structure landscape.
Some of the metrics are blocked by your
consent settings
A Radiation-Tolerant g-C3N4 Dielectric Insulator: Local Structure Redistribution under γ-Irradiation
(2026-06-05)
Maluangnont, Tosapol
;
Chaithaweep, Kanokwan
;
Worathat, Supakarn
;
Sangtawesin, Tanagorn
;
Wasapinyokul, Kamol
Graphitic carbon nitride (g-C<inf>3</inf>N<inf>4</inf>) is a defect-rich polymeric material whose local structure is difficult to resolve using techniques dominated by average structural motifs. Here, pristine and γ-irradiated g-C<inf>3</inf>N<inf>4</inf> samples are examined using solid-state nuclear magnetic resonance (NMR) spectroscopy. Combined 13C, 15N, and 1H NMR reveal decreased terminal −NH<inf>2</inf> species and redistribution of interheptazine −NH– linkages with dose, while the heptazine framework remains intact. X-ray diffraction shows a non-monotonic evolution of stacking coherence, accompanied by IR evidence of C–N linkage modification. Despite these changes, the electrical resistivity remains extremely high at ∼109 Ω·cm and nearly independent of irradiation dose (10–400 kGy), temperature (RT–350 °C), and frequency (104–106 Hz). The dielectric permittivity decreases slightly from ∼7.2 to ∼4.7–5.2, while the dielectric loss tangent remains low (∼0.02). The refractive index similarly decreases from ∼2.6 in pristine g-C<inf>3</inf>N<inf>4</inf> to ∼2.2–2.3 after γ-irradiation. Analysis of the frequency dependence follows the universal dielectric response, consistent with correlated barrier hopping conduction with predominantly three-dimensional charge transport. Together, these observations show that γ-irradiation primarily reorganizes linkage environments without significantly perturbing the π-conjugated heptazine framework that governs charge transport. These characteristics make γ-irradiated g-C<inf>3</inf>N<inf>4</inf> promising for radiation-resistant dielectric and insulating components in nuclear and high-radiation electronic environments.
Some of the metrics are blocked by your
consent settings
Comments on “tuning electrical conductivity in lithium-doped sodium titanate via sonochemical synthesis”
(2026-04-01)
Maluangnont, Tosapol
da Silva et al. (Mater. Sci. Eng. B 323 (2026) 118836) recently reported the sonochemical synthesis of lithium-doped sodium titanate Na<inf>2-x</inf>Li<inf>x</inf>Ti<inf>3</inf>O<inf>7</inf> (x = 0, 0.01, 0.02 and 0.03). They proposed three-phase products: (i) lithium-doped Na<inf>2-x</inf>Li<inf>x</inf>Ti<inf>3</inf>O<inf>7</inf> with the layered structure, (ii) undoped Na<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> with tunnel structure, and (iii) the NaLiTi<inf>3</inf>O<inf>7</inf> impurity (at high x). It is argued that that the formation of Na<inf>2-x</inf>Li<inf>x</inf>Ti<inf>3</inf>O<inf>7</inf> is unlikely. Two major products could be assigned as undoped Na<inf>2</inf>Ti<inf>3</inf>O<inf>7</inf> and undoped Na<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf>. Also, the NaLiTi<inf>3</inf>O<inf>7</inf> impurity (which has completely different structure from the layered alkali titanate) could be the structurally related Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf> spinel. The present interpretation can explain the invariant unit cell parameters, the decrease of optical band gap, and the improvement of electrical conductivity observed by the original authors.
Some of the metrics are blocked by your
consent settings
Comments on “Interlayer Atomic Voids by Partial Cesium Defect in Layered Titanate Activate Photo(electro)catalytic H2 and O2 Generation”
(2026-03-23)
Maluangnont, Tosapol
Üstünel et al. ( ACS Appl. Energy Mater., DOI:10.1021/acsaem.5c01514) recently proposed the interesting concept of interlayer Cs voids formation in lepidocrocite-type Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf>. This was accomplished via treatment of the titanate with an aqueous solution of cetyltrimethylammonium bromide, followed by heat treatment at 700 °C. We present an alternative explanation focusing on: (i) unintended proton exchange from the medium; and (ii) subsequent thermal dehydration/dehydroxylation to anatase and “defective Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf>”. Our interpretation based on the classical chemistry of layered materials is consistent with their experimental results.
Some of the metrics are blocked by your
consent settings
An architected silk fibroin-lignin multilayer with deep-level trapping states for high-output triboelectric nanogenerators
(2026-03-01)
Suktep, Natdanai
;
Sae-tang, Chanachot
;
Ukasi, Sirinya
;
Pakawanit, Phakkhananan
;
Supansomboon, Supitcha
Biopolymer-based triboelectric nanogenerators (B-TENGs) are promising power sources for sustainable and flexible electronics, but their performance is often limited by severe charge recombination at the triboelectric interface. To overcome this critical bottleneck, we report an architected multilayer B-TENG featuring a silk fibroin (SF)/MgAl LDH composite as the charge-generating layer and, to our knowledge, for the first time, a lignin-functionalized SF film as a dedicated charge-trapping layer. The strategic incorporation of lignin, an abundant and sustainable biopolymer, introduces deep-level electronic trapping states originating from its abundant aromatic moieties. That effectively suppresses interfacial charge recombination and prolongs charge lifetime. By optimizing the contents of MgAl LDH and lignin, the device achieves a measured open circuit output voltage ( V <inf> OC </inf>) and current density ( J <inf> SC </inf>) of 96 V and 6.56 μA/cm3, with a maximum output power ( P <inf> max </inf>) of 205 μW, corresponding to a power density of 22.7 μW/cm2. We also propose a mechanistic linking of deep-level traps to prolonged charge lifetime and increased net transferable charge. The interface-engineering strategy demonstrated here paves the way for developing high-performance and sustainable biopolymer-based TENGs and motion sensors.
Some of the metrics are blocked by your
consent settings
Complex Impedance Formalism for Probing Dehydration, Dehydroxylation, and Rehydroxylation Dynamics of UiO-66-Based Metal–Organic Frameworks
(2026-02-12)
Maluangnont, Tosapol
;
Chaithaweep, Kanokwan
;
Sriphan, Saichon
;
Meejaiyen, Parinya
;
Anutrasakda, Wipark
It is known that the UiO-66 metal–organic framework (MOF) undergoes dehydration of physisorbed water and dehydroxylation of the zirconium clusters from RT to ∼300 °C, while the porous structure remains intact. These two processes are typically studied by thermogravimetric analysis and its derivative method (TGA/DTG), as well as differential scanning calorimetry (DSC). Here, we probe the same phenomena using temperature-dependent complex impedance spectroscopy. Peaks observed in the AC conductivity and in the real and imaginary parts of the dielectric permittivity (σ<inf>AC</inf>, ε′, and ε″) are due to thermally accelerated proton (Grotthuss) hopping competing with the loss of proton carriers during guest removal and dehydroxylation up to 350 °C. Meanwhile, peaks in the loss tangent (tan δ) and phase shift (Θ) identify the temperature at which dielectric-to-heat conversion is maximized. Additionally, peaks in the imaginary part of the impedance (−Z″) and in the real part of the electric modulus (M′) mark the temperature at which the material exhibits its highest insulating character. The MOFs examined include UiO-66 with the 1,4-benzenedicarboxylate linker and UiO-66-Py with the 2,5-pyridinedicarboxylate linker, the latter further modified through trifluoroacetic acid modulation, 1-bromopropane functionalization, and optional intermediate heat treatment. Impedance measurements under cooling reveal composition-dependent rehydroxylation behavior, with the conductivity recovery as early as at 250 °C in some Py-based derivatives vs flat response in pristine UiO-66. Overall, our work provides a comprehensive analysis of several complex electrical quantities and their physical interpretation, offering complementary insights into the dehydration, dehydroxylation, and rehydroxylation dynamics of UiO-66-based MOFs.
Some of the metrics are blocked by your
consent settings
Gamma irradiation produces graphitic carbon nitride with decreased water affinity
(2026-01-15)
Maluangnont, Tosapol
;
Worathat, Supakarn
;
Chaithaweep, Kanokwan
;
Sangtawesin, Tanagorn
;
Khamman, Orawan
Absorption of water on surfaces of graphitic carbon nitride (g–C<inf>3</inf>N<inf>4</inf>) can be lessened by organic molecules functionalization or post-annealing treatment. In contrast to this knowledge, we show that γ-irradiation (10–400 kGy) of g–C<inf>3</inf>N<inf>4</inf> results in a defective material with decreased water affinity on surface and at bulk alike without those modifications. Irradiated g–C<inf>3</inf>N<inf>4</inf> samples show diminished water content (2.52 wt% to 1.91–0.96 wt%) and decreased crystallinity but slightly increased surface area, including slit-shape pores formation in platy particles. However, their IR spectra and optical bandgap do not change. Despite the radiation-induced increase of N/C, the diminished water content is consistently observed on surfaces by XPS, and at the depth ∼1 μm deeper by EDX. It is found that γ-irradiation generates a higher proportion of pyridinic N which disfavors water adsorption. This is correlated to a decreasing apparent activation energy of water evaporation in a γ-irradiated material compared to a pristine one (29 vs 47 kJ·mol−1). Also, γ-irradiation generates dangling bonds which facilitate bonding/agglomeration between particles such that the access of water to adsorption sites is prohibited. The demonstrated application of γ-irradiation to reduce water wettability, which is chemical-free and easily controllable, encourages further studies to other hydrophilic materials.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results