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Start date: 2020Subject: search.filters.subject.Annealing process

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    Post-annealing effects on (00l) texture, Cl/Se ratio, and electrical and glass-like thermal transport in Bi₄O₄SeCl₂
    (2026-04-25)
    Somdock, Nuttakrit
    ;
    Theekhasuk, Nattharika
    ;
    Voraud, Athorn
    ;
    Limsuwan, Pichet
    ;
    Naemchanthara, Kittisakchai
    Bi₄O₄SeCl₂ is a heteroanionic layered material with intrinsically low lattice thermal conductivity and anisotropic charge transport. In this work, the effects of post-annealing temperature on the crystallographic texture, anion chemistry, defect evolution, and transport properties of Bi₄O₄SeCl₂ were systematically investigated. Polycrystalline Bi₄O₄SeCl₂, synthesized by solid-state reaction combined with high-energy ball milling, was post-annealed at 400–700 °C. X-ray diffraction and electron microscopy revealed that post-annealing eliminated the residual BiOCl precursor phase, enhanced the (00 l) preferred orientation, and promoted grain growth up to 600 °C, followed by partial texture degradation at 700 °C due to recrystallization. Energy-dispersive spectroscopy showed progressive Se and Cl volatilization during annealing, leading to an increased Cl/Se ratio. The carrier mobility and electrical conductivity reached maximum values at 600 °C, consistent with improved texture and layered-domain connectivity. Thermal transport remained lattice-dominated and only weakly temperature-dependent. The phonon mean free path, estimated using kinetic theory, was in the sub-nanometer range (∼0.25–0.57 nm), comparable to the interatomic spacing, indicating glass-like phonon transport. Representative HRTEM observations also revealed dislocation-related lattice defects and locally distorted regions, suggesting that vacancy disorder and local strain fields may provide additional phonon scattering. These results demonstrate that post-annealing optimizes electrical transport through phase purification, texture development, and defect-mediated carrier regulation, while the lattice thermal conductivity remains fundamentally limited by intrinsic glass-like phonon transport in Bi₄O₄SeCl₂.
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    The influence of annealing on a large specific surface area and enhancing electrochemical properties of reduced graphene oxide to improve the performance of the active electrode of supercapacitor devices
    (2021-02-01)
    Karaphun, Attaphol
    ;
    Phrompet, Chaiwat
    ;
    Tuichai, Wattana
    ;
    Chanlek, Narong
    ;
    Sriwong, Chaval
    Influence of annealing process on microstructure, large specific surface area and enhancing electrochemical properties to synthesize reduced graphene oxide (rGO) for the supercapacitor electrode was investigated. Thermal annealing process of rGO (rGO_An) was improved crystallinity and electrical conductivity. BET analysis of rGO_An sample exhibited the occurrence of large mesoporous and macrospores with a huge specific surface area of 672.1 m<sup>2</sup>/g and an average pore size of 46.2 nm, resulting the rGO_An sample activates more electrodes than rGO sample. Specific capacitance (C<inf>s</inf>) was affected by improving conductivity through annealing process with an excellent cycling stability after 750 cycles for GCD tests of 97.32%, which exhibited the highest value and an average energy density of 412.096 F g<sup>−1</sup> and 74.5 Wh kg<sup>−1</sup>, respectively at 1 A g<sup>−1</sup>. Thus, annealing process can occur with large mesoporous and macrospores pore improving the electrical conductivity and stability to be applied as an electrode in supercapacitor.