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Author: search.filters.author.Kamonpha, PhitsamaiStart date: 2020

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    Cold sintering-assisted low temperature fabrication of dense Ba5Nb4O15 ceramics
    (2026-06-08)
    Sukkha, Usa
    ;
    Teandam, Apichayaporn
    ;
    Pakawanit, Phakkhananan
    ;
    Kamonpha, Phitsamai
    ;
    Vittayakorn, Wanwilai
    This study presents a novel approach for fabricating Ba<inf>5</inf>Nb<inf>4</inf>O<inf>15</inf> (BNO) ceramics at low sintering temperatures via the cold sintering process (CSP), using Ba(OH)<inf>2</inf>·8H<inf>2</inf>O (BOH) as a transient liquid phase. CSP was performed under an external pressure of 10MPa with a sintering temperature range of 150°C to 300°C. Optimally, BNO-BOH ceramics achieved a relative density of 93.7 ± 0.43 when sintered at 250°C for 1h. Scanning electron microscopy (SEM) suggested that particle densification occurred via a dissolution-precipitation process, which filled pores and formed necks between particles. The study demonstrates that the residual liquid content is crucial for ceramic densification. Annealing the as-cold sintered BNO-BOH ceramics at 1000°C for 1h successfully eliminates the BaCO<inf>3</inf> secondary phase. Furthermore, dielectric properties of annealed ceramics were also characterized at room temperature from frequency range of 20Hz to 2MHz. The dielectric permittivity is reported to be 39.2 and 0.01 for tanδ at 1.8MHz. The cold sintering process provides an effective strategy to reduce the sintering temperature while achieving high relative density. This method offers a promising alternative for the fabrication of advanced ceramics.
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    Research Article Biosynthesis of Silver Nanoparticles Using Garcinia cowa Aqueous Leaf Extract and Their Antifungal Activity Against Durian Dieback Pathogen
    (2023-09-01)
    Sukkha, Usa
    ;
    Khejonrak, Awadol
    ;
    Kamonpha, Phitsamai
    ;
    Ruangvittayanon, Anuchit
    ;
    Pakdeepromma, Sirichatnach
    Silver nanoparticles (AgNPs) were synthesized under different pH and reaction time using the Garcinia cowa aqueous leaf extract. The formation, crystal structure and morphology of synthesized AgNPs were investigated using UV-Vis spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The UV-Vis result indicated that the AgNPs were synthesized using Garcinia cowa aqueous leaf extract at all pH conditions within 10 min. The synthesis of AgNPs was significantly affected by pH condition which was shown by the TEM micrographs. The particle sizes of AgNPs were in a nano-sized range; 6.30 ± 3.52 nm for pH 4, 3.87 ± 2.51 nm for pH 7 and 13.97 ± 11.84 nm for pH 10. Furthermore, the AgNPs prepared in pH 4, pH 7 and pH 10 (120 min reaction time) at different concentrations were assessed for their antifungal activity against durian dieback pathogen. It was found that the 800 mL/L of AgNPs prepared at pH 7, the smallest particle size and good dispersion, showed the highest inhibition mycelial growth at 47.33%, whereas the larger nanoparticles prepared at pH 4 and pH 10 conditions showed lower inhibition of mycelial growth at 43.22% and 32.55%, respectively.
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