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    Platelet Ceria Catalysts from Solution Combustion and Effect of Iron Doping for Synthesis of Dimethyl Carbonate from CO2
    (2025-01-01)
    Rusta, Nicoletta
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    Mameli, Valentina
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    Ricci, Pier Carlo
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    Porcu, Stefania
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    Solution combustion (SC) remains among the most promising synthetic strategies for the production of crystalline nanopowders from an aqueous medium, due to its easiness, time and cost-effectiveness, scalability and eco-friendliness. In this work, this method was selected to obtain anisometric ceria-based nanoparticles applied as catalysts for the direct synthesis of dimethyl carbonate. The catalytic performances were studied for the ceria and Fe-doped ceria from SC (CeO<inf>2</inf>-SC, Ce<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf>-SC) in comparison with the ceria nanorods (CeO<inf>2</inf>-HT, Ce<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf>-HT) obtained by hydrothermal (HT) method, one of the most studied systems in the literature. Indeed, the ceria nanoparticles obtained by SC were found to be highly crystalline, platelet-shaped, arranged in a mosaic-like assembly and with smaller crystallite size (≈6 nm vs. ≈17 nm) and higher surface area (80 m<sup>2</sup> g<sup>−1</sup> vs. 26 m<sup>2</sup> g<sup>−1</sup>) for the undoped sample with respect to the Fe-doped counterpart. Although all samples exhibit an anisometric morphology that should favor the exposition of specific crystalline planes, HT-samples showed better performances due to higher oxygen vacancies concentration and lower amount of strong basic and acid sites.
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    Rapid synthesis of potassium sodium niobate (K 1/2Na 1/ 2NbO3) lead-free piezoelectric powder using the combustion method
    Potassium sodium niobate (K1/<inf>2</inf>Na1/<inf>2</inf>NbO<inf>3</inf>) powder was synthesized successfully by the combustion synthesis. The raw materials of KNO<inf>3</inf>, NaNO<inf>3</inf> and Nb<inf>2</inf>O<inf>5</inf> were used with glycine as fuel. The thermal behaviour of the precursor was determined using thermo gravimetric analysis (TGA) and derivative thermo gravimetric (DTG) analysis. The conditions for preparing perovskite phase formation, influence of the fuel-to-oxidizer molar ratio, and crystal structure were characterized by the X-ray diffraction technique (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphology and particle size were investigated through a scanning electron microscope (SEM). © 2013 Copyright Taylor and Francis Group, LLC.
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    Ba0·5Sr0·5(Co0·8Fe0.2)1-xTaxO3-δ perovskite anode in solid oxide electrolysis cell for hydrogen production from high-temperature steam electrolysis
    (2021-02-08)
    Prasopchokkul, P.
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    ;
    Kim-Lohsoontorn, P.
    Among perovskite anodes in solid oxide electrolysis cell (SOEC), Ba<inf>0·5</inf>Sr<inf>0·5</inf>Co<inf>0·8</inf>Fe<inf>0·2</inf>O<inf>3-δ</inf> (BSCF) has gained much attention due to its dominantly high performance. However, the BSCF still suffers from chemical instability. In this study, the B-site of BSCF is partially substituted by a higher valence Ta<sup>5+</sup> (5, 10, 15 and 20 mol%) to improve its structural stability - Ba<inf>0·5</inf>Sr<inf>0·5</inf>(Co<inf>0·8</inf>Fe<inf>0.2</inf>)<inf>1-x</inf>Ta<inf>x</inf>O<inf>3-δ</inf> (BSCFTax, 0 ≤ x ≤ 0.20). It is found that doping with higher valence Ta<sup>5+</sup> increases both chemical stability and electrochemical performance of BSCF. Although the BSCFTa0.10 shows the lowest oxygen vacancies indicating by the ratio of adsorbed oxygen vacancies (O<inf>adsorbed</inf>) to lattice oxygen (O<inf>lattice</inf>), the electrochemical performance increases. The decrease in Co<sup>3+</sup>/Co<sup>4+</sup> ratio results in increasing electronic conductivity in the anode. It is likely that proper amount of Ta<sup>5+</sup> doping provide a balance between ionic and electronic conductivity in the anode and improved electrochemical performance. The symmetrical half-cells with electrolyte support (BSCFTa/YSZ/BSCFTa) are fabricated to determine the area specific resistance (ASR) and activation energy of conduction - BSCFTa0.10 shows the best performance. Cathode-supported Ni-YSZ/YSZ/BSCFTa0.10 also shows higher durability than Ni-YSZ/YSZ/BSCF (operating at current density −0.45 A cm<sup>−2</sup> in electrolysis mode, 80 h, 800 °C and H<inf>2</inf>O to H<inf>2</inf> ratio of 70:30).
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    Ultrasonically assisted surface modified CeO2 nanospindle catalysts for conversion of CO2 and methanol to DMC
    (2022-11-01)
    Kulthananat, Tachatad
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    Kim-Lohsoontorn, Pattaraporn
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    This study developed a facile and effective approach to engineer the surface properties of cerium oxide (CeO<inf>2</inf>) nanospindle catalysts for the direct synthesis of dimethyl carbonate (DMC) from CO<inf>2</inf> and methanol. CeO<inf>2</inf> nanospindles were first prepared by a simple precipitation method followed by wet chemical redox etching with sodium borohydride (NaBH<inf>4</inf>) under high intensity ultrasonication (ultrasonic horn, 20 kHz, 150 W/cm<sup>2</sup>). The ultrasonically assisted surface modification of the CeO<inf>2</inf> nanospindles in NaBH<inf>4</inf> led to particle collisions and surface reduction that resulted in an increase in the number of surface-active sites of exposed Ce<sup>3+</sup> and oxygen vacancies. The surface modified CeO<inf>2</inf> nanospindles showed an improvement of catalytic activity for DMC formation, yielding 17.90 mmol·g<inf>cat</inf><sup>−1</sup> with 100 % DMC selectivity. This study offers a simple and effective method to modify a CeO<inf>2</inf> surface, and it can further be applied for other chemical activities.
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    Superhydrophobilization of SiO2 surface with two alkylsilanes for an application in oil/water separation
    (2018-04-01) ;
    Pasupong, Patchara
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    ;
    This study reported a novel approach to superhydrophobilize silica (SiO<inf>2</inf>) surface by silanizing with two alkylsilanes including non-polar short hydrocarbon chains of chlorotrimethylsilane (CTMS) followed by long hydrocarbon chains of octadecyltrichlorosilane (OTS). The silanization of CTMS prior to OTS affected the increase in the density of short and long alkyl chains throughout SiO<inf>2</inf> surface resulting in the surface with low surface energy and high degree of hierarchical micro-nanoscale roughness which were responsible for the superhydrophobicity. The oil/water separation filters prepared by coating cotton fabric with the CTMS- and OTS-modified SiO<inf>2</inf>/polystyrene (PS) composite using a weight ratio of the modified SiO<inf>2</inf>:PS at 2:1 possessed the highest water contact angles of 156° ± 1°. The superhydrophobic/superoleophilic filters showed excellent water repellent, oil/water separation efficiency, and reusability. The results obtained in this study suggest that salinizing the two different structure alkylsilanes, CTMS followed by OTS, can provide synergetic benefit in improving the superhydrophobicity by enhancing the density of alkyl chains on SiO<inf>2</inf> surface. This alternative strategy can be extensively applied for development of other superhydrophobic materials.
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    Asymmetric dot-patterned wettable and antibacterial wound dressings from bacterial cellulose–alginate composites coated with stearic acid-modified ZnO/chitosan/AgNPs
    (2025-01-01)
    Ieamviteevanich, Pimchanok
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    Onklam, Panida
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    Kampechdee, Wariya
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    Churiwan, Achana
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    To improve the wound dressing characteristics of bacterial cellulose-based materials and address the issue of asymmetric wound dressing with one hydrophilic side and another hydrophobic side, this study developed a new concept for the fabrication of an asymmetric wettable and antibacterial wound dressing by selective drop coating of stearic acid-modified ZnO, chitosan, and AgNPs to form a dot pattern on both surfaces of a bacterial cellulose–alginate composite (BA-ZnS/Ch/Ag). The coated surface was hydrophobic, with a WCA of 150° due to the formation of a low surface energy zinc stearate (C<inf>17</inf>H<inf>35</inf>COO)<inf>2</inf>Zn) monolayer on the ZnO particles and a high degree of hierarchical roughness. The asymmetric wettable BA-ZnS/Ch/Ag wound dressing maintained good water absorptivity (swelling rate 417%) and natural breathability (water vapor transmission rate 792 g.m<sup>−2</sup> day<sup>−1</sup>) of the superhydrophilic bacterial cellulose-alginate composite that consisted of dense outer surfaces and porous inner layers and simultaneously possessed the superhydrophobic property of the coating area that can reduce the risk of infection from external fluids and improve the blood repellency and anti-adhesion properties. The BA-ZnS/Ch/Ag wound dressing showed good antibacterial activity against S. aureus and E. coli and non-toxicity to human keratinocyte immortal cells (HaCaT), making it suitable for clinical applications.
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    Utilization of eggshell as a low-cost precursor for synthesizing calcium niobate ceramic
    (2018-07-18)
    Kamkum, Phonphan
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    ; ;
    Woramongkolchai, Somsak
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    This study investigated the possibility of using calcium carbonate (CaCO<inf>3</inf>) from chicken eggshell biowaste as a starting material for synthesizing calcium niobate (CaNb<inf>2</inf>O<inf>6</inf>) powder through the conventional solid-state reaction. Phase formation of calcium niobate was studied as a function of calcination conditions by X-ray diffraction (XRD), Fourier transform infrared spectroscopy and Raman spectroscopy. The X-ray fluorescence results showed that the chicken eggshell contained more than 96·0% of calcium carbonate by weight. The structural characteristics of the calcium carbonate and calcium niobate powder were quantitatively evaluated by Rietveld refinement method from the XRD data. Rietveld refinement results verified that the eggshell powder exhibited a rhombohedral calcite (calcium carbonate) structure with lattice parameters a = b = 4·9812 ± 0·00059 Å (1Å = 0·1 nm) and c = 17·0342 ± 0·00292 Å with α = γ = 90° and β = 120°. Furthermore, the single phase of calcium niobate corresponded to the orthorhombic structure for space group Pbcn(60) obtained after the calcination process. The non-isothermal kinetic of calcium niobate was investigated by the Ozawa methods. Activated energy calculated using Ozawa methods was 1168 ± 29 kJ mol<sup>-1</sup>. Also, there was no significant difference in dielectric properties between calcium niobate ceramic using chicken eggshell waste as a starting material and calcium niobate ceramic using analytical-reagent-grade calcium carbonate. This study showed that calcium carbonate from chicken eggshell biowaste is an alternative starting material for synthesizing microwave dielectric calcium niobate ceramic.
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    Non-isothermal kinetics of the thermal decomposition of sodium oxalate Na2C2O4
    (2012-03-01)
    Chaiyo, Nopsiri
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    Niemcharoen, Surasak
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    The thermal transformation of Na<inf>2</inf>C<inf>2</inf>O<inf>4</inf> was studied in N<inf>2</inf> atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na<inf>2</inf>C<inf>2</inf>O<inf>4</inf> and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger-Akahira-Sunose (KAS) methods. The activation energies (Eα) of Na<inf>2</inf>C<inf>2</inf>O<inf>4</inf> decomposition were found to be consistent. Decreasing Eα at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated through the Liqing-Donghua method was 'cylindrical symmetry (R <inf>2</inf> or F<inf>1/2</inf>)' of the phase boundary mechanism. Thermodynamic functions (DH*, DG* and DS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy pathway and revealed a very hard mechanism. © Akadémiai Kiadó, Budapest, Hungary 2011.
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    A sensitive and selective colorimetric sensor for reduced glutathione detection based on silver triangular nanoplates conjugated with gallic acid
    Silver triangular nanoplates conjugated with gallic acid (AgTNPs⋅GA) was designed and synthesized for colorimetric detection of reduced glutathione (GSH). The surface plasmon resonance (SPR) properties of AgTNPs⋅GA were strongly influenced by the addition of GSH. The detection principle was based on the aggregation of AgTNPs⋅GA, which leads to the significant bathochromic shift of the SPR spectra from 602 nm to 650 nm. The dramatic color changes from the initial dark blue to light blue can be observed, which allowed simple monitoring of GSH ether by naked eye and UV–vis spectrophotometer. With UV–vis spectrophotometer measurements, a quantitative linearity was established in the range of 0.5–5.0 nM (R<sup>2</sup> = 0.9919) and with a limit of detection (LOD) of 0.12 ± 0.02 nM. Relative standard deviation (RSD) of 3.46% and 1.82% (n = 10) were achieved for the determination of 1.0 and 3.0 nM, respectively. No interfering substances such as ascorbic acid, glucose, sucrose, citric acid, cysteine, Ca<sup>2+</sup>, Mg<sup>2+</sup>, Fe<sup>3+</sup> and K<sup>+</sup> were revealed in the AgTNPs⋅GA based assay. The proposed colorimetric strategy could be extended as the general platform for detection of GSH in dietary supplements and no significant differences in accuracy and precision were observed compared to HPLC standard method.
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    Sonochemical synthesis of monodispersed perovskite barium zirconate (BaZrO3) by using an ethanol-water mixed solvent
    (2015-07-01)
    Charoonsuk, Thitirat
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    ; ; ;
    Maensiri, Santi
    Perovskite barium zirconate (BaZrO<inf>3</inf>) was synthesized successfully in an ethanol-water mixed solvent under ultrasonic irradiation. Four compositions, including 0%, 30%, 50%, and 70% by volume of ethanol in ethanol/water mixed solvent, were used. The effect of ethanol content and irradiation time on the phase formation and morphology of product particles was studied and discussed. As a result, a pure perovskite BaZrO<inf>3</inf> phase was formed completely at a short irradiation time of about 15 min in 70% by volume of ethanol without the calcination process. The average particles size decreases and particle size distribution becomes narrower by increasing the percentage of ethanol volume. On the other hand, the monodispersibility of BaZrO<inf>3</inf> particles was improved significantly through ultrasonic irradiation.