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Suriya Ounnunkad 《Solid State Communications》2006,138(9):472-475
La or Pr substituted barium hexaferrites, Ba1−x(La or Pr)xFe12O19, x=0.00-0.20, were successfully prepared by a citrate combustion process. The sintered bodies were structurally and magnetically studied by powder X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). All XRD patterns show the single phase of the magnetoplumbite barium ferrite without other intermediate phases. Magnetization (MS) and coercive field (HC) could be improved by substitutions of La or Pr ions on Ba ion basis sites. The MS reveal magnetic behavior with respect to La or Pr ions content, showing an increase at first and then a decrease. The HC increases remarkably with increasing La or Pr ions content. 相似文献
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Paralee Waenkaew Suwaphid Themsirimongkon Kontad Ounnunkad Napapha Promsawan Aunanong Pinithchaisakula 《Composite Interfaces》2018,25(4):317-333
Successive electropolymerization of dopamine and electrodeposition of Pd and/or Pt on a graphene oxide (GO) support were used to prepare anode catalysts for low-temperature fuel cells. Transmission electron microscopy images were used to investigate the morphologies and distribution of the prepared catalysts, which showed the metal formed as nanoparticles on the catalysts. The GO surface was favorable for the modification with electropolymerized polydopamine (PDA) and the electrodeposition of metal catalyst nanoparticles using a simple preparation process. The PDA-loaded GO composite was used as a matrix for the dispersion of Pt and Pd nanoparticles. GO could be simultaneously modified by PDA and reduced without using reducing agents. The electrocatalytic performance of the catalysts for the oxidation of selected small molecule fuels (e.g., methanol, ethanol and formic acid) was examined. An outstanding catalytic activity and stability was found for the prepared Pt/Pd/PDA/GO composite, which was attributed to the high active surface area. 相似文献
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Napapha Promsawan Supawadee Uppamahai Suwaphid Themsirimongkon Burapat Inceesungvorn Paralee Waenkaew Kontad Ounnunkad Surin Saipanya 《Journal of nanoparticle research》2018,20(9):258
Preparation, characterization, and electrocatalytic study of the electrodeposited Pt and Pd (e.g., Pt and PtPd) catalysts on titanium dioxide (TiO2) modified reduced graphene oxide (rGO) support for formic acid oxidation were performed. The catalyst composites are labeled as xPt/rGO-TiO2, xPtyPd/rGO-TiO2, and yPd/rGO-TiO2 where x and y are cycle numbers of metal electrodeposition (x and y?=?2–6). The characterizations of the catalysts were performed by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Small and dispersed metal nanoparticles are obtained on rGO-TiO2. The catalytic performances for formic acid oxidation were measured by cyclic voltammetry (CV) and chronoamperometry (CA). The electrocatalytic results reveal that the bimetallic 4Pt2Pd/rGO-TiO2 catalyst facilitates formic acid oxidations at the lowest potentials and generates the highest oxidation currents and also improves the highest CO oxidation compared to the monometallic 6Pt/rGO-TiO2 catalyst. According to the experimental data, the Pd and TiO2 enhance the electrocatalytic activity of the catalysts towards the formic acid oxidation; the improved catalytic performance of the prepared catalysts strongly relates to the high electrochemically active surface area (ECSA) investigated. 相似文献
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The Cr-substituted M-type barium hexaferrites, BaFe12−xCrxO19, with x=0.0–0.8 have been successfully prepared by nitrate–citrate auto-combustion process using citric acid as a fuel/reductant and nitrates as oxidants. The resulting precursors were calcined at 1100 °C for 1 h and followed by sintering at 1200 °C for 12 h in oxygen atmosphere. The ferrites were systematically investigated by using powder X-ray diffractometer (XRD), magnetic hysteresis recorder, Mössbauer spectrometer, and scanning electron microscope (SEM). The XRD data show the formation of pure magnetoplumbite phase without any other impurity phases. Both a and c lattice parameters calculated by the Rietveld method systematically decrease with increasing Cr content. The effects of Cr3+ ions on the barium ferrites were reported and discussed in detail. The site preference of Cr3+ and magnetic properties of the ferrites have been studied using Mössbauer spectra and hystereses. The results show that the magnetic properties are closely related to the distributions of Cr3+ ions on the five crystallographic sites. The saturation magnetization systematically decreases, however, the coercivity increases with Cr concentration. The magnetization and Mössbauer results indicate that the Cr3+ ions preferentially occupy the 2a, 12k, and 4fVI sites. The average size of hexagonal platelets obtained by SEM photographs tends to decrease with respect to Cr content. 相似文献
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