Panpailin Seeharaj

Non-isothermal kinetics of the thermal decomposition of sodium oxalate Na2C2O4

The thermal transformation of Na2C2O4 was studied in N2 atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na2C2O4 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 Na2C2O4 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 (R2 or F1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), 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.

Sonochemical Synthesis of Spherical BaTiO3 Nanoparticles

Monosized spherical barium titanate (BaTiO3) nanoparticles have been synthesized successfully via sonochemical reaction. The as-synthesized BaTiO3 nanoparticles were characterized using X-ray diffraction of powder, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The XRD pattern of BaTiO3 particles, which were synthesized under irradiation of ultrasonic sound for 0.5 h, showed sharp diffraction peaks that corresponded to the cubic BaTiO3 phase. Only a small amount of BaCO3 contamination was present in the sample. The Raman active modes of the samples in this study were similar to the cubic phase of BaTiO3. The average diameter of sonochemical synthesized particles was ∼99.54 ± 18.25 nm. The synthesized BaTiO3 nanoparticles were almost spherical.

Synthesis of Monodispersed Perovskite Barium Zirconate (BaZrO3) by the Sonochemical Method

Barium zirconate (BaZrO3) was synthesized successfully by the sonochemical method. The monophase of BaZrO3 was formed completely in short irradiation time without the calcination process. X-ray diffraction, Fourier transform and Raman spectroscopy were used to characterize formation of the perovskite BaZrO3 phase, which occurs in a 60 minute single phase with a cubic crystal structure at room temperature. Therefore, sonochemical irradiation could accelerate the formation of BaZrO3 particles significantly. Furthermore, scanning electron microscopy investigated the uniform shape and size. The size distribution became narrow with increasing time, as a function of irradiation.

Influence of Mn Doping on the Magnetic Properties of CoFe2O4

A series of CoFe2−x Mn x O4 ceramics were synthesized successfully by conventional solid state reaction. The X-ray diffraction analysis proved that all samples were found to have a cubic spinel structure. Diffractograms were used for Rietveld refinement to determine lattice parameters, of which lattice parameter increased with increasing Mn concentration. The microstructure of the samples was studied using scanning electron microscopy. The vibrating sample magnetometer measurements showed that the highest saturated magnetization of 118.11 emu/g and coercivity of 46.89 Oe were observed in CoFe1.85Mn0.15O4 ceramic. Furthermore, X-ray absorption spectra of the samples were recorded to determine the Co, Fe and Mn valence states and their preferentially sites of the spinel structure.

Surface modification of TiO2 particles with the sono-assisted exfoliation method

This study reported a novel approach to optimize the photocatalytic property of anatase TiO2 particles by delaminating their outer surface into highly reactive nanosheets via the sono-assisted exfoliation method. To modify the surface, TiO2 particles were dispersed in aqueous solution of 10M sodium hydroxide (NaOH) and tetrabutylammonium hydroxide (TBAOH), followed by irradiation with high intensity ultrasonic wave (20kHz, 150W/cm2) for 60min. The intercalation and exfoliation processes were accelerated with the driving force of the extreme acoustic cavitation leading to the delamination of TiO2 nanosheets with highly reactive exposed {001} facets from the mother TiO2 crystals. The presence of TBAOH increased yield of nanosheets formation and stabilized the nanosheet structure. The unique morphology of the surface modified TiO2 particles provided benefits in increasing the specific surface area and lowering the optical band gap energy (Eg) and electron-hole recombination rate resulting in an enhancement of methylene blue dye degradation efficiency. The surface modification of TiO2 particles by the sono-assisted exfoliation method can optimize the photocatalytic activity by yielding synergetic effects of the high surface reactive sites of the nanosheets and the high degree of crystallinity of the bulk structure.

Synthesis and Characterization of PolyHIPEs Composites with Silica and Iron Oxide Nanoparticles

This study investigated the synthesis and modification of the properties of polyHIPEs by incorporating co-additives into the polymer matrix i.e. silica (SiO2)nanoparticles (1 wt%) to improve physical and mechanical properties and iron oxide (Fe3O4) nanoparticles (5, 10 and 15 wt%) to induce magnetic and heavy ion adsorption properties. PolyHIPEs composites were prepared in water in oil (w/o) emulsion system using the ratio of organic phase to aqueous phase of 20 to 80 vol%. The physical and mechanical properties of the polyHIPEs composites were found to decrease with SiO2 and Fe3O4 addition while the magnetic and adsorption properties increased with increasing Fe3O4 contents. The composites with 1 wt% SiO2 and 15 wt% Fe3O4 exhibited the highest saturated magnetization at 12.9 emu/g and they could be used for adsorption of iron ions (Fe3+) in iron(III) sulfate solution with 98.3 % adsorption at equilibrium.

Characterization and Dielectric Properties of Nanocomposite Made of Lead Zirconate Nanofibers and Polyvinylidene Fluoride Improved with Carbon Nanotubes

A three-phase PZ/CNT/PVDF nanocomposite comprising lead zirconate (PZ) nanofibers, polyvinylidene fluoride (PVDF) and a small volume fraction of carbon nanotubes (CNT) was prepared by the solvent casting technique followed by composite heating at 80°C. The PZ/CNT/PVDF composites were characterized by X-ray diffraction, FT-IR and scanning electron microscopy (SEM). The dielectric properties of the composite were studied as a function of the frequency by an LCR meter. The dielectric constant of the PZ/CNT/PVDF nanocomposite was found to be in the range of 18–61 within the measurement frequencies from 100 Hz to 2 MHz. This value is higher than the dielectric constant of the PZ/PVDF nanocomposite. The measured dielectric properties demonstrate that the addition of CNT can improve the dielectric property appearance of the composite.

Effect of Pb(Ni1/2W1/2)O3 on the Phase Transition Behavior of PbZrO3 Ceramic

Solid solution of (1−x)PbZrO3−xPb(Ni1/2W1/2)O3;(1−x)PZ-xPNW ceramics, where x = 0.02-0.10, were prepared by solid state reaction. Dense (1−x)PZ – xPNW ceramics were obtained by sintering at 1,100°C for 4 h. Effect of PNW on crystal structure, phase transitions and thermal and electrical properties was investigated using X-ray diffraction, dielectric spectroscopy, hysteresis measurement and differential scanning calorimetry. The results indicated that the solubility limit of the (1−x)PZ–xPNW system was found at x = 0.04. It was proved that the intermediate phase is an antiferroelectric in the PZ-PNW system. Stability of the AFE intermediate phase was seen to improve with increasing PNW content.

Combustion Synthesis of Lead-free Piezoelectric Alkali Metal Niobate Family

Nano-crystalline alkali metal niobate (ANbO3; A = K and Na) powders were synthesized by the combustion of nitrate compounds and Nb2O5 using glycine as the fuel. The chemical reaction, nucleation mechanisms and influence of the fuel-to-oxidizer ratio to phase formation were studied. The precursor and product powders were characterized, using the thermo gravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) technique, and scanning electron microscopy (SEM). Different fuel-to-oxidizer ratios were found to be a key factor of the process. As-prepared and calcined powders provided the perovskite structure with a nano-scale of mean crystalline size.

BaZr0.3Ti0.7O3 Nanoparticles Synthesized by Glycine-Nitrate Autocombustion

BaZr0.3Ti0.7O3 (BZT) nanoparticles were prepared by glycine-nitrate autocombustion method. The effects of synthesis condition and calcination temperature on phase formation and microstructure of the BZT were investigated. XRD and FT-IR study indicated that BZT with cubic perovskite-type structure can be obtained from the synthesis condition using glycine-to-nitrate molar ratio of 2:3 and calcined in air at 1000°C for 4 h. The microstructure examined by SEM and TEM showed that BZT had agglomerate particles consisted of primary spherical nanocrystals with the crystallite sizes of 8–20 nm.