Jutharatana Klinkaewnarong

Structure and optical properties of CeO2 nanoparticles prepared by using lemongrass plant extract solution

The synthesis and optical properties of cerium oxide (CeO2) nanoparticles by a simple, cost-effective and environment-friendly method using cerium(III) acetate hydrate and lemongrass plant extract. The CeO2 nanoparticles having sizes of 10–40 nm were obtained by calcining the precursors in air at 400, 500, and 600 °C, for 2 h. Results from X-ray diffraction (XRD), and Raman spectroscopy indicated that the synthesized CeO2 nanoparticles have the fluorite structure of the bulk CeO2 samples. The PL intensity of CeO2 increases with increasing calcination temperature. The CeO2 sample calcined at 600 °C shows a stronger emission spectrum than the CeO2 samples calcined at 400 and 500 °C, suggesting its better crystalline and optical properties than the other samples.

Synthesis of Nanocrystalline Hydroxyapatite by Natural Biopolymers Based Sol-Gel Technique

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by natural biopolymers based sol-gel technique. The biopolymers were extracted from the leaves of Yanang (Tiliacora triandra), Krueo Ma Noy (Cissampelos pareira) and Konjac (Amorphophallus konjac). To obtain HAp powders, the prepared precursors were calcined in air at 600, 700, and 800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of β-tricalcium phosphate (β-TCP). The crystalline sizes of the samples were found to be 20-50 nm as evaluated by the XRD line broadening method. TEM investigation revealed that the synthesized HAp samples consisted of nanoparticles with a particle size in the range of 50-100 nm in diameter. The corresponding selected area electron diffraction (SAED) analysis further confirmed the formation of hexagonal structure of HAp.

Magnesium Substitution in Hydroxyapatite Synthesized by Sol-Gel Method

The ionic substitutions have been proposed as a tool to improve the biological performance of hydroxyapatite (HAp) based materials. In the present work, the systems of Ca(10-x)Mgx(PO4)6(OH)2 (MgHAp, x = 0, 1, 2, and 3) were successfully synthesized by solgel method. To obtain nanocrystalline of MgHAp, the prepared precursors were calcined in air at 600 °C for 2 h. The samples were characterized by Xray diffraction (XRD) and transmission electron microscope (TEM) observation. The XRD results confirm the formation of pure phase of HAp with the lattice parameter a in the range of 0.94170.9479 nm and c of 0.68410.6919 nm. The crystallite sizes of the powder are found to be 3546 nm as evaluated by the XRD line broadening method. The morphology of the samples are spherical shape of diameter less than 100 nm as evaluated by TEM. The corresponding selected area electron diffraction (SAED) analysis further confirms the formation of hexagonal structure of HAp.

Adsorption of Methyl Violet Dye from Aqueous Solutions by Activated Carbon Produced from Tamarind Seeds

The present work proposes the adsorption of methyl violet (MV) from two solution systems including single MV and binary MV-Cu2+ systems by activated carbon (AC) prepared from tamarind seeds in a batch system. Parameters including contact time, solution pH, adsorbent dose, and initial dye concentration were studied. The morphology of the AC was determined by scanning electron microscopy (SEM). The results showed the maximum adsorption of MV dye onto the AC at a contact time of 60 min, solution pH of 9.0 and adsorbent dose of 0.2 and 0.5 g for the single and binary solution systems, respectively. The presence of copper ions in binary solution system decreased the adsorption efficiency of MV dye onto the AC. The equilibrium adsorption data were analyzed using Langmuir, Freundlich and Temkin isotherms.

Effects of additives on sintering of nanocrystalline hydroxyapatite

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by a simple method using polymerized complex method. To obtain HAp nanopowders, the prepared precursor was calcined in air at 750–1,000°C for 12 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of β-TCP phase. With increasing calcination temperature the crystallinity of the HAp increased, showing the hexagonal structure of HAp with the lattice parameter a in a range of 0.9351–0.9446 nm and c of 0.6843–0.6906 nm. The particle sizes of the powder were found to be 16–125 nm and as evaluated by the XRD line broadening technique. The morphology of the powders was spherical of size less than 200 nm, as revealed by TEM. Increasing the calcination temperature resulted in the transition from polycrystalline to single crystalline phase of the HAp, as clearly confirmed by the analysis of TEM diffraction patterns. The study of sintering behavior was carried out by pressureless-sintering of the calcined HAp powders in air at 1250 °C for 2 h. The densities of the sintered HAp ceramics measured by Archimedes method were found to be 88 % of theoretical density, whereas those of the ceramics with sintering additives of La2O3, and CaO 2.5 wt.% were ∼93 % of theoretical density. The grain sizes of the sintered HAp ceramics were 1.35–1.76 µm for the pure HAp ceramics and HAp ceramics with sintering additives of La2O3 or CaO 2.5 wt.% respectively.