Pat Sooksaen

Sol-Gel Synthesis of SrTiO3 Nanoparticles Using Acetic Acid as a Chelating Agent

SrTiO3 nanoparticles were synthesized by sol-gel method using acetic acid as a chelating agent. Complete decomposition from thermogravimetric analysis occurred at 650°C. The –OH ligand should be gradually replaced by the acetyl group, slowing down the reactivity between the Ti and Sr cations. X-rays diffraction demonstrated only SrC2O4 with a small trace of anatase TiO2 between 400°C and 500°C. Perovskite peaks were observed starting at 600°C. The crystallite sizes were smaller at higher amount of acetic acid; this could be explained by retardation in the hydrolysis reaction. The nanoparticles were isotropic in shape with agglomeration due to partial sintering.

Powder Injection Moulding of Alumina Using PEG/PVB Binder Systems

Powder injection moulding (PIM) is a process that is suitable for a fabrication of small and complex shape components. It consists of 4 main steps: feedstock preparation by mixing powder and binder, injection moulding of the prepared feedstock into the desired mould, removal of the binder and finally sintering to obtain materials with specific properties. In this study, powder injection moulding of alumina (Al2O3), using polyethylene glycol (PEG) based binder systems, was investigated. PEG is soluble in water; therefore, the use of organic solvents required for debinding of wax-based binder system can be avoided. PEG with a molecular weight of either 1500 or 4000 was used as a major constituent together with polyvinyl butyral (PVB) as a minor component. Stearic acid was also added during feedstock preparation to act as a lubricant. After mixing the powder with the binder, a variety of Al2O3 feedstocks were injected into the moulds. The mouldings were prepared by a laboratory-scaled plunger-typed machine. Debinding was carried out using a combination of solvent extraction and thermal debinding. Water leaching tests were performed at 30 and 50 °C to study PEGs removal rate. The pyrolysis of PVB was completed during ramping up of the mouldings to the sintering temperature. The mouldings were subjected to sintering at 1500 °C in air. It was found from the study that PEG/PVB binder systems can be used for the preparation of alumina powder injection moulding feedstocks. Specimens retained their shapes during and after leaching of the PEGs.

Photocatalytic Degradation Study of Titania Sol-Gel Coated on Commercial Unglazed Ceramic Tiles

In this research photocatalytic degradation of nanotitania synthesized via sol-gel method and coated on commercial unglazed ceramic tiles was investigated. The starting precursors were titanium (IV) tetraisopropoxide (Ti [OCH(CH3)2]4; TIP), ethanol, hydrochloric acid and distilled water. Unglazed ceramic tiles were sintered at 900°C and 1100°C. The nanotitania based sols were applied on the tile surface using air-brush and calcined at 500°C for 3 h. The particle size of the synthesized TiO2 varied in the range 8-20 nm. The photocatalysis of nanotitania was studied through the photodegradation of methylene blue solution under UVC irradiation using UV-Vis Spectrophotometer. The presence of nanotitania on unglazed ceramic tiles was confirmed by a scanning electron microscope equipped with energy dispersive X-ray spectrometer (EDS). Ceramic tiles sintered at 900°C gave higher % open porosity and hence higher amount of nanotitania embedded on the ceramic surface. The results showed that all unglazed ceramic tiles coated with nanotitania were able to show photodegradation of methylene blue.

Characterization of Gelatin Composite with Low Content Hydroxyapatite and the Influence on Mesenchymal Stem Cell Culture

In tussue engineering, hydrogel-based scaffold is one of the most common method for bone tissue engineering. Gelatin is a common material for scaffold, whereas hydroxyapatite (HA) has a similar composition and structure to natural bone mineral. HA can also increase cell adhesion ability of the scaffold. This research focuses on the fabrication of hydrogel scaffolds using gelatin composite with nanocrystalline hydroxyapatite (nHA). Then the mechanical and physical caharacteristics of the scaffold is investigetad. Low contents nHA is introduced into gelatin in order to modulate mesenchymal stem cell (MSC) behavior. There are three types of scaffolds which contain various HA content. The gelatin is crosslinked with glutaraldehyde before freeze-drying. The Young’s modulus of the surface is investigated using Atomic force microscopy (AFM). The pore size is investigated using scanning electron microscope (SEM). Human MSCs are culture on the scaffold for 3 weeks. The result shows the sucesse in cell cultivation. However, the human MSCs cultured on the fabricated hydrogels do not show any lineage-specific differentiation.

Variation of Hydroxyapatite Content in Soft Gelatin Affects Mesenchymal Stem Cell Differentiation

Gelatin is a common material used in tissue engineering and hydroxyapatite (HA) has a composition and structure similar to natural bone mineral. HA is also used to increase the adhesion ability of scaffolds. The physical and mechanical properties of gelatin, together with the chemical properties of HA, can affect cell differentiation. The main purpose of this study is to investigate the gene expression of human mesenchymal stem cells (HMSCs) upon culturing on gelatin composite with HA. Low amounts of HA were introduced into the gelatin in order to modulate properties of gelatin. Three types of hydrogel were fabricated by glutaraldehyde crosslinking before lyophilization to produce the porous 3D structure: (1) pure gelatin, (2) 0.5 mg/ml HA in gelatin, and (3) 1 mg/ml HA in gelatin. The fabricated hydrogels were used as scaffolds to cultivate HMSCs for two periods - 24 hours and 3 weeks. The results showed that all types of fabricated hydrogels could be used to cultivate HMSCs. Changes of gene expressions indicated that the HMSCs cultured on the 1 mg/ml HA in gelatin showed neuronal lineage-specific differentiation.

Apatite-Wollastonite Bioactive Glass-Ceramic Scaffolds for Hard Tissue Engineering

Apatite-wollastonite bioactive glass-ceramic scaffolds were fabricated from the SiO2-CaO-P2O5 MgO-CaF2 glass system by controlled crystallization between 800 and 1200C of the melted and quenched glass powder. Wood powder with controlled particle size distribution was used to obtain bioactive glass-ceramic scaffolds by burning-out process during crystallization of glass. Bioactive phases of apatite and wollastonite were found in all crystallized samples but the relative amount depended on the crystallization temperature. The bioactivity was studied via simulated body fluid (SBF) solution from 2 to 12 weeks. After soaking for 2 weeks, a porous hydroxyl-carbonate apatite (HCA) layer formed at the SBF-glass ceramic interface and the HCA layer thickness increased at longer soaking periods. This study led to a promising platform for hard tissue engineering.

Effect of Alumina Content on the Properties of Ceramic Foams Crystallized with Nano-Sized Mullite Crystals

Ceramic foam is a class of materials with high porosity and three-dimensional network of struts. In this study, ceramic foams were fabricated by polymeric sponge method using commercial PVA foam as a replica template. The study focused on the effect of alumina content on the physical and mechanical properties of such ceramic foams sintered at 1500°C for different sintering times. It was found that ceramic composition with higher amount of alumina required higher sintering temperature than that used in the present study. Physical properties and mechanical strengths depended upon ceramic composition as well as sintering time. Microstructural analysis revealed the evolution of primary cuboidal mullite and needle-like nano-sized mullite phase in the sintered sample. This fine needle-like phase added to mechanical strengths of ceramics.

Fabrication of Lightweight Concrete Composites Using Natural Fibers in Thailand

This study developed lightweight concretes by using three different natural fibers from agricultural industries in Thailand which were corn husk fiber, bagasse fiber and coconut husk fiber. Low cost lightweight concretes in this study were fabricated using Ordinary Portland Cement type-1, coal fly ash, un-treated natural fibers and NaOH-treated natural fibers. The specimens were tested for bulk density, compressive strength, microstructure and deterioration. The result showed that the strongest concrete composite was obtained using 30 vol% fine coconut husk fiber in the concrete composition. The treated fibers showed an improvement in surface adhesion between cement matrix and fibers which resulted in higher compressive strength value.

Microwave Synthesis of Nanocrystalline Hydroxyapatite and the Application in Bio-Composite

This research synthesized nanocrystalline hydroxyapatite (HA) via microwave assisted heating method. The morphology and crystallinity of nanocrystalline hydroxyapatite were affected by heating power and pH of the mixed solution. Nanocrystalline HA was best obtained when synthesized at pH = 11. Crystal size increased and crystal shape changed from spherical to rod and plate-like when the microwave power was increased from 320 to 800 watts. The synthesized nano-HA could be fabricated into bio-composite films using poly lactic acid (PLA) as the matrix and solvent casting method was utilized. In-vitro study for bioactivity was carried out in the SBF solution which formed hydroxyl-carbonate apatite (HCA) layer on the PLA/nano HA composite surface. The layer thickness increased in the background with increasing soaking time in the SBF.

Properties of Unglazed Ceramics Containing Aluminum Dross as a Major Component

Aluminum dross residue is a by-product produced at secondary re-melt plants where aluminum scraps are recycled. In this study, aluminum dross residue was utilized as a major component in the fabrication of unglazed ceramics for wall tile applications. The use of this by-product can reduce the landfill and environmental problems. The amount of aluminum dross residue used in the ceramic compositions varied in the range 50-90 wt.%. Other components utilized in the ceramic compositions included recycled glass alumino-silicate based clays. Firing was carried out between 1140 and 1200°C with 4h holding time which resulted in strong ceramic samples. Alpha-alumina, α-Al2O3 was the main crystalline phase found in all sintered ceramic samples. The appearance of mullite phase, Al6Si2O13 was evident in all fired samples. Overall, the synthesized ceramics had excellent densification characteristics when the amount of aluminum dross residue was less than 70 wt% in the ceramic composition.