Wilaiwan Leenakul

Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica.

45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts--the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300 °C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050 °C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650 °C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050 °C, with a high density of 2.27 g/cm(3), 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7 days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive.

Effects of NiO Nanoparticles on Physical and Mechanical Properties of BNKT Lead-Free Ceramics

In this research, The effects of NiO nanoparticles on the physical and mechanical properties of Bi0.5(Na0.81,K0.19)0.5TiO3 (BNKT) were investigated. The ceramics were synthesized by solid state reaction technique. The powder of BNKT was calcined at 850 °C for 4 h. The ceramics of BNKT/x NiO vol.% ( i.e. x= 0.0, 1.0, 2.0 and 3.0) were sintered at 1000-1150 °C for 2 h for optimize condition. Densification, phase formation, microstructure and micro hardness of samples were characterized via Archimedes method, X-ray diffraction techniques (XRD), scanning electron microscope (SEM) and Vickers micro hardness tester. The X-ray diffraction analysis of the ceramics suggests that all samples exhibited a perovskite structure. Densification of samples tended to increase with increasing amount of NiO content with minimun at 1.0 vol.% NiO additive. The NiO additive influenced densification as well as the mechanical properties of the samples. The results of this research suggest that NiO nanoparticles have influence on physical and mechanical properties of BNKT ceramics.

The Acoustic Impedance and other Properties of (1-3) Piezoceramics Polymer Composite

The work is focused on an attempt to develop a route for the fabrication of piezoceamic-polymer composites having (1-3) type connectivity. The process included the extrusion of rods of diameter approximately 200 mm. A commercial piezoelectric, PC-5 was modified by addition of a lithium/bismuth based glass former together with excess PbO to lower the sintering temperature to about 1000 °C. The fast firing sintering was employed. The rods were assembled and impregnated with an epoxy resin to form 1-3 composites containing approximately 50 and 20 vol% piezoceramic. The measurement values showed that, the piezoelectric constant, d33 = 232 pCN-1 and 215 pCN-1, thickness electromechanical coupling coefficient, kt = 0.51 and 0.5 and the mechanical quality factor, Qm = 14 and 5 for the composites containg PZT rods at 50 vol% and 20 vol% respectively. Their acoustic impedances were 5.1 and 3.6 for the 50 vol% and 20 vol% of PZT rods respectively. The results show that with lower volume% of PZT could result in lower acoustic impedance which can be further improved for biomedical imaging and hydrophone applications.

Conductivity Modification of Carbon-Based Nanocomposites

The combination of carbon materials and polymer has been well studied according to their compatable mixture in polymer with promising properties. Due to their excellent electrical and thermal properties for some types of carbons such as carbon nanotubes and graphite, they have been selected as component for nanocomposites. Here, capability of multi-walled carbon nanotubes (MWNTs) and graphite for nanocomposites were demonstrated. Nanotubes were functionalized by chemical process, and added into polyvinyl chloride (PVA) matrix. They were then used as main filler to modify thermal and electrical conductivities. Conductivities of different composite mixtures were finally investigated. With the use of low total amount of carbon materials, it was found that although there is no significant change in electrical and thermal conductivities, the highest conductivities could be obtained from MWNT to graphite ratio of 1:1 in PVA matrix, while the G-band mode does not give a rise to electron transfer.

Effects of Rate-Controlled Sintering on Phase Formation, Dielectric and Ferroelectric Properties of Cobalt Oxide Doped BNKT Ceramics

Lead-free powders of Bi(Na0.81K0.19)O3 doped 0.3 wt.% CoO were prepared by a conventional mixed oxide technique. The sintering process was controlled with various rate up and down temperature. The samples were sintered at 1,050 °C for 4 h which difference heating rate controlled i.e. 100, 300, and 600 °C/h. The XRD pattern analysis of all studied samples showed a single phase perovskite structure Dielectric and ferroelectric properties of the ceramics were investigated as a function of rate controlled sintering temperature. The sample heating rate at 600 °C/h showed maximum dielectric constant (~5961) at Tm. In addition, the ferroelectric properties were analyzed and discussed.

Phase Transition and Electrical Properties of Ba 0.8 Sr 0.2 TiO 3 : Comparison of Different Preparation Techniques

This research studied the effect of the different preparation technique on phase transition and electrical properties of Ba0.8Sr0.2TiO3. The samples compared 3 preparation technique, there are conventional mix-oxide, molten-salt and seed-induced method. The samples prepared by molten-salt calcined at 800 °C, the samples prepared by conventional mix-oxide and seed-induced method was calcined at 1200 °C for 3 h. All of samples sintered at 1400 °C for 3 h. The phase formation and morphology of samples were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The dielectric properties of the samples were measurement by LCR-meter.

Effect of MnFe2O4 and the Heat Treatment Temperature on the Bioactive Glass Properties

In this study, the effects of heat treatment temperatures on structural and magnetic properties in MnFe2O4(MF)/SiO2-Na2O-CaO-P2O5 (bioglass) bioactive glass ceramics were investigated. The MF/SiO2-Na2O-CaO-P2O5 bioactive glass ceramics were fabricated under various heat treatment temperatures in a range of 600-1000 °C. X-ray diffraction (XRD) technique, the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize phase and microstructure. The magnetic properties were determined from Vibrating Sample Magnetometer (VSM). The X-ray diffraction peaks presented two major crystalline phases: MnFe2O4 and Na2Ca2Si3O9. It was found that the heat treatment temperatures are the most influential parameter on microstructure and magnetic properties of the bioactive glass ceramics. The highest magnetic properties of studied ceramics were found in the sample heated at 1000 °C with adding 20 wt%. MF. The microstructural properties of the studies samples were investigated and the results were then correlated with the characteristics of heat treatment temperatures as well as the microstructure of the bioactive glass ceramic.

Effects of BST on Optical and Dielectric Properties of Na2O-B2O3-SiO2 Glasses

In this research, the effects of Ba0.7Sr0.3TiO3 (BST) on optical and dielectric properties of Na2O-B2O3-SiO2 glasses were investigated. From the study, the optically transparent glass from BST system was successfully prepared by using melt-quench method. The composition of BST used in this study are ranging between 20-60 wt.% BST. It was found that the addition of BST enhanced conductivity, but in turn reduced the percentage of transmittance in the glasses. The dielectric constant (ɛr) of the BST/Na2O-B2O3-SiO2 glasses improved with increasing the content of BST, which in turn plays an important role in controlling the properties of the BST/Na2O-B2O3-SiO2 glasses.

Fabrication of SrFe12O19-P2O5-CaO-Na2O Bioactive Glass-Ceramics at Various Sintering Temperatures

The effects of sintering temperatures on the physical, and bioactivity of SrFe12O19 (SF)-P2O5-CaO-Na2O bioglass ceramics were investigated. XRD results confirmed the existence of the strontium ferrite and calcium phosphate phases. SEM images showed that grain size, and hardness were related to density and liquid phase present in the samples. A maximum coercivity value of 3138 Oe was obtained for the bioglass ceramic sintered at 600°C. The remanence (Mr) and saturation magnetization (Ms) of the bioglass ceramic sintered at 500°C possess the maximum value of 6.35 and 10.64 emu/g, respectively. Moreover, the apatite was formed on the surface layers of the bioglass ceramics confirming their biocompatibility.

Effects of the Sintering Temperature on Structural and Bioactivity in BaFe12O19-P2O5-CaO-Na2O Bioactive Glass Ceramic

In this research, the effects of sintering temperatures on structural and bioactivity in BaFe12O19 (BF) /P2O5-CaO-Na2O bioactive glass ceramics were investigated. The BF/P2O5-CaO-Na2O bioactive glass ceramics were fabricated under various sintering temperatures in a range of 550-700 oC. X-ray diffraction (XRD) technique and the scanning electron microscopy (SEM) are used to characterize phase and microstructure. The studied samples were evaluated for mechanical properties by hardness testing. Moreover, the bioactivities of studied samples were studied by using simulated body fluid (SBF) in vitro. It was found that, the sintering temperatures are the most influential parameter on microstructure and mechanical properties of the bioactive glass ceramics. The highest density of studied ceramics was found in the sample sintered at 700 oC. The microstructural properties of the studies samples were investigated and the results were then correlated with the characteristics of sintering temperature as well as the microstructure of the bioactive glass ceramic. Moreover, the covering of bone-like apatite layer on the surface sample after a 7 day immersion in SBF suggested that the BF/P2O5-CaO-Na2O glass ceramics have acceptable bioactivities.