Abstract: The aim of this study is to develop a new test method for determining dynamic fracture toughness of brittle material using the izod impact tester. Poly (methyl methacrylate) (PMMA) is used in this study. Test setup and load calibration methods are proposed. The proposed method can be successfully used to determine near-mode I fracture toughness under dynamic load. The effects of notch tip preparation and specimen thickness are also studied and discussed. Stress intensity factor at maximum load (Kmax) is determined based on a numerical simulation. It is found that the notch preparation method has a minimal effect on total fracture energy, except in the case of saw notch. Moreover, fracture toughness increases with increasing of specimen thickness.
Abstract: Recently, Thai herbs are widely used as medicine to treat some illnesses. Zingiber cassumunar Roxb., known by the Thai name “Plai”, is a popular anti-inflammatory, antispasmodic herbal body and muscle treatment. This research aimed to prepare herbal patches that incorporated the 3 g of crude Z. cassumunar oil. The herbal patches made from different polymer blends were 2 g of 3.5%w/v chitosan and 5 g of 20%w/v hydroxypropyl methylcellulose (HPMC), or 2 g of 3.5%w/v chitosan and 5 g of 20%w/v polyvinyl alcohol (PVA) using 2 g of glycerin as a plasticizer. They were prepared by mixing all ingredients in a beaker and produced by solvent casting method in hot air oven at 70±2oC. The completed herbal patches were evaluated for their mechanical properties including Young’s modulus, ultimate tensile strength, elongation at break, T-peel strength, and tack adhesion. The thickness of blank and herbal patches was 0.263-0.282 mm and 0.269-0.275 mm, respectively. Young’s modulus, ultimate tensile strength, elongation at break, T-peel strength, and tack adhesion were 104.73-142.71 MPa, 87.92-93.28 MPa, 154.39-174.98 %, 3.43-4.88 MPa, and 5.29-7.02 MPa, respectively, for blank patches, and 116.83-147.28 MPa, 89.49-100.47 MPa, 133.78-159.27 %, 2.01-3.98 MPa, and 4.03-5.19 MPa, respectively, for herbal patches. We prepared herbal blended patches made from chitosan/PVA or chitosan/HPMC polymer matrix blends incorporating the crude Z. cassumunar oil. They had good mechanical properties that might be developed for herbal medicinal application.
Abstract: A Dissolved Oxygen (DO) sensor has been designed and fabricated on an 8.5 x 22.5 mm Alumina substrate using thick film technology. The structure of the sensor device consisted of AgPd working/counter electrode, Ag/AgCl reference electrode, RuO2 active layer, KCl electrolyte, and TiO2 membrane. Formation of the Ag/AgCl reference electrode was done by chlorination of Ag layer using FeCl3, and the TiO2 membrane was formed by screen printing of TiO2 paste. Measurement was done to study the sensor’s performance based from the current-voltage characteristics between 1.1 – 1.6 V. The results showed that a stable diffusion current was obtained when the input voltage was 1.4 V, resulting in the best sensor performance with a sensitivity of 0.560 μA l/mg and a stable step response time of 4 min. The device showed highly potential to be used as candidate for online water quality monitoring system.
Abstract: A study on the effect of heat treatment condition on the characteristics of MnO2 added-Fe2TiO5 ceramics for NTC thermistor has been carried out. The ceramics were produced by pressing an homogenous mixture of Fe2O3 (local/ yarosite), TiO2 and MnO2 (2.0 mole %) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1050 °C for 3 hours in oxygen gas. Some sintered pellets were heat treated by heating them at 300 °C for 5, 15 and 25 minutes in Ar + 7% H2 gas. The XRD analyses showed that the Fe2TiO5 ceramics with and without heat treatment time had orthorhombic structure. No peak from second phase was observed from the XRD profiles. From the electrical characteristics data, it was known that the heat treatment could change the electrical characteristics of the Fe2TiO5 based-thermistor. The thermistor constant (B) and room temperature resistivity (ρRT) decreased with the increasing of heat treatment time. All ceramics made had thermistor characteristics namely B = 3459-7596 K and ρRT = 1.056-6936.062 MΩcm. Thermistor constant of the ceramics was relatively big, indicated that ceramics made from local iron oxide in this work fit the market requirement for NTC thermistor.
Abstract: The FeS2 films were deposited by using the spray pyrolysis method using mixed aqueous solutions of CH4N2S and FeCl3, with different S:Fe molar ratios. The homogeneous FeS2 nanocrystalline films with good crystallinity were synthesized. The structure, composition, and properties of these films were very sensitive to the S:Fe molar ratios. The direct transition of the pyrite FeS2 films were about 0.9 - 1.25 eV. High absorption coefficients and suitable band gaps were observed. FeS2 thin films were synthesized for new biomaterial applications such as glucose.
Abstract: Fabrication of Fe2TiO5 pellet/disk ceramics-based NTC thermistor has been performed, in order to know the effect of sintering tempertures on the electrical characteristic of 1.0 mole % MnO2 doped-Fe2TiO5 ceramics. These ceramics were made by mixing commercial powders of Fe2O3, TiO2 and MnO2 with proportional composition to produce Fe2TiO5 based ceramic. The raw pellet was sintered at 1100 °C, 1200 °C and 1300 °C temperature for 2 hours in air. Analysis of the microstructure and crystal structure were performed by using a scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. XRD pattern showed that all of Fe2TiO5 ceramics made at various sintering temperatures are orthorhombic The SEM images showed that the grain size of pellet ceramics increase with increasing sintering temperatures. From electrical data that was measured at temperature 30-300 °C, showed that the addition of sintering temperature decreased the thermistor constant (B), activation energy (Ea), thermistor sensitivity (α) and room temperature resistance (RRT). Thermistor constant (B) of the ceramics was relatively big of 5778 K to 6707 K. The value of B indicated that ceramics made in this work fit the market requirement for NTC thermistor.
Abstract: The development of high-performance cathodes is essential towards the operation of proton-conducting fuel cells (PCFCs) at intermediate temperatures. To that end, the performance of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes is very attractive. In the present works, LSCF cathode powders were synthesized by a sol-gel method with the aid of ethylene glycol which served as the dispersing agent. The pristine and modified samples were each denoted as LSCF64 and LSCF-EG5. The phase formation and morphology of the cathode powders were examined by X-Ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM), respectively. In order to evaluate the cathode performance, a symmetrical cell of electrolyte supported PCFCs were examined using an electrochemical impedance spectroscopy (EIS) at a 700 oC in atmosphere containing humidified air. The formation of LSCF single phase was attained at 700 °C for both prepared samples. The FESEM images confirms an improvement in the microstructure of the modified cathode. The impedance spectra obtained from the electrochemical impedance measurement were resolved by a fitting procedure using an equivalent circuit that consists of a combination of two parallel pairs of resistor-constant phase element (R-Q) in series. The area specific resistance (ASR) determined for LSCF64 and LSCF-EG5 is 1.55 and 0.23 Ωcm2 , respectively. The better performance exhibited by LSCF-EG5 is attributed to its higher cathode reaction site due the improved microstucture. This study reveals that the application of ethylene glycol as dispersing agent is effective in producing a high quality cathode material for better PCFCs performance.
Abstract: Solid oxide electrolysis cell (SOEC) cathodes require a good porosity and a fine microstructure in order to maximize the triple phase boundary (TPB) between electronic conductor, ionic conductor and the gas phase involved in the reaction. Nickel oxide and yttria stabilized zirconia (NiO/YSZ) composite, one of the most desired candidates for SOEC cathode material, is synthesized via the glycine-nitrate combustion process and mixed with corn starch and carbon black pore formers in order to observe how they modify its microstructure and porosity. XRD spectra indicate a distinct cubic phases of both NiO and YSZ. SEM micrographs were able to confirm that the addition of selected pore formers lead to an increase in porosities. Apparent and relative density measurements show that corn starch pore former produces the lowest density among the sintered pellets. EIS measurements revealed that samples with lower density also showed lower total conductivity.
Abstract: The chlorine-doped complex oxide Ba2CaNbO5.475Cl0.05 based on barium calcium niobate was synthesized using the solid state method. It was found that the introduction of chloride ions leads to the increase of the cell volume. Structure and electrical properties have been investigated. Electrical conductivities were measured by varying the temperature in dry (pH2O=3.5·10-5 atm) and wet (pH2O=2·10-2 atm) air. The composition Ba2CaNbO5.475Cl0.05 is capable to dissociative dissolution of water vapor and can exhibit proton transport. Chlorine doping increases the conductivity of matrix compound Ba2CaNbO5.5, the difference between un-and chlorine-doped samples is up to one order of magnitude at low temperatures.
Abstract: Lanthanum strontium manganite (LSM) and yttria-stabilized zirconia (YSZ) composite is a promising material as an anode for solid oxide electrolysis cell (SOEC) applications. In this study, LSM/YSZ with a 1:1 LSM to YSZ weight ratio was synthesized via solid state reaction method using oxide precursors of commercial micrograined size LSM with varying YSZ precursor grain size. For the YSZ precursor, both nanograined (nanoYSZ) and micrograined YSZ (microYSZ) precursors were studied. Graphite was added at 10% weight ratio as a pore former. Density measurements using Archimedes principle revealed that LSM/nanoYSZ had the highest relative density of 97.8%, whereas LSM/nanoYSZ with graphite had the lowest density of 89.1%. The addition of graphite to LSM/nanoYSZ reduced the density by 8.7% compared to the decrease of 5.5% for LSM/microYSZ. Scanning electron microscopy confirms that the addition of graphite has a greater effect on the microstructure of LSM/nanoYSZ as compared to LSM/microYSZ. The electrochemical impedance spectroscopy results show that the samples with nanoYSZ had a higher total conductivity than the samples with microYSZ. LSM/nanoYSZ and LSM/nanoYSZ with graphite revealed a total conductivity values of 0.0470 Scm-1 and 0.0440 Scm-1 at 700 °C with activation energies of 0.0178 eV and 0.0234 eV, respectively.