Applied Mechanics and Materials Vol. 804

Abstract: A composite nanofiber containing poly (vinylidene fluoride) (PVDF) and silica (SiO₂) were prepared by electrospinning of their mixtrues.The various amount of SiO₂ nanoparticle was add with 15 wt.% PVDF solution in mixed solvent of N,N-dimethylacetamine (DMAc) : acetone at a ratio of 4:6 with the applied voltage of 8 kV, tip to collector distance of 10 cm and flow rate of 1 ml/hr. The morphology of the PVDF/SiO₂ membranes was investigated by scanning electron microscope (SEM). The effect of SiO₂ concentration on the morphology of the composite membranes were discussed. Crystallinity of the composite membranes was investigated by differential scanning calorimetry (DSC). It was found that SiO₂ concentration have significant influence on the morphology and crystallinity of PVDF/SiO₂ membranes.

Abstract: This work is focused on the preparation of Mg doped ZnO films by ultrasonic spray pyrolysis and investigated the physical, optical and electrical properties of the films. These films were prepared from 0.02 M of Zn (CH₃OO)₂.2H₂O and MgCl₂ was used for doping. The atomic percentage ratio of Mg/Zn was varied from 0 to 9 at.%. The crystalline phase of all films was identified as ZnO polycrystalline structure with preferred orientation along the (002) plane. While, the grain shape of ZnO film was irregular shape, this shape changed to spherical shape with doped Mg concentration and changed again to rod shape with doped Mg concentration to 9 at.%. Although, the Mg dopant affects the shape of ZnO films but don’t affect resistivity of the films. Moreover, the Mg dopant shifts the absorption edge in transmittance spectra of films to lower wavelength and increases band gap of the films.

Abstract: In the present day, inorganic scintillating crystals become a main part in detection and spectroscopy of nuclear particles and high energy photons, more spectively in X/g-ray imaging. The good properties for the scintillating crystals used in these applications require high photon yield, high stopping power, good energy resolution, good light yield proportionality, and minimal afterglow. The main useful of Ce-doped Lu_0.7Y_0.3AlO₃ (LuYAP(Ce)) are high stopping power and non-hygroscopic which are expected to be key ingredients for medical imaging. In this work, we studied the light yield non-proportionality and energy resolution of LuYAP(Ce) crystal with the energy range from 31 to 1,274.5 keV using photomultiplier tube (PMT) readout. The intrinsic resolution of the LuYAP(Ce) crystal has been determined after correcting the measured PMT resolution. The results showed that the non-proportional response of the crystals was strongly correlated with the intrinsic resolution of the crystals.

Abstract: Bulk Y₂NiMnO₆ samples were prepared by thermal decomposition technique at 800 °C for 6 hours. The effects of temperature on the structure of ceramics were investigated for different sintering temperatures in the range of 1000-1300 °C, while kept constant the sintering time of 12 hours. Structural characterization had been investigated via X-ray diffraction (XRD) on samples of different sintering temperatures. Results from the experiment had revealed that high temperature affected oxide in ceramic materials. Further analysis with X-ray photoelectron spectroscopy (XPS) technique had revealed an outstanding point of ceramics by investigating the Ni 2p, 2p_3/2, Mn 2p_1/2, 2p_3/2, and Y 3d_3/2, 3d_5/2 at the surface of Y₂NiMnO₆ ceramics. The changes in relative intensity of XPS peaks and the shifts in their binding energy (eV) were observed in the results, while the effect of temperature on oxide in ceramics may be investigated with dielectric property in the future.

Abstract: Thermal barrier coatings (TBCs) are used in the cooled parts of gas turbines to reduce the temperature of blades and hot engine components, allowing higher operating temperatures and yielding increased efficiency. The corrosive gases which come from combustion of low grade fuels can penetrate into the TBCs and reach the metallic components and bond coat and cause hot corrosion and erosion damage. Mullite thin films have been applied onto the top layer of yttria-stabilized zirconia (YSZ) coatings by sol-gel dipping process in order to decrease the porosity as well as improve thermal stability of the coatings. Glazing the top layer by laser beam is an advanced approach to seal TBCs surface. The laser beam has the advantage of forming a dense thin layer composed of micrograins. CO₂ laser beam assisted in the densification of the surface by remelting a thin layer of the exposed surface. The laser glazing converted the rough surface of TBCs into smooth micron-sized grains with size of 1-4 microns. Mullite compounds have remained on the surface after laser treatment since alumina and silica are still present, as indicated in EDX spectra. The results revealed that the roughness increases as the grain size decreases.

Abstract: The high dielectric permittivity of Y₂NiMnO₆ ceramics were measured by Agilent E4294A (Impedance Measurement) range of frequency 100 to 10 MHz in this research. In this sample ceramics, passing by a sintering temperature of 1400°C at 6 hours to 24 hours. The phase and microstructure of the deposited materials were investigated as a function of sintering temperature, using X-ray diffraction (XRD) and scanning electron microscopy (SEM). We found that the dielectric properties are very sensitive to the several sintered follow by time, and high temperature can be related to the change ordering of Ni²⁺ and Mn⁴⁺ ions.

Abstract: This research article presents the mechanical and thermal properties of cement-based composite for thermal energy storage materials enriched with containing nanoTiO₂ particle size (25 nm) and concentration (1-5 wt.%) were systematically investigated. Thermal properties coefficients were tested using a direct measuring instrument with surface probe (ISOMET2114). The influence of nanoTiO₂ on the performance, such as compressive strength, bulk density, thermal conductivity, volume heat capacity and thermal diffusivity of hardened composite cement pastes were studied for future solar thermal energy materials with better performance. According to the development of thermal storage materials and their application environment requirement in solar thermal power, the specimens were subjected to heat at 350°C and 900°C. It was observed that, before heating, the compressive strength is optimized at nanoTiO₂ amount of 2 wt%. Moreover, after heating at 350 °C and 900°C, the thermal conductivity and volume heat capacity of the cement paste enriched with nanoTiO₂ were significantly lesser than that of the before heating one.

Abstract: The microstructure and dielectric properties of lead niobate zirconate titanate (PNZT), rice husk ash (RHA) and Ordinary Portland cement (OPC) composites were investigated. Ordinary Portland cement was partially replaced with rice husk ash at 20% by weight of binder. The rice husk ash was ground for 180 minutes before using. PNZT of mid particle sizes (450μm) were used at 30%, 50% and 70% by volume to produce the composites. The composites were mixed and pressed together and cured with 97%RH in chamber water bath for 3 days before measurements. The dielectric properties were measured under room temperature at different frequency. The results indicated that the dielectric constant of the 0-3 PC/RHA-PNZT composites increased with increasing PNZT content.

Abstract: The microstructure and mechanical properties of Portland cement (PC)- natural rubber latex (NRL)- rice husk ash (RHA) composites have been investigated. The proportions of PC-NRL-RHA composites with NRL to cement ratio (NRL/C) that use in this experiment were 0, 0.10, 0.15 and 0.20 respectively. Portland cement (PC) was partially replaced with rice husk ash at 20% by weight of binder. The rice husk ash (RHA) was ground for 180 minutes before using. Water to cement ratio (W/C) equal of 0.5 by weight not include water in NRL. Nonionic surfactant was added in cement before mixed with NRL. In addition, to provide latex from natural rubber, the ammonia solution is added into natural rubber. The specimens were casting in standard mold which samples size of 50x50x50 and 40x40x160 mm³ respectively. Moreover, the PC-NRL-RHA composites were cured in water for 3, 7 and 28 days at room temperature before measurement. Then, mechanical properties (compressive strength and flexural strength) and microstructure were studied.

Abstract: This research studies the potential for using waste ash from industrial and agricultural by-products as a pozzolanic material. Classified fly ash (FA) and ground rice husk ash (RA) were the materials used. Water requirement, compressive strength and porosity of cement mortar were investigated. Test results indicated that FA and RA (waste ash) have a high potential to be used as a good pozzolanic material. The water requirement of mortar mix decreases with the increases in fly ash content. For ground rice husk ash (RA), the water requirement of mortar mix increases with the increases in rice husk ash content. In addition, the reduction in porosity was associated with the increase in compressive strength.