Abstract: The aim of this in vitro study was to investigate the changes in surface roughness of different nanocomposite restoratives and enamel after application of 1.23% acidulated phosphate fluoride (APF) gel. Twelve specimens were prepared for each composite material and human enamel. The APF gel was applied to the surface of the six specimens of each experimental group for 60 sec every 24 h for 4 days. The other six specimens did not receive APF treatment (control). The surface roughness was measured using a VSI microscope. One-way ANOVA and Tukey’s test were used to compare surface roughness between materials for each experimental group at a level of significance of a=0.05. There were no statistically significant differences in Ra values among the composites which did not receive APF treatment (p>0.05). After APF treatment the lowest surface roughness exhibited enamel (0.18±0.04 Ra) and the highest Dyract Extra (0.62±0.07 Ra) followed by Tetric EvoCeram (0.59±0.06 Ra) and Beautifil II (0.51±0.06 Ra). Filtek Z350 XT presented the lowest Ra values (0.23±0.03). All the experimental groups exhibited higher Ra values after APF treatment (p<0.05), except for Filtek Z350 XT (p>0.05). Application of APF gel on the specimen surfaces influenced the surface roughness of enamel and the tested dental composite restoratives depending on their composition.
Abstract: In this paper, a tunable TiO2 nanorod cross-link structure with ultra-high surface area (up to 109.81 m2/g) has been successfully prepared via hydrothermally treating elongated sodium titanate nanotubes. XRD, SEM, HRTEM and BET analysis were employed to characterize the morphology and inner structure of the samples. The preparation conditions (the hydrothermal temperatures and the pH values of the solutions) of the obtained TiO2 products were systematically studied. The maximum length of nanorod reaches to 1 μm while the lateral size could be limited less than 10 nm. The surface area can be easily tuned by modifying the stirring rate during the hydrothermal process. In addition, the photocatalytic performance of synthesized TiO2 nanorods were also measured, and the nanorod structure with ultra-high surface area showed much better photocatalytic activity than the sample produced without stirring process, which can be attributed to the influence of the large difference in specific surface area of the obtained TiO2 products.
Abstract: The non-local Timoshenko beam theory has been implemented to investigate the free vibration of armchair single-walled carbon nanotubes embedded in elastic medium including the thermal effects. The mechanical properties of nano-composite (carbon nanotubes and polymer matrix) are treated as functions of temperature change and the analytical solution is derived according to the governing equations of non-local Timoshenko beam models. The equivalent Young’s modulus and shear modulus for armchair single-walled carbon nanotubes are derived using an energy-equivalent model. Inﬂuence of small-scale coefficient, vibrational mode number, matrix of nano-composite and aspect ratio on the frequency ratio of the armchair single-walled carbon nanotubes including the thermal effect are studied and discussed. The research work reveals the significance of the small-scale coefficient, the vibrational mode number, the elastic medium and the aspect ratio on the frequency ratio. It is also demonstrated that some properties of free vibrations of single-walled carbon nanotubes are dependent on the change of temperature.
Abstract: A facile method has been developed to fabricate ZnO microstructures by a solution route at an 80°C. The microstructures with various morphologies were fabricated in water or anhydrous ethanol by using polyvinylpyrrolidone and cetyltrimethylammonium bromide as surfactants. ZnO rods with aspect ratios up to 30 have been created successfully in water through a hydrothermal process, while novel shuttle-like ZnO microstructures were fabricated in anhydrous ethanol using a similar procedure. ZnO rods revealed wurtzite-type crystal structure according to their X-ray diffraction (XRD) patterns. The morphologies of ZnO microstructures were adjusted conveniently by changing solvents and surfactants. In addition, the sizes of ZnO microstructures decreased under a long reaction time. This morphological evolution of ZnO microstructures indicated that the growth of ZnO is susceptive to reaction time due to the reaction between ZnO and aqueous ammonia. The facile strategy described here would be utilizable for the preparation of various metal oxide microstructures.
Abstract: In the present work, chemical-free aluminium nanoparticles (Al NPs) have been incorporated inside active layer of organic solar cell (OSC) using a new ultrasonic ablation technique, by which the Al NPs have been physically prepared in 1,2-dichlorobenzene (DCB) as a solvent for preparing solar cell active layer. The concentration of Al NPs inside active layer can be increased by increasing the volume of DCB-Al NPs and, also, by increasing the ultrasonication time applied upon DCB-Al NPs mixture. The prepared Al NPs are incorporated inside the common P3HT:PCBM active layer without accumulation and with low distribution. Optical absorption of the P3HT:PCBM active layer is improved through plasmon resonance induced by Al NPs inside active layer. The fill factor (FF) is, also, improved by the presence of Al NPs which facilitate charge carrier transfer in the P3HT:PCBM solar cell. The FF can be reduced due to presence of Al bulk pieces inside active layer. However, these Al bulk pieces are dissociated under the effect of ultrasonic irradiation for longer time. Optical absorption as well as charge carrier transfer induced by Al NPs are the responsible to increase performance parameters of the P3HT:PCBM solar cell under increasing the concentration of Al NPs inside OSC. As a conclusion, the incorporation of Al NPs inside P3HT:PCBM solar cell induces a significant improvement of the FF by 35% and consequently, the PCE is improved with about 39%.
Abstract: Gd and La codoped multiferroics with the formula Bi(La,Gd)FeO3 (0%≤La≤10%; 0%≤y≤10%) have been synthesised by low temperature sol gel method. XRD analyses confirm the phase formation of all the samples. The decrease in the intensity and shifting of (104) and (110) diffraction peaks of the doped samples towards the higher 2θ region confirms the lattice shifting with the addition of La and Gd but still exhibits perovskite structure. FTIR studies show the presence of the necessary bonds in the samples. Dielectric properties such as dielectric constant, ε' and dielectric loss, tanδ were studied as a function of frequency and compositions of La and Gd. The dispersive behaviour of both ε' and tanδ are explained in accordance to the double mechanism of grain and grain boundaries. However, the actual amount of contributions made by the grains and grain boundaries to the dielectric response and total resistance are not yet discussed. Enhanced dielectric constant and reduced loss factor has been observed with increasing Gd content (decreasing La content). Magnetic measurements of all the samples show an increment in the values of both coercivity (HC) and saturation magnetisation (MS) with the increase in Gd dopant (decrease in La dopant). The modification of the structural, dielectric and magnetic properties of the doped samples was explained on the basis of the size effect of the dopants.
Abstract: Titanium dioxide is prepared by sol gel method from titanium tetraisopropoxide (TTIP) as precursor and likewise zinc oxide is prepared by sol gel method from zinc acetate dehydrate (ZAD) as precursor. The composite sols are prepared in three different molar ratios 90TiO2:10ZnO, 70TiO2:30ZnO and 50TiO2:50ZnO. Thin film deposition is carried out by dip coating technique. Crystal structure, surface morphology and photocatalytic activity of the prepared nanocomposite thin films are investigated. The antibacterial activity of the prepared nanocomposite thin film against E-coli ATCC 25922 bacteria is examined by placing the thin film in standard aqueous E-coli medium under UV light for 1, 2, 3 and 4 hours and then counting the bacteria with Standard Plate Count Agar (SPC) technique. The prepared thin films have shown strong antibacterial activity in the presence of UV light and by increasing the ZnO molar ratio from 10 to 50, antibacterial activity of the thin films decreases because of decreases in the anatase phase of the TiO2. In the dark conditions by increasing the molar ratio of ZnO, the antibacterial activity of the thin films increases and this phenomenon is related to increasing the zinc ions in the thin films.
Abstract: TiCN thin coatings with various different carbon contents were deposited using cathode arc evaporation of pure titanium in a mixture of N2 and C2H2 gasses at a constant pressure of 1.5 Pa. The analyses show a transition from a stoichiometric to a non-stoichiometric coating structure with an increasing C2H2 content. Moreover, the increase in the acetylene in the gas mixture leads to a decrease in the crystal phase from pure polycrystalline to pure amorphous. Nanohardness changes from 30.4 to 4.4 GPa and the cohesive failure of the coatings is in the range of 61 - 72 N. The tribology is estimated by the Ball-on-Disc method and an Si3N4 ball as the counterpart. The measured coefficient of friction is in the range of 0.2 - 0.56.
Abstract: Fatigue and corrosion fatigue of 50KhN and 60Kh2M roll steels with surface nanocrystalline structure induced by mechanical-pulse treatment were studied. The increment of fatigue and corrosion fatigue of the steels with surface nanocrystalline structure were shown and revealed the factors which causes this increment.