Papers by Keyword: Nanostructured

Abstract: Thin film is a thin material that is resulting from the condensation of species through the deposition of atoms on the substrate. Thin films are usually used in the production of electronic devices, optical coatings, solar cells, and for decorative items. The bilayer of TiO₂/ZnO and ZnO TiO₂ thin films have some advantages such as can enhance the surface state and surface atomic mobility, which are useful for improving the photocatalytic activity. The motivation to a used double layer of ZnO and TiO₂ is to enhance the properties and photocatalytic activity using the different deposition temperature between the layers. The structural of ZnO/TiO₂ thin films were studied using X-Ray diffraction (XRD). Field Emission Scanning Electron Microscope (FESEM) was used to determine the surface morphology of ZnO/TiO₂ thin films. The photocatalytic activity of ZnO/TiO₂ thin films was analysed using the photodegradation of methylene blue (MB) solution. The XRD analysis revealed that highest anatase crystalline phase for TiO₂ growth with orientation (1 0 1), while the ZnO crystal phase, zincite occurred at the highest intensity with (1 0 1) orientation.. The bilayer TiO₂/ZnO thin film had the highest reaction rate, K, which is 0.0972 h-1 for photocatalytic activity. The characteristics of bilayer TiO₂/ZnO and ZnO/TiO₂ thin-film is strongly influenced by the calcination temperature and the presence and combination between the two types of materials.

Abstract: Conventional and nanometer aggregate ZrO₂-7wt.%Y₂O₃ ceramic powders taken as raw materials, plasma spraying and plasma spraying-laser remelting compound technology was used to prepare conventional and nanostructured thermal barrier coatings on the TiAl alloy surface. Effects of powder structure (feedstock) and laser remelting on organizational structure and phase of the coatings were analyzed using scanning electron microscope (SEM) and X-ray diffractometer (XRD). Results indicate that: conventional plasma sprayed ceramic coating presents typical lamellar stacking features; plasma sprayed nanostructured coating consists of fully melted region and partially melted region, presenting a two-phase structure. Under the comprehensive impacts of laser power, energy density, temperature field distribution in the laser action region, ceramic heat conductivity coefficient and coating thickness and other factors, the coating presents obvious lamellar structural features after laser remelting; the upper part is compact columnar crystal remelting region and the lower part is residual plasma spraying region. Due to toughening effect of residual nanoparticles in the remelting region of laser remelted nanostructured coating, grain-boundary strength is high and there are a considerable number of transgranular fractures, but the fractures in the remelting region of laser remelted conventional coating are basically intergranular fractures. Conventional plasma sprayed ceramic coating is mainly of tetragonal phase together with a small quantity of monoclinic phases, but nanometer plasma sprayed ceramic coating only has non-equilibrium tetragonal phases. After laser remelting, both conventional coating and nanometer coating mainly have non-equilibrium tetragonal phases with a small quantity of cubic phases.

Abstract: The influence of СаСО₃ on nano-structured, flowability and plastic strength of alkali activated alumonosilicate binders based on metakaolin for the range of oxide ratios in a structural formula of the Na₂O∙Al₂O₃∙(2.5-4.5)SiO₂∙(12-17)H₂O + (5-15%)CaCO₃ system was studied. The results of the study showed that the ratios of SiO₂/Al₂O₃ – 3.8, H₂O/Al₂O₃ – 13.75, and content of СаСО₃ of 5% by mass were the most optimal ones from the point of view of meeting requirements for these binders to be used as base in protective coatings.The results of the study showed that process flowability of the binder with optimal ratios of oxides and 5 % by mass of additive 2 hours after preparation was by 5.4% lower, being by 5 times lower than that of the binder without the additive (СаСО₃). The binder containing 5% СаСО₃ by mass during 2 hours after preparation exhibited the same plastic strength (37 Pa), whereas this value of the binder without CaCO₃ has increased, in average by 5.5 times, affecting negatively shelf life of this binder to be used as base in protective coatings.A conclusion was made that the addition of СаСО₃ intensified the nano-structured formation processes in the direction of formation of Na-Ca zeolite-like phases; shortening time required the cement stone to gain water resistance in normal conditions.

Abstract: In this research, the effect of different hydrothermal treatment temperature (100, 150, and 200 °C) on the products obtained by hydrothermal method was studied. Various characterization techniques was carried out such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive of x-ray spectroscopy (EDX) and fourier transform infrared spectroscopy (FTIR). XRD analysis shows that titanate phase was formed at 150 and 200 °C hydrothermal treatment. On the other hand, at 100 °C anatase TiO₂ phase structured was gained which is similar with the TiO₂ precursor. Morphological study using FESEM revealed that nanofibers and nanorods samples obtained at 150 °C and 200 °C, respectively. At 100°C, irregular shaped particle was attained similar with TiO₂ precursors. FTIR spectra for the all studied sample displayed three main broad peaks at the range of 3700-2800, and 1800-1400 assigned to –OH stretching and deformation mode due to H₂O molecules and M-O stretching mode at 900-400 cm^-1 assigned to Ti-O bond.

Abstract: The CrN thin films were deposited on silicon (100) substrate using reactive magnetron sputtering technique. The films were characterized by XRD, FE-SEM, EDS and nanoindentation techniques to examine the effect of deposition time on crystal structure, compositions, microstructure and hardness. The crystal structure, microstructure, element composition and hardness. The higher crystallinity through longer deposition time were investigated. The grain aggregration with columnar structure were obtained from FE-SEM. The Cr and N contents were not direct relationship with deposition time. The CrN coated sample performed hardness varied between 9 - 16 GPa.

Abstract: The melt-spun Y₂(Fe,Mn)₁₇ ribbons were synthesized by rapid quenching from the melt. The phase composition, crystal structure and magnetocaloric effect (MCE) in low-cost iron-based pseudo-binary Y₂(Fe,Mn)₁₇ ribbons were investigated respectively by using x-ray diffraction and direct measurements of MCE. It was found that crystal structure of the as-spun ribbons retains hexagonal Th₂Ni₁₇-type because of the weak glass-forming ability. The Y₂Fe₁₄Mn₃ and Y₂Fe₁₃Mn₄ nanostructured ribbons demonstrate higher MCE compare to polycrystalline alloys.

Abstract: Ceramics of Pb_1.02(Zr_0.53Ti_0.47)O₃ (PZT) comprise the majority of piezoelectric devices in use today. In general, these ceramics are obtained by solid-state reaction, which favors the formation of micrometric grains. Recent studies have shown that reducing the particle size from micro to nanoscale, it generates PZT ceramics with superior dielectric properties. In this way, this study aimed to obtain nanostructured PZT ceramics from the coprecipitate method, using precursor materials as oxides reagents. From the Differential Thermal Analysis (DTA) was observed that the formation of PZT through the proposed methodology is initiated at 550^oC. However, the full phase crystallization was observed at 850^oC confirmed by X-Ray Diffraction (XRD). Spherical particles near 200nm were observed using scanning electron microscopy (SEM). This powder was sintered in conventional and microwave oven. The ceramics obtained from both sintering methods showed substantial differences in microstructure such as presence of piroclore phase and grain morphology.

Abstract: pH control is significant in electrodeposition because they affect the characteristics of electrolyte and the deposit. This paper mainly analyses the processing conditions of electrolyte pH value on the electrodeposited SAC. Sn2+ ions will be obtained from the tin methane sulphonate acid while the Cu2+ and Ag+ ions will be obtained from their respective sulfate salts. Ammonium acetate helps in raising the pH of the bath. The FESEM analysis was carried out to examine the morphology of the electrodeposited nanocomposites. A variety of morphological patterns for the electrodeposits with different electrolyte pH is obtained. At low pH (2) electrolyte value, the electrodeposits show a very poor quality with rough surface. With increasing pH value (2.5), the averaged grain sizes decreased. The surfaces of the films electrodeposited at this pH value are generally quite smooth, uniform and compact. Later increment of pH values (3~4) has lead to the formation of porous and non-uniform electrodeposits. From the study, it is possible to observe that, even with the same composition, the deposits have different morphologies under different controlled parameter.

Abstract: In this study, the effect of nanonization on antioxidant activity of Zingiber officinale (ginger) Ross rhizome prepared using a wet milling process were investigated. The antioxidant activity was estimated based on the Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) and measured using FRAP, ABTS and DPPH assays. Particle size of the initial ginger rhizome (approximately 20μm) was successfully reduced to 222.3 nm after the wet milling process. Higher degree of granules surface destruction occurred as a result of nanonization process based on FESEM image. Findings revealed that nanostructured ginger (NG) had the highest TPC and TFC which were 946.43 mgGAE/g and 20.16 mgQE/g followed by submicron ginger (SM) (712.68 mgGAE/g; 16.22 mgQE/g) and micron ginger (MG) (700.89 mgGAE/g; 14.45 mgQE/g) of dry matter respectively. Moreover, NG rhizome showed around 30 to 40% (p<0.05) greater radical scavenging activity as well as ferric reducing antioxidant power as compared to the other samples tested. The antioxidant activity was in the following in sequence: NG>SM>MG. Hence it can be concluded that reduction of particle size of ginger rhizome into nanoparticles using a wet milling process enhanced its antioxidant activity as compared to micron and submicron particles.

Abstract: Titanium nitride (TiN) thin films of different crystal structure and morphologies were deposited by direct current (dc) reactive magnetron sputtering method under conditions of various deposition times (3090 min). The crystal structure, crystal size, thickness and surface morphology properties of the films were studied and the results were discussed with respect to deposition time. The films were deposited on Si (100) and stainless steel substrates with constant Ar to N₂ ratio of 15:2 sccm and sputtering power of 280 W. The crystal structure was characterized by X-ray diffraction. The Scherrers formula was used to calculated crystal size. The surface morphology and thickness were evaluated by Atomic Force Microscope (AFM). The golden coloured with uniformnity of TiN films were obtained at deposition time for 30 min. The as-deposited films color was varied with the deposition times from gold, brown and dark brown. The polycrystalline films showed reflections corresponding to the (111), (200), (220) and (311) orientations of the face center cubic TiN structure. The crystallinity of the films was increased with increased the deposition times. The AFM results indicate that the grain size of surface morphologies changed through the deposition times. With increase in deposition time, the roughness and films thickness were increased from 5.0 nm to 21.0 nm and 551.0 nm to 1.4 μm, respectively.