Papers by Keyword: Nanostructured

Abstract: Nano-structured and micron Al2O3-13%TiO2 coatings were deposited by air plasma spraying.Wear properties of the coatings under different temperature trough SRV friction and wear testing machine were studied, the results shows that the friction coefficient of nano and micron Al2O3-13%TiO2 coatings both have rising trend.with the temperature increases.The wear volume of micron coating is 1.8-2 times that of the nano coating..The nanometer Al2O3-13%TiO2 coating slide with ZrO2 is still compact and has no large crack after abrasion.

Abstract: Zinc Oxide (ZnO) nanostructured was successfully synthesis by electrochemical deposition method. In this paper present the ZnO nanorods growth in a zinc nitrate/hexamethylenetetramine solution at 90°C with different potential applied. The effect of the growth process was investigated by the cyclic voltametric curve and the current-time curve. The structural of ZnO nanorods evidence that it has single crystalline, a wurtzite crystal structure with markedly preferential orientation along (001) direction was measured x-ray diffraction. The observation of ZnO nanorods was measured on field emission scanning electron microscopy that diameter of ZnO rods were below than 100 nm sizes. Uv-Vis spectrophotometer used to determine the transparency of ZnO nanorods through the UV light. The ZnO nanorods show the average transmittance (<90%) for all potential applied. The piezoelectric property of ZnO nanorods were measuring connected with two electrodes to the metal contact on the film that was driven by an ultrasonic wave. The piezoelectric output current was gained and characteristics curve have been illustrated for different voltage with constant driving frequency of ultrasonic wave at 40 kHz.

Abstract: The effects of 2at.% Ga addition on the microstructure and mechanical properties of the TiCu-base nano/ultrafine bimodal structured alloy were investigated systematically through XRD, OM, compressive test and SEM. The results showed that constitutional phases were changed from bcc -Ti(M) to unknown nanostructure + bcc -Ti(M), content of nanostructured matrix is increased, the calculated mean crystalline size was decreased from 12.6 to 11.7nm, and also, the yield and maximum strengths and plasticity were enhanced markedly. The reasons, which caused these phenomenons, were discussed.

Abstract: Pure nanostructured LaFeO₃ with crystallite size of around 13 nm and specific surface area of 48 m²/g were prepared using high energy ball milling. 0.4, 2 and 5 wt% of Pd was impregnated on synthesized LaFeO₃. TPD-O₂, TPD-CO and TPR-H₂ were performed to find the effect of Pd loading on perovskite oxide properties.CO gas sensing properties of doped and pure formulation were investigated. These results showed that 2 wt% Pd had optimum response ratio which had a maximum response ratio of 1200% with respect to 100 ppm CO in air at 140°C.

Abstract: Phase-pure nanostructured silver-doped hydroxyapatite (nAgHA) of various Ag contents was synthesised. These nAgHA were then evaluated in-vitro using human mesenchymal stem cells (hMSCs) and Escherichia coli (E. coli). Results revealed that hMSCs grew generally well on all nAgHA at all time points. In addition, fewer E. coli were seen attaching on the surface of all nAgHA. Hence, this work demonstrated that nAgHA offers considerable potential as a biomaterial.

Abstract: Nanostructured WC-17Co coatings, nanostructured WC-12Co coatings, conventional WC-17Co coatings were prepared by means of High Velocity Oxygen Flame (HVOF) technique. The characteristic of powders and coatings of nanostructured WC-17Co coatings, hardness of different coatings, distribution gradient of the hardness of the nanostructured WC-17Co coatings in the depth direction, fracture toughness and interface fracture toughness of different coatings, residual stress of different coatings, different phase and distribution of WC phase in the depth direction were investigated. The results indicated that the micro-crack is spread along the phase interface where the brittle phase are more in the Co rich area , where there are more different properties in the Co rich area and W rich area, where there are more defects close to the intend end in the W rich area, even spread through the WC particles in microcosmic and the different residual stress of different phase are because of different melting point and different expansion coefficient , so the WC, W₂C produced compressed stress, the Co₆W₆C produced tensile stress. The residual stress manifested from higher to lower in the depth direction of the coatings.

Abstract: Microstructures, thermal shock resistance and isothermal oxidation resistance of plasma-sprayed nanostructured ceria stabilized zirconia (CSZ) coatings were investigated. The results revealed that the nanostructured CSZ coatings mainly included two kinds of typical microstructures, nanosized CSZ particles embedded in the so-called matrix and micrometer-sized columnar grain structures of CSZ similar to those of the conventional coatings. Compared with the conventional CSZ coatings, the nanostructured CSZ coatings were denser and had finer and fewer porous structures and microcracks. Further study showed that the nanostructured CSZ coatings had higher thermal shock resistance and isothermal oxidation resistance compared with conventional CSZ coatings. The improved properties of the nanostructured CSZ coatings were attributed to the better coating toughness and decreased porosities and microcracks in the coatings.

Abstract: Several structural states of nanostructured zirconium were achieved by high pressure torsion (HPT) at pressures of 2 and 4 GPa with and without subsequent low temperature annealing. The nanostructured Zr was studied by X-Ray Diffraction, Transmission Electron Microscopy and Differential Scanning Calorimetry to reveal the microstructure, phase composition and the thermal stability of this material. The fine grained structure being achieved by HPT had an average grain size of 100-200 nm. It was shown that HPT at 4 GPa leads to a phase transformation from α-Zr to ω-Zr, which has been demonstrated to be reversible by annealing at 300 °C without considerable change of the grain size. The evaluation of texture evolution in Zr during HPT exhibits activity of prismatic slip systems. DSC curves confirm the presence of HPT deformation induced lattice defects and the occurrence of the ω-α phase transition in Zr.

Abstract: Black aluminium dross produced from a local aluminium smelting plant was used in this study. Solvothermal method was used to produce nanostructured alumina from this waste. Initial product obtained is of low quality with 86.9% Al2O3 content and mixed crystalline phases of 71% α-alumina and 29% calcium dodeca aluminate (CaO(Al2O3)6). The introduction of the fractional precipitation stage into the process helps in improving the purity of the alumina product to 96.5% and also produces 100% α-alumina crystalline phase. The study also shows that the crystallite size of the α-alumina products produced from this process is less than 100nm.

Abstract: Severe plastic deformation processes are used to refine grain structure by means of very high deformations. Equivalent Von-Mises strains in the range of 5.06 to 11.57 were obtained using the accumulative roll-bonding (ARB) process. The effect of the initial microstructure is analyzed. Microstructure, microhardness and tensile strength of the alloy, both starting with previously cold-rolled material and after a 30 minute, 300 °C heat treatment, are compared. The effect of a heat treatment after 5 steps of ARB ( = 8.11) is also presented. Results show that even though both the microhardness and tensile strength go up with increasing deformation, they are not related to each other by a factor of 3. The highest values of these parameters depend more on the initial microstructure than on the total deformation. A better distribution of the second phase and an increase in solid solubility are also observed after ARB.