Advanced Materials Research Vols. 875-877

Abstract: Pure eulytite Bi₄(SiO₄)₃ crystals were prepared by high temperature melt cooling method using Bi₂O₃ and SiO₂ as starting materials. In this study, the properties of the samples were characterized by thermo gravimetric (TG),differential scanning calorimeter (DSC), field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that eulytite Bi₄(SiO₄)₃ was crystallized when high temperature glass-melt were cooled to 943°C and obvious exothermal peak is shown on the DSC curve; and pure eulytite Bi₄(SiO₄)₃ crystals were synthesized by keeping the processing temperature for 8 hours. Bi₄(SiO₄)₃ grains grew larger and the amount of vacancy increased along with the extension of holding time, while Bi₄(SiO₄)₃ grains still presented a structure of partial ordering. Eulytite Bi₄(SiO₄)₃ prepared through melt-cooling method is of high purity and good stability, and can be applied as starting materials of preparation of Bi₄(SiO₄)₃ thin film and high quality Bi₄(SiO₄)₃ macrocrystal.

Abstract: Copper matrix was simultaneously reinforced with nano- and micro-sized Al2O3 particles via high-energy milling of the mixture of inert gas-atomized prealloyed Cu-1 wt.% Al powder and 0.6 wt.% commercial Al2O3 powder. At the maximum of microhardness (2400 MPa) the grain size reaches the smallest value as a result of the synergetic effect of nano- and micro-sized Al2O3 particles. The relatively low decrease in microhardness during HTE may be explained by grain growth which is retarded by Al2O3 nano-sized particles precipitated at the grain boundaries.

Abstract: This paper presents the preliminary results of geological and geomechanical studies on the laterite stone exploited at Dano quarry in Burkina Faso. The field work described the geological structure of quarry sites and their environment to determine the rocks alteration and the links between the bedrock and lateritic material. Physic-mechanical properties have been studied for assessing the potentiality of this material for lightweight housing, to be completed with thermal and environmental considerations. Some social and economic evaluations are in progress in order to foster its utilization under local conditions

Abstract: This paper reports the fabrication of nanofiber scaffolds with dual gradients in both mineral content and fiber orientation, which can be used to mimic the composition and collagen fiber organization at native tendon-to-bone insertion site. Such scaffolds show great potential for rotator cuff injury repair.

Abstract: The electric papers have a wide variety of uses like in transformers, cables and power capacitors. Each application involves different requirements related to its mechanical and electric properties. The kraft is the dielectric paper most used due its high mechanical resistance and a dielectric strength of around 5 kV/mm that is increased up to 30 kV/mm when is impregnated with mineral oil and typically has a density of 0.7, nevertheless continuous improvements in the design, for example, of power transformers raise the need to improve its electrical properties particularly those related to its relative permittivity. In this article, structural parameters such as distribution and pore size of kraft paper and theoretical analysis for possible addition of nanofillers to improve their dielectric behavior are reported. A possible and better criterion for designing transformers can be the employment of kraft paper nano-inserted with 5 % of TiO2 or BaTiO3 stew in mineral oil and immersed in natural ester liquid.

Abstract: Using plasma electrolytic oxidation technique we obtained ferromagnetic coatings on titanium and alluminium. The measured coercive force, ~ 100 Oe at room temperature, is closer to the values corresponding to magnetically hard materials. The coatings are of interest as protective electromagnetic screens. The coatings were studied by XRD, XPS, XSA and SEM. There are crystallites of ~50 nm in size containing reduced and oxidized iron in the pores of the coatings. We consider that magnetic properties of the coatings are related with these crystallites.

Abstract: Ni nanoparticles dispersed in Al2O3 are prepared in-situ by the reduction of Ni(acac)2 under steady stream of [H2Al(OtBu)]2 in a cold walled CVD reactor. The decomposition temperature is moderate (~500°C) and the by-products are removed as soon as produced. The resulting powder of Ni/Al2O3 nanocomposite is characterized by powder XRD giving diffraction pattern for metallic Ni only. Elemental composition of the powder is confirmed by EDX analysis. SEM and TEM are used for the study of morphology and particle size determination. The aliphatic double bond in 1,2-trans-diphenylethene is reduced under hydrogen environment using the as prepared Ni/Al2O3 nanocomposite as catalyst. The reduction of 1,2-trans-diphenylethene is carried out at low temperature (~80°C) and atmospheric hydrogen pressure. The hydrogenation of aliphatic double bond is followed by IR and NMR spectroscopy.

Abstract: Silicon-containing oxide layers deposited on titanium using the plasma electrolytic oxidation (PEO) method were modified with manganese and cobalt compound through impregnation followed by annealing. The obtained manganese composites are catalytically active in the process of oxidation of CO at 100 оС, while cobalt-containing structures demonstrate this type of activity at temperatures above 200оС. The composition and surface structure of the obtained systems were investigated by means of X-ray phase and energy dispersive analyses and by high resolution scanning electron microscopy (SEM). Granule-like particles with diameters of a few dozens of nanometers were observed on the surface of oxide-cobalt layers on titanium, whereas the surface of oxide-manganese layers was coated by nano-whiskers of diameters <50 nm and length <1 μm. The presence of manganese-containing nano-whiskers substantially increases the catalyst specific surface, thus facilitating the attainment of higher degree of transformation of initial gaseous substances.

Abstract: The determinants of heat pipe performances are its wick and working fluid, instead of controlled by the material, dimension, and the shape of heat pipe. This study aimed to determine the effect of using nanofluid on the performance of Loop heat pipes (LHP) with CuO-water nanofluid that using biomaterials wick. LHP was made of 8 mm diameter copper pipe, with the diameter of evaporator and the condenser was 20 mm respectively and the length of the heat pipe was 100 mm. The wick was made of biomaterials Collaria Tabulate and the working fluid was CuO-water nanofluids where the CuO nanoparticles were synthesized by sol-gel method. The characteristic of the Tabulate Collaria biomaterial as a wick in LHP was also investigated in this experiment. The results of the experiments showed that the temperature differences between the evaporator and condenser sections with the biomaterial wick and CuO-water nanofluid were less than those using pure water. These results make the biomaterial (Collar) and nanofluids are attractive both as wick and working fluid in LHP technology. Keywords: loop heat pipe, wick, biomaterial, nanofluid.

Abstract: In this article, the CdS and CdS/ZnO quantum dots (QDs) were prepared by hydrothermal synthesis method. The optimal reaction conditions of CdS/ZnO QDs were obtained through experiment as follows: the pH value of solution is 10.0, the reaction temperature is 140 °C and reaction time is 24 h. While the pH value is up to10.0, Zinc ion exist in solution with Zn (OH)₂ and Zn (OH)₄^2-, which is apt to adsorb on the surface of CdS, and form to ZnO shell under the hydrothermal condition, so CdS/ZnO QDs are synthesized successfully. The photographic images and fluorescence emission spectra results showed that the colour and the peak position of fluorescence spectra of CdS/ZnO QDs is consistent with literatures, which confirming the feasibility of this method.