Advanced Materials Research Vols. 236-238

Abstract: In this work, needlelike precipitated calcium carbonate (PCC) nanometer particles were synthesized by industrial carbonation route using EDTA as crystal control agent. The morphological characterization shows that the as-synthesized needlelike PCC particles have an average diameter of 52 nm and an aspect ratio of around 14:1. The results indicate that EDTA plays a crucial role in the formation of needlelike PCC nanometer particles. A possible mechanism for the formation of needlelike PCC particles assisted by the crystal control agent EDTA is also proposed.

Abstract: We have investigated the magnetic properties, the electronic structure, and the formation energy of wurtzite GaN nanowires (NWs) with gallium vacancies by using the density-functional theory. The NW has been constructed along the [0001] direction. It was found that Ga vacancies prior to reside on the NW surface due to the lower formation energy. Interestingly, it was found that the GaN NWs with a Ga vacancy can show induced local magnetic moment in N atoms, with a magnetic moment about 0.60 uB. The study of vacancy-vacancy interactions indicates that the NWs prefer ferromagnetic ground state. We further confirmed that the total magnetic moments can be increased by increasing the Ga vacancy concentration without significant energy cost. The theoretical results are in good agreement with the recent experimental observations. Our findings are helpful to gain a more novel understanding of structural and spin properties of Ga vacancy in wurtzite GaN NWs, and also provide a possible way to generate the low dimensional magnetic GaN nanostructures by introducing Ga vacancies instead of doping with transition-metal atoms.

Abstract: Mesoporous silica microsphere was prepared by microwave hydrothermal synthesis，using hexadecyl trimethyl ammonium bromide (CTAB) as template agent and tetraethylorthosilicate (TEOS) as silica source. And mesoporous silica microspheres doped with TiO₂ was prepared by sol-gel method. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR) and N₂ adsorption-desorption analysis. Then methylene blue decoloration test was investigated to verify the mechanism proposed elsewhere, with respect to concentration, amount of samples, pH and light illumination. Results indicate that low concentration, large amounts of samples, alkaline and UV illumination are more favorable to adsorption, and TiO₂/MSM has higher decoloration rate than MSM.

Abstract: Using self-determined design of SPJ-40 experimental twin-screw extruder to extrude the banana peel is investigated in this study. Results revealed that the best extrusion conditions were: banana peel and starch at rate of 2:8, feed moisture at 16%, screw speed at 268r/min, extrusion temperature at 150°C, and feeding rate at 20r/min. The structures of the products were determined after the extrusion. The electron microscopy showed that the structure of the starch powders and fibers had been greatly damaged, leading to the great increasing of surface area of processed products. Compared to the raw material, the crystallinity of products was down to 13.06% from 19.85%, but soluble dietary fiber was increased by 30.3 percent. The final product tastes delicate with palatable aroma. Overall, this extrusion technology for processing banana peel has bright prospect in application.

Abstract: In this paper, a strain gradient model is constructed to predict the bending size dependence of the elastic property of nanofibers under three-point tests. The model prediction shows that there are two kinds of size dependency for the bending tests: one is related to the diameter of the nanofiber, which can be named as Diameter Size Dependency (D-SD), the other is related to the length of the nanofiber, which can be termed as Length Size Dependency (L-SD). Mechanical testing on PCL nanofibers was performed to verify the model for D-SD, and good agreement is found between the model prediction and the data obtained in the experiment. The model can be applied to explain the size dependency in bending test for polymeric nanofibers.

Abstract: A novel missile-like ZnO structure has been synthesized solvo-thermally in absolute alcohol using Zn(NO₃)₂·6H₂O and NaOH as starting materials, and characterized by Scanning Electron Microscopy, powder X-ray diffraction and room temperature photoluminescence. The missile-like ZnO crystal, with a wurtzite structure and a blue-green emission at 459 nm, is made up of two symmetrical rocket-like crystals possessing a prismatic base and a hexagonal pyramid linking with each other along plane (0001(_)).

Abstract: In this paper, a higher order strain gradient model is constructed to predict this size dependence of the elastic property of nanofibers under uniaxial tensile tests. We can show that the size effects in tensile test can be explained using a new model based on the higher order strain gradient elasticity (HSGE). A series of mechanical testing were performed to verify the model, and good agreement is found between the model prediction and the data obtained in the experiment. Compared with the model prediction based on surface effect (SE), our model can better capture the size effect in tensile test.

Abstract: Bulk nanocrystalline Fe₃Al based materials with 5, 10 and 15 wt. % Cu were prepared by aluminothermic reaction in which the melts were superheated about 1600 K before solidification. Microstructures of those materials were investigated by optical microscope, electron probe microanalysis, X-ray diffraction and transmission electron microscope. It was shown that microstructures of the materials consisted of a nanocrystalline matrix phase and a little contamination Al₂O₃ and Fe₃AlC_x fiber phases. The nanocrystalline matrix phase was composed of Fe, Al and Cu elements and disordered bcc which did not change with content of Cu. Average grain sizes of the nanocrystalline phase of the materials with 5, 10 and 15 wt. % Cu were 18, 24 and 25 nm respectively and that of the material with 5 wt. % Cu was the smallest. Compressive properties of the materials were tested. The material with 5 wt. % Cu has good ductility compared with the materials with 10 and 15 wt. % Cu. Yield strength of the materials was about two times higher than that of coarse grained Fe₃Al material. The compressive yield strength of the material with 5 wt. % Cu was higher than those of the materials with 10 and 15 wt. % Cu and its flow stress in compression was up to about 1500 MPa.

Abstract: Silver nanoparticles pastes were formatted by mixing different volumetric silver nanoparticles with the mixture of 12.7wt% bismuth subgallate and 87.3wt% organic vehicle. Rheological and flocculated properties of silver nanoparticles pastes were examined. All pastes demonstrated pseudoplastic flow behaviors and shear thinning characters over the solids-loading and shear-rate range studied. The viscosities of pastes reduce with increasing the shear rate in a logarithmic plot. G' (storage modulus) and G" (loss modulus) increase with increasing silver nanoparticles content and frequency. At high loading, G' and G" begin to level off and exhibit plateau in the low-frequency range. The appearance of the plateau at low frequency is due to the presence of silver nanoparticles in the system and forming the three-dimensional network structure. The shear stress increases with increasing silver nanoparticles content. Apparent yield value estimated by casson equation exhibits a power-law dependence on particle volume fraction.

Abstract: The factors such as power, action mode and action time of ultrasound were studied about their effects on the sulphitation and neutralization process in cane juice. The best result was achieved when the ultrasound was applied at the power of 300 W and in the progress of neutralization. The result showed that ultrasound could help to improve the quality of clarified juice. Compared with those without ultrasound field, the residuals of Ca²⁺ and SO₂ decreased by 4% and 21.4%, respectively, and the color value decreased by 10.2%, and apparent purity improved by 0.91% in average. The result of this study provided reference for the application of ultrasound in the sulphitation and neutralization process.