Advanced Materials Research Vols. 690-693

Abstract: The characteristics and the synthesis principle of nanocrystalline materials prepared by electrodeposition are summaried in this paper. The research status of nanocrystalline materials and the common methods preparing nanocrystalline materials are reviewed, such as direct current electrodeposition, pulse electrodeposition, composite electrodeposition and jet electrodeposition. Finally, some prospects on development and applications of nanocrystalline materials in material science are proposed in this paper.

Abstract: The hydroxyapatite (HA) colloids were prepared with precipitator method and characterized by means of TEM and XRD .The effect of surfactant on particle nanoHA was investigated. The results show that after modified by Polyethylene glycol (PEG), the best sample was prepared by adding 3.5% PEG solution and the HA-PEG molar ratio was 3:1. the size was about 50nm long and 20nm wide.

Abstract: Nano-hydroxyapatite colloid was prepared by the method of precipitation. when the colloid was dried and sintered,it always agglomerated.The CTAB and SDS were added to disperse it . The effects of surfactants on the size and phase of HA crystals were studied by TEM and XRD .The results showed that Nanometer columnar HA powders of 40nm long and 20nm wide with narrow distribution of particle size and dispersion performance can be prepared when we added CTAB aqueous solution into HA colloid,CTAB concentration is 0.3%, mol ratio between CTAB and HA is 3:10. As SDS aqueous solution was added into HA colloid, the best process is that SDS concentration is 0.6%, mol ratio between SDS and HA is 1:1. The prepared powder with wide distribution of particle size is 30-60nm long and 10-30nm wide.

Abstract: Fe-N amorphous alloy and ε- FexN alloy were prepared by mechanical ball milling with Fe and solid hexagonal boron nitride (h-BN) as nitrogen resource. The microstructural and magnetic transforming rules of different volume ratios of mixtures of Fe and h-BN (1:12.5, 1:5.4, 1:1.2, and 1:0.38) was studied under different ball-to-powder weight ratios. phase transition and magnetism were characterized with X-ray diffraction and vibrating sample magnetometer (VSM). According to the results, samples of the first three volume ratios have similar phase transition rules in different ball-to-powder weight ratios, and the sample with smaller ball-to-powder weight ratio costs more time in alloy formation. The changing rules and mechanisms of coercivity of four ratio samples with the extension of ball milling time has been clarified.

Abstract: In this paper, we presented a novel system of electrospinning to directly prepare fibrous meshes with micro/nanoparticles. Acetate cellulose (CA) as the material of micro/nanoparticles was dissolved in the mixture of acetone and dichloromethane as well as polyvinyl alcohol (PVA) was dissolved into deionized water, respectively. We successfully fabricated CA microspheres by an oil-in-water (O/W) emulsion/solvent evaporation technique, instilling CA solution into the stirring PVA aqueous solution. Then the hybrid solution was fabricated into a fibrous mat through electrospinning. CA micro/nanoparticles were wrapped in PVA fibers which indicated that the hybrid system of electrospinning had great potential in biomedicine when combing biodegradable microspheres with drugs.

Abstract: The field emission (FE) of the carbon nanotubes (CNTs) modified by hydrocarbon ion treatment with an energy of 80 eV has been demonstrated. Compared with untreated CNTs, the turn-on field and the threshold field of the modified CNTs decreased significantly. Scanning electron microscopy and transmission electron microscopy indicate that, after hydrocarbon ion treatment, the CNTs are coated by amorphous carbon layer at 300°C of substrate temperature and nanoparticles of graphene stacks at 700°C. It is considered that both amorphous carbon and stacked graphene coating layer can decrease the effective surface work function of CNTs and thus increase FE.

Abstract: Aluminum nanoparticles were prepared by laser and inducting heating methods, then the phase, structure and thermal properties of them were characterized by X-ray diffraction, electron microscope and simultaneous thermal analyzer, respectively. The results showed that there was great difference between micro- and nanoparticles in oxidation behavior. Aluminum micron particles had a very strong endothermic peak at the temperature of about 660°C and the absorption heat enthalpy is 328J/g.The release heat enthalpies of aluminum nanoparticles oxidized by oxygen are 4.219 kJ/g and 3.584 kJ/g. Because of the size decreases to nano-size, the aluminum nanoparticles can be oxidized directly by oxygen and release a large amount of heat, which is beneficial to the propellants when it been burn. However, the micro-particles should absorb heat which other components released, and release heat slowly after melted, which are not as good as the nano-ones.

Abstract: In this study, we prepared porous nano-hydroxyapatite/ polyamide 66 (n-HA/ PA66) porous scaffolds by injection molding method. The morphology, macrostructure and mechanical strength of the scaffolds were characterized. Osteoblasts (OBs) derived from cranial bone of SD rats were cultured and seeded on n-HA/ PA66 scaffolds. The OB/scaffold constructs were cultured for up to 18 days and the adhesion, proliferation and osteogenic activity of OBs were observed by scanning electron microscope and detected by alkaline phosphatase activity. The results showed that the porous n-HA/PA66 porous scaffolds are biocompatible and have no negative effects on the OBs in vitro. The scaffolds fulfill the basic requirements of bone tissue engineering scaffold, and have the potential application in orthopedic, reconstructive and maxillofacial surgery areas.

Abstract: The surface features of modified nano-TiO₂ were characterized by FI-TR. PP/nano-TiO₂ composites were prepared via melt blending. The mechanical properties and crystallization were analyzed by mechanical properties tests, DSC and POM. The results show that filling nano-TiO₂ to PP matrix result in the improvements of impact and tensile strength at the same time, and nano-TiO₂ plays a role of heterogeneous nucleation so that crystallization grain can be refined, crystallinity and crystallization speed of PP are increased.

Abstract: An effective and convenient method about molybdenum metal thin film microcircuit was developed on diamond anvil cell(DAC) under high pressure. Alumina film was used as the protective layer and sputtered on DAC. By using this method, we studied the electrical resistance variation about nanoparticles ZnS power up to 36GPa. The reversible phase transition had been reflected clearly by the electrical resistance measurements with sample.