查看更多>>摘要：TiC/TiAl composites with different TiC content were fabricated by rapid heating technique of spark plasma sintering (SPS). The effect of TiC particles on microstructure and mechanical properties of TiAl matrix was investigated. The results indicate that grain sizes of TiAl matrix decrease and mechanical properties are improved because of the addition of TiC panicles. The composites display a 26.8 percent increase in bending strength when 10 wt percent TiC is added and 43.8 percent improvement in fracture toughness when 5 wt percent TiC is added compared to values of TiC-free materials. Grain-refinement and dispersion-strengthening were the main strengthening mechanism. The improvement of fracture toughness was due to the deflexion of TiC particles to the crack.
查看更多>>摘要：Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS_3)]~(2-) on the surface of kaolinite. The correlation among structure, chemical bond and stability was discussed. Several models were selected with [Au (AsS_3)]~(2-) in different directions and sites. The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au - O covalent bond, so these models are mare stable than these with gold abate or under the layer. The models with gold near to [AlO_2(OH)_4] octahedra are mare stable than these with gold near to the vacancy without aluminium. These two stable tendencies in kaolinite-[Au(AsS_3)]~(2-) are stronger than that in kaolinite-Au systems. The interaction between [Au(AsS_3)]~(2-) and kaolinite is stronger than that between gold and kaolinite, and this interaction is strong enough to form the surface complexes.
查看更多>>摘要：BaTiO_3/PVDF nanocomposites were prepared via in-situ growth of nanosized BaTiO_3 particles in PVDF matrix by using the sol-gel method. The present elements of BaTiO_3/PVDF nanocomposites were analyzed by an electron probe X-ray microanalyser. Nanosized BaTiO_3 grown in the composite films was characterized by an X-ray diffractometer and a transmission electron microscope, and the dielectric properties of the composite films were measured. The distribution of BaTiO_3 nanoparticles in-situ grown in the PVDF matrix was examined using a scanning electron microscope.
查看更多>>摘要：To study the osteogenic ability of tissue engineered bone constructed by compounding zinc-sintered bovine cancellous bone with rabbit marrow stromal cells (MSCs) in viva, the sine- sintered bovine cancellous bone of beta-tricalcium phosphate (TCP) type was prepared by sintering the fresh calf cancellous bone twice and then loading it with zinc ion. The rabbit MSCs were cultured, induced and seeded onto the zinc-sintered bovine cancellous bones. The tissue engineered bones were then implanted into the rabbits' back muscles. The newly formed bone tissues were observed by histological methods and the areas new osseous tissues were measured at the end of the 4th and 8th week. The zinc sintered bovine cancellous bones alone were implanted on the other side as control. The osteogenic activity of MSCs was identified by alkaline phosphatase (ALP) staining and calcification nod chinalizarin staining. At the end of 4th week, a small amount of new bone tissues was observed. At the end of 8th week, there were many newly formed bone mature tissues. Moreover, the area of the latter was significantly larger than that of the former (P <0.01), while in the control group there was no new bone formation. The tissue-engineered bone, which was constructed by combining zinc sintered bovine cancellous bone with MSCs, has satisfactory osteogenic capabilities in vivo.
查看更多>>摘要：TiO_2 nanometer thin films with photocatalytic antibacterial activity were prepared by the sol-gel method on fused quartz and soda lime glass precoated with a SiO_2 layer. The thin films were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that sodium and calcium diffusion into nascent TiO_2 film is effectively retarded by the SiO_2 layer precoated on the soda lime glass. The antibacterial activity of the films was determined. The crystalline of TiO_2 nanometer thin film has important effects on the antibacterial activity of the film
查看更多>>摘要：Modified sensing membranes based on fluorescence quenching were prepared by the sol-gel method, using formamide as the drying control chemical additive, tetraethoxysilane as the main material, Ru(phen)_3Cl_2 as the indicator. The membrane with the optimum thickness of 20-50 mu m is uniform and crack-free, in which the indicator has a very small leaking rate. The membrane is immersed in water for 50h, the membrane sensing parameter M decreases by less than 5 percent. The fiber optic oxygen sensor with the sensing membrane has a detection limit of 5 X 10~(-6) M (ppm), a response time of less than 30s, excellent reproducibility and stability.
查看更多>>摘要：(Ni_(0.81)Fe_(0.19))_(0.66)Cr_(0.34) has a high resistivity and a crystal structure close to that of Ni_(0.81)Fe_(0.19). The electrical and X-ray diffraction measurements prove that a thin NiFeCr seed layer induces a well (111)-oriented Ni_(0.81)Fe_(0.19) film. Post-annealing treatment improves the magnetic properties of (Ni_(0.81)Fe_(0.19))_(0.66)Cr_(0.34) (45A)/Ni_(0.81)Fe_(0.19) (150A)/Ta(55A) thin film prepared under a deposition field, whereas the inter-diffusion of NiFe/Ta deteriorates the magnetoresistance properties of the film.
查看更多>>摘要：Polyacrylate-based conductive coatings were prepared from polyacrylate emulsion as matrix and carbon black (CB) whose surface was treated with titanate coupling agent as conducting particles. One kind of organic crystal was added to study its effects on the electrical conductivity and PTC (positive temperature coefficient) effect of the conductive coatings. Experimental results show that the coatings containing only polyacrylate emulsion and CB exhibit an excellent electrical conductivity bat bad PTC effect, and when organic crystal is added, PTC effect is characterized and can increase by 2 orders of magtitude. The critical transformation temperature of polyacrylate emulsion/CB PTC composites is decided by melting point of organic crystals.
查看更多>>摘要：The microemulsion copolymerizations of acrylic acid (AA), acrylamide (AM), N-methylol acrylamide (NMA), methylmethacrylate (MMA), butyl acrylate (BA) and acrylonitrile (AN) initiated by the redox initiator ammonium persulfate (APS) and N, N, N', N'-tetramethylethylenediamine (TMEDA) at ambient temperature were investigated. With this process high solids-content (44.0 wt percent) and small (less than 50 nm) particle diameter copolymer latexes were attained. The effects of surfactants, the mechanical stabilities and application properties as an environmentally friendly self-crosslinking pigment printing binder with multifunctional groups were studied.
查看更多>>摘要：High performance liquid chromatography with a C18 reverse-phase column was used to separate the five components in cough syrup, including acetaminophen, p-aminophenol, caffeine, chlorphenamine maleate and guaifenesin. The mobile phase consists of 15 wt percent acetonitrile, 0.004 mol/L sodium heptyl sulfonate, 0.03 mole/L potassium di-hydrogen phosphate and triethylamine (volume ratio 13:40:44:3), the pH of which is adjusted to 3.0 by phosphoric acid. The contents of the five components are analyzed on an ultraviolet spectrophotometer at 254nm, with a flow rate of 0.4 mL/min. The results show that the calibration curves are linear in a certain range. The average recovery of five components is between 96.31 percent and 102.3 percent.
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