Materials Science Forum Vols. 663-665

Abstract: The ZnSe thin films are co-deposited in the ZnSO4, Na2SeO3 and sodium citrate acidic solution, and the mechanism of the ultrasonic and pulse electrodeposition for ZnSe films is explained by the electrode-solution interface action model. Ultrasonic increases the activation energy of the [ZnCit]- and HSeO3 - and improves flow field of the solution between electrode and solution interface. The pulse current promotes the diffusion of solution and advantageously realizes the co-deposition of ZnSe films. The ZnSe thin films are pulse electrodeposited in zinc sulfate, selenite sodium and sodium citrate acidic solution with the action of ultrasonic. Finally, the ZnSe films have been characterized by the scanning electron microscope (SEM), the energy dispersion analysis of X-ray (EDAX) and X-ray diffraction (XRD).

Abstract: The experimental results on the microstructural and physical properties of the TEOS-based silica cryogels have been reported. The cryogels were produced by two-step sol-gel process followed by vacuum freeze drying. The wet gels were synthesized via acid-base catalysis using tetraethoxysilane (TEOS) as a silica precursor, the different solvents containing ethanol (EtOH), methanol (MeOH) and tert-butanol (TBA), the molar ratio of TEOS / solvent were varied from 1:6 to 1:13. Further, the microstructure and specific surface area of the cryogels were analysed by Scanning Electron Microscopy (SEM) and nitrogen absorption/desorption isotherms. The hydrophobicity of the cryogels was studied by contact angle. It was found that the highest specific surface area (1040.17 m2 / g) was obtained with the solvent of MeOH. The lowest density (0.074 g/cm3) was acquired with the solvent of EtOH.

Abstract: In recent years, ZnO/SiO2 nanocomposite thin films have attracted much attention for a wide range of device applications based on their specific optical and electrical properties. Traditionally, the ZnO/SiO2 nanocomposites were prepared at the form of thin film because the ZnO/SiO2 nanocomposite gels are difficult to synthesize. Therefore, in the present study, a novel route of the mixed ZnO/SiO2 nanocomposite cryogels were prepared by sol-gel technology and dried by vacuum freeze drying. The wet gels were synthesized by co-precursor method with the precursors containing tetraethoxysilane [Si(OC2H5)4,TEOS] and zinc acetate [Zn(CH3COO)2.2H2O]. After vacuum freeze drying, the nanocomposites were annealed at different temperature. The properties of the resulting ZnO/SiO2 nanocomposite cryogels were characterized using Scanning Electron Microscopy (SEM), nitrogen absorption/desorption isotherms, thermogravimetric and differential scanning calorimeter (TG-DSC).

Abstract: Titanate nanotubes were successfully synthesized by means of an alkaline hydrothermal method and further appropriate post-treatments. The effect of different washing treatments on the formation of titanate nanotubes were systematically studied in this paper. It was found that the washing treatments play an important role in the formation of nanotubes. Treating with 0.1M NaCl aqueous solution mainly resulted in titanate nanosheets while treating with deionized water or 0.1M HCl aqueous solution (1 time, PH>7) can obtain highly crystallized titanate nanotubes. Furthermore, if the PH values of solutions after acid washing processes were below 7, trace of nanotubes can be found but almost all of them were damaged. On the basis of all the present experimental results, we can conclude that titanate nanotubes can be prepared as long as the driving force induced by the imbalance of sodium ion (Na+) concentration on two different sides of nanosheets was appropriate, and meanwhile they were instable in acidic solutions.

Abstract: BN coated Ni nanocapsules were prepared by arc evaporating Ni-B amorphous alloy powders synthesized by a mechanochemical reaction, and their microstructure, surface component as well as electromagnetic properties (2-18 GHz) were investigated by means of high-resolution transmission electron microscopy, X-ray diffraction , photoluminescence spectra (PL) and a network analyzer, respectively. The reflection loss R (dB) of the nanocapsules less than -20 dB was obtained in the frequency range of 4.3-18 GHz for an absorber thickness of 1.4-6 mm. An optimal reflection loss of -32.0 dB was reached at 13 GHz with an absorber thickness of 2 mm. The microwave absorptive mechanisms of BN-coated Ni nanocapsule absorbent were discussed.

Abstract: A new type of antiferromagnetic CoAl2O4 coated ferromagnetic Co solid solution is synthesized by arc-discharging. Typical HRTEM images show that the nanocapsules form in a core-shell structure. The size of the nanocapsules is in range of 10-90 nm and the thickness of the shell is about 3-10 nm. X-ray photoelectron spectrum (XPS) and X-ray diffraction (XRD) reveal that the core consists of Co solid solution, while the shell is CoAl2O4. The magnetic field and temperature dependence of magnetizations confirm that the Co solid solution nanocapsules are basically in the ferromagnetic state below Curie temperature. In addition, the antiferromagnetic order occurs with Neél temperature TN of about 5 K. The saturation magnetization of Ms = 76.1 Am2/kg and the coercive force of Hc= 23.28 kA/m are achieved at room temperature for the Co solid solution nanocapsules.

Abstract: The stochastic resonance of the laser systems which the color noise correlation intensity is modulated by the time period and the noise is modulated by the signal is investigated. By means of the linear approximation method, we calculate the signal-noise ratio of the laser intensity. We discuss the influence of the noise to the evolution of the signal-noise ratio with the noise self-correlation time, and discuss the influence of the signal modulation frequency to the evolution of the signal-noise ratio with the pump noise self-correlation time. It is found that the quantum noise and pump noise present different influence, the influence of the signal modulation frequency is interrelated with the time period modulation frequency.

Abstract: Using sodium hydroxide as its alkali catalyzer, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride as its quaternary agents, cationic starch with high degree of substitution was made by semi-dry process. The prepared cationic starch contains quaternary ammonium groups by the infrared spectrum analysis. From the scan electron microscope pictures of starch and cationic starch, cationic starch can be clearly seen to have substituted the quaternary ammonium salt groups and the structure of mutual penetration of flexible quaternary ammonium salt groups and rigid starch has formed. The tensile strength of paper improved by cationic starch with high degree of substitution is far more than that by cationic starch with low degree of substitution and poly diallyl dimethyl ammonium chloride. The scan electron microscope pictures of the surface and fracture of the paper show that the distribution of the paper fiber which added additives are apparently tight and uniform and there are many small fibers obtained on the surface of paper samples. The fibers of the paper sample which added additives have more fracture themselves and have less extraction entirely. It indicates that the force between fibers has been strengthened by cationic starch additive.

Abstract: The influences of concentration of initiator, reaction temperature, concentation of monomer and reaction time on the graft rate, the graft efficiency and the monomer conversion rate of starch polyacrylamide graft copolymer were studied by orthogonal trials, and the corresponding optimum conditions were investigated firstly. Then the synthesized starch polyacrylamide graft copolymer was used to treat waste water from the bleaching workshop of one papermaking mill. Finally the first pass retention of furnish to make paper packaging material and the influences of starch polyacrylamide graft copolymer on the mechanical properties of paper packaging material were investigated. It shows that the first pass retention of furnish to make paper packaging material with the increase of dosage of starch polyacrylamide graft copolymer. With the increase of dosage of starch polyacrylamide graft copolymer, the tensile strength, the breaking length of paper packaging material increase, but the tear strength and the folding endurance decrease.

Abstract: Semiconducting orthorhombic BaSi2 films were synthesized on Si(111) substrates using magnetron sputtering (MS) and subsequent annealing by interdiffusion between the deposited Ba film and Si(111) substrate. The structural and morphological features of the result films are analysed. The growth mechanism and the evolution of the silicides are discussed. The effects of annealing temperature and annealing time on the growth of the BaSi2 film are studied.