Abstract: Ni foam with 3D porous structure has attracted attention in the field of catalysis. Expanding the specific surface area of Ni foam is an important method to enhance its chemical properties. In this study, the Cu-Ni/Ni foam were obtained by electroless plating copper on Ni foam and then heat treatment for homogenizing at 750°C. The dealloying of the Cu-Ni/Ni foam was carried out by electrochemical etching for obtaining the Ni foam with hierarchical pore structure. The microstructure, phase and electrochemical performance were characterized by SEM, XRD and electrochemical testing. The results showed that the optimized temperature of electroless plating Cu on Ni foam is 60oC. Ni-Cu alloy can be obtained by counter diffusion above 750°C. With prolonging time of etching, the content of Cu component decreased and the size of pores on the sturts of the Cu-Ni/Ni foam changed from nano to micro scale. The electrochemical properties of the alloywere significantly higher than that of the pure nickel foam.
Abstract: Stable TiO2 aqueous dispersion with an averaged secondary particle size of about 10 nm was achieved by using commercially available dispersant Di-7N. The stability of the dispersion was measured by Zeta-potential test. And the results showed that the optimal mass fraction of Di-7N was 12 wt%. The adsorption mechanism examined by FTIR analysis indicates that the carboxylate groups in Di-7N is absorbed on the surface of nano-TiO2 particles and the adsorbed structure is proposed to be bidentate chelating.
Abstract: In this study, a comparative investigation of the effect of two solvents on cadmium-doped zincoxide (Cd-ZnO) nanoparticles synthesized via the sol-gel method is presented and discussed. Zinc acetate was used as the precursor with ethanol and methanol as solvents, and cadmium nitrate tetrahydrate was used as the cadmium dopant source. The properties of the synthesized ZnO nanoparticles were examined by XRD, SEM, TEM,TG-DTA and UV-vis spectroscopy (UV-vis). It was found that the crystallite sizes of the ZnO nanoparticles ranged from 35 to 50nm and had spherical shapes, and that the particle size decreased with Cd doping. Consequently, absorbance spectra showed that the Cd-doped ZnO nanoparticles extended the light absorption properties of the material into the visible region. Furthermore, the ZnO nanoparticles synthesized with ethanol had a relatively smaller sizethan methanol which resulted in higher absorbance of ZnO synthesized with ethanol than methanol.
Abstract: Highly crystalline and dispersible zirconia, synthesized by solvothermal reaction of zirconium (IV) isopropoxide isopropanol complex in benzyl alcohol, were functionalized with silane coupling agent and dispersed with o-phenylphenoxyethyl acrylate (OPPEA). Silane coupling agents such as 3-aminopropyltriethoxysilane (APTES) of amino functional silane, decyltrimethoxysilane (DTMS) of alkyl functional silane and 3-(trimethoxysilyl) propyl methacrylate (MPS) of acrylate functional silane have been used to modify nanoparticle surfaces and obtain dispersion of nanoparticles within OPPEA. The surface modified zirconia was compared according to silane coupling agent, FT-IR and TGA demonstrated that APTES, DMTS and MPS are chemically attached to the surface of the zirconia. The MPS-zirconia is dispersed as about 5 nm sized, whereas the APTES-zirconia, DTMS-zirconia are agglomerated. The MPS-zirconia/tetrahydrofuran (THF) sol at 15wt% loading shows high transmittance of 68 % at 550 cm-1 and the 50wt% surface modified-zirconia/OPPEA sol show refractive index of 1.657.
Abstract: The ZrO2 nanoparticles for highly refractive index nanocomposite are synthesized according to reaction temperature, zirconium precursor concentration, and kinds of precursor such as zirconium iso-propoxide (ZIP) and zirconium n-propoxide (ZNP). At lower reaction temperature the monoclinic phase is formed, whilst higher temperature favors the tetragonal and cubic phases. As the precursor concentration increased, the particle size of ZrO2 nanoparticle slightly increased. TEM images prove that the ZrO2 nanoparticles are spherical and monodisperse with a diameter of about 4 nm. The synthesized ZrO2 was modified methacryloxy propyltrimethoxy silane (MPS) for dispersibility in organic solvent. Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) illustrate that MPS are chemically attached to the surface of the ZrO2. The ZrO2 synthesized from ZNP and ZIP dispersed in o-phenylphenoxyethyl acrylate (OPPEA) is the highly transparent and the refractive index of this nanocomposite is 1.649 and 1.670, respectively.
Abstract: Ho3+/Yb3+ co-doped ZnO-TiO2 composite system were synthesized by powder-solution mixing method and their upconversion (UC) luminescence characteristics were investigated under the 980 nm laser excitation. The effect of various ZnO/TiO2 mixing ratios, and Ho3+ and Yb3+ concentrations were also studied. The XRD patterns showed that the product fired at 1300 °C consisted of Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Ho3+ and/or Yb3+) phases. The green emission centered at 538 nm wavelength was detected as the strongest emission intensity which it was in accordance with the 5F4, 5S2 → 5I8 transition of Ho3+ ion. The emission intensity of the product changed by varying ZnO/TiO2 mixing ratios, and Ho3+ and Yb3+ concentrations. Brightest UC emission was observed in the sample of 1ZnO:1TiO2 (in mole) doped with 0.03 mol% Ho3+, 9 mol% Yb3+ fired at 1300 °C for 1 h. Besides, the dependence of the UC emission intensity on the excitation power indicated that the two-photon process was responsible for this UC system.
Abstract: Comprehending the current-voltage properties of CdZnTe device is an essential step toward improving its spectroscopic performance. Thus an in-depth analysis of I-V characteristics on Au/Cd0.9Zn0.1Te/Au device is carried out in this work. Typical non-linear transitions observed in I-V curve are found to be closely correlated with deep donor in CdZnTe. Profile of deep donor ionization probability is calculated under various biases. Afterwards the distribution of space charge and electric field is obtained. Based on these results, reasons for transitions in I-V curve are revealed. Also, related carrier transport mechanisms are confirmed.
Abstract: In this paper, a high-dense alumina ceramics were prepared through the two-step pressureless sintering process with high-purity alumina powder as raw materials and high-purity MgO as sintering aids. The effects of the sintering temperature in the first-step (T1) and the soaking time (t) in the second sintering step (T2) on the density, microstructure and mechanical properties of the alumina ceramics were studied. The results indicated that the relative density increased with the increase of T1 temperature whereas it increased and then decreased with the increase of MgO content. Higher T1 temperature and extended soaking time caused larger grain size, which accompanied with the Ostwald ripening of the grain and led to non-uniformity of grain size distribution. The addition of MgO was beneficial to the decrease in grain size due to pinning effect of the second phase. For samples with shorter soaking time, sintering with higher T1 temperature led to better mechanical properties because of its high density. However, for the long soaking time, all samples after sintering at different T1 temperature were fully-densified, so the grain size become to the dominant factor of strength, thus samples with lower T1 temperature exhibited better mechanical properties due to the refinement grain. Excessive addition of MgO resulted in defects, by which the strength increased firstly and then decreased slightly with the increased MgO content. For the samples with 2.5wt.% MgO, the optimum condition for the two-step pressureless sintering was T1=1450°C and T2=1400°C for 20h, and the obtained sample achieved the relative density of 96% and the strength of 507±32MPa.
Abstract: Siliconized graphite was prepared by liquid silicon infiltration (LSI) of carbon preforms composed of mesocarbon microbeads (MCMBs), petroleum coke and graphite powder as the carbon source with binder of phenolic resin. Effects of the carbon source, binder contents, ball-milling time and moulding pressure on the properties of the porous carbon preforms and the siliconized graphite were investigated. The results showed that the moulding pressure was the main factor influencing the open porosity of the carbon preforms. The carbon preforms with porosity of above 45% could be infiltrated completely with Si, and maximum open porosity of 56% could be reached for the carbon preforms. For the siliconized graphite, high MCMBs contents contributed to high density, while high graphite content led to increased carbon remaining. The densities, open porosities, and the highest bending strength of the siliconized graphite were ranged between 2.90-3.01g·cm-3, less than 1.5%, and 317 MPa, respectively.