Advanced Materials Research Vols. 399-401

Abstract: In this study, we report one-pot biological fabrication of gold nanoparticles by a facile procedure using lixivium of Syzygium samarangense leaf without extra surfactant, capping agent, and/or template. The resulting gold nanoparticles showed good performance in the catalytic reduction of 4-nitrophenol.

Abstract: The nanoindentation of diamond crystal [100] surface is studied in this paper, by using molecular dynamics simulation method and Tersoff potential. The total number of atoms in the model is exceed to 2,000,000. The crystal structure changes and the bond formations of C atoms under pressure load are analyzed. A light load causes lattice distortion but cannot cause bond breaking or hybridization transition from sp3 to sp2. When the load is enough heavy, the energy be imposed on the workpiece will beyond the range of lattice distortion, which can cause bond break and hybridization transition from sp3 to sp2.

Abstract: Ti film sputtered on flexible stainless steel substrate that rolled by 20-high Sendzimir Mill, was anodized in ethylene glycol bath in the presence of 0.5 wt.% NH4F and 3 vol.% H₂O at a high voltage of 60 V. High-aspect-ratio porous-nanotube arrays (PNTAs) of TiO2 with the tubes length of 6.2 µm were quickly prepared from Ti film, at the high growth rate of 20.7 nm·s^-1. Then the morphology and structure of PNTAs were characterized by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD), respectively. Finally, a DSSC with the photoanode of PNTAs exhibited a performance of J_sc = 2.40 mA·cm^-2, V_oc = 0.79V, FF = 0.57 and η = 1.08%.

Abstract: Synthesized spherical nano metal particles produced in aqueous solution have applications in printing technologies. However, an alternate method for achieving a percolation threshold is to mix the spherical shape of the particles and become net-shaped copper oxide with a minimum weight percent of particles. In this study, before reducing to copper metal, copper oxide was synthesized first without the chelating agent for achieving a net shape and copper metal nano particles were synthesized with the chelating agent, bypassing the process of creating copper oxide. Potassium sodium tartrate was the chelating agent used to control the shape of copper metal nano particles in an alkaline solution. Various concentrations of potassium sodium tartrate changed the shape of these particles from web-like at low concentrations to needlelike and more spherical at higher concentrations. Potassium sodium tartrate restrained the coordination bonds around the metal particles, controlling the shape to be more spherical. Altering the pH in absence of potassium sodium tartrate changed the conditions for the formation of particles according to the Eh-pH diagram for copper, forming net-shaped copper oxide particles when the pH was 12-13 and a cubic shape when the pH was 5-6. The composition of the nano particles in both cases was confirmed using examination by XRD. These shapes have the potential to possess favorable electrical and thermal properties as predicted by bond percolation and the percolation theory.

Abstract: In this article, a new ternary Al-Cu-Sn alloy system has been exploited through chemical dealloying in a 20wt% NaOH solution for 8 hours at different temperatures. The experimental results show the dealloying temperature plays a significant role in the formation of Cu₆Sn₅ and the length scales of the small-sized ligament/channels in fixed delloying duration. With the increase of dealloying temperature, more new phase Cu₆Sn₅ emerges and the length scales of the small-sized ligament/channels increase. Additionally, the as-dealloyed samples have three-dimensional (3D) structure composed of large-sized channels (hundreds of nanometers) and small-sized channels (tens of nanometers). Both large and small-sized pores are 3D, open and bicontinuous.

Abstract: CuO and MnCO₃ doped SrTiO₃-based multifunction ceramics were prepared respectively with solid state reaction method under vacuum condition. The electrical properties’ change with the oxidation temperature and microstructure were investigated. The results show that acceptor dopants behaves differently with the same sintering conditions. CuO-doped ceramic possess relative higher dielectric loss, dielectric constant and relative lower nonlinear coefficient, varistor voltage in contrast with MnCO₃ doped ceramic with the same contents under the same sintering conditions. The grain size of CuO-doped sample is significantly larger than the sample doped with MnCO₃. The grain distributions of CuO-doped sample is more homogeneous. The electrical properties of the ceramics are different due to the different behaviors of CuO and MnCO₃ accepter dopants during the sintering process.

Abstract: In Al-Si-C system, there are many compounds, of which Al₄SiC₄ is useful as high-temperature structure material and the antioxidant in carbon-containing refractory. In this paper, Al₄SiC₄ powders were synthesized by using kaolin grog, aluminum and activated carbon as raw materials. The phase changes of the synthesized samples were examined by X-ray diffraction (XRD), and the microstructure was observed by scanning electron microscope (SEM). The effects of synthesis temperature and the proportion of aluminum on phase compositions of Al-Si-C system were investigated. The results show plate-like Al₄SiC₄ powders can be prepared with optimal ratio of starting materials and synthesis temperature.

Abstract: Cermets Ti(C，N)_80%Co_(10-x)% TiC_10% Cu_x%(wt%，x=0，1，2，3， 4， 5) were prepared by powder metallurgy method under vacuum condition at 1500°C and the effects of Cu element to the electrical resistivity and flexural strength were studied in this paper. It turns out the electrical resistivity of the samples obviously decreases with the introduction of Cu element, but the electrical resistivity of the samples increases when the amount of Cu element in the samples becomes more. The flexural strengths of the samples decrease with the amount of Cu element increasing. Ti（C，N）_80% Co_9%TiC_10% Cu_1% shows the lowest electrical resistivity and the biggest flexural strength, 7.35*10-7Ω•m and 50.6Mpa. This may be due to the big wetting angle between Cu and the powders of the based body. With the amount of Cu element increasing, the obvious interfaces are made thus the electrical resistivity becomes bigger.

Abstract: Pure, La³⁺ doped at A site, V⁵⁺ doped at B site, and La³⁺ and V⁵⁺ co-doped ferroelectric Bi₄Ti₃O₁₂ (BTO), Bi_3.25La_0.75Ti₃O₁₂ (BLT), Bi₄Ti_2.98V_0.02O₃ (BTV) and Bi_3.25La_0.75Ti_2.98V_0.02O₁₂ (BLTV) were successfully prepared by conventional sintering technique. The structures of the ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. X-ray diffraction indicated that assemblages of all sintered ceramics consist of a single phase of Bi₄Ti₃O₁₂, implying that the A-site La³⁺ and B-site V⁵⁺ substitutions in this case do not affect the layered structure. Among these ceramics, BLTV ceramic exhibited the best electrical properties. The leakage current density of BLTV ceramic was only 1.3×10^-4 Acm^-2 at 40 KVcm^-1, two orders of magnitude lower than BTO ceramic. Besides, a saturated ferroelectric hysteresis loops with largest remnant polarization 2Pr of 30.6μC/cm² was observed for this sample. These suggested that the co-doped Bi₄Ti₃O₁₂ ceramic by La³⁺ and V⁵⁺ at A and B sites showed advantages in application over the pure BTO, doped BLT and BTV ceramic, respectively.

Abstract: The MgO-Al₂O₃ system materials were prepared at 1600°C for 3h with magnesia powder and alumina powder as raw materials and with ferric oxide powder as additive. The effect of the ferric oxide additive on the sintering and thermal shock resistance of the composite materials was studied. The results showed that increasing the ferric oxide dosage could improve the densification of the MgO-Al₂O₃ system materials. In sample MAF-0, crystal phases all are spinel phase. With the ferric oxide dosage increased from 2% to 6% in MAF-2, MAF-4 and MAF-6, the MgAl2O4 (spinel) became the primary crystal phases, and less amount of sosoloid 20MgO•19Al2O3•Fe2O3. In comparison with samples MAF-0, MAF-2, MAF-6, sample MAF-4 has better structure compactness and thermal shock resistance, the optimum ferric oxide dosage was added in MgO-Al₂O₃ system material is equal to 4%. The MgO-Al₂O₃ system material is acceptable for application in cement rotary kiln linings and high temperature gas filter support.