Advanced Materials Research Vols. 554-556

Abstract: One new rare-earth ternary complex with 1-naphthylacetic acid and 1,10-phenanthroline, [Eu_0.5Gd_0.5(C₁₂H₉O₂)₂(C₁₂H₈N₂)₂(H₂O)₂]•(C₁₂H₉O₂)•H₂O were synthesized. The structures were established by single crystal X-ray diffraction. The europium (gadolinium) ion is eight-coordinate with four oxygen and four nitrogen atoms forming a coordination polyhedron best describable as a distorted dodecahedral. The luminescence spectra of the complex in a solution of DMF were studied. The complex display characteristic Eu(III)-originated red emission as a sharp band at 617 nm. It is concluded that the metal-centered red emission is promoted by the ligand-assisted energy transfer.

Abstract: A research study has been undertaken to develop the fundamentals of a method for the direct dissolution of Metal Palladium. At room temperature and pressures, the reaction between sodium cyanide and platinum group metals (PGMs) does not occur because of poor kinetics. However, at elevated temperatures between 100°C and 180°C, PGMs can be dissolved by sodium cyanide like the reaction of gold. In this work, the dissolution of Palladium was measured in pressure clear cyanide solution. The data at different cyanide concentrations, different temperature and different oxygen pressure are obtained. With increasing cyanide concentration and oxygen pressure, the dissolution first increased to a maximum value and then decreased. With increasing temperature the dissolution is increased. The dissolution was found to have a relation of the cyanide and oxygen level. The dissolution were independent of rotation speed for oxygen-saturated solutions and cyanide concentrations above 5 mol.m-3 and were well below chemical reaction-limited for cyanide and oxygen.

Abstract: Wettability and interfacial characteristic of the Sn-3.0Ag-0.5Cu/Ni system are investigated by sessile drop method at the temperature range of 503~673K. The reactive wetting processes demonstrate that: contact angles between the solder and Ni substrate decrease as exponential decay and the equilibrium contact angles decrease monotonously with the temperature increasing. Triple-line mobility is enhanced as the temperature increases. Interface of the Sn-3.0Ag-0.5Cu /Ni interface are identified by EPMA and EDS analysis as (Cu,Ni)6Sn5 adjacent to the solder and Ni3Sn4 adjacent to the Ni substrate, respectively. Cu is condensed at the interface, the composition of (Cu,Ni)6Sn5 is (23.16~23.46)Ni- (36.56~37.52) Cu-(39.02~40.27)Sn (atom %). The formation of the (Cu,Ni)6Sn5 IMC was known to greatly improve the reliability of the solder joints in integrated circuits.

Abstract: The morphology and particle size of boehmite play a decisive role on the application of alumina that derived from it. In this paper, we employed pseudoboehmite that produced from Al2 (SO4)3•18H2O and NH3•H2O at 70 °C, pH 7.5 as precursor to synthesize boehmite, and utilized different seeding when preparing pseudoboehmite and boehmite. To identify the influence of seeding on the microstructure of pseudoboehmite and boehmite, the products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and BET. The results indicate that the pseudoboehmite seeding has a significant influence on the morphology and particle size of pseudoboehmite to which we should pay high attention. However, the boehmite seeding does not play the role of crystal nucleus as expected. The further intrinsic mechanism study is ongoing.

Abstract: In our work, some anomalous changes, namely the temperature-induced liquid-liquid structure transitions, were observed at the temperature hundreds degrees above the corresponding liquidus in some binary alloys. Based on the results of liquid structure transitions, corresponding solidification experiments have been carried out on the alloys melted and held at the temperature above or under the liquid-liquid structure transition (L-LST), respectively. It is found that L-LST has a significant effect on solidification behavior and microstructure. There is a general rule that the super-cooling degree increases and the microstructure becomes finer cast from the liquid experienced L-LST.

Abstract: Friction and wear tests of Al₂O₃ and SiC were conducted from room temperature to 1200 °C both in air and in vacuum. Results show that the wear mechanism of Al₂O₃ is dominated by micro fracture, debris abrasive and delamination at temperatures below 600 °C, while is controlled by plastic deformation and recrystallization among 600~1200 °C, resulting in an obvious decrease of wear loss. The wear rate and surface microstructure of SiC are closely depending on the testing temperature, atmosphere and contact pressure. Oxidation of SiC at elevated temperatures plays important role on the wear rate. Self lubrication of both Al₂O₃ and SiC at high temperatures was observed, which is mainly depending on the formation of a specific surface layer composed of nano-particles or very thin glassy film.

Abstract: The microstructure and properties of the perovskite-type SrFeCoO_3-δ (SFC) oxides synthesized by different methods were analyzed in detail in the paper. The oxide powders were synthesized by the citrate method (CM) and solid state reaction (SSR). X-ray diffraction (XRD) results reveal that the main crystal structure of the SFC powders is cubic structure SrFe_0.5Co_0.5O₃. Scanning electron microscopy (SEM) observation shows that the two kinds of powders have different grain morphologies and microstructure. Thermal gravimetric analysis and differential scanning calorimeters (TGA/DSC) results indicate that the composition loss and phase transition of the powders are related to the synthesis methods. The SFC powders synthesized by CM method show a more weight loss of various compositions than that synthesized by SSR method.

Abstract: The influence of added quantity of SiO₂ micro-powder on ceramic core properties was investigated in this paper. The results show that, the quantity of added SiO₂ powder has significant effect on the properties of ceramic core, and the room temperature flexural strength of ceramic core samples, sintered at 1550°C for 4~5 hours' holding time, increases with the increasing quantity of SiO₂. The room temperature flexural strength can reach 35MPa, when the amount of SiO₂ powder is 15%. The XRD results show that new mullite phase was detected in the composite material, and that is the key factor that helps to increase the strength.

Abstract: The syntheses, physico-chemical and spectroscopic characterization of ovan-type Schiff-base ligands (L1, L2) and their novel mononuclear Pd(II) complexes (PdL1, PdL2) are reported herein. Elemental analysis, FT-IR, ¹H NMR as well as magnetic susceptibility measurements characterised the compounds. The catalytic potential of the Pd(II) complexes for Heck coupling reaction were investigated and monitored using GC. It was observed that both Pd(II) complexes displayed properties of good catalysts for the reaction, indicated by 100% conversion of the starting materials to the subtituted alkene product after 6 hours of reaction time at 100°C in inert conditions. The catalytic activity was compared with the reaction without Pd(II) complexes.

Abstract: In the present study, CoO, which is hard to synthesize because of the chemical activity of cobalt metal, and the popular Co₃O₄ have been successfully controlled produced by a salt-assisted combustion method (SACM), in which Co(NO₃)₂•6H₂O, polyethylene glycol (PEG2000) were chosen as oxidant and fuel respectively. The CoO and Co₃O₄ nanoparticles were investigated by high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray diffraction (XRD), simultaneous thermogravimetric and differential thermal analysis (TG-DTA) and N₂ adsorption. It is found that the pure CoO were obtained whatever adjusting the weight ratio of Co(NO₃)₂•6H₂O and PEG2000 in the absence of inert salt. While, well-dispersed Co3O4 nanoparticles with a high specific surface area were successfully obtained with the introduction of NaCl or KCl in the system, which results from the fact that the introduction of inert inorganic salt as a agglomeration inhibitor into the redox mixture precursor led to the breakup of fractal nanocrystallite agglomerates. A mechanism was proposed to illustrate the possible formation processes and the role of the inert inorganic salt.