Advanced Materials Research Vols. 239-242

Abstract: Research the kinetic mechanism of grain growth of recrystallization of Cu-20Ni-5Sn alloy. The research result shows that the recrystallization temperature declines with the increase of cold-deformation. The recrystallization temperature is at about 500°C ~650°C respectively for 50% and 60% total cold deformation, and is about 470°C ~620°C respectively for 70% and 85% total deformation. The grains grow up with the increase of annealing temperature and holding time. The mathematic model of average grain size can be described as that Cu-20Ni-5Sn alloy annealed at 620°C ~680°C holding 2~10hours.

Abstract: The surface of brass strip is easily oxidized to cause discoloration when exposed in the air. If it contacts with the electrolyte, there will be an electrochemical reaction in the surface that lead to increasing dezincification corrosion. To improve the anti-tarnish ability, the best method is to form a protective membrane in the strip surface. Phytic acid is easily formed a stable chelate complex compound with metal ions, so that forming a dense layer to protect brass strip. It is necessary to develop a new type surface passivator which rich in phytic acid and aquae hydrogenii dioxide but without Cr which pollutes the environment. The study results show that: This passivator enable the anti-tarnish capacity significantly, and do much better results and without so much pollution than now often used dichromate passivator. The passivator solution is stable and can use longer.

Abstract: The influence of three kinds of biocide, sodium hypochlorite, dodecyl dimethyl benzyl ammonium bromide and isothiazolinone on the anti-corrosion performance of TP304 stainless steel in cooling water was studied by anodic passivation curves in this paper. The results showed that the sodium hypochlorite with the concentration above 10mg/L or the dodecyl dimethyl benzyl ammonium bromide with the concentration above 100mg/L may increase the pitting corrosion sensibility of the stainless steel in the cooling water, and the erosiveness of the cooling water to the stainless steel will increase as time goes by. Isothiazolinone with different concentrations did not influence the polarization curves of stainless steel, which indicated that isothiazolinone is a kind of safe biocide for stainless steel condensers.

Abstract: Luminescence film material plays a very important role in display technology. In this paper, electrochemical deposition of luminescent Y₂O₃:Eu or Y₂O₃:Tb thin films on transparent conducting optically ITO glass substrates by cathodes reduction of yttrium nitric was investigated. Y(OH)₃ deposits were obtained using a conventional three electrode cell that potential of work electrode was –1.2v vs. Ag/AgCl electrode for 400 s in a 0.1mol/L Y(NO)₃ with 4%(mol/mol) Eu(NO)₃ at 65°C.Then this glass was sintered for 2h at 500°C.The luminescence spectrum of the film prepared by this method was tested. Its luminescent spectrum is the same as that of powder which prepared by solid method. Its XRD confirmed the formation of Y₂O₃ and SEM revealed uniformity of film.

Abstract: A facial chemical etching method was developed for fabricating stable super-hydrophobic surfaces on aluminum alloy foils. The microstructure and wettability of super-hydrophobic surfaces were characterized by scanning electron microscopy, water contact angle (CA) measurement, and optical methods. The surfaces of the modified aluminum alloy substrates exhibit superhydrophobicity, with a CA of 164.8°±1.6° and a water sliding angle of about 5°. The etched surfaces have binary structure consisting of the irregular microscale plateaus and caves in which there are the nanoscale block-like convexes and hollows.

Abstract: A simple method to prepare hollow hydroxyapatite (HAP) microspheres with mespores on the surfaces is performed using a precipitation method assisted with Li₂O-CaO-B₂O₃(LCB) glass fabrication process. This research is concerned with the effect of sintering temperature on the microstructure evolution, phase purity, surface morphology, specific surface area, and porosity after sintering process. The microspheres were sintered in air atmosphere at temperatures ranging from 500 to 900 °C. The starting hollow HAP microspheres and the sintered specimens were characterized by scanning electron microscope, X-ray diffractometer, specific surface area analyzer, and Hg porosimetry, respectively. The as-prepared microspheres consisted of calcium deficient hydroxyapatite. The results showed that the as-prepared hollow HAP microspheres had the highest specific surface areas, and the biggest total pore volume. The pore size distribution of the as-prepared hollow HAP microspheres were mainly the mesopores in the range of 2～40 nm. The specific surface area and total pore volume of hollow HAP microspheres decreased with increasing sintering temperature. Whereas the mean pore size increased with increasing sintering temperature. It showed that at 700°C, Ca-dHAP decomposes into a biphasic mixture of HAP and β-calcium phosphate(TCP).

Abstract: The influences of rapid quenching on the structures and electrochemical behaviors of La-Mg-Ni system (PuNi₃-type) La_0.7Mg_0.3Co_0.45Ni_2.55-xFe_x (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys were systemically investigated. The results show that the rapid quenching, instead of changing the phase structures of the alloys, leads to c axis enlarged and the a axis and cell volumes of the LaNi₅ and (La, Mg)Ni₃ major phases decreased slightly. The morphologies of the as-quenched alloys exhibit a massive structure, which differ from that of the as-quenched AB₅-type alloy. The rapid quenching clearly impairs some electrochemical performances of the alloys, involving discharge capacity, high rate discharge ability (HRD) and discharge potential, but it significantly prolongs the cycle life of the alloy. With an increase in the quenching rate from 0 (As-cast was defined as quenching rate of 0 m/s) to 30 m/s, the discharge capacity of the alloy (x = 0.4) decreases from 351.06 to 313.36 mAh/s, the HRD from 69.36 to 50.54%, whereas its cycle life increases from 106 to 166 cycles at a charging discharging current density of 600 mA/g.

Abstract: The reduction rates of manganese oxide by carbon and SiC was examined by heating MnO₂-carbon and MnO₂-SiC mixtures in a 7-kW industrial microwave oven. The results show that the rate of the reduction increased with the amount of carbon in MnO₂-carbon mixture and with SiC in MnO₂-SiC mixture. The rate of the MnO₂ reduction by carbon was proportional to the reaction time, and that by SiC was proportional to 2/3 power of the reaction time. The reduction was found to be controlled by chemical reaction. The reaction rate constant of the reduction of MnO₂ k_C increased with increasing the amount of carbon in the mixtures but k_SiC decreased with increasing the amount of SiC in the mixtures.

Abstract: The two-sheets model was proposed to investigate interlayer structure and properties of Mg/Al layered double hydroxides (LDHs) containing F^-, Cl^-, Br^-, I^- and OH^- using density functional theory (DFT). The results show that four types of halogen anions in the interlayer of LDHs have the same configurations due to simple sphere structures of isolated anions. As the size of halide anions increasing, the interlayer spacing d_c increase. Mulliken charge analysis illustrates that the host layers interact with the guest anions by the electrostatic interaction and hydrogen bonding, and the charge transfers from anions to layers. The frontier orbital of the host layer interacts with that of the guest anions, and the electron transfers from HOMO of anions to LUMO of the host layer. Moreover, the order in the absolute value of binding energy is: OH^- >F^- >Cl^- >Br^- >I^-, that remains consistent with ion-exchange ability of LDHs reported.

Abstract: A magnetorheological (MR) rotary brake is a device that transmits torque by the shear stress of the MR fluids. In this paper, Bingham model is used to describe the constitutive characteristics of MR fluids subject to an applied magnetic field. The operational principle of the MR rotary brake is introduced. The torque transmitted by MR fluids is analyzed to compute the torque transmission ability in the MR rotary brake.