Advanced Materials Research Vols. 1004-1005

Abstract: Multi-walled carbon nanotubes (MWCNT) was first treated by concentrated H₂SO₄/HNO₃, and then epoxy (EP) was filled with as-received and acid treated MWCNT. Fourier transform infrared spectroscopy (FT-IR) was used to analyze the surface characteristics of MWCNT. Result of electrical conductivity analysis reveals that the surface treatment could affect the formation of conductive network. Dynamical mechanical analysis indicates that the loss factor of composite was impaired by the incorporation of acid treated MWCNT. The tensile strength was increased with the increasing content of acid treated MWCNT.

Abstract: A series of ZnO-TiO₂ nanocomposite photocatalysts were prepared to remove TOC in Power plant Boiler Make-up Water. The catalysts were prepared by solid-state method and characterized by the means of XRD, TEM and UV-Vis. Compared with pure TiO₂, the catalytic activity of the nanocomposite photo-catalyst was improved significantly. The experiment results show that the ZnO-TiO₂ nanocomposite with ZnO/TiO₂ molar ratios of 2:1 was the most efficient photocatalysts. Under the solar irradiation (3.5×10⁴ lux) for 5 h at pH 7.0, the photocatalytic effect could be as high as 92.6% and the TOC removal efficiency was 89.4%, which indicates that photodegradation and mineralization of HA are synchronous, the two results correlate well.

Abstract: In this paper, LaMnO₃/α-Al₂O₃ magnetic nanocomposites were synthesized through using a soft-chemistry route. The synthesis strategy in this work is based on a soft-chemistry process using a polyacrylamide gel route in which citric acid is employed as the chelating agent. The composites were characterized by thermogravimetric and differential scanning calorimetry analyses, X-ray diffraction, scanning electron microscope, energy dispersive x-ray spectroscopy and vibrating sample magnetometer. Scanning electron microscope observation reveals that the content of α-alumina decreases with the increase of number of sample surface particle in the composites. Magnetic hysteresis loop measurement shows that the LaMnO₃ sample exhibit paramagnetism at room temperature. Interestingly, the weak ferromagnetism at room temperature was observed for a composition of 0.7 α-Al₂O₃ / 0.3 LaMnO₃. The forming mechanisms and magnetic properties of α-Al₂O₃ / LaMnO₃ composites have been discussed based on the experimental results.

Abstract: Corrosion behaviour of AZ91DSm1.0 with different preparation methods(vacuum melting and common melting) is investigated. X-ray diffraction(XRD), optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), corrosion weightless experiment and the potentiodynamic polarization curve are applied to characterize the corrosion behaviour. Results show that vacuum melting alloy possess higher corrosion resistance than common melting alloy. This is attributed to the rod-shaped Al3Sm which was formed in common melting alloy will have certain fragmentation effect on matrix that can lead to defects.

Abstract: Magnesium-calcium binary alloys were prepared with pure Mg and pure Ca to study the influence of Ca on the microstructure of Mg-Ca binary alloys. The results showed that with the increase of the content of Ca, there is a sharp decrease of the grain size of Mg alloy with Ca content in the range of 0 to 0.5%, then there is slight decrease of grain size with increasing the content of Ca from 0.5 to 2%; the grain size becomes increasing with further increasing the content of Ca.

Abstract: Effect of pulsed magnetic field treatment on the microstructure and mechanical properties of Mg₉₇Y₂Zn₁ alloy has been investigated. When the pulsed magnetic field is applied on the alloy in semi-solid state, the α-Mg was modified from developed dendrite to fine rosette, resulting in a refined solidification microstructure with the grain size decreased from 4 mm to 0.5 mm. The volume fraction of the second phase ( X phase) increased by about 10 %. The yield strength, fracture strength and plasticity were improved by 21 MPa, 38 MPa and 2.4 %, respectively. The improvement of mechanical properties was attributed to the refined grain size and increased volume fraction of X phase.

Abstract: High strength tungsten alloys with different deformation of 20%, 40%, 50% and 60% were prepared by swaging, and the impact strength and impact fracture morphologies were tested and observed respectively by Charpy tester and SEM to study the influence of deformation degree on fracture behavior. The results show that with the deformation degree increasing from 20% to 40%, 50% and 60%, the toughness reduces from 99J to 51J, 43J and 29J. The fracture mode of impact changes from intergranular to cleavage fracture.

Abstract: The state analysis and evaluation of the furnace pipe including of riser pipe, collecting gas pipe run over service period by EPMA, dye penetration inspection, macro and microstructure analysis, mechanical properties at room and high temperature and high temperature rupture property. The results show that the chemical composition meets the technical requirements, Macro-and microstructure are good, corrosion of inside and outside surface is minor, the remaining life of pipe analyzed is longer by fitting extrapolation of data of rupture property in the L-M curve. It is good proposal to production enterprises that higher level of material is selected to reduce the wall thickness properly, expand the diameter and improve efficiency.

Abstract: It is very important to study on the corrosion of aluminum in marine atmospheric environment, because aluminum alloy structure of weapon equipment usually serves in marine atmospheric environment. On the basis of marine atmospheric environment corrosion features, the paper summarizes the influence of marine atmospheric environment influencing factors (e.g., Relative Humidity, Concentration of cl^-, Alternate Drying-Wetting, Rainfall) on corrosion rule and corrosion rate of aluminum alloy, and analyses the mechanism of pitting, inter-granular corrosion and denudation. Then the natural environment exposure test and accelerated test were compared. Finally, the key research direction in the field of aluminum alloy corrosion in marine atmosphere was pointed out.

Abstract: The fatigue crack propagation behaviors of an Al-Cu-Mg alloy are investigated in different environments and with varying stress ratios. Fatigue experiments are carried out via a fatigue crack growth rate test in laboratory air, a 3.5% (mass fraction) NaCl solution and a tank seeper. The results show that a corrosion environment has an obvious influence on the fatigue crack growth rate, and the degrees of influence of the two different corrosive environments are basically identical. When the stress ratio is R = 0.5 and 0.06 with a decrease of the stress intensity factor, the difference in the crack propagation rates for the corrosion and air environments gradually increases. However, the corrosion acceleration in each stage of crack propagation is obvious while R=−1.