Advanced Materials Research Vols. 189-193

Abstract: In this work, the green chemistry conversion coating on 6063 aluminium alloy surface was made and studied by means of (NH₄)₂Ce(NO₃)₆-H₂O₂ as inhibitor, HF-FeCl₃ as accelerator. The coating was evaluated in 3.5% NaCl at room temperature by using polarization curve and electrochemical impedance spectroscopy (EIS). The results show the corrosion current density and the conversion coating resistance, for the untreated or treated alloy, are 1.566 uA•cm^-2 and 6.621kΩ cm², 0.0545 uA•cm^-2 and 208.56 kΩ cm² respectively. It indicates the (NH₄)₂Ce(NO₃)₆-H₂O₂ treated surface presents better corrosion behaviour in chloride media than the original material surface. The morphologies, composition and valence state of the coating were examined by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS), respectively. The result indicates that the Ce-Mn conversion coating was made on aluminium alloy surface.

Abstract: This paper studies the technology of Electrochemical Mechanical Finishing (ECMF) on rolling bearing raceway. The principle of the technology is introduced, and the finishing results are presented. The results show that the surface roughness, supporting length rate, profile roundness, waveness and wave velocity are all improved greatly. Also, the main affecting factors such as the inter-electrode gap, electrochemical process and mechanical process are discussed in this paper. The bearings finished by ECMF have better service performance and life.

Abstract: With wide applications of FRP in civil engineering, it is necessary to study the durability of FRP reinforced concrete structure. Based on the related research both at home and abroad, the factors affecting durability of FRP reinforced concrete structures and the corresponding improvements have been put forward by analyzing the durability of concrete, FRP materials and reinforced structures, respectively.

Abstract: Nano-sized as-synthesized MCM-41 (with template) particle, whose pore channels and outer surface are full of organic CTAB template, is used as compatibilizers for immiscible polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM) blends. The mechanical properties of PP/EPDM/mesoporous MCM-41 ternary composites are investigated. The nano-structured MCM-41 (without template) material constituted by an ordered network of hexagonal channels is selected to compare with as-synthesized MCM-41 (with template) in mechanical properties of PP/EPDM blend. The results shows that tensile strength of the blend is increased by 13.6% and the impact strength is increased by 71.6% by addition 2 wt% content of as-synthesized MCM-41 (with template) compared to pure PP/EPDM. The presence of MCM-41(without template) in the blend cannot improve the mechanical properties obviously. SEM reveals that the enhancement of the interface is obtained by adding MCM-41 (with template). SEM also indicates that incorporation of as-synthesized MCM-41 (with template) into PP/EPDM blend can act as compatibilizer, which results in a decreased particle size of dispersion phase together with morphological evidence of interfacial adhesion. However, with the presence of MCM-41 (without template), the interface do not show clearly change compared with the PP/EPDM blend. The PP/EPDM/MCM-41 (with template) composites show higher tensile strength and impact strength than the PP /EPDM / MCM-41 (without template).

Abstract: A thick Fe-based amorphous and nanocrystalline composite coating was prepared by in-situ tungsten inert gas (TIG) cladding method. The results show that the cladding coating mainly consists of amorphous phase and nanocrystalline grains. The microstructure study shows that the Fe-based composite coatings have unique microstructure including nano-sized grains surrounded by nano-scale amorphous shell layer (encapsulated structure) and the homogeneously distributed dendrites/cellular crystals. The unique microstructure gives rise to the superior micro-hardness and wear resistance of the coating. The Fe-based coatings have great potential as promising wear-resistance structural materials used in electric power and cement industry.

Abstract: The effects of extraction conditions on Extraction of Dioscin from D.zingiberensis was studied in this paper. It was shown that when the ultrasonic frequency was 35.74KHz, solid-liquid ratio(D.zingiberensis:ethanol)was 1:10, ethanol volume fraction was 75%, and extracted for 30 minutes and for 3 times, the extraction rate of dioscin from D.zingiberensis reached the highest. The method of ultrasonic-assisted ethanol extraction can not only cut down extraction time, but also increase extraction yield.

Abstract: In order to improve corrosion and wear resistance of magnesium alloy, Al coating was prepared on the AZ31 magnesium alloy by the thermal spraying, then the Al-rich layer was obtained by using a CO2 laser re-melting. The microstructures and phases of the alloying layer were analyzed by canning electron microscope (SEM) and X-ray diffraction apparatus (XRD). The mechanical properties were investigated by using hardness measurement and ring-on-flat apparatus. The corrosion behaviour was investigated in 3.5% (mass fraction) NaCl solution by electrochemical measurements. The results show that there are several different microstructures in the alloying layer, such as columnar, snowflake and network structure; the alloying layer consist of Mg2Al3, Mg17Al12 and α-Mg phases. The microhardness of alloy layer is about 170HV, higher than that of the AZ31 matrix (about 50HV). The wear tests show that the wear resistance of alloying layer is considerably improved comparing with the matrix. The potentiodynamic polarization results indicate that the corrosion resistance by laser alloying is enhanced.

Abstract: The effect of direct current on the semi-solid isothermal heat-treated microstructure of ZA84 alloy is investigated. The results indicate that it is possible to produce ZA84 alloy with non-dendritic microstructure by semi-solid isothermal treatment. Furthermore, imposing direct current during the semi-solid isothermal treatment of ZA84 alloy can accelerate the non-dendritic structure evolution of the alloy. Under the experimental conditions of this work, higher the current density, quicker is the rate of non-dendritic structure evolution for the semi-solid isothermal heat-treated ZA84 alloy. Further investigations need to be considered in order to optimize the current density, isothermal temperature and holding time.

Abstract: Micro-contaminants on SUS304 stainless steel were observed and confirmed by atomic force microscope, and the micro-contaminant removal was carried out by ultraviolet (UV) illumination. The amount of micro-contaminants on the specimen surface decreased with an increase in the UV illumination time, with extensive removal of the organic substance in the contaminants but leaving part of the contained water in the contaminants. The surface for macro-droplets after the UV illumination became hydrophilic, while no large change of the wettability for micro-droplets on the same surface can be observed.

Abstract: Monitoring of tool condition is one of the most important techniques to be developed in the automatic cutting processes as it can help to prevent damages of machine tools and work pieces. Power monitoring technique is an effective method for identifying tool states. However, it is difficult to distinguish sources which led to the power signal drop. In order to solve the problem, wavelet transform algorithm was adopted to define inflexion of power signal, and wavelet threshold denoise technique was used to separate the characteristic inflexion of power signal. The simulation results show that the method is capable of detecting the cutting condition effectively.