Advanced Materials Research Vols. 399-401

Abstract: This work aims to eliminate contamination of the surface of crucible with silicon carbide during fusion preparation sample of the X-ray fluorescence analysis used in relation to electroless Ni–P plating process on the surface of SiC crucible in the alkaline bath. The structure, morphology and component of the coated layers were clarified by means of XRD, SEM and EDAX. Also, the electrochemical measurements was carried out to characterize the reduction mechanism of Ni deposition. The bath compositions were nickel sulfate 20 g/L, sodium hypophosphite 30 g/L, sodium citrate 10 g/L，ammonium chloride 20 g/L, containing a mixed additives of thiourea, sodium lauryl sulfate and coumarin. The thickness of coating was 3.47 μm after plating for 15 min from this bath at 318 K. The coating is relatively dense and smooth and has a nodular surface morphology. The uniform Ni–P film is a mixture of microcrystalline of Ni₅P₄ and crystalline phases of Ni in the alkaline bath, with the components of 4.74%P and 95.26%Ni. The nickel deposition reaction occurs at -1.07 V appropriately with the peak current density of 32 mA/cm² and the electrochemical deposition of nickel is mainly controlled by the electrochemical process.

Abstract: Ni–B₄C composite coatings on carbon steel substrates with various contents of B₄C nano-particulates were prepared by electrodeposition in Ni plating bath containing B4C nano-particulates. Microhardness, Scanning Electron Microscopy (SEM), Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) measurements were used to compare pure nickel coatings and Ni–B₄C composite coatings. Pure Ni coating microhardness is lower than that of Ni–B₄C coatings and the microhardness of the composite coatings increases with the increase of the content of B₄C nano-particulates. The effects of various contents of B₄C nano-particulates on the corrosion resistance were investigated and it was found that the best anti–corrosion property of Ni–B₄C composite coatings is at 6 g/L B₄C in the bath formulation.

Abstract: NiCr-Cr₃C₂-Ni/MoS₂ composite coating was prepared by supersonic plasma spraying (S-PS) process. The tribological properties of the composite coating at 25°C, 300°C, 500°Cand 750°C were studied. The wear mechanism for the coating was discussed considering the microstructures, compositions and mechanical properties of the composite materials. Results show that the coating exhibits good tribological properties at 750°C, which was attributed to the compact and continuous Cr₃O₂ transfer film formed on the friction surface. The wear rate of the coating increases with the temperature increase, which was associated with the decrease of the mechanical strength and stress-resistance of the coatings.

Abstract: Cu-Ni-Fe alloy-layer was prepared by the method of copper oxide- nickel oxide mixed powder deposited on the surface of mild steel samples and then treated under high temperature and hydrogen gas atmosphere. Polarization techniques and Mott-Schottky analysis in conjunction with the point defect model (PDM) have been used to investigate the semiconductor properties of the passive films formed on the surface of Cu-Ni-Fe alloy layer in borate buffer solution at pH 8.4. The results showed that the passive film formed on the surface was more compact, highly protective with higher heating temperature. Carriers density and vacancies diffusion coefficient of the passive film formed on Cu-Ni-Fe alloys decreased with higher heating temperature. The vacancies diffusivity is about magnitude of 10-20m2•s-1 in borate buffer solution at pH 8.4.

Abstract: Zn、Al alloy coatings were prepared by high velocity arc spraying technology on 16MnR steel substrates, With the design salt spray test, Study on the corrosion resistance of the Zn、Al alloy coating in the grotto environment. The porosity of the metal coating and the compact of the corrosion are infection on the corrosion resistance of the coating. Al coating and Zn/Al(300/100) coating corrosion resistance better than others on 16MnR steel.

Abstract: The basic formulation and technologies of phosphating for 6063 aluminum alloys were discussed to enhance the corrosion resistance. The effect of phosphating time, pH, ZnO, H₃PO₄ and NaF content on corrosion resistance was investigated using Tafel polarization methods. The results show that the optimum phosphating technologies of 6063 aluminum alloys are as follows: 7 g/L ZnO, 20 mL/L 85% H3PO4, 1.2 g/L NaF, pH 3.0, temperature 45±2°C, phosphating time 7 min. After phosphating treatment the anodic and cathodic corrosion processes of 6063 alloys are suppressed greatly, and the corrosion resistance is enhanced.

Abstract: In this study, conductive polyaniline (PANi)–titania (TiO₂) nanocomposites with core–shell structure were prepared and their anticorrosion properties were investigated. PANi/nano-TiO₂ composite were prepared by in situ polymerization of aniline monomer in the presence of TiO₂ nanoparticles. The morphology and structure of the polymer nanocomposite was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. SEM and FTIR spectra measurements show that PANi and TiO₂ nanoparticles are not simply blended or mixed up, and a strong interaction exists at the interface of nano-TiO₂ and PANi. From the anticorrosion investigation in 3.5%NaCl, it is revealed that the protective performance of epoxy paint containing PANi/nano-TiO₂ composite is significantly improved than PANi or a mixture of polyaniline and nano-TiO₂. From the improved anticorrosion performance, it also indicate that PANi and TiO₂ nanoparticles are not simply blended or mixed up, the strong interaction exists at the interface of PANi and nano-TiO2. It is the strong interaction that results in the coordinated effect and more excellent anticorrosion performance.

Abstract: Welded AA6061 Al alloy using ER5356 (Al-5Mg) filler was oxidized in flowing air gas for 40hrs at 600oC at a total pressure of approximately 1 atm. The morphology and microstructure of welded joint after exposure was characterized by using optical metallurgy microscopy and Scanning Electron Microscope (SEM). Different oxide morphologies and textures were observed on parent and fusion metal due to the differences of the alloying element. The oxidation mechanism represented a complex reaction occur where the morphology and phase formation of the oxide shows the protective oxide scales showed the protective oxide were developed on parent metal side, meanwhile non-protective oxide scale formed on fusion metal of the welded Al alloy. It can be concluded that the welded area failed to resist oxidation behavior compared to the parent metal. The differ results are discuss in term of microstructure changes caused by high temperature oxidation exposure and alloying element.

Abstract: The chemically activated method has been applied to prepare activated carbon from the incinerated medical waste. The preparation process of activated carbon was investigated under various conditions set by several factors, including the type of active agent used, the ratio of active agent and carbonized product, the activation temperature, the dwell time and heating rate. The results demonstrated KOH had shown the best performance as the active agent. The optimal preparation conditions could be described as follows: ratio of KOH and carbonized product 3:1, heating rate 5 °C/min, activation temperature 800 °C with activation time 1 hour. The activated carbon prepared under the optimal preparation conditions showed good adsorption performance. The adsorption capacities for methylene blue and iodine were 24~28 ml/0.1g and 965~1150 mg/g, respectively. BET surface area of activated carbon obtained was as high as 985.1634~1387.4586 m²/g. The activated carbon prepared from medical waste exhibited excellent characteristics of sorbent.

Abstract: Alumina nanostrips were prepared on aluminum plate surface by anodizing in oxalic acid and etching in phosphonic acid sequentially. The alumina nanostrips were characterzed by scanning and transmission electron microscopes for the morphologies structuzes,and crystal structures, by an energy dispersive x-ray spectroscope for the chemical composition, and by a photoluminescence measurement system for the photoluminescence. The results show that the alumina nanostrips are amorphous, have a chemical composition of Al2O3-x , and can emit a blue light about 440nm in photoluminescence.