Chun Lin He

Effect of Al2O3 Powders on Properties of Electrodeposited Ni Matrix

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Effects of Particle Size and Volume Fraction on Extrusion Texture of SiCp/Al Metal Matrix Composites

The texture development was investigated in the extruded Al and Al metal matrix composites (MMCs) reinforced with SiC particles of different sizes and volume fractions. During extrusion, both the unreinforced Al and the MMCs develop a strong fiber texture with two components: <111> and <100>. When SiC is introduced into aluminum, the main component of texture is not modified, but the intensity of the component evolves with the volume fraction and average size of SiC particles. For the MMCs reinforced with 3.5μm SiC particles, the texture intensity of the Al matrix tends to decrease as the SiC volume fraction increases, and it is lower than that in the unreinforced Al. However, for the MMCs reinforced with 25 nm and 150 nm SiC particles, the texture intensity of the Al matrix is higher than that in the unreinforced matrix, and it increases with increasing the SiC volume fraction. It is found that superfine particles may introduce some new component into the deformation texture, and the texture intensity increases as the SiC particle size decreases.

Corrosion Resistance of SiCp/Al Metal Matrix Nanocomposites

The effect of volume fraction of SiC nanoparticles on the corrosion resistance of the SiCp/Al metal matrix composites (MMCs) in 3.5 wt.% NaCl aqueous solution were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that pitting susceptibility is about the same for the nanocomposites and the correspondingly unreinforced matrix metal Al, and the corrosion potentials of the MMCs are about 50 mV-60 mV more positive than that of the unreinforced Al, and is independent of the volume fraction of SiC nanoparticles. The corrosion resistance for the nanocomposite slightly decreases when the volume fraction increases due to both SiC nanoparticle agglomeration and promoting galvanic corrosion between SiC and Al.

Effect of Nanocalcium Oxide Addition on the Cast Microstructure of Pipeline Steel

This experiment takes the X80 pipeline steel as the research object, the thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding nanocalcium oxide into the steel with the method of carrier dispersion addition. The effect of nanocalcium oxide addition on the cast microstructure of X80 pipeline steel was analysed. The results show that the cast microstructure is consist of the ferrite and a small amount bainite. And the bainite is distributed at the boundary of the ferrite grains. When adding 0.02 wt% nanocalcium oxides, there is more bainite in the microstructure by contrast. The number of the acicular ferrite significantly increases in the cast microstructure, and the grains become more fine and uniform. Simultaneously, the granular bainite is uniformly distributed at the grain boundary and edge of the ferrite.

Effect of Nanometer Calcium and Magnesium Oxides Addition on the Inclusions in the Cast Microstructure of X80 Pipeline Steel

Nanometer calcium and magnesium oxides were added into molten steel by the carrier method in the experiment. The experiment takes the X80 pipeline steel as the research object and analyses the effect of nanometer calcium and magnesium oxides addition on the inclusions in the cast microstructure of the X80 pipeline steel. The scanning electron microscope (SEM) was used to analyse the morphology and distribution of the inclusions in the cast microstructure of the X80 pipeline steel. The results reveal that there are a small amount of inclusions in the sample of no nanometer oxides addition. With the amount of the nanoMgO oxide addition rising, the number of the inclusions in the sample firstly increases and then decreases gradually. When adding 0.05 wt% nanoMgO or CaO oxides, the size of the inclusions is big and the aggregation phenomenon appears. When adding 0.02 wt% nanoMgO or CaO oxides, the number of the inclusions in the cast microstructure is the most, whose size is smaller, about 2~4 μm and the inclusions are the most uniformly distributed.

Effect of Artificial Aging on Intergranular Corrosion of 6063 Al Alloy

The effect of artificial aging on the corrosion properties of 6063 Al alloy was investigated by optical microscope, field emission scanning electron microscope and accelerated corrosion test. Accelerated corrosion test revealed that the alloy was susceptible to intergranular corrosion (IGC) in the artificial aged conditions according to the surface corrosion morphology, and the IGC resistance was reduced as the aging time was prolonged, resulting from more Mg2Si grain boundary precipitates formed. However, the corroded cross-sections showed that the IGC was very local. Additionally, the surface corrosion morphology also showed that pitting corrosion took place, resulting from galvanic corrosion between (FeMn)3Si12Al15 particles and matrix Al.

Preparation of Anodic Aluminum Oxide Nano-Templates on Polycrystalline Silicon Substrates

The anodic aluminum oxide (AAO) templates on polycrystalline silicon substrate are studied for growth of ordered nano-dot arrays in order to fabricate the porous silicon layers. The AAO templates on polycrystalline silicon substrate with pores of average diameter 50nm were successfully prepared by one-step anodization of high pure aluminum layer deposited on polycrystalline silicon in oxalic acid solution. Scanning electron microscopy (SEM) showed that alumina nano-pore arrays were nicely constructed with smooth wall morphologies and well-defined diameters.

Fabrication of Anti-Reflecting Silicon Surfaces for Solar Cells Using Ag Assisted Chemical Etching

Antireflection of silicon surface is one key technology for manufacture of efficient solar cells. The noble metal assisted chemical etching Si wafer can quickly produce a black Si surface with a high porosity in HF-H2O2-H2O solution at room temperature. The pores formed are straight and vertical to the surface of Si. The porous Si surface exhibits a reflectivity of 2 % in the range of 200-1000 nm, which shows that this process is beneficial to improve the conversion efficiency and to decrease the cost of Si solar cells.

Effect of SiC Particle Size on Microstructure and Tensile Behavior of Aluminum Matrix Composites

The aluminum metal matrix composites (Al MMCs) reinforced by SiC particles with different sizes (25 nm, 150 nm and 3.5 m) were fabricated by powder metallurgy technique, and the microstructure and tensile properties of the Al MMCs were investigated. When the volume fraction of SiC particles is fixed to be 5 %, the Al MMCs reinforced by nanosized and submicron particles exhibit much higher ultimate tensile strength and yield strength, and much lower ductility compared with those of the non-reinforced aluminum. However, for the MMC reinforced by 3.5 m SiC particles, almost no strengthening effect is found. The strengthening effect of the Al MMCs is analyzed in terms of dislocation mechanism. Moreover, the tensile fracture surface shows that the damage mechanism of the Al MMCs can be changed as the size of SiC particles is changed.

Surface Morphologies of Sealed Film on Anodized Al Alloy

Surface morphologies of sealed films on anodized aluminum alloy extraordinarily affect on their corrosion resistance. Two-dimensional surface morphologies and three-dimensional surface morphologies of sol sealing, sodium dichromate sealing, boiling water sealing and unsealed films were obtained by OLS3100 laser scanning confocal microscope (LSCM). The three-dimensional surface morphologies show that the amounts of pores are greatly reduced when anodized aluminum 2024 are sealed by these methods. Surface roughness of sealed anodized aluminum 2024 films is increased comparing with the unsealed films, especially the boiling water sealing film. The results of two-dimensional surface morphologies show that unsealed films have plenty of spherical particles; there are raised blocks on sol film; there are much round or chrysalis cavities inside sodium dichromate sealing and boiling water sealing film. Especially there are the most and the deepest cavities with the largest diameter on the boiling water sealing film.