Journal of Advanced Processes in Materials Engineering
Year:2009 | Volume:3 | Issue:2 (9)|Papers Count:8

Uniform distribution of reinforcement particles in matrix is one of the most important parameters in composites fabrication. One way to obtain homougenous distribution is using mechanical milling for mixing powders. Therefore, it is worth identifying the optimum conditions for mechanical milling. The aim of this study is investigation of the optimum conditions for mechanical milling of Ni3Al reinforcement particles and Al powder in order to manufacture Al/5vol.% Ni3Al composite. In order to evaluate the effect of reinforcement particles on composite properties, two different kinds of reinforcement particles, i.e., oxide reinforcement particles (Al2O3) and intermetallic reinforcement particles (Ni3Al), were used. Since morphology and powder properties are affected by mecahanical milling conditions, dependency of composite properties on the mecahanical milling condition is expected. It was concluded that mechanical milling in optimum conditions causes decreasing density, increasing hardness and ultimate strength. Also, oxide reinforcement particles in compare to intermtallics cause lower increasing in hardness and considerable increase in strength and ducility.

The melting processes of Ag-x %Au (atom%) disorder alloys as well as Ag3Au and Au3Ag order alloys were studied by molecular dynamics simulation technique at the NPT ensemble. Interaction between atoms in the model alloy system was calculated by quantum Sutton-Chen (Q-SC) type of embedded atom method. The trajectories of phase space were computed by Velocity Verlet algorithm. We have computed the variation of the melting temperature with the concentration of Au. Furthermore, the variation of the thermal properties including the cohesive energy, the latent heat, the thermal expansion coefficient, the isobaric heat capacity, the density and order parameter were also calculated at different temperatures and concentrations for these materials. Our computed results show good agreement with the experimental results where they have been available.

One of the most important parameter on the forging process, is friction between Surfaces. It is sometimes useful and sometimes harmful. Most common and best friction and wear control procedure is regular lubrication. Lubricant evaluation has important role in forging process Because lubrication is cheap and easy during manufacturing. Ring test is one of the best procedures for lubricant evaluation. In this research the effect of some lubricants such as grease and Antimony oxide on the reduction of friction coefficient between part and mold investigated experimentally with ring test. Effect of lubricant on the final dimension of part and reduction of friction coefficient observed. adhesive friction change to slip friction. The friction coefficient between surfaces estimated using final dimension and simulation with ABAQUS finite element method software in various conditions. ABAQUS software calculated friction coefficient are concert with friction calibration curves in different conditions.

In this investigation mechanical alloying was used for dispersing different contents (2 and 5 wt%) of carbon nanotube (CNT) in the Al alloy (6061) powder particles. The distribution of CNTs in aluminum powder was investigated by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The size distribution of different powder mixture was evaluated by laser particle size analyzer (LPS) and the effect of milling process parameters on particle size distribution was quantified. The wear properties of bulk samples produced by hot extrusion were studied and simulated by related equations. It was concluded that the homogeneous distribution of CNTs in flattened Al powder particles could be achieved by 4h milling of Al-5 wt% CNT powder. Further milling resulted in equiaxed aluminum particles that contained embedded CNT particles. LPS results showed that the average particle size (D50) and the extension of size distribution (D90-D10) decreased during milling by increasing milling time and decreasing CNTs content. Compared with the wear properties of Al without CNTs, the results show the wear properties of Al-2 wt% CNT and Al-5 wt% CNT have increased 32% and 38% respectively. Also the simulation results of wear behavior as distance have a good agreement with experimental results.

To produce nano size hydroxyapatite aqueous solutions of calcium hydroxide and ortho-phosphoric acid were used as reactants. firstly, an aqueous suspension of ortho-phosphoric acid was slowly added gradually to an aqueous suspension of Ca(OH)2 while stirring vigorously. Concentrated NaOH was added until a final pH of 10 was obtained. The obtained material was washed using deionized water and dried in oven at 85oC for 24 h and milled using a planetary ball mill. X-ray diffraction (XRD), thermo gravimetry analysis (TGA) tests were done to elucidate crystallinity and thermal behaviour of produced nano size hydroxyapatite respectively. Transmission electron microscope (TEM) was used to investigate the particle size. The results of XRD and TEM tests proved that the produced hydroxyapatite is in nano scale with grain size of about 30 nm. The results of TGA test showed that the percentage of weight loss of all powders retained at -23, 25 and 160oC is less than 5% showing little dependency of degradation on retained temperature.

Silicon oxycarbide glass was synthesized by cohydrolysis of a precursor composed of tetraethyl orthosilicate (TEOS) and vinyltrimethoxysilane (VTMS). The effect of heat treatment on thermal stability behavior of silicon oxycarbide glass was carefully characterized by means of different techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Thermal gravimetry analysis (TGA). Silicon oxycarbide network was amorphous up to 1300oC. By increasing the temperature up to 1400oC the amorphous network undergoes structural rearrangements that lead to the precipitation very fine particle of SiC crystallites in to amorphous silica. The FTIR results showed Si-C and Si-O band in final glass. Experimental results clearly indicate the very good high temperature stability behavior and small weight loss in superior temperature.

Use of wollastonite (CaSiO3) in different industries has caused attension to produce this mineral artificially. Stone industry in Iran makes several million tones of stone waste per year which can be used as a source of CaCo3. In this study combinations of stone waste, microsilica, silica, calcium carbonate with different sizes of 400, 800, 1500, 2500 mesh are used. By different compositions, different Ca/SiO2 ratios are fired at 1100 to 1400oC. Auto clave test is used to measure free CaO and optical microscopy, XRD and SEM studies are performed. Results show that CaO/SiO2 ratio of 0.85 fired at 1300°C is the best.

Keratin film without any additive is too fragile, 10-30 wt% of chitosan addition gave strong and flexible film (ultimate strength: 27-34 MPa, ultimate elongation: 4-9%). Glycerol (20 wt%) also afforded flexibility to keratin film (ultimate strength: 1 MPa, ultimate elongation: 28%). Further addition of chitosan to glycerol-containing keratin film increased the ultimate strength to 9-14 MPa but gave little effect on ultimate elongation. Keratin-chitosan composite film was prepared by casting the mixed solution of both biopolymers in 75% acetic acid. Waterproof characteristics such as swelling behavior and mechanical properties after swelling were much ameliorated for the composite film compared with keratin-chitosan-gelatin films, respectively. Chitosan/gelatin composite films are more permeable, transparent, flexible and biocompatible films and could potently be used for contact lens material. These data suggest that mechanical properties of keratin film are adjustable by appropriately adding chitosan and glycerol.