JOURNAL OF NEW MATERIALS
Year:2014 | Volume:4 | Issue:3 (15)|Papers Count:9

Hydroxyapatite (HA) is a ceramic with wide application in medical and dentistry due to its most important feature, bioactivity. So, researchers have tried to customize its properties such as bioactivity, mechanical strength, solubility and sinter-ability by controlling its composition, morphology and particle size. The present work deals with the synthesis of HA fabricated by calcium nitrate tetra hydrate (Ca (NO3)2.4H2O and triethyl phosphate (C2H5O)3PO4, through sol–gel method. In sol-gel method several parameters affect on the purity of HA. Since various factors, e.g. pH, aging time, calcining temperature, etc., influencing the purity of the HA, Taguchi robust design method of system optimization was used to determine the percent of contribution (%r) of each factor. It was found that the calcinning temperature had the most influence on the purity (60%).

This paper studies, the effect of input parameters (cutting speed and feed rate) on the output parameters (cutting special energy and surface roughness) in machining of ADI cost iron and 42CrMo4 steel and the machinability of these materials compared. Based on the results it was found that ADI cutting special energy is greater than 42CrMo4 steel and with increasing cutting speed in both types of materials, cutting special energy decreases. Also, the results show that ADI surface roughness is much less than the surface roughness of 42CrMo4 steel parts. The comparison was determined with increasing feed rate cutting special energy for both materials decreased and surface roughness of machined components increase.

The aim of this work is to optimize the factors affecting amorphization in synthesis of Fe-B alloy nanoparticles through chemical reduction with iron sulfate hydrated (FeSO4.7H2O) as a source of iron and sodium borohydride (NaBH4) as a reducing agent. Taguchi method with combined L9 orthogonal array was implemented and amorphization degree was considered as the property to be optimized.Four effective factors were determined such as addition rate, reaction temperature, Fe2+ ions concentration, and pH in three levels. Analysis of variance (ANOVA) was carried out over the test results and the optimal condition was determined as, follows; adding rate: 5 mlit/min, reaction temperature: 10 oC, Fe2+ ions concentration: Addition of Solution at rate of 5 mlit/min, Reaction temperature 10 oC, Fe2+ions concentration 0.1 mol/lit and reaction pH of 7. In the foregoing condition, the expected result was 96.7% and the confirmation test reached 100% amorphization degree. Moreover, Fe2+ions concentration with 55.31% contribution percent was stated as the most effective factor.

Forming limit diagram (FLD) is an effective tool to evaluate the limiting strain in various conditions. In this study the formability of tantalum has been investigated and led to forming limit diagram of tantalum. For this propose three groups of tests has been carried out on the tantalum. At first, Erichsen test has been performed on sheets of tantalum to obtain the forming limit diagram (FLD). Then for evaluating the result of Erichsen test, compression test has been carried out. The obtained FLD of Erichsen test presented a good conformity with the FLD from compression test. In addition, the strain-hardening exponent, n, for tantalum has been obtained from tensile test. The n value from results of tensile test is close to the minimum point of forming limit diagram that indicate the strain-hardening exponent.

In this study the effect of milling speed on Al/ZrO2/H3BO3 combustion system is evaluated.The powders were milled at different speed (350, 450 and 500 rpm) for 15 hours. Also, differential thermal analysis (DSC) was performed on the samples. In order to investigate the formed phases, XRD phase analysis was done on the samples. The results showed that the formation of composite has not been achieved at low speeds, and only some intermetallic phases (such as Al-B) were appeared. Also, by increasing the speed of milling, the probability of composite synthesis (in the chamber) will increase. However, increasing the milling speed up to 500 rpm leads to the formation of the composite inside the mill by mechanochemical method with releasing substantial amount of heat. Scanning electron microscopy results show that the morphology of the synthesized composite is highly porous one. The average grain size of alumina and zirconium borides were measured 58 and 42 nm, respectively.

In this paper, the effect of mechanical surface preparation such as grinding of surface by 180 grade emery papers, sand blasting and shot blasting on the quality of zinc phosphate coating is discussed. The investigation of formed layer by Scanning Electron Microscopy (SEM) technique shown that the very rough shot blasted surface was not created the suitable condition for applying a compact and fine-grained coating. On the other hand, Preparation of surface by sand blasting produced a great number of active centers on the surface and therefore reduced the final size of phosphate crystallites in comparison with grinding operation. Furthermore, the protection properties of samples were described and compared through the neutral salt spray (NSS) test and the electrochemical measuring techniques such as polarization and Electrochemical Impedance Spectroscopy (EIS). The results showed that surface preparation operation by sand blasting before phosphating, has evident influence on improving corrosion resistance. Also, the dry adhesion investigation of two diverse paint types including air dry paint (Epoxy-Polyurethane) and oven paint (alkyd - melamine paint, (Series YS)) shown that sandblasting of surface, before applying coating, improved the paint adhesion

Age hardenable aluminum alloys exhibit appropriate mechanical properties due to the formation of finely dispersed precipitates. Combination of various forming methods and heat treatment (thermomechanical processing) produce finer dispersion of precipitates. In this study influence of cold rolling on the mechanical properties of solution treated 2024 Al alloy was investigated. The results show if the samples are cold rolled immediately after quenching the roll processing could be performed successfully with higher strains. Therefore, fine dispersion of precipitates formed dynamically in the rolling direction that results inlarge enhancement in the strength of the material.

In this article, pressureless sintering of B4C-Si nano composite has been investigated. At first before beginning any laboratory operation and by using Factsage and HSC softwares, the free energy changes of reactions and the ability to reaction was examined. Then composition containing 2.5-10 wt% Si placed under uniaxial pressing and pressureless sintered at 2200oC. To evaluate the physical and mechanical properties of specimens, determination of density, micro-hardness, young modulus and fracture toughness were carried out. Also to study the microstructure of samples, microscopic images were taken by SEM. The results of the experiments showed that maximum properties were obtained for the sample containing 7.5 wt% Si which was 92% relative density, 32.2 GPa hardness, 308.45 GPa elastic modulus and 4.09 MPa.m1/2 fracture toughness.

In this study, Nano crystalline Lithium-Zinc ferrites with the chemical composition of Li0.5ZnxFe2.5-xO4 (where x=0, 0.1, 0.2, 0.3, 0.4, 0.5) was synthesized by glycine nitrate process using glycine as a fuel and nitrate as an oxidizer. Oxygen positional parameter, lattice parameter and crystallite size were estimated by Rietveld analysis of the X-ray diffraction data. Interionic distances and bound angles in the spinel structure of the as-synthesized ferrite powders were calculated using lattice parameter and oxygen positional parameter. Magnetic moment per formula unit was calculated using vibrating sample magnetometer (VSM) measurements. Phase analysis results show nanostructured Li-Zn ferrites with crystallite size in the range 29-59 nm have been formed successfully in the all samples. Saturation magnetization and magnetic moment increases with the increase in zinc concentration up to x=0.2 and after that it decreases with the increase in zinc content. The variation of magnetic moment with Zinc content x can be explained on the basis of Neel’s theory for x=0.0 to 0.2 and Yafet-Kittel model for x>0.2.