Advanced Materials Research Vols. 264-265

Abstract: This paper reports the production and weldability and toughness evaluation of TiB2 (ceramic particles) reinforced steel matrix composites. These ceramic particles are optimal reinforcements for steel matrix composites because of their high thermal stability at higher temperatures, high modulus of elasticity, good weldability, low density and relative stability within a steel matrix. This new composite family has received much attention as potential structural materials due to their high specific strength and stiffness. Thus, there is significant interest in developing iron and steel matrix composites and evaluating their dynamic behaviors due to their potential for use in the automotive industry. The goal of the research described in this paper is to study the usage of this new steel family in the manufacture of light structures. Therefore, titanium diboride TiB2 reinforced steel matrix composites were characterized by optical and scanning electron microscopy. The dynamic behaviours of the base metal and welded specimens were tested under impact crash test conditions.

Abstract: The recently developed indentation techniques are awfully advantageous as they are performing in determination of hardness and local elasticity modulus for particular conditions; also they are being able to deal with small sample sizes. This technique is well used to characterize mechanical properties as hardness, elasticity and creep for coating thin layers. Experimental comparison of common nano and micro scales for hardness evaluation has been performed on metal samples and discussed in details in the literature review [1-3]. In fact, it was well detailed that instrumented indentation was found advantageous in both repeatability and a number of measured parameters over classical hardness methods for different materials. As far as thin materials are being very used in various industrial fields, the mechanical characterization moves to micro level scale, with micro-indentation tests of thin films and from Newton -to- micro Newton for loading conditions. A big step forward has been reached for load-depth monitoring during loading and unloading in indentation cycle. Nowadays, hardness and Young’s modulus can be easily defined using Oliver-Pharr [4-5] equations based on a micro scratch test of a very thin film. In this paper an experimental study is conducted and has been validated with a numerical FE model based on a micro indentation test of a metal matrix composite material 110A, used in aeronautic applications.

Abstract: In many industrial conditions, light thin titanium shells are well used under various severe loading conditions. It is of interest to know the real conditions that govern the instability of a cracked panel subject to buckling loads in order to conserve as maximum as possible the strength of the structure. Several parameters can be varied in order to achieve this objective. The aim of this study is to determine the evolution of these parameters in order to achieve optimal crack propagation conditions while keeping these parameters within “reasonable” limits of physical and economic feasibility. For the purpose of the current study the considered structure can be regarded as thin cylindrical shell of radius r, thickness t with an initial through crack of length a. The titanium cylindrical shell is sealed on one edge and compression is applied on the other. An additional applied pressure can generates a stress and deformation field around the crack tip that has bending stresses and membrane stresses and appears as a bulge around the crack area. This paper give details of a simulation with FEA numerical analysis that determine governing instability conditions of a Titanium shell under particular loading conditions and to put in light the effect of bulging on the stress intensity factor at the crack tips. This bulging factor measures the severity of the stress intensity in the bulged crack compared to a plane shell subjected to equivalent loading conditions.

Abstract: Nanocrystallite Mg-3Al-Zn alloy was synthesized by ball milling of elemental powders of Mg, Al and Zn under hydrogen atmosphere. The powders of Mg, Al and Zn were mechanical alloying and disproportionated by ball milling under hydrogen and desorption-recombination was then performed. The structural changes due to both the milling in hydrogen and the subsequent desorption-recombination treatment were characterized by X-ray diffraction (XRD). The desorption–recombination behavior of the hydrogenation alloy was investigated by differential scanning calorimetry (DSC). The morphology and microstructure of the final alloy powders subject to desorption–recombination treatment were observed by TEM and HRTEM, respectively. The results showed that, by milling in hydrogen for 60 h, the Mg-3Al-Zn alloy was disproportionated into nano-structured with average size of about 60-70 nm, and a subsequent desorption–recombination treatment at 320°C for 30 min alloy didn’t vary the average crystallite size of powders.

Abstract: Impact of heat treatment on hot isostatically pressed (HIP) Ni-base superalloy has been investigated before and after conducting HIP process. HIP was performed by applying a stress of 120 MPa at a temperature of 1200 °C for 2 hours under argon atmosphere followed by furnace cooling to room temperature. Heat treatment cycle was conducted on the samples according to GEB50A563. Microstructural observation demonstrated the deleterious change of  morphology after HIP process which causes to decrease of hardness and creep strength. However, pre heat treatment in compared with cast specimen show slight changes in microstructure but, post heat treatment can revert this change of  morphology completely and also increase the mechanical properties.

Abstract: Experimental glass ionomer cement was prepared for the purpose of this study. Twenty disk specimens (16mm diameter x 10mm height) of test-GIC were prepared for the diametral tensile strength (DTS) test and twenty cylindrical specimens (6 mm diameter x 16mm height) were prepared for the compressive strength (CS) test. Specimens were stored in an artificial saliva at 37º C and (50±10%) of relative humidity in an incubator until testing. Five specimens of each GIC were submitted to CS and DTS test in each period, namely 1 hour, 24 hours, 7 days and 28 days. The specimens were tested in a Universal Testing Machine (Instron 1122, Instron corp., High Wycombe, U.K.) at a crosshead speed of 1.0mm/min for CS and 0.5mm/min for the DTS test until failure occurred. The results have revealed that incorporation of lithium fluoride in the formula of the test GIC might impart an increase in the mechanical properties of the GICs

Abstract: This paper reports the investigation on the flexural properties of activated carbon filled epoxy composites. The Comparison of the properties between different sources of activated carbon, are illustrated. It has to be disposed safely or used for recovery of valuable materials as agricultural wastes like bamboo stem, coconut shell and Empty Fruit Bunch (EFB). Therefore these wastes have been explored for the preparation of activated carbon and carbon black employing chemical activation by H3PO4 and physical activation, respectively. The effect of pyrolysis and chemical activation on the activated carbon filled epoxy composite properties including mechanical (flexural strength), 5 % percent of carbon filler and Scan Electron Microscope SEM micrograph were analyzed. These determined the interaction between activated carbon filled epoxy composite. This study is to compare the effect of the nature of the different types of fillers on the epoxy composites material properties. The microstructures of the farcture surface was examined using a scanning electron microscope (SEM) were formed during the different preparation stages.

Abstract: This paper reports on the effect of Sm doping concentration on structural and static magnetic properties of electrodeposited NiFe thin films. A reduction of Ni concentration from 80 to 50 percent was observed as the Sm concentration increased from 0 to 25%. XRD analyses revealed that a transition from crystalline to partially disordered state occurred on the Sm-doped NiFe thin films and ultimately transformed to amorphous state at higher concentration. The saturation magnetization decreased to ~50% at 25% Sm doping as compared to that of NiFe thin films.

Abstract: In this paper, we report on structural and magnetic properties of NiZn ferrite powders prepared by chemical co-precipitation method and calcined at different temperatures. Structural, topological and compositional analyses were performed by XRD, SEM, AFM and EDX techniques. The cation distributions in Ni0.8Zn0.2Fe2O4 ferrites were investigated by XPS (Al K
radiation: h
=1486.6 eV). Particle sizes were measured using AFM techniques and results were compared with BET technique and magnetic measurements were carried out using a vibrating sample magnetometer at room temperature.

Abstract: Silver nanoparticles protected by Tetradecyltrimethyl Ammonium Bromide (TTAB) were prepared in a one-phase electrochemical system. Electrochemical procedure, based on the dissolution of a metallic anode in an appropriate solvent, has been used to get silver nanoparticles. It is possible to get different particle size by changing the current density. The optical properties of the silver Nanoparticles were investigated by UV-Vis and Photoluminescence (PL) Spectroscopy. Absorption peak were found 424 nm which confirm the presence of Ag nanoparticles. The structural properties of the samples were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. XRD confirmed the preferential growth of Ag nanoparticles whose average size is ≈ 20 nm in the <111> orientation as well as purity of silver clusters.