Advanced Materials Research Vol. 856

Abstract: The behaviour of metallic powders is very important for manufacturing parts and for realize the prototypes. Manufacturing of the orthopaedic implants by selective laser sintering process can be used in medicine. The powders necessary for SLS process are biomaterials who must assure a good osteointegration of endobone implants like the Ti powder (Ti-6Al-4V) and the hydroxyapatite powder. The conditioned powders is a very important process and is necessary in SLS to obtain medical prothesis and influence the final properties of prothesis. Materials must present a gradient for porosity and one for composition (presents of a bioactive phase in titan matrix). The exterior porosity, in the contact zones with the bone tissue, favors the incipient cellular processes (the adhesion and attachment of osteoblastes, proliferation and cellular differentiation and nucleation of mineral bone). The pores must be open and with a specific surface more great. Its preferred the exterior intercommunicating porosity. The presence of phosphates of calcium in the contact zone of the implant with bone favors the mineral kernel on bone. The report Ca/P of phosphates mineral bone has an ascending evolution towards 10/6 according to hydroxyapatite.

Abstract: Polyurethane foam is widely used in numerous applications. The quasi-static mechanical behaviour of polyurethane foam shows a nonlinear elasticity and a viscoelasticity in large compression deformation. In this paper, the uniaxial compression / decompression tests in three different strain rates are performed. The purpose of this paper is to propose three visco-hyperelastic models and to identify the parameters based on the experimental results. A difference-stress proper identification method is used to obtain the model parameters. The results show that the three models can predict the mechanical behaviour of polyurethane foam very well. Finally, the three models are compared according to the model results.

Abstract: A new and efficient method is presented for the analysis of arbitrarily shaped discontinuities. The technique obtains closed form expressions for the equivalent circuits which are used to model these discontinuities. Then it would be easy to handle and to characterize complicated structures like T and Y junctions, truncated junctions, arbitrarily shaped junctions, cascading junctions and more generally planar multiport junctions. Another advantage of this method is that the edge line concept for arbitrary shape junctions operates with real parameters circuits. The validity of the method was further confirmed by comparing our results for various discontinuities (bend, filters) with those from HFSS as well as from other published sources.

Abstract: For the numerical simulation of fluid mechanics problems in complex geometries, the use of the classical grid methods such as the finite element method and the finite volume method can give rise to several problems related to the deformation of the mesh. In this work, a meshfree Lagrangian method is used to avoid these problems. This method called Finite Point Method (FPM) has been developed by Kuhnert. It consists in representing the fluid domain by a set of particles. The efficiency of this method is pointed by studying the problem of polyurethane foaming. To do so, we have adopted a theoretical model describing the contribution of the chemical kinetics and the rheological coupling characterizing such process. This coupling is displayed through the dependency of the fluid viscosity to the evolution of the temperature and the chemical reactions present during the foaming process. The expansion of the mixture is governed by the front velocity which is calculated by solving the Navier-Stokes equations. Compared to the experimental results for polyurethane foaming process in a conical beaker, the numerical results using the FPM code are acceptable.

Abstract: BiFeO₃ nanoparticles have been synthesized by sol-gel method. The deposition of Au on the surface of BiFeO₃ has been done using photo-deposition method. X-ray diffraction confirms that the synthesized nanoparticles are possessing rhombohedral structure with R3c space group. The average particles size of the synthesized nanoparticles found to be 26 nm. Synthesized nanoparticles possess band gap 2.28 eV, in the visible region. The dye-sensitized solar cells (DSSCs) have been fabricated using synthesized nanoparticles. The effect of Au-deposition on photovoltaic performance of DSSCs has been investigated. The different performance parameters of fabricated DSSCs viz. open-circuit voltage (V_OC), short circuit current-density (J_SC) and fill factor (FF) found to be 0.75 V, 6.5 mA/cm², 0.62, respectively. The high energy-conversion efficiency 2.99%, has been achieved in Au-deposited BiFeO₃ based DSSCs.

Abstract: To improve the electrical performance and reduce the fabrication cost of the solar cell, thin-film solar-cell concepts are widely explored. In this context, many studies have been carried out to study the impact of the thin thickness of the material on the solar cell behavior. Recently, the Si_1-xGe_x/Si heterostructure is considered as attractive alternative for photovoltaic applications due to their band structures, which allow getting an additional gain in the device efficiency. However, the growth of this material is not totally controlled, and the presence of interfacial defects is more than estimated after a growth run of this material. Therefore, new experimental and numerical investigations which capture the Si1-xGex/Si heterostructure behavior should be developed in order to build a complete Si_1-xGe_x/Si-based solar cell model for photovoltaic applications. In this paper, we aim at highlighting the immunity of the Si_1-xGe_x/Si heterostructure against the defects degradation effect at nanoscale level (thin films). The effect of interface defect on the heterostructure has been carried out by extensive simulation using Atlas 3-D simulator, including the device dimension and the Ge Mole fraction effects.

Abstract: In this paper, AZO thin films of different thicknesses were deposited on glass substrates as transparent conducting (TCO) films by changing the deposition time using a DC magnetron sputtering method. The effect of film thicknesses on the structural and optical properties of AZO films was investigated using X-ray diffractometer (XRD) and spectrophotometer, respectively. Results show that increasing the film thickness results in decreasing the optical transmittance. The optimum properties were obtained for a film with 500 nm thickness and 90 min deposition time, which exhibited a transmittance of 95%.

Abstract: View of the importance that has the development in the field of advanced technology transmission in human life, smart materials draws the attention of many researchers. In this contribution, we are interested in synthesizing a new smart material of the ceramic type based on Pb, Zr, Ti (PZT) doped La in the site A, and Sb, Zn in site B from a solid solution of pure oxides. The synthesized samples are thermally treated at 800°C. The techniques of x-ray diffraction (XRD) and SEM (scanning electron microscopy) are used to characterize the microstructure (the crystallographic phase), and the densities of the obtained samples were determined from their weights and volumes. The effect of sintering temperature on the microstructure properties was studied.

Abstract: X-ray diffraction method has been used to analyze the residual stress distribution across the joint of Al-Si-12Cu alloy just after welding process. On the other hand, isothermal heat treatments have been applied in order to study the residual stress evolution in this material. Optical microscope observation and Vickers hardness measurement have been carried out as complementary microstructure techniques. The different zones of welded joint have been analyzed, where the fusion zone was characterized by dendritic structure and different to heat affected zone. We have found a softening phenomenon in welded joint after heat according to microhardness results.

Abstract: Hydroxyapatite (HA) is bioactive and biocompatible bioceramics that is commonly used as a filler to replace amputated bone or as a coating to promote bone ingrowth into prosthetic implants. The need to overcome biocompatibility problems and improve the bone bonding ability enforced the researchers to develop suitable coating techniques. Feasibility of Powder Mixed Electrical Discharge Machining of Ti-6Al-4V alloy with HA additives in water dielectric liquid is studied as an alternative coating technique. Machined samples are analyzed by means of optical, scanning electron microscopy and energy dispersive spectroscopy. The experimental results have revealed that it is possible to deposit HA powders onto the work material surface by using the process. The morphology of the deposited material signified the dependency with respect to the operational parameters such as pulse on duration and current. Moderate pulse currents together with low pulse on duration were found to be the plausible choices for HA coating applications.