Thermodynamic Assessment of Molten Bix-Sn1-x (x = 0.1 to 0.9) Alloys and Microstructural Characterization of Some Bi-Sn Solder Alloys.

Properties such as lower melting temperature, good tensile strength, good reliability, and well creep resistance, together with low production cost, make the system Bi-Sn an ideal candidate for fine soldering in applications such as reballing or reflow. The first objective of the work was to determine the thermodynamic quantities of Bi and Sn using the electromotive force measurement method in an electrolytic cell (Gibbs' enthalpies of the mixture, integral molar entropies, and the integral molar excess entropies were determined) at temperatures of 600 K and 903 K. The second objective addressed is the comprehensive characterization of three alloy compositions that were selected and elaborated, namely Bi25Sn75, Bi50Sn50, and Bi75Sn25, and morphological and structural investigations were carried out on them. Optical microscopy and SEM-EDS characterization revealed significant changes in the structure of the elaborated alloys, with all phases being uniformly distributed in the Bi50Sn50 and Bi75Sn25 alloys. These observations were confirmed by XRD and EDP-XRFS analyses. Diffractometric analysis reveals the prevalence of metallic Bi and traces of Sn, the formation of the Sn0.3Bi0.7, Sn0.95Bi0.05 compounds, and SnO and SnO2 phases.

Design of Ti-Mo-W Alloys and Its Correlation with Corrosion Resistance in Simulated Body Fluid (SBF).

Titanium and its based alloys are frequently selected for designing biomedical implants and it is thus necessary to study as detailed as possible their corrosion behavior in biological solutions, such as those in the human body environment. In this paper, with the use of molecular orbital calculation, we designed and developed alloys in the Ti-19Mo-xW system (x = 7, 8, 9, and 10 wt%) and investigated the influence of different contents of tungsten on the behavior of Ti-19Mo-xW alloy samples following corrosion in simulated body fluid (SBF). The values of Bo¯ (bond order) and Md¯ (the metal-orbital energy level) were calculated for each alloy and correlations were established between Bo¯ and the content of tungsten. It was found that with the increase in tungsten content, the value of Bo¯ increases. Regarding the values of the corrosion resistance in SBF that resulted from the investigated alloys, the Ti19Mo7W alloy is distinguished by the lowest value of the corrosion current density and the lowest corrosion rate.

Investigations into Ti-15Mo-W Alloys Developed for Medical Applications.

The ß-Ti alloys have attracted the attention of researchers due to their excellent properties and their remarkable biocompatibility. The present study evaluated the mechanical behavior analysis (hardness, compressive strength, and modulus of elasticity) of the Ti-15Mo-W system. For experimental research, we chose the TiMo15 biocompatible alloy as a starting material. In order to improve the mechanical properties, we added tungsten amounts of 3.88 to 12.20 wt.% and analyzed the results obtained. The successive melting of the samples was done using a vacuum arc furnace in a copper crucible cooled with water. Following micro-structural investigations, we found this alloy possessed a homogeneous structure and showed ß-phase predominance. The investigated alloys have good mechanical properties-the mean Vickers micro-hardness values are between 251 to 321 HV, the compressive strength values range from 717 to 921 MPa, and the modulus of elasticity is between 17.86 and 45.35 GPa. These results are compatible to the requirements of a metallic material for medical applications as artificial implant devices.

Studies on mathematical modeling of the leaching process in order to efficiently recover lead from the sulfate/oxide lead paste.

Increasing global lead consumption has been mainly supported by the acid battery manufacturing industry. As the lead demand will continue to grow, to provide the necessary lead will require an efficient approach to recycling lead acid batteries. In this paper was performed a mathematical modeling of the process parameters for lead recovery from spent lead-acid batteries. The results of the mathematical modeling compare well with the experimental data. The experimental method applied consists in the solubilisation of the sulfate/oxide paste with sodium hydroxide solutions followed by electrolytic processing for lead recovery. The parameters taken into considerations were NaOH molarity (4M, 6M and 8M), solid/liquid ratio - S/L (1/10, 1/30 and 1/50) and temperature (40°C, 60°C and 80°C). The optimal conditions resulted by mathematical modeling of the electrolytic process of lead deposition from alkaline solutions have been established by using a second-order orthogonal program, in order to obtain a maximum efficiency of current without exceeding an imposed energy specific consumption. The optimum value for the leaching recovery efficiency, obtained through mathematical modeling, was 89.647%, with an error of δy=3.623 which leads to a maximum recovery efficiency of 86.024%. The optimum values for each variable that ensure the lead extraction efficiency equal to 89.647% are the following: 3M - NaOH, 1/35 - S/L, 70°C - temperature.

Simultaneous recovery of Zn and MnO2 from used batteries, as raw materials, by electrolysis.

High purity electrolytic manganese dioxide (EMD) is the main raw material used for manufacturing of zinc and manganese based portable batteries (alkaline with manganese AlMn and zinc carbon Zn-C). Lately, due to the progressive depletion of MnO(2) natural resources, the quantity of artificially electrolytic produced MnO(2) has started to increase to satisfy the demand. This paper describes an electrolytic process for the simultaneous production of the following components:The electrolysis process was conducted in a specialized laboratory facility. The study was particularly focused on the following electrolysis process parameters:

[Considerations on in vitro and in vivo magnetic nanoparticles hemocompatibility testing]. / O evaluare asupra metodelor de apreciere a hemocompatibilitatii nanoparticulelor magnetice.

The aim of this paper is to summarize few aspects and underline some difficulties that hemocompatibility testing come up. The purpose of hemocompatibility testing is to look for possible undesirable changes in the blood caused directly by a medical device, by chemicals leaching from a device or biomaterials. Undesirable effects of device materials on the blood may include alterations in coagulation parameters, thrombus formation, hemolysis, and immunological changes. For each different event the literature is rich in showing tests, not different in principle, but in testing conditions. ISO 10993-4 describes hemocompatibility tests in five different categories (thrombosis, coagulation, platelets, hematology, and immunology). Here we put together the tests that ISO 10993 and/or American Society for Testing and Materials (ASTM) suggest to evaluate hemocompatibility and we emphases on their utility for magnetic nanoparticules testing. The individual tests are not discussed in detail; they may be performed either in vivo or, preferably, in vitro. For each test we made few considerations with criticism. There is still some uncertainty with respect to what is actually required by the regulatory authorities for the hemocompatibility test, and there is still no harmony between ASTM and ISO 10993 regulations regarding some aspects to be standardised.

Simulating the embolization of blood vessels using magnetic microparticles and acupuncture needle in a magnetic field.

Computer models were developed to simulate the capture and subsequent deposition of magnetic microparticles (MMPs) in a blood vessel adjacent to a ferromagnetic wire (e.g., acupuncture needle) magnetized by a uniform external magnetic field. Process parameter conditions were obtained to enable optimal capture of MMPs into the deposit. It was found that the maximum capture distance of the MMPs was within 0.5-2.0 mm when the particles were superparamagnetic and had large size (>1.0 microm) and relative large flow rates (2.5-5.0 cm/s) as in a healthy artery. It was also found that the deposits were asymmetrical and that their size was between 1.0 and 2.0 mm. For the case of lower flow rates as can be found in a tumor (<1.0 mm/s) and using small magnetite particles (0.25-2.0 microm) the maximum capture distance was larger, ranging between approximately 0.5 and 6.4 mm, depending on the blood flow rate, the radius of wire, and particle clustering. The range of embolization (deposition) in this later case was between 0.5 and 5.9 mm. The potential of this technique to generate MMPs deposits to embolize blood vessels inhibiting the blood supply and thus facilitating necrosis of tumors located deep within the patient (3-7 cm) is discussed.