Mirela Sohaciu

Characterization and Application Results of Two Magnetic Nanomaterials

The toxicity of heavy metals for the environment can be solved by using the adsorption properties of magnetic nanomaterials. These types of nanomaterials can remove pollutants, especially from wastewaters. This study was conducted to determine whether two magnetic nanomaterials can be used as adsorbents for heavy metals (Cr, Cd, Cu, Zn, and Ni) from aqueous solutions under acidic conditions. Qualitative and quantitative elemental information and structural and surface characteristics before and after use as adsorbents were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The obtained data showed a good correlation with the Langmuir adsorption model using the two magnetic nanomaterials in aqueous solutions. The crystalline structure of the FeO powder was identified with XRD. The TEM images of FeO nanoparticles indicated a good dispersion of particles of 85.5 nm. The SEM analysis for FeO-PAA (magnetite covered with sodium alginate) showed spherical particles of magnetite wrapped into the polymer with dimension of ∼200 nm. According to the adsorption Langmuir model, the removal efficiency for uncoated FeO decreased in order: Cr(VI) > Cu(II) > Zn(II) > Ni(II) > Cd(II). For the FeO-PAA nanocomposite (45% w/w Fe in a mass of polymer), the adsorption phenomena appears as follows: Cr(VI) > Cd(II) > Cu(II) ∼ Zn(II) > Ni(II). Langmuir parameters indicated a favorable monolayer adsorption at pH 2.5. The nanocomposite FeO-PAA can be used as an adsorbent with the same performance as uncoated FeO but with the advantage of stability under conditions where industrial wastewaters have an acidic pH.

New Bond Coat Materials for Thermal Barrier Coating Systems Processed Via Different Routes

This paper aims at describing the development of new Ru-based Bond Coats (BC) as part of Thermal Barrier Coatings. The challenge of this research was to obtain an adherent and uniform layer of alumina protective layer after high temperature exposure. We have prepared a RuAl 50/50 at% alloy in an induction furnace which was subsequently subjected to oxidation in an electric furnace, in air, at 1100C, for 10h and 100h. Mechanical alloying of Ru and Al powders was another processing route used in an attempt to obtain a stoichiometric RuAl. The alloy was sintered by Spark Plasma Sintering (SPS) and then oxidized at 1100C for 1 and10h. The alloys obtained as such were analysed before and after oxidation using advanced microscopy techniques (SEM and TEM). The encouraging results in case of RuAl alloys prepared by induction melting reveal that we obtained an adherent and uniform layer of alumina, free of delta-Ru. The results for the samples processed by powder metallurgy were positive but need to be further investigated. We should note here the novelty of this method for this particular type of application – as a BC part of a TBC system.

Metallurgical Characterization of the Failed Motor Shaft Component from an Electric Surgical Motor used in Orthopedic Surgery

The paper presents the results of research conducted to determine the causes that led to the fracture of a motor shaft component from an electric surgical motor used in orthopedic surgery.The chemical and structural analysis emphasized a structure rich in complex silicate and sulfides inclusions. They form areas of weakness, acting like stress concentrators which induce fatigue shaft breakage. Their high density and non-uniform shape and distribution suggest a non-adequate technology of making and casting of steel, destinated to work in difficult conditions and having an important operational role.

Failure Analysis of a Metallic Component Used in Hospital Cooling Equipment

The paper presents the investigations made on samples taken from the related rotor blade of an hospital cooling equipment.The failure analysis was made in order to find if the failure appear because the metallic material used or was functional problem.The objectives of our analysis and techniques used are described below:determining the chemical composition by optical emission spectrometry;determining the hardness of the material;metallographic analysis by optical microscopy;micro compositional and microstructural analysis by scanning electron microscopy (SEM) and by microanalysis, energy dispersive X-ray (EDAX). Research has highlighted the quality of piece elaboration and casting, which led to a long life of its use.