Bucharest, Romania
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This paper presents a study on the corrosion behaviour of coatings by electroless deposition on the steel strips surfaces. For Ni-P and Ni-P-Al2O3 composite and nanocomposite layers, the variation of corrosion rate in two representative corrosive environments: an acid environment (H2SO4 solution of 5% concentration) and basic environment (NaOH solution of 10% concentration), it has been established, respectively. The corrosion rate was appreciated by using the gravimetric method (mass loss) reported to the area submitted to corrosive attack and the process duration. The study was conducted over a period of 7 days (168 hours) for the acid environment and 28 days (672 hours) in basic environment. The macroscopic appearance of the corroded surfaces was also investigated. The experimental results have emphasized a better behaviour in basic environment of composite coatings, comparatively with the Ni-P coatings with high phosphorus content. In acidic environment, a remarkable behaviour presented the composite Ni-P-Al2O3 and Ni-P alloy coatings, while samples with nanocomposite coating of Ni-P-Al2O3 were completely destroyed. © 2016, Procema SA. All Rights Reserved.

Corban M.,METAV Research Development SA | Roman I.,METAV Research Development SA | Trusca R.,University of Bucharest | Dinischiotu A.,University of Bucharest | And 3 more authors.
Revista de Chimie | Year: 2012

The titanium alloys Ti6Al4V, Ti5Al2.5Fe and Ti6Al7Nb sintered in high vacuum, about 10 -3 Pa, at 1300°C, of element powders with 200μm grain size presents spontaneous passivation in Ringer solution and submicron corrosion rate, higher electrochemical stability properties than sintered pure titanium. Titanium alloying improves the sintering quality, achieving thus a reduction of the material porosity by 10 ÷ 20% and a corresponding increase in mechanical strength. The porosity and the large specific surface area, of about 0.4m 2/g, promote cell growth and bone anchoring at the interface. The Ti6Al7Nb sintered titanium alloy was identified as the most valuable candidate for the medical implants manufacturing, based on its best passivation and hFOB cells citocompatibility properties.

Volceanov E.,ICEM SA | Aldica G.V.,National Institute of Materials Physics Bucharest | Volceanov A.,Polytechnic University of Bucharest | Constantinescu D.M.,Polytechnic University of Bucharest | Motoc S.,ICEM SA
Ceramic Engineering and Science Proceedings | Year: 2010

The aims of this study are to clarify the effect of different fast sintering techniques on densification behavior, microstructure and mechanical properties of a ZTA type composite obtained with 15 % vol. (Ca-Mg)-ZrO 2 nanosized zirconia dispersed in 85% vol. Al2O 3 matrix. Three kind of heat consolidation techniques were applied respectively on coprecipitated nanosized alumina-zirconia powders by: 1) conventional sintering; 2) microwaves field sintering at 2.45 GHz and 3) external pulsed electrical field (Spark Plasma Sintering), making possible very high heating rates. Microwave sintering of ceramics can offer certain advantages over conventional firing methods, including fast firing times and improved properties. Heat generated by the interaction of microwaves with the ceramic material results in volumetric heating of the ceramic, thus high heating rates is possible. On the other hand, a newly developed rapid sintering method, the Spark Plasma Sintering (SPS) which involves the application of electrical field and an external pressure is currently used to consolidate ceramic, metal and composite powders. SPSed high density zirconia toughened alumina (ZTA) ceramics show excellent mechanical strengths. Microstructural coarsening within ZTA is found to produce a fracture toughness increment, mainly associated with the effect of zirconia particles phase transformability. The obtained mechanical properties and grain growth kinetics are discussed in terms of microstructural features. The effects of heating technique on the far infrared and Raman spectra were investigated. Additional bands development was observed on spectra as the crystal symmetry is lowered, and certain of these bands are highly sensitive to strain-induced distortions of the crystal lattice.

Neagu Manicatide M.,ICEM SA | Neagu Manicatide P.,ICEM SA | Veteleanu A.,Transilvania University of Brasov | Ciobanu I.,Transilvania University of Brasov | Brailoiu M.,ICEM SA
Metalurgia International | Year: 2011

In the framework of the paper herein, the critical points of the phase changes and the dilatation coefficients were determined for the micro-alloyed steel of the type C-Mn-V, elaborated in order to satisfy the necessities of the auto industry, with the chemical composition: C=0,41%; Si=0,25 %; Mn=1,42 %; V=0,10 %; Al =0,025 %; S= 0,012 %; P= 0,012 %. These technological parameters were determined through the dilatometric analysis, which consists in registering the curves of the change temperatures, during heating and cooling the micro-alloyed steel, using the dilatometer. The determinations were achieved within the laboratory of physical metallurgy from ICEM SA.

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