Papers by Author: Eugeniu Vasile

Abstract: Apatite containing-polymer beads have been prepared using two methods. The first series of scaffolds is obtained using an effortless procedure consisting in mixing the mineral phase in the polymer precursors, followed by crosslinking. The resulting materials contained agglomerates of inorganic particles. The second series of materials is generated through a more complex synthesis involving the alternate Ca²⁺/PO₄^3- soaking of the polymer beads. This leads to formation of nanometric apatite phase homogeneously distributed within and on the surface of the polymer substrates. The resulting materials have been characterized by infrared spectrometry, X-ray diffraction and scanning electron microscopy.

Abstract: Casein is a phosphoprotein and accordingly, its capacity to induce formation of apatite was investigated using a biomimetic method. The protein was physically immobilized into a synthetic polymer network generating hybrid scaffolds. The obtained hydrogels contained uniformly distributed nanosized casein grains. The incubation of such materials in synthetic body fluid (SBF 1.25x) led to formation of nanosized biologic-like apatite. The resulting materials have been characterized by infrared spectrometry and scanning electron microscopy.

Abstract: Samples of 316L austenitic steel were submitted to a thermochemical treatment which implies surface diffusion of Al and Ti. The technique of pack cementation with NH4Cl as activator was employed. The powder mixture was made of aluminium, titanium, aluminium oxide and ammonium chloride. The same ratio of Al : Ti = 1 : 5 was used in all experiments. The variables were temperature and time. As a function of these parameters, diffusion layers of different thicknesses were obtained. The samples were analyzed by optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX), X-ray diffraction and Vickers microhardness trials. All layers were formed by diffusion with reaction and present two zones with different structures and compositions and therefore different properties. The Ti3NiAl2N compound was identified by X-ray diffraction. The presence of this compound in the diffusion coatings increases the superficial hardness of the samples.

Abstract: Many researchers have assumed that a combination of hydroxyl apatite (HAP) and collagen (COL) may be the best solution for bone replacement and have prepared their composites by several techniques [1]. However, such HAP/COL composite had no nanostructure similar to bone, and consequently indicated no bone-like mechanical properties. These results demonstrate that the chemical composition similar to bone only is insufficient for bone metabolism and mechanical properties. Mechanical and biological performance of this type of materials could be improved by adding TiO2 within the initial mixture of nanostructured composites [2]. Ternary nanostructured systems consisting of hydroxyl apatite, TiO2 aerogel and collagen were prepared for the first time by hydrothermal procedure in high pressure conditions. Among many advantages, the synthesis method proposed in this paper could lead to formation of chemically bonded compounds as a consequence of high pressure conditions. The resulted material could find applications in bone tissue regenerative medicine, either in powder form for bone defects treatment, or in matrix form as osteoconductive coating for metal implants. Further studies are necessary to evaluate the osteoconductive properties.

Abstract: The new structural applications of aluminum materials are determined by intelligent lightweight design: the demand of safety, ecology, recycling and by economics. Al-Si alloys allow complex shapes to be cast. Metallurgical a high volume fraction of fine dispersoid which are less about 0.1 microns in size are useful for retaining a fine grain. In the 6061 series of alloys, iron combines with aluminium and silicon to form two types of commune inter-metallic, (beta AlFeSi and alpha AlFeSi).The type of inter-metallic that is present these alloys will have an important bearing on the homogenization time, workability and quality of the surface finish. The microstructure of the as-cast samples was evaluated by electronic microscopy and the morphology of inter-metallic compounds related to the efficiently modification. Mn-Ti-Sr modification of Al-alloys is normally accompanied by an increase in porosity in the casting.