Stage I

• Selection of the bioalloy composition based on the new research tendencies for orthopaedic implants with functionalisation surface and of the obtaining methods for structured surface.
• Selection of the characterisation methods regarding the chemical composition, structure and mechanical properties of the bioalloy and of the structured surface.
• Needs for medical devices imposed by the national and European lows and the new research tendencies on the world and European level for to be take in the consideration to the design of the new alloy composition.
• Establishment of the alloy composition based on titanium with non-toxic alloying elements (Zr, Nb, Ta), that to assure high biocompatibility and physico-mechanical characteristics destined to orthopaedic implants.
• Two methods for the controlled surface modification with the aim to be bio-functionalised were selected: green chemical method and electrochemical method. These two methods were not approched in Romania and so, an important improvement of the bioactivity, biocompatibility and tribological properties will be obtained.
• Methods for chemical, physico-structural and mechanical characterisation of the new bioalloy were established: for chemical analysis – X-ray fluorescence spectroscopy; for structural analysis – optical microscopy; for mechanical properties – elongation resistance, Young’s modulus.
• Following methods for the characterisation of the bioalloy structured surface were selected: transmission electron microscopy – TEM; scanning electron microscopy – SEM; Raman microscopy; cyclic voltametry; linear polarisation; electrochemical impedance spectroscopy – EIS; monitoring of the open circuit potentials and corresponding open circuit potential gradients; statistical method.
• 2 communications at International Congress.

Stage II

• The alloy composition was established: Ti-20Nb-10Zr-5Ta.
• The synthesis method of the alloy was the melting in vacuum in furnace with magnetic induction, in levitation, with cold crucible.
• The corresponding laboratory technological flux was elaborated and experimentation.
• The samples from the casting alloy were obtained for the characterization.
• The chemical analysis reveals a composition very closed to the calculated composition
• The technology for the thermo-mechanical processing was designed and experimented.
• The flux and the technological parameters are: forging of the casting ingot at 1000⁰C; deformation with intermediary sub-critical annealing treatments, of re-crystallization in α range, the heating temperature being 700⁰c for 10 minutes, with cooling in furnace.
• The chemical, physico-structural and mechanical characterization of the casting and thermo-mechanical processed alloy was carried out.
• The workability of the new alloy is slight better than of the Ti and Ti-6Al-4V alloy.
• The corrosion resistance (2000 immersion hours) of the new alloy was studied in Ringer-Brown and Ringer (of different values of pH) physiological solutions.
• The corrosion rates placed the new alloy in the Perfect Stable and Very Stable resistance class.
• Open circuit potentials presented electropositive values with the ennobling tendency on the whole monitoring period, attesting the stable passive state of the alloy.
• Open circuit potential gradients have low values that can not generate galvanic or local corrosion.
• The new alloy presented spontaneous passivity in the studied physiological solutions, its passive film formed very easy and was stable on a large potential range.
• The corrosion mechanisms consists in the formation of a passive film with two layers: an inner, compact, barrier layer responsible for the good resistance of the alloy and an outer, porous layer, formed at the interface with the electrolyte, through the slight dissolution processes can take place.
• The electrochemical and chemical methods for the controlled structuring of the new Ti-20Nb-10Zr-5Ta alloy were elaborated and their parameters were estimated.
• Two types of implants were selected and designed.
• Work meeting with partners from Slovenia, September 2010, Bucharest.
• 1 scientific paper was published in journal with ISI index.
• 1 communication at International Congress.

Stage III

• The test lot from Ti-20Nb-10Zr-5Ta alloy was elaborated in furnace with levitation, with cold crucible, that assures the high temperatures, minimal losses of the elements with low vapour tensions (Ti, Zr), a much reduced content of the metallic and gaseous impurities and a compact, fine, homogeneous structure concerning both chemical composition and grains dimensions and forms.
• Material balance sheet per charge show an output in the melting phase of 92.26% - 99.89%, taking into account the resulted recoverable materials.
• Chemical analysis reveals a chemical composition very close with the calculated composition, because the un-recoverable losses have very low values.
• Mechanical tests evidence the fact that the new Ti-20Nb-10Zr-5Ta has a low Young’s modulus, close to that of the human bone (59.26 GPa and respectively 30 GPa) and a very good mechanical resistance in as-cast state. These characteristics associated with a high biocompatibility due to Ti and non-toxic alloying elements recommend the new bioalloy as a material for orthopaedic implants.
• For the controlled structuring of the new bioalloy surface were design and tested two electrochemical technologies:

- technology for controlled structuring of the new bioalloy surface by he method of the anodic potentiostatic polarization in Ringer solution;

- technology for controlled structuring of the new bioalloy surface by the method of the anodic galvanostatic polarization in orthophophoric acid solution.

• The characterization of the electrochemical processed surfaces was carried out by measurements of: X-ray diffraction (XRD), infrared spectroscopy (FT-IR), Raman spectroscopy (RS), optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM).
• The characterization of the interface bioalloy with structured surface / biological fluids was realised using cyclic potentiodynamic and linear polarization, electrochemical impedance spectroscopy (EIS) and the monitoring of the open circuit potentials and of the corresponding open circuit potential gradients for a period of 300 hours of immersion in the biological fluids.
• It resulted a superior behaviour of the bioalloy with galvanostatic structured surface because, all electrochemical parameters have better values than those of the un-processed alloy and of the potentiostatic processed alloy, proving that the galvanostatic processing produces a very compact and resistant film with a better protective capacity than that of those obtained by potentiostatic polarization.
• The international Worksop „Titanium alloys for automotive, aerospace and biomedical applications” was organised with partners from Romania, Slovenia, France and Italy where were presented 5 scientific communications regarding the partial results of the project.

Stage IV

• For the controlled structuring of the new Ti-20Nb-10Zr-5Ta bioalloy surface was design and tests o green chemical technology.
• The characterisation of the chemical processed surface was carried out by measurements of RS, XRD, and SEM.

- RS confirmed the existence of the hydroxyapatite coating.

- XRD identified the presence of crystalline hydroxyapatite on the sample surface.

- SEM evidenced the continuously films with a globular morphology which completely covered the bioalloy surface.

• The characterization of the interface bioalloy with structured surface / biological fluids was realised using cyclic potentiodynamic and linear polarization, EIS and the monitoring of the open circuit potentials and corresponding open circuit potential gradients for a period of 2000 immersion hours in the biological fluids.
• The following results were obtained: a self-passive metal behaviour with reduced passive currents, lower than those of the un-processed alloy, attesting that the film formed on the chemical processed alloy surface acts as a protective layer, improving the alloy corrosion resistance; reduced corrosion currents and rates (in the “Perfect Stable” resistance class), smaller than for the un-processed surface, as result of the protective effect of the hydroxyapatite film formed on the alloy surface; impedance parameters show a capacitive behaviour i.e., a protective film that has a barrier character against the aggressive ions.
• The workshop “Titanium alloys for biomedical applications” was organised in Slovenia by Josef Stefan Institute, Ljubljana and University of Primorska where 2 scientific communications regarding the partial results of the project were presented, realisation of the project stages and of the following stages were verified, the tasks and deadlines for every partner were established.

Stage V

• Followed to the comparative analysis, the optimal method of the functionalisation of the new Ti-20Nb-10Zr-5Ta bioalloy surface was selected the green chemical method that leads to the direct deposition of the hydroxyapatite by a chemical, rapid, without power consumption procedure, assuring a very good bioactivity and osteoinduction and shortening the ossteointegration time of the implant.
• The structure, composition, and functionality of the hydroxyapatite coating were evidenced by SEM, RS, EDX, and XRD and by the monitoring of the electrochemical parameters for long-term. It resulted that the coating maintained its stability and thickened in time by the new depositions from the physiological solutions, namely, this coating is bioactive, osteoinductive and osteoconductive.
• The experiments for the demonstration of the bioalloy synthesis technology established the materials balance sheet of the melting process evidencing an output of 99.21% – 99.99%, the un-recoverable losses of 0.01% - 0.18% and an output per ingot of 89.1% - 91.59%.
• The experiments for the demonstration of the thermo-mechanical processing technology of the as-cast alloy were carried out in concordance with the technological flux and established parameters using the equipments selected in the phase of the technology elaboration.
• The demonstration of the applicability of the controlled functionalised technology (electrochemical and chemical) of the implants was realised by the monitoring for a period of 3000 h of the corrosion rates in Ringer and Ringer-Brow solutions.

- The oxidic, electrochemically obtained coating improved the corrosion resistance of the alloy and permitted depositions of the protective compounds from the simulated human fluid.

- The chemical obtained hydroxyapatite coating proved ability to form new HA layers (the main inorganic component of the human bone), consequently, the increased ability of the osteoinduction and osteoconduction.

• The technology for the implant model was designed and tested and orthopaedic and dental implants were realised.
• The characterization of the implants covered with hydroxyapatite by the chemical method was carried out by the study of the coating morphology and homogeneity (SEM), and its composition (EDX). The structural and compositional stability of the functionalised implant surface was demonstrated.
• The technical-economic analysis took into consideration the application of the technologies for the new implants with the functionalised surface to the economic partner from project; the necessary investment was estimated and the principal technical-economic indicators were calculated. This analysis demonstrated a high efficiency of the investment and the achievement of the main project objective to put at the patient’s disposal orthopaedic implants with high biocompatibility and osteointegrative properties at low, very accessible cost prices.
• The workshop “In-vitro biocompatibility and corrosion resistance of advanced developed alloys with biofunctionalised surface” was organised by Institute of Physical Chemistry in period 17-20 May 2012 and 5 scientific communications were presented; also, the realisation of the project stages and a work visit were organised.
• The workshop “Characterisation of bioactive coatings on the titanium alloys surface” was organised in Slovenia in period 25-26 September 2012 by the Josef Stefan Institute from Ljubljana and University of Primorska; 6 scientific communications that syntheses o part from the project results were presented; the realisation stage of the last project stage was analysed; the results for publication were selected; the development prospects of the materials studied in the project frame were discussed; the plans for the realisation of new biocompatible alloys for future project proposals were approached.