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The properties of the interface between biomaterials and the host tissue play an important role for the process of successful adaptation of implants. Extensive research has focused on shortening the time of osseointegration by modifying the surface in adding a coating such as hydroxyapatite (HAp). We have developed a new type of biocompatible nanohydroxyapatite (n-HAp) coatings, which are characterized before and after deposit on a Ti-6Al-4V substrate using neutron diffraction and scanning electron microscopy. Three months after the implantation in the sheep tibias, high-energy synchrotron radiation (ID15B, ESRF, Grenoble, France) diffraction studies of the cortical bone identify that the c-axes of HAp are preferentially oriented in the direction of the stresses that bone usually withstands. This non destructive analysis of the bone-implant interface proves that bone maturation is achieved successfully with this novel n-HAp coating and demonstrates that the mineralization is completed without spatial organization. None of these findings are obtained with uncoated titanium alloys. The presence of this n-HAp coating on Ti-6Al-4V substrate is decisive in obtaining this mature bone at the interface.

In this paper we present two studies in order to evaluate the residual stresses in two materials. The first one, the residual stresses regenerated in shot peened aluminium plate by neutron diffraction on the strain imaging instrument SALSA at the Institut Laue Langevin, Grenoble, France, also the validation of a model of finite element analysis permitting to predict the final deformation. The second example of this work we use the cobalt-alloys coating deposited on stainless steel forging tools via Plasma Transfer Arc (PTA) process, the evaluation of the residual stresses and characterization of phases close to substrate/coating interface were done by Synchrotron X-ray diffraction.

The aim of the present study was to study the interface implant-bone by synchrotron radiation, the implant has two faces the first one coated with hydroxyapatite and the second uncoated. In orthopaedic surgery, Titanium (Ti-Al-4V) implants are currently coated with hydroxyapatite (HAp), Ca10(PO4)6(OH)2, in order to obtain a stable and functional direct connection between the bone and the implant. At the implant-bone interface, the new bone reconstituted after two months of implantation must have the same properties like the natural bone in order to accept the implant. Therefore we studied the texture of the reconstituted bone crystals at the interface applying non destructive x-ray diffraction. The required high spatial resolution was achieved utilizing high-energy synchrotron radiation on ID15 at ESRF in Grenoble, France.

Synchrotron X-ray diffraction is reliable to measure residual stresses and characterize existing phases close to substrate/coating interface. In the present study, we focus on the cobalt-alloys coating deposited on stainless steel forging tools via Plasma Transfer Arc (PTA) process. Forging tools always work in high temperature conditions. Since fatigue crack is often detected near to the interface, we used synchrotron radiation to characterize residual stress profiles both in the substrate and coating sides. Also, we defined phases inside diluted substrate layers and in the stellite coating using a Rietveld refinement.

The quantitative evaluation of the preferential orientation of crystallites by the synchrotron and neutron diffraction techniques during regeneration at the interface with implant gives a good prediction of the mechanical properties of the bone. During the process of bone healing after implantation, the speed and quality of regeneration is affected by the nature of the implant surface. Titanium alloy (Ti-Al-4V) is currently coating with the hydroxyapatite (HAp), Ca10(PO4)6 (OH)2, in order to obtain a stable and functional direct connection between bone and implant. At the interface implant-bone, the new bone reconstituted after implantation must have the same mechanical properties of bone in order to accept the implant. Therefore, it is necessary to study by means of two non destructive techniques: neutron diffraction and synchrotron radiation, the crystal growth and texture of this new bone crystals reconstituted at the interface.

In recent years, nanostructured coatings by Plasma Thermal Spraying (PTS) attracted intense interest due to their enhanced mechanical properties as hardness, strength and ductility. The aim of this study was to evaluate the influence of coating the implant by nanohydroxyaptite, n-HAp, Ca10 (PO4)6(OH)2. The results obtained with n-HAp will also compared with the implant coated with HAp. Bone is a composite material in which are associated a mineral phase in the form of crystals of HAp and an organic matrix constituted by collagen. The c-axes of HAp and the collagen fibers are preferentially oriented in the direction of the stresses that the bones need to withstand. At the interface implant-bone, the new bone reconstituted after implantation must have the same proprieties of the original bone in order to have good fixation with the implant. Therefore, it is necessary to study the mechanical properties of this new bone crystals reconstituted at the interface with the implants coated with n-HAp and HAp by neutrons diffraction on D20 at ILL.

The aim of this study was to create a nano-structured coating using Plasma Thermal Spraying (PTS). This process consists in introducing pre-agglomerated nanosized particles in a high-temperature and high-velocity gas jet and projected them onto the substrate to form, layer by layer, a nanostructured coating. In order to retain nanometer grain sizes in the deposited coating through specific PTS technologies, a thermal field and velocity distribution in the plasma jet are analytically calculated. A finite element analysis is employed to calculate the thermal field evolution inside the agglomerated particles and the thermal induced internal stress distribution is determined. The parameters determined by the theoretical analysis are used for experimental coatings. The average crystallite size of nano-hydroxyapatite powder was 90nm. After deposit via Plasma Thermal Spraying (PTS) process and followed by a 2 hours heat treatment to reduce amorphous fraction, the experimental deposited coating shows that it retains the nanometer crystallite sizes. The substructure of nanocrystals was evaluated at about 120nm in size. Such a nanocoating may play the role of nucleation site to bone, allowing a faster stabilization of the implant.

The aim of the present study was to study the interface implant-bone by synchrotron radiation and neutron diffraction, the implant has two faces the first one coated with hydroxyapatite and the second uncoated. In orthopaedic surgery, Titanium alloy (Ti-Al-4V) implants are currently coated with hydroxyapatite (HAp), Ca10 (PO4)6 (OH)2, in order to obtain a stable and functional direct connection between the bone and the implant. At the implant-bone interface, the new bone reconstituted after two months of implantation must have the same properties like the natural bone in order to have good mechanical properties at the interface with the implant. Therefore, we studied the texture of the reconstituted bone crystals at the interface applying two non-destructive diffraction methods, as well as the influence of the coating on crystallinity index. The required high spatial resolution was achieved utilizing high-energy synchrotron radiation on ID15 at ESRF in Grenoble, France, and the second method was done by neutron diffraction, the high-intensity with two-axis diffractometer was used, equipped with variable resolution: D20, at Institut Max von LauePaul Langevin (ILL) in Grenoble, France. In orthopaedic surgery, it is necessary to use biocompatible implants in order to have good mechanical and fracture resistance. Bone is a composite material whose components are primarily collagen and HAp. The c-axes of the apatite crystallites and the collagen fibres are preferentially oriented, e.g., in the long bones in the directions of the stresses that the bones need to withstand. HAp crystallizes in the hexagonal system and its unit cell parameters are a=9,4 A and c=6,8 A its space group is P63/m. Bone occurs in two principal structural forms: cortical, or compact bone, which forms a dense matrix, and spongy bone. We use cortical bone in this work. The long-term success of biomedical implants largely depends on the stable fixation of the implant to bones. Composite materials, in which metals have coated with ceramics, have been extensively reported as an alternative to plain materials in favour of a long-term fixation. The development of bioactive ceramic-alloy structures for implants has focused by the idea of combining the bioactivity of ceramics with the mechanical properties of selected metallic alloys. Ti-6Al-4V presents good mechanical proprieties and is biocompatible. HAp has low mechanical strength, but has a very good osteointegration and biocompatibility. The idea is to combine these two materials in order to have mechanical strength and good osteointegration proprieties at the interface. Plasma spraying is the most popular method for coating implant parts with HAp. In order to improve these coatings, it is necessary to investigate the texture and crystallinity evolutions of the bone’s crystal structure, as a function of the distance from the implant-interface.