Sliding friction and wear performance of the nano-bioceramic α -Al 2 O 3 prepared by high energy milling

The structural evolution and morphological changes of the nanostructured α-Al2O3 powder using different milling times (1, 8, 16 and 24 h) were studied. It is observed that the crystallite size of the particles reduced to 2 nm after milling for 24 h. Morphological studies of powder particles indicated that the powder particle size continuously decreases with increasing milling time. The sliding wear rate and wear coefficient of friction were lower in the nanocrystalline samples milled at 24 h at same applied load (3, 6 or 10 N). The improved friction and wear resistance is attributed to the finer microstructure of the sample milled for 24 h

FRICTION AND WEAR BEHAVIOUR OF Ti-6AI-7Nb BIOMATERIAL ALLOY

Titanium and its alloys have been used as implant materials due to their very good mechanical and corrosion resistance and biocompatibility [1,2]. The most used biomaterials were commercially pure titanium (CP-Ti} issued in clinics, although CP- Ti has been pointed out to have disadvantages of low strength, difficulty for polishing, and poor wear resistance. Therefore, Titanium is still insufficient for high-stress applications ; e.g., long spanned fixed prostheses and the frameworks of removable partial dentures.Ti-6Al-4V alloy, originally developped as an aeronautical material, has been tested as a replacement for CP-Ti, because of its high mechanical properties with sufficient corrosion resistance[3], however, the cytoxicity of elemental Vanadium is questionable. Subsequently, some researches prove that vanadium and aluminum ions released from this ternary alloy can induce cytoxic effects or neurological disorders, respectively [4]. Also, for long-term, this alloy has transferred in sufficient load to adjacent bones, resulting in good resorbption and eventual loosening of the implant. Another ternary alloy used as implants was vanadium free, a+ii alloy, especially Ti-6Al-7Nb alloy that revealed improved mechanical characteristics, corrosion resistance and biocompatibility , developed for orthopedics application as a wrought material, has been evaluated as a new alloy for total hip prostheses. Niobium exhibits a similar effect to vanadium instabilizing ii phase in the Ti-Nb binary system, which is necessary for providing the a -ii two-phase structure. Therefore, niobium was used as the ternary element to produce the desirable microstructure in the Ti-6Al-7Nb alloy. Ascompared with Ti-6Al-4 V alloy, in a tensile test, these alloy show slightly lower strength and about 40% higher elongation

Friction and Wear Behavior of Ti-6Al-7Nb Biomaterial Alloy

Titanium has been increasingly applied to biomedical application because of its improved mechanical characteristics, corrosion resistance and biocompatibility. However their application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the friction and wear behavior of high-strength titanium alloys: Ti-6Al-7Nb used in femoral stem (total hip prosthesis). The oscillating friction and wear tests have been carried out in ambient air with oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a, ASTM G 133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm·s−1), and as a counter pair we used the ball of 100C 6, 10 mm of diameter. The surface morphology of the titanium alloys has been characterized by SEM, EDAX, micro hardness, roughness analysis measurements. The behav-ior observed for both samples suggests that the wear and friction mechanism during the test is the same for Ti alloys, and to increase resistance to wear and friction of biomedical titanium alloys used in total hip prosthesis (femoral stems) the surface coating and treatment are required

L'individualisation du problème du dopage : déficits structuraux dans les discours du dopage

Comment les fédérations sportives, les institutions sportives, les acteurs économiques, politiques du système sportif et les médias se déchargent de toute responsabilité en mettant le dopage sur le compte d'une déviance individuelle du sportif. Le dopage est alors vécu comme un 'normal accident' (Perrow, 1984) auquel il faut s'attendre. Dans ce contexte, le regard désindividualisant du sociologue devient une condition importante pour rendre possible une autre pratique du sport de haut niveau

Friction and Wear Behavior of Ti-6Al-7Nb Biomaterial Alloy

International audienceTitanium has been increasingly applied to biomedical application because of its improved mechanical characteristics, corrosion resistance and biocompatibility. However their application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the friction and wear behavior of high-strength titanium alloys: Ti-6Al-7Nb used in femoral stem (total hip prosthesis). The oscillating friction and wear tests have been carried out in ambient air with oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a, ASTM G 133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm·s−1), and as a counter pair we used the ball of 100C 6, 10 mm of diameter. The surface morphology of the titanium alloys has been characterized by SEM, EDAX, micro hardness, roughness analysis measurements. The behav-ior observed for both samples suggests that the wear and friction mechanism during the test is the same for Ti alloys, and to increase resistance to wear and friction of biomedical titanium alloys used in total hip prosthesis (femoral stems) the surface coating and treatment are required

From nanospheres to micelles: simple control of PCL-g-PEG copolymers amphiphilicity through thiol–yne photografting

International audienceA simple method for the synthesis of a family of poly(ε-caprolactone)-g-polyethylene glycol (PCL-g-PEG)copolymers of controlled amphiphilicity and their use in generating nanospheres or micelles are reported.PCL-g-PEGs with various compositions are prepared from a single strategy relying on a combination ofpost-polymerization modification and subsequent thiol–yne photografting. Alkyne-functional PCL (PCLyne)was first obtained by anionic activation and reaction with propargyl bromide to yield PCL-yne with8% alkyne groups. PEG-thiol is then reacted on PCL-yne under UV activation to yield the targeted graftcopolymer by thiol–yne photoaddition. The advantage of the approach is that control over the compositionis easily achieved, yielding amphiphilic graft copolymers with ethylene glycol/caprolactone (EG/CL)ratios ranging from 0.1 to 1.3. Starting from this single strategy, it was therefore possible to obtain nanospheres(DH ∼ 55 nm) or micelles (DH ∼ 30 nm) by copolymer self-assembly depending on the EG/CLratio. The potential of PCL-g-PEG micelles as drug carriers was finally evaluated with curcumin thatwas efficiently encapsulated, protected and released over 80 days. Interestingly it was found that drugencapsulation efficiency and drug loading were higher for PCL-g-PEG copolymers compared to blockPCL-b-PEG

Tribological behavior of Ti-6Al-4V and Ti-6Al-7Nb Alloys for Total Hip Prosthesis

The aim of the study is to evaluate the friction and wear behavior of high-strength alloys Ti-6Al-7Nb used in femoral stem and compare it with a Ti-6Al-4V alloy cylindrical bar corresponding to ISO 5832-3 part 3/01-07-199 standard. The tribological behavior was investigated by wear tests, using ball-on-disc and pin-on-disc tribometers. These tests consisted of measuring the weight loss and the friction coefficient of samples. The oscillating friction and wear tests have been carried out in ambient with oscillating tribotester in accordance with standards ISO 7148, ASTM G99-95a, and ASTM G133-95 under different conditions of normal loads (3, 6, and 10 N) and sliding speeds (1, 15, and 25 mm·s−1). As counter pairs, a 100Cr6 steel ball with 10 mm in diameter was used. Results show that the two alloys had similar friction and wear performance, although their grain structures and compositions are different. Occurrence of large frictional occurred, is probably caused by formation and periodic, localized fracture of a transfer layer. Higher friction with larger fluctuation and higher wear rate was observed at the higher siding speed. The Ti-6Al-4V wear mechanism transforms from ploughing and peeling off wear at low sliding speed to plastic deformation and adhesive wear

Iterative Photoinduced Chain Functionalization as a Generic Platform for Advanced Polymeric Drug Delivery Systems

International audienceAdvanced drug delivery systems (DDS) are easily designed following a photoiterative strategy. Multifunctional polymers are obtained by coupling building blocks of interest to an alkynated PCL platform via an efficient thiol-yne photoaddition. Fine tuning over the design is achieved as illustrated with targeting and enzyme-responsive DDS.-