1,721,022 research outputs found
Simulazione del processo di saldatura HIP di una lega CCrZr e individuazione dei trattamenti termici per il recupero delle caratteristiche meccaniche e fisiche
No full textTribological characterization of surface-treated commercially pure titanium for femoral heads in total hip replacement: A feasibility study
No full text Most noncemented total hip replacements combine a titanium alloy stem, a CoCrMo femoral head and an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. In spite of its nickel content of up to 1% and the resulting biocompatibility issues in some clinical situations, the higher cost and some difficulties in machining, CoCrMo alloy is preferred to titanium alloys thanks to its outstanding tribological properties, higher hardness and elastic modulus. Nowadays most of the heads of hip prostheses use CoCrMo as bearing material. The present study investigates the effect of various surface treatments and combinations of treatments, such as electrochemical oxidation (anodization), laser surface melting and barrel polishing, on the tribological properties of commercially pure grade 2 titanium. The aim of the study was to characterize surface treatments capable of improving the tribological properties of titanium surface to the same extent as CoCrMo. The tribological properties were characterized by multidirectional pin-on-flat screening wear tests, using UHMWPE pins as bearing surface. The experiments showed the possibility of improving the wear resistance of titanium to the degree of CoCrMo. Although further efforts will be required to optimize the treatments studied, the results are encouraging enough to warrant pursuing this direction of investigation. </jats:p
Excitation functions and yields for cyclotron production of radiorhenium via deuteron irradiation : natW(d, xn)181, 182(A+B), 183, 184(m+)g, 186gRe nuclear reactions and tests on the production of 186gRe using enriched 186W
No full textExcitation functions, thin- and thick-target yields for the 181−186gRe and 187Wradionuclidesweremeasured by the activation stacked-foil thecnique on natural tungsten foils for deuteron energies up to 18.0MeV. These cross sections were validated by comparing the experimental results for thick-target yields with those calculated
by integration of the thin-target yields. It was found that the maximum 186gRe content by irradiation of natural tungsten is about 55%, a higher value compared with the one found for proton beam, but not sufficient to use natural tungsten for medical purposes yet. Thus, in order to have a higher specific activity AS of 186gRe, the use of enriched 186W target is necessary. Therefore the irradiation of a thick target of enriched 186Wby accelerated deuterons was studied and the results for the production of 186gRe were compared with those obtained from the irradiation of the same target by accelerated protons. It was found that the deuteron irradiation is preferable for three reasons: larger yield, less contamination by tantalum radioisotopes
and smaller required amount of the target, which simplify the separation of the 186gRe from the target itself
Excitation functions and yields for Re-18x production by cyclotron irradiation
No full textExcitation functions, thin- and thick-target yields (tty and TTY) for the 181-186Re radionuclides were measured with the activation method on stacked natural W foils for proton energies up to 22 MeV. Besides, TTYs obtained irradiating highly enriched tungsten targets are presented. In conclusion, a new data set has been given for the investigated radionuclides. These results are compared both with the experimental literature values and the ones calculated by the EMPIRE II code (version 2.19). In particular, the attention is focused on Re-186g due to its remarkable applications in Nuclear Medicine for metabolic radiotherapy of tumors. Finally these results are compared with some preliminary data obtained by deuteron cyclotron irradiation on thin natural W foils
Excitation functions and yields for Re-186g production by proton and deuteron cyclotron irradiation
No full textThe 186gRe is a beta-gamma emitter that, thanks to its suitable nuclear properties (t1/2 = 90.64 h, Emax-beta 1.07, 0.93 MeV, main E-gamma 137 keV), is presently used in palliation metabolic radiotherapy, with optimal perspectives for applications in radioimmunotherapy (RIT) too. In particular the energy range of the beta particles suggests that this radionuclide is a good candidate for cancers with small dimensions (from few mm to a few cm in soft tissue). The possibility to use this radionuclide for therapeutic purposes is strictly related to the possibility of increasing its specific activity (AS). This improvement is reached by substituting the common 185Re(n,gamma) production route in thermal nuclear reactor with the 186W(p,n) and/or (d,2n) cyclotron production ones, due to the possibility of radiochemical separation of the product from the target in no-carrier-added form, reaching a AS(NCA) value close to the theoretical carrier-free one AS(CF) = 6.88 GBq.microg-1
Surface treatments to enhance the wear properties of titanium as bearing surface for artificial organs
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