TITANIUM FUNCTIONALIZING AND DERIVATIZING FOR IMPLANTABLE MATERIALS OSSEOINTEGRATION PROPERTIES ENHANCING

The article focuses on titanium functionalizing and derivatizing reactions for implantable materials osseointegration properties enhancing. Thus, the titanium dioxide was activated to the titanium hydroxide (functionalization), being further immobilized on the titanium surface by ethanolamine covalent reactions and (3-aminopropyl)triethoxysilane (APTS) for the osseointegration membranes reactive coating. The derivatizing was based on ether forming reactions between hydroxyl group from the titanium hydroxide surface and the ethanolamine hydroxyl groups and hydrolyzed APTS respectively. The obtained materials were characterized by scanning electron microscopy, FT-IR infrared spectroscopy, contact angle and X-Ray fluorescence

Welding-induced microstructure in austenitic stainless steels before and after neutron irradiation

The effects of neutron irradiation on the microstructure of welded joints made of austenitic stainless steels have been investigated. The materials were welded AISI 304 and AISI 347, so-called test weld materials, and irradiated with neutrons at 300 degrees C to 0.3 and 1.0 dpa. In addition, an AISI 304 type from a decommissioned pressurised water reactor, so-called in-service material, which had accumulated a maximum dose of 0.35 dpa at about 300 degrees C, was investigated. The microstructure of heat-affected zones and base materials was analysed before and after irradiation, using transmission electron microscopy. Neutron diffraction was performed for internal stress measurements. It was found that the heat-affected zone contains, relative to the base material, a higher dislocation density, which relates well to a higher residual stress level and, after irradiation, a higher irradiation-induced defect density. In both materials, the irradiation-induced defects are of the same type, consisting in black dots and Frank dislocation loops. Careful analysis of the irradiation-induced defect contrast was performed and it is explained why no stacking fault tetrahedra could be identified. (c) 2006 Elsevier B.V. All rights reserved

Mechanical properties-micro structure correlation in neutron irradiated heat-affected zones of austenitic stainless steels

The effects of neutron irradiation on austenitic stainless steels, usually used for the manufacturing of internal elements of nuclear reactors (e.g. the core shrouds), are the alteration of the microstructure, and, as a consequence, of the mechanical properties. The present study is aimed at extending knowledge upon the impact of neutron-irradiation on the heat-affected zone of welded materials, which was influenced by the thermal cycles upon fusion welding. An austenitic stainless steel weld type AISI 304 from a decommissioned experimental pressurised water reactor has been used in the present study. The welded material has been irradiated during 11 reactor cycles to a maximum dpa dose of 0.35 and a temperature of around 573 K. The mechanical properties and microstructure are determined on specimens from heat-affected zone and base materials, with different dose levels. The mechanical properties were determined by performing tensile tests on small flat specimens at two deformation temperatures: room temperature and about 573 K. The characterisation of the microstructure was made by transmission electron microscopy. The correlation between mechanical properties and microstruclure after neutron irradiation is made using the dispersed obstacle hardening model. It was found that the measured radiation hardening cannot be explained solely by the presence of the irradiation-induced defects observed in TEM. Smaller irradiation-induced features not resolvable in TEM may also contribute to radiation hardening. (C) 2007 Elsevier B.V. All rights reserved

Assessment of irradiation embrittlement of the Eurofer97 steel after 590 MeV proton irradiation

The irradiation hardening of the Eurofer97 steel following 590 MeV proton irradiations was determined at three different irradiation temperatures, 50 °C, 250 °C and 350 °C, and various doses up to about 1.3 displacement per atom. The dose and temperature dependence of the irradiation hardening was characterized by a linear relationship between the irradiation hardening and the square root of the dose as: delta_yield_stress=k(T)dpa^1/2. Mini pre-cracked bend bar (1x1x16 mm3) were also tested in the lower ductile to brittle transition region before and after irradiation at 300 °C and 0.5 dpa. The effective fracture toughness-temperature curves, Ke(T), were indexed on an absolute temperature scale at To for Ke=100 MPa m1/2 for both the unirradiated and irradiated condition. The irradiation-induced temperature shift delta_To of the Ke(T) curves yielded a coefficient Co, defined as Co=delta_To /delta_yield_stress, of about 0.53. For these low doses, helium effects could not be identified on the fracture properties

Azimuthal anchoring of nematic on undulated substrate: Elasticity

We measure the azimuthal anchoring energy of the nematic 5CB on sinusoidal holographic unidimensional and bidimensional gratings. We find that the anchoring strength is almost the same for all of the gratings and up to one order of magnitude stronger than expected by the topographic mechanism proposed by Berreman. We observe strong memory effects which dominate both the elastic anchoring and the easy axis gliding. We show that these memory effects limit from below the anchoring energy and are the main obstacle in the realization of substrates with weak anchoring conditions

Space Communications and Navigation (SCaN) Network Simulation Tool Development and its Use Cases

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