Search results for "A titanium"
showing 8 items of 8 documents
A Straightforward Route to Homoallyl-Homocrotylamines Promoted by a Titanium Complex
2012
I�-Allyltitanium complexes, generated in situ from 1,3-dienes and Cp2TiH, react with benzotriazole derivatives to give homoallylic amines in good yields. Under similar conditions, triple cascade reactions (allyltitanation followed by cationic 2-aza-Cope rearrangement followed by a second allyltitanation) occur from bis(benzotriazolyl) compounds affording a straightforward route to homoallyl-(E)-homocrotylamines. A theoretical study provides further insight into the factors that govern the selectivity of this sequence of reactions. The titanium-promoted reductive coupling of 1,3-dienes with bis(benzotriazolyl) compounds as substrates led selectively to homoallyl-homocrotylamines through a tr…
Osseointegration of one-piece zirconia implants compared with a titanium implant of identical design: a histomorphometric study in the dog
2010
Objective: The aim of this study was to evaluate osseointegration of one-piece zirconia vs. titanium implants depending on their insertion depth by histomorphometry. Material and methods: Four one-piece implants of identical geometry were inserted on each side of six mongrel dogs: (1) an uncoated zirconia implant, (2) a zirconia implant coated with a calcium-liberating titanium oxide coating, (3) a titanium implant and (4) an experimental implant made of a synthetic material (polyetheretherketone). In a split-mouth manner they were inserted in submerged and non-submerged gingival healing modes. After 4 months, dissected blocks were stained with toluidine blue in order to histologically asse…
Adaptive response of osteoblasts grown on a titanium surface: morphology, cell proliferation and stress protein synthesis.
2005
Titanium is one of the most widely used biomaterials in orthopaedic, dental and trauma surgery. Superficial adhesion and cell proliferation represent the first steps of cell-biomaterial interactions. The efficacy of this early phase influences the subsequent ability to differentiate, and hence the knowledge of these cell activities is important for studying and improving the biocompatibility of biomaterials. The aim of this study was to test the adaptive ability of osteoblastic cells grown on titanium surfaces, including morphologic, proliferative and adaptative aspects.
Comparison of the friction and wear properties of titanium and oxidised titanium in dry sliding against sintered high speed steel HS18-0-1 and agains…
2005
Abstract The paper presents the results of conformal pin-on-disc tribological tests concerning the hard oxidised zone, α-Ti(O), created at the surface of a titanium specimens sliding against the sintered and hardened up to 850 HV30, Grade T1 high speed steel (HS18-0-1) counterspecimens. Comparison with the results obtained for the tests performed against hardened up to 620 HV30 C45 carbon steel counterspecimens has been done. Testing was carried out at room temperature and at unlubricated conditions. After tests the structures and compositions of the worn surfaces and wear debris were a subject of LOM, SEM observations and X-ray microanalyses. In comparison with the baseline—the Ti/T1 HSS c…
ChemInform Abstract: A Straightforward Route to Homoallyl-Homocrotylamines Promoted by a Titanium Complex.
2013
This publication also contains theoretical studies and calculations concerning the reaction.
NaCl induced corrosion of Ti-6Al-4V alloy at high temperature
2016
International audience; This paper presents a study on the Ti-6Al-4V behaviour in presence of NaCl deposit under dry and moistair environments at 560◦C. The results evidence a detrimental effect of the NaCl deposit with a synergisticeffect in presence of moist air environment. Treatments under dry and moist air with NaCl deposit for600 h, lead respectively to weight gains per unit area 5 and 15 times higher than observed under classicoxidation in dry air. Enhancement of the corrosion phenomenon is attributed to the presence of gaseousmetal chlorides, leading to the establishment of an active corrosion process.
Kinetic studies of two-step polymerization of propylene over a titanium-aluminum catalyst
1997
The influence was studied of the modification of an unsupported titanium-aluminum catalytic system with an internal Lewis base incorporated, via prepolymerization, on the activity of this system in propylene polymerization. In order to clarify the reasons for the activating effect of prepolymerization, comparative studies were carried out on the kinetics of polymerization catalyzed by a titanium system and its prepolymerized counter part. Based on the kinetic model suggested for the polymerization mechanism, the concentration of active sites and rate constants were determined for chain propagation, chain transfer and termination reactions. The following conclusions were deduced: (i) the ini…
The effect of prepolymerization of a titanium catalyst on its deactivation in propylene polymerization
1997
Propylene polymerization rate was investigated in the presence of anunsupported titanium catalyst (TiCl3) that had been modified with a Lewis base (di-n-butyl ether) and activated (precat), or not activated (cat), by being used in a suspension prepolymerization (70°C, 0.6 MPa) of an identical monomer. The initial polymerization rate was higher with the precat than with the cat catalyst. Prepolymerization was also found to enhance the kinetic stability of catalyst's active sites, presumably by reason of the prepolymerization-induced modification of catalyst's morphology. Deactivation rate constants were evaluated for the active sites of either catalyst examined.