Authors: U. Lembke, Regina Lange, Ulrich Beck, Hans Georg Neumann
Abstract: A nanoporous calcium phosphate (CaP) coating on metallic surfaces is presented. The
coating consists of a stack of (a) a TiNbN layer deposited by physical vapor deposition and acting
as diffusion barrier against allergenic ions, (b) a SiO2 xerogel layer providing good adhesion
properties and designing the nanoporosity of the outer CaP layer (c) precipitated electrochemically.
SEM results verified a homogeneous nanoscale porous structure of the CaP coating. It is
characterized by a high adhesion strength. If applied to stent covering the nanoporous CaP coating
has promising properties to initiate rapid endothelium formation and reduced risk of restenosis.
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Authors: Dan Ying Gao, Hua Fan, Jie Lei
Abstract: Based on the experiments on 4 specimens with the dimension of 700mm×700mm and different thickness, the failure mode and anti-crack performance of the steel fiber reinforced high strength concrete four-pile cap was studied. The results show that the steel fiber mixed in high strength concrete in four-pile cap enhances its cracking load, limits the propagation of crack obviously and raises the ductility greatly. It also indicates that the ultimate load-carrying capacity of four-pile cap can be improved significantly with the increase of effective thickness.
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Authors: Roseli Marins Balestra, Alexandre Antunes Ribeiro, M.C. Andrade, Luiz Carlos Pereira, Marize Varella
Abstract: Studies show that calcium phosphate coatings on titanium implants improve osseointegration at the implant-bone interface, due to the mineral biocompatibility. Titanium implants can be coated with calcium phosphates by a biomimetic precipitation method. This work studied a biomimetic method under a simplified solution with calcium and phosphorus ions. As substrates, commercially dense titanium sheet and macroporous titanium samples produced by powder metallurgy were used, both ASTM F67 grade 2. The substrates were submitted to chemical and heat treatment and then immersed in the solution for 10 days. Samples characterization was performed by Optical Microscopy (OM), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS), low angle X-ray Diffractometry (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Powder metallurgy successfully produced macroporous titanium substrates. Calcium phosphate coatings were deposited on both substrates, confirmed by FTIR bands. Such results indicated the potential of this methodology for calcium phosphate coatings on titanium substrates.
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Authors: Ayako Oyane, Ikuko Sakamaki, Yoshiki Shimizu, Kenji Kawaguchi, Yu Sogo, Atsuo Ito, Naoto Koshizaki
Abstract: The present authors recently developed a new calcium phosphate (CaP) coating technique on an ethylene-vinyl alcohol copolymer substrate utilizing a laser-assisted biomimetic (LAB) process. In the present study, the LAB process was applied to a sintered hydroxyapatite (sHA) substrate for CaP coating. The LAB process was carried out by irradiating the sHA substrate immersed in a supersaturated CaP solution with a low-energy Nd-YAG pulsed laser. Within 30 min of irradiation, contiuous CaP layers with different morphologies were successfully formed on the laser-irradiated sHA surface. A submicron cavernous structure of the CaP layer was developed into a micron flake-like structure as the laser power increased from 1 to 3 W. This result suggests that the secondary nucleation and growth of CaP crystals were accelerated by laser irradiation in a power-dependent manner. Laser absorption by the sHA substrate and the resulting increase in ambient temperature locally near the surface should be responsible for the accelerated CaP nucleation and growth. The present CaP coating technique using the LAB process is simple and quick, hence it would be useful in orthopedic and dental applications as an on-demand surface-functionalization method for biomaterials consisting of sHA.
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