Shoujie Liu

Ca-P bioactive coating prepared by combining microwave-hydrothermal and supersonic atmospheric plasma spraying methods

Ca-P based coatings on carbon/carbon composite (C/C) were manufactured via a combined method comprising of microwave-hydrothermal (MH) and supersonic atmospheric plasma spraying (SAPS) techniques. However, a weak mutual interaction between the coating and C/C substrate has been a critical issue for a long time. Herein, we reported a new method for shear strength enhancement without compromising the osteoconductivity and osteoproductivity. Results showed that the inner layer has a strong mechanical interlocking with C/C substrate and the failure mode of outer layer changed from the coating cohesion (within the coating) to adhesive (at the coating/substrate interface) fracture. The shear strength between Ca-P bioactive coating-C/C substrate by MH/SAPS was significantly improved as compared to that prepared by SAPS. The Ca-P bioactive coating exhibited a good bioactivity as evidenced by the formation of a uniform carbonate-apatite layer formed on coating after immersing into stimulated body fluid for a specified period of time.

In simulated body fluid performance of polymorphic apatite coatings synthesized by pulsed electrodeposition

Surface modification is to modify biological responses through changing surface properties without reducing the mechanical properties of the implant. Specifically bioactive coatings, such as hydroxyapatite, carbonate apatite and dicalcium phosphate dehydrate, have been deposited on carbon/carbon (C/C) composites to change the bio-inert surface state. This work focused on the effects of voltages and electrolyte concentrations of pulsed electrodeposition on apatite layer. The apatite coatings thus synthesized were then structurally, morphologically and chemically characterized using X-ray diffraction, scanning electron microscopy, Transmission electron microscopy and Fourier-transform infrared spectroscopy. Remarkably, the voltages and electrolyte concentrations changed the structure, morphology and crystallinity of the obtained coatings. In vitro bioactivity evaluation of polymorphic apatite coatings was performed by soaking the apatite layer coated C/C composites in simulated body fluid (SBF). The corrosion behavior was investigated via the potentiodynamic polarization test in SBF solution. The results confirmed that the increasing deposition voltage and concentration of electrolyte resulted in promoting bioactivity and corrosion resistance by altering the morphologies and phases.

Preparation and properties of in-situ growth of carbon nanotubes reinforced hydroxyapatite coating for carbon/carbon composites

Carbon nanotubes (CNTs) possess excellent mechanical properties for their role playing in reinforcement as imparting strength to brittle hydroxyapatite (HA) bioceramic coating. However, there are few reports relating to the in-situ grown carbon nanotubes reinforced hydroxyapatite (CNTs-HA) coating. Here we demonstrate the potential application in reinforcing biomaterials by an attempt to use in-situ grown of CNTs strengthen HA coating, using a combined method composited of injection chemical vapor deposition (ICVD) and pulsed electrodeposition. The microstructure, phases and chemical compositions of CNTs-HA coatings were characterized by various advanced methods. The scanning electron microscopy (SEM) images indicated that CNTs-HA coatings avoided the inhomogeneous dispersion of CNTs inside HA coating. The result show that the interfacial shear strength between CNTs-HA coating and the C/C composite matrix reaches to 12.86±1.43MPa. Potenitodynamic polarization and electrochemical impedance spectroscopy (EIS) studies show that the content of CNTs affects the corrosion resistance of CNTs-HA coating. Cell culturing and simulated body fluid test elicit the biocompatibility with living cells and bioactivity of CNTs-HA coatings, respectively.