No abstract

No abstract

No abstract

Diamond-like carbon (DLC) and silicon carbide (SiC) coatings are attractive because of low friction coefficient, high hardness, chemical inertness and smooth finish, which they provide to biomedical devices. Silicon wafers (Si waf ) and silicone rubber (Si rub ) plates were coated using plasmaenhanced chemical vapour deposition (PE-CVD) techniques. This article describes: 1-the characterization of modified surfaces using attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FTIR) and contact angle measurements, 2-the results of three in-vitro haemocompatibility assays. Coated surfaces were compared to uncoated materials and various substrates such as polymethylmethacrylate (PMMA), polyethylene (LDPE), polydimethylsiloxane (PDMS) and medical steel (MS). Thrombin generation, blood platelet adhesion and complement convertase activity tests revealed the following classification, from the most to the least heamocompatible surface: Si rub / DLC-Si rub / DLC-Si waf / LDPE/ PDMS/ SiCSi waf / Si waf / PMMA/ MS. The DLC coating surfaces delayed the clotting time, tended to inhibit the platelet and complement convertase activation, whereas SiC-coated silicon wafer can be considered as thrombogenic. This study has taken into account three events of the blood activation: coagulation, platelet activation and inflammation. The response to those events is an indicator of the in vitro haemocompatibility of the different surfaces and it allows us to select biomaterials for further in vivo blood contacting investigations.

Polarized microscope observation of ferroelastic domains in a SrBi2Ta2O9 (SBT) single crystal reveals the presence of domains up to Tc1≃770 K, which supports the ferroelasticity and Amam symmetry of the intermediate phase between ferroelectric and paraelectric phases. Far-infrared spectra of SBT ceramics, single crystal and thin films show a well underdamped optical soft mode at 28 cm−1, which partially softens to 21 cm−1 near the ferroelectric transition temperature (Tc2≅600 K). This softening does not explain the entire anomaly of low-frequency permittivity observed near Tc2. On the basis of high-frequency measurements, which do not show a significant dispersion, central-mode-type dispersion in the 10–100 GHz range is proposed as an explanation. So, the phase transition at Tc2 apparently shows a crossover behavior between the displacive and the order–disorder type.