Ca-and P-based bioactive glasses are excellent candidates for design and manufacture of biomaterials. Understanding the structure and physico-chemical-thermal behaviour of bioactive glasses is a fundamental step towards the design of a new generation of biocompatible materials. In this study, the structure of SiO 2-CaO-Na 2 O glasses and its derivatives, obtained by substituting Na 2 O with P 2 O 5 and prepared by melt-quench technique, was studied with neutron and electron diffraction techniques combined with thermal analysis, high-resolution electron microscopy and X-ray photoelectron spectroscopy. Neutron and electron diffraction data were analysed with reverse Monte Carlo simulation and pair distribution function analysis, respectively. Bioactivity of P 2 O 5 substituted glasses was also investigated and proven in vitro using simulated body fluid. Based on the structural analysis, it was found that Si and P atoms are in well-defined tetrahedral units with a bond distance of 1.60 Å for both Si-O and P-O bonds, although P exhibits a higher average coordination number than Si. With increasing phosphate content, tendentious changes in the glass behaviour were observed. Linear increase in T g , supported by the changes in the average coordination numbers of Si and P, indicates strengthening of network structure with increasing P content and formation of P-O-Ca atomic linkages, which lead to CaP rich atomic environments in the silicate network. These CaP rich environments trap volatile elements and thus decrease the total weight loss during heating at higher P concentrations. In the case of the highest investigated P 2 O 5 content (5 mol%), nanoscale structural inhomogeneity and the formation of CaP rich clusters were also revealed by electron diffraction and atomic resolution imaging. This type of Ca-(Na)-P clustering has a key role in the behaviour of phosphate-substituted silicate glasses under physiological conditions.
A B S T R A C T This paper presents the results of various experimental analysis regarding a permanent Magnetic AssistedBall Burnishing (MABB) tool. This type is a special tool using the magnetic field to produce the necessary force for burnishing, it is applicable especially to rolling flat and 3D harmonic surfaces. For the correct operation of this special kind of tool, the set up for optimal distance between the tool and workpiece was introduced also taking into the account the measured rolling force (Fz), which occurs between the tool and workpiece because the magnetic force pulls the rolling balls on a cone which is located at the end of the tool. In this paper the optimisation of the process parameters for burnishing of C45 normalized premachined steel is also presented. To determine the dominant machining parameters the resulted surface roughness and the tribological parameters were also anaysed. The evaluation was completed by advanced measuring and IT equipment.
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