Linda Fröberg

Corrosion of Glazes Coated with Functional Films in Detergent Solutions

The goal of this work was to establish the compatibility of mat glazes with functional films known to render the surfaces with self-cleaning or easy-to-clean properties. Glazes with wollastonite, pseudowollastonite, diopside and zircon as the main crystalline phases in the surfaces were coated with fluoropolymer as well as ceramic, sol-gel derived titania and zirconia films. The glazes were soaked in typical detergent solutions used in everyday life up to four days. The surface roughness was measured with confocal optical microscope and the surface was imaged and analyzed with SEM/EDXA. When applied on wollastonite and pseudowollastonite containing glazes the functional films readily reacted in water solutions by pitting of the surface in the vicinity of the crystals. The ceramic titania and zirconia films showed better chemical resistance on wollastonite –free glazes, while the fluoropolymer film corroded in the most alkaline environments. The results indicate that functional films could be used also on rough surfaces without markedly affecting the surface topography. However, the films should be applied only on glazes with an excellent chemical resistance.

Porous Bioactive Glasses with Controlled Mechanical Strength

Porous implants were sintered of three different grain size fr actions of two established bioactive glasses. The sintering parameters for the implants we re carefully recorded. The porosity of the implants was measured from SEM-images. The compression stre ngth of the implants was measured with a Crush Tester. The data was used to find the sinter ing pa ameters desired in the manufacture of bioactive glasses needed to obtain a specific porosity and mechanical strength. Introduction The goal of the work was to study the densification and concurrent evoluti on of mechanical strength of porous implants manufactured by sintering crushed bioactive glasses. The formation of a firm bonding of bone is enhanced when using a porous implant structure [1]. Melt-der ived porous bioactive glass implants have successfully been manufactured by sint ering spherical particles of a narrow size fraction [2]. The porosity of the implant is regulated by the sintering parameters time and temperature, while the maximum pore size depends on the particle fraction used to manufacture the spheres. However, the method used to manufacture the spheres is res tricted only to relatively small particles with maximum diameter less than roughly 300 μm. In some applications the desired pore texture is larger. In this work the porosity and mechanical st rength of implants made by sintering two crushed bioactive glasses of three different grain size fractions larger than 300 μm were measured. Materials Sintering of glasses takes place through viscous flow above their tr ansfo mation temperature. Any devitrification process slows down the sintering, and inhibits the bioact ivity of the glass. The experimental glasses were chosen according to devitrification me asurements performed for four established bioactive glasses [3]. The glasses could be divided into t wo groups, i.e. glasses that devitrify easily just above their transformation temperature, and g lasses that devitrify at relatively high temperatures. The bioactive glasses Glass 13-93 and Glass 1-98 a re supposed to be interesting materials for manufacture of porous implants [3]. The implants were sintered using three different fractions of Gl ass 1-98 and Glass 13-93. The glasses were melted from analytical grade raw materials and Belgian quartz sand according to a standard procedure for achieving homogeneous glasses. The chemical composi ti n of the glasses is given in Table 1. The final glasses were crushed and screened into t he desired fractions. The fractions 300-500 μm, 500-800 μm, and 800-1000 μm were used for the sintering experiments. Table 1. The chemical composition of the experimental glasses in wt-% (mol-%). Glass Code SiO 2 Na2O K2O MgO CaO B2O3 P2O5 1-98 53 (53,8) 6 (5,9) 11 (7,1) 5 (7,5) 22 (23,9) 1 (0,9) 2 (0,9) 13-93 53 (54,6) 6 (6,0) 12 (7,9) 5 (7,7) 20 (22,1) 0 (0) 4 (1,7) Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 973-976 doi:10.4028/www.scientific.net/KEM.254-256.973