Nuevas aplicaciones de las fritas cerámicas: vidrios bioactivos

Abstract

Companies in the frit, glaze, and ceramic colour producing subsector know a great deal

about the different frit-manufacturing process stages such as raw materials milling and

mixing, as well as fusing the raw materials mixture to obtain the frit. This knowledge can

be used to break new ground in frit applications and to obtain products with high added

value, such as bioactive glasses.

Bioactive glasses are amorphous materials that are able to interact with bone cells,

thanks to surface growth of a hydroxycarbonate apatite (HCA) layer when they enter into

contact with a biological fluid. This bioactivity, together with their relatively low cost

compared to that of the materials used at present, makes such materials particularly

attractive for obtaining prosthesis and implant coatings. Among the numerous coating

methods, atmospheric plasma spraying is one of the most widely used techniques for

industrial-scale deposition of this type of coating owing to its versatility, simplicity, and

relatively low cost.

This study presents a methodology for obtaining bioactive glass coatings by thermal

plasma spraying. The methodology includes: frit synthesis; design, preparation and

characterisation of appropriate powders and bioactive glass suspensions for thermal

plasma spraying; optimisation of the deposition conditions for the obtainment of coatings

from powders as well as from suspensions; and characterisation of the end coatings.

It was verified that, after deposition, the resulting coatings exhibited the typical

microstructure of layers deposited by thermal plasma spraying. In this case, as feedstock

of a glassy nature was involved, the microstructure consisted of a matrix of flattened

drops of molten glass, together with rounded pores and cracks. The results obtained also

indicated that the amorphous nature of the jetted frit was maintained in the end coating,

as was intended. However, low adhesion to the substrate was also observed, it being

necessary to use a bonding layer between the substrate and the bioactive glass layer.

Consequently, further investigation is needed to improve the bond strength and other

properties of these coatings, as well as to evaluate their bioactivity.