Abstract
The role of the effect of electroosmosis in the process of electrochemical deposition of a biocompatible coating on the inner surfaces of porous nanostructured ceramics, a material used to make endoprostheses and implants in medicine, is discussed. The biocompatibility of endoprostheses and implants with the human body is ensured by applying a special coating on the internal and external surfaces of the base material. The commonly acepted chemical compound used to form this coating is hydroxyapatite Ca10(PO4)6(OH)2. Multicomponent ceramic materials, from which the basis of endoprostheses and implants are made, are usually obtained by the traditional method of powder metallurgy - sintering, i.e., exposure of a mixture of powders at an elevated temperature under pressure. The material obtained in this way is a polycrystal. In addition, the structure of such a material contains a certain amount of voids in the form of individual pores or their associations (capillaries). The paper shows that the use of nano-structured ceramic materials with a characteristic average size of structural elements (grains, pores and their aggregations) of the order ≈(10–9–10–7)м as a material for the manufacture of implants may determine the greater efficiency of the process of electrochemical application of a biocompatible coating on them, since the resulting large electroosmotic pressure in the capillaries leads to a greater degree of filling of the porous system with electrolyte. The magnitude of the electroosmotic pressure can be increased by increasing the strength of the acting electric field or by decreasing the dielectric constant of the electrolyte ε when additional chemical additives are introduced into the electrolyte. The maximum degree of hollow channels (capillaries) filling with electrolyte, and, consequently, the efficiency of applying a biocompatible coating to the internal surfaces of ceramics using the electrochemical method, is achieved with the capillary system of the material being completely open.
Highlights
One of the important areas of modern materials science is the synthesis of mechanically durable and wearresistant materials having biocompatibility with the human body
For example, ceramics based on the so-called MAX phases; ceramics made of refractory oxides Al2O3, Y2O3; "Amorphous" ceramics (Si, B, N, C), obtained by polycondensation [7] and others
The above discussion suggests that nano-structured ceramic materials are characterized by the much higher electroosmotic pressure Pe compared to micro-sized ceramics
Summary
One of the important areas of modern materials science is the synthesis of mechanically durable and wearresistant materials having biocompatibility with the human body (bone and fabric). In the process of implementing the above-described method of applying a coating on the internal surfaces of porous ceramics, conditions arise for development of the socalled electrokinetic effects, in particular, of the electroosmosis effect [14] This effect is due to the interaction of an external electric field with the double charged layer of thickness δ≈10–9m, formed at the interface of the liquid electrolyte and the solid phase. The electric field directed along the boundary interface causes the liquid flow relative to the solid phase with a velocity v It is this effect is directly related to the process of a biocompatible coating applying on the internal surface of the ceramic material. This paper is devoted to the consideration just of the electroosmosis effect role when using the electrochemical method of a biocompatible coating applying on the internal surfaces of porous nano-structured ceramics
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