Surface Coating of Oxide Powders: A New Synthesis Method to Process Biomedical Grade Nano-Composites

Abstract

Composite and nanocomposite ceramics have achieved special interest in recent years when used for biomedical applications. They have demonstrated, in some cases, increased performance, reliability, and stability in vivo, with respect to pure monolithic ceramics. Current research aims at developing new compositions and architectures to further increase their properties. However, the ability to tailor the microstructure requires the careful control of all steps of manufacturing, from the synthesis of composite nanopowders, to their processing and sintering. This review aims at deepening understanding of the critical issues associated with the manufacturing of nanocomposite ceramics, focusing on the key role of the synthesis methods to develop homogeneous and tailored microstructures. In this frame, the authors have developed an innovative method, named “surface-coating process”, in which matrix oxide powders are coated with inorganic precursors of the second phase. The method is illustrated into two case studies; the former, on Zirconia Toughened Alumina (ZTA) materials for orthopedic applications, and the latter, on Zirconia-based composites for dental implants, discussing the advances and the potential of the method, which can become a valuable alternative to the current synthesis process already used at a clinical and industrial scale.

Ceramics and ceramic coatings in orthopaedics

“…While the current standard in bioinert ceramics is BIOLOX ® delta (CeramTec, Plochingen, Germany), its position may eventually be challenged by other ZrO 2 and ZTA compositions having both high strength and little or no LTD, or by non-oxide ceramics such as Si 3 N 4 with elevated strength and no LTD. As an example of an improved ZrO 2 , Matsui et al demonstrated that addition of a small amount of germanium oxide (0.30 mol%) to a 3 mol% Y 2 O 3 -doped ZrO 2 coupled with low-temperature sintering produced a fully dense nano-crystalline Y-TZP (grains <300 nm) which exhibited no LTD for 4 years in a steam autoclave at 140 • C [572]. As other examples, ZTA nano-composites which exclude the use of yttria, or which incorporate zirconia nano-particles (<500 nm) evenly dispersed within alumina grains have been developed [154,573]. Both composites result in high strength, tough, and highly LTD resistant ceramics.…”

Initial osteoblast adhesion and subsequent differentiation on zirconia surfaces are regulated by integrins and heparin-sensitive molecule

“…16 As reported, zirconia is a biocompatible material with great mechanical properties. 17 Our previous works reported the similar bioactivity of NANOZR, Y-TZP and CpTi after being polished. 18 However, the mechanisms of osteoblast adhesion onto zirconia material needed further investigation.…”

Structural Ceramic Nanocomposites: A Review of Properties and Powders’ Synthesis Methods

“…Besides the method investigated by Schehl et al [ 153 ], based on the use of organic precursors, also inorganic salts were used to coat the surface of commercial Al 2 O 3 particles and to induce the crystallization of second-phases upon calcination. Yuan et al [ 156 ], for instance, added cerium and aluminum nitrates to the isopropanol suspension of ZrO 2 powder, in order to obtain ceria-stabilized ZrO 2 /2 wt. %Al 2 O 3 composites.…”