The hydrolysis behavior of aqueous AlN powder suspensions (5–25 wt%) at 5°C has been investigated to explore the impact of low temperatures on the hydrolysis behavior. Throughout the 312-hours-long experiment, the pH value of the suspensions was below 9, where the hydrolysis remained in the induction period and was eventually suppressed due to the formation of a few-nanometers-thick film of amorphous aluminum hydroxide gel around the AlN particles, acting as a passivation layer. Moreover, the aqueous part of the suspension possessed a remarkably high value of dissolved [Al(III)]aq, being an order of magnitude higher at a given pH value than the aqueous AlCl3 solution.
COBISS.SI-ID: 26570023
A novel method for the synthesis of a thin β-tricalcium phosphate (β-TCP) coating on zirconia implants has been developed. The synthesis procedure involves two steps: (i) rapid wet-chemical deposition of a biomimetic CaP coating and (ii) subsequent post-deposition processing of the biomimetic CaP coating, which includes a heat treatment at 900 °C followed by a short sonication in a water bath. The obtained β-TCP coating showed a uniform and dense morphology with a thickness of ≈500 nm and displayed a roughness in the nanometre range (Ra = 28 nm). The β-TCP coating demonstrated an apatite-mineralization ability in a simulated body fluid and enhanced the adsorption of serum proteins on the zirconia. Moreover, the β-TCP coating adhered firmly to the zirconia substrate, developing a notable scratch resistance and tensile strength and showed strong resistance towards mechanical forces present during implantation of the coated zirconia implant into the artificial bone.
COBISS.SI-ID: 26983975
The first part of this article describes the basic properties of yttria stabilized tetragonal zirconium oxide ceramics (Y-TZP) important for the use in clinical medicine; high strengthand fracture toughness, biocompatibility and negligible radiation. The ageing issue of this particular material, which is attributable to the thermo-dynamical instability of tetragonal zirconium oxide in hydrothermal conditions, is also discussed. In the second part of this work the clinical application of zirconia oxide ceramics in dental medicine is also presented. Conventional porcelain fused to metal technique is successfully replaced with Y-TZP ceramics in some clinical situations that are described in detail. It is important that computer design of the zirconia frameworks shortens and simplifies laboratory procedures and contributes to a precise final product.
COBISS.SI-ID: 27418919
This chapter reviews the structure, mechanical properties and biocompatibility of load bearing ceramics used in dentistry. The literature on polycrystalline alumina and zirconia dental implants is reviewed. Today, the trend is to replace alumina and zirconia ceramics in less aesthetic regions and applications by their respective mixtures, yielding ceramic composites, such as zirconia-toughened alumina (ZTA) and alumina-toughened zirconia (ATZ). At the end, the adhesion issue related to chemically inert alumina and zirconia is addressed.
COBISS.SI-ID: 27062055
High-performance, porous, Y-TZP nanoceramics with hierarchical heterogeneities originating from uniform, intra- and inter-particle packing were prepared by colloidal processing and partial sintering of a mesoporous powder. The powder consisted of 100–150-nanometer-sized secondary particles initially composed of smaller, loosely aggregated, primary, nanoscale crystallites. Green bodies were prepared by centrifugal slip casting of weakly flocculated suspensions. During the initial stage of sintering, necking between the secondary particles was accompanied by intra- particle pore coalescence, while the pores originating from the secondary particle packing remained intact.
COBISS.SI-ID: 26881831