Thermal shock resistance of two micro-structured alumina obtained by natural sintering and SPS

cited By 8International audienceIn the present work, the indentation air quenching technique was used to evaluate thermal shock behavior of a micro-structured alumina obtained with different sintering techniques (Spark Plasma Sintering and natural sintering) and conditions (varying dwell time, dwell temperature and pressure). The main objective is to evaluate the effect of the sintering technique on the thermal shock properties, by comparing the mechanical and thermal shock properties between samples prepared by natural sintering and SPS. Another objective is to determine how the grains size and porosity affect the initiation and growth of cracks in samples submitted to thermal shocks of different amplitudes. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Preparation of porous hydroxyapatite scaffolds

International audienceIn this work, the sintering and grain growth of hydroxyapatite green bodies are analyzed in order to identify the optimum heat treatments for the preparation of porous hydroxyapatite scaffolds. Sintering in air at temperatures ranging between 1100 and 1200 °C yields dense materials with narrow grain-size distributions. The scaffolds are formed by the infiltration of polymer foams with hydroxyapatite slurries or by robocasting, a novel rapid-prototyping technique. Examples of the microstructures achieved with each approach are presented. It is observed that both techniques can be used to fabricate scaffolds with adequate pore size to promote bone ingrowth

Interplay between internal stresses and matrix stiffness influences hydrothermal ageing behaviour of zirconia-toughened-alumina

International audienceZirconia based bio-ceramics such as ZTA (Zirconia-toughened alumina) composite are often used in orthopaedic and dental implants. The hydrothermal ageing behaviour of zirconia in humid environments is an important factor affecting the lifetime of these biomaterials. It is a tetragonal-to-monoclinic phase transformation that has been shown to be both temperature-and stress-dependant. Here, ZTA composites with zirconia inclusion particles of different sizes were prepared. The influence of zirconia inclusions on internal stresses and thus on ageing behaviour was studied by Raman micro-spectroscopy and X-ray diffraction. The results show that the ageing kinetics result from a balance between stiffer matrix and increased tensile stress in the zirconia inclusion as the local alumina fraction increase. As a result, the maximum monoclinic fraction formed after1200 h ageing at 134°C decreases with increasing alumina content, showing the predominance of the stabilization of tetragonal particles by a stiff matrix over their destabilization by tensile stress. Wei et al. Internal stresses and matrix stiffness influences ageing of ZTA, Acta Mater. 2020

Reliability assessment in advanced nanocomposite materials for orthopaedic applications.

Alumina-zirconia nano-composites were recently developed as alternative bearing materials for orthopedics. Previous, preliminary reports show that such alumina-zirconia nanocomposites exhibit high crack resistance and low wear rate. In this paper, additional information is given in terms of wear, crack resistance and ageing behaviour: femoral heads are inspected after 7 million cycles of wear testing on a hip simulator, crack resistance is measured and compared to other ceramics used today in orthopedics, slow crack growth is reported under static and cyclic fatigue, and aging resistance is assessed. We also report on the load to failure of femoral heads prototypes during compression tests. This overall reliability assessment ensures a potential future development for these kinds of new nanocomposites in the orthopedic fiel

Slow Crack Propagation in Ceramics at the Nano- and Micro-Scale: Effect of the Microstructure

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