A review of the influence of environmental humidity and water on friction, lubrication and wear

In the early 1970s in Japan, the United States and France it was found that additions of nitrogen into aluminum oxide resulted in new spinel-like phases. At about the same time there was much increased interest in oxynitrides, stimulated by Professor K. Jack in the UK and Y. Oyama in Japan. Following these activities a major research program in this area was initiated at the Army Materials and Mechanics Research Center in Watertown, Massachusetts in 1974. These efforts resulted in the first complete Al2O3–AlN phase equilibrium diagram and a process to reactively sinter to nearly full density, translucent aluminum oxynitride spinel ceramic, which was named AlON. Subsequently, the Raytheon Company further developed AlON into a highly transparent material (ALON™) with many applications including transparent armor and EM domes and windows, among others—the technology was recently transferred to the Surmet Corporation. This paper will review the early history, phase equilibrium, crystal chemistry, and properties of this material, along with more recent work in our laboratory on transient liquid phase sintering and new data on lattice parameter measurements. In addition, recent results of collaborative work on AlON's dynamic mechanical properties using plate impact, Kolsky bar and edge-on impact (EoI) experimental techniques, including preliminary modeling at the microstructural scale of AlON in the EoI test, will be presented.

AlON: A brief history of its emergence and evolution

The processing of laminar ceramic composites from stacking of layers obtained by tape casting is described. In the case of composites for structural applications, the reinforcement mechanisms are briefly reviewed. It is shown that both strength and toughness can be improved. The evaluation of residual stresses allows a strategy for tailoring the mechanical properties of such composites to be developed. As an example, results are given in the case of laminar composites with layers made of alumina with various zirconia contents.

Laminar ceramic composites

The need for new materials to substitute injured or damaged parts of the human body has led scientists of different areas to investigate bioceramics since the 70's, when other materials in use started to show rejection problems. Ceramics show some advantages like being the material that best mimics the bone tissue, although present low toughness when compared with the metallic materials. As patients have become more and more demanding regarding esthetic and biocompatibility aspects of their dental restorations, ceramic material has become a main object of scientific interest especially from the material point of view. The alumina-zirconia composites are one of the relatively good and promising candidate for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where Y-TZP zirconia content was varied from 5 to 80 wt.% These systems can achieve a flexural strength 93 % and fracture toughness 29 % superior when compared to the pure alumina ceramics. These results showed that ceramic abutments components can be prepared for prosthetic rehabilitations with dental implants.

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Mechanical properties of alumina-zirconia composites for ceramic abutments

Material-specific wear mechanisms : relevance to wear modelling

Strength and fracture toughness of reaction-sintered mullite/zirconia composites (RSMZ) and reaction-sintered mullite/alumina/zirconia composites have been investigated as a function of temperature. Thermal shock resistance has also been determined. It was found that dispersion of zirconia particles and the particular microstructure of mullite obtained by means of anin situ reaction process leads to improved properties, with a room temperature fracture toughness of about 5.25 MPa m1/2. Up to 1000° C fracture strength and toughness values are quite high, which make these materials potential candidates for high temperature applications.

High temperature mechanical properties of reaction-sintered mullite/zirconia and mullite/alumina/zirconia composites

Mechanical behavior of Al2O3-based ceramics can be improved by dispersion of pure or partially stabilized ZrO2 particles. The effective toughening or strengthening effect, which is operating in these composite materials, is determined by microstructural characteristics (composition, processing conditions) and environmental conditions (temperature, loading rate,…). The objective of this work has been to make a correlation between mechanical properties and wear resistance of alumina-zirconia composites. Wear tests were conducted employing a bloc-on-ring tribometer which consists of a steel ring rotating against plane ceramic specimens. Different environmental conditions were investigated: ambient air, and water. The wear volume is determined as a function of sliding distance. The dispersion of ZrO2 particles in Al2O3 matrix improves the fracture behavior but reduces the wear resistance. However, the addition of ZrO2 limits the water corrosion effect observed in Al2O3 materials. Wear seems to be controlled b...

Relationship between mechanical properties and wear resistance of alumina-zirconia ceramic composites

Etude des proprietes mecaniques de composites ceramiques Al 2 O 3 −AlON obtenus par frittage reactif a partir d'un melange Al 2 O 3 −AlN

Reaction-sintering of an Al2O3-AION composite determination of mechanical properties

Effect of γ-aluminum oxynitride dispersion on some alumina properties

Resume Des ceramiques alumineuses renforcees par de l a zircone ont Gte preparees par deux procedes d i f f e r e n t ~ a pa r t i r des memes matieres premieres (poudres). Le premier u t i l i s e l e broyage par a t t r i t i o n e t l a compression I chaud ; l e second, une dispersion 6lectrochimique, l e coulage en barbotine e t l e f r i t tage sans charge. L'influence des parametres d'elaboration sur les proprietes mecaniques des pieces denses e s t examinee. L'influence des teneurs en ZrOz e t Y203 e s t discutee. Abstract Zi rconia Toughened A1 umina (ZTA) ceramics were prepared by two different methods from the same raw materials (powders). The f i r s t one using a t t r i t i on milling and hot-pressing ; the second, electrochemical dispersion, s l i p casting and pressureless sintering. The influence of the processing parameters on the mechanical properties of dense material i s examined. The influence of Zr02 and Y203 contents i s discussed.

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G. Orange

Papers

High temperature mechanical properties of reaction-sintered mullite/zirconia and mullite/alumina/zirconia composites

Relationship between mechanical properties and wear resistance of alumina-zirconia ceramic composites

Reaction-sintering of an Al2O3-AION composite determination of mechanical properties

Effect of γ-aluminum oxynitride dispersion on some alumina properties

Mechanical properties of zirconia toughened alumina prepared by different methods