https://zirconia.typepad.com/files/zirconia-as-a-ceramic-biomaterial---piconi---biomaterials-1999.pdf

Zirconia as a ceramic biomaterial

On discute des mecanismes de renforcement des ceramiques par pontage des fissures a l'aide de trichites et d'autres types de renforcants discontinus. On montre que le renforcement par pontage des fissures peut etre combine avec d'autres mecaniques de renforcement (par exemple par transformation de phase) et que l'on peut obtenir des effets de synergie. La conception des materiaux renforces repose fortement sur le controle des proprietes des materiaux et des constituants microstructuraux

/pdf/microstructural-design-of-toughened-ceramics-1o4ydn67o9.pdf

Microstructural design of toughened ceramics

and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Nanoscaled metal borides and phosphides: recent developments and perspectives

The toughening behavior of whisker-reinforced ceramics is analyzed in terms of a whisker bridging zone immediately behind the crack tip. This approach is consistent with microscopy observations which reveal that intact bridging whiskers exist behind the crack tip as a result of debonding of the whisker-matrix interface. The theoretical results based on both the stress intensity and the energy change introduced by bridging whiskers reveal the dependence of toughening upon the composition and matrix, interface, and whisker properties. Furthermore, the analytical models of whisker bridging accompanied by very limited pullout accurately describe experimental observations of the toughening behavior in several SiC-whisker-reinforced ceramics. Such analytical descriptions also indicate that increases in whisker size and strength and modification of interface properties will result in further increases in toughness by whisker reinforcement.

Toughening Behavior in Whisker-Reinforced Ceramic Matrix Composites

Directionally solidified eutectic ceramic oxides

Toughening of whisker-reinforced (or fiber-reinforced) ceramics by whisker pullout requires debonding at the whisker/matrix interface. Compressive clamping stresses, which would inhibit interface debonding and/or pullout, are expected in composites where the matrix has a higher thermal expansion coefficient than the whisker. Because such mismatch in thermomechanical properties can result in brittle composites, it is important to explore approaches to modify the thermal stresses in composites. As a result, the effects of a film at the whisker/matrix interface on the stresses due to thermal contraction mismatch upon cooling are considered in this study. Analysis of various properties of the film are considered for the whisker/matrix systems, in particular for SiC/Al2O3, SiC/cordierite, and SiC/mullite composites. Reduction of thermomechanical stresses is shown to occur when the interfacial film has a low Young's modulus. Also, when the whisker has a lower thermal expansion coefficient than the matrix (e.g., SiC/Al2O3), the interfacial stresses generated during cooling decrease as the thermal expansion coefficient of the film increases.

Effects of Interfacial Films on Thermal Stresses in Whisker Reinforced Ceramics

Raman spectral characterization of silicon carbide nuclear fuel coatings

TiB/sub 2/ coatings were chemically vapor deposited by hydrogen reduction of TiCl/sub 4/ and BCl/sub 3/. Process variables investigated were deposition temperatures from 750 to 1050/sup 0/C and the TiCl/sub 4/ and BCl/sub 3/ flow rates. Various grades of commercially available cemented carbides and experimental nickel-bonded TiB/sub 2/ were used as substrates. Resistance of the coatings to erosion was evaluated using a hot, coal-oil slurry impingement test. The TiB/sub 2/ deposition rate was temperature dependent ranging from 0.1 to 2.9 ..mu..m/min between 750 and 950/sup 0/C. The surface morphology of the coatings was nodular with the size of the nodules increasing with temperature. The coatings were dense and adherent. The grain size varied with deposition conditions. TEM showed the grain size to be very small (2 to 300 nm), increasing with distance from the substrate. Electron microscopy and x-ray diffraction indicated only the presence of single-phase TiB/sub 2/ and ion microprobe analysis revealed a constant Ti/B ratio across the coating thickness. Energy dispersive fluorescence analyses showed coatings deposited at 800/sup 0/C contained more chlorine than coatings deposited at the higher temperatures. Coating microhardness and erosion resistance were temperature dependent. The hardness of coatings deposited at 800 and 900/sup 0/C weremore » 15 and 32 GPa, respectively. Coatings deposited at 850/sup 0/C or below experienced extensive erosion (up to 30 ..mu..m deep craters during a 1 h test) while those deposited at 900/sup 0/C and above showed very little or no erosion (0 to 2 ..mu..m).« less

Chemical Vapor Deposition of Erosion‐Resistant TiB2 Coatings

The microstructure and chemistry of grain-boundary phases in silicate-doped Y{sub 2}O{sub 3}-ZrO{sub 2} ceramics were evaluated by analytical electron microscopy Two different silicate compositions were used: one an aluminosilicate and the other a borosilicate glass These grain-boundary phases had a significant impact on the grain morphology, the chemical composition of the grains, and the crystallization of second phases These results indicate that controlled additions of specific glass phases may provide a means for tailoring the microstructure and physical properties of zirconia ceramics

P. Angelini

Papers

Toughening Behavior in Whisker-Reinforced Ceramic Matrix Composites

Effects of Interfacial Films on Thermal Stresses in Whisker Reinforced Ceramics

Raman spectral characterization of silicon carbide nuclear fuel coatings

Chemical Vapor Deposition of Erosion‐Resistant TiB2 Coatings

Microstructural and Chemical Influences of Silicate Grain-Boundary Phases in Yttria-Stabilized Zirconia