Authors: Małgorzata Lewandowska, Joanna Siejka-Kulczyk, Mariusz Andrzejczuk, Krzysztof Jan Kurzydlowski
Abstract: Currently, nanopowders and nanocomposites reinforced with nanofillers are one of the
most rapidly developing groups of materials possessing excellent prospects for a wide range of
industrial and medical applications. This paper presents several examples of the nanomaterials
developed in the Faculty of Materials Science and Engineering of Warsaw University of
Technology which can have dental applications.
Ceramic-polymer composites are the most popular materials for dental fillings. The influence of
the nanofiller additions on the relevant properties of ceramic-polymer dental composites are
discussed in the paper.
The other group of nanomaterials applicable as dental materials are based on nanostructured yttrium
stabilized zirconium oxide ceramic. This ceramic is widely used for the fabrication of crowns,
bridges, inlays and other dental elements for which high strength, durability and esthetical
appearance is required. The effect of the nano-grain size of the ceramic powder on the sintering
parameters, microstructure and properties of the zirconia is discussed.
Abstract: A model for designing sandwich nanocomposite ceramic tool materials with symmetrical distribution was presented. By adding nano-sized Al2O3 particles into the submicro-sized Al2O3 and TiCN, Al2O3/TiCN sandwich nanocomposite ceramic tool materials were fabricated by means of powder-laminating and hot-pressing technique. The experimental results showed that optimal mechanical properties were achieved for the composite with the addition of 35 vol.% TiCN particles in the middle layer and 45 vol.% TiCN particles in the outer layers, layer thickness ratio is 0.3, with the flexural strength reaching respectively 900MPa，fracture toughness and Vicker's hardness in the surface layers being 6.5MPa•m1/2 and 19.2GPa.
Authors: Feng Jiao Liu, Ming Hao Fang, Yan Gai Liu, Zhao Hui Huang
Abstract: The erosion wear resistance of YSZ ceramics is worth studying because solid particle erosion is one of the main causes of destroying the materials and apparatuses. In this paper, 8YSZ ceramics reinforced by NiCr alloy and Al2O3 particles were pressureless sintered at an optimized sintering condition. The facture toughness reached a maximum value of 4.6 MPa•m 1/2 when the addition of NiCr alloy is 12 vol.%, which was much higher than that of the pure 8YSZ ceramic (2.0 MPa•m 1/2) fabricated in the same condition. Solid particle erosion wear behavior of NiCr-Al2O3-ZrO2 (8Y) ceramics composites was performed by self-designed sand blasting type solid particle erosion wear equipment, using 36# SiC particles as abrasive particles with the 90o erosion angle. The effect of the volume addition of NiCr alloy on the erosion wear of NiCr-Al2O3-ZrO2 (8Y) ceramic composites at room temperature was investigated. The results show that the volume erosion rate of the ceramic composites decreased as the volume addition of the NiCr alloy increasing. Crossing cracks, plastic deformation and minor chipping are the major erosion mechanisms.
Abstract: Considered in this paper is a semi-infinite cellular ceramic solid containing an edge crack. The solid is subjected to a sudden cooling on its surface. The temperature field and associated thermal stress field for the uncracked solid are calculated. The stress for uncracked medium is used as the crack surface stress with opposite sign to formulate the mixed boundary value problem. The stress intensity factors as the function of crack length, time and relative density are calculated. It is found that the presence of porosity in the ceramic is generally beneficial to increasing the thermal shock strength of the ceramics if the failure is dominated by a pre-existing crack. The paper may be helpful for the design and manufacturing of advanced thermal shock resistive cellular ceramics.