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Tribochemistry
Published in Czesław Kajdas, Ken'ichi Hiratsuka, Tribocatalysis, Tribochemistry, and Tribocorrosion, 2018
Czeslaw Kajdas, Ken’ichi Hiratsuka, Gustavo Molina, Akira Sasaki, Roberto C. Dante
Silicon nitride is appreciated especially for its excellent resistance to thermal shock, fracture toughness and wear resistance. It is used for bearings, rotors, valve seats, pistons and piston heads, helicopter gearboxes, etc. High hardness, fracture toughness, and wear resistance. Sialon, which is basically a silicon nitride containing small amounts of sintering agents, is used in machining the alloys that cannot be machined by the aluminum oxide-base tools, for internal combustion engine parts, for example the rings, injectors, bearings, turbo-superchargers, rotors, cam followers, valve-sleeve guides, and so on [15].
Ceramics
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
The main properties of sialons is that they retain their hardness at higher temperatures than alumina. They are tough but rather less so than a cemented carbide of equal hardness. Sialons are used for cutting-tool materials, dies for drawing wire and tubes, rock-cutting and coal-cutting equipment, nozzles and welding shields. Because they have a good combination of high-temperature and thermal-shock resistance, sialons are used for the manufacture of thermocouple sheaths, radiant heater tubes, impellers, small crucibles and other purposes involving temperatures up to 1250°C.
Ceramics: Processing, Properties, and Applications
Published in Noureddine Ramdani, Polymer and Ceramic Composite Materials, 2019
On the other hand, silica (SiO2) represents a simple silicate mineral that has, as a repeating unit, the SiO− tetrahedron. In either vitreous or fused SiO2, the main crystal unit is SiO4− tetrahedron, but there is no long-range order in the arrangement of this unit. Traditional glasses are silica-based ceramics to which oxides of A1, Ca, Mg, B, Na, and K, etc. have been attached; these oxides decrease the melting point and reduce the viscosity of glass, thus markedly easing the shaping of glass into very complex objects [4, 5]. Glass is an amorphous solid solution of various oxides, since SiO2 content exceeds 50% and is considered the main constituent. Glasses show a disordered or liquid-like atomic structure. As a solid-solution alloy of ceramic oxides, glasses do not exhibit a single melting temperature and they are characterized by a melting range. Several other naturally-existing ceramics also are constituted from SiO2; this includes kaolinite clay, talc, and mica [6]. In addition to the SiO4, tetrahedral structures can be detected in other chemical compositions, such as A1O4, SiN4, and A1N4. These tetrahedrons have a similar size as SiO4, thus, they can replace each other in silicate structures. It has been reported that two-thirds of the Si element in α-Si3N4 can be substituted by A1 atom without modifying the Si3N4 crystalline structure, where the amount of nitrogen is replaced by oxygen. This type of ceramic mixture is called a sialon, which is mainly composed from a solid solution of both Si3N4 and A12O3. Similar types of sialons have also been produced, in particular those based on θ-Si3N4 and Si2N2O structures.
Sialon from synthesis to applications: an overview
Published in Journal of Asian Ceramic Societies, 2021
Ahmed A. M. El-Amir, A. A. El-Maddah, Emad M. M. Ewais, Said M. El-Sheikh, Ibrahim M.I. Bayoumi, Y.M.Z. Ahmed
Currently, sialons are one of the most important advanced structural materials since they have a good combination of properties including high dimensional stability, high-strength at elevated temperatures, good wear and corrosion resistance, low weight density, high hardness, good resistance to thermal shock resistance, and high elastic modulus. In spite of that, they suffer indelibly from defects of a rather weak fracture toughness (3–8 MPa m1/2) [1,41–43]. Because of their low fracture toughness, reliability of sialons is not yet adapted to production commitment. Several techniques have been developed and many challenges have been overcome to manufacture strengthened and toughened sialon-based products. These techniques included fabrication of α/β-sialon composites [41,44–47], fiber-reinforced sialons using high quality carbon fiber and/or SiC fiber [48–52], particle/whisker-reinforced sialons [53]. The best method to enhance the fracture toughness of sialons was the preparation of a sialon matrix composite using a reinforcement material. Sialon-reinforced composites exhibited improved toughness with better reliability, reduced crack propagation, and even more resistance to failure.
High mechanical properties of β-SiAlON/TiC0.3N0.7 ceramic composite prepared by pressureless spark plasma sintering
Published in Journal of Asian Ceramic Societies, 2021
J.Q. Li, Q.Z. Chen, Y.L. Lan, C.H. Zhang, Y. Li, L.P. Hu, F.S. Liu, W.Q. Ao, H.P. Xie
Silicon nitride ceramic is an advanced ceramic material with low density, high strength, good friction and oxidation resistance and high chemical corrosion resistance, which is widely used in cutting tools, bearings, reciprocating engine parts, wear and metal forming components [1–4]. β-SiAlON is a β-Si3N4 solid solution by substitution of a silicon-nitrogen bond with aluminum-oxygen bond [5–7], named after the elements they contain silicon (Si), aluminum (Al), oxygen (O) and nitrogen (N). SiAlON shows similar physical and mechanical properties to those of Si3N4 ceramics, but better thermal shock resistance because of its lower thermal expansion. However, the SiAlON matrix composites still exhibit some inadequacies such as the inherent brittleness of ceramic [8–10]. Many efforts have been made to improve the brittleness properties of the ceramics via well-definable composition and microstructure by carefully controlling the process parameters and methods [11–13].