Microstructure sintered ceramic

For second-phase sintered ceramics, these phases control the plasticity and they are responsible for the asymmetric behaviour when deformed in tension or compression, because there is a crucial difference in the microstructure evolution associated with tension and compression creep. There are few explanations for this asymmetry. 

Considerable development has occurred on sintered ceramics as bone substitutes. Sintered ceramics, such as alumina-based ones, are uru eactive materials as compared to CBPCs. CBPCs, because they are chemically synthesized, should perform much better as biomaterials. Sintered ceramics are fabricated by heat treatment, which makes it difficult to manipulate their microstructure, size, and shape as compared to CBPCs. Sintered ceramics may be implanted in place but cannot be used as an adhesive that will set in situ and form a joint, or as a material to fill cavities of complicated shapes. CBPCs, on the other hand, are formed out of a paste by chemical reaction and thus have distinct advantages, such as easy delivery of the CBPC paste that fills cavities. Because CBPCs expand during hardening, albeit slightly, they take the shape of those cavities. Furthermore, some CBPCs may be resorbed by the body, due to their high solubility in the biological environment, which can be useful in some applications. CBPCs are more easily manufactured and have a relatively low cost compared to sintered ceramics such as alumina and zirconia. Of the dental cements reviewed in Chapter 2 and Ref. [1], plaster of paris and zinc phosphate... 

The first feature discussed above has been well recognized, and much modern research has been focussed on developing biocompatible calcium-based ceramics. Manipulation of the microstructure, however, has not been attempted sufficiently, and much of the rapid prototyping has been to develop suitable macroscopic forms for sintered ceramics. 

Ceramic powder characteristics are important because the purity of the powder sets the maximum purity level of the final processed ceramic part, and the particle size and size distribution play major roles in defining the microstructure and properties of the final parts. Both the purity and the microstructure of sintered ceramics influence the properties of ceramic materials, including mechanical, thermal, electrical, and magnetic properties and chemical corrosion resistance. 

The ceramic industry has developed various highly sophisticated manufacturing methods to meet the material requirements of homogeneous microstructure and phase distribution of the sintered ceramic. These are the key factors for predictable mechanical and functional properties. 

The microstructure observation of the sintered ceramics surface was performed by means of scanning electron microscopy (SEM, JEOL JSM 6400, Japan). The crystalline phase of sintered ceramics was identified by X-ray diflfaction (XRD, RIGAKU D/max 2.B) with CuKa radiation (X=l. 541SA at 40 kV and 30 mA) and scanned from 20° to 70° with scanning speed of 4°/min. The bulk densities of the sintered pellets were measured by the Archimedes method. The dielectric constant ( ,) and the quality factor values (Qxf) at microwave frequencies were measured using the Hakki-Coleman dielectric resonator method which had been modified and improved by Courtney The dielectric resonator was positioned between two brass plates. Microwave... 

Kleebe HJ, Reimanis IE, Cook RL (2005) Processing and microsbucture charactoization of transparent spinel monohths. In DiAntonio CB (ed) Characterization and modeling to control sintered ceramic microstructures and proptaties, pp 61-68... 

Adder, H. D. and Chiang, Y.-M., Effect of initial microstructure on final intergranular phase distribution in liquid phase sintered ceramics, J. Am. Ceram. Soc., 82, 183-89, 1999. 

The microstructure of a sintered ceramic and microstructure development during sintering are also controlled by the thermodynamics of the system. Thermodynamics determines what interfaces are formed, what porosity can be eliminated, the size and shape of the grains and pores, and whether or not densification occurs during sintering. 

In solid-state sintered ceramic systems, densification and microstructure development can be assessed on the basis of the dihedral angle, 0, formed as a result of the surface energy balance at the pore-grain boundary intersection. 

Pressure sintering can also be useful to further density sintered ceramics. The density of liquid-phase sintered PZT was improved from —97% to -98% of theoretical density by HIPing for 7.5—60 min at 1300 °C and 7—21 MPa. Consistent with the microstructural evidence of liquid formation and redistribution (Figure 5.7), and the preferential annihilation of the fine, submicrometer porosity within the micro-structure, the majority of densification occurs rapidly, within the first few minutes of HIPing. 

Techniques Desmarquest, Saint-Gobain Ceramiques Industrielles). The spread of the lines accounts for variations of wear behavior related to differences in the microstructure of the sintered ceramics. 

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