Tailored ceramics

Other multiphase ceramics. Numerous multiphase ceramic formulations for conditioning of various wastes have been designed (Harker 1988). These so-called tailored ceramics were developed for immobilization of complex defence wastes at the Savannah River Plant and Rockwell Hanford Operation (Harker 1988). Tailored ceramics include ACT and REE hosts (fluorite-structure solid solutions, zirconolite. 

Harker, A. B. 1988. Tailored ceramics. In Lutze, W. Ewing, R. C. (eds) Radioactive Waste Form for the Future. Elsevier Science Publishers B.V., Amsterdam, 335-392. 

In contrast to dielectric losses permittivity is not, in general, sensitive to small amounts of impurities and for homogeneous dielectrics values can be calculated as described in Section 2.7.1, and the various mixture rules allow good estimates to be made for multiphase dielectrics. For Ba- and Sr-based dielectrics having the perovskite structure the variation of permittivity with temperature, which determines rf (see Eq. (5.37)), can be correlated with the tolerance factor t (see Section 2.7.3) [13] providing guidance for tailoring ceramics to have xf = 0. 

Naslain R, Pailler R, Bourrat X, Bertrand S, Heurtevent F, Dupel P, Lamouroux F (2001) Synthesis of highly tailored ceramic matrix composites by pressure-pulsed CVI. Solid State Ion 141-142 541-548... 

Naslain R Pailler R., Bourrat X., Bertrand S., Heurlevent F., Dupel P. and Lcmouroux F. Synthesis of Highly Tailored Ceramic Matrix Composites by Pressure-pulsed CVI // Solid State Ion. 2001. V. 141. P. 541-548. 

Biichler, O., Serra, J.M., Meulenberg, W.A. et al. (2007) Preparation and properties of thin Lax jSrjjC0i j,Fej,O3 5 perovskitic membranes supported on tailored ceramic substrates. Solid State Ionics, 178, 91-99. 

The research efforts made to tailor ceramic microstructure so as to improve properties are described in this chapter. Although many material properties are affected by the microstructure, the emphasis here is placed on the mechanical properties, especially strength and fracture toughness. In particular, attention is focused on silicon nitride ceramics, the mechanical properties of vhich have been improved substantially through microstructure tailoring during the past tv o decades. 

An important part of the current work is carried out in the field of the FP7-European project GRASP (Green Advanced Space Propulsion) [9]. As a GRASP partner, CTI Company manufactures tailored ceramic samples that differ in nature, channel shape (squares or triangles) and channel density (400 and 600 cpsi). One example of procedure to prepare the catalysts is as follows ... 

R. Naslain, R. Pailler, X. Bourrat, S. Bertrand, F. Heurtevent, P. Dupel, F. Lamouroux, Synthesis of highly tailored ceramic matrix composites by pressure-pulsed CVl, Solid State Ionics, 141, 541-548 (2001). 

Piezocomposite ceramic can be tailored to our needs in contrast to conventional piezoceramic. The first parameter we can modify is the ceramic volume fraction. Fig. 2 indicates that the thickness coupling factor of the 1-3 composite is higher over a wide range of ceramic volume fraction between 15% and 95% than the coupling factor for PZT of about 0.52. Between 25% and 70% of volume fraction it is nearly constant at a high level of approximately 0.65. 

Because of their unique combination of physical and chemical properties, manufactured carbons and graphites are widely used in several forms in high temperature processing of metals, ceramics, glass, and fused quartz. A variety of commercial grades is available with properties tailored to best meet the needs of particular appHcations (45). Industrial carbons and graphites are available in a broad range of shapes and sizes. 

Glaze coatings (58) are appHed to dry or bisque-fired clay ceramics to form a strong, impermeable surface that is aesthetically pleasing. Protective ceramic coatings can also be deposited by CVD (68,90). Plasma activated CVD has been used extensively to produce diamond and diamondlike films. Diamond films can also be used to make optical coatings with a tailored refractive index. 

S.3.2 Sol-Gel Encapsulation of Reactive Species Another new and attractive route for tailoring electrode surfaces involves the low-temperature encapsulation of recognition species within sol-gel films (41,42). Such ceramic films are prepared by the hydrolysis of an alkoxide precursor such as, Si(OCH3)4 under acidic or basic condensation, followed by polycondensation of the hydroxylated monomer to form a three-dimensional interconnected porous network. The resulting porous glass-like material can physically retain the desired modifier but permits its interaction with the analyte that diffuses into the matrix. Besides their ability to entrap the modifier, sol-gel processes offer tunability of the physical characteristics... 

Chemical engineers could also work to devise processes to improve the flow characteristics of powders after they are formed. Such research would help control agglomeration of particles in subsequent processing steps as well as facilitate the production of compacted ceramic preforms. For example, gas-solid chemical reactions might be used to tailor the chemical composition of powders. As another example, better methods of componnding powders with binders might be achieved by processes that mix powders with suitable binders in a liquid and then spray dry the resulting suspension. 

Improved characterization of the morphological/microstructural properties of porous solids, and the associated transport properties of fluids imbibed into these materials, is crucial to the development of new porous materials, such as ceramics. Of particular interest is the fabrication of so-called functionalized ceramics, which contain a pore structure tailored to a specific biomedical or industrial application (e.g., molecular filters, catalysts, gas storage cells, drug delivery devices, tissue scaffolds) [1-3]. Functionalization of ceramics can involve the use of graded or layered pore microstructure, morphology or chemical composition. 

Testinon A, Buscaglia MT, Viviani M, Buscaglia V, Nanni P (2004) Synthesis of BaTi03 particles with tailored size by precipitation from aqueous solutions. J Am Ceram Soc 87 79-83... 

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