Graded microstructures

Controlled or graded microstructures, for example, zirconia toughened alumina (ZTA), can be made by depositing a Zr02 slurry onto an AI2O3 substrate (Gebhardt 2006). 

A multilayered glass composite concept has been considered for the safe recycling of hazardous waste containing sihcate phases [60]. in this concept, the use of layered and graded microstructures in multiphase glass-containing composites has two major objectives [60] ... 

As shown in Figure 8, the optimised concept for recycling hazardous components in a glass matrix involves layered and graded microstructures. The basic concept (Fig 8-a) consists of a well dispersed discontinuous inclusion phase containing the hazardous elements... 

Figure 2.3 Examples of different types of functionally graded microstructures.

Roschger, P., Goldenberg, F., Klaushofer, K. and Fratzl, P. (2001) Graded microstructure and mechanical properties of human crown dentin. Calcified Tissue International, 69,... 

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. 

In addition to bilayered electrodes with a functional layer and a support layer, electrodes have also been produced with multilayered or graded structures in which the composition, microstructure, or both are varied either continuously or in a series of steps across the electrode thickness to improve the cell performance compared to that of a single- or bilayered electrode. For example, triple-layer electrodes commonly utilize a functional layer with high surface area and small particle size, a second functional layer (e.g., reference [26]) or diffusion layer with high porosity and coarse structure, and a current collector layer with coarse porosity and only the electronically conductive phase (e.g., reference [27]) to improve the contact with the interconnect. 

Although the electrode performance can be improved by the introduction of compositional and microstructural gradients into the anode or cathode, the processing required to produce such graded layers also increases in complexity as the number of discrete layers increases, particularly when separate deposition and firing steps are required for each increment in layer composition or structure. 

The combination of various SOFC component performance, microstructural, and property requirements has led to a variety of structures, such as the composite, graded, and multilayered electrodes and electrolytes described above. The need... 

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