Advances in Functionally Graded Ceramics – Processing, Sintering Properties and Applications

Abstract

In multilayered structures, sharp interface is formed between the layers of dissimilar materials. "t this interface, the large difference in thermal expansion coefficients of the two dissimilar materials generates residual thermal stresses during subsequent cooling. These stresses lead to cracking at the interface, and these cracks lead to the deterioration of mechanical properties, and finally crack propagation leads to the delamination of the multilayered structure. Scientific progress in the field of material technology, and the continuing developments of modern industries have given rise to the continual demand for ever more advanced materials with the necessary properties and qualities. The need for advanced materials with specific properties has brought about the gradual transformation of materials from their basic states monolithic to composites. Recent advances in engineering and the processing of materials have led to a new class of graded multilayered materials called Functionally Graded Materials FGMs . These materials represent a second generation of composites and have been designed to achieve superior levels of performance. This chapter looks at the best processing technologies and the uses and applications of the advanced, high quality products generated, and also presents an extensive review of the recent novel advances in Functionally Graded Ceramics FGCs , their processing, properties and applications. The manufacturing techniques involved in this work have involved many concepts from the gradation, consolidation and different sintering processes. Each technique, however, has its own characteristics and disadvantages. In addition, the FGC concept can be applied to almost all material fields. This chapter covers all the existing and potential application fields of FGCs, such as engineering applications in cutting tools, machine parts, and engine components, and discusses properties of FGCs such as heat, wear, and corrosion resistance plus toughness, and their machinability into aerospace and energy applications.

A particle swarm-based algorithm for optimization of multi-layered and graded dental ceramics

“…What the model gives a user as outputs are (i) an optimal compositional exponent from which porcelain/zirconia volume fraction can be evaluated for each layer; (ii) an optimal number of layers constituting the structure; and (iii) an optimal thickness of each layer. Two main steps of FGCs fabrication are gradation and consolidation (Besisa and Ewais, 2016;Naebe and Shirvanimoghaddam, 2016). The former is the building of the spatially inhomogeneous graded structure and the consolidation is to transfer this graded structure into the bulk material.…”

“…The former is the building of the spatially inhomogeneous graded structure and the consolidation is to transfer this graded structure into the bulk material. The gradation process is commonly categorized as constitutive, homogenizing and segregating processes (Besisa and Ewais, 2016). The gradation process of a FGC dental restoration is made by mixing different volume fractions of the porcelain and zirconia components.…”

“…Moreover, some challenges involved in stacking process include warping, crack initiation and propagation and frustum formation. Lamination can take place in final products owing to unpredictable distribution of particles (Besisa and Ewais, 2016;Naebe and Shirvanimoghaddam, 2016). In the subsequent processes, the consolidation can be performed by a variety of production methods, such as (1) powder sintering as the main mechanism of powder consolidation in a solid component; (2) hot pressing under temperature and pressure, simultaneously, with induction heating; (3) cold pressing by a cold pressing followed by sintering; (4) spark plasma sintering by charging the intervals between powder particles with electrical energy (Besisa and Ewais, 2016;Naebe and Shirvanimoghaddam, 2016;Chai et al, 2014;Tsukada et al, 2014;Villefort et al, 2017).…”

Functionally graded ceramics for biomedical application: Concept, manufacturing, and properties

“…Different examples of FGMs are available in literature, showing gradation in composition, micro/nanostructure (grain size, grain shape, texturization level, etc. ), density and other physico‐chemical properties.…”

“…Two main key features characterize FGMs: on the one hand, the spatially varying property is designed to optimize a desired performance across the whole volume; on the other hand, the sharp interfaces existing in traditional composite materials—which is where failure is often initiated, are here eliminated. For these reasons, FGMs are reported to exhibit superior mechanical properties when compared to basic (monolithic) and composite structures …”