Advances in Sintering Techniques for Calcium Phosphates Ceramics

Abstract

Calcium phosphate (CaP) biomaterials are extensively used to reconstruct bone defects. They resemble a chemical similarity to the inorganic mineral present in bones. Thus, they are termed as the key players in bone regeneration. Sintering is a heat treatment process applied to CaP powder compact or fabricated porous material to impart strength and integrity. Conventional sintering is the simplest sintering technique, but the processing of CaPs at a high temperature for a long time usually leads to the formation of secondary phases due to their thermal instability. Furthermore, it results in excessive grain growth that obstructs the densification process, limiting the application of CaP’s ceramics in bone regeneration. This review focuses on advanced sintering techniques used for the densification of CaPs. These techniques utilize the synergy of temperature with one or more parameters such as external pressure, electromagnetic radiation, electric current, or the incorporation of transient liquid that boosts the mass transfer while lowering the sintering temperature and time.

Solid‐State Li Ion Batteries with Oxide Solid Electrolytes: Progress and Perspective

“…[20,51] On the other hand, the high-temperature sintering process is a prerequisite for achieving low grain boundary resistance for grain boundary conductivity. Hence, the suitable sintering conditions [52] determine the overall ionic conductivity of SSEs. With the continuous advancement of engineering technology, advanced sintering technology has been developed.…”

“…The LATP column represents the Li ion conductivity in x ¼ 0. of sintering and is promoted at elevated temperatures. [52] For traditional sintering methods, material composition, material particle size, microstructure, temperature, atmosphere and additives will affect the diffusion and mass transfer process, which in turn affects the sintering of materials. [14]…”

“…Conversely, samples must be withdrawn from the press for drying in the isostatic CSP. [52,71] After that, the second stage starts, where solid particles make contact and give rise to a rigid framework. Three phenomena take place, that is, a) particle rearrangement, b) solvent evaporation, and c) precipitation.…”

“…In addition, if pressure is maintained in stage II, the fourth phenomenon occurs as that the sintering leads to mass transfer and particle shape modification. [52,75] Among nonconventional sintering methods, the CSP can take a complementary positioning in the powder densification process space for enabling significant energy saving and ceramic matrix polymer composite fabrication. [77] Related works demonstrate the great potential of CSP for the preparation of dense oxide SSEs.…”

Sintering behavior of nanostructured -CPP powder obtained from avian eggshell waste

“…This has stimulated the study of the sintering behavior and improvement of the mechanical properties of calcium phosphate bioceramics. The sintering of calcium phosphate bioceramics is mainly done via the conventional sintering process, but other methods such as two-step sintering, hot isostatic pressing, microwave sintering, and spark plasma sintering have also been tested [18][19][20][21][22][23]. Such methods have been used mainly for the sintering of HAp, -TCP, and HAp/-TCP mixtures.…”