**1. Introduction**

Nowadays, the new era of development of the sintering process has begun. The sintering of metal and ceramic powders plays an important role in our industry.

Sintering is a one-way processing technique which allows the production of density-controlled materials and components from metal or/and ceramic powders through particle bonding. This process of powder consolidation is quite famous and has been applied in different fields for more than 5000 years [1–4].

In general, sintering processes can be classified according to the material state during the sintering process as solid-state sintering and liquid phase sintering. The ability to achieve consolidation without melting is made possible by the thermal activation of mass transport processes driven by reduction of surface and grain boundary energies. To optimize thermal activation and attain high density with concomitant strength, sintering is carried out at high temperatures, relative to the melting point of the material. Optimal parameters for sintering result from a combination of material variables and process parameters [5], as shown in **Table 1**.

The sintering process generates an increase in the compact strength and rigidity, together with a dimensional change of the powder particles, with the formation of necks between contacting spheres. Typically, longer sintering times produce larger necks and, therefore, samples with higher strength.

Money-saving reasons moved the scientific research toward a variety of means of thermal activation and, in particular, electric current, in order to produce highdensity objects in a faster way and using lower temperatures. Spark plasma sintering (SPS) and pulsed electric current sintering (PECS) techniques are only a few examples of how far the research is pushing the performance of sintering, at both fundamental and applied levels [7–9].

In terms of heating methods, the most common can be synthesized as follows: (i) contact methods, such as thermal conduction, radiation, or convection and (ii) noncontact heating methods, such as induction, radio frequency (RF), or microwave heating.

This book consists of six sections; the new era of sintering is presented at the beginning of the book. This first section opens with the introduction on sintering followed by an overview on the different sintering techniques and thermodynamics and kinetics of sintering. The second section focuses on the influence of sintering on microstructure and mechanical properties. The third section provides a comprehensive summary on the solid-state sintering of materials (intermetallics, ceramics, metals, and composites). The fourth section is dedicated to sintering-based 3D printing as a new technology. The fifth section addresses on the composite sintering and applications. The mathematical models and numerical methods for continuous sintering approaches are fully discussed in the last section.


**Table 1.**

*Summary of the major sintering parameters (adapted from [6]).*

The book aims to provide informative chapters to the readers, researchers, and material engineering and industrial material scientists. The chapters in this book are from specialists in their respective disciplines. In addition, this book is very important for the diffusion of the scientific knowledge.
