News

It is typically carried out at high temperatures well above 1000°C for most ceramics. The use of such high temperatures poses several challenges for ceramic manufacturing, such as high energy consumption and carbon emissions, unwanted chemical side reactions and secondary phase formation, limited microstructural control and materials integration possibilities. Therefore, recent research has been focused on developing alternative sintering techniques that can lower the sintering temperature. Recently, ultralow-temperature densification was demonstrated by the cold sintering process (CSP), which densifies a wide range of ceramic systems at temperatures not exceeding 350°C and down to room temperature. It involves the addition of a chemically active transient liquid phase and the application of external pressure in the range of several hundred megapascals. The process is enabled through chemical interactions, activating diffusional sintering at these low temperatures. 

Owing to the unprecedent low temperature densification, CSP opens new opportunities for grain boundary and composite designs with enhanced functionalities, combining ceramics with polymers, metals and even 2D materials. Although CSP has been successfully deployed for densifying a wide range of functional ceramics and composites, the structural integrity of cold sintered materials remains unexplored.

Our team at the Chair of Structural and Functional Ceramics (ISFK) in Leoben, together with Dr. Clive Randall from Materials Research Institut (MRI) at Penn State University, have explored the effect of the liquid phase chemistry and processing conditions on the mechanical strength of cold sintered parts. We found that the chemistry of the liquid phase does not only affect densification, but it has a remarkable effect on the mechanical strength and microstructure evolution on cold sintered parts. Moreover, the used sintering protocol (heating rate and pressure homogeneity) plays a critical role in the densification process and can be a significant source of defects if not chosen correctly. Recently, we have demonstrated the feasibility of scaling up the CSP to produce multiple parts in a single cycle as a batch process. This demonstrates the potential of CSP to transform the ceramic industry into a green and sustainable industry, complying with global efforts towards net-zero emissions.

Currently, our goal is to understand the structural reliability of cold sintered materials under different loading and environmental conditions and compare their performance to conventionally sintered counterparts. This is an important step for accelerating the industrial implementation of the cold sintering process.

     Figure: General process flow of the cold sintering process starting from nanopowder to final parts with different sizes up to 4.5 cm in height and 3 cm in diameter.

Abdullah Jabr

Chair of Structural and Functional Ceramics (ISFK), Department of Materials Science, Montanuniversitaet Leoben Franz-Josef-Strasse 18

A-8700 Leoben

Austria

abdullah.jabr@unileoben.ac.at 

https://isfk.unileoben.ac.at