Application of Electric Current‐Assisted Sintering Techniques for the Processing of Advanced Materials

Abstract

Highly efficient energy conversion and storage technologies such as high‐temperature solid oxide fuel and electrolysis cells, all‐solid‐state batteries, gas separation membranes, and thermal barrier coatings for advanced turbine systems depend on advanced materials. In all cases, processing of ceramics and metals starting from powders plays a key role and is often a challenging task. Depending on their composition, such powder materials often require high sintering temperatures and show an inherent risk of abnormal grain growth, evaporation, chemical reaction, or decomposition, especially in the case of long dwelling times. Electric current‐assisted sintering (ECAS) techniques are promising to overcome these restrictions, but a lot of fundamental and practical challenges must be solved properly to take full advantage of these techniques. A broad and long‐term expertise in the field of ECAS techniques and comprehensive facilities including conventional field‐assisted sintering technology/spark plasma sintering (FAST/SPS), hybrid FAST/SPS (with additional heater), sinter forging, and flash sintering (FS) devices are available at the Institute of Energy and Climate Research: Materials Synthesis and Processing (IEK‐1). Herein, main advantages and challenges of these techniques are discussed and the concept to overcome current limitations is introduced on selected examples.

Promoting microstructural homogeneity during flash sintering of ceramics through thermal management

“…Thermal homogeneity through the use of insulation has been attempted by researchers developing a flash-SPS hybrid. 90 Similar effects may be applicable to microwave sintering or microwave flash, which can display a similar thermal runaway mechanism. 67 Future efforts should explore both engineering solutions for insulation and alternate creative technical approaches.…”

Processing of MAX phases: From synthesis to applications

“…199,200 This strategy has been performed on a Ti 2 AlC gear wheel processed by injection molding and sintering at 1350°C and 50 MPa of uniaxial pressure ( Figure 7B,C). 201 The gear wheel had a relative density of 98.2%, while only 89.6% was achieved by pressureless sintering at the same temperature.…”

Development of a processing map for safe flash sintering of gadolinium‐doped ceria

“…Recent advancements in electric current activated/assisted sintering techniques (ECAS) are shown to be promising for the processing of advanced materials due to significant enhancement of densification kinetics at lower furnace temperatures, when compared with conventional sintering technologies [28][29][30][31] . Technologies like, Spark Plasma Sintering (SPS) also referred in the literature as Field Assisted Sintering/Spark Plasma Sintering (FAST/SPS) 30 or flash sintering 32,33 are attractive due to the lower furnace temperature and shorter dwell time required for fabricating dense materials.…”