Sintering Innovations for Ceramic Manufacturing
Sintering units that combine several classic sintering methods are described as hybrids. How can they benefit ceramic manufacturing?
In addition to classic sintering methods such as vacuum and gas pressure sintering, sinter hot isostatic pressing (HIP) and hot pressing, sintering processes enhanced by electrical fields have grown considerably in importance in the last decade. Terminologies include field-assisted sintering technology (FAST), spark plasma sintering (SPS) and flash sintering (FS); individual variations include FAST/SPS, FAST², FAST/hybrid and FAST/flash.
Most recently, the newest trend emerging in sintering technology takes the form of hybrid designs, initially in the area of laboratory applications before the technology is transferred (more or less rapidly) to industrial applications. Sintering units that combine several traditional sintering methods are described as hybrids. In the case of FAST/hybrid for example, the classic hot-pressing method was combined with an additional direct heating of the powder compact with a pulsed electric current (FAST/SPS). In addition to the possibilities of FAST/SPS, this combination makes it possible to further enhance the heating rates with even better temperature homogeneity compared to hot pressing.
The combination of gas pressure and uniaxial pressure is required for the development and optimization of processes, which are increasingly used when densifying ultra-clean materials or when synthesizing materials, for example. Depending on specific requirements, this hybrid concept makes it possible to use a maximum gas pressure of up to 100 bar and varying pressing forces, depending on the size.
Just like the conventional sintering technology, for combined debindering/sintering processes and for reactive bonding processes, these units can be equipped with the corresponding retorts with defined gas flow, as well as the correspondingly required specific exhaust gas treatment (thermal post combustion, flaring apparatus, acid scrubber, etc.). In addition, it is possible to visualize and record the sinter shrinkage of the product in real time. This is standard with mechanical pressing force and is achieved by precisely measuring the press punch movement. In other units, an optional dilatometer makes this possible.
Hybrid sintering technologies provide combinations of sintering procedures, along with various additional options. These solutions offer previously unattainable possibilities for developing and optimizing innovative materials that are currently the subject of intensive research worldwide, such as electro technology, electro mobility and aerospace applications, as well as other future-oriented fields.
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