Ceramics high-temperature, sintering

A significant recent advance has been the development of microfiltration and ultrafiltration membranes composed of inorganic oxide materials. These are presently produced by two main techniques (a) deposition of colloidal metal oxide on to a supporting material such as carbon, and (b) as purely ceramic materials by high temperature sintering of spray-dried oxide microspheres. Other innovative production techniques lead to the... 

Quasicrystalline powders behave while consolidation in many features like ceramic materials and are consolidated with difficulties. Usually it is performed by HIP technique, but this process takes rather much time and requires complicated equipment. In our former works [1] it was shown that the consolidation of ceramic powders is significantly easier when using high quasihydrostatic pressure that activates particle contact interaction, and high-temperature sintering requires 2-3 min. 

The sintered microstructure of thick film ceramic devices can be quite complex. This is caused by two factors (1) the ceramic itself may be multiphase, such as low-firing glass—ceramic packaging material and (2) dissimilar materials, such as ceramics and metals, are in contact during the high-temperature sintering process. Therefore, a variety of characterization techniques must be used in concert to determine adequately the phase and composition distributions in these materials. The following examples illustrate this point. 

Ceria has been used as the ceramic part (or as an addition) in nickel- or ruthenium-cermet anodes for hydrogen oxidation. " Beneficial effects have been reported and interpreted as most likely being due to the broadening of the three-phase boundary zone. However, one of the major drawbacks of using ceria in cells with YSZ-based electrolytes is its chemical reactivity with the YSZ electrolyte at high temperatures. Sintering of a doped ceria anode on a YSZ electrolyte at high temperatures (>1200°C) results in the formation of a reaction (diffusion) zone with limited oxide ion conductivity. ... 

Calcium carbonate (CaC03 ) acts as a melting facilitator in ceramic pastes and increases porosities when high temperature sintering is used because of CO2 liberation. 

As noted, the oxidation resistance of silicon nitride ceramics depends on the type and concentration of the sintering aids. In materials designed for high temperature appHcations the specific weight gain resulting from oxidation upon a 500-h air exposure at 1200°C and 1350°C is about 1—2 g/m and 2—4 g/m, respectively. The kinetics of the oxidation process have been iavestigated (63,64) as has the corrosion resistance (65). Corrosion resistance is also dependent on material formulation and density. 

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