Paper‐derived stoneware ceramics: Improvement of properties by calendering and evaluation of pyroplastic deformation behaviour

Abstract

Paper‐derived ceramics are a new approach to produce thin, lightweight ceramic structures. These ceramics are derived from preceramic papers produced in a paper technological process. The amount of inorganic filler (e. g. stoneware) in the paper is increased up to 85 wt‐%. By firing at high temperatures the cellulose fibres are pyrolized and the inorganic content is sintered. One part of the technological process to produce papers is calendering. A calender consists of two rolls, between which the paper is rolled under pressure. By calendering the paper thickness is reduced and the surface of the paper is improved. Different calender parameters (pressure and temperature) are applied to the preceramic paper and ceramic properties like strength, density and surface roughness are investigated. The strength of paper‐derived stoneware ceramics can be improved by 125% to over 185 MPa by optimizing the calender process. Additionally paper‐derived stoneware ceramics were fired at 1180°C, 1200°C and 1220°C for 1 and for 2 hours at different support distances (10–150 mm) in order to determine the dependence of pyroplastic deformation on support distance. The results show a linear increase between maximum deformation and support distance by 1 hour dwell and a polynomic at 2 hours dwell. Furthermore the Pyroplastic Index (PI) was evaluated according to recent literature. The Pyroplastic Index was correlated to the amorphous content of the differently fired samples. With longer dwell and/or higher temperature the content of amorphous phase increases which lowers the bulk viscosity and supports the pyroplastic deformation. These investigations should give a direction for using paper‐derived stoneware ceramics for special design applications. Paper‐derived ceramics can be systematically deformed in many possible ways to achieve specific shapes.

Highly Filled Papers, on their Manufacturing, Processing, and Applications

“…More detailed lists of applications, together with exemplary pictures of relevant paper‐derived components for all mentioned applications are shown in Figure (a) and (b). By calendering the highly filled papers with additional filler materials, the produced sintering products of preceramic papers can become significantly denser . Also, by infiltrating, coating or printing the preceramic papers or the paper‐derived sintering products, the density of papers or sintering products is significantly increased .…”

“…When stoneware ceramics were introduced to preceramic papers as particulate fillers, sintering products with a lower pyroplastic deformation in comparison to tape‐casted stoneware ceramics could be achieved. The elevated shape stability during sintering proved to be beneficial for designing specifically complex geometries, such as one‐piece corner tiles or aesthetic art designs . Fully‐dense infiltrated paper‐derived Si/SiC composites enabled applications that require the combination of a high‐temperature resistance and a high tribological wear resistance, such as materials inside combustion chambers or inside gas turbines, bearings, seal rings, and engine parts .…”

“…An overview of the different process routes for the heat treatment of highly filled papers is shown in Figure . The final sintering products or reaction products generated can be divided in the following groups: Oxide Ceramics Non‐Oxide Ceramics Ceramic‐Based Composites Metal‐based Composites …”

“…When the oven reaches a sufficiently high temperature, the filler materials either undergo a sintering process or chemical reactions are initiated, yielding paper‐derived ceramics, ceramic‐, or metal‐based composites. Optionally, the green body can be infiltrated by a hot melt, such as liquid silicon or a liquid Cu–O alloy …”

Laminated Object Manufacturing of Ceramic‐Based Materials

“…The type of ceramic filler in preceramic papers could be an oxide or a nonoxide ceramic. In optional dry‐processing steps, preceramic papers could be compressed to generate narrower pores from burnt‐off pulp fibers, or, could be printed or coated by a ceramic slurry, closing‐up pore spaces within the papers . Preceramic papers could be prepared by instruments on laboratory scale, such as by a dynamic handsheet former, either to be tested prior to a potential application in LOM or to be used in first RP parts from LOM.…”