Injection Moulding of Oxide Ceramic Matrix Composites: Comparing Two Feedstocks

Abstract

Ceramic materials are suitable for use in the high temperature range. Oxide ceramics, in particular, have a high potential for long-term applications under thermal cycling and oxidising atmosphere. However, monolithic oxide ceramics are unsuitable for use in high-temperature technical applications because of their brittleness. Thin-walled, oxidation resistant, and high-temperature resistant materials can be developed by reinforcing oxide ceramics with ceramic fibres such as alumina fibres. The increase of the mechanical stability of the composites in comparison to the non-fibre reinforced material is of outstanding importance. Possible stresses or cracks can be derived along the fibre under mechanical stress or deformation. Components made of fibre-reinforced ceramic composites with oxide ceramic matrix (OCMC) are currently produced in manual and price-intensive processes for small series. Therefore, the manufacturing should be improved. The ceramic injection moulding (CIM) process is established in the production of monolithic oxide ceramics. This process is characterised by its excellent automation capability. In order to realise large scale production, the CIM-process should be transferred to the production of fibre-reinforced oxide ceramics. The CIM-process enables the production of complicated component shapes and contours without the need for complex mechanical post-treatment. This means that components with complex geometries can be manufactured in large quantities.To investigate the suitability of the injection moulding process for the production of OCMCs, two different feedstocks and alumina fibres (Nextel 610) were compounded in a laboratory-scale compounder. The fibre volume fractions were varied. In a laboratory-scale injection moulding device, microbending specimens were produced from the compounds obtained in this way. To characterise the test specimens, microstructure examinations and mechanical-static tests were done. It is shown that the injection moulding process is suitable for the production of fibre-reinforced oxide ceramics. The investigations show that the feedstocks used have potential for further research work and for future applications as material components for high-temperature applications in oxidising atmospheres.

Short fiber‐reinforced oxide fiber composites

“…1,2 These reinforcements are mainly used as continuous fibers, in the form of woven fabrics, [2][3][4][5][6][7][8][9][10][11][12] Honoring Dr. Mrityunjay Singh unidirectional (UD) layers, [13][14][15] or braiding. 4,16 However, only few studies [17][18][19][20][21][22] dealt with Nextel™ 610 short fiber-reinforced oxide ceramics.…”

“…25 Short fiber-reinforced OFCs can be produced automatically via ceramic injection molding or a fiber spraying process. Currently, there are two [17][18][19][20] known research activities on ceramic injection molding of complex nearnet-shape OFC components. Previous studies reported that during the injection molding process (kneading, extrusion, and injection), Nextel™ 610 fiber bundles were broken, separated into single fibers, and oriented.…”

“…Tülümen et al 18 described that the fiber length decreased from 3200 μm in the feedstock to only 200-300 μm in the sintered OFC. Both studies did not discuss the fracture behavior of the short fiber-reinforced OFC in detail, but Böttcher et al 20 mentioned that a damage tolerant fracture behavior was not achieved.…”

Assessing the electrical property of carbon nanotube reinforced oxide ceramic matrix composites produced by ceramic injection moulding

“…However, the brittleness of oxide ceramic materials is the issue. Therefore, fibre-reinforced oxide ceramics (OCMC) are gaining great of attention compared to monolithic oxide ceramics owing to their higher fracture toughness and damage tolerance under thermal and mechanical load [3].…”

“…Several progresses are driven toward the enhancement of these properties using several type of reinforcements. In fact, two types of fiber reinforcements were frequently used in the literature [3]. Oxide fibers such as alumina fiber were incorporated within oxide ceramics as they offer excellent oxidation resistance and good mechanical properties but creep faster at high temperature comparing to non-oxide fibers.…”