Complex-shaped ceramic composites obtained by machining compact polymer-filler mixtures

Journal of the American Ceramic Society

Mera

Riedel

et al. 2010

1,524

657

Preceramic polymers were proposed over 30 years ago as precursors for the fabrication of mainly Si-based advanced ceramics, generally denoted as polymer-derived ceramics (PDCs). The polymer to ceramic transformation process enabled significant technological breakthroughs in ceramic science and technology, such as the development of ceramic fibers, coatings, or ceramics stable at ultrahigh temperatures (up to 20001C) with respect to decomposition, crystallization, phase separation, and creep. In recent years, several important advances have been achieved such as the discovery of a variety of functional properties associated with PDCs. Moreover, novel insights into their structure at the nanoscale level have contributed to the fundamental understanding of the various useful and unique features of PDCs related to their high chemical durability or high creep resistance or semiconducting behavior. From the processing point of view, preceramic polymers have been used as reactive binders to produce technical ceramics, they have been manipulated to allow for the formation of ordered pores in the meso-range, they have been tested for joining advanced ceramic components, and have been processed into bulk or macroporous components. Consequently, possible fields of applications of PDCs have been extended significantly by the recent research and development activities. Several key engineering fields suitable for application of PDCs include high-temperature-resistant materials (energy materials, automotive, aerospace, etc.), hard materials, chemical engineering (catalyst support, food- and biotechnology, etc.), or functional materials in electrical engineering as well as in micro/ nanoelectronics. The science and technological development of PDCs are highly interdisciplinary, at the forefront of micro- and nanoscience and technology, with expertise provided by chemists, physicists, mineralogists, and materials scientists, and engineers. Moreover, several specialized industries have already commercialized components based on PDCs, and the production and availability of the precursors used has dramatically increased over the past few years. In this feature article, we highlight the following scientific issues related to advanced PDCs research: (1) General synthesis procedures to produce silicon-based preceramic polymers. (2) Special microstructural features of PDCs. (3) Unusual materials properties of PDCs, that are related to their unique nanosized microstructure that makes preceramic polymers of great and topical interest to researchers across a wide spectrum of disciplines. (4) Processing strategies to fabricate ceramic components from preceramic polymers. (5) Discussion and presentation of several examples of possible real-life applications that take advantage of the special characteristics of preceramic polymers. Note: In the past, a wide range of specialized international symposia have been devoted to PDCs, in particular organized by the American Ceramic Society, the European Materials Society, and the Materials Research S...

Section: Processing Of Preceramic Polymersmentioning

confidence: 99%

Polymer‐Derived Ceramics: 40 Years of Research and Innovation in Advanced Ceramics

Journal of the American Ceramic Society

Mera

Riedel

et al. 2010

1,524

657

“…In the present work, we investigated the crystallization kinetics of mullite produced using a novel synthesis method, based on γ‐alumina nanoparticles and a silicone resin, proposed recently by Bernardo et al 22 This approach has several technological advantages over sol–gel‐based precursors, as preceramic polymers can be easily shaped using conventional plastic‐forming technologies, do not have any drying problems that hamper the possibility of fabricating bulk components, and do not require any specialized handling procedures 23–25 . Other researchers studied the formation of mullite starting from a silicone resin and various fillers (α‐alumina and/or metallic Al), 26–29 but they were unable to obtain phase‐pure mullite at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Studies of Mullite Synthesis from Alumina Nanoparticles and a Preceramic Polymer

Griggio

Bernardo

Journal of the American Ceramic Society

et al. 2008

The crystallization kinetics of mullite formation in a diphasic precursor consisting of a silicone resin filled with commercial c-alumina nanoparticles (15 nm mean particle size, specific surface area of 100 m 2 /g), heated in air from 12501 to 13501C, was studied by X-ray diffraction. Transitional c-alumina and amorphous silica from the pyrolysis of the preceramic polymer exhibited a remarkable reactivity, as demonstrated by a very low incubation time (from 500 s at 12501C to 20 s at 13501C), a high mullite yield (about 80 vol%, after 100 s at 13501C), and a low activation energy for nucleation (677760 kJ/mol). The activation energy values found were lower than those reported previously for other diphasic systems, including sol-gel precursors. Besides the high specific surface of nanosized c-alumina particles, the low energy barrier could be attributed to the highly reactive silica deriving from the oxidation of Si-CH 3 bonds in the silicone and to the homogeneous dispersion of the nanosized filler inside the preceramic polymer. Furthermore, the possibility of applying plastic shaping processing methods to the mixture of a preceramic polymer and nanosized filler makes this approach particularly valuable, in comparison, for instance, with sol-gel based alternatives.

“…Therefore, they can be subjected to a large variety of different forming methods, some of them unique or at least much more easily exploitable for polymers than ceramic powders or pastes. These include casting (Melcher et al 2003), infiltration (Satoa et al 1999), pressing (Galusek et al 2007), injection moulding (Walter et al 1996), extrusion (Eom & Kim 2007;Eom et al 2008), machining (Rocha et al 2005), fibre drawing (Okamura et al 2006), blowing/ foaming (Colombo 2008), ink jetting (Mott & Evans 2001), rapid prototyping (Friedel et al 2005), electrohydrodynamic spraying/spinning ), aerosol spraying (Bahloul-Hourlier et al 2001, self-assembly (Malenfant et al 2007) and microcomponent processing such as UV/X-ray lithography, nano/micro-casting, replication, micro-extrusion and embossing/forging (Schulz 2009). …”

Section: Introductionmentioning

confidence: 99%

Ceramic microparticles and capsules via microfluidic processing of a preceramic polymer

Chen

et al. 2010

J. R. Soc. Interface.

We have developed a robust technique to fabricate monodispersed solid and porous ceramic particles and capsules from single and double emulsion drops composed of silsesquioxane preceramic polymer. A microcapillary microfluidic device was used to generate the monodispersed drops. In this device, two round capillaries are aligned facing each other inside a square capillary. Three fluids are needed to generate the double emulsions. The inner fluid, which flows through the input capillary, and the middle fluid, which flows through the void space between the square and inner fluid capillaries, form a coaxial co-flow in a direction that is opposite to the flow of the outer fluid. As the three fluids are forced through the exit capillary, the inner and middle fluids break into monodispersed double emulsion drops in a single-step process, at rates of up to 2000 drops s 21. Once the drops are generated, the silsesquioxane is cross-linked in solution and the cross-linked particles are dried and pyrolysed in an inert atmosphere to form oxycarbide glass particles. Particles with diameters ranging from 30 to 180 mm, shell thicknesses ranging from 10 to 50 mm and shell pore diameters ranging from 1 to 10 mm were easily prepared by changing fluid flow rates, device dimensions and fluid composition. The produced particles and capsules can be used in their polymeric state or pyrolysed to ceramic. This technique can be extended to other preceramic polymers and can be used to generate unique core -shell multimaterial particles.