Engineering porosity in polymer-derived ceramics

Ultramicroporous silicon nitride ceramics for CO2 capture

“…This is, during the polymer-to-ceramic transformation, the decomposition of organic groups, and the release of gaseous species, e.g., H 2 , CH 4 , occurs mainly at temperatures around 500-700°C. [27][28][29] Hence, the evolution of these gaseous species creates an intrinsic microporosity in as-formed products. Stopping the pyrolysis at this conversion stage leads to microporous materials in a hybrid state called ceramers, i.e., the as-formed ceramic product contains reactive sites from the unconverted polymer.…”

Ceramic microparticles and capsules via microfluidic processing of a preceramic polymer

“…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). …”

Processing of polysiloxane-derived porous ceramics: a review

“…Macrocellular foams with a cell size ranging between 100 and 600 µm were fabricated from methyl polysiloxane using a direct foaming approach, whereas microcellular foams, with a cell size of about 8 µm, were fabricated using PMMA microbeads as sacrificial templates [82]. SiOC ceramics with hierarchical porosity can also be produced either by controlled pyrolysis, deposition of various meso-porous layers, etching or the addition of suitable fillers [19,[111][112][113]. The pore size, pore morphology and the specific surface areas of polymer-derived ceramic bodies strongly depend on the composition of the preceramic material and on the maximum pyrolysis temperature.…”

“…The processing of porous ceramics using preceramic polymers offers many advantages compared to ceramic powders. These include (i) low processing temperatures or low energy consumption for the synthesis compared to high temperatures required for sintering of ceramic powders [13][14][15][16][17], (ii) no additives required for densification [1,4], (iii) a variety of low-cost plastic-forming techniques can be applied with easy control over rheological properties by modified molecular architecture; important plastic-forming techniques include injection molding, extrusion, resin transfer molding, melt spinning [4,9,15], (iv) machining before ceramization can be avoided, thereby reducing tool wear and brittle fracture [1,5,10], (v) easy handling before heat treatment, because preceramic polymers can effectively bind the parts at low temperatures [10], (vi) utilization of unique polymeric properties that cannot be found in ceramic powders, such as appreciable plasticity, in situ gas evolution ability, appreciable CO 2 solubility, and appreciable solubility of preceramic polymers in organic solvents [9,10,18,19], (vii) nanostructures (wires, belts, tubes, etc) can be created directly during the pyrolysis of catalyst-containing preceramic polymers [10,11], and (viii) ceramic products containing unique combination of polymer-like nanostructures with ceramic-like properties (hardness, creep resistance and oxidation resistance) can be obtained [6,9,10]. Hence, several polymers with different substituents were synthesized, blended and used as precursors for fabricating a variety of porous ceramics such as zirconia, alumina, silica, silicon carbide, silicon oxycarbide, mullite, cordierite, etc.…”