Abstract
A simple and inexpensive method for the preparation of porous SiC microspheres is presented. Polysiloxane microspheres derived from polyhydromethylsiloxane (PHMS) cross-linked with divinylbenzene (DVB) were ceramized under conditions leading to the removal of oxygen from the material. The content of free carbon (Cf) in highly crystalline silicon carbide (SiC) particles can be controlled by using various proportions of DVB in the synthesis of the pre-ceramic material. The chemical structure of the ceramic microspheres was studied by elemental analysis for carbon and oxygen, 29Si MAS NMR, 13C MAS NMR, SEM/EDS, XRD and Raman spectroscopies, and their morphology by SEM, nitrogen adsorption and mercury intrusion porosimetries. The gaseous products of the thermal reduction processes formed during ceramization created a porous structure of the microspheres. In the SiC/Cf microspheres, meso/micro pores were formed, while in carbon-free SiC, microspheres macroporosity dominated.
Highlights
Silicon carbide (SiC) has outstanding mechanical properties and chemical stability at high temperatures [1,2,3,4] as well as remarkable electronic and optical properties [5,6]
A few years ago, we developed the synthesis of polysiloxane microspheres from polyhydromethylsiloxane (PHMS), which proved to be good precursors for the fabrication of silicon oxycarbide (SiCO) ceramic microspheres [35,36]
We demonstrated that porous SiC and SiC/Cf ceramic microspheres can be obtained by a simple and inexpensive method from PHMS cross-linked with DVB polysiloxane microspheres
Summary
Silicon carbide (SiC) has outstanding mechanical properties and chemical stability at high temperatures [1,2,3,4] as well as remarkable electronic and optical properties [5,6]. For this reason, SiC ceramics have found practical applications in very harsh conditions [1,2]. Spherical particles confined in dimensions within the micrometer range exhibit superior properties to their bulk counterparts They provide good flowability, high packing density and easy access to particle surfaces [7,8,9,10]. Porous SiC-based microspheres could be used in many fields, such as: catalysis [11,12], hot gas filtration [13], thermal insulation [10], sensors [14], absorbers [15,16], molten metal filtering [17], membranes [18,19], and tissue engineering [20]
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