SiBCN Ceramics from the Pyrolysis of Poly(boro)silazanes

 

            While SiCN has excellent high temperature stability (up to 1500 deg-C), exhibiting very low

creep at those temperatures it is, nevertheless, susceptible to significant oxidation at temperatures

above 1000 deg-C.  In view of such susceptibility, chemical modification of various silicon-based

preceramic polymers, such as poly(silazanes) with boron has been effected.  When such polymers are

pyrolyzed, amorphous Si(B)CN ceramic is formed.  For instance, the oxidation of Si(B)CN/Cf (Cf =

carbon fiber) composites at temperatures of 800 deg-C, 1000 deg-C, 1200 deg-C, and 1500 deg-C

resulted in the formation of both SiO2 and B2O3 .  The borosilicate subsequently formed melted at 

higher temperatures, spread on the surface, and prevented further oxidation.  High weight retention of

the Si(B)CN ceramic at temperatures as high as 1200 deg-C occurs. 

            SiBCN ceramics thus exhibit excellent resistance to high temperatures, making them suitable

for applications where materials need to withstand extreme conditions.  Such stability and oxidation

resistance make them suitable for applications in harsh environments, such as aerospace, energy, and

industrial processes.  They can be used as components in composites or as protective coatings for other

materials.  SiBCN ceramics have shown potential for electromagnetic wave absorption, with some

research focusing on developing materials with strong attenuation at low frequencies.  SiBCN ceramics

can also be used in composite electrodes, providing mechanical strength and electrical conductivity. 

Studies have explored the use of SiBCN ceramics in combination with reduced graphene oxide (rGO)

for applications like electrodes.  Other studies explored the synthesis and properties of SiBCN

nanofibers, which have shown potential for microwave absorption.