Recently, silicon carbide (SiC) attracted interest for environmental and energy applications according to its mechanical and chemical properties at high temperature. Yet, most of the actual and future industrial challenges of silicon-based ceramics require materials with compositions, shapes and textures tuned on demand. Common techniques are energy-ineffective and limit the shape and texture complexities of the parts made. Moreover, the control of the product purity and crystalline form is restricted. These difficulties can be overcome by synthetic paths where molecular chemistry and chemistry of materials are combined rationally, like the Polymer- Derived Ceramics (PDCs) route. This process is applied here to make boron-modified SiC foams. The polymer was synthesized by reaction of allylhydridopolycarbosilane (AHPCS) with borane dimethyl sulfide to get highly crosslinked polymers. The polymers are fully characterized by infrared and solid state NMR. By mixing the polymer with PMMA spheres, then applying a warm-pressing, hybrid pellets are made. A pyrolysis up to 1000°C under argon allowed converting the inorganic part into SiC and removing the organic part leaving voids in the pellets. This produced microcellular foams are characterized by mercury porosimetry and SEM. The structural evolution of the amorphous SiC has been followed by XRD and Raman spectrometry. Application will be briefly described.