| Abstract Scope |
Refractory boron compounds and phenolic resins are commonly used together as sintering aids for silicon carbide. Oxides of boron are not typically used due to their volatility at sintering temperatures. To investigate the role of boric acid-phenolic resin complexes as possible sintering aids, slurries were made using aqueous solutions of resol phenolic resin, Washington Mills FPG silicon carbide powders, and varied boron sources, including H3BO3, B4C, BN, and amorphous boron. Boron complexation and bonding were investigated using NMR, IR, and Raman spectroscopy. Test parts included pressed pellets of dried granulated slurry, and hollow robocast samples produced using nozzle diameters <1 mm. Samples were debinded in Ar/4% H2, then pressureless sintered at 2200 °C in argon. Sample densities were determined through geometric and Archimedes density measurements, routinely exceeding 95% of theoretical density. Initial results indicate boric acid-phenolic resin based compositions provide enhanced densification compared to typical boron sources. |