Nano-ZrO2@C, Nano-(ZrC, ZrO2)@C and Nano-ZrC@C Composites Prepared by Plasma-Assisted Carbonization of Zr-Loaded Iminodiacetate-Functionalized Styrene-Divinylbenzene Copolymers

We have developed an easy route to prepare (nano-ZrO2,nano-ZrCx)@C composites with varying ZrO2/ZrCx content. The process consists of preparing a zirconium-loaded, iminodiacetate-functionalized styrene-divinylbenzene (STY-DVB) copolymer, and its subsequent carbonization in a tube furnace and/or a thermal plasma reactor. Depending on the zirconium salt used (zirconyl chloride, zirconyl nitrate or zirconium (IV) sulfate) in the Zr loading, the Zr-loaded resins resulted in ZrO2@C pre-pyrolizates with C to Zr molar ratios of 5.8, 6.8 and 6.60. This carbon surplus is sufficient for the partial or even complete reduction of ZrO2 into ZrC0.58 at 1400 degrees C. The reaction products also contain 5 to 55 mass% residual free carbon. The plasma processing of the ZrO2@C composite formed at 1000 degrees C in a tube furnace led to ZrC0.94@C composites. The transformation of amorphous carbon content during the plasma treatment strongly depended on the atmosphere (He or H-2) in the reactor and the anion type of the Zr salt. In the presence of He, amorphous carbon could be completely transformed into graphite. In the presence of H-2, amorphous carbon and graphite were found at roughly the same ratio. No ZrO2 could be detected in the plasma-treated samples, whilst different ZrO2 polymorphs were found in the samples prepared in the tube furnace, depending on the synthesis conditions.