High-grade MWCNT/ZrO2 composites prepared by sol–gel method and high-pressure technique (4.0 GPa): mechanically resistant, porous, and conductive.

Preparation of bulk samples with high content of carbon nanotubes and still maintaining their impressive properties is not usual because the connection between them is very difficult. Several attempts to obtain carbon nanotube bulk samples have been made; however, the samples presented insufficient mechanical properties being brittle and difficult to handle. In the present work, multiwalled carbon nanotube/zirconia (MWCNT/ZrO₂) composite compacted samples, containing nearly 40% of multiwalled carbon nanotubes or functionalized carbon nanotubes (MWCNT or f-MWCNT) dispersed in a zirconia matrix (ZrO₂), were prepared for the first time. The sol–gel method was applied to warrant the connection between the MWCNT, associated with the high-pressure technique to impart mechanical properties. The samples that present the best characteristics in compaction and handling were the ones made with composite powders heat-treated at 300 °C. Subsequently, these powders were processed under high pressure (4 GPa) and high pressure/temperature (4 GPa/400 °C). These samples maintain significant content of MWCNT even after heat treatments. The physical and morphological integrity of the MWCNT were retained and yielded samples with impressive properties, such as high surface area (near 150 m² g⁻¹), load resistance (load/mass ratio >8000) and electrical conductivity (3 × 10¹ S m⁻¹). Picture of high- grade MWCNT/ZrO₂ composites prepared using sol–gel method and high- pressure technique. The best- compacted samples are presented, showing also the pore size distribution curves and the main characteristics of the samples, that are, conductivity and load resistance. Highlights: High-grade MWCNT/ZrO₂ composites were obtained by sol–gel method and high-pressure technique. The integrity of the MWCNT was preserved so as to provide electrical conductivity (3 × 10¹ S m⁻¹). CNT composite samples with impressive properties such as high surface area (close to 150 m² g⁻¹). Connection between MWCNT and ZrO₂ matrix provides resistant samples with load/mass ratio >8000. [ABSTRACT FROM AUTHOR]