Plasma-assisted preparation of nano-(ZrC, ZrO2)@carbon composites from Zr-loaded sulfonated styrene–divinylbenzene copolymers

Abstract

We have developed a simple method to prepare nano-(ZrC0.93, ZrO2-polymorphs)@carbon composites with graphite/amorphous carbon content and adjustable Zr/C ratio based on using a multistep tube furnace and plasma-assisted heat treatment of zirconium-loaded sulfonated styrene–divinylbenzene (STY-DVB) copolymers. Pre-pyrolysis of zirconium-loaded sulfonated STY-DVB ion exchangers with 2 and 8 mass % DVB at temperatures between 1000 and 1400 °C for 2 h produced nano-ZrO2@C intermediates with particle sizes of ~ 30–60 nm with no ZrC formation. Plasma processing of nano-ZrO2@C resulted in nano-(ZrC0.93, ZrO2)@C composites with 11% (under a He atmosphere) (C/Zr = 73) or 13% (under a H2 atmosphere) (C/Zr = 58) ZrC0.93 content. Three polymorphs of the zirconium dioxide (tetragonal, monoclinic and cubic, between 18 and 27 nm) were found in the products. The amounts of tetragonal and monoclinic ones are comparable to that of ZrC0.93. The average particle size of ZrC0.93 prepared in this way was found to be 21–23 nm. The BET surface area of the nano-(ZrC0.93, ZrO2)@C(graphite) composites prepared in He and H2 was over 250 and 300 m2/g, respectively. We developed a reproducible and easy method to prepare nano-(ZrC, ZrO2)@C products by setting the DVB content, sulfonation degree, Zr loading and the thermal treatment conditions, which have an influence on the ZrC and graphite/amorphous carbon content of nano-ZrO2@C intermediates. The zirconium-loaded sulfonated styrene–divinylbenzene (STY-DVB) copolymers (2 and 8 mass% DVB) or their thermal decomposition was characterized with vibrational spectroscopy, thermal analysis and DSC or powder XRD, BET, XPS and HRTEM methods, respectively.

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

“…The line positions of the corresponding oxygen, O 1s 531.2 eV and carbon, C 1s 182.0 eV agreed with the literature data [39]. The appearance of the ZrO 2 minor phase can be attributed to the high affinity between Zr and O [37,38]. Some of the oxygen is chemically bound to carbon (O 1s 533.0 ± 0.2 eV, C 1s 286.7 ± 0.2 eV).…”

“…The main features of ZrC 0.94 @C samples are the complete transformation of ZrO 2 into ZrC. The amorphous carbon is expected to transform into graphite during the plasma treatment [37]. The average size of ZrC crystallites ranged between 35 and 62 nm, which is higher than that of the samples made in a tube furnace.…”

“…Senczyk's equation [36] valid for samples 0.65 < x < 01.0 did not give results in this range, which shows that x is out of the validity range of the equation. Residual amorphous carbon content would be enough to form stoichiometric ZrC by incorporating carbon into the ZrC 0.58 structure at high-temperature heat treatment [37,38]. Thus, two sets of heat-treatment tests were carried out at 1400 • C with treatment times of 2 h and 8 h, and an RF plasma treatment was also performed in an H 2 and He atmosphere on nano-ZrO 2 @C samples with Zr/C atomic ratios of ~5.8, ~6.8 and 6.64.…”

“…In general, the low DVB content (2%) of L-Zr-X samples resulted in a relatively high ratio of organic volatiles during carbonization, resulting in high ZrO 2 /C and high ZrC/C ratios in the precursor and product samples. The incorporation of iminodiacetate functional groups for Zr loading instead of sulfonyl groups [37] increased ZrC content in the ZrC@C composites. The composition of ZrC in the RF plasma-treated samples was almost the same, Zr 0.93 and Zr 0.94 , for the samples prepared from sulfonated [37] and iminodiacetate-loaded resins, respectively.…”

“…The incorporation of iminodiacetate functional groups for Zr loading instead of sulfonyl groups [37] increased ZrC content in the ZrC@C composites. The composition of ZrC in the RF plasma-treated samples was almost the same, Zr 0.93 and Zr 0.94 , for the samples prepared from sulfonated [37] and iminodiacetate-loaded resins, respectively. However, the ZrC 0.94 content and ZrC 0.94 /ZrO 2 ratio were far higher in the case of iminodiacetate-loaded than the sulfonated resins [37].…”