In situ synthesis of ZrB₂–ZrC–SiC ultra-high-temperature nanocomposites by a sol–gel process

Abstract

ZrB 2 -ZrC-SiC is one of the ultra-high-temperature ceramic composites with excellent properties. In this research, high-purity ZrB 2 -ZrC-SiC nanopowders were synthesised using a carbothermal reduction reaction at a relatively low temperature (1370°C) from cost-effective zirconium(IV) chloride by a sol-gel method. The effect of heat treatment temperature on the synthesis of ZrB 2 -ZrC-SiC composite powder was studied. X-ray diffractometry results showed that the phases ZrB 2 , β-SiC and ZrC were synthesised at 1370°C. The mean crystallite sizes for each of the phases were calculated using the Scherrer method. The specific surface area for the sample calcined at 1370°C was 81.479 m 2 g −1 . SEM observation revealed that the particles had a size lower than 250 nm. Backscattered electron image and map analysis with scanning electron microscopy showed that a suitable phase homogeneity was achieved, as confirmed by energy-dispersive X-ray spectroscopy.

In-situ synthesis of ultra-fine ZrB2–ZrC–SiC nanopowders by sol-gel method

“…The peak located at cm -1 is ascribed to B-O-C bond [26,27]. The peak at 939 cm -1 is related to Zr-O-C bond [26]. The appearance of these two peaks demonstrates the connection between glucose and hydrolysates of ZrOCl 2 •8H 2 O and H 3 BO 3 .…”

“…The band at 1237 cm -1 is caused by B-O bond [25]. The peak located at cm -1 is ascribed to B-O-C bond [26,27]. The peak at 939 cm -1 is related to Zr-O-C bond [26].…”

A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

“…13 The solution-derived precursor indicates a homogeneous atomic or molecular distribution among different components, which is beneficial for the conversion from precursor to ceramic with superior purity and compositional homogeneity at a low temperature in a relatively short time. 14 The oxygen for formation of metal-oxygen bonds in nonhydrolytic solution-derived precursor is provided by the solvent (ethers, alcohols, ketones, or aldehydes) or by the organic constituent of the precursor (alkoxides or acetylacetonates) via several possible condensation steps such as alkyl halide, ether or ester elimination, and an aldol-like condensation. 15,16 The solution-derived precursor method is affected by several parameters including the characteristics of the precursor (concentration, rheology, ceramic yield, reactivity, and crosslinking), nature of the solvent, pH of the solution, type of additives, aging of the solution, type of the polymer used for condensation, atmosphere condition (inert/reactive/vacuum) during shaping or ceramization, pre-and post-heat-treatment process, heating rate, and dwelling time.…”

“…In order to obtain HfB 2 powders with better properties at moderate temperatures, many researchers prefer to use mechanochemical synthesis, 8 mechanically activated borothermal reduction, 2 chemical rout with autoclave processing, 9 solution‐based processing combined with spark plasma sintering (SPS), 10 sol‐gel, 11 hydrothermal synthesis, 12 and preceramic polymer methods 13 . The solution‐derived precursor indicates a homogeneous atomic or molecular distribution among different components, which is beneficial for the conversion from precursor to ceramic with superior purity and compositional homogeneity at a low temperature in a relatively short time 14 . The oxygen for formation of metal‐oxygen bonds in nonhydrolytic solution‐derived precursor is provided by the solvent (ethers, alcohols, ketones, or aldehydes) or by the organic constituent of the precursor (alkoxides or acetylacetonates) via several possible condensation steps such as alkyl halide, ether or ester elimination, and an aldol‐like condensation 15,16 .…”

Enhanced fracture properties of ZrB2-based composites by in-situ grown SiC nanowires

“…In the last decade, great efforts have been made on the fabrication process and performance improvement of the ZrB 2 -based composites [4,5]. However, the intrinsic brittleness of ceramics makes ZrB 2 -based composites sensitive to the processing and machining defects, which would lead to the unexpected failure and further limit their engineering application [6]. Therefore, it is necessary to take some measures to produce the ZrB 2 -based composites with high damage tolerance and reliability.…”