Preparation and high‐temperature behavior of HfC–SiC nanocomposites derived from a non‐oxygen single‐source‐precursor

Abstract

A single-source precursor for the preparation of HfC-SiC ceramics was synthesized via a Grignard reaction using bis(cyclopentadienyl)hafnium(IV) dichloride, trans-1,4-dibromo-2-butene, and (chloromethyl)trimethylsilane as raw materials. The composition, structure, pyrolysis process and high-temperature behavior of the precursor were investigated. The results show that the precursor with a backbone comprising Hf-C, Si-C and CH=CH groups exhibits good solubility in common solvents, such as tetrahydrofuran, dimethylbenzene, and chloroform.Pyrolysis of the precursor at 1000°C yielded a microcrystalline HfC phase with a ceramic yield of 63.86 wt%. The pyrolytic products at 1600°C were HfC-SiC nanocomposite ceramics, which exhibited good thermal stability up to 2400°C.The formation of a (Hf,Si)C solid-solution would be beneficial for densification during the sintering process. The non-oxygen structure, high ceramic yield, homogeneous composition and excellent high-temperature behavior of the pyrolytic products make the as-prepared precursor a promising material for the preparation of high-performance ultra-high-temperature ceramics. K E Y W O R D SHfC-SiC, high-temperature behavior, precursor, pyrolysis, ultra-high-temperature ceramics

High‐temperature phase and microstructure evolution of polymer‐derived SiZrCN and SiZrBCN ceramic nanocomposites

“…28,29 Moreover as corroborated with in situ FT-IR spectroscopy, it is also likely that C 2 H 4 (m/z = 25-28) has been released from the reaction between ≡Si-CH = CH 2 and = N-H. Within the same temperature range, transamination processes between ≡Si-N = and ≡Zr-N = groups occur with the release of ethane (m/z = 29,30) and amine fragments (m/z = 29,30,[41][42][43]. Moreover the generation of amines may result also from the decomposition of -NMe 2 end groups.…”

“…The subsequent annealing of the obtained amorphous, single‐phasic SiHfBCN ceramic resulted in nanocomposites with interesting phase compositions, namely HfC/HfB 2 /SiC in argon and HfN/Si 3 N 4 /SiBCN in nitrogen at 1700°C. The formation of such ceramic nanocomposites upon high‐temperature annealing procedures of amorphous single‐phase ceramics may be considered as thermodynamically driven process, thus allowing to anticipate and consequently adjust/tailor the phase composition of the nanocomposites 28‐30 …”

“…The formation of such ceramic nanocomposites upon high-temperature annealing procedures of amorphous single-phase ceramics may be considered as thermodynamically driven process, thus allowing to anticipate and consequently adjust/tailor the phase composition of the nanocomposites. [28][29][30] Given the characteristics of UHTCs and PDCs, UHTC phases can be precipitated in situ as secondary phases within nano-scaled silicon-based PDC matrices by the preceramic-polymer-based technique. 23,[31][32][33][34][35][36][37][38] This synthetic approach towards UHTC/PDC nanocomposites may have high relevance for the preparation of coatings, CMCs (via PIP) or for the purpose of densification of UHTCs, where UHTC/ PDC nanocomposites may be used as sintering additives as well as silica-former phases.…”

Single-source-precursor synthesis and phase evolution of SiC-TaC-C ceramic nanocomposites containing core-shell structured TaC@C nanoparticles

“…Polymer derived ceramics (PDCs) are synthesized via solid-state thermolysis of preceramic polymers and exhibit a unique combination of remarkable properties and tailorable microstructure [33]. The PDC approach is effective to fabricate this kind of SiC-UHTC nanocomposite family [1,34,35,[44][45][46][47][48]. For example, ZrC-ZrB 2 -SiC ceramic nanocomposites were effectively prepared by a single-source-precursor route, with allylhydridopolycarbosilane (AHPCS), triethylamine borane, and bis(cyclopentadienyl)zirconium dichloride as starting materials [48].…”

ZrC–ZrB2–SiC ceramic nanocomposites derived from a novel single-source precursor with high ceramic yield

“…Therefore, the polymer-derived ceramic (PDC) approach is a promising method for preparing UHTCbased nanocomposites since the chemical composition, phase composition, and even the microstructures of ceramic nanocomposites can be designed and tailored. Polymer-derived MB 2 /SiC and MC/SiC (M = Zr, Hf) ceramic nanocomposites have drawn great attention during the past 5 years [23][24][25][26][27]. Moreover, the PDC approach is an additive-free method which can prepare the ceramic nanocomposites at low temperature, thus the resultant PDCs are more stable and green [28].…”