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

Abstract

Ultra-high temperature ceramics (UHTCs) are proposed to be the most promising material candidates for structural and thermal protection components in the aerospace field, due to their extremely high melting points, high hardness and strength, good thermal and chemical attack resistance. 1-4 When considering engineering manufacturing and application in very harsh environment, silica formers (silicon-containing materials such as SiC, Si 3 N 4 , SiBCN, MoSi 2 , TaSi 2 etc) are generally introduced into UHTCs to significantly improve their sinterability, mechanical property, as well as oxidation and ablation resistance. 5-8 Among them, SiC as a typical effective additive can not only modify the sintering behavior of ZrB 2 ceramic by pinning grains from overgrowth, but also enhance the oxidation resistance by forming a protective surface layer of borosilicate glass or ZrSiO 4. 2,6,9 Meanwhile, it has been shown that the particle size of SiC has important effects on the microstructure and mechanical property of ZrB 2-SiC composites. 10,11 Thus nano-sized

Monolithic ZrB2‐based UHTCs using polymer‐derived Si(Zr,B)CN as sintering aid

“…25,55 The phase composition of SiCN, SiZrCN and SiZrBCNbased sintering aids in the densified monolithic ZrB 2 samples seems to be slightly different than that found in the neat materials as exposed to similar thermal treatment condition, as reported recently. 25 Thus, SiCN, SiZrCN, and SiZrBCN exposed to 1700℃ in N 2 atmosphere were shown to consist of mainly β-SiC/C as for SiCN and of ZrC(N), β-SiC, β-Si 3 N 4 as for SiZrCN and SiZrBCN. 25 Additionally, a turbostratic graphite-like BCN phase was unambiguously found in SiZrBCN, 25 similar to the finding made in the present work in ZrB 2 /SiZrCN and ZrB 2 /SiZrBCN.…”

“…No references were found on modeling for CMCs, though experimental studies o ing process have been reported. Studies o derived SiC ceramic 25 and SiC/SiC c shown that porosity decreases and mecha prove with the increasing number of PIP show that increasing pyrolysis temperatu tration of SiC fillers in polycarbosilane improved mechanical properties in two-d SiC (C/SiC) composites fabricated using Starting with pyrolysis of a "cured prepreg-based composite, each processin process involves infiltration of a precera porous ceramic preform followed by a py which the polymer is converted into ceram cess modeling is focused on these two ste Modeling of infiltration of liquids in well-studied subject, especially in the where it is used to model seepage of wa soils and rocks. 29,30 The physics of resin under pressure is similar to the seepage pr lar approaches have been used also to mod into a mold containing fiber mats.…”

“…Thus, the respective polymeric precursors were dissolved in anhydrous toluene and the ZrB 2 powder was subsequently added into the solutions. The content of ZrB 2 powder was set to 85 wt.% relative to that of Si(Zr)(B)CN, based on the ceramic yield of the precursors upon pyrolysis at 1100℃, which is 65 wt.% for SiCN, 77 wt.% for SiZrCN and 78 wt.% for SiZrBCN 25 …”

A novel TiO2-TiC-TiC0.3N0.7-C-SiCN multiphase ceramic nanocomposite from preceramic polymer pyrolysis

“…[31,32] For instance, Zr doping to SiCN lead to the precipitation of t-ZrO 2 phases, which reinforces the nanocomposites and hence enhances thermal stability towards crystallization, oxidation and corrosion even at temperatures above 1300 o C. [27,28,33] B-doping into SiCN ceramic resulted in the high temperature stability towards crystallization up to temperature as high as 2200 o C. [14,34] Further, incorporation of B into SiZrCN ceramics diminishes the crystallization of ZrC x N y and suppress the reaction of SiN x with C, resulting in an improved thermal stability of SiZrBCN as compared to SiZrCN ceramics. [35] Hf-doping to the SiCN matrix improved the thermal stability as well as oxidation and corrosion resistance. [5,13,36] A new class of SiC/Hf y Ta 1−y C x N 1−x /C nanocomposite with improved oxidation resistance was synthesized at 1900 o C, and the composition as well as thickness of the HfC x N 1−x and TaC x N 1−x core shell structures can be tuned with varying the Hf:Ta atomic ratio.…”

Micro‐/nanostructure evolution of C/SiFeO(N,C) polymer‐derived ceramic papers pyrolyzed in a reactive ammonia atmosphere

“…The resulting polymer-derived ceramics (PDCs) are monophasic or undergo phaseseparation leading to PDC-nanocomposites, depending on the composition and processing of the precursor. 1 Numerous PDCs have been investigated in the past years and were shown to exhibit good creep and oxidation resistance, 2 exceptional temperature stability, 3,4 or interesting functional properties such as high piezoresistivity, 5 biocompatibility, 6 or sensing capabilities, 7 offering promising aspects for future research and applications. One of the most compelling attributes of polymer precursors is that they can be chemically and structurally modified with, for instance, metal complexes or functional groups; accordingly, allowing to tailor the properties of the resulting ceramics to the needs of their respective application.…”