Polymer-Derived Ultra-High Temperature Ceramics (UHTCs) and Related Materials

Ionescu, Emanuel; Bernard, Samuel; Lucas, Romain; Kroll, Peter; Ushakov, Sergey V.; Navrotsky, Alexandra; Riedel, Ralf

doi:10.1007/978-3-030-85776-9_9

Cited by 10 publications

(22 citation statements)

References 180 publications

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“…The zirconia typically observed in these ZrB 2 ‐based systems stems from the surface coverage of SiO 2 and B 2 O 3 of the Si 3 N 4 and ZrB 2 particles, respectively 41,42 . Another class of materials suitable as buffer‐layer additive are PDCs, as their chemical composition can be tailored resulting in ceramics with a favorable and adjusted chemistry and a well‐defined nanostructure 29,30 . Here, the ternary and pentanary systems, SiCN and SiHfBCN, were used as possible buffer‐layer dopants.…”

Section: Resultsmentioning

confidence: 99%

“…Regarding the densification behavior, SiCN preserves its amorphous state up to 1400°C. At higher temperatures though, SiCN decomposes into its thermodynamically stable products SiC and Si 3 N 4 30,29 . Moreover, it was reported that annealing SiCN/ZrB 2 composites at 1500°C resulted in the formation of the high‐temperature stable phases ZrC, ZrN, Zr(C,N) solid solution, and ZrO 2 43 …”

Section: Resultsmentioning

confidence: 99%

“…41,42 Another class of materials suitable as buffer-layer additive are PDCs, as their chemical composition can be tailored resulting in ceramics with a favorable and adjusted chemistry and a well-defined nanostructure. 29,30 Here, the ternary and pentanary systems, SiCN and SiHfBCN, were used as possible bufferlayer dopants. Regarding the densification behavior, SiCN preserves its amorphous state up to 1400 • C. At higher temperatures though, SiCN decomposes into its thermodynamically stable products SiC and Si 3 N 4 .…”

Section: Performance Of the Buffer Layers Upon Hot Pressingmentioning

confidence: 99%

“…The approach here is to study the efficiency of the buffer layers and the corresponding microstructure evolution, in particular, the microstructural variation of the SiC fibers during sintering and subsequent high‐temperature oxidation. Apart from Si 3 N 4 , a promising material group as buffer‐layer additive are polymer‐derived ceramics (PDCs), as their chemical composition can be tailored resulting in ceramics with a favorable and adjusted chemistry as well as a well‐defined nanostructure 29,30 …”

Section: Introductionmentioning

confidence: 99%

“…Apart from Si 3 N 4 , a promising material group as buffer-layer additive are polymer-derived ceramics (PDCs), as their chemical composition can be tailored resulting in ceramics with a favorable and adjusted chemistry as well as a well-defined nanostructure. 29,30 Three samples were prepared with an architecture as sketched in Figure 1 and investigated via scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) upon hot pressing at 1700 • C for 10 min and upon oxidation at 1500 • C and 1650 • C for 15 min.…”

Section: Introductionmentioning

confidence: 99%

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Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB₂‐based ultra‐high temperature ceramics

2022

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A ZrB2‐based ceramic, containing short Hi‐Nicalon SiC fibers, was fabricated with a Mo‐impermeable buffer layer sandwiched between bulk and the outermost oxidation resistant ZrB2–MoSi2 layer, in order to prevent inward Mo diffusion and associated fiber degradation reactions. This additional layer consisted of ZrB2 doped with either Si3N4 or with the polymer‐derived ceramics (PDCs) SiCN and SiHfBCN. Scanning electron microscopy imaging and elemental mapping via energy‐dispersive X‐ray spectroscopy showed that this tailored sample geometry provides an effective diffusion barrier to prevent the SiC fibers from deterioration due to reactions with Mo or Mo‐compounds. In contrast, the structure of the SiC fibers in a reference sample without buffer layer is strongly degraded by MoSi2 diffusion into the fiber core. The comparison of the three buffer‐layer systems showed a moderate alteration of the fiber structure in the case of Si3N4 addition, whereas in the PDC‐doped samples hardly any structural change within the fibers was observed. A stepwise reaction mechanism is deduced, based on the continuous progression of a reaction zone that propagates toward the ZrB2–MoSi2 top layer. The progression of such a reaction zone as a consequence of the different eutectic melts forming in the different layers, that is, first in the SiC‐fiber‐containing bulk, then in the buffer layer itself, and finally in the top layer at high temperature, allows for an effective separation of the ZrB2–MoSi2 top layer from the SiC fibers. Subsequent oxidation at 1500°C and 1650°C for 15 min did not affect the efficiency of all three buffer layers, since no structural changes regarding buffer layer and fibers were observed, as compared to the non‐oxidized samples.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Performance Of the Buffer Layers Upon Hot Pressingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB₂‐based ultra‐high temperature ceramics

2022

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Single‐source‐precursor derived bulk Si₃N₄/HfB_xN_1‐x ceramic nanocomposites with excellent oxidation resistance

Tian

et al. 2022

Zeitschrift anorg allge chemie

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In the present work, bulk Si3N4/HfBxN1‐x ceramic nanocomposites were successfully fabricated via a polymer‐derived ceramic approach. The chemical reaction to form the single‐source precursor was confirmed by FT‐IR and XPS, in which both Si−H and N−H groups of perhydropolysilazane react with borane dimethyl sulfide complex and tetrakis(dimethylamido) hafnium(IV). The investigation of the polymer‐to‐ceramic transformation of the synthesized precursors indicates that Hf‐ and B‐modified PHPS exhibits high ceramic yields of up to 100 wt % after pyrolysis at 1000 °C under ammonia. Moreover, XRD and TEM results show that the SiHfBN ceramics with a molar ratio of B : Hf=5 and 10 resist crystallization at temperatures up to 1500 °C and separate after annealing at 1700 °C into nanocomposites comprising of an α‐Si3N4 matrix with embedded ternary HfBxN1‐x phases, solid solutions of rock salt‐type HfN and HfB. Based on the investigation, warm‐pressing was applied to fabricate bulk SiHfBN specimens, and the oxidation behavior of samples annealed at 1700 °C was recorded at 1500 °C over a range of oxidation times between 1 and 50 h. The weight changes of Si3N4/HfBxN1‐x ceramics with B : Hf molar ratios of 2 : 1, 5 : 1 and 10 : 1 are 4.31 %, 4.37 % and 2.57 %, respectively. The formation of HfSiO4, B2O3 and SiO2 during oxidation plays a crucial role for the improvement of the oxidation resistance of the Si3N4/HfBxN1‐x ceramics.

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“String and bead” model of copper modified polycarbosilane: synthesis and applications

et al. 2022

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Polymer-Derived Ultra-High Temperature Ceramics (UHTCs) and Related Materials

Cited by 10 publications

References 180 publications

Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB₂‐based ultra‐high temperature ceramics

Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB₂‐based ultra‐high temperature ceramics

Single‐source‐precursor derived bulk Si₃N₄/HfB_xN_1‐x ceramic nanocomposites with excellent oxidation resistance

“String and bead” model of copper modified polycarbosilane: synthesis and applications

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Polymer-Derived Ultra-High Temperature Ceramics (UHTCs) and Related Materials

Cited by 10 publications

References 180 publications

Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB2‐based ultra‐high temperature ceramics

Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB2‐based ultra‐high temperature ceramics

Single‐source‐precursor derived bulk Si3N4/HfBxN1‐x ceramic nanocomposites with excellent oxidation resistance

“String and bead” model of copper modified polycarbosilane: synthesis and applications

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Product

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Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB₂‐based ultra‐high temperature ceramics

Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB₂‐based ultra‐high temperature ceramics

Single‐source‐precursor derived bulk Si₃N₄/HfB_xN_1‐x ceramic nanocomposites with excellent oxidation resistance