Phase content prediction in polymer‐derived ceramics with metal additives

Abstract

Recently, polymer-derived ceramics (PDCs) have raised great interest due to a series of advantages over other traditional ceramics, such as chemical, thermal, and oxidation stabilities. [1][2][3] PDCs can be divided into different categories: binary (e.g., SiC), ternary (e.g., SiCN, SiOC), or quaternary systems (e.g., SiOBC). 4 SiOC can be described as a nanosystem composed of SiO x C 4x units with dispersed turbostratic carbon, SiO 2 , or SiO 2 plus SiC 2,5-7 and exhibits remarkable application potentials in biomedical devices, 8 supercapacitors, 9 optoelectronics, 10 and lithium-ion batteries. 11 With the development of SiOCs, introducing metal species into the SiOC matrix becomes exciting as magnetic, 12,13 catalytic, 14,15 and electrical properties 16,17 can be extended to intrinsically non-functional glassy systems. In our previous studies, 12,16,18 a ferromagnetic nickel-containing SiOC with electrical conductivity up to ~247 S/m at 900°C in an argon atmosphere was successfully fabricated from a base polysiloxane (PSO) with the addition of nickel (II) 2,4-pentanedionate. The in-situ formed Ni crystallites accelerate the graphitization of free carbon and result in more percolating conductive network formation. They also simultaneously offer soft ferromagnetism. Pyrolysis of polysiloxane (PSO) and titanium (IV) isopropoxide (TTIP) at 1200-1400°C leads to hightemperature resistant Si-O-C-Ti, 16 which is thermally stable up to 1000°C in air with >99.8 wt% mass retention. Thus, it can be stated that when more elements are incorporated into the framework of polymer precursors, new avenues for attractive properties from SiOC-based systems become possible.Quantifying polymer-derived SiOC phases is still a task of great challenge. 29 Si nuclear magnetic resonance

New insight into SiOC atomic structure evolution during early stage of pyrolysis

“…Our 4D scanning TEM work attempted to distinguish the phase distribution of SiOC systems, but the information is for a specific pyrolyzed state 1 . On the theoretical side, we have developed a Gibbs energy minimization approach to calculate the percentages of different amorphous phases 2–4 . Still, the exact thermodynamic process is unknown and the calculated phase amounts cannot be verified.…”

Conversion of a polysilazane‐modified cellulose‐based paper into a C/SiFe(N,C)O ceramic paper via thermal ammonolysis

“…13 At even higher temperatures (usually >1100 • C), the additional formation of Fe 3 Si was recorded. 14,15 It is assumed that the detected Si 2 N 2 O phase (Figure 5) is formed via the vapor-liquid-solid (VLS) process. 19…”

“…11,12 It was furthermore shown that the metal (M)-containing polymer-derived ceramic systems Si-M-O-C, Si-M-C, or Si-M-C-N-O are thermodynamically controlled regarding their partitioning and crystallization behavior at elevated temperatures. 13,14 Consequently, the phase composition and microstructure can be predicted and thus tailored accordingly. For instance, extensive studies showed that metal-containing Si-O-C systems provide preparative access to ceramic nanocomposites consisting of a SiOC matrix and incorporating metal oxide secondary phases (as for early transition metals, e.g., belonging to group IV), metal carbides (as for groups V and VI transition metal), pure metals (e.g., Sn, Ni), metal silicides (e.g., Fe, Co, Pd) or metal silicates (e.g., alkaline or earth alkaline metals) as nanostructured precipitates.…”

“…For instance, extensive studies showed that metal-containing Si-O-C systems provide preparative access to ceramic nanocomposites consisting of a SiOC matrix and incorporating metal oxide secondary phases (as for early transition metals, e.g., belonging to group IV), metal carbides (as for groups V and VI transition metal), pure metals (e.g., Sn, Ni), metal silicides (e.g., Fe, Co, Pd) or metal silicates (e.g., alkaline or earth alkaline metals) as nanostructured precipitates. [13][14][15] Iron-containing polymer-derived ceramics such as Si-Fe-C, Si-Fe-O-C and Si-Fe-C-N-O were synthesized and structurally characterized in the past years. [16][17][18][19] These Femodified composites were shown to be highly interesting with respect to their magnetic properties 15,[20][21][22][23] or interaction with electromagnetic waves.…”

The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane‐Derived Silicon Oxycarbide

“…Substantial work with the prospects of understanding decomposition mechanisms, phase/microstructure evolution, and properties/performance of PDCs modified with transition metals was investigated over the past decade. [9][10][11][12][13][14] Combining PDCs with intermetallic or metallic nanoparticles (NPs) on the molecular level before pyrolysis can extend the applications in catalytic and other areas. For example, García et al [15] reported that the novel Ce/SiOC composite via the polymer-derived route performed porous thermocatalysts, which produced the maximum amount of CO gas at 1200-1300 °C.…”