Carbon content and pyrolysis atmosphere effects on phase development in SiOC systems

Bawane, Kaustubh; Erb, Donald; Lu, Kathy

doi:10.1016/j.jeurceramsoc.2019.03.032

Cited by 32 publications

(19 citation statements)

References 33 publications

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“…The specific fractions of various phases (f i ) at different temperatures can be calculated by the minimization of G am−SiOC/M method using Mathematica software based on the stoichiometric constraints for O, C, and M elements (Details are provided in the Supporting Information). Similar to our previous studies, 21,41 ) can be calculated by assuming their structures as mixed tetrahedra with SiO (4-i) C i (where i = 1 to 3) compositions, which can be given as follows:…”

Section: Sioc/m Thermodynamic Modelsmentioning

confidence: 99%

“…In our recent studies, 21,22 a thermodynamic model for the ternary SiOC ceramic system has been developed to calculate the amorphous phase fractions of the Si-O-C systems from the polymer-derived ceramics. The approach can be separated into two steps.…”

Section: Metal-containing Sioc Systemmentioning

confidence: 99%

“…However, it is a surface analysis method for oxidation states and the resolution is never suited for quantitative phase analysis. Our earlier work 21,22 introduced a thermodynamic method to calculate the phase contents in the SiOC system based on Gibbs free energy minimization. However, the quantitative studies were focused on pure SiOC systems without any metal additives.…”

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confidence: 99%

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Phase content prediction in polymer‐derived ceramics with metal additives

Yang

2021

J Am Ceram Soc

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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

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Section: Sioc/m Thermodynamic Modelsmentioning

confidence: 99%

Section: Metal-containing Sioc Systemmentioning

confidence: 99%

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confidence: 99%

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Phase content prediction in polymer‐derived ceramics with metal additives

Yang

2021

J Am Ceram Soc

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“…When the pyrolysis temperature continues to rise, a carbothermal reaction between SiO 2 and C occurs according to Eq. 25‐28

2 SiOC \to {SiO}_{2} false(amorphous false) + SiC false(normalβ false) + C false(amorphous false)

{SiO}_{2} false(amorphous false) + 3 C false(graphite false) \to SiC false(normalβ false) + 2 CO false(normalg false)

…”

Section: Introductionmentioning

confidence: 99%

“…2. [25][26][27][28] To obtain a polysiloxane-derived SiC-TiC system, phase conversion into carbide crystals should be facilitated. For the formation of TiC, pyrolysis of titanium alkoxide modified polysiloxanes has been confirmed to promote heterometallic Si-O-Ti bonds, followed by the formation of TiO 2 and SiO 2 upon bond redistribution.…”

Section: Introductionmentioning

confidence: 99%

Electrically conductive and thermally stable SiC‐TiC containing nanocomposites via flash pyrolysis

Zheng

2021

J Am Ceram Soc

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Flash pyrolysis, which combines conventional pyrolysis with flash sintering, was first conducted to produce polymer derived SiC‐TiC nanocomposites. Pre‐pyrolysis at 800℃ allows the conversion from titanium isopropoxide (TTIP) modified polysiloxane to an amorphous SiTiOC ceramic. The subsequent application of an electric field gives rise to the formation of turbostratic carbon and creates Joule heating to obtain a sample internal temperature of ~1400℃. The precipitation of β‐SiC, TiC, as well as titanium oxides is realized upon carbothermal reduction of extensively phase separated SiO2 and TiO2 with carbon. Increasing TTIP content embodies the nanocomposites with prominent electrical percolation behaviors. The electrical transport of the synthesized ceramics follows an amorphous semiconductor mechanism. High thermal stability in air is guaranteed, thanks to the in‐situ formed TiC nanocrystals and preferentially reduced amorphous carbon. Flash pyrolyzed nanocomposite with a Ti:Si molar ratio of 0.20 exhibits the highest electrical conductivity (0.696 S/cm) and minimum mass change (~2%) at 1000℃, serving as a competitive candidate for electro‐discharge machining (EDM) applications or self‐standing conducting devices that must withstand high temperature conditions.

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Polymer‐Derived High‐Temperature Nonoxide Materials: A Review

Zhou

2023

Adv Eng Mater

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The synthesis of polymer-derived nonoxide materials such as carbides, borides, and nitrides started in the 1970s and slowly progressed into the 1980s, with silicon carbide (SiC) fibers as the prime examples. [1] In the 1990s, the research activities in this area became more intensive, with multiple efforts devoted to understanding the polymer-to-ceramic conversion mechanisms, resulting microstructures, and mechanical properties. In the 2000s, relying on the liquid precursor nature and advancement in chemistry, new techniques (e.g., electrospinning, coating, and precursor infiltration) and new precursors were introduced. Understanding of the crosslinking and thermal conversion process was improved. For example, SiC fibers were improved from amorphous silicon oxycarbide (SiOC) to low-oxygen SiC fibers and then to near-stoichiometric SiC fibers. SiC thin films of 8-190 μm thickness were reported in 2009. [2] These films can stand alone, and high mechanical properties and optoelectronic properties were achieved. Because of these advantages, they were proposed to be used in microelectromechanical systems (MEMS) and optoelectronic devices. In recent decades, additive manufacturing was used to form complex shapes. [3] Also, different one-pot precursor synthesis approaches were reported. [4] The pyrolyzed ceramic systems were frequently used in a powder format and can be further processed with traditional forming processes such as spark plasma sintering, hot pressing, thermal treatment, etc. [5,6] The advantages of using the polymerderived approach for such high-temperature nonoxide material formations involve several aspects. Compositions can be designed based on molecular-level interactions and conversion of polymeric precursors to composites. Through a synergistic selection and combination of polymer molecules of different architectures and additives, a large family of functional, structural, resilient, and versatile materials can be created. Pyrolysis conditions can also be varied to create different property systems. Species intermixing can be achieved at the true atomic level. It enables functional properties for inert systems and harsh environmental stability for far-from-equilibrium conditions. Additional advantages include low processing temperature (such as a few hundred degrees Celsius lower) and versatile shape achievement. The final materials can be fibers, coatings, membranes, powders, bulk parts, porous forms, infiltrating phases, and complex 3D-printed shapes, [3a] among others. Using the polymer-derived approach to form high-temperature ceramics also enables composition homogeneity and purity, thanks to the uniform mixing of different precursors and additives and high-purity chemical precursors. It can also create compositions that may be impossible with conventional routes, [7] such as sintering.The common challenges are as follows. Polymer-derived nonoxide composites are in a metastable state. At high temperatures, the composition and microstructure can continue to evolve and

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Carbon content and pyrolysis atmosphere effects on phase development in SiOC systems

Cited by 32 publications

References 33 publications

Phase content prediction in polymer‐derived ceramics with metal additives

Phase content prediction in polymer‐derived ceramics with metal additives

Electrically conductive and thermally stable SiC‐TiC containing nanocomposites via flash pyrolysis

Polymer‐Derived High‐Temperature Nonoxide Materials: A Review

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