Spectroscopic studies of the structure of amorphous and microcrystalline SiC prepared by the polymer route

Ting, S.-J; Chu, C.-J.; Mackenzie, John D.

doi:10.1557/jmr.1992.0164

Cited by 12 publications

(2 citation statements)

References 7 publications

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“…The three sharp peak positions agree with the carbon sites in 6H-SiC or 15R-SiC superposed with fI-SiC structure for which the resonance position will be close to 23.7 ppm [10]. The broad resonance line around 133 ppm is characteristic of aromatic carbon [1] but the behavior above 1200~ suggests also the presence of amorphous SiC. Increasing the annealing temperature leads to a development of a broad peak at 33 ppm and lowering of the structured band related to et-SiC structure.…”

Section: Si and 13c Mas Nmr Characterizationssupporting

confidence: 70%

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EPR investigations of SiC and SiOC nanometric powders

Charpentier

Kassiba

Fusil³

et al. 1997

Appl. Magn. Reson.

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Abstraer. EPR investigations are performed in SiC and SiOC nanometric powders armealed between 1200 and 1800~ By using different EPR frequency bands anda suitable speetra analysis, three quite different paramagnetic defects with well defined gi (i = 1, 2, 3) and hyperfme ,~ (i = 1, 2) tensors aeeount for the EPR signal in these materials. The defeets are charaeterized by gl (g~q= 2.0046(3), g~~ = 2.0023(3)), g2 (g~~ = 2.0037(3), g~ = 2.0028(3)) and an isolropic g3 (2.0030(3)) tensors. In SiC powders, the defects assignment is discussed with respeet to the different SiC forms, namely tx-SiC and 13-SiC polytypes as well as amorphous SiC and earbon present in minor eoncentration in the network. In SiOC powders, the above defeets are evideneed only at high annealing temperature (T, >_ 1200~ when the oxygen contained is highly redueed.

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Section: Si and 13c Mas Nmr Characterizationssupporting

confidence: 70%

“…Electron paramagnetic resonance (EPR) technique is a suitable tool in identifying the paramagnetic defects involved in the network. The type of defects, their local structural environments as well as their concentration could be inferred from EPR measurements [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

EPR investigations of SiC and SiOC nanometric powders

Charpentier

Kassiba

Fusil³

et al. 1997

Appl. Magn. Reson.

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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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