Characterization of β‐Silicon Carbide by Silicon‐29 Solid‐State NMR, Transmission Electron Microscopy, and Powder X‐ray Diffraction

Abstract

Increased interest in ceramic materials, particularly for high-temperature, high-stress applications, has created the need for rapid and reliable analytical techniques to monitor microcrystalline structure of commercial ceramic powders. A comparative evaluation of commercially available PSiC powders is undertaken to analyze the potential of nuclear magnetic resonance (NMR) in the characterization of PSiC powder. NMR provides an acceptable, rapid method for characterization of powders both during powder manufacturing as well as for powder analyses prior to sintering studies. The results of transmission electron microscopy and X-ray diffraction are correlated with the NMR spectra to explain some newly observed features in the NMR spectra of PSiC powders and to illustrate the sensitivity of NMR to microcrystalline disorder. [Key words: microscopy, nuclear magnetic resonance, transmission electron microscopy, X-ray diffraction, silicon carbide.]

Pyrolytic conversion of an AlSiNC precursor prepared via hydrosilylation between [Me(H)SiNH]4 and [HAlN(allyl)]m[HAlN(ethyl)]n

“…The signal at approximately −48 ppm corresponds to the reported chemical shift for Si 3 N 4 (−48.5 ppm). 59 The signal at −16 ppm and the shoulder at −20 ppm appear to be similar to the chemical shifts for β-SiC (−16.3 ppm) 60 and 2H-SiC (−20.0 ppm). 61 In the Raman spectrum of the residue, two bands are observed at 1337 and 1595 cm −1 , which are consistent with the Raman spectrum of amorphous carbon.…”

Computer Simulations of Diffraction Effects due to Stacking Faults in β‐SiC: II, Experimental Verification

“…[5][6][7] Although TEM techniques have been instrumental in establishing this correlation, determining the average distribution of stacking errors in the starting powders or monitoring changes in error distribution/polytypic transformations during sintering can be tedious, if not practically impossible, using TEM. Carduner et al 8 recently reported a correlation between stacking disorder and features in NMR spectra, and demonstrated the applicability of NMR techniques in gaining qualitative information about stacking disorder in SiC. The present paper illustrates the utility of our simulation model in gaining qualitative information about the spatial distribution of stacking errors from XRD patterns, which can complement information obtained from NMR.…”

Microstructure and thermal stabilities in various atmospheres of SiB0.5C1.5N0.5 nano-sized powders fabricated by mechanical alloying technique

“…To further investigate the polytypes of SiC in the SiBCN powders, 29 Si solid-state NMR studies were introduced. Previous 29 Si solid-state NMR studies have outlined the relationship of the spectra to phase properties of SiC [18][19][20][21][22]. Typically, a single resonance line is observed in the spectrum of b-SiC while up to three closely spaced resonances characterize the a-SiC materials.…”