Solid-state NMR investigations of Si-29 and N-15 enriched silicon nitride

Leonova, Ekaterina; Grîns, Jêkabs; Shariatgorji, Mohammadreza; Ilag, Leopold L.; Edén, Mattias

doi:10.1016/j.ssnmr.2009.03.001

Cited by 19 publications

(20 citation statements)

References 33 publications

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“…(c) . A strong and sharp peak at −8.53 ppm and weak peaks at −12.4 and −14.87 ppm signify C–Si–N type bonds that arise from the environment present around the silicon in ceraset, similar to previous studies . These sharp peaks were not observed in 29 Si NMR of liquid ceraset (prior to the addition of trimethyl borate), implying an obvious change in Si magnetic surrounding caused by long range coupling, possibly caused by boron based functional group forming either B–C or B–N type chemical bonds.…”

Section: Resultssupporting

confidence: 84%

Synthesis, Characterization, and High Temperature Stability of Si(B)CN‐Coated Carbon Nanotubes Using a Boron‐Modified Poly(ureamethylvinyl)Silazane Chemistry

Bhandavat

Singh

2012

J. Am. Ceram. Soc.

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Carbon nanotubes (CNT) and polymer‐derived ceramics (PDCs) are of interest due to their unique multifunctional properties. CNTs, however, tend to lose their well‐defined structure and geometry at about 400°C in air. PDCs on the other hand are structureless in X‐ray diffraction but show high chemical and thermal stability in air (up to ~1400°C). Herein, we demonstrate synthesis of a composite nanowire structure consisting of polymer‐derived silicon boron‐carbonitride (Si–B–C–N) shell with a multiwalled carbon nanotube core. This was achieved through a novel process involving preparation of a boron‐modified liquid polymeric precursor through a reaction of trimethyl borate and poly (ureamethylvinyl) silazane under normal conditions; followed by conversion of polymer to ceramic on carbon nanotube surfaces through controlled heating. Chemical structure of the polymer was studied by liquid‐Nuclear Magnetic Resonance (NMR) while evolution of various ceramic phases was studied by solid‐NMR, Fourier transform infrared and X‐ray photoelectron spectroscopy. Electron microscopy and X‐ray diffraction confirm presence of amorphous Si(B)CN coating on individual nanotubes for all specimens processed below 1400°C. Thermogravimetric analysis, followed by Raman spectroscopy and transmission electron microscopy revealed high temperature stability of the carbon nanotube core in flowing air up to 1000°C.

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Section: Resultssupporting

confidence: 84%

Synthesis, Characterization, and High Temperature Stability of Si(B)CN‐Coated Carbon Nanotubes Using a Boron‐Modified Poly(ureamethylvinyl)Silazane Chemistry

Bhandavat

Singh

2012

J. Am. Ceram. Soc.

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“…The 29 Si spectra of the polyborosilylcarbodiimide-derived HN1B ceramic contain primarily one heterogeneously broadened Gaussian peak with a 29 Si isotropic chemical shift (d iso ) of~À48 ppm, characteristic of tetrahedrally coordinated Si atoms in SiN 4 tetrahedra. 32 A minor peak at À106 ppm can also be seen in the 29 Si MAS NMR spectrum of HN1B-800 collected at a spinning speed of 14 KHz [ Fig. 2(b)].…”

Section: Resultsmentioning

confidence: 99%

Effect of Precursor on Speciation and Nanostructure of SiBCN Polymer‐Derived Ceramics

et al. 2013

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A comparative structural study of silicon borocarbonitride polymer‐derived ceramics synthesized using polyborosilylcarbodiimide and polyborosilazane precursors is carried out using high‐resolution, multinuclear, one‐ and two‐ dimensional NMR spectroscopy. The polyborosilylcarbodiimide‐derived ceramics contain relatively pure Si3N4 and C nanodomains with the BN domains being present predominantly at the interface such that the bonding at the interface consists of Si–N–B, Si–N–C, and B–N–C linkages. In contrast, the structure of the polyborosilazane‐derived ceramics consists of significant amount of mixed bonding in the nearest‐neighbor coordination environments of Si and B atoms leading to the formation of SiCxN4−x (0 ≤ x ≤ 4) tetrahedral units and BCN2 triangular units. The interfacial region between the SiCN and C nanodomains is occupied by the BCN phase. These results demonstrate that the chemistry of the polymeric precursors exerts major influence on the microstructure and bonding in their derived ceramics even when the final chemical compositions of the latter are similar.

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“…However, a fast spin-lattice (T 1 ) relaxation requires molecular motions to modulate the NMR-interaction frequency at a rate comparable to the Larmor frequency; this does not apply to rigid inorganic materials, where minute paramagnetic impurities are often mainly responsible for driving relaxation [15,154,155]. Similar misbeliefs apply for 1 H: the very rapid relaxation frequently observed from organic molecules stem predominantly from molecular segments that exhibit fast internal rotations (such as CH 3 /NH 3 groups) coupled with 1 H spin diffusion.…”

Section: T 1 Relaxation and Pulse Delaysmentioning

confidence: 99%