CW and Pulse EPR Study of Paramagnetic Centers in Silicon Carbide Nanomaterials

2018 ◽  
pp. 225-242
Author(s):  
Dariya Savchenko ◽  
Andreas Poppl ◽  
Abdel Hadi Kassiba
Keyword(s):  
Silicon Carbide ◽  
Paramagnetic Centers ◽  
Pulse Epr

scholarly journals Magnetic properties of the natural and isotope-modified diamond and silicon carbide

2018 ◽  
Vol 185 ◽  
pp. 04007 ◽  
Author(s):  
A.N. Taldenkov ◽  
A.V. Inyushkin ◽  
E.A. Chistotina ◽  
V.G. Ralchenko ◽  
A.P. Bolshakov ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Magnetic Properties ◽  
Isotopic Composition ◽  
Single Crystals ◽  
High Purity ◽  
Diamagnetic Susceptibility ◽  
Synthetic Diamond ◽  
Paramagnetic Centers ◽  
Natural Isotopic Composition ◽  
Ferromagnetic Component

The magnetic properties of single crystals of synthetic diamond and crystals of silicon carbide were studied. High-purity samples of diamonds synthesized with HPHT and CVD technologies were used. The crystals of silicon carbide were grown by sublimation and industrial technology. Along with samples with a natural isotopic composition, monoisotopic crystals of diamond (99.96% 12C and 99.96% 13C) and silicon carbide (99.993% of 28Si) were studied. On the basis of the data obtained, the diamagnetic susceptibility was determined and the concentration of paramagnetic centers and the content of the ferromagnetic component were evaluated. The results are discussed.

scholarly journals Paramagnetic centers in detonation nanodiamonds studied by CW and pulse EPR

2010 ◽  
Vol 493 (4-6) ◽  
pp. 319-322 ◽  
Author(s):  
A.V. Fionov ◽  
A. Lund ◽  
W.M. Chen ◽  
N.N. Rozhkova ◽  
I.A. Buyanova ◽  
...  
Keyword(s):  
Detonation Nanodiamonds ◽  
Paramagnetic Centers ◽  
Pulse Epr

scholarly journals Electron nuclear interactions in spin-3/2 color centers in silicon carbide: A high-field pulse EPR and ENDOR study

2021 ◽  
Vol 104 (12) ◽  
Author(s):  
Victor A. Soltamov ◽  
Boris V. Yavkin ◽  
Georgy V. Mamin ◽  
Sergei B. Orlinskii ◽  
Ilia D. Breev ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
High Field ◽  
Color Centers ◽  
Field Pulse ◽  
Nuclear Interactions ◽  
Pulse Epr

scholarly journals N-Doped Graphene Oxide Nanoparticles Studied by EPR

2020 ◽  
Vol 51 (11) ◽  
pp. 1481-1495
Author(s):  
Francesco Tampieri ◽  
Matteo Tommasini ◽  
Stefano Agnoli ◽  
Marco Favaro ◽  
Antonio Barbon
Keyword(s):  
Epr Spectroscopy ◽  
Density Functional ◽  
Continuous Wave ◽  
Graphene Quantum Dots ◽  
Paramagnetic Centers ◽  
Nitrogen Doped ◽  
Wide Range ◽  
Doped Graphene ◽  
Pulse Epr ◽  
Unpaired Electrons

AbstractGraphene-derived materials attract a great deal of attention because of the peculiar properties that make them suitable for a wide range of applications. Among such materials, nano-sized systems show very interesting behaviour and high reactivity. Often such materials have unpaired electrons that make them suitable for electron paramagnetic resonance (EPR) spectroscopy. In this work we study by continuous wave and pulse EPR spectroscopy undoped and nitrogen-doped graphene quantum dots (GQD) with a size of about 2 nm. The analysis of the spectra allows identifying different types of paramagnetic centers related to electrons localized on large graphenic flakes and molecular-like radicals. By hyperfine spectroscopies on nitrogen-doped samples, we determine the hyperfine coupling constant of paramagnetic centers (limited-size π-delocalized unpaired electrons) with dopant nitrogen atoms. The comparison of the experimental data with models obtained by density functional theory (DFT) calculations supports the interpretation of doping as due to the insertion of nitrogen atoms in the graphene lattice. The dimension of the delocalized regions in the flakes observed by pulse EPR is of about 20–25 carbon atoms; the nitrogen dopant can be classified as pyridinic or graphitic.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

Microstructural Evaluation of Silicon Carbide Whisker Reinforced Alumina Fabricated with Carbon-Coated Whiskers

1991 ◽  
Vol 49 ◽  
pp. 920-921
Author(s):  
K. B. Alexander ◽  
P. F. Becher
Keyword(s):  
Silicon Carbide ◽  
High Resolution Electron Microscopy ◽  
Ceramic Composites ◽  
Interface Debonding ◽  
Resolution Electron ◽  
Microstructural Evaluation ◽  
Carbon Coated ◽  
Electron Energy Loss ◽  
Interfacial Films ◽  
Debonding Process

The presence of interfacial films at the whisker-matrix interface can significantly influence the fracture toughness of ceramic composites. The film may alter the interface debonding process though changes in either the interfacial fracture energy or the residual stress at the interface. In addition, the films may affect the whisker pullout process through the frictional sliding coefficients or the extent of mechanical interlocking of the interface due to the whisker surface topography.Composites containing ACMC silicon carbide whiskers (SiCw) which had been coated with 5-10 nm of carbon and Tokai whiskers coated with 2 nm of carbon have been examined. High resolution electron microscopy (HREM) images of the interface were obtained with a JEOL 4000EX electron microscope. The whisker geometry used for HREM imaging is described in Reference 2. High spatial resolution (< 2-nm-diameter probe) parallel-collection electron energy loss spectroscopy (PEELS) measurements were obtained with a Philips EM400T/FEG microscope equipped with a Gatan Model 666 spectrometer.

TEM of grain growth and phase transformations during creep of SCS-6 silicon carbide fibers

1995 ◽  
Vol 53 ◽  
pp. 350-351
Author(s):  
L. A. Giannuzzi ◽  
C. A. Lewinsohn ◽  
C. E. Bakis ◽  
R. E. Tressler
Keyword(s):  
Silicon Carbide ◽  
Creep Rate ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Primary Creep ◽  
Excess Carbon ◽  
Silicon Carbide Fibers ◽  
Sic Fiber ◽  
Carbon Core ◽  
Grain Width

The SCS-6 SiC fiber is a 142 μm diameter fiber consisting of four distinct regions of βSiC. These SiC regions vary in excess carbon content ranging from 10 a/o down to 5 a/o in the SiC1 through SiC3 region. The SiC4 region is stoichiometric. The SiC sub-grains in all regions grow radially outward from the carbon core of the fiber during the chemical vapor deposition processing of these fibers. In general, the sub-grain width changes from 50nm to 250nm while maintaining an aspect ratio of ~10:1 from the SiC1 through the SiC4 regions. In addition, the SiC shows a <110> texture, i.e., the {111} planes lie ±15° along the fiber axes. Previous has shown that the SCS-6 fiber (as well as the SCS-9 and the developmental SCS-50 μm fiber) undergoes primary creep (i.e., the creep rate constantly decreases as a function of time) throughout the lifetime of the creep test.

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