Microstructural study of silicon carbide fibers through the use of Raman microscopy

Naslain

Prentice

et al. 2005

The chemical, structural and thermomechanical properties of SiC and diamond CVD-monofilaments have been investigated. Electron and Raman microprobe analyses showed graded radial atomic and phase distributions in the SiC filaments. Thermomechanical investigations (tensile/bending elastic modulus/creep tests) were carried out on single filaments and these properties were correlated with the physicochemical features. The thermal behaviour of the CVD-SiC filaments is strongly related to the nature and the amounts of intergranular secondary phases (free carbon or silicon). The strong covalent bonds and the microcrystalline state of the CVD-diamond filaments give rise to an outstanding thermal behaviour.

Section: Methodsmentioning

confidence: 99%

High temperature properties of SiC and diamond CVD-monofilaments

Naslain

Prentice

et al. 2005

“…1). [1][2][3] The broad carbon features correspond to a very disordered form (turbostratic, with heavily distorted graphene layers). The various optical modes evidenced for the 6H-SiC crystal are also present for the outer CVD-SiC.…”

Section: Raman Features Of Sic-based Materialsmentioning

confidence: 99%

“…3,15,16 In order to investigate the disorder ranges induced by irradiation, a phonon confinement model was applied to 3C-SiC to simulate the Raman spectra. 3,15,16 The intensities I i (ω) of the various phonons i were integrated along all the acoustic (TA, LA) and optic (TO, LO) branches ω i (q), within the Brillouin zone (0 ≤ q ≤ 1), using the weighing function f(q, L) = exp(−q 2 L 2 /4), centred on q = 0, where q is the reduced wave vector, L is a dimensionless parameter (L = 1 correspond to the nearest-neighbour Si (or C) planes) and Γ 0i are the linewidths of the undistorted Raman lines (all arbitrary fixed at Γ 0i = 10 cm −1 , Eq. (1))…”

Section: Rms Analysis Of the Irradiated 6h-sic Crystal And Htr Particlementioning

confidence: 99%

“…CVD-SiC is deposited for instance on tungsten or carbon monofilament cores, for the reinforcement of metal matrix composites. [1][2][3] The filaments obtained display outstanding mechanical properties such as high strength, stiffness and creep resistance. CVD-SiC coatings are also constituents of the nuclear fuel particles which are considered for the fourth generation fission reactors.…”

Section: Introductionmentioning

confidence: 98%

“…It is therefore particularly suited to the local analysis of few micrometers-thick CVD coatings. 3 The aim of the present paper is to investigate the structural and textural evolution of various CVD-SiC coatings, induced by room and high temperature plastic deformations and by irradiation. For this purpose, the specimens, a commercial SiC-CVD filament and a model C/SiC/C/ZrO 2 nuclear fuel particle, were submitted to (i) tensile creep at high temperature, (ii) indentation at room temperature and (iii) proton irradiation at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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Structural and textural changes of CVD-SiC to indentation, high temperature creep and irradiation

Vallerot

Helary

et al. 2007

The structure and microtexture of different SiC-based CVD coatings have been studied by RMS, in their as-processed state and after high temperature annealing, creep, indentation and irradiation. Both annealing and creep resulted in the same degree of SiC crystal growth and decrease of stacking faults. A slight influence of stress was however observed on the structure and texture of the co-deposited free-carbon, likely as a consequence of the intergranular creep mechanism. Room temperature indentation induces substantial structural disorders (dislocations, stacking faults, small grains) near the contact and more extended damages due to dislocation slip parallel to the compact Si-C planes. These structural changes were found to depend on the single crystal orientation and therefore, on the texture of polycrystalline SiC. Room temperature proton irradiation produced only small amounts of disorders. The specific alterations of the Raman features were explained using a phonon confinement model. This approach supports the existence of very low scale defects, likely as punctual defects.

Synthesis and characterization of monolithic CVD-SiC tubes

Drieux

Jacques

et al. 2016

International audience† The authors dedicate this article to the memory of our colleague P. Weisbecker who has recently passed away Abstract : The high open porosity of SiC/SiC composites is problematic for uses in advanced thermal or confinement systems. A strong and gas-tight SiC sheath would helpfully complete the composite structure. The aim of this work was to prepare and characterize long, free standing and high strength SiC tubes prepared through a rapid near net shape manufacturing process. The tubes were produced by continuous chemical vapor deposition (CVD) at atmospheric pressure using CH 3 SiHCl 2 /C 3 H 6 /H 2 mixtures. The composition, morphology and microstructure of the CVD-SiC tubes were analyzed in details. The Si/C ratio and crystalline state through wall thickness are related to the progress of gas phase reactions during continuous deposition. The silicon excess in the CVD-SiC coating can be reduced by preheating gases and adding C 3 H 6. C-ring specimens cut from the obtained tubes were submitted to compressive tests at room and high temperature to assess the failure properties and thermomechanical behavior