young’s modulus and hardness of pyrolytic carbon coatings used for containment of nuclear fuels
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DESCRIPTIONYoung’s modulus and hardness of pyrolytic carbon coatings used for containment of nuclear fuels. Huixing Zhang, Eddie.Lopez-Honorato, Athar Javed, Jill Meadows, Ping Xiao Material Science Centre, School of Materials, the University of Manchester, M1 7HS, UK. Application in TRISO coating. - PowerPoint PPT Presentation
Youngs modulus and hardness of pyrolytic carbon coatings used for containment of nuclear fuels
Huixing Zhang, Eddie.Lopez-Honorato, Athar Javed, Jill Meadows, Ping Xiao Material Science Centre, School of Materials, the University of Manchester, M1 7HS, UK
Application in TRISO coating
ContentsPyC coatings were deposited on spherical particle using in the TRISO fuel
Deposition temperature was varied from 1250 - 1450 C
Mechanical properties were measured using Nanoindentation
Microstructure was shown in as deposited, and heat treated PyC coatings, using SEM, XRD and TEM.
PyC coatings preparation and propertiesPyC coatings density under different deposition conditionsOrientation angle Domain size La (in graphene plane) and Lc (c-direction)
PyC orientation angle and densityPyC domain size and density relationshipPyC coatings preparation and properties (Continued)
Density effectMechanical properties in as-deposited PyCDomain size: 1.7 nm domain size: 1.1 nm domain size: 1.1 nm(a)(b)(c)(a)(b)(c)Low density PyC, the microstructure difference does not affect theYoungs modulus.
Density effect (continued)In low density PyC, both the Youngs modulus and hardness increase with the density linearly.LaminarGranularMixture of granular and laminar(a)(c)(b)(a)(b)(c)However, in high density region, the mechanical properties do not correlate directly with the density.Three kinds of microstructure were found in high density PyC.
Orientation angle, domain size and microstructure effectThe Youngs modulus and hardness in high density PyC are not dominate by any single element, e.g. density, orientation angle and domain size.The only trend is: Youngs modulus and hardness increase with microstructure change from granular to laminar, and then to mixture structure. Since the particle bonding area and bonding strength dominates the mechanical properties of porous material [1,2]. We presume that in laminar structure the bonding area is bigger than in granular structure, while granular structure has stronger bonding strength. There is a maximum point where the maximum bonding area and strength could be reached, then the mechanical properties are maximum.  J.L.Kaae, Carbon, 1971, Vol. 9, pp. 291-299  J.C.Bokros and R.J.Price, carbon, 1966, vol 3, pp, 503-509
Thermal treatment effect on mechanics and structureSlightly changes could be seen in low density PyC; the mediate density specimen are experiencing the decrease. Youngs modulus and hardnessHigh densityLow densityYoungs modulusHardnessHigh density sample mechanical properties decrease dramatically;13001300
Graphitization process in dense PyC is quicker than in porous structure, because porous structure has stronger cross link than dense PyC.The increase of Lc in laminar structure is more than granular and mixture structure PyC;13001300Laminar Domain size change
After 1800 C heat treatment As-deposited In high density laminar structure PyC 1250 C 50% AcetyleneMicrostructure changeMicrostructure change is not uniform through the whole layer in laminar structure PyC.
In high density granular structure PyC, 1350 C 33% Acy/PropBefore heat treatment After heat treatmentMicrostructure change (continued)SAED with 200 nm aperture; OA: 43SAED with 200 nm aperture; the crystal phase nucleation, did not see the diffraction angle change.
- SummaryWith low density (