Young’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.
Young’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
PyC coatings preparation and properties
PyC coatings density under different deposition conditions
Orientation angle Domain size La (in graphene plane) and Lc (c-direction)
PyC coatings preparation and properties (Continued)
PyC orientation angle and density
PyC domain size and density relationship
Mechanical properties in as-deposited PyC
Low density PyC, the microstructure difference does not affect theYoung’s modulus.
Domain size: 1.7 nm domain size: 1.1 nm domain size: 1.1 nm
Density effect (continued)
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.
In low density PyC, both the Young’s modulus and hardness increase with the density linearly.
Mixture of granular and laminar
Orientation angle, domain size and microstructure effect
The Young’s 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:
Young’s 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 structure
Young’s modulus and hardness
High density sample mechanical properties decrease dramatically;
Slightly changes could be seen in low density PyC; the mediate density specimen are experiencing the decrease.
Domain size change
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;
In high density laminar structure PyC 1250 C50% Acetylene
Microstructure change is not uniform through the whole layer in laminar structure PyC.
After 1800 C heat treatment As-deposited
Microstructure change (continued)
In high density granular structure PyC, 1350 C33% Acy/Prop
Before heat treatment After heat treatment
SAED with 200 nm aperture; the crystal phase nucleation, did not see the diffraction angle change.
SAED with 200 nm aperture; OA: 43°