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1/36September 2019
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Philippe Ouzilleau1,2, Marc Monthioux3
1. The University of Manchester, United Kingdom
2. Université de Sherbrooke, Canada
3. Université de Toulouse, France
(Harris, 2005)(Monthioux, 2002)(Oberlin, 1984)
The perspective of thermodynamics on why
some carbons may or may not graphitize
and
the (potential) link to irradiation damage in
nuclear graphites
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Dr Who?Intr
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PhD
2019
Joint postdoctoral researcher
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Why am I here?
• I would like to thank the late Prof Malcolm Heggie for
valuable discussions on the link between
graphitization and defects in graphenic carbons.
• I hope to continue said discussions.
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Thermal GraphitizationIntr
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FIGURE 1: The (secondary) Carbonization
(~800 K to ~2000 K) and Graphitization (~2000 K +)
processes (Marsh, 1991)
3000 K
1000 K
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My wording of graphitization
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-Immature carbon
-Graphenic carbon
-Turbostratic carbon
-Graphitic carbon
-Graphite
-Carbonisation
-Graphitization heat treatment
-Graphitizable carbon
-Non-graphitizable carbon
-Graphitization
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Studying graphitization
FIGURE 2: Idealised representation of
a graphenic crystallites(Ouzilleau, 2015)
• Graphites is constructed
froms stacks of graphenic
layers.
• Average distance between
layers (d002):
– d002 = 0.3354 nm (Perfect 3D)
– d002 ≥ 0.344 nm (2D)
• ‘’Diameter’’ of the crystallite
La
• Height of the crystallite
Lc
• If La = ∞ and Lc = ∞;
– d002 = 0.3354 nm (perfect graphite)
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Scope of the work
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• Single phase carbon material (e.g. HOPG)
• Study of the impact of changes in nanostructure on
graphitic ordering (measured through d002)
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FIGURE 3: Variable potentials of graphitization (graphitizability)
To graphitize or not to graphitizeIntr
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• IUPAC recommends the term graphitization for the
thermal transformation process of graphitizable
carbons.
• IUPAC recommends the term graphitization heat
treatment for the thermal transformation process of
non-graphitizable carbons.
Graphitizable
Non-
graphitizable
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Graphitizability: Franklin’s modelIntr
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FIGURE 4b:
Structure of a high graphitizability carbon
(graphitizable carbon) (Franklin, 1951)
Graphenic crystallite« Non-organized carbon »
(crosslinking carbon)
FIGURE 4a:
Structure of a low graphitizability carbon
(non-graphitizable carbon) (Franklin, 1951)
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Graphitizability: Oberlin’s model
FIGURE 5a: Mesostructural arrangements
of LMOs (Oberlin, 1989)
Oriented domain:
Local Molecular Orientation
(LMO)
FIGURE 5b: Nanostructure within
a singular LMO (Monthioux, 2002)
Crosslinking chemical functions
Basic Structural Unit
(BSU)
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Graphitizability model of Oberlin
FIGURE 6a : Average size of LMOs as
a function of chemical composition
following primary carbonization (~800 K)(Oberlin, 2006)
FIGURE 6b: Graphitizability of LMOs as
a function of chemical composition
following primiary carbonization
carbonisation primaire (~800 K)(Oberlin, 1989)
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Research QuestionT
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• Can we model the graphitizability of some
graphitizable and non-graphitizable carbons, with a
thermodynamic formalism, on the basis of Oberlin and
Franklin graphitizability statements?
Graphitizability is function of :
Local crystallite-crystallite
interactions
Franklin
Graphitizability is function of :
Size of the oriented domains
(LMOs)
Oberlin
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Structural modelT
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a) mGBs = mesoscale Grain Boundaries
LMO = Local Molecular Orientation clusters of Oberlin
b) IM = Intercrystalline Matter clusters
CC = Crystallite clusters
c) Idealized graphenic crystallite (i.e. carbon crystallite)
FIGURE 7: Proposed structural model
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Thermodynamic hypothesisT
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• #1: Local thermodynamic equilibrium hypothesis :*Critical hypothesis for the application of
reversible equilibrium thermodynamic formalism to
irreversible non-equilibrium processes (like graphitization)
• #2: Based on (Franklin, 1951), for La> 2.5 nm, for the
Gibbs energy (G) of graphitizable carbons :
𝑮𝑪−𝒈𝒓𝒂𝒑𝒉𝒊𝒕𝒊𝒛𝒂𝒃𝒍𝒆~𝑮𝑪−𝑪𝒂𝒓𝒃𝒐𝒏 𝑪𝒓𝒚𝒔𝒕𝒂𝒍𝒍𝒊𝒕𝒆𝒔
• #3: Very high activation energy for graphitization in
mGBs :
𝒅𝟎𝟎𝟐(𝑻)~ 𝒅𝟎𝟎𝟐(𝑻) 𝑳𝑴𝑶𝒔
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• A scenario of defect generation and consumption:
The proposed graphitization
mechanism
*Calculated threshold temperatures T0i = 1700 K; Tc = 2550 K; T0
e = 3400 K
ATD (Annealable
Topological Defect)
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Example of a possible ATD
The double heptagon/pentagon pair (Dienes, 1952):
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The thermodynamic graphitization
Order Parameter Ω
• Ω models the density difference between the IM and the
CC during the succession of local equilibrium states
FIGURE 8:
The graphitization Order Parameter (Ω)
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Differential equation model for ATDs
• From δ, we model the thermodynamic effect on d002 of a
change of local equilibrium states during graphitization
by self-diffusion of ATDs (Fischbach, 1971)
δ
δ
*δ = [d002(2073 K) - d002(2400 K)]ATDs generated but not
consumed below Tc
ATDs generated and
consumed below Tc
FIGURE 9: Impact of δ on graphitizability
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Thermodynamic parameters of
the model
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Critical exponent to model a
second-order thermodynamic
transformation in 3D(Gronvold, 1976)
Thermodynamic parameter for the
change of linearity in d002(T)(Ouzilleau, 2016)
Thermodynamic temperature threshold
for “true” graphitization (Ouzilleau, 2015) (Abrahamson, 1971)
Dimensionality of the
merging process of crystallitesDimensionality of the
annealing process of ATDs
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Experimentally derived parameters
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• The mathematical model has two constants :
– δc = Normalization constant
– C1 = Proportionality constant
• We derive both from
the data of (Monthioux, 1982):
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Graphitizability modelBetween 1700 K and 3400 K
• In the end, we have :
d002(T) = f( d002(2073 K), d002(2400 K))
• Validation procedure : predict d002(T) for
– some graphitizable carbons
– some non-graphitizable carbons
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Tα = 2073 K
Tβ = 2400 K
Ex 1: graphitizable carbons
• For selected values of d002(2073 K), d002(2400 K) :
d002,graphite = 0.3354 nm
d002,turbo = 0.344 nm
ηG = 0.9-1 (graphitizable)
ηG = 0.5-0.9 (semi-graphitizable)
ηG < 0.5 (non-graphitizable)
Figure 10: Graphitizability of various asphalts
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Tα = 2073 K
Tβ = 2400 K
Ex 2: graphitizable carbons
• For selected values of d002(2073 K), d002(2400 K) :
d002,graphite = 0.3354 nm
d002,turbo = 0.344 nm
ηG = 0.9-1 (graphitizable)
ηG = 0.5-0.9 (semi-graphitizable)
ηG < 0.5 (non-graphitizable)
Figure 11: Graphitizability of graphitizable
Polyimide film (KAPTON)
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Tα = 2073 K
Tβ = 2400 K
Ex 3: graphitizable carbons
• For selected values of d002(2073 K), d002(2400 K) :
d002,graphite = 0.3354 nm
d002,turbo = 0.344 nm
ηG = 0.9-1 (graphitizable)
ηG = 0.5-0.9 (semi-graphitizable)
ηG < 0.5 (non-graphitizable)
Figure 12: Graphitizability of two types of PYROCARBONS
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Tα = 2073 K
Tβ = 2400 K
Ex 4: semi-graphitizable carbons
• For selected values of d002(2073 K), d002(2400 K) :
d002,graphite = 0.3354 nm
d002,turbo = 0.344 nm
ηG = 0.9-1 (graphitizable)
ηG = 0.5-0.9 (semi-graphitizable)
ηG < 0.5 (non-graphitizable)
Figure 13: Graphitizability of some
emi-graphitizable PYROCARBONS
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Tα = 2073 K
Tβ = 2400 K
Ex 5: non-graphitizable carbons
• For selected values of d002(2073 K), d002(2400 K) :
d002,graphite = 0.3354 nm
d002,turbo = 0.344 nm
ηG = 0.9-1 (graphitizable)
ηG = 0.5-0.9 (semi-graphitizable)
ηG < 0.5 (non-graphitizable)
Figure 14: Graphitizability of some
carbon blacks
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Ex 6: non-graphitizable carbons
-Fischbach, 1967:
Polymer- based
Glassy Carbon
-Monthioux, 1982:
Non-graphitizable
asphalt
-Yamada, 1964:
Glassy Carbon
Figure 15: Graphitizability of some non-graphitizable carbons
Gra
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• For selected values of d002(2073 K), d002(2400 K) :
Tα = 2073 K
Tβ = 2400 K
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Implicit validation-A new model is proposed to model the
graphitizability of some carbons between
temperatures 1700 and 3400 K.
-The model is implicitly in agreement with Franklin’s
graphitizability statement as;
Graphitization by self-diffusion of ATDs is affected
by the local orientation of crystallites
- The model is also in implicit agreement with
Oberlin’s statement as;
Larger LMOs can (usually) accommodate more
ATDs than smaller LMOs and graphitization events
are more prevalent in larger LMOs
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The effect of irradiation on d002
Figure 16: Effect of irradiation on
the d002 of nuclear graphite (Zhou, 2017)
Figure 17: Effect of irradiation on
the d002 of nuclear graphite (Tanabe, 1991)
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Simplified conceptualization of
irradiation damage
Figure 18: Proposed conceptualization of irradiation damage on
the graphitic order of nuclear graphite(Zhou, 2017) (Tanabe, 1992)
-Adolphe Pacault, founder of the French Carbon
Group, and others proposed that graphitic
degradation (“turbostratification”) by irradiation
could be viewed as “degraphitization”. (Miccaud, 1969)
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The proposed turbostratification
mechanism
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Graphitic degradation at higher
irradiation dose
Figure 19: Effect of high temperature high high irradiation
on the d002 of HOPG before and after annealing(Gallego, 2018)
***Competition between
two phenomena?***
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The reversibility of
turbostratification by irradiation
Figure 20: Effect of annealing (7 hours holding time) on the
graphitic order (d002) of highly irradiated graphite(Nightingale, 1957)
Prediction:
d002(3400 K),
7 hours holding
time,
= 0.3367 nm
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Conclusions
• A thermodynamic model for graphitization has been presented.
• This thermodynamic model is in agreement with the
graphitizability statements of:
– Franklin, i.e. graphitizability is function of local crystallite orientation
– Oberlin, i.e. graphitizability is function of LMO size
• Does the present model appears reasonable as a reasonable
(simplified) approach to irradiation if we accept irradiation as a
turbostratification (degraphitization) phenomena?
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Acknowledgement
• I would like to thank the organisers of INGSM-20 for allowing
me to present my work.
• The present research was supported by the Natural Science
and Engineering Research Council of Canada, Rio Tinto, Alcoa,
Constellium, Hydro Aluminium and the FRQNT (Fonds de
Recherche du Québec – Nature et technologies)
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References
[6] Ouzilleau, Gheribi, Chartrand, Soucy and Monthioux, Why some
carbons may or may not graphitize? The point of view of
thermodynamics, Carbon, 2019, 149, p.419
[7] Ouzilleau, Gheribi, Eriksson, Lindberg and Chartrand, Carbon, 2015, 85,
p.99
[8] Zhou et al., Journal of Nuclear Materials, 2017, 487, p.323
[9] Gallego, Contescu, Burchell, XRD and SANS Evaluation of HOPG and
polycrystalline graphite, 2018, ORNL/TM-2018/871 report
[10] Tanabe, Muto, Niwase, Appl. Phys. Lett., 1992, 61, p.1638
[1] Franklin, Proceedings of the Royal Society of London, 1951, 209,
p.196
[2] Oberlin, Carbon, 1984, 22, p.521
[3] Oberlin, Bonnamy and Rouxhet, Chemistry and Physics of Carbon,
1989, vol 22, p.1-143
[4] Nightingale, Snyder, Distribution of radiation damage in graphite, U.S.
atomic energy commission, 1957
[5] Miccaud et al., Journal de Chimie Physique et de Physico-Chimie
Biologique, 1969, 66, .129
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Impact of time of time
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Relative sensitivity of the model
