Novel approach to plasma facing materials in
nuclear fusion reactors
V. Livramento1, J.B. Correia1, D. Nunes3, P.A. Carvalho3, H. Fernandes2,
C. Silva2, K. Hanada4, N. Shohoji1, E.Osawa5
1INETI, Departamento de Materiais e Tecnologias de Produção, Estrada do Paço do Lumiar,
1649-038 Lisboa, Portugal
2Associação Euratom/IST, Centro de Fusão Nuclear, Instituto Superior Técnico, Av. Rovisco
Pais, 1049-001 Lisboa, Portugal
3Associação Euratom/IST, Departamento de Engenharia de Materiais, Instituto Superior
Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
4 National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki,
Tsukuba, Ibaraki 305-8564, Japan
5NanoCarbon Research Institute, Ltd. Shinshu University, 386-8567 Ueda-shi Tokida 3-15-1,
Nagano, Japan
Instituto Nacional de Engenharia, Tecnologia e Inovação, I.P.
Objective
Produce a W-nDiamond composite, using High Energy milling of
powders and consolidation in order to develop a suitable material
for the first wall of nuclear fusion reactors.
Why W?
Highest melting point;
• Highest resistance to irradiation
(doesn’t contaminate the plasma);
• High corrosion resistance;
• Doesn’t produce armful radioactive
elements
•
Why nD?
•
•
High thermal condutivity;
Very hard material
Why Nanostructure?
Nanoparticles act as effective
sink for radiation defects.
W-nD nanocomposite
is a good option!
Challenge: Avoid the
carbide formation!
Experimental Procedures
Mechanical Alloying
Planetary Ball
Mill
Inside the Container
Container & Balls
Processing
of elemental powders in high energy ball mills;
Dynamic balance between cold welding and fracture  gradual mixture;
Nanostructure in the end;
Especially suited for the production of composite materials.
Experimental Procedures
Used Powders:
• Pure elemental W (99.95% purity; median particle size 1 m)
• nD particles; (agglomerates that have diameters of 2-3 m)
Mechanical Alloying:
WC balls with 10 mm of diameter
250 ml WC containers
The container was first evacuated and then filled with Argon
Retsch PM 400 Planetary Ball Mill
Rotation speed = 200 rpm
Experimental Procedures
XRD
Scanning
Electron
Microscopy
Characterization
of the Resulting
Powders
Optical
Microscopy
Microhardness
Measurments
Experimental Procedures
Milled Powders
Consolidation
Consolidated
Powders were consolidated by:
•
SPS at 800ºC
•
Hot-Rolling at 800ºC
•
SPS & Hot-Rolling
Material
Experimental Procedures
Spark Plasma Sintering- SPS
Hot-Rolling
Experimental Procedures
SPS at AIST Japan
Results
Processing Parameters and Microhardness of all produced batches
Batch
W-nD-2H
Milling Time
[h]
Observations
Microhardness [HV]
2
Heterogeneous powders
(several kind of
particles)
1558.0±282.8
W-nD-4H
4
Heterogeneous powders
(2 kind of particles)
W-nD-4H
SPS 800ºC
4
Homogeneous powders
(1 kind of particles)
W-nD-4H
Hot-rolling 800ºC
W-nD-4H
SPS and Hot-rolling
800ºC
4
4
Heterogeneous powders
(2 kind of particles)
Heterogeneous powders
(2 kind of particles)
Homogeneous particles (bright)
2427.5±290.2
Heterogeneous and darker particles
1461.0±205.9
2796±271.2.6
Homogeneous particles (bright)
2780,6±553,2
Heterogeneous and darker particles
1444,0±417,7
Homogeneous particles (bright)
2706,5±282,9
Heterogeneous and darker particles
1433,1±335,5
Results
XRD patterns for W+nD powders milled for 2 and 4 hours and consolidated
samples:
5,5
W
WC
W2C
WO2
Diam.
5
4,5
4
W-nD - 4H - 200rpm Roll + SPS 800ºC
3,5
W-nD - 4H - 200rpm SPS 800ºC
3
W-nD - 4H - 200rpm roll. 800ºC new
2,5
W-nD - 4H - 200rpm Lam. 800ºC
W-nD - 4H - 200rpm
2
W-nD - 2H - 200rpm
1,5
1
20
40
60
80
2q
100
120
140
160
Results
SEM/BSE pictures of W+nD
respectively (200rmp):
powders milled for
2 h and 4h
Results
SEM/BSE image of W+nD subjected to MA (4 h at 200 rpm) and
rolling at 800ºC and respectively EDS chemical analysis:
Results
W-nD subjected to MA (4 h at 200 rpm) and rolling at 800ºC and
exposed to the edge plasma:
Conclusions
 It is possible to performe MA of W and nD powders at room
temperature without agglomeration
 Short milling time of only 2 and 4 hours provides a favourable
condition for the least contamination of ball material in the
mechanical alloying.
High-energy milling at 200 rpm followed by SPS at 800ºC
represents the best combination of processing parameters for
obtaining dense W-nD nanocomposite.
 Bulk specimens were obtained without significant carbide
formation.
Exposure to plasma of rolled W-nD produced surface modification
of structure. However, below 1 mm the W-nD nanocomposite was
essentially preserved.
Perspectives of Future work
Optimize the consolidation parameteres for W-nDiamond
Thermal conductivity tests on the way
More exposure experiments at ISTTOK and at FTU of the
Consolidated materials
Novel approach to plasma facing materials in
nuclear fusion reactors
V. Livramento1, J.B. Correia1, D. Nunes3, P.A. Carvalho3, H. Fernandes2,
C. Silva2, K. Hanada4, N. Shohoji1, E.Osawa5
1INETI, Departamento de Materiais e Tecnologias de Produção, Estrada do Paço do Lumiar,
1649-038 Lisboa, Portugal
2Associação Euratom/IST, Centro de Fusão Nuclear, Instituto Superior Técnico, Av. Rovisco
Pais, 1049-001 Lisboa, Portugal
3Associação Euratom/IST, Departamento de Engenharia de Materiais, Instituto Superior
Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
4 National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki,
Tsukuba, Ibaraki 305-8564, Japan
5NanoCarbon Research Institute, Ltd. Shinshu University, 386-8567 Ueda-shi Tokida 3-15-1,
Nagano, Japan
Instituto Nacional de Engenharia, Tecnologia e Inovação, I.P.
Plasma
W
W-nD
W-Cu
Cu
LAYERS
Properties
W
Density W = 19.3 g/cm^3
Hardness Hv W = 3.04 GPa
Thermal Conductivity W = 163.3
W/(m-k)
nD
Density nD = 3.51 g/cm^3
Micro-Hardness HV nD = 88 147 GPa
Thermal Conductivity nD =
2000 W/(m-k)
SPS
- The pulsed DC passes through the graphite die and the compacted
powders;
- The heat is generated internally, that provides a very high rates of
heating and cooling;
- This process has the potential of densifying the powders with
nanosize or nanostructure avoiding the coarsening which normally
accompanies the normal densification routes.
Hot-Rolling
- Metallurgical process, where the material is passed, deformed
between rolls, applying a controlled load;
- permits large deformation of the material with a low number of
rolling cycles;
- Do not affect microstructural properties;
- It’s possible to obtaine material with a certain specification or size.