development of a copper matrix composite reinforced with graphene and analysis of its thermal...
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Development of a copper matrix composite reinforced with graphene
and analysis of its thermal conductivity
Università degli studi di Roma Tor VergataTecnun Universidad de Navarra
Laurea Magistrale in Ingegneria Meccanica
Under the supervision of
Prof. Maria Elisa Tata
Dr. Nerea Ordas
Ing. Girolamo Costanza
Presented by
Stefano Mascellino
Objective
Background knowledge
Experimental procedure
Results
Conclusions
Future work
TABLE OF CONTENTS
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
OBJECTIVEDevelopment of a copper matrix composite reinforced with
graphene oxides and analysis of its thermal conductivity
STEPS
1. Dispersion of graphene oxides in copper matrix
2. Reduction of interface resistance by introducing a third phase element
3. Microstructural analysis of the composite
4. Analysis of thermal conductivity
5. Comparison of results
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
BACKGROUNDHighly conductive materials
• Many engineering applications require high thermal conductivity
• Increasing calculation capacities of electronic devices induce heat dissipation issues
• Most common material used when high thermal performances are required is copper
• New materials are under investigation to ensure high thermal conductivity and low CTE
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Graphene oxidesGraphene oxides are produced from graphite. Oxides are generally reduced to obtain reduced graphene oxide. The process is as follows:
• strong oxidation of graphite with H2SO4 and KMn04 solutions in water
• exfoliation of oxidized graphite and separation of exfoliated fraction• reduction with hydrazine or green agents• desiccation
rGO, reduced graphene oxide: in the form of powder between 40 and 70µm in size.
dGO, dried graphene oxide: in the form of flakes 2÷5mm x 5÷10mm, tens of µm thick , being desiccated on a support, cut and carbonized at 1100ºC.
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
EXPERIMENTAL PROCEDUREPowder selection
Mixing and mechanical alloying
Hot press
Grinding and polishing
Microstructural and thermal analysis
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Laser flash analysisIn laser flash technique a laser pulse hits one face of the sample and a detector on the front reveals the increase in temperature. The variation of temperature is described by the equation:
where and with Parker’s approximation: .
• Radial distance between the section of incident laser pulse and the section of detection allows the measurement of in plane thermal conductivity
• Thickness of the sample should be thin to reduce the error
RESULTSSummary of samples1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Pure copper samples
Copper – chromium samples
Cu – Cr – rGO samples
Cu – Cr – dGO samples
Graphitized graphite samples
Pure copper samples1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
• The grade of compaction achieved is above 95%.
• Reduced powder has an oxygen content of 250ppm, while unreduced reaches 900 ppm.
• Thermal conductivity of reduced Cu sample is 20% higher compared to unreduced Cu: oxygen is detrimental to thermal properties.
• Maximum values are 9% lower than those of bulk copper.
• Reduced copper• Unreduced copper
Copper – chromium samples1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
• Chromium is needed to create an
interphase between copper and carbon.
• Samples produced to verify the solubility
of chromium in copper lattice.
• Solubility of chromium: 0.7% wt. at HP
temperature, 0.2% at room temperature
3 percentages chosen: 1% wt., 0.15%
and 0.5%.
• Reduced Cr powder used to decrease
the oxygen content.
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
MicrostructureCu 1% Cr
Cu 0.15% Cr Cu 0.5% Cr
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Thermal conductivity Cu-Cr samples
Cr adding is detrimental to thermal conductivity of copper due to lattice distortion
Differences between 0.15% wt. Cr and 0.5% are limited
• reduced Cu• 0.15% Cr• 0.5% Cr• 1% Cr 20’ MA• 1% Cr 10’ MA• 1% Cr annealed
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Cu – Cr – rGO samples• Chromium is needed to create an interphase between copper and
carbon, 0.15% and 0.5% wt..• rGO in the shape of a powder distribution between 40 and 70µm.
• 2% wt. rGO alloyed in SPEX with Cu and Cr for 20’.
• Production of annealed samples.
MicrostructureCu 0.15% Cr 2%rGO
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work0.5% Cr Ann.980°C, 30’ Structure of rGO
Cu 0.5% Cr 2%rGO
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Thermal conductivity Cu – Cr - rGO samples• 0.5 Cr 2rGO ann.• 0.15 Cr 2rGO ann.• 0.15 Cr 2rGO• 0.5 Cr 2rGO
• rGO addition is lowering thermal conductivity: this is due to impurities and disordered structure
• Annealing changes the trend of the curves
• Cr is effective on reducing the interface resistance
best specimen: annealed 0.5%Cr
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Cu – Cr – dGO samples
MicrostructureCu0.5%Cr, 2% dGO. Turbula 60’
• Chromium is needed to create an interphase between copper and carbon, 0.5% wt..
• dGO in the shape of flakes: 2÷5mm x 5÷10mm, tens of µm thick .
• 2% wt. dGO alloyed in turbula with balls. Different milling times: 60’, 30’, 5’.
• Production of annealed samples.
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Turbula 30’ Turbula 5’
Effects of annealing: 980°C, 60’
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Thermal conductivity Cu – Cr - dGO samples• reduced Cu• Turbula 30’• Turbula 5’• Turbula 60’
• Annealed samples not analyzed due to voids caused by gas formation
• Results are worse than using rGO: more difficult dispersion in the matrix
• Better performances for sample treated 30’ in Turbula
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Graphitized graphite samples• Graphene oxides substituted with graphitized
graphite
• Graphitization removes impurity in graphite structure
• Graphite particles are big, it is difficult to obtain a homogeneous distribution in the matrix
• Samples produced with graphitized graphite and Ni
• Ni substitutes Cr since it has a lower affinity with oxigen
• Ni has a complete solubility in copper lattice; 0.5% and 1% chosen
Samples with nickel
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
Thermal conductivity of graphitized graphite samples
• reduced Cu• 0.5% Cr 2% G1 graph.• 0.5% Ni 2% G1 graph.• 1% Ni 2% G1 graph.
• Annealed samples not analyzed due to voids caused by gas formation
• Results are worse than using rGO: more difficult dispersion in the matrix
• Ni is not effective in covering graphite particles
1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
CONCLUSIONS1. A very limited addition of chromium is responsible for a
sensible decrease in conductivity figures
2. rGO gives always worse results compared to pure copper
• structure is not ordered
• impurities are present
3. dGO has similar problems to rGO
• absence of microstructural long-range order
• presence of impurities: among them traces of volatiles
4. Graphitized graphite leads to higher thermal conductivities compared to graphene oxides
5. Ni is not effective in covering graphite particles
FUTURE WORK1. Objective
2. Background
3. Experimental procedures
4. Results
5. Conclusions
6. Future work
High heat conductive materials are of increasing interest: future work could be dedicated to investigate reinforcement to improve the very good thermal conductivity of copper.
Some of the routes that could be analyzed are:
1. use nano-crystalline diamond dispersed in a copper matrix through a powder metallurgy route
2. reengineer the process of reinforcing copper with GOs
• electroless coat graphene oxide particles with Cr
• substituting Cr with other elements (Ti, Mo, W)
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