Novel Metal-Carbon Materials
called Covetics
Iwona Jasiuk
Department of Mechanical Science and Engineering
University of Illinois at Urbana-Champaign
Contact: ijasiuk@Illinois.edu
Industry Session “Enablers for Transportation Electrification”
34th Annual IEEE Applied Power Electronics Conference and Exposition
Anaheim, CA, March 20, 2019
Introduction
• Covetics are novel metal-carbon materials
• Carbon is infused into metal using a unique electrical process.
• Cross-cutting process: copper, aluminum, iron, silver, and others.
• Carbon amounts far higher than predicted by phase diagrams.
• Notable increases in mechanical properties, electrical and thermal conductivities,
oxidation resistance.
Invented by Roger Scherer in 1997
Shugart & Scherer US 8541335 2013
Shugart & Scherer US 20100327233 2010
Knych et al. Archives of Metallurgy and Materials 2014
Salamanca-Riba et al. Advanced Functional Materials 2015
Bakir and Jasiuk (2017) “Novel metal-carbon nanomaterials: A review on covetics,” Advanced Materials
Letters 8(9), 884-890.
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Covetics - Definition and Concept
• Term Covetic = Covalent and Metallic bonding. Terms based on a
hypothesis that a covalent bond forms between C and metal.
• Carbon in Metals – low solubility
• Conventional methods – formation of carbides (e.g., Al4C3).
• Alternative methods
• electrochemical deposition
• solid state processing - mixing in expensive nano-carbon fillers
(CNTs, GNPs). Metal-carbon bonding is weak.
Cu-C phase diagram
• Covetics – nano-carbon phase is formed, strongly bonded to a metal.
• Carbon does not separate after remelting, laser ablation, and magnetron
sputtering.
• Covetics can be remelted, diluted, alloyed, and post-processed.
Alternating graphene layers within a
metallic lattice forming in a covetic
Knych et al., Met Trans B (2014)
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Industrial Relevance
• Covetics are cost effective
• Raw material cost is low
• Carbon added is in the form of a low cost amorphous activated carbon
• Conventional furnaces and equipment can be used for the manufacture
• Covetics can be processed using traditional methods (remelting, extrusion)
• Covetics process is scalable
• More economical than infusing metal with carbon nanotubes or graphene
nanoplatelets
• Covetics are excellent candidates for various industrial applications
• Replacement for aluminum, copper and other metals.
• Many energy applications
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Industrial relevance
Potential applications and benefits of covetics:
Applications
Benefits
Heat exchangers
Higher efficiency for a $12B annual market
High-voltage power transmission cable
40% higher strength; 40% higher electrical
conductivity -> $10B annual savings for US power
grid
Substitution of covetic aluminum for copper
in electrical wiring
Weight reduction and improved efficiency (aircraft
and automotive); cu: 50lbs/car, Al: 20lbs/car
Nuclear fuel rods
Reduce thermal gradients to improve service
performance
Fuel cell and supercapacitor electrodes
Higher efficiency electrodes
Thermal management in microelectronics
Higher currents, faster switching at higher
temperatures
U. Balu Balachandran, Covetic Materials CPS Agreement Number 28418, Argonne National Laboratory, May 2015 5
Industrial relevance
Replacing Cu with Al Covetics Enables Significant Vehicle Lightweighting
Uses
Copper
50 lbs/car
Uses Aluminum
Covetics
20 lbs/car
• DOE seeks target of 30% vehicle lightweighting by 2022
• Covetics is a new metallurgical pathway for alloy development and offer OEMs
the design freedom to extend range by increasing battery pack size
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Industrial relevance
Covetics can not only enable lightweighting, but also enhance performance
DC/DC Converters & AC/DC Chargers
Interconnects, Bus Bars,
& Enclosures for Inverters
Chassis
Cabling
Battery Pack
Heat Exchanger
Electric Motor
Housing
• All of these subsystems benefit from the weight savings, 40% higher strength,
higher electrical conductivity, and high thermal conductivity, offered by covetics.
Department of Energy Goals for Plug-In Electric Vehicles by 2022, https://www.nrel.gov/transportation/vehicle-tech-targets.html
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Covetics – Manufacture
Invented by Roger Scherer in 1997
Combined plastic and aluminum, and added
electric current
First independent verification
of the covetics process
• How are covetics made?
•
•
•
•
Melt metal in an induction furnace
Add carbon and stir
Apply electric current while stirring
Conventional equipment: furnaces,
stirring; infrastructure is available
Experimental set-up for covetics synthesis
Knych et al., Met Trans B (2014)
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Properties of Covetics
• Covetics exhibit enhanced properties.
• Based on data published so far:
•
•
•
•
Higher strength (40%), hardness (40%), and toughness (in aluminum and copper),
Higher thermal conductivities (13% increase in copper),
Higher electrical conductivities (28-37% increase in copper),
Increased oxidation resistance in thin copper films.
• Challenges
• Properties are highly dependent on processing parameters.
• No guaranteed improvements => Processing is the focus of current research.
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Thermal/Electrical Properties
• Thermal conductivity: 13% increase in copper (earlier data 50%)
• Electrical conductivity (28-37% increase in copper)
• Increased oxidation resistance in thin copper films (Isaacs et al. 2015)
ASTM E1461
@ 22.1°C Sheet resistance 782.7 mΩ, 137% IACS
Balu Balachandran, Argonne National Laboratory
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Mechanical Properties
Ultimate Tensile Strength (UTS)
7075 Al covetics
(warm rolled)
0 wt%C
3 wt%C
5wt%C
Iftekhar Jaim et al. Carbon (2016)
• UTS increased for covetics as compared to base 7075 Al
• Similar results for 0.2% yield strength
Tests done at the University of Illinois
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Mechanical Properties
Ultimate Tensile Strength (UTS)
10200 Cu covetics (as cast)
0.2% Yield Strength
• UTS increased for covetics as compared to base copper
• Similar results for 0.2% yield strength
Tests done at the University of Illinois
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Mechanical Properties
10200 Cu covetics (as cast)
3 wt%
C
Before
0 wt% C
After (0 wt%C)
After (3wt% C)
Strain (mm/mm)
• Stress-strain curve comparison
• Increase in strength and toughness for 3
wt%C covetics as compared to 0 wt%C.
0 wt %C
3wt %C
SEM images of Cu 10200 covetics
Tests done at the University of Illinois
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Mechanical Properties
Comparison with 10200 Cu covetics (as cast) with 3 wt%C
10200 Cu
Tensile Strength
(MPa)
Elongation
(%)
Vickers Hardness
(HV)
Maximum Energy
(J)
Annealed
210
40
55 max
61 (Izod)
Half Hard
245
10
75 - 90
-
Hard
310
7
90 - 115
34 (Izod)
Our Data (for 3
wt%C Cu covetic)
223 ± 9
33.5 ± 3
70 ± 3.1
43 ± 2.1
(Charpy)
Mechanical properties of 10200 Cu (MatWeb Materials Property Data)
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Properties - Summary
• Increase in ultimate tensile strength, 0.2% yield strength, energy absorption
and hardness in aluminum- and copper-based covetics
• Increase in both strength and toughness (copper covetics)
• The increased electrical and thermal conductivity of copper covetics
Challenges
•
•
•
•
Reliably achieve improved properties
Covetics exhibit porosity due to high surface tension
Heterogeneous distribution of carbon
Measurement of carbon content (e.g., combustion techniques do not work
due to a strong metal-carbon bond)
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Industrial relevance
Covetics not only enable lightweighting, but also enhance performance
Vehicle
Sub-System
Design Benefit of Covetics
Heat
Exchanger
Higher efficiency, weight savings &
high thermal conductivity
Chassis
Weight savings, corrosion resistance
Battery Pack
Case
Weight savings, high electrical
conductivity, high thermal
conductivity, reduced integration cost
Interconnects
& Bus Bars
Weight savings, high electrical
conductivity, high thermal
conductivity
Cabling
Weight savings, 40% higher strength,
40% higher electrical conductivity,
high
thermal conductivity
Enclosures
for Inverter &
Chargers
Weight savings & high thermal
conductivity
Note: Integration opportunities could facilitate final reduced system level cost at scale
Department of Energy Goals for Plug-In Electric Vehicles by 2022, https://www.nrel.gov/transportation/vehicle-tech-targets.html
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Concluding Remarks
Covetics have multiple benefits:
• A scalable process, low cost of raw materials
• Low cost carbon used => nano-carbon (instead of expensive CNTs, GNPs)
• Carbon strongly bonds to metal, difficult to achieve with conventional processes
• Increase in mechanical, thermal and electrical properties
• The process should be applicable to a wide range of metals and alloys
• Novel materials – multiple research opportunities
• Open field for materials exploration.
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References
Bakir M, Jasiuk I (2017) Novel metal-carbon nanomaterials: A Review on covetics, Advanced Materials Letters 8(9), 884-890.
Balachandran BU (2015) Covetic Materials CPS Agreement Number 28418, Argonne National Laboratory, May 2015
Iftekhar Jaim H, Isaacs RA, Rashkeev SN, Cole DP, LeMieux M, Jasiuk I, Nilufar S, Salamanca-Riba LG (2016) Sp2 carbon in Al6061 and Al-7075 alloys in the form of crystalline graphene nanoribbons, Carbon 107, 56-66.
Isaacs RA, Zhu H, Preston C, Mansour A, LeMieux M, Zavalij PY, Iftekhar Jaim HM, Rabin O, Ku L, Salamanca-Riba LG (2015)
Nanocarbon-copper thin film as transparent electrode, Applied Physics Letters 106, 193108-1-5.
Knych T, Kwasniewski P, Kiesiewicz G, Mamala A, Kawecki A, and Smyrak B (2014) Characterization of nanocarbon copper
composites manufactured in metallurgical synthesis process, Metallurgical and Materials Transactions 45B, 1196-2000.
Salamanca-Riba LG, Isaacs RA, LeMieux MC, Wan J, Gaskell K, Jiang Y, Wuttig M, Mansour AN, Rashkeev SN, Kuklja MM,
Zavalij PY, Santiago JR, Hu L (2015) Synthetic crystals of silver with carbon: 3D epitaxy of carbon nanostructures in the silver
lattice, Advanced Functional Materials 25, 4768-4777.
Varnell JA, Bakir M, DiAscro MA, Chen X, Nilufar S, Jasiuk I, Gewirth AA (2019) Understanding the influence of carbon
addition on the corrosion behavior and mechanical properties of Al alloy “covetics,” J. Materials Science 54 (3), 2668–2679.
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Thank you!
Questions?
Acknowledgments
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National Science Foundation (NSF)
Department of Energy (Dr. David Forrest)
Air Conditioning and Refrigeration Center at University of Illinois
NSF Industry/University Cooperative Research Center on
Novel High Voltage and Temperature Materials and Structures
Contact:
Dr. Iwona Jasiuk, e-mail: ijasiuk@Illinois.edu
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