ARL-CR-0763 ● MAR 2015

US Army Research Laboratory

Advances in Nanocarbon Metals: Process

by P Chris Pistorius and Pengcheng Yan

Carnegie Mellon University

5000 Forbes Avenue

Wean Hall 4313

Pittsburgh, PA 15213

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ARL-CR-0763 ● MAR 2015

US Army Research Laboratory

Advances in Nanocarbon Metals: Process

by P Chris Pistorius and Pengcheng Yan

Carnegie Mellon University

Approved for public release; distribution is unlimited.
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Advances in Nanocarbon Metals: Process

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P Chris Pistorius and Pengcheng Yan

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Carnegie Mellon University

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14. ABSTRACT

The addition of nanoscale carbon (C) to a variety of metals was developed by Third Millennium Metals and this class of 

materials has been called covetics. These materials have several unusual mechanical and physical properties, with potential 

benefits in improved energy efficiency and material performance over a broad range of applications. During this project, a 

laboratory scale covetic production system was designed and built. This system addressed the 3 distinct reaction steps: 1) C

dissolves in copper (Cu), where the temperature is locally higher, 2) supersaturated C precipitates out on the surface of the 

liquid Cu as graphene sheets, where the temperature is lower, and 3) stirring disperses the graphene sheets into the Cu. The

precipitation of C was demonstrated and shown by scanning electron microscopy and Raman spectroscopy using an arc melter 

instead of a high‐temperature microscope. The main outcome was that the maximum feasible C content in covetics is the C 

solubility in the metal at the temperature of the arc hot‐spot; this maximum is approximately 200 parts per million by mass.

15. SUBJECT TERMS

covetics, carbon, copper, oxidation, mechanical properties, local heating

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Kevin J Doherty

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iii

Contents

Acknowledgments iv

1. Introduction 1

2. Conclusions 3

Appendix. Covetics 5

Distribution List 18
iv

Acknowledgments

This work was supported by the Defense Advanced Research Projects Agency’s

Tactical Technology Office.
1

1. Introduction

A new process technology provides the ability to add greater than 6-wt% nanoscale 

carbon (C) to a broad variety of metals. The resulting materials, developed by Third 

Millennium Metals, LLC, are known as “covetic” nanomaterials.

1 These materials 

have several unusual properties, notably increased strength, increased thermal 

conductivity, and increased electrical conductivity, with potential benefits in 

improved energy efficiency and material performance over a broad range of 

applications and industries including defense.

This examination of covetics is part of a Defense Advanced Research Projects 

Agency–funded program involving the University of Maryland (UMD), Carnegie 

Mellon University (CMU), and the Naval Surface Warfare Center, Carderock 

Division. The proposed project at CMU specifically deals with copper (Cu)-based 

covetics (see Appendix). The procedure used to produce the material has been 

described in the patent from Third Millennium Metals. The essential elements of 

the process are: 1) a C source is brought into contact with molten Cu, 2) current is 

applied to the Cu by means of C electrodes, and 3) mechanical stirring is applied 

simultaneously. Through this combination of steps, what appears to be nanosized 

C is produced and dispersed into the molten Cu. The overall process is endothermic, 

where a drop in the temperature of the melt is witnessed when current is applied.

The problem addressed in this research is that the fundamental steps that lead to the 

formation of covetics are not known; the patent1contains the following:

While the exact chemical structure of the disclosed metal-carbon material 

is currently not known, without being limited to any particular theory, it is 

currently believed that the steps of mixing and applying electrical energy 

result in the formation of chemical bonds between the metal and carbon 

atoms, thereby rendering the disclosed metal-carbon compositions unique 

vis-a-vis known metal-carbon composites and solutions of metal and 

carbon.... Furthermore, without being limited to any particular theory, it is 

believed that the disclosed metal-carbon material is a nanocomposite 

material and ... the amount of electrical energy (e.g., the current) applied to 

form the disclosed metal-carbon composition initiates an endothermic 

chemical reaction.

This creates a difficult problem. While the practical steps required to produce 

covetics have been described by the inventors, there is no information on the 

fundamental mechanism of covetic formation. In further refining the process, the 
2

current approach by the developer of the technology (Third Millennium Metals) is 

to rely on empirical knowledge. An obvious limitation to this empirical approach 

is that there is little or no quantitative basis for scaling-up or optimizing the process.

The current project proposes that the process can be separated into 3 distinct 

reaction steps. If this is indeed the case, each of these steps can be executed in a 

separate reactor. Such separation of process steps would allow tighter control of 

process conditions and allow the process to be converted readily to continuous 

production (rather than the current batch process).

The essential technical idea is captured in the following hypotheses:

 Covetic consists of graphene sheets distributed within the metal (Cu).

 The applied current causes local heating where the electrodes enter the Cu

melt.

 C dissolves in Cu where the temperature is locally higher (Step 1).

o Where the temperature is lower, supersaturated C precipitates out on 

the surface of the liquid Cu as graphene sheets (Step 2).

 The role of stirring is to disperse the graphene sheets into the Cu (Step 3).

o The observed endothermicity results from the small exothermic 

bonding energy between liquid Cu and graphene, which is much 

smaller than the energy involved in breaking Cu-Cu bonds when 

dispersing graphene in the Cu.

o Previous combustion analysis failed to detect C in Cu covetic material 

because the oxidation rate of the covetic material is significantly lower 

than that of pure Cu.

The proposed scope and deliverables of the program are described in the following 

6 procedural tasks:

1) Design and build a laboratory‐scale system for Cu covetic production. Also, 

produce additional samples of covetic Cu, to be analyzed by the team at the 

UMD.

2) Theoretical evaluation of the energy balance of the process.

3) Experimental measurement of the oxidation rate of molten Cu and molten 

covetic Cu in pure oxygen (O).
3

4) Experimental test, using a high‐temperature microscope (laser scanning 

confocal microscopy), of the proposal that C dissolves from the C source at 

higher temperature and precipitates as graphene upon cooling.

5) Experimental test, using the laboratory‐scale covetic process, of the extent 

of local heating caused by the applied current to determine whether the local 

heating is sufficient to sustain C dissolution (as a necessary step before C

precipitation as graphene).

6) Preparation of an overall summary report, stating the process implications 

of the fundamental information obtained in this project.

2. Conclusions

This project was successful in completing all of the tasks contained within the 

proposal scope. While not all of the research organizations came to the exact 

conclusions, a significant amount of data was created that can be interpreted for 

any future covetics research. The new laboratory-scale covetic production facility 

at CMU could be an instrumental part of a potential larger program.

The following outcomes were achieved for the proposed program tasks:

1) Completed the design and build of a laboratory‐scale system for covetic 

production. Cu and silver (Ag) covetic samples were produced for UMD

analysis.

2) Completed the theoretical evaluation of the energy balance of the process.

This assessed the creation of Cu-C interfaces as a possible cause of the 

endothermic effect reported by Third Millennium. However, given the 

small concentration of C actually produced, this effect is negligible.

3) The experimental measurement of the oxidation rate of molten Cu and 

molten covetic Cu in pure O was completed. No difference in oxidation 

behavior was seen. Testing of C concentration in Cu and Ag was developed 

via full oxidation in O (with infrared analysis of off‐gas). Material produced 

by Third Millennium was tested and found to contain less than 50 parts per 

million (by mass) of C in all cases.

4) Demonstrated precipitation of C shown by scanning electron microscopy 

and Raman spectroscopy using an arc melter instead of a high‐temperature 

microscope.

5) Completed the measurement of the local heating caused by the applied 

current using the laboratory‐scale covetic process. Using an infrared 
4

camera, the local hot‐spot temperature (beneath the arc) was measured as 

approximately 2,000 °C.

6) In addition to this report, a draft paper on the project results has been written 

and will be submitted for journal publication. A copy of that submission 

will be supplied as soon as it is sent to the journal. The processing

knowledge collected during this work is summarized in a kinetic model. 

The main outcome is that that the maximum feasible C content in covetics 

is the C solubility in the metal at the temperature of the arc hot‐spot; this 

maximum is approximately 200 parts per million by mass.
5

Appendix. Covetics

 

This appendix appears in its original form, without editorial change.
6

Advances in nanocarbon

metals: process

Final report, Nov 21, 2014

Pengcheng Yan and Chris Pistorius 

Department of Materials Science and Engineering

Carnegie Mellon University

CMU|CISR 2

Content

Focus of project: produce covetics

• Covetics

o Challenges

o Process mechanism

• Experimental & results

o Small scale arc melting

o Covetics production

• Kinetics model

• Summary
7

CMU|CISR 3

Covetics

• Metal – nanocarbon composite

o Au, Ag, Cu, Zn, Al etc

o “Single phase”

o Upto 6 wt % carbon

• Improved properties

o Thermal/electrical conductivity

o Strength

o Density 

CMU|CISR 4

Challenge 

• Carbon content 7 wt% C
8

CMU|CISR 5

Challenge

• Carbon content by 

o EDS, XPS, SIMS (microanalysis)

o LECO (o.5 gram, fast combustion), full slow oxidation 

1. Pre-heating: Al2O3crucible in O2 at 1200 oC for 2 hour 

2. Calibration 

• pure Cu oxidised for 30 mins (background) 

• known graphite in Cu tube (∆=~0.5%)

3. Measurement: oxidation at 1200 oC for 30 mins

CMU|CISR 6

Full oxidation 

Cu2O

CuO

Heterogeneous oxidation

• Cu droplets at bottom

• Cu2O in bottom region

• CuO appears in top region

30 min oxidation 

Cu2O

CuO

Improved oxidation

• No Cu droplets

• Cu2O rich in bottom region

15 min oxidation 

Cu

Cu2O

Cu2O

CuO
9

CMU|CISR 7

Process mechanism

1. Carbon source dissolves in liquid copper at hot 

spot beneath arc.

2. Copper flows away from arc; dissolved carbon 

precipitates as nano-carbon at the free surface 

of the melt.

3. Mechanical stirring distributes nano-carbon 

through the melt.

CMU|CISR 8

Small scale arc melting 

• Arc-melt Cu/Ag under purified argon

– in high-purity graphite crucibles, for different times

– to test steps  and 

cm
10

CMU|CISR 9

Small scale arc melting 

• Carbon on Cu surface

1 min 3 min

CMU|CISR 10

Small scale arc melting 

• Carbon on & in Cu 

o C film on Cu surface

• Thickness increases with arcing duration

• sp2 carbon

o Broad peak in bulk: amorphous carbon

o Steps  and  confirmed for Cu

Al2O3

C

Al2O3
11

CMU|CISR 11

• Carbon on Ag

Small scale arc melting 

Carbon amount/thickness - increase 

1 min 3 min 7 min

CMU|CISR 12

• Carbon on & in Ag

o C film/particles on Ag surface

• Thickness increases with arcing duration

• sp2 carbon

o No or limited carbon in bulk

o Steps  and  confirmed for Ag

Small scale arc melting 
12

CMU|CISR 13

Covetics production 

• One electrode in melt; another one just above carbon source

• Temperature: thermocouple-before arcing; thermal camera-during arcing

• Set-up

CMU|CISR 14

Covetics production 

• Melting

– Solid Cu e=0.2

– Molten Cu e=0.06

• Stirring

– e=0.2

– Temp. vibration 

– ~150 rpm

– ~23 mm/s @ r= 1.8 cm

– ~35 mm/s @ r= 2.7 cm

• Arcing

– e=0.2

– Large Temp. increase

e: emissivity; observation window 

becomes dirty, leading to low e 

Temp.&stirring speed test Arcing test

Arc

* If need the original videos, please contact CMU

Stirring rod

Stirring
13

CMU|CISR 15

Covetics production 

Sample Remarks Stirring / min Arcing / s Graphite / wt% Activated Carbon wt%

Measured Carbon

IR LECO

0

Cu

0 0 0 - 0 12

1 5 0 5 - 0 12

2 5 78 5 - 9 14

3 5 32 0 - 1.5

4 30 237 5 - 48.5 17

5 10-5 60 0.003 - 40

6 10-5 300 5 - 33

7 15-5 360 - 2.5 107

8 15-5 180 - 2.5 30

9 10-5 0 - 2.5 6

10 10-5 240 - 2.5 32

11 10-5 60 - 0.5 29.5

12 10-5 120 - 0.5 45

13 10-5 180 - 0.5 51.5

14 10-5 150 - 0.5 63

15 -5 600 - 0.5 99

16 -5 600 - 0.5 102.5

17 -5 1020 - 0.5 70

18 -5 1020 - 0.5 40.5

19 -5 1410 - 0.5 134.5

20 -5 90 - 0.5 40

1 Ag -5 300 - 0.5 73

CMU|CISR 16

Ag covetic

o Nano particle or pores

o Carbon peak

o D and G peaks, sp2 carbon

o Steps  confirmed for Ag
14

CMU|CISR 17

• Short arcing samples

o No Carbon in covetic samples (short time arcing)

Cu covetic

CMU|CISR 18

Cu covetic

• long arcing samples

o Nano pores on polished samples

o Small carbon peak with EDS 

o Broad peak, amorphous carbon?

o Steps  confirmed for Cu
15

CMU|CISR 19

Carbon content

• With XPS

o Carbon on surface not in bulk -5

5

15

25

35

45

55

65

75

85

95

105

0 5 10 15 20 25 30

Composition ( Atomic %)

Sputtering Time (Minutes)

Atomic % C

Atomic% O

Atomic % Cu

Cu Covetic CMU No. 2, polished

C at % O at % Cu at %

1.0±0.9 0.1±0.2 98.9±1.0

CMU|CISR 20

Carbon content

• With SIMS

o Higher carbon in covetics than raw materials

o Need bulk analysis
16

CMU|CISR 21

Carbon content

• With full oxidation

o Increases with arcing, reaching 150 ppm in mass

o Limiting step?

CMU|CISR 22

Kinetics model

• Assumption 

o Limited by carbon diss0lution in hot spot

• Hot spot size

• Stirring speed/flow rate

• Temperature 

(I)

(II)

o Constant volume, density (ρC, Cu) and initial C particles diameter (do)

o Nano-carbon homogeneously dispersed in Cu bulk

• Conditions

o Precipitated nano-carbon particles redissolution

• Ct’

0 = α Ct’’0

, α =0-1
17

CMU|CISR 23

Kinetics model

Parameters: 

• k=7e-4 m/s

 Re=32632

 Sc=0.22

 DC=5.2e-7 (DO @ 2000 

oC)

 k=~2-3e-4 m/s in liquid 

Fe @ 1550 oC

• Cs=220 ppm @ 2000 oC

• Ah=1e-4 m2

• h=2e-4m

• Vh=2e-8 m3

• d

o=1e-3m

• ∆t=0.1s
18

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