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ARL-CR-0762 ● MAR 2015

US Army Research Laboratory

Advances in Nanocarbon Metals: Fine 

Structure

prepared by Lourdes Salamanca-Riba

University of Maryland

1244 Jeong H. Kim Engineering Building

College Park, MD 20742

under contract W911NF-13-1-0058

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ARL-CR-0762 ● MAR 2015

US Army Research Laboratory

Advances in Nanocarbon Metals: Fine 

Structure 

prepared by Lourdes Salamanca-Riba

University of Maryland

under contract W911NF-13-1-0058

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

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Lourdes Salamanca-Riba

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University of Maryland

1244 Jeong H. Kim Engineering Building

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US Army Research Laboratory

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14. ABSTRACT

This study is an investigation of the structure and some properties of silver, copper, and aluminum alloy covetics. Covetics 

can incorporate large amounts of carbon (C) in a nanoscale form to alter physical and mechanical properties of the base metal 

or alloy. Once the C has been incorporated into the matrix, it is highly stable and remains dispersed in the material after 

remelting and resolidification. Characterization of the thin film and bulk covetics was accomplished using X-ray diffraction, 

Raman spectroscopy, and transmission electron microscopy. Interesting property changes were detected for the different 

covetic materials. However, the samples always had nonuniformity of the C incorporation. Going forward, it is important to 

develop a method that will give rise to a more uniform distribution of the C so that a correlation between C content and 

properties can be obtained.

15. SUBJECT TERMS

covetic, nanocarbon silver, aluminum, copper

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56

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Kevin Doherty

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iii

Contents

1. Introduction 1

2. Discussion 1

3. Conclusions 3

4. Reference 4

Appendix. Advances in Nanocarbon Materials: Fine Structure Final 

Report 5

Lists of Symbols, Abbreviations, and Acronyms 49

Distribution List 50
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1

1. Introduction

Recent advances in nanomanufacturing have made it possible for large amounts 

(>8 wt%) of carbon (C) to be incorporated as nanoscale C during a reaction 

process in molten aluminum (Al), copper (Cu), silver (Ag), and other elements. 

These materials, developed by Third Millennium Materials, LLC, are called 

“covetics”.

1 The process of conversion to covetics consists of heating the metal to 

a temperature above its melting point, adding C in various forms and applying a 

direct current to the melt while stirring. This process is a relatively simple process 

that produces a material with many unique and improved properties over the base 

metal from which it is generated. After the conversion process, the C is highly 

stable, despite its form not being predicted in phase diagrams, and remains 

dispersed in the material after remelting and resolidification. The C is bonded to 

the metal matrix and has an effect on several of the properties of the material.

2. Discussion

In this study we investigated the structure and some properties of Ag, Cu, and Al

alloy covetics. We also deposited Cu covetic films by e-beam evaporation and 

pulsed laser deposition (PLD) and examined the electrical and transmittance 

properties of Cu covetic films compared with pure Cu films of the same thickness. 

The bulk samples for this investigation were obtained from Third Millennium 

Materials, LLC. Pieces of the bulk material were used as targets for the film 

deposition. The attached PowerPoint presentation (Appendix) given at a meeting 

at the Defense Advanced Research Projects Agency on 30 September 2014 has 

more details on the results for the project. The team members with their respective 

responsibilities are presented on slide 2 of the presentation. 

We characterized the structure of the bulk covetics by X-ray diffraction (XRD)

and transmission electron microscopy (TEM). No sample showed indications of 

any of the different allotropes of C by XRD. In TEM, however, we found

localized regions of Ag and Al6061 covetics that showed weak spots in the 

diffraction patterns corresponding to graphitic carbon. These regions not only had 

crystalline graphitic spots, but also indicated a 3-dimensional epitaxial 

configuration with the metal host. The epitaxial relationship is (111)Ag

(Al)//(0001)Graphite and < 11̅0 >Ag (Al)//< 112̅0 >Graphite. Furthermore, both Ag and 

Al covetics show graphitic modes in their Raman spectra indicating that C in 

these samples has sp2 bonding in agreement with the electron diffraction patterns 

and electron energy loss spectroscopy (EELS) data. Additionally, our discrete 

Fourier transform (DFT)–based calculations of the phonon density of states in Ag 
2

and Al covetics with layers of graphite reproduced the Raman active modes 

obtained experimentally not only for the D and G peaks of graphite but also for 

new weak modes corresponding to Ag-(Al)-C bonding that were obtained in the 

Raman spectra from Ag and Al covetics. The metal-C bonds form at edges of 

graphene-like sheets and wherever there is a C vacancy within the graphene layer. 

DFT indicates bond energy of 1.2-2.2 eV/C atom. More details of the results from 

Ag and Al covetics can be found, respectively, in slides 5–20 and 21–31 of the 

Appendix. A paper on Ag covetic is ready for submission to the journal Advanced 

Functional Materials. Another paper on Al covetic is in preparation. 

Cu covetic has a different structure than Ag and Al covetics. The XRD spectra 

from Cu covetic appear just like pure Cu. No evidence for any allotrope of C, 

CuO, or Cu2O was found in any of the bulk Cu covetic samples. The electron 

diffraction patterns in TEM also show no evidence for any of these phases. 

Instead, weak spots were visible in the diffraction pattern of Cu covetic that 

correspond to modulations of approximately 1.6 nm along several 

crystallographic directions of the Cu host lattice that are visible in the images 

from the areas with the weak spots. The intensity of the weak spots increases with 

increasing C content in the local region. Results from bulk Cu covetic are 

presented in slides 32–39 of the Appendix. 

Slides 40–56 present analysis of Raman and EELS spectra as indications of sp2 

bonding in covetics. The temperature dependence of the electrical resistivity of 

Ag covetic is presented in slides 57–59. It is remarkable that the conductivity of 

Ag covetic with 6-wt% C at room temperature is 90% that of 99.999 Ag. We 

believe that further improvement in the processing of covetics could give rise to 

even higher values of the conductivity. 

Using pieces of bulk Cu covetic as targets, we deposited films by e-beam 

evaporation and PLD. Pairs of films were deposited at the same time where one 

film was deposited on silicon and one on glass substrates for further analysis of 

the films. For comparison, films of Cu metal (0% C) were also grown using the 

same conditions. The e-beam deposited films were crystalline with preferred 

orientation along <111>. The films were continuous with fairly flat surfaces and 

columnar structure. Cu covetic films deposited on glass were consistently more 

transparent to light than Cu films of the same thickness, indicating that C 

incorporation in the films assists in making the film more transparent. 

Furthermore, the covetic films were also more stable to the environment, as 

concluded from the smaller changes in resistivity with time in the Cu covetic 

films compared with the Cu metal films. 
3

Our preliminary results from PLD Cu covetic films showed further improvement 

in the transmittance of the films compared with the e-beam deposited films, but 

the films had some problems with C separating from the Cu. The results from the 

films look very promising, although further attempts to optimize the deposition 

parameters are necessary to improve the performance and stability of Cu covetic 

films grown by PLD. Slides 60–81 present our results on Cu covetic films. We 

have submitted a paper on Cu covetic films for transparent electrodes for 

publication in the journal Applied Physics Letters. 

3. Conclusions

In conclusion, we have obtained very interesting results of Ag, Al, and Cu 

covetics both in bulk and film form. Carbon in covetics changes the properties of 

the material. However, the samples always had nonuniformity of the C 

incorporation. It is important to develop a method that will give rise to more 

uniform distribution of the C so that a correlation between C content and 

properties can be obtained. Once this is achieved, the properties of covetics could 

be tuned by the C content and postprocessing conditions. It is also important to 

investigate what is the maximum C content that can be introduced in the host 

lattice by this method.
4

4. Reference

1. Shugart JV, Scherer RC, inventors; Third Millennium Metals, LLC, assignee. 

Metal-carbon compositions. United States patent US 8,349,759. 2013 Jan 8.
5

Appendix. Advances in Nanocarbon Materials: 

Fine Structure Final Report

 

This appendix appears in its original form, without editorial change.
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49

Lists of Symbols, Abbreviations, and Acronyms

Al aluminum

Ag silver

C carbon

Cu copper

DFT discrete Fourier transform

EELS electron energy loss spectroscopy

PLD pulsed laser deposition

TEM transmission electron microscopy

XRD X-ray diffraction
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