The world's first copper with carbon: introduction of eco-copper, we achieve a low-carbon society by copper with carbon with its high strength and high conductivity.


1. What is Eco-Copper?

Eco-copper is copper with a carbon additive, especially, it has now become possible to add it so that it will become uniformly distributed, and can practically withstand graphite-type carbon which is of the hexagonal type on the copper. In the past, for iron which contains steel mixed with carbon (carbon steel), it was known that depending on the amount of carbon added, the tensile strength and hardness may be increased, but for non-ferrous metals aside from iron, it was said that it is impossible to disperse the carbon uniformly and improve the tensile strength to the same level as iron.

Tsukuba University and Shirogane Co., Ltd., as a result of the research conducted through industry-university collaboration, they have discovered a way to add carbon into copper. To be specific, under a constant high temperature (1200 - 1250ºC ) carbon with a graphite structure was added 0.01wt.% - 0.6wt.% to melted copper, and they succeeded in adding and uniformly dispersing the carbon.
After measuring the tensile strength, yield stress, and electrical conductivity of eco-copper which is copper with carbon added, an improvement was seen compared to pure copper.

2. Results of the Measurement of Electrical Resistance

Using 3 types of samples, pure copper, copper with 0.03wt.% of carbon added, and copper with 0.3wt.% of carbon added, electrical resistance was measured. For pure copper, it was 1.97(x 10-8[Ωm]), for eco-copper with 0.03wt% of carbon added, it was 1.89(x 10-8[Ωm]), for eco-copper with 0.3wt% of carbon added, it was 1.71(x 10-8[Ωm]), and we found out that the electrical resistance of each one decreased.
In the 0.03wt.% and 0.3wt.% carbon amount, the result was that the more carbon was added, the lower the electrical resistance. According to this experiment data, the eco-copper which has 0.3wt.% of carbon added has more than 13% decrease in electrical resistance compared to pure copper.

Sample Electrical Resistance (x 10-8[Ωm])
Cu 1.97
Cu-0.03wt.%C 1.89
Cu-0.3wt.%C 1.71

3. Results of the Tensile Test

Using 3 types of samples, pure copper, copper with 0.03wt.% of carbon added, and copper with 0.3wt.% of carbon added, a tensile test was conducted. Compared to the tensile strength of pure copper, 159 (Mpa), the tensile strength of copper with 0.03wt% of carbon added was 195 (Mpa), while the tensile strength of copper with 0.3wt.% of carbon added was 189 (Mpa). It was found out that compared to pure copper, the tensile strength of eco-copper with carbon added increased. In addition, regarding yield stress, likewise, eco-copper which has carbon added has better results than pure copper. Regarding the tensile strength and yield stress, if you compare the samples whose added carbon amounts were 0.03wt.% and 0.3wt.%, the sample whose added carbon amount was 0.03wt.% has better results, and we speculate that from the point of view of tensile strength, 0.3wt.% has exceeded the peak of the added carbon amount. From now on, we plan to clarify the most appropriate carbon amount added by conducting experiments.

Sample Tensile Strength (MPa) Yield Stress(Mpa)
Cu 159 33
Cu-0.03wt.%C 195 95
Cu-0.3wt.%C 189 76

4. Electron Microscope Picture of Eco-Copper

The following picture is an electron microscope picture of eco-copper (Cu-0.3wt.%C) which has 0.3wt.% of carbon added to pure copper. (Accelerating Voltage: 200kV, manufactured by Philips, CM20FEG).
We think that carbon particles which have a size of about 0.01-0.02μm are dispersed in the copper.