FRAUNHOFER INSTITUTE FOR mANUFAcTURINg TEcHNOlOgy
A N d A d vA N c E d m AT E R I A l S I F A m , b R A N c H l A b d R E S d E N
11
2
3
2 µm
4
2 µm
2 µm
1 Dispersible CNT
2 Powder made out of Cu and
CNT before sintering
3 Cu/CNT tensile bar during
mechanical testing
Metal / Carbon nanotube
CoMposites
4 Fracture surface of a
composite made out of Cu and
5 Vol. % CNT
Fraunhofer Institute for
motivation
Approach
and Advanced materials IFAm
Carbon Nanotubes (CNT) provide, based on
Carbon Nanotubes of various suppliers are
branch lab dresden
their high strength, electrical and thermal
conditioned to dispersible CNT (picture 1).
conductivity, the potential to manufacture
The following ultra sonic mixing of copper
Winterbergstrasse 28
composites made out of a metal matrix
powder and dispersible CNT in an aqueous
01277 Dresden I Germany
and CNT as reinforcement component. The
medium provides the opportunity to gene-
composites are characterized by an increase
rate homogenous powder mixtures (picture
of strength while the electrical and thermal
2). These mixtures can be consolidated by
manufacturing Technology
Contact
conductivity is the same or nearly that of
hot pressing, spark plasma sintering and
Dr.-Ing. Thomas Weißgärber
the pure matrix metal. The manufacturing
hot isostatic pressing. The semi-finished
Telefon +49 351 2537 305
of metal/CNT composites using powder
parts have a density greater than 90 % of
E-Mail: Thomas.Weissgaerber
metallurgical processes is one topic in the
the theoretical density and can be trans-
@ifam-dd.fraunhofer.de
research field of the Dresden branch of
formed by hot extrusion and/or drawing
Dipl.-Ing. Thomas Hutsch
the Fraunhofer Institute for Manufacturing
out a wire. Depending on the production
Telefon +49 351 2537 396
Technology and Advanced Materials. The
process, the alignment of the CNT can be
E-Mail: Thomas.Hutsch
metals copper, aluminium, iron and their
influenced from one-dimensional up to
respective alloys are used.
three-dimensional alignment.
@ifam-dd.fraunhofer.de
Fax
+49 351 2537 399
www.ifam-dd.fraunhofer.de
1
2
2 µm
2
1
characterization
extrusion direction with increasing volume
Electrical conductivity
content of CNT. Figure 1 displays the stressThe composites made out of a metal and
strain curves of composites made out of a
The Cu/CNT composites show an anisotro-
CNT are chracterized regarding microstruc-
copper matrix and up to 10 vol. % CNT of
pic behaviour of the electrical conductivity
ture, mechanical and thermophysical
one supplier.
caused by the alignment of the CNT (figure
properties.
Different types of CNT show a different
3). When being parallel to the hot extrusion
increase of strength at the same volume
direction, the electrical conductivity is
content of CNT (figure 2). For a composite
higher than perpendicular. This endorses
made out of copper and 3.5 vol. % CNT,
the a priori statement that the hot
an increase of the yield strength Rp0.2 at
extrusion process leads to a nearly one
Hot extruded composites made out of
200 % and the tensile strength Rm at 125
dimensional alignment of the CNT. The
copper and CNT provide the opportunity to
% compared to pure copper (Rp0.2 = 70
influences of different CNT types are also
increase the strength parallel to the
MPa, Rm = 210 MPa) was detected.
visible. For a composite made out of copper
mechanical strength
and 3.5 vol. % CNT, the specific electrical
conductivity is comparable to pure copper.
Fig. 1 Stress-strain curves of composites
Fig. 2 Strength-strain-curves of composites
Fig. 3 Specific electrical conductivity of Cu/
made out of copper and CNT with different
made out of copper and 3.5 vol. % CNT of
CNT composites parallel and perpendicular
volume content of CNT
the same CNT type
to the hot extrusion direction in comparison to reference materials
1 Wire made out of copper and
10 Vol. % CNT
2 Alignment of CNT in the Cu/
CNT composite