Aluminum is widely used in modern industry as a structural material because of its low density. However, it is not without a number of shortcomings such as low hardness and strength. The high thermal conductivity of aluminum can be an advantage (heat sink) and a disadvantage (insulator). In this work, we solve a problem to investigate a possibility to improve the strength properties of aluminum composite with a controllable thermal conductivity while maintaining the low density of aluminum.
To solve these problems, we used an original approach of creating a composite material, namely the growth of carbon nanotubes (CNT) on the surface of the catalyst-coated aluminum particles using catalytic chemical vapor deposition method. CNT concentration was 1 wt. %. The resultant material was sintered at a pressure of 2-5 GPa at a temperature of 600-1500 oC and at a processing time of 15-600 seconds.
A composite material with a hardness of 58–60 HB, which is two times higher than the hardness of original aluminum with an adjustable thermal conductivity of 50–150 W/(m*K) and with a low density of 2.7 g/cm3 have been obtained. It was found that the hardness and thermal properties could be adjusted depending on the temperature during hot pressing by controlling the formation of Al3C4 carbide (chemical reactions between the aluminum and CNT) [1].
Figure 1. Dependence of the hardness (A) and thermal conductivity (B) of composite materials compacted at pressures of 5 GPa and 2 GPa for 60 s depending on the sintering temperature. The red curve (circles are experimental points) at 5 GPa, the black curve (squares are experimental points) at 2 GPa. The blue arrows show the reference values of the hardness and thermal conductivity of pure aluminum.
It has been found that it is possible to produce a composite material aluminum-CNTs with a hardness of up to 60HB (by two times higher than pure Al) and a variable thermal conductivity of 50–150W/(m*K) by controlling temperature during hot pressing. It is also necessary to control the formation of aluminum carbide Al3C4, which makes a key influence on the properties of the aluminum-CNTs composite material.
As a result, the developed method opens up broad prospects for the production of finished products with high-performance properties.
References
1. AA Vozniakovskii, SV Kidalov, TS Kol'tsova, Development of composite material aluminum-carbon nanotubes with high hardness and controlled thermal conductivity, Journal of Composite Materials, 2019, https://doi.org/10.1177/0021998319829894