1. Introduction Methods Results Conclusions
Effect of Carbon Nano Tubes, Micro and Nano dispersions of SiC and
Al2O3 on the Mechanical and Physical Properties in pure Copper
A. Y. Shash, M. Adly, A.El-Habak and S.El-Khatib
Mechanical Design and Production Engineering Dept., Faculty of Engineering, Cairo university, Egypt.
Introduction
Methods
Results
Figure 4
For electro and mechanical technical materials the main objective is attaining the best combination of high strength and high conductivity that could be crucial for some application, for example for the use as wires in high field pulse magnets in many ovens and winding wires.
In this study using pure copper (99.9%) and 2–3 μm in diameter has the required characteristic in electric conductivity in electric transfer with high efficiency and quality, but with all of these specifications it can't resist tension, compression and machining conditions. So that it must be resist with adding reinforcement and strengthening materials as ceramics in powder form in a way that don’t effect its physical properties and increase its mechanical properties.
Ceramics powders will be add in a various ranges appear the difference and get the best results and having the best performance.
On the other hand could replace the ceramic powder as Al2O3 and SiC with carbon nano-tubes in percentage rang between (1-5 vol. %) and decide the optimum way to use in manufacturing and machining operation.
The effect of the Multi-walled CNT, Al2O3 and SiC Micro and Nano-size particles on the mechanical and physical properties, the electrical and thermal conductivities were evaluated and the results have shown positive enhancements.
First way to add the reinforcement as ceramic powder or Multi-walled carbon nano-tubes (MWCNTs) produced by a chemical vapor deposition (CVD) process, to copper powder using powder metallurgy method.
Adding CNT with various percentage value to copper powder and compressed the mixed powder under a pressue of 250 MPa to get a copper matrix composite specimen and then do sintering at sintering temperature 80-90% of the melting temperature of pure copper to get a new material with better mechanical, physical and electrical properties.
First mixing the copper powder with carbon nanotubes was very difficult because it was noticed that during mixing every component will be separated from the other and the CNT will be agglomerated. Therefore a chemical solution as cyclohyxane-C6H12- and Paraffin wax was used to make a suitable environment for mixing the CNT with the copper powder and then putting it in a die subjected to pressure that could transform the powder and mixed components into a a compacted specimen and then performing the sintering process compacted into the die under a high heat for a period of 1 h, to form a very hard bonding that takes place between during the diffusion of the particles. After that the specimen was cooled and the powder particles has bonded and fused together forming a solid piece, to get a new material with different properties suitable for using in many fields with a certain requirements and conditions.
Sintering is the main method used in this experimental work for carbon nanotubes and copper powders depending on powder metallurgy theory that was performed in a certain temperature [950°C] ranging from 0.8 to 0.9 of the melting temperature of pure copper, holding it for 1 hour. After that getting the specimen out of the metallic die which was the container of the mixture consisting of pure copper powder and [1-3 Wt.%] CNT of copper powder Wt.%, adding to it an organic solution of cyclohyxane-C6H12- to solute the Paraffin wax with a certain amount and percentage from Cu powder Wt.% for enhancing the distribution of the CNT in the Cu powders. The testing specimens, containing 1–2 wt% of CNTs, were 20 mm in diameter and 10 mm in height, in which the density of the nano-composite was calculated as the specific quantity by dividing the weight by the volume. In such a case, the density of copper and the CNTs is alternately 8900 and 1400 Kg/m3. Since these are clear values; cyclohyxane-C6H12- and Paraffin wax together do as a collecting to CNT and copper powder because copper powder and CNT was separate from each other when mixed ; and then required to put the mixture in a furnace at a temperature around 100 to 120°C that allow to melt the wax and being separated from the mixture .
Then putting mixture in die which subject to a pressure of 250 MPa using a compression machine to get a compressed compacted specimen that was discribed before will be subjected to a high temperature in sintering method.
The results shown that adding CNT to copper powder has high effect on increasing hardness, wear resistance, mechanical durability and thermal conductivity and decreasing the density of copper and that was evidently investigated through the tests that was made after creating the specimen of the wear, compression and doing the tension test on a tension specimen which was formed in anther die.
The Rockwell hardness test was performed to evaluate the hardness of the Cu/CNT nano-composite. A considerable enhancement of the hardness was observed by the addition of the CNTs to the Cu matrix. The hardness increased almost linearly with increasing CNT mass fraction up to 2% from [88.28 HRB] to [ 93 HRB]. The tension and compression test of the samples with the addition of 1 Wt.% CNT shown results of 8.4 MPa, MPa, respectively. And increasing in specimen with 2% CNTs to record 8.7 MPa and MPa, respectively.
Optical micrograph of the nanotube/Cu
SEM images of Cu/CNT nano-composite material after sintering.
Conclusions
Figure 2
In this work, Cu/CNT nano-composites were prepared via a powder metallurgy method between CNT with nano size and very fine copper powder. By changing the sintering temperature, the pressure and harness of this material were reported. The following conclusions can be derived from the present studies, in which the density of the Cu/CNT nano-composite increases with increasing sintering temperature. The hardness and wear of the Cu/CNT nano-composite increases with increasing percentage of mass fraction of the reinforcement material from 0 to 2 wt.% CNTs at a 950°C sintering temperature to fabricate Cu/CNT nano-composites.
The fabricated Cu/CNT nano-composite powders are consolidated into bulk Cu/CNT nano-composite via a compacting in a compression machine under (250 Mpa) that was equal to (142.6 KN ) using a tension die and wear die with a certain deimension after getting a very good mixing between copper powder and CNT using chemical ways with organic composite as cyclohyxane-C6H12- and Paraffin wax that was an organic solution to solute the wax with certain amount and percentage from copper powder volume .
During sintering, the necks at the contact areas between the powder particles grew. As a consequence, a clear evolution of the pore morphology could be observed. and this sintering was at temperature from of the melting point temperature of pure copper (1083oC) .
The result specimen subjected to a tension and wear test that produce the required material with a very high hardness and excellent material resist wear to use it in an electro and mechanical technical materials with best combination of high strength and high conductivity that could be crucial for some application like wires in high field pulse magnets in many ovens and winding wires.
Figure 1
Figure 3
MWCNT %
Tensile [MPa]
Hardness [HRB]
Compression [MPa]
1% MWCNT
8.4
88.28
735.29
2% MWCNT
8.7 93
740.4