Boron Nitride, Carbon Nanotube Reinforced Aluminum Matrix Resistant Antifriction Composites

This article presents the preparation and properties of BN/carbon nano-tubes (CNTs) contained Al-based alloys, the preparation of nano BN is also involved. Results indicat BN and CNTs are both helpful to decrease friction factor and wear amount of Al-based alloys.Nano BN was synthesized from H3BO3 and CO(NH2)2 in N2 atmosphere at 800 for 1 hour. X-ray diffractometry (XRD) reveals that the average grain size of BN is about 10 nm. Though the conventional coarse-grained BN was milled by high-energy ball milling for 5 hours with carbinol, the grain size was scarcely changed.Powder metallurgy method was used to produce BN/CNTs contained Al-based alloys. BN/CNTs and Al powder were mixed by ball milling, and then pressed at 1GPa to disks. The pellets were heated at 700 , 800 , 900 respectively for 1 hour in inert gases. XRD, Differential Thermal Analysis (DTA), and Vickers hardness measurements were carried out for these specimens. The experimenal results reveal that the hardness increases with increasing BN content and decreasing CNTs content. Tenacity increases with increasing heating temperature. A1N was found in these samples by XRD, which indicats that the reaction between BN and Al happened during heating. Though DTA reveals that Al powders were melt at about 660 , the pressed pellets still kept their sharp edges even they were heated up to 900 . It is suggested that the alumina shells on the Al powders were strong enough to prevent the growth of Al particles even at 900 .Pressureless infiltration method was also used to fabricate BN/CNTs contained Al-based alloys. Al, Mg and BN/CNTs powders were mixed with ball milling in inert gases, then infiltrated with the LD10(2A14 for new standard) alloy in N2 atmosphere at 800 . XRD, Scanning electron microscopy (SEM), Frictional wear test, and Vickers hardness measurement were used to characterize the specimens. The experimental results reveal that Mg and N2 are necessary for pressureless infiltration,and the heat rate is critical condition for producing big samples. Infiltration is sensitive to environmental atmorspher, impurities and oxide shells of Al powders. A1N was observed in XRD patterns for the powders milled for 10 hours and the samples infiltrated in N2 atmosphere at 800 for 1 hour. It is believed that the formation of A1N is not only helpful for improving the properties of samples, but also helpful for bonding.BN and Al. SEM photos show the river pattern which is bond with tough fracture, BN particles and CNTs are also observed. Hardness measurement, frictional wear test results reveal that the contents of BN and CNTs have apparent influence on the properties of specimens. Experimental results indicated that the A185wt%-Mg10wt%-BN2wt%-C3wt% alloy has better mechanical properties.