چكيده به لاتين
Due to the wide range of applications of Cu-NbC nanocomposites in electric and electronic industries, thermal managements, and abrasive applications, the synthesis and evaluation of the physical and mechanical properties of this nanocomposite were considered. Using a simple synthesis method for the first time and inexpensive raw materials to achieve the expensive and valuable products was one of the main benefits of this research. In order to achieve the goal of manufacturing Cu-NbC nanocomposite, NbC-Cu nanocomposite was initially produced by a magnesiothermic combustion in the mechanically induced self-propagating reaction (MSR) regime. In the Nb2O5 / CuO / Mg / C system, the self-propagating combustion reaction occurred at 28 min. In order to study the mechanism of progressing the main reaction, sub-reactions of this system were studied. The combustion reaction of magnesium/niobium oxide has been identified as the main stimulus for the overall reaction, which releases a huge amount of heat and increases the temperature of the system. The increase in temperature at the combustion moment causes the reduction of copper oxide by magnesium. NbC is obtained from the reaction of a product from combustion with carbon in a powder mixture. These sub-reactions were evaluated and confirmed with the results of various characterization techniques by XRD, SEM and TEM. The average particle size of combustion product obtained from the SEM images is about 60 nm. Appropriate amounts of NbC-Cu nanocomposite powder were mixed with copper powder to produce Cu based nanocomposite with 0, 5, 10, 15 and 20 volumetric concentrations of NbC; The milled powder was then sintered by spark plasma sintering (SPS) method under 50 MPa pressure and at 850 °C. By increasing NbC content in the nanocomposite, the relative density of the sintered specimens decreased (from 95.5% for pure copper to 88.1% for the composite with 20 vol.% NbC). Microhardness values for the composite specimens with 0, 5, 10, 15, and 20 vol.% NbC were obtained as 113.9, 147.9, 179.1, 181.7, and 217.2 Vickers, respectively. This corresponds to the increase of the NbC reinforcement in the composite which is a very hard ceramic material. With increasing NbC content, the tensile strength of the nanocomposite increased initially up to 10 vol.% and then decreased. The declining trend of strength after 10 vol.% may be attributed to the agglomeration of nanoscale reinforcements at higher concentraions and formation of clusters which may be detrimental in crack nucleation and growth.
