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Copper-carbon composites are a group of materials with excellent mechanical, electrical, thermal, and tribological properties. However, bulk size copper-carbon composites made by the traditional manufacturing processes, like rolling or extrusion, fall short of reaching some of these properties predicted by theory or demonstrated only by samples at centimeter scale or smaller. The two main challenges to the successful scaling-up are: 1) to uniformly disperse carbon in the metal matrix; 2) to avoid degradation due to oxidation or reaction from overheating. In this work, we first demonstrate friction extrusion as a new method to make bulk-size void-free copper-carbon composite wires withmore » homogenized carbon dispersion. Three different carbon varieties, graphite powder, graphene nanopowder, and carbon nanotubes, were added to the copper matrix with the concentration ranging from 0.5 wt% to 15 wt%. Special tooling, processing parameters, and procedures were developed, especially for high carbon content samples. Ten-fold reductions of both copper grain size and carbon particle size were achieved and attributed to the high shear deformation. Notably, energy dispersive X-ray spectrometry indicates the carbon powder was refined to a sub-micron level and uniformly dispersed in the copper matrix. Compared with that of pure copper, the thermal capacity of the composite wire increases by 30 % while density reduces by 29 %.« less

A recent study on the intrinsic magnetic properties of CeFe_11–yCo_yTi has revealed that substituting one Co for Fe retains the favorable magnetocrystalline anisotropy H_a found in the ternary Fe end member, while enhancing the Curie temperature T_c and saturation magnetization 4πM_s. These findings warrant further optimization around Co substitution y = 1 to try to exploit the hard magnetic properties of these Ce-based magnets. Both Ce and Co concentrations in Ce_1+xFe_11–yCo_yTi have been optimized in the range of x = 0 – 0.2 and y = 0 –1.5. It was found that Co substitution effectively enhances all hard magnetic properties,more » although the values are still lower than those predicted from the intrinsic magnetic properties. Specifically, T_c increases from 210 °C to 285 – 350 °C; 4πM₁₉ (magnetization at 19 kOe) from 8.9 kG to 10.5 – 11.5 kG, remanence Br from 3.1 kG to 4.1 – 4.5 kG, and most importantly, H_ci from 1.1 kOe to 1.5 kOe. As a result, the room temperature energy product (BH)_max has been increased by over 100% from 0.7 MGOe in Ce_1.1Fe₁₁Ti to 1.5 MGOe in Ce_1.05Fe_9.75Co_1.25Ti. Microscopy analysis indicates that the addition of Co refines the grain size and promotes chemical homogeneity at the microscopic scale. As a result, the beneficial effect of Co on the microstructure contributes to the improved hard magnetic properties.« less