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To investigate the effect of Ag or SiC nano-powder additions on the superconducting properties of MgB2, a series of superconducting (Ag)(x)wt.-%(MgB2)(100-x)wt.-%(Agx-MgB2) and (SiC)(x)wt.-%(MgB2)(100-x)wt.-%((SiC)x-MgB2)(0≤x≤20), containing Ag and SiC nano-powders, respectively, of different diameters (30 nm and 130 nm), were prepared by a simple solid-state reaction route, cold-pressed into a pellet form and investigated. To maintain the same environment of MgB2/stainless-steel tapes/wires, Agx-MgB2 and (SiC)x-MgB2 pellets made out of the mixed powders were put inside stainless steel tubes and then sintered at 900°C for two hours in Ar atmosphere. Characterization performed included both X-ray diffraction and magnetization. No impurity phase was identified for as-rolled samples. However, both the Agx-MgB2 and (SiC)x-MgB2 composite pellets, when sintered, contain various impurity phases. The isothermal magnetizations M(H) of a series of samples were measured at temperatures between 5 and 50 K in fields up to 5 T, using a PPMS-9 (Quantum Design). The optimal amounts of Ag and SiC nano-powder in Agx-MgB2 and (SiC)x-MgB2 to obtain the largest flux pinning effect are ∼8 and ∼4 wt.-%, respectively. The "two-step" structures in ZFC M(T) curves of (SiC)x-MgB2 were more developed than Agx-MgB2. The best flux pinning centers can be created by adding a suitable size and amount of SiC nano-powder, not too large to increase the decoupling between the MgB2 grains.