Three different Co-MOFs, [Co₃(L)₂(DPDP)]_n (1), [Co(HL)(DPDP)]_n (2) and {[Co(HL)(1/2DPDP)₃(H₂O)]·H₂O}_n (3) (H₃L = 4,4′,4′′-(nitrilotris(methylene))tribenzoic acid, DPDP = 4,4′-(2,5-dibutoxy-1,4-phenylene)dipyridine) have been co-crystallized in a one-pot reaction. Based on the significant differences between the three structures, we adopt solvents to ultimately regulate acquisition of pure crystals of the three compounds.

Ultrasonic surface rolling extrusion (USRE) processing is applied on quenched and tempered 40Cr. Microstructure observations of USRE specimen surfaces indicate that the processing can both get nano-structured layers, with grain size of 3～7 nm, and reduce the surface roughness to 0.05 μm; plastic flow is formed from top surface to about 200 μm deep with graded distribution of grain size. Tests of mechanical properties show that microhardness of USRE specimen surface is increased by 63%; residual stress at the top surface can reach to –846 MPa and depth of residual stress layer is more than 1 mm. It has been determined by contrast wear test that USRE can reduce friction coefficient and improve the wear-resistant property.