No abstract

In this article, The CF surface was modified by the synergistic modification of electrochemical oxidation and sizing treatment. Firstly, the electrochemical oxidation was carried out using fatty alcohol polyoxyethylene ether phosphate (AEOPK) as the electrolyte. The content of active groups on the modified CF surface increased by 235%. However, the strength of CF monofilament decreased due to the etching. Then, the electrochemically oxidized CFs were sized with the phosphate modified epoxy resin (PAEK). The etched defects on CF surface caused by the electrochemical oxidation were repaired by sizing agent molecules according to the AFM results. Furthermore, the spreadability of PAEK emulsion on the CF surface, the content of CF surface groups and the interaction of CFRC were characterized by using the monofilament contact angle, XPS and Raman spectroscopy. The results suggested that the synergistic modification could improve the CF surface activity, facilitate the spreading of PAEK on the CF surface, and increase the interaction between the CFs and the resin matrix. There were 20.3 and 22.6% enhancement in the breaking strength and elongation of CF monofilament. In addition, the interlaminar shear strength (ILSS) of CFRC prepared with synergistically modified CFs was increased from 12.81 to 33.04 MPa.

No abstract

Magnetorheological fluid (MRF) is a widely utilized intelligent material that faces the in‐use thickening (IUT) problem caused by wear. As commonly being used polar antiwear agents aggravate the sedimentation of MRF, a new method to improve the tribological properties of MRF using nonpolar oil‐soluble graphene rather than polar additives is proposed. Orthogonal and control experiments conducted with a four‐ball machine show that oil‐soluble graphene greatly improves the antiwear performance of MRF. More specifically, the MRF with oil‐soluble graphene reduces wear volume up to about 90% compared with all control experiments, including blank samples without any additives, the samples with the surfactant but without graphene, and the ones with the commercial antiwear agent ZDDP. The results also indicate that both lubricant and MRF get the best antiwear effect when graphene concentration in the base oil is 2 mg ml−1. This implies that oil‐soluble graphene improves the tribological properties of the systems primarily by enhancing the pressure‐bearing capacity of the carrier fluid. Moreover, oleophilic graphene increases the magnetorheological effect of MRF and reduces its off‐state viscosity by about 4% through isolating particles and filling gaps. In summary, the proposed method can solve the IUT problem of MRF along with ensuring its performance.

No abstract