ABSTRACT
Acrylamide (AM) was copolymerized with ethylene glycol dimethacrylate (EGDMA) in the presence of (R)-1,1'-binaphthalene-2-naphthol (BINOL) as the template molecules on the surface of silica gel by a free radical polymerization to produce a chiral stationary phase based on the surface molecularly imprinted polymer (SMIP-CSP). The SMIP-CSP showed a much better separation factor (α = 4.28) than the CSP based on the molecularly imprinted polymer (MIP-CSP) without coating on the silica gel (α = 1.96) during the chiral separation of BINOL enantiomers by high-performance liquid chromatography. The influence of the pretreatment temperature and the content of the template molecule ((R)-BINOL) of the SMIP-CSP, and the mobile phase composition on the separation of the racemic BINOL were systematically investigated.
ABSTRACT
Recent years have witnessed a growing research interest in graphene-reinforced alumina matrix composites (Al2O3-G). In this paper, to better achieve the dispersion of graphene in composites, a ball milling method for adding raw materials step by step, called stepwise feeding ball milling, was proposed. The Al2O3-1.0 wt % graphene composites were prepared by this stepwise feeding ball milling and hot pressing. Then, the effects of sintering temperature and sintering pressure on the microstructure and mechanical properties of composites were studied. Results showed that the bending strength, fracture toughness and Vickers hardness of composites increased firstly and then decreased with increasing sintering temperature. The mechanical properties of composites were all at their maximum with the sintering temperature of 1550 °C. For example, the bending strength of composites reached 754.20 MPa, which was much bigger than 478.03 MPa at 1500 °C and 364.01 MPa at 1600 °C. Analysis suggested that the strength of composites was mainly related to the grain size, microflaw size and porosity.
ABSTRACT
Metastable ω phase is common in body-centred cubic (bcc) metals and alloys, including high-alloying steels. Recent theoretical calculations also suggest that the ω structure may act as an intermediate phase for face-centred cubic (fcc)-to-bcc transformation. Thus far, the role of the ω phase played in fcc-bcc martensitic transformation in carbon steels has not been reported. In previous investigations on martensitic carbon steels, extra electron diffraction spots were frequently observed by transmission electron microscopy (TEM), and these spots were historically ascribed to the diffraction arising from either internal twins or carbides. In this paper, an intensive TEM investigation revealed that the extra spots are in fact attributed to the metastable ω phase in particle-like morphology with an overall size of several or dozens of nanometres. The strict orientation relationships between the ω phase and the ferrite matrix are in good agreement with those of the hexagonal (P6/mmm) ω phase in other bcc metals and alloys. The identification of the ω phase as well as the extra diffraction spots might provide a clue to help understand the physical mechanism of martensitic transformation in steels.