Study On In Situ Growing SiC On Carbon Nanotubes Surface With Enhanced Cement-based Composite Mechanical Properties

Multi-walled carbon nanotubes(MWCNTs)is a typical nanostructures that exhibit high tensile strength,high aspect ratio,radial elastic deform ability and toughness,which make them the ideal reinforcing material.MWCNTs incorporated into matrices are known to impart enhanced mechanical to the composites formed.SiC in situ growing on carbon nanotubes surface have been successfully fabricated by spark plasma sintering,The crystal structure of SiC was investigated by X-ray diffraction(XRD),the microstructure and surface morphology of SiC/MWCNTs was analyzed by scanning electron microscope(SEM)and transmission electron microscopy(TEM),and the influence of SiC's existence on carbon nanotube structure was detected by Raman spectra,the anti-oxidation behavior of SiC/MWCNTs was measured by a differential scanning calorimeter(DSC-TG),the SiC/MWCNTs in aqueous solution dispersion stability was monitored by spectrophotometer and electrophoretic light scattering method.A preliminary study on the treatment of carbon nanotubes by molten salt has obtained the excellent dispersion performance of carbon nanotube suspension,which is the basis for further experiments.By adjusting the experimental parameters and the proportion of ingredient,the test results show that when the temperature to 1300? and the dosage of silicon powders is 15 wt.%,the fabricated SiC/MWCNTs presents the best performance.The SiC/MWCNTs were added to oil well cement to prepare SiC/MWCNTs reinforced oil well cement composites.The density and flow performance of oil well cement paste have a modest decline.When the oil well cement is reinforced by pristine MWCNTs and SiC/MWCNTs,its flexture strength increases with the dosage of SiC/MWCNTs and curing time.When the oil well cement contains 0.2wt.% pristine MWCNTs,its flexture strength reaches the maximum value.The flexture strength of 7 day and 28 day is 5.83 MPa,6.51 MPa,respectively,compared with the pure oil well cement flexural strength increased by 34.6%,37.6%.But when the oil well cement contains the same degree of SiC/MWCNTs,its flexture strength can be improved obviously,the flexture strength of 7 day and 28 day is 8.63 MPa,9.18 MPa,respectively,which is almost 2 times higher than that of the pristine MWCNTs reinforced oil well cement.15-0.2 wt.% of SiC/carbon nanotubes oil well cement has the most excellent compressive strength,the 7 days and 28 days compressive strength values were 59.33 MPa,60.02 MPa is relatively pure oil cement respectively increased by 44.6%,49.6%.In-situ growth of SiC carbon nanotubes added,greatly promote the hydration process of cement,hydration products in the surface of SiC/carbon nanotubes generated,can significantly improve the mechanical properties.