Study On The Preparation And Properties Of Nano-diamond And Its Composites

Detonation synthesized nanodiamond(ND)possesses peculiarities of super hard material.The huge specific surface area,abundant of structure defects and oxygen-containning surface functional groups make ND a potential substance on developing new material with specific performance.Composite material with novel structure and nature prepared by ND and other substance complexd at nanometer scale has becomes to be the edge subject of crossed branch of physical chemistry and material science etc.In this dissertation,based on the systematic study of characteristic of ND, ND/Cu was prepared and studied on there character and applying performance of lubricating and catalysis.And ND/PP(nanodiamond/polypropylene)as well as NCC/PP (nano-condensed carbon/polypropylene)composites were also prepared and studied on their mechanic properties.The main research results are as follows:At first,nano-condensed carbon and ND were synthesized by explosive detonation, and their structures and properties was characterised by X-ray diffraction(XRD),Raman spectroscopy,transmission electron microscope(TEM),scanning electron microscope (SEM),infrared spectroscopy(IR),electron paramagnetic resonance(EPR)and thermal analysis.Nano-condensed carbon was treated with various acidic oxidizing solutions in order to obtain ND.XRD studied showed that the best purifying effect can be attained using HNO₃ at high pressure and high temperature.The reasons of aggregation of ND were discussed and a model was proposed.Cu nanoparticles or ND/Cu nanocomposites with guava-like structure were prepared by reducing cupric salt solution with or without ND suspended in.The feasibility and mechanism of heterogeneous nucleationreaction was analyzed from the point of energy. Infect of reactive condition to product was researched.It was found heterogeneous nucleation was dominant at relatively high concentration of CuCl₂ solution.And the size of product reduced as reduction of reactive time.ND/Cu has the familiar IR spectra as Cu nanoparticles.There are abundant of flee radicals in ND,Cu and ND/Cu.So they are all chemical active.The concentration and kind of the cupric salt has great influence to product.CTAB has been found to be not as effective as SDBS and PVP for dispersion of the product.At the same time,Cu and ND/Cu with different morphology and structure including self organization strnctrue of ring-patten and straw-patten were prepared by microemulsion. The UV-Vis and TEM results indicate:in the microemulsion system,the temperature has great influnce to the product.Cu prepared at 75℃was spheres below 10nm and exhibits plasma excitation peak at 560nm in UV-Vis spectrum.Yet ND/Cu prepared at 75℃was polygonal particles and exhibits absorbance peak at 640nm in UV-Vis spectrum. Substitution isooctane with cyclhexalkly will increase the size of product.Different surfactant will cause the different aggregate station of product.The size of product increased as the ratio of H₂O to surfactant.DTA and TG result indicated both Cu and ND/Cu nanoparticulates were strong catalysts for NH₄ClO₄(AP)and 1,3,5-trimethylene trinitramine(RDX)thermal decompositiom, moreover ND/Cu is more effective.The catalytic mechanism was explored and the better catalytic performance of ND/Cu may due to the reciprocity of the oxygen-containning surface functional groups of ND and Cu.Cu and ND/Cu with guava-like structure prepared by liquid reduction were added to paraffin to study there tribological property.As increase of content of Cu in paraffin,the friction coefficient and mass loss reduced firstly and then increased.At the content of 0.1%, Cu exhibits good lubricating performance at relatively low and high load but bad performance at middle load because of rupture of lubricant film and un-formation of transfer film by melting of Cu.The adding of ND/Cu has better anti-wear property than Cu and can improve the tribological performance of Cu under middle and high load through supportion and ball beating function of ND released after melting of Cu.Furthermore,low filling polymer matrix NCC/PP and ND/PP nano-composites were prepared.XRD,Differential scanning calorimeter(DSC),SEM were used to study the crystallization behavior and mechanical properties of nano-composites.The result showed that although the impact strength of the nano-composites was decreased,the crystallization degree of theαcrystalline form was increased and the tensile strength was improved.