Preparation Of Fluorescent Nanoparticles And In Situ Characterization On Their Dispersion State In Quartz Fiber Composites

Due to the novel physical and chemical properties which lots of macroscale materials do not have,nanoparticles had become widely recognized as one of effective methods to significantly improve the mechanical and functional properties of resin composite materials.However,as the reinforcements for composite,the reinforcing and functional effects of nanoparticles heavily depend on its dispersion in matrix or interphase.Therefore,the effective characterization of dispersion of nanoparticles in composite has become one of the key scientific issues.In this paper,using zero dimensional silica microspheres and one dimensional carbon nanotubes as two representative nanoparticles,multi-walled carbon nanotubes(MWCNTs-FITC)and silica microspheres(SiO2-FITC)labeled with FITC are successfully prepared.The methods of the fluorescence imaging the two dimensional nanoparticles enhancements in the matrix and interphase have been systematically studied.The probability of particle spacing is innovatively applied.Using the theory of probability density of particle spacing to establish a scientific method for quantitative characterization the nanoparticles dispersion in large scale range of three dimensional space in the matrix and interphase,and finally provide the theoretical basis and basic data for the fine design and controllable preparation of the resin-based composites.Based on atomic transfer free radical polymerization(ATRP)and fluorescence labeling method,three sizes of fluorescent silica microspheres(SiO2-FITC)were 190nm,280nm and 540nm were successfully prepared.The chemical structure and micromorphology of SiO2-FITC were characterized by infrared(FTIR),fluorescence spectroscopy(FL)and laser scanning confocal(CLSM).The results showed that the silica microspheres were successfully connected to FITC,and SiO2-FITC has good fluorescence under 488nm excitation wavelength.Based on the principle of fluorescence tracing,CLSM was used to characterize the Si02-FITC dispersion in large scale range(200-1000nm)in the resin matrix and the interphase of SiO2-FITC/quartz fibers composites.Due to the existence of Van der wals’force,physical entanglement/stacking and other interactions,Si02-FITC is difficult to realize monodisperse morphology in the composite,but is dispersed in the composite system by the initial morphology of the coexistence of single nanoparticle enhancements and their aggregates.With the increase of the size of SiO2-FITC and the increase of curing temperature,the size of the aggregate will increase,which makes the dispersion in resin matrix become worse,and the diffusion form of SiO2-FITC in interphase of SiO2-FITC/quartz fibers composite is not uniform.The theoretical calculation of the particle spacing probability density shows that the dispersion of SiO2-FITC in resin matrix is good when the particle size is less than 280nm and the curing temperature is less than 40 ℃,and the conclusion is basically consistent with the conclusion obtained by CLSM.Based on chemical co-precipitation and fluorescence labeling method,fluorescent multi-walled carbon nanotubes(MWCNTs-FITC)were successfully prepared.The chemical structure and micromorphology of SiO2-FITC were characterized by infrared(FTIR),fluorescence spectroscopy(FL)and laser scanning confocal(CLSM).The results showed that the multi-walled carbon nanotubes were successfully connected to FITC,and MWCNTs-FITC has good fluorescence under 488nm excitation wavelength.Based on the principle of fluorescence tracing,CLSM was used to characterize the MWCNTs-FITC dispersion in large scale range(200-1000nm)in the resin matrix and the interphase of MWCNTs-FITC/quartz fibers composites.It is found that MWCNTs-FITC have a large length to diameter ratio,so when the content of MWCNTs-FITC is higher,the easier for MWCNTs-FITC to tangle,which is not conductive to its uniform dispersion and diffusion.The higher of the heat treatment temperature,the more active group of the MWCNTs-FITC were reacted with the sizing agent on the surface of quzrtz fiber,it is not conducive to MWCNTs-FITC diffusion,and the high curing temperature is helpful to the MWCNTs-FITC.To diffuse to the resin from quartz fibers.The theoretical calculation of the particle spacing probability density shows that when the MWCNTs-FITC content is 0.05 wt.%and the curing temperature is less than 40℃,the dispersion of MWCNTs-FITC in resin matrix is good.The conclusion is basically consistent with the conclusion obtained by CLSM.In this paper,based on the different geometric shapes of the two dimensional nanoparticles enhancements,the influence of the interaction of the nanoparticles enhancements,the microscopic thermal diffusion and the resin curing thermal stress on the fluorescence imaging of the two dimensional nanoparticles enhancements has been studied,and the regulation method of the fluorescence imaging of two dimensional nanoparticles enhancements in resin matrix and interfphase of composites has been established.The visualized in situ characterization of the dynamic evolution of the two dimensional dispersion states of nanoscale reinforcements has provided a feasible scientific approach for the characterization of the micro state of the composite in the large scale.