Preparation And Thermal Transformation Of Hollow Glass Microspheres/Resorcinol Formaldehyde Composite Hollow Spheres

The resorcinol formaldehyde resin(RF)hollow microspheres combine the performance of high carbonation rate,good ablation resistance,low price and easy to preparation with a special hollow structure.So RF hollow microspheres have important applications in many areas,such as adsorbent,catalyst supporter,insulation materials and so on.The traditional methods to prepare hollow microspheres need to synthesize template in prior,and post-treatment to remove template.Especially,the hollow microspheres,prepared by traditional methods,usually have interpenetrated and even partly broken shell due to removal of template.In order to simplify the preparation method and improve the structural integrity of the hollow microspheres,hollow glass microspheres/resorcinol formaldehyde(HGS/RF)composite hollow microspheres were prepared by in-situ polymerization of resorcinol and formaldehyde on the surface of hollow glass microspheres(HGS),and the structure of HGS/RF was regulated.Furthermore,heat treatment of HGS/RF was carried out and its thermal transformation mechanism was explored.In the preparation of HGS/RF,HGS were pretreated to remove impurities,and then HGS were modified by cationic surfactant cetyltrimethylammonium bromide(CTAB),and finally HGS/RF composite hollow microspheres were successfully prepared after in-situ polymerization of resorcinol formaldehyde on the surface of HGS.The structural regulation of HGS/RF composite hollow microspheres was achieved by adjusting the amount of CTAB,reaction time,reaction temperature and RF precursor concentration.The results of Zeta potential test showd that adding a amount of CTAB could succefully modify the HGS surface electrical properties from negative to positive charge.Fourier transform infrared spectrometer(FT-IR)and Scanning electron microscopy(SEM)analyses showed that spherical resorcinol formaldehyde particles were coated on the surface of HGS with a diameter from 150 nm to 250 nm.In addition,it was found from EDS and TG results that increasing CTAB content,reaction time,reaction temperature and RF precursor concentration would be favorable for coating of resorcinol formaldehyde nanospheres on the surface of HGS.On the basis of above investigation,glass/carbon composite hollow microspheres(C-HGS/RF)were prepared by further heat-treatment of HGS/RF.SEM results showed that the shell of HGS was crushed after heat treatment at 800 ℃.However,the shell thermal stability of the HGS/RF were improved after RF coating.With the increase in RF content,the integrity of C-HGS/RF shell tends to be enhanced.The structure and thermal stability of the composite hollow microspheres was studied by Thermogravimetric analysis(TG),Thermogravimetry-Fourier transform infrared spectroscopy(TG-FTIR),X-ray photoelectron spectroscopy(XPS)and Raman analysis.What’s more,the transformation mechanism was further studied.The results showed that RF decomposed to produce CO2,H2 O,CH4 and CO in the process of HGS/RF heat-treatment,which may consume a part of the heat.At the same time,RF was carbonized,and finally a partly graphited aromatic ring structure with heterogeneous atom was formed,which could protect the structure of HGS from heat damage.C-HGS/RF had a good thermal stability with a maximum decomposition rate temperature of 526 °C in an air atmosphere.The prepared C-HGS/RF had lightweight and easy separation characteristics.The carbon content of the typical sample is about 18.2 wt% and its specific surface area is about 122.91 m2/g.When typical C-HGS/RF(50 mg)were used as a absorbnet to adsorb 5 mg/L methylene blue(50m L),the absorption rate was 99.99%.