Study On Synthesis Of SiO₂ Based Oxides Nanocomposites By Gaseous Detonation

Compared with ordinary nanoparticles,the optical,electrical,chemical and mechanical properties of nanocomposites can be adjusted and controlled by changing their functional composition,which makes them have great applied potential in the field of catalysis,sensing,materials,optics,etc.The preparation,performance and related application of nanocomposite particles have become a research hotspot.In this paper,nano SiO₂-Fe₂O₃ and SiO₂-TiO₂ composite oxides with different structures and morphology were synthesized by gas phase detonation method,and the morphology,crystalline size,particle size of these nanocomposite particles were characterized by XRF,XRD,TEM,FTIR,etc.Then the synthesis mechanism had also been studied.The main work and results are as follows:?1?The basic theory of gas detonation were introduced,and the related detonation parameters?eg.detonation heat,detonation temperature and detonation pressure,etc.?were estimated.Then the detonation pressure of hydrogen-air deflagration and hydrogen oxygen detonation were measured.In the explosion of hydrogen and air,the maximum detonation pressure is about 2.6 Mpa.While in the explosion of hydrogen and oxygen,the maximum pressure is about 2.9 Mpa,which is a little larger than the calculation value.?2?Using silicon tetrachloride and iron sheets as the source,the experiments for synthesizing nano SiO₂-Fe₂O₃ composite oxide were carried out by detonating the premixed gas of H2 and air.The effects of different calcination temperature on nano SiO₂-Fe₂O₃ composite oxide were also investigated.The structures and properties of these nano composite particles were characterized.Results show that the nano SiO₂-Fe₂O₃ composite oxides with high purity,good dispersion and standard spherical particles can be prepared by gas phase detonation method.These nano-particles have the average particle size of about 50 nm and typical layer cladding structure.In addition,it's also found that as the increase of calcination temperature,the dispersion of Si O2-Fe₂O₃ nanometer oxide powder will be improved and the grain size will become more uniform.?3?Using silicon tetrachloride and titanium tetrachloride as the source,the experiments for synthesizing nano-SiO₂-TiO₂ composite oxide were carried out by detonating the premixed gas of H2 and O2.The effects of initial ambient temperature,feed ratio of different precursors and calcination temperature on the nanosized Si O2-TiO₂ composite oxides were investigated.The composition and morphology of detonation products were characterized.It was found that the purity of nanosized Si O2-TiO₂ composite oxide was more than 94%.Among the SiO₂-TiO₂ particles TiO₂ wasthe mixture of rutile and anatase,and SiO₂ wasamorphous.Ti-O-Si bonds were formed between SiO₂ and TiO₂.The synthetic products included spherical nano SiO₂,polyhedral nano TiO₂ and some composite structure,which was amorphous SiO₂ binding on TiO₂.When Si: Ti ratio was smaller,SiO₂ as a cover layer was bound to TiO₂.While Si: Ti ratio was equal to or more than 1:1,the large amorphous SiO₂ was bound on small TiO₂.And the composite structure of the nano SiO₂-TiO₂ composite oxides could be adjusted by different feed ratio of the precursor.In addition,it was found that the dispersibility of nano SiO₂-TiO₂ composite oxides can become more uniform with the increase of initial ambient temperature and post-treatment calcination temperature,and the content of anatase and rutile of TiO₂ was also to be changed.