TiO₂/SiO₂ Composite Fibers Derived From Polymer Precursor

In this work,an investigation on using polycarbosilane(PCS) and titanium tetrabutoxide(TBT) to synthesize the precursor polytitanocarbosilane(TPTC),and to generate the fibres by using the TPTC was performed.The spun fibres were first matured at 100℃for a different period of time,then cured at 200℃,and subsequently sintered at different temperatures.In the first part of the work,a series of precursors were obtained by varying mixture ratio,reaction time and temperature.After analyzed by using TG,FT-IR,NMR,it was found that the weight loss of TPTC at 250～680℃was due to the transformation of Ti(OH)₄ to TiO₂ and the dehydration of Si-OH.The transformation of organic phase to inorganic phase underwent above 680℃.It was aslso found that the numbers of Si-H groups and Si-O groups decreased and increased,respectively,with the increase in the amount of excessive TBT in the precursors as the TBT contents in the system increased. And the reaction time and temperature showed little effects on the changes in Si-H and Si-O groups as well as the excessive amount of TBT.The group of H-CH₂-C was derived from the reaction of Ti-O-CH₂-C₃H₇ and Si-H.The results of melt-spinning indicated that only TPTC-Ti(0.5)-t(2)-T(200) precursor possessed the ability of melt-spinning because of the existances of Si-O and the excessive amount of TBT.In the second part,fibers from precursor TPTC-Ti(0.5)-t(2)-T(200) were obtained. After analyzed by using FT-IR,XPS,XRD,and tensile-strength test,it was found that the organic phase disappeared above 400℃.It was also found after maturing,that the element of Si in the fibers was in the forms of Si-O and Si-O₂,and the element of Ti was in the forms of Ti-O_x(x=1,3,4) and Ti-O₂.Without maturing,the element of Si was in the form of Si-O,and the element of Ti was in the form of Ti-O₂.The fibers,matured at 100℃for 20～100 h and sintered at 1200℃,were composed of anatase-TiO₂ along with amorphous silica,while the fibers,matured at 100℃for 0 h and sintered at 1200℃,were composed of rutile-TiO₂ along with crystalized SiO₂.The strength of fibers increased with the increase of the sintering temperatures from 400℃to 1200℃.