| Poly(ferrocenylene), is a type of polymers with transition metal ion and organosilane units in the main chain, which can be employed as precursor of Fe/Si/C ceramics. The corresponding ceramics has excellent electromagnetic and catalytic properties due to the introduction of Fe, which has potential application in the area of nano electronic devices of high performance and special carrier materials.Firstly, linear poly(ferrocenylene) named as PFDMS was synthesized by living anionic polymerization, which is not suitable to be precursor due to its low ceramic yield of 17% under 1000 ?. Then hyperbranched Fe-containing organometallic polymers, named as hb-PFS(1), hb-PFS(2) and hb-PFS(3), respectively, were prepared by polycondensation via convenient “A2+B3” approach. All of the three types of polymers have similar crosslinking molecular structure and bonding formation. hb-PFS(1) and hb-PFS(2) have good solubility and high ceramic yield(49.3% and 50.3% under 1000? respectively), which can be used as precursor of Fe/Si/C ceramics. However, although with higher ceramic yield of 58.7%, hb-PFS(3) has poor solubility.The three types of hyperbranched poly(ferrocenylene) have similar thermal stability and processes of inorganization. The polymers were stable under 250?. Parts of the Si-CH3 were broken and H2?CH4 were produced between 250 and 400 ?. Along with the release of H2 ? CH4, Si O and ferrocene, the ferrocene moieties of the organometallic polymers decomposed and Cipso-Si were broken among 400?~700?. Above 700?, the pyrolysis almost finished and the crystallization and growth of the amorphous phase began.The polymer-derived Fe/Si/C ceramics were prepared by using hyperbranched poly(ferrocenylene). Under nitrogen atmosphere, the element Fe existed mainly as ?-Fe at 900?. Under argon atmosphere, the element Fe existed mainly in Fe3 Si and ?-Si C was also observed when the temperature was above 1200 ?. Under ammonia atmosphere, The ceramics had a high saturation magnetization and the element Fe existed mainly in ?-Fe and ?'-Fe4 N at 900?.The organometallic polymer microspheres of hierarchically porous structure were prepared by the solvent extraction /evaporation-based microencapsulation technology. Take the both advantages of this technique and polymer-derived approach, the microspheres of Fe/Si/C ceramics were prepared. The hierarchically porous structure remained under 600?, which was destroyed with appearance of massive nano particles when the pyrolytic temperature reached 900?. With further investigation, The growth of massive nanowires inside the porous microspheres occurred under heat treatment at 700??800? or 900?. Under the same condition, the ceramic microspheres prepared by using hb-PFS(1) had compact surface and internal construction, while those made by hb-PFS(2) were fragile with porous surface.The synthesis of hb-PFS(2) and hb-PFS(3), the investigation of the inorganization process and the preparation and characterization of Fe/Si/C ceramics, have not yet been reported before. It is completely new to prepare Fe/Si/C ceramic microspheres of hierarchically porous structure by the combination of the solvent extraction /evaporation-based microencapsulation technology and polymer-derived approach using hyperbranched poly(ferrocenylene) as the starting materials. The successful preparation of the ceramic microspheres indicated that hyperbranched poly(ferrocenylene) can also be used to prepare ceramic fibers or films due to their excellent shape retention. With hierarchically porous structure and massive well-dispersed catalytic Fe nano particles, the Fe/Si/C ceramic microspheres have great potential in the application as catalyst carrier. These work has laid good foundation for the use of hyperbranched poly(ferrocenylene) as preceramic polymers. |
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