Genesis of Nanostructured, Magnetically Tunable Ceramics from the Pyrolysis of Cross-Linked Polyferrocenylsilane Networks and Formation of Shaped Macroscopic Objects and Micron Scale Patterns by Micro
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- 作者：Madlen Ginzburg ; Mark J. MacLachlan ; San Ming Yang ; Neil Coombs ; Thomas W. Coyle ; Nandyala P. Raju ; John E. Greedan ; Rolfe H. Herber ; Geoffrey A. Ozin ; and Ian Manners
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：March 20, 2002
- 年：2002
- 卷：124
- 期：11
- 页码：2625 - 2639
- 全文大小：775K
- 年卷期：v.124,no.11(March 20, 2002)
- ISSN：1520-5126
文摘
The ability to form molded or patterned metal-containing ceramics with tunable properties isdesirable for many applications. In this paper we describe the evolution of a ceramic from a metal-containingpolymer in which the variation of pyrolysis conditions facilitates control of ceramic structure and composition,influencing magnetic and mechanical properties. We have found that pyrolysis under nitrogen of a well-characterized cross-linked polyferrocenylsilane network derived from the ring-opening polymerization (ROP)of a spirocyclic [1]ferrocenophane precursor gives shaped macroscopic magnetic ceramics consisting of
pha.gif" BORDER=0>-Fe nanoparticles embedded in a SiC/C/Si3N4 matrix in greater than 90% yield up to 1000 
C. Variationof the pyrolysis temperature and time permitted control over the nucleation and growth of pha.gif" BORDER=0>-Fe particles,which ranged in size from around 15 to 700 Å, and the crystallization of the surrounding matrix. The ceramicscontained smaller pha.gif" BORDER=0>-Fe particles when prepared at temperatures lower than 900 C and displayedsuperparamagnetic behavior, whereas the materials prepared at 1000 C contained larger pha.gif" BORDER=0>-Fe particlesand were ferromagnetic. This flexibility may be useful for particular materials applications. In addition, thecomposition of the ceramic was altered by changing the pyrolysis atmosphere to argon, which yieldedceramics that contain Fe3Si5. The ceramics have been characterized by a combination of physical techniques,including powder X-ray diffraction, TEM, reflectance UV-vis/near-IR spectroscopy, elemental analysis,XPS, SQUID magnetometry, Mössbauer spectroscopy, nanoindentation, and SEM. Micromolding of thespirocyclic [1]ferrocenophane precursor within soft lithographically patterned channels housed inside siliconwafers followed by thermal ROP and pyrolysis enabled the formation of predetermined micron scale designsof the magnetic ceramic.
pha.gif" BORDER=0>-Fe nanoparticles embedded in a SiC/C/Si3N4 matrix in greater than 90% yield up to 1000 C. Variationof the pyrolysis temperature and time permitted control over the nucleation and growth of pha.gif" BORDER=0>-Fe particles,which ranged in size from around 15 to 700 Å, and the crystallization of the surrounding matrix. The ceramicscontained smaller pha.gif" BORDER=0>-Fe particles when prepared at temperatures lower than 900 C and displayedsuperparamagnetic behavior, whereas the materials prepared at 1000 C contained larger pha.gif" BORDER=0>-Fe particlesand were ferromagnetic. This flexibility may be useful for particular materials applications. In addition, thecomposition of the ceramic was altered by changing the pyrolysis atmosphere to argon, which yieldedceramics that contain Fe3Si5. The ceramics have been characterized by a combination of physical techniques,including powder X-ray diffraction, TEM, reflectance UV-vis/near-IR spectroscopy, elemental analysis,XPS, SQUID magnetometry, Mössbauer spectroscopy, nanoindentation, and SEM. Micromolding of thespirocyclic [1]ferrocenophane precursor within soft lithographically patterned channels housed inside siliconwafers followed by thermal ROP and pyrolysis enabled the formation of predetermined micron scale designsof the magnetic ceramic.