Chemical Precursor Routes to Nanostructured Non-oxide Ceramics
- PDF / 2,876,736 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 90 Downloads / 254 Views
Chemical Precursor Routes to Nanostructured Non-oxide Ceramics
Kersten M. Forsthoefel, Mark J. Pender and Larry G. Sneddon Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, U.S.A. ABSTRACT An efficient route to boron carbide, boron nitride, and silicon carbide ceramic nanofibers and nanotubules has been developed which employs newly developed molecular and polymeric precursors in conjunction with porous alumina templating methods. Melt infiltration or vacuum filtration of solutions of 6,6 -(CH2 )6-(B10H13)2 or polyhexenyldecaborane through alumina templates followed by pyrolysis and dissolution of the membranes in 48% HF yielded boron carbide nanofibers or nanotubules. Boron nitride nanotubules were generated in a similar fashion by employing polyborazylene as a precursor, while silicon carbide nanotubules were generated from the commercially available allylhydridopolycarbosilane (AHPCS) polymeric precursor. In all cases, SEM and TEM analyses showed aligned, monodispersed ensembles of nanofibers or nanotubules. Structural control of the end products can be achieved through changes in concentration of the precursor solution, the number of alumina membrane treatments, and/or pore size of the alumina template.
INTRODUCTION The polymer precursor route to ceramics has been widely used to produce micron scale materials [1]; however, new technologies are demanding smaller sizes. Nanoscale ceramic materials are of particular interest due to the their potential applications as electronic and optical devices, structural reinforcements, catalyst supports and membranes for gas separations [2]. Porous alumina templating methods have recently been used to generate nanostructures from a variety of materials including polymers, carbon, metals, semiconductors and ceramics [3]. In this paper, we report the utilization of these templating techniques in conjunction with new molecular and polymeric precursors to produce nanoscale boron carbide, boron nitride, and silicon carbide materials.
EXPERIMENTAL DETAILS Ceramic nanotubules were generated through application of the method [3a,3j] outlined in Figure 1. Boron carbide nanotubule preparation employed 20% (w/w) toluene solutions of either polyhexenyldecaborane [4] or 6,6 -(CH2)6-(B10H13)2 [5]. As indicated in Figure 1, these solutions (~1 mL) were vacuum filtered through commercially available alumina membranes (Whatman Anapore filters) which have a thickness of 60 µm and a nominal pore size of 200 nm (+/-50 nm). The membranes were then transferred to an alumina boat and pyrolyzed in a tube furnace under a flow of high-purity argon to 900oC or 1025oC at 10oC/min and held at the final temperature for 1 h to yield amorphous or crystalline nanotubules, respectively. After the S8.18.1 Downloaded from https://www.cambridge.org/core. UCSD University of California San Diego, on 22 Jun 2020 at 10:54:24, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-728-S8.18
samples were cooled ov
Data Loading...
