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Ceramic Fibers (ceramic + fiber)
Selected AbstractsSuperhydrophobic Mats of Polymer-Derived Ceramic FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Sourangsu Sarkar Solid preceramic polyaluminasilazane was synthesized through the reaction between liquid cyclosilazane and aluminum tri-sec-butoxide at 160°C. Electrospinning of polyaluminasilazane/polyethyleneoxide (1/0.0001 mass ratio) in chloroform solutions generated smooth fibers while the electrospun fibers from the chloroform/N,N -dimethylformamide solutions had submicrometer structures on the fiber surfaces. Smooth and rough SiCNO ceramic fibers were obtained by the pyrolysis of the green fibers with an 80% yield. Superhydrophobic mats of ceramic fibers were fabricated via a chemical vapor deposition of perfluorosilane onto the rough fibers. These superhydrophobic mats possess good chemical and thermal stability. [source] Zirconia,Silica,Carbon Coatings on Ceramic FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004Emmanuel E. Boakye Precursors for zircon,carbon mixtures were made to coat fibers for ceramic-matrix composites. Precursors were characterized using XRD, TGA, and DTA. Zircon formed from vanadium- or lithium-doped precursors after heat treatments at ,900°C in air, but it did not form at 1200°,1400°C in argon when large amounts of carbon were added. Some precursors were used to coat NextelÔ 720 and Hi-NicalonÔ fibers. The coatings were characterized using SEM and TEM, and coated-fiber tensile strengths were measured. Although zircon formed in powders, only tetragonal-zirconia,silica mixed phases formed in fiber coatings at 1200°C in air. Loss of vanadium oxide flux to the fibers may have caused the lack of conversion to zircon. The strengths of the coated fibers were severely degraded after heat treatment at ,1000°C in air, but not in argon. The coated fibers were compared with zirconia,carbon-coated fibers made using similar methods. Mechanisms for fiber strength degradation are discussed. [source] Preparation of Boron-Carbide/Carbon Nanofibers from a Poly(norbornenyldecaborane) Single-Source Precursor via Electrostatic Spinning,ADVANCED MATERIALS, Issue 7 2005T. Welna Pyrolysis of poly(norbornenyldecaborane) that has been electrostatically spun provides a route to non-woven mats of boron-carbide/carbon ceramic nanofibers with narrow distributions and controllable dimensions (see Figure). This approach allows the fabrication of composite ceramic fibers with varying composition, which could be tailored to suit specific applications. [source] Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010Paolo Colombo Preceramic polymers were proposed over 30 years ago as precursors for the fabrication of mainly Si-based advanced ceramics, generally denoted as polymer-derived ceramics (PDCs). The polymer to ceramic transformation process enabled significant technological breakthroughs in ceramic science and technology, such as the development of ceramic fibers, coatings, or ceramics stable at ultrahigh temperatures (up to 2000°C) with respect to decomposition, crystallization, phase separation, and creep. In recent years, several important advances have been achieved such as the discovery of a variety of functional properties associated with PDCs. Moreover, novel insights into their structure at the nanoscale level have contributed to the fundamental understanding of the various useful and unique features of PDCs related to their high chemical durability or high creep resistance or semiconducting behavior. From the processing point of view, preceramic polymers have been used as reactive binders to produce technical ceramics, they have been manipulated to allow for the formation of ordered pores in the meso-range, they have been tested for joining advanced ceramic components, and have been processed into bulk or macroporous components. Consequently, possible fields of applications of PDCs have been extended significantly by the recent research and development activities. Several key engineering fields suitable for application of PDCs include high-temperature-resistant materials (energy materials, automotive, aerospace, etc.), hard materials, chemical engineering (catalyst support, food- and biotechnology, etc.), or functional materials in electrical engineering as well as in micro/nanoelectronics. The science and technological development of PDCs are highly interdisciplinary, at the forefront of micro- and nanoscience and technology, with expertise provided by chemists, physicists, mineralogists, and materials scientists, and engineers. Moreover, several specialized industries have already commercialized components based on PDCs, and the production and availability of the precursors used has dramatically increased over the past few years. In this feature article, we highlight the following scientific issues related to advanced PDCs research: (1) General synthesis procedures to produce silicon-based preceramic polymers. (2) Special microstructural features of PDCs. (3) Unusual materials properties of PDCs, that are related to their unique nanosized microstructure that makes preceramic polymers of great and topical interest to researchers across a wide spectrum of disciplines. (4) Processing strategies to fabricate ceramic components from preceramic polymers. (5) Discussion and presentation of several examples of possible real-life applications that take advantage of the special characteristics of preceramic polymers. Note: In the past, a wide range of specialized international symposia have been devoted to PDCs, in particular organized by the American Ceramic Society, the European Materials Society, and the Materials Research Society. Most of the reviews available on PDCs are either not up to date or deal with only a subset of preceramic polymers and ceramics (e.g., silazanes to produce SiCN-based ceramics). Thus, this review is focused on a large number of novel data and developments, and contains materials from the literature but also from sources that are not widely available. [source] Superhydrophobic Mats of Polymer-Derived Ceramic FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Sourangsu Sarkar Solid preceramic polyaluminasilazane was synthesized through the reaction between liquid cyclosilazane and aluminum tri-sec-butoxide at 160°C. Electrospinning of polyaluminasilazane/polyethyleneoxide (1/0.0001 mass ratio) in chloroform solutions generated smooth fibers while the electrospun fibers from the chloroform/N,N -dimethylformamide solutions had submicrometer structures on the fiber surfaces. Smooth and rough SiCNO ceramic fibers were obtained by the pyrolysis of the green fibers with an 80% yield. Superhydrophobic mats of ceramic fibers were fabricated via a chemical vapor deposition of perfluorosilane onto the rough fibers. These superhydrophobic mats possess good chemical and thermal stability. [source] Effects of Oxidation Curing and Sintering Additives on the Formation of Polymer-Derived Near-Stoichiometric Silicon Carbide FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008Lifu Chen The effects of oxygen pick-up and sintering additives on the formation of silicon carbide (SiC) fibers from polyaluminocarbosilane are studied. It has been found that the strict control of oxygen pick up during the oxidation curing is essential to produce near-stoichiometric SiC fibers. When the molar ratio of oxygen to excess carbon in the pyrolyzed fibers (SiCxOy) is slightly over 1 (O/CExcess=y/(x,1)>1), the excess carbon is eliminated during the subsequent sintering as CO and CO2 as a result of the decomposition of SiCxOy; the remaining oxygen is removed as SiO and CO vapor, leaving near-stoichiometric SiC as the residue. However, with still increasing oxygen pick up, the final ceramic fibers become more porous and rich in silicon. The evolution of CO, CO2, and SiO generates high porosity in the absence of a sintering additive, leading to low fiber density. The inter-connected and open porosity favors the formation of CO. In contrast, for the fibers containing aluminum (Al) or Al/B sintering additives, the pores are much smaller and essentially closed, favoring the formation of CO2. Therefore, after sintering at 1800°C, the fibers without sintering additives contain excess silicon, while those with sintering additives are near stoichiometric. Al is beneficial to the densification but it alone cannot produce fibers of high density. When B is added in addition to Al, the fibers can be sintered to nearly full density. [source] GC-MS and 13C NMR Investigation of Lead Zirconate Titanate Precursor Sols for Fiber PreparationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007Mei Zhang Different macroscopic properties of PZT fibers have been obtained when using acetic acid and methacrylic acid to modify the PZT precursor. In order to clarify the role of the acids the molecular structure of the acidified PZT precursors was investigated and compared by gas chromatography-mass spectrometry, Fourier transform infrared, 13C nuclear magnetic resonance (NMR) spectroscopy (solution and solid state 13C NMR) and the reason for obtaining long PZT fibers is discussed. The results indicate that when methacrylic acid was used, long gel and ceramic fibers have been obtained because strongly co-ordinating carboxylate groups of methacrylic acid were formed. Linear chains, like those of methacrylic acid propyl ester and methacrylic acetate, have been formed in the PZT precursor sols. In addition, after heat treatment the polymer decomposed quickly so that pure perovskite could be obtained at low temperature in the PZT fibers. When acetic acid was used short fibers were obtained. Acetic acid may act as chelate agent to form oxo acetate in the precursors; this oxo acetate nature also resulted in PZT fibers drawing. However, the longest gel and ceramic fibers have been prepared from precursors with methacrylic acid. [source] Processing and Structure Relationships in Electrospinning of Ceramic Fiber SystemsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Wolfgang Sigmund During the last years, several groups across the world have concentrated on the adaptation and further development of electrospinning (e-spinning) to enable ceramic fiber synthesis. Thus far, more than 20 ceramic systems have been synthesized as micro- and nanofibers. These fibers can be amorphous, polycrystalline, dense, porous, or hollow. This article reviews the experimental and theoretical basis of ceramic e-spinning. Furthermore, it introduces an expanded electro hydrodynamic (EHD) theory that allows the prediction of fired fiber diameter for lanthanum cuprate fibers. It is hypothesized that this expanded EHD theory is applicable to most ceramic e-spinning systems. Furthermore, electroceramic nanofibers produced via e-spinning are presented in detail along with an overview of electrospun ceramic fibers. [source] | ||||||||||