Fabrication of Porous Cellular SiC Ceramics from Wood by Embedding in Si/SiO2 Powder Mixture

Ha, Jung Soo; Lim, Byong Gu; Doh, Geum Hyun; Kang, In Aeh

doi:10.4028/www.scientific.net/KEM.336-338.1113

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HomeKey Engineering MaterialsHigh-Performance Ceramics IVFabrication of Porous Cellular SiC Ceramics from...

Fabrication of Porous Cellular SiC Ceramics from Wood by Embedding in Si/SiO₂ Powder Mixture

Abstract:

Wood has strongly anisotropic cellular structure with 50-80 vol% porosity. It can be converted into porous ceramics (e.g., SiC, SiC/Si, TiC, C/C, and TiO2) replicating the wood structure by various processes. Previously porous cellular SiC ceramic was prepared by reaction of wood charcoal with gaseous SiO generated remotely from an equimolar mixture of Si and SiO2. In the present work, poplar charcoal was simply embedded in the powder mixture of Si and SiO2 and heated at 1600°C for 1 h in Ar to produce porous SiC. Samples were also prepared by infiltration of Si melt (1500-1600°C, 2 h) and vapor (1700°C, 2 h) into the charcoal for comparison. Samples prepared by Si melt infiltration showed 15-52% conversion to SiC. Samples prepared by Si vapor infiltration showed severe damage such that the conversion degree could not be measured. In contrast, samples prepared by the embedding process showed full conversion to SiC (mostly β form) with good retention of the cellular structure of the original wood. The embedding process is a simple and efficient way to produce porous cellular SiC from wood.

Info:

Periodical:

Key Engineering Materials (Volumes 336-338)

Main Theme:

High-Performance Ceramics IV

Edited by:

Wei Pan and Jianghong Gong

Pages:

1113-1116

DOI:

https://doi.org/10.4028/www.scientific.net/KEM.336-338.1113

Citation:

J. S. Ha et al., "Fabrication of Porous Cellular SiC Ceramics from Wood by Embedding in Si/SiO₂ Powder Mixture", Key Engineering Materials, Vols. 336-338, pp. 1113-1116, 2007

Online since:

April 2007

Authors:

Jung Soo Ha, Byong Gu Lim, Geum Hyun Doh, In Aeh Kang

Keywords:

Cellular Structure, Embedding Process, Porous SiC, Wood

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References

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Paper TitlePages

Effects of Different Kinds of Embedding Media on the Image Definition of Animal Fibers using Differential Interference Contrast Light Microscopy

Authors: Bai Hua Wang, Xiang Guo, Zhi Yu Hu, Li Ping Kong, Bao Guo Zhang

Abstract: In this study, the image definition of animal fibers captured by Axioskop 2 MOT PLUS differential interference contrast (DIC) light microscope using 1-bromonaphthalene, diethylene glycol, n-decyl alcohol, and ethylene glycol monomethyl ether as embedding medium, respectively, is compared with the image definition obtained using paraffin wax, the reference embedding medium. The effects of the four kinds of embedding media on the image definition of camel cashmere, yak cashmere, wool, and cashmere are also analyzed. Results show that topographical feature, scale structure, and pigmentation are better visualized when n-decyl alcohol is used as embedding medium compared to when the other kinds of embedding media are used. This meets the requirement of computer image analysis method for the identification of camel cashmereand yak cashmere fibers. Furthermore, the image definition of wool and cashmere is clearly improved when n-decyl alcohol is used as the embedding medium compared to when paraffin wax is used in the same condition.

Fabrication of Scattering Spheres-Embedding Three-Dimensional Ordered Macroporous Titania and Application in Dye-Sensitized Photoanode

Authors: Cheng An Tao, Jian Fang Wang, Yin Long, Ya Nan Lv, Guang Tao Li

Abstract: Scattering spheres-embedding three-dimensional ordered macroporous (3DOM) titania(TiO₂) was fabricated, by the route of colloidal spheres self-assembly, infiltration and template removal. The procedures of 3DOM structure preparation were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD). The silica@PMMA core-shell spheres were prepared and self-assembled into colloidal crystal template. Solid material was deposited in the colloidal crystal template by spin-coating of titania nanoparticle dispersions. Subsequently, the samples were heated to 400 °C to form anatase TiO₂ and to remove the polymer of template, which resulted in macroporous structure with a silica sphere in each lattice pore. The conventional TiO₂ film, 3DOM TiO₂ photoanodes were also fabricated. It was found that SiO₂-embedding 3DOM photoanode has the higher photocurrent efficiency than both of TiO2 film and 3DOM, because there are scattering spheres in its lattice pores which enhance the light scattering and improve the light harvest of the dye.

395

Researches Regarding the Nature of the Embeddings in the Cast Pieces Made of Aluminium Alloys

Authors: Predescu Cristian, Vasile Eugeniu, Predescu Andra Mihaela, Sohaciu Mirela Gabriela, Berbecaru Andrei Constantin

Abstract: The paper presents the results of the investigations made on cast pieces consisting of aluminium with Si and Mg mixed metals, in order to establish the nature of the embeddings and the causes that led to their appearance.

128

The Forecasting of Short-Term Wind Speed on Wind Farm Based on Phase Space Reconstruction and Neural Network

Authors: Ying Ying Su, Fei Ma, Hai Yan Zhang, Zhi Qiang Liao, Peng Jun

Abstract: The forecasting precision of short-term wind speed is not high for its chaos and time-varying. Aimed at the problem, the novel data space is reconstructed with the best embedding dimension and time delay according to the phase space reconstruction. On the basis, neural network (NN) is used as the modeling tool with the novel sample data. Meanwhile, the structure of NN is confirmed compared with the others on the precision. In the end, the model of short-term wind speed is able to be obtained. The results show that the method is available and the Mean absolute error (MAE) is decreased to 16.2% for 2 hours.

496

Identification Method of Tool Wear Based on Locally Linear Embedding and Support Vector Machine

Authors: Zheng Qiang Li, Peng Nie, Shu Guo Zhao

Abstract: Aiming at the nonlinear characteristics of the tool wear Acoustic Emission signal, tool wear state identification method is proposed based on local linear embedding and vector machine supported. The local linear embedding algorithm makes high dimensional information down to low dimension feature space through commutation, and thus to compress the data for highlighting signal features. This algorithm well compensates for the weakness of linear dimension reduction failing to find datasets nonlinear structure. In this paper, acoustic emission signal is firstly made by phase space reconstruction. Using local linear embedding method, the high dimension space mapping data points are reflected into low-dimensional space corresponding data points, then extracting tool wear state characteristics, and using vector machine supported classifier to identify classification of the tool wear conditions. Experimental results show that this method is used for the exact recognition of the tool wear state, and has widespread tendency.

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