Effect of SiCxOy Decomposition on Densification of SiCO(Al) Fibers during Sintering Process

doi:10.15541/jim20160066

Abstract

Abstract:

The transformation from SiCO(Al) fiber to SiC(Al) fiber by high temperature heat-treatment was studied. The characteristics of SiC_xO_y decomposition and effects of different heating approaches on microstructure and densification processing of SiCO(Al) fibers were investigated. It was found that SiC_xO_y phase typically decomposed at temperature ranged from 1430℃ to 1850℃. The SiC_xO_yphase in the core area of fiber could not be eliminated completely by continuous heat-treatment, even at the temperature as high as 1800℃. Furthermore, large pore faults and grain coarsening tended to generate in the fibers due to over-high decomposition rate, which led to loose structure of fibers. By contrast, static heat-treatment could increase the degree of SiC_xO_y decomposition. The SiC_xO_y phase could be completely removed when the fibers were heat-treated at 1650℃ for 1 h, and big pores and heterogenous grains were suppressed. Finally, densified SiC(Al) fibers with large β-SiC grains could be achieved after sintering at 1900℃.

Key words: SiCO(Al) fibers, SiC(Al) fibers, SiCxOy phase, β, -SiC, densification

CLC Number:

TQ343

YUAN Qin, SONG Yong-Cai. Effect of SiC_xO_y Decomposition on Densification of SiCO(Al) Fibers during Sintering Process[J]. Journal of Inorganic Materials, 2016, 31(12): 1320-1326.

Figures/Tables 10

Table1 Chemical compositions of SiCO(Al) fibers

Sample	Si/wt%	C/wt%	Al/wt%	O/wt%
SiCO(Al)	54.69	35.03	0.57	9.71

Fig. 1 29Si-NMR spectrum (a) and XRD pattern (b) of SiCO (Al) fibers

Fig. 2 Oxygen content and β-SiC crystallite size of SiCO(Al) fibers vs. heated temperature

Fig. 3 SEM micrographs of SiCO(Al) fibers after continuously heat-treatment at 1800℃^(a) Surface (×8000); (b) Cross-section; (c) Surface (×30000); (d) EDS pattern of coarse grains on fibers

Fig. 4 TG-DTA curves of SiCO(Al) fibers

Fig. 5 Oxygen content of SiCO(Al) fibers vs. holding time at various temperatures

Fig. 6 Surface morphologies of SiCO(Al) fibers after heat- treatment at different temperatures for 1 h^(a,b) 1450℃; (c,d) 1550℃; (e,f) 1650℃; (g,h) 1700℃

Fig. 7 29Si-NMR spectra of SiCO(Al) fibers after heat-treated at 1650℃ for 1 h

Fig. 8 XRD patterns of SiCO(Al) fibers after heat-treatment under different conditions^(a) 1650℃-1h; (b) 1700℃-1h; (c) 1800℃-continuously heat-treatment

Fig. 9 Surface morphologies of SiC(Al) fibers prepared from SiCO(Al) fibers preheated at different temperature and then sintered at 1900℃^(a,b) Preheated at 1650℃; (c,d) Preheated at 1700℃

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