HEAT TREATMENT OF SILICA-FIBER-REINFORCED
and Yong-Gang Jiang
Translated from Novye Ogneupory, No. 8, pp. 49 – 52, August 2007.
Original article submitted January 26, 2007.
A new wave-transparent composite reinforced by silica fibers with a hybrid matrix comprising BN and Si
was prepared by precursor infiltration and pyrolysis, and it was heat-treated at elevated temperatures. The
variations of the composite during heat treatments were characterized and investigated by Fourier transform
infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The as-re
ceived composite exhibits good mechanical properties, and it is almost amorphous. When treated at 1600°C, it
turned brittle, and silica fibers in it were fused; the composite showed a good crystalline form. When treated at
2100°C, the composite broke into pieces, and the composition showed only BN. Si
was decomposed, and
silica fibers were volatilized. The presence of BN probably affected the phase transitions of silica fibers.
Silica fibers have attracted more and more interest be-
cause of their excellent dielectric properties, high-tempera-
ture stability, thermal shock damage resistance, adiabatic
properties, and ablation resistance . In recent decades, si-
lica fibers have been used to fabricate high-temperature elec
tromagnetic window materials to meet the requirements of
communication, and control and thermal protection of hyper
sonic missiles and spacecraft ; a series of silica-fiber-rein
forced ceramic matrix composites has been developed, such
/phosphate, and SiO
[3 – 6].
However, as the temperature increases, the mechanical
properties of silica fibers drop calamitously. If the residual
strength is very low, the fibers will bring little efficient rein
forcement for the composite [7 – 8]. Therefore, the status of
silica fibers at high temperature is significant.
In this paper, a new wave-transparent composite rein
forced by silica fibers with a hybrid matrix comprising BN
was prepared by the process of precursor infiltra
tion and pyrolysis, and its high-temperature behavior was
studied. The variations in composition and microstructure of
the composite during heat treatments were characterized and
investigated by Fourier transform infrared spectroscopy
(FT-IR), X-ray diffraction (XRD), and scanning electron mi-
Silica fibers used in the present study were produced by
Jingzhou Feilihua Quartz Glass Corporation (Hubei, China)
with properties listed in Table 1. Three-dimensional fabrics,
with fiber volume fraction about 45%, were woven by
Beijing FRP Research and Design Institute (Beijing, China).
The starting preceramic precursor, a low-viscosity trans
parent liquid, was synthesized by mixing perhydropoly
silazane (PHPS) and borazine , the ratio between them
being no more than 1/10 (vol.). Borazine was synthesized by
thermolysis of H
in a pressure vessel , and PHPS
was synthesized by the ammonolysis of dichlorosilane-
The composites were prepared by precursor infiltration
and pyrolysis according to the following steps. Firstly, the
fabric was infiltrated with hybrid precursor in vacuum. Then,
the preform filled with precursor was cured at about 100°C
Refractories and Industrial Ceramics Vol. 48, No. 4, 2007
1083-4877/07/4804-0280 © 2007 Springer Science+Business Media, Inc.
State Key Laboratory of Advanced Ceramic Fibers & Composi
tes, College of Aerospace & Materials Engineering, National
University of Defense Technology, PR China.
TABLE 1. Properties of Silica Fibers
2.2 1700 78 6 – 8