Abstract: The Mg,Al-hydrotalcite/PE-EVA flame-retardant nanocomposites were prepared by the
co-mixing method at atmospheric pressure successfully. Moreover, the preparation of Mg,Alhydrotalcite/
PE-EVA nanocomposites was investigated according to the mechanical and flame-retardant
tests of the samples. And the results show that the Mg,Al-hydrotalcite nanocrystalline is a highperformance
inorganic flame-retardant agent.
Abstract: After removal of the resin from PAN-carbon fibers, the fibers were coated with C or SiC by
chemical vapor deposition (CVD) and the effects of these CVD coatings on the mechanical and chemical
properties of carbon fibers were investigated. DTG analysis was conducted at different temperatures
(993K, 1053K and 1113K) to establish the oxidation reaction models of the C/C or C/SiC coated fibers.
The results showed that the CVD coatings enhance the oxidation resistance of the carbon fibers. The
surface morphology of the CVD C or SiC fibers was investigated by SEM. The tensile strength of the
fibers was found to decrease rapidly after CVD, while the Young’s modulus remained almost constant.
These changes can be explained by the interface performance of the carbon fibers and the mechanism of
CVD C or SiC deposition. The difference in dilatability between the CVD C or SiC layers and the carbon
fibers was the main reason for the tensile failure.
Abstract: C/SiC, C/Si-O-C and C/C composites reinforced with T300 carbon fiber were fabricated via
polycarbosilane (PCS), polysiloxane (PSO), and phenolic resin precursor polymers infiltration/pyrolysis,
respectively. Flexural strength and fracture toughness of the composites were evaluated. The results
showed that all the composites had poor mechanical properties, less than 160 MPa in flexural strength and
5 MPa•m1/2 in fracture toughness. Deep investigation illuminated that the fiber was damaged severely
during the preparation of the composites, especially in the first cycle of precursor pyrolysis. Great
degradation of the fiber has relationship with coarsening of the microstructure. Bad in-situ strength of the
fiber resulted in poor performance of the composites.
Abstract: Two-dimensional carbon fiber cloth reinforced silicon oxycarbide (2D-Cf/Si-O-C) composites
were fabricated with silicone resin (SR) as precursors, ethanol as solvent and SiC as inert fillers by
precursor infiltration pyrolysis (PIP). Effects of the pyrolysis temperatures in the first cycle and the last
but third cycle on the microstructure and mechanical properties of 2D-Cf/Si-O-C composites were
investigated. The results showed that, when the pyrolysis temperature of the first cycle was 1200°C,
2D-Cf/Si-O-C composites exhibited good mechanical properties, which can be attributed to the better
fiber/matrix interfacial bonding. When the pyrolysis temperature of the last but third cycle was 1400°C,
the mechanical properties of 2D Cf/Si-O-C composites were further enhanced. The flexural strength and
fracture toughness of the composites reached 263.9MPa and 12.8 MPa·m1/2, respectively.
Abstract: Carbon fiber cloth reinforced silicon carbide (2D-Cf/SiC) composites were prepared through
polycarbosilane(PCS) /divinylbenzene(DVB) pyrolysis with SiC as inactive filler. Effects of the molding
pressure on the microstructure and mechanical properties of 2D-Cf/SiC composites were investigated.
With increasing molding pressure from 0MPa to 3MPa, the fiber volume fraction of the composites was
increased. As a result, the strengths of the composites were enhanced. But when the molding pressure
exceeded 3MPa, SiC particles would damage the carbon fibers seriously. Therefore, although the fiber
fraction of the composites was increased further, the flexural strengths of the composites were decreased.
It was found that the composites fabricated with the molding pressure of 3 MPa exhibited highest flexural
strength, reached 319.4 MPa.
Abstract: Three-dimensional textile SiC fiber reinforced SiC composites with pyrolytic carbon
interfacial layer (3D-SiC/C/SiC) were fabricated by chemical vapor infiltration. The microstructure and
complex permittivity of the 3D textile SiC/C/SiC composites were investigated. The flexural strength of
the 3D textile SiC/C/SiC composites was 860 MPa at room temperature. The real part (ε′) and imaginary
part (ε″) of the complex permittivity of the 3D-SiC/C/SiC composites are 9.11~10.03 and 4.11~4.49,
respectively at the X-band frequency. The 3D-SiC/C/SiC composites would be a good candidate for
structural microwave absorbing material.
Abstract: A novel composite, 3D C/SiC-Cu, which contained copper as transpiration agent, was designed
and prepared. The influence of copper contents (2.18, 4.86, 6.53vol %) upon the mechanical and
anti-ablative properties was investigated. The flexural strengths of three composites were over 450MPa,
and fracture toughness over 15.0MPa•m1/2. After being ablated for 35 seconds in flowing oxyacetylene
torch environment, the composites remained integral, and the flexural strength and strength retention ratio
of the composite increased with the copper content increase. The maximum recession rate of the samples
in oxyacetylene torch test was as low as 0.0490mm/s.
Abstract: The microstructure and its evolution of 3D-Cf/SiC composites derived from organic precursor
are studied by using scanning electronic microscopy, mercury intrusion porosimetry, isothermal N2
sorption and bubble point method, etc. As the results shown, MIP is preferable to N2 sorption for the
characterization of pore size distribution (PSD) because of its wider effective probing ranges. The typical
porosity of fabricated 3D-Cf/SiC composites is 10-15vol.%, and all the pores distribute in a quite wide
size ranging from some dozens of nanometers to hundreds of microns and can be divided into three
groups, according to their sizes, contents and locations: the inter-bundle macro-pores/paths, the
intra-bundle pores and the micro-pores/cracks around the interfaces or in the matrixes. The
macro-pores/paths constitute a porous network, which is partially open throughout the composites.
Abstract: An improved chemical liquid vaporized infiltration process was developed to fast densify
carbon/carbon (C/C) composites. A disc-shaped carbon felt was chosen as preform, whose upper and
lower sides were fixed and heated simultaneously by two flat surfaces of two heat sources, and the
precursor was heated by the third heat source separated. By this method, carbon felts (bulk density
~0.2 g/cm3) were densified to C/C composites with density of 1.29, 1.61 and 1.72 g/cm3 when prepared
for 3h at 900°C, 1000°C and 1100°C, respectively. Scanning electron microscopy (SEM) reveals that the
carbon fibers of the composite are surrounded by ring-shaped pyrocarbon. The deposition process is
analyzed by dividing the reactor into four regions associated with specific functions and the reasons for
the rapid fabrication are proposed as the short convection and diffusion path for the precursor and the
existing thermal gradients across the preform.
Abstract: In this paper, 2D C/SiC composites with different carbon cloth filaments (1K, 3K) were
prepared via precursor infiltration and pyrolysis (PIP) process. The flexural strength of 2D-1K C/SiC
composites was 380MPa, and fracture toughness was 16.8MPa-m1/2, while those of 2D-3K C/SiC were
305MPa and 14.4MPa-m1/2, respectively. The differences of these two composites were analyzed from
fiber volume ratio in the composites, density, and fracture surface (SEM) of the samples.