Abstract: Grafting of maleic anhydride (MAH) onto high density polyethylene (HDPE) was carried
out in melt state through the mechanical force initiation caused by high-speed rotation of the
twin-screw, investigating its functional reaction and the grafting degree influenced by the rotation of
the twin-screw, observing the influence on its mechanical property. The results showed that the
increase of grafting degree made the interface phase produce a firm chemical coupling, which
improved the tensile-strength and flexural strength of the composites. The produced interfacial
stress from the shrinkage of specimen melts in injection molding process can strain-induce the
forming of the extended-chain crystals in the matrix and obviously improve the notched impact
strength of the composites.
Abstract: An inexpensive fly ash (FA), which is from a waste production, has been employed to
fabricate fly ash/epoxy composites in our work. Three kinds of fly ash with the most probable
diameters of 74"m, 119"m and 146"m were filled in the modified epoxy resin (EP). The purpose of
this study is to characterize the dynamic mechanical properties of such composites, and the dynamic
mechanical behaviors of the composites are investigated in the temperature range from -40 to 150oC
using a tension-compression mode. The results indicate that the dynamic elastic moduli for the fly
ash/epoxy composites are (1.4~2.0) GPa, and the peak values of loss factor (tanδ) for these
composites can reach (0.79~0.90) in the test specification. In addition, a scanning electron
microscope (SEM) has been used to observe the distribution of fly ash particles in the matrix, as well
as the photographs of fracture surface of composites.
Abstract: The graphite/2024Al composites have been fabricated by improved Squeeze Exhaust
Casting (SQEC) method. Two kinds of graphite preforms with porosities of 13% and 17%
respectively were infiltrated with 2024Al (Al-5Cu-2Mg) alloy under the pressure of 73MPa. The
disadvantages of traditional Squeeze Casting (SQC) were avoided and the distribution of aluminum
alloy appeared homogenous 3D network in the composites. Flexural strength and Young’s modulus
were determined at room temperature. Compared to graphite preform, the composites exhibited a
significant enhancement of mechanical properties. The flexural strength and Young’s modulus of
X-Y direction of G186/2024Al composites increased from 38.6MPa to 99.7MPa and from 10.1GPa to
19.7GPa, respectively. The fracture mechanism of the composites was discussed on the basis of
Abstract: The Si3N4- Si2N2O composites were fabricated with amorphous nano-sized silicon nitride
powders by the liquid phase sintering(LPS) method. The sintering temperatures ranged from 1500°C
to 1700°C. Microstructure and component of the composites were performed by scanning electron
microscopy (SEM) and X-ray diffraction (XRD). Results show that sintered body consists of Si2N2O
and β-Si3N4, with an average grain size about 1μm. The maximum value of flexural strength of the
material is 680MPa when sintered at 1700°C. Transcrystalline cracking is the main fracture
mechanism of the composites.
Abstract: Nanoparticles can be made into bulk material by sintering process in order to obtain some
excelled properties of nanomaterials. Because ZrO2 has a good thermal-resistance property, it has
been widely used as thermal-barrier material, including functionally graded material (FGM) and
thermal barrier coating (TBC). In the present paper, ZrO2 nanoparticles with a size of 10, 50, 80 and
100 nm were fabricated into bulk material respectively with the help of cold and isostatic pressing
processes. The thermal diffusion coefficient, the hot expand coefficient and the specific heat of
these bulk materials were measured. The experimental results showed that after ZrO2 nanoparticles
being pressed and sintered, the nanoparticles were found in a state of aggregation in the bulk
materials, but there are some nanometer size effects in their thermal physic properties. It was found
that the thermal diffusion coefficients between 100-150oC were obviously different, as the samples
were made of ZrO2 with different nanometer dimensions. The less the nanometer size of particles,
the higher the thermal diffusion coefficient. The hot expand coefficient of the sample from 100 nm
ZrO2 particles was 96.9741×10-7 K-1 between 30-300 oC. However, the hot expand coefficient of the
sample from 10 nm ZrO2 particles was 100.2345×10-7 K-1. On the other hand, the specific heat of
the bulk material from ZrO2 nanoparticles was much higher than that of the bulk material from
micron ZrO2 particles. When the temperature was over 350 oC, the size of ZrO2 nanoparticles
influenced the specific heat of bulk material even more. With the decreasing of size of ZrO2
nanoparticles the specific heat of bulk material increased continuously.
Abstract: Metal particles were embedded in a silicon carbonitride (SiCN) matrix, derived from the
commercially available polysilazane Ceraset®. Metal powders, such as Fe, Mn, Co, Ni, were mixed
and milled with pre-cross-linked polysilazane and subsequent pyrolysis. The metals act as active
fillers to increase the density of composite. The phases and microstructures of metal/ceramic
composites were studied using XRD, SEM and EDS. The magnetic property was measured with
Magnetic Property Measurement System at –196oC and 27oC. The results show that there were two
main domains in composites, one was metal-rich domain and another was metal-poor domain. The
reaction compound between metal and matrix had great effect on the magnetic properties of
composites, filled with different metals.
Abstract: SiC/SiC composites were fabricated by hot pressing (HP) via liquid phase sintering (LPS)
using carbon coated 2D woven Tyranno SA fabrics as reinforcement. Both nano-SiC and micro-SiC
powders with sintering additives were used for matrix. The effects of preparation conditions on the
microstructure and mechanical properties of the composites were characterized. Highly densified
composite was obtained at 1780°C under 20MPa with nano-SiC particles. The strength and elastic
modulus of the composite were enhanced. When micro-SiC powder was used, higher strength
revealed for the composite sintered at 1780°C under 15MPa, although it was not densified enough.
Higher sintering temperature (1800°C) is beneficial for the densification of the composite, but is not
obvious for the improvement of mechanical properties.
Abstract: The emerging cause of arc-microcracks is interpreted and the interaction between
ceramic particles and arc-microcracks is accounted for determining the average disturbance strain
and equivalent eigen strains by using Mori-Tanaka method. Then the micromechanical stress field
of the cermets is estimated. Results show that the micromechanical stress field is not associated
with the distribution of arc-microcracks. The stress in matrix and ceramic particles will increase
when the volume fractions of arc-microcracks increases.
Abstract: The influences of different sintering aids, including Fe2O3, Fe(NO3)3·9H2O, Y2O3+Al2O3
and MgO+Al2O3+SiO2, on the nitridation of reaction bonded Si3N4/BN ceramics were conducted at
1350°C for 2h. Results indicate that the addition of sintering aids could facilitate the nitridation
process resulting in higher nitridation percent due to the reactions between sintering aids and surface
silica on silicon powder. When 5wt. % of Y2O3 and 2wt. % Al2O3 were added, the nitridation percent
reached to 94.4%. The addition of sintering aids has obvious effect on the ratio of α-Si3N4/β-Si3N4.
The increase of β-Si3N4 ratio was attributed to the direct reaction of silicon with nitrogen.
Abstract: The feasibility of fabricating h-BN-SiC high-temperature ceramics by in-situ combustion
synthesis was demonstrated by igniting the mixture of boron carbide and silicon powder under
100MPa nitrogen pressure. The reaction thermodynamics and the adiabatic combustion temperature
were calculated theoretically. The phase composition, microstructure and mechanical properties of
composite were identified by XRD and SEM. The maximum bending strength and fracture
toughness of the composite were 65.2 MPa and 1.4 MPa·m1/2 under room temperature, respectively.
The effects of h-BN and SiC dilution contents on the mechanical properties of composite were also