Abstract: The K2SO4-Na2SO4 system was studied by differential scanning calorimetry (DSC) with the
aim of developing a new phase-change thermal energy storage material. The temperature range of phase
change is from 800°C to 1069°C according to the phase diagram. A new shape-stabilized phase-change
material made of molten salts impregnated by capillary forces in a porous-fiber matrix was presented.
These materials were characterized by X-ray diffraction analysis and differential scanning calorimetry
analysis. The results indicated that the compound included 70~80% of molten salts, meanwhile the heat
storage material could keep its shape without any leakage during the heating process.
Abstract: The uniaxial tension under various strain rates, creep under various sustained loads, and equalamplitude-
strain loading and unloading tests are carried out at room temperature with polyamide 6/nano-
SiO2 composite specimens. According to the elasticity recovery correspondence principle, the recovered
elastic stresses (strains) in the case of prescribed strain (stress) history are calculated, and the instantaneous
elastic constitutive equations are deduced. The nonlinear viscoelastic constitutive relations in single
integral form on the basis of the instantaneous elastic constitutive equations are constructed and applied
to model the current stress (strain) responses of polyamide 6/nano-SiO2 composite. The theoretic results
agree well with the experimental data, which demonstrates that the single integral constitutive relations
used in this work can accurately simulate the physical nonlinear viscoelastic properties of polyamide
6/nano-SiO2 composite. Finally, the creep curve at higher stress level is horizontally shifted along logarithmic
timescale using a stress shift factor in terms of the time-stress superposition principle and superposed
on that at relative lower stress level to form a master creep compliance curve that spans a longer
timescale interval than the short-term test curve does, which suggests that TSSP provides an accelerated
characterization method for the long-term creep performance of polyamide 6/nano-SiO2 composite.
Abstract: A theoretical model considering the distribution of the grain sizes and grain-boundary ledges
was developed for cavity nucleation in creeping ceramics containing viscous grain boundary phase. The
critical stress involving the effects of various shapes of cavities and viscosity coefficient (η) for cavity
nucleation was presented. Then, the local stress concentration factor concerning different distributions of
grain-boundary ledges was calculated and discussed. The results showed that various shapes of cavities
and η are not the main influencing factors on the critical stress. The stress concentration factor increases
with the increase of grain-boundary ledge size or the density. Therefore, it would be liable to cause cavity
nucleation at gain boundary when the density of grain-boundary ledges is high and the size is large.
Abstract: The high-temperature friction and wear characteristics of different ceramics and ceramic
matrix composites (CMCs) incorporated with various solid lubricants have been investigated from room
temper- ature to 1000oC. The solid lubricants considered in this paper include representative precious
metals, hexagonal boron nitride, graphite, fluorides, soft oxides, chromates, sulfates, and combinations of
various solid lubricants. General design considerations relevant to solid lubrication were proposed on the
basis of friction and wear data of self-lubricating CMCs. The self-lubricating composites incorporated
with SrSO4 or/and CaSiO3 exhibits low and stable friction coefficients of 0.2 to 0.3 and small wear rates in
the order of 10-6 mm3/Nm from room temperature to 800oC. The optimized composites appear to be
promising can- didates for long-duration, extreme environment applications with low friction and small
Abstract: Friction and wear tests of Al2O3 and SiC were conducted from room temperature to 1200°C
both in air and in vacuum. Results show that the wear mechanism of Al2O3 is dominated by micro
fracture, debris abrasive and delamination at temperatures below 600 °C, while is controlled by plastic
deformation and recrystallization among 600~1200 °C, resulting in an obvious decrease of wear loss. The
wear rate and surface microstructure of SiC are closely depending on the testing temperature, atmosphere
and contact pressure. Oxidation of SiC at elevated temperatures plays important role on the wear rate. Self
lubrication of both Al2O3 and SiC at high temperatures was observed, which is mainly depending on the
formation of a specific surface layer composed of nano-particles or very thin glassy film.
Abstract: Al alloy reinforced with SiCp (size: 70-220μm) was fabricated by pressureless-infiltration. Its
wear resistant property was investigated under different heat-treatment conditions, and morphology of
worn surface was examined. The results showed that the composite was integrated, uniform and compact,
and its wear resistant property was better than that of the unreinforced matrix alloy. It was indicated that
some rigid SiCp in the abraded surface of the composite could support part of loads and replace matrix to
wear-tear, which improved the wear resistant property. Compared to annealing, solution aging
strengthens Al alloy matrix and cohesion with SiCp, and the wear resistant property of composites was
better. Combining interface is also an important factor which influences on wear resistant property.
During the wear test, the smaller SiCp size, the more interfaces, there are more SiCp falling off because of
loosening combining interface, which results in more wear-tearing value. The wear rate of composite
increases with decreasing SiCp size, thus, the composite with larger SiCp has better wear-resistant
property than that with smaller SiCp. At last, the wear mechanism of the composite was also studied, and
it showed that abrasive wear dominated in the abrasion process.
Abstract: The transition-metal carbide cemented by metal has excellent combined properties. In this
study, cermets were prepared by vacuum sintering from carbide-metal composite powders. The
transition- metal oxides (Cr2O3, MoO3, V2O5, Nb2O5 and TiO2), cementing-metal oxides (Co3O4 and
NiO), and carbon black were used as raw materials to pre-synthesize composite powders such as
Cr3C2-Co, Mo2C-Co, VC-Co, NbC-Co and TiC-Ni, by a direct reduction and carburization process in
vacuum. Results show that the participation of Co3O4 and NiO as well as the vacuum circumstance were
greatly propitious to the carburization of transition-metal oxides into carbides. The carbothermal
condition was greatly improved by the direct reduction and carburization process.
Abstract: The chemical composition and solid state reaction of the nano-Ti(CN) base cermets in different
sintering temperature were studied. The total carbon and oxygen content in compact were declined
gradually with the increasing of sintering temperature, the nitrogen content in compact began to decline
above 1100°C, the peak of de-gassing of N2 was formed before the emergence of liquid phase, the
decomposition of N2 was arisen acutely above 1500°C. Mo2C and TaC diffused and took part in solid
state reaction with Ti(CN) above 900°C, the solid state reaction was finished below 1200°C. WC diffused
and took part in solid state reaction with Ti(CN) above 1100°C, it was dissolved below 1250°C, there
were only two phases, Ti(CN) and Ni(Ni+Co), in the alloy.
Abstract: Pure Ti, TiN and graphite powders were mechanically alloyed to synthesize Ti(C,N) powder
with nanocrystalline microstructure. The effect of milling variables on the synthesizing behavior of the
powders was investigated. As a result of milling, nano Ti(C,N) phase was synthesized by mechanical
alloying. After that, Ti(C,N)-based cermets were fabricated with the powders as raw ceramic materials. It
was found that the grain size was affected by the content of mechanical alloyed (MAed) Ti(C,N). The
grains of the cermet with suitable MAed Ti(C,N) powder were smaller than that of the typical cermets
prepared from the commercial powders, and the rim phase surrounding the hard core was also complete.
As a result of this, the transverse rupture strength and hardness of the cermets were improved.
Abstract: In this paper, the TiCN-based cermets were fabricated with ultrafine TiCN, metal binders and
carbide additives. Different content of C and Al were separately added to eliminate the oxygen
contamination. The composition of the mixture was TiCN-10Mo-20WC- 20Ni-xC/Al. Effect of the C and
Al addition on microstructure and mechanical properties was investigated. Results indicated that cermets
with carbon addition had higher relative density and more homogenous microstructure while the Al
addition had the opposite effect. Proper addition of carbon improved the mechanical properties.