Abstract: Based on the relation between the stress intensity factor Ki and the crack velocity V, lifetime
prediction and control were discussed and studied for machinable Ce-ZrO2/CePO4 ceramics. The
relationship among lifetime, starting cracks and grain sizes were investigated by a set of designed
simulation setting with a definite actual environmental conditions. It was concluded that crack started
from larger weak interfaces of two phases and linking of cracking weak interfaces each other, and the
lifetime of Ce-ZrO2/CePO4 composites could be controlled and predicted by adjusting of grain sizes of
CePO4, which was depended on design of composites.
Abstract: The electronic structures of anatase titanium oxides (TiO2) substitutional doping with N, F, C,
P and S for O have been studied by first-principles method based on the density functional theory. The
lattice distortion and densities of states of nonmetal-doped anatase TiO2 as well as photocatalytic activity
were discussed. Comparing the effects of these five nonmetal ions (N, F, C, P and S) in the anatase TiO2,
the substitutional doping of N is the most effective to get better visible-light activity because of its least
lattice distortion and a large band-gap narrowing effect and the suitable relative position of the impurity
states in band gap.
Abstract: The full potential linearized augmented plane wave method within the generalized gradient
approximation was used to calculate electronic structure of nanocrystalline BaTiO3 ceramics. We
calculated the total and partial density of states of 50 nm BaTiO3 ceramics. The results show that the
atoms distribution of nanograin BaTiO3 ceramics is different from those of coarse BaTiO3 ceramics. It is
also revealed that the hybridization between Ti 3d and O 2p is very strong, which is very important to the
ferroelectric stability of nanocrystalline BaTiO3 ceramics.
Abstract: A micromechanical approach is developed to investigate the behavior of composite materials,
which undergo interfacial delamination. The main objective of this approach is to build a bridge between
the intricate theories and the engineering applications. On the basis of the spring-layer model, which is
useful to treat the interfacial debonding and sliding, the present paper proposes a convenient method to
assess the effects of delamination on the overall properties of composites. By applying the Equivalent
Inclusion Method (EIM), two fundamental tensors are derived in the present model, the modified Eshelby
tensor, and the compliance tensor (or stiffness tensor) of the weakened inclusions. Both of them are the
fundamental tensors for constructing the overall constitutive law of composite materials. By simply
substituting these tensors into an existing constitutive model, for instance, the Mori-Tanaka model, one
can easily evaluate the effects of interfacial delamination on the overall properties of composite materials.
Therefore, the present method offers a pretty convenient tool. Some numerical results are carried out in
order to demonstrate the performance of this model.
Abstract: First-principles calculations have been widely used to describe the ground state properties of
materials over almost 20 years. Recently, a great progress was made in the first-principle calculations.
Thermodynamic properties can also be gotten by calculations of the phonon densities of states (phonon
DOS) and phonon dispersions of materials, which show widely potential applications in material
researches. In the present work, the energetics and bonding properties of interfaces between ZrO2 and Ni
metal were given by first-principles calculations. The results show that alloy element impurities (Al, Cr
and Y) influence remarkably the adhesion of the ceramic and metal. On the other hand, the phonon
densities of states and phonon dispersions of ZrO2 were calculated with density functional perturbation
theory. From the phonon DOS, the thermodynamic properties were derived and the phase transformation
of ZrO2 was discussed. By this method, the thermodynamic properties of material can be gotten from
atom and electron levels without any experiment data. It is a new approach to design and study the
thermodynamic properties in new material system.
Abstract: The adsorption of Au on clean Si(001) surface is investigated by the local density
approximation using first-principles pseudopotentials. We found that the adsorption energy of Au on ideal
Si(001)-(1×1) surface is lower than that on reconstructed Si(001)-(2×1) surface, suggesting that adsorbed
Au atoms chemically react with the surface Si atoms and break Si-Si dimer bonds of the substrate.
Furthermore, the intermixing of Au and Si is also considered and the calculation suggests that intermixing
will not take place at low temperature. But due to the small energy barrier for Au atoms to diffuse into Si
substrate, we can conclude that the Au-Si alloy is easily formed at relatively high temperature. This result
should be one of the reasons of the lack of consensus on the issue of intermixing of Au and Si.
Abstract: Based on the observation that the ratio of the perimeter, P, to the square root of the area,
A0.5, of the grains for a given material is nearly constant, it is suggested that the grain shape may be
treated as a regular polygon with a non-integral side number. Examining the variation of P/A0.5-ratio
with sintering holding time may provide useful information for sintering dynamics. Further analysis
suggests that the P/A0.5-ratio may be a potential parameter for studying the grain-boundary effect in
Abstract: The composite ceramics that contains nano-fibers and transformation particles, fabricated
through SHS process, is performed with high fracture toughness and high plasticity. The matrix of
composite ceramics was mainly composed of fiber eutectics with nano-fibers. The transformation
particles were distributed along boundaries of the fiber eutectic structures. First, Mori-Tanaka method
was used to predict the stiffness of the fiber eutectic. The fiber eutectic is transverse isotropy and has five
independent elastic constants. Then considering random orientation of the fiber eutectic, the Young’s
modulus and Poisson’s ratio of the matrix is determined by even strain. The matrix is isotropy. Finely,
assuming the transformation particles as spheres distributed in the matrix, the effective stiffness for
composite ceramics was computed. When the volume fraction of fibers and particles increase, the
Young’s modulus of composite ceramics decrease and are little smaller than the volume average value,
the Poisson’s ratio of composite ceramics decrease and are little bigger than the volume average value.
Abstract: The SEM observation on a conch’s shell shows that the shell is a kind of laminated bioceramic
composite composed of aragonite layers and organic matrix. Each aragonite layer is parallel with the
surface of the shell and consists of many thin aragonite sheets. These aragonite sheets are perpendicular to
the layer where they are located. The observation also shows that the orientations of the sheets in different
layers are different and these aragonite sheets compose various layups. A kind of lambdoidal layup is
found. The maximum pullout force of the lambdoidal layup is analyzed based on its representative model.
The result shows that the lambdoidal layup can markedly increase the pullout force of the layup and
improve the fracture toughness of the shell.
Abstract: An improved serial computation method is proposed for simulating ceramic grain growth at an
atomic scale. The data structure of a ternary tree is used to store orderly the atomic information and speed
up the editing of data. Combining with the idea of space partition, an index for space searching is
established to reduce the computation time. Simulation results demonstrate that the speed of the serial
computation is increased significantly and simulated images are in good agreement with micrographs of
practical ceramics. It is illustrated that kinetic exponents and fractal dimensions during the simulation of
grain growth are also reasonable in compare with quantitative analyses.