Advanced Materials Research Vols. 150-151

Abstract: Based on Density Functional Theory (DFT), using first-principles pseudopotential plane wave method, elastic properties and electronic structure of TiB2 and ZrB2 were calculated. The elastic constants of these compounds were calculated by Voigt-Reuss-Hill method. The results show that the elastic modulus of TiB2 and ZrB2 are 594 and 520 GPa, and the shear modulus are 268 and 229 GPa, respectively. Pugh empirical criterion and Poisson's ratio show that the two compounds are very brittle, and the brittleness of TiB2 is higher than ZrB2. Finally, the differences in elastic properties between TiB2 and ZrB2 result form their electronic structures.

Abstract: Taking modified unsaturated polyester as the matrix resin, methyl ethyl ketone peroxide (MEKPO) and cobalt naphthenate as the redox system, and TiO2, SiO2 and hollow glass beads as the functional fillers, a thermosetting heat-reflective coating with good temperature-reduction effects and wearing resistance, which can be quickly solidified under the room temperature has been produced. In accordance to the research, the amount of solidifying agent and accelerant has great bearing on the gelation time of the coating, and the optimum usage for this system of which will be: 2.5% cobalt naphthenate and 2% MEKPO or 3% cobalt naphthenate and 2% MEKPO; as the increase of the fillers, the temperature reduction effects will be quickly enhanced at the beginning, and then tend to be stable, when the quantity of the fillers is less than 10%, the covering effect of the coating is not obvious, when it is more than 20%, construction difficulties will occur because of the excessive viscosity of the coating. Fillers of 14% with low viscosity and better temperature reduction effect is recommended; as the ratio of TiO2 to SiO2 decreases, the temperature reduction effect of the coating is weakened while the abrasion resistance strengthened and the glossiness reduced; the addition of hollow glass bead can better realize the temperature reduction of the coating, however the glossiness of which will be increased; Colored pigments have slightly negative impact on the temperature reduction of coating. The prepared coating has good abrasion resistance, and can reduce the pavement temperature by almost 10 during hot seasons when it is applied on pavement.

Abstract: Titanium alloys are susceptible to sand erosion, hard zirconium nitride coatings have been deposited onto titanium alloys by Physical vapor deposition (PVD) in order to improve erosion resistance. Al and Cu were added into ZrN coatings to strength and toughing the coating. The microstructure and mechanical properties of ZrAlCuN coating were studied. Erosion tests were conducted to evaluate anti-erosion ability. Erosion rates were measured and characteristic damage features were identified on the surface of eroded specimens. The mechanisms of erosion are discussed in order to explain the promising performance of materials in erosive conditions. It was found that there is an significant increase of erosion resistance because of the increase of hardness and toughness.

Abstract: The new type of Pb-B shielding alloys with high tensile strength and hardness were prepared by casting. The microstructure and morphology of the Pb-B alloys were investigated by scanning electron microscope (SEM) analysis. Mechanical properties and radiation shielding effect of the alloys were compared with other Pb-based shielding alloys. The results indicate that the tensile strength and hardness increased up to 116 MPa and 160 HB with the 1.0 wt.% content of B. The fractographic examination conducted by SEM indicate that the Pb-B alloys are in form of plastic fracture, and the fracture model changes from the dimple to the intergranular quasi-cleavage with the increasing of B content. Furthermore, the composites are of the excellent shielding properties. Especially at the thickness of 20 mm, the shielding ratios for γ-ray and neutron reach 49.7% and 92.7%, respectively.

Abstract: Li[Ni1/3Co1/3Mn1/3]O2 was synthesized by modified combustion method and effect of calcination temperature on characteristics was investigated. The cycle of Li[Ni1/3Co1/3Mn1/3]O2 was determined by electrochemical measurements, the microscopic structural features were investigated using Fourier transform infrared spectroscope(FTIR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD). The results show that the compound has layered structure with hexagonal lattice. With the increase of calcination temperature, the size of primary particle rises. The Li[Ni1/3Co1/3Mn1/3]O2 calcined at 900 oC shows excellent electrochemical performances with large reversible specific capacity of 152 mAhg-1 in the voltage range of 2.75-4.20 V.

Abstract: Electrodeposited copper foil was prepared by direct current electrodeposited method. Effects of different RE additions including 0, 3mg/L, 6mg/L and 9mg/L on the morphology, roughness, and mechanical properties of electrodeposited copper foil are investigated at high current density and high flow rate by SEM (scanning electron microscope), roughness measuring instrument, microcomputer control electronic universal testing machine and high temperature drawing machine. The results reveal that with increasing in RE content, the grain size in the copper foil is refined with more homogeneous distribution and denser, mechanical properties can be improved also. The desirable grain size in the copper foil with maximum value of the mechanical properties and the roughness can be obtained with approximately 6 mg/L RE content.

Abstract: Ni-doped Cu3N films were prepared by radio frequency (RF) reactive magnetron sputtering method under different N2/(N2+Ar) ratios at room temperature. X-ray diffraction (XRD) patterns show that Ni-doped Cu3N films have the preferred growth along the (100) plane. The lattice parameters of Ni-doped Cu3N films increases obviously compared with the pure Cu3N films, which indicate that some Ni atoms are incorporated into the Cu3N host lattice. The electrical resistivity of Ni-doped Cu3N films has a remarkable change and decreases as the nitrogen ratio decreases. The optical energy gap of Ni-doped Cu3N film is around 1 eV which has no obvious change. The morphology and the thermal stability of doped Cu3N films were also studied.

Abstract: Optical Microscope and SEM(Scanning Electron Microscope) are used to observe the crack evolution of rock under compression. Two kinds of rock (marble and granite) are investigated. The evolution of crack pattern shows that localization is a key factor inducing brittle failure. Crack of granite readily tends to localize and show more brittle. Contrarily, randomly distributed cracks induced by compression load results into the low brittle of marble. The mechanism underline this phenomenon is that marble has higher heterogeneous than granite. So, the key point to describe the brittle failure mechanism of rock is to determine the micro-mechanical and the damage evolution properties.

Abstract: Crystallization of a glass containing high dielectric performance components can be controlled in the nucleation and growth processes in order to meet the requirements of enabling the glass-ceramic dielectric composites to obtain the desired high electric energy storage densitiy. In this paper, the controlled crystallization technique was employed to synthesize glass-ceramic composites with addition of Gd2O3 in BaO-Na2O- Nb2O5- SiO2 glass system. The results show that both the dielectric constant and the breakdown strength of the glass-ceramic composites demonstrate an increasing tendency with the addition of Gd2O3 from 0 mol% to 7 mol% (relative to SiO2), being responsible for remarkable improvement of the energy storage density of the glass-ceramic composites from 1.7 J/cm3 to 4.7 J/cm3.

Abstract: The composites (-Al2O3+TiB2+TiC)/Al has been fabricated by using exothermic dispersion synthesis. Thermodynamic analysis indicated that the reaction between the Al and TiO2 can spontaneously occur due to the negative Gibbs free energy of the Al-TiO2 reaction system. With the increase of B4C/TiO2 mole ratios, the exothermic peaks increase move to the higher temperature and the corresponding ignite temperatures also increase. The reaction results indicate that when the B4C/TiO2＝0, the reinforcements are composed of -Al2O3, Al3Ti, with the increase of B4C/TiO2, the amount of Al3Ti decreases and the TiC and TiB2 form simultaneously. When the B4C/TiO2 increases to 1/3, the Al3Ti almost disappear and the reinforcements of the composites are consisted of -Al2O3, TiC and TiB2.