Key Engineering Materials Vols. 368-372

Abstract: To enhance the high-temperature stability of zirconate pyrochlore structures, one has to focus on their transformation to the disordered state, fluorite. An atomistic simulation calculation is presented in this paper to predict the propensity of rare earth zirconate pyrochlores to transform to fluorite at high temperature. By detailed calculation of defect formation energy of cation antisites and Frenkel pair, as well as their interactions, the mechanisms of disorder transformation are ascertained. The results show that the tendency of cation disorder is less than the anion’s and disorder transformation will accelerate in advanced stage. The calculation of defect energy in pyrozirconates with different cation on the A site have proved helpful in unraveling their different order-disorder transformation tendency.

Abstract: The positive temperature coefficient of resistivity (PTCR) behavior of semiconductive BaTiO3 ceramics is often explained by the Heywang model. However, Heywang model couldn’t explain some experimental phenomena of jump range more than 106. This paper considered that the migration of donors, electrons and holes has important influence on grain boundary effect. A differential equation about Fermi level was established on the base of Heywang model. By solving the equation the jump range can be calculated quantitatively. It was found that a potential well exists on the edge of grain due to the donor ionization, and the experimental phenomena of PTC jump range more than 106 could be explained.

Abstract: A scanning electron microscope (SEM) was used for observing the microstructures of a Mactridae shell. It showed that the shell is a kind of natural bioceramic composite, which consists of aragonite sheets and organic matrix with laminated structure. It also showed that there are various reinforced microstructures in the shell, which include a kind of lambdoidal one. The maximum pullout force of the lambdoidal reinforced microstructure, which is related to the fracture toughness of the shell, was analyzed and compared with that of a conventional 0°-structure based on their representative models. The result indicated that the maximum pullout force of the lambdoidal reinforced microstructure is markedly larger than that of the 0°-structure, which was experimentally verified.

Abstract: Performing ab-initio total-energy calculations to investigate the adsorption and diffusion processes of the Au atoms with both the clean Si(001)-(1×1) and H-terminated Si(001)-(2×1) surfaces. It was found that, on the clean Si(001)-(1×1) surface, the most stable adsorption sites for Au atoms are middle part of four Si atoms, while on H-terminated Si(001)-(2×1) surface, the most stable sites are the middle part of a Si-Si dimer. The result showed that surface hydrogenation make most stable site transfer and affect the adsorption of Au on Si(001) surface.

Abstract: In this work, a numerical simulation model is proposed with the purpose of determining the minimum and maximum measuring time for the hot wire parallel technique. An alternative experimental arrangement is also proposed for materials with thermal conductivity higher than 15W/mk. In this case, the experimental thermal transient is detected very close to surface of the hot wire, and it will be called hot wire surface technique. When using this arrangement, the time interval considered for the calculations may be several times bigger than that one corresponding to the parallel technique. Experimental results obtained with the surface technique are also checked against those ones obtained with the parallel technique.

Abstract: A novel templating method for preparing nanoporous materials has been developed. Spherical nickel phosphate particles synthesized through a homogeneous precipitation method were used as templates after annealing to fabricate porous metals. Effort of annealing temperature on the morphology of the spherical particles and the structure of outcome materials were studied. Hierarchical nanoporous metal with a high surface area was obtained using a template annealed at 200 oC.

Abstract: The activated Al-Sr alloy powder hydrolyzed in pure water to prepare Al(OH)3 and Sr(OH)2 composite powder and had been treated at the temperature of 700°C. The structure, properties and heat treatment of composite powder were investigated by XRD, SEM, BET, TG-DTG. The experimental results showed that the hydrolysate of Al-Sr alloy powder is the composite powder of Al(OH)3 and Sr(OH)2 by means of hydrolyzation reaction. The micrograph of the composite powder is piled up by many sheet powders of 1-3μm. The specific surface area is great, up to 45.2 m2/g. The experimental results also showed that, the crystalline water was dehydrated at 70-190°C and Sr(OH)2 and Al(OH)3 decomposed at 190-650°C. Their phase, micrograph and the surface area changed greatly after heat treatment at the temperature of 700°C for 1 h.

Abstract: The silica-alumina-pillared montmorillonite materials (SiAl-MMT) were developed by a novel method, which combined several techniques such as ion-exchange, intercalation and surfactant modification. The morphology, composite structure and pore properties of such composite materials, were investigated by X-ray powder diffraction (XRD), Scanning Electronic Microscopy (SEM), Fourier-transform infra-red (FTIR) spectra, as well as Nitrogen Adsorption-Desorption Isotherms. The layer structure of the prepared materials retained and their pore structures were found to be slit-shaped pores located between plate-like particles. The prepared SiAl-MMT materials had a BJH pore volume of 0.63cm3 g-1, a remarkably high BET specific surface area beyond 1000 m2 g-1, and a narrow pore size distribution in the mesoporous region 3.5-4 nm after thermal treatment at 600 °C.

Abstract: In this research, applications of different TiO2 electrode structures on Dye-Sensitized Solar Cell were investigated. The different TiO2 electrode structures include: (1) synthesis of TiO2 nano-particles and TiO2 film electrode by sol-gel and spin-coating method; (2) fabrication of the TiO2 film electrode by RF Sputtering; (3) fabrication of the rod TiO2 electrode by photo lithography. X-ray diffraction patterns show that the best sintering temperature of nano-TiO2 thin film is 500oC, at which TiO2 anatase phase forms best and the smallest particle-size (8-10 nm) can be obtained. Ultraviolet-visible absorption spectra reveal that the rod TiO2 electrode with TCPP sensitizer adsorbed on has the best optical absorption from 400 nm to 700 nm. The results of current-voltage analyses reveal that the solar cell with rod TiO2 electrode has higher conversion efficiency than the others. This result also provides clear evidence for the contact area between TiO2 electrode and TCPP sensitizer plays an important role on the efficiency of dye-sensitized solar cell.

Abstract: There are seven ceramic companies listed in Shanghai and Shenzhen Stock Exchanges. Because they belong to traditional industry sector, the profitability of most companies is weak. Listed companies experienced reform from 2005, and all of their shares can be liquid 12 or 24 months later. In the paper, we analyze the impact of the reform on those companies.