Li2CO3 – Al2O3 Composite Solid Electrolytes Prepared by Sol Gel Method

Composite solid electrolytes in the system (1-x)Li2CO3-xAl2O3, where x = 0.1–0.7 were prepared by sol gel method using lithium carbonate and aluminum oxide precursors in ethanol. The gels obtained due to the addition of citric acid were calcined at 80 and 100 oC. Their structural, thermodynamic and electrical properties were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. The results indicated that interface phases of crystalline and amorphous exist in this composite system of (1-x)Li2CO3-xAl2O3. The presence of the interface phases are due to the chemical and physical interactions between both crystalline Li2CO3 and Al2O3. The Arrhenius plot of the composite system showed non-linear curves and reached maximum values of ∼10−4 - 10−5 S cm-1 at 150 -180 °C. Based on the results of this study, it can be concluded that the sol gel method used in the preparation of the composite system, has an important role to crystal morphology changes that results in high ionic conductivity.

Microstructure and Mechanical Property of Al2O3/Y3Al5O12 (YAG) Eutectic Ceramic In Situ Composite Prepared by Laser Zone Melting

Directionally solidified Alumina-based eutectic ceramic in situ composite is a kind of promising candidate for high temperature structural material applied at elevated temperature above 1923K because of its excellent properties. With laser zone melting directional solidification, Al2O3/Y3Al5O12 (YAG) eutectic ceramics are successfully prepared. The relationship between the eutectic microstructure and the processing parameter is studied, and the mechanical property of the composite is measured. The results show that: (1) Laser power density and scanning rate strongly affect the eutectic microstructure. With proper processing parameters adjusted, the binary lamellar eutectic microstructure is obtained, in which Al2O3 and YAG phases are three-dimensionally coupled and continuously connected without grain boundaries and amorphous interface phases. (2) The eutectic spacing decreases to about 1μm with increasing scanning rate. (3) The maximum hardness of 19.5GPa and the room fracture toughness of 3.6MPa.m1/2 are obtained by Vickers indentation measurement.

Parametric study of the effect of phase anisotropy on the micromechanical behaviour of dentin–adhesive interfaces

A finite element (FE) model has been developed based upon the recently measured micro-scale morphological, chemical and mechanical properties of dentin–adhesive (d–a) interfaces using confocal Raman microspectroscopy and scanning acoustic microscopy (SAM). The results computed from this FE model indicated that the stress distributions and concentrations are affected by the micro-scale elastic properties of various phases composing the d–a interface. However, these computations were performed assuming isotropic material properties for the d–a interface. The d–a interface components, such as the peritubular and intertubular dentin, the partially demineralized dentin and the so-called ‘hybrid layer’ adhesive-collagen composite, are probably anisotropic. In this paper, the FE model is extended to account for the probable anisotropic properties of these d–a interface phases. A parametric study is performed to study the effect of anisotropy on the micromechanical stress distributions in the hybrid layer and the peritubular dentin phases of the d–a interface. It is found that the anisotropy of the phases affects the region and extent of stress concentration as well as the location of the maximum stress concentrations. Thus, the anisotropy of the phases could effect the probable location of failure initiation, whether in the peritubular region or in the hybrid layer.

A New Numerical Model for Electron-Probe Analysis at High Depth Resolution

Characterizing dimensionally and chemically nanometric structures such as surface segregation or interface phases can be performed efficiently using electron probe (EP) techniques at very low excitation conditions, i.e. using small incident energies (0.5<E0<5 keV) and low incident overvoltages (1<U0<1.7). In such extreme conditions, classical analytical EP models are generally pushed to their validity limits in terms of accuracy and physical consistency, and Monte-Carlo simulations are not convenient solutions as routine tools, because of their cost in computing time. In this context, we have developed an intermediate procedure, called IntriX, in which the ionization depth distributions Φ(ρz) are numerically reconstructed by integration of basic macroscopic physical parameters describing the electron beam/matter interaction, all of them being available under pre-established analytical forms. IntriX’s procedure consists in dividing the ionization depth distribution into three separate contributions:

Microstructure and contact-resistance temperature dependence of Pt/Ti/Ge/Pd ohmic contacts to GaAs

The development of GaAs device technology has demonstrated the need for fabrication of low resistance thermally stable ohmic contacts. Gold based contacts have been the overwhelming choice for ohmic contacts in device applications. In particular, Au/Ge/Ni and Zn/Au alloyed contacts have been used for n and p-GaAs respectively. Numerous investigations have shown that Au-based contacts to GaAs have avery complex morphology after annealing. Specifically, structural interface inhomogeneities, such as protrusions and newly formed lateral interface phases lead to non-planar metalsemiconductor interfaces which in turn cause nonuniform current flow and consumption of the GaAs substrate. This type of interface morphology is not acceptable for device applications where a large electrical field or a shallow contact is required. In particular, devices such as heterojunction bipolar transistors (HBT's) cannot tolerate contacts with lateral and vertical interface inhomogeneities.This study employed crosssectional transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and electrical measurements (transmission line mode), to systematically investigate the structural, chemical and electrical properties of the Pt/Ti/Ge/Pd contacts to both n and p+ GaAs as a function of annealing temperatures.