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Interfacial reaction and microstructure evolution in a Zr2Al3C4 reinforced Cu composite were studied by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Decomposition of Zr2Al3C4 was triggered by the deintercalation of Al atoms. In the initial reaction stage, depletion of Al occurred locally. ZrC and Cu platelets as well as thin twinned ZrC slices were observed inside the Zr2Al3C4 grains. In the later reaction stage, all Al atoms depleted from Zr2Al3C4 and were dissolute into the Cu matrix. The final reaction products were a Cu-Al solid solution, ZrC0.5, and highly disordered graphite, which resulted in large volume shrinkage. These experimental results provided a baseline for controlling interfacial reaction and microstructure development in Cu/Zr2Al3C4-based particle-reinforced Cu composites for optimized mechanical and electrical properties. [ABSTRACT FROM AUTHOR]

Diffusion bonding of Ti3SiC2 and nickel has been conducted at temperatures of 800 °C-1100 °C for 10-90 min under 6-20 MPa in a vacuum. The phase composition and microstructure of the joints were investigated by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The total diffusion path of the joining is determined to be Ni/Ni31Si12 + Ni16Ti6Si7 + TiCx/Ti3SiC2 + Ti2Ni + TiCx/ Ti3SiC2. The growth of the reaction layer follows parabolic law, and the temperature dependence of the reaction constant, k, can be expressed as k = 1.68 x 10-4 exp(-118 ± 12 kJ/RT) m/s 1/2. The diffusion of nickel through the reaction zone toward Ti3SiC2 is the main controlling step in the bonding process. Joint strengths were determined through shear tests. The maximum shear strength of 121 ± 7 MPa, which is close to the shear strength of Ti3SiC2, has been obtained under the condition of 1000 °C for 10 min under 20 MPa. [ABSTRACT FROM AUTHOR]

In order to meet increasing requirement for the evaluation and design of damage tolerance of brittle materials, a simple expression was proposed to estimate the damage tolerance quantitatively using basic material parameters, based on the features of damage tolerance and fracture mechanics. The calculated results from this equation indicated that the damage tolerance of nanolayer grained ceramics was over 10 times higher than that of some brittle ceramics, while glass has the lowest damage tolerance. Therefore, the damage tolerance of various ceramics can be estimated directly using their basic properties data without the necessity of additional tests. SEM examination and finite element simulation showed that the high damage tolerance of the layer grained ceramics was attributed to delamination in grains, interlocking microstructures and crack deflection. [ABSTRACT FROM AUTHOR]

The microstructural characteristics of the bulk Ti 3 AlC 2 ceramic, synthesized by a solid-liquid reaction and simultaneous in-situ hot pressing, have been studied by electron diffraction and high-resolution transmission electron microscopy. It was found that the as-synthesized ceramic is fully dense and free from amorphous phase at the grain boundaries. The ceramic is predominantly a single phase of hexagonal Ti 3 AlC 2 with a minor volume of tetragonal Al 3 Ti and cubic TiC. The Al 3 Ti grains are crystallographically independent of the Ti 3 AlC 2 , whereas TiC is intergrown with Ti 3 AlC 2 , forming thin platelets and maintaining a close orientational relationship with the Ti 3 AlC 2 matrix. [ABSTRACT FROM AUTHOR]

The nanocrystalline nickel coating was synthesized by pulse-jet electrodeposition from modified Watts bath. Pulse and jet plating was employed to increase the deposition current density, decrease diffusion layer, increase the nucleation rate and in this case the prepared method would result in fine-grained deposits. Transmission and scanning electron microscopy and X-ray diffraction (XRD) were used to study the microstructure, the surface morphology, the crystal preferred orientation and the variety of the lattice parameter respectively. The influence of pulse parameters, namely peak current density, the duty cycle and pulse frequency on the grain size, surface morphology, crystal orientation and microstructure was studied. The results showed that with increasing peak current density, the deposit grain size was found to decrease markedly in other parameters at constant. However, in our experiment it was found that the grain size increased slightly with increasing pulse frequency. For higher peak current density, the surface morphology was smoother. The crystal orientation progressively changed from an almost random distribution to a strong (111) texture. This means that the peak current density was the dominated parameter to effect the microstructure of electrodeposited nanocrystalline nickel coating. In addition, the lattice parameter for the deposited nickel is calculated from XRD and it is found that the calculated value is less than the lattice parameter for the perfect nickel single crystal. This phenomenon is explained by the crystal lattice mismatch. [ABSTRACT FROM AUTHOR]

The effects of europium (Eu) content on the microstructure, fatigue endurance, leakage current density, and remnant polarization (2Pr) of Bi4-xEuxTi3O12 (BET) thin films prepared by metal-organic decomposition method at 700 °C annealing temperature were studied in detail. The results showed that 2Pr (82 μC/cm2 under 300 kV/cm), fatigue endurance (2% loss of 2Pr after 9.0×109 switching cycles), and leakage current density (1×10-8 A/cm2 at 200 kV/cm) of BET thin film with x=0.85 are better than those of thin films with other contents. Additionally, the mechanism concerning the dependence of ferroelectric properties on Eu content was discussed. [ABSTRACT FROM AUTHOR]

In this letter, we report the predictions on the effective piezoelectric coefficients and electromechanical coupling factors of ferroelectric ceramics BaTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) with various fiber textures, including [001], [011], and [111], using a two-scale micromechanical model that accounts for microstructural phenomena at both domain and grain levels. It was observed that for BaTiO3 the [011] texture is optimal with highest d31 and d33, while for PMN-PT [001] texture is optimal despite the fact that [011]-oriented single-crystalline PMN-PT has higher d32 than that of [001]-oriented PMN-PT single crystal. In fact, [011]-textured PMN-PT ceramics have much smaller piezoelectric coefficients d32 and d33 than does [011]-oriented PMN-PT single crystal. It is also noted that [001]-textured BaTiO3 and PMN-PT ceramics have even higher electromechanical coupling factor k31 than that of [001]-oriented single crystals. [ABSTRACT FROM AUTHOR]