Effects of Homogenization Treatment on Dispersoid Characteristics and Recrystallization Behavior in an Al-Zn-Mg-Cu-Zr Alloy

In the present research, a comprehensive study on the effect of the homogenization treatment on the characteristics of dispersoid and recrystallization behavior in an Al-Zn-Mg-Cu-Zr alloy has been conducted by means of optical micrography, scanning electron micrography and transmission electron micrography. The influence of three process parameters of the homogenization treatment, first stage holding temperature, holding time and heating rate, on the dispersoid characteristics has been throughly studied. The result shows that holding at 400°C for sufficient time is highly beneficial for obtaining fine and uniformly distributed Al3Zr particles. Compared with the high heating rate treatment, the slow one apparently leads to significantly smaller Al3Zr dispersoids, the dimension of the dispersoids decreases from 35 nm to 22 nm, and the number density of Al3Zr particle in the center of the grains increases from 13/μm2 to 35/μm2. The percentage of recrystallized grains of the alloy is found to be affected by dispersoid distribution.

Design of novel high-performance Al–Cu–Mg alloys containing Zn and Li

To design novel high-performance aluminium alloys, the properties and microstructure of Al–4.2Cu–1.4Mg alloy containing Zn and Li have been investigated by tensile tests, fatigue crack propagation test, slow strain-rate tensile test, Kahn tear test, scanning electron micrography and transmission electron micrography. The stress corrosion cracking resistance and toughness of Al–4.2Cu–1.2Mg alloy can be markedly improved by small Zn addition. Independent Li addition has no significant effect on the corrosion resistance of Al–4.2Cu–1.2Mg alloy, but the tensile strength is improved and the fatigue crack propagation is restrained. Small Zn addition promotes the precipitation of S′ phase during age treatment, and the grain boundary precipitates are scarcer than those of the base alloy. The co-effect of Li and Zn addition promotes the fine and dispersed precipitation of the S′ (non-equilibrium Al2CuMg) phases in Al–4.2Cu–1.2Mg alloy. The comprehensive performance (the fracture toughness, tensile properties, stress corrosion resistance and fatigue crack propagation resistance) of Al–4.2Cu–1.2Mg alloy with 0.25% Zn and 1.0%Li is outstanding. This alloy could lay the foundation for the design of new aluminium alloys.

On Monocarpus (Monocarpaceae, Marchantiopsida), an isolated salt-pan complex thalloid liverwort

The phylogenetic placement of Monocarpus sphaerocarpus D.J.Carr (Monocarpaceae), a member of the complex thalloid liverworts with highly specialised morphology, presumably related to its saltpan habitat, has been determined on the basis of molecular data. Within the complex thalloid liverworts, Monocarpus resolves as sister to the Sphaerocarpales clade. A new line drawing of Monocarpus is provided, as are the first colour photographs of living plants. Detailed ornamentation of the spores of Monocarpus collections from Australia and South Africa, as revealed by scanning electron micrography, is reported, and some of the morphological features that unite and separate Monocarpus and the Sphaerocarpales s.str. are discussed.

The Effect of Tribomechanical Micronization and Activation on Rheological, Thermophysical, and Some Physical Properties of Tapioca Starch

The aim of this research was to investigate the effect of tribomechanical treatments on rheological, thermophysical, and some physical properties of tapioca starch. Samples of tapioca starch were treated using laboratory equipment for tribomechanical micronization and activation (TMA equipment). Before and after the TMA treatment, analysis of the particle size and particle size distribution was carried out, in addition to scanning electron micrography in tapioca starch. Scanning electron micrography showed that tribomechanical processing of tapioca starch resulted in breaking accumulations of starch granules in the form of granules. Pasting parameters have shown that maximal viscosities of model starch suspension have been decreasing after tribomechanical treatment. On the basis of gelatinization curves, it can be concluded that there are changes in the gelatinization point after treatment, and there is decrease in enthalpy of gelatinization for model suspension. After tribomechanical treatment, changes in physical properties of starch suspensions were determined, as well as specific swelling capacity, solubility index, and turbidity of tapioca starch suspensions.

Mesoporous Co–B amorphous alloy films with enhanced catalytic efficiency prepared from a mixed-surfactant solution

Co–B films were synthesized through the solvent evaporation-assisted chemical reduction method by using a mixed-surfactant solution containing Span 40 and (1S)-(+)-10-camphorsulfonic acid. With the characterization of x-ray diffraction, selected-area electron diffraction, x-ray photoelectron spectroscopy, scanning electron micrography, and transmission electron micrography, the resulting Co–B films were identified to be amorphous alloys with mesoporous structure. The synergistic effect of two kinds of surfactants is essential for the formation of mesoporous structure. During liquid-phase cinnamaldehyde hydrogenation to cinnamyl alcohol, the mesoporous Co–B amorphous alloy films exhibited a much higher activity and better selectivity than the solid Co–B nanoparticles prepared by direct reduction of cobalt ions with borohydride. The enhanced activity is attributed to both the mesoporous and the film structure, which provides more Co active sites for the adsorption and diffusion of reactant molecules. The improved selectivity may be related to the difference in surface curvature.