Effect of nano-Al2O3 addition on the densification of YSZ electrolytes

This work investigates the effect of nanosized Al2O3 addition on the sinterability of YSZ electrolyte. (1-x)YSZ + Al2O3 ceramics with compositions x = 0 to 0.01 were prepared by the conventional mixed oxide route from a commercial powder suspension (particle size <50 nm), and sintered at 1200 to 1500 degrees C for 2 hours in air. Densification, phase evolution, and microstructure were characterized by SEM/EDS and XRD. An improvement in sintered density was observed for the samples with 0.2 to 0.5 mol% Al2O3, though depending on the sintering temperature. Only cubic zirconia was detected as crystalline phase, although XRD features suggested chemical interactions depending upon the amount of Al2O3. The grain size of YSZ was homogeneous and no second phase segregation was detected in the tested range of incorporated nano-Al2O3 and sintering temperatures.

Effects of the density on compressive properties in cellular aluminum produced by the sintering method

The cellular aluminum materials with relative densities of 0.1"-'0.25 were fabricated by the sintering method and effects of the density on mechanical properties of the cellular aluminum were investigated by compressive tests. The cellular aluminum exhibited a plateau region with a nearly constant flow stress. The stress in the plateau region increased with increasing relative density, on the other hand, the densification strain decreased with increasing relative density. Observation of the deformed cells revealed that the cell walls were bent. Besides, the stress in the plateau region was proportional to 1.9 power of the density. These suggest that plastic collapse is dominated by bending of the cell walls for the cellular aluminum produced by the sintering method.

Towards elucidating microscopic structural changes in Li-ion conductors Li1+yTi2–yAly[PO4 ]3 and Li1+yTi2–yAly[PO4 ]3–x [MO4 ]x(M=V and Nb) : X-ray and27Al and31P NMR studies

A combination of X-ray powder diffraction (XRD) and nuclear magnetic resonance (NMR) studies has demonstrated that attempted substitutions of Al, V and Nb into the framework of LiTi₂(PO₄)₃ yield several impurity phases in addition to direct substitutions of Al into Ti and V, Nb into P sites. Direct substitutions were confirmed by changes in the unit cell dimensions as indicated by the peak shifts observed in the X-ray diffractographs and by analyses of the ²⁷Al and ³¹P magic angle spinning (MAS) spectra. A major impurity phase was identified as AlPO₄ (found in at least two polymorphs) and the amount present increases with increasing Al additions. The formation of AlPO₄ appeared to be enhanced by further V but suppressed by Nb substitution. These results suggest that the presence of AlPO₄ , together with the non-stoichiometric modified LTP, may be the cause for the observed densification of this material upon sintering and the increased ionic conductivity.

A framework to determine if Australia's suburbs have ever been sustainable

Australia is a suburban society. It has been since Europeans came. Unlike many other urban societies at the time, there was no existing hard infrastructure to provide the essential needs of human urban life - clean water, food, shelter and waste management. These had to be met by individual residents in the emerging cities and towns until infrastructure could be provided to local communities by Government. This reality led to Governor Phillip establishing the block size in Sydney as being large enough to provide food and treat waste within its boundaries. The block dimensions were a major influence on Australia’s urban form for the next two centuries and with social developments not only led to low density urban form, but also fostered a strong connection with the backyard and a societal love of gardening at home. Despite a push to densification in the past two decades, low density suburban form is physical and cultural and is likely to be dominant for the foreseeable future. Gardening at home is also likely to continue to be a favourite pass time. While some Australian research has started to explore the role of backyards and gardening in increasing urban sustainability, little work has been done on to what extent the suburban block has and can meet the core needs of people. Even less has been done on determining the impact of suburbs on underlying ecosystem services that provide these core needs. This paper provides a brief history of backyards in suburban Australia, a conceptual framework for assessing the sustainability of Australian suburbs over time and a description of the major ecosystem types in what is now urban Geelong at the time of European settlement. It provides the foundation for future sustainability assessments of the residential block in various periods of suburban development in Geelong.

Temperature-dependence of mechanical properties of open-cell titanium foam

An open-cell titanium foam with relative density of 0.2 was prepared by powder metallurgical process. The compressive mechanical properties of the foam at the different temperatures in the range of 20-600°C were measured and the temperature-dependence of its mechanical properties was discussed. The results indicate that the foam material exhibit fragile fracture characteristic at room temperature. When it is deformed over 200°C, the stress-strain curves exhibit plastic deformation characteristic, including three distinct regions: the linear elasticity region, the plastic collapse region, and the densification region. The Young's modulus, yield stress and elastic limit decrease with increasing of temperature. The temperature-dependence of these properties can be expressed as E*=1.5217 × 10 9-5.988 × 10 5T, σ cl*=85.7-0.095T, σ ys*=99.1-0.167V7.02 × 10 -5T 2 respectively.

Compressibility of a Ti-based alloy with varying amounts of surfactant prepared by high-energy ball milling

The combined effects of varying amounts of surfactant (ethylene bis-stearamide; EBS) and milling time on the compressibility of ball-milled Ti-10Nb-3Mo (wt.%) alloy were investigated. Ball milling process was performed on the elemental powders with different amounts of EBS (0-3. wt.%) for 5 and 10. h, and the ball-milled powders were consolidated by a uniaxial cold pressing in the range of 500-1100. MPa. Results indicated that the addition of surfactant in ball milling process lead to significant changes in particle packing density. The relative density was higher for powders ball milled with larger amounts of EBS and for the shorter milling time. The compressibility of powders was examined by the compaction equation developed by Panelli and Ambrosio Filho. The densification parameter (A) increased with the increasing amount of EBS, and decreased with increasing milling time.

Comparison of different extrusion methods for compaction of powders

Densification of metallic powders by means of extrusion is regarded as a very attractive processing technique that allows obtaining a high level of relative density of the compact. However, the uniformity of the relative density depends on that of strain distribution and on the processing parameters. Several variants of extrusion can be used for compaction of metal particulates, including the conventional extrusion (CE) and equal channel angular pressing (ECAP), often referred to as equal-channel angular extrusion. Each of these processes has certain advantages and drawbacks with respect to compaction. A comparative study of these two extrusion processes influencing the relative density of compacts has been conducted by numerical simulation using commercial finite element software DEFORM2D. The results have been validated by experiments with titanium and magnesium powders and chips.