Microstructure and mechanical properties of high pressure die cast magnesium alloy AE42 with 1% strontium

The addition of 1 wt-%Sr to AE42 results in an improvement in the tensile strength of the alloy at elevated temperatures of 150 and 175degreesC and an improvement in the constant load creep properties at 175degreesC. The improved elevated temperature tensile and creep strength of the alloy can be attributed to the presence of a strontium-containing phase in the microstructure of the alloy along with an increase in the stability of the microstructure of the alloy at high temperatures. (C) 2004 W. S. Maney Son Ltd.

Formation and mechanical properties of Mg65Cu25Er10 and Mg65Cu15Ag10Er10 bulk amorphous alloys

Mg65Cu25Er10 and Mg65Cu15Ag10Er10 bulk amorphous alloys were produced by a copper mould casting method. The alloys have high glass-forming ability and good thermal stability. The maximum diameter of glass formation (D-c), glass transition temperature (T-g), crystallization onset temperature (T-x), temperature interval of the supercooled region (Delta T-x), melting temperature (T-m), liquidus temperature (T-1) as well as heats of crystallization (Delta H-x) and melting (Delta H-m) are reported for these alloys. Both alloys exhibit high hardness and high strength at room temperature. (c) 2005 Elsevier B.V. All rights reserved.

Structural and mechanical properties of nanostructured granular alumina catalysts

Granular gamma-Al2O3 support and 8 wt % CuO/gamma-Al2O3 catalyst were synthesized by a sol-gel granulation method. The pore structure, crush strength, hardness, and elasticity of these sol-gel-derived catalysts were studied and compared with similar commercial catalysts prepared by non-sol-gel methods. Alumina and CuO-coated alumina granular particles prepared by different methods have different macro- and microstructure. The sol-gel-derived granular gamma-alumina and CuO-coated gamma-alumina granular particles have a structure defined by compact packing of uniform, nanosized gamma-alumina crystallites. They are characterized by a more uniform pore size distribution and larger surface area as compared to similar commercial samples with a structure defined by packing of aggregates consisting of nonuniform gamma-alumina crystallites. Because of the differences in the macro- and microstructure, the sol-gel-derived granular samples offer higher crush strength and greater hardness than the commercial samples.

Impacts of morphological, physical and chemical properties of sludge flocs on dewaterability of activated sludge

This study examined how the floc characteristics affect dewaterability of activated sludge. The floc properties were characterized by morphological parameters (floc size distribution, fractal dimension and filament index), physical properties (flocculating ability, surface charge, relative hydrophobicity and viscosity), and chemical constituents in sludge and extracted extracellular polymeric substances (EPS), including the polymeric compounds protein, humic substances, carbohydrates and the ions Ca2+, Mg2+, Fe3+ and Al3+. The dewaterability was defined in terms of the bound water content and capillary suction time (CST). The bound water and CST corresponded to a similar indication with respect to dewaterability of activated sludge. The floc physical parameters were the most important factors which effect significantly on the water binding ability of the sludge flocs. The morphological characteristics had relatively weak impact on the dewaterability. The polymeric components protein and carbohydrate had a significant contribution to enhance the water binding ability of the sludge flocs. The effect of humic substances in the sludge on the dewaterability was, however, insignificant. The CST had good statistical correlations with the polymeric constituents measured in both sludge and the extracted EPS, and the bound water was only correlated well with the individual polymers measured in the sludge. High concentration of Ca2+, Mg2+, Fe3+ and Al3+ had significant improvement for dewaterability. (C) 2003 Elsevier B.V. All rights reserved.

Characterizing the physical and chemical properties of a vermicompost filter bed

Vermicompost filtration is a new on-site waste treatment system. Consequently, little is known about the filter medium properties. The aim of this preliminary study was to quantify physical and compositional properties of vermicompost filter beds that had been used to treat domestic solid organic waste and wastewater. This paper presents the trials performed on pilot-scale reactors filled with vermicompost from a full-scale vermicompost filtration system. Household solid organic waste and raw wastewater at the rate of 130 L/m(2)/d was applied to the reactor bed surface over a four-month period. It was found that fresh casts laid on the bed surface had a BOD of 1290 mg/g VS while casts buried to a depth of 10 cm had a BOD of 605 mg/g VS. Below this depth there was little further biodegradation of earthworm casts despite cast ages of up to five years. Solid material in the reactor accounted for only 7-10% of the reactor volume. The total voidage comprised of large free-draining pores, which accounted for 15-20% of the reactor volume and 60-70% micropores, able to hold up water against gravity. It was shown that water could flow through the medium micropores and macropores following a wastewater application. The wastewater flow characteristics were modeled by a two-region model based on the Richards Equation, an equation used to describe porous spatially heterogeneous materials.

Synthesis and mechanical properties of Cu-based bulk metallic glass composites containing in-situ TiC particles

Cu-based bulk metallic glass matrix composites (BMGMCs) containing in-situ TiC particles were fabricated successfully. The yield and fracture strength increased from 1930 MPa, 2250 MPa to 2210 MPa, 2500 MPa, respectively. The ductility was improved and the hardness was also enhanced by 25%. The fracture mechanism was investigated in detail. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The physical and chemical properties of eumelanin

In this article, we review the current state of knowledge concerning the physical and chemical properties of the eumelanin pigment. We examine properties related to its photoprotective functionality, and draw the crucial link between fundamental molecular structure and observable macroscopic behaviour. Where necessary, we also briefly review certain aspects of the pheomelanin literature to draw relevant comparison. A full understanding of melanin function, and indeed its role in retarding or promoting the disease state, can only be obtained through a full mapping of key structure-property relationships in the main pigment types. We are engaged in such an endeavor for the case of eumelanin.

The effect of organic mulch amendments on the physical and chemical properties and revegetation success of a saline-sodic minespoil from central Queensland, Australia

Saline-sodic clay minespoil materials excavated during open-cut coal mining in central Queensland, Australia, pose significant challenges for revegetation, particularly where suitable topsoil capping is not available. We examined the ability of sawdust or straw mulch amendments to ameliorate the adverse properties of these minespoils and improve the success of revegetation efforts. In laboratory studies, mulch application improved infiltration, increased soil moisture retention and reduced surface crust strength. In the field, mulches incorporated to a depth of 0.15 m at application rates of at least 20 t/ha straw or 80 t/ha sawdust were needed to mitigate against capillary rise of salts during drying cycles and support satisfactory vegetation cover. Further research is needed to determine whether improvements are maintained beyond the 4-year trial period reported here.

The effect of aluminium content on the mechanical properties and microstructure of die cast binary magnesium-aluminium alloys

This paper investigates the relationship between mechanical properties and microstructure in high pressure die cast binary Mg-Al alloys. As-cast test bars produced using high pressure die casting have been tested in tension in order to determine the properties for castings produced using this technique. It has been shown that increasing aluminium levels results in increases in yield strength and a decrease in ductility for these alloys. Higher aluminium levels also result in a decrease in creep rate at 150 degrees C. It has also been shown that an increase in aluminium levels results in an increase in the volume fraction of eutectic Mg17Al12 in the microstructure.

Effect of over-doped yttrium on the microstructure, mechanical properties and thermal properties of a Zr-based metallic glass

The effects of over-doped yttrium on the microstructure, mechanical properties and thermal behaviour of an oxygen-contaminated Zr51Cu20.7Ni12Al16.3 bulk metallic glass are studied systematically. It has been found that, when yttrium doping is beyond the optimum doping, the glass-forming ability enhancement effect induced by yttrium addition decreases and the mechanical properties are adversely affected. In this study, a new phase with an orthorhombic structure (a = 0.69 nm, b = 0.75 nm and c = 0.74 nm) is identified in the yttrium over-doped alloys. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.