Corrosion of aluminium metal in OPC- and CAC-based cement matrices

Corrosion of aluminium metal in ordinary Portland cement (OPC) based pastes produces hydrogen gas and expansive reaction products causing problems for the encapsulation of aluminium containing nuclear wastes. Although corrosion of aluminium in cements has been long known, the extent of aluminium corrosion in the cement matrices and effects of such reaction on the cement phases are not well established. The present study investigates the corrosion reaction of aluminium in OPC, OPC-blast furnace slag (BFS) and calcium aluminate cement (CAC) based systems. The total amount of aluminium able to corrode in an OPC and 4:1 BFS:OPC system was determined, and the correlation between the amount of calcium hydroxide in the system and the reaction of aluminium obtained. It was also shown that a CAC-based system could offer a potential matrix to incorporate aluminium metal with a further reduction of pH by introduction of phosphate, producing a calcium phosphate cement

Direct electrodeposition of aluminium nano-rods

Electrodeposition of aluminium within an alumina nano-structured template, for use as high surface area current collectors in Li-ion microbatteries, was investigated. The aluminium electrodeposition was carried out in the ionic liquid 1-ethyl-3-methylimidazolium chloride:aluminium chloride (1:2 ratio). First the aluminium electrodeposition process was confirmed by combined cyclic voltammetry and electrochemical quartz crystal microbalance measurements. Then, aluminium was electrodeposited under pulsed-potential conditions within ordered alumina membranes. A careful removal of the alumina template unveiled free standing arrays of aluminium nano-rods. The nano-columns shape and dimensions are directly related to the template dimensions. To our knowledge, this is the first time that direct electrodeposition of aluminium nano-pillars onto an aluminium substrate is reported

Advances in the Production of Infiltrated Aluminium Parts Using Selective Laser Sintering

Recent advances in a rapid freeform fabrication process for the production of aluminium parts are considered. The methodology involves the formation of an unconstrained, resin bonded aluminium powder part by Selective Laser Sintering, the burnout of the resin, the partial transformation of the aluminium into a rigid aluminium nitride skeleton by reaction with the atmosphere under a magnesium/alumina blanket and the subsequent infiltration with a second aluminium alloy. Here we describe the process and consider potential applications. Strategies for controlling the growth of the aluminium nitride are also to be discussed.Mechanical Engineerin

Palladium gates for reproducible quantum dots in silicon

We replace the established aluminium gates for the formation of quantum dots in silicon with gates made from palladium. We study the morphology of both aluminium and palladium gates with transmission electron microscopy. The native aluminium oxide is found to be formed all around the aluminium gates, which could lead to the formation of unintentional dots. Therefore, we report on a novel fabrication route that replaces aluminium and its native oxide by palladium with atomic-layer-deposition-grown aluminium oxide. Using this approach, we show the formation of low-disorder gate-defined quantum dots, which are reproducibly fabricated. Furthermore, palladium enables us to further shrink the gate design, allowing us to perform electron transport measurements in the few-electron regime in devices comprising only two gate layers, a major technological advancement. It remains to be seen, whether the introduction of palladium gates can improve the excellent results on electron and nuclear spin qubits defined with an aluminium gate stack

Applications solution using the system 2000 graphite furnace

In patients with chronic renal failure, on treatment with haemodialysis, clinical symptoms may develop, which are associated with abnormally high levels of aluminium in the blood and tissues. Such patients are exposed to aluminium via the dialysate fluid, from dietary sources, and from the ingestion of aluminium-containing antacids given to reduce phosphate absorption in the gut. Serum and plasma are now established as the most suitable body fluids for monitoring aluminium levels in these patients.peer-reviewe

Effects of flux application and melting parameters in investment casting of pure aluminium by in-situ melting technique

Investment cast aluminium suffers porosity defect attributed to the complex combination of various factors including melt quality, casting process parameter and pouring technique. Even though, melt treatment and controlled of the process parameter have promising result, however turbulence developed during pouring of molten aluminium increasing the formation of porosity as a result of the entrainment of the surface oxide (Al2O3) film known as bifilm. Currently, turbulence free filling system was applied in casting process using tilt casting, bottom filling integrated with low pressure and also in-situ casting or in-situ melting techniques to address the porosity problem. However, in-situ melting technique has not been studied to reduce the porosity of the investment cast aluminium due to the oxidation of the granular aluminium occurs during heating hinders the complete melting of the granules. This research develops a procedure for investment casting of aluminium granules of 99.4% purity by in-situ melting technique. The aluminium granules were filled in ceramic moulds and heated at four different temperatures of 700, 750, 800 and 850oC for 30 and 60 min in a high temperature muffle furnace in ambient. As the heating temperature and duration were increased, the aluminium granules incompletely melt and produced a casting, however the granules agglomerate and replicate the shape of the ceramic mould. The aluminium granules oxidised during heating, encapsulated by a layer of complex oxides composed of stable [α-Al2O3], metastable [γ-Al2O3] and hydroxides. The thickness of the oxide layer formed on the surface of the air-heated granules increased as the heating temperature and duration were increased. The aluminium granules then were heated at the temperature of 850oC for 30 min in argon environment at the flow rate of argon gas 0.5, 2.5 and 5 l/min to reduce the oxidation of the aluminium granules. The thickness of the oxide layer formed on the argon-heated granule (5 l/min) was reduced by 60%, but failed to produce a casting. NaCl-KCl flux was applied, which was mixed and sprinkled on the aluminium granules at the Al:Flux ratio of 1:0.2, 1:0.25 and 1:0.33 and heated at the temperature of 850oC for 30 min to break the oxide layer that encapsulate the granules during heating. At the Al:Flux ratio of 1:0.33, 99% of the aluminium granules were successfully melted and produced a casting. The granules began melting at the temperature range 657.2 to 658.4oC and completely melted in 16 min with final melting temperature between 660.1 and 660.6oC. The average porosity level of the casting was 1.22%, which is lower than the investment cast aluminium produced by current pouring technique (2.48%). The low porosity level was attributed to micro-intergranular porosity present in the casting due to volume shrinkage. Investment casting of aluminium granules by in-situ melting technique with application of NaCl-KCl flux at the Al:Flux ratio of 1:0.33 mixed and sprinkled on the granules heated at the temperature of 850oC for 30 min producing low porosity aluminium casting

Interaction of aluminium hydrolytic species with biomolecules

In this contribution the formation of bioinorganic assemblies between the basic globular protein lysozyme and aqueous aluminium species including Al 13 -mer, Al 30 -mer and colloidal aluminium hydroxide have been explored and comparison made to previous interaction studies performed with bovine serum albumin (BSA). Specific charge-stabilised bioinorganic assemblies involving aluminium species and lysozyme were observed to form in contrast to the gel like structures formed on interaction of BSA with aluminium species. As demonstrated by infrared spectroscopy (structural assignment, 2D correlation spectroscopy), interactions mostly involve acidic surface groups of the proteins (Asp, Glu), with strong complexation and deprotonation in the case of BSA interacting with Al 13 and Al 30 and through hydrogen bonding for lysozyme interacting with the same species and aluminium hydroxide particles interacting with both biomolecules

Specific heat of aluminium-doped superconducting silicon carbide

The discoveries of superconductivity in heavily boron-doped diamond, silicon and silicon carbide renewed the interest in the ground states of charge-carrier doped wide-gap semiconductors. Recently, aluminium doping in silicon carbide successfully yielded a metallic phase from which at high aluminium concentrations superconductivity emerges. Here, we present a specific-heat study on superconducting aluminium-doped silicon carbide. We observe a clear jump anomaly at the superconducting transition temperature 1.5 K indicating that aluminium-doped silicon carbide is a bulk superconductor. An analysis of the jump anomaly suggests BCS-like phonon-mediated superconductivity in this system.Comment: 4 pages, 2 figure

Experimental study of sandwich structures as armour against medium-velocity impacts

An experimental impact study has been conducted on sandwich structures to identify and improve armour solutions for aeronautical applications. The objectives are to find the best configurations, i.e. the non-perforated targets with the minimal weight and back deformations. Medium-velocity impacts (120 m/s) have been conducted using a 127 g spherical projectile. The targets are simply supported at the rear of the structure. Two potential choices of front skin have been identified for the sandwich structure: 3 mm thick AA5086-H111 aluminium plates and dry aramid stitched fabrics (between 8 and 18 plies). The dry stitched fabrics appear to be an original solution, which associates a lightweight structure and a good perforation resistance. Moreover, a strong coupling has been found between the front skin and the core. The impact tests indicate that aluminium honeycomb core associated with aluminium skins show mitigated results. However, the combination of dry fabric front skin and aluminium honeycomb show better performances than aluminium sandwiches, with a global weight decrease

Modelling of the low-impulse blast behaviour of fibre–metal laminates based on different aluminium alloys

A parametric study has been undertaken in order to investigate the influence of the properties of the aluminium alloy on the blast response of fibre–metal laminates (FMLs). The finite element (FE) models have been developed and validated using experimental data from tests on FMLs based on a 2024-O aluminium alloy and a woven glass–fibre/polypropylene composite (GFPP). A vectorized user material subroutine (VUMAT) was employed to define Hashin’s 3D rate-dependant damage constitutive model of the GFPP. Using the validated models, a parametric study has been carried out to investigate the blast resistance of FML panels based on the four aluminium alloys, namely 2024-O, 2024-T3, 6061-T6 and 7075-T6. It has been shown that there is an approximation linear relationship between the dimensionless back face displacement and the dimensionless impulse for all aluminium alloys investigated here. It has also shown that the residual displacement of back surface of the FML panels and the internal debonding are dependent on the yield strength of the aluminium alloy