A comparison of phosphorus and fluorine containing IL lubricants for steel on aluminium

Ionic liquids have been shown to be highly effective lubricants for a steel on aluminium system. This work shows that the chemistry of the anion and cation are critical in achieving maximum wear protection. The performance of the ILs containing a diphenylphosphate (DPP) anion all showed low wear, as did some of the tris(pentafluoroethyl)trifluorophosphate (FAP) and bis(trifluoromethanesulfonyl)amide (NTf2) anion containing ILs. However, in the case of the FAP and NTf2 based systems, a cation dependence was observed, with relatively poor wear resistance obtained in the case of an imidazolium FAP and two pyrrolidinium NTf2 salts, probably due to tribocorrosion caused by the fluorine reaction with the aluminium substrate. The systems exhibiting poor performance generally had a lower viscosity, which also impacts on their tribological properties. Those ILs that exhibited low wear were shown to have formed protective tribofilms on the aluminium alloy surface.

Tracking single bubble in Hall-Héroult aluminium cell : an experimental and numerical study

In simulations of the hydrodynamics of the multiphase flow in gas– liquid systems with finite sizes of bubbles, the important thing is to compute explicitly the time evolution of the gas–liquid interface in many engineering applications. The most commonly used methods representing this approach are: the volume of fluid and the phase field methods. The later has gained significant interest because of its capability of performing numerical computations on a fixed Cartesian grid without having to parametrise these objects (Eulerian approach) and at the same time it allows to follow the interface ( for example bubble’s shape) that change the topology. In this paper, both numerical (phase field method) and experimental results for the bubble shapes underneath a downward facing plane is presented. Experiments are carried out to see the bubble sliding motion underneath a horizontal and inclined anode. It is assumed that the bubble formed under the anode surface is deformed (flattened) due to buoyant field before it goes around the anode corner. The bubble elongates to form a tail-like shape. The change in shape of the bubble is almost instantaneous and has a significant effect on the localised hydrodynamics around the bubble, which could influence the dynamics of the flow patterns in the Hall–Héroult cell. This deformation is the main cause of the bubble wake and the induced flow field in the aluminium cell. Various parameters such as bubble size, deformation and its sliding mechanism at different surface tensions are discussed and compared with experimental results.

Insight into reactions and interface between boron nitride nanotube and aluminium

Nature and mechanism of interfacial reactions between boron nitride nanotubes (BNNTs) and aluminum matrix at high temperature (650 °C) are studied using high-resolution transmission electron microscopy (HRTEM). This study analyzes the feasibility of the use of BNNTs as reinforcement in aluminum matrix composites for structural application, for which interface plays a critical role. Thermodynamic comparison of aluminum (Al)-BNNT with analogous Al-carbon nanotube (Al-CNT) system reveals lesser amount of reaction in the former. Experimental observation also reveals thin (~7 nm) reaction-product formation at Al-BNNT interface even after 120 min of exposure at 650 °C. The spatial distribution of the reaction-product species at the interface is governed by the competitive diffusion of N, Al, and B. Morphology of the reaction products are influenced by their orientation relationship with BNNT walls. A theoretical prediction on Al-BNNT interface in macroscale composite suggests the formation of strong bond between the matrix and reinforcement phase.

Roll forming cryo-rolled nano-structured aluminium sheet

Commercial purity aluminium plate was reduced by rolling under nitrogen in 30 passes from an initial material thickness of 10 mm to a final thickness of 2 mm (80% reduction). Analysis of the microstructure showed that the material produced in this way had an ul-trafine grained microstructure. The sheet was roll formed at room temperature to a V-section using commercial roll forming equipment. Two sets of experiments were per-formed; one with a 15 mm radius in the base of the V and the other with a 5 mm radius. The performance in terms of final shape and springback is compared with the same part shape formed by V-die bending. The mechanical properties of the sheet were determined using the tensile test. It has been found that even if the total tensile elongation is close to zero and bending of the material is very limited, ultra-fine grained and low ductile sheet metals can be roll formed to simple section shapes.

Electrochemical etching of aluminium alloy in ionic liquids

AA5083 aluminium alloy has been shown to be partially passivated by a 2-step anodic pre-treatment in Trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([P6,6,6,14][NTf2]) ionic liquid. Surface characterisation revealed that an electrochemical etching process had occurred, comparable to acid etching of aluminium. Scanning electron microscopy/energy dispersive x-ray spectroscopy results have established that magnesium dealloyed from the Mg2Si intermetallic particles and metal fluorides were deposited onto the remaining Mg2Si sites, which subsequently led to decreased anodic corrosion kinetics (to one third of the control) as well as an increase in the corrosion and pitting potentials. This unique electrochemical etching process offers a simple and quick method to improve the corrosion resistance of an aluminium alloy as it leads to a more uniform surface, in terms of defect size and distribution, compared to conventional acid etching. This process has the potential to be used as a pre-treatment to inhibit corrosion of AA5083 alloy.