Aluminum based energetic nanomaterials attract significant attention for various applications owing to their ultrahigh energy density. The main obstacle in the application of nano-Al based energetic ...materials is the slow combustion reaction kinetics and reduced energy output resulting from the inert Al2O3 shell. In this paper, an efficient surface self-activation strategy is proposed to significantly improve the combustion performance and energy output of nano-Al based energetic materials. A porous AlF3 shell is formed on the surface of the nano-Al particle by an etching reaction between perfluorododecanoic acid and the Al2O3 dense layer. The porous AlF3 shell provides a new reaction channel for the reaction of Al and the oxidizer, thus significantly improving the energy output and combustion reaction kinetics. The energy output and combustion reaction speed of polytetrafluoroethylene (PTFE)/nano-Al coated with C11F23COOH are 6304 J/g and 670 m/s, which are 3.0 and 2.6 times higher than those of PTFE/nano-Al, respectively. The mechanism of the self-activating process is proposed to explain the enhanced combustion reaction kinetics and energy output of the nano-Al based energetic materials. The proposed surface self-activation strategy for nano-Al particles can efficiently to enhance the reactivity and energy output and promote the development of the nano-Al based energetic materials.
Magnesium is pivotal for activating a large number of enzymes; hence, magnesium plays an important role in numerous physiological and biochemical processes affecting plant growth and development. ...Magnesium can also ameliorate aluminium phytotoxicity, but literature reports on the dynamics of magnesium homeostasis upon exposure to aluminium are rare. Herein existing knowledge on the magnesium transport mechanisms and homeostasis maintenance in plant cells is critically reviewed. Even though overexpression of magnesium transporters can alleviate aluminium toxicity in plants, the mechanisms governing such alleviation remain obscure. Possible magnesium-dependent mechanisms include (i) better carbon partitioning from shoots to roots; (ii) increased synthesis and exudation of organic acid anions; (iii) enhanced acid phosphatase activity; (iv) maintenance of proton-ATPase activity and cytoplasmic pH regulation; (v) protection against an aluminium-induced cytosolic calicium increase; and (vi) protection against reactive oxygen species. Future research should concentrate on assessing aluminium toxicity and tolerance in plants with overexpressed or antisense magnesium transporters to increase understanding of the aluminium–magnesium interaction.
Aluminum recycling currently occurs in a cascading fashion, where some alloys, used in a limited number of applications, absorb most of the end-of-life scrap. An expected increase in scrap supply in ...coming decades necessitates restructuring of the aluminum cycle to open up new recycling paths for alloys and avoid a potential scrap surplus. This paper explores various interventions in end-of-life management and recycling of automotive aluminum, using a dynamic substance flow analysis model of aluminum and its alloying elements with resolution on component and alloy level (vehicle-component-alloy-element model). It was found that increased component dismantling before vehicle shredding can be an effective, so far underestimated, intervention in the medium term, especially if combined with development of safety-relevant components such as wheels from secondary material. In the long term, automatic alloy sorting technologies are most likely required, but could at the same time reduce the need for magnesium removal in refining. Cooperation between the primary and secondary aluminum industries, the automotive industry, and end-of-life vehicle dismantlers is therefore essential to ensure continued recycling of automotive aluminum and its alloying elements.
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•The microstructures of four NAB alloys are characterized by SEM and TEM.•The added Ni suppresses the formation of β' phase and increases the amount of κ phase.•The corrosion ...resistance and yield strength are improved via Ni addition.•The corrosion mechanism is analysed based on the EIS results and surface morphology.
The mechanical properties and corrosion behaviour in 3.5 wt.% NaCl solution of as-cast nickel-aluminium bronze (NAB) alloys with four Ni contents were investigated. The increase in Ni content leads to more precipitated κ phases, therefore improving the yield strength and hardness of the NAB alloys. Ni addition was found to significantly suppress the formation of corrodible β' phase and increase the Ni concentration in α solid solution. The electrochemical impedance spectroscopic and static immersion tests showed that the increase in Ni content (4.5–10 wt.%) improved the corrosion resistance of the NAB alloys in 3.5 wt.% NaCl solution.
Aluminum is an ideal material for metallic fuel cells. In this research, different grain sizes of aluminum anodes are prepared by equal channel angular pressing (ECAP) at room temperature. ...Microstructure of the anodes is examined by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Hydrogen corrosion rates of the Al anodes in 4 mol L−1 NaOH are determined by hydrogen collection method. The electrochemical properties of the aluminum anodes are investigated in the same electrolyte using electrochemical impedance spectroscopy (EIS) and polarization curves. Battery performance is also tested by constant current discharge at different current densities. Results confirm that the electrochemical properties of the aluminum anodes are related to grain size. Finer grain size anode restrains hydrogen evolution, improves electrochemical activity and increases anodic utilization rate. The proposed method is shown to effectively improve the performance of Al–air batteries.
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•Higher electrochemical performance of Al anode with finer grain size.•The capacity and energy density of 2308 mAh g−1 and 3525 mWh g−1 with finer grain size Al anode.•Improvement by 41.5% of capacity density and 55.5% of energy density as compared with the cast anode.
Aluminum oxide (Al2O3) and Magnesium-Aluminum oxides (MgAl2O4) are well known refractory materials used in engineering industries. They are built to withstand high temperatures and possess low ...thermal conductivities for greater energy efficiency. Dross, a product/byproduct of slag generated in aluminum metal production process is normally comprised of these two oxides in addition to aluminum nitride (AlN). Worldwide, thousands of tons of aluminum dross are generated as industrial wastes and are disposed of in landfills causing serious environmental hazard. This paper explores the potential to synergize the characteristics of the favourable contents of aluminum dross and its availability (in tons) via synthesis of refractories and thereby develop a value added product useful for the modern industries. In this work, Al-dross as-received from an aluminum industry which comprised of predominantly Al2O3, MgAl2O4 and AlN, was used to develop the refractories. AlN possesses high thermal conductivity values and therefore was leached out of the dross to protect the performance of the developed refractory. The washed dross was calcined at 700° and 1000°C to facilitate gradual elimination of the undesired phases and finally sintered at 1500°C. The dross refractory pellets were subjected to thermo-physical and structural properties analysis: XRD (structural phase), SEM (Microstructure), EDS (chemical constituents) and thermal shock cycling test by dipping in molten aluminum and exposing to ambient (laboratory). The findings include the favourable prospects of using aluminum dross as refractories in metal casting industries.
In situ nitridation of pre-compacted aluminium flakes is shown to be a key to lightweight composites for many engineering applications such as more efficient and cost-effective construction vehicles. ...This new composite has the mechanical properties of high-strength streels while being ∼3.4 times lighter. This composite was produced by: (i) compaction of micrometric Al flakes into porous blanks, (ii) partial melting through rapid heating to 870 K in N2 and (iii) annealing of the pre-melted blanks at 750 K in N2, where different Al flake deoxidisers were used to control a sufficiently low level of H2O/O2 activating in situ nitridation. The nitrided composites contained stellar dendrites composed of Al, AlN and γ-Al2O3, in which the ceramic fraction increases over the nitridation stage. The traces of H2O in the N2 atmosphere were found to be beneficial for strengthening, due to oxidation and suppression of the composite dendrites from overgrowing and segregation.
•Activation of hindered in situ nitridation in pre-melted Al flakes.•Discovery and control of in situ growth of AlN stellar microdendrites in an Al matrix.•Novel lightweight (∼2.3 g cm-3) syntactic Al/AlN-Al2O3 foam with superior failure stress, 874 MPa and strain, 6.8%.
•Maximum adsorption of fluoride on AlFu MOF occurred at 293K.•Maximum adsorption capacity for fluoride was 600mg/g at 293K.•The MOF exhibited adequate charge characteristic and high surface area ...(1156m2/g).•Second order reaction and intra particle diffusion (first 1.5h) was prevalent.•AlFu MOF exhibited high potential for fluoride removal from water.
Potential of aluminium fumarate metal organic framework (MOF) for fluoride removal from groundwater has been explored in this work. The laboratory produced MOF exhibited characteristics similar to the commercial version. MOF was found to be micro-porous with surface area of 1156m2/g and average pore size 17Å. Scanning electron micrograph of the AlFu MOF showed minute pores and texture was completely different from either of the parent materials. Change in the composition of AlFu MOF after fluoride adsorption was evident from powder X-ray diffraction analysis. Thermal stability of the AlFu MOF up to 700K was established by thermo-gravimetric analysis. Incorporation of fluoride phase after adsorption was confirmed by X-ray fluorescence analysis. As observed from FTIR study, hydroxyl ions in AlFu MOF were substituted by fluoride. 0.75g/l AlFu MOF was good enough for complete removal of 30mg/l fluoride concentration in feed solution. The maximum adsorption capacity for fluoride was 600, 550, 504 and 431mg/g, respectively, at 293, 303, 313 and 333K.
•In-situ and ex-situ confocal Raman measurements revealed chemical states of vanadium compounds.•The inhibition effect is mostly provided by a polymerized film with mixed V(V) and V(IV) ...species.•Intermetallic particles in the alloy have a strong influence on the vanadate inhibition process.•Deposition of polymerized vanadate compounds is mainly connected with micrometer-sized IMPs.•The inhibition mechanism involves first reduction and then re-oxidation of the vanadium species.
Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V+4 and V+5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V+5 species are first reduced to V+4 or V+3 species above cathodic IMPs, and then oxidized to mixed-valence V+5/V+4 polymerized compounds.
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