Aluminum Oxygen Research Articles

Surface modification and structure evolution of aluminum under argon ion bombardment

The surface properties is an important factor in the surface activated bonding of aluminum. The effect of argon (Ar) bombardment on the surface properties of aluminum was investigated in this work. The changes in surface chemical composition, wettability and structure were analyzed. The results revealed that the AlO bonds of surface oxide film were broken by Ar ion bombardment. The positive aluminum ions (Al+) and oxygen radicals (O*) produced by breaking of AlO bonds could react with the adsorbed water molecules to form hydrophilic hydroxyl (OH groups) and AlOH groups, which improved the wettability of aluminum surface. A large number of dislocations and subgrains with lattice distortion accumulated in the bombard-induced modification layer near the surface. The stress distribution on the surface was transformed from tensile stress into compressive stress with the bombardment power enhanced. The simulation results showed that the regular structure was broken and the point defects were produced from the collision. In the later stage of collision, most of the disordered atoms rearranged with the point defects annihilated, and finally a crater with several stable point defects was left near the surface.

Effect of the Aluminum Particle Size, Solid Content, and Aluminum/Oxygen Ratio on the Underwater Explosion Performance of Aluminum-Based Explosives

Several aluminum-based explosives are prepared and their underwater explosion performances, including the specific bubble energy and specific shock wave energy, are measured in underwater explosion experiments. The formulation characteristics of the explosives involve the aluminum/oxygen (Al/O) ratio, aluminum particle size, and the total content of all solid components, including ammonium perchlorate (AP), aluminum (Al), and cyclotrimethylenetrinitramine (RDX). The results indicate that the Al/O ratio of the explosives produces a great effect on the specific shock wave energy and specific bubble energy of the explosives. The total specific energy of the explosive reaches the maximum value at Al/O = 0.44. It is notable that an increase in the total solid content (AP, Al, and RDX) in the explosive formulation can effectively increase the specific total energy of the explosives. When the total solid content is increased by 2% (by weight) in the explosive formulation, the total energy of the explosive can be increased by about 0.1 times the TNT equivalent. Moreover, the particle size of the aluminum powder can also significantly affect the energy of the explosives. The smaller particle size of the aluminum powder is beneficial to the energy release of aluminum and can increase the total explosion energy.

Toward a Structural Model for the Aluminum Tellurite Glass System

Neutron diffraction, 27Al MAS NMR, and 27Al Double Quantum MAS NMR results are presented and analyzed to determine the local environments of the cations in a series of aluminum tellurite glasses. Total scattering results show that, within a maximum Te–O distance of 2.36 Å, tellurium exhibits a mix of [TeO3E] and [TeO4E] environments (E = electron lone-pair), with a linear reduction in the average tellurium–oxygen coordination number as Al2O3 is added to the glass. This is accompanied by a linear decrease in the average aluminum–oxygen coordination number as [AlO4] units form at the expense of [AlO6] units, while the fraction of [AlO5] units remains roughly constant. A consideration of the bonding requirements of the five structural units in the glass, [TeO3E], [TeO4E], [AlO4], [AlO5], and [AlO6], has allowed a direct quantitative relationship between tellurium–oxygen and aluminum–oxygen coordination numbers to be derived for the first time, and this has been successfully extended to the boron tellurite system. Double Quantum 27Al MAS NMR indicates that, in contrast to previous reports, the shortest Al...Al separations are significantly smaller (∼3.2 Å) than expected for a uniform distribution and there is a preference for [AlO6]–[AlO6] and [AlO4]–[AlO4] corner sharing polyhedra. These associations support a new structural model which successfully applies the principle of charge balance to describe the interaction of tellurium and aluminum and identifies and explains the clustering of [AlOn] polyhedra in the glass and their preferred associations. [AlO6] and [TeO4E] units dominate the network in TeO2-rich glasses and [AlO4]− units form to stabilize the [TeO3E]+ units as alumina is added to the glass.

Measurement of Aluminum and Chemical Oxygen Demand in the Effluent of Mordanted Cotton Against Environmental Regulations

Despite toxicity concerns of chemical mordants used in natural dyeing, there is limited research on the measurement, quality, and safe disposal of the chemical mordant effluent. This study measured the aluminum ions across the premordanting process of cotton print cloth using inductively coupled plasma mass spectrometry and calculated the oxidizable organic matter in the effluent through chemical oxygen demand (COD). The amount of aluminum absorbed by the cotton print cloth was low (2.31%–5.16%). The effluent COD was 23.91g COD/kg. Upon neutralization of the acidic condition, the aluminum in the effluent met discharge to freshwater regulations, and the COD met discharge to U.S. municipal sewage systems. However, the Global Harmonized System restricts aluminum acetate dibasic from organic certification due to its boric acid content. The high mordant concentration in the effluent supports the reuse of mordant baths but not direct disposal to the land or standing waters.

Focused Ion Beam Milling of Single-Crystal Sapphire with A-, C-, and M-Orientations.

Sapphire substrates with different crystal orientations are widely used in optoelectronic applications. In this work, focused ion beam (FIB) milling of single-crystal sapphire with A-, C-, and M-orientations was performed. The material removal rate (MRR) and surface roughness (Sa) of sapphire with the three crystal orientations after FIB etching were derived. The experimental results show that: The MRR of A-plane sapphire is slightly higher than that of C-plane and M-plane sapphires; the Sa of A-plane sapphire after FIB treatment is the smallest among the three different crystal orientations. These results imply that A-plane sapphire allows easier material removal during FIB milling compared with C-plane and M-plane sapphires. Moreover, the surface quality of A-plane sapphire after FIB milling is better than that of C-plane and M-plane sapphires. The theoretical calculation results show that the removal energy of aluminum ions and oxygen ions per square nanometer on the outermost surface of A-plane sapphire is the smallest. This also implies that material is more easily removed from the surface of A-plane sapphire than the surface of C-plane and M-plane sapphires by FIB milling. In addition, it is also found that higher MRR leads to lower Sa and better surface quality of sapphire for FIB etching.

Solids management in freshwater-recirculating aquaculture systems: Effectivity of inorganic and organic coagulants and the impact of operating parameters

Coagulants are widely used for solids (uneaten food, faeces, etc.) management in recirculating aquaculture systems (RAS), but no recent research has been performed on the effectiveness of different coagulants in treatment of aquaculture sludge. This study examined the effectivity of selected inorganic (polyaluminium chloride, PAC) and organic products (polyamine- and starch-based) as coagulant agents for solids management in RAS. Reductions in residual concentrations of total phosphorus (tot-P), phosphate‑phosphorus (PO4-P), suspended solids (SS) total nitrogen (tot-N), nitrate‑nitrogen (NO3-N), ammonium‑nitrogen (NH4-N), aluminium (Al) and chemical oxygen demand (COD) in reject water were determined. The effect of process parameters (coagulant type, dose, mixing and sedimentation time) on sludge treatment was also evaluated. The PAC products tested were most effective at concentrating pollutants (Tot-P, PO4-P, SS, COD) in RAS sludge into the solid phase. The organic products tested, especially a high-molecular-weight polyamine product (pAmine1), achieved good performance and can be considered a valid alternative to inorganic salts. At optimum dose, PAC (dose 32 mg/L) and pAmine1 (dose 15 mg/L) removed, respectively, 99.4% and 82.8% of turbidity, 98.2% and 65.4% of PO4-P and 97.7% and 73.6% of SS. The mixing time applied in flocculation and the time allowed for sedimentation had significant effects on coagulant performance, with the organic coagulants being most affected. Flocculation times of 5–15 min and sedimentation times of 15–60 min showed good results and can be used as a starting point in process optimisation with both inorganic and organic coagulants. The use of coagulants for treatment of RAS sludge enhances flock formation and improves particle settling characteristics, substantially decreasing nutrient, organics and solids concentration in reject water.

A study of the interaction of oxygen with the α2 phase in the model alloy Ti–7wt%Al

Atom Probe Tomography is used to show that the α2 phase (Ti3Al) forms upon ageing Ti–7Al at 550 °C with as little as 500 wppm oxygen. Notably, it is found that oxygen consistently partitions away from the α2 precipitates to the α matrix. The role of aluminium concentration and oxygen solubility on oxygen partitioning preference is also investigated. Based on our observations, we propose a mechanism by which oxygen encourages α2 formation despite partitioning away from it. Furthermore, nanohardness systematically measured with respect to ageing time and oxygen concentration suggests that α2 precipitation is not the dominant hardening mechanism during ageing.

Equilibrium Sorption of Histidine on Clinoptilolite

Sorption of histidine in the cationic and zwitterionic forms on a framework aluminosilicate, clinoptilolite, has been investigated. The contributions of the exchange and nonexchange mechanisms of sorption to the sorption capacity have been determined. It has been shown that monolayer histidine sorption on clinoptilolite by the ion-exchange mechanism proceeds due to the electrostatic interaction between $${\text{NH}}_{3}^{ + }$$ groups of the amino acid and electronegative sites of the sorbent matrix. In the region of equivalent exchange, a smaller value of the ion-exchange component of the sorption of histidine zwitterions is due to the Coulomb repulsion between the dissociated carboxyl groups of the amino acid and the negatively charged aluminum–oxygen clinoptilolite matrix. The isotherm of histidine sorption from dilute solutions has been described using the Langmuir theory. The equilibrium sorption parameters have been found. It has been concluded that polymolecular layers of the amino acid are formed as a result of association via hydrogen bonding, as well as dipole–dipole and hydrophobic interactions.

Investigation of the specularite/chlorite separation using chitosan as a novel depressant by direct flotation

Chlorite is one of the representative iron-bearing silicates gangue minerals existed in the specularite ores which the traditional depressants are incapable of action in specularite/chlorite separation flotation. An attempt was conducted for the separation of specularite/chlorite with chitosan as a novel depressant through microflotation tests, Zeta potential measurements, adsorption tests, FT-IR, and XPS analysis. The microflotation results show that chitosan selectively depresses chlorite while specularite still keeps in high floatability. Zeta potential measurements and adsorption tests indicate that chitosan mainly adsorbed on chlorite surface, hindering the subsequent adsorption of dodecan-1-amine and leading the hydrophobicity distinction. The FT-IR spectra of chlorite validate the adsorption of chitosan on chlorite. The results of XPS illustrate that electrons partially transferred from chitosan to the aluminum, iron, magnesium, silicon, and adjacent oxygen atoms of silicon atoms in chlorite during the adsorption process.

Inhibition of different types of inert dust on aluminum powder explosion

Aluminum powder explosion accidents occurred frequently, but the mechanism of aluminum powder explosion is unclear. Therefore, the inhibitive effect of aluminum powder explosion plays a key role. To evaluate the inhibition capacity of different kinds of carbonates and phosphates: NaH2PO4, (NH4)2HPO4, NH4H2PO4, KHCO3 and NaHCO3 on aluminum deflagrations, a standard 20-L spherical chamber was used to determine the explosion severity, characterized by the maximum explosion pressure (Pmax). New parameters have been proposed: the minimum significant inert concentration (MSIC) and the minimum complete inert concentration (MCIC), which characterized the effect of inert. Experimental results showed that from the minimum significant inert concentration (MSIC) and the minimum complete inert concentration (MCIC), phosphate can have a significant inhibiting effect. 40% NaH2PO4 can totally inert the aluminum explosion, and 50% (NH4)2HPO4 or 50% NH4H2PO4 can also suppress the explosion. Through simulation, phosphate mainly acts via a chemical inhibition pathway, which inhibits the reaction of aluminum powder and oxygen by catalyzing the recombination of H atoms and O atoms. Carbonate performs inhibition in chemically, producing CO2, diluting the oxygen around the aluminum powder. Studies indicated that the explosion pressure of the mixture decreases as the concentration of inert dust increases. However, when the concentration of carbonates was low, SEEP (suppressant enhanced explosion parameter) phenomenon was found. This research work has a potential industrial application in high hazard aluminum working condition, which can help decrease the explosion pressure and reduce the accident loss.

Optical and structural investigations of MLaAlO4:Eu3+ (M = Mg2 +, Ca2+, Sr2+, and Ba2+) nanophosphors for full-color displays

A series of Eu3+ -doped MLaAlO4 (M = Mg2+, Ca2+, Sr2+, and Ba2+) was synthesized via self-sustained solution combustion method. The samples were prepared at 600 °C, using large range of Eu3+ ion concentration (0.01–0.05 mol) to investigate the effect of concentration of dopant on the luminescence. The optimal dopant ion concentration obtained was 0.03 mol for the prepared aluminate lattice. Upon excitation at 393 nm, the samples showed the dominant photoluminescence emission bands in red region of the spectrum. The red emission of Eu3+ -activated phosphors corresponds to 5D0 → 7F2 (forced electric dipole) transition positioned at 606–611 nm. The samples were also calcined to a higher temperature to analyze the influence of temperature on the luminous efficacy. The structural determination was done via the combined efforts of Powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM) analysis. PXRD patterns of samples contain sharp peaks in 10°–80° region. Diffraction Pattern of CaLaAlO4 material has been found in close agreement to JCPDS card no. 85-1071 confirming the tetragonal crystal structure with 14/mmm space group. The crystalline nature of materials increases with rise in temperature. TEM micrographs exhibited the spherical shape of particles in 13–30 nm size. FT-IR spectra of materials showed peaks in 400–1000 cm−1 corresponding to lanthanum–oxygen and aluminum–oxygen bond vibrations. Due to excellent photoluminescent and suitable CIE coordinates, the Eu3+ -doped MLaAlO4 could have brilliant applications in the development of effective red phosphor for modern display devices and white light-emitting diodes.

Al Valence Controls the Coordination and Stability of Cationic Aluminum-Oxygen Clusters in Reactions of Aln+ with Oxygen.

The reactivity of cationic aluminum clusters with oxygen is studied via a customized time-of-flight mass spectrometer. Unlike the etching effect for anionic aluminum clusters exposed to oxygen, here, the cationic Aln+ clusters react and produce a range of small AlnOm+ clusters. Relatively large-mass abundances are found for Al3O4+, Al4O5+, and Al5O7+ at lower O2 reactivity, while at higher O2 concentration, oxygen addition leads to Al2O7+, Al3O6,8-10+, and Al4O7,9+, showing relatively high abundance, and Al5O7+ remains as a stable species dominating the Al5Om+ distribution. To understand these results, we have investigated the structures and stabilities of the AlnOm+ clusters. First-principles theoretical investigations reveal the structures, highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps, fragmentation energies, ionization energies, and Hirshfield charge of the AlnOm+ clusters (2 ≤ n ≤ 7; 0 ≤ m ≤ 10). Energetically, Al3O4+, Al4O5+, and Al5O7+ are calculated to be most stable with high fragmentation energies; however, they still allow for the chemisorption of additional O2 with large binding energies leading to clusters with higher O/Al ratios. The stability of the species is consistent with Al possessing three valence electrons, while O typically accepts two, leading to the expectation that Al3O4+, Al5O7+, and Al7O10+ are reasonably stable. In addition to this, Al3O+, Al5O3+, and Al7O5+ are found to exhibit large HOMO-LUMO gaps associated with the different oxidation states of Al. The oxygen-rich species such as Al2O7+, Al3O10+, and Al4O9+ all display superoxide structures providing further insights into the oxidation of aluminum clusters.

Use of Synthetic and Natural Zeolites for Fabricating Immobilized Olefin Polymerization Catalysts and Polyolefin-Based Composite Materials

Synthetic zeolites differing in composition, framework parameters, and exchange cations that balance charges of aluminum–oxygen framework tetrahedra and natural finely divided clinoptilolite-containing tuffs have been used for heterogenization of metal complex catalysts. In the reaction of incomplete hydrolysis of alkylaluminum compounds with water contained on the surface and in the intracrystalline cavities of synthetic zeolites, bonded alkylalumoxanes have been synthesized and further used to create immobilized zirconocene olefin polymerization catalysts, close in activity to similar homogeneous Zr-cene systems, and heterogenized vanadium catalysts. Based on finely divided natural zeolites and ultrahigh-molecular-weight polyethylene, the following materials have been fabricated using the polymerization filling method: a composite that combines high wear-resistant properties with a low friction coefficient, has good strain–stress characteristics, and can be used for manufacturing friction units under load; an organomineral sorbent suitable for solving environmental problems associated with the treatment of natural water for the removal of cesium and strontium radionuclides, heavy metals, and ammonium.

Space charge control of point defect spin states in AlN

One barrier to developing quantum information systems based on impurity point defects is that the desirable spin states of the defects are often unstable for Fermi levels obtained at increased impurity concentrations. The space charge induced band bending near the interface of Si/Mg aluminum nitride (AlN) homojunction is investigated computationally as a method to control the concentration, spin state, and position of such point defects. This is done by solving Poisson's equation with the charge density described by a grand canonical defect chemistry model informed by hybrid-functional density functional theory (DFT) calculations. Previous experimental works have found unintentional carbon and oxygen impurities pervade AlN homojunctions. First principles calculations have predicted the neutral complex between an aluminum vacancy and oxygen impurity on a neighboring nitrogen site (vAl-1ON)0 has a spin triplet configuration, which is stable in a region when the Fermi level is below midgap. From defect equilibrium simulations considering 602 possible defects, vAl-1ON was found to be unstable on the Mg-doped side of the homojunction and isolated oxygen impurities are preferred. On the Si-doped side, vAl-1ON forms but as (vAl-1ON)–2, not (vAl-1ON)0. This makes vAl-1ON a prototypical test case for the proposed strategy. Simulations of the Si/Mg:AlN homojunction showed (vAl-1ON)0 is stabilized within 6 nm of the interface in the Si-doped portion. This result indicates space charge induced band bending enables control over the concentration, spin state, and position of point defects, which is critical to realizing point defect based quantum information systems.

Aluminum dual doping and oxygen transport pathway in novel Sr11Mo4−xAlxO23 oxide-ion solid electrolytes

Three new electrolytes of composition Sr11Mo4-xAlxO23-δ (x = 0.5, 1.0 and 1.5) were synthesized by wet-chemistry procedures (citrate method) as polycrystalline samples. They were crystallographically studied from synchrotron and neutron diffraction techniques. They derive from the Sr11Mo4O23 complex perovskite, which can be rewritten as Sr1.75□0.25SrMoO5.75, highlighting the relationship with double perovskites A2B′B″O6. From these analyses via Rietveld refinement, a dual doping was found from synchrotron data, where the aluminum is equally allocated at both Sr (B′) and Mo (B″) sites. A detailed analysis of the neutron data from Difference Fourier Maps (DFM) unveiled the oxygen delocalization around the Mo site. From the refined crystal structures at room and high temperatures, a Bond Valence Sum Map (BVSM) analysis was useful to find the oxygen pathway in the crystal structure, and the minimum density to allow connections among oxygen atoms. The structural characterization was complemented with thermogravimetric and thermodilatometric analysis. The ionic conductivity was measured from electrochemical impedance spectroscopy (EIS) in wet and dry air and nitrogen atmospheres.

Preparation of Adsorbent from Fly Ash for Methylene Blue Wastewater Treatment

Fly ash contains SiO2 and Al2O3, which account for more than 60% of the total. This is similar to the composition of zeolite which is frequently be used for adsorbent. Therefore, fly ash is used to prepare adsorbent for wastewater treatment by microwave-assisted hydrothermal method. The optimal reaction conditions were determined: alkali-ash ratio of 15:1, reaction temperature of 100°C and reaction time of 0.5h. The removal rate of methylene blue is up to 97.6%. The adsorbent was characterized by SEM and FT-IR. Large number of silicon (aluminum) oxygen tetrahedrons and the porous lattice structure contribute high adsorption performance of the adsorbent.

Enhancement of molecular formation in fiber-optic laser ablation with a long nanosecond pulsed laser

Fiber-optic laser-induced breakdown spectroscopy (LIBS) can be used for on-site chemical analysis in harsh environments with a flexible light delivery system. In this work, the use of a long-pulse laser (100 ns) is proposed for the detection of molecular emission signals, instead of a normal-pulse laser (6 ns). We show a significant enhancement of AlO signals using an aluminum metal target in air. We also elucidate the enhancement mechanism of the AlO formation by measuring species-specific images of the emission from aluminum atoms, oxygen atoms, and AlO molecules in the plasma. The internal structure of the plasma suggests that the formation origin of AlO molecules in the long-pulse-produced plasma is essentially different from that in the normal-pulse-produced plasma. The long-pulse laser causes a rise of the ablation plume and facilitates the flow of oxygen from the ambient air. This is a key factor to enhance the molecular emission signals.

Comparison study of the ignition and combustion characteristics of directly-written Al/PVDF, Al/Viton and Al/THV composites

The aluminum–fluorine reaction is attracting growing interest due to its higher density over aluminum–oxygen. Fluorine rich polymers are particularly interesting for their applications as an energetic binder in advanced additive manufacturing of energetic materials. In this paper, three soluble polymers of PVDF (59 wt% F), Viton (66 wt% F) and THV (73 wt% F) are incorporated with aluminum nanoparticles (Al NPs) and prepared as free-standing films using solvent-based direct writing. The three composite films are compared for their mechanical properties as well as the ignition and combustion performance. Tensile stress was found to order as Al/PVDF > Al/THV > Al/Viton while the elasticity of Al/Viton is much higher than the other two. The burn rate of different composite films increases with Al content, while the flame temperature peaks slightly fuel-rich. The Al/PVDF had the highest burn rate, however, the flame temperature ordered as Al/THV (∼2500 K) > Al/Viton (∼2000 K) > Al/PVDF (∼1500 K), consistent with fluorine content. With higher fluorine and lower hydrogen content, THV releases more CFx gas than HF, which generates higher temperature. However, HF which is predominantly produced from PVDF has the lowest ignition by far and may be responsible for its high flame speed.

Research on Photo-Radiation Darkening Performance of Ytterbium-Doped Silica Fibers for Space Applications

Yb3+/Al3+-doped and Yb3+/Al3+/P5+-doped silica fibers with almost identical Yb3+ doping concentrations were prepared using modified chemical vapor deposition methods. A harsh experimental environment for simultaneous photo-darkening (PD) and radio-darkening (RD) of an ytterbium-doped silica fiber (YDF) was established. The RD, PD, and photo-radio-darkening (PRD) of the YDF were characterized at two dose rates of 0.1 rad(Si)/s and 1 rad(Si)/s. The laser performances before and after the darkening process were tested under 974-nm pumping. The results demonstrated that the PD largely dominated the PRD kinetics of the YDF at a low dose rate (e.g., that in space) and that the PRD was not a superposition of RD and PD owing to the pump light bleaching if the induced loss was larger than the PD equilibrium level. The induced loss and defect types were investigated through absorption spectra and electron paramagnetic resonance. The results revealed that the P doping could enhance the PD, RD, and PRD resistances by inhibiting the formation of aluminum–oxygen hole centers.

Radiation Effects on Aluminosilicate Optical Fibers: Spectral Investigations From the Ultraviolet to Near‐Infrared Domains

Online X‐ray radiation induced attenuation (RIA) has been performed in aluminosilicate optical fibers having different Al concentrations. The studied UV‐visible spectral range revealed the presence of absorption bands related to Al defects. Their generation is shown to be not noticeably dependent on the dose rate. Furthermore, the Al content (2–4 wt%), the core sizes, and the manufacturing processes (SPCVD or MCVD) of the preforms have no significant influence on the RIA levels and kinetics, as well as the drawing parameters within the range used for specialty fiber production. The Aluminum–Oxygen Hole Center (Al–OHC) presence was proved by their 2.3 eV absorption band and by their electron paramagnetic resonance (EPR) signature. The growth kinetic of their concentration versus dose is linear up to 2–3 kGy (SiO2). While, at higher doses, EPR data highlight a saturation, suggesting that the Al–OHC generation results from a process involving precursors. To explain the E'Si growth kinetic with the dose, two processes are necessary, the first is from precursors and the second by breaking SiOSi links. The study of the RIA induced in the NIR demonstrates that the tail of the 2.3 eV Al–OHC band cannot explain the fiber degradation and that additional defects contribute to the induced losses.