Synthesis and characterization of high purity aluminum sec-butoxide from aluminum dross

Aluminum sec-butoxide (ASB) was synthesized to a high purity grade from Al dross through dissolution reaction and vacuum distillation under the condition of 3 mol C₄H₉OH/mol Al as a stoichiometric reactant ratio and 10⁻³ mol HgI₂/mol Al as a catalyst. The dissolution reaction proceeded for 24 hours, then pure ASB was recovered by vacuum distillation from the Al solution obtained after the dissolution. The ASB thus synthesized was quantitatively analyzed by a complexometric method for purity. This reaction gave a 99.2% purity and 28% yield. Characteristics of the synthesized ASB were analyzed by FT-IR, ²⁷Al-NMR, and ¹H-NMR. The result of analysis revealed that the crystalline structure between the synthesized ASB and commercial ASB was identical. Especially, the yield synthesized through this experiment corresponded to the total amount of Al metal existing in Al dross.     

Synthesis of aluminum isopropoxide from aluminum dross

Synthetic reaction of aluminum isopropoxide, which is used as a starting material for catalytic-grade alumina, has been studied in the presence of a small amount of HgI₂, HgCl₂, I₂ or FeCl₃ from aluminum dross. It was synthesized by solid-liquid reaction between the aluminum metal and isopropyl alcohol, using vacuum distillation process. The purity of the synthesized aluminum isopropoxide was obtained over 97.6% experimentally, which had been analyzed quantitatively by complexometric method. The initial amount of sodium, which directly affects the catalytic activation in the alumina catalyst, was in the range of 0.926 to 1.563 wt% in the aluminum dross. Finally, it was decreased to 0.007 wt% in the aluminum isopropoxide product. Yield was changed according to the amount of aluminium existing in the aluminum dross. Aluminum could mostly be recovered regardless of the amount of aluminium existing in the aluminum dross.     

Further insights on the thermal degradation of aluminum metaphosphate prepared from aluminum dihydrogen phosphate solution

A study of the high temperature (up to 1200 °C) degradation of aluminum metaphosphate Al(PO₃)₃ has been carried out to evaluate the stability of this compound used for many purposes. For the preparation of Al(PO₃)₃, an aluminum dihydrogen-phosphate Al(H₂PO₄)₃ solution has been heated at 700 °C. Thermal degradation of Al(PO₃)₃ has been followed through the measurement of weight loss on isothermal mode at 1000 and 1200 °C and by thermogravimetric analysis coupled with mass spectroscopy (TGA-MS). Structural data have been obtained by ²⁷Al, ³¹P and ¹H MAS NMR spectroscopy. NMR analyses have shown that [A] and [B] allotropic forms of Al(PO₃)₃ are formed after the preparation procedure. In addition, NMR revealed that hydroxyls groups are also present in the sample, and they form POH groups. TGA-MS showed that they are decomposed at a temperature of 875 °C, while the decomposition of Al(PO₃)₃ into AlPO₄ and P₂O₅ begins at 1000 °C.     

Electroless immobilization and electrochemical characteristics of nickel hexacyanoruthenate film at an aluminum substrate

The surface of an aluminum (Al) electrode was modified with a thin film of nickel hexacyanoruthenate (NiHCR) as a novel electrode material. The modification procedure of Al surface, includes two consecutive procedures: (i) the electroless deposition of metallic nickel on the Al electrode surface from NiCl₂ solution, and (ii) the chemical transformation of deposited nickel to nickel hexacyanoruthenate films in solution of 20 mM K₃[Ru(CN)₆] + 0.5 M KNO₃. Cyclic voltammogram of the modified Al electrode showed a well-defined redox reaction due to [Ni^IIRu^III/II(CN)₆]^1−/2− system. The effects of different supporting electrolytes and solution pH were studied on the electrochemical characteristics of the modified electrode. The diffusion coefficients of K⁺ and Na⁺ cations in the film (D), the transfer coefficient (α), and the charge transfer rate constant at the modifying film/electrode interface (k_s), were calculated in the presence of both K⁺ and Na⁺ cations. The stability of the modified electrode was investigated under various experimental conditions.     

High-temperature resistant ambient pressure-dried aluminum doped silica aerogel from inorganic silicon and aluminum sources

Aluminum doped silica aerogel (ASA) exhibiting improved high-temperature resistance is usually prepared via supercritical drying from organic silicon and/or aluminum precursors, which propels the production cost significantly. Herein we demonstrate a simple and effective method to prepare highly thermal resistant ASA via the sol-gel and ambient pressure drying route by using water glass and aluminum chloride as precursors. Effects of the Al/Si molar ratio in precursor, the calcination temperature and the modifier type on the crystallinity, morphology, pore structure of ASA are investigated. Results show that the Al/Si molar ratio and the calcination temperature have significant effects on the structure and heat resistance performance of ASA at temperature of 600–1000 °C. The sample with Al/Si molar ratio of 0.15 shows the highest specific surface area of 805.9 m²/g and pore volume of 5.038 cm³/g after heated to 600 °C, and retains 179.5 m²/g and 1.295 cm³/g respectively after heated to 1000 °C. Mechanism analysis indicates that, though the actual aluminum content is extremely low (0.18%, wt%), the high-temperature resistance of ASA is greatly improved owing to the effective doping of aluminum in the lattice of SiO₂ and the corresponding electrostatic repulsion between neighboring nanoparticles induced by the replacement of Si⁴⁺ by Al³⁺ ions.     

Electrochemical characteristics of dopamine oxidation at palladium hexacyanoferrate film, electroless plated on aluminum electrode

A novel electrode material was obtained at an aluminum electrode (Al) by a simple electroless method including two consecutive procedures: (i) the electroless deposition of metallic palladium on the Al electrode surface from PdCl₂ + 25% ammonia solution and (ii) the chemical transformation of deposited palladium to the palladium hexacyanoferrate (PdHCF) films in a solution containing 0.5 M K₃[Fe(CN)₆]. The modified Al electrode demonstrated a well-behaved redox couple due to the redox reaction of the PdHCF film. The PdHCF film showed an excellent electrocatalytic activity toward the oxidation of dopamine (DA). The effect of solution pH on the voltammetric response of DA has been investigated. A linear calibration graph was obtained over the DA concentration range 2-51 mM. The rate constant k and transfer coefficient α for the catalytic reaction and the diffusion coefficient of DA in the solution D, were found to be 4.67 × 10² M⁻¹ s⁻¹, 0.63 and 2.5 × 10⁻⁶ cm² s⁻¹, respectively. The interference of ascorbic acid was investigated and greatly reduced using a thin film of Nafion on the modified electrode. The modified electrode indicated reproducible behavior and a high level stability during electrochemical experiments, making it particularly suitable for the analytical purposes.     

Preparation of alumina fibers from aluminum salts by the sol-gel method

Alumina fibers were synthesized from two different systems, AlCl₃-Al powder-H₂O and Al(NO₃)₃-Al powder-H₂O, by the sol-gel method. For the former system, gel fibers were obtained from solutions in a composition range of Al powder/AlCl₃ molar ratios of 2 to 5. For the latter system, the spinnable range was narrower compared to the aluminum chloride system. The thermogravimetry analysis (TGA) curve of the aluminum chloride system showed a weight loss up to 700‡C while the TGA curve of the aluminum nitrate system showed no weight loss above 400‡C, which indicates that thermal decomposition of Cl_- is more difficult than that of NOgk-/3.     

Optimization of pulsed electrodeposition of aluminum from AlCl3-1-ethyl-3-methylimidazolium chloride ionic liquid

In this study, Al was electrodeposited on a platinum substrate at room temperature from an ionic liquid bath of EMIC containing AlCl₃ using potentiostatic polarization (PP), galvanostatic polarization (GP), monopolar current pulse polarization (MCP) and bipolar current pulse polarization (BCP). Transition of current or potential during galvanostatic or pulse polarization revealed that the initial stage of the deposition process was controlled by a nucleation process depending on the polarization condition. For example, the average size of Al deposits decreased with increasing current density in the case of GP. FE-SEM observation showed that dense and compact Al deposits with a smooth surface were obtained by the current pulse method. Roughness factor evaluated from electrochemical impedance measurement confirmed the smooth surface of these deposits. Adhesion strength of Al deposits was greatly improved using BCP in which an anodic pulse was combined with a cathodic pulse for electrodeposition. In this study, the optimal parameters for BCP were found to be I_C = −16.0 mA cm⁻², I_A = 1.0 mA cm⁻², r_C (duty ratio) = 0.5, and f = 2 Hz. The mechanisms of electrodeposition by these three methods are discussed.     

Efficient ring-opening polymerization of -caprolactone using anilido-imine–aluminum complexes in the presence of benzyl alcohol

A number of new anilido-imine–Al complexes ortho-C₆H₄(CHNAr¹)(NAr²)AlMe₂ [Ar¹ = C₆H₅, Ar² = C₆H₅ (2a); Ar¹ = 2,6-Me₂C₆H₃, Ar² = 2,6-Me₂C₆H₃ (2b); Ar¹ = 2,6-Et₂C₆H₃, Ar² = 2,6-Et₂C₆H₃ (2c); Ar¹ = 2,6-ⁱPr₂C₆H₃, Ar² = 2,6-Me₂C₆H₃ (2d); Ar¹ = 2,6-ⁱPr₂C₆H₃, Ar² = 2,6-Et₂C₆H₃ (2e)] were synthesized, characterized and used as initiators for the ring-opening polymerization of -caprolactone in the presence of benzyl alcohol. The effect of initiator structure and reaction conditions, such as benzyl alcohol/Al molar ratio and reaction temperature on the reactivity, and polymer molecular weight were investigated. The polymerization of -caprolactone initiated by these complexes was found to take place in an immortal fashion.     

Effect of NiS addition on nitridation of alumina to aluminum nitride using polymeric carbon nitride as a nitridation reagent

We investigated the effect of adding nickel(II) sulfide (NiS) on nitridation of alumina (Al₂O₃) to aluminum nitride (AlN) using polymeric carbon nitride (PCN), which was synthesized by polymerization of dicyandiamide at 500 °C. The product powders obtained from nitridation of a mixture of δ-Al₂O₃ and NiS powders (mole ratio of 1:0.01) at various reaction temperatures were characterized by powder X-ray diffraction, ²⁷Al magic-angle spinning nuclear magnetic resonance, and Raman spectroscopy. δ-Al₂O₃ began to convert to AlN at 900 °C and completely converted to AlN at 1300 °C. The as-synthesized sample powders contained nitrogen-doped carbon microtubes (N-doped CMTs) with a length of several tens of mm and thickness of ca. 3 µm. The addition of NiS to δ-Al₂O₃ resulted in the enhancement of the amount of N-doped CMTs and nitridation rate, which might be due to the catalytic action of Ni particles on the thermal decomposition of vaporized PCN. The change in Raman spectra with reaction temperatures indicated that the crystallinity of N-doped CMTs was increased by calcining at higher reaction temperatures.     

Anodic behavior of aluminum in organic solutions with different electrolytic salts for lithium ion batteries

The anodic polarization behavior of aluminum (Al) as a current collector of lithium (Li) ion battery has been investigated in organic electrolyte solutions containing different lithium salts. The Al current collector has suffered serious corrosion in the solution containing Li(CF₃SO₃)₂N (LiTFSI) under an anodic polarization condition, whereas, it was anodically stable in the LiPF₆ solution. In the solution of Li(C₂F₅SO₂)₂N (LiBETI), the Al anode showed an intermediate character between those in the LiPF₆ and LiTFSI solutions. The corrosion behavior of the Al electrode was much influenced by its surface condition. The addition of LiPF₆ in the imide-salts (LiTFSI and LiBETI) solutions suppressed the anodic corrosion of Al. The results of electrochemical quartz crystal microbalance (EQCM) experiments proved that the anodic processes on Al in the organic electrolytes consist of the formation of surface films and their dissolution. The X-ray photoelectron spectroscopy (XPS) analysis suggests that the anodic stability of the Al electrode in the imide-salts solutions containing LiPF₆ is associated with the formation of a fluoride (AlF₃)-rich film on the Al surface.     

Rapid synthesis of garnet-type Li7La3Zr2O12 solid electrolyte with superior electrochemical performance

Li₇La₃Zr₂O₁₂-based garnet-type solid electrolytes are promising candidates for use in all-solid-state lithium batteries (ASSLBs). However, their potential in large-scale commercial applications is largely hindered by the time/energy-consuming and lithium-wasting synthetic method which typically needs a long-duration high temperature solid state reaction process. Herein we invent a fast preparation route that involves a short-period thermal reaction (1100 °C for 10 min) in laboratory muffle furnaces following by conventional hot pressing technique to get almost fully dense (Al, Ga, Ta, Nb)-doped garnet-type electrolytes with high phase purity (>99.9 %). The large and compact grains, low porosity and high phase purities of garnet ceramic electrolytes synthesized in this study ensure superior electrochemical performance. Particularly, Ga-doped cubic Li₇La₃Zr₂O₁₂ shows extremely low E_a values (0.17?0.18 eV) and record-high lithium ionic conductivities (>2 × 10^?3 S cm^-1 at 25 °C).     

Application of magnetite modified with aluminum/silica to adsorb phosphate in aqueous solution

BACKGROUND: Phosphate is one of the main contaminants responsible for the eutrophication of surface waters, and adsorption is a potential treatment method for this pollutant. A magnetic adsorbent manufactured from magnetite (Fe₃O₄) can be recovered easily from treated water by magnetic force, without requiring further downstream treatment. In this research, the surface of magnetite modified with aluminum and silica (Al/SiO₂/Fe₃O₄) was used to adsorb phosphate in an aqueous solution in a batch system. RESULTS: The optimum solution pH for phosphate adsorption by Al/SiO₂/Fe₃O₄ was found to be 4.5. The phosphate adsorption behavior of Al/SiO₂/Fe₃O₄ was in good agreement with both the Langmuir and Freundlich adsorption isotherm, and the maximum adsorption capacity (q_m) and Gibbs free energy of phosphate was 25.64 mg g^?1 and ? 21.47 kJ mol^?1, respectively. A pseudo‐second‐order model could best describe the adsorption kinetics, and the derived activation energy was 3.52 kJ mol^?1. The optimum condition to desorb phosphate from Al/SiO₂/Fe₃O₄ is provided by a solution with 0.05 mol L^?1 NaOH. CONCLUSIONS: Magnetic adsorbent is a potential material for a water treatment method. The results of this study will be helpful in the development of aluminum modified silica magnetic adsorbents that can be used to remove phosphate in aqueous solution. Copyright © 2011 Society of Chemical Industry     

Hydrogen in aluminum during alkaline corrosion

The thermodynamic state of hydrogen in aluminum during alkaline corrosion was investigated, using a two-compartment hydrogen permeation cell with an Al/Pd bilayer membrane. The open-circuit potential of the Pd layer in a pH 7.0 buffer solution was monitored to sense the hydrogen chemical potential, μ_H. At pH 12.5-13.5, the measurements established a minimum μ_H of 0.55 eV relative to the ideal gas reference, equivalent to a H₂ gas pressure of 5.7 GPa. Statistical mechanics calculations show that vacancy-hydrogen defects are stable in Al at this condition. A dissolution mechanism was proposed in which H at very high μ_H is produced by oxidation of interfacial aluminum hydride. The mechanism explains the observed rapid accumulation of H in the metal by extensive formation of vacancy-hydrogen defects.     

Mechanical activation-assisted combustion synthesis of in situ aluminum matrix hybrid (TiC/Al2O3) nanocomposite

The aim of this study is the synthesis of aluminum-based metal matrix nanocomposites reinforced with in situ TiC and Al₂O₃ hybrid reinforcements by the mechanically activated combustion synthesis. The composites were fabricated from the powder blends consisting of aluminum, rutile and graphite with an excess amount of aluminum following the 14Al–3TiO₂−3C system and milled up to 30 h. Phase evolutions and structural changes during ball milling and combustion synthesis were studied by X-ray diffraction technique, field-emission gun scanning electron microscopy and transmission electron microscopy. The results showed that even after 10 h of milling, no new phases were formed. The increasing of milling time caused the broadening of all the peaks indicating a decrease in the crystallite size and an increase in the lattice strain. These results showed that Al, C and TiO₂ nanocrystallites could be obtained during the ball-milling process. The result of combustion synthesis of un-milled powders confirmed that no new phases were found. In comparison with un-milled powder mixture, the 10 h milled powder could be easily ignited and XRD, HRSEM and TEM results confirmed that Al/TiC–Al₂O₃ nanocomposite was successfully synthesized through combustion method from the mechanical activated powder mixture. Mechanical activation via high energy ball-milling provided to the initial powder mixture extra energy, which is needed to increase the reactivity of powder mixture and to make possible the ignition and the sustaining of combustion.     

Synthesis of High‐Purity Ti3SiC2 by Microwave Sintering

High‐purity ternary laminated compound Ti₃SiC₂ was successfully synthesized by a microwave heating method in the flowing argon for the first time. The mixtures of titanium, silicon, and graphitic carbon (C_gc) or activated carbon (C_ac) with different molar ratios were used to investigate the reaction mechanisms. It was confirmed that Ti₃SiC₂ with high purity of 98 vol.% was achieved without the aids of Al. The optimum experimental parameters were determined as Ti/Si/C_gc having the molar ratio of 3/2.2/2, first holding at 1480°C for 30 min, and subsequent dwelling at 1300°C for 60 min.     

Synthesis of Ti3SiC2 MAX phase powder by a molten salt shielded synthesis (MS3) method in air

Titanium silicon carbide (Ti₃SiC₂) powder was synthesized by molten salt shielded synthesis route of elemental reactants. Potassium bromide (KBr) was used for gas-tight encapsulation of the consolidated reaction mixture for further high temperature processing. The synthesis of Ti₃SiC₂ powder was carried out in air, the salt cladding and molten salt pool provided for the protection of the material against oxidation both at low and high temperature. The process yielded free flowing Ti₃SiC₂ powders without the need of a milling step. Al addition to the reaction mixture resulted in a high purity (96 wt. %) of Ti₃SiC₂ at a synthesis temperature of 1250 °C. The synthesized micro-metric Ti₃SiC₂ can be milled to nano-metric powders.     

Synthesis of Li/Al LDH using aluminum and LiOH

The synthesis of Li/Al layered double hydroxide (LDH) within the ternary system of LiOH–Al–H₂O was investigated to determine the feasibility of a one-step synthetic process and the optimal yield composition for the process. The dissolution of Al metal in LiOH solutions was spontaneous and resulted in the generation of H₂ gas and heat. Pure Li/Al LDH precipitate was obtained when the Al/Li molar ratio was between 0.1 and 2 and was independent of the LiOH concentration. The yield of Li/Al LDH was correlated with the initial amounts of LiOH and Al in the system and inversely correlated to the quantity of water. However, the Al metal could not be completely dissolved if there was not enough water content due to its consumption in the reaction. The optimal yield of Li/Al LDH, as defined by the efficient conversion from Al and LiOH to Li/Al LDH, was obtained with a LiOH concentration = 3 mol kg^− 1 and an Al/Li molar ratio = 2. The reaction mechanism involves the dissolution of the Al metal in LiOH and the formation of aluminate ions in solution. The aluminate ion and the hydrated Li⁺ ion subsequently form an ion pair, and the polarizing effect of the Li⁺ on the water in its hydration shell leads to the acid hydrolysis of the aluminate ion and the formation of Li/Al LDH. This study demonstrated a synthetic process for Li/Al LDH with a high anion exchange capacity. This synthetic process will have additional economical and environmental benefits if recycled Al metal can be used in the synthesis and the evolved hydrogen gas and heat from the process can be further utilized.     

Reinforcement of the MCFC matrix by Al-based additives: Effect of lithiation

The matrix material in a Molten Carbonate Fuel Cell, usually LiAlO₂, has an important role in the ionic conduction, gas sealing and electrolyte retention. To avoid cracking, this material has been reinforced with various additives, mostly Al-based, which are subject to in situ lithiation. In this work, matrices were systematically synthesized through a fast and more environmentally friendly route and characterized, with two types of reinforcing agent, either Al powder or Al₂O₃ fibers, both with and without carbonates. Then, a comparative analysis was done, in terms of mechanical strength and porosity, on the effect of adding Al powder and Al₂O₃ fibers and their subsequent lithiation. This reaction was found to be quantitative after 50 h at 650 °C, and matrices with reinforcing agent and carbonates featured increased mechanical strength by a factor up to 2 compared to matrices with only reinforcing agent, reaching 0.61 kgf.mm^?2. Al powder was also found to be better suited than Al₂O₃ fibers for addition in a matrix, also contributing to enhance the porosity, particularly after lithiation.     

Cathodic reaction kinetics and its implication on flow-assisted corrosion of aluminum alloy in aqueous ethylene glycol solution

The cathodic reaction kinetics and anodic behavior of Al alloy 3003 in aerated ethylene glycol–water solution, under well-controlled hydrodynamic conditions, were investigated by various measurements using a rotating disk electrode (RDE). The transport and electrochemical parameters for cathodic oxygen reduction were fitted and determined. The results demonstrate that the cathodic reaction is a purely diffusion-controlled process within a certain potential region. The experimentally fitted value of diffusion coefficient of oxygen is 3.0 × 10⁻⁸ cm² s⁻¹. The dependence of cathodic current on rotation speed was in quantitative agreement with Levich equation. At potentials more positive than the diffusion controlled region, the cathodic process was controlled by both diffusion and electrochemical kinetics. The electrochemical reaction rate constant, k ₀, was determined to be 1.1 × 10⁻⁹ cm s⁻¹. There is little effect of electrode rotation on anodic behavior of Al alloy during stable pitting. However, fluid hydrodynamics play a significant role in formation of the oxide film and the Al alloy passivity. An enhanced electrode rotation would increase the mass-transfer rate of solution, and thus the oxygen diffusion towards the electrode surface for reduction reaction. The generated hydroxide ions are favorable to the formation of Al oxide film on electrode surface.