Aluminum Chloride Solution Research Articles

Investigation of Filiform Corrosion on Coated Aluminum Alloys by FTIR Microspectroscopy and Scanning Kelvin Probe

Fourier transform infrared microspectroscopy has been used to provide a better understanding of filiform corrosion processes on coated aluminum alloys. Results from scanning Kelvin probe microanalysis are also presented. The investigations were performed on untreated or chromium-free pretreated AA6016 covered with an organic coating. An active head with a Volta potential approximately 400 mV lower than that of the tail of the filament was identified. The head was filled with a partially hydrolyzed aluminum chloride solution, containing monomeric and polymeric cations of aluminum, which are highly soluble and hygroscopic, and contain monomeric and polymeric cations of aluminum. The aluminum ions produced by the anodic reaction in the front of the head are hydrolyzed by the hydroxyl ions generated by the cathodic oxygen reduction, which occurs at the back of the head and the tail. Complete neutralization of the aluminum chloride solution in the back of the head and in the tail leads to the formation of an aluminum hydroxide gel. During the precipitation process, carbonate ions are also incorporated in the gel. A carbonate containing the mineral, dawsonite, was formed in the scratch. © 2002 The Electrochemical Society. All rights reserved.

Early chronic aluminium exposure impairs long-term potentiation and depression to the rat dentate gyrus in vivo

As an important neurotoxin, aluminium can cause cognitive dysfunctions and mental diseases. Previous studies have reported that aluminium impaired long-term potentiation (LTP) in vivo and in vitro. Here, we utilise two models of synaptic plasticity, LTP and long-term depression (LTD) to study the effects of aluminium on synaptic plasticity in vivo. Neonatal Wistar rats were chronically exposed to aluminium from birth to weaning via the milk of dams fed with 0.3% aluminium chloride solution. Excitatory postsynaptic potential (EPSP) and population spikes (PS) were recorded from the dentate gyrus (DG) of adult rats by electrically stimulating the perforant path. The following results were obtained: (1) The input/output function indicated that, as compared to controls, aluminium increased the baseline amplitude of the PS, but decreased the baseline slope of EPSP. (2) Aluminium significantly prevented LTD in PS (controls: 77.36±6.7%, n=7; aluminium-exposed: 102.01±9.1%, n=7; P<0.05) and decreased the LTD amplitude in EPSP (controls: 76.61±4.1%, n=7; aluminium-exposed: 94.31±7.9% n=7, P<0.05). (3) Aluminium reduced the amplitude of LTP in both PS (controls: 190±16.1%, n=7; aluminium-exposed: 135±9.7%, n=7; P<0.05) and EPSP (control: 132±9.3%, n=7; aluminium-exposed: 115±10.6%, n=7; P<0.05). As for LTD and LTP, PS was impaired more seriously than EPSP in aluminium-exposed rats. (4) Aluminium exposure decreased the paired-pulse facilitation (PPF) of PS at 30–150 ms interpulse interval (IPI), and reduced 93.5% of PPF at 80 ms IPI in PS (controls: 243.4±39.8%, n=7; aluminium-exposed: 149.9±12.3%, n=7). There was no significant difference in EPSP of PPF. From these results we conclude that aluminium exposure in neonatal rats thus reduces the amplitude of LTP and PPF and blocks the induction of LTD in the DG. We suggest that aluminium affects both presynaptic and postsynaptic mechanisms of synaptic transmission.

Preparation of aluminum oxide particles using ammonium acetate as precipitating agent

The effect of ammonium acetate on the preparation of alumina particles as precipitating agent was investigated. Alumina particles were prepared by precipitation of aqueous aluminum chloride solution by using ammonium acetate and ammonium hydroxide. The thermal behaviors, morphologies and surface area were studied for alumina particles formed by ammonium acetate and compared with those of particles formed by ammonium hydroxide. The particles formed by ammonium acetate showed a narrower size distribution, spherical shape, larger surface area and lower crystallinity. These results were explained based on the chelating effects of acetate ions.

MD+QM calculations of the OH vibrational stretching band in an aqueous aluminium(III) chloride solution

The OH stretching vibrational band has been calculated by an ‘MD+QM’ approach for the water molecules in the first hydration shell of the Al 3+ ion in a dilute AlCl 3 aqueous solution. Molecular Dynamics-generated geometrical snapshots provided the molecular positions, which were subsequently used in ab initio calculations of charge-embedded ion-water clusters at the HF and B3LYP levels. The ion-water clusters which were treated quantum-mechanically were Al 3+(H 2O) 6(H 2O) x ( x=2 or 3), where a few water molecules from the second hydration shell were included. 60 oscillators were selected from the MD dumps, and anharmonic vibrational frequencies were computed from the ab initio-weighted energy curves. Density-of-states bands as well as infrared-intensity-weighted bands are presented. Our average frequency downshift is only 60% of the experimental downshift. Further refinement of the method will concentrate on the description of the remaining part of the second, and the third, hydration shells.

Lack of effects of vitamin E on aluminium-induced deficit of synaptic plasticity in rat dentate gyrus in vivo

Aluminium (Al), has the potential to be neurotoxic in humans and animals, and is present in many manufactured foods and medicines and is also added to drinking water for purification purposes. Our previous study demonstrated that chronic Al exposure induced deficits of both long-term potentiation (LTP) and long-term depression (LTD) of excitatory postsynaptic potential (EPSP) and population spike (PS) in rat dentate gyrus (DG) of hippocampus in vivo (Wang et al., 2001). The purpose of the present study was to investigate whether the Al-induced impairment of synaptic plasticity could be reversed by dietary supplementation with vitamin E (Vit E; α-tocopherol). Neonatal Wistar rats were exposed to Al from parturition throughout life by drinking 0.3% aluminium chloride (AlCl 3) solution or a diet supplemented with Vit E at 500 μg/g/day with 0.3% AlCl 3. The input/output (I/O) function, EPSP and PS were measured in DG area of adult rats (80–100 days of age) in response to stimulation applied to the lateral perforant path. The results showed that: (1) chronic Al exposure reduced the amplitudes of both EPSP LTP (control: 130.4±3%, n=7; Al-exposed: 110±2%, n=9, P<0.001) and PS LTP (control: 241±19%, n=7; Al-exposed: 130±7%, n=9, P<0.001) significantly. Vit E had no significant effects on the Al-induced deficits of EPSP LTP (Al-exposed: 110±2%, n=9; Al-exposed+Vit E: 112±2%, n=8, P>0.05) and PS LTP (Al-exposed: 130±7%, n=9; Al-exposed+Vit E: 129±4%, n=8; P>0.05); (2) the amplitudes of EPSP LTD (control: 84±4%, n=7; Al-exposed: 92±7%, n=9, P<0.01) and PS LTD (control: 81±4%, n=7; Al-exposed: 98±5%, n=9, P<0.001) were also decreased by Al treatment. The impaired EPSP LTD (Al-exposed: 92±7%, n=9; Al-exposed+Vit E: 93±4%, n=8, P>0.05) and PS LTD (Al-exposed: 98±5%, n=9; Al-exposed+Vit E: 94±6%, n=8, P>0.05) were also not significantly affected by Vit E treatment. It was suggested that dietary supplementation with Vit E did not reverse the impairment of synaptic plasticity induced by Al in DG in vivo.

Water Vapor Adsorption of Porous Materials of AlOOH-Al2O3.

Porous materials of AlOOH-Al2O3 were prepared by precipitation of aluminium chloride solution using aqueous ammonia, and by heating at various temperatures below 400°C. The obtained porous materials showed steep increase of water vapor adsorption in the relative humidity range of 55-90%. This porous material is, thus, considered to be a candidate for intelligent humidity control materials (Humidity Self-controlled materials). Pores formed by sublimation of coexisting ammonium chloride in the sample contribute to the improvement of the humidity conditioning property.

Synthesis and characterization of micro-mesoporous solids: pillared clays

In this work, the synthesis and characterization of micro-mesoporous materials obtained from clays, with Fe, Co and Rh are presented. These materials can be used in Catalysis or Adsorption when the necessary active phases are those metals. The porous materials were Pillared Clays — PILCs — synthesized from a natural Spanish laminar clay with two kinds of Aluminum oligocations. One of these oligocations was obtained from a suspension of a commercial product, Locron (aluminum chlorhydrate), and the other was synthesized in the laboratory from Aluminum chloride and sodium hydroxide solutions. Two Al-PILCs were prepared from these oligocations: the first one (from Locron) by a quick method; the second one by a conventional method. Both Al-PILCs show differences in their acidity and porous distribution related to the presence of Al-pillars with different structure. They also show a great increase in their basal distance and their specific area, which is associated to the formation of microporous. Both pillared clays were impregnated with Co, Fe or Rh solutions and then characterized by different techniques — AAS, XRD, N 2-sorption and acidity studies by TGA — obtaining data about their porosity and location of the metals in oxidize state. After the impregnation, the specific area decreases but keeps some of their porous structure if compared with the PILCs. To conclude, materials with stable porous characteristics are obtained from natural clays in order to be used in catalytic and adsorption processes.

Vasopressin reverses aluminum-induced impairment of synaptic plasticity in the rat dentate gyrus in vivo

Aluminum (Al), an important neurotoxin, contributes to a variety of cognitive dysfunction and mental diseases. Previous studies have demonstrated that Al impairs hippocampal long-term potentiation (LTP) in vitro and in vivo. In the present study, both LTP and LTD (long-term depression) were recorded in the same animal to investigate the Al-induced impairment of synaptic plasticity. Another aim of the present research was to verify whether the impairment of synaptic plasticity induced by Al could be reversed by vasopressin (VP) treatment. Neonatal Wistar rats were exposed to Al from parturition through adulthood (pre- and post-weaning) by the drinking of 0.3% aluminum chloride (AlCl 3) solution. The input–output (I/O) function, paired-pulse reaction (PPR), excitatory postsynaptic potential (EPSP) and population spike (PS) amplitude were measured in the dentate gyrus (DG) of adult rats (60–90 days) in response to stimulation applied to the lateral perforant path. The results showed: (1) Al reduced the amplitudes of both EPSP LTP (control: 132±7%, n=7; Al-exposed: 115±10%, n=8, P<0.05) and PS LTP (control: 242±18%, n=7; Al-exposed: 136±7%, n=8, P<0.01) significantly. The amplitudes of EPSP LTD (control: 82±6%, n=7; Al-exposed: 92±7%, n=8, P<0.05) and PS LTD (control: 81±4%, n=7; Al-exposed: 98±5%, n=8, P<0.05) were also decreased by Al treatment. The Al-induced impairments of PS LTP and PS LTD were more serious than that of EPSP LTP and EPSP LTD. (2) In control rats, VP had an increase in the PS LTP amplitude (control: 242±18%, n=7; control+VP: 358±23%, n=6, P<0.01), while it had no significant effects on PS LTD (control: 81±4%, n=7; control+VP: 76±7%, n=6, P>0.05). (3) In Al-exposed rats, VP had a significant increase in the amplitudes of both PS LTP (Al-exposed: 136±7%, n=8, Al-exposed+VP: 255±16%, n=6, P<0.01) and PS LTD (Al-exposed: 98±5%, n=8; Al-exposed+VP: 81±6%, n=6, P<0.05). After the application of VP, the range of synaptic plasticity (PS LTP+PS LTD) in Al-exposed rats increased from 38% to 174%, which surpassed that in control rats (161%). It was suggested that VP could reverse Al-induced impairment of synaptic plasticity and might be an effective medicine to cure Al-induced neurological disorders.

Role of chromate, molybdate and tungstate anions on the inhibition of aluminiumin chloride solutions

The effect of CrO4 2−, MoO4 2− and WO4 2− anions on the inhibition of aluminium corrosion in 0.5 M NaCl solution was investigated. The study comprised potentiodynamic polarization, potentiostatic current–time measurements complemented by SEM–EDAX and XPS investigations. It was found that, the pitting potential of an Al electrode in 0.5 M NaCl solution shifts in the positive direction by addition of CrO4 2−, MoO4 2− and WO4 2− anions, and the shift in potential increases with increase in concentration. A pronounced inhibiting influence was achieved on addition of CrO4 2−, MoO4 2− and WO4 2− anions to the electrolyte during potentiostatic current–time measurements. Chromate anions exhibit a great passivating influence during I/t measurements. This can be explained by the fact that the chromate anion, as a powerful oxidizing agent, is capable of oxidizing the corrosion sites to give a stable Al2O3 film. The inhibition observed on addition of molybdate anions is attributed to the adsorption and reaction of MoO4 2− anions on the electrode surface forming a molybdate layer which selectively impedes the ingress of Cl− ions and hence inhibits the pitting attack. The adsorption of WO4 2− anions at flawed areas and developing pits was found to be the main factor for the observed inhibition.

Preparation of Mullite Ceramics from Coprecipitated Aluminum Hydroxide and Kaolinite Using Hexamethylenediamine

Mullite ceramics have been prepared from an aqueous suspension of kaolinite (raw or ground) and aluminum hydroxide. The precursor was coprecipitated in the mixture using hexamethylenediamine (HMDA) or ammonium hydroxide, and a solution of aluminum chloride from acid dissolution of wastes of aluminum metal. The precursor and the resulting materials were characterized and studied by X‐ray diffraction, thermal methods, and mechanical strength and porosity measurements. The feasibility of the proposed chemical processing route for mullite preparation was demonstrated, in particular using HMDA as a precipitating agent for aluminum hydroxide instead of ammonium hydroxide, which adversely affects the system reactivity. The use of HMDA, as compared with ammonium hydroxide, and ground kaolinite produces single‐phase mullite and enhances the flexural strength (maximum of 49 MPa) of the resultant ceramic porous bodies (porosity ca. 52–45 vol%) fired at 1550–1600°C for 30 min.

Bench-Scale Decomposition of Aluminum Chloride Hexahydrate to Produce Poly(aluminum chloride)

Partial thermal decomposition of aluminum chloride hexahydrate was carried out in a rotary glass tube at temperatures of 230−260 °C. The decomposition solid product was dissolved in water to produce a ploy(aluminum chloride) (PAC) solution. The effects of the decomposition temperature, the rotation speed of the tube, and the feed rate of aluminum chloride hexahydrate on the properties and morphology of the basic chloride resulting from the decomposition were investigated. The basicity of the PAC obtained by dissolving the decomposition solid product in water was related to the extent of decomposition by the linear equation Y = 2.025 + 1.063X, where Y is the basicity (%) and X is the extent of decomposition (%). The PAC solution prepared by the present method showed a flocculation capacity comparable to that of an existing PAC made from aluminum hydroxide and hydrochloric acid.

Sol–gel synthesis of YAG/Al 2O 3 long fibres from water solvent systems

Y 3Al 5O 12(YAG)/Al 2O 3 long fibres were prepared by a sol–gel method using water as the solvent. They were synthesized from aluminium nitrate and chloride solutions, aluminium salt, aluminium metal and Y 2O 3. The starting materials were dissolved by refluxing at 100°C for 2–18 h and were then condensed. The fibre spinnability was examined by a hand drawing method using a glass rod. In the nitrate solution system, the composition range available for fibre preparation was very limited because nitrate ions decomposed during the refluxing, raising the solution pH and precipitating the Y component. On the other hand, the composition range of the fibres prepared from the chloride system was 0/10⩽YAG/Al 2O 3⩽6/4 (volume ratio) and was wider than that from the nitrate system. The YAG/Al 2O 3 fibres prepared by firing at 1300°C became denser with faster heating rates. The grain size in the fired fibres was small, below the firing temperature at 1400°C, but increased greatly above that temperature.

Thermodynamic investigations of aqueous solutions of aluminium chloride

The activity of water in {x1AlCl3+ (1 −x1)H2O } has been determined by measurement of vapour pressures in the temperature range (300 to 342) K, and the molality range (0.421 to 3.033)mol · kg−1. The behaviour of the solution is described by the Pitzer model. The[Al(OH)(H2O)5]2+ in the system is calculated by considering the first hydrolysis step in the aluminium chloride solutions.

Molecular dynamics simulation of an aqueous aluminium(III) chloride solution with three‐body interactions

Molecular dynamics simulation of an aqueous aluminium(III) chloride solution with three‐body interactions

Molecular dynamics simulation of an aqueous aluminium(III) chloride solution with three-body interactions

A molecular dynamics simulation of a 0.28 molar aqueous AlCl3 solution was performed with the flexible Bopp, Jancsó, and Heinzinger (BJH) model for water and a newly developed three-body potential for Al3+–(H2O)2 interactions derived from ab initio calculations. The simulations extended over 25 ps at an average temperature of 300 K. The structural properties of the solution are discussed on the basis of radial distribution functions and the orientation of the water molecules. Dynamical properties and OH frequency shifts were calculated from autocorrelation functions for the hydration shells of the ions. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 892–906, 2000

Porous mullite and mullite-based composites by chemical processing of kaolinite and aluminium metal wastes

Porous mullite and mullite-based composites have been prepared from a chemical processing route starting from a precursor obtained using an aqueous suspension of kaolinite and aluminium hydroxide. This was coprecipitated with kaolinite using ammonium hydroxide or hexamethylenediamine (HMDA), and a solution of aluminium chloride prepared from dissolved recycled wastes of aluminium metallic powders. Raw and ball-milled kaolinite during 30 minutes have been employed. The precursors and the obtained materials were characterized by X-ray diffraction (XRD) and thermal diffractometry, simultaneous differential thermal analysis (DTA) and thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), flexural strength test at room temperature and Hg intrusion porosimetry. The feasibility of using HMDA as a precipitating agent in the proposed chemical processing route for mullite preparation has been demonstrated. The advantageous use of HMDA, as compared with ammonium hydroxide, and ground kaolinite, as compared with raw kaolinite, produced single-phase mullite materials and enhanced the flexural strength of the resultant ceramic porous bodies by firing at 1550–1600 °C (porosity 50–45 vol%). These materials would have application as refractories, substrates, filters and thermal isolating materials.

The inhibition mechanism of pitting corrosion of pure aluminum by nitrate and sulfate ions in neutral chloride solution

The inhibition mechanism of pitting corrosion of natural oxide film-covered pure aluminum by NO− 3 and SO2− 4 ions has been examined in 0.1 M NaCl solution using potentiodynamic polarization experiments, a.c. impedance spectroscopy, Auger electron spectroscopy and a combination of the potentiostatic current transient method and optical microscopy. It was found that NO− 3 ions can be incorporated into the natural oxide film on pure aluminum at open-circuit potential, but the incorporation of SO2− 4 ions into the film hardly occurs. The incorporation of NO− 3 ions lowered the pitting susceptibility of pure aluminum in 0.1 M NaCl solution. Based upon the experimental results, it is suggested that the pitting corrosion inhibition mechanism by anions can be classified into two different groups: inhibition by competitive adsorption of anions (SO2− 4) with Cl− ions and inhibition by the incorporation of anions (NO− 3) into the film rather than competitive adsorption. Both cases may impede the incorporation of Cl− ions into the film, thus inhibiting pitting corrosion of natural oxide film-covered pure aluminum in chloride solutions.

Synthesis, characterization and first application of new alumina hydrosols

An alumina hydrosol is synthesized by controlled hydrolysis of an aqueous solution of aluminium chloride using the thermal decomposition of urea. After dialysis, a transparent and fluid colloidal dispersion is obtained which can be used to prepare alumina coatings. The characteristics of the sol, the structure and the thermal evolution of the resulting alumina gels are studied.

Mechanical Properties and Microstructure of Nano-SiC–Al 2O 3 Composites Densified by Spark Plasma Sintering

Heterogeneous precipitation method has been used to produce 5 vol% SiC–Al 2O 3 powder, from aqueous suspension of nano-SiC, aqueous solution of aluminium chloride and ammonia. The resulting gel was calcined at 700°C. Nano-SiC–Al 2O 3 composites were densified using spark plasma sintering (SPS) process by heating to a sintering temperature at 1350, 1400, 1450, 1500 and 1550°C, at a heating rate of 600 °/min, with no holding time, and then fast cooling to 600°C within 2–3 min. High density composites could be achieved at lower sintering temperatures by SPS, as compared with that by hot-press sintering process. Bending strength of 5 vol% SiC–Al 2O 3 densified by SPS at 1450°C reached as high as 1000 MPa. Microstructure studies found that the nano-SiC particles were mainly located within the Al 2O 3 grains and the fracture mode of the nanocomposites was mainly transgranular fracture.

SiC-ZrO 2(3Y)-Al 2O 3 nanocomposites superfast densified by spark plasma sintering

Heterogeneous precipitation method has been used to produce 5 wt% SiC-15 wt% ZrO 2-Al 2O 3 powder, from aqueous suspension of nano-SiC, aqueous solutions of zirconium oxychloride, yttrium nitrate and aluminium chloride and ammonia. The resulting gel was calcined at 1100 °C. Nano-SiC-ZrO 2(3Y)-Al 2O 3 composites were superfast densified using spark plasma sintering (SPS) process by heating to a sintering temperature in the range of 1350 to 1600 °C, at a heating rate of 600 °C/min, with no holding time, and then fast cooled to 600 °C within 2–3 minutes. High density composites could be achieved at lower sintering temperatures by SPS, as compared with that by hot-press sintering process. Bending strength of 5 wt% SiC-15 wt% ZrO 2(3Y)-Al 2O 3 superfast densified by SPS at 1450 °C reached as high as 1.2 GPa. Microstructure studies found that the nano-SiC particles were mainly located within the Al 2O 3 grains and the fracture mode of the nanocomposites was transgranular fracture.