Aluminum Isopropoxide Research Articles

Synthesis, characterization and thermal analysis of microencapsulated alumina–myristic acid phase change material for thermal energy storage

Alumina (Al2O3) is an inorganic shell material with desirable properties such as high thermal conductivity, chemical stability, resistance to corrosion and high thermal diffusivity. In this work, microcapsules with myristic acid (MA) core and alumina shell were generated by sol–gel technique. Aluminum isopropoxide (AIP) has been used as a shell forming reagent. The analytical and thermal characterizations of microencapsulated MA@Al2O3 are reported. Three weight ratios of MA/ (AIP), (1:1), (1:0.75) and (1:0.5) were made by varying the compositions of MA and AIP. SEM results revealed that the MA@Al2O3 microcapsules have a spherical shape with a grain size of 2–5 μm. The maximum weight loss of microcapsules is comparatively higher than pristine material. Thermal stability of the MA improved after encapsulation. The DSC results revealed an encapsulation ratio 88% and encapsulation efficiency of 92% for the (1:1) ratios with a latent heat of 150 J/g during solidification and 147 J/g during crystallization.

Vibration and Corrosion Analysis of Modified Alumina Coating over Aluminum Alloy

This analysis is concerned with the investigation of the capability of alumina coating deposited by spray coating method using oxime-modified aluminum(III) isopropoxide as a sol–gel precursor to improve vibration damping and anti-corrosion properties of aluminum alloys. Coating microstructures, thickness and roughness were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies, respectively. To this end, the quality of the coating was determined by the corrosion rate which was analyzed by mean of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The vibration and noise technique were applied to measure comparison of vibration and noise damping of bare and alumina coated samples. The results indicate the alumina coating deposited over aluminum alloy by spray coating method is uniform, homogenous, crack free, having high vibration damping and anti-corrosive behavior.

Nanoremediation of dimethomorph in water samples using magnesium aluminate nanoparticles

Abstract The present work aims to prepare magnesium aluminate nanoparticles (MgAl2O4 NPs) using aluminum isopropoxide and magnesium ethoxide by hydrolysis reaction and to investigate them as new adsorbent materials for the extraction and clean-up of dimethomorph pesticide from tap water. The MgAl2O4 NPs were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The XRD result confirmed the formation of the spinal cubic structure in the fabricated sample. A solid-phase extraction (SPE) cartridge packed with MgAl2O4 NPs was used to extract dimethomorph pesticide from water samples. The extracted pesticide solution was quantified using a validated liquid chromatography mass spectrometry (LC-MS-MS) method. The limit of quantification (LOQ) was found to be 1 μ g/L, signifying the sensitivity of the LC-MS-MS. The water samples were passed through the cartridges and investigated to find the adsorption strength of the pesticides under the influence of temperature, volume of sample, flow rate, pH and ionic strength on the efficiency of the cartridge. The extraction efficiency of the developed MgAl2O4 NPs SPE was found to be higher than that of commercially available SPE- C 18 cartridge. The average recoveries of the pesticides ranged from 90%–94% which was obtained at two different fortification levels of 1 and 10 μ g/L using MgAl2O4 NPs SPE.

Influence of Aluminum Sources on Synthesis of SAPO-34 and NH3-SCR of NOx by as-Prepared Cu/SAPO-34 Catalysts

The full article will be published in the English version of the journal "Catalysis in Industry" No. 1, 2021.The synthesis of the microporous SAPO-34 molecular sieve goes from a combination of three templates: triethylamine, tetraethylammonium hydroxide, and morpholine under hydrothermal conditions. Two aluminum sources, namely aluminum hydroxide, and aluminum isopropoxide, were used exclusively to synthesize SAPO-34 zeolites. The effects of aluminum sources on the crystallization and physicochemical properties of SAPO-34 were studied thoroughly. The synthesized samples were characterized by using different characterization methods, including XRD, FE-SEM, N2 isotherm, EDS, and NH3-TPD. The results illustrate that the various sources of aluminum used for the synthesis of SAPO-34 materials extremely affect the crystallinity, morphology, and density of acid sites. Besides, the influence of aluminum sources on the performance of NH3-SCR technology was studied with Cu/SAPO-34 catalysts in a fixed-bed flow reactor. The two Cu/SAPO-34 catalysts promoted different NO and NH3 conversions between 200–600 °C though they share similar Cu content, which was loaded by the ion-exchange method in aqueous solution. In addition, the different Cu species in the two catalyst samples are surveyed by H2-TPR, while the EPR method is also used to assess the coordination of the copper element in the two catalysts.

Synthesis and characterization of sol-gel derived monophasic mullite powder

Abstract High-purity microfine mullite precursor powder of stoichiometric chemical composition, 3Al2O3.2SiO2, was synthesized through the sol-gel route using aluminum isopropoxide and tetraethyl orthosilicate. The derived mullite precursor powder was characterized by BET surface area, particle size distribution, Fourier-transform infrared spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy. Phase analysis of the precursor powder and calcined samples at different temperatures was done by XRD. Non-isothermal crystallization kinetics of mullite precursor was studied by TG-DTA in static air using heating rates of 5.0, 7.5, 10.0, 12.5, and 15 K.min-1. Grain morphology was studied by SEM. The results showed that synthesized mullite precursor powder possessed homogeneity of Al and Si components, and the amorphous precursor powder was converted to monophasic mullite crystal when heat-treated at 970 °C. Based on Flynn-Wall-Ozawa and Kissinger equations, the activation energy associated with the crystallization of mullite was determined to be 1189.8 and 1189.0 kJ.mol-1, respectively.

Enhanced Cathode Performance: Mixed Al2O3 and LiAlO2 Coating of Li1.2Ni0.13Co0.13Mn0.54O2.

Li-rich, manganese-based cathode materials are attractive candidates for Li-ion batteries because of their excellent capacity, but poor rate and cycle performance have limited their commercial applications. Herein, Li-rich, manganese-based cathode materials were modified with aluminum isopropoxide as an aluminum source modifier using a sol-gel technique followed by a wet chemical method. To investigate the structure, morphology, electronic state, and elemental composition of both pristine- and surface-modified Li1.2Ni0.13Co0.13Mn0.54O2, various characterizations were performed. Based on density functional theory simulations and the results of electrochemical tests, the surface of the modified cathode material was found to contain at least part of the LiAlO2 phase. This was attributed to the aluminum isopropoxide reacting with a Li2CO3/LiOH byproduct on the material surface to form LiAlO2 with a three-dimensional Li-ion channel structure. Electrochemical testing revealed that a 3 wt % aluminum isopropoxide coating of cathode materials exhibited excellent electrochemical performance. Furthermore, the initial Coulombic efficiency and discharge capacity at 0.1 C were up to 88.55% and 272.7 mAh g-1, respectively. A final discharge capacity of 186.4 mAh g-1 was achieved, corresponding to a capacity retention of 83.55% after 300 cycles at 0.5 C. This was attributed to LiAlO2 partially accelerating the diffusion of Li ions and Al2O3 aiding the avoidance of side reactions in the mixed coating layer by partially protecting the structure.

Synthesis of Fine-Crystalline SAPO-11 Zeolites and Analysis of Their Physicochemical and Catalytic Properties

Results of crystallization of two 1.0Al2O3 ⋅ 1.0P2O5 ⋅ 0.4SiO2 ⋅ 1.0DPA ⋅ 50H2O silicoaluminophosphate gels are compared; the gels are synthesized using pseudoboehmite in one case and aluminum isopropoxide in the other. It is shown that the choice of aluminum source significantly affects the phase composition of the resulting silicoaluminophosphate gels and the physicochemical properties of SAPO-11 samples crystallized from the gels and their catalytic properties in the vapor-phase isomerization of cyclohexanone oxime to caprolactam.

Influence of boehmite intermediate layer as covalent linker on synthesis of LTA zeolite coatings

The incorporation of nanostructured materials, such as LTA-type zeolite on the silicon wafers, opens a very interesting door to the use of these materials within silicon based microfabrication technologies. This work studies the deposition and intergrowth of defect-free LTA-type zeolite layer onto 3-inch Silicon wafers with a layer of SiO2 subjected to pretreatment. The main disadvantage associated with zeolite layer synthesis are crack the formation of cracks and difficulty of obtaining a uniform layer. By modifying the supports with boehmite, a substantial improvement was observed in terms of layer continuity and crystal intergrowth in comparrison to coatings prepared on cationic polymer, poly (diallyldimethylammonium chloride). An LTA- type zeolite layer was synthesized in a range of 350 to 1300 nm via hydrothermal ex-situ method at 363 K for 12 h. Tetramethylammonium hydroxide (TMAOH) was used as a template, and aluminum isopropoxide and colloidal silica were used as Al and Si sources, respectively.

Synthesis and characterizations of different aluminosilicate nano matrices

Aluminosilicates are interweaved network of aluminates and silicates having intermolecular and intramolecular porosity for which they find application in the area of adsorption, catalysis, pyrolysis and so on. They maintain the thrust of their existing applications and still entail new applications within the fields of chemical process and separation. The product phase and properties of the aluminosilicate vary with varying synthetic methods such as the sequence of addition of reagents which is outlined here in this study. The sequence of addition of aluminium iso propoxide and sodium silicate is divided into three parts. The phases obtained are zeolite, and crystoballite alpha in part-1. The phases of part-2 are sodalite and crystoballite beta. In part-3 the phases are mostly zeolite.

Effect of Aluminum Doping on the Performance and Microstructure of Methyl-Modified SiO2 Sol

With methyltriethoxysilane as hydrophobic precursors and aluminum isopropoxide as the aluminum source, the Al2O3/SiO2 sols and their gel materials were prepared. The effects of aluminum content (nAl) on the viscosity (η), density (ρ), reaction rate constant (k), Gibbs energies of activation for viscous flow (ΔG*), particle size of Al2O3/SiO2 sols were studied. And the high temperature calcined materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results show that, with the increase of nAl, the η, n and ΔG* values of the Al2O3/SiO2 sols decrease while the k and ρ values and average particle sizes increase. There is strong intermolecular interaction between the Al2O3 and SiO2 sol molecules. The Al-O-Si bond exists in the Al2O3/SiO2 materials before and after calcination at 350 °C. Calcination at 350 °C in N2 atmosphere can change the phase structure of Al2O3/SiO2 sample greatly, which can make the γ-AlOOH in the Al2O3/SiO2 gel material convert to γ-Al2O3 through dehydration.

Solvent Effects in the Homogeneous Catalytic Reduction of Propionaldehyde with Aluminium Isopropoxide Catalyst: New Insights from PFG NMR and NMR Relaxation Studies.

Solvent effects in homogeneous catalysis are known to affect catalytic activity. Whilst these effects are often described using qualitative features, such as Kamlet‐Taft parameters, experimental tools able to quantify and reveal in more depth such effects have remained unexplored. In this work, PFG NMR diffusion and T 1 relaxation measurements have been carried out to probe solvent effects in the homogeneous catalytic reduction of propionaldehyde to 1‐propanol in the presence of aluminium isopropoxide catalyst. Using data on diffusion coefficients it was possible to estimate trends in aggregation of different solvents. The results show that solvents with a high hydrogen‐bond accepting ability, such as ethers, tend to form larger aggregates, which slow down the molecular dynamics of aldehyde molecules, as also suggested by T 1 measurements, and preventing their access to the catalytic sites, which results in the observed decrease of catalytic activity. Conversely, weakly interacting solvents, such as alkanes, do not lead to the formation of such aggregates, hence allowing easy access of the aldehyde molecules to the catalytic sites, resulting in higher catalytic activity. The work reported here is a clear example on how combining traditional catalyst screening in homogeneous catalysis with NMR diffusion and relaxation time measurements can lead to new physico‐chemical insights into such systems by providing data able to quantify aggregation phenomena and molecular dynamics.

Life Time Improvement of Hierarchically Structured SAPO-34 Nanocatalyst in MTO Reaction via Applying Clinoptilolite: Investigating of Composite Design via RSM.

The research focuses on recent progress in the production of light olefins. Hence, as the common catalyst of the reaction (SAPO-34) deactivates quickly because of coke formation, we reorganized the mechanism combining SAPO-34 with a natural zeolite in order to delay the deactivation time. The synthesis of nanocomposite catalyst was conducted hydrothermally using experimental design. Firstly, Clinoptilolite was modified using nitric acid in order to achieve nano-scaled material. Then, the initial gel of the SAPO-34 was prepared using DEA, aluminum isopropoxide, phosphoric acid and TEOS as the organic template, sources of Aluminum, Phosphor, and Silicate, respectively. Finally, the modified zeolite was combined with SAPO-34's gel. 20 different catalysts due to D-Optimal design were synthesized and the nanocomposite with 50 weight percent of SAPO-34, 4 hours Crystallization and early Clinoptilolite precipitation showed the highest relative crystallinity, partly high BET surface area and hierarchical structure. Different analyses illustrated the existence of both components. The most important property alteration of nanocomposite was the increment of pore mean diameters and reduction in pore volumes in comparison with free SAPO-34. Due to the low price of Clinoptilolite, the new catalyst renders the process as economical. Using this composite, according to the formation of multi-sized pores located hierarchically on the surface of the catalyst and increased surface area, significant amounts of Ethylene and Propylene, in comparison with free SAPO-34, were produced, as well as the deactivation time was improved.

Catalytic performance of ferrierite and omega zeolites obtained through 2D-3D-3D transformation from Na-RUB-18 layered silicate

Abstract Synthetic zeolites have been consistently preferred for industrial and commercial purposes because of their uniform crystalline structure, highly pure composition and the possibility to modulate their intrinsic properties during the crystallization aiming at specific applications. This work explores an original hydrothermal route to obtain ferrierite zeolite using the layered silicate Na-RUB-18 as precursor. For that, the transformation was carried out in the presence of aluminum isopropoxide in various Si/Al molar ratios and using pyrrolidine or 1,3-diaminepropane as OSDA. The hydrothermal transformation from Na-RUB-18 led to pure ferrierite zeolite without other zeolitic crystalline phases. Also, omega zeolite was obtained through an interzeolitic conversion, in which the ferrierite was the parent structure. The samples were characterized by XRD, 27Al and 29Si MAS-NMR, SEM, XRF and NH3-TPD. In addition, the catalytic properties of the ferrierite and omega zeolites obtained were studied. The acid characteristics of these materials were evidenced by the high ethanol conversion presented and by the major dehydration to ethylene, a product catalyzed by Bronsted acid sites. Ferrierite synthesized using 1,3-diaminopropane as OSDA in particular showed promising catalytic performance, a result possibly related to the nanosized crystals obtained, in the shape of aggregated sheets.

Effect of Precursors on the Preparation and Texture of Mesoporous γ-Al2O3 Powders

We have studied processes underlying the formation of γ-Al2O3 from different precursors (aluminum hydroxide, aluminum isopropoxide, and aluminum nitrate) and synthesized mesoporous γ-Al2O3 powders at temperatures of 500 and 600°C. Texture parameters of the powders (specific surface area, average crystallite size, pore volume, pore shape, and pore size distribution) have been studied using low-temperature nitrogen adsorption measurements and X-ray diffraction, and the effect of the precursors on the texture parameters of γ-Al2O3 has been examined. We have demonstrated the possibility of obtaining γ-Al2O3 with a unimodal pore size distribution (2.5–4.5 and 4.5–8.0 nm, depending on the precursor) and a pore volume of ~0.550 cm3/g. The experimental results obtained here show that the texture characteristics of the synthesized γ-Al2O3 powders as catalyst supports compare well to those of their foreign analogues.

Solvent-free synthesis of mesoporous platinum-aluminum oxide via mechanochemistry: Toward selective hydrogenation of nitrobenzene to aniline

Mesoporous alumina (meso-Al2O3) supported noble metal catalysts have been widely used in heterogeneous catalysis. However, these catalysts are generally prepared via wet chemistry, which suffers from several drawbacks, such as: excessive use of solvents and time-consuming drying process. In this manuscript, a mechanochemical method for solid-state processing between aluminum isopropoxide and block copolymers (P123) were introduced to synthesize meso-Al2O3 supported platinum catalyst (Pt/m-Al2O3). The resulting Pt-meso-Al2O3 catalyst shows high surface area (up to 465 m2/g) and uniform pore size (~3.9 nm). Interestingly, the solvent-free ball milling method enables the processing of bulky micrometer-scale Pt precursors into well dispersed Pt nanoparticles (~4.8 nm). Moreover, Pt/m-Al2O3 catalyst affords good performance in the selective hydrogenation of nitrobenzene to aniline (Conversion: >99%, Aniline Selectivity: >99%). This mechanochemical route provides a solvent-free and one-step method for synthesizing meso-Al2O3 supported noble metal catalysts.

Microstructure, doping and optical properties of Co2+:ZnAl2O4 transparent ceramics for saturable absorbers: Effect of the ZnF2 sintering additive

Transparent cobalt-doped zinc aluminate spinel (gahnite), Co2+:ZnAl2O4, ceramics were fabricated by hot pressing of (Zn,Co)Al2O4/ZnF2 nanopowders at 1520 °C for 4 h. A novel approach was suggested for the preparation of (Zn,Co)Al2O4 precursor: the (Zn,Co)Al2O4 powders were synthesized by mixing an alcohol solution of aluminium isopropoxide with a joint aqueous solution of zinc formate (the source of zinc), cobalt nitrate and zinc fluoride (the sintering additive) followed by drying and calcination in air. The study of the thermal behavior of precursors revealed an optimum calcination temperature (700 °C) preventing the loss of the sintering additive (ZnF2). The effect of the ZnF2 content (3–10 wt%) on the microstructure, the cobalt doping concentration, absorption and luminescence of ceramics was systematically studied. The ceramics exhibit a close-packed microstructure with a mean grain size of 50–70 μm and high in-line transmission (about 84% at ∼2 μm). The actual concentration of Co2+ ions in tetrahedral (Td) sites of gahnite is lower than the Co2+ doping level and it decreases with the ZnF2 content. We propose a possible mechanism of this variation including both the losses of Co2+ via evaporation of the intermediate CoF2 phase and a partial location of Co2+ ions in octahedral (Oh) sites of gahnite due to its partly inverse spinel structure. The developed ceramics are promising for saturable absorbers of erbium lasers.

Morphology, microstructure and mechanical properties of electrospun alumina nanofibers prepared using different polymer templates: A comparative study

Alumina nanofibers with excellent mechanical properties are an ideal candidate as the reinforcements for composites. In this study, alumina nanofibers were fabricated via electrospinning technique combined with the sol–gel method. Alumina precursor sol was prepared using aluminum nitrate and aluminum isopropoxide. The morphology, microstructure, and mechanical properties of the nanofibers prepared using polyvinyl alcohol, polyvinyl butyral, and polyvinyl pyrrolidone as the polymer templates after calcination at 900 °C were investigated and compared. The three fiber samples exhibited continuous structure and the same phase composition of γ-Al2O3. However, the surface roughness, diameter distributions, densification degrees, crystallization temperatures, grain sizes, tensile strength, and elastic modulus were completely different. Possible mechanisms for these differences were discussed on the basic of the homogeneity of spinning solutions, the decomposition behaviors of polymers, and the quantities and sizes of defects and grains. The findings of this study can help in understanding an often-neglected concept on the important role of polymer categories on the structure and properties of electrospun oxide nanofibers, particularly required with enhanced mechanical properties.

Synthesis and Polymorphism of Mixed Aluminum-Gallium Oxides.

The synthesis of a new solid solution of the oxyhydroxide Ga5–xAlxO7(OH) is investigated via solvothermal reaction between gallium acetylacetonate and aluminum isopropoxide in 1,4-butanediol at 240 °C. A limited compositional range of 0 ≤ x ≤ 1.5 is produced, with the hexagonal unit cell parameters refined from powder X-ray diffraction (XRD) showing a linear contraction in unit cell volume with an increase in Al content. Solid-state 27Al and 71Ga nuclear magnetic resonance (NMR) spectroscopies show a strong preference for Ga to occupy the tetrahedral sites and Al to occupy the octahedral sites. Using isopropanol as the solvent, γ-Ga2–xAlxO3 defect spinel solid solutions with x ≤ 1.8 can be prepared at 240 °C in 24 h. These materials are nanocrystalline, as evidenced by their broad diffraction profiles; however, the refined cubic lattice parameter shows a linear relationship with the Ga:Al content, and solid-state NMR spectroscopy again shows a preference for Al to occupy the octahedral sites. Thermal decomposition of Ga5–xAlxO7(OH) occurs via poorly ordered materials that resemble ε-Ga2–xAlxO3 and κ-Ga2–xAlxO3, but γ-Ga2–xAlxO3 transforms above 750 °C to monoclinic β-Ga2–xAlxO3 for 0 ≤ x ≤ 1.3 and to hexagonal α-Ga2–xAlxO3 for x = 1.8, with intermediate compositions of 1.3 < x < 1.8 giving mixtures of the α- and β-polymorphs. Solid-state NMR spectroscopy shows only the expected octahedral Al for α-Ga2–xAlxO3, and for β-Ga2–xAlxO3, the ∼1:2 tetrahedral:octahedral Al ratio is in good agreement with the results of Rietveld analysis of the average structures against powder XRD data. Relative energies calculated by periodic density functional theory confirm that there is an ∼5.2 kJ mol–1 penalty for tetrahedral rather than octahedral Al in Ga5–xAlxO7(OH), whereas this penalty is much smaller (∼2.0 kJ mol–1) for β-Ga2–xAlxO3, in good qualitative agreement with the experimental NMR spectra.

One-pot synthesis of core-shell structured SSZ-13 zeolite using aluminum isopropoxide as an aluminum source

SSZ-13 zeolite with core-shell structure was successfully synthesized by a facile one-step hydrothermal synthesis method using aluminum isopropoxide as an aluminum source. The obtained samples were characterized by XRD, SEM and N2 adsorption/desorption techniques. According to the results, the synthesized SSZ-13 zeolite showed unequivocally the core–shell structure with sub-micron crystalline aggregated SSZ-13 shell formed by epitaxial growth. Moreover, the core-shell structured SSZ-13 possessed distinct pore structure compared with conventional SSZ-13 synthesized by using aluminum nitrate as aluminum source. SEM images demonstrated the formation process of the core-shell structure. Crystals with an spherical morphology were formed from the dissolved Si and Al species, and then amorphous gel precursors deposited on the surface of large SSZ-13 cores and converted into sub-micron SSZ-13 crystals.

Electrospinning preparation and microstructure characterization of homogeneous diphasic mullite ceramic nanofibers

In this work, diphasic mullite (3Al2O3·2SiO2) nanofibers with good homogeneity were prepared by electrospinning method. Aluminum nitrate (AN) and aluminum isopropoxide (AIP) were used as alumina sources, commercial colloidal silica as silica source, and polyvinyl alcohol (PVA) as polymer additive. Precursor nanofibers with continuous and uniform structures were acquired at mass ratio of PVA to precursor sol from 0.06 to 0.09. γ-Al2O3 phase was obtained at 878 °C and mullite phase formed at 1322 °C upon heating of the precursor under air atmosphere. Calcined samples suggested mullite as dominant phase at 1300 °C and amorphous SiO2 could even exist at 1400 °C. As-prepared nanofibers possessed continuous structures with subequal average diameters at 900–1200 °C. However, such morphological characteristics were lost at temperatures above 1300 °C due to rapid growth of crystal grains. Al and Si elements were uniformly distributed in fibers and mixed at nanoscale, confirming homogeneity and diphasic features of nanofibers.