Ammonium Aluminum Research Articles

Synthesis of mesoporous alumina microfibres by ammonium carbonate precipitation

Mesoporous alumina microfibres were successfully synthesised through a facile ammonium carbonate precipitation route. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectrometry, thermal gravimetry–differential scanning calorimetry, N2 adsorption and desorption as well as transmission electron microscopy were used to characterise the samples. It was observed that the phases of the samples transformed from gibbsite into ammonium aluminium carbonate hydroxide with an increase in aging time from 0 to 18 h, while the molar ratio of ammonium carbonate to aluminium nitrate nonahydrate was 3. At the same time, well dispersed ammonium aluminium carbonate hydroxide microfibres with a layer by layer packing structure were obtained. The fibrous morphology was maintained after the calcination. The calcined alumina microfibres possessed wormhole-like mesopores with a pore diameter of ∼4 nm. The Brunauer–Emmett–Teller surface area of the alumina microfibres was 298·7 m2 g−1, and the pore volume was 0·36 cm3 g−1.

Coagulation/Flocculation of Tannery Wastewater Using Immobilized Chemical Coagulants

Chemical coagulants were immobilized into bead form using sodium alginate to treat tannery wastewater samples. The used chemical coagulants were ammonium aluminium sulphate (NH4Al(SO4)2), aluminium sulphate (Al2(SO4)2, calcium carbonate (CaCO3), sodium citrate (Na3C6HsO7). The effect of the chemical coagulant dose and tannery wastewater pH was studied on wastewater electrical conductance (EC), total dissolved solids (TDS), sulphates, chlorides, phenolphthalein alkalinity, total alkalinity and chemical oxygen demand (COD). The quantity of various pollutants present in waste water was reduced after treatment. The optimized dose and pH for maximum decrease in EC and TDS were 5g/L and 7, respectively. The maximum reduction in the amount of sulphates and chlorides present in tannery wastewater was observed at dosage of 0.5g/L and pH 7. A dosage of 5g/L and pH 7 was also found most favorable for maximum reduction in values of COD, phenolphtalein and total alkalinity. The chromium concentrations in tannery wastewater before and after treatment were determined by atomic absorption spectrophotometer. A reduction in chromium concentration was observed after treatment. The promising results of the present study demonstrate that immobilization of chemical coagulants can make them more effective for wastewater treatment.

Thermal and XRD analysis of synthesis of fluoro-topaz

The present work deals with thermal and XRD analysis of fluoro-topaz synthesis by sintering of aluminium and silicon oxides (in the form of corundum and quartz) with ammonium fluoride and carried out in open Pt crucibles (for XRD studies) and a closed furnace of simultaneous DTA/TG thermoanalytical apparatus called MOM Derivatograph. The furnaces are connected to a gas suction device to remove gas decomposition products.The study shows the endothermic peak at 125–155°C, representing the formation of ammonium aluminium hexafluoride and cryptohalite. The endothermic peak at 220–240°C represents the beginning of dissociation of ammonium aluminium hexafluoride to the more stable ammonium aluminium tetrafluoride. The endothermic peak at 340–350°C represents the dissociation of cryptohalite and ammonium aluminium tetrafluoride with the formation of aluminium fluoride.The formation of fluoro-topaz is represented by the wide endothermic peak at 770–800°C. The medium wide or sharp endothermic peaks at 950°C and 1000°C represent the subsequent dissociation of fluoro-topaz to corundum or mullite, respectively.

Photoluminescence properties of Tb3+ doped Al2O3 microfibers via a hydrothermal route followed by heat treatment

Uniform Al2O3:Tb3+ microfibers were synthesized via a hydrothermal route and thermal decomposition of a precursor of Tb3+ doped ammonium aluminum hydroxide carbonate, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and decay curves. XRD results indicate that various crystallographic phase Al2O3:Tb3+ microfibers are obtained by postannealing at different temperatures. SEM results show that the length and diameter of these Tb3+ doped α-Al2O3 microfibers are about 6–8μm and 300nm, respectively. The PL spectra indicate that the 5D4→7F5 (545nm) electric dipole transition is the most intensive when excited at 240nm. It is shown that the 2.0mol% of doping concentration of Tb3+ ions in α-Al2O3:Tb3+ is optimum. According to Dexter's theory, the critical distance between Tb3+ ions for energy transfer was determined to be 12.7Å. It is found that the decay curves follow the single-exponential decay.

Catalytic properties of nitrided V/Al/O-mixed oxides in the ammoxidation of propane and new efficient preparation method for the catalysts

V/Al/O oxides have been prepared and tested as catalysts for the ammoxidation of propane into acrilonitrile at 500°C. The high efficiency of these catalysts, which were partially nitrided under catalytic reaction conditions, is confirmed. The best catalysts characterized by a V/Al ratio around 0.30, exhibited selectivity to acrilonitrile of 51% at 58% conversion. Testing at low conversion showed that propene was the main primary product from propane ammoxidation and that the reaction pathway on these catalysts was similar to that on other efficient catalytic systems. A new method of synthesis based upon the decomposition at low temperature of a mixed ammonium aluminum–vanadium oxalate was developed. It leads to highly active catalysts, which displayed increased selectivity to acrylonitrile. The gain in activity and selectivity was attributed to a better dispersion of vanadium with a higher concentration of isolated vanadium species in the bulk and presumably at the surface of the catalysts.

Single step hydrothermal synthesis of 3D urchin like structures of AACH and aluminum oxide with thin nano-spikes

3D urchins like ammonium aluminum carbonate hydroxide (AACH) nanostructures with nano-spikes of dia. 20–30nm were synthesized by a simple, single step hydrothermal technique by using aluminum nitrate and urea as precursor materials. It was found that morphology of the produced structure strongly depends upon the urea concentration. With increasing the amount of urea, the AACH particles having embedded rods like surface features transformed into 3D urchins. The added urea decomposed during hydrothermal treatment and increased the pH of the solution, which affected the morphology of the produced nanostructures. SEM, XRD, FTIR and TGA were employed to characterize the produced structures. On heating, the volatile ingredients of AACH were removed, leaving behind the alumina urchins.

Meso/macroporous γ-Al2O3 fabricated by thermal decomposition of nanorods ammonium aluminium carbonate hydroxide

Through exploring the reaction parameters during the synthesis of the AACH, rod-like ammonium aluminium carbonate hydroxide (AACH) with high crystallinity has been successfully prepared via a facile hydrothermal method. The synthesis parameters like time, the molar ratio of NH4HCO3/Al and the properties of starting materials were systematically investigated. The structure was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), IR and transmission electron microscopy (TEM). The experimental results display that the obtained γ-Al2O3 materials possess meso/macroporosity and large pore volume, which are mainly attributed to the removal of gas molecules during the decomposition of AACH. Moreover, using the rod-like AACH as precursor, γ-Al2O3 nanorods were obtained via a low-temperature thermal decomposition method.

Effect of sintering temperature on properties of Al2O3 whisker reinforced 3 mol% Y2O3 stabilized tetragonal ZrO2 (TZ-3Y) nanocomposites

In present study, effect of sintering temperature on density and hardness of 3mol% yttria-stabilized tetragonal zirconia (referred to as TZ-3Y) composite reinforced with alumina whiskers (5, 10, 15 and 20wt.%) has been studied. Initially, Ammonium Aluminum Carbonate Hydroxide (AACH) whiskers were added in TZ-3Y composite and transformed into alumina during sintering performed at different temperatures i.e. 1400, 1500 and 1650°C. Results revealed that for all sintering temperatures, with increase in whisker concentration, sintered density decreased and hardness increased conversely. Maximum hardness of 14.47GPa was achieved with 10wt.% whiskers addition when sintered at 1500°C. However, with addition of CTAB (1wt.%) as deflocculating agent the hardness was further improved to 15.11GPa. While sintering at 1650°C a decrease in hardness was observed. It was mainly due to high temperature morphological change of whiskers i.e. transformation of whiskers into alumina rich grains.

Facile Synthesis of Ammonium Aluminum Carbonate Hydroxide Multilayered Nanofiber by Using Solid State Reaction

In this paper, we make systematical investigation for the new synthesis pathway of AACH multilayered nanofiber, which has been prepared by a low-temperature solid-state reaction. The phase transformation sequence of AACH on heating is found that the precursor converts into γ-Al2O3at 700-900°C and elevated temperature results in the θ-Al2O3and α- Al2O3crystal phase formation at 1000°C. With a higher calcination temperature at 1100°C, α- Al2O3pattern appears. The specific surface area (SBET) of aluminum oxide specie calcined at 500°C for 4h is still in 420.2m2/g. Meanwhile, it suggests a partial change in particle sizes and morphology of sample calcined at 500°C for 4h.

A simple hydrothermal route to bimodal mesoporous nanorod γ-alumina with high thermal stability

AbstractIn the presence of polyethylene glycol, bimodal mesoporous nanorod γ-alumina was successfully synthesized via the thermal decomposition of ammonium aluminium carbonate hydroxide precursor which was prepared via hydrothermal processing with inorganic aluminium salt. The alumina exhibits high surface area (494 m2g–1), large porosity (1.1 m3g–1) and a particular double-pore structure after calcination at 500 °C. The smaller pore diameter is concentrated on about 3 nm and the larger one is exhibited in the range of 10 – 38 nm. The scaffold-like aggregation of γ-alumina nanorods endows this novel material with excellent thermal stability. A possible formation mechanism of bimodal mesoporous structure is also proposed in this study.

Effect of binder on the structure and mechanical properties of lightweight bubble alumina ceramic

The effect of binders such as ammonium aluminum sulphate, phosphoric acid and composite binder on the properties of lightweight bubble alumina ceramic was studied. The composite binder was composed of ammonium aluminum sulphate and phosphoric acid. Ammonium aluminum sulphate solution can improve compressive strength of alumina bubbles effectively but can not improve that of lightweight bubble alumina ceramic due to the fewer nano-alumina powders in situ decomposed of ammonium alumina sulphate. Trans-ball fractures occurred in thermal shock test. Phosphoric acid solution can improve compressive strength of alumina bubble ceramic because of promoting sintering properties of aluminum phosphate in situ produced by phosphoric acid and alumina component during sintering but decrease that of alumina bubbles. Along-ball fractures occurred in thermal shock test. The composite binder combined with the advantages of ammonium alumina sulphate and phosphoric acid and improved the compressive strength of both alumina bubbles and lightweight bubble alumina ceramic, and effectively reduce the amount of the binders and lower the product cost. At the sintering temperature of 1700 °C, with composite ammonium alumina sulphate and phosphoric acid as binder, the density of lightweight bubble alumina ceramic was between 1.20 and 1.60 g/cm 3, and the compressive strength was 18–42 MPa.

Preparation of Alumina from Heated Kaolin Leached by Citric Acid with AACH as an Intermediate

Because the supply of bauxite ores in many countries is becoming deficient, a process of preparing alumina from an alternative resource, namely, kaolin, is proposed in this work. First, kaolin was heated at 600 °C for 2 h before being leached with 1 M citric acid solution, about 75% of the Al in kaolin entered the leachate as aluminum citrate (AlCit) solution. Then, about 50% of the Al(III) in the leachate could be precipitated as ammonium aluminum carbonate hydroxide (AACH) by addition of NH4HCO3 at pH 9.00 ± 0.50. The morphology of AACH characterized by SEM and TEM was spherical particles composed of many nanorods with sizes of about 500 × 25 nm. Finally, mesoporous γ-Al2O3 was obtained by roasting AACH at 700 °C. The Fe and Na contents in the obtained γ-Al2O3 product determined by XRD and ICP-AES were 2 and 0.1 ppm, respectively. The obtained γ-Al2O3 had a morphology similar to that of AACH, and its BET surface area was as high as 235.2 m2/g.

Synthesis of ammonium aluminum oxalate from Bayer aluminum hydroxide

The synthesis of ammonium aluminum oxalate was performed using Bayer aluminum hydroxide as a raw material. For this aim, Bayer aluminum hydroxide of 99.7% purity was dissolved in oxalic acid to produce an aqueous aluminum solution. As a result, it was found that a mixing ratio of ethanol to Al solution exceeding 2:1 and a pH adjusted to greater than 8.0 should be employed in the synthesis of ammonium aluminum oxalate. From the chemical analysis of ammonium aluminum oxalate prepared in this work, the NH 4, Al and C content were found to be 14.5, 7.18 and 17.4%, respectively which are very close to the theoretical values of (NH 4) 3Al(C 2O 4) 33H 2O.

Synthesis of Al 2O 3 whisker-reinforced yttria-stabilized-zirconia (YSZ) nanocomposites through in situ formation of alumina whiskers

Enhanced mechanical properties of yttria-stabilized zirconia based composites were obtained by introducing alumina whiskers as reinforcement. The alumina whiskers were formed in situ by decomposition of ammonium aluminum carbonate hydroxide (AACH) whiskers during calcination. The whiskers thus formed were amorphous and were converted to α-alumina during sintering at 1450 °C. The AACH whiskers were produced by hydrothermal treatment of an aqueous solution of urea and aluminum nitrate at 120 °C for 24 h. The Vickers hardness of the sintered composite sample increased with an increase in the alumina content up to 10 wt% and then decreased. The maximum hardness achieved at 10 wt% of alumina whiskers was 13.8 GPa, which further increased to 14.4 GPa with the addition of 1.0 wt% of cetyl-trimethyl-ammonium bromide (CTAB). The improved mechanical strength of the composites was attributed to the enhanced dispersion of alumina whiskers due to four times volume decrease during transformation of AACH to alumina and relatively lower aspect ratio of AACH whiskers as well as the deflocculating effect of CTAB.

Characteristics of the underwater explosion of a nonideally detonating aluminum-rich energetic material

An experimental study of the characteristics of the explosion of mixtures of ammonium perchlorate, aluminum, and nitromethane with a large excess of aluminum (1.45 to 1.66 g/cm3 in density) confined in plastic enclosures and immersed in small elastic-wall reservoirs with water is conducted. It is shown that composite charges, 20 mm in diameter, surrounded by a water layer of thickness 20–30 cm and detonate in a nonideal detonation mode. High-speed cinematography records show the possibility of the intense mixing of the detonation products with the surrounding water and of the burning of excess aluminum particles in a heterogeneous cloud. The time scales of the development of secondary energy release by burning of aluminum particles in water are estimated. The possibility of controlling the characteristics of the pressure waves generated by the explosion, for example, by means of a preliminary bubbling of the water with air near the charge, is demonstrated.

Effect of Content of Mg(NO3)2·6H2O on Fabrication of α-Alumina Nanopowders by Thermal Decomposition of Ammonium Aluminum Carbonate (AACH)

An alpha-Al2O3 and MgAl2O3 spinel phase doped alpha-Al2O3 nanopowders were fabricated by the thermal decomposition and synthetic of ammonium aluminum carbonate hydroxide (AACH). Crystallite size of 5 to 8 nm were fabricated when reaction temperature of AACH was low, 8 degrees C, and the highest [NH4+][AlO(OH)2-][HCO3] ionic concentration of pH 10 from the ammonium hydrogen carbonate (AHC) aqueous solution. The phase transformation of amorphous-s, theta-, alpha-Al2O3, MgAl2O3 spinel phases was examined at each temperature according to the amount of Mg(NO3)2 x 6H2O and AACH. A time-temperature-transformation (TTT) diagram for thermal decomposition in air was determined. Homogeneous, spherical alpha-Al2O3 nanopowders with a particle size of 60 nm were obtained by firing the crystallites, which had been synthesized from AACH at pH 10 and 8 degrees C, at 1050 degrees C for 6 h in air.

PH-dependent formation of AACH fibers with tunable diameters and their in situ transformation to alumina nanocrystals with mesoporous structure

Through a simple hydrothermal and thermal decomposition process of the ammonium aluminum carbonate hydroxide (denoted as AACH) precursors, we prepared mesoporous γ-Al2O3 fibers with tunable diameters by manipulating the amount of urea (pH-adjuster) in the reaction mixture (i.e., pH control). The experimental results show that the diameter of the obtained AACH fibers decreased obviously when the pH values of the reaction mixtures changed from 2.5 to 5.0. The as-formed precursors could transform to the morphology-remained cubic γ-Al2O3 with a slight shrinkage in diameter of the fibers after an annealing process. N2 adsorption–desorption experiment indicates that the as-synthesized alumina microfibers and nanofibers have large surface area (176 and 230m2/g, respectively) and narrow pore-size distributions. Both the γ-Al2O3 microfibers and nanofibers are powerful in the removal of Congo red pollutant from waste water.

Preparation of BaMgAl10O17:Eu2+ phosphor with small particle size by co-precipitation method

A BaMgAl10O17:Eu2+ phosphor with fine particle size was synthesized by a chemical co-precipitation method. Co-precipitation of Ba2+, Al3+, Mg2+, and Eu2+ was achieved under precisely controlled precipitation conditions. The Al3+ ions were precipitated as ammonium aluminum carbonate hydroxide (AACH). Phase transition and particle growth processes of the precipitate mixture during calcining process were investigated, and the formation mechanism of the BaMgAl10O17 phase was discussed. The results show that the formation temperature of the BaMgAl10O17 phase in the co-precipitation mixture was significantly lower than that of a high temperature solid state reaction method. The BaMgAl10O17 phase was formed from the reaction between the BaAl2O4 phase and γ-Al2O3 phase; no α-Al2O3 phase appeared during the entire process. Well-dispersed BaMgAl10O17:Eu2+ phosphor powder in the form of hexagonal flakes with small particle size (1–2μm) could be prepared by this method.

The Effect of Different Solvent on the Microstructure of Gibbsite during Hydrothermal Treatment

Phase structure and micromorphology of gibbsite after hydrothermal treated in different solvents were studied. Results showed that there was a relationship between micromorphology and phase structure of as-synthesized product. The cubic slice-like boehmite microstructure can be obtained in water. The 3D flowerlike boehmite microstructure can be obtained in isopropanol or sodium carbonate solution. The global ammonium aluminum carbonate hydroxide (AACH) architectures assembled by the lathes can be obtained in urea solvent. Gibbsite can transform to boehmite after 12h hydrothermal treatment in water. In isopropanol or sodium carbonate solution, this time decreased to 6h. In urea solution, Aluminum hydroxide turned from gibbsite to the mixture of boehmite, gibbsite and AACH. Finally, AACH is synthesized. This procedure needs 24h.

Synthesis of Gallium-Aluminum Dawsonites and their Crystal Structures

Solid solutions of dawsonites, ammonium aluminum carbonate hydroxide–ammonium gallium carbonate hydroxide, were obtained by the addition of aqueous solutions of mixtures of aluminum and gallium nitrates to an excess ammonium carbonate solution. The dawsonite solid solutions were calcined at 700°C to give γ-Ga2O3–Al2O3 solid solutions. The structures of these two types of solid solution were discussed on the basis of their X-ray diffraction patterns and X-ray absorption fine structure spectra.