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Three different alumina sources (boehmite, aluminium nitrate and α-alumina particles) and 12Ce-TZP powder containing 1 wt% lanthanum oxide were used to prepare 12Ce-TZP-based alumina-toughened-zirconia (ATZ) composites. The obtained ATZs had similar density and phase composition, whereas the microstructures were significantly different. Alumina-particle addition gave rise to a typical ATZ microstructure consisting of equiaxial sub-micrometer zirconia and alumina phases, while the lanthanum hexa-aluminate phase was formed in large and non-homogenously distributed precipitates (∼3.5 μm in length). The boehmite and aluminium nitrate-based composites contained not only sub-micrometer equiaxial alumina and zirconia grains but also small-sized lanthanum hexa-aluminate precipitates (∼1.2 μm in length) that were inter- and transgranularly positioned in the zirconia matrix and effectively promoted crack deflection and toughening. In combination with a higher t-ZrO2 transformability, the boehmite-based composites had a higher indentation fracture resistance, strength and reliability compared to the aluminium-nitrate and alumina-particle based equivalents.

Porous mullite ceramics with ultra-low shrinkage and high porosity were prepared by solid state reaction between MoO3 and mullite precursor powders which were synthesized from tetraethylorthosilicate and aluminium nitrate nonahydrate via sol-gel methods. The synthetic process of mullite precursor powder and effects of MoO3 amount on the phase composition, microstructure, physical properties such as firing shrinkage, open porosity, bending strength, water absorption and bulk density of porous mullite ceramics were investigated. The results indicated that the addition of MoO3 not only lowered the mullite forming temperature from 985.4 to 853.3 °C, but also restrained densification behavior of samples due to the formation of mullite and Al2O3–MoO3 solid solution, besides, MoO3 also improves the formability, open porosity and bending strength of samples. The optimal amounts of MoO3 is 8 wt%, and the resultant samples exhibit outstanding properties, including a low shrinkage rate of 1.86 ± 0.07%, an open porosity of 61.91 ± 0.16% and a bending strength of 9.35 ± 1.11 MPa.

Fine alpha-alumina (α-Al2O3) powder was prepared by simple precipitation technique using aluminium salt and ammonia as a precipitating agent. In this method, an aqueous solution of aluminium nitrate and ammonia were mixed with continuous stirring both in the presence and in the absence of polyethylene glycol (PEG). A controlled pH range of 7.5–8.5 was maintained throughout the synthesis process. A comparative study between the alumina powder prepared in the presence and absence of PEG was drawn into attention. The washing of the precipitate was deliberately avoided in one case to study the effect of washing on phase formation temperature. The synthesized powders were calcined at different temperatures and characterized by X-ray diffraction study, thermal analysis, infrared analysis, microstructural study, and particle size analysis. The results showed less agglomerated fine alumina powder formation in its pure α-Al2O3 phase at 1050°C in the presence of PEG.

In the current scenario, biosynthesis has a major trend in the world due to its eco-friendly approach, effectiveness and low cost. In this experiment Aluminium Oxide nano powder was extracted from ‘Muntingia Calabura’ leaf with aluminium nitrate as precursor. An attempt has been made to develop the properties of sisal/coir, sisal/banana and banana/coir based hybrid composite with addition of aluminium oxide (Al2O3) nano powder. Compression moulding technique was adapted to fabricate the epoxy based natural fiber composites. Nano Al2O3 powder was added in 0, 1, 2 and 3 wt%. The results demonstrate that addition of nano powder up to 3 weight (wt) percentage improvise the tensile, flexural and impact properties for all incorporated hybrid fibers. Residual wt% for sisal/coir, sisal/banana and banana/coir hybrid composites enhanced from 27.15 to 29.14, 26.07 to 31.33% and 23.76 to 27.50% by 3% nano substitution. Degradation temperature improved in different stages of hybrid combinations. Scanning electron microscope (SEM) images clearly showed the reduction of fiber breakage, matrix breakage and void gaps due to alumina nano powder addition.

In this paper, composite membranes based on polyvinyl chloride (PVC) has been prepared and then filled with 0.125-0.250 wt% of iso-phthalic acid/aluminium nitrate nanoparticles. All of the polymeric and nanocomposite membranes were fabricated by solution casting using tetrahydrofuran (THF) solvent. The performance of the prepared membranes was studied for CO2/N2 at the feed pressure of 2.5, 3, and 3.5 bar at 35 °C. Results showed that in most cases, increasing the percentage of PVC increased the permeability of CO2/N2. Also, with the addition of iso-phthalic acid/aluminium nitrate nanoparticles in the membrane, gas permeability in all cases increased. The highest gas pair selectivity for CO2/N2 could be obtained from PVC (30 wt%) loaded with 0.250 wt% of iso-phthalic acid/aluminium nitrate nanoparticles. For characterization of samples, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used. These results also suggest that PVC membranes with the higher loading percentage of nanoparticles are good candidates for the CO2/N2 separation, offering better selectivity for CO2/N2 in the range of 63.78 to 230.42, depending on the loading percentage.

This paper deals with the preparation and evaluation of a zeolite prototype developed from an aluminosilicate precursor for its possible application as a hydrocracking catalyst. Aluminium nitrate and tetraethyl orthosilicate at definite proportions were the primary reagents for the gel synthesis. Nickel loading and stipulated post-synthesis treatment of the material are also addressed in this paper. The characteristics of the calcined aluminosilicate gel were estimated using X-ray diffraction (XRD), scanning electron microscope (SEM) study with energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) with thermogravimetry (TG) and Fourier-transformed infrared spectroscopy (FTIR) at different temperatures. A preliminary laboratory-scale investigation of hydrocracking performance of this zeolite prototype was also conducted.

Al-doped ZnO, which emits a yellowish orange light at the excitation of blue light, is prepared by means of a sol-gel combustion method, using zinc acetate, aluminium nitrate, and urea as precursors. XRD analysis reveals that the obtained material shows hexagonal wurtzite structure of ZnO. This phosphor material is excitable in a wide range of wavelength from 350 to 500 nm with an excitation maximum at 470 nm. The concentration of Al varies from 5 mol% to 15 mol% with respect to Zn and a maximum photo-luminescent emission intensity is obtained at 15 mol%. At 455 nm excitation, Al-doped ZnO shows a broad band yellowish orange emission starting from 470 to 620 nm with an emission maximum at 530 nm. At a blue LED excitation, it emits a warm white light with a CRI of 91 and CIE color co-ordinates of (x = 0.50, y = 0.39). This Al-doped ZnO can be used as a blue light converted yellowish- orange emitting phosphor material for applications in WLEDs.

In this research, nano-sized γ-Al2O3 particles were synthesized by modified sol–gel method using new precursors. In this study, aluminium nitrate, ethylene glycol (EG), citric acid (CA) and triethanolamine (TEA) were used as an Al3+ source, gel, chelating and surfactant agents, respectively. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA) and infrared spectroscopy (IR). Then, the removal efficiency of heavy metal ions (lead and cadmium) in the adsorption process by the as-synthesized alumina nanoparticle has been investigated and the effect of various experimental parameters such as pH, adsorbent dosage and exposure time were examined. The maximum removal was obtained at pH 5.0 by the as-synthesized adsorbent at the contact time of the 20 min and 30 min for Pb(II) and Cd(II) respectively. The equilibrium study showed that the adsorption data of both metal ions followed the Freundlich isotherm model. Then, regeneration study on the synthesized adsorbent was performed and it was found that the adsorbent can be successfully regenerated up to 3 times with the high level of adsorption.

This paper studied the effect of the variation of citrate to nitrate ratio on the sol-gel synthesis of nanocrystalline α-alumina powder. The process involves the formation of a sol using aluminium nitrate and citric acid which then transferred to a transparent gel and finally to a powdery mass. The prepared alumina powder was thoroughly characterised by different techniques such as phase analysis, thermal analysis, microstructure study, etc. Variation in citrate to nitrate molar ratio (C/N) influenced the thermal decomposition behaviour, particle size distribution, phase transformation temperature and specific surface area of the developed powder. The complete formation of α- Al2O3 was obtained at around 950 °C for C/N=1.5. The unimodal distribution of the particles within a narrow size range and higher particle to particle linking through solid bridging are the characteristics of the powder prepared at C/N=1.5. It was found higher citrate to nitrate ratio in the fuel rich condition is responsible for better properties of synthesised alumina powder.

Novel ZrO2/Al2O3 nanofibers with the average diameter of around 110 nm are fabricated by heat treatment of electrospun zirconium oxychloride (ZrOCl2)/aluminium nitrate (Al(NO3)3)/polyvinylpyrrolidone (PVP) composite fibers at temperature of 1200 °C. Intermediate and the final ceramic filaments are characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). The ZrO2/Al2O3 nanofibers contain mainly tetragonal zirconium dioxide in contrast to pure ZrO2 nanofibers consisting of monoclinic zirconia. It is revealed that Al2O3 impedes the ZrO2 grain growth and stabilizes the tetragonal phase of zirconia forming Al2O3-ZrO2 solid solution. Fabricated zirconia nanoscale filaments with varying phase composition can be considered, for instance, as promising one-dimensional high-temperature supports for heterogeneous catalysts with controlled activity and selectivity.

MgAl 2 O 4 nanoparticles (NPs) were prepared by sol–gel method using aluminium nitrate, magnesium nitrate and citric acid as starting materials, phenolic formaldehyde resin and carbon black as additives. Growth of MgAl 2 O 4 NPs in different heat treatment conditions (temperature, atmosphere, carbon additives and in Al 2 O 3 -C system) was investigated. MgAl 2 O 4 NPs were formed at 600 °C in air atmosphere with serious agglomeration of nanoparticles having diameter of approximate 30 nm. The size of MgAl 2 O 4 NPs increased greatly from 40 to 50 nm to several hundreds of nanometres as the temperature was raised from 800 °C to 1400 °C. Partial sintering of NPs was observed upon heating at temperatures higher than 1200 °C in air. In reducing atmosphere, the size of MgAl 2 O 4 NPs (about 30–50 nm) changed slightly with increasing temperature. This was attributed to the dispersion of carbon inclusions in the MgAl 2 O 4 grain boundaries, inducing a steric hindrance effect and inhibiting the growth of particles. MgAl 2 O 4 NPs (30–50 nm) in the Al 2 O 3 -C system were in-situ formed at high temperatures with the use of dried precursor gels. MgAl 2 O 4 NPs can contribute to improving the thermal shock resistance of Al 2 O 3 -C materials.

Deposition of aluminium oxide (Al 2 O 3 ) coatings from liquid feedstocks using a high enthalpy hybrid water-stabilized plasma torch was investigated. The entire process included the optimization of spraying parameters using a commercial ready-to-spray suspension, optimization and deposition of custom-made suspensions and one solution and evaluation of mechanical properties of the most durable coatings. Acquired coating microstructures varied from porous with typical columnar morphology to well-sintered dense structures with low porosity. The microstructural features were clearly linked to the feedstock formulation. The most durable coating with the highest density microstructure prepared from ethanol-based suspension showed outstanding mechanical properties, e.g. high values of hardness (up to 1211 HV0.3), tensile adhesion strength (up to 51 MPa) and wear resistance (material removal rate as low as 1.94·10 − 5 mm 3 ·N − 1 ·m − 1 as measured by pin-on-disc test). Moreover, deposition from a water-based solution of aluminium nitrate resulted in deposition of highly porous coating composed predominantly of stable α-alumina phase.

CoAl 2 O 4 nanoparticles were prepared via coprecipitation technique through mixing 1:1 M ratio of cobalt nitrate and aluminium nitrate solutions at pH 10. CoAl 2 O 4 crystalline phase was confirmed by X-ray diffraction. Scanning electron microscopy (SEM) result reveals that the particles of CoAl 2 O 4 fired at 900 °C were relatively small (21 nm) and uniform. Increased temperature to 1200 °C gives rise to blocky particles and changes in the powders shape, that because of agglomeration came from the calcination of CoAl 2 O 4 . Furthermore, the particle size increase with increasing the calcinated temperature. The crystalline sizes were evaluated by using X-ray peak broadening analysis suggested by Williamson-Hall (W-H) analysis. It was successfully applied for lattice strain and to calculate mechanical stress and energy density values using different three models namely uniform deformation model (UDM), uniform deformation stress model (UDSM) and uniform deformation energy density model (UDEDM). Also, the root mean square strain was determined. These models gave a different strain values which suggested an isotropic nature of the nanoparticles. Besides, the obtained results W-H analysis are in good agreement with that deduced from SEM analysis and Scherrer's formula.

Nanostructured zinc oxide (ZnO) and Al doped ZnO (ZnO:Al) thin films are deposited on glass substrate by the Spray Plasma technique. Zinc nitrate and aluminium nitrate are used as Zn and Al precursors, respectively. The effect of the growth time on structural and optical properties of undoped films is studied by X-ray diffraction, atomic force microscopy, and UV–Vis spectroscopy. The effect of Al doping on microstructural, optical and electrical characteristics of ZnO:Al films is also investigated. The results show that the grain size and the film thickness both increase with the growth time. The band gap of the layers varies from 3.17 to 3.24 eV depending on the thickness. The increase of the Al doping results in the enlargement of the peak (002) and the shift of its position to higher 2θ values. Average optical transmittance decreases from 90 to 65% with the growth time because of the thickness increase while there is no significant influence of the aluminium doping on the transmittance which is above 80% in most of the visible and near-IR range for all ZnO:Al films. The electrical properties characterized by Hall measurements show that all the deposited films exhibit high resistivity, between 4 and 104 Ω cm. The carrier concentration decreases from 2.1019 to 2.1013 cm− 3 when the concentration of Al increases from 1.5 to 5 atm%.

The effect of aluminium nitrate hydrate (Al(NO3)3·9H2O) on the crystalline, thermal and mechanical properties of PVA was studied in this paper. The interaction between Al(NO3)3·9H2O and PVA was investigated by Fourier transform infrared (FT-IR) spectroscopy. The influence of Al(NO3)3·9H2O on the crystalline, thermal, and mechanical properties of PVA was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing, respectively. The results indicated that Al(NO3)3·9H2O could form interaction with the hydroxyl group on PVA chain. The XRD studies revealed that the crystallites of PVA were destroyed by Al(NO3)3·9H2O. DSC studies showed that Al(NO3)3·9H2O could increase the flexibility of PVA chains and decrease the Tg of PVA. Tensile testing showed that after the addition of Al(NO3)3·9H2O the tensile strength of PVA film decreased and elongation at break increased. All these results show that Al(NO3)3·9H2O has a high plasticizing efficiency for PVA. However, Al(NO3)3·9H2O is a Lewis acid and the acidic property of Al(NO3)3·9H2O would cause the significant decrease of the thermal stability of PVA.

YAG ceramics with good dielectric properties were prepared via a modified pyrolysis method, with yttrium nitrate as the yttrium source and combined aluminium sulphate and aluminium nitrate as aluminium sources, and subsequent sintering in a muffle furnace. The effects of the different aluminium sources on the powder characteristic and the impact of sintering temperature, sintering aids (TEOS) and additive (TiO2) on the dielectric properties of the ceramics were studied. The results show that well-dispersed pure YAG nano-powders can be obtained after calcination at 1000 °C with an aluminium sulphate and aluminium nitrate molar ratio of 1.5:2. The relative density, permittivity (er) and quality factor (Q×f) of the YAG ceramics increase with sintering temperature and TEOS addition. TiO2 can greatly promote τf to near-zero but decreases Q×f. The relative density, er, Q×f and τf of the YAG–1 wt% TEOS–1 wt% TiO2 ceramic obtained at 1520 °C are 97.6%, 9.9, 71, 738 GHz and −30 ppm/°C, respectively.

Aluminium oxide was prepared from aluminium nitrate by precipitation in presence of cationic cetyl trimethyl ammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) surfactants. Effects of surfactant type and concentration, pH, aging temperature and aging time on development of porous structure of aluminium oxide were investigated and compared. Surface area of samples prepared with CTAB was higher compared to that prepared with SDS at all preparation conditions. Mainly mesopores were obtained with SDS, whereas in presence of CTAB micropores were also obtained, particularly at lower surfactant concentration. The bayerite and boehmite were predominant structures in presence of CTAB and SDS, respectively. Formation of mesopores was favored at higher pH in presence of SDS and at lower pH in presence of CTAB. Surface area and pore volume of aluminium oxide increased with aging time in presence of SDS, but the effect was not significant for CTAB.

The present work involved solution combustion synthesis of high alumina cements from their metal nitrate precursors, using urea as an organic fuel. Combusted aluminium nitrate, calcium nitrate and urea complexes leads to formation of high alumina cement at temperature as low as 800 °C. The prime cementing phases observed were CA, CA 2 and C 12 A 7 . The second stage of work evaluates, the role of this high alumina cement (HAC) on bauxite based low cement castables. The effect of micro-fine Cr 2 O 3 and MgO additions on the sinterability and thermo-mechanical strength of these castables was also investigated. Phase identification and microstructural evaluation of the sintered castables confirms spinel and corundum phase formation. Addition of nano structured cements in refractory castables improved the thermo-mechanical properties to a significant extent.

A simple low temperature chemical route, which was based on the reactions of aluminium nitrate and hexamethylenetetramine in aqueous medium at 473 K for 36 h, was proposed for the synthesis of α-Al2O3 quantum dots (QDs). The characterisation results from X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy along with selected area diffraction pattern are revealed the formation of α-Al2O3. Ultra-violet spectra indicated that the as-synthesised α-Al2O3 has a direct band gap of about 3.6 eV and also disclosed semiconducting behaviour of α-Al2O3 QDs using defect chemistry.

Mullite nanofibres with diameters of 85–110 nm were obtained by electrospinning of solutions containing different amounts of polyvinyl alcohol (PVA, as the template) ranging from 0 wt% to 10 wt%, which were added to the sol, and sintered at different temperatures. The sol was prepared by the sol–gel method, using aluminium isopropoxide (AIP), hydrated aluminium nitrate (AN) and tetraethylorthosilicate (TEOS) as the precursors. The details of crystal development, microstructure and thermal decomposition behaviour of the electrospun nanofibres were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and simultaneous thermal analysis (STA). The optimal content of 6 wt% of PVA in the electrospinning polymeric solutions was found to be the suitable viscosity for the electrospinning and ultimately resulted in the formation of the most pure and uniform mullite nanofibres.

In this paper, the synthesis of continuous mullite (3Al2O3·2SiO2) nanofibres by combination of the sol–gel and electrospinning technique is reported. To find out the optimum viscosity of the electrospinning solution for obtaining the high quality mullite nanofibers, solutions containing different amounts of polyvinyl butyral (PVB, 0–8 wt%) and the precursor sol were prepared for the electrospinning process. The precursor sol was made by using proper amounts of aluminium isopropoxide (AIP), hydrated aluminium nitrate (AN) and tetraethylorthosilicate (TEOS). Crystal phase, microstructure and thermal decomposition behaviour of the electrospun mullite nanofibres were investigated by conventional methods of analysis. The optimal amount of PVB in the electrospinning polymeric solutions was found to be between 4 and 6 wt% and the mullite nanofibres obtained as such were pure, smooth and uniform with diameter sizes of 85–130 nm after calcination at 1200 °C.

Zinc aluminate compounds have been dispersed in silica matrix prepared by sol-gel method with different compositions for (1 − x)ZnAl2O4–xSiO2. Continuous stirring of ethylene glycol solution contained zinc nitrate, aluminium nitrate and silicon dioxide to produces gel precursor. Structural and morphological studies of (1 − x)ZnAl2O4–xSiO2 thin films were examined by field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD) analysis. The FESEM images showed the spherical structures with porosity for (1 − x)ZnAl2O4–xSiO2 thin films. XRD analysis indicated that the crystallite size for (1 − x)ZnAl2O4–xSiO2 increased from 39.79 to 44.34 nm. Fourier transform infra-red analysis showed that the existence of H2O molecules and the presence of nitrate group within the samples. Dielectric permittivity (e r ) of (1 − x)ZnAl2O4–xSiO2 samples were measured within frequency range from 1 Hz to 1 MHz. The dielectric permittivity, e r decreased as frequency was applied to the sample. The performance of the patch antenna can be measured using return loss analysis. The highest result shows that the patch antenna resonated at frequency 3.46 GHz and gives −14.25 dB return loss bandwidth.

A study of the leaching behaviour of spent pot-lining (SPL), a hazardous waste generated at the end-of-life of aluminium smelting cells, has been carried out using Al(NO3)3· 9H2O and HNO 3 solutions. Following an initial water wash, a single leaching step using 0.5 M HNO3 and 0.36 M Al(NO3)3 at 60 C extracted a total of 96.3 wt.% of the remaining fluoride, complete extraction of magnesium and 90% of the calcium content, originally in the form of MgF 2 and CaF2. In the absence of Al(NO3) 3, iron extraction is almost complete when SPL is treated with 0.5 HNO3 M solution at 60 C. CN- was selectively extracted when 0.2 M HNO3 at 60 C was used, and could be selectively precipitated from the scrubbing solution in the form of salts of transition metals for catalytic applications. Experimental observations have been correlated with a mathematical model of the solution equilibria, which identified AlF2 + and AlF2 + as the main species responsible for fluoride extraction from Na3AlF6 and CaF2. Selective precipitation by pH adjustment is proposed as a means to recover fluoride and metal values. Aluminium and fluoride can be selectively precipitated as AlF2OH·1.4H2O for conversion into smelter grade (SG) AlF3.

Al2O3-YAG composite was obtained by sintering of porous Al2O3 preforms infiltrated with water solution of aluminium nitrate nonahydrate, Al(NO3)3•9H2O and yttrium nitrate hexahydrate, Y(NO3)3•6H2O. Al2O3 preforms with porosity varying from 26 to 50% were obtained after sintering at temperature ranging from 1100 to 1500°C. Sintering of the infiltrated Al2O3 preforms led to formation of YAG particles due to reaction between Y2O3 and Al2O3 at high temperature. It was found that variation of porosity of alumina preforms and sintering temperature is an effective way to fabricate Al2O3-YAG composite with an unusual combination of properties. Open porosity was in the range 15-35%, specific surface was 0.6-6.1 m2/g, pore size was 150-900 nm whereas compressive strength was from 50 to 250 MPa. The effect of sintering temperature on YAG formation and phase composition were investigated using X-ray diffractometry whereas microstructure of the composite was analysed by scanning electron microscopy. [Projekat Ministartsva nauke Republike Srbije, br. 45012]

A novel method for preparation of nano-crystalline gadolinium aluminate (GdAlO 3 ) powder, based on combustion synthesis, is reported. It was observed that aluminium nitrate and gadolinium nitrate exhibit different combustion characteristics with respect to urea, glycine and β-alanine. While urea was proven to be a suitable fuel for direct formation of crystalline α-Al 2 O 3 from its nitrate, glycine and β-alanine are suitable fuels for gadolinium nitrate for preparation of its oxide after combustion reaction. Based on the observed chemical characteristics of gadolinium and aluminium nitrates with respect to above mentioned fuels for the combustion reaction, the fuel mixture composition could be predicted that could lead to phase pure perovskite GdAlO 3 directly after the combustion reaction without any subsequent calcination step. The use of single fuel, on the other hand, leads to formation of amorphous precursor powders that call for subsequent calcination for the formation of crystalline GdAlO 3 . The powders produced directly after combustion reactions using fuel mixtures were found to be highly sinterable. The sintering of the powders at 1550 °C for 4 h resulted in GdAlO 3 with sintered density of more than 95%. T.D.

Thin films of aluminium incorporated Fe 2 O 3 , synthesized by simple chemical spray pyrolysis on to glass substrates using aqueous solutions of analytical reagent grade ferric trichloride and aluminium nitrate as precursors. The influence of aluminium doping on to morphological properties, contact angle, X-ray photoelectron spectroscopy, photoluminescence and thermal conductivity properties have been investigated. The preparative parameters have been optimized to obtain good quality thin films which are uniform and well adherent to the substrate. The FE-SEM and AFM micrographs depict the films are compact and homogeneous (spindle-shaped hematite nanostructures) with varying grain sizes (average grain size ~ 20–60 nm). Contact angle measurement show the films are hydrophobic in nature. The chemical composition and valence states of constituent elements in Fe 2 O 3 are analyzed by X-ray photoelectron spectroscopy. The excitonic strong violet emission has been observed in photoluminescence. The specific heat and thermal conductivity study shows the phonon conduction behavior is dominant in these polycrystalline films. We studied interparticle interactions like grains, grain boundary effects using complex impedance spectroscopy.

The aluminium incorporated iron oxide samples were prepared by combustion route using aluminium nitrate and ferric trichloride as precursors. The samples were characterized for their morphological, dielectrical, impedance and thermal conductivity properties as a function of temperature. A strong low frequency dielectric dispersion is found to exist in these samples; this is ascribed to the presence of the ionized space charge carriers such as oxygen ion vacancies and interfacial polarization. The room temperature dielectric constant and the loss tangent (tan δ ) at 1 kHz are 315 and 0.0855 for optimized 10 at.% Al:Fe 2 O 3 sample, respectively. The frequency analysis of dielectric and ac conduction properties of these samples suggests the conduction process in these samples to be via oxygen ion vacancy motion through various defect sites. Impedance spectroscopy is used to characterize the electrical behavior. Results indicate that the relaxation mechanism of the material is temperature and frequency dependent and has dominant bulk contribution in different temperature ranges.

Nanocomposites of aluminium integrated hematite α-Fe2O3 are synthesized by combustion route using aqueous solutions of AR grade ferric trichloride and aluminium nitrate as precursors. The influence of aluminium incorporation on to the morphology, XPS, photoluminescence and thermal properties has been investigated. The FESEM and AFM micrographs depict that the samples are compact and have homogeneously distributed grains of varying sizes (∼20–60 nm). Chemical composition and valence states of constituent elements in hematite are analyzed by XPS. In room temperature photoluminescence (PL) study, we observed strong violet emission around 436 nm without any deep-level emission and a small PL FWHM indicating that the concentrations of defects are responsible for deep-level emissions. The specific heat and thermal conductivity study shows the phonon conduction behavior is dominant. We studied interparticle interactions using complex impedance spectroscopy. We report a new potential candidate for its possible applications in optoelectronics and magnetic devices.

An environmentally clean aluminium-based conversion coating on AZ91D magnesium alloy was studied in aluminium nitrate solutions. The morphology, composition, structure, and formation mechanism of the coating were investigated in detail using scanning electron microscopy/energy dispersion spectrometry, X-ray diffraction, transmission electron microscopy, and electrochemical corrosion tests. The results show that the conversion coating is composed of magnesium, aluminium, and oxygen, and shows an amorphous structure. In the initial stage of coating formation, the grain-like nucleus is composed of Al10O15·xH2O, (Al2O3)5.333, Al2O3, AlO(OH), MgAl2O4, (Mg0.88Al0.12)(Al0.94Mg0.06)2O4, and (Mg0.68Al0.32)(Al0.84Mg0.16)2O4. The conversion coating formed in the 0.01 mol/L aluminium nitrate solution for 15 min can improve the corrosion resistance of the magnesium alloy greatly. The discussion reveals that the possible formation mechanism for the aluminium-based conversion coating is the reduction reaction on micro-cathodic sites due to the electrochemically heterogeneous magnesium alloy substrate.

Sol–gel and electrospinning techniques were incorporated to produce polyvinylpyrrolidone (PVP)/titanium (IV) oxide composite fibers from solutions containing PVP and titanium tetraisopropoxide, with or without aluminium nitrate as the source of aluminium dopant. Upon the calcination of the as-spun fibers, the neat and the aluminium-doped titania fibers were obtained. Increasing the calcination temperature resulted in the decrease in the fraction of anatase phase within the fibers, as well as the increase in titania crystallite sizes. The presence of aluminium dopant, however, was found to greatly affect both physical and chemical properties of the synthesized titania fibers. Aluminium nitrate accelerated condensation of titanium oxide species during the sol–gel process, which resulted in increased viscosity of the spinning solution and consequently affected the diameters of the as-spun fibers. Aluminium dopant also played the major roles in both regulating the nucleation rate during crystallization of titania and controlling the growth mechanism of titania crystallites. As a result, the aluminium dopant caused the crystallite size of titania to decrease and retarded phase transformation from anatase to rutile.

Ultrafine pre-mullite powders, which yield mullite at high temperatures, have been prepared from colloidal silica and aluminium nitrate via carbonate coprecipitation and followed by calcination. The chemical and structural evolutions of the as-prepared precipitation powder during thermal treatment were studied and the sinterability of pre-mullite powders were investigated. The as-prepared powders are comprised of ammonium aluminum carbonate hydroxide and amorphous silica, which convert to mullite via the Al–Si spinel phase at 1250 °C. Calcination of the as-prepared powders at 1000 °C gives a very active powder which can be reactively sintered to 98.2% theoretical density at 1550 °C. The sintered body possesses a relatively uniform chemical composition with Al2O3/SiO2 mole ratio of 1.48 and exhibits a very fine interlocking equiaxed and polygonal grain morphology with grain size of 100–200 nm.

The zirconia–alumina nanocomposite powders with 3–48 mol% of alumina are prepared by aqueous combustion synthesis technique using stoichiometric amounts of aluminium nitrate, zirconyl nitrate and glycine. The nanopowders are compacted uniaxially and sintered at 1000 °C temperature in a muffle furnace. Thermodynamic modeling of the combustion reaction shows that, as the alumina content increases, the amount of gases produced increases with a decrease in the adiabatic flame temperature. The green and sintered densities of cold press composite powders decrease with an increase in the mol% of alumina.

Using glucose as a structuring additive and aluminium nitrate as the Al precursor, a novel kind of mesoporous Al2O3 microspheres with flower-like structure were synthesized hydrothermally at 180°C for 20 h. When the synthesis temperature was lowered to 140°C, the carambola-like Al2O3 can be synthesized. This approach is convenient and simple, and flower-like Ce-Al2O3 and La-Al2O3 spheres have also been prepared in this way. It may be applied to synthesize other metal oxides when suitable precursor salts are used. From an analysis of the experimental results, a mechanism for the formation of the flower-like Al2O3 spheres has been proposed and discussed.

Nanocrystalline single-phase neodymium monoaluminate (NdAlO3) has been prepared from neodymium oxide and aluminium nitrate by modified Pechini’s method. Malic acid has been used for the first time as a new complexing agent in the sol–gel process. It has facilitated, without adding 1,2-ethanediol, a low-temperature synthesis at 1,050 °C compared to the temperature of 1,630 °C needed for the solid-state preparation. The characterisation of the nanoparticles has been carried out by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy in the range 75–4,000 cm−1. The smallest particles have size of 30 nm and are anisometric; agglomerates of particles have been also observed. The material has pyknometric density of 3.956 g/cm3 at T = 293.15 K and specific surface area 5.2 m2/g. The binding energies of O 1s, Al 2p, Nd 3d, and Nd 4d electrons have been found chemically shifted in NdAlO3 compared to the values for the respective elements.

Spinel copper aluminate (CuAl 2 O 4 ) nanoparticles were synthesized with the aid of sonication by a precursor approach. The precursors were prepared by sonicating an aqueous solution of copper nitrate, aluminium nitrate, and urea. Upon heating at 900 °C for 6 h, the precursor formed nanosized CuAl 2 O 4 particles with an average size of 17 nm and with a surface area of about 110 m 2 g −1 . The nanosized copper aluminate particles as well as the precursors were characterized by elemental analysis, powder X-ray diffraction, transmission electron microscopy (TEM) image with electron diffraction pattern, thermogravimetric analysis, differential scanning calorimeter (DSC), Fourier transform of infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET) surface area measurements. The photocatalytic degradation was investigated using methyl orange under the irradiation of Hg lamp ( λ > 400 nm). The resulting degradation rates of the methyl orange were measured to be as high as 98% in 2 h.

Nanocrystalline Al 2 O 3 powders containing different amounts of MgO (0.1–5.0 mol%) or added boehmite (AlOOH) have been synthesized by combustion synthesis from aluminium nitrate and magnesium nitrate, using urea or sucrose as fuels. The as synthesized alumina powders were deagglomerated, compacted by dry pressing and sintered at 1625 °C for 2 h. For comparison purposes, a commercial high purity α-Al 2 O 3 powder (ACC) was also processed following the same route. The sintered materials were characterized for bulk density (BD), apparent porosity (AP), and water absorption (WA) capacity, microstructure using SEM, and XRD phase composition. In comparison to boehmite, the MgO had a considerable effect on the densification behaviour of combustion-synthesized powder.

The precursor for combustion synthesis was a mixed citrate/nitrate gel prepared from aluminium nitrate, zirconium oxychloride and citric acid. The combustion synthesis of this gel produces nanometer-sized zirconia–alumina nanopowder. The influence of citrate/aluminium nitrate molar ratio of the precursor on the combustion rate and phase transformation was investigated. The α-Al 2 O 3 phase transformation temperature differs with the citrate/aluminium nitrate molar ratios. X-ray diffraction analysis shows that the phases present at 1200 °C are α-Al 2 O 3 and t-ZrO 2 irrespective of initial citrate/aluminium nitrate molar ratio. TEM micrograph of calcined powder revealed that the particles size is significantly influenced by the citrate/aluminium nitrate molar ratio. EDAX confirms the presence of alumina and zirconia particle in the nanopowder calcined at 1200 °C.

Powder precursor in the form of hydroxyhydrogel was prepared from yttrium nitrate and aluminium nitrate, using ammonium hydroxide as precipitant by flash polycondensation technique. Precursor powder obtained in the hydroxyhydrogel form was characterized by TG/DTA, FTIR, SEM and XRD analysis. This method produced material which could be transformed into YAG at comparatively lower temperature (800 °C) and was phase pure.

The aim of the presented work was to study formation of magnesium aluminate spinel precursor powder during the co-precipitation of magnesium and aluminium nitrate with ammonium carbonate and its thermal transformation to spinel powder. After precipitation, the only crystalline phase is NH 4 Al(OH) 2 CO 3 ·H 2 O (ammonium dawsonite). The second one, Mg 6 Al 2 (CO 3 )(OH) 16 ·4H 2 O (hydrotalcite) appears during ageing. As found by DTA-MS and HT-XRD measurements, co-existence of both phases in very close contact results in their easier decomposition. On the base of the results obtained the scheme of phase transformations of co-precipitated precursor leading to formation of MgAl 2 O 4 is proposed.

Batch culture techniques and a kinetic model were used to examine the effects of Al3+ and NO3− ions on the cell replication rates of iron oxidising bacteria. Aluminium ions at a concentration of 2240 ppm (85 mM) were shown to reduce the cell replication rate to 85% of that observed for cells in minimal media. Nitrate ions (NO3−) at a concentration of 920 ppm (15 mM) were shown to reduce the cell replication rate to 65% of that observed for cells cultured in minimal media and the culture was not viable beyond three sequential batchculture cycles. The inhibition produced by nitrate is greater than that previously observed for chloride ions, but the impact of aluminium is similar to that observed with salts such as potassium, sodium and ammonium sulphate i.e. a small reduction in replication rate associated with increased concentration but without long term effects on culture viability. The results of this study are significant for South American bio-leach operations that have reported elevated concentrations of Al3+ ions in process water. The impact of varying substrate (FeSO4) concentration was also examined; it was found that iron oxidising cells are subject to substrate inhibition.

The effect of surface pretreatments on the micro-morphology, composition and the corrosion resistance of the anodic films formed on AZ91D magnesium alloys was investigated. The results showed that the aluminium content increased layer can be formed on the surface of the AZ91D magnesium alloys by the immersion pretreatment in aluminium nitrate solution with or without ultrasound. The pretreated surface with ultrasound was more uniform except for some pits. The anodic oxidation films on the pretreated magnesium alloys with ultrasound contained more aluminium and the pretreatment improved the uniformity of the anodic films. The use of ultrasound in the pretreatment process could significantly decrease the quantity and size of the micro-pores on the anodic films. The corrosion resistance of the anodic films formed on the pretreated magnesium alloys was improved. The corrosion resistance with ultrasound was better than that without ultrasound in the pretreatment process. In this paper, the effect and mechanism of the ultrasound during the immersion pretreatment process in aluminium nitrate solution was also discussed.

Spinel-type AlON, Al2.75□0.25O3.74N0.26, was obtained by ammonia nitridation of an oxide precursor prepared by peptizing a glycine gel with aluminum nitrate. To achieve crystallization, the nitrided product had to be annealed at 1500°C for 10 min in flowing nitrogen. The use of glycine instead of citric acid was important for obtaining a white product without residual carbon. A similar preparation method was used for adding small amounts of europium below 10 mol%. A strong blue emission was observed for products ranging from 0.5 to 3.0 mol% Eu doping. The product with 0.5 mol% doping had a maximum emission intensity at 400 nm for an excitation of 254 nm. The products with 1 and 3 mol% doping showed double maxima at 475 and 520 nm. These three emissions were due to the presence of divalent europium in the EuAl12O19 magnetoplumbite-like aluminum oxynitride impurity mixed with the AlON spinel major phase. The 1 mol% Eu-doped product exhibited expanded hexagonal lattice parameters (a=0.5591 and c=2.236 nm) compared with the values for EuAl12O19 magnetoplumbite itself, observed in the 7.7 mol%-doped product without any strong emission. The above spectrum change was discussed in relation to the coordination around Eu2+.

Powder precursors lithium aluminosilicate (LAS) of low expansion characteristics were synthesized by following the wet interaction technique in the hydroxyhydrogel form using lithium carbonate (Li2CO3), hydrated aluminium nitrate [Al(NO3)3·9H2O], fume silica (SiO2) and zirconium oxychloride (ZrOCl2·8H2O). Dilatometry, X-ray diffraction (XRD), IR analysis, Scanning Electron Microscopy (SEM) and Image analysis were done to study sintering, characteristics phase transformation and microstructure on the sintered specimens. ZrO2 was found to promote the formation of β-eucryptite, and grain size of the sintered specimens could be related to the amount of ZrO2 present in the starting powder precursor. The thermal expansion characteristics were also found to be strongly influenced by ZrO2 content in the specimens.

Large plate crystals of boehmite up to 4 μm were prepared from Al(NO3)3 solutions with the addition of NaOH under hydrothermal conditions at 250°C for 6 h. The conditions to obtain monodispersed boehmite large plate crystals were determined to be in the range of OH/Al molar ratio from 3.5 to 3.8 and Al concentration from 1.3 to 2.0 mol/kg. Bayerite formed by mixing the starting materials changed to gibbsite at 200°C, and at the same time boehmite started to crystallize from gibbsite. Even after complete phase change from gibbsite, small boehmite crystals grew larger by dissolution and precipitation mechanism. The key to obtain boemite large plate crystals is the preparation of homogenous fine boehmite crystals by quickly heating fine gibbsite crystals to the boehmite stable region, as well as the selection of OH/Al molar ratio and Al concentration.

Aluminium nitrate and aluminium isopropoxide were used as aluminium precursors to prepare bimodal porous alumina–silica mixed oxides via the sol–gel method with the addition of nonionic surfactant C16EO10 as the structure-directing agent. The characterization of the mixed oxides was performed using scanning electron microscopy (SEM), nitrogen adsorption/desorption measurements, chemical composition measured by X-ray fluorescence (XRF), and surface acidity was investigated by the Hammett indicator method and Fourier transform infrared spectroscopy (FT-IR) of adsorbed pyridine. It is found that the resultant mixed oxides possess micrometer-range interconnected macropores and nanometer-range mesopores. Studies have shown that relatively large mesopore size materials can be obtained with aluminium nitrate precursor, but relatively high Al content materials can be synthesized using aluminium alkoxide as aluminium precursor. Surface acidity analysis results indicate that the alumina–silica mixed oxides synthesized by present sol-gel method have Lewis acid sites and Bronsted acid sites, and these acid sites exhibit mild strong acidity. Moreover, two different synthesis pathways have little influence on the acidity of alumina–silica prepared by the present method. In addition, the adsorption capacity of such acidic mixed oxides, with bimodal pore structures, for pyridine from diesel oil was studied. The adsorption experiments indicate that these mild strong acidic adsorbents with high surface areas and large macropores are effective in removing basic nitrogen compounds (BNC) such as pyridine from diesel oil, and are easily regenerated by washing with polar solvents.

TiO 2 -containig single-phase gels with (Al 2 O 3 + TiO 2 )/(SiO 2 ) molar ratios 3/2 and 2/1 were prepared by gelling mixtures of aluminium nitrate, tetraethylorthosilicate and titanium isopropoxide. Gels were fast heated at several temperatures up to 1100 °C. Dried and heated gels were characterized by differential thermal analysis (DTA), magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray powder diffraction (XRD), and scanning and transmission electron microscopies (SEM and TEM). Coupled DTA and XRD results of gels fast heated at 900 °C showed the crystallisation of two mullites as well as a small amount of alumina-silica spinel. 27 Al NMR spectra showed the formation of pentacoordinated aluminium before mullite crystallization. The increase of lattice parameters of single-phase mullites heated at 1100 °C indicated that the amount of TiO 2 incorporated into the mullite structure increased on raising the amount of nominal TiO 2 in both series. SEM and TEM images of heated gels at 1100 °C displayed the formation of well-shaped parallelepiped of titanium-doped mullite nanocrystals with crystalline anisotropy.

The effects of Zn acetate or/and Zn chloride as ZnO precursors have been studied on the c-preferred orientations of pure ZnO and ZnO films doped with aluminium obtained by spray pyrolysis. We have used aluminium nitrate and aluminium chloride as precursors for aluminium doping. The experiment uses factorial designs to reveal possible interactive effects between the ZnO precursors, and the aluminium doping on the crystalline texture obtained. We have determined the conditions to obtain c-preferred orientated thin films using mixtures of both ZnO precursors.

Summary: This study examines the use of a PMMA-mediated assembly of BaTiO3 nanoparticles directly onto Cu electrodes under an electric field. The compatibility of the interface between BaTiO3 nanoparticles and PMMA in a mixed organic solvent system enables the homogeneous dispersion of nanoparticles in a solid polymer matrix. This results in the effective packing of particles, which is desirable from the point of view of achieving a high dielectric constant in the composite. In this study, three-phase Al/BaTiO3/PMMA nanocomposite films from stable colloidal suspensions containing aluminium nitrate salts were also designed using an electrodeposition process. The simultaneous formation of Al metallic inclusions in the BaTiO3 nanoparticles in the PMMA matrix significantly improved the dielectric constant of nanocomposite films. HRTEM micrographs of BaTiO3 (240 nm)/PMMA and magnified view of BaTiO3 (50 nm)/PMMA/Al(NO3)3 · 9H2O composite particles in each suspension, and FESEM micrograph of electrodeposited three-phase nanocomposite film.

Single phase mullite gels with composition 2Al 2 O 3 ·SiO 2 (2:1) were prepared by the slow hydrolysis method using aluminium nitrate nonahydrate and tetraethylorthosilicate as reagents. The evolution to mullite from gels was studied by infrared (IR) spectroscopy and X-ray diffraction (XRD). Gels thermally treated under fast schedules showed mullite formation below 900 °C. Compositional and microstructural changes in 2:1 mullites through the range of temperature from 900 to 1600 °C were determined by the measurement of lattice parameters and field emission scanning electron microscopy. The alumina-rich mullites formed at low temperatures become almost the nominal 2:1 at 1600 °C. This result is consistent with available thermodynamic data for mullite formation from alumina and silica. Microstructural examination indicated an almost constant grain size for mullite from 900 to 1600 °C.

Mullite powders were obtained by suspension combustion synthesis. The reaction was performed in a combustion reactor designed in the laboratory, which presents some advantages over other classical procedures (heating with a hot-plate, a furnace or a microwave oven). Aluminium nitrate, as a source of Al, and either TEOS or a colloidal silica suspension, as a source of Si, were used as reagents. Urea, at either 100 or 200% excess over the stoichiometric ratio, was used as fuel. NH4NO3, HNO3, NH4Cl and H2O2 were compared as combustion aids. Mullite phase with a high crystallinity and a high specific surface area was directly obtained by using aluminium nitrate, colloidal silica suspension, a 100% excess of urea and either NH4NO3 or H2O2. The selection of a combustion aid determines the characteristics of the as-synthesized powders. In addition to enthalpy predictions the reduction potential is a key parameter for the combustion to occur.