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LaFeO3 nanoparticles of different sizes are prepared by varying the molar concentration of oleic acid to metal nitrate using emulsion combustion method. X-ray diffraction analysis confirms that LaFeO3 nanoparticles are crystalline in nature with an orthorhombic structure. The average particle size and saturation magnetization decreases from 56 to 32nm and 0.20 to 0.08emu/g, as molar concentration of oleic acid to metal nitrate increases from 0.25 to 1. The Fourier transform infrared (FTIR) spectra show the lower frequency bands are assigned to Fe-O stretching vibration (579cm -1) and O-Fe-O deformation vibration (475 and 400cm-1). The experimental results suggest that molar concentration of oleic acid to metal nitrate plays an important role in the particle size and magnetic property of combustion synthesized lanthanum ferrite nanoparticles. Copyright � Taylor & Francis Group, LLC.

Cobalt aluminate (CoAl2O4) nanopowders were synthesized by reverse microemulsion process using cyclohexane, a nonionic surfactant, and aqueous solutions of cobalt (II) nitrate hexahydrate and aluminum nitrate nonahydrate. The influence of water to surfactant molar ratio on the size of powders has been studied. The X-ray diffraction analysis shows that the powders calcined at 1000 �C have single phase cubic spinel structure. The average size of the particles increases with increasing water to surfactant molar ratio. The mean diameter of the particles varies between 42 and 57 nm. The Fourier transform infrared spectra also confirm the formation of CoAl2O4. Magnetization study reveals that the CoAl 2O4 sample exhibits superparamagnetic behavior. � 2010 Elsevier B.V. All rights reserved.

In this research, a sol-gel auto combustion route has been proposed to synthesize LaAlO3 nanopowders, using lanthanum nitrate, aluminum hexahydrate, and different fuels such as citric acid, oxalic acid, and tartaric acid. The formation temperature of LaAlO3 and its crystallite size in the presence of different fuels were compared together. The results showed that the lowest formation temperature as well as the smallest crystallite size in the presence of citric acid was 750�C and 28.7nm. Copyright � Taylor & Francis Group, LLC.

In this research, a sol-gel auto combustion route has been proposed to synthesize alumina-ceria composite powder, using aluminium nitrate, cerium(III) nitrate hexahydrate and various fuels such as citric acid, acetyl acetone and oxalic acid. DTA shows the phase transformation of ?-Al2O3 and CeO2 varies with fuel. XRD confirms the formation of ?-Al2O3 and CeO2 phase irrespective of fuels at 1200 �C. X-ray line broadening results showed smallest crystallite size of ?-Al2O3 and CeO2 is produced in the presence of citric acid. SEM micrograph revealed homogenous distribution of ceria nanoparticle in the alumina matrix. FTIR analysis show peaks at 460 and 400 cm-1 corresponds to ?-Al2O3 and CeO2 formation at 1200 �C. � 2008 Elsevier B.V. All rights reserved.

Nanocrystalline Al2O3–ZrO2 powder was synthesized by a simple method using oxalic acid as a chelating agent. The formation temperature of α - Al2O3 was investigated by differential thermal analysis. X-ray diffraction (XRD) analysis shows that t-ZrO2 was stabilized in alumina matrix with oxalic acid content 0.5 M and 1 M, respectively. In addition, the data from XRD showed α-Al2O3 and t-ZrO2 phase can be formed at 1100°C with 1 M oxalic acid content. Transmission electron microscope (TEM) micrograph of calcined powders revealed as the oxalic acid content in the precursor solutions is increased from 0.25 M to 0.5 M concentration. The obtained materials could be modified from segregated nanoparticles to agglomerated nanoparticles and finally to large agglomerate with 1 M concentration of oxalic acid. The Fourier transform infrared spectra (FTIR) confirms the formation of α-Al2O3 in corroboration with X-ray studies.

Alumina fibers were prepared by sol–gel process using α-Al2O3 seeded boehmite sol. The starting material used for the preparation of boehmite sol was aluminium-tri-isopropoxide. Extended ball milling of boehmite sol using alumina grinding media was carried out to incorporate nucleating seeds of α-Al2O3 to boehmite sol. Differential thermal analysis showed that the phase transition to α-Al2O3 takes place at a much lower temperature by seeding α -Al2O3. The presence of α-Al2O3 seeds decreases the sintering temperature and a relatively dense microstructure with very fine grain size is formed at 1300°C. The fibers sintered at 1300°C have the highest tensile strength.

Alumina fibres were prepared by extrusion using boehmite sol as binder. The microstructure and mechanical properties of the fibres were studied. The fibres sintered at 1400 oC have relatively dense microstructure and the highest strength.

Alumina fibres were prepared by sol-gel process. The sol was prepared by mixing aluminium-tri-isopropoxide in distilled water and refluxed in the presence of acid catalyst. Binder was added in different amount to the sol to obtain spinnability. At the appropriate viscosity, the sol was taken in a syringe and fibres were drawn in the ammonia solution. The fibres were dried at room temperature and then sintered at 1600 �C for 2 h, ?-alumina is the only phase present in the sintered fibres. Differential thermal analysis indicated that the phase transition to ?-alumina takes place at 1100 �C. Thermogravimetric analysis indicated the removal of most of the volatile up to 600 �C. Scanning electron microscopic analysis reveals dense microstructure is formed with 10 wt.% hydroxyl ethyl cellulose. The tensile strength is found to be good for sample containing 10 wt.% hydroxy ethyl cellulose. � 2005 Elsevier B.V. All rights reserved.

Alumina fibers were prepared by sol-gel method using an in-house fabricated extruder. The starting material used for the preparation of alumina sol was aluminium-tri-isopropoxide. A suitable binder was added to the sol and aged at room temperature for gelation to occur. When the sol became a paste appropriate for extrusion, the fibers were drawn through the extruder and dried at room temperature and subsequently sintered at 1200�, 1400�, and 1600�C in air. It was found that regardless of sintering temperature, the XRD traces indicated that the only phase present in sintered fibers was a-Al 2 O 3 . Thermogravimetric analysis of the extruded fibers indicated that most of the volatile compounds were burned out at 500�C. The DTA and FTIR studies confirmed the phase transition to a-Al 2 O 3 and this was in good agreement with the XRD analysis. The SEM investigation revealed that a dense microstructure formed when fibers sintered at 1600�C. In addition, the SEM micrograph revealed that an intergranular fracture was the predominant fracture mode. Mechanical tests indicated that the optimum tensile strength was achieved for fibers sintered at 1600�C.

Alumina-zirconia fibres were prepared by sol-gel process. The starting materials used for the preparation of alumina and zirconia sol were aluminium-tri-isopropoxide and zirconium oxychloride, respectively. Alumina sol and zirconia sol were mixed in definite proportions, so that the final composition contains 10 wt.% ZrO 2. Fibres were drawn from the gel using an extruder and dried at room temperature and subsequently sintered at 1200, 1400 and 1600 �C. Differential thermal analysis showed that �-Al 2O 3 phase transition occurs at 1290 �C. The phases present in the sintered fibres were �-Al 2O 3, t-ZrO 2 and m-ZrO 2. Scanning electron microscope revealed dense microstructure is formed at 1600 �C. Tensile strength was found to be the highest for fibres sintered at 1600 �C. ? 2005 Elsevier B.V. All rights reserved.