Physical Properties of BaFe12O19 Materials Obtained Under Different pH Using Hexamine as Novel Fuel by Auto Combustion Followed by Annealing Route.

Hexamine was used as a fuel for the first time to synthesize BaFe12O19 materials under different pH (2, 6, 8, 10 and 12) condition. Though all the combustion products exhibited mixed phases of mainly γ-Fe2O3 and BaCO3, the annealed (1000 °C for 2 h) powders yielded good quality hexagonal BaFe12O19 phase materials. The optical properties of these materials were investigated by Fourier-transform infrared (FT-IR), near-infrared (NIR), and photoluminescence (PL) spectroscopic techniques. Plate-like shaped sticks/rods of nanometric (~33 to 40 nm) edge sizes of particles are observed for the present BaFe12O19 materials. A considerable improvement in NIR reflectivity of BaFe12O19 materials is noted for the present method than the mechano-thermal solid-state synthesis. The thermal analysis (TGA) and ferromagnetic hysteresis loop (M-H) measurements reveal an important change in weight and magnetic parameters, respectively due to variation in pH. It is found that the present pristine BaFe12O19 materials have feeble antibacterial activity as compared to the reported nanocomposite consists of cotton fabric coated with BaFe12O19 nanoparticles against Gram-negative Pseudomonas aeruginosa bacterium.

Impact of Different Set of Precipitants on the Formation of BaFe12O19 Phase Nanomaterials.

This work deals with the preparation of BaFe12O19 materials by soft chemical co-precipitation method using a different set of precipitants namely, (i) NaOH and Na2CO3, (ii) NH2CONH2 and NH4OH, and (iii) NH4HCO3 and NH4OH. The influence of these precipitants on the different properties is also investigated by various characterizations. The precipitants used in this work considerably affected the phase formation of BaFe12O19 materials. The thermal analyses reveal the thermal decomposition of the intermediate phase as well as the crystallization of BaFe12O19 phase. Due to the amorphous nature, all the co-precipitated products were annealed for 2 h at 1000 °C. Among the different annealed samples, the NaOH and Na2CO3 set of precipitant derived materials exhibit nearly single hexagonal phase of crystalline BaFe12O19 nanomaterials with an average crystalline size of ˜48 nm with a = 0.5888(4) nm and c = 2.320(2) nm. The particle size observed in micrograph was rather much higher than the average crystalline size obtained from XRD for the best sample. The BaFe12O19 nanomaterials studied in the present work have been found potential applications in magneto-optic recording media, biomolecular separations, magnetic carriers for drug targeting, permanent magnet, chip inductors, microwave absorbers, and hyperthermia cancer treatment.

Morphological Structure, Optical and Microbial Findings of Ferrites.

In this article, we report the interesting results on the effect of high energy ball milling (under 350 rpm for 0, 1, 3, 5, and 10 h) on the salt (NaCl:KCl) flux synthesized SrFe12O19 powder. The different processed powder was analyzed by powder X-ray diffraction (XRD), thermogravimetric analysis (TG/DTA), field emission scanning electron microscope (FESEM), Fourier-transform infrared (FT-IR) and near infra-red (NIR) reflectance spectroscopic techniques. From the present research findings, we note that the SrFe12O19 phase is susceptible to the high-energy ball milling process. The unmilled SrFe12O19 powder crystallized in hexagonal structure with the platelet-shaped SrFe12O19 grains exhibits high near-infrared (NIR) reflectance. The average crystalline size (XRD) of the unmilled (84.9 nm) SrFe12O19 powder is reduced to 22.2 nm after 1 h of ball milling. Ball milling of good quality SrFe12O19 powder for >1 h, mixed nanocrystalline phases of SrFe12O19 and α-Fe2O3 materials are formed. By increasing the ball milling time, the thermal features also vary accordingly. The platelet-shaped SrFe12O19 grains are strongly affected by ball milling of the salt flux synthesized SrFe12O19 powder for 1, 3, 5 and 10 h. Ball milling of SrFe12O19 powder has a strong effect on the NIR reflectance and color of the resultant ball-milled powders. The 1 h as-milled powder shows relatively strong inhibition zone as compared to other powder samples (0, 3, 5, 10 h) against Pseudomonas aeruginosa bacterium.

Synthesis of BaFe12O19 Materials by Mechano-Thermal Route: Novel Inorganic Pigment with High Near-Infrared Reflectance.

We have prepared BaFe12O19 materials by annealing the ball milled reaction mixture at 1000 degrees C and studied by various characterization techniques. Among the several annealed samples, the samples prepared from 2-5 h ball milled powder show (nearly) single phase of BaFe12O19 materials with reduced average particle size of -42 nm, whereas the reaction mixture ball milled for longer duration (≥10 h) yielded contaminated BaFe12O19 phase. The platelet hexagonal shape grain is seen in the high resolution scanning electron microscope (HRSEM) micrographs for the BaFe12O19 materials. The HRSEM images indicate sizes of grains are in the range of 418 nm to 2.58 µm in hexagonal basal plane and a range of 1 to 2.5 Am in direction of hexagonal axis. The highlight of the work is the present BaFe1201, materials may be used as novel inorganic pigment due to high near infrared (NIR) reflectance.