Low-temperature Auto-combustion Method Research Articles

Tailoring the Physicochemical and Magnetic Properties of an Mn Substituted Cobalt Ferrite System

An Mn substituted cobalt ferrite system was prepared using a simple, low temperature auto-combustion method followed by heating at 600 °C for 3 h. In this method, the thermochemical decomposition of amino acids such as glycine at elevated temperatures in the presence of salt nitrates, especially iron nitrate, produced a ferrite system. The as-prepared Mn-Co ferrite was characterized by XRD, SEM, IR and EDX techniques. These techniques revealed that the employed preparation method led to formation of a single phase of nanocrystalline spinel Mn0.5Co0.5Fe2O4 powder. However, various structural and morphological properties of the as-synthesized ferrite were determined. Porous and agglomerated morphology of the bulk sample was displayed in the scanning electron microscopy image. The VSM technique displayed the saturation magnetism of Mn0.5Co0.5Fe2O4 as 51.53 emu/g.

Synthesis, Magneto-structural Properties and Colloidal Stability Studies of Ni0.3Zn0.7Fe2O4 Nanoparticles Coated with Pluronic P123 Block Copolymer for Potential Biomedical Applications

Spinel Ni0.3Zn0.7Fe2O4 (NZFO) magnetic nanoparticles was prepared by the low temperature auto-combustion method using a glycine fuel-rich composition without any further heat treatment at high temperature. Subsequently, the synthesized MNPs were coated with Pluronic P123 (PP123) after its surface was functionalized with oleic acid (OA). The effect of the coatings on the morphology, structural and magnetic properties of NZFO nanoparticles was studied using powder X-ray diffraction (XRD), Fourier transform infrared, thermogravimetric analysis, field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM). The colloidal behaviour of coated MNPs in physiological saline medium like water or phosphate buffer saline (PBS) was also studied by zeta potential measurements. XRD results showed the formation of cubic spinel crystalline phase with and without OA–PP123 coatings. Also, after OA–PP123 coating, the crystallite size (from Scherrer formula) decreases from 55 to 53 nm. However, an enlargement in the particle size and a reduction in agglomeration were observed from FE-SEM results when the nanoparticles were coated with OA–PP123. VSM measurements showed ferromagnetic behaviour at room temperature before and after coating. The colloidal stability study of the coated sample revealed a considerable high zeta potential value at physiological pH (7.4) highlighting its potential biomedical applications.

Structural, dielectric and magnetic properties of nickel substituted cobalt ferrite nanoparticles: Effect of nickel concentration

Nickel substituted cobalt ferrite nanoparticles with composition Co1−xNixFe2O4 (0.0 ≤ x ≤ 1.0) was synthesized using simple, low temperature auto combustion method. The X-ray diffraction patterns reveal the formation of cubic phase spinel structure. The crystallite size varies from 30-44 nm with the nickel content. Porous and agglomerated morphology of the bulk sample was displayed in the scanning electron microscopy. Micro Raman spectroscopy reveals continuous shift of Eg and Eg(2) stokes line up to 0.8 Ni substitution. The dispersion behavior of the dielectric constant with frequency and the semicircle nature of the impedance spectra show the cobalt nickel ferrite to have high resistance. The ferromagnetic nature is observed in all the samples, however, the maximum saturation magnetization was achieved by the 0.4 Ni substituted cobalt ferrite, which is up to the 92.87 emu/gm at 30K.

Magneto-structural properties of Ni–Zn nanoferrites synthesized by the low-temperature auto-combustion method

Using nickel, zinc and ferric nitrates, and glycine in a fuel-rich composition, Ni1−x Zn x Fe2O4 nanoparticles were prepared by a simple low-temperature auto-combustion method without further sintering at high temperatures. The auto-combusted powders obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDAX) analysis and vibrating scanning magnetometer measurements. XRD confirms the formation of pure nanocrystalline spinel phases with an average diameter of about 55 nm. Raman spectra show tetrahedral and octahedral sites in the structure of Ni1−x Zn x Fe2O4 and also imply the doping of Zn2+ and displacement of Fe3+ ions from the tetrahedral site. EDAX showed that the samples were close to the nominal compositions. The magnetic measurement shows that the saturation magnetization and remanence magnetization decreases with the increase in the zinc content.

MoP/Hβ catalyst prepared by low-temperature auto-combustion for hydroisomerization of n-heptane

Molybdenum phosphide supported on Hβ zeolite (MoP/Hβ) was prepared via the low-temperature auto-combustion method, and characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption, and temperature-programmed desorption of NH3. The as-synthesized MoP/Hβ was employed as the bifunctional catalyst for the hydroisomerization of n-heptane, and gave a much higher activity compared to the counterpart MoP/Hβ catalyst prepared by the traditional impregnation method. The promoted effect of the low-temperature auto-combustion method on the catalytic performance is attributed to the less blockage of β pores and more strong acid sites of the as-synthesized MoP/Hβ.

Low temperature combustion synthesis and magnetostructural properties of Co–Mn nanoferrites

In the present work, Co1−xMnxFe2O4 nanoparticles were synthesized by the low-temperature auto-combustion method. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis (TG-DTA) that showed the precursor yield the final product above 450°C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction (XRD). Microstructural features observed by scanning electron microscopy (SEM) demonstrates that the fine clustered particles were formed with an increase in average grain size with Mn2+ content. Fourier transform infrared spectroscopy (FTIR) study confirms the formation of spinel ferrite. Room temperature magnetization measurements showed that the magnetization Ms increases from 29 to 60emu/g and Hc increases from 13 to 28Oe with increase in Mn2+ content, which implies that these materials may be applicable for magnetic data storage and recording media.

The effect of chelating/combustion agent on catalytic activity and magnetic properties of Dy doped Ni–Zn ferrite

The spinel ferrite Ni0.8Zn0.2Fe1.98Dy0.02O4 was prepared by sol–gel low temperature autocombustion method using four different chelating/combustion agents: citric acid, tartaric acid, urea and cellulose. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) specific surface area measurement, the catalytic H2O2 decomposition and the magnetic behavior were employed to investigate the influence of the combustion agents on structural characteristics, catalytic activity and magnetic properties. Spinel-type phase in the nano-scale domain was accomplished during sol–gel synthesis and was confirmed by XRD and IR. The best catalytic activity is belonging to the sample obtained using urea, which shows the smallest grain size (SEM), the highest specific surface area (BET measurements) and DyFeO3 phase (XRD), while ferrimagnetic behavior prevails for all the samples independently of fuel agent.

Optimization of Magnetic and Structural Properties of Sr Ferrite Prepared by Low-Temperature Combustion

Fine strontium hexaferrite particles were prepared by the low temperature auto-combustion method. Aqueous solution of the corresponding metal salts and a combustible co-reactant compound — glycine were used as initial precursor. The resulting powders were calcined at various temperatures from 750◦C up to 1100◦C. The microstructure and magnetic properties were investigated by the Mossbauer spectroscopy, thermomagnetic analysis, scanning electron microscopy, and vibrating magnetometer. The particles of sizes less than 1 μm have monophasic hexagonal structure. Coercivity Hc ≈ 400 kA/m, specific saturation polarization Js−m ≈ 72 × 10−6 Tm kg−1 and remanence polarization Js−r ≈ 43 × 10−6 T m kg−1 were achieved for the Sr ferrite annealed at 850◦C for 6 h.