Self-Assembly Fabrication of Hollow Mesoporous Silica@Co–Al Layered Double Hydroxide@Graphene and Application in Toxic Effluents Elimination

Here, we propose a self-assembly process to prepare hierarchical HM-SiO2@Co–Al LDH@graphene, with the purpose of combining their outstanding performance. Hollow mesoporous silica was first synthesized as the core, using a novel sonochemical method, followed by a controlled shell coating process and chemical reduction. As a result of the electrostatic potential difference among HM-SiO2, Co–Al LDH, and graphene oxide, the HM-SiO2 spheres were coated by Co–Al LDH and graphene. Subsequently, the HM-SiO2@Co–Al LDH@graphene spheres were introduced into an epoxy resin (EP) matrix for investigation of their toxic effluents capture and elimination effectiveness during combustion. The amount of toxic CO and volatile organic compounds from the epoxy resin decomposition significantly suppressed after incorporating the HM-SiO2@Co–Al LDH@graphene hybrids, implying a reduced toxicity

Comparative Study of the Effects of Rare Earth Ions in a High Frequency Ni-Zn Ferrite

Some effects of the rare-earth ions on the properties of the polycrystalline stoichiometric ferrite with formula Ni0.7Zn0.3Fe1.98R0.02O4(R=Yb, Er, Dy, Tb, Gd, Sm and Ce) are described. The results obtained reveal that by introducing a relatively small amount of R2O3 instead of Fe2O3, an important modification of both structure and properties can be obtained. R2O3 facilitates the formation of the crystalline secondary phases (orthoferrite, garnet) on the grain boundary which inhibit the ferrite grain growth. The R ions tend to flatten the µi- T curve, shift the Curie point to lower temperature and increase the electrical resistivity. The variation of these properties with the R species has been explained as an effect of the ionic radius size which varies from 0.86 for Yb to 1.07 for Ce

Lithium Ferrite Nanocrystals Embedded in a non-Magnetic Glass Matrix

Nanocrystalline LiFe5O8 particles embedded in an amorphous matrix were obtained by heat treatments of the non-magnetic oxide glass 32Li2O-8FeO3-60B2O3, between 200 and 770°C. The X-ray spectra reveal the formation of the spinel phase of Li-ferrite in the initially amorphous materials only for annealing temperatures higher than 440°C and the hybrid structure becomes more evident with the increase of temperature. The occurrence of the magnetic spinel phase (LiFe5O8) was proved by magnetization and Curie temperature measurements too. The evolution of the magnetic properties of these glass-ceramic compounds in terms of annealing temperature was investigated. The magnetic properties (σs, Hc) are correlated with the average size of the LiFe5O8 nanoparticles dispersed in the glass matrix. The X-ray diffraction data indicated an evident increase in the average crystal block size from 3.5 to 50 nm with the increase of annealing temperature from 440° to 770°C

Magnesium-zinc ferrite with copper substitutions

The effects of Mg substitution by Cu on the properties of MgZn ferrites sintered at low temperature are investigated. The densification of MgCuZn ferrites is dependent upon Cu content in the composition Mg0.5-xCuxZn0.5Fe2O4 + 0,5 MgO. From the sintering experiments carried out between 800 and 1100° C it was established the optimum amount of CuO (x = 0.3) which is sufficient to promote sintering at low temperature (1050°C) and to yield a dense material (4,5 g/cm3). It was evidenced a break in the resistivity for x > 0,3 when it decreases by four orders of magnitude. The strong dependence of the material parameters on the Cu ions content is consistent with the microstructural changes induced by copper ions which favour the lattice diffusion process

Ignat M. “Nanostructured lanthanum manganite perovskites in catalyst applications

Finding less expensive alternatives to noble metals catalysts is vital for implementing catalytic combustion on a wide scale, and lead substituted lanthanum manganites are a promising option. Nanometer particles of La 0.6 Pb 0.4 MnO 3 and La 0.6 Pb 0.4 MnO 3 + 0.2MeO (where Me = Mg or Ca) with perovskite structure were prepared by self-combustion method followed by heat treatment at 1000 o C in air. The effects of excess divalent ions (Ca 2+ and Mg 2+ ) in La 0.6 Pb 0.4 MnO 3 manganite perovskite on the catalyst properties were investigated. The morphological and surface properties are of great importance in the catalyst activity. Structure, specific surface area and grain size were determined using XRD, nitrogen adsorption (BET) and SEM analysis. X-ray diffraction evidenced the crystallinity and the nanosize of the perovskite crystallites. Following Mg or Ca addition to La 0.6 Pb 0.4 MnO 3 , a decrease in the grain size was detected by SEM. Rather large values for specific surface areas were obtained (of about 8 m 2 /g).The perovskite manganite powders have been tested in the catalytic combustion of three diluted gases: acetone/air, ethanol/air and methanol/air. The experimental results revealed that it was possible to start the catalytic combustion of the gases over the surface of the three perovskite at much lower temperatures than catalyst-free combustion

Magnetostatic Energy Associated with Variation of Local Magnetization Direction in Field Annealed Amorphous Ribbons

It is shown that in field annealed amorphous ribbons (with oblique intrinsic anisotropy), the magnetostatic energy associated with spatial fluctuations of the local magnetization depends on the magnetization state. The corresponding magnetostatic interactions can play an important part in the magnetic behaviour of the amorphous ribbons with small macroscopic anisotropy