SrFeO amorphous underlayer for fabrication of c-axis perpendicularly orientated strontium hexaferrite films by pulsed laser deposition

10.1016/j.jmmm.2013.04.026Journal of Magnetism and Magnetic Materials34136-39JMMM

In-situ synthesis of NiCo/(Ni,Co)O/(Ni,Co)Fe2O4 composite as high-performance microwave absorber

NiCo/(Ni,Co)O/(Ni,Co)Fe2O4 composites were in-situ prepared by solution combustion method using metal nitrates as oxidant and glycine as organic fuel. The amounts of various intermetallic and oxide phases were controlled by amounts of metal precursor. The magnetic properties proved the presence of Ni1-xCox phase instead of pure Ni and Co phases. The combusted composites showed spongy microstructure without any special morphology for various phases. The (Ni,Co)O-49 wt % NiCo composite powders had the effective absorption bandwidth (EAB) of 3.6 GHz at a matching thickness (1.8 mm) in Ku band. By using the ferric precursor, the (Co,Ni)O-30 wt %NiCo-15 wt % (Co,Ni)Fe2O4 composite exhibited a rather broader EAB of 3.9 GHz at a smaller matching thickness of 1.2 mm in Ku band

Cation Distribution Tuning of Solution Combusted CoFe2O4 Powders

In this work, the different fuels (citric acid, glycine and urea) were used for solution combustion synthesis of CoFe2O4 powders. X-ray diffraction, Raman spectroscopy, electron microscopy and vibrating sample magnetometry techniques were employed for characterization of phase evolution, cation distribution, microstructure and magnetic properties of the as-combusted CoFe2O4 powders. Single phase CoFe2O4 powders with partially inverse structure in which the Co2+ cations are distributed in both tetrahedral and octahedral sites were synthesized by the citric acid, glycine and urea fuels. The as-combusted CoFe2O4 powders by the citric acid fuel exhibited the highest inversion coefficient. The crystallite size of the as-combusted CoFe2O4 powders synthesized by urea fuel was 15 nm, increased to 41 and 52 nm for the glycine and citric acid fuels, respectively. Furthermore, the solution combusted CoFe2O4 powders showed ferromagnetic behavior with saturation magnetization of 61.9, 63.6 and 41.6 emu/g for the citric acid, glycine and urea fuels, respectively. The high crystallinity and particle size of the as-combusted CoFe2O4 powders using glycine fuel led to the highest magnetization and the moderate coercivity. &nbsp

Correlation between shear punch and tensile measurements for an AZ31 Mg alloy processed by equal-channel angular pressing

An AZ31 magnesium alloy was extruded and then processed by equal-channel angular pressing (ECAP) at 200 °C for 1, 2 and 4 passes. The grain structure was refined from 20.2 to 1.6 ?m after 4 passes. The shear punch testing (SPT) technique and uniaxial tensile tests were employed to evaluate the mechanical properties of the extruded and ECAP samples. The 4 pass ECAP alloy showed lower yield stress and higher ductility compared to the as-extruded condition, indicating that texture softening overcame the strengthening effects of grain refinement. The same trends in strength and ductility were also observed in shear punch testing. Three different linear correlations between the shear data and tensile data were established for ductility, yield stress, and ultimate strength. It is shown that SPT is a useful method for evaluating the mechanical properties of small quantities of fine-grained materials processed by ECA

Microstructure and magnetic properties of La-Co substituted strontium hexaferrite films prepared by pulsed laser deposition

10.1016/j.jmmm.2013.04.066Journal of Magnetism and Magnetic Materials342134-138JMMM

Oxalate-assisted solvothermal synthesis of octahedral LiMn1.5Ni0.5O4 particles for lithium-ion batteries

Submicron octahedral LiMn1.5Ni0.5O4 particles were easily prepared by solvothermal synthesis method. The effects of synthesis conditions including precursors' concentration (0.09 and 0.18 M), calcination temperature (700 and 800 °C), and calcination time (2 and 8 h) were studied by modern characterization techniques. The octahedral LiMn1.5Ni0.5O4 particles with disordered spinel structure (space group of Fd3¯m) were obtained by calcination at 800 °C for 2 h. With the increase of precursors’ concentration and prolonging the calcination time, the particle size increased from 220 to 845 nm and the particle size distribution became wider. Furthermore, the corners and edges of the octahedral particles were chamfered by appearing the (100) family planes at longer calcination times. The truncated LiMn1.5Ni0.5O4 particles showed a high discharge specific capacity of 133 mAh g−1 at current rate of 0.1C and a high capacity retention of 99.3% following 50 cycles

Preparation of strontium hexaferrite film by pulsed laser deposition with in situ heating and post annealing

10.1016/j.jmmm.2012.04.034Journal of Magnetism and Magnetic Materials324182894-2898JMMM

Magnetic properties of strontium hexaferrite films prepared by pulsed laser deposition

10.1016/j.jmmm.2012.03.040Journal of Magnetism and Magnetic Materials324172654-2658JMMM

Ultra-broadband FeNi3/NiZnFe2O4/ZnO composite powders for microwave absorption

FeNi3/NiZnFe2O4/ZnO composite powders were in-situ prepared for microwave absorption by solution combustion synthesis method in a closed system. The effects of fuel content and composition on the structural, microstructural, and magnetic and microwave absorption properties were studied by X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, and vector network analyzer techniques. There were FeNi3, NiZnFe2O4 and ZnO phases in the samples obtained at higher fuel contents and higher amounts of Zn2+ substitution. The synthesized powders had porous and spongy microstructure in which the porosity and particle size decreased with the fuel contents. The values of permittivity and permeability decreased with Zn2+ addition. By controlling over the amounts of fuel and substituted Zn2+ species, the values of saturation magnetization and the coercivity were tuned in the range of 30–70 emu/g and 153–131 Oe, respectively. The composite sample containing NiZnFe2O4-34 wt.% FeNi3-8 wt. % ZnO exhibited a minimum reflection loss of −40 dB and an effective absorption bandwidth of 4.6 GHz in Ku band at the matching thickness of 1.5 mm. The NiZnFe2O4-17 wt.% FeNi3-32 wt. % ZnO composite powders had the broader effective absorption bandwidth of 6.7 GHz at the matching thickness of 2.3 mm, but with the minimum reflection loss of −24 dB at a matching frequency of 16.5 GHz