Effect of milling atmosphere on structural and magnetic properties of Ni–Zn ferrite nanocrystalline

Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni–Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres (argon, air, and oxygen), milling time (from 0 to 30 h) and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni–Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600 °C for 2 h leads to the formation of a single phase of Ni–Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated

Influence of CaO and SiO2 co-doping on the magnetic, electrical properties and microstructure of a Ni–Zn ferrite

Effect of CaO and SiO2 additions on the grain growth and magnetic and electrical properties of a Ni-Zn ferrite was studied. The common oxides (x = 0.4CaO + 0.8SiO2) were added in different moles (x = 0, 0.02, 0.06, 0.012, 0.24 and 0.48) to Fe2O3, Zn, and NiO. The mixed powders were mechanically alloyed for 12 h using a high energy ball mill before heating at 1200 °C for 240 min. The products were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, vibrating sample magnetometer and static hysteresisgraph, and later by an impedance analyzer with a frequency range from 1 MHz to 1.8 GHz. The XRD results indicate a formation of single phase spinel structure in all the samples. The average grain size was affected by the additive contents so that their sizes grew, up to x = 0.06, and after that their sizes reduced from 0.631 to 0.371 μ at x = 0.48. The experimental density of the samples displayed an upward trend for x < 0.06, increasing from 5.39 g cm-3 (x = 0) to 5.51 g cm-3 (x = 0.06): afterwards, their values presented a downward trend, reducing to 4.01 g cm-3 at x = 0.48. Magnetic behaviors such as saturation magnetization (Ms) and induction magnetization (Bs) degraded as well as the real permeability of the samples by increasing the x content. The loss factor i.e. hysteresis loss also remarkably decreased by accumulation of SiO2 and CaO in the grain boundaries. The electrical resistivity was determined in the order of 6.9 × 1010 cm for x = 0 and 6.4 × 1011 cm for x = 0.48. Therefore, low relative loss factor and high resistivity make these ferrites particularly useful as inductor and transformer materials for high frequency applications

Carbosilisiothermic reduction of rutile to produce nano-sized particles of TiC and its composite with SiO2

Ceramic nanoparticles of TiC were successfully synthesized in a matrix of SiO2 by high-energy ball milling with subsequent heat treatment. The milling procedure includes milling of a mixture of TiO2, Si, and graphite powders at ambient temperature in an inert gas (Ar) atmosphere. The structural evaluation of powder particles has been accomplished by XRD, TEM, SEM, EDX, and DSC. XRD results suggest that the TiC-SiO2 nonocomposite was produced after 10 hours of mechanical activation with subsequent heat treatment at 1473 K (1200 °C) for 7 minutes. TEM images reveal that the TiC and SiO2 crystallites are <14 and 12 nm in size, respectively. The fracture toughness, and Vickers hardness values of the TiC-SiO2 nanocomposite are measured to be 3.82 MPa m1/2 and 19.9 GPa, respectively. Dimethylsulfoxide is used to eliminate SiO2 from the final products

Improvement of Wear Resistance of AZ31 B Mg Alloy by Applying Oxide-Sic Nanocomposite Coating via Plasma Electrolytic Oxidation

Abstract -Ceramic coatings were produced on the surface of AZ31 B Mg alloy using a plasma electrolytic oxidation (PEO) process from an aluminate-silicate electrolyte containing SiC nanoparticles at different coating times. Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy was employed to monitor morphological and chemical changes of obtained oxide coatings. It was found that in presence of SiC nanoparticles, porosity as well as mean diameter of pores decreased. Meanwhile, the mean diameter of pores increased with prolonging coating time. The wear tests were conducted using a pin-on-disk tribometer under normal load of 5 N for 1500 cm. The wear results showed that the wear rate of ceramic-SiC nanocomposite coatings was less than ceramic ones. The higher hardness of ceramic-SiC nanocomposite coatings could be the main reason of decrease in wear of these coatings in comparison with simple coatings

Fabrication, bio-corrosion behavior and mechanical properties of a Mg/HA/MgO nanocomposite for biomedical applications

The Mg/HA/MgO nanocomposites were fabricated with pure magnesium and the addition of different amounts of hydroxyapatite and periclase nanopowders using a blend-cold press-sinter powder metallurgy technique to improve the bio-corrosion and mechanical properties of the resulting material. Potentiodynamic polarization, immersion and mechanical tests were used to investigate bio-corrosion and mechanical properties of the nanocomposites produced. The compositions of the corrosion products and surface morphologies of the corroded specimens were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and field-emission scanning electron microscopy. The corrosion resistance of the nanocomposites is shown to increase from 0.25kOcm2 to 1.23kOcm2 with the addition of 10wt.% MgO; additionally, decreasing the amount of HA from 27.5 to 12.5wt.% is shown to yield an increase in the compressive failure strain from 4.2 to 11.5%. The corrosion products of the composite surface are shown to be primarily Mg(OH)2, HA and Ca3(PO4)2. During immersion in SBF solution, the growth of the Mg(OH)2 nanorods on the nanocomposites increased the contact angle between the SBF solution and the substrate; as a result, the corrosion rate and hydrogen evolution rate decreased. The cell culture results indicate that Mg/HA/MgO nanocomposite is biocompatible with osteoblasts

Synthesis and structural characterization of nano-sized nickel ferrite obtained by mechanochemical process

NiFe2O4 nanoparticles were synthesized by a mechanochemical reaction of NiO and Fe2O3 powders in a high energy planetary ball milling machine. The XRD characterization results suggested that in the case of nano ferrite, milling up to 18 h formed NiFe2O4 particles of 10 nm with some residual Fe2O3 particles through a solid state reaction. By extending milling time to 30 h, the amorphous phase of NiFe2O4 was produced due to the high energy released during mechanical activation. The mechanism was identified as one of diffusion and counter-diffusion of Ni+2 and Fe+3 ions of the starting materials into each other. FT-IR analysis showed two absorption bands in the nickel ferrite structure related to octahedral and tetrahedral sites, respectively, in the range of 400–600 cm−1. The vibrating sample magnetometric (VSM) studies showed that the nano-sized particles of nickel ferrite exhibited a ferromagnetic behavior and its coercivity was approximately negligible

New Approach for Preparing In Vitro Bioactive Scaffold Consisted of Ag-Doped Hydroxyapatite + Polyvinyltrimethoxysilane

Recently, researchers have focused on the biocompatibility and mechanical properties of highly porous structures of biomaterials products. Porous composites are a new category of bioengineering that possess excellent functional and structural properties. In this study, the physical and mechanical properties of prepared doped silver (Ag)-hydroxyapatite (HA) by the mechanochemical and spark plasma sintering (SPS) methods were investigated. The influence of dopant on phase formation, structural properties, mechanical properties and morphological characteristics was investigated. Furthermore, in this case, as a new approach to produce a porous scaffold with an average size of &gt;100 µm, the hair band was used as a mold. According to the Monshi–Scherrer method, the crystal size of scaffold was calculated 38 ± 2 nm and this value was in the good agreement with average value from transmission electron microscopy (TEM) analysis. In addition, the stress–strain compression test of scaffold was considered, and the maximum value of compressive strength was recorded ~15.71 MPa. Taking into account the XRD, TEM, Fourier-transform infrared (FTIR), scanning electron microscope (SEM) and energy dispersive X-Ray analysis (EDAX) analysis, the prepared scaffold was bioactive and the effects of doped Ag-HA and the use of polyvinyltrimethoxysilane (PVTMS) as an additive were desirable. The results showed that the effect of thermal treatment on composed of Ag and HA were impressive while no change in transformation was observed at 850 °C. In addition, PVTMS plays an important role as an additive for preventing the decomposition and creating open-microporous in the scaffold that these porosities can be helpful for increasing bioactivity