Controlling the structural,microstructure and magnetic properties of barium W-type hexaferrite elaborated using tartaric acid precursor strategy

In this study, barium W-type hexaferrite (BaCo₂Fe₁₆O₂₇) nanopowders have purposefully fabricated through tartaric acid precursor method using inexpensive starting materials. In this regards, the impact of the synthesis conditions namely the annealing temperature and the Ba:Co molar ratio on the crystal structure, crystallite size, microstructure and magnetic structure was explored using X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. For instance, well crystalline W-type hexaferrite was realized for the precursors annealed at a low temperature of 1100 °C for 2 h using two different Ba:Co molar ratios of 1.1:2.2 and 1.2:2.4. The crystallite size, the lattice constant, the aspect ratio as well as the unit cell volume were substantially affected with the Ba:Co molar ratio and the annealing temperature. Remarkably, the morphology of hexaferrite powders can be controlled by adjusting the annealing temperature and the Ba:Co molar ratio. Clearly, the microstructure of the formed powders was improved to a hexagonal platelet-like structure by raising the annealing temperature. Eventually, maximum saturation magnetization Ms?=?72.3 emu/g was accomplished for W-hexaferrite particles obtained with Ba:Co molar ratio 1.1:2.2 annealed at 1350 °C for 2 h. Wide coercivities (196–1097 Oe) were achieved at the different synthesis conditions.     

Impacts of the colemanite on the enhancement of the radiation shielding capacity of polypropylene

Journal of Materials Science: Materials in Electronics - Colemanite–polypropylene polymeric material has been fabricated by doping Colemanite material with different ratios 5, 15, 25, and 35...     

Transformation of silica fume into chemical mechanical polishing (CMP) nano-slurries for advanced semiconductor manufacturing

Silica nanoparticles have been synthesized from silica fume using alkali dissolution–precipitation process. The dissolution efficiency of 99% at a temperature of 80 °C and a time of 20 min was achieved. Sodium silicate solution was obtained by dissolving the fume with NaOH solution. Then, silica nanoparticles were precipitated using sulfuric acid. Silica nanoparticles (175 nm) were achieved using 12% sulfuric acid at pH 7 and 200 ppm sodium dodecyl sulfate (SDS). The silica morphologies appeared as a spherical shape with narrow particle size distribution. The silica samples were used for the formulation and testing of chemical mechanical polishing (CMP) slurries. The morphology of the polished wafer surface and its roughness were examined by atomic force microscope (AFM).The results indicated that the surface roughness was greatly improved after application of CMP. It was found that the surface roughness of the polished wafer is 0.226 nm at an applied pressure of 7 psi. The removal rate was found to be 1200 Å. These values confirm the quality of polished wafers.     

Magnetic behavior of cobalt ferrite nanowires prepared by template-assisted technique

Spinel cobalt ferrite nanowires were successfully prepared in mesoporous silica SBA-15 as a host matrix followed by slow thermal decomposition of the precursors inside the silica-based template. The formation and phase control of as-synthesized nanostructured cobalt ferrites were confirmed by X-ray diffraction (XRD) measurements at different annealing temperatures ranging from 500 to 1000 °C. The one-dimensional spinel nanostructures were identified by recording the transmission electron microscopy (TEM) images after a selective removal of the silica template in aqueous solution of NaOH. The final product was also characterized using infrared spectroscopy (FT-IR) and vibration sample magnetometer (VSM). The presence of SBA-15 lowers the formation temperature of cobalt ferrite nanowires compared to the corresponding bulk material. The nanowires annealed up to 700 °C exhibited magnetic behavior characteristic for soft magnetic materials, whereas samples annealed at temperature higher than 700 °C revealed magnetic behavior characteristic for hard magnetic materials with rectangular form and large coercive field.     

Application of ZnO–NiO greenly synthesized nanocomposite adsorbent on the elimination of organic dye from aqueous solutions: Kinetics and equilibrium

Organic dyes are discharged into aquatic systems from several industries causing severe environmental problems and toxicity to aquatic life. Therefore, it should be removed from water with a suitable process. Among several treatment processes, adsorption is one of the most attractive because of its simplicity, efficiency, and low operating cost. Moreover, adsorption supports environmental sustainability if a suitable adsorbent is used. In this work, a green route was followed to prepare ZnO: NiO nanocomposites using the Neem leaf extract as a stabilizing agent instead of harmful chemicals. Four different samples with three different ZnO:NiO ratios were prepared, namely: 3Z:1 N, 1Z:1 N, 1Z:3 N and 1Z:1 N without extract. The samples were characterized by XRD, TEM, SEM, IR, and UV, which all confirmed the successful synthesis of the nanocomposites. The nanocomposites were used for the adsorption of methyl orange (MO) from aqueous solutions. The four nanocomposites prepared with the aid of the extract showed a high sensitivity with 100% removal of MO from 6.25 ppm solutions. Furthermore, all the samples have a relatively fast kinetic with an equilibrium time less than 1 h. Also, the three samples maintained 100% removal efficiency after 5 adsorption-desorption cycles. The difference in particle size distribution obtained for the 1Z:1 N prepared with and without the extract confirms the important rule of the extract as a capping agent with an average size of 18 nm for the sample with the extract and 88 nm for the sample prepared without the extract. This difference in the particle sizes has been reflected on the adsorption performance of the two samples with a maximum adsorption capacity of 33 mg/g for the sample prepared with the extract compared to 6 mg/g for the sample without the extract.     

Synthesis of molybdenum silicide/mullite composites for high-temperature applications

Molybdenum silicide/mullite composite having about 31 wt. % MoSi₂ has been SHS-produced from a reactive blend composed of MoO₃, SiO₂, and Al. Additional amounts of silica were added to undergo mulHte formation reaction. The overall reaction involves both exothermic and endothermic ones. The endothermic mullite formation reaction is loaded onto the exothermic reaction of the reactive mixture. The effects of Al grain size (from 45 to 20 μm) and pre-heating temperature (from room temperature to 500°C) on the synthesis of the target composite were studied. Al grain size and preheating temperature were found to have decisive influence on the mullitization reaction. The sample containing 36-μm Al and ignited at 400°C was found to undergo complete mullitization reaction. The mechanism of the overall combustion reaction was postulated. In addition, oxidation resistance of this composite at 1100–1300°C in open atmosphere was determined.     

Influence of aging on microstructure,martensitic transformation and mechanical properties of NiTiRe shape memory alloy

Aging is an effective way to adapt the microstructure, phase transformation and consequently the mechanical properties of NiTi shape memory alloys. In the present study, Ni₅₂Ti_47.7Re_0.3 shape memory alloy was solution treated at 1000 °C for 24 h then aged at various temperatures of 300, 400, 500 and 600 °C for 3 h. The influence of aging treatment on microstructure, martensitic transformation and mechanical properties of Ni₅₂Ti_47.7Re_0.3 was investigated. The microstructure of the solution treated alloy was martensite as a matrix phase and precipitates of Ti₂Ni phase. The aged alloys had a microstructure as same as that of solution treated alloy in addition to the existence of other types of precipitates like Ni₄Ti₃ and Ni₃Ti. The martensitic — austenitic transformation during heating and cooling was going through one stage of transformation. The martensitic phase transformation temperature increased by the increase of aging temperature but still lower than that of solution treated alloy.     

Phytoextract assisted hydrothermal synthesis of ZnO–NiO nanocomposites using neem leaves extract

This work represents the synthesis of zinc oxide nanorods, nickel oxide nanoparticles, and zinc oxide-nickel oxide nanocomposites by combining Neem leave extract with hydrothermal synthesis. Five samples were prepared by green synthesis which is based on Neem leaves aqueous extract followed by hydrothermal treatment at 250 °C for 2.5 h. The five prepared samples are: 100% NiO (N100), 75% NiO: 25% ZnO (Z25-N75), 50% NiO: 50% ZnO (Z50-N50), 25% NiO: 75% ZnO (Z75-N25), and 100% ZnO (Z100). The prepared nanoparticles and nanocomposites were characterized by FTIR, XRD, SEM, and TEM. The XRD results show that the ZnO formed as a hexagonal wurtzite phase and NiO as a cubic phase. The microstructure of the formed samples is versatile with nanorods ZnO and spherical NiO. The nanocomposites microstructure appears as a heterostructure of both oxides with NiO particles on the surface of ZnO rods. The TEM confirms the nanosize and the crystallinity of samples.     

Preparation and characterization of some ferromagnetic glass–ceramics contains high quantity of magnetite

Ferrimagnetic glass–ceramics are promising candidates for magnetic induction hyperthermia, which is one form of inducing deep-regional hyperthermia, by using a magnetic field. The aim of this work was to study the effect of increasing the amount of crystallized magnetite on the magnetic properties of glass–ceramic samples. Two different ferrimagnetic glass–ceramics with the composition based on wollastonite or hardystonite with high quantity (∼60%) of magnetite were prepared by melting the starting materials at 1450 °C for 2 h. The influences of chemical composition, amount of crystallized magnetite and microstructure of ferrimagnetic glass–ceramics on magnetic properties of ferromagnetic glass–ceramics were investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The X-ray diffraction patterns show the presence of nanometric magnetite crystals in a glassy matrix after cooling from melting temperature. The amount of crystallized magnetite varies as a function of the chemical composition and heat treatment schedule. The presence of ZnO in the glass–ceramics was found to decrease the viscosity and so cases higher degree of mobility of ions leading to higher degree of crystallinity. The higher heat treatment parameters and so the lower viscosity of the glass containing ZnO are assumed to allow the magnetite to grow to larger crystallite size. Glass transition temperature and thermal stability were found to be functions of chemical composition. Magnetic hysteresis cycles were analyzed using a vibrating sample magnetometer (VSM) with a maximum applied field of 15 kOe at room temperature in quasi-static conditions. From the obtained hysteresis loops, the saturation magnetization (Ms), remanance magnetization (Mr) and coercivity (Hc) were determined. The results showed that these materials are expected to be useful in the localised treatment of cancer.     

Catalytic activity and magnetic properties of barium hexaferrite prepared from barite ore

Barium hexaferrite (BaFe₁₂O₁₉) has traditionally been used in permanent magnets and more recently used for high density magnetic recording. The classical ceramic method for the preparation of barium hexaferrite consists of firing mixture of chemical grade iron oxide and barium carbonate at high temperature. In this paper a mixture of chemical grade hematite, barium oxide and predetermined mixtures of iron oxide ore and barite ore containing variable amounts of coke were used to prepare barium hexaferrite (BaFe₁₂O₁₉) as a permanent magnetic material. The mixtures were mixed in a ball mill and fired for 20 h in a tube furnace at different temperatures (1100, 1150, 1200 and 1250 °C). XRD, magnetic properties, porosity measurements and catalytic activity were used for characterization of the produced ferrite. The results of experiments showed that the optimum conditions for the preparation of barium hexaferrite are found at 1200 °C for the mixture of chemical grade hematite and barium oxide. It was also found that the barium hexaferrite can be prepared from the iron and barite ores at 1200 °C. The addition of coke enhanced the yield of barium hexaferrite and improved its physicochemical properties. Samples prepared from ores with coke% = 0 show the most acidic active sites, they show a higher catalytic activity towards H₂O₂ decomposition. With addition of coke the catalytic activity decreases due to the poisoning effect of carbon on the available active site.