Spin-Coating Technique for Fabricating Nickel Zinc Nanoferrite (Ni0.3Zn0.7Fe2O4) Thin Films

Functional nanoferrite thin films are used in various fields of our life. There are many different methods used to fabricate thin films including sputter deposition, flash laser evaporation pulsed laser deposition (PLD), chemical vapor deposition (PVD) and spin-coating process. In each of these methods, it produces an amorphous phase of the deposited film. To produce a crystalline film, an additional high-temperature processing is required. The high-temperature process can lead to considerable constraints in combining the desirable characteristics of a crystalline nanoferrite thin film with those of thermally unstable substrates and other device components. High-temperature thin-film processing is also a considerable cost to manufacturing. This chapter will report a simple procedure of the sol-gel precursor method for fabrication of NiZn nanoferrite (Ni0.3Zn0.7Fe2O4) thin films and spin-coating method in coating a chemical solution. This method generally provides for both low-temperature deposition and crystallization of NiZn nanoferrite thin films

Sintering Temperature Effect on Microstructure and Magnetic Evolution Properties with Nano- and Micrometer Grain Size in Ferrite Polycrystals

The morphology and evolution of magnetic properties in multisample sintering (MSS) of yttrium iron garnet (Y3Fe5O12, YIG) and single-sample sintering (SSS) of nickel zinc ferrite (Ni0.6Zn0.4Fe2O4, NZF) were studied in detail, focusing on the parallel evolving relationship with their dependences on sintering temperature. Sintering is an important process in ferrite fabrication which involved the process of transforming a noncrystalline powder into a polycrystalline solid by heating process. Under the influence of heat, the surface area is reduced through the formation and growth of bond between the particles associated with reduction in surface energy. This makes the particles move closer, grains to form by the movement of grain boundaries to grow over pores, and results in decreasing the porosity and increasing the density of the sample. Technological applications, especially in electronics applications, require high-density nanostructured ferrites, integrated by sintering from nanoparticles. The evolution from low to high sintering temperature will result in the transition from disordered to ordered ferromagnetism behavior. Multisample sintering (MSS) of yttrium iron garnet (Y3Fe5O12, YIG) and single-sample sintering (SSS) of nickel zinc ferrite (Ni0.6Zn0.4Fe2O4, NZF) have been used as a studied material in this research work

Photothermal effect of modulating laser irradiation on the thermal diffusivity of Al2O3 nanofluids

Modulated continuous wave (CW) lasers cause photothermal effect that leads to rapid optical absorption and generation of thermal waves around the irradiated nanostructures. In this work, we examined the effect of modulated CW laser irradiation on the particle fragmentation process to enhance the thermal diffusivity of nanofluids. A facile and cost-effective diode laser was applied to reduce the agglomerated size of Al2O3 nanoparticles in deionized water. The thermal wave generation, which was determined by the modulated frequency of the laser beam and the optical and thermal properties of the nanofluid, is also briefly discussed and summarized. The influence of laser irradiation time on nanoparticle sizes and their size distribution was determined by dynamic light scattering and transmission electron microscopy. The thermal diffusivity of the nanofluid was measured using the photopyroelectric method. The data obtained showed that the modulated laser irradiation caused the partial fragmentation of some agglomerated particles in the colloids, with an average diameter close to the original particle size, as indicated by a narrow distribution size. The reduction in the agglomerated size of the particles also resulted in an enhancement of the thermal diffusivity values, from 1.444 × 10ˉ³ to 1.498 × 10ˉ³ cm2/s in 0 to 30 min of irradiation time. This work brings new possibilities and insight into the fragmentation of agglomerated nanomaterials based on the photothermal study

Evolution of Nanometer-to-Micrometer Grain Size in Multiferroic Properties of Polycrystalline Holmium and Yttrium Manganite

The parallel evolution of microstructure development via grain size changes from a nano-to-micron size regime toward multiferroic property development has been established in this research work. This kind of observation is not present in the literature in this research area, and studies of the link between morphological properties and ferroelectric properties of multiferroic materials have been focusing solely on the product of the ultimate sintering temperature, mostly neglecting the parallel evolutions of morphological properties and their relationship at varied chosen sintering temperatures. Holmium manganese oxide and yttrium manganese oxide were both prepared via high-energy ball milling (HEBM) in a hardened steel vial for 12 h. The pressed pellet went through multi-sample sintering, whereas the samples were sintered starting from 600 to 1250°C with 50°C increments for any one sample being subjected to only one sintering temperature. Orthorhombic HoMn2O5 and YMn2O5 phases were observed to exist in both as milled powder. The degree of crystallinity increased with increasing sintering temperature. Hexagonal HoMnO3 peaks were observed for sintering temperature ≥1050°C. As for YMnO3 series, the single phase of hexagonal YMnO3 started to appear at sintering temperature ≥1000°C. FESEM micrographs revealed that as the sintering temperature increased, the grain size increased, consequently increasing the geometric ferroelectric behavior. The polarization-electric field (P-E) plot reveals that HoMnO3 and YMnO3 are highly leaky ferroelectrics with a P-E curve shape different from the normal shape of highly insulating ferroelectrics. It shows that the remanent polarization and electric field increased generally with increasing grain size. For both series, there existed a difference based on their difference of crystallinity, microstructure data, and phase purity changes. Larger grain size is known to give ease for polarization to take place

synthesis and characterization of hematite Fe2O3 nanofiller for enhanced dielectric and microwave-absorbing properties in PTFE composites

This paper presents the synthesis of hematite Fe2O3 nanofiller from mill scales and its application in polytetrafluoroethylene (PTFE) composites for enhanced dielectric and microwave-absorbing properties. The nanofiller was obtained through 9 hours of high-energy ball milling, resulting in a particle size reduction 43.6 to 11.05 nm. The PTFE/Fe2O3 composites were fabricated by dispersing different concentration of Fe2O3 nanofillers using the dry powder processing technique. The structural and morphological characterization of the nanofiller and PTFE/Fe2O3 composites was carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The composites’ microwave absorption properties were analyzed utilizing vector network analyzer (VNA) measurements in the 8–12 GHz frequency range. Based on the findings from the results, as the percentage of filler increased from 5 to 15%wt, the composites' loss tangent and dielectric constant increased from 0.0272 to 0.0478 and 2.12 to 3.25, respectively, while their reduced signal transmission speed was between 2.21 and 2.07 x 108 m/s at 8 GHz and from 2.24 to 2.11 x 108 m/s at 12 GHz. These findings demonstrate that Fe2O3 nanoparticles are a suitable material for developing microwave-absorbing polymer composites within the 8–12 GHz frequency range

Photoluminescence studies of cobalt (II) doped zinc silicate nanophosphors prepared via sol-gel method

In this study, cobalt(II) doped zinc silicate nanophosphors were prepared via a sol-gel route which the solution mixed, stirred and dried in the oven at 100 °C around 6–8 h then undergone different heat treatment (600, 700, 800, 900, and 1000 °C). The nanophosphors powder sample was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transforms infrared spectroscopy (FTIR), and photoluminescence (PL) spectroscopy. XRD analysis revealed the α & β- Zn2SiO4 at 800 °C and it turned to pure α-Zn2SiO4 phase at 1000 °C. FESEM images showed the samples have irregular in shapes and proved the formation of the nanophosphor. The obtained zinc silicate nanophosphors was further confirmed by FTIR analysis. PL emission revealed two peaks at blue emission (420 and 480 nm) and one at green emission (525 nm). This result shows that Co2+: Zn2SiO4 is potentially good to use as blue and green phosphors for luminescent optical material

Elemental analysis and IR band characteristics of α-Fe2O3 and BaFe12O19 steel waste product based

This project focused on the elemental analysis and IR band characteristic of -Fe2O3 derived from recycled steel waste product. The steel waste flakes were ball milling for several hours to form a fine powder. The steel waste powder had been purified by using impurity separation technique and magnetic separation technique. The purified steel waste powder then oxidized at 500 oC to form hematite (Fe2O3). The hematite were used to synthesize BaFe12O19 by using salt-melt method. The samples were characterized using X-ray Fluorescence (XRF), Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX). The XRF and FTIR results show the formation of Fe2O3, the IR characteristic bands of Fe2O3 and single phase BaFe12O19 is obtained from recycled steel waste product

Effect of PVP as a capping agent in single reaction synthesis of nanocomposite soft/hard ferrite nanoparticles

Nanocomposite magnets consist of soft and hard ferrite phases are known as an exchange spring magnet when they are sufficiently spin exchange coupled. Hard and soft ferrites offer high value of coercivity, Hc and saturation magnetization, Ms respectively. In order to obtain a better permanent magnet, both soft and hard ferrite phases need to be “exchange coupled”. The nanoparticles were prepared by a simple one-pot technique of 80% soft phase and 20% hard phase. This technique involves a single reaction mixture of metal nitrates and aqueous solution of varied amounts of polyvinylpyrrolidone (PVP). The heat treatment applied was at 800 °C for 3 h. The synthesized composites were characterized by Transmission Electron Microscope (TEM), Fourier Transform Infra-red (FT-IR), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD) and Vibrating sample magnetometer (VSM). The coexistence of two phases, Ni0.5Zn0.5Fe2O4 and SrFe12O19 were observed by XRD patterns. It also verified by the EDX that no impurities detected. The magnetic properties of nanocomposite ferrites for 0.06 g/ml PVP gives a better properties of Hc 932 G and Ms 39.0 emu/g with average particle size obtained from FESEM was 49.2 nm. The concentration of PVP used gives effect on the magnetic properties of the samples

Magnetic and microwave properties of polycrystalline gadolinium iron garnet

The microwave loss in nanosized GdIG particles synthesized using mechanical alloying technique was investigated. There were very few of research on the microwave properties of nanosized particle GdIG and there is no attempt investigating on the material at C-band frequency range and its correlation with the microstructure. Gadolinium (III) iron oxide and iron (III) oxide, α-Fe2O3 were used as the starting materials. The mixed powder was then milled in a high-energy ball mixer/mill SPEX8000D for 3 hours. The samples were sintered at temperature 1200°C for 10 hours in an ambient air environment. The phase formation of the sintered samples was analyzed using a Philips X’Pert Diffractometer with Cu-Kα radiation. Complex permeability constitutes of real permeability and magnetic loss factor were measured using an Agilent HP4291A Impedance Material Analyzer in the frequency range from 10 MHz to 1 GHz. A PNA-N5227 Vector Network Analyzer (VNA) was used to obtain the information on ferromagnetic linewidth broadening, ΔH that represents the microwave loss in the samples in in frequency range of 4 to 8 GHz (C-band). The ΔH value was calculated from the transmission (S21) data acquired from VNA. The single phase GdIG showed low initial permeability and low magnetic loss when applied with low-frequency range energy. From these data, it is validated that GdIG is a suitable material for microwave devices for the high-frequency range

Effect of variation sintering temperature on magnetic permeability and grain sizes of Y3Fe5O12 via mechanical alloying technique

This work will focus on the preparation of yttrium iron garnet (Y3Fe5O12, YIG) via mechanical alloying technique derive by steel waste product. The Fe2O3 powder derived from the steel waste purified by using magnetic and non-magnetic particles (MNM) and Curie temperature separation (CTS) technique. The purified powder was then oxidized in air at 500 °C for 9 hours in air. The Fe2O3 was mixed with Y2O3 using high energy ball milling for 9 hours. The mixed powder obtained was pressed and sintered at different temperature 500/600/700/800/900/1000/1100 °C. X-ray diffraction (XRD) shows the YIG is completely form at 1100 °C. The field emission scanning electron microscopy (FESEM) images shows the grain size increases as increase the sintering temperatures. The frequency dependence on the complex permeability, µ’ and magnetic loss, µ’’ in the frequency range 10 MHz to 1 GHz were measured in this study. The results showed that the highest μ΄ is 5.890 obtained from 1100 °C