Kesan Gantian Kecil Kation Co²⁺, AL³⁺, Ti⁴⁺ dan Sn⁴⁺ ke Atas Sifat Magnet Utama Ferit Ni₀.₂₅Cu₀.₁Zn₀.₆₅Fe₂O₄

Penggantian kation logam ke dalam struktur kekisi hablur bahan ferit memainkan peranan yang besar dalam mengubah sifat-sifat magnet bahan tersebut. Tujuan utama penyelidikan yang telah dijalankan ini adalah untuk mengenalpasti jenis kation yang paling sesuai, daripada empat jenis kation iaitu Co²⁺, AL³⁺, Ti⁴⁺ dan Sn⁴⁺, untuk meningkatkan kestabilan ketelapan awal terhadap perubahan suhu bagi ferit berteraskan NiCuZn. Empat siri sampel dalam bentuk toroid telah disediakan, masingmasingnya melalui penggantian ion Ni²⁺ dalam ferit Ni₀.₂₅Cu₀.₁Zn₀.₆₅Fe₂O₄ dengan satu daripada kation di atas dalam julat 0.5 % sehingga 2.5 % mol. Sampel-sampel disediakan melalui kaedah yang berasaskan tindakbalas keadaan pepejal campuran serbuk oksida dengan saiz purata zarah ~ 1µm. Di samping ketelapan awal, kesan ke atas faktor kehilangan dan parameter-parameter gelung histeresis telah turut dikaji untuk melihat kesan menyeluruh penggantian ke atas sifat-sifat magnet utama bahan. Hasil kajian mendapati bahawa ion Co²⁺ dan ion Ti⁴⁺ berjaya mengurangkan pengaruh suhu dan juga pengaruh frekuensi ke atas ketelapan awal, di samping melebarkan julat frekuensi operasi. Namun begitu, kedua-dua kation telah menurunkan suhu Curie dan penurunannya adalah begitu ketara oleh ion Ti⁴⁺

Dielectric properties of nickel zinc ferrite-polypropylene composite

Nickel-zinc ferrite (Ni0.2Zn0.8Fe2O4) was prepared using conventional solid-state method. It acts as a filler with polypropylene as the matrix. The samples were characterized by XRD and dielectric measurement was done using Agilent 4291B Impedance/Material Analyzer. It was observed that the composition of 30% doped nickel-zinc ferrite (Ni0.2Zn0.8Fe2O4) gives the highest value of the dielectric constant in the frequency range of 1 MHz to 1.5 GHz at room temperature

Dielectric behavior of Ni0.1Zn0.9Fe2O4-Polypropylene composites at low microwave frequencies.

In the last decade, studies and research toward polymer-clay composites draw significant attention for a suitable filler that can improve mechanical, thermal, electrical, optical and pharmaceutical properties as compared with pure polymer. Ni0.1Zn0.9Fe2O4 (NZF) was prepared using conventional solid-state method. A twophase composite was fabricated with blend filled Ni0.1Zn0.9Fe2O4 added to isotactic polypropylene matrix. The samples were characterized by XRD and dielectric measurements were done using Agilent 4291B Impedance/Material Analyzer. It was observed that the composition of 30 wt% NZF gave the highest dielectric constant in the frequency range of 1 MHz to 1.8 GHz at room temperature

Influence of aluminum substitution on microstructural, electrical, dielectric and electromagnetic properties of sol-gel synthesized yttrium iron garnet (YlG)

Aluminum-substituted Yttrium iron garnet, Al-YIG (Y3AlxFe5-xO12; x = 0.4, 0.8, 1.2, 1.6 and 2.0) samples were synthesized via auto combustion sol-gel technique. The obtained powder was heated at 950 °C, pressed into pellets and sintered at 1200 oC. The samples microstructures were studied using Field emissions scanning electron microscopy (FESEM). The average grain size decreased from 0.46 µm at x = 0.4 to a minimum value of 0.33 µm at x = 2.0. Elemental composition of the samples was studied by energy dispersive x-ray (EDX), while bulk density was measured by Archimedes principle. Electrical and dielectric measurements were carried out using Agilent impedance analyzer. Generally, the samples resistivity decreased with Al concentration. At 1 MHz frequency, the sample x = 0.4 has the highest resistivity of 2.19 × 105 Ωm which decreases down to its minimum value of 1.75 × 104 Ωm at x = 2.0. The dielectric constant for all the samples decreased with frequency. For the sample x = 0.4, the ε'r decreased from 49.03 at 40 Hz to 8.08 at 1 MHz. The dielectric loss tangent, tan δ decreased with increasing frequency, while it increased with Al substitution. Permeability values were calculated from permittivity data. The real ermeability decreases from 1263.12 at x = 0.4 to 6.96 at x = 1.2, and the decreased down to 11.74 at x = 2.0. The high dielectric constant, low resistivity and low loss values of the samples indicate their suitability for miniaturization of radio frequency devices, antenna and filter resonator

Electrical and microstructural properties of ZnO-Bi2O3-TiO2-Sb2O3-Al2O3-based varistor ceramics fabricated by solution coating method

This paper presents the electrical and microstructure properties of ZnO-Bi2O3-TiO2-Sb2O3- Al2O3 varistor synthesized via solution coating technique. The mixed ZnO powder were sintered at 1250 C in air at various holding time of 90, 120, 150, 180 and 240 min. The prepared powder was characterized by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), and particle size distribution. The results demonstrated that the ZnO composite powder is homogeneously coated and ultrafine. The densification, phase composition, and microstructure of ZnO varistors was studied by VPSEM, X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDX), respectively. The electrical parameters shows that 150 mins holding time has the highest value of nonlinear coefficient and (α = 16.93), highest value of breakdown electric field (Eb =66.35 V/mm) and the lowest values of leakage current (6.37 × 10−5 mA/cm2). This result well documented that solution coating is a promising route to prepare ZnO varistors

Structural, electromagnetic and microwave properties of magnetite extracted from mill scale waste via conventional ball milling and mechanical alloying techniques

This study presents the utilization of mill scale waste, which has attracted much attention due to its high content of magnetite (Fe3 O4 ). This work focuses on the extraction of Fe3 O4 from mill scale waste via magnetic separation, and ball milling was used to fabricate a microwave absorber. The extracted magnetic powder was ground-milled using two different techniques: (i) a conventional milling technique (CM) and (ii) mechanical alloying (MM) process. The Fe3 O4 /CM samples were prepared by a conventional milling process using steel pot ball milling, while the Fe3 O4 /MM samples were prepared using a high-energy ball milling (HEBM) method. The effect of milling time on the structural, phase composition, and electromagnetic properties were examined using X-ray diffraction (XRD) and a vector network analyzer (VNA). XRD confirmed the formation of magnetite after both the magnetic separation and milling processes. The results revealed that Fe3 O4 exhibited excellent microwave absorption properties because of the synergistic characteristics of its dielectric and magnetic loss. The results showed that the Fe3 O4 /CM particle powder had a greater absorption power (reflection loss: <−10 dB) with 99.9% absorption, a minimum reflection loss of −30.83 dB, and an effective bandwidth of 2.30 GHz for 2 mm thick samples. The results revealed the Fe3 O4 /MM powders had higher absorption properties, including a higher RL of −20.59 dB and a broader bandwidth of 2.43 GHz at a matching thickness of only 1 mm. The higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure. Furthermore, the magnetite, Fe3 O4 showed superior microwave absorption characteristics because of the lower value of permittivity, which resulted in better impedance matching. This study presents a low-cost approach method by reutilizing mill scale waste to fabricate a high purity crystalline Fe3 O4 with the best potential for designing magnetic nano-sized based microwave absorbers

Structural and magnetic properties of type-m barium ferrite– thermoplastic natural rubber nanocomposites

Structural and magnetic properties of type-M barium ferrite (BaFe12O19) nanoparticles (~ 20 nm) embedded in non-magnetic thermoplastic natural rubber (TPNR) matrices were investigated. The TPNR matrices were prepared from high density polyethylene (HDPE) and natural rubber (NR) in the weight ratios of 80:20 and 60:40, respectively, with 10 wt% of NR in the form of liquid natural rubber (LNR) which act as a compatibiliser. BaFe12O19 – filled nanocomposites with 2 – 12 wt% BaFe12O19 ferrite were prepared using a melt- blending technique. Magnetic hysteresis was measured using a vibrating sample magnetometer (VSM) in a maximum field of 10 kOe at room temperature (25oC). The saturation magnetisation (MS), remanence (MR) and coercivity (Hc) were derived from the hysteresis loops. The results show that the structural and magnetic properties of nanocomposites depend on both the ferrite content and the composition of the natural rubber or plastic in the nanocomposites. All the nanocomposites exhibit an exchange bias-like phenomenon resulting from the exchange coupling of spins at the interface between the core ferrimagnetic region and the disordered surface region of the nanoparticles

Effect of sintering temperatures on structural, magnetic and microwave properties of barium ferrites/epoxy composites

This research highlights the structural magnetic and microwave properties of nanoparticles of M-type hexagonal barium ferrites (BaFe12O19). The samples were sintered at varied sintering temperatures (800, 900, and 1000 °C). The effect of temperatures on the structural, magnetic and microwave properties was highlighted. Barium ferrites are well-known materials used for radar absorbing materials (RAM). RAM materials with good absorbing performance should have high permeability, small permittivity and high magnetic or dielectric loss at microwave frequency. High microwave absorption can be created effectively in magnetic materials, as well as wideband absorption. The structural, microstructural and microwave properties were analyzed via an X-ray Diffractometer (XRD), a Field Emission Scanning Electron Microscope (FESEM) and a Vector Network Analyzer (VNA), respectively. The XRD results showed a full phase hexagonal structure was formed in the samples sintered at 900 and 1000 ºC. BaFe12O19 composite with a thickness of 3 mm showed a minimum Reflection Loss (RL) at −9.01 dB at a frequency of 9.16 GHz at temperature 1000 ºC

Structural, microstructural, magnetic and electromagnetic absorption properties of spiraled multiwalled carbon nanotubes/barium hexaferrite (MWCNTs/BaFe12O19) hybrid

Microwave absorption properties were systematically studied for synthesised barium hexaferrite (BaFe12O19) nanoparticles and spiraled multiwalled carbon nanotubes (MWCNTs) hybrid. BaFe12O19 nanoparticles were synthesised by a high energy ball milling (HEBM) followed by sintering at 1400 °C and structural, electromagnetic and microwave characteristics have been scrutinized thoroughly. The sintered powders were then used as a catalyst to synthesise spiraled MWCNTs/BaFe12O19 hybrid via the chemical vapour deposition (CVD) process. The materials were then incorporated into epoxy resin to fabricate single-layer composite structures with a thickness of 2 mm. The composite of BaFe12O19 nanoparticles showed a minimum reflection loss is − 3.58 dB and no has an absorption bandwidth while the spiraled MWCNTs/BaFe12O19 hybrid showed the highest microwave absorption of more than 99.9%, with a minimum reflection loss of − 43.99 dB and an absorption bandwidth of 2.56 GHz. This indicates that spiraled MWCNTs/BaFe12O19 hybrid is a potential microwave absorber for microwave applications in X and Ku bands