Hc Values Research Articles

Giant coercivity enhancement in a room-temperature van der Waals magnet through substitutional metal-doping.

FexGeTe2 (x = 3, 4, and 5) systems, two-dimensional (2D) van der Waals (vdW) ferromagnetic (FM) metals with high Curie temperatures (TC), have been intensively studied to realize all-2D spintronic devices. Recently, an intrinsic FM material Fe3GaTe2 with high TC (350-380 K) has been reported. As substitutional doping changes the magnetic properties of vdW magnets, it can be a powerful means for engineering the properties of magnetic materials. Here, the coercive field (Hc) is substantially enhanced by substituting Ni for Fe in (Fe1-xNix)3GaTe2 crystals. The introduction of a Ni dopant with x = 0.03 can enhance the value of Hc up to ∼200% while maintaining the FM state at room temperature. As the doping level increases, TC decreases, whereas Hc increases up to 7 kOe at x = 0.12, which is the highest Hc reported so far. The FM characteristic is almost suppressed at x = 0.68 and a spin glass state appears. The enhancement of Hc resulting from Ni doping can be attributed to domain pinning induced by substitutional Ni atoms, as evidenced by the decrease in magnetic anisotropy energy in the crystals upon Ni doping. Our findings provide a highly effective way to control the Hc of the 2D vdW FM metal Fe3GaTe2 for the realization of Fe3GaTe2 based room-temperature operating spintronic devices.

Understanding the performance, emissions, and combustion behaviors of a DI diesel engine using alcohol/hemp seed oil biodiesel/diesel fuel ternary blends: Influence of long-chain alcohol type and concentration

In this study, it was aimed to examine the influences of biodiesel–diesel-higher alcohol (1-pentanol, 1-hexanol, and 1-heptanol) blends on the performance, emission and combustion behaviors of a single-cylinder diesel engine. The tests were performed at a fixed speed of 1500 rpm and variable loads (25%, 50%, 75%, and 100%). For the tests, 80% diesel and 20% hemp seed oil biodiesel were blended and called as B20. Biodiesel fuel was produced by transesterification from hemp seed oil in the presence of methanol and potassium hydroxide for the preparation of B20 binary test fuel and other ternary fuels. Furthermore, nine ternary blend fuels [20% HSOB + 70%, 60% and 50% diesel, respectively + 10%, 20% and 30% higher alcohol (pentanol, hexanol and heptanol) respectively] were prepared. The calculations made with the experimental data revealed that the minimum brake specific energy consumption values were 12,48 MJ/kW h, 13,06 MJ/kW h, 13,27 MJ/kW h, 13,35 MJ/kW h, 13,47 MJ/kW h, and 13,59 MJ/kW h, respectively, for diesel fuel at full load, for fuels B20, B20Hx10, B20Hp10, B20Hx20 and B20Pe10, the maximum brake thermal efficiency values were obtained as 28.85%, 27.56%, 27.14%, 26.97%, 26.73% and 26.49%, respectively, for the same fuels at the same load. The increment in higher alcohol concentration in the blend delayed start of combustion and therefore the ignition delay period was prolonged. In the fuel line pressure data, changes were observed depending on the amount, viscosity and density of the fuel. Furthermore, B20Hx10 and B20Hp10 fuels gave the maximum in-cylinder pressure, heat release rate, average gas temperature and pressure rise rate values after diesel and biodiesel. The addition of biodiesel and higher alcohol to diesel fuel resulted in a decrease in NOX, CO and unburned HC and smoke emissions and an increase in CO2. NOX, CO and unburned HC values of higher alcohol blended fuels at full load showed lower results, between 3.04–22.24%, 22.85–56.35% and 5.44–22.83%, respectively, compared to diesel fuel. It can be concluded that the use of hemp seed oil biodiesel and higher alcohol in the diesel engine will make a significant contribution to the reduction of NOX emissions.

The Investigation of Bioethanol as a Fuel in an SI Engine with Fuel and Ignition Systems Converted to Electronic Control

In this study; a four-stroke, air-cooled, spark-ignition engine was used. It’s aimed to improve the performance and emissions by renewing the existing ignition and fuel system of the engine in a way that can be controlled via computer. Classical ignition system was modified with an electronic ignition system and a computer-controlled system was established by using an injector instead of the carburetor. Gasoline and bioethanol fuels were compared with the original and updated version of the engine by conducting various experiments. In these experiments, engine power and torque, specific fuel consumption, thermal efficiency, exhaust emissions and combustion analysis results were examined. When the results obtained are evaluated; with the use of electronically controlled fuel and ignition system in engine torque and power, an increase of 11.58% in maximum torque obtained from gasoline and an increase of 14.4% in average power was observed compared to the standard system. Specific fuel consumption decreased by 18.32% for gasoline and 26.95% for bioethanol at full load. At full load, thermal efficiency was 22.43% for gasoline, 36.9% for bioeth-anol and in-cylinder max. pressure was a 4% increase for gasoline and an 8% in-crease for bioethanol. In the emission values, at full load, the CO value decreased by 6.2% for gasoline, 20% for bioethanol and HC value decreased by 3.8% for gasoline and 7.5% for bioethanol. CO2, NOx and O2 values increased by 4.1%, 14.9%, 0.7% for gasoline and 0.7%, 5.6%, 0.4% for bioethanol.

Exploring the structural and magnetic trends in Ba0.9Sm0.1Fe12−xAlxO19 M-type Hexaferrites

The current study describes the structural and magnetic properties of Ba0.9Sm0.1Fe12−x Al x O19 (x = 0.0, 0.5, 1.0, 2.0, 3.0) M-type hexaferrites. The conventional ceramic route was implied to prepare all the nominal samples. Morphological analysis suggested the non-presence of secondary phases as well as the formation of the hexaferrites material. X-ray Diffraction technique was used for structural analysis from which microstructural parameters are calculated and discussed. Magnetic properties are measured at room temperature. The saturation magnetization (Ms) and coercivity (Hc) values show a cyclic and converse trend for synthesized samples. Firstly, a decrease in Ms and an increase in Hc was observed up to intermediate dopant incorporation and becomes converse for higher doping levels. The maximum coercivity and minimum magnetization are observed for Ba0.9Sm0.1Fe11Al1O19. The c/a and Mr/Ms ratio suggest the formation of perfect M-type hexaferrites. This work suggests that synthesized material is a good option for magnetic applications e.g., transformer and inductor cores, microwave devices, recording heads, and magnetic shielding.

Combustion synthesis of nanocrystalline porous CoFexAl2-xO4 spinels: Structural, textural, magnetic, and electrical properties

A simple ammonia fueled combustion route was used to synthesize a series of nanocrystalline porous CoFexAl2-xO4 spinel samples with different Fe concentration (0.00 ≤ x ≤ 2.00) at 400 °C. The structural, morphological, and textural properties of the synthesized powders were analyzed by using XRD, FT-IR, FESEM, TEM, SAED, and N2-physisorption techniques. The electrical and magnetic properties of the spinels were also studied using electrical conductivity and vibrating sample magnetometer (VSM) techniques. The XRD and SAED analyses results revealed that the synthesized samples possessed partially inverse cubic spinel structure with Fe3+ and Al3+ cations distribution. The crystallite size was observed in the range of 14–45 nm, whereas the diameter of the particles obtained from FESEM analysis is in the range of 143–284 nm. The CoAl2O4 sample exhibited low saturation magnetization (Ms) and coercivity (Hc) values, however the magnetic parameter and conductivity values increased monotonically with incorporation of Fe3+ ions. In addition, N2 adsorption isotherm change, Type IV to Type II was observed with increase of Fe concentration in the spinel structure. The achieved results indicate that the ammonia fueled combustion method could be a promising method to produce nanosized porous ferrite spinels.

Rapid microwave-assisted synthesis and magnetic properties of high-entropy spinel (Cr0.2Mn0.2Fe0.2Co0.2-xNi0.2Znx)3O4 nanoparticles

High-entropy oxide (HEO) has recently become popular because of its unique multifunctional performance. In this study, we developed a novel microwave-assisted method for the production of HEO nanoparticles with the composition (Cr0.2Fe0.2Mn0.2Co0.2-xNi0.2Znx)3O4 (x = 0, 0.05, 0.1, and 0.2). The results revealed that all metallic elements were uniformly distributed throughout the single-phase cubic spinel structure of the HEO nanoparticles. The particle size distributions of four fabricated samples ranged from 10 to 50 nm. Because of its numerous advantages such as the ultrafast and low-temperature fabrication of nanoscale and high-purity products at a relatively low cost, the suggested methodology is an excellent synthesis method. The original HEO spinel (x = 0) achieved saturated magnetization (Ms) and coercivity (Hc) values of 24.3 emu/g and 160 Oe, respectively, at room temperature. Zinc substitution in the HEO composition indicated that Ms and Hc decreased with increasing zinc concentration owing to its non-magnetic nature.

Study on the structural and magnetic properties of e-beam evaporated Co thin films annealed in vacuum

The present paper investigates the effects of thermal annealing on the structural and magnetic properties of Co thin films. The films were prepared by using electron-beam evaporation method onto Si (100) wafers and annealed in vacuum at 200 °C, 300 °C and 400 °C. A combination of X-ray diffraction, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrometry were used to characterize structural properties and the composition of the films, while magnetic behavior was studied by magneto-optical Kerr effect measurements. It was found that as deposited Co layer show predominantly uniaxial magnetic anisotropy, while after annealing at 200 °C and 300 °C a strong influence of fourfold contribution is observed, which is assigned to the thermally induced HCP→FCC phase transition. With further increase in annealing temperature of 400 °C the isotropic contribution becomes the main component of magnetization. Besides, a strong variation in coercive field with annealing temperature was observed, where the coercivity seems to depend closely on the crystallite size. The highest value of HC equals ∼70 Oe and was found for the temperature of 400 °C, where also mixing at the interface has started and formation of CoSi was observed.

Multifunctionality of AlBaFe12O19 /CoZnFe2O4 hybrid nanocomposite: Promising structural, elastic, morphological, compositional, optical, and magnetic properties

A detailed report on the influence of Aluminum doped Barium Hexaferrite (ABH) on structure, elasticity, morphology, composition, and optical and magnetic behavior of hybrid ABH-CZF (AlBaFe12O19)1-x/(CoZnFe2O4) x with X = 0.1, 0.2, 0.3, 0.4 nanocomposites is presented. A new study on the role of ABH in the composite made by the physical mixing method. The composites were characterized by XRD, SEM, EDAX, FTIR, UV, PL, and VSM analysis. XRD confirms the formation of hexagonal and spinel structures in the composite along with their cell volume, lattice parameters, stress, strain, and other structural parameters. Elastic parameters and Debye temperature were measured using FTIR. The composite AC 60–40 is found best suited for high-density optical storage devices and as lead-free radiation shielding materials. From the UV analysis, Both the direct and indirect band gap energies are found to be increasing with increasing ABH concentration. The overall structural and optical properties also prove that the material can be used in tunable photonic applications. The refractive index of the composite is between 3.0 and 3.2, which can be used for photo-electrochemical cells, optical detectors, or reflectors. Magnetic properties examined using VSM showed a decrease in Ms, Mr, and Hc values along with ABH concentration which may be suitable for data storage applications such as rewritable storage hard drives. The maximum values for Ms (7.85 emu/g), Mr (20.44 emu/g), and Hc (2.01 kOe) are found for AC90-10 nanocomposite material. By plotting loop width (ΔH) versus magnetization (M), the magnetic interaction between the composite is studied.

Optimizing the effect of a mixture of light naphtha, diesel and gasoline fuels on engine performance and emission values on an HCCI engine

In this study, the effects of using naphtha-diesel and naphtha-gasoline fuel mixtures were investigated using experimental and statistical methods on homogeneous charge compression ignition (HCCI) engine performance and emission values. Response Surface Method (RSM) was used as a statistical method. Fifty-two experiments were specified in the experimental set created by the RSM central composite design method, which were carried out under the same conditions. As a result of the experimental study, effective torque, brake-specific fuel consumption (BSFC), CO, HC, and NO emissions values were examined. The experimental results extrapolation equations were obtained with the RSM method, and the contour graphs were drawn. Optimum input parameters were determined to obtain the targeted output parameters. After the optimization, it was seen that the usage of gasoline fuel gave better results than diesel. Among the optimum input parameters, the gasoline ratio was determined as 0.297 %, the injection duration was 11.97 ms, and the engine speed was 1325.21 rpm. Effective torque was 12.79 Nm, BSFC value was 589.79 g/kWh, CO emission value was 0.11 %, HC emission value was 519.86 ppm, and NO emission value was 0 ppm depending on the optimum input parameters.

Enhancement of magnetic properties of Sm-Co nano composite ribbons by heavy lanthanide doping

Sm-Co magnets becoming more and more interesting among research community since 1950′s due to its essential role in space and transport industry to be used in some precious instruments such as, sensors, actuators, motors, and gyroscope. The combination of Rare-earth (RE) and Transition metal (TM) is an ideal combination to make a high-performance magnet, as the RE provides the high magneto crystalline anisotropy (HA) and the TM provides the high magnetization (Ms) and high Curie temperature (Tc). SmCo5 compound possesses Tc as high as ∼ 700 °C. Previous studies have reported that HRE (Gd, Dy, Er and Ho) could be used as a temperature compensation material as unpaired 4f electrons in shell gives rise to maximum magnetic moment. In this study, effect of lanthanides (HREs - Gd and/ Dy) on microstructure and magnetic properties of Sm-Co-based rapidly solidified alloy ribbons have been reported. Phase analyses confirmed the presence of 1:5H phase which was prevalent along with a fraction of 2:17R phase in all the alloy ribbons. Hc value was increased from 10.9 to 13.3 kOe (1.09 to 13.3 T) and Br value was increased from 12.5 to 16.2 kG (1.25 to 1.62 T) with Dysprosium addition.

Structure and magnetism of novel high-entropy rare-earth iron garnet ceramics

A new type of high-entropy rare-earth iron garnet ceramic structure (Gd0.2Dy0.2Er0.2Y0.2RE0.2)3Fe5O12 (RE = Sm, Eu, Tm, Yb) powders were synthesised using a solid-phase method. In addition, the microstructure and magnetic properties of the (Gd0.2Dy0.2Er0.2Y0.2RE0.2)3Fe5O12 (RE = Sm, Eu, Tm, Yb) powders were evaluated. The (Gd0.2Dy0.2Er0.2Y0.2RE0.2)3Fe5O12 (RE = Sm, Eu, Tm, Yb) ceramics presented garnet crystal structure (Ia-3d), and their lattice parameters ranged between 12.3921 and 12.3644 Å. Moreover, the saturation magnetisation (Ms) and coercivity (Hc) of the ceramics ranged between 12.29 and 13.27 emu/g and between 18.46 and 19.87 Oe, respectively. The Ms and Hc values of the samples were comparable, indicating that magnetism of high-entropy rare-earth iron garnet ceramic can be fine-tuned by customising their composition. The magnetic properties of high-entropy rare-earth iron garnet ceramics have not yet been elucidated; however, previous studies have demonstrated that high-entropy rare-earth iron garnet ceramics present unique magnetism.

Spontaneous exchange bias and large dielectric constant in Bi0.8Tb0.2Fe0.8Mn0.2O3 multiferroic

The structural, dielectric, and magnetic properties of Bi0.8Tb0.2Fe0.8Mn0.2O3 have been studied in detail. A structural shift from rhombohedral (space group R3c) to orthorhombic (space group Pn21a + Pnma) phase is observed with doping. The substitution of Mn and Tb gives a very large value of the dielectric constant. It has been demonstrated that the observed spontaneous exchange bias is larger than the conventional exchange bias at room temperature. Moreover, doping reduces the Neel temperature from 643 to 521 K and magnetization increases. Thermoremanent magnetization studies at room temperature show that the system is composed of an interfacial layer of an antiferromagnetic core and a two-dimensional diluted antiferromagnet shell with a net magnetization under the field. Furthermore, the system's reasonable HEB and HC values at room temperature make it intriguing and appealing for a variety of multifunctional devices.

Pechini citrate-gel synthesised In3+ substituted X-type barium zinc hexaferrites: An investigation on structural, optical, magnetic and dielectric properties

Indium substituted X-type Ba2Zn2InxFe28-xO46 (0.0≤x≤2.0) ferrites were synthesised by a citrate-gel aqueous combustion technique, and heated at 1300 °C. XRD, FTIR, SEM with EDX, magnetic hysteresis, Mössbauer spectroscopy, UV–visible spectroscopy, and dielectric measurements up to 20 GHz have been carried out to study the modification of the structural, morphological, magnetic, optical and frequency dependant dielectric properties when indium is introduced, replacing iron in the lattice of X-type hexaferrites. XRD analysis reveals formation of a major X-type phase in all compositions. The systematic rise in lattice constants (a, c) along with cell volume (V) confirm the replacement of iron by indium. Magnetic hysteresis loops reveal a soft ferrite nature with low Mr/MS values, suggesting a multidomain structure in all samples. The HC values decrease from 22.22 kA m-1 to 12.18 kA m−1 (279 Oe to 153 Oe) with increasing indium, while magnetisation remained high between 56 A m2 /kg and 62 A m2/kg for all samples. Room temperature Mӧssbauer spectra of all samples were fitted with six Zeeman sextets of five different magnetic sublattices. It was ascertained that In-substitution reduces the Fe population in the k (spin up) sublattice, resulting in a reduction in magnetisation. The average hyperfine magnetic field <Hf> is also reported to decrease with Indium substitution for all samples. The value of the isomer shift (δ) confirmed that the iron-ions are in high spin Fe3+ state. The complex impedance and electric modulus plots reveal non-Debye type relaxation in all samples at 100 Hz to 2 MHz.

PERBANDINGAN SISTEM PENGAPIAN CONTACT POINT, TRANSISTOR CONTROLLED IGNITION (TCI -K) DAN PENGAPIAN FULL TRANSISTOR TERHADAP EMISI GAS BUANG PADA MOBIL L300 BENSIN 1500 CC

Basically any engine that undergoes a combustion system to produce power allows for exhaust emissions. Exhaust gas emissions are the residue from the combustion of fuel (gasoline) and air in the combustion engine which is released through the engine exhaust system. Therefore, one of the efforts to reduce exhaust gas levels is to innovate to create a more perfect ignition system. This study aims to determine how the effect of the comparison of the ignition system Contact point, TCI and Full Transistor on the resulting exhaust emissions. The test was carried out using a gas analyzer on a Mitsubishi L300 gasoline with engine speed variations of 700 rpm, 1000 rpm, 2000 rpm and 3000 rpm to determine the concentration values of CO and HC. Based on the test results, it was found that the use of the TCI ignition system resulted in the lowest concentration reduction, namely at 3000 rpm engine speed with 1.43% CO levels and 115 ppm HC.Keywords: Contact point, TCI, Full transistor, Exhaust Emission

Tailoring the structural and magnetic traits of copper modified BaFe12O19 nanostructured hexaferrites for recording media application

Barium nanohexaferrites, with a chemical composition of Ba1-0.5xCu0.5xFe12O19 (x = 0.0, 0.1, 0.2, 0.3) have been successfully produced using the sol–gel auto-combustion approach for tuning its structural, morphological, optical and magnetic properties. The current work has been carried out to control the coercivity of synthesized specimens, with the modification of copper ions at the barium sites of BaFe12O19 hexaferrites. The XRD patterns of synthesized specimens’ shows the formational of hexagonal-like crystal structure with P63/mmc space geometry. In the XRD diffraction patterns, the characteristic peaks (110), (008), (107), (114), (108), (203), (205), (206), (1011), (300), (217), (2011), (220), (2014)along with some impurity phases of hematite (α-Fe2O3) were observed. The crystallite size “D” was estimated from the observed XRD patterns using the Debye-Scherrer formula in the range of 41.94–83.91 nm respectively. The FESEM studies of the BM2 and BM3 specimens reveal the presence of agglomerated grains with a hexagonal shape and an average size of ∼ 277 and ∼ 469 nm respectively. The energy dispersive X-ray spectra of synthesized nanohexaferrites shows only peaks of copper, iron, barium, and oxygen which clearly confirms the higher purity of pure and doped barium hexagonal nanoferrites. The transmission electron micrograph of BM1 nanohexaferrite illustrates the production of the nanoparticles that are agglomeratedand spherical, and have an average particle size of 53.32 nm. The Raman spectrum of undoped and copper doped BaFe12O19 hexagonal nanoferrites shows the formation of seven Raman active vibrational modes in the frequency range of 200–800 cm−1. At room temperature (300 K), the magnetic traits of the produced barium hexagonal nanoferrites were measured, and using these measurements, a variety of magnetic parameters (Ms, Hc, Mr, and Ha) were reported. The value of saturation magnetization (Ms) increases from 37.75 emu/g to 59.97 emu/g with increased low copper content up to x = 0.1. In contrast, with the increasing copper content up to x = 0.3, the value of Ms shows a decline to 28.31 emu/g. In this work, admirable values of Ms (28.31–59.97 emu/g) and Hc (684–2563 Oe) were obtained, making these nanohexaferrites as beneficial candidates for the recording media and EMI shielding applications.

Study of the structural and magnetic properties at high temperature of Ni-Co-Mn-Al Heusler alloy prepared by an unconventional route

ABSTRACT Ni, Co, Mn, and Al elemental powders have been ball milled in a planetary mill for various periods, up to 32 h. The obtained powder was characterized with XRD, SEM-EDS, DSC, high-temperature-XRD, and VSM techniques to study morphology, composition, thermal transitions, structural and magnetic changes occurring at high temperatures. At the end of the milling process, a particle mixture consisting of agglomerated grains with a rounded shape and an average size of about 60 µm was formed. XRD patterns of the as-milled powders revealed the presence of a nanocrystalline solid solution mixture with (L10) and (B2) structures. HT-In-situ XRD characterizations confirmed the complete formation of the B2 ordered structure from 573 K. The austenitic Heusler phase B2 remains stable during one hour of isothermal holding and its proportions increase between 648 and 773 K. Under the heating effect, crystallites size grows up greatly with increasing holding temperature, nevertheless the micro-strains decrease sharply from 0.98% at room temperature to 0.31% at 773 K. Magnetic features of the milled alloy enhance further during the heating process, making it magnetically soft with the most intriguing values of Ms, Mr, and Hc between 648 and 773 K. This is owing to the complete development of the homogeneous and ordered Heusler B2 phase and the significant increase in crystallite size with the relaxation of residual stresses resulting from the direct effects of temperature.

Production and Characterization of Nanostructured Powders of Nd2Fe14B and Fe90Al10 by Mechanical Alloying.

The objective of this work is to evaluate the applicability of exchange coupling between nanoparticles of Nd2Fe14B (hard magnetic material) and Fe90Al10 (soft magnetic material), as permanent magnets produced by surfactant-assisted mechanical alloying. The obtained powders were then mixed with 85% of the Nd2Fe14B system and 15% of the Fe90Al10 system and subsequently sintered at 300 °C, 400 °C and 500 °C for one hour. The results obtained by Mössbauer spectrometry (MS) show a ferromagnetic behavior with six magnetic sites represented by sextets (16k1, 16k2, 8j1, 8j2, 4c and 4e), characteristic of the Nd2Fe14B system. X-ray diffraction (XRD) results show a tetragonal and BCC structure for the Nd2Fe14B and FeAl systems, respectively. The results obtained by vibrating sample magnetometry (VSM), for mixtures of the Nd2Fe14B and Fe90Al10 sy stems sintered at 300 °C, 400 °C and 500 °C, allow for the conclusion that the coercive field (Hc) decreases drastically with temperature and the percentage of soft phase at values of Hc = 132 Oe compared to the coercive field values reported for Nd2Fe14B Hc = 6883 Oe, respectively. Images obtained by transmission electron microscopy (TEM), for the Fe90Al10 system, show a tendency for the nanoparticles to agglomerate.

Experimental Investigation of the Effect of Nitromethane Addition to Gasoline Fuel on A Single-Cylinder Spark-Ignition Engine Performance and Emissions

In this study, the effect of nitromethane addition to gasoline fuel on engine perfor-mance and emissions in a single-cylinder spark-ignition engine was experimentally inves-tigated. By adding 5% and 10% nitromethane to gasoline, experiments were carried out at full load at six different cycles. Engine load, fuel consumption, exhaust gas tempera-ture, and emissions were measured during the experiments. According to the measured experimental data, engine power, torque, specific fuel consumption, exhaust gas tem-perature, average effective pressure, thermal efficiency, CO, CO2, HC, and NOx values were compared with each other. According to these results, nitromethane's addition im-proved engine power, torque, specific fuel consumption, and thermal efficiency. It is un-derstood that the addition of nitromethane to gasoline improves combustion efficiency and increases thermal efficiency. With the addition of nitromethane, an increase in CO2 emission, which is a product of complete combustion, and a decrease in CO emission occurred. This supports the increase in combustion efficiency. HC emissions have de-creased. There has been an increase in NOx emissionsIn addition, since the addition of more than 10% nitromethane causes engine instability, it has created difficulties in using it without modification in the engine.

A systematic investigations on effect of annealing temperature on magnetic properties of a promising soft magnetic Co35Cr5Fe10Ni30Ti20 HEA

The present study investigates the effect of different annealing temperatures on phase formation, microstructure, and their correlation with magnetic properties of a promising soft magnetic Co35Cr5Fe10Ni30Ti20 High Entropy Alloy (HEA) design developed by our research group previously. We reproduced the Co35Cr5Fe10Ni30Ti20 HEA through the mechanical alloying and found the mixture of fcc and R-phase having Ms = 74.8 emu/g and Hc= 12.92 Oe. The different annealing temperature was decided based on the DTA analysis of the synthesized sample. The samples were annealed at 200, 500, 700, 790, 870, and 965 ͦ C for 2 h to study the change in the phase evolution and magnetic behavior. Phase transformation was observed for 500 ͦ C annealed HEA, and the value of Ms (82.38 emu/g) and Hc (41.49 Oe) increased after annealing at 500 ͦC. Interestingly, the samples annealed at high temperatures (>700 °C) have a high value of Ms and a significantly low value of Hc (<2 Oe). Among annealed Co35Cr5Fe10Ni30Ti20 HEA, 790 ͦ C annealed HEA has the highest value of Ms (90.79 emu/g) and the lowest Hc (1.66 Oe)of HEAs reported so far. The concluding reason behind the high value of Msfor annealed HEAs area decrease in lattice parameter, i.e., improved magnetic interaction and a change in volume phase fraction of synthesized phases. However, the soft magnetic behavior of high-temperature annealed HEA is attributed to the synergetic effect of the decrease in magneto-crystalline anisotropy, particle size, and surface anisotropy. The value of Ms and Hc for the 790 ̊C annealed HEA is comparable to some commercial soft magnets, such as Supermalloy, Ni-Zn ferrite, and Mn-Zn ferrite. Thus, the designed and developed Co35Cr5Fe10Ni30Ti20HEA showed excellent soft magnetic characteristics even after annealing at high temperatures and may be further considered for industrial applications.

Substitutional effect of Ni-Al in electromagnetic properties of Sr-hexaferrite based non-rare earth magnet with high energy density for motor applications

Strontium hexaferrite is a hard magnet that can help to develop rare-earth-free magnets for permanent magnet applications. A composition of SrFe12-x-yNixAlyO19 (0.005 ≤ x ≤ 0.02; 1 ≤ y ≤ 4) is successfully synthesized with by the sol-gel auto-combustion process, and the effect of Ni-Al substitution is studied on the structural, magnetic, dielectric, and electrical properties. The XRD analysis confirms the formation of magnetoplumbite hexagonal structure with P63/mmc space group. Magnetic studies have shown a massive improvement in the coercivity (Hc) of the samples. The highest ever Hc value of 24.44 kOe in strontium hexaferrite-based rare-earth free magnet is attained for the SrFe7.98Ni0.02Al4O19 ferrite composition. The energy density (BH)max is effectively tuned to 16.2 MGOe for the SrFe8.985Ni0.015Al3O19 composition. The dielectric properties have shown the typical behavior of ferrites and are explained according to the Maxwell-Wagner and Koop model. The proposed work is expected to offer an immense possibility to improve the hard magnetic properties of strontium hexaferrite magnets comparable to the expensive NdFeB magnets in order to fully/partially replace them in different permanent magnet applications.