Chemical Homogeneity Research Articles

Cr-doped LiNi0.5Mn1.5O4 derived from bimetallic Ni/Mn metal-organic framework as high-performance cathode for lithium-ion batteries

Metal-organic frameworks (MOFs) have potential applications in the field of electrochemical energy storage due to their unique characteristics, such as structural diversity, tolerability, and chemical homogeneity. LiNi0.5Mn1.5O4 (LNMO) is a great cathode material due to its wide working voltage, high energy density, and excellent rate capability. In this study, bimetallic Ni/Mn-MOFs and Cr-doped Ni/Mn-MOFs have been prepared by solvothermal reaction, which can be used as the precursor for the synthesis of pristine and Cr-doped LNMOs. The results indicate that the MOF-derived LNMO has better electrochemical behavior than the sample obtained from the conventional co-precipitation route. The resulting MOF-derived LNMO exhibits a high specific capacity (SC, 132.4 mAh/g at 0.2C), good rate ability (116.5 mAh/g at 10C), and remarkable long-cycle performance (80.1 % capacity retention for 200 cycles at 4C). More significantly, the full lithium-ion batteries (LIBs) incorporated with the MOF-derived LNMO as a cathode and Li4Ti5O12 (LTO) as an anode exhibit superior energy storage properties. This finding provides an efficient strategy for preparing high-performance LNMO cathode materials.

Antioxidant Evaluation of Facial Toner Formulations Containing Ethyl Acetate Fraction from Garcinia Mangostana L. Fruit using ABTS 2,2'-Azinobis 3-ethyl benzothiazoline 6-sulphonic Acid Method

The mangosteen fruit is rich in polyphenols, particularly xanthones, which have potent antioxidant effects. Given the various effects of facial toners and the growing demand for natural skincare products, mangosteen rind may serve as an alternative ingredient in facial toner formulations. This laboratory experimental study aimed to assess the antioxidant activity of facial toner preparations containing the ethyl acetate fraction of mangosteen rind (Garcinia mangostana L.) using the ABTS method at different concentrations (0.2%, 0.4%, and 0.6%). Four facial toner formulas were formulated, with Formula 1 being the control formula without any active substance and Formulas 2-4 containing the ethyl acetate fraction of mangosteen rind at different concentrations. The prepared formulas underwent physical and chemical stability tests, including organoleptic, homogeneity, pH, viscosity, and humidity tests, before and after six cycles of cycling. The antioxidant activity of the formulas was also evaluated using the ABTS method. The results showed no significant difference (p>0.05) in the organoleptic, viscosity, pH, and humidity tests before and after cycling. Formula 3 showed significant (p<0.05) antioxidant activity compared to the other formulas. Therefore, it can be concluded that the ethyl acetate fraction of mangosteen rind (Garcinia mangostana L.) can be formulated into a facial toner with potent antioxidant activity.

Mechanical Properties of Ti–5Al–5V–5Mo–3Cr Alloy Sintered From Blended Elemental Powders

The field-assisted sintering technique (FAST) was successfully used to sinter, homogenize, and age the Ti–5Al–5V–5Mo–3Cr (Ti-5553) aerospace alloy from blended elemental powders in a single processing run. Sintering at a comparatively high temperature of 1500 °C assured chemical homogeneity of the material. Subsequently, without cooling to the room temperature, the temperature was lowered to 600 °C for 30 min to provide annealing treatment and to produce a desired lamellar α + β microstructure. Using an in-house designed assembly, a fully dense rod of 15 mm in diameter and 70 mm in length was successfully sintered. Microstructural and mechanical properties of the alloy were investigated and compared with the conventionally processed Ti-5553 alloy. A good combination of strength (1183 MPa) and ductility (6 pct) was achieved; these values are fully comparable to the conventional cast, forged, and aged Ti-5553 alloy. It was shown that homogeneous Ti-5553 alloy can be produced by FAST, FAST can instantly provide necessary annealing steps, and the FAST process can be upscaled to produce homogeneous rods.

Recrystallization effect on mechanical parameters and increasing of Ag+ ionic conductivity in Ag7(Si1-xGex)S5I ceramic materials

This paper presents the preparation and investigation of Ag7(Si1-xGex)S5I (х = 0.2; 0.4; 0.6; 0.8) ceramic materials. Powder patterns of Ag7(Si1-xGex)S5I indicate the formation of a continuous series of solid solutions with the F-43m cubic cell. Ag7(Si1-xGex)S5I ceramic discs with a porosity of 10 ± 1% were obtained by cold pressing followed by annealing at 700°С. Fabricated ceramics were studied by the SEM, EDS, EIS methods and microhardness measurement. The obtained ceramics are characterized by chemical homogeneity and close values of the average crystallite size in the range of 2.52–2.70 μm. Frequency and temperature dependences of electrical conductivity were analyzed by Nyquist plots. The compositional behavior of ionic conductivity is non-linear and is characterized by a conductivity maximum (8.10 × 10−2 S/cm) at x = 0.6. The temperature dependence of the ionic component obeys to Arrhenius law. The influence of the recrystallization process on the electrical parameters of Ag7(Si1-xGex)S5I solid solution microceramics is discussed.

Characterization of a novel AlLiMgTiZr-type light high entropy alloy

Al11Li10Mg23Ti21Zr35 was designed as a novel Light High Entropy Alloy (LHEA) considering terms and parameters of respective phase formation rules. The alloy was vacuum melted utilizing high-purity elements, then suction cast and homogenized. The experimentally measured density of the ingot was 4.43 g/cm3 compared to the theoretical density of 4.02 g/cm3. Chemical composition, microstructural properties, phase structure, compressive mechanical properties, and microhardness were characterized. Approximate chemical homogeneity was observed in the microstructure and the Hexagonal Close-Packed (HCP) solid solution phase with c/a = 1.544 and AlZr2 intermetallic compounds were identified. High specific hardness (230 Vickers. cm3/g) was achieved satisfying among all LHEAs introduced up to now. Different hardness values were measured at various points of the microstructure connected to the presence of AlZr2 intermetallic. The lattice distortion of alloys' crystal structures was analyzed accurately, and the distorted solid solution structure consists of elements with different atomic radii, proposed as the dominant mechanism (contributed more than 80%) among grain boundary, dislocation strengthening and solid solution strengthening mechanisms. The alloy's ductility was fair due to the HCP lattice and intermetallic compounds.

The Importance of Structural Uniformity and Chemical Homogeneity in Cobalt-Free Lithium Excess Nickel Manganese Oxide Cathodes.

This study explores the relationships between material quench rate during processing and the resulting structural and electrochemical properties of Li[Ni0.25 Li0.167 Mn0.583 ]O2 . Samples of this lithium-rich material are prepared with highly contrasting postfiring cooling methods: a rapid water emersion quench or closed-door oven cooling. The contrasting approaches result in samples with different structural, chemical, and electrochemical behaviors; after cycling the rapidly quenched material yields greater capacity, greater stability, and initially lower, but more stable voltages than the slower cooled samples. Through the use of scanning tunneling electron microscopy, X-Ray Diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) it is demonstrated that rapidly quenched powders are more structurally uniform and chemically homogenous before cycling. By comparing these precycling sample to postcycling samples, it is then examined how this increased structural uniformity and chemical homogeneity leads to the superior electrochemical properties of the rapidly quenched samples.

High entropy effect on double exchange interaction and charge ordering in half doped Nd0.5Sr0.5MnO3 manganite

The entropy stabilized oxides i.e., the so-called high-entropy oxides are of great interest in recent time due to their intriguing physical properties. This new category of advanced materials is stabilized by the high configurational entropy of randomly mixed elements, where a specific lattice site is populated by five or more elements. The present study is devoted to explore the high entropy effect in well-known charge ordered manganite Nd0.5Sr0.5MnO3 where a delicate balance exists between the ferromagnetic double exchange and the antiferromagnetic superexchange interactions. Powder X-ray diffraction analyses confirm phase purity of the samples. FE-SEM imaging revealed the microstructure and elemental mapping confirmed the chemical homogeneity of the samples as well as nominal cationic composition. Bond valence sum (BVS) calculation using refinement parameters supports the expected cationic valence in all the samples. Replacement of Nd3+ by five trivalent cations as in (La0.1Pr0.1Nd0.1Gd0.1Bi0.1)Sr0.5MnO3 with larger average A-site ionic radius,<rA>and smaller size variance, σ2 compared with Nd0.5Sr0.5MnO3 dramatically suppressed the ferromagnetic double exchange interaction. This observation is in contrast with the expected variation in<rA>and σ2. In (La0.1Nd0.1Gd0.1Bi0.1Y0.1)Sr0.5MnO3 with smaller<rA> and marginally higher σ2 the ferromagnetic state ceases to exist. In both the multicationic compositions, a long-range antiferromagnetic state is evolved around 200 K with the retention of charge ordering. In the high entropy (La1/6Nd1/6Dy1/6Ca1/6Ba1/6Sr1/6)MnO3 composition with nominal<rA> and larger σ2 values the high temperature long-range ordering is completely suppressed and a new antiferromagnetic state is evolved at 45 K without manifestation of any charge ordering. This composition also avoids magnetic frustration unlike the dopant variant with larger σ2. The present investigation thus highlights the role of local lattice distortion or high entropy effect apart from the<rA>and σ2 in manganites.

Micro- and nanostructure of additively manufactured, in-situ alloyed, magnetic spinodal Fe54Cr31Co15

Exploring the chemical micro- and nanostructure of metal alloys is essential to understand their physical properties, such as magnetism or hardness. Additively manufactured (AM) materials, e.g. via laser powder bed fusion (LPBF) followed by various heat treatments, can raise further questions concerning the printed material. For the in-situ alloyed, spinodal Fe54Cr31Co15 system, the macroscopic magnetic behaviour is greatly influenced by subsequent homogenisation and heat treatment steps. Here we show that the decomposition takes place on the nanometre scale, resulting in ferromagnetic FeCo-rich particles embedded in a Cr-rich matrix. By studying phenomena like chemical homogeneity, grain structure, and texture of the in-situ alloyed material at different scales, we reveal correlations between the heat treatment and the resulting nanostructure and its ferromagnetic properties. We found that the isothermal heating conditions determine the degree of phase segregation and that a homogenization step can be omitted for additively manufactured, in-situ alloyed FeCrCo alloys. The approach thereby offers insight and a path for also tailoring specific manufacturing parameters to provide the right quality printed materials with desired functionalities. For example, magnetic FeCrCo alloys are often used in electric motors or magnetic sensors, and the flexibility of the presented approach can lead to optimal use of the material.

Microstructure and Corrosion Behavior of Fe-Based Austenite-Containing Composite Coatings Using Supersonic Plasma Spraying

The Fe-based austenite-containing composite coatings with various contents (3 vol.%, 6 vol.%, 9 vol.%, 12 vol.%) of austenite powder additions were created by supersonic plasma spraying on 45 steel substrates. The microstructure, phase composition, microhardness, and porosity of the composite coatings were examed. Moreover, special attention was paid to the effect of austenite powder on the corrosion resistance of the austenite-containing composite coatings. The results found that the addition of austenite powders could significantly improve the corrosion resistance of Fe-based coatings, which is mainly due to three correlated phenomena caused by the austenite particles. First, austenite particles significantly reduce the porosity of the austenite-containing composite coatings and form a denser coating structure due to their low melting point and good chemical compatibility with the Fe-based alloy. Further, austenite particles help to refine the grains and increase the grain boundary density. Last but not least, austenite particles help to generate more diffusely distributed second phases in the coating, improving the chemical homogeneity and hardness of the coating.

Deformation-induced homogenization of the multi-phase senary high-entropy alloy MoNbTaTiVZr processed by high-pressure torsion

Dendritic microstructures are frequently observed in as-solidified refractory high-entropy alloys (RHEAs), and their homogenization typically requires a long-term heat treatment at extremely high temperatures. High-pressure torsion (HPT) has been shown to be capable of mixing immiscible systems at room temperature, and therefore represents a promising technique for homogenizing dendritic RHEAs. In this work, the as-solidified RHEA MoNbTaTiVZr was processed up to 40 revolutions by HPT. It was found that the dendritic microstructure was eliminated, resulting in a chemical homogeneity at a von Mises equivalent shear strain of about 400. The study of deformation mechanism showed an initial strain localization, followed by a co-deformation of the dendritic and interdendritic regions. In the co-deformation step, the Zr-rich interdendritic region gradually disappeared. The deformation-induced mixing also led to the formation of an ultra-fine grained (UFG) microstructure, exhibiting a grain size of approximately 50 nm. The microhardness increased from 500 HV in the as-solidified to 675 HV in the homogenized UFG state. The underlying mechanisms responsible for the microhardness enhancement, such as grain refinement and solid solution strengthening, were also discussed.

Effect of High-Anisotropic Co2+ Substitution for Ni2+ on the Structural, Magnetic, and Magnetostrictive Properties of NiFe2O4: Implications for Sensor Applications.

This work reports on the effect of substituting a low-anisotropic and low-magnetic cation (Ni2+, 2μB) by a high-anisotropic and high-magnetic cation (Co2+, 3μB) on the crystal structure, phase, microstructure, magnetic properties, and magnetostrictive properties of NiFe2O4 (NFO). Co-substituted NFO (Ni1-xCoxFe2O4, NCFO, 0 ≤ x ≤ 1) nanomaterials were synthesized using glycine-nitrate autocombustion followed by postsynthesis annealing at 1200 °C. The X-ray diffraction measurements coupled with Rietveld refinement analyses indicate the significant effect of Co-substitution for Ni, where the lattice constant (a) exhibits a functional dependence on composition (x). The a-value increases from 8.3268 to 8.3751 Å (±0.0002 Å) with increasing the "x" value from 0 to 1 in NCFO. The a-x functional dependence is derived from the ionic-size difference between Co2+ and Ni2+, which also induces grain agglomeration, as evidenced in electron microscopy imaging. The chemical bonding of NCFO, as probed by Raman spectroscopy, reveals that Co(x)-substitution induced a red shift of the T2g(2) and A1g(1) modes, and it is attributed to the changes in the metal-oxygen bond length in the octahedral and tetrahedral sites in NCFO. X-ray photoelectron spectroscopy confirms the presence of Co2+, Ni2+, and Fe3+ chemical states in addition to the cation distribution upon Co-substitution in NFO. Chemical homogeneity and uniform distribution of Co, Ni, Fe, and O are confirmed by EDS. The magnetic parameters, saturation magnetization (MS), remnant magnetization (Mr), coercivity (HC), and anisotropy constant (K1) increased with increasing Co-content "x" in NCFO. The magnetostriction (λ) also follows a similar behavior and almost linearly varies from -33 ppm (x = 0) to -227 ppm (x = 1), which is primarily due to the high magnetocrystalline anisotropy contribution from Co2+ ions at the octahedral sites. The magnetic and magnetostriction measurements and analyses indicate the potential of NCFO for torque sensor applications. Efforts to optimize materials for sensor applications indicate that, among all of the NCFO materials, Co-substitution with x = 0.5 demonstrates high strain sensitivity (-2.3 × 10-9 m/A), which is nearly 2.5 times higher than that obtained for their intrinsic counterparts, namely, NiFe2O4 (x = 0) and CoFe2O4 (x = 1).

Structural, magnetic and electrical transport properties of the sol-gel derived La1-xCaxMnO3 (0≤x≤0.3) nanoparticles

Sol-gel (SG) prepared calcium doped La1-xCaxMnO3 (0 ≤ x ≤ 0.3) nanoparticles (>35 nm) show a phase transformation from rhombohedral-R3c to orthorhombic-Pnma. The dopant concentration influences the bond length and lattice parameters and their variations as observed from the rietveld refinement. The phase stability and chemical compositions are confirmed using the Thermogravimetric and differential thermal analysis (TG-DTA) and Fourier transform infrared (FTIR) spectroscopy measurements. The latter confirms the presence of dangling bonds from the changes in the characteristic vibrational frequencies and intensities. Field emission scanning electron microscope-energy dispersive X-ray analysis (FESEM-EDAX) confirms the nano-dimension of the particles and good chemical homogeneity of the samples. The Curie temperature Tc, estimated from the field cooled magnetization curve, shifts towards room temperature (Tc = 160–270 K) with the increase of dopant concentration. The samples exhibit a clear metal to insulator transition, the temperature of which shifts to higher values (169–267 K) with increase in dopant content. With the application of an external magnetic field, local ordering of magnetic moments occurs and the evolution of a ferromagnetic metallic phase suppresses the existing paramagnetic insulating phase, decreasing the value of resistivity. Three different temperature ranges demarked in the resistivity curves are studied using different theoretical models. The observed low temperature resistivity upturn is explained on the basis of the Kondo-like model while the ferromagnetic metallic region is studied using different scattering processes like electron – electron, electron – magnon etc. The variable range and small polaron hopping (VRH and SPH) models are used in the high-temperature region data and with the aid of Holstein's relation the non-adiabatic SPH model it is found to be most suitable to understand the conductivity behavior. The temperature dependent evolution of the Griffith's like phase can explain and correlate the electric transport and magnetic properties exhibited by the samples. This highlights the evolution of Mn3+-O2--Mn4+ FM oriented networks, which form conduction channels with the lowering of temperatures. These channels mediate the enhanced conduction and helps set in long-range FM ordering in the samples/

Development of Bituminous Paint from Agbabu Natural Bitumen for Coat Coat-Protecting the Underparts of Automobile Chassis against Corrosion and Wear

To date, there has been continued demand for more effective, less expensive, and accessible coating systems for durable corrosion and wear protection of auto auto-bodies, with a research need to meet the demands. The rationale behind this study was to create a high high-quality, low low-cost bituminous paint for use in protecting the under parts of automobile chassis against corrosion and wear, particularly in Nigeria. Five paint blends containing various proportions of 70 –100% Agbabu natural bitumen, 02 02–5% kerosene, 0 0–8.5% cobalt, 0 0–1% pigment, and 0 0–2.1% lead drier were produced and characterized by their basic physicochemical properties. The blends were brush brush-coated to a 1.78 1.78-mm average thickness on plate samples of mild steel, a commonly and widely applied but highly corrosion corrosion-susceptible chassis material type. Corrosion and wear tests performed on the steel samples under 1.78 1.78-mm -thick hard hard-dried coatings of the paint blends revealed that the blend with 75% bitumen, 15% kerosene, 8% cobalt, 0.6% pigment, and 1.4% lead drier content could perform exceptionally well in protecting the steel a t the coating thickness. X X-ray fluorescence and scanning electron microscopy analyses of that paint blend were conducted to understand its distinct chemical compositions and microstructural homogeneity level. The 1.78 1.78-mm -thick coating of that paint blend’s adhesion adequacy to the steel was also investigated. Analyses of the collected data revealed that the blend contained 25 different chemical species that are benign to steel corrosion, had a more or less uniform microstructure demonstrating its homogeneity, had minimal intergranular boundaries indicating minimal ingress of corrosion corrosion-causing agents to the steel underneath its coatings, and its hard hard-dried thin coatings would have excellent adhesion to any ferrous chassis material..

Structural and optical properties of Mg1−xMnxP2O6(x = 0–1.0) magnesium metaphosphate

AbstractStructural and optical properties of Mg1−xMnxP2O6(x = 0–1.0) magnesium metaphosphate were investigated in detail. The complete solid solution of MgP2O6–MnP2O6is confirmed as monoclinic space groupC2/c. The dynamic luminescence was studied by changing the Mn2+content (0–100 mol%) and temperature (10–300 K). There is a good chemical homogeneity in Mg1−xMnxP2O6(x = 0–1.0), which can be supported by the linearly varying cell size and the gradually changing vibration spectrum. However, the optical properties of the solid solution do not show a continuous change trend, that is, an obvious inflection point appeared whenx = 0.5. Mg1−xMnxP2O6(x = 0.1–0.5) shows a dominant O2− → Mn2+charge transfer (CT) absorption in the near UV region and feeble d–d transitions of Mn2+in visible wavelength region. However, Mg1−xMnxP2O6(x = 0.6–1.0) presents a strong d–d absorption transition and nearly disappeared CT band. The changing trend of optical absorption is also maintained in the excitation and emission of the solid solutions. In Mg1−xMnxP2O6(x = 0.1–0.5), (Mn, Mg)O6octahedron has slight distortion, and the effective luminescence only occurs when CT band excitation is used. In contrast, in Mg1−xMnxP2O6(x = 0.6–1.0), (Mn, Mg)O6octahedron is highly distorted, and only excitation at d–d transition produces effective luminescence. This research highlights the critical role of MnO6octahedral distortions in the luminescence properties of Mn2+activators. The research provides a reference for developing optical materials.

Atmosphere and cooling rate effect on the dielectric behavior of the lead-free piezoelectric Bi1/2K1/2TiO3

The electromechanical behavior and phase transition of lead-free piezoelectric Bi1/2K1/2TiO3 (BKT) can be modified without changing the processing parameters, composition, or microstructure through post-densification thermal treatment. Although this provides a method to control the disorder and, thereby, the thermal stability, the role of annealing atmosphere remains not well understood. In this work, solid-state processed BKT was annealed with varying cooling rates (5 K/min to 0.1 K/min) and atmospheres (air, oxygen, nitrogen) in order to investigate influence on the functional properties. Crystal structure analysis revealed an enhanced evaporation of volatile constituents of BKT ceramics, namely Bi3+ and K+ after the annealing in oxygen atmosphere, leading to decreasing properties, i.e., dielectric response. Also, a suppression of the relaxor-to-ferroelectric transition is observed in the dielectric response at lower cooling rates, demonstrating the influence of the atmosphere and cooling rate during thermal process in BKT. The findings are linked to structural changes respectively defect content (A-sites vacancies) and chemical homogeneity of A-site cations in BKT atmospherically annealed samples.

Predicting the chemical homogeneity in laser powder bed fusion (LPBF) of mixed powders after remelting

Predicting the chemical homogeneity in laser powder bed fusion (LPBF) of mixed powders after remelting

Effects of chemical ordering and homogeneity on microwave dielectric properties of LaGaO3-SrTiO3 compounds

(1-x)LaGaO3-xSrTiO3 (x = 0–0.6) microwave dielectric ceramics were synthesized by using conventional solid-state reaction method and sintered at 1450 °C with different sintering conditions. The variations of microstructure, relative density, and phase formation were observed by different composition and sintering conditions. The microwave properties, such as permittivity/dielectric constant (εr), quality factor (Qf), and temperature coefficient of resonant frequency (TCF, τf) at a high frequency were investigated in terms of lattice distortion, chemical ordering, and chemical homogeneity according to the composition and equilibrium sintering conditions. A maximum Qf ∼64,900 GHz was observed at x = 0, and the best τf ∼ 0 ppm/°C was obtained at x = 0.4. Consequently, it was found that the permittivity is related mainly to the lattice distortion, whereas the quality factor is primarily affected by chemical ordering and chemical homogeneity of the microstructure-induced composition.

Effect of Zr4+ on Lithium-Ion Conductivity of Garnet-Type Li5+xLa3(Nb2−xZrx)O12 Solid Electrolytes

Garnet-type structured electrolytes are considered a key technology for the next generation of lithium-ion batteries such as all-solid-state batteries. Cubic Garnet-type solid oxides with composition Li5+xLa3(Nb2−xZrx)O12 (x between 0 and 1.5) were synthesized by solid-state reaction and sintered by spark plasma sintering. Powder characterization indicates the formation of solid solution with high chemical homogeneity and spherical particles. High relative densities (&gt;96%) were obtained by spark plasma sintering at 950 °C for 10 min and pressure application of 50 MPa. Although the formation of secondary phase La2Zr2O7 was identified by the X-ray diffraction patterns of Zr-doped pellets, it has been eliminated for x = 0.75 and 1 by conventional heat treatment at 850 °C for 1 h. High ionic conductivity values were attained for x ≥ 0.75, reaching a maximum value in the order of 10−4 S.cm−1 at 25 °C with activation energy of 0.38 eV. The results indicated that Zr4+ promoted significant increasing of the lithium-ion conductivity by lowering the activation energy.

Nanoscale chemical and structural investigation of solid solution polyelemental transition metal oxide nanoparticles

Although it has been shown that configurational entropy can improve the structural stability in transition metal oxides (TMOs), little is known about the oxidation state of transition metals under random mixing of alloys. Such information is essential in understanding the chemical reactivity and properties of TMOs stabilized by configurational entropy. Herein, utilizing electron energy loss spectroscopy (EELS) technique in an aberration-corrected scanning transmission electron microscope (STEM), we systematically studied the oxidation state of binary (Mn,Fe)3O4, ternary (Mn, Fe, Ni)3O4, and quinary (Mn, Fe, Ni, Cu, Zn)3O4 solid solution polyelemental transition metal oxides (SSP-TMOs) nanoparticles. Our findings show that the random mixing of multiple elements in the form of solid solution phase not only promotes the entropy stabilization but also results in stable oxidation state in transition metals spanning from binary to quinary transition metal oxide nanoparticles.

Synergistically tailoring the microstructure and chemical heterogeneity of nanocrystalline multi-main-phase Nd–Ce–Fe–B magnet: Critical role in magnetic performance

The microstructure and chemical heterogeneity play critical roles in the magnetic performance of nanocrystalline multi-main-phase (MMP) Nd–Ce–Fe–B magnets. In this work, we report a strategy to synergistically tailor the microstructure and chemical heterogeneity of MMP magnet through optimizing sintering temperature (Ts). An optimum Ts of 700 °C has been obtained for nanocrystalline MMP Nd–Ce–Fe–B magnets. When sintered at Ts = 700 °C, the nanocrystalline MMP magnet exhibits the maximum intrinsic coercivity Hcj, the preferable remanence Br, and the resultant optimum maximum energy product (BH)max, which is attributed mainly to the appreciable density, controlled grain size, and better chemical heterogeneity. Comparably, lower or higher Ts leads to the inferior magnetic properties. At lower Ts below 700 °C, the poor magnetic properties are mainly due to the insufficient densification. However, at higher Ts above 700 °C, the decreased Hcj originates mainly from the excessive grain growth and gradual chemical homogenization. The above findings deepen our understanding on the relationship among the microstructure, chemical heterogeneity, and Ts, concurrently providing an effective approach for fabricating low-cost high-performance nanocrystalline MMP Nd–Ce–Fe–B magnets.