Phase Composition Analysis Research Articles

Analysis of serum phase proteins and emulsifiers on the whipping capabilities of aerated emulsions: From the perspective of air-liquid interface rheology

In aerated emulsions, the serum phase plays a crucial role in determining whipping capabilities. However, the effects of serum phase components on emulsion properties remain largely unexplored and continue to be a mystery. This study takes a micro-level approach, focusing on the air-liquid interfacial rheology by incorporating different types of surfactants (proteins and emulsifiers) into the serum phase. It systematically explores the effects on the serum phase interface, emulsion properties, whipping capabilities, and foam stability in a stepwise manner. Proteins only slightly affect the strength of the air-liquid interface, primarily improving the capacity to trap bubbles at the initial whipping stage, thereby boosting the overrun of the aerated emulsion. The high viscoelastic modulus of the interface membrane is greatly influenced by the presence of solid lipid nanoparticles of glycerol monostearate (GMS SLN), leading to a reduction in whipping time and improved surface-mediated partial coalescence. This ultimately enhances the quality and stability of the foam system. Tween 80, due to its hydrophilic properties, is able to quickly adsorb at the air-liquid interface using the Gibbs-Marangoni mechanism. This helps to expedite the end of the whipping process and ultimately improves the foam quality. On the contrary, glycerol monooleate (GMO), a lipophilic emulsifier for liquids, struggles to effectively adsorb at the interface, leading to decreased stability of the air-liquid interface in the system and resulting in poor whipping capabilities. This paper delves into the mechanism by which different surfactants affect the whipping capabilities of aerated emulsions through an analysis of serum phase composition, laying the groundwork for enhancing formulation design.

Recycling of environmental harmful industrial wastes in eco-friendly building materials production suitable for specific applications

Sustainable building materials are one of the main principles to achieve sustainable construction. It refers to the potential of utilizing environmentally harmful industrial wastes to reduce the consumption of raw materials/energy used in producing ordinary Portland cement (OPC). Ground-granulated blast-furnace slag (GGBFS), lead-bearing sludge (LBS), metakaolin (MK) and fly ash (FA) were used in this work to develop eco-green binding materials with several advanced applications. Five specimens were prepared, including a control specimen (100 % GGBFS, S0) and four ternary-blended geopolymers (TBGs; GGBFS/LBS/FA and GGBFS/LBS/MK) with different proportions. The experimental work examined the mix-design's influence of the TBGs on the fresh/hardened characteristics and resistance against elevated-temperature (200–900 °C), high-dose gamma-radiation (1000–3000 kG y) and mico-organisms (Salmonella-typhi, Bacillus-Cereus, Aspergillus-oryzae and Aspergillus-fumigatus). Also, the XRD, TGA/DTG (phase composition analysis) and SEM/EDX (microstructure analysis) were studied. The findings revealed that LBS significantly reduces workability compared to MK and FA. Although the LBS, MK, and FA mixture elongated the setting time, its values are still within acceptable limits. The strength values obtained by TBGs after 28 days ranged from 51.0 to 66.7 MPa, revealing that these wastes are good alternatives to OPC. TBGs proved effective in resisting elevated-temperatures and high-dose gamma-radiation compared to S0 by forming highly-stable zeolitic compounds. The S0 specimen cannot hinder Salmonella typhi's growth; unlike TBGs, the existence of PbO2, Fe2O3, and TiO2 in the matrix inhibits all microorganisms' growth.

Laser and thermal control over structure and magnetic properties of PrDy-FeCo-B microwires

Magnetic microcombs are necessary in microrobotics, MEMS technologies, actuator and magnetic flow analyzer industries. Usually, magnetic microcombs are artificial linear magnets of periodic shape. We propose another type of microcombs based of microwires, where periodicity of magnetization is caused by equidistant alternation of natural domains. We have demonstrated the presence of quasi-periodic radial magnetization and the effect of temperature and magnetic field on magnetic relief in PrDyFeCoB microwires. Accurate analysis of chemical, phase and structural composition of the microwires allowed us to reveal necessary conditions for the creation of periodical magnetic relief. Annealing affects magnetic relief and changes structure of initially amorphous microwires. Crystal structure of inclusions enriched with Fe and Co instead of Dy and Pr is body-centered cubic (BCC), while the bulk of the microwire has tetragonal structure. We have found laser stimulated amorphization of surface of PrDy-FeCo-B microwires. Partial restoration of the amorphous structure in polycrystalline microwires under single laser pulse of irradiation of 1mJ power and 120 ns duration has been found in 1–2 μm depth.

Evolution of microstructure and properties of nanocrystalline NiCo alloy under high-energy laser shock

In this study, nanocrystalline NiCo alloy was prepared through electrodeposition and subjected to high-energy laser shock (HELS) treatment to investigate the influence of laser shock on the microstructures and properties. An analysis of phase composition, microstructural evolution, texture evolution, and hardness was conducted. The results indicated that under HELS, there was no change in phase composition, while there was a slight reduction in grain size, as well as in the quantities of Low-angle grain boundaries (LAGBs) and twin boundaries (TBs). The texture evolution revealed that HELS led to a more uniform overall texture due to grain boundary (GB) mediate deformation mechanisms, along with the generation of a significant amount of 9R phases, causing a shift in texture orientation from (110) to (100). The internal structure of nanocrystalline NiCo showed an accumulation of numerous dislocations post-laser shock, with randomly oriented dislocations interacting to form Lomer-Cottrell Locks (L-C Locks) and 9R phases. Additionally, interactions with large stacking faults (SFs) also resulted in their dissociation into multiple 9R phases. The hardness enhancement was mainly attributed to the accumulation of dislocations within the grain and the generation of a significant quantity of 9R phases.

Impact of barium oxide on the structure and surface properties of glass-crystalline glazes

The influence of barium oxide on glazes in the SiO2-Al2O3-CaO-MgO-K2O system was investigated. Samples were prepared with 0, 2.5, 5 and 7.5 wt% of barium oxide added to this system. The glazes were fired at 1240 °C and the structure and surface properties were determined. Qualitative and quantitative analyses of phase composition, surface properties, structural mid-infrared analysis, and microstructure were performed.Diopside was detected in all glazes as the MgO content was higher than 2.5 wt%. Hyalophane crystals were observed when the BaO content increased to 5 wt%. Mid-infrared studies showed that the appearance of crystalline phases ordered the structure of the glazes; on the other hand, the amorphous phase increased its disorder related to the higher amount of modifying barium cations. The addition of barium oxide did not significantly affect the color of the surface but caused an increase in roughness due to surface crystallization. The microhardness increased with an increased amount of barium in the amorphous phase.

Boriding of Low-Carbon Steel by Plasma Method: Microstructure and Coating Properties

In materials science, steel boration is a promising type of thermochemical diffusion process, the purpose of which is the introduction of hard and wear-resistant boride particles into the surface layers of the metal. The main disadvantage of boration is the fragility of borated layers, especially boride. Currently, there are promising methods for the formation of a composite structure, which are based on the treatment of surface layers of steels with concentrated energy flows (laser, electron beam and plasma). The work includes studies of microstructure, hardness measurements, analysis of phase composition, and determination of chemical composition in local locations, wear tests under various conditions, and adhesion testing of the coatings obtained after plasma boration. As the degree of alloying of the molten layer decreases in the direction from the surface to the base metal, zones of overeutectic, eutectic and pre-eutectic types with a different combination of structural components are formed. The material obtained after borating a mixture of 40% B + 10% Fe is characterized by the highest level of microhardness, which is 1000...1300 HV. The highest results in friction tests are provided by boration of a powder mixture of 40% B + 10% Fe.

Enhancing the high-temperature oxidation resistance of C-103 niobium alloy via hybrid treatment combining nickel plating with molten-salt siliconising

ABSTRACT A multi-phase silicide protective coating was prepared by electroplating nickel on the surface of C-103 niobium alloy (89Nb–10Hf–1Ti), followed by molten-salt non-electrolytic siliconising to enhance the high-temperature oxidation resistance of the substrate. The phase composition, microscopic morphology and elemental analysis of the coating were analysed via X-ray diffraction, scanning electron microscope, energy-dispersive spectrometer and hardness distribution. Oxidation characteristics were evaluated by comparing the oxidation inhibition effect of the coating on niobium alloy substrate and that of coating prepared via molten-salt infiltration alone at a constant temperature of 1100°C for 9 h. Results show that a silicide infiltration coating containing about 200-μm-thick compound layer with Ni2Si, NiSi, Nb5Si3, NbSi2, Ni3Si2 and TiNiSi multi-phase composition and ∼10–15-μm-thick diffusion layer were dense with few defects. In the hybrid synthesis process, the upper electroplated nickel coating can promote and modify the growth of subsequent siliconised coating. The duplex prepared silicon infiltration coating can reduce the oxidation rate of niobium alloy substrate by about 1/10, indicating good high-temperature oxidation resistance. This is because the siliconised coating is considerably thick, has a dense blocking structure and generates Ni4Si7Ti4, thereby blocking oxygen.

Discrepancy evaluation in mechanics and corrosion resistance of reactive plasma sprayed TiN coatings fabricated under different heat treatment

Ceramic coatings have positive feedback to annealing treatment, but improper annealing treatment can also bring disastrous consequences. In this article, a thick TiN coating without a bonding layer was prepared by reactive plasma spraying technology and then subjected to heat treatment at three different temperatures in atmospheric and argon atmospheres. By exploring the hardness, modulus, and corrosion resistance of the coatings, combined with analysis of microstructure, phase composition, and interatomic bonding conditions, it was found that the TiN coating exhibited the lowest porosity after atmospheric heat treated at 500 °C. Meanwhile, it also showed the highest hardness, modulus, and optimal corrosion resistance. After heat treated at 650 °C in the atmosphere, the protective performance of the coating was decreased, but it was still far superior to the as-sprayed coating. The coating after heat treated in the argon atmosphere did not achieve ideal performance. The coating heat treated at 650 °C even exhibited inferior comprehensive performance to the as-sprayed coating. Therefore, it was summarized that the atmospheric environments and the temperature above the phase transition temperature were suitable for obtaining the optimal TiN coating.

Morphology-Dependent Photocatalytic Activity of Nanostructured Titanium Dioxide Coatings with Silver Nanoparticles.

This study aims to improve the photocatalytic properties of titanium dioxide nanorods (TNRs) and other related nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) by modifying them with silver nanoparticles (AgNPs). This preparation is carried out using a two-step method: sol-gel dip-coating deposition combined with hydrothermal crystal growth. Further modification with AgNPs was achieved through the photoreduction of Ag+ ions under UV illumination. The investigation explores the impact of different growth factors on the morphological development of TiO2 nanostructures by modulating (i) the chemical composition, the water:acid ratio, (ii) the precursor concentration involved in the hydrothermal process, and (iii) the duration of the hydrothermal reaction. Morphological characteristics, including the length, diameter, and nanorod density of the nanostructures, were analyzed using scanning electron microscope (SEM). The chemical states were determined through use of the X-ray photoelectron spectroscopy (XPS) technique, while phase composition and crystalline structure analysis was performed using the Grazing Incidence X-ray Diffraction (GIXRD) method. The results indicate that various nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) can be obtained by modifying these parameters. The photocatalytic efficiency of these nanostructures and Ag-coated nanostructures was assessed by measuring the degradation of the organic dye rhodamine B (RhB) under both ultraviolet (UV) irradiation and visible light. The results clearly show that UV light causes the RhB solution to lose its color, whereas under visible light RhB changes into rhodamine 110, indicating a successful photocatalytic transformation. The nanoball-like structures' modification with the active metal silver (TNRs 4 Ag) exhibited high photocatalytic efficiency under both ultraviolet (UV) and visible light for different chemical composition parameters. The nanorod structure (TNRs 2 Ag) is more efficient under UV, but under visible-light photocatalyst, the TNRs 6 Ag (dense nanorods) sample is more effective.

Modification of cement-based circulating fluidized bed combustion slag: Physical grinding and chemical excitation

This study investigates the effects of physical grinding (ball, impact, and jet milling) and chemical modification (using various dosages of Na2SO4, CaO, triethanolamine (TEA), and their composite modifiers) on CFBCS. The fluidity, flexural strength, compressive strength, and expansion rate of different modification methods were tested. Microstructural and phase composition analyses were conducted using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, mercury intrusion porosimetry, and thermogravimetry-differential thermogravimetry. The results indicated that impact milling improved mortar fluidity by 2.9 % compared to ball milling, while jet milling reduced it by 5.7 %. Chemical modifications decreased paste fluidity but increased mortar strength and reduced expansion rates. Impact milling and jet milling improved 28-day compressive strength by 13.76 % and 16.01 %, respectively, and reduced the 90-day expansion rate by 0.007 % and 0.012 %, respectively. Composite chemical modification (CM-C) enhanced 28-day compressive strength by 23.88 % and reduced the 90-day expansion rate by 0.019 %. Microscopic analysis shows that modification reduced the pores and pore size of the mortar while increasing the hydration products. After TEA modification, rod-shaped AFt forms a reticulated structure, with C–S–H gel and CH crystals adhering to it. The hydration products of CFBCS mortar formed a network after jet milling, and the addition of composite modifiers resulted in a layered, dense structure.

CaTiO3 nanoparticles as functional additives for the BaTiO3-based X8R type dielectric ceramics

This research investigates the potential of Calcium titanate (CaTiO3 or CT) nanoparticles as functional additives to enhance the dielectric properties of Barium titanate (BaTiO3 or BT)-based ceramic dielectrics. To address the need for high-temperature stability in MLCC (multilayer ceramic capacitor) applications, especially within the automotive and aerospace sectors, we have explored BT-based complex perovskite solid solutions comprising various cation substitutions, including Ca2+ and Yb3+, into barium titanate (BT) as a method to suppress the dielectric property anomaly near the Curie temperature effectively. The focus is on the impact of the application of CT nanoparticles as additive materials on phase formation, microstructure development, and dielectric behavior of the resulting ceramics to align with the Extended 'Temperature Coefficient of Capacitance (TCC)' criteria defined by the EIA X8R specification. When the hydrothermally synthesized CT nanopowder was applied in the Ca-doped BT ceramics fabrications as source material of the Ca dopants, it was beneficial to achieve both temperature stability and high dielectric constant. The CT nanoparticles are believed to play multiple roles during the solid-state reaction with BT and rare earth dopant (Yb). Since the Yb3+ ions can be more easily dissolved into the CT lattice than BT with their amphoteric character, the CT nanoparticles in the BT-CT-Yb2O3 mixture can act as an intermediary, dissolving the Yb3+ first in its A- or B-site before the final solid-solution formation with the BT. The sequential substitutions of the Yb3+ and Ca2+ into BT via CT nanoparticles could affect the site occupancy of Ca2+ in the BT lattice, which is very important in determining the dielectric properties of the Ca-doped BT processed in reducing atmospheres. Through a comprehensive experimental approach, including phase composition analysis via X-ray diffraction (XRD) and microstructural examination using Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM), this work reveals the significance of synthetic methodology and dopant incorporation strategy on achieving a desired core-shell microstructure and improved dielectric performance. This research underscores the efficacy of CT nanoparticles as a promising route towards the development of BT-based dielectric ceramics with superior temperature stability, offering valuable insights for the advancement of MLCC technology to cater to high-temperature applications.

A developed highly selective and sensitive electrochemical sensor using gold nanoparticles on Cerium Stannate/MXene as an electrode matrix for detection of metol in various environmental and biological samples

Metol (MTL) is a highly significant organic compound that plays a crucial role in numerous applications as a monochromatic material. It has an impact on humans, plants, and animals and it raises serious environmental concerns. The present scenario necessitates the development a rapid, cost-effective, precise, and specific method for detecting metol in environmental and biological samples. In this study, the electrochemical sensor was developed using a modified electrode based on the Au@Ce2Sn2O7/MXene nanocomposite. The nanocomposite was thoroughly examined through phase composition analysis, elemental analysis, and morphological studies. The modified electrode exhibits exceptional selectivity, cyclic stability, storage stability, and reproducibility. The proposed sensor shows a wide linearity range (0.00125 to 1021.96 μM), low detection limit (5.63 nM), and high sensitivity (0.403 μA·μM–1·cm–2). The suggested sensor's consistency was confirmed by real-time monitoring of MTL in several environmental and biological samples with a high percentage of recovery.

The study of interaction of the high energetic plasma and electron pulses with multicomponent alloy surface

This paper investigates the impact of high-energy sources, namely, high-energy plasma pulses and high-energy electron beam pulses, on materials in the form of layer through separate and combined exposures. Experimental setups utilizing a Rod Plasma Injector (RPI) and an electron gun were employed for irradiation tests. The studies involved pre- and post-treatment analysis of morphology, chemical, and phase composition using scanning electron microscopy and x-ray diffraction measurements. Surface modifications under different exposure conditions were characterized, revealing that both sources induced significant alterations in surface composition and crystal structure. These interactions result in a more uniform chemical composition, reduced surface roughness, and a shift from an amorphous phase to a nanocrystalline or amorphous-nanocrystalline state. The results underscore the potential of high-energy sources for efficient surface engineering, offering opportunities for customized material surface modifications through meticulous adjustment of these generation parameters.

Comparative Analysis of Chemical and Phase Compositions of Rolling Scale of Metallurgical Enterprises

Comparative Analysis of Chemical and Phase Compositions of Rolling Scale of Metallurgical Enterprises

Optimizing the grain boundary structure of sintered Nd-Fe-Co-B magnets by Dy-Al-Cu alloys grain boundary diffusion

The substitution of Fe by Co can effectively increase the Curie temperature of Nd-Fe-B magnets. However, the enrichment of Co in the grain boundary phase makes the grain boundary phase change from nonmagnetic to ferromagnetic, which has a harmful effect on the coercivity. In this paper, Dy70Al10Cu20 alloy was used as the diffusion source for grain boundary diffusion of sintered Nd-Fe-Co-B magnets. The magnetic properties and microstructure of the magnets were investigated by controlling the coating thickness of the diffusion source (thickness of 0.03 mm, 0.09 mm, and 0.15 mm). The results show that the coercivity of the magnet after diffusion is increased to 17.63 kOe, which is 9.69 kOe higher than that of the undiffused magnet. The phase composition analysis shows that the original magnet contains the soft magnetic 2:17 phase, and the 2:17 phase is significantly reduced after diffusion. The microstructure observation shows that the main phase is connected and the grain boundary phase is absent in the high Co original magnet. After diffusion, the thin grain boundary phase in the magnet increases, which effectively isolates the main phase grains. Dy-rich shell is formed on the surface of the main phase grain, which is beneficial to the improvement of coercivity. Therefore, magnetic hardening of Dy-rich shells and exchange-decoupling strengthening of adjacent 2:14:1 grains isolated by intergranular phases contributed to further coercivity increment Hcj of magnet simultaneously. Studies have shown that grain boundary diffusion is an effective way to improve the microstructure of Nd-Fe-Co-B magnets.

Formation of Ca, P, and Zn-doped ZrO2/TiO2 coating layer via plasma electrolytic oxidation and magnetic sputtering: Improving surface characteristics and biocompatibility of Ti–6Al–4V alloy

The study demonstrated the Ca, P, and Zn-doped ZrO2/TiO2 coating layer via plasma electrolytic oxidation (PEO) and radiofrequency magnetron sputtering (RF-MS) for improving surface characteristics and biocompatibility of Ti–6Al–4V alloy. The process involved sandblasting (SB) to create micro-scale irregularities on the alloy surface, followed by RF-MS and PEO. The coating's morphology, elemental composition, phase composition, and chemical analysis were examined by FE-SEM with energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman analysis. The dual surface treatment resulted in the formation of composite coatings with TiO2, ZnO, ZrO2, and HA presence and displayed anisotropic multi-scale porous morphology while the surface texturing created by the SB process facilitated mechanical interlocking during the oxide layer growth. In the SB-Zr + PEO-Zn sample, the phase analysis indicated the strain-induced stabilization of t-ZrO2 in the PEO coating layer due to the incorporation of Ca2+ ions, and the formation of zinc-substituted hydroxyapatite was observed that showed enhanced roughness and wettability. Also, reduced hardness and elastic modulus (comparable to that of cortical bone) were observed due to transformation toughening under stress from t-ZrO2 to m-ZrO2. The presence of TiO2, ZrO2, ZnO, and HA within the coating, all act as protective barriers in effectively reducing corrosion rates. The biological analysis demonstrated better biocompatibility, including promoting cell proliferation, cell adhesion, osteoblast differentiation, ALP activity, and mRNA expression of several osteogenic markers of the cells cultured on the SB-Zr + PEO-Zn sample. These results demonstrated the higher potential of the PEO coating system with higher biocompatibility and osseointegration ability for dental implants.

Preparation and hydration mechanism of composite cementitious materials based on iron and steel solid waste

Three groups of composite cementitious materials (CCMs) were prepared by separate grinding, mixed grinding, and cascade grinding using iron and steel solid waste (ISSW) materials (granulated blast furnace slag (GBFS), iron ore tailings (IOTs), steel slag (SS) and desulfurization gypsum (DG)), and the influence on the strength of CCMs was investigated under different water-binder ratios (w/b). Then, the hydration hardening mechanism of the CCMs was revealed via hydration heat analysis, phase composition and structural analysis of hydration products. The results show that the properties of the CCMs prepared by cascade grinding (CGC) is better than that prepared by separate grinding and mixed grinding. When the mass percentage of IOTs and SS in the CGC was 2:3, the mix proportion of CGC is SS+IOTs: GBFS: DG=36:51.5:12.5, mixed with 1.0 % Na2SO4 and 1.2 % Na2SiO3ˑ9 H2O of the CGC, the compressive strength (CS) of mortar sample containing CGC in 28-days and 180-days reach 52.3 MPa and 70.7 MPa respectively under the conditions of standard curing and low water-binder ratios. The hydration degree of pure cement is higher than that of CGC, but types of the hydration products were similar with cement, mainly were Ca(OH)2, iolite, ettringite (AFt) and C-S-H gel. The CGC can greatly reduce the hydration heat of CCMs system in early age, and is suitable for massive concrete structures in which elevated temperature can be kept for a long time.

Influence of pressure and powder characteristics on the properties and microstructure of Colmonoy-5 alloy sintered by spark plasma sintering

This study investigates the microstructure and final properties of Colmonoy-5, a nickel-based hardfacing alloy, consolidated via spark plasma sintering (SPS) as an alternative to traditional welding deposition on stainless steel substrates. Two batches of Colmonoy-5 alloy powders with different particle sizes used for sample processing. Sintering occurred at 900 °C under pressures of either 50 MPa or 60 MPa for 15 min. The evaluation of the sintered samples included density measurement through Archimedes' method, morphology assessment via confocal microscopy, phase composition analysis by X-ray diffraction (XRD), microstructural examination using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and hardness testing by Vickers method. Findings indicate that SPS is an effective technique for producing Colmonoy-5, achieving satisfactory densification. The study also reveals that the initial morphology of the precursor powders can influence the size of phases precipitated within the nickel matrix. Sintering pressure of 50 MPa seems to be the most effective in processing Colmonoy-5 via SPS.

Effect of in-situ generated MgAl2O4 spinel on thermal shock resistance of magnesia-zirconia refractories

This study aims to advance the application of magnesia-zirconia (MgO–ZrO2) refractories in non-ferrous metal smelting furnaces by enhancing their thermal shock resistance. To fabricate MgO–ZrO2–MgAl2O4 refractories, tabular corundum particles and activated α-Al2O3 powder are integrated into MgO–ZrO2 refractories. The analysis of thermal shock resistance, phase composition, and microstructure of the samples was conducted to gain insights into the toughening mechanisms. The results reveal a substantial enhancement in thermal shock resistance with the addition of 15 wt% tabular corundum (1–0.5 mm) and activated α-Al2O3. Compared to samples without these additives, a notable increase of over 50.0 % in the ratio of residual cold modulus of rupture is shown. The enhancement in thermal shock resistance is primarily attributed to the in-situ generated MgAl2O4 spinel. This process involves volume expansion and increased thermal expansion mismatch, which induce microcrack toughening. Additionally, larger tabular corundum particles form in-situ MgAl2O4 spinel, causing crack deflection and branching, thus extending the crack propagation pathway. Furthermore, the presence of micropores in the spinel zone absorbs the energy required for crack propagation, thereby improving toughness and thermal shock resistance. Consequently, the MgO–ZrO2–MgAl2O4 refractories containing in-situ MgAl2O4 spinel with micropores are promising candidate for chrome-free refractories used in non-ferrous metal smelting furnaces.

Improvement of thermal stability by co-introducing Dy and Co with dual-alloy method in NdFeB magnets

A dual-main-phase magnet with excellent thermal stability was prepared by co-mixing two types of magnetic powders, which was the conventional N55-grade powder without Dy elements, while the Co and Dy contents reached 50 wt% and 6 wt% respectively in another Co-rich powder. Studies showed that the magnetic properties along with the thermal stabilities of the magnets exhibited significant differences with the changes in the mixing ratio of the two powders. Especially, when mixing the two powders in equal proportions, a great remanence temperature coefficient of −0.0725 %/°C at 20–100 °C was obtained with a rather high Curie temperature of 581 °C, possessing its magnetic properties with Br = 12.58 kGs, Hcj = 15.9 kOe, and (BH)max = 36.88 MGOe. Note that as the proportion of Co-rich powder increased to 2/3, although the Curie temperature of the prepared magnets further increased to 622 °C, both the remanence temperature coefficient and the magnetic properties deteriorated significantly. The phase composition and microstructure analyses revealed that when the proportion of added Co-rich component exceeded 1/2, the RE(Fe,Co)2B phase transformed into the RE(Fe,Co)4B phase, and a significant amount of RE(Fe,Co)1.8B0.2 phase precipitated at the grain boundaries, leading to a deterioration in magnetic performance. In addition, dynamic domain evolution analyses under variable temperature conditions demonstrated the positive effect of the appropriate introduction of Co/Dy on the anti-demagnetization in high temperatures. This work provides insights and an experimental foundation for the development of high-performance magnets with high thermal stability, used in high-temperature environments.