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To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications, the eutectic Tb80Fe20 (wt%) alloy powders were intergranular added into the Nd-Fe-B sintered magnets to enhance the coercivity (Hcj) and thermal stability. The microstructure, magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb80Fe20 contents were studied. The experimental results demonstrate that the coercivity (Hcj) of the sintered Nd-Fe-B magnet is significantly enhanced to 27.78 kOe from 14.12 kOe, and the remanence (Br) decreases not obviously by introducing 4 wt% Tb80Fe20 alloy. Meanwhile, the reversible temperature coefficients of coercivity (β) and remanence (α) of the Nd-Fe-B magnets are increased from −0.5634%/°C to −0.4506%/°C and −0.1276%/°C to −0.1199%/°C at 20–170 °C, respectively. The Curie temperature (TC) of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb80Fe20 content. Moreover, the irreversible flux magnetic loss (hirr) is obviously reduced as Tb80Fe20 addition. Further analysis of the microstructure revealed that a modified microstructure, i.e. clear and continuous RE-rich grain boundary layer, is acquired in the sintered magnets by introducing Tb80Fe20 alloy. The associated mechanisms on improved coercivity and thermal stability are comprehensively researched.

The structural and magnetic properties were studied for recycling Nb-Fe-B powders from Nb-Fe-B sintered magnets sludge via reduction diffusion (RD) with calcium hydride (CaH2) particles. For comparison, traditional reducing agent calcium granules were applied to prepare recycled Nb-Fe-B powders. Finer particle size and better size distribution as well as lower impurity content are achieved by using CaH2 instead of Ca. In detail, the average particle size of the recycled Nb-Fe-B powder is reduced from 4.66 to 3.43 μm, and the bimodal distribution disappears. Moreover, the residual calcium content and oxygen content are reduced to about 0.080 wt% and 0.32 wt%. As a consequence, the room-temperature magnetization of the CaH2-recycled Nb-Fe-B powder is increased to 146.30 emu/g, 6.8% and 33% higher, respectively, than that of Ca-reduced powder and the initial sludge. Further analysis indicates that CaH2 is able to reduce the sludge at lower temperature to fabricate well-dispersed, uniform recycled powder with high magnetization arise from a combination factors of its low melting point, low thermodynamic behavior, and the release of hydrogen during the reaction.

The as-solution-treated Sm2Co17-type magnets exhibiting a single 1:7H phase with different average grain sizes (D) are designed. Anisotropy of bending strength (Rbb) and compressive strength (Rmc) of the magnets was investigated. Moreover, the Rbb increases from 86 to 173 MPa with D decreasing from ∼52 to ∼18 μm for group c//h samples. The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets, giving deep understand the mechanical anisotropy characteristics. The relatively high Hall-Petch coefficient KRbb (0.79 MPa·m1/2) gives rise to the largest Rbb (173MPa) for group c//h samples. The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features (grain boundaries). Grain refinement is an effective way to enhance the mechanical properties of Sm2Co17-type sintered magnets.

To produce nanocomposite materials with high magnetic properties, studies concerning on nanostructural processing technologies and control mechanisms are urgently required in aspects of achieving perfect alignment of the hard phase while keeping desired sizes and distributions of the soft phase. In the present study, a designed low-rate electroless deposition method is found to be an effective way in producing strong textured anisotropic Sm-Pr-Co/Co nanocomposites with unusual continuous soft-phase coatings when assembling Co particles on the ball-milled anisotropic Sm-Pr-Co hard phase. The average particle size of the soft-phase coatings is 18–50 nm and the obtained Sm-Pr-Co/Co composites exhibit a high intrinsic coercivity of Hci=748 kA/m with an enhanced remanence of Mr=79 A·m2/g, as compared to Hci=836 kA/m and Mr=68 A·m2/kg for uncoated Sm-Pr-Co hard phase. Moreover, the coating process study reveals a nucleation control mechanism for the formation of the continuous coating structures. Down-sized Sm-Pr-Co/Co nanocomposites with tailored size below 300 nm or even below 100 nm were also produced by this designed method. This study is of theoretical and practical importance for developing advanced nanostructures including the next generation permanent magnets.

(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process. Effects of Ho contents on the corrosion resistance and mechanical properties of (Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester, an electrochemical workstation, a microhardness tester, a bending tester, a scanning electron microscope and an X-ray diffractometer. Results show that the addition of Ho can change the main phase structure, optimize the distribution of rare-earth rich (RE-rich) phases in grain boundary, and improve the corrosion resistance and mechanical properties of NdFeB magnets. When the content of Ho increases from 0 to 21.0 wt%, the weight loss of magnets decreases from 2.672 to 0.933 mg/cm2, and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa, respectively.

The main difficulty for the recovery of Nd-Fe-B bonded magnet wastes is how to completely remove the epoxy resins. In this study, chemical reaction and physical dissolution were combined to remove the epoxy resins by adding ammonia-water and mixed organic solvents. Ammonia-water can react with the epoxy functional group of epoxy resin to generate polyols. Mixed organic solvents of alcohol, dimethyl formamide (DMF), and tetrahydrofuran (THF) can dissolve the generated polyols and residual epoxy resins. Under the optimum processing conditions, the epoxy resins in the waste magnetic powders are substantially removed. The oxygen and carbon contents in the recycled magnetic powder are reduced from 13500 × 10−6 to 1600 × 10−6 and from 19500 × 10−6 to 2100 × 10−6 with the reduction ratio of 88.1% and 89.2%, respectively. The recycled magnetic powder presents improved magnetic properties with Ms of 1.306 × 10−1 A∙m2/g, Mr of 0.926 × 10−1 A∙m2/g, Hcj of 1.170 T, and (BH)max of 125.732 kJ/m3, which reach 99.8%, 99.4%, 95.9%, and 96.9% of the original magnetic powders, respectively.

The influence of Tb80Fe20/Al co-adding on coercivity and temperature stability of sintered Nd–Fe–B magnets was studied. Compared with the Tb80Fe20 added samples, the coercivity of the Tb80Fe20/Al co-added samples enhances with the increase of Al contents. The excellent magnetic properties are acquired in the 1 wt% Tb80Fe20/0.2 wt% Al co-added magnets. The coercivity (Hcj) is enhanced from 14.33 to 19.08 kOe, and the remanence (Br) decreases slightly by introducing 1 wt% Tb80Fe20/0.2 wt% Al alloy. Meanwhile, the reversible temperature coefficients of coercivity (β) of the Nd–Fe–B magnets are increased from − 0.598 to − 0.579%/°C at 20–140 °C. Moreover, the irreversible flux magnetic loss (hirr) of the Tb80Fe20/Al co-added magnets is obviously reduced with the addition of Al. Further analysis of the microstructure reveals that a modified microstructure, i.e., continuous and clear Nd-rich grain boundary (GB) layers, is acquired in the sintered magnets by introducing Tb80Fe20/Al alloy. In addition, the average grain size decreases to 3.7 from 4.5 μm, which indicates that Tb80Fe20/Al co-adding provides an effective way to prepare for the excellent-performance of sintered Nd–Fe–B magnets.

The grain boundary diffusion (GBD) technology was used to prepare high performance Nd-Fe-B sintered magnets by NdH3 and TbH3 nanoparticle diffusion. The factors affecting the coercivity of GBD magnets include distribution of rare earth rich grain boundary phase and substitution of the heavy rare earth. In order to distinguish the influence of various factors on the coercivity, the microstructure and magnetic domain evolution of the original, reference, Nd-diffused, and Tb-diffused magnets were analyzed. The core-shell structure formed by heavy rare earth substitution is the main factor of coercivity enhancement, and it can transform the magnetic domain reversal mode from easy-nucleation (EN) to difficult-nucleation (DN). With increasing the diffusion depth, the shell of the core-shell structure gradually becomes thinner, DN grains gradually decrease while the EN grains gradually increase, indicating that the magnetic domain reversal mode is directly related to the core-shell structure.

Nd–Fe–B sintered magnets were heat-treated in Dy vapor atmosphere for achieving (Nd,Dy)–Fe–B magnets by grain boundary diffusion (GBD). The magnetic properties, microstructure, and corrosion resistance of (Nd,Dy)–Fe–B magnets were systematically investigated. Results show that the intrinsic coercivity of magnets increases significantly after Dy diffusion. Dy atoms penetrate into the magnets through the grain boundaries, which not only increase the total amount of rare earth and widen the grain boundary but also form (Nd,Dy)2Fe14B phase with higher anisotropic field on the grain surface layer. The intrinsic coercivity $H_{\mathrm {cj}}$ of (Nd,Dy)–Fe–B magnets increases from 16.86 to 21.60 kOe. When the testing time of highly accelerated aging tester is 96 h, the weight loss of pristine Nd–Fe–B magnets is 0.436 mg/cm2, while that of (Nd,Dy)–Fe–B magnets is 1.922 mg/cm2. The results of weight loss test and potentiodynamic polarization curves show that the corrosion resistance of (Nd,Dy)–Fe–B magnets is worse than that of pristine magnets due to more rare earth amount and wider grain boundary.

Nanostructured anisotropic Nd-Fe-B/Fe(C) composite powders were prepared by coating Fe(C) soft-magnetic nanoparticles on HDDR Nd-Fe-B hard magnetic powders using iron pentacarbonyl Fe(CO)5 as soft-phase precursor. The effect of Fe(CO)5-loading amount on soft-phase purity, coating morphology and magnetic properties of the composite powders was investigated. Dense and continuous Fe(C) soft-phase coatings with average particle sizes of 58–68 nm are obtained at Fe(CO)5 loading amounts of x ≤ 12 wt%, leading to enhanced remanence and improved energy product of the coated powders. Positive value in δM-plots and single-phase-like demagnetization curves are observed in the Nd-Fe-B/Fe(C) composite powders, indicating the exchange coupling effect between the coated Fe(C) soft phases and the Nd-Fe-B hard phase.

It is highly desired to simplify the technology of electroless plating on inert polymer. Herein we developed a new kind of catalytic solution (mixture of H2O, AgNO3 and 3-aminopropyltriethoxysilane), which can write onto inert polymer directly with good stability, resolution and catalytic performance. Then, a facile method combined with catalyst solution printing and electroless plating to fabricate selective metal (copper and nickel) coating on polymer (polypropylene and polyethylene terephthalate) surface. The growth behavior, electrical, and structural properties of plated coating were investigated. The minimum width of copper coating is 250 μm, thickness is 2.2 μm, resistivity is 2.6 × 10−6 Ω cm, adhesion of 2.2 μm thick coating maintain 5B. In addition, the selective metal coating have excellent bending and fatigue resistance.

In this work, a facile method combined with catalyst solution (mixture of AgNO3, 3-aminopropyltriethoxysilane, alcohol, SiO2 particle and deionized water) printing and electroless deposition to fabricate selective copper coating is demonstrated. The catalyst solution can write onto (polyethylene terephthalate (PET)) surface directly with good stability and resolution. The structure can catalyze plating reaction. SiO2 particle can enhance surface roughness (Sr) of catalyst coating. Effects of Sr on electronic, adhesive force and structural properties of copper coating are investigated. High Sr can facilitate the enhancement of Ag-adsorbed amount, deposition rate, adhesive force, crystallinity and electrical stability of plated coating. When the Sr is 0.78 µm, the thickness of copper coating is 2.5 µm, minimum width of copper line is 250 µm, the resistivity is 2.1 × 10−6 Ω cm, adhesion of 2.5 µm thick coating is 5B.

Amino acid sequence from 65th to 76th residue of the N-terminus of Chromogranin A (CGA-N12) is an antimicrobial peptide (AMP). Our previous studies showed that CGA-N12 reduces Candida tropicalis mitochondrial membrane potential. Here, we explored the mechanism that CGA-N12 collapsed the mitochondrial membrane potential by investigations of its action on the mitochondrial permeability transition pore (mPTP) complex of C. tropicalis. The results showed that CGA-N12 induced cytochrome c (Cyt c) leakage, mitochondria swelling and led to polyethylene glycol (PEG) of molecular weight 1000 Da penetrate mitochondria. mPTP opening inhibitors bongkrekic acid (BA) could contract the mitochondrial swelling induced by CGA-N12, but cyclosporin A (CsA) could not. Therefore, we speculated that CGA-N12 could induce C. tropicolis mPTP opening by preventing the matrix-facing (m) conformation of adenine nucleotide transporter (ANT), thereby increasing the permeability of the mitochondrial membrane and resulted in the mitochondrial potential dissipation.

A easy method to prepare selective copper coating on polyethylene terephthalate (PET) surface via writing activated solution on primer-modified PET sheet combined with electroless plating is demonstrated, the effects of PET surface structure on resolution and adhesion of copper coating were investigated. Results showed that the PET sheet modified with different primer (SiO2 particles-emulsion mixed liquors) could adsorb the stannum(II) and silver ions, which used as catalyst for selective electroless copper plating. When the SiO2 content increased from 0% to 10%, average surface roughness value, Ag-adsorption capability, plated coating thickness and adhesive force of thick plated coating were enhanced, surface resistivity was decreased, but resolution of activated coating was firstly enhanced and then reduce. The average roughness value was measured to be 12 μm for PET sheet modified with 6% SiO2-primer, resulting in good wettability and high resolution simultaneously. The region-selective copper coating could plate on PET surface and through hole, leading to a high conductivity of both sides. The plated coating was a composite of continuous layer of copper and randomly scattered SiO2 particles, resulting in a better adhesion of the copper coating. The minimum width of copper line was about 250 μm and the thickness of copper coating was 2.4 μm, surface resistivity was 8.6 × 10−6 Ω cm. No matter how the region-selective plated PET sheet was compressed or stretched, even for folded sheet, conductivity and mechanical properties were not affected.

The corrosion behavior of zinc subjected to Liaoning Hongyanhe nuclear power station (a typical coastal-industrial atmospheric environment) has been investigated by weight-loss measurement, scanning electron microscopy (SEM) observation, x-ray diffraction (XRD), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental results reveal that the corrosion kinetics of the corrosion of zinc in coastal-industrial atmospheric environment followed empirical equation D = At n , and with the increase of the exposure time polarization resistance ( R p ) and charge transfer resistance ( R ct ) increased, the corrosion rate decreased gradually. XRD, SEM and EDS indicated that the depth and width of all pits increased with time and the surface corrosion gradually transformed into a uniform corrosion. The components of the rust layers were composed of Zn 5 (CO 3 ) 2 (OH) 6 , NaZn 4 SO 4 Cl(OH) 6 ·6H 2 O and Zn 12 (OH) 15 Cl 3 (SO 4 ) 3 ·5H 2 O. In the initial exposure period, the corrosion products was Zn 5 (CO 3 ) 2 (OH) 6 , while with prolonged exposure, a two-layer structured corrosion products formed, which were comprised of NaZn 4 (SO 4 )Cl(OH) 6 ·6H 2 O and Zn 12 (OH) 15 Cl 3 (SO 4 ) 3 ·5H 2 O, all these products were flaky-structured and compact enough to provide excellent protection.

A new reduction–diffusion method for preparing submicron-sized Sm2Fe17N3 was developed. First, submicron-sized α-Fe/Sm2O3 composite precursors with good dispersibility were prepared directly by ultrasonic spray pyrolysis and hydrogen reduction (USP-HR). Then, the precursor was successfully converted into Sm2Fe17N3 powder by Ca reduction–diffusion and nitridation. The results displayed that the precursor prepared by USP-HR was a monodisperse homogeneous composite of spherical particles of α-Fe and Sm2O3. α-Fe and Sm2O3 exist in an intercalated structure in the composite spherical particles. This creates conditions for the preparation of ultrafine Sm2Fe17N3 particles with uniform sizes and dispersity. The results show that Sm2Fe17N3 is a single-phase, composed of submicron-sized particles with no other impurity phases. The physical property measurement system shows that the coercivity of 0.616 ± 0.347 µm particles reaches 14.7 kOe.

In this paper, Fe-based soft magnetic composites (SMCs) hydrothermally coated with lithium aluminum oxide (Li–Al–O) with better magnetic properties and lower core losses than Al2O3 coated layers have be investigated. The microstructure and composition of the coating and magnetic properties of the composites were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and B–H curve analyzer. Those results revealed that when Li2CO3 was added to the aluminum nitrate solution, the originally formed Al2O3 coating layer converted to a layer with a mixture of several lithium aluminum oxides. Fe-based SMCs coated with lithium aluminum oxide showed lower core losses, higher and stable effective permeability as compared with iron rings coated with Al2O3, especially in high frequency range of 100–300 kHz.

Electroless plating on polymer surface is a low-cost process for surface metallization, but it exhibits low adhesive force and complex production process, which makes it difficult for practical application. We employ a facile method combined with novel catalyst solution printing and electroless plating to fabricate high-adhesion copper coating on (polyethylene terephthalate (PET). The catalyst solution is a mixture of AgNO3, PVA, KH550, alcohol and deionized water. On the one hand, hydrophilic PVA and hydrophobic KH550 condense to helical conformation catalyst solution, which could synergistically absorb Ag. On the other hand, the two phases separation structure facilitate the formation of roughness surface. As a result, the catalyst solution can form highly active polymer brush/Ag particle structure on the PET surface, and realize to modify and activate PET simultaneously. Region-selective copper coating could plate on PET surface, the maximum effective thickness is 3.6 μm, rupture work is 4.5 J/m2, adhesion is 5B, electrical resistivity is 2.3 × 10−6 Ω cm. While maintaining reliability even after over 6 times of folding test and 1000 times of bending. Our results provide the underlying insights needed to guide the design of the fabrication of metal polymer.

In this work, a facile method combined with PdCl2 solution immersing and electroless deposition to fabricate nickel-plated plant fiber non-woven sheet is demonstrated. The effect of [Formula: see text] concentration on the structural property of plated sheet was investigated using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. Results showed that increasing activated time and PdCl2 concentration would facilitate the enhancement of Pd-adsorbed amount on the substrate surface. It would facilitate the deposition of nickel atom, the reduction of the surface electrical resistivity and the crystallization of plated coating due to the high catalytic sites. In addition, the lowest PdCl2 effective concentration was reduced with the increased of activated time.

Nd-Fe-B sintered magnets with different thicknesses of up to 10 mm were fabricated by combining TbH3 nanoparticles as diffusion sources and the grain boundary diffusion (GBD) technique. TbF3 microparticle-diffused magnets were also prepared for comparison. TbH3 nanoparticles diffusion increased the coercivity by 6.9 kOe for the magnets with thicknesses of 10 mm, which is 5.21 kOe larger than that of TbF3 microparticle-diffused magnets. Deeper, thicker and consecutive (Nd,Tb)2Fe14B layers are observed in TbH3 nanoparticle-diffused magnets compared to TbF3 microparticles, indicating the superiority of TbH3 nanoparticles in the GBD process, which can effectively inhibit the nucleation of reversed domains and thus enhance the coercivity.

The effect of heat treatment on the microstructure and thermal stability of sintered Nd-Fe-B magnets was investigated. The results show that the microstructure of the magnets was greatly affected by heat treatment. The intrinsic coercivity (Hcj) was increased and the temperature coefficient of coercivity (β) was decreased by heat treatment. As the annealing temperature changes from 500°C to 770°C, Hcj first increases and reaches a maximum, then starts to decrease, but β remains unchanged from 500°C to 680°C and increases rapidly when annealed over 680°C. A magnet with Hcj= 30.55 kOe, β (from 20°C to 200°C) = -0.4079%°C was obtained after annealed at 620°C for 2 h. The relationship between the annealing temperature and magnetic properties was studied.

The effects of DyHx addition on magnetic properties and microstructure of Nd-Fe-B sintered magnets were investigated. In order to obtain the best magnetic properties, the effects of sintering temperature and annealing time on magnetic properties were also investigated. The results shown that the addition of DyHx can affect the microstructure, increase the intrinsic coercivity (Hcj), and improve the thermal stability of sintered Nd-Fe-B magnets. The remanence (Br) and Hcj showed different variation trends as sintering temperature changes. Within a reasonable range, sintering at higher temperature can get higher Br but lower Hcj. The Hcj was further increased by heat treatment and annealing time was extended.

The effects of hydriding degree on the microstructure and magnetic properties of sintered NdFeB magnets have been studied. The degree of crushing depends on the absorption content of hydrogen and affects the magnetic properties of final magnet. Insertion of hydrogen atoms leads to a significant increase of the unit cell volume. And the crush mechanism depends on the internal stress resulting from differences in the expansion rates of the two phases. The remanence of final magnets increases monotonously while the coercivity decreases sharply with the increasing of hydriding degree, attributed to the strip fracture features and the morphology of particles.