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Annealing has been widely recognized as a crucial approach to modify the microstructure and enhance the coercivity of Nd–Fe–B magnets. However, in the context of Nd–Y–Ce–Fe–B magnets with multiple rare earths (REs) exhibiting different diffusion behaviors, annealing effects on the magnetic properties become more complicated and remain unknown. In present work, through a comparative study between as-sintered and annealed Nd–Y–Ce–Fe–B magnet upon 50 wt% Y–Ce co-substitution of total REs, we found that annealing process surprisingly enhances the remanence from 1.17 to 1.20 T, with simultaneous coercivity increment from 612.9 to 660.7 kA·m−1, resulting in drastically improved maximum energy product from 242.0 to 263.5 kJ·m−3. Such a peculiar remanence enhancement is closely correlated to the preferential Y/Nd infiltration into RE2Fe14B main phase and Ce segregation into REFe2 intergranular phase, which consequently improve the intrinsic magnetism, as evaluated by Curie temperature (TC), saturation magnetic polarization (JS) and magnetocrystalline anisotropy field (HA). Present work delights that different metallurgical behaviors of Nd/Y/Ce exert influential effects on the intrinsic and extrinsic magnetic properties and provide a novel approach toward high-performance 2:14:1-type permanent magnets based on abundant RE mixtures.

Anisotropy engineering serves as an effective method to achieve unique properties and enhanced performance of materials. Here MOF-71 and derivatives with tuned anisotropy have been achieved via facial tuning the proticity of the solvents, giving rise to nanoflake assemblies into bellows-, boat- and flower-like microstructures. Three anisotropy dimensions including Faceting, Aspect ratio and Arrangement have been proposed to describe the anisotropy of the assemblies, which are further evaluated by heterotype ( H ¯ ), flatness ( F ¯ ) and orderliness ( O ¯ ). Combined off-axis electron holography and electromagnetic scattered field simulation visualize uniform distribution of magnetic lines due to enhanced anisotropy of the bellows-like derivatives. This gives rise to strengthened magnetic loss and electromagnetic wave absorption for the anisotropy evolution from the flower-, boat-to bellows-like structure. As such the work not only provides versatile strategy for anisotropy engineering and reification of the anisotropy for complicated assembled structures, but also insights on impacts of the anisotropy on the distribution of stray field, magnetic dipoles and scattered field for the design of electromagnetic absorbers, which are extendable to various areas including but not limited to magnetics, electrics and optics.

MnZn soft magnetic ferrites have been widely utilized in power electronics, owing to the combined merits of high permeability and low energy loss. However, their deployment would result in a drastic increase in power dissipation at >3 MHz, thus limiting the scope extent of miniaturization, together with their efficiency. Here, we report a high-performance MnZn ferrite by doping multiple ions (La, Ti, Si, Ca) at grain boundaries, achieving the most optimized power loss of 267 kW/m3 at 5 MHz (10 m T, 100 °C) and initial permeability of 644, which is much better than the previously reported results and commercial products. Such an improvement is attributed to weakened magnetic exchange coupling at grain-boundary regions, associated with a significant transition from the multi- to mono-domain structures, originating physically from large crystallographic mis-orientations (>25°). The present study bears important significance in understanding the intrinsic correlation between the crystallographic mis-orientation and magnetic domain structure, and provides an alternative way for optimizing high-frequency soft magnetic ferrites.

The formation of ordered magnetic domains in thin films is important for the magnetic microdevices in spin-electronics, magneto-optics, and magnetic microelectromechanical systems. Although inducing anisotropic stress in magnetostrictive materials can achieve the domain assembly, controlling magnetic anisotropy over microscale areas is challenging. In this work, we realized the microscopic patterning of magnetic domains by engineering stress distribution. Deposition of ferromagnetic thin films on nanotrenched polymeric layers induced tensile stress at the interfaces, giving rise to the directional magnetoelastic coupling to form ordered domains spontaneously. By changing the periodicity and shape of nanotrenches, we spatially tuned the geometric configuration of domains by design. Theoretical analysis and micromagnetic characterization confirmed that the local stress distribution by the topographic confinement dominates the forming mechanism of the directed magnetization.

The demand for high-performance spintronic devices has boosted intense research on the manipulation of magnetism in van der Waals (vdW) magnets. Despite great efforts, robust ferromagnetic transitions above room temperature still face significant hurdles. Strain engineering can reversibly regulate magnetic exchange, but the degree of regulation is still impractical for most magnetic applications. Hereby we employ a large-strain transferrer to produce tunable strains of up to 4.7%, which induces authentic room-temperature ferromagnetism in large-area Fe3GeTe2 nanoflakes with 20-fold improvement in magnetization. The record increment of the Curie temperature (TC) of well above 400 K originates from the strain-enhanced magnetic anisotropy and excellent magnetoelastic coupling. The correlation between the emerging ferromagnetism and Raman spectral evolution is also established, which complements well the TC phase diagram in a large-strain region. In addition, an unusual exchange bias effect with a vertical magnetization shift is tracked for the first time upon bending, which reveals the hidden competition between antiferromagnetic and ferromagnetic coupling. The reversible strain manipulation of single-domain ferromagnetic order in a single nanoflake further opens up a route to develop low-power wearable spintronic devices. The findings here provide vast opportunities to exploit the possibility of practical applications of more vdW magnets.

The chain-like carbon nanotubes (CNTs) decorated with CoFeB (CoFeB/CNTs) prepared by oxidation-reduction method is introduced into MgH2 to facilitate its hydrogen storage performance. The addition of CoFeB/CNTs enables MgH2 to start desorbing hydrogen at only 177 °C. Whereas pure MgH2 starts hydrogen desorption at 310 °C. The dehydrogenation apparent activation energy of MgH2 in CoFeB/CNTs doped-MgH2 composite is only 83.2 kJ/mol, and this is about 59.5 kJ/mol lower than that of pure MgH2. In addition, the completely dehydrogenated MgH2−10 wt% CoFeB/CNTs sample can start to absorb hydrogen at only 30 °C. At 150 °C and 5 MPa H2, the MgH2 in CoFeB/CNTs doped-MgH2 composite can absorb 6.2 wt% H2 in 10 min. The cycling kinetics can remain rather stable up to 20 cycles, and the hydrogen storage capacity retention rate is 98.5%. The in situ formation of Co3MgC, Fe, CoFe and B caused by the introduction of CoFeB/CNTs can provide active and nucleation sites for the dehydrogenation/rehydrogenation reactions of MgH2. Moreover, CNTs can provide hydrogen diffusion pathways while also enhancing the thermal conductivity of the sample. All of these can facilitate the dehydrogenation/rehydrogenation performance and cyclic stability of MgH2.

C16H11N5O10S, triclinic, P 1 ‾ $P‾{1}$ (no. 2), a = 4.6658(1) Å, b = 12.2129(4) Å, c = 17.0355(5) Å, α = 74.925(2)°, β = 86.398(2)°, γ $\gamma $ = 88.040(2)°, V = 935.31(5) Å3, Z = 2, R gt (F) = 0.0642, wR ref (F 2) = 0.1744, T = 295 K.

Crystal morphology has a significant effect on the properties and applications of energetic materials (EMs). Here, we have combined the single-crystal X-ray diffraction (SCXRD) and rotation imaging...

The solid-state magnetic cooling (MC) relying on magnetocaloric effect (MCE) of magnetic materials is recognized as a promising energy efficiency and environmentally friendly technology. However, there is still a large gap between the fundamental materials in the laboratory developing stage and the practically realizable applications. In this paper, a new series of B-site ordered RE2ZnMnO6 (RE = Gd, Dy and Ho) perovskites are successfully fabricated, and their structural and magnetic properties together with the cryogenic magnetocaloric performances are studied in detail. All the RE2ZnMnO6 compounds are found to crystallize in the B-site ordered orthorhombic (double perovskites) structure with the space group of P121/C1. The magnetic ground state are confirmed to be a ferromagnetic (FM) coupling for Gd2ZnMnO6, whereas, ferrimagnetic (FIM) coupling for Dy2ZnMnO6 and Ho2ZnMnO6 based on the magnetic measurements and first principle calculations. The ordering temperatures (TM) are determined to be ~6.4 K for Gd2ZnMnO6, ~10.4 K for Dy2ZnMnO6, and ~6.8 K for Ho2ZnMnO6, respectively. Furthermore, several vital parameters for determining the magnetocaloric performances including -ΔSMmax (magnetic entropy change peak values), TEC(2) (temperature-averaged magnetic entropy change) and RCP (relative cooling powers) are evaluted to be 15.17, 14.44 J/(kgK) and 226 J/kg for Gd2ZnMnO6, 8.32, 8.17 J/(kgK) and 208 J/kg for Dy2ZnMnO6, and 13.19, 12.68 J/(kgK) and 246 J/kg for Ho2ZnMnO6, with the field change ΔH = 50 kOe, respectively. It is worthly noted that Gd2ZnMnO6 exhibits relatively great magnetocaloric performances below 10 K, which suggests that Gd2ZnMnO6 is a competitive candidate for cryogenic magnetic cooling.

Waste sorting is being gradually implemented as a key measure for circular and sustainable development in China, food waste will be separately collected and separated from municipal solid waste (MSW), thus the plastic content in food waste also will be reduced. In this study, supercritical water gasification (SCWG) of food waste with different contents of plastic (0–3.5 wt%) was experimentally investigated to simulate the influence of waste sorting on the food waste treatment. The results showed that lower plastic content in food waste favored higher gas yield and gasification efficiencies. The highest H2 yield and total gas yield were 3.11 mol/kg and 8.41 mol/kg in the plastic-free case, respectively. When the plastic content decreased from 3.5 wt% to 0 wt%, the cold gas efficiency (CGE), carbon conversion efficiency (CE) and hydrogen gasification efficiency (HE) increased by 125.97%, 173.48% and 94.09%, respectively. However, lower plastic content negatively affected the quality of produced syngas through decreasing H2 mole fraction and LHV. The solid residues from SCWG of food waste with lower plastic content had higher ratio of fixed carbon to volatile matter (FC/VM). Based on the analysis of pyrolysis properties and combustion behavior, decreasing the plastic content in food waste helped to improve the thermal stability of solid residues. Moreover, lower plastic content resulted in a decrease of total organic carbon (TOC) concentration in liquid effluent, which is favorable for further treatment of liquid effluent.

Massive rare earth oxides inevitably form at high La–Ce substitution, causing inadequate liquid-phase-sintering, direct exchange coupling of ferromagnetic grains, obscure core–shell morphology and severe coercivity degradation of multi-main-phase (MMP) Nd–La–Ce–Fe–B sintered magnets. To fully exploit the abundant La–Ce for application, here we designed a facile approach, (Pr, Nd)Hx grain boundary diffusion that combines the joint benefits of forming thick non-ferromagnetic grain boundary layer and PrNd-rich hardening shell, yielding a nearly threefold coercivity of 14.2 kOe with enhanced energy product of 38.5 MGOe for LaCe-40 magnet. These findings suggest a reliable recipe for relieving the main constraints of MMP Nd–La–Ce–Fe–B magnets.

A crystal engineering strategy has been adopted to prepare porous high explosive, cyclotrimethylenetrinitramine (RDX). Raw RDX was crystallized with TMS, CAM and HMPT (TMS=Tetramethylene Sulfone, C...

The influences of minor Y addition on the thermal stability, crystallization behavior, magnetic property and bending ductility of Fe–Si–B amorphous ribbons have been systematically investigated. The results show that all the ribbons with Y addition are fully amorphous structure, and the introduction of Y can enhance the glass forming ability of Fe–Si–B amorphous alloy. With Y addition, crystallization temperature of the first and second phase shift to high temperature side, the temperature interval between the two crystallization peaks are enlarged, the third phase transitions process of Fe–Si–B amorphous alloy with Y addition corresponds to the precipitation of Fe3B phase. The activation energy of the first and second phase calculated by Kissinger’s formula increased with Y addition. Appropriate Y addition is beneficial for Ms. The measured coercivity Hc gradually decreased with the Y addition increased. The amorphous alloys exhibit good bending ductility in the quenched state. The ductile to brittle temperature increase to 300 °C with 1 at% Y addition. Furthermore, the mechanism of ductile to brittle for amorphous alloy was discussed.

Parabolic trough collector is the most mature and widely deployed concentrated solar power technology with temperature ranging from 325 to 700 K. In this study, three different absorber tube geometries (smooth absorber tube, absorber tube with twisted tape insert and tube with longitudinal fins) of commercially available LS-2 collector are modeled and investigated using engineering equation solver. The objective of this study is to present a numerical comparative analysis of the available thermal enhancement techniques. Comprehensive energetic and exergetic performance of different tube geometry configurations using Al2O3/water as a heat transfer fluid has been compared to assess the nature of exergy destruction due to the fluid’s pressure, due to the heat transfer between sun and the receiver wall and due to the temperature difference between receiver wall and heat transfer fluid temperature. Furthermore, pure base fluid (water) along with the nanofluid is used to evaluate the system’s performance (thermal efficiency, exergetic efficiency, heat transfer coefficient, receiver temperature, pressure drop, pumping work demand and friction factor). Smooth absorber tube with pure base fluid is the reference case, while five cases (smooth tube with nanofluid, tube with pure water and fins inserted, tube with nanofluid and fins inserted, tube with pure water and twisted tape inserted, tube with nanofluid and twisted tape inserted) are investigated. Thermal efficiency of absorber tube with twisted tape insert and nanofluid is almost 72.26%, followed by tube with internal fins (72.10%), while smooth absorber tube has nearly 71.09%. Heat transfer coefficient of twisted tape inserted tube with nanofluid and longitudinal fins tube with nanofluid is greater than smooth absorber tube to almost 118.23% and 103.26%, respectively. The emphasis is also given to the pressure drop of the examined cases as it depends up on the friction factor of the absorber tubes. The use of nanofluid and twisted tape inserts leads to higher thermal enhancement, followed by the nanofluid and internal fins inserted tube. The nanoparticle concentration is also varied to investigate its effect on different performance parameters of the system.

In order to improve the hydrogen storage performance of MgH2, graphene and CeF3 co-catalyzed MgH2 (hereafter denoted as MgH2+CeF3@Gn) were prepared by wet method ball milling and hydriding, which is a simple and time-saving method. The effect of CeF3@Gn on the hydrogen storage behavior of MgH2 was investigated. The experimental results showed that co-addition of CeF3@Gn greatly decreased the hydrogen desorption/absorption temperature of MgH2, and remarkably improved the dehydriding/hydriding kinetics of MgH2. The onset hydrogen desorption temperature of Mg + CeF3@Gn is 232 °C，which is 86 °C lower than that of as-milled undoped MgH2, and its hydrogen desorption capacity reaches 6.77 wt%, which is 99% of its theoretical capacity (6.84 wt%). At 300 °C and 200 °C the maximum hydrogen desorption rates are 79.5 and 118 times faster than that of the as-milled undoped MgH2. Even at low temperature of 150 °C, the dedydrided sample (Mg + CeF3@Gn) also showed excellent hydrogen absorption kinetics, it can absorb 5.71 wt% hydrogen within 50 s, and its maximum hydrogen absorption rate reached 15.0 wt% H2/min, which is 1765 times faster than that of the undoped Mg. Moreover, no eminent degradation of hydrogen storage capacity occurred after 15 hydrogen desorption/absorption cycles. Mg + CeF3@Gn showed excellent hydrogen de/absorption kinetics because of the MgF2 and CeH2-3 that are formed in situ, and the synergic catalytic effect of these by-products and unique structure of Gn.

Ni/Al2O3 catalyst is the one of promising catalysts for enhancing H2 production from supercritical water gasification (SCWG) of biomass. However, due to carbon deposition, the deactivation of Ni/Al2O3 catalyst is still a serious issue. In this work, the effects of lanthanum (La) as promoter on the properties and catalytic performance of Ni/Al2O3 in SCWG of food waste were investigated. La promoted Ni/Al2O3 catalysts with different La loading content (3–15 wt%) were prepared via impregnation method. The catalysts were characterized using XRD, SEM, BET techniques. The SCWG experiments were carried out in a Hastelloy batch reactor in the operating temperature range of 420–480 °C, and evaluated based on H2 production. The stability of the catalysts was assessed by the amount of carbon deposition on catalyst surface and their catalytic activity after reuse cycles. The results showed that 9 wt% La promoter is the optimal loading as Ni/9La–Al2O3 catalyst performed best performance with the highest H2 yield of 8.03 mol/kg, and H2 mole fraction of 42.46% at 480 °C. La promoted Ni/Al2O3 catalysts have better anti-carbon deposition properties than bare Ni/Al2O3 catalyst, resulting in better gasification efficiency after reuse cycles. Ni/9La–Al2O3 catalyst showed high catalytic activity in SCWG of food waste and had good stability as it was still active for enhancing H2 production when used in SCWG for the third time, which indicated that La promoted Ni/Al2O3 catalysts are potential additive to improve the SCWG of food waste.

REFe2 (RE = rare earth) phase has been considered to form spontaneously in Nd-Ce-Fe-B cast strips and inherit into sintered magnets. However, here we report that REFe2 phase, which is absent in starting strip, occurs in as-sintered magnet with an identical composition of 25 wt% Ce. More interestingly, the formation of REFe2 induces apparent Ce-enriched shell surrounding RE2Fe14B grain, which is further exacerbated in annealed magnet containing a higher fraction of REFe2 phase. Influences of increasing REFe2 fraction on magnetic performance are revealed. Above findings on REFe2 phase evolution and resultant Ce segregation may shed lights on fabricating high-performance Nd-Ce-Fe-B.

An integrated system of supercritical water gasification (SCWG) and combined cycle has been developed for H2 production and power generation. Sewage sludge and lignite coal were selected as raw material in this simulation. The effects of feed concentration (10–30 wt%) and lignite coal addition (0–50 wt%) on syngas yield and H2 yield were also investigated in the temperature range of 500 °C–700 °C. Several heat exchangers were considered in the proposed integrated system to minimize energy loss. High pressure syngas was expanded by using turbo-expander to produce electricity, resulting in the improvement of the total efficiency. The results showed that the minimum feed concentrations of 14.25 wt%, 18.75 wt%, and 25.50 wt% were required to achieve self-sufficient energy at 500 °C, 600 °C, and 700 °C, respectively. However, the lower feed concentration and higher temperature were preferable for syngas production. The highest syngas and H2 yield were obtained at 700 °C and 10 wt% feed concentration. The SCWG could produce 178.08 kg syngas from 100 kg feed and 9.06 kg H2 were obtained after H2 separation. The total power generation from turbo-expander and combined cycle module was 48.37 kW. By combining SCWG and combined cycle, the total efficiency could reach 63.48%. It worth mentioning that the addition of lignite coal could help reduce the minimum feed concentration to achieve autothermal condition, but did not have significant improvement on H2 production.

Food waste is a kind of wet bio-waste which has been a challenge for the ecological environment and disposal. In this paper, hydrogen production from subcritical water gasification (SbWG) of food waste with and without catalyst loading was systematically investigated. The effects of reaction temperature (300–360 °C), residence time (30–90 min), food waste concentration (10–30 wt%) and catalysts (Ni/γ-Al2O3, Ni/ZrO2, NaOH, KOH, and FeCl3) were studied within a pressure range of 10.5–20 MPa. The optimal process condition for SbWG of food waste without catalysts loading was determined to be 360 °C and 90 min with 10 wt% food waste. The liquid products and hydrochar were characterized by TOC, TGA/DTG, and SEM. The TOC concentration of liquid products decreased vastly with increasing reaction temperature. The highest H2 yield (1.88 mol/kg), H2 mole fraction (35.01%), and H2 selectivity (53.86%) were achieved at 360 °C for 90 min with 5 wt% loading of KOH. It can be concluded that the performance of the catalysts for improving hydrogen production in SbWG of food waste was in the following order: KOH > NaOH > Ni/γ-Al2O3 > Ni/ZrO2 > FeCl3. The catalytic SbWG can be a potential alternative for energy conversion of food waste and hydrogen production.

Surface nitridation has been used to fabricate the insulation coatings of the Fe, FeSi, FeSiAl and FeSiCr soft magnetic composites (SMCs). Effects of the nitridation conditions on the magnetic performance of the SMCs have been investigated. Detailed growth mechanism and models of the coating layers for different alloy systems have been established based on combined thermodynamic and kinetics analysis. For Fe and FeSi SMCs, nitride coatings containing α-Fe(N) forms, while coexistenc of α-Fe(N) and Fe4N is obtained for the FeSiAl SMCs. For the FeSiCr system, the nitride coating is composed of α-Fe(N) and CrN with relatively large electrical resistivity, giving rise to enhanced magnetic performance compared with that of the SMCs prepared via traditional phosphoric acid passivation.

This paper presents the results from experimental study of syngas production by catalytic cracking of tar in wastewater under supercritical condition. Ni/Al2O3 catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina, and calcined at 600 °C for 4 h. All catalysts showed mesoporous structure with specific surface area in a range of 146.6–215.3 m2/g. The effect of Ni loading (5–30 wt%), reaction temperature (400–500 °C), and tar concentration (0.5–7 wt%) were systematically investigated. The overall reaction efficiency and the gas yields, especially for H2, were significantly enhanced with an addition of Ni/Al2O3 catalysts. With 20%Ni/Al2O3, the H2 yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 °C with the addition of 20%Ni/Al2O3 had a comparable efficiency to the reaction without catalyst at 500 °C. The maximum H2 yield of 46.8 mol/kgtar was achieved with 20%Ni/Al2O3 at 500 °C and 0.5 wt% tar concentration. The catalytic performance of the catalysts gradually decreased as the reuse cycle increased, and could be recovered to 88% of the fresh catalyst after regeneration. 20%Ni/Al2O3 has a potential to improve H2 production, as well as a good reusability. Thus, it is considered a promising catalyst for energy conversion of tar in wastewater.

The Fe–Si–B amorphous ribbons with various CO ventilation amount were prepared by planar-flow melt spinning method. The effect of CO gas on surface quality, magnetic properties and core loss of amorphous ribbons were investigated. With the increasing CO ventilation, the wheel side surface roughness, average air pocket size and air pocket quality decrease, the ribbon grows thicker, but air side surface roughness remains almost no changes. The three samples have reached to a fully amorphous structure. Meanwhile the diffraction angle corresponding the maximum intensity of each broad diffraction peak decrease slightly with increasing CO ventilation. There is no significant differences in the onset temperate of second exothermic peak (Tx2) and the crystallization peak temperature (Tp1 and Tp2) among the amorphous ribbons prepared with various CO ventilation, but the onset temperate of first exothermic peak (Tx1) increases slightly with the increasing CO ventilation. The room temperature hysteresis loops of amorphous ribbons show that surface quality have significant effect on magnetic properties. The coercivity (Hc), core loss (P1.35/50), magnetic polarization (B80) and permeability (µ) among the ribbons are improved with better surface quality, though the saturation magnetic flux density almost keeps same. Core loss are separated by the scaling theory, and experiment dates show a good agreement with the predicted data. Thus the scaling theory is suitable for Fe–Si–B amorphous alloys. The surface quality has more significant effect on hysteresis losses than eddy current loss at low frequency.

Magnetostriction deterioration has been observed in slowly cooled Fe-Ga alloys when compared with the high temperature quenched ones. To reveal the underlying origin, here we investigated the microstructure of Fe81Ga19 thin-sheet samples quenched after slow cooling (at ∼0.3 K/min) to near and below the decomposition phase boundary between A2 and (A2’ + L12) phases. In comparison with the sample quenched at 1273 K (much higher than the decomposition phase boundary, ∼793 K) or the one quenched near the decomposition boundary (773 K), magnetostriction deterioration is observed for the one quenched below the decomposition boundary (673 K). Besides the A2 matrix phase, quenching at 673 K also promotes the formation of secondary L12 phase with negative magnetostriction and the phase transformation induced dislocations located close to the grain boundaries. Simultaneously, weak D03 ordering of the untransformed bcc matrix is also observed. All these microstructural changes deteriorate the magnetostriction. Our work provides important information why the magnetostriction of Fe81Ga19 greatly depends on the thermal history.

Two-step post-sinter annealing (PSA) treatment, due to its universal applicability, has been one of the most effective strategies for enhancing the coercivity of Nd-Fe-B sintered magnets. Here we report a peculiar phenomenon that the as-sintered multi-main-phase (MMP) Nd-La-Ce-Fe-B magnet exhibits the highest reported to date coercivity of 13.0 kOe upon 25 wt% La-Ce substituting for Nd, combined with Br = 13.12 kG, and (BH)max = 41.67 MGOe. Further annealing cannot enhance the coercivity whereas the remanence and energy product are drastically lowered, i.e. to 11.0 kOe, 12.57 kG, and 38.71 MGOe after two-step PSA, being remarkably different from the conventional Nd-Fe-B. Microstructural analysis reveals that the as-sintered Nd-La-Ce-Fe-B magnet with coexisting REFe2 (Fd 3 ¯ m) and RE-rich (Fm 3 ¯ m) intergranular phases possesses continuous GB layer isolating adjacent ferromagnetic grains. Hence the beneficial role of PSA on modifying the microstructure and strengthening the coercivity is tiny. Additionally, high-temperature PSA destroys the initial chemical heterogeneity of MMP magnets, leading to the formation of REs homogeneously distributed grains and resultant reduction of the intrinsic magnetic properties. As evidenced by in-situ Lorentz TEM characterization, PSA sample with reduced chemical gradient exhibits quick domain wall motion, compared to the as-sintered one with basically unchanged magnetic domain structure upon the same applied field. The proof-of-principle micromagnetic simulation further confirms that retaining the inhomogeneous La/Ce/Nd distribution is essential to suppress the magnetic dilution effect. These findings demonstrate the realistic prospect of skipping PSA treatment in MMP magnets, which can not only reduce the production process and cost, but also delight the scenario for designing high-performance 2:14:1-type sintered magnets based on abundant La/Ce.

In this study, the model food waste was gasified to hydrogen-rich syngas in a batch reactor under supercritical water condition. The model food consisted of rice, chicken, cabbage, and cooking oil. The effects of the main operating parameters including temperature (420–500 °C), residence time (20–60 min) and feedstock concentration (2–10 wt%) were investigated. Under the optimal condition at 500 °C, 2 wt% feedstock and 60 min residence time, the highest H2 yield of 13.34 mol/kg and total gas yield of 28.27 mol/kg were obtained from non-catalytic experiments. In addition, four commercial catalysts namely FeCl3, K2CO3, activated carbon, and KOH were employed to investigate the catalytic effect of additives at the optimal condition. The results showed that the highest hydrogen yield of 20.37 mol/kg with H2 selectivity of 113.19%, and the total gas yield of 38.36 mol/kg were achieved with 5 wt% KOH addition Moreover, the low heating value of gas products from catalytic experiments with KOH increased by 32.21% compared to the non-catalytic experiment. The catalytic performance of the catalysts can be ranked in descending order as KOH > activated carbon > FeCl3 > K2CO3. The supercritical water gasification (SCWG) with KOH addition can be a potential applied technology for food waste treatment with production of hydrogen-rich gases.

Single-phase cobalt ferrite nanoparticles were synthesized by coprecipitation method and annealed at different temperatures. The structural, dielectric and magnetic properties were investigated, which showed an obvious dependence on annealing temperature. The average crystallite size increased from 20 to 60 nm with increase of annealing temperature. Meanwhile, the shape of nanoparticles also changed from spherical to octahedron and then cubic. Dielectric constant showed dispersion behavior and decreased with increasing annealing temperature, while the relaxation peaks observed in dielectric loss were shifted to lower frequencies. The ac conductivity originates from Polaron hopping which decreased with increase of crystallite size (less surface area and defect density) due to higher annealing temperature. The saturation magnetization increased from 59 to 81 emu/g and coercivity dropped from 1316 to 428 Oe with the increase of particle size.

3D asymmetric structure could induce asymmetric diffraction with spatial coupling behavior for various optical applications, but the study still faces challenges due to the complicated local-field coupling mechanism within structures. In this study, the spatial asymmetry based on inclined all-dielectric structure was theoretically modeled. The normal reflection of the 2D array shows that the increasing structural inclination selectively enhances the Fano resonance between different polarization directions which is mainly due to the oriented spatial coupling effect by increasing structural asymmetry, proved with the near-field distribution. The angular-resolved reflection shows the selected enhancement of first-order diffraction even over that of zero order by combining the structural asymmetry and oblique incidence. Our study provides a new insight for exploring asymmetric photonic structures and relative devices in practical applications.

Inferior intrinsic magnetic properties of (La/Ce)2Fe14B to Nd2Fe14B compound pose a big challenge for the Nd-La-Ce-Fe-B sintered magnets to provide an equivalent performance to the commercial Nd-Fe-B ones. To suppress the magnetic dilution, La/Ce distributions within 2:14:1 phase are intentionally tailored in the present work. At the same La-Ce substitution level of 12 wt%, the coercivity has been substantially increased to 1.36 T by constructing the coexisting Nd-rich shell @ La/Ce-rich core and La/Ce-rich shell @ Nd-rich core morphologies, compared to the La/Ce homogenously distributed magnet (0.76 T) and the one with singular Nd-rich core surrounded by La/Ce-rich shell (0.82 T). This is attributed to combined effects of magnetically hardening Nd-rich shell in suppressing the reversal domain nucleation, and continuous grain boundary layer in reducing the short-range exchange coupling between adjacent ferromagnetic grains. It may act as part of endeavors to promote the Nd-La-Ce-Fe-B sintered magnets for commercial application.

In this paper, a conceptual process design of the integrated supercritical water gasification (SCWG) and reforming process for enhancing H2 production has been developed. The influence of several operating parameters including SCWG temperature, SCWG pressure, reforming temperature, reforming pressure and feed concentration on the syngas composition and process efficiency was investigated. In addition, the thermodynamic equilibrium calculations have been carried out based on Gibbs free energy minimization by using Aspen Plus. The results showed that the higher H2 production could be obtained at higher SCWG temperature, the H2 concentration increased from 5.40% at 400 °C to 38.95% at 600 °C. The lower feed concentration was found to be favorable for achieving hydrogen-rich gas. However, pressure of SCWG had insignificant effect on the syngas composition. The addition of reformer to the SCWG system enhanced H2 yield by converting high methane content in the syngas into H2. The modified SCWG enhanced the productivity of syngas to 151.12 kg/100kgfeed compared to 120.61 kg/100kgfeed of the conventional SCWG system. Furthermore, H2 yield and system efficiency increased significantly from 1.81 kg/100kgfeed and 9.18% to 8.91 kg/100kgfeed, and 45.09%, respectively, after the modification.

In order to enhance the hydrogen storage properties of LiBH4, activated charcoal (AC) was used as the scaffold to confine LiBH4 in this paper. Ball milling was used to prepare LiBH4/AC composites. Experimental results show that dehydrogenation properties of ball-milled LiBH4/AC (LiBH4/AC-BM) are greatly improved compared with that of pristine LiBH4, ball-milled LiBH4 (LiBH4-BM) and hand-milled LiBH4/AC (LiBH4/AC-HM). The onset dehydrogenation temperature of LiBH4 for LiBH4/AC-BM is around 160 °C, which is 170 °C lower than that of pristine LiBH4. At around 400 °C, LiBH4/AC-BM finishes the dehydrogenation with a hydrogen capacity of 13.6 wt%, which is approximately the theoretical dehydrogenation capacity of pure LiBH4 (13.8 wt%), while the dehydrogenation processes for LiBH4-BM and LiBH4/AC-BM do not finish even when they were heated to 600 °C. The isothermal dehydriding measurements show that it takes only 15 min for LiBH4/AC-BM to reach a dehydrogenation capacity of 10.1 wt% at 350 °C, whereas the pristine LiBH4 and the LiBH4/AC-HM release hydrogen less than 1 wt% under the same conditions. The dehydrogenation process and the effect of AC were discussed.

Three inorganic-organic hybrids have been designed by incorporating epoxy-modified silicone resin (ESR) with SiO2, Fe3O4 and their mixture in the application as the coating of Fe soft magnetic composites (SMCs). The introduced SiO2 nanoparticles are well dispersed in the ESR, while the Fe3O4 tends to agglomerate or even separate from the ESR. Simultaneous addition of the SiO2 and Fe3O4 gives rise to satisfactory distribution of both nanoparticles and optimized magnetic performance of the SMCs with high permeability (124.6) and low loss (807.8 mW/cm3). On one hand, introduction of the ferromagnetic Fe3O4 reduces the magnetic dilution effect, which is beneficial for improved magnetization and permeability. On the other hand, SiO2 incorporation prevents the agglomeration of the Fe3O4 nanoparticles and gives rise to increased electrical resistivity for reduced core loss as well as enhanced mechanical strength of the SMCs.

Hydrolysis precipitation as a new method was used in the preparation of oxide insulation matrix for FeSiAl soft magnetic composites (SMCs). The growth and composition of the matrix can be tuned by the concentration of the Al(NO3)3 solution, reaction temperature and pH value during the hydrolysis. With optimized Al(NO3)3 concentration of 0.6 mol/L and hydrolysis temperature of 75 °C, two mechanisms have been revealed in the formation of the insulation coating depending on the pH of the Al(NO3)3 solution. When pH = 3, the coating layer contains a mixture of Al2O3 and Fe2O3, while Al2O3 and SiO2 form as the coating for pH = 8. Despite that the Al2O3 dominates for both conditions, it grows via different routes. The Al(OH)3 as the precursor forms through Al3+ hydrolysis and heterogeneous nucleation for pH = 3. With increased pH to 8, the Al3+ directly reacts with OH− to form Al(OH)3 colloidal particles which adsorb onto the surface of FeSiAl powders via electrostatic attraction. Both mechanisms give rise to satisfactory magnetic performance with high effective permeability (μe = 103.5 and 113.4) and low core loss (Pcv = 278.4 mW·cm−3 and 237.8 mW·cm−3) for pH = 3 and 8 measured at 100 mT, 50 kHz.

A novel principle of approaching an instable phase boundary (IPB) is developed for achieving large magnetostriction in Fe-Ga alloys. Unlike the usual approach by quenching at high temperature, the present Fe81Ga19 alloy was quenched near the decomposition phase boundary (773 K) between A2 and (A2 + L12) after slow cooling to approach the equilibrium condition. The obtained magnetostriction is 120 ppm, 71.4% higher than that of the sample quenched at high temperature (1273 K). The enhanced magnetostriction is due to the lattice softening by quenching near IPB, which may add important insight into developing high-performance magnetostrictive materials.

Multi-main-phase (MMP) Nd-Ce-Fe-B magnets prepared by sintering the mixture of Ce-free and Ce-containing RE 2 Fe 14 B (RE, rare earth) powders have been found to possess superior magnetic properties to the single-main-phase (SMP) ones. Purpose of this work is to further enhance the coercivity through restructuring the grain boundaries (GBs), which have strong influence on the short-range exchange coupling between adjacent grains. By incorporating 4 wt.% NdH x powders as the intergranular additive, coercivity of the (Pr, Nd) 22.3 Ce 8.24 Fe bal B 0.98 (wt.%) MMP magnet has been substantially increased from 8.2 kOe to 13.1 kOe. Magnetic domain characterizations and the recoil loop measurements showed that the exchange coupling between adjacent grains has been weakened significantly due to the formation of continuous and smooth RE-rich GBs by the extra Nd after NdH x dehydrogenation. Elemental distribution analysis revealed that thicker Nd-rich 2:14:1 shells with stronger magnetocrystalline anisotropy have been formed in the outer region of the Ce-rich main phase grains, which is beneficial to enhance their effective anisotropy. In addition, the Ce-rich 2:14:1 shells surrounding the Nd-rich 2:14:1 grain cores became thinner, which is beneficial to weaken the magnetic dilution effect of such grains. Micromagnetic simulation results also suggest that the coercivity can be further enhanced once the grain boundary is nonmagnetic. Technically, enriching RE elements or reducing Fe content can weaken the ferromagnetism of the grain boundary phase as well as the exchange coupling between adjacent grains. The above findings might shed new insights into enhancing the coercivity of low cost Nd-Ce-Fe-B magnets.

MnZn power ferrites for MHz and wide temperature applications were prepared by ceramic process and effects of Co2O3 and MoO3 co-doping on the microstructure and magnetic properties have been investigated, and MnZn power ferrite with ultra-high cut-off frequency of 14.2 MHz has been prepared. It has been revealed that the grain size of the MnZn ferrite can be homogenize via the co-doping of Co2O3 and MoO3, giving rise to enhanced electrical resistivity, compensated magnetocrystalline anisotropy and reduced domain wall displacement. Effective reduction of the power loss with improved temperature stability and cut-off frequency have been achieved by synergistic function of Co2O3 and MoO3 via liquid-phase sintering increasing the possibility of Co2+ cation entering into the spinel lattice.

Aluminium hydride (AlH3) is a promising hydrogen storage material because it possesses a high theoretical hydrogen capacity of 10.01 wt%. However, the stability and decomposition mechanism of some AlH3 polymorphs (e.g., γ-AlH3) still remain unclear. In this work, the hydrogen desorption behaviours of γ-AlH3 with or without TiF3 addition were investigated by hydrogen desorption measurement and thermal analysis. It was revealed that the decompositions of the outer layer and the inner part of γ-AlH3 particle follow diverse decomposition mechanisms. The outer layer of γ-AlH3 particle tends to decompose directly, while the inner part of γ-AlH3 particle prefers to first transform to more stable α-AlH3 and then decompose. TiF3 addition significantly lowers the temperature for the direct decomposition of outer layer γ-AlH3 by about 30 °C but scarcely impacts the decomposition of inner part γ-AlH3, which further confirms the decomposition mechanism of γ-AlH3. It was suggested that the particle size plays an important role in the thermal stability of γ-AlH3. The results of this work will help understanding the decomposition mechanisms of other AlH3 polymorphs for hydrogen storage.

Exploiting high-performance 2:14:1-type permanent magnet at high La–Ce substitution level remains a bottleneck concern due to the severe magnetic dilution from inferior intrinsic magnetism and microstructural deterioration. In present work, to promote the La–Ce application, (Pr, Nd)Hx is introduced into LaCe-40 sintered magnet (La–Ce/TRE = 40 wt%, TRE: total rare earth) through two approaches, grain boundary restructuring (GBR) and grain boundary diffusion process (GBDP). Results show that (Pr, Nd)Hx GBR leads to a twofold coercivity by optimizing the distribution of GB phase and forming a Pr/Nd-rich magnetically hardening shell. However, the remanence is lowered drastically due to massive formation of REFe2 phase during high-temperature sintering. Comparably, (Pr, Nd)Hx GBDP magnet with an identical average composition to GBR one yields a nearly threefold coercivity without sacrificing the remanence, ascribing to the formation of more continuous RE-rich GB layer and thicker Pr/Nd-rich shell near the surface region. Above comparative study highlights the crucial role of surface magnetic isolation in enhancing the coercivity of Nd–La–Ce–Fe–B sintered magnet, and delights the prospect of abundant La–Ce for industrial application.

Interfacial polarization is critical in electromagnetic (EM) wave absorption for dielectric materials. The underlying mechanisms and related factors of the interfacial polarization, however remain veiled, refraining the advance of dielectric absorbers with enhanced attenuation. Herein, two-dimensional (2D) SnO nanosheets have been used as a template, whose dominating interface evolves from SnO-(0 0 1)/SnO-(1 1 0) to SnO-(1 1 0)/SnO2-(1 0 1) and SnO2-(1 0 1)/SnO2-(2 1 1) via controllable oxidation. Combined off-axis electron holography and first-principle calculations indicate that larger difference in the work function of the SnO-(1 1 0)/SnO2-(1 0 1) (1.986 eV) compared with those of the SnO-(0 0 1)/SnO-(1 1 0) and SnO2-(1 0 1)/SnO2-(2 1 1) (0.338 eV and 0.534 eV, respectively) gives rise to distinctive charge density distribution. As such enhanced interfacial polarization can be achieved for favorable electromagnetic wave absorption of the SnO/SnO2 heterojunctions. This study not only provide a versatile method to fabricate 2D heterojunctions with tuned interfaces, correlations among work function, charge separation and interfacial polarization are also established, which is instructive for electric polarity manipulation for various applications.

CeF 3 as a catalyst is first added to activated carbon (AC) by ball milling under low rotation speed. Then the treated AC was used as the scaffold to confine LiBH 4 by melt infiltration process. The combined effects of confinement and CeF 3 doping on the hydrogen storage properties of LiBH 4 are studied. The experimental results show that LiBH 4 and CeF 3 are well dispersed in the AC scaffold and occupy up to 90% of the pores of AC. Compared with pristine LiBH 4 , the onset dehydrogenation temperature for LiBH 4 -AC and LiBH 4 -AC-CeF 3 decreases by 150 and 190 °C, respectively. And the corresponding dehydrogenation capacity increases from 8.2 wt% to 13.1 wt% for LiBH 4 -AC and 12.8 wt% for LiBH 4 -AC-CeF 3 , respectively. The maximum dehydrogenation speed of LiBH 4 -AC and LiBH 4 -AC-CeF 3 is 80 and 288 times higher than that of pristine LiBH 4 at 350 °C. And LiBH 4 -AC andLiBH 4 -AC-CeF 3 show good reversible hydrogen storage properties. On the during 4th dehydrogenation cycle, the hydrogen release capacity of LiBH 4 -AC and LiBH 4 -AC-5 wt% CeF 3 reaches 8.1 and 9.3 wt%, respectively.

The phase composition, magnetic and microstructural properties of Nd 2 Fe 14 B/(α-Fe, Fe 3 B) nanocomposite magnets produced by injection casting technique have been studied. Magnetic hysteresis loop of the Nd 7 Y 6 Fe 61 B 22 Mo 4 permanent magnet demonstrates the coercivity as high as 1289 kA/m. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe, Fe 3 B and hard Nd 2 Fe 14 B/Y 2 Fe 14 B nanograins (20–50 nm) separated by ultra-thin grain boundary layer. The Henkel plot curve of the Nd 7 Y 6 Fe 61 B 22 Mo 4 magnet yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet magnet is obtained due to high glass forming ability of the Nd 7 Y 6 Fe 61 B 22 Mo 4 alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the magnet is attributed to the magnetically hard phase increment, nucleation of reverse domains and the presence of thin grain boundary phase. Good magnetic properties such as remanence of 0.51 T, coercivity of 1289 kA/m and maximum energy product of 46.2 kJ/m 3 are obtained in directly casted Nd 7 Y 6 Fe 61 B 22 Mo 4 sheet magnets.

LiBH4 can be destabilized by AlH3 addition. In this work, the hydrogen desorption kinetics of the destabilized LiBH4 AlH3 composites were investigated. Isothermal hydrogen desorption studies show that the LiBH4 + 0.5AlH3 composite releases about 11.0 wt% of hydrogen at 450 °C for 6 h and behaves better kinetic properties than either the pure LiBH4 or the LiBH4 + 0.5Al composite. The apparent activation energy for the LiBH4 decomposition in the LiBH4 + 0.5AlH3 composite estimated by Kissinger's method is remarkably lowered to 122.0 kJ mol−1 compared with the pure LiBH4 (169.8 kJ mol−1). Besides, AlH3 also improves the reversibility of LiBH4 in the LiBH4 + 0.5AlH3 composite. For the LiBH4 + xAlH3 (x = 0.5, 1.0, 2.0) composites, the decomposition kinetics of LiBH4 are enhanced as the AlH3 content increases. The sample LiBH4 + 2.0AlH3 can release 82% of the hydrogen capacity of LiBH4 in 29 min at 450 °C, while only 67% is obtained for the LiBH4 + 0.5AlH3 composite in 110 min. Johnson−Mehl−Avrami (JMA) kinetic studies indicate that the reaction LiBH4 + Al → ‘Li Al B’ + AlB2 + H2 is controlled by the precipitation and subsequently growth of AlB2 and Li Al B compounds with an increasing nucleation rate.

In order to improve the hydrogen storage properties of LiBH4–MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4–MgH2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH4–MgH2 system was investigated. The experimental results show that LiBH4–MgH2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320 °C, and there is a long period of incubation time (around 220 min) for the occurrence of the second decomposition step even at high temperature of 450 °C. It needs more than 10 h to complete the decomposition process and release around 9 wt% H2. After addition of 5 mol% NbF5, the starting decomposition temperature for the first dehydrogenation step is around 150 °C, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.

To improve the thermal stability of the Nd-Ce-Fe-B sintered magnets, Y was incorporated via the binary main phase (BMP) approach. At the same substitution level for Nd (9 wt%), the absolute value of the coercivity temperature coefficient from 293 to 393 K for the Nd-Ce-Y-Fe-B magnet is 16.2% lower than that for the Nd-Ce-Fe-B one. This is attributed to the weakened temperature dependence of the magnetocrystalline anisotropy field and the magnetization as Y preferably enters into the 2:14:1 phase. It suggests that Y and Ce co-substitution for Nd is appealing to prepare low-cost RE-Fe-B permanent magnets with improved thermal stability.

SnO 2 films exhibiting room temperature ferromagnetism (RTFM) have been prepared on Si (001) by pulsed laser deposition. The saturation magnetization (M s ) of the films experiences a decreasing trend followed by increasing with the growth temperature increased from RT to 400 ℃. The growth temperature affects both the concentration and the location of the oxygen vacancies as the origin of the RTFM. With lower growth temperatures ( O + ) in the inner film are the origin of the magnetism in SnO 2 films.