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The superelastic behavior and elastocaloric effect of a [001]-textured Ni50Mn23Ga25Cu2 polycrystal have been investigated below room temperature (256–294 K). The adiabatic temperature change caused by rapid unloading of uniaxial stress reached −4.3 K at 259 K. A small stress hysteresis of 14 MPa was observed. Due to the low hysteresis energy loss (0.37 MJ m−3) stemming from the texture structure, the coefficient of performance (COPmat) of our alloy was calculated to be 18, indicating that it is a promising elastocaloric candidate for low-temperature refrigeration.

The Fe69.5–xNd7B21Nb2.5Gax (x = 0–1) permanent magnets in the form of rods were prepared by annealing the bulk amorphous alloys. The magnetic properties, phase evolution and microstructure of the alloys were investigated systematically. It is found that the glass forming ability (GFA), microstructure and magnetic properties are sensitive to Ga content for Fe69.5–xNd7B21Nb2.5Gax (x = 0–1) bulk alloys. The annealed alloys are mainly composed of soft α-Fe, hard Nd2Fe14B and nonmagnetic Nd1.1Fe4B4 phases. When x = 0.3, the optimally annealed magnets exhibit magnetic properties of the remanence Br = 0.63 T, intrinsic coercivity Hcj = 368.68 kA/m and maximum energy product (BH)max = 33.73 kJ/m3. Furthermore, magnetic field heat treatment at the temperature close to Curie temperature of Nd2Fe14B phase was applied to the annealed Fe69.2Nd7B21Nb2.5Ga0.3 magnet. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the magnetic field heat treatment can be beneficial for the precipitation of α-Fe. Thus, the Br, Hcj and (BH)max are enhanced by 8.7%, 6.3% and 16.3%, respectively.

In this work, we investigate the evolution with x of the microstructure and alternating current (AC) magnetic properties of FeCoNi(MnSi)x (0 ≤ x ≤ 0.4) high-entropy alloys (HEAs) with the motivation of exploring the potential applications of soft magnetic HEAs. The suitable addition of MnSi improves AC remanence (AC Br), AC coercivity (AC Hc) and especially specific total loss (Ps) while it suppresses amplitude permeability (μa) and AC maximum magnetic flux density (AC Bm), which suggests that the HEAs can be used as a new soft magnetic material with low Br and low Hc. Ps can be divided into two parts: hysteresis loss (Ph), eddy current loss (Pe), and further studies show that the Ph plays an important role at the frequency of 50 Hz, while the Pe is dominant in the total losses when the frequency is 950 Hz. This provides the direction of efforts to reduce the Ps. The XRD, SEM and TEM results show that these alloys contain simple FCC structure, but a new Mn6Ni16Si7 intermetallic compound appears when x ≥ 0.3, and it has a big influence on the AC magnetic properties of HEAs.

The FeCoNi(CuAl)0.8Ga0.06 high-entropy alloy (HEA) was prepared by the vacuum arc melt casting method, then annealed at different temperatures for 1 h. The microstructure, phase constitution, and magnetic and mechanical properties of the FeCoNi(CuAl)0.8Ga0.06 HEA during the phase transition were investigated. The experimental results showed that the as-cast alloy consisted of FCC and BCC duplex phases, and there were numerous nano-precipitates uniformly distributed in the BCC matrix. After annealing at different temperatures, the phase transformed from FCC to BCC. The relative volume fraction of the BCC phase increased, and the size of the nano-precipitates in the BCC matrix were larger after annealing than that of the as-cast sample. STEM-EDS images showed that there was a Cu-rich zone in the phase boundary region between FCC and BCC phases, and annealing may have significant influence on this region. Based on XRD, SEM, TEM and STEM-EDS results, a phase transition mechanism was proposed, which may have a close relationship with the Cu-rich nano-precipitates in the BCC matrix and the Cu-rich zone in the phase boundary region. In addition, it was found that the volume fraction of BCC (or FCC) phase can govern the magnetic properties. This study may help to deepen the fundamental understanding of the phase transition mechanism in HEAs.

In this paper, the effects of vanadium addition on the mechanical properties of Ti-Zr-Ni-Cr amorphous ribbons with high spinning speed were studied. It was found that the mechanical properties of samples were obvious promoted by adding vanadium into Ti-Zr-Ni-Cr amorphous alloys. The rapidly solidified Ti-Zr-Ni-Cr (V = 0, V = 0.1) ribbons at a speed of 45 m/s is an amorphous structure. But the amorphous structure of Ti-Zr-Ni-Cr-V alloys is even more uniform than that of the V-free alloys samples. In particular, Ti-Zr-Ni-Cr-V amorphous ribbons showed better mechanical properties that the tensile strength ( $$\sigma_{b}$$ ) of the amorphous ribbons samples that had been significantly increased from 542 MPa for V = 0–675 MPa for V = 0.1. The elongation (δ) exhibited a tiny increase from 1.1% for V = 0–1.29% for V = 0.1. The fractured surface of amorphous ribbons for V = 0 showed more cleavage features, it was the obviously brittle fracture. The fracture surface for amorphous ribbons for V = 0 were more vein-like patterns, they are attributed to a local change of viscosity. It’s likely that adding V into Ti-Zr-Ni-Cr amorphous alloys is beneficial to enhance rheological units and massive accumulation of free volume in ribbons. It contributes to mechanical properties, especially for the tensile strength and the plastic deformation of the amorphous ribbons.

The as-cast FeCoNi(CuAl)0.8Gax (0 ≤ x ≤ 0.08) high-entropy alloys (HEAs) were produced by vacuum arc melting. The correlation between the magnetic properties and phase constitution of the HEAs was thoroughly investigated. The results reveal that all samples contain BCC plus FCC duplex phases and the addition of Ga can promote the formation of BCC phases. Energy dispersive spectroscopy (EDS) results revealed that Cu and Ga elements are enriched in the BCC phases and they are more seriously in the phase boundary regions. Furthermore, the magnetic properties are closely related to the phase constitution of the as-cast FeCoNi(CuAl)0.8Gax (0 ≤ x ≤ 0.08) HEAs. The values of saturated magnetization (Ms), maximum magnetic flux density (Bm), remanence (Br), coercivity (Hc) and hysteresis losses (Pu) increase with the increase of the volume fraction of BCC phases, while the values of initial permeability (μi) and maximum permeability (μmax) increase with the increase of the volume fraction of FCC phases. In addition, the mechanical property of FeCoNi(CuAl)0.8Gax (0 ≤ x ≤ 0.08) HEAs was also discussed in the work.

Magnetocaloric effect by employing direct measurements of the adiabatic temperature changes (ΔTad) with a low magnetic field change (ΔH) up to 1.2 T are investigated, for the Gd based alloys with Zn and Cd substituted for Gd individually or synchronously. A comparative study of the adiabatic temperature change (ΔTad) and magnetic entropy change (ΔSM) near room temperature has been reported in three different alloys of Gd1 − xZnx, Gd1 − yCdy and Gd0.95(Zn1 − zCdz)0.05. Effects of Zn and Cd content on magnetocaloric effect and the Curie temperature (Tc) are studied in different alloys. A direct correlation between phase structure and ΔTad, ΔSM, Tc was discussed in three different types alloys of Gd1 − xZnx, Gd1 − yCdy, and Gd0.95(Zn1 − zCdz)0.05. Mechanism of Zn improving the ΔTad and Cd increasing the Tc is revealed. It is expected that magnetic refrigeration near room temperature has a potential for superseding the traditional gas refrigeration. Keywords: Gd1 − xZnx, Gd1 − yCdy, Gd0.95(Zn1 − zCdz)0.05, Magnetocaloric effect

In the present work, (Nd 0.8 Ce 0.2 ) 2− x Fe 12 Co 2 B ( x = 0–0.6) permanent alloys are prepared by melt-spinning method. The hard magnetic properties of (Nd 0.8 Ce 0.2 ) 2− x Fe 12 Co 2 B ( x = 0–0.6) alloys annealed at optimum temperatures have been investigated systematically. Depending on the Nd, Ce concentration, the maximum energy product ( (BH) max ) and remanence ( B r ) increase gradually with x in the range of 0 ≤ x ≤ 0.4, whereas decrease gradually in the alloys with 0.4 x ≤ 0.6. It is found that the optimum magnetic properties are obtained at x = 0.4: H ci = 4.9 kOe, B r = 10.1 kG, (BH) max = 13.7 MGOe. Specifically, magnetic field heat treatment below the Curie temperature is applied for (Nd 0.8 Ce 0.2 ) 1.6 Fe 12 Co 2 B ( x = 0.4) annealed ribbons. The magnetic properties B r , (BH) max and squareness are all enhanced after the magnetic field heat treatment. The (BH) max shows a substantial increase from 13.7 MGOe to 16.0 MGOe after the heat treatment at 623 K with a magnetic field of 1 T, which gets 17% improvement compared with that of the sample without a magnetic field heat treatment. We demonstrate that the magnetic field heat treatment plays a certain role in the magnetization reversal behavior and can improve the microstructure of (Nd 0.8 Ce 0.2 ) 1.6 Fe 12 Co 2 B alloy.

Nonlinear optical materials are essential for the development of solid-state lasers. KBe2BO3F2 (KBBF) is a unique nonlinear optical material for generation of deep-ultraviolet coherent light; however, its industrial application is limited. Here, we report a new material NH4B4O6F, which exhibits a wide deep-ultraviolet transparent range and suitable birefringence that enables frequency doubling below 200 nm. NH4B4O6F possesses large nonlinear coefficients about 2.5 times that of KBBF. In addition, it is easy to grow bulk crystals and does not contain toxic elements.

The atomic-scale structural evolution and crystallization mechanism of Ti-Zr-Ni-Cr amorphous ribbons subjected to hydrogen absorption have been studied. The atomic degree of order and amount of one-dimensional (1D), two-dimensional (2D) or three-dimensional (3D) ordered atomic packing structure of Ti-Zr-Ni-Cr amorphous ribbons were found to increase in the process of hydrogen absorption, resulting in excellent mechanical and hydrogen absorption properties. When the hydrogen absorption capacity reached 22.4 mL/g, crystallization occurred on the basis of 1D, 2D or 3D ordered atomic packing structure. Hydrogen atom induced Ti-Zr-Ni-Cr amorphous ribbons to crystallize into ZrH2, TiH2 hydride and (ZrTi)2Ni7 phases during the process of hydrogen absorption. When the samples absorbed hydrogen for a long time, formation of crystalline phases of ZrH2, TiH2 hydride and (ZrTi)2Ni7 led to degraded mechanical properties.

The Ce46La5C49 alloy was first prepared in a 25 kg vacuum induction melting furnace. The La-doped CeO2 nanopowders were then prepared by hydrolysis and oxidation of Ce46La5C49 at room temperature. These nanopowders were calcinated at different temperatures in order to improve their catalytic activities. The lanthanum ions were used to partially replace the cerium ions in the CeO2 lattice, forming a solid solution of cerium lanthanum. Compared to the pure CeO2, the thermal stability of La-doped CeO2 was increased due to the lanthanum doping. The La-doped CeO2 nanopowders show enhanced CH4 catalytic performance.

In the present work, the effects of phase constitution on the magnetic and mechanical properties of FeCoNi(CuAl)x (x = 0–1.2, in molar ratios) high-entropy alloys (HEAs) have been investigated by using vibrating sample magnetometer (VSM), mechanical tester combined with X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimeter (DSC). From the experimental results, the crystallographic structures of FeCoNi(CuAl)x HEAs transform from single face-centered cubic (FCC) phase for 0 ≤ x ≤ 0.6 to body-centered cubic (BCC) phase combined with minor FCC phase for 0.9 ≤ x ≤ 1.2, whereas FCC plus BCC duplex phases are found in the range of 0.7 ≤ x

In this paper, the magnetocaloric properties of Gd1&minus, xTbx alloys were studied and the optimum composition was determined to be Gd0.73Tb0.27. On the basis of Gd0.73Tb0.27, the influence of different Fe-doping content was discussed and the effect of heat treatment was also investigated. The adiabatic temperature change (&Delta, Tad) obtained by the direct measurement method (under a low magnetic field of 1.2 T) and specific heat capacity calculation method (indirect measurement) was used to characterize the magnetocaloric properties of Gd1&minus, xTbx (x = 0~0.4) and (Gd0.73Tb0.27)1&minus, yFey (y = 0~0.15), and the isothermal magnetic entropy (&Delta, SM) was also used as a reference parameter for evaluating the magnetocaloric properties of samples together with &Delta, Tad. In Gd1&minus, xTbx alloys, the Curie temperature (Tc) decreased from 293 K (x = 0) to 257 K (x = 0.4) with increasing Tb content, and the Gd0.73Tb0.27 alloy obtained the best adiabatic temperature change, which was ~3.5 K in a magnetic field up to 1.2 T (Tc = 276 K). When the doping content of Fe increased from y = 0 to y = 0.15, the Tc of (Gd0.73Tb0.27)1&minus, yFey (y = 0~0.15) alloys increased significantly from 276 K (y = 0) to 281 K (y = 0.15), and a good magnetocaloric effect was maintained. The annealing of alloys (Gd0.73Tb0.27)1&minus, yFey (y = 0~0.15) at 1073 K for 10 h resulted in an average increase of 0.3 K in the maximum adiabatic temperature change and a slight increase in Tc. This study is of great significance for the study of magnetic refrigeration materials with adjustable Curie temperature in a low magnetic field.

Magnetic field annealing is an important method to enhance the magnetic properties of amorphous alloys. In this work, the effects of magnetic field annealing intensity on the magnetic properties, mechanical properties, and microstructure of Fe80Si9B11 amorphous ribbons were investigated. It can be seen from the results that the magnetic induction at 1600 A/m (B1600), maximum permeability (μm), coercivity (Hc), Elastic modulus (Er), and Hardness were improved with an increase of the magnetic field intensity. When the magnetic annealing intensity was 2.5 × 10−4 T, the B1600, μm, Hc, Er and Hardness of the sample were improved by 9%, 298%, 67%, 23% and 3%, respectively, compared with those of the as-spun sample. TEM results showed that there are some spherical symmetric clusters present in the 653 K × 2.5 × 10−4 T sample. This may be an important reason for the improvement of the magnetic properties. Compared with the 653 K × 1 T sample, the magnetic field intensity of the 653 K × 2.5 × 10−4 T sample was only 0.025%. However, the values of B1600, μm, Hc, Er and Hardness of the latter reached 96%, 82%, 115%, 90% and 94% of the former, respectively. It means that during the magnetic field annealing process, applying only a small magnetic field can obviously enhance the magnetic and mechanical properties of Fe80Si9B11 amorphous alloy. This provides a theoretical basis for the further improvement of the magnetic and mechanical properties of Fe80Si9B11 alloys, and in the energy saving. The reasons for the changes of magnetic and mechanical properties caused by different magnetic field intensities are discussed.

The characteristic magnetic domains at the surfaces of melt-spun La–Fe–Si ribbons under different thermal processing conditions are explored using room-temperature Lorentz force microscopy and electron holography. In as-quenched ribbons, the magnetic domain structure is found to change from a tree-like morphology on the surface far from the copper wheel during quenching to a vortex-type domain structure on the surface in contact with the wheel. In the initial stages of annealing, domains on both surfaces developed a vortex behavior. Detailed microstructural observations demonstrated nanocrystalline α -(Fe,Si) regions embedded in the majority La(Fe,Si) 13 phase due to a partially completed peritectoid reaction between α -(Fe,Si) and LaFeSi. The room temperature magnetic domains disappeared along with the residual α -(Fe,Si) upon extended heat treatment, yielding a homogeneous La(Fe,Si) 13 material. Magnetometry measurements and analysis reveal the absence of strong coupling between the α -(Fe,Si) and La(Fe,Si) 13 phases, so that the presence of α -(Fe,Si) nanocrystallites with a vortex-type structure does not favor an enhanced magnetocaloric response in the ribbons.

The structure and magnetocaloric properties of La-Ce-Fe-Si alloys have been studied. The samples were prepared by melt spinning, the surface speed of the Cu wheel being 55 m/s. The as-spun ribbons were subsequently annealed at 1273 K for different times (10 min−1 h) and then quenched to room temperature. When the annealing time was 20 min, on a 1.5-T applied magnetic field, the maximum magnetic entropy change (ΔS M) of the ribbons reached values of 33.8 J/kg K at the Curie temperature of T C ∼ 182 K. When the annealing time was longer than 20 min, the maximum magnetic entropy change (|ΔS M,Max|) tended to decrease while the T C remained almost unchanged. In the annealing process, La/Ce located at grain boundaries was easily oxidized on the ribbon surface. The presence of large grain sizes and La2O3 or LaO were shown to degrade the magnetocaloric properties. On the other hand, the substitution of Ce for La improved the magnetocaloric effect of La-Fe-Si compounds, which is of practical importance for magnetic refrigeration.

We undertook a novel batch production approach for the synthesis of CeO2 nanopowders doped with rare earth elements. Solid solution nanopowders of Ce1−x La x O2−δ (x = 0.15) were successfully synthesized in a large-scale and low-cost production by hydrolyzing and oxidizing Ce-La-C alloys at room temperature and subsequent calcining of their powders at different temperatures (873–1073 K) for 1 h. The Ce-La-C alloys were prepared in a vacuum induction melting furnace. The final products were characterized by x-ray diffraction, transmission electron microscopy, Brunner–Emmet–Teller (BET) surface area analyzer, and Raman spectroscopy. The calculated lattice parameters of the cubic fluorite-type phase of CeO2 tended to increase when La3+ was incorporated into CeO2. The F 2g band shift and the absence of a peak corresponding to La2O3 in the Raman spectra consistently confirmed the incorporation of the La3+ ion into CeO2, and the formation of Ce1−x La x O2−δ solid solutions as manifested by increased oxygen vacancy defects. High-quality Ce1−x La x O2−δ nanopowders of ~10–15 nm diameter with a high BET surface area of ~77 m2 g−1 were obtained. The average crystallite size of Ce1−x La x O2−δ was found to be smaller than that of CeO2 for the same calcination temperature of 1073 K, demonstrating that the introduction of La3+ into CeO2 can stabilize the host lattice and refine the grain size at high temperatures.

In this paper, the effects of different melt spinning speeds on the mechanical properties of (TiZr)0.5(Ni0.6Cr0.1V0.1)2.1 amorphous ribbons were studied. Tensile tests of the specimens were used to investigate mechanical behavior and mechanical properties of amorphous ribbons. The effects of cooling rate on the glass transition temperature of amorphous ribbons was discussed. The correlation between the microstructure of serrated flow behavior in stress-strain curves and melt spinning speeds of ribbons was also evaluated. In addition, when the spinning speed was 45 m/s, a large number of dense and uniform dimples appeared on the fractured surface of the specimens. Furthermore, characteristics of serrated flow behavior were obvious, which meant that Ti-Zr-Ni-Cr-V amorphous ribbons showed minor plastic behavior. It is assumed that the influence of free volume led to a serrated flow behavior of the amorphous materials, and made the amorphous material exhibit partially plastic properties. Increasing the strain rate sensitivity meant the free volume increased with the increasing spinning speed. Tensile strength (&sigma, b) and elongation (&delta, ) of samples exhibited a dramatic increasing trend with an increase in the spinning speed. In particular, Ti-Zr-Ni-Cr-V amorphous ribbons showed better mechanical properties, namely the tensile strength of the amorphous ribbon samples significantly increased from 321 MPa at a spinning speed of 30 m/s to 675 MPa at a speed of 45 m/s. The elongation increased from 0.53% at a speed of 30 m/s to 1.29% at a speed of 45 m/s.

In this study, ferrocenedicarboxylic acid (FDA) has been introduced between an ITO electrode and ZnO interlayer to improve the performance of inverted polymer solar cells. The highest power conversion efficiency (PCE) of 9.06% is achieved among the measurements. Besides, the average PCE of FDA/ZnO based devices is observed with 11.9% enhancement (8.73% vs. 7.80%) compared to ZnO-only devices. Electrical characterization, surface morphology, wetting properties, as well as exciton generation rate and dissociation probability were investigated to understand the impact of FDA insertion on the interfacial properties. It was found that exciton dissociation efficiency and charge collection efficiency were significantly improved after inserting FDA, while the surface morphology, average roughness and water contact angle of the ZnO film were not changed. It was thought that FDA connected to the ITO electrode and ZnO film because of its carboxyl groups, which lead to a compact interfacial contact and reduced charge recombination. In addition, the devices based on the FDA/ZnO interlayers displayed improved stability in the argon-filled glove box without any encapsulation for about 1000 h compared to the ZnO-only devices. This study provides a new idea to introduce materials with functional groups between ITO/metal oxides interfaces to achieve more efficient charge collection and device performance.

Optimizing of alloy composition and heat-treatment for rapidly solidified Ce–Fe–B magnets can lead nanocrystalline products with enhanced magnetic properties. In this work, the magnetic properties and domain structures of the nanocrystalline Ce[Formula: see text]Fe[Formula: see text]Co1Zr[Formula: see text]B6 have been investigated. The results show that hard Ce2Fe[Formula: see text]B magnetic phase and paramagnetic CeFe2 phase are crystallized for the heat treated alloys, while the volume fraction and grain size of Ce2Fe[Formula: see text]B and CeFe2 phases change significantly with the increase of annealing temperature. The enhanced coercivity H[Formula: see text] of 6.32 kOe and maximum energy products (BH)[Formula: see text] of 5.52 MGOe have been observed for the Ce[Formula: see text]Fe[Formula: see text]Co1Zr[Formula: see text]B6 ribbons at the optimal annealing temperature of 520[Formula: see text]C and 580[Formula: see text]C, respectively. Meanwhile, the magnetization reversal behaviors and the nucleation field of the annealed sample were discussed in detail. The domain structures analysis provides more information on the characteristic of the domain width W as well as the exchange interactions.