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Owing to the complexity and heterogeneity of coal during pyrolysis, the ex situ analytical techniques cannot accurately reflect the real coal pyrolysis process. In this study, according to the joint investigation of Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), the structural evolution characteristics of lignite-subbituminous coal-bituminous coal-anthracite series under heat treatment were discussed in depth. The results of the infrared spectrum of coal show that the different functional groups of coal show different changes with the increase of coal rank before pyrolysis experiment. Based on in situ infrared spectroscopy experiments, it was found that the infrared spectrum curves of the same coal sample have obvious changes at different pyrolysis temperatures. As a whole, when the pyrolysis temperature is between 400 and 500°C, the coal structure can be greatly changed. By fitting the infrared spectrum curve, the infrared spectrum parameters of coal were obtained. With the change of temperature, these parameters show regular changes in coal with different ranks. In the XRD study of coal, the absorption intensity of the diffraction peak (002) of coal increases with increasing coal rank. The XRD patterns of coal have different characteristics at different pyrolysis temperatures. Overall, the area of (002) diffraction peak of the same coal sample increases obviously with the increase of temperature. The XRD structural parameter of coal was obtained by using the curve fitting method. The changing process of two parameters (interlayer spacing (d002) and stacking height (Lc)) can be divided into two main stages, but the average lateral size (La) does not change significantly and remains at the 2.98 ± 0.09 nm. In summary, the above two technologies complement each other in the study of coal structure. The temperature range of both experiments is different, but the XRD parameters of coal with different ranks are reduced within the temperature range of less than 500°C, which reflects that the size of coal-heated aromatic ring lamellae is reduced and the distance between lamellae is also reduced, indicating that the degree of condensation of coal aromatic nuclei may be increased. Correspondingly, the FTIR parameters of coal also reflect that, with increasing temperature, the side chains of coal are constantly cracked, the oxygen-containing functional groups are reduced, and the degree of aromatization of coal may be increased.

This paper aimed to perform systematical study on the distribution of landslide thrust in pile-anchor support system, which has been a widely applicable treatment method in landslide control with safety, highly efficiency and adaptation. The advantage of photoelastic technique is visualization of strain and stress fields, therefore photoelastic model tests are conducted to show the distribution of landslide thrust in pile-anchor structure before failure in landslide. The effects of different materials and pile lengths are investigated by 6 photoelastic test cases under different loading conditions. It can be found from quantitative analysis of experimental results that load proportion of anchor would increase gradually with the decrease of pile embedded depth or the increase of landslide thrust force. Meanwhile, landslide thrust distribution in pile-anchor structure is directly affected by the stiffness of piles. The pile-anchor structure is significantly better at reducing bending moment value and optimizing bending moment distribution of pile. Finally, some theoretical analysis and design suggestions are proposed based on the experimental study.

Sodium-ion batteries (SIBs) are a promising alternative for the large-scale energy storage owing to the natural abundance of sodium. However, the practical application of SIBs is still hindered by the low working voltage, poor rate performance, and insufficient cycling stability. A sodium-ion based full battery using a multi-ion design is now presented. The optimized full batteries delivered a high working voltage of about 4.0 V, which is the best result of reported sodium-ion full batteries. Moreover, this multi-ion battery exhibited good rate performance up to 30 C and a high capacity retention of 95 % over 500 cycles at 5 C. Although the electrochemical performance of this multi-ion battery may be further enhanced via optimizing electrolyte and electrode materials for example, the results presented clearly indicate the feasibility of this multi-ion strategy to improve the electrochemical performance of SIBs for possible energy storage applications.

Simultaneous improvement of strength and toughness is a challenge in composite materials, as an improvement in one is generally at the expense of the other. The filler-matrix interface has a crucial role in such improvement. It appears that modification of the interfacial structure/geometry may have wider possibilities and benefits than the classical chemical bonding approach. Using a model glass-epoxy fiber-reinforced composite, we modified the regular cylindrical fiber-matrix interface by applying intermittent epoxy beads along the fiber, taking advantage of the Plateau-Rayleigh liquid instability phenomenon. Under load, the beads serve as fiber anchors in the matrix, thus exploiting the fiber strength to its maximum. During fracture, the pullout of beads through the matrix appears to dissipate more plastic deformation energy compared to the pullout of regular fibers. Fragmentation tests of beaded fibers in epoxy matrix demonstrate these failure mechanisms; single-bead fiber pullout tests with different bead sizes and surface treatments provide strength and toughness data that substantiate this approach. The concept of intermittent beading has ample possibilities for optimization. It is also scalable and therefore practical.

Electrolysis of molten carbonates provides an effective means to achieve the direct conversion of the greenhouse gas carbon dioxide to readily available carbonaceous fuel or chemicals. In this study, CO2 was electrolyzed in a Li–Na–K ternary carbonates mixture using galvanized Fe as the cathode and nickel as the anode. In particular, the effect of BaCO3 on the generation of carbon was studied. The results demonstrate that BaCO3 addition facilitates the deposition of compact carbon materials. Moreover, decreasing the temperature and increasing the current density lead to the formation of loosened carbon products. Though Li–Na–K–Ba electrolysis exhibits a higher cell voltage than that using Li–Na–K carbonates, BaCO3 addition can significantly ease anode corrosion and the corresponding corrosion inhibiting action is discussed. In summary, a facile CO2 absorption and a mitigatory nickel anode corrosion were observed when BaCO3 was dissolved in Li–Na–K carbonates and further investigation is expected.

Mn-containing Heuslers are important magnetic shape-memory alloys for fast and precise actuators in manufacturing, robotics, surgery, and other applications. Among the key requirements are a high magnetization and favorable thermal properties, especially a high Curie temperature. In this work, the effect of Fe and Co substitution on the structure and magnetism of Mn2NiSn alloys is investigated. The Heusler alloys have been produced by melt spinning and characterized by X-ray diffraction, magnetometry, and electron-transport measurements. It was found that Co substitution for Mn enhances the Curie temperature of Mn2NiSn and both Co and Fe substitution improve its magnetization. These improvements are accompanied by reduced thermal and magnetic hysteresis losses and by interesting structural changes, namely improved chemical order and site occupancies characteristic of quaternary (Y-ordered) Heuslers.

Alloys with nominal compositions of Mn2CrGa1-xAlx (x = 0.0, 0.2, 0.5, 1.0) have been studied by X-ray powder diffraction (XRD). Detailed structural investigation of the alloys with x = 0.2 and 0.5 has been further carried out using transmission electron microscopy (TEM). The alloys, in the typical Heusler composition, were prepared using rapid quenching and subsequent annealing. The XRD analysis revealed that a disordered cubic phase was present in the alloys with x = 0.0 and 1.0 while a spinodal decomposition with phase separation has been observed in the alloys with x = 0.2 and 0.5. TEM study confirms a segregation of two crystalline phases, one of them a cubic phase with the β–Mn prototype structure and the other a new crystalline phase with a tetragonal structure. Energy-dispersive X-ray spectroscopy (EDS) analysis was used to determine the compositions of the two crystalline phases. The mass ratio of the tetragonal phase and the β–Mn prototype cubic phase is derived as t/c ≈ 2.41 by fitting the average compositions of the two crystalline phases to the nominal composition. The orientational relationship of two crystalline structures has been determined by selected-area electron diffraction (SAED) and stereogram analysis. The structures of the two crystalline phases have been investigated by high-resolution transmission electron microscopy (HRTEM) and image simulation. The structural model of the tetragonal phase is proposed and compared with the experimental results in SAED and HRTEM studies.

Crystal structure and magnetic properties of Heusler alloys MnXNiSn (X = Mn, Fe, Co) are investigated using density functional theory and compared with experimental results. The parent alloy Mn2NiSn, which crystallizes in the inverse Heusler structure, is found to be ferrimagnetic, in agreement with previous experimental and theoretical work. The Fe and Co substitutions cause the alloys to assume a fairly well-ordered Y structure and enhance the magnetization substantially. We find that the strong nearest neighbour Mn-X exchange changes from antiferromagnetic (X = Mn) to ferromagnetic (X = Fe, Co), which explains and actually overestimates the experimental changes. A striking feature of the system is that Fe and Co have opposite effects on the Curie temperature Tc: they reduce and enhance Tc, respectively. We qualitatively explain this behaviour in terms of two-sublattice model based on the nearest-neighbour exchange.

The manuscript focuses on the dispersion of magnetic nanoparticles within self-assembling block copolymers, on the preferential localization of nanoparticles and on the effect of their concentration on the magnetic properties of the nanocomposites and on the self-assembly features of the matrix. Carbon-coated nickel nanoparticles dispersed within polystyrene–block polyisoprene–block polystyrene have been investigated by Raman, X-ray, SQUID, differential scanning calorimetry, and electron microscopy. The effect of nanofiller on the self-assembly features of the block copolymer is reported. Preferential localization of nanofiller within the soft phase was noticed below 20 wt% nanofiller. Higher loadings with nanoparticles showed an uniform distribution of nanofiller within the block copolymer, consistent with the destruction of self-assembly. The effect of nanoparticles’ concentration on blocking temperature is discussed.

The structural and magnetic properties of Nd12Fe82B6 and Nd10M2Fe82B6 (M = Nb, Ti, Zr, Cr) alloys prepared using arc melting and melt spinning have been investigated. All the samples are found to crystallise with a tetragonal Nd2Fe14B phase without any alloy or elemental impurities. There is a small decrease in the unit cell volume of Nd2Fe14B due to transition metal (M) addition. The substitution of Nb and Ti refines and homogenises the nanostructure of the alloys, promoting intergrain exchange coupling leading to an increase in the remanence and energy product. For example, the remanence and energy product of Nd12Fe82B6 and Nd10Nb2Fe82B6 are 8.4 kG and 15 MGOe, and 9.9 kG and 20 MGOe, respectively. The J(T) curves are similar to those of a single phase ferromagnetic material suggesting no segregation of ferromagnetic impurities. The observed structural and magnetic properties are consistent with the fact that the substitutional transition metal atoms occupy the Nd site of the tetragonal Nd2Fe14B...

Structural, magnetic, and magnetocaloric properties of iron-deficient (Nd1−xCex)YFe17 alloys in the rhombohedral Th2Zn17–type crystal structure prepared by arc-melting and vacuum annealing have been investigated. Among the investigated alloys, (Nd0.7Ce0.3)YFe17 shows the highest values of magnetic entropy change and relative cooling power, namely 5.45 J kg−1 K−1 and 504 J kg−1 for a magnetic field change of 5 T. The Curie temperature and saturation magnetization of the (Nd0.7Ce0.3)YFe17 alloy are 301 K and 162 emu/g, respectively. The absence of thermal and magnetic hysteresis with relatively high cooling capacity near room temperature suggests that Fe-deficient (Nd0.7Ce0.3)YFe17 carries significant potential for room-temperature magnetic refrigeration.

Intermetallic compounds and micro-structures in Ni–Mn–In alloy system were investigated with transmission electron microscopy, selected-area and nano-beam electron diffraction, and energy-dispersive x-ray spectroscopy. Together with two types of Heusler phases, a decagonal quasicrystalline phase and a structurally related crystallite were found in the Ni–Mn–In system. As is well-known, most of the decagonal quasicrystals are aluminum-based intermetallic phases. It is interesting to investigate the aluminum-free decagonal quasicrystalline phase as a new member of the quasicrystal family. Structural characterization was carried out on the decagonal quasicrystalline phase and the crystalline approximant in the Ni–Mn–In alloy system.

The effect of micromagnetic boundary conditions on the Berry curvature and topological Hall effect in granular nanostructures is investigated by model calculations. Both free surfaces and grain boundaries between interacting particles or grains affect the spin structure. The Dzyaloshinskii-Moriya interactions yield corrections to the Erdmann-Weierstrass boundary conditions, but the Berry curvature remains an exclusive functional of the local spin structure, which greatly simplifies the treatment of nanostructures. An explicit example is a model nanostructure with cylindrical symmetry whose spin structure is described by Bessel function and which yields a mean-field-type Hall-effect contribution that can be related to magnetic-force-microscopy images.

Permanent-magnet materials are one cornerstone of today’s technology, abundant in disk drives, motors, medical equipment, wind generators, and cars. A continuing challenge has been to reconcile high permanent-magnet performance with low raw-material costs. This work reports a Mn-Bi-Sn alloy exclusively made from inexpensive elements, exhibiting high values of Curie-temperature, magnetization, anisotropy, coercivity, and energy product. The samples are produced by field annealing of rapidly quenched Sn-containing MnBi alloys, where the improvement of the magnetic properties is caused by the substitutional occupancy of the 2c sites in the hexagonal NiAs structure by Sn. The substitution modifies the electronic structure of the compound and enhances the magnetocrystalline anisotropy, thereby improving the coercivity of the compound. The energy product reaches 114 kJ/m3 (14.3 MGOe) at room temperature and 86 kJ/m3 (10.8 MGOe) at 200 °C; this value is similar to that of the Dy-free Nd2Fe14B and exceeds that of other rare-earth-free permanent-magnet bulk alloys, as encountered in automotive applications.

A nonequilibrium rapid-quenching method has been used to fabricate NiMnIn and NiMnGa alloys that are chemically and morphologically similar but crystallographically and physically very different. NiMnGa crystallizes in a Ni2In-type hexagonal structure, whereas NiMnIn is a cubic Heusler alloy. Both alloys yield a topological Hall effect contribution corresponding to bubble-type skyrmion spin structures, but it occurs in much lower magnetic fields in NiMnIn as compared to NiMnGa. The effect is unrelated to net Dzyaloshinskii-Moriya interactions, which are absent in both alloys due to their inversion-symmetric crystal structures. Based on magnetic-force microscopy, we explain the difference between the two alloys by magnetocrystalline anisotropy and uniaxial and cubic anisotropies yielding full-fledged and reduced topological Hall effects, respectively. Since NiMnIn involves small magnetic fields (0.02–0.3 kOe) at and above room temperature, it is of potential interest in spin electronics.

The structural, magnetic and magnetocaloric properties of Fe deficient Pr2-xNdxFe17 (x = 0.5, 0.7) alloys prepared by arc-melting and melt-spinning have been investigated. The room temperature x-ray diffraction patterns show that the samples are nearly single-phase and crystallize in the rhombohedral Th2Zn17-type crystal structure. The Curie temperatures determined from the thermomagnetic curves are 302 K and 307 K for Pr1.5Nd0.5Fe17 and Pr1.3Nd0.7Fe17, respectively. The peak magnetic entropy change and the relative cooling power at field change of 50 kOe are 3.01 J/kgK and 345 J/kg for Pr1.5Nd0.5Fe17, and 4.31 J/kgK and 487 J/kg for Pr1.3Nd0.7Fe17, respectively. The absence of magnetic and thermal hysteresis with relatively high cooling efficiency suggests that the alloys have potential for magnetic refrigeration.The structural, magnetic and magnetocaloric properties of Fe deficient Pr2-xNdxFe17 (x = 0.5, 0.7) alloys prepared by arc-melting and melt-spinning have been investigated. The room temperature x-ray diffraction patterns show that the samples are nearly single-phase and crystallize in the rhombohedral Th2Zn17-type crystal structure. The Curie temperatures determined from the thermomagnetic curves are 302 K and 307 K for Pr1.5Nd0.5Fe17 and Pr1.3Nd0.7Fe17, respectively. The peak magnetic entropy change and the relative cooling power at field change of 50 kOe are 3.01 J/kgK and 345 J/kg for Pr1.5Nd0.5Fe17, and 4.31 J/kgK and 487 J/kg for Pr1.3Nd0.7Fe17, respectively. The absence of magnetic and thermal hysteresis with relatively high cooling efficiency suggests that the alloys have potential for magnetic refrigeration.

Mn2CrGa-based Heusler compounds combining small magnetization with high spin polarization, fabricated by Fe and Pt substitution for Cr, are investigated experimentally and discussed in terms of sublattice site occupancies. X-ray diffraction and electron diffraction indicate that the parent alloy and Mn2Cr0.6Fe0.4Ga are normal cubic Heusler alloys with substantial chemical disorder, whereas Mn2Cr0.6Pt0.4Ga crystallizes in the tetragonal D022 structure. Magnetization measurements indicate that the spin structure of the parent alloy is essentially ferrimagnetic, but alloying with Fe or Pt reduces the net magnetization per formula unit from 0.40 µ B in the parent alloy to nearly zero in the Fe case. The Curie temperature, the magnetoresistance, and the Andreev-reflection transport-spin polarization are less affected by the substitutions, the last changing from 65% in Mn2CrGa to 60% and 61% in the Fe- and Pt-substituted alloys, respectively. The properties of these alloys are favorable for spintronics applications.

The effect of Y addition and magnetic field on texture and magnetic properties of arc-melted alnico 9 magnets has been investigated. Small additions of Y (1.5 wt.%) develop a (200) texture for the arc-melted alnico 9 magnet. Such a texture is hard to form in cast samples. To achieve this goal, we set up a high-field annealing system with a maximum operation temperature of 1250 °C. This system enabled annealing in a field of 45 kOe with subsequent draw annealing for the solutionized buttons; we have been able to substantially increase remanence ratio and coercivity, from 0.70 and 1200 Oe for the Y-free alnico 9 to 0.90 and 1400 Oe for the Y-doped alnico 9, respectively. A high energy product of 7.3 MGOe has been achieved for the fully heat-treated Y-doped alnico 9. The enhancement of coercivity is believed to arise from the introduction of magnetocrystalline anisotropy from 80 nm Y2Co17-type grains, which are exchange-coupled to the main-phase alnico rods.

The magnetic and magnetocaloric properties of iron-substituted Co2VGa alloys, Co2-xFexVGa (x = 0, 0.1, 0.15, 0.2, 0.3), were investigated. The Fe-substituted samples, prepared by arc melting, melt spinning, and annealing, crystallized in the L21 Heusler structure, without any secondary phases. The Curie temperature and high-field magnetization at 50 K decreased from 345 K and 44 emu/g (1.90 μB/f.u.) for Co2VGa to 275 K and 39 emu/g (1.66 μB/f.u.) for Co1.7Fe0.3VGa, respectively, but the maximum entropy change remained almost insensitive to Fe concentration for x ≤ 0.2, the highest value being 3.3 J/kgK at 7 T for Co1.85Fe0.15VGa. First-principle calculations show that Co2VGa retains its half-metallic band structure until at least 30% of the cobalt atoms are replaced by Fe atoms. The wide operating temperature window near room temperature and the lack of thermal and magnetic hysteresis are the interesting features of these materials for application in room-temperature magnetic refrigeration.

It is investigated how magnetostatic interactions affect the coercivity of alnico-type magnets. Starting from exact micromagnetic relations, we analyze two limits, namely cooperative reversal processes operative on short lengths scales and noncooperative reversal processes on long length scales. In alnicos, intrawire interactions are predominantly cooperative, whereas interwire effects are typically noncooperative. However, the transition between the regimes depends on feature size and hysteresis-loop shape, and interwire cooperative effects are largest for nearly rectangular loops. Our analysis revises the common shape-anisotropy interpretation of alnicos.

Bulk alloys and thin films of Fe-substituted Ti3Co5B2 have been investigated by first-principle density-functional calculations. The series, which is of interest in the context of alnico magnetism and spin electronics, has been experimentally realized in nanostructures but not in the bulk. Our bulk calculations predict paramagnetism for Ti3Co5B2, Ti3Co4FeB2 and Ti3CoFe4B2, whereas Ti3Fe5B2 is predicted to be ferromagnetic. The thin films are all ferromagnetic, indicating that moment formation may be facilitated at nanostructural grain boundaries. One member of the thin-film series, namely Ti3CoFe4B2, is half-metallic and exhibits perpendicular easy-axis magnetic anisotropy. The half-metallicity reflects the hybridization of the Ti, Fe and Co 3d orbitals, which causes a band gap in minority spin channel, and the limited equilibrium solubility of Fe in bulk Ti3Co5B2 may be linked to the emerging half-metallicity due to Fe substitution.

High-anisotropy arc-melted and field-annealed Mn100−x Bi x (x = 50–65) alloys have been investigated. Samples predominantly consist of low-temperature phase (LTP) MnBi and elemental Bi, where the LTP volume fraction and sample magnetization decrease with increasing x. All samples are hard ferromagnetic at room temperature and demonstrate a structural and magnetic phase transition at 630 K. For Mn35Bi65, the highest values for coercivity (4.6 kOe), magnetization remanence ratio (0.97), and energy product (4.9 MGOe) are measured at 540 K, near the melting point of bismuth. We explain the trend in magnetic properties as a consequence of c-axis alignment of MnBi grains facilitated by the molten Bi during magnetic field annealing.

The role of B on the microstructure and magnetism of Zr16Co82.5-xMo1.5Bx ribbons prepared by arc melting and melt spinning is investigated. Microstructure analysis show that the ribbons consist of a hard-magnetic rhombohedral Zr2Co11 phase and a minor amount of soft-magnetic Co. We show that the addition of B increases the amount of hard-magnetic phase, reduces the amount of soft-magnetic Co and coarsens the grain size from about 35 nm to 110 nm. There is a monotonic increase in the volume of the rhombohedral Zr2Co11 unit cell with increasing B concentration. This is consistent with a previous theoretical prediction that B may occupy a special type of large interstitial sites, called interruption sites. The optimum magnetic properties, obtained for x = 1, are a saturation magnetization of 7.8 kG, a coercivity of 5.4 kOe, and a maximum energy product of 4.1 MGOe.

Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc); Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc) that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.