Cr Composites Research Articles

Encapsulating Halide Perovskite Quantum Dots in Metal–Organic Frameworks for Efficient Photocatalytic CO2 Reduction

Halide perovskite has shown great potential in photocatalysis owing to its diversity, suitable energy band alignment, rapid charge transfer, and excellent optical properties. However, poor stability, especially under humid conditions, hinders their practical application in photocatalysis. In this work, we report the encapsulation of inorganic–organic hybrid perovskite QDs into MIL-101(Cr) through an in situ growth strategy to prepare a series of MAPbBr3@MIL-101(Cr) (MA = CH3NH3+) composites. The perovskite precursors, i.e., MABr and PbBr2, were successively introduced into the pores of MOF, where the perovskite quantum dots were self-assembled in the confined environment. In photocatalytic CO2 reduction, 11%MAPbBr3@MIL-101(Cr) composite displayed the best performance among the composites with a total CO and CH4 yield of 875 μmol g−1 in 9 h, which was 8 times higher than that of the pure MAPbBr3. Such high gas production efficiency could be maintained for 78 h at least without structural and morphologic decomposition. The remarkable stability and catalytic activity of composites are mainly due to the synergistic effect and improved electron transfer between MAPbBr3 and MIL-101(Cr). Moreover, these composites revealed a novel mechanism, showing switched CH4 selectivity with the controlling of the perovskite location and contents. Those with perovskites encapsulated in the mesopores of MIL-101(Cr) were more preferential for CO production, while those with perovskites encapsulated in both meso- and micropores could produce CH4 dominantly.

Influence of the processing route on the mechanical properties of Cu–35Cr metal matrix composites

Cu–Cr-based composites with Cr content ranging from 20 to 50 wt% are widely used as electrical contacts for vacuum interrupters for medium voltage applications because of their excellent combination of mechanical, thermal, and electrical conductivity. Cu–Cr electrical contacts are usually processed by sintering or casting. Their mechanical properties have been the interest of some studies to enhance their percussion welding performance. However, a detailed microstructure-mechanical properties relationship for such composites is yet to be established. Herein, we report an in-depth multi-scale microstructural characterization of solid-state sintered and vacuum arc-remelted Cu–35Cr composites, coupled with the characterization of their mechanical properties. The strengthening mechanisms in both Cu and Cr phases are discussed in light of the microstructure differences caused by the processing route. The presence of large and interconnected pores at the Cu/Cr interfaces in the sintered Cu–Cr composites reduces the load transfer from the Cu matrix to the Cr reinforcing particles and leads to a lower dislocation density by differential thermal mismatch in the Cu matrix. We shed light on the influence of the processing routes on the microstructure-mechanical property relationships for Cu–35Cr composite materials.

Enhanced plastic deformation ability of copper matrix composites through synergistic strengthening of nano-Al2O3 and Cr particles

The commercial application of Al2O3/Cu composites (ODS copper) with high Al2O3 content is consistently restricted by their plastic deformability. In order to synergistically improve the plastic deformability of Al2O3/Cu composites, Al2O3/Cu–Cr composites with different Cr contents are prepared by internal oxidation combined with heat treatment by replacing part of the Al2O3 particles with Cr phases heat treatment. The effects of Cr content on the microstructure and plastic deformability of Al2O3/Cu–Cr composites are investigated. It is found that the nano-Al2O3 (8 nm) and Cr (25 nm) particles are uniformly distributed in the copper matrix, and both reach a semi-congruent interface with copper matrix. Meanwhile, the copper matrix undergoes a transition from a [111]Cu hard orientation to a [100]Cu soft orientation, and the increase in Cr content leads to a more pronounced degree of recrystallization in the Al2O3/Cu–Cr composites. The results of geometric phase analysis (GPA) show that the coordinated deformability between Cr and Cu is better than that between Al2O3 and Cu. The elongation of 2.5Al2O3/Cu-0.3Cr composite increased to 24.48 % from 22.47 % of the Cr-free 2.8Al2O3/Cu composite. The results of tensile strength calculations show that the tensile strength of Al2O3/Cu–Cr composites is mainly dominated by matrix strengthening and Orowan strengthening induced by Al2O3 particles, while grain strengthening, dislocation strengthening, and Orowan strengthening induced by Cr particles play a secondary role. The correlation coefficient (R2) is 0.95 after fitting the experimental and theoretical values of tensile strength of Al2O3/Cu–Cr composites.

Evaluating the efficiency of functionalized zinc oxide based curing system for polychloroprene composites and analyzing its effect on curing, physical, and morphological properties for the application in specialty power transmission belts

Polychloroprene rubber (CR) is one of the most abundantly used elastomer in power transmission belt section due to its excellent oil resistance, weather resistance, antistatic and dynamic properties. However, due to the negative impact of Zinc Oxide (ZnO) used with CR rubber towards marine environment, it is necessary to minimize the use of ZnO in CR based rubber compounds. Functionalized-ZnO(F–ZnO) being emerged as a suitable replacement for regular ZnO in rubber compounding, the effect of F–ZnO on the curing, mechanical and morphological properties of polychloroprene (CR) based composites to use in power transmission belt applications are evaluated in this work. The curing properties of F–ZnO based composites were characterized using various techniques and results were reported as a comparison with the properties of conventional ZnO (C– ZnO) based CR composites. Properties of various ZnO were analyzed using X-ray Diffraction (XRD) analysis and Field-Emission Scanning Electron Microscopy (FESEM) studies. The replacement of C–ZnO with F–ZnO help to reduce 80 % of Zn content from the end products without effecting the cure time and cross-link density of the same. 5 PHR of C– ZnO from regular compound is replaced with 1 and 3 Phr of F–ZnO and its effect on power transmission belt properties were analyzed thoroughly.

Integration of [Cr3O(HCOO)6(H2O)3]NO3 into MIL-101(Cr) for enhanced separation of CO2/N2 mixture

Developing novel adsorbents for CO2 capture and separation offers an efficient approach to relieving global environmental problems. To promote CO2 capture from flue gas, novel Cr3O@MIL-101(Cr) composites was synthesized through packing [Cr3O(HCOO)6(H2O)3]NO3 into MIL-101(Cr) cages. The resultant composite Cr3O@MIL-101(Cr) presents higher CO2 uptakes at lower pressure ranges, benefiting from the increased content of unsaturated Cr(III) ions and micropores relative to MIL-101(Cr). Meanwhile, IAST selectivity for CO2/N2 mixture reached 50.2 under standard temperature and pressure, outperforming most of the reported materials. Further GCMC simulations reveal that the synergistic effect of [Cr3O(HCOO)6(H2O)3]+, NO3− and MIL-101 (Cr) could effectively facilitate the interactions with CO2 molecules and hinder N2 molecules from approaching the optimal adsorption sites. Thus the [Cr3O(HCOO)6(H2O)3]NO3 encapsulated MIL-101(Cr) can be recommended as a promising adsorbent for superior CO2/N2 separation.

Strengthening Fe1.4Co0.8Ni0.8Cr high-entropy alloy composites via in-situ synthesis of TiC: Perspective from experiments and first principles calculations

Achieving a harmonious balance between strength and plasticity is a long-standing problem in single-phase face-centered-cubic (fcc) high-entropy alloys (HEAs). Herein, in-situ TiC ceramic particle reinforced fcc-structured Fe1.4Co0.8Ni0.8Cr HEAs is designed and investigated by combining the experiments and first-principate calculations. The results show that the y (TiC)–Fe1.4Co0.8Ni0.8Cr (y = 0, 2.5, 5.0, 7.5 and 10.0 %, y: volume fraction) composites consist of fcc phase with submicron/micron TiC after the co-addition of Ti and C element, and the formation of TiC facilitates to refine the microstructure of the composites. Such microstructural evolutions significantly enhance the mechanical performances of the composites. Particularly, the 7.5 % (TiC)–Fe1.4Co0.8Ni0.8Cr composite exhibits a high yield strength of ∼562.7 ± 7.7 MPa and tensile strength of ∼971.3 ± 5.4 MPa, which are respectively increased by 169.0 % and 88.3 % as compared with the Fe1.4Co0.8Ni0.8Cr based alloy, yet with the fracture elongation decreases to 35.9 ± 0.3 %. The increment in yield strength is mainly driven from the combined effect of the grain refinement strengthening, dislocation strengthening and precipitation strengthening. Density functional theory (DFT) results reveal that the increase of C–Ti bonds and the formation of covalent bonds in the 7.5 % (TiC)–Fe1.4Co0.8Ni0.8Cr composite lead to relatively higher strength and lower ductility, which are well agreed with the experimental results.

Simultaneous enhancement of CO2 adsorption capacity and kinetics on a novel micro-mesoporous MIL-101(Cr)-based composite: Experimental and DFT study

MIL-101(Cr), a class of metal-organic framework, is a potential candidate for CO2 capture applications because of its high capacity of adsorption and separation capability. However, the intrinsic microporous structure of this nanomaterial poses limitations on its adsorption kinetics. Techniques employed to enhance its adsorption kinetics often adversely impact its adsorption capacity at equilibrium. Herein, as a new approach, we prepared amine-functionalized FAC@MIL-101(Cr) composites with adjustable micro-mesoporous structure and tunable nitrogen content by embedding different ratios of amine-functionalized activated carbon throughout the framework of MIL-101(Cr). This led to a simultaneous improvement in both kinetics and adsorption capacity for CO2. The best adsorbent, FAC-6@MIL-101(Cr), has excellent textural properties with a high surface area (1763.1 m2.g−1), great pore volume (1.29 cm3.g−1), and suitable nitrogen content (4.7 wt%). The adsorption analysis revealed that the modification of MIL-101(Cr) improved its CO2 adsorption capacity from 3.21 to 5.27 mmol/g under standard conditions of 1 bar and 25 °C. Furthermore, the FAC-6@MIL-101(Cr) adsorbent demonstrated fast CO2 adsorption kinetics (three times more relative to the pure MIL-101(Cr)), high CO2/N2 selectivity, and remarkable cyclic stability. The results confirmed that hybridization enhanced the polarizability of FAC@MIL-101(Cr) samples, causing more robust CO2-adsorbent surface interactions. Simultaneously, the existence of mesopores in the structure facilitated the transport of CO2 into the interior pores, resulting in a more efficient contact of CO2 molecules with all of the amine sites and a faster adsorption rate as well as more efficient regeneration. According to density functional theory (DFT) calculations, hybridization process induces significant changes in composites’ electronic structure, enhancing their capacity to interact with CO2 molecules more effectively. On the other hand, DFT calculations confirm that N2 molecule is less activated on the FAC@MIL-101(Cr) as evidenced by calculated small adsorption energy and charge-transfer values.

Enhanced hot deformation property of Al2O3/Cu–Cr composite fabricated by internal oxidation

The plastic deformability of ODS copper (Al2O3/Cu composite) always limits its widespread commercial application. In this work, the thermodynamically metastable mono-phase CuCr alloy was used to fabricate 2.5 vol%Al2O3/Cu-0.3 vol%Cr by an internal oxidation method with a subsequent solution treatment to improve the plastic deformation ability. The influence of dissolved Cr on the hot deformation property and dynamic recrystallization (DRX) behavior of Al2O3/Cu composite was studied, and the softening mechanism of Al2O3/Cu–Cr composite was revealed. The results show that the solid solution of Cr at high temperature can significantly improve the hot deformability of Al2O3/Cu composite. The maximum reduction of peak stress of 2.5 vol%Al2O3/Cu-0.3 vol%Cr composite is 57 % lower than that of 2.8 vol% Al2O3/Cu composite. Furthermore, the DRX critical values of 2.5 vol%Al2O3/Cu-0.3 vol%Cr composite is lower than that of 2.8 vol% Al2O3/Cu composite, and the DRX occurs earlier in Al2O3/Cu–Cr composite. The strain-compensated constructive model of Al2O3/Cu–Cr composite was established with a relation coefficient (R2) of 0.92, which proves the accuracy of the model. Finally, the hot processing map of Al2O3/Cu–Cr composite was constructed based on a dynamic analysis model, and the appropriate hot processing parameter of Al2O3/Cu–Cr composite was obtained with temperature of 1205 K–1223 K and strain rate of 0.022 s−1-0.97 s−1. The results are beneficial to improve hot deformation property of Al2O3/Cu–Cr composite and large sized bulks fabrication.

Effect of Nb addition on microstructure and mechanical properties of TiC/Ti-7.8Cr composites

The morphology of TiC is not difficult to control when the titanium matrix composites with high TiC content are prepared by the melting-casting method. TiC tends to grow into dendrites, increasing the brittleness of the Ti matrix composites. In this study, in-situ TiC-reinforced titanium matrix composites with varying Nb content were prepared by adding Nb. The effects of adding Nb on the microstructure evolution and mechanical properties of the composites were studied. The results show that with the increase of Nb content, the grain size of the composites decreased gradually from 276 μm to 122.8 μm, the primary TiC content decreased, and the eutectic TiC content increased. On the other hand, the orientation relationship between TiC (111)//β-Ti (110) and TiC [10 1‾]//β-Ti [1‾ 11] was studied by HTEM. The two-dimensional mismatch of TiC (111)//β-Ti (110) is only 9.06 %, which means that TiC can be used as a nucleation particle of β-Ti. Furthermore, there was a gradual increase in the Rockwell hardness of the composites as the Nb content was incrementally raised from 0 wt% to 1.5 wt%, with the highest recorded value being 47.4 HRC. Notably, when the Nb addition reached 1.0 wt%, the composite achieved its maximum tensile strength of 1352.9 MPa, signifying a 69 % enhancement compared to the absence of Nb. This is due to the combined effect of fine grain strengthening, solution strengthening, and second-phase strengthening in the composites. It introduces a novel approach to regulate the in-situ formation of TiC morphology during the preparation of titanium matrix composites through melting and casting.

Solution heat treatment of electron beam freeform fabricated in-situ TiC-γ'/ Ni–Fe–Cr composite: Strength-toughness synergy by regulating TiC and γ′ precipitates

Nickel matrix composites reinforced by ceramic particles typically exhibit elevated strength but diminished toughness. In this paper, a novel in-situ micron-size TiC and nano-size γ′ phases reinforced Ni–Fe–Cr matrix composite was successfully prepared using the electron beam freeform fabrication (EBF3). Subsequently, the as-built composite was subjected to solution heat treatment at different temperatures. At a solution temperature of 1150 °C, the composite demonstrates superior strength-toughness synergy (ultimate tensile strength = 1109.4 ± 25.4 MPa, elongation = 12.08 ± 0.62%), exhibiting an increase of 17.1% and 104.4%, respectively, compared to the as-built composite. A systematic analysis of the strengthening and toughening mechanisms revealed that the γ′ phase played a predominant role in enhancing strength, while the size, morphology, and content of TiC phase significantly influence fracture toughness. After being solution heat treated at 1150 °C for 2 h, the γ′ phase precipitated uniformly with its size coarsening to 93.85 nm, demonstrating an optimal strengthening effect by shearing mechanism. Meanwhile, the TiC phase partially dissolved into the matrix and transformed from a long-strip shape to a more stable spherical shape. This transformation significantly reduced the formation of microvoids along the TiC/matrix interface during tensile loading, enhancing the fracture toughness. The γ′ and TiC phases were regulated by solution heat treatment to reach a balance of optimising properties, achieving synergistic enhancements in strength and toughness.

MoO3/MeMoO4 (Me = Cu, Ni, Co, Fe, Mn, and Cr) composites as materials for prospective optical and electrical applications

The composite MoO3/MeMoO4 (Me = Cu, Ni, Co, Fe, and Mn) ceramics were obtained by standard high-temperature sintering. Their structure was tested using XRD, SEM, EDS, and XPS. The occurrence of two phases was determined. The main MoO3 phase exhibited an orthorhombic Pnma space group related to the ceramic grain of micrometre size. The second phase was induced by doping with the Me atom. It showed various monoclinic structures and a smaller grain size. The XPS test confirmed the coexistence of the phases, which was reflected in several lines in the patterns. The valence band of the undoped MoO3 was located ∼3.3 eV below the Fermi level. An additional subband attributed to the Me 3d state was detected within the energy gap. The MoO3/MeMoO4 composites showed a valence band shifted toward the Fermi level and overlapped with the subband, originating from hybridized Mo 4d – Me 3d states. Magnetic susceptibility showed an antiferromagnetic state below ∼20 K for the Ni- and Fe-doped composites. The estimated magnetic moment magnitudes indicated the contribution from Me2+ and Me3+ ions that marked the occurrence of oxygen vacancies. Diffuse reflectance spectra exhibited anomalies in the Vis (∼500–650 nm) and the NIR (∼700–850 nm) ranges and tails in the ∼900–1000 nm range. The estimated magnitudes of energy gaps were attributed to defect-induced states. They corresponded to deduced oxygen vacancies (2.05–2.38 eV) and states or subbands induced by the introduced Me atoms (1.34–1.89 eV). Electric dc resistivity temperature dependence showed thermally activated dependence. The estimated activation energy varied from 0.27 eV to 0.58 eV, depending on the doping of the Me atom. The electric features were consistent with the electronic structure determined using XRD and XPS tests.

Refinement and enhancement of high-Nb TiAl alloy via in-situ precipitation of Ti2AlC and TiB2 nanoparticles

An in-situ dual morphology of Ti2AlC/TiB2 nanoparticles was refined and enhanced to fabricate Ti-47.7Al-7.1Nb-2.3V-1.1Cr composites via induction hot-pressing sintering with nano-B4C addition. The generation process of nanoparticles, lamellar refinement mechanism, and effect of nanoparticles on the microstructure evolution/mechanical properties were meticulously analysed. With 0.2 at% nano-B4C addition, Ti2AlC/TiB2 nanoparticles were uniformly distributed in the matrix following sintering. In addition, upon sintering at 1425 °C for 10 min under a pressure of 50 MPa, the lamellar colony size decreased from 280 ± 145 μm to 55 ± 16 μm, and the ultimate tensile strength (UTS) increased by 116 MPa, 142 MPa, and 176 MPa, when tested at room temperature, 800 °C, and 900 °C, respectively. The enhanced mechanical properties were attributed to the synergistic effects of grain refinement strengthening, solid solution strengthening, the Orowan mechanism, and twinning strengthening.

Efficient removal and transformation of Cr(VI) from alkaline wastewater to form a ferrochromium spinel multiphase via a modified ferrite process

Chromium-containing wastewater causes serious environmental pollution due to the harmfulness of Cr(VI). The ferrite process is typically used to treat chromium-containing wastewater and recycle the valuable chromium metal. However, the current ferrite process is unable to fully transform Cr(VI) into chromium ferrite under mild reaction conditions. This paper proposes a novel ferrite process to treat chromium-containing wastewater and recover valuable chromium metal. The process combines FeSO4 reduction and hydrothermal treatment to remove Cr(VI) and form chromium ferrite composites. The Cr(VI) concentration in the wastewater was reduced from 1040 mg L−1 to 0.035 mg L−1, and the Cr(VI) leaching toxicity of the precipitate was 0.21 mg L−1 under optimal hydrothermal conditions. The precipitate consisted of micron-sized ferrochromium spinel multiphase with polyhedral structure. The mechanism of Cr(VI) removal involved three steps: 1) partial oxidation of FeSO4 to Fe(III) hydroxide and oxy-hydroxide; 2) reduction of Cr(VI) by FeSO4 to Cr(III) and Fe(III) precipitates; 3) transformation and growth of the precipitates into chromium ferrite composites. This process meets the release standards of industrial wastewater and hazardous waste and can improve the efficiency of the ferrite process for toxic heavy metal removal.

Microstructure and hydrogen storage properties of MgH2/MIL-101(Cr) composite

In this paper, a new hydrogen storage composite based on magnesium hydride and metal-organic framework MIL-101(Cr) (an acronym for Material Institute Lavoisier) has been mechanically synthesized and investigated. The hydrogen sorption and desorption behavior in the composite was investigated for the temperature and pressure ranges of (593−653) K and (0−3) MPa, respectively. According to the pressure-composition-temperature isotherms of hydrogen sorption/desorption, the MgH2–5 wt%MIL-101(Cr) composite starts to absorb hydrogen at a lower pressure at 593 K. In addition, the hydrogen release peak for composite shifts to lower temperatures by about 140 K compared to the pure milled MgH2 during temperature programmed desorption at a heating rate of 6 K/min. The activation energy of hydrogen desorption from the composite is 120 ± 2 kJ/mol, which is 36% lower than the activation energy of hydrogen desorption from magnesium hydride (189 ± 2 kJ/mol). The enthalpy of hydrogen absorption was found to be 73 kJ/mol H2 and 60 kJ/mol H2 for milled MgH2 and MgH2–5 wt%MIL-101(Cr) composites, respectively. It is showed that the MIL-101(Cr) MOF structures decompose during ball milling and the chromium oxide nanoparticles form a core-shell structure with MgH2 particles. Thus, composite has better sorption and desorption properties than pure magnesium/magnesium hydride due to the nanoconfinement of MgH2. The chromium oxide nanoparticles act as active sites on the surface of the magnesium particles and facilitate the dissociative chemisorption or recombinative desorption of hydrogen. The main regularities of the phase transition in the magnesium-hydrogen system for the composite and magnesium hydride during dehydrogenation have been studied for temperatures in the range of 298–750 K. The in situ analysis of the phase transitions during the dehydrogenation of MgH2 and MgH2–5 wt%MIL-101(Cr) composite indicates a pronounced catalytic effect of the addition of MIL-101(Cr) to the Mg/MgH2. Based on the experimental results and ab initio calculations, a mechanism for the sorption and desorption of hydrogen by the composite has been proposed.

Double step heating synthesis of MIL-101(Cr) composites for water harvesting applications

Energy storage is a valuable mechanism for managing fluctuations in energy demand by allowing the distribution of energy production needed during peak demand over a more extended period. Thermal energy storage is among the most valuable categories of energy storage. The optimal sorbent material must satisfy thermal, physical, chemical, and environmental requirements for designing sorption heat storage systems. MIL-101(Cr) is a Metal-Organic Framework (MOF) with remarkable properties such as a high surface area, hydrothermal stability and good water sorbent capacity that make it a potential candidate as a working sorbent. Their physicochemical properties can be modulated by functionalizing the organic linker or by modifying its structure, improving the interaction with the target sorbate, mainly environmentally friendly and non-toxic sorbates such as water. However, good water sorption capacity is not the only characteristic to be considered when selecting the sorbent material for sorption heat storage systems. Here, we propose an alternative method to obtain a sorbent material with the objective of reducing the reaction time and achieving a good balance between the physical properties of the material, such as the density and the thermal conductivity, without substantially decreasing its water uptake capacity. For this aim, we show that structural modification of MIL-101(Cr) induced by CaCl2 and graphene oxide (GO) can improve the water sorption capacity and optical properties compared to the pristine sorbent. The MIL-101(Cr)/GO/CaCl2 composite had a higher water uptake capacity of 1.08 gwater g−1composite-1, even compared with MIL-101(Cr)/CaCl2 composite with a water uptake capacity of 0.68 gwater g−1composite. Additionally, MIL-101(Cr)/GO and MIL-101(Cr)/GO/CaCl2 sorbents tend to absorb light toward the near-infrared region and increase the temperature around twice as much compared to sorbents without GO when illuminated with a flash lamp. These results demonstrate that GO added at the MIL-101(Cr) structure allows a better distribution of CaCl2 in the MIL-101(Cr) pores and it may be advantageous in the water desorption process making use of renewable infrared radiation sources such as solar energy.

A green synthesis of CuInS2/MIL-101(Cr) nanocomposite with efficient visible light induced photocatalytic activity

This study demonstrates the sustainable synthesis of multifunctional CIS@MIL-101(Cr) composites for water treatment applications. The composites were prepared via hybridization of CuInS2 with MIL-101(Cr) resulting in the formation of CIS nanoplates incorporated into MIL-101(Cr). The composites exhibited enhanced visible light photocatalytic activity due to their low bandgap energy and were tested for tetracycline photodegradation achieving a degradation efficiency of 98.8%. The material showed high stability after four cycles, and the effects of reactive species on photodegradation were investigated. The kinetics and mechanism of the photocatalytic process were studied, and LC-MS analysis was conducted to identify intermediate products. These results demonstrate the potential of using waste PET to create new semiconductors for water pollution control, promoting a circular material pathway.

Encapsulation of ionic liquid, phosphotungstic acid inside the nanocages of MIL-101(Cr): Effective and reusable catalyst for efficient solvent-free oxidative desulfurization from fuel oil

Oxidative desulfurization from fuel oil is one of the important methods for deep desulfurization. The development of efficient oxidative desulfurization catalysts is crucial for improving the desulfurization performance. Successful encapsulation of phosphotungstic acid (HPW) and ionic liquid (BMImBr) inside the mesoporous cages of MIL-101(Cr) was accomplished through a combination of “bottle around ship” and “ship in bottle” methods. The obtained BMImPW@MIL-101(Cr) composite was characterized by XRD, FTIR, BET, SEM, XPS and ICP methods. Results indicated that the BMImPW@MIL-101(Cr) composites with PW3− loading of 23.1–50.7 wt% were obtained, demonstrating that the “bottle around ship” method is beneficial to make full use of nanocages of MIL-101(Cr) to obtain expected high loading of active PW3−. The BMImPW@MIL-101(Cr) exhibits excellent reusability with no evidence of leaching of active PW3− and BMIm+, and well-preserved structure after successive cycles of regeneration and reuse. The significantly improved stability of BMImPW@MIL-101(Cr) as compared to HPW@MIL-101(Cr) is possibly because the leaching of the active PW3−− sites can be greatly suppressed by forming large size of BMImPW owing to introduction of BMIm+ cation. The BMImPW@MIL-101(Cr) exhibited excellent catalytic activity for solvent free oxidative desulfurization of refractory sulfides. The enhanced oxidative desulfurization activity as compared to HPW@MIL-101(Cr) can be explained by the intimate contact of sulfides with active PW3− sites owing the strong attraction of BMIm+ cation with the sulfides.

Fabrication of visible light responsive nitrogen-doped carbon quantum dots/MIL-101(Cr) composites for enhanced photodegradation of Rhodamine B

In this study, an environmentally friendly hydrothermal process was successfully utilized for the fabrication of MIL-101(Cr) (MIL-Cr) and nitrogen-doped carbon quantum dots (N-CQDs) without employing toxic and hazardous hydrofluoric acid and organic solvents. Then, a simple solvent-deposition technique was used to prepare MIL-Cr/N-CQDs(x) composites without requiring specialized equipment. To assess the photocatalytic capabilities of the synthesized materials, Rhodamine B (RhB) was chosen as one of the wastewater toxic organic dye pollutants for photo-degradation experiments. The optimum amount of N-CQDs in composite structure was determined by mixing different volumes of N-CQDs with MIL-Cr, in which MIL-Cr/N-CQDs(2) composite exhibited the highest photocatalytic performance (95%) under visible light illumination. Also, all composites showed better photocatalytic activity in comparison with pristine MOF and N-CQDs individually because N-CQDs can operate as electron acceptors when coupled with MOF, which can prevent the fast electron-hole recombination and increase the visible light absorption. Based on the results of the kinetic investigation, the MIL-Cr/N-CQDs(2) depicted the highest kinetic rate, which is 2.63 and 9.5 times larger than pristine MIL-Cr and N-CQDs under the same experimental conditions. Furthermore, a photocatalytic mechanism was postulated through reactive species scavenging experiments, and it was found that •OH and photo-generated h+ were crucial to the degradation process.

Fabrication and Soft Magnetic Properties of Fe–Si–Cr Composites with Double-Insulating Layers Suitable for High-Frequency Power Applications

Soft magnetic composites (SMCs) are composed of alloy materials with the core and insulating layers as the shell. These composites exhibit high saturation magnetic sensitivity and low hysteresis loss, making them a promising material for various applications. The investigation of double layers is considered valuable as it can effectively address the issues of low resistivity and high dynamic loss that arise from non-uniform insulating layers in SMCs. In this study, Fe-Si-Cr/SiO2 particles with a core–shell heterostructure were produced via chemical vapor deposition (CVD). The Fe-Si-Cr/SiO2 materials were coated with different weight percentages (1–6%) of sodium silicate (SS). Subsequently, Fe-Si-Cr-based SMCs were synthesized through high-pressure molding and heat treatment. The effect of the SS weight percentage on microscopic changes and magnetic characteristics was investigated. These findings indicated that a concentration of 4 wt% of SS was the most effective at enhancing magnetic characteristics. The resultant SMCs exhibited high resistivity (21.07 mΩ·cm), the lowest total loss (P10 mt/300 kHz of 44.23 W/kg), a relatively high saturation magnetization (181.8 emu/g), and permeability (35.9). Furthermore, it was observed that the permeability exhibited stabilization at lower frequencies. According to these findings, the combination of CVD and double layers could lead to the further development of SMCs in a variety of applications.

Probing the texture transition sequence of near β titanium matrix composites by observing the uneven hot deformation microstructure

This study is focused on the sequence of texture transformation and uneven microstructure evolution during hot compression of 2 vol% TiC/Ti-4Al-1Sn-2Zr-5Mo-8 V-2.5Cr composites. After hot compression, the uneven microstructures, including local high deformed region (HDR) and low deformation region (LDR), are observed by EBSD. The area and width of elongated grains decrease in the HDR, but the LDR shown the opposite trend as temperature and deformation rate rise. The sequence of texture transformation with different lattice rotation axis during hot compression of TMCs is established based on lattice rotation during continuous recrystallization (CDRX). At a low temperature (850 °C), initial as-cast (110)//CD (ζ fiber) texture first changes to (111)//CD (γ fiber) texture, and then stable (001)//CD texture (θ fiber: {001} 〈0−10〉). The rotation axis is the 〈110〉 direction on the {001} plane. Low-temperature stable (001)//CD texture can be further changed into near-(110)//CD with varied rotation axis of 〈111〉 direction on the {110} plane if the deformation temperature is sufficiently high and strain rate is low (for instance, at 940 °C with 0.001 s−1). Meanwhile, the effect of TiC particles on β matrix texture is limited, and an orientation relationship of [−1−11]β//[−1−10]TiC1¯1¯1β//1¯1¯0TiC is identified between TiC particles and the β matrix.