Interfacial Reaction Mechanism Research Articles

Enhanced Cyclability of Cr8O21 Cathode for PEO-Based All-Solid-State Lithium-Ion Batteries by Atomic Layer Deposition of Al2O3

Cr8O21 can be used as the cathode material in all-solid-state batteries with high energy density due to its high reversible specific capacity and high potential plateau. However, the strong oxidation of Cr8O21 leads to poor compatibility with polymer-based solid electrolytes. Herein, to improve the cycle performance of the battery, Al2O3 atomic layer deposition (ALD) coating is applied on Cr8O21 cathodes to modify the interface between the electrode and the electrolyte. X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy, etc., are used to estimate the morphology of the ALD coating and the interface reaction mechanism. The electrochemical properties of the Cr8O21 cathodes are investigated. The results show that the uniform and dense Al2O3 layer not only prevents the polyethylene oxide from oxidization but also enhances the lithium-ion transport. The 12-ALD-cycle-coated electrode with approximately 4 nm Al2O3 layer displays the optimal cycling performance, which delivers a high capacity of 260 mAh g−1 for the 125th cycle at 0.1C with a discharge-specific energy of 630 Wh kg−1.

Oxygen electrochemistry in Li‐O2 batteries probed by in situ surface‐enhanced Raman spectroscopy

AbstractSurface‐enhanced Raman spectroscopy (SERS), as a nondestructive and ultra‐sensitive single molecular level characterization technique, is a powerful tool to deeply understand the interfacial electrochemistry reaction mechanism involved in energy conversion and storage, especially for oxygen electrochemistry in Li‐O2 batteries with unrivaled theoretical energy density. SERS can provide precise spectroscopic identification of the reactants, intermediates and products at the electrode|electrolyte interfaces, independent of their physical states (solid and/or liquid) and crystallinity level. Furthermore, SERS's power to resolve different isotopes can be exploited to identify the mass transport limitation and reactive sites of the passivated interface. In this review, the application of in situ SERS in studying the oxygen electrochemistry, specifically in aprotic Li‐O2 batteries, is summarized. The ideas and concepts covered in this review are also extended to the perspectives of the spectroelectrochemistry in general aprotic metal‐gas batteries.

Layered double hydroxide photocatalysts for solar fuel production

Splitting water or reducing CO2via semiconductor photocatalysis to produce H2 or hydrocarbon fuels through the direct utilization of solar energy is a promising approach to mitigating the current fossil fuel energy crisis and environmental challenges. It enables not only the realization of clean, renewable, and high-heating-value solar fuels, but also the reduction of CO2 emissions. Layered double hydroxides (LDHs) are a type of two-dimensional anionic clay with a brucite-like structure, and are characterized by a unique, delaminable, multidimensional, layered structure; tunable intralayer metal cations; and exchangeable interlayer guest anions. Therefore, it has been widely investigated in the fields of CO2 reduction, photoelectrocatalytic water oxidation, and water photolysis to produce H2. However, the low carrier mobility and poor quantum efficiency of pure LDH limit its application. An increasing number of scholars are exploring methods to obtain LDH-based photocatalysts with high energy conversion efficiency, such as assembling photoactive components into LDH laminates, designing multidimensional structures, or coupling different types of semiconductors to construct heterojunctions. This review first summarizes the main characteristics of LDH, i.e., metal-cation tunability, intercalated guest-anion substitutability, thermal decomposability, memory effect, multidimensionality, and delaminability. Second, LDHs, LDH-based composites (metal sulfide-LDH composites, metal oxide-LDH composites, graphite phase carbon nitride-LDH composites), ternary LDH-based composites, and mixed-metal oxides for splitting water to produce H2 are reviewed. Third, graphite phase carbon nitride-LDH composites, MgAl-LDH composites, CuZn-LDH composites, and other semiconductor-LDH composites for CO2 reduction are introduced. Although the field of LDH-based photocatalysts has advanced considerably, the photocatalytic mechanism of LDHs has not been thoroughly elucidated; moreover, the photocatalytic active sites, the synergy between different components, and the interfacial reaction mechanism of LDH-based photocatalysts require further investigation. Therefore, LDH composite materials for photocatalysis could be developed through structural regulation and function-oriented design to investigate the effects of different components and interface reactions, the influence of photogenerated carriers, and the impact of material composition on the physical and chemical properties of the LDH-based photocatalyst.

Wettability and interfacial reaction mechanism between Ag–Cu alloy and Si3N4 ceramics in air atmosphere

The wetting behaviour and interfacial reaction mechanism between Ag–Cu alloy fillers (with varying copper contents) and Si3N4 ceramics using reactive air brazing at 970 °C were systematically investigated. As the copper content increased, the contact angles of the Ag–Cu filler on the Si3N4 ceramics decreased. A violent boiling-like interfacial reaction was observed during the experiment, and mass spectrometry analysis identified the gaseous products as N2, NO and NO2. The solid products SiO2 and Cu–O formed at the interface, and the interfacial reactions improved the wettability of the Ag–Cu filler on the Si3N4 ceramics. Owing to buoyancy and the pushing of the gases, the interfacial products floated to the surface of the filler and their distribution increased along with the increasing copper content. Two different microstructures were formed at the interface near the triple line. Thick and thin SiO2 layers were respectively formed on the triple line interface of the fillers with low (Ag–3Cu/Ag–5Cu) and high (Ag–6.6Cu/Ag–16Cu) copper content. The interfacial bonding zones formed in Ag–5Cu, Ag–6.6Cu, and Ag–16Cu samples indicated that the corresponding Ag–Cu fillers were effectively brazed with the Si3N4 ceramics.

Reactive wetting and interfacial reaction mechanism of ZrC-SiC ceramic and Ag-Zr filler

In this study, the isotherm wetting and spreading behaviors of molten Ag-Zr filler on ZrC-SiC ceramic surface was investigated using a sessile drop method in vacuum. The effect of Zr content in Ag-Zr filler on the wetting behavior was studied, and the wetting mechanism was revealed in details. The results showed that the contact angle of Ag-Zr filler on the ZrC-SiC surface decreased from 140 ° to 20 ° with the Zr content varied from 0 to 8 wt.%, and the Zr was the key factor to the wetting process. The wetting dynamic analysis illustrated that the interfacial reaction controlled the wetting of Ag-Zr filler on the ZrC-SiC surface. Due to the Zr activity difference at Ag-Zr/ZrC interface, the ZrC released C into Ag-Zr filler, and reacted with Zr to form new-born ZrC with higher Zr content. The formation of the new-born ZrC promoted wetting and spreading of Ag-Zr filler on ZrC-SiC surface.

Mechanisms of Si Nanoparticle Formation by Molten Salt Magnesiothermic Reduction of Silica for Lithium‐ion Battery Anodes

AbstractMolten salt methods enable the synthesis of Si nanostructures by moderating the thermal energy evolved in highly exothermic magnesiothermic reduction reactions (MRR) of silica. Due to their cost‐effectiveness and scalability, these techniques are well suited for producing nanoscale Si for a number of applications, including energy storage. To control the microstructure morphology and particle size, it is necessary to understand the formation mechanism of the Si produced. By evaluating the time‐resolved phase evolution, when NaCl moderates the thermal energy generated by MRR of SiO2, we elucidate 3 parallel interfacial reaction mechanisms yielding Si nanoparticles – via Mg vapor, Mg‐rich eutectic liquid, and Mg ions dissolved in molten NaCl. These individual Si nanoparticles offer a striking contrast to the typical by‐product of MRR of SiO2 with and without NaCl, which yields a 3‐dimensional (3‐D) porous network of sintered Si nanoparticles. Lithium‐ion battery half‐cells with electrodes composed of individual Si nanoparticles showed a greater first‐cycle irreversible discharge capacity and faster capacity loss over the first 5 cycles at a current density of 200 mA g−1 compared to half‐cells with electrodes of a porous 3‐D Si network–indicative due to thicker solid electrolyte interphase (SEI) formation on individual particles. At a higher current rate of 400 mA g−1, once SEI formation and activation of Si are established, both cells exhibit a similar capacity retention rate over 100 cycles.

Unraveling the multiple roles of Ag species incorporation into OMS-2 for efficient catalytic ozonation: Structural properties and mechanism investigation

Silver incorporated manganese oxide octahedral molecular sieves (Ag-OMSX-T) were successfully synthesized via a hydrothermal-calcination method. Due to the multiple roles of Ag species doping, the optimal Ag-OMS0.2-180 nanocatalyst with the Ag/Mn molar ratio of 0.2 had the highest TOF value (2.94 × 10−5 mol g−1 h−1), which could completely degrade 50 mg L−1 OA at pH 5.0 in 30 min much higher than those of OMS-2 (22.3%) in catalytic ozonation system. The results of systematic characterization (such as XRD, XPS, Py-IR, and O2-TPD) and catalytic performance tests of Ag-OMS0.2-180 clearly demonstrated that the proper amount of Ag incorporation not only facilitated the electron transfer but also induced more formation of Lewis acid sites in Ag-OMS0.2-180 as well as metals (Ag and Mn) as activation sites to collectively favor the catalytic ozonation degradation of OA. In addition, the higher mineralization rate has been achieved (79.6%) and the Ag-OMS0.2-180 exhibited the satisfactory stability and reusability with low metal release during multiple consecutive cycles (≥ 5). Meanwhile, the electron spin resonance spectra and radical scavenger tests confirmed that superoxide radical and singlet oxygen were the main reactive oxygen species in catalytic process. The mechanism of solid-liquid interface reaction and the pathway of cycling of oxygen vacancies were also elaborated, which present a new insight for water decontamination.

Enhanced photocatalytic reduction of Cr(VI) by the novel hetero-system BaFe2O4/SnO2

In this study, BaFe2O4 nanoparticles with a crystallite size of 86 nm were produced using the sol–gel method and applied in the photoreduction of chromate. The spinel phase was identified by X-ray diffraction and scanning electron microscopy-energy-dispersive X-ray analysis. The structure was refined in orthorhombic symmetry by Rietveld analysis. A forbidden band (Eg) of 2.03 eV was extracted from the diffuse reflectance data and the optical transition was directly permitted. The thermal dependence of the electrical conductivity (σ) followed an exponential law with an activation energy of 0.23 eV. In addition, photo-electrochemical characterization of the spinel was conducted to establish the energy diagram for the hetero-system BaFe2O4/SnO2/HCrO4− solution in order to assess the interfacial reaction mechanism. Similar to most spinels, BaFe2O4 exhibits p-type behavior with a flat band potential (Efb) of 0.52 VSCE. Therefore, the potential of the conduction band (ECB) is sufficiently negative to be involved in an electronic injection with SnO2. The photoluminescence spectrum obtained for the rutile contained an intense peak at 590 nm and its intensity was substantially reduced in the hetero-system. Electrochemical impedance spectroscopy detected a depressed arc assigned to a constant phase element and its resistance (1.64 kΩ cm2) decreased to 1.05 kΩ cm2 under visible light, thereby confirming the semiconductor behavior. The reduction of Cr(VI) was successfully achieved with the BaFe2O4/SnO2 hetero-system under visible light as an application. Photocorrosion was prevented by using oxalate (C2O42−) as a scavenger to captures the holes and improve the photo-activity. The quasi-total chromate reduction had a reduction efficiency of 99% with a concentration of 30 mg L−1 under a light flux of 16 mW cm−2. The kinetics followed a first-order model with a photocatalytic half-life of 38 min and the results were fitted in an appropriate manner to the Langmuir–Hinshelwood model. Moreover, BaFe2O4/SnO2 exhibited photocatalytic efficacy for five successive runs and the final reduction efficiency was still 92%.

Doping and facet effects synergistically mediated interfacial reaction mechanism and selectivity in photocatalytic NO abatement

The surface atomic coordination and arrangement largely determine photocatalytic properties. Whereas, the intrinsic impact of surface microstructures on the reaction mechanism and pathway is still unclear. Herein, via constructing N-doped Bi2O2CO3 photocatalysts with diverse exposed facets, (1 1 0) and (0 0 1) facet, we testify that the pivotal roles of crystal facet and doping effect on the intermediate production and reactivity for photocatalytic nitric oxide (NO) abatement. The photoreactivity of N-doped Bi2O2CO3 is documented to be higher than that of the pure samples because of the enhanced light absorption and charge transfer. Further in situ probing experiments and theoretical calculations verify that the unique adsorption patterns and activated intermediates on the (1 1 0) facet facilitate the formation of final products and inhibit the generation of toxic NO2 by-product in terms of thermodynamics. More importantly, we found that the selective and nonselective oxidation processes are emerged over (1 1 0) and (0 0 1) facets of Bi2O2CO3, respectively.

Laser welding of 6082 aluminum alloy to TC4 titanium alloy via pure niobium as a transition layer

A Ti/Al joint with an Nb transition layer was obtained, where aluminum alloy and Nb sheet partially melted to form the weld and diffusion bonding was formed at Ti/Nb interface. The remaining transition layer Nb acted as a diffusion barrier between TC4 titanium alloy and 6082 aluminum alloy thus successfully prevented the formation of brittle TiAl, TiAl2 and TIAl3 phases. A flat Ti–Nb diffusion zone composed of (Ti, Nb) solid solution was formed at Ti/Nb interface, while a narrow Al–Nb reaction zone was formed at the Nb/Al–FZ (aluminum alloy fusion zone) interface with the main microstructures of NbAl3, Nb2Al and Al-based solid solution. The simulation of welding temperature field and thermal cycle curve by finite element software was conducted to provide theoretical data support for clarifying the formation of the joint and interface reaction mechanism. The mechanical property of the joint was determined by the Al–Nb reaction zone which could be witnessed by observing the fracture location and hardness distribution of the joint. The joint fractured at the Al–Nb reaction zone and adjacent Al–FZ with the maximum tensile strength of 288.97 MPa.

Effect of Zr addition on the interfacial reaction of the SiC joint brazed by Inconel 625 powder filler

Ni-based alloys are believed to be the most suitable brazing fillers for SiC ceramic application in a nuclear environment. However, graphite, which severely deteriorates the mechanical property of the joint, is inevitable when Ni reacts with SiC. In this paper, Different amounts of Zr powders are mixed with Inconel 625 powders to braze SiC at 1400 °C. When Zr addition reaches 40 wt%, the brazed seam confirms the absence of graphite. This research proves that Zr can avoid the graphite’s formation by suppressing Ni’s activity. The room-temperature shear strength of the joint with graphite’s absence is tested to be 81.97 MPa, which is almost three times higher than that of the joint with graphite. The interfacial reaction process and mechanism of the SiC joint are investigated and explained in this paper using thermodynamic calculations.

Fe-Ti Co-Doped Alumina-Induced Surface Dual Reaction Center for Catalytic Ozonation to Remove Pollutants from Water

Multiphase catalytic ozone oxidation technology has received wide attention for its effectiveness in removing organic pollutants from water. However, the existence of a rate-limiting step in the metal oxide-catalyzed ozonation process based on single-site redox, which inhibits the activity, greatly limits the practical application of the multiphase catalytic ozonation technology. To solve this bottleneck problem, lattice doping of metal oxide γ-Al2O3 substrates with transition metal species Fe and Ti was used to prepare novel dual reaction center catalysts (FT-A-1 DRCs). Characterization of their morphological structures and chemical compositions was conducted by XRD, TEM, XPS, and other techniques, and it was demonstrated that the lattice substitution of Fe and Ti for Al resulted in the formation of surface-poor electron-rich microregions (electron-rich Fe microcenters and electron-deficient Ti microcenters). The FT-A-1 DRCs were used to catalyze the odor oxidation process and exhibited excellent activity and stability for the removal of a range of non-degradable organic pollutants, such as ibuprofen. The interfacial reaction mechanism was revealed using EPR and electrochemical techniques. It was found that in the catalytic odor oxidation process, O3/H2O was directionally reduced at the electron-rich microcenters to produce·OH, whereas the contaminants could be oxidized at the electron-deficient microcenters as electron donors to continuously supply electrons to the reaction system. This reaction process utilizes the pollutant's own energy to achieve two-way degradation of the pollutant (·OH attack and direct electron donor), thereby overcoming the rate-limiting step in the metal-oxide-catalyzed ozone oxidation process.

Interfacial microstructure and reaction mechanism with various weld fillers on laser welding-brazing of Al/Cu lap joint

The influence of pure Al, Al-Si and Zn-Al weld fillers on microstructure and mechanical properties was investigated during lap laser welding-brazing of Al to Cu. Al 4.2 Cu 3.2 Zn 0.7 IMC layer and plate-like Al 2 Cu phase were observed at Al/Cu interface with pure Al and Al-Si weld fillers. Microcrack was easy to generate in Al 2 Cu phase decreasing the joint strength. When the Zn-Al weld filler was adopted, the formation of Al 2 Cu brittle phase was limited by low Al content and the CuZn and CuZn 5 IMC layers were observed at Al/Cu interface. According to the chemical potential, the diffusivity of Cu atoms in Zn-Al weld filler was much lower than that of pure Al and Al-Si weld fillers, which prevented from the formation of coppery phases near the Al/Cu interface. Si atoms tended to concentrate at Al/Cu interface. It played a role in obstructing the diffusion of Cu atoms, enhancing the Al/Cu joint strength to some extent. According to nanoindentation result, the mechanical property of the formed phases (CuZn and CuZn 5 ) in the case of Zn-Al weld filler was better than that formed with pure Al and Al-Si weld fillers such as Al 2 Cu and Al 4.2 Cu 3.2 Zn 0.7 . The highest tensile strength was 148 MPa with Zn-Al weld filler.

Effective removal of hexavalent chromium from aqueous solution by ZnCl2 modified biochar: Effects and response sequence of the functional groups

In view of the high toxicity and carcinogenicity of the Cr(VI), it is necessary to take some effective technologies to remove the Cr(VI) from the contaminated water, and the investigation into interface reaction mechanism in the process is particularly important for the technology optimization. In this study, the ZnCl2 modified sea buckthorn stones biochar (Z-SSBC) was successfully prepared and used for removing Cr(VI) from aqueous solution, and the SEM, BET, FT-IR analyses demonstrated that the biochar possessed rough surface, large specific surface area (1031 m2/g), mesoporous structure and abundant functional groups. The maximum removal efficiency (98%) of Cr(VI) was obtained at initial pH 2 and 30 ℃, and the media pH had significant impact on the adsorption of Cr(VI) onto the Z-SSBC. The analyses of adsorption kinetics and isotherms demonstrated that the process of Cr(VI) removal by the Z-SSBC included the chemisorption and some degree of intraparticle diffusion, and the Z-SSBC exhibited the fine reusability in five adsorption–desorption cycles. The two-dimensional correlation spectroscopy (2D COS) analysis revealed the sequence of the main functional groups participating in the reaction process (–OH>C=O>–COOH>–CH3). Furthermore, as the electron-donors, the –OH and C=O groups transform Cr(VI) anions into Cr(III), and the reduced Cr(III) ions were immobilized on the surface of the biochar. These results revealed that the prepared adsorbent had a great potential in the application of Cr(VI) removal.

Interfacial Engineering of Bi19Br3S27 Nanowires Promotes Metallic Photocatalytic CO2 Reduction Activity under Near-Infrared Light Irradiation.

Developing highly efficient photocatalysts to utilize solar radiation for converting CO2 into solar fuels is of great importance for energy sustainability and carbon neutralization. Herein, through an alkali-etching-introduced interface reconstruction strategy, a nanowire photocatalyst denoted as V-Bi19Br3S27, with rich Br and S dual-vacancies and surface Bi-O bonding introduced significant near-infrared (NIR) light response, has been developed. The as-obtained V-Bi19Br3S27 nanowires exhibit a highly efficient metallic photocatalytic reduction property for converting CO2 into CH3OH when excited solely under NIR light irradiation. Free of any cocatalyst and sacrificial agent, metallic defective V-Bi19Br3S27 shows 2.3-fold higher CH3OH generation than Bi19Br3S27 nanowires. The detailed interfacial structure evolution and reaction mechanism have been carefully illustrated down to the atomic scale. This work provides a unique interfacial engineering strategy for developing high-performance sulfur-based NIR photocatalysts for photon reducing CO2 into alcohol for achieving high-value solar fuel chemicals, which paves the way for efficiently using the solar radiation energy extending to the NIR range to achieve the carbon neutralization goal.

Ion-exchange mechanisms and interfacial reaction kinetics during aqueous corrosion of sodium silicate glasses

The ion-exchange and associated interfacial reaction mechanisms of silicate glasses are critical in elucidating their aqueous corrosion behaviors, surface modification and property changes, hence have potential impact on both science and technology. This work reports findings of the atomic and nanoscale details of the glass–water interfacial reactions revealed by applying reactive force field (ReaxFF) based molecular dynamics (MD) simulations, from which the key mechanisms of the ion exchange, as well as the kinetics of associated interfacial reactions, are elucidated. It was found that the Na+ and H+ ion exchange can happen between two oxygen ions on a single silicon oxygen tetrahedron or adjacent tetrahedra. In addition, the clustered reaction of two non-bridging oxygens mediated by an adjacent water molecule was also identified. The latter reaction might be the main mechanism of water transport after initial surface reactions that consume the non-bridging oxygen species on the surface. Water molecules thus can play two roles: as an intermediate during the proton transfer processes and as a terminator of the clustered reactions. Statistical analyses were performed to obtain reaction kinetics and the results show that silanol formation is a more favored process than the silanol re-formation within the first 3 ns of interfacial reactions. The results obtained thus shed lights on the complex ion-exchange mechanisms during glass hydration and enable more detailed understanding of the corrosion and glass–water interactions of silicate glasses.

A rechargeable aqueous zinc/sodium manganese oxides battery with robust performance enabled by Na2SO4 electrolyte additive

Rechargeable aqueous Zn ion batteries (ZIBs) have recently attracted immense interest for large-scale energy storage systems stemming from their high natural abundance, environmental benignity, and high safety. However, the frustrating structural degradation in the cathode and the inherent Zn dendrite growth on the anode severely hinder the progress for future application. Herein, we report a zinc/sodium manganese oxides (denoted as Zn/NMO) battery with pre-inserted Na+ ions and crystal water in the cathode interlayer, which greatly facilitates cations diffusion without serious structural distortion. More importantly, Na2SO4 additive in ZnSO4-based electrolyte can eliminate Zn dendrites by modifying the deposited pattern of Zn2+ ions. Consequently, the Zn/NMO battery exhibits a high capacity (367.5 mAh g−1 at 0.65 C) and super long-term cyclic stability (only 0.007% capacity fading after 10000 cycles at 6.5 C). Besides, operando and ex situ electrochemical characterizations demonstrate that the formation of byproducts in the cathode surface leads to improved capacity and low Coulombic efficiency during the electrochemical activation process. Density functional theory (DFT) calculation further reveals the interface reaction mechanism, in which the solvation energy of electrolyte ions is responsible for the H+/Zn2+ insertion/extraction in the cathode material.

Understanding the interfacial properties in BN-SiO2 diphase ceramic/TiNiNb filler alloy systems: First-principles and mechanical studies

Improved understanding of interfacial reaction mechanism between the ceramic and filler alloy is critical for the applications in a variety of industries, including aerospace and biomedical, etc. However, many mechanistic details remain confused, such as how the interfacial microstructure is formed in the process of interfacial reaction. In this work, we combine the First-principles method with experimental studies to elaborate the formation of the reaction layer at the BN-SiO2 diphase ceramic/TiNiNb filler alloy interface. Compared with conventional ceramic, it has been confirmed that the interfacial competitive reaction contributes significantly to the BN-SiO2 diphase ceramic/TiNiNb filler alloy system and can further influence the formation of the reaction layer. In addition, experimental results indicate that TiN is firstly generated, while indeed playing an effective role in improving the wettability of TiNiNb filler alloy on BN-SiO2 diphase ceramic, and turning out to be the key to enable a desirable connection between the BN-SiO2 diphase ceramic and the TiNiNb filler alloy.

In situ loading of MoO3 clusters on ultrathin Bi2MoO6 nanosheets for synergistically enhanced photocatalytic NO abatement

Synthesis of high-efficiency photocatalysts and revealing of the interfacial reaction mechanism are two major prerequisites for the commercial application of photocatalytic technology. Herein, the ultrathin Bi2MoO6 nanosheets modified by MoO3 clusters are synthesized through a surfactant-assisted one step hydrothermal process. The ultrathin two-dimensional (2D) structure shortens the carrier transmission distance, thereby reducing the recombination probability during the transport process. The surface clusters highly favor the interfacial charge transfer via giving a fire-new electron migration pathway from Bi2MoO6 nanosheets to MoO3 clusters directly. With the pivotal effect of directed electrons migration, the separation efficiency of carriers could be largely enhanced. The Bi2MoO6 nanosheets loaded with MoO3 clusters demonstrated highly efficient photocatalytic performance for NO removal under relative humidity from 25 to 100% due to the synergistic strategy of ultrathin structure and clusters. This work can provide a novel synergistic strategy for efficient carrier transfer, and also can put forward deep insights into the photocatalytic NO oxidation mechanism.

Characterizations on phase reconstruction, microstructure evolution and separation of magnetic ferrite ceramics from low-grade manganese ores by novel uphill reaction diffusion and magnetic separation

Traditional utilization of ferruginous manganese ore has mainly concentrated on the separation of Mn and Fe. However, an alternative process of novel uphill reaction diffusion followed by magnetic separation was developed for the synchronous recovery of manganese and iron as the form of ferrite ceramics from the ferruginous manganese ore in this work. The phase reconstruction, interfacial uphill reaction diffusion, ferrite size quantification and separation behavior were characterized via various means of XRD, XPS, TEM, VSM, SEM-EDS, optical microscopy, microhardness and thermodynamic analyses. In the phase reconstruction course, manganese and iron oxides reacted to form ferrites, whereas the impurities were enriched in liquid silicate phases due to the uphill reaction diffusion. Meanwhile, the ferrite particles grew and the liquid silicates aggregated owing to the intensified reaction diffusion by CaO addition. During the water quenching process, microcracks at the cleavage plane between the silicate and ferrites are preferentially generated due to fast cooling shrinkage of liquid silicates. Huge differences in hardness, magnetism, fusibility and cooling shrinkage of ferrites and silicates provided excellent mineralogical conditions for the successful grinding and magnetic separation of ferrites. Eventually, a soft magnetic manganese ferrite precursor with recoveries of 89.2 wt% iron and 85.6 wt% manganese was obtained. The interfacial reaction mechanisms for the formation of ferrites and silicates were also discussed in this work.