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An innovative technical route has been proposed to improve recycling efficiency of Ni and Fe from low-grade nickel laterite via the duplex process between direct reduction-magnetic separation and rotary kiln-electric furnace. The results indicated that the high‑nickel concentrates produced from direct reduction-magnetic separation process, which were combined with optimization of slag types can not only increase the grade of furnace burdens and decrease quantity of slag, but also improve the fluidity of slag and smelting efficiency as well as reduce the power consumption of smelting. For the industrial application of duplex process, a preferable stainless-steel master alloy with 10.02% Ni was obtained at a lower cost of 8420 RMB/t than that of 8731 RMB/t for a stainless-steel master alloy containing 8.14% Ni in conventional rotary kiln-electric furnace process, and the recovery of nickel also increased from 91.27% to 95.51%, which shows an obvious superiority for treating the low-grade nickel laterite.

In this study, direct reduction-magnetic separation process was applied to enrich phosphorus and iron to prepare Fe-P crude alloy from a high phosphorus oolitic hematite ore (HPOH). The results show that at lower temperatures and with absence of any of additives, Fe cannot be effectively recovered because of the oolitic structure is not destroyed. In contrast, under the conditions of 15% Na2SO4 and reducing at 1050 °C for 120 min with a total C/Fe ratio (molar ratio) of 8.5, a final Fe-P alloy containing 92.40% Fe and 1.09% P can be obtained at an overall iron recovery of 95.43% and phosphorus recovery of 68.98%, respectively. This metallized Fe-P powder can be applied as the burden for production of weathering resistant steels. The developed process can provide an alternative for effective and green utilization of high phosphorus iron ore.

Low-grade saprolite nickel laterite, characterized by complicated minerals composition and fine-grained and complex dissemination, was commonly treated with a low recovery efficiency of Ni and Fe by conventional methods. Hence, an improved direct reduction and magnetic separation process was proposed. Meanwhile, the mechanisms on the enhanced growth of the Ni–Fe particles and the phase transformation in the nickel laterite pellets were explored. The low-nickel concentrates as a nucleating agent can obviously decrease the activation energy for growth of Ni–Fe alloy particles during the improved direct reduction process from 197.10 to 154.81 kJ/mol when the low-nickel concentrates were added from 0 to 20%. Hence, it is able to decrease nucleation barrier, induce the growth of Fe–Ni alloy particles and increase their average size. As a result, the size of Ni–Fe particles in the pellets from less than 10 μm grew to more than 20 μm, which is beneficial for the full liberation and recovery of Ni and Fe in subsequent magnetic separation process. Therefore, the preferable Ni–Fe alloy concentrates with 6.44% Ni and 82.48% Fe can be prepared with corresponding recovery rates of 96.90% and 95.92%, respectively, when adding 20% low-nickel concentrates.

The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated. The fired pellets in the basicity range of 0.09 (natural basicity) to 1.00 show superior reducibility and low-temperature disintegration performance. However, in the basicity range of 0.20–0.80, the abnormal swelling of the fired pellets occurs. Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets, and accelerates the growth and densification of hematite crystals, impeding the reduction of hematite particles and the formation of metallic iron shell. In addition, the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process, which leads to the large reduction swelling of pellets.

Development of a p-n heterojunction to achieve efficient degradation of organic pollutants is a promising approach in the field of photocatalysis. Herein, BiVO4 with bioinspired hierarchical structures was prepared with the sol-gel method and combined with BiOCl nanoplates to construct a 3D/2D configuration via an in situ deposition route. The hierarchical BiVO4 served as an excellent substrate to achieve the uniform loading of BiOCl nanoplates. The obtained 3D/2D BiVO4/BiOCl hybrids exhibited significantly enhanced photocatalytic efficiency for degrading phenol under visible light irradiation, with a first-order reaction rate constant that was 9.9 and 1.9 times higher than those of hierarchical BiVO4 and the BiVO4/BiOCl hybrids without hierarchical structures, respectively. Moreover, the hierarchical BiVO4/BiOCl also displayed good photochemical stability for the degradation of phenol after three recycles. The p-n heterojunction and hierarchical structure worked together to form a spatial conductive network framework, which possessed improved visible light absorption, high specific surface area, as well as effective separation and transfer of photogenerated charge carriers.

Iron ores always contain several forms of alumina, which may have different effect on sintering performance. In this paper, sinter pot tests were systematically conducted with various alumina types and contents by means of alumina additives substituting for the corresponding types of alumina, and the relevant action mechanism on sintering performance was clarified by the mineralogy of product sinter. The results show that kaolinite is beneficial to the granulation process rather than other three alumina types. In addition, it contributes to relatively better sintering performance while aluminous goethite ranks the only next, followed by gibbsite and free alumina. Mechanism analysis indicates that kaolinite and aluminous goethite are preferable to achieve relatively lower sinter porosity and higher amount of silico-ferrite of calcium and alumina (SFCA) compared with gibbsite and free alumina. Besides, the former two alumina types are apt to promote the formation of higher strength SFCA such as dendritic and acicular SFCA. Furthermore, much tighter interlocking texture in product sinter is formed as alumina occurs in kaolinite or aluminous goethite. Kaolinite and aluminous goethite are the preferably desirable alumina types for sintering rather than free alumina and gibbsite.

This study is aimed to obtain better-quality Ni–Cr composite sinter for the production of 300 series stainless steel via the sintering-blast furnace process at lower cost. Based on the complementary advantages of limonitic nickel laterite and chromite, co-sintering pot tests of the two ores were conducted in various chromite proportions and then strengthened by multi-force fields. Mechanistic analysis was performed, including the chemistry and mineralogy of product sinter and the thermodynamic and kinetic conditions of the co-sintering process. The results indicate that the addition of chromite effectively improves tumble index and productivity, especially at a chromite ratio of 15%, due to the improvement of sinter microstructure and the thermodynamic and kinetic conditions during sintering. However, solid fuel rate is increased gradually because of the greater amount of high smelting minerals. With the application of multi-force fields, higher tumble index is obtained owing to the further densification of sinter bed and the formation of tighter interlocking texture. Solid fuel rate is greatly decreased due to the efficient supply of extra physical heat. Productivity is weakened to some extent as the flame fronts speed is reduced. In addition, excellent metallurgical performance is achieved. The co-sintering process of limonitic nickel laterite and chromite is significantly improved via multi-force fields.

Zinc-bearing dusts from steel plants were classified as hazardous solid waste, but are important secondary resources to extract iron and zinc through direct reduction technology. In this study, three kinds of Zinc-bearing dusts from a steel plant were made into carbon-containing pellets and reduced at 1323 K–1473 K. The results showed that the efficiency of zinc removal was controlled by the Jander three-dimensional diffusion. The mechanism of zinc removal from the pellets was analyzed by optical microscope, scanning electron microscope, energy dispersive spectrometer, X-ray diffraction and thermodynamic calculation. It was found that the zinc element in the zinc-bearing dust pellets presented in the form of zinc ferrite, hardystonite and zinc chloride. The process of the zinc removal from the pellets in direct reduction could be divided into four stages according to the efficiency of zinc removal and the microstructure of the reduced pellets.

In order to reduce the materials cost of COREX ironmaking process, sinter has been introduced into the composite burden in China. This work explored the reducing process of sinter in COREX shaft furnace to clarify its reduction properties change and then the effect of sinter proportion on metallurgical performance of composite burden was investigated. The results show that the reducing process of sinter in COREX shaft furnace was basically same with that in blast furnace but sinter seems like breaking faster. Under reducing condition simulated COREX shaft furnace, sinter possessed the worst reduction degradation index (RDI) and undifferentiated reduction index (RI) compared with pellet and iron ore lumps. Macroscopic and microscopic mineralogy changes indicated that sinter presents integral cracking while pellet and lump ore present surface cracking, and no simple congruent relationship exists between cracks of the burden and its ultimate reduction degradation performance. The existence of partial metallurgical performance superposition between composite and single ferrous burden was confirmed. RDI+6.3≥70% and RDI+3.15≥80% were speculated as essential requirements for the composite burden containing sinter in COREX shaft furnace.

As a promising 19F MRI tracer, the relatively slow lattice-spin relaxation of CaF2 nanocrystals leads to an unacceptable scanning time in MR imaging, hampering their application. We herein controlled the size and lattice distortion of CaF2 nanocrystals and showed that the shortened interplanar spacing pronouncedly sped up the longitude relaxation.

The widely studied Pt/C catalyst for direct methanol fuel cells (DMFCs) suffers severe carbon corrosion under operation, which undermines the catalytic activity and durability. It is of great importance to develop a carbon-free support with co-catalytic functionality for improving both the activity and durability of Pt-based catalysts. The direct loading of Pt on the smooth surface of oxides may be difficult. Herein, the Cu assisted loading of Pt on CeO2 is developed. Cu pre-coated CeO2 was facilely synthesized and Pt was electrochemically deposited to fabricate the carbon-free PtCu/CeO2 catalyst. The PtCu/CeO2 catalyst has a mass activity up to 1.84 and 1.57 times higher than Pt/C towards methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), respectively. Better durability is also confirmed by chronoamperometry and accelerated degradation tests. The strategy in this work would be greatly helpful for developing an efficient carbon-free support of Pt-based catalysts for applications in DMFCs.

In this paper, coal-based rotary kiln direct reduction‑hydrogen reduction process was demonstrated to an efficient way to prepare the PMIP. Under the optimum conditions, a superior PMIP with 98.5% iron grade and only 0.31% H2-loss can be achieved. Meanwhile, PMIP have the perfect physical properties of 2.45 g/cm3 bulk density, 38 s·50 g−1 flow rate and 6.40 g/cm3 compressibility, which all meet the standard of MHF80·235 (first class goods). Moreover, the enhancing mechanism of PMIP properties was investigated as well, and the results show that the growth of metallic iron grains can obviously reduce the porosity and promote the densification of PMIP structure, which is beneficial for the bulk density and flow rate. This finding can point a new direction to improve the performances, including bulk density and by appropriately extending carbon reduction duration to promote the grain growth and improve the densification of PMIP structure.

Three adsorbents, trichosanthes kirilowii maxim shell activated carbon (TKAC), nickel alginate/activated carbon (NA/AC) aerogel and nickel alginate/graphene oxide (NA/GO) aerogel were prepared in the present study. The three-dimensional network structure of the NA/AC aerogel and NA/GO aerogel was found to effectively control the dispersion state of TKAC and GO. The adsorption behavior was systematically investigated in terms of adsorption temperature and time, initial adsorbate pH and concentration, as well as the dose of adsorbents. The methylene blue (MB) adsorption process of TKAC was in accordance with the Langmuir isotherm model and followed a pseudo-second order mechanism. The adsorbing capacity of TKAC was 505.050 mg/g at 303 K while the BET surface area was 349.400 m2/g. Thermodynamic analysis demonstrated the spontaneous and endothermic properties of the entire adsorption process. The MB adsorption of the NA/AC aerogel satisfied the Langmuir isotherm and Freundlich isotherm models. Moreover, the MB adsorption on the NA/AC aerogel followed a pseudo-second order mechanism. The adsorbing capacity of the NA/AC aerogel was observed to be 465.120 mg/g at 303 K while the BET surface area was 100.690 m2/g. Thermodynamic investigation demonstrated a spontaneous and exothermic nature of the overall adsorption process. The MB adsorption of the NA/GO aerogel aligned with the Langmuir isotherm model and followed pseudo-second order mechanism. The adsorbing capacity of NA/GO aerogel was found to be 537.630 mg/g at 303 K, while the BET surface area was 5.050 m2/g. Furthermore, thermodynamic studies exhibited spontaneous and exothermic properties of the entire adsorption process.

Tungsten carbide (WC) with imperfect structures determined by phase engineering and heteroatom doping has attracted a great deal of attention with respect to hydrogen evolution reaction (HER). Howe...

Since the water splitting rate-limiting oxygen evolution remains sluggish, engineering a rational architecture for photocatalysts to fulfill water oxidation needs becomes a vital issue. Here, we detail a 0D/2D all-carbon hybrid strategy for constructing a heterostructure of carbon dots (CDots) and reduced graphene oxide (rGO) to enhance the photocatalytic water oxidation of monoclinic-BiVO4 nanosheets (CBrG). Given the visible-light-harvesting ability and up-conversion characteristics of 0D CDots, more photogenerated electron-hole pairs participated in water oxidation under visible and near-infrared light irradiation. Meanwhile, 0D CDots behaved as electron acceptors on 2D rGO to suppress the recombination of electron-hole pairs. This nature licenses for the feasible electron transfer from excited m-BiVO4 to 0D CDots via electron transfer channels of 2D rGO, facilitating the separated holes to migrate onto the m-BiVO4 surface for water oxidation. Compared with the rGO decorated m-BiVO4 nanosheets (BrG), these merits endow the CBrG with an over 212% enhancement in O2 yield under visible light irradiation as well as notable O2 yield under near-infrared light irradiation, and a 1.57-fold increase in apparent quantum efficiency. The enhancement is also verified by the significant growth of ·OH radicals derived from OH−/H2O oxidation and ·OOH/·O2− radicals originated from O2 reduction. This work paves a new way for the 0D/2D all-carbon hybrid architecture applied in solar energy conversion.

The alumina content of iron ores for sintering is gradually increasing with the growing depletion of high-grade iron ores, which is harmful to the sintering process. Therefore, it is essential to reveal the action mechanism of alumina on sinter quality. In this paper, the aluminum occurrence of various iron ores was determined by applying X-ray diffraction (XRD), optical microscopy, scanning electron microscopy and energy dispersive spectrum analysis (SEM-EDS). Then, the effects of iron ore type, aluminum occurrence (free alumina, gibbsite, diaspore, alumogoethite and kaolinite) and alumina content on formation characteristics of SFCA bonding phases as well as sinter matrix strength were investigated based on laboratory compact sintering tests. The results show that the discrepancy of aluminum occurrence contributes to different SFCA formation characteristics and then sinter matrix strength, due to different reactivity of various aluminum-containing minerals with iron oxides and fluxes. Increasing alumina content generally results in an increase in the porosity of sinters and deterioration of sinter matrix strength for all aluminum occurrence. Aluminum in the form of kaolinite is more conducive to form dendritic or acicular SFCA with superior sinter matrix strength compared with other aluminum occurrences. In contrast, aluminum occurring in free alumina presents greatest adverse impacts on sinter matrix strength due to its poor reactivity and high porosity of resultant sinters.

The poor sintering performance of limonitic laterite hinders its utilization. Hot exhaust-gas recirculation sintering was conducted to improve its sintering performance and intensification mechanism was revealed. Evaluating sinter indices in systematical sinter pot tests were substantially improved with tumble index and productivity increased by 18.01% and 7.22% respectively and solid fuel rate lowered by 13.71%, further proved by extensive industrial application. Effective CO2 emissions reduction and huge economic benefits were realized. The improvement of thermodynamic conditions converted sinter microstructure from large thin-wall pores into small thin-wall or large thick-wall pores. The amount of silico-ferrite of calcium and alumina in sinter pot tests and industrial application was increased from 8.78% to 18.61% and 21.25% respectively. Grains aggregation and growth of hercynite and close adhesion between solid phases and liquid bonding phases were achieved. Hot exhaust-gas recirculation sintering of limonitic laterite contributed to dramatically improving sinter performance and reducing CO2 emission.

Direct reduction-magnetic separation process (DRMSP) is a highly effective and clean method to upgrade the complex resources, which has been widely used to recovery the value metals in copper slag (CS) and nickel laterite (NL) in recent years. Adequate growth of the alloy particles is a key parameter influencing the complete extraction of alloys from CS and NL in this process. Therefore, the liquid phase formation mechanism, growth kinetics of the alloy particles, and the correlation between the alloy particle growth and liquid phase formation were studied to reveal the synergistic effect of the co-reduction of CS and NL. The results indicated that fayalite in the copper slag reacted with forsterite in nickel laterite to form augite group minerals with low melting points, resulting in more liquid phase formation in the reductive roasting process. A comparison with the reduction kinetic parameters of the single nickel laterite showed that the growth index and activation energy decreased significantly from 2.85 and 272.98 KJ/mol to 2.08 and 171.99 KJ/mol, respectively, after the addition of 40% copper slag, which confirmed that copper slag promoted the particle growth. Moreover, the liquid phase increased the total cohesive force between the alloy particles, revealing the correlation between alloy particle growth and liquid phase.

In order to obtain the effect of second phases on Charpy impact energy and crack propagation behavior of Hastelloy N sheet, Charpy notched impact toughness test have been accomplished with different directions (RD, ND) of V-notch after solution treatment. The fracture morphology and microstructure are observed by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). It is shown that the dominant second phases in Hastelloy N after solution treatment includes molybdenum-riched Ni-Mo phase, which dissolve some elements such as chromium, silicon and ferrum, and a few carbides. The Charpy impact energy of sample 2# (RD) is 225J, almost twice as much as sample 1# (ND). Based on the reconstruction of morphology and distribution of second phases, the mechanism for effect of second phases on crack propagation behavior is discussed. The islands of second phase particles modify the stress triaxiality state, resulting in the propagation path of crack in 2# is totally different from that in 1#.

A new process for manufacturing organically compounded bentonite was developed successfully based on the organic intercalation and layered structure of bentonite. The main steps in the proposed process included wet sodium activation of bentonite ore, organic compounding and high-pressure roll grinding. The optimum procedure is recommended as follows: 5 mass% of sodium carbonate powder and 30 wt.% water are added to activate the bentonite ore for 24 h to prepare activated bentonite; 0.5 wt.% of organic molecules are added into the activated bentonite for organic compounding for 12 h; then, the high-pressure roll grinding is followed to treat the organically compounded bentonite; and finally, drying and fine grinding are performed for preparing the final organically compounded bentonite product with 10 wt.% moisture and 98% passing 0.074 mm. The obtained organically compounded bentonite was characterized using an X-ray diffractometer, a scanning electron microscope and an X-ray photoelectron spectrometer. To confirm the effect of organically compounded bentonite on green balls, the pelletizing tests were carried out. The results showed that high-pressure roll grinding can not only enhance the ability of the crystal layer to hold the combined water, but also strengthen the intercalation compounding of the organic additive, which is beneficial for the formation of a fiber-interlaced structure of the organically compounded bentonite and improves the quality index of the bentonite itself. Also, the organically compounded bentonite is helpful to improve the indexes of green balls.

For improving the strength of pellets made of ultrafine and super-high-grade magnetite concentrates, the influence of basicity (CaO/SiO2 ratio) on the roasting and consolidation of pellets was investigated. The results showed that with the basicity of pellets increasing from 0.09 to 0.60, the compressive strength of both preheated and roasted pellets achieved an evident improvement from 502 and 2519 to 549 and 3096 N/pellet, respectively; meanwhile, the roasting time decreased from 15 to 9 min. The low-viscosity liquid phases were easily generated in fired pellets at the basicity range of 0.40–0.60 under the roasting temperature of 1240 °C, filled the voids between hematite particles and tightened the bonding among particles, effectively restraining the generation of concentric cracks and decreasing the porosity of fired pellets; low-viscosity liquid phases facilitated the solid diffusion of hematite, leading to the formation of coarse hematite crystals and thicker connecting necks.

As is well known, the process of direct reduction and magnetic separation is effective route to deal with low-grade saprolite laterite, but generally limited by the reduction of nickel (iron)-bearing minerals and growth of Fe-Ni alloy particles in the reduction process, causing the low recovery of nickel and iron. To improve beneficiation of nickel and iron from low-grade saprolite laterite with 1.29 wt.%Ni and 16.31 wt.%Fe, co-reduction with limonitic laterite ore and basicity optimization were adopted as strengthening measures in this paper with better economic efficiency than before. The enhancing mechanism was investigated via the thermodynamics analysis and mineralogical study. The phase transformation and growth behaviors of metallic alloy particles during reduction process were revealed as well. The results indicated that co-reduction with limonitic laterite ore is capable of promoting phase transformation from Ni2SiO4 in saprolite laterite to NiFe2O4. CaCO3 can not only destroy the structure of magnesium silicate to release nickel(iron)-bearing phase, but also enhance the reduction of Fe2SiO4 to form efficiently iron-based eutectoid with nickel and liquid phases to accelerate the growth of Fe-Ni fine particles larger than 40 μm. A superior crude alloy was obtained with 5.11 wt.%Ni and 82.15 wt.%Fe with corresponding recovery rates of 91.89% and 85.15% respectively. Keywords: Nickel laterite ore, Co-reduction, Basicity, Phase transformation, Particle growth, Fe-Ni alloy

usc Owing to the sluggish water oxidation process, unearthing an ideal model for disclosing the impact of an architectural approach on the water oxidation activity of photocatalysts becomes a vital issue. Here, we propose an innovative in situ modification strategy for constructing ultrapure BiVO4 nanosheets on graphene (u-BVG) toward the accelerated photocatalytic water oxidation reaction. Considering the Mott-Schottky heterojunctions at the contact interface in u-BVG, the feasible electron transfer from excited BiVO4 to graphene facilitates the holes to migrate onto the BiVO4 surface for the water oxidation reaction. Compared with the conventional synthesis strategies, our strategy avoids the introduction of Cl impurities. This modification allows for not only a ca. 0.1 eV deeper valence band edge position to generate holes with a stronger oxidation potential but the extraction of the impurity level to suppress the carrier recombination. And density functional theory calculations are in accordance with the above results. Impressively, these merits endow the u-BVG with ca. 16.8 times growth in the amount of OH radicals derived from OH-/H2O oxidation, an over 260% enhancement in O2 yield and a 1.6-fold increase in the apparent quantum efficiency relative to the impure counterpart. This work paves the way for the reconstruction of graphene-based binary systems with high performance in solar-to-chemical energy conversion. Refereed/Peer-reviewed

Sulfur resilient steam reforming catalysts are of great interest for the development of solid oxide fuel cell systems for aeronautic applications. We demonstrate that nickel–manganese catalysts exhibit substantially improved stability during steam reforming of sulfur containing fuels via a sulfur spillover strategy as compared to monometallic nickel catalysts. This is established via detailed deactivation studies of catalysts in steam reforming conditions with sulfur containing model fuels and real jet fuels (JP-8). Through detailed characterization of spent catalysts, we establish that the increased sulfur resilience is imparted by an increased sulfur capacity due to scavenging by manganese oxide species in close proximity to active nickel particles. Results presented in this work could pave the way for practical application of precious-metal-free steam reforming catalysts in sulfur rich streams, both in aeronautic SOFC systems and other applications.

On the basis of hydrothermal synthesis of Ag-CeO2 microspheres, Ag-CeO2/g-C3N4 composite photocatalyst with heterostructure was prepared by simple solvent evaporation of Ag-CeO2 and g-C3N4. To characterize the composition, structure, morphology and light absorption properties of the as-prepared Ag-CeO2/g-C3N4 composites, XRD, FTIR XPS, SEM, TEM, PL, BET and UV-vis DRS were used, respectively. The as-prepared photocatalyst was subjected to photocatalytic degradation of pollutants, and the prepared composite material has excellent photocatalytic activity for photodegradation of methylene blue (MB). The research shows that the photocatalytic properties of Ag-CeO2/g-C3N4 composites were related to the mass ratio of Ag-CeO2 microspheres and g-C3N4 nanosheets. When the ratio of Ag-CeO2 microspheres: g-C3N4 is 1:5, the composites have the highest photocatalytic activity, which was 9.6 and 3.3 times that of single Ag-CeO2 and g-C3N4, respectively. The improvement of photocatalytic activity is attributed to the heterostructure between the composite materials and the addition of noble metal silver, and the degradation of methylene blue by the visible light irradiation material is greatly improved. Finally, an attempt was made to analyze the principle of photocatalytic degradation of pollutants in prepared materials.

Electrolytic hydrogen evolution reaction (HER) that can be performed efficiently in neutral conditions enables the direct splitting of seawater. However, the sluggish water dissociation kinetics in neutral media severely limits the practical deployment of this technology. Herein, we present a simple strategy to rationally design oxophilic and nucleophilic moieties through the in situ reconstruction of a free-standing bimetallic cobalt-iron phosphate electrode. Through an electrochemical reduction step, the electrode surface undergoes self-reconstruction to generate a thin (oxy)hydroxide layer, enabling a significantly improved HER activity in both buffered electrolyte and natural seawater. Our mechanistic investigations reveal the essential role of oxophilic (oxy)hydroxide species in improving the HER activity of nucleophilic bimetallic phosphate sites. In a buffer electrolyte (pH = 7), the resultant electrocatalyst only requires overpotentials of 97 and 198 mV to deliver a current density of 10 and 100 mA cm-2, respectively, which outperforms that of the Pt benchmark. The in situ reconstruction strategy of active sites within such electrodes brings significant opportunity in developing active electrocatalysts that are capable of direct seawater splitting.

Some basic properties of granules, including the granule size distribution, packed-bed permeability, and chemical composition of the adhering layer, were investigated in this study for four iron ore blends consisting of 5wt%, 25wt%, and 45wt% ultrafine magnetite and 25wt% ultrafine hematite concentrates. The effects of varying the sinter basicity (CaO/SiO2 mass ratio = 1.4 to 2.2) and adding ultrafine concentrates on the variation of the adhering-layer composition and granule microstructure were studied. Moreover, the effect of adhering-layer compositional changes on sintering reactions was discussed in combination with pot sintering results of ore blends. Increasing sinter basicity led to an increase in the basicities of both the adhering layer and the fine part of the sinter mix, which were higher than the overall sinter basicity. When the sinter chemistry was fixed and fine Si-bearing materials (e.g., quartz sand) were used, increasing the amount of ultrafine ores in the ore blends tended to reduce the adhering-layer basicity and increase the SiO2 content in both the adhering layer and the fine part of the sinter mix, which will induce the formation of low-strength bonding phases and the deterioration of sinter strength. The adhering-layer composition in granules can be estimated in advance from the compositions of the −1 mm fractions of the raw materials.

Supported single atom catalysts (SACs), emerging as a new class of catalytic materials, have been attracting increasing interests. Here we developed a Ni SAC on microwave exfoliated graphene oxide (Ni-N-MEGO) to achieve single atom loading of ∼6.9 wt%, significantly higher than previously reported SACs. The atomically dispersed Ni atoms, stabilized by coordination with nitrogen, were found to be predominantly anchored along the edges of nanopores (

An innovative technology for direct reduction-magnetic separation with the addition of Na2CO3 and CaO was studied to upgrade copper slag assaying 40.33% Fetotal and 0.65% Cu. It is difficult to recover iron and copper from the slag by direct reduction since the iron mainly occurs in fayalite and the copper exists in copper sulfide. Additives such as Na2CO3 and CaO has been proven to be capable of reinforcing the reduction of refractory iron ore in many papers. In this study, the effect of Na2CO3 dosage and binary basicity (CaO/SiO2) on the coal-based reduction of copper slag was investigated. The results show that the addition of CaO at 0.5 basicity and 8% sodium carbonate, the recovery of the iron and copper can be significantly improved to 94.3% and 86.5%, respectively. Meanwhile, the iron and copper content of magnetic concentrate are maintained at 90.5% and 1.2%, respectively, which can be used as burden for smelting of weathering steel, and the nonmagnetic tailings obtained in this process can be applied as raw materials in cement and industry, and the dust collected from the direct reduction process contains 50.65% Zn and 8.56% Pb at a recovery of 99.16% and 91.89%, and can be used as feed for extraction of Zn and Pb.

Attempts to economically upgrade low nickel content laterite ore face a number of challenges, including limited ability to beneficiate the ore prior to processing due to its complex association and dissemination structure. Limonitic nickel laterite, characterized by its relatively high iron grade and low nickel content, is very difficult to upgrade. The current work explores improving the beneficiation of nickel from limonitic laterite ore through interaction of silica and calcium sulfate in a selective reduction-wet magnetic separation process. The results show that the ferronickel concentrate assaying 5.0% Ni can be obtained at a nickel recovery of 95.9%, when limonitic laterite ore is reduced at 1250 °C for 60 min with the addition of 3 wt% CaSO4, 8 wt% silica and 3 wt% graphite. The mechanism of additives in promoting the selective reduction of nickel laterite ore was also investigated by XRD, VSM, SEM-EDS and EPMA. The silicate reacted with iron oxide to form the liquid, which decreased the iron metallization ratio. S2 from the thermal decomposition of CaSO4 in a strong reducing atmosphere significantly promoted γ Fe–Ni particle growth by formation of an Fe-FeS eutectic with a low melting point.

In this paper, the combined effects of MgO and basicity (CaO/SiO2), varied by changing the ratio of dolomite and burnt lime to sinter mix, on sintering of magnetite concentrates were investigated in pilot scale. Mineralogy of sinter with various MgO and basicity was analyzed by light microscope and scanning electron microscope (SEM). The results show that increasing MgO led to lower sinter strength and higher fuel consumption, while increasing basicity behaved in the opposite way. Regardless of MgO content, minimum sinter strength occurred in basicity 1.2–1.6, which should be avoided in sinter production. Less SFCA (silicoferrites of calcium and aluminum) and more magnetite were observed in sinter with higher MgO content. Aside from hematite and magnetite, the dominant phases in sinter with low (0.8) and high (2.2+) basicity were glass and SFCA respectively. Sinter with basicity 1.6 had highest crack density and this would inevitably reduce its cold strength.

The storage and conversion of the surplus electricity generated by photovoltaic (PV) cells call for efficient electrochemical devices, such as water electrolyzers and metal–air batteries. Catalyst materials are normally the key in determining the efficiency of these devices, as the electrochemical processes involved are normally sluggish in reaction kinetics. Herein, we found that by encapsulating Ni, Co and Fe alloyed cores inside graphitic carbon shells (NiCoFe@C), a versatile catalyst material can be obtained, showing decent activity towards the oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The encapsulation of the NiCoFe alloyed core induces the electronic structure change of the outer graphitic carbon shell, which tunes the binding strength of reaction intermediates thereby improving the catalytic activity.

High MgO content and the dehydroxylation of laterite ore particles lead to poor compressive strength of fired chromium-nickel bearing iron ore pellets at natural basicity. For improving the compressive strength of the fired chromium‑nickel bearing iron ore pellets, burnt lime was applied as the additive to improve the pellet structure. Results showed that with an increase in quaternary basicity, the compressive strength of fired pellets was enhanced obviously. The optimum basicity of fired chromium-nickel bearing iron ore pellets is suggested at 1.15. Under the optimal test conditions, the compressive strength of fired pellets with natural basicity is only 607 N/pellet, but the compressive strength of fired pellets reaches 1991 N/pellet at basicity of 1.15. The structure of fired chromium-nickel pellets at 1.15 basicity greatly depends on the liquid bonding phases among chromite, hematite and enstatite particles, which are composed of kirschsteinite, SFCA and glass, and amount to 19.27% in fired pellets. The liquid bonding phases fill in the voids among mineral particles and interconnect them to form the intertwined structure, which increases the shrinkage and significantly improves the compression strength of fired pellets.

Shape memory photonic crystals (SMPCs) combining the main characteristics of shape memory materials and photonic crystals have drawn increasing research interest. In sharp contrast to traditional responsive photonic crystals, the temporary shape of SMPCs can be "frozen" and photonic configurations can be modulated by temperature. However, the large-scale fabrication of SMPCs still remains a big challenge, making the practical application difficult. Herein novel scalable SMPC films with both mechanochromic and thermochromic properties are reported. Unlike traditional template-based methods resulting in only a small size, SMPC films are fabricated by a facile hot-pressing method and post-photocuring technology to give large-area freestanding polymer films. The films are mechanically robust and flexible, featuring an excellent structural color which can be changed upon stretching, similar to the color change process of chameleons in response to the environment. The blue-shift of the reflection peak up to 120 nm can be observed when the film is stretched. The films can be reversibly stretched and recovered in 25 cycles without obvious changes in reflection spectra. The temporary shape accompanied by tremendous color changes in the corresponding SMPC films after mechanical stress induced hot programming could be simply fixed by cooling the structure below the glass transition temperature of the polymer matrix. Incorporated programmed optical properties could afterwards be erased by temperature, and initial optical properties could be fully restored. Based on the fully reversible programmable shape as well as optical properties, the investigated SMPC films are expected to be promising candidates for various potential applications, such as smart monitoring, sensors, anti-counterfeiting, and displays.

An updraft pre-reductive sintering process was proposed to convert the iron and steelmaking wastes with high Zn and Pb content into a pre-reduced sinter with low Zn and Pb suitable for blast furnace smelting process. In this work, the migration and distribution characteristics of Zn, Pb and As along the vertical direction of sinter bed were particularly studied by analyzing the compositions of quenched samples obtained from different bed depth. The microstructure of the quenched samples and the micro-area composition analysis were performed by using scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The result showed that the sintering bed can be roughly divided into five different zones along the bed, i.e., sinter product, combustion and pre-reducing, drying and preheating, over wet and original material zones from the bottom to the top. The content of Zn, Pb and As varies with different zones. Generally, the contents of above-mentioned elements reach their minimums in the product sinter zone and while that reach the maximums in the drying-preheating zone. In contrast, the combustion zone contains intermediate contents of Zn, Pb and As. The migration of Zn, Pb and As in the sinter bed occurs according to the following rule: The ZnO, PbO and As2O5 were first reduced and volatilized in the combustion and pre-reducing zone, and then re-oxidized and condensed on the surface of the dried and preheated balls in the drying and preheating zone. As the combustion zone moves upward, the ZnO, PbO and As2O5 that condensed on surface of dried and preheated balls would be re-reduced, re-volatilized, re-oxidized and re-condensed at upper zones until the sintering process reaches the burnt-through point when the Zn, Pb and As volatiles enter into the flue gas.

In order to establish the kinetics of oxidation of artificial magnetite pellets, we comprehensively studied kinetics of the oxidation of artificial magnetite pellets from low temperature to high temperature using chemical analysis. The results show that when the oxidation temperature is below 1 073 K (800 °C), the reaction is controlled by the step of internal diffusion, and the model function is 2 G(a) = 1−3(1−x)2/3 + 2(1−x) (α, reaction degree). When the temperature is above 1 073 K (800 °C), the reaction mechanism was chemical reaction, and the model function is 1 G(a) = 1−(1−x)1/3. The apparent activation energy for the oxidation of artificial magnetite pellets was also determined, which was 8.90 kJ/mol for the low temperature and 67.79 kJ/mol for the high temperature. Based on the derived kinetic equation for the oxidation of artificial magnetite pellets, the calculated value is consistent with the experimental data. Compared with that of nature magnetite pellets, the apparent activation energy is decreased obviously, which indicates that the artificial magnetite pellets are oxidized more easily than nature magnetite pellets.

Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: 1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. 2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. 3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu, magnetic concentrate, containing 90.21% TFe and 0.4% Cu, direct reduction dust, including 65.17% ZnO and 2.66% PbO, common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application.

This paper describes the principle of measuring the thickness of a pulse reflection method, in accordance with the principle of thickness measurement of the pulse reflection method, we proposed a new method of extraction and analysis of the echo signal. The thickness measurement ultrasonic pulse reflection control system is designed. The differential detection circuit and the zero-crossing comparator form the peak detection circuit. The pulse echo signal is processed to improve the measurement accuracy.

Aiming at the effective utilization of the abundant high-alumina iron ores with low iron grade, the influence of alumina concentration and type on high-temperature characteristics was clarified based on the analyses of eight typical iron ores. The results indicate that high-temperature characteristics of iron ores in various alumina types are different. Higher Al2O3 concentration is deleterious to assimilability and liquid phase fluidity, but the influence extent of each alumina type is substantially different. Kaolinite (Al2O3&middot, 2SiO2&middot, 2H2O) contributes to correspondingly better assimilability, followed by hercynite (Fe(Fe, Al)2O4), gibbsite (Al(OH)3), diaspore (AlO(OH)), and free state alumina (Al2O3) in turn. Diaspore promotes relatively higher liquid phase fluidity, followed by kaolinite, free state alumina, and hercynite, while gibbsite possesses the maximum adverse impact. Kaolinite and hercynite are more beneficial to form dendritic or acicular silico-ferrite of calcium and alumina (SFCA) with high strength due to the better reactivity, and gibbsite and diaspore lead to more formation of relatively lower strength lamellar or tabular SFCA, while free state alumina is preferable to form disseminated SCFA with rather poorer strength. Kaolinite and hercynite are the most desirable alumina types for sintering rather than free state alumina.

Limonitic laterite contains low iron and nickel grades and much high smelting minerals and loss on ignition (LOI), identified as refractory iron ore for sintering. Thus, sinter pot tests of limonitic laterite via pressurized densification sintering and its intensification mechanism were conducted, and the industrial application prospect was explored. The results indicate that the sintering performance of the limonitic laterite of the new process is significantly improved with the tumble index and productivity increased by 19.2% and 18.6%, respectively, and solid fuel rate lowered by 10.3%. The external pressure field promotes the synchronization of heat front velocity and combustion front velocity for better sintering heat and mass transfer conditions, which also greatly improves the mineral compositions and microstructure of the product sinter. The microstructure is converted from large thin-wall pores into small thin-wall or large thick-wall pores with the sinter porosity decreased by 42.4%. Much close interlocking texture between hercynite and silico-ferrite of calcium and alumina (SFCA) is formed with hercynite grains aggregation and growth, and SFCA amount substantially increased. The better sintering performance will bring about a remarkable economic benefit of 282.78 million RMB/a if the industrial application is implemented. The pressurized densification sintering process is considered as one of the effective technologies for improving limonitic laterite sintering.

Ferronickel tailings, by-products from nickel laterite direct reduction-magnetic separation process, are now stored up in large quantities with low utilization because of the high MgO content. In this paper, ferronickel tailing with 5.82% Fe, 0.51% Ni, 44.08% SiO2, and 31.98% MgO was adopted to replace the traditional Mg-bearing flux, i.e. serpentine. The laboratory pot sintering tests show that, this new technique increases sinter productivity and tumble index by 4.12% and 10.63%, respectively, and reduces solid fuel rate by 6.35%. The mineralogical study of product sinter shows that the addition of ferronickel tailing contributes to the increase of the amount of SFCA by 4.03%. Mg and Al elements were found to migrate into magnetite grains to form three types of spinel solid solutions, i.e. (Fe, Mg)Fe2O4, Fe (Fe, Al)2O4, and (Fe, Mg)·(Fe, Al)2O4. Meanwhile, eutectic compound melts were obtained by the co-melting of kirschsteinite (CaO·FeO·SiO2), monticellite (CaO·MgO·SiO2), and fayalite (2FeO·SiO2).

Thermodynamic analysis of chlorination of zinc-bearing phases in pyrite cinder was conducted by FactSage thermochemical software. The effects of temperature and main components of pyrite cinder on the chlorination of ZnO and ZnFe2O4 were studied. The results show that the presence of CaO and MgO has no effect on the chlorination of ZnO while the starting chlorination temperatures of ZnO decrease from 1525 °C to 1200, 950, 850 °C with the presence of Fe2O3, SiO2, and Al2O3, respectively. In contrast, the presence of Fe2O3 and MgO has no effect on the chlorination of ZnFe2O4 while the starting chlorination temperatures of ZnFe2O4 change from 1350 °C to 825, 1075, 1525 °C with the presence of SiO2, Al2O3, and CaO, respectively. The thermodynamic analysis is consistent with the experimental results available in the literature.

With a growing demand for high-grade pellet feeds as well as a considerable increase in ore price, using cost-effective and high-grade sinter feeds for oxidized pellets production becomes more attractive. In this paper, one hematite concentrate from the wet grinding of a typical coarse sinter feed (GSF#) was used as raw material for manufacturing oxidized pellets. The effect of GSF# proportion in ore mixture, up to 40 wt% on roasting and metallurgical properties of oxidized pellets was investigated. Moreover, the effects of binary basicity and MgO content were also studied. The results show that in the case of natural basicity and MgO content, increasing the proportion of GSF# improves high-temperature softening–melting properties of oxidizing pellets, whereas imposes negative impacts on pellet strength as well as reduction swelling performance. The adverse effects can be eliminated by increasing binary basicity and MgO content to produce Mg-bearing fluxed pellets, which indicates the feasibility of using high proportion of ground sinter feed to manufacture high-quality oxidized pellets at low production cost.

This research proposed an efficient, innovative and environmentally friendly technology named smelting reduction-sulfurizing process, which uses one waste (waste ferric-oxide desulfurizer) to treat another (waste copper slag). In the new process, the waste ferric-oxide desulfurizer was employed not only as a sulfurizing agent to sulfurize and collect the copper lost in copper slag, but also as a reductant to reduce the magnetite to “FeO” and thus improve slag fluidity. It was revealed that 90.81% Cu was recovered and enriched in copper matte under the smelting conditions. The matte contained 15.87% copper, 20.25% S and 49.56% Fe, which can be returned to the copper smelting process as a feeding. Meanwhile, the removal rate of hazardous elements, such as Ni, Pb, Zn, As, Sb, Bi and Hg, from the initial copper slag by the new process was also determined, and the elimination rate of those elements was all over 90%.The leaching toxicity was used to further evaluate the environmental impact of the cleaned slag, indicating that the concentrations of toxic element ions in the leachate are all much lower than the thresholds, which confirmed that the cleaned slag with trace toxic elements is safe and harmless.

The characteristics of iron ore fines were considered to have tremendous effects on their subsequent sintering performances, but it is difficult to judge their sintering performances only based on ...

Conducting layered capacitive materials that utilize interlayer space to store charges usually exhibit higher areal and volumetric capacitive performance than porous carbons as a result of the bulk storage mechanism. Here, an organic-inorganic hybrid conducting layered material is designed through a ‘bottom-up’ strategy, and is synthesized facilely using a ‘one-pot’ approach. This material consists of periodically stacked nanosheets with a large lamellar period of 11.81 A. It is postulated that each nanosheet is composed of parallel oriented fully oxidized polyaniline (pernigraniline) molecular chains that are crosslinked by monomeric/oligomeric protonated tungstate molecules, both of which are self-organized through multiple side-chain hydrogen bonds. The binder-free high-loading electrodes made from this material can deliver high volumetric and areal capacitance in neutral electrolyte, along with moderate gravimetric capacitance. As exemplified, a 40 mg cm−2 binder-free electrode achieves an areal capacitance of 4.62 F cm−2 and a volumetric capacitance of 219.4 F cm−3 at 1 mA cm−2.

In this study, a novel process was established for extraction of Fe and Al from a complex high aluminum iron ore (33.43% Fetotal and 19.09% Al2O3). The main steps in the proposed process included pre-reducing high alumina iron ore and subsequent smelting to produce pig iron and rich-alumina slag, followed by alkaline leaching of the slag to obtain sodium aluminate solution and a clean slag. When smelting the pre-reduced high alumina iron ore pellets at 1625 &deg, C for 30 min with a slag basicity of 0.40, the pig iron yielded 97.08% Fe and extracted 0.13% Al2O3, together with an iron recovery of 94.54%. In addition, more than 68.93% Al2O3 was recovered by leaching the slag, which was achieved by firstly roasted the slag at 900 &deg, C for 2 h and then alkaline leaching at 95 &deg, C for 2 h with a liquid-to-solid ratio of 10 mL/g. In addition, the alkaline leaching slag could potentially be used as raw material for construction purpose, which mainly consisted of SiO2 and CaO.

Although high mechanical and electronic properties have made carbon nanotube (CNT) a promising active material for lithium ion batteries, the relatively low theoretical specific capacity (372 mAh g−1) of CNT has hindered its application. Here we have developed a general and efficient template strategy in synthesizing a new family of CNTs with controllable hollow walls and explored their promising applications in LIBs. The hollow structure formed between CNT core and nitrogen-doped graphene shell can be effectively used for lithium storage, and a reversible specific capacity of 635 mAh g−1 was achieved as anode material in LIB. Interestingly, the hollow structure has been further incorporated with silicon to offer even higher specific capacity of 930 mAh g−1 with good cyclic stability.