锰矿直接还原合金化模型与实验研究

依据锰矿直接还原热力学理论,并基于转炉冶炼的基本条件,建立锰收得率和经济效益预测模型。通过实验验证模型的可靠性,分析提高锰收得率的途径和转炉常规冶炼条件下采用锰矿直接还原合金化工艺的经济效益。

加钒合金化方法对钢筋组织性能的影响

研究了加钒铁合金直接合金化、加五氧化二钒和钒球还原合金化方法下,钒对400MPa级热轧带肋钢筋的组织、力学性能、夹杂物、析出物等的影响。结果表明：钒含量为0.06%~0.08%,钢筋各项力学性能指标均能达到GB1499-98标准要求;加钒合金化方法对钒的析出比例和析出物平均尺寸无影响。通过适当增加吹氩时间到5min,加钒球或五氧化二钒合金化就可达到与加钒铁合金化一样的钢水洁净度,钢筋伸长率可得到保证。

用等离子体促进渣─金属液间的反应

分析了等离子体的冶金属性，简要报导了用等离子体强化钒在渣铁间的还原，及在等离子体条件下用V2O5代替钒铁对钢液进行还原合金化的研究结果，提出直接在钢包内进行还原合金化的可能性及前景．

Electrochemical mechanism of electrolysis codeposition of Mg-Sr alloy in molten salt

The electrochemical process of Mg-Sr codeposition was studied in MgCl2-SrCl2-KCl melts containing different MgCl2 concentrations at 700 ℃ by cyclic voltammetry, chronopotentiometry and chronoamperometry. The results show that the actual precipitation potential of Sr reduces by nearly 0.5 V because of the depolarization effects of Sr activity reduced by forming Mg-Sr alloy. The codeposition potential condition of Mg and Sr to form Mg-Sr alloy is as follows： When electrode potential is more negative than -1.5 V, the magnesium will precipitate; when electrode potential is more negative than -2.0 V, the magnesium and strontium will both deposit. The control step of codeposition process of Mg and Sr is not diffusion control step. The codeposition current condition of Mg and Sr to form Mg-Sr alloy by chronoptentiometry is as follows： cathode current densities are higher than 0.71, 1.57 and 2.83 A/cm^2 in MgCl2-SrCl2-KCl melts with MgCl2 concentrations of 2%, 5% and 10% （mass fraction）, respectively. Key words：

Rational design and synthesis of one‐dimensional platinum‐based nanostructures for oxygen‐reduction electrocatalysis

Fuel cells have attracted extensive attention due to their high conversion efficiency and environmental friendliness.However,their wider application is limited by the poor activity and high cost of platinum(Pt),which is widely used as the cathode catalyst to overcome the slow kinetics associated with oxygen reduction reaction(ORR).Pt‐based composites with one‐dimensional(1D)nanoarchitectures demonstrate great advantages towards efficient ORR catalysis.This review focuses on the recent advancements in the design and synthesis of 1D Pt‐based ORR catalysts.After introducing the fundamental ORR mechanism and the advanced 1D architectures,their synthesis strategies(template‐based and template‐free methods)are discoursed.Subsequently,their morphology and structure optimization are highlighted,followed by the superstructure assembly using 1D Pt‐based blocks.Finally,the challenges and perspectives on the synthesis innovation,structure design,physical characterization,and theoretical investigations are proposed for 1D Pt‐based ORR nanocatalysts.We anticipate this study will inspire more research endeavors on efficient ORR nanocatalysts in fuel cell application.

Preparing low-oxygen Ti-6Al-4V alloy powder through direct reduction of oxides and its synergistic reaction mechanism

Ti-6Al-4V alloy powder was prepared through a two-step reduction of a mixture of TiO_(2),V_(2)O_(5) and Al_(2)O_(3) in this study.The oxide mixture was first reduced by Mg in MgCl_(2) at 750℃ in argon,where oxygen was reduced to 2.47 wt%from 40.02 wt%.The oxygen content in the final powder was eventually reduced to an extremely low level(0.055 wt%)using calcium at 900℃ in argon,and the final powder had the composition of 90.12 wt%Ti,5.57 wt%Al,and 3.87 wt%V,which meets the standard specification of Ti-6Al-4V(ASTM F1108-09).Between the two reductions,a heat treatment step was designed to help controlling the specific surface area and particle size.The effect of the heat treatment temperature on the morphology,and composition uniformity of the powder was investigated in detail.Heat treatment above 1300℃ attributed to a dense powder with a controlled specific surface area.Thermodynamic modeling and experimental results indicated that onlyα-Ti enriched with Al andβ-Ti enriched with V exist in the final powder,and other possible phases including Al-Mg and Al-V were excluded.This study also offers a triple-step thermochemical process for producing high-purity Ti-based alloy powder.

Electrocatalytic H_(2)O_(2)generation for disinfection

Epidemics are threatening public health and social development.Emerging as a green disinfectant,H_(2)O_(2)can prevent the breakout of epidemics in migration.Electrochemical H_(2)O_(2)production powered by renewable electricity provides a clean and decentralized solution for on-site disinfection.This review firstly discussed the efficacy of H_(2)O_(2)in disinfection.Then necessary fundamental principles are summarized to gain insight into electrochemical H_(2)O_(2)production.The focus is on exploring pathways to realize a highly efficient H_(2)O_(2)production.Progress in advanced electrocatalysts,typically single-atom catalysts for the two-electron oxygen reduction reaction(2e−ORR),are highlighted to provide high H_(2)O_(2)selectivity design strategies.Finally,a rational design of electrode and electrolytic cells is outlined to realize the on-site disinfection.Overall,this critical review contributes to exploiting the potentials and constraints of electrochemical H_(2)O_(2)generation in disinfection and pinpoints future research directions required for implementation.

Low temperature synthesis and thermal properties of Ag-Cu alloy nanoparticles

Ag-Cu alloy nanoparticles were synthesized by simple low temperature chemical reduction method using metal salts（acetate/sulphates） in aqueous solution with sodium borohydride as reducing agent.The chemical reduction was carried out in the presence of nitrogen gas in order to prevent the oxidation of copper during the reaction process.The alloy nanoparticles were characterized by XRD,UV-Vis,particle size analysis,EDS,TG-DTA and SEM analysis.From the XRD analysis,the crystallite sizes of the prepared samples were calculated using Scherrer formula and the values were found to be in the range of 15 nm.UV-Vis studies conform the formation of alloy nanoparticles.EDS analysis shows the presence of silver and copper in the samples.The SEM observation reveals that the samples consist of grains with average grain size up to 40 nm,and the particle size dependant melting point was studied by TG-DTA.

An alternate aqueous phase synthesis of the Pt3Co/C catalyst towards efficient oxygen reduction reaction

Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction(ORR)for the application in low temperature fuel cells and beyond,thus their facile and green synthesis is highly demanded.Herein we initially report an alternate aqueous phase one-pot synthesis of such catalysts(containing nominally ca.20 wt.%Pt)based on dimethylamine borane(DMAB)reduction.The as-obtained electrocatalyst(denoted as Pt3Co/C-DMAB)is compared with the ones obtained by NaBH4 and N2H4·H2O reduction(denoted as Pt3Co/C-NaBH4 and Pt3Co/C-N2H4·H2O,respectively)as well as a commercial Pt/C,in terms of the structure and electrocatalytic property.It turns out that Pt3Co/C-DMAB exhibits the highest ORR performance among all the tested samples in an O2-saturated 0.1 mol/L HClO4,with the mass activity(specific activity)ca.4(6)times as large as that for Pt/C.After 10000 cycles of the accelerated degradation test,the half-wave potential for ORR on Pt3Co/C-DMAB decreases only by 4 mV,in contrast to 24 mV for that on Pt/C.Pt3Co/C-NaBH4 or Pt3Co/C-N2H4·H2O shows a specific activity comparable to that for Pt3Co/C-DMAB,but a mass activity similar to that for Pt/C.ICP-AES,TEM,XRD and XPS characterizations indicate that Pt3Co nanoparticles are well-dispersed and alloyed with a mean particle size of ca.3.4±0.4 nm,contributing to the prominent electrocatalytic performance of Pt3Co/C-DMAB.This simple aqueous synthetic route may provide an alternate opportunity for developing efficient practical electrocatalysts for ORR.

Efficient electrocatalytic reduction of carbon dioxide to ethylene on copper–antimony bimetallic alloy catalyst

The exploration of efficient electrocatalysts for the reduction of CO2 to C2H4 is of significant importance but is also a challenging subject.Cu-based bimetallic catalysts are extremely promising for efficient CO2 reduction.In this work,we synthesize a series of porous bimetallic Cu–Sb alloys with different compositions for the catalytic reduction of CO2 to C2H4.It is demonstrated that the alloy catalysts are much more efficient than the pure Cu catalyst.The performance of the alloy catalysts depended strongly on the composition.Further,the alloy with a Cu:Sb ratio of 10:1 yielded the best results;it exhibited a high C2H4 Faradaic efficiency of 49.7%and a high current density of 28.5 mA cm?2 at?1.19 V vs.a reversible hydrogen electrode(RHE)in 0.1 M KCl solution.To the best of our knowledge,the electrocatalytic reduction of CO2 to C2H4 using Cu–Sb alloys as catalysts has not been reported.The excellent performance of the porous alloy catalyst is attributed to its favorable electronic configuration,large surface area,high CO2 adsorption rate,and fast charge transfer rate.

Photoelectrocatalytic CO2 reduction based on metalloporphyrin-modified TiO2 photocathode

The conversion of CO2 and water to value-added chemicals under sunlight irradiation, especially by photoelectrocatalytic reduction process, is always a dream for human beings. A new artificial photosynthesis system composed of a metalloporphyrin-functionalized TiO2 photocathode and BiVO4 photoanode can efficiently transform CO2 and water to methanol, which is accompanied by oxygen release. This photoelectrocatalytic system smoothly produces methanol at a rate of 55.5 μM h^–1 cm^– 2, with 0.6 V being the membrane voltage in plants. The production of hydrogen can also be observed when the voltage is more than 0.75 V, due to photocatalysis. Our results evidently indicate that the molecules of metalloporphyrin attached onto the surface of anatase (TiO2) behave as chlorophyll, NADP, and Calvin cycle in plant cells.

Combustion synthesis of FeAl−Al2O3 composites with TiB2 and TiC additions via metallothermic reduction of Fe2O3 and TiO2

Combustion synthesis involving metallothermic reduction of Fe2O3 and TiO2 was conducted in the mode of self-propagating high-temperature synthesis(SHS)to fabricate FeAl-based composites with dual ceramic phases,TiB2/Al2O3 and TiC/Al2O3.The reactant mixture included thermite reagents of 0.6Fe2O3+0.6TiO2+2Al,and elemental Fe,Al,boron,and carbon powders.The formation of xFeAl−0.6TiB2−Al2O3 composites with x=2.0−3.6 and yFeAl−0.6TiC−Al2O3 composites with y=1.8−2.75 was studied.The increase of FeAl causes a decrease in the reaction exothermicity,thus resulting in the existence of flammability limits of x=3.6 and y=2.75 for the SHS reactions.Based on combustion wave kinetics,the activation energies of Ea=97.1 and 101.1 kJ/mol are deduced for the metallothermic SHS reactions.XRD analyses confirm in situ formation of FeAl/TiB2/Al2O3 and FeAl/TiC/Al2O3 composites.SEM micrographs exhibit that FeAl is formed with a dense polycrystalline structure,and the ceramic phases,TiB2,TiC,and Al2O3,are micro-sized discrete particles.The synthesized FeAl−TiB2−Al2O3 and FeAl−TiC−Al2O3 composites exhibit the hardness ranging from 12.8 to 16.6 GPa and fracture toughness from 7.93 to 9.84 MPa·m1/2.

Reduction behaviour of Odisha Sands Complex,India ilmenite-coke composite pellets

Presently,ilmenite concentrates from Odisha Sands Complex at Chhatrapur,India are utilized to produce TiO2 slag by direct smelting in an electric arc furnace.However,the process involves the consumption of excess electrical energy and difficulty in handling the arc furnace due to frothing effects.A more efficient process of pre-reducing the ilmenite before smelting has been proposed in the present communication.In particular,studies have been undertaken on the reduction process of ilmenite-coke composite pellets.The difference in the reduction behaviour of raw ilmenite and ilmenite-coke composite pellets has been established and compared with that of the pre-oxidized raw pellets.The effects of various processing parameters like temperature,residence time,and reductant percentage on the metallization of composite pellets in a static bed have been investigated.Metallization of about 90%has been achieved at 1250°C for a reduction period of 360 min with a 4%coke composition.Furthermore,the reduced pellets have been characterized through chemical analysis,optical microscopy,field emission scanning electron microscopy and X-ray diffraction analysis.The reduction behaviour of composite pellets has also been found better than that of pre-oxidized pellets indicating the former to be more efficient.

Corrosion behavior of bulk two-phase Ag-25Cu alloys with different microstructures in NaCl aqueous solution

In order to have a better understanding on the corrosion mechanisms of bulk two-phase Ag-25Cu (at.%) alloys with different microstructures, two bulk nanocrystalline Ag-25Cu alloys and one coarse grained counterpart were prepared by liquid phase reduction (LPR), mechanical alloying (MA) and powder metallurgy (PM) methods, respectively. Their corrosion behavior was investigated comparatively using electrochemical methods in NaCl aqueous solution. Results show that the microstructure of the coarse grained PMAg-25Cu alloy is extremely inhomogeneous. On the contrary, compared with PMAg-25Cu alloy, the microstructures of the nanocrystalline LPRAg-25Cu and MAAg-25Cu alloys are more homogeneous, especially for LPRAg-25Cu alloy. The corrosion rate of MAAg-25Cu alloy is higher than that of PMAg-25Cu alloy, but lower than that of LPRAg-25Cu alloy. Furthermore, the passive films formed by three Ag-25Cu alloys exhibit n-type semiconducting properties. The passive current density of LPRAg-25Cu alloy is lower than that of PMAg-25Cu alloy, but higher that of MAAg-25Cu alloy.

Regulating Pd‐catalysis for electrocatalytic CO_(2) reduction to formate via intermetallic PdBi nanosheets

Electrocatalytic CO_(2) reduction plays an important role in the reduction of the CO_(2) concentration in atmosphere and consequently the mitigation of greenhouse effects.Pd has been extensively inves‐tigated as an electrocatalyst for the CO_(2) reduction to formate,which is an important raw material in the production of organic chemicals.However,the low selectivity and competitive reaction(hydro‐gen evolution reaction(HER))have hindered the performance of monometallic Pd catalysts.In this paper,intermetallic PdBi nanosheets(NSs)are prepared for efficient CO_(2) reduction to formate.The highest Faradaic efficiency(FE)of formate on fully ordered PdBi NSs reaches 91.9%at−1.0 V vs.RHE,which outperforms that of the disordered PdBi and pure Pd catalysts.Density functional theo‐ry calculations suggest that compared to disordered PdBi NSs,the ordered structure can decrease the free energy barrier of*OCHO(a key intermediate of formate formation)and inhibit H_(2) evolution as well,thereby enhancing the activity and selectivity for formate production.

Reducing process of sinter in COREX shaft furnace and influence of sinter proportion on reduction properties of composite burden

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.

Constrained-volume assembly of organometal confined in polymer to fabricate multi-heteroatom doped carbon for oxygen reduction reaction

The design and preparation of non-precious metal and carbon-based nanocomposites are critical to the development of efficient catalysts for technologies ranging from water splitting to fuel cell. Here, we present a constrained-volume self-assembly process for the one-step continuous precipitation-induced formation of soft colloidal particles, in which hydrophobic organoferrous compound,（Ph3P）2Fe（CO）3, is encapsulated within poly（styrene-co-acrylonitrile） nanoparticles（NPs）. The protective and confining polymer matrix ensures uniform carbonization and dispersion of（Ph3P）2Fe（CO）3 within a carbon matrix after a pyrolysis process. The obtained carbon NPs are successfully co-doped with Fe, P and N with a relatively high surface area of-380 m^2 g^（-1）. The Fe-P-N-doped carbon catalyst exhibits high catalytic performance and stability toward oxygen reduction reaction in both alkaline and acidic electrolytes via a favorable four-electron pathway. Meanwhile, the catalytic capability of Fe-P-N-doped carbon can be tailored by the tunable nanostructures.