Dynamic active sites on plasma engraved Ni hydroxide for enhanced electro-catalytic urea oxidation

The urea oxidization reaction(UOR)is an important anodic reaction in electro-catalytic energy conversion.However,the sluggish reaction kinetics and complex catalyst transformation in electrocatalysis require activity improvement and better mechanistic understanding of the state-of-the-art Ni(OH)_(2) catalyst.Herein,by utilizing low-temperature argon(Ar)plasma processing,tooth-wheel Ni(OH)_(2) nanosheets self-supported on Ni foam(Ni(OH)_(2)-Ar)are demonstrated to have improved UOR activity compared to conventional Ni(OH)_(2).The theoretical assessment confirms that the edge has a smaller cation vacancy formation energy than the basal plane,consequently explaining the structural formation.Operando and quasi-operando methods are employed to investigate the dynamic evolution of the Ni(OH)_(2) film in UOR.The crucial dehydrogenation products of Ni(OH)_(5)O^(-)intermediates are identified to be stable on the etched edge and explain the enhanced UOR in the low potential region.In addition,the dynamic active sites are monitored to elucidate the reaction mechanism in different potential ranges.

Clean production of Fe-based amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore and apatite

Separated preparation of prealloys and amorphous alloys results in severe solidification-remelting and beneficial element removal-readdition contradictions,which markedly increase energy consumption and emissions.This study offered a novel strategy for the direct production of FePC amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore(HPIO)and apatite.First,the thermodynamic conditions and equilibrium states of the carbothermal reduction reactions in HPIO were calculated,and the element content in reduced alloys was theoretically determined.The phase and structural evolutions,as well as element migration and enrichment behaviors during the smelting reduction of HPIO and Ca_(3)(PO_(4))_(2),were then experimentally verified.The addition of Ca_(3)(PO_(4))_(2)in HPIO contributes to the enrichment of the P element in reduced alloys and the subsequent development of Fe_(3)P and Fe_(2)P phases.The content of P and C elements in the range of 1.52 wt% -14.63 wt% and 0.62 wt% -2.47 wt%,respectively,can be well tailored by adding 0-50 g Ca_(3)(PO_(4))_(2)and controlling the C/O mole ratio of 0.8-1.1,which is highly consistent with the calculated results.These FePC alloys were then successfully formed into amorphous ribbons and rods.The energy consumption of the proposed strategy was estimated to be 2.00×10^(8) kJ/t,which is reduced by 30% when compared with the conventional production process.These results are critical for the comprehensive utilization of mineral resources and pave the way for the clean production of Fe-based amorphous soft magnetic alloys.

Elastic Modulus,Hardness,and Fracture Toughness of Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12) Solid Electrolyte

Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO) is a promising inorganic solid electrolyte due to its high Li+conductivity and electrochemical stability for all-solid-state batteries.Mechanical characterization of LLZTO is limited by the synthesis of the condensed phase.Here we systematically measure the elastic modules,hardness,and fracture toughness of LLZTO poly crystalline pellets of different densities using the customized environmental nanoindentation.The LLZTO samples are sintered using the hot-pressing method with different amounts of Li2CO3 additives,resulting in the relative density of the pellets varying from 83% to 98% and the largest grain size of 13.21 ± 5.22 μm.The mechanical properties show a monotonic increase as the sintered sample densifies,elastic modulus and hardness reach 158.47± 10.10 GPa and 11.27± 1.38 GPa,respectively,for LLZTO of 98% density.Similarly,fracture toughness increases from 0.44 to 1.51 MPa·m^(1/2),showing a transition from the intergranular to transgranular fracture behavior as the pellet density increases.The ionic conductivity reaches 4.54 × 10^(-4 )S/cm in the condensed LLZTO which enables a stable Li plating/stripping in a symmetric solid-state cell for over 100 cycles.This study puts forward a quantitative study of the mechanical behavior of LLZTO of different microstructures that is relevant to the mechanical stability and electrochemical performance of all-solid-state batteries.

Purifying Fe-based amorphous alloys to enhance glass-forming ability by designing a novel refining slag

Designing low melting point and low basicity refining slag suitable for Fe-based amorphous alloys and understanding the inclusions’formation,removal,influencing mechanisms are quite vital in the fields of metallurgy and materials.In this study,a novel 13%SiO_(2)-32%CaO-30%Al_(2)O_(3)-25%B_(2)O_(3)(wt.%)refining slag was designed after careful calculations of the liquid phase region,slag-metal equilibrium,surface tension,viscosity,deoxidation capability and sulfur distribution ratio.After refining with our designed slag,the content of impurities and the number density of inclusions in a representative Fe_(83)Si_(2)B_(15)(at.%)amor-phous alloy were significantly reduced.Moreover,the glass-forming ability(GFA)of the alloy was also enhanced,enabling the preparation of amorphous ribbons with a lower cooling rate.Based on the impu-rities in Fe-based amorphous alloys as well as the calculated oxide and sulfide free energy diagrams,CaO,SiO_(2),Al_(2)O_(3) oxides and CaS,TiS,MnS sulfides will form in the master alloy.The high melting point in-clusions in the melt are generally removed via a floatation-separation-absorption process and the Mn,Ti,S impurities are removed via slag-metal interface reactions during refining.As for the detrimental effect of inclusions on glass formation,the small lattice disregistry between Ti,Mn-containing inclusions and primaryα-Fe gains reveal that these inclusions are effective in promoting the heterogeneous nucleation,and therefore greatly deteriorate the GFA.These findings are important and provide an ideal solution to purifying the Fe-based amorphous alloys by refining and enhancing the GFA for industrial production.

Heterostructured crystallization mechanism and its effect on enlarging the processing window of Fe-based nanocrystalline alloys

The harsh melt-spinning and annealing processes of high saturation magnetization nanocrystalline softmagnetic alloys are the biggest obstacles for their industrialization. Here, we proposed a novel strategy to enlarge the processing window by annealing the partially crystallized precursor ribbons via a heterostructured crystallization process. The heterostructured evolution of Fe_(84.75)Si_(2)B_(9)P_(3)_(C0.5)Cu_(0.75)(at.%)alloy ribbons with different spinning rate were studied in detail, to demonstrate the gradient nucleation and grain refinement mechanisms. The nanocrystalline alloys made with industrially acceptable spinning rate of 25-30 m/s and normal annealing process exhibit excellent magnetic properties and fine nanostructure. The small quenched-in crystals/clusters in the free surface of the low spinning rate ribbons will not grow to coarse grains, because of the competitive grain growth and shielding effect of metalloid elements rich interlayer with a high stability. Avoiding the precipitation of quenched-in coarse grains in precursor ribbons is thus a new criterion for the composition and process design, which is more convenient than the former one with respect to the homogenous crystallization mechanism, and enable us to produce high performance nanocrystalline soft-magnetic alloys. This strategy is also suitable for improving the compositional adjustability, impurity tolerance, and enlarging the window of melt temperature,which is an important reference for the future development of composition and process.

三江平原土壤动物群落多样性对CO_2浓度升高的响应

为研究大气CO_2浓度升高条件下土壤动物的响应,本文采用开顶式气室(OTC)控制大气CO_2浓度,设置了3个梯度,分别为低浓度370 ppm背景CO_2 (AC)、中浓度550 ppm CO_2 (EC1)和高浓度700 ppm CO_2 (EC2)。于2017年秋季取样并用改良Tullgren干漏斗法和Baermann湿漏斗分离土壤动物。结果表明:(1)共捕获土壤动物6,268头,隶属于7纲15目,优势类群为甲螨亚目,占捕获量的88.13%;常见类群为弹尾目和双翅目幼虫,合计占捕获量的9%。不同CO_2浓度水平下,优势类群(甲螨亚目)和常见类群(弹尾目、双翅目幼虫)相同,但是稀有类群存在一定差异。(2)CO_2浓度升高显著增加了甲螨亚目的类群数和个体密度,显著降低了弹尾目的类群数和个体密度,对其他土壤动物无显著影响。(3)三江平原不同浓度条件下土壤动物的Shannon-Wiener多样性指数、Pielou均匀度指数均为AC>EC1> EC2,而优势度指数为EC2> EC1> AC,丰富度指数为AC> EC2> EC1。研究表明,气候变化有可能影响土壤动物的群落结构以及土壤动物的多样性。

An updated Vegetation Map of China(1:1000000)

Vegetation maps are important sources of information for biodiversity conservation,ecological studies,vegetation management and restoration,and national strategic decision making.The current Vegetation Map of China(1:1000000)was generated by a team of more than 250 scientists in an effort that lasted over 20 years starting in the 1980s.However,the vegetation distribution of China has experienced drastic changes during the rapid development of China in the last three decades,and it urgently needs to be updated to better represent the distribution of current vegetation types.Here,we describe the process of updating the Vegetation Map of China(1:1000000)generated in the 1980s using a‘‘crowdsourcing-change detection-classification-expert knowledge"vegetation mapping strategy.A total of 203,024 field samples were collected,and 50 taxonomists were involved in the updating process.The resulting updated map has 12 vegetation type groups,55 vegetation types/subtypes,and 866 vegetation formation/sub-formation types.The overall accuracy and kappa coefficient of the updated map are 64.8%and 0.52 at the vegetation type group level,61%and 0.55 at the vegetation type/subtype level and 40%and 0.38 at the vegetation formation/sub-formation level.When compared to the original map,the updated map showed that 3.3 million km^2 of vegetated areas of China have changed their vegetation type group during the past three decades due to anthropogenic activities and climatic change.We expect this updated map to benefit the understanding and management of China’s terrestrial ecosystems.