With the rapid iteration of portable electronics and electric vehicles, developing high-capacity batteries with ultra-fast charging capability has become a holy grail. Here we report rechargeable ...aluminum-ion batteries capable of reaching a high specific capacity of 200 mAh g
. When liquid metal is further used to lower the energy barrier from the anode, fastest charging rate of 10
C (duration of 0.35 s to reach a full capacity) and 500% more specific capacity under high-rate conditions are achieved. Phase boundaries from the active anode are believed to encourage a high-flux charge transfer through the electric double layers. As a result, cationic layers inside the electric double layers responded with a swift change in molecular conformation, but anionic layers adopted a polymer-like configuration to facilitate the change in composition.
To investigate the interfacial reaction of metal powder after absorbing microwave radiation, pure metal powder composed of five elements, Fe, Co, Ni, Cr, and Mn, was microwave heated at four ...temperature gradients of 500, 800, 1000, and 1200 °C. At 1200 °C, the powder particles diffused to form an alloy. Mechanical alloying of the mixed metal powder was performed for 5, 10, 24, and 48 h to observe the changes of the powder. The size of the alloy particles first increased, then decreased, and then increased again. The powder mechanically alloyed for 48 h was microwave heated at 700, 800, 900, 1000, and 1200 °C. The alloy only formed at 1200 °C.
The amount of steel produced using electric arc furnaces (EAFs) has been increasing in recent years. In this study, stack gases from EAFs in steelmaking plants were analyzed to determine if they are ...also dominant sources of polybrominated dibenzo-p-dioxin and dibenzofuran (PBDD/F) emissions in China. Isotope dilution high-resolution gas chromatography high-resolution mass spectrometry for qualitative and quantitative analysis of PBDD/F congeners revealed that the mean PBDD/F mass concentrations were 271.1–9467.8 pg Nm−3 for the preheating stages (PS) of three EAF plants and that the corresponding toxic equivalents (TEQs) were 10.8–971.2 pg TEQ Nm−3. The PBDD/F mass concentration from the smelting stage (SS) at plant E3 was 261.9 pg Nm−3 (4.5 pg TEQ Nm−3). The PBDD/F emission factors (EF) during the preheating stage for the three plants were 0.0356–1.51 μg TEQ t−1, and the EF was 0.0359 μg TEQ t−1 during the E3 smelting stage. PBDD/Fs were found to contribute 2.39–67.85% to the total mass and 2.84–57.68% to the total dioxin TEQ. These wide fluctuations were caused by differences in the composition of feeding materials and the working temperature of bag filters. Overall, the results indicate that PBDD/F emissions from EAF steelmaking should receive increased attention. The PBDD/F congener patterns among the three EAF plants were variable, possibly because of differences in raw materials. The results presented herein will facilitate assessment of the contribution of EAFs to total PBDD/F emissions in China and investigations of PBDD/F emissions at different stages of steelmaking processes using EAFs.
•PBDD/Fs emissions from electric arc furnaces deserve more attention.•Emissions from the scrap preheating stage were higher than from the smelting stage.•The composition of raw materials is a key factor influencing PBDD/F emissions.•APCD and its operating temperature are also important to PBDD/F emissions.
A new strategy for the high-throughput characterization of the mechanical homogeneity of metallurgical materials is proposed. Based on the principle of hydrostatic transmission and the synergistic ...analysis of the composition, microstructure, defects, and surface profile of the chosen material, the microstrain characteristics and changes in surface roughness after isostatic pressing were analyzed. After isostatic pressing, two types of microstrains were produced: low microstrain (surface smoothening with decreasing roughness) and large microstrain (surface roughening with increasing roughness). Furthermore, the roughness of the roughened microregions could be further classified based on the strain degree. The phenomenon of weak-interface damage with a large microstrain (plastic deformation, cleavage fracture, and tearing near nonmetallic inclusions) indicated that the surface microstrain analysis could be a new method of high-throughput characterization for microregions with relatively poor micromechanical properties. In general, the effect of isostatic pressing on the surface microstrain of heat-resistant steel provides a promising strategy for achieving high-throughput screening and statistically characterizing microregions with poor micromechanical properties, such as microregions containing microcracks, nonmetallic inclusions, pores, and other surface defects.
The use of electric arc furnaces is important in steelmaking, notably to recycle scrap steel, yet arc furnace is an unintentional source of persistent organic pollutants (POPs) such as chlorinated ...dioxins and furans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs) and brominated dioxins and furans (PBDD/Fs). Here, we review the level, profiles, influencing factors and formation mechanisms of such pollutants from arc furnaces of steelmaking plants. Comparison of various industrial sources shows that pollutant concentrations in the stack gas from the arc furnace in steelmaking plants are lower than that in the fly ash of all industrial sources. Preheating the scrap steel could increase the formation and emission of pollutants. The composition of raw materials is suggested to be an important influencing factor in pollutant formation. Air pollution control devices significantly reduce emissions of pollutants.
Inconel 718 (IN718) nickel-based superalloy is widely used in aerospace and nuclear applications owing to its excellent comprehensive mechanical properties, oxidation resistance, and hot corrosion ...resistance. However, the elemental segregation caused by heterogeneous solidification during casting has great influence on the mechanical properties. Therefore, accurately characterizing the segregation behavior is necessary. Traditional quantitative characterization of elemental segregation uses various sampling methods, in which only macroscopic segregation results are obtained. In this study, micro-beam X-ray fluorescence (μ-XRF) is used for the quantitative characterization of element micro-segregation in IN718 superalloy. The concentration distributions of Cr, Fe, Mo, Nb, and Ti in IN718 alloy are determined with optimized testing parameters, and the degree of elemental segregation in different regions of the analytical area is calculated. It is found that the segregation degree of Nb and Ti in the testing area is larger than other alloying elements. The correlation between the microstructure distribution and the segregation degree of Nb and Ti has been studied using scanning electron microscopy (SEM) combined with energy-dispersive spectrometry (EDS). There is severe segregation of Nb and Ti in areas where Nb-containing precipitates are accumulated. The distribution of abnormal signals of Nb with a high fluorescence intensity has a close relationship with the area of precipitates-enriched Nb.
The railway wheel is the key component of high-speed railway train. To assure the safety in service, higher requirements are put forward in this study for the composition, microstructure uniformity, ...and comprehensive properties of wheel materials. In this paper, the high throughput quantitative distribution characterization methods of composition, microstructure, inclusions and Vickers hardness of high-speed railway wheel materials based on the spark source original position analysis technique, high throughput scanning electron microscope (SEM) combined with image batch processing technology, and automatic two-dimensional quantitative distribution analysis technique of inclusions and micro hardness have been studied. The distribution trend of the content of nine elements, size and quantity of sulfides and oxides, ferrite area fraction, and Vickers hardness from the wheel tread surface to the radial depth of about 50 mm below the surface has been discussed. The influence of inclusions distribution on the element segregation and the effect of rim-chilling process with different water spraying angle on the distribution of microstructure and micro hardness have been investigated. It was found that unsynchronized cooling on both sides of the rim altered the phase behavior of ferrite and pearlite and obvious inhomogeneity distribution of ferrite appeared, which led to the asymmetrical Vickers hardness in areas near or away from the flange. Based on the quantitative characterization of area fraction and micro hardness on the same location of wheel rim, a statistical mapping relationship between ferrite area fraction and Vickers hardness was established.
Heat-resistant P91 martensitic steel is used to produce high-temperature steam pipelines in (ultra) critical power plants. However, non-metallic inclusions are inevitably produced in the ...metallurgical process. The type, composition, morphology, quantities, size and distribution of these inclusions have significant influences on the properties of materials. The present work developed an original position statistical distribution analysis method to characterize non-metallic inclusions in P91 steel based on scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). Two samples from P91 steel pipes fabricated by different processes were examined. The non-metallic inclusions in these samples could be divided into spherical oxides, strand-shaped oxides, spherical sulfides, spherical oxygen–sulfur compounds, strip sulfides and other inclusions. The amount, proportional area, particle sizes, original positions and statistical distribution results of non-metallic inclusions in different processed samples were assessed, and the causes and effects of these inclusions were analyzed. This novel method could provide diversified information on inclusions, which is helpful for the improvement of metallurgical processes and service performance evaluations.
Dendrites are important microstructures in single-crystal superalloys. The distribution of dendrites is closely related to the heat treatment process and mechanical properties of single-crystal ...superalloys. The primary dendrite arm spacing (PDAS) is an important length scale to describe the distribution of dendrites. In this work, the second-generation single crystal superalloy HT901 with a diameter of 15 mm was imaged under a metallurgical microscope. An automatic dendrite core identification and full-field quantitative statistical analysis method is proposed to automatically detect the dendrite core and calculate the local PDAS. The Faster R-CNN algorithm combined with test time augmentation (TTA) technology is used to automatically identify the dendrite cores. The local multi-directional algorithm combined with Voronoi tessellation is used to determine the local nearest neighbor dendrite and calculate the local PDAS and coordination number. The accuracy of using Faster R-CNN combined with TTA to detect the dendrite core of HT901 reaches 98.4%, which is 15.9% higher than using Faster R-CNN alone. The algorithm calculates the local PDAS of all dendrites in H901 and captures the Gaussian distribution of the local PDAS. The average PDAS determined by the Gaussian distribution is 415 μm, which is only a small difference from the average spacing λ¯ (420 μm) calculated by the traditional method. The technology analyzes the relationship between the local PDAS and the distance from the center of the sample. The local PDAS near the center of HT901 are larger than those near the edge. The results suggests that the method enables the rapid, accurate and quantitative dendritic distribution characterization.
The proportion of steel produced using electric arc furnaces (EAFs) is increasing. In this study, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) concentrations and patterns in stack ...gas samples from three typical EAFs in steelmaking plants were determined to allow the contributions of EAFs in steelmaking plants to PCDD/Fs emissions in China to be assessed. Samples collection was accomplished by adopting the automatic isokinetic sampling technique, then the PCDD/Fs congeners concentrations were analyzed qualitatively and quantitatively by isotope dilution high-resolution gas chromatography high-resolution mass spectrometry (HRGC-HRMS). The mean PCDD/Fs mass concentrations in stack gases emitted during the scrap preheating phase of plants E1, E2, and E3 were 0.48, 385.55, and 0.34 ng Nm−3, respectively, and the total toxic equivalent (WHO2005-TEQ) concentrations were 0.05, 33.16, and 0.03 ng Nm−3, respectively. The PCDD/Fs mass concentration in stack gases emitted during the melting phase at plant E3 was 0.12 ng Nm−3 (0.02 ng WHO2005-TEQ Nm−3). The operational temperature of the bag filter of the preheating in the E2 EAF was as high as 230 °C, which is conducive to the generation of PCDD/Fs, whether the temperature in the bag filter of E1 (150 °C) and E3 (120 °C) are not. Moreover, the bag filter temperature is suggested to be best controlled to below 150 °C. The emission factors (EF) for PCDD/Fs released into the air during the scrap preheating phase for plants E1, E2, and E3 were 0.13, 52, and 0.10 μg WHO2005-TEQ t−1, respectively, and the EF for the smelting phase from plant E3 was 0.14 μg WHO2005-TEQ t−1. The emission factor in E2 is 5 times higher than the highest current UNEP toolkit factor for EAFs (10 μg TEQ/tonne steel). Therefore, an update for the UNEP toolkit emission factor for a few case plants is suggested. Several congeners, including 2,3,7,8-TeCDF, 1,2,3,4,6,7,8-HpCDF, and 1,2,3,4,6,7,8-HpCDD, were dominant during the preheating phase, while 2,3,7,8-TeCDF, 1,2,3,7,8-PeCDF, and 2,3,4,7,8-PeCDF were dominant during the smelting phase. The monitoring data from the case plants helps to better understand the PCDD/Fs emissions of EAFs using preheating process stages. However, a more complete emission inventory requires more case investigations on the PCDD/Fs emissions from representative EAFs steelmaking plants.
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