Three-dimensional Core Research Articles

Metal-faced sandwich composite panels: A review

This review paper discusses the challenges in improving the mechanical and structural performance of metal-faced sandwich composite panels while reducing weight and cost. It focuses on the core and facesheet structural trends of metal-faced sandwich panels, highlighting innovative design concepts and mechanical performance with respect to failure modes. The paper categorizes recent core geometries used in metal-faced sandwich structures into three types: cellular foam cores, two-dimensional periodic cores, and three-dimensional periodic cores, each with unique characteristics and advantages. The performance of metal sandwich panels with different core structures in response to various mechanical tests is also summarized, including high and low-velocity impact, flexural, and blast and fire resistance. The review emphasizes that the core geometry, facesheet thickness, and core-face interfacial bonding of sandwich composites play a critical role in determining their structural performance and potential applications. Overall, this review paper provides valuable insights into the challenges of improving the mechanical and structural performance of metal-faced sandwich composite panels and highlights the importance of innovative design concepts for achieving optimal performance.

Morphology and Depositional Processes of a Carbonate-Filled Canyon in the Carboniferous KT-II Formation of the Eastern Precaspian Basin, Kazakhstan: Insight from 3D Seismic Data

Canyons in carbonate depositional settings, as important elements of the source-to-sink system, remain poorly studied compared to those in siliciclastic depositional environments. The latest high-resolution three-dimensional seismic data, well logs, and core data at the eastern edge of the Precaspian Basin are used to investigate the geomorphology, infillings, and depositional process of a unique carbonate-filled canyon in the Carboniferous KT-II formation parallel to the carbonate platform, which is distinct from other slope-perpendicular canyons. The canyon has a total length of more than 52.3 km with a nearly N-S orientation and an S-shaped geometry, and the whole canyon can be divided into three segments by two knickpoints. The slope-parallel orientation of the canyon is mainly controlled by the palaeogeomorphology and reverse faults. Due to the collision of the Kazakh and European plates in the early-middle Visean (early Carboniferous), the canyon was formed in a northern tilted, elongated, and restricted palaeotopographic feature between uplifts. The development of reverse faults related to tectonic movement controlled the variations in the width of the canyon and the positions of the knickpoints. Tectonics controlled the orientation and formation of the canyon, while sedimentary processes contributed to its infilling. The well-seismic tie analysis indicated two distinct periods of the canyon fillings, Ss1 and Ss2, which were separated by a second-order sequence boundary. The lower part contained sediments supplied by both sides of the canyon through channels or gullies, and the upper part was dominated by a carbonate platform that prograded from the eastern side of the canyon. The evolution of the canyon can be subdivided into three stages. The increasing stage was mainly characterized by significant upslope erosion through headward retrogressive mass failures in the slope-parallel confined negative relief to form the canyon during the lowstand system tract of Ss1. Subsequently, in the early filling stage, the carbonate factory was productive during the highstand, and massive excess carbonate sediments were transported into the adjacent canyon by channels or gullies on both sides and deposited. The canyon was basically filled, and the morphology became much gentler. During the subsequent late filling stage, the carbonate platform was flooded again during the highstand, and the production rates of the carbonate factory greatly increased. The lateral progradation of carbonate platforms accelerated on the canyon of the early filling stage and further into the inner sag.

Types and sedimentary genesis of barriers and interlayers in the composite turbidite sand bodies of a deep-water canyon: A case study of the Central Canyon in the Qiongdongnan Basin

Deep-water oil and gas is currently the hot spot and difficulty of global oil and gas exploration, and the complex flow process inside the turbidite channels of deep-water canyons makes it difficult to characterize reservoir structures, identify barriers and interlayers and clarify the spatial distribution laws of reservoirs, which restricts the development of deep-water oil and gas. Taking the Central Canyon of the Qiongdongnan Basin as an example, this paper identifies and characterizes the barriers and interlayers of composite channel scale by means of seismic sedimentology, based on three-dimensional seismic and core data. Then, based on the turbidite filling process, barriers and interlayers are classified, and their genesis and control factors are analyzed. Finally, a development model of deep-water barriers and interlayers is established based on the quantitative analysis of sediment transportation system parameters. And the following research results are obtained. First, based on sedimentary genesis, barriers and interlayers are classified into four types, namely mudstone interlayers of lateral (aggradational) turbidite channel genesis (type A), mudstone interlayers of fine-grained turbidite channel genesis (type B), barriers of hemipelagic deep-water sediment genesis (type C), and calcareous petrophysical interlayers (type D). Second, based on the filling stage, barriers and interlayers are divided into four combination sequences, i.e., the initial canyon formation stage with strong sediment supply conditions (type A + type C and type B+ type C), the initial canyon formation stage with weak sediment supply conditions (type B + type C), the stable canyon development/late reworking stage with strong sediment supply conditions (types A + type D), and the stable canyon development/late reworking stage with weak sediment supply conditions (type D). Third, the development types and combination sequences of barriers and interlayers are controlled by the change of sediment transportation volume and terrain slope in the canyon. In the initial canyon formation stage, there is sufficient space for the development of turbidite, and the development of thin barriers and interlayers is controlled by sediment dischage volume, while the development of thick barriers and interlayers is controlled by terrain slope change. In the stable canyon development/late reworking stage, turbidite undergoes superimposed development and overbank. The sediment supply is the primary control factor of barrier and interlayer thickness, and the terrain slope change is the secondary factor. In conclusion, the development model of barriers and interlayers can be used to describe and predict the reservoir structure models under the same sedimentary background and provides a technical support for the exploration and development of deep-water oil and gas.

Tectonic-geomorphological evolution and provenance-sedimentary response: Insights from the Middle Jurassic–Lower Cretaceous, Junggar Basin, China

Understanding the complex depositional systems within lake basins requires a comprehensive analysis of the interplay between tectonic-geomorphological evolution and climate change. Based on three-dimensional seismic data, outcrops, well logging, cores, thin sections, and heavy mineral data, this study reconstructed the tectonic-geomorphological evolution of the Middle Jurassic–Lower Cretaceous in the Junggar Basin and analysed the responses of sequence stratigraphy, sediment provenance, and depositional systems. The Jurassic Xishanyao and Cretaceous Qingshuihe Formations developed third-order sequences (SQ1 and SQ2, respectively), which both consisted of lake transgressive (TST) and regressive system tracts (RST). During the SQ1 period, the Chepaizi-Mosuowan palaeo-uplift underwent substantial erosion and supplied sediment to the surrounding sub-basins, where deposited braided-river deltas were formed. Middle Yanshanian tectonism resulted in rapid subsidence, and the Chepaizi-Mosuowan palaeo-uplift submerged. During the early TST stage of SQ2, sediment from the northeast and northwest formed shallow braided-river deltas in topographic lows surrounding the residual Chepaizi-Mosuowan palaeo-uplift and reduced topographic roughness, resulting in a gentle slope to the south. The rapid lacustrine transgression from southeast to north in the late TST stage of SQ2 formed local beach-bars at shallow depths. During the RST stage of SQ2, a climate transition occurred from arid to humid, resulting in depositional systems that evolved from braided to meandering river deltas. The sedimentary fillings of the SQ1 and SQ2 stages were mainly controlled by tectonic-geomorphology and climate change, respectively. Collectively, our results suggest that the tectonic-geomorphological evolution and climate change jointly controlled the sediment sources and determined the depositional features in the basin.

Research on a New Reconstruction Technology and Evaluation Method for 3D Digital Core Pore Structure

This study analyses the main techniques for constructing a three-dimensional (3D) digital core, and summarizes the advantages and disadvantages of each reconstruction technique. The direction for the development of reconstruction technology for 3D digital cores is also proposed. The integration of multiscale, multicomponent, and nanoscale technology under different resolutions will play a significant role in future research efforts surrounding the physical properties of 3D digital cores. This study also introduces the main evaluation methods of digital cores, while analyzing and comparing the applicable scenarios of each method. The results of the pore statistics method, based on the seed filling algorithm, can be used as a new and effective evaluation method for the 3D reconstruction of digital cores.

A Fast Workflow for Automatically Extracting the Apparent Attitude of Fractures in 3-D Digital Core Images

Fractures play a crucial role as fluid conduits and reservoir spaces in reservoirs. The distribution and characteristics of fractures determine the presence of high-quality reservoirs. To accurately analyze and observe fracture parameters, three-dimensional (3-D) digital cores generated from computed tomography (CT) are utilized. However, the current process of extracting fracture properties from these digital cores is time-consuming and labor-intensive. This paper introduces a new, fast, and automatic workflow for extracting the apparent dip angle and direction of fractures from 3-D digital core images. The proposed workflow involves several steps. Firstly, two perpendicular cross-sections are obtained from the digital core and converted into binary images. Next, the coordinates of four fracture feature points within the core image are automatically extracted. The fracture plane is then fitted using the least squares method based on the extracted coordinates. Finally, the apparent dip angle and direction of the fracture are calculated using the plane’s normal vector. By comparing and analyzing the proposed workflow with the original method, it becomes evident that the method proposed in this paper allows for quick, automated, and accurate extraction of the apparent dip angle and direction of fractures. The application of this workflow to extract fracture attitudes in 3-D micro-CT and full-hole digital core images significantly enhances efficiency.

Lightweight hybrid composite sandwich structures with additively manufactured cellular cores

This study focuses on advancing sandwich structures by designing and fabricating complex two- and three-dimensional cellular cores combined with Carbon Fiber Reinforced Polymer (CFRP) skins. Numerical analysis is used to investigate the effect of core design and density on the bending performance. Optimal configurations are identified and experimentally validated. Professional Fused Filament Fabrication (FFF) equipment with a heating chamber is employed for manufacturing the core samples to enhance layer cohesion and material joint stiffness. A high-performance technical polymer with a superior strength-to-weight ratio is employed to maximize structural capabilities. Hybrid sandwich structures with PEI Ultem cellular cores demonstrate stiffness and strength comparable to reference materials, outperforming foam cores while slightly trailing behind Nomex® and aluminum honeycombs. In addition, the results demonstrate more efficient cell morphologies achievable through additive manufacturing technologies, surpassing the hexagonal design. This work provides valuable insights into hybrid composite materials and the potential of additive manufacturing in creating lightweight, high-performance sandwich panels.

Formation of core–shell structure on azurite with DMTD surface modification and its response to flotation

2,5-Dimercapto-1,3,4-thiadiazole (DMTD) is an excellent activator of carbonate minerals containing Cu. However, few studies have been conducted on this activation mechanism. In this study, the effects of DMTD modification on the floatability and flotation interface characteristics of azurite and xanthate adsorption were systematically investigated. Micro-flotation tests demonstrated that pretreatment with an appropriate concentration of DMTD in the range of 20–40 mg/L increased the flotation recovery of azurite by 50% when potassium butyl xanthate (KBX) was used as the collector. FESEM-EDS, XPS, UV–Vis, ICP-OES, ToF-SIMS and contact angle analyses demonstrated that DMTD surface modification proceeded through a chemical reaction, resulting in the formation a three-dimensional core–shell structure consisting of a core (azurite) and a shell (Cu(I)-DMTD). Compared to the surface of natural azurite, that of azurite modified with DMTD had an increasing number of Cu active sites, which promoted the effective adsorption of KBX on azurite, thus significantly improving azurite hydrophobicity. The decreased floatability of azurite is closely related to the formation of colloidal Cu(I)-DMTD components in solutions with excess DMTD. This study improves our understanding of DMTD modification and presents a direction for enhancing the xanthate flotation of copper oxide minerals using DMTD as an activator.

A flexible asymmetric supercapacitor with organohydrogel electrolyte for high voltage operation over wide temperature range

It is highly desirable for supercapacitors to achieve mechanical flexibility and temperature tolerance, as well as high energy density, to fully utilize their superior characteristics of high-power density and long cycle stability to realize their potential as practical wearable energy storage devices. We devise a novel strategy to fabricate a flexible asymmetric supercapacitor based on dual network organohydrogel, exhibiting high energy density and electrochemical stability over a wide temperature range spanning 100 ℃.A three-dimensional core–shell NiCo2O4@MnO2 nanostructure is selected as the positive electrode to supply multiple ion diffusion channels through its mesoporous structure, and nano structured N-doped carbon nanofibers as the negative electrode to increase the contact area with electrolyte, and 6 M KOH based organohydrogel as electrolyte. The resulting supercapacitor exhibits high electrochemical performance including a high operation voltage of 1.7 V and high energy density of 51.1 Wh kg−1 at a power density of 850 W kg−1 and is stable over temperature changes between –20 and 80 ℃. This work demonstrates a high-performance supercapacitor designed with 3D asymmetric electrodes and a dual network organohydrogel, suitable as a practical energy storage device, requiring mechanical stability and stability against temperature change.

Superior strength–ductility synergy in three-dimensional heterogeneous-nanostructured metals

Heterogeneous microstructural design has been proven to be an effective strategy in breaking the strength–ductility dilemma in nanostructured metals. However, the precise control of heterogeneous microstructures to achieve strength–ductility synergy remains challenging. Here, we demonstrate a novel powder metallurgy approach for creating three-dimensional (3D) core–shell nanostructures with highly tunable shell thickness and grain size distributions. These 3D nanostructures enable superior strength–ductility synergy in pure copper, pushing the boundary of the Ashby map to unchartered territory. A combination of microstructural characterization, atomistic simulations and crystal plasticity modeling reveals that the generation and accumulation of geometrically necessary dislocations near the core–shell interface play a pivotal role in accommodating the strain gradient and sustaining a high strain-hardening rate during plastic deformation. Our work provides a viable approach for designing bulk nanostructured materials with 3D heterogeneous ingredients and demonstrates a promising pathway for the development of strong and ductile materials.

Study on oil seepage mechanisms in lamellar shale by using the lattice Boltzmann method

The shale oil and gas resources in the world are rich and are an important part of unconventional oil and gas resources. In this paper, firstly, by comprehensively using CT scanning technology, the three-dimensional pore-fracture structure characteristics of shale core samples of different sizes is characterized, and a three-dimensional digital core is established; Secondly, SEM and FIB-SEM techniques are systematically used to describe the microstructure and fracture network development characteristics of shale matrix pores and fractures, and a three-dimensional pore and fracture network model is established; Thirdly, Combined with LBZ simulation method, the mechanism of two-phase fluid transport in shale cross-scale fracture network is explored. Results show that: (a) The relatively dispersed mesopores and macropores in space constitute the main storage space of methane. Some pores in the study area of shale samples have good connectivity, and some samples only have connected pores in the study area of their magnification. (b) A large number of intergranular pores and fissures developed together with the intergranular pores of clay minerals, forming a good network connection system between microscopic pores in laminated shale. (c) when the hydrophilic mineral proportion is increased from 30% to 70%, the relative permeability of oil phase at water saturations of 20%, 40% and 60% has an increase of 6.8%, 7.8% and 4.2%, respectively, and the relative permeability of water phase at water saturations of 20%, 40% and 60% has a decrease of 1.8%, 2.6% and 6.5%, respectively. (d) When the oil phase contact angle is increased from 30° to 70°, the relative permeability of oil phase at water saturations of 20%, 40% and 60% has an increase of 1.9%, 2.7% and 2.2%, respectively, and the relative permeability of water phase at water saturations of 20%, 40% and 60% has a decrease of 1.2%, 2.1% and 3.5%, respectively.

Unprecedented heat resistance of Fe-based soft magnetic composites realized with tunable double insulation layer: Synergy of MgO diffusion barrier and void-filling SiO2 layer

Soft magnetic composites (SMCs) comprising surface-insulated Fe powders have attracted significant attention owing to their capability of producing innovative three-dimensional cores with high magnetic flux density and their potential utilization in various electrical machinery fields. The aim of this study is to fabricate SMCs with an inorganic double insulating layer, which can substantially enhance heat resistance and enable enhanced magnetic and mechanical performance through high-temperature annealing. Herein, SMCs with different inorganic coating materials (single layers of SiO2, MgO, and PO4 and double-layers of MgO and SiO2) were prepared by a sol–gel method and powder compaction. In particular, a certain double-layered SMC core (Fe@MgO@SiO2) exhibited retention of internal insulation matrix even after annealing at 900 °C and a significantly suppressed core loss owing to synergistic effects of a diffusion barrier in the primary layer and an electrical insulator in the secondary layer. As anticipated, high-temperature heat treatment at > 700 °C reduced coercivity, which enhances permeability and hysteresis loss of SMCs. The double-layered SMCs also showed an increase in flexural strength of 280% when the annealing temperature was increased from 600 to 900 °C.

Deep learning method of stochastic reconstruction of three-dimensional digital cores from a two-dimensional image.

Digital cores can characterize the true internal structure of rocks at the pore scale. This method has become one of the most effective ways to quantitatively analyze the pore structure and other properties of digital cores in rock physics and petroleum science. Deep learning can precisely extract features from training images for a rapid reconstruction of digital cores. Usually, the reconstruction of three-dimensional (3D) digital cores is performed by optimization using generative adversarial networks. The training data required for the 3D reconstruction are 3D training images. In practice, two-dimensional (2D) imaging devices are widely used because they can achieve faster imaging, higher resolution, and easier identification of different rock phases, so replacing 3D images with 2D ones avoids the difficulty of acquiring 3D images. In this paper, we propose a method, named EWGAN-GP, for the reconstruction of 3D structures from a 2D image. Our proposed method includes an encoder, a generator, and three discriminators. The main purpose of the encoder is to extract statistical features of a 2D image. The generator extends the extracted features into 3D data structures. Meanwhile, the three discriminators have been designed to gauge the similarity of morphological characteristics between cross sectionsof the reconstructed 3D structure and the real image. The porosity loss function is used to control the distribution of each phase in general. In the entire optimization process, a strategy using Wasserstein distance with gradient penalty makes the convergence of the training process faster and the reconstruction result more stable; it also avoids the problems of gradient disappearance and mode collapse. Finally, the reconstructed 3D structure and the target 3D structure are visualized to ascertain their similar morphologies. The morphological parameter indicators of the reconstructed 3D structure were consistent with those of the target 3D structure. The microstructure parameters of the 3D structure were also compared and analyzed. The proposed method can achieve accurate and stable 3D reconstruction compared with classical stochastic methods of image reconstruction.

Three-dimensional core reconstruction and performance evaluation of CO2 displacement in a tight oil reservoir

In this study, a three-dimensional tight sandstone core was reconstructed digitally using serials thin sections cut from a core sample used in laboratory carbon dioxide (CO2) flooding experiments. Based on the digital core, multiphase flow simulations were carried out to evaluate the performance of three prior laboratory-tested injection strategies: CO2 continuous injection, water alternative gas (WAG: CO2) injection, and cyclic CO2 injection. The chosen image-based reconstruction led to a close porosity and permeability match with the sampled core in an economical way. The numerical evaluation closely replicated the laboratory-tested procedures, thus providing realistic fluid distributions before CO2 injection. To determine saturation functions for CO2 injection after water flooding, sensitivities of endpoint relative permeability and capillary pressure to CO2 continuous injection were quantified. Water relative permeability was identified as a key factor. The saturation functions were used in a history match between simulations and laboratory data where close agreements were observed for all three CO2 injection strategies. Then critical enhanced oil recovery (EOR) operational parameters (soaking time, slug ratio, cycle size, and test duration) were optimized to maximize CO2 displacement performance, which led to the following observations: (1) While extended soaking after CO2 continuous injection increased incremental oil recovery, such increase was limited due to concurrent soaking during low-rate CO2 injection. (2) In WAG injection, CO2 and brine slug sizes and ratios were optimized: increasing the cycle size performed better than adjusting the slug ratio for favorable mobility control and efficient CO2 EOR. (3) For cyclic CO2 injection, the total CO2 injection volume was the most important factor, followed by the number of cycles, to allow CO2 diffusion into tight core to maximize the swept pore volumes. The history-matched simulations suggest that both WAG and cyclic CO2 injection can achieve high displacement effectiveness for the tight reservoir, compared with that achieved with slight soaking after CO2 continuous injection. The injected brine slugs in the WAG injection reduced the CO2 needed at the expense of reduced storage capacity. Compared to WAG, cyclic CO2 injection, though realizing the highest oil recovery and gas storage, requires more CO2.

Modeling of multi-mineral-component digital core based on Res-Unet

Abstract As the exploration of oil and gas moves further into less conventional reservoirs, effective methods are required for the fine evaluation of complex formations, particularly digital core models with multiple mineral components. The current technology cannot directly produce digital core images with multiple minerals. Therefore, image segmentation has been widely used to create digital multi-mineral core images from computed tomography (CT) images. The commonly used image segmentation methods do not provide satisfactory CT images of complex rock formations. Consequently, deep learning algorithms have been successfully applied for image segmentation. In this paper, a novel method is proposed to develop an accurate digital core model with multiple mineral components based on the Res-Unet neural network. CT images of glutenite and the corresponding results of quantitative evaluation of minerals by scanning electron microscopy are used as a training dataset for the automatic segmentation of CT core images. The used quantitative metrics show that compared with the multi-threshold and U-Net segmentation methods, the Res-Unet network leads to better results of mineral morphology and distribution recognition. Finally, it is demonstrated that the proposed Res-Unet-based segmentation model is an effective tool for creating three-dimensional digital core models with multiple mineral components.

Analysis of magnetic field characteristics and no-load losses of three-dimensional wound core transformer

Three-dimensionally wound core transformers (TWCTs) are widely used because of their low iron loss. This paper investigates the triangularly arranged TWCT core structure and a conventional planar laminated core transformer’s flat “E” core structure (PLCT). First, the magnetic field structures of the two transformers are analyzed using the equivalent magnetic circuit method to study the symmetry of the three-phase reluctance. Then, using the finite element method, a three-dimensional simulation model was built to analyze the no-load performance of TWCT and PLCT with the same dimensional parameters and the same core material. The no-load flux of each coil, the induced voltage on the secondary side, and the no-load iron loss of the core are analyzed. The analysis results show that TWCT has a 7.48% lower no-load loss than PLCT, which verifies the superiority of TWCT in terms of no-load loss.

Study on the Quantitative Characterization and Heterogeneity of Pore Structure in Deep Ultra-High Pressure Tight Glutenite Reservoirs

The precise characterization of a tight glutenite reservoir’s microscopic pore structure is essential for its efficient development. However, it is difficult to accurately evaluate using a single method, and its microscopic heterogeneity is not fully understood. In this study, a combination of X-ray diffraction, casting thin section observations, scanning electron microscopy, high-pressure mercury injection, constant-speed mercury injection, X-ray computed tomography, and the advanced mathematical algorithms in the AVIZO 8.0 visualization software was used to construct the three-dimensional digital core of a glutenite reservoir at the study site, and the parameters of the pore network model were extracted. The overall microscopic pore structure characteristics were quantitatively investigated from multiple scales. Based on this, the mineral quantitative evaluation system (QEMSCAN) examined the microscopic heterogeneity of the glutenite reservoir and its impact on seepage. The results show that the glutenite reservoir in the study block can be classified into three categories based on lithology and capillary pressure curve characteristics. The type I reservoir samples have large and wide pore throats, low threshold pressure, and high reservoir quality; type II reservoir samples are characterized by medium-sized pore throat, medium threshold pressure, and moderate reservoir quality; and the small and narrow pore throat, high threshold pressure, and poor reservoir quality are characteristics of type III reservoir samples. The various pore throat types and mineral distributions are due to the differences in dissolution, compaction, and cementation. The continuous sheet pores have good connectivity, which is related to the interconnection of primary intergranular pores and strip fractures, while the connectivity of isolated pores is significantly poor, which is related to the development of intragranular dissolved pores and intercrystalline pores. This suggests the deterioration of physical properties and pore throat connectivity, reduced average pore radius, and decreased pore sorting as decreasing permeability. The tight glutenite pores range in size from 5 nm to 80 μm and primarily feature Gaussian and bimodal distribution patterns, and submicron–micron pores contribute more to seepage. The effective pores were found to be attributed to the slowing effect of abnormally high pressure on the vertical stress, and the protective effect was positively correlated with the high-pressure strength. Notably, there is strong microscopic heterogeneity in the distribution of the reservoir matrix minerals and the pore throat size. As a result, the injected fluid easily flows along the preferential seepage channel with pore development and connectivity. This study provides new insights into the exploration and development of similar tight reservoirs.

Will ALMA reveal the true core mass function of protoclusters?

ABSTRACT Characterizing pre-stellar cores in star-forming regions is an important step towards the validation of theoretical models of star formation. Due to their sub-arcsecond resolution, ALMA observations can potentially provide samples of pre-stellar cores up to distances of a few kpc, where regions of massive star formation can be targeted. However, the extraction of real cores from dust-continuum observations of turbulent star-forming clouds is affected by complex projection effects. In this work, we study the problem of core extraction both in the idealized case of column-density maps and in the more realistic case of synthetic 1.3 mm ALMA observations. The analysis is carried out on 12 regions of high column density from our 250 pc simulation. We find that derived core masses are highly unreliable, with only a weak correlation between the masses of cores selected in the synthetic ALMA maps and those of the corresponding three-dimensional cores. The fraction of real three-dimensional cores detected in the synthetic maps increases monotonically with mass and remains always below 50 per cent. Above $\sim 1\, {\rm M}_{\odot }$ , the core mass function derived from the column-density maps is steeper than that of the three-dimensional cores, while the core mass function from the synthetic ALMA maps has a slope closer to that of the real three-dimensional cores. Because of the mass uncertainties, proper guidance from realistic simulations is essential if ALMA observations of protoclusters at kpc distances are to be used to test star formation models.

Fabrication of Ni/NiFe-LDH Core–Shell Schottky Heterojunction as Ultrastable Bifunctional Electrocatalyst for Ampere-Level Current Density Water Splitting

The practical application of NiFe-based materials as high-performance water splitting electrocatalysts is severity restricted by their inferior hydrogen evolution reaction (HER) activity and long-term stability under large current density. Herein, we report a three-dimensional core–shell Ni/NiFe-layered double hydroxide (LDH) Schottky heterojunction on iron foam (Ni/NiFe-LDH/IF) electrode, in which a Ni metal nano-layer was directly deposited on the NiFe-LDH support grown in situ on commercial IF. Such an assembly enhanced the interfacial strength of the Ni/NiFe-LDH/IF electrode, promoted electron transfer and increased the adsorption energy of OH– as proved by density functional theory calculations. Consequently, the ultralow overpotentials (η) of 56 and 277 mV for HER and 140 and 330 mV for the oxygen evolution reaction (OER) resulted in the current densities of 10 and 1000 mA cm–2, respectively. The fabricated Ni/NiFe-LDH/IF two-electrode electrolyzer exhibited excellent water splitting characteristics, which produced the current densities of 10 and 1000 mA cm–2 at cell voltage of only 1.49 and 1.87 V, versus a reversible hydrogen electrode, respectively, which exceeded that of a commercial Pt/C||RuO2 catalyst. Moreover, the Ni/NiFe-LDH/IF electrolyzer demonstrated extremely high stability at 1000 mA cm–2 without a significant decay for more than 1500 h in a 1 M KOH solution and for 250 h at 60 °C in a 6 M KOH solution. This study proposes a scalable and extendable strategy for designing highly efficient and ultrastable electrocatalysts for hydrogen production at an ampere-level current density.

Fabrication of three-dimensional CuS2@CoNi2S4 core–shell rod-like structures as cathode and thistle-derived carbon as anode for hybrid supercapacitors

The unique 3D rod-like structure has a broad range of potential applications for energy storage. In this work, a three-dimensional core–shell cathode material CuS2@CoNi2S4 and a porous rod-like anode material thistle-derived carbon (TDC) are synthesized for hybrid capacitors. Among them, the cathode CuS2@CoNi2S4 was prepared by straightforward in-situ growth and solvothermal method, showing excellent specific capacitance (1191.6 C g−1 at 1 A g−1), as well as enhanced cyclic stability (85.7% after 10,000 cycles). And the anode TDC was prepared by alkali activation and high temperature calcination, which showed a better double-layer energy storage behavior compared with activated carbon. The assembled hybrid capacitors which benefit from the synergistic effect of cathode core and shell and the porous structure of anode show high energy density (79.5 Wh kg−1 at 800 W kg−1) and long cycle performance (84.5% after 10,000 cycles), indicating that they have great application potential in the domain of supercapacitors. In short, the distinct cathode and anode structural designs offer a novel approach to the synthesis of electrode materials in the realm of energy storage.