Solid Ones Research Articles

Comprehensive study of electrokinetic-assisted phytoextraction of metals from mine tailings by applying direct and alternate current

Electrokinetic-assisted phytoextraction (EKPH) involves the use of electric current to improve the mobilization of metals in soils and, therefore, their removal efficiency. It emerges as an interesting sustainable technology for the rehabilitation of abandoned mining areas. The goal of this research was to conduct a comprehensive study of this technique applied to real mine tailings from an abandoned Pb/Zn mine by using ryegrass as plant species and two types of electric current: direct with polarity reversal (DC-PR) and alternate (AC). The EKPH tests were conducted in specially designed plastic containers that allowed recording the main parameters of the electrokinetic process and sampling the different matrices studied, i.e. water, soil and plants. This intensive sampling program allowed detailed monitoring of the metal mobilization processes for the different treatments applied. The changes caused in metal mobility and physicochemical parameters of the tailings due to the application of electric current were reflected to a greater extent in the water samples than in solid ones. Accumulation of Pb, Zn, Cd and Cu in ryegrass tissues increased significantly by 41%, 17%, 34% and 32% when applying 1 V cm−1 of AC current, with respect to the results of phytoextraction without electric current. The application of DC-PR current did not lead, in general, to statistically significant increases in the plant metal uptake. These findings were adequately correlated with the changes found in the metal concentrations of soil pore water and, to a lesser extent, with those observed from the BCR sequential extraction applied to tailings samples.

Elastic Critical Resistance of the Simple Beam Grillage Resulting from the Lateral Torsional Buckling Condition: FEM Modelling and Analytical Considerations.

Transversely loaded beam grillages are quite often used in industrial construction. In order to produce a safe design of such structures, it is necessary to account for the lateral torsional buckling phenomenon, which reduces load-bearing capacity. To be able to calculate the relevant reduction factor, the elastic critical load must be determined. As regards the existing design practice for such structures, simplified conditions are assumed for the mutual restraint of the component beams. However, this approach does not correspond to reality. This study discusses the results of numerical investigations and analytical calculations concerning the effect of the elastic action of simple beam grillage (SBG) joints on the critical load, which results from the lateral torsional buckling (LTB) condition. The SBG was defined as a flat system of interconnected beams, unstiffened laterally and loaded perpendicularly to the grillage plane. The analysis covered H-shaped grillages with different span ratios of component beams, in which the main (coupling) beam was decisive for instability. The effectiveness of the use of closed-section stiffeners at the grillage joints was also investigated. The grillage elastic critical resistances (ECR) were determined for two variants of joint stiffening. The computations were performed by means of FEM numerical simulations. The spatial models were discretised with the following elements: (1) solid ones in Abaqus, (2) shell ones in ConSteel, and (3) thin-walled bars in ConSteel. The LTB critical moments of the weakest beam (critical beam), elastically restrained against warping and against lateral rotation (in the LTB plane), were computed using the analytical methods developed by the authors. To this end, the methods were proposed to determine the indexes of the critical beam elastic restraint in the adjacent stiffening beams. In the study, it was demonstrated that (1) taking into account the conditions of mutual elastic restraint and interaction of the component beams provides a more accurate assessment of the grillage ECR, (2) the use of closed-section stiffeners in the grillage joints increase the ECR compared with classic flat stiffeners, (3) the grillage ECR can be estimated based on the critical moment Mcr of the weakest beam (critical beam) when the conditions of its elastic restraint in joints are accounted for.

Extraction of Broken Interlocking Tibial Nails: A Review of Surgical Techniques and Practical Management

Breakage of tibial interlocking nails is a rare complication and is associated with tibial nonunion. The distal part of a broken tibial nail is difficult to extract and can be a real challenge. Preoperative planning is important, as the retrieval techniques of broken implants are not routine operations. There are various techniques and instruments described by different authors with none being uniformly successful. Therefore, surgeons should know as many methods as possible to choose the most suitable one. Minimally invasive retrieval techniques should be favored because of their reduced morbidity, while fenestration extraction methods should be used as the second intention. Cannulated intramedullary nails are more prone to benefitting from minimally invasive retrieval techniques than solid ones. This paper reviews and describes the present techniques used to extract the distal part of broken tibial nails, to serve as a quick guide for surgeons who need it.

Scalable preparation of practical 1Ah all-solid-state lithium-ion batteries cells and their abuse tests

All-solid-state lithium-ion batteries are considered as a promising electric energy storage platform for electric vehicles due to the replacement of flammable liquid organic electrolytes in current lithium-ion batteries by inflammable solid ones; thus promoting high safety. Despite plenty of research on various solid electrolytes and other components, reports on the scalable production of all-solid-state lithium-ion batteries using electrodes with meaningful areal capacities are rather scarce. Consequently, the safety of all-solid-state lithium-ion batteries has not been systematically investigated yet, especially on cells with higher than lab-scale capacities. The aim of this report is to build a bridge between academic research and more industrially meaningful information on the safety of all-solid-state lithium-ion batteries. Thus, three 1Ah all-solid-state lithium-ion batteries were fabricated, where hybrid solid electrolyte consisting of PEO-LiTFSI polymer matrix with Lithium Ionic Conductive Glass Ceramic (LICGC™, Ohara Inc.) particle as active filler was sandwiched between NMC622 cathode and advanced graphite MCMB anode, both of which have a practically valuable areal capacity of higher than 1.0 mAh/cm2. Initial formation cycling was performed to build conformal interface between solid electrolyte film and electrodes. Comparable specific capacity of cathode active materials (∼90.0 mAh/g @ C/10 & 60 °C) could be achieved in three pouch cells with high consistence. Typical abuse tests including overcharge, external short, and nail penetration were conducted, the three 1Ah all-solid-state lithium-ion batteries cells showed excellent safety performance: there was no thermal runaway, no explosion, only slight increase of temperature was observed. This work demonstrates the scalable fabrication of practical all-solid-state lithium-ion batteries with consistent electrochemical performance and thereafter confirms their intrinsic safety.

Polyacrylate Backbone Promotes Photoinduced Reversible Solid-To-Liquid Transitions of Azobenzene-Containing Polymers

The development of polymers with efficient photoinduced reversible solid-to-liquid transitions is desirable for the design of healable materials, reconfigurable devices, and switchable adhesives. Herein, we demonstrate that an azobenzene-containing polyacrylate P-H exhibits more efficient photoinduced reversible solid-to-liquid transitions than its polymethacrylate analogue P-Me. The side chain of P-H or P-Me contains a hexamethylene spacer, a photoresponsive azobenzene group, and an n-decyl tail. Both P-H and P-Me show reversible cis–trans photoisomerization. Solid transP-H and P-Me change to liquid cis ones via UV-light-induced trans-to-cis isomerization; liquid cisP-H and P-Me revert to solid trans ones via visible-light-induced cis-to-trans back isomerization. Differential scanning calorimetry and rheology measurements revealed that photoinduced reversible solid-to-liquid transitions occur because P-H and P-Me have photoswitchable glass transition temperatures. Although P-Me exhibits a slightly faster rate for trans-to-cis photoisomerization than P-H due to fewer aggregates in solid state, cisP-H flows 20 times faster than cisP-Me because P-H has a more flexible polymer backbone. The low viscosity of cisP-H makes photoinduced solid-to-liquid transition efficient and enables the design of rapidly healable coatings. Our study shows that the design of a flexible backbone is a new strategy to develop rapidly healable polymers with more efficient photoinduced solid-to-liquid transitions.

Effective cultivation of corn on the drylands with the use of CAM liquid fertilisers by the “Tuman” innovative complex

In the presented material of the Samara State Agrarian University and Don State Technical University, the results of research on improving technologies for cultivating grain corn on the drylands using nitrogen, mineral, liquid fertilisers based on a carbamide-ammonia mixture — CAM are considered: CAM-32, CAM+S produced by PJSC “Kuibyshev-Azot” (Togliatti, Samara region), introducing them with an innovative, agrochemical, modular, multifunctional complex “Tuman...” (LLC “Pegas-Agro” — Samara). With a significant demand of corn for moisture and nitrogen fertilisers, it is very difficult to get a high yield without irrigation on the drylands, and therefore various technologies for using more effective liquid fertilisers instead of solid ones are being investigated in a region with insufficient moisture supply: in the Samara region of the Volga region of the Russian Federation. CAM has specific properties to cause “burns” of corn leaves; corn is a promising, highly productive crop with a great need for a macronutrient-nitrogen in the composition of a carbamide-ammonia mixture, and therefore to minimise this disadvantage, special extension hoses should be applied to hose sprayers, but they also have a technological disadvantage: corn foliar feeding requires additional moisture in the form of intense summer precipitation for the delivery of fertilisers through the soil layer to the root system zone. Thanks to the appearance of the foreign “Duport” aggregate, this problem is solved by special injection working bodies when applying CAM in the soil internally. The successful import substitution of the Duport unit was carried out by LLC “Pegas-Agro” (Samara, Russia) as well as by many other enterprises, creating a special module: the multi-injector “Tuman” for injecting more effective CAM.

Characteristics and Mechanism of Local Scour Reduction around Pier Using Permeable Sacrificial Pile in Clear Water

To improve the local scour protection of the pier using solid sacrificial piles, a kind of permeable sacrificial pile filled with stones is put forward in this study. Four influencing factors, including the size of the filling gravel of the permeable sacrificial pile, the distance between the pile and pier, the diameter ratio D1/D (D is the diameter of the pier and D1 is the diameter of the pile.), and the submergence rate of the pile, are studied in clear water condition with indoor tests and numerical simulations. The test results show that it has the best reduction effect on the local scour of the pier when the filled gravel size is 0.2–0.25 D, the distance between the pile and pier is 3.0 D, the diameter ratio is 1.0, and the submergence rate is 0.8. Results of the numerical simulation show that the permeable sacrificial pile has a significant weakening effect on the downflow in front of the pile and the flow velocity around the pile. In the same conditions, the reduction effects of the permeable sacrificial pile and the solid sacrificial pile on the pier are similar, but the local scour around the permeable sacrificial pile is less than that around the solid one. The pressure difference outside and inside the permeable pile causes the water to flow in the direction perpendicular to the isobars. This significantly impacts the flow velocity, the vortex system, and the shear stress around the permeable sacrificial pile and pier, which leads to a huge decrease in the local scour depths. The maximum shear stress on both sides of the permeable sacrificial pile and the pier is about 1/2 and 1/4 of those around the solid sacrificial pile respectively. And the area with lower velocity and shear stress behind the permeable sacrificial pile is larger than the area behind the solid ones.

Porous-fin microchannel heat sinks for future micro-electronics cooling

Porous-fin microchannel heat sinks offering high solid-fluid interfacial areas have the potential to be an integral part of future microelectronic cooling systems. Replacing solid with porous fins reduces the pressure drop penalty of the straight plate-fin microchannel heat sinks. However, prior research has shown that in some cases porous fins adversely affect the thermal performance of the microchannel heat sinks. The reduced effective thermal conductivity of the porous fins compared to the solid ones has been considered the main reason for the reduced thermal performance of porous-fin microchannels. In this work, a detailed study is conducted to assess the feasibility of using porous fins to simultaneously improve the thermal and hydraulic performances of the straight plate-fin microchannel heat sinks. Results revealed that the porous-fin microchannels outperform the solid-fin microchannels at small channel heights. However, at high channel heights, the low effective thermal conductivity of porous fins results in a weak vertical thermal diffusion. Consequently, replacing solid with porous fins degrades the thermal performance of the microchannel at high channel heights. Additionally, the porous-fin microchannels exhibit better thermal performance than the solid-fin microchannels at fin to fluid width ratios above 0.25. The increased coolant mass flow penetrated the porous fin section is the main reason for the enhanced heat transfer rate of the porous-fin microchannels at higher width ratios. Moreover, the porous-fin microchannels offer a lower pressure drop penalty than the solid-fin microchannels under all examined operating conditions. This research confirms the potential of substituting solid with porous fins to simultaneously improve the thermal and hydraulic performances of the straight plate-fin microchannel heat sinks.

Methane production from ethanolic and acid fermentations of the organic fraction of municipal solid waste under different pH and reaction times

Thermodynamically, lactic acid and ethanol allow the best energy recovery among all common metabolites for methane production. When faster methane production is required, previously fermented organic fraction of municipal solid waste (OFMSW) can be essential for methane production. This research deals with OFMSW fermentation in batch reactors at pH values of 4, 5, and 6 at 35 °C. Samples were taken at reaction times of 1, 3, and 6 days for every pH, characterized, and exposed to methane production at 35 °C. The results show that lower pH and shorter fermentation times allow better ethanol and lactic acid production. Without exception, the fermented liquid fractions produce more methane than the solid ones. Fermented OFMSW produced 19% more methane than unfermented ones. The first methanization stage of the liquid fractions required 1–2 days and the solid fractions from 4 to 8 days. According to Michaelis & Menten, the reaction rate Vmax values are significantly higher for the liquid fractions than for the solid ones. Vmax shows that the lowest tested pH (4) during fermentation delivers the best substrate for methane production. The liquid digestates show significantly lower Km values than the solid ones, indicating a good affinity of the methanogens for the substrate. These results show the possibility of producing methane fast and efficiently using liquid fermented digestates. The solid fraction produces methane, but only slower than the liquid fraction.

Balance of total mass and nitrogen fluxes through consecutive digestate processing steps: Two application cases

The high water content and low nutrient concentration of digestate complicate its storage, transportation, and utilization. Subsequent digestate processing can effectively remove water and influence nutrient partitioning among digestate fractions and final products.The current study was carried out to evaluate the performance of two typical digestate processing chains, solid and liquid ones, respectively, and to give practical recommendations for optimization. Two fully operating biogas plants with advanced heat utilization were considered as data sources. The digestate mass flow balance of dry matter (DM), water, total N (TN), and ammonium-N mass flows was performed and the efficiency of the examined processing units was calculated.It was found that solid-liquid separation of raw digestate shifted 73–87% of TN and 60–93% of NH4–N to the liquid phase. Subsequent drying of separated solid fraction removed about 6% of the initial water and required 84% less thermal energy per kg N recovered than the processing of separated liquid. The final product, pellets, contained 14% of initial TN, but only 2% of initial NH4–N as a result of microbial conversion of inorganic N during drying.Vacuum evaporation of separated liquid fraction removed 34% of the initial water and left a DM-rich concentrate. At the same time, an ammonium sulfate solution (ASS) containing 21% of initial TN and 34% of initial NH4–N was produced.Both evaluated processing chains showed specific advantages and challenges. Solid products were characterized by a high share of recalcitrant organic compounds and could serve as a soil improver. Liquid processing concentrated plant-available N in ASS, which could be used as valuable inorganic fertilizer.

Immunological conversion of solid tumours using a bispecific nanobioconjugate for cancer immunotherapy.

Solid tumours display a limited response to immunotherapies. By contrast, haematological malignancies exhibit significantly higher response rates to immunotherapies as compared with solid tumours. Among several microenvironmental and biological disparities, the differential expression of unique immune regulatory molecules contributes significantly to the interaction of blood cancer cells with immune cells. The self-ligand receptor of the signalling lymphocytic activation molecule family member 7 (SLAMF7), a molecule that is critical in promoting the body's innate immune cells to detect and engulf cancer cells, is expressed nearly exclusively on the cell surface of haematologic tumours, but not on solid ones. Here we show that a bispecific nanobioconjugate that enables the decoration of SLAMF7 on the surface of solid tumours induces robust phagocytosis and activates the phagocyte cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes (cGAS-STING) pathway, sensitizing the tumours to immune checkpoint blockade. Our findings support an immunological conversion strategy that uses nano-adjuvants to improve the effectiveness of immunotherapies for solid tumours.

Design, mechanical properties and optimization of lattice structures with hollow prismatic struts

Lattice structures with hollow struts exhibit superior mechanical properties as compared to solid ones. In this study, we introduce a new type of body-centered cubic (BCC) lattice, consisting of hollow prismatic struts with mechanical properties defined by an inner hollow parameter. The mechanical properties and deformation behavior of the BCC lattice structures with different inner hollow parameters are investigated under periodic boundary conditions. It is shown that the elastic modulus of the hollow-strut BCC lattice structure improves significantly by 598%-1460% and their deformation mechanism gradually changes from bending-dominated to stretching-dominated, when the inner hollow size increases. In contrast, there are little influences on shear deformation. Interestingly, tunable Poisson's ratio and isotropic elasticity can be achieved by adjusting the inner hollow size. In addition, the BCC lattice structures with different inner hollow parameters are fabricated by digital light processing for compression tests, and the experimental results are in good agreement with the simulation with relative errors of less than 14.6%. Finally, a high-fidelity interpolation model is employed to describe the effective elastic matrix of lattice structures, and a new optimization framework is proposed to simultaneously optimize the distribution of the volume fraction and inner hollow size of hollow-strut lattice structures. This proposed approach significantly improves the stiffness (compliance decreased by 15.8% to 53.1%) of the cantilever beam as compared to traditional optimal designs, demonstrating the potential application of the proposed approach in lightweight designs.

Propulsion, deformation, and confinement response of hollow nanocellulose millimotors

HypothesisMicromotor and nanomotor particles are typically made using dense solid particles that can sediment or be trapped in confined flow environments. Creation of much larger motors should be possible if a very low-density system is used with sufficient strength to carry liquid and still experience propulsive motion. Light, dense millimotors should also be able to deform more than dense solid ones in constrictions. ExperimentsMillimotors are created from permeable capsules of bacterial cellulose that are coated with catalse-containing metal–organic frameworks, enabling reactive propulsion in aqueous hydrogen peroxide. The motion of the motors is quantified using particle tracking and the deformation is measured using microcapillary compression and flow through confined channels. FindingsTwo different propulsion mechanisms are dominant depending on the motor surface chemistry: oxygen bubbles are expelled from hydrophilic millimotors, driving motion via recoil force and buoyancy. Hydrophobic millimotors remain attached to growing bubbles and move by buoyancy alone. Despite their large size, the low-density capsules compress to pass through contractions that would impede and be blocked by solid motors. The sparse structure but relatively large size of the motors enables them to transport significant volumes of liquid using minimal solid mass as a motor support structure.

Ultra-high Sensitivity Surface-Enhanced Raman Spectroscopy (SERS) Substrates Based on Au Nanostructured Hollow Octahedra

Current standard tissue biopsy methods detect abnormal cells in an advanced stage mainly due to its inherent limitation of low-resolution and low-sensitivity. Under this context, plasmonic nanostructures are emerging as an alternative to current diagnostic methods because they are fast, accurate and with spatial resolution. In this work, through a facile, low-cost, reproducible and fast method, ultra-high sensitive reusable SERS substrates based on Au macroscale nanoassemblies with topographical features extending into three dimensions are developed from electrodeposited Ag octahedral structures via galvanic replacement reaction (GRR) onto ITO substrates. These materials are tested by impregnation of Rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP) as analytes to verify their effectiveness as ultra-high sensitivity SERS substrates with high spatial resolution. Amazingly, high resolution SERS spectra are still detected from R6G and 4-ATP solutions with concentrations as low as 1×10−15 M and 1×10−18 M respectively; which, to the best of our knowledge, are the lowest analyte concentrations detected by a SERS octahedra-based substrate to date. Furthermore, the corresponding enhancement factors (EF) of the SERS substrates are estimated to be approximately 1012 and 1015, which demonstrates their ultra-high sensitivity. Such results are theoretically confirmed via the discrete dipole approximation (DDA) combined with Mie's theory by determining the polarizability, as well as the intensities of the inner and outer main electric fields of many polarizable Au nanospheres which constitute the nanostructured hollow octahedron, and predicted results match quite well. Likewise, finite element modeling (FEM) visually demonstrates that hollow structures present better surficial electric field detection performance than solid ones.

Strong coupling with directional scattering features of metal nanoshells with monolayer WS2 heterostructures

Realizing and manipulating strong light–matter coupling in 2D monolayer semiconductors are of the utmost importance in the development of photonic devices. Hollow nanostructures of noble metals are particularly interesting because of their stronger local electromagnetic field compared with solid nanoparticles, which facilitate the strong coupling of single metal nanostructures. Here, the tunable single nanocavity plasmon–exciton coupling was demonstrated at room temperature in hybrid systems consisting of Ag@Au hollow nanocubes (HNCs) and monolayer WS2 underneath, where a large vacuum Rabi splitting of 131.3 meV was observed. Mode splitting can be clearly observed from the dark-field scattering spectrum of the single hybrid nanocavity, which is ascribed to the strong coupling between the nanocavity mode and the excitonic mode. Then, we used the finite difference time domain method to simulate these hybrid systems. By changing the thickness of the shell of the Ag@Au HNC, we can tune the surface plasmon resonance peak position of HNCs to match the exciton energy of the monolayer WS2. The strong couplings were realized via the calculated scattering spectra. The calculated results were consistent with the experimental results. Furthermore, the mode volume of different nanostructures was discussed, and the mode volume of HNCs is smaller than other solid ones at the same plasmonic resonance wavelength, which also indicates that its ability to restrict an electromagnetic field is stronger. This study provides an ideal platform for the strong coupling of a single nanocavity at room temperature and has broad application prospects in the field of single-photon devices.

Kinetic Mechanism Development for the Direct Reduction of Single Hematite Pellets in H2/CO Atmospheres

Increasing interest in the direct reduction process of iron ore has revived investigations on gaseous and heterogeneous iron oxides’ kinetics. Despite extensive studies on the reduction of iron oxides with pure hydrogen or syngas, the development of a generic reduction mechanism for iron oxides is still lacking. The conventional shrinking core model hardly distinguishes between transport and reaction processes, leading to biases or even errors in the kinetic models. In the present study, a porous solid model, which solves mass balances of the individual gas‐phase species and solid ones assuming spherical symmetry, is used for developing a heterogeneous kinetic mechanism accounting for different iron oxidation stages (Fe2O3, Fe3O4, FeO). It also accounts for carbon accumulation and cementite formation to model the carburization phenomena when using carbon‐containing reducing agents like syngas. The proposed generic mechanism successfully reproduces 49 experimental data sets from the literature for single iron oxide pellets’ isothermal reduction with syngas of varying hydrogen content up to pure hydrogen without any adjustment of its parameters. The model predictions are in excellent agreement with the experimental data. Finally, the carburization kinetics are explained, and the factors (e.g., temperature, hydrogen content) affecting the carbon deposition are analyzed.

A New Comparative Potentiometric Method for Analysis of Omarigliptin Using Three Different Sensors

AbstractThis work represents first attempt for potentiometric determination of the most recent antidiabetic; omarigliptin. Three sensors, employing potassium tetrakis (p‐chlorophenyl) borate as a lipophilic cation exchanger, were developed and compared. One liquid contact ion‐selective electrode and two carbon paste‐based solid contact ones, plain one and another one modified with polyaniline nanoparticles, were employed. Performances of fabricated sensors were assessed as per IUPAC recommendations. Incorporation of hydrophobic polyaniline nanoparticles as ion‐to‐electron transducer layer at solid contact/ion‐sensitive membrane interface enhanced sensitivity and stability of the third sensor showing LOD of 2.5×10−7 mol L−1 and slope of 58.57 mV decade−1. The three sensors were applied for omarigliptin determination in presence of its degradation products, in dosage form and spiked human plasma.

Titanium Oxynitride Spheres with Broad Plasmon Resonance for Solar Seawater Desalination.

The facile production of hollow and solid nitridized submicrometer titania spheres has been successfully realized, with potential for mass production. The nitridation process gives submicrometer titanium oxynitride spheres, which possess a strong and broadband light absorption property. Interband-transition-induced resonance and plasmon resonance have been found to coexist in titanium oxynitride spheres through single-particle dark-field scattering measurements. Theoretical modeling has further confirmed that the excellent light absorption properties of the oxynitride spheres originate from the supported dual-mode optical resonance. A highly efficient, easy-to-build, and self-sustainable device is rationally designed for solar-driven seawater desalination, where the titanium oxynitride spheres function as photothermal transducers. The hollow spheres possess a higher water evaporation rate than the solid ones as the inner surface of the hollow spheres also provides surface sites for interaction with water molecules. Given the outstanding light absorption capability and the unique morphology of the hollow spheres, a water evaporation rate of ∼1.49 kg m-2 h-1 with a solar-to-thermal conversion efficiency of ∼89.1% has been achieved under the illumination of simulated solar light (1 sun, 1 kW m-2). This marks the record performance among reported plasmon-based solar seawater desalination systems.

Hollow mesoporous atomically dispersed metal-nitrogen-carbon catalysts with enhanced diffusion for catalysis involving larger molecules

Single-atom catalysts (SACs) show great promise in various applications due to their maximal atom utilization efficiency. However, the controlled synthesis of SACs with appropriate porous structures remains a challenge that must be overcome to address the diffusion issues in catalysis. Resolving these diffusion issues has become increasingly important because the intrinsic activity of the catalysts is dramatically improved by spatially isolated single-atom sites. Herein, we develop a facile topo-conversion strategy for fabricating hollow mesoporous metal-nitrogen-carbon SACs with enhanced diffusion for catalysis. Several hollow mesoporous metal-nitrogen-carbon SACs, including Co, Ni, Mn and Cu, are successfully fabricated by this strategy. Taking hollow mesoporous cobalt-nitrogen-carbon SACs as a proof-of-concept, diffusion and kinetic experiments demonstrate the enhanced diffusion of hollow mesoporous structures compared to the solid ones, which alleviates the bottleneck of poor mass transport in catalysis, especially involving larger molecules. Impressively, the combination of superior intrinsic activity from Co-N4 sites and the enhanced diffusion from the hollow mesoporous nanoarchitecture significantly improves the catalytic performance of the oxidative coupling of aniline and its derivatives.

Geometric Accuracy and Mechanical Behavior of PA6 Composite Curved Tubes Fabricated by Fused Filament Fabrication (FFF)

Herein, the effect of processing parameters including infill pattern and reinforcement type on the dimensional accuracy of products manufactured by the fused filament fabrication (FFF) process as well as the mechanical performance is studied. The reinforcements used to manufacture the PA6 composite are carbon, Kevlar, and glass fibers. The compression properties of the stated composites are compared. The results show that the rectangular fill pattern is less deformed compared with triangular, hexagonal, and solid ones. However, the compression strength is decreased by changing the infill pattern from the solid infill to hexagonal, triangular, and rectangular. Although there is no significant difference in terms of compression behavior, the printed PA6 reinforced with carbon fiber which is deformed outward contrary to Kevlar and glass fibers, which are deformed inward. Finally, the results confirm that the selection of the appropriate types of reinforcements and infill patterns among the several available types during the printing process is effective in improving the mechanical properties and also in providing better geometrical quality of the surfaces and the consequent dimensional precision improvement of the parts printed by the FFF process.