Solid Materials Research Articles

The Cut-Cell Method for the Conjugate Heat Transfer Topology Optimization of Turbulent Flows Using the “Think Discrete–Do Continuous” Adjoint

This paper presents a topology optimization (TopO) method for conjugate heat transfer (CHT), with turbulent flows. Topological changes are controlled by an artificial material distribution field (design variables), defined at the cells of a background grid and used to distinguish a fluid from a solid material. To effectively solve the CHT problem, it is crucial to impose exact boundary conditions at the computed fluid–solid interface (FSI); this is the purpose of introducing the cut-cell method. On the grid, including also cut cells, the incompressible Navier–Stokes equations, coupled with the Spalart–Allmaras turbulence model with wall functions, and the temperature equation are solved. The continuous adjoint method computes the derivatives of the objective function(s) and constraints with respect to the material distribution field, starting from the computation of derivatives with respect to the positions of nodes on the FSI and then applying the chain rule of differentiation. In this work, the continuous adjoint PDEs are discretized using schemes that are consistent with the primal discretization, and this will be referred to as the “Think Discrete–Do Continuous” (TDDC) adjoint. The accuracy of the gradient computed by the TDDC adjoint is verified and the proposed method is assessed in the optimization of two 2D cases, both in turbulent flow conditions. The performance of the TopO designs is investigated in terms of the number of required refinement steps per optimization cycle, the Reynolds number of the flow, and the maximum allowed power dissipation. To illustrate the benefits of the proposed method, the first case is also optimized using a density-based TopO that imposes Brinkman penalization terms in solid areas, and comparisons are made.

Preparation and alkali excitation mechanism of coal gangue-iron ore tailings non-sintering ceramsite

Non-sintering ceramsite is known for its simplicity in preparation technology and low production costs. The efficient utilization of industrial solid waste for non-sintering ceramsite production has garnered significant attention in green building materials within the framework of low carbon and environmental protection principles. This study focuses on preparing non-sintering ceramsites using non-active solid waste materials, specifically coal gangue and iron ore tailings. Firstly, a single-factor test was conducted to determine the optimal dosage of coal gangue and iron ore tailings. Subsequently, orthogonal tests were performed to investigate the influence of fly ash, NaOH, and aluminum powder on the mechanical properties of non-sintering ceramsite. Finally, the alkali excitation mechanism was elucidated through X-ray diffraction and SEM electron microscope scanning. The results reveal that the optimal proportions for coal gangue and iron ore tailings are 10 % and 35 %, respectively. Among the factors examined, NaOH dosage exerts the most significant impact on the compression strength and bulk density of non-sintering ceramsite, while aluminum powder dosage has the greatest effect on the 1-hour water absorption of the material. The optimal mixing ratio was determined with a total solid waste dosage of 73 %, meeting the national 600-grade standard for non-sintering ceramsite across all performance criteria. Furthermore, the alkali excitation process effectively activates the reactivity of fly ash and coal gangue. This activation leads to the generation of calcium alumina and C-S-H gel, along with other hydration products, which intertwine to form a dense gel structure. This structural enhancement further contributes to the improved performance of non-sintering ceramsite.

Aqueous mineral carbonation of three different industrial steel slags: Absorption capacities and product characterization

Heavy carbon industries produce solid side stream materials that contain inorganic chemicals like Ca, Na, or Mg, and other metals such as Fe or Al. These inorganic compounds usually react efficiently with CO2 to form stable carbonates. Therefore, using these side streams instead of virgin chemicals to capture CO2 is an appealing approach to reduce CO2 emissions. Herein, we performed an experimental study of the mineral carbonation potential of three industrial steel slags via aqueous, direct carbonation. To this end, we studied the absorption capacities, reaction yields, and physicochemical characteristics of the carbonated samples. The absorption capacities and the reaction yields were analyzed through experiments carried out in a reactor specifically designed to work without external stirring. As for the physicochemical characterization, we used solid-state Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Using this reactor, the absorption capacities were between 5.8 and 35.3 g/L and reaction yields were in the range of 81–211 kg CO2/ton of slag. The physicochemical characterization of the solid products with solid FTIR, XRD and SEM indicated the presence of CaCO3. This suggests that there is potential to use the carbonated products in commercial applications.

Enhanced degradation and removal of ciprofloxacin and ofloxacin through advanced oxidation and adsorption processes using environmentally friendly modified carbon nanotubes.

This study explores the utilization of adsorption and advanced oxidation processes for the degradation of ofloxacin (OFL) and ciprofloxacin (CIP) using a green functionalized carbon nanotube (MWCNT-OH/COOH-E) as adsorbent and catalyst material. The stability and catalytic activity of the solid material were proved by FT-IR and TG/DTG, which also helped to elucidate the reaction mechanisms. In adsorption kinetic studies, both antibiotics showed similar behavior, with an equilibrium at 30min and 60% removal. The adsorption kinetic data of both antibiotics were well described by the pseudo-first-order (PFO) model. Different advanced oxidation processes (AOPs) were used, and the photolytic degradation was not satisfactory, whereas heterogeneous photocatalysis showed high degradation (⁓ 70%), both processes with 30min of reaction. Nevertheless, ozonation and catalytic ozonation have resulted in the highest efficiencies, 90%, and 70%, respectively, after 30-min reaction. For AOP data modeling, the first-order model better described CIP and OFL in photocatalytic and ozonation process. Intermediates were detected by MS-MS analysis, such as P313, P330, and P277 for ciprofloxacin and P391 and P332 for ofloxacin. The toxicity test demonstrated that a lower acute toxicity was observed for the photocatalysis method samples, with only 3.1 and 1.5 TU for CIP and OFL, respectively, thus being a promising method for its degradation, due to its lower risk of inducing the proliferation of bacterial resistance in an aquatic environment. Ultimately, the analysis of MWCNT reusability showed good performance for 2 cycles and regeneration of MWCNT with ozone confirmed its effectiveness up to 3 cycles.

Efficiently tuning the electrical performance of PBTTT-C14 thin film via in situ controllable multiple precursors (Al2O3:ZnO) vapor phase infiltration

Conjugated polymer-based organic/inorganic hybrid materials become the current research frontier and show great potential to integrate flexible polymers and rigid solid materials, which have been widely used in the field of various flexible electronics and optical devices. In this study, based on the multiple vapor phase infiltration (VPI) process, various precursor molecules (diethylzinc DEZ, trimethylaluminum TMA, H2O) are applied for the in situ modification of PBTTT-C14 films. The conductivity of the PBTTT-C14/Al2O3:ZnO (AZO) film is significantly enhanced, and the maximum value of conductivity is 1.16 S cm−1, which is eight orders of magnitude higher than the undoped PBTTT-C14 thin film. Here, the change of morphologies and crystalline states are analyzed via SEM, AFM, and XRD. And the chemical changes during the VPI process of PBTTT-C14 are characterized through Raman, XPS, and UV–vis. During the AZO VPI process, the formation of new ZnS matrix in the polymer subsurface can generate new additional electron conduction pathways through the crosslinking of polymer chains with inorganic materials, and the addition of Al2O3 can bring about the increase of average grain size of ZnO crystals, which is also benefit to the conductivity increase of PBTTT-C14 thin film. Generally, the synergistic effect between the inorganic and polymer constituents results in the significantly enhancement of the conductivity of PBTTT-C14/AZO thin films.

Solid materials microwave dielectric properties: features of methods practical use

Features of methods practical use for material dielectric properties measurement in different (factory and metrological) laboratories and influence of above mentioned features on measurements results are considered. Results are obtained by Obninsk Research and Production Enterprise “Technologiya” A. G. Romashin radiophysics laboratory and by East-Siberian branch Federal State Unitary Enterprise “Russian metrological institute of technical physics and radio engineering” department of radio engineering measurements. Results of microwave permittivity and loss tangent solid materials measurements are analysed. This investigation made it possible to get additional information about features of standard methods practical use for material dielectric properties measurement, which was absent in literature earlier. In laboratories for measurements used the waveguide resonator and the standardized techniques. The factory laboratory applied a measurement method at the fixed frequency with control in a resonance movement of the plunger, and in metrological laboratory a measurement method with the fixed length of the resonator and measurement at resonant frequencies. Results of measurements showed good reproducibility of results for samples that are meeting method requirements. It was revealed reducing reproducibility of measurements of hygroscopic, heterogeneous samples and in the case of nonobservance of diameter method requirements. Obtained results can be applied for reproducibility improvement of dielectric properties measurements in practical use of considered methods.

Experiments and investigation of planar high-strength steel joints with Additive Manufacturing

This paper investigates the application of high-strength steel in planar steel joints, specifically X-joints and T-joints, which are crucial connecting components in structural engineering, ensuring structural stability in buildings, bridges, and tower cranes. Conventional steel joints, mainly constructed from low-carbon steel, encounter challenges arising from the low ductility of high-strength steel and its strict welding criteria. The Solid Isotropic Material with Penalization (SIMP) method is employed to perform topology optimization on X-joints with different brace width to chord width ratios and T-joints, enabling the manufacturing of high-strength steel components through the Additive Manufacturing method (AM). The impact of different additive manufacturing orientations on material strength is tested, with results indicating improved mechanical properties when the loading direction is perpendicular to the normal direction of the additive manufacturing layer. Compression tests are conducted using 2D/3D Digital Image Correlation methods (2D/3D-DIC) alongside traditional measurement techniques. The results indicate that the stress distribution of the optimized joint is more rational, and the strength of the optimized joint has improved compared to the tubular joint. The optimized joint exhibits a more distinct load path and apparent failure mode. This optimized joint enables a uniform stress redistribution, enhancing ductility and achieving a strong-joint and weak-component structural mechanism that satisfies the serviceability limit state (SLS). In comparison to non-penetrative tubular joints, no significant cracks are observed under identical loading conditions.

Performance of a rotating latent heat thermal energy storage unit with heat transfer from different surfaces

Due to the rapid growth in the demand for fast and efficient latent heat thermal energy storage system, multiple heat transfer enhancement techniques have been proposed and widely investigated. Actively or passively, rotation of the energy storage unit affects the internal natural convection and the heat transfer performance. Hence, this study is conducted to evaluate the potential of the heat transfer enhancement by rotation. A two-dimensional model with the phase change material filled in the annular space of a double tube energy storage unit is developed. The numerical simulations for the heat transfer through the internal or external surfaces of the annular space are respectively conducted. Both solidification and melting of the phase change material are taken into account by the enthalpy-porosity method. According to different heat transfer surfaces and the occurrence of solidification or melting, four arrangements are formed. It is found that the rotation of the thermal energy storage unit can reduce the solidification time as high as 46 % compared to its still counterpart, but variation of the rotation speed only produces a minor influence. The effect of rotation on the melting depends on the heat transfer direction (or surface). When the heat is transferred into the solid phase change material through the internal wall, the melting time can be gradually reduced as the rotation speed increases with a maximum of 69 %. However, when the heat is transferred through the external wall, influence of the rotation results in adverse effect. This study can guide the design of innovative high performance latent heat thermal energy storage system containing rotation unit.

Differential metamaterial based sensor for solid dielectric characterization with improved sensitivity

PurposeThe purpose of this study is to introduce a new type of sensor which uses microwave metamaterials and direct-coupled split-ring resonators (DC-SRRs) to measure the dielectric properties of solid materials in real time. The sensor uses a transmission line with a bridge-type structure to measure the differential frequency, which can be used to calculate the dielectric constant of the material being tested. The study aims to establish an empirical relationship between the dielectric properties of the material and the frequency measurements obtained from the sensor.Design/methodology/approachIn the proposed design, the opposite arm of the bridge transmission line is loaded by DC-SRRs, and the distance between DC-SRRs is optimized to minimize the mutual coupling between them. The DC-SRRs are loaded with the material under test (MUT) to perform differential permittivity sensing. When identical MUT is placed on both resonators, a single transmission zero (notch) is obtained, but non-identical MUTs exhibit two split notches. For the design of differential sensors and comparators based on symmetry disruption, frequency splitting is highly useful.FindingsThe proposed structure is demonstrated using electromagnetic simulation, and a prototype of the proposed sensor is fabricated and experimentally validated to prove the differential sensing principle. Here, the sensor is analyzed for sensitivity by using different MUTs with relative permittivity ranges from 1.006 to 10 and with a fixed dimension of 9 mm × 10 mm ×1.2 mm. It shows a very good average frequency deviation per unit change in permittivity of the MUTs, which is around 743 MHz, and it also exhibits a very high average relative sensitivity and quality factor of around 11.5% and 323, respectively.Originality/valueThe proposed sensor can be used for differential characterization of permittivity and also as a comparator to test the purity of solid dielectric samples. This sensor most importantly strengthens robustness to environmental conditions that cause cross-sensitivity or miscalibration. The accuracy of the measurement is enhanced as compared to conventional single- and double-notch metamaterial-based sensors.

Mechanical Properties and Hydration Mechanism of Iron Tailings–Cement-Based Supplementary Cementitious Materials

The preparation of cement-based supplementary cementitious materials is an important method for the efficient use of iron tailings and the reduction in CO2 emissions. The aim of this study is to improve the reactivity of iron tailings by mixing them with steel slag, slag, and fly ash through orthogonal tests to solve the problem that iron tailings cannot be utilised on a large scale. The compressive strength, hydration products, and microstructure of the iron tailings–cement-based supplementary cementitious materials were investigated using ICP-OES, XRD, TG, FTIR, and SEM. The results revealed that each solid waste raw material played a distinct role in the hydration reaction. In the iron tailings–cement-based supplementary cementitious materials system, steel slag provided Ca2+, OH−, and Si4+ ions, slag provided Ca2+ and Al3+ ions, fly ash contributed a significant amount of Ca2+ and Al3+ ions, and iron tailings offered more nucleation sites and some Si4+ ions for the hydration products. Moreover, there was a synergistic effect among these four materials, promoting the formation of hydration products such as ettringite, C-(A)-S-H gels, and others. When the proportion of IOTs:SS:FA:SL was 9:8:8:2, the highest 7 d compressive strength of cementitious material was 24.8 MPa. When the proportion of IOTs:SS:FA:SL was 9:6:8:4, the highest 28 d compressive strength of cementitious material was 35.0 MPa. This study provides a comprehensive solution for the utilisation of iron tailings and contributes to the high-value green utilisation of solid waste.

Potential prediction in aqueous organic redox-targeting flow batteries: DFT calculation and experimental validation

Aqueous organic redox flow batteries (AORFBs) face challenges of low energy density, which can be addressed by the strategy of redox-targeting (RT) reaction integrating solid materials (SMs) with redox mediators (RMs). However, the potential matching between SM and RM is demanding and complex. In this work, we establish a precise density functional theory (DFT) protocol to predict redox potential in RT-AORFB with anthraquinone-2,7-disulfonic acid (AQDS) derivatives as RM and poly(N-anthraquinoyl pyrrole) (PAQPy) as SM. Theoretical redox potentials are calculated from the Gibbs free energy (GFE) of various molecular models. The results suggest a precise potential match for 1,8-dihydroxyanthraquinone-2,7-disulfonic acid (1,8-DHAQDS) and PAQPy (-1.08 V and -1.09 V vs. SHE). Additionally, hydrogen bonding is involved to make simulation results more realistic, demonstrating a positive potential shift with increased GFE difference for both AQDS derivatives and PAQPy. To further elucidate the influencing mechanism of hydrogen bonding, electrostatic potential (ESP) and HOMO-LUMO gap are integrated together with GFE. The results indicate the introduction of hydrogen bonding results in extended distance for electron tunneling and a larger HOMO-LUMO gap, leading to higher GFE difference and a positive potential shift. Remarkably, results of experimental validations agree well with theoretical potential calculation. Based on predictions results, the RT-AORFB is successfully constructed with the well-matched 1,8-DHAQDS and PAQPy, exhibiting a 3.86-fold capacity enhancement compared to blank AORFB with 1,8-DHAQDS. The integrated DFT approach with GFE, ESP and HOMO-LUMO gap in this work emerges as a promising method for accurately predicting redox potentials in RT systems.

Fe/Cu doped black ceramic coating on magnesium alloy by plasma electrolytic oxidation method based on first principles

The absorption of visible light by a solid material can correspond to its color. If all visible light is absorbed, the material is black, and the band width of the material defines the wave limit of visible light absorption. Based on this, the transition metal elements Fe and Cu were chosen to dope MgO, and the transition metal elements Fe or Cu were substituted to dope MgO using first-principles simulation. The doped elements' 3d and 4 s levels were introduced to shift the locations of MgO's valence and conduction bands, respectively, lowering the band gap width of MgO. The MgO ceramic coating may respond to light wave wavelength redshifting to 780 nm and entirely absorb visible light; The black MgO ceramic coating was prepared on the surface of AZ31 magnesium alloy utilizing Fe salt and Cu salt as plasma electrolytic oxidation (PEO) electrolyte additions, and the visible light absorption rates were 94.2 % and 94.1 %, respectively. The test findings show that the band gap of the MgO ceramic coating has been lowered from 4.97 eV to 1.58 eV and 1.60 eV, respectively, which is the primary reason for the achievement of strong absorption in all visible light bands. The first principle calculation of the influence of doping elements on the band gap of MgO ceramic coating can serve as a theoretical guidance for selecting coloring elements for the fabrication of black ceramic coating.

Rewritable printing of ionic liquid nanofilm utilizing focused ion beam induced film wetting

Manipulating liquid flow over open solid substrate at nanoscale is important for printing, sensing, and energy devices. The predominant methods of liquid maneuvering usually involve complicated surface fabrications, while recent attempts employing external stimuli face difficulties in attaining nanoscale flow control. Here we report a largely unexplored ion beam induced film wetting (IBFW) technology for open surface nanofluidics. Local electrostatic forces, which are generated by the unique charging effect of Helium focused ion beam (HFIB), induce precursor film of ionic liquid and the disjoining pressure propels and stabilizes the nanofilm with desired patterns. The IBFW technique eliminates the complicated surface fabrication procedures to achieve nanoscale flow in a controllable and rewritable manner. By combining with electrochemical deposition, various solid materials with desired patterns can be produced.

Topology optimization of gyroid structure-based metal hydride reactor for high-performance hydrogen storage

Numerous engineering applications stand to gain substantial advantages by mitigating structural weight. While methods for optimizing continuous solids and discrete frame structures have long been available, the advent of additive manufacturing techniques has ushered in the potential for intricate geometries. In contrast, the hydrogen fuel sector confronts a pivotal challenge: the need to develop efficient hydrogen storage systems. Solid-state compounds like metal hydrides (MH) present a compelling solution among various hydrogen storage technologies thanks to their inherent safety attributes and superior hydrogen volumetric density. Nonetheless, the limitation of MH lies in its gravimetric density, impeding its application in mobility contexts. A transformative strategy addresses this limitation by seamlessly integrating the reactor tank into the vehicle's frame and chassis. This study introduces a pioneering concept—an optimally designed MH container incorporating a gyroid structure. Subsequently, this innovative design underwent rigorous analysis, employing finite element analysis (FEA) and computational fluid dynamics, assessing mechanical properties, heat transfer capabilities, and the efficiency of hydrogen charging into the MH within the structure. Using topology optimization of solid isotropic material with penalization method, a 17 % increase in the chamber volume and a concurrent reduction of the material by nearly 50 %. This profound transformation positively impacted the reactor's volumetric and gravimetric density. Despite a measurable reduction in strength, the optimized structure demonstrated resilience, successfully withstanding prescribed mechanical shear loads. Furthermore, the structure exhibited impressive rigidity, with displacement below 0.2 mm, rendering it suitable and highly competent for integration into assembly components like vehicle frames or chassis. Notably, the optimized structure exhibited a promising enhancement in hydrogen charging rate.

Study on hot isostatic pressing conditions of ARAA for fabrication of the breeding blanket first wall

The helium-cooled concept with solid breeding materials is one of the candidates for demonstration fusion power reactor (DEMO) breeding blanket. The first wall (FW) is a core component of the breeding blanket. The FW should keep the structural integrity during the normal plasma operation which is subject to high surface heat flux, neutron wall load, and high coolant pressure simultaneously. Various fabrication methods have been studied for the development of the FW fabrication technologies. This study focuses on FW fabrication technologies with hot isostatic pressing (HIP) bonding which is considered as the most promising method for achieving such complex shape like FW having internal cooling channels. We investigated the HIP bonding conditions using Advance Reduced Activation Alloy, ARAA, which is a reduced activation ferritic-martensitic steel under development in Korea. Temperature, holding time and pressure were considered as the parameters to optimize the HIP bonding conditions. The microstructures around the HIP joints changed with respect to the HIP bonding temperature. The amount of oxide particles around the HIP joints varied depending on the degassing conditions. The tensile strength of the HIP joint was not greatly affected by the presence of the HIP bonding line and degassing conditions. On the other hand, it has been confirmed that the Charpy absorbed energy of the HIP joint was significantly affected by degassing conditions. An increase in oxide particles around the HIP joints occurred when degassing temperature and vacuum level were low, and as the quantity of oxide particles increased, the Charpy absorbed energy of the HIP joint decreased substantially.

Populating the Milky Way. Characterising planet demographics by combining galaxy formation simulations and planet population synthesis models

Stellar populations and their distribution differ widely across the Galaxy, which is likely to affect planet demographics. Our local neighbourhood is dominated by young, metal-rich stars in the galactic thin disc, while the stellar halo and galactic bulge host a large fraction of older, metal-poor stars. We study the impact of these variations on planet populations in different regions of the Galaxy by combining a high-resolution galaxy formation simulation with state-of-the-art planet population synthesis models. We constructed a population model to estimate occurrence rates of different planet types, based on the New Generation Planet Population Synthesis (NGPPS). We applied this model to a simulated Milky Way (MW)\ analogue in the HESTIA galaxy formation simulation. We studied the planet occurrence rate in the metal-rich regions of the inner Galaxy, namely, in the galactic bulge and thin disc. We compared these result with the frequencies in the more distant, metal-poor region such as the thick disc and stellar halo. We find that the planet demographics in the central, metal-rich regions of the MW analogue differ strongly from the planet populations in the more distant, metal-poor regions. The occurrence rate of giant planets ($>300 M_ is 10 to 20 times larger in the thin disc compared to the thick disc, driven by the low amounts of solid material available for planet formation around metal-poor stars. Similarly, low-mass Earth-like planets around Sun-like stars are most abundant in the thick disc, being 1.5 times more frequent than in the thin disc. Moreover, low-mass planets are expected to be abundant throughout the galaxy, from the central regions to the outer halo, due to their formation processes being less dependent on stellar metallicity. The planet populations differ more strongly around Sun-like stars compared to dwarfs with masses 0.3 -- 0.5 $M_ caused by a weaker correlation between Fe/H metallicity and planet mass. However, it is important to note that the occurrence rates of low-mass planets are still uncertain, making our findings strongly model-dependent. Massive planets are more comprehensively understood and our findings are more robust. Nonetheless, other systematic effects have the potential to alter the giant planet population that we have not addressed in this study. We discuss some of these limitations and offer further directions for future research.

A polyurethane solid–solid phase change material for flexible use in thermal management

Phase change materials (PCMs) have received great attention in thermal management of electronic devices due to their high energy storage density and no need for additional energy supply. Yet the leakage problem after phase change limits their application greatly. In this paper, the block copolymerization was used to prepare a novel solid–solid phase change material (SSPCM) with a melting enthalpy of 90.26 J/g, starting pyrolysis at a temperature of more than 300 °C, and its physicochemical and thermal properties remained basically unchanged after 100 heating/cooling cycles. Notably, this SSPCM has excellent shape stability and can be pressed into phase change film with flexibility, thermally induced self-healing capability and recyclability. Finally, we innovatively combined this SSPCM, copper foam (CF), and polyimide tape (PI) to obtain a composite phase change material (CPCM) with both high thermal conductivity (1.1994 W/m·K) and high electrical insulating properties. Thermal management experiment shows that this CPCM has good thermal management performance and can significantly reduce the temperature rise rate of the simulated CPU. The SSPCM prepared in this study shows great potential for application in thermal management of portable electronic devices and flexible wearable electronic devices.

Design of metadevices based on isotropic materials for eigenfrequency recovery in lightened structures

This work presents a novel approach for the design of metadevices conceived to recover a prescribed set of the natural eigenfrequencies of a structure lightened by machining arbitrary shape holes, using classical topology optimization (TO) techniques. This TO metadevice design (TOMD) is performed by minimizing the error of an eigenfrequency recovery task, using the finite element method (FEM) as an analysis tool, ensuring manufacturability via the solid isotropic material with penalization (SIMP) approach with Heaviside filtering to reduce intermediate-density areas. The spatial variation of mechanical properties derives from the macroscopically distinguishable dual material distribution obtained from the TOMD problem. The methodology was first tested on lightened thin steel plates and then extended to a real-world 3D mechanical component with additional mechanical performance testing. In all cases, the optimized metadevice yielded lower error in recovering eigenfrequencies compared to the lightened component without the metadevice. Furthermore, the metadevice generally achieved further mass reduction, demonstrating its potential for lightweight design while restoring its original eigenfrequencies.

Sustainable application of waste eggshell as fillers in alkali-activated solid waste-based materials: Varying treated methods and particle sizes

The incorporation of waste eggshells as fillers in construction materials is currently constrained by factors such as shell-membrane separation, particle size, and proportion of incorporation. This study aims to assess the feasibility of utilizing non-calcined eggshell particles (EPs) in alkali-activated solid waste-based materials. Initially, the micro characteristics of water-treated and alkali-treated eggshells were evaluated. Subsequently, nine groups of alkali-activated slag-based paste samples were prepared by using EPs as fillers, and the influence of the particles on the physical and mechanical properties of the materials was assessed based on flowability, density, and compressive strength. Furthermore, the impact of shell-membrane separation and particle size on the microstructure and composition of the alkali-activated materials (AAMs) was characterized by using a combination of SEM-EDS, XRD, FTIR, and TG-DSC techniques. Finally, six groups of alkali-activated slag-red mud-fly ash-based mortar samples were prepared with EPs as fillers, which demonstrates the feasibility of EPs in multi-waste-based materials and expands the application range of non-calcined eggshells. The results show that water treatment and alkali treatment of EPs provide viable methods for shell-membrane separation, albeit with some loss of fine particles. The physical filling of membranes in AAMs does not affect the chemical composition. The EPs (with a particle size less than 0.5 mm) can be used as fillers in AAMs without shell-membrane separation. Moreover, when the EPs content is increased to 33%, the 90-d flexural strength of the AAMs increases by 60% compared to the control group (without EPs), while the compressive strength remains unchanged. Thus, it is feasible to directly crush and sieve non-calcined eggshells for use as fillers in alkali-activated waste-based cementitious materials without the need for shell-membrane separation, and this method does not produce any negative impact. The findings of this research provide an effective technical approach for the application of waste eggshells in eco-friendly construction materials.

Experimental and simulation research on rupture behavior of coal-based solid waste material backfilling column under non-uniformly distributed load with different loading ratios

Artificial construction backfilling columns underground based on coal-based solid waste materials is an important method to slow down surface subsidence and reduce the environmental pollution caused by coal gangue hills and fly ash. Taking the Xinyang coal mine as an example, based on a self-developed non-uniform load application device, acoustic emission (AE) and digital image correlation (DIC) monitoring technology, the evolution law of rupture behavior of coal-based solid waste material backfilling columns under different loading ratios was revealed. When the loading ratios are 1, 1.1319, 1.3585, 1.6371, and 2.0631, the average compression strength with the same material ratio is 3.96 MPa, 4.05 MPa, 4.22 MPa, 4.57 MPa, and 3.94 MPa, respectively. It is indicated that an increase in the loading ratio within the critical range is beneficial for stimulating the collaborative bearing of different parts inside the backfilling columns. From the perspective of the internal rupture behavior of the backfilling columns, the increase in loading ratio promotes a significant increase in the proportion of shear cracks, which has increased from 17.07% to 37.02%, resulting in the shear failure of backfilling columns. Meanwhile, as the loading ratio increases, the crack initiation position gathers from the left and right sides to the middle, and the final crack shape gradually transitions from two inclined and parallel main cracks to an inverted "V" shaped intersecting main cracks. The research is of great significance for improving the understanding of the failure law of backfilling columns and the safety evaluation of engineering-bearing structures under non-uniform loads.