Foam Structure Research Articles

Development of mechanical properties of concrete in vacuum tunnel of vacuum-based maglev train

The vacuum-based maglev train is an emerging transportation system currently under development worldwide. While concrete is a technically viable material for constructing vacuum tunnels, its mechanical performance in this unique environment remains unclear. This paper investigates the behavior of concrete in vacuum using a large customized vacuum tube. The results show that concrete undergoes significant water loss in vacuum, resulting in impeded cement hydration and porous hydration products with a foam structure. Vacuum exposure during the early ages of concrete has negative effects on mechanical properties. However, once the cement hydration reaches a high level of maturity, further vacuum exposure has little influence. Compared with atmospheric conditions, the shrinkage of concrete in vacuum is significantly increased. These findings provide a valuable experimental database and new insights for the use of concrete in vacuum-based maglev trains.

Cell topology during coarsening of simulated three-dimensional dry liquid foams.

Cell topology provides a deep insight into the structure of dry liquid foams. This paper analyses the cell topology of simulated 3-dimensional monodisperse dry liquid foams through the process of coarsening, where gas slowly diffuses through the cell interfaces. The coarsened foams are polydisperse, yet show a difference in cell types to annealed, low energy foams of comparable polydispersity. These two types of foams are analysed using average face degree of the cells and a measure of combinatorial roundedness, a new concept from combinatorial topology. We see that the spectrum of cell types changes drastically through the evolution of the foam via coarsening, from cells with a face degree between 12 and 14, with many 4-, 5-, and 6-side faces, to a combination of very large cells with many faces alongside a high frequency of tetrahedra and other cells with low face degree. These results demonstrate the insight that topological methods can give into foams and other complex structures.

Improving thermal stability and reliability of power chips by sintering foam structure layer

In order to ensure the high-temperature reliability of device in high temperature service, a new sintered structure layer, nano-Ag paste filling graphene reinforced Ni foam, was designed to realize the chip packaging in this work. This layer had excellent reliability and high-temperature heat dissipation stability, which benefit from the higher proportion of low-angle grain boundaries, finer grains and excellent heat dissipation capacity of graphene. The foam structure had favorable stress release effect, which made the sintered layer had high service reliability. The excellent heat dissipation ability of graphene overcomes the inherent defect of slow heat dissipation of the device under high temperature environment.

Model geometries of random porous materials

We describe a method for modeling the geometry of random porous materials. The approach enables the independent selection of crucial parameters, including porosity, pore size distribution, pore shape, and connectivity. Consequently, it can effectively model a wide range of porous systems. Due to the diverse and systematic variation possibilities, the method is suitable for developing and optimizing porous structures. The geometries can be exported as triangular meshes, facilitating their immediate use in numerical simulation and further digital processing. We showcase the method’s capabilities by minimizing the foam structure’s thermal conductivity through geometry optimization.

Analysis of charging performance of thermal energy storage system with graded metal foam structure and active flip method

The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is characterized by high energy storage density, small volume change, and constant operation temperature, which is widely employed in waste heat recovery, solar thermal utilization, and equipment thermal management. This paper introduces active flipping and graded porous to strengthen natural convection and heat conduction to alleviate the issue of low thermal conductivity and non-uniform phase change of PCM. Based on the fixed grid system, the enthalpy-porosity method combined with time-dependent gravity and non-Darcy porous effect is employed to solve the solid-liquid phase change problem under different porosity gradients, dimensionless flipping times (t*), and modified Ra (Ra*) numbers. Furthermore, the effects of the Ra* on the optimal t* and porosity gradient are also discussed. The results show that the flipping method can significantly enhance flow and heat transfer within the container, improve temperature field uniformity, and increase the proportion of latent heat storage. With the increase of porosity gradient and t*, the melting time initially decreases and then increases and the optimal thermal performance is achieved at a 6 % porosity gradient and t* = 0.4. Compared to the uniform porous structure without flipping, it can shorten melting time by 49.37 % and improve thermal energy storage rate (TESR) by 76.23 %. Additionally, the optimal porosity gradient is 6 % under different Ra*, but the optimal t* decreases with the increase of Ra*. This paper explores the charging performance of the thermal energy storage system with the graded metal foam structure and active flip method, which can contribute to the study of heat transfer enhancement in LHTES technology.

Effect of diacylglycerol on partial coalescence of aerated emulsions: Fat crystal-membrane interaction and air-liquid Interface interaction insights

Currently, the poor whipping capabilities of anhydrous milk fat (AMF) in aerated emulsion products are a major obstacle for their use in beverages like tea and coffee, as well as in cakes and desserts, presenting fresh hurdles for the food industry. In this study, the mechanism of action of diacylglycerols (DAGs) with different carbon chain lengths and degrees of saturation on the partial coalescence of aerated emulsions was systematically investigated from three fundamental perspectives: fat crystallization, air-liquid interface rheology, and fat globule interface properties. The optimized crystallization of long carbon chain length diacylglycerol (LCD) based on stearate enhances interactions between fat globules at the air-liquid interface (with an elastic modulus E' reaching 246.42 mN/m), leading to a significantly reduced interface membrane strength. This promotes fat crystal-membrane interactions during whipping, resulting in a thermally stable foam structure with excellent shaping capability due to enhanced partial coalescence of fat globules. Although Laurate based medium carbon chain length diacylglycerol (MCD) promoted fat crystallization and optimized interface properties, it showed weaker foam properties because it did not adequately encapsulate air bubbles during whipping. Conversely, oleate long carbon chain length diacylglycerol (OCD) proved to be ineffective in facilitating fat crystal-membrane interaction, causing foam to have a subpar appearance. Hence, drawing from the carefully examined fat crystal-membrane interaction findings, a proposed mechanism sheds light on how DAGs impact the whipping abilities of aerated emulsions. This mechanism serves as a blueprint for creating aerated emulsions with superior whipping capabilities and foam systems that are resistant to heat.

20-Fold Increased Limiting Currents in Oxygen Reduction with Cu-tmpa by Replacing Flow-By with Flow-Through Electrodes.

Electrochemical oxygen reduction is a promising and sustainable alternative to the current industrial production method for hydrogen peroxide (H2O2), which is a green oxidant in many (emerging) applications in the chemical industry, water treatment, and fuel cells. Low solubility of O2 in water causes severe mass transfer limitations and loss of H2O2 selectivity at industrially relevant current densities, complicating the development of practical-scale electrochemical H2O2 synthesis systems. We tested a flow-by and flow-through configuration and suspension electrodes in an electrochemical flow cell to investigate the influence of electrode configuration and flow conditions on mass transfer and H2O2 production. We monitored the H2O2 production using Cu-tmpa (tmpa = tris(2-pyridylmethyl)amine) as a homogeneous copper-based catalyst in a pH-neutral phosphate buffer during 1 h of catalysis and estimated the limiting current density from CV scans. We achieve the highest H2O2 production and a 15-20 times higher geometrical limiting current density in the flow-through configuration compared to the flow-by configuration due to the increased surface area and foam structure that improved mass transfer. The activated carbon (AC) material in suspension electrodes, which have an even larger surface area, decomposes all produced H2O2 and proves unsuitable for H2O2 synthesis. Although the mass transfer limitations seem to be alleviated on the microscale in the flow-through system, the high O2 consumption and H2O2 production cause challenges in maintaining the initially reached current density and Faradaic efficiency (FE). The decreasing ratio between the concentrations of the O2 and H2O2 in the bulk electrolyte will likely pose a challenge when proceeding to larger systems with longer electrodes. Tuning the reactor design and operating conditions will be essential in maximizing the FE and current density.

Vibration response on the rod of vortex bladeless wind power generator for a sandwich beam with various face sheets and cores based on different boundary conditions

Vortex-bladeless wind power generators are revolutionary concepts that use wind vortex-induced vibration to generate electricity through oscillation and vibration. This unique approach allows for a simpler design, environmental friendliness, on-site production, and lower initial costs than traditional wind turbines. This article presents a vibration analysis on the rod of a vortex bladeless wind power generator for a sandwich Timoshenko beam with various face sheets, including carbon nanotube (CNT), graphene platelets (GPL), and carbon nanorods (CNR), and cores, including positive and negative Poisson’s ratios in honeycomb structure, porous material, and metal foam. The governing equations of motion are derived using Hamilton’s principle and solved using trigonometric functions for different boundary conditions. The results of this research are compared with previous studies, and the maximum error is 3.05%. This study examined the effects of various parameters on the dimensionless natural frequencies. To obtain the highest peak amplitude for maximum energy harvesting, to choose the best rod for the bladeless wind power generator among the four types of cores and three types of factsheet layers, the honeycomb core with a positive Poisson’s ratio and the GPL-reinforced composite with the SNUPD distribution are selected because they have the most deflection. Some researchers have worked in the field of sandwich beams. Still, in this study, the main goal is to investigate the Timoshenko sandwich beam by examining all types of cores and reinforcements to increase efficiency and optimize bladeless wind generators to achieve maximum power.

Optimizing Mid-Temperature Sodium Iodine Batteries for Sustainable Large-Scale Energy Storage: A Comprehensive Modeling Approach and Experimental Validation

The need for safe, eco-friendly, low-cost batteries for large scale implementation rises in the presence of the expansions of renewable energy sources. High-temperature liquid sodium batteries (e.g. sodium-sulfur) are a well-established technology for large-scale grid storage. Combining the molten sodium anode with an aqueous iodine cathode overcomes the problems of thermal loses and sealing by reducing the operating temperature to about 100°C. This leads to higher cost efficiency, energy density and a simplified cell design.Here we present a novel modelling approach for complex carbon-based cathode structures and its limits and abilities on enhancing the utilizable capacity. Due to their sustainability and high efficiency, which is comparable to Li-Ion –batteries, mid-temperature sodium-iodine batteries are a promising candidate for stationary energy storage applications. With a high specific energy of around 200 Wh kg-1, sodium-iodine batteries have the ability to meet the growing demand of short-term energy storage caused by the integration of renewable energy sources into the power grid. Up to this day, the detailed processes inside the battery are not well-understood. Quantities like initial species concentrations, C-rate, cell design and cathode geometry have large impacts on the overall battery performance. A deeper understanding of these processes is inevitable for enhancing the battery performance by choosing the optimal abovementioned quantities. We set up a fully resolved 3D Simulation model to gain insight into microstructural processes inside the battery, as experimental studies are limited to macroscopic quantities like electronic current and potential. The methodology is based on continuum hypothesis by using an open-source CFD software, which is rewritten accordingly. The proposed spatially resolved three-dimensional simulation model takes charge and mass transport, heterogeneous and homogeneous reactions as well as the electrochemical processes into account. Results show that transport limitations confine the utilizable capacity of the battery [1].This contribution focuses on enhancing the battery energy density and efficiency by including open-pored glassy carbon foam structures in the cathode half-cell [2, 3]. We state simulation predicted, optimal morphology properties of such a structure. Furthermore, we describe the evaluation of improved thermodynamic data of the aqueous iodine solution by refitting simulation results to polarization curves. We utilize a novel impedance spectroscopy simulation method for sodium iodine batteries to improve parameterization of the underlying electrochemical model by comparing the results with experimental data. References Gerbig, F., Cernak, S., Nirschl, H. (2021). 3D Simulation of Cell Design Influences on Sodium–Iodine Battery Performance. Energy Technology, vol. 9, no. 6, p. 2000857Gerbig, F., Cernak, S. and Nirschl H. (2021), Towards a Novel Sodium-Iodine Battery with an Aqueous Catholyte: Numerical Investigations of Complex Cathode Structures, ECS Trans., vol. 104, no. 1, pp. 123–130Gerbig, M. Holzapfel, and H. Nirschl, Simulating the Impact of Glassy Carbon Foam Electrodes on the Performance of Sodium Iodine Batteries, J. Electrochem. Soc., vol. 170, no. 4, p. 40517, 2023, doi: 10.1149/1945-7111/accab7. Figure 1

Multiphase Modeling of Enhanced Bubble Evacuation in Alkaline Water Electrolysis Cells Based on Laterally-Graded 3-D Electrodes

To mitigate the challenges posed by anthropogenic climate interference, substantial efforts are imperative in order to limit the rise in global average temperature. One major declaration made by the international community through various climate agreements [1,2] calls for an elimination of greenhouse gas emissions, necessitating a shift from fossil fuels to sustainable renewable energy sources. Hydrogen and hydrogen-based fuels emerge as promising candidates to decarbonize a wide range of sectors – including transport, industry and chemical manufacture – due to hydrogen’s remarkable flexibility and storage capacity. At present, water electrolysis conducted by renewable electricity is considered as the most sustainable technology to produce green hydrogen.Among the various approaches for water electrolysis, two commercially available methods stand out: alkaline and proton exchange membrane (PEM) [3]. Alkaline water electrolysis (AWE) has the advantage of presenting the lowest cost per kilowatt of electricity but yields lower hydrogen production rates. In contrast, PEM electrolysis achieves superior performance, thanks to the use of costly and scarce electrocatalytic materials like Ir and Pt. Considering the unique strengths of each system, it is appealing to try to integrate the best of these two technologies, yielding high production rates per electrode area while benefiting from more cost-effective electrode materials.To this end, recent experimental work in our group has focused on the conception and analysis of flow-engineered 3-D electrodes into a novel laterally-graded cell configuration to allow alkaline water electrolysis to become PEM-like [4,5]. More specifically, 3-D electrodes such as foams were integrated into a zero-gap cell using a bi-layer configuration in which a fine foam (450 µm pore size) working as a catalytic electrode is put in contact with a coarser foam (3000 µm pore size) acting as a porous transport layer (PTL). Because of the high production rate in the 450 µm foam, a high forced upstream electrolyte flow is used to favour bubble removal and hence decrease the Ohmic resistance of the system. Thanks to the use of a bi-layer configuration in flow-through upstream flow mode, the many bubbles generated near the diaphragm were believed to be evacuated laterally towards the coarser foam, keeping the catalytic surface of the finer foam active throughout the process. The enhanced performance of this PEM-like system was confirmed experimentally and current densities of 2 A/cm2 were observed at cell voltages lower than 2 V (for 2 x 2 x 0.56 cm3 electrodes).The aim of this work is to use Computational Fluid Dynamics (CFD) simulations in order to assess flow behaviour into the bi-layer and validate the assumptions that were made based on the experimental results. First of all, a single-phase model (i.e. considering only the electrolyte) was used to solve the incompressible Navier-Stokes equations in OpenFOAM. The objective is to shift towards multiphase simulations by considering a simple mixture model to account for the presence of gas bubbles. The driftFluxFoam solver will be used to solve the general mixture model equations, in which velocity, density and viscosity are weight-averaged based on gas fraction and on the properties of both phases. This work also highlights two ways of incorporating porous media in the numerical simulations. The first way, called explicit, is based on the exact geometry of the foams, obtained thanks to high-resolution micro-CT (computed tomography) scanned data, but is extremely costly from a numerical point of view. The other method, called implicit, uses the Darcy-Forchheimer approximation to spatially average porosity over a given domain, which is less representative of the exact foam structure but generally allows to get first useful insights of the flow behaviour in porous media.An example of a laterally graded bi-layer configuration and some initial multiphase results are shown in Figure 1. The velocity vectors and the lateral velocity profile confirm that hydrogen bubbles can indeed be expected to be evacuated from the fine catalytic 450 µm into the coarser 3000 µm PTL foam. The main objective of our modeling approach is to demonstrate the relation between the observed electrochemical performance enhancement with multiphase mass transport phenomena occurring inside the 3-D electrodes in order to show the intrinsic interest of using such laterally graded bi-layer approach in all future alkaline water electrolysers. Figure 1

A deep-learning-boosted surrogate model of a metal foam based protonic ceramic electrolysis cell stack for uncertainty quantification

Protonic ceramic electrolysis cells (PCECs) are widely considered as an emerging technology that shows capability for enabling environmentally friendly large-scale production of hydrogen. PCEC stacks’ performance is considerably lower compared to smaller, lab-scale button cells. This performance gap is largely attributed to the highly uneven distribution of reactants throughout the larger cell or stack, which presents a significant challenge to the development of PCEC stack. The issue of non-uniform reactant distribution in PCEC stacks can be effectively addressed by incorporating metal foam structures to replace the conventional rib design of the interconnect components. A 3D multiphysical model is developed to train a deep-learning-boosted surrogate model for PCEC with metal foam, which is subsequently used for parameter screening and sensitivity analysis. A collection of 12 inputs that encompass operating/structural/microstructural/material parameters are chosen, in which the operating parameters are identified as influential parameters. Three distribution uniformity indices maintain strong consistence to variations in the inputs, implying the positive role of metal foam. Faradaic efficiency (FE) is primarily influenced by the operating voltage with a total Sobol index of 0.6. The current density and FE are determined as the most stable performance indicators, exhibiting standard deviations of 0.15 and 0.81 respectively. According to a safety threshold of 10 K cm−1 for temperature gradient, the probability of the stack operating below this threshold is 88.61 %. Valuable insights into the design and performance of PCEC stacks that incorporate metal foam structures are provided. The workflow developed in this work can be further leveraged to explore and optimize PCECs.

Electron diffraction of foam-like clusters between xenon and helium in superfluid helium droplets.

We report electron diffraction results of xenon clusters formed in superfluid helium droplets, with droplet sizes in the range of 105-106 atoms/droplet and xenon clusters from a few to a few hundred atoms. Under four different experimental conditions, the diffraction profiles can be fitted using four atom pairs of Xe. For the two experiments performed with higher helium contributions, the fittings with one pair of Xe-He and three pairs of Xe-Xe distances are statistically preferred compared with four pairs of Xe-Xe distances, while the other two experiments exhibit the opposite preference. In addition to the shortest pair distances corresponding to the van der Waals distances of Xe-He and Xe-Xe, the longer distances are in the range of the different arrangements of Xe-He-Xe and Xe-He-He-Xe. The number of independent atom pairs is too many for the small xenon clusters and too few for the large clusters. We consider these results evidence of xenon foam structures, with helium atoms stuck between Xe atoms. This possibility is confirmed by helium time-dependent density functional calculations. When the impact parameter of the second xenon atom is a few Angstroms or longer, the second xenon atom fails to penetrate the solvation shell of the first atom, resulting in a dimer with a few He atoms in between the two Xe atoms. In addition, our results for larger droplets point toward a multi-center growth process of dopant atoms or molecules, which is in agreement with previous proposals from theoretical calculations and experimental results.

Advances in Inorganic Foam Materials Fabricated Via Blowing Strategy: A Comprehensive Review.

Two-dimensional (2D) materials with excellent properties and widespread applications have been explosively investigated. However, their conventional synthetic methods exhibit concerns of limited scalability, complex purification process, and incompetence of prohibiting their restacking. The blowing strategy, characterized by gas-template, low-cost, and high-efficiency, presents a valuable avenue for the synthesis of 2D-based foam materials and thereby addresses these constraints. Whereas, its comprehensive introduction has been rarely outlined so far. This review commences with a synopsis of the blowing strategy, elucidating its development history, the statics and kinetics of the blowing process, and the choice of precursor and foaming agents. Thereafter, we dwell at length on across-the-board foams enabled by the blowing route, like BxCyNz foams, carbon foams, and diverse composite foams consisting of carbon and metal compounds. Following that, a wide-ranging evaluation of the functionality of the foam products in fields such as energy storage, electrocatalysis, adsorption, etc. is discussed, revealing their distinctive strength originated from the foam structure. Finally, after concluding the current progress, we provide some personal discussions on the existing challenges and future research priorities in this rapidly developing method.

Influence of foaming additives on the porous structure and properties of lightweight geopolymers based on ash–slag waste

Lightweight geopolymer is a promising thermal insulation material that conserves energy used for heating and cooling buildings. This study investigates foaming agents that influence the porous structure and properties of geopolymer foams based on ash–slag waste from thermal power plant using a 12 M sodium hydroxide solution, waterglass, and foaming agents (30 % hydrogen peroxide solution, aluminum, silicon, and zinc powders). The study demonstrates the feasibility of foaming geopolymers by water evaporation without foaming additives, where the best density of 949 kg/m3 and compressive strength of 4.2 MPa were achieved in samples foamed by microwave radiation, but such properties cannot attribute geopolymers as lightweight. Foaming with H2O2 is hard to synchronize with geopolymerization reactions. Aluminum and silicon powders lead to rapid reactions in alkaline conditions, resulting in uneven pore sizes. Zinc powder was the most effective foaming agent, producing materials with a density of 331 kg/m3 and compressive strength of 1.17 MPa, and it also integrates into the geopolymer gel structure. The foaming process should occur at room temperature. Elevated temperatures increase curing rates and result in incomplete geopolymerization, preventing uniform pore formation. Synthesized geopolymers are suitable for building insulation, basements, underground pipelines, and utility networks.

A Cost-Effective Approach to Creating Large Silicone Rubber Molds Using Advanced Rigid Polyurethane Foam.

In practical applications, polyurethane (PU) foam must be rigid to meet the demands of various industries and provide comfort and protection in everyday life. PU foam components are extensively used in structural foam, thermal insulation, decorative panels, packaging, imitation wood, and floral foam, as well as in models and prototypes. Conventional technology for producing PU foam parts often leads to defects such as deformation, short shots, entrapped air, warpage, flash, micro-bubbles, weld lines, and voids. Therefore, the development of rigid PU foam parts has become a crucial research focus in the industry. This study proposes an innovative manufacturing process for producing rigid PU foam parts using silicone rubber molds (SRMs). The deformation of the silicone rubber mold can be predicted based on its wall thickness, following a trend equation with a correlation coefficient of 0.9951. The volume of the PU foam part can also be predicted by the weight of the PU foaming agent, as indicated by a trend equation with a correlation coefficient of 0.9824. The optimal weight ratio of the foaming agent to water, yielding the highest surface hardness, was found to be 5:1. The surface hardness of the PU foam part can also be predicted based on the weight of the water used, according to a proposed prediction equation with a correlation coefficient of 0.7517. The average surface hardness of the fabricated PU foam part has a Shore O hardness value of approximately 75. Foam parts made with 1.5 g of water added to 15 g of a foaming agent have the fewest internal pores, resulting in the densest interior. PU foam parts exhibit excellent mechanical properties when 3 g of water is added to the PU foaming agent, as evidenced by their surface hardness and compressive strength. Using rigid PU foam parts as a backing material in the proposed method can reduce rapid tool production costs by about 62%. Finally, an innovative manufacturing process for creating large SRMs using rigid PU foam parts as backing material is demonstrated.

Visual depiction and numerical characterization of intricate flow in triply periodic minimal surface foams

Benefiting from the structural specificity and programmability, the bioinspired triply periodic minimal surfaces (TPMSs) bring excellent physicochemical properties that are distinct from conventional topologies. Especially with the rapid development of additive manufacturing and high-performance computing capacities, function-oriented design and synthesis of smart TPMS materials or devices have become feasible. Therefore, understanding the flow characterizations induced by TPMS foams is of remarkable importance to the successful design and practical operation. However, the in-depth studies and theoretical guidance on the relationship between structure and flow characterizations of TPMS foams are still limited. In this study, an Eulerian and Lagrangian coupled model is developed to investigate the internal flow behaviors and flow regime transition mechanism from creeping to inertial flow in four representative TPMS foams. The simulation accuracy is then validated by a high-resolution pore-scale flow field observation. Results show that the flow morphology and pressure drop characteristics are highly influenced by TPMS geometry and Re. Among which, Schwarz Diamond (D), Schoen Gyroid (G), and Fischer-Koch S (S) foams are more susceptible to radial flow disturbance, while Schoen inverted Weissenberg periodic foam to axial flow disturbance. In addition, higher porosities delay the transition to transitional regime of the flow. This work establishes firm theoretical and methodological foundations for the customization and intelligent development of bioinspired TPMS foam materials in broad fluidic applications.

Cover Feature: Simple Method to Assess Foam Structure and Stability using Hydrophobin and BSA as Model Systems (ChemPhysChem 15/2024)

Cover Feature: Simple Method to Assess Foam Structure and Stability using Hydrophobin and BSA as Model Systems (ChemPhysChem 15/2024)

Polyphenol improve the foaming properties of soybean isolate protein: Structural, physicochemical property changes and application in angel cake

With the increasing demand for food foaming, how to enhance the foaming properties of protein has gradually become the research focus. This work studied the effect of synephrine (SY) on foaming properties, structure properties, and physicochemical properties of soybean protein isolate (SPI). When the mass ratio of SY to SPI was 1:2, compared with SPI alone, the foam capacity and foam stability of the SY-SPI complex were significantly enhanced. Optical microscopy and confocal laser scanning microscope showed that the improvement in foaming performance was mainly due to the reduction of bubble size and uniform protein distribution. Circular dichroism spectrum and fluorescence spectra indicated that the hydrogen bond of SPI was destroyed and blue shifted with the addition of SY. What's more, the absolute value of Zeta potential, solubility, and hydrophobicity all increased, while the particle size decreased. As a result of molecular docking, surface hydrogen bonds, Van der Waals forces and hydrophobic interactions are the main driving forces. The addition of SY and SPI improved the specific volume and texture of angel cake. This study shows that SY has the potential to be developed into a new type of blowing agent.

An inspection of the metal-foam beam considering torsional dynamic responses

Metal foam is a multifunctional material with a lower specific weight, high stiffness and compressive strength, and high energy absorption. These remarkable properties make metal foams a promising candidate for conventional materials in different industrial fields. Despite numerous researches on mechanical behavior either static or dynamic of structures made of metal foams, torsional vibration analysis of metal foam structures is still uninvestigated. In this investigation, the influence of various imperfection distribution patterns on the torsional dynamic response of metal foam beams is examined within the framework of Timoshenko-Gere's theory. Two common materials i.e. SUS304 and Aluminum foams are considered the constructive materials of structure. Moreover, three imperfection distribution patterns are taken into account. The virtual work's principle has been employed to derive the torsional governing equation of metal foam beams. Then, the derived governing equation has been solved via an analytical method. The accuracy of the employed methodology has been compared with the findings of former research in the literature. Finally, the influences of different notable parameters on the variation of natural torsional frequency have been examined and demonstrated in a group of tables and diagrams.

Fire alarm nano-coating with the controlled release of phosphorus-containing free radical for considerable flame retardant performance

The colloidal properties and surface charge characteristics of graphene oxide (GO) often lead to flocculation during the layer-by-layer (LBL) assembly. Innovatively, the charged flame retardant molecule, amino-tris(methylene phosphonic acid) (ATMP), is encapsulated within the inner cavity of halloysite nanotubes (HNTs). This integration exploits the unique structural features of HNT's inner cavity and outer wall. A composite nano-coating is constructed on the three-dimensional skeletal structure of melamine foam (MF) by assemblying GO with HNT-ATMP. This composite nano-coating exhibits both condensed-phase and gas-phase flame retardant functions. During the thermal decomposition process, phosphorus-containing radicals released from the HNTs' inner cavities enhance the flame retardancy. Moreover, the composite nano-coating demonstrates sensitive fire warning performance. A composite MF coated with 10 layers of this nano-coating emits a warning signal within 8 s fire exposure and maintains this signal without circuit failure. This study elucidates the mechanisms of flame retardancy and fire warning based on the thermal decomposition process and char layer analysis. By addressing the issue of GO flocculation during the assembly process, this research not only clarifies the underlying flame retardant and fire warning mechanisms of composite nano-coating but also proposes solutions for prolonging the duration of fire warning signals in advanced materials.