Foam Layer Research Articles

Performance of ultrathin K2O·nSiO2 based laminated anti-fire glass: Influence of viscosity and morphology

The ultrathin K2O·nSiO2 based laminated anti-fire glass with super-multilayer morphology is prepared by a gradient heating method using a high SiO2 content (55 wt%) and low viscosity (684.5mPa.s ± 43.8mPa.s, 48 rpm) SiO2 core-shell emulsion. Meanwhile, K2O·nSiO2 with uniform morphology as a comparison sample is prepared by a thermostatic method using the same SiO2 emulsion. This article systemically characterized and analyzed the viscosity, morphology, hardness, ultraviolet (UV), and fire-resistant performance. The mechanism of shear-thinning characteristics is obtained by monitoring the viscosities of these SiO2 core-shell emulsions. The super-multilayer and uniform morphology are shown in SEM micrographs, and the UV-resistant capacity is more than 3000 h for outdoor use. Still, the hardness of the former is more than the latter. The foaming expansion layer has ensured window integrity under the fire. This work has provided a new simple routine for preparing ultrathin K2O·nSiO2 based laminated anti-fire glass for architectural safety applications.

Flexural testing of structural insulated panels before and after creep testing

The effect of duration of load testing on flexural properties of structural insulated panels was investigated herein. Structural insulated panels were manufactured by a member of the Structural Insulated Panel Association (SIPA) in accordance with International Code Council-Evaluation Service Report 4689. Two panel depths 16.5 cm and 31.1 cm (6.5 in. and 12.25 in.) were tested in short duration 1/3-point bending per American Society for Testing and Materials standards. All structural insulated panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Failure mode for all panels was horizontal shear within the foam layer. Within each panel depth, no statistically significant differences were detected between the maximum load values before and after creep testing. This finding indicates that the creep test loading was not detrimental to the strength of the structural insulated panels. While the results were not deemed to be statistically different for the Δymax (midspan deflection at Pmax) for the 31.1 cm depth class, they were statistically different from the 16.5 cm depth class. Overall, it appeared that there was minimal effect of the creep test loading on Δymax of the SIPs.

Kinetics of drying in a Mentha crispa foam layer and adjustment of mathematical models

Mentha crispa is a plant commonly used in folk medicine to treat illnesses and has wide industrial application. Dehydration has been used for several types of plants in order to reduce the levels of water content and water activity, so that it would allow na adequate storage due to the conservation of the active principles. The objective of this work is to investigate the process of drying mint in a foam layer. The foam was physically characterized in terms of density, expansion percentage, air incorporation capacity and stability. Drying was carried out according to a factorial experimental design, in which the input variables were: temperature (50, 60 and 70 °C), concentration of foaming agent (3, 5 and 7 %) and stirring time (3, 5 and 7 min); and the output variables were: drying time and water content (Xbs) of the product. The physical properties of the foam depended only on the foaming concentration. The rise in the temperature significantly reduced the drying time and the water content of the foam. The Page, Henderson & Pabis, Newton and Modified Page mathematical models were adjusted to the experimental data and Page’s model was the one that showed to be the most adequate to represent the drying phenomenon.

Tropical Red Fruit Blends: The Effect of Combination of Additives on Foaming, Drying and Thermodynamic Properties

Blends combine advantageous characteristics of each species, resulting in products with different flavors and nutritional substances. Moreover, transforming them into powder provides numerous advantages. This work evaluated the properties of three blended foam formulations made from the pulps of tropical red fruits (acerola, guava and pitanga) to determine the foam layer drying kinetics and thermodynamic properties. The foam formulations were prepared by mixing the three pulps in equal proportions (1:1:1), all added with 6% albumin and 1% stabilizing agent. The foams were analyzed for density, volumetric expansion, stability and porosity in six mixing times. Subsequently, they were subjected to drying in an oven with forced air circulation at 4 temperatures, with a layer 0.5 cm thick. Seven mathematical models were fitted to the drying kinetics experimental data to determine the effective diffusivity and thermodynamic properties of the samples. The best mixing times were 5 min for the E2 sample and 30 min for the others. Formulation E2 presented the best results in the foam physical properties, and E3 presented the shortest drying times. All models tested were satisfactorily adjusted, but Page’s model was the most adequate to describe the process. Sample E3 showed the highest diffusivity and sample E2 the lowest activation energy. The drying temperature increase caused reductions in enthalpy and entropy, as well as an increase in Gibbs free energy, indicating an endergonic process. The combination of additives incorporated into the blend influences the drying process: formulation E2 shows greater efficiency in removing water, and formulation E1 presents the highest energy demand.

Ballistic performance of integral body armor with closed-cell aluminum foam: A numerical study

This numerical study is dedicated to investigating the ballistic performance of three-component integral body armor comprising ceramic façade, layers of ultra-high molecular weight polyethylene fiber-based composite (Dyneema) and closed-cell aluminum foam against NIJ-Type IV armor-piercing bullets. A numerical model of integral armor with a ceramic façade and a fiber-reinforced composite backing plate was developed in IMPETUS Afea Solver and verified against experimental data. The verified model was used to design a "baseline configuration" of two-component integral armor that can stop the NIJ-Type IV projectiles. Three-component armor configurations were obtained by introducing layer(s) of closed-cell aluminum foam into the laminate. Laminates with different stacking sequences of composite and porous layers and different foam relative densities were studied and compared with the baseline two-component configuration. The study presents new insights into the mechanics of perforation of integral armor with closed-cell foam and provides design recommendations for such armor systems.

Photocatalytic inactivation of airborne bacteria onto g-C3N4/TiO2/Ni-polydopamine/Ni bifunctional coupling filter with non-size dependent capture effect

Most commercial air purifiers rely on dense fibrous filters for bioaerosols control, which filter the particulate matter size-dependently without bactericidal activity. Herein, the non-size-dependent bifunctional nickel foam filters (g-C3N4/TiO2(CT)/Ni-polydopamine(PDA)/Ni bifunctional filter) with two layers of coupling nickel foams deposited by CT and PDA, respectively, were developed. The bifunctional filter shows remarkable non-size dependent bacteria removal efficiency (93.5 %) and inactivation efficiency (∼70 %) within 20 min at high airflow (12.5 L min−1). The inactivation efficiency can be further increased to 99.99 % with prolong irradiation time and enhancement of light intensity. The non-size dependent capture effect of the CT/Ni-PDA/Ni provided by adhesive force and charge was verified. In addition, the assumption that reactive oxygen species (ROSs) could be transferred into air during bacteria inactivation was first proved by chemiluminescent. This pioneered study may provide new insights into the development of bifunctional filters for non-size dependent capture and photocatalytic inactivation of bacteria in bioaerosols.

Effects of combined porous media on quenching and re-ignition characteristics of methane/air premixed combustion in a duct

During the study of foam metal suppression of methane combustion in ducts, it was found that under certain conditions, after the flame is extinguished, a re-ignition phenomenon occurs in the area upstream of the foam metal. In this paper, the process and mechanism for the occurrence of this phenomenon were investigated. The porous media used in the experiments is a two-layer structure consisting of a combination of iron-nickel foam and copper foam and was mounted in a transversal position. Each layer of foam metal has a thickness of 5 mm and a pore size of 20 or 40 holes pores per inch (ppi). The results show that flame extinguishment and re-ignition are highly dependent on the material and pore density of the porous media used. After the flame was quenched by the combination of iron-nickel foam with the same pore density of 40ppi, the re-ignition intensity was higher (a dazzling white light could be observed) and the flame area was larger. However, when a combination of iron-nickel foam with different pore densities was used, the re-ignition intensity, flame oscillation frequency and amplitude were significantly lower. However, both re-ignition flames can last for a long time. In addition, the incorporation of copper foam with high thermal conductivity resulted in the decay of flame propagation speed and the overpressure before and after quenching increased significantly with the increase of pore density of the first layer of iron-nickel foam.

Evaluation of Biosurfactant Property within Plant Probiotic Species

The present study focusses on proving the biosurfactant activity of the 7 isolated bacterial strains. Plants could not absorb enough nutrients as a result of contamination in the soil. This contaminants can be chemical pollutants or oil spillage. By considering the earlier potential applications of biosurfactants, this research was aimed to prove the role of a plant probiotic bacteria as oil degrading bacteria. In order to prove this approach, many screening methods were performed such as drop collapse, oil spreading (mm), emulsification stability testing by calculating emulsification index (E24%), penetration assay etc. Among the 7 selected isolates, isolate KL-015 have shown positive results with all the biosurfactant screening analysis. A unique role was proven by KL-011 isolate as it has shown a high oil degrading zone, i.e., 0.6 mm in diameter as well as the formation of more foam layer or emulsified layer with the emulsification index of 17.39% which indicates its role in having a biosurfactant molecule within it.

Boron separation by adsorption and flotation with Mg–Al-LDHs and SDBS from aqueous solution

Layered double hydroxides (LDHs) have been shown to be effective adsorbents for boron. However, solid–liquid separation is still a problem when separating boron from industrial radioactive waste liquid. In this research, three types of Mg–Al-LDHs including Mg–Al-LDH(NO3–), Mg–Al-LDH(Cl–) and Mg–Al-LDH(SO42–) were applied to adsorb boron, and moreover sodium dodecylbenzenesulfonate (SDBS) was used to float the LDH particles from aqueous solution after boron adsorption. The results showed that 60 min was sufficient for the equilibrium adsorption of the three LDHs. The boron adsorption capacity of three LDHs was determined as follows: Mg–Al-LDH(NO3–) > Mg–Al-LDH(Cl–) > Mg–Al-LDH(SO42–), and was 2.0, 0.98 and 0.2 mmol·g−1, each ranging from 0 to 80 mmol·L–1 with the initial boron concentration. The efficiency of boron removal by Mg–Al-LDH(NO3–) and SDBS can reach up to 89.7%. Furthermore, the boron flotation mechanism of SDBS and LDHs has been studied, since SDBS as a flotation agent can react with LDHs and penetrate into the interlayer of LDHs in addition to electrostatic attraction. Therefore, LDHs in solution can be floated onto the foam layer to be separated from the solution, and the clarified solution was obtained. The method is simple and promising for boron removal from aqueous solution.

Fabrication of the double-layer millimeter wave frequency selective surface by femtosecond laser

With the rapid development of communication technology, frequency selective surface (FSS) operating at higher frequencies is required and it is necessary to design and fabricate new FSS. In this paper, a broadband double-layer FSS is proposed which is composed of one layer of foam, two metal layers, and four layers of substrate. The simulation result shows that a high transmission in the band of 60.03–89.33 GHz (covering the E band) with a relative bandwidth up to 29 % is achieved. In addition, the effects of the key structural parameters, oblique incidence angle, and TE/TM polarization on the transmission performance are further explored. The results indicate that the proposed FSS has good oblique incidence angular stability and polarization insensitivity up to 60°. Finally, the proposed FSS is fabricated by the femtosecond laser and measured by the waveguide method. Experimental results show that the machined sample has high precision and the machining error is within 1 µm, and good agreement between the simulated and measured results is observed. Therefore, the proposed FSS could be used as spatial filters or sub-reflectors of multiband antennas and the corresponding processing method could be extended to other millimeter wave functional devices, such as absorbers, radomes, etc.

The influence of a thin, natural cellulose fibre membrane on the acoustic absorption of a layer of melamine foam

Porous materials such a melamine foam are commonly used to absorb noise and to control reverberation time in buildings. However, the ability of a thin porous layer to absorb noise at acoustic wavelengths that is much greater than the layer thickness is limited. This work investigates theoretically and experimentally the influence of a very thin, natural cellulose membrane on the sound absorption coefficient of a melamine foam substrate. The experimental results demonstrate that the presence of a 120 μm cellulose membrane can more than double the sound absorption coefficient of a relatively thin (17.4 mm) layer of melamine foam at frequencies above 600 Hz (577 mm wavelength). The theoretical part of work explains this effect through a careful simulation. The results show that there are analytical models that can accurately predict the acoustical behaviour of the cellulose membrane combined with a layer of melamine foam. The effects of the flow resistivity and thickness of a cellulose fibre membrane on the acoustic absorption coefficient of the melamine foam substrate are also studied through modelling and experiment. It is found that the optimum thickness of the cellulose fibre membrane should be between 75 and 100 µm when laminated on the top of a 20 mm melamine foam substrate. This work suggests that thin layers of sustainable natural materials such as cellulose fibres can be used to significantly improve the ability of traditional porous media to absorb sound.

Boiling Heat Transfer in Copper Foam Bilayers in Positive and Inverse Gradients of Pore Density

Gradient metal foam is an advanced heat transfer material that decreases resistance to bubble escape and enhances the transfer of boiling heat. In this study, boiling heat transfer and bubble behavior were studied in an experimental set-up with copper foam bilayers configurated either in positive or inverse gradients, utilizing deionized water as working fluid. Positive gradient refers to arranging metal foam layers with high pore density at the bottom, above the heat source, and low pore density on the top. Results show that the heat transfer is higher for gradient metal foam surfaces, of 6.14×105 W/m2, versus a uniform metal foam surface, of 3.94×105 W/m2. For the positive gradient configuration, boiling heat transfer performance first increased with the pore density, then decreased when the pore density was higher than 60 pores per inch (PPI). By contrast, for the inverse gradient, the heat transfer performance was nearly constant with increasing pore density. At the low pore density, the inverse gradient performed better than the positive gradient during the whole boiling process. At high pore density, the positive gradient structure performed better in heat transfer at the early boiling stage. Three main types of bubble escape were observed: For the positive gradient bilayer, the bubbles moved up or down without lateral interference. In contrast, for inverse gradient, the bubbles mostly escape from the sides, which is easy to induce bubble merging. The inverse gradient surface generates larger bubbles, while the positive gradient surface produces a higher frequency of bubble detachment. Accordingly, two liquid replenishment models are proposed: for the positive gradient, external liquid replenishes from the side into the copper foam, while for inverse gradient, the liquid is mainly replenished from the top.

Breathable Encapsulated Liquid Metal Foam‐Based Soft Stress Sensor

AbstractLiquid metal (LM)‐based soft and wearable sensors have great potential for applications in human motion monitoring and human‐machine interfaces. To avoid smearing of exposed LM, it is necessary to encapsulate LM with elastomers, which decreases the breathability and results in discomfort and even skin irritation. To solve this problem, this work proposes a breathable encapsulated LM foam (BELMF)‐based soft stress sensor. By using two polydimethylsiloxane foam layers, the BELMF‐based sensor achieves non‐smearing and breathability. Meanwhile, a three‐dimensional electrode is designed to implement the electric connection without decreasing breathability. Appling stress to the BELMF‐based sensor makes the LM foam collapse and forms new conductive paths, which reduces the resistance of the sensor. The sensitivity of the BELMF‐based sensor can reach 1.4 Pa−1. The mechanisms of the breathable encapsulation and the sensor are investigated through experiments and simulations. In addition, the potential applications of the BELMF‐based sensor for monitoring human motion are demonstrated.

Robust, Scalable, and Cost-Effective Surface Carbonized Pulp Foam for Highly Efficient Solar Steam Generation.

Recently, a solar-driven evaporator has been applied in seawater desalination, but the low stability, high cost, and complex fabrication limit its further application. Herein, we report a novel, low-cost, scalable, and easily fabricated pulp-natural rubber (PNR) foam with a unique porous structure, which was directly used as a solar-driven evaporator after facile surface carbonization. This surface carbonized PNR (CPNR) foam without interface adhesion or modification was composed of a top photothermal layer with light absorption ability and a bottom hydrophilic foam layer with a porous and interconnected network structure. Due to the strong light absorption ability (93.2%) of the carbonized top layer, together with the low thermal conductivity (0.1 W m K-1) and good water adsorption performance (9.9 g g-1) of the bottom layer, the evaporation rate and evaporation efficiency of the pulp foam evaporator under 1 sun of illumination attained 1.62 kg m-2 h-1 and 98.09%, respectively, which were much higher than those of most cellulose-based solar-driven evaporators. Furthermore, the CPNR foam evaporator with high cost-effectiveness presented high light-thermal conversion, heat localization, and good salt rejection properties due to the unique porous structure. Additionally, the CPNR foam evaporator exhibited potential applications in the treatments of simulated sewage, metal ion concentration, and seawater desalination. Its cost-effectiveness was clearly higher than that of most reported evaporators as well. Therefore, this novel, low-cost, and stable pulp foam evaporator demonstrated here can be a very promising solution for water desalination and purification.

Optimized Process for Melt Pyrolysis of Methane to Produce Hydrogen and Carbon Black over Ni Foam/NaCl-KCl Catalyst

Methane pyrolysis transforming CH4 into hydrogen without a CO2 byproduct is a potential hydrogen production process under the net-zero emission target. The melt pyrolysis of methane is a technology that could simultaneously obtain hydrogen and carbon products. However, its catalytic activity and stability are still far from satisfactory. In this work, a new strategy for the melt pyrolysis of methane to hydrogen production was proposed using Ni foam and molten NaCl-KCl. The increase in the amount of Ni foam was found to enhance the methane conversion rate from 12.6% to 18%. The process was optimized by the different amounts of catalysts, the height of the Ni foam layer, and the filling method of Ni foam, indicating that the methane conversion rate of the string method could reach 19.2% at 900 °C with the designed aeration device. Furthermore, we observed that the addition of molten salt significantly alleviated the carbon deposition deactivation of the Ni foam and maintained its macrostructure during the reaction. The analysis of the carbon products revealed that carbon black could be obtained.

Ultra-wideband flexible radar-infrared bi-stealth absorber based on a patterned graphene.

In this work, an ultra-wideband flexible radar absorber with low infrared emissivity for a radar-infrared bi-stealth application utilizing multilayer patterned graphene is proposed. The proposed absorber consists of three layers of graphene films with different patterns, flexible substrates, lightweight foam, and a ground layer. The flexible graphene films, rather than the conventional lumped resistors, are adopted as omnidirectional resistors to achieve dual polarization and flexibility. On the top of the absorber, an infrared shielding layer (IRSL) consists of patterned Indium tin oxide (ITO) separated by a thin foam layer. Due to the low-pass characteristics and the high filling ratio of the top ITO layer, the infrared emissivity of the whole structure is reduced effectively while the radar absorption property is slightly affected. As a result, the 90% absorption band is from 1.96 GHz to 20.72 GHz (fractional bandwidth 165.4%), with a low infrared emissivity of about 0.35. Besides, a miniaturized unit is achieved with the period of 0.079 λl at the lowest absorption frequency, and the oblique angle incidence response is up to 45° for TE mode and 60° for TM mode. A plane and a bending prototype are fabricated and measured, respectively. The screen-printing technology is adopted to print the graphene resistive films, and the measurement results agree well with the simulation.

Latent heat thermal energy storage in a shell-tube: A wavy partial layer of metal foam over tubes

The melting thermal energy storage and heat transfer of paraffin wax in a storage unit was modeled in the presence of a wavy copper foam. The phase-change energy and natural convection effects were modeled using the enthalpy porosity approach. The control equations were solved using the finite element method over a structured mesh. The energy storage was simulated for the wavenumber and amplitude of the foam layer. It was found that the higher wavenumber, the shorter the charging time and better energy storage power. A lower wave magnitude was also better than a longer wave magnitude. The shortest melting time was obtained for a flat foam layer, which was 20 % better than a low wave long amplitude foam layer. The current work intends to reduce the weight of applied metal foams in thermal energy storage applications by enhancing the geometry design. Here, a wavy form layer of metal foam was used to guide the natural convection flows and also boost the heat transfer mechanism. The phase change heat transfer has not been investigated in a wavy form metal foam layer.

Effect of calcium carbonate particle size and content on the thermal properties of PVC foamed layer used for coated textiles.

The goal of this research is to see how the amount and particle size of calcium carbonate (CaCO3) used in the foamed layer in use for PVC-coated textiles affects the thermal properties of the material. Two different particle sizes were used at various concentrations. The impact of different CaCO3 loadings and particle sizes on the PVC foamed layer's thermal properties were examined. Thermogravimetry (TGA and DTG) and differential scanning calorimetry (DSC) measurements were utilized to investigate the thermal properties of the PVC foamed layer and the samples have been also characterized by FTIR spectroscopy. According to the findings, the thermal stability of the foamed layer was improved with the addition of calcium carbonate. Through the higher surface area between the filler and the PVC matrix, smaller particle sizes have produced the best results. The PVC foamed layer shows also changes in FTIR spectra after adding CaCO3, and the intensity of peaks increases with decreasing CaCO3 particle size.

Segmentation algorithm of coal slurry foam with double-point directional extension based on the improved FCM clustering algorithm

In flotation production, the visual surface information of the flotation foam reflects the flotation effects, which are closely related to the flotation conditions and directly reflect the degree of mineralization of the foam layer. In this study, it was proposed a novel and efficient segmentation algorithm to extract the edge information of slime bubbles, as the boundaries are typically blurred and difficult to segment, due to the slime bubbles sticking to each other in the slime flotation foam image. First, the improved clustering algorithm and image morphology operation were used to extract the edges of the foam spots. Second, the image morphological operations were used as a starting point to look around the foam edge points. The pseudo-edge points were then removed using a region and spatial removal algorithm. Finally, the foam edges were extracted using the double-point directed expansion algorithm. A new criterion was proposed for segmentation effect determination based on the particularity of the segmented object. The feasibility and effectiveness of the foam segmentation method were investigated by comparative experiments. The experimental results showed that the proposed algorithm could obtain the foam surface properties more accurately and provide effective guidance for flotation production.

Разработка и настройка алгоритма программной идентификации отклонений в пенном слое калийной флотомашины

The article deals with the problems that arise in the practical application of the method of glare recognition of the parameters of the froth layer of a potash ore flotation machine. These include choosing the best statistical characteristic, filtering and averaging settings, checking the possibility of taking into account anti-glare, and the need for adaptive signal renormalization. Objective of the study is to develop an algorithm for identifying a flotation cell as an object of automatic control, which is possible only after solving these problems. Materials and methods of research. The study was carried out on the materials of an experimental survey of a potash flotation machine. During the shooting, a standard step signal was applied to the machine cell, which was expressed in a change in the composition of the amino-oil mixture, which caused a transient process. For different statistical characteristics (the number of bubbles, the number of red components in the frame, the average and median distances between the centers of the bubbles), various methods of filtering and averaging the data were tested. At the same time, the problem of identifying the gain and the time constant of the object was solved. The best characteristic and methods of its processing were chosen on the basis of the root-mean-square deviation of the calculated transient process from field data obtained by glare recognition of the foam layer surface. Results. Processing several frames in a row, taken at the same position of the foam, slightly improves the result, but significantly loads computing power. Blind filtering by ten points has practically no effect on the data processing time. To improve the identification, data renormalization was used, which consists in the adaptive selection of the zero and single signals in the conditions of noisy data. The localization method was used to determine the optimal delay from the point of view of the quadratic deviation before the start of the transient process. Conclusion. As a result, the best filtering and data averaging settings were obtained, providing the smallest identification error. The time constant of the cell turned out to be close to the results of previous authors, obtained, among other things, by visual observation of the flotation machine. Accounting for antiglare does not significantly affect the parameters of the object. An important conclusion is that one statistical characteristic describes well the beginning of the transient process, and the other describes its end. This must be taken into account when building a deviation signaling system.