Foaming Agent Research Articles

A Catalyst-Like System Enables Efficient Perovskite Solar Cells.

High-quality perovskite films are essential for achieving high performance of optoelectronic devices; However, solution-processed perovskite films are known to suffer from compositional and structural inhomogeneity due to lack of systematic control over the kinetics during the formation. Here, the microscopic homogeneity of perovskite films is successfully enhanced by modulating the conversion reaction kinetics using a catalyst-like system generated by a foaming agent. The chemical and structural evolution during this catalytic conversion is revealed by a multimodal synchrotron toolkit with spatial resolutions spanning many length scales. Combining these insights with computational investigations, a cyclic conversion pathway model is developed that yields exceptional perovskite homogeneity due to enhanced conversion, having a power conversion efficiency of 24.51% for photovoltaic devices. This work establishes a systematic link between processing of precursor and homogeneity of the perovskite films.

Stabilization and strengthening effects of filamentous nanocellulose in the foam forming of quartz paper

Compared with traditional papermaking, foam forming is a new papermaking technology that uses foam instead of water to disperse fibres, which can effectively solve the problem of poor evenness of ceramic paper, but the instability of foam itself affects the application of foam forming technology. Herein, a highly stable foaming agent for foam forming technology was prepared via physical reaction of lauryl dimethyl amine oxide (OB-2) with filamentous nanocellulose (cellulose nanofiber (CNF-C) and bacterial cellulose (BC)). Then, the quartz paper was prepared by foam forming technology. Firstly, hydrogen bond interactions between hydroxyl groups of the filamentous nanocellulose and hydrophilic moieties on OB-2 enabled the formation of a 3D nanonetwork layer on the surface of the bubble, which extended the half-life of the bubble and effectively prevented the bubble from bursting or coalescing. Then, the foam was extruded and cracked, and the filamentous nanocellulose was retained on the quartz fibres to prepare filamentous nanocellulose/quartz fibre paper by foam forming technology. The quartz paper exhibited excellent evenness and mechanical properties. In conclusion, the research of foam forming technology is of great significance to the application and development of special paper.

Research on EOR for ultralow interfacial tension foam in high-temperature and high-salinity reservoirs: flooding simulation and application in Shengli Oilfield

For high temperature and high salinity reservoirs, the foam formulation system is required to have better foaming capacity and foam stability under formation conditions in tertiary EOR. In order to obtain a new foam agent suitable for this type of oil reservoir, through the compounding and testing of 7 common oilfield foam chemical agents, 15 formulated foam agents are tested and screened. Then the foam displacement experiment of the dual sand packs model was established to simulate the new foam flooding process. The production dynamic of the high-permeability sand pack and the low-permeability sand pack was captured and analyzed, and EOR mechanism of the foam system in the heterogeneous reservoir was clarified. The experimental results show that the formulation of B4(anionic & nonionic combined surfactant) & FSN100(fluorinated surfactant) with a mass proportion of 2:3 (BF23) has the best performance in terms of foaming properties, low interfacial tension reduction, and oil washing efficiency. Furthermore, BF23 foam injection greatly increased the recovery factor from 36.7% to 61.6%, clearly displacing the remaining oil in the low-permeability pack. Finally, the new foam agent solution used in Shenger block of Shengli Oilfield shows its good value for enhanced oil recovery.

Mechanical Characteristic and Energy Absorption Behavior of Closed-Cell Pure and A356 Alloyed Aluminum Foams during Compression

The goal of this study is to evaluate the mechanical characteristics and energy absorption capabilities of both closed-cell pure Aluminum foam and closed-cell A356 foam. A portion of the lightweight pure foam samples (17.12, 17.77 and 15.27 g) is produced through casting of raw material (99.9 % pure aluminum) using Titanium Hydride (TiH2) as a foaming agent, which lead to (7.5, 7 and 8) Pores Per Inches (PPI); and samples of A356 foam (38.24, 38.18 and 35.88 g) is produced through casting of A356 alloyed material with same procedure which lead to (11, 10 and 12) PPI. In order to determine the maximum compressive strength, strength-to-weight ratio, energy absorption density, complementary energy, and energy absorption efficiency, a uniaxial compression test is conducted. The results indicate that compression of pure foam structure smashed in a ductile manner and shows a lamellar eutectic structure while A365 foams under compression are crashed with brittle character with complex phases distribution inside (polyhedral and globular morphologies), A noticeable enhancement is observed in the mechanical characteristics of the A356 foam. The maximum compressive strength and specific energy absorption of alloyed foam are increased by a factor nearly of 4 and 2 respectively for all tested samples. Also, the result shows a significant decreasing in compressive strength with increasing of PPI for both pure and alloyed foam. The notable enhancements in the properties of alloyed closed cell foam render these advanced materials a viable option for high-strength applications.

Repeated foaming of A1050 porous aluminum with densification by compression and friction stir processing and remaining foaming agent

Repeated foaming of A1050 porous aluminum with densification by compression and friction stir processing and remaining foaming agent

Effect and mechanism on the flotation desulfurization of high-sulfur bauxite by using the mixed collector of PYDH

Desulfurization of high sulfur bauxite is an important issue in Bayer alumina production. In this study, by using two anionic sulphydryl collectors (HX, HD) as mixed collectors (PYDH), the selectivity of flotation separation between pyrite and diaspore was improved, thereby reducing the sulfur content of high sulfur bauxite and ultimately meeting the production requirements of Bayer alumina. The findings showed that under the optimized conditions of 500 g/Mg collector, 150 g/Mg inhibitor, 200 g/Mg activator, 100 g/Mg foaming agent, and a slurry pH of 9, the sulfur content of bauxite can be reduced from 3.35% to 0.33% through one rough selection, one fine selection, and one scavenging flotation. Moreover, the interaction mechanism between mixed collectors and pyrite was studied through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Zeta potential analysis, and contact angle testing. SEM-EDS research confirmed that PYDH adsorbed on the surface of pyrite. The contact angle measurement analysis showed that compared to individual collectors, pretreated pyrite with mixed collectors had better hydrophobicity. Zeta potential, FTIR, and XPS results indicated that PYDH selectively adsorbed pyrite through chemical adsorption. The mixed collector PYDH is an effective collector for pyrite in high sulfur bauxite flotation desulfurization.

Exploring a Novel Material and Approach in 3D-Printed Wrist-Hand Orthoses

This article proposes the integration of two novel aspects into the production of 3D-printed customized wrist-hand orthoses. One aspect involves the material, particularly Colorfabb varioShore thermoplastic polyurethane (TPU) filament with an active foaming agent, which allows adjusting the 3D-printed orthoses’ mechanical properties via process parameters such as printing temperature. Consequently, within the same printing process, by using a single extrusion nozzle, orthoses with varying stiffness levels can be produced, aiming at both immobilization rigidity and skin-comfortable softness. This capability is harnessed by 3D-printing the orthosis in a flat shape via material extrusion-based additive manufacturing, which represents the other novel aspect. Subsequently, the orthosis conforms to the user’s upper limb shape after secure attachment, or by thermoforming in the case of a bi-material solution. A dedicated design web app, which relies on key patient hand measurement input, is also proposed, differing from the 3D scanning and modeling approach that requires engineering expertise and 3D scan data processing. The evaluation of varioShore TPU orthoses with diverse designs was conducted considering printing time, cost, maximum flexion angle, comfort, and perceived wrist stability as criteria. As some of the produced TPU orthoses lacked the necessary stiffness around the wrist or did not properly fit the palm shape, bi-material orthoses including polylactic acid (PLA) inserts of varying sizes were 3D-printed and assessed, showing an improved stiffness around the wrist and a better hand shape conformity. The findings demonstrated the potential of this innovative approach in creating bi-material upper limb orthoses, capitalizing on various characteristics such as varioShore properties, PLA thermoforming capabilities, and the design flexibility provided by additive manufacturing technology.

Physicochemical properties and flow behavior of natural sweetener and colorant from foam‐mat dried grape powder

AbstractThe effects of whey protein concentrate, glycerol monostearate, methyl cellulose at a concentration of 1‐3% and gum arabic on the expansion, density and stability of the foam as well as the physicochemical properties of the powder were investigated. The findings identified that the simultaneous addition of foaming and stabilizer agents noticeably affected the quality of the foam. The most stable foam occurred at 3% WPC and 3% MC with density 0.374, expansion 134.4, and stability 95.6. The dried grape powder with a higher proportion of GMS and WPC exhibited the most brightness. The higher level of foaming agents demonstrated lower moisture content, aw, cohesiveness and higher hygroscopicity, flow ability and wettability compared to the non‐foamed one. The study demonstrated the potential use of grape powder as a hygroscopic ingredient in an instant food product, Furthermore, it highlights the importance of selecting appropriate foaming agents to achieve desired properties in the products.Practical applicationsConsidering today's hectic lifestyles and people's increasing awareness of nutrient consumption, consumers prefer ready‐to‐eat and readily available foods that are also health‐oriented. Foam mat drying is an economical alternative to drum, spray, and freeze drying in the production of fruit powders. This process can be used for large‐scale production, because of its suitability for all types of juices, rapid drying at lower temperature, retention of nutritional quality, easy reconstitution, and cost‐effective for producing easily juice powders. Fruit juice powders obtained through this process have high economic potentials over their liquid counterparts such as reduced volume or weight, reduced storage space, simpler handling and transportation, and much longer shelf life. Thus, by conducting this comparative study, valuable insights can be gained into the potential use of foam‐mat dried grape syrup powder as a desirable natural sweetener, colorant, and hygroscopic ingredient for ready meals.

The Effect of Foaming Agents on the Thermal Behavior of Aluminum Precursors.

Various foaming agents can be used to achieve foaming of the precursors obtained by using the powder metallurgy method. However, the thermal behavior of pure aluminum precursors with different foaming agents has been studied very little in recent times. For the production of aluminum foams with closed cells, 1 wt.% of calcium carbonate (CaCO3), titanium hydride (TiH2), heat-treated TiH2 and zirconium hydride (ZrH2) were used. The foaming capability of the compacted precursors was investigated at temperatures 700, 720 and 750 °C. CaCO3 and TiH2 showed the best foamability at all considered temperatures, while ZrH2 achieved relatively good foaming only at the highest temperature, 750 °C. Due to their low onset temperature of the decomposition compared to the melting point of the unalloyed aluminum, in hydride-based foaming agents the drainage occurred at the bottom part of the foam samples. Among the investigated foaming agents, precursors with heat-treated TiH2 had the worst foaming properties, while CaCO3 showed the best foamability without the occurrence of drainage.

Thermal characteristics of fire extinguishing agents in compartment fire suppression.

Water and foam have different fire-extinguishing mechanisms. Traditional foam and compressed air foam (CAF) have different bubble structures. These differences result in different thermal characteristics, which affect the extinguishing abilities during a fire. In this study, the differences in the thermal characteristics of three different extinguishing agents (water, traditional foam, and CAF) were investigated by suppressing a compartment fire. With an ignition source in the compartment (6 m × 3 m × 3 m), the agent was preferentially applied to the outside wall of the compartment. The effects of internal cooling and burnback resistance generated from the outer wall were evaluated. The performance of each agent in shielding firefighters from radiant heat while suppressing the fire inside the compartment was evaluated. When the outside wall of the compartment was covered with each of the agents, all agents were found to reduce the room temperature. When CAF was applied, the delay time until temperature re-rise was approximately 1.76-4.5 times longer than that when water was used. In addition, foaming agents exhibited a higher heat-shielding effect than water during the initial suppression. Thus, considering the thermal characteristics of these agents, fire suppression can be more effective if foam agents are used.

Quality characteristics of plant-based whipped cream with ultrasonicated pea protein

The rise in popularity of vegetarian and plant-based diets has led to extensive research into plant-based whipped creams. Whipped cream is an oil-in-water emulsion that creates foam through whipping, stabilizing the foam with proteins and fats. Pea protein is an excellent emulsifier and foaming agent among plant-based proteins, but its application in whipped cream is currently limited. The objective of this study was to investigate the quality characteristics of plant-based whipped cream made with ultrasonicated pea protein. The whipped creams were evaluated based on their quality characteristics. A commercially available dairy whipped cream (CON) was used as a control. Plant-based creams were evaluated using pea protein solution, cocoa butter, and canola oil to produce un-ultrasonicated pea protein whipped cream (PP) and ultrasonicated pea protein whipped cream (UPP) at 360 W for 6 min. UPP significantly reduced whipping time and foam drainage compared with CON and PP, resulting in significantly increased overrun, fat destabilization, and hardness. Optical microscopy showed that UPP had smaller fat globules and bubble size than PP. The fat globules of UPP and CON were mostly below 5 μm, whereas those of PP were distributed at 5-20 μm. Finally, ultrasonication significantly improved the overrun, foam drainage, fat destabilization, and hardness of UPP, which are significant quality characteristics of whipped creams. Therefore, ultrasonicated plant-based pea protein whipped cream is believed to be a viable alternative to dairy whipped cream.

Microwave-assisted foam mat drying of red beet pulp: influence of milk protein concentrate (MPC) and maltodextrin as a foaming agent, optimization and quality attribute

Microwave-assisted foam mat drying of red beet pulp: influence of milk protein concentrate (MPC) and maltodextrin as a foaming agent, optimization and quality attribute

Effect of Mineral Powders on the Properties of Foam Concrete Prepared by Cationic and Anionic Surfactants as Foaming Agents.

Foam concrete is a type of cement mortar in which air bubbles are introduced using an appropriate foaming agent. The complex conditions for the preparation of solid particle stabilized foams limit their wide application in construction. In this study, a method of adding small amounts of calcite (Cal) and muscovite (Mus) to the cement paste matrix is proposed to improve the properties of foam concrete prepared with cationic and anionic surfactants as foaming agents. The effects of mineral powders on the flowability, compressive strength, water absorption, pore characteristics, thermal conductivity and frost resistance of foam concrete were investigated and the enhancement mechanism was revealed by the results of XRD, low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR) and SEM. The results showed that the mineral powders interacted with anionic and cationic surfactants through physical adsorption. Whether anionic or cationic surfactants were used as foaming agents, the addition of mineral powders promoted the formation of shell-like structures around the foam, thus enhancing the performance of foam concrete. As a result, the fluidity, compressive strength and frost resistance of the foam concrete increased, the water absorption and thermal conductivity decreased, and the average size of the pores decreased.

Fully Biobased Degradable Vitrimer Foams: Mechanical Robust, Catalyst-Free Self-Healing, and Shape Memory Properties.

Thermosetting foams have limited capabilities for recycling, reprocessing, or reshaping. Moreover, most of the foaming agents currently employed in these foams are derived from organic compounds sourced from petrochemicals, thereby posing a significant environmental threat due to heightened pollution. To solve these problems, a fully biobased degradable vitrimer foam (EPC-X) was fabricated using an environmentally friendly all-in-one foaming strategy by cross-linking epoxidized malepimaric anhydride (EMPA), 1,5-diaminopentane (PDA), and 1,5-diaminopentane carbamate (PDAC) as a latent curing-blowing agent. To our delight, the vitrimer foams exhibit excellent mechanical properties (2.86 ± 0.11 MPa compressive strength) owing to their unique rigid rosin backbone and cross-linking networks. The presence of dynamic β-hydroxy ester bonds and the self-catalytic behavior of tertiary amine groups facilitate network rearrangement without requiring additional catalysts, thereby resulting in the development of EPC-X with rapid self-healing and shape memory properties. The self-healing foam could support a weight of 500 g (approximately 562 times its own mass). Moreover, these high-performance vitrimer foams can also be easily degraded in an ethanolamine (EA) or NaOH solution under mild conditions. Such a design strategy offers an alternative approach for developing superior degradable and thermal stimuli-responsive thermosetting foams.

Fabrication and characterization of aluminum foam reinforced with nanostructured γ-Al2O3 via friction stir process for enhanced mechanical performance

AbstractThis study focuses on the fabrication and characterization of aluminum foam reinforced with nanostructured γ-Al2O3, utilizing AA5083 plates. The fabrication process involved the integration of TiH2 foaming agent particles and reinforcing nanoparticles via the friction stir process (FSP), resulting in the creation of precursor specimens. Subsequently, a separate foaming stage was conducted within a laboratory furnace. The integration of these particles was achieved through the machining of parallel grooves in a single aluminum plate. The initial phase of the experimental study focused on investigating the effect of varying amounts of the foaming agent. Large-scale foams were then produced, achieving a medium porosity of 70%. Electro-discharge machining was employed to prepare specimens for compression testing to analyze their stress–strain response. The results revealed a plateau stress of 27 MPa, a relative Young’s modulus of 4.44 × 10−3, and an energy absorption close to 17 MJ/m3 at 50% strain. Significantly enhanced plateau stress was observed in the manufactured reinforced aluminum foam compared to similar foams produced through conventional methods.

Microstructure and microwave‐absorbing properties of B4C/C composite powders produced by combustion synthesis with an AC foaming agent

AbstractTo develop microwave‐absorbing properties of dielectric ceramics, B4C/C composite powders were prepared by combustion synthesis with B2O3, polyvinyl alcohol, and Mg as the raw materials in this work. The XRD, Raman, scanning electron microscope with energy‐dispersive spectroscopy, and VNA network analysis carried out the effects of the addition of azodicarbonamide (AC) foaming agent on the phase compositions, microstructure, and dielectric and microwave‐absorbing properties of the products. The results indicated that the addition of an AC foaming agent contributed to the formation of distinct morphologies with a larger specific surface area and uniform distribution of the free carbon in the B4C/C composite powders and improved its graphitization degree, which resulted in the formation of equivalent microcapacitors, enhanced interfacial polarization, improved conductive network, and leading to a low reflection loss (RL) and a broadened effective absorb bandwidth (EAB). Due to the dielectric loss as the dominant loss mechanism, C‐1.5 (1.5 wt.% AC foaming agent addition) exhibits the EAB of 3.02 GHz and the minimum RL (RLmin) of −22.90 dB at the thickness of 2.20 mm.

Design and performance of lightweight high–temperature resistant microwave penetrating foamed ceramics

To develop lightweight microwave penetrating materials capable of operating at high temperatures, the technical potential of preparing foamed ceramics (FCs) from a simple material system using boron nitride (BN) as the foaming agent was studied. The preparation mechanism of the FCs is that the oxidation–derived nitrogen from BN blows up the molten ceramic body during sintering. The FCs sintered at 1000 °C from the material system containing 0.3 wt% ferric oxide have a uniform pore structure with a mean pore diameter of 1.0 mm, high total/closed porosities of 82 %/81 %, a low density of 0.45 g/cm3, and an adequate compressive strength of 6.9 MPa. The high porosity and simple composition allow the FCs to have a low permittivity of 2.09+j0.024 in the X–band and over 95 % penetration of incident microwaves in the 8.0–18.0 GHz frequency range. The FCs are potentially lightweight, moisture resistant and thermal insulating due to their low density, high closed porosity, and uniform pore structure, which are expected to be an excellent high–temperature microwave penetrating material based on their retention of pore structure and physical–mechanical properties at 800 °C.

Evaluation of foaming agents for high‐temperature, high‐pressure, and high‐salinity reservoirs based on a new foam evaluator

AbstractIn this study, a novel high‐temperature and high‐pressure foam evaluator with variable diameters inner cell and cylinder flip function was designed on our own, which can solve the problems such as difficulties in foam generation and inaccurate determination of various foam parameters by the same type of instruments, through which the foaming performance of more than 10 betaine surfactants was evaluated. The results show that: (1) the higher the pressure, the higher the foaming rate of the foaming agent and the more stable the foam, but the foam stability of the foamers at low and high pressures, and low and high temperatures do not correspond exactly, and the foaming agent used needs to be screened under simulated reservoir conditions. (2) The comprehensive foaming performance of different types of foamers with different molecular structures found that hydroxy sulfobetaine with longer carbon chains has a relatively better foaming performance. Therefore, for the reservoir conditions of temperature 130°C, pressure 30 MPa, and salinity 22 × 104 mg/L, hydroxy sulfobetaine, which does not contain an amide group in the molecule, can be considered preferentially as a foaming agent. The results can guide the selection of foaming agents for high‐temperature and high‐salinity reservoirs.

Porous Lithium Disilicate Glass-Ceramics Prepared by Cold Sintering Process Associated with Post-Annealing Technique.

Using melt-derived LD glass powders and 5-20 M NaOH solutions, porous lithium disilicate (Li2Si2O5, LD) glass-ceramics were prepared by the cold sintering process (CSP) associated with the post-annealing technique. In this novel technique, H2O vapor originating from condensation reactions between residual Si-OH groups in cold-sintered LD glasses played the role of a foaming agent. With the increasing concentration of NaOH solutions, many more residual Si-OH groups appeared, and then rising trends in number as well as size were found for spherical pores formed in the resultant porous LD glass-ceramics. Correspondingly, the total porosities and average pore sizes varied from 25.6 ± 1.3% to 48.6 ± 1.9% and from 1.89 ± 0.68 μm to 13.40 ± 10.27 μm, respectively. Meanwhile, both the volume fractions and average aspect ratios of precipitated LD crystals within their pore walls presented progressively increasing tendencies, ranging from 55.75% to 76.85% and from 4.18 to 6.53, respectively. Young's modulus and the hardness of pore walls for resultant porous LD glass-ceramics presented remarkable enhancement from 56.9 ± 2.5 GPa to 79.1 ± 2.1 GPa and from 4.6 ± 0.9 GPa to 8.1 ± 0.8 GPa, whereas their biaxial flexural strengths dropped from 152.0 ± 6.8 MPa to 77.4 ± 5.4 MPa. Using H2O vapor as a foaming agent, this work reveals that CSP associated with the post-annealing technique is a feasible and eco-friendly methodology by which to prepare porous glass-ceramics.

A comparative study of polyurethane foam by substituting LBA using green polyurethane foam CFA‐1

AbstractPolyurethane foams are well‐known optimal thermal‐insulating materials, which have good thermal insulation performance, high strength, and lightweight properties. Here, we describe a chlorine‐free and fluorine‐free polyurethane chemical foaming agent (CFA‐1) that can react with isocyanate to release CO2 gas and foam polyurethane. We systematically studied its application performance in the field of polyurethane spraying by substituting the current most advanced and environment‐friendly physical foaming agent 1‐chloro‐3,3,3‐trifluoroprop‐1‐ene in different proportions. The results show that highly competitive mechanical properties lead to economical, environment‐friendly, and efficient features. The lower thermal conductivity, more compact and smaller bubble structure, and excellent compression strength were achieved by tuning the proportion of CFA‐1 from 20% to 60%. Thus, a promising material system was established for the development of the rigid polyurethane foam industry.