Foam Template Research Articles

Effect of Physical Treatments on Functional Properties of Whey and Soy Protein Isolates in Oleogel Production Through Foam Template Method.

This study aimed to investigate the impact of physical treatments, namely heat (70 °C for 48 h), atmospheric cold plasma (10 kW for 20 min), and ultrasonic frequency (40 kHz for 15 min), on the physicochemical and interfacial properties of soy protein isolate (SPI) and whey protein isolate (WPI) in the context of oleogel production by foam template (cryogel) method. The physical modification of both SPI and WPI was monitored using SDS-PAGE, Fourier transform infrared spectroscopy (FTIR) spectroscopy, and differential scanning calorimetry (DSC), measuring interfacial tension, color, solubility, foam volume, foam stability, and, finally, the density and oil absorption of the produced cryogel. The findings revealed that the application of ultrasonic waves resulted in a significant reduction in the content of alpha-helical of SPI and WPI while the other treatments increased the content of random coil proteins. FTIR analysis further showed that ultrasonic and heat treatment led to a decrease in C-N tensile vibration within the range of 1200-1650 cm-1 in SPI. Meanwhile, in cold plasma treatment, an increase was observed which was confirmed by the elevation of enthalpy from 100 to 128 kJ/kg. Physical treatments significantly altered the surface properties of both SPI and WPI, where this value was reduced in SPI and increased in WPI. The cold plasma method demonstrated superior performance in enhancing the solubility of SPI from 10 to 58.2%, while the solubility of WPI decreased from 96.4 to 90.4%. By modifying the proteins, the foam volume and oil adsorption ability of the related cryogel improved, as shown by the maximum oil absorption obtained after ultrasonic treatment for SPI (11.6 g/g) and cold plasma (9.17 g/g) for WPI. These results could be useful in applying physical treatments to modify proteins and create the cryogel as an oleogel template for structuring liquid oil and producing innovative health value-added foods.

Lightweight reticulated mullite foams of zero strut porosity from preceramic polymer resins

This study presents a novel approach for fabricating reticulated mullite and zirconia-mullite ceramic foams by using in-house synthesized preceramic polymers. Unlike traditional aqueous slurry methods, this technique employs polymeric resins, specifically aluminosiloxane (AS) and zirconoaluminosiloxane (ZAS), in a toluene medium. The process utilizes polyurethane (PU) foam template, with a two-time impregnation and squeezing method to ensure adequate resin loading. X-ray diffraction confirmed silica devitrification and vitrification at 1500°C and 1600°C, respectively, enhancing mullite densification. SEM imaging revealed the formation of nonporous struts and ligaments with needle-shaped grains and tetragonal zirconia nanocrystals at 1600°C. The foams demonstrated porosity between 83 and 95.2%, compressive strength from 0.44 to 0.11 MPa, and thermal conductivity from 0.15 to 0.08 W/mK. This research highlights the potential of using AS and ZAS resins for the production of high-performance ceramic foams, marking a significant innovation in the field.

Arginine-Biofunctionalized Ternary Hydrogel Scaffolds of Carboxymethyl Cellulose-Chitosan-Polyvinyl Alcohol to Deliver Cell Therapy for Wound Healing.

Wound healing is important for skin after deep injuries or burns, which can lead to hospitalization, long-term morbidity, and mortality. In this field, tissue-engineered skin substitutes have therapy potential to assist in the treatment of acute and chronic skin wounds, where many requirements are still unmet. Hence, in this study, a novel type of biocompatible ternary polymer hybrid hydrogel scaffold was designed and produced through an entirely eco-friendly aqueous process composed of carboxymethyl cellulose, chitosan, and polyvinyl alcohol and chemically cross-linked by citric acid, forming three-dimensional (3D) matrices, which were biofunctionalized with L-arginine (L-Arg) to enhance cellular adhesion. They were applied as bilayer skin biomimetic substitutes based on human-derived cell cultures of fibroblasts and keratinocytes were seeded and grown into their 3D porous structures, producing cell-based bio-responsive hybrid hydrogel scaffolds to assist the wound healing process. The results demonstrated that hydrophilic hybrid cross-linked networks were formed via esterification reactions with the 3D porous microarchitecture promoted by foam templating and freeze-drying. These hybrids presented chemical stability, physicochemical properties, high moisture adsorption capacity, surface properties, and a highly interconnected 3D porous structure well suited for use as a skin substitute in wound healing. Additionally, the surface biofunctionalization of these 3D hydrogel scaffolds with L-arginine through amide bonds had significantly enhanced cellular attachment and proliferation of fibroblast and keratinocyte cultures. Hence, the in vivo results using Hairless mouse models (an immunocompromised strain) confirmed that these responsive bio-hybrid hydrogel scaffolds possess hemocompatibility, bioadhesion, biocompatibility, adhesiveness, biodegradability, and non-inflammatory behavior and are capable of assisting the skin wound healing process.

A Review of New Materials and Methods Used in the Production of Protein-Based Fat Replacers for the Food Industry

In the last decade, with the rise in customer awareness about the quality of the food they consume and its health benefits, new methods for producing food fat replacers have been developed. Since then, significant progress has been made in enhancing these techniques. Methods such as emulsion template, foam template, and solvent exchange are frequently employed for creating fat replacers known as oleo- or emulsion gels, commonly used in food products. As the interest in developing fat replacers continues to grow, it has become essential to explore and pursue new materials suitable for producing protein-based fat replacers. Given the increasing food consumption, food waste is on the rise. The goal is to maximize food utilization and create high-protein, nutritionally rich foods with minimal waste. This involves using new materials, such as alternative proteins or food by-products, and finding effective methods for their utilization. This review aims to provide insights into the variety of materials and methods employed to prepare protein-based fat replacers as documented in the available literature.

Achieving Complete Conversion from Nickel Foam to Nickel Sulfide Foam for a Freestanding Hybrid‐Supercapacitor Electrode

AbstractWe present a unique, one‐step, hydrothermal process to prepare nickel sulfide (Ni3S2) foam by a simple and direct conversion from nickel foam, which contributes both as a scaffold for the reaction and as reactant. The Ni3S2 foam exhibits remarkable mechanical stability, retaining the structural integrity of the foam and excellent crystallinity even after ultrasonication at 200 W for 30 mins. We document the transformation of the nickel foam template into a Ni3S2 foam, highlighting the role of synthesis duration on the phase evolution and unique morphology of Ni3S2. PXRD and SEM analyses reveal a complete transformation after 24 hours from the nickel foam to a pure Ni3S2 foam, which has a highly porous and interconnected ultra‐thin nanosheet architecture. This significantly enhances the surface area and provides many electrochemical reaction sites. In a three‐electrode cell, the capacity of the Ni3S2 foam electrode is 3.9 C cm−2 at 8 mA cm−2, which is higher than previous reports for Ni3S2. In a hybrid supercapacitor device, the Ni3S2 foam demonstrates significant increase in capacitance through 500 cycles and the capacitance plateaus after 2000 cycles. Even after 8500 continued charge‐discharge cycles, the device exhibits excellent cycle stability indicating improvement with age.

High-performance direct borohydride-hydrogen peroxide fuel cell using Ni foam-supported Ni-Co nanoparticles as a noble-metal free anode electrocatalyst

The Ni-Co nanoparticles with various Ni/Co ratios are immobilized on a Ni foam (NF) template, coated with reduced graphene oxides (rGO), and used as a novel noble-metal-free anode electrocatalyst for enhanced performance direct borohydride fuel cells. The electrochemical active surface area (EASA) of Ni50Co50 /rGO/NF (1515 cm2) catalyst is 45.5 times larger than NF (33.3 cm2). A comprehensive study of direct borohydride-hydrogen peroxide fuel cell (DBHPFC) by Pt/C (0.5 mg cm−2) as a cathode and Ni50-Co50/rGO/NF as an anode is accomplished, so an open-circuit potential (OCP) of 1.90 V and the maximum power density of 309 mW cm−2 is obtained at 60 ◦C. These results show that electrocatalyst Ni50Co50/rGO/NF is a suitable candidate for use as an electrocatalyst in DBHPFC due to its low cost, ease of synthesis, excellent structural stability, and high catalytic performance.

Methodology for Liquid Foam Templating of Hydrogel Foams: A Rheological and Tomographic Characterization

AbstractHydrogel foams are widely used in many applications such as biomaterials, cosmetics, foods, or agriculture. However, controlling precisely foam morphology (bubble size or shape, connectivity, wall and strut thicknesses, homogeneity) is required to optimize their properties. Therefore, a method is proposed here for generating, controlling, and characterizing the morphology of hydrogel foams from liquid foam templates: Using the example of Alginate‐CaHPO4‐based hydrogel foams, a highly controllable foaming process is provided by bubbling nitrogen through nozzles into the solution, which produces hydrogel foams with millimeter‐sized bubbles. A rheological characterization protocol of the foam's constituent material is first implemented and highlights the impact of the initial liquid foam properties and of the competition between the solidification kinetics and the foam aging mechanisms on the resulting morphology. X‐ray tomographic characterization performed on solidifying and solidified samples then demonstrates that by controlling the temporal evolution of the foam via its formulation, it is possible to tune the final morphology of the alginate foams. This method can be adapted to other hydrogel or polymer formulations, foam characteristics and length scales, as soon as solidification processes happen on timescales shorter than foam destabilization mechanisms.

Coal gasification slag for preparation of environmentally friendly superabsorbent composites with rapid water absorption and salt tolerance

It is crucial to design the novel low-cost and salt-tolerant superabsorbent for safeguarding food security and achieving sustainable agriculture. Herein, the porous superabsorbent composites with excellent salt tolerance were fabricated by redox-initiated grafting polymerization using water-based Pickering foam template co-stabilized with solid waste of coal gasification slag and plant particles Sapindus mukorossi pericarp. The stabilization mechanism of Pickering foams, swelling performance and salt-resistance of porous superabsorbent composites were studied in detail. Due to the abundant porous structure and the presence of coal gasification slag, the obtained superabsorbent composites exhibited rapid swelling rate and excellent water absorption capability, and the maximum water absorption in distilled water and 0.9 wt% NaCl solution reached 910 g/g and 126 g/g after 30 min, respectively. As 1.5 wt% the optimal superabsorbent composites was added into the saline-alkali soil, the growth of cabbages was significantly improved, and the plant height and chlorophyll content increased by 45.0% and 12.5%, respectively. This work served as a significant reference for preparing novel environmentally friendly water-saving materials for arid saline-alkali soil improvement.

Fabrication of porous materials using quinoa husk and attapulgite co-stabilized foam templates for dye adsorption and post-treatment of soil remediation

Water-based foam has great potential in the preparation of porous materials, but there is still a lack of green and simple preparation methods. In this study, a stable water-based foam that co-stabilized with saponin leached from agricultural waste quinoa husk (QH) and nano-clay attapulgite (APT). The thickening effect and interface stability of modified APT played a crucial role in the formation and stabilization of Pickering foam. The free radical polymerization occurred in the continuous phase without affecting the foam stability, and the obtained pore-rich adsorbent displayed high-performance adsorption for methylene blue (MB) and methyl violet (MV), with the adsorption capacities reaching up to 291.95 mg/g and 430.01 mg/g, respectively. In keeping with the idea of sustainable development, the spent adsorbent was pyrolyzed and converted into mineral biochar. The pot experiments showed that the mineral biochar could improve the soil properties and promoted the plant growth. This work provided a new approach to the production of green and stable Pickering foam and also an alternative to realize the sustainable high value utilization of waste QH.

Freestanding 3D graphite foam prepared by compressed growth template for superior electro-photo thermal performance

As a promising three-dimensional (3D) graphene architecture, graphene foam has excellent structural, electrical and thermal properties. However, due to the growth template limitation of commercial nickel/copper foam, graphene foam prepared by chemical vapor deposition (CVD) has a fixed 3D framework architecture, which limits its performance and application scenarios. In this paper, independent 3D graphite foam (GF) with different thickness and longitudinal compressibility was prepared by CVD method, and it was confirmed that mechanical compression of nickel foam template before graphite film deposition had a positive effect on the electrothermal, photothermal and mechanical properties of GF. At a low driving voltage of 3 V, the heating temperature of compressed GF with a low density of 8.9 mg/cm3 and a high porosity of 99.59 % can reach nearly 600 °C, which is nearly 250 °C higher than that of uncompressed GF. The excellent electrothermal performance of compressed GF is mainly attributed to the high crystallinity and thicker thickness (150–350 nm) of the graphite layers that make up the 3D framework, thus resulting in higher electrical conductivity. Under 1 and 2 sun illumination, the temperature of compressed GF can reach 83 °C and 109 °C respectively, which is 4–7 °C higher than that of the original GF. Compressed GF has better electrothermal, photothermal and radiant heating properties than traditional graphene/graphite foam and 2D graphene/graphite film. It not only has great application potential in high-efficient and energy-saving high-temperature electric heaters and photothermal converters, but also can be used as conductive supports or fillers with better performance, and has broad application prospects in flexible electronics, household appliances, artificial intelligence, medical care and other fields.

The hollow GrF@Ni foam etched for high accuracy health management regardless of temperature

Next-generation strain sensor with excellent sensing performance is an indispensable section for wearable applications containing smart healthcare, soft robotics and human-computer interaction. Composite sensitive materials are considered as an attractive strategy because of the possibility to combine advantages of each component. But the general preparations are complex and high cost by creating the additional component. Herein, we fabricated a novel composite only through the controllable etching of nickel (Ni) foam template, without any secondary growths on the obtained graphene films (GrF). The hollow Ni skeleton not only endows this composite with an enhanced sensitivity, but also improves its sensing accuracy by compensating the thermal current effect of GrF. The obtained hollow GrF@Ni foam has been processed into a piezoresistive sensor with excellent sensing accuracy (strain error<1.7%), high gauge factor (GF=601), fast response time (<106 ms), wide sensing range (≥80%), and good cyclic stability (≥3000 cycles). Such an ideal strain sensor can be served as wearable electronics for human health management by monitoring the pulse, heart rate and joint motions reliably even in the variable temperatures.

Shortening replacement by hydroxypropyl methylcellulose-based oleogels obtained by different indirect approaches. Texture and sensory properties of baked puff pastry

Shortening in puff pastry products contains high levels of saturated and even trans-fatty acids that may be hazardous to human health. One efficient way to reduce such unhealthy fat in food is to employ gelators to structure liquid oils for the production of oleogels, thereby replacing shortening. In this paper, two types of HPMC (Hydroxypropyl Methyl Cellulose) oleogels (emulsion template and foam template) were used to replace shortening in puff pastry. Full-HD images, TPA (Texture Profile Analysis) and penetration tests, as well as TDS (Time-Dominant Sensation) sensory analysis, were used to assess the products' cross-sectional morphology, texture, and sensory attributes. The appearance of baked pastry made with 50/50 (shortening/oleogel) was similar to the control (100% shortening). In contrast, the crumb texture of baked pastry prepared with 100% oleogel was more compact and less airy than control. All samples showed similar firmness. TPA test showed that puff pastry made with 100% foam-based oleogel did not substantially differ to the control group, while samples prepared with emulsion-based oleogels were significantly harder and chewier than the control. Regarding sensory analysis, all puff pastries were mainly perceived as "crunchy" during chewing. The increase in oleogel content resulted in denser pastry, but the 50/50 foam template samples were "easier to chew". Attribute "compact" also became one of the main perceptions when the oleogel content increased to 100%, which would be related to the dense structure observed in the crumb morphology. This study confirms the feasibility of HPMC oleogels as healthy fat source in puff pastry.

Incorporating Nanoparticles in Porous Foam Templating for Enhanced Sensitivity of Capacitive Pressure Sensors

AbstractCapacitive pressure sensors based on porous foams have been demonstrated for various biomedical applications (0–10 kPa). Many different methods for fabricating porous foams have been reported. In this work, for the first time, the incorporation of silica nanoparticles are reported into the templating process of porous foams fabricated through a combination of particle and emulsion templating, in order to enhance the formation of smaller microstructures in polydimethylsiloxane foams. The foams are coated with graphene, and pressure sensors developed using these foams showed increased sensitivity, up to 4.08 kPa−1. The incorporation of nanoparticles also improves the linearity of the sensitivity, giving a linear sensitivity for the pressure sensors over a pressure range of 0–6 kPa. Further, these pressure sensors have a low limit of detection of ≈13 Pa. These results indicate that incorporation of suitable nanoparticles in the templating of foams is a promising strategy for developing foam‐based pressure sensors with high and linear sensitivity.

Construction of alumina framework with a sponge template toward highly thermally conductive epoxy composites

AbstractCeramic‐based polymer composites are commonly utilized as thermal management materials due to their high thermal conductivity and electrical insulation properties. One efficient method to enhance the thermal conductivity of these composites is by constructing a three‐dimensional thermal conductive network within the polymer matrix. In this study, alumina was coated onto the surface of polyurethane (PU) foam, followed by high‐temperature removal of the PU foam and sintering of the alumina sheets to obtain a continuous alumina framework. Epoxy resin was then infiltrated into this alumina framework to fabricate highly thermally conductive EP/f‐Al2O3 composites. The EP/f‐Al2O3 composite achieved a thermal conductivity of 2.44 W m−1 K−1 when the filler content of 26.8 vol%, representing a 400% improvement compared to EP/Al2O3 composite with randomly dispersed fillers, and a remarkable 1180% enhancement compared to epoxy resin. Infrared thermal imaging also confirmed the excellent heat dissipation capability of the EP/f‐Al2O3 composites. Overall, this research presents an effective method for producing highly thermally conductive and electrically insulating composites that can be used in electronic thermal management applications.Highlights Fabrication of porous Al2O3 frameworks/epoxy composites. Porous Al2O3 frameworks were fabricated by polyurethane foam template. The obtained EP/f‐Al2O3 composite exhibited excellent thermal conductivity.

Structure and properties study of magnesium oxide porous ceramics prepared by Organic Foam Template Method

Magnesium oxide (MgO) porous ceramics with high porosity, compressive strength and low thermal conductivity were prepared by Organic Foam Template Method. The effects of the sintering temperature, polycarboxylic acid (PCE) dispersant and pore size of organic foam template on the properties of MgO porous ceramics were investigated. The experiment results showed that with the increase of sintering temperature, the MgO porous ceramic shrinkage, skeleton density and compressive strength increased. PCE could increase the fluidity of slurry and make the framework clearer, as well as reduce the cracks formed in the process of drying effectively. When the content of PCE was 0.5 wt-%, the porosity, compressive strength and thermal conductivity of MgO porous ceramics were 88.5%, 1.6 MPa and 0.045 W/(m·K), respectively. In addition, as the pore size of the organic foam template decreased, the porosity decreased, and the resistance increased and the thermal conductivity increased.

Porous superabsorbent composites prepared from aqueous foam template and application evaluation.

Rapid water absorption is very important for the application of superabsorbent polymers under dry or semi-dry conditions, but there are currently few relevant studies. In this context, a novel porous superabsorbent of chitosan-grafted acrylic copolymer-2-acrylamido-2-methylpropanesulfonic acid/sapindus mukorossi pericarp/calcined oil shale semi-coke (CS-g-P(AA-co-AMPS)/SMP/COSSC) was prepared by a green and convenient foam template method, which was triggered by redox polymerization. The rich pore structure of the porous superabsorbent was conducive to accelerating the water absorption rate. It only took 15 min to reach a swelling capacity of 650 g g-1 in distilled water. Soil experiments show that even with the addition of 0.5 wt% porous superabsorbent, the soil water retention time can be extended to 7 days. Finally, it was applied to the growth of cabbage seeds and it was found that the growth was significantly improved. Based on these excellent properties, we expect to provide a valuable reference for the preparation of fast-absorbing materials through the green water-based foam template method, contributing to sustainable agriculture.

Fabrication of porous adsorbent by quinoa husk stabilized foam templates for dye adsorption and carbonization for soil remediation

In this study, a novel adsorbent with a sufficient porous structure was fabricated using a green and highly stable water-based foam template. This template was stabilized with agricultural waste quinoa husk (QH) and applied to remove dye pollutants in wastewater. The porous adsorbent exhibited a high adsorption capacity of 740.95 mg/g for methylene blue and 1022.1 mg/g for methyl violet. The adsorption process was well described by the Langmuir-Freundlich model and the pseudo second-order kinetic model. A sustainable concept for handling the spent adsorbent was also proposed, involving its conversion into biochar and safe return to the soil. An additional benefit was observed, as the biochar effectively adjusted the physicochemical properties of the soil and improved crop growth with the addition of 1 wt%. The potential application of porous adsorbent in wastewater treatment and the reference of sustainable strategy for disposing of other adsorbents are both noteworthy.

Fabrication and characteristics of sulfonated carbon foam via high internal phase emulsions with polypyrrole-modified carbon nanotubes

Highly conductive carbon foam with a high specific surface area was fabricated using a microporous polymer foam template with an open-cell structure. The cell size, specific surface area, electrical conductivity, and compressive properties of the foam were controlled by the polymerization, sulfonation, and carbonization of a carbon nanotube (CNT)-based high internal phase emulsion. The CNT surface was modified using polypyrrole (PPy), a conductive polymer, to increase the affinity of the CNT toward the oil phase in the high internal phase emulsion and to improve the electrical conductivity of the microporous foam after polymerization. An increase in the PPy-CNT content reduced the cell size and increased the electrical conductivity of the foam. The electrical conductivity and thermal stability of the foam were significantly improved through sulfonation. The cell morphology of the foam was maintained even after high-temperature carbonization due to its densely crosslinked structure with thioether bridges. The sulfonation of the polymer foam with PPy-CNT 1 wt%, followed by carbonization at 1000 °C, resulted in the formation of sulfonated carbon foam, which exhibited a smaller cell size (∼2 μm) and improved electrical conductivity (∼102 S/m), crush strength (∼4 MPa), and thermal stability (∼90% remaining) compared to microporous polymer foams. However, the specific surface area (∼500 m2/g) of the sulfonated carbon foam carbonized at 800 °C was significantly higher than that of the sulfonated carbon foam carbonized at 1000 °C.

Porous adsorbent prepared from eco-friendly aqueous foam templates and carbonized for soil remediation

Porous adsorption materials have garnered extensive attention in environmental remediation in recent years, but green preparation and effective post-treatment remain the main challenges in practical applications. Here, a novel porous adsorbent was successfully fabricated from the aqueous foams templates stabilized by the natural plant Sapindus mukorossi (S. mukorossi) and nano-clay attapulgite (APT) via a thermally-initiated polymerization. The as-prepared porous adsorbents exhibited abundant interconnected pore structures and demonstrated excellent adsorption properties for chlortetracycline hydrochloride (CTC) and tetracycline hydrochloride (TC), with a maximum adsorption capacity of 620 mg/g and 538 mg/g, respectively. After adsorption, the waste porous adsorbent was converted into carbon/APT material through anaerobic calcination. At a carbonization temperature of 400 °C, carbon/APT with large amounts of negative charges and oxygen-containing functional groups exhibited a good adsorption capacity for Cd2+ and showed potential as a soil remediation agent. In summary, this study presents a feasible new idea for the green preparation and post-processing of waste adsorbents, offering a promising solution to the challenges faced in practical applications.

Fabrication of rice bran protein - sodium alginate - calcium double cross-linked foam template for oleogel preparation

In this study, a flexible double-crosslinked rice bran protein (RBP) foam template was developed for oleogel preparation based on Maillard reaction and physical gelation. The Maillard reaction of RBP and sodium alginate (SA) was optimized based on foaming properties of the conjugates. The best foaming capability and foam stability were observed when RBP (50 mg/mL) and SA (30 mg/mL) were mixed at a ratio of 2:1, under ultrasonication at 320 W for 45 min. The cryogel was prepared from RBP-SA foam under freeze drying. The pore structure, density and oil affinity of RBP-SA cryogels were significantly enhanced compared to those of the RBP cryogel, leading to better oil absorption and oil holding capacity of the resultant oleogels. Calcium ion was further introduced into the conjugates to prepare the double-crosslinked foam template (RBP-SA-Ca2+). The prepared cryogel exhibited improved flexibility and oil holding capacity with reduced storage modulus, yield stress and compressive strength. In conclusion, the chemical cross-linking mainly affected the oil absorption capacity and oil holding capacity of RBP cryogel and oleogel, while the physical cross-linking mainly affected the mechanical properties of RBP cryogel. This study provided further insights into preparation of foam-templated oleogel with tunable performance and practical application.