Hybrid Foams Research Articles

Synthesis of ultrathin porous C3N4-modified Co3O4 nanosheets for enhanced oxygen evolution reaction

Oxygen evolution reaction (OER) plays important roles in energy storage and conversion technologies, but the sluggish kinetics of OER may result in a large overpotential, and thus there is urgent need for the exploration of new electrocatalysts with a low overpotential and good stability. In this research, we integrate the melamine-assisted alkaline cobalt carbonate (CoCH) nanosheets pyrolysis with high-temperature solid phase fusion to construct the 1-C3N4/Co3O4/Ni foam hybrid electrode with Co3O4 ultrathin porous nanosheets as the host, trace C3N4 as the guest, and Ni foam (NF) as the current collector. Benefiting from the unique structure, the obtained 1-C3N4/Co3O4 hybrid nanosheets can significantly reduce the charge transfer distance between the catalysts to electron collector and improve the electron transportation during the OER process. Moreover, the intimate interaction of Co3O4 with C3N4 can induce a charge redistribution at the interface. Consequently, the 1-C3N4/Co3O4/NF hybrid electrode exhibits an enhanced OER performance (166 mV at 10 mA•cm−2) and good stability, superior to the commercial RuO2 particles and the reported transition metal-based electrocatalysts.

Development and characterization of sawdust and sisal fiber reinforced vegetable based polyurethane foam hybrid composites

ABSTRACT Polyurethane foam derived from vegetable oils can be used as a matrix in composites with Pinus taeda sawdust and Agave sisalana fibers. The aim of this work was to obtain and characterize polyurethane foam composites derived from vegetable oil reinforced with Pinus taeda sawdust and dispersed sisal short fiber. The composites were produced in five different proportions and were analyzed by images, mechanical and physical tests. Composites with 50% foam, 37.5% sawdust and 12.5% sisal had the highest bending resistance, 11.31 MPa, and the best results after 2 hours of immersion. Composites were considered suitable for furniture and craft use.

Cellulose nanofibrils-based hybrid foam generated from Pickering emulsion toward high-performance microwave absorption

The development of multifunctional microwave absorbers that worked in complex environments remains challenging. In this study, oil-in-water Pickering emulsion gelation approach was combined with freeze-drying to prepare foam-based microwave absorbers along with appealing photo-thermal conversion and thermal insulation. In hybrid foam, cellulose nanofibrils (CNF) and polylactic acid (PLA) serve as three-dimensional skeleton, where carbon nanotubes (CNT) and Fe3O4 nanoparticles are homogeneously incorporated, which forms a conductive network with hetero-interfaces. The optimal reflection loss value of the foam reaches −65.14 dB with a thickness of 3.0 mm. The foam also demonstrate high photo-thermal conversion performance with its surface temperature up to 97 °C after irradiation under 1 Sun for 5 min. Additionally, the foam shows superior thermal insulation comparing with the commercial polyvinyl alcohol and polyurethane foams. This study may offer a promising approach to develop ultralight and high-performance microwave absorber with great potential for multifunctional applications.

Dynamic impact testing of cellular solids and lattice structures: Application of two-sided direct impact Hopkinson bar

Direct impact testing with a Hopkinson bar is, nowadays, a very popular experimental technique for investigating the behavior of cellular materials, e.g., lattice metamaterials, at high strain-rates as it overcomes several limitations of the conventional Split Hopkinson Pressure Bar (SHPB). However, standard direct impact Hopkinson bars (DIHB) have only single-sided instrumentation complicating the analysis. In this paper, a DIHB apparatus instrumented with conventional strain-gauges on both bars (a so called Open Hopkinson Pressure Bar - OHPB) is used for dynamic impact experiments of cellular materials. Digital image correlation (DIC) is used as a tool for investigating the displacements and velocities at the faces of the bars. A straight-forward wave separation technique combining the data from the strain-gauges with the DIC is adopted to increase the experiment time window multiple times. The experimental method is successfully tested at impact velocities in a range of 5−30m·s−1 with both linear elastic and visco-elastic bars of a medium diameter. It is shown that, under certain circumstances, a simple linear elastic model is sufficient for the evaluation of the measurements with the visco-elastic bars, while no additional attenuation and phase-shift corrections are necessary. The applicability of the experimental method is demonstrated on various experiments with conventional metal foams, hybrid foams, and additively manufactured auxetic lattices subjected to dynamic compression.

Carbon Fiber and Syntactic Foam Hybrid Materials via Core–Shell Material Extrusion Additive Manufacturing

AbstractBiological materials often employ hybrid architectures, such as the core–shell (C–S) motif present in porcupine quills and plant stems, to achieve unique specific properties and performance. Drawing inspiration from these natural materials, a new method to fabricate lightweight and stiff C–S architected filaments is reported. Specifically, a C–S printhead conducive to printing highly loaded fiber‐filled inks, as well as a new low‐density syntactic foam ink, are utilized to 3D‐print C–S architectures consisting of a syntactic epoxy foam core surrounded by a stiff carbon fiber‐reinforced epoxy composite shell. Effective printing of test specimens and structures with controlled geometry, composition, and architecture is demonstrated. The new foam ink exhibits density as low as 0.68 g cm−3 and C–S structures exhibit up to 25% higher specific flexural stiffness (E1/3/ρ) than either constituent alone. Finally, a new mechanical model is presented to predict this performance improvement while accounting for potential eccentricity of the core.

Green one-pot synthesis of binder-free porous edge-functionalized graphitic carbon nitride/iron oxide nanoparticles nanocomposite as an outstanding electrode for supercapacitors

Herein, a novel and facile electrophoretic/electrochemical deposition (EPD/ECD) method is reported for the fabrication of binder-free high-performance Fe3O4/functionalized g-C3N4 nanocomposite. In this method, through a simple EPD/ECD procedure, Fe3O4 nanoparticles are in situ simultaneously synthesized onto the edge-functionalized g-C3N4 (ef-g-C3N4) sheets electrophoretically deposited onto Ni foam. For comparison, pristine Fe3O4 nanoparticles and ef-g-C3N4 are deposited onto Ni foam via EPD and ECD procedures, respectively. The prepared materials are fully analyzed through XRD, TGA, FT-IR, Raman, FE-SEM, TEM as well as BET/BJH techniques. These analyses results verified co-deposition of fine Fe3O4 particles along with porous ef-g-C3N4 sheets onto the Ni-foam cathode, and formation of Fe3O4@ef-g-C3N4@Ni foam hybrid electrode. The formation mechanism of Fe3O4/ef-g-C3N4 nanocomposite through EPD/ECD was proposed and described in details. The electrochemical behaviors of the prepared electrodes were investigated as a binder-free supercapacitor electrodes. The results charge-discharge tests revealed that Fe3O4@ef-g-C3N4/NF is capable to deliver specific capacitance of 197.2 mA h g−1 at 0.5 A g−1 and cycle life of 96.1 % and 88.5 % after 4000 continuous cycling at current densities of 0.5 and 3 A g−1, respectively, whereas the pristine Fe3O4/NF delivered only specific capacitance of 76.9 m g−1 at 0.5 A g−1 and cycling stability of 87.6 % and 60.8 % at the similar conditions. These findings proved surprising positive synergistic contribution between Fe3O4 and edge-functionalized g-C3N4 to present high supercapacitive ability.

Characterization and properties of hybrid foams from nanocellulose and kaolin-microfibrillated cellulose composite

Hybrid nanocellulose-based foams are a desirable class of low-density and porous materials for their potential in many applications. This study aims at characterizing and understanding the structure-properties relationship of four foam formulations prepared from combinations of cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), and kaolin-microfibrillated cellulose composite. All the foams were crosslinked with a polyamide-epichlorohydrin crosslinker (Polycup) to impart stability under wet conditions without additional functionalization. Foams containing 25 wt% kaolin exhibited excellent shape recovery promoted by a higher load of crosslinker (5 wt%), and superior compressive properties. The addition of CNC at 33.3 wt% and 50 wt% did not seem to enhance the properties of the foam and also reduced the specific surface area. A preliminary comparative study between the four tested formulations was conducted to assess the feasibility of the foam as an adsorbent of methylene blue dye.

Mechanical and thermal properties of PVC and polyurethane foam hybrid composites

Abstract Sandwich foam composites are mostly used today in structural applications in aerospace and automobile industries due to light weight and high stiffness of the sandwich composites. In this research work, the composites were fabricated by using polyurethane and PVC foam and carbon fiber as skin. Sandwich composites were fabricated by the hand lay-up method. Mechanical tests such as tensile, flexural, impact, double shear, inter delamination and hardness tests were conducted. A thermo gravimetric analysis (TGA) test was also performed for the analysis of the temperature characteristics of the sandwich composites. The internal structures of tested samples were analyzed through a scanning electron microscope (SEM). The results show that the tensile, flexural, impact, thermal and inter delamination strengths of PVC foam composites are superior to those of other composites.

Hierarchical, seamless, edge-rich nanocarbon hybrid foams for highly efficient electromagnetic-interference shielding

Lightweight, flexible, ultrahigh-performance electromagnetic-interference (EMI) shielding materials are urgently required in the areas of aircraft/aerospace, portable and wearable electronics. Herein, 1D carbon nanotubes (CNT) and carbon nanofibers (CNF) with 2D edge-rich graphene (ERG) are used to form a lightweight, flexible CNT-ERG-CNF hybrid foam. This foam was fabricated through a self-sacrificial templating chemical vapor deposition process, where nanocarbons bond through covalent bonding, forming a hierarchical 3D hybridized carbon nanostructure. Multistage conductive networks and heterogeneous interfaces were constructed using edge-rich nanocarbons to increase the induced currents and interfacial polarization which makes great contributions to achieve high absorption electromagnetic shielding effectiveness (SEA). The CNT-ERG-CNF hybrid foam exhibits EMI shielding effectiveness (SE) exceeding 55.4 dB in the X-band while the specific SE (SSE, SE divided by mass density) achieves 9200 dB cm3 g-1, which surpasses that of nearly all other carbon-based composite materials. Furthermore, the structural stability and durability of the flexible CNT-ERG-CNF hybrid foams is examined by measuring EMI SE after 10000 times cyclic bending. Remarkably, this work not only provides a new idea for preparing hierarchical carbon materials for a wide range of applications, but presents some fundamental insights for achieving higher absorption losses in EMI shielding materials.

Fabrication of Green Diatomite/Chitosan-Based Hybrid Foams with Dye Sorption Capacity.

The latest tendency of the scientific community regards the development of different classes of green materials able to solve pollution problems caused by industrial and human activity. In this paper, chitosan and diatomite were used to produce a broad-spectrum hybrid adsorbent, either in powder or in monolithic form for environmental pollutant removal. Diatomite–chitosan-based powders and porous diatomite–chitosan hybrids were prepared and characterized by chemical-physical, thermal and morphological analysis. Moreover, their adsorbent capacity towards anionic dye (Indigo Carmine) was also evaluated. Obtained data showed that chitosan improves the adsorption capacity of both systems, increasing the uptake of dye in both diatomite–chitosan systems.

Mechanical behavior of sandwich panels with hybrid face sheets and embedded super-elastic SMA wires under quasi-static loading: An experimental investigation

In this paper the experimental behavior of sandwich panels with hybrid composite face sheets and SMA wires under quasi-static loading test was investigated. The square-shaped sandwich panel was composed of a foam core and hybrid composite face sheets consisted of carbon-epoxy and glass-epoxy laminates, in which pre-strained super-elastic SMA wires were placed between the laminates. Sandwich panels had three types of layouts, with symmetric and asymmetric face sheets and with or without the SMA wires between the layers of the faces of the panel. The panels were subjected to quasi-static loading using the Universal testing machine Zwick 250H. The response of quasi-static loading was presented as force-displacement diagrams for sandwich panels. Moreover, the damage morphology of panels after quasi-static loading test was presented by scanning electron microscope (SEM) and the damaged surfaces of the panels were estimated by active infrared thermography of the damage surface. Through comparing the damage level on the sandwich panels, the effect of the presence of the SMA wires, as well as the symmetry or asymmetry of the panel surfaces in reinforcing the structure and reducing the level of damage caused by quasi-static loading were investigated. The comparison of the behavior of the panels under the quasi-static loading test indicated that the use of SMA wires in the front face and the asymmetry of the surfaces were more effective and reinforced by applying more carbon layers in the back face to increase panel resistance.

Micromechanical Characterisation of Ni/PU Hybrid Foams.

The computer-aided design of individual parts and the desire for weight reduction and material savings require further development of new hybrid materials. Ni/PU hybrid foams as a new hybrid material offer great potential for the production of components that are lightweight and yet can absorb large amounts of energy. The development of this structured material is at its beginning and mechanical characterisation on all scales is necessary. Experimental investigations on individual struts must be carried out on the micro scale to understand the structure-properties-relationship. Inspite of the challenges raising due to the complex geometry of the struts, tensile tests, three-point bending tests and micro sections are presented in this work. Due to the stiff Ni coating on the outer diameter of the struts, the resistance against bending is around five times as high as against tensile loading. The correlation between the behaviour of the struts and the macroscopic material behaviour validates the planned use of the foams as energy absorbers.

Three dimension phenolic resin derived carbon-CNTs hybrid foam for fire retardant and effective electromagnetic interference shielding

Three dimension fire retardant carbon-CNTs hybrid foams for electromagnetic interference (EMI) shielding effectiveness (SE) were fabricated using a polyurethane (PU) template. Phenolic resin with different contents (0.2–2 wt.%) of mutltiwalled carbon nanotubes (MWCNTs) was mixed using a magnetic stirrer for making a homogenous slurry and then PU foam was impregnated in this slurry followed by carbonization at 1000 °C. The foams were characterized for their morphological, structural, mechanical, EMI shielding, and fire-retardant properties. The total EMI shielding effectiveness (SE) of -57.2 dB was achieved for the carbon foam containing 1 wt.% MWCNTs in the frequency range of 8.2–12.4 GHz. Moreover, the addition of MWCNTs into phenolic resin also enhanced the compressive strength (6.5 MPa), thermal stability and fire retardant performance of carbon-CNTs hybrid foams. The multifunctional carbon-CNTs hybrid foams demonstrate that they are outstanding materials with potential applications in EMI shielding and thermal management for defense and aerospace sectors.

High-temperature Compressive Performance of Mg Alloy Foams Coated with Ni-P Layer

Mg/Ni hybrid foams were fabricated by the electroless method. The Ni-P (Nickel-Phosphorous) coatings were deposited on the surface of closed-cell Mg alloy foams. The composition, microstructure and phases of the Ni-P coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The compressive tests were performed on the Mg/Ni hybrid foams at 400 °C using the Mg alloy foams as a reference. The experimental results show that the yield strength, plateau stress and energy absorption capacity of the closed-cell Mg alloy foams at high temperature were improved by the Ni-P coating. And there are four main modes for the Mg/Ni hybrid foam failure at 400 °C, i e, shearing in cell wall, bending in cell edge, shedding and cracking in Ni-P coating.

Fabrication of ultra-light LM13 alloy hybrid foam reinforced by MWCNTs and SiC through stir casting technique

In the present work, a novel approach was used for the synthesis of ultra-light closed cell Al-hybrid foam reinforced with functionalized Multiwall carbon nanotubes (MWCNTs) and silicon carbide (SiC) particles through stir casting technique. In this work, up to 93%, porous hybrid foam with uniform cell size were successfully prepared. For uniform dispersion of MWCNTs within the matrix, first MWCNTs were functionalized in HNO3 solvent with magnetic stirring followed by partial ball milling with Al powder and SiC particles. Obtained results show that the plateau stress and energy absorption capacity of prepared ultra-light foams are excellent.

Lightweight carbon-red mud hybrid foam toward fire-resistant and efficient shield against electromagnetic interference

Lightweight, porous, high-performance electromagnetic interference (EMI) shielding and fire-resistant materials are highly demanded in aerospace and defense applications. Due to the lightweight, open porosity and high surface area, carbon foam has been considered as one of the most promising candidates for EMI shielding applications. In the present investigation, we demonstrate the development of novel carbon-red mud hybrid foams with excellent EMI shielding effectiveness (SE). The carbon-red mud hybrid foams are prepared using phenolic resin as a carbon source and red mud (industrial waste) as filler. We observed that the inclusion of red mud in carbon-red mud hybrid foams significantly enhances their dielectric, magnetic, EMI shielding and thermal properties. The EMI shielding results show that absorption is the main contributor to the total EMI SE. The maximum total EMI shielding effectiveness is achieved to be 51.4 dB in the frequency range of 8.2–12.4 GHz for carbon-red mud hybrid foam having 20 wt. % of red mud. The CF-RM20 also showed excellent fire resistance and high thermal stability at elevated temperatures.

Multifunctional Bulk Hybrid Foam for Infrared Stealth, Thermal Insulation, and Microwave Absorption.

Taking serious microwave pollution issues and the complex application environment into consideration, it is quite urgent to integrate several functions into one material. Electromagnetic (EM) absorbing materials with multiple functions are highly attractive to next-generation wireless techniques and portable electronic devices. Herein, melamine foam provides a decent platform for the uniform growth of Co-based metal-organic frameworks (MOFs), which bring the as-obtained hybrid foam with three-dimensional porous network structure and combination of dielectric along with magnetic attenuation abilities as advanced materials in multifunctional fields. Remarkably, the relevant microwave absorption (MA) performance of the hybrid foam can reach an extremely high reflection loss value of -59.82 dB. Furthermore, the hybrid foam exhibits excellent infrared stealth and optimiztic heat insulation function, demonstrating the potential in plenty of practical applications. These results may arouse interests and inspirations of the elaborately design and facilely synthesis of high-performance foamlike microwave absorbers with multiple functions.

Well-connection of micro-platinum and cobalt oxide flower array with optimized water dissociation and hydrogen recombination for efficient overall water splitting

Integrating the merits of various catalytic materials into one novel hybrid is significant yet challenging in developing multifunctional electrode for overall water splitting. In this work, micro-platinum modification strategy is developed to construct the bifunctional Pt@Co3O4/Ni foam (NF) hybrid electrode for overall water splitting. The resultant Pt@Co3O4/NF electrode exhibits low overpotentials and favorable kinetics for both hydrogen (30 mV@10 mA cm−2, 31 mV dec−1) and oxygen evolution (263 mV@10 mA cm−2, 69 mV dec−1). Moreover, a voltage of ~ 1.53 V can drive a current density of 10 mA cm−2 for the two-electrode electrolyzer. The enhanced performance of Pt@Co3O4/NF hybrid could be attributed to the synergistic effect of micro-Pt modified Co3O4 nanorod array with the optimized water cleavage and hydrogen recombination. This work not only reports an efficient hybrid electrode for overall water splitting but also offers valuable insights in designing multifunctional electrocatalysts for energy conversion technologies.

Reusable hybrid foam catalyst for hydrolytic dehydrogenation of amine adducts of borane: Porous PVA-Immobilized Co–Ru nanoparticles

Abstract In this study, reusable hybrid foam catalyst was synthesized, based on reduction of cobalt and ruthenium ions into polyvinyl alcohol (Co–Ru/PVA), for hydrolysis of ammonia borane (NH3BH3, AB) and its derivative methylamine borane, (CH3NH2BH3, MeAB), to generate hydrogen. Sixteen different hybrid catalysts were synthesized under different preparation conditions. The effect of different independent variables such as reduction medium and temperature, solvent, and post-treatment on hydrogen evolution rate as a dependent variable was evaluated using the Analysis of Variance (ANOVA). It was found that Co–Ru/PVA-16 was exhibited the highest catalytic activity for the NH3BH3 hydrolysis reaction based on the statistical analysis observations. The Co–Ru/PVA-16 hybrid catalyst was characterized by several advance techniques as X-ray diffraction (XRD), X-ray photoelectron electron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), inductively coupled plasma mass spectrometry (ICP-MS) and Fourier transform Infrared spectroscopy (FT-IR). High initial turnover frequency (TOF) of 3384.23 molH2mol−1CoRumin−1 and 346.16 molH2mol−1CoRumin−1 were reported for NH3BH3 and CH3NH2BH3 hydrolysis, respectively. Besides high catalytic activity, Co–Ru/PVA-16 hybrid catalyst was reused in the hydrolysis of NH3BH3 over 46 cycles without decrease in H2 evolution rate.

Surface Modification of Cured Inorganic Foams with Cationic Cellulose Nanocrystals and Their Use as Reactive Filter Media for Anionic Dye Removal.

In this work, a surface cationized inorganic–organic hybrid foam was produced from porous geopolymer (GP) and cellulose nanocrystals (CNCs). GPs were synthesized from alkali-activated metakaolin using H2O2 as a blowing agent and hexadecyltrimethylammonium bromide (CTAB) as a surfactant. These highly porous GPs were combined at pH 7.5 with cationic CNCs that had been synthesized from dissolving pulp through periodate oxidation followed by cationization in a deep eutectic solvent. The GP-CNC hybrid foams were employed as reactive filters in the removal of the anionic dye, methyl orange (MO; 5–10 mg/L, pH 7). The effects of a mild acid wash and thermal treatments on the structure, properties, and adsorption capacity of the GPs with CNCs and MO were investigated. The CNCs aligned as films and filaments on the surfaces of the neutralized GPs and the addition of CNCs improved MO removal by up to 84% compared with the reference sample. In addition, CTAB was found to disrupt the attachment of CNCs on the pores and improve adsorption of MO in the GPs with and without CNCs.