Monolithic Foam Research Articles

3D-printed thermally expanded monolithic foam for solid-phase extraction of multiple trace metals.

Digital light processing (DLP) 3DP, commercial acrylate-based photocurable resins, and thermally expandable microspheres-incorporated flexible photocurable resins were employedto fabricate an SPE column with athermally expanded monolithic foam for extracting Mn, Co, Ni, Cu, Zn, Cd, and Pb ions prior to the determination using inductively coupled plasma mass spectrometry. After optimizationofthe thermally activated foaming, the design and fabrication of the SPE column, and the automatic analytical system, the DLP 3D-printed SPE column with the thermally expanded monolithic foam extracted the metal ions with up to 14.8-fold enhancement (relative to that without incorporating the microspheres), with absolute extraction efficiencies all higher than 95.6%, and method detection limits in the range from 0.5 to 5.2ng L-1. We validated the reliability and applicability of this method by determination ofthe metal ions in several reference materials (CASS-4, SLRS-5, 1643f, and Seronorm Trace Elements Urine L-2) and spikedseawater, river water, ground water, and human urine samples. Theresults illustrated that to incorporate the thermally expandable microspheres into the photocurable resins with a post-printing heating treatment enabled the DLP 3D-printed thermally expanded monolithic foam to substantially improve the extraction of the metal ions, thereby extending the applicability of SPE devices fabricated by vat photopolymerization 3DP techniques.

3D monolithic composites TiO2/HKUST-1/RGO@melamine foam with improved surface mass transfer for efficient photocatalytic degradation of toluene gas

Currently, photocatalytic technology mostly uses powdered TiO2 catalysts, which are not conducive to recycling, limit the contact between volatile organic compounds (VOCs) and the photocatalyst, and result in lower mass transfer efficiency in gas-solid reactions. Meanwhile, TiO2 catalysts including the electrospun TiO2 nanofibers with hydrophilic surfaces are not favorable for the infiltration and adsorption of non-polar VOCs. To solve these problems, in this work, the monolithic composites TiO2/HKUST-1/RGO@melamine foam (named MRTH) with improved surface mass transfer composed of metal-organic framework (HKUST-1), graphene oxide (GO) and electrospun TiO2 nanofibers was designed. The metal-organic framework HKUST-1 plays a role in promoting the adsorption of toluene, while the reduced graphene oxide (RGO) facilitates the infiltration of non-polar molecules on the surface of the composite and has better electron transport capability. A type II heterojunction between the electrospun TiO2 nanofibers and HKUST-1 formed in the monolithic composites suppresses the recombination of electron-hole pairs and extends their lifespan. Comparing with the bare electrospun TiO2 nanofibers, the MRTH foam composites exhibit a wider light absorption range, hydrophilic and oleophobic properties and a higher separation efficiency of photogenerated carriers. In 90 min of dark adsorption, the removal rate of toluene over MRTH-8 was 52.32 %, while under irradiation by xenon lamp for 150 min, the removal rate over MRTH-8 reached 90.15 %. The amount of monolithic foam composites can also be easily adjusted in the reactor to achieve the best possible removal of the contaminant. The prepared composite materials have been characterized in detail, and the possible mechanisms have also been discussed. The foam composites prepared in this work have high catalytic activity and gas-solid reaction mass transfer efficiency, so they have wide practical application prospects in the field of VOCs abatement.

КАРКАС ЛСТК И ПЕНОБЕТОН: ПОВЫШЕНИЕ КАЧЕСТВА СТРОИТЕЛЬ-СТВА ЖИЛЬЯ

The article presents a frame made of galvanized bent lightweight profiles, which is filled with non-autoclaved monolithic foam concrete of light density grades in a non-removable formwork made of waterproof plates

Thermochemical Oxygen Pumping with Perovskite Reticulated Porous Ceramics for Enhanced Reduction of Ceria in Thermochemical Fuel Production

AbstractWithin this work, reticulated monolithic foams and granules made from CaMnO3 − δ and strontium substituted variations are demonstrated to significantly improve the performance of a water splitting redox oxide when employed as a thermochemical oxygen pumping material. Two different process procedures are tested and foams made from Ca0.9Sr0.1MnO3 − δ with a strontium content of 10% outperform all other specimens in both process configurations. Additionally, the performance of Ca1 − xSrxMnO3 − δ with varying strontium content as a thermochemical oxygen pumping material is studied by means of a newly developed theoretical process model. While the model does not precisely predict the excellent experimental performance of strontium‐substitute compositions, it provides valuable insights into the impact of geometry and structure on the specimen's performance in thermochemical oxygen‐pumping processes. This work demonstrates the practical application of monolithic 3D structures made entirely from perovskite material in thermochemical oxygen pumping processes and provides a process model that can serve as basis for material screening and process optimization in future work.

Superhydrophobic foam combined with biomass-derived TENG based on upcycled coconut husk for efficient oil-water separation.

The ocean ecological environments are seriously affected by oil spilling and plastic-debris, preventing and significantly reducing marine pollution via using biocomposite production from natural fiber reinforcement is a more friendly way to deal with marine oil pollution. Herein, we upcycled coir-coconut into lignin and coconut shell into spherical TENG by a combination of dip-dry and chemical treatment and used the SiO2 nanoparticles together with cellulose nanofibrils to prepare serial sugar-templated, anisotropic and hybrid foams. The as-prepared lignin/SiO2 porous sponge (LSPS) with a hierarchical porous morphology and uniformly dispersed nanoparticles structure benefits from the advantages of biomass-based additives, which presents reversible large-strain deformation (50%) and high compressive strength (11.42 kpa). Notably, the LSPS was significantly more hydrophobic (WCA ≈150°) than pure silicone-based foams, and its selective absorbability can separate oil from water under continuous pumping. Meanwhile, the coconut husk was also upcycled as a spherical TENG shell by a combination of the nanofiber-enhanced polymer spherical oscillator (CESO), which possessed high triboelectric properties (Uoc = 272 V, Isc = 14.5 μA, Q = 70 nC) and was comparable to the plastic shell TENG at low frequency (1.6 Hz). The monolithic foam structure developed using this clean synthetic strategy holds considerable promise for new applications in sustainable petroleum contamination remediation.

Combining structure design and surface modification of BPO4 solid acid catalyst to boost the anti-coking performance in dehydration reaction of glycerol

Catalytic vapor-phase dehydration of glycerol is an energy-efficient and environmentally friendly route for producing acrolein, a valuable organic chemical intermediate. However, anti-coking is one of the key problems due to the excessively acid catalytic sites and sluggish mass transfer, restricting the industrial application of this reaction. Herein, potassium element modified BPO4 monolithic foams with the hierarchically porous structure were synthesized by adding potassium element in the gel precursor of BPO4. The catalyst introducing 3% K exhibited the best acrolein selectivity of 81.0% with nearly complete glycerol conversion. In a 10-hour run of the reaction at 320 °C, the selectivity of acrolein could remain at 75.9% with 94.5% glycerol conversion, indicating the superior stability. The excellent activity and stability for 3% K-BPO4 is mainly attributed to the synergetic effect between hierarchical structure providing favorable mass transfer and appropriate acid catalytic sites inhibiting over dehydration reaction. They not only boost activity but also reduce coking, providing a unique approach for the design of solid acid catalyst.

Solar Desalination with Monolithic Foams Containing a Combination of Graphite and SnSe Featured with a Hierarchical Structure and Bimodal Pores for Spontaneous Salt Rejection

The increasing interest in solar water evaporation technology is due to its potential to replace conventional desalination systems. In this study, we suggest a new solar desalination system that has a hierarchical photothermal structure and is structurally monolithic. The overall membrane is made up of a macroscale porous melamine foam frame that acts as a porous insulator and a mass transfer layer. The mass transfer layer is designed with a bimodal porous structure of melamine foam, with large pores coated with a composite of graphite and SnSe (G-SnSe) and small pores. This simple structure provides many benefits. First, it combines two photothermal mechanisms, thermal vibration in graphite and non-radiative relaxation in SnSe, to achieve synergies in the conversion of light to heat energy. Second, compared to the single materials, graphite or SnSe alone, the nanocomposite of G-SnSe has a higher effective surface area, resulting in increased solar absorption. Finally, the melamine foam structure with bimodal pores enhances seawater wicking and has a high salt rejection capacity due to its volumetric porosity bimodal configuration of up to 35%. The monolithic melamine foam with a hierarchical photothermal structure minimizes interference with water transport due to the resistance-free presence of a continuous interfacial layer.The monolithic structure evaporaters (MSE) achieved a high evaporation rate of 1.303 kg m-2h-1 under 1 sun condition due to increased capillarity by the small-scale pores in the photothermal layer. Furthermore, spontaneous salt rejection was observed during solar desalination, attributed to the presence of intrinsic large-scale pores in melamine foam for draining the concentrated salt water from the surface. The feasibility of outdoor solar desalination was established, with a high evaporation rate of 1.259 kg m-2h-1. The mechanical stability of MSE was achieved by incorporating a small amount of binder (less than 3% of total photothermal materials), maintaining efficient performance for up to 30 days without degradation. The proposed strategy in the simple monolithic structure with bimodal porosity provides a general toolkit for designing high-performance solar desalination devices due to high evaporation rate and spontaneous salt rejection capability.In summary, the solar water evaporation technology is becoming increasingly popular as a possible replacement for traditional desalination systems. We propose a novel monolithic solar desalination system with a hierarchical photothermal structure, which is composed of a macroscale porous melamine foam as a skeleton which has both roles : an insulator and a mass transfer layer. The bimodal porous structure of melamine foam with large pores coated with a composite of graphite and SnSe provides many benefits, including increased solar absorption and a high salt rejection capacity. The MSE structure achieves a high evaporation rate and spontaneous salt rejection, making it a feasible option for outdoor solar desalination. The proposed strategy provides a general toolkit for designing high-performance solar desalination devices.

Flexural stiffness of lightweight steel-concrete slab panels made of low-density foam concrete

Lightweight steel-concrete structures (LSCS) are a type of steel-concrete structures where the filling concrete is monolithic (pouring) foam concrete with density 100-1000 kg/m3, the profile steel is lightweight steel thin-walled structures (LSTS), and fiber cement panels perform the function of non-removable formwork. As a rule, these structures are made of structural and heat-insulating foam concrete, which has good insulation and technical characteristics and sufficient strength. The object of the study is lightweight steel-concrete slab panels, which are one of the special cases of LSCS, made of monolithic foam concrete with density of 400 kg/m3. An analysis of the bending stiffness of LSBC slab panels by comparing the experimental data with analytical calculations was carried out. It was found that bendable LSCS made of monolithic foam concrete with density of 400 kg/m3 operate in physical nonlinear way. It was shown that the bending stiffness of LSCS floor panels can be determined as the sum of stiffnesses of profiled steel and foam concrete at the linear stage of work. The reliability of the proposed methodology within the limits of linear operation was demonstrated. It was proved both experimentally and theoretically that the bending stiffness of panels based on LSCS is higher than the bending stiffness of similar panels made of lightweight thin-walled steel (LTSS) by about 30%.

Исследование продуктов гидратации пенобетонов неавтоклавного твердения

The published work presents an X-ray phase analysis of non-autoclaved foam concrete. According to the results of X-ray phase analysis of non-autoclaved foam concrete, it was found that by 56 days of normal hardening, further reactions of cement hydration and binding of $Ca(OH)_2$ occur, reflections of tobermorite-like low-basic calcium hydrosilicates CSH (II) increase with d = (3.07; 2.10 ) Å, which are involved in the hardening process, which consists in the monolithic foam concrete matrix, the formation of a glossy porous layer, the healing of defects in the interpore partitions, which leads to a significant increase in the operational characteristics of the material.

Monolithic foam of oriented boron nitride bowl for selective oxidative dehydrogenation of propane and pollutant removal

Bowl-like structures have great potential in the field of catalysis, environmental remediation, energy storage, etc., because of the large surface area, porous structure, and buffer hollow space. Herein, we developed a unique approach to control the opening direction of bowl-like structures via self-assembly strategy at the gas/liquid interface of liquid B2O3 environment foam. BN@BPO4 self-supporting monolithic foam with oriented bowl-like structure was obtained, which is built by numerous oriented bowl-like blocks and shows a double layer structure with face-to-face opening. The opening size can be adjusted by changing the amount of Cu(NO3)2 additives that is beneficial for the production of hexagonal boron nitride (h-BN). We believe the as-generated h-BN can enhance the gas trapping capacity of liquid B2O3 environment foam to precisely control pressure differential between large and small bubbles and thus favors the oriented opening of bowl-like structure. Further, pure h-BN monolithic foam with oriented bowl-like structure prepared at higher temperature possessed multimodal hierarchically porous structure and excellent performance in the catalytic oxidative dehydrogenation of propane into propene and the removal of organic pollutants. This work provides an extended assembly interface strategy of oriented bowl-like structure materials for different applications.

Catalytic Pt/Al2O3 Monolithic Foam for Ethanol Reforming Fabricated by the Competitive Impregnation Method.

Here, the synthesis of Pt/Al2O3 catalysts on a monolithic foam employing the competitive impregnation method is presented. NO3 - was used as a competitive adsorbate at different concentrations in order to delay the adsorption of Pt, minimizing the formation of Pt concentration gradients throughout the monolith. The catalysts' characterization includes the BET, H2-pulse titration, SEM, XRD and XPS techniques. The catalytic activity evaluation was performed under partial oxidation and autothermal reforming of ethanol in a short contact time reactor. The competitive impregnation method was able to produce better dispersion of the Pt particles through the Al2O3 foams. XPS analysis indicated the catalytic activity of the samples, by the presence of metallic Pt and Pt oxides (PtO and PtO2) in the internal regions of the monoliths. Compared to other Pt catalysts reported in the literature, the catalyst produced by the competitive impregnation method was revealed to be selective toward H2. Overall, the results showed that the competitive impregnation method employing NO3 - as the co-adsorbate is a promising technique to synthesize well dispersed Pt catalysts over α-Al2O3 foams.

Steel profile corrosion resistance in contact with monolithic foam concrete

The study evaluates corrosion resistance of steel profiles in contact with monolithic foam concrete with a thickness of 5 and 10 mm. There are two types of samples: structural steel ones and cold-formed galvanized steel ones. A visual examination of samples exposed to high temperature and relative humidity is carried out. The corrosion resistance of profiles made of structural steel and cold-formed galvanized steel in full contact with monolithic foam concrete provides. Metal passivation (formation of a protective film) occurs due to the high alkalinity of foam concrete. The pH values of concrete and concrete mixture, experimentally obtained, vary in the range of 12.18 ... 12.36 at all stages of the structural behavior. This indicates a favorable highly alkaline environment for profile steel.

Fabrication of γ-Al2O3 Nanoarrays on Aluminum Foam Assisted by Hydroxide for Monolith Catalysts.

Heat distribution and good adhesion of the washcoat on monolith catalysts are critical to improving catalytic activity and long-term stability. Compared with cordierite, metal foam presents a high thermal conductivity coefficient. Also, the availability of "washcoat" in situ grown on metal substrates opens the door to eliminating the problem of coating peeling. Generally, hydrothermal or thermal methods are used for the fabrication of in situ grown washcoat on metal substrates. In this research, the aluminum foam monolith vertically aligned Al2O3 nanowire array is successfully prepared at ambient temperature in an alkaline solution for the first time. Furthermore, the Pt-loaded Al2O3 nanowire array (0.5 gPt/L monolith) is applied to C2H4 degradation. The catalyst converts 90% C2H4 at 147 °C with a gas hourly space velocity (GHSV) of 20,000 h-1. And a little decrease (1%) is observed in catalytic activity, even in 15 vol % water vapors. The catalysts show good thermal stability and water resistance property over 36 h at 300 °C. Above all, this study presents a simple way of in situ growth of washcoat on metal-substrate monolith with potentially scaled manufacturing. And the monolith catalyst shows good catalytic performance on C2H4, which can be applied for volatile organic compound treatment.

Graphite/SnSe hybrid-embedded monolithic foams with hierarchical and bimodal pores for high performance solar desalination membranes with spontaneous salt rejection

Solar water evaporation techniques have attracted considerable interest due to their strong potential to disrupt existing desalination systems. As the interfaical solar steam generation has been heavily studied to explore the strategies to increase light absorption, recent effort has been focused on the development of mass transfer-based interfacial layer. Here, we propose monolithic solar evaporator (MSE) having a hierarchical mass transfer layer made of a melamine foam skeleton coated with graphite and tin selenide photothermal materials (G-SnSe). Unlike conventional solar evaporator structures consisting of double or three layers, the MSE has a monolithic configuration on top of wihch G-SnSe forms the bimodal porous structure (50–60% porosity) for enhancing the mass transfer. Due to the reinforced capillarity at the small-scale pores in the bimodal structure, the MSE structure achieves a high evaporation rate of 1.303 kg m-2h−1 when exposed to 1 sun irradiation. Furthermore, large-scale pores in the bimodal structures would simultaneously promote the autonomous rejection of salts at the MSE surface during solar desalination. We show that optimizing the bimodally porous structure and the interfacial properties significantly improves the solar evaporation efficiency, demonstrating the intricated structure for the next generation solar evaporation and desalination systems.

An efficient nanodiamond-based monolithic foam catalyst prepared by a facile thermal impregnation strategy for direct dehydrogenation of ethylbenzene to styrene

Nanodiamond (ND) has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation (DDH). However, the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process. In this work, we report a facile hexamethylenetetramine nitrate (HN)-assisted thermal impregnation (HNTI) strategy for fabricating a novel nanodiamond-based monolithic foam (ND/CNT-SiC-ms-HN) catalyst through a two-step approach: One is to soak the carbon nanotube-modified SiC foam (CNT-SiC) with the slurry composed of HN, KCl, LiCl, and dispersed ND, and the other is to heat the slurry-soaked CNT-SiC (ND-HN-KCl-LiCl/CNT-SiC) in N2 atmosphere at 750 °C. The as-synthesized ND/CNT–SiC-ms-HN monolithic foam features the enriched surface kenotic CO by promoted ND dispersion and O-doping, abundant stuctural defects, and improved nucleophilicity by N-doping, originating from the promoted ND dispersion by thermal impregnation (TI) in KCl-LiCl molten salt (MS) and the presence of HN in the annealing process. As a result, the ND/CNT–SiC-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate (5.49 mmol g−1 h−1) associated with 98.4% of styrene selectivity compared to the ND-based monolithic foam catalyst (ND/CNT-SiC). Moreover, the ND/CNT–SiC-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene. This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.

Novel Pd-loaded self-standing hierarchical pore structure silicalite for low temperature toluene catalytic combustion

A novel Pd-loaded self-standing hierarchical pore structure silicalite were obtained by a handy polymer form board assisted hydrothermal method. The selected foam-shaped form board of a polyurethane (PU) foam monolith was regarded as the precursor of the self-standing hierarchical pore structure silicalite. The fruiting silicalite can steadily hold unique macroporous network structure and shape of the anterior original PU foam board . By means of the BET and BJH pore size distribution tests, the as-synthesis silicalite demonstrated hierarchical pore structure. The method of in-situ reduction was wielded to load palladium on the silicalite, and the catalytic performance of the catalyst to decompose toluene was tested at multiple burning temperatures. The experimental results revealed that the Pd-loaded catalyst can effectively decompose toluene at nearly 230°C, realizing low-temperature catalytic combustion of toluene.

Surfactant-free oil-in-oil emulsion-templating of polyimide aerogel foams

Abstract A surfactant-free oil-in-oil emulsion-templating method is presented for fabrication of monolithic polyimide aerogel foams using monomer systems that produce fast sol–gel transition. An aerogel foam is a high porosity (∼90%) material with coexisting meso- and macropores inherent to aerogels with externally introduced micrometer size open cells (macrovoids) that are reminiscent of foams. The macrovoids are introduced in polyimide sol using surfactant-free emulsion-templating of droplets of an immiscible liquid that are stabilized against coalescence by fast sol–gel transition. Three immiscible liquids – cyclohexane, n-heptane, and silicone oil – are considered in this work for surfactant-free emulsion-templating. The aerogel foam monoliths, recovered by supercritical drying, exhibit smaller size macrovoids when n-heptane and cyclohexane are used as emulsion-templating liquid, while the overall porosity and the bulk density show weak dependence on the emulsion-templating liquid.

Self-structured monolithic TiO2-Mn2O3-Na2WO4-foam catalyst towards efficient oxidative coupling of methane

A monolithic TiO2-Mn2O3-Na2WO4-foam catalyst is developed via a self-structuring method for the oxidative coupling of methane reaction. The TiO2-Mn2O3-Na2WO4 slurry is injected into a hard template of polyurethane activated carbon sponge (PACS); and polyvinyl alcohol (PVA) is introduced into the slurry to increase its macroscopic viscosity. The calcination at 800 °C in air removes PACS and PVA to form the foam structure, and simultaneously, the interpenetrating nanorods of TiO2-Mn2O3-Na2WO4 are generated, which grants this foam monolith strong mechanical strength. Such catalyst effectively couples advanced catalysis of TiO2-Mn2O3-Na2WO4 with enhanced heat/mass transfer stemmed from the foam structure. At 740 °C, CH4/O2 molar ratio of 5/1, 0.1 MPa, and gas hourly space velocity of 6000 h−1, 25.3% CH4 conversion and 71.6% C2-3 selectivity can be achieved over the preferred catalyst. The self-structuring strategy is efficient to fabricate the more-advanced monolithic OCM catalyst.

Thermal Properties of Lightweight Steel Concrete Wall Panels under Different Humidity Conditions.

The paper presents the thermal properties of lightweight steel concrete wall panels under different humidity conditions: under normal operation conditions and high moisture of the structure. The total thermal resistance (considering thermal inhomogeneity) of the enclosing lightweight steel concrete structure with a thickness of 310 mm using monolithic low-density foam concrete (density grade of D200), at an equilibrium humidity of 5% and 8%, was experimentally established. It was equal to 4.602 m2.0C/W and 4.1 m2.0C/W, respectively. In the dry state, the total thermal resistance of this structure was 5.59 m2.0 C/W, which corresponds to a thermal conductivity coefficient of 0.057 m °C/W. The influence of both horizontal and vertical joints of lightweight steel concrete wall panels and the absence of thermoprofiles on thermal properties was insignificant when using heat-insulating gaskets. The actual total thermal resistance of the structure was 2.5–2.8 times higher than that obtained by calculation under high-humidity conditions (29–32%). At the same time, the decrease in the value compared to the same value at an equilibrium humidity of 5% was only 4–6%. This indicates the good workability even of a structure with high-humidity foam concrete if the reduced total thermal resistance is complied with by the standardized one.

Tailored boron phosphate monolithic foam with multimodal hierarchically porous structure and its applications

Tailored boron phosphate monolithic foam with multimodal hierarchically porous structure and its applications