Ceramic Foam Research Articles

A comprehensive investigation of porous media’s effects on the performance of photovoltaic thermal systems

Porous media in thermal collectors have been found to enhance the performance of photovoltaic thermal systems. However, there is a lack of comprehensive research on the benefits of using porous media in this context. This paper represents the first comprehensive study comparing various types of porous materials and their effects on system performance. The study employs a three-dimensional simulation to analyze the influence of factors such as material type, porosity, permeability, and thermal conductivity on module efficiency in top, middle, and fully filled configurations. In particular, it has been observed that each material has an optimum porosity, and there is little difference among metal foams, ceramic foams, and ordinary materials, such as aluminum and copper screens. Among the different configurations, the middle configuration had the lowest thermal efficiency improvement (∼17 %), the top configuration increased efficiency by ∼7 %, and the full porous configuration had the highest thermal efficiency improvement, 32 %. Materials with very low conductivity, such as wood, perform better in the middle than in the top configuration. Graphite, despite its high thermal conductivity, has low permeability, which leads to lower thermal efficiency compared to that of most other materials in the top configuration. In the full configuration and particularly in the middle configuration, graphite shows the smallest thermal efficiency improvement due to its significant longitudinal conduction heat transfer. Therefore, in these configurations, graphite is not recommended for use as a porous medium. Regarding added mass, metal foam materials add the most mass to the system, followed by ceramic foam materials, which present considerably lower figures. In all cases, the pump power consumption growth is negligible compared to the photovoltaic power output. In all materials and configurations, there was a small improvement in electrical efficiency, reaching 1.25 % in the full porous configuration. From a holistic perspective, this study showed that porous media can improve the overall equivalent power by up to 9.8 %, compared to a smooth channel.

60 Years of Open‐Celled Ceramics Based on Replica Technique: Applications, Obstacles, and Opportunities

Open‐celled ceramics look back on a remarkable history of development and innovation spanning around 60 years. Starting with the first patents to produce ceramic foams in the 1960s, the Schwartzwalder process became established industrially for manufacturing molten metal filters. Since then, a wide range of potential applications for these specific structured materials has been identified and discussed in the literature, such as porous burners, direct heaters, structured catalyst supports, filters, bone substitute materials, energy absorbers, preforms, and lightweight or acoustic construction components. For such high‐performance applications, ceramic foams require high quality in terms of purity, mechanical strength, high temperature, and chemical resistance or structural design. On this account, production technologies and material variety of ceramic foams have developed rapidly over the past few decades, and there are numerous applications in the industrial sector. This article gives an overview of the current state of development of open‐celled ceramic foams for various applications. Based on selected examples, it is demonstrated for which applications an industrial implementation is successfully realized and why some applications will never get beyond the proof‐of‐concept stage in research.

Ultra-high strength ZTA ceramic foams with large amounts of intragranular structures resulting from dual-phase sol

A creative way to overcome the general problem of high-porosity ceramic foams with low intensity has been proposed here. For the first time, zirconia toughened alumina (ZTA) ceramic foams with a large number of intragranular structures have been prepared by particle-stabilized foams using boehmite sol and ZrO2 sol as raw materials. The grain boundary mobility of alumina in ceramic foams is much higher than that of zirconia due to the extremely high sintering activity of the boehmite nanoparticles, and then a typical intragranular structure of alumina grains wrapping around zirconia grains is formed. Based on the strengthening effects of intragranular zirconia grains, the as-prepared ZTA foams have excellent mechanical properties, with ultra-high compressive strength of 10.3–88.0 MPa and high porosity of 91.0–79.1 %. This paper provides a novel strategy for the preparation of high-performance ceramic foams.

Numerical simulation of solar-driven biomass gasification by using ceramic foam

This study aimed to investigate the potential of silicon carbide (SiC) foam to enhance the reaction rate in solar-driven gasification within a packed bed reactor. A validated gasification model was employed to evaluate the performance of biomass reaction in terms of biomass conversion χ and energy utilization η, under varying conditions of SiC foam porosity ϕSiC, steam equivalence ratio α, and radiation power QG. The findings revealed that the incorporation of SiC foam significantly enhanced the thermal conductivity of the packed bed. The bed temperature exhibited a prominent increase in response to the enhanced radiation power. It is crucial to adjust the amount of steam introduced in response to the bed temperature. The biomass conversion χ saw a remarkable increase under optimal conditions of ϕSiC = 0.85, α = 0.4, and QG = 3600 W, doubling from 35% to 73%. Additionally, by identifying a range of favorable operating parameters, we were able to achieve a higher energy utilization η. These significant findings underscore the critical role of SiC foam in mitigating the challenges associated with low heat and mass transfer rates in packed bed reactors. The use of SiC foam provides a promising solution for enhancing the reaction rate in solar-driven gasification processes, ultimately leading to improved biomass conversion and energy efficiency.

Open-cell cordierite-based foams from eco-friendly geopolymer precursors via replica route

Open-cell cordierite-based foams with high porosity were synthesized by a facile replica route, using geopolymers as precursors and polyurethane foams as polymer templates. The geopolymer precursors, incorporating MgO as an additional magnesium source, were prepared using metakaolin and fly ash under activation of NaOH solution and sodium silicate solution. Polyurethane foams with geopolymer were obtained by an impregnation method. The hybrid foams comprising polyurethane foam and geopolymer were cured/solidified at 75 °C for 24 h. Subsequently, the hybrid foams were subjected to ammonium ion-exchange followed by sintering at 1200 °C for 2 h to produce porous cordierite-based ceramics. The resulting foamed ceramics were characterized in terms of bulk density, porosity, structural evolution, and mechanical properties. Porous cordierite-based ceramic foams exhibiting a total porosity of approximately 88.64 vol% and a compressive strength of around 0.47 MPa were successfully fabricated by the replica route.

The effect of the viscoelastic support and GRPL-reinforced foam material on the thermomechanical vibration response of piezomagnetic sandwich nanosensor plates

This paper investigates the vibration characteristics of a sandwich nanosensor plate composed of piezoelectric materials, specifically barium and cobalt, in the upper and lower layers, and a core material consisting of either ceramic (silicon nitride) or metal (stainless steel) foams reinforced with graphene (GPRL). The study utilized the novel sinosoidal higher-order deformation theory and nonlocal strain gradient elasticity theory. The equations of motion for nanosensor sandwich graphene were derived using Hamilton's principle, considering the thermal, electroelastic, and magnetostrictive characteristics of the piezomagnetic surface plates. These equations were then solved using the Navier method. The core element of the sandwich nanosensor plate can be represented using three distinct foam variants: a uniform foam model, as well as two symmetric foam models. The investigation focused on analyzing the dimensionless fundamental natural frequencies of the sandwich nanosensor plate. This analysis considered the influence of three distinct foam types, the volumetric graphene ratio, temperature variation, nonlocal parameters, porosity ratio, electric and magnetic potential, as well as spring and shear viscoelastic support. Furthermore, an analysis was conducted on the impact of the metal and ceramic composition of the central section of the sandwich nanosensor plate on its dimensionless fundamental natural frequencies. In this context, the use of ceramic as the central material results in a mean enhancement of 33% in the fundamental natural frequencies. In contrast, the incorporation of graphene into the core material results in an average enhancement of 27%. The thermomechanical vibration behavior of the nanosensor plate reveals that the presence of graphene-supported foam and a viscoelastic support structure in the core layer leads to an increase in thermal resistance. This increase is dependent on factors such as the ratio of graphene, porosity ratio of the foam, and parameters of the viscoelastic support. Metal foam or ceramic foam has been found to enhance thermal resistance when compared to solid metal or ceramic core materials. The analysis results showed that it is important to take into account the temperature-dependent thermal properties of barium and cobalt, which are piezo-electromagnetic materials, and the core layer materials ceramics and metal, as well as the graphene used to strengthen the core. The research is anticipated to generate valuable findings regarding the advancement and utilization of nanosensors, transducers, and nano-electromechanical systems engineered for operation in high-temperature environments.

Effect of flow velocity on the permeability of ceramic foam filters (CFFs)

The structural uniformity of commercial Al2O3-based Ceramic Foam Filters (CFF) of Grades 30, 50, 65 and 80 was investigated using the permeability of samples from five different locations of the CFF tiles/Blocks, specifically from the four corners and the centre. Statistical analysis at 95 % confidence interval revealed no significant variations in the permeability values among these locations. Additionally, the impact of different flow regimes within the CFF structure, namely laminar, transitional, and turbulent regimes, on the permeability was explored. It was demonstrated that permeability, as a parameter of fluid velocity, exhibited a notable increase with increasing pore diameter. In CFF samples with pore diameters greater than 0.5 mm, the deviation in permeability between turbulent flow and creeping flow was attributed to large eddies occupying a substantial portion of the pore volume. This phenomenon resulted in the narrowing of the flow channels and reduction in the viscous boundary layer. The correlation between filtration efficiency and velocity, as well as CFF pore diameter, is discussed in view of the influence of streamlining and the size of the eddies on the re-entrainment of captured particles.

Novel high thermal conductivity alumina/salt composites for thermal energy storage: Effect of wettability on microstructure and properties

In this work, alumina foam ceramics (AFC) were prepared by foaming method, and AFC/salt composite phase change materials were prepared by melt infiltration method using AFC as skeleton materials. The results showed that AFC had good chemical compatibility with Na2SO4 and NaCl. The salt contents of AFC/Na2SO4 and AFC/NaCl were 37.8 wt% and 31.7 wt%, respectively, with compressive strength of 100.1 MPa and 72.8 MPa, thermal conductivity of 5.53 W/m·K and 6.40 W/m·K, and energy density of 1129 J/g and 1019 J/g, respectively. Due to the better wettability, AFC and Na2SO4 form a chimeric structure, which has better binding and bonding strength, and is not prone to molten salt leakage. AFC/ Na2SO4 is expected to be applied to industrial waste heat recovery and solar thermal power generation with periodic temperature changes.

Digital light processing bio-scaffolds of hydroxyapatite ceramic foams with multi-level pores using Pickering emulsions as the feedstock

To prepare bio-scaffolds with multi-stage pores, excellent mechanical and biological properties to meet the requirements of personalized bone repair, digital light processing using Pickering emulsion as paste has been proposed here firstly for porous hydroxyapatite scaffolds with complex shape and fine microstructure. It is found that dispersant content, solid loading and oil to water ratio of Pickering emulsions play vital roles on the controlling of pore morphology and pore size distribution of final hydroxyapatite ceramic foams. The multi-stage pores consist of millimeter-scale pores designed by 3D models and micro-pores below 10 µm derived from emulsion droplets. Due to the integration of hierarchical pores at different scale levels and micropores, hydroxyapatite ceramic foams possess outstanding compressive strength of 4.46–8.03 MPa at porosity of 76.59-72.96%. In vitro cell experiments illustrate that rat bone mesenchymal stem cells can spread and adhere to bio-scaffolds, promoting cell proliferation effectively and further verifying their good biocompatibility.

Development of Catalytically Functionalized Polyester-Based Filters Produced by Flame Spray Pyrolysis

For industrial processes—like waste incineration—it is necessary to reduce solid components (like dust or fly ash) as well as gaseous components (like dioxins, CO and other harmful hydrocarbons) to fulfill legal requirements. Therefore, catalytically functionalized filters based on polymers already exist. However, it is known that such filters are always constructed in multiple layers to prevent the migration of catalyst particles. This study demonstrates that it is possible to prepare a stable catalytic functionalized single-layer filter based on polyester needle felt by using flame spray pyrolysis. The catalyst is a low temperature active Pt/TiO2 with a loading weight of 38 g/l on the filter. Via SEM images the uniform distribution of the catalytic particles even in the deeper regions of the single-layer filter was proven. The structure was confirmed after experiments under realistic conditions—migration could not be obtained. Likewise, it was obtained that the oxidative conversion of carbon monoxide (CO) to carbon dioxide (CO2) is completely even at temperatures below 100 °C. Furthermore, comparative studies with catalysts on a honeycomb and a ceramic foam have shown that the conversion on the polyester needle felt textile catalyst is comparable.

Numerical and experimental characterization of high-temperature heat transfer in a ceramic foam with dual-scale porosity

In this paper, we compare numerical predictions and measurements of the high-temperature apparent thermal conductivity of an insulating alumina foam with dual-scale porosity: the foam contains ▪-sized cells and also ▪-sized pores in the highly scattering foam skeleton. Simulations of the apparent thermal conductivity are performed on tomography-reconstructed foams, with a three-part multi-scale approach to account for the dual-scale porosity. The effective phonon thermal conductivity of the foam is first computed using a finite element homogenization technique. The spectral and temperature-dependent effective radiative properties of the foam are next computed through an improved Monte Carlo ray-tracing approach, with foam skeleton scattering modeled using a physical-optics-based approach. The apparent thermal conductivity of the foam is then simulated by resolving the coupled conductive-radiative heat transfer through a semi-infinite homogeneous slab. The simulated high-temperature apparent thermal conductivity is found to be in good agreement with experimental data up to ▪, obtained by parallel hot wire measurements coupled with an improved quadrupolar model for low-density insulating materials. The large influence of scattering at the cell-skeleton interface is shown through a numerical parametric study. It is also shown that the Rosseland conductivity calculated directly from the simulated spectral radiative properties provides a good estimation of radiative heat transfer for optical thicknesses exceeding 30.

Coal gangue‐based ceramics foams by water spray granulation and post particle stacking method

AbstractFoamed ceramics were prepared by the water spray granulation and post particle stacking method using coal gangue as the main raw material. The effects of raw material weight ratio (i.e., raw material composition by varying the content of dolomite and talc), calcination temperature, time, and heating rate on the pore structure and properties of the samples were investigated and the foaming mechanism of foamed ceramics was revealed. The crystalline phase of foamed ceramics mainly consisted of quartz, anorthite, and enstatite. The decrease of dolomite content and the increase of talc content in the raw materials led to the initial decrease and then increase of the pore size dispersion coefficient, while the apparent porosity and water absorption of the samples gradually decreased, and the apparent density increased. The sample with a composition of gangue:waste glass:dolomite:albite:talc of 65:5:10:10:10 and calcined at 1200°C for 10 min with a heating rate of 1°C/min has the optimized uniform pore structure. This study provides a high value‐added utilization of coal gangue, and the experimental basis for the preparation of low‐cost foamed ceramics.

Preparation of multifunctional ceramic foams for sound absorption, waterproofing, and antibacterial applications.

Using porous materials for sound absorption is an effective approach to alleviating noise pollution, although their hydrophilic properties potentially cause concerns regarding public safety and health risks. This work provides a facile strategy for establishing a multifunctional ceramic system by using sponges as the sintering template, adjusting the pore structure of ceramic foams by varying the ceramic slurry weights and fluorinating the sintered ceramic foams via hydrolysis and condensation processes to provide low surface energy. The obtained porous ceramic foams demonstrate sound-absorbing, waterproof, and antibacterial properties. The results reveal that the increase in ceramic slurry weight decreases the pore size and porosity due to the formation of more compact structures, and the decrease in porosity compromises the sound absorption performance. In the middle-range sound frequency, the maximum sound absorption coefficient reached 0.92. In addition, the fluorination of the rough ceramic surfaces endows the ceramic foams with waterproof properties, which enables them to float on water and display the silver mirror phenomenon. In addition, due to the waterproof property reducing the contact area between the ceramic surface and the bacterial suspension, as well as the lipophilic fluorine chain disrupting the bacterial structures, these ceramic foams exhibited antibacterial rates above 95%. In addition, the mechanisms underlying the sound-absorbing, waterproof, and antibacterial properties of these porous ceramic foams are elucidated. Therefore, this work provides a facile approach to developing a multifunctional ceramic system. Their practical features make these ceramic foams more significant in the field of noise reduction.

Numerical Simulation of the out-of-plane mechanical properties of tall foam ceramic (FC) partition wall

Abstract This paper conducts simulation research using Abaqus software and Finite Element Software on the out-of-plane mechanical properties of large-scale FC partition walls. Exploring the structural columns of 1.2m, 1.8m, and 3m, respectively, in large-size FC partition walls under out-of-plane loading, the cracking pattern of wall panels, the distribution of cracks, the damage pattern, the load-deflection curve, and the weak parts of the wall panels and the weak points of the wall panels under out-of-plane loading. The simulation results of experimental software in this paper show that the three specimens meet the design requirements, have good integrity before cracking, and are interoperable with steel bone and foam ceramic. Then, the finite element models of the steel frame-embedded foam ceramic wall with different densities were established, and the influence of the density of the foamed ceramic on the out-of-plane mechanical properties of the wall was further studied. The results show that when the density of foamed ceramics increases from 400kg/cm3 to 500kg/cm3, the fracture performance is significantly improved, while when the density increases from 400 kg/cm3 to 500 kg/cm3, the fracture performance is not significantly improved. It is also found that the out-of-plane bearing capacity of foamed ceramic walls with embedded steel frames increases with the increase of foamed ceramic density, and the mid-span deflection decreases with the increase of density. However, with the rise of embedded steel frame spacing, the influence of foam ceramic density on the out-of-plane load and mid-span deflection gradually diminishes. The results of this paper can provide some guiding significance for the design and construction of large-size and story-building partition walls in the future.

Ultra-high porosity of open-cell alumina ceramic foams prepared by adding tiny amounts of γ-AlO(OH) sol

A creative and environmentally friendly preparation of high-porosity open-cell ceramic foams was investigated. The samples were prepared from the ?-Al2O3 slurry with 25 wt.% solid loading in which a tiny amount of boehmite (?-AlO(OH)) sol was added for the formation of particle-stabilized foams without introducing any sacrificial phases. The volumetric shrinking of ?-AlO(OH) enables the formation of open-cell while avoiding the generation of polluting gases. The resulting alumina ceramic foams have a synergistic increase in porosity and compressive strength, reaching a compressive strength of 1.17MPa and an ultra-high porosity of 94.8%. This is due to the fact that the pore struts (connecting neighbouring cells) are almost defect-free, while the high sintering activity of ?-AlO(OH) promotes the sintering of ceramic phase and formation of alumina with small grains which has the strengthening effect on the obtained structures. By achieving open-cell, the heat conduction path increased, which reduces the thermal conductivity of the ceramic foam. This work provides an alternative and environmentally friendly new strategy for open-cell ceramics processing.

Effect of silver inhibition on the ceramic foam as flame suppression

Aluminium dust explosions pose significant safety and economic challenges in various industrial processes. Due to this, the current research explores an innovative approach by inhibiting the silver nanoparticles (Ag NPs) to ceramic porous form substrate as a flame suppressant in order to mitigate the risks associated with these explosions. The antimicrobial and non-toxic qualities of silver are also attractive to be applied in medical and food technology. However, the interfacial adhesion between the metallic (nanosilver) and non-metallic (silica-based-ceramic) is still vaguely studied due to the mechanical and surface energy mismatch between the organic surface and the inorganic layers. From this study, the physicochemical and mechanical properties of the silver-coated ceramic foam were analyzed using X-ray diffraction, field emission scanning electron microscopy with energy dispersive X-ray, thermogravimetric analysis, and compression test. From the mechanical testing, it was found that the percentage increase of maximum load for silver-ceramic foam from the original ceramic foam was about 60%. The results indicate that silver-coated foam has a better compressive strength of 0.93 MPa as compared to 0.58 MPa by the original ceramic. The inhibition effect of Ag NPs powder on the explosion pressure evolution and flame spread mechanism of aluminium powder at different concentrations and particle sizes was tested using the Hartmann experimental system.

The effect of the preparation method of asphalt waste foam ceramic loaded Pd/Ce-P-Al2O3 coatings on their properties

Asphalt waste-based foam ceramics were prepared by organic foam impregnation, followed by ultrasound-assisted impregnation and calcination to deposit 3-5 wt.% Pd/Ce-P-Al2O3 active coatings. The results show that γ-Al2O3 as an aluminum source provides a higher specific surface area and facilitates the dispersion of the catalytic components, so that low-temperature conversion of CO can be achieved, but the coating uniformity, stability, and the ability to modify the defects on ceramic surfaces are lower than those of the aluminum nitrate calcination products. Aluminum dihydrogen phosphate as a P source could rapidly convert 60% of CO, but the performance decreased at a later stage, while phosphoric acid as a P source could achieve the complete conversion of CO at a lower temperature. The mechanical properties of the samples with the addition of aluminum dihydrogen phosphate and aluminum nitrate baked products were better, which was 0.6 MPa higher than the uncoated foam ceramics.

Relevance of Sulfate Functionalization and Porous Structure of TiO2 Ceramic Foams in Photocatalytic Degradation of Dye Molecules

A one-step route was developed for sulfate functionalization of titania foam, consisting of integrating the sol-gel process with an emulsion template. The resulting material was used to evaluate the relevance of the porous structure and surface sulfate groups in the photocatalytic degradation of Rhodamine B molecules in water under UV irradiation. X-ray diffraction (XRD) analysis showed that the anatase crystalline phase was metastabilized by functionalization of the surface with sulfate species, which caused the crystallite size to decrease from 21 to 10 nm, while the specific surface area increased from 4 to 42 cm2 g-1. Small-angle X-ray scattering (SAXS) measurements during heating of the non-sulfated (E-TiO2) and sulfated (E-TiO2/SO42-) sols emulsified with sodium dodecyl sulfate (SDS) as surfactant and isopropyl myristate as the nonpolar phase, revealed formation of the liquid crystalline structure. Elimination of this mesophase template allowed the preparation of ceramic foams with hierarchical structure formed by meso- and macropore families. The kinetics of photodegradation reaction of Rhodamine B followed a pseudofirst order mechanism. The most efficient photocatalytic activity (higher rate constant and shorter half-life time) was obtained for the foam templated using 20% of SDS (E-TiO2/SO42- 20SDS), which exhibited the highest values for porosity (93%) and specific surface area (80 m3 g-1).

Advanced Light Weight Ceramic Foams for Hypersonic Vehicles

Advanced Light Weight Ceramic Foams for Hypersonic Vehicles

CeO2-modified monolithic ceramic foams for efficient catalytic ozonation of refractory organic pollutants in a continuous-flow reactor

The monolithic catalyst of CeO2-loaded ceramic foam for the catalytic ozonation of organic pollutants operated in a continuous-flow mode was developed, achieving effective TOC removal of organic pollutants and high utilization efficiency of ozone.