Ceramic Foam Research Articles

Suppressing the thermal conduction in glass–ceramic foams by controlling crystallization

AbstractGlass‐based insulating materials have attracted considerable attention owing to their tailorable properties. It is known that the thermal conductivity of glass ceramics can be greatly influenced by varying their crystallinity. However, the mechanism of such influence in glass–ceramic foams remains poorly understood. In this study, we demonstrate our new findings regarding the correlation between thermal conductivity and crystallinity in silicate glass–ceramic foams. The foams were produced by mixing ZrO2‐containing soda‐lime glass powder with CaCO3 as foaming agent and foam them using a thermochemical approach. ZrO2 was introduced as a nucleation agent. The crystallinity of the foams was varied by adjusting the heating protocol, i.e., by varying temperature, time, and number of heating cycles. The glass–ceramic foams exhibited relative crystallinities of <30%. The identity of the crystalline phases in the glass–ceramic foams varies with crystallinity. Specifically, cristobalite diminished, but devitrite grew with increasing crystallinity. It was observed that the crystallinity had a nonmonotonic impact on the thermal conductivity of the glass–ceramic foams. The optimum crystallinity for achieving the lowest thermal conductivity was 8–10%, resulting in an approximately 20% lower thermal conductivity compared to noncrystalline. Our findings have implications for the future design of glass–ceramic foams.

Fabrication and characterization of foam ceramics from recycled waste concrete powder and waste glass powder

Incorporating multi-solid wastes to prepare foam ceramics has attracted widespread attention due to its excellent characteristics and environmental protection. In this study, foam ceramics were prepared by sintering method using recycled waste concrete powder (RWCP) and waste glass power (WGP) as the major material, Na2CO3 as foaming agent and borax as fluxing agent. The effect of sintering temperature on the physical properties and pore structure of foam ceramics were studied. The phase transformation and reaction mechanism were also discussed. The results reveal that when the RWCP content was 40%, the WGP content was 60% and the sintering temperature was 890 °C, the foam ceramics showed the best overall performance. The compressive strength, bulk density, water absorption and porosity were 2.39MPa, 0.83g/cm3, 8.27% and 66.68%, respectively. At this time, the pore size distribution was optimal, and mesopore occupied the vast majority. The fractal dimension of pore reached the minimum of 1.09. In addition, The XRD results showed that WGP and RWCP gradually depolymerized and reconstructed under the action of flux. Then the foam ceramics with mullite, pyroxene and wollastonite as the main phases were formed. The experimental results showed that it was feasible to prepare foam ceramics using RWCP. This study can provide a new train of thought for the reuse of RWCP.

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.

Electrochemically Switchable Sulfurized Polyacrylonitrile for Controllable Recovery of Copper in Wastewater Based on Reversible Adsorption/Desorption Regulation.

Within the context of circular economy and industrial ecology, adsorption offers an effective manner for recycling resources from wastewater, but controllable desorption remains a challenge. Inspired by metal-thiol binding and reversible thiol-disulfide redox transformation in biological systems, this study reports the development of a reversible adsorption/desorption (RAD) system for controllable recovery of copper based on electrochemically switchable sulfurized polyacrylonitrile (SPAN). Density functional theory calculations offered theoretical prediction for the formation of S-Cu bonds and reversible weak interaction between S-S bonds and Cu2+. The SPAN anchored onto titanium suboxide ceramic foam (SPAN@TiSO) could regulate Cu2+ adsorption/desorption stimulated by the electrode potential, indicated by the adsorption capacity of 243.3 mg g-1 (30 min) at 0.2 V vs SHE and a desorption efficiency of 98.4% (5 min) at 0.8 V vs SHE. Electrochemical analysis revealed that the reversible redox transformation of S-S/-S- groups in SPAN was responsible for selective adsorption and rapid desorption in response to the electrode potential. This study provides a proof-of-concept demonstration of an electrochemically switchable polymer to build up a reversible RAD system for controllable recovery of heavy metals in wastewater, making value-added resource recovery more efficient, more intelligent, and more sustainable.

Integrated utilization of recycled waste concrete powder and waste glass power for preparation of foam ceramics

Integrated utilization of recycled waste concrete powder and waste glass power for preparation of foam ceramics

High-Temperature Electrolysis with Superheated Steam Provided by Volumetric-Type Steam Generator

High-temperature steam is essential for operating solid oxide electrolysis cells (SOEC). This paper demonstrated a new type of high-temperature solar steam generator that uses ceramic foam as a porous absorber. Water is sprayed into the porous absorber as microdroplets by using a nozzle. Experiments show that the solar steam generator is capable of generating superheated steam beyond 800 oC. The peak thermal efficiency in the steady state can reach 60.92% under a mass flow rate of 2.359 kg/h corresponding to an outlet temperature of 877.3 oC. The superheated steam will be supplied to a SOEC system to generate hydrogen. Thus, a comprehensive model is developed in this paper to research the performance of the solar SOEC system under fluctuated solar irradiation

Porous Monolithic Perovskite Structures for High-Temperature Thermochemical Heat Storage in Concentrated Solar Power (CSP) Plants and Renewable Electrification of Industrial Processes

A novel approach towards thermal energy storage of surplus renewable energy (RE) is introduced via a hybrid thermochemical/sensible heat storage concept implemented with the aid of porous structures made of redox metal oxides, capable of reversible reduction/oxidation upon heating/cooling in direct contact with air, accompanied, respectively, by endothermic/ exothermic heat effects and demonstrating fully reversible dimensional changes under cyclic operation. The proposed modular storage units can be heated during the day to a level exceeding the metal oxide’s reduction onset temperature either by hot air streams from air-operated Concentrated Solar Power (CSP) tower plants or via surplus/cheap RE-electricity from photovoltaics, wind, or other renewable sources (“charging”/energy storage step). When this RE sources become non-available or upon demand, the fully charged system can transfer its energy to a controlled airflow that passes through the porous oxide block and initiates the exothermic oxidation of the reduced metal oxide. Thus, a hot air stream is produced which can be used to provide electricity or exploitable heat for industrial processes. The present work elaborates on the operating principles and the potential application of this concept and reports progress in the preparation and shaping of reticulated porous ceramics (RPCs also known as “ceramic foams”) from CaMnO3-based perovskite compositions and their preliminary testing with respect to cyclic reduction-oxidation.

Overview of Multifunctional (Ultra-)Lightweight Materials for a Sustainable Future

Abstract In line with the ongoing advancement of high-performance materials that are multifunctional and environmentally friendly, this paper provides an overview of recent developments in lightweight and ultra-lightweight multifunctional materials. We primarily examine the various types of low-density multifunctional materials, their production techniques, and their applications within the context of a sustainable future. From a structural point of view, ultra-light materials are classified into three main groups: aerogels, foam, and micro/ nanolattice. In terms of composition, they can be derived from ceramic, metallic, or polymeric materials. This overview pays particular attention to silica, carbon and composite aerogels, as well as metal, ceramic (carbon), and polymer foams.

Sustainable recycling of pure aluminum from waste chips under supergravity-enhanced separation: A cleaning process

Large quantities of chips containing high levels of aluminum are always inevitably produced during machining process of aluminum products, which is a valuable renewable resource. In this paper, an environmental-friendly method for direct and continuous recovery of same-level recycled Al from waste chips under supergravity-induced was proposed. The oxide film covering the surface of the molten Al-chips was easily disrupted under super-gravity, and subsequently almost all of Al melt detached from the oxide film and flowed rapidly through the microporous ceramic foam filter, with a yield ratio of more than 97 %. During this process, all fine broken oxide-film particles and large amounts of primary iron-rich particles in the melt were captured in the complex channels of the filter, resulting in clean 1xxx series recycled Al with free inclusions and impurity iron content of less than 0.28 wt%. In addition, a sustainable process and a continuous centrifugal unit for recycling aluminum chips were designed, the economic and environmental advantages of which demonstrate the feasibility of sustainable regeneration of aluminum chip resources on an industrial scale via supergravity technique.

Nonlinear temperature dependent and visco-elastic foundation effects on the free vibration of functionally graded sandwich plates with ceramic foam core

This paper investigates the vibrations of a functionally graded sandwich plate (FG sandwich plate) with a ceramic foam core resting on a viscoelastic foundation. The focus is on the influence of temperature changes on sandwich plates that have foam core and FG face sheet on the free vibration. The damping coefficient and different schemes of sandwich plate have been considered in the current work. The analysis uses a quasi-3D theory, which reduces the number of unknown displacements and simplifies the equations by incorporating integral terms. Two models are employed to represent the non-uniformity of the ceramic foam core. To account for the influence of the supporting layer, a viscoelastic foundation is included. The governing equations are derived using Hamilton’s principle and solved using the Navier solution method. The paper comprehensively discusses how the volume fraction index k, geometric properties, ceramic foam distribution, viscoelastic foundation, and different temperature rise profiles impact the vibration response of the FG sandwich plate.

Carbonaceous Shape-Stabilized Octadecane/Multi-Walled Carbon Nanotube Composite Materials for Enhanced Energy Storage and Electromagnetic Interference Shielding.

Developing materials for efficient energy storage and effective electromagnetic interference (EMI) shielding is crucial in modern technology. This study explores the synthesis and characterization of carbonaceous shape-stabilized octadecane/MWCNT (multi-walled carbon nanotube) composites, utilizing activated carbon, expanded graphite or ceramic carbon foam, as shape stabilizers for phase change materials (PCMs) to enhance thermal energy storage and EMI shielding, for energy-efficient and advanced applications. The integration of octadecane, a phase change material (PCM) with carbonaceous stabilizers ensures the material's stability during phase transitions, while MWCNTs contribute to improved thermal storage properties and EMI shielding capabilities. The research aims to develop novel composites with dual functionality for thermal storage and EMI shielding, emphasizing the role of carbon matrices and their MWCNT composites. SEM and CT microtomography analyses reveal variations in MWCNT incorporation across the matrices, influenced by surface properties and porosity. Leaching tests, infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) confirm the composite's stability and high latent heat storage. The presence of nanotubes enhances the thermal properties of octadecane and ΔH values almost reached their theoretical values. EMI shielding effectiveness measurements indicate that the composites show improved electric properties in the presence of MWCNTs.

Experimental evaluation of novel gas liquid contactor packing based on triply periodic minimal surfaces (TPMS)

Additive manufacturing has widened the possibilities of design for gas–liquid packing geometries in recent years, allowing for new unexplored shapes. A novel design approach based on triply periodic minimal surfaces (TPMS11Triply periodic minimal surfaces.), an interesting class of smoothened curved surfaces, led to the conception of new periodic structures with complex geometrical features. The present study aims to assess the applicability of these new TPMS-based geometries as packing for gas–liquid contactors and the effect of their topology on performance. Liquid holdup, pressure drop, flooding and mass transfer efficiency were evaluated for three TPMS-based prototypes, with distinct characteristic dimensions. A new experimental setup was developed for the estimation of liquid holdup based on the measure of the liquid weight during operation by a set of load cells. Results show good repeatability and precision, allowing to distinguish liquid holdup between the prototypes for various gas and liquid flow rates. Two of the studied prototypes presented higher holdup than the 5 ppi ceramic foam and the 15 mm Raschig rings for lower liquid rates. Prototypes also showed good results for pressure drop, with flooding reached at gas load factors above 3Pa0.5. In terms of mass transfer efficiency, HETP results for the new prototypes remained between 0.35m and 0.45m, comparable to Mellapak 250Y.

Open-cell ceramic foam filters for melt filtration: Processing, characterization, improvement and application

Open-cell ceramic foams are widely used as filters for the purification of molten metals due to their high permeability and high efficiency for capturing non-metallic inclusions. With the consideration of manufacture and filtration behaviour, most filters are produced by replica methods. The intrinsic multiscale porous structure requires the ceramic foams to have sufficient strength. As a consequence, different processing approaches, material compositions and characterizations are investigated. Meanwhile, to further enhance the filtration performance, the functionalization of ceramic foam filters is often conducted with surface coating. This review summarizes the processing and characteristics of ceramic foam filters (CFFs), the nature and formation of non-metallic inclusions (NMIs), the filtration mechanism and applications of CFFs. The characterization of mechanical and filtration performance, as well as the corresponding strengthening and functionalization methods are also presented.

Optimization of microwave-produced coal-derived char insulation foam using response surface methodology

A new char-based insulation foam (CIF) is developed using coal-derived pyrolysis char (PC) and lignin, a paper and pulp industry byproduct. In this study, CIF is prepared by adopting the microwave method and Response Surface Methodology (RSM) is utilized to optimize predictions about the properties such as thermal conductivity, foam texture, compressive strength, and pore distribution of CIF. The three independent variables including percent char content, lignin/char ratio, and foaming agent/polyol ratio are considered in the RSM methodology. The face-centered central composite design is selected to obtain 17 test runs. Optimization of the predicted responses is performed to find the recipe considering a composite desirability function. Confirmatory test results show agreement between the predicted and observed values, with the percent error ranging from 0.00 % to 11.35 %, thereby confirming the accuracy of the prediction equations. The optimized CIF exhibits a thermal conductivity of 0.0633 W/m.K and a compressive strength of 695 kPa making it comparable to or better than traditional building insulation products such as fiber insulation, polymer composite, particle board, and ceramic glass foam. Therefore, this new CIF has the potential to be used as an energy-saving insulation material for building envelopes.

Experimental study of the out-of-plane mechanical properties of tall foam ceramic (FC) partition wall

Foamed ceramic (FC) partition wall is a non-structural component which has a broad application prospect. At present, most of the relevant specifications and studies on partition walls are limited to ordinary floor heights. In practical engineering applications, the partition wall exceeding the specification height limit often appears in scenes such as hotel halls and airport terminal. It would pose a life safety threat to the building in the event of out-of-plane damage of this type of partition wall under wind loads. Therefore, this paper aims to study the out-of-plane mechanical properties of tall FC partition walls under static loading. Experimental studies were conducted on the influence of different connection forms, as well as different construction column spacings on the out-of-plane mechanical performance of tall FC partition walls. It can be found that different connection forms had almost no effect on the cracking load. The cracking load decreased gradually with the increasing of the structural column spacings. The specimens with more rigid connection had better crack resistance ability during the service phase. With the increasing of the spacing of structural columns, the restraining effect of the steel skeleton on the FC wall panel, its out-of-plane bearing capacity and stiffness all decreased; The configuration of the steel skeleton reduced the brittleness of FC material; The weak part of tall FC partition wall was in the bonding area between FC wall panel and square steel tube, which should be paid attention to in practical engineering.

Preparation of LMO@FC catalysts and degradation of tetracycline by catalytic ozonation

Developing efficient catalysts with good stability holds great significance for better applying catalytic ozone oxidation in advanced wastewater treatment. Therefore, we designed a novel catalyst of LaMnO3-loaded foam ceramics (LMO@FCs) for catalytic ozonation of tetracycline hydrochloride (TCH) in water. The LaMnO3 (LMO) active components were uniformly loaded on the foam ceramics (FCs) to form an LMO@FC catalyst with mesoporous structure. The total organic carbon (TOC) removal rate by ozonation with LMO@FCs was 2.13 times that of ozone alone. After five repeated uses, the removal rate of TCH and TOC reached more than 99 % and 51.3 %, respectively. The conversion of ozone to reactive oxygen species (ROS) increased with the growth of initial pH. When pH reached zero point of charge (pHpzc), the ozone adsorption on the catalyst surface decreased, leading to the worst degradation efficiency. The Mn3+/Mn4+ and lattice oxygen (OL2−) and surface hydroxyl radical (·OH) were distributed on the catalyst surface. ·OH, superoxide anion (·O2−), and singlet oxygen (1O2) coexisted in the process of ozonation catalyzed by LMO@FCs. The surface ·OH of the catalyst was the catalytic active site. The electrostatic balance between Mn3+ and Mn4+ and the oxidation-reduction between O2− and O2 also played a crucial role in catalytic activity. The TCH experienced a series of reactions in the O3/LMO@FCs process, such as hydroxylation, demethylation, ring-opening oxidation and defunctionalization, and finally was mineralized into CO2, H2O, and NH4+. These results demonstrated that LMO@FCs are promising catalysts for catalytic ozonation of pharmaceutical wastewater treatment.

Dispersivity calculation in digital twins of multiscale porous materials using the micro-continuum approach

The micro-continuum method is a novel approach to simulate flow and transport in multiscale porous materials. For such materials, the domain can be divided into three sub-domains depending on the local porosity ε: fully resolved solid phase, for which ε = 0, fully resolved pores, for which ε = 1.0, and unresolved pores, for which 0 < ε < 1.0. For such domains, the flow can be solved using the Darcy-Brinkman-Stokes (DBS) equation, which offers a seamless transition between unresolved pores, where flow is described by Darcy’s law, and resolved pores, where flow is described by the Stokes equations. Species transport can then be modelled using a volume-averaged equation. In this work, we present a derivation of the closure problem for the micro-continuum approach. Effective dispersivity tensors can then be calculated through a multi-stage process. First, high resolution images are chosen for characterizing the structure of the unresolved pores. Porosity, permeability and effective dispersivity for the unresolved parts are calculated by solving a closure problem based on Direct Numerical Simulation (DNS) in the high-resolution images. The effective dispersivity is then expressed as a function of the Péclet number, which describes the ratio of advective to diffusive transport. This relationship, along with porosity and permeability, is then integrated into the multiscale domain and the effective dispersivity tensor for the full image is calculated. Our novel method is validated by comparison with the numerical solution obtained for a fully-resolved simulation in a multiscale 2D micromodel. It is then applied to obtain an effective dispersivity model in digital twins for two multiscale materials: hierarchical ceramic foams and microporous carbonate rocks.

Three-Dimensional Printing of Cuttlebone-Inspired Porous Ceramic Materials.

Lightweight and strong ceramic materials are attractive for tissue engineering, aerospace, armor systems, and many high-temperature applications. Cuttlebone, primarily composed of bioceramics, features a unique S-shaped wall structure that contributes significantly to its remarkable mechanical properties. Here, we explore the hierarchical structure and components of the cuttlebone and reveal the high ceramic content in S-shaped walls. Inspired by the design of the cuttlebone, we developed a high ceramic loading slurry for three-dimensional printing cuttlebone-like structures. As shown in the compression test, the fabricated bioinspired ceramics exhibit excellent mechanical properties and can withstand 1.07 million times their own weight, outperforming traditional ceramic foams. The specific strength and modulus are 59.5 and 785.6 MPa/(g cm-3), 9 and 36 times that of the natural cuttlebone. The failure mechanisms are also systematically studied on the basis of tuning the structural parameters. These findings provide effective solutions and inspiration in fabricating high-performance ceramic structural materials.

Preparation of β-SiAlON/SiC composite ceramic foam filters and their oxidation resistance

In this study, ceramic foam filters with high porosity, strength, and oxidation resistance are produced at low temperatures by preparing porous β-SiAlON/SiC composite ceramic foams using the foam impregnation method with Si, Si, α-Al2O3, AlN, and SiC as the raw materials. The presence of SiC inhibits the growth of β-SiAlON grains, which reduces the amount of β-SiAlON produced. As the proportion of β-SiAlON increases, the porosity of the β-SiAlON/SiC composite ceramic foam decreases, whereas the bulk density and compressive strength increase. Non-isothermal oxidation experiments show that β-SiAlON/SiC composite ceramic foams exhibit high oxidation resistance and their macroscopic morphology does not change significantly after oxidation. As the proportion of β-SiAlON increases, the smooth SiO2 oxide layer on the surface of the ceramic foam gradually changes to acicular and columnar mullite crystals, and the oxidation resistance increases. Therefore, β-SiAlON acts as a high-temperature binder when it is added to SiC. Hence, the prepared β-SiAlON/SiC composite ceramic foams can be used as ceramic filters in the field of molten metal filtration.

Effect of alumina sol on the preparation of magnesia‐alumina spinel foam ceramics by foaming‐sol method

AbstractIn this work, magnesia‐alumina spinel foam ceramics were prepared by foaming‐sol method using magnesia alumina spinel as raw material, anionic surfactant potassium oleate (PO) as foaming agent, and alumina sol as curing agent. The curing mechanism and the effect of alumina sol content on the stability of foam slurry and the properties of foam ceramics were investigated. In the foam slurry, the alumina sol can react with PO, so magnesia‐alumina spinel can be fixed in the foam structure through the gel network to improve the stability of the foam slurry. The gelation process reduces the viscosity of the foam slurry. The pores of magnesia‐alumina spinel foam ceramics sintered at 1500°C are mostly closed pores and the average pore was 29.7–42.1 µm. With the increase of alumina sol content, the bulk density of magnesia‐alumina spinel foam ceramics increased from 1.3 to 1.9 g/cm3, the cold compressive strength from 8.8 to 22.7 MPa, and the thermal conductivity from .417 to .806 W·m−1·K−1(350°C).