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Low‐cost ceramic membrane support is important for the filtration performance of a asymmetry filtration membrane. In this study, the oil‐based drilling cutting pyrolysis residues (ODPRs) were used as raw materials incorporating with fly ash, and carbon particles were used as pore‐forming agents to prepare high‐flux low‐cost ceramic membrane supports. Besides the strength of the supports was decreased with increased carbon particles addition and size, the porosity, pore size and consequently the Darcey permeability k1 and pure water permeability of the support were increased with the increased carbon particle addition and size. The chemical stability of the support was deteriorated with the increased carbon particles addition. A leaching test on the support with 10% 12 µm carbon particle addition indicates that the support obtained by using the ODPRs incorporating with fly ash as raw materials is safe for aqueous filtration. This study showcased the utilization of ODPRs as a primary resource to manufacture a high‐permeability support for water filtration. This approach aligns with the principles of sustainable development, following a waste‐to‐product‐to‐environment pathway. [ABSTRACT FROM AUTHOR]

The conventional approach to generate pores in ceramic membranes involves the incorporation of a pore-forming element. However, this method tends to diminish the mechanical properties of the membranes and poses challenges in effectively regulating both pore size and membrane porosity. In this work, low-cost ceramic filtering membranes with enhanced mechanical strength have been successfully prepared mainly from abundant clays and without the need for pore-forming agents. The Porosity and pore size were controlled by adding a finely-grained clay (d 90 = 22 μm) by-product to coarse clay (d 90 = 50 μm) within a specified range of 33–66 wt%. The microstructure evolution of prepared membranes was examined by XRF, FTIR, XRD, SEM, and DTA-TGA analysis, while the technological properties were evaluated by permeability, porosity, density, and mechanical measurements. The findings indicated that the increase in the amount of finely grained clay mixed with coarse clay and the sintering temperature had a synergistic effect on the porosity and pore size of the obtained membranes. The incorporation of finely-grained clays, accompanied by an elevation in sintering temperature, led to a reduction in porosity from 31.3 ± 0.7 % to 6.2 ± 0.5 % and pore size, along with the crystallization of the α-mullite (12 %) and anorthite (30 %) phase with a quartz phase and an improvement in mechanical strength reaching up to 251 ± 3 MPa. A formulation comprising 33 wt% of finely-grained clay by-products and 67 wt% of coarse clay, sintered at 1000 °C, emerged as a promising ultrafiltering membrane with enhanced mechanical strength reaching 120 ± 1 MPa, and a permeability of 1000 L/h.m2 at 1 bar. [ABSTRACT FROM AUTHOR]

Porous calcium silicate ceramic has been prepared by ultrafast high‐temperature process in several minutes. The effect of sintering current and starch content on the phase composition, pore structure, compressive strength, and air permeability have been investigated. Homogeneous pores can be formed during the fast decomposition of calcium silicate hydrate, calcium carbonate, and starch. The optimized composition shows the high compressive strength (over 7 MPa), porosity (60.8%), and air permeability (379.4 L/m2 s). Results showed that the ultrafast high‐temperature sintering method can achieve homogenous porous structure in much shorter time than conventional furnace sintering. [ABSTRACT FROM AUTHOR]

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This review article provided a thorough examination of porous ceramic materials, concentrating on production, characteristics, and the involvement of pore-forming agents. The primary objective of this research was to evaluate the effects of various ceramic materials and pore-forming agents on the structure, porosity, and mechanical characteristics of porous ceramics. The study's scope included a thorough investigation of key sources of literature, such as academic publications, review articles, and industry reports, to provide a comprehensive understanding of porous ceramic technology. According to the literature review, the selection of ceramic material and pore-forming agents has a significant influence on the pore size distribution, porosity, and mechanical strength of porous ceramics. Various manufacturing methods, including foaming, sintering, and sol-gel procedures, were explored in terms of their influence on porous ceramic microstructure and characteristics. Furthermore, the study emphasized the need to optimize processing settings and select pore-forming agents to obtain the necessary qualities in porous ceramic materials. Overall, this review is useful for researchers, engineers, and practitioners who desire to learn more about porous ceramic manufacturing, characteristics, and applications.

Abstract Porous ceramics were synthesized using porcelain tile polishing residue (PTPR) and slaked lime (Ca(OH)2) as a reinforcing agent through a hydrothermal autoclaving method. The process parameters, including the quantity of slaked lime added, the hydrothermal autoclaving temperature, and the reaction duration, were optimized meticulously. The composition, structure, thermal and physical properties of the samples were thoroughly analyzed via Brunauer–Emmett–Teller (BET) measurements, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The results indicated that the incorporation of slaked lime and hydrothermal autoclaving led to the formation of calcium silicate hydrate, which corresponded with an enhancement in the strength of the sample. Notably, when the quantity of slaked lime added was optimized at 30 wt%, the formation of tobermorite (5CaO·6SiO2·5H2O) was detected. At a hydrothermal autoclaving temperature of 150 °C, the formation of only sheet-like calcium silicate hydrate was observed. In contrast, at an elevated temperature of 180 °C and 210 °C, needle-like tobermorite was successfully synthesized. The porous ceramic with the most favorable structure was obtained through autoclaving at 180 °C for 10 h with 30 wt% slaked lime, exhibiting a total pore volume of 0.11 mL/g, a specific surface area of 26.35 m2/g, and a mesoporous volume fraction of 90.40%.

Porous ceramics were synthesized using porcelain tile polishing residue (PTPR) and slaked lime (Ca(OH)2) as a reinforcing agent through a hydrothermal autoclaving method. The process parameters, including the quantity of slaked lime added, the hydrothermal autoclaving temperature, and the reaction duration, were optimized meticulously. The composition, structure, thermal and physical properties of the samples were thoroughly analyzed via Brunauer–Emmett–Teller (BET) measurements, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The results indicated that the incorporation of slaked lime and hydrothermal autoclaving led to the formation of calcium silicate hydrate, which corresponded with an enhancement in the strength of the sample. Notably, when the quantity of slaked lime added was optimized at 30 wt%, the formation of tobermorite (5CaO·6SiO2·5H2O) was detected. At a hydrothermal autoclaving temperature of 150 °C, the formation of only sheet-like calcium silicate hydrate was observed. In contrast, at an elevated temperature of 180 °C and 210 °C, needle-like tobermorite was successfully synthesized. The porous ceramic with the most favorable structure was obtained through autoclaving at 180 °C for 10 h with 30 wt% slaked lime, exhibiting a total pore volume of 0.11 mL/g, a specific surface area of 26.35 m2/g, and a mesoporous volume fraction of 90.40%. [ABSTRACT FROM AUTHOR]

This review article provided a thorough examination of porous ceramic materials, concentrating on production, characteristics, and the involvement of pore-forming agents. The primary objective of this research was to evaluate the effects of various ceramic materials and pore-forming agents on the structure, porosity, and mechanical characteristics of porous ceramics. The study's scope included a thorough investigation of key sources of literature, such as academic publications, review articles, and industry reports, to provide a comprehensive understanding of porous ceramic technology. According to the literature review, the selection of ceramic material and pore-forming agents has a significant influence on the pore size distribution, porosity, and mechanical strength of porous ceramics. Various manufacturing methods, including foaming, sintering, and sol-gel procedures, were explored in terms of their influence on porous ceramic microstructure and characteristics. Furthermore, the study emphasized the need to optimize processing settings and select pore-forming agents to obtain the necessary qualities in porous ceramic materials. Overall, this review is useful for researchers, engineers, and practitioners who desire to learn more about porous ceramic manufacturing, characteristics, and applications. [ABSTRACT FROM AUTHOR]

Porous silica ceramics were prepared by a freeze-casting method using dual solvents as a template, and their microstructure can be regulated by different ratios of solvents. As the camphene content increases, the pore shape gradually changes from prismatic pores to spherical pores, and the pore size first decreases and then increases. A porous silica ceramic showed 76 % porosity and a uniform pore size of 6 µm. It presents excellent thermal insulation properties (thermal conductivity ∼0.17 W m−1 K−1), good compressive strength, and a stable dielectric constant (∼1.48). The results of this work shed light on the promising aerospace application of porous ceramics prepared by freeze-casting using dual solvents as a template. [ABSTRACT FROM AUTHOR]

In this study, a two-step method combining the direct foaming process with the control of solid content and heat treatment temperature was employed to prepare ZrP 2 O 7 -CePO 4 composite porous materials with varying porosities. The results indicate that an increase in solid content and heat treatment temperature leads to a reduction in porosity and average pore size while simultaneously improving the mechanical properties. The porosities, compressive strengths, thermal conductivities, ε and Tanδ ranged from 63.2 to 85.3 vol%, 19.43 to 0.99 MPa, 0.089 to 0.088 W/(m·K), 1.64 to 2.72, and 0.88 × 10−3 to 1.99 × 10−3, respectively. Electromagnetic simulations have validated that ZrP 2 O 7 -CePO 4 composite porous ceramics, when used as the core layer material for A-sandwich antenna radomes, exhibit excellent transmittance properties. This suggests the potential application of these materials for supersonic aircraft antenna radomes. • A novel ZrP 2 O 7 -CePO4 porous ceramic were prepared by foaming method combining a two-step method. • Our work greatly improved the compressive strength of high-porosity ZrP 2 O 7 with low thermal conductivity. • The dielectric properties of ZrP 2 O 7 ceramics with high porosity were studied for the first time in this study. • The feasibility of ZrP 2 O 7 -CePO 4 ceramics for supersonic aircraft is verified by electromagnetic simulation. [ABSTRACT FROM AUTHOR]

In this study, alumina ceramics with hierarchical pores were successfully fabricated using freeze casting. Experimental studies show that both the solid loading of the slurry and the thermal insulation layer at the interface of the slurry and cooling plate can influence the pore characteristics of cast samples. In order to examine the pore characteristics and evaluate the permeability of the freeze-cast samples fabricated under different conditions, a generative adversarial network (GAN) method was employed to reconstruct the three-dimensional (3D) microstructure from two-dimensional (2D) scanning electron microscopy (SEM) images of the samples. Furthermore, GAN 3D reconstruction was validated against X-ray tomography 3D reconstruction results. Based on the GAN reconstructed microstructures, the permeability and pore distribution of the various samples were analyzed. The sample cast with 35 wt.% solid loading shows an optimal permeability. [ABSTRACT FROM AUTHOR]

Porous ceramics for aerostatic bearing restrictors were fabricated using carboxymethyl cellulose and polystyrene microspheres as pore formers. The three‐dimensional morphology of the porous ceramics was nondestructively obtained using laser scanning confocal microscopy, and the processing information was eliminated by fitting the pore area fractal dimensions at different heights. A mathematical model was developed based on the assumption of elliptical tortuous capillaries to relate microstructural pore parameters to permeability by combining fractal theory, Darcy's law, and the gas conservation equation. The calculated permeability closely matched the experimental results, with an error of less than 3.5%. This method has promising potential as an alternative to pressure drop experiments. Moreover, the capacity of the fractal calculation model to establish a correlation between microstructural parameters and permeability paves a new way to design future porous aerostatic bearings. [ABSTRACT FROM AUTHOR]

Porous ceramic filters with high porosity and high filtration are in urgent need of high-temperature gas filtration. Here a lightweight and low thermal conductivity mullite fiber porous ceramic filter was prepared through vacuum filtration method using solution blow spun mullite fiber as the matrix material and silica sol as the high-temperature binder. Mullite fiber porous ceramic with a mass ratio of 10:1 has uniform pore structure, low density (0.58 g cm−3), high porosity (78.11%), high compressive strength (1.79 MPa), as well as low thermal conductivity (0.095 W m−1 K−1) at a sintering temperature of 1300 ℃. When the air flow is 6 L min−1, the pressure drop is 180 Pa, the filtration efficiency of PM 2.5 and PM 10–2.5 is 98.85% and 99.61%, respectively, and the filtration quality factor is 0.025 Pa−1. The mullite fiber porous ceramic filter have outstanding quality factor, which has broad application prospects in high-temperature gas filtration. [ABSTRACT FROM AUTHOR]

The porous TiCO ceramic was synthesized through a one-step sintering method, utilizing phenolic resin, TiO2 powder, and KCl foaming agent as raw materials. Ni(NO3)2·6H2O was incorporated as a catalyst to facilitate the carbothermal reaction between the pyrolytic carbon and TiO2 powder. The influence of Ni(NO3)2·6H2O catalyst content (0, 5, 10 wt.% of the TiO2 powder) on the microstructure, compressive strength, and thermal conductivity of the resultant porous TiCO ceramic was examined. X-ray diffraction and X-ray photoelectron spectroscopy results confirmed the formation of TiC and TiO in all samples, with an increase in the peak of TiC and a decrease in that of TiO as the Ni(NO3)2·6H2O content increased from 0% to 10%. Scanning electron microscopy results demonstrated a morphological change in the pore wall, transforming from a honeycomb-like porous structure composed of well-dispersed carbon and TiC-TiO particles to rod-shaped TiC whiskers, interconnected with each other as the catalyst content increased from 0% to 10%. Mercury intrusion porosimetry results proved a dual modal pore-size distribution of the samples, comprising nano-scale pores and micro-scale pores. The micro-scale pore size of the samples minorly changed, while the nano-scale pore size escalated from 52 nm to 138 nm as the catalyst content increased from 0 to 10%. The morphology of the pore wall and nano-scale pore size primarily influenced the compressive strength and thermal conductivity of the samples by affecting the load-bearing capability and solid heat-transfer conduction path, respectively. [ABSTRACT FROM AUTHOR]

High entropy pyrochlore oxide ceramics with hierarchical porous structures were prepared by coprecipitation, freeze-casting, and press-less sintering methods. In the fabrication process, a Ca2+-crosslinked alginate network was utilized to control the growth of ice crystals, resulting in uniformly dispersed micro-scale circular pores. The submicron pores were formed in the high entropy oxide ceramic during the press-less sintering method. The XRD was employed to explore the phase of the high entropy pyrochlore oxide ceramic. The porous structures of high-entropy ceramic were analyzed through the discussion of microstructure and pore size distribution. The tests show that the prepared series of ceramics with high porosity have optional compressive strength and thermal insulation properties. The high entropy oxide ceramic (La 0.2 Y 0.2 Gd 0.2 Sm 0.2 Nd 0.2) 2 Zr 2 O 7 with hierarchical porous structures possess moderate density (0.4 g/cm3) and low thermal conductivity (0.04 W m−1 K−1). The excellent comprehensive performance makes the porous high entropy oxide ceramic could be applied as a thermal insulating material. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) porous ceramic foams were fabricated using YSZ microspheres with holes on the surface to determine their properties as insulation materials. Highly porous YSZ ceramics with bimodal pore structures, such as internal pores in single hollow spheres and external pores between the spheres, were successfully prepared using YSZ spheres as raw materials. Additionally, holes were added to the shells to reduce continuous thermal pathways and significantly enhance the insulation properties. Furthermore, by adding holes on the surface of the sphere, the porous foams using a hollow sphere exhibit a maximized porosity of 80.69%, remarkably enhanced their insulation properties with low thermal conductivity (0.10 W/m-K), and have sufficient compressive strength to protect the green body (5.7 MPa). The mechanical strength of the YSZ porous foam was maintained owing to the uniform arrangement of the supports. • Highly porous YSZ ceramic foams using hollow spheres with holes were prepared. • The formation mechanism of the hollow sphere was investigated. • The holes on the surface of spheres have a significant effect on maximizing porosity. • Obtained compressive strength is higher than references due to the uniform skeleton. [ABSTRACT FROM AUTHOR]

The influence of the removal of carbonates on the ceramic properties made of Moroccan red clay as a main material and tea waste as pore-forming agent, has been investigated. ATD-TG, dilatometry, dimensional changes, weight loss, water absorption, open porosity, bulk density, flexural and indirect tensile strengths were assessed at different firing temperatures within the range of 900–1150 °C. SEM was used to evaluate the microstructures of the fired samples, while XRD was used to study the phase evolution. At varying firing temperatures, the materials which contains the carbonate (CC) exhibit greater weight loss, water absorption, and porosity compared to the materials without carbonate (NCC). On the other hand, NCC materials has greater mechanical strength than that CC materials. The microstructural analysis conducted through SEM revealed distinct changes in the fired samples when comparing observations at 1100 °C to those at 900 and 1000 °C. At 1100 °C, there was a noticeable increase in particle contacts and layered structures, which can be attributed to the presence of dehydroxylated clay minerals (illite and chlorite), quartz particles, and pores formed during firing. Subsequently, at 1150 °C/ 2 h, further alterations in the microstructures were observed due to a higher degree of vitrification in the fired samples. This resulted in material consolidation, interparticle and neck contacts, leading to the formation of vitrified bridges. Firing has resulted in the formation of closed and open pores of varying sizes, in the vitrified structures associated with anorthite, hematite, and quartz, a thin crystal precipitation of small particles was observed. This alteration in microstructure made it possible to conclude that the flexural and indirect tensile strength increased during firing, reaching its pinnacle at 1150 °C. As a result of the firing process, the ceramic supports underwent heightened sintering, leading to a gradual decline in open porosity. The present inquiry proved to be intriguing as it led to a deeper understanding of the utilization of Moroccan red clay as a ceramic’s raw material.

The significant shrinkage of porous ceramics after sintering has produced a number of issues with their use and development. As a result, we proposed an in-situ hollow sphere method for producing non-shrinkage alumina porous ceramics. The obtained green samples were made up of Al 2 O 3 and Al powders, with pores emerging inside the materials due to the Kirkendall effect of Al particles after sintering. The expansion of hollowing particles exactly offsets the shrinkage generated by sintering throughout the process. When 50 vol. % Al powder (10 µm) is added, the linear shrinkage rate of the sample after sintering at 1500 °C can reach −3.47 %, and its apparent porosity and flexural strength are 30.69 % and 44.03 MPa, respectively. According to approximate calculations, the pores formed by the oxidation of Al powder are smaller than the initial size of Al powder. This method suggests a novel approach for producing controlled shrinkage porous ceramics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous ceramic from MSWI FA and WG prepared via loose powder sintering method. • The removal efficiency of Pb, Cd and Zn was higher than 90% at 1200 °C above 30 min. • The bulk density of ceramic dropped to 1.48 g/cm3 with 4% SiC addition at 1200 °C. • Increasing WG content reduced sintering temperature and MSWI FA: WG = 1:2 was proposed. Loose powder sintering was used to prepare porous ceramic from municipal solid waste incineration fly ash (MSWI FA) and waste glass (WG). Sintering experiments at various temperatures, holding times, Al 2 O 3 and SiC were conducted to investigate their effect on the ceramic properties and volatile heavy metal removal efficiency. The results show that increasing temperature from 1100 °C to 1250 °C promoted the transition of the mixtures from loose powder to a densified sintered matrix, with a bulk density increase of 31.10% and an open porosity decrease of 70.41%. The bulk density of the ceramic increased to 2.44 g/cm3 with 3% Al 2 O 3 addition. The removal rates of Pb, Zn, Cu and Cd were higher than 90% at 1200 °C for 90 min, and promoted by the increasing temperature and holding time. Notably, 3% Al 2 O 3 addition inhibited the volatilisation of Zn, Cu and Cd, particularly for Zn, the removal rate of which reduced to 61.66% at 1200 °C. The bulk density of the ceramic decreased to a minimum value of 1.48 g/cm3 with 4% SiC. The ratio of MSWI FA:WG:Al 2 O 3 :borax of 28.3:56.7:10:5 was proposed to obtain ceramic with a bulk density of 1.54 g/cm3 and a water absorption rate of 8.59% at 1150 °C. The leaching concentration of the porous ceramic met the Chinese regulatory standard (GB 8978-1996). Preparation of MSWI FA-based porous ceramics using the powder sintering method is a promising route for the harmless utilisation of MSWI FA. The porous ceramic is potentially applicable as a thermal-insulation building material. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the role of thermal treatment on the crystallinity and pore characteristics of porous ceramic, which was prepared from natural clay (NC) and chitosan (CS) biopolymer using the gel casting method. CS was used as an environmentally friendly pore-forming agent. The applied temperature treatment was based on thermal analysis (TGA/DTA) results and followed a sintering temperature of 900 to 1100 °C. The results showed that at sintering temperatures from 900 to 1000 °C, the crystallinities of the ceramic decrease (from 76.06 to 74.06%) and the crystallite size decreases (from 35.71 to 34.47 nm) while the lattice strain increases (calculated from the Full Width at Half Maximum (β) of the diffraction peak). The highest porosity of ceramic occurred at a sintering temperature of 1000 °C of 37.82 ± 0.19, but the formation of heterogeneous microstructure was observed. The resulting pore size for all temperature treatments was almost mesoporous (19.1 Å). Based on the results obtained, it is emphasized that the sintering temperature can be used to adjust the porosity and microstructure of porous ceramics.

Porous mullite ceramics were prepared by pressing molding and sintering method, using coal gangue and bauxite as raw materials, hollow glass microspheres as pore-forming agent. The effects of addition amount of hollow glass microspheres and sintering temperature on phase composition, microstructure, flexural resistance and acid and alkali corrosion resistance were studied. The results show that increasing the amount of hollow glass microspheres can increase the porosity of porous ceramics; the addition of hollow glass microspheres can promote the formation of mullite phase and reduce the sintering temperature. In a certain temperature range, increasing the sintering temperature can also increase the porosity, but when the sintering temperature is over 1350 ℃, the porosity begins to decline. Porous mullite ceramics with porosity of 33.23% and flexural strength of 56.41 MPa can be obtained by keeping the molar ratio of Al2O3∶SiO2=3∶2 and adjusting the addition amount of hollow glass microspheres to 1.68%(mass fraction) and sintering at 1350 ℃ for 2 h, which has good acid and alkali corrosion resistance.

Highly porous kaolin ceramics composites were produced by adding space-holder materials during dry pressing. To increase the strength of porous kaolin ceramic composites different ratios of cobalt-nickel ferrite nanoparticles (5, 10, 15, and 20%) were added. The sol-gel auto-combustion method prepared the nano cobalt-nickel ferrite particles (CNF). Space-holder materials were removed by preheating, and solid specimens were produced by sintering. X-ray diffraction (X-RD) and Fourier transform infrared spectroscopy (FT-IR) was used to examine the structural characteristics. Up to 47.05% porosity was achieved when 20% CNF was added to the porous kaolin ceramics composites. The results indicated that the higher percentages of nano CNF 20% decreased linear shrinkage and the loss of ignition by 4.4% and 30.4%, respectively. While increased apparent density and diametrical strength of 1.42 g/cm3, and 9.03MPa respectively. Diametrical strength nanoparticles increased the strength attributed to the formation of a secondary phase in the porous ceramics, improving the crack bridging mechanism.

The porous TiCO ceramic was synthesized through a one-step sintering method, utilizing phenolic resin, TiO2 powder, and KCl foaming agent as raw materials. Ni(NO3)2·6H2O was incorporated as a catalyst to facilitate the carbothermal reaction between the pyrolytic carbon and TiO2 powder. The influence of Ni(NO3)2·6H2O catalyst content (0, 5, 10 wt.% of the TiO2 powder) on the microstructure, compressive strength, and thermal conductivity of the resultant porous TiCO ceramic was examined. X-ray diffraction and X-ray photoelectron spectroscopy results confirmed the formation of TiC and TiO in all samples, with an increase in the peak of TiC and a decrease in that of TiO as the Ni(NO3)2·6H2O content increased from 0% to 10%. Scanning electron microscopy results demonstrated a morphological change in the pore wall, transforming from a honeycomb-like porous structure composed of well-dispersed carbon and TiC-TiO particles to rod-shaped TiC whiskers, interconnected with each other as the catalyst content increased from 0% to 10%. Mercury intrusion porosimetry results proved a dual modal pore-size distribution of the samples, comprising nano-scale pores and micro-scale pores. The micro-scale pore size of the samples minorly changed, while the nano-scale pore size escalated from 52 nm to 138 nm as the catalyst content increased from 0 to 10%. The morphology of the pore wall and nano-scale pore size primarily influenced the compressive strength and thermal conductivity of the samples by affecting the load-bearing capability and solid heat-transfer conduction path, respectively.

Replacement of bone defects with bone graft or implant is an important therapeutic strategy that has been used in routine practice. However, the identification of biomaterials that can mimic natural bone properties and serve as bone substitutes remains a major challenge. In this context, alumina-zirconia (Al2O3/ZrO2) nanocomposites emerge as potential alternatives for biomedical applications, owing to their high mechanical strength, wear resistance, and biocompatibility. In this sense, in this study, we prepared porous Al2O3/ZrO2 nanocomposites (scaffolds) using the gelcasting method and biomimetically coated them with calcium phosphate (CaP). We evaluated the biocompatibility of the scaffolds using the quantitative MTT cytotoxicity test in L929 cells. Moreover, rabbit adipose-derived mesenchymal stem cells (rADMSCs) were seeded with CaP-containing and CaP-free porous samples to evaluate cell proliferation and cell–scaffold interaction in vitro. Our results showed that the Al2O3/ZrO2 scaffolds were non-cytotoxic, and there were no significant differences between CaP-containing and CaP-free scaffolds in terms of cell growth and adhesion. In contrast, when co-cultured with rADMSCs, the scaffolds enhanced cell proliferation and cell adhesion. The rADMSCs adhered and migrated through the pores of the scaffold and anchored to different poles with differentiated elongated structures. These results suggest osteogenic differentiation of rADMSCs in response to mechanical loading of Al2O3/ZrO2 scaffolds. Therefore, we conclude that Al2O3/ZrO2 scaffolds have demonstrated significant implications in bone tissue engineering and are valuable biomaterials for bone replacement.

Tissue engineering requires new materials that can be used to replace damaged bone parts. Since hydroxyapatite, currently widely used, has low mechanical resistance, silicate ceramics can represent an alternative. The aim of this study was to obtain porous ceramics based on diopside (CaMgSi2O6) and akermanite (Ca2MgSi2O7) obtained at low sintering temperatures. The powder synthesized by the sol-gel method was pressed in the presence of a porogenic agent represented by commercial sucrose in order to create the desired porosity. The ceramic bodies obtained after sintering thermal treatment at 1050 °C and 1250 °C, respectively, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) to determine the chemical composition. The open porosity was situated between 32.5 and 34.6%, and the compressive strength had a maximum value of 11.4 MPa for the samples sintered at 1250 °C in the presence of a 20% wt porogenic agent. A cell viability above 70% and the rapid development of an apatitic phase layer make these materials good candidates for use in hard tissue engineering. [ABSTRACT FROM AUTHOR]

Ceramic atomization cores are a new application of porous ceramics; however, the challenging regulation of the pore structures of porous ceramics has limited their application. To improve the low liquid absorption rates and low liquid storage capacity of porous ceramics in the field of atomization, this study used three substances, polymethyl methacrylate (PMMA), starch, and diatomaceous earth, to produce porous ceramics with a three-dimensional interconnected triple-porous structure by sacrificial templating. In the porous ceramics, large pores resulting from PMMA increase liquid storing capacity, medium pores resulting from the starch facilitate the transport of liquid, and small pores resulting from diatomaceous earth enhance capillary action, significantly increasing the rate of liquid absorption. By varying the PMMA contents and type of starch in the preform, water and oil storage capacities of up to 123% and 143%, respectively, can be achieved. We found that an optimized porous ceramic with dimensions of 15 mm × 15 mm × 15 mm absorbs water rapidly (reaching saturation in only 1.67 s), demonstrates good solid–liquid properties and shape stability, and is recyclable (requires drying before reuse). The proposed porous ceramics have promising atomization core and oil–water separation applications. [ABSTRACT FROM AUTHOR]

The process of anaerobic digestion used for methane production can be enhanced by dosing various additive materials. The effects of these materials are dependent on various factors, including the processed substrate, process conditions, and the type and amount of the additive material. As part of the study, three different materials—iron powder, lime, and milled porous ceramic—were added to the 30-day anaerobic digestion of the brewer's spent grain to improve its performance. Different doses ranging from 0.2 to 2.3 gTS × L−1 were tested, and methane production kinetics were determined using the first-order model. The results showed that the methane yield ranged from 281.4 ± 8.0 to 326.1 ± 9.3 mL × gVS−1, while substrate biodegradation ranged from 56.0 ± 1.6 to 68.1 ± 0.7%. The addition of lime reduced the methane yield at almost all doses by −6.7% to −3.3%, while the addition of iron powder increased the methane yield from 0.8% to 9.8%. The addition of ceramic powder resulted in a methane yield change ranging from −2.6% to 4.6%. These findings suggest that the use of additive materials should be approached with caution, as even slight changes in the amount used can impact methane production. [ABSTRACT FROM AUTHOR]

Mullite and mullite–alumina ceramics materials with dominance of the mullite phase are used in different areas of technology and materials science. Porous mullite ceramics materials can be used simultaneously as refractory heat insulators and also as materials for constructional elements. The purpose of this work was to investigate the WO3 nanoparticle influence on the evolution of the aluminum tungstate and zircon crystalline phases in mullite ceramics due to stabilization effects caused by different microsize ZrO2 and WO3. The use of nano-WO3 prevented the dissociation of zircon in the ceramic samples with magnesia-stabilized zirconia (MSZ), increased porosity by approximately 60 ± 1%, increased the intensity of the aluminum tungstate phase, decreased bulk density by approximately 1.32 ± 0.01 g/cm3, and increased thermal shock resistance by ensuring a loss of less than 5% of the elastic modulus after 10 cycles of thermal shock. [ABSTRACT FROM AUTHOR]

Huge amounts of unwanted sewage sludge are generated in the process of wastewater treatment, calling for methods to recycle sewage sludges into value-added materials and fuels. Here, we review the use of sewage sludge to produce glass and porous ceramics, with focus on sewage sludge production, properties, dewatering mechanism and solidification. We present the process parameters that control the formation of sewage sludge porous ceramics. The effect of heavy metals on solidification is discussed. [ABSTRACT FROM AUTHOR]

Porous materials with wrinkled surfaces could have broad applications in catalysis and adsorption. However, designing cellular ceramics with similar structures is challenging. Herein, we demonstrated the binary colloidal self-assembly of γ-Al 2 O 3 nanoparticle/silica gelation network for constructing such materials. The competitive effect between volume shrinkage and surface bend during water evaporation of silica gel contributed to wrinkled aperture surface. During calcination, silica nanoparticles were highly active to react with alumina to form mullite nanocrystals, bringing about high compressive strength at low relative densities. After calcining at 1350 °C, resultant products with hierarchical structure exhibited an outstanding compressive strength of 4.2 MPa, a relatively high surface area of 7.23 m2/g at a porosity level of 83.3%. The current strategy provides a feasible and affordable approach for producing high performance ceramic foams towards practical application fields in catalysis and adsorption. [ABSTRACT FROM AUTHOR]

Waste porous ceramic (WPC), which remains in the industrial manufacturing process, is difficult to be disposed of. This study proposes a new idea for resource utilization of WPC, which means that WPC as a bacterial carrier applies in self-healing cemented paste backfill. The authors investigated the effects of WPC pore size, initial crack size, and bacterial concentration on the crack self-healing ratio of the backfill, analyzed the crack self-healing evolution process by photographing, and finally used a series of instruments to characterize the physical phase at the sample fracture and explain the mechanism. The results showed that the crack self-healing ratio of WPC with small pore size (pore size distribution of 1–2 mm) as the bacterial carrier was 13–22% higher than that of WPC with large pore size (pore size distribution of 3–4 mm) at 3–7 days. Also, the strength recovery ratio of the cemented paste backfill can be improved to 10–23% when adding bacteria-WPC. The self-healing ratio can reach 100% in 28 days for initial crack widths less than 1 mm, while the self-healing ratio decreases to 98% for widths near 2 mm. Additionally, the biomineralization ratio of the 1.5 mol/L embedded bacterial solution was 2.77–4.68% higher than that of 1.0 mol/L. WPC can effectively release the embedded bacterial solution once the backfill cracks appear, which proves the feasibility of WPC as a bacterial carrier. This study also lays the experimental and theoretical foundation for porous ceramic management. [ABSTRACT FROM AUTHOR]

Al/TiB2-SiC composites were prepared based on TiB2-SiC porous ceramic preforms. The advantages of this work were characterized by the in-situ synthesized TiB2 in porous ceramic preforms which directly formed interconnected pores as well as TiB2-SiC ceramic skeletons during the one-step ceramic sintering. By controlling in-situ synthesized TiB2 volume fraction, it is possible to tailor TiB2-SiC preform structures so as to determine the structures and mechanical properties of Al/TiB2-SiC composites. The porous ceramic preforms with 20 vol% TiB2 addition achieved the highest porosity, the biggest pore size, but the lowest flexural strength. Al/TiB2-SiC composite with 20 vol% TiB2 addition showed the optimum mechanical properties. The improvement of mechanical properties of Al/TiB2-SiC composites was mainly ascribed to TiB2 additions as well as dense composite structures which were fully infiltrated with Al. This special interpenetrating structural feature and TiB2 addition also constituted an improved toughness through complex crack patterns such as branching, bridging, and deflection.

This paper describes the fabrication of kaolinite (Al2O3-2SiO2-2H2O) spherical bulbs by slip casting. The bisque-fired parts present a porosity of about 30% with submicron porosity confirmed by scanning electron microscopy. In addition, plate-like grains with channels were observed. After nickel infiltration of the specimens, nanosized Ni particles covered the surfaces of the channels of these grains. Permeation tests in 5% H2 at 400 and 600 °C resulted in fluxes between 0.05 and 0.06 mol·m−2·s−1 at a pressure gradient of 200 MPa·m−1. Potential applications of these specimens include supports for hydrocarbon (namely ethanol) steam reforming. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present an overview of the development of gel casting methods on synthesis techniques and the characteristics of gel casting porous ceramics and its applications. The gel casting method is a colloidal ceramic synthesis method that requires a short period for the ceramic body to develop. This review provides the latest developments in the gel casting process of synthesizing porous ceramics. At the beginning of the gel casting method development, the acrylamide (AM) system was the most commonly utilized system. Over time, the use of the AM system began to be minimized because of its toxicity. Researchers began to develop natural polymers as pore templates and natural minerals as raw materials in the gel casting method. In addition to polymers and raw materials, the gel casting process also requires additives such as gelling agents and dispersants. At the end of this review, a mapping of how to select the additives in the gel casting process, for AM systems and non-AM systems for the fabrication of porous ceramics is presented. The characteristic of porous ceramics produced by AM and non-AM systems are almost similar. Porous ceramic applications have been used as bone tissue supports, energy storage, filters, and catalyst support. This review will be a reference for future research related to the process of fabrication of advanced porous ceramics using the environmentally friendly gel casting method. [ABSTRACT FROM AUTHOR]

Considering the low-cost and environmental protection, the porous ceramics with high porosity using natural diatomite powder were successfully prepared by utilizing hot injection moulding and sacrificial fugitives. The impacts of different content of starch as a pore-forming agent on the phase composition, mechanical properties, thermal conductivity, and micro-structure of porous ceramics were investigated. The results demonstrate that starch content can significantly affect the mechanical properties and thermal conductivity of diatomite-based porous ceramics. When the starch content increased from 0 wt % to 50 wt %, the porosity increased from 61.2% to 80%, while the thermal conductivity decreases from 0.239 W/(m K) to 0.098 W/(m K). The low thermal conductivity of porous ceramics may be related to the macroporous–mesoporous composite structure. With the starch content increased, a greater chance of starch granule contact, higher internal pore sizes and a wider pore size distribution in the prepared samples, which resulting in lower mechanical strength, such as the three-point bending strength from 2.83 MPa to 0.46 MPa. [ABSTRACT FROM AUTHOR]

Mullite porous ceramics were prepared by in-situ sintering using zirconia-containing sillimanite as the main raw material, α-Al2O3 powder as the auxiliary material and modified starch as the pore-forming agent. The effects of the sintering temperature (1 400 -1 600 °C,an interval of 50 °C) on the phase composition, the microstructure and the properties of the samples were studied. The results show that: (1) with the increase of the sintering temperature, the intensity of the mullite diffraction peaks increases and the mullite crystals gradually grow up; moreover, steps are observed on mullite surfaces, indicating that the mullite grows by two-dimensional nucleation mechanism; (2) with the increase of the sintering temperature, the bulk density of the samples decreases firstly and then increases, while the apparent porosity and the linear change show the opposite trends, but the cold compressive strength increases gradually; (3) when the sintering temperature is 1 550 -1 600 °C, the samples show the optimal comprehensive properties; mullite crystals grow up and combine closely, which makes mullite porous ceramics suitable for application at high temperatures. [ABSTRACT FROM AUTHOR]

Silica sol is widely used in the preparation of mullite-based fiber porous ceramics (MFPCs), but it aggregates at the top surface of MFPCs during the drying process. This leads to the decrease in mechanical strength and porosity. To overcome the problem and fabricate homogeneous MFPCs, the sodium silicate solution and glass fibers were applied in the fabrication process of MFPCs. The effects of concentrations of sodium silicate solution and silica sol, amounts of glass fibers and sintering temperatures on the properties of prepared MFPCs were studied. The sodium silicate solution consolidated the silica sol and mullite fibers, forming a homogeneous structure and ensuring the even distribution of silica sol. Compared with other reported MFPCs, this process required low sintering temperature while maintaining high compressive strength (2.14 MPa) and porosity (75.93%). This study provides an effective method for preparing MFPCs with high strength, uniformity and porosity. • Mullite-based fiber porous ceramics (MFPCs) with high performances were fabricated. • Sodium silicate solution and glass fibers were applied for the preparation of MFPCs. • Sodium silicate solution consolidated silica sol and ensured even distribution. • Interlaced mullite fibers and glass fibers formed 3D structures and improved strength. • The fabrication process in this study required a low sintering temperature. [ABSTRACT FROM AUTHOR]

Porous functional graded ceramics (porous FGCs) offer immense potential to overcome the low mechanical strengths of homogeneously porous bioceramics used as bone grafts. The tailored manipulation of the graded pore structure including the interfaces in these materials is of particular interest to locally control the microstructural and mechanical properties, as well as the biological response of the potential implant. In this work, porous FGCs with integrated interface textures were fabricated by a novel two-step transfer micro-molding technique using alumina and hydroxyapatite feedstocks with varied amounts of spherical pore formers (0–40 Vol%) to generate well-defined porosities. Defect-free interfaces could be realized for various porosity pairings, leading to porous FGCs with continuous and discontinuous transition of porosity. The microstructure of three different periodic interface patterns (planar, 2D-linear waves and 3D-Gaussian hills) was investigated by SEM and µCT and showed a shape accurate replication of the CAD-designed model in the ceramic sample. The Young’s modulus and flexural strength of bi-layered bending bars with 0 and 30 Vol% of pore formers were determined and compared to homogeneous porous alumina and hydroxyapaite containing 0–40 Vol% of pore formers. A significant reduction of the Young’s modulus was observed for the porous FGCs, attributed to damping effects at the interface. Flexural 4-point-testing revealed that the failure did not occur at the interface, but rather in the porous 30 Vol% layer, proving that the interface does not represent a source of weakness in the microstructure.

Mullite ceramics are well known as materials with a high temperature stability, strength and creep resistance. In this research, the effect of a modification with magnesia-stabilized zirconia and yttria-stabilized zirconia, separately, as well as in a mixture with WO3, in 1:1 and 1:2 ratios on the thermal properties of porous mullite ceramics was investigated. The porous mullite-containing ceramics were prepared by a slip casting of the concentrated slurry of raw materials with the addition of a suspension of Al paste for the pore formation due to the H2 evolution as a result of the reaction of Al with water. The formed samples were sintered at 1600 °C and the holding time was 1 h. The materials were characterized using X-ray diffractometry, scanning electron microscopy, mercury porosimetry, the laser flash contactless method, thermal shock resistance testing and the non-destructive impulse excitation method for determining the elasticity modulus. The modification of the porous mullite ceramic with a mixture of ZrO2 and WO3 oxides had a positive effect by decreasing the thermal conductivity, due to the increased porosity, in comparison to the undoped samples and samples with only ZrO2. The doubling of the WO3 amount in the modifying oxide mixtures improved the ceramic thermal shock resistance. The porous mullite ceramics which were modified with magnesia-stabilized zirconia (2.8 mol% MgO) and WO3 had a lower thermal conductivity and improved thermal shock resistance than the samples with yttria-stabilized zirconia (8 mol% Y2O3) and WO3. [ABSTRACT FROM AUTHOR]

To further resource industrial solid waste, porous ceramics with high porosity were prepared by a gelcasting method using nickel slag and kaolin as raw materials and hydrophilic nontoxic SiO 2 aerogel as a gelling agent. The effects of nickel slag content, dispersant and solid content on the properties and microstructure of porous ceramics were investigated in detail in terms of density, compressive strength, porosity, phase composition and micromorphology. The results confirmed that a certain amount of nickel slag can effectively improve the porosity of porous ceramics, while the addition of dispersant can promote the flow of the slurry, enhanced the denseness of the raw billet and significantly improved the compressive strength. However, its excessive use had a negative effect on the ceramic density and porosity. At the same time, the solid content played a key role in the performance of porous ceramics prepared by gelcasting, and too much solid content was also not conducive to the generation of pores. When the nickel slag content was 55%, the amount of dispersant was 2%, and the solid content was 60 vol%, the porous ceramic had a better overall performance, the density of the porous ceramic was 510 kg/m3, the compressive strength was 1.3 MPa, and the porosity reached 80.1%. The major crystalline phases of porous ceramics prepared by nickel slag were cordierite and anorthite. [ABSTRACT FROM AUTHOR]

Porous ceramics are often produced by using pyrolisable additives to generate porosity during the sintering step. The examination of the experimental microstructures of the resulted porous ceramics revealed certain levels of anisotropy, even if the original soft additives used as pore forming agents were spherical. The paper shows that anisotropic porosity may result in ceramics when using equiaxed soft polymeric additives for generating porosity, due to the deformation of soft inclusions during the pressing step. It has been found, by means of analytical and numerical calculations, that uniaxial pressing of a mixture of solid particles with contrasting mechanical properties (hard/soft) generates modifications in the shape of the soft phase. As a result, anisotropic shape distribution of the soft inclusions in the green ceramic body and elongated porosity in the final ceramic product are obtained. The elongated pores are statistically oriented with the major axes perpendicular to the pressing direction and will generate anisotropy-related functional properties. Analytical calculations indicate the deformation of a single soft inclusion inside a continuum solid. Further, by finite element simulations performed in 2D planes along the transversal and radial directions of the pressing axis, a bimodal angular distribution of the long axes of the soft inclusions has been found. [ABSTRACT FROM AUTHOR]

Enhancing the mechanical strength of macro-porous ceramics and simultaneously endowing them with bactericidal activity are considered to be beneficial for their application as membrane support materials for water and wastewater treatment. In this study, Cu-containing Al 2 O 3 porous ceramics were prepared by powder mixing, cold pressing and subsequent sintering. The microstructures of as-fabricated ceramics consisted of large α-Al 2 O 3 particles as matrix, as well as inter-particle NaAlSiO 4 , CuAl 2 O 4 and CuO phase. With increased sintering temperature from 1430 to 1560 °C, the proportion of band-shaped CuO phase, which exhibited stronger binding tendency with Al 2 O 3 than NaAlSiO 4 , gradually increased, while that of particle-shaped CuAl 2 O 4 phase decreased. Increasing the Cu content from 2 to 8 wt% at a fixed sintering temperature of 1500 °C resulted in the presence of more band-shaped CuO phase in Al 2 O 3 matrix which tightly bonded Al 2 O 3 particles together. The increase of sintering temperature and Cu content could both lead to enhanced bending strength and reduced porosity, while the later factor showed stronger modulatory effects than the former one. Moreover, the bactericidal rates of Cu-containing Al 2 O 3 porous ceramics towards Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were found to increase with increased Cu content in a Cu content-dependent manner. Together, the Cu-containing Al 2 O 3 porous ceramic added with 8 wt% Cu and sintered at 1500 °C exhibited the highest bending strength and strongest bactericidal activity, which could be a promising candidate material for membrane support application. [ABSTRACT FROM AUTHOR]

Al/TiB2-SiC composites were prepared based on TiB2-SiC porous ceramic preforms. The advantages of this work were characterized by the in-situ synthesized TiB2 in porous ceramic preforms which directly formed interconnected pores as well as TiB2-SiC ceramic skeletons during the one-step ceramic sintering. By controlling in-situ synthesized TiB2 volume fraction, it is possible to tailor TiB2-SiC preform structures so as to determine the structures and mechanical properties of Al/TiB2-SiC composites. The porous ceramic preforms with 20 vol% TiB2 addition achieved the highest porosity, the biggest pore size, but the lowest flexural strength. Al/TiB2-SiC composite with 20 vol% TiB2 addition showed the optimum mechanical properties. The improvement of mechanical properties of Al/TiB2-SiC composites was mainly ascribed to TiB2 additions as well as dense composite structures which were fully infiltrated with Al. This special interpenetrating structural feature and TiB2 addition also constituted an improved toughness through complex crack patterns such as branching, bridging, and deflection. [ABSTRACT FROM AUTHOR]

Titanium carbide ceramics with high porosity were fabricated by gelcasting process with methacrylamide as a chain forming monomer, methylenebisacrylamide as a cross-linker monomer and tetramethylammonium hydroxide as a dispersant. The stability of suspension, mechanical properties, phase composition and microstructure were investigated by zeta potential, bending and compressive strengths, X-ray diffraction and scanning electron microscopy (TEM) analyses, respectively. The results show that the optimal concentration of dispersant for the best homogeneous unagglomerated microstructures is 0.4 wt% at pH 9. The highest green strength of 33 MPa is obtained from the suspension with 40 vol% solid loading and 25 wt% monomer. The porosity increases with the increase in monomer content and the decrease in solid loading. Also, the strength of porous TiC ceramic decreases with the content of pores increasing in the sintered ceramics. [ABSTRACT FROM AUTHOR]