Porous Ceramic Materials Research Articles

Characterization, thermal and ceramic properties of clays from Alhabia (Almería, Spain)

Clays from Alhabia (Almería, Spain) have been investigated in this work using several analytical techniques: X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), thermal analysis (Thermogravimetry, TG, and its first derivative, DTG), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Texture characteristics (granulometry) and plasticity have been examined. The main ceramic properties (firing shrinkage, water absorption, bulk density, open porosity, flexural strength and thermal conductivity) have been determined using pressed and fired clay samples. Thus, the mineralogical, chemical, textural and ceramic features of these clays have been evidenced for the first time. The mineralogical analysis by XRD indicated that the clay samples are constituted by a mixture of chlorite and illite, as main clay minerals, being quartz and other minerals in lower relative proportion (calcite, gypsum and hematite). This finding is important because the investigations on chlorite-illite-calcitic clays are very scarce. The chemical analysis by XRF showed that silica and alumina are predominant, as expected by the mineralogy, with medium contents of calcium oxide, from calcite, and alkalis, from illite, being ∼8 and ∼5%, respectively, besides iron and titanium oxides (∼8%). The particle size analysis showed 71.76% of “clay fraction” (<2 μm) and 21.66% of silt fraction (2–50 μm). The plasticity index (Atterberg) was 14.3%, with acceptable moulding and extrusion properties. Thermal analysis by TG/DTG indicated a weight loss associated to dehydroxylation of structural water of the clay minerals and decarbonation of calcite by progressive heating. After the characterization of raw clays, the next step was the determination of ceramic properties of mixed and ground clays after firing using pressed bodies. For this purpose, two firing temperatures were selected (900 and 1100 °C) for 1 h. The examination of the resultant fired bodies indicated that porous ceramic materials (∼36% open porosity and ∼22% of water absorption capacity) can be obtained by firing at 900 ᵒC, with small variations in dimensions (<0.8% at 1100 °C). The porosity changed at relatively lower values by firing at 1100 °C (∼34–35%), being associated to the presence of decomposed calcite. Bulk density was found almost constant from 900 to 1100 °C, with a maximum value of ∼1.67 g/cm3 at 1100 °C. Flexural strength reached a maximum value of 34.47 MPa at 1100 °C for the ground sample. Finally, thermal conductivity after firing the clay bodies was found almost constant at 900 and 1100 °C (0.457 and 0.479 W/mK, respectively). Taking into account these results, the main applications of the Alhabia clays have been evaluated. These clays can be used for the fabrication of porous ceramic supports and tiles by firing at 900 °C. Firing the clays at higher temperature (1100 °C) is of great interest for the fabrication of ceramic tiles and ceramic bricks of higher flexural strength with variable porosity and practically constant in dimensions. It is economically important although at higher processing costs. Finally, it can be emphasized that this work is a contribution of a better scientific knowledge of chlorite-illite-calcitic clays as ceramic raw materials.

Metal nanoparticles market worth $4.2 bn by 2026

Bone reconstruction after tissue loosening due to traumatic, pathological or surgical causes is in increasing demand. 3D scaffolds are a widely studied solution for supporting new bone growth. Bioactive glass–ceramic porous materials can offer a three-dimensional structure that is able to chemically bond to bone. The ability to surface modify these devices by grafting biologically active molecules represents a challenge, with the aim of stimulating physiological bone regeneration with both inorganic and organic signals. In this research work glass ceramic scaffolds with very high mechanical properties and moderate bioactivity have been functionalized with the enzyme alkaline phosphatase (ALP). The material surface was activated in order to expose hydroxyl groups. The activated surface was further grafted with ALP both via silanization and also via direct grafting to the surface active hydroxyl groups.Enzymatic activity of grafted samples were measured by means of UV–vis spectroscopy before and after ultrasonic washing in TRIS–HCl buffer solution. In vitro inorganic bioactivity was investigated by soaking the scaffolds after the different steps of functionalization in a simulated body fluid (SBF). SEM observations allowed the monitoring of the scaffold morphology and surface chemical composition after soaking in SBF. The presence of ALP enhanced the in vitro inorganic bioactivity of the tested material.

Fabricating porous monolithic ceramic materials via phase separations in solutions of poly(Vinyl alcohol) and sol nanoparticles

Fabricating porous monolithic ceramic materials via phase separations in solutions of poly(Vinyl alcohol) and sol nanoparticles

Preparation of Porous Ceramic Building Decoration Materials by Foaming Method and Research on Nanomechanical Properties.

Because of its excellent properties, mullite porous ceramics are widely used in thermal insulation materials, catalyst carriers, gas-liquid filtration, separation materials, etc. At the same time, zirconia not only has the advantages of high melting point, good chemical stability, and high strength but also can significantly improve the strength of ceramics through phase transformation and particle dispersion in the matrix and is widely used in the reinforcement of ceramics. In this paper, using mullite powder as the raw material, Al2O3 and SiO2/ZrSiO4 as the starting material for the mullite self-bonding phase, and AlF3·3H2O, ZrO2, and Y2O3 as additives, the zirconia-reinforced mullite was prepared by the foaming-injection method. The volume density, linear shrinkage rate, microstructure, room temperature, etc. of nanozirconia-reinforced mullite porous ceramics were studied by the amount of the foaming agent, the amount of mullite self-bonding phase powder, the type and amount of additives, etc. Effects of mechanical properties and thermal conductivity were also analyzed. The research results show that zirconia-reinforced mullite porous ceramics were prepared with mullite powder and 6 wt% AlF3·3H2O as raw materials, and ZrO2 and Y2O3 as additives. Adding an appropriate amount of ZrO2 and Y2O3 can significantly improve the mechanical properties of porous ceramics. When ZrO2 is 6 wt% and Y2O3 is 8 wt%, the porosity is 66.4% and the flexural strength and compressive strength of porous ceramics with a large pore size of 168 μm can reach 14.3 MPa and 36.3 MPa, respectively, which are obviously better than the strength of mullite porous ceramics without adding Y2O3 (flexural strength 11.3 MPa, nanocompressive strength 29.4 MPa).

Fabricating porous ceramic materials via phase separations in blends of cellulose acetate and ceramic nanoparticles

AbstractAs applications of porous ceramic materials have gradually expanded, the novel technologies for the fabrication of porous ceramic materials with a delicate and controllable structure are still attractive. In this work, three types of porous monolithic ceramic materials, including Al2O3–SiO2, TiO2, and SiC, have been fabricated by thermally impacted and non‐solvent‐induced phase separations in blends of cellulose acetate and ceramic nanoparticles. These materials possessed three‐dimensional interconnected porous structures with low densities, high porosities, and hierarchical pores ranging from 5 nm to 6 μm. The relationships between microstructures and phase separations were systematically investigated. Furthermore, electromagnetic shielding effectiveness of 20 dB from 5 to 18 GHz in porous SiC materials has been achieved, revealing that those materials have potential applications in the electromagnetic shielding. This work provides a powerful and general approach to fabricate porous monolithic ceramic materials with a wide range of various ceramic nanoparticles.

Evaluation of thermal performance for bionic porous ceramic phase change material using micro-computed tomography and lattice Boltzmann method

Recently, bionic bone porous aluminum nitride ceramics have been synthesized and corroborated to be skeleton for composite phase change materials (PCM), which possess the advantages of high thermal conductivity and excellent corrosion resistance. Due to the complexity of preparation and measurement of the samples, a reliable pore-scale simulation approach can well predict their effective thermal conductivity (ETC) and melting process. In this work, the real three-dimensional geometry structure is reconstructed by micro-computed tomography (CT) method, and a numerically generated Voronoi structure is adopted to mimic the porous structure for comparison. The effective thermal conductivity of the two structure models is calculated based on lattice Boltzmann method (LBM). The results show the numerically predicted ETC of two structures is consistent. Furthermore, the melting of molten salt PCM in the complex porous ceramic is simulated by 3D enthalpy-based LBM. The melting rate increased remarkably because of the connected heat transfer path. The thermal contact resistance between PCM and skeleton is considered by setting an interfacial layer. A larger thermal contact resistance leads to a smaller melting rate and weakens the enhancement effect of the porous skeleton. The numerical simulation based on CT scanning and LBM may reflect a better insight for the heat transfer mechanism and provide a quick analysis to design the optimal porous skeleton.

DENSE AND POROUS CERAMIC MATERIALS FROM COAL SLUDGE OF THE INTA DEPOSIT

Dense and porous thermal-insulating ceramic materials were obtained from the flotation tailings of coal sludge of the processing plant of Inta town. The thermal behavior, changes in the phase and chemical composition during firing in the temperature range from 800 to 1280 °C were studied. During firing, carbonates dissociated, magnetite oxidized, kaolinite amorphized, layers in layered silicates compressed, at 1100 °C cristobalite and spinel were formed, at 1150 °C – mullite, the content of the amorphous phase increased. Dense ceramic materials were obtained at firing temperatures of 800 – 1150 °C, and porous materials at temperatures 1200 – 1280 °C. The physical, mechanical and technical characteristics of the obtained ceramic materials were studied. Porous ceramics, sintered at 1280 °C, belongs to the class of heat-insulating materials with increased thermal conductivity.

Correlation of the Chemical Composition and Structural Characteristics in the Partially Substituted Spinel Ferrites

An urgent task in the field of creating new functional oxide materials is to obtain products with specified properties for specific requirements, which will expand the field of application of such materials in practice. The result of work on this problem will be discussed. The paper presents the results of obtaining and studying the structure and properties of nickel-zinc ferrites doped with cobalt, with the general formula Ni0.3Zn0.7-xCoxFe2O4 (with the substitution x equal to 0; 0.1; 0.3; 0.5). The samples were obtained by solid-phase synthesis in a tube furnace with silicon carbide heaters at a temperature of 1150 °C. The porosity of the materials obtained was calculated. For porous ceramic materials, it is one of the quality criteria.

Synthesis and Structure of a New Ruthenium(II) Clathrochelate and the Use of a Highly Porous Ceramic Material with an Immobilized Complex in the Oxidative Conversion of Methane

Synthesis and Structure of a New Ruthenium(II) Clathrochelate and the Use of a Highly Porous Ceramic Material with an Immobilized Complex in the Oxidative Conversion of Methane

Comparative Properties of Porous Phyllosilicate-Based Ceramics Shaped by Freeze-Tape Casting

Porous phyllosilicate-based ceramics were manufactured by freeze-tape casting from clays of different particle size and morphology in order to characterize their microstructure and stress to rupture changes before and after firing. Three raw clays were selected: HCR (77% Halloysite–10Å), KORS (29% kaolinite), and KCR kaolin (98% kaolinite). These clays exhibited a monomodal distribution and were used to prepare four slurries, three with each clay material and one consisting of a mixture of KCR and HCR labeled KHCR. After shaping by freeze-tape casting, the porosity and stress to rupture obtained by a biaxial flexural test were collected for disk-like samples after drying and sintering at 1200 °C. Results showed that KCR ceramic materials had the highest biaxial bending strength (70 ± 1.1 MPa) and those from KORS had the highest porosity value (80 ± 1%). SEM observation revealed a difference in microstructure and texture for the manufactured porous ceramic materials. In the KCR ceramic disks, the flattened pores appeared more textured, and the primary mullite crystallites formed a rigid skeleton within the amorphous phase. KORS ceramic materials showed a small quantity of secondary mullite needles which were randomly dispersed in a vitreous phase. The relatively important vitreous phase in the porous materials of HCR led to the bulk formation of small mullite particles. The biaxial flexural strength values were related to the presence of the mullite, as well as to the microstructure (volume, morphology, and size distribution of pores) after sintering.

Use of Arc Furnace Slag and Ceramic Sludge for the Production of Lightweight and Highly Porous Ceramic Materials.

The utility of recycling some intensive industries’ waste materials for producing cellular porous ceramic is the leading aim of this study. To achieve this purpose, ceramic samples were prepared utilizing both arc furnace slag (AFS) and ceramic sludge, without any addition of pure chemicals, at 1100 °C. A series of nine samples was prepared via increasing AFS percentage over sludge percentage by 10 wt.% intervals, reaching 10 wt.% sludge and 90 wt.% AFS contents in the ninth and last batch. The oxide constituents of waste materials were analyzed using XRF. All synthesized samples were investigated using XRD to detect the precipitated minerals. The developed phases were β-wollastonite, quartz, gehlenite, parawollastonite and fayalite. The formed crystalline phases were changed depending on the CaO/SiO2 ratio in the batch composition. Sample morphology was investigated via scanning electron microscope to identify the porosity of the prepared ceramics. Porosity, density and electrical properties were measured; it was found that all these properties were dependent on the composition of starting materials and formed phases. When increasing CaO and Al2O3 contents, porosity values increased, while increases in MgO and Fe2O3 caused a decrease in porosity and increases in dielectric constant and electric conductivity. Sintering of selected samples at different temperatures caused formation of two polymorphic structures of wollastonite, either β-wollastonite (unstable) or parawollastonite (stable). β-wollastonite transformed into parawollastonite at elevated temperatures. When increasing the sintering temperature to 1150 °C, a small amount of fayalite phase (Fe2SiO4) was formed. It was noticed that the dielectric measurements of the selected sintered samples at 1100 °C were lower than those recorded when sintering temperatures were 1050 °C or 1150 °C.

Thermo-mechanical characterization of carbon-based ceramic foams for high temperature space application

The successful development of aerospace reusable launch vehicles (RLV) require to realize effective thermal protection systems (TPS) for preserving spacecraft integrity from the severe thermal loads during re-entry phase. To such an aim, due to the need of reducing payload transportation costs, applied research is driven towards lightweight materials with advanced thermo-mechanical properties. Space TPS are often based on sandwich structures, where the core material has the main function of thermal insulation. Ceramic porous materials, as carbon (C) and silicon carbide (SiC) foams, represent ideal candidates for application as structural TPS component, thanks to both low density and significant thermal stability at very high temperatures. The paper presents a joint experimental study of carbon-based ceramic foams proposed as sandwich’s core for TPS design. A full thermal characterization of commercial C- and SiC-foam materials is reported, including measurements of thermo-mechanical combined stress, temperature-induced outgassing behavior and heat transfer properties. These latter, in particular, are studied by means of a robust numerical technique, known as the inverse method, which allows to evaluate materials thermal conductivity and heat capacity over a wide range of temperatures, thus establishing the required material behavior for potential use in spacecraft TPS.

Flexible and Porous Nonwoven SiCN Ceramic Material via Electrospinning of an Optimized Silazane Solution

Electrospinning is a versatile method for the generation of ultrathin fibers forming highly porous mats. To extend the technique to preceramic polymers, the rheological properties of SiCN-precursor/solvent solutions are investigated systematically to control and predict the non-woven morphology during electrospinning as described in article number 2100321 by Luiz F. B. Ribeiro, Günter Motz, Sergio Y. G. González, and co-workers. After pyrolysis the resulting highly porous ceramic mats are suitable as high-performance filter systems and catalytic supports in harsh environments.

Модификация пористой α-Al2O3 керамики нанолистовыми структурами бемита

Modification of porous ceramic materials makes it possible to improve their functional characteristics. In this work, we demonstrate the possibility of modifying macroporous Al2O3 ceramics with boehmite nanosheet structures using electroexplosive Al/AlN nanoparticles. To do this, the porous ceramic was impregnated with a suspension of nanoparticles in ethanol, after which the reaction of hydrolysis and oxidation of the nanoparticles fixed in the volume of the porous ceramic was carried out at 60 °C. As a result of the reaction, nanosheet structures of fine-grained boehmite were formed on the ceramic surface. This made it possible to substantially increase the specific surface area of the sample to 25.9 m2/g. and significantly improve the sorption characteristics of macro-simple Al2O3 ceramics in relation to the eosin dye. During the protective action, it was possible to adsorb up to 2.9 mg/g of the dye at a linear flow rate of 0.15 cm/s.

Structure and Properties of Highly Porous Alumina-Based Ceramic Materials after Heating by Concentrated Solar Radiation

Three ceramic fibrous materials of the Al2O3-SiO2 system with different densities have been treated using concentrated solar radiation. The experiment was performed using technological capabilities of the Big Solar Furnace in the 2 modes: the first mode includes heating up to 1400–1600 °C, holding for 1.5–2 h; the second mode (the fusion mode) includes heating up to 1750–1900 °C until the sample destruction, which is accompanied by fusion. Upon completion of the experiment, the phase composition, microstructure, and compressive strength of the materials were studied. It was shown that the investigated materials retained their fibrous structure under prolonged treatment in the first mode up to temperatures of 1600 °C. The phase composition of the ceramic materials changes during the experiment, and with a decrease in the density, the modification is more pronounced. Treatment of all three materials under study in the fusion mode resulted in the formation of the eutectic component in the form of spherulites. The compressive strength of the materials was found to be slightly reduced after exposure to concentrated solar radiation.

DEVELOPMENT OF RESOURCE-SAVING TECHNOLOGY OF POROUS-HOLLOW CERAMIC STONES

A resource-saving technology of porous ceramic materials using low-quality non-sintering sandy loam as a basic raw material has been developed. Based on the analysis of the plastic properties of two- and three-component ceramic masses, including sandy loam, expanded clay and fuel slag in various ratios, it was found that the required level of their plasticity provides the content of the main raw material in the following range (wt%): fuel slag – 15 – 20; sandy loam – 50 – 65; expanded clay – 20 – 30. By the method of planning the experiment, the rational composition of the three-component ceramic mass was substantiated. This which contains: 62.5 wt. % sandy loam, 20 wt. % medium-sintering plastic clay as a plasticizer and 17.5 wt. % fuel slag of TPP as a porous agent. For the developed mass, the main technological properties were investigated, which made it possible to recommend the drying mode of the raw material – 60 hours, the optimal firing temperature – 950 °С. Such conditions ensure that samples are obtained without drying cracks and signs of deformation. Оn the results of dilatometric analysis of mass the rational mode of firing high-hollow semifinished products was designed. The firing mode provides for a 44-hour firing and a decrease in the heating rates in the areas of dehydration of clay minerals, direct quartz transition and intensive sintering of the mass, as well as a decrease in the cooling rate in the area of the reverse quartz transition. The proposed firing mode provides the degree of sintering and their properties necessary for ceramic materials. Based on the developed mass under the recommended drying and firing modes, porous ceramic materials with an apparent density of 1.48 g/cm3, a compressive strength of 18.2 MPa and frost resistance of 30 cycles were obtained. The developed materials belong to the group of conditionally effective, and if 50% of the voids are organized, they can be classified as effective.

Anisotropic porous ceramic material with hierarchical architecture for thermal insulation

Porous ceramic materials are attractive candidates for thermal insulation. However, effective ways to develop porous ceramics with high mechanical and thermal insulation performances are still lacking. Herein, an anisotropic porous silica ceramic with hierarchical architecture, i.e. long-range aligned lamellar layers composed of hollow silica spheres, was fabricated applying a facile bidirectional freezing method. Due to such anisotropic structure, the as-prepared porous silica ceramic displays low thermal conductivity across the layers and high compressive strength along the layers. Additionally, the anisotropic porous silica ceramic is fire-resistant. As a proof of concept, a mini-house was roofed with the anisotropic porous silica ceramic, showing that the indoor temperature could be stabilized against environmental temperature change, making this porous ceramic a promising candidate for energy efficient buildings and other industrial applications. Our study highlights the possibility of combining intrinsically exclusive properties in engineering materials through constructing biomimetic porous structures.

Heat-insulating porous material based on glauconite-containing sands and aleurites of the Novodvorskoye deposit of the Republic of Belarus

The results on the research of heat-insulating porous ceramic materials produced using overburden rocks of the Novodvorsk deposit of Pinsk district of the Brest region as the main component of raw materials are presented in the study and the use of bulk rock consisting of glauconite sands and aleurites is recommended. Low-melting clay, basalt and a blowing agent are used as additional components, rational combination of which would ensure the forming ability of ceramic masses and the required set of the physicochemical properties of the material. The dependence of the bulk density, swelling coefficient, coefficient of thermal conductivity on the chemical and mineral composition of the used and raw materials is established, wich is the criteria for choosing composition with the maximum use of overburden and the necessary plasticity of the ceramic mass required for the molding process of raw granules. The obtained results can serve as a basis for the large-scale use of not only the minerals of the Novodvorsk deposit (basalts and tuffs), but also associated – glauconite-containing overburden. This will make a significant contribution to the expanding the mineral resource base of the Republic of Belarus.

Highly porous building ceramics based on «clay-ash microspheres» and «zeolite-ash microspheres» mixtures

The possibility of obtaining highly porous heat-insulating ceramic materials based on compositions of mineral binding components (clay and zeolite rock) with ash-containing waste from the combustion of solid fuel (ash microspheres) is considered.It has been established that the pore-forming effect of ash microspheres in mixtures with low-melting clay is due to both the porous macrostructure of the ash component (the presence of hollow spherical particles) and the nature of physicochemical processes in the “clay – ash microspheres” and “zeolite – ash microspheres” systems (the synthesis of anorthite and mullite proceeding with an increase in molar volume).The creation of highly porous ceramic structures from mixtures of ash microspheres with zeolite rock, in addition to the structural features of microspheres, is also due to the structural (channel) porosity of zeolite minerals. The established pore-forming effect of zeolite rock and ash microspheres made it possible to develop a method for preparing a semi-dry masses from these compositions and to propose a technological scheme for obtaining a highly porous ceramic brick.The use of zeolite rock as a binder in a mixture with ash microspheres in content up 60–95 wt%, modified with zeolite-lignosulfonate slip, makes it possible to obtain a highly efficient constraction and thermal insulation ceramic brick with a compressive strength of 18–30 MPa, volume weight 930–1100 kg/m3 and thermal conductivity 0.22–0.31 W/m·K at a firing temperature of 950–1000 °C.

Highly Stretchable, Crack-Insensitive and Compressible Ceramic Aerogel.

Ceramic aerogels are attractive candidates for high-temperature thermal insulation, catalysis support, and ultrafiltration materials, but their practical applications are usually limited by brittleness. Recently, reversible compressibility has been realized in flexible nanostructures-based ceramic aerogels. However, these modified aerogels still show fast and brittle fracture under tension. Herein, we demonstrate achieving reversible stretch and crack insensitivity in a highly compressible ceramic aerogel through engineering its microstructure by using curly SiC-SiOx bicrystal nanowire as the building blocks. The aerogel exhibits large-strain reversible stretch (20%) and good resistance to high-speed tensile fatigue test. Even for a prenotched sample, a reversible stretch at 10% strain is achieved, indicating good crack resistance. The aerogel also displays reversible compressibility up to 80% strain, ultralow thermal conductivity of 28.4 mW m-1 K-1, and excellent thermal stability even at temperatures as high as 1200 °C in butane blow torch or as low as -196 °C in liquid nitrogen. Our findings show that the attractive tensile properties arise from the deformation, interaction, and reorientation of the curly nanowires which could reduce stress concentration and suppress crack initiation and growth during tension. This study not only expands the applicability of ceramic aerogels to conditions involving complex dynamic stress under extreme temperature conditions but also benefits the design of other highly stretchable and crack-resistant porous ceramic materials for various applications.