Porous Ceramic Materials Research Articles

Criteria of a Controllable Process of Producing Heat-Insulating Porous Ceramic Materials Using Magmatic Rocks

Criteria of a Controllable Process of Producing Heat-Insulating Porous Ceramic Materials Using Magmatic Rocks

Reliability assessment and lifetime prediction of TBCs on gas turbine blades considering thermal mismatch and interfacial oxidation

Thermal barrier coatings (TBCs) – as porous ceramic materials – have varying lifetimes because of their unstable mechanical properties and harsh working conditions. In this paper, a probabilistic approach to quantify the risk of interface spallation in TBCs by thermally grown oxide (TGO) growth and thermal mismatch, along with a lifetime prediction method based on the critical failure probability is proposed. First, a failure criterion for TBCs is set to determine a boundary between the failure and safe region. Second, parameters relating to failure, along with the stochastic characteristics of these parameters, are analysed thoroughly. Third, the failure probability is calculated. Finally, the lifetime of TBCs on turbine blades in a hot gas stream is predicted. Under furnace isothermal cycling, the predictive failure probabilities of TBCs are 0.1% (300 cycles), 1.5% (600 cycles), and 7.49% (1000 cycles). The experiment results for turbine blades are 1.03% (300 cycles), 1.73% (600 cycles), and 5.12% (1000 cycles). Under a hot gas stream, the maximum failure probabilities of TBCs after 200, 300, 500, and 1000 h are 40%, 45% 50%, and 70%, respectively. The lifetimes of TBCs are 273, 332, 406, and 523 h if the critical area ratio of the metal substrate exposed to the hot gas is 5%, 10%, 15%, and 20%, respectively.

Synthesis and characterization of porous ceramics from spodumene tailings and waste glass wool

Glass wool waste remains a challenging waste fraction with relatively little utilization prospects. The present study investigated the development of porous ceramic materials from glass wool waste and spodumene tailings mainly made of quartz feldspar sand (QFS), with 0.05–0.5% silica carbide (SiC) as a pore-forming agent. The formulated compositions were sintered at 950 °C and analyzed in terms of mechanical properties, phase composition, and microstructure using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray micro-computed tomography. The results showed that a synergetic effect of glass wool and SiC started to be significant from 15 wt% glass wool and 0.05 wt% SiC, the strength reducing and the porosity increasing with the increase of SiC. The porous ceramics were largely amorphous, with compressive strength ranging from 5 to 30 MPa while the water absorption and apparent density ranged from 2 to 10% and 0.7–1.2 g/cm3, respectively. The total porosity varied between 20 and 75%, and the wall thickness between 62 and 68 μm; besides, most of the prepared materials floated in water. These results are of interest for the repurposing of glass wool waste in the development of non-flammable lightweight materials for potential filtering or high-rise building applications.

Nondestructive Structural Investigation of Yttria-Stabilized Zirconia Fiber Insulation Tile by Synchrotron X-ray In-Line Phase-Contrast Microtomography

Zirconia (ZrO2) aerogels show excellent insulating performance and have been widely applied as a thermal protector in furnaces, nuclear reactors, and spacecraft. The nondestructive determination of their interior microstructure is significant for evaluating their mechanical and insulating performance. In this study, we performed nondestructive structural investigation of an yttria-stabilized ZrO2 fiber insulation tile using synchrotron X-ray in-line phase-contrast microtomography at a pixel resolution of 6.5 µm. Taking advantage of the edge enhancement of phase-contrast imaging, single yttria-stabilized ZrO2 fibers were clearly distinguished; furthermore, interior aggregates were nondestructively observed at this spatial resolution. This work demonstrates the advantages and potential of synchrotron X-ray microtomography for the structural analysis of porous ceramic materials. By combining higher-brilliance synchrotron radiation sources and CCD detectors with higher spatial and temporal resolutions, we anticipate that we can further understand the relationship between aerogel microstructure and function, especially under in-service conditions at high temperatures.

Structure Optimization of a High-Temperature Oxygen-Membrane Module Using Finite Element Analysis

The oxygen transport membrane (OTM) is a high-density ion-conducting ceramic membrane that selectively transfers oxygen ions and electrons through the pressure differential across its layers. It can operate at more than 800 °C and serves as an economical method for gas separation. However, it is difficult to predict the material properties of the OTM through experiments or analyses because its structure contains pores and depends on the characteristics of the ceramic composite. In addition, the transmittance of porous ceramic materials fluctuates strongly owing to their irregular structure and arbitrary shape, making it difficult to design such materials using conventional methods. This study analyzes the structural weakness of an OTM using CAE software (ANSYS Inc., Pittsburgh, PA, USA). To enhance the structural strength, a structurally optimized design of the OTM was proposed by identifying the relevant geometric parameters.

Significantly toughened SiC foams with enhanced microwave absorption via in situ growth of Si3N4 nanowires

Porous ceramic materials with high electromagnetic absorption capacity, low density, high thermal resistance and excellent mechanical properties are highly desirable in aerospace applications. Here, we synthesized one type of hierarchical SiC composite foams with in situ grown Si3N4 nanowires via a pyrolysis process. The existence and structure of Si3N4 nanowires were characterized by multiple techniques and analysis revealed that the growth of nanowires was based on a typical vapor-solid mechanism. Owing to the presence of a large amount of Si3N4 nanowires, both the mechanical performance and electromagnetic absorption were significantly enhanced. The minimum Reflection loss (RL) of 1.25 mm SiC composite foam reaches −50.3 dB at 16.48 GHz with an effective bandwidth (RL < −10 dB) of 3.6 GHz (14.4–18 GHz), while the toughness and specific compressive strength increased by 356% and 126%, respectively. Especially, a ductile and steady fracture behavior was observed for the mechanically enhanced composite foam, rather than the typical catastrophic failure usually seen for ceramic materials. Owing to the excellent electromagnetic wave absorption capability and enhanced mechanical properties, as well as low density and high thermal resistance, this type of composite ceramic material may find applications in aviation, aerospace and other extreme environments.

Bionic hierarchical porous aluminum nitride ceramic composite phase change material with excellent heat transfer and storage performance

In this paper, we synthesized bionic bone hierarchical porous AlN ceramics which encapsulate polyethylene glycol2000 (PEG2000) to form a new composite phase change material. Argon adsorption and SEM demonstrate that the AlN ceramic has hierarchical structure with most probable diameters of 2.4 nm and 27.3 nm. Raman spectroscopy show that no aluminum vacancies are formed inside the material, which effectively reduce the probability of phonon scattering and improve the thermal performance. EDS and XRD demonstrate that the main crystalline phase of the ceramics is AlN with a small amount of impurity peaks. The thermal conductivity of AlN ceramics with a porosity of 75.2% and 67.5% are 5.10 and 13.86 W/m·K, and that of the composite material is 17.16 W/m·K. The latent heat of melting of the composite material is 88.73 J/g and the melting point is 54.75 °C. The material breaks through the defects of slow dynamic response time and low thermal conductivity of traditional energy storage materials.

An efficient optimization based microstructure reconstruction approach with multiple loss functions

Stochastic microstructure reconstruction involves digital generation of microstructures that match key statistics and characteristics of a (set of) target microstructure(s). This process enables computational analyses on ensembles of microstructures without having to perform exhaustive and costly experimental characterizations. Statistical functions-based and deep learning-based methods are among the stochastic microstructure reconstruction approaches applicable to a wide range of material systems. In this paper, we integrate statistical descriptors as well as feature maps from a pre-trained deep neural network into an overall loss function for an optimization based reconstruction procedure. This helps us to achieve significant computational efficiency in reconstructing microstructures that retain the critically important physical properties of the target microstructure.A numerical example for the microstructure reconstruction of bi-phase random porous ceramic material demonstrates the efficiency of the proposed methodology. We further perform a detailed finite element analysis (FEA) of the reconstructed microstructures to calculate effective elastic modulus, effective thermal conductivity and effective hydraulic conductivity, in order to analyse the algorithm’s capacity to capture the variability of these material properties with respect to those of the target microstructure. This method provides an economic, efficient and easy-to-use approach for reconstructing random multiphase materials in 2D which has potential to be extended to 3D structures.

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

The processing of nonwoven porous ceramics by combining the polymer‐derived ceramic (PDC) route with electrospinning offers an excellent strategy for developing new porous ceramic structures. Currently, the manufacturing of nonwoven porous materials from preceramic polymers is conducted by trial and error approaches. The necessity to predict the e‐spinnability conditions from properties assessment offers a potential tool to control the manufacture and the resulting material morphology. This work assesses the relationship between the preceramic polymer solutions and the resulting electrospun nonwoven morphology. For this, a commercially available liquid oligosilazane (Durazane 1800) is selectively cross‐linked to achieve a reliable and spinnable preceramic polymer (HTTS), which is then dissolved in tetrahydrofuran (THF). Based on the investigation of the rheological behavior of various polymer concentrations, three different polymer solution regimes (diluted, semidiluted, and concentrated) are identified and correlated with the resulting morphology of the e‐spun material (spherical particles, beaded fibers, and seamless fibers). After the pyrolysis, the nonwoven ceramics manufactured from the solution with 65 wt% of HTTS is converted to a SiCN ceramic nonwoven with 86% of open porosity, profiling as a promising candidate for developing high‐performance filter systems and catalytic supports in harsh environments.

Recycling of waste glass as raw materials for the preparation of self-cleaning, light-weight and high-strength porous ceramics

With rapid economic development in recent years, the efficient utilization of waste glass has received increasing attention. The major challenge is to improve the economic and social benefits of waste glass recycling and to improve the self-driving force of waste glass recycling in related industries. In this paper, the researchers proposed a new recycling strategy for waste glass, using low-cost waste glass powder as raw material to prepare light-weight and high-strength porous ceramic materials with self-cleaning properties by combining the emulsion template self-assembly method with a surface hydrophobic coating treatment technology. The open porosity of the prepared ceramics can be controlled at 50–70% and the ceramics have ultra-high compressive strength (i.e., 50–141 MPa). The water contact angle on its surface is as high as 162.2°, which affords remarkable anti-dirt properties, stability, and superhydrophobic performance for milk, coffee, beer, soy sauce, and other staining liquids. Moreover, the water contact angle remains unchanged at a high temperature (500 °C) and in an acid-base environment. More importantly, even if the hydrophobic coating on the surface is destroyed, the superhydrophobicity and self-cleaning ability of the ceramic materials can be restored after remodification and the reuse is excellent. Ceramic materials offer the advantages of low price, a simple process, environmental protection, and high energy efficiency, and they show great potential and broad prospects for application. At the same time, the proposed method provides a very effective way to comprehensively utilize waste glass and has remarkable economic and social benefits.

Production of Porous Ceramic Materials from Spent Fluorescent Lamps

Spent fluorescent lamps (SFL) are classified as hazardous materials in the European Waste Catalogue, which includes residues from various hi-tech devices. The most common end-of-life treatment of SFL consists in the recovery of rare earth elements from the phosphor powders, with associated problems in the management of the glass residues, which are usually landfilled. This study involves the manufacturing of porous ceramics from both the coarse glass-rich fraction and the phosphor-enriched fraction of spent fluorescent lamps. These porous materials, realizing the immobilization of Rare Earth Elements (REEs) within a glass matrix, are suggested for application in buildings as thermal and acoustic insulators. The proposed process is characterized by: (i) alkaline activation (2.5 M or 1 M NaOH aqueous solution); (ii) pre-curing at 75 °C; (iii) the addition of a surfactant (Triton X-100) for foaming at high-speed stirring; (iv) curing at 45 °C; (v) viscous flow sintering at 700 °C. All the final porous ceramics present a limited metal leaching and, in particular, the coarse glass fraction activated with 2.5 M NaOH solution leads to materials comparable to commercial glass foams in terms of mechanical properties.

The feasibility study on development of porous ceramic composites for ion-exchanger

During normal operation of the nuclear reactor, several corrosion elements (CRUD) can be produced due to the degradation of the reactor structural materials. These impurities must be removed from the reactor coolant system to preserve the performance of the reactor coolant. We are developing a new porous ceramic adsorption material to replace current bead-type polystyrene resins at the ion exchanger. We performed experimental and numerical studies to investigate the feasibility of using Zeolite as a ceramic ion-exchange composite, which is stable at high temperatures and has high adsorption capacity for the constituent elements of CRUD. We are also proposing a new configuration of the ceramic composite, which is a Twisted Honeycomb shape printed by a 3D printer. First, the experimental analysis was performed to find the optimal sintering temperature of Zeolite in terms of removal rate and material strength, and a compressive strength test for a 3D printed ceramic composite was carried out to confirm structural integrity. Then, we conducted a CFD analysis to investigate the effect of flow velocity and pressure drop distribution through the conventional packed bead ion exchange (PB-IEX) resins and the proposed Twisted Honeycomb ion exchanger (TH-IEX). We focused on the pressure force distribution, which is important for ion exchange immobilization and degradation. The flow velocity and retention time through the ion exchanger play an essential role regarding the adsorption rate. A wide range of beads diameter [0.001–1.0 mm] has been analyzed. Larger beads decrease the pressure drop with a reduction of removal rate. The proposed twisted honeycomb shape shows better flow velocity distribution and less pressure drop. Finally, structural analysis was performed using ANSYS FEM to investigate the influence of flow distribution on the integrity of the Twisted Honeycomb ion exchanger, in which the FEM model was validated against the compressive strength experimental data. As a result, we are proposing the prototype of high efficiency ion exchanger.

Effect of the Sintering Temperature on the Compressive Strengths of Reticulated Porous Zirconia

Porous ceramics have separation/collection (open pore) and heat-shielding/sound-absorbing (closed pore) characteristics not found in conventional dense ceramics, increasing their industrial importance along with dense ceramics. Reticulated porous ceramics, a type of porous ceramic material, are characterized by a three-dimensional network structure having high porosity and permeability. Although there have been numerous studies of porous zirconia, which is already widely used, there are insufficient reports on reticulated porous zirconia, and it is still challenging to improve the compressive strength of reticulated porous ceramics thus far, especially considering that too few studies have been published on this topic. Therefore, we prepared reticulated porous zirconia specimens using the replica template method. In this study, the compressive strength outcomes of reticulated porous zirconia were analyzed by controlling the PPI value (25, 45, 60, and 80 PPI) of the sacrificial polymer template, the average zirconia particle size (as-received, coarse, intermediate, and fine), and the sintering temperature (1400, 1500, and 1600 °C). Consequently, we confirm that it is possible to prepare reticulated porous zirconia with a wide range of strengths (0.16~1.26 MPa) as needed with an average particle size and while properly controlling the sintering temperature.

Incorporation of functionalized Ag-TiO2NPs to ormosil-based coatings as multifunctional biocide, superhydrophobic and photocatalytic surface treatments for porous ceramic materials

Microbial fouling on the surface and water retention are common problems affecting porous ceramic materials (stone, concrete…) that can alter their properties, shorten their service life and even pose a health risk. Though proper maintenance (disinfection, drainage…) can mitigate these issues, it is a time and resource intensive process and preventive measurements are desired, such as hydrophobic or anti-fouling coatings.In this work, we report a simple sol-gel route to obtain a multifunctional coating combining superhydrophobic, biocide and photoactive properties, by incorporating TiO2 nanoparticles (NPs), functionalized with –SH or –NH terminated alkoxysilanes, and AgNPs into an organically modified silica matrix (ormosil). The low surface energy of the ormosil, combined with the nano-roughness created by the accumulation of Ag-TiO2NPs on the surface promotes a Cassie-Baxter wetting state, leading to water repellence and a lower bioreceptivity of the coatings due to a decreased cell attachment. The influence of this factor was evidenced by the comparatively higher cell attachment on the smoother surface of xerogels samples prepared from the ormosils, where TiO2 surface charge plays a major role. The incorporation of AgNPs increases the photocatalytic effectiveness of the TiO2 and effectively inhibits the growth of the tested microorganisms (Escherichia coli and Saccharomyces cerevisiae), even in the absence of light. Surface functionalization of the TiO2NPs affects the distribution, size and stability of the AgNPs, and thus, the biocide and photocatalytic effectiveness of the treatments.

ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ КЕРАМИЧЕСКИХ МАТЕРИАЛОВ ДЛЯ ПОТРЕБНОСТЕЙ АПК

As a result of poor quality, parts of tillage equipment have to be replaced 3-7 times a year. One of the reasons is the lack of attention to the possibility of using technical ceramics in agricultural engineering to improve the wear resistance and durability of machine parts. (Research purpose) The research purpose is in assessing the state of research and prospects for the use of ceramic materials in the Russian Federation for the needs of the agro- industrial complex. (Materials and methods) For the experiments has been used nanostructured boehmite obtained by hydrothermal synthesis to improve the properties of materials and coatings. The crack resistance was determined by the indentation method, and the methane content in the biogas was determined by the chromatographic method. (Results and discussion) The article presents the results of the use of aluminum oxide ceramics for the manufacture of parts of tillage equipment, which allows increasing the resource of parts for processing loamy soils by 2.4-4.5 times. The creation of nanocomposites is promising to increase the strength, wear resistance and crack resistance of the material. In the composition of the non-stick coating, the addition of boehmite increases the abrasion strength of the coating and the compressive strength of the samples by 2.2-2.7 times, and improves the quality of casting. The use of highly porous ceramic materials in the gating system helps to reduce waste, reduce production costs, and improve the quality of foundry products. (Conclusions) Ceramic materials due to their high hardness, wear resistance and corrosion resistance are becoming promising for use in the agro-industrial complex. The widespread use of modern ceramic materials as parts of tillage equipment, non-stick coatings and for the filtration of melts will improve the quality of casting, the durability of products, and reduce the cost of their production. Positive results on wastewater treatment with the use of highly porous ceramics allow us to consider it an innovative material for such purposes and it is advisable to continue research in this direction.

Porous mullite fiber nonwoven separator materials containing Nano-MgO particles for the design of thermal batteries

Porous ceramic separator materials have been used to enhance the performance of thermal batteries but they are not sufficiently effective. In this study, we developed a porous ceramic fiber separator substrate using Mullite fiber (a kind of ceramic fiber) employing the wet-laid technology. The substrate was modified using magnesium acetate precursors to obtain a porous, flexible, strong ceramic fiber separator (CFS) containing Nano-MgO particles. Although the diameter of CFS exceeded 11.3 cm, it was relatively thin (approximately 0.3 mm). Application of CFS clearly improved the electrochemical performance of the conventional Li-B/LiF-LiCl-LiBr/FeS2 electrochemical system. Li-B/LiF-LiCl-LiBr/FeS2 electrochemical system fitted with CFS increases the specific capacity of the battery by 24% and yields a polarization resistance of 0.011 Ω even with a high current pulse density of 5000 mA·cm−2. The findings of this study demonstrate that CFS can effectively improve performance of current thermal battery electrochemical systems.

Porous glass ceramic materials with decorative-protective coating

This study was aimed at producing a porous layered glass ceramic material with a decorative-protective coating via one-stage firing. Waste products were used as gas-forming agents to fabricate a glass ceramic material, which partially solves a problem of their utilization; available natural raw materials were also used as gas-forming agents. A decorative-protective coating was applied simultaneously with the formation of the main layers of the material. It consisted of glass cullet and various amounts of coloring oxide. Firing of the samples was carried out at the temperature of 7500С. The coating containing 99.9 wt.% of glass cullet and 0.1 wt.% of Cr2O3 with the thickness of 425 m and having a greenish color was stated to be the coating of the highest quality. As a result of the research, a three-layer porous glass ceramic material was obtained with a low coefficient of thermal conductivity (0.056 W m–1 K–1). The presence of a fourth front decorative-protective layer will allow using this material in construction as a heat-insulating and structural material without additional cladding.

Hierarchical highly porous composite ceramic material modified by hydrophobic methyltrimetoxysilane-based aerogel

A highly porous composite material consisting of silicon dioxide microfibers filled with nanoporous methyltrimethoxysilane-based aerogel was synthesized by a sol–gel procedure followed by supercritical drying in isopropanol and CO2. The textural and mechanical properties of the composite were studied. A synergism of the mechanical properties of components was demonstrated. The material showed high hydrophobic properties—the water drop contact angle was 142° after 14 days under 100% humidity and low water absorption was found. The composite material retained its mechanical integrity after several freeze-thaw procedures.

Effect of porosity on thermal conductivity of Li2TiO3 ceramic compact

The thermal conductivity of the porous ceramic materials strongly depends on its temperature and porosity. Li2TiO3 ceramic is considered as a tritium breeder material for the Indian fusion blanket concept. Inside the blanket, higher lithium content is vital in terms of lithium burn up, whereas porosity is essential for the diffusion of tritium from its grains to the surface. As the helium gas will continuously pass through the ceramic breeder's pores, all heat transfer modes, i.e. conduction, convection and radiation will appear within the breeder canister. For evaluation of the heat transfer behaviour inside the fusion blanket, it is substantial to determine the porosity dependent thermal conductivity of Li2TiO3 along with a good relationship. In this work, Li2TiO3 compacts of different porosity, i.e. 4–6 %, 11 %, 24 %, 26 % and 39 % are prepared by uni-axial hydraulic pressing. Compacts are sintered at 1073 K, 1173 K, 1273 K and 1423 K for desired porosity. Thermal diffusivity of Li2TiO3 compacts are measured by laser flash apparatus from room temperature to 973 K. Thermal conductivity of porous Li2TiO3 compacts is calculated by multiplication with respective density and specific heat to the measured thermal diffusivity. In this study, the mercury intrusion technique and Scanning Electron Microscopy technique was used for the density, porosity and surface morphology, respectively. The effect of the temperature and porosity on the thermal conductivity of Li2TiO3 are presented here. As the thermal conductivity changes with porosity by virtue of temperature, the correlations are presented by fitting various models such as Maxwell model, modified Maxwell-Eucken model, Loeb model, modified Loeb model, and EMT model. Among these models, the best-fitted model was evaluated. The geometrical factor (β, α) and thermal conductivity at 0 % porosity (k0) for the modified Maxwell-Eucken model and modified Loeb model were calculated. The porosity and temperature-dependent thermal conductivities of Li2TiO3 were calculated with newly obtained coefficients and discussed in this paper.

Chemical Structure and Microstructure Characterization of Ladder-Like Silsesquioxanes Derived Porous Silicon Oxycarbide Materials.

The aim of this work was to synthesize porous ceramic materials from the SiOC system by the sol-gel method and the subsequent pyrolysis. The usage of two types of precursors (siloxanes) was determined by Si/C ratio in starting materials. It allows us to control the size of the pores and specific surface area, which are crucial for the potential applications of the final product after thermal processing. Methyltrimethoxysilane and dimethyldiethoxysilane were mixed in three different molar ratios: 4:1, 2:1, and 1:1 to emphasize Si/C ratio impact on silicon oxycarbide glasses properties. Structure and microstructure were examined both for xerogels and obtained silicon oxycarbide materials. Brunauer-Emmett-Teller (BET) analysis was performed to confirm that obtained materials are porous and Si/C ratio in siloxanes precursors affects porosity and specific surface area. This kind of porous ceramics could be potentially applied as gas sensors in high temperatures, catalyst supports, filters, adsorbents, or advanced drug delivery systems.