Porous Ceramic Materials Research Articles

Measuring and Extracting the Complex Permittivity of Porous Ceramic Materials in the Y-Band

ABSTRACT Porous ceramics find extensive applications in aerospace and other fields, and the measurement of their electromagnetic parameters is helpful in optimization of material properties and device designs. In this paper, a free-space 8f quasi-optical measurement system consisting of a vector network analyzer, a 325–500 GHz frequency expansion module, and four off-axis parabolic mirrors have been established to measure the transmission parameter S21 of porous ceramics. The complex permittivity was extracted according to the Newton-Raphson iterative method utilizing its measured S21 parameters based on flat mode. The porous ceramics with different porosity and density were measured and the relationships between their permittivity and porosity and density was established, respectively. These results are beneficial to the quality evaluation and application design of porous ceramic materials in the aerospace field.

High‐temperature thermal conductivity measurement of porous ceramic coatings with a high heat flux CO2 laser rig

AbstractYttrium‐stabilized zirconia (YSZ) plays a crucial role in thermal barrier coatings widely used to protect metallic components in gas turbine engines against high‐temperature combustion product gases and harsh environments. The thermal conductivity of these coatings is a critical parameter influencing the gas turbine design, performance, and service life. In this study, a laser temperature gradient method is utilized to measure the thermal conductivity of porous YSZ coatings. The method employs specialized laser energy delivery to create a one‐dimensional temperature gradient through the sample thickness, closely simulating the operational condition. This approach provides an effective, direct means to determine the thermal conductivity of high‐temperature heat‐resistant porous ceramic materials.

3D microstructure reconstruction and characterization of porous materials using a cross-sectional SEM image and deep learning

Accurate assessment of the three-dimensional (3D) pore characteristics within porous materials and devices holds significant importance. Compared to high-cost experimental approaches, this study introduces an alternative method: utilizing a generative adversarial network (GAN) to reconstruct a 3D pore microstructure. Unlike some existing GAN models that require 3D images as training data, the proposed model only requires a single cross-sectional image for 3D reconstruction. Using porous ceramic electrode materials as a case study, a comparison between the GAN-generated microstructures and those reconstructed through focused ion beam-scanning electron microscopy (FIB-SEM) reveals promising consistency. The GAN-based reconstruction technique demonstrates its effectiveness by successfully characterizing pore attributes in porous ceramics, with measurements of porosity, pore size, and tortuosity factor exhibiting notable agreement with the results obtained from mercury intrusion porosimetry.

Highly Porous Ceramic Materials Based on Coarse-Dispersed αAl2O3

Highly Porous Ceramic Materials Based on Coarse-Dispersed αAl2O3

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

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

Influence of initial powders morphology on structural-dimensional characteristics of porous ceramic materials based on SiC/MgO–SiO2

Synthesis of porous ceramic materials based on fine SiC with sintering silicon oxide and magnesia binders at T = 800–1300 °C is considered. Special attention is paid to the influence of the shape and morphology of the initial powder particles on structural parameters and characteristics of porous ceramic materials. The SiC membranes sintered at 1000–1300 °C had average pore sizes of 0.5–1 μm, open porosity - up to 50 %, bending strength - up to 48.5 MPa and high water permeance - up to 7890 l⋅m−2⋅h−1⋅bar−1. The established filtration efficiency was ∼99 % in the case of screening out model particles of D50 = 0.5 μm in size with maintaining stable permeance and physico-mechanical characteristics after multiple filtration-regeneration cycles.Comprehension of the initial powders morphology impact on the synthesized porous ceramics parameters makes it possible to forecast and ensure the preset structural, dimensional and physico-mechanical parameters of the materials under study properly. This work can be used for practical low-cost production of highly efficient SiC membranes for micro- and ultrafiltration processes, as well as base for catalysts.

A developed convolutional neural network model for accurately and stably predicting effective thermal conductivity of gradient porous ceramic materials

Accurate and stable prediction of the effective thermal conductivity (ETC) of porous ceramic materials is of great significance for their application in areas such as optimizing the design of thermal barrier coatings and improving energy conversion efficiency. Porous ceramic materials exhibit complex porous structures with gradient porosity distributions that pose a great challenge for effective medium theory (EMT) and conventional convolutional neural networks (CNN) in attempting to accurately and stably predict the ETC of porous media. In this study, a CNN model that integrates self-attention and a multiscale feature-fusion mechanism is proposed to predict the ETC of porous media with greater accuracy and stability. The integration of the self-attention and multiscale feature-fusion mechanisms enhances the CNN's ability to learn long-range dependencies and preserve detailed information. The optimization of the CNN's accuracy and stability is visually illustrated using gradient-weighted class activation mapping (Grad-CAM) for ETC. Additionally, by employing the proposed gradient quartet structure generation set (QSGS), a gradient porous ceramic media dataset comprising 10 000 images was built to train the CNN model. Finally, the prediction results and relative error distribution of the ETC were compared across different models. Our model demonstrated improvements in statistical metrics, including a 33.7 % decrease in mean error, 25.2 % decrease in median error, and 59.6 % decrease in maximum error. The decreases in these metrics and Grad-CAM for the ETC strongly demonstrates that the model proposed in this work greatly improved the accuracy and stability of predicting the ETC of ceramic materials with gradient porosity distributions.

Analysis of electric power generated by zeolite grain size variables for porous ceramic materials in battery

The battery component with the most important role is the separator. The separator is used as a battery cell to store a source of electricity and separate the cathode and anode. The separator in a battery is often damaged because its material is easily crushed or broken. This study aimed to create a new separator cell using a porous ceramic made from a mixture of zeolite sand and corn flour. This porous ceramic as a battery separator is sought to increase the ionic conductivity and thermal stability of the battery. The ceramic is divided into 4 grain size variables, namely grain size using 100, 30, and 16 mesh sieves—and grain size without using a sieve, or coarse grain. The making process begins with zeolite sand sifting. The sifted zeolite is then mixed with corn flour. The composition of the mixing is 92% zeolite and 8% corn flour. Then green ceramics molding are carried out at a pressure of 15 MPa. Then sintering is carried out in the furnace for 4 hours at a temperature of 900°C. The resulting porous ceramics are assembled onto batteries. The finished batteries are then tested for mains voltage. The porous ceramics are micro-photo tested. The results of the stress test show that the 100 mesh sieve zeolite variation has a voltage of 3.97 volts, the 30 mesh sieve zeolite variation has a voltage of 3.72 volts, and the 16 mesh sieve zeolite variation has a voltage of 3.43 volts. Whereas the zeolite variation without using a sieve cannot be molded because it is easily crushed so testing is impossible. Furthermore, the results of the micro-photo test show that for the 100 mesh sieve zeolite variation, the pores are relatively tight; for the 30 mesh sieve zeolite variation, there are several more pores when compared to the 100 mesh sieve; and for the 16 mesh sieve zeolite variation, the most (largest) pores among the three grain size variables are found

Freeze-cast porous Al2O3/MgO ceramics as potential acoustic sound absorption

In acoustic engineering and architecture, materials called acoustic absorbers are widely used. There are currently numerous options for such materials, and many more are being researched. This study is conducted on porous ceramics produced via the freeze-casting process to propose new solutions with unique properties, like resistance to harsh environments. The freeze-casting method allows for the controlled creation of open-connected porous structures for different class materials through the cryogenic freezing of the suspension. The material samples are produced with Al2O3 (alumina)/MgO (magnesium oxide) material using camphene as solvent. The specimen samples are prepared using three different concentrations of the two solid components (60/40, 72/28, and 90/10 in weight). Each sample concentration achieves different morphology phase compositions and porous structures. Hence, we explore in the paper how those concentration parameters could interfere with acoustic absorption. Further, the samples were characterised using numerical and experimental methods related to sound absorption and microstructure. The 60/40 and 90/10 samples achieve sound absorption coefficient values upwards of 0.7 around the 2000-3000 Hz frequency range. The microstructure characteristics show the porosity gradually changing along its thickness, interfering with their sound absorption properties. Our findings highlight the complexities of characterising porous ceramics and emphasise the significance of understanding some material composition factors affecting sound absorption. Hence, this study provides valuable insights into the intricate nature of porous ceramic freeze-cast materials and their acoustic properties, substantially contributing to the ongoing exploration in this domain.

Pore Space Characteristics and Morphology of Highly Porous Sc2O3 Ceramic Materials Synthesized

Pore Space Characteristics and Morphology of Highly Porous Sc2O3 Ceramic Materials Synthesized

Study of Lightweight Ceramic Matrix-Less Syntactic Foam Composed of Cenosphere Using Spark Plasma Sintering.

The current investigation presents porous ceramic materials prepared with cenospheres (CS) by using spark plasma sintering. The impact of sintering temperature, mould diameter (20, 30 and 50 mm) and cenosphere size on the properties of the sintered material was investigated. Shrinkage of the samples during sintering started at 900 °C. Total sample shrinkage during sintering increases with increasing temperature and decreases with increasing mould size; increasing sample sintering temperature increases the apparent density of all sample series CS 63-150 µm in a 20 mm mould from 0.97 to 2.3 g·cm-3 at 1050-1300 °C; in a 30 mm mould, 0.81-1.87 g·cm-3 at 1050-1200 °C; in 50 mm mould, 0.54-0.75 g·cm-3 at 1050-1150 °C; while CS 150-250 µm in a 20 mm mould is 0.93-1.96 g·cm-3 at 1050-1200 °C. Total porosity decreases from 61.5% to 3.9% by increasing sintering temperature from 1050 to 1250 °C, while open porosity reduces at lower temperatures, with closed porosity being highest in samples sintered at 1150 °C. When the sintering temperature increases from 1050 to 1300 °C, the compressive strength of the CS 63-150 samples produced in a 20 mm mould increases from 11 MPa to 312 MPa. These results correlate with the Rice model, which describes an exponential dependence of compressive strength on material porosity and fully dense material compressive strength.

A review of pore-forming agents on the structures, porosities, and mechanical properties of porous ceramics

<p>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.</p>

HYDROGEN ABSORBERS BASED ON POROUS CERAMICS SYNTHESIZED IN A SOLAR FURNACE

In this study, we investigated the processes of hydrogen absorption in porous ceramic materials sythesized in a solar furnace. We used burning additives inserted into ceramic materials and melted in a solar furnace in a high-density stream of concentrated solar radiation (200 W/cm<sup>2</sup>). The melt was cooled by pouring it into water at a cooling rate of 10<sup>3</sup>-10<sup>4</sup> degree/s. The castings were characterized by a fine-grained microstructure (in which the grain size did not exceed 10 µm). The crushed and molded samples were fired at a temperature of 1150°C for 2 hours. Thr results obtained showed that the sodium aluminosilicate zeolite ceramic porous material based on a mixture of aluminum powder, quartz sand, and polyvinyl alcohol exhibited high hydrogen absorption-up to 13% (at temperature = 250°C and pressure = 13 atm).

Highly porous ceramic materials based on coarsely dispersed αAl2O3

Highly porous ceramic materials based on coarsely dispersed αAl2O3

Study of the structure of yttrium-based nanoporous ceramic materials

Porous ceramic materials with high filtration performance are widely used in conditions of high chemical, thermal and radiation loads. The results of studying the structure and morphology of the pore space of ceramic membranes are presented. Ultradispersed refractory powder Y2O3 was used as a main component-filler. The synthesis was carried out using compaction, technological combustion and self-propagating high-temperature synthesis. The use of ultradisperse sintering additives with highly developed surface (MgO — 5 μm, SiC — 3, SiO2 — 5 μm) allowed us to ensure the energy efficiency of synthesis of high- porous ceramic materials at low temperatures. Analysis of the structure and pore space using mercury porometry and alternative methods showed that the average pore size in the synthesized 3D matrix composite material based on yttrium orthosilicate matrix with yttrium oxide filler is 1.1 μm, the equivalent hydraulic pore diameter being about 100 nm. The difference is attributed to the variability of cross sections and high tortuosity of pore channels. Since the density of the material is 2.3 g/cm3 and the compressive strength is about 2 MPa, it can be easily machined with carbide tools being a promising material for manufacturing products with complex shapes. The obtained results can be used in developing energy-efficient technologies of one-stage production of yttrium oxide-based filters with high porosity to be used under conditions of exposure to radiation, aggressive media and high temperatures.

Preparation and Characteristics of High-Performance, Low-Density Metallo-Ceramics Composite.

By applying the physical vapour deposition method, hollow ceramic microspheres were coated with titanium, and subsequently, they were sintered using the spark plasma sintering technique to create a porous ceramic material that is lightweight and devoid of a matrix. The sintering process was carried out at temperatures ranging from 1050 to 1200 °C, with a holding time of 2 min. The samples were subjected to conventional thermal analyses (differential scanning calorimetry, thermogravimetry, dilatometry), oxidation resistance tests, and thermal diffusivity measurements. Phase analysis of the samples was performed using the XRD and the microstructure of the prepared specimens was examined using electron microscopy. The titanium coating on the microspheres increased the compressive strength and density of the resulting ceramic material as the sintering temperature increased. The morphology of the samples was carefully examined, and phase transitions were also identified during the analysis of the samples.

Refined express method for evaluation of porous structure ceramic materials

The express method for evaluating the porous structure of ceramic materials has been refined by replacing a smooth change in gas pressure with a stepwise one with pressure holding at each stage. After determining the average radius, the maximum pressure drop is determined until only one chain of gas bubbles remains. The average coordination number for the solid phase and the coefficient of capillary tortuosity were calculated. The experimental and calculated mean radii are in good agreement with the data, while the tortuosity coefficients differ.

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

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

Study of the effect of the morphology of initial powders on the structural and dimensional characteristics of SiC-based porous ceramic materials

The realization of the necessary energy-efficient technological solutions for the production of highly porous SiC-ceramic materials requires appropriate research. The results of developing energy-efficient one-step methods for the synthesis of porous SiC-based ceramics and studying the characteristics of the obtained ceramics are presented. The effect of the morphology of initial powders on the synthesized product is considered. Ultrafine silicon carbide powders of two types, identical in characteristic particle size, but quite different in the surface morphology, were used as fillers in the synthesis of experimental samples of porous ceramics. The first one was obtained by the traditional furnace method (SiCf), the second one was synthesized by the technology of self-propagating high-temperature synthesis (SiCshs). It is shown that the particle morphology of initial powder components determines the structural parameters and characteristics of synthesized porous ceramics. The pore space parameters (average pore size, specific surface area, equivalent hydraulic diameter, permeability, etc.) can vary significantly. Porous ceramic materials synthesized on the basis of SiCf have an open porosity of 47%, high liquid permeability (up to 2 mDarcy), overwhelming dominance of α-SiC phase, and a narrow pore distribution with an average pore size of about 1 μm. High open porosity (more than 58 %), highly developed nanostructured pore space surface with an area of more than 12 m2/g, and wider pore size distribution (average pore size — 140 nm) are observed in porous ceramic materials based on SiCshs. The obtained results can be used to improve energy-efficient synthesis technologies and methods for predicting the properties of highly porous SiC-based ceramic materials. This will make it possible to create highly porous SiC ceramics within a priory predicted limits of effective applicability for the processes of ultrafiltration or catalysis.

Automatic micro-scale modelling and evaluation of effective properties of highly porous ceramic matrix materials using the scaled boundary finite element method

This paper presents an approach to the numerical estimation of effective properties of highly porous materials based on the scaled boundary finite element method (SBFEM). The latter can be formulated on quadtree meshes with hanging nodes and thus facilitates the efficient mesh generation and analysis of a large number of randomly created samples. To generate the corresponding Representative Volume Elements (RVEs), an improved Random Sequential Addition (RSA) method with overlap is used. Moreover, an alternative image-based digital matrix method for generating random assemblies of circular particles of the same size is proposed. In addition, a modified smoothing algorithm to treat the staircase boundaries present in a quadtree mesh is developed in order to accurately and efficiently capture the sinter-neck features of overlapping circular particles. The proposed image-based mesh generation and analysis procedure is used to evaluate the relationship between microstructural parameters and effective Young’s modulus considering a large number of samples. In this context, a new dimensionless morphological parameter Nfc is proposed. The latter represents the morphology and connectivity of voids and is shown to be a useful indicator with respect to the effective elastic properties of highly porous ceramic matrix material.