Properties Of Ceramic Materials Research Articles

Significantly improved mechanical properties of mullite ceramics by adding AlOOH with different sizes and morphologies

AbstractMullite ceramics with high purity and toughness were prepared by hot‐press sintering of pyrophyllite at 1300°C using AlOOH nanomaterials with different sizes and morphologies (nanoparticles, nanorods, nanoflakes, and micro‐sized sea urchin–like) as additives. Among the four types of AOOH additives, the incorporation of nanoflakes and sea urchins resulted in the formation of a relatively uniformly distributed and tightly packed microstructure within the ceramics, which significantly improved the density and mechanical properties of the ceramic materials. Compared to nano‐sized AlOOH, the addition of micron‐sized sea urchin–like AlOOH could produce mullite ceramics with best purity and flexural strength. The flexural strength and fracture toughness of ceramics prepared from micro‐sized sea urchin–like AlOOH and pyrophyllite reach 427.34 ± 1.99 MPa and 4.68 ± .31 MPa m1/2, respectively. During the ball milling process, the originally micron‐sized sea urchin–like AlOOH particles were broken down into micro‐ and nano‐sized AlOOH particles. The resulted micron and nanoscale AlOOH particles exhibited synergistic and multi‐scale effects with pyrophyllite, which contributed to the formation of uniformly sized and densely arranged mullite crystals within the ceramics. Additionally, the bridging between the mullite crystals further improved the mechanical properties of the mullite ceramic material.

Merits and Demerits of Machine Learning of Ferroelectric, Flexoelectric, and Electrolytic Properties of Ceramic Materials

In the present review, the merits and demerits of machine learning (ML) in materials science are discussed, compared with first principles calculations (PDE (partial differential equations) model) and physical or phenomenological ODE (ordinary differential equations) model calculations. ML is basically a fitting procedure of pre-existing (experimental) data as a function of various factors called descriptors. If excellent descriptors can be selected and the training data contain negligible error, the predictive power of a ML model is relatively high. However, it is currently very difficult for a ML model to predict experimental results beyond the parameter space of the training experimental data. For example, it is pointed out that all-dislocation-ceramics, which could be a new type of solid electrolyte filled with appropriate dislocations for high ionic conductivity without dendrite formation, could not be predicted by ML. The merits and demerits of first principles calculations and physical or phenomenological ODE model calculations are also discussed with some examples of the flexoelectric effect, dielectric constant, and ionic conductivity in solid electrolytes.

Nanomechanical properties of ceramic materials from the SiO2–Al2O3-(Na2O)–K2O–MgO system with an addition of SrO

The ceramic materials studied in this paper consist of finely dispersed crystalline phases embedded in a glassy matrix, which is similar to glass-ceramic materials, porcelain, and VC products. The strength depends then not only on the properties of the individual crystalline phases but also on their interactions and the matrix. Differences in mechanical properties for materials with similar chemical compositions are most likely related to diverging microstructures. Crystal orientation, grain-size distribution and shape, the ratio of the glass matrix to the crystalline phase, and homogeneity control the flexural strength of glass-ceramic materials. The subject of the study is whiteware ceramic materials from the SiO2–Al2O3–Na2O–K2O–MgO–SrO system, fired similarly to the regime used for VC products. The effect of the type of alkali oxide and the share of SrO were tested. This paper presents the results of hot-stage microscopy, X-ray diffraction (XRD), scanning electron microscopy with a micro-analyzer (SEM-EDS) and biaxial flexural strength measurements. Additionally, nanoindentation technique was used to access local mechanical properties.

Reinforcement Induced Microcracking during the Conversion of Polymer-Derived Ceramics

This study investigates the role of discontinuous reinforcement on the microcracking of a preceramic polymer matrix during polymer to ceramic conversion. The material system comprised a carbosilane-based, preceramic polymer reinforced with mullite particles. The preceramic resin slurry was formulated for photopolymerization on a digital light projection 3D printer. Micro X-ray computed tomography, using a synchrotron light source, monitored a printed composite part during pyrolysis. The conversion of the carbosilane matrix into Si(O)C generated microcracks in the matrix that radially extended from particles. The likelihood of microcrack formation positively correlated with particle size. The largest particles (>104 µm3 volume or >60 µm side length) always abutted microcracks, while the matrix surrounding smaller particles (<5 µm) was free of microcracks. Numerical calculations showed the particles resist the shrinking matrix during its conversion. This created tensile stresses within the matrix. The driving force for microcrack growth was also analyzed with regard to the influence of matrix material parameters, particle form-factor and crack length. These results reveal the need to consider the form factor of discontinuous reinforcements, with regard to the polymer-derived ceramic material properties, in order to reduce or eliminate defects in the final part.

Ceramic Material Properties in High-Temperature Environments: Recent Trends in Finite Element Analysis Research

The finite element method is commonly utilized for high-temperature ceramics, such as cutting tools, thermal/environmental barrier coatings, and aerospace applications. Cutting performance is influenced by both internal and external factors, including heat transfer, and cutting speed. Friction coefficients and heat transfer issues reveal limitations on cutting tool efficiency, requiring accurate modeling and validation. Although oxide formation and crack failure for barrier coatings are discussed, ceramic materials and geometry must be studied. Extensive research on the nucleation and propagation of micro-crack is needed for next-generation spacecraft component applications by validating the established model based on experimental observation. Modeling and verification research improves ceramic reliability under more stress conditions.

Microwave absorption properties of bismuth ferrite-based ceramics

The paper presents the results of a study of the microwave absorption properties of ceramic materials based on bismuth ferrite containing rare earth elements, as well as systems of solid solutions ([Formula: see text])BiFeO3–xPbFe[Formula: see text]Nb[Formula: see text]O3 in a wide range of component concentrations. The methodology for measuring and calculating the parameters of samples of the materials under study is described. The influence of structural and microstructural factors on the average and maximum level of microwave absorption of the materials under study in a wide frequency range is analyzed. A comparison of the microwave absorbing properties of these materials with industrial absorbers has been carried out, and prospects for application in microwave technology have been shown.

Study on a novel Si3N4-based composite with the incorporation of N-GQDs produced from nano-lignin

In order to enhance the mechanical properties of ceramic materials and realize the high value utilization of lignin, the nano-lignin precursor was added into the silicon nitride matrix as the second phase to obtain a novel ceramic composite material with excellent mechanical performance in this study. During the preparation, the nano-lignin was transformed into nitrogen-doped graphene quantum dots(N-GQDs) in the ceramic matrix by the pyrolysis-hot pressing sintering coupling process. Aiming to reveal the pyrolysis conversion process of lignin, the segmented products at the different temperature gradient were prepared, and their phase composition and microstructure were deeply analyzed by various test methods. In addition, the continuous pyrolysis process of nano-lignin was further studied by simultaneous thermal analyzer. The results showed that, nano-lignin was transformed into solid products (amorphous carbon) in the temperature range of room temperature to 800 °C and produced a large number of volatiles. Subsequently, in the temperature range of 800∼1400 °C, part of amorphous carbon began to transform into N-GQDs, and part of α-Si3N4 also began to transform into β-Si3N4. When the temperature rose to the temperature of 1700 °C, all amorphous carbon was transformed into N-GQDs through carbon structure rearrangement and nitrogen doping, and meanwhile the most of α-Si3N4 was transformed into β-Si3N4. At the final stage, β-Si3N4 columnar grains were covered by an overlayer composed of N-GQDs, and a novel ceramic composite with a special “core-shell” microstructure was obtained and exhibited excellent mechanical performance. This study presents a promising approach for the preparation of high-performance ceramic materials, and can also intrigue great interests in lignin graphitization and lignin-derived carbon materials.

Numerical modeling and statistical analysis of the effect of thermomechanical properties on residual stresses in feldspar‐based ceramic materials after thermal tempering

AbstractThis study focuses on the investigation of the impact of the thermomechanical properties of ceramic materials on residual stresses generated after the thermal tempering process. A sodium feldspar matrix was chosen for numerical simulations, with variations in its thermomechanical properties of up to ± 20%, to encompass a range of properties exhibited by other ceramic materials. The simulations demonstrated that the viscosity of the material had the most significant influence on residual stress generation, while the coefficient of thermal expansion, modulus of elasticity, and effective diffusivity also contributed to residual stress formation. A statistical analysis based on a 24 factorial design revealed that increasing residual compressive stress on the surface was achievable by increasing the coefficient of thermal expansion and modulus of elasticity, as well as the viscosity, while reducing the effective thermal diffusivity. Finally, a mathematical model was proposed to relate the thermomechanical properties of the ceramic material to the residual stresses observed on the surface following thermal tempering.

Керамика на основе сложнооксидного твердого раствора диоксида циркония в тетрагональной форме для ортопедической стоматологии

The paper deals with physical and mechanical properties of ceramic material containing complex oxide solid solution Zr1–n[YbNd]nO2 and corundum microfase, taking into account aesthetic and strength requirements of clinical practice of prosthetic dentistry. It has been shown that the developed ceramic has a static bending strength of 850 MPa and according to the international standard ISO 6872:2015 “Dentistry – Ceramic materials” belongs to the 4th and 5th class of dental ceramic materials. This makes it possible to use it for the manufacture of not only single crowns, but also four-units dentures of any localization and any type of fixation. The developed ceramics meet the requirements of prosthetic dentistry and color characteristics, have high opacity, which makes it possible to mask the color of supporting structures.

Cold-Sintered ZnO Ceramic Composites Co-Doped with Polytetrafluoroethylene and Oxides.

Grain boundaries play a significant role in determining the performance of ceramic-based materials. The modulation of interfacial structures provides a promising approach to improve the physicochemical and electrical properties of ceramic materials. In this work, the grain boundary structures of ZnO-based ceramics were manipulated by incorporating polytetrafluoroethylene (PTFE) and metal oxides through the cold sintering process (CSP). It was found that the grain size of ZnO-based ceramics can be effectively reduced from 525.93 nm to 338.08 nm with an addition of PTFE and metal oxides of CoO and Mn2O3. Microstructural results show that most of the PTFE phase and metal oxides were distributed along the grain boundaries, which may lead to the increased grain boundary resistance from 1.59 × 106 ohm of pure ZnO to 6.21 × 1010 ohm of ZnO-based ceramics doped with PTFE and metal oxides, and enhanced Schottky barrier height from 0.32 eV to 0.59 eV. As a result, the breakdown field and nonlinear coefficient of the ZnO-based ceramics were improved to 3555.56 V/mm and 13.55, respectively. Therefore, this work indicates that CSP presents a feasible approach to design functional ceramic composites through the integration of polymer and metal oxides.

Influence of grain‐scale microstructural parameters on fracture toughness of polycrystalline ceramics: Dual scale finite element method

AbstractFracture toughness is a basic property of ceramic materials, and it is strongly influenced by their microstructures. However, the influences of grain‐scale microstructural factors, including grain fracture energy, boundary fracture energy, and grain size of the microstructure, on the fracture toughness remain unclear. To investigate this, a dual‐scale finite element method was developed. Models were established to assess the microstructural mechanical properties, with an average grain size of 0.1–100 μm, and different grain boundary fracture energies and grain fracture energies. Based on the microstructural mechanical properties, a macroscale three‐point bending model, combined with the extended finite element method was used to evaluate the fracture toughness. The results indicated that fracture toughness increased with the decrease in the grain size when the grain size was below 5 μm. Conversely, when the grain size was greater than 5 μm, the fracture toughness remained relatively constant. Additionally, the grain boundary fracture energy played a more important role for the fracture toughness than the grain fracture energy. Finally, a formula that quantitatively describes the relationship between the microstructure and fracture toughness was obtained. This work provides a valuable reference for evaluating the performances of structural ceramics.

The Effect of Sliding Speed on the Tribological Properties of Ceramic Materials

Ceramics are considered to be candidate materials for galvanising pot bearing materials due to their excellent corrosion resistance in many molten metals. Galvanising pot roll bearings must have excellent wear resistance, and, therefore, it is important to understand the wear behaviour of prospective bearing materials. This study investigates the friction- and wear-resistant properties of select ceramics, namely, pure hBN, BN M26, AlN-BN, Macor, 3YSZ, Al2O3 and Si3N4. The ceramics were tested at different sliding speeds using a pin-on-disc device equipped with SiC pins. The lowest coefficient of friction (COF) achieved was below 0.1, and it was measured for pure hBN at a 3.14 m/min sliding speed. However, a wear scar analysis showed that the BN grades suffered from severe wear. The highest wear rate was obtained for BN M26 at a 9.42 m/min sliding speed and was equal to 17.1 × 10−6 mm3 N−1 m−1. It was shown that the wear coefficient of the tested ceramics varied exponentially with hardness. The lowest wear was observed on the 3YSZ, Al2O3 and Si3N4 ceramics, which showed no volume loss, and, for this reason, they can be potentially used as bearing materials in continuous galvanising lines.

How highly efficient power electronics transfers high electrocaloric material performance to heat pump systems

Electrocaloric heat pumps for cooling or heating are an emerging emission-free technology, which could replace vapor-compression systems, harmful refrigerants, and mechanical compressors by a solid-state solution with theoretically even higher coefficient of performance. Existing electrocaloric ceramics could reach around 85% of the Carnot-limit, and existing electrocaloric polymers could enable a compact and high power density system. However, the performance of published system demonstrators stays significantly below this performance, partly because of the external electronic charging loss (cyclic charging/discharging of electrocaloric capacitors). This work analyzes how the latest 99.74% ultra-efficient power electronics enables to maintain a high performance even at the system level. A first-principle analysis on material and system parameters also shows the effect of significantly different material properties of ceramics (PMN, PST) and PVDF-based polymers on system parameters. A system benchmark provides insight into system characteristics not covered by material analysis.Graphical abstract

Ceramic Materials Based on Clay and Soapstone Waste: Thermo-Mechanical Properties and Application

In order to assess the feasibility of utilizing soapstone waste, which is generated during the production of stone blocks for fireplaces and other energy-saving devices, the effect of its addition to clay on the technological and thermal properties of ceramic materials was investigated. Two local clays and soapstone processing waste were characterized using XRD, SEM-EDS, XRF, DTA-TG, and granulometric analysis. The linear firing shrinkage, water absorption, density, flexural strength, thermal conductivity, specific heat capacity, and thermal shock resistance of the fired ceramic samples were analyzed. The results have shown that addition of soapstone waste to clay in an amount of 40 wt.% increases flexural strength, enhances thermal stability, and, additionally, reduces the thermal conductivity of the experimental samples. The technological properties of the final product meet the standard requirements for ceramic tiles.

Electron-Beam Processing of Aluminum-Containing Ceramics in the Forevacuum Pressure Range

Aluminum–ceramic materials based on Al2O3 and AlN are widely used in the electronics industry and, according to a number of electrophysical and technical and economic parameters, are among the most suitable for the production of electrical and radio engineering products. In this study, it is shown that the treatment of ceramics based on Al2O3 with an electron beam with a power of 200–1100 W and a current of 10–50 mA leads to heating of the ceramic surface to a temperature of 1700 °C. When heated to a temperature of 1500 °C and kept at this temperature for no more than 10 s, an increase in the roughness of the ceramic surface is observed by more than an order of magnitude. At the same time, for ceramic substrates based on aluminum nitride, an increase in the temperature of electron beam treatment from 1300 to 1700 °C leads to an increase in thermal conductivity from 1.5 to 2 times. The edge angle of water wetting of the AlN surface can vary from 20 to 100 degrees depending on the processing temperature, which allows one to control the transition of the material from a hydrophilic to a hydrophobic state. At the same time, electron beam exposure to Al2O3 does not change the wettability of this material so much. Electron beam processing in the forevacuum pressure region allows controlled changes in the electrophysical properties of ceramic materials based on Al2O3 and AlN.

Influence of pregranulation and low-pressure compaction on the properties of ceramic materials incorporating clay and spent coffee grounds

Spent coffee grounds (SCG) possess the potential to serve as an effective pore-forming additives ceramic materials productions. Nonetheless, a significant challenge arises when attempting to incorporate substantial quantities SCG, leading to a loss of consistency for extrusion moulding. Additionally, a drawback includes the pronounced drying shrinkage observed high SCG-content masses during plastic clay body moulding. In this study, the pregranulation process was employed to overcome these issues and produce a new material. SCG, in quantities of up to 20% by weight, were granulated with clay into assorted sized granules before being subjected to low-pressure pressing (0.05, 0.15, 0.25, and 0.5 MPa). The resulting samples underwent drying and firing, followed by evaluation of volume density, water absorption, compressive strength, and thermal. This article highlights the distinctions between materials shaped from plastic clay bodies and those formed using pregranulation. The findings demonstrate that by employing clay pregranulation process with or without the addition of spent coffee grounds, it is possible to produce low-density ceramic materials possessing excellent thermal insulation properties and sufficient strength.

Design of Supports to Avoid Deformations in the Process of Alumina Printing by Stereolithography

The excellent properties of ceramic materials make them essential for fields such as aeronautic, biomedical, dental, jewelry or electronic. However, the main drawback when manufacturing parts with these materials is their high brittleness. Additive manufacturing processes for ceramic materials allow this limitation to be overcame. Nevertheless, the required stages for additive manufacturing of ceramic parts make the process extremely difficult and with significant influence on the dimensional and geometrical precision.The stereolithography additive process for ceramic is similar to the conventional polymeric process, excepting that the raw material is a slurry of ceramic particles mixed with photosensitive resins. Consequently, two thermal post-processes are necessary to obtaining the final part: (i) debinding and (ii) sintering. Each of the stages in the process is critical because deformation, cracks or fractures can happen, mainly due to temperature changes during the post-processes. Consequently, a deep study of the stages of printing, debinding and sintering is necessary for optimizing them and to produce high-quality parts.In this work, two different types of supports have been studied to prevent deformations during the printing stage. Despite the great importance of supports in this additive manufacturing process, scarce information is available about their design beyond very general recommendations. This paper contains a preliminary study that reveals the effectiveness of using adequate supports to avoid deformations in the printing process. Parts have been scanned with a 3D structured light scanner and the obtained meshes compared with the nominal CAD. This comparison has revealed deformations during the sintering process; therefore, the need to extend the study of support design to the post-processing stages. Future work is necessary to extend this preliminary analysis of support design to improve the quality of SLA ceramic parts with different shape and size.

Study of the illite-kaolinite-CaCO3 mixtures during firing

The raw materials used in traditional ceramics include highly plastic clay minerals such as illite or kaolinite. Non-plastic materials are usually added to the mixtures, which affect their workability and sintering process. The formation of a new crystalline phase (e.g. anorthite) is often observed in mixtures that contain a large amount of CaO. The improvement of final properties of ceramic materials is attributed to the formation of anorthite. The aim of this paper is to study the firing of anorthite ceramics in the system illite-kaolinite-CaCO3. Four sets of samples with different illite:kaolinite ratio (8:2, 6:4, 4:6, 2:8), and with a constant addition of CaCO3 are produced. The samples were subjected to the thermal and structural analyses. A significant mass loss is observed for all studied samples during the process of dehydroxylation and decomposition of CaCO3. An exothermic peak around 950 °C, which is connected with the formation of anorthite, is observed during differential thermal analysis. Above this temperature, no significant length changes are recorded. The presence of anorthite is confirmed by XRD analysis. The most formation of anorthite is observed in the illite-kaolinite sample with ratio 8:2.

Effect of the polystyrene particle size on dielectric and piezoelectric properties of PZT piezoelectric ceramics via vat photopolymerization (VPP)

The fabrication of lead zirconate titanate (PZT) ceramics using VPP technology presents a significant challenge due to the suboptimal curing performance and printability of PZT ceramic slurry. In this study, we successfully manufactured PZT ceramics utilizing vat photopolymerization (VPP) technology by incorporating polystyrene (PS) powders of varying particle sizes into the PZT ceramic slurries. Our investigation revealed that the incorporation of PS powders dramatically enhances the curing performance of the PZT slurry. Furthermore, it was found that the electrical properties of resultant ceramics are intrinsically linked to the morphology and dimensions of the induced pores. However, our research findings indicate that an excessive particle size of PS can negatively impact the dielectric and piezoelectric properties of the PZT ceramics, underscoring the need for careful control over PS powder size during fabrication. The pronounced discrepancy in particle size between PZT and PS powders may lead to suboptimal interlayer combination within specific regions of the green body. Consequently, this could render the PZT ceramics susceptible to additional defect formation. Nonetheless, the fabricated PZT piezoelectric ceramics with a PS particle size of 3 µm demonstrate exceptional electrical characteristics. This research proposes a straightforward and productive approach for broadening the spectrum of processable ceramics within the domain of VPP technology, while offering a comprehensive understanding of the influence exerted by the morphology and dimension of pores on dielectric and piezoelectric properties of ceramic materials.

Structure and Physical Properties of Ceramic Materials Based on ZrO2-Sc2O3 for SOFC Electrolytic Membranes Obtained from Powders of Melted Solid Solutions with a Similar Composition.

This paper presents the results of studying the phase composition, luminescent characteristics, and ionic conductivity of ceramic scandium-stabilized solid solutions of zirconium dioxide containing 9 and 10 mol% Sc2O3. Ceramic samples were prepared by sintering powders obtained by grinding melted solid solutions of the same composition. A comparative analysis of the obtained data with similar characteristics of single crystals has been carried out. Differences in the phase composition of ceramics and initial single crystals were found. The effect of the structure and properties of grain boundaries on the ionic conductivity of ceramic samples is discussed. It is shown that the differences in the ionic conductivity of ceramic samples and crystals are mainly due to changes in the structure and phase composition.