Hasil untuk "Clay industries. Ceramics. Glass"

Nabil Daghbouj, Ahmed Tamer AlMotasem, Bingsheng Li et al.

Helium accumulation in structural ceramics used in nuclear, fusion, and aerospace systems causes swelling, cracking, and early failure, yet controlling this damage has remained elusive. Here, we introduce defect landscape engineering, the deliberate creation of vacancy clusters prior to helium exposure, as a general strategy to suppress helium-induced degradation. Using α-SiC as a model, we combine advanced microscopy, strain mapping, helium depth profiling, positron annihilation spectroscopy, and atomistic simulations to demonstrate that tailored pre-damage transforms helium defect evolution. Instead of forming extended platelets and nanocracks, helium is trapped in stable, uniformly dispersed nanobubbles. Simulations reveal that small vacancy clusters act as dual-function sinks for irradiation-induced interstitials and preferential helium traps, fundamentally altering cascade recombination dynamics. This mechanism is composition-independent and scalable, offering a new design principle for radiation-tolerant ceramics across carbides, nitrides, and oxides. By viewing defect control as a tunable parameter instead of a fixed material property, this work outlines a possible design route toward enhanced radiation tolerance in ceramics used in extreme environments.

Ashley Bonilla, Alina Pruna, Rut Benavente et al.

Given the raising environmental concerns over lead toxicity, replacing the common lead-based piezoelectric ceramics with a proper alternative became a hot topic. (Na0.5K0.5)NbO3 (KNN) is considered a potential replacement for such ceramics. This work presents the synthesis of KNN-type ceramics based on conventional solid-state reaction, where the effect of precursor particle size is studied. A combined mechanical activation by ball milling and calcination at low temperature of 800 °C is applied. The phase structure evolution, morphology and mechanical properties are investigated systematically with the particle size and the calcination rate. The results indicate a marked effect of the precursor particle size on the properties of obtained ceramics. Secondary phase content could be lowered and tetragonality improved by the applied approach. Despite the presence of secondary phases, dielectric measurements indicated typical values of dielectric constant and loss for piezoelectric materials. Resumen: La sustitución de las cerámicas piezoeléctricas comunes a base de plomo por una alternativa adecuada, se convirtió en un tema importante debido a las crecientes preocupaciones medioambientales por la toxicidad del plomo. Los (Na0.5K0.5)NbO3 (KNN) se consideran un posible reemplazo para cerámicas piezoeléctricas comunes a base de plomo. Este trabajo presenta la obtención de cerámicas tipo KNN mediante una reacción convencional en estado sólido donde se estudia el efecto del tamaño de las partículas precursoras. El método de síntesis ha empleado una combinación de molienda de atrición para activar la mezcla de precursores y de calcinación a baja temperatura de 800 °C. La evolución de las fases, la morfología y las propiedades mecánicas se investigan sistemáticamente con el tamaño de partícula y la rampa de calcinación. Los resultados indican un marcado efecto del tamaño de partícula del precursor sobre las propiedades de las cerámicas obtenidas. El contenido de fases secundarias y de la fase tetragonal se pueden ajustar ligeramente mediante el método presentado. Las medidas dieléctricas han indicado valores típicos para las cerámicas piezoeléctricas (constante dieléctrica y pérdidas) a pesar de la presencia de fases secundarias.

Zixiang Xiong, Jian Zhu, Xueqian Geng et al.

Transparent piezoelectric ceramics (TPCs) have great application potential in electro-optical-mechanical multi-functional devices. Preparing high-performance TPCs, especially improving the transparency through microstructure regulation, has recently caused extensive discussion. However, there is still controversy about the influence of grains and pores on the transmittance of ceramics, and there is arbitrariness in the estimation of the theoretical transmittance limit. In this paper, taking PMN-PT-based ceramics as an example, theoretical mechanisms for the transmittance are discussed. An inhomogeneous reflection model is derived to improve the theoretical limit of transmittance. The effects of pores and grains scattering on transmittance are investigated. Rayleigh and RGD approximation are discussed to reveal the underlying scattering mechanisms. It is found that Rayleigh approximation is suitable for describing pore scattering, while RGD approximation is suitable for grain scattering. Thus, a Rayleigh-RGD combined model is proposed to describe light scattering in TPCs and successfully employed to fit experimentally measured transmittance curves.

Dominik Krengel, Jian Chen, Zhipeng Yu et al.

Clay minerals are non-spherical nano-scale particles that usually form flocculated, house-of-card like structures under the influence of inter-molecular forces. Numerical modeling of clays is still in its infancy as the required inter-particle forces are available only for spherical particles. A polytope approach would allow shape-accurate forces and torques while simultaneously being more performant. The Anandarajah solution provides an analytical formulation for van der Waals forces for cuboid particles but in its original form is not suitable for implementation in DEM simulations. In this work, we discuss the necessary changes for a functional implementation of the Anandarajah solution in a DEM simulation of rectangular particles and their extension to cuboid particles.

Awais Qadir, Shoaib Ali, Jan Dusza et al.

This study presents a data-driven framework based on machine learning (ML) using extreme gradient boosting (XGBoost) for predicting the hardness of silicon nitride (Si3N4) ceramics reinforced with graphene. The XGBoost model takes into account various factors such as graphene type and content, characteristics of the raw Si3N4 powder, the parameters of the sintering process (sintering technique, temperature, pressure, holding time), and the characteristics of the sintered samples, i.e., the density, αβ content and Vickers hardness. The parameters that influence the Si3N4 hardness most strongly are identified, with sintering pressure, sintering time and density being the most influential. The addition of graphene content up to a certain threshold (1 wt%) has a positive impact on hardness. However, beyond that it leads to a lower density and a lower mechanical performance. Sintering parameters, particularly the sintering pressure, temperature, holding time and technique, strongly affect the density, final grain size, αβ Si3N4 composition and subsequently the hardness. The study highlights the importance of density and the densification process in achieving high hardness in Si3N4 ceramics. The developed ML model provides a valuable tool for predicting the hardness of Si3N4+graphene ceramics composites and offers insights into selecting suitable graphene type, content, and processing parameters. While the study primarily focuses on Si3N4+graphene composites, this novel approach holds promise for the in-silico design and analysis of diverse ceramic materials.

Le Lu, Tianlong Liu, Zhaofeng Chen et al.

Flash sintering (FS) is a novel technique for rapidly densifying silicon carbide (SiC) ceramics. This work achieved a rapid sintering of SiC ceramics by the utilization of ultra-high temperature flash sintering within 60 s. Pyrolysis carbon (PyC) “bridges” were constructed between SiC particles through the carbonisation of phenolic resin, providing a large number of current channels. The incubation time of the flash sintering process was significantly reduced, and the sintering difference between the centre and the edge regions of the ceramics was minimized, with an average particle size of the centre region and edge region being 12.31 and 9.02 μm, respectively. The results showed that the porosity of the SiC ceramics after the flash sintering was reduced to 14.79% with PyC “bridges” introduced, and the Vickers hardness reached 19.62 GPa. PyC “bridges” gradually evolved from amorphous eddy current carbon to oriented graphite carbon, indicating that the ultra-high temperature environment in which the sample was located during the flash sintering was successfully constructed. Ultra-high temperature flash sintering of SiC is expected to be applied to the local repair of matrix damage in SiC ceramic matrix composites.

Davi Costa, Clay Córdova, Michele Del Zotto et al.

Global Categorical Symmetries are a powerful new tool for analyzing quantum field theories. This volume compiles lecture notes from the 2022 and 2023 summer schools on Global Categorical Symmetries, held at the Perimeter Institute for Theoretical Physics and at the Swiss Map Research Station in Les Diableret. Specifically, this volume collects the lectures: * An introduction to symmetries in quantum field theory, Kantaro Ohmori * Introduction to anomalies in quantum field theory, Clay Córdova * Symmetry Categories 101, Michele Del Zotto * Applied Cobordism Hypothesis, David Jordan * Finite symmetry in QFT, Daniel S. Freed These volumes are devoted to interested newcomers: we only assume (basic) knowledge of quantum field theory (QFT) and some relevant maths. We try to give appropriate references for non-standard materials that are not covered. Our aim in this first volume is to illustrate some of the main questions and ideas together with some of the methods and the techniques necessary to begin exploring global categorical symmetries of QFTs.

Marc Christ, Conrad Zimmermann, Sascha Neinert et al.

Quantum technologies are advancing from fundamental research in specialized laboratories to practical applications in the field, driving the demand for robust, scalable, and reproducible system integration techniques. Ceramic components can be pivotal thanks to high stiffness, low thermal expansion, and excellent dimensional stability under thermal stress. We explore lithography-based additive manufacturing of technical ceramics especially for miniaturized physics packages and electro-optical systems. This approach enables functional systems with precisely manufactured, intricate structures and high mechanical stability while minimizing size and weight. It facilitates rapid prototyping, simplifies fabrication and leads to highly integrated, reliable devices. As an electrical insulator with low outgassing and high temperature stability, printed technical ceramics such as Al2O3 and AlN bridge a technology gap in quantum technology and offer advantages over other printable materials. We demonstrate this potential with CerAMRef, a micro-integrated rubidium D2 line optical frequency reference on a printed Al2O3 micro-optical bench and housing. The frequency instability of the reference is comparable to laboratory setups while the volume of the integrated spectroscopy setup is only 6 ml. We identify potential for future applications in compact atomic magnetometers, miniaturized optical atom traps, and vacuum system integration.

W.C. N'cho, A. Gharzouni, J. Jouin et al.

The impact of metakaolin mixtures on geopolymer formation and corresponding properties was evaluated by synthesizing geopolymers from mixtures of different metakaolins and 5 M potassium silicate. Mixture reactivity was investigated by viscosity, thermogravimetric (DTA-TGA), and in situ infrared spectroscopy (FTIR) measurements. Furthermore, mechanical strength and porosity measurements were undertaken on consolidated materials. The results have shown that the aluminum molar concentration governs the setting time and oligomer formation energy. Indeed, the high aluminum content associated with the high purity of the metakaolins lead to a low formation energy of oligomer, whereas for the metakaolins containing more impurities, the energy required for oligomer formation was higher. Regardless of the formulation, the mechanical strength and porosity trends were similar. Network characteristics were assessed by amorphous material content and in situ infrared spectroscopy (FTIR) analysis. It was demonstrated that (i) for Si/Al < 1.5, an amorphous network is formed with a constant Si/Al ratio, and for (ii) Si/Al > 1.5, different networks are formed. The zeta potential values of the different metakaolin mixtures corroborated these findings. Zeta potential values of metakaolins are governed by the impurities present in the metakaolins, which limit the release of aluminous species from the metakaolins in solution, emphasizing that knowledge of raw materials is essential to understand the local networks formation.

Yuxuan Wang, Guoqiang Lan, Jun Song

High entropy ceramics are highly promising as next generation thermal barrier coatings due to their unique disorder structure, which imparts ultra-low thermal conductivity and good high temperature stability. Unlike traditional ceramic materials, the thermal resistance in high entropy ceramics predominantly arises from phonon-disorder scattering rather than phonon-phonon interactions. In this study, we propose a calculation method based on the supercell phonon unfolding (SPU) technique to predict the thermal conductivity of high entropy ceramics, specially focusing on rocksalt oxides structures. Our prediction method relies on using the reciprocal value of SPU phonon spectra linewidth as an indicator of phonon lifetime. The obtained results demonstrate a strong agreement between the predicted thermal conductivities and the experimental measurements, validating the feasibility of our calculation method. Furthermore, we extensively investigate and discuss the atomic relaxation and lattice distortion effects in 5-dopants and 6-dopants rocksalt structures during the process.

Julian Jauk, Lukas Gosch, H. Vašatko et al.

In this paper we will demonstrate a digital workflow that includes a living material such as mycelium and makes the creation of structural designs possible. Our interdisciplinary research combines digital manufacturing with the use of mycelial growth, which enables fibre connections on a microscopic scale. We developed a structure that uses material informed toolpaths for paste-based extrusion, which are built on the foundation of experiments that compare material properties and growth observations. Subsequently, the tensile strength of 3D printed unfired clay elements was increased by using mycelium as an intelligently oriented fibre reinforcement. Assembling clay-mycelium composites in a living state allows force-transmitting connections within the structure. This composite has exhibited structural properties that open up the possibility of its implementation in the building industry. It allows the design and efficient manufacturing of lightweight ceramic constructions customised to this composite, which would not have been possible using conventional ceramics fabrication methods.

Parkpoom Jarupoom, Pharatree Jaita

Lead-free (1-x) (Bi0.5Na0.5)TiO3-xBi(Mg0.5Ti0.5)O3 or (1-x)BNT-xBMT (x = 0–0.20) piezoelectric ceramics have been investigated for phase evolution, microstructure, dielectric, ferroelectric, piezoelectric, electric field-induced strain, energy storage density, energy harvesting, and magnetic properties. All compositions exhibited high density sintered ceramics (~ 6.13–6.30 g/cm3). With increasing modifier content, the crystal structure changed from rhombohedral to cubic phase. When BMT content was added, the grain size and Tm were found to increase. The x = 0.05 ceramic showed good piezoelectric (low-field d33 = 159 pC/N) and ferroelectric (Pr = 23.84 µC/cm2, Ec = 34.41 kV/cm) properties. The BMT additive also produced an improvement in electric field-induced strain, energy storage efficiency, and magnetic properties. The highest piezoelectric voltage constant (g33 = 26.29 × 10−3 Vm/N) and the off-resonance figure of merit (FoM) for energy harvesting (~ 4.18 pm2/N) were also obtained for the x = 0.05 ceramic, which was ~ 3.4 times (240%) as compared to the pure BNT ceramic. This suggested that the ceramic has a potential to be one of the promising lead-free piezoelectric candidates for further use in piezoelectric energy harvesting applications.

Parisa Edalati, Masayoshi Fuji, Kaveh Edalati

High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications. The application of severe plastic deformation (SPD), particularly the high-pressure torsion (HPT) method, combined with the CALPHAD and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials. This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials. These superfunctional properties include (i) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys, (ii) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys; (iii) high strength, low elastic modulus, and high biocompatibility in high-entropy alloys, (iv) fast and reversible hydrogen storage in high-entropy hydrides, (v) photovoltaic performance and photocurrent generation on high-entropy semiconductors, (vi) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides, and (vii) CO2 photoreduction on high-entropy ceramics. These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.

M. G. Norton

Ipeknaz Özden, Aljaž Iveković, Andraž Kocjan

Ceramics are a class of materials delicate to shape due to their inherent inability to plastically deform. Conventional shaping processes utilizing thermoplastic feedstock that mimic plastic deformation were successful in providing ceramic parts with high quality, but with limited shape complexity. Additive manufacturing (AM) has revolutionized the shaping of ceramics, allowing for realization of components with increased complexity and precision. This paper reviews the current state of AM technologies with emphasis on the techniques based on modelling of thermoplastic feedstocks. Namely, fused filament fabrication (FFF) is widespread and cost-effective AM technology, however, limited by relatively low resolution and poor surface finish. On the other hand, thermoplastic 3D printing (T3DP), emerged recently as a high-precision, high surface finish AM technology. With further development in these processes as well as materials that can be shaped, it is expected that thermoplastic feedstock based processes will be more prominent in AM of ceramics.

Naohiro Horiuchi, Kaede Ryu, Akiko Nagai et al.

Sodium ion conductor with the composition of Na4.0Y0.6P0.2Si2.8O9 was prepared using a sol-gel method (polymerized complex method). The homogeneous gel was prepared by dissolving citric acid and ethylene glycol in mixtures of water solutions of metal salts. Drying the gel provides the uniform precursor. The sintered pellet obtained from the precursor had a single crystalline phase of Na5YSi4O12-type structure and exhibited ionic conductivity of 3.7 × 10−2 S/cm at 300 °C.

Shoulei Yang, Sirui Yang, Haiyang Liu et al.

This study investigated the in-situ growth of carbon nanotubes (CNTs) in silica (SiO2) powder by polymer pyrolysis chemical vapor deposition with a polyethylene glycol (PEG) carbon source and cobalt nitrate catalyst. The mass ratio of PEG:citric acid:cobalt nitrate was determined to control the microstructures of the in-situ CNTs. Results indicated that with an increase in the mass ratio of PEG:citric acid:cobalt nitrate, the in-situ generated CNTs content in the SiO2 powder increased, the CNTs diameters (approximately 40 nm) did not significantly change, and the CNTs lengths decreased from 400–800 nm to 200–400 nm. Additionally, the in-situ CNTs that were anchored on the surfaces of SiO2 particles presented fewer defects and a high degree of graphitization. However, when the mass ratio of PEG:citric acid:cobalt nitrate exceeded the critical value, excessive amounts of amorphous carbon grown in situ on SiO2 particles were obtained. The suspension experiments showed that unlike the CNTs/SiO2 powders prepared by a combination of surfactant and ultrasonic methods with commercial CNTs, in-situ CNTs grown in SiO2 powders exhibited improved separation resistance in water. This would favor the uniform dispersion of CNTs within the matrix, improving the performance of nanocarbon-modified cement-based composites.

Cuiping Xi, Jianmin Zhou, F. Zheng et al.

One of the major advances of this research is to produce porous glass ceramics (PGCs) via a feasible and cost-effective powder forming chemistry to convert solid wastes, extracted titanium tailing (ETT) and waste glass (WG) into the value-added PGCs. The maximum handling amount of ETT (30%) is determined from systematic experiments, based on the end use of these PGCs, which are manifested as controlled-crystalline porous structures of hybrid matrices. These multiscale porous networks are composed of a tunable pore size, high surface area and accessibility. The synthetic PGCs are found to display enhanced physical properties, as a result, the stewardship of their intrinsic chemical behaviors can be secured. To elucidate, the PGC shows an apparent density of 0.60 ± 0.01 g cm-3, a porosity of 76.0 ± 0.4%, a high compressive strength of 3.8 ± 0.2 MPa, an available water adsorption ratio of 4.4 ± 0.1%, a heat conductivity of 0.103 ± 0.003 W m-1 °C-1 and an applicable coefficient of thermal expansion ((5.43 ± 0.05) × 10-6 m m-1 °C -1). This study indicates that indeed the powder forming chemistry provide a simple method to advance the conversion of industry and municipal solid waste (ETT & WG) into value-added PGCs with improved physical and chemical properties.

P. Xu, T. Erdem, E. Eiser

Inspired by the relationship between the well-ordered architecture of aragonite crystals and biopolymers found in natural nacre, we present a facile strategy to construct large-scale organic/inorganic nacre-mimetics with hierarchical structure via a water-evaporation driven self-assembly process. We connect LAPONITE®-nanoclay platelets with each other using carboxymethyl cellulose, a cellulose derivative, thus creating thin, flexible films with a local brick-and-mortar architecture. The dried films show a pronounced resistance against tensile forces allowing for stronger thin films than nacre. In terms of functionalities, we report excellent glass-like transparency along with exceptional shape-persistent flame shielding. We also demonstrate that through metal ion-coordination we can further strengthen the interactions between the polymers and the nanoclays, and thus enhanced mechanical, and thermal properties as well as resistance against swelling and dissolution in aqueous environments. We believe that our simple pathway to fabricate such versatile polymer/clay nanocomposites can open avenues for inexpensive production of environmentally friendly, biomimetic materials in aerospace, wearable electrical devices, and in the food packaging industry.

Jorge Suárez-Macías, Juan María Terrones-Saeta, F. J. Iglesias-Godino et al.

Mining activity is essential for the social welfare of the population. However, this activity produces a series of mining waste. These mining wastes, if not properly treated, can produce significant environmental pollution. This study develops the incorporation of tailings from washing plants in ceramic materials for bricks in order to retain the contaminating elements in the ceramic matrix. To this end, firstly, a physical and chemical characterisation of the mining waste is carried out and different groups of samples are conformed with clay and mining waste. These conformed samples with mining waste are evaluated through different physical and mechanical tests typical in the ceramic industry, studying the variation of properties by the incorporation of the waste. In turn, the leachates from the groups of conformed samples are analyzed, confirming the retention of the contaminating elements of the mining waste in the ceramic matrix. The results of these tests showed that ceramics can be made for bricks with up to 90% mining waste, obtaining physical and mechanical properties acceptable regarding the regulations and retaining the contaminating elements in the ceramic matrix, as confirmed by the leachate tests.