Abigail Parra Parra, Rene Guardian Tapia, Ximena Cecilia Ramírez López
et al.
This work analyzes phase transformations in quaternary mixtures (clay–glass–hematite–waste activated sludge (WAS)), processed at 800–1000 °C under conditions of oxygen deficiency. The results of the study showed that, depending on the temperature treatment of mixtures of different compositions, the processes of carbon formation from WAS, carbon participation in reductive processes, and phase transformations in silicate subsystems occur simultaneously. After Ttr = 800 °C the main phases are fayalite and quartz, additional phases are wollastonite and feldspars. After Ttr = 900 °C the main phases are fayalite, quartz, wollastonite, and the additional phases are feldspars. After Ttr = 1000 °C the main phases are wollastonite, iron, quartz, additional phases are hematite, fayalite.
A simple, fast and energy efficient microwave-assisted hydrothermal method was developed for the preparation of nanocrystalline zirconia from commercially available ZrOCl2·8H2O and KOH. The synthesis was conducted at 180 °C for 20 min by two ways: direct decomposition of ZrOCl2·8H2O (sample Z), and precipitation of ZrOCl2·8H2O with KOH and dehydration of hydroxides (sample ZK). The as-synthesized powders were calcined at 500 °C, and all the resulting products were characterized by XRD, FE-SEM, HR-TEM and SAED. Both the as-synthesized and calcined nanoparticles were highly crystalline. A single monoclinic phase was obtained for sample Z, while for sample ZK a tetragonal phase was achieved as the main phase with a minor fraction of monoclinic. The particles of the as-synthesized sample Z showed irregular and semi-hexagonal shapes, although they changed to spherical or ellipsoidal shapes during heat treatment. The particles of the sample ZK, both as-synthesized and calcined, exhibited nearly spherical or ellipsoidal shapes. The average crystallite size for the as-synthesized samples Z and ZK were 3.2 ± 0.8 and 5.5 ± 0.9 nm, respectively, while for the calcined ones the values were 8.5 ± 1.2 and 7.6 ± 1.2 nm, respectively. Resumen: Se ha desarrollado un método hidrotermal asistido por microondas, simple, rápido y eficiente energéticamente, para la preparación de circona nanocristalina a partir de ZrOCl2·8H2O y KOH comercialmente disponibles. La síntesis se ha realizado a 180 °C durante 20 min por dos caminos: descomposición directa de ZrOCl2·8H2O (muestra Z), y precipitación de ZrOCl2·8H2O con KOH y deshidratación de hidróxidos (muestra ZK). Los polvos sintetizados fueron calcinados a 500 °C, y todos los productos resultantes fueron caracterizados por XRD, FE-SEM, HR-TEM y SAED. Tanto las nanopartículas sintetizadas como las calcinadas fueron altamente cristalinas. En el caso de la muestra Z, se obtuvo únicamente fase monoclínica, mientras que, en el caso de la muestra ZK, se obtuvo fase tetragonal como fase principal con una pequeña fracción de monoclínica. Las partículas de la muestra Z sintetizada mostraron formas irregulares y semihexagonales, aunque durante el tratamiento térmico cambiaron a formas esféricas o elipsoidales. Las partículas de la muestra ZK, tanto sintetizada como calcinada, presentaron formas prácticamente esféricas o elipsoidales. El tamaño medio de los cristales de las muestras sintetizadas Z y ZK fue 3.2 ± 0.8 y 5.5 ± 0.9 nm, respectivamente, mientras que el de las muestras calcinadas fue 8.5 ± 1.2 and 7.6 ± 1.2 nm, respectivamente.
Alumina-based insulators are widely used in regions with extreme temperature fluctuations, such as polar areas, due to their high mechanical strength, low thermal expansion, and excellent electrical insulation properties. To improve the reliability of electrical transmission lines in such environments, a detailed understanding of their structural and physical characteristics is needed. This study investigates the mechanical and microstructural properties of high-strength alumina-based insulators using X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDAX). The manufacturing process is analyzed, focusing on density, porosity, and phase structure validation. The results show that increased mullite formation within the insulator structure improves mechanical strength, especially with low porosity (10.8%), having homogeneous size distribution and high density (2.73 g/cm3). Strength tests indicate that the produced insulators resist forces up to 14 kN. Among the samples, those produced using alumina powder show better mechanical strength and reliability, likely due to more controlled mullite formation and reduced impurity content. As a result, an improved production process for reliable alumina-based C12.5-650 insulators was produced. These findings provide valuable insights for significantly improving the production of alumina-based insulators for harsh environments. Resumen: Los aisladores a base de alúmina se utilizan ampliamente en regiones con fluctuaciones extremas de temperatura, como las zonas polares, debido a su alta resistencia mecánica, baja expansión térmica y excelentes propiedades de aislamiento eléctrico. Para mejorar la fiabilidad de las líneas de transmisión eléctrica en dichos entornos, es necesario comprender detalladamente sus características estructurales y físicas. Este estudio investiga las propiedades mecánicas y microestructurales de aisladores a base de alúmina de alta resistencia mediante difracción de rayos X (DRX) y microscopía electrónica de barrido con análisis de rayos X por dispersión de energía (SEM-EDAX). Se analiza el proceso de fabricación, centrándose en la densidad, la porosidad y la validación de la estructura de fases. Los resultados muestran que una mayor formación de mullita en la estructura de alúmina mejora la resistencia mecánica, especialmente con una baja porosidad (10,8%), una distribución de tamaño homogénea y una alta densidad (2,27 g/cm3). Las pruebas de resistencia indican que los aisladores producidos resisten fuerzas de hasta 14 kN. Entre las muestras, las producidas con polvo de alúmina de alta pureza presentan mayor resistencia mecánica y fiabilidad, probablemente debido a una formación más controlada de mullita y a un menor contenido de impurezas. Como resultado, se desarrolló un proceso de producción mejorado para aisladores C12.5-650 fiables a base de alúmina. El proceso produjo aisladores con una porosidad del 10,8%, una densidad de 2,27 g/cm3 y un rendimiento mecánico superior al de los tipos tradicionales C8-650. Estos hallazgos aportan información valiosa para mejorar significativamente la producción de aisladores a base de alúmina para entornos hostiles.
In this work, transparent Y2O3 ceramics were obtained by direct ink writing (DIW) followed by vacuum sintering at 1720°C for 32 h. The optimal ink composition was identified as 78 wt.% of solid loading, 1.5 wt.% of Dolapix CE64, 8 wt.% of Pluronic and 5 wt.% of ethylene glycol. The ink exhibits pseudoplastic behaviour and optimal viscoelastic properties for printing. Transparent Y2O3 ceramics were characterized by mostly uniform dense microstructure with the presence of some large defects caused by the printing process. In-line transmittance of the obtained ceramics is 43 % in the range of 3–5 μm.
Muhammad Sheeraz, Sung Sik Won, Jong Pil Kim
et al.
The development of high-strain piezoelectric materials has presented a longstanding challenge, particularly in the development of high-strain polycrystalline lead-free piezoelectric thin films. In this work, we present a strategy for customizing the electrostrain in lead-free thin films through phase transition engineering. In this study, we achieved a high recoverable electrostrain in a Bi1/2Na1/2TiO3–BiAlO3 (BNT–BA) film. To accomplish this, ferroelectric BNT and BNT–BA films with identical thicknesses of 500 nm were fabricated on Pt(111)/TiO2/SiO2/Si(100) substrates via a sol-gel method. Compared with the BNT film, the BNT–BA film exhibited a greater polarization response and superior field strength endurance, maintaining the energy storage density beyond the breakdown field strength of the BNT. The BNT–BA film demonstrated a large unipolar strain of S = 0.43% with a normalized strain (maximum strain/maximum applied electric field (Smax/Emax)) of 203 pm/V, followed by an effective transverse piezoelectric coefficient (e31,f∗) of ~2.48 C/m2, which was more than two times greater than the value obtained for BNT (i.e., maximum strain/maximum applied electric field (Smax/Emax) = 72 pm/V and e31,f∗ of ~1.09 C/m2). This high strain response in the BNT–BA film can be attributed to the electric-field-induced phase transition of the mixed (i.e., cubic and rhombohedral) phases into rhombohedral and tetragonal phases (mainly the rhombohedral structure), which recover back to the original state when the electric field is removed. These findings suggest new pathways for achieving significant strain levels via alternative mechanisms, potentially enhancing the effectiveness and expanding the applications of piezoelectric materials.
The lifetime of Si bond coats in environmental barrier coatings (EBCs) is constrained by phase transition-induced cracking at the SiO₂ scale. In this study, reactive self-consumption and lattice solid solution strategies are employed to address this limitation via Si–Yb₄Al₂O₉ composite coatings. The formation of an Yb₂Si₂O₇ layer, through the consumption of the thermally grown SiO₂ scale and Yb₄Al₂O₉, reduces the SiO₂ thickness and significantly lowers the cracking driving force. Furthermore, the incorporation of Al into the SiO₂ lattice stabilizes high-temperature β-SiO₂, preventing phase transition-induced cracking. The proposed coating demonstrated an oxidation lifetime 20 times longer than that of pure Si at 1370 °C, highlighting its potential as an EBC bond coating.
Since decades VALOREF has developed solution to recover refractory lining from glass furnace. From dismantling glass plant, different technology for sorting refractories has been implemented and many possibilities define to reuse refractory material. Flow chart will be discussed during the presentation. This reclamation program concern many types of products such as dangerous and non-dangerous refractories, fibers, abrasives, dust from regenerators, blasting material and other ceramics. By entrusting waste management to Valoref, glass industry can rely on solutions implemented to maximize the recycling of refractory waste while complying with the most stringent environmental standards.
Wagner Benedet Rebelo, A. Zaccaron, Emily Saviatto
et al.
Mineral extraction of coal in the carboniferous region of southern Santa Catarina (Brazil) plays a significant role in the regional economy. However, this activity has severe environmental impacts, with approximately 65% of the extracted mineral being discarded as a rejected material (deposited in landfills). The identification of the technological potential of these materials, based on the geological aspects of the extraction site and the beneficiation operations applied to obtain coal, provides the opportunity to add value to different residual fractions that can be reused. Thus, waste valorization, the main objective of this work, has recently become a strategy for the application of these minerals in the production of clay ceramics using a systematic approach named CPQvA, which means “classification, potentiality, quantity/viability, and applicability”. The use of these materials as secondary mineral sources can avoid the deposition of these materials in industrial landfills and help to reduce the pressure on landfills, which receive an average of four million tons of material annually. In this study, the residual fraction, part of the tailing from coal beneficiation, known as coal fines, was evaluated for formulation valorization in clay ceramics. This residual fraction was classified as non-hazardous (class II-A, non-inert). X-ray fluorescence spectrometry, X-ray diffraction, and thermogravimetric analysis were performed to characterize the moisture content, particle-size distribution, and coal content to be used in the development of different formulations using the residual fraction of coal tailings (ranging from 0 to 40%) that are of technological interest to the sector. Processing parameters, such as firing at different temperatures (750, 800, 850, and 900 °C), were also correlated with these formulations. The results were compared with those of a reference ceramic formulation from the local productive arrangement of Morro da Fumaça (Arranjo Produtivo Local Cerâmica Vermelha de Morro da Fumaça). The various relationships between the materials were characterized in terms of their thermal shrinkage, water absorption, and mechanical resistance. Leaching and solubilization environmental tests revealed that both the industrial standard formulation and formulations with the application of the residual fraction were classified as non-hazardous materials. Thus, the method of using a mining residual fraction in the formulation of clay ceramics proved to be beneficial for the circular economy in the regional mineral sector through productive and environmental gains; the primary mineral resource and energy consumptions and the impacts related to waste generation were reduced. The results of this study can be applied to similar situations in other parts of the world.
Clay minerals deposits, which include, kaolin, ball-clay, fireclay and zircon, were investigated and used in fabrication of ceramic floor tiles. X-ray diffractometer (XRD-6100, Japan), was used to examine the various compositions and structures of the clay samples. 2000 grams of 0.005 mm grain size of each sample were homogeneously mixed into dough, compressed in metallic mould of 12 mm × 36 mm dimension, and allowed to dry for about 5 hours. Kiln draught oven, at 1200°C was set for glazing and firing of the moulded tiles, to ensure glossy appearance, smoothness and improved strength. XRD test showed higher content of alumina (Al2O3) and Silicon (iv) oxide (SiO2) in all the clay samples. The percentage composition of Critobalite, Diphosphorus trioxide (P2O3), Potassium Oxide (K2O) and Sodium Oxide (Na2O), were reasons for their excellent workability, improved mechanical and rheological properties of ceramics floor-tiles. Water absorption, chemical resistance, shrinkage properties of the different ceramic tiles were compare to some commercial products. This investigation had shown that locally available clay minerals could be fully integrated into ceramic industries to reduce cost of ceramic importation and create job opportunities for youths.
Raghvendra Kumar Mishra, Jayati Sarkar, Kartikey Verma
et al.
MXenes, a rapidly growing family of two-dimensional (2D) transition metal carbides, nitrides, or carbonitrides (Mn+1XnTx, where M is a transition metal, X is carbon, nitrogen, or both, and T represents surface functional groups), have captured the scientific community's interest due to their exceptional physicochemical properties and diverse technological applications. This comprehensive review explores the latest breakthroughs in MXene synthesis and characterisation, emphasising their multifaceted applications in energy storage, catalysis, sensing, and other cutting-edge domains. This review examines the most widely used MXene synthesis strategies, including selective etching and delamination, and highlight recent advancements in controlling surface terminations, composition, and morphology. The influence of these synthetic parameters on MXene properties is discussed in detail. Characterisation techniques, ranging from spectroscopic methods to electron microscopy, are essential for elucidating MXenes' structure-property relationships. Research into energy storage leverages MXenes' high electrical conductivity, large surface area, and chemical tunability. This has led to significant progress in the field. This paper presents research efforts focused on optimising MXenes for both battery and supercapacitor applications. Additionally, the catalytic prowess of MXenes, particularly in electrocatalysis and photocatalysis, is explored, emphasising their role in green energy technologies and environmental remediation. MXenes' remarkable sensitivity and selectivity make them promising candidates for sensing various gases, biomolecules, and ions, offering exciting possibilities in healthcare and environmental monitoring. Importantly, this review underscores the need for continued optimisation of MXene synthesis protocols to achieve large-scale production, enhanced stability, and precise control over properties across various fields.
Luca Zoli, Francesca Servadei, Simone Failla
et al.
Carbon fibre-reinforced ultra-high temperature ceramics (UHTCs) are considered a class of promising materials for several applications, the most appealing ones being in the aerospace sector. Reinforcement is necessary to overcome the brittleness and low thermal shock resistance of ceramics and is often provided through the addition of carbon fibres or other carbon-based phases, such as nanotubes, graphene, and graphite. The present work is focused on the toughening of UHTCs through incorporation of 30−50 vol% thin, ordered graphite layers from conventional filter paper followed by hot pressing sintering. Cellulose filter paper was selected because it undergoes thermolysis with no melting stage forming a strong carbonaceous residue that can be used as toughener. Microstructure and mechanical properties of toughened composites were compared to those of other materials reinforced with short carbon fibres and the effect of different distribution of graphite was studied. Addition of graphite allowed toughness to be increased from 3−4 MPa·m1/2 (for un-reinforced materials) to 5.1−5.5 MPa·m1/2, similar to results obtained with short fibre reinforcement. The high-temperature properties, such as strength and toughness as well as oxidation resistance at 1500 ℃, were also examined.
Ceramics are classified as inorganic and non-metallic materials that are essential to our daily lifestyle and have a long history of development. Archeologists have uncovered human-made ceramics that date back to at least 24,000 BC. Clay minerals of alumina-silicates remain the most widely used raw materials for producing traditional ceramic products (Carter, 2013). The ceramic products from clay includes earthenware, porcelain and bricks which have also been in use in our daily life for a long time. Development of advanced ceramics has led to production of ceramic matrix composites, ceramic coatings, electro-ceramics, bioceramics and optical glass fibres, etc. Nowadays ceramics are found in products like watches, snow skies, automobiles and phone lines. Depending on their method of formation, ceramics can be dense or/and lightweight. Typically, ceramics demonstrate excellent strength and hardness properties, being stable and chemically inert in corrosive environments (Carter, 2013). Various mechanical, chemical, electrical, magnetic, optical and thermal properties can be obtained using various ceramics, which would be difficult with other materials. However, ceramics are often brittle in nature. It is more difficult to manufacture ceramic components than is the case with metals and polymers. In addition, a wide range of ceramics have been investigated for industrial applications, and different processing techniques have developed to manufacture ceramics (Carter, 2013). Therefore, multi-disciplinary investigation is required for study of ceramic materials and it is difficult for a single scientific journal to cover all ceramic research topics. Thus, a new journal “Frontiers inCeramics”has been launchedwith intent to cover four sections initially:Ceramic Processing,Ceramic Structure-property Relationship, Ceramic Applicationswith focus on functional ceramics, and Ceramic Technology to cover coating technology, nanotechnology, and traditional ceramics in additional to advanced ceramics. Both chemical and physical methods have been used to produce ceramic powders. Ceramic powders can be transformed into green ceramics of different shapes via ceramic forming techniques, followed by sintering of green ceramics into consolidated ceramics (Reed, 1995). On the other hand, different ceramic processing techniques have been and are being developed to produce ceramics which are difficult or expensive to produce via the powder forming and sintering route. Ceramic processing routes are much wider than those used tomanufacture metallic and polymer products, although some ceramic forming techniques are similar to those employed for manufacture of metal and polymer components, e.g., casting and extrusion. Overall, it is difficult to summarise all ceramic processing techniques, as they are wide range, evolving and progressing continuously. Ceramic structure controls properties including mechanical, electrical, thermal and optical properties (Lee and Rainforth, 1994). Progress in ceramic processing, coupled with advances in ceramic characterisation techniques, has promoted fundamental understanding of ceramic microstructure-property relationships and led to invention of many new ceramic products with OPEN ACCESS
Yttrium aluminum garnet (YAG) with cerium admixture (Ce:YAG) was plasma sprayed using two different devices – gas-stabilized plasma (GSP) torch and water-stabilized plasma (WSP) torch. Coatings on stainless steel as well as self-standing plates were produced. Besides microstructure and crystallographic characterizations, dielectric tests were performed on these coatings. They included capacitance (i.e. relative permittivity), loss tangent and volume resistivity measurements. After spraying, the YAG crystal phase was preserved without any decomposition, but an amorphous fraction was detected in the as-sprayed coatings deposited by both processes. The dielectric behavior of the coatings was influenced by imperfections like splat boundaries, pores and thin cracks. The Ce:YAG samples were successfully plasma sprayed by both spray techniques. Selected aspects of wear were measured and compared with a single-crystal. The dielectric properties are comparable with the single-crystal and highly promising, particularly the loss tangent with values so low that they were not found in any other as-sprayed ceramic coating. Resumen: Se proyectó con plasma granate de itrio-aluminio (YAG) con aditivo de cerio (Ce:YAG) utilizando dos dispositivos diferentes: antorcha de plasma estabilizado con gas (GSP) y antorcha de plasma estabilizado con agua (WSP). Se produjeron recubrimientos sobre acero inoxidable y placas autoportantes. Además de las caracterizaciones microestructura y cristalográficas, se realizaron pruebas dieléctricas en los revestimientos. Incluyeron medidas de capacitancia (es decir, permitividad relativa), factor de pérdida y resistividad de volumen. Después de la proyección, la fase cristalina de YAG se conservó sin descomposición alguna, pero se detectó una fracción amorfa por ambos procesos. El comportamiento dieléctrico de los revestimientos fue influenciado por imperfecciones como límites, poros y grietas delgadas. Las muestras de Ce:YAG de proyección con plasma con éxito mediante ambas técnicas sin una pérdida irreversible de la fase cristalina deseada. Las propiedades dieléctricas son prometedoras, particularmente el factor de pérdida con valores tan bajos que no se encuentran en ningún revestimiento cerámico pulverizado.
Владимир Алексеевич Ерофеев, V. Erofeev, А. Родин
et al.
Obtaining the foam-glass ceramic building materials bypassing the process of high-temperature glass melting and the use of local rocks as raw materials, which can significantly reduce the cost of the final product, is an urgent task of modern building materials science. The aim of this work is to study the physical, mechanical and thermal properties of foam- glass ceramic building materials obtained by one heating of the mixture consisting of silica-containing rock (tripoli) and soda ash. The developed heat-insulating building materials have an average density of 200 to 600 kg/m3, compressive strength of 1.2 to 9.8 MPa, thermal conductivity of 0.053 to 0.065 W/m °C. Studies establishes a rational ratio of components in the composition of foam glass ceramics based on silica rock. In the production of foam materials, the heating rate of the charge should vary from 3 to 4.5 ° C / min, and the maximum heating temperature from 800 to 850 ° C. The developed material will expand the range of thermal insulation building materials and can be used in the construction of industrial and civil facilities, nuclear power plants, in the gas and oil industry.
This study reports the investigation of the influence of adding waste glass on the properties of fired clay specimen. Four different particle sizes (smaller than 100 μm, 300μm, 500μm, and 800 μm) of waste glass were mixed with a clay material at contents of 0%, 2%, 6% and 10% per weight. Specimen samples were fired at 750℃ in an electrical furnace for 6 hours, at a heating rate of 5℃/min. The physical and mechanical properties of terracotta are studied. The chemical analysis revealed that the clays were dominated by kaolinite and montmorillonite with small proportion of mixed layers clay. The fine grained texture (0.002 mm > 25%) and high plasticity (WP > 30%) of the clays were responsible for the moderate and high values of shrinkage upon oven drying and firing. The firing color variation from reddish brown shade was due to the amounts of iron and titanium oxides present in the obtained material. The water absorption was varied between 17.40% and 13.70%, while the linear shrinkage was estimated to be between 0.70% and 1.20% and the flexural strength from 5.30 to 8.10 MPa. These results showed that mixing clay with waste glass at 750℃ is an interesting approach to obtain reddish brown ceramics destined for bricks or roofing tiles.
Abstract The Numidian Aquitano-Burdigalian nappe from the Jijel region (northeast Algeria) shows an important clay-rich basal series. In this study, seven representative clay samples were collected from the Djimla and El-Milia areas of this region in order to analyse their mineralogy using X-ray diffraction and Fourier-transform infrared spectroscopy, chemical composition by X-ray fluorescence, particle size, plasticity, morphology by scanning electron microscopy and their ceramic properties. Samples were prepared by pressing the clays and firing them at 800–1100°C, and bulk density, water absorption, linear firing shrinkage, weight loss and bending strength values were determined on the fired samples. The clays are mainly composed of kaolinite and illite, with a small amount of 10–14 Å interstratified clay minerals and chlorite, associated with quartz and feldspars. The main oxides in the samples were SiO2, Al2O3 and Fe2O3. The clays may be classified as moderately plastic according to their Atterberg limits. Ceramic tiles have been produced by dry pressing. At all tested firing temperatures, the clays present the required standard values for linear firing shrinkage, weight loss, bulk density, water absorption and bending strength, and they are defect-free. The main transformations were observed at 1000°C with the appearance of new crystalline phases. The measured technological properties of the investigated deposits confirm that the Numidian clays from the Djimla and El-Milia regions are suitable materials for the production of high-quality structural ceramics.