Synthesis Of Ceramics Research Articles

Oxidation of Cr (III) to Cr (VI) in the Synthesis of Bismuth-Chromium Oxide Ceramics

Oxidation of Cr (III) to Cr (VI) in the Synthesis of Bismuth-Chromium Oxide Ceramics

Synthesis and Characterization of Zirconia-Based Ceramics: A Comprehensive Exploration of Film Formation and Mixed Metal Oxide Nanoparticle Synthesis

Due to its strong ionic conductivity and superior mechanical qualities, zirconia-based ceramics are frequently used in electrochemical devices. Today, zirconium oxychloride octahydrate and ethanol have been developed for the purpose of reducing zirconium thin films on glass, single-crystal silicon p-type, substrates. The phase composition and properties of the films, as well as the physicochemical processes involved in film formation, have all been investigated. Zirconia mixed metal oxide nanoparticles with various physicochemical properties can be created using a variety of synthetic processes in conjunction with additional variables like concentration, PH, type of precursor utilized, etc. In order to create zirconia mixed metal oxide nanoparticles, many synthetic techniques, including sol-gel, hydrothermal, and coprecipitation methods are discussed in this article.

Synthesis of Sustainable Binary Calcium Monosilicate Ceramics from Bio-waste: Effect of Sintering Temperature on Microstructure and Electrical Properties

This study was conducted to synthesise calcium monosilicate ceramics using rice husks and raw eggshells and investigated the effect of sintering temperature on the physical,microstructure and electrical properties of the final product. The high content of calcium and silicon in eggshells and rice husks, respectively promote the use of waste materials in the production of calcium monosilicates by mixing in a molar ratio 1CaO:1SiO2 and fired at different sintering temperatures for 2 hours with a heating rate of 10°C/min. A good correlation between sintering temperature, structural, microstructure, and electrical properties of calcium silicate was observed. The structural and morphological evolutions were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with electron dispersive X-ray analysis (EDX). XRD analysis showed that the main crystalline phases of synthesised calcium monosilicate are pseudowollastonite (ICSD 98-005-2598) at 1250°C, and the phases of SiO2 also exist in different types of minerals. Besides, a small amount of larnite, Ca2SiO4 was traced at 1100°C and 1200°C. Fourier Transforms Infrared (FTIR) spectra showed the presence of characteristic functional groups in the precursor powder. In Nyquist plots, the summit frequency of the dominant arc decreases with increasing sintering temperatures. It may be attributed to the co-effect of the grain size and pore. A larger value of impedance at a lower frequency suggests an essential role of boundaries in governing the electrical properties of the sintered ceramics. As the sintering temperature increases, the microstructure of the sintered samples becomes denser while conductivity performance decreases. This is due to the reduction of particle interfaces and charge transfer.

Synthesis of La2Ti2O7 nanoscale powder and ceramics based on it by sol-gel and spark plasma sintering

The application of ceramics as matrices for the immobilization of radionuclides for the purpose of their safe long-term disposal or beneficial use is being studied with an emphasis on phase stability, structural integrity, hydrolytic stability, etc. In this work, a combined approach was investigated, based on the sol-gel citrate synthesis of nanosized La2Ti2O7 powder and its subsequent spark plasma sintering to produce dense ceramics. The phase composition and structure of the nanosized La2Ti2O7 powder and ceramic samples based on it, obtained in the temperature range of 900–1300 °C, were studied by XRD and SEM. It has been shown that the powder synthesis conditions ensure the formation of nanosized crystalline La2Ti2O7 grains, whose consolidation under spark plasma heating conditions proceeds with a change in the phase composition from single-phase La2Ti2O7 of monoclinic structure to orthorhombic with an admixture of LaTiO3 at temperatures above 1200 °C. It was revealed that the change in the ceramic structure is accompanied by the formation of non-porous and defect-free monolithic samples. It was determined that such a change leads to an increase in relative density (81.3–95.7%) and compressive strength (78–566 MPa) of the ceramic samples. However, the hydrolytic stability of the ceramics decreases, as indicated by an increase in the leaching rate of La3+ from 10–7 to 10–5 g/cm2·day. The obtained results are useful for the systematic study of materials suitable for immobilization technologies of radioactive waste in ceramics.

Studies on synthesis, Raman, and electrical properties of novel spinel high entropy ceramics

Studies on synthesis, Raman, and electrical properties of novel spinel high entropy ceramics

Design and synthesis of high-entropy A2B2O7-type pyrochlore ceramics for the immobilization of molten salt radwastes

Pyrochlore-based high-entropy ceramics can encapsulate multiple elements with different valences, making them promising for immobilizing high-level radioactive nuclides in molten salt radwaste. This approach addresses key challenges in dry reprocessing and molten salt reactor waste management. In this study, a single-phase pyrochlore-based high-entropy ceramic is synthesized to incorporate NdF3 and CeF3 as simulated molten salt radwastes. Various synthesis components have been explored, and the ceramics were characterized using x-ray diffraction (XRD) and Raman spectroscopy. Comparative analysis revealed that the size disorder is the critical factor to synthesize single-phase pyrochlore-based high-entropy ceramics. The effects of elemental ratio and the presence of variable valence elements on the synthesis of single-phase pyrochlore-based high-entropy ceramics are elucidated through the concept of size disorder. Two single-phase pyrochlore compositions have been successfully synthesized: #HE4 (Nd2(Ti0.25Zr0.25Hf0.25Sn0.25)2O7) and #HECe0.1 (Nd2(Zr0.3Hf0.2Sn0.2Nb0.2Ce0.1)2O7). These samples were tested with a 7-day leaching experiment using the Product Consistency Test Method PCT-B. The normalized release rates of all elements in #HE4 ranged from 10-7 to 10-9 g·m-2·d-1, indicating excellent chemical durability. These findings suggest that medium- and high-entropy pyrochlore-based ceramics are effective for immobilizing radioactive nuclides in molten salt radwastes.

Features of synthesis of ZnSe ceramics from nanopowders obtained using a high-power laser

The reasons for the occurrence of optical inhomogeneities in ZnSe or Fe:ZnSe ceramics, which were made from nanoparticles, obtained using a continuous wave ytterbium fiber laser, were investigated. Evaporation of ZnSe at T ≤ 900 ˚С results in formation of large pores (0.5 - 10µm) in the ceramics. When the material is oxidized by means of oxygen adsorbed from air onto the surface of nanoparticles, such refractory phases as ZnO and ZnSeO3 are formed. Even a low content of these phases ( < 1wt. %) results in formation of accumulations of small crystallites ( 0.2 - 3 μm) in the ceramics. Numerous pores and extended accumulations of small crystallites are optical non-uniformities that scatter and absorb light. Changes in the chemical composition and contamination of ZnSe during the production of nanopowders and ceramics turned out to be too small for such inhomogeneities to form.

Synthesis and high electromagnetic wave absorption performance of carbon-enriched porous SiOC ceramics

The carbon-enriched porous SiOC ceramics with enhanced electromagnetic wave (EMW) absorption properties were synthesized through the hydrothermal method followed by a polymer-derived ceramics (PDCs) process. As the annealing temperature rises from 1200 °C to 1500 ℃, SiC and SiO2 crystals are gradually separated from the porous amorphous SiOC matrix, and the degree of graphitization of free carbon increases. The porous SiOC ceramics annealed at 1400 °C exhibit the presence of SiC, SiO2, turbostratic graphite, and amorphous SiOC phases, which significantly impact the impedance matching and attenuation constant of the material. The minimum reflection loss (RLmin) value of the SiOC ceramics reaches −67.98dB with a matching thickness of 3.19mm and the effective absorption bandwidth (EAB) is 4.45GHz at 1.39mm. The carbon-enriched porous SiOC ceramics with strong absorption capacity and wide absorption bandwidth are primarily owing to appropriate impedance matching and multiple attenuation mechanisms, such as conduction loss, interfacial polarization, and defect-induced polarization, indicating that the SiOC ceramics exhibit significant potential as a high-performance EMW absorbing material.

Synthesis of Complex Oxide Ceramics in a Fast Electron Beam

Synthesis of Complex Oxide Ceramics in a Fast Electron Beam

Formation kinetics and equilibrium thermodynamics study on the Bi2O3-TiO2 system for synthesis of the bismuth titanate ceramics

Formation kinetics and equilibrium thermodynamics are fundamental knowledge for predicting microstructure and properties during materials processing and utilization. This work prepared high purity Bi12TiO20, Bi4Ti3O12 and Bi2Ti4O11 compounds and characterized these compounds by in-suit X-ray diffraction, scanning electron microscope, energy dispersive spectrometer as well as calorimetry. Based on the experimental data obtained in this work and the literature, a thermodynamic description of the Bi2O3–TiO2 system was carried out, a thermodynamic database as well as the calculated phase diagram of the system was provided. The discrepancy between the present calculation with the experimental data were discussed, the formation kinetics of the compounds was explained and the bismuth titanate ceramics with tailored structure and specific physical properties were sintered.

One-step ultrafast Joule heating synthesis of EuB6 ceramics and their electronic transport and magnetic properties

The synthesis of high-performance rare-earth borides (e.g., RB2, RB4, R2B5, RB6, RB12, and RB66) typically necessitates sintering at high temperatures and high pressures for prolonged durations. Traditional methods, such as hot-pressing sintering and spark plasma sintering, are marked by high production costs and low efficiency. Here, using EuB6 as an example, we demonstrate the successful synthesis of rare-earth boride ceramics utilizing the one-step ultrafast joule heating technology. Using this method, we optimized the sintering temperature and duration and synthesized EuB6 ceramics with superior electronic and magnetic properties at 1600 °C in just 5 min. The EuB6 ceramics prepared under optimized conditions show distinct paramagnetic to ferromagnetic phase transition, significant negative magnetoresistance, and enhanced magnetization. The combination of the one-step ultrafast Joule heating technology and boron thermal reduction method offers a simple and fast synthesis approach for fabricating polycrystalline EuB6 and may be extended to prepare other rare-earth and transition-metal borides.

Synthesis and thermophysical properties of rare-earth tantalate ZrO2-Dy3TaO7 ceramics

Abstract Thermal Barrier Coatings (TBCs) are of major concern to researchers because of their outstanding properties, such as high-temperature resistance, compressive resistance, hardness, and toughness. Its applications are wide-ranging and critical. Examples include hypersonic vehicles, aero-engines, and service in high-temperature and high-impact extreme environments. This work focuses on the preparation, thermal properties (coefficient of thermal expansion, thermal conductivity), and performance evaluation (thermal shock resistance, thermal shock resistance, and bonding) of ZrO2-Dy3TaO7 rare earth tantalate ceramic coating materials. The results show that ZrO2-Dy3TaO7 possesses a low thermal conductivity (1.25-1.50 W K−1 m−1, 900°C), a high thermal expansion coefficient (10.80-11.14×10-6 K−1, 1200°C), which is about half of the value of the thermal conductivity of 7YSZ (2.8-2.2 W K−1m−1). It is better than that of the 7YSZ (10.04×10−6 K−1, 1200°C), which meets the performance requirements of the new thermal barrier coating. In addition, ZrO2-Dy3TaO7 can achieve more than 6, 000 thermal fatigue cycles at 1200°C, and the ideal number of thermal shock cycles is 4, 040 cycles at the same temperature. These outstanding test results demonstrate that the ceramic coating can effectively protect the substrate material and provide long-term service in high-temperature copper liquid. This research lays the theoretical foundation for the development of next-generation coating materials, particularly for thermal barrier/environmental barrier integrated coating materials.

Ball milling and annealing effect in structural and magnetic properties of copper ferrite by ceramic synthesis

This study aims to better understand the relationship between the microstructure and magnetic properties of copper ferrite, which is an inverse spinel that present a body-centered tetragonal structure associated with a remarkable Jahn–Teller (JT) effect. For this goal, a sample has been synthesized by the ceramic route from a stoichiometric mixture of high-purity CuO and Fe2O3 powders activated mechanically in a high-energy planetary ball mill. This sample was calcined in air furnace at 1000 ºC for 6 h. As synthetized sample with a cubic structure was divided into two parts and one of them was annealed at 650 ºC for 3 h and slowly cooled to room temperature to obtain a pure tetragonal spinel sample. Furthermore, these two samples were subjected to the same processes of severe plastic deformation by milling for up to 70 h and subsequent annealing at temperatures ranging between 300 and 600 ºC to obtain samples with a mixture of phases in different proportions. For the cubic one, there is no change in its structure due to milling, always remaining 100 % cubic, and the evolution in the saturation magnetization was related to the changes in the density of defects present. On the other hand, copper cations are always found in the octahedral sites of spinel with a tetragonal structure. The small decrease in the degree of inversion to 0.95 induced by milling in this sample is capable of breaking the JT distortion, giving rise to the appearance of a cubic phase. This work demonstrates how the structure, microstructure, defects like stacking faults and deformation twins, and degree of inversion of the different phases are related to changes in magnetic properties.

Synthesis and ionic conductivity of glass ceramics with general composition (2-х)Na2О : хМІ2О : 3CoО : 2P2O5 (х = 0 or 0.05, МІ – Li, K)

Synthesis and ionic conductivity of glass ceramics with general composition (2-х)Na2О : хМІ2О : 3CoО : 2P2O5 (х = 0 or 0.05, МІ – Li, K)

Effects of different valence of starting oxides on the structure and properties of Co-Mn-Fe-Zn-Ni-O high-entropy ceramics

In this work, using different manganese sources, Co-Mn-Fe-Zn-Ni-O high-entropy ceramics (HECs) were synthesized via the solid-phase method. X-ray diffraction (XRD) data showed that the HECs consist of rock salt and spinel phases, and the choice of raw materials has a great influence on the phase composition and lattice distortion of HECs. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) analyses showed that the HECs have dense microstructures, with the major elements conforming to iso-atomic ratios. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy data showed that Mn3+ ions with Jahn-Teller effects distort the [MnO6] octahedra, affecting the electrical properties and aging stability of the material. The room-temperature resistivity of the HEC systems ranged from 20.81 kΩ cm to 35.43 kΩ cm, and the B25/50 resistivity values varied between 4037 K and 4048 K. The resistance drift was observed to be less than 0.70 % after aging at 125 °C for 1000 h. Impedance analyses suggested that the electrical properties of the high-entropy ceramics can be modulated by tailoring the grain size and grain boundary morphology. Selecting suitable raw materials based on valence-induced effects and the tendency of ions to occupy specific sites offers new insights into the design and synthesis of tailor-made high-entropy NTC ceramics.

Synthesis of high-entropy ceramics (Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 by electron beam heating

High-entropy ceramic materials are promising for creating functional ceramics for various purposes. The unique properties of such materials make it possible to create new thermal barrier coatings based on them. Reducing costs, time and simplifying the technology of synthesis of high-entropy ceramics is the subject of numerous studies. In this work, the synthesis of high-entropy ceramics (Y0,2Yb0,2Lu0,2Eu0,2Er0,2)3Al5O12 in a powerful beam of fast electrons was carried out for the first time. A powder mixture of initial oxides, placed in the volume of a massive copper cell, was exposed in air to a short-term exposure to a beam of powerful fast electrons with an energy of 2 MeV and a beam current of 12 mA. The speed of movement of the cuvette with the powder mixture under the beam was 1 cm/s. The total irradiation time was 10 s. During the irradiation process, at least 96 % of the mass of the powder mixture melted, resulting in the formation of highly porous ceramic formations in the form of droplets. X-ray phase analysis showed that the melt droplets are high-entropy ceramics (Y0,2Yb0,2Lu0,2Eu0,2Er0,2)3Al5O12. The powder product remaining in the cuvette and not participating in the formation of droplets contains phases of the original oxides and intermediate phases of synthesized high-entropy ceramics. Electron microscopy with EDS showed a uniform distribution of elements on the surface and in the volume of the formed ceramic droplets.

Synthesis and dielectric performance of new calcium boro-stannate microwave ceramics

Synthesis and dielectric performance of new calcium boro-stannate microwave ceramics

Characterization of ZnWO4, MgWO4, and CaWO4 Ceramics Synthesized in the Field of a Powerful Radiation Flux

This paper presents the results of a study on the morphology, structure, and luminescent properties of ceramics synthesized in the radiation field of MeWO4 compositions (where Me is Mg, Ca, and Zn). The synthesis of ceramics was carried out by the direct action of the electron flux on an initial mixture of powders of the given stoichiometric composition. WO3, ZnO, MgO, and CaO powders with particle sizes in the range of 1–50 microns were used for the synthesis of the samples. It was found that the yield of the radiation synthesis reaction (the ratio of the mass of the sample and the charge used), when treated with an electron flux with an energy of 1.4 MeV and a flux power density of 15–18 kW/cm2, was in the range of 75–99%. The synthesis of all compositions was carried out under the same radiation treatment modes, although the melting temperatures of the starting materials varied significantly and ranged from 1473 °C (WO3) to 2825 °C (MgO). The study of the ceramic structure showed that under the radiation effect of powerful radiation fluxes on the charge, a crystalline phase of the appropriate composition formed, regardless of the synthesis modes. The results of XRD studies show that during the radiation treatment of the charge, ceramics are formed mainly with the crystalline phases ZnWO4, MgWO4, and CaWO4. These resulting MeWO4 ceramics can be used for the same purposes as crystals. Photoluminescence (PL) and cathodoluminescence (CL) were studied under excitation using stationary ultraviolet radiation and nanosecond pulses of electron flux. In general, the PL and CL of synthesized ceramic samples ZnWO4, MgWO4, and CaWO4 showed that their luminescent properties are similar to those of luminescence in corresponding crystalline materials. This indicates the formation of a crystalline phase in synthesized ceramic samples.

Synthesis of La2Ti2O7 Nanoscale Powder and Ceramics Based on It by Sol–Gel Synthesis and Spark Plasma Sintering

Synthesis of La2Ti2O7 Nanoscale Powder and Ceramics Based on It by Sol–Gel Synthesis and Spark Plasma Sintering

Low-temperature synthesis of dense Si-based nitride ceramics for solar thermal storage: Role of cordierite as sintering additive

Direct nitridation method was used to prepare dense Si-based ceramics for solar thermal storage, and the effect of cordierite as sintering additive on the sintering behaviors of the ceramics was studied. The influence priority between densification and nitride content on the properties of thermal storage ceramics was discussed. Cordierite exhibited a good capability of promoting densification, and the densification temperature could reach 1500 °C. The liquid formed by cordierite helped to construct an interlocking structure of well-grown Si2N2O flakes. Results of hot stage microscopy and DTA indicated that the endothermic silicothermic reaction between Si and cordierite proceeded at 1440–1460 °C, and released SiO gas. The SiO gas inhibited the densification, but resulted in the low-temperature synthesis of nano-sized Si3N4 whiskers. Samples added with more cordierite showed the cost-effective merits as the smaller costs of raw materials, lower densification temperature, higher thermal conductivity (1.72 W m−1 K−1 deviation), and higher bending strength (34.3–68.1 MPa deviations), compared with the samples having the larger nitride content. Densification by adding cordierite as sintering additive showed the priority on the properties of thermal storage ceramics than increasing the nitride content.