Synthesis Of Ceramics Research Articles

Remarkably improved nonlinearity and thermal stability of CaYNbMnO7 thermosensitive ceramics via the cold‐sintering process

AbstractThe cold‐sintering process (CSP) uses a transient low‐temperature solvent, such as water or water with dissolved solutes consistent with the ceramic composition, to achieve functionalization at lower temperatures via the dissolution and precipitation principle. Here, during the CSP, the use of molten NaOH as a flux solvent promoted the rearrangement and precipitation of CaYNbMnO7 particles. CaYNbMnO7 ceramics were successfully obtained at 350°C and under a uniaxial pressure of 700 MPa. The ceramic was not a single‐phase structure but consisted of a cubic‐phase structure and a layered perovskite structure. To verify the high‐temperature thermal stability of CaYNbMnO7 ceramic prepared at 350°C, a comparative study was conducted with conventional sintering (CS). Results indicate that the ceramics obtained by CSP and CS have negative temperature coefficient characteristics. The cold‐sintered ceramic has a wider temperature range and better aging stability. (The minimum value of the aging coefficient is ∼2.49%.) Simultaneously, CSP is beneficial for promoting the linearization of the relationship between the logarithm in the resistivity (lnρ) and the reciprocal for the absolute temperature (1000/T) in the ceramic. However, the CSP has little effect on the material constant B and thermal activation energy Ea of the ceramic, providing a basis for the low‐temperature synthesis of high melting point thermosensitive ceramics.

One pot synthesis of high entropy rare earth zirconate ceramics with low thermal conductivity for high performance thermal-barrier coatings

By using the one pot synthesis method, zirconate rare earth ceramic powders with high entropy and low thermal conductivity were prepared. The phase and microstructure of the prepared powder and sintered ceramics were analyzed by x-ray diffraction, Raman spectroscopy and scanning electron microscopy. The results show that the prepared powder may be used directly for atmospheric plasma spraying. The ceramic prepared from this powder exhibited a density of 96.87 %, improved thermal conductivity and thermal expansion coefficient. Coating materials were prepared using an atmospheric plasma spraying system, with the LSZC coating demonstrating the highest bond strength of 48.81 MPa and thermal shock resistance of 18 cycles.

Effect of sintering temperatures on the physical, structural properties and microstructure of mullite-based ceramics

<abstract> <p>This study explored the impact of sintering temperature variations on the synthesis and characteristics of mullite ceramics derived from a composite blend of kaolinite clay, silica (silicon dioxide), and feldspar. Sintering temperatures ranging from 1100 to 1200 ℃ were systematically examined to analyze alterations in shrinkage, density, microstructure, elemental composition, and phase formation. The study revealed that an increase in sintering temperature led to decreased shrinkage due to improved particle packing and reduced porosity. Ceramic density showed a direct relation with sintering temperature, reaching the optimal density at 1175 ℃ and indicating efficient particle packing and compaction. Analysis through field emission scanning electron microscopy (FESEM) provided insights into microstructural changes, including alterations in grain morphology, porosity, and connectivity. Energy dispersive X-ray spectroscopy (EDS) clarified element distribution within the microstructure, offering valuable information on compositional variations. X-ray diffraction (XRD) examinations unveiled temperature-dependent phase transformations, which confirmed the successful formation of mullite during the sintering process. A sintering temperature of 1175 ℃ yielded the optimal ceramic quality and cost-effectiveness for high-temperature heating processes.</p> </abstract>

Composite solid electrolytes based on Li7La3Zr2O12 for all-solid-state lithium power sources

Currently development of all-solid-state lithium batteries are in great demand all over the world. Li7La3Zr2O12 (LLZ) compounds are considered as perspective solid electrolyte for such power sources. However, these solid electrolytes of garnet family have some disadvantages – high temperatures of ceramic synthesis, poor wettability by Li and low stability to air components. The creation of composite solid electrolytes based on LLZ is one of the ways to solve these problems. It was established that the temperature and/or sintering time of the solid electrolyte could be reduced by the introduction of different additives with maintaining lithium-ion conductivity values (10–5–10–4 S/cm at room temperature). It should be noted that the used sintering additive should meet the following requirements: low softening temperatures, high values of lithium-ion conductivity, stability in contact with lithium metal and absence of chemical interaction between components leading to the formation of low-conductivity impurity phases. Thus, the development of composite solid electrolytes based on LLZ is perspective for all-solid-state power sources.

Ferroelectric Ceramic Synthesis and Breakdown Characterization on Pulsed Condition Using High-Voltage Half-Sine Pulses of Microsecond Duration

Ferroelectric Ceramic Synthesis and Breakdown Characterization on Pulsed Condition Using High-Voltage Half-Sine Pulses of Microsecond Duration

Effect of alkaline oxides (CaO and MgO) on the mechanical properties of SiC-based foam ceramics

Fly ash is potentially useful as a sintering additive in the synthesis of SiC-based foam ceramics (SFC). However, the influence of CaO and MgO, the main alkaline oxides in fly ash, on the performance of SFC is not well understood. This study synthesized SFC using SiC and fly ash as the primary raw materials (mass ratio of 7:3), and systematically investigating the effects of CaO and MgO on the properties of SFC, including porosity, density, strength, apparent morphology, and phase composition. The results indicated that addition of CaO and MgO promoted oxidation of SiC at relatively low temperatures. With a CaO content of 1.5 wt% or an MgO content of 2 wt%, SFC with uniformly distributed porous structures and exceptional properties was achieved at sintering temperatures as low as 1150 °C. Additionally, CaO and MgO facilitated formation of crystalline phases such as wollastonite, calcium feldspar, and cordierite, enhancing the thermophysical properties of SFC. However, excessive CaO or MgO led to over-sintering of the SFC samples. With a CaO content of 1.5 wt% and a sintering temperature of 1175 °C, SFC was completely deformed. This was also observed with an MgO content of 3 wt% and a sintering temperature of 1250 °C, indicating that CaO promotes SiC oxidation more effectively than MgO. It is suggested that addition of appropriate amounts of CaO and MgO is conducive to production of high-quality SFC at low sintering temperatures, significantly enhancing their commercial viability.

Study of the Conditions for Ceramic and Mechanochemical Synthesis of CuO/ZnO/γ-Al2O3 Composites

Study of the Conditions for Ceramic and Mechanochemical Synthesis of CuO/ZnO/γ-Al2O3 Composites

Aluminothermic synthesis of ceramics from the hercynite-alumina system, using mill scale and aluminum chips

Aluminothermic synthesis of ceramics from the hercynite-alumina system, using mill scale and aluminum chips

Recent Advancements in the Synthesis of High-Entropy Boride Ceramics: A Review

Recent Advancements in the Synthesis of High-Entropy Boride Ceramics: A Review

Radiation Synthesis of High-Temperature Wide-Bandgap Ceramics.

This paper presents the results of ceramic synthesis in the field of a powerful flux of high-energy electrons on powder mixtures. The synthesis is carried out via the direct exposure of the radiation flux to a mixture with high speed (up to 10 g/s) and efficiency without the use of any methods or means for stimulation. These synthesis qualities provide the opportunity to optimize compositions and conditions in a short time while maintaining the purity of the ceramics. The possibility of synthesizing ceramics from powders of metal oxides and fluorides (MgF2, BaF2, WO3, Ga2O3, Al2O3, Y2O3, ZrO2, MgO) and complex compounds from their stoichiometric mixtures (Y3Al3O12, Y3AlxGa(5-x) O12, MgAl2O4, ZnAl2O4, MgWO4, ZnWO4, BaxMg(2-x) F4), including activators, is demonstrated. The ceramics synthesized in the field of high-energy electron flux have a structure and luminescence properties similar to those obtained by other methods, such as thermal methods. The results of studying the processes of energy transfer of the electron beam mixture, quantitative assessments of the distribution of absorbed energy, and the dissipation of this energy are presented. The optimal conditions for beam treatment of the mixture during synthesis are determined. It is shown that the efficiency of radiation synthesis of ceramics depends on the particle dispersion of the initial powders. Powders with particle sizes of 1-10 µm, uniform for the synthesis of ceramics of complex compositions, are optimal. A hypothesis is put forward that ionization processes, resulting in the radiolysis of particles and the exchange of elements in the ion-electron plasma, dominate in the formation of new structural phases during radiation synthesis.

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

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

Mechanochemical synthesis of nanostructured and composite oxide ceramics: From mechanisms to tailored properties

AbstractMechanochemical synthesis is a technology formed in the 1950s. By applying mechanical energy, mechanochemical synthesis stimulates chemical reactions, causing structural and phase changes and enabling difficult or otherwise impossible reactions to occur. Mechanochemical reactions are relatively safe, clean and efficient. At present, the synthesis of oxide ceramic materials by mechanochemical methods has attracted widespread attention. In the production of oxide ceramic materials, the characteristics of ceramic powder have a certain influence on the molding, sintering, microstructure, and mechanical properties of subsequent ceramics. In this paper, the research progress of mechanical chemistry in the synthesis of nanostructures and composite oxide ceramic powders is reviewed. The effects of process parameters such as ball milling time, speed, atmosphere, grinding media, additives, and ball‐to‐powder ratio on reaction kinetics, phase formation, and powder properties are summarized. In addition, challenges and opportunities for ceramic powder synthesis are also discussed.

Low temperature sintering of iron-barium co-doping bismuth sodium titanate lead free piezoelectric

This work reports a detailed study of the crystal structure and electrical properties of a potential lead-free piezoelectric Bi0.5Na0.5TiO3 co-doped with Ba2+ and Fe3+ sintered at relatively low temperature (900 °C). The effect that co-dopants have over the electric properties in (Bi0.5Na0.5)1-xBaxTi1-yFeyO3-0.5y, varying x from 0 to 0.075, Δx = 0.025, and y from 0 to 0.075, Δy = 0.025, was evaluated. XRD analysis showed a successful synthesis of co-doped BNT ceramics with a rhombohedral structure for samples with x < 0.075. In contrast, the sample with x = 0.075 exhibited the coexistence of the rhombohedral and tetragonal structures, confirmed by Rietveld refinement. The co-doping promotes the grain size growth and increase the pellets’ density from 93 % to 98 %. Dielectric spectroscopy analysis, conducted in the range from 25 to 500 °C, showed an increase in the relative permittivity with the dopant concentration, specifically at high temperatures. Electric analysis validate the piezoelectric behavior and the electric polarization of the co-doped BNT ceramics, unveiling a maximum remnant polarization (Pr) of 25.6 μC/cm2 and, a maximum piezoelectricity coefficient of 53 pC/N, which varied depending on the composition. The obtained results demonstrate that co-doping BNT ceramics with Ba2+ and Fe3+ cations lower the sintering temperature typically used in the solid-state reaction to obtain pure BNT, showing similar properties compared to those of the same material sintered at higher temperatures and longer times.

Preceramic Polymers for Additive Manufacturing of Silicate Ceramics.

The utilization of preceramic polymers (PCPs) to produce both oxide and non-oxide ceramics has caught significant interest, owing to their exceptional characteristics. Diverse types of polymer-derived ceramics (PDCs) synthesized by using various PCPs have demonstrated remarkable characteristics such as exceptional thermal stability, resistance to corrosion and oxidation at elevated temperatures, biocompatibility, and notable dielectric properties, among others. The application of additive manufacturing techniques to produce PDCs opens up new opportunities for manufacturing complex and unconventional ceramic structures with complex designs that might be challenging or impossible to achieve using traditional manufacturing methods. This is particularly advantageous in industries like aerospace, automotive, and electronics. In this review, various categories of preceramic polymers employed in the synthesis of polymer-derived ceramics are discussed, with a particular focus on the utilization of polysiloxane and polysilsesquioxanes to generate silicate ceramics. Further, diverse additive manufacturing techniques adopted for the fabrication of polymer-derived silicate ceramics are described.

Ultra-fast high-temperature synthesis and densification of high-entropy diborides and diboride-carbide ceramics

The strong covalent bonds and low self-diffusion coefficients of high-entropy diboride (HEBs) and diboride-carbide (HEB-HEC) ceramics render their densification difficult, which limits their applications. Here, we used an ultra-fast high-temperature sintering technique to synthesize and densify several HEBs and HEB-HEC (containing 5–8 cations) ceramics within an isothermal duration of 1 min and a total sintering period of 6 min. All ceramics formed a single-phase or dual-phase high-entropy solid solution, and showed high density, high hardness and good fracture toughness. The rapid densification mechanisms were determined, and the preferential dissolution of metal cations in HEB and HEC phases was explained using a simplified ideal solution model. A good fracture toughness in the range of 3.6-5.4 MPa·m1/2 resulted from crack deflection or blunting and bridging of the rod-like diboride or boron-rich phase. This paper presents a simple, economical, and efficient method for the synthesis and densification of high-entropy ceramics and other advanced materials.

Dependence of pore space structure and characteristics of SiC-based ceramic materials on the morphology of the initial components

Ultrafine silicon carbide powders of two types were used as fillers for synthesis of porous ceramics. The first powder was obtained by the furnace method (SiCF), the second sample was synthesized using the SHS technology (SiCSHS). The fillers had identical average particle size, but different morphology of their surface. It is established that with the same size, the morphology of initial powder components determined structural parameters and characteristics of the synthesized porous ceramics. It determines effective applicability of various materials for ultrafiltration or catalysis processes.

Reduction of Firing Temperature by Utilization of Secondary Materials for the Synthesis of Forsterite Ceramics

The main aim of this research was to investigate the effect of the addition of coal fly ash as a secondary waste material on the synthesis and properties of forsterite ceramics. The utilization of fly ash as a raw material, which contains flux oxides, reduce the necessary firing temperature for the synthesis of forsterite ceramics in comparison with forsterite ceramics synthetized from high purity or industrial materials, while preserving its refractory properties. The results revealed that forsterite was synthesized as a major crystalline phase in all samples. The optimal firing temperature for obtaining good physico-mechanical parameters was found to be between 1400-1600°C for high purity or industrial materials, while mixtures containing fly ash could achieve similar parameters at lower firing temperatures between 1200-1300°C. The decrease in refractoriness was found to be within acceptable limits for utilization as a refractory material. These findings demonstrate the potential for cost reduction and energy savings through the use of secondary waste materials and reduced firing temperature in the synthesis of forsterite ceramics.

Phase evolution during conventional and reactive flash sintering of (Mg,Ni,Co,Cu,Zn)O via in situ X‐ray diffraction

AbstractReactive flash sintering (RFS) enables the simultaneous synthesis and sintering of ceramics and has been shown to affect the reaction pathway of different materials. Herein, in situ synchrotron X‐ray diffraction (XRD) is used to investigate the (Mg,Ni,Co,Cu,Zn)O entropy‐stabilized oxide formation during: (i) conventional heating and (ii) RFS under current rate‐controlled mode. The same reaction pathway is verified in both instances: the starting rock‐salt (RS), spinel (Co3O4), tenorite (CuO), and wurtzite (ZnO) phases transform into a single RS phase with a (1 1 1) to (2 0 0) intensity ratio of 0.67, consistent with a random distribution of the cations into the structure. Pt lattice peak shift from the XRD patterns is used as standard to monitor the sample surface temperature, revealing a strong endothermic reaction during the RS single‐phase formation (Pt peaks shift toward higher angles while increasing sample temperature/current density). In RFS, the single‐phase RS structure is formed in just 60 s at a furnace temperature of 600°C and a current rate of 220 mA mm−2/min. Therefore, RFS greatly accelerates the synthesis of (Mg,Ni,Co,Cu,Zn)O, however, it does not play a role in the reaction pathway for this material formation.

Synthesis and Research of Critical Parameters of Bi-HTSC Ceramics Based on Glass Phase Obtained by IR Heating

In this paper influence of the excess Ca and Cu cations on the critical temperature (Tc) and critical transport current density (Jc) of high-temperature superconducting ceramics of the compositions (HTSC) Bi1.6Pb0.4Sr2Ca2.1Cu3.1Oy, Bi1.6Pb0.4Sr2Ca2.25Cu3.25Oy and Bi1.6Pb0.4Sr2Ca3Cu4Oy synthesized by the glass-ceramic method has been studied. The synthesis of superconducting ceramics was carried out on the basis of the glass phase, obtained by ultra-fast quenching of the melt. Melting of the mixture of starting components was carried out without the use of a crucible under the influence of IR radiant heating. Analysis of the elemental composition of the samples of the initial precursors showed a significant deviation from stoichiometry in oxygen (increase), as well as a decrease in calcium content. The synthesis of HTSC ceramics was carried out at a temperature of 849–850 °C for 96 h with intermediate grinding every 24 h. Studies of the phase composition of ceramic samples by X-ray diffraction have shown that HTSC ceramics consist only of a superconducting high-temperature phase Bi-2223. Studies of current-carrying characteristics by the four-point probe method according to the criterion of 1 µV/cm2 have shown that high-temperature superconducting ceramics of the compositions Bi1.6Pb0.4Sr2Ca2.1Cu3.1Oy, Bi1.6Pb0.4Sr2Ca2.25Cu3.25Oy and Bi1.6Pb0.4Sr2Ca3Cu4Oy have an increased density of critical transport current of 9.12 A/cm2, 7.62 A/cm2 and 7.26 A/cm2, respectively. At the same time, it was found that with a decrease in the content of Ca and Cu cations in HTSC ceramics, an increase in the critical current density is observed.

Effects of conditions on thе synthesis and properties of Bi-2234 HTSC ceramic produced from the melt

The article presents the results of a study aimed at obtaining the formation of superconducting phases and the formation of a high texture of particles that affect the current-carrying characteristics in ceramics of the composition Bi1.6Pb0.4Sr2Ca3Cu4Oy and the study of their properties. For the synthesis of ceramics, precursors from the glass phase were used, which were obtained by melting the starting material under the influence of radiant flux (IR radiation) and quenching the melt in a facility rotating at a speed of 3000 rpm. Platinum wire was used as a substrate. During the heat treatment of samples in the temperature range of 845–850 °C and a holding time of 72 hours (with intermediate grinding every 24 hours), the superconducting high-temperaturephase Bi-2223 crystallized in the studied samples. Critical temperatures and resistances of superconducting samples were measured by the four-probe method by measuring the dependence of resistance on the temperature in the range from 300 K to 60 K.