Structure Of Ceramics Research Articles

Synthesis and coating properties of (La0.5Eu0.25Y0.25)2Zr2O7 ceramic powder

The (La0.5Eu0.25Y0.25)2Zr2O7 (LEYZ) ceramic powder for spraying was prepared and synthesised by combining spray granulation and solid phase reaction phase, and a double ceramic layer structure with (La0.5Eu0.25Y0.25)2Zr2O7 ceramic surface coating and YSZ intermediate coating was prepared by atmospheric plasma spraying. Experimental characterisation revealed that the moulding state of spray granulated powders was significantly influenced by the solid content. When the solid content is small, the viscosity of the slurry is insufficient, and the prepared powder has poor formability and small overall particle size. When the solid content is large, the slurry is too viscous, which easily leads to unfavourable conditions such as sticky walls. The best formability of the pelletised powder was obtained with a solid content of 55 wt-% and a binder content of 2.0 wt-%. Compared with La2Zr2O7 (LZ) ceramics, the fracture toughness of the rare-earth co-doped modified LEYZ ceramic coating was increased by 8.4% and the bond strength was increased by 49.9%, showing good toughness and crack resistance. Moreover, LEYZ coating has significantly better resistance to solid phase particle erosion than LZ coating, with 46.3% and 45.4% reduction in erosion rate at 45° and 90°, respectively.

Composite castings based on ferrous alloys reinforced by ceramic spatial structure

A method is presented for manufacturing composite castings that are reinforced by ceramic preforms that have a porous spatial structure. The ceramic preforms were made from oxide ceramic in the form of ZrO2 and Al2O3. Composite castings were produced using the pressure-less infiltration method of ceramic preforms with cast steel (CS) and high-chromium cast iron (HCCI). A chemical analysis indicated the positive role of Cr, which promoted a physiochemical interaction between the matrix and the phase reinforcement. The hardness of each of the composite zones was higher by at least 150–350 HV0.1 as compared to the base alloys. The presence of the ceramic phase in the microstructure of the composite zones resulted in improved wear resistance of up to 20%.

SiO2 and Fe cation synergistically modify the LaMnO3 NTC thermistors with high stability

SiO2 insulator and Fe2O3 dopant was simultaneously used to modify the crystalline phase, morphology and electric properties of LaMnO3 ceramics. Results show that there are several merits after modification. On the one hand, the addition of SiO2 is demonstrated to have multifunction to the LaMn1-xFexO3 (0 ≤ x ≤ 0.5) (LMFO) ceramics. After adding SiO2, the surface of LMFO ceramics tend to be flat, the degree of densification increases, the porosity decreases, and the pores almost disappear. Meanwhile, the resistance drift rate of LaMnO3 with SiO2 is reduced and the aging stability is improved. In addition, the crystalline structure of LMFO ceramics transform from hexagonal perovskite phase (x ≤ 0.2) to cubic perovskite phase (x ≥ 0.25) along with the Fe-doping contents increase. Moreover, the grain size decreases and the grain boundaries increase with the increase of Fe content. X-ray photoelectron spectroscopy (XPS) spectra show that both the Mn4+/Mn3+ ratio and the oxygen vacancy concentration decrease with increasing Fe content. Resistivity ρ25°C raised from 2.84 Ω cm to 65.38 Ω cm, and material constant B25/50 increased from 139.36 K to 1751.78 K. Fe doping significantly improves the stability of LMFO ceramics, and the minimum value of resistance drift rate is 0.168 % after aging at 125 °C for 500 h. The above results confirm that the SiO2 modified LMFO ceramic is a high stability negative temperature coefficient (NTC) thermistor.

Impact of Ceramic Micropillar Array and Fiber Layer Composite Structure on Kinematic and Heat Transfer Characteristics of Single Droplet Impacting a Wall.

The well-known limitations of spray cooling on high-temperature solids at the Leidenfrost temperature point have been significantly improved by a composite structure of steel micropillar arrays and insulating thin films. However, the physical mechanism of a single droplet impact on the walls of high-temperature composite structures in spray cooling remains elusive. We have experimentally studied and quantified the kinematic and thermal transfer characteristics of a single droplet impacting high-temperature micropillar arrays with fiber membrane composite structures. In particular, micropillar arrays of ceramic materials of different shapes (rectangular and cylindrical) used in this study were made using the more flexible PμSL technique, for which precision reaches the micron level. The results show that the presence and different layouts (embedded or placed on top) of the fiber layer significantly affect the spreading coefficient and thermal transfer efficiency of the droplets after impact. In terms of kinematic characteristics, unrelated to the structure of micropillar arrays, compared to structures without film, the maximum spreading coefficient of droplets significantly increased by more than 40% (43% for rectangular, 46% for cylindrical) when the fiber film was placed on top, and increased by more than 20% (20% for rectangular, 33% for cylindrical) when the fiber film was embedded. In terms of thermal transfer characteristics, at a temperature of 200 °C, the presence of the fiber layer changed the wettability of the surface of the micropillar structure, leading to a certain extension of the total evaporation time of the droplets compared to the surface of the micropillar structure without film.

Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage.

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (Wrec) and high ES efficiency (η) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (ΔP) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (Eb) and enhance ΔP. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable Wrec of 6.85 J/cm3 and η of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in Wrec (3.0%) and η (4.4%) over the temperature range of 20-110 °C. Additionally, BNKT-0.15SLZTVPP exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm3, a large power density of 164.2 MW/cm3, and a short discharge time (t0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZTVPP for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.

Energy-efficient rapid additive manufacturing of complex geometry ceramics

Energy-intensive industries are one of the key greenhouse gas emitters, and decarbonization of such industries is a top priority to promote global sustainability. As one of the top energy-intensive industries, ceramic manufacturing industries are urged to boost energy efficiency in ceramic structure production. In this paper, we present a rapid and low carbon footprint strategy for freeform manufacturing spatial ceramic composites. Our approach integrates layer-by-layer deposition, photothermal in-situ solidification, and self-sustaining ceramization, enabling consolidation using only 1920 J energy. Compared to state-of-the-art processes, energy consumption can be reduced by over 100-fold, resulting in an estimated 1000-fold decrease in CO2 emissions. This energy-efficient process also demonstrates the rapid fabrication of ceramic gyroid heat exchangers, capable of withstanding extreme environments.

Moderation of [Bi3+/Na1+] molar ratio for enhancement of dielectric and energy storage properties of NaNbO3 ceramics

Lead-free (Na1−3xBix)(Nb0.75Ti0.25)O3 (x = 0.0, 0.05, 0.1, 0.125 and 0.15) (NN-BT) ceramics were synthesized using solid-state reaction technique. The effect of Bi3+ into the crystal structure, dielectric, ferroelectric and energy storage properties of NNT ceramics were investigated. Pure NNT shows present perovskite structure with orthorhombic crystal structure at x ≤ 0.125, while Na3NbO8-NaNbO3 composite phase has been detected at x = 0.15. The tolerance factor (τ) decreased from 0.97 (x = 0.0) to 0.82 (0.15) which signified the composition deviated from perovskite structure at 0.15. Significant enhancement of dielectric constant at room temperature has been achieved by increasing Bi-content and the maximum value (∼1500) obtained at 0.1. The largest value of maximum polarization (Pmax) and smallest value of remnant polarization (Pr) were achieved at x = 0.1 due to orthorhombic NaNbO3 and rhombohedral (Na0.5Bi0.5)TiO3 coexistence phases. The substitution of monovalent (Na1+) by trivalent (Bi3+) lead to create sodium vacancies into the A-sites of NNT lattice subsequently increased the cations disorder and charge misfit. The maximum recoverable energy storage density (Wrec = 17.5 J cm−3) and energy storage efficiency (η = 80%) were achieved at x = 0.1, E ∼ 700 kV cm−1. Partially, (NNTB0.1) exhibit an outstanding stability of energy storage properties in terms of temperature range (25 to 150 °C) and frequency stability (2–20Hz). The present results imply the moderation ratio of Bi/Na plays an important role for enhancement of energy storage properties of NaNbO3 anti-ferroelectric ceramics.

Effects of different light and heavy rare-earth compositions on structure and magnetic properties of high-entropy garnet ceramics

Effects of different light and heavy rare-earth compositions on structure and magnetic properties of high-entropy garnet ceramics

Forming ability and quality of fine ceramic structure fabricated by vat photopolymerization

In recent years, ceramic additive manufacturing technology based on vat photopolymerization has been widely used in various fields. This technology has amazing structural design freedom and forming precision. However, the printed structure can't be regarded as a simple reproduction of the virtual model. In our work, by analyzing the characteristic edge structure caused by the uneven propagation of exposure energy in ceramic slurry, we explore the manufacturing limits of fine structure in ceramic vat photopolymerization and the reasons for the decline in fine structure printing quality. The ability of ceramic vat photopolymerization to construct fine structures was improved by personalized selection of exposure energy. This work plays an important role in studying and expanding the ability of ceramic vat photopolymerization to construct fine structures.

Preparation and performance of aluminosilicate fibrous porous ceramics-supported catalyst for NOx removal

In this study, we report a new aluminosilicate fibrous porous ceramics-supported catalyst for the removal of [Formula: see text]. The influence of raw materials and sintering process on the structure and properties of aluminosilicate fibrous porous ceramics was studied. The composition and the structure of the catalysts were characterized by XRF, XRD, SEM-EDS, and XPS analysis, and the experiments of denitrification were performed to determine the influence of the porous structure and the calcination process on the denitrification efficiency. The results indicated that the glass fibers facilitate the formation of a uniform porous network structure within aluminosilicate fibrous porous ceramics, and that the optimal sintering temperature is 1000∘C. Under the condition, the loaded catalysts were highly dispersed on the surface of aluminosilicate fibrous porous ceramics, which possessed high porosity and large average pore sizes. The aluminosilicate fibrous porous ceramics-supported catalyst exhibited excellent denitrification efficiency and catalytic stability, which is expected to be used for the treatment of [Formula: see text] in flue gas.

Advances in Biomass and Nature‐Derived Ceramic Membranes and Their Environmental Applications in Wastewater Treatment

The water shortage crisis and industrial progress have led to the upgrading of wastewater treatment processes. Hence, the remediation of wastewater and removal of contaminants are becoming a significant issue for environmentalists. However, the design and optimization of affordable treatment procedures with better removal performance are still challenging for researchers. Although porous ceramics with excellent porosity are appropriate for the separation and adsorption of wastewater and water pollutants owing to their enlarged surface area, fluid permeability, and capacity for water absorption, their production is an expensive process. Therefore, using low‐cost and benign compounds for the production of ceramics is an important issue. This review provides the application of the ceramic manufactured from natural sources and biomass for wastewater treatment and removal of pollutants. The effect of these compounds on the structure and efficiency of ceramics is discussed and suggestions are offered for further research.

A novel co-continuous Si–Zr hybrid phenolic aerogel composite with excellent antioxidant ablation enabled by sea-island-like ceramic structure at high temperature

Lightweight phenolic matrix composites are highly potential in ablative thermal protective materials for future aerospace vehicles, and hybrid modification is considered as one of effective ways to improve the oxidation and ablation resistance of phenolic matrix. Herein, the co-continuous silica zirconium hybrid phenolic resin (SZRx) was synthesized, which can be used to prepare lightweight ablation resistant aerogel composites by the sol-gel method. The SZRx aerogel showed stable porous structure and excellent hydrophobicity, and the silicon zirconium hybrid greatly improved the high temperature carbon residue and oxidation resistance of phenolic resin. The SZRx aerogel composites also possessed excellent integrated characteristics of heat protection and insulation, with a linear ablation rate as low as 0.032 mm/s and a back temperature below 200 °C. The synergistic effect of silicon and zirconium formed the multiphase ceramic layer (C, SiO2, SiC and ZrO2) with the sea-island-like structure on the surface of the composite material, which can effectively resist high-temperature ablation and aerodynamic exfoliation. This can indicate that silicon zirconium dual element hybrid phenolic resin is the highly competitive matrix for lightweight and ablation resistant composite materials.

Structural Evolution and Mechanical Behavior of Ytterbia Doped Hafnia Biphasic Ceramics under Annealing at 1500 °C

HfO2 has become a promising thermal barrier coating material due to its similarity in structure and chemical properties with ZrO2 and its higher phase structure transition temperature. However, the fracture toughness of HfO2 is not ideal, greatly limiting its application. In this report, we find a special sandwich structure of ceramics, comprising a cubic (C) phase /monoclinic (M) phase/cubic (C) phase. The microstructural evolution and mechanical properties of these ceramics were investigated under annealing at 1500 °C. The results indicate that, with an increase in annealing duration, there was a gradual augmentation in the proportion of the monoclinic (M) phase and the fracture toughness increased from 2.18 MPa·m0.5 to 2.83 MPa·m0.5 after 48 h of annealing, which is higher than many potential TBC materials. The residual compressive stress present in the M phases during the progression of crack propagation served to facilitate the bridging and deflection of cracks. As such, this process led to the alleviation of stress concentration at the crack tip, ultimately enhancing the toughening effect.

Sintering characteristics, phase structure and microwave dielectric properties of novel BaCeO3 ceramics

It is a known fact that BaCeO3 (BC) is a material widely used in catalysts and electrochemistry, but its microwave dielectric performances have not been explored. Herein, novel BC microwave dielectric ceramics are prepared by the solid-state reaction method. The single-phase BC ceramic with orthorhombic structure (Pnma space group) is confirmed via Rietveld refinements and synthesized. Raman analysis reveals that the Q × f value of ceramics is negatively correlated with the full width at half maximum of the Raman peak. High surface densification and uniform grain size are obtained at 1650 °C and exhibit decent microwave dielectric properties: εr = 14.68, Q × f = 27,037 GHz(at 9.32 GHz), and τf = -63.67 ppm/ °C. The XPS results show that the oxygen vacancy content is the lowest and the Q × f value is the largest at the sintering temperature of 1650 °C. The results indicate that the ceramic is a good candidate for microwave dielectric materials.

Crystal structure and microwave dielectric properties of Li2(Mg1–xCux)2Mo3O12 ceramics sintered at ultra‐low temperature

AbstractLi2(Mg1–xCux)2Mo3O12 (0 ≤x ≤0.1) ceramics were prepared using the conventional solid‐phase method to study the effect of the Cu2+ substitution for Mg2+ on the sintering behavior, crystal structure, and microwave dielectric properties of ceramics. The experimental results show that the substitution of Cu2+ for Mg2+ reduces the sintering temperature of the ceramics to 550°C. X‐ray diffraction patterns show that the introduction of Cu2+ does not produce a new phase, but rather promotes the formation of Li2(Mg1–xCux)2Mo3O12 solid solution. The microwave dielectric properties of the ceramics are influenced by the cell parameters, bond lengths, and structural stability. However, Cu2+ creates oxygen vacancies during sintering, thereby deteriorating the dielectric properties (Q × f decreases). The microwave dielectric properties of Li2(Mg1–xCux)2Mo3O12 ceramics are optimal at a sintering temperature of 550°C and x = 0.02, with εr = 9.17, Q × f = 7960 GHz, and τf = –58.77 ppm/°C. Additionally, these ceramics are compatible with Al electrodes.

Zirconia Toughened Alumina Ceramics via Forming Intragranular Structure.

The distribution of second phase particles in the microstructure of composite ceramics affects the mechanical properties, and the intragranular structures often result in better properties compared to the intergranular structures. However, it is difficult to obtain composite ceramics with intragranular structure by conventional route. To produce composite ceramics with an intragranular structure in a simpler route. In this work, starting powders with different phase compositions were obtained by the co-precipitation method, and zirconia toughened alumina (ZTA) composite ceramics were prepared with these starting powders by spark plasma sintering (SPS). The results show that it is easier to fabricate ZTA composite ceramics with an intragranular structure by using composite powders containing amorphous or transition phase Al2O3 as starting materials. The phase composition of the powder prepared by the co-precipitation method after calcination at 1100 °C is θ-Al2O3 and t-ZrO2, and the average grain size after sintering at 1500 °C is 1.04 ± 0.28 µm, and the maximum Vickers hardness and fracture toughness of the specimens reach 19.37 ± 0.43 GPa and 6.18 ± 0.06 MPa·m1/2, respectively. The ZrO2 particles were the core of crystallization and grow together with the Al2O3 matrix, forming the intragranular structure of ZTA ceramics. This work may provide a new idea for preparing composite ceramics with intragranular structure.

Induced porous structure with a slight change in mechanical properties of hydroxyapatite-based nanocomposites synthesized from waste bovine bone and their bioactivity

Porous hydroxyapatite (HAp) ceramics have been widely used in several biomedical applications. However, efforts to enhance the porous structure in HAp ceramics often lead to a decline in their mechanical properties. In the present study, by adding a small amount of aluminum nitride (AlN) nanoparticles to HAp ceramics, we achieved the formation of porous HAp with a slight change in grain size and mechanical properties. The starting powder of the HAp was obtained from a natural source of bovine bone. The HAp/xAlN nanocomposites were fabricated by a simple conventional technique. The 0.06 mol% AlN-added sample (HAp/0.06AlN) presented the maximum mechanical properties (Vickers hardness = 3.68 GPa, elastic modulus = 94.04 GPa, and fracture toughness = 0.97 MPa∙m1/2) with favorable porosity. Simulated body fluid and cell viability assays showed that all the studied nanocomposites possessed desirable bioactivity with high cell viability. The HAp/0.06AlN samples were coated with antimicrobial agents. The samples coated with silver nitrate (AgNO3) had high antibacterial efficiency against S. aureus (66.2%) and P.aeruginosa (67.3%). Based on the obtained results, the nanocomposites exhibited promising potential for development and utilization in biomedical applications.

Tunable yellow and orange emission of Ce, Eu doped multilayered YSZ/YAG ceramics

Eu3+ and Ce3+ doped YSZ/YAG multilayered luminescent ceramics were consolidated by the Spark Plasma Sintering (SPS) method. The optimal modes were explored during the SPS process for functionally graded ceramics (FGCs) structure fabrication. The introduction of rare-earth (RE) oxides into FGCs with different concentration leads to a shift in the temperature range of intense shrinkage to lower temperatures from 1280 °C to 1100–1190 °C and a decrease in the relative shrinkage during the SPS process by 3–6%. Morphological, optical and luminescent properties have been investigated in detail for fabricated YSZ/YAG ceramics with different arrangement of the layers. The nature of luminescent centers in FGCs was studied using time-resolved cathodoluminescent and steady-state photoluminescent (PL) spectroscopy. The PL efficiency of YSZ/YAG ceramics were analyzed and optimal compositions of the FGCs layers were determined. The YSZ/YAG novel functional multilayered ceramics could be promising candidate for light-emitting devices application.

Boosting effective capacitance of nanograined BaTiO3-based ceramics via a precise core-shell-structure optimization strategy

The continued miniaturization of multilayer ceramic capacitors (MLCCs) means that thinner dielectric layers are exposed to stronger electric fields, degrading their capacitance. Thus, improving the DC-bias stability is urgent to maintain capacitance under strong electric fields and satisfy the requirements of high-end MLCCs. This work proposes a strategy for optimizing the DC-bias performance by tuning the core-shell structure of ceramics. Both numerical and experimental results indicate that the DC-bias performance of core-shell-structure ceramics can be significantly optimized under the double action of thickening the shell and increasing the shell dielectric constant, which simultaneously achieves considerable dielectric constant under DC-bias. Dy-Mg co-doped BaTiO3-based ceramics with an average grain size of about 180 nm prove extremely DC-bias stability and have a high dielectric constant of about 2000 and a low DC-bias attenuation coefficient of −23.6% at 4 kV/mm, which guarantees a high effective capacitance, especially under high electric fields.

Effects of F− substitution on crystal structure, band characteristics and microwave dielectric properties of Li3Mg2NbO6 ceramics for high frequency applications

The structure–performance mechanism is essential to achieve comprehensive characteristics for advanced communication system. In the present work, F− ions were adopted to fabricated Li3Mg2NbO6-x/2Fx ceramics at a nitrogen atmosphere to modify dielectric characteristics. Correlation between bond characteristics, crystal structure and enhanced microwave dielectric characteristics was investigated through vibration analysis, P–V-L theory, Rietveld refinement, and First-principle calculations. Raman analysis and Rietveld refinement show that F− substitution led to a single phase. First-principle calculations indicates a high energy gap of 3.676 eV and p orbit contributed to Fermi energy. F− substitution led to the increase of Nb O bond ionicity and lattice energy, accounting for the variation in Q×f value and dielectric constant. The τf value was related to the expansion coefficient of the Li–O bond. Remarkably, the samples (x = 0.08) exhibited comprehensive dielectric characteristics with εr = 15.9, Q×f = 143,000 GHz and near-zero τf = −2.1 ppm/°C, proving an effective strategy for collaborative regulation. Based on structure simulation, 5G filter with ultra-low loss and high-suppression was designed through introducing transmission zeros from cross coupling. More specifically, a dielectric filter exhibited an interpolation loss of 0.2 dB at 3.3–3.6 GHz and high attenuations of 15 dB for 20 MHz outside the passband, verifying the feasibility for 5G applications.