Preparation Of Ceramics Research Articles

Preparation of biomorphic porous SiC and SiO2 ceramics by sol infiltration into biotemplate followed by controlled sintering

Preparation of biomorphic porous SiC and SiO2 ceramics by sol infiltration into biotemplate followed by controlled sintering

Composite Materials Used for Dental Fillings.

This article explores the properties of composite materials employed in dental fillings. A traditional nano-hybrid composite containing nanofiller particles exceeding 82% by weight served as a benchmark. The remaining samples were fabricated from ormocer resin, maintaining an identical nanofiller content of 84%. In all specimens, the nanoparticles were dispersed randomly within the matrix. This study presents findings from investigations into surface geometry, hardness, wettability, and tribological behavior. The microscopic observations revealed that ormocer-based samples exhibited greater surface roughness than those composed of the traditional composite. Hardness testing indicated that both ceramic addition and sample preparation significantly influenced mechanical properties. Ceramic-enhanced samples demonstrated superior hardness, surpassing the reference composite by 30% and 43%, respectively. Contact angle measurements revealed hydrophilic characteristics in the classic composite, contrasting with the hydrophobic nature of ceramic-containing samples. Tribological evaluations revealed the superiority of the classic composite in terms of friction coefficients and volumetric wear compared to ormocer-based materials.

Effect of Sintering Process on Microstructure and Properties of (Zr0.2Ta0.2Ti0.2Cr0.2Hf0.2)Si2 High-Entropy Silicide Ceramics

In this study, five kinds of (Zr0.2Ta0.2Ti0.2Cr0.2Hf0.2)Si2 high-entropy ceramics were prepared by a two-step method under different vacuum pressureless pre-sintering processes, and the microstructures and mechanical properties of the ceramics under different parameters of the pre-sintering process were systematically discussed. The results show that the physical structure of the ceramic samples remains basically unchanged by changing the pre-sintering conditions; the longer the holding time of the initial pre-sintering, the higher the densification of the samples and all of them are above 95%. The hardness of the ceramics was around 10 GPa, with the best hardness of 10.11 GPa at 1300 °C for 3 h. This conclusion provides data support for the optimization of the high-entropy ceramics preparation process.

Heterogeneous oxidation involving different atomic clusters in sintering-free amorphous SiBCN ceramic with MA@PDC-SiBCN structure

Amorphous SiBCN monoliths featuring a structure of three-dimensional PDC-SiBCN network encapsulating MA-SiBCN nanoparticles (MA@PDC-SiBCN), were prepared without the need for sintering densification (>1800°C), enabling preparation of dense ceramics at a much lower temperature (1100°C). The continuous PDC-SiBCN network effectively inhibits oxygen diffusion, reducing the mass loss from B-C-N cluster oxidation and mass gain from silicon-containing clusters by 51.5% and 86.9%, respectively. Besides, the phase-separation coupled heterogeneous oxidation behaviors and kinetics of different atomic clusters in MA@PDC-SiBCN ceramic during non-isothermal oxidation up to 1500°C were investigated. Finally, the evolution of the different atomic clusters within the oxide layer during the heterogeneous oxidation process was analyzed to elucidate the micro-mechanisms behind the enhanced oxidation resistance.

Preparation of La-doped SrTiO3 ceramics with colossal permittivity and high insulation resistivity via controlling the particle diameters of the powders

Ceramic capacitors are widely studied and applied in the electronic industry. We utilized the sand-milling technique to produce a series of La-doped SrTiO3 powders with varying particle diameters and investigated the effect of particle size on the resulting dielectric properties for the first time. We found that reducing the particle diameter significantly enhances the permittivity from approximately 7000 to 32000 (at 1 kHz, room temperature). Furthermore, a colossal permittivity of ∼32000 (at 1 kHz, room temperature), combined with ultra-high resistivity (>7 × 1011 Ω cm), low loss (0.004), and excellent frequency/temperature stability, were simultaneously achieved in the ceramic. Lastly, the sintering temperature is as low as 1360 °C, making it suitable for industrial production. By analyzing scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) results, we discuss the possible mechanism behind the enhancement of permittivity with increased sand-milling time. The low sintering temperature and highly controllable permittivity of the ceramics by adjusting the sand-milling time of the powders offer a new strategy for the scientific study and industrial application of materials with colossal permittivity.

Preparation and Photostriction Properties of BiFeO3-BaTiO3 Ceramics

Preparation and Photostriction Properties of BiFeO3-BaTiO3 Ceramics

Efficient and Controllable Preparation of Super-Hydrophobic Alumina-Based Ceramics Coating on Aviation Al-Li Alloy Surface for Corrosion Resistance and Anti-Icing Behavior

Al-Li alloys have been widely applied in aircraft structural component and shell material. However, Al-Li alloys are prone to corrosion failure, which leads to a considerable safety risk in the aerospace field and greatly limits their industrial application. Herein, a simple, low-cost, and large-scale air-spraying technique is developed for the preparation of an alumina-based ceramics coating with enhanced corrosion resistance and anti-icing behavior. The results show that the static contact angle of the as-prepared coating is 157.2 ± 0.4°, and the rolling angle is only 9.8°, suggesting a super-hydrophobic surface. Meanwhile, the electrochemical corrosion potential of the coating is 70 mV higher than that of the substrate, and the corrosion current density of the coating also decreases by 1 order of magnitude, indicating a significantly improved corrosion resistance. In addition, the fabricated super-hydrophobic coating also shows excellent anti-pollution and anti-icing characteristics. This work provides positive guidance for expanding the application of hydrophobic coating in the aerospace industry, especially in some complex corrosion, icing, and pollution environments.

Effect of SiO2/AlOOH double-coated SiC powders on the properties of SiC ceramics by vat photopolymerization

Vat Photopolymerization (VPP) technology is expected to address the challenges of preparing high-strength, precise, and complex SiC ceramics. However, the poor printability of SiC powders and the low strength of the resulting SiC ceramics remain significant obstacles. To overcome these issues, this study proposes a SiO2/AlOOH double-coating method for modifying SiC powders. The effects of AlOOH content in the double coating on the properties of SiC powders, slurries, and ceramics were investigated. Additionally, the impact of sintering additives on the densification behavior and mechanical properties of SiC ceramics was examined. The results indicated that increasing the AlOOH content in the double coating decreased the UV absorption of the powders and increased the curing depth of the slurries, but also increased the viscosity of the pastes. Moreover, while increasing the AlOOH content in the double coating improved the densification and flexural strength of the ceramics, the effect was significantly less compared to optimizing the sintering additive. Using SiO2/AlOOH double-coated SiC powders containing 2.5 wt% AlOOH and 10 wt% Al2O3-Y2O3-MgO (mass ratio 1:8:1) sintering additives, SiC ceramics were prepared with a relative density of 91.1 ± 3.5 %, a Vickers hardness of 1685.6 ± 86.4 HV, and a flexural strength of 281.7 ± 14.4 MPa, much higher than that of other SiC ceramic prepared using the same process. This represents the highest flexural strength of SiC ceramics prepared by VPP technology to date, providing a new method for the preparation of high-strength SiC ceramics via VPP.

Synergic process of molybdenum recovery and ceramic preparation for clean and efficient utilization of industrial leaching residues

Ammonia-leaching residues of roasted molybdenite concentrates are intractable wastes and are mostly stockpiled in factories. Common treatments suffer from low Mo recovery and secondary pollution. This study has developed a synergistic process involving a single-step roasting with the addition of Al2O3 and MoO3 to recover Mo and simultaneously prepare porous refractories from the residues containing 5.6% Mo. The Mo separation efficiency, ceramic properties, and thermal behaviors—including chemical reactions, melting transformations, ceramic structure evolutions, and Mo species migrations—were comprehensively investigated. It was found that the addition of Al2O3 facilitated CaMoO4 decomposition to release volatile MoO3, thus promoting Mo recovery. The mullite started to form at about 900 °C, grew into whiskers, and further into interconnected clusters, under the catalytic effect of liquid MoO3 and the sintering effect of glassy melt. Liquid MoO3 was scattered on the outer surface of whisker clusters, achieving a high separation efficiency of over 98% after roasting at 1300 °C for 150 min. Meanwhile, a ceramic with a high porosity of 64.2% and a high compressive strength of 21.2 MPa was obtained, exhibiting promise for serving as a high-temperature insulation refractory. Overall, this study presents a novel approach for both the profound recovery of Mo and the value-added utilization of gangue minerals derived from CaMoO4-bearing wastes.

Piezoelectric Ceramic Hardening Through Defect Distribution Optimization in Multicomponent Systems

AbstractAcceptor doping is a common method for hardening modified piezoelectric ceramics. The mechanism through which the hardening effect can be improved has been widely studied and verified. However, the effect of defects caused by different valence states of the B‐site ions on the properties of multicomponent piezoelectric ceramics remains to be discussed. Therefore, in this work, a novel Pb(Ni1/3Nb2/3)O3–Pb(In1/2Nb1/2)O3–Pb(Mn1/3Nb1/2)–PbTiO3 quaternary hard ceramic with excellent performance is prepared and studied. The interaction between grain‐boundary defects and defect dipoles is proposed to be the mechanism behind the observed excellent performance. It is found that different types of defects improve the hardening effect in various ways. These results can provide a theoretical basis for the preparation of multicomponent piezoelectric ceramics with better properties.

Influences on the structure, magnetic, and magnetocaloric effect of La0.8Sr0.2MnO3 ceramics by Co ion doping with sol-gel method and first-principles calculations

This paper investigated the impact of Co ions doping on the structure, magnetic properties, and magnetocaloric effect for La0.8Sr0.2Mn1-xCoxO3 ceramics (LSMCO) by sol-gel method and first-principles calculations The use of first-principles calculations was provided for subsequent experiments. The sol-gel preparation of LSMCO ceramics and sintered at 950 °C for 10 h. It was shown that the samples' cell volume and lattice constants changed slightly with increasing Co2+ doping but remained a rhombohedral structure (No.167, R-3c space group) by statistics of TEM and XRD. The average particle size for the LSMCO ceramics ranged from 130 nm to 170 nm. LSMCO's chemical composition was verified by EDS and XPS and it was demonstrated that Co2+ was successfully doped. The oxidation state of La was found to be +3, Mn is a mixture of Mn3+ and Mn4+ valence states, and Co is a mixture of Co3+ and Co2+ valence states using XPS. In the vicinity of Tc, all samples presented the second-order magnetic phase transition from ferromagnetic to paramagnetic resorting to normalization and the Banerjee criterion. The Tc dropped from 292 K to 237 K with increasing Co2+ doping. The blocking temperature and the saturation magnetization were suppressed by the Co2+ substitution while the maximum magnetic entropy change of the LSMCO ceramics was observed to reduce as Co2+ increased. When the external magnetic field is 5 T, the La0.8Sr0.2Mn0.95Co0.05O3 ceramics has a Tc of 292 K and a maximum magnetic entropy change value of 3.47 J/(kg K).

Effect of Al2O3 coating on the properties of Si3N4 ceramics prepared by vat photopolymerization

The preparation of Si3N4 ceramics by vat photopolymerization (VPP) has motivated increasing research interest. However, it is challenging to prepare Si3N4 ceramics by VPP due to the high UV-light absorbance and refractive index of powder. In this paper, a method for Al2O3-coated Si3N4 powder was proposed. Combined with the boehmite-coated and high-temperature treatment, Al2O3 was successfully coated on the surface of Si3N4 powder. The effect of Al2O3 content on the properties of Si3N4 powders, slurry and the sintered Si3N4 samples were investigated. The Al2O3 coating layer not only improves the curing forming ability of Si3N4 slurries, but also can directly act as one of the sintering aids of Si3N4 ceramics. The bulk density of the samples decreases from 3.04 ± 0.02 g/cm3 to 2.97 ± 0.01 g/cm3 with the increase of coating content, while the porosity increases from 5.38 ± 0.89 % to 7.54 ± 0.63 %. The sample of 5 wt % Al2O3 coating content has the maximum flexural strength of 474.28 ± 16.38 MPa and the highest relative density of 94.62 ± 0.89 %. This work can not only obtain a great modification effect, but also promote the dense sintering of Si3N4 ceramics during subsequent stages, which provides a constructive method for modifying Si3N4 powders to achieve photopolymerization.

Preparation of diatomite-based porous ceramics and their adsorption properties for Cu2+

Diatomite-based porous ceramics were prepared by wet grinding and high temperature calcination with diatomite as the main raw material. The structure and properties of the ceramics were characterized by SEM, XRD, and FI-TR detection techniques. The results show that the diatomite-based porous ceramics are mainly quartz crystal phase and contain a large amount of Si-OH. Their pore size distribution is 500∼3500 nm, the specific surface area is 6.14 m2/g, and the porosity is 47.8%. The static adsorption process of Cu2+ in water by ceramic particles conforms to the quasi-second-order kinetic model, and the adsorption equilibrium is reached after 6 h with the maximum adsorption capacity of 4.5 mg/g. The Thomas model can be applied to represent the dynamic adsorption of Cu2+ in water. In the adsorption of Cu2+, pH exerts a strong influence. In solution, Cu2+ forms a ligand with hydroxyl surface functional groups on the surface of ceramics and pores through electrostatic interaction, and the hydrogen on the hydroxyl group exchanges with Cu2+, so that Cu2+ can be removed.

Sintering, microstructure and mechanical properties of anorthite-based ceramics prepared from iron-extracted steel slag

Steel slag is a promising source of ceramic materials, but it causes a waste of iron resources and inferior ceramic performance because the slag contains over 30 % iron oxides. To deal with this problem, we proposed a two-step utilization process for steel slag, including iron extraction by smelting reduction and ceramics preparation from residual slag. In this work, the effect of the reduced slag addition on phase constituents, microstructure, and properties of this novel ceramic was studied. The major crystalline phase is anorthite for all the ceramics. Although abundant liquid is expected theoretically in conventional ceramics at 1175 °C, it did not achieve vitrification until 1250 °C. The slag addition plays different roles in sintering under various slag contents. After introducing 15 wt% slag, the sintering and pore elimination are accelerated significantly because of the slag’s fluxing effect although the ceramic shows no change in the theoretical liquid content. The ceramics have no advantage in producing liquids with further increasing the slag content. Therefore, limited densification is observed with 30 wt% slag addition owing to the lack of liquid phase. Fortunately, solid solution diopside is largely generated in the anorthite matrix with 45 wt% slag addition, greatly enhancing the ion diffusion and grain growth. This effect contributes to a highly dense and uniform sintered structure with small rounded pores at 1175 °C, at which its flexural strength increases by 92 % compared to the conventional ones. However, a higher slag addition in the ceramic should be avoided to ensure satisfactory structure integrity.

Effect of the SiC powder microscopic morphology on properties of Si/SiC ceramics prepared by spark plasma sintering

AbstractTo solve the problem that Si was volatile and dense Si/SiC ceramics were difficult to achieve by spark plasma sintering (SPS) under a low sintering temperature and pressure, three kinds of SiC powders were used for particle grading and then ball‐milled with different time to further change and regulate their particle size and morphology, and finally nearly dense Si/SiC ceramics were prepared by SPS. The effect of milling time on particle size, morphology, tap density, phase, and microstructure of the SiC powders, as well as on bulk density, microhardness, thermal conductivity, phase, and microstructure of the Si/SiC ceramic, was researched. When the mixed SiC powders were ball‐milled for 12 min, the bulk density, microhardness, and thermal conductivity of Si/SiC ceramic were 2.96 g/cm3, 22.95 GPa, and 152.84 W/(m K), respectively. Ball milling changed the particle gradation and micro‐powder morphology and then affected the powder particle stacking state. Forming continuous pore channels was conducive for the volatile liquid Si to flowing and filling pores in a short time, resulting in denser Si/SiC ceramics at a lower sintering temperature and pressure. This study was useful for the preparation of ceramics containing volatile liquid phase by SPS.

Rapid preparation of MgTiO3–CaTiO3 microwave ceramics with high quality factor Q via microwave-assisted sintering

The rapid preparation of high-performance microwave dielectric ceramics has always been a technical challenge in the field of electronic ceramics. In this investigation, we rapidly fabricate MgTiO3–CaTiO3 microwave ceramics with homogenous microstructure and high quality factor Q by microwave-assisted sintering, highlighting the efficiency gains and sintering time reductions. As the sintering time increases from 15 min to 45 min, the bulk density and relative density of MT-CT ceramic rapidly increase. The relative density of samples sintered for 30 min exceeds 97 %, which is difficult to achieve through conventional sintering methods. Combined with Rietveld refinement and Raman spectra, it is confirmed that the cell volume of MT-CT ceramics shrinks with the extension of sintering time, resulting in the weaken of Ti–O bond strength. More refined grain size distribution and uniform microstructure obtained by microwave-assisted sintering are likely to be pivotal factors in enhancing the microwave dielectric properties of MT-CT ceramics. MT-CT ceramics sintered at 1300 °C for only 45 min by microwave-assisted sintering exhibit excellent dielectric properties: Q×f = 87, 300 GHz, εr = 20.42, and τf = 2.11 ppm/°C, thereby demonstrating the potential of achieving rapid densification of microwave ceramics through microwave-assisted sintering.

Research progress in the study of textured piezoelectric ceramics

Piezoelectric ceramics have the advantages of uniform composition, excellent performance, good electromechanical coupling performance, and high cost performance. They are currently one of the important materials for manufacturing sensors and semiconductor components on the market. Although piezoelectric ceramic materials are widely used because of their many advantages, how to improve their piezoelectric properties is still a hot and difficult research spot. Previously, the piezoelectric properties of piezoelectric ceramics were affected by adjusting the grain size, but due to its limited enhancement effect, researchers hope to find other ways to improve the piezoelectric properties of ceramics more efficiently. Research has found that texture process can enable isotropic ceramics to obtain similar characteristics to single crystals that exhibit anisotropy. This greatly improves the piezoelectric properties of ceramics. During the texture process, the type and content of the template, texture degree and texture orientation, and other factors will significantly affect the piezoelectric properties of textured ceramics. With the continuous development of texture technology and process, the piezoelectric properties of textured ceramics have been significantly improved, but the practical application is less. Based on this, this article expounds the design principles of textured ceramics, summarizes the progress in the preparation of textured piezoelectric ceramics, and systematically explains the importance of template and texture orientation selection in texture processing. Finally, this paper also analyses the application of textured ceramics, and looks forward to the optimization methods and development prospects of piezoelectric ceramics. It is hoped to help the application and development of piezoelectric ceramics.

Fabrication of Si3N4 ceramic balls by SPS method with SiC powder bed

AbstractSpark plasma sintering (SPS) is an ultrafast sintering method for the preparation of ceramics and ceramic composites with simple geometrical shapes, with the combined application of uniaxial pressure. This study aims to propose an SPS densification method for Si3N4 ceramic balls without necessitating alterations to tools and equipment. The Si3N4 ceramic balls intended for sintering are positioned within a SiC powder bed inside the conventional die used in SPS. The study systematically investigates the effects of presintering temperature (1400°C, 1500°C, and 1600°C) and SPS temperature (1600°C, 1700°C, and 1800°C) on the sphericity, relative density, phase composition, microstructure, and mechanical properties of Si3N4 ceramic balls. Experimental findings reveal that Si3N4 ceramic balls exhibiting an optimal combination of sphericity (0.94 ± 0.02), relative density (98.4%), and mechanical properties (Vickers hardness: 17.5 ± 0.4 GPa, fracture toughness: 6.4 ± 0.1 MPa·m1/2) were successfully achieved at a pre‐sintering temperature and SPS temperature of 1600°C, coupled with the use of a SiC powder bed and SPS method. Consequently, the SPS method demonstrates its capability to fabricate Si3N4 ceramic balls with excellent performance.

Preparation of cost-effective and self-reinforced porous mullite ceramics for advanced heat insulation and sound absorption applications

Self-reinforcing porous mullite ceramics have attracted considerable attention in the field of insulation and sound absorption materials, due to their precise and controllable porous structure, high temperature and corrosion resistance, and low thermal conductivity. However, the high cost and relatively low performance obstruct their practical applications. In this work, self-reinforcing porous mullite ceramics were fabricated by utilizing construction waste via foam-gel casting and freeze-drying methods, and the impact of blowing agent dosage and sintering temperatures on the microstructures, sound absorption, and thermal insulation properties were systematically investigated. In addition, the related mechanism was also discussed in detail. The results show that, at a sintering temperature of 1000 °C and blowing agent dosage of 0.10 wt%, the self-reinforcing porous mullite ceramics can be successfully obtained, which exhibited a bulk density as low as 0.24 g/cm³ and porosity more than 90 %. Consequently, at a frequency of 2000 Hz, its absorption coefficient reached about 0.81. Furthermore, its thermal conductivity also decreased to about 0.06266 W/(m·K). This development not only unveils innovative avenues for the cost-effective fabrication of porous ceramics but also significantly broadens their potential applications within high-performance thermal insulation and sound absorption domains.

Particle grading and debinding process of zirconia ceramic based on digital light process

Digital light processing technology has the advantages of high molding accuracy and the ability to prepare complex structures, which is commonly used in the preparation of resin or ceramics. By mixing two particle sizes of zirconia powders, this paper successfully prepared a 60 vol% slurry with a low viscosity of 1.28 Pa s at shear rate was 50 s−1. By systematically studying the rheological properties of the mixed slurry, the curing depth was exceeding 100 μm at exposure time of 3 s. Furthermore, by investigating the debinding process of the printed sample, it is found that the sintering sample after debinding in vacuum has the highest density. This work has a positive significance for the preparation and debinding process of high solid loading ceramic slurry.