Open Ceramics最新文献

α-tricalcium phosphate (α-TCP) is the most widespread raw material for hydraulic calcium phosphate cements (CPCs). CPCs are widely used in bone repair due to their injectability, setting ability, and osteoconductivity. This study investigated the reactivity of α-TCP powders, focusing on the impact of minor phase impurities, β-calcium pyrophosphate and hydroxyapatite, and the synthesis temperature. The α-TCP powders were synthesized via a solid-state reaction of calcium carbonate and anhydrous dicalcium phosphate, with varying Ca/P molar ratios (1.4850–1.5075) and synthesis temperatures (1175°C–1350 °C). Powders produced with a Ca/P molar ratio below 1.50 and synthesized at a temperature above the melting point of β-CPP (1296 °C) had a broader size distribution and a two to fourfold lower hydraulic reactivity. Conversely, a higher Ca/P molar ratio improved reactivity. The study underscores the importance of precise control over synthesis parameters to enhance the performance of α-TCP-based CPCs, offering insights for optimizing material design in biomedical applications.

In this study, advanced solar steam technologies are explored for their potential applications in seawater desalination and wastewater purification. We have developed a three-dimensional photothermal evaporator using MXene, luffa sponge (LS), graphitic-carbon nitride (GCN) and activated carbon (AC). The hierarchical Ti₃C₂T_x MXene/GCN/AC@LS composite photothermal evaporator exhibits superior thermostability, pH stability, and mechanical durability. The Ti₃C₂T_x MXene/GCN/AC@LS composite evaporator having a dimension of 1.25 cm displays excellent performance, leading to a high evaporation rate of 2.6 kg m⁻²h⁻¹ and a high solar-thermal conversion efficiency of 96 % under 1 sun illumination. This high efficiency is attributed to the good light absorption by the Ti₃C₂T_x MXene/GCN/AC@LS composite coupled with a better wetting through the internal microchannels of the LS, which envisages a faster water delivery and evaporation of water. The Ti₃C₂T_x MXene/GCN/AC@LS composite captures the residual heat from the sidewall surface as an additional source of energy.

A barium-based perovskite structured ceramic with five different B-site cations was prepared by a solid-state synthesis method. The phase and chemical homogeneity of the synthesised material was verified using x-ray diffraction and energy dispersive x-ray spectroscopy, showing the successful synthesis of a single-phase perovskite structure with Ba A-site and Ti, Hf, Zr, Y, Nb, B-site cations. Ultra-high vacuum x-ray photoelectron spectroscopy was used to reveal the valence states of the constituent elements. Conventional, two-step and spark plasma sintering were used to form dense pellets with limited grain growth. The room temperature electrical characteristics of the sintered pellets were investigated by electrochemical impedance spectroscopy where a conductivity increase of two orders of magnitude was observed in a water-bearing atmosphere. Synchrotron-based ambient-pressure x-ray photoelectron spectroscopy performed under water-bearing and dry conditions suggest that the conductivity increase is related to the incorporation of hydroxyl groups into the perovskite structure.

Managing the vast quantities of waste constantly generated by mining activities is one of the major environmental and economic problems facing mankind today. Fluorapatite is separated from the associated gangue minerals by a series of crushing and screening, washing, and flotation processes. These processes produce a significant amount of phosphate sludge, which is stored on the mine site in drift rock and large surface ponds. One possible environmental option is to reuse it as an alternative raw material in ceramics and building materials. Consequently, two phosphate sludges from two different Moroccan towns, Youssoufia and Khouribga, were studied. Due to the complexity of these raw materials resulting from long geological processes, in-depth physical, chemical, mineralogical, and thermal characterization is required. Dry compressed powder pellets were sintered at 900 °C, 1000 °C, and 1100 °C for 2 h. The study focuses on the effect of sintering temperature on mineralogical transformations and ceramic properties such as apparent porosity, water absorption, and mechanical strength. At 1100 °C, a slight increase in density was observed for both phosphate sludges. Water absorption was reduced by 2.51 % in both sludges for pellets sintered at 1100 °C compared to those sintered at 900 °C. Mechanical strength improved significantly, with an increase of about 60 % for samples sintered at 1100 °C, recording 227 N for Youssoufia sludge and 247 N for Khouribga sludge. This work has provided new data on the physical, chemical, mineralogical, and thermal changes in ceramics as the sintering temperature increases. These data will be useful for the manufacture of high-value ceramics.

Silicon nitride and boron nitride (Si₃N₄/h-BN) based ceramic composites were prepared by Spark Plasma Sintering (SPS) using aluminium oxide (Al₂O₃) and/or yttrium oxide (Y₂O₃) as sintering additives. The amount of h-BN introduced varied from 0 vol.% to 20 vol.% in order to study its influence on ceramic properties. In the same way, the amount of oxide additives has been controlled and the influence of the additive's nature on the final properties has been underlined. The sintering temperature has been selected in order to obtain equivalent relative densities. The formation of β-SiAlON has been underlined by XRD and TEM analysis. Moreover, due to the fast-sintering process, amorphous secondary phase has been formed. Mechanical properties (hardness, fracture toughness, Young modulus) and thermal diffusivity have been evaluated. It appears that the nature of the oxide additive used plays an important role on the mechanical and thermal behaviour of Si₃N₄/h-BN composites.

This study proposes the use of Al-added Si–Mg composite fillers for low-temperature joining of SiC while maintaining high-temperature reliability of the joints. SiC was brazed at 1100 °C using the fillers with various compositions, based on Mg-evaporation-induced isothermal solidification of Si. The interfacial microstructure and mechanical properties of the joint were determined for different Al and Mg compositions in the filler. The added Al promoted Mg evaporation during joining, which increased the joint strength by mitigating the brittleness of the Si-based bonding layers. However, metallic Al remained in the bonding layers, which deteriorated the high-temperature joint strength. Higher Mg and Al concentrations in the filler promoted MgAl₂O₄ formation in the bonding layers that correlated with Al particle refinement. This contributed to an improvement of the joint properties, with the flexural strength at 1200 °C in air exceeding 60 MPa.

This in vitro study examines the electrochemical responses and surface degradation of alumina and feldspar dental ceramic materials in acidic environments using cyclic polarization and electrochemical impedance spectroscopy (EIS). Alumina and feldspar demonstrate balanced responses in both Fusayama Artificial Saliva and acidic solutions, indicating effective passivation. SEM/EDX analyses after 168-h immersion reveal significant elemental variations, suggesting complex surface phenomena and chemical reactions leading to oxide layer formation. Alumina exhibits increased Si, O, Al, Na, K, and C counts, while feldspar shows increased Si, O, Al, Na with reduced C and Ca levels, indicating complex reactions. Immersion induces notable elemental composition modifications, with alumina showing remarkable corrosion resistance and feldspar undergoing selective dissolution. This study provides insights into the electrochemical and surface degradation of these materials, emphasizing long-term stability and the need for continuous monitoring of protective layer dynamics in future research on corrosion-resistant dental biomaterials.

Filling the cyan gap is the key element in achieving full-spectrum illumination using violet chip to excite red, green and blue phosphors. However, designing cyan phosphors suitable for violet light excitation with excellent performance remains challenging. Herein, a novel cyan phosphor Ba₉Lu_2-x-nSi₆O₂₄:xCe (n-BLS:Ce) with multiple crystal sites of Ba²⁺ and Lu³⁺ for Ce³⁺ ions was designed and prepared via crystal-site engineering. The Ce³⁺ ions at Ba²⁺ sites emit ultraviolet light at 385 nm under 325 nm ultraviolet light excitation, and the Ce³⁺ ions at Lu³⁺ sites emit cyan light at 485 nm under 395 nm violet light excitation. The favorable occupation of Ce³⁺ ions at Lu³⁺ sites could be realized by introducing Lu vacancies. Significantly, the cyan light emission intensity of Ba₉Lu_1.4Si₆O₂₄:0.3Ce (n_0.3-BLS:Ce) with Lu vacancies is effectively improved by 47 % compared to Ba₉Lu_1.7Si₆O₂₄:0.3Ce (n₀-BLS:Ce) without Lu vacancies. And the emission intensity at 150 °C retains 96 % of that at room temperature. The color rendering index increases from 87.9 to 94.5 after supplementing Ba₉Lu_2-x-nSi₆O₂₄:xCe cyan phosphor in w-LEDs devices combining commercial red, green, and blue phosphors with a violet chip, indicating its potential practical application in full-spectrum lighting. This work also provides new ideas for the design and development of new and efficient high-quality light-emitting materials.

Cold sintering is a recently introduced densification method that is of interest due to the lower energy used in the process, the ability to densify metastable materials, the ability to integrate materials to develop unique composites, and the ability to synthesis materials that can be more easily recycled. Collectively, these advantages make cold sintering a promising approach for processing of battery components, and co-sintering into all solid-state batteries. To obtain high electrochemical performance with cold sintering, detailed control of the surface chemistry of powders is needed, to avoid or minimize the impact of carbonate formation in grain boundaries, and to limit concentrations of secondary phases that are a result of incongruent dissolution processes. In this paper, we outline the importance of surface chemical reactions of powders in cold sintering, and the mitigating processes that can be adopted to control these reactions and obtain high performance and unique opportunities for Li and Na-oxide secondary batteries. We focus on a series of examples that demonstrate how the control of low temperature densification (cold sintering) can address the environmental sensitivity of many battery materials, and highlight the issues faced and open questions. These examples include cold sintering of air-sensitive solid electrolytes, re-processing of crushed solid electrolytes, surface passivation of air-sensitive active materials for processing in air, and fabrication of solid-solid macroscopic interfaces for solid-state batteries.

The booming of the electric mobility together with the need of storing renewable energies have increased the demand of lithium-ion batteries which will bring about increasing amounts of electronic waste. Besides, the need for alternative sources of certain raw materials considered critical has changed the perception of determined wastes, which are no longer considered residues but sources of raw materials. In this work, the active cathode material present in end-of-life lithium-ion batteries (Ni, Co, and Mn) was used as secondary raw material, after being properly separated, in the synthesis of a cobalt iron nickel manganese chromium black spinel ((Co, Fe, Ni, Mn) (Fe,Cr)₂O₄). The pigment was used in the formulation of a ceramic inkjet ink which was deposited over a single-fired porous tile and porcelain tile. Texture and brightness of the ink were not affected by the use of this waste, thus presenting excellent prospects for the industrial ceramic application.