International Journal of Ceramic Engineering & Science最新文献

Hafnium carbide (HfC) is an ultrahigh-temperature ceramic with high melting point, chemical stability, hardness, and wear resistance. However, its low fracture toughness and poor thermal shock resistance limit its structural applications in extreme environments. In this study, co-curing of liquid precursors was carried out prior to complete pyrolysis of individual polymeric precursors. First, HfC preceramic polymer precursor was cured, followed by silicon carbonitride (SiCN) precursor curing on a 2D carbon fiber (CF) cloth using the drop-coating process. The infiltrated CFs were pyrolyzed at 800°C to achieve CF/HfC-SiCN ceramic mini-composites. The cross-linked precursor-to-ceramic yield was observed to be as high as 65% when the procedure was carried out in an inert environment. Although stable up to 1200°C, CF/HfC-SiCN samples demonstrated susceptibility to oxidation at 1500°C in ambient air. The oxidation of HfC in the presence of SiC leads to the formation of a hafnium-containing silicate (Hf_xSi_yO_z) along with hafnia (HfO₂). This compound of silicate and hafnia limits oxygen diffusion better than SiO₂ and HfO₂ individually. The incorporation of SiCN in HfC ceramic led to improved phase stability compared to a neat HfC system. The results of this study also show that the use of liquid-phase precursors for HfC and SiCN in the polymer-infiltrated pyrolysis method is a promising approach to fabricating high-temperature structural ceramic matrix composites with good oxidation resistance.

Supplementary cementitious materials (SCMs) are partial substitutes for ordinary Portland cement (OPC) to reduce cost, the production of carbon dioxide (CO₂), and fossil fuel consumption. Recent studies illustrated the effectiveness of calcined kaolinite clay as a proper partial replacement for OPC. Hence, schist-type materials containing sufficient clay contents are regarded as promising candidates for OPC replacement. This study focuses on the possible use of activated calcium carbonates (CaCO₃) to augment pozzolanic reactions of schists as a substitute for OPC. The use of activated calcium carbonates proved to be successful in expediting pozzolanic reactions and facilitating the formation of additional calcium aluminosilicate hydrate (C-A-S-H). In this study, the optimal strength performance for blended cement was achieved by adjusting the total carbonate content to 30 wt.% of the schist. The decision to introduce carbonate to the schist was guided by calculations determining the need for an excess of calcium ions to fully harness the potential for C-A-S-H formation. Virgin and augmented schists were activated by up to 80% of their respective potentials by heat treatment. Phase content and decomposition behavior of the active components were investigated by thermogravimetric analysis (TGA), x-ray diffraction (XRD), and scanning electron microscopy (SEM). Cement paste samples incorporating 30 wt.% replacement of OPC with activated schist SCMs were prepared. The phase distribution and compressive strengths of these samples were assessed at hydration intervals of 2, 7, 28, 50, and 90 days. Cement formulations with activated calcium-augmented SCMs exhibited compressive strength values at 109%, 101%, 96%, 95%, and 94% compared to pure cement paste at 2, 7, 28, 50, and 90 days, respectively. These values surpassed 90% of the compressive strength of pure OPC at equivalent hydration time points.

A series of low-carbon fly ash cenosphere plates was prepared using solid waste based cementitious material as binder through a simple process; meanwhile, effects of cenosphere's particle size and size distribution on microstructure and properties were investigated. In the range of 20–200 mesh, as particle size decreases, sound absorption performance decreases while strength improves. Appropriate particle grading can effectively improve the compressive strength, but it will lead to a significant decrease in sound absorption performance. Samples prepared from fly ash cenosphere with a particle size of 20–40 mesh show good sound absorption performance: when the cavity size is 0 mm, the maximum sound absorption coefficient is 0.64 and the average value is 0.36 in the range of 50–1 600 Hz; when the cavity size is 100 mm, sound absorption coefficient at 100 Hz is 0.47, the maximum sound absorption coefficient in the range of 50–1 600 Hz is 0.90, and the average value is 0.57 in the range of 100–500 Hz. The prepared low-carbon fly ash cenosphere plates show excellent sound absorption performance at low-frequency and are expected to have broad application prospects in low-frequency noise reduction and absorption.

The focus of this paper centers on an exploration of optical glasses with high transmittance within the infrared spectrum at wavelength of 1 060 nm, while concurrently demonstrating full absorption within the ultraviolet and visible spectral ranges. The paper analyzes the present state of glasses demonstrating necessary transmittance at IR range, considering their inherent strengths and limitations. In this context, an R₂O–PbO–SiO₂ glass system with Cr₂O₃–Mn₂O₃ colorants system emerges as the subject of this research. Research was conducted to comprehensively assess the impact of this colorant system on the glass spectral characteristics, while considering the potentially detrimental influence of FeO.

The principles underlying the industrial production of these glasses are systematically elucidated and presented. It was discovered that using gas heating during the cooling phase of glass melting resulted in the disruption of the spectral homogeneity of the glass, ultimately leading to defective product outcomes. Implementing the methodology of gasless temperature reduction (inertial cooling process) before glass pouring has created a favorable environment for producing high-quality items. Glass samples from the laboratory tests were obtained, and the researched glass was integrated into serial production.

Hydroxyapatites have been investigated since past six decades as laser host materials. Because of their important roles in bone and teeth, these have been subjects of recent investigations. Gallium and titanium have great potential for decreasing the depletion of calcium and reducing osteoporosis. The electrical properties and polarity play important roles in regeneration of the bones. We observed growth of grains in selenium-doped gallium and titanium containing silicate hydroxyapatites. Observed morphology showed non-facetted microstructures and it helped in achieving larger grains. For the material processed for the period of longer than 70 h, we did not observe any difference in the dielectric constant and resistivity of the selenium-doped materials. For irradiating the materials, a Cs-137  γ-radiation with 5 µm curie dose was used up to 100 h. We observed that the dielectric constant and resistivity at different frequencies ranging from 100 to 100 000 Hz were affected by the high energy radiation. However, bias voltage in the range of 50–1 000 mV did no alter the dielectric constant or resistivity. This indicated that the breakdown of the material did not occur for this bias range.

Owing to economic reasons and the morphology of the surface of particles, carbothermal reduction is a suitable method for the synthesis of the desired materials. In this research, ZrC nanopowder was synthesized using phenolic resin as the carbon source and ZrO₂ powder as the source of zinc by the carbothermal method. ZrO₂ powder was milled for 1, 2, 3, 4, 6, and 7 h followed by combining with phenolic resin and ethanol with stoichiometric and nonstoichiometric ratios, and then the samples were pyrolyzed for 60 min at 800°C. Then, the samples were heat treated in an argon atmosphere in two stages at 1,600°C for 60 and 90 min. XRD and FE-SEM were used to investigate the microstructure of the samples. By increasing the molar ratio and increasing the heat treatment time, the ZrC phase content in the samples increased so that the highest amount of ZrC phase was observed in the samples with the carbon to zirconium ratios of 1:6 and 1:9 and the holding time of 90 min. By increasing the heat treatment time, the average size of ZrC particles increased from 130 to 180 nm and the size of crystallites increased from 36 to 46 nm.

The main dielectric properties of several ceramic materials having niobium in their composition, proposed to take part in 5G telecommunication devices, are reviewed. A preliminary basic presentation of 5G systems, the requirements for implementing their use, a concise review of the ceramic compositions containing niobium that have been studied thus far, and an evaluation of their performance are detailed. A survey is presented, including more than 80 different compositions containing niobium, focusing on key parameters, such as dielectric constant, quality factor, temperature coefficient, and sintering temperature. These parameters play a role for assessing the potential application of these ceramics in 5G devices.

Ce³⁺-activated silica nitride phosphors (lanthanum silicate-nitride [LSN]) are promising thermostable conversion components for white-light-emitting diodes, screen technologies, and other optoelectronic applications. Cr³⁺-activated TiO₂, on the other hand, is a strongly absorbing material depending on its size and optical microenvironment. In this work, we gathered Cr³⁺-doped TiO₂ and La₃Si₆N₁₁:Ce³⁺ in an optically transparent polymethylmethacrylate matrix. Photoluminescence of the binary blends of La₃Si₆N₁₁:Ce³⁺/TiO₂ and La₃Si₆N₁₁:Ce³⁺/TiO₂:Cr³⁺ has been investigated under two different excitation energies by steady-state and lifetime-based measurements, respectively. When the microscale La₃Si₆N₁₁:Ce³⁺ phosphor and nanoscale TiO₂:Cr³⁺ particles were gathered at a critical concentration, the resulting composite exhibited 3.14-fold enhancement in the emission signal intensity with respect to the additive-free phosphor. Upon excitation, the La₃Si₆N₁₁:Ce³⁺–TiO₂:Cr³⁺ blend exhibited different excited-state lifetimes for the nano- and microsecond time-scales compared to the LSN. The microsecond time-scale measurements performed under 378 nm excitation supported the existence of a potential energy transfer from the TiO₂:Cr³⁺ to the La₃Si₆N₁₁:Ce³⁺.

Supercrystalline nanocomposites (SCNCs) are a new category of hybrid materials consisting of inorganic nanoparticles surface-functionalized with organic ligands and with periodic nanostructures, featuring multi-functionality and able to reach exceptional mechanical properties. Although efforts have been made to explore their mechanical behavior, their response to cyclic loading remains to be unveiled. Here, the fatigue behavior of SCNCs with different degrees of organic crosslinking is investigated via nanoindentation. The nanocomposites’ fatigue life is assessed, and it emerges that SCNCs without crosslinking are more efficient in dissipating energy under cyclic loading and thus feature a longer fatigue life. Chipping is identified as the main fatigue failure mechanism, whereas different mechanisms, intrinsic or extrinsic, dominate in the indentation depth propagation, again depending on crosslinking.

This article reviews promising studies on the design, manufacturing, microstructure, properties, and applications of glass-ceramics containing ZrO₂ and relevant glass-ceramic matrix composites. After the addition of ZrO₂ to a glass-ceramic composition, it can persist in the residual glassy phase, facilitate nucleation, and/or precipitate as ZrO₂ or another zirconate crystalline phase. Also, ZrO₂-reinforced or ZrO₂-toughened glass-ceramics can be designed as composites. In this article, the term “ZrO₂-containing glass-ceramics” encompasses all these scenarios in which ZrO₂ is present. Such glass-ceramics offer a wide range of applications in modern industries, including but not limited to architecture, optics, dentistry, medicine, and energy. Since S. Donald Stookey's discovery of glass-ceramics in the early 1950s, the most important scientific efforts reported in the literature are reviewed. ZrO₂ is commonly added to glass-ceramics to promote nucleation. As a result, the role of ZrO₂ in structural modification of residual glass and stimulating the nucleation in glass-ceramic is first discussed. ZrO₂ can also be designed into the main crystalline phase of glass-ceramics, contributing achieving super high fracture toughness above 4 MPa·m^0.5. Experimental and computational studies are reviewed in detail to elucidate how the transformation toughening and other mechanisms help to achieve such high values of fracture toughness. Sintered and glass-ceramic matrix composites also show promise, where ZrO₂ contributes to improved stability and mechanical properties. Finally, we hope this article will provoke interest in glass-ceramic materials in both the scientific and industrial communities so that their tremendous technological potential in developing, for example, tough, thermally stable, transparent, and biologically compatible materials can be realized more widely.