Ceramics International最新文献

During electroslag remelting (ESR), high MgO contents are typically added to CaF₂–CaO–Al₂O₃ slag to control magnesium content in iron- and nickel-based alloys. The melting temperature and viscosity of ESR slag are pivotal for energy consumption, production efficiency, smooth operation, and ingot quality. However, there is currently a notable scarcity of research on the melting temperature and viscosity of CaF₂–CaO–Al₂O₃–MgO slag with high MgO levels. Thus, the melting temperatures and viscosity of CaF₂–CaO–Al₂O₃–MgO slags with varying MgO contents and CaO/Al₂O₃ (C/A) ratios were investigated. The results show that as the MgO content increases from 7.83 % to 13.18 %, the final precipitation content of the MgO phase significantly increases, resulting in an increase in the melting temperature from 1306 °C to 1319 °C. With the increase in the C/A ratio from 0.86 to 1.16, the precipitation completion temperatures of the Ca₁₂Al₁₄F₂O₃₂ and MgO phases significantly decrease and the MgAl₂O₄ phase transforms into the CaO phase. Hence, the melting temperature decreases from 1329 °C to 1314 °C. Further increasing the C/A ratio to 1.40, the final precipitation content of the CaO phase increases, resulting in a decrease in the melting temperature from 1314 °C to 1282 °C. Moreover, as the MgO content and C/A ratio increase, the slag viscosity exhibits different change trends within various temperature ranges. This depends on which of the depolymerization of the slag structure and the precipitation and clustering of the MgO phase has a greater effect on the slag viscosity.

Excellent properties are required for refractories used for secondary refining because of the harsh service conditions. The current study investigated the effect of calcium boride (CaB₆) on the properties of magnesium oxide (MgO)‒based refractories. The sample with 0.4 wt.% CaB₆ exhibited excellent properties. It possessed the highest bulk density indicating that a suitable content of CaB₆ can increase the compactness of the refractories. The in-situ formation of aluminum oxycarbonitride (Al₃CON) at high temperatures in the MgO-based refractories was from the reaction of Al, Al₄C₃, AlN, and Al₂O₃ due to the addition of Al powders, which endowed them with high strength. The refractory containing 0.4 wt.% CaB₆ also exhibited the highest hot modulus of rupture (HMOR) of 26.6 MPa, which was around 2.5 times the strength of commercial MgO‒CaO bricks and 1.5 times that of the samples without CaB₆ addition. In addition, it exhibited the best oxidation resistance revealed by the minimum thickness of the decarbonization zone, because the addition of CaB₆ promoted the formation of a dense magnesium aluminate spinel (MgAl₂O₄, MA) layer between the oxidized and non-decarburized zone in the refractories, thereby promoting the resistance of the samples to oxidation. It also exhibited excellent thermal shock resistance, and the residual strength ratio reached 76.6%. The corrosion depth of the sample containing 0.4 wt.% CaB₆ was 9.8% that of the MgO‒CaO bricks. This work indicates a potential alternative for producing high‒performance resin‒bonded MgO-based refractories with CaB₆ in secondary refining furnaces.

In the field of stored energy materials, lead-free amorphous thin films have the advantages of high breakdown strength, excellent stability, environmental protection and pollution-free, and are a very competitive energy storage material. However, the difficulty of simultaneous optimization of polarization and breakdown strength has always been a difficulty in improving the energy storage properties of amorphous thin films. Entropy can be used to design multi-ion doping to improve the energy storage performance of amorphous film. Amorphous films with different entropy are prepared by sol-gel method doped with 50% Zr⁴⁺ and 5%, 10%, 15%, 20% Bi(Mn_0.5Ti_0.5)O₃. The Bi_0.1Ba_0.85Sr_0.05Mn_0.05Ti_0.45Zr_0.5O₃ amorphous thin film prepared at medium entropy (S = 1.37) has a recoverable energy storage density of 107.4 J cm^-3 at 8.42 MV cm^-1, and the energy storage efficiency is 93.9%. Under the interaction of multiple elements, entropy design can give full play to the advantages of composite effects, improve breakdown field strength and energy storage efficiency, and is a new method to enhance energy storage performance.

Smart polymeric coatings play a crucial role in protecting steel surfaces from corrosion and wear. One of progressive smart behavior is self-healing behavior especially in self-healing epoxy coatings. Creating or improving the second smart behavior is known as a new trend for these smart materials. This study aims to investigate the effects of ZrO₂ nanoparticles on the self-lubricating behavior as the second smart behavior of the linseed oil-loaded microcapsule/ epoxy composite coatings. To do so, the in-situ polymerization method was used for the synthesis of linseed oil-loaded microcapsule. Results showed that the average size of prepared linseed oil-loaded microcapsules was 563 nm. The composite coatings were prepared by different content of ZrO₂ nanoparticles (0, 3, 6, 9, 12, and 15 wt.%) and constant content of linseed oil-loaded microcapsules (5 wt.%). The tribological performance of samples was studied using pin-on-disk test. The worn surface of the samples was also studied using field emission scanning electron microscope (FESEM) images. Results proved that the frictional coefficient and wear rate of the samples were significantly decreased by increasing the concentrations of the ZrO₂ nanoparticles up to 9 wt.%. The lowest friction coefficient and wear rate values of 0.085 and 0.142 ×10^-6 mm³/Nm were obtained for 5 wt.% linseed oil-loaded microcapsules/ epoxy with 9 wt.% ZrO₂ which were about 82% and 88% lower than those of pure epoxy coating.

The effects of B₂O₃ on viscosities, structures and phase transitions of CaO-MgO-Al₂O₃-SiO₂-MnO-(0-8.0wt%)B₂O₃ slags were investigated in this work. From the viscosity experimental results, the slag viscosities declined and the E_η decreased from 205.19 to 175.95 kJ/mol with the addition of B₂O₃ in slags from 0 to 8.0 wt%. From the structure analysis by using FTIR and XPS, B₂O₃ entered into the silicate network to increase the slag polymerization degree, while the formation of simple two-dimensional BO₃ trihedral units could significantly decline the symmetry and stability of the structure. The effects of decreasing the network stability and forming low-melting eutectics were more dominated than the effects of increasing the structure polymerization degree, which could reduce the slag viscosity. Furthermore, adding B₂O₃ could decrease the slag initial precipitation temperature and change the primary crystal phase of the slag from melilite to spinel. The comprehensive effects of reducing the slag structure stability and decreasing the influence of solid phase on viscosity eventually resulted in the improvement of the slag fluidity.

To better understand the variations in physical, mechanical, and electrical properties, (Ge₂S₈)_100-xTe_x chalcogenide glasses have been synthesized. These glasses encompass a composition range of 0 ≤ x ≤ 12. The mechanical properties have been studied by determining the longitudinal (ν_L) and transverse (ν_T) ultrasonic velocities. A network structure evaluation with composition has been performed via parameters like coordination number (<N_r>), crosslinking density (D_CL), glass transition temperature (T_g), etc. Also, the elastic parameters trend values have been associated with the decrease in the cohesive energy value of the system. An overall physical analysis of the Ge-S-Te systems reveals that the system’s rigidity and the cross-linking density are decreasing. Within the temperature range of 300 to 420 K, the temperature dependency of the dark conductivity and photoconductivity has been investigated. The intensity-dependent photoconductivity is governed by a power law, with intensity (I_ph = G^δ) with δ lying between 0.5 and 1. The photosensitivity values reveal that the glassy system may be suitable for applications in optoelectronic devices. A correlation among the parameters has been established by calculating elastic parameters and conductivity measurements and evaluating the network structure theoretically. The present efforts clarify the composition-structure dependence and relationship in the Ge-S-Te glass series.

To improve the ablation resistance of C/C composites, Y₂O₃ with different contents modified HfC-MoSi₂ multi-phase coating was prepared by supersonic atmospheric plasma spraying. The microstructural and phase compositional evolution of as-prepared coating was studied both before and after ablation. The effect of Y₂O₃ content on the ablation resistance and behavior of the coating was investigated in detail. The results showed that the incorporation of Y₂O₃ enhances the high-temperature stability of SiO₂ oxide films and suppresses their volatilization at elevated temperatures. Furthermore, the formation of Y₂Hf₂O₇ and Y₂Si₂O₇ through the reaction between Y₂O₃, HfO₂ and SiO₂ promotes the development of a compact oxide scale, effectively inhibiting gas diffusion into the interior of the coating. Consequently, these improvements contribute to enhanced ablation resistance of the coating.

Nighttime driving safety is a key focus in transportation research due to accidents caused by drivers' inability to clearly see road obstacles, leading to delayed or incorrect decisions. To address this, the use of mechanoluminescent materials on surfaces like roads and buildings offers a potential solution for better object contour detection in poor visibility. This study investigates the use of SrAl₂O₄ as a phosphor matrix, exploring its luminescence characteristics and the effects of doping with Eu²⁺ and Dy³⁺. The optimal doping ratios were determined to be 2% Eu and 1% Dy by trap modulation, producing phosphors with significant mechanical luminescence and a prolonged afterglow. Spectroscopic analysis and image assessment demonstrated a visible afterglow lasting up to 60 minutes, along with impressive mechanical luminescence performance. By combining the developed SrAl₂O₄:Eu²⁺, Dy³⁺ phosphor-based coating with polydimethylsiloxane, a real-time surface stress sensing system was devised utilizing digital camera and other optical sensors. This advancement facilitates the visualization of stresses in complex or confined environments, potentially improving nighttime driving safety through enhanced object contour detection.

In the study, a BN_f/SiBN composite was fabricated through precursor infiltration and pyrolysis (PIP) method. The oxidation resistance of the composite was investigated at different oxidation temperatures, focusing on the micro-structure evolution, the phase composition and oxidation kinetics of bare fibers versus fibers protected by the matrix under various oxidation states. The result indicates that the BN_f/SiBN composite remains stable at 1100°C in air atmosphere, while the fibers protected by matrix maintain their complete structure even at 1500°C. Furthermore, we elucidated the oxidation mechanism of SiBN matrix: SiBN matrix undergoes a prior oxidation stage and transforms into amorphous SiO₂ and B₂O₃ at high temperatures to impede the oxygen attachment to fibers while preserving the integrity of internal structure. The emergence of ultra-high temperature resistant BN_f/SiBN composite and along with the exploration of oxidation behavior has opened up new approach for advancing radome material development.