Journal of the American Ceramic Society最新文献

Methods for determining the dissolution rate of glass networks vary based on the application, glass chemistry, and morphology. Research spanning many glass systems has resulted in a substantial amount of dissolution data, but inconsistencies limit the utility of the data collected. Furthermore, predicting the dissolution of any glass system remains a critical challenge for many industrial glass applications. This work compares the dissolution of five single modified (Na, K, Ca, Sr, and Ba) aluminoborate glasses to their optical basicity values to gain fundamental understanding of how the glass composition influences dissolution at 37°C in alkaline water. X-ray photoelectron spectroscopy (XPS) was used to directly measure the binding energy of the oxygen in each glass to evaluate the underlying glass structure. Results showed that aluminoborate glasses synthesized with monovalent cations exhibit approximately an order of magnitude faster dissolution of the modifier ion compared to divalent cation glasses. Further grouping in the monovalent and divalent glasses is observed in the normalized dissolution rate of B and Al from the glass network. No correlation was observed between the normalized forward dissolution rate of boron, the primary network former, and the measured binding energy of the aluminoborate glasses. Furthermore, no defined trend was observed between the optical basicity and O1s binding energy in the modified aluminoborate glass compositions.

A new molar volume model for multicomponent olivine solid solutions, considering the linear summation of molar volumes of individual configurations weighted by their respective cation distribution fractions, is developed in this study. The model encompasses four possible configurations within olivine, each involving two distinct divalent ions occupying two different sites. Using available experimental data and employing the compound energy formalism to calculate cation distribution fractions, the study derives temperature-dependent molar volume expressions for various olivine configurations. Strong correlations between the estimated molar volume and the effective ionic radii of constituent cations are established, allowing for the estimation of molar volume for olivine configurations without experimental data. The results provide a robust framework for accurately estimating the molar volume of olivine across diverse compositions and temperatures, enhancing our understanding of its thermal expansion characteristics. Moreover, these estimated molar volume expressions and observed correlations enable comprehensive insights into the thermal expansion behavior of multicomponent olivine solid solutions.

In response to the urgent demand for windows with multi-mode self-calibrated temperature feedback operating over a wide range in extreme environments, herein, Pr³⁺–Er³⁺ co-doped Y₂Zr₂O₇ (YZO) transparent ceramics were developed. After annealing treatment to remove defects, these ceramics exhibit high transparency and temperature-dependent wide-range photoluminescence, in which the in-line transmittance is up to 77.8% at 760 nm (theoretical limit is 78%), and the luminescence band spans blue to red. Furthermore, based on the luminescence intensity ratio technology, a multi-mode temperature sensing window using highly transparent YZO:Pr/Er ceramics was designed. The developed photothermal window shows relatively high sensitivity, in which absolute sensitivity (S_a) and relative sensitivity (S_r) reached 0.0105 K⁻¹ at 363 K and 1.295% K⁻¹ at 301 K, respectively. The developed thermometer could provide a reference for self-calibrated thermometer window, and its wide spectral operating range ensures the reliability of temperature measurement, which has the potential to be used in some extreme conditions.

Nitride inclusions such as TiN and AlN often appear in the smelting process of aluminum‒titanium alloy steel. The phase diagram of nitrogen-containing slag system is crucial for guiding the design of the denitrification slag system. In the present work, the high-temperature equilibration-quench experiment was employed, and the types and compositions of equilibrium phases were identified by electron probe micro analysis and X-ray diffraction. The 1500°C isothermal section of CaO‒Al₂O₃‒TiN system and the 1500°C isothermal space phase diagram of CaO‒Al₂O₃‒Ti₂O₃‒TiN system in specific compositional ranges were constructed for the first time. Among them, the isothermal section of CaO‒Al₂O₃‒TiN system includes six three-phase fields, one two-phase field, and a single liquid phase field; the isothermal space phase diagram of CaO‒Al₂O₃‒Ti₂O₃‒TiN system includes four four-phase fields, six three-phase fields, six two-phase fields, and a single liquid phase field. By comparison, it can be found that the CaO‒Al₂O₃‒Ti₂O₃ slag system has a higher equilibrium solubility of nitride than that of the CaO‒Al₂O₃ slag system. In addition, the dissolution type and the equilibrium solubility of nitride inclusions (AlN and TiN) in slag were analyzed and discussed using the experimental phase diagram of CaO‒Al₂O₃‒Ti₂O₃‒TiN system.

The growing focus on reducing CO₂ emissions has promoted the use of alternative raw materials in cement production. Most heavy metal ions from these materials are preferentially incorporated into tetracalcium aluminoferrite (C₄AF), making it important to understand the effect of this incorporation on C₄AF hydration. In this work, we examined the hydration properties of manganese (Mn)-doped C₄AF by combining well-defined density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The results indicate that Mn doping stabilizes the Mn–O octahedral structure, reducing charge transfer between water molecules and the surface. This change lowers adsorption energy and interfacial bond strength, weakening the potential for dissociative water adsorption. Mn doping reduces the initial hydration reaction rate of C₄AF, with the following hierarchy of reaction rates observed: pure C₄AF > Mn-doped C₄AF surface > Mn-doped C₄AF interphase. The hydrogen bonding density at the interface becomes localized upon Mn addition, reducing charge transfer between the water and the surface. Mn near the interface further delays the reaction by anchoring water molecules and hydroxyl groups. These findings provide valuable insights into the early hydration of Mn-doped C₄AF.

Recently, gahnite (ZnAl₂O₄) is gaining attraction as a potential refractory ceramic because of the similarity of its structure and properties with those of magnesium aluminate (MgAl₂O₄) spinel refractories. Formation of MgO and hibonite solid solution (CaMg_xAl_12−xO_19−0.5x; 0 ≤ x ≤ 0.18), CAM-I (Ca₂Mg_2−3xAl_28+2xO₄₆ (0 ≤ x ≤ 0.3), and CAM-II (CaMg_2−3xAl_16+2xO₂₇, 0 ≤ x ≤ 0.2) phases with platelet and interlocking microstructure in the CaO–Al₂O₃–MgO ternary system significantly enhances the high temperature mechanical properties of refractory castables. The CaO–Al₂O₃–ZnO ternary system has been studied, for the first time to our knowledge, in a selected compositional range with reference to the CaO–Al₂O₃–MgO system from 1650°C to 1700°C. The formation of ZnO and hibonite solid solution (CaZn_xAl_12−xO_19−0.5x; 0 < x < 0.18), CAZ-I (Ca₂Zn_2−3xAl_28+2xO₄₆; 0 ≤ x ≤ 0.3), and CAZ-II (CaZn_2−3xAl_16+2xO₂₇; 0 ≤ x ≤ 0.2) phases with platelet and interlocking morphology have been found. The crystal structures and lattice parameters of ZnO and hibonite solid solution, CAZ-I, and CAZ-II are comparable, respectively, with MgO and hibonite solid solution, CAM-I, and CAM-II. Furthermore, CAZ-I and CAZ-II phases also form due to reaction between hibonite (CaO·6Al₂O₃) and ZnAl₂O₄.

Studying the nanoindentation behavior of materials at the atomic level is crucial for advancing technologies involving energetic atom bombardment, ion implantation, and nanomechanical testing. Using molecular dynamics simulations with two typical rigid ion interatomic potentials (fixed charges), we showed that the mechanical responses and dislocation nucleation of alumina ($�\alpha$-$��{\mathrm{Al}}_2�O_3�$) are highly temperature- and orientation-dependent. The complex behavior in dislocation dynamics has been rationalized by computing the distribution of stacking fault energy. It is further found that SHIK potential provides better accuracy in describing dislocation dynamics at a much lower computational cost.

Herein, we report on the structural, magnetic, dielectric, and optical properties of La-doped Sr_2-xLa_xFe_0.5Hf_1.5O₆ (SLFHO, 0.0 ≤ x ≤ 2.0) double perovskite oxides synthesized by solid-state reaction method. X-ray powder diffraction data and their Rietveld refinement reveal that the SLFHO powders crystallize in an orthorhombic structure with the Pnma space group. The SLFHO powders exhibit spherical morphology with an average particle size of 160 nm, as shown from SEM images. Their molar ratios of the Sr:La:Fe:Hf elements were determined as 1.77:0.50:0.50:1.95 by energy dispersive X-ray spectroscopy data, approaching their nominal stoichiometry. X-ray photoelectron spectra verified that Sr²⁺, La³⁺, Fe³⁺, and Hf⁴⁺ (Hf^x+) ions existed in the SLFHO powders, and oxygen existed in species lattice oxygen and adsorbed oxygen, respectively. The SLFHO powders exhibit ferromagnetic behavior at 2 and 300 K, respectively, and at 2 K the saturated magnetization was 5.66 emu/g (or 0.60 μ_B/f.u.). Magnetic transition temperature, T_C was determined to be 867 K. Dielectric measurements demonstrated a strong frequency-dependent dielectric behavior observed in the SLFHO ceramics and a relaxor-like dielectric behavior appearing in the temperature range of 200–600 K. Such relaxor-like dielectric behavior is ascribed to the dielectric response of the singly-ionized oxygen vacancies ($��V_O^{·}��)���\mathrm{associated}��\mathrm{with}����$ an activation energy of 0.54 eV. Room temperature optical properties of the SLFHO powders examined by using UV–vis diffuse reflectance spectroscopy exhibit high optical absorption in this wavelength region, and a wide indirect optical bandgap (E_g = 3.39 eV) was estimated using the Tauc's relation from the diffuse reflectance spectra. The SLFHO double perovskite oxides display high-temperature ferrimagnetism, relaxor-like dielectric behavior, and wide optical bandgap, making them potential to be employed in the fields of high-temperature spintronics and magnetic semiconductor devices.

As a functional crystal, LiNbO₃ plays a significant role in nonlinear optics, optical storage, illumination, and three-dimensional display. Recent investigations have suggested that the precipitation of LiNbO₃ in a nonequilibrium system shows unique crystallite geometry and orientation, leading to fascinating nonlinear optical properties. This work focuses on the effect of alkaline earth metal ions on the properties of Li₂O–Nb₂O₅–SiO₂ glass ceramics. The results demonstrate that within the Li₂O–Nb₂O₅–SiO₂ glass matrix, irregularly shaped crystals of approximately 5 µm in size precipitate through volume crystallization. Upon incorporation of Mg²⁺, the glass ceramic remains in volume crystallization while LiNbO₃ crystals grow to 10 µm and become spherical. In contrast, the compositions containing Ca²⁺, Sr²⁺, and Ba²⁺ change to surface crystallization, producing submicron or even nano-sized crystals. Besides, the nonlinear optical response can be improved after the hybridization of alkaline earth metal oxides. This research offers insights into the crystallization behavior of LiNbO₃ crystals from the nonequilibrium environment.