The phase transition of Sm₃TaO₇ with orthorhombic fluorite-related structure was investigated. Solid solutions (Sm_1−xNd_x)₃TaO₇ and (Sm_1−xEu_x)₃TaO₇ were prepared, and their structures at room temperature are well described with the space group C222₁. The phase transition temperature for (Sm_1−xNd_x)₃TaO₇ decreases from 1340 K with increasing Nd concentration, while that for (Sm_1−xEu_x)₃TaO₇ increases with Eu concentration. However, both of these solid solutions show the same trend, i.e., with decreasing average rare earth radii, the phase transition temperature of (Sm_1−xLn_x)₃TaO₇ (Ln = Nd, Eu) increases. This trend is the same as that observed for Ln₃MO₇ (M = Mo, Ru, Re, Os, or Ir). That is, the phase transition occurs with lattice contraction. Above the transition temperature, crystal structures for (Sm_1−xLn_x)₃TaO₇ (Ln = Nd, Eu) are well described with space group Pnma.

This paper reports on an investigation of time-dependent proportional limit stress of carbon fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs). The temperature-dependent material parameters are considered to determine the proportional limit stress. The effects of the fiber volume fraction, interface properties and matrix fracture energy on the time-dependent proportional limit stress and interface debonding of C/SiC composite are discussed. The temperature-dependent proportional limit stress increases with the fiber volume fraction, interface shear stress, interface debonded energy and matrix fracture energy. The fiber/matrix interface debonded length increases as the oxidation time increases, leading to a decrease in the proportional limit stress. The experimental time-dependent proportional limit stresses of C/SiC composites corresponding to different oxidation times are predicted.

For the first time, Ni–ZrO₂ nanocomposite coatings have been successfully co-electrodeposited by varying the concentration of ZrO₂ particles in the bath. For this, to prevent agglomeration of ZrO₂ nanoparticles in the plating bath and enhance the mass fraction of nano-particles in the composite coatings, the effects of surfactants and ZrO₂ content on the Ni–ZrO₂ nanocomposite coatings have been investigated. It was shown that the ZrO₂ fraction and the microhardness of the composite coatings are improved by using less than 20 g L⁻¹ ZrO₂ and adding anionic and cationic surfactants, respectively. A high concentration of nanoparticles can cause agglomeration, which affects the Orowan strengthening effect. The addition of a cationic surfactant increases the charge on the ZrO₂, migrates faster toward the cathode, and aids improvement of the ZrO₂ nanoparticle fraction. In contrast, the anionic surfactant, due to its dispersion and ZrO₂ fraction with a small increase, enhances the Orowan strengthening, which limits the plastic deformation of the coating and increases the improvement in coating hardness. Furthermore, the microhardness of the Ni–ZrO₂ composite coating is further increased after a high-temperature annealing process up to a maximum temperature of 900°C, which results from the oxidation of nickel and the dispersion of ZrO₂ nanoparticles.

The fracture mechanism and reliability of typical dense ceramics can be statistically analyzed using a Weibull distribution as a basis for device design. However, it is not understood if the Weibull distribution can even be applied to highly porous ceramics. In this study, porous Siliconized Silicon Carbide (Si–SiC) ceramics with anisotropic three-dimensional network structures in a porosity range of 71–92% were fabricated and subjected to a fracture analysis using the results of three-point bending tests. Observations of fracture behavior during the bending tests were conducted using a high-speed camera, image analysis of stress distribution, and observation of crack distribution inside the partially damaged specimens using X-ray computed tomography. The results indicate non-linear behavior with multiple peaks in the load–displacement curves. In this regard, the fracture mechanism of the porous Si–SiC ceramics was intrinsically different from the brittle fracture of dense ceramics and did not appear to be based on the weakest-link model. However, the Weibull distribution was found to be applicable to the bending strength of the porous ceramics with a confidence coefficient of 0.90. This was because although strain and cracks were generated sporadically during loading, the catastrophic fracture of the porous Si–SiC ceramic specimens occurred with a macroscopic crack opening at the bottom of the test specimens, almost the same as a Mode I crack opening in dense ceramics. Furthermore, graded three-layer structures can be formed integrally using the proposed novel replication method with uniaxial pressing, taking the plateau of the stress–strain curve of the template polyurethane foam into account, providing a kind of damage tolerance owing to the sporadic generation and sequential propagation of cracks, manifested as the multiple peaks shown in the load–displacement curves.

The ferroelectric state in a simple-perovskite mixed-oxide system (1 − x)Na_0.5Bi_0.5TiO₃–xBaTiO₃ (NBT–xBT) for 0.30 ≤ x ≤ 1.0 was investigated primarily via in situ transmission electron microscopy observation. Dielectric permittivity measurements reveal that the NBT–xBT samples for 0.30 ≤ x < 0.80 exhibited hysteresis with a temperature width of approximately 20–50°C. This result suggests that a successive phase transition was present and that the ferroelectric state at room temperature was not a simple tetragonal symmetry. In situ transmission electron microscopes observation reveals that the ferroelectric state in the BT-rich end had an M_C-type monoclinic symmetry with 〈201〉_C polarization vectors in {100}_C planes. The ferroelectric M_C state was characterized by a 79° (pseudo 90°) domain with a (110)_C twin structure and 180° domain. Thus, the continuous change at room temperature from the ferroelectric tetragonal state in BT for x = 1.0 to the monoclinic M_C state for x = 0.30 can be explained by the introduction of a 〈100〉_C component perpendicular to the original [001]_C polarization vector in the tetragonal system.

The model used to predict the liquid viscosity value of clay based ceramics was determined in this study. The viscosity values of liquid phases in clay based ceramic were measured precisely in a closed tube furnace by rotating the spindle in the melts at high temperature. The chemical compositions of the glassy phases in the ceramics were analyzed. The glassy phases were prepared by the pure chemicals after the analysis. The viscosity values of the melts followed Arrhenius assumption. Four different models were applied to calculate the viscosity values of melts in the present study. The predicted results of Urbain model and Riboud model were far away from the experimental results. However, the calculated results of Shaw model (SW model), used to predict the viscosity value of lava), and Modification of Shaw model (M-SW model) were found to be much closer to the experimental results but were still with some deviations. The calculated viscosity values of M-SW model were smaller than the experimental results. On the other hand, M-SW was a reliable predictor of viscosity values of liquid phases in clay based ceramics after modification. The modification of M-SW considered “FeO” as network-modifier and got rid of a part of excess Al₂O₃. The assumptions of SW model and M-SW model limited the accuracy of the prediction results of liquid viscosity values in the clay based ceramics. More experiments were needed to revise the slope intercept data of K₂O and “FeO”.

In this study, the foam ceramics based on ceramic tile polishing waste (CTPW) were successfully prepared by a simple solid phase sintering method. The CTPW was used as the main raw material, SiC inside CTPW as the foam agent and (NH₄)₆Mo₇O₂₄ as the sintering additive. Effects of the amounts addition of (NH₄)₆Mo₇O₂₄ (0–6 wt %) and sintering temperature (1080–1200°C) on the sintering properties, structural evolution, phase composition and mechanical properties have been investigated. During the sintering process, the SiC inside CTPW could react with oxygen and then produce the gases such as CO and CO₂, which caused a closed-pore structure. After adding (NH₄)₆Mo₇O₂₄ and increasing the sintering temperature, a better porous structure with suitable pore size and high compressive strength could be obtained. It was found that the foam ceramics doped with 2 wt % (NH₄)₆Mo₇O₂₄ and sintered at 1200°C for 30 min showed excellent properties: a low bulk density (0.362 g/cm³), the appropriate pore size (0.94 mm), a uniform pore size distribution and a very high compressive strength (8.16 MPa).

Hydroxyapatite having nanometer/micrometer-size pores was formed from the olive oil/amorphous calcium phosphate (ACP)-poly(vinyl alcohol) (PVA) gel emulsion. An ACP-PVA gel was prepared by a freeze-thaw process to form an interconnected nanoporous structure. An emulsion templating method was used to form micrometer-size pores. Nanometer/micrometer-size pores were formed from the olive oil/ACP-PVA gel emulsion. The blending of oils (olive oil/squalane) resulted in the formation of bimodal nanometer/micrometer-size pores.

Production and utilization of carbon fibers (CFs) and CF reinforced plastic composites have been greatly widespread because of their distinguished properties. Although recycling of post-consumer CFs is required, recycled CFs often suffer from surface defects which diminish their quality. This article presents a process that create ceramic thin layers on the CF surfaces. CFs covered with α-Si₃N₄ and β-SiC layers were prepared readily and they were characterized by significantly improved oxidation resistivity. The method would be available to recuperate properties of the recycled CFs and might convert the post-consumer CFs into value-added products.