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Because of their rapid response, high sensitivity, and excellent thermal and chemical stabilities, photochromic ceramics have attracted great potential for optical applications in anti-counterfeiting and optical information storage. However, the inferior photochromic contrast restricted the further development of photochromic ceramics. Herein, a novel modification strategy for photochromic behavior is proposed in a KSr 2 Nb 5 O 15 -based system. A new heterojunction band structure was established at the interfaces in ceramics by compositing with transition metal oxides and generated novel transition paths for the excited carriers. After compositing with the Nb 2 O 5 second phase, the photochromic contrast △ R dec was almost doubled by additional color centers from the heterojunction structure. The related mechanism was confirmed by the photochromic behavior, thermoluminescence spectra and band structure features. Moreover, rapid, convenient and reversible laser bleaching behaviors was explored, and a more flexible anti-counterfeiting method was attempted through secondary laser adjustment of the photochromic pattern. This work aims to present a new modification viewpoint into photochromic ceramics by building a heterojunction structure. [ABSTRACT FROM AUTHOR]

The Na 0.54 Bi 0.46 TiO 2.96 compound was prepared by the sol-gel means and sintered at different temperatures. The effect of sintering temperature on the electrical properties and diffusion behavior of oxygen ions was systematically studied. The bulk conductivity of Na 0.54 Bi 0.46 TiO 2.96 compound increases first and then decreases with the increase of sintering temperature. At the sintering temperature of 1273 K, the highest bulk conductivity of the Na 0.54 Bi 0.46 TiO 2.96 sample can reach up to 3.35 × 10-4 S/cm. The total conductivity of the Na 0.54 Bi 0.46 TiO 2.96 sample shows a monotonous upward trend with increasing sintering temperature. The internal friction spectrum results present that the oxygen vacancy concentration and the relaxation activation energy of the Na 0.54 Bi 0.46 TiO 2.96 sample show an upward trend, but the mobility of the oxygen vacancy diffusion decreases with the sintering temperature. The Na 0.54 Bi 0.46 TiO 2.96 sample sintered at 1273 K is characterized by a higher oxygen vacancy concentration and mobility, resulting in the high grain conductivity. [ABSTRACT FROM AUTHOR]

The electrical performance and relaxation behavior of Na+ doped BaBiNb 5 O 15 compound were investigated. The grain conductivity of the BaBi 0.96 Na 0.04 Nb 5 O 15-δ compound is 4.71 × 10−5 S/cm at 763 K, which is an order of magnitude lower than the parent sample at the same measuring temperature. The highest total conductivity of the BaBi 0.96 Na 0.04 Nb 5 O 15-δ and BaBiNb 5 O 15 sample can reach 1.12 × 10−4 S/cm and 4.0 × 10−5 S/cm at 643 K, respectively, which indicates that the slight Na+ doping can improve the total conductivity. A dielectric relaxation peak related to thermal activation was observed. The activation energy values are E = 0.47 eV for BaBiNb 5 O 15 sample, and E = 0.49 eV for BaBi 0.96 Na 0.04 Nb 5 O 15-δ sample, which indicates that the relaxation activation energy increases with the Bi3+ ions partially replaced by Na+ ions in the BaBiNb 5 O 15 compound. In addition, the oxygen relaxation peak position shifts to the low-frequency direction, which indicates that Na+ ions doping causes the decrease of oxygen vacancy mobility. The lower oxygen vacancy mobility results in the lower grain conductivity in the BaBi 0.96 Na 0.04 Nb 5 O 15-δ sample. After aging for the different time at 773 K, the excellent thermal stability of the BaBi 0.96 Na 0.04 Nb 5 O 15-δ sample can be found. [ABSTRACT FROM AUTHOR]

To address the issues of existing powder metallurgy particle reinforced composites, such as poor wettability between ceramic reinforcement and Al matrix, the toxicity of quasicrystal, the compositional limitations of high entropy alloy, and poor thermal stability of amorphous alloy reinforcement, etc. Al matrix composites reinforced with Co-based hard particles (M7) were synthesized by a powder metallurgy process. The effects of sintering temperature, M7 hard particle content, and particle size on the microstructure and mechanical behavior of the composites were investigated. The results show that as the sintering temperature rises, the interdiffusion reaction between M7 particles and Al matrix is enhanced, the diffusion layer becomes thicker, the in-situ generated intermetallic compounds such as Al 3 Ni 2 , Al 13 Cr 2 , Co 2 Al 9 and Al 72.5 Co 16.5 Ni 11 become more abundant, and parts of M7 particles gradually dissolve in the Al matrix and the interdiffusion layer disappeared. When the sintering temperature was raised from 580°C to 640°C, the microhardness and yield strength were improved from 23.9 to 34.7 HV 0.1 and 40.9–175.2 MPa, respectively. The composites' microhardness and strength increase as the M7 particle content increases. Meanwhile, the smaller the particle size, the greater the microhardness and yield strength. The strengthening mechanism of M7/Al composites is mainly attributed to the synergistic effects of the in-situ generated multiphase intermetallic compounds strengthening, solid solution strengthening, and M7 hard particles dispersion strengthening. Furthermore, the M7/Al composites' microhardness and strength were respectively 27.6% and 146.1% higher than those of the SiC/Al composites containing the same size and content of SiC particles, which is mainly due to the good interfacial wettability between M7 and Al matrix. It indicates that metal-based hard particles could be better alternative reinforcements to produce high performance composites. • Al matrix composites reinforced with Co-based hard particles were synthesized by PM. • There was a significant improvement in the mechanical properties of the M7 /Al composites. • The synergistic reinforcement mechanism for M7 /Al composites is proposed. [ABSTRACT FROM AUTHOR]

Grains of a Cu–Al–Ni–Mn–Ti shape memory alloy (SMA) were remarkably refined by the Al–La–B inoculant. Evolution of microstructures and changes of both martensitic transformation (MT) temperatures and damping property of the Cu–Al–Ni–Mn–Ti SMA were also systematically investigated. It was found that with increasing the adding amount of inoculant, the grain size decreased first and then increased, whereas the damping increased first and then decreased. When the adding amount of inoculant reached 2.5 wt%, the smallest grains and the highest damping could be obtained. The improvement of damping could be attributed to the increased density of interfaces between matensite lamellae and between twins. Moreover, with increasing the adding amount of inoculant, all characteristic temperatures of both reverse and forward MT shift to high temperature side. This could be ascribed to the decreased Al content in the Cu–Al–Ni–Mn–Ti SMA due to the formation of Al 11 La 3 phase. In addition, this is also related to the changes of the density of grain boundaries and the order degree of the Cu–Al–Ni–Mn–Ti SMA. • Cu–Al–Ni–Mn–Ti SMA were refined by Al–La–B inoculant for the first time. • Evolution rule of microstructures after grain refinement were investigated. • The damping capacity could be remarkably improved after grain refinement. • Interestingly, Ti-rich precipitated particles were covered with Al 11 La 3 band. • The related mechanisms were analyzed in detail. [ABSTRACT FROM AUTHOR]