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The effects of the rolling process and microstructure on the brittle crack initiation and arrest of marine steel were systematically investigated. The microstructures of two steel plates produced by different rolling processes were observed and analyzed. The results demonstrated that the rolling process significantly influenced the microstructure. As the rolling temperature decreased, the grain size decreased, the high‐angle grain boundary (HAGB) content increased, and the average grain misorientation angle increased. The brittle crack initiation and the arrest abilities were evaluated by initiation fracture toughness and crack arrest toughness, respectively. The initiation fracture toughness and crack arrest toughness increased with the decreasing grain size and the increasing content of HAGBs. Finally, the influence of microstructure on the brittle crack initiation and arrest ability was explained from two aspects: (1) the critical event of crack initiation at low temperatures, and (2) the hindering effect of HAGB on the propagation of brittle cracks. Highlights: The average grain size decreased with the decreasing rolling temperature.The high‐angle grain boundary content and the grain misorientation angles increased with the decreasing rolling temperature.The critical fracture stress increased with the decrease in the critical crack size.The high‐angle grain boundary altered the brittle crack propagation path and improved the crack arrest ability. [ABSTRACT FROM AUTHOR]

Bismuth layer‐structured ferroelectrics (BLSFs) are promising candidates for a variety of applications because of their high Curie temperature and environmentally benign nature as compared to their lead contained counterparts. Featured by the mica‐like grain growth habit and spontaneous polarization along crystallographic a‐b plane, it is difficult to obtain excellent ferroelectric properties for most of the BLSFs fabricated by the conventional ceramic route. Herein, a new approach is reported to obtain Bi2WO6 and Bi4Ti3O12 BLSF ceramics with non‐sheet‐like polyhedral microstructures. The intriguing ferroelectric hysteresis behavior, dielectric tunability, and domain structures are successfully observed. The Bi2WO6 ceramic with a unique single‐domain structure in each grain shows a typical ferroelectric polarization‐electric field hysteresis loop with a remnant polarization of ~17.8 μC cm−2 and a coercive field of ~43 kV cm−1. These values have never been obtained in Bi2WO6 ceramics with sheet‐like microstructure. The Bi4Ti3O12 ceramic with irregular‐shaped and curved tiny domains exhibits an antiferroelectric‐like behavior, which is significantly different from the reported Bi4Ti3O12 counterparts that have plate‐like anisotropic grains. The present study would stimulate microstructure design and property modulation for other layer‐structured materials. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped BaTiO3 (BT) ceramics were produced by the solid‐state reaction method in conjunction with ammonia gas treatment. The optical absorption spectra results show that the bandgap of BT ceramic is narrowed after N‐doping, suggesting that the N‐doping is an effective route to increase light absorption. Polar properties measurements indicate that the ferroelectricity of BT ceramic is well maintained after the N‐doping. In addition, the electric‐field–induced strain is prominently improved to ~0.8% after N‐doping, a value superior to that of PZT. Furthermore, the influence of N‐doping on photoelectric properties of BT ceramics was also investigated. Large increase in photoconductivity and fast response to light illumination conditions were observed in N‐doped BT ceramics. This work provides a novel route to enhance the (photo)electric properties of ferroelectric materials. [ABSTRACT FROM AUTHOR]

Nanocrystalline Ni1− x Zn x Fe2 O4 (0 ≤ x ≤ 1.0) powder with grain size of 30 nm was prepared using the spraying-coprecipitation method. The obtained nanocrystalline Ni1− x Zn x Fe2 O4 powder was sintered using conventional and microwave sintering techniques. The results show that the microstructure and magnetic properties of the sintered samples are obviously improved by microwave sintering of nanocrystalline Ni1− x Zn x Fe2 O4 ferrite powder. The initial permeability of Ni1− x Zn x Fe2 O4 ferrite increases with the increase in zinc concentration, although its resonance frequencies shift from high frequency to low frequency. The maximum initial permeability for microwave-sintered Ni0.4 Zn0.6 Fe2 O4 ceramic obtained at the temperature of 1170°C for 30 min reaches up to 360.9, and its resonance frequency is ~10 MHz. It may be attributed to the nanocrystalline Ni1− x Zn x Fe2 O4 raw powder as well as the microwave sintering process, which results in a synergistic effect on improvement of the microstructure and magnetic properties. [ABSTRACT FROM AUTHOR]

α-SiAlON/α-SiC composites with 0-40 wt% α-SiC were synthesized by spark plasma sintering for 5 min at 1800°C under 20 MPa pressure. A self-reinforcing microstructure with both elongated α-SiAlON and α-SiC grains, was formed. Flexural strength and fracture toughness were significantly improved due to the in situ reinforcement. High fracture toughness up to 8.2 MPa ∙m1/2 was obtained in the 40 wt% SiC composition. [ABSTRACT FROM AUTHOR]

The TaC0.7 composition was spark plasma sintered (SPS) at 1600°-1900°C using TaC and Ta as the starting powders. Densification process, phase evolution, microstructure development, and the mechanical properties of the composites were investigated. The results indicated that the TaC0.7 composition could be SPS to >95% of theoretical density in 5 min at 1600°C or above. The phase formation was associated with carbon diffusion from the starting particles TaC to Ta to form Ta2C and Ta6C5 as intermediate phases, and subsequently the equilibrium phases of TaC y and ζ-Ta4C3− x. The presence of lamellar ζ-Ta4C3− x regions enhanced the flexure strength (up to 972 MPa) and fracture toughness (up to 13.8 MPa·m1/2). [ABSTRACT FROM AUTHOR]