Irradiation response of Al2O3-ZrO2 ceramic composite under He ion irradiation

The dense Al₂O₃-ZrO₂ ceramic composite prepared by spark plasma sintering was irradiated by 500 keV He ions with different fluences and temperatures. The microstructural evolution and mechanical properties were investigated. The results showed that peak broadening and shifts at RT revealed by GIXRD and Raman are associated with damage induced microstrain and formation of point defects. The recovery at 500 °C suggested the reduction of irradiation induced damage. Compared with α-Al₂O₃, t-ZrO₂ exhibited a reverse trend in lattice parameters change and lattice expansion. Many helium bubbles with oblate and ribbon-like shape were mainly formed in α-Al₂O₃ grains at He concentration peak at 1.0 × 10¹⁷ ions/cm². With increasing of fluence at RT, ribbon-like helium bubbles developed into microcracks at 4.0 × 10¹⁷ ions/cm². Though evident structural changes, no full amorphization was observed at 4.0 × 10¹⁷ ions/cm². Formation of ribbon-like bubbles and microcracks is the main mechanism for degradation of mechanical properties of irradiated Al₂O₃-ZrO₂ composite.     

The damage evolution of He irradiation on Ti3SiC2 as a function of annealing temperature

The radiation damage response of Ti₃SiC₂ irradiated by 110 keV helium ions at room temperature (RT), the subsequent evolution of damage including helium bubble growth as a function of annealing temperatures are investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and transmission electronic microscopy (TEM). In addition to collision cascade effects leading to TiC nanocrystal formation near the surface of Ti₃SiC₂, He ion irradiation produces damage due to the growth of He bubbles, which cause a structural transformation into a large grain TiC crystalline phase at high temperatures. The displacement of matrix Si atoms adjacent to the He bubbles along the Si layer in Ti₃SiC₂ either via bubble growth or the production of inter-bubble fracture is the reason for the structural transformation. Depending on the He damage level, a significant recovery of the He irradiation damage can occur at moderate temperatures. This property may play a positive role in the damage resistance of Ti₃SiC₂, making it a potential candidate for future nuclear reactor applications.     

Preparation of Li2TiO3 by hydrothermal synthesis and its structure evolution under high energy Ar+ irradiation

Ultrafine lithium titanate (Li₂TiO₃) powder was synthesized by hydrothermal method. The phase formation and transition condition among α, β, and γ-Li₂TiO₃ were discussed. XRD and ICP-AES showed the single α-phase was formed at 180 °C with 2 h hydrothermal reaction, and it transited into β-phase at 400 °C. SEM observation and EDS analysis confirmed the dissolution of TiO₂ and the formation of α-Li₂TiO₃ proceeded simultaneously with preferable growth direction of (-133) lattice. During the phase transition, the powder maintained the small crystallite, which facilitated the fabrication of Li₂TiO₃ bulk with small grain size. After the Ar⁺ irradiation, the surface region to the depth of 3 μm of Li₂TiO₃ ceramic was affected, where the decrease of crystallization and disturbance of short-range order were confirmed by GIXRD and Raman spectroscopy. In spite of the structure change at the surface area, the ceramic bulk maintained the same.     

Phase Transformation of Iron Oxide Nanoparticles by Varying the Molar Ratio of Fe2+:Fe3+

Co‐precipitation from a solution of ferrous/ferric mixed salt with the ratio of Fe²⁺:Fe³⁺ = 1:2 in air atmosphere is not a reliable method to synthesize magnetite (Fe₃O₄) nanoparticles because of the fact that Fe²⁺ oxidizes to Fe³⁺ and the molar ratio of Fe²⁺:Fe³⁺ changes. Therefore, the phase composition changes from magnetite to maghemite (γ‐Fe₂O₃). The influence of the initial molar ratio of Fe²⁺:Fe³⁺ on the phase composition of nanoparticles, their crystallinity and magnetic properties was studied. Experimental data from XRD, FTIR, SEM, and VSM reveal that the appropriate method to synthesize magnetite nanoparticles is reverse precipitation from only ferrous salt. It is found that by decreasing the synthesis temperature and by increasing the concentration of alkaline solution and the ratio of Fe²⁺:Fe³⁺ the crystallinity and the specific saturation magnetization (σ_s) are increased.     

In-situ TEM investigations on the microstructural evolution of SiC fibers under ion irradiation: Amorphization and grain growth

SiC/SiC composites are attractive candidates for many nuclear systems. As reinforcements, SiC fibers are critical to the in-service performance of composites. In this work, the temperature effects on the irradiation-induced microstructural evolution of Cansas-III SiC fibers were investigated using in-situ transmission electron microscopy (TEM). With in-situ 800 keV Kr ion irradiation, at room temperature (RT) the SiC fiber experienced heterogeneous amorphization and became completely amorphous at ～2.6 dpa. Above the critical temperature of crystalline-to-amorphous (T_c), SiC fibers underwent a simultaneous process of carbon packet disappearance and nano-grain growth at 300 °C and 800 °C. Possible mechanisms were discussed.     

Domain evolution and phase transition dynamics of BaTiO3 ferroelectric single crystal under high pressure with various loading methods: Phase field simulation

The microstructure and macroscopic properties of ferroelectric materials at high pressure are of great interest in both the engineering and scientific arenas. The effect ofthe pressure value, loading time (the time taken for the pressure to increase from atmospheric pressure to the highest pressure) and loading direction on the evolution of domains and the ferroelectric phase transition for a BaTiO₃ single crystal was investigated using a phase field approach. It was found that under symmetrical compression loading the pressure loading time affected the phase transition path and rate but did not affect the phase transition pressure or the ultimate stable phase. For example, at room temperature, even when the loading time increased from 1 ns to 10 μs, the phase transition pressure remained stable at 2.1 GPa, but the phase transition time was prolonged. At −70 °C the orthorhombic–cubic phase transition was induced when the loading pressure was 5 GPa and the loading time was 1 ns, whereas the orthorhombic–tetragonal–cubic phase transition occurred when the loading time increased to 10 μs. In addition, it was found that the application of symmetrical pressure tended to reduce the degree of ferroelectricity, while one-dimensional compression favored the ferroelectric phase.     

Synthesis of novel p-n heterojunction Cu2SnS3/Ti3+-TiO2 for the complete tetracycline degradation in few minutes and photocatalytic activity under simulated solar irradiation

In this research work, p-n heterojunction Cu₂SnS₃/Ti³⁺-TiO₂ photocatalysts were synthesized by using a facile hydrothermal method to degrade tetracycline and produce hydrogen energy. The properties of Cu₂SnS₃/Ti³⁺-TiO₂ was analyzed by using XRD, SEM, TEM, HRTEM, BET, PL and UV–vis characterization. The HPLC-MS and TOC analyzer systems were used to analyze the intermediate products during the photocatalysis deprivation and total organic carbon. The characterizations showed that the addition of self-doped Ti³⁺ and Cu₂SnS₃ into TiO₂ enhanced the material's crystallinity, increased the absorption region from 450 nm to 750 nm, increased the surface area of the material from 234 to 583 m²/g and reduced the recombination of charge carriers. Under visible light irradiation, Cu₂SnS₃/Ti³⁺-TiO₂ exhibited excellent degradation performance and stability. The increase in the efficiency of the material is due to the creation of an internal electric field induced by the p-n heterojunction and reduction in the bandgap of the material, which efficiently reduced the rate of recombination, increased the surface area for light absorption and increased the transfer of charge carriers. The Cu₂SnS₃/Ti³⁺-TiO₂ photocatalyst degraded 100 % tetracycline and produced 510 μmol/hg hydrogen energy. The Cu₂SnS₃/Ti³⁺-TiO₂ composite exhibited good stability even after six cycles Cu₂SnS₃/Ti³⁺-TiO₂ degraded 98–99 % TC under visible light irridiation. The efficiency of Cu₂SnS₃/Ti³⁺-TiO₂ was also analyzed in the outdoor environment, confirming that this material can be effectively used in practical applications.