Manipulation of Shallow-Trap States in Halide Double Perovskite Enables Real-Time Radiation Dosimetry.

Storage phosphors displaying defect emissions are indispensable in technologically advanced radiation dosimeters. The current dosimeter is limited to the passive detection mode, where ionizing radiation-induced deep-trap defects must be activated by external stimulation such as light or heat. Herein, we designed a new type of shallow-trap storage phosphor by controlling the dopant amounts of Ag+ and Bi3+ in the host lattice of Cs2NaInCl6. A distinct phenomenon of X-ray-induced emission (XIE) is observed for the first time in an intrinsically nonemissive perovskite. The intensity of XIE exhibits a quantitative relationship with the accumulated dose, enabling a real-time radiation dosimeter. Thermoluminescence and in situ X-ray photoelectron spectroscopy verify that the emission originates from the radiative recombination of electrons and holes associated with X-ray-induced traps. Theoretical calculations reveal the evolution process of Cl-Cl dimers serving as hole trap states. Analysis of temperature-dependent radioluminescence spectra provides evidence that the intrinsic electron-phonon interaction in 0.005 Ag+@ Cs2NaInCl6 is significantly reduced under X-ray irradiation. Moreover, 0.025 Bi3+@ Cs2NaInCl6 shows an elevated sensitivity to the accumulated dose with a broad response range from 0.08 to 45.05 Gy. This work discloses defect manipulation in halide double perovskites, giving rise to distinct shallow-trap storage phosphors that bridge traditional deep-trap storage phosphors and scintillators and enabling a brand-new type of material for real-time radiation dosimetry.

IBIL Measurement and Optical Simulation of the DI Center in 4H-SiC.

In this paper, DI defects are studied via experiments and calculations. The 2 MeV H+ is used to carry on an ion-beam-induced luminescence (IBIL) experiment to measure the in-situ luminescence of untreated and annealed 4H-SiC at 100 K. The results show that the luminescence intensity decreases rapidly with increasing H+ fluence, which means the losses of optical defect centers. In addition, the evident peak at 597 nm (2.07 eV) is the characteristic peak of 4H-SiC, and the weak peak between 400 nm and 450 nm is attributed to the DI optical center. Moreover, the first-principles calculation of 4H-SiC is adopted to discuss the origin of DI defects. The optical transition of the defect SiC(CSi)2 from q = 0 to q = 1 is considered the experimental value of the DI defect center.

Mechanically Robust Irradiation, Atomic Oxygen, and Static-Durable CrOx/CuNi Coatings on Kapton Serving as Space Station Solar Cell Arrays.

The polymers that served for solar cell arrays are constantly subject to various hazards, such as atomic oxygen (AO), ion irradiation, or electrostatic discharge (ESD) events. To address these issues, we fabricated and sifted CrO0.16/CuNi-coated Kapton with a gradient structure with the goal of reaching an equilibrium between AO durability and resistance. The resulting material exhibits an impressively low Ey of 6.61 × 10-26 cm3 atom-1, 2.20% of which was detected as pristine Kapton. Self-evolution of the CrO0.16 coating under 525.4 displacement per atom (dpa) Fe+ ion irradiation indicated that it can still maintain a good state of ultrafine nanocrystalline in addition to local amorphization. Its AO-based degradation and irradiation evolution are demonstrated by molecular dynamics (MD) simulations. It is mechanically robust enough to endure the cyclic folding treatments attributed to its gradient structure fabrication. Moreover, the CrO0.16/CuNi-coated Kapton exhibits alleviated electrostatic accumulation capability and sufficient conductivity. Our strategy has promising potential for creating surface protection on flexible polymers operating in the low Earth orbit (LEO).

Tribological Behaviors of Super-Hard TiAlN Coatings Deposited by Filtered Cathode Vacuum Arc Deposition.

High hardness improves the material's load-bearing capacity, resulting in the enhancement of tribological properties. However, the high hardness is difficult to achieve for TiAlN coating due to the transformation of the close-packed structure from cubic to hexagonal and the increase in the grain size when the Al content is high. In the present study, the ultrahard TiAlN coatings (hardness > 40 GPa) are successfully developed by filtered cathodic vacuum arc technology to study the effect of nitrogen flux rate on tribological behaviors. The highest hardness of 46.39 GPa is obtained by tuning the nitrogen flux rate to achieve the regulation of Al content and the formation of nanocrystalline. The stable fcc TiAlN phase is formed via the solid-phase reaction under a high nitrogen concentration, and more aluminum atoms replace the titanium atoms in the (Ti, Al)N solid solution. The high Al content of the Ti0.35Al0.65N coating has a nanocrystalline structure and the average crystalline size is 16.52 nm. The TiAlN coating deposited at a nitrogen flux rate of 60 sccm exhibits the best properties of a combination of microhardness = 2972.91 Hv0.5, H = 46.39 GPa, E = 499.4 Gpa, ratio H/E* = 0.093 and ratio H3/E*2 = 0.403. Meanwhile, the TiAlN coating deposited at 60 sccm shows the lowest average friction coefficient of 0.43 and wear rate of 1.3 × 10−7 mm3 N−1 m−1 due to the best mechanical properties.

Atomic-Oxygen-Durable and Antistatic α-AlxTiyO/γ-NiCr Coating on Kapton for Aerospace Applications.

Polymers used for the exteriors of spacecraft are always exposed to risks such as atomic oxygen (AO) or electrostatic discharge (ESD) degradation. In this work, an AlxTiyO/NiCr coating with excellent mechanical stability, AO durability, and electrostatic dissipative properties was deposited via ion implantation (IIP), filter cathode vacuum arc (FCVA), and high-power impulse magnetron sputtering (HiPIMS) on a flexible Kapton substrate. Scratch and cycle folding tests indicated good adhesion and toughness of the AlxTiyO/NiCr-coated Kapton, which were due to the gradient structure fabricated by the multitechnology combination. AO exposure tests demonstrated an extremely low erosion yield (Ey = 5.15 × 10-26 cm3 atom-1) of the AlxTiyO/NiCr-coated Kapton, only 1.72% of that observed for pristine Kapton. Moreover, Rutherford backscattering spectrometry (RBS) and Kelvin probe force microscopy (KPFM) results showed that the AlxTiyO/NiCr-coated Kapton has elevated surface electrostatic dissipative properties and sufficient conductivity. The multitechnology combination offers great flexibility for customizing the gradient structure to realize a comprehensive performance improvement. In addition, such a coating has great prospects for aerospace applications.