Search

Optical transparency is of paramount importance for visual armor and certain optical devices when subjected to severe impact conditions. Shock wave loading not only generates high pressure during hypervelocity impacts but also diminishes optical transmittance. To investigate optical transparency of transparent polycrystalline ceramic under harsh shock wave compression, this study performed experimental measurements considering the grain size effect. The findings, which pertain to polycrystalline magnesium aluminate spinel (PMAS), indicate that PMAS with nano-sized grains within the 900–1500 nm wavelength range demonstrates superior optical transparency compared to conventional PMAS with micrometer-sized grains. This result highlights the excellent optical properties of nano-grain transparent ceramics and raises hopes for their widespread application at high shock pressures. [ABSTRACT FROM AUTHOR]

Shock wave is associated with dynamic loading that can result in phase transition (PT), optical and mechanical property changing, and chemical reaction on materials. Here, we report recent progress about shock-induced PT of polycrystalline iron, the underlying mechanism of the optical emission from sapphire, and the synthesis from single-phase RuSi in the National Key Laboratory of Shock Wave and Detonation Physics. Results indicated that grain boundary (GB) could affect the PT pressure threshold and rate of iron, the pressure threshold decreases with decreasing GB defects, and the PT rate shows a variation with increasing GB size; wavelength-dependent optical emissivity (non-gray-body emission) would be generated that was not revealed previously for shocked sapphire, and the observed luminescence was from the shock-induced shear bands, but without superheating phenomenon; shock compression could be an effective way to synthesis Ru-Si nanocrystals, when the shock pressure was appropriate; and Ru-Si powder could completely transform to fine-grain structure CsCl-type Ru-Si at 40.4 GPa. [ABSTRACT FROM AUTHOR]

Shock recovery experiments were performed on ruthenium–silicon powder mixtures by a flyer plate impact technique. The flyer velocities were in the range of 0.46–2.73 km/s, and the incident shock pressures were calculated to be ∼2.9–∼40.4 GPa by the impedance matching method. The recovered samples were characterized by X-ray diffraction and scanning electron microscopy. Results indicate that shock could induce a reaction between ruthenium and silicon. The shock pressure was found to affect reaction kinetics and microstructure of the recovered sample significantly. The dynamic reaction has a threshold pressure, and the samples loaded above threshold pressure almost completely reacted to a single-phase intermetallic compound of CsCl-type RuSi. These results indicate that shock compression could be an effective way to synthesize RuSi. [ABSTRACT FROM AUTHOR]

In shock wave precision physical measurements, the shock impedance of sapphire (Al 2 O 3) transparent windows and Fe samples cannot be completely matched, which seriously affects the measurement accuracy. Adjusting the components of the anion and cation in the γ-Al 2 O 3 structure is a possible solution. N3- and Mg2+ were introduced into the γ-Al 2 O 3 matrix to form Al (8+ x)/3 □ (1/3- x /3) O 4- x N x (□ denotes the vacancy, AlON) or Mg 1- y Al 2+ y O 4- y N y (MgAlON). Using the first-principles method coupled with the shock wave theory, the shock response behaviors and optical properties of AlON and MgAlON were studied in this work. Due to a more obvious effect was induced by Mg2+ than N3-, MgAlON had a wider shock impedance adjustment range compared with AlON. The simulation results of the shock pressure-particle velocity curves (σ xx -U) demonstrated that the shock impedance of MgAlON can be completely matched with that of the Fe samples in a wide pressure range (0–20 GPa) by tuning its composition. In addition, AlON and MgAlON show good transparency between 0 and 20 GPa. This discovery provides theoretical guidance for selecting transparent ceramic windows with optimized structures and compositions that match the shock impedance of the Fe samples. • A new transparent window material was found. • The shock impedance of Al (8+ x)/3 □ (1/3- x /3) O 4- x N x and Mg 1- y Al 2+ y O 4- y N y was calculated for the first time. • The shock impedance of Al (8+ x)/3 □ (1/3- x /3) O 4- x N x and Mg 1- y Al 2+ y O 4- y N y match that of Fe in a wide pressure region. • Al (8+ x)/3 □ (1/3- x /3) O 4- x N x and Mg 1- y Al 2+ y O 4- y N y has good transparency within 20 GPa. [ABSTRACT FROM AUTHOR]