Search

Mesoscale imperfections, such as pores and voids, can strongly modify the properties and the mechanical response of materials under extreme conditions. Tracking the material response and microstructure evolution during void collapse is crucial for understanding its performance. In particular, imperfections in the ablator materials, such as voids, can limit the efficiency of the fusion reaction and ultimately hinder ignition. To characterize how voids influence the response of materials during dynamic loading and seed hydrodynamic instabilities, we have developed a tailored fabrication procedure for designer targets with voids at specific locations. Our procedure uses SU-8 as a proxy for the ablator materials and hollow silica microspheres as a proxy for voids and pores. By using photolithography to design the targets' geometry, we demonstrate precise and highly reproducible placement of a single void within the sample, which is key for a detailed understanding of its behavior under shock compression. This fabrication technique will benefit high-repetition rate experiments at x-ray and laser facilities. Insight from shock compression experiments will provide benchmarks for the next generation of microphysics modeling. [ABSTRACT FROM AUTHOR]

Medium/high entropy alloys have some excellent properties, such as high strength, high plasticity, high toughness, high wear resistance, etc., which are better than those of traditional metal alloys. The mechanical properties of medium/high entropy alloys have always been the focus of academic research, but research on their interface mechanical behaviors is still missing. In this paper, we have designed a fretting friction and wear testing system, whose accuracy has been verified. A series of friction experiments have been carried out on the medium entropy alloy–steel friction pair. The friction responses have been investigated, and the factors affecting the friction coefficient have been revealed. Results show that the friction coefficient increases with the increase in the maximum horizontal displacement and decreases with the increase in the normal pressure. The sliding velocity and the normal load together affect the friction coefficient between the friction pairs. Compared with the commonly used titanium alloy and nickel alloy, the friction coefficient between the medium entropy alloy–steel friction pair is smaller during the fretting cycle process. Despite the experimental results, a theoretical model is also proposed to qualitatively explain the corresponding experimental phenomena. Our research sheds light on revealing the interfacial mechanical properties of the medium entropy alloy and provides a basis for tribological design and its internal mechanism. [ABSTRACT FROM AUTHOR]

We derive a generalized theory of a dual photoelastic modulator system designed for the measurement of the Stokes parameters of an arbitrary light beam. Based on the theory, a critique of various potential configurations that could be used to effect such measurements is presented. A calibration procedure for the entire optical system is introduced which, among other things, renders a knowledge of the frequency response of the detector system unnecessary. An analysis of the errors due to incorrect setting of optical components is presented for some of the more practical cases. This allows an assessment of the relative merit of different experimental configurations. [ABSTRACT FROM AUTHOR]

We report in this paper a generalized theory that describes the interaction between a monochromatic light beam and an optical system that includes one photoelastic modulator, one analyzer, and one photodetector. Based on the theory, a detailed four-step procedure is presented, which allows a precise measurement of the four Stokes parameters. An analysis of the systematic and random errors arising from the four-step measurements is also given as well as a calibration procedure that involves the use of a general retardation plate. As a practical application the procedure is used to analyze the magneto-optical properties of magnetic thin films grown on GaAs(001) substrates. [ABSTRACT FROM AUTHOR]

Ce-doped BaTiO[sub 3] (BTO) films were grown by pulsed laser deposition. Highly c-axis-oriented BTO:Ce/YBa[sub 2]Cu[sub 3]0[sub 7−x] bilayer structures on a SrTiO[sub 3] (100) substrate were fabricated for electrical property characterization. Typical hysteresis and butterfly type C-V plots were observed. The remanent polarization and coercive field are 3 μC/cm² and 20 kV/cm, respectively. Highly α-axis-oriented Ce-doped and undoped BTO films were also deposited on MgO(100) substrates. Their linear and quadratic electro-optic effects were measured and compared. The Ce-doped films showed a larger linear electro-optic coefficient and obvious hysteresis in the quadratic electro-optic coefficient. [ABSTRACT FROM AUTHOR]