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Effect of temperature fields on optical properties of La <sub/>2</sub> Ti <sub/>2</sub> O <sub/>7</sub> thin films
摘要： In order to study the effect of temperature ?elds on the microstructure, optical properties and response to laser damage of La2Ti2O7 ?lms, a group of ?lms were prepared by electron beam evaporation using the same parameters on Si and fused silica substrates. Then, rapid thermal annealing at different temperatures was applied to simulate the application of a temperature ?eld. The structure, optical constants and response to laser damage of La2Ti2O7 ?lms were investigated by XPS, XRD, ellipsometry and laser damage testing. The results showed that Ti4+ is gradually converted to Ti3+ with increasing temperature resulting in a higher refractive index, larger extinction coef?cient and more serious absorption. When the temperature was higher than 800 °C, the loss of oxygen was more pronounced. The density of annealed ?lms ?rst increased and then decreased when the temperature rises from 600 to 1000 °C, and reached its maximum at 800 °C. And the crystallization, oxygen loss and densi?cation were found to be related to the laser damage threshold of La2Ti2O7 ?lm. The laser damage threshold of the ?lm decreased sharply when the temperature is above 900 °C.
关键词： temperature ?eld,optical properties,La2Ti2O7 ?lm,laser-induced damage
更新于2025-09-23 15:21:21
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Temperature Gradient Designing and Optical Properties of SrI2 and SrI2:Eu Crystals Grown by Edge-Defined Film-Fed Growth (EFG) Method
摘要： In this work, SrI2 and SrI2:Eu5% single crystals with size of ?10 9 60 mm3 and ?10 9 30 mm3 were successfully grown by edge-de?ned ?lm-fed growth (EFG) method. In the crystal growth process, the crack and turbidity of the crystal were solved by designing a temperature ?eld, thereby optimizing crystal quality and obtaining crack-free crystals. X-ray diffraction analysis was performed on the grown crystals, and the optical properties of these crystals have been investigated at room temperature. Under the excitation of ultraviolet (UV) light, the crystals exhibit a single luminescence peak centered at 435 nm (kex = 350 nm), and the photoluminescence (PL) decay time is 0.594 ls. In addition, the designed temperature ?eld also provides a reference value for other crystals grown by EFG method.
关键词： Crystal growth,temperature ?eld,scintillation materials,optical properties
更新于2025-09-10 09:29:36
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Finite Element Simulation of Temperature and Stress Field for Laser Cladded Nickel-Based Amorphous Composite Coatings
摘要： In this paper, a nickel-based amorphous composite coating was obtained on the carbon steel surface by the laser cladding process. The thermal ?eld and stress distribution were simulated by using ANSYS ?nite element software where the moving heat source and powder feeding were modelled by the “Element birth and death” method. The simulation results were veri?ed by comparing the cross-sectional pro?le of fusion lines and X-ray stress measurements, respectively. The results on thermal ?eld showed that the cooling rate of the coating could reach up to 10389.15 K/s and it gradually decreased from the outside surface to the interior, which promoted the formation of amorphous phase. The simulated stress ?eld showed that the coating was in the state of tensile stress after cladding and the longitudinal stress was larger than the transverse stress. The coating was experienced with tensile plastic deformation along the laser scanning direction, which resulted in longitudinal residual stress. A higher stress concentration was occurred between the coating layer and substrate, which increased the susceptibility of crack formation. The test results on transverse residual stress were generally consistent with the simulation. On the contrary, the measured longitudinal stress was nearly close to zero, which was not in agreement with the model due to the formation of cracks.
关键词： stress ?eld,temperature ?eld,laser cladding,amorphous,numerical simulation
更新于2025-09-04 15:30:14