Papers by Author: Lin Zhang

Abstract: Recently we demonstrated that CaAl2Si2O8: Eu2+ showed novel strong mechanoluminescence (ML). In order to improve the mechanoluminescence intensity, we partly substituted the Ca2+ ions by Sr2+ ions. It was found that the ML intensity was enhanced about three times as great as the one of CaAl2Si2O8: Eu2+ by substituting 40% of Ca2+ ions to Sr2+ ions. Furthermore it was revealed that the main peaks in XRD pattern shifted to lower angle side and the emission peak shifted to a short wavelength from 428 to 418 nm, indicating that the substitution resulted in the cell volume expansion and the change of luminescent color. Based on the results of thermoluminescence and electroluminescence measurements, the possible mechanisms for the improvement of ML intensity were proposed.

Abstract: We have demonstrated a novel blue-violet emitting mechanoluminscent(ML) material with calcium aluminosilicate(CaAl2Si2O8:Eu2+). The ML was clearly visible to the naked eye in the atmosphere and showed a similar spectrum to photoluminescence with a peak at 430nm. In order to enhance the ML intensity, various rare earth ions were selected as co-dopants including La, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. It was found that the intensity of ML was strongly dependent on the kinds of the codoped rare earth ion, especially the co-doping of Ho3+ was found to greatly enhance the ML intensity. From the results of thermoluminescence(ThL) measurements, the enhancement of the ML intensity was closely related with the filled trap concentration and trap depth.

Abstract: Dynamic visualization of stress distribution even due to a small deformation has been realized by coating the surface of the test object of metal with a upgrade mechanoluminescence (ML) material of SrAl2O4:Eu (SAO). In this paper we report the application of this ML sensing technique to stress concentration analysis on an aluminium plate. And the comparison with a theoretical calculation demonstrated that the ML intensity of SAO sensing film correlates linearly with von Mises stress on metal surface and the observed real-time ML images quantitatively reflect stress concentration.

Abstract: In this paper, we demonstrate that a dynamic stress concentration around Lüders band can be directly displayed using mechanoluminescence (ML) sensing film of SrAl2O4:Eu (SAO) coated on the surface of metal. Uniaxial tensile test of an aluminum alloy (2.5% Mg) plate coated with the SAO sensing film was performed and the ML images were recorded using a high-speed camera. Captured ML images confirmed the formation and propagation of Lüders band clearly in real time.

Abstract: We have successfully developed a multifunctional ceramics, europium-doped feldspar MAl2Si2O8:Eu (MASE, M=Ca, Sr, Ba) and demonstrated that MASE was able to emit high mechanoluminescence (ML), strong photoluminescence (PL) and electroluminescence (EL). According to the XRD measurement result, the space group of MASE was identified to P1 .The ML intensity increased proportionally with the increase of the compressive load, which suggests an efficient conversion of mechanical to optical energy. Furthermore, strong PL and EL emission from MASE were confirmed. The PL, ML, and EL spectra were found to be similar in both peak shape and position, which indicates all the emissions result from 5d-4f transition of Eu2+.

Abstract: We have successfully demonstrated that the stress distribution of a metal substrate can be directly displayed by coating SrAl2O4:Eu (SAO), a representative of strong mechanoluminescent materials, on the surface of test objects. An aluminum plate with SAO sensing film had been applied to experimental analysis of stress concentrations, and a numerical calculation via a finite element method confirmed that the observed real time mechanoluminescence images displayed the stress distribution. As a result, visualization of stress distribution on metal surface has been realized by ML images using SAO sensing film, and this novel visualization technique can be applied for viewing the stress concentration in various fields such as modeling, manufacturing and demonstration of an industrial product.

Abstract: We successfully developed a novel elasticoluminescent (EML) material with water resistance, CaAl2Si2O8:Eu2+ (CAS). The crystal structure, photoluminescence (PL) and EML properties were characterized for both CAS and the typical EML material SrAl2O4:Eu2+(SAO). Contrary to SAO, CAS showed superior water resistance property. No changes were found in the XRD patterns, and the PL, EML intensities, during the whole examination of water immersion test.