Innovative mechanoluminescent (ML) particles emit light repeatedly in response to small stresses applied, such as
deformation, friction, or impact. When dispersedly coated on a structure, each particle acts as a sensitive mechanical
sensor, while the 2-dimentional emission pattern of the whole assembly reflects well the dynamical stress distribution
inside the structure and mechanical information around crack and defect. Thus, we have applied the remarkable strong
points of ML sensing technique to a bridge in use as a real social structure for the first time. For the first ML monitoring
test at bridge, we selected a relatively old bridge (established in 1954, 3-span continuous T-type RC bridge, length 24.4
m, width: 7.89 m). The ML sheet type sensors were put around the central area (700×400 mm) of the main girder, and
ML images originated from dynamic load application via general traffic vehicles had recorded by using lab-made CCD
camera under roughly dark condition. As the result, we successfully detected intense ML patterns not only along visible
crack but also at round soundless part on the girder at a glance with responding ML intensity reflecting the crack mouth
opening displacement (CMOD) of visible crack and invisible progressing microcrack.
Mechanoluminescence (ML) materials have recently attracted considerable attention due to their potential applications as
an imaging sensor for detecting damages and measuring stress distributions in complex structures, which is difficult for
conventional methods. SrAl<sub>2</sub>O<sub>4</sub>:Eu<sup>2+</sup> (SAOE) is a ML material with the best performance but it hydrolyzes rapidly under
humid environment, which limits the scope of its applications especially in outdoor environments, e.g. structural health
monitoring for buildings, bridges and tunnels. Thus ML materials with water resistance such as silicates and
aluminosilicates have been developed, but the brightness of which is still much lower than SAOE. In this study, we
report a novel method to improve the impact-induced ML in ML materials using the swift heavy ion (SHI) irradiation.
The impact-induced ML intensity of CaSrAl<sub>2</sub>Si<sub>2</sub>O8:Eu<sup>2+</sup> was dramatically enhanced by about one order of magnitude
using SHI irradiation. Furthermore, higher electronic stopping power and higher irradiation fluence were found to be
more effective for improving the impact-induced ML. It is considered that the trap density suitable for the impactinduced
ML was increased by the SHI irradiation, resulting in the impact-induced ML enhancement. The underlying
mechanism was discussed, which is of great importance for developing new ML materials for structure health
Full-field measurement of dynamic stress has been realized by coating the surface of the test object metal with a upgrade
mechanoluminescence sensing film of SrAl<sub>2</sub>O<sub>4</sub>:Eu (SAOE). Mechanoluminescent materials are attractive smart materials
that can emit light induced by mechanical deformation. The ML sensing film of SAOE has been developed to make
possible to visualize dynamic stress. Consequently this visualization technique has been become a promising
experimental technique to investigate full-field stress analysis.
In this paper we report the applications of the SAO ML sensing film for full-field stress analysis in aluminum alloy 5052
samples. Using the SAOE ML sensing film, the stress concentration produced by a circular hole was observed with the naked eyes
in real time and the two-dimensional stress distribution was quantitatively measured; the complex and dynamic Portevin-Le Chatelier
(PLC) effect, known as instability during plastic deformation, has been visualized, and the propagating characteristics of PLC
bands were precisely investigated.
We developed an AFM-based new apparatus with a photomultiplier in order to measure the weak light emission
from a single microparticle induced by applying a micro force and measured the emission intensity as a function of the
applied micro force and speed. The emission intensity was approximately proportional to the speed of the applied micro-
force and the square of the micro stress.
This investigation deals with determination of optical parameters of thin PLZT films prepared by pulsed laser deposition on fused silica substrates at different oxygen pressure. Film composition and structure are investigated by WDX and XRD. Defects concentration in the films is studied using triboluminescence. Changes of film refractive index n((lambda) ), extinction k((lambda) ) with wavelength in the spectral region 0.3 - 1.1 micrometers and film thickness d are determined as a result of transmittance spectra processing. Waveguiding properties of the films are investigated.
We have investigated the effect of ZnO films used as buffer layers on the triboluminescence (TrL) intensity of ZnS:Mn thin films on quartz substrates using RF magnetron sputtering method and annealing technique. Highly oriented film of ZnO was firstly deposited on quartz glass substrate and then the ZnS:Mn film was successfully deposited on the ZnO film with orientation. By annealing at 5% H<SUB>2</SUB> in Ar ambient, the crystallinity of both ZnO and ZnS:Mn films was increased. It was found that the addition of the ZnO buffer layer greatly improve the TrL intensity of the ZnS:Mn films.
Mechanoluminescence (ML) materials are known to emit light due to the application of mechanical stress. The ML responding to elastic deformation, plastic deformation and fracture is referred here as elasoticoluminescence, plasticoluminescence and fractoluminescence, the former two belong to non-destructive ML and the later belongs to destructive ML. Until now, the destructive ML has been observed in various inorganic and organic materials, whereas the non-destructive ML has been found in very limited cases. No practice application of non-destructive ML has been realized so far. On the other hand, ML material as it transfers a mechanical stress into a light emission, is believed to be a new smart material for various mechano- optical applications. Recently we have done a series research on ML both in fundamental and application aspects. This paper focuses on the investigation of elastico- luminescence. The results of the present work reveal that the ML coatings on the surface of solid can direct display the stress distribution by a mechanolumnescnce image.
The PLZT (7/60/40) thin films were prepared on ITO/Glass and LNO/Glass substrates by sol-gel process. The crack-free, uniform and dense films were obtained by post-annealing at the temperature between 450 degree(s)C and 600 degree(s)C. Pyrochlore phase was completely changed to perovskite phase above 570 degree(s)C with the increase of annealing temperature. The crystal buffer layer of ITO or LNO can promote the growth of perovskite. Films deposited on LNO/Glass substrates possesses good ferroelectric characteristics, P<SUB>r</SUB> equals 18 (mu) C/cm<SUP>2</SUP>, E<SUB>c</SUB> equals 55 kV/cm. The asymmetrical switching characteristics can be observed for the films deposited on LNO/Glass substrates, which is mainly due to the difference between top electrode Au and bottom electrode LNO.
The temperature dependence of photoluminescence (PL) of rare- earth ions activated Y<SUB>2</SUB>SiO<SUB>5</SUB> was investigated from room temperature to 573 K. Ion activators such as Eu<SUP>3+</SUP>, Ce<SUP>3+</SUP>, Sm<SUP>3+</SUP>, Tb<SUP>3+</SUP>, Tm<SUP>3+</SUP> and some of their combinations were studied in this work. The most efficient blue, green and red phosphors at elevated temperature were found by doping the (Ce<SUP>3+</SUP> + Tb<SUP>3+</SUP>), Tb<SUP>3+</SUP> and Eu<SUP>3+</SUP> respectively, in this material system. Meanwhile, the relationship between the unit cell volume of Re<SUB>x</SUB> Y<SUB>2-x</SUB>SiO<SUB>5</SUB> and the temperature dependence of PL was also revealed.
We report the realization of the dynamic image of stress distribution by developing a remarkably strong mechanoluminescence (ML) material of Sr<SUB>0.975</SUB>Al<SUB>2</SUB>O<SUB>3.985</SUB>:Eu<SUB>0.01</SUB>(SAO- E), which can emit four orders of magnitude larger intensity than that of the reported strong ML material of quartz crystal. This ML material can be mixed in the target composite or coated on the surface to sense stress by emitting visible light. This method is applicable to the dynamic visualization of stress distribution in a solid not only in the atmosphere but also in an aqueous environment. A simulation result confirms that such a ML image successfully reflects the stress distribution. A kinetic model for ML of SAO-E is proposed.
We have investigated the triboluminescence (TrL) intensities of as-grown and thermally annealed ZnS thin films doped with manganese on quartz substrates. The ZnS:Mn thin films were deposited by rf magnetron sputtering and thermally annealed in a reducing gas (5% H<SUB>2</SUB>/Ar) at 500 degrees Celsius, 600 degrees Celsius, 700 degrees Celsius and 800 degrees Celsius. The crystallinity and the triboluminescence intensities of the films were greatly enhanced by postannealing up to 700 degrees Celsius, accompanied by an increase in the adherent strength of the film. An X-ray diffractometer and a Scratch Adhesion Tester were used to study the crystallinity and adhesion of the as-grown and annealed films respectively. Results based on crystallographic and acoustic emission data were used to explain the failure mechanisms in the films during the triboluminescence measurement.