Papers by Keyword: Triboluminescence

Abstract: Mechanism of mechanoluminescence of the composite of Mn-doped ZnS particles and polyester resin is developed based on the principle of Fermi-level shift, associated by piezoelectric effect. As the electron-hole recombination is responsible for light emission, it is possible to determine the number of emitted photons from the difference in number of conducting electrons between the stressed state and the thermal equilibrium condition. For the given emission color, characteristics of photomultiplier tube and deformation conditions, the emitted photons can be approximated. The model is expressed as A[exp (Bσ²) - 1] where σ is the applied stress, a pre-exponential A illustrates the efficiency of luminescent centers and the influences of dielectric and piezoelectric constants of ZnS host and temperature are displayed as the exponent factor B.

Abstract: Triboluminescence properties of chemical compound based on Terbium (III) - Tb (АА)₃Phen - are studied by means of new experimental technique developed in this work. It is found that the synthesized complex manifests 20% higher integral intensity of triboluminescence in comparison with that for compound based on Europium (III) –ТЕА[Eu (DBM)₄] which is one of best triboluminophores in the visible spectral range.

Abstract: The present paper reports both the experimental and mathematical aspects of elastico-mechanoluminescence (EML), plastico-mechanoluminescence (PML) and fracto-mechanoluminescence (FML) of coloured alkali halide crystals in detail, and thereby provides a deep understanding of the related phenomena. The additively coloured alkali halide crystals do not show ML during their elastic and plastic deformation. The ML emission during the elastic deformation takes place due to the mechanical interaction between bending dislocation segments and F-centres, and the ML emission during plastic deformation takes place due to the mechanical interaction between the moving dislocations and F-centres. The ML emission during fracture is also caused by the mechanical interaction between the moving dislocations and F-centres; however, in certain hard crystals like LiF, NaCl, NaF, etc., fracto ML also occurs due to the gas discharge caused by the creation of oppositely charged walls of cracks. The EML, PML, and solid state FML spectra of coloured alkali halide crystals are similar to their thermoluminescence spectra and afterglow spectra. However, the fracto ML spectra of certain hard crystals like LiF, NaCl, NaF, etc., also contain gas discharge spectra. The solid state ML spectra of coloured alkali halide crystals can be assigned to deformation-induced excitation of halide ions inV₂-centres or in other hole-centres. Whereas, the intensity of EML and FML increases linearly with the applied pressure and the impact velocity, the intensity of PML increases quardratically with the applied pressure and the impact velocity because of the plastic flow of the crystals. Both I_m and I_T increase with the density of F-centres in the crystals and strain rate of the crystals; however, they are optimum for a particular temperature of the crystals. The ML of diminished intensity also appears during the release of applied pressure. Expressions are derived for the elastico ML, plastico ML and fracto ML of coloured alkali halide crystals, in which a good agreement is found between the experimental and theoretical results. Many parameters of crystals such as band gap between the dislocation band and interacting F-centre energy level, radius of interaction between dislocations and F-centres, pinning time of dislocations, work hardening exponent, velocity of cracks, rise time of applied pressure, lifetime of electrons in the dislocation band, lifetime of electrons in shallow traps, diffusion time of holes, critical velocity of impact, etc., can be determined from the ML measurements. The ML of coloured alkali halide crystals has potential for self-indicating method of monitoring the microscopic and macroscopic processes; mechanoluminescence dosimetry; understanding dislocation bands in crystals; interaction between the dislocations and F-centres; dynamics of dislocations; deformation bleaching of coloration, etc. The ML of coloured alkali halide crystals has also the potential for photography, ML memory, and it gives information about slip planes, compression of crystals, fragmentation of crystals, etc.Contents of Paper

Abstract: Material properties in the process of tribo-emission decides the characteristics of both spectra and intensity of triboluminescence. ZnS:Mn semiconductor material was proved to be a high emission triboluminescent material in many investigations; Ce- and Yb-doped hexacelsian possess the excellent shortwave triboluminescence character due to f-d electronic transition of doping element with position valances ions; the fracto-mecha-luminescence and photoluminescence spectra of phthalic acid, 4-hydroxy coumarin monohydrate, etc. present obviously a broad ultraviolet and violet waveband emissions, showing the disadvantage of these organic crystals as shortwave triboluminescence materials. Triboluminescence test apparatus of drop tower type have the tribo-emission of impact friction effect; the pin-on-disk type apparatus can perform the triboluminescent experiments with sliding friction mechanism; the twin ring tribometer is used to measure the triboluminescence of polymer material friction rings. These units supply a suitable conditions for obtaining triboluminescence with shortwave emission and persistent high intensity.  

Abstract: SrAl2O4:Eu films on an inconel 600 substrate with good adhesion were successfully prepared by the radio frequency sputtering method. The crystallinity and surface morphology of the SrAl2O4:Eu films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM). The films exhibited an intensively green photoluminescence (PL) and high triboluminescence (Tribo-L) intensity.

Abstract: Strongly adherent SrAl2O4:Eu films were fabricated on the rough surface of an alumina substrate by a combination of the RF magnetron sputtering technique and a post-annealing treatment. A crystalline SrAl2O4:Eu2+ film was achieved after annealing at 1000°C in reduced atmosphere and it exhibit a intensively green PL and triboluminescence (TL) while an as-deposition film showed the amorphous state and weakly red photoluminescence (PL). It was found that the fabricated films possessed a strong durability of a friction, exhibiting no peeling, cracking, and breaking in the films after TL measurements. These results will facilitate a development of novel TL skin sensors.