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Excellent exciton luminescence of CsPbI3 red quantum dots in borate glass
摘要： We have fabricated CsPbI3 perovskite quantum dots in a borate glass by melt-quenching technique. Three representative samples with different treatment conditions are investigated. As treatment condition enhances, energy gap is extracted as 1.75-1.76eV, and photoluminescence peak is adjustable from 675 to 691nm. Full width at half-maximum (FWHM) varies from 43 to 37 nm. PL intensity first increases and then decreases with increasing excitation wavelength, but the peak wavelength and line-shape are independent. High PLQY values of 23.8%-61.4% are obtained. The high PLQY values are attributed to good crystal quality and less energy dissipation. PL lifetime is fitted as 24.0-28.2ns and 100.2-123.0ns for short and long lifetime components in bi-exponential function. For temperature from 25 to 125 oC, PL intensity decreases, but it is reversible. Exciton binding energy is extracted in the level of 375-454meV. The FWHM broadening from 39 to 49nm and peak blue-shift from 690 to 685nm are investigated.
关键词： Photoluminescence quantum yield,Lifetime,CsPbI3,Temperature dependence,Quantum dots glass,Exciton
更新于2025-11-14 15:23:50
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Enhanced green photoluminescence of erbium doped Zn2SiO4 glass-ceramics as phosphor in optoelectronic devices
摘要： This paper reported the fabrication of Er3+-doped zinc silicate (Zn2SiO4:xEr3+) glass-ceramics using recycle waste glass bottles. The glass-ceramics samples were synthesized with different percentage doping of Er2O3 using conventional melting and quenching method. The structural of α-Zn2SiO4:Er3+ crystal phase and microstructure growth were analysed via X-ray diffraction and field emission scanning electron microscopy, respectively. Fourier transform infrared spectroscopy has confirmed the network structure of α-Zn2SiO4:Er3+ crystal phase. The three excited transition states from UV-visible absorption spectra were enhanced significantly at the states 4F7/2, 2H11/2, 4F9/2. The wide-ranging green emission at around 553-559 nm under excitation 385 nm from α-Zn2SiO4:Er3+ crystal exhibit the energy transition of Er3+ ions from 4S3/2 → 4I15/2. Such luminescence of α-Zn2SiO4:Er3+ based glass-ceramics are probably to have a huge prospective application for glass phosphor devices.
关键词： emission,phosphor,zinc silicate,waste glass,glass-ceramic
更新于2025-09-23 15:23:52
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Fast-curing halogen-free flame-retardant epoxy resins and their application in glass fiber-reinforced composites
摘要： A series of novel fast-curing halogen-free flame-retardant epoxy resins were formulated and used to prepare glass fiber-reinforced composites. Dynamic mechanical analysis showed that the optimized epoxy system could be completely cured in 0.5 h at 150°C and had a glass transition temperature (Tg) of above 130°C. The optimized epoxy system was also used as matrix resin to make glass fiber prepregs and composite panels. The flame-retardant properties of the glass fiber-reinforced composites were investigated, including the limiting oxygen index (LOI) and flaming, smoke and toxicity properties. The glass fiber-reinforced composite had good flame retardancy with a UL-94 V-1 rating and high LOI of ≥36%. More significantly, the composite based on the flame-retardant epoxy resin showed lower smoke density compared with those based on phenolic resins. Finally, the glass fiber prepregs were used to fabricate honeycomb sandwich composites. The peel strength of the epoxy-based composites was almost twice that of the composites based on phenolic resin.
关键词： prepregs,fast cure,glass fiber-reinforced composites,halogen-free flame retardancy,epoxy resins
更新于2025-09-23 15:23:52
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Molecular dynamics simulation study on the structure and properties of polyimide/silica hybrid materials
摘要： A type of polyimide/silica (PI/SiO2) copolymer model was established through the dehydration of tetraethyl orthosilicate molecules (TEOS) and bonding to a silane coupling agent. The content of SiO2 was controlled by adjusting the number of molecules which bound to the TEOS. Finally, the silica was formed into a hybrid model (hybrid PI/SiO2) with a small molecule embedded in the PI. The model was optimized by geometric and molecular dynamics and the changes in the model structure, Young’s modulus, shear modulus, and glass-transition temperature (Tg) were analyzed. The results showed that the density and cohesive energy density of the composites could be improved by doping SiO2 in PI. Young’s modulus and shear modulus of PI/SiO2 hybrid materials were higher than undoped PI. The tensile strength reached 568.15 MPa when the doping content was 9%. Therefore, the structure design and content control of SiO2 was an effective way to improve the performance of a PI/SiO2 composite. The variation of Tg and tensile strength of PI/SiO2 hybrid composites is consistent with that of PI/SiO2 composite synthesized in real experiment, which will be a convenient method for new material design and performance prediction. ? 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 136, 47335.
关键词： molecular dynamics,shear modulus,Young’s modulus,polyimide/silica,glass-transition temperature
更新于2025-09-23 15:23:52
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Characterization, optical and luminescence features of cobalt ions in multi-component PbO Al2O3TeO2GeO2SiO2 glass ceramics
摘要： Glass ceramics of the composition PbOeAl2O3eTeO2eGeO2eSiO2 doped with CoO (ranging between 0 and 1.0 mol %) were prepared by melt quenching technique followed by heat treatment. The techniques such as XRD, SEM, EDS and DTA were employed for the characterization of the prepared samples. Conventional spectroscopic studies viz., optical absorption, photoluminescence, FTIR and Raman were also performed on these samples. The optical absorption spectra of the titled glass ceramics exhibited two principal absorption bands, one at about 594 nm and the second one consisting of multiplets with the meta centre at about 1455 nm ascribed to the 4A2 (4F) → 4T1 (4P) and 4A2 (4F) → 4T1 (4F) transitions of tetrahedrally coordinated Co2+ ions, respectively. Besides these, the spectra also exhibited two feeble bands at about 532 and 643 nm which are the characteristics of octahedrally coordinated Co2+ and Co3+ ions, respectively. Using Tanabe Sugano diagram the crystal field splitting parameter Dq, Racah parameters B, C and nephelauxetic ratio, β were evaluated for Co2+ ions. The photoluminescence spectra of the titled glass ceramics have exhibited two broad emission bands at 628 and 870 nm ascribed to 4T1 (4P) → 4A2 (4F) and 4T1 (4P) → 4T2 (4F) tetrahedral transitions of Co2+ ions, respectively. FTIR and Raman spectra of the titled samples exhibited various asymmetrical and symmetrical vibrational bands due to viz., silicate, germanate, PbO4, PbO6, AlO6, TeO4, TeO3 and CoIIIeO vibrations in the glass ceramic matrix. The spectroscopic investigations on the titled glass ceramics have revealed that if CoO is present in small quantities the cobalt ions predominantly occupy the octahedral sites in the glass network, whereas the tetrahedrally coordinated Co2+ ions are found to increase if the concentration of nucleating agent CoO is gradually increased up to 1.0 mol%. As a result the degree of depolymerization of the glass network decreases which in turn enhances its rigidity with increasing the concentration of nucleating agent CoO. From these investigations we report that the glass ceramics doped with 1.0 mol% of CoO are suitable for insulating devices as well as for photonic devices.
关键词： Photoluminescence,Raman spectra,XRD,Multi-component glass ceramics,SEM,Optical absorption,Cobalt ions
更新于2025-09-23 15:23:52
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Structural and photoluminescence investigations of Cr3+ mixed Li2O—Bi2O3—ZrO2—SiO2 glass ceramics for optoelectronic device application
摘要： Chromium oxide mixed Li2O―Bi2O3―ZrO2―SiO2 (Cr3+:LBZS) glasses were crystallized by heat treatment. Structural (X-ray di?raction, surface morphology, energy dispersion, DTA, FT-IR and Raman) and spectroscopic (optical absorption and luminescence), of these Cr3+:LBZS glass ceramics were studied. XRD pattern of Cr3+: LBZS glass ceramic samples exhibited distinct crystalline peaks. SEM images of the Cr3+: LBZS glass ceramic materials have revealed well identi?ed and distributed crystals of reformed size. The glass transition (Tg) and various crystallization temperatures (Tc1), (Tc2) and (Tc3) of these ceramics were identi?ed by DTA analysis. The shift in the wavenumbers of di?erent symmetrical and asymmetrical band positions of these glass ceramics were analysed by FT-IR and Raman studies. The optical bandgap (Eo), CFSE (Dq) and nephelauxetic ratio (β) were calculated. Photoluminescence properties were also investigated.
关键词： Luminescence,FTIR,DTA,Structure,Cr3+: LBZS glass ceramics,Optical
更新于2025-09-23 15:23:52
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Determination of high-temperature radiative properties of porous silica by combined image analysis, infrared spectroscopy and numerical simulation
摘要： The influence of the texture of fused silica glasses ? containing unconnected spherical bubbles ? on their thermal radiative properties was investigated by combining experimental measurements and numerical simulations. Exact numerical replicas of the porous samples were obtained from X-ray microtomography and image analysis showed that their bubble populations include two lognormal distributions of radii. The complex refractive index of the silica matrix was extracted from emittance measurements acquired at 1200 K on two reference silica samples. The comparison between direct measurements of the normal spectral emittance of the porous samples and those generated by applying Monte-Carlo ray tracing, performed on the numerical replicas, validated the use of geometric optics. The OH content of the porous samples was evaluated to be around 210 ppm. Ray tracing simulations carried out on a set of virtual samples having a similar texture proved to be a flexible means to address experimental limits when characterizing semi-transparent materials. The simulations also provided a natural framework to test the ability of the modified two-flux approximation model to predict the thermal radiative response of the porous silica investigated.
关键词： Radiative properties,X-ray microtomography,Porous silica glass,Spectral emittance,Monte-Carlo ray tracing
更新于2025-09-23 15:23:52
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Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
摘要： Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A di?usion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements con?rmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.
关键词： Refractive index,Glass-ceramics,Photoluminescence,Dielectric properties,Crystallization kinetics,Hysteresis loop
更新于2025-09-23 15:23:52
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Surface and bulk crystallization of Ba1-xSrxZn2Si2O7 from glasses in the system BaO/SrO/ZnO/SiO2 doped with Nb2O5 or Ta2O5
摘要： Stoichiometric 0.5 BaO·0.5 SrO·2 ZnO·2 SiO2 glass was doped with 5 mol% Nb2O5 or Ta2O5. The effect of these additives on the crystallization behavior was studied using thermal analyses, X-ray diffraction, as well as scanning electron microscopy including elemental analyses. The addition of Nb2O5 or Ta2O5 significantly increases the glass stability enabling the preparation of crystal-free BaO·SrO·ZnO·SiO2 glasses with almost stoichiometric composition. Besides the desired main crystal phase Ba1-xSrxZn2Si2O7, also alkaline earth tantalates and niobates as well as Zn2SiO4 are observed. The Nb-containing glass shows solely surface crystallization, whereas in the Ta-containing glass, additionally numerous Ba0.44TaO2.94 crystals precipitate in the bulk acting as seeds for the nucleation of Ba1-xSrxZn2Si2O7. If the surface crystallized layer of Ba1-xSrxZn2Si2O7 approaches such a Ba0.44TaO2.94 crystal or gets close to it, then the crystallization of Ba1-xSrxZn2Si2O7 is initiated. It is supposed that these nucleation processes are notably facilitated by the stresses present in these glass-ceramics.
关键词： barium strontium zinc silicate,heterogeneous nucleation,Glass crystallization
更新于2025-09-23 15:23:52
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Mitigating the electromagnetic radiation by coupling use of waste cathode-ray tube glass and graphene oxide on cement composites
摘要： With technological development, the rapid growing numbers of electronic devices generate severe electromagnetic interference (EMI) and radiation to human environment. In this study, the coupling effect of graphene oxide (GO) addition (up to 0.10 wt.% of cement) and waste cathode-ray tube (CRT) glass replacement for fine aggregates (30 and 60 wt.%) in cement-based composites on mitigating EMI was studied. The electric permittivity obtained using a decoupling method was applied for evaluating the EMI shielding capacity of cement-based composites, while direct current (DC) electrical resistance measurement is conducted using four-probe method. The DC electrical resistivity of specimens increases insignificantly with increasing in GO content, but remarkably with increasing CRT glass content from 30 to 60 wt.%. The 60 wt.% replacement of waste CRT glass with 0.1 wt.% GO addition increases the relative permittivity by about 50% and 200% when the frequency is in the ranges of 104–5 × 106 Hz and 101–103 Hz, respectively. It is concluded that a significant increase in the permittivity can be obtained owing to the synergetic interaction between waste CRT glass and GO. The improvement in the EMI shielding ability of cement-based composites not only enables the applications of these composites in mitigating electromagnetic pollution, but also promotes large-volume recycling of toxic waste CRT glass.
关键词： Permittivity,Waste CRT glass,Cement composite,Graphene oxide,Electromagnetic interference
更新于2025-09-23 15:23:52