Objective: To evaluate the color stability of a composite resin modified with ZnO and TiO2 nanoparticles (both pure and silver decorated), synthesized via polymeric precursor and hydrothermal methods. Material and Methods: Filtek™ Z350 XT resin was modified with 2 wt% of nanoparticles, specimens were prepared (n=180), and photoactivated. Specimens were immersed in coffee and artificial saliva; color changes were measured spectrophotometrically, converted to NBS units, and analyzed using repeated measures ANOVA (p<0.001). Results: Coffee immersion caused the greatest discoloration, with the unmodified resin reaching ΔE* = 15.48 after 90 days. Resins containing ZnO/Ag and TiO2/Ag exhibited even higher color instability (ΔE* = 23.14 and ΔE* = 18.71, respectively). Conclusion: While ZnO and TiO2 tested nanoparticles may offer antimicrobial advantages, their incorporation, particularly in silver-decorated forms, can negatively impact the color stability of composite resins exposed to chromogenic agents like coffee. KEYWORDS Coloring agents; Composite resins; Nanoparticles; Titanium; Zinc oxide.

Energy harvesting from mechanical compression and stretching movements is an effective strategy for powering electronic devices. Piezoelectric materials are robust and can be activated by small movements or physical disturbances across various frequencies. With this in mind, the present study proposes the fabrication of monocrystalline lithium niobate (LiNbO3) piezoelectric fibers, grown using the laser-heated pedestal growth (LHPG) technique and their application as high-efficiency energy converters. Electrical power generation was observed in response to mechanical deformations applied to the fabricated monocrystalline piezoelectric generator (PG). Under compression and stretching deformations of the LiNbO3 piezoelectric monocrystalline fiber, one can find electric power generation in the range of 9.85 to 32.41 mu W for stretching, and 19.55 mu W at 34.13 mu W for compression, with the application of 1 V. These results underscore the efficiency of monocrystalline lithium niobate (LiNbO3) fibers in converting ambient mechanical energy into electrical energy, positioning them as a viable and environmentally friendly (lead-free materials) alternative to traditional piezoelectric materials in energy harvesting devices.

This study presents an experimental investigation of single-crystal lithium tantalate (LiTaO3) fiber grown using the laser-heated pedestal growth (LHPG) technique and its application as a high-efficiency energy converter. Structural analysis was performed by employing Raman spectroscopy and X-ray diffraction, confirming the crystallization of the fiber and the formation of the LTO as a single-phase. Compression and stretching deformations, coupled with the application of 0.5 and 1 V, demonstrated an increase in electrical power with higher deformation. By applying a voltage of 1 V to the LiTaO3 single-crystal fiber under compression and stretching deformations, electrical energy generation was observed in the ranges of 3.44 to 3.46 mW (stretching) and 3.52 to 3.53 mW (compression). These results demonstrate the high efficiency of lithium tantalate (LiTaO3) single-crystal fibers in converting mechanical energy into electrical energy, making them a promising and sustainable alternative to conventional piezoelectric materials that do not contain lead in their structure.

This study focuses on the growth and characterization of crystalline LiNbO3 (LN) piezoelectric fibers pulled by the Laser Heated Pedestal Growth (LHPG) technique. The electrical properties of the fibers were investigated using an impedance analyzer, which yielded values for resonance frequency, anti-resonance frequency, and phase angle. Subsequently, elastic constants and coupling factor were determined through calculations based on thickness resonance modes. The accuracy of the resonance method was validated through numerical simulations utilizing COMSOL software, demonstrating a close agreement between experimental and simulated results. Additionally, a temperature sensing was conducted, subjecting the fibers to a wide temperature range from 30 degrees C to 236 degrees C to assess their sensitivity to temperature variations. The coupling factors of K = 0.37 for LN-1 and K = 0.35 for LN-2 demonstrated efficient performance of the crystalline fibers. Furthermore, the numerical simulations exhibited strong correlation between simulated and experimental data. The sensitivity analysis revealed the potential of LN fibers for temperature sensor applications, exhibiting a sensitivity of -87 Hz.degrees C- 1. These findings underscore the promise of LN piezoelectric fibers in advanced sensing technologies.

The activation procedures of metals and alloys for hydrogen absorption might be a considerable challenge for large-scale applications of metal hydrides. In this work, the Pulsed Laser Activation (PLA) method for hydrogen storage alloys is introduced for the first time. We show that the hydrogen storage ability of an aged (air-exposed for 30 days) Ti11V30Nb28Cr31 body-centered cubic alloy is restored by scanning the sample with a nanosecond pulsed laser for only three minutes. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) analyses were performed to investigate structural features that changed in the Ti11V30Nb28Cr31 samples after ageing and after the PLA treatment. Surface remelting, oxide layers and crack formation seem to be factors that affect the hydrogen storage ability of the Ti11V30Nb28Cr31 alloy activated via PLA. Although the mechanisms involved in the PLA are not clear yet, this procedure opens a new path for the development of activation methods based on laser-metal interactions which can be easily applied in alloys and metals for hydrogen storage systems.

Se reporta el crecimiento de fibras monocristalinas de SrTiO3 utilizando la técnica LHPG, en las cuales se observó fotoconductividad persistente (PPC). El estudio se realizó en tres casos de inducción de fotoconductividad persistente. Se determinó el tiempo medio de la PPC en cada caso, a partir de la estimación de los tiempos de vida de los portadores de carga en los estados de recombinación y de trampas. También se estimó la presencia de trampas superficiales y profundas, junto con sus respectivas energías de activación.

Electro-ceramics based on the KNbO3 ferroelectric system were synthesized from the solid-state reaction sintering method. In particular, the electrical properties have been investigated at room temperature in the (1−x)KNbO3−xBaNi1/2Nb1/2O3−δ (KBNN) solid-solution. The dielectric relaxation mechanisms have been analyzed as a function of the oxygen vacancy (δ) concentration and the frequency dispersion of the complex dielectric permittivity was analyzed in a wide frequency range. The obtained results were discussed within the framework of the current models reported in the literature for the dielectric relaxation processes.

Femtosecond laser micmmachining has potential application in integrated photonics thanks to its ability to produce micrometer-size three-dimensional structures in different types of materials, including the ones whose properties can be externally altered, which allows for the fabrication of optically active devices. In this work, we demonstrate the fs-laser fabrication of magneto-optical waveguides in CaLiBO (calcium-lithium tetraborate) glasses codoped with Yb+3 and Tb3+ ions. Single-mode type waveguides were produced using fs-pulses with similar to 0.1 J/cm(2) and 6.5 x 10(5) pulses/spot, an important feature for integrated photonic devices. The fabricated waveguides display Faraday effect, with a Verdet constant of 560 degrees T-1 m(-1), for the sample containing 2% of Tb3+, which is equivalent to the one observed for the bulk. Such a result demonstrates that fs-laser micro-machining, in the conditions used here, does not negatively affect the magneto-optical properties of the sample. Thus, our results open a new pathway towards the processing of magneto-optical waveguides aimed at applications in magneto-optical photonic microdevices.

The structural ordering process in complex perovskites has a pivotal role for tuning many physical properties for broad applications, ranging from microwave technology, proton-conduction, multiferroicity, and so on. Therefore, the characterization of order type in these materials is essential for designing new devices with high-performance. Here, the coexistence of B-site 1:1 and 1:2 order types in mixed ordered A(3)CaNb(2)O(9) (A = Ba, Sr) perovskite was investigated by combining Raman spectroscopy and high-resolution synchrotron X-ray powder diffraction. High-wavenumber interval 700-825 cm(-1) exhibits two bands concerning the symmetric breathing modes of [NbO6] octahedra in A(3)CaNb(2)O(9), which were ascribed to the 1:1 and 1:2 domain regions in coexistence. This model was fully corroborated using two phases for describing the synchrotron X-ray pattern of the Ba3CaNb2O9 sample. Therefore, the Raman spectroscopy can be indeed applied as a rapid tool for probing the achievement of ordered, partially ordered, or disordered structures in complex perovskites. For the first time, BaLaCaNbO6 was synthesized and structural characterized, being indexed by the monoclinic unit cell belonging to the space group I2/m$$ I2/m $$.

In spite of the widespread use of natural rubber in regenerative therapies, thermally induced modifications of its complex chemical structure and their effect on the surface properties and the cell response (attachment-adhesion-proliferation) are still an unexplored topic. Here, we demonstrate how thermal treatments enhance the cell response due to changes to the inner and surface structures of natural rubber. In situ studies of the temperature effects conducted via infrared spectroscopy revealed both molecular rearrangements and anharmonic effects in the polymeric lattices. Thermal treatments at different temperatures allowed to control the wetting regime. Contributions of different surface parameters to the wettability were decoupled by statistical analysis of the principal component. The polar component of the surface free energy was recognized as the main surface player, which influences cell spreading, attachment, proliferation, and tissue growth. A simple thermal annealing of the natural rubber film at 373 K alters the local structure of the latex inducing an increase in cell viability. The experimental-statistical analysis approach allows an accurate correlation of physicochemical properties with cell supportability. The results highlight the potential of natural rubber polymers by tuning surface wettability, via simple thermal treatment, for biomedical applications.

PbTiO3 (PT) thin films were prepared by chemical route to study the effects of heat treatment on the phase transformations. Different pyrolysis temperatures between 250°C and 450°C have been studied to obtain films free of undesirable phases. The pyrolysis temperature directly affects the residual stresses and suppression of pyrochlore phases observed. The prediction of the preparation conditions is not straightforward. X-ray diffraction and Raman scattering results reflect a tetragonal structure obtained for the films. The results of X-ray diffraction for films produced above the pyrolysis temperature of 400°C showed a dominant orientation in the plane (111), which coexists with a small tendency along the plane (100). Raman spectroscopy with polarized light was used to evaluate the orientation effects of the ferroelectric domains present in the sample. The phase transformations in the films are discussed in terms of experimental calculations of residual stress.

Laser-heated pedestal growth (LHPG) is an advantageous technique for crystalline fibers pulling due to its fast growth rate, related to the high axial thermal gradient. However, internal cracks can occur if the radius of the fiber is greater than the so-called thermal critical radius. For this reason, it is important to accurately determine the maximum axial thermal gradient to obtain crystalline fibers free of cracks. Herein, we improved the current method for critical radius determination by considering that the maximum temperature gradient is not present in the liquid/solid interface, but occurs directly on fiber, at a certain distance Delta from the liquid/fiber interface. In order to evaluate such improvement, cracks-free fibers of SrTiO3 (Melting Point = 2353 K) and Al2O3 (2345 K) were grown with this new criterion.

We report the stress-strain effect of a stretchable natural rubber (NR)-calcium phosphate composite on the surface wettability (SW) using an innovative approach coupling a uniaxial tensile micromachine, goniometer, and microscope. In situ contact angle measurements in real time were performed during mechanical tension. Our results show that SW is guided by the stress-strain relationship with two different characteristics, depending on the static or dynamic experiments. The results evidenced the limits of the classical theory of wetting. Furthermore, based on the mechanically tunable SW of the system associated with the cytocompatibility of the NR composite, we have modeled such a system for application as a cell support. From the experimental surface energy value, our proposed 3D modeling numerical simulation predicted a window of opportunities for cell-NR survival under mechanical stimuli. The presented data and the thermodynamics-based theoretical approach enable not only accurate correlation of SW with mechanical properties of the NR composite but also provide huge potential for future cell supportability in view of tissue engineering.

Borate glasses present the ability to host various modifier ions and, therefore, are adaptable for a wide range of applications. Specifically, calcium-lithium tetraborate (CaLiBO) glasses doped with rare earths have been investigated for applications involving energy transfer processes. In this work, waveguides were inscribed by femtosecond laser microfabrication in CaLiBO glasses containing Tb3+ and Yb3+ ions, displaying emission in the green region. Single-mode guiding at 632.8 nm, with propagation losses of approximately 2.0 dB/cm, was ob- tained in 7.0-mm long waveguides with a diameter on the order of 2 mu m, produced in the glass bulk, at approximately 100 mu m below the sample surface. By coupling 488 nm light, the fabricated waveguide showed the capability of guiding the typical emission of Tb3+ ions. Such glasses containing rare earths could be suitable for the development of green light-emitting microdevices.

Submitted for the MAR10 Meeting of The American Physical Society Optical and structural characterization of yttrium calcium borate glasses1 CRISTIANE SANTOS, DOMINGOS D.S. MENESES, PATRICK ECHEGUT, CEMHTI-CNRS, Orléans, France, DANIEL R. NEUVILLE, IPGPCNRS, Paris, France, ANTONIO C. HERNANDES, IFSC-Universidade de São Paulo, São Carlos, Brazil, ALAIN IBANEZ, Institut Néel-CNRS, Grenoble, France — Structural and optical properties of new stable glasses in the Y2O3 – CaO – B2O3 system, containing the same Y/Ca ratio as the YCa4O(BO3)3 (YCOB) crystal, were determined from Raman and reflectance infrared spectroscopy [1]. We have obtained the optical functions using a dielectric function model and their evolution with composition are associated with an increase in the number of non-bridging oxygen and to calcium/yttrium oxides content with the formation of pentaborate, metaborate, orthoborate and pyroborate groups. The orthoborate and pyroborate signatures increase with increasing the modifier cations. Refractive indexes values (from 1.597 to 1.627 at λ = 2 μm) are in good agreement with those of the YCOB crystal, an indication that these glasses are potential candidates for doping with rare-earth ions for optical applications. [1] C. N. Santos, D.D.S. Meneses, P. Echegut, D. R. Neuville, A. C. Hernandes, A. Ibanez, Appl. Phys. Lett. 94, 151901(2009). 1This work was supported by the Brazilian agencies CAPES (No. 455/04-1) and FAPESP (No. 04/00093-0). Cristiane N. Santos CEMHTI-CNRS Date submitted: 21 Nov 2009 Electronic form version 1.4

This work investigates the influence of transition metals oxides (Ta2O5 and ZrO2) on the nonlinear refraction of niobium-borotellurite glasses prepared by melt-quenching technique. The closed-aperture Z-scan technique was used to measure the nonlinear refractive index (n(2)) spectrum from 470 nm to 800 nm. Also, the BGO (Boling, Glass, and Owyoung) approach was used to model nonlinear spectra, considering the oxygens present in the sample as the major contribution to the nonlinearity. The samples' molar electronic polarizability was determined to further understanding the effect of the transition metals oxides on the optical properties. Structural analysis was performed by differential scanning calorimetry, Raman and Infrared spectroscopies. The results indicate that although the modifier oxides affect the structural units and glass polarizability, they are not enough to change the behavior of the nonlinear refractive index spectra, being the glass-matrix the main responsible for optical nonlinearity in the system studied here. (C) 2021 Elsevier B.V. All rights reserved.

KNbO3-based ferroelectric materials have been largely investigated as a result of many interesting physical properties that make them suitable for designing multifunctional electronic components. In particular, ferroelectric (1–x)KNbO3–xBaNi1/2Nb1/2O3–δ (KBNN) solid solutions have received special attention for optical applications, including for high-performance photovoltaic devices. In this work, KBNN ceramics were produced via conventional solid-state sintering, followed by a comprehensive study of their (micro)structural, electrical and optical properties. The processed data are analyzed and discussed in terms of the effect from structural oxygen-vacancy defects in such materials and from the grain size, in the specific case of the observed electrical response. Overall, the results suggest these perovskite-structured semiconducting ferroelectric oxides as a good alternative for solar cell applications.

We report on the study of the spectroscopic properties in Ytterbium-Terbium (Yb3+-Tb3+) co-doped calcium lithium borate (CaLiBO) glasses, with the study’s focus being on the upconversion process. Intensity parameters Ωλ for CaLiBO:Tb3+ are determined by the Judd-Ofelt method to be Ω2 = 15.5 × 10-20 cm2, Ω4 = 1.90 × 10-20 cm2 and Ω6 = 3.69 × 10-20 cm2. We have also obtained electric-dipole (and magnetic-dipole) radiative transition probabilities, branching ratios, and lifetime for the Tb3+:5D4 and 5D3 levels. In addition, an evaluation of the upconversion processes by luminescence and time-resolved spectroscopy were carried out. The upconversion rise and decay times, energy transfer probability from Yb3+ to Tb3+ ions, and the efficiency of the processes that depopulate the Tb3+:5D4 level after resonantly pumping the Yb3+:2F5/2 level were estimated. Our results showed that a cooperative energy transfer (CET) from two Yb3+ ions to one Tb3+ ion is the origin of the Tb3+ upconversion luminescence in the visible region. While, CET followed of the cross relaxation or/and excited state absorption is responsible for the upconversion luminescence in the ultraviolet region.