Search Results (66)

Nanoparticle floating gate (NPFG) transistors have gained attention as synaptic devices due to their discrete charge storage capability, which minimizes leakage currents and enhances the memory window. In this study, we propose and evaluate a mesh-type floating gate transistor (Mesh-FGT) designed to emulate the characteristics of NPFG transistors. Individual floating gates with dimensions of 3 µm × 3 µm are arranged in an array configuration to form the floating gate structure. The Mesh-FGT is composed of an Al/Pt/Cr/HfO₂/Pt/Cr/HfO₂/SiO₂/SOI (silicon-on-insulator) stack. Threshold voltages (Vth) extracted from the transfer and output curves followed Gaussian distributions with means of 0.063 V (σ = 0.100 V) and 1.810 V (σ = 0.190 V) for the erase (ERS) and program (PGM) states, respectively. Synaptic potentiation and depression were successfully demonstrated in a multi-level implementation by varying the drain current (I_ds) and Vth. The Mesh-FGT exhibited high immunity to leakage current, excellent repeatability and retention, and a stable memory window that initially measured 2.4 V. These findings underscore the potential of the Mesh-FGT as a high-performance neuromorphic device, with promising applications in array device architectures and neuromorphic neural network implementations. Full article

Integrated optical waveguide amplifiers, with their compact footprint, low power consumption, and scalability, are the basis for optical communications. The realization of high gain in such integrated devices is made more challenging by the tight optical constraints. In this work, we present efficient amplification in an erbium–ytterbium-based hybrid slot waveguide consisting of a silicon nitride waveguide and a thin-film active layer/electron-beam resist. The electron-beam resist as the upper cladding layer not only possesses the role of protecting the waveguide but also has tighter optical confinement in the vertical cross-section direction. On this basis, an accurate and comprehensive dynamic model of an erbium–ytterbium co-doped amplifier is realized by introducing quenched ions. A modal gain of above 20 dB is achieved at the signal wavelength of 1530 nm in a 1.4 cm long hybrid slot waveguide, with fractions of quenched ions f_q = 30%. In addition, the proposed hybrid waveguide amplifiers exhibit higher modal gain than conventional air-clad amplifiers under the same conditions. Endowing silicon nitride photonic integrated circuits with efficient amplification enriches the integration of various active functionalities on silicon. Full article

Transition dairy cows face severe oxidative stress that disrupts mammary epithelial homeostasis through intertwined oxidative, inflammatory, and endoplasmic reticulum (ER) stress pathways. This study hypothesized that rutin, a natural flavonoid, alleviates hydrogen peroxide (H₂O₂)-induced oxidative damage in bovine mammary epithelial cells (BMECs) via AMPK/NFE2L2 signaling activation. In this study, BMECs were pre-incubated with rutin. Subsequently, cells were treated with or without H₂O₂. Additionally, by transfecting BMECs with NFE2L2 siRNA (siNFE2L2), we investigated how AMPK/NFE2L2 signaling mediated by rutin may prevent H₂O₂-induced oxidative damage. The results show that increases in reactive oxygen species (ROS), expression of inflammatory cytokines, expression of proteins related to endoplasmic reticulum stress and the apoptosis rate induced by H₂O₂ in cells, were attenuated in rutin cultures. Challenges with H₂O₂ led to a lower abundance of proteins related to AMPK and NFE2L2. Comparatively, these effects were reversed in cultures with rutin. Transfection with siNFE2L2 reversed the protection of rutin, suggesting that NFE2L2 is essential for the protective mechanism of rutin. These results elucidated the molecular mechanism of rutin’s resistance to H₂O₂-mediated oxidative injury through the AMPK/NFE2L2 signaling pathway and suggested that it could be used as a potent in vivo antioxidant for ruminants during periods of stress, such as before and after calving. Full article

This study successfully synthesizes SiO₂-encapsulated nano-phase change materials (NPCMs) via a sol–gel method, using paraffin as the thermal storage medium. The encapsulation process is validated through FTIR, XRD, and XPS analyses, confirming the formation of an amorphous SiO₂ shell without any chemical interaction between the core and shell. SEM imaging reveals a well-defined core–shell structure with uniform spherical geometry, with the smallest particle size (190 nm) observed in the sample with a 4:1 paraffin/SiO₂ ratio (PARSI-4). TGA results demonstrate enhanced thermal stability, with thicker SiO₂ shells effectively protecting against thermal degradation. The DSC analysis indicates that an increased core–shell ratio improves thermal performance, with PARSI-4 exhibiting the highest melting (160.86 J/g) and solidifying (153.93 J/g) enthalpies. The encapsulation ratio (ER) and encapsulation efficiency (EE) have been accomplished at 87.83% and 87.04%, respectively, in the PARSI-4 sample. Thermal cycling tests confirm the material’s long-term stability, with 98.16% enthalpy retention even after 100 cycles. Additionally, leakage resistance tests validate the structural integrity of the encapsulated paraffin, preventing spillage at elevated temperatures. These findings demonstrate the potential of SiO₂-encapsulated NPCMs for efficient thermal energy storage (TES), making them promising candidates for sustainable and energy-efficient applications. Full article

Carbonaceous shale has garnered significant interest as a viable alternative source of rare earth elements (REEs) besides conventional REE-bearing ores. This study characterized rare earth element + Yttrium+ Scandium (REYs) enrichment in the 11 core samples of carbonaceous shale (7) and coal (4) collected from Arnot Mine. Major elements of the studied carbonaceous shale (CS) and coal showed high amounts of SiO₂, Al₂O₃, and Fe₂O₃, indicating a high content of aluminosilicate and iron-rich minerals. The plots Na₂O + K₂O against SiO₂ suggested alkali granite, granite, and granodiorite provenance sources for the studied shale and coal. The samples showed enrichment in low and heavy rare elements crystallized from a low potassium tholeiitic and medium calc-alkaline magma based on the plots of La_N/Yb_N and K₂O vs. SiO₂. The mineralogical and maceral analysis revealed the dominant presence of kaolinite (15%–45%), and it was suggested as the cation exchange site resulting from the isomorphous substitution of Al³⁺ for Si⁴⁺. Additionally, siderite was suggested as one of the REY hosts due to the Fe³⁺ site forming a complex with the REE³⁺ ions. Furthermore, the samples were classified as lignite to sub-bituminous coal category with dominant minerals including kaolinite, quartz, and siderite. The outlook coefficient (Coutl) of REY in CS revealed a promising area for economically viable, having two enrichment types, including low (La, Ce, Pr, Nd, and Sm) and heavy (Ho, Er, Tm, Yb, and Lu). The Eu_N/Eu_N* and Ce_N/Ce_N* ratio for the current studied samples exhibited a weak negative to no anomaly, and most of the studied samples were characterized by distinctive positive Gd anomalies derived from sediment source regions weathered from alkali granite, granite, and granodiorite provenance formed from a low potassium tholeiitic and medium calc-alkaline magma. Full article

This study employs advanced structural characterization techniques, including anomalous small-angle X-ray scattering (ASAXS), small-angle X-ray scattering (SAXS), and X-ray photoelectron spectroscopy (XPS), to investigate erbium (Er³⁺)-doped silica-based glass-ceramic thin films synthesized via the sol–gel method. This research examines the SiO₂-TiO₂ and SiO₂-TiO₂-PO_2.5 systems, focusing on the formation, dispersion, and structural integration of Er³⁺-containing nanocrystals within the amorphous matrix under different thermal treatments. Synchrotron radiation tuned to the L_III absorption edge of erbium enabled ASAXS measurements, providing element-specific details about the localization of Er³⁺ ions. The findings confirm their migration into crystalline phases, such as erbium phosphate (EPO) and erbium titanate (ETO). SAXS and Guinier analysis quantified nanocrystal sizes, revealing trends influenced by their composition and heat treatment. Complementary XPS analysis of the Er 5p core-level states provided detailed information on the chemical and electronic environment of the Er³⁺ ions, confirming their stabilization within the crystalline structure. Transmission electron microscopy (TEM) highlighted the nanoscale morphology, verifying the aggregation of Er³⁺ ions into well-defined nanocrystals. The results offer a deeper understanding of their size, distribution, and interaction with the surrounding matrix. Full article

The paper presents the results of developing Er-doped optical fibers for creating random single-frequency lasers in the wavelength range of 1570–1610 nm. The possibility of broadening the luminescence band of Er³⁺ ions in silicate glasses in the long-wavelength region of the spectrum by introducing a high concentration of P₂O₅, as well as by additional doping with Sb₂O₃, is investigated. It is found that both approaches do not improve the dynamics of luminescence decay in the L-band. In addition, Er₂O₃-GeO₂-Al₂O₃-SiO₂ and Er₂O₃-GeO₂-Al₂O₃-P₂O₅-SiO₂ glasses were studied as the core material for L-band optical fibers. The developed fibers exhibited high photosensitivity and a high gain of 5 and 7.2 dB/m, respectively. In these fibers, homogeneous arrays of extended weakly reflecting Bragg gratings were recorded directly during the fiber drawing process. Samples of arrays 5 m long and with a narrow reflection maximum at ~1590 nm were used as the base for laser resonators. Narrow-band random laser generation in the wavelength region of 1590 nm was recorded for the first time. At a temperature of 295 K, the laser mode was strictly continuous wave and stable in terms of output power. The maximal power exceeded 16 mW with an efficiency of 16%. Full article

For the first time, inductively coupled plasma mass spectrometry (ICP-MS) was developed for determining the target elemental composition of gadolinium–aluminum garnets with the varying composition Gd_3–xCe_xSc_yAl_5–yO₁₂, where x = 0.01–0.16 and y = 0.25–1.75. This fact has a fundamental importance for obtaining optical ceramics with predictable properties. Using the proposed acid mixture and temperature-time program, microwave digestion of these materials and complete transfer of the sample’s components into solution were possible. Moreover, we estimated the influence of the matrix composition, sample introduction system and collision cell on the limits of determination (LOD) of impurity elements by ICP-MS (Mg, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, La, Pr, Nd, Sm, Eu, Tb, Er, Ho, Tm, Yb, and Lu). It has been shown that the conditions of mass spectral analysis proposed in this work provide LOD of target analytes in the range of 1∙10⁻⁶–4.15∙10⁻³ wt.%. The accuracy of the obtained results has been confirmed by the added-found method and by analyzing samples with known chemical composition. The standard deviation of repeatability (S_r) of the developed technique lies in the range from 1 to 6%. The developed analysis method is characterized by sensitivity, robustness and multi-elementality. It has application potential for other optical and ceramic materials of similar composition. Full article

Activating metal inert gas (AMIG) welding was designed to address difficulties with MIG welding, such as the limitation on workpiece thickness that may be welded in a single pass. This investigation was carried out on 304L stainless steel using ER 308L as a filler metal. Five oxides (SiO₂, TiO₂, Fe₂O₃, Mn₂O₃, and Cr₂O₃) have been investigated without edge preparation. The welded joints were evaluated for weld morphology, microstructure, mechanical properties, and corrosion, and the findings were compared. The depth of the AMIG weld was determined to be greater than that of the MIG weld. The microstructure is composed of austenitic and retained delta ferrite with 3.3% for MIG and up to 8% for AMIG weld carried out with Cr₂O₃ oxide flux, the tensile strength is up to 604 MPa when using Cr₂O₃ oxide against MIG weld (532 MPa), and the resistance to sudden load in AMIG welds (189 J/cm²) is higher than that of MIG weld (149 J/cm²). The corrosion resistance of the weld made with Fe₂O₃ oxide flux is greater than that of the other AMIG and MIG welds, as well as the parent metal. The AMIG welding technique variant enhances productivity and decreases the cost and energy consumption of the welding material compared to the traditional MIG process. This allows for joining the same thickness without affecting mechanical properties and corrosion resistance, meeting the industry’s requirements. Full article

Exploring the intrinsic mechanisms of rare-earth ions entering the crystal phase has great significance for finely tuning the luminescent properties of glass–ceramics. Using Er³⁺ ions as a probe, X-ray diffraction was employed to precisely measure the crystallinity of SiO₂-PbF₂-Er₂O₃ glass–ceramics synthesized under various heat treatment conditions, confirming the occurrence of a rapid crystallization process. Additionally, by combining Judd–Ofelt theory with comprehensive analyses of absorption and fluorescence spectra, we calculated the relative proportions of Er³⁺ ions present in the crystal phase. We found that the crystallization process in the glass–ceramics and the incorporation of Er³⁺ ions into the crystal phase did not occur synchronously. This discovery provides new theoretical foundations and practical guidance for understanding the mechanism of rare-earth ion incorporation into crystal phases, which is significant for the development of functional materials with specific luminescent properties. Full article

Nanoscale oxides grown in c-silicon, implanted with low-energy (2 keV) H⁺ ions and fluences ranging from 10¹³ cm⁻² to 10¹⁵ cm⁻² by RF plasma immersion implantation (PII), have been investigated. The oxidation of the implanted Si layers proceeded in dry O₂ at temperatures of 700 °C, 750 °C and 800 °C. The optical characterization of the formed Si/SiO_x structures was conducted by electroreflectance (ER) and spectroscopic ellipsometric (SE) measurements. From the ER and SE spectra analysis, the characteristic energy bands of direct electron transitions in Si are elaborated. The stress in dependence on hydrogenation conditions is considered and related to the energy shifts of the Si interband transitions around 3.4 eV. Silicon oxides, grown on PII Si at a low H⁺ fluence, have a non-stoichiometric nature, as revealed by IR-SE spectra analysis, while with an increasing H⁺ fluence in the PII Si substrates and/or the subsequent oxidation temperature the stoichiometric Si-O₄ units in the oxides become predominant. The development of surface morphology is studied by atomic force microscopy (AFM) imaging. Oxidation of the H⁺-implanted Si surface region flattens out the surface pits created on the Si surface by H⁺ implants. Based on the evaluation of the texture index and mean fractal dimension, the isotropic and self-similar character of the studied surfaces is emphasized. Full article

In this work, we present an advancement in the encapsulation of lithium yttrium fluoride-based (YLiF₄:Yb,Er) upconversion nanocrystals (UCNPs) with silica (SiO₂) shells through a reverse microemulsion technique, achieving UCNPs@SiO₂ core/shell structures. Key parameters of this approach were optimized to eliminate the occurrence of core-free silica particles and ensure a controlled silica shell thickness growth on the UCNPs. The optimal conditions for this method were using 6 mg of UCNPs, 1.5 mL of Igepal CO-520, 0.25 mL of ammonia, and 50 μL of tetraethyl orthosilicate (TEOS), resulting in a uniform silica shell around UCNPs with a thickness of 8 nm. The optical characteristics of the silica-encased UCNPs were examined, confirming the retention of their intrinsic upconversion luminescence (UC). Furthermore, we developed a reliable strategy to avoid the coencapsulation of multiple UCNPs within a single silica shell. This approach led to a tenfold increase in the UC luminescence of the annealed particles compared to their nonannealed counterparts, under identical silica shell thickness and excitation conditions. This significant improvement addresses a critical challenge and amplifies the applicability of the resulting UCNPs@SiO₂ core/shell structures in various fields. Full article

Silica (SiO₂), accounting for the main component of fly ash, plays a vital role in the heterogeneous formation of polychlorinated thianthrenes/dibenzothiophenes (PCTA/DTs) in high-temperature industrial processes. Silica clusters, as the basic units of silica, provide reasonable models to understand the general trends of complex surface reactions. Chlorothiophenols (CTPs) are the most crucial precursors for PCTA/DT formation. By employing density functional theory, this study examined the formation of 2-chlorothiophenolate from 2-CTP adsorbed on the dehydrated silica cluster ((SiO₂)₃) and the hydroxylated silica cluster ((SiO₂)₃O₂H₄). Additionally, this study investigated the formation of pre-PCTA/DTs, the crucial intermediates involved in PCTA/DT formation, from the coupling of two adsorbed 2-chlorothiophenolates via the Langmuir–Hinshelwood (L–H) mechanism and the coupling of adsorbed 2-chlorothiophenolate with gas-phase 2-CTP via the Eley–Rideal (E–R) mechanism on silica clusters. Moreover, the rate constants for the main elementary steps were calculated over the temperature range of 600–1200 K. Our study demonstrates that the 2-CTP is more likely to adsorb on the termination of the dehydrated silica cluster, which exhibits more effective catalysis in the formation of 2-chlorothiophenolate compared with the hydroxylated silica cluster. Moreover, the E–R mechanism mainly contributes to the formation of pre-PCTAs, whereas the L–H mechanism is prone to the formation of pre-PCDTs on dehydrated and hydroxylated silica clusters. Silica can act as a relatively mild catalyst in facilitating the heterogeneous formation of pre-PCTA/DTs from 2-CTP. This research provides new insights into the surface-mediated generation of PCTA/DTs, further providing theoretical foundations to reduce dioxin emission and establish dioxin control strategies. Full article

Ce-based selective catalytic reductions with an NH₃ (NH₃-SCR) catalyst have emerged as a focal point in denitrification catalyst research. However, the correlation between the structural characteristics of Ce-based catalysts and the influence of CeO₂ nanoparticle size on SO₂ resistance remains unclear. CeO₂ nanospheres with different sizes of less than 10 nm were synthesized, and a series of supported CeO₂/SBA-15 catalysts were prepared according to the 10 nm pore size of SBA-15. These catalysts were used to explore the influence of the size of the CeO₂ nanospheres on these catalysts, specifically on their SO₂ resistance in NH₃-SCR reactions. With the increase in size, their SO₂ resistance became stronger. The results of NH₃-TPD, H₂-TPR, and XPS indicated that the catalyst with the largest particle size had the lowest adsorption of SO₂, which was attributed to more acid sites and a mutual effect between Si and Ce, resulting in the best SO₂ resistance. It was also observed that there was less sulfate deposition on the catalyst by thermogravimetric analysis. In situ DRIFTs revealed that after SO₂ poisoning, the NH₃-SCR reaction on the catalyst predominantly follows the E-R mechanism. This study offers recommendations for the development of Ce-based SO₂-resistant NH₃-SCR catalysts, specifically focusing on the synthesis and interaction of nanomaterials. Full article

This paper presents the investigations toward the direct use of bentonite clay (Al₂H₂O₆Si) nanoparticles to act like a saturable absorber (SA) for the Q-switched pulse operation of an erbium-doped fiber laser (EDFL). The measured results reveal that with the incorporation of bentonite clay nanopowder as a SA, an EDFL is realized with a Q-switching mechanism starting at a pump power of 30.8 mW, and a Q-switched emission wavelength was noticed at 1562.94 nm at 142 mW pump power. With an increased pump from 30.8 mW to 278.96 mW, the temporal pulse parameters including minimum pulse duration and maximum pulse repetition rates were reported as 2.6 µs and 103.6 kHz, respectively. The highest peak power, signal-to-noise ratio, output power and pulse energy were noticed to be 16.56 mW, 51 dB, 4.6 mW, and 47 nJ, respectively, at a highest pump power of 278.96 mW. This study highlights the significance of bentonite clay (Al₂H₂O₆Si) nanoparticles as a potential candidate for a saturable absorber for achieving nonlinear photonics applications. Full article