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Effect of K2O addition on glass structure, complex impedance and energy storage density of NaNbO3 based glass-ceramics
摘要： (40-x)Na2O-xK2O-40Nb2O5-20SiO2 (x=0, 5, 10, 15mol%) glass-ceramics are synthesized by traditional melts method. The glass-ceramics are tested by X-ray diffraction (XRD) techniques, and NaNbO3 as major phase led a high permittivity. A microstructure with nanoscale grains enclosed by glass phase is observed by scanning electron microscope (SEM). With the increase of content of K2O, a relaxed glass network structure is obtained, and more kinds of phase are formed. Permittivity comes to 174 approximately when x=5mol%. In addition, the activation energy (Ea) of residual glass phase for Na2O-K2O-Nb2O5-SiO2 glass-ceramics firstly increase then decrease. Breakdown strength (BDS) of all samples increase and then decrease with the increase of content of K2O, and maximum BDS is obtained when x=10mol%. And maximum theoretical energy density is 1.43J/cm3 when x=5mol%.
关键词： breakdown strength,glass network structure,Na2O-K2O-Nb2O5-SiO2 glass-ceramics
更新于2025-11-14 17:28:48
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Ultrathin, Core–Shell Structured SiO <sub/>2</sub> Coated Mn <sup>2+</sup> ‐Doped Perovskite Quantum Dots for Bright White Light‐Emitting Diodes
摘要： All-inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion-exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO2 coated Mn2+ doped CsPbX3 (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX3 core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well-controlled within 2 nm, which gives the CsPbMnX3@SiO2 QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr3 QDs with green emission and CsPbMnX3@SiO2 QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light-emitting diode (LED) is successfully prepared by the combination of a blue on-chip LED device and the above perovskite mixture. The as-prepared white LED displays a high luminous efficiency of 68.4 lm W?1 and a high color-rendering index of Ra = 91, demonstrating their broad future applications in solid-state lighting fields.
关键词： quantum dots,white light-emitting diodes,core–shells,Mn2+-doping,SiO2-coating
更新于2025-11-14 15:32:45
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Photodegradation of thiophene over ZrO2–SiO2 nanoparticles: impact of copper decoration on their photocatalytic activity
摘要： A sol–gel technique was useful for the synthesis of zirconia–silica nanoparticles. Metallic copper has decorated zirconia–silica nanoparticles via photo-assisted deposition method, decorated copper mass percent was varied from 0.5, 1.0, 1.5, and 2.0 wt%. XRD results confirm that decoration of zirconia–silica nanoparticles by copper did not alert XRD pattern of zirconia–silica nanoparticles and there are no peaks for copper or copper oxide, due to high dispersion of copper above a surface of zirconia–silica nanoparticles. The decoration of zirconia–silica nanoparticles by copper was reduced band gap energy of zirconia–silica nanoparticles from 3.20 to 2.35 eV with 1.5 wt% Cu decoration. Photocatalytic oxidation of thiophene in presence of visible light was selected to measure the impact of metallic copper on photocatalytic activity of zirconia–silica nanoparticles. 1.5 wt% Cu-decorated zirconia–silica nanoparticles can degrade 100% of thiophene within 90 min.
关键词： ZrO2–SiO2,Sol–gel,Thiophene degradation,Cu decoration,Enhanced photocatalysis,Visible light
更新于2025-11-14 15:26:12
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Enhanced Selectivity for Oriented Catalyzing Tetracycline by the Functional Inorganic Imprinted ZnFe <sub/>2</sub> O <sub/>4</sub> @Ag <sub/>3</sub> PO <sub/>4</sub> /SiO <sub/>2</sub> Photocatalyst with Excellent Stability
摘要： A novel functional inorganic imprinted ZnFe2O4@Ag3PO4/SiO2 photocatalyst was synthesized by a facile sol-gel method combined with the surface imprinting technique, which possessed excellent stability. By optimizing the amount of materials to determine the preferable addition amounts of tetraethoxysilane (TEOS) and tetracycline are 0.06 mL and 0.06 g, respectively. This as-prepared functional inorganic imprinted ZnFe2O4@Ag3PO4/SiO2 photocatalyst was proved to not only exhibit high photocatalytic activity (the photodegradation rate was 61.52% under the simulated sunlight irradiation of 60 min), but also possess a strong oriented ability to selectively recognize and photocatalyze tetracycline (the coe?cient of selectivity (kselectivity) was 5.14 for ciprofloxacin and 3.63 for gatifloxacin). Moreover, the functional inorganic imprinted ZnFe2O4@Ag3PO4/SiO2 photocatalyst prepared with SiO2 as the inorganic imprinted layer have good stability and can be recycled many times. This work not only puts forward a novel design idea of functional semiconductor materials but also is expected to be widely applied to the oriented catalysis for a target substance according to the practical requirement.
关键词： selectivity,stability,ZnFe2O4@Ag3PO4/SiO2,Inorganic imprinted photocatalyst,tetracycline oriented catalysis
更新于2025-09-23 15:23:52
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Enhanced optoelectronic performance of plasma electrolytic oxidized monocrystalline silicon using rGO incorporation
摘要： rGO/SiO2 composite coating was successfully prepared by plasma electrolyte oxidation (PEO) process on monocrystalline silicon (mc-Si) substrate. Investigating the effect of rGO incorporation into the SiO2 coating revealed that the addition of rGO leads to a significant increase in the photo-trapping ability due to the high specific surface area and excellent electron transfer efficiency. The PL intensity of the composite sample was found to decrease, which signified the suspension of the electron-hole pairs’ recombination. As a result, the photocurrent gain of the composite coating enhanced about 5.5 times. Likewise, the time-response switching featured an over two-fold increase for the rGO/SiO2 coating, impressively.
关键词： Semiconductors,Plasma electrolyte oxidation,Optoelectrical properties,Composite materials,rGO/SiO2 composite
更新于2025-09-23 15:23:52
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Silica-coating of nano-$$\hbox {Y}_{3} \hbox {Al}_{5} \hbox {O}_{12}{:}\hbox {Ce}^{3+}$$Y3Al5O12:Ce3+ synthesized by self-combustion
摘要： Y2.91Ce0.09Al5O12 is obtained by self-combustion, grinding and sol–gel coating. X-ray diffraction, transmission electron microscopy, photoluminescence and absorption measurements were used to identify the structural and optical properties of each step of the process. The process is composed of a combination of chemical and physico-chemical processes including combustion and thermal steps, followed by grinding, powder dispersion by acidic passivation, stabilization of particle dispersions with citrate ligands and embedding of yttrium aluminium garnet (YAG) particles into SiO2 shells using a seeded growth process before drying. The initial state of the obtained powder is composed of 35 nm crystallites, sintered and agglomerated. The grinding step breaks the sintered bridge, while the passivation and citrate adsorption steps separate the particles by electrostatic repulsion before the silica coating. The optical characterizations are performed and compared separately for the powdered samples that represent the initial and ?nal states of our process, and the dispersion sample represents the intermediate state of our process. The optical measurement revealed an important amount of optical defects at the surface of the particles, compared with micrometric commercial particles. The grinding, nitric acid and citrate steps remove some of these defects. The ?nal state of the sample still possesses lower quantum ef?ciency than that of a micrometric sample, but the SiO2 coating allows for a perfect separation of the particle, suitable for implementation in small devices.
关键词： Self-combustion,YAG,core–shell,SiO2 coating
更新于2025-09-23 15:23:52
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Porous SiO2-coated Au-Ag alloy nanoparticles for the alkyne-mediated ratiometric Raman imaging analysis of hydrogen peroxide in live cells
摘要： We prepared an ultrathin porous silica shell-coated Au-Ag alloy nanoparticle (AuAg@p-SiO2NP) and developed it as a novel alkyne-based surface-enhanced Raman scattering (SERS) nanoprobe for the ratiometric Raman imaging of exogenous and endogenous H2O2 in live cells. The AuAg@p-SiO2NPs functionalized with 4-mercaptophenylboronic acid (MPBA) and 4-mercaptophenylacetylene (MPAE, 1,986 cm-1) as internal standard were first incubated with dopamine (DA) to incorporate the bridging molecules through the formation of borate bond between DA and MPBA on the surface of nanoparticle. Then, the signaling alkyne molecules of 3-(4-(phenylethynyl) benzylthio) propanoic acid (PEB, 2,214 cm-1) were conjugated to the surface of nanoparticle through the formation of amide bond between the carboxyl group on the PEB and the amino group on the DA, forming the ratiometric SERS nanoprobe. In the presence of H2O2, the alkynyl on the PEB is released from the surface of the Au-Ag alloy nanoparticle due to the boronate-to-phenol switch, decreasing the Raman signal at 2,214 cm-1 significantly. Since the Raman signal of MPAE at 1,986 cm-1 remains unchanged, quantitative analysis of H2O2 concentration can be achieved based on the ratiometric value of I1986/I2214. Under the optimized conditions, the plot of the ratiometric value of I1986/I2214 versus the H2O2 concentration in the range from 0.12 to 8 m M revealed a good linear response with a detection limit of 52 nM based on a signal-to-noise ratio of S/N = 3. The porous SiO2-coated Au-Ag alloy nanoparticle provides a novel SERS substrate with excellent biocompatibility, high stability, and effective anti-interference ability. Together with the alkynyl derivatives as internal standard, the SERS nanoprobe reported here allows the ratiometric detection of H2O2 in live cells and can be further applied to quantify many other biomolecules by using different signaling agents.
关键词： porous SiO2-coated Au-Ag alloy nanoparticle,SERS,alkyne,cell imaging,hydrogen peroxide
更新于2025-09-23 15:23:52
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Crystallization kinetics and thermal stability of ZrO <sub/>2</sub> monolithic aerogel improved by SiO <sub/>2</sub> layer
摘要： ZrO2 aerogel modified by SiO2 (ZSA) was synthesized by aging ZrO2 gel in tetraethoxysilane (TEOS) solution using ZrOCl2·8H2O as precursor, and 1,2-propylene oxide (PO) as gelation agent followed by ethanol supercritical fluid drying. Crystallization kinetics and thermal stability of ZSA while calcined at elevated temperature were studied comparing with pure ZrO2 aerogel. The prepared samples were characterized using TG-DSC, N2 adsorption/desorption, SEM and TEM. The results show that thermal stability of ZSA are highly improved due to the SiO2 layer hindering the proliferation, nucleation and growth process of ZrO2.
关键词： ZrO2,thermal stability,aerogel,SiO2,crystallization kinetics
更新于2025-09-23 15:23:52
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SiO2@Graphene Composite Materials Obtained through Different Methods Used as Substrate Materials
摘要： In this work, two different methods were applied to prepare SiO2-Graphene composite materials (SiO2-G). One way to synthesize composite materials was stirred carboxyl functionalized graphene and tetraethyl ortho silicate (TEOS) together at low temperature. In other way, SiO2-G were obtained via an one-pot hydrothermal reaction. We employed SEM to characterize the direct structure and morphology information of materials, subsequently. It could be clearly observed that their morphology were greatly affected by the different preparation methods and resulted in a tremendous change occurred. It is no question that the as-prepared materials with different structure can be used as different substrate materials.
关键词： SiO2,Graphene,Composite,Materials
更新于2025-09-23 15:23:52
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In-situ synthesis of mullite-SiCw composite ceramics in Li2O-Al2O3-SiO2 ternary system for solar heat transmission pipeline
摘要： Nano-SiC whiskers (nano-SiCw) were in-situ synthesized in Li2O-Al2O3-SiO2 ternary system for preparing highly densified mullite-SiCw composite ceramics used for solar heat transmission pipeline. Mechanisms on the in-situ synthesis of nano-SiCw in the ternary system were investigated and the impact of nano-SiCw on the performances of the composites had been studied. Results showed that the growth processes of nano-SiC whiskers in Li2O-Al2O3-SiO2 ternary system were dominated by liquid-solid (LS) mechanism and the Li2CO3 additive could improve the SiCw yield through increasing the content of liquid phase and lowering the liquid viscosity. Sample BS3 (with 2.22 wt% Li2CO3 additive) sintered at 1440 °C obtained the highest SiC content of 47.9%. Nano-SiC whiskers with a diameter of 20e30 nm were interlocking with rod-like mullite crystals to improve the mechanical properties of the composites, and sample BS1 sintered at 1420 °C showed the highest bending strength of 115.4 MPa. The in-situ synthesized SiCw also shew significant effects on improving the thermophysical properties of the composites and sample BS1 exhibited a 3.6 times higher thermal conductivity than that of blank sample B1 without the introduction of nano-SiCw.
关键词： Li2O-Al2O3-SiO2 ternary system,Thermal conductivity,Mullite-SiCw composite ceramics,Solar heat transmission pipeline,SiC whiskers
更新于2025-09-23 15:23:52