- 标题
- 摘要
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- 实验方案
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Effects of carbon nanotube thermal conductivity on optoacoustic transducer performance
摘要： CNT-PDMS composite is regarded as a promising candidate for optoacoustic transducer application. However, the relationship between the CNT thermal conductivity and optoacoustic transducer performance is still unde?ned. To explore this relationship, four types of CNTs with different diameters and lengths were employed to successfully fabricate four types of optoacoustic transducers. The thermal properties of CNTs were analyzed and discussed in this paper; the laser-generated ultrasound and optoacoustic conversion ef?ciency of the transducers were experimentally and theoretically investigated. Results of comparison revealed the CNT with a diameter and length of 8 nm and 10e30 mm, respectively, to have the highest thermal conductivity. With this type of CNT/PDMS composite, the optoacoustic conversion ef?ciency reached as high as 9.59 (cid:1) 10-3. Overall, the results demonstrate that higher CNT thermal conductivity corresponds to better optoacoustic transducer performance.
关键词： Laser-generated ultrasound,Thermal conductivity,Optoacoustic transducer,Optoacoustic conversion ef?ciency,CNT
更新于2025-09-23 15:23:52
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Highly efficient solar steam generation via mass-produced carbon nanosheet frameworks
摘要： Carbon nanosheet frameworks are synthesized on the gram scale by exploiting the reaction between Mg powder and CS2 vapor. This fluffy carbon nanomaterial coated on fabric shows high performance in solar steam generation. The carbon film has high optical absorption of ~98% in visible and infrared spectrum. When under 1 sun solar-simulated light irradiance (1000 W m-2), the surface temperatures of dry and water-saturated carbon films reach 104 and 45 oC, respectively, indicating good heat localization. As a result, the carbon film under 1 sun illumination shows a high solar-to-vapor efficiency of 93%, which is higher than that of most photothermal conversion materials reported previously. The as-prepared carbon material may pave the way for harvesting solar energy to produce clean water at low cost.
关键词： solar steam generation,Mg thermoreduction,photothermal conversion,carbon nanosheet,vapor-solid reaction
更新于2025-09-23 15:23:52
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Porous WO3 monolith-based photoanodes for high-efficient photoelectrochemical water splitting
摘要： We report a successful fabrication of low-cost, high-efficient, structurally-rigid, porous WO3 photoelectrochemical (PEC) catalysts using polystyrene as the template by a sol-gel method and a high-temperature annealing treatment. The scanning electron microscopy and Brunauer-Emmett-Teller surface analysis results indicate that such WO3 monoliths possess a porous structure and a large specific surface area, which can supply lots of photogenerated charge transfer pathways as well as more surface PEC active sites. Compared with a commercially available WO3, our highly porous WO3 PEC catalysts show an excellent PEC water splitting activity. Particularly, the porous WO3 photoanodes calcinated in the presence of oxygen atmosphere at 450 °C for 7 h show the best PEC performance exhibiting the photocurrent density of 0.97 mA/cm2 at 1.23 V versus reversible the hydrogen electrode and the incident photon-to-current conversion efficiency up to 48.9% at 420 nm in 0.5 M Na2SO4 electrolyte under AM 1.5 G irradiation. Such excellent PEC performance is due to the high porosity of the WO3, promoting the fast transfer and the separation rate of photogenerated carriers during the PEC water splitting process.
关键词： Water splitting,Porous structures,Energy conversion,WO3,Photoanode
更新于2025-09-23 15:23:52
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Broadband Linear Polarization Conversion Metasurface Based on Grounded Vias
摘要： An anisotropic high-impedance surfaces is applied to achieve perfect polarization rotation. Three multiple resonances are generated by electric and magnetic resonances which contributed to bandwidth expansion of the proposed polarization converter. The simulation results showed that maximum conversion ef?ciency is nearly 100% at mentioned three resonance frequencies. Here, 107 % bandwidth with polarization conversion ratio of above 90% is achieved. The proposed polarization conversion unit-cell is examined for oblique incidence, as well. It is observed that the bandwidth of the proposed unit-cell is not sensitive to the non-orthogonal incidence angles up to 40?. This observation veri?es applicability of proposed polarization rotator unit-cell.
关键词： polarization conversion,metasurface,high impedance surface
更新于2025-09-23 15:23:52
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Pressure dependence of high order harmonic generation in nitrogen molecular gas and atmospheric air
摘要： The effect of the variation of the gas pressure on the high harmonic generation (HHG) from nitrogen molecular gas (N2) and atmospheric air with ultrashort intense laser pulses is measured. The optimum pressure in the interaction region of a gas jet for maximizing the HHG yield is determined for both gases. Enhancement of the HHG output and its extension to higher harmonic orders are observed around the optimum pressure value of 0.33 bar. Theoretical calculations based on one-dimensional models explain this effect and provide reasonable agreement with experimental results.
关键词： Femtosecond laser,Conversion efficiency,High-order harmonic generation (HHG),Phase matching,XUV radiation,Pressure optimization
更新于2025-09-23 15:23:52
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Modulated up-conversion luminescence and low-temperature sensing of Gd3Ga5O12:Yb3+/Er3+ by incorporation of Fe3+ ions
摘要： Yb3+/Er3+ co-doped crystals show strong up-conversion luminescence and their temperature dependence of luminescence intensity enable the application of temperature sensors. Such sensors usually work at hundreds Kelvin with high sensitivity, while the sensors appropriate to very low temperatures are rarely reported. In this study, we report the low temperature sensing of Gd3Ga5O12:Yb3+/Er3+ nanocrystals by partial or total substitution of Ga3+ by Fe3+ ions. The up-conversion photoluminescence of the nanocrystals is measured on cooling from 300 to 4.2 K. The low-temperature sensing performance is improved, and the structure, magnetic and optical properties are modulated by the substitution of Fe3+ ions, rendering the nanocrystal useful for multi-functional sensing application.
关键词： Temperature sensor,Magnetic doping,Photoluminescence,Up-conversion
更新于2025-09-23 15:23:52
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Fabrication and up-conversion fluorescence property of Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped Ca-Si-Ti biomaterials
摘要： This work demonstrates bulk-type up-conversion biomaterials which could be used as a bone repair material with the ability to monitor bone mineralization. Er3+/Yb3+ co-doped Ca-Si-Ti (CST3: TiO2 content is 30 mol%) bulk biomaterials were prepared via containerless processing technique in an aerodynamic levitation furnace and with subsequently heat treatment. The up-conversion fluorescence property was influenced by Yb3+ doping concentration, heat-treatment and mineralization in simulated body fluid (SBF). Optimum emission intensities were obtained for the sample with 20 mol% of Yb3+ doping concentration and heat treatment at 937 °C for 2 h. Hydroxyapatite (HAP) deposition was observed on the surface of the samples after soaking in SBF for 14 days, and the up-conversion fluorescence intensity of the samples decreased with the increase of soaking time. This indicates that Er3+/Yb3+ co-doped CST3 materials are bioactive, in which the HAP mineralization in bone repair could be monitored by measuring the intensity change of up-conversion fluorescence.
关键词： Heat treatment,Up-conversion fluorescence,Containerless processing,Mineralization,Er3+/Yb3+ co-doped Ca-Si-Ti biomaterial
更新于2025-09-23 15:23:52
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Preparation of Pd/TiO2 nanowires for the photoreduction of CO2 into renewable hydrocarbon fuels
摘要： In this study, various Pd-loaded TiO2 nanowire (Pd/TiO2–NW) catalysts were prepared using the hydrothermal method, and their photocatalytic activity toward the photoreduction of CO2 into methane (CH4) and carbon monoxide (CO) was evaluated. The photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, UV–vis spectroscopy, X-ray photoelectron spectroscopy and photoluminescence analysis. The addition of Pd on TiO2–NWs can improve the production yield of CO2 photoreduction to CH4 and CO. The 0.5 wt% Pd/TiO2–NWs showed optimal CO and CH4 yields of 50.4 and 26.7 μmol/g, respectively. Moreover, the 0.5 wt% Pd/TiO2–NWs could be used repeatedly with only a small loss of photocatalytic activity noted after 30 days. Furthermore, a mechanism for the photoreduction of CO2 was proposed. Therefore, Pd/TiO2–NWs are an efficient photocatalyst for the reduction of CO2 to CH4 and CO.
关键词： Renewable hydrocarbon fuels,CO2 conversion,Photocatalyst,Pd-loaded TiO2 nanowires
更新于2025-09-23 15:23:52
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2D Ti2C (MXene) as a novel highly efficient and selective agent for photothermal therapy
摘要： Photothermal therapy (PTT) has shown significant potential for anti-cancer modality. In this report, according to our best knowledge, we explore for the first time Ti2C-based MXene as a novel, highly efficient and selective agent for photothermal therapy (PTT). Ti2C superficially modified with PEG was obtained from the layered, commercially available Ti2AlC MAX phase in the process of etching aluminum layers using concentrated HF, and characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HREM) as well as X-Ray photoelectron spectroscopy for chemical analysis (ESCA-XPS). The PEG-coated Ti2C flakes showed a satisfactory photothermal conversion efficacy (PTCE) and good biocompatibility in wide range of the tested concentrations. Through in vitro studies, the PEG-modified Ti2C demonstrated notable NIR-induced ability to cancerous cells’ ablation with minimal impact on non-malignant cells up to the concentration of 37.5 μg ml-1. The applied doses of Ti2C_PEG in our work were even 24 times lower comparing other MXene-based photothermal agents. This work is expected to expand the utility of 2D MXenes to biomedical applications through the development of an entirely novel agents for photothermal therapy.
关键词： photothermal therapy,biological activity,light-to-heat conversion,2D Ti2C MXenes,anticancer therapy
更新于2025-09-23 15:23:52
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Single-Phase Transformer based HF-Isolated Z- Source Inverters with Voltage Clamping Techniques for Solar PV Applications
摘要： In this research article, a new family of impedance source inverters is presented. It employs high frequency electrical isolation between the inverter bridge switches and the load along with voltage clamping across the DC-link voltage. Conventional Z-source inverters (ZSIs) employs an impedance network that consists of inductors and capacitors. It has unique features which realize both step-up/step-down functions and eliminates the need of dead/overlap times. This paper extends this novel concept by using electrical isolation in impedance source inverters. High frequency isolation has many advantages in terms of immunity and reliability; when applied with impedance source inverters this makes ZSIs a preferable choice for industrial applications. In PV systems, the addition of the high frequency transformer provides safety by avoiding the injection of DC circulating current into the grid, without the need of an external bulky line frequency transformer. The gain of the proposed inverter design can be accurately selected by choosing the turns ratio of the HFT or by adjusting the shoot-through duty cycle (STDC) to the inverter. This allows for greater freedom especially when utilizing a higher modulation index, with the STDC allowing dynamic gain adjusts to be done speedily during operation of the inverter. Additionally, a DC-rail voltage clamping technique for the proposed class of isolated ZSIs is also discussed. This technique provides benefits not only in improving the output voltage quality, but also in reducing voltage stress of the active and passive components by minimizing the voltage spikes across the switching devices. In this paper, several high frequency isolated ZSIs are presented, and an example isolated improved ΓZSI design is shown and discussed in detail. Simulations are provided for the proposed class of isolated inverters to verify their working. Further experimental investigation has been done for which results for the isolated improved ΓZSI are reported. These empirical results have largely confirmed the expected benefits that were determined through simulation and accurate model-based testing.
关键词： Single stage power conversion,Higher voltage gain,Impedance source,frequency isolation,High frequency transformers
更新于2025-09-23 15:23:52