[en] In this work, well dispersed ethylene glycol (EG) based nanofluids containing ZnO nanoparticles with different mass fractions between 1.75% and 10.5% were prepared by a typical two-step method. Structural properties of the dry ZnO nanoparticles were measured with X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Thermal transport properties including thermal conductivity and viscosity were experimentally measured for the nanofluids. The experimental results show that thermal conductivity increases slightly with increasing the temperature from 15 to 55 °C. It depends strongly on particle concentration and increases nonlinearly with the concentration within the range studied. The enhanced value is higher than the value predicted by the Hamilton and Crosser (H–C) model. Moreover, viscosity increases with concentration as usual for ZnO nanoparticles and decreases with temperature. For an analysis of the rheological behaviors, it shows that ZnO-EG nanofluids with mass fraction wt.% ≤ 10.5 demonstrate Newtonian behaviors

[en] Yttrium oxide (Y₂O₃) is a promising ceramic material for electronic and optical applications due to its excellent properties. The purpose of this study is to characterize the effects of deposition parameters on the structure and composition of Y₂O₃ films. The films are grown on Si substrates by reactive magnetron sputtering at different substrate temperatures and oxygen pressures. The composition and structure of the films are studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It is shown that the Y₂O₃ films deposited by reactive magnetron sputtering are mainly cubic phase and polycrystalline. The films are composed of Y-O, Y-O-Si, and Si-O bonds. Increasing substrate temperature induces the monoclinic to cubic phase transition and results in the formation of oxygen vacancies in the film. The preferred growth orientation of Y₂O₃ film is the (110) plane at low temperature, and it changes to the (111) plane at high temperature. The low temperature is preferable for the formation of Y-O bonds. The oxygen pressure influences on the concentration of Y-O bonds significantly. An optimal oxygen partial pressure for the formation of Y-O bonds exists during the film deposition. In addition, the deposited Y₂O₃ films exhibit excellent mechanical properties.

[en] In order to explore effects of cadmium stress on the growth and development of pecan seedling, pecan seedling was used as testing material, nutrient solution culture method was adopted and the physiological indexes of pecan seedlings were measured under different concentration of cadmium [0 (CK), 5, 10, 20, 40, 80 mg · L^-1]. The results showed that cadmium stress has a significant inhibitory effect on the growth and development of pecan. The inhibitory effect is more obvious with higher concentration of cadmium. With the increase of the cadmium concentration, biomass and root length decreased significantly, which decreased by 40.11% and 56.64% compared with the control group at the concentration of 80 mg · L^-1. The cadmium content in roots, stems and leaves of seedlings rose significantly, and reached 5582 mg · kg^-1, 2235 mg · kg^-1, 479 mg · kg^-1 at the concentration of 80 mg · L^-1. The contents of Mn, Zn, Mg and K in roots and stems were inhibited, but the contents of K and Mg in leaves increased significantly. When the concentration of cadmium was 20 mg · L^-1, the activity of POD and CAT in leaves reached the highest level, and increased by 726.62%, 86.47% compared with the control group. At the concentration of 20 mg · L^-1, the net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of leaves dropped dramatically by 81.44%, 81.59% and 75.22% compared with the control group, respectively. And leaf fluorescence parameters-efficiency of primary conversion of light energy (ΦPSII), apparent electron transfer rate (ETR) and photochemical quenching (qP) decreased significantly while non-photochemical quenching (qN) increased significantly, and photosynthesis was severely inhibited. To sum up, cadmium stress inhibited the biomass accumulation of pecan seedlings and affected the absorption of elements in roots and stems, and significantly reduced the photosynthesis intensity of leaves, causing serious damage to seedling growth. This study laid the foundation for revealing the cadmium tolerance and cadmium enrichment mechanism of pecan. (authors)

[en] Yttrium oxide films were prepared on silicon wafers by reactive magnetron sputtering at different oxygen flow rates to investigate the microstructure and optical properties for desirable planar optical waveguiding applications. Under the different conditions of target surface, the deposition rate, structure, and optical properties have great changes. The deposition rate increases to the maximum, and then monotonically decreases. Oxygen content in films increases and the composition of films transforms from stoichiometry to an oxygen-rich state. Y₂O₃ films grow with the (222) preferred growth orientation at low oxygen flow rate, and then turn into the (622) orientation; the microstructure evolves from crystal structure to amorphous state as oxygen flow rate increases from 2 to 12 sccm. Sufficient oxygen makes films low-order structure and oxygen-rich films have poor crystallinity. Very smooth film has been obtained at oxygen flow rate of 12 sccm. The refractive index can be greatly modulated by the oxygen-content factor. It is convincing that the controllable structure and optical properties of Y₂O₃ films can be achieved by adjustment the oxygen flow rate for desired optical design and applications. (orig.)

[en] An electroplating method was used for the first time to synthesize 3D porous graphene oxide (PGO) architectures, exhibiting ultrahigh capacitance and energy density as electrodes of supercapacitors. Scanning electron microscopy illustrated the porous structures which promoted the stability and alleviated the stacking of the graphene oxide layers. As investigated in a three-electrode supercapacitor cell, PGO electrodes exhibited the maximum capacitance and energy of 973 F · g"−"1 and 98.4 Wh · Kg"−"1, which are better than current reports and comparable to batteries. At 4 A · g"−"1 for high-power applications, PGO electrodes reached a capacitance, energy, and power density of 493 F · g"−"1, 49.9 Wh · Kg"−"1, and 1700 W · Kg"−"1, and they retained ∼97.83% of capacitance after 10 000 charge/discharge processes. Furthermore, when the PGO was bent exaggeratedly, it still displayed identical properties, which is of important significance for supporting wearable devices. (paper)

[en] A simple and effective strategy is introduced for the direct growth of SiC nanowires, carbon nanotubes (CNTs), and graphene on target substrates via a solid-state process based on the use of a solid amorphous carbon source. The desired products were synthesized in large quantities via the thermal treatment of laminated sandwich film precursors at 900 °C under a protective Ar atmosphere. The growth mechanisms and evolution models of the SiC nanowires, CNTs, and graphene were studied in detail and were proposed to be a combination of a dissolution–precipitation process and a confined reaction from a laminated sandwich film precursor. The combination of this fabrication process (which also enables the simultaneous patterning of the proposed nanostructures) with the inherent properties of SiC nanowires, CNTs, and graphene therefore represents significant progress in the functional patterning of nanomaterials for use in a range of potential applications.

[en] Two-dimensional crystals-based surface-enhanced Raman scattering (SERS) substrates are a research hot spot in the realm of chemistry and biology. Herein, a novel hybrid substrate based on AuNPs/GaTe/Au-film is proposed and fabricated for SERS activity. Finite-difference time-domain numerical simulations demonstrate that the plasmonic coupling in the hybrid structure, particularly the LSPs coupling of AuNPs and Au-film, promotes an enhanced electric field and consequently, greatly enhances the Raman activity. Impressively, the enhancement factor of 3 × 10⁵ and the limiting detection concentration of 10⁻¹⁴ M have been achieved for the rhodamine 6G molecules, which are equivalent to the best results achieved from the patterned graphene substrates. Due to its simple structure, cost-effectiveness, good uniformity, reproducibility, and stability, it is expected that such a SERS substrate will open up a new way toward the ultrasensitive detection of molecules.

[en] The influences of indium doping and subsequent annealing in nitrogen and air atmospheres on the microstructure and optical properties of cadmium oxide films were studied in detail with the aid of various characterizations. X-ray photoelectronic spectroscopy analysis shows that indium atom forms chemically oxidized bonds in Cd-O matrix. X-ray diffraction results demonstrate that CdO structure remains FCC structure with indium doping, whereas the preferential orientation transforms from (222) into (200) orientation. Indium doping prevents the large crystalline growth, and this role still works under both nitrogen and air annealing processes. Similarly, CdO films show rough surface under annealing conditions, but the force has been greatly weakened at high doping level. It is clear that refractive index and extinction coefficient are closely correlated with crystalline size for undoped films, whereas it turns to the doping level for doped films, which can be performed by the mechanism of indium atom substitution. This work provides a very useful guild for design and application of optical-electronic devices. (orig.)

[en] The effect of carrier concentration on the Fermi level and bandgap renormalization in over 30 indium-doped cadmium oxide (CdO : In) films with carrier concentrations ranging from 1 to 15 × 10²⁰ cm⁻³ was studied using the two-band k · p model with electron–electron and electron–ion interactions. It is shown that the Tauc relation, which is based on parabolic valence and conduction bands, overestimates the optical bandgap in the CdO films. Theoretical calculations of the optical bandgap give good agreement with experiments by taking into account the Burstein–Moss effect for a nonparabolic conduction band and bandgap renormalization effects. The band filling and bandgap renormalization in these CdO : In films are about 0.5–1.2 eV and 0.1–0.3 eV, respectively. (paper)

[en] Highlights: • An analysis coupled with Radiation transfer, Maxwell and Energy equation is developed. • Plasmonic Au and Ag nanofluids show better photo-thermal conversion properties. • Collector height and particle concentration exist optimum solutions for efficiency. - Abstract: A one-dimensional transient heat transfer analysis was carried out to analyze the effects of the Nanoparticle (NP) volume fraction, collector height, irradiation time, solar flux, and NP material on the collector efficiency. The numerical results were compared with the experimental results obtained by silver nanofluids to validate the model, and good agreement was obtained. The numerical results show that the collector efficiency increases as the collector height and NP volume fraction increase and then reaches a maximum value. An optimum collector height (∼10 mm) and particle concentration (∼0.03%) achieving a collector efficiency of 90% of the maximum efficiency can be obtained under the conditions used in the simulation. However, the collector efficiency decreases as the irradiation time increases owing to the increased heat loss. A high solar flux is desirable to maintain a high efficiency over a wide temperature range, which is beneficial for subsequent energy utilization. The modeling results also show silver and gold nanofluids obtain higher photothermal conversion efficiencies than the titanium dioxide nanofluid because their absorption spectra are similar to the solar radiation spectrum.