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Nanofluids that are produced by dispersing nanoparticles into traditional heat transfer fluids, show greater thermal conductivities than regular fluids. An interfacial nano-shell between the nanoparticle and the base fluid was used to derive an expression for the effective thermal conductivity of nanofluids. Unlike with traditional models, the effective thermal conductivity predicted by the present model is not only affected by the ratio of the thermal conductivities of the particle and the media and their relative volume fractions, but is also affected by the nanoparticle radius and the thermal conductivity and thickness of the interfacial nano-shell. The calculated results predicted by this model agree quite well with available experimental data. [ABSTRACT FROM AUTHOR]

Abstract: We have prepared the gallium oxide (Ga2O3) nanomaterials on Si (111) substrates by thermal evaporation of gallium in the ammonia atmosphere. The self-catalytic vapor–solid mechanism is used in explaining the formation mechanism. Scanning electron microscopy (SEM) revealed that the products contained many special structures, including spiral nanobelts, nanotrees and nanotubes locating in different temperature zones, respectively. The selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) observations suggest that these as-synthesized products have a single-crystalline structure with a width ranging from 100nm to several micrometers. Possible mechanism leading to the formation of Ga2O3 nanomaterials, especially the relation between temperature and some special structures is to be discussed in this paper. Photoluminescence spectrum under excitation at 396nm showed a green emission, which is probably attributed to vacancies in Ga2O3. [Copyright &y& Elsevier]

Sodium-ion batteries with potentially low cost is an alternative to lithium-ion batteries for large-scale energy storage. However, developing high energy density and ultralong cycle life electrodes for sodium-ion batteries is a key issue due to the larger radius of Na+ than Li+ and the sluggish sodium intercalation kinetics. One-step electrospinning process has been applied to synthesis Sb 2 S 3 nanocrystals hosted in multichannel porous N-doped carbon nanofiber (CNF). Sb 2 S 3 nanoparticles with diameter of 10–50 nm were uniformly embedded in CNF, while the multichannel pores of CNF act as a buffer to restrict the volume expansion of Sb 2 S 3 during cycling. Sb 2 S 3 @N-doped carbon nanofiber (Sb 2 S 3 @CNF) delivered a specific capacity of 311 mAh g−1 at 100 mA g−1 with a capacity retention of 87% after 1000 cycles at 1A g−1, corresponding to a capacity decay rate of only 0.013% per cycle. Benefited from the unique multichannel mesoporous structure, charge storage of Sb 2 S 3 @CNF is mainly contributed by a surface capacitive process indicating significantly enhanced mass diffusion properties. The as-developed nanofibers with a cylindrical porous structure by a one-step electrospinning method can be an excellent host for electroactive materials to achieve ultralong cycle life. A one-step electrospinning process has been applied to synthesis multichannel porous N-doped carbon nanofibers (CNF) hosted with Sb 2 S 3 nanocrystals. Sb 2 S 3 @CNF delivered an ultralong cycle life with a capacity retention of 87% after 1000 cycles at 1A g−1. Image 1 • Sb 2 S 3 nanocrystals (10–50 nm) embedded in multichannel CNF (Sb 2 S 3 @CNF) have been fabricated by one-step electrospinning. • Mesoporous CNF has multichannel cylindrical pores with diameter of ~10 nm. • The cylindrical mesopores of CNF effectively buffer the volumetric change of Sb 2 S 3 and lead to ultralong cycle stability. • Sb 2 S 3 @CNF has a capacity retention of 89.1% after 1000 cycles, significantly higher than that of Sb 2 S 3 @C (56.3%) and Sb 2 S 3 powder (21.3%). [ABSTRACT FROM AUTHOR]

Higher working temperatures could help to improve the solar-electricity efficiency of concentrating solar power plant. However, the high temperature also induces structure variations and optical degradation of solar absorbers, and how the structure evolutions affect the optical performances remains largely unclear. To address the problems, we conducted cyclic heat-treatment on the AlCrSiO-based solar selective absorbers at a temperature of 650 °C. Then the microstructures and optical properties of the absorbers before and after annealing were systematically investigated. Finite-Difference Time-Domain simulations were used to establish the relationships between the microstructures and optical properties. The results showed that the absorber can maintain its multilayered structure after cyclic heat-treatment at 650 °C in air with a solar selectivity of 0.928/0.171. Oxidation of micro-droplets on surface can enhance solar absorption in the UV–Vis region due to the reduction of backscattering. The weak oxidation of the absorbing layers would lead to the enhancement of interference effects in the whole solar spectrum. The combination of the above effects can actually enhance the solar absorptance. The diffusion of carbon from the substrate into the infrared reflective Cr layer would slightly improve the thermal emittance. These results suggested the AlCrSiO-based solar selective absorber can be a possible candidate for applications in the next-generation concentrating solar power plant system. • AlCrSiO-based solar absorber exhibited thermal stability at 650 °C in air with a selectivity of 0.93/0.17. • Oxidation of micro-droplets on absorber surface enhanced solar absorption in UV–Vis region. • Weak oxidation of absorbing layers led to enhancement of interference effects in whole solar spectrum. [ABSTRACT FROM AUTHOR]