Abstract
Nickel-based complex oxides have served as a playground for decades in the quest for a copper-oxide analog of the high-temperature superconductivity. They may provide clues towards ...understanding the mechanism and an alternative route for high-temperature superconductors. The recent discovery of superconductivity in the infinite-layer nickelate thin films has fulfilled this pursuit. However, material synthesis remains challenging, direct demonstration of perfect diamagnetism is still missing, and understanding of the role of the interface and bulk to the superconducting properties is still lacking. Here, we show high-quality Nd
0.8
Sr
0.2
NiO
2
thin films with different thicknesses and demonstrate the interface and strain effects on the electrical, magnetic and optical properties. Perfect diamagnetism is achieved, confirming the occurrence of superconductivity in the films. Unlike the thick films in which the normal-state Hall-coefficient changes signs as the temperature decreases, the Hall-coefficient of films thinner than 5.5 nm remains negative, suggesting a thickness-driven band structure modification. Moreover, X-ray absorption spectroscopy reveals the Ni-O hybridization nature in doped infinite-layer nickelates, and the hybridization is enhanced as the thickness decreases. Consistent with band structure calculations on the nickelate/SrTiO
3
heterostructure, the interface and strain effect induce a dominating electron-like band in the ultrathin film, thus causing the sign-change of the Hall-coefficient.
This paper reports on the results of an experimental study on the heat transfer and flow performance of multiwalled carbon nanotubes (MWCNT) in aqueous suspensions flowing in multiport minichannel ...flat tubes with smooth/micro-fin surface under a constant heat flux condition. The MWCNT–water nanofluids volume concentrations are 0.001%, 0.005%, 0.01%, and 0.1%. Results indicate that the friction factor and the Nusselt number of the nanofluids are higher than those of water. The Nusselt number does not increase with volume concentration. The heat transfer of nanofluids in the micro-fin tubes is higher than that of nanofluids in the smooth tube. However, the heat transfer enhancement of nanofluids in the micro-fin tubes is lower than that of nanofluids in the smooth tube. The effect of micro-fin spacing is more evident in nanofluids than in water. Nanofluids with a concentration of 0.01% flowing in the tube with closely spaced micro-fin tube exhibit the optimal thermal performance in accordance with the performance evaluation criterion.
Display omitted
•Flow and heat transfer characteristics of MWCNT–water nanofluid are studied.•The concentration of nanofluid for the optimum thermal performance is obtained.•Heat and flow characteristics for two kinds of tubes are compared.•The PEC of nanofluid in multiport minichannels with micro-fin surface is reported.
An experimental energy storage system has been designed using a new type flat micro heat pipe heat exchanger that incorporates a moderate-temperature phase change material paraffin with a melting ...point of 58°C. The basic structure, working principles, and design concept are discussed. The heat transfer process during the charging and discharging of the heat exchanger under various operating conditions has been experimentally investigated. Results show that the performance of the new type flat micro heat pipe was steady and efficient during charging and discharging. The average thermal storage power and absorption efficiency have been determined to be approximately 537 W and 92.5%, respectively.
In this study, the heat transfer characteristics of a new-type flat micro-heat pipe thermal storage unit, which uses a moderate-temperature paraffin as heat storage phase change material, were ...investigated. The basic structure, working principle, and design concept of the thermal storage unit were discussed. Experiments were conducted to study the charging and discharging heat transfer processes of the thermal storage unit under different inlet temperatures and flow rates for the cold/hot heat transfer fluid (HTF). Experimental results show that the performance of the thermal storage unit was steady and efficient during heat charging and discharging, and the average charging and discharging powers of the thermal storage unit were approximately 658 and 894 W, respectively, under specific experimental parameters.
•A thermal storage unit using new-type flat micro-heat pipes was presented.•The performance of the thermal storage unit was investigated experimentally.•The thermal storage unit has good performance in the charging/discharging process.
•Pool boiling heat transfer characteristic and critical heat flux of Cu-R141b nanorefrigerant is investigated experimentally.•Adding surfactant and (or) nanoparticles in pure liquid of R141b could ...enhance pool boiling heat transfer.•The deposition of nanoparticles has a significant effect on the boiling heat transfer.
The pool boiling heat transfer and critical heat flux (CHF) of the Cu-R141b–SDBS nanorefrigerant and SDBS–R141b solution are experimentally investigated on a flat surface under atmospheric pressure. The nanorefrigerant concentrations are 0.008vol.%, 0.015vol.%, and 0.05vol.%. Pure R141b is also boiled on the nanorefrigerant-deposited surface to isolate the effect of the fluid properties. Experimental results show that the Cu-R141b–SDBS nanorefrigerant can enhance the pool boiling heat transfer. The enhancement ratio of the Cu-R141b–SDBS nanorefrigerant is different from that of the R141b–SDBS solution compared with pure R141b. The CHF of the nanorefrigerant on the bare surface is lower than that of pure R141b on the deposited surface.
Different aluminum-doped ZnO (AZO)/metal composite films, including AZO/Al, AZO/Ag/Al and AZO/Ag/NiCr/Al, were utilized as the back reflectors for p-i-n hydrogenated amorphous silicon germanium ...(a-SiGe:H) thin film solar cells. It was found that AZO/Al had a better performance than single Al electrode and the thickness of AZO film could strongly affect the short-circuit current density (Jsc) of the solar cells. However, AZO/Ag/Al, which was expected to improve the back reflectance further, gave out a bad effect, due to the inter diffusion of Ag and Al. While a nickel–chromium (NiCr) film was inserted between Ag and Al as a diffusion barrier, the highest Jsc was achieved. So AZO/Ag/NiCr/Al could be utilized as an improved AZO/metal back reflector for p-i-n a-SiGe:H solar cells.
► Nickel–chromium (NiCr) diffusion barrier was inserted between Ag and Al. ► Both NiCr and Al layers protected the Ag layer very well against oxidation. ► Aluminum-doped ZnO(AZO)/Ag/NiCr/Al back reflector improved the SiGe cell performance.
A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × ...10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.
Electronic correlation is believed to play an important role in exotic phenomena such as insulator-metal transition, colossal magnetoresistance, and high-temperature superconductivity in correlated ...electron systems. Recently, it has been shown that electronic correlation may also be responsible for the formation of unconventional plasmons. Herewith, using a combination of angle-dependent spectroscopic ellipsometry, angle resolved photoemission spectroscopy, and Hall measurements, all as a function of temperature supported by first-principles calculations, the existence of low-loss high-energy correlated plasmons accompanied by spectral weight transfer, a fingerprint of electronic correlation, in topological insulator (Bi0.8Sb0.2)2Se3 is revealed. Upon cooling, the density of free charge carriers in the surface states decreases whereas that in the bulk states increases, and the recently reported correlated plasmons are key to explaining this phenomenon. Our result shows the importance of electronic correlation in determining correlated plasmons and opens an alternative path in engineering plasmonic-based topologically insulating devices.
R values measured with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV are fitted to determine resonance parameters (mass, total width, electron width) of the high mass ...charmonium states, ψ(3770), ψ(4040), ψ(4160) and ψ(4415). Various effects, including the interferences and relative phases between the resonances, the energy-dependence of the full widths, and the initial state radiative correction, are examined. The results are compared to previous studies.
6H-SiC single crystal implanted with N+ ions with an energy of 160keV and a dose of 1×1017cm−2 at room temperature was analyzed by atomic force microscopy (AFM), positron annihilation lifetime ...spectroscopy (PALS) and superconducting quantum interference device (SQUID). AFM analysis results show the morphological characteristics of degraded implanted sample. PALS analysis indicated the main defect type was silicon vacancy (VSi) and the concentration of VSi increased in the SiC after N ion implantation. SQUID results showed that N-implanted 6H-SiC sample exhibits room-temperature ferromagnetic (RTFM) behavior. It is demonstrated that room temperature ferromagnetism can be obtained by metal-free doping. The possible mechanism of ferromagnetic order was briefly discussed.
► The main defect type was silicon vacancy (VSi). ► The concentration of VSi increased in the SiC after N ion implantation. ► Clearly loop at 300K indicate FM ordering dominated the sample.
PDF
