Wintersweet Branch‐Like C/C@SnO2/MoS2 Nanofibers as High‐Performance Li and Na‐Ion Battery Anodes

Structure and morphology of molybdenum disulfide (MoS₂) play an important role in improving its reversible lithium storage and sodium storage as anodes. In this study, a facile method is developed to prepare C/C@SnO₂/MoS₂ nanofibers with MoS₂ nanoflakes anchoring on the core–shell C/C@SnO₂ nanofibers through hydrothermal reaction. By adjusting the concentration of MoS₂ precursors, the synthesized MoS₂ with different slabs dimensions, size, and morphologies are obtained, constituting budding and blooming wintersweet branch‐like composite structure, respectively. Owing to scattered MoS₂ nanoparticles and sporadic MoS₂ nanoflakes, the budding wintersweet branch‐like composite nanofibers processes less slabs of staking in number and large specific surface area. Benefiting from the exposed C@SnO₂ shell layer, the synergistic effect among SnO₂, carbon, and MoS₂ is strengthened, which maximizes the advantage of each material to exhibit stable specific capacities of 650 and 230 mAh g^?1 for Li‐ion batteries and Na‐ion batteries after 200 cycles.     

Optimized permeation and antifouling of PVDF hybrid ultrafiltration membranes: synergistic effect of dispersion and migration for fluorinated graphene oxide

Nanoparticles may have suffered from low modification efficiency in hybrid membranes due to embedding and aggregating in polymer matrix. In order to analyze the modification mechanisms of nanoparticle migration and dispersion on the properties of hybrid membranes, we designed different F/O ratios (R _F/O ) of fluorinated graphene oxide (FGO, diameter = 1.5 ~ 17.5 μm) by carbon tetrafluoride (CF₄) plasma treatment GO for 3, 5, 10, 15, and 20 min and successfully prepared novel PVDF hybrid membranes containing FGO via the phase inversion method. After a prolonged plasma treatment, the R _F/O of FGO was enhanced sharply, indicating an increasing compatibility of FGO with the matrix, especially FGO-20 (GO treated for 20 min). FGO contents in the top layer, sublayer, and the whole of membranes were probed by X-ray photoelectron spectroscopy, energy-dispersive spectrometer, and indirect computation, respectively. In the top layer of membranes, FGO contents declined from 13.14 wt% (PVDF/GO) to 4.00 wt% (PVDF/FGO-10) and 1.96 wt% (PVDF/FGO-20) due to the reduced migration ability of FGO. It is worth mentioning that PVDF/FGO-10 membranes exhibited an excellent water flux and flux recovery rate (up to 406.90 L m^?2 h^?1 and 88.9%), which were improved by 67.3% and 14.6% and 52.5% and 24.0% compared with those of PVDF/GO and PVDF/FGO-20 membranes, respectively, although the dispersion and migration ability of FGO-10 was maintained at a moderate level. It indicated that the migration and dispersion of FGO in membranes could result in dynamic equilibrium, which played a key role in making the best use of nanomaterials to optimize membrane performance.     

Experimental study on the phase change and thermal properties of paraffin/carbon materials based thermal energy storage materials

In order to enhance the thermal energy storage efficiency of phase change materials, in this paper, expanded graphite (EG), multi-layer graphene nanoplatelet (MGN), graphite powder (GP) and multi-walled carbon nanotube (MWCNT) as the effective heat transfer promoters in different mass fraction (0.1, 0.5, 1.0, 1.5 and 2.5 wt.%) were added into the paraffin. The chemical properties, latent heat capacities, thermal conductivities and heat storage performances of paraffin and the composites were investigated. The results showed that the addition of EG, MGN, GP and MWCNT could increase the thermal conductivity of paraffin. At 20 °C, the thermal conductivity of the paraffin was increased by 61.04%, 51.2%, 12.18% and 10.22% with 2.5 wt.% EG, MGN, GP and MWCNT, respectively. In addition, with the same mass fraction, the heat storage and release time of the composite were 56.03% and 54.26%, respectively, shorter than that of paraffin when the additive was EG.     

Fabrication of gradient refractive index ball lenses using the method of combination of ion exchanging and sagging

Based on the Fick’s diffusion equations, the distribution function of refractive index of a gradient refractive index ball lens (GRIN ball lens/GBL) is derived. Lithium containing silicate glass is fabricated and GRIN ball lenses (GBLs) which diameters are from 0.3 mm to 3.0 mm are made by the method of combination of Ion exchanging and sagging in sodium nitrate. Refractive index profiles of these GBLs are measured by interferometer, and the performances such as effective focal length (EFL), back focal length (BFL) and numerical aperture (NA) between GBLs and homogeneous ball lenses (HBLs) are compared. Results show that the distribution of the index of refraction is parabolic curve and its Δn is about 0.0002, the performances of the former are super to the latter.     

Spectroscopic properties of Er<Superscript>3+</Superscript> in Sc:LiNbO<Subscript>3</Subscript> crystal

The results of Er³⁺ ion spectroscopic analysis in Sc:LiNbO₃ crystals were reported. The line strengths from the ground state to the excited state were evaluated from the measured unpolarized absorption spectrum and analyzed by using standard Judd–Ofelt theory. For Sc(3 mol. %):Er (1 mol. %):LiNbO₃ crystal, the obtained intensity parameters are: Ω₂=3.72×10^-20 cm², Ω₄=1.07×10^-20 cm², and Ω₆=0.98×10^-20 cm². The fluorescence spectra and microsecond time-resolved spectra were investigated in the visible region. The excited state absorption transition strengths at 800 nm excitation were evaluated based on Judd–Ofelt theory. The results obtained here were compared to results from other research on Er:LiNbO₃ crystals. PACS 71.20.Eh; 77.84.Dy; 42.70.Hj; 42.62.Fi; 42.65.Ky     

水下声学浮标南中国海海洋环境噪声实测分析

海洋环境噪声是多种自然噪声和人为噪声的复杂组合,其谱级大小和频率组成是影响声呐系统探测性能的重要参数,鉴于海洋环境噪声时空域特性非常复杂,需要对海洋环境噪声进行长时间和大范围的观测才足以分析其特性。该文通过在多剖面水下浮标平台基础上集成声学测量系统,研制了一种具有海洋环境噪声监测能力的水下声学浮标平台,该浮标平台可多次上浮、下潜,具备原位坐底和定深漂流两种工作模式,能连续观测海洋环境噪声时长多达数月。利用2019年8月在南中国海海区组织的多台水下声学浮标试验某一天的数据,给出了20 Hz、63 Hz、100 Hz、200 Hz、400 Hz、800 Hz、1.6 kHz和3.15 kHz 8个频点中心处海洋环境噪声谱级随时间变化,讨论了附近航船噪声对其的干扰影响。试验表明,水下声学浮标可作为一种潜在的优势水下漂流移动平台,用于监测关注海域海洋环境噪声特性。     

插值法在低温温度测量中的应用

依托建立的低温精馏装置,针对低温环境中温度测量问题,提出一种基于LabVIEW的低温温度测量方法。该方法将插值法引入到数据分析中,通过软件编程实现数据处理、显示、存储等功能。经过理论分析与实验对比,该方法准确度提高到0.01 K,可移植性强,是低温环境中温度测量的可行方法。     

修饰酶电极的响应特性

在考虑电极电位、浓度极化等影响因素的情况下, 提出了介体型酶电极响应的数学表达式, 并对吸附法制备的修饰酶电极进行了初步的实验验证和模拟计算, 其实验结果与理论推导是一致的.     

Developing cold-resistant high-adhesive electronic substrate for WIMPs detectors at CDEX

Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles(WIMPs)detectors at the China Dark Matter Experiment(CDEX).Because the bulky high-purity germanium(HPGe)detectors operate under liquid-nitrogen temperatures and ultralow radiation backgrounds,the desired electronic substrates must maintain high adhesivity across different layers in such cold environment and be free from any radioactive nuclides.To conquer these challenges,for the first time,we employed polytetrafluoroethylene((C2F4)n)foil as the base substrate,in conjunction with ion implantation and deposition techniques using an independently developed device at Beijing Normal University for surface modification prior to electroplating.The remarkable peeling strengths of 0.88±0.06 N/mm for as-prepared sample and 0.75±0.05 N/mm for that after 2.5-days of soaking inside the liquid nitrogen were observed,while the regular standards commonly require 0.4 N/mm^0.6 N/mm for electronic substrates.