SiOx encapsulated FeSi2–Si eutectic nanoparticles as durable anode of lithium-ion batteries

Low-cost and high-efficiency production of silicon-based material is the key to improve the energy density of lithium-ion batteries. Herein, we propose a novel structure of FeSi₂–Si eutectic nanoparticles protected by the SiO_x shell. FeSi₂, as a buffer phase can improve the electrochemical stability of the electrode. A SiO_x shell is formed on the surface of the nanoparticles through the passivation process. SiO_x encapsulated FeSi₂–Si eutectic nanoparticles exhibit excellent capacity of 674.9 mAh/g after 500 charge/discharge cycles. The capacity retention rate is above 90% after the stabilization process. This work provides a new nanomaterial design for high performance silicon-based anode materials of lithium-ion batteries.     

利用多项式拟合测量飞机油箱油量

飞机飞行中,测量剩余油量是关乎飞行安全的重要工作。以往采用的查表法存在存储数据量过大的问题,而插值法的计算又过于复杂,为此,提出了一种基于多项式数据拟合的油箱剩余油量测量方法,该方法通过存储多项式系数减少数据存储量,通过将多元插值计算改为多项式计算降低运算量。实验中,首先通过地面实验数据拟合获取多项式参数,再利用飞机飞行中获取的测量数据进行计算,所得结果与油箱内剩余油量的实际测量结果相比较,测量误差满足使用要求。通过理论和实验分析,在多项式拟合的阶数选择上明确了使用三阶多项式的合理性。该方法有较好的实用性,已在实践中应用。     

液-固色谱流动相体积分数层次结构模型与保留值的关系

用液-固色谱流动相"假定"的体积分数层次结构模型,可得到质点团溶解溶质时的体积分数,进而得到共溶剂中溶质的溶解度、固定相上的溶质吸附量,从而推导出多元流动相组成与溶质保留值的关系.如三元流动相与溶质保留值的关联式为:lnk'=φB3lnk'B3 φB2lnk'B2 φB1lnk'B1 φB1(φB20.5 φB30.5)ln(q)(外Ⅱ) φB30.5φB21.0φB11.5ln(q)(外Ⅰ),经实验数据拟合,本式较其他关联式略胜一筹.     

锰基液流电池电解液的体积性质研究

体积性质是锰基液流电池电解液的重要热力学性质,常用于解释溶液中复杂的离子间相互作用关系。本文在283.15-318.15 K温度范围内,测定了浓度为0.5-3.0 mol/kg的MnSO₄水溶液的密度值,得到了MnSO₄溶液的几个热力学参数和弱分子间的相互作用关系。结合Pitzer电解液表观摩尔体积热力学模型,得到了体积参数β(0)V MX,β(1)V MX和CV MX,而且计算值与实验值的相关系数能够达到0.988。这一研究可以更好地理解锰电解液中离子相互作用机制,为优化电解液成分和提高电池性能提供理论支撑。     

Novel correlations between the critical constants of the noble gases

For any particular fluid, the set of three critical constants (CC) – pressure P_c, temperature T_c and molar volume V_c – has a central importance in defining the physical behaviour of the fluid in the gas and liquid states. However, little attention seems to have been paid in the past to the relations between the CC of different substances. In the present paper, some simple and apparently novel relations have been found between the three CC for the set of four noble gases: Ne, Ar, Kr, Xe. Defining the critical quotient Q_c ≡ RT_c/P_c (where R is the Gas Constant) the correlations may be summarised by the dual equation: (V_c/cm³ mol⁻¹) = 27 + 0.31 (T_c/K) = 3.3 + 0.280 (Q_c/cm³ mol⁻¹), which describes the CC data for the quartet Ne–Xe with an average uncertainty of 0.5%. Regarding the other two noble gases, the two isotopes of the lightest member, ³He and ⁴He, show the deviations from these relations that are expected from quantal effects and their low molar masses; while for the heaviest member, Rn, the correlations enable a value of 145(5) cm³ mol⁻¹ to be estimated for V_c that is not otherwise well defined in the literature. By contrast, and contrary to the general assumption, the second lightest member, Ne, apparently does not show appreciable quantal effects in the area, so that Ne–Xe may be considered together as a group. These correlations are compared with the behaviour of a selection of polyatomic fluids; in these comparisons, the NG dual correlation equation provides a reference line defining the presumed simplest behaviour. This and related areas show a “Residual Volume Effect”, in that extrapolating the equivalent temperature and energy parameters to zero for the state of zero-mass point particles, referred to here as the hypothetical element zeronium (Ze), the system in each case still has a finite intercept; this intercept amounts to essentially 34% of the average volume for the present quartet Ne–Xe, rather than the zero volume expected for this condition.     

A new polar nephelometer for measurement of atmospheric aerosols

The angular dependence of light scattered by aerosol particles in the atmosphere—the aerosol phase function—is one of the key properties of every radiative transfer and climate model. Side-scattering in the atmosphere is currently believed to be underestimated by most of the radiative transfer models in certain cases. The aerosol phase function can be measured with polar nephelometers.An innovative polar nephelometer able to measure the phase function of ambient aerosol directly is presented in this publication. The performance of the device was simulated completely using ray-tracing techniques. The results of these simulations are used to interpret the measurement data precisely. The measurements with the new polar nephelometer are fully automated. The quality of the measurement results was verified using different approaches. The values of the statistical and systematic error in measuring atmospheric aerosol are about 4% each. Scattering angles from 10° to 160° were measured and it is shown that with the same design this range can be extended to 3-177° in steps of 0.16° with an aperture of less than 1.8°.Measurements of the aerosol phase function are presented and compared with data taken with an integrating nephelometer and measurements of the particulate matter concentration. All data correlate very well. The described polar nephelometer can measure the phase function and the scattering coefficient of atmospheric aerosol with high accuracy and can be used for continuous monitoring measurements as well as in field campaigns.     

Propagation characteristics of annular laser beams passing through the reflection Bragg grating with deformation

When high-power annular laser beams produced by the unstable resonator pass through the volume Bragg grating (VBG), absorption of light in the VBG will induce a temperature increment, resulting in changes in surface distortion. Considering that the surface distortion of the grating induces index and period differences, the scalar wave equations for the annular laser beams propagating in the VBG have been solved numerically and iteratively using finite-difference and sparse matrix methods. The variation in intensity distributions, the total power reflection coefficient, and the power in the bucket (PIB) for the annular laser beams passing through the reflection VBG with deformation have been analyzed quantitatively. It can be shown that the surface distortion of the VBG and the beam orders of the annular beams affect evidently the intensity distributions, the power reflection coefficient, and the PIB of the output beam. The peak intensity decreases as the deformation of the VBG increases. The total power reflection efficiency decreases significantly with the increase in deformations of the VBG. The PIB of the output beam decreases as the obscuration ratio β and the deformation of the VBG increase. For the given obscuration ratio β, the influence of deformation of reflection VBG on the PIB of the annular beams is more sensitive with increase in distortion of the VBG and decrease in beam order.     

Digital volume gratings

An optical element constructed by stacking a set of binary-phase grating sheets can simulate the functions of optically recorded volume gratings. Our electromagnetic numerical study also shows that if one of the grating sheets is replaced by another one with different grating period, power spectrum of the diffracted wave changes completely with extra diffraction orders. This property will claim strong advantage in security document applications. Analysis of alignment error reveals interesting phenomena concerning to how misalignment affects diffraction efficiency.     

Improvement of the dynamic range of a fiber specklegram sensor based on volume speckle recording in photorefractive materials

In this work, the improvement of the dynamic range of a micro displacement sensor based on fiber specklegrams holographically stored in a photorefractive BSO (Bi₁₂SiO₂₀) crystal is reported. In our experimental setup, a plastic optical fiber (POF) was used to generate a subjective speckle pattern that was recorded in the crystal using a two-wave mixing arrangement. The speckle size was controlled by modifying the diameter of a pupil aperture adjacent to a lens producing the image of the speckle. Fringe patterns were obtained at the output of the system by producing micro displacements of the fiber output end. An increase in the visibility of the fringe patterns was appreciated when the pupil aperture diameter decreased even without controlling the average modulation of the intensity of the light pattern, i.e. when the speckle length increased and the average light modulation simultaneously decreased. This behavior allowed recovering the autocorrelation functions of fringe patterns associated with displacements that initially led to decorrelation, and therefore, significantly to improve the dynamic range of the metrological system. To the best of our knowledge this is the first report about the influence of speckle size on the dynamic range of fiber specklegrams sensors recorded on photorefractive materials.     

三聚氰胺-甲醛系凝胶老化过程中的体积收缩影响因素

 介绍了三聚氰胺-甲醛凝胶老化过程的溶剂效应及其对体积收缩的影响。从凝胶的离浆-溶胀平衡以及溶剂效应等两个方面对湿凝胶老化过程中的体积收缩作了分析,通过测量形状规则的湿凝胶在溶剂交换和老化过程中的体积变化研究湿凝胶组成、交换溶剂的成分及步骤对凝胶体积收缩的影响。结果表明：控制交换溶剂的组成能显著改善湿凝胶后处理过程中的体积收缩。合适的湿凝胶交换步骤是先使用凝胶体内液体和目标溶剂的混合溶剂进行交换,逐次增大目标溶剂的含量,直至最后使用纯目标溶剂进行交换,即可获得体积收缩较小的湿凝胶体系。