[100]LiF单晶在60 GPa以内冲击加载下的高压屈服强度特性

获取光学窗口自身的高压强度特性是开展材料高压高应变率冲击响应行为精密测量和数据反演的重要基础。利用平板撞击和双屈服面法,通过冲击-卸载、冲击-再加载原位粒子速度剖面精细测量和数据反演,获得了约60 GPa范围内[100]LiF屈服强度特性随冲击压力的变化规律。结果表明:在实验压力范围内,[100]LiF的屈服强度随加载压力的提高而显著提高,压力硬化效应显著;同时,LiF在冲击加载下的屈服强度高于磁驱准等熵加载结果,应变率硬化效应强于热软化效应。采用Huang-Asay模型确定了可描述冲击加载[100]LiF强度特性的本构模型参数,为LiF在强度、相变、层断裂等加窗测量实验中的深入应用和数据准确解读提供了重要支撑。     

Preparation of highly crystalline blue emitting MVO4:Tm (M=Gd, Y) spherical nanoparticles: Effects of activator concentration and annealing temperature on luminescence, lifetime and quantum yield

Highly crystalline spherical nanoparticles of MVO₄:Tm³⁺ (M=Gd, Y) having a size of 20–45 nm were prepared using ethylene glycol as both capping agent and reaction medium. X-ray diffraction study shows linear decrease in the unit cell volume with an increase in Tm³⁺ concentrations in MVO₄ (M=Gd, Y; Tm³⁺=0, 2, 5, 7, 10, 15, 20, 40, 60, 80 and 100 at%), indicative of quantitative substitution of Gd³⁺/Y³⁺ lattice sites by Tm³⁺ ions in MVO₄. Blue light emission at 475 nm is observed after excitation at 310 nm due to energy transfer from VO₄³⁻ absorption band to Tm³⁺. Emission intensity and average decay lifetime increase with an increase in heat treatment from 500 to 900 °C. This has been attributed to an extent of reduction in non-radiative process arising from surface. The emission intensity of Tm³⁺ in GdVO₄ host is higher than that in YVO₄ and thus the former host is better. Quantum yield increases with increase in heat-treatment temperature. This material will be the alternative blue light emitter.     

Comparative study on fatty acid composition of olive (Olea europaea L.), with emphasis on phytosterol contents

The present study was designed to determine the fatty acid composition and phytosterol contents of Turkish native olive cultivars, namely Kilis Yağlık and Nizip Yağlık cv. In this context, olive fruits from 34 locations were sampled and then screened for their components in comparison. Fifteen different fatty acids were found in both olive oils. In the order of abundance, the most important ones were oleic acid (18:1) > palmitic acid (16:0) > linoleic acid (18:2) > stearic acid (18:0). Significant differences were observed in the contents of oleic acid (18:1), palmitic acid (16:0), linoleic acid (18:2) but not for stearic acid content in comparison both oils (p < 0.01). There were significant differences in terms of unsaturated fatty acids, saturated fatty acids and polyunsaturated fatty acids (p < 0.01). The seven phytosterols – cholesterol, campesterol, stigmasterol, β ‐sitosterol, Δ‐5‐avenasterol, Δ‐7‐stigmastenol and Δ‐7‐avenasterol – were studied in both oil sources. The predominant sterols were β ‐sitosterol, Δ5‐avenasterol and campesterol in the samples analysed. However, no significant differences were found in the levels of the phytosterols between the two olive cultivars.     

Particle-in-Cell/Monte Carlo Collision simulation of planar DC magnetron sputtering

In this paper a numerical simulation of a planar DC magnetron discharge is performed with the Particle-in Cell/Monte Carlo Collision （PIC/MCC） method. The magnetic field used in the simulation is calculated with finite element method according to experimental configuration. The simulation is carried out under the condition of gas pressure of 0.665 Pa and voltage magnitude of 400V. Typical results such as the potential distribution, charged particle densities, the discharge current density and ion flux onto the target are calculated. The erosion profile from the simulation is compared with the experimental data. The maximum erosion position corresponds to the place where the magnetic field lines are parallel to the target surface.     

铝的动态屈服强度测量及再加载弹性前驱波的形成机理分析

利用激光干涉测速技术(VISAR)测量LY12铝合金在20—34 GPa冲击压力下经历加载-卸载和加载-再加载过程的样品/窗口界面粒子速度剖面，采用AC方法确定了具有较高精度的动态屈服强度值.实验结果和文献发表的数据具有较好的一致性.通过以平面焊接方式制作组合飞片，克服了组合飞片在气炮发射过程中可能发生分离的技术困难，使铝的动态屈服强度测量压力范围从22 GPa扩展到了34 GPa.同时，根据对不同实验条件下的加载-再加载过程的比较，对再加载弹性前驱波的形成机理进行了讨论，认为位错是形成该现象的主要原因.     

The effect of heat and IR radiation on the fluorescence of cellulose

The emission spectra of pure cellulose samples of various origins were monitored during several heating/cooling cycles. During heating the emission intensity decreased due to the greater probability for internal conversion at higher temperatures. Cooling resulted in an emission recovery that was nearly reversible over several heating/cooling cycles, provided that the final 0temperature was sufficiently low. The change in the relative emission yield with temperature showed two regimes, both with linear decreases but different slopes, suggesting different mechanisms for the internal conversion in these regions. Heating to temperatures higher than 160°C for filter papers and higher than 145°C for microcrystalline cellulose initiated reactions that caused changes in the emission spectra typical of thermal degradation. If the samples were heated beyond these threshold temperatures the emission recovery on cooling after the first heat treatment occurred to a much higher intensity level than that observed initially, indicating the formation of a multitude of new chromophores due to thermal reactions. Exposure of the samples to IR radiation caused a slow increase in the emission intensity for almost 600h.     

The effect of liquid crystal structure on the rheological properties of nitrocellulose-dimethylacetamide solutions

Solutions of Pyro grade nitrocellulose (NC) in dimethyl acetamide (DMA), containing between 42.5% and 60% NC (w/w), have been studied by differential scanning calorimetry and polarised light microscopy. The results showed that NC forms a lyotropic liquid crystal structure in DMA. A transition from the liquid crystal phase to an isotropic phase occurred over the temperature range 27 °C to 67 °C, and the enthalpy of transition increased with NC concentration. Rheological properties were determined using an extrusion rheometer with a slit die. The solutions were shown to have a yield stress for flow which increased with increasing NC concentration. The solutions were also found to be thixotropic.     

K-shell fluorescence yields for potassium and calcium compounds

The K-shell fluorescence yields for potassium and calcium compounds were investigated using a Si(Li) X-ray detector system ( at ). The target samples were excited using gamma rays from an ²⁴¹Am annular source of strength . Chemical effects on K-shell fluorescence yield for potassium and calcium were observed. The values were compared with theoretical values of pure potassium and calcium.     

A functionalized dianthryl tetraaza macrocycle having the recognizing and switching ability

The synthesized macrocycle L is the novel fluorescent receptor having the switching ability by the external stimuli as well as having the recognizing ability of various metal ions. In particular, this macrocycle L shows the possibility of the selectivity of metal ions even in the same charge ions of a different metal, and the values of association constant (M⁻¹) of that for metal ions are consistent with the tendency of increasing charge number of metal ion. In addition, the values of quantum yield (Φ_F) of metal complexes of macrocycle L were ranged from 0.021 to 0.111 enough to recognize the metal ions in macrocycle L. We know from the fluorescent pH titration of macrocycle L by acid/base that the change of fluorescence intersects at about pH=5.