通讯波段禁带胶体光子晶体的制备及实验参数研究

采用直径为700nm的二氧化硅微球,通过垂直沉积法在玻璃基片上制备了位于光通讯波段的禁带胶体光子晶体。研究了不同蒸发温度、湿度条件、干燥过程对样品晶体质量的影响。用扫描电子显微镜(SEM)对其形貌进行了观测。实验结果表明,在温度为65℃,相对湿度为70%,缓慢干燥条件下制备出的样品具有较好的晶体质量,晶体在大范围内保持了面心立方(FCC)单晶结构,其(111)面平行于生长基片。     

Electronic properties of nanocrystalline tin oxide dispersed in monolithic mesoporous silica

This paper is devoted to the study of the electrical properties of nanocrystalline tin oxide dispersed in the mesoporous silica. By immersing the silica in precursor solutions with different concentrations and heat-treatment, different samples were obtained. With precursor concentrations increasing from 0.1 to 4.0 M, the resistivities of the samples decrease from 3.15×10⁶ to 2.43×10³ Ω cm. The resistivity changes with the measurement time, and the deviations from Ohm's law in the voltage–current (V–I) measurements illustrate the capacitance property of these nanocomposites. For this new kind of nanocomposites, the obtained results provide experimental evidence of the conducting mechanism for tin oxide nanoparticles.     

Polymer adsorption on the surface of highly dispersed silica

Attempts at modification of silica surface with a polymer (natural latex) directly in the course of the precipitation process have been made. The effects of temperature, non-ionic surfactants and silane coupling agent in preparation of poly[cis-isoprene]-coated silica on the precipitation of polymer/silica composites initiated by ammonium salts (NH₄Cl, (NH₄)₂SO₄, NH₄HCO₃), have been studied. The influence of the process parameters on the quality of the silicas obtained and the character of the polymer adsorption on the silica surface has been determined along with the effect of the surface impregnation with natural latex on physicochemical parameters of the silicas (bulk density, capacities to absorb water, dibutyl phthalate and paraffin oil) and their surface structure.     

Synthesis and electron paramagnetic resonance study of a nitroxide free radical covalently bonded on aminopropyl-silica gel

A solid spin-labeled material was obtained starting from 2-chloro-3,5-dinitro-N-(4-(2,2,6,6-tetramethyl-piperidine-1-oxyl)-benzamide) and aminopropyl-silica gel. Stability tests showed that even after several months the spin-labeled material had the same properties as immediately after synthesis. EPR properties of the TEMPO-derivatized silica were studied as a function of solvent polarity and temperature. Rotational correlation times were calculated from EPR spectra and correlated with solvent characteristics and temperature. Polar solvents induce a fast motion of the spin-label, clearly seen in the EPR spectra by the apparition of the well-known TEMPO radical triplet. The solid spin-labeled (dry) sample showed a high interspin interaction, which can be disrupted not only by different (liquid) solvents, but also by absorption of different solids, like cyclodextrins, dendrimers or polyethyleneglycols. Also, changes induced by the temperature were studied in the case of toluene wet sample. From 150 to 370 K, the spectrum is changing from a slow motion spectrum type to a fast motion regime. The preparative procedures to obtain the spin-labeled silica as well as some of its parameters are described.     

准分子激光全固态脉冲电源设计与实验研究

针对脉冲能量5~8 mJ的ArF准分子激光器,设计了基于可控硅开关结合三级磁脉冲压缩开关的全固态脉冲电源,采用国产可控硅和磁开关材料,获得了上升时间约150 ns,电压10~14 kV,传递能量0.35~0.68 J的激励脉冲,并实现了对准分子激光器快放电激励。三级磁开关总效率35%,分析表明磁开关损耗较大主要原因为电容能量转移不充分、导线铜损及磁芯材料铁损较大,并提出了相应改进办法。     

预应力对熔石英损伤的影响

采用ANSYS进行形变-应力模拟。对不同应力状态下的熔石英表面进行三倍频激光损伤测试,结果发现,预加压应力为0~50 MPa时损伤阈值有明显提高的趋势,用应力耦合作用对此给出了解释：0~50 MPa的预加压应力可以降低和抵消激光辐照产生的张应力破坏,大于50 MPa预应力的耦合作用会使得该处机械性能下降,另外,损伤增长在预应力存在时更容易发生。因此,0~50 MPa预加压应力时的表面预应力可以提高熔石英的抗激光辐照能力。     

Rectifying resistance switching behaviors of SnO2 microsphere films modulated by top electrodes

Based on the bipolar resistive switching (RS) characteristics of SnO₂ films, we have fabricated a new prototypical device with sandwiched structure of Metal/SnO₂/fluorine-doped tin oxide (FTO). The SnO₂ microspheres film was grown on FTO glass by template-free hydrothermal synthesis, which was evaporated with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au), respectively. Typical self-rectifying resistance switching behaviors were observed for the RS devices with Al and Au electrodes. However, no obvious rectifying resistance switching behavior was observed for the RS device with Ag electrode. Above results were interpreted by considering the different interface barriers between SnO₂ and top metal electrodes. Our current studies pave the ways for modulating the self-rectifying resistance switching properties of resistive memory devices by choosing suitable metal electrodes.     

Tunable Upconversion Emissions from Lanthanide-doped Monodisperse β-NaYF4 Nanoparticles

We report upconversion multicolor tuning based on uniform β-NaYF₄:Yb/Tm/Er nanoparticles. The as-synthesized nanoparticles with an average diameter of 25 nm are well dispersed in a wide range of nonpolar solvents including hexane, cyclohexane, dichloromethane, and toluene. These nanoparticles show intense upconversion emissions and the color output can be precisely modulated by adjusting activator ratios of Tm³⁺ to Er³⁺. Dopant-concentration dependent emission properties of the triply doped particle system are also investigated. In addition, we demonstrate that these nanoparticles can be readily transferred to polar solvents such as ethanol and water by growing a thin silica layer (10 nm) around the particles, providing potential applications in biological labeling and imaging.     

高功率氙灯脉冲放电过程中石英管壁热损伤机理

基于高功率激光装置对脉冲氙灯工程运行可靠性的要求,利用现有的能源模块开展了氙灯放电考核实验。实验结果表明：虽然氙灯运行在安全的能量负载水平,当能源模块单个放电回路的峰值功率超过300 MW时,氙灯石英玻璃管壁存在热损伤风险。肉眼观察到管壁损伤后在反射器对侧的灯管内壁出现乳白色沉积层。经扫描电镜和X射线光电子能谱测试分析,证实热损伤形成的乳白色沉积物为二氧化硅。为探究管壁热损伤机制,采用高速摄影观测了氙灯放电等离子体沟道发展过程。图像显示放大器内金属反射器的几何形状对放电沟道的分布产生了显著影响,尤其是在侧灯箱,灯内电弧沟道会靠近反射器一侧集中分布,因此,导致等离子体对灯管的偏烧。当放电峰值功率超过石英热负载极限时,管壁表面二氧化硅材料会被烧蚀至蒸发、气化,并随后沉积在灯管较冷部位。研究结果表明放电回路的放电峰值功率过高、放大器内金属反射器均会对氙灯造成热损伤。     

CO_2激光光栅式扫描修复熔石英表面缺陷的实验研究与数值模拟

基于熔石英材料对波长为10.6μm的CO2激光具有强吸收作用这一特点,提出采用CO2激光光栅式多次扫描修复熔石英光学元件表面密集分布的划痕和抛光点等缺陷的方法.实验结果表明,在合理的扫描参数下,元件表面的划痕和抛光点等缺陷可被充分地消除.损伤阈值测试结果表明,表面划痕和抛光点等缺陷被完全消除的元件的损伤阈值可回复到或超过基底的损伤阈值.同时结合有限元软件Ansys的模拟结果分析了CO2激光扫描修复及消除元件表面划痕和抛光点等缺陷的过程.本文为消除元件表面划痕和抛光点等缺陷提供了非常有意义的参考.