Effects of acid and alkaline based surface preparations on spray deposited cerium based conversion coatings on Al 2024-T3

Cerium based conversion coatings were spray deposited on Al 2024-T3 and characterized to determine the effect of surface preparation on the deposition rate and surface morphology. It was found that activation of the panel using a 1-wt.% sulfuric acid solution increased the coating deposition rate compared to alkaline cleaning alone. Analysis of the surface morphology of the coatings showed that the coatings deposited on the acid treated panels exhibited fewer visible cracks compared to coatings on alkaline cleaned panels. Auger electron spectroscopy depth profiling showed that the acid activation decreased the thickness of the aluminum oxide layer and the concentration of magnesium on the surface of the panels compared to the alkaline treatment. Additionally, acid activation increased the copper concentration at the surface of the aluminum substrate. Based on the results, the acid based surface treatment appeared to expose copper rich intermetallics, thus increasing the number of cathodic sites on the surface, which led to an overall increase in the deposition rate.     

Structural, optical, and electrical properties of p-type NiO films and composite TiO2/NiO electrodes for solid-state dye-sensitized solar cells

p-Type nickel oxide thin films were prepared by sol-gel method, and their structural, optical and electrical properties were investigated. The Ni(OH)₂ sol was formed from nickel (II) acetate tetrahydrate, Ni(CH₃COO)₂·4H₂O, in a mixture of alcohol solution and poly(ethylene glycol), and deposited on an ITO substrate by spin coating followed by different heat treatments in air (50-800 °C). The formation and composition of NiO thin film was justified by EDX analysis. It is found that the thickness of the NiO film calcined at 450 °C for 1 h is about 120 nm with average particle size of 22 nm, and high UV transparency (∼75%) in the visible region is also observed. However, the transmittance is negligible for thin films calcined at 800 °C and below 200 °C due to larger particle size and the amorphous characteristics, respectively. Moreover, the composite electrode comprising n-type TiO₂ and p-type NiO is fabricated. The current-voltage (I-V) characteristics of the composite TiO₂/NiO electrode demonstrate significant p-type behavior by the shape of the rectifying curve in dark. The effect of calcination temperature on the rectification behavior is also discussed.     

360 GHz辐射计探测地面目标试验

为验证亚毫米波辐射计在弹药末制导中的应用可行性,计算了不同天气条件下天空亮温和视在温度,利用360 GHz辐射计对地面金属目标和涂层隐身目标进行了模拟探测试验。计算和试验表明,在寒冷干燥的季节,辐射计可以探测到地面金属目标,随着温度和湿度的升高,辐射计很难再探测到目标;对于高温涂层隐身目标,辐射计可以探测到,而不受天气的限制。     

狭小间距间Cu/Al薄膜相互作用的分子动力学模拟

采用分子动力学模拟软件基于Lennard-Jones-9-6势函数研究了狭小间距Cu/Al纳米薄膜间的相互作用.我们通过计算薄膜表面单位面积上的范德华相互作用能,综合讨论了非接触Cu/Al薄膜间的相互作用.结果表明,当两薄膜的间距从12减小到3时,相互作用能呈现两个阶段:起初几乎不变,然后迅速增大.临界间距在7附近.在两薄膜相互靠近的过程中,相互作用能受体系尺寸、空位缺陷尺寸、表面涂层及薄膜间距的影响较大,然而几乎不受空位缺陷形状的影响.     

等离子体结合六甲基二硅胺烷处理提升增透膜抗真空污染性能研究

本文采用溶胶-凝胶法制备了SiO₂增透膜,然后对其进行等离子体结合六甲基二硅胺烷（HMDS）表面改性处理。研究了后处理改性对增透膜表面形貌、微观结构、光学性能及激光损伤性能的影响规律,获得了抗真空有机污染的二氧化硅增透膜。结果表明,增透膜在采用等离子体结合HMDS表面改性处理后,膜层收缩、粗糙度下降、极性羟基等有机基团含量减少;两步后处理改善了增透膜膜层结构和光学性能,显著提高了膜层疏水能力和真空条件下的抗污染性能,并且对溶胶-凝胶二氧化硅增透膜的高损伤阈值属性不产生影响。     

Study on the changes of ultrasonic parameters over supercritical Ni-Co electroplating process

This work discusses the influence of changes to ultrasound (US) parameters over the nickel cobalt (Ni-Co) metal thin film properties produced by supercritical CO₂ (SC-CO₂) electroplating. Additionally, Ni-Co films were produced by conventional electroplating and silent SC-CO₂ and compared against each other.The discussion on metal thin film properties revolves around variations to the bath type ultrasonic power (15 W and 20 W) and frequency (42 k Hz and 72 kHz) during experiments. The properties provided by the three electroplating processes and analyzed include: grain sizes, film elemental content analyses, surface microstructures, film hardness, corrosion resistance, surface roughness, crystalline structure and preferential growth, etc. From the results it was clear that quality of films produced by US-SC-CO₂ was improved compared to that of films produced by silent SC-CO₂, which itself was better than those produced by conventional electroplating. However, when US power was varied we observed a decline in the mechanical properties of the produced films.The combination of ultrasonic agitation with SC-CO₂ allows for improved mechanical properties such as: lower surface roughness, finer grain size and surface morphologies, increased corrosion resistance and film hardness. The ultrasound agitation applied to SC-CO₂ electroplating enhanced the formation of alloyed metal as ultrasonic agitation increased the electrolyte flowability during electroplating process resulting in increased mass transfer while at the same time achieving a surface cleaning effect which removed metal ions with poor adhesion and other unwanted particles. Moreover, application of ultrasonic agitation avoids the use of surfactants so only changes to the physical phenomena and no changes to the chemical composition of the deposited thin films were observed, meaning less pollution to the electrolyte and higher purity of the deposited films.The US-SC-CO₂ electroplating method described in this work effectively enhanced the mechanical properties of the deposited thin films compared to those produced by both silent SC-CO₂ and conventional electroplating processes.     

基于表面阻抗边界条件的等离子体薄涂层电磁散射的时域有限差分分析

基于表面阻抗边界条件时域有限差分(FDTD)方法研究了一维斜入射情况下非磁化等离子体薄涂层涂敷金属材料的电磁散射特性, 该方法忽略对薄层背景材料进行网格剖分, 大大减少了计算量. 首先推导了理想导体涂敷等离子体薄涂层的表面阻抗频域表达式, 然后代入边界条件并变换到时域, 再用分段线性递推卷积方法将时域表达式离散得到FDTD迭代式. 编程计算了垂直及斜入射情形下的平行极化和垂直极化反射系数, 通过验证算例与解析解对比, 结果表明该方法的准确性和有效性. 最后利用该方法分析了不同入射角对反射系数的影响.     

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.     

多孔金属薄膜阻尼减振微观机理研究

研究了多孔金属薄膜的阻尼性能和微观机理. 采用分子动力学方法及扫描电镜(SEM) 原位观察实验手段对多孔金属薄膜阻尼进行研究, 得出金属薄膜应变滞后于应力周期性变化以及弹性势能周期性衰减的规律, 并通过应变滞后应力的时间差求得损耗因子; 从微观结构上可看出, 在薄膜孔缺陷附近\langle110angle晶向上经历了位错产生、 并且位错呈阶梯状向前发射的变化; 在SEM原位拉伸、卸载实验中观察到有微裂纹的萌生、斜向阶梯扩展、收缩及消失的周期过程. 结果表明: 在周期载荷作用下, 多孔金属薄膜的孔缺陷附近产生的位错可以挣脱开弱钉扎点并限制在强钉扎点上, 由于位错的变化及附近晶界间的相对滑动产生内摩擦, 消耗了系统的部分弹性势能, 引起金属薄膜的阻尼减振效应, 从而揭示了多孔金属涂层阻尼产生的微观机理.     

光学薄膜诱导偏振像差对大数值孔径光学系统聚焦特性的影响

大数值孔径光学系统表面光线的入射角较大, 会导致薄膜的偏振分离, 诱发偏振像差, 影响光学系统的聚焦特性. 本文利用矢量光衍射理论, 建立了光学薄膜各参量与光学系统聚焦光场的模型. 利用该模型分析了线偏振光入射时, 光学薄膜对光学系统聚焦光斑的扰动. 在此基础上, 探讨了应用了不同约束条件下得到的光学薄膜对最终聚焦光场的影响, 确定了减小薄膜扰动光学系统光斑的设计方法, 即额外添加透射率差和位相差的约束条件, 并且适当增加位相差约束的权重. 利用该方法优化设计的薄膜, 相比于普通减反膜而言, 对系统聚焦光场中心强度的提升可达约12.5%.