Preparation and UV property nickel nanoparticles （〈10 nm） of size-controlled monodisperse by reductive method

Nickel nanoparticles (<10 nm) were successfully synthesized using a reductive method of nickel chloride with sodium borohydride in the ethanol/poly- vinylpyrrolidone (PVP) system. The effects of three factors, such as the concentration of the nickel ions, the time of reaction, and the amount of PVP (surfactant), were discussed. The possible growth process of the particles and optimum reactive conditions was also investigated. The result of transmission electron microscopy (TEM) reveals that these nickel nanoparticles are spherical. The average diameter could be controlled as 2-5 nm under selected conditions. High-resolution TEM and energy-dispersive spectroscopy results indicates that the nickel nanoparticles are pure. The UV-visible light absorption spectrum shows that the peaks of nickel nanoparticles moves toward the short wavelength along with the decrease of sizes.     

Molecular structure of synthetic hydrocarbon oils and their rheological properties governing traction characteristics

Correlations between rheological properties governing traction and the molecular volume or structure of synthetic hydrocarbon oils are presented. A simplified thermal theory is applied to the traction curves experimentally determined on a four-roller machine, and characteristic parameters are obtained. It is shown that effects of molecular volume on the parameters are small and that the parameters are primarily related to the molecular structures. Further, the maximum traction coefficients of the oils are critically dependent on the effective viscosity—pressure coefficient among the parameters.     

An evanescent-field optical microscope

The classic diffraction limit of resolution in optical microscopy (～γ/2) can be overcome by detecting the diffracted field of a submicrometre-size probe in its near field. The present stage of this so-called scanning near-field optical microscopy (SNOM) is reviewed. An evanescent-field optical microscope (EFOM) is presented in which the near-field regime is provided by the exponentially decaying evanescent field caused by total internal reflection at a refractive-index transition. A sample placed in this field causes a spatial variation of the evanescent field which is characteristic for the dielectric and topographic properties of the sample. The evanescent field is frustrated by a dielectric probe and thus converted into a radiative field. In our case the probe consists either of an etched optical fibre or of a highly sharpened diamond tip. The probe is scanned over the sample surface with nanometre precision using a piezo-electric positioner. The distance between probe and sample is controlled by a feedback on the detected optical signal. The resolution of the microscope is determined by both the gradient of the evanescent field and the sharpness of the tip. Details of the experimental set-up are discussed. The coupling of the evanescent field to the submicrometre probe as a function of probe-sample distance, angle of incidence and polarization has been characterized quantitatively. The observed coupling is generally in agreement with presented theoretical calculations. Microscopy has been performed on a regular latex sphere structure, which clearly demonstrates the capacity of the evanescent-field optical microscope for nanometre-scale optical imaging. Resolution is typically 100 nm laterally and 10 nm vertically. The technique is promising for biological applications, especially if combined with optical spectroscopy.     

原位固化黑荆树单宁对La3+、Pr3+、Nd3+的吸附特性

以富含单宁的黑荆树树皮为原料,通过甲醛交联剂原位固化黑荆树单宁制备吸附材料,研究该吸附材料对轻稀土离子La3+、Pr3+、Nd3+ (RE3+)的吸附特性。实验表明：该吸附材料对La3+的吸附最适宜的pH为5.0左右,对Pr3+、Nd3+的吸附最适宜的pH为5.5左右,此时pH升高或降低,吸附量有较大幅度下降。和pH因素的影响相比较,温度对平衡吸附量影响较小,反应温度为303 K时,原位固化黑荆树单宁对RE3+的吸附效果最好。当RE3+溶液的初始浓度为5.0 mmol·L-1时,在温度为303 K和最适宜的pH条件下,吸附剂用量为0.10 g, 平衡吸附量可达到La3+为217.26 mg·g-1,Pr3+为228.56 mg·g-1,Nd3+为329.76 mg·g-1,其吸附等温线符合Freundlich方程。这种吸附剂对RE3+的吸附动力学可用拟二级速率方程来描述,由拟二级速率方程计算所得到的平衡吸附量与实测值的偏差在7%以内,具有很好的一致性。     

三光束光内同轴送丝激光熔覆成形新方法研究

目的研究"三光束光内同轴送丝"激光熔覆新方法以及单向、多向单道熔覆成形效果。方法采用光线追迹法分析了三光束光斑几何特性,运用TracePro分析了光斑能量分布。利用研制的三光束光内送丝装置进行了单向以及多向单道熔覆实验,对其展开成形表面质量以及单道熔覆层的组织和硬度分析。结果 "三光束光内同轴送丝"激光熔覆新方法可以将原始圆形激光束整形为周向均匀分布的三个扇形光斑,三个光斑光通量均沿着z轴方向呈"尖顶状"分布,丝材能够被三个光斑均匀包裹。基材和丝材采用不锈钢304材料,丝材线径为0.8 mm,负离焦量为2.5 mm,激光功率为1500 W,扫描速度为3.5 mm/s,送丝速度为20.5 mm/s,展开单向和多向单道熔覆成形测试,丝材熔化充分,熔覆层表面均匀平滑。熔覆层形貌和质量基本不受扫描方向的影响。单道熔覆层和基体结合良好,组织整体比较细密,无气孔和裂纹等缺陷,熔覆层底部到顶部晶粒形态主要为树枝晶、柱状晶、胞状晶和树枝晶,熔覆层组织为铁素体δ和奥氏体γ,凝固模式为FA模式,熔覆层底部到顶部铁素体δ的主要形态为板条状铁素体、蠕虫状铁素体、骨架状铁素体和板条状铁素体。熔覆层的平均硬度(228HV)明显高于基材硬度,熔覆层底部到顶部的硬度过渡平稳,不存在明显软化区,组织整体比较细小致密,晶粒分布均匀。结论 "三光束光内同轴送丝"激光熔覆新方法可以实现光、丝耦合,基材和丝材采用不锈钢304材料,选择合理的工艺参数,可以获得理想的单向以及多向单道熔覆成形效果。     

海洋中石油烃类降解与微生物腐蚀关系研究

在工程实践中,国家重要的海洋工程设施（如海底输油管线和船舶燃料系统等）发生的腐蚀破坏案例常常涉及到油水环境,并与微生物腐蚀作用密切相关,而了解海洋含油环境中石油烃类的生物转换机制是了解微生物腐蚀的关键。阐述了海洋环境中降解石油烃类的主要微生物及其降解机制,其在有氧和无氧条件下呈现不同的特点。微生物降解石油烃类过程中非常重要的一步即为接受电子,该过程将生物无法直接利用的化学能转换成可直接利用的能量形式,即腺苷三磷酸（ATP）。有氧条件下的烃类降解以氧气作为最终电子受体,而在缺氧条件下可利用硝酸盐、铁离子、硫酸盐等作为电子受体。海洋环境中的石油烃类会促进腐蚀性硫化物的生成,因此油水环境下的微生物腐蚀机理以硫化物的腐蚀破坏为主。此外,烃类降解过程产生的琥珀酸等酸性中间代谢物也会加剧腐蚀的发生。但目前关于海洋油水环境中微生物群落作为一个整体展现出的功能性及其对钢铁设施的破坏机理,仍然缺乏系统性的研究,而基于高通量测序的微生物组学研究技术将成为有效解决这些问题的手段之一。     

Synthesis and photocatalytic performance of Ag-loaded β-Bi2O3 microspheres under visible light irradiation

The visible-light-driven photocatalyst Ag/β-Bi₂O₃ microspheres were synthesized by a simple chemical method. First, β-Bi₂O₃ microspheres were obtained by a thermal treatment of sphere-like Bi₂O₂CO₃ precursor at 360 °C for 3 h in air and then Ag nanoparticles were in situ incorporated into β-Bi₂O₃ microspheres by impregnation method. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and photoluminescence measurements. The experimental results demonstrated that the visible light absorption of β-Bi₂O₃ photocatalyst is greatly enhanced with the incorporation of Ag nanoparticles. The SEM and TEM observations revealed that the Ag nanoparticles can be homogenously incorporated in the β-Bi₂O₃ microspheres. The photocatalytic activity of Ag/β-Bi₂O₃ sample was evaluated by the photodegradation of the Rhodamine-B under visible light irradiation as a function of Ag content. It is found that the photocatalytic efficiency of β-Bi₂O₃ can be significantly improved with the incorporation of Ag nanoparticles up to 2.0 wt% Ag. The mechanism for the enhanced photocatalytic activity is also presented.     

蓝光过滤多层功能薄膜的遗传算法设计

目的设计出一种在380~455 nm波段具有高反射率,但在500~760 nm波段具有低反射率的多层薄膜结构。方法采用遗传算法,采取截断选择策略,并引入小生境技术,选择灵活性较好的容差型评价函数,通过改变目标反射率,使功能薄膜在可见光波段具有增透与增反两种特性。采用八层不同折射率材料交替结构,计算得出满足光谱特性要求的全局膜系结构参数。结果当材料为硫化锌和氟化镁,厚度为324、142、68、46、51、51、56、145 nm时,380~455 nm波长处的平均反射率高达88.54%,500~760 nm波长处的平均反射率仅为2.00%。由几种常用光学薄膜材料的不同搭配,发现材料的折射率差与两波段的平均反射率差呈现相同趋势。当两种材料的折射率差为0.92时,两波段的平均反射率差为86.54%。结论采用的遗传算法可以简单有效地对多层薄膜结构进行优化,为获得较为理想的蓝光过滤功能薄膜,应尽可能选择折射率差大的两种材料。     

臭氧气氛下LED灯光对银质文物模拟材料腐蚀变色的影响

目的研究臭氧与LED灯光共同作用于银质文物模拟材料的腐蚀行为和规律。方法采用石英晶体微天平(QCM)反应性监测及SEM-EDS等方法,研究了暴露于臭氧和LED灯下的银质文物模拟材料的腐蚀行为及其表面特征。结果暴露于LED灯或臭氧条件下的石英晶振片频率均有所下降,而暴露于LED灯加臭氧复合条件下的石英晶振片频率下降速率更快且最终下降值更多。此外,升高LED灯色温、增大臭氧浓度或提高环境温度,均会使石英晶振片频率下降速率更快且最终下降值更大。在臭氧质量浓度为5μg/L环境中,与无光照条件相比,LED光照下的银片表面的腐蚀产物及氧元素含量较多,并且LED灯的色温越高,其光照下的银片表面生成的腐蚀产物越多,但不同品牌的LED灯下的银片表面腐蚀产物生成量及氧元素含量均相近。结论臭氧与LED灯光均会加速银的腐蚀,两者共同作用时,会使银腐蚀更严重。升高LED灯色温、增加臭氧浓度或提升环境温度也同样会加速银的腐蚀,但不同品牌LED灯对银腐蚀的影响却相差无几。     

橙红色荧光粉YPO4:Gd3+,Eu3+的制备及发光特性

采用高温固相法在1100℃下合成了橙红色荧光粉YPO₄:Gd₃₊,Eu₃₊,研究了Eu₃₊离子掺杂浓度、碱金属碳酸盐、助熔剂、敏化剂对荧光粉发光性能的影响。XRD检测结果显示：合成荧光粉为单相的YPO₄。Eu₃₊离子较佳掺杂浓度为2.5%,碱金属碳酸盐 Na₂CO₃能有效提高荧光粉的发光强度。添加助熔剂NH₄F可将荧光粉的煅烧合成温度从1100℃降低到800℃,并可促进发光中心进入晶格。Gd₃₊离子能将吸收的激发能有效传递给发光中心Eu₃₊离子,提高荧光粉的发光强度。色坐标分析显示,合成YPO₄:0.025Eu₃₊荧光粉色坐标为(0.61,0.39) ,位于橙红光的色坐标范围内。