伽玛线辐射对环氧树脂表面电荷积聚特性的影响

采用静电电位计测量经60Co伽玛射线源辐射的环氧树脂表面电位分布,结合频域介电谱和衰减全反射傅立叶变换红外光谱分析,研究总辐射量对材料表面电荷积聚特性的影响。结果表明,随着总辐射量的增大,表面电荷密度最大值及总电荷量均减小。文中认为伽玛线辐射引起的化学反应使环氧树脂表层的陷阱密度和能级发生变化,导致其表面电荷积聚能力下降。     

氢键对纳滤膜截留率的影响

纳滤膜与极性分子在形成氢键的过程中伴随着电子的传递现象,导致纳滤膜表面的电荷密度降低和荷电效应的减弱,从而引起截留率发生变化.文章从氢键出发,通过测试纳滤膜表面的电荷密度,探索氢键与截留率之间的关系.结果表明:随着对硝基苯酚浓度的增大,膜表面的电荷密度逐渐降低,即形成的氢键数目增多,截留率呈现下降的趋势.     

真空中纳秒脉冲下绝缘子表面电荷积聚和消散特性的研究

真空器件中绝缘子的沿面闪络电压远低于绝缘子自身以及同等长度真空间隙的闪络电压,影响沿面闪络电压的重要因素是绝缘子表面电荷的积聚,其严重制约着真空器件的性能。为了提高真空中纳秒脉冲作用下的沿面闪络电压,绝缘子表面电荷分布的研究十分重要。本文搭建了一套真空纳秒脉冲下绝缘子表面电荷测量平台来研究绝缘子表面电荷分布。本文采用静电容探头法得到不同类型的陶瓷试样的表面电荷分布状况,并对电荷的积聚和消散特性进行了对比分析。试验结果表明不含添加剂的试样表面电荷积聚明显,而掺有添加剂的试样测不到表面有电荷或是存在低于探头灵敏度的电荷积聚。所有试样加压3次以后与加压1次相比较,整体电荷积聚量均有增加。不同试样的电荷消散特性试验结果表明,静置一个小时后,不同试样的电荷消散量均小于10%。     

单层石墨烯表面钠原子吸附行为的第一性原理

构建了3种典型的石墨烯吸附钠原子模型(Na_xC_(72)(1≤x≤7)),采用密度泛函理论对其进行了系统计算,研究了最低能量构型的吸附能、平均电压、重叠布居以及原子布居、电荷密度差分、电子局域密度和态密度等性质。通过吸附能确定石墨烯表面最可能的钠原子吸附形式,当钠原子吸附数量x5时,钠原子优先以双面吸附的形式吸附于石墨烯表面;当x≥5时,钠原子以团簇的形式吸附于石墨烯表面。平均电压计算结果表明,随着x的增加,平均电压先降低后出现升高趋势,对应x=4时石墨烯吸附钠的最大容量达124 mAh/g。电荷密度差分、电子局域密度及Mulliken布居分析表明,临近石墨烯表面的钠原子3s电子转移至石墨烯的反键π轨道,钠原子和碳原子之间形成弱离子键,距离石墨烯表面较远的钠原子3s电子与周围钠原子共享,钠原子之间形成金属键。态密度计算结果表明,随着x的增加,Na_xC_(72)(1≤x≤7)的费米能级向石墨烯反键π轨道移动,导电性增强。     

微纳米尺度下聚酰亚胺薄膜表面电荷的生成实验

为进一步研究聚合物电介质材料聚酰亚胺表面电荷的生成规律和特性,利用Dimension 3100型扫描探针显微镜在微纳米尺度下对聚酰亚胺表面进行摩擦产生了电荷,并用静电力显微镜观察了电荷的消散过程.通过对实验结果的分析,得出微纳米尺度下聚酰亚胺表面电荷生成的规律和特性:表面电荷的极性与探针针尖所加偏压保持一致,且表面电荷的密度和作用区域会随着探针针尖所加电压的增加而加大,并随着探针摩擦速度的增加而减小.为探索聚合物电介质材料表面电荷生成规律及特性提供了一条新途径.     

金红石型TiO2(110)表面吸附TiCl4的微观机理

采用密度泛函理论平面波赝势方法研究了TiCl₄分子在TiO₂(110)表面桥位氧上的吸附,对稳定吸附构型的吸附能、电荷密度、差分电荷密度、电子态密度、Mulliken电荷布居等进行计算和分析。研究结果表明,TiCl₄在完整晶胞表面不能吸附;在有氧空位的晶胞表面,TiCl₄以面心向下吸附最稳定,吸附过程为放热。当表面氧空位密度为12.5%、25%时,面心向下吸附方式的吸附能分别为-29.780 9 kJ·mol-1和-48.641 9 kJ·mol-1,表明氧空位密度越高,吸附强度越强;带隙从1.304 eV分别减小到0. 074 eV、0.015 eV,能带结构的带隙宽度变窄,表明氧空位密度越高,带隙宽度越窄;TiCl₄分子向晶胞表面转移的电荷分别为0.2 eV、0.26 eV,说明随着表面氧空位密度增加,TiCl₄分子向晶胞表面转移的电荷量增加,表面对分子的氧化作用越强。     

不同冲蚀角条件下QAl9-4铝青铜的冲蚀磨损特性

利用自主研发的转盘式冲蚀实验装置,通过失重分析、表面形貌观察以及表层粗糙度测定,探讨了QAl9-4铝青铜在不同冲蚀角度条件下的冲蚀磨损特性。结果表明,在0~30°冲蚀角度范围内,铝青铜试样的累积质量损失随角度增大而增加;当冲蚀角度大于30°后,累积质量损失降低。随着冲蚀角度的逐步增大,冲蚀磨损形成的试样表面缺陷逐渐从沿水流方向的长程犁沟向带有凹坑的短程犁沟变化,且试样表面平均粗糙度逐渐降低。     

扫描探针显微镜测壳聚糖材料的表面电荷分布

提出一种测量材料表面电荷是非均匀的、没有中性区的弱电荷的方法.即测试时,利用扫描探针显微镜(SPM)的静电力显微镜(EFM)测量技术,依靠轻敲模式(Tapping Mode)和抬举模式(Lift Mode),用相位成像测量有机高分子膜--壳聚糖膜(CHI)的表面电荷密度空间分布,但由于仪器设计中相位的泰勒展开是:sin△φ≈1/2△φ,所以所获的电荷图像只能确定材料的表面电荷分布和表面电荷密度的近似值.然而,嵴宽约为2.12μm表面正电荷微沟槽结构的这种特殊电荷形貌分布有利于细胞的生长,因此获得的表面电荷分布补充了生物材料表面理化性质.     

水冷壁镍涂层Na盐结渣的密度泛函理论研究

通过第一性原理(First principles)的密度泛函理论,利用Material studio的CASTEP模块,计算了不同覆盖度下Na盐在NiO涂层表面不同吸附位的吸附结构、吸附能、差分电荷密度及局域态密度,从原子层面研究通过铁基材料表面Ni涂层减轻结渣的机理。由表面吸附的分析可知,Na在涂层NiO(111)面的吸附稳定位为洞位;由差分电荷密度分析可知,涂层水冷壁表面发生的煤灰粘结过程主要是物理吸附过程;由洞位局域态密度分析可知,计算模型越接近实际模型,Na3s轨道和Ni3d轨道反键态电子越多,成键态电子越少,平均成键电子数越少,Na与Ni之间的相互作用越弱,导致吸附能数值减小,从而说明通过Ni涂层技术可以大大减轻Na盐结渣。     

冲击荷载下石墨矿石破碎能耗特征

为了研究晶质石墨矿石试样在冲击荷载作用下的破碎能耗特征，采用?50 mm的分离式霍普金森压杆(SHPB)试验装置，设置气压间隔为0.1 MPa, 0.2～0.6 MPa共5组冲击气压，进行不同加载速率条件下石墨矿石试样冲击压缩试验，并分析石墨矿石试样破碎能耗规律。试验结果表明：在冲击荷载作用下，石墨矿石试样的动态抗压强度与平均应变率具有较强的三阶多项式关系，且石墨矿石在冲击荷载作用下具有动态硬化作用，其动态抗压强度随着应变率的增大呈非线性增大，呈现明显的应变率效应；石墨矿石试样破碎耗能与入射能具有显著的对数关系，随着入射能增大，试样破碎耗能也随之增大，但其试样破碎耗能所占比例随应变率增大逐渐由0.38下降至0.11;随着平均应变率增大，石墨矿石试样破碎耗能密度呈非线性增长，具有较强的应变率效应；石墨矿石试样的破碎平均粒径与破碎耗能密度具有显著的三阶多项式相关关系，随着石墨矿石试样耗能密度增加，石墨矿石试样破碎程度加剧，可以采用石墨矿石试样破碎块度平均粒径实现对石墨矿石试样破碎程度进行定量描述。     

Effects of shapes of electrodes on freezing of supercooled water in electric freeze control

In order to clarify the effects of electric charge on freezing of supercooled water, experiments were carried out. Two kinds of shapes were used for tips of electrodes. One was the sharp end surface. The other was the flat end surface. Aluminum was selected as the material. Water sample was kept in a test tube and cooled down at a constant cooling rate. When the water sample was maintained under a supercooling state, an electric charge was applied to the water sample with a small electric current. The degree of supercooling and the electric current were measured, continuously. Then the degree of supercooling at freezing was determined. It was found that the effects of electric charge were distinct according to the shapes of electrodes. The degree of supercooling at freezing was the lower in the case of flat end surface of the anode than that in the case of sharp end surface of the anode.     

The use of environmental scanning electron microscopy for imaging wet and insulating materials

The environmental scanning electron microscope (ESEM) is a direct descendant of the conventional SEM, but also permits wet and insulating samples to be imaged without prior specimen preparation. A low pressure (up to around 10 torr) of a gas can be accommodated around the sample. When this gas is water, hydrated samples can be maintained in their native state. Whether the gas is water or some other gas, ions formed on collisions between electrons emitted from the sample and the gaseous molecules drift back towards the sample surface helping to reduce charge build up. This eliminates the need for insulators to be subjected to a conductive surface coating. These two key advantages of ESEM open up a wide range of materials to the power of scanning electron microscopy.     

钛表面自组装牛血清白蛋白以控制血小板粘附行为的研究

将牛血清白蛋白通过自组装方法组装到钛表面,以改善其血液相容性.首先,用氢氧化钠活化钛,得到有活性羟基且带负电荷的多孔表面,然后浸入带正电荷的聚赖氨酸溶液,最后浸入带负电荷的牛血清白蛋白溶液.通过扫描电子显微镜(SEM)和原子力显微镜(AFM)观察自组装前后表面形貌变化,通过傅立叶红外漫反射(FTIR)检测各步处理层表面基团变化,通过视频接触角观察各步处理后钛表面接触角变化,通过体外血小板粘附实验评价自组装前后表面血液相容性变化.实验结果表明,牛血清白蛋白组装到钛表面后,血小板的粘附行为得到有效控制,钛表面的血液相容性显著改善.     

Charge injection on insulators via scanning probe microscopy techniques: towards data storage devices

The idea of contact electrification aiming the development of nano-scale data storage devices has been explored through a careful investigation of charge injection on insulating films (SiO2 and PMMA) via scanning probe microscopy techniques. A complete route for data storage, showing simple and effective ways to write (inject the charge with an atomic force microscopy (AFM) tip), to read (detect the charge with electric force microscopy), to store (keep sample charge by changing ambient and surface conditions) and to erase the information (make the discharge process faster) is proposed and discussed. A detailed study of the influence of several parameters like AFM mode, bias voltage, relative humidity and surface hydrophobicity is also presented to optimize both charge injection and discharge processes. Results show that monitoring parameters such as ambient relative humidity and surface hydrophobic/hydrophilic character enable the control of pattern size, lateral dispersion, and storage time. The charge polarity is also dependent on the surface hydrophobicity and either positive or negative charges can become more appropriate for storage depending on the surface hydrophobic/hydrophilic character.     

恒栅流负电晕充电的Si基SiO2驻极体的电荷稳定性

本文讨论了在不同充电参数条件下的恒恒流电晕充电的Ｓｉ基ＳｉＯ２薄膜驻极体的空间电荷储存稳定性,并和栅控恒压电晕充电的结果进行了比较。利用电容－电压（Ｃ－Ｖ）分析技术确定了空间电荷重心的漂移,并利用等温表面电位衰减测量,开路热刺激放电实验及Ｃ－Ｖ分析技术讨论了Ｓｉ基ＳｉＯ２薄膜驻极体的空间电荷储存和输动特性。     

Effect of mesoscopic semiconductor perturbations on the electromagnetic field distribution in near-field optical microscopy

The effect of mesoscopic semiconductor perturbations in the volume of a dielectric sample on the electromagnetic field intensity distribution was theoretically studied for a scanning near-field optical microscope operating in the collecting mode for the surface structure investigation. A system of integral equations is constructed which takes into account for the first time the possibility that inhomogeneities are present simultaneously on the surface and in the bulk of the sample. It is shown that the near-field distortions introduced by the above perturbations significantly depend both on the location of a perturbation and on the properties of free charge carriers in this region. This effect must always be taken into account in near-field optical microscopy.     

BaTiO3颗粒对分散剂PMAA-NH4的吸附机制研究

通过ζ电位测量及PTIR分析，研究了BaTiO3颗粒对阴离子型分散剂PMAA－NH4的吸附机制。结果表明，加入PMAA－NH4后，由于BaTiO3颗粒表面上存在Ba-OH2^ 的正电荷中心，从而吸附了分散剂的阴离子，使BaTiO3表面带电特性改变，等电点由pH＝5.1移至pH=3.5，当pH=10，PMAA－NH4的加入量为0．8wt％时，BaTiO3颗粒表面吸附达到饱和，可以得到稳定性好的BaTiO3悬浮体。     

The effect of ionizing radiation on metoprolol

The influence of ionising radiation on physico-chemical properties of metoprolol tartrate (MT) in solid phase was studied. The compound was irradiated by radiation produced by a beam of high-energy electrons in an accelerator, in doses from 25 to 400 kGy, and the possible changes in the samples were detected by organoleptic analysis (colour, forms, clarity), chromatographic and spectrometric methods. Already at the standard sterilisation dose of 25 kGy, the presence of free radicals (0.3764 × 10¹⁶ spin/g) and a decrease in the melting point by 1°C were noted. At higher doses of irradiation products of radiolysis appeared (100 kGy) and the colour was changed from white to pale cream (200 kGy). Our observation was that with increasing mass loss of MT after irradiation with 100, 200 and 400 kGy, the concentration of free radicals increased from 1.0330 to 1.6869 × 10¹⁶ spin/g. The radiolytic yield of total radiolysis was 4.54 × 10⁷ mol/J for 100 kGy, 7.42 × 10⁷ mol/J for 200 kGy and 4.74 × 10⁷ mol/J for 400 kGy. No significant changes were observed in the character of FT–IR spectra, but in UV an increase in intensity of the band at the analytical wavelength was noted. As follows from the results MT shows high radiochemical stability for the typical sterilisation doses 25–50 kGy, and will probably be able to be sterilised by radiation in the dose of 25 kGy.     

Electron-beam-irradiated rice husk powder as reinforcing filler in natural rubber/high-density polyethylene (NR/HDPE) composites

The use of rice husk (RH) powder as a reinforcing filler in blends of natural rubber and high-density polyethylene (NR/HDPE) was studied via surface modification of the particle surface. The RH powder was pre-washed with sodium hydroxide (NaOH) prior to coating with liquid natural rubber (LNR) and reinforced by electron beam (EB) irradiation. The effects of the radiation dosage on the LNR-coated rice husk (RHr) as a reinforcing agent in the composite were evaluated from the mechanical and thermal properties, as well as from the blend homogeneity. The mechanical properties enhanced with the dosage of radiation on the RHr, and reached an optimum dose in the range 20–30 kGy. The composites filled with radiated RHr showed the highest storage modulus (E′) and low tangent delta (tan δ) a radiation dosage of 30 kGy. The scanning electron microscopy (SEM) micrograph of the fractural tensile surface showed that an effective RHr particle matrix interaction occurred in the RH powder at a radiation dosage of 20 kGy. Improved RH filler–matrix interfacial bond strength and adhesion to the matrix were achieved by coating the RH powder and curing the rubber coat by electron beam irradiation.     

Electron-beam-irradiated rice husk powder as reinforcing filler in natural rubber/high-density polyethylene (NR/HDPE) composites

The use of rice husk (RH) powder as a reinforcing filler in blends of natural rubber and high-density polyethylene (NR/HDPE) was studied via surface modification of the particle surface. The RH powder was pre-washed with sodium hydroxide (NaOH) prior to coating with liquid natural rubber (LNR) and reinforced by electron beam (EB) irradiation. The effects of the radiation dosage on the LNR-coated rice husk (RHr) as a reinforcing agent in the composite were evaluated from the mechanical and thermal properties, as well as from the blend homogeneity. The mechanical properties enhanced with the dosage of radiation on the RHr, and reached an optimum dose in the range 20–30 kGy. The composites filled with radiated RHr showed the highest storage modulus (E′) and low tangent delta (tan δ) a radiation dosage of 30 kGy. The scanning electron microscopy (SEM) micrograph of the fractural tensile surface showed that an effective RHr particle matrix interaction occurred in the RH powder at a radiation dosage of 20 kGy. Improved RH filler–matrix interfacial bond strength and adhesion to the matrix were achieved by coating the RH powder and curing the rubber coat by electron beam irradiation.