氟化时间对环氧树脂绝缘表面电荷积累的影响

为抑制环氧树脂绝缘的表面电荷积累、研究处理时间对表面电荷积累的影响, 使用氟/氮混合气在实验室反应釜中对环氧试样进行了不同时间(10 min, 30 min和60 min)的表面氟化处理. 衰减全反射红外分析与SEM断面和表面观察表明随氟化时间的增加, 氟化层的氟化度和厚度增大, 表面微观粗糙度降低、表面组织变得致密. 与开路热刺激放电电流测量所表明的、未氟化(原)试样有深的表面电荷陷阱和稳定的表面电荷相比, 这些氟化试样的表面不能存储电荷. 沉积在它们表面上的电晕电荷于室温下分别约在2 min, 10 min和15 min内快速衰减为零, 展现随氟化时间的延长而减慢的电荷释放速率. 表面电导率和接触角测量及表面能计算表明氟化引起表面电导率和表面润湿性与极性的显著增加, 但它们随氟化时间的延长而减小. 氟化试样表面电导率的显著增大归因于表面电荷陷阱的非常可能的实质变浅和表面吸附的水分. 表面充电电流测量进一步地表明, 与原试样几乎为零的稳态表面电流相比, 这些氟化试样在连续充电期间显现大的稳态表面电流. 这意味着这些氟化试样在充电期间比原试样有少得多的表面电荷积累.     

表层氟化聚乙烯中的空间电荷

本文试图简要地汇集近年来与近期我们所取得的关于表面氟化对聚乙烯(PE) 空间电荷行为影响的研究结果, 总结与探讨PE中的空间电荷积累与其氟化层特性和特征间的关联. 这些结果显示在氟化反应气中没有氧存在时一个非常薄的氟化层能产生有效的电荷抑制, 而当氧存在时为达到有效的电荷阻挡、需要一个具有高氟化度的非常厚的氟化层. 在影响空间电荷的诸电学因素中, 氟化层的电荷传导特性比其电荷俘获特性和介电常数或极性对阻止电荷注入材料内部更为重要, 尽管氟化层的高介电常数和被俘获的电荷会降低界面电场、因此减少电荷的电极注入. 氟化层的电荷传导特性密切关联于其自由体积, 反应混合气中存在的氧对减小自由体积、因此对电荷的抑制具有强的负面影响.     

射频反应磁控溅射法制备的氟化类金刚石薄膜摩擦特性研究

以高纯石墨做靶,CHF3和Ar气为源气体,采用射频反应磁控溅射法在不同流量比条件下制备了氟化类金刚石(F-DLC)薄膜.利用原子力显微镜、纳米压痕仪、拉曼光谱和红外光谱、摩擦磨损测试仪对薄膜的表面形貌、硬度、键结构以及摩擦性能做了具体分析.表面形貌测试结果表明,制备的薄膜整体均匀致密,表现出了良好的减摩性能.当CHF3与Ar气流量比r为1:6时,所得薄膜的摩擦系数减小至0.42,而纳米压痕结果显示,此时薄膜的硬度也最高.拉曼和红外光谱显示,随着r的增加,薄膜中的F浓度呈上升趋势,薄膜中的芳香环比例减小.研究表明,F原子的键入方式是影响F-DLC薄膜摩擦系数的一个重要因素,CF2反对称伸缩振动强度的减弱和CC中适量碳氢氟键的形成都能导致薄膜具有相对较低的摩擦系数.     

SSZ-13分子筛上甲醇转化过程中甲氧基物种的生成与活性研究

本文使用固体核磁共振（NMR）技术研究了SSZ-13分子筛上甲醇制烯烃反应过程中表面甲氧基物种的生成以及反应活性.通过二维¹³C-²⁷Al HMQC NMR方法确证了甲醇在分子筛骨架Brønsted酸位上生成的甲氧基物种,以及在Lewis酸位上生成的另外一种表面甲氧基物种.¹³C NMR结合气相色谱-质谱（GC-MS）实验结果表明,这两种甲氧基物种在甲醇制烯烃反应中均具有较高的反应活性,既可以导致烃池物种的生成,也可以参与烃池反应生成碳氢化合物.     

含氮氟化类金刚石(FN-DLC)薄膜的研究：(Ⅲ)疏水性能分析

不同沉积条件下，在单晶硅基底上沉积了含氮氟化类金刚石(FN-DLC)薄膜，用静滴接触角/表面张力测量仪测量了水与FN-DLC膜表面的接触角.用X射线光电子能谱、Raman光谱和傅里叶变换吸收红外光谱(FTIR)分析了薄膜的组分和结构.用原子力显微镜观测了薄膜的表面形貌.结果表明，FN-DLC薄膜疏水性能主要取决于薄膜表面的化学结构、薄膜表面极化强度的强弱、以及薄膜的表面粗糙度的大小.sp³/sp²的比值减小，CF₂基团含量增加，薄膜粗糙度增加，接触角增大；反之，则接触角减小.在工艺上，沉积温度和功率的减小，气体流量比r(r=CF4/［CF₄+CH₄］)的增加，都会使水的浸润性变差，接触角增大. 关键词： 氟化类金刚石膜 疏水性 接触角     

表层氟化温度对聚乙烯中空间电荷积累的影响

在实验室反应釜中于不同的温度(35 ℃, 55 ℃和70 ℃) 下, 以氟气体积浓度为12.5%的氟/氮混合气对热压制备的聚乙烯(PE) 片状试样(厚约0.8 mm) 进行了相同时间(2 h) 的表层氟化改性. 利用压力波法研究了氟化温度对PE中空间电荷积累的影响. 结果显示, 随着氟化温度的提高直流高压作用下的氟化试样中的空间电荷积累明显减少, 这个70 ℃的氟化试样中几乎没有空间电荷. 衰减全反射红外分析表明, 氟化引起了试样表层化学组成的本质变化及氟化度随氟化温度的明显提高. 接触角测量与表面能计算间接地表明了这些氟化层有显著增大的介电常数. 开路热刺激放电电流测量进一步揭示了这些氟化层 不同的电荷捕获特性, 及随着氟化温度的提高氟化层对化学杂质从半导性电极向PE扩散的增强的阻挡特性, 因此表明氟化层中自由体积的相应减小. 表层自由体积的减小对抑制空间电荷的积累, 比介电常数的增大和电荷陷阱的变化起到更加显著的作用.     

不同射频输入功率下制备的氟化类金刚石碳膜疏水性研究

以高纯石墨作靶、氩气（Ar）和三氟甲烷（CHF₃）为源气体，用反应磁控溅射法在不同射频功率下制备了氟化类金刚石碳（F-DLC）膜，并对其疏水性进行研究.双蒸水液滴与膜表面接触角的测试结果表明，所制备薄膜表面的最大水接触角可达115°左右.通过原子力显微镜获得的薄膜表面AFM图谱、拉曼光谱以及傅里叶变换红外光谱探讨了影响薄膜的疏水性的因素.结果表明，薄膜的疏水性与薄膜的表面粗糙度和表面键结构直接相关，表面粗糙度越大，疏水性越好，但与薄膜中的F含量和sp³/sp²的比值并未呈单调增加或减小的对应关系.射频输入功率影响着薄膜的沉积速率，与薄膜表面粗糙度、薄膜中芳香环单核的比例以及薄膜表面的键结构（F的接入方式）直接相关. 关键词： 疏水性 反应磁控溅射 氟化类金刚石膜 射频功率     

等离子体介质阻挡放电氟化改性环氧树脂的时效性

等离子体对材料的改性效果随放置时间会有所减弱,即表现出一定的时效性,限制了等离子体改性技术的进一步发展。为了探究等离子体介质阻挡放电（DBD）氟化改性环氧树脂的时效性,利用等离子体介质阻挡放电实现了环氧树脂表面氟化改性,并利用扫描电镜（SEM）、表面轮廓仪、X射线光电子能谱分析（XPS）、接触角测试仪、高阻计和闪络电压、表面电位测试系统对改性前和改性后放置在25 ℃老化箱中0～30 d的环氧树脂表面进行了物理形貌和化学组分的表征以及电气性能的测试。测试结果表明,DBD氟化改性实现了氟元素在环氧树脂表面接枝,这使得环氧树脂表面能降低,表面电阻率减小,陷阱能级变浅,从而加快了表面电位衰减速度,进而提升了沿面闪络电压。同时,等离子体DBD氟化改性环氧树脂表现出一定的时效性,放置30 d后,氟元素含量减少,表面能增大,表面电位衰减速度略有减慢,闪络电压也有所下降,但仍高于未处理的试样。     

DCEL材料的包铜新工艺

通过包铜过程的分析,了解到包铜反应主要是表面化学吸附反应,ZnS颗粒表面状况对生成的CuxS性质影响很大,据此设计了淬火包铜工艺,并得到形成功率较低,抗老化性能好的DCEL粉.本文初步分析了淬火生成的CuxS相,认为它的初态处于一种高度无序状击,经一段时间可自然发生某种相变.新相比较稳定,从而可能抑制由Cu+迁移造成的老化.     

氟化石墨红外谱图的量子化学模拟

氟化石墨作为一种高储能材料广泛用于一次锂电池中,氟化石墨材料的微观结构影响其电化学储能性能.以量子化学模拟计算为基础,建立了氟化石墨类材料中微观结构单元与红外谱图特征频率的关系,指出了在氟化石墨类材料中,碳原子以sp2型杂化形式为主与氟原子形成氟碳键,石墨的氟化反应以形成氟碳比为1∶1的结梅较为有利,是氟化右墨材料中的主要成分.     

Effect of fluorination on electrical properties of single walled carbon nanotubes and C60 peapods in networks

We present a comparative study of fluorinated single wall carbon nanotubes and C₆₀ peapods. The fluorination was carried out by xenon difluoride treatment at moderate temperature (100 °C). The fluorination level was determined by EDX. In empty nanotubes a fluorination level of 0.8 at.% was obtained, whereas the same treatment leads to 18 at.% in peapods (corresponding to a gross stoichiometry of C₄F). TEM images show that this fluorination procedure does not affect the peapod structure. The elemental mapping carried out by EELS reveals homogenous distribution of fluorine along the carbon nanotube bundle. This chemical treatment is found to change the electrical properties of carbon nanotubes in bucky papers. Four-probe measurements indicate a conductivity decrease by up to two orders of magnitude at room temperature. The temperature dependence of the conductivity indicates a significant change in the charge carrier density of this system. Moreover, a non-linear behavior of the I–V characteristic is observed below 50 K in fluorinated peapods.     

Effect of surface fluorination on the photocatalytic and photo-induced hydrophilic properties of porous TiO2 films

Porous surface-fluorinated TiO₂ (F-TiO₂) films were prepared through PEG modified sol-gel method and surface fluorination. The as-prepared films were characterized with XRD, FTIR, AFM, XPS and UV-vis DRS. The effects of surface fluorination on the photocatalytic activity and hydrophilicity of porous TiO₂ film were studied by photocatalytic degradation of rhodamine B (RhB) as well as water contact angle (CA) on porous TiO₂ film. The results showed that the surface fluorination increased the adsorption of RhB on the porous TiO₂ film and enhanced the photocatalytic degradation of RhB. The concentration and pH of NaF solutions affected much the photocatalytic activity of porous TiO₂ film. Porous F-TiO₂ film prepared in 40 mM NaF solution at pH 4.0 showed the highest photocatalytic activity. Because of its porous structure, the porous F-TiO₂ film had original water CA of 22.7°, which is much smaller than that of normal F-TiO₂ film. Under UV light irradiation, the water CA of porous F-TiO₂ film decreased to 5.1° in 90 min.     

氟气处理孔洞聚丙烯膜显著改善的电荷存储特性

通过衰减全反射(attenuated total reflection，ATR)红外光谱分析与开路热刺激放电(thermally stimulated discharge，TSD)电流、原位实时电荷TSD和电荷等温衰减的测量，研究了氟气对孔洞聚丙烯(PP)膜的氟化改性及氟化改性对其驻极性能的影响.研究结果表明：尽管在负压状态且较低的氟气分压及较低的反应温度(约60℃)和较短的反应时间(约15min)下，氟气能有效地氟化孔洞PP膜，更易于氟化预氧化的孔洞PP膜，氟化改性的孔洞PP膜，尤其是预氧化后的氟化改性 关键词： 孔洞聚丙烯膜 氟气 氟化改性 电荷稳定性     

Inducing superconductivity and structural transformations by fluorination of reduced YBCO

Bulk superconductivity with T_c up to 94 K has been induced by fluorination of non-superconducting YBa₂Cu₃O_6.11 using XeF₂ as a fluorination agent. Strong changes on X-ray patterns were found after fluorination of reduced YBCO. High resolution electron microscopy of superconducting samples showed the presence of a new phase with c ≈ 13 Å which exists as noticeable areas included within a matrix of the 123 structure or which occurs as isolated defects with a limited extension. All fluorinated compounds exhibited a strong disorder along the c-direction resulting in a ‘loss’ of c-parameter on X-ray patterns. The present results demonstrate that fluorine indeed enters the YBCO structure with a significant structural rearrangement for the high level of fluorination. The structure of the fully fluorinated YBa₂Cu₃O₆F₂ phase, possibly responsible for superconductivity, has been deduced from high resolution electron microscopy.     

Fabrication of superhydrophilic or superhydrophobic self-cleaning metal surfaces using picosecond laser pulses and chemical fluorination

Bioinspired superhydrophilic/phobic self-cleaning surfaces have recently drawn a lot of interest in both fundamental and applied research. A hybrid method to produce the self-cleaning property of micro/nanostructured surface using ultra-fast laser pulses followed by chemical fluorination is proposed. The typical micro/nanocomposite structures that form from microporous arrays and microgroove groups have been processed by picosecond laser on titanium alloy surface. The surface hydrophilic/phobic and self-cleaning properties of micro/nanostructures before and after fluorination with fluoroalkyl-silane were investigated using surface contact angle measurements. The results indicate that surface properties change from hydrophilic to hydrophobic after fluorination, and the micro/nanostructured surface with increased roughness contributes to the improvement of surface hydrophobicity. The micro/nanomodification can make the original hydrophilic titanium alloy surface more hydrophilic or superhydrophilic. It also can make an originally hydrophobic fluorinated titanium alloy surface more hydrophobic or superhydrophobic. The produced micro/nanostructured titanium alloy surfaces show excellent self-cleaning properties regardless of the fluorination treatment, although the fluorinated surfaces have slightly better self-cleaning properties. It is found that surface treatment using ultra-fast laser pulses and subsequent chemical fluorination is an effective way to manipulate surface wettability and obtain self-cleaning properties.     

Electret properties and chemical modification of cellular polypropylene films

The electret properties of virginal cellular polypropylene (PP) films and chemically modified cellular PP films by extraction from CH₂Cl₂ solution, oxidation in a mixture solution of H₂SO₄, CrO₃ and H₂O and fluorination in a hydrofluoric acid (HF) solution, were systematically studied by measuring the open-circuit thermally stimulated discharge (TSD) current spectra, charge TSD spectra and isothermal charge decay. The results point out that there are more deep traps than shallow traps in the surface region while the contrary case occurs in the bulk region. The thermal stability of charge storage of the chemically modified cellular PP film is significantly improved in comparison with that of the virginal one. Light irradiation or reacting at elevated temperature has remarkable promotion effect on the reaction of HF with the extracted and oxidized film. Moreover, a method for investigating the dynamic changes of mean charge depth relative to its initial value during heating was proposed.     

Fluorinated nanocarbons using fluorinating agent: Strategies of fluorination and applications

The fluorination method strongly influences the physical properties of the resulting fluorinated carbon materials. Two fluorination ways, direct fluorination under pure fluorine gas and controlled fluorination by the decomposition of TbF₄, have been used for the fluorination of particular nanocarbons: carbon nanofibers and a mixture of carbon nanodiscs and nanocones. Then, fluorocarbon matrix structures have been determined owing to solid state ¹⁹F NMR for MAS conditions at a spinning speed of 30 kHz. It reveals that the fluorination mechanism depends on the fluorination conditions but not on the starting nanocarbons morphology, i.e. tubular or planar. Finally, the electrochemical properties of carbon nanofibers fluorinated by the two ways are detailed. Controlled fluorination allows an increase of the power densities of fluorinated carbon nanofibers used as electrode in primary lithium batteries.