Structure and optical properties of nanocrystalline NiO thin film synthesized by sol–gel spin-coating method

NiO thin film was prepared by sol–gel spin-coating method. This thin film annealed at T = 600 °C. The structure of NiO thin film was investigated by means of X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). The optical properties of the deposited film were characterized from the analysis of the experimentally recorded transmittance and reflectance data in the spectral wavelength range of 300–800 nm. The values of some important parameters of the studied films are determined, such as refractive index (n), extinction coefficient (k), optical absorption coefficient (α) and band energy gap (E_g). According to the analysis of dispersion curves, it has been found that the dispersion data obeyed the single oscillator of the Wemple–DiDomenico model, from which the dispersion parameters and high-frequency dielectric constant were determined. In such work, from the transmission spectra, the dielectric constant (_∞), the third-order optical nonlinear susceptibility χ⁽³⁾, volume energy loss function (VELF) and surface energy loss function (SELF) were determined.     

Electron work function and the surface tension of a metallic surface with an insulating coating

The electron work function, contact potential difference, and surface tension of elastically deformed faces of metal with an insulating coating have been calculated within the Kohn-Sham method. The calculations demonstrate the opposite deformation dependences of the electron work function and contact potential difference. An insulating coating leads to a negative change in the work function and a positive change in the contact potential difference. It is shown that the measurements of the contact potential difference of a deformed face by the Kelvin method give only the change in the value of the one-electron effective potential on the plane of a virtual image behind the surface rather than the value of the electron work function. The calculated values of the electron work function and surface tension for Al, Au, Cu, and Zn are in agreement with the results of experiments for polycrystals and first-principles calculations.     

Kinetics of oxide film growth on metal crystals: Space-charge-modified thermal electron emission and ionic diffusion. Part 1. Pertinent equations

A complete prototype coupled-currents calculation for metal oxidation has been carried out for a model based on ionic diffusion and thermal electron emission in the presence of space charge of the diffusing ionic species. This theoretical and numerical work is presented in two parts. In Part 1, the analytical equations for species transport are developed, and the approach for coupling these equations to deduce the kinetics of metal oxidation is outlined. The space-charge-modified ionic defect profiles can be expressed exactly in terms of Airy functions. These profiles lead in turn to analytical expressions for the total energy barrier for thermal electron emission. This is important both for metal oxidation and in devices utilizing electron emission from metals which are covered with oxides and similar dielectric layers. In Part 2, the results of extensive numerical computations for the model are presented. These calculations have led to a full understanding of the predictions of the model, the most important of which are the following: (a) In the early growth stage, the negative surface-charge field is an order of magnitude or so larger than its homogeneous field counterpart; this significantly aids the injection of rate-limiting electronic carriers into the conduction band of the oxide, and the oxide growth rate is thereby enhanced, (b) In the later stages of growth where the ionic species becomes rate-limiting, the space charge of the diffusing ions causes a marked retardation of the ionic current and the accompanying oxide film growth, (c) The transition from electron rate-limited growth occurs shortly after the classical electron energy barrier maximum switches from inside the film (Schottky-type emission) to a space-charge-produced barrier maximum at the outer interface of the film.This research was performed at Auburn University in partial fulfillment of the requirements for the Ph.D. degree.     

彩色超疏水不锈钢表面的制备

目的解决普通彩色不锈钢表面能高、易被污染的缺点,制备既有装饰效果又具有超疏水自清洁性能的彩色超疏水不锈钢表面。方法通过简单的化学蚀刻法在不锈钢表面建立微纳米尺度的二元微结构,在此基础上进一步由铬酸化学氧化法(INCO法)在不锈钢表面生成微纳米结构彩色膜,经全氟硅烷分子修饰后,最终获得低表面能类荷叶粗糙结构。通过着色曲线、扫描电镜、电子能谱分析仪以及接触角测试等手段研究了化学蚀刻前处理对不锈钢着色性能、微观结构、表面浸润性以及耐腐蚀性能的影响。结果蚀刻处理后,着色过程减缓,所着终点颜色有轻微改变,着色后表面保留了微纳米粗糙结构。由全氟硅烷分子修饰后,获得超疏水彩色不锈钢表面,水接触角为152.6°,其耐腐蚀性能较普通彩色不锈钢更为优异。结论成功制备了耐蚀彩色超疏水不锈钢表面。     

A novel microwave absorption and dielectric spectrum detection technology in photoelectron dynamic study for solar cells

The photoelectron property is directly related to the light-energy conversion efficiency of solar cells. In this paper, the photoelectron dynamic of semiconductor was analyzed. The diffusion of electrons has influence on the dielectric function of the solar cell material. And the amplitude variance of the imaginary andreal part of the dielectric function is in direct proportion to the dynamic process of free and shallow-trapped electrons. Based on the untouched detection technique, the method is present to detect the amplitude change of the microwave signal which is passing through the material whose dielectric function changes after exposure. A35GHz oscillator was used as a microwave source. The absorptionand dispersion microwave signals, which contain the dynamic information of free and shallow-trapped electron signal, are split respectively with phase-sensitive instrument. The photoelectron character of n-type Si(100) thin film was investigated by the novel equipment, and the lifetime of different kinds of electronswith the resolution of 1 ns was obtained. The equipment can be directly used inthe study of the optoelectronic conversion mechanism of solar cells.     

利用扫描电镜Inlens探头观测择优取向的SrTiO3薄膜微观结构

择优取向的介电薄膜是介电材料研究中的热点。利用溶胶-凝胶法在金属和单晶基底上沉积了择优取向的钛酸锶介电薄膜，并利用扫描电镜Inlens探头对其微观结构进行了直接观测。Inlens探头对于样品表面原子层的信息非常敏感，对于导电性较差的薄膜，不需进行常规的喷金或喷碳处理，即可直接观测，大大提高了分析效率。利用二次电子像探头和Inlens探头分别对半导体性的SrTiO3薄膜的微观结构进行对比分析发现，Inlens探头的分辨率明显优于二次电子探头的。在20万倍的放大倍数下，仍能清晰观测到薄膜的表面和截面结构。     

STUDY ON MICROWAVE DIELECTRIC PROPERTIES OF EPOXY RESIN MIXTURES USED FOR RAPID PRODUCT DEVELOPMENT

1. Introduction and BackgroundRapid prototyping is the dominating technology for fast production of plastics modelsand prototypes since more than a decade. Despite the successes already being notched upas a result of the deploymellt of these techniques like Stereolithography and Selective LaserSintering, large-scale industrial application of these innovative technologies are hamperedboth by their low profile and by current limitations concerning their efficiency. One of thetypical problems i…     

Nano-multilayer Ti-Zr-N coating by a central configured multi-arc coating process

In this work, a novel arc ion plating (AIP) system, consisting of a centrally configured multi-arc source array (CCMA), is developed. This system is aimed to satisfy the present industrial demands for the large-scale production of multicomponent, multilayered, and superlattice coatings. The central array is made up of three flat, independently powered, arc sources. These form a triangular pillar.The newly developed CCMA AIP system is used to deposit TiN/ZrN coatings, in order to evaluate its performance. The surface hardness of the specimens is measured by micro Vickers indentation. A scratch test is used to determine the adhesive strength of the coatings. Scanning electron microscopy (SEM) is used to observe the cross-sectional morphology and to measure the film thickness. An energy dispersive spectrometer (EDS) is used to characterize film composition. The crystal structures of the coatings are characterized by an X-ray diffractometer and transmission electron microscope (TEM).The deposited coatings range from a micro- to nano-layered (TiN/ZrN) structure as the rotation speed of the substrate table was increased. Each layer exhibits a (111) preferred orientation. At rotating speeds in excess of 10 rpm, a nano-multilayered Ti(Zr)N structure is formed, again with each layer having (111) preferred orientation. At the highest rotation speeds the greatest surface hardness and film adhesion strength are attained. This is attributed to the maximized stress accommodation of the nano-multilayer structure, through the different shear elastic modulus of each layer. This research demonstrates that this novel CCMA AIP system is highly flexible in coating material design and capable of mass production.     

低介电聚酰亚胺/氟化石墨烯复合薄膜的制备及表征

目的为了解决超大规模电路高度集成所引起的RC延迟、信号串扰、能耗及噪声等一系列问题,制备具有低介电常数的聚酰亚胺/氟化石墨烯复合薄膜。方法分别采用液相剥离法和两步法制备了氟化石墨烯溶液和聚酰胺酸前驱体溶液,通过溶液共混法制备聚酰亚胺/氟化石墨烯复合薄膜,并通过透射电镜、红外光谱仪、X射线衍射仪以及精密阻抗分析仪,对氟化石墨烯、聚酰亚胺及聚酰亚胺/氟化石墨烯复合薄膜的微观结构和介电性能进行表征研究。结果氟化石墨烯和聚酰亚胺成功复合得到了聚酰亚胺/氟化石墨烯复合薄膜,且复合薄膜的介电常数由3.63降到了2.52。结论成功制备了低介电常数的聚酰亚胺/氟化石墨烯复合薄膜。     

Super-hydrophobic film prepared on zinc as corrosion barrier

Potentiostatic electrolysis was carried out to prepare super-hydrophobic film on the surface of metallic zinc. The resultant film was examined by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical measurements, and contact angle test. The super-hydrophobic property of the film results from the air trapped among the sheets of zinc tetradecanoate. This air behaves as a dielectric for a pure parallel plate capacitor, thereby inhibiting electron transfer between the electrolyte and the substrate. The air can also enhance the contribution of the film itself to protection performance.     

Synthesis of thin film photonic crystals

We describe a synthesis procedure for fabricating thin film photonic crystals at optical length scales from a ceramic slurry of nanocrystalline titania and polystyrene spheres. Self assembly of the spheres is performed simultaneously with the introduction of the dielectric background. Thin film photonic crystals are grown on glass or semiconductor substrates. The photonic crystals are characterized with both surface and cross-sectional scanning electron microscope images. The photonic crystals exhibit a reflection peak and transmission dip at the wavelength of the first stop band.     

氧化铝包覆SrTiO3纳米纤维/聚偏氟乙烯复合材料的制备与介电储能性能

目的 通过开发出工作场强更高、储能效率更高的电介质储能材料,从而提高电力设备的性能、减小电力设备体积。方法 采用静电纺丝工艺结合溶胶凝胶工艺制备具有一维核壳结构的SrTiO3@Al2O3纳米纤维填料,并结合流延成型工艺制备出聚偏氟乙烯(PVDF)电介质复合材料。系统地研究了SrTiO3纳米纤维填料表面包覆Al2O3对PVDF电介质复合材料界面极化、介电性能、储能性能的影响。结果 制备的一维纳米填料具有良好的核壳结构,其中芯层为SrTiO3,壳层为Al2O3, Al2O3包覆厚度为6 nm。低填充量下,一维核壳结构SrTiO3@Al2O3纳米纤维填料均匀地分散在PVDF基体中。在相同的体积分数填料填充下,SrTiO3@Al2O3纳米纤维/PVDF复合材料表现出更低的介电损耗和漏电流、更强的耐击穿场强、以及更高的储能密度和放电效率。SrTiO3@Al2O3纳米纤维/PVDF电介质复合材料的最大储能密度达到8.9 J/cm³。结论 Al2O3包覆层可以阻止SrTiO3纳米纤维填料在复合材料中的接触,减小Maxwell-Wagner-Sillars界面极化,降低漏电流,进而提高复合材料薄膜的击穿强度和储能性能。     

AZ91D压铸镁合金激光局部重熔区气孔的形成机制

采用扫描电镜(SEM)、X光电子能谱分析仪(XPS)等分析手段,研究了NiTi合金表面绝缘膜的结构及成分,从而探讨非阀金属NiTi合金表面微弧氧化陶瓷膜层的形成机制.结果表明,NiTi合金微弧氧化过程中的电流密度-时间曲线与纯钛形状基本一致,也可分为3个阶段,但其最大的电流密度为后者的13倍;NiTi合金表面的绝缘膜主要是通过电化学沉积形成的Al2O3及少量的TiO2、Ni2O3和磷酸盐薄膜,这一绝缘膜就相当于阀金属的阳极氧化膜,为NiTi合金进行微弧氧化处理提供了前提条件;NiTi合金表面的陶瓷膜层主要来源于电解液中的铝酸根离子和少量的基体Ni和Ti(包括固态的和溶解于电解液中离子态的),经反复的放电、熔融、喷射、冷却、凝固,发生一系列的电化学、等离子体化学和热化学反应最终形成表面粗糙多孔陶瓷膜层.     

Cu-Al-Mg合金表面氧化膜分析

利用俄歇能谱、Ｘ射线电子能谱和扫描电镜对Ｃｕ－Ａｌ－Ｍｇ合金表面氧化膜进行了分析。结果表明：氧化膜的ＭｇＯ和Ａｌ２Ｏ３组成;没有进行过氧化处理的样品膜内的Ａｌ和Ｏ含量高于过氧化处理的样品,而Ｍｇ则相反;Ａｌ２Ｏ３的键合能Ｅ２ｐ３／２值大于ＭｇＯ的Ｅ２Ｐ３／２值,表明Ａｌ２Ｏ３不易被分解;进行电子轰击后,膜内Ｍｇ含量减少,ＭｇＯ被部分分解,而Ａｌ则增加,由ＭｇＯ和Ａｌ２Ｏ３组成的复合型氧化膜使得合金     

应用铜型纳米自修复材料原位修复喷油泵柱塞偶件的研究

将平均粒径为20～50 nm的铜粉均匀分散到柴油中,在12PSDB75型喷油泵试验台上利用纳米铜微粒的磨损自修复性能,在不拆卸零件的情况下对磨损失效的喷油泵柱塞偶件进行了原位修复,利用扫描电镜(SEM)、能谱仪(EDS)等对修复前后柱塞表面进行了形貌与微区成分分析.结果表明,在试验台转速500 r/min的条件下修复后的喷油量较修复前提高了33.3 %.这主要是因为在喷油泵运转过程中,添加到柴油中的纳米铜颗粒能在柱塞及柱塞套内表面形成一定厚度的铜保护膜,从而减小偶件的配合间隙,增大喷油压力与喷油量,改善喷油泵性能.     

应用铜型纳米自修复材料原位修复喷油泵柱塞偶件的研究

将平均粒径为20~50 nm的铜粉均匀分散到柴油中，在12PSDB75型喷油泵试验台上利用纳米铜微粒的磨损自修复性能，在不拆卸零件的情况下对磨损失效的喷油泵柱塞偶件进行了原位修复，利用扫描电镜（SEM）、能谱仪（EDS）等对修复前后柱塞表面进行了形貌与微区成分分析。结果表明，在试验台转速500 r/min的条件下修复后的喷油量较修复前提高了33.3 %。这主要是因为在喷油泵运转过程中，添加到柴油中的纳米铜颗粒能在柱塞及柱塞套内表面形成一定厚度的铜保护膜，从而减小偶件的配合间隙，增大喷油压力与喷油量，改善喷油泵性能。     

氧对CIS薄膜太阳能电池开路电压的影响

采用硫化Cu-In前驱膜的方法制备CuInS2薄膜,通过分析CIS薄膜制备过程中不同阶段样品中的氧,讨论了氧的来源及其存在形态,以及对CIS层开路电压可能造成的影响。用扫描电镜（SEM）和能量色散谱仪（EDS）研究前驱膜的形貌及其成分,用X射线衍射仪（XRD）表征薄膜的结构,用俄歇电子能谱（AES）对硫化薄膜中各元素沿深度方向的分布进行了检测,最后用I-V测试仪对硫化膜的开路电压进行测量。结果表明,CuInS2薄膜中的氧来源于Cu-In前驱膜,氧主要以Cu2In2O5的形式存在于CIS/Cu-In界面处,由于氧化物在硫化反应过程中影响了Cu和In向外表面的扩散,从而影响了CIS薄膜的成分和CIS太阳能电池的性能。     

Plasma biasing to control the growth conditions of diamond-like carbon

It is well known that the structure and properties of diamond-like carbon, and in particular the sp³/sp² ratio, can be controlled by the energy of the condensing carbon ions or atoms. In many practical cases, the energy of ions arriving at the surface of the growing film is determined by the bias applied to the substrate. The bias causes a sheath to form between substrate and plasma in which the potential difference between plasma potential and surface potential drops. In this contribution, we demonstrate that the same results can be obtained with grounded substrates by shifting the plasma potential. This “plasma biasing” (as opposed to “substrate biasing”) is shown to work well with pulsed cathodic carbon arcs, resulting in tetrahedral amorphous carbon (ta-C) films that are comparable to the films obtained with the conventional substrate bias. To verify the plasma bias approach, ta-C films were deposited by both conventional and plasma bias and characterized by transmission electron microscopy (TEM) and electron energy loss spectrometry (EELS). Detailed data for comparison of these films are provided.     

Surface modification of a polyester non-woven with a dielectric barrier discharge in air at medium pressure

In this paper, a polyester non-woven is plasma treated with a dielectric barrier discharge (DBD) in air at medium pressure (5.0 kPa) and at different discharge powers. Results show that an increasing power leads to a better plasma treatment of the sample. The barrier discharge is characterized by a voltage and current waveform, by a Lissajous figure and by Lichtenberg figures. The surface properties of the plasma treated samples are examined using X-ray photoelectron microscopy (XPS) and scanning electron microscopy (SEM). XPS analysis reveals that surface oxidation by the formation of oxygen-containing functional groups enhances the surface wettability. SEM analysis shows that the sample is not etched by the used barrier discharge. This is due to the low surface energy density of the DBD used in this paper. Therefore, a DBD in air at medium pressure provides an efficient modification of the chemical surface properties of textiles without destroying the physical structure.     

Study of gas film quality in electrochemical discharge machining

Electrochemical Discharge Machining (ECDM) has been demonstrated to be an alternative spark-based micromachining method for fabricating microholes and microchannels in non-conductive brittle materials. However, the mechanism for attaining accurate control of the contour shape and dimensions remains to be explored. In ECDM process, the gas film on the electrode surface is used as the dielectric medium required for discharge generation. Quality of gas film is the dominant factor that determines the machining qualities such as geometric accuracy, surface roughness and repeatability. Nevertheless, it is difficult to assess the gas film quality of ECDM. In this study, current signals and machined contours were taken as indexes of gas film quality. Experimental results showed that a stable and dense gas film could be obtained when the applied voltage exceeded the critical voltage and reached a specific level, which is called the “transition voltage” in this study. At the transition voltage, a stable electrochemical discharge activity could be generated, thus producing the smallest deviation of contour dimensions. Moreover, when the drilling process reached a certain critical depth, bubbles inside the hole could not easily escape. In order to reduce the interface energy between bubbles, a thicker gas film is formed at the hole entrance, resulting in unstable discharge performance that undermined machining results. In summary, information provided by current signals can shed light on the changes in gas film structure, which serve as useful reference for varying process parameters to achieve better efficiency and accuracy.