The importance of fabric structure in the construction of 2D textile radiation dosimeters

A range of fabrics was selected for examination as material for construction of 2D radiation dosimeters as a consequence of previously obtained results confirming the possibility of radiation dose measurement with the modified polyamide textiles. These fabrics were surface finished with either 2,3,5-triphenyltetrazolium chloride (TTC) or nitrotetrazolium blue chloride (NBT). Under UV light irradiation the fabrics change colour to reddish (TTC) or bluish (NBT). The tinge intensity depends on the absorbed dose, which was analysed through the reflectance of light measurements. Some parameters of the samples are discussed in this work, such as dose sensitivity, quasi-linear and dynamic dose response, which allowed the samples that were potentially attractive for 2D dosimetry to be selected. The textile samples were assessed in terms of 2D measurements with the application of a computer operated scanner. The accuracy of 2D measurements was found to depend on the type and structure of fabric and tinge distribution after irradiation as well as additional polymer finishing of the textiles.     

Two-dimensional residual charge density distribution measurement of surface leader

The charge density distribution of the surface leader has never been measured before. Because the surface leader usually covers a long distance, and the surface potential caused by leader discharge is usually very high, this creates difficulties in measuring the potential distribution of the surface leader. In this paper, with a feedback type electrostatic probe based on a field-nullify technique, a charge density distribution scanning system is developed. A two-layer structure pipe is designed to lower the surface potential after discharge. In this way, the surface potential distribution caused by the residual charge of the leader discharge under the application voltage as high as to 40 kV can be measured. The surface charge density distribution including the leader and streamer is perfectly measured, which is in good agreement with the photograph.     

Electric-potential-measurement-based methodology for estimation of electric charge density at the surface of tribocharged insulating slabs

The auto-compensated electrostatic induction probe (ACEIP) is widely used for measuring the electric potential at the surface of conductive or insulating bodies. The aim of this paper is to elaborate a methodology for using this probe in view of performing the estimation of electric charge density at the surface of tribocharged insulating slabs. In such cases, the electric potential is not uniformly distributed on the surface under investigation. Metallic plates trimmed with different shapes were used to characterize the probe. Thus, a first series of experiments enabled a crude evaluation of the shape and size of the area “seen by the probe”: a 10-mm-diameter circle. Other experiments served to determine the transfer function that relates the value measured by the probe to the potential of a small area of constant electric potential located at a well-defined distance from it. By dividing the surface under investigation into a large number of small elementary areas, it was possible to use this transfer function to express the potential measured by the ACEIP as the sum of the contributions of each such element. An inverse matrix computation method enabled the estimation of the actual surface electric potential. Based on the results of a final set of experiments, the distribution of the electric charge density was estimated for slabs charged by corona-respectively triboelectric-effect.     

氮离子注入对聚四氟乙烯表面电荷积聚和消散特性的影响北大核心CSCD

为了抑制聚四氟乙烯材料表面电荷积聚,采用射频产生氮等离子体对其表面进行等离子体浸没离子注入以改善其表面性能。对注入前后的聚四氟乙烯材料样品进行了X射线光电子能谱分析(XPS)、傅里叶红外光谱测试(FTIR)、水接触角测量、表面电阻率测量以及表面电位衰减测量,并基于等温表面电位衰减理论对其表面陷阱能级和密度分布进行了计算,以分析聚四氟乙烯样品经离子注入处理后其表面成分和物理性能的变化,并研究了这些变化对聚四氟乙烯样品表面电荷积聚和消散特性的影响。结果表明:氮离子注入后,聚四氟乙烯材料表面化学成分的主要变化是自身分子结构的破坏和转化,部分CF2结构转变为CF和CF3结构,导致样品表面陷阱能级变浅;水接触角升至140°左右,比未处理样品上升了约27°,表面电阻率降至3×10^15Ω,比未处理样品下降了两个数量级;表面电晕放电1 min后,经氮离子注入处理的聚四氟乙烯材料表面积聚电荷量减少,消散速度加快,这是因为表面陷阱能级变浅有利于表面电荷脱陷,同时表面电阻率降低也促进了表面电荷沿面传导的消散过程,聚四氟乙烯样品表面陷阱能级分布曲线也证实了这一论点。     

Enhancement of the hydrophobicity of silk fabrics by SF6 plasma

Hydrophobic properties are of interest in fabric and textile manufacture. We have used radio-frequency inductively coupled SF₆plasma to modify the surface of Thai silk fabrics for the enhancement of the hydrophobic property. The water contact angle of fabrics increased from 0°up to 145°after SF₆ plasma treatment. The measured water absorption time was found to depend upon the treatment time and RF power, for SF₆ pressures lower than 0.05 Torr. At higher SF₆ pressures, all samples achieved absorption times in excess of 200 min, regardless of the treatment time and RF power. The morphology changes of fabrics after plasma treatment were characterized by scanning electron microscopy and atomic force microscopy. After plasma treatment, the RMS surface roughness of the fibres increased from about 10 to 30 nm. From X-ray photoelectron microscopy analysis, we found that the hydrophobicity of the fabrics is the highest when the fluorine/carbon ratio at the surface increases. A small decrease of the oxygen/carbon ratio was also observed on the fabrics that showed the longest absorption times.     

Effect of humidity in charge formation and transport in LDPE

Charge distribution and transport have been investigated in LDPE films with different humidity content under electric fields up to 130 MV/m. Pulsed electroacoustic measurements showed that, as water content increases, positive charge packets formation in the anode is enhanced and they propagate toward the cathode with higher transit speeds. Fits of surface potential decay measurements showed that charges in dry samples are injected directly into the volume, but the presence of moisture generates new trap centers in the surface of the material. This new trap level causes a charge accumulation on the surface, that gradually passes into the bulk. The observed behavior in development and propagation of charge packets are explained according to these results. Thermally stimulated depolarization current measurements showed a non-distributed relaxation associated to the new trap levels on the surface of the wet samples.     

Long range interactions between micro spheres and alloy surfaces in water changed by ion implantation

Ion implantation was adopted to change the surface potentials of samples made of aluminum bronze. The interactions between the SiO₂ particles and the sample surfaces in water were changed from attractive to repulsive. According to the surface element integration method, this interaction was simulated and the electrostatic double layer force was considered to be the dominated factor. This long range repulsive interaction was proved to have effect on preventing micro particles approaching the alloy surface by the fluorescent particles adhesion experiment, and the technology of ion implantation may have potential applications in adhesion resistance and abrasion reduction for alloys running in water.     

光电反馈式静电悬浮的机制研究

本文主要讨论光电反馈式静电悬浮的理论问题。研究在静电场作用下导电悬浮体的静电感应机制和绝缘悬浮体的静电极化机理,推导出悬浮体表面的感应电荷或极化电荷的计算公式,以及作用于悬浮体上的静电悬浮力的计算公式,在理论上揭示了静电力与电极电压、电极面积、悬浮间距及悬浮体电学特性等因素之间的关系。结果表明,导电悬浮体表面的感应电荷量比绝缘悬浮体表面的极化电荷量多,因此前者所受的静电悬浮力比后者大,但两者均可实现静电悬浮,这些结论与实验结果完全符合。本文工作为实现静电悬浮的光电反馈控制提供了理论依据。     

Numerical study on electrostatic potential distribution of large cylindrical oil tanks

This study carried out a numerical simulation of electrostatic potential distribution in the cylindrical oil tank, focusing on spatial distribution of electrostatic potential and the variation tendency of the potential in the filling operation. Electrostatic potential distribution of stationary oil was illustrated, and the relationship between the electrostatic potential distribution and some parameters of the tank and oil was analyzed as well. Dynamic electrostatic distribution was studied when charged oil is filling into the tank, and ESD prevention measures’ effects on electrostatic potential distribution were simulated. Finally, calculation results of two other types of oil tanks were presented in brief.     

Plasma enhanced CVD of SiOxCyHz thin film on different textile fabrics: Influence of exposure time on the abrasion resistance and mechanical properties

In order to improve textile fabric abrasion resistance, in this work a SiO_xC_yH_z thin film was realized by low pressure plasma chemical vapour deposition (PCVD) at room temperature, using hexamethyldisiloxane (HMDSO) as precursor compound. To test changes in the performance properties of the surface finished samples as a function of the type of the substrate, the deposition was carried out on different textile fabrics. The polymerization processes were followed by weight measurements of textile fabrics. It was found that, after PCVD, a significantly lower fabric weight loss was observed on treated samples after rubbing than on the untreated samples. The morphology, elemental composition and type of chemical bonding present in the film applied on textile fabrics were also investigated using electron scanning microscopy (SEM), energy dispersive X-ray (EDX) and infrared spectroscopy techniques (FT-IR (ATR)). The results showed a substantial enhancement of wear resistance for the surfaces modified with the presented process, while tensile and tearing strength were adversely affected.     

Effect of sonochemical scouring on the surface morphologies,mechanical properties,and dyeing abilities of wool fibres

Ultrasonics has the potential to reduce the cost and environmental impact of textile processing. This work investigates the effects of ultrasonic irradiation during wool scouring on fibre surface morphologies, fibre mechanical properties, and fibre dyeing abilities. A range of ultrasonic frequencies were used in the scouring bath to examine the forms of fibre cuticle damage. It is observed that wool fibres underwent ultrasonic irradiation at a low frequency have severe modifications of the fibre surface structure. Despite some visible disruptions to the fibre scale structure however, ultrasonic irradiation has shown a negligible impact on the fibre mechanical properties, especially bending abrasion resistance which depends largely on the fibre surface conditions, and is responsible for the handle and pilling propensity of the resultant fabrics. Dyeing abilities were investigated on wool samples using commercially available acid dye and reactive dye. It is found that ultrasonically scoured wool has a quicker dye uptake in the early stage of low temperature dyeing for both acid dye and reactive dye, than the conventionally scoured wool.     

Closed-form expressions of the electrostatic potential close to a grid placed between two plates

The potential distribution between a grid and two plates is an electrostatic problem already solved for various applications such as MultiWire detectors used in Nuclear Physics, or electrostatic precipitators in Engineering. Since references and notations for this analytical solution are ancient and rather bewildering, the first part of this paper presents a revisit and a discussion of the formulations that assume a line charge on the wire. This is completed by establishing a ready-to use closed-form expression valid for the general configuration where the plates are not grounded. The second part is about the investigation of the line model accuracy close to the wires, using both analytical and numerical approaches. In the symmetric case where the grid is placed at equal distances between two grounded plates, it is shown that the error can be modelled using a quadrupole charge. For the asymmetric case, a larger discrepancy of the line model is brought to light, with an error featuring a dipole-like distribution. In order to cope with this small but not negligible error, a classical dipole model is implemented, leading to an accurate theoretical expression of the potential.     

等离子体表面梯度硅沉积对环氧树脂电气性能的影响

环氧树脂作为常见的绝缘材料,在高压直流电场作用下易在其表面积累电荷,发生电场畸变,导致材料绝缘性能下降,影响电力系统运行可靠性。为改善气固界面的电荷特性和绝缘性能,在大气压等离子体射流技术的基础上,对环氧树脂表面进行等离子体梯度硅沉积处理。对改性前后环氧树脂表面理化特性、表面电导率、表面电荷消散和沿面耐压特性进行了多参数测量。实验结果表明,梯度改性对材料表面的物理形貌和化学组分均有明显影响,不同区域的电导率实现了梯度分布,加快了表面电荷消散速度,表面陷阱能级变浅;梯度改性后的样品沿面闪络电压提升幅度可达30.16%。通过等离子体表面梯度硅沉积处理能够改善环氧树脂表面电气性能,在高压直流设备的绝缘设计方面具有广阔的应用前景。     

The preparation and antibacterial effects of dopa-cotton/AgNPs

Silver nanoparticles (AgNPs) have been known to have powerful antibacterial activity. In this paper, in situ generation of AgNPs on the surface of dopamine modified cotton fabrics (dopa-cotton/AgNPs) in aqueous solution under room temperature is presented. X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM) were used to analyze the surface chemical composition and the morphology of the modified cotton fabrics, respectively. The results indicated that the surface of cotton fabrics was successfully coated with polydopamine and AgNPs. The cotton fabrics with AgNPs showed durable antibacterial activity.     

Excimer laser irradiation of synthetic fibres as a new process for the surface modification of textiles — a review

A characteristic modification of the surface topography of highly absorbing and orientated synthetic fibres was found after irradiation with several excimer laser pulses. This basic effect has the potential to affect the technical properties of the fibre, e.g. particle and coating adhesion or wetting properties, as a new physical treatment of textiles in contrast to the common addition of chemical agents or wet-chemical preprocessing.An overview is given of the dependence of the properties of the surfaces generated on laser parameters and material constants. Experimental observations are compared to the basic understanding of laser-polymer interactions and a thermomechanical model is reported which has been published recently and interprets the experimentally observed surface modification as the generation of dissipative structures.Examples of textile applications and possible concepts of industrial irradiation procedures for yarns and moving fabrics are discussed. A pilot irradiation plant has been installed recently, and the basic layout as well as first experiences are reported.     

A study of the metal-ionic conductor interface capacitances. II. Capacitance versus surface potential

Using the experimental method described in the preceding paper to determine the interface capacitances, the influence of surface potential value on these capacitances is analysed on thin film samples elaborated with gold as electrodes and lead fluoride as ionic conductor. The experimental capacitance-surface potential curve is compared to the theoretical curve calculated from Poisson's equation and supposing a Boltzmann distribution of the ionic carriers. The results seem to show the presence of a saturation region obtained for negative values of the surface potential, and corresponding to a strong accumulation of fluorine vacancies.     

Forced corona method for the evaluation of fabrics with conductive fibres

Modern fabrics for protective clothing, used in environment where the level of static charge must be controlled, are composites where a grid or stripes of conductive fibres are present inside a matrix of highly resistive base fabric. In protective clothing, where the conductive fabric elements are not effectively grounded, corona discharge is the major limiting mechanism for fabric charging. In this paper, corona discharge of electrostatic discharge protective fabrics has been studied. A new experimental method, forced corona, was developed for the measurement of corona onset and offset potentials as well as corona current. According to results, the residual level of fabric surface potential after corona discharge was the lowest in fabrics containing core conductive fibres. The behaviour is because of the small dimensions and sharp edges of the core conductive fibres.     

天器背面接地介质材料等离子体充电研究

处于等离子体环境中的航天器的介质材料受到带电粒子的作用,表面将产生电位。对背面接地的介质材料,上表面将与接地背面形成电势差。当电势差达到一定阈值时将产生放电,表面充电电位对充放电效应影响至关重要。综合考虑等离子体中粒子的质量、温度及密度,介质材料的二次电子效应,体电流泄漏以及介质材料的运行速度等因素,基于气体动理论,利用粒子的麦克斯韦速度分布函数理论推导得出等离子体环境中背面接地介质材料表面充电电位一般表达式。讨论了地球同步轨道环境下,表面电位与等离子体环境及材料表面电阻等各个参数的关系,总结出等离子环境背面接地介质材料表面充电规律,为航天器介质材料静电防护设计提供一定的理论基础。     

Projective approximation of the stochastic model of collective motion of minority charge carriers generated by a broad electron beam in semiconducting material

The method of approximating the statistical characteristics (expectation and autocorrelation function) of the depth distribution of minority charge carriers (MCCs) generated by a broad electron beam in the homogeneous semiconducting material is described. This method developed for analyzing the model of collective motion of MCCs is based on the projective approach and the matrix operator theory. It is assumed that the electrophysical parameters (lifetime, diffusion coefficient, and surface recombination rate of MCCs) of a material are random quantities and obey the truncated normal distribution law. The influence of the variance of these parameters on the MCC distribution over depth is estimated. The potential of the method is illustrated by solving the problem of determining the statistical characteristics of the MCC distribution when MCCs are produced by a broad electron beam of moderate energy.