Effect of the electrothermopolarization on the electret properties and the charge state of polyethylene nanocomposites with Cr and PbCrO4 additives

The results of studying the effect of electrothermopolarization on the electret properties and charge state of PE + Cr and PE + PbCrO₄ composites are described. It is shown that an increase in the polarization field intensity to E _p = 5 × 10⁶ V/m leads to an improvement in the polarization processes in the composites; at E _p > 5 × 10⁶ V/m, the space charge concentration apparently increases, which results in the deterioration of the electret properties. The observed effect can be attributed to the repeated electron capture by deeper traps owing to the internal electric field. In addition, the intensity of the TSD peaks and therefore the number of stabilized charges for the composites polarized at high intensities are higher than for the samples polarized at low intensities.     

The effect of gamma irradiation on electret properties of polyethylene

The paper describes the electret properties of low-density polyethylene and the effect of gamma irradiation on them. It is shown that the thicker polyethylene film the more stable the surface potential, electric field strength, and effective surface charge density values. The negative impact of gamma-radiation on the electret properties of the films that is caused by the release of the injected charge carriers from the traps due to clearing the energy barrier thanks to radiation energy is revealed. Irradiated polyethylene films, in turn, are polarized badly in a corona discharge because of the oxygen-containing groups on the surface formed during gamma-irradiation that act as charge carrier traps with low capture energy. It was found that the formation of cross bonds in the bulk of the polymer and carbonyl groups on its surface slightly raises the degree of crystallinity and the specific volume resistivity and decreases the specific surface resistivity.     

Study on fracture characteristic of welded high-density polyethylene pipe

Crack opening displacement (COD) was applied to characterize the fiacture initiation of the tough high density polyethylene. Normal single side notched three-point bend specimens and silica rubber replica techniques were used to study the characteristic COD of high-density polyethylene pipe and its butt-fusion joints including the weld fusion zone and heat affected zone at different temperature from - 78℃ to 20℃. Testing results show that the characteristic COD appears to depend on the structural features that are determined by welding process and the testing temperature. As the temperature is lowered, the characteristic COD of all zones studied decreases. Because the welding process significantly changes some structural feature of the material, characteristic COD of the weld fusion zone is the smallest one among those of the three zones. The results can be used for the engineering design and failure analysis Of HDPE pipe.     

The characterization of high-density polyethylene/organoclay nanocomposites

Polymeric nanocomposites, which are hybrids of polymers and modified inorganic clay with organic surfactants, are extremely attractive in both science and industry. These materials present improvements in such polymer properties as modulus, heat capacity, thermal stability, flame resistance, and so on. Research has been conducted in recent decades to obtain high-quality materials that can be used in applications like food packing, car components, and combustible cells. Polymeric nanocomposites present many advantages in relation to composites due to the quantity of filler added to the polymer and also to the improved properties. In a composite, the quantity of filler must be as high as possible (i.e., over 30%). In the polymeric nanocomposite the quantity of filler varies from 1% to 5% because of the nanosize of the particles. These nanoparticles often have a large surface area that results in improved polymer-matrix properties.     

基于局部法高密度聚乙烯管道材料的断裂行为

作者主要对低温下高密度聚乙烯(HDPE)管道材料的断裂参量进行了测试，并对三点弯试样进行了有限元数值计算，分析了低温下具有不同裂纹尺寸的三点弯试样裂纹尖端应力应变场。利用试验和有限元计算结果，基于局部法对HDPE材料的抗开裂行为进行了研究。结果表明，采用局部法可对具有不同原始裂纹长度三点弯试样之间的断裂行为进行相互预测，并且预测结果与试验结果吻合良好。一方面验证了表征材料脆性断裂特征的参量m和σu与初始裂纹长度无关，为一材料常数；另一方面也表明局部法能有效地描述HDPE材料的脆性断裂行为。对于HI)PE管道材料，威布尔应力可以作为有效的断裂控制参量。     

高密度聚乙烯管道电熔焊接头基本力学行为

焊接技术是工程塑料管道的主要连接方法，直接影响高密度工程塑料管道的安全应用。研究焊接接头在不同温度下的基本力学行为，具有重要的意义。有鉴与此，采用文中设计的试样形式，对不同温度下高密度聚乙烯燃气管道电熔焊接头的基本力学行为进行了研究。结果表明，常温下，焊缝结合面所能承受的力高于管材和套筒材料；为了得到该接头的剪切强度，必须采用在接头电熔套筒侧开人工槽的方式，来缩短有效结合面的长度；随着温度的降低，要得到接头在不同温度下的剪切强度所对应的焊缝结合面的有效长度缩短，剪切强度呈上升的趋势；随着温度的降低，高密度聚乙烯材料对尖锐缺口的敏感性急剧上升。     

高密度聚乙烯燃气管材及其对接接头力学行为的研究

对高密度聚乙烯管材及其对接接头在不同温度下的基本力学行为进行了测试。试验结果发现随着试验温度的降低，HDPE以及对接接头的强度逐渐提高，最大断裂伸长率(应变)则逐渐下降。而且其断裂形式也有相应的变化，并且对于整个管件而言，对接接头及其附近区域仍可能是易发生断裂的薄弱环节。该结果对高密度聚乙烯管材进行其它方面的深入研究具有深远的意义。     

Statistical modeling of crack growth and reliability assessment of high-density polyethylene

In this work, a statistical evaluation of the crack-growth process in high-density polyethylene (HDPE) was carried out. The specimens were compression molded from virgin, molding-grade HDPE. Edgenotched specimens for replicate fatigue testing were prepared from compression-molded sheets. Fatigue test results were then analyzed, and it is shown that if the crack-growth process can be characterized as a random process following a power-law-type behavior, then the time to reach a critical crack length will be distributed according to an inverted lognormal model.     

The response of carbon black filled high-density polyethylene to microwave processing

Microwave processing has numerous advantages over traditional methods of heating. Most thermoplastics, such as high-density polyethylene (HDPE), are nearly transparent to electromagnetic radiation. Carbon black (CB) filled HDPE was prepared in order to improve the microwave heatability of HDPE. The heating response of HDPE/CB composites to microwave exposure and the effects of this exposure on the mechanical and physical properties of material were investigated. The addition of CB particles improved the microwave heatability of HDPE, and microwave heatability of composites varied with CB content, in which an average temperatures of up to 139 °C above ambient were measured for 20 wt% CB composites after a exposure duration of 150 s. Microwave exposure had no obvious effect on rheological property of HDPE/CB composites. Mechanical properties of HDPE/CB composites are relatively improved after microwave exposure. Scanning electronic micrograph (SEM) analysis presented that the interface defects between CB particles and HDPE matrix are significantly reduced and a better combination was found after microwave exposure. Differential scanning calorimetry (DSC) analysis showed that the melt point of HDPE with CB shifted toward high temperature and degree of crystallinity increased after microwave exposure.     

Diffusion barrier performance of novel RuTiN material for high-density volatile memory capacitor

The electrical properties for the new RuTiN barrier material were investigated and compared with those for the TiN barrier. In case of the TiN barrier in the sputtered-(Ba,Sr)TiO₃ simple stack-type structure, the TiN film was partially oxidized in the as-deposited state and was almost completely oxidized at 550 °C, leading to a degradation of the capacitance. In contrast, the new RuTiN barrier was not oxidized up to 600 °C, and exhibited an improved capacitance of >30 fF/cell, although the leakage current is very high (~10⁻⁹ A/cell) due to low work function (4.43 eV). Correspondingly, the diffusion barrier performance of new RuTiN film, as an oxygen diffusion barrier for high-density volatile capacitor, is better than that of the TiN barrier.     

Large-area and uniform surface modification of polymers by barrier discharge plasmas

A barrier discharge experimental setup for low-pressure and large-area (400 mm × 600 mm) surface modification of polymers is reported. The low-pressure barrier discharge plasma consists of pulsed and glow-like breakdowns with peak widths of several microseconds and leads to the uniform surface modification of polymers. In contrast, the filamentary discharges produced at atmospheric pressure cause surface damage and nonuniform treatment of polymers. This study indicates that barrier discharge plasmas generated in the small gas spacing at low discharge pressure result in efficient collisions between polymer surface and activated species, and an extremely low consumption of feed gas and discharge power.     

Plasma enhanced CVD of fluorocarbon films by low-pressure dielectric barrier discharge

Low-pressure dielectric barrier discharge (DBD) plasmas have been used to deposit polymerized fluorocarbon (FC) films on silicon substrates. The effects of discharge pressure and frequency of power supply on the film quality have been systematically investigated. The deposited films were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and static contact angle measurements. Experimental results show that FC films with a less crosslinked structure may be deposited at a relatively high pressure. Increasing the frequency of power supply leads to a significant increase in the deposition rate. All deposited FC films with a uniform microstructure show the hydrophobic property. Decreasing the frequency of power supply or increasing the deposition pressure results in the deposition of FC films with the extremely low surface roughness. The relationship between plasma parameters and the analyzed properties of deposited FC films is discussed.     

纳米氧化锆热障涂层组织结构和高温稳定性能分析

采用大气等离子喷涂技术制备了纳米氧化锆热障涂层.利用FESEM和XRD对纳米氧化锆热障涂层的微观组织和物相组成进行研究.微观组织分析结果表明,纳米氧化锆热障涂层展现出独特的微观复合结构,包括未熔纳米颗粒和柱状晶组织.物相分析结果表明,纳米氧化锆热障涂层主要由非平衡四方相组成.纳米氧化锆热障涂层高温稳定性能试验结果表明,涂层晶粒度随着服役温度和服役时间的增加而增加,但仍保持纳米结构;涂层物相组成不随服役环境的变化而变化.     

热障涂层的研究现状与发展趋势

热障涂层是一类高温防护涂层,由于其应用的广泛性,已成为近年来涂层研究领域的热点之一。对热障涂层国内外的研究进展进行了综述,重点阐述热障涂层成分的选择、热障涂层的结构设计、热障涂层的制备工艺、热障涂层的失效机理、寿命预测以及热障涂层的发展趋势。     

VNbMoTaWCo高熵合金氮化物扩散阻挡层的制备及其热稳定性

利用直流磁控溅射镀膜机设置不同氮气流量参数,制备VNbMoTaWCoN_x薄膜,氮气流量为20%时,在洁净的硅基底上沉积厚度约为15 nm的VNbMoTaWCoN₂₀高熵合金氮化物薄膜,并在其上面再溅镀一层厚度约为50 nm的Cu膜,最终形成Cu/VNbMoTaWCoN₂₀/Si 三层复合结构。采用四点探针电阻测试仪(FPP)、X射线衍射仪(XRD)、原子力显微镜(AFM)、场发射扫描电镜(SEM)对三层复合结构500 ℃退火前后的方块电阻、物相结构、粗糙度以及表面形貌进行了分析表征,研究了VNbMoTaWCoN₂₀高熵合金氮化物薄膜作为扩散阻挡层的热稳定性。研究结果表明,当氮气流量占比为20%时,VNbMoTaWCo₂₀高熵合金氮化物薄膜为非晶态,且出现了微量纳米晶;此氮气流量占比下制备的薄膜表面平整光滑、致密度最佳、粗糙度数值最小。Cu/VNbMoTaWCoN₂₀/Si三层复合结构进行500 ℃退火8 h后,Cu膜的方块电阻仍然维持在较低的数值,即0.065 Ω/sq,虽然Cu膜发生团聚,但是并未检测到高阻态Cu-Si化合物。VNbMoTaWCoN₂₀高熵合金氮化物薄膜作为扩散阻挡层在500 ℃温度下退火8 h后,表现出了优异的热稳定性。     

AlCrTaTiZrV高熵合金氮化物扩散阻挡层的制备及其热稳定性

为研究氮气含量的变化对AlCrTaTiZrV高熵合金薄膜性能的影响,检验在最佳氮气含量下厚度为15 nm的(AlCrTaTiZrV)N扩散阻挡层的热稳定性.采用直流磁控溅射设备在N型Si(111)基底上溅射不同氮气含量的高熵合金氮化物;选取最佳氮气含量为制备条件,在硅基底上沉积15 nm厚的AlCrTaTiZrVN10...     

放电能量对线切割加工表面质量的影响

在电火花线切割加工中,放电能量(电流的峰值和脉宽)在很大程度上影响被加工面的表面粗糙度,为了找出它们之间的规律,用有限元法对电火花线切割的加工蚀除进行了热分析,分析和实验结果表明,具有相同脉冲能量的放电电流,虽然表面粗糙度一样,但表面形貌不一样,在精加工时,更适合选用窄脉宽、高峰值的放电电流。     

Effect of high-density current electropulsing on corrosion cracking of titanium aluminide intermetallic

The effect of electropulsing on the corrosion cracking of titanium aluminide produced by self-propagating high-temperature synthesis has been investigated. The electropulsing treatment led to improved corrosion resistance in sodium fluoride solution and also eliminated corrosion cracking at the α₂/γ interface during corrosion in a solution of nitric and hydrofluoric acids. This behavior was attributed to thermal and athermal effects resulting from electropulsing and leading to the interaction of conduction electrons with the defect structure. The effect of magnetic field accompanying electropusling on depinning of dislocations also has been discussed. Support for this is provided on the basis of X-ray diffraction analysis and microhardness testing.     

Dielectric barrier discharge assisted chemical vapor deposition of boron nitride phosphide films on a quartz substrate

Boron nitride phosphide films were deposited on a quartz substrate by dielectric barrier discharge assisted chemical vapor deposition. From results of X-ray photoelectron and UV-Vis absorption spectral measurements, the chemical composition of the films may be defined as BN_1 − xP_x, where the mole number (x) is variable between 0.25-0.58, through modifying the PH₃ flow rate in the film deposition process, and the corresponding optical band gap may be modulated between 4.17-3.25 eV. From measurements of X-ray diffraction and high resolution transmission electron microscopy, an amorphous matrix embedded with a hexagonal crystalline phase of BNP with a crystal lattice spacing of 0.35 nm and a textured pattern is observed. The BN_1 − xP_x films are smooth, well-adhered to the quartz substrate, and display dark resistivities on the order of 10¹¹ Ω cm and ultraviolet light photo/dark conductivity ratios higher than 10³, with negligible sensitivity in the visible region, indicating a potential application in visible/blind UV detectors.