Durable transparent carbon nanotube films for flexible device components

This paper describes a durable carbon nanotube (CNT) film for flexible devices and its mechanical properties. Films as thin as 10 nm thick have properties approaching those of existing electrodes based on indium tin oxide (ITO) but with significantly improved mechanical properties. In uniaxial tension, strains as high as 25% are required for permanent damage and at lower strains resistance changes are slight and consistent with elastic deformation of the individual CNTs. A simple model confirms that changes in electrical resistance are described by a Poisson's ratio of 0.22. These films are also durable to cyclic loading, and even at peak strains of 10% no significant damage occurs after 250 cycles. The scratch resistance is also high as measured by nanoscratch, and for a 50 μm tip a load of 140 mN is required to cause initial failure. This is more than 5 times higher than is required to cause cracking in ITO. The robustness of the transparent conductive coating leads to significant improvement in device performance. In touch screen devices fabricated using CNT no failure occurs after a million actuations while for devices based on ITO electrodes 400,000 cycles are needed to cause failure.These durable electrodes hold the key to developing robust, large-area, lightweight, optoelectronic devices such as lighting, displays, electronic-paper, and printable solar cells. Such devices could hold the key to producing inexpensive green energy, providing reliable solid-state lighting, and significantly reducing our dependence on paper.     

高压换热器U形管管口开裂分析

对高压换热器U型管泄漏进行了化学成分分析、力学性能测试、显微组织和断口的宏微观分析。检验结果显示，换热管材料的化学成分和力学性能符合相关标准的要求，显微组织正常；换热器管口开裂为连多硫酸应力腐蚀开裂。     

宝钢冷轧1550电镀锌机组导电辊失效分析

宝钢1550电镀锌机组导电辊表面筒体使用的是哈氏合金材料。在长期使用过程中哈氏合金的焊缝腐蚀和开裂,是导电辊最大的问题。因此,本文主要对采用填丝TIG焊的导电辊哈氏合金筒体的失效进行了分析,揭示了其产生应力腐蚀开裂并最终导致失效的原因,为采取相应的改进措施,提高导电辊焊缝的抗蚀性提供理论依据。     

Flexible organic light-emitting diodes with a polymeric nanocomposite anode

Flexible organic light-emitting diodes (FOLEDs) are facing mechanical issues arising from failure of the indium-tin oxide (ITO) films fabricated on flexible substrates. Polymeric nanocomposite anodes were fabricated by including single-wall carbon nanotubes (SWCNTs) in aqueous poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The conductivity, transmittance and flexibility of the polymeric nanocomposite anode were characterized. The polymeric nanocomposite anodes fabricated on a poly(ethylene terephthalate) (PET) substrate exhibited superior bending properties to ITO anodes on PET. The FOLEDs fabricated on the polymeric nanocomposite anodes had a low turn-on voltage and higher luminous intensity than those fabricated on ITO/PET anodes. This flexible nanocomposite polymeric anode is a very promising for fully FOLEDs and other optoelectronics.     

A study on axial cracking failure of drill pipe body

Frequently happening drill pipe failure accidents in oil and gas wells not only affect drilling speed, but cause enormous economic losses and many safety issues. Most of these accidents are transverse cracking of drill pipe body and pin thread or axial cracking of box thread. Based on the axial cracking failures of drill pipe body in an ultra-deep well in China, this paper give a systematic analysis of axial cracking failure in consideration of service condition, material quality and stress corrosion mechanism. Measurement and inspection are performed on macroscopic and microscopic morphology of crack surface, corrosion products and circumferential residual stress. Then stress corrosion cracking experiments against hydrogen sulfide is conducted. Finally, the critical stress value for sulfide stress corrosion cracking of the drill pipe material is obtained, and the mechanisms of axial cracking failure and corresponding preventive measures are proposed.     

Stress corrosion cracking of a 60 MW steam turbine rotor

The paper presents a root cause analysis of a steam turbine rotor blade groove cracking. The scope of analyses included material testing and mechanical integrity calculations. In scope of material testing, fracture microstructure was assessed and basic mechanical property characteristics of the rotor discs were determined. In scope of integrity analyses, the stress fields in the blade grooves were calculated and the possibility of cracking due to different mechanisms was assessed. Both calculations and material tests confirmed the stress corrosion cracking to be the root cause of the rotor failure. This was a basis for proposing the rotor discs repair by overlay welding with a lower strength material and modifications to the groove geometry.     

Interface Stress-Induced Degradation of the Performance of Electrically Conductive Adhesives

Electrically conductive adhesives are of increasing importance as a powerful alternative to eutectic bonding. In the use of electrically conductive adhesives in soldering applications, a lack of conductivity of the adhesive bond between surface mounted devices (SMD) and the printed circuit board was frequently observed. This lack of conductivity caused failure of the unit because of an unacceptable series resistivity in the circuit. A failure analysis proved that the resistance of the contact between the adhesive and device depends on the stress situation in the bonded interface induced by the shrinkage of the adhesive during curing. Under stress, the formation of a resin segregation layer of low conductivity results. The outer shape of the electrical component as well as the SMD assembly process has strong influence on the electrical performance.     

A transparent and flexible organic bistable memory device using parylene with embedded gold nanoparticles

In this work, we demonstrate the fabrication of a transparent and flexible memory device in the simple structure of metal/dielectric/metal (MIM). Here, the MIM structure consists of gold electrode/200 nm Parylene-C/20 nm gold nanoparticles/100 nm Parylene-C/indium-tin-oxide (ITO) coated polyethylene terephthalate (PET). The use of parylene as the dielectric layer is important to ensure that there is no thermal stress induced on the flexible ITO/PET substrate compare to other reported works using various organic dielectrics that require high temperature curing. In addition, parylene deposition does not disturb the drop-casted gold nanoparticles. Hence, the use of parylene will be the right step forward in the fabrication of mechanically flexible and optically transparent devices. Current versus voltage (I–V) plot shows the presence of hysteresis suggesting the charge storage capability as a memory device. In the I–V plot, three distinct regions based on the slope have been identified and the transport mechanisms are discussed and explained. The fabricated device shows similar behavior as write-once-read-many memory device and can be programmed with either positive or negative bias voltage. However, the memory device shows unstable current state when being bent under different curvature diameters.     

Embedded Nickel-Mesh Transparent Electrodes for Highly Efficient and Mechanically Stable Flexible Perovskite Photovoltaics: Toward a Portable Mobile Energy Source

The rapid development of Internet of Things mobile terminals has accelerated the market's demand for portable mobile power supplies and flexible wearable devices. Here, an embedded metal-mesh transparent conductive electrode (TCE) is prepared on poly(ethylene terephthalate) (PET) using a novel selective electrodeposition process combined with inverted film-processing methods. This embedded nickel (Ni)-mesh flexible TCE shows excellent photoelectric performance (sheet resistance of ≈0.2–0.5 Ω sq⁻¹ at high transmittance of ≈85–87%) and mechanical durability. The PET/Ni-mesh/polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS PH1000) hybrid electrode is used as a transparent electrode for perovskite solar cells (PSCs), which exhibit excellent electric properties and remarkable environmental and mechanical stability. A power conversion efficiency of 17.3% is obtained, which is the highest efficiency for a PSC based on flexible transparent metal electrodes to date. For perovskite crystals that require harsh growth conditions, their mechanical stability and environmental stability on flexible transparent embedded metal substrates are studied and improved. The resulting flexible device retains 76% of the original efficiency after 2000 bending cycles. The results of this work provide a step improvement in flexible PSCs.     

Highly Efficient (>10%) Flexible Organic Solar Cells on PEDOT‐Free and ITO‐Free Transparent Electrodes

A novel approach to fabricate flexible organic solar cells is proposed without indium tin oxide (ITO) and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using junction‐free metal nanonetworks (NNs) as transparent electrodes. The metal NNs are monolithically etched using nanoscale shadow masks, and they exhibit excellent optoelectronic performance. Furthermore, the optoelectrical properties of the NNs can be controlled by both the initial metal layer thickness and NN density. Hence, with an extremely thin silver layer, the appropriate density control of the networks can lead to high transmittance and low sheet resistance. Such NNs can be utilized for thin‐film devices without planarization by conductive materials such as PEDOT:PSS. A highly efficient flexible organic solar cell with a power conversion efficiency (PCE) of 10.6% and high device yield (93.8%) is fabricated on PEDOT‐free and ITO‐free transparent electrodes. Furthermore, the flexible solar cell retains 94.3% of the initial PCE even after 3000 bending stress tests (strain: 3.13%).     

塑料基TiO2电致变色薄膜制备及性能研究

采用溶胶-凝胶法分别在镀有ITO透明电极的玻璃和塑料基体上制备了TiO2电致变色薄膜,对比研究了不同基体上溶胶的成膜性及薄膜的电致变色性能.结果表明:在相对湿度低于15%的环境中,采用0.4mol/L的溶胶可以通过多次提拉制得表面光洁的较厚透明TiO2薄膜;随热处理温度的升高,薄膜的电色可逆性变好,循环寿命变大,但离子储存能力下降;塑料基TiO2薄膜与相同条件下制备的玻璃基薄膜具有相似的性能,呈现出较弱的阴极电致变色效应和较强的Li 储存能力,有望用作柔性电致变色器件的对电极.     

A map of competing buckling-driven failure modes of substrate-supported thin brittle films

Our in situ experiments of polyimide-supported thin indium tin oxide (ITO) films reveal buckling-driven film cracking in some samples and buckling-driven interfacial delamination in other samples. Although studies of individual buckling-driven failure mode exist, it still remains unclear what governs the competition between these two different failure modes in a given film/substrate structure. Through theoretical analysis and numerical simulations, we delineate a map of competing buckling-driven failure modes of substrate-supported thin brittle films in the parameter space of interfacial adhesion and interfacial imperfection size. Such a map can offer insight on the mechanical durability of functional thin films. For example, interestingly, we show that strongly bonded thin brittle films are more prone to buckling-driven cracking, a more detrimental failure mode for thin brittle ITO transparent conductors widely used in displays and flexible electronics.     

Cracking analysis on joint lug of aluminum alloy framework of an airplane

An aluminum alloy joint lug of the framework of an airplane was found to have a crack near the bolt hole after serving for a period. To find out the failure mode and cause, macro and micro observation, microstructure examination, EDS analysis, chemical composition analysis and dimensional check were carried out. The results show that the failure mode of the joint lug is stress corrosion cracking under the co-effect of tensile stress and corrosive environment. The cracking of the surface anodic oxidation film near the bolt hole and the exposure of part of the bolt hole inner surface to air are the main causes for the stress corrosion cracking. In addition, the outer diameter of the steel sleeve inside the bolt hole exceeded the design requirement, which resulted in greater tensile stress near the bolt hole and promoted the stress corrosion cracking. The manufacturing procedure should be adjusted to avoid the cracking of anodic oxidation film, the uncovered part of the inner surface of the bolt hole should be covered, and the outer diameter of the steel inside the bolt hole should be controlled properly to meet the design requirement, so that stress corrosion cracking near the bolt hole can be avoided.     

Frequent Failures of Motor Shaft in Seawater Desalination Plant: Some Case Studies

The failure of a shaft from a motor in a pump or a compressor has been a phenomenon of common occurrence in seawater desalination plants. The origin of the problem in majority of cases is either the inability of the material to withstand the level of dynamic stresses to which shaft is subjected during operation and/or inadequacy of the design. The shortcoming in the design may be responsible for initiating localized corrosion which ultimately leads to failure of the component. The mode of failure of the shaft could be stress-related failure such as stress corrosion cracking, mechanical fatigue or corrosion fatigue, and/or localized corrosion such as crevice corrosion. This paper describes some recent case studies related to shaft failures in seawater desalination plants. The case studies include shearing of a shaft in brine recycle pump in which a combination of environment, design, and stresses played important role in failure. In another case, ingress of chloride inside the key slot was the main cause of the problem. The failure in a high pressure seawater pump in a SWRO plant occurred due to cracking in the middle of the shaft.     

Large scale, highly conductive and patterned transparent films of silver nanowires on arbitrary substrates and their application in touch screens

The application of silver nanowire films as transparent conductive electrodes has shown promising results recently. In this paper, we demonstrate the application of a simple spray coating technique to obtain large scale, highly uniform and conductive silver nanowire films on arbitrary substrates. We also integrated a polydimethylsiloxane (PDMS)-assisted contact transfer technique with spray coating, which allowed us to obtain large scale high quality patterned films of silver nanowires. The transparency and conductivity of the films was controlled by the volume of the dispersion used in spraying and the substrate area. We note that the optoelectrical property, σ(DC)/σ(Op), for various films fabricated was in the range 75-350, which is extremely high for transparent thin film compared to other candidate alternatives to doped metal oxide film. Using this method, we obtain silver nanowire films on a flexible polyethylene terephthalate (PET) substrate with a transparency of 85% and sheet resistance of 33 Ω/sq, which is comparable to that of tin-doped indium oxide (ITO) on flexible substrates. In-depth analysis of the film shows a high performance using another commonly used figure-of-merit, Φ(TE). Also, Ag nanowire film/PET shows good mechanical flexibility and the application of such a conductive silver nanowire film as an electrode in a touch panel has been demonstrated.     

The effectiveness of stress relief features in austenitic drillcollar connections

Standards designs for stress relief features and unmodified joints in non-magnetic (austenitic) drillcollar connections are investigated using finite element stress analysis. An NC-61 connection containing API pin and box stress relief grooves and box boreback features are compared. In addition to the recognized problem of fatigue failure from critically loaded threads, instances of stress corrosion cracking in pin bores have focused attention on this region and the effect which the presence of a pin stress relief groove has on the stresses there. The results of the analyses confirm the failure sites noted in service, and predict that the pin stress relief groove gives considerable benefit in terms of reducing the pin last engaged thread peak stress (fluctuations in which can cause fatigue), but causes an unexpected increase in the maximum pin bore axial stress (which can drive stress corrosion cracking).     

Mechanical properties of ZnO thin films deposited on polyester substrates used in flexible device applications

ZnO is growing in importance as a functional film in flexible devices because of the wide range of electrical properties that can be achieved through appropriate doping and the relative abundance of Zn. We have deposited ZnO films with various thicknesses by sputtering on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) flexible substrates and measured their mechanical properties using compression and scratch tests coupled with in-situ optical microscopy. The cracking of ZnO, during compression, is thickness dependent and at lower thicknesses the films sputtered on PEN exhibit the highest crack onset strains, around 2%. During scratch testing, two major scratch failure mechanisms are observed, analyzed and discussed. It is also found that scratch resistance of ZnO is thickness dependent for both PET and PEN. At high scratch loads a secondary failure mechanism due to impregnation of film debris into the polymer substrates is observed.     

酒精蒸发釜爆炸分析

一种用于生产醋酸和醋酸酐的酒精蒸发Fu在服役中发生爆炸。对蒸发Fu的爆炸现场、Fu的内外表面、焊缝、断口、显微组织及力学性能进行了检验分析。结果表明,该蒸发Fu的失效为典型的应力腐蚀破坏。而蒸发Fu工作介质中较高氯元素的存在是形成应力腐蚀的特定介质条件;焊接工艺不当是造成Fu产生应力腐蚀,并快速失效的主要原因。     

Comparison of ZnO:Al,ITO and carbon nanotube transparent conductive layers in flexible solar cells applications

In the paper the mechanical, optical and electrical parameters of transparent conductive layers (TCLs) made of carbon nanotubes and metal conductive oxides are explored and compared. All investigated materials are deposited on transparent, flexible polymer foils used for solar cell applications. Obtained results are compared with available parameters of rigid transparent conductive oxides (TCOs) as well as literature reports about Indium–Tin Oxide (ITO) on flexible substrates. Presented paper is a report from the preliminary stage of a new flexible solar cell construction.     

Das Verhalten rostfreier Stahlgußlegierungen unter gleichzeitiger mechanischer und korrosiver Belastung

Behaviour of stainless cast alloys under combined mechanical and corrosive attack In media with 3000 mg B/1 (as boric acid, H₃BO₃) and varying chloride contents down to 1 mg Cl^?/1 13%-Cr-steels show pitting. Under constant load cracks appear simultaneously. As can be expected, 17%-Cr-steels are more resistant and duplex ferritic austenitic steels exhibit no corrosion cracking in 3% NaCl-solution even after 10 000 hrs. Generally, corrosion resistance improves with increasing contents of ferrite forming elements. Corrosion cracks are interpreted in termes of anodic stress corrosion cracking. Notch impact bending tests with hydrogen charged specimens show that deformability is reduced.