Fabrication and characterization of Zr and Co co-doped LiMn2O4 nanowires using sol–gel–AAO template process

The Zr and Co co-doped LiMn₂O₄ nanowires are fabricated successfully by using sol–gel process with porous anodic aluminum oxide (AAO) as the template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization show that the synthesized LiZr _x Co _y Mn_(2-x-y)O₄ nanowires are uniformly distributed, high-ordered, and parallel to each other, and few microscopic defects are found. Selected area electron diffraction (SAED) pattern, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) investigations jointly demonstrate that the synthesized nanowires have a similar single spinel structure of LiMn₂O₄ crystal though Zr and Co are doped. Since the LiZr _x Co _y Mn_(2-x-y)O₄ nanowires can be mass-produced by using this method, it is expected to find promising application as a new cathode material in lithium ion battery.     

Correlation between electrochemical reactions with bare surfaces and corrosion fatigue crack growth in steels

The results of this preliminary correlation demonstrate the relationship between electrochemical reactions with bare metal surfaces and CF crack growth for steels in aqueous environments, and is very encouraging. These findings provide further support for the hypothesis of surface/electrochemical react control, and indicate the effectiveness of the in-situ fracture technique in providing unambiguous measurements of bare-surface reaction kinetics. For quantitative modeling, efforts will be needed to provide measurements of current and charge densities, and to address the issue of actual surface areas of cracks. Additional research is in progress and will be reported.     

The progressive wear of tubes: The volumes of the intersections of cylinders with each other and with flats

It is shown that cylinders can wear against each other or against flats in only a very few ways, each of which can be defined geometrically. For each geometry the volume of any intersection varies with a few easily measured dimensions. When dealing with a wear scar on a tube it is relatively easy to relate the volume already lost as a fraction of the volume that must be removed before any particular depth is reached. The results are presented graphically so that calculations can be reduced to a minimum and the results made as widely applicable as possible.The methods developed here have already been employed to predict the lifetimes of irreplaceable tubes showing wear scars. Amongst other possible uses of these methods, one discussed in this paper is a better way of calculating specific wear rates in wear testing using crossed cylinder geometries.     

The Dependence of Energy Dissipation on the Elastic Energy Density of Friction Pairs in Hard Coating Films

The influence of different pairs on the energy dissipation of a given hard coating during fretting has been discussed. Based on the view of the competition between the elastic and plastic deformations in a fretting experiment, it suggests that the energy dissipation rate is proportional to the elastic energy density of pairs. This trend is in agreement with the reported experimental data. For comparison, hardness of pairs is used as the index to relate the antiwear properties of a DLC film against different pairs. It is obvious that the elastic energy density of pairs is more appropriate to predict the antiwear properties of the DLC film against different pairs.     

The synthesis of novel fluorine-containing random polymer and application in modification of solid surfaces

The novel fluorine-containing random polymers, poly (2, 3, 4, 5, 6-pentafluorostyrene)-r-poly (4-vinyl benzocyclobutene) random copolymer was synthesized, which can effectively decrease the surface energy and provide a good corrosion protection for some metals. Additionally, textured silicon was fabricated by an optically assisted electrochemical etching process to study the effect of the random copolymer modification on the binary geometric structures of the solid surface. After modification the superhydrophobic property can easily be obtained, which show long-term stability and good superhydrophobicity in corrosive solutions over a wide pH range, including acidic and basic solutions.     

Improvement of oxide layer stability by use of chemical surface attack

A new method is proposed to improve the adhesion and temperature cycling stability of oxide layers on nickel-base structural alloys. In contrast with other approaches in which reactive metals, rare earth elements or dispersions of stable oxides were added, an active surface modification technique is applied in this work. An aluminium dipping-removal procedure is used which results in a smoothing of the surface, locally enriches the aluminium and creates nuclei for the development of oxide pegs during subsequent controlled oxidation.Deuterium permeation measurements have been used as a means of quantifying the damage state of the oxide scales which is a result of temperature cycling. The results demonstrate that chemical surface treatment leads to superior stability of the oxide scales. This is attributed mainly to the occurrence of oxide pegs which could be identified after metallographic preparation and examination.     

Superior Micro‐Supercapacitors Based on Graphene Quantum Dots

Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric micro‐supercapacitor is prepared using a simple electro‐deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as‐made GQDs micro‐supercapacitor has superior rate capability up to 1000 V s^?1, excellent power response with very short relaxation time constant (τ₀ = 103.6 μs in aqueous electrolyte and τ₀ = 53.8 μs in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO₂ asymmetric supercapacitor is also built using MnO₂ nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specific capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro‐supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.     

激光重熔对NiCrBSi等离子喷涂层显微结构和性能的影响

1Crl8Ni9Ti不锈钢表面的NiCrBSi等离子喷涂层存在孔洞及与基体结合差等缺陷,为此进行了激光重熔处理.采用扫描电镜和显微硬度压痕仪分别对涂层的显微结构和力学性能进行了对比研究,采用SRV试验机评价了涂层激光重熔前后的滑动摩擦磨损性能,研究了激光重熔对NiCrBSi等离子喷涂层结构和性能的影响.结果表明:经过激...     

油溶性离子液体作为镍基合金润滑添加剂的摩擦学性能研究

目的 合成一种无卤素油溶性离子液体润滑添加剂(P88816-Phosphate,以下简称PP),提高PAO 40作为硬质合金/镍基合金Inconel 690润滑剂的摩擦学性能。方法 以PP为添加剂,在PAO 40基础上配制质量分数为0.5%、1%、2%的润滑剂,与PAO 40进行对比。采用同步热分析仪分析其热稳定性,采用SRV-IV微动摩擦磨损试验机、MicroXAM-800非接触三维表面轮廓仪考察该离子液体减摩抗磨添加剂的摩擦学性能。结果 在50 ℃条件下,PP可以明显地提高PAO 40的减摩抗磨性能。1% PP的效果最为明显,摩擦因数降低了约22%,磨损体积减小了约48%。150 ℃条件下,0.5% PP的摩擦因数最低,而且磨损体积也是最小。结论 PP中活性元素P与金属基底发生摩擦化学反应,生成了摩擦化学反应膜。油溶性离子液体在镍基合金表面形成的润滑膜结构,可以揭示油溶性离子液体在减少金属摩擦和磨损方面的作用机制。PP有望为镍基合金提供更好的润滑保护,减少摩擦和磨损,延长设备的使用寿命,提高工业生产效率。