Experimental study on physical properties of nanoporous anodic aluminum oxide by proton implantation

Implantation is a promising method to control the surface characteristics by changing surface energy of target materials. Previously, polymer surfaces have been investigated for the change of their morphology and the corresponding contact angle after implantation. Furthermore, oxide thin films have been studied for how their surface properties are changed by implantation. However, nanoporous oxide materials have rarely explored for the effect of implantation. Here, we investigated the effects of proton implantation on morphological, mechanical, electrical, and surface properties of anodic aluminum oxide (AAO). We prepared nanoporous amorphous AAO films with different thicknesses (5 and 10 μm). Atomic force microscopy (AFM), contact angle (CA) measurements, two-probe electrical measurements, and nanoindentation were used to analyze the physical properties. By increasing fluences from 10¹⁵ to 10¹⁶ ions/cm², CA is significantly changed up to about 40°, but the other properties hardly changed.     

Effect of rare earths on mechanical and tribological properties of carbon fibers reinforced PTFE composite

The effect of a rare earth (RE) surface treatment on the mechanical and tribological properties of carbon fiber (CF) reinforced polytetrafluoroethylene (PTFE) composites was experimentally investigated. The tensile properties of the CF reinforced PTFE (CF/PTFE) composites treated with air oxidation and RE modifier were superior to those of untreated CF/PTFE composites, while RE treatment was most effective in promoting the tensile strength and strain at break of the CF/PTFE composite. The bending strength of the RE treated CF/PTFE composite was improved by about 16% compared with that of untreated composites, while 2% improvement was achieved by air oxidation. Under oil-lubricated conditions, RE treatment was more effective than air oxidation to reduce the friction coefficient and wear of PTFE composite. RE treatment effectively improved the interfacial adhesion between CF and PTFE. The strong interfacial coupling of the composite made CF not easy to detach from the PTFE matrix, and prevented the rubbing-off of PTFE, accordingly improved the friction and wear properties of the composite.     

Ion implantation and surface modification in tribology

Ion implantation is a vacuum process by which virtually any element can be injected into the surface regions of a solid target. Current interest in materials technology and recent developments in ion implantation machines have resulted in ion-induced surface property changes in a variety of different fields including tribology. Large changes in friction coefficient (up to ± 60%) have been recorded on steel surfaces implanted with such ions as Pb⁺ and Sn⁺. Implantation of boron, nitrogen and molybdenum reduces wear by more than a factor of 10, from measurements with a pin-and-disc machine. An outline is given of the scope and application of ion implantation and the results evaluated in the context of the testing methods used. Examples are given of some present and future applications of ion implantation to tribology.     

An experimental work on using conductive powder-filled polymer composite cast material as tool electrode in EDM

This paper introduces the composite tool electrodes made of electrical conductive powder-filled polyester resin matrix material, providing promise for the electrical discharge machining (EDM) process. The dendrite-shaped copper powder, graphite powder, and their mixture were used as conductive fillers. Six different types of composite electrodes, namely, plain copper-polyester, pressed copper-polyester, furnaced copper-polyester, plain copper-graphite-polyester, pressed copper-graphite-polyester, and furnaced copper-graphite-polyester were prepared. It is found experimentally that increasing v _f improved workpiece material removal rate, tool wear rate, relative wear, and electrical conductivity of electrodes. The pressed copper-polyester electrodes were found to be promising in the ED finishing of workpieces at low machining current settings. The practical applicability of the proposed composite electrodes in the industry was also illustrated.     

剧烈塑性变形制备高强度高导电纯铜的研究

研究了纯铜多道次反复镦压剧烈塑性变形后的组织、力学性能及导电性能。结果表明,通过反复镦压能在保持试样原始形状和尺寸的情况下在材料内部累积很大的应变,实现材料组织的超细化,退火纯铜经B路线15道次反复镦压变形后,晶粒细化至亚微米级。随镦压次数的增加,纯铜的硬度和抗拉强度明显提高,抗拉强度达到459.1MPa,伸长率明显下降,但仍在20%以上。纯铜的导电率随镦压次数的增加而下降,但15道次镦压后仍然保持在91.7%IACS,说明反复镦压剧烈塑性变形工艺可以制备出具有高强度和良好导电性的块体纯铜材料。     

Lightweight material for the speed reducer housing of a car chassis

Lightweight materials improve the fuel efficiency and carbon emissions of vehicles. The purpose of this study is to develop a light-weight, injectable, high-stiffness plastic composite material to replace aluminum in the housing of the speed reducer of a car chassis. The material was tested computationally and experimentally by analyzing the physical properties of specimens with different amounts of reinforcement in the base materials. POM, PA, PEI, PES, PPS and PPA were used as the base materials, while Glass fiber (GF) and Carbon fiber (CF) were used as reinforcement material. The computations were carried out using Moldflow insight software to simulate the injection molding process. The volumetric shrinkage and shear rate of the PA66+GF70 % specimen were 5.3 % and 2985.25 1/s, respectively. The mold material must withstand this shear rate. This sample had the most suitable properties, and the tensile strength, elongation, flexural strength, and thermal expansion coefficient were 312.15 MPa, 1.5 %, 329.2 MPa and 0.022 (10^-5/°C), respectively. As a result of this study, a patent was received for this lightweight material technology.     

Conductive composite of UHMWPE and CB as a dynamic contact analysis sensor

There has long been a need to experimentally measure the dynamic contact conditions of important engineering tribological systems, especially those with polymeric bearing surfaces that prove difficult to model. In order to experimentally quantify the dynamic contact conditions of geometrically complex polymeric bearing surfaces, a composite sensor material has been developed. In this study, qualitative morphological analysis of virgin ultrahigh molecular weight polyethylene (UHMWPE) and carbon black (CB) powders, as well as UHMWPE and CB powder mixtures of varying percentages was performed using field emission scanning electron microscopy (FESEM). Quantitative structure and friction analysis using atomic force microscopy (AFM) was performed on cryoultrasectioned block surfaces of compression-molded CB/UHMWPE composite. In addition, the mechanical properties of the composites were quantified using tensile testing, and the force dependence of the electrical properties was examined under dynamic compressive loading.     

Effect of rare earth solution on mechanical and tribological properties of carbon fiber reinforced thermoplastic polyimide composite

Rare earth solution (RES) surface modification and air-oxidation methods were used to improve the interfacial adhesion of the carbon fiber reinforced polyimide (CF/PI) composite. The mechanical and tribological properties of the PI composites reinforced by the carbon fibers treated with different surface modification methods were comparatively investigated. Results showed that both the strength parameters (tensile and flexural) of the CF/PI composites improved remarkably due to RES treatment along with enhancement in friction and wear performance.     

Microstructural evolution of Cu-1 at% Ti alloy aged in a hydrogen atmosphere and its relation with the electrical conductivity

Copper alloys with titanium additions between 1 and 6 at% Ti emerge currently as attractive conductive materials for electrical and electronic commercial products, since they exhibit superior mechanical and electrical properties. However, their electrical conductivity is reduced owing to the residual amount of Ti solutes in the Cu solid solution (Cu_ss) phase. Since Cu shows only poor reactivity with hydrogen (H), while Ti exhibits high affinity to it, we were inspired by the idea that hydrogenation of Cu–Ti alloys would influence their microstructure, resulting in a significant change of their properties. In this contribution, the influence of aging under a deuterium (D₂) atmosphere of Cu-1 at% Ti alloys on their microstructure is investigated to explore the effects on the electrical conductivity. The specimens were investigated by means of transmission electron microscopy (TEM), field ion microscopy (FIM), computer-aided field ion image tomography (cFIIT), and atom probe tomography (APT).     

A study on development of advanced environmental-resistant materials using metal ion processing

The development of the oxidation, wear and corrosion resistant materials that could be used in severe environmental conditions is needed. The elementary technologies for surface modification include ion implantation and/or thin film coating. Furthermore, in order to develop ion implantation technique to the specimens with three-dimensional shapes, plasma-based ion implantation (PBII) techniques were investigated. As a result, it was found that the ion implantation and/or thin film coating used in this study were/was effective for improving the properties of materials, which include implantations of various kinds of ions into TiAl alloy, TiN films formed on surface of base material and coatings in high-temperature steam. The techniques proposed in this study provide useful information for all of the material systems required to use at elevated temperature. For the practical applications, several results will be presented along with laboratory test results.     

Development of a universal serial bus interface circuit for ion beam current integrators

A universal serial bus (USB) interface circuit has been developed to enable easy interfacing of commercial as well as custom-built ion beam current integrators to personal computer (PC) based automated experimental setups. Built using the popular PIC16F877A reduced instruction set computer and a USB-universal asynchronous receiver-transmitter/first in, first out controller, DLP2232, this USB interface circuit virtually emulates the ion beam current integrators on a host PC and uses USB 2.0 protocol to implement high speed bidirectional data transfer. Using this interface, many tedious and labor intensive ion beam irradiation and characterization experiments can be redesigned into PC based automated ones with advantages of improved accuracy, rapidity, and ease of use and control. This interface circuit was successfully used in carrying out online in situ resistivity measurement of 70 keV O(+) ion irradiated tin thin films using four probe method. In situ electrical resistance measurement showed the formation of SnO(2) phase during ion implantation.     

Mechanical property behavior and aging mechanism of carbon-black-filled EPDM rubber reinforced by carbon nano-tubes subjected to electro-chemical and thermal degradation

Ethylene propylene diene monomer (EPDM) rubber filled with Carbon black (CB) has been mainly used for the rubber hose of a cooling radiator in the internal combustion engine system. Moreover, EPDM aging occurs because of electro-chemical and thermal stresses. In this study, Carbon nanotubes (CNTs) with 0, 2 and 4 parts per hundred grams of rubber (phr) were added to EPDM rubber filled with 75 phr CB to form CNT reinforced CB-filled EPDM rubber. Under conditions of 3 temperatures (60, 80 and 100 °C) and constant voltage (DC 12 V), 3 types of EPDM rubber (CB75, C2CB7 and C4CB75) were immersed in coolant water and aged for 7 days (168 h). This study investigated the effects of CB and CNT concentrations in EPDM rubbers on electro-chemical and thermal degradation behaviors and mechanical properties (tensile strength, elongation at the breaking point and IRHD hardness). A conductive mechanism was also proposed for the addition of CNT and CB.     

Effect of high-speed thermal treatment followed by ion-beam nitriding on physicomechanical properties of steel 40X

The effect of high-speed thermal treatment followed by ion-beam nitriding on the structure and physicomechanical properties of structural steel 40X is studied. The phase composition and structure of the steel and the modified layer after high-speed hardening and nitriding are determined. The effect of nitrogen ion implantation on the tribological behavior and impact strength of steel 40X is considered. The wear resistance of nitrogen-modified steel 40X increases approximately twofold compared to its initial state and damage work under applied load to the hardened surface increases by 40–50 J/cm².     

Enhancing electrical conductivity and electrical thermal characteristics of a PEDOT:PSS thin layer by using solvent treatment and adding Ag nanoparticle solution

A method of enhancing the electrical conductivity of 3,4-ethylenedioxythiophene:poly styrene sulfonate (PEDOT:PSS) by combining solvent treatment (adding high polar solvent: 5 wt% ethylene glycol) and adding a small amount of silver (Ag) nanoparticles in a solution was investigated. The main purpose of this was to apply a PEDOT:PSS conductive layer to micro-thermal devices driven by electricity and, for this, to reduce the layer thickness (for low stiffness) while maintaining necessary high electrical conductivity. Layers with thicknesses of less than about 10 μm were examined for electrical conductivity and temperature when electricity was applied. The solvent treated PEDOT:PSS had suitable electrical resistance to generate appropriate temperature properties. The added Ag nanoparticles reduced the electrical resistance by 30–70% over the measured thickness range. The electric conductivity applied with this method was 200–260 Ω⁻¹ cm⁻¹ for thicknesses of 1–2 μm (conductive area: 12 mm × 10 mm) and the generated temperature increase was 20–50 °C at applied voltages of 3–5 V. These characteristics are considered to be suitable to use the conductive layer as a heating element. In addition, the method we used scarcely degraded the transparency of the layer. Measurements of the conductive area in a layer with conductive atomic force microscope (AFM) indicated that the added Ag nanoparticles contributed to increasing the conductive areas and distributing them more uniformly.     

Synergetic effect of BN for the electrical conductivity of CNT/PAN composite fiber

Carbon nanotube (CNT) fillers in composite materials improve electrical conductivity, thermal stability, and mechanical properties. Boron nitride (BN) is an insulating material that is also thermally stable. Therefore, CNT and hexagonal boron nitride (hBN) fillers have been used to obtain composite materials’ high electrical conductivity. In this study, CNT-hBN/polyacrylonitrile (PAN) fibers were spun using simple wet-spinning and the effect of hBN on the electrical conductivity of the CNT-hBN/PAN composite was investigated. Contrary to predictions, as the content of the insulating material, BN, increased up to 15 wt%, the electrical resistance of the composite fiber decreased.

     

Friction and Wear Properties of Polyimide-Based Composites with a Multiscale Carbon Fiber-Carbon Nanotube Hybrid

A multiscale carbon fiber-carbon nanotube (CF-CNT) hybrid was fabricated via chemical method, and then the corresponding polyimide (PI) composites were prepared using hot pressing technique. The microstructure and chemical composition of the CF-CNT hybrid were characterized, and its enhancement mechanisms on the tribological properties of PI were investigated systematically. Results showed that the CF-CNT hybrid had many functional groups and increased roughness, which was good for ameliorating the interfacial combination between the CF and PI matrix, further indicating that the PI/CF-CNT composite possesses excellent friction and wear properties. The friction coefficient and wear rate of the PI/CF-CNT composite were 0.213 and 1.79 × 10^?6 mm³/Nm, i.e., a decrease of 22 and 72%, respectively, compared to pure PI. In particular, the friction coefficient and wear rate of the PI/CF-CNT composite decreased with increasing applied load or sliding rate, suggesting that PI/CF-CNT was an excellent self-lubricating material. This was closely related to the enhanced interfacial adhesion between CF and PI. More importantly, CNT onto a CF-CNT hybrid surface could stretch into the PI matrix, which had a reinforcing effect on the PI matrix and also, just like many fibrous roots around the main root of a tree, helped the CF not break under repeated stresses during the friction and wear process, even under high load or sliding rate.     

Microstructure and wear resistance of thermal sprayed steel coatings ion beam implanted with nitrogen

In the present study, the high-current-density nitrogen ion implantation technique is applied to enhance mechanical properties of thermal sprayed steel coatings. XRD measurements and optical microscopy of ion implanted coatings show clearly the presence of nitrogen solid solutions and precipitates of new phases in the surface layers of coatings. Phases formed are controlled by the temperature of ion beam processing, initial chemical composition and microstructure of coatings. Wear tests demonstrate that properly selected parameters of ion implantation dramatically improve wear and score-resistance of coatings. The influence of the microstructure and phase composition of nitrogen ion implanted layers on tribological properties is discussed.     

Non Destructive Geophysical Monitoring of Water Content and Fluid Conductivity Anomalies in the Near Surface at the Border of an Agricultural

We use in this paper advanced geophysical techniques for the characterization and monitoring of subsurface properties such as porosity, water content and electrical conductivity of water. Ground Penetrating Radar (GPR) and electrical conductivity measurements were recorded monthly during one year at the border of a corn field. Velocity analyses of multioffset GPR data were conducted to determine total porosity and to monitor vertical transport of water from the soil surface to the water table. The use of novel and original techniques for GPR processing (GPR velocity estimation by the Common Reflection Surface (CRS) method, kriging applied to GPR velocity) improved the estimate and the resolution of GPR velocity maps compared with the classical Normal MoveOut (NMO) and the bi-linear interpolation. Electrical resistivities were used to determine the effective porosity. The combination of GPR and electrical data permitted to estimate the electrical conductivity of water and to highlight high conductivity zones, possibly due to contamination by agricultural fertilizers. Independent determinations (grain size fractions, electrical conductivity, major ion content of water samples and porosity) were obtained, that validate our geophysical investigation. This study demonstrates the efficiency of non destructive geophysical approaches for providing accurate models of water content, porosity and electrical conductivity of water down to a depth of several meters in a poorly conductive soil.     

7075/6009铝合金层状复合板材的固溶时效热处理工艺

对7075/6009铝合金层状复合板材进行了不同的固溶时效处理,优化得到了该复合板最佳的热处理工艺,并对热处理后复合板的力学性能和拉伸断口进行了分析。结果表明:该复合板最佳的热处理工艺为485℃×30min水淬+175℃×8h炉冷,其抗拉强度为404MPa,屈服强度为364MPa,伸长率为15.3%;外层6009铝合金的拉伸断口上分布着大量韧窝,内外层合金间实现了良好的冶金结合。     

A study of the improved wear performance of nitrogen-implanted Ti-6Al-4V

The unlubricated wear behaviour of nitrogen-implanted Ti-6Al-4V was studied using a pin-on-disc wear tester. It is shown that, under suitable conditions, nitrogen implantation may reduce the wear rate by over two orders of magnitude. Detailed investigations of the dose dependence of this improved wear performance were carried out. The friction and wear data show a clear breakthrough type of transition from the implanted to the unimplanted modes of wear. The time to breakthrough is seen to be directly dependent on the nitrogen ion dose. Metallographic examination of the wear tracks reveals that a thin layer of TiO in the wear track is associated with the low friction-low wear behaviour of the implanted material. The observed transition in the wear process is discussed in terms of the surface and subsurface modifications produced by nitrogen implantation.