Combinations Of Contact Materials Research Articles

Comparison of Contact Electrification Mechanisms of Selected Polymers and Surface-Functionalized Molecules.

Among the possible alternatives for the improvement of contact electrification for triboelectric energy harvesting purposes, the functionalization of contact surfaces has attracted wide attention due to its versatility and cost-efficiency. Similarly, low-stiffness polymeric materials such as poly(dimethylsiloxane) (PDMS) are regarded as a promising choice of contact material for the same purpose. However, for defining the most efficient combinations of materials of the aforementioned types, a number of theoretical questions still frequently pose difficulties for practical implementation-related tasks. In this regard, the presented study theoretically assesses the possibilities of consistently selecting optimum performance combinations of contact materials. Here, the optimum is defined as the minimum energy of the charge transfer reaction and, consequently, the maximum density of the predicted triboelectric surface charge. With this aim, the most promising combinations in terms of electron-transfer energies were identified among the candidates of functionalized molecules and polymers. Based on the ordering of materials according to the basic characteristics of charge-transfer reactions─electron and hole affinities─certain differences were observed. These findings indicate that for the materials under consideration, it is not possible to establish a single triboelectric series solely based on a single characteristic. Furthermore, to evaluate the potential compatibility of charge-transfer reaction mechanisms based on electron and material transfer, molecular dynamics simulations were conducted using structures that depict pairs of polymers and self-assembled monolayers of functionalized molecules in contact and separated types of operations. The obtained results indicate that the formation of equally charged free fragments of polymer chains is likely taking place in the contact electrification for N-(2-aminoethyl)-3-aminopropyl trimethoxysilane/PDMS interfaces. At variance, a contact electrification mechanism by charge-dependent material transfer may occur for 1H, 1H, 2H, 2H-perfluorooctyl trimethoxysilane/PDMS interfaces.

Facile fabrication of triboelectric nanogenerators based on paper and natural rubber as low-cost bio-derived materials

Triboelectric nanogenerators (TENGs) are devices capable of effectively harvesting electrical energy from mechanical motion prevalent around us. With the goal of developing TENGs with a small environmental footprint, herein we present the potential of using rubber and paper as biological materials for constructing triboelectric nanogenerators. We explored the performance of these TENGs with various contact material combinations, electrode sizes, and operational frequencies. The optimally configured TENG achieved a maximum open circuit output voltage of over 30 V, and a short circuit current of around 3 µA. Additionally, this optimally configured TENG was capable of charging various capacitors and achieved a maximum power output density of 21 mW/m2. This work demonstrates that biologically derived materials can be used as effective, sustainable, and low-cost contact materials for the development of triboelectric nanogenerators with minimal environmental footprint.

Influence of contact parameters on the tribological behaviour of various graphite/graphite sliding electrical contacts

Sliding electrical contacts are used in devices for the conduction of electrical power or the electrical signals between stationary and moving parts. The most widely used electrical-sliding system is still the conventional slip ring and brush assembly. In the last decade, the lifetime of ring-brush contacts was extended through the use of better contact-material combinations and design improvements. However, the extremely rapid electrification of many more components has put severe demands on this extended lifetime. This paper presents a novel, patented design for two sliding discs that allows the use of advantageous graphite/graphite contacts. In the literature there is a serious lack of understanding the performance of sliding electrical contacts with graphite/graphite pairs, which depends on the key contact parameters, as well as the influence and potential of the different available graphite materials. The normal load, the contact velocity, the electric current, and the three self-mated graphite contacts, i.e., hard carbon, electrographite and polymer-bonded graphite, were investigated. The results indicate that the contact conditions influence the performance, which is also very dependent on the graphite materials. The polymer-bonded graphite showed the best results in this study.

A Study on Plastic Deformations due to Contact Fatigue Wear on a Metallic Coating Deposed in Electric Arc

This paper studies the way how a sample with a 40Cr130 coating behaves to contact fatigue wear from the perspective of plastic deformations. The sample is made of an 18MnCr11 alloy steel. The coating was deposited in electric arc using the Smart Arc 350 installation from Sulzer Metco. The samples was subjected to fatigue wear on the AMSLER installation in limit and mixed lubrication conditions. The samples were subjected to wear for 30 hours, at a loading force of 177 N. The moving sample had a rotational speed of 375 rot/min. Different combinations of contact materials were used for the test samples: coating coating and coating base material. The results were highlighted using the QUANTA 200 3D DUAL BEAM electron microscope.

Sliding Wear of Inlay Clad Metals and Electrodeposited Cobalt-Gold

Clacl noble metals are of interest for the contacts of electronic connectors,because they are often less expensive to fabricate than electroplates. A wear study was conducted with a number of inlay claddings of pure metals and alloys of palladium, gold, and silver. Hemispherically ended riders of solid gold and coated with electrodeposited cobalt-gold (0.2 percent Co) were mated to fiats in reciprocation. Coupons plated with cobalt-gold were used as controls. The solid gold riders and the clad metals were found to be significantly more prone to transfer and wear than electroplated cobalt-gold. The relative hardnesses of the metals on the members determined the direction of transfer, with the softer moving initially to the harder, although prows sometimes formed on the rider which reversed the direction of net metal movement. The sliding performance of combinations of contact materials can be ranked as follows: electrodeposited cobalt-gold versus itself (best), electrodeposited cobaltgold versus claddings, and solid gold versus claddings. The harder clad materials such as DG 60Pd40Ag (also called DG R156)---an alloy of gold, palladium, and silver with a graded composition, from a gold-rich (55-85 percent) surface to 60Pd40Ag in the body of the metai--60Pd40Ag, and 40Au36Pd24Ag were superior to those which were softer, like 70Au30Ag and 69Au25Ag6Pt. Clad palladium was also relatively poor. A polyphenyl ether fluid lubricant improved sliding significantly, with electroplated cobalt-gold against itself still the best material combination. The clad metals of this study may be satisfactory replacements for electrodeposited cobalt-gold in connector contacts provided the opposing member has a plated cobalt-gold finish and a good boundary lubricant is used.