Search

In graphite/copper composites, the intrinsic non-wettability of graphite and copper makes it difficult for the copper melt to realize effective infiltration into the porous graphite matrix. The res...

As common electric contact materials, copper‐carbon electrode pairs are widely used in the field of electric contact such as in high‐speed railways, motor collector rings and grounding brushes. They play a key role in energy transmission in the above‐mentioned systems. Arc erosion has become a key issue threatening system safety. In this work, a dedicated arc erosion platform was built to study the polarity effect of copper‐carbon electrode pairs. It was found that arc dynamics and electrodes erosion behaviours were significantly different under different polarities, which could be understood from the mechanism of heat transfer, cooling and electron emission of the electrode. Then, when the carbon material was used as an anode, the arc caused carbon transfer: the carbon material sublimated quickly due to electron condensation and thermal conduction and quickly condensed on the low‐temperature metal electrode, while the carbon material transfer could partly inhibit the oxidation of the cathode metal electrode. In addition, the rapid sublimation of the carbon material produced high‐temperature airflow, which would make the arc impedance fluctuate and cause the arc voltage to jump. Finally, the anode heat transfer and cathode cooling mechanism directly affected the material state, and the erosion of the anode material was more serious.

Using Fe reaction products to overcome the poor wettability between copper and carbon, C/Cu-Fe composites with excellent properties were prepared by gas pressure infiltration technique. The element...

Carbon/copper composites are widely used in collector brushes, pantograph sliders, collector shoes and other fields due to their excellent mechanical friction, wear, thermal conductivity and electr...

By copper-alloying with different content of B element forming binary alloy to improve the bonding force between carbon and copper, and the Cu-B/sintered-carbon composites were prepared successfully by gas pressure impregnation. The mechanism of boron on interface enhancement, mechanical and electrical properties of composites was studied. The results showed that the mechanical strength and electrical conductivity were proportion to the boron content, while the contact angle was in inverse proportion to the B content. When the doping amount was 2.5wt%, the flexural strength and electrical conductivity were increased by 65% and 54% respectively compared with composites without modification and the contact angle decreased to 21°. The reason was that the boron carbide with moderate thickness at the interface could enhance the Cu/C interfacial bonding by transforming from physical bonding to chemical bonding. This study proves that the moderate addition of boron can improve the wettability of C/Cu system, which resulting in the improvement of mechanical and electrical properties of Cu-B/ sintered-carbon composites.

Pantograph strip is one kind of carbon-metal composites, which plays the key role of supplying the electrical energy to the electrified train through the sliding contact with the overhead lines. However, due to the natural non-wetting of metal with the carbon graphite matrix, the interface bonding strength of composite materials is weak, which significantly restricts the electro-mechanical properties. In this study, the method of using active element to modified pantograph strip material, we successfully improved the wettability between the metal with carbon matrix, and the interface performance can be effectively optimized, the electro-mechanical properties of the impregnated mental carbon strip have been both improved. The compressive and flexural strength of the C/Al composite pantograph strip increased by 70% and 52% respectively, and the electrical conductivity increased by 79%; The compressive and flexural strength of the C/Cu composite pantograph strip increased by 37.4% and 120.4% respectively, and the electrical conductivity increased by 140.8%. This study is helpful for understanding the wetting behavior of metal with carbon, and is conducive to promoting development pantograph strip in high-speed railway.

The use of carbon/copper (C/Cu) composites as electrical contact materials has developed rapidly owing to their superior mechanical strength, electrical conductivity, and self-lubricity. However, the non-wettability of carbon and copper restricts further improvement in their performance. In this work, a strategy based on copper-boron alloying is proposed, to improve C/Cu interfacial bonding, and Cu-B/sintered-carbon composites were successfully prepared using a gas pressure impregnation technique. The results show that the compressive and flexural strengths of the modified composites increased by 39% and 54%, respectively, and the C/Cu contact angle decreased from 123.6° to 21.3° in the case of 2.5 wt% B doping. A minimum electrical resistivity of 1.7 μΩ·m was achieved when a moderate boron content (1.2 wt%) was selected. The role of boron carbide was examined, and competitive mechanisms of C/Cu interfacial bonding level and electrical conductivity are proposed, based on aspects of interfacial resistance and scattering of conducting electrons.

Carbon/Copper (C/Cu) composites have been widely used in aerospace, transportation and military products because of their excellent properties of mechanical strength, self-lubrication and electrical conductivities. One of the challenges in preparing C/Cu composites materials is how to overcome the poor wettability between Cu and carbon. In this study, ultrafine iron oxide (Fe2O3), as a precursor, was introduced into the carbon matrix to improve the C/Cu interfacial bonding of C/Cu composites prepared by pressure infiltration. The effect of Fe on the phase composition, microstructure and properties of C/Cu composites were systematically evaluated. The results revealed that the interfacial bonding between Cu and carbon was enhanced by the “bridge architecture” of iron carbide (Fe3C). The wettability between Cu and carbon improved for the contact angle decreased from 124° to 38°. Compared with the unmodified composites, the composites doping 5 wt% Fe2O3 exhibited best performance. The compression and flexural strength increased by 37.4% and 120.4% respectively. Meanwhile, the electrical conductivity improved by 283.7%. It was concluded that the Fe3C layer had an important effect on the electron transport and crack propagation of the C/Cu composites.