Thermophysical Properties of Cu-Matrix Composites Manufactured Using Cu Powder Coated with Graphene

JMEPEG (2016) 25:3146–3151 DOI: 10.1007/s11665-016-2174-5 ÓThe Author(s). This article is published with open access at Springerlink.com 1059-9495/$19.00 Thermophysical Properties of Cu-Matrix Composites Manufactured Using Cu Powder Coated with Graphene T. Babul, M. Baranowski, N. Sobczak, M. Homa, and W. Leśniewski (Submitted November 15, 2015; in revised form May 19, 2016; published online June 17, 2016) Compact Cu matrix composites reinforced with graphene were prepared by thermochemical processes and cold isostatic pressing. Thermophysical properties were investigated using laser flash analysis, differential scanning calorimetry, and dilatometry. From the results of the measurements, it follows that within the entire investigated temperature range, both the thermal diffusivity and the calculated values therefrom of the thermal conductivity of copper-graphene composites change according to the temperature changes. Above 500 °C, abnormal decrease of the thermal diffusivity was registered for sample prepared from pure copper powder. In this case, the elevated temperature of test could cause sintering of copper particles, which were not coated by graphene. The as-received composites had higher thermal diffusivity and the thermal conductivity at the room temperature in comparison to the material obtained by standard pressing of pure copper powder. However, the production methods of some samples could cause their partial sintering. Based on the study, it could not be concluded that graphene only has impacts on the thermophysical properties. Keywords cold isostatic pressing, graphene, metal-matrix composites, powder metallurgy 1. Introduction The increasing demands for technical solutions enforce increased durability of products and improvement of their mechanical or physical properties. This makes the topic of modern materials as the subject of intense research in all the highly developed countries. One group of very popular materials, which appeared in numerous studies, is represented by carbon materials such as graphene (CGn) or carbon nanotubes (CNTs). In recent years, graphene has become a popular reinforcement material for metal matrix composites (Ref 1-7). Graphene is two-dimensional, flat form of carbon, which has a single atom thickness and a hexagonal arrangement of atoms and possesses extraordinary mechanical, thermal, and electrical properties (Ref 8, 9). The combination of unique properties of graphene as a dispersed phase provides great potential to change properties of a new generation of advanced composite materials in aerospace or electronic fields (Ref 10). Copper-graphene (Cu-CGn) composite is one of the scarcely studied metal matrix composites. However, driven by the Wan This article is an invited submission to JMEP selected from presentations at the Symposium ‘‘Metal-Matrix Composites,’’ belonging to the topic ‘‘Composite and Hybrid Materials’’ at the European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2015), held September 20 to 24, 2015, in Warsaw, Poland, and has been expanded from the original presentation. T. Babul and M. Baranowski, Institute of Precision Mechanics, 3 Duchnicka St., 01-796 Warsaw, Poland; N. Sobczak, Foundry Research Institute, 73 Zakopianska St., 30-418 Krakow, Poland; and Motor Transport Institute, 80 Jagiellonska St., 03-301 Warsaw, Poland; and M. Homa and W. Leśniewski, Foundry Research Institute, 73 Zakopianska St., 30-418 Krakow, Poland. Contact e-mail: . 3146—Volume 25(8) August 2016 der Waals forces, graphene nanoplatelets are prone to agglomerate during the fabrication process. As agglomeration and structural destruction of carbon reinforcement often take place during ball-milling process or conventional powder metallurgy, some novel methods are developed for the manufacturing graphene on powders (Ref 11, 12). The manufacturing of graphene on powders is a new approach in comparison to applying flat surfaces in previous, conventional methods. As a result, Graphene 3DIMP powder is obtained—a composite material, where graphene covers powders of Cu. Graphene 3DIMP is produced by thermochemical processes. The method for producing Graphene 3DIMP is the combination of several processes, including CarboTermoFluidÒ technology and the technology described in the patent application P.409141 of 2014 (Ref 6, 10, 13). The low cost of technological process opens up various possibilities for the use of Graphene 3DIMP for the production of a new generation of advanced materials. The technology enables coating of three-dimensional surface by graphene, which allows obtaining uniform materials—composites; Cugraphene coatings on substrates made of steel, light metals, and ceramics (Ref 7, 10). Formation of elements from copper-graphene composite opens up a wide field for applications of this material, among others, in heat exchangers. For this reason, it is interesting to obtain information on the thermophysical properties (thermal diffusivity and thermal conductivity) of the Cu-CGn composite. The paper presents the preliminary results of thermal conductivity studies conducted on Cu-graphene composites fabricated from Graphene 3DIMP. 2. Experimental 2.1 Fabrication of Graphene 3DIMP and Bulk Cu-Graphene Composites Studies of the thermophysical properties were conducted on fabricated in the Institute of Precision Mechanics Warsaw Cu- Journal of Materials Engineering and Performance graphene composites obtained by fluidization processes described elsewhere (Ref 13). Thermochemical processes were carried out on the stand for fluidization, which was produced by the Institute of Precision Mechanics. In the Graphene 3DIMP manufacturing, an analogy to the chemical vapor deposition (CVD) method was shown, where gases containing hydrocarbon also are the carbon source. CVD method allows coating large surfaces with graphene. However, in fluidization processes, it provides the movement of the small elements, the gas flows around each of them, and in this way, this method allows for the adsorption of graphene onto the base material in the powder form. The procedure for the adsorption of graphene onto Cu powders included the following steps: (1) fluidization under gases containing hydrocarbons in working chamber (the process is assisted by the introduction of vibrations); (2) high-temperature decomposition of hydrocarbons which act as the carbon source in the production of Graphene 3DIMP; (3) nucleation and growth of carbon structures on the surface of the Cu (which occurs through interaction of gases containing hydrocarbon, surrounding the particles of powder) (Ref 13). Cu-graphene specimens (disks) were obtained by isostatic pressing at the Institute of High Pressure Physics of the Polish Academy of Sciences. For the preparation of Cu-graphene specimens, the different proportions of the Cu powders, Graphene 3DIMP powders and their mixtures were used (Table 1). The pressures of isostatic pressing were set minimum to ensure t (...truncated)