## 3 Results and Discussion
### Analysis of Wetting Properties
#### 3.2.1 Wetting Analysis of Cu-SiC Surfaces Processed by Abrasive Materials
The high sintering temperature of composite materials contributes to the subsequent intensification of the adsorption and deposition of hydrocarbon contaminants. To prove it, special experiments were conducted. Samples No. 2-5 were placed in methyl alcohol, which is a solvent for organic contaminants, for 1 h. The samples were then dried under laboratory conditions for 3 h. After cleaning, the static contact angles on the Cu-SiC surfaces decreased to \(\theta_{\text{No. 4}}\approx 73^{\circ}\), \(\theta_{\text{No. 3}}\approx 78^{\circ}\), \(\theta_{\text{No. 2}}\approx 80^{\circ}\), \(\theta_{\text{No. 5}}\approx 84^{\circ}\).The contact angle decreased more on surfaces produced at higher sintering temperatures. The contact angle hysteresis also slightly decreased by 2-3%. The decrease in the contact angle and hysteresis is due to the removal of hydrocarbon contaminants. It can be seen from Figure 3b that there is no clear relationship between the surface wetting properties and the change in the SiC content in the Cu-SiC composition (samples No. 5-8) at the sintering stage. It should be noted that some of the conclusions made for the group of samples No. 2-5 (Figure 3a) are also valid for the group of samples No. 5-8 (Figure 3b): the difference in the wetting properties of surfaces No. 5-8 and contact angle hysteresis (more than \(10^{\circ}\)) are mainly due to the inhomogeneous elemental composition of the surfaces. It should be noted that the difference in the contact angles of Cu-SiC composite materials in Figure 3b, taking into account the hysteresis, is more than \(18^{\circ}\):  
\[\Delta\theta_{min}=(\theta_{\text{No. 5}}-\Delta\theta_{\text{No. 5}}/2)-(\theta_{\text{No. 8}}+\Delta\theta_{\text{No. 8}}/2)=\]  
\[=(88.9-14.4/2)-(56.4+13.2/2)=18.7^{\circ}.\]  
In addition, Figure 3b presents the SCA and the CAH measured on copper sample No. 1 (without SiC) and SiC No. 9 (without copper) surfaces from [41]. It can be seen that the change in the content of SiC from 5 to 20 wt.% in the composition of the initial powder makes it possible to obtain a Cu-SiC composite material with a wide range of wetting properties (from 57 to 90 degrees). Moreover, the wetting properties of Cu-SiC composite materials differ significantly from the properties of materials made from Cu (No. 1) and SiC (No. 9) components. In the same way as the group of samples No. 5-8 (Figure 3a), samples No. 2-5 (Figure 3b) were cleaned in a methanol medium. After cleaning, the wetting properties of samples No. 2-5 improved. The surfaces exhibited angles: \(\theta_{\text{No. 5}}\approx 84^{\circ}\), \(\theta_{\text{No. 6}}\approx 60^{\circ}\), \(\theta_{\text{No. 7}}\approx 71^{\circ}\), \(\theta_{\text{No. 8}}\approx 54^{\circ}\). The contact angle hysteresis also decreased by 2-3%. This is due to the removal of adsorbed hydrocarbons. After removal of the hydrocarbons, the difference in wetting properties of samples No. 2-5 was preserved and exceeded the contact angle hysteresis value. Most likely, the implicit relationship between the surface wetting properties and the change in the SiC content in the composition at the sintering stage is due to the following reasons: (1) uneven distribution of SiC grains in the bulk and over the surface of the Cu-SiC composite material; (2) uncontrolled processes of formation of the Cu melt during sintering of the bulk product, as a result of which SiC grains are immersed in the copper melt at the sintering stage.