## 4 Discussion  
### Solid-Phase Oxidant Tribochemical Reaction Oxygen Generation Mechanism  
From Figure 2, it can be seen that the solid-phase oxidant fills between the SiC and the polishing pad during the polishing process, but under the polishing pressure, the SiC specimen and the polishing pad or solid-phase oxidant can be in contact at the micro-convex body [25]. Friction, local compression, or micro-collisions may occur on the micro-convex body at the polishing interface, which will generate concentrated local stresses at the point of contact (several gigapascals [26])and high flash point temperatures(up to 1000 degrees Celsius [27; 28]). Then, under the action of friction and high flash point temperatures, etc., the solid-phase oxidant decomposes oxygen and oxidizes SiC or reacts with SiC by friction chemistry with other media [25; 29; 30; 31]. Sodium percarbonate (Na\({}_{2}\)CO\({}_{3}\)--1.5 H\({}_{2}\)O\({}_{2}\)) is an inorganic substance and white granular solid commonly known as solid H\({}_{2}\)O\({}_{2}\); it is a strong oxidant. It is easy to separate out oxygen when exposed to moisture to obtain Na\({}_{2}\)CO\({}_{3}\), H\({}_{2}\)O, and O\({}_{2}\).In addition, sodium percarbonate is a heat-sensitive substance, dry Na\({}_{2}\)CO\({}_{3}\)--1.5 H\({}_{2}\)O\({}_{2}\) at 120 \({}^{\circ}\)C decomposition. However, in the presence of water, heat, or if mixed with heavy metal and organic material, it is very easy to decompose into Na\({}_{2  
form intermediates with the reactants, which reduces the activation energy of the reaction and accelerates the reaction. It can be considered that the autocatalytic decomposition of sodium percarbonate proceeds in the following steps. \[\text{Na}_{2}\text{CO}_{3}\text{--}1.5\ \text{H}_{2}\text{O}_{2}\text{--} \text{[Na}_{2}\text{CO}_{3}\text{--}1.5\ \text{H}_{2}\text{O}_{2}\text{--} \text{H}_{2}\text{O]} \tag{3}\]  
\[\text{[Na}_{2}\text{CO}_{3}\text{--}1.5\ \text{H}_{2}\text{O}_{2}\text{--} \text{H}_{2}\text{O]}\text{--} \text{Na}_{2}\text{CO}_{3}\text{+ [1.5\ \text{H}_{2}\text{O}_{2}\text{--} \text{H}_{2}\text{O]}} \tag{4}\]  
\[\text{[1.5\ \text{H}_{2}\text{O}_{2}\text{--} \text{H}_{2}\text{O]}}\text{--} \text{2.5H}_{2}\text{O}+0.75\text{O}_{2}\text{$\uparrow$} \tag{5}\]  
The Na\({}_{2}\)CO\({}_{3}\)--1.5 H\({}_{2}\)O\({}_{2}\) molecule first combines with H\({}_{2}\)O to form the activation complex [Na\({}_{2}\)CO\({}_{3}\)--1.5 H\({}_{2}\)O\({}_{2}\)--H\({}_{2}\)O], which is unstable and quickly decomposes into Na\({}_{2}\)CO\({}_{3}\). The reactive intermediate [1.5 H\({}_{2}\)O\({}_{2}\)--H\({}_{2}\)O], [1.5 H\({}_{2}\)O\({}_{2}\)--H\({}_{2}\)O] is also unstable and decomposes into H\({}_{2}\)O and O\({}_{2}\). Where Equation (3) proceeds slowly, Equations (4) and (5) proceed more rapidly and reach an equilibrium quickly [33]. Sodium hydroxide (melting point is 318.4 \({}^{\circ}\)C, the boiling point is 1390 \({}^{\circ}\)C) powder will turn into molten sodium hydroxide under the action of frictional heat. In addition, the oxidant sodium hydroxide is easily deliquesed in air and reacts with CO\({}_{2}\) to form Na\({}_{2}\)CO\({}_{3}\) and H\({}_{2}\)O [35]. See Equation (6). \[\text{2 NaOH}+\text{CO}_{2}\text{$\rightarrow$}\text{Na}_{2}\text{CO}_{3}+ \text{H}_{2}\text{O} \tag{6}\]  
Potassium chlorate (KClO\({}_{3}\)) is an inorganic compound, a colorless or white crystalline powder, that is a strong oxidantandis stable at room temperature. When heated to approximately 360 \({}^{\circ}\)C (the melting point of potassium chlorate), oxygen is released, and the reaction mechanism can be expressed in Equation (7). At continuous heating to 610 \({}^{\circ}\)C, the rate of oxygen release becomes slower, and the viscosity of the system thickens. At this point, the reaction is as in Equation (8); that is, potassium chlorate is oxidized to potassium perchlorate (KClO\({}_{4}\)) by self-disproportionation.