## 3 Results and Discussion
### Microscopic Morphology and Organizational Structure
#### 3.1.2 X-Ray Analysis of Ceramic Coatings  
During the curing process, the ceramic components of the nano-TiO\({}_{2}\) composite coatings may undergo chemical reactions, which may affect their phase composition and properties. In order to investigate whether new phases are generated after curing at 400 \({}^{\circ}\)C and the effect of different temperature increase rates on the properties of ceramic coatings, the physical phases of the coatings were analyzed by X-ray diffraction (XRD) in this study.  
As shown in Figure 6, by comparing the PDF standard cards (TiO\({}_{2}\) (PDF#97-017-2916); Al\({}_{2}\)O\({}_{3}\) (PDF#97-005-2648); Al(PO\({}_{4}\)) PDF#97-028-0308); TiP\({}_{2}\)O\({}_{7}\) (PDF#97-029-0278); Ti\({}_{3}\)(PO\({}_{4}\))\({}_{4}\)(PDF#97-008-2282); Cu(AlO\({}_{2}\))\({}_{2}\) (PDF#97-003-1701)) show that the modified TiO\({}_{2}\) nanocomposite ceramic coatings at 20 = 20.3\({}^{\circ}\), 22.5\({}^{\circ}\), 25.3\({}^{\circ}\), 34.9\({}^{\circ}\), 37.8\({}^{\circ}\), 43.3\({}^{\circ}\) in order of Al(PO\({}_{4}\)) (\(-\)2 1 3), TiP\({}_{2}\)O\({}_{7}\) (2 0 0), TiO\({}_{2}\) (1 0 1), Ti\({}_{3}\)(PO\({}_{4}\))\({}_{4}\) (1 1 2), Cu(AlO\({}_{2}\))\({}_{2}\) (0 1 2), and Al\({}_{2}\)O\({}_{3}\) (1 1 3) major crystalline peaks [48; 49; 50; 51; 52; 53].  
After sintering at 400 \({}^{\circ}\)C for 1 h under two heating rates of 5 \({}^{\circ}\)C/min and 2 \({}^{\circ}\)C/min, the formed phase compositions of the TiO\({}_{2}\) nanocomposite ceramic coating showed slight differences. New phases of aluminum phosphate (AlPO\({}_{4}\)), titanium pyrophosphate (TiP\({}_{2}\)O\({}_{7}\)), and a small amount of Cu(AlO\({}_{2}\))\({}_{2}\) were detected under both heating rates. This phenomenon indicates that the following main chemical reactions occurred in the coating components at 400 \({}^{\circ}\)C: Formation of aluminum phosphate (AlPO\({}_{4}\))**: Under high-temperature, aluminum dihydrogen phosphate (Al(H\({}_{2}\)PO\({}_{4}\))\({}_{3}\)) decomposed, and its H\({}_{2}\)PO\({}_{4}\)\({}^{-}\) ions combined with Al\({}^{3+}\) to form aluminum phosphate (AlPO\({}_{4}\)); Formation of titanium pyrophosphate (TiP\({}_{2}\)O\({}_{7}\))**: Nano-TiO\({}_{2}\) reacted with phosphoric acid to generate titanium pyrophosphate (TiP\({}_{2}\)O\({}_{7}\)), which indicates that TiO\({}_{2}\) underwent a certain degree of phase transformation during the sintering process. Notably, a new phase of titanium phosphate (Ti\({}_{3}\)(PO\({}_{4}\))\({}_{4}\)) was formed in the coating prepared at a heating rate of 2 \({}^{\circ}\)C/min. This phase exhibits excellent high-temperature resistance and can maintain good chemical stability in high-temperature  
Figure 6: XRD patterns of nano-TiO\({}_{2}\) composite ceramic coatings with different heating rates: (a) 5 \({}^{\circ}\)C/min, (b) 2 \({}^{\circ}\)C/min.  
environments. This characteristic confirms that coatings prepared at lower heating rates show better adaptability to high-temperature conditions [53].  
In addition, at a sintering temperature of 400 \({}^{\circ}\)C, some unreacted nano-TiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) particles still exist in the coating. During the cooling process, excessive TiO\({}_{2}\) will pre-precipitate from the coating, thereby affecting the final microstructure.  
In summary, for the ceramic coatings prepared by the slurry method at 400 \({}^{\circ}\)C, the ceramic aggregates mainly react with the aluminum phosphate binder, while no obvious chemical reaction occurs between the coating and the substrate. This indicates that the coating is mainly attached to the surface of the substrate through mechanical bonding force.