# Polymer-Derived SiOC Ceramics by Digital Light Processing-Based Additive Manufacturing
## 3 Results and Discussion
### Blending of the Polymers  
The MK resin and TMSPM underwent acid-catalyzed hydrolysis and condensation reactions, as illustrated in Figure 2. During this reaction, the hydroxyl and methoxy groups on the polysiloxane molecules underwent hydrolysis and condensation under acid-catalyzed conditions, forming a chain-like Si-O-Si structure. The condensation reaction enhanced the interchain entanglement of the Si-O bonds, thereby increasing the crosslinking density. During the ultraviolet curing process, photoinitiators induced free radical reactions, promoting the cross-linking of double bonds. This process increased the crosslinking density of the resin, stabilizing its shape and eliminating its fluidity. Figure 3 shows the infrared spectra of the MK resin and MK-TMSPM resin samples. Both curves, a and b, exhibited absorption peaks at specific wavenumber positions. For instance, the absorption peaks observed at 1273 cm\({}^{-1}\) (symmetrical bending vibration of Si-CH\({}_{3}\)), 1100 cm\({}^{-1}\) (characteristic Si-O-Si bond), 763 cm\({}^{-1}\) (stretching vibration of Si-CH\({}_{3}\)), and 630-480 cm\({}^{-1}\) (characteristic Si-C bond) corresponded to the structure of the MK resin [61]. The characteristic absorption peak of -OCH\({}_{3}\) at 2840 cm\({}^{-1}\), which was associated with incomplete hydrolysis, became notably more pronounced [62], while peaks at 940 cm\({}^{-1}\) and 1142 cm\({}^{-1}\) also intensified, indicating that hydrolysis and condensation  
Figure 1: Process diagram of the DLP-printed SiOC composite ceramics. Figure 2: The hydrolysis condensation reaction process. reactions produced additional Si-O-Si structures [63]. Additionally, peaks corresponding to C-H symmetrical and asymmetrical bending vibrations of methylene at 1409 cm\({}^{-1}\) and 1471 cm\({}^{-1}\)[64], C=O stretching vibrations at 1720 cm\({}^{-1}\)[65], and C=C stretching vibrations at 1639 cm\({}^{-1}\) confirmed the successful introduction of the methacrylate group into MK resin, thus completing the anticipated hydrolysis and condensation reactions [66]. The rheological properties of the MK-TMSPM ceramic slurry were evaluated by measuring the compound viscosity (\(\eta^{*}\)), the storage modulus (G\({}^{\prime}\)), and the loss modulus (G\({}^{\prime\prime}\)) under static test conditions. Figure 4 presents the composite viscosity (\(\eta^{*}\)) of the slurry as a function of the shear rate, ranging from 1 s\({}^{-1}\) to 400 s\({}^{-1}\), which was measured under static test conditions at 25 \({}^{\circ}\)C. The results demonstrate that the precursor ceramic slurry exhibited shear-thinning behavior, with the viscosity remaining nearly constant at low shear rates (<40 s\({}^{-1}\)). As the shear rate increased, the \(\eta^{*}\) of the slurry decreased substantially, further confirming its shear-thinning behavior. In its fluid state, the mixed material system demonstrated a low viscosity (~1.5 Pa\(\cdot\)s), rendering it highly suitable for light-curing molding with DLP printers. Figure 4: The rheological properties of the MK-TMSPM ceramic slurry. Figure 3: The FT-IR spectra of the polysiloxane resin: (a) MK and (b) MK-TMSPM. Figure 5 illustrates the pyrolysis process of the MK-TMSPM light-cured products, which were analyzed using a thermogravimetric analyzer. The thermogravimetric analysis revealed that the residual weight of the MK-TMSPM light-cured products at 800 \({}^{\circ}\)C was 55.4%, with three distinct mass loss peaks observed at approximately 200 \({}^{\circ}\)C, 350 \({}^{\circ}\)C, and 450 \({}^{\circ}\)C. The weight loss process can be divided into three stages: The first stage (room temperature to 200 \({}^{\circ}\)C) primarily involves the removal of residual water, unreacted solvent THF, and small organic molecules. In the second stage (200 \({}^{\circ}\)C to 450 \({}^{\circ}\)C), the polymer chains undergo cleavage and rearrangement of organic groups, including acrylate groups.