# Photopolymerization of Ceramic Resins by Stereolithography Process: A Review
## 4 Ceramic Suspensions and Effects on the Process
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Ceramic Powder**} & \multirow{2}{*}{**Monomer**} & \multirow{2}{*}{**PI**} & \multicolumn{2}{c}{**Particle Size (\(\upmu\)m)**} & \multirow{2}{*}{**RI**} & \multirow{2}{*}{\(\Delta\)RI} & \multirow{2}{*}{\(\lambda\)**(nm)**} & \multirow{2}{*}{**Ref.**} \\ \hline \multirow{8}{*}{Alumina} & Acrylates & Irgacure 651 & 0.8–4.4 & 1.7 & 0.16–0.23 & 351–364 & [35] \\  & PEAAM \({}^{1}\) + HDDA \({}^{2}\) & DMPA \({}^{3}\) & 0.5–2.3 & 1.787 & 0.299–0.331 & 365 & [32] \\  & Acrylamide solution + & - & 0.5 & 1.7 & 0.16–0.24 & - & [12] \\  & HDDA & - & - & 1.7 & 0.3 & 364 & [54] \\  & HDDA + PTTA \({}^{4}\) & TPO \({}^{5}\) & 0.4–0.7 & 1.76 & 0.3 & 405 & [29] \\  & HDDA & - & 0.34–0.46 & 1.7 & 0.282–0.312 & 366 & [55] \\ \hline \multirow{8}{*}{Zirconia} & Acrylates & Irgacure 651 & 4.2 & 1.85 & 0.31–038 & 351–364 & [35] \\  & PEAAM + HDDA & DMPA & 0.65 & 2.249 & 0.761–0.793 & 365 & [32] \\  & HDDA + PTTA + Acrylic & - & 0.2 & 2.27 & 1.5 & - & [56] \\  & HDDA + TMPTA + IBOA \({}^{6}\) & & & & & & \\  & + HEA \({}^{7}\) + HEMA \({}^{8}\) + PHA & TPO & 1 & 2.2 & 0.682–0.758 & 405 & [36] \\  & \({}^{9}\) + IDA \({}^{10}\) & & & & & & \\ \hline \multirow{8}{*}{Silica} & Acrylates & Irgacure 651 & 3.5 & 1.5 & 0.03–0.04 & 351–364 & [35] \\  & PEAAM + HDDA & DMPA & 2.25 & 1.564 & 0.076–0.108 & 365 & [32] \\  & HDDA & - & 2.29 & 1.56 & - & 366 & [54] \\ \hline \multirow{2}{*}{Silicon nitride} & Lithuanite 720 \({}^{11}\) & - & - & 2.0167 & 0.5537 & 460 & [57] \\  & HDDA & - & 0.44 & 2.1 & 0.818 & 366 & [55] \\ \hline Silicon carbide & PEAAM + HDDA & DMPA & 12.25 & 2.553 & 1.065–1.097 & 467–691 & [32] \\ \hline Lead zirconate & HDDA & Irgacure 184 & 1.68 & 2.5 & 1.04 & 350 & [58] \\ titanate (PZT) & HDDA & - & - & 2.4 & 1 & 364 & [54] \\ \hline \(\beta\)-Tricalcium & \multirow{2}{*}{HDDA + OPPEA \({}^{12}\)} & \multirow{2}{*}{TPO} & \multirow{2}{*}{0.7} & \multirow{2}{*}{1.627} & \multirow{2}{*}{0.103} & \multirow{2}{*}{405} & \multirow{2}{*}{[41]} \\ phosphate (\(\beta\)-TCP) & & & & & & & \\ \hline \multirow{2}{*}{Barium Titanate (BT)} & \multirow{2}{*}{HDDA} & Irgacure 184 & 1.27–2.09 & 2.4 & 0.96 & 350 & [58] \\ \hline \multirow{8}{*}{Barium Titanate (BT)} & \multirow{2}{*}{HDDA} & \multirow{2}{*}{Irgacure 184} & \multirow{2}{*}{1.62–1.09} & \multirow{2}{*}{2.4} & \multirow{2}{*}{0.96} & \multirow{2}{*}{350} & \multirow{2}{*}{[58]} \\  & & & & & & & \\ \hline \multirow{8}{*}{Barium Titanate (BT)} & \multirow{2}{*}{HDDA} & \multirow{2}{*}{Irgacure 184} & \multirow{2}{*}{1.68} & \multirow{2}{*}{2.5} & \multirow{2}{*}{1.04} & \multirow{2}{*}{350} & \multirow{2}{*}{[58]} \\  & & & & & & & \\ \hline \multirow{8}{*}{Barium Titanate (BT)} & \multirow{2}{*}{HDDA} & \multirow{2}{*}{-} & \multirow{2}{*}{2.4} & \multirow{2}{*}{0.96} & \multirow{2}{*}{350} & \multirow{2}{*}{[58]} \\  & & & & & & & \\ \hline \hline \end{tabular}  
\({}^{1}\) Modified polyther acrylate, \({}^{2}\) 1,6-Hexaneediol diacrylate, \({}^{3}\) 2,2-dimethoxy-1,2-phenylacetophenone, \({}^{4}\) Ethoxy-lated pentaerythtriol tetraacrylate, \({}^{5}\) 2,4,6 Trimethylbenzoyl diphenylphosphine oxide, \({}^{6}\) isobornyl acrylate, \({}^{7}\) 2-hydroxyethyl acrylate, \({}^{8}\) 2-hydroxyethyl methacrylate, \({}^{9}\) 2-phenoxietily acrylate, \({}^{10}\) isodecyl acrylate, \({}^{11}\) Commercial resin, \({}^{12}\) 2-([1,1’-phenyl]-2-yloxy) ethylacrylate.  
\end{table} 
Table 1: Refractive Index of most commons ceramic powders used for stereolithography. \(\lambda\) is the wavelength of the irradiation. Known scattering theories such as Rayleigh-Gans or Mie are based on the assumption that scattering takes place in very dilute suspensions, so they are not applicable to high solid loading ceramic suspensions for stereolithographic applications. Variability of the phenomenon, due to different aspects, makes analytical treatments difficult, so a semi-empirical method is preferable [54; 59]. [PERSON] et al. [60] investigated variation in polymerization geometry due to scattering and absorption effect.