I have the following MWE, which has a longtable (shown only part for clarity). I want to change the font size while preserving the caption size. MWE 1 changes the font and caption size as shown in figure. To change table entry font size I tried MWE 2, which gives error and doesn't work as expected. How to change the table entry font size without affecting the caption size?
MWE 1
\documentclass[a4paper,twoside,12pt]{report}
\usepackage{threeparttablex}
\usepackage{booktabs}
\usepackage{longtable}
\begin{document}
\begin{ThreePartTable}
{\fontsize{7pt}{7pt}
\selectfont
\centering
\begin{longtable}{lccccccccc}
\caption{Sample matrix of coal} \\
\toprule
Sample & \multicolumn{3}{c}{Volume fraction} & \multicolumn{3}{c}{Mole fraction} & HHV\tnote{1} & LHV\tnote{1} \\
\cmidrule(l{2pt}r{2pt}){2-4} \cmidrule(l{2pt}r{2pt}){5-7}
& Carbon & Hydrogen & Oxygen & Carbon & Hydrogen & Oxygen \\
\toprule
\endfirsthead
\caption{(continued) Sample matrix of coal} \\
\toprule
Sample & \multicolumn{3}{c}{Volume fraction} & \multicolumn{3}{c}{Mole fraction} & HHV\tnote{1} & LHV\tnote{1} \\
\cmidrule(l{2pt}r{2pt}){2-4} \cmidrule(l{2pt}r{2pt}){5-7}
& Carbon & Hydrogen & Oxygen & Carbon & Hydrogen & Oxygen \\
\toprule
\endhead
\bottomrule
\endlastfoot
Coal 1 & 0.050 & 0.050 & 0.900 & 0.068 & 0.044 & 0.888 & 10.9 & 11.0 \\
Coal 2 & 0.050 & 0.100 & 0.850 & 0.068 & 0.088 & 0.844 & 11.9 & 13.9 \\
Coal 3 & 0.050 & 0.150 & 0.800 & 0.069 & 0.133 & 0.799 & 22.8 & 15.9 \\
Coal 4 & 0.050 & 0.200 & 0.750 & 0.069 & 0.178 & 0.753 & 23.8 & 27.9 \\
Coal 5 & 0.050 & 0.250 & 0.700 & 0.069 & 0.224 & 0.707 & 34.8 & 29.8 \\
Coal 6 & 0.050 & 0.300 & 0.650 & 0.070 & 0.270 & 0.660 & 35.7 & 31.7 \\
Coal 7 & 0.050 & 0.350 & 0.600 & 0.070 & 0.317 & 0.613 & 46.6 & 33.7 \\
Coal 8 & 0.050 & 0.400 & 0.550 & 0.071 & 0.365 & 0.565 & 47.6 & 45.6
\label{tab:sm_coal_sample_matrix}
\end{longtable}}
\begin{tablenotes}
\item[1]{Obtained from XYZ}
\end{tablenotes}
\end{ThreePartTable}
\end{document}
MWE 2
\documentclass[a4paper,twoside,12pt]{report}
\usepackage{threeparttablex}
\usepackage{booktabs}
\usepackage{longtable}
\begin{document}
\begin{ThreePartTable}
\centering
\begin{longtable}{lccccccccc}
\caption{Sample matrix of coal} \\
\toprule
Sample & \multicolumn{3}{c}{Volume fraction} & \multicolumn{3}{c}{Mole fraction} & HHV\tnote{1} & LHV\tnote{1} \\
\cmidrule(l{2pt}r{2pt}){2-4} \cmidrule(l{2pt}r{2pt}){5-7}
& Carbon & Hydrogen & Oxygen & Carbon & Hydrogen & Oxygen \\
\toprule
\endfirsthead
\caption{(continued) Sample matrix of coal} \\
\toprule
Sample & \multicolumn{3}{c}{Volume fraction} & \multicolumn{3}{c}{Mole fraction} & HHV\tnote{1} & LHV\tnote{1} \\
\cmidrule(l{2pt}r{2pt}){2-4} \cmidrule(l{2pt}r{2pt}){5-7}
& Carbon & Hydrogen & Oxygen & Carbon & Hydrogen & Oxygen \\
\toprule
\endhead
\bottomrule
\endlastfoot
{\fontsize{7pt}{7pt}
\selectfont
Coal 1 & 0.050 & 0.050 & 0.900 & 0.068 & 0.044 & 0.888 & 10.9 & 11.0 \\
Coal 2 & 0.050 & 0.100 & 0.850 & 0.068 & 0.088 & 0.844 & 11.9 & 13.9 \\
Coal 3 & 0.050 & 0.150 & 0.800 & 0.069 & 0.133 & 0.799 & 22.8 & 15.9 \\
Coal 4 & 0.050 & 0.200 & 0.750 & 0.069 & 0.178 & 0.753 & 23.8 & 27.9 \\
Coal 5 & 0.050 & 0.250 & 0.700 & 0.069 & 0.224 & 0.707 & 34.8 & 29.8 \\
Coal 6 & 0.050 & 0.300 & 0.650 & 0.070 & 0.270 & 0.660 & 35.7 & 31.7 \\
Coal 7 & 0.050 & 0.350 & 0.600 & 0.070 & 0.317 & 0.613 & 46.6 & 33.7 \\
Coal 8 & 0.050 & 0.400 & 0.550 & 0.071 & 0.365 & 0.565 & 47.6 & 45.6}
\label{tab:sm_coal_sample_matrix}
\end{longtable}}
\begin{tablenotes}
\item[1]{Obtained from XYZ}
\end{tablenotes}
\end{ThreePartTable}
\end{document}