My table is going out of the right margin, please help how to extend it vertically of fix it?

Question

\begin{table}[hbpt!]
\begin{tabular}{|c|c|c|c|c|}
\hline
\textbf{Synthesis} &
  \textbf{Technique} &
  \textbf{Product} &
  \textbf{Temperature (°C)} &
  \textbf{properties} \\ \hline
\multirow{4}{*}{SiC powders} & Reduction of silica by carbon                    & $\beta$-SiC     & 1800               & Fine   powder           \\ \cline{2-5} 
                             & Siliconization   of carbon                         & $\beta$-SiC     & 1380   or 1200-300 & Coarse   powder         \\ \cline{2-5} 
                             & Chemical   vapor deposition (CVD)                  & $\beta$-SiC     & -                  & Fine   powder           \\ \cline{2-5} 
 &
  \begin{tabular}[c]{@{}c@{}}Liquid-phase raw materials\\ and precursor method\end{tabular} &
  $\beta$-SiC &
  1600-1800°C &
  Fine   powder \\ \hline
\multirow{5}{*}{SiC in bulk} & Lely   method                                      & $\alpha$-SiC     & $\sim$2700°C       & Large   single crystals \\ \cline{2-5} 
                             & Molten   metal method                              & Polytypes & High   Temperature & Inorganic   crystals    \\ \cline{2-5} 
                             & \multirow{2}{*}{Chemical   vapor deposition (CVD)} & $\alpha$-SiC     & 2000-2300°C        & single   crystals       \\ \cline{3-5} 
                             &                                                    & $\beta$-SiC     & \textless{}2000°C  & single   crystals       \\ \cline{2-5} 
                             & Aqueous   solution method                          & SiC       & -                  & Polycrystalline   films \\ \hline
\end{tabular}
\caption{Classification of methods for SiC synthesis (powders and bulk) \cite{3}}
\label{tab:1}
\end{table}

Answer 1

I would like to recommend allowing automatic line breaks in columns 2, 4, and 5. This may be achieved by employing a tabularx environment; see below for a specific implementation. I would also employ hanging indentation to make it easier to see where the cells are.

Furthermore, I would like to suggest that you get rid of the \multirow directives and replace all \cline directives with (vertical) whitespace, in order to give the table a more open and inviting look. Separately, do consider employing the line-drawing macros of the booktabs package instead of the basic \hline and \cline macros.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tabularx,ragged2e,booktabs}
\newcolumntype{L}{>{\RaggedRight\hspace{0pt}\hangindent=0.75em\hangafter=1}X}
\newlength\mylen
\settowidth\mylen{Polytypes} % measure width of column #3
\begin{document}
\begin{table}[hbpt!]
\setlength\tabcolsep{3pt} % default: 6pt
\begin{tabularx}{\textwidth}{@{} l L p{\mylen} L L @{}}
\toprule
  \textbf{Synthesis} &
  \textbf{Technique} &
  \textbf{Product} &
  \textbf{Temperature} &
  \textbf{Properties} \ 
\midrule
SiC powders
  & Reduction of silica by carbon
  & $\beta$-SiC
  & 1800°C
  & Fine powder \ 
  \addlinespace 
  & Siliconization of carbon 
  & $\beta$-SiC

  & 1380°C or \mbox{1200--1300°C}
  & Coarse powder \ 
  \addlinespace 
  & Chemical vapor deposition (CVD) 
  & $\beta$-SiC & --  & Fine powder  \ 
  \addlinespace 
  & Liquid-phase raw materials and precursor method 
  & $\beta$-SiC 
  & 1600--1800°C 
  & Fine powder \ 
\midrule
SiC in bulk
  & Lely method 
  & $\alpha$-SiC 
  & $\approx$2700°C 
  & Large single crystals \ 
  \addlinespace 
  & Molten metal method 
  & Polytypes 
  & High temperature 
  & Inorganic crystals \ 
  \addlinespace 
  & Chemical vapor deposition (CVD) 
    & $\alpha$-SiC \newline $\beta$-SiC 
    & 2000--2300°C \newline $<$,2000°C
    & single crystals \newline single crystals \ 
  \addlinespace

  & Aqueous solution method 
  & SiC
  & --
  & Polycrystalline films \ 
\bottomrule
\end{tabularx}
\caption{Classification of methods for SiC synthesis (powders 
         and bulk) \cite{3}}
\label{tab:SiC_methods}
\end{table}
\end{document}