## 3 Results  
The identification of the functional group by FTIR is shown in Figure 1. The redshift of the absorption peak of the FTIR spectrum is observed. The spectra from 1031.92 cm\({}^{-1}\) to 1035.77 cm\({}^{-1}\) corresponds to the P-O stretching vibrations. This indicates a chemical interaction of n-HA (PO4\({}^{3-}\) functional group) with Ch and CMC. The blueshift is detected from the absorption peak of the FTIR spectrum from 1656.85 cm\({}^{-1}\) to 1591.27 cm\({}^{-1}\). This peak corresponds to N-H stretching vibrations. This peak has resulted from the chemical interaction of Ch (NH3\({}^{+}\) functional group) with n-HA and CMC. The CH2 functional group of CMC in the samples is detected at 1467.83 cm\({}^{-1}\) for sample B, \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Samples** & **n-HA:Ch:CMC (wt\%)** & **n-HA (g)** & **Ch (g)** & **CMC (g)** \\ \hline A & 40:60:0 & 4 & 6 & 0 \\ \hline B & 40:55:5 & 4 & 5.5 & 0.5 \\ \hline C & 40:50:10 & 4 & 5 & 1 \\ \hline D & 40:45:15 & 4 & 4.5 & 1.5 \\ \hline E & 40:40:20 & 4 & 4 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition details of nano-hydroxapatite (n-HA), chitosan (Ch), and carboxymethyl cellulose (CMC). and at 1460.11 cm\({}^{-1}\) for samples C, D, and E. The COO\({}^{-}\) functional group of CMC has disappeared in samples C, D, and E, at 1591.27, 1589.34, and 1591.27 cm\({}^{-1}\), respectively. The COO\({}^{-}\) functional group of CMC is undetectable in sample B, probably due to its small composition (CMC 5 wt%). It is important to note that the COO\({}^{-}\) in the CMC acts as a crosslink with NH\({}_{3}\)\({}^{+}\) in the Ch. According to FTIR results, the COO\({}^{-}\) have similar spectrum energy with NH\({}_{3}\)\({}^{+}\) around 1610-1580 cm\({}^{-1}\). This indicates strong bonding to enhance the compressive strength of the samples. To understand the porosity of the samples, we used a liquid displacement method to quantify the porosity. Figure 2 (black line) shows the relations of porosity in the samples with CMC contents. The samples (B, C, D, and E) have porosity around 37.51-61.72%. This is predicted as a standard value of porosity required for the scaffold to use as a template for bone cell regeneration and growth [5]. High porosity is found in the sample without CMC (sample A) at about 85.92%, due to its high Ch content. We found that the porosity decreases with increasing CMC contents. The mechanical strength of the samples increases with increasing CMC content. The highest compressive strength coefficient is found at 5.47 MPa for sample E, as depicted in Figure 2 (blue line). A minimum mechanical strength of the scaffold for cancellous bone application is about 2 MPa. This condition is fulfilled in samples C, D, and E. Moreover, according to Figure 2, we found that the porosity and mechanical strength are strongly correlated. The Ch, which acts as pore-forming [12], has hydrophilic ability to generate a strong bonding with CMC. Consequently, the porosity decreases [18], but it can enhance the compressive strength. Figure 1: FTIR spectrum of nanocomposite n-HA/Ch/CMC with variation in CMC composition. We visualized the porosity of the samples by SEM measurements, as depicted in Figure 3. The SEM images are taken from the surface (Figure 3a-e) and cross-section (Figure 3f-j) areas of the samples. The SEM results of both surface and cross-sectional areas of the sample reveal the average pore sizes of \(\sim\)100 \(\upmu\)m. This is known as the minimum size required for bone cell regeneration and growth templates [2]. These results explicitly show that the porosity decreases with increasing CMC content, in agreement with the quantification of porosity using liquid displacement method results, as shown in Figure 2.  
The scaffold for BTE application should be able to degrade gradually, since it is implanted in the human body. This gradual degradation is important, because the cells of bone need some time to grow in the scaffold.