Coupled effect of particle size of the source materials and calcination temperature on the direct synthesis of hydroxyapatite

We report the effect of controlled particle size (obtained by using 80, 100, 120, 140 and 200 mesh) of the source materials on the synthesis of a well-known biomaterial, hydroxyapatite (Hap). In addition to this, we have also mapped the consequence of applied temperature (700°C, 800°C and 900°C) on the crystallographic properties and phase composition of the obtained Hap. Nevertheless, although with Hap, in each case, β-tricalcium phosphate (β-TCP) was registered as the secondary phase the ANOVA test revealed that the results of the crystallographic parameters are significantly different for the applied sintering temperature 700°C and 800°C (p < 0.05), while the data obtained for calcination temperature 800°C are not significantly different from that acquired at 900°C (p > 0.05). Fourier transform infrared spectrophotometer data ensured that, irrespective of mesh size and calcination temperature, the synthesized Hap samples were of carbonated apatite with B-type substitution. Interestingly, for all cases, the % of carbonate content was below the maximum limit (8%) of the CO32− ion present in bone tissue hydroxyapatite.


1.
In present manuscript shows more number of self-citations. Rather, I suggest authors to include recently available appropriate references related to the current work. 2.
Page No. 7 (Table no. 1) … Next to examine the effect of mesh size together with the calcination temperature on the crystallographic properties of Hap, the crystallite size (Dc), crystallinity degree (Xc) and crystallinity index (CI), dislocation density (δ) and micro-strain (Ɛ) of all the Hap samples were calculated using well-established equations and summarized. Authors should justify it by adding more discussion and references. 3. Figure 13, In the FT-IR spectrum, Give the more information of presence of Phosphate band for the formation of Hap. Authors should justify it by adding more discussion and references. 4. Figure 14, In the Raman Spectra, elaborate more with adding more discussion and references.

5.
There are few type grammatical errors; authors need to check throughout the manuscript.

Comments to the Author(s)
The paper reports a significant finding about the synthesis of HAP, but certain facts has to be made clear before it being accepted for publication (see Appendix A).

Decision letter (RSOS-210684.R0)
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Dear Dr AHMED: Title: Coupled effect of particle size of the source materials and calcination temperature on the direct synthesis of hydroxyapatite Manuscript ID: RSOS-210684 Thank you for submitting the above manuscript to Royal Society Open Science. On behalf of the Editors and the Royal Society of Chemistry, I am pleased to inform you that your manuscript will be accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the reviewers' comments at the end of this email.
The reviewers and handling editors have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your manuscript.
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Supplementary files will be published alongside the paper on the journal website and posted on the online figshare repository (https://figshare.com). The heading and legend provided for each supplementary file during the submission process will be used to create the figshare page, so please ensure these are accurate and informative so that your files can be found in searches. Files on figshare will be made available approximately one week before the accompanying article so that the supplementary material can be attributed a unique DOI. ********************************************** RSC Associate Editor: Comments to the Author: Accept with minor revisions RSC Subject Editor: Comments to the Author: (There are no comments.) ********************************************** Reviewer comments to Author: Reviewer: 1 Comments to the Author(s) In this manuscript the authors described the effect of controlled particle size (obtained by using 80, 100, 120, 140 and 200 mesh) of the source materials on the synthesis of well-known biomaterial, hydroxyapatite. In addition to this, we also mapped the consequence of applied temperature (700⁰C, 800⁰C and 900⁰C) on the crystallographic properties and phase composition of the obtained Hap. Nevertheless, though with hydroxyapatite, in each case β-tricalcium phosphate (β-TCP) was registered as the secondary phase but the ANOVA test revealed that the results of the crystallographic parameters are significantly different for the applied sintering temperature 700⁰C and 800⁰C (p<0.05) while the data obtained for calcination temperature 800⁰C are not significantly different from that acquired at 900⁰C (P>0.05). So I recommend the Manuscript to be accepted for publication. However, before publication minor revisions are required to improve the manuscript.
1. In present manuscript shows more number of self-citations. Rather, I suggest authors to include recently available appropriate references related to the current work. 2. Page No. 7 (Table no. 1) … Next to examine the effect of mesh size together with the calcination temperature on the crystallographic properties of Hap, the crystallite size (Dc), crystallinity degree (Xc) and crystallinity index (CI), dislocation density (δ) and micro-strain (Ɛ) of all the Hap samples were calculated using well-established equations and summarized. Authors should justify it by adding more discussion and references. 3. Figure 13, In the FT-IR spectrum, Give the more information of presence of Phosphate band for the formation of Hap. Authors should justify it by adding more discussion and references. 4. Figure 14, In the Raman Spectra, elaborate more with adding more discussion and references. 5. There are few type grammatical errors; authors need to check throughout the manuscript.

Recommendation? Accept as is
Comments to the Author(s) Arthurs have satisfactory gave the answers to comments in the review manuscript

Recommendation? Accept as is
Comments to the Author(s) As they revised the manuscript satisfactorily, it may be accepted in the present form

Decision letter (RSOS-210684.R1)
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Dear Dr AHMED:
Title: Coupled effect of particle size of the source materials and calcination temperature on the direct synthesis of hydroxyapatite Manuscript ID: RSOS-210684.R1 It is a pleasure to accept your manuscript in its current form for publication in Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
The comments of the reviewer(s) who reviewed your manuscript are included at the end of this email.
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Thank you for your fine contribution. On behalf of the Editors of Royal Society Open Science and the Royal Society of Chemistry, I look forward to your continued contributions to the Journal. The manuscript entitled "Coupled effect of particle size of the source materials and calcination temperature on the direct synthesis of hydroxyapatite" submitted to Royal Society Open Science appears to be an interesting piece of scientific finding done in the area of biomaterials science. The findings are well supported by the experimental results followed by adequate discussions to support the findings. The manuscript could be published to a wider audience provided the authors could make some corrections regarding few details they have provided in the manuscript.

#1
In the introduction, the authors have stated that the paper is "intended to examine the coupled effect of particle size of the source materials and calcination temperature to synthesize hydroxyapatite by solid state method, but later they state "Apparently it is visualized from Table 1 and Figs. 11 & 12 that neither the particle size of the raw materials nor the calcination temperatures effect the crystallographic parameters (apart from crystallinity degree) data significantly". Then what do the really intent to report in this paper? The authors need to clarify this.

# 2
For synthesizing the HAP samples, heating was achieved through oven and calcination.
The temperature for oven drying and the time duration was not mentioned. It would give more clarity.

#3
While reporting for HAP through FTIR (Fig. 13), a typical band around 3450 cm -1 which is characteristic of HAP otherwise it could be other calcium phosphate also. Why has it not been observed or accounted?

#4
The XRD analysis of samples (Figs. 5 -10) show significant percentage of  -TCP even after 700  C, which should have been otherwise showing a complete phase transformation to HAP. Can the authors give their rationale?

#5
Significant amount of CO2 is present in the resulting HAP samples raises doubt whether it was incomplete decomposition of calcite or just atmospheric trapping?

#6
There are few grammatical errors which could be corrected during the revision of the manuscript Overall Comment : The manuscript could be accepted after "Minor Revision"

1.
In the introduction, the authors have stated that the paper is "intended to examine the coupled effect of particle size of the source materials and calcination temperature to synthesize hydroxyapatite by solid state method, but later they state "Apparently it is visualized from Table 1 and Figs. 11 & 12 that neither the particle size of the raw materials nor the calcination temperatures effect the crystallographic parameters (apart from crystallinity degree) data significantly". Then what do the really intent to report in this paper? The authors need to clarify this.
Ans. We, here in this paper attempted to examine the dual effect of particle size of the source materials and calcination temperature on the direct synthesis of hydroxyapatite. Consequently, we investigated various crystallographic properties e.g. crystallite size (Dc), crystallinity degree (Xc) and crystallinity index (CI), dislocation density () and micro-strain () of all the Hap samples prepared under the present experimental protocol. The data as shown in Table 1 and Figs. 11 & 12 though apparently shows no significant changes but in terms of percentage the changes were important. For instance, the calculated crystallite size (Dc) for C-2 (120 mesh sieved and calcined at 800C) Hap is 41 nm while for D-1 (140 mesh sieved and calcined at 700C) it is 105 nm. Hence an inflation of 256% was achieved which is obviously significant. Again crystallinity index (CI) varied from 0.8 to 1.6 (i.e. 200% variation), dislocation density () varied from 0.09 to 0.56 (622% variation) etc. Though the values seem to be small but their variations are large and significant. For this reason, we considered the ANOVA analysis to make a conclusion regarding the dual effect of particle size of the source materials and calcination temperature on the direct synthesis of Hap. Necessary clarification added in the relevant section (marked with red ink)

2.
For synthesizing the HAP samples, heating was achieved through oven and calcination. The temperature for oven drying and the time duration was not mentioned. It would give more clarity.