Cold Spraying of Thick Biomimetic and Stoichiometric Apatite Coatings for Orthopaedic Implants
Round 1
Reviewer 1 Report
The manuscript presents an interesting study about the deposition of hydroxyapatite coating by cold spraying in order to improve the osteointegration properties of the metallic implant. The coating characteristics were studied by XRD, SEM, FTIR etc. The paper needs major revisions before it is processed further, some comments follow:
Title
The title is unclear. Please consider replacing the title with a clear formula that reflects the content of the manuscript.
Abstract
Add a brief description of the main methods used to characterize the coating. Also, it is very important to know the material used as substrate. Please write this information.
Materials and Methods
Add a table with the chemical composition of the Ti6Al4V used in this study. Also, add some words about the preparation of the samples.
Please add a table with the sample acronym and different characteristics.
Figure 1 doesn’t have scientific value, please remove it.
Results
In order to be easier for the reader to follow, please split this section into subsections taking considering the characterization type, and do the same in the discussion section.
Figures 4, 5, 8, 9. Please introduce figure labels to highlight the interest zone for the reader (cracks, residual corundum grains, the type of the grain etc.
Figures 1, 3, 4, 5 and 6 are unclear. Please replace them.
Figure 12. It will be recommended that the authors add a table with the %wt of chemical elements.
Conclusions
The conclusion section should be improved. Conclusions present some of the results discussed above in the paper with very limited discussion. The conclusions can be written by points with highlights.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript presents the feasibility of producing cold spray coatings on metallic substrates using biomimetic and stoichiometric apatite powders. The manuscript is well written and supported by XRD, FTIR, and EDX analysis. However, the manuscript needs more characterization to claim the conclusion. Authors should address the following before it is considered for publication. Some comments and suggestions are
- Novelty of the work should be stated more precisely
- What is meant by biomimetic apatite? Poorly crystalline apatite is biomimetic?
- Cazalbou et al. have prepared poorly crystalline apatite according to ref.30. The authors also used the same procedure to prepare apatite and claim it is biomimetic. More clarification is needed in this aspect based on the literature.
- Why did the authors use "apatite" instead of "hydroxyapatite"?
- Synthesis of procedure for biomimetic apatite should be included.
- What is meant by Stoichiometric hydroxyapatite? How did authors claim without precise characterization like XPS?
- How do authors claim prepared HAp is nanocrystalline? May particle size be calculated using the Scherrer equation using XRD. It is recommended to take SEM and TEM at high magnification because particle size and shape are vital in their characteristics.
- In XRD: X-axis is 20-100. However, data is provided only below 80. Why? However, in the characterization part, it is 10-90?
- Provide proper X-axis and y-axis labels in FTIR. Refer literature.
- BNAc powder is A-type of B-type apatite? Clarify it with the help of literature data?
- Detailed elemental composition should be included to claim the conclusion.
- Typographical errors should be checked and corrected in the overall manuscript.
- Already a lot of work exists on cold spray coatings of HAp on the metal substrate? Authors may state the novelty and scientific significance more precisely.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors addressed all of my comments. The manuscript can be accepted as it is.
Author Response
Dear Reviewer,
once again, thanks for your help in improving our paper.
On behalf of all authors,
Best regards,
Ambra Paterlini
Reviewer 2 Report
The revised version is recommended for publication
Author Response
Dear Reviewer,
once again, thanks for your help in improving our paper.
On behalf of all authors,
Best regards,
Ambra Paterlini
