Impact Evaluation of High Energy Ball Milling Homogenization Process in the Phase Distribution of Hydroxyapatite-Barium Titanate Plasma Spray Biocoating
, Abel Hurtado Macias 1, Guillermo Herrera Pérez 1 and VÃctor M. Orozco Carmona 1,*
Round 1
Reviewer 1 Report
The authors evaluate the impact of high energy ball milling homogenization process in the phase distribution of Hydroxyapatite-Barium Titanate plasma spray biocoatings. The manuscript is concise and the data supports the conclusion. There are some things which need to be further improved:
- Authors should improve the quality of Figures 4 and 5. The EDX data is quite difficult to read (either improve the text size in the percentage and legends, or replot the graph). Also, the data to be read is only up to 10keV, so showing the data up to 20keV is just a waste of space in figures.
- Cracks in Figure 6 in the cross-sections images could be indicated in the images.
- Citations should be properly introduced, e.g. in cases like this "as mentioned by Okasaki M. et al. and LeGeros et al., the crystallite shrank of HA may..." after et al. the reference number is also required.
- English corrections are necessary before the article is published
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Reviewer 2 Report
Title: Impact evaluation of high energy ball milling homogenization process in the phase distribution of Hydroxyapatite-Barium Titanate plasma spray biocoating
Authors: Roberto Gómez Batres, Zelma S. Guzmán Escobedo, Irene Leal Berumen, Víctor M. Orozco Carmona
This manuscript, is focused on the influence of powder homogenization treatment by high-energy ball milling (HEBM) in developing a novel Hydroxyapatite-Barium titanate (HA/BT) composite coating deposited by APS (air plasma spray technique) in order to compare the impact of milling process. The phase and crystallite size were analyzed by X-Ray diffraction patterns (XRD); the BT-phase distribution in coating was analyzed by backscattered electron image (BSE) with scanning electron microscope (SEM); the energy-dispersive X-ray spectroscopy (EDS) analysis. Also the results of the adherence test is reported.
In my opinion, this manuscript could be considered for publication, after the following major changes:
- The authors should provide elemental mapping of the samples in order to highlights the distribution of the constituent elements in the samples.
- Can the authors add the results of the AFM studies for a better understanding of the surface morphology of the samples?
- Please provide more focused introduction section.
- Please provide SEM images at higher magnification.
- Furthermore, in the EDX spectra and XRD patterns it is difficult to understand the writing inside the figures. Please provide figures with an increased font size.
- Did the authors determine the thickness of the layers? Please add the results in the manuscript.
- Moreover please see and refer: http://dx.doi.org/10.1155/2013/194854, doi:10.1155/2015/926513,DOI:10.2478/s11532-014-0554-y, https://doi.org/10.3390/ma11081350
Regarding the biological assays, the results of cell adhesion and cell viability should be added to the manuscript
Comments for author File: 
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Reviewer 3 Report
Comments to "Impact evaluation of high energy ball milling homogenization process in the phase distribution of Hydroxyapatite Barium Titanate plasma spray bio coating".
1- The quality of presentation is poor and the text should be deeply revised starting from the use of English.
2- Hydroxyapatite is indicated with HA - line 14 - or HAp - line 42. Please choose one. Furthermore define acronyms/labels the first time they are used.
3- line 37 - what is "tor"?
4- line 45 - please cut "than the other".
5- please correct the hydroxyapatite formula into Ca10(PO4)6(OH)2
6- lines 54,55 are not clear: please re-write.
7- line 79- please give a reason for choosing these wt%.
8- line 82-84- do these materials consist of spherical particles? and is it 35-60 nanometers? Were the sizes measured by the Authors? Size distribution should be also taken into account.
9- line 99- what does "ELI" stand for?
10- line 123 section 2.3- description for statistical analysis method is missing.
11- lines 136,137- what do Authors mean with "two-homogenization process does not compromise crystal modification, phase transition, or possible reaction between HA and BT during the homogenization process"?
12- line 138 what is "thickness" in XRD?
13- lines 139,140- I would not refer to structures here. The comment should only refer to qualitative phase determination.
14- figure 1 and all the following- sample labels do not correspond to Table 1 and generate confusion.
15- line145- "In Figure 2 shows": please correct.
16- line 149 - I suppose the compound is CaO and not Ca0. Also please correct card number into 01-082-1690.
17- line 154 and following- please add details in the use of Scherrer's equation. How is it possible to calculate crystallite size if the peaks of the different phases are fused together?
18- lines 158-159- this comment is very qualitative and should be improved.
19- line 166- "be observed"?
20- lines 171 to 181- It is not possible to justify the increase of Ca/P molar ratio after phase conversion: the amount of Ca and P can not change because of thermal degradation (elements can not appear or disappear). Furthermore EDS is not a quantitative technique, unless treatment is performed properly. This section has to be deeply revised.
21- line 181- please revise the sentence "decrease in the Ca/P ratio may be due to the BT phase promoting the thermal stability of HA". In figure 2, when BT is present in high amount, the crystallinity of HA is definitely lower.
22- figure 3 b,d,f is in contrast with figure 5, where BSE images show BT phase aggregates (especially 5b and 5c). Please explain.
23- table 3 how many measurements were performed? Error is missing. Please see also comment #20.
24- Figure 6- how were cross-sections produced. Please describe the process in Experimental Section.
25- lines 198 to 204- characterization of pristine powders before coating deposition should be performed. Are there any differencies in the particles that would explain this different behaviour in the final coating?
26- Figure 6- cross section images show that HA and BT distributions are not homogeneous in the coatings (especially for HA50BT) for both mixing methods. Please comment on this in the text.
27- section3.2- Evaluation of coatings thickness is missing. It is an important parameter for mechanical performance that must be considered.
28- line 229- what is BSEI?
29- lines 237, 238- HA coating shows the highest value. Please comment these data accurately.
30- figure 7 Statistical analysis of data is missing.
31- lines 270 to 277- this discussion is obscure. Please re-write, also using correct punctuation.
32- line 281- please revise this part: high temperature can not cause "HA dehydration", simply because HA is not an hydrated phase and does not contain water. Once more, comprehension of observed phenomena would be easier after a characterization of starting powders. Indeed it is well known that hydroxyapatite does not convert into any other phase when it is highly crystalline and stoichiometric.
33- lines 284 to 289- please, see previous comments. This Discussion is not acceptable in the present form.
34- TTCP and TCP phases has been identified on the basis of 1 or 2 peaks into poorly crystalline mixtures of phases. Basing a discussion on this phase identification is a critical point.
35- line 321- the best BT concentration has been found to be 30wt%. In between. What about 20 or 40%. Considered concentrations are very large points.
36- many references are definitely old, i.e. ref 9, 10, 11. Please cite recent literature, that is very abundant on this topic.
Author Response
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Round 2
Reviewer 1 Report
The authors have made improvments to the manuscript. Nevertheless, it would have been nicer if the authors' justified the made changes in the answer to the reviewer comments (e.g. the modifications to XRD, the addition of 2 authors, the addition of the nanomechanical properties).
The manuscript is significantly improved after revision. There are still some issues to further improve: e.g. quality of Figure 4 (Rietveld - difficult to read), Figure 7, 8 (thought the tables with the composition from EDX are enlarged, there are not possible to read). Authors should check on improving the methods for saving figures with more DPI and better quality (this for most figures except for SEM, as the text on the axis is a bit blurry).
Author Response
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Reviewer 3 Report
The work has been improved by adding many new data and by rewriting large parts of the manuscript. Some points still need revision:
1 -The evaluation of crystalline domains by Scherrer equation using deconvolution of peaks is not accurate and is not useful for the general meaning of this work. The decrese in crystallinity is clear looking at the patterns, and should be only commented based on general peaks broadening. Please cut the numerical evaluation.
2-SEM images are poor and phase identification (and relative comments) is not properly conducted.
3 -The Statistical analysis of data (for example, please see figure 14 and table 5) is still missing. Please use a statistical evaluation test such as ANOVA test.
4 -All through the manuscript values are reported with errors (for example, line 285, line 329, table 3,4,5) without taking into account significant figures: i.e. 46.71 +- 7.32 is not correcvt and should be changed into 47+-7. Please revise all numbers.
5- Old references has been changed and very old references have been added. Please use more recent literature on coatings, that is very abundant.
Author Response
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