Synthesis and Morphological Characterization of Nanoporous Aluminum Oxide Films by Using a Single Anodization Step
Reviewer 1 Report
The authors present a study of the effect of various synthesis parameters upon the morphology of nanoporous aluminium oxide films obtain in a single step from an aluminium alloy.
Overall the presented results show nicely how varying each synthesis parameter has the expected effect of either increasing or decreasing different morphological parameters of the films and that generally higher temperature, higher voltages and higher electrolyte concentrations give better films...with the proviso that eventually if certain synthesis parameters are increased too far then oxide dissolution becomes dominant which hinders the film growth.
However I do not feel that the authors go far enough in this work; they make the point of stating that there can be advantages of doing single step (rather than double step) anodization using an Al alloy (rather than pure Al) for certain applications but they do not in anyway compare their films to films prepared in other ways in the literature. Additionally the authors claim that there cheaper and quicker to prepare films, despite being lower in quality, would still be suitable for various applications and I feel that the authors should demonstrate that their films can fulfill at least one of the applications they discuss. Both of these issues need to be addressed, along with the other more minor points listed below, before this manuscript can be considered suitable for publication.
1. Generally all sections need a thorough proof read to improve upon the clarity of the writing. Also current density should be j not i.
2. Detailed information (Supplier, grade etc.) need to be given for all materials used in the Materials and Methods section.
3. In the first paragraph of the Results and Discussion section a reference is made to a Table seems to be missing? Later on the only Table that appears in the manuscript is labelled as "Table 2" rather than "Table 1" so something is definitely missing here?
4. In the second and third paragraphs of the Results and Discussion section, whilst discussing Figure 1 a and Figure 1b, claims are made about what the data shows which is impossible to verify with the way the Figures are currently presented. Figure 1 needs to be redesigned so that it is possible to see that the statements made in these paragraphs are true. In addition in these Figures it is not clear whether all the samples do indeed show the behaviour explained in Figure 1c, the authors could use insets in Figure 1a and Figure 1b in order to make this clear. Also I am not sure that O0.3 T20 V60 is the best example to use to explain the behaviour in Figure 1c.
5. When discussing the results in Figure 4 at points the authors are stating that values are different when their error bars overlap...are these differences actually significant?
6. In the graphs in Figure 4 I do not think that curves should be fitted to the data points as they have no meaning. Additionally the formatting of the axes needs work, if nothing else then the symbols that are used to describe the different parameters in the text should be included on the y axis in the relevant graph.
7. In Table 2 the ranges, as well as the averages, should be given for the measured dp, dt, p and e values.
8. If possible it would be good to compare the behaviour of one of the samples made here, to a high quality hexagonal parralel pore sample, for one of the applications discussed?
9. The authors should at the least comment on what values of dp, dt, p and e would be good for the different potential applications they discuss.
Coming up next we disaggregate the comments of the reviewers (in blue text) and we answer each one separately (in bold black text).
We have redesigned Figures 1 and 4 and Table 2, also we have added 9 new references to support information incorporated to the text. In addition, we have considered necessary adding an Appendix A with relevant information requested by reviewers.
The changes in the content in the new version of the manuscript (reviewed) were highlighted in light blue text and the changes of English language were highlighted in green text.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1.The authors should indicate more clear in introduction and conclusions why and were are the result important for practical applications.
2.Table 1.: there are no indications about the analytical methods, which were used and there precision and reproducibility
3.The authors should give a scientific explanation how the concentration of oxalic acid influences the pore film thickness.
Coming up next we disaggregate the comments of the reviewers (in blue text) and we answer each one separately (in bold black text).
We have redesigned Figures 1 and 4 and Table 2, also we have added 9 new references to support information incorporated to the text. In addition, we have considered necessary adding an Appendix A with relevant information requested by reviewers.
The changes in the content in the new version of the manuscript (reviewed) were highlighted in light blue text and the changes of English language were highlighted in green text.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article presents a structural correlation analysis between AAO films and the primary synthesis parameters of temperature, acid concentration, and anodization voltage. In general the manuscript is well written with an explicit statement of the need/purpose of the study, a clear description of the experimental synthesis parameters, and the resulting data and conclusions. The results provide a straightforward addition to the well-established field of AAO porous films.The following comments are offered to improve the final version of the manuscript.
1.The use of the acronym OAA in the abstract for "anodic aluminium oxide" is more conventionally presented as AAO in many manuscripts. It is recommended to use AAO.
2.The nominal Aluminum film thickness is provided in Section 2.1 as 0.3 cm. The AAO film thickness results and corresponding discussion in Figure 4d would be more meaningful if the film thicknesses after pre-treatment are provided. Also, how were film cross sections prepared? How was the AAO film relative to the Al substrate optically determined?
3.Temperature control of the anodization bath is not specified. Was the bath temperature controlled and if so how? If not controlled, was there a temperature increase during the deposition process?
4.Was there a reason for the selection of 20, 30 and 40V and 0.3 and 0.9 M acid concentrations? If so, an explanation would better place the synthesis conditions and results in context.
5.Line 123: the use of the word "melt" is out of context and conveys the wrong connotation for the process being described.
6.Figure 1b would benefit from a smaller Y-axis interval.
7.What was the deposition time used for SEM images in Figure 2? Figure 1a and 1b show a 5 min deposition time, while Figure 1c shows 60 min. Explicitly specifying the deposition time used for samples shown and analyzed in Figure 2 will make the results more useful to readers.
8.Line 164-165: the suggestion of increased oxide solubility at elevated temperatures to account for differences in pore variation does not seem likely with a 40C temperature difference between 20 and 60C, unless actual oxide solubilities are detailed.
9.While not necessary for this manuscript, electrochemical impedance spectroscopy of the films to back-calculate the electrochemical specific surface area as a function of the synthesis conditions would be an interesting addition that would add value to surface area dependent applications.
10.Figure 4 lines connecting data points should be removed unless there is discussion of curve fitting and a rationale for the fitting (this would not be appropriate for the 0.9 M data with only 2 data points). Otherwise the data with error bars seems more appropriate.
Coming up next we disaggregate the comments of the reviewers (in blue text) and we answer each one separately (in bold black text).
We have redesigned Figures 1 and 4 and Table 2, also we have added 9 new references to support information incorporated to the text. In addition, we have considered necessary adding an Appendix A with relevant information requested by reviewers.
The changes in the content in the new version of the manuscript (reviewed) were highlighted in light blue text and the changes of English language were highlighted in green text.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
In this revision the authors have made great efforts to address the issues that were highlighted with the original manuscript for which they should be commended and it is now in my opinion essentially suitable for publication.
There is however still one small issue I would like to see worked on further before publication.
1.In Figure 1, which is now much improved thanks to the authors changes, I believe that the insets in part a and part b should be over only the first minute (rather than the first five minutes) so that it is easier to see whether or not the minimum current density is reached quicker as the authors state. Currently in these insets it is not really possible to tell whether this is true or not.
Coming up next we disaggregate the comments of the reviewers (in blue text) and we answer each one separately (in bold black text).
We have redesigned Figures 1 and 4 and homogenized the sizes of the SEM images of Figures 2 and 3.
The changes in the content in the new version of the manuscript (2nd time reviewed) were highlighted in red text and the changes of English language were highlighted in green text.
Author Response File: Author Response.pdf
Reviewer 2 Report
Thank you for the corrections! Congratulations.
Changes in the first revised version of the manuscript, which were highlighted using the light-blue and green text, were all accepted in the new (2nd) revised version.
Coming up next we disaggregate the comments of the reviewers (in blue text) and we answer each one separately (in bold black text).
We have redesigned Figures 1 and 4 and homogenized the sizes of the SEM images of Figures 2 and 3.
The changes in the content in the new version of the manuscript (2nd time reviewed) were highlighted in red text and the changes of English language were highlighted in green text.
Author Response File: Author Response.pdf
Reviewer 3 Report
The edits and figure modifications resulted in a much improved manuscript that is recommended for publication. In particular the conceptual flow of the paper is now better linked to the details/data provided and figure representations.
Here are a few notes to consider for the final editing for publication:
1.Figure 1a: consider moving the legend outside the plot region so as to not obstruct the I-t curves. Consider decreasing the number of labeled y-axis tick marks on the inset graph.
2.Line 204: "synthetized" should be "synthesized"
3.Figure 4d: should the 4d y-axis label have an overbar on the "e" to correspond to the text in Line 244?
Changes in the first revised version of the manuscript, which were highlighted using the light-blue and green text, were all accepted in the new (2nd) revised version.
Coming up next we disaggregate the comments of the reviewers (in blue text) and we answer each one separately (in bold black text).
We have redesigned Figures 1 and 4 and homogenized the sizes of the SEM images of Figures 2 and 3.
The changes in the content in the new version of the manuscript (2nd time reviewed) were highlighted in red text and the changes of English language were highlighted in green text.
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
Thank you for making the improvements I suggested to Figure 1, they finish this paper off nicely.
