Review Reports

Round 1

Reviewer 1 Report

1. Test can be extended for other mechanical properties because, with hardness, it is hard to conclude the material property for a specific application

2. Overall volume of the article seems very less. So adding some more mechanical testing is appreciable. 

3. As the article focuses on hardness, discussing the homogenesis dispersion of materials directly relates to hardness, which answers the value obtained.

4. Please elaborate on specific load application in N with the hardness value obtained for 45Fe-Cu-HA and 50Fe-Cu-HA and state the inference.

5. As whole specific inferences are missing, which can be possibly included in the concluding session. 

6. References can be included seems very minimum. Also, the latest reference is only one in 2022.  

7. It would be great with test results to include this particular composite that can be used for a specific application. 

Author Response

1. Test can be extended for other mechanical properties because, with hardness, it is hard to conclude the material property for a specific application

 Response. Thanks the reviewer for the valuable comment. The study is new and this manuscript represents the first important results of the evaluation of the produced materials. The study of microhardness allows to evaluate several parameters of the material. Those tests are carried out in a wide range of loads, which makes it possible to determine the hardness not only in the surface layer, but also in the structure of materials, as well as to determine their heterogeneity. In addition, the values of the materials microhardness are affected by the shape of the indenter, the magnitude of the applied load and the dimensions of the diagonals of the indenter print [Matyunin V. M., Abusaif N., Marchenkov A. Y. Analysis of the indentation size effect on the hardness measurements of materials //Journal of Physics: Conference Series. – IOP Publishing, 2019. – Т. 1399. – №. 4. – С. 044016.], [Petrík J. et al. The automatic testers in microhardness measurement and ISE effect //Acta Metallurgica Slovaca. – 2016. – Т. 22. – №. 3. – С. 195-205].

There are many works published in high-rating journals including this research method as the main or the only one. Examples of such publications are below. [Muslić M. et al. Indentation Size Effect of Composite A356+ 6% FA Subjected to ECAP //Metals. – 2022. – Т. 12. – №. 5. – С. 821.]

2. Overall volume of the article seems very less. So adding some more mechanical testing is appreciable.

Response. Overall volume of the article satisfies the requirements of the journal.

3. As the article focuses on hardness, discussing the homogenesis dispersion of materials directly relates to hardness, which answers the value obtained.

Response. Our material is a solid heterogeneous system, since it is a composite material consisting of several phases, which does not allow one specific hardness value to be obtained. Therefore, the Vickers hardness for each sample was measured in the load range from 0.25 to 9.8 N, with different indentation depths and in different areas of the surface throughout the material. Small applied loads make it possible to investigate only the near-surface layer of the material, and with increasing load, the indentation depth increases. However, the most stable hardness values for all the samples are observed at loads of 2.94 and 4.9N, at which the microhardness for 50Fe-Cu-HA is 940±70 and 870±7 MPa, for 45Fe-Cu-HA - 1140±45 and 1160±30 MPa, and for the 40Fe-Cu-HA sample, the hardness is 1050±45 and 1020±55 MPa, respectively. Thus, it was found that the microhardness of the samples significantly decreases with increasing load from 0.25 to 2.94 N, and with a further increasing the load, microhardness changes insignificantly. This behavior of the material’s mechanical properties is due to the presence of a thin near-surface layer with high hardness. In addition, statistical analysis shows that the distribution of the random value of microhardness obeys the normal (Gaussian) law.        

4. Please elaborate on specific load application in N with the hardness value obtained for 45Fe-Cu-HA and 50Fe-Cu-HA and state the inference.

Response. Additions describing the results of the study of samples 45Fe-Cu-HA and 50Fe-Cu-HA are inserted into the article.

5. As whole specific inferences are missing, which can be possibly included in the concluding session.

Response. Some additions have been added to the article in the results section. In addition, the conclusion already contains following information: “The 45Fe-Cu-HA samples were characterized by the highest microhardness values, 1623-965 MPa at a load of 0.25-10 N, which is on average 26% higher than for the 50Fe-Cu-HA samples with the lowest microhardness values. This result is in a good agreement with the results obtained by the SEM method. In the 45Fe-Cu-HA composite, the most uniform distribution of iron and HA particles was observed, which contributed to an increase in its mechanical.”

6. References can be included seems very minimum. Also, the latest reference is only one in 2022.

Response. Thank you for the recommendation, we have included new links in the article with more recent publications.

7. It would be great with test results to include this particular composite that can be used for a specific application.

Response. Specific results of the study of samples with the best mechanical properties were included in the conclusion section. The composite material obtained as a result of the study can be recommended as a bone substitute for the temporary performance of its functions. For example, to create implants for osteosynthesis.

Reviewer 2 Report

The manuscript deals with ‘Bioresorbable Fe-Cu-Hydroxyapatite Composite by 3D printing. The proposed research topic has high scientific values. Some comments are given bellow for the authors, need to be clarified for making final decision on the manuscript.

The statement at Line 82 “Based on these two competing factors, the most optimal polymer is EVA EA28025 with a content of 28 wt. %VA” need to be supported with proper reference.

Paragraph 112-115: To prevent further oxidation of the metal part of the powder the polymer part was plasticized by heating under acetone at a temperature of 100 °C in an ultrasonic bath Ferroplast VU- 09-”Ya-FP”-03 (Ferroplast, Yaroslavl, Russia) which allowed to limit the direct contact of the atmosphere with Fe and Cu particles.

Please clarify whether the above procedure is feasible in presence of acetone at 100 °C. Has it been practiced by any other researchers?

It is suggested to compare the microhardness values of Fe-Cu-HA samples with bone/other biomedical implants. It would give us an idea to understand the scope of the Fe-Cu-HA biocomposites.

Studies on antibacterial and bioactive properties are not shown in this paper. You may suggest in the conclusion of the paper as future direction of this work.

Author Response

The statement at Line 82 “Based on these two competing factors, the most optimal polymer is EVA EA28025 with a content of 28 wt. %VA” need to be supported with proper reference.

Response. Thank you for your comment. We have added a link to a study confirming our information in the introduction section.

Paragraph 112-115: To prevent further oxidation of the metal part of the powder the polymer part was plasticized by heating under acetone at a temperature of 100 °C in an ultrasonic bath Ferroplast VU- 09-”Ya-FP”-03 (Ferroplast, Yaroslavl, Russia) which allowed to limit the direct contact of the atmosphere with Fe and Cu particles. Please clarify whether the above procedure is feasible in presence of acetone at 100 °C. Has it been practiced by any other researchers?

Response. Thank you for pointing this out. We heated the mixture of powders and polymer under acetone at 50°C. We corrected this mistake in the text of the manuscript.

It is suggested to compare the microhardness values of Fe-Cu-HA samples with bone/other biomedical implants. It would give us an idea to understand the scope of the Fe-Cu-HA biocomposites.

Response. Your comment has been taken into account. Information on hardness studies of other biodegradable materials has been added in the results and discussion section [https://doi.org/10.1016/j.heliyon.2022.e11712].

 

Studies on antibacterial and bioactive properties are not shown in this paper. You may suggest in the conclusion of the paper as future direction of this work.

Response. Thank you for your comment, we will definitely add an information about biological testing of samples. The next step in our study is to carry out the biological tests on composites of these compositions to determine the optimal concentrations of the polymer binder in medical devices.

Reviewer 3 Report

March, 30, 2023

Dear authors

 

Thank you for an interesting report.

 

In this study, you examined bioresorbable Fe-Cu-Hydroxyapatite composite by 3D printing. In view of the rapid progress of digitization in many medical and dental fields have resulted in the contribution to improve the workability and functions of many materials, this research will be of interest to many readers of this journal.

I agree to some parts of your claims and guessed that the subject of this paper will be of interest to the readership of Coating. However, I think that minor revisions are required as follows:

 

1. Introduction

1. Regarding the use of Cu, although some merits such as antibacterial properties can be expected, demerits such as the development of allergies are also conceivable. You do not mention that. Considering the usage, I think you should mention that point.

 

2. Materials and Methods

1. To make it easier for the reader to read this article, I think you should insert an image of the samples, Fe-Cu(-HA) powders, and flow charts or simple diagrams of the experimental method in this section.

2. It is not stated how many samples were prepared for each compounding condition and whether the number of samples is reasonable. I think you should analyze statistically for the values of hardness.

 

3. Results

1. You should revise this section title to “4. Results and Discussion''.

2. It is not scientific to mention about comparison of hardness without statistical analysis. You should perform a statistical analysis and document its results in this section.

 

Author Response

Introduction

1. Regarding the use of Cu, although some merits such as antibacterial properties can be expected, demerits such as the development of allergies are also conceivable. You do not mention that. Considering the usage, I think you should mention that point.

Response. Thanks for the reminder of the possible toxic effects of copper at certain concentrations. We have added information about this to the introduction section.

 Materials and methods

1. To make it easier for the reader to read this article, I think you should insert an image of the samples, Fe-Cu(-HA) powders, and flow charts or simple diagrams of the experimental method in this section.

Response. Thank you for the important note. We have added the schema to section 2. Materials and Methods.

2. It is not stated how many samples were prepared for each compounding condition and whether the number of samples is reasonable. I think you should analyze statistically for the values of hardness.

Response. Thank you for the fair comment. To study microhardness 3 samples were prepared with different ratios of powder and polymer components. This information has been added to the materials and methods section.

Conclusions

1. You should revise this section title to “4. Results and Discussion''

Response. Your comment has been taken into account. The title of the «results» section has been changed to «Results and Discussion». Section «conclusions» contains only main inferences of the article.

2. It is not scientific to mention about comparison of hardness without statistical analysis. You should perform a statistical analysis and document its results in this section.

Response. We thank you for this remark. In the work, the processing of experimental data was carried out and a statistical analysis was performed. Information on the amount of samples prepared for testing has been added to the materials and methods section. In addition, Table 3 and Figure 10 show confidence intervals that indicate the statistical processing of the results obtained. Additional considerations are included in the results and discussions section.

Reviewer 4 Report

-The method employed to produce the nanopowders is initially referred to as electric explosion of wire (EEW) (line 97), however later it has been referred to as in different forms such as EEP (line 98), and EET (line 183). It needs to be consistent!

-Figure 3(c), the elements' names can hardly be read, and are very blurry. 

-Line 205: "(40, 50, and 60%)" is mentioned when discussing the powder ratio, however, aren't the powder ratios 40, 45, and 50%?

-In figure 9, the XRD peaks, at lease for one of the lines, can be labeled so that it is easier for the reader without going back to the initial XRD figure. 

-Starting from line 256, are the tables misnamed in the text? for example in lines 257 and 261, isn't table 2 rather than table 3 being referred to? and in line 267, isn't table 3 being referred to rather than table 4? (in fact there is no table 4 in the paper)

-It has been concluded that a powder to polymer ratio of 45 to 55 wt. % would be preferred as a biomaterial, but is that a correct conclusion considering the fact that this paper has not evaluated the materials in-vitro or a more realistic environment, whereby the performance in that situation might also need to be taken into account?

Author Response

1. The method employed to produce the nanopowders is initially referred to as electric explosion of wire (EEW) (line 97), however later it has been referred to as in different forms such as EEP (line 98), and EET (line 183). It needs to be consistent!

 Response. Thank you for pointing out these inconsistencies. We have corrected these misprints.

 2. Figure 3(c), the elements' names can hardly be read, and are very blurry.

 Response. Figure 3 has been corrected and replaced.

 3. Line 205: "(40, 50, and 60%)" is mentioned when discussing the powder ratio, however, aren't the powder ratios 40, 45, and 50%?

Response. Thank you for noticing this point, the mistake has been corrected.

4. In figure 9, the XRD peaks, at lease for one of the lines, can be labeled so that it is easier for the reader without going back to the initial XRD figure.

 Response. Thank you for the important note. Figure 9 has been modified according to the reviewers recommendation.

 5. Starting from line 256, are the tables misnamed in the text? for example in lines 257 and 261, isn't table 2 rather than table 3 being referred to? and in line 267, isn't table 3 being referred to rather than table 4? (in fact there is no table 4 in the paper)

 Response. Misprints in table references have been corrected.

6. It has been concluded that a powder to polymer ratio of 45 to 55 wt. % would be preferred as a biomaterial, but is that a correct conclusion considering the fact that this paper has not evaluated the materials in-vitro or a more realistic environment, whereby the performance in that situation might also need to be taken into account?

 Response. Thank you for your valuable comment. We reformulated this sentence and added it to the conclusions section.

Thus, a composite with a ratio of 45 to 55 wt. % of the cermet and polymer parts showed a higher microhardness compared to other composites and a more uniform distribution of antibacterial copper particles and bioactive hydroxyapatite particles, which can improve the biological properties of the material. In the future, a comparative study of the in vitro biological properties of three groups of composites is planned.