Synthesis and Formation Mechanism of Metal Oxide Compounds
, Zhuldyz Sagdoldina 1, Kyztore Torebek 3, Daryn Baizhan 1,*, Yedilzhan Kambarov 1, Michael Yermolenko 4, Saule Abdulina 5 and Meruyert Maulet 1
Round 1
Reviewer 1 Report
The Authors present a conclusive study of the synthesis and formation of metal oxide coatings. Only a few remarks should be addressed before publication.
1. The noise level is high in the diffractograms d) and e) in Figure 2. Please try to reduce it as the presence of some XRD peaks is questionable.
2. Please correct the presentation of phases, e.g. TiO2 should be presented as TiO2.
3. I would suggest presenting crystallite size values for the formed phases.
4. Please avoid using the word „gray“ for different bands on SEM images, it confuses the readers.
5. Table 5: Please divide the data for each sample by horizontal lines or sufficient spacing.
6. Please explain how the phase composition correlates with the mechanical and tribological characteristics of the formed coatings.
Author Response
We thank the reviewer for his in-depth analysis of our manuscript and his comments and suggestions, which helped us to significantly improve the quality of our data analysis and presentation. In the revised version of this paper, we have tried, as much as possible, to take into account the comments and suggestions presented in the review.
Below are the responses to the comments
Comments for Author:
- The noise level is high in the diffractograms d) and e) in Figure 2. Please try to reduce it as the presence of some XRD peaks is questionable.
Response: We agree with the reviewer. A change has been made to the article.
- Please correct the presentation of phases, e.g. TiO2 should be presented as TiO2.
Response: We agree with the reviewers, The article was amended.
- I would suggest presenting crystallite size values for the formed phases.
Response: Since the diffraction background is very high and the diffraction peak intensity is low, it is impossible to determine the crystal size of the titanium oxide (Ti 2O 3, TiO 2) forming phase.
- Please avoid using the word „gray“ for different bands on SEM images, it confuses the readers.
Response: We agree with the reviewers The article was amended.
- Table 5: Please divide the data for each sample by horizontal lines or sufficient spacing.
Response: We agree with the reviewers, Table 5 has been modified.
- Please explain how the phase composition correlates with the mechanical and tribological characteristics of the formed coatings
Response: We agree with the reviewers The article was amended.
Reviewer 2 Report
What about the repeatability of the method?
Even getting the same phase will be a problem.
From SEM, it is clear that the coating is not uniform.
Author Response
Comments for Author:
What about the repeatability of the method?
Even getting the same phase will be a problem.
From SEM, it is clear that the coating is not uniform.
Response:
Detonation coating is a discrete process, carried out by sequentially performing the following operations included in a single cycle (shot):
- filling the detonation gun barrel with an explosive gas mixture;
- feeding powder into the barrel of the gun;
- explosion of a gas mixture in the barrel.
The composition of the explosive mixture and the degree of filling of the barrel significantly affect the energy characteristics of the detonation products. The percentage of fuel, oxidizer and diluent, as well as their volume depends on:
- the amount of heat released during detonation;
- degree of thermal dissociation of detonation products;
- chemical activity of detonation products in relation to the applied material;
- temperature and rate of discharge from the powder barrel.
CCDS2000 installation is fully automated. So getting the same phase won't be a problem. In this study, we wanted to show that the technological parameters of the detonation plant strongly affect the structure and phase composition of titanium-based coatings.
Author Response File: 
Author Response.docx
Reviewer 3 Report
The manuscript presents an interesting study about the formation of metal-oxide compounds on the basis of titanium. However, the paper needs major revisions before it is processed further, some comments follow:
Abstract:
The abstract is too long, please make it shorter.
Introduction
The introduction section must be improved.
Also, multiple citations have been introduced in bulk form "[1-7]", "[12-16]", "[24-26]" , "[27-29]" and not distributed in the text in accordance with the affirmations that must be supported. Please introduce citations in a specific position to ensure clear correspondence between the affirmations from the introduction section and the previous publication. Moreover, to avoid this type of citing, please cite review type of studies.
In the last paragraph of the Introduction, please write shortly about the methods used to characterize the coating.
Materials and methods
Divide this section into two: one about materials and one about the spraying and characterizing methods. Also, in order to be easier for the reader, please add a table or a new column in table 1 with the acronyms for each sample studied.
How was determined the chemical composition of titanium? Please introduce this information in the text. Also, if is given by the producer mention it in the text.
Results and discussion
Figures 2, 8 and 9 are not clear, please replace them.
Figures 4, 5 and 6. Introduce figure labels to highlight the zone of interest for the reader.
Add more discussion in this section comparing the results obtained with other studies.
Conclusions
The conclusion must be improved. Conclusions can be written with points. Also, add limitations and suggestions.
Author Response
We thank the reviewer for his in-depth analysis of our manuscript and his comments and suggestions, which helped us to significantly improve the quality of our data analysis and presentation. In the revised version of this paper, we have tried, as much as possible, to take into account the comments and suggestions presented in the review.
Below are the responses to the comments
Comments for Author:
Abstract:
The abstract is too long, please make it shorter.
Response: We agree with the reviewer. A change has been made to the article.
Introduction
The introduction section must be improved.
Also, multiple citations have been introduced in bulk form "[1-7]", "[12-16]", "[24-26]", "[27-29]" and not distributed in the text in accordance with the affirmations that must be supported. Please introduce citations in a specific position to ensure clear correspondence between the affirmations from the introduction section and the previous publication. Moreover, to avoid this type of citing, please cite review type of studies.
In the last paragraph of the Introduction, please write shortly about the methods used to characterize the coating.
Response: We agree with the reviewer. A change has been made to the article.
Materials and methods
Divide this section into two: one about materials and one about the spraying and characterizing methods. Also, in order to be easier for the reader, please add a table or a new column in table 1 with the acronyms for each sample studied.
How was determined the chemical composition of titanium? Please introduce this information in the text. Also, if is given by the producer mention it in the text.
Response: We agree with the reviewer. A change has been made to the article.
Results and discussion
Figures 2, 8 and 9 are not clear, please replace them.
Response: We agree with the reviewer. Changes have been made in Figures 2 and 8.
Figures 4, 5 and 6. Introduce figure labels to highlight the zone of interest for the reader.
Response: We agree with the reviewer. A change has been made to the article.
Add more discussion in this section comparing the results obtained with other studies.
Response: We agree with the reviewer. A change has been made to the article.
Author Response File: Author Response.docx
Reviewer 4 Report
1. In the first line of frame 2 in Fig.1, is N3 marked correctly?
2. At O2/C2H2 mixture ratio = 1.026, acetylene+propane+oxygen was used as a fuel. However, the contents of acetylene, propane and butane mixtures were not introduced clearly.
3. The roughness of the original substrate without coatings should be compared with the deposits.
4. Check the orders of the figures described in section 3. For example, Figure 6-8 was before Fig.4 and Fig.5.
5. Check the subscript of the titanium oxide.
6. Is anatase or rutile in the TiO2 coating?
7. In comparison of frictional coefficient and wear volume, the substrate without coatings and others’ works could be compared with the detonated coatings.
8. Ti2 coating had the lowest frictional coefficient and lest depreciation amount after wear test. While, the microhardness of Ti2 coating was 335±87HV0.1, which was not the highest one nor the lowest one.
9. In adjusting the coatings’ wear characterization, which took the most important effects.
10. There lacked the wear scars, which were the most important proofs reflected the wear characters.
11. What was the aim to design the gradient metal-oxide coatings?
12. After the wear tests, had the top layers with high content of oxide been worn out?
13. After the long-term wear, would the gradient coating experience the variation of frictional coefficient? It would correspond to different wear mechanism during the long-term wear service. It need be to thought.
Author Response
We thank the reviewer for his in-depth analysis of our manuscript and his comments and suggestions, which helped us to significantly improve the quality of our data analysis and presentation. In the revised version of this paper, we have tried, as much as possible, to take into account the comments and suggestions presented in the review.
Below are the responses to the comments
Comments for Author:
- In the first line of frame 2 in Fig.1, is N3marked correctly?
Response: We agree with the reviewer. Changes have been made in Figure 1.
- At O2/C2H2mixture ratio = 1.026, acetylene+propane+oxygen was used as a fuel. However, the contents of acetylene, propane and butane mixtures were not introduced clearly.
Response: The mixture is adjusted by jets.
- The roughness of the original substrate without coatings should be compared with the deposits.
Response: The roughness of the original uncoated substrate should not be compared with other coatings. Since the roughness of the substrate depends on sandblasting.
- Check the orders of the figures described in section 3. For example, Figure 6-8 was before Fig.4 and Fig.5.
Response: We believe that the drawings are arranged in the correct order. because the purpose of the study is to first analyze the coatings and obtain coatings with a gradient structure.
- Check the subscript of the titanium oxide.
Response: We agree with the reviewer. A change has been made to the article.
- Is anatase or rutile in the TiO2coating?
Response: Anatase.
- In comparison of frictional coefficient and wear volume, the substrate without coatings and others’ works could be compared with the detonated coatings.
Response: I have not found an article comparing detonation coatings with a substrate.
- Ti2 coating had the lowest frictional coefficient and lest depreciation amount after wear test. While, the microhardness of Ti2 coating was 335±87HV0.1, which was not the highest one nor the lowest one.
Response: Titanium oxide phases are present in the Ti2 sample. Hardness and wear resistance do not always confirm each other.
- In adjusting the coatings’ wear characterization, which took the most important effects.
Response: The wear characteristics were evaluated by the coefficient of friction and the intensity of wear.
- There lacked the wear scars, which were the most important proofs reflected the wear characters?
Response: We studied the signs of wear using the Model 130 profiler.
- What was the aim to design the gradient metal-oxide coatings?
Response: Recently, gradient coating has found wide application in various industries. We know that oxidized titanium has high corrosion resistance, so we additionally study the corrosion properties of coatings. And we will study the adhesive properties of coatings. The adhesive properties of metal to metal will be more durable than that of metal to ceramics.
- After the wear tests, had the top layers with high content of oxide been worn out?
Response: Yes.
- After the long-term wear, would the gradient coating experience the variation of frictional coefficient? It would correspond to different wear mechanism during the long-term wear service. It need be to thought.
Response: In our cases, the coefficient of friction of the gradient coating has not changed (there was no transition). We need to change the friction trajectory or force to make the transition happen. Next, we study these properties.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Please show that the coating is uniform
Author Response
The following is the reply to the comment
Reviewer comments:
Please prove that the coating is uniform.
reply:
Figure 1 1 and 2, 3 give micrographs of the cross section of the coating (general view of the coating completed in secondary electron mode and structure of the coating in electron backscatter mode). In the spraying of powder materials without chemical reaction, coating delamination occurs only through the tandem precipitation of particles on the substrate. The phase distribution formed in the deposition process when titanium interacts with detonation products and carrier gas is determined by the degree of chemical reaction. The coating formed under the high conversion rate of titanium has the chemical property of layering: the layers in the sprayed coating have different chemical compositions,
Figure 1 shows micrographs of the cross section and a diffractogram of the Ti1 coating. The diffractogram proved that the coatings consist of titanium and the structure showed that the coatings consist of a light area correspond to metallic titanium.
With an increase in the volume of the explosive mixture, both the thermal and chemical effects of detonation products on the sprayed material increase. It follows from the comparison of the phase composition of Ti1 and Ti2 samples that an increase in the volume of the explosive mixture from 48 to 64% of the barrel volume leads to a sharp increase in the number of titanium reaction products with detonation products and carrier gas.
Metal-ceramic coatings formed at high degrees of titanium transformation under conditions of titanium oxide formation are layered systems with alternating layers enriched with either ceramic phases or metallic titanium (Figures 2 and 3).
Therefore, under the condition of titanium oxide formation, the coating is a system of layered structure matrix with ceramic phase enrichment, in which titanium particles (non reactive particles) are distributed. In reactive spraying, the delamination in the coating structure has a "chemical" origin, because the formed layers are different in chemistry and phase composition. This is due to the formation of new phases on the surface of accelerated particles, and the particles become debris when they hit the substrate. The chemical reaction may involve the entire particle volume, but the chemical composition of the internal and surface layers are different.
Author Response File: Author Response.docx
Reviewer 3 Report
The authors addressed all of my comments. The manuscript can be published in the present form.
Author Response
We thank the reviewer for his in-depth analysis of our manuscript and his comments and suggestions, which helped us to significantly improve the quality of our data analysis and presentation.
Author Response File: Author Response.docx
Reviewer 4 Report
The author has revised the manuscript. But there were still some important aspects needed to be clarified and some additional experiments need to be characterized. Detail comments were followed.
1. Although the mixtures of acetylene, propane and butane were adjusted according to the jets, the detail ratio should be in a reasonable range to generate enough enthalpy to heat the feedstocks and high kinetic energy to speed the powders. It would be better to understand the deposition behavior and the oxidation mechanism of titanium powders through detonation spraying with the detailed contents of acetylene, propane and butane mixtures.
2. The roughness of the substrate can be adjusted by sandblasting. What was the substrate’s roughness after sandblasting in the work? The comparisons of roughness between the as-sprayed coating and the sandblasted substrate would be helpful to investigate the effects of detonation sprayed particles filling up pits on the sandblasted substrate and the pre-deposited coating.
3. Generally, the wear mechanism of metal or alloys is different to oxides. To better understand the wear mechanism difference, the detonation sprayed coatings and the substrate could be compared in frictional coefficient, wear volume and scars.
4. The author studied the signs of wear using the Model 130 profiler. While, there lacked effective evidence or figures.
5. The most important to prepare the gradient metal-oxide coatings was to adjust the huge difference between metal and oxide, which could bring out high stress and lead to crack between the substrate and the coating.
Author Response
Comments for Author:
- Although the mixtures of acetylene, propane and butane were adjusted according to the jets, the detail ratio should be in a reasonable range to generate enough enthalpy to heat the feedstocks and high kinetic energy to speed the powders. It would be better to understand the deposition behavior and the oxidation mechanism of titanium powders through detonation spraying with the detailed contents of acetylene, propane and butane mixtures.
Response: The chemical composition of the sputtering medium, as well as the temperature of the particles and their velocity can be regulated by changing the ratio of the oxidizer and fuel, as well as the volume of the explosive mixture. Detonation products can have very high oxidative activity due to the presence of atomic oxygen.
The temperature of the detonation products decreases with an increase or decrease in the acetylene content in the explosive mixture relative to the specified value. It should be taken into account that the temperature of the particles is determined not only by the temperature of the detonation products, but also by the velocity of the particles, which determines the time of their interaction with hot gases. The particle velocity also depends on the Oxidant/Fuel ratio. Particles moving at a slower speed can heat up to higher temperatures before exiting the barrel. Thus, when switching from Oxidant/Fuel ratio =1.026 to Oxidant/Fuel ratio=1.856, a decrease in the particle velocity can lead to an increase in their temperature at a constant volume of the explosive mixture.
- The roughness of the substrate can be adjusted by sandblasting. What was the substrate’s roughness after sandblasting in the work? The comparisons of roughness between the as-sprayed coating and the sandblasted substrate would be helpful to investigate the effects of detonation sprayed particles filling up pits on the sandblasted substrate and the pre-deposited coating.
Response: The roughness of the BT1-0 substrate after sandblasting showed values of Ra = 5.39 μm. We agree with the reviewer. A change has been made to the article.
- Generally, the wear mechanism of metal or alloys is different to oxides. To better understand the wear mechanism difference, the detonation sprayed coatings and the substrate could be compared in frictional coefficient, wear volume and scars.
Response: We agree with the reviewer. A change has been made to the article.
- The author studied the signs of wear using the Model 130 profiler. While, there lacked effective evidence or figures.
Response: The wear marks of the coatings obtained using the Model 130 profiler are shown in Figures 1-4. We believe that there is no need to insert these images into the article. It confuses readers. Drawings are poorly visible.
- The most important to prepare the gradient metal-oxide coatings was to adjust the huge difference between metal and oxide, which could bring out high stress and lead to crack between the substrate and the coating.
Response: Microstructure of the gradient coating cross-section no visible cracks were found at the coating/substrate interface, indicating good surface contact.
Author Response File: Author Response.docx
