Effect of Trace Elements on the Thermal Stability and Electrical Conductivity of Pure Copper

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

It’s a pity, but this manuscript cannot be accepted in its present form due to the poor quality of the text and numerous technical errors and mistakes. Several examples are given below. Several chapters like chapter 2 or 3.1 need not editing, but, instead, they need to be translated into English to be understood properly. 

1. It is not clear, in particular, what “4N electrolytic copper with different S contents was selected as the raw material” means. Why this amount was different, as only one pure copper is used as a reference sample, and how much sulfur is contained in these different samples of copper? It is not clear also how the sulfur was introduced into the Ti- and Cr-Ni-Ag doped copper alloys before their melting, and how much sulfur was added. What do they mean by monomers in these alloys (“trace transition elements are 99.99% purity in the form of monomers to join”)? Careful revision and editing of the text are necessary before its resubmission.

2. Due to this feature it is not clear also, what Fig. 1 means. What are these points of the different colors in Fig. 1, and why their amount is different for the different samples?

3. “As can be seen from Figure 3, trace transition group elements can significantly refine the grain size of pure copper.”

- This statement is not correct. It cannot be seen from Figure 3. The magnification is too small so the microstructures in Fig. 3 are indistinguishable. You have to use larger magnification or just skip this figure with corresponding comments. In fact, it concerns all optical micrographs of this manuscript.

4. “4N Cu-Cr-Ni-Ag-S pure copper has an average grain size of 1.5 μm, which is 58% smaller than that of 4N Cu pure copper”.

- This statement is not correct too because (a) the average grain size of Cu-Cr-Ni-Ag-S is 31 μm, not 1.5 μm, (see Fig. 3d); (b) because neither 1.5 μm nor 31 μm are 58% smaller than 200 μm (average grain size of pure copper, see Fig. 3d).

Comments on the Quality of English Language

The quality of English is rather nonuniform; the text is probably written by several different co-authors with very different level of English without further editing.

Author Response

Comments 1 :( It is not clear, in particular, what “4N electrolytic copper with different S contents was selected as the raw material” means. Why this amount was different, as only one pure copper is used as a reference sample, and how much sulfur is contained in these different samples of copper? It is not clear also how the sulfur was introduced into the Ti- and Cr-Ni-Ag doped copper alloys before their melting, and how much sulfur was added. What do they mean by monomers in these alloys (“trace transition elements are 99.99% purity in the form of monomers to join”)? Careful revision and editing of the text are necessary before its resubmission.)

Response 1: Thank you very much for pointing this out. Considering your comments, I will explain this.First of all, about "4N electrolytic copper with different S contents was selected as the raw material" this sentence.We utilize 4N electrolytic copper as raw material, in the smelting process, after the copper liquid melts, trace S element and transition elements Ti and Cr, Ni, Ag are added in the form of copper foil wrap at the same time.The purpose of adding the S element is as follows: Firstly, since we require samples with varying S contents, I respectively added 50 ppm of S to samples #2 and #3. Secondly, because the content of the S element in 4N electrolytic copper is relatively low, adding a trace amount of S is conducive to subsequent experimental observation and analysis.It might be because I was not clear about the statement of "4N electrolytic copper with different S contents was selected as the raw material", because I directly regarded 4N electrolytic copper with different S content as a whole entity, making it difficult for you to understand. Secondly, the original meaning I intended to express was simple substance rather than monomers, which was caused by my translation error. I have rectified the aforementioned errors in the original text and indicated them in red font, as presented on page 3 of the article.

Comments 2 :(  Due to this feature it is not clear also, what Fig. 1 means. What are these points of the different colors in Fig. 1, and why their amount is different for the different samples?)

Response 2: Thank you very much for pointing this out. Considering your comments, I will explain this. The dots of different colors are merely a symbol mark, aiming to make the picture more beautiful, and do not represent any special meaning. Maybe my description is notclear, which leads to your misunderstanding. Therefore, I redrew a simple and clear graph of "Influence of trace elements on the cold-rolled conductivity of 4N pure copper", As shown in Figure 2 of the article.

 

Comments 3 :(  As can be seen from Figure 3, trace transition group elements can significantly refine the grain size of pure copper.”- This statement is not correct. It cannot be seen from Figure 3. The magnification is too small so the microstructures in Fig. 3 are indistinguishable. You have to use larger magnification or just skip this figure with corresponding comments. In fact, it concerns all optical micrographs of this manuscript)

Response 3: Thank you very much for pointing this out. Considering your comments, I will explain this. Figure 4 (a, b, c) is a metallographic picture of 500 times under metallographic microscope (OM), because we are compared with pure copper, using Figure 4 (b, c) and Figure 4 (a) for comparison, it can be intuitively seen that Figure 4 (b, c) is smaller than Figure 4 (a), especially the grain size of Figure 4 (c) is smaller. Moreover, I also made corresponding grain size measurements, as shown in Figure 4 (d). It may be due to the misunderstanding caused by my incomplete expression of this sentence, so I re-edit this sentence（As can be seen from Figure 3, trace transition group elements can significantly refine the grain size of pure copper.”）, as shown in the red font on the fifth page of the article.

Comments 4 :(  4N Cu-Cr-Ni-Ag-S pure copper has an average grain size of 1.5 μm, which is 58% smaller than that of 4N Cu pure copper”.- This statement is not correct too because (a) the average grain size of Cu-Cr-Ni-Ag-S is 31 μm, not 1.5 μm, (see Fig. 3d); (b) because neither 1.5 μm nor 31 μm are 58% smaller than 200 μm (average grain size of pure copper, see Fig. 3d)

Response 4: Thank you very much for pointing this out. Considering your comments, therefore, we carefully checked the chapter and indeed found that the average grain size of 4N Cu-Cr-Ni-Ag-S pure copper is 1.5μm,which is 58% smaller than that of 4N Cu pure copper data is incorrect, which is caused by our negligence, so we have re-edited the data and marked it in red font on the fifth page of the article.

Finally, I have re-polished and revisedmy manuscript to make the language more coherent and clear, and the logic more rigorous.

Reviewer 2 Report

Comments and Suggestions for Authors

The introduction provides a solid background on the influence of trace elements on the thermal stability and electrical conductivity of pure copper. However, it can be improved by including more recent references and a clearer context for the study's importance. A deeper discussion on why specific trace elements (Ti, Cr, Ni, Ag) were chosen and how they compare to other potential elements could provide better justification for your study.

The research design is appropriate and well-structured. The choice of high-temperature treatment at 900°C for 30 minutes to study grain size stability is logical. However, providing more details about the sample preparation and experimental setup would strengthen the methodology section. For example, details on how the trace elements were introduced into the copper and the specific methods used for measuring conductivity and grain size would be beneficial.

While the methods are described, they could be more detailed. Clarify the techniques used for analyzing the grain size and conductivity. Were specific instruments or protocols followed? This would help in replicating the study and understanding the precision of your measurements. Additionally, including a flowchart or diagram summarizing the experimental process could enhance clarity.

The results are clearly presented and indicate significant findings regarding the thermal stability and conductivity of copper with trace elements. To further improve this section, consider adding more comparative data or visual aids, such as graphs or tables, to highlight key differences and trends. A discussion on the statistical significance of the results would also be beneficial.

The conclusions are well-supported by the results. The discussion on the mechanisms by which trace elements enhance thermal stability is insightful. However, expanding on potential applications or implications of these findings in real-world scenarios could add value. Additionally, addressing any limitations of the study and suggesting directions for future research would provide a more comprehensive conclusion.

The originality of the study is average. While the topic of enhancing copper's properties with trace elements is well-known, your specific focus on the combination of Ti, Cr, Ni, and Ag and their effects is noteworthy. Further emphasizing what sets your study apart from existing literature could enhance its perceived novelty.

The content is significant as it contributes to the understanding of how trace elements can improve the properties of copper, which has numerous industrial applications. However, linking your findings to specific industries or technologies where these improvements could be most beneficial would increase the impact of your work.

The presentation quality is average. The manuscript is well-organized, but as mentioned earlier, it would benefit from additional visual aids and a more detailed methodology section. Ensuring consistency in terminology and improving the flow of the text would also enhance readability.

The scientific soundness of your study is high. The experimental design and analysis are robust, and the conclusions are well-supported by the data. Addressing any potential sources of error and discussing the reproducibility of your results would further strengthen this aspect.

The interest to readers is average. Researchers and professionals in materials science and metallurgy will find your study relevant. However, broadening the discussion to include practical applications and potential future developments could attract a wider audience.

Overall, your study is of average merit. It contributes valuable insights into the thermal stability and conductivity of copper with trace elements. By addressing the suggested improvements, you can enhance the clarity, impact, and overall quality of your manuscript.

 

Author Response

Comments 1:(  The introduction provides a solid background on the influence of trace elements on the thermal stability and electrical conductivity of pure copper. However, it can be improved by including more recent references and a clearer context for the study's importance.)

Response 1: Thank you very much for pointing this out. Considering your comments, In order to increase the importance of the research, we have made some updates to the references, as shown in the references.

 

Comments 2:(  The research design is appropriate and well-structured. The choice of high-temperature treatment at 900°C for 30 minutes to study grain size stability is logical. However, providing more details about the sample preparation and experimental setup would strengthen the methodology section. For example, details on how the trace elements were introduced into the copper and the specific methods used for measuring conductivity and grain size would be beneficial.)

Response 2: Thank you very much for pointing this out. Considering your comments, I will explain this.Details about how trace elements are introduced into copper and the specific methods used to measure electrical conductivity and grain size.

• Grain size measurement method: Area method was adopted (Image-pro plus software was used to calculate the total area and total number of grains in 5 gold photographs, the average area of a single grain was obtained, and the average equivalent diameter of grains was calculated as the average grain size) to obtain the average grain size of the sample.
• Conductivity test: Sigma 2008B eddy-current conductivity meter was used to conduct the electrical conductivity test. The surface of the sample was polished with W5 metallograph sandpaper first, and then the Sigma 2008B eddy-current conductivity meter was calibrated and the conductivity of each sample was measured at room temperature, and each sample was tested no less than 7 times. After the maximum and minimum values of each sample were removed, The average value obtained is the measured conductivity of the sample.
• Trace element addition method: In the smelting process, 4N electrolytic copper is selected as the raw material, each furnace weighs 2.5kg, and the melting temperature is controlled at about 1200℃. The trace elements are wrapped in copper foil according to the required content in advance and then extruded into a block suspended above the copper liquid. After the copper liquid is melted, the trace elements are added to the copper liquid by the way of heat drop coupling.

I have supplemented the above content in the article, as shown in the red font on the third and fourth pages of the article.

Comments 3:(  While the methods are described, they could be more detailed. Clarify the techniques used for analyzing the grain size and conductivity. Were specific instruments or protocols followed? This would help in replicating the study and understanding the precision of your measurements. Additionally, including a flowchart or diagram summarizing the experimental process could enhance clarity.)

Response 3: Thank you very much for pointing this out. Considering your comments,Techniques for analyzing grain size and conductivity, We used tools such as Metallographic Microscopy (OM), Sigma 2008B eddy-current conductivity meter, and Image-pro plus software. I supplemented the experimental process chart in the experimental methods section of Chapter 2 of the paper, As shown in Figure 1 of the article.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors studied the effect of introduced elements on the thermal stability and electrical conductivity of copper. The introduction of other elements into copper formed the precipitates, decreasing electrical conductivity. On the other hand, alloying increased the thermal stability of copper. There might be a tradeoff between electrical conductivity and thermal stability. This investigation is very helpful for the readers working on such research. However, there are some concerns about the results and discussion. If the authors appropriately revise the manuscript, this study will meet the criteria for the publication in coatings.

 

Comment 1: Do the authors have other data about crystal structure (Ex. XRD, and so on)? XRD can easily clarify the existence of precipitates.

 

Comment 2: I recommend the authors’ measuring the dependences of some properties on annealing speed. In the present manuscript, the authors only measured the properties of the samples formed at the annealing speed of 900 degrees Celcius/30 min. I wonder if the speed is optimal or not.

 

Comment 3: TEM observation revealed the existence of CrS precipitates. The precipitates usually form the energy barrier height at the interface between medium and precipitate. The interfaces with barrier heights play a role in decreasing electrical conductivity. Using the famous Seto’s equation, the authors easily consider the carrier transport. The authors should measure temperature dependence of electrical conductivity (mobility) and discuss the carrier transport with a reference to the famous previous studies (ACS Appl. Mater. Interfaces 10, 37709 (2018)., J. Appl. Phys. 116, 143704 (2014).).

 

  

Author Response

Comments 1 :( Do the authors have other data about crystal structure (Ex. XRD, and so on)? XRD can easily clarify the existence of precipitates.)

Response 1: Thank you very much for pointing this out. Considering your comments, I will explain this. I am extremely regretful that subsequent to the EDS analysis of the precipitated phase, we ascertained the elemental composition of the precipitated phase. Hence, we did not carry out a further XRD test on the sample. I will undertake a further analysis of the sample in the subsequent XRD test.

Comments 2 :( I recommend the authors’ measuring the dependences of some properties on annealing speed. In the present manuscript, the authors only measured the properties of the samples formed at the annealing speed of 900 degrees Celcius/30 min. I wonder if the speed is optimal or not.)

 Response 2: Thank you very much for pointing this out. Considering your comments, I will explain this. At present, we have only done the research on the thermal stability of pure copper by adding trace elements under different states (hot extrusion state, cold rolling state), and finally found that the effect is better under cold rolling state according to the experimental data. At present, we only tested the sample at 900℃/30min, and the effect may not be optimal. If you want to get the best annealing time and temperature, the workload of the experiment may be relatively large. Therefore, we have only studied the thermal stability of pure copper under different states at a single annealing temperature and time. In later work, we may test the sample at different annealing temperatures and times to find the best annealing time and temperature.

Comments 3 :( TEM observation revealed the existence of CrS precipitates. The precipitates usually form the energy barrier height at the interface between medium and precipitate. The interfaces with barrier heights play a role in decreasing electrical conductivity. Using the famous Seto’s equation, the authors easily consider the carrier transport. The authors should measure temperature dependence of electrical conductivity (mobility) and discuss the carrier transport with a reference to the famous previous studies (ACS Appl. Mater. Interfaces 10, 37709 (2018)., J. Appl. Phys. 116, 143704 (2014).)

 Response 3: Thank you very much for your valuable suggestions, which are very helpful to our paper and have important guiding significance for our research. This direction will be carefully considered in our later experiments.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

In most cases I am satisfied by significant revisions made by authors. However, more careful revision of English is still necessary.

Comments on the Quality of English Language

The progress is obvious, but one more careful revision is still necessary.

Author Response

Comments 1 :(  In most cases I am satisfied by significant revisions made by authors. However, more careful revision of English is still necessary.The progress is obvious, but one more careful revision is still necessary.)

Response 1: Thank you very much for pointing this out. Considering your comments, We have used the English editing service recommended by you and invited an expert fluent in English writing to help check my manuscript and make corresponding revisions and refinements.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have not addressed my concerns at all. The response letter from the authors only said that no XRD measurement was performed and no temperature dependence of electrical conductivity was measured. In response 3, the authors told “This direction will be carefully considered in our later experiments.”. My comment is directed to the present study, not a future study. If the authors do not faithfully revise the manuscript, this study will be rejected.

Author Response

 I have incorporated a summary of the relevant charts and responses included in the previous round of manuscripts into the article, as indicated by the red font and Figure 3 of the article.

Author Response File: Author Response.pdf