Raman Spectroscopy and Microstructural Characterization of Hot-Rolled Copper/Graphene Composite Materials
, Jean-Louis Bobet 1, Amélie Veillere 1 and Jean-François Silvain 1,5,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors still need to work on the manuscript
Comments for author File: 
Comments.pdf
English language is clear
Author Response
Reviewer 1
Comment 1: Even before 2000, it was demonstrated that the introduction of carbon nanostructures into the bulk of various materials changes their properties: the dielectric polymer becomes conductive, the strength of the metal or its alloys increases, and the mechanical properties of ceramic materials also increase. Articles on this topic can be found in sufficient quantities on the Internet. Since the effect has been known for a long time, the mechanism of this phenomenon has always been of interest. From the presented manuscript it is impossible to understand the mechanism of the influence of graphene on the structure of the copper matrix.
Answer:
There is an effect of the nano reinforcement on the structure of the inorganic matrix this effect is mainly link with grain growth, Ended, for materials fabricated with liquid matrix, the presence of nanomaterials inside the liquid matrix inhibits the grain growth (grain size is then smaller than for materials fabricated with same process but without nanoscale reinforcement) and so improve the mechanical properties of the non-reinforced inorganic material. For powder metallurgy materials the improve of the mechanical properties can be associated with pure composite effect, for reinforcement having mechanical properties higher than le matrix, and/or to effect of the nano reinforcement which act as obstacle the dislocation movement (see page 14: Several parameters can play a role on the increase of the hardness for non-reinforced and reinforced metals. In nanocomposites, nanoparticles act as a barrier for the movement of dislocations, known as Orowan strengthening [38]. As indicates by Hall-Petch relationship, finer grains results in higher yield strength [39]). A review article on the characterization of nanoreinforcement dispersion in inorganic nanocomposite is added in the introduction is added ref 17):
Nouari Saheb, Najam UI Qadir, Muhammad Usama Siddiqui, Abul Fazi Muhammad Arif, Characterization of Nanoreinforcement Dispersion in Inorganic Nanocomposites: A Review, Materials 2014, 7(6), 4148-4181, https://doi.org/10.3390/ma7064148
Comment 2: In the common method of graphene synthesis (chemical vapor deposition) on a copper substrate, the mechanism of interaction between copper and carbon, which consists in graphitization of the copper surface, has been studied in sufficient detail. Therefore, it is obvious that with heat and pressure a carbon film is formed, and the copper grain size cannot increase. In the best case, the authors observe a sandwich of copper grains and multilayer graphene. Following the initial data of the starting materials, the thickness of graphene did not exceed 3 nm. The main issue in creating a composite is the uniform distribution of nanostructures in the matrix. It is not clear how the authors controlled this. A change in copper grain size of 2 μm in a specific zone confirms the accumulation of graphene particles.
Answer:
The explanation of the fabrication process of our Cu/Graphene composite materials is given in paragraph 2.2.1 and in ref. 30. Another reference (ref 31) is added in this paper in order to give even more details on the fabrication procedure. Even if, from our analysis, we did not observe any accumulation of graphene after the fabrication and post treatment it is impossible to argue that our materials did or did not have some graphene cluster and that some change of Cu grains cannot be attributed to that phenomena.
Ref 31: Bident A., Delange F., Labrugere C., Debiemme-Chouvy C., Lu Y., Silvain J-F., Fabrication and characterization of copper and copper alloy reinforced by graphene Journal of Composite Materials, 2024, 58(1), pp. 109-117 DOI: 10.1177/00219983231215210
Comment 3: Regarding the mechanical properties of Cu/Gr composite. The composite material began to have a higher hardness than pure copper (67.6HV versus 55.8HV or 64.1HV and 75.1HV, respectively). The authors explain this increase by an increase in the number of dislocations. How can increasing the number of defects, hence stress, improve mechanical properties?
Answer: This increase is not due to deformation of the material by rolling, but to the introduction of graphene, which is a much stiffer material. Consequently, the addition of graphene results in an increase in hardness due to the composite effect. However, the increase in hardness after rolling (55.8 to 67.6 Hv for the initial material and 67.6 to 75 Hv for the material after 15 pass of rolling) is indeed due to a phenomenon of hardening of the material by application of a mechanical stress (movement of dislocations).
Comment 4: Photographs of the surface presented in Fig. 4 must be of the same magnification.
Answer: The SEM photographs in Fig. 5 (old Fig. 4) have been changed so that the magnifications match
Comment 5: The work does not show a single Raman spectrum for the composite. The presence of characteristic three modes can demonstrate the state in which graphene materials are located in the composite. A change in the ratio (ID/IG) can only indicate an increase in graphitization in the composite.
Answer: A Raman spectrum of the initial Graphene material was added, with the followed sentence: “An example of Raman spectrum of our material is presented in Fig. 2. and the evolution of the ID/IG ratio of Gr are shown on Fig. 3.”
Figure 2. Typical Raman Spectrum of graphene material.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper deals on the study of CU/Gr composite. The improvement of electrical conductivity of Cu is of paramount importance because would also help to mitigate heat generated by Joule heating effects.
The study performed by the authors is suitable to understand how to transfer the properties between the reinforcement and the matrix.
The paper is interesting and can be published after minor revisions:
1) A more detailed discussion on EBSD measurements and CLS of twins. It should be better explained the signifiance of terms for the reader not strictly involved in the field and the presented figures/maps maps have to be more clearly discussed, in particular the color code.
2) It is stressed the importance of graphene orientation, but it is not more discussed in the whole text tha final angle orientation of the flake and the correlation (if there is) between flake orientation and the measured mechanical properties.
Comments on the Quality of English LanguageThe english should be slightly improved due also to some typing mismatch.
Author Response
Reviewer 2
Comment 1: A more detailed discussion on EBSD measurements and CLS of twins. It should be better explained the signifiance of terms for the reader not strictly involved in the field and the presented figures/maps maps have to be more clearly discussed, in particular the color code.
Answer:
A sentence has been added on page 12 and the legend to figure 7 has been expanded to explain the signification of the color code on EBSD orientation maps.
The meaning of the term CSL has been added (page 13) and the legend of figure 8 has been completed.
Comment 2: It is stressed the importance of graphene orientation, but it is not more discussed in the whole text that final angle orientation of the flake and the correlation (if there is) between flake orientation and the measured mechanical properties.
Answer: In fact, the text refers to the orientation of the graphene sheets perpendicular to the application of pressure and to quantifying the impact on the electrical properties. Polarised Raman spectroscopy allows us to obtain the evolution of the average orientation of the sheets after different rolling passes, without being able to quantify the precise evolution of this orientation.
Author Response File: Author Response.docx
