Synthesis of Cobalt–Nickel Aluminate Spinels Using the Laser-Induced Thermionic Vacuum Arc Method and Thermal Annealing Processes
Round 1
Reviewer 1 Report
The authors report a method potentially suitable for the preparation of thin film electrolytes (or also anodes) consisting of cobalt-nickel aluminate spinel with small crystallite sizes. Starting from CoNiAl alloy films being deposited by Laser-induced Thermionic Vacuum Arc (LTVA) methodology the product cobalt-nickel aluminate spinel could be obtained by thermal annealing in air. Precursor and product were well characterized structurally and according to their electrical properties for potential electrochemical applications.
The results are interesting, also for practical application. The manuscript is well structured and the manuscript has a clear focus. I support therefore acceptance of the manuscript for publication in nanomaterials. Minor changes could however improve the manuscript (see below).
Minor comments:
1) The abstract could be clearly improved by addition of a short comment on the motivation (application direction => specific electric properties) and in particular by addition of the analytical tools, from which the conclusions (crystallite size, film thickness, phase identification) were drawn. The last sentence should be checked: electric conductivity or resistance?! (Ohm/sq).
2) The reader would probably appreciate a short general comment (only very few sentences) on the principle preparation procedure (only principles, the details are found well described in the experimental part Materials and Methods) leading to the characterization part at the very beginning of the Results chapter. Normally the reader does not start reading with the Materials and Methods.
3) Page 5-6: the elemental distribution concluded from EDX could be defined and “formulated” more clearly (“atomic concentrations … depending on evaluated area” is not really comprehensible; Fig. 4: “on three points”?).
4) Similarly, a discussion / explanation of the Co/Ni ratio in the precursor phase and the final spinel (where is the original cobalt excess? = “evolution of the atomic concentrations before and after …”) would be helpful.
5) The English is understandable, but could be improved (e.g. adjectives-adverbs, …). Specific scientific terms should be improved however: e.g. crystallite (not crystalline) size, make weight?, elemental analysis (not analyze).
Author Response
Thank you. See the attached.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comment：
In this paper, the authors prepared CoNiAl alloy thin films by Laser-induced Thermionic Vacuum Arc (LTVA) and then via thermal annealing in air to obtain ceramic oxidic (Co, Ni)Al2O4. The structure, resistivity and dielectric properties of the alloy thin films before and after annealing were investigated by XRD, SEM, EDX, Ossila four-point probe, UC2878 precision LCR meter. There are still some issues that need to be addressed before considering the publication in this journal.
1. In page 2 (rows 56~60), section 1, the authors say that the composition and crystallinity of ceramic oxides are controllable, but the regulatory tests of different compositions and crystallinity are not seen in the paper, so it needs to be supplemented.
2. In page 2 (rows 71~76), section 2, how to ensure that the composition of the alloy thin films obtained by LTVA method is uniform?
If it is not uniform, whether there is a significant difference in the test results of different areas for the sample?
The melting points of Co, Ni and Al are different, how to confirm that the metal thin films does not occur delamination phenomenon?
3. In page 3 (rows 86~93), section 2, in the process of alloy thin films deposition and annealing, whether there is atoms interdiffusion between alloy thin films and substrates?
4. In page 6 (row 173), section 3 (b), the authors say “The initial atomic percentage in CoNiAl alloy is 3:1.”, which ratio is 3:1 between CoNiAl and CoNi? There may be a mistake.
According to the EDX test in Fig. 4, the ratio of Co/Ni atoms is 3:1 before annealing, but why does it change to 1:1 after annealing?
5. In page 9 (rows 259~261), section 4, the authors say that during the annealing procedure, Al atoms diffuse to the surface, what is the mechanism of diffusion? And will Co/Ni atoms also diffuse to the surface?
6. In page 11 (row 315~317), section 5, the authors say that since the presence of Co can enhance the non-oxidizing, high sulfur tolerance and the oxidation potential, it is suggested to carry out additional experiments for electro-catalytic reaction to verify the actual effect.
Author Response
Thank you. See the attached file.
Author Response File: Author Response.pdf
