Multilayer-Structured Wood Electroless Cu–Ni Composite Coatings for Electromagnetic Interference Shielding
Round 1
Reviewer 1 Report
1) The introduction must be improved to show the novelty of the presented work. The authors should mention the main advantage of the proposed multi-layer structure compared to other EM absorbers working at this frequency.
2) The authors mentioned wrongly the frequency band in section 3.7. The frquency band from 1-2 GHz is L-band not the X-band. X band is from 8-12GHz.
3) How was the shielding effectiveness measured? The authors need to describe it more carefully.
4) Also, the authors did not describe the effect of the temperature variation. Both wood and CU-Ni metal surface will expand and shrink differently over temperature variation. This will create possible cracks in the metal layer and the shielding effectiveness will be badly effected. This has to be taken into account.
5) A comparison with other new types of shielding structure working over different frequency range will be needed to show the usefulness of the proposed multi layer structure. Some examples of the new shielding structure can be found in the following references:
A. Uz Zaman, V. Vassilev, P. Kildal and A. Kishk, "Increasing parallel plate stop-band in gap waveguides using inverted pyramid-shaped nails for slot array application above 60GHz," Proceedings of the 5th European Conference on Antennas and Propagation (EUCAP), Rome, 2011, pp. 2254-2257.
Stuardo, P.; Pizarro, F.; Rajo-Iglesias, E. 3D-Printed Sievenpiper Metasurface Using Conductive Filaments. Materials 2020, 13, 2614.
Nisanci, M. H., “A novel pinned cover design with an array of three-dimensional n-pole ele-ments for low-frequency filtering of microwave circuit packages,”IEEE Trans. on Electromagn.Compat., Vol. 60, No. 6, 1819–1824, 2018.
Author Response
Dear editor,
Thank you for your message. The manuscript was revised according to your advice. I made some additional changes and marked those changes with red color in revised manuscript. I am looking forward to your reply.
With best wishes,
Yanfei PAN Ph.D.
College of Materials Science and Art Design
Inner Mongolia Agricultural University
Hohhot, 010018
P.R.China
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Please check format in reference [2]
Please include reference for this sentence “The shielding effectiveness of the electromagnetic shielding materials based on wood due to low cost-effective, lightweight and easy to manufacture nearly reached 60 dB”
English grammar must be reviewed intensively (by a native better) even the title. I think that sentences are sometimes too long. Probably shorter sentences would help.
Please can you explain in the text what are we looking at in figure 1 in the results section? This may help the readers to understand it.
Instead of stating ‘It was obvious’ authors can use other expressions that may be more useful for the readers such as from this fact we can see that …, or Since this fact can be appreciated we can conclude that …
Please explain in the text clearly what at we looking at in figure 2. Case of experimentation.
In section 3.7 everything is better explained.
What do you mean in line 277 by ‘interfacial polarization’?
Any explanation for this sentence? ‘Electromagnetic wave shielding in low-frequency was better than high-frequency’
Why the optimal SE is not for 4 depositions, one could think the more the conductive material the higher the SE.
In line 360 I don’t think you can divide R=R1+R2 since after the first layer what it is reflected in the second layer is reflected again in the first one partially. That’s why we have the multiple reflection mechanism.
Conclusions and the abstract are very similar. I wouldn’t provide too many numerical results in the abstract.
Author Response
Dear editor,
Thank you for your message. The manuscript was revised according to your advice. I made some additional changes and marked those changes with red color in revised manuscript. I am looking forward to your reply.
With best wishes,
Yanfei PAN Ph.D.
College of Materials Science and Art Design
Inner Mongolia Agricultural University
Hohhot, 010018
P.R.China
Author Response File: Author Response.pdf
Reviewer 3 Report
OVERVIEW
The authors deal with the lightweight multilayer-structured electromagnetic interference shielding composite coatings. The lightweight multilayer-structured EMI shielding composite coatings were prepared on the wood surface via a simple multiple electroless copper-nickel (Cu-Ni) approach. By using multiple electroless copper-nickel (Cu-Ni) approach controllable electromagnetic gradient on the wood surface was achieved. In the article, the authors analyze and compare the physical parameters of the composite coatings such as electrical conductivity, hydrophobic property, and electromagnetic shielding effectiveness. The authors discuss the measured results of EMI shielding effectiveness of Cu and Ni coatings as a function of the number of deposition steps. The composite coatings during different deposition steps were characterized by SEM, LCM, contact angle measurements, XPS analysis, and EMI SE tests. The authors state that the coatings were compact and homogeneous as the deposition Cu run was three and that the composite coatings based wood exhibited the optimal electromagnetic shielding performance (average 90.69 dB) in the X-band ranged from 300 kHz to 2.0 GHz.
POSITIVE ASPECTS
1. In the introduction, the authors made a suitable overview of the problems related to the physical characteristics of wood and the problems associated with the shielding of electromagnetic interference.
2. The authors prepared Cu-Ni composite coatings in four deposition steps using multiple electroless Cu-Ni methods equipped with the artificially modified coatings technique on pretreated wood samples.
3. The authors characterized the prepared Cu-Ni composite coatings by SEM, LCM, contact angle measurements, XPS analysis, and EMI SE tests.
4. The authors found out that the composite coatings based wood exhibited the optimal electromagnetic shielding performance.
SHORTCOMINGS
The work is useful but contains some deficiencies that need to be removed. I have some comments that can be used to improve the paper.
Minor Comments
1. In the article, there are missing spaces before some references (e.g., line 45, 46, 47). Corrections need to be done throughout the article.
2. The authors use two ways to denote the mathematical operation of multiplication (see, for example, Table 1). Correct according to ISO 80000-1: 2009.
3. In chemical formulas and mathematical formulas, subscripts and superscripts are used instead of reduced fonts (e.g. Table 1, lines 85, 86, 225, …). Corrections need to be done throughout the article.
4. Signs of physical quantities need to write in italics according to ISO 31-4 (ISO 80000-5: 2007), e.g. line 114, 366, 381-383… Corrections need to be done throughout the article.
5. The authors of the article use the unusual phrase “... angle were was less ...” on line 115.
6. The authors use two ways to refer to figures (e.g. line 165, 176, 221 – with or without space), which does not correspond to the template used in MDPI. Corrections need to be done throughout the article.
7. It appears that the authors of the article used parentheses with a different font than in the text in the description of Figure 1 (lines 145-146). If this is the case, a corresponding correction must be made. Also, a dot should be given at the very end of a sentence. The same applies to the description of Figure 2. Corrections need to be done throughout the article.
8. The part of the sentence in lines 236-238 repeats the sentence in lines 222-223. Similarly, the part of the sentence in lines 238-239 repeats the sentence in lines 227-229. Corrections need to be done throughout the article.
9. In line 255, an unusual character is used, the meaning of which is confusing. Make correction.
10. The authors of the article claim that: “… the Ni crystallites decreased rapidly with the increasing in number of deposition steps as shown in Table 9 …” on lines 264-265. However, comparing the values of the calculated crystallite sizes given in Table 9, there is no apparent downward trend in the decrease in crystallite size with an increasing number of deposition steps. Make correction.
11. According to ISO 80000-1: 2009, it is preferred to use a lowercase letter k for a multiple of 1000 (e.g. lines 273, 275). Correct accordingly.
12. Equation (1) fits more into line 341.
13. It is not clear to me what the term wave frequency in line 353 means. It is necessary to explain what the term wave frequency means.
14. It seems that in lines 365 and 366 is not used the correct symbol for the Greek letter beta. If this is the case, a corresponding correction must be made.
15. The part of the sentence in lines 370-371 repeats the sentence in lines 375-377. Corrections need to be done throughout the article.
16. In my opinion, the description of Figure 9 is not complete. Correct accordingly.
17. The term “free body space impedance” in the description of Figure 10 is unusual. Correct accordingly.
18. The authors use two ways to denote the physical quantity L0. Correct accordingly.
Major Comments
1. The authors of the article state that: “The electromagnetic shielding effectiveness of composite coatings based wood was measured in the X-band (0.3-3.0×103 MHz) ...” However, in communication engineering, the frequency range of the X-band is rather indefinitely set at approximately 7.0–11.2 GHz. Similarly, in radar engineering, the frequency range is specified by the Institute of Electrical and Electronics Engineers (IEEE) at 8.0–12.0 GHz. The frequency range reported by the authors does not correspond at all to the X-band. Make the appropriate correction.
2. The authors of the article used the DR-S01 Shielding effectiveness test device to measure the SE of the samples prepared per the ASTM 4935. However, the measurement method is valid over a frequency range of 30 MHz to 1.5 GHz. These limits are based on decreasing displacement current as a result of decreased capacitive coupling at lower frequencies and on overmoding, excitation of modes other than the transverse electromagnetic mode, at higher frequencies for the size of specimen holder. What is the measurement accuracy of the set-up used above 1.5 GHz?
3. The article lacks photos of samples that were used in the measurement set-up to measure the shielding effectiveness. Make appropriate correction.
4. The authors of the article do not state whether the samples used to measure the shielding effectiveness were also deposited at the edges around the perimeter or not. In the case of deposition also at the edges around the perimeter of the sample, the layers are short-circuited. The corresponding comment needs to be added.
5. The meaning of the numbers 1 and 2 given in Figure 10 is not explained either in the description of the figure or in the whole text. Make appropriate correction.
6. The authors of the article use the same abbreviation to denote the wave impedance of wood as to denote the wave impedance of air. Make appropriate correction.
CONCLUSION
Regretfully, the paper cannot be accepted in its present form. Deficiencies need to be corrected.
Author Response
Dear editor,
Thank you for your message. The manuscript was revised according to your advice. I made some additional changes and marked those changes with red color in revised manuscript. I am looking forward to your reply.
With best wishes,
Yanfei PAN Ph.D.
College of Materials Science and Art Design
Inner Mongolia Agricultural University
Hohhot, 010018
P.R.China
Author Response File: Author Response.pdf
