Design, Construction and Programming of a Low-Cost Pulsed High-Voltage Direct Current Power Supply for the Electrophoretic Deposition of Silicon Carbide Mixed with Graphite and/or Alumina for Thermoelectric Applications

Round 1

Reviewer 1 Report

This work introduces the design, construction and programming of a low-cost pulsed high-voltage DC power supply for electrophoretic deposition of graphite and/or alumina. It is rich in workload and substantial in content. It can be accepted after minor revisions:

1. In the Introduction, the author takes up a lot of space to explain the importance of TE devices. However, as a research paper, readers are more concerned about the current application status and existing problems of SiC in TE technology. It's a pity that this is not mentioned much in the Introduction.

2. In the manuscript, the author extensively introduces the design and structure of a pulsed high-voltage DC power supply using a quadruple voltage system. Is this device an innovative design of the author's team? What’s the point of highlighting it here?

3. There are duplicate pictures in Page 5, please delete the redundant parts. Similarly, there are duplicate images in Page 8.

4. What is the connection between "Error! Not a valid book mark self-reference" in Page 10 and what comes before and after? The same problem also exists in Page 14, such as "Error! Reference source not found."

5. It is mentioned in Page 10 that "Finally, suspensions were prepared of only SiC and mixtures of SiC and aluminum (SiC-Al), SiC and graphite (SiC-C) and SiC mixtures with graphite + aluminum (SiC C+Al ), using different concentrations of alumina and graphite. Error! Not a valid book mark self-reference. shows the nomenclature and compositions of the deposited samples." Why choose Al2O3 and graphite as composite agents? This does not seem to be explained in the previous article.

6. The picture of Fig. 18 is not clear enough, please provide high-definition pictures.

7. The picture of Fig. 19 is repeated.

8. In Fig. 20, except for SiC 6C-6Al, the conductivity of other samples at different temperatures changes relatively slowly. However, between 100-300°C, the conductivity of SiC 6C-6Al increases significantly. Please provide a reasonable explanation.

9. Page 19 states that “The Seebeck coefficient of the SiC 6C-4Al sample was relatively large (-2500 μV/K at 200°C) compared with the other samples.” Please provide a reasonable explanation.

10. There are few articles in the past 5 years in the references. Please update the references to prove the innovation of this work.

the Quality of English Language can be further improved

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

After reading the presented manuscript “Design, Construction and Programming of a low-cost pulsed high-voltage direct current power supply for electrophoretic deposition of SiC mixed with graphite and/or alumina for thermoelectric applications”, it was found that it should be significantly improved to the further consideration to the publication.
First of all, the material choose in introduction section should be improved. At the moment it just postulated, that SiC is promising candidate as a thermoelectric material, but no obvious comparison with the other possible materials. There is no information, why exactly SiC and Al2O3 and/or graphite as additives were chosen. It is not clear how “extraordinary hardness, resistance to corrosion…” could help to thermoelectric material? Also, it is mentioned, that “at high temperatures that allow you to work in hostile environments”, but the manuscript deals with temperatures up to 500°C, is that a high temperature? As a consequence, there is no straight goal of the investigation and its explanation.
Further, in experimental section, there is no information about powders of alumina and graphite, which were used (particles size, morphology, phase composition etc). Also, it is not clear information on how the properties of coatings, which you have produced by electrophoresis was measured? On the substrate? How for example thermal conductivity was calculated, as the Hyper Flash – is method for thermal diffusivity measurement, you also need heat capacity and density of the material. How you calculate what thermal diffusivity is for the coating, and which is for substrate?
There are multiply mistakes, such as “Error! Not a valid book-mark self-reference” or figure caption and figure itself are at different pages.
At the page 13 a lot of text is presented, which repeat the information, that could be easily be understand from the figure 14. But no explanation, why the authors consider, that there is a mixture of cubic and hexagonal SiC, as from figure it could be suggested, that it is common hexagonal SiC: all peaks are corresponding to that phase, and at the same time no special peaks, which corresponds exclusively to the cubic phase. No peak label is presented for the blue one (fig. 15 about 35°). The main conclusion could be made from XRD, that the mixture of SiC, Al and / or graphite is achieved by electrophoresis, as it should be.
From that point a lot of troubles arises.
Table 3 and all crystallite size calculation are mean less. It could be calculated for each separate phase, but not for the whole mechanical mixture, it has no sense. SiC crystallite size cannot change within electrophoresis as well as alumina and graphite. As well as lattice constant, there is no solid solution, that forces to change it. Hence “perturbation of the lattice increases” is not acceptable. The samples differ by phases content (SiC, Al2O3, C) but not changes in lattice. Also, the samples could differ in their package (porosity), that effect, for example, thermal conductivity. So on, term “undoped” or “doped” are not applicable for mixture of several powders. And particle size of separate powders cannot change within electrophoresis, it could be suggested, that the average particle size increases (if coarse particle are added) or decreases (v.v.), but never “increases crystal growth”.
EDX analysis is a semiquantative technique, that badly works with light elements, such as C or O. Moreover, there is no chemical reactions, it just deposition of SiC, Al2O3 and/or C on the substrate, chemical composition primary depends on raw mixture ratio, so it is almost no sense to analyze chemical composition of the samples with EDX.
No acceptable information about properties change is presented. For example, why addition of alumina, which is not electrical conductor increases the overall conductivity? Can it be connected with, for example, porosity? Why such trends are observed is not obvious, and there is no explanation, just only one more time repeat of the information from the figure.
The same thing with thermal conductivity. The conclusion, that the phonons and not free electrons are responsible for thermal conduction is not obvious. And also it is surprisingly, that thermoelectric material should be an electrical conductor, hence electron part in thermal conductivity should be notable. That can bring to the result, that SiC is not a good choice as a thermoelectric material.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper is devoted for design, construction and programming of a low-cost pulsed high-voltage direct current power supply for electrophoretic deposition of SiC mixed with graphite and/or alumina for thermoelectric applications. The topic is generally interesting, however the paper contain unexplained places and need major revision.

The aim of the paper should be more clearly formulated.

Fig. 20, please explain the temperature behavior of the conductivity.

Fig. 21, please explain why for sample SiC 6C-6Al at temperature 200 C the value of the Seebeck coefficient is much smaller than for other temperatures or other samples? Why temperature dependence of the Seebeck coefficient is so scattered?

The text ‘’these results are lower than previously reported’’ reference is needed. The text ‘’not free electrons’’ what You mean there?

Conclusions and Abstract should be rewritten in more informative way.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1. One method commonly used to sinter silicon carbide is creating an oxide-bonded SiC. This process involves adding aluminum oxide to SiC, which interacts with the surface oxide film SiO2 to form mullite at temperatures exceeding 1400°C. The aluminum oxide modification employed is more reactive; however, the necessity of sintering the sample at such low temperatures as 500°C remains unclear. The references cited [24-26] pertain to high-temperature procedures, rendering the comparison irrelevant considering the sintering temperature specified in this article is 500°C.

2. Has the XRD data been analyzed using the Rietveld method to confirm the presence of a mixture of 3C and 6H – SiC? Initially, it appears that the main peaks of 3C and 6H coincide, making it challenging to ascertain the existence of a cubic phase within silicon carbide. While the Raman shift indicates the presence of two SiC phases, it would be beneficial to conclusively demonstrate the existence of a cubic phase through both methods utilized.

3. Calculations regarding the size of crystallites are inconclusive. The particle size likely remains unchanged following sintering at 500°C, as these temperatures are insufficient for sintering refractory materials. Consequently, the section concerning crystallite size calculations should be omitted.

4. Figure 18 does not explicitly indicate whether it depicts powders or non-sintered ceramics. The absence of sintering indications suggests there have been no chemical transformations, implying it simply portrays a blend of various powders, compacted and subjected to thermal treatment at 500°C.

5. Conducting EDX analysis may be redundant since no chemical alterations have occurred, implying the current sample composition is dictated by the initial reagent proportions.

6. Considering the absence of sintering based on the temperatures and SEM data, attributing changes in electrical or thermal conductivity to enhanced sintering through the addition of aluminum oxide is invalid.

7. The lack of data on sample porosity necessitates inclusion and is crucial. It is plausible that utilizing powders of varying dispersity impacts the density of their arrangement (random close packing), thereby influencing the properties under investigation. Given the inadequate sintering temperature applied to the samples, any potential effects resulting from sintering remain inconclusive.

8. The style of corrections make it considerably hard to read the manuscript. The previous version should be deleted.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Authors make proper corrections according to reviewer remarks and I suggest to publish the paper as it is.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

In its current form, the article can be accepted for publication