The Influence of Viscosity on Heat Dissipation under Conditions of the High-Frequency Oscillating Magnetic Field

Round 1

Reviewer 1 Report

The manuscript by Molcan and co-authors reports the experimental data on the heat production of three ferrofluid samples with controlling parameters. The main idea is get the samples with the same nanoparticles (magnetite in oil, stabilized by the oleic acid), the granulometric composition of which are very close to each other (as shown in Fig.1), but the viscosity of the carrier liquids of which differ in several times (as shown in Fig. 3). The saturation magnetizations of samples are also very close (as shown in Table 1). Thus, three samples have approximately coincident granulometric and magnetic characteristics, but they differ in effective viscosity. The heating of samples at 500 kHz ac magnetic field were measured at varying field amplitude, and the parabolic dependence was discovered (as shown in Fig. 7), indicating the validity of the well-known Rosensweig expression.

The main experimental result is presented in Fig. 8, where the influence of the viscosity is clearly shown.

The manuscript is written very clear, and the results are very important for the biological and technical applications. I recommend the paper for publication in Magnetochemistry.

I’d like to suggest one minor remark for improving the manuscript. I think that it is useful for the readers to explain in details the main methodology of the experimental study. I mean the coincidence of the granulometric and magnetic parameters of the samples to clarify the part of viscosity. The examples of the successive application of such methodology is known in the literature.

Author Response

Dear reviewer, the answer to your remark is uploaded as the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this manuscript, the authors report the influence of viscosity on heat dissipation under an oscillating magnetic field. The main characterization was done by SQUID-VSM, rheology, and specific heating and absorption rate experiments. I can recommend the publication of this work if my following comments are well addressed:

- In the presented manuscript, I am missing information on the synthesized magnetite nanoparticles, especially their morphology and physical particle size. The only information provided is the size distribution obtained from the VSM analysis. Is the obtained size distribution in line with the physical size distribution from another technique? Could you please provide more information about the synthesized sample? 

- Regarding the VSM experiments, could you provide the fits of magnetization data from which you obtained magnetic size distribution? Is the magnetic size comparable with the physical nanoparticle size?

- the saturation magnetization of magnetite at RT is very small compared to the typically reported values in the literature (around 80 Am2/kg). Could you please comment on what the reason is behind this? What is the particle magnetic moment? 

- the caption of Table 1 is very concise and does not introduce any of the listed parameters. Please introduce and describe all parameters.

- I am slightly concerned if the oleic acid ligand is at the magnetic nanoparticle surface, looking at the synthesis protocol. Did you perform FTIR measurements to see if the oleic acid is at the nanoparticle surface or just free? How stable are magnetic nanoparticles in mineral oil? Did you notice any precipitation after some time?  

- In the rheological experimental part, what measurement mode did you use - rotational or oscillatory measurement mode?

Author Response

Dear reviewer, the answers to your remarks are uploaded as the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have answered all my raised questions satisfactorily, and the manuscript in this form can be published.