Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder
, Tomoaki Namioka 3, Takashi Fujii 1, Hirotsugu Takizawa 2 and Hideoki Fukushima 4
Jiping Cheng
Round 1
Reviewer 1 Report
The authors please add some detailed description of the sample preparation methods, such as how to mix the SiC fiber with the oxide powders, how to put the mixed sample powder into the microwave cavity - in a pellet form, or in loose powder form, and any container used?
Author Response
Suggestion: The authors please add some detailed description of the sample preparation methods, such as how to mix the SiC fiber with the oxide powders, how to put the mixed sample powder into the microwave cavity - in a pellet form, or in loose powder form, and any container used?
Response: Thank you for the suggestions. We have added information regarding the sample state and the procedure to place the mixed sample powder into the microwave cavity using a container.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript presents the study of dielectric properties and behaviour under microwave heating of several SiC fibre mixtures. The observation of thermal gradients at microscale is very interesting. The introduction, background and methods are well based and explained. Some issues should be addressed to clarify/improve some points:
Lines 41-42: Please rephrase the sentece "... is convenient to transfer to the material to the furnace." Line 68: Please change "dielectric constants" by "dielectric properties" Line 67: What do you mean by "spatially separated MWs"? Line 88: Please specify if the sample is placed in a holder and the geometry employed Line 83: Please specify if the waveguides are rectangular Line 92 and 124: Please specify the heating rate in appropriate units K/s or K/min, etc. Line 90-91: The authors state that reflected power is maintained below 1W. But with heating rates as fast as 300ºC/s the material properties change very fast and the resonance frequency of the cavity is also changing very fast. How can the authors follow these fast changes to ensure that only 1W is lost during the whole process? It is a difficult task that requires a mechanical adjusment of the cavity dimensions with a really fast response following the rapid changes during the process. More details about this implementation are needed. In the case that these changes are not followed, then the reflected power would fluctuate importantly during the trials and also big differences would be observed between trials, making impossible a fair comparison between them (i.e. heating rates would be different because of differences in the reflected power, masking the effect of dielectric properties) Lines 95-104: The measurement set-up is different from the heating device. However, measurements of dielectric properties at different temperatures are provided. Please specify how the samples are heated for the measurements. Is a conventional furnace used? Are the samples cooled down during dielectric measurements? How is the effect of the silica tubes accounted for in the dielectric properties determination? Please provide more details about the heating/measurement method. Lines 105-107: Is the temperature measured through the silica tube? Is the surface temperature? Which is the considered emissivity? Have the authors performed any temperature calibration method or are they providing directly dielectric properties as a function of the surface measurements? Please provide more details. Line 143, please rephrase the sentence ”… loss tangent shows the same tendency the heating behavior” Figure 4: Please include intermediate temperature values in the color scale (not only 600ºC and 1500ºC) to help the reader to identify the temperature gradients in the Figure. Lines 176: Please explain the expansion of the term (which conditions are fulfilled) Line 177: The authors state “Hence, the MW absorption of a SiC fiber is always reduced upon surrounding it with a medium that has a positive complex permittivity” Please explain why and how is this inferred and what do you mean by “positive complex permittivity”.Author Response
Response for Reviewer #2
We gratefully acknowledge the efforts of the referees toward providing useful comments and suggestions, which have strengthened our manuscript. We agree with the suggestions provided, and have revised the manuscript accordingly. All major revisions suggested by the reviewers are shown in red in the revised manuscript.
We hope that the revised manuscript is now suitable for publication. Should you require any clarifications, please contact me.
Sincerely,
Keiichiro Kashimura
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Lines 41-42: Please rephrase the sentece "... is convenient to transfer to the material to the furnace."
Line 68: Please change "dielectric constants" by "dielectric properties"
Response: Thank you for your suggestions. We have rephrased this sentence and word.
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Line 67: What do you mean by "spatially separated MWs"?
Response: We have added a description for this term.
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Line 88: Please specify if the sample is placed in a holder and the geometry employed
Response: We have added a description to clarify the geometry of the sample holder and protocol of treatments conducted.
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Line 83: Please specify if the waveguides are rectangular
Response: We have added a description for the shape of the waveguides and model number.
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Line 92 and 124: Please specify the heating rate in appropriate units K/s or K/min, etc.
Response: We have accordingly added the appropriate unit.
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Line 90-91: The authors state that reflected power is maintained below 1W. But with heating rates as fast as 300ºC/s the material properties change very fast and the resonance frequency of the cavity is also changing very fast. How can the authors follow these fast changes to ensure that only 1W is lost during the whole process? It is a difficult task that requires a mechanical adjusment of the cavity dimensions with a really fast response following the rapid changes during the process. More details about this implementation are needed. In the case that these changes are not followed, then the reflected power would fluctuate importantly during the trials and also big differences would be observed between trials, making impossible a fair comparison between them (i.e. heating rates would be different because of differences in the reflected power, masking the effect of dielectric properties)
Response: We recognize this as a very important suggestion, and accordingly, conducted a new trial with a new measurer. As a result, we found that the reflected wave hardly changed, as shown in the figure of the sending (even a beginner of this system was able to suppress the reflected wave to 5 W or less). Therefore, we believed that a skilled measurer could suppress the reflection to 1W or less. This is why we believe the following:
The absorption characteristics of SiC gradually change with respect to the temperature. SiC is known to possess an unchanged conductivity at 400-600 ° C; therefore, no drastic change is observed. Due to the high absorption of the SiC fiber, resonance with the device can be easily obtained.
Please let us know if you require further clarifications and we will be glad to carefully consider and provide them. Your suggestions are highly appreciated.
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Lines 95-104: The measurement set-up is different from the heating device. However, measurements of dielectric properties at different temperatures are provided. Please specify how the samples are heated for the measurements. Is a conventional furnace used? Are the samples cooled down during dielectric measurements? How is the effect of the silica tubes accounted for in the dielectric properties determination? Please provide more details about the heating/measurement method.
Response: We apologize for the lack of information here. This system was established to measure the electrical permittivity. We have accordingly added detailed descriptions for the cavity perturbation methods and the method for removing the influence of the quartz holder.
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Lines 105-107: Is the temperature measured through the silica tube? Is the surface temperature? Which is the considered emissivity? Have the authors performed any temperature calibration method or are they providing directly dielectric properties as a function of the surface measurements? Please provide more details.
Response: Thank you for your comments. The sample temperature was measured not-thorough the silica tube: the surface of the mixed powders was measured directly. Figure R1 shows detailed experimental setup on measurement using two-color thermography. Two-color thermography did not have to consider the sample emissivity to determine the sample temperature. This device is calibrated using blackbody before the experiment by Mitsui Photonics Ltd.
Figure R1. Experimental setup of two-color thermography.
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Line 143, please rephrase the sentence ”… loss tangent shows the same tendency the heating behavior”
Response: In order to avoid ambiguity, we have replaced the suggested text with specific references.
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Figure 4: Please include intermediate temperature values in the color scale (not only 600ºC and 1500ºC) to help the reader to identify the temperature gradients in the Figure.
Response: We are deeply grateful for this suggestion. An intermediate temperature has been added to the color contour diagram. In addition, new pixel calculation results for hotspots have been added. Further, the expression “approximately” was used in the sense that the uncertainty arising from the unevenness of the powder could not be considered.
We have added the above figure, as well as information on the temperature gradient by adding the temperature measurement results at the hotspots.
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Lines 176: Please explain the expansion of the term (which conditions are fulfilled)
Line 177: The authors state “Hence, the MW absorption of a SiC fiber is always reduced upon surrounding it with a medium that has a positive complex permittivity” Please explain why and how is this inferred and what do you mean by “positive complex permittivity”.
Response: Certainly, the complex part of the dielectric constant can be negative. We have revised the argument and corrected it to a broad expression. Thank you for bringing this to our attention.
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Author Response File: Author Response.pdf
Reviewer 3 Report
The paper investigates the effect of Microwave Heating Behavior in SiC fiber–MO2 3 mixtures (M = Ce, Zr)—Selective Heating of 4 Micrometer-Sized Fibers Facilitated by ZrO2 Powder.
The overall idea looks promising, however the authors failed to show the originality of their work. The introduction failed to explain the current challenges, as a stage the objectives seems a series of experiments with no purpose. Few ideas to improve the quality of the paper
80 W looks a random number is this supported by a thermodynamic calculation, what is the energy required to heat your sample up to 1000°C How do you make sure that your electric field in homogenous and is the edge effect really coming from plasma? Figure 2 why 600 is the maximum temperature almost constant however, this does not align with the heating rate reported. Big discrepancies between heating rate and dielectric properties measurements, this means something is missing and I would question the data produced. “ZrO2 introduces hot spots to the mixed powder on MW heating” this possibly due to skin effect however hot spots seems all over the place and hence need to establish the purpose of the temperature measurements and how you can use them to support your data. Overall the paper is hard to follow and at this stage doesn’t add new finding to the scientific community
Author Response
Response for Reviewer #3
We are grateful to the referees for their useful comments and suggestions, which have strengthened our manuscript. All major revisions suggested by the reviewers are shown in red in the revised manuscript.
Sincerely,
Keiichiro Kashimura
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The paper investigates the effect of Microwave Heating Behavior in SiC fiber–MO2 3 mixtures (M = Ce, Zr)—Selective Heating of 4 Micrometer-Sized Fibers Facilitated by ZrO2 Powder.
The overall idea looks promising, however the authors failed to show the originality of their work. The introduction failed to explain the current challenges, as a stage the objectives seems a series of experiments with no purpose. Few ideas to improve the quality of the paper
Response: Thank you for your comment. The purpose of this paper is to clarify how multi-particles behave under microwave absorption. We have accordingly added the relevant description and literature to communicate this purpose.
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80 W looks a random number is this supported by a thermodynamic calculation, what is the energy required to heat your sample up to 1000°C
Response: Thank you for your comment. Although thermodynamics is involved, we believe you are referring to the first law of thermodynamics. We have added the corresponding description.
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How do you make sure that your electric field in homogenous and is the edge effect really coming from plasma?
Response: As all furnaces have an electric field distribution, this is conventionally calculated by numerical calculation. The measurements to this effect are not aimed at homogenizing the electric field distribution, because a device that makes the effect of the magnetic field negligible is used.
For better understanding, we will send you the electric field distribution calculations for the cavity resonator used in this research.
Electrical field strength for 1 W microwave simulated by JMAG
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Big discrepancies between heating rate and dielectric properties measurements, this means something is missing and I would question the data produced.
Response: In terms of trends, the correlation coefficient between the density and dielectric loss is -0.97, which is negative, whereas that between the density and maximum temperature is -0.86, and that between the density and heating rate is -0.61, which is a weak negative. Therefore, we believe these trends are in agreement.
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Author Response File: Author Response.pdf
