The Influences of Stirring on the Recrystallization of Ammonium Perrhenate
Round 1
Reviewer 1 Report
The submitted manuscript by Junjie Tang et al describes effects of stirring on the recrystallization of ammonium perrhenate. Authors investigates 3 types of stirring paddle and speed of their rotation. The effect is examined by various techniques. Therefore, I assume the manuscript as a complex study and find it very interesting.
Following are my comments:
I find introduction as a short, but sufficient and clear.
The section materials and methods is too compressed and requires more details. Although the sample preparation can be, there is completely missing information about used techniques for structure investigations that are used. I suggest authors to add this to the revised manuscript.
SEM imaging seems to be one of the most important techniques. I am not sure if just from the 3 micrographs on Fig 3 one can say, that crystals on Fig. 3a are smoother than the rest. Well, authors used in the inset nice smooth image with higher magnification but looking to the low-mag images there are many crystals with rough surface. Therefore, I recommend authors to perform detailed image analysis of recorded SEM images to show data in more quantitative way. Better situation is on Fig. 4 where, although SEM micrographs are quite unsharp, the structure information is clearer.
Other techniques seem to be more convincing to me.
As mentioned above, the manuscript is interesting and showed interesting results. However, I think that after adding more information to the materials and method section and improving SEM analysis the manuscript will be interesting for readers of the Applied Sciences journal.
Author Response
Response to Reviewer 1 Comments
Point 1: The section materials and methods is too compressed and requires more details. Although the sample preparation can be, there is completely missing information about used techniques for structure investigations that are used. I suggest authors to add this to the revised manuscript.
Response 1: Thank you for your recognition of our work. We have improved the materials and methods.
Point 2: SEM imaging seems to be one of the most important techniques. I am not sure if just from the 3 micrographs on Fig 3 one can say, that crystals on Fig. 3a are smoother than the rest. Well, authors used in the inset nice smooth image with higher magnification but looking to the low-mag images there are many crystals with rough surface. Therefore, I recommend authors to perform detailed image analysis of recorded SEM images to show data in more quantitative way. Better situation is on Fig. 4 where, although SEM micrographs are quite unsharp, the structure information is clearer.
Response 2: The morphologies of most crystal particles prepared by disc turbine impeller were regular and the crystal surfaces were smooth, and a few crystal particles had rough surfaces, indicating that most crystal particles development were relatively complete. The crystal particle with high magnification was the representative of the complete growth crystal particles. However, the morphologies of most crystal particles prepared by propulsive propeller and Intermig impeller which had uneven surface topographies, indicating that the crystals were not fully developed. The crystal particles with high magnification were the representative of the incomplete growth crystal particles. This suggests that under the same operating conditions, the stirring effect of disc turbine impeller is more suitable for homogeneous recrystallization process.
The low magnification macroscopic morphology of the samples prepared by the three agitators was shown in the figure below. It can be seen from the figure that most of the samples prepared by disk turbine propeller have smooth surfaces. There are relatively few grains with rough surface. This was the primary reason for choosing the paddle type. In this paper, the reason for the difference of crystal morphology under the same stirring intensity was explained by PIV physical simulation. This was the part of the initial discovery of this work, through which the effect of agitation intensity on crystal growth had been studied. The differences in morphologies caused by different growth rates of crystals did not mean that there are defects in the crystals. Due to the limitation of the picture size in this article, you cannot see the experimental results clearly. We are sorry about that. Finally, thank you for your professional comments and recognition of our work. If you can't see the reply pictures I uploaded in the webpage, please see the attachment (PDF)
(a) (b)
(c)
(a) NH4ReO4 particles were prepared by Disc turbine impeller
(b) NH4ReO4 particles were prepared by Propulsive propeller
(c) NH4ReO4 particles were prepared by Intermig impeller
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is an interesting and relevant manuscript which deserves to be published. However, the text requires more explanation at a number of places before it can be accepted fore publication.
Line 74: ‘This study enhanced the mass and heat …..’ -> The aim of the present study is to enhance the mass and heat ……‘
Line 103 :‘ The hot supersaturated solution was passed into the recrystallization condensation reactor; the stirring strength of the reactor was adjusted to cool during crystallization; and the samples were filtered, washed and dried prior to being measured.’
Please expand in more detail, how and why was stirring speed adjusted, how was filtering done, others should be ale to duplicate the experiments.
Line 106: Physical simulation experiment methods: In this study, the laboratory homogeneous crystal reactor was taken as the prototype, and the water model was established based on the similarity principle. The ratio of water model to prototype is 5:1.
It is not clear what simulations were performed, what software, details of the methods, references.
Line 135 ‘ Ammonium perrhenate is tetragonal 4/m’ à ?? -> The ammonium perrhenate crystal is tetragonal 4/m’
3.2. The influences of stirring intensities
were experiments repeated? The impeller speed was varied ‘ only’ between 150 and 250 rpm and differences between formed crystals described but seems not extremely different. So how sure can one be about the stated differences?
Figure 5:
Please name in order of appearance of diffractograms, from top to bottom (this facilitates reading)
Line 180: ‘ the crystallinity of the sample decreased. If the relative crystallinity of the samples prepared at 200 rpm was treated as 100%’
Beforehand it is mentioned the samples are polycrystalline. Now here one speaks about crystallinity decreasing. What are absolute crystallinity levels? The diffractogram exhibits sharp peaks only, how much does the amorphous phase vary?
And for the diffractograms shown, and in relation to the phrasing ‘the crystallinity of the sample reached an ideal state’ , please discuss why the difference in the diffractograms are what they are, the differences can be (in part) the result of orientation. How sure are the authors the entire sample in polycrystalline so we have a proper averaging (the case of a pure single crystal being the other extreme)
In 3.3 Reduction experimental the authors speak about two different samples, the second one being an industrial sample. In the materials section however only one material is mentioned: materials: NH4ReO4 (99.99%, Re≥69.4%) Halin Chemical Co. LTD.
Then it needs explained why the one sample is reduced at 700C and the other one at 1000C. Please explain why these two different samples are used, and why the industrial is not reported in the sections before.
Line 205: ‘ PIV physical simulation technique was used to simulate the flow field distribution in the reactor’ This approach is not well explained at all in the manuscript. Furthermore, it seems more logical that the discussion at the beginning of ‘ Section 4 Discussion’ is moved to earlier in the manuscript where the selection for an impeller is made based on the experimental data reported here.
Regarding the statement at the beginning ‘
How does this change following the present study?
Typo in Figure3 5 reference: Process for Plamsa Synthesis of
Author Response
Response to Reviewer 2 Comments
Point 1: Line 74: ‘This study enhanced the mass and heat …..’ -> The aim of the present study is to enhance the mass and heat ……‘
Line 103:‘ The hot supersaturated solution was passed into the recrystallization condensation reactor; the stirring strength of the reactor was adjusted to cool during crystallization; and the samples were filtered, washed and dried prior to being measured.’
Response 1: Thank you for your recognition of our work. The aim of this work is to recrystallize ammonium perrhenate to reduce the particle size and increase the specific surface area. The recrystallized ammonium perrhenate can improve the solid reaction rate in the reduction process, and thus improve the mass transfer and heat transfer efficiency in the reduction process. Moreover, ammonium perrhenate was completely reduced at lower temperature to obtain rhenium powder with excellent phase parameters. We have submitted a detailed study of the restoration process to another journal and are reviewing the manuscript. This paper mainly described the recrystallization process of perrhenate before reduction, and compared the reduction experimental results with the traditional preparation process of rhenium powder. As you mentioned, one of the reduction samples was ammonium perrhenate without recrystallization (NH4ReO4（99.99％，Re≥69.4％）Halin Chemical Co. LTD.), and the other was ammonium perrhenate after recrystallization. This work has optimized the process of preparing rhenium powder by hydrogen reduction of ammonium perrhenate, and put it into actual production. Related patents have also been applied. Patent application number: CN201910706692.4.
The recrystallization of ammonium perrhenate was accompanied by agglomeration, and appropriately increasing the stirring intensity reduced the agglomeration effect. The SEM and XRD analysis showed that an appropriate reduction of the agglomeration effect was conducive to increasing the growth rates of the ammonium perrhenate crystals. Therefore, the agglomeration during recrystallization was controlled by adjusting the stirring intensity. We have studied the recovery of ammonium perrhenate from superalloy waste, and the recrystallized ammonium perrhenate in the centrifuge has serious agglomeration, which affects the reduction process. The results were published in Appl. Sci. 2018, 8(11), 2016; https://doi.org/10.3390/app8112016. Therefore, recrystallization of ammonium perrhenate was carried out by mechanical stirring in recrystallization reactor.
We have described the experimental procedure in detail.
Point 2: Line 106: Physical simulation experiment methods: In this study, the laboratory homogeneous crystal reactor was taken as the prototype, and the water model was established based on the similarity principle. The ratio of water model to prototype is 5:1.
It is not clear what simulations were performed, what software, details of the methods, references.
Response 2: We have added a detailed physical simulation of the experimental process, and this experimental method is often used to describe engineering processes.
Point 3: were experiments repeated? The impeller speed was varied ‘ only’ between 150 and 250 rpm and differences between formed crystals described but seems not extremely different. So how sure can one be about the stated differences?
Response 3: We had repeated the experiment many times. The stirring strength was within the range of 100~200rpm, and the growth rate of the crystal increased gradually with the increase of the stirring strength. When the stirring intensity was 200 rpm, the crystal growth reached an ideal state. However, when the stirring intensity was 250 rpm, the agglomeration of the system was excessively reduced, resulting in slow and incomplete crystal development. This suggested that the induction period for nucleation was reduced and the formation of crystal nuclei and growth of crystals reached an ideal equilibrium state when an appropriate reduction in the agglomeration was obtained. The high stirring intensity also made the large sedimentary particles collide, transition into the secondary crystallization stage, and maintain a uniform grain size in the crystal. However, the excessive stirring intensity enhanced the collisions between the particles, and the agglomeration was excessively weakened. Therefore, the excessive stirring intensity broke the balance for the nucleation process; the generated crystal nuclei collide and break up under excessive stirring intensity, resulting in the decrease of the number of crystal nuclei and the increase of the grain size and led to unsatisfactory crystal development.
The purpose of our work is to reduce the size of ammonium perrhenate and enhance the specific surface area. Therefore, it is determined that 200rpm is an ideal recrystallization condition.
Point 4: Figure 5: Please name in order of appearance of diffractograms, from top to bottom (this facilitates reading)
Response 4: We've corrected the naming order.
Point 5: Line 180: ‘ the crystallinity of the sample decreased. If the relative crystallinity of the samples prepared at 200 rpm was treated as 100%’
Beforehand it is mentioned the samples are polycrystalline. Now here one speaks about crystallinity decreasing. What are absolute crystallinity levels? The diffractogram exhibits sharp peaks only, how much does the amorphous phase vary?
And for the diffractograms shown, and in relation to the phrasing ‘the crystallinity of the sample reached an ideal state’ , please discuss why the difference in the diffractograms are what they are, the differences can be (in part) the result of orientation. How sure are the authors the entire sample in polycrystalline so we have a proper averaging (the case of a pure single crystal being the other extreme)
Response 5: According to the literature provided by other reviewers, we found that perrhenic acid belongs to single crystal. Ammonium perrhenate is tetragonal 4/m (isostructural with the scheelite CaWO4), and it is a typical form of monometric crystals [20].
[20]P. Swainson; R.J.C. Brown. Refinement of Ammonium Perrhenate Structure Using a Pseudo-Spin Model for the Ammonium Ion Orientation. Acta Cryst. 1997, B53, 76-78.
We simplified the XRD analysis results according to the comments of other reviewers. And we have modified the representation of the XRD analysis results more strictly. We only discussed the crystallinities and crystal growth rates of the samples under different agitation intensities. When the stirring intensity was 200 rpm, the diffraction peaks had the strongest intensities and narrowest widths among the samples herein; thus, their FWHMs were minimal. This indicated that when the stirring intensity was 200 rpm, the crystallinity of the sample reached an ideal state. The differences of crystal plane growth rates are the main reason for the difference of diffraction peak strength, which leaded to different crystallinity of the stamps within the same crystallization time.
Point 6: In 3.3 Reduction experimental the authors speak about two different samples, the second one being an industrial sample. In the materials section however only one material is mentioned: materials: NH4ReO4 (99.99%, Re≥69.4%) Halin Chemical Co. LTD.Then it needs explained why the one sample is reduced at 700C and the other one at 1000C. Please explain why these two different samples are used, and why the industrial is not reported in the sections before.
Response 6: We already mentioned this in Response 1.As you mentioned, one of the reduction samples was ammonium perrhenate without recrystallization (NH4ReO4（99.99％，Re≥69.4％）Halin Chemical Co. LTD.), and the other was ammonium perrhenate after recrystallization.
The aim of this work is to recrystallize ammonium perrhenate to reduce the particle size and increase the specific surface area. The recrystallized ammonium perrhenate can improve the solid reaction rate in the reduction process, and thus improve the mass transfer and heat transfer efficiency in the reduction process. Moreover, ammonium perrhenate was completely reduced at lower temperature to obtain rhenium powder with excellent phase parameters.
Point 7: Line 205: ‘ PIV physical simulation technique was used to simulate the flow field distribution in the reactor’ This approach is not well explained at all in the manuscript. Furthermore, it seems more logical that the discussion at the beginning of ‘ Section 4 Discussion’ is moved to earlier in the manuscript where the selection for an impeller is made based on the experimental data reported here.
Response 7: We have improved the materials and methods; the steps and methods of PIV physical simulation experiment and the applied image processing software are explained in detail. The results of PIV physical simulation were to discuss the sample differences of different agitator types. Therefore, we decided to include this in the discussion. In most literatures, the results of physical simulation are usually discussed in the discussion section of the paper.
Point 8: Typo in 5 reference: Process for Plamsa Synthesis of
Response 8: We have corrected the spelling mistakes. Finally, thank you for your professional review
Author Response File: Author Response.pdf
Reviewer 3 Report
The research topic is important due to the numerous applications of ammonium perrhenate. The presented results could be interesting for the readers.
The authors used PIV physical simulation technique to simulate the flow field distribution in the reactor. Please add details about the method and procedure.
Please, describe blue and red lines in Figure 6.
Please add the definition of the ideal state of crystal growth. It could be interesting for some readers.
Please correct the shortcomings in text editing, i.e.:
Line 26: Should be “stirring” instead of “strring”.
Line 31: What is the meaning of the “growth gate”?
Line 66: Should be “an ammonium”
Line 82: Should be ”a theoretical”
Line 113: Should be “means”
Line 232: Should be “the growth”
Libe 237: Should be: “an unsatisfactory”
& many, many more…
Tables 1 and 4: “2” should be in the upper index.
Please, check the manuscript very carefully.
Author Response
Response to Reviewer 3 Comments
Point 1: The authors used PIV physical simulation technique to simulate the flow field distribution in the reactor. Please add details about the method and procedure.
Response 1: Thank you for your recognition of our work .We have add details about the method and procedure
Point 2: Please, describe blue and red lines in Figure 6.
Please add the definition of the ideal state of crystal growth. It could be interesting for some readers.
Response 2: The red line represents particle size (µm), the blue line represents the accumulation. We have added instructions to the diagram.
The ideal state of crystal growth in this paper is relative. There is very little literature on recrystallization of ammonium perrhenate, so we have no other literature for comparison. Therefore, we judged the ideal state of the crystal according to the macroscopic morphology and the XRD test results.
Point 3: Please correct the shortcomings in text editing.
Response 3: We have corrected the shortcomings in text editing. Finally, thank you for your professional review.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript is improved, but still there are missing parts like description of SEM imaging (sampe preparation, imaging parameters).
Author Response
Point 1: The manuscript is improved, but still there are missing parts like description of SEM imaging (sampe preparation, imaging parameters).
Response 1: Thank you for your recognition and professional comments on our work. We have added further instructions to the Materials and Methods.
Author Response File: Author Response.pdf
Reviewer 2 Report
The aim of my first remark, not taken into account by the authors,
Line 74: ‘This study enhanced the mass and heat …..’ -> The aim of the present study is to enhance the mass and heat ……‘
was to improve the English, e.g. improve the meaning of what the authors want to say.
Line 104 and beyond. ‘ the prototype, and the water model was established based on the similarity principle. The water model and prototype met the following conditions：N2= N1（T1/T2）x 119 ( Formula 1), T1 was the inner 120 diameter of the water model,’
There exist many water models, different theories, for different lengths of scale and different purposes. It is far from clear what this model is. Include references.
Furthermore, ‘laboratory homogeneous crystal reactor’ is not a known terminology. Therefore it must be explained what is meant.
Line 135 ‘ Ammonium perrhenate is tetragonal 4/m’ à ?? -> The ammonium perrhenate crystal is tetragonal 4/m’ English to be improved as indicated
Were experiments repeated? The impeller speed was varied ‘ only’ between 150 and 250 rpm and differences between formed crystals described but seems not extremely different. So how sure can one be about the stated differences?
The authors have written a long rebuttal, but the results are not well taken up into the manuscript. Variation in the results. ……….
Line 191: ‘The XRD peaks were strong and sharp, indicating excellent crystallinity of the samples [24-26].’ This is a new formulation as it seems. However, it is still not quite so correct. Strong and sharp peaks as such are not a qualification for excellent crystallinity. Firstly, I believe the authors mean high and not excellent crystallinity. Excellent would refer more to crystal with some remaining defects. But high crystallinity as such cannot be concluded from sharp peaks, because the amorphous contribution is generally highly smeared out, with low intensity along the intensity axis but still non-negligible amount. This must be clarified. I think the samples look very crystalline from the diffractograms, but whether this is 99% ???? How important is this, and how do the authors want to prove this?
The authors gave a long rebuttal to one of the points I raised, I first copy from their cover letter:
‘Point 5: Line 180: ‘ the crystallinity of the sample decreased. If the relative crystallinity of the samples prepared at 200 rpm was treated as 100%’ Beforehand it is mentioned the samples are polycrystalline. Now here one speaks about crystallinity decreasing. What are absolute crystallinity levels? The diffractogram exhibits sharp peaks only, how much does the amorphous phase vary? And for the diffractograms shown, and in relation to the phrasing ‘the crystallinity of the sample reached an ideal state’ , please discuss why the difference in the diffractograms are what they are, the differences can be (in part) the result of orientation. How sure are the authors the entire sample in polycrystalline so we have a proper averaging (the case of a pure single crystal being the other extreme)
Response 5: According to the literature provided by other reviewers, we found that perrhenic acid belongs to single crystal. Ammonium perrhenate is tetragonal 4/m (isostructural with the scheelite CaWO4), and it is a typical form of monometric crystals [20]. [20]P. Swainson; R.J.C. Brown. Refinement of Ammonium Perrhenate Structure Using a Pseudo-Spin Model for the Ammonium Ion Orientation. Acta Cryst. 1997, B53, 76-78. We simplified the XRD analysis results according to the comments of other reviewers. And we have modified the representation of the XRD analysis results more strictly. We only discussed the crystallinities and crystal growth rates of the samples under different agitation intensities. When the stirring intensity was 200 rpm, the diffraction peaks had the strongest intensities and narrowest widths among the samples herein; thus, their FWHMs were minimal. This indicated that when the stirring intensity was 200 rpm, the crystallinity of the sample reached an ideal state. The differences of crystal plane growth rates are the main reason for the difference of diffraction peak strength, which leaded to different crystallinity of the stamps within the same crystallization time.’
This is in my view not complete. The authors state this compound is normally a single crystal. But later they note ‘ the crystallinity of the sample decreased.’ Also the wording polycrystalline is used. From the diffractograms I tend to think the sample is highly crystalline but the orientational distribution is different for the different samples. But if that is the case (to be proven by the authors from their data) then there is no ideal crystalline state.
The authors should get more experience in how these diffractograms are properly analysed.
Regarding
‘ Point 6: In 3.3 Reduction experimental the authors speak about two different samples, the second one being an industrial sample. In the materials section however only one material is mentioned: materials: NH4ReO4 (99.99%, Re≥69.4%) Halin Chemical Co. LTD.Then it needs explained why the one sample is reduced at 700C and the other one at 1000C. Please explain why these two different samples are used, and why the industrial is not reported in the sections before.
Response 6: We already mentioned this in Response 1.As you mentioned, one of the reduction samples was ammonium perrhenate without recrystallization (NH4ReO4（99.99％， Re≥69.4％）Halin Chemical Co. LTD.), and the other was ammonium perrhenate after recrystallization. The aim of this work is to recrystallize ammonium perrhenate to reduce the particle size and increase the specific surface area. The recrystallized ammonium perrhenate can improve the solid reaction rate in the reduction process, and thus improve the mass transfer and heat transfer efficiency in the reduction process. Moreover, ammonium perrhenate was completely reduced at lower temperature to obtain rhenium powder with excellent phase parameters. ‘
I thank the authors for the elucidation. However, this explanation should be in the text of the manuscript! Moreover, the response does not reveal that we have one laboratory and one industrial sample, I assume the word industrial should be avoided.
Regarding
Point 7: Line 205: ‘ PIV physical simulation technique was used to simulate the flow field distribution in the reactor’ This approach is not well explained at all in the manuscript. Furthermore, it seems more logical that the discussion at the beginning of ‘ Section 4 Discussion’ is moved to earlier in the manuscript where the selection for an impeller is made based on the experimental data reported here.
Response 7: We have improved the materials and methods; the steps and methods of PIV physical simulation experiment and the applied image processing software are explained in detail. The results of PIV physical simulation were to discuss the sample differences of different agitator types. Therefore, we decided to include this in the discussion. In most literatures, the results of physical simulation are usually discussed in the discussion section of the paper
This is still not very understandable and the new version of the manuscript does not help here.
It reads ‘Physical simulation experiment methods:’ but is this simulation or is it experiment, and is Particle Image Velocimetry simulation? Whereas it is stated it the software is used for processing to get the vector images.
Author Response
Point 1: The aim of my first remark, not taken into account by the authors,
Line 74: ‘This study enhanced the mass and heat …..’ -> The aim of the present study is to enhance the mass and heat ……‘
was to improve the English, e.g. improve the meaning of what the authors want to say.
Response 1: We have revised the English expression according to your suggestion.
Point 2: Line 104 and beyond. ‘ the prototype, and the water model was established based on the similarity principle. The water model and prototype met the following conditions：N2= N1（T1/T2）x 119 ( Formula 1), T1 was the inner 120 diameter of the water model,’
There exist many water models, different theories, for different lengths of scale and different purposes. It is far from clear what this model is. Include references.
Furthermore, ‘laboratory homogeneous crystal reactor’ is not a known terminology. Therefore it must be explained what is meant.
Response 2: In this paper, only one water model was established, and the purpose was to simulate the flow field distribution in the recrystallization condensation reactor. In order to study the effects of agitator types on recrystallization, PIV physical simulation technique was used to simulate the flow field distribution in the reactor. This design of the water model was based on geometric similarity. ‘3.1. The influences of paddle types’ presented that the morphologies of ammonium perrhenate crystals under different stirring types by means of SEM. The result of physical simulation was the explanation of this phenomenon. We have already made changes in the corresponding parts of the article.
For the design of the water model, we added the cited literature, and put the illustrations in the reply, please review, as shown in the figure below.
The ‘laboratory homogeneous crystal reactor’ is the 1 L self-designed recrystallization condensation reactor. We corrected this statement in the article.
Point 3: Line 135 ‘ Ammonium perrhenate is tetragonal 4/m’ à ?? -> The ammonium perrhenate crystal is tetragonal 4/m’ English to be improved as indicated
Response 3: We have corrected the English expressions.
Point 4: Were experiments repeated? The impeller speed was varied ‘ only’ between 150 and 250 rpm and differences between formed crystals described but seems not extremely different. So how sure can one be about the stated differences?
The authors have written a long rebuttal, but the results are not well taken up into the manuscript. Variation in the results. ……….
Response 4: We have made appropriate modifications in Results and Discussion.
Point 5: This is in my view not complete. The authors state this compound is normally a single crystal. But later they note ‘ the crystallinity of the sample decreased.’ Also the wording polycrystalline is used. From the diffractograms I tend to think the sample is highly crystalline but the orientational distribution is different for the different samples. But if that is the case (to be proven by the authors from their data) then there is no ideal crystalline state
Response 5: We have carefully referred to your comments and revised the article.
In order to research the relationship between the difference of crystal morphologies and the selectivity of crystal growth directions, XRD analysis were performed. The XRD peaks were strong and sharp, indicating selective growth of crystal plane. [25-27]. The XRD patterns of the samples at different stirring speeds and the same crystallization time (2 h) are shown in Figure. 5 and the XRD information are given in Table 2. The main diffraction peaks were from the NH4ReO4, and other crystalline species were not observed. However, these diffraction peaks had different intensities. When the stirring intensity was 200 rpm, the diffraction peaks had the strongest intensities. This indicated that when the stirring intensity was 200 rpm, the selective growth rates of the crystal planes corresponding to the characteristic peaks were higher than that of other samples. In this paper, the selectivity of the crystal growth directions on the (101) crystal planes and (112) crystal planes at different stirring speeds can be calculated by the Scherrer formula, where D = Kλ /(B cosƟ), and the results are given in Table 3. Table 3 shows that the growth rates of the (101) crystal planes and (112) crystal planes were promoted with increasing stirring speeds (100 rpm~200 rpm). However, the growth rates of the (101) crystal planes and (112) crystal planes were subdued at the excessive stirring speed (250 rpm).
The above is the modification of the XRD analysis made by us according to your opinion.
When the stirring intensity was 200 rpm, the growth rates of the crystal planes corresponding to the characteristic peak of the crystals were relatively fast. Therefore, the crystal development was more complete at the same crystallization time. However, when the stirring intensity was 250 rpm, the agglomeration of the system was excessively reduced; the growth rates of the crystal planes corresponding to the characteristic peak of the crystals were subdued, resulting in slow and incomplete crystal development. This suggested that the induction period for nucleation was reduced and the formation of crystal nuclei and growth of crystals reached an ideal equilibrium state when an appropriate reduction in the agglomeration was obtained. The high stirring intensity also made the large sedimentary particles collide, transition into the secondary crystallization stage, and maintain a uniform grain size in the crystal. However, the excessive stirring intensity enhanced the collisions between the particles, and the agglomeration was excessively weakened. Therefore, the excessive stirring intensity broke the balance for the nucleation process; the generated crystal nuclei collide and break up under excessive stirring intensity, resulting in the decrease of the number of crystal nuclei and the increase of the grain size and led to an unsatisfactory crystal development.
The above are the modifications we made to the discussion part of the XRD analysis results
Point 6: I thank the authors for the elucidation. However, this explanation should be in the text of the manuscript! Moreover, the response does not reveal that we have one laboratory and one industrial sample, I assume the word industrial should be avoided.
Response 6: We have revised the expression of the manuscript.
Point 7: This is still not very understandable and the new version of the manuscript does not help here.
It reads ‘Physical simulation experiment methods:’ but is this simulation or is it experiment, and is Particle Image Velocimetry simulation? Whereas it is stated it the software is used for processing to get the vector images.
Response 7: The physical simulation presented in this paper is discussed as a means of analyzing the flow field distribution in the reactor. The physical simulation results discussed the difference of the shapes of the propellers to the crystal morphologies.
The velocity vector cloud diagrams of flow field distribution with different agitator types at the same agitator speed and agitator position were shown in Figure 7. It can be seen that the flow field in the reactor was more evenly distributed when using the disc turbine impeller, and a relatively uniform velocity liquid flow area was formed in the whole reactor, while the low-velocity liquid flow area was smaller，as shown Figure 7 (a). Combined with SEM test results (Figure 3) suggests that under the uniform flow field, the large particles collided and broke into the small particles of uniform size, these particles became nuclei again and grew into complete crystals under uniform flow. Therefore, the stirring effect of disc turbine impeller is more suitable for homogeneous recrystallization process.
Therefore, we have adjusted the process of physical simulation to 2.3 Analytical Methods
Finally, thank you for your professional comments. I hope you are satisfied with our reply.
Author Response File: Author Response.pdf
Reviewer 3 Report
The revised manuscript is much more readable. The authors have added important descriptions.
Author Response
Point 1: The revised manuscript is much more readable. The authors have added important descriptions.
Response 1: Thank you for your recognition and professional comments on our work. Your support is the motivation of our work.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
please see attached file, thanks, good luck with final version!
Comments for author File: 
Comments.doc
Author Response
Point 1: the fact that peaks are strong and sharp as such is NOT a proof for selective growth: a perfect single crystal has sharp and intense peaks
Response 1: We revised the article according to your Suggestions.
Point 2: The former sentence reads strange: MAIN peaks from NH4ReO4, but no other crystalline species present. This suggests there are also other than the MAIN peaks, what do these come from? why HOWEVER, of course they do, this is normal isn’t it, depending on the crystal structure
Response 2: We revised the article according to your Suggestions. The raw material for this work is ‘NH4ReO4 (99.99%, Re≥69.4%) Halin Chemical Co. LTD.’ Therefore, only perrhenate ammonium in the sample, no other magazines.
In order to research the relationship between the difference of crystal morphologies and the selectivity of crystal growth directions, XRD analysis were performed. The XRD patterns of the samples at different stirring speeds and the same crystallization time (2 h) are shown in Figure. 5 and the XRD information are given in Table 2. The diffraction peaks were from the NH4ReO4, and other crystalline species were not observed. Tthese diffraction peaks had different intensities.
Point 3: Why were they fast, how did you see, but more importantly is that important whether it is fast? Was it really reduced, do you have evidence for smaller crystals?
Response 3: We revised the statement in the article: When the stirring intensity was 200 rpm, the growth rates of (101) and (112) crystal planes corresponding to the characteristic peaks of the crystals were relatively fast, as shown in Table 3. Therefore, the crystal development was more complete at the same crystallization time. However, when the stirring intensity was 250 rpm, the agglomeration of the system was excessively reduced; the growth rates of (101) and (112) crystal planes corresponding to the characteristic peaks of the crystals were subdued, resulting in slow and incomplete crystal development.
This discussion is based on the calculation of the growth rates of the 101 and 112 crystal planes, which is the D-values.
Finally, thank you again for your professional review, which has helped us a lot.
Author Response File: Author Response.pdf
