Structural and Mechanical Properties of Amorphous Si3N4 Nanoparticles Reinforced Al Matrix Composites Prepared by Microwave Sintering
Round 1
Reviewer 1 Report
The authors have done "Effect of ceramic reinforcement (Si3N4) on physical and mechanical
properties of aluminum matrix nanocomposites prepared by microwave sintering".
1. The title shows "Nanocomposites"- but in the manuscript, I didn't observed any study about nanoparticles/nanograins/nanocomposites. Please if the particles are not in nano, remove the word from the title.
2. Please try to change the title as structural and mechanical properties.....microwave sintering.
What Physical properties have you been studied. Only XRD, SEM and EDX studied by you.
They are structural properties.
3. Do you have any comparable study on the same composite by other sintering methods? If yes, please compare with them.
4. In Materials and methods, you didn't used balls while doing milling. How did you mill without balls by using ball milling.
5. What is the purpose ball milling in the present work.
6. How many set of samples have you been prepared for this whole study.
7. In XRD, around 65 and 80, the intensity peaks shows splitting. Could you please explain about it.
8. Figures are not in consistency. Please make them correct.
9. In Section 3.5, Fracture surface shows 45o to the compression loading axis. I didn't see anything. Could you please make it clear this. How do you tell this.
Author Response
Review Report Form :1
The authors thank the editor and the reviewers for reviewing the manuscript and providing constructive comments to improve the quality of the manuscript. The authors have tried their best to respond to reviewer comments and hope the reviewers are satisfied by the responses.
The authors have done "Effect of ceramic reinforcement (Si3N4) on physical and mechanical properties of aluminum matrix nanocomposites prepared by microwave sintering".
Reviewer #1
Comment 1: The title shows "Nanocomposites"- but in the manuscript, I didn't observed any study about nanoparticles/nanograins/nanocomposites. Please if the particles are not in nano, remove the word from the title.
Response to Comment 1: Thank you for pointing this out. Please note that nano-sized Si3N4 paritlces were used as reinforcement to Al matrix. Corrections have been made in the revised manuscript.
Comment 2: Please try to change the title as structural and mechanical properties.....microwave sintering.
What Physical properties have you been studied. Only XRD, SEM and EDX studied by you.
They are structural properties.
Response to Comment 2: The authors thank the reviewer for his suggestions and agree with the reviewer. The title has been chaged to “Structural and mechanical properties of amorphous Si3N4 nanoparticles reinforced Al matrix composites prepared by microwave sintering” as suggested by Reviewer.
Comment 3: Do you have any comparable study on the same composite by other sintering methods? If yes, please compare with them.
Response to Comment 3: Thank you for your insightful review. A comparison of the hardness and compressive strength properties of Al-Si3N4 composites synthesized using microwave sintering in this study with other AMCs fabricated by PM routs indicates that comparable properties can be achieved even with a significant reduction in processing time.
Composition
Microhardness (Hv)
CYS
(MPa)
UCS
(MPa)
Failure strain
(%)
Pure Al
38±3
70±4
305±3
>7
Al-1wt. % Si3N4
43±5
86±5
325±5
>7
Al-2wt. % Si3N4
58±3
104±3
349±4
>7
Al-3wt. % Si3N4
77±2
127±4
364±2
>7
Al-3wt. % Si3N4 [29]
57±2
198±21
292±18
--
Al-9wt. % Si3N4 [35]
59.5
--
--
--
Al alloy-3wt. % Si3N4 [36]
82
---
---
--
35. Ankit, T.; Deepak, Sharma. Characterization of AA6082/Si3N4 Composites. 21st International Conference on New Frontiers in Engineering, Science & Technology, New Delhi, India, January 8-12, 2018.
36. Pardeep, S.; Satpal, S.; Dinesh, K. Production and some properties of Si3N4reinforced aluminium alloycomposites. J. Asian Cer. Soc. 2015, 3, 352–359.
Comment 4: In Materials and methods, you didn't used balls while doing milling. How did you mill without balls by using ball milling.
What is the purpose ball milling in the present work.
Response to Comment 4: We are thankful to referee for pointing this out. The mixture of matrix and reinforcement powders was blended at room temperature using a Retsch PM400 planetary ball mill for 2 h with the milling speed of 200 rpm in order to get a homogeneous particle (Si3N4) distribution in Al matrix.
Comment 5: How many set of samples have you been prepared for this whole study.
Response to Comment 5: In this current study, for each composition, three samples were tested to ensure repeatable values.
Comment 6: In XRD, around 65 and 80, the intensity peaks shows splitting. Could you please explain about it.
Response to Comment 6: Thank you for your insightful review. The diffraction angle, 2 theta, at 65°, and 80° corresponds to {220} and {222} planes of hexagonally close packed (HCP) aluminum crystal respectively. Gernerally, the crystalline substances have long range order. The amorphous substances do not possess this long range order. However, when amorphous Si3N4 content added with Al, the peak splitting corresponding to higher 2theeta was also observed. This peaks splitting happens when crystalline and amorphous phases are together.
Comment 7: Figures are not in consistency. Please make them correct.
Response to Comment 7: We are thankful to referee for pointing this out. The quality of figures has been improved as suggested by the Reviewer.
Comment 8: In Section 3.5, Fracture surface shows 45o to the compression loading axis. I didn't see anything. Could you please make it clear this. How do you tell this.
Response to Comment 8: We are thankful to referee for pointing this out. Under compressive loading, fracture surfaces were at approximately 45 degrees, with respect to the compression testing direction. Shear bands were observed (see Figure 6d), which is an indication of shear mode of failure.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
All data should include error (bars) and average values in Fig. 2,5, 6, and Table 1. Without the error and the average of (density, strength, etc ), we cannot believe and trust the result of mechanical and physical values. Authors should present high magnification photos showing Si3N4 nanoparticles and the interface of Si3N4 particle and the matrix. Unfortunately, all photos have poor resolution under low magnification.
There are too many colloquialisms and wasted words in the text and sentences. Scientific writing is needed and a proof reading by a native speaker is needed
Author Response
Review Report Form: 2
The authors thank the editor and the reviewers for reviewing the manuscript and providing constructive comments to improve the quality of the manuscript. The authors have tried their best to respond to reviewer comments and hope the reviewers are satisfied by the responses.
Comment 1: The data should include error (bars) and average values in Fig. 2,5, 6, and Table 1. Without the error and the average of (density, strength, etc ), we cannot believe and trust the result of mechanical and physical values. Authors should present high magnification photos showing Si3N4 nanoparticles and the interface of Si3N4 particle and the matrix. Unfortunately, all photos have poor resolution under low magnification.
Response to Comment 1: The authors thank the reviewer for his suggestions and agree with the reviewer.
In this current study, for each composition, three samples were tested to ensure repeatable values. Ther error (bars) are included in the revised Fig. 2,5,6 and Table:1.
As suggested by the reviewer, We have included new SEM images with high magnification for better visibility.
Comment 2: There are too many colloquialisms and wasted words in the text and sentences. Scientific writing is needed and a proof reading by a native speaker is needed.
Response to Comment 2: We agree with the reviewer and have removed such wordings. In the revised manuscript, the English and grammatical errors are corrected and the interpretations and flow have been significantly improved.
Author Response File: Author Response.pdf
Reviewer 3 Report
Following concerns need to be addressed before publication in any journal:
The material characterization data is very poor. There is no reason to believe that SiN is uniformly distributed in the metal matrix. Figure 4: SEM EDS mapping or line scan or point scan is needed.
What was the reason for not preparing specimen at higher weight loading than 3 wt. %?
Microscope of the indent area would be useful.
Figure 7: Si3N4 particles no visible.
SEM of Si3N4/Al at various stages is recommended--as obtained, mixing, green body etc.
Digital camera image of experimental setup and failed specimen need to be included.
Author Response
Review Report Form: 3
The authors thank the editor and the reviewers for reviewing the manuscript and providing constructive comments to improve the quality of the manuscript. The authors have tried their best to respond to reviewer comments and hope the reviewers are satisfied by the responses.
Following concerns need to be addressed before publication in Ceramics journal:
Comment 1: The material characterization data is very poor. There is no reason to believe that SiN is uniformly distributed in the metal matrix. Figure 4: SEM EDS mapping or line scan or point scan is needed.
Response to Comment 1: The authors thank the reviewer for his suggestions. We have included new SEM images with high magnification for better visibility in the revised manuscript. SEM images of the synthesized composites provided good enough evidence of near-uniform distribution of the nanoparticles in the aluminum matrix. XRD justifies that Al-Si3N4 is a model system and hence doesn’t form any secondary reaction products. EDS spectrum (See below) of Al-Si3N4 composite capture no other elements other than Al, Si and N in the mapping and EDX data clearly confirm the presence of Si3N4 nanoparticles. However, the authors will bear in mind the importance of EDS mapping or line scan or point scan results and will incorporate in future studies. I hope, you will accept our humble justification keeping in view our experimental limitations.
Comment 2: What was the reason for not preparing specimen at higher weight loading than 3 wt. %?.
Response to Comment 2: The authors thank the reviewer for his question and agree with the reviewer. Our preliminary studies indicates that the addition of 5wt. % Si3N4 to Al matrix did not yield favourable results. In the present case, it can be concluded that Al-3wt. % Si3N4 exhibits the best combination of overall properties with all the properties such as strengths and hardness have improved results with the increasing amount of reinforcement up to 3 wt.%.
Recently nano-sized reinforcements (SiC, Al2O3, B4C, Si3N4 etc., of size usually<50 nm) have been used. The major advantage of using nano-reinforcements is that the enhancement in properties can be attained at lower volume fractions (<2 %),whereas for micron-scale particle reinforced MMCs higher volume fractions (≫10 %) are required. However, in order to produce sound nanocomposites with enhanced mechanical properties, good dispersion of the nano-reinforcement phase within the matrix is necessary, which is in turn strongly governed by the selection of a suitable production process.
Comment 3: Microscope of the indent area would be useful.
Response to Comment 3: The authors thank the reviewer for his suggestions. Unfortunately, the authors do not have access to examine the Atomic Force Microscopy indentation studies. I hope, you will accept our humble justification keeping in view our experimental limitations.
Comment 4: Figure 7: Si3N4 particles no visible.
Response to Comment 4: We are thankful to referee for pointing this out. The magnification of the compression fractography images are taken at a lesser magnification as to why which the reinforcement particles aren't visible. However we can see that, the matrix failure determines the fracture of the Al composites.
Comment 5: SEM of Si3N4/Al at various stages is recommended--as obtained, mixing, green body etc.
Response to Comment 5: The authors thank the reviewer for his suggestions. Unfortunately, the authors do not have green samples to examine the SEM analysis. SEM images of the synthesized nanocomposites provided good enough evidence of near-uniform distribution of the nanoparticles in the aluminum matrix. XRD justifies that Al-Si3N4 is a model system and hence doesn’t form any secondary reaction products. However, the authors will bear in mind the importance of grean samples for further studies and will incorporate in future studies. I hope, you will accept our humble justification keeping in view our experimental limitations.
Comment 6: Digital camera image of experimental setup and failed specimen need to be included.
Response to Comment 6: The authors thank the reviewer for his suggestions. Corrections have been made in the revised manuscript (see figure 1 pls).
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have done all the changes according to my comments. Now it is acceptable.
Author Response
Review Report Form :1 (Round 2)
Reviewer #1
Comment 1: The authors have done all the changes according to my comments. Now it is acceptable.
Response to Comment 1: We appreciate the positive feedback from the reviewer.
Author Response File: 
Author Response.doc
Reviewer 2 Report
Do not use the abbreviation of (MWS) in the abstract,
Provide in detail information on the equipment which you used
Ex. Hitachi FESEM-S4300, which Country?).
Provide (a) and (b) label, respectively on the figure, and modify the caption, Figure 2. Variation of experimental density (a) , and porosity (b) with Si3N4 content.
Indicate (a) and (b) label on Fig. 3
Figure 3. (a) XRD pattern of Al-Si3N4 nanocomposite, (b) Al-3wt. % of Si3N4 nanocomposites.
In Figure 4. (a) Label is missing.
Do not separate Figure 4. (e) from Fig. (a)-(d) and merge all together.
Add wt.% unite on the X-axis of title of Figure 6 (b)
8 . Provide (1), (2).. serial number for each equation (formulas) in the text.
Author Response
Review Report Form :2 (Round 2)
We truly appreciate all the constructive comments and suggestions from both reviewers. We have adopted all the suggestions in our revised manuscript. The following are our point-to-point responses to the reviewers’ comments.
Comment 1: Do not use the abbreviation of (MWS) in the abstract.
Response to Comment 1: The correction has been made.
Comment 2: Provide in detail information on the equipment which you used, Ex. Hitachi FESEM-S4300, which Country?).
Response to Comment 2: The text has been revised as suggested.
Comment 3: Provide (a) and (b) label, respectively on the figure, and modify the caption, Figure 2. Variation of experimental density (a) , and porosity (b) with Si3N4 content.
Response to Comment 3: As per reviewer suggestion, the correctiobs has been made in the revised manuscript. See Figure 2 pls.
Comment 4: Indicate (a) and (b) label on Fig. 3. Figure 3. (a) XRD pattern of Al-Si3N4 nanocomposite, (b) Al-3wt. % of Si3N4 nanocomposites.
Response to Comment 4: The correction has been made. See Figure 3 pls.
Comment 5: In Figure 4. (a) Label is missing. Do not separate Figure 4. (e) from Fig. (a)-(d) and merge all together.
Response to Comment 5: We have merged all together and have been incorporated in the revised manuscript. See Figure 4 pls.
Comment 6: Add wt.% unite on the X-axis of title of Figure 6 (b)
Response to Comment 6: Correction has been made in the revised manuscript. See Figure 6 (b) pls.
Comment 7: Provide (1), (2).. serial number for each equation (formulas) in the text.
Response to Comment 7: Correction has been made in the revised manuscript.
Author Response File: Author Response.doc
Reviewer 3 Report
Revised version looks okay.
Author Response
Review Report Form :3 (Round 2)
Reviewer #3
Comment 1: Revised version looks okay.
Response to Comment 1: We thank the reviewer for his positive response.
Author Response File: Author Response.doc
