This article deals with the buckling of periodic lattices in order to generate an auxetic behavior, sometimes called "metamaterials" for unknown reasons. The title of the paper is misleading since designing auxetics is not at the core of this work, as a matter of fact the design considered has been around for a few years now, as the literature review given by the authors shows. One important reference on plasticity of auxetics has been forgotten: R. Gilat and J. Aboudi, Behavior of Elastoplastic Auxetic Microstructural Arrays, Materials, 6, 726-737 (2013). There are only 2 references on this topic, Dirrenberger et al. (2012) and the latter, which happens to be published in the present journal. Moreover, in lines 84-87, it is stated that Andersson et al. (2008) developed an anisotropic compressible plasticity framework for auxetics, although there is no such things in the cited paper which deals with compression experiments on polyurethane foams. I believe the authors refer to the anisotropic compressible plasticity framework developed in Dirrenberger et al. (2012). This is just an example of several miscitations that I have observed in the paper. For instance, the original paper of Lakes on auxetics should be cited: Lakes, R., Foam structures with a negative Poisson's ratio. Science, 235(4792), 1038-1040 (1987). Another example, line 254, Shen et al. is cited but as reference 41 instead of 42. The authors should verify every citation for potential publication. Regarding the form of the paper, some formulations are clumsy, but one is just not acceptable for a scientific paper and should be removed: line 212-213, "a complicated casting process provided by Shapeways company".The authors should always be clear and specific. The authors should always be clear and specific. Which brings me to the scientific soundness of the paper. Firstly, in a community obsessed with modelling and simulation, it is courageous and very useful to make actual experiments on auxetics. Nevertheless, only a few technical details are given regarding the material behavior and propreties, it is eluded in one sentence line 160-161 for yield strength the reader is sent to another recent paper by the same group (quite redundant with this one by the way) instead of just giving the value directly. For studying plastic buckling I think that yield strength should be presented and discussed in more details. Nothing is stated about potential anisotropy for the constitutive material behaviour. Also, the constitutive plasticity law used is not described explicitely, nor justified. Except these few remarks, the experiments and simulations seem sound and are analysed properly. An interesting result is discussed line 571-572 about the increasing hardening ratio enhancing the auxetic behavior, this is in accordance with what was shown by Dirrenberger et al. (2012), i.e. increasing the isotropic hardening modulus resulted in an enhanced auxetic effect (NPR closer to -1), I think it would add value to the discussion if the connection was made betwenn these two independent results, although this is just a suggestion. Also, it was appreciated that the authors took some precautions in the last paragraph of the conclusions regarding the experiments and their limit of validity, it is not often seen in the experimental mechanics community, especially regarding auxetics, or worse: metamaterials. This paper should be considered for publication after minor revision.
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The authors investigated the effect of 2 different organic compounds (PA and CM) in 3 different concentrations (0.5, 1, 2 and 3 wt%) on fabrication of Fe-Al intermetallic foams. The subject fits to the Special Issue and is of high interest. Overall, the manuscript reports about an interesting piece of work, and is well organized and synthetic in text (not redundant or too long). However, some clarifications, partly in language and partly in presentation (redundant or inappropriate illustrations) are required before acceptance.
1. Line 46: remove newline.
2. Lines 49-50: replace "and due to their volumetric expansion during combustion allowed to form highly porous materials" with ", which allowed to form highly porous materials thanks to their volumetric expansion during combustion"
3. Fig.1 text: in text-box "the regulating punch fence" remove "the".
4. Line 56: "combustion synthesized", insert hyphen in between
5. Lines 60-63: “As expected, the final porosity of obtained sinters is lowest for samples sintered without additives and the highest for samples doped 3 wt. % of chemical compounds regardless of whether palmitic acid or cholesteryl myristate was used”: for the sentence to make sense, the final “was used” shoud be removed.
6. I do not like, and there is no reason for, that the level of zero additive porosity is represented as an horizontal bar spanning all x axis, in Fig.3: just represent as the other datapoints, i.e.e as a single point with its error bars, corresponding to x axis (chemical compound wt%) value =0.
7. About Fig.3 and related text: The highest wt% seems to give the highest % porosity, but: - the trend is not monotonic: the second highest porosity seems to occur for the second lowest (apart from 0) compound concentration, 0.5; - so, probably the differences are, in most cases, not statistically significant: the authors, in addition to showing mean+-std. dev bar, should analyze sets of raw data (all datapoints for each case) and carry out ANOVA with pairs comparisons, and say which couple are statistically significant in difference (at 0.05 level). Is, thus, case of concentrations 3% really different from 0.5? Maybe not. From 1? Probably yes. Please add this part and few consequent comments.
8. Line 74: ": (a)" change to “(a)”
9. Line 76: "(d))" change to "(d)."
10. Table 1: for all values, replace "," with "."
11. Table 1 values: should be approximated differently, given the error: e.g. 36.20+-0.72 should read 36.2+-0.7 43.08+-1.03 become 43.1+-1.0, and so on 47.15+-0.96 is more difficult: 47.2+-1.0
12. Line 64: “, Kirkendall” change to “, thus either Kirkendall”
13. In each first occurrence of the respective acronym, the full working should be defined first. So, for example: Line 64: “SEM” replace with “Scanning electron microscope (SEM)” Line 83: “XRD” replace with “X-ray diffraction (XRD)” Line 85: “EDS” replace with “energy-duspersive spectroscopy (EDS)”
14: Do not define acronyms in the abstract, not self-standing: So, remove “(PA)” and “(CM)” on line 18 and 19, respectively.
15. Remove “(PM)” from line 48: this acronym is not used in the manuscript after that.
16. Line 89: “diffraction pattern (XRD)” change to “XRD pattern”
17. Line 101: “3” change to “4”
18 Same line: “Thus, only amorphous, carbon containing, phases” change to “Thus, only amorphous carbon-containing phases”
19. Line 103: “methods poor accuracy” change to “poor accuracy of the technique”
20. Frankly speaking, in Fig.5 the different abundance of elements should appear as maps of different colors (e.g. red for Fe, blue for Al) overlayed on different SEM imaged areas. However, let’s say that the reader will believe the ‘arrows’ assignement.
21. Fig.6 and 7 are quite redundant: they are not strictly useful to the paper, also given the limitation pointed at item 20 above, that no color elemental mapping is shown. So I would really think about removing or at least limiting their number. For example, in both cases (MC for Fig.6 and PA for Fig.7), at both concentrations (0.5 and 3) a low and high magnification image is shown, and the EDS is taken only from the high magnification image; (additionally, it is not clear if the high mag image is taken from the same region, as a closeup of the low mag image: if so, a rectangle with the are of the hi mag image should be overlaid on the – previous – low mag image). Everything would actually be much easier, if the all the low mag images are removed; alternatively, all the hi mag images may be removed:
22. in fact, in ant case, also the arrow pointing to the EDS table should be removed, as it is again not clear where it comes from: a single point, at the base (starying point) of the arrow? Or the whole image area? In the former case, is it really representative of the specimen? Finally: I would remove either low or (maybe better) high mag images, so halving them (from 8 to 4); the thus reduced 4 SEM images (2 additives x 2 concentrations) could be combined in a single figure, so from fig.6 and 7 to 6 only.
The info about EDS composition can then be presented separately, better in the form of a plot: a bar plot would do the job nicely: 4 groups of 4 bars (1 bar for each element).
23. Line 122: “mentioned above chemical additives combustion temperature” change to “the combustion temperature of the above-mentioned chemical additives”
24. Same line: “is” change to “was”
25 Line 123: “Volumetric expansion of the gases, increased pressure” change to “Volumetric expansion of the gases occurred accompanied by increased pressure,”
26. Line 128: Insert neline before “Therefore”
27. Line 132: “agents, however” too long, split: “agents. However”
28 Lines 133-134: “elements what seemed previously as unavoidable” change to “elements, what previously seemed to be unavoidable”
29 Line 136 “is while” change to “occurs when”
30 Line 137: “other, undesired” remove comma
31 Line 139 “while” change to “when” Same at line 144.
32 Line 146: “were” change to “are”
33. Line 149. “However the shorter hydrocarbon chain, the more eager combustion undergo and the lower temperature of sintering is effective for the foaming” change to “However, the shorter the hydrocarbon chain, the easier is the combustion, and the lower is the sintering temperature effective for the foaming”
34 Line 162: “Φ25 mm” change to “25 mm diameter”
35 Line 168: “scanning microscope” change to “SEM”
36 Line 173: “compounds” change to “coumpounds such as palmitic acid and cholesteryl myristate”
- Review of
The authors presented a detailed characterization of some samples of Fe-Al-Ti ternary alloys fabricated by LENS technology. The results are of interest for high temperature applications. A very thoroughful discussion is presented, with extensive comparison with literature. I think that the work should be accepted after minor revisions, detailed in the following. I wish to congratulate with the authors for two different reasons: i) they definitely showed no ‘salami slicing’ style: they could have made at least three different high quality research articles with the amount of presented experimental data; ii) their writing is very plain and clear, which makes even the scientist not expert in their field to understand almost everything: this is the style that scientific/technical reports should always exhibit.
1. The SEM images in Fig.1 appear all laterally stretched (expanded), each one to different extent. The worse is panel a, where the spherical particles clearly appear to be elongated horizontally. Please check and restore the images to their original and true aspect ratio.
2. Line 383: remove “from Sandvik Osprey” as this is redundant, the source of this material has already been specified correctly few lines above.
3. Line 385: Remove “standard”
4. Line 391: “powder flow rate of the powder feeders”: remove the first “powder”
5. Lines 401 and 403: in parentheses, please add the country of the company, after the company name and a comma. Same at lines 429, 432, 434, and 438.
6. Line 396: remove “cylindrical”
7. 414: “transmition”, fix.
8. Line 419: why the end is empyt? Check for extra hidden characters such as Tab, spaces, etc.
9. 436: decimal separator must be point, not comma
10. 438: “test load of 100 G”: what unit or quantity is G?
11. 155 & 445: “5 x 5mm”, change to “5x5 mm^2”
12. 456: “finegrained”, I think that “fine-grained” should be preferred.
13. 32, 137, 358, 458: “rapid cooling rate”: either you meen the cooling, and is rapid, or the rate, and is high, so replace with either “rapid cooling” alone or “high cooling rate”. Since the simplest is the best, I would prefer the first option.
- 145 “crack”, change to “cracks”
15. At lines 124, 151, 152, 157, 133, Legends from Fig.3 to 11, 1st col Table 1, 198, 204 226, 231, 242, 253, 261, 294, 299, 301, 307, 310, 316, 334, 347, and maybe elsewhere where I skipped to notice: The word “alloy” (“alloys”) should be replaced by “sample” (“samples”), always when acocmpanied by the respective ID number.
16. 189: remove “by XRD”
17. 190: “with grain size”, change to “of grain size”
18. Fig.4: I would remove the question marks, and, if possible, increase all text size a bit (axis title and values, inset legends)
19. Line 388: Before “The nominla compositions…” it should be written clearly that “Four samples of alloys were investigated in details, which have been called sample no. 1 to 4.”
20. 202: Remove “unidentified”; replace “because the presence of” with “by”; remov “was found in the investigated alloy”
21. 221-222: “the colors are based on a color-coded inverse pole figure inserted in this map”: not clear, rephrase.
22. Why Fig.7.b is much higher magnification than a? Not clear. Or, alternatively: it is not clear why DF is used in this case instead of BF.
23. Table 1, column HV0.1: add also the quantity name, in addition to symbol, e.g. “Vickers hardness”
24. Insert a blank line above (before) Fig. 8
25. Fig.8: exchange panels a with d and b with e
26. 340: “Figs.11” change to “Fig.11” Conversely at line 345 “Fig.12b,d” to “Figs.12b,d”.
- Review of
The authors have performed a thorough in vitro investigation of the behavior of a substrate of porous titania as a surface for incubation of living cells or bone and cartilage. The results are very interesting, of potentially high impact. The technical and scientific work is sound. The quality of the presentation should be definitely improved: make figure text readable, and rearrange the figures to select only the important ones and pack together into fewer illustrations. Also, next time authors please have an english mother tongue colleague go through the paper and fix the language issues. After major revisions and a second review round to verify them, the work should be acceptable.
Mandatory corrections of technical/scientific contents:
1. In the title, ‘allow’ is a bit weak: many surfaces ‘allow’, mean they are not cytotoxic or too smooth. Rather make it stronger by replacing wil ‘allow enhanced’, or more simply, ‘enhance’ or ‘promote’
2. In the abstract line 2, I wouldn’t write that Ti-alloy is a low-modulus material. I can imagine that the authors mean, low with respect to unalloyed Ti (say, perhaps, 105 GPa instead of 110), anyway this decrease is not that much, and still classifies the material as a high modulus one. One wouldn’t use it for dental or orthopedical applications if it was a low modulus material! Anyway, low or hi are always qualitative statements, depends on application, term of comparison etc, what is low in one case may be hi in another case. So, simply: ‘properties, tensile strength, biocompatibility, low modulus and corrosion resistance’ change to ‘properties, such as high tensile strength, good biocompatibility, appropriate modulus and low corrosion resistance’
3. Line 3: ‘Earlier studies…metals’: this is of no interest, remove it. You should focus only on your workin the abstract, the Introduction will come later.
4. ‘Microscopic examination’ change to ‘We carried out microscopic examination’
5. ‘, for evaluate’ change to ‘ to evaluate’
6. ‘reveals increased cell adhesion, and cellular biocompatibility’ change to ‘to investigate cell adhesion and cellular biocompatibility’
7. ‘for growing of’ change to ‘to grow’
8. Intro, paragraph 2: ‘Pathologies like’ change to ‘These tissues are affected by pathologies like’
9. ‘; osteoporosis is defined as’ change to ‘and osteoporosis,’ Plus: ‘It is considered as the second’ change to ‘These pathologies are considered second’
10. In the intro, among the cited literature of TiO2 applications, a recent advanced characterization of nanotubuklar TiO2 would better be added, which is ‘Anodic oxidation of titanium in sulphuric acid and phosphoric acid electrolytes’, by Sureeporn Uttiya, Daniele Contarino, Sonja Prandi, Maria Maddalena Carmasciali, Gianluca Gemme, Lorenzo Mattera, Ranieri Rolandi, Maurizio Canepa, Ornella Cavalleri, Journal of Materials Science & Nanotechnology, in press. In this paper, by SEM, AFM and XPS, it is discussed that anodization in phosphoric acid instead of sulphuric acid would be better for bioapplications, thanks to the inclusion of likely bioactive phosphates.
11. ‘This work strategy’ change to ‘Our work strategy’
12. ‘Chondrocyte growth, adhesion and biocompatibility on 80 nm TiO2 nanotubes had not been reported.’: remove! redundant
13. Subsequent, sentence: ‘In vitro … response.’ Is already reporting results, which is not appropriate for the Intro. Either move this to the Conclusion, integrating it with already existing summary there, or simply remove!
- Section ‘Synthesis…’: ‘Electrolytically anodized’: seems the Ti-alloy come from the company already anodized, is this the case? Hope not. If not, remove! (it’s you who anodize, right?)
15. After writing the complex solution used for anodization, you should write if this is overall acid or not, e.g. write its typical pH. Please also specify that the anodization was carried out at RT, if this is the case, as T is important to control during anodization. What is the reason to add salts to the solution, in addition to the acid? Anodization is usually carried out only in simple acidic solutions.
16. ‘using an acoustic chamber to prevent electromagnetic noises’: funny! Anti-acoustic chamber is used against mechanical noise vibration transmitted through the air. Do you mean that the antiacoustic box is also metal coated to shield em noise? Specify it, this is not its default application (very often the box is just made of soft coating inside like PS foam, and of wood outside as a supporting material structure).
17. ‘A 20 um scanner’ change to ‘A 20 um X-Y scanner’, the Z scope of scanner is also there, have to avoid confusion. And, how much was the scope in Z? 2 um? 5 um?
18. ‘cells; isolated’ change to ‘cells were isolated’
19. ‘experiments were conducted for PCC cultures at passage 1 - 3 to avoid any lose of phenotype. For PPO cultures passages 1-3 were used.’ So, both 1-3 passages? If so, what is the reason to write this complicate sentence structure? Whay not to write simply: ‘experiments were conducted for both PCC and PPO cell cultures at passage 1 - 3 to avoid possible loss of phenotype.’
20. ‘cell viability experiment was evaluated’: remove experiment!
21. I suggest to change the times from h to days, because it’s simpler to understand; so use 1 day in vitro (DIV) instead of 24 h, and 3 DIV instead of 72 h.
22. Sputter coated with gold: what approximate thickness? 10 nm? 50 nm?
23. In the Experimental section, I recommend to change the title of subsection ‘Surface characterization’ to ‘Substrate surface characterization’, Stressing that this is done on substrates without cells. Also, remove the sub-subsections SEM, EDS and AFM, and put all in the same subsection level.
24. When later on the subsections come titled ‘Cell morphology analyzed by scanning electron microscopy’ and ‘Cell topography analyzed by atomic force microscopy’, use technique acronyms already in the title, and avoid duplication of intormation: remove the initial ones on SEM and AFM, and include the correspoding info into the subsequent ones. For example:’ The morphology of PCC and PPO cells were observed under a SEM (JSM-6360, JEOL) and the images were taken at a 5kV accelerating voltage.’ Change to only: The morphology of PCC and PPO cells were observed under SEM. (typical conditions already specified previously). And subsequently, delete ‘(Quesant Q-Scope 350, AMBIOS, Agura Hills, Ca, USA)’, and ‘were examined using a 20-μm scanner equipped with silicon tips with 10 nm tip curvature. In addition, the cells were scanned at 1 Hz over a 10 x 10μm region at scale angle of 0°.’ Change to ‘were examined by scanning at 1 Hz over a 10 x 10 μm^2 region’’
25. Previously, you wrote ’25 um^2’ for a scan area, now ’10 um x 10 um’ (BTW, it was ‘10x10 um’, wrong’. Please use a uniform style! Either 5 um x 5 um and 10 um x 10 um, or 5x5 um^2 and 10x10 um^2.
26. I actuanlly don’t know the style of the journal, but, generally, whereas the Experimental section is conveniently separated into different subsections corresponding to the different techniques, this should not occur for the results section: there, the results from different techniques should be merged into a single body. Thus, I suggest to remove the subsections in the Results section. Going to new paragraph (new line) should suffice, when changing the technique.
27. Fig.1: the size (ie magnification) of the image in Fig.1a must be same as the size (ie magnification) of Fig.1b and c: otherwise, it is not possible to say that there are no pores in 1a! Even if there, they would not be visible, due to the pixel size (100 times larger)
28. Still in Fig.1: magnification of 1b and 1c is the same! The bar is half length on the image, in 1c, and is also half length in the real space of the sample (100 nm instead of 200). So, remove either 1b or 1c, as these are duplicated. Since the pores in 1b look strangely stretched, I would remove 1b, and rename current 1c as new 1b.
29. Fig.2: clamp the y-axis to 2.5 (or even less: 2.3, 2.4) values.
30. Legends are not visible! Diminish the number of tick labels, but increase the font such that one can read them!
31. Merge current Fig.2 with Fig.1: So new Fig.1 will be: Panel 1a: current 1a Panel 1b: current 1c Panel 1c: current 2a Panel 1d: current 2b. This will help limit the number of figures (15 is crazy!) and compact the information so as to make it more readable.
32. Current Fig.3: One doesn’t need both top-view and 3D of same image! So, choose one or another. Since 3D is more for posters and presentation slides, while top-view is more scientific, I would leave top-view only. Also, put Ti first, vs anodized-Ti, same as previous figs (no reason to change). Also, another chance to compact: merge into Fig.1. So, in summary: Current panel 3a, 3b: removed; Current 3c becomes 1e Current 3d becomes 1f (Make characters readable!)
33. Current fig.4 becomes fig.2, good as is.
34. ‘Also anodized titanium illustrates a tubular, uniform structure along the surface’ It is false the tubules are visible in the AFM image. However, it is quite acceptable, due to small pore size. So, replace above text with the following: ‘The tubule mouths could unfortunately not be resolved, due to convolution with the used probe tips, which were not ultrasharp. However, anodized titanium showed much increased roughness, which is clearly associated with the tubular porous surface.’
35. Fig.5: again legends are terrible in font size and distorsion (compressed? Why?) Also, the white bars are not clearly visible: fill also themn, just use a different shade of gray.
36. I would rather make current fig.6 come earlier, soon after current fig.4, and then the extracted quantitative information of current fig. 5 and 7 come together in a single fig. So I recommend to take current Fig.6 and rename it 3, and merge current 5 and 7 into panels 4a and 4b of 4 (again after fixing characters!)
37. Moreover was observed Moreover it was observed
38. At each interval time At each time interval
39. Current figs.8,9: That the corresponding position image show more blue spots for 9, is true for panels a and b, but not for c and d. Additionally, current 9c is same as 8c, just blurred and decreased in intensity: please fix. Select appropriate representative images for panels c and d. (Anyway, these figs. Should be now no. 5 and 6).
40. Current figs. 9 and 11 should be merged into panels a and b of new fig. 7.
41. Fig.12 rename to fig.8 And 13 rename to 9.
42. Fig.14 and 15 merge into a and b of fig. 10. Again, only keep the more professional and serious style of top-view figures only (remove the childy 3D, it was used to present them some 20 yrs ago, at the birth of AFM!)
43. ‘showed a greater flatter’? maybe ‘appeared flatter’?
44. ‘enhance a better osteoblast morphology’ change to ‘enhance osteoblast-like morphology’
45. ‘better number’ change to ‘higher number’ or ‘increased number’
46. ‘showing a high increased area of 508.4 nm’: what does it mean?!? First area would be nm^2, not nm. You mean height? Ok, write that. However, no need to put it 3D to display height: rather, use a color bar by the side! Or simply write the min-max range for the colors (eg 0-1300 nm, in the figure legend text).
47. Beginning of Discussion: ‘Improve tissue development around grafts is a process, which’ change to ‘Enhancing tissue development around grafts is a process that’
48. ‘, on Ti and its alloys’: remove, trivial: it is required on whatever the substrate.
49. ‘. Although’ change to ‘, while’
50. ‘25.51% of oxygen, attributed to the induced oxidation and 3.28% of flour associated to the electrolyte used for anodization’: Change flour to fluor…
51. ‘AFM micrographs demonstrate’ change to ‘AFM micrographs suggest’
52. ‘But we detected’, change to newline + ‘Unexpectedly, we detected’
53. Which is agree’ change to ‘which is in agreement’
54. Final lines of discussion: ‘Inthis study… interface’ sound more like conclusion. However, the same info is already presented in the actual Conclusion. So, simply remo ve these duplicated lines.
55. Do you really need to repeat the abbreviations for each legend? They are defined once forever in the manuscript body text.
- Review of
The results are interesting but the paper has some minor flaws. The percentage of self-citations should be reduced. Deficient literature review. Important papers are missing The electrical conductivity method was first suggested by Rassk & Bhaskar: Rassk, E.; Bhaskar, M. - Pozzolanic activity of pulverized fuel ash. Cement and Concr. Res. 5,1975, 363–376. Feng et al. also used the rapid method of Luxan to assess the pozzolanic properties of rice husk ash: Feng, Q.; Yamamichi, H.; Shova, M.; Sugita, S. - Study on the pozzolanic properties of rice husk ash by hydrochloric acid pretreatment. Cement and Concrete Research 34, 2004,pp.521-526. Tashiro et al. suggested that only 72h testing are required to assess the pozzolanic behavior with electrical conductivity if the lime-pastes were cure under steam at 70 °C. Mc Carter & Tran also mentioned that the calcium hydroxide consumption after 72h correlates with the electrical resistance of several artificial pozzolans. Tashiro, C.; Ikeda, K.; Inoue, Y. - Evaluation of pozzolanic activity by the electric resistance measurement method. Cement and Concrete Research 24, 1994, 1333-1139. McCarter, W.; Tran, D. - Monitoring pozzolanic activity by direct activation with calcium hydroxide. Construction and Building Materials 10, 1996, 179-184. The reviewer also does not understand why the review by Donatello et al. was not cited Donatello, S.; Tyrer, M.; Cheeseman, C. - Comparison of test methods to assess pozzolanic activity. Cement & concrete composites 32, 2010, 121-127. Reference 11 is not appropriate for an ISI journal The has a weak start. The paper should start with a short overview on the importance of pozzolans for sustainable construction. In line 113, statistics on the volume of FCC must be added. The chapter “Artificial pozzolans in eco-efficient concrete“p.105-122, Woodhead Publishing Limited, authored by M. Frías Rojas and M. I. Sánchez de Rojas Gómez mention 1100 ton/day.Reviewed by
The work is of great interest and the analysis and discussion is original and sound. However, since a single first-pop-in event is analyzed, the authors should comment and clarify on this point. It is reasonable that they do not need now to change completely the text or make new measurements, if not really required. However, wether indeed this is the case for the other measurements done in addition to the one analyzed in the MS, the authors could probably tackle this point by just adding a sentence stating something like that the curve they analyze is typical and representative of most observed cases, and they have detected some (approximate number?) other first pop-in events that were all at similar Pc (typical deviation was +-? percent), and this would eventually affect all subsequent derivations, accordingly.
Here and there, some language mistakes hinder the true meaning of the text. The following additional edits are therefore compulsory as well, before that the MS can be accepted for publication.
line 39: remove 'behaviors'
line 45: remove comma before Er
line 48: report both values with some more reasonable (ie less pretentious) accuracy (at least one less digit after the comma)
line 56: remove 'in this study.
lines 61-63: newly added text is not clear in that form. Also, it is probably a wrong justification! Rather replace with the following one: 'Since the first pop-in typically appears at indentation depth below 100 nm, at such a low depth (within the limit of the same size as the diameter of the tip apex) equations 1 and 2 are still a reasonable approximation also for the Berkovich indenter'.
line 63: remove 'Also'
line 65: replace 'was' with 'are also'.
lines 66-67: remove the sentence 'The results...films'. It's redundant. Furthermore, we are in the Intro here, not in the Conclusion section!
The authors tend again to misuse the Sections structure of the paper: the sentence at lines 71-73 (after preliminary replacing of the initial 'The' with 'In previous work') should rather be moved from the Experimental section to the beginning of Results and discussion.
Also, the new text added at lines 89-93 should be moved as well at a later point, in the discussion.
line 69: remove 'In this work'.
line 70: 'the helicon sputtering system', replace with 'helicon sputtering'. Even if details are elsewhere, still the authors have to write at least the instrument model and manufacturer.
line 81: replace 'are' with 'were'.
lines 105-106: remove 'the origin of'.
legend fig.1 'times the displacement', replace with 'times the sudden incremental displacement at constant load'
end of line 146: insert newline.
line 162: replace 'obtained' with 'reported'.
line 167: 'shear stress', add 'required'.
18. line 171: remove 'that'.
line 183: remove 'in both cases '.
line 187 and eq.7: add index c to tau.
eq 8: isn't it e^2 instead of e^3? In case, this would give 1.85 r_core and finally r_c=0.8 nm not 2.1
22. line 193: remove' with the popin event'.
line 195: remove 'might have been'.
legend fig 2: remove 'immediately'.
line 220: remove 'materials'.
lines 220-221: remove 'governed by'.