Investigation of Ti_0.92+xZr_0.1−xCr_1.0Mn_0.6Fe_0.4 Alloys for Use as 25 MPa Hydrogen Compression Materials

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The sustainable development of our civilization and the decarbonization of key technological processes require the use of low-carbon technologies. Hydrogen energy is the main direction in this area. In this regard, the development of hydrogen compression technologies using metal hydride materials is extremely relevant. This paper describes the synthesis and study of the properties of a promising titanium-based alloy for compressing hydrogen to a pressure of 250 atmospheres.

The paper has high quality and importance for science. By combining the experimental results and discussions, it was clearly described the reasons of obtained result. This paper is new, original and well organized. English language is good in the paper and all references are adequate. Also all parts of paper are important and conclusion is fine. I recommend this paper for publication, after minor revisions:

1.     What is the accuracy of determining the sorption and desorption characteristics? Please include this information in the article.

2.     Please add information in the article about the role of manganese and iron on hydrogen sorption characteristics of alloys.

3.     The EDS results as well as refinement data accuracy should be discussed.

4.     Information on the cyclic stability of the processes of sorption and desorption of hydrogen by alloys will greatly improve this work.

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

The performance of a new metal hydride s presented in the form of PCT-curves. This ought to be published.

It is claimed that the metal hydride has good kinetics and in Figure 4. the hydrogenation kinetics curves of Ti0.92+xZr0.1-xCr1.0Mn0.6Fe0.4 (x = 0, 0.01, 0.02, 0.03) alloys 212 is given under 9 MPa at -10 °C.

But the sample of 2-gram powder is contained in a steel tube. This means that the heat flow in and out of the sample is very restricted. The reaction heat that is ´not given will heat the powder high above -10 °C significantly speeding up the kinetics. The authors need to record the temperature in the powder bed to get a more correct understanding of the kinetics f the powder bed. It will still be dominated by the reaction heat flowing in and out of the sample bed. If they want to determine the hydrogen absorption and desorption rates, they must redesign their sample holder to improve its heat conductivity. No desorption kinetics is presented.

In the present paper Fig. 4 contributes nothing and it can be eliminated with the corresponding discussion. The whole paper can be drastically shortened as most of the items have been discussed in many earlier papers when metal hydrides were in vogue after the oil crises in the seventies.  

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

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Comments for author File: Comments.pdf

Comments on the Quality of English Language

·         There are some typos, correctness, and syntax issues.

Author Response

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Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Some improvements have been made but still we do not have any details about the intrinsic reaction kinetics. It is fast but that is common for all interstitial metal hydrides of this type. It is in the order of part per second.

In heat pump applications as well as in hydrogen storage in metal hydride powder beds, the kinetics is mainly determined by how fast reaction heat can be added and removed from the powder bed.

The authors suggest that they will make a second paper examining the kinetics in more detail. I suggest that they remove their study of the kinetic, which is very blunt using a large 2-gram sample in a steel tube.  This only shows that they are amateurs in this area. Better to do it professionally later.

They still have interesting PCT-curves and structural information to present in their paper. 

Author Response

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Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

OK now.