Use of Low Melting Point Metals and Alloys (T_m < 420 °C) as Phase Change Materials: A Review

Round 1

Reviewer 1 Report

The paper is well-structured and written, the authors have done an extensive review of the literature, and the figures and tables are clear and support the article well. On the other hand, the authors present research of scientific and technological interest in the field of storage for applications at temperatures below 420 °C. Therefore, I consider that the information presented in the article can be useful for the development of new PCM for thermal storage using metals, which has aroused the interest of the reseachers. This review article could be improved if a section were included on what would be the main future works (future trens) that must be carried out to achieve progress in this type of material in the coming years.

Author Response

Dear Reviewer

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This review aimed to conclude the latest achievements in the field of low melting point metallic phase change materials (PCMs). The authors claim that the criteria for the selection of PCMs are evaluated. But the authors only listed the physical properties and chemical stability simply, and the deep mind or underlying logic for the selection and design PCMs is not given. Although some new application potentials are presented such as novel applications in casting design, rare latest reports are presented in this review. Additionally, the figures in this review are demonstrated rashly and hastily. Thus, I suggested a major reversion before considering an acceptance.

Some of the comments are given as follows:

1. This paper aims to present a comprehensive and detailed account of metallic phase change materials (phase change materials) PCMs, thereby the mechanism diagram of PCMs is suggested to describe the concept coherently and briefly for readers before the subsequent discussion.
2. Similar to comment 1, about the conclusion of the criteria for PCM selection, the detailed parameters such as the melting point, latent heat, thermal conductivity, density, thermal expansion, and so on are preferred to plot a logical figure network to guide the reader easily. Moreover, are there the connection and underlying logic for this physical or performance parameter? A deeper conclusion for the selection criteria is suggested to be concluded in this section. Additionally, this suggestion is also recommended and applied to section 4 “Encapsulation of PCMs”.
3. For section 5, the subtitles are recommended to sort different pure metal-based PCMs i.e., 5.1 Zn, 5.2 Ga, 5.3 Sn. Besides, figure 6 (a) with the low resolution is suggested to be replaced by the uniform format and high-resolution figures.
4. The evolution of PCMs from pure metal, binary, ternary, to quarterly alloys is suggested to make a simple conclusion concluding their advantages, disadvantages, or application areas at the end of section 6.
5. The reasons why the metal matrix composite PCMs and Miscibility Gap Alloys are developed must be introduced at the beginning of section 7.
6. Too little exhibition of the innovative application using PCMs is not enough to attract more readers. The latest literature is preferred for this review. This review only contained below 20% of the literature published around 2020-2021.

Author Response

Dear Reviewer

Please see the attachment.

Author Response File: Author Response.pdf