Research Progress of Cryogenic Materials for Storage and Transportation of Liquid Hydrogen

1. Introduction

Liquid hydrogen is the main fuel for low-temperature rockets, especially large-scale low-temperature heavy-duty rockets such as the cz-7 series, cz-5 series in service, cz-8, and the new generation of manned rockets in future planning that need to use liquid hydrogen as a propellant. With the development of deep space exploration, manned lunar landings, space station missions, Beidou networking, Internet satellite systems, and other missions, the scale of its use shows a strongly growing demand. In addition, liquid hydrogen also has a wide range of civil and industrial applications, which is an important direction of new energy technology development. In particular, in the energy law of the people’s Republic of China (Draft) issued by the National Energy Administration on 10 April 2020, hydrogen energy is listed as energy, which is the first time that China has legally confirmed that hydrogen energy belongs to energy [ 1 ]. The importance of liquid hydrogen as a clean energy shared by the military and civilians can be seen.

In the liquid hydrogen industry, there are dozens of liquid hydrogen plants worldwide, with a total liquid hydrogen capacity of 470 tons/day. North America accounts for more than 85% of the total global liquid hydrogen capacity. There are more than 15 liquid hydrogen plants in the United States, with a liquid hydrogen production capacity of more than 326 tons/day, ranking first in the world. Four liquid hydrogen plants in Europe have a liquid hydrogen capacity of 24 tons/day. There are 16 liquid hydrogen plants in Asia, with a total capacity of 38.3 tons/day, of which Japan accounts for two-thirds of the capacity in Asia. The only liquid hydrogen plants in use in China are Wenchang in Hainan, 101 Institute in Beijing, and Xichang Base, all serving for space rocket launches, with low production capacity and high cost, which directly restricts the application of liquid hydrogen in the high-end manufacturing, metallurgy, electronics, and energy industries [ 2 ]. Therefore, liquid hydrogen and the hydrogen energy industry have become the key direction of energy development in China.

As an important carrier of large-scale storage and transportation of liquid hydrogen, the cryogenic storage and transportation vessel of liquid hydrogen is the key equipment in the field of space and energy. The design and manufacture of liquid hydrogen storage and transportation vessels are supported by the scientific use of low temperature materials. It is an important guarantee for the safe, reliable, and long-term operation of the cryogenic propellant storage and transportation vessel to systematically and thoroughly grasp the comprehensive properties of the cryogenic materials of the storage and transportation containers. In the United States, Europe, Japan, and other countries, liquid hydrogen and other low temperature propellant storage and transportation containers have been widely used in space propulsion systems, civil energy, chemical, and other fields, who have accumulated a rich experience in material performance research and high efficiency and safe use of liquid hydrogen storage and transportation containers. They mastered the system of the low temperature material performance test method, and formed a perfect design, standard selection system, and specification.

In China, the design and development of cryogenic propellants, especially liquid hydrogen storage and transportation containers as well as the mechanical properties and selection standards of related materials have only been preliminarily studied in the aerospace field. However, the civil field is basically blank, the development of related technologies is relatively limited, and the relevant standard system is not perfect. In the past, the performance requirements of metal materials were only regulated to 77 K in the relevant standards of pressure vessels and metal materials in China, but there were no clear regulations on the performance parameters and design selection requirements of metal materials at the liquid hydrogen temperature. Generally, the material properties at 77 K are selected and determined, but there is a lack of data support. In recent years, the research on the properties of low-temperature metal materials has become an important direction of materials science. Scholars from all over the world have done significant work in this field. According to the published data, the Soviet Union studied this aspect earlier and involved many kinds of materials including nickel manganese steel, titanium alloy, aluminum alloy, and copper alloy, while the United States studied it later. However, later, with the continuous development of American space technology, they established a perfect material database for low-temperature materials, and the key data in the database were not released to the public. For example, the low-temperature material properties published by the National Institute of Standards and Technology (NIST) include the specific heat capacity, coefficient of linear expansion, Young’s modulus, and thermal conductivity of aluminum alloy, stainless steel, titanium alloy, and other materials. It can be seen that the main properties are thee physical parameters, but there is no relevant report on the low-temperature mechanical properties of different brands of materials.

With the continuous improvement in the independent and controllable requirements of China’s aerospace equipment, more and more attention has been paid to this aspect. However, the series and standards of low-temperature metal materials have not been established, and detailed data support is lacking. For example, the low-temperature design temperature of steel vessels in China’s pressure vessel industry (GB150-2011) has been extended from 77 to 20 K, and the minimum design temperature of aluminum vessels has reached 4.2 K. Although the design temperature has been lowered to the liquid hydrogen temperature zone in the standard specification, the material strength and strength of pressure vessels in low-temperature environments have been improved. The lack of basic mechanical property data such as plasticity and impact toughness restricts the domestic independent production of cryogenic propellant storage and transportation container equipment to a great extent. In order to fully grasp the development status of liquid hydrogen storage and transportation container materials, the research status of cryogenic materials for liquid hydrogen storage and transportation containers was systematically reviewed in this paper including material category and low-temperature mechanical properties.