MAIN TRENDS OF SUPERINSULATION RESEARCH

Only a few works have been devoted to the matters of electro-adsorption interaction of SVHI screens with the residual gas [1-5]. At the same time, the F. F. Vol’kenshtein’s monograph [48] is devoted to electronic process on semiconductor surfaces where the results of the 40-year work of the author and his colleagues in the field of physics and chemistry of semiconductor surfaces are summarised. The semiconductor surface in the work cited above is considered from the positions of the interface between two phases. The interaction between gas molecules of the residual medium and free semiconductor electrons and holes occurs at this interface. As the majority of metals have an oxide film, then their surfaces in most cases are semiconductor surfaces. Among works devoted to the physics and chemistry of semiconductor surfaces, the most substantial are monographs by K. Haufe [49] and S. Morrison [50], F. F. Vol’kenshtein [48], A. V. Rzhanov [51]. It is necessary to note a great contribution of the V. S. Kohan’s school into the theory of interaction of active gases with metal films [52]. A very meaningful is the monograph of the Indian physicist K. L. Chopra [38]
devoted to the investigation of physical processes passing in thin films of metals, semiconductors and dielectrics.

By the present time, the main tendencies of further development of the superinsulation have been carried out in the following directions. First of all, studies devoted to the optimal installation of the superinsulation [53], the process of vacuuming of the cryogenic equipment superinsulation [54-57], investigations of gas permeability of the superinsulation [58, 59], the determination of diffusion coefficients of residual gases in the superinsulation [60], investigations of the kinetics of gas release of heat-insulating materials in vacuum [61], investigations on studying of the distribution law of residual gases in superinsulation layers [62], investigations on studying if the unsteady pressure field in the superinsulation [63], investigations of the properties of superinsulation materials [64, 65], investigations of heat and mass exchange in the superinsulation [66-68]. The work [69] has a high theoretical and practical value, Mikhalchenko with colleagues have detected therein a hundred-fold pressure ratio in the middle of the sample over its thickness and on the outer insulation layer with the temperature of 77K. In the work [70], it has been obtained that the pressure in the superinsulation grows proportionally to the squared insulation thickness. In addition, it has been detected that the pressure distribution over the insulation thickness in the steady mode has a parabolic nature.

In order to improve the conditions of superinsulation vacuuming, it has been proposed to perforate screens [71]. Barron [72] has come to a conclusion that if the perforated hole area equals to 10% of the screen area, then the rate of gas pumping-out from the insulation increases approximately by 1000 times. In the work [73], it has been shown that gas releases of screens can be absorbed inside the insulation, for example, by means of the use of glass — fibre paper with filaments from activated charcoal as a pad’s material. In the work [74], it has been determined that gas releases of screens can be absorbed inside the insulation, for example, by means of a low-temperature gas absorber.

Studies are known devoted to surface effects on a dimension-quantised screen — vacuum heat-insulation in the conditions of cryogenic temperatures and vacuum [75], influence of surface centres on the gas medium formation in HIC, selection of a metallised coating of the superinsulation, optimisation of the technology of manufacture of a metallised film with the account of electro-adsorption phenomena on the film surface: selection of the crystal size to be applied onto the polymer film substrate, values of the thickness of the metal spraying onto the film, management of the metallised film properties by the introduction of special alloying gases at the manufacture, etc.

Quite a few works have been devoted to operational methods and means of maintaining and monitoring of the optimal mode of the superinsulation functioning [76, 77].

The investigations devoted to surface effects on dimension-quantised films in the superinsulation, influence of the surface centres of superinsulation screens on the gas medium formation in HIC, selection of the metallised coating of superinsulation screens, optimisation of the technology of manufacture of a metallised film with the account of electro­adsorption phenomena on the film surface, selection of the crystal size to be applied onto the polymer film substrate, values of the thickness of the metal spraying onto the film, management of the metallised film properties by the introduction of special alloying gases at the manufacture, management of the value of the surface potential of superinsulation screens by means of connection of the superinsulation screen to an external potential, etc., are completely absent.

In addition, the matters of selection of the protective casing of the reservoir, introduction of an additional "dry" volume into the cryogenic reservoir design between the
casing and the additional moisture-insulating shell are completely missed. The shell can be made with an overflow moisture-impermeable valve. As to the matter of exclusion of a moisture film on the outer heat insulation surface, we are aware of only one work [78].

It is well-known that the film alloying by gas impurities can lead to the improvement of their properties [79]. The task of management of the film properties by their alloying with impurities was stated in a number of works [80].

A special attention will be paid to the management of properties of screens on the polymer basis by means of their modification by the ion implantation. By the present time, a sufficiently large volume of work on the investigation of kinetic phenomena in conducting organic films has been carried out [81-86].

The complexity and diversity of processes being observed in heat-insulating cavities cause a necessity of the conduction of additional emergent experiments with the use of newest measuring apparatus.

The urgency of investigations on the development of a fundamentally new superinsulation is in the present time dictated by the beginning of intensive works on the development of ecologically clean transport on hydrogen in all developed countries.