According to the scientists, the suspension absorbs a shock impact energy in milliseconds. The results of the study were published in the Colloid and Interface Science journal
The MEPhI researchers studied the usage of special suspensions to protect objects from shock impact energy - strikes or explosions. These suspensions consist of nanoporous particles and a fluid that does not invade the pores under normal conditions (does not make material wet). The scientists have studied the properties of such suspensions in special experimental chambers, which can serve as a prototype for real devices, as well as on unique experimental stands, which were developed in MEPhI.
Furthermore, they have found that such suspensions can efficiently absorb shock impact energy in milliseconds. The scientists have also discovered that by specifying the materials and their quantities it is possible to control impact pressure on the object protected.
The authors of the research have proposed filling porous materials with non-wetting fluids, which is possible only at an atmospheric pressure above 1atm.
“It is also important that fluids can flow out of the pores of materials when the pressure is reduced. The difference between the pressures at which the fluid penetrates the pores and flows out of them (pressure hysteresis) determines the proportion of the energy absorbed by the suspension. The greater the difference, the greater the share of the energy absorbed,” Anton Belogorov, Assistant Professor at the Institute for Nanoegineering in Electronics, Spintronics and Photonic of MEPhI said.
According to him, the heating of such suspensions during the process when fluids invade pores or flow out of them equals the percentage of the energy absorbed, and a device based on the studied principle almost doesn’t heat up during operation.
Nowadays work on the creation of devices operating on the principle proposed is carried out not only in Russia, but also in the USA, France, China and Japan.
So far, two types of devices have been used to absorb shock impact energy. First of all, spring-type devices which, by means of elastic deformation, increase the time of impact and practically fail to absorb the energy. Second, hydraulic systems that convert energy into heat by transferring fluid through thin channels, but do not allow reuse.
A classic example of a device in which a combination of spring and hydraulic systems is implemented is a car shock absorber. The device is capable of dissipating energy, and the return of the device to its initial state.
According to the MEPhI scientists, the main disadvantages of the classical systems are the overheating and increased shock impact on the protected object at the increased power of the impact (the increase of shock impact energy and reduction of its duration). Besides, shock energy absorption schemes by irreversible deformation (crushing) of the material upon impact are also implemented, for example, in cellular structures in bumpers with high energy consumption.
In turn, the suspension proposed by the MEPhI scientists allows the combination of high energy intensity (up to 20 J per gram of a material), fixed impact pressure on the protected object, repetition in use and low heat output.
Scientists are currently working on new materials for suspensions as well as on the identification of patterns that allow the computation of device characteristics in accordance with the known characteristics of materials.
Research was carried out in MEPhI and TIPS RAS (A.V.Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences) within the framework of the Russian Science Foundation 18-13-00398 project on “Collective dynamic phenomena in nanofluid systems in a nanoporous medium”.