Water vapor from the ambient air will condense spontaneously inside the porous material or between touching surfaces. But this ubiquitous and important phenomenon still lacks understanding as the liquid layer is only a few atoms thick.
Researchers at the University of Manchester, led by Nobel laureate Andre Game, who, along with Kostya Novoselov, won the Nobel Prize in Physics 10 years ago this month – have made artificial blood vessels normal for water vapor, making them smaller in ambient conditions. .
The Manchester study is titled ‘Capillary Condensation Under Atomic-Scale Limits’ and will be published in Nature. The capillary condensation in the research, a basic microscopic phenomenon involving several molecular layers of water, provides a solution for a centuries-and-a-half-old puzzle that can be reasonably described using bulk water macroscopic equations and macroscopic characteristics. Is it a coincidence or a hidden law of nature?
Condensation of blood clots, a textbook phenomenon, is ubiquitous in the surrounding world and important properties such as friction, adhesion, stationary, lubrication and corrosion are strongly affected by capillary condensation. This phenomenon is important in many technological processes used by microelectronics, pharmaceuticals, food and other industries – and even sandcastles cannot be made by children if the capillaries are not for condensation.
Scientifically, the phenomenon is often described by the 150-year-old Kelvin equation, which has proven to be significantly more accurate even for capillaries as small as 10 hair nemometers, which are in the thousands of human hair widths. Still, for condensation to occur under normal humidity of say 30% to 50%, the capillaries should be as low as about 1 nm. This is comparable to the diameter of a water molecule (about 0.3 nm), so that only a few water molecular layers can fit inside the pores responsible for normal condensation effects.
The Moros Croscopic Kelvin equation cannot be justified to describe the properties associated with the atomic scale and in fact, there is little understanding of this equation in this scale. For example, it is impossible to determine the curvature of the water meniscus, which enters the equation, if the meniscus is only a few atoms wide. Accordingly, for lack of proper description, the Kelvin equation has been used as a weak man’s approach. Scientific progress is hampered by many experimental problems and especially surface roughness which makes it difficult to make and study capillaries with size at the required molecular scale.
To create such capillaries, Manchester researchers assembled flat crystals in the form of molecules of mica and graphite from the entrepreneur. They place two such crystals on top of each other with narrow stripes Graphene, Another atom is being placed between thin and flat crystals. The strips acted as spacers and could have different thicknesses. Blood capillaries of different ights height were allowed by this trailer assembly. Some of them were just one Atom can contain high, lowest possible capillaries, and a layer of water molecules.
Manchester experiments have shown that the Kelvin equation can describe, at least qualitatively, the deposition of capillaries in small capillaries. This is not only surprising but contradicts general expectations as water changes its properties on this basis and its structure becomes clearly discharged and layered.
“It simply came to our notice then. I expected a complete breakdown of traditional physics, ”said Dr. Nature, lead author of the report. Qian Yang said. “The old equation worked well. A little frustrating but also exciting to finally solve a century old mystery.
“So we can rest, all of these numbers of condensation effects and related properties are now supported by harder than the hardest evidence that ‘it works so it should be ok to use this equation’.”
Manchester researchers argue that the agreement reached is strong despite being qualitative. The pressure involved in the condensation of capillaries under ambient humidity is more than 1000 bar at the bottom of the bare bars deep sea. Due to such pressure the capillaries adjust their size by a fraction of the angstrom, which is sufficient to accommodate the integer number of molecular layers inside in a snug manner. These microscopic adjustments can better capture the Kelvin equation by suppressing the favorable effect.
“Good theory often works beyond its applicable limits,” Game said.
“Lord Calvin was a remarkable scientist, he made a lot of discoveries, but he would surely be surprised to know that his theory – originally considering millimeter-sized tubes – was also based on a single atom. In fact, in his seminal paper Calvin commented on exactly this impossibility.
“Therefore, our work has proved him right and wrong at the same time.”
Lord Calvin
Sir William Thomson, later Lord Calvin (1824-1907) referred to his famous equation in an article entitled ‘On the Equilibrium of Steam on the Curved Surface of Liquids’ published in Philosophical Magazine in 1871. Kelvin’s significant contributions to science include the development of a second law of thermodynamics; Absolute temperature scale (measured in Kelvins); Dynamic principle of heat; Mathematical analysis of electricity and magnetism, including basic ideas for the electromagnetic theory of light; Plus basic function in hydrodynamics.
Ref: “Capillary condensation under atomic-scale captivity” 9 December 2020, Nature.
DOI: 10.1038 / s41586-020-2978-1
