We know that everything on the earth will reflect light except black holes, but the intensity is different, but as long as there is light, we can basically see it with the naked eye. Is this wall like a black hole that can be swallowed up?
Black holes are celestial bodies with very strong gravity in the universe. It can devour everything, including light. Because it doesn't emit light or reflect light, it is surrounded by darkness, so it is called a black hole.
Black hole is the last stage of star evolution, and its formation conditions are very harsh. Even the sun is too small to evolve into a black hole. At the end of life, it will first become a red giant, which will devour most of the planets, including the earth, and then begin to collapse inward under the action of gravity. Because of its small mass and low gravity, it can only be reduced to a white dwarf.
The life of the sun is at least several billion years. Maybe mankind was extinct long ago at that time, or maybe technology has advanced enough to make the earth leave the solar system, so there is no need to worry about the end of the world.
Although there can't be black holes on the earth, scientists can develop new materials, and the light absorption effect can be infinitely close to black holes. The black wall of Korea Modern Exhibition Hall is also coated with a layer of light-absorbing material, which was developed by Surrey Nanosystems Company in Britain.
The abbreviation of English name is VantaBlack, which translates to Vantablack, which means vertically arranged carbon nanotube array.
At the beginning of its appearance, Van Gogh claimed to be the blackest substance on the earth and the closest thing to a black hole in the universe. If it is used to make clothes, the wearer may be regarded as a monster. Because only the head and limbs can be seen, the body is dark and empty, and even the outline of the body can't be seen.
Wearing black clothes and standing in the sun in summer will obviously feel hotter, and wearing white clothes will be much cooler, because the darker the object, the stronger its light absorption ability.
Light is actually photons moving at high speed, and their speed reaches 300,000 kilometers per second. Once it hits an object, it will inevitably collide and reflect with particles, and only some photons will be converted into heat and absorbed, unless black objects are not easy to be found in dark places.
Vantage Black can also reflect light, but its surface is made of carbon nanotubes, whose diameter is only one tenth of that of hair. If you look at it under a microscope, you will find that there are countless vertical black pipes on its surface. These tiny carbon nanotubes can change the reflection path of light.
When light enters these pipes, carbon nanotubes will absorb most of the light first, and the remaining light will be gradually converted into heat absorption by carbon nanotubes after numerous refractions, and only a little light can be reflected.
The principle seems simple. For a simple example, pouring a pot of water on the concrete floor quickly will splash 100%. If the cement floor is replaced by grass, only tiny water droplets will splash out. Moreover, carbon nanotubes also have ultra-high thermal conductivity, absorbing light just like a sponge absorbs water.
Therefore, Van Gogh can only reflect 0.35% of the light, which cannot be observed by the naked eye. In 20 14, it reached the Guinness Book of Records as the darkest one in the world, but this record was broken by the team of MIT in 20 19.
Professor Brian Wald of the team publicly stated that they created a material that was 65,438+00 times blacker than the Vatican. This material is also made of carbon nanotubes, but the diameter of carbon nanotubes is only one fiftieth of that of human hair, so it can only reflect 0.005% of light, making it the darkest material in history.
Professor Brian didn't think of using carbon nanotubes to make extremely black materials at first. Carbon nanotubes have not only excellent thermal conductivity, but also good mechanical properties. Its density is only 1/6 of that of steel, but its tensile strength is 0/00 times that of steel, and its hardness is equivalent to that of diamond.
If other engineering materials and carbon nanotubes are made into composites, they can show good strength, elasticity and fatigue resistance, which will greatly improve the properties of composites.
Russian scientists once put carbon nanotube composites under the water pressure of 1 01MPa, which is equivalent to the pressure of deep sea110,000 meters. Composite carbon nanotubes were crushed by huge pressure and recovered immediately after the pressure was removed. This good toughness is an excellent material for making springs.
In addition, the conductivity of carbon nanotubes is 1 10,000 times that of copper. Professor Brian originally planned to grow carbon nanotubes on the surface of aluminum to improve its electrical conductivity and thermal properties, but aluminum will form an oxide film in the air, which is very corrosion-resistant.
Moreover, oxides generally have the function of insulation, which will reduce the electrical conductivity and thermal conductivity of aluminum, so chloride ions have to be used to erode the surface of aluminum. This etching technique is very common in metal processing.
Because of its small radius and strong permeability, chloride ion can easily penetrate the tiny pores in the oxide film, reach the surface of aluminum metal and form soluble compounds with it, changing the structure of the oxide film and slowly eroding it. Finally, the etched aluminum is heated in a microwave oven, and then carbon nanotubes are grown by chemical vapor deposition.
This method is also called pyrolysis of hydrocarbon gas. Gaseous hydrocarbons will decompose at the high temperature of 1000 to generate carbon nanotubes, which are attached to aluminum foil under the action of catalyst particles.
Professor Brian finally found that the combination of carbon nanotubes and aluminum foil achieved the expected experimental purpose, and the thermal conductivity and electrical conductivity of the composites were significantly improved. But the most surprising thing is that this material is too dark to be believed, so the optical reflectivity test was carried out.
The test results show that the material can absorb 99.995% incident light from all angles, which is second only to black holes in the current universe. Whether its surface is uneven or has other morphological characteristics, it is invisible to the naked eye, just a void of darkness.
Professor Brian and his team have applied for a patent for this technology, but they plan to let artists use it for non-commercial artistic creation for free. A local tyrant covered a diamond worth $2 million with aluminum carbon nanotubes, making the original shiny diamond look completely opposite, so it turned black and disappeared. It was named "Redemption of Vanity" and exhibited in new york Stock Exchange.
BMW also used Van Gogh Black as paint, and specially designed an X6 SUV for display. No matter at night or during the day, no matter how strong light you shine on it, it looks almost black. If the windows, lights and other parts are dull, you may even think that the car is painted on the wall, because you can't see its surface edges and lines at all.
This is the mercy of the designer, and the light reflectivity of 1% is reserved for it, so that the outline of the car is almost invisible, so as not to look like a piece of paper, which just makes the car look luxurious and full of mystery and dignity.
However, this car can't drive on the road because of technical limitations. Van Gogh black, as a pigment, falls off easily. If it falls, there is no way to touch up the paint. Moreover, some netizens ridiculed that it is estimated that the paint of this car is more expensive than that of the car, and it can only be seen after buying it.
So what is the practical use of this ultra-black material besides bringing the ultimate visual effect?
John Mather, an astrophysicist who won the Nobel Prize, said that this ultra-black material can improve the sensitivity of optical instruments, and it can eliminate the interference light from the lens of space telescope.
For example, the infrared space telescope being developed in the United States, whose main task is to image and investigate the infrared sky in a wide field of view and solve the basic problems in the fields of dark energy and infrared astrophysics.
However, this kind of space optical instrument must remove unnecessary glare, so it is necessary to design a "star-shielding umbrella" to block stray light in space and bear the high temperature caused by rocket launch. Aluminum foil carbon nanotubes are undoubtedly the best basic material for manufacturing star-shielding umbrellas because of their super light absorption and high temperature resistance.
Because aluminum foil carbon nanotubes can not reflect light and can hide the ups and downs of objects, they are an ideal camouflage coating material, so they have great application space in the field of military weapons. In 2020, Japan introduced a black pigment with a light absorption rate as high as 99.4%, which can be easily planarized, overhead, frosted or even invisible.
Secondly, it also has excellent electrical and thermal conductivity, as well as the function of efficiently absorbing photons, so aluminum foil carbon nanotubes can be applied to the fields of heat dissipation system, power transmission and photovoltaic new energy.
However, both Vantage Black and aluminum foil carbon nanotubes are too difficult to get out of the laboratory, let alone put into mass production.
Finally, to sum up, at present, carbon nanotube black materials still have the problems of difficult preparation and high production cost, which can not be quickly popularized and applied to related industries. However, it does have broad application prospects and is worthy of further study by scientists.
Just like when the steam engine was first invented, it was expensive and the benefits could not keep up with manual labor. However, after Watt improved the steam engine, human society quickly entered industrial civilization.
Maybe one day, with more advanced technology, human beings can change the world with "black".