) together with specialists from the Polytechnic School of Engineering at New York University created a new metal composite that is so light that it can float on water and not sink.
Magnesium alloy matrix composite is a so-called syntactic foam, a type of composite material created by filling a metal, polymer or ceramic matrix with hollow particles. AT this case the magnesium alloy matrix is filled with silicon carbide hollow particles, developed by DST. That is, it is a kind of metallic foam.
The scientists claim that the result is the world's lightest syntactic foam with a metal matrix. The "foam" structure allows the material to have a density of 0.92 grams per cubic centimeter, less than water, so that the material can float on the surface of a liquid and not sink.
The extremely strong silicon carbide balls are capable of withstanding over 1,757.6 kilogram-force per square centimeter. Such spheres can also provide impact resistance by acting as energy absorbers.
Changing the number of spheres that are added to the matrix allows the composite to acquire some other properties that can be customized depending on the purpose of the application.
In the future, similar material can be used for construction sea vessels, which will remain afloat even after receiving damage to the hull. In addition, the material turned out to be dense enough that the vessel made from it could withstand the harsh sea conditions.
The material also boasts heat resistance, making it a viable alternative to lightweight polymer matrix composites, which have been the focus of much research in recent years and have been used to make marine and automotive components (instead of heavier metal-based components).
"This new development in the field of composite materials, a very light material that will allow you to return to the manufacture of metal components, - says professor of mechanical and aerospace engineering Nikhil Gupta (Nikhil Gupta), co-author of the study. "The ability of metals to withstand higher temperatures can be a huge advantage if components are made for an engine or have to come into contact with exhaust gases."
Some of the potential uses for the material include not only lining the bottom of a ship, but also, according to the creators, it will be useful for creating automotive parts, floating vehicles and armor for military vehicles. Last example explains why DST is being developed with the support of the US Army Research Laboratory.
According to the developers, prototypes of devices made from the new material will be tested over the next three years.
Details are in a scientific article published in the Journal of Impact Engineering.
Helped to conduct Denis Zelenov. 10 years.
In the summer, Denis swam on the Volga-Don Canal. I watched the big ships go through the canal, rise and fall in the lock chamber. And I thought: what allows them not only to stay on the water, but also to carry heavy loads?
Why can ships walk on water?
There are several reasons.
1. Density
Experience 1
We all know that if you throw a wooden board into water, it will lie on its surface, but a metal sheet of the same size immediately begins to sink.
Why it happens? This is determined not by the weight of the object, but by its density. Density is the mass of a substance enclosed in a certain volume.
Experience 2
We took cubes of the same size 70x40x50 mm from different materials - metal, wood, stone and foam and weighed them. And we saw that the cubes have different weights and, consequently, different densities.
Cube weight from:
- stone -264 gr.,
- polystyrene - 3 gr.,
- metal - 1020 gr.,
- tree - 70 gr.
From this they concluded that the densest material of the cubes is metal, then stone, wood and foam.
Experience 3
And what happens if these cubes are lowered into water? As can be seen from the experience, the stone and metal drowned - their density is greater than the density of water, but the foam and wood do not - their density is less than the density of water. This means that any object will float if its density is less than the density of water.
Therefore, in order for a ship to float on water, it must be made so that its density is less than the density of water. Suppose we make it from a material that has a density less than the density of water and does not sink - for example, from wood. We know from history that it was from wood that man first made rafts, and then boats, using the property of wood - buoyancy.
Today we see many ships made of metal, but they don't sink. The reason is that their body is filled with air. Air is much less dense than water. The ship is formed, as it were, the total, total density of air and metal. As a result, the average density of the ship, together with the huge volume of air in its hull, becomes less than the density of water. That is why a heavy ship does not sink. Let's confirm this with experience.
Experience 4
We lower a flat sheet of metal into the water - it immediately sinks, and any vessel with sides remains afloat - a reserve of buoyancy is formed in it. You can even put a load there.
Life-saving equipment also works: a vest or a circle dressed on a person. With their help, it is possible to stay afloat until the rescuers arrive.
2. Buoyancy
In addition, a buoyant force acts on a body immersed in water. In the figure, we see that pressure forces act on the body from all sides:
Forces acting in the horizontal direction, i.e. on board the vessel, mutually compensate each other. The pressure on the lower surface - on the bottom, exceeds the pressure from above. As a result, an upward buoyant force is generated.
This is clearly seen from the following experiment.
Experience 5
A ball with air inside, immersed in water, flies up with force from it.
This acts on the ball buoyant force (Archimedes force). She then keeps the ship afloat and allows the ship to float.
1-Force of maintenance; 2-Water pressure on board
What does the effect of the buoyant force depend on?
First- this is from the volume of the ship and the second - from the density of the water in which the ship floats. This force is greater, the greater the volume of the immersed body. Let's check this experience.
Experience 6
Let's put a small load on a floating board - they sink. And here is the volume inflatable boat significantly larger, and it can even withstand a few people.
Second— the buoyant force changes with increasing water density. The density of water can be increased by adding a lot of salt to it.
We will prove this by the following experiment.
A Russian-American team of researchers has presented a revolutionary development: ultra-light aluminum that does not sink in water.
Chemists from the Russian Southern Federal University and the University of Utah (USA) have developed a new ultra-light crystalline form of aluminum. It does not sink in water and can be used in various sectors of the economy and industry. To create a new material, an innovative approach was applied using computer technology. The study is reported by Science Daily.
Professor Alexander Boldyrev from the University of Utah, together with colleagues from the Southern federal university restructured ordinary aluminum at the molecular level. To do this, experts used computer modeling and "assembled" a new crystal lattice.
Boldyrev explains: his team worked with the diamond crystal lattice. Taking its structure as a basis, scientists replaced every carbon atom aluminum tetrahedron.
The result was a new metastable form of the lightest aluminum. Its density – 0.61 grams per cubic centimeter
(for comparison: ordinary aluminum has a density of 2.71 grams per cubic centimeter).
And this means that aluminum with a new crystal form will float on the surface of the water
, whose density is one gram per cubic centimeter.
This property opens up huge prospects for the use of a new metal - a relatively inexpensive and easy-to-manufacture, corrosion-resistant paramagnet. Aerospace construction, medicine, electronics, automotive industry - these are just some of the areas in which ultra-light aluminum will find application, the authors of the work are sure. True, they have yet to test new material under various conditions, first of all - to check its strength.
The word "metal" is often associated with heaviness. This is far from true. All metals have very different properties. Some of them are so light that they do not even sink in water. What is the lightest metal? What properties does it have? Let's find out.
The lightest metals in the world
Light metals are metals that have a low density. This is by no means a rare occurrence. Substances with such characteristics make up approximately 20% of the mass of the earth's crust. They are actively mined and widely used in industry.
The lightest metal is lithium. In addition to the smallest atomic mass, it also has the lowest density, which is two times lower than that of water. After lithium come potassium, sodium, aluminum, rubidium, cesium, strontium, etc. These include titanium, which has the highest strength among metals.
Aluminum is also lightweight and durable. In the earth's crust, it is the third most common. Until people learned how to get it industrially, the metal was more expensive than gold. Now a kilogram of aluminum can be bought for about $2. It is used both in rocket technology and the military industry, and for the manufacture of food foil and kitchen items.
Lithium
Lithium is in the first group of the periodic table of elements. It stands at number 3, after hydrogen and helium, and has the smallest atomic mass of all metals. A simple substance - lithium, under normal conditions has a silvery-white color.
It is the lightest alkali metal with a density of 0.534 g/cm³. Because of this, it floats not only in water, but also in kerosene. It is usually stored in paraffin, gasoline, mineral oils or petroleum ether. Lithium is very soft and ductile, easily cut with a knife. To melt this metal, it must be heated to a temperature of 180.54 °C. It will boil only at 1340 °C.
In nature, there are only two stable isotopes of the metal: Lithium-6 and Lithium-7. In addition to them, there are 7 artificial isotopes and 2 nuclear isomers. Lithium is an intermediate product in the reaction of converting hydrogen into helium, thus participating in the process of formation of stellar energy.
Reactions with lithium
Given its alkaline nature, it can be assumed that it is very active. However, metal is the calmest member of its group. At normal room temperature, lithium reacts weakly with oxygen and many other substances. He shows his "stormy temper" after heating, then he reacts with acids, various gases and bases.
Unlike other alkali metals, it reacts gently with water, forming hydroxide and hydrogen. There is practically no reaction with dry air. But if it is wet, then lithium slowly reacts with its gases, forming nitride, carbonate and hydroxide.
At certain temperatures, the lightest metal is active with ammonia, ethyl alcohol, halogens, hydrogen, carbon, silicon, and sulfur.
lithium alloys
The properties of lithium increase the individual qualities of metals, which is why it is often used in alloys. Useful is its reaction with oxides, hydrogen, sulfides. When heated, it forms insoluble compounds with them, which are easy to extract from molten metals, having cleaned them of these substances.
To give the alloy corrosion resistance and ductility, it is mixed with magnesium and aluminum. Copper in an alloy with it becomes denser and less porous, conducts electricity better. The lightest metal increases the hardness and ductility of lead. It also raises the melting point of many substances.
Thanks to lithium, the metal becomes strong and resistant to damage. However, it does not weigh them down. That is why alloys based on it are used in space engineering and aviation. Mixtures with cadmium, copper, scandium and magnesium are mainly used.
Being in nature and meaning
The lightest metal has about 30 minerals of its own, but only 5 of them are used in industry: pentalite, amblygonite, lepidolite, zinnwaldite, and spodumene. In addition, it is located in salt lakes. In total, the earth's crust contains 0.005% of this metal.
Large industrial reserves of lithium are found on all continents. It is mined in Brazil, Australia, South Africa, Canada, the USA and other countries. After that, it is used in electronics, metallurgy, laser materials, nuclear energy and even medicine.
In our body, it is found in the liver, blood, lungs, bones and other organs. Lack of lithium leads to malfunctions nervous system and brain. It increases the body's resistance to disease, activates the activity of enzymes. With it, they fight Alzheimer's disease, mental disorders, sclerosis, as well as various addictions.
Toxicity
Despite the important biological role of lithium in our body, it can be dangerous. The lightest metal is quite toxic and can cause poisoning. When burning, it provokes irritation and swelling of the mucous membranes. If a piece of whole metal gets on them, the same thing will happen.
Lithium should not be handled without gloves. Interacting with moisture in the air or moisture on the skin, it easily causes a burn. With molten metal, you need to be even more careful, since its activity increases significantly. When working with it, you need to remember that it is alkali. You can reduce its effect on the skin with ordinary vinegar.
In the body, lithium increases the resistance of the immune system and improves the functioning of the nervous system. But its excess is accompanied by dizziness, drowsiness, loss of appetite. Metal poisoning leads to decreased libido, muscle weakness, and weight gain. In this case, vision, memory, and coma may worsen. When working with lithium, always wear gloves, a protective suit and goggles.