Looking for interesting topics in physical chemistry

In ancient China, the use of steel knives was very particular, and high-quality and sharp steel knives were called "treasure knives". During the Warring States Period, it is said that some people in the State of Yue made valuable swords such as "Ganjiang" and "Mo Xie", which were extremely sharp and "cut iron like mud". If you put your hair on the blade, you will break it in half as soon as you breathe. Of course, the legend is inevitably a bit exaggerated, but it is a fact that the "treasure knife" is sharp. In the past, only a few craftsmen mastered the technology of making this "treasure knife". Now we know through scientific research that the main secret of making this "treasure knife" is that it contains elements such as tungsten and molybdenum.

In fact, adding tungsten and molybdenum to steel, even if it is only a little bit, such as a few percent or even a few thousandths, will have a great impact on the properties of steel. This fact was not recognized until the middle of19th century, and then it greatly promoted the development of tungsten and molybdenum industry. By adding one or more elements such as tungsten and molybdenum alloying elements to ordinary steel in a planned way, various special steels with excellent properties-alloy steel can be manufactured.

Identification of gold purity by flame reaction

The purity of gold is also called fineness in our country. Some of the ten parts of gold are pure gold, which is usually called the fineness of gold.

There are many ways to identify gold. Archimedes of ancient Greece used buoyancy to identify the authenticity of King Lelong II's golden crown. The ancient Romans used touchstones to identify the purity of gold.

China has some sayings, such as "nine purple has seven colors, eight yellows and ten reds", "Gold is incomplete when it is put into fire" and "If it is put into fire, there must be copper in it". This is actually to identify the purity of gold by using the color of the flame produced when gold burns. As we know, many metals or their compounds can make the flame show a special color when burning, which is called flame reaction in chemistry. For example, the common flame colors of several metals or ions: potassium purple, sodium yellow, lithium purple, barium yellow green, verdigris and so on. The above method of identifying gold by burning the flame color of gold is based on the principle of flame reaction, and the flame color of gold varies with its purity. Interested friends might as well give it a try and burn the gold with a faint flame.

Colored gold alloy

Gold is the most malleable metal. 1 g gold can be drawn into filaments up to 4000 meters. If 300 grams of gold is drawn into filaments, it can start from Nanjing and extend along the railway line to Beijing. A ton of gold is drawn into a filament, which can travel five times from the earth to the moon.

Gold can also be pressed into gold foil much thinner than paper, with a thickness of only 500,000 cm. Such a thin gold foil looks almost transparent with a little green or blue. Gold, thin to a certain extent, can not only insulate heat, but also transmit light, so the gold film can be used as a heat insulation material for astronauts and firefighters' masks. In winter, the heat rays radiated by the sun are reflected indoors with gold film, which makes the room warm as spring; In summer, a golden coating is put on the outside of the glass of the house, which can reflect most of the sun's heat rays, and the room will not be stuffy.

Although gold has so many advantages, it also has many disadvantages. For example, soft texture, expensive price and monotonous color. If gold is combined with other metals to make gold alloy, it can not only make up for the deficiency, but also make the performance better. Modern gold alloys have been widely used in rocket, supersonic aircraft, nuclear reactor and aerospace industries. In addition, gold coins and gold jewelry made of gold alloy are also deeply loved by people. The 22K and 18K gold jewelry we usually see are all gold and yellow with different weights.

The alloy made of gold will become golden yellow, red, rose, gray and green until it becomes white. Green gold alloy contains 75% gold, 16.6% silver and 8.4% cadmium. There is a kind of gold-copper alloy called copper; An alloy of gold and silver is called red silver. These two alloys appear purple or light blue-black after being treated with salt solution.

There is a lot of gold in the earth's crust. It is estimated that it covers about five-tenths of the earth's crust, but it is very scattered. It is really "arachis duranensis"! In addition, there is gold in the hot steam around the sun; There is also gold in meteorites; There are really "stars full of gold" in the sky; The gold content in the ocean is very rich, and it is a "big treasure house"

Identification of jewelry and diamonds

Intuitive recognition

Perspective test-clean the gem with a round diamond cutter, put it on a piece of white paper with lines, and judge whether the gem is a diamond by observing the lines on the paper. If it is a standard round cut diamond, the lines on the paper cannot be seen through the diamond (synthetic strontium titanate and synthetic rutile are similar to diamonds and have no perspective effect). However, due to the different refractive index, most imitations have enough light leaking from the pavilion surface, and some lines on the paper can be seen through perspective observation.

Brightness estimation-the ability of external reflection and total internal reflection of gem crown to refract light, which is called brightness. When diamonds and their imitations are placed in the same light source and environment, the standard round diamonds with fine cuts are observed from the bottom, and almost all the light entering from the crown is reflected by the crown, showing strong brightness. However, the refractive index and cut of imitation are different from that of diamond, and the light entering from the crown will leak out from the pavilion to varying degrees, thus reducing the brightness.

Oiliness test-Draw a line on the diamond table with a special pen or ballpoint pen dipped in oily ink, which will leave an uninterrupted straight line. However, other imitations are not lipophilic, leaving intermittent dotted lines at the scribe line.

In the water drop test, clean the mesa of diamond and imitation, drop a little water each, and observe the time and contour of the water drop. The water droplets on the diamond will remain spherical for a long time, while the water droplets on the imitation will disperse in a relatively short time.

Breath test-put the sample to be tested and the known diamond sample together on the glass, blow on them and observe the disappearance of the fog. The fog on the diamond disappears quickly, but the fog on the imitation disappears slowly.

Sensory test-diamond and its imitation are touched with the tip of your tongue at room temperature. The diamond is much cooler than the imitation.

instrument identification

Magnification detection-observation under a magnifying glass or gem microscope. (1) Diamonds generally contain a small amount of fine mineral inclusions in addition to their extremely high quality. Common inclusions are: black graphite, brown spinel, red chrome spinel, garnet, colorless transparent stone and so on. (2) Due to the scarcity, preciousness and high hardness of diamonds, the cutting and polishing of diamonds are very particular, and the cutting ratio, crown angle and pavilion angle of diamonds are all calculated. The table and facet of the diamond are straight and there is no warping phenomenon. The edges and corners are straight and sharp, and three or more edges strictly intersect at one point, while imitations are often smooth because of their low hardness and poor cutting. (3) The extremely high hardness of diamond makes it difficult to be worn, even if the wear is limited to the edges and corners of a single facet. However, imitations are often rough after wearing because of their low hardness.

Thermal conductivity meter test-Thermal conductivity meter can quickly, simply and accurately identify diamonds and their imitations, especially for the identification of diamond jewelry. Different substances have different thermal conductivities, and the thermal conductivity of diamond is the best among gems (the thermal conductivity is 1000 ~ 2600 W/m℃). Touch the probe of the thermal conductivity meter to the sample, turn on the power supply, and according to the heat transfer speed of the thermocouple, the LED will display the number of lights or the words displayed on the LCD screen, so as to know the authenticity of the diamond.

Test of reflector-The advantages and disadvantages of reflector and thermal conductivity meter are just complementary, that is, gems that are easily confused on thermal conductivity meter can be clearly distinguished on reflector, while gems with similar characteristics on reflector can be clearly distinguished by thermal conductivity meter.

X-ray fluorometer test-the application of X-ray in gem identification is very important. X-rays belong to high-energy rays, which will cause lattice damage and change the color of gems. This identification method is generally not used.

Electronic balance or other weighing instruments-It is a very effective and simple method to test the density of bare diamonds and imitations with electronic balance or other weighing instruments. The density of diamond (3.529g/cm3) is quite different from that of most imitations, and only the density of natural topaz (3.56g/cm3) is similar to that of diamond.

The difference between diamonds and imitations

The difference between a diamond and a natural colorless gem-the gem most similar to a diamond is zircon, because colorless zircon also has a large refractive index and dispersion, and the processed zircon also has a radiant appearance, so it is one of the best natural substitutes for diamonds. The difference between diamond and zircon is actually very simple. Diamonds are equiaxed gems without polarization and birefringence, while zircon has polarization and large birefringence. Looking down at the edge of its pavilion from its crown, you will find that one edge has become two, that is, there is a "ghost" phenomenon, and the diamond is still an edge. In addition, it is easy to distinguish by hardness method. Just carve an artificial sapphire on the gem to be identified. If the mark can be drawn, it is a diamond; If it slips and cannot be scratched, it is not a diamond. Other natural colorless gems, because of their low refractive index, are difficult to have a "radiant" and "colorful" appearance even after good cutting and polishing. The refractive index of diamond is 2.42, which is beyond the reading range of general refractometer. The refractive index of ordinary gems is easy to measure, such as colorless topaz and crystal (if other features are similar to diamonds, the refractive index is generally not measured to avoid scratching the refractometer). In addition, the processing of general gemstones is often not strict, and light leakage often occurs, while slightly larger diamonds (such as more than 30 points) are often strictly processed and generally do not leak light because of their high value.

The difference between diamond and artificial imitation diamond-another imitation that is most similar to diamond is cubic oxidation milling, abbreviated as CZ. Because this synthetic gem was first developed by the Soviets and is very similar to diamonds, many people call it "Soviet diamond" (it is worth noting that some customers think that Soviet diamonds are fake, but in fact, the Soviet Union is also a country rich in natural diamond resources). Cubic zirconia belongs to the equiaxed crystal system, with hardness as high as 8.5 and large refractive index and dispersion. Processed "Soviet diamonds" also have the attractive appearance of sparkling fire, and sometimes their "beauty" even exceeds that of general poorly processed natural diamonds. It is not difficult to distinguish natural diamonds from other artificial imitation diamonds. (1) The hardness of all synthetic products is less than 9. For gems without inlays, the hardness score can be used to distinguish them. Diamonds can carve artificial sapphires, but not diamonds. This method can also effectively distinguish some glass imitations with coated surfaces. (2) Generally, the colors of artificial substitutes are "white" and clean, while natural diamonds, except some high-grade products with 96 colors and above VVS, are mostly yellow, and some "flaws" can be seen. (3) Synthetic substitutes have low hardness and low price, so the processing is rough, and the ground gems often have "light leakage", "burr" or rounded edges.

The difference between diamonds and synthetic diamonds, color-changing diamonds and sandwich diamonds-The third kind of counterfeit diamonds are synthetic diamonds, which often have almost the same physical properties as natural diamonds, such as hardness, refractive index, dispersion, etc., and cannot be distinguished by the senses alone. The simple distinction is that synthetic diamonds usually contain some metallic mineral inclusions, which are "magnetic", while natural diamonds do not. The method is: put a magnet in front of the microphone and move the diamond quickly in front of the microphone. Synthetic diamonds make tiny noises, indicating that they are magnetic. The discoloration of diamonds was discovered at the beginning of this century after the radioactivity of radium was discovered. Colored diamond with good color is more valuable than colorless diamonds, which promotes the development of turning light brown or yellowish diamonds into colored diamond. It is necessary to distinguish between natural diamonds and colored diamonds. Looking down from the mesa of artificial colored diamond (produced by radiation or bombardment of high-energy accelerator), there will be some umbrella-shaped color circles or shadows, and there will be a characteristic absorption line of 594nm in the absorption spectrum. In addition, its fluorescence, radioactivity and conductivity are also different from those of natural colored diamonds. Sandwich diamonds are mainly due to the special shape of raw materials. Craftsmen often "splice" two originally smaller diamonds into a larger diamond, while others make a double-layer diamond with a diamond top and a crystal or colorless synthetic corundum bottom, and cover the bottom with a "golden claw" or "Phnom Penh" to deceive customers. For this kind of diamond, you can carefully observe whether there is a bonding interface at the waist with a magnifying glass. You can often see some small bubbles and glue, and you can also feel a layer of fog on a certain level inside the diamond. If the gem is not inlaid, it will be better to observe it in diiodomethane or clear water.

The difference between diamond and coated diamond-the fourth fake, coated diamond may be the most advanced imitation on the market at present, which is made by combining high pressure and chemical vapor deposition. This synthetic diamond has low cost and simple conditions. When the coating thickness of this synthetic diamond is greater than 10 micron, it has similar reaction with natural diamond when measured by "thermal conductivity meter". However, this substitute is still flawed. First, the coating surface is small diamond polycrystal, and the general appearance is gray. Second, the ratio of coated diamonds to natural diamonds is different, which is the key to identification.

Silver, a metal that can kill bacteria.

In ancient times, people knew that milk and other foods could be kept in silver bowls for a long time without spoilage. Because silver will also "dissolve" in water, when food comes into contact with silver, the water in food will turn a very small amount of silver into silver ions. The bactericidal ability of silver ions is quite strong. As long as there are two grams of silver ions in every liter of water, it is enough to kill bacteria.

The bactericidal effect of silver ions can also be used for disinfection and surgical rescue. The ancient Egyptians already knew that it was effective to cover the wound with silver. Later, some people used "silver gauze" to dress wounds and treat skin wounds and intractable ulcers, sometimes with good results. In modern medicine, doctors often drop 1% silver nitrate solution into newborn eyes to prevent neonatal eye diseases. Small silver needle was first used in acupuncture and is famous at home and abroad.

Silver also has many uses. It is a good conductor for making wires. Electroplating, mirror making, photography and other industries are also in great need.

Chemical action of gastric function

The digestive function of the stomach is very strong, relying on hydrochloric acid, pepsin and mucus in the stomach. Hydrochloric acid is a very corrosive acid. After food enters the stomach, hydrochloric acid will kill bacteria in the food. The concentration of hydrochloric acid in the stomach is high enough to melt zinc. Pepsin can decompose protein in food. Mucus can wrap food, not only lubricate it, but also protect gastric mucosa from mechanical damage caused by food. The combination of hydrochloric acid, pepsin and mucus in the stomach can digest almost all food.

Since the digestion ability of the stomach is so strong, why can't it be digested by itself? This question was put forward more than 100 years ago, and has not been answered satisfactorily so far. Some scientists believe that the stomach can't digest itself because there is a special substance in gastric mucosa or gastric juice that can resist the effects of hydrochloric acid and pepsin. Scientists believe that: first, after the gastric wall secretes hydrochloric acid, it will not flow back because it is blocked by epithelial cells on the mucosal surface, so it will not corrode the gastric wall. In case epithelial cells are destroyed, mucous membrane will secrete mucus, which has a certain buffering effect on hydrochloric acid and can also prevent hydrochloric acid adhered to the surface of gastric mucosa from entering the interior. The gastric mucosa also has the ability of "saving the car", which enables epithelial cells to constantly renew their metabolism, prevents the absorption of pepsin on the mucosa, and achieves the purpose of protecting the gastric wall. In addition, some glycoproteins in mucus contain more sugar and have large molecular weight, which can inhibit the activity of pepsin.

Secondly, human gastric mucosal cells shed about 500,000 cells per minute, which can be completely renewed within three days. Such a strong regenerative ability can make up for the temporary damage caused by digestive juice to the stomach wall.

Therefore, under the conditions of political parties, the stomach cannot digest itself. If there is too much stomach acid in the stomach, or taking medicine on an empty stomach, the stomach wall is damaged and the stomach begins to digest itself, diseases such as gastric ulcer will occur.

Beryllium, a metal that lives in jadeite.

There is an emerald glittering gem called beryl. It used to be a treasure enjoyed by nobles, but now it has become a treasure of working people.

Why do we also regard beryl as a treasure? This is not because it has a beautiful and attractive appearance, but because it contains a precious and rare metal-beryllium.

Beryllium means "emerald". Almost thirty years later, people reduced beryllium oxide and beryllium chloride with active metals calcium and potassium, and made the first low-purity beryllium. It was nearly 70 years before beryllium was processed and produced on a small scale. In recent thirty years, the output of beryllium has surged year by year. Now, the era of beryllium "anonymity" has passed, and people produce hundreds of tons of beryllium every year.

Seeing this, some children may ask such a question: Why was beryllium discovered so early and applied in industry so late?

The key is the purification of beryllium. It is very difficult to purify beryllium from beryllium ore, but beryllium especially likes "cleanliness". As long as beryllium contains a little impurity, its properties will change greatly and many excellent qualities will be lost.

Of course, the situation has changed a lot now. We have been able to produce high-purity beryllium by modern scientific methods. We all know many characteristics of beryllium: its specific gravity is one third lighter than that of aluminum; Its strength is close to that of steel, and its heat transfer capacity is three times that of steel, so it is a good conductor in metal. X-ray has the strongest penetrating power and is called "metallic glass".

Once had so many excellent properties, no wonder people praised it as "steel in light metal"!

Undaunted beryllium bronze

At first, a small amount of beryllium was only used in special circumstances, such as X-ray tube light window, neon lamp parts, etc. Because of insufficient smelting technology, beryllium contains impurities, which are fragile, difficult to process and easy to oxidize when heated.

Later, people opened up a broad and important new field for the application of beryllium alloy, especially for the manufacture of beryllium bronze-beryllium bronze.

As we all know, copper is much softer than steel, and its elasticity and corrosion resistance are not strong. However, after adding some beryllium to copper, the properties of copper have changed greatly. Beryllium bronze containing 1% to 3.5% beryllium has excellent mechanical properties, enhanced hardness, excellent elasticity, high corrosion resistance and high conductivity. Springs made of beryllium bronze can be compressed hundreds of millions of times.

The indomitable beryllium bronze has recently been used to manufacture deep-sea detectors and submarine cables, which is of great significance to the development of marine resources.

Beryllium bronze containing nickel also has a valuable feature-it will not produce sparks when it is hit. This function is very useful for explosive factory. You see, inflammable and explosive materials are afraid of fire, such as explosives and detonators, which will explode at the sight of fire. However, tools such as hammers and drills will generate sparks when used. How to do this? Obviously, it is most suitable to make these tools with this beryllium bronze containing nickel. In addition, beryllium bronze containing nickel will not be attracted by magnets or magnetized by magnetic fields, so it is a good material for manufacturing antimagnetic parts.

Didn't we say that beryllium has the nickname "metallic glass"? In recent years, beryllium with small specific gravity, high strength and good elasticity has been used as the reflector of high-precision TV fax, and the effect is really good. It only takes a few minutes to send a photo.

Building a "house" for atomic boilers

Beryllium has many uses, but among many elements, it is still an unknown "nobody" and is not valued by people. However, in the 1950s, the "fate" of beryllium was greatly improved, and it became a hot commodity for scientists.

Why is this?

It turns out that in the coal-free boiler-atomic reactor, in order to release a lot of energy from the nucleus, it is necessary to bombard the nucleus with great force to split it, just like bombarding the solid explosive magazine with shells to explode it. This "shell" used to bombard the nucleus is called neutron. Beryllium is an efficient "neutron source" and can provide a large number of neutron shells. It is not enough for an atomic boiler to be "ignited" by neutrons. After lighting, it must be really "lit".

Neutrons bombard the nucleus, which splits, releasing atomic energy and producing new neutrons. New neutrons are extremely fast, reaching tens of thousands of kilometers per second. It is necessary to slow down this fast neutron and turn it into a slow neutron, so that it is easy to bombard other nuclei and cause new division. One changes to two, two changes to four ... "Chain reaction" continues to develop, making the atomic fuel in the atomic boiler really "burn". Beryllium has a strong "braking" ability to neutrons, so it has become an efficient retarder in atomic reactors.

Not counting this, in order to prevent neutrons from running out of the reactor, it is necessary to set up a "warning line"-neutron reflector around the reactor to order those neutrons that attempt to "cross the border" to return to the reaction zone. In this way, on the one hand, it can prevent invisible rays from harming human health and protect the safety of workers; On the other hand, it can reduce the number of neutrons escaping, save "ammunition" and maintain the smooth progress of nuclear fission.

Beryllium oxide has a small specific gravity, high hardness and a melting point as high as 2450 degrees Celsius. It can reflect neutrons back like a mirror and is a good material for building atomic boilers.

Now, almost all kinds of atomic reactors use beryllium as neutron reflector, especially when building small atomic boilers for various vehicles. It usually takes two tons of polymetallic beryllium to build a large atomic reactor.

Show your talents in the aviation industry

The development of aviation industry requires airplanes to fly faster, higher and farther. Of course, beryllium with light weight and high strength can also show this ability.

Some beryllium alloys are good materials for making airplane rudder, wing box and jet engine metal parts. After many parts of modern fighter are made of beryllium, the weight is reduced and the number of assembly parts is reduced, which makes the aircraft move more quickly and flexibly. There is a newly designed supersonic fighter-Beryllium plane, which can fly at a speed of 4000 kilometers per hour, which is more than three times the speed of sound. Beryllium and its alloys will be more widely used in future atomic aircraft and short takeoff and landing aircraft.

Since the 1960s, the use of beryllium in rockets, missiles and spaceships has also increased dramatically.

Beryllium is the best conductor among metals. At present, many brakes of supersonic aircraft are made of beryllium, because beryllium has good heat absorption and heat dissipation performance, and the heat generated during "braking" will soon be lost.

When artificial earth satellites and spacecraft pass through the atmosphere at high speed, the friction between objects and air molecules will produce high temperature. Beryllium, as their "heat-proof coat", can absorb a lot of heat and excite it quickly to prevent excessive temperature rise and ensure flight safety.

Beryllium is also an effective rocket fuel. Beryllium can release huge energy during combustion. The heat released by complete combustion of beryllium per kilogram is as high as 15000 kcal, which is a high-quality rocket fuel.

A panacea for "occupational diseases"

It is a normal physiological phenomenon that people will feel tired after working and laboring for a period of time. However, many metals and alloys will also be "tired". The difference is that after a rest, fatigue will disappear automatically, and people can continue to work, but not metals and alloys. When they are too tired, the things they make can't be used any more. What a pity!

How to treat this "occupational disease" of metals and alloys?

Scientists have found a "panacea" to cure this "occupational disease", that is beryllium. If a small amount of beryllium is added to steel, the spring for automobile can bear 6.5438+0.4 million impacts, and there will be no trace of fatigue.

Sweet metal

Does metal taste sweet?

Of course not. Then why is the topic "Sweet Metal"?

It turns out that some metal compounds are sweet, so people call this kind of gold "sweet metal", and beryllium is one of them.

But don't touch beryllium, because it is poisonous. As long as there is one milligram of beryllium dust per cubic meter of air, people will be infected with acute pneumonia-beryllium lung disease. The broad masses of workers in China's metallurgical front launched an attack on beryllium poisoning, and finally reduced the content of beryllium in one cubic meter of air to less than 100 thousand grams, successfully solving the problem of protection against beryllium poisoning.

Compared with beryllium, beryllium compounds are more toxic. Beryllium compounds can form soluble colloidal substances in animal tissues and plasma, and then react with hemoglobin to form a new substance, thus causing various pathological changes in tissues and organs. Beryllium in lungs and bones may also cause cancer. Although the compound of beryllium is sweet, it is a "tiger's ass" and must not be touched.

"Fire King Kong" and "Corrosion Champion"-Niobium and Tantalum

This time we are going to meet the twin brothers of niobium and tantalum.

It is meaningful to introduce them together, because they belong to the same family in the periodic table of elements, have similar physical and chemical properties and are often "inseparable". They are really a pair of lifelike twin brothers.

In fact, when people first discovered niobium and tantalum at the beginning of19th century, they thought they were the same element. About forty-two years later, people first separated them by chemical methods, and only then did it become clear that they were two different metals.

Niobium, tantalum, tungsten and molybdenum are rare metals with high melting point, and their properties and uses are similar.

Since they are called rare high melting point metals, the most important characteristic of niobium and tantalum is of course heat resistance. Their melting points are as high as 2400 degrees Celsius and nearly 3000 degrees Celsius respectively. Don't say that ordinary fires can't burn them, and even the blazing flames in the steelmaking furnace can't help them. No wonder metallic tantalum is a very suitable material in some counties with high temperature and high fever, especially for making vacuum heating furnaces with temperature exceeding 1600 Baidu.

When we introduce W-Mo alloy steel, we see that the excellent properties of one metal can often be "transplanted" to another metal. This is also the case now. Adding niobium as an alloying element to steel can increase the high temperature strength of steel and improve its processability. Niobium and tantalum cooperate with a series of metals such as tungsten, molybdenum, vanadium, nickel and cobalt to obtain a "thermal strength alloy", which can be used as structural materials for supersonic jets, rockets and missiles. At present, scientists have begun to turn their attention to niobium and tantalum when developing new high-temperature structural materials. Many high temperature and high strength alloys have these twin brothers.

Niobium and tantalum have strong toughness, and their carbide ability is stronger, which is no different from tungsten and molybdenum. The cemented carbide made of niobium carbide and tantalum carbide has high strength, compression resistance, wear resistance and corrosion resistance. Tantalum carbide has the highest hardness among all hard compounds. The tool made of carbide carbide can withstand the high temperature below 3800 Baidu, the hardness can be comparable to that of diamond, and the service life is longer than that of tungsten carbide.

The magical uses of surgery and medicine

Tantalum also plays an important role in surgery. It can not only be used to manufacture medical devices, but also be a good "biocompatible material".

For example, tantalum sheets can make up for the damage to the skull, tantalum wires can be used to sew nerves and tendons, tantalum strips can replace broken bones and joints, and tantalum gauze or tantalum nets made of tantalum wires can be used to compensate muscle tissue. ...

In the hospital, there will be such a situation: after replacing the broken bones in the human body with tantalum strips, after a period of time, muscles will grow on the tantalum strips, just like they grow on real bones. No wonder people call tantalum "bionic metal".

Why can tantalum play such a peculiar role in surgery?

The key is that it has excellent corrosion resistance, does not interact with various liquid substances in the human body, and hardly damages biological tissues. It can adapt to any sterilization method, so it can be combined with organic tissues for a long time and remain in the human body harmlessly.

In addition to such good uses in surgery, niobium and tantalum can also be used to manufacture electrolytic capacitors, rectifiers and so on by their good stability.

At present, more than half of tantalum is used to produce solid electrolytic capacitors with large capacity, small volume and high stability. Hundreds of millions of such products are produced all over the world every year.

Tantalum electrolytic capacitor has not "failed" people's high expectations, and it has many incomparable advantages over other materials.

It is five times larger than other capacitors of the same size, very reliable, earthquake-resistant, wide working temperature range and long service life. Now it has been widely used in electronic circuits such as computer, radar, missile, supersonic aircraft, automatic control device, color TV, stereo TV and so on.

Work miracles at ultra-low temperature

However, what surprises us most is that they can not only work tenaciously in extreme high temperature environment, but also serve us well in ultra-low temperature conditions. They are really amazing.

My friends, some of you may know that there is such a temperature, which is called "absolute zero", and its zero degree is equivalent to MINUS 273 degrees Celsius. Absolute zero is considered as the lowest temperature.

It has long been found that when the temperature drops to near absolute zero, the chemical properties of some substances will suddenly change and become "superconductors" with almost no resistance. The temperature at which a substance begins to have this strange "superconducting" property is called the critical temperature. Needless to say, the critical temperatures of various substances are different.

You know, ultra-low temperature is hard to come by, and people have paid a huge price for it; The closer to absolute zero, the greater the cost. Therefore, our requirement for superconducting materials is of course that the higher the critical temperature, the better.

There are many superconducting elements, among which niobium has the highest critical temperature. The critical temperature of niobium alloy is as high as 18.5 to 2 1 degree, which is the most important superconducting material at present.

People have done such an experiment: a niobium ring cold to superconducting state is electrified and disconnected, and then the whole instrument is sealed and stored at low temperature. Two and a half years later, people turned on the instrument and found that the current in the niobium ring was still flowing, and the current intensity was almost the same as when it was first electrified!

It can be seen from this experiment that superconducting materials will hardly lose current. If the superconducting cable is used to transmit electricity, because it has no resistance, there will be no energy loss when the current passes, so the transmission efficiency will be greatly improved.

Someone has designed a high-speed maglev train whose wheels