introduction
In 1974, when Yang Zhifa, a farmer in Xiyang Village in Lintong, Xi'an, was digging a dry well on the mountain, he inadvertently dug up many fragments of pottery figurines. After the excavation of archaeologists, a treasure of Qin figurines buried in the ground for more than 2,000 years appeared in front of the world, known as the "Eighth Wonder of the World".
Although after more than 40 years of uninterrupted excavations, the scientific expedition to the Terracotta Warriors and Horses of Qinling is far from over. During this period, the scientific expedition personnel encountered many difficulties, but also harvested too many surprises, especially some of the "black technology" of the Qin Dynasty, which has far exceeded the cognition of modern people. Today we will talk about: the 2 black technologies of the Qinling Terracotta Warriors and Horses show the superb scientific and technological level of ancient China, which 2?
A bronze sword that is incorruptible for a thousand years
In 1994, 19 bronze swords were unearthed from Pit 2 of the Qinling Terracotta Warriors, and these unearthed bronze swords were as bright as new and sharp. Seeing these bronze swords that seemed to be left here yesterday, the experts at the scene were stunned, which was incredible!
You know, these bronze swords have been buried underground for more than 2,000 years. In such a harsh environment, it is impossible for bronzes of any material not to be corroded, so why can these swords shine as new?
In order to find out the secret of the thousand-year-old incorruptible bronze swords of the Terracotta Warriors and Horses of Qinling, scientists have conducted in-depth research on these bronze swords. Scientists have found that these swords are not the bronze swords used by ordinary soldiers, they are carefully forged swords, which are the best in bronze swords.
Although the material of these bronze swords is mainly copper, this bronze is an alloy composed of copper, tin and lead, that is to say, the material of these bronze swords is not only copper, but an "alloy sword" doped with other metals. It is precisely this alloying element that improves the corrosion resistance of copper.
Subsequently, experts found a 15-micron thick layer of chromium salt compound on the swords of these bronze swords, and this layer of chromium salt compounds is the ultimate code that keeps the bronze sword incorruptible for thousands of years.
Chromium is a rare metal with the chemical symbol Cr, which is the hardest metal in nature, with only 0.01% of the earth's crust. Chromium is a metal with very good oxidation resistance and corrosion resistance, and after the 1940s, chromium was widely used, mainly to make stainless steel.
The sword body of each bronze sword excavated from the No. 2 pit of the Qinling Terracotta Warriors and Horses is evenly coated with a layer of chromium salt compound only 15 microns thick, which shows that more than 2,000 years ago, China's sword casting craftsmen have mastered the chrome plating process, and the chrome plating technology is quite exquisite.
The bronze sword that has traveled through more than 2,000 years of time and space can still be as bright as new and sharp, mainly due to the credit of this layer of chromium salt compound on the sword, which is definitely a "black technology" ahead of the times in the Qin Dynasty.
A bronze sword with the function of a metal for morphological memory
Of the 19 bronze swords unearthed in Pit 2, one was crushed under the body by a 250-pound terracotta warrior before it was excavated. At that time, the sword had been bent and deformed, twisting more than 45 degrees, and experts saw this situation and thought that the sword would be difficult to return to its original form. Who knew that after the experts removed the terracotta warriors pressed on the sword, they found that the sword had instantly returned to its original shape, which surprised the experts present.
Why does a bronze sword instantly return to its original shape after being deformed by a heavy pressure for more than 2,000 years?
After carefully studying the bronze sword, experts believe that this bronze sword has the characteristics of a morphological memory alloy.
Morphological memory alloy is known as "magical functional material", which is a material with more than two metal elements with a shape memory effect through thermoelastic and martensitic phase transition and its inversion. The blunt explanation is that the morphological memory alloy is actually an alloy made of more than two metals with different properties, and such metals can produce memory after being fused together.
For example, the parabolic antenna used in artificial satellites is made of morphological memory alloys. The parabolic antenna is huge and does not have the conditions for direct installation and emission, and scientists have used a morphological memory alloy to manufacture a foldable parabolic antenna. Before launching the satellite, the parabolic antenna is folded up and loaded into the satellite body, and after the artificial satellite enters the predetermined orbit, the temperature only needs to be increased, and the folded satellite parabolic antenna will be extended according to the form of memory because it has a "memory" function, and the parabolic shape will be restored.
The bronze sword excavated from the Qin Figurine No. 2 pit is a form memory alloy, experts through the analysis of the material of the bronze sword, found that its sword body is copper, nickel, tin, lead and other metal elements forged into a surface of the alloy, the craftsman through copper, nickel, tin, lead and other metal raw materials for proportional mixing, so that it has reached an alloy with memory performance.
In ancient China, casting swords was a job that took a long time. Gu Shiyun: "Good work has been training for several years, casting a sword named Dragon Spring", if a sword wants to reach the level of "sword", it not only needs thousands of hammers and hammers, but also the details of the sword casting requirements are very strict, only the extremely skilled sword casting master can create this kind of sword.
Morphological memory alloy was only popularized and applied in the 1930s, and the discovery of the bent and deformed bronze sword in the No. 2 pit of the Qin figurines proved that China's sword casting craftsmen had mastered the casting technology of the morphological memory alloy as early as more than 2,000 years, which had to make people sigh how advanced the "black technology" of China's Qin Dynasty was.
epilogue
The Qin Dynasty was the first unified dynasty in Chinese history, and it left a strong mark on the historical stage. The bronze sword found in the Qinling Terracotta Warriors and Horses Pit that is incorruptible for thousands of years and has the characteristics of the morphological memory alloy is the precious heritage left to us by the ancestors, even in the 21st century today, these "black technologies" created by the ancient working people of our country with wisdom can still amaze us, let us work together, and look forward to the birth of more science and technology and inventions in the land of China!