Silver among silver medals, also a champion

The symbol Ag for silver comes from its Latin name Argentum, which means "light, bright". The English word Silver comes directly from the Old English word seolfor, which means silver.

The Chinese character 银 is composed of 金 and 艮. 金 means this is a metal, while 艮 is a phonetic and semantic character. The phonetic character indicates the pronunciation of "银" "yin", while the semantic character is the abbreviation of "跟", which means to follow or follow. The Chinese characters of the "艮" family are all related to the meaning of "boundary" and "limit". Therefore, the original meaning of 银 is "a metal with a value close to that of gold".

1. Historical Origins of Silver

Silver is a precious metal with a long history of application. Humans have had a certain understanding of silver in ancient times, and its use has a history of more than 4,000 years.

The abundance of silver in the earth's crust is much greater than that of gold, about 15 times that of gold, but because its chemical properties are more active than gold, it mostly exists in the form of compounds in nature. It is for this reason that silver was discovered later than gold.

Historically, silver has had dual value as currency and decoration. The British pound and my country's previous silver dollars are silver-copper alloys with silver as the main component.

In ancient times, due to technological limitations, people only had a small amount of silver, so its value was higher than gold. For example, between 1780 BC and 1580 BC, the Egyptian dynasty's code stipulated that the value of silver was twice that of gold. Even in the 17th century, the value of gold and silver in Japan was still equal.

2. History of Silver as Money

Historically, silver, like gold, has been the legal tender of many countries, with financial reserve functions and an important means of international payment.

In China, the recognition and use of silver has a long history. It was made into handicrafts and currency very early. After the Tang and Song dynasties, silver was used as currency in large quantities. In the Yuan Dynasty, the silver standard was further strengthened, and silver was used as a major currency. During this period, "silver ingots" and "yuanbao" appeared (Figure 1).

Figure 1 Yuan Dynasty Yuanbao (picture from the Internet)

By the Ming and Qing dynasties, the silver standard was continuously consolidated and strengthened. Silver coins became the official currency in the Ming Dynasty, and ingots, broken silver and silver dollars became legal tender in the Qing Dynasty. The role of silver in the economic development of the Ming and Qing dynasties was crucial.

In the early Ming Dynasty, merchants and gold, silver, copper and tin were prohibited from going out to sea. Copper coins were used domestically, and private silver coins were strictly prohibited. In the late years of Yongle, the court began to pay attention to the mining of silver mines in order to cope with expenses. Officials were sent to mine minerals in Shaanxi, Fujian and other places, and the Gerongxi Silver Field Bureau and the Dali Silver Smelting Bureau in Yunnan were established. After the Xuande period, the mining of gold and silver was suspended from time to time, and disputes between private, official and private mining continued. The government army and "mine robbers" often fought armed battles. Officials sent by the court to supervise taxation in each silver field. After that, the silver mining boom began in Henan, Yunnan, Shandong, Sichuan and other places, reaching its peak during the Jiajing and Wanli periods. Silver had become the currency in circulation throughout the country. All transactions of high value were priced in silver, and silver was also widely used by the people (Figure 2). Until the end of the Ming Dynasty, there were many private miners in various places.

Figure 2 Ming Yuanbao (picture from the Internet)

The monetary system of the Qing Dynasty basically followed that of the Ming Dynasty, mainly using copper coins and silver, with a short period of partial use of official notes from the Ministry of Revenue and Qing Baochao. Generally, silver was used for large transactions, and copper coins were used for small and sporadic transactions. With the development of social economy, the status of silver became more important. After the middle of the Qing Dynasty, silver coins were widely used in the market, and machines were purchased from foreign countries to cast silver dollars, which circulated in parallel with the popular Spanish and Mexican silver dollars and other foreign silver dollars, as well as the newly cast copper dollars, as shown in Figure 3. In the 14th year of the reign of Emperor Guangxu, Zhang Zhidong served as the governor of Guangdong and cast silver coins in imitation of foreign coinage styles. Later, Li Hongzhang succeeded as the governor of Guangdong and officially cast the silver dollar named "Guangxu Yuanbao" (commonly known as Longyang). Since then, China has begun to cast its own silver dollar standard currency. Due to the expansion of Sino-Western trade and economic exchanges, by the late Qing Dynasty, the currency in circulation was mainly silver dollars and bank exchange certificates (Figure 4).

Figure 3 Qing Yuanbao (picture from the Internet)

Figure 4 Bank of Qing Exchange Notes (Photo from the Internet)

During the Beiyang government period of the Republic of China, the national currency circulated more and more widely, but various old silver dollars did not completely withdraw from the market circulation, and trade was still based on silver taels, and silver dollars had to be converted into silver taels for calculation. After the establishment of the Nanjing National Government, in order to consolidate the regime, a unified currency system was carried out. In 1933, the National Government of the Republic of China tried to "abolish the tael and change the yuan" in Shanghai. From March 10, all transactions in Shanghai were calculated in silver coins. After that, the Ministry of Finance promulgated the corresponding casting regulations, stipulating that the central mint should uniformly cast silver standard coins. The silver standard coin was named "yuan", each weighing 26.6971 g, with a fineness of 0.88, that is, the silver content was 88%, the copper content was 12%, and the tolerance did not exceed 3‰. "Abolishing the tael and changing the yuan" established the silver standard system and unified the national currency; the silver currency was changed from weight to count, which was conducive to its function as a value scale and a means of circulation, weakened the power of money houses and foreign banks, and was conducive to the accelerated development of domestic banks.

In 1935, the Nationalist government announced the issuance of legal tender and the abolition of the silver standard. The use of silver as currency was restricted, but silver dollars continued to circulate among the people until 1949 (Figure 5).

Figure 5 Silver Dollar of the Republic of China (Picture from the Internet)

In 1949, the People's Republic of China was founded, and everything was revived. In order to stabilize the RMB, the People's Bank of China formulated and issued the "Gold and Silver Management Measures" (draft) in April 1950, freezing private gold and silver transactions, and the People's Bank of China implemented a unified purchase and distribution policy, and severely cracked down on silver dollar speculation and smuggling activities. The implementation of this policy increased national reserves and consolidated the RMB's status as a local currency.

The silver industry of the People's Republic of China has flourished with the continuous development of China's economy and the reform of its management system. The domestic silver supply has also changed from being insufficient in the past to becoming one of the world's major silver producers, and a large amount of silver is exported every year. China's silver industry has already played an important role in the world, and silver consumption has continued to increase, making it one of the most promising emerging markets in the global silver market.

3. Silver's electrical conductivity

3.1 Importance of Electricity

The importance of electricity to human beings is self-evident. Electricity makes life more convenient. People cannot live without electricity in their daily life. All electrical appliances need electricity, such as air conditioners, trams, rice cookers, electric kettles, etc. Electricity has driven inventions. For example, the invention and widespread use of electric motors have greatly improved the level of productivity. Electricity is highly efficient, clean and easy to use. Electricity enables information to be spread, so that information can be transmitted accurately and quickly to every corner of the world. For example, communication equipment, mobile phones, computers, etc. cannot live without electricity for a moment (Figure 6).

Figure 6 Electricity is the blood of the national economy (Picture from the Internet)

The discovery and application of electricity has greatly saved human physical and mental labor, given wings to human power, and extended human information tentacles.

In modern times, electricity is an indispensable kinetic energy. Without it, it is like food without salt for seasoning, chocolate without rich taste, storybooks without lively illustrations, and everything becomes dull.

In the morning, take out a hot breakfast from the rice cooker. At this time, electricity appears in the form of "thermal energy". Then look at the clock. It is the "kinetic energy" converted from electricity that pushes the pointer forward. The sound of the bell is the "sound energy" converted from electricity. When you go to the office and turn on the light, electricity becomes "light energy" again.

Imagine what would happen if there was no electricity? “One day without electricity, everything is barren.” Although it is actually only a regression of more than 100 years, does it make us feel like we have returned to primitive society?

3.2 Importance of Wires

We cannot see or touch "electricity", but it does exist. Moreover, electricity can only be used by people through transmission. Electricity is transmitted through wires, which are necessary elements for using electricity. The most basic function of wires is to connect circuits and conduct electricity to form loops. Specifically, it can be divided into heat generation (wires of heating wires), magnetism (coils of electromagnets), force generation (wires of motors), light emission (LED wires), etc.

Materials that can conduct electricity are called conductors. When the current is transmitted through the conductor, it will encounter resistance and cause loss. Resistance can be simply understood as the resistance of the material to the current. It goes without saying that when we choose a wire, we hope that its resistance is as small as possible, that is, we hope that the conductor's conductivity is as strong as possible.

3.3 Conductivity of silver and its applications

"Silver" is the most conductive metal known to mankind so far. Figure 7 is a comparison of the conductivity of some common metals. For ease of understanding and comparison, Figure 7 is based on the conductivity of silver (100%). It can be seen that the conductivity of copper can reach 95% of silver, aluminum can reach more than 60%, tungsten can only reach about 30%, and the conductivity of iron is less than 1/6 of silver, and chromium is less than 1/8.

Figure 7 Electrical conductivity of common metals

The most commonly used wires in industry and daily life are copper rather than silver. The main reason is that although copper's conductivity is slightly inferior to silver, it is much cheaper than silver. For economic reasons, copper is mostly used. Aluminum wires are sometimes used for high-voltage power transmission. In addition to economic reasons, aluminum is very light. Its density (2.7 g/cm3) is only about 1/4 of silver (10.49 g/cm3) and less than 1/3 of copper (8.96 g/cm3). In terms of the conductivity of the conductor per unit mass, aluminum is better than silver or copper.

Silver is widely used in the field of electronic and electrical materials due to its excellent conductivity. Electronics and electrical appliances are the industries that use the most silver, and its use is divided into electrical contact materials, composite materials and welding materials. Silver and silver-based electrical contact materials can be divided into: pure silver, silver alloys, silver-oxides, sintered silver alloys, etc. The annual output of silver and silver-based electrical contact materials in the world is 2900-3000 tons. Composite materials are materials prepared using composite technology, which are divided into silver alloy composite materials and silver-based composite materials. From the perspective of silver-saving technology, silver composite materials are a new material with great development prospects. Silver welding materials include pure silver solder, silver-copper solder, etc.

Silver wire can be used to make extremely sensitive physical instrument components. The joints of important contact points in various relays are made of silver, and important components in radio systems also use silver as solder when welding (Figure 8). There are a large number of contact points in various automation devices, rockets, submarines, computers, nuclear devices, and communication systems. During use, each contact point will work (connect and disconnect) millions of times. In order to meet such strict working requirements, the contact points must have good conductivity, wear resistance, reliable performance, and must also meet many special technical requirements. These contact points are generally made of silver because silver can fully meet various requirements. If rare earth elements are added to silver, the performance may be even better. The life of the contact points made of this rare earth element silver can be extended several times.

Figure 8 Silver-based contact material (picture from the Internet)

4. Silver’s thermal conductivity

4.1 Importance of Heat Conduction

The phenomenon of heat transfer from one part of a system to another or from one system to another is called heat transfer. Heat conduction is one of the three heat transfer modes: heat conduction, convection, and radiation. It is the main way of heat transfer in solids.

As long as there is a temperature difference, there is heat conduction. Heat transfer is the process of heat transfer caused by temperature difference. Heat transfer phenomenon is commonplace in our daily life. Human beings' understanding of heat conduction is much earlier than that of electrical conduction. As early as the beginning of human civilization, people learned to burn fire for heating, which is the application of heat conduction. With the advent of the Industrial Revolution, thermal power machinery such as steam engines and internal combustion engines appeared one after another, and the application of heat transfer has developed rapidly, widely appearing in industrial and agricultural production and people's daily life. In today's world, the competition between countries is economic competition. And with the rapid development of the economy, it has also brought about major international issues such as resources, population and environment. The study of heat transfer plays a vital role in promoting economic development and strengthening environmental protection.

Heat conduction has many applications in the industrial field, such as heating and vulcanization of rubber products, heat treatment of steel forgings, etc. The laws of heat conduction are also needed in the design and calculation of kilns, heat transfer equipment and thermal insulation, and the design of high-temperature and high-pressure equipment (such as waste heat boilers in ammonia synthesis towers).

4.2 Thermal conductivity of silver

All objects can transfer heat, but different materials have different thermal conductivity properties. Objects that transfer heat easily are called good thermal conductors, while objects that do not transfer heat easily are called poor thermal conductors. Metals are basically good thermal conductors, and silver has the strongest thermal conductivity.

Figure 9 is a comparison of the thermal conductivity of some common metals. As with Figure 7, the thermal conductivity of silver is used as the benchmark (100%). It can be seen that the conductivity of copper can reach 94% of silver, aluminum can reach nearly 56%, tungsten can only reach about 42%, while the conductivity of iron is only about 20% of silver, and lead is only about 8% of silver.

Figure 9 Thermal conductivity of common metals

4.3 The importance of heat dissipation

"Heat dissipation" is an important part of the manufacturing process of electronic components and electrical appliances, which directly affects the performance and life of electronic components and electrical appliances. This is caused by the resistance of the wires in the circuit, which inevitably generates heat during the working process. At the same time, "heat dissipation level" is also an important factor in considering the technology and design level of electrical appliances.

The harm caused by the heating of electronic components can be serious. Let's take a look at the impact of excessive temperature on electrical circuits. The heat generated by electronic components cannot be dissipated in time, which will generate very high temperatures, thereby causing electron migration, which will damage the chip and circuit. Once damage occurs, the situation will become more and more serious, and finally cause the entire circuit to short-circuit, and even cause the entire machine and equipment to burn, explode, etc. (Figure 10), posing a great hazard to the safety of people and buildings.

Figure 10 Laptop spontaneously ignites (Picture from the Internet)

Heat dissipation of electronic and electrical equipment is a very important topic. There are many ways to dissipate heat, such as fan cooling, heat pipe cooling, water cooling, and heat dissipation through the equipment itself. However, for many small and thin devices, due to the limitation of volume and space, it is difficult to set up fans, heat pipes, water cooling and other cooling methods, and they can only rely on their own heat dissipation. At this time, the thermal conductivity of the material becomes extremely important.

Of course, humans now know of other materials that have better thermal conductivity than silver, such as diamond. But considering toughness, processing performance, thermal conductivity, etc., silver is the best choice. It is reported that developers are trying to use silver, the metal material with the highest thermal conductivity, as the cooling system of mobile phones. This news caused a sensation. If silver can be used in the cooling system of mobile phones, the cooling capacity of mobile phones will be greatly improved, and the effect is exciting.

5. Conclusion

Finally, a seven-character poem is used as a summary of "silver".

It’s crazy to be the second place. It’s not called a gold shop but a bank.

Although poison testing is controversial, sterilization is indeed a sure thing.

It is the leader in electrical and thermal conductivity, and it is also used as a currency and an ornament with a long history.

The marriages among the stars are all beautiful, and the elderly with white hair are admired.

About the author: Jia Chengchang, professor and doctoral supervisor at University of Science and Technology Beijing. Graduated from the Department of Metal Materials of Beijing Iron and Steel Institute in 1982 with a bachelor's degree. Obtained a master's degree from Tohoku University, Japan in 1987. Obtained a doctorate from Tohoku University, Japan in 1990. Postdoctoral fellow and chief engineer at Kanagawa Science City, Japan from 1990 to 1994. Won more than 30 national invention patents. Published more than 200 papers in domestic and foreign academic journals, including 76 SCI-indexed papers and 127 EI-indexed papers, and a single article has been cited more than 100 times. Edited 15 academic monographs: "Composites Tutorial", "Introduction to Ceramic Matrix Composites", "Sintered Metal Oil-bearing Bearings", "Introduction to Metal Matrix Composites", "Superhard Materials and Tools", "Metal Powder Gel Injection Molding", "Sintering Practice and Scientific Foundation", "Professor Han Fenglin's Papers", etc. He has won the second prize of Science and Technology Progress of the Ministry of Education, the first prize of Excellent Textbooks of China Metallurgical Education Association, the first prize of National Teaching Achievement in Higher Education (participated), the first prize of Education and Teaching Achievement of Beijing, the second prize of Excellent Journal of China Nonferrous Metals Society, the Outstanding Worker of China Metal Society, the Outstanding Instructor of the "Challenge Cup" National College Student Science and Technology Competition, the Outstanding Editorial Board Member of "Journal of Composite Materials" of the Composite Materials Society, "I Love My Teacher - the Best Teacher in My Mind" of Beijing University of Science and Technology, Advanced Individual in Teacher Ethics, Outstanding Party Member, Advanced Worker, First Prize for Teaching Achievement, SCI Inclusion Award for Scientific Papers and other honors. Main social part-time jobs: Honorary Director of China Composite Materials Society, Honorary Director of Powder Metallurgy Branch of China Metal Society, Executive Director of Powder Metallurgy Branch of China Mechanical Engineering Society, Director of Powder Metallurgy and Ceramics Branch of China Nonferrous Metals Society, Honorary Director of Powder Metallurgy Branch of China Steel Structure Association, Distinguished Expert of China Nonferrous Processing Association, Director of Powder Branch of China Building Materials Industry Association, Distinguished Expert of Powder Metallurgy Branch of China Machinery Association, Editorial Board Member of Journal of Composite Materials, Consultant of Powder Metallurgy Technology, Editorial Board Member of Powder Metallurgy Industry, Editorial Board Member of China Molybdenum Industry, Editorial Board Member of Powder Metallurgy Materials Science and Engineering, Editorial Board Member of China Materials Science and Equipment, Guest Contributor of Metal World