Traditional materials used by humans to make useful objects
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The so-called traditional materials refer to the materials traditionally used by human beings to make useful objects;Materials are the material basis for human survival and development, and an important pillar of human civilization.
New materials refer to a class of materials that have more excellent properties than traditional materials and are recently developed or under development.
Every major breakthrough in material science and technology will lead torevolutionAnd greatly accelerate the process of social development.
Historical stages: Stone AgePotteryTimesBronze Age, Iron Age, Silicon Age.
That is, ductility and malleability. Ductility is the property that can be extended, for example, iron can be made into iron wire;Expandability is the property that can be unfolded. Aluminum can be made into very thin aluminum foil.Generally speaking, the material ductility with good ductility is also good, so it can be collectively called ductility.
stability
It belongs to chemical properties, such as whether it is easy to decompose when exposed to light or heated, and whether it is easy to interact withoxygenReaction, etc.
Plasticity
It means that when the material istemperatureUnder pressure and pressure, deformation may occur under the action of external force, and the state under force can still be maintained after the external force is removed.
Traditional material classification
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Metallic materials
It includes pure metals and alloys, which are mixtures.
The alloy is composed of two or more metals. Generally, it has the advantages of various metal components in function, and even some new functions will appear.
steel
Iron making: iron ore, limestone and coke are mixed and heated in air to obtain pig iron.
Steelmaking: pig iron is heated in oxygen enriched air to obtain steel after reducing carbon content.
Comparison between pig iron and steel: pig iron is generally hard and brittle, suitable for casting in industry, not suitable for forging.Steel generally has a certain toughness, which is suitable for both casting and forging, so the use of steel is more extensive.
Rust of steel: in fact, it is a process of slow oxidation of iron in the presence of water.
Due to loose rust, good air permeability and water absorption, once the steel products are rusted, if not handled in time, the rusty process will not stop automatically, but will be faster and faster.
About metal pollution: First, the pollution caused by waste gas and slag when smelting metal;The second is the environmental pollution caused by waste metals.
copper
Physical properties of copper: pure copper is purplish red, with a melting point of 1083.4 ℃, a boiling point of 2567 ℃, a density of 8.92g/cm3, and good ductility.1g pure copper can be drawn into 3000m fine copper wire or rolled into nearly transparent copper foil with an area of 10m2.
Pure copper is second only to silver in conductivity, but much cheaper than silver, so more than half of the world's copper is used in power and telecommunications industries today.
Copper is easy to form on its surface in humid airBasic copper carbonate(copper green).Copper is often used in the manufacture of copper wires, electrodes and electroplating industries.
aluminum
Physical properties of aluminum:
Pure aluminum is a metal with silver white luster and good ductility. It can be made into aluminum foil to pack cigarettes and candy.
The conductivity of aluminum is only inferior to silver and copper (the conductivity is 64% of copper, the density is less than 2.70g/cm3, which is 30% of copper), so aluminum is widely used to replace copper as cable.
Aluminum has good thermal conductivity and is widely used in cooking utensils and solar energy absorption devices.
Aluminum is the third widely used metal after copper and iron.
The chemical properties of aluminum are very active. A dense oxide film is quickly formed in the air to prevent further oxidation. This oxide film is insoluble in water, so that aluminum does not interact with water.
When heated in oxygen, aluminum burns violently, emitting dazzling white light and a large amount of heat.
Aluminum has a strong ability to combine with oxygen. It is an oxyphilic element. It can take oxygen from many metal oxides, and generate a lot of heat. The high temperature can melt the free metal.From this, metals can be produced, often called thermit process. In metallurgical industry, the thermit process is used to prepare chromium, manganese, vanadium, etc.For example:
Cr2O3 + 2Al = Al2O3 + 2Cr
Aluminum is an amphoteric metal, which can react with dilute acid (hydrochloric acid or sulfuric acid) and strong alkali solution to generate salt and release hydrogen.
Put aluminum in cold nitric acid, it will be "passivated" instead of reacting with dilute acid.
The main use of aluminum is to manufacture various light alloys. With the advantages of light weight and high hardness, aluminum alloys are widely used in aviation, automobile industry and national defense industry. At the same time, they are also increasingly used in daily life, such as manufacturing doors and windows, furniture and drinking utensils.Pure aluminum is also widely used for making wires and cables, and also for making special paints, ointments, cosmetics hoses, containers and packaging foils.Organic aluminum compounds, such asTriethyl aluminumIt is a stereospecific polymerization catalyst.
Use of aluminum
(1) The density of aluminum is very small, only 2.7g/cm3. Although it is relatively soft, it can be made into various aluminum alloys, such as hard aluminum, super hard aluminum, rust proof aluminum, cast aluminum, etc.These aluminum alloys are widely used in aircraft, automobile, train, ship and other manufacturing industries.In addition, space rockets, space shuttles and artificial satellites also use a large amount of aluminum and its alloys. For example, a supersonic aircraft is composed of about 70% aluminum and its alloys.Aluminum is also widely used in ship building. A large passenger ship often uses thousands of tons of aluminum.
(2) The conductivity of aluminum is only second to silver and copper. Although its conductivity is only 2/3 of copper, its density is only 1/3 of copper, so the quality of aluminum wire is only half of that of copper wire when delivering the same amount of electricity.The oxide film on the aluminum surface not only has corrosion resistance, but also has a certain degree of insulation, so aluminum has a wide range of applications in the electrical manufacturing industry, wire and cable industry and radio industry.
(3) Aluminum is a good conductor of heat. Its thermal conductivity is three times greater than that of iron. In industry, aluminum can be used to make various heat exchangers, heat dissipating materials and cookware.
(4) Due to the dense oxide protective film on the surface of aluminum, it is not easy to be corroded, and is often used to manufacture chemical reactors, medical devices, refrigeration devices, oil and natural gas pipelines, etc.
(5) Aluminum powder has silver white luster (generally, the color of metal in powder form is black). It is often used as paint, commonly known as silver powder and silver paint, to protect iron products from corrosion and beautiful.
(6) Aluminum burning in oxygen can give off a lot of heat and dazzling light, and is often used to make explosive mixtures, such as ammonium aluminum explosives (mixed with ammonium nitrate, charcoal powder, aluminum powder, soot and other combustible organic substances), combustion mixtures (such as thermite bombs and shells can be used to attack targets that are difficult to fire or tanks, artillery, etc.)And lighting mixture (such as barium nitrate 68%, aluminum powder 28%, shellac 4%).
(7) Thermit is often used to melt refractory metals and weld rails.Aluminum is also used as deoxidizer in steelmaking.Aluminum powder and graphitetitania(or the oxides of other high melting point metals) are uniformly mixed at a certain ratio, coated on the metal, and calcined at high temperature to make high-temperature resistantcermetIt has important applications in rocket and missile technology.
(9) The aluminum plate also has good reflective performance to light. The purer the aluminum is, the better its reflective ability is. Therefore, it is often used to manufacture high-quality reflectors, such as solar cooker reflectors
(10) Aluminum has sound absorption performance and sound effect is also good, so the ceiling of broadcasting room and modern large buildings are also commonly used aluminum.
Biological function of aluminum:
Aluminium is not only one of the essential trace elements for human body, but also can be used as medicine to treat diseases. For example, Al (OH) 3 has been used to treat stomach diseases and duodenal ulcers for many years. "Weishuping "and other drugs also contain aluminum.The trace aluminum in the human body can block the absorption of phosphorus in the intestinal tract, reduce blood phosphorus, and prevent the increase of blood phosphorus, soft tissue calcification and the formation of kidney stones caused by secondary hyperparathyroidism. However, excessive aluminum intake can also cause harm to the body.Due to the wide application of aluminum products and aluminum compounds, the aluminum content in modern people's bodies has increased twice as much as that of ancient people.When aluminum products contain salty, acidic or alkaline food, their surface protective film will be damaged, and aluminum oxide will be dissolved into colloidal solution. When this aluminum oxide is fused in the food, it will increase the aluminum intake of the human body, which is bound to affect health over time.
When the aluminum accumulated in human body exceeds the normal value by more than 5 times, it can destroy the activity of some enzymes, reduce gastric acid, and causeDigestive dysfunction。
Aluminum can also inhibit the absorption of phosphorus in the digestive tract, interfere with phosphorus metabolism, destroy the normal proportion of calcium and phosphorus, affect the development of bones and teeth, and make bones demineralized, softened and loose.
In the brain of normal people, the content of aluminum is only 2 mg~3 mg.Due to the excessive intake of aluminum, it will also accumulate in the brain over time, especially in the cerebral cortex and the hippocampus of the brain that moves at will, resulting in memory loss, emotional indifference, slow reaction, irritabilityMental malaiseThe aging of human brain tissue is accelerated, which is called Alzheimer's disease.
In addition, taking too much aluminum for a long time will increase skin wrinkles, make hair fall off easily and reduce vision.
Another biggest disadvantage of using aluminum cookware is that it cuts off an important channel for people to ingest iron, making the number of people suffering from iron deficiency anemia increasing, especially women and children.
In order to reduce the excessive intake of aluminum in aluminum cookware, the following points should be paid attention to when using aluminum cookware: 1. Avoid friction with other hard appliances to prevent the oxide film on the aluminum surface from being damaged;2. For aluminum products, seasonings and beverages such as salt, sauce, vinegar, wine, tea, fruit juice, fermentation powder, milk should not be put for a long time to prevent aluminum from dissolving into food;3. The cooking time of food in aluminum pan should not be too long, and should be controlled within 4h. Do not fry food in aluminum pan;4. Due to the strong corrosiveness of fluorine to aluminum, the use of aluminum cookware should be minimized in water with high fluorine content.
In acid rain areas, acid rain seeps into the ground, causing groundwater acidification. The content of aluminum, copper, zinc and cadmium in acidified water is dozens of times higher than that in neutral groundwater.
aluminium alloy
An alloy based on aluminum and composed of other elements.Pure aluminum has good conductivity, heat conduction and corrosion resistance, and is mainly used for conductingThermal conductive material, but the strength is low, so it is not suitable for structural materials.Aluminium can be alloyed with many chemical elements to improve its properties.Aluminum alloy has a light specific gravity, a specific strength close to that of alloy steel, a specific stiffness higher than that of steel, good plasticity, good casting and machinability, and is suitable for manufacturing structural parts with light weight. Therefore, it has become an indispensable material in the aviation industry. It is also widely used in transportation, construction, light industry, chemical industry, instrumentation and machinery and other sectors, as well as in household appliances.Aluminum and some aluminum alloys are treated by anodic oxidation and other methods, and various colors are generated through coloring process, which are widely used for packagingDecorative materialsuse.
The main application fields of aluminum alloy: fighter aircraft, ships, missiles, rockets, artificial satellites, combat vehicles, high-speed trains, automobiles, high-rise buildings, etc.
Non metallic materials
cement
Cement is the most commonly used building material, which is also called Portland, and ordinary cement is also called Portland cement.It is made of limestone and clay, heated to the extent that it can be sintered, and then crushed and ground. In the old days, it was also called cement, which was transliterated from English.
Main properties of cement: cement can harden in air or water.
Cement production
Reaction conditions: high temperature
Main equipment: cement rotary kiln
Main raw materials: clay, limestone, gypsum (auxiliary materials)
Ceramic is an ancient product, which is formed, dried and baked from clay or a mixture of clay and quartz and feldspar.Ceramic is a general term. Unlike porcelain, pottery is a coarser ceramic product, while porcelain is a finer, opaque or translucent ceramic product.The metal surface is covered with a layer of ceramic material, which is called ceramic coating.
Enamel: the surface of steel and other products is treated with ceramic materials to form a corrosion resistant coating, which is called enamel.High temperature resistance, but easy to crack.
Ceramic properties: oxidation resistance, acid and alkali corrosion resistance, high temperature resistance, insulation, easy molding
ceramic material
1. Traditional ceramics
Raw materials: natural minerals (rock, sand, clay...)
Preparation: firing
For example, cement, glass, brick and tile, refractory
With the development of rocket, artificial satellite, atomic energy and other advanced technologiesHigh temperature resistant materialNew requirements are put forward. People hope that materials can not only maintain high strength and hardness at high temperature, can withstand intense mechanical vibration and temperature changes, but also have oxygen corrosion resistance and high insulation properties. However, neither high melting point metals nor ceramics can meet these requirements at the same time.
Cermet is a heterogeneous composite material composed of ceramic and bonded metal.Ceramics are mainly high temperature resistant oxides such as alumina and zirconia or their solid solutions, and bonding metals are mainly high melting point metals such as chromium, molybdenum, tungsten and titanium.The cermet can be made by grinding and mixing the ceramic and bonding metal evenly, and sintering in an inactive atmosphere after forming.
Cermet has the advantages of both metal and ceramic. It has small density, high hardness, wear resistance, good thermal conductivity, and will not be brittle due to sudden cooling or heating.In addition, coating a layer of ceramic coating with good air tightness, high melting point and poor heat transfer performance on the metal surface can also prevent oxidation or corrosion of metal or alloy at high temperature.
Cermets are widely used in rockets, missilesSupersonic aircraftAnd the flame nozzle of the combustion chamber.
Plastic originally refers to materials that can be molded, or have plasticity. It should include materials such as clay and gypsum.Now, the concept of "plastic" has specifically referred toPolymer synthetic materialsThere is no strict boundary between plastic, fiber and rubber, for example, before the fiber is stretched directionally, or rubber is plastic at low temperature.
Polyethylene, polypropylene, polyvinyl chloride and polybutylene, whose raw materials all come from oil or natural gas, are the most productive varieties in plastics.Polyethylene is its representative. For example, food packaging bags and oil drums are our most familiar applications.However, its main disadvantages are that it is not heated and easy to age in the air.
The main disadvantage of PVC is its poor heat resistance, deformation when temperature exceeds 60 ℃, and certain toxicity.But non-toxicPVC resin。
rubber
Natural rubberIt can be obtained from nearly 500 different plants, but mainly from the tropical plant rubber tree, with an annual output of 3 million tons.Natural rubber is superior to allsynthetic rubber。
