ALUMINUM

aluminyum-periyodik-sistem

aluminum-periodic-system

Aluminum, chemical element with atomic number 13 and symbol Al. It is a ductile silver metal. It is generally found in the form of bauxite ore in nature and is known for its superior resistance to oxidation. Passivation feature underlies this resistance. It is used in the production of millions of different products in many branches of the industry and has a very important place in the world economy. Structural components made of aluminum are indispensable for the aerospace and aviation industry. It finds wide use in the transportation and construction industry, which requires lightness and high strength properties.

 

ALUMINUM PROPERTIES

Aluminum is a soft and light metal with a matt silvery color. This color is due to the thin oxide layer that forms when exposed to air. Aluminum is non-toxic and non-magnetic. It does not spark. While the tensile strength of pure aluminum is about 49 megapascals (MPa), this value increases to 700 MPa when alloyed. Its density is about one-third that of steel or copper. It can be forged, machined and cast easily. It has very superior corrosion properties, it is because the oxide layer formed on it is protective. The electrical conductivity is 64.94% IACS (pure Al at 2 ° C). Its melting temperature is 660 ° C and its boiling temperature is 2519 ° C.

 

ALUMINUM HISTORY

The ancient Greeks and Romans used the salts of aluminum (æljʊˈmɪniəm) to fix the colors of the dyes and as a blood-stopper. Alum is still used as an astringent and vascular constrictor in today’s medicine.

aluminum-history-art

aluminum-history-art

Although Friedrich Wöhler is known to be the first person to decompose aluminum in 1827 by mixing anhydrous aluminum chloride with potassium, the metal was produced in an impure form by Hans Christian Øersted, a Danish physicist and chemist, about two years before that date. Therefore, in the almanacs and chemical literature, Øersted’s name is referred to as the inventor of aluminum. French Henri Saint-Claire Deville developed Wöhler’s method in 1846, using sodium instead of the more expensive potassium.

American Charles Martin Hall filed a patent application (patent no: 400655) on the production of aluminum by an electrolytic process in 1886, the same year, French Paul Héroult, completely unaware of Hall’s invention, also developed the same technique in Europe. For this reason, the Hall-Heroult process, named by two scientists, is the basic method used all over the world today to extract aluminum from ore.

Aluminum was decided to be used in the construction of the Washington Monument summit in the USA, and at that time the cost of approximately 30 grams of aluminum was equivalent to twice the wage of a worker working on this project.

In the years immediately after Adolf Hitler came to power, Germany became the world leader in aluminum production. But in 1942, the commissioning of new hydroelectric power plant projects in the US (for example, the Grand Coulee Dam) gave the US an edge that Nazi Germany could not handle. This superiority has emerged in the form of aluminum production sufficient to make 60,000 warplanes in four years.

 

Finding Aluminum in Nature

Although it is abundant in the earth’s crust (7.5-8.1%), it is very rare in free form and therefore once considered even more precious than gold. The history of commercial production of aluminum is just over 100 years.

Aluminum was a very difficult metal to separate from its ore in the first years of its discovery. Aluminum is one of the most difficult metals to refine. The reason for this is that it oxidizes very quickly, this oxide layer is very stable and unlike rust in iron, it does not peel off from the surface.

aluminyum-doğada-bulunuşu

aluminum-occurrence-in-nature

Recovery of aluminum from scraps has become an important component of today’s aluminum industry. The recovery process is based on the simple remelting of the metal, which is much more economical than producing the metal from its ore. Aluminum refining requires very high amounts of electrical energy, whereas the recovery process consumes 5% of the energy used in its production. The recovery process has been implemented since the early 1900s and it is not new. The phenomenon of recycling, which continued as a low profile activity until the end of the 1960s, came to the fore more intensely with the start of making beverage cans from aluminum at that time. Other sources of recycled aluminum include auto parts, windows and doors, appliances, and containers.

Aluminum is a reactive metal and its recovery from its ore (aluminum oxide, Al2O3) is very difficult. Production takes place with 2 methods. The first is the Bayer method and the other is direct reduction with carbon. Since the melting temperature of aluminum oxide is around 2000 ° C, it is far from being economical. Therefore, aluminum is obtained by electrolysis method. In this method, aluminum oxide is dissolved in molten cryolite and then reduced to pure metal. In this method, the operating temperature of the reduction cells is around 950-980 ° C. Cryolite is a natural mineral found on the island of Greenland but is made synthetically for aluminum production. Cryolite is a mixture of fluorides of aluminum and sodium and its formula is Na3AlF6. Aluminum oxide (white powder) is produced by refining bauxite, which is red in color since it contains about 30-40% iron. The name of this process is the Bayer process and it replaces the Deville process that was previously used.

In the electrolysis method, which replaced the Wöhler process, both electrodes are made of carbon. Once the ore has melted, the ions begin to circulate freely. Reaction taking place at the negative electrode (cathode):

Al3 + + 3e- → Al

This indicates that the aluminum ion is reduced by acquiring electrons. Aluminum metal then collapses to the bottom of the cell in liquid form and is siphoned out from here.

On the other hand, oxygen gas is formed at the positive electrode (anode):

2O2- → O2 + 4e-

The anode carbon is oxidized and depleted by this oxygen and therefore needs to be renewed at regular intervals:

O2 + C → CO2

Cathodes are not depleted during the electrolysis process, unlike anodes, because there is no oxygen output at the cathode. The carbon of the cathode must be protected as it is covered with liquid aluminum inside the cell. On the other hand, cathodes are subject to erosion due to electrochemical processes. Depending on the current applied in electrolysis, the cells must be completely renewed every 5-10 years.

Although aluminum electrolysis with the Hall-Héroult process consumes a lot of electrical energy, alternative methods are far from being economically and ecologically viable. Worldwide, the average specific energy consumption is about 15 ± 0.5 kilowatt-hours per kg Al (52-56 MJ / kg). In modern plants, this figure is around 12.8 kW h / kg (46.1 MJ / kg). While the electric current carried by the reduction line is 100-200 kA in old technologies, this value has increased up to 350 kA in modern facilities and it is known that trial studies have been carried out in 500 kA cells.

Electrical energy accounts for 20-40% of the aluminum production cost, depending on the location of the facility. Therefore, aluminum producing businesses tend to be close to areas where electricity is abundant and cheap, such as South Africa, the South Island of New Zealand, Australia, China, the Middle East, Russia, Iceland, and Québec in Canada.

As of 2004, China is the world leader in aluminum production.

Aluminum Safety Precautions

It has not been observed that aluminum has a beneficial function on living cells. In some people, contact dermatitis (skin inflammation), which can be caused by any form of aluminum, styptic (blood-stopper) or itchy rash associated with the use of antiperspirant products, digestive disorders caused by eating dishes cooked in aluminum pots, and stopping the absorption of nutrients, and Rolaids, Amphojel, and allergic reactions in the form of intoxication symptoms such as vomiting caused by the use of antacid drugs such as Maalox. In other people, although aluminum is not as toxic as heavy metals, and the use of kitchen utensils made of aluminum (preferred because of its high corrosion resistance and good thermal conductivity) is generally not proven to cause aluminum poisoning, it can show signs of poisoning when taken in high doses. Overdose of antacids containing aluminum compounds and excessive use of aluminum-containing antiperspirants can cause poisoning. Although aluminum has been claimed to cause Alzheimer’s disease, that research, on the contrary, has been disproved that the damage caused by Alzheimer’s disease causes aluminum accumulation in the body. In summary, if there is aluminum poisoning, it must occur by a very specific mechanism. Because the contact of the natural clay mineral in the soil with the aluminum in the soil is already sufficiently high throughout human life.

Aluminum should avoid contact with certain chemicals that cause it to corrode rapidly. For example, a tiny amount of mercury dripped onto the surface of a piece of aluminum easily pierces the protective aluminum oxide layer, and even massive structural beams can be significantly weakened within a few hours. For this reason, many airlines do not allow mercury thermometers, as aluminum occupies an important place in the structural framework of aircraft.

Truths

Discovery Date: 1825
Discovered By: Hans Christian Oersted
Name Origin: From the Latin word alumen
Uses: airplanes, soda cans
Obtained: bauxite

Aluminum Chemistry

Oxidation stage

  • AlH is produced when aluminum is heated to 1500 ° C under a hydrogen atmosphere.
  • Al2O is produced when the normal oxide of aluminum (Al2O3) is heated with silicon at 1800 ° C under vacuum.
  • Al2S is produced by heating Al2S3 with aluminum chips at 1300 ° C under vacuum. However, it quickly decomposes into starting materials. Divalent selenium is made similarly.
  • Trivalent halides can be obtained in the gas phase -AlF- -AlCl- and -AlBr- when heated with aluminum.

Basic Knowledge

Name: Aluminum
Symbol: Take
Atomic Number: 13
Atomic Mass: 26.981539 amu
Melting Point: 660.37 ° C (933.52 K, 1220.666 ° F)
Boiling Point: 2467.0 ° C (2740.15 K, 4472.6 ° F)
Number of Protons / Electrons: 13
Number of Neutrons: 14
Classification: Other Metals
Crystal Structure: Cubic
Density @ 293 K: 2.702 g / cm 3
Color: Silver
British Spelling: Aluminum
IUPAC Spelling: Aluminum

Atomic structure

  Number of Energy Levels: 3
First Energy Level: 2
Second Energy Level: 8
Third Energy Level: 3

 

Isotopes

Isotope Half life
Al-26 730000.0 yıl
Al-27 Determined
Al-28 2.3 minute

Oxidation stage

  • When aluminum powder burns with oxygen, the presence of aluminum sub-oxide (AlO) can be demonstrated.

Oxidation stage

  • The Fajans rule shows that a simple trivalent cation (Al3 +) cannot be found in anhydrous salts or binary compounds such as Al2O3. Hydroxide is a weak base and aluminum salts that are weak base such as carbonate cannot be prepared. Strong acid salts such as nitrate are stable and soluble in water. They form hydrates with at least six molecules.
    It can be produced using aluminum hydride (AlH3) n, trimethyl-aluminum and excess oxygen. It burns explosively in the air. It can also be produced by treating aluminum chloride with lithium hydride in ether solution. However, it cannot be separated from the solvent.
    It can be produced by heating the mixture of aluminum carbide (Al4C3) elements above 1000 ° C. The light yellow crystals have a complex lattice structure and give off methane gas with water or dilute acid. Acetylide (Al2 (C2) 3) is produced by passing acetylene over heated aluminum.
    Aluminum nitride (AlN) can be produced from its elements at 800 ° C. It gives ammonia and aluminum hydroxide by hydrolysis with water.
    Aluminum phosphite (AlP) is made similarly and hydrolyzes by giving phosphine.
    Aluminum oxide (Al2O3) is found in nature as corundum and is obtained by burning aluminum with oxygen or heating its hydroxide, nitrate or sulphate. As a precious stone, its hardness comes after diamond, boron nitride and carborundum. It is almost insoluble in water.
    Aluminum hydroxide can be obtained in the form of a gelatinous precipitate by adding ammonia to an aqueous solution of an aluminum salt. It is amphoteric; It is both a very weak acid and makes aluminates with alkalis. It is found in different crystal forms.
    Aluminum sulfide (Al2S3) can be produced by passing hydrogen sulfide through aluminum powder. It is polymorphic.
    Aluminum fluoride (AlF3) is produced by the treatment of its hydroxide with HF or from its elements. It has a giant molecular structure that passes into the gas phase at 1291 ° C. It is very inert. Other trivalent species are dimeric and bridge-like.
    There are organo-metallic compounds with the empirical formula AlR3 and are at least dimeric or trimeric if not giant molecules. They are used in the field of organic synthesis (eg trimethyl aluminum).
    Alumino-hydrides are the most electro-positive structures known. The most useful of these is lithium aluminum hydride (Li [AlH4]). When heated, it breaks down into lithium hydride, aluminum and hydrogen and hydrolyzes with water. It has many uses in organic chemistry. Alumino-halides also have a similar structure.

Usage areas

Since aluminum is a metal that cools easily and absorbs heat, it finds a wide place in the cooling industry. It is a metal used in many industries because it is cheaper and more available than copper, easy to process and soft.

Aluminum is generally used in the production of coolers, spotlights, kitchen utensils, and the construction of lightweight vehicles (aircraft, bicycles, automobile engines, motorcycles, etc.). In addition, aluminum, which is an important material in the industry, is a metal that we always encounter in daily life.

Another usage area of ​​aluminum is asynchronous motors. Pure aluminum (~ 99.7% Al) is used in the production of rotors of asynchronous motors by the pressure casting method. Compared to copper, its lightness, cheapness and relatively good electrical conductivity (~ 59-60% IACS) make aluminum a large place in the asynchronous motor industry.

Aluminum Name

In English-speaking countries, it is common for the name to be spelled both aluminum and aluminum and to be read in the appropriate style. Aluminum is not well known in the USA and mostly aluminum is used. In other countries outside of the USA, the situation is the opposite and the way of spelling in aluminum is better known. However, both spelling styles are common in Canada.

In countries other than English, the spelling of “ium” is more common. The word is aluminum in both German and French.

The “International Union of Pure and Applied Chemistry” (IUPAC) organization approved the use of aluminum as a world standard in 1990. However, three years later he sanctioned the word aluminum as an acceptable term.

Cited from Mla: <http://www.chemicalelements.com/elements/al.html>.

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