He aluminum oxide (To the 2 OR 3 of chemical formula), also called alumina, aluminum oxide, corundum or aluminum trioxide, is a metal oxide that is produced from the reaction between a metal and oxygen (O). It is also known as basic oxide, for the ease of forming hydroxides when they react with water.
This is because the aluminum that is in the IIIA family of the periodic table has tendency to yield the electrons of the last energy level. This trend is due to its metallic character and its low electronegativity (1.61 on the Pauling scale), which give it electropositive properties and make it a cation.
In contrast, oxygen is a non-metal and is more electronegative due to its high electronegativity (3.44 on the Pauling scale). Therefore, it tends to stabilize the electronic energy of its last level by accepting electrons, which makes it an anion.
The bonds formed are strong bonds, which gives the aluminum oxide great strength. In nature, aluminum is not found in native form such as gold, silver, copper, sulfur and carbon (diamond).
This means that aluminum is not combined with any other element; This metal is mixed with oxygen, forming compounds such as corundum or emery, which are highly resistant and abrasive compounds.
Index
- 1 Formula and chemical structure
- 2 Physical properties
- 3 Chemical properties
- 4 Applications
- 5 References
Formula and chemical structure
Molecular formula: Al 2 OR 3
Structural formula:
Physical properties
- It is commercially available as a white powder, odorless and non-toxic.
- As a mineral compound corresponds to the group of hematite. It is a very hard material that has high resistance to wear, so it is used as an abrasive material.
- It conducts electricity easily and is also a good thermal conductor.
- It is resistant to reactions with acids and bases at high temperatures.
- It can appear in different colors: red or ruby (where aluminum ions have been replaced by Cr 3+ ), yellow, pink, sapphire blue, purple, green, gray and even colorless.
- Its brightness is vitreous or adamantine (diamond)
- It has a very delicate white stripe due to its hardness.
- Its hardness in the scale of Mohs is 9. This means that it can scratch other minerals of lower hardness than it; however, it can not scratch the diamond that has a hardness of 10 on the same scale.
- Its density is 3.96 g / cm 3
- Its molecular weight (molar mass) is 101.96 g / mol.
- Its melting point is 2040 ° C.
- Its boiling point is 2977 ° C.
- It is insoluble in water.
Chemical properties
Aluminum oxide does not react with water unless it is in the presence of a strong base.
However, when it reacts with acids it behaves as if it were a base:
It also shows acidic properties when reacted with bases:
Although water is not formed in this reaction, it is considered acid-base because Al 2 OR 3 neutralizes NaOH. Therefore, the Al 2 OR 3 It is classified as an amphoteric oxide because it has both acidic and basic properties.
In the formation of alkenes and cycloalkenes, one of the most used forms in the industrial and laboratory is through the dehydration of alcohols.
For this, alcohol vapor is circulated on a hot catalyst of alumina or aluminum oxide (Al 2 OR 3 ); in this case it is considered a Lewis acid.
Applications
- Alumina is used in the industry to obtain aluminum.
- It is used as a ceramic material due to its high resistance to corrosion at high temperatures and wear.
- It is used as thermal insulation, especially in electrolytic cells.
- It has the capacity to absorb water, which makes it suitable for use as a drying agent.
- It is used as a catalytic agent in chemical reactions
- Due to its high thermal stability, it is used as an oxidant in chemical reactions that are carried out at high temperatures.
- Prevents the oxidation of cathode and anodic terminals in an electrolytic cell.
- Because of its great hardness and resistance, it is used in dentistry for the preparation of dental pieces.
- It is a good electrical insulator in the spark plugs of vehicles that work with gasoline.
- It is widely used in ball mills for the preparation of ceramics and enamels.
- Due to its light weight, in engineering processes it is used to make airplanes.
- Because of its high boiling point, it is used to make kitchen implements such as frying pans and refractory pans.
- It is used in the instrumentation of thermal testing machines.
- In the electronics industry, it is used in the manufacture of passive components for electrical interconnection and in the manufacture of resistors and capacitors.
- Used in the manufacture of fillers for welding.
- Aluminum oxide is used for the coating of titanium oxide (pigment used for paints and plastic papers). This prevents reactions between the environment and this type of pigments, which does not decompose or rust.
- It is used as an abrasive in toothpastes.
- It is used in hemodialysis.
- As an additive in the food industry, since it is used as a dispersing agent.
- It is an antiperspirant agent of deodorants.
- Aluminum oxide has been used as orthopedic material. Because it is an inert and porous material, it makes it suitable for use in this type of implants. These implants allow fibrovascular growth, which is why fibroblasts and osteoblasts proliferate rapidly in this material.
- The bioceramic implant is made with alumina. It is lightweight and has a uniform pore structure very well interconnected with each other. The microcrystalline structure is smoother than the rough surface. It presents less flammability after a postoperative period compared to other materials used for implants.
- Aluminum oxide flakes produce reflective effects inside paints used for automobiles.
- In some refineries, aluminum oxide is used to convert the toxic gases of hydrogen sulfide into elemental sulfur.
- The form of alumina called activated alumina has great benefits in the treatment of wastewater such as aquifers due to its ability to adsorb many pollutants harmful to the environment, as well as to filter waste material that is dissolved in water and that is larger than the pore of the alumina sheets.
References
- Chang, R; Chemistry , 1992, (fourth edition), Mexico. McGraw-Hill Interamericana de México.
- Pine.S; Hendrickson, J; Cram, D; Hammond, G (1980), Organic Chemistry , (fourth edition), Mexico, McGraw-Hill de México
- Kinjanjui, L., (s.f) Properties & Uses of Aluminum Oxide, It Still Work, Recovered, itstillworks.com
- Panjian L., Chikara, O., Tadashi, K., Kazuki, N., Naohiro, S.,"and"Klaas de G., (1994). The role of hydrated silica, titania, and alumina in inducing apatite on implants. Journal of Biomedicals materials Research. Volume 18, pp. 7-15. DOI: 10.1002 / jbm.820280103.
- Complete Information Guide to Rocks, Minerals, & Gemstones., Mineral.net., Recovered, minerals.net
- LaNore, S. (2017), Physical Characteristics of Aluminum Oxide, Sciencing, Recovered, sciencing.com