Zinc Oxide - ZnO

With the formula ZnO, it is an inorganic compound. In water, ZnO is a white powder that is insoluble. Zinc Oxide, also known as Calamine or Zinc White, is an inorganic compound. Naturally, it is found as a zincite mineral. It is mostly synthetically generated. It is a slightly astringent and antiseptic chemical compound that acts as a topical protective agent.

It is used as an additive in cosmetics, dietary supplements, plastics, ceramics, glass, cement, lubricants, paints, ointments, adhesives, sealants, pigments, meats, batteries, ferrites, fire retardants, and first-aid tapes, in various materials and products. While it occurs naturally as the mineral zincite, it synthetically produces most zinc oxide.

Structure of Zinc Oxide

O = Zn

Zinc Oxide Properties

Physical Properties of Zinc Oxide

• Zinc oxide color is white

• Zinc Oxide formula - ZnO

• Molecular Weight of Zinc Oxide - 81.406 g/mol

• The density of Zinc Oxide - 5.6 g/cm3

• Boiling Point of Zinc Oxide -1,974 °C

• Melting Point of Zinc Oxide -1,974 °C

• Zinc oxide crystallizes hexagonal wurtzite and cubic zinc blende in two primary forms. The structure of wurtzite is most stable and thus most common under ambient conditions. It is possible to stabilize the zincblende shape by increasing ZnO on substrates with a cubic lattice structure. In both cases, the centers of zinc and oxide are tetrahedral, the most distinctive geometry for Zn (II). ZnO converts around 10 GPa to the rock salt motif at reasonably high pressures. Its elastic softness, which is typical of tetrahedral coordinated binary compounds close to the transition to octahedral structures, can be explained by the many remarkable medical properties of creams containing ZnO.

• ZnO is a moderately soft substance on the Mohs scale, with an approximate hardness of 4.5. Its elastic constants, such as GaN, are lower than those of the related III-V semiconductors. For ceramics, the high heat capacity and heat conductivity, low thermal expansion and high ZnO melting temperature are advantageous. 

• At room temperature, ZnO has a relatively large direct bandgap of ~3,3 eV. Higher breakdown voltages, the ability to withstand massive electric fields, lower electronic noise, and high-temperature and high-power activity are the advantages associated with a large bandgap. Via its alloying with magnesium oxide or cadmium oxide, the ZnO bandgap can further be tuned to ~ 3-4 eV. 

Chemical Properties of Zinc Oxide

Zinc oxide is an amphoteric oxide. It is almost insoluble in water, but in most acids, such as hydrochloric acid, it can dissolve: 

ZnO + 2 HCl ZnCl2 + H2O + H2O 

In order to have soluble zincate, solid zinc oxide can also dissolve in alkalis: 

Na2[Zn(OH)4] ZnO + 2 NaOH + H2O 

To produce the corresponding carboxylates, such as oleate or stearate, ZnO reacts slowly with fatty acids in oils. When combined with a strong aqueous solution of zinc chloride, ZnO forms cement-like products and these are better identified as zinc hydroxy chlorides. This cement has been used in dentistry.

Uses Of Zinc Oxide 

Zinc oxide is also used in:

1. Cigarette Filters

2. Breakfast Cereals

3. Paint pigments

4. Paint coatings

5. Piezoelectricity (delivering alternating current by stretching and releasing zinc oxide nanowires)

6. Laser diodes

7. Light-emitting diodes (LEDs)

8. Spintronics

Applications of Zinc Oxide

Manufacturing Rubber: 

The rubber industry accounts for between 50% and 60% of ZnO consumption. In the vulcanization of rubber, zinc oxide along with stearic acid is used. The ZnO additive also protects rubber against fungi and UV light.

Ceramic Industry:

A significant quantity of zinc oxide is consumed by the ceramic industry, particularly in ceramic glaze and frit compositions. In the manufacture of ceramics, the relatively high thermal power, thermal conductivity and high-temperature stability of ZnO coupled with a comparatively low expansion coefficient are desirable properties.

Therapeutics: 

Zinc oxide is called calamine and is used in calamine lotion as a mixture of around 0.5 percent iron(III) oxide (Fe₂O₃). Historically, two minerals, zincite and hemimorphite, have been called calamine. A ligand, zinc oxide eugenol, which has applications as a restorative and prosthodontic in dentistry, is formed when combined with eugenol.

Food Additives: 

In several food products, including breakfast cereals, zinc oxide is added as a source of zinc, a critical nutrient. (Zinc sulfate is often used for the same purpose.) Even though it is not intended as a nutrient, some prepackaged foods also contain trace amounts of ZnO.

Did You Know?

As a bulking agent and a colorant, zinc oxide is used. It is used as a skin protectant and sunscreen in over-the-counter drug products. By reflecting and scattering UV radiation, zinc oxide acts as a sunscreen. Sunscreens decrease or eliminate the skin from sunburning and premature aging.