| Zinc Oxide | |
|---|---|
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| Other names | Zinc white, calamine Zincum oxydatum |
| Identifiers | |
| CAS number | [1314-13-2] |
| Properties | |
| Molecular formula | ZnO |
| Molar mass | 81. CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 4084 g/mol |
| Appearance | White solid |
| Density | 5. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 606 g/cm³, solid |
| Melting point | 1975 °C (decomposes) |
| Solubility in water | Insoluble |
| Thermochemistry | |
| Std enthalpy of formation ΔfH | −348. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. The standard enthalpy of formation or "standard heat of formation" of a compound is the change of Enthalpy that accompanies the formation of 1 mole of a 0 kJ/mol |
| Standard molar entropy S | 43. In Chemistry, the standard molar entropy is the Entropy content of one mole of substance under standard conditions (not standard temperature and pressure 9 J. K−1. mol−1 |
| Hazards | |
| EU classification | Dangerous for the environment (N) |
| NFPA 704 |  1 |
| R-phrases | R20, R36, R37. Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws regulations and administrative provisions relating to the classification packaging and labelling Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous |
| S-phrases | S60, S61. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. |
| Related compounds | |
| Other anions | Zinc sulfide Zinc selenide Zinc telluride |
| Other cations | Cadmium oxide Mercury oxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Zinc oxide is a chemical compound with the formula ZnO. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Zinc sulfide (or zinc sulphide is a Chemical compound with the formula Zn[[Sulfur S]] Zinc selenide ( Zn[[Selenium Se]] is a light yellow binary solid compound Zinc telluride is the Chemical compound with the formula ZnTe An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Cadmium oxide is an Inorganic compound with the formula CdO CdO is one of the main precursors to other cadmium compounds It crystallizes in a cubic lattice Mercury(II oxide, also called mercuric oxide, has a formula of Hg[[oxygen O]] and a formula weight of 216 In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes It is nearly insoluble in water but soluble in acids and alkalis. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, an alkali (from Arabic: Al-Qaly القلي القالي) is a basic, ionic salt of an Alkali metal It occurs as white hexagonal crystals or a white powder commonly known as zinc white. Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Zinc oxide occurs in nature as the mineral zincite. Zincite is the Mineral form of Zinc oxide ( Zn[[Oxygen O]] In nature its Crystal form is rare with the exception of Franklin New Jersey Crystalline zinc oxide exhibits the piezoelectric effect and is thermochromic, changing from white to yellow when heated. Piezoelectricity is the ability of some materials (notably Crystals and certain Ceramics including bone to generate an Electric potential in response to Thermochromism is the ability of Substance to change Color due to a change in Temperature.
Contents |
Chemical properties
Zinc oxide decomposes into zinc vapor and oxygen only at around 1975 °C, reflecting its considerable stability. Heating with carbon converts the oxide into zinc:
- ZnO + C → Zn + CO
It remains white when exposed to hydrogen sulfide, where it converts to the sulfide:
- ZnO + H2S → ZnS + H2O
Single-crystalline ZnO is almost transparent. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S.
Zinc oxide is an amphoteric oxide as indicated by its reactivity toward both acids and bases:
- in acid: ZnO + 2 HCl → ZnCl2 + H2O
- in base: ZnO + 2 NaOH + H2O → Na2[Zn(OH)4]
Applications
Medical applications
Zinc oxide lozenges are a popular over-the-counter cold remedy, but numerous studies have failed to demonstrate any significant effect. [1] Zinc oxide in a mixture with about 0. 5% iron(III) oxide (Fe2O3) is called calamine and is used in calamine lotion. Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is For the mineral see Calamine (mineral, for other uses of the word see Calamine (disambiguation. There are also two minerals, zincite and hemimorphite, which have been called calamine historically (see: calamine (mineral)). Hemimorphite, is a sorosilicate Mineral which has been mined from days of old from the upper parts of Zinc and Lead Ores chiefly This article is about calamine in mineralogy For calamine used in calamine lotion see Calamine, for other uses of the word see Calamine (disambiguation. When mixed with eugenol, zinc oxide eugenol forms which has restorative and prosthodontic applications in dentistry. Eugenol (C10H12O2 is an allyl chain-substituted Guaiacol. Eugenol is a member of the Phenylpropanoids class of chemical compounds Combining Zinc oxide and Eugenol (contained in Oil of cloves) forms zinc oxide eugenol which can be used as a filling or cement material used in Dentistry A dental restoration or dental filling is a Dental restorative material used artificially to restore the function integrity and morphology of missing tooth Prosthodontics is one of the 9 specialties recognized by the American Dental Association, Royal College of Dentists of Canada, and Royal Australasian College Dentistry' is the "evaluation diagnosis prevention and/or treatment (nonsurgical surgical or related procedures of diseases disorders and/or conditions of the oral cavity
Zinc peroxide, ZnO2 . A peroxide is a compound containing an Oxygen -oxygen single bond. ½ H2O, is a white to yellow powder that is used in antiseptic ointments. Antiseptics (from Greek αντί - anti, '"against" + σηπτικός - septikos, "putrefactive" are antimicrobial
Chemical and Biosensor applications
Zinc oxide (ZnO) has received considerable attention because of its unique optical, semiconducting, piezoelectric, and magnetic properties. ZnO nanostructures exhibit interesting properties including high catalytic efficiency and strong adsorption ability. Recently, the interest has been focused toward the application of ZnO in biosensing because of its high isoelectric point (9. 5), biocompatibility, and fast electron transfer kinetics. Such features advocate the use of this material as a biomimic membrane to immobilize and modify biomolecules [2]
As a food additive
Zinc oxide is added to many breakfast cereals, as a source of zinc; a necessary nutrient. A breakfast cereal (often simply called cereal is a packaged food product made from Cereal intended to be consumed as part of a Breakfast. A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment (Other cereals may contain zinc sulfate, for the same purpose. Zinc sulfate ( Zn[[Sulfate SO4]] is a colorless crystalline water-soluble Chemical compound. ) Some prepackaged foods also include trace amounts.
As a pigment
Zinc white is used as a pigment in paints and is more opaque than lithopone, but less opaque than titanium dioxide. Paint is any Liquid, liquifiable or mastic composition which after application to a substrate in a thin layer is converted to an opaque Solid Lithopone is a white Pigment, a mixture of Barium sulfate and Zinc sulfide. Titanium dioxide, also known as titanium(IV oxide or titania, is the naturally occurring Oxide of Titanium, chemical formula Ti[[oxygen It is also used in coatings for paper. Chinese white is a special grade of zinc white used in artists' pigments. For the drug referred to as "pigment" see Black tar heroin. Because it absorbs both UVA and UVB rays of ultraviolet light, zinc oxide can be used in ointments, creams, and lotions to protect against sunburn and other damage to the skin caused by ultraviolet light (see sunscreen). Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays A lotion is a low- to medium- Viscosity, topical preparation intended for application to unbroken Skin; creams and gels have a higher viscosity A sunburn is a burn to living tissue such as Skin produced by overexposure to Ultraviolet (UV radiation commonly from the Sun 's rays Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Sunscreen (also known as sunblock or suntan lotion) is a Lotion, spray or other Topical product that absorbs or reflects the Sun 's It is the broadest spectrum UVA and UVB absorber that is approved for use as a sunscreen by FDA, and is completely photostable. It is also a main ingredient of mineral make-up mainly because of its vast array of colors.
Rubber manufacture
Zinc oxide and stearic acid are ingredients in the commercial manufacture of rubber goods. Stearic acid (first syllable rhymes with either bear or gear) ( IUPAC Systematic name: octadecanoic acid) is a saturated A mixture of these two compounds allows a quicker and more controllable rubber cure. Zinc oxide can also be used as a filler in some rubber mixtures.
Electronic materials
ZnO is a semiconductor with a direct bandgap energy of 3. 37 eV at room temperature. The most common applications are in laser diodes and light emitting diodes since it has an exciton and biexciton energies of 60 meV and 15 meV, respectively. It is expected that this exciton properties of ZnO will be improved further by epitaxy.
Most ZnO has n-type character, even in the absence of intentional doping. Native defects such as oxygen vacancies or zinc interstitials are often assumed to be the origin of this, but the subject remains controversial[3]. Interstitials are a variety of Crystallographic defects, ie atoms which occupy a site in the Crystal structure at which there is usually not an atom or two or more atoms sharing An alternative explanation has been proposed, based on theoretical calculations, that unintentional substitutional hydrogen impurities are responsible[4].
n-type doped films are often used in thin film technology, where zinc oxide serves as a TCO (transparent conducting oxide). In Semiconductor production doping is the process of intentionally introducing impurities into an extremely pure (also referred to as intrinsic) semiconductor to Thin films are thin material layers ranging from fractions of a Nanometre to several Micrometres in thickness n-type doping is possible by introduction of aluminium, indium, or excess zinc[5]. WikipediaNaming Indium (ˈɪndiəm is a Chemical element with chemical symbol In and Atomic number 49 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 p-type doping is difficult and is currently an active area of research, with arsenic as the leading candidate dopant[6]. A P-type semiconductor (P for Positive) is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 Thin-film solar cells, LCD and flat panel displays are typical applications of this material. A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect. Appropriately doped ZnO may be transparent and conductive, and can therefore be used as a transparent electrode. An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e Indium tin oxide (ITO) is another transparent conducting oxide often used in microelectronics. Uses ITO is mainly used to make transparent conductive coatings for Liquid crystal displays Flat panel displays Plasma displays touch panels
ZnO has also been considered for spintronics applications because of theoretical predictions of room temperature ferromagnetism. Spintronics (a Neologism meaning "spin transport electronics" also known as magnetoelectronics is an Emerging technology which exploits the intrinsic Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it Unsubstantiated reports of ferromagnetism have been made, but presence of dilute magnetic semiconductors remains a large unanswered question in physics. Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it Magnetic semiconductors are materials that exhibit both Ferromagnetism (or a similar response and useful Semiconductor properties
The piezoelectricity in textile fibers coated in ZnO have been shown capable of "self-powering nanosystems" with everyday mechanical stress generated by wind or body movements. A textile is a flexible material comprised of a network of natural or artificial Fibres often referred to as thread or Yarn. [7][8]
ZnO layers are mainly deposited by sputter deposition and chemical vapor deposition (CVD). Sputter deposition is a Physical vapor deposition (PVD method of depositing Thin films by Sputtering, i Chemical vapor deposition (CVD is a Chemical process used to produce high-purity high-performance solid materials The latter method allows the growth of a rough layer, which can diffuse the incoming light by scattering, increasing the efficiency of solar cells. Scattering is a general physical process whereby some forms of Radiation, such as Light, Sound or moving particles for example are forced to deviate from
ZnO has been observed to act as a chemical reagent for Friedel-Craft Acylation Reaction.
Pyroelectric coefficients
- Primary pyroelectric coefficient: -6. Pyroelectricity is the ability of certain materials to generate an Electrical potential when they are heated or cooled 8 µC/m²·K
- Secondary pyroelectric coefficient: -2. 5 µC/m²·K
- Total pyroelectric coefficient: -9. 4 µC/m²·K
Production methods
- See also: Zinc smelting
Zinc oxide is produced by two main processes:
French process
Metallic zinc is melted in a graphite crucible and vaporized above 907 °C. Zinc smelting is the process of converting zinc concentrates (ores Zinc vapor instantaneously reacts with the oxygen in the air to give ZnO, accompanied by a drop in its temperature and bright luminescence. Zinc oxide particles are transported into a cooling duct and collected in a bag house. This indirect method is commonly known as the French process (FP) which was popularised by LeClaire (France) in 1844. A typical FP, zinc oxide normally consists of agglomerated zinc oxide particles with an average size of 0. 1 micrometres to a few micrometres. By weight, most of the world's zinc oxide is manufactured via French process and major applications involve industries related to rubber, varistors, sunscreens, paints, healthcare, and poultry nutrients. Recent developments involve acicular nanostructures (rods, wires, tripods, tetrapods, plates) synthesized using a modified French process known as catalyst-free combust-oxidized mesh (CFCOM) process. Acicular nanostructures usually have micrometre-length nanorods with nanometric diameters (below 100 nm).
The so-called direct method is related to the FP. In this process, zinc ores or roasted sulfide concentrates are mixed with coal. In a reduction furnace, ore is reduced to metallic zinc and the vaporized zinc is allowed to react with oxygen to form zinc oxide.
American process
In this process ore of zinc (zinc ash) is dissolved (as ZnCl2) and precipitated with alkali. Zinc chloride is the name of Chemical compound with the formula Zn[[chlorine Cl]]2 and its hydrates Zinc oxide made from this process is known as "Active Zinc Oxide".
Safety
As a food additive, Zinc oxide is on FDA's Generally recognized as safe, or GRAS, substances[9]. Generally Recognized as Safe ( GRAS) is a United States of America Food and Drug Administration (FDA designation that a chemical or substance added to food
Zinc oxide itself is non-toxic, however it is hazardous to breathe zinc oxide fumes. Fumes of zinc oxide are generated when zinc or zinc alloys are melted and oxidized at high temperature. This occurs while melting brass, because the melting point of brass is close to the boiling point of zinc. Brass is any Alloy of Copper and Zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties [10] Exposure to zinc oxide in the air, which also occurs while welding galvanized (zinc plated) steel, can result in a nervous malady called metal fume fever. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Metal fume fever is illness caused primarily by exposure to certain metal fumes [11] For this reason, typically galvanized steel is not welded, or the zinc is removed first.
See also
References
- ^ Caruso TJ, Prober CG, Gwaltney JM (2007). Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 "Treatment of naturally acquired common colds with zinc: a structured review". Clin. Infect. Dis. 45 (5): 569-74. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17682990.
- ^ Kumar, S. Ashok; Chen, Shen-Ming (2008-01). "Nanostructured Zinc Oxide Particles in Chemically Modified Electrodes for Biosensor Applications". Analytical Letters 41 (2): 141-58. doi:10.1080/00032710701792612. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Look, D. C. ; Hemsky, J. W. ; Sizelove, J. R. (1999). "Residual Native Shallow Donor in ZnO". Physical Review Letters 82 (12): 2552-2555. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Janotti, A. ; Van De Walle, C. G. (2007). "Hydrogen multicentre bonds.". Nat Mater 6 (1): 44-7. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Hirschwald, W. H. (1985). "Zinc oxide: an outstanding example of a binary compound semiconductor". Accounts of Chemical Research 18 (8): 228-234. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Braunstein, G. ; Muraviev, A. ; Saxena, H. ; Dhere, N. ; Richter, V. ; Kalish, R. (2005). "p type doping of zinc oxide by arsenic ion implantation". Applied Physics Letters 87: 192103. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Keim, Brandon. "Piezoelectric Nanowires Turn Fabric Into Power Source", Wired News, CondéNet, February 13, 2008. Events 1258 - Baghdad falls to the Mongols, and the Abbasid Caliphate is destroyed 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Retrieved on 2008-02-13. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1258 - Baghdad falls to the Mongols, and the Abbasid Caliphate is destroyed
- ^ Yong Qin, Xudong Wang & Zhong Lin Wang (October 10, 2007). Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. "Letter/abstract: Microfibre–nanowire hybrid structure for energy scavenging". Nature 451: 809-813. Nature Publishing Group. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. cited in Editor's summary: Nanomaterial: power dresser. Nature. Nature Publishing Group (February 14, 2008). Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Retrieved on 2008-02-13. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1258 - Baghdad falls to the Mongols, and the Abbasid Caliphate is destroyed
- ^ Database of Select Committee on GRAS Substances (SCOGS) Reviews. Retrieved on 2008-03-22. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 238 - Gordian I and his son Gordian II are proclaimed Roman emperor.
- ^ The Safety of Zinc Casting
- ^ Zinc and Cadmium
Bibliography
- Physics Today, volume 58, No. 8, p. 33, August 2005.
- "Introduction and recovery of point defects in electron-irradiated ZnO", Tuomisto, F. , Saarinen, K. , Look, D. C. , and Farlow, G. C. , Physical Review B 72, 085206 (2005).
- "Nanostructure of ZnO fabricated via French Process and its correlation to electrical properties of semiconducting varistors", S. Mahmud, M. J. Abdullah, J. Chong, A. K. Mohamad, M. Z. Zakaria, J. Syn. React. Inorg. , Met-org. and Nano-metal Chem. , 36, pp155-159 (2006).
External links
- International Chemical Safety Card 0208.
- NIOSH Pocket Guide to Chemical Hazards.
- Nav Bharat Metallic Oxide Industries. (describes industrial uses of zinc oxide)
- External MSDS (Material Safety Data Sheet) on zinc oxide.
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