Manganese(II) phosphate

Manganese(II) phosphate

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Names
IUPAC name Manganese (II) Phosphate
Other names Manganese diphosphate; Manganese phosphate tribasic
Identifiers
CAS Number	51349-94-1
ChemSpider	8126114
Jmol 3D model	Interactive image
SMILES [O-]P(=O)([O-])[O-].[O-]P(=O)([O-])[O-].[Mn+2].[Mn+2].[Mn+2]
Properties
Chemical formula	Mn3(PO4)2
Molar mass	354.76 g/mol
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Manganese(II) phosphate is a chemical compound with the chemical formula Mn₃(PO₄)₂.

Formation

Manganese phosphates often combine with iron phosphates through paragenesis. In the process of paragenesis, each mineral affects the manner in which the other is crystallized. The minerals combine in isomorphic series, meaning that they crystallize in similar forms, producing a sequence of solids. Some examples of “isomorphic series” formed by Mn and Fe include triphylite Li(Fe,Mn)PO₄, lithiophylite Li(Mn,Fe)PO₄, heterosite (Fe,Mn)PO₄, purpurite (Mn,Fe)PO₄, zwieselite (Fe,Mn)₂PO₄F, triplite (Mn,Fe)PO₄, and the list goes on. Nearly all of these series that are formed are inorganic phosphates of salts and esters, called orthophosphates.

Reactions

Manganese, phosphate, and iron can be combined with lithium to form what is called an olivine structure. This is a very stable structure and the phosphate has the advantage of strong P-O covalent bonds. Moreover, experimental data shows that these compounds are able to withstand high temperatures of over 700˚C. On the other hand, when combined with iron in a series, higher concentrations of manganese make the combination less stable and more likely to separate. This indicates that iron-rich materials are better than manganese-rich ones.

Processing

The immersion method is used for the processing of Manganese phosphate coatings. The steps of immersion include degreasing/cleaning, water rinses, pickling in mineral acid, activation, manganese phosphating, an optional final drying, and lubrication using oils or emulsion. The first step of this method is to degrease and clean, typically with strong alkaline cleaners. Pickling in mineral acid is a useful process described by the removal of oxide, resulting in a clean surface. The water pre-rinse activation allows the cleaning and pickling to take place while avoiding the formation of coarse-crystalline phosphate. Manganese phosphating is performed, typically in a bath of dilute phosphoric acid that is at approximately 95˚C for about 5–20 minutes (the time varies with the state of the surface being coated). The elements that were coated are then allowed to dry, possibly in an oven. The final step of manganese phosphate coating is to lubricate the materials with oil by immersing them in the oil bath and then letting them drain. This results in different thicknesses of oil when different concentrations and types of oil are used.

Applications

Manganese phosphate, when combined with lithium and iron, is a very useful contributor to the cathode of lithium rechargeable batteries. This is due to the olivine structure created when lithium is combined with manganese, iron, and phosphate (as described above). The olivine structures of lithium rechargeable batteries are significant, for they are affordable, stable, and can be safely stored as energy.

Manganese phosphate can also be used for coatings (which are processed as described above). These coatings are useful for protection against corrosion and wear over time, due to their toughness. Manganese phosphate coating can often be found in the oil and gas industry, firearms and ordnance, aerospace, gears and bearings, and in marine equipment. They are also common in engines, screws, nuts and bolts, washers, and the list continues.

Hazards

Some hazards that apply if there is contact with compounds containing manganese include skin and eye irritation or nausea, vomiting or diarrhea if the manganese is ingested. If eye contact occurs, water should be used to wash them out for about 15 minutes and medical attention should be sought. If skin contact occurs, soap and water should be used. A doctor should be contacted if ingestion occurs.