Praseodymium metal (PR) material is one of the products of light rare earth metals. Because of its unique physical and chemical properties, it has been widely used in the fields of rare earth permanent magnets, hydrogen storage materials, non-ferrous metals and alloys, ignition alloys, steel and iron, and has a promising prospect. In the middle of the 1950s, China began to develop metal praseodymium. In the 1960s, the metal gradually went into industrial production, and a small quantity of products were provided to the market. 70 time production of metal praseodymium main technology is praseodymium chloride molten salt electrolysis method, and used for a number of domestic smelting plants, and output growth is fast, can meet the needs of the market and users. In the early 80’s, as a result of using praseodymium oxide molten salt electrolytic method to prepare metal praseodymium research success, so increased the production method of the metal, and has a relatively advanced technology.
At present, the above two methods can be used in industrial production. Since the 1990s, with the application and development of praseodymium metal and the market demand, its varieties, output and quality are constantly improving and developing. Especially in the new materials such as rare earth permanent magnet, hydrogen storage materials and other fields have more development prospects. China has the most abundant rare earth resources in the world. The identified industrial reserves are about 43 million tons (REO), ranking first in the world. Praseodymium resources of about 3 million t, more than any country, this is the advantage of our country, but also for the future sustainable development of praseodymium metal production to provide a solid material basis.
Praseodymium fluoride is a fluoride of praseodymium metal, molecular formula Prf3 ·2H2O=233.93, green hexagonal crystal. The relative density is 6.14, melting point 1370℃(anhydrous salt), boiling point 2327℃(anhydrous salt). Insoluble in water, it reacts with concentrated sulfuric acid to release hydrogen fluoride gas. It is prepared by the interaction of praseodymium salt solution and hydrofluoric acid.
Praseodymium fluoride is an important raw material for the preparation of rare earth metals by thermal reduction method, and can also be used for the preparation of plexiglass-coated films. Examples of its application are as follows:
1. Preparation of a one-way perspective glass. The inner layer of glass and the outer layer of glass are provided with a one-way glass layer between the inner layer of glass and the outer layer of glass. The inner layer of glass, the outer layer of glass and the one-way glass layer are bonded directly or indirectly through the PVB film layer. The one-way glass layer is a multi-layer glass, and the inner or outer surface of the multi-layer glass is separated by a total of two one-way reflecting films. The unidirectional reflection film is high polymer composite film or fluoride coating film, fluoride coating film is yttrium fluoride or praseodymium fluoride coating film, the prepared unidirectional perspective glass has good unidirectional perspective effect, the front transmittance is lower, the reflectivity is higher, the back transmittance is higher, the reflectivity is lower.
2. Preparation of a dysprosium metal alloy. The alloy is composed of 10%~50% dysprosium and 50%~90% neodymium or 50%~90% neodymium and 0%~30% praseodymium by weight percentage. Electrolytic method was used to metal tungsten or molybdenum cathode, with graphite as anode, with 10% ~ 65% of dysprosium fluoride, 15% ~ 20% of lithium fluoride, and 15% ~ 70% of neodymium fluoride or 15% ~ 70% and 0% ~ 30% neodymium praseodymium fluoride fluoride electrolyte, dysprosium oxide with 10% ~ 65%, and 35% ~ 90% of neodymium oxide or 35% ~ 90% of neodymium oxide and 0% ~ 30% praseodymium oxide as raw materials, in the condition of molten salt electrolysis, separation of dysprosium metal on the cathode, collected and pouring into ingots.