Views: 0 Author: Site Editor Publish Time: 2022-07-22 Origin: Site
Tantalum has a wide range of applications due to its characteristics. In the equipment for preparing various inorganic acids, tantalum can be used to replace stainless steel, and its service life can be dozens of times longer than that of stainless steel. In addition, in chemical, electronic, electrical and other industries, tantalum can replace the tasks that used to be undertaken by platinum, which greatly reduces the cost. Tantalum is made into capacitors and equipped in military equipment. The United States has an exceptionally developed military industry and is the world's largest arms exporter. Half of the world's Tantalum production is used in the production of tantalum capacitors, and the logistics administration of the United States Department of defense is the largest owner of tantalum, once buying out one third of the world's tantalum powder.
Tantalum niobium ore is often accompanied by a variety of metals. The main steps of tantalum smelting are decomposing concentrate, purifying and separating tantalum and niobium, so as to produce pure compounds of tantalum and niobium, and finally produce metals.
Hydrofluoric acid decomposition method, sodium hydroxide melting method and chlorination method can be used for ore decomposition. Tantalum and niobium can be separated by solvent extraction [common extractants are methyl isobutyl ketone (MIBK), tributyl phosphate (TBP), SEC octanol and acetamide], fractional crystallization and ion exchange.
Separation: first, the concentrate of tantalum niobium iron ore is decomposed with hydrofluoric acid and sulfuric acid. Tantalum and niobium are dissolved in the leaching solution as fluorotantalic acid and fluoroniobic acid. At the same time, associated elements such as iron, manganese, titanium, tungsten, silicon are also dissolved in the leaching solution to form a strong acidic solution with complex components. Tantalum niobium leaching solution uses methyl isobutyl ketone to extract tantalum niobium and extract it into the organic phase at the same time. The trace impurities in the organic phase are washed with sulfuric acid solution to obtain a pure organic phase containing tantalum niobium. The washing solution and the raffinate are combined, which contains trace tantalum niobium and impurity elements. It is a strong acidic solution and can be comprehensively recovered. The pure organic phase containing tantalum and niobium was back extracted with dilute sulfuric acid solution to obtain the organic phase containing tantalum. Niobium and a small amount of tantalum enter the aqueous solution phase, and then tantalum is extracted with methyl isobutyl ketone to obtain a pure niobium containing solution. Pure tantalum containing organic phase is back extracted with water to obtain pure tantalum containing solution. The organic phase after stripping tantalum is returned to extraction for recycling. Pure fluotantalic acid solution or pure fluoniobic acid solution reacts with potassium fluoride or potassium chloride to form potassium fluotantalate (K2TaF7) and potassium fluoniobate (k2nbf7) crystals, respectively, and can also react with ammonium hydroxide to form tantalum hydroxide or niobium hydroxide precipitates. Tantalum or niobium hydroxide is calcined at 900~1000 ℃ to form tantalum or niobium oxide.
① Tantalum powder can be prepared by metal thermal reduction (sodium thermal reduction). Under inert atmosphere, potassium fluotantalate is reduced with metal sodium: K2TaF7 + 5na - → TA + 5naf + 2kf. The reaction is carried out in a stainless steel tank. When the temperature is heated to 900 ℃, the reduction reaction is completed quickly. The tantalum powder prepared by this method has irregular particle shape and fine particle size, which is suitable for making tantalum capacitors. Tantalum powder can also be prepared by molten salt electrolysis: using the molten salt of potassium fluotantalate, potassium fluoride and potassium chloride mixture as electrolyte, tantalum pentoxide (Ta2O5) is dissolved in it, and the purity of 99.8 ~ 99.9% can be obtained by electrolysis at 750 ℃.
② Tantalum can also be obtained by carbothermic reduction of Ta2O5. Reduction is generally carried out in two steps: first, the mixture of Ta2O5 and carbon with a certain proportion is made into tantalum carbide (TAC) at 1800 ~ 2000 ℃ in hydrogen atmosphere, and then the mixture of TAC and Ta2O5 with a certain proportion is made into tantalum in vacuum. Tantalum can also be prepared by thermal decomposition or hydrogen reduction of tantalum chloride. Dense tantalum can be prepared by vacuum arc, electron beam, plasma beam smelting or powder metallurgy. High purity tantalum single crystals were prepared by crucible free electron beam zone melting.
Tantalum is one of the rare metal mineral resources and an indispensable strategic raw material for the development of electronic industry and space technology.
Tantalum and niobium have similar physical and chemical properties, so they coexist in natural minerals. The classification of tantalum ore or niobium ore is mainly based on the content of tantalum and niobium in minerals. When the content of niobium is high, it is called niobium ore, and when the content of tantalum is high, it is called tantalum ore. Niobium is mainly used to manufacture carbon steel, super alloy, high-strength low alloy steel, stainless steel, heat-resistant steel and alloy steel; Tantalum is mainly used in the production of electronic raw devices and alloys. The occurrence forms and chemical compositions of tantalum and niobium minerals are complex. In addition to tantalum and niobium, they often contain rare earth metals, titanium, zirconium, tungsten, uranium, thorium and tin. The main minerals of tantalum include: tantalite [(Fe, Mn) (TA, Nb) 2o6], heavy tantalite (feta2o6), fine crystal [(Na, CA) ta2o6 (O, oh, f)] and Heixi gold mine [(y, CA, CE, u, th) (Nb, Ta, Ti) 2o6]. The waste residue of tin smelting contains tantalum, which is also an important resource of tantalum. It has been found that the world's Tantalum reserves (in tantalum) are about 134000 short tons, with Zaire taking the lead. In 1979, the output of Tantalum Minerals in the world (calculated by tantalum) was 788 short tons (1 short ton =907.2 kg). China has made achievements in the process of extracting tantalum from minerals with relatively low tantalum content .
Capacitors are the main final consumption area of tantalum, accounting for about 60% of the total consumption. The United States is the country with the largest consumption of tantalum, with a consumption of 500 tons in 1997, of which 60% was used to produce tantalum capacitors. Japan is the second largest country in tantalum consumption, with a consumption of 334 tons. At the beginning of the 21st century, with the rapid development of capacitor production, the market is in short supply. It is estimated that the production of tantalum capacitors in the world will reach 250million pieces, and 1000 tons of tantalum will be consumed. According to the statistics of the U.S. Geological Survey, the natural reserves of tantalum in the earth's crust are 150000 tons, and the exploitable reserves exceed 43000 tons. In 2004, the world's Tantalum mining volume was 1510 tons, including 730 tons in Australia, 280 tons in Mozambique, 250 tons in Brazil, 69 tons in Canada and 60 tons in Congo. China's resources are mainly distributed in Jiangxi, Fujian, Xinjiang, Guangxi, Hunan and other provinces. From the perspective of future development needs, capacitors are still the main application field of tantalum. If the reserve base is 24000 tons, it can only guarantee the demand for 24 years. Nevertheless, the prospect of tantalum resources is still promising. First of all, there are a lot of tantalum resources associated with the world's very rich niobium deposits. Among them, the tantalum resources of gadal niobium and tantalum mine in southern Greenland amount to 1million tons. Secondly, the West has begun to use a large amount of tin furnace slag containing less than 3% Ta2O5. In addition, the research and utilization of substitutes have also developed rapidly, such as aluminum and ceramics replacing tantalum in the field of capacitors; Silicon, germanium and cesium can replace tantalum in the manufacture of rectifiers for electronic instruments.
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