The texture of the crucible is very hard and the hardness can reach 6 to 6.5. Its melting point up to 2996 deg.] C, after tungsten and rhenium, third.é’½ It is malleable and can be drawn into a thin foil. Its thermal expansion coefficient is very small, and it only expands by 6.6% for every one degree Celsius increase. In addition, it has a strong toughness and is superior to copper .
It also has excellent chemical properties and is extremely resistant to corrosion. It does not react with hydrochloric acid, concentrated nitric acid and "Aqua regia" under both cold and hot conditions. However, the crucible can be corroded in hot concentrated sulfuric acid. Below 150 °C, the crucible will not be corroded by concentrated sulfuric acid. Only above this temperature will it react. In 175 degree concentrated sulfuric acid for 1 year, the thickness is corroded. For 0.0004 mm, the crucible was immersed in 200 ° C sulfuric acid for one year, and the surface layer was only damaged by 0.006 mm. At 250 degrees, the corrosion rate increases, and the thickness of the corrosion is 0.116 mm per year. At 300 degrees, the corrosion rate is accelerated. After soaking for 1 year, the surface is corroded by 1.368 mm. The corrosion rate of fuming sulfuric acid (containing 15% of SO 3 ) is more serious than that of concentrated sulfuric acid. It is immersed in the solution at 130 degrees for 1 year, and the surface is corroded to a thickness of 15.6 mm. Tantalum also be phosphate corrosion at high temperature, but the reaction is generally only occurs above 150 degrees, 85% phosphoric acid at 250 degrees, soaked in 1, surface corrosion 20 mm Further, in hydrofluoric acid and tantalum The mixed acid of nitric acid dissolves quickly and can also be dissolved in hydrofluoric acid. However, cockroaches are more afraid of strong alkali. In a 110% 40% caustic soda solution, strontium is quickly dissolved. In the same concentration of potassium hydroxide solution, it will dissolve rapidly as long as 100 degrees. In addition to the above, the general inorganic salt generally does not corrode ruthenium below 150 degrees. Experiments show that, at room temperature, tantalum, alkali solution, chlorine, bromine water, dilute sulfuric acid, and many other agents are ineffective, react only in hydrofluoric acid and hot concentrated sulfuric acid. In this case the metal is relatively rare.
However, at high temperatures, the oxide film on the surface of the crucible is destroyed, so that it can react with various substances, and it can react with fluorine at normal temperature. At 150 degrees, chloro bromo iodo showed tantalum on an inert, at 250 degrees, the dried tantalum chlorine corrosion resistance still is heated to 400 degrees in the chlorine containing water vapor, light still remains at 500 degrees It begins to corrode, reacts with bromine at temperatures above 300 degrees, and is inert to iodine vapors before the temperature reaches red heat. Hydrogen chloride reacts with hydrazine at 410 degrees to produce pentachloride, and hydrogen bromide reacts with hydrazine at 375 degrees. When heated to a temperature of 200 degrees or lower, S can react with Ta, and carbon and hydrocarbons act at 800 to 1100 degrees with hydrazine.
The characteristics of é’½ make its application field very broad. In equipment for the production of various inorganic acids, niobium can be used to replace stainless steel, and its life can be increased by several times compared with stainless steel. In addition, in the chemical, electronic, electrical and other industries, helium can replace the task that was required to be carried out by the precious metal platinum in the past, so that the cost is greatly reduced.é’½ was built into capacitors for military equipment. The US military industry is extremely developed and is the world's largest exporter of arms. Half of the world's base metal production is used in the production of tantalum capacitors. The US Department of Defense Logistics Department is the largest owner of base metals. It once bought out one-third of the world's tantalum powder.
The main absorption line of é’½ and its main parameters are shown in Table 1.
Table 1 Main absorption line of é’½ and its main parameters
λ(nm) | f | w | F | S* | CL | R·S |
271.5 | 0.055 | 0.2 | NA | 30 | 1.0 | |
260.9(D) | 0.2 | NA | twenty three | 2.1 | ||
265.7 | 0.2 | NA | 2.5 | |||
293.4 | 0.2 | NA | 2.5 | |||
255.9 | 0.2 | NA | 2.5 | |||
264.8 | 0.2 | NA | ||||
265.3 | 0.2 | NA | 2.7 | |||
269.8 | 0.2 | NA | 2.7 | |||
275.8 | 0.2 | NA | 3.1 | |||
277.6 | 0.2 | NA | 58 |
f: vibrator strength
W: monochromator spectral passband
NA (nitrous oxide-acetylene flame)
S*: characteristic concentration of the element (1% absorption sensitivity)
CL: detection limit of the element
R·S: relative sensitivity between the main absorption lines of the same element
F: Flame type
The chemical symbol Ta, steel gray metal, belongs to group VB in the periodic table, atomic number 73, atomic weight 180.9479, body-centered cubic crystal, common valence is +5.
It was discovered in 1802 by the Swedish chemist AGEkeberg and named tantalum according to the Greek mythology Tantalus. In 1903, the German chemist W. von Bolton first prepared a plastic metal crucible for use as a filament material. In 1940, large-capacity tantalum capacitors appeared and were widely used in military communications. During the Second World War, the demand for cockroaches increased dramatically. After the 1950s, as the application of tantalum in capacitors, superalloys, chemical and atomic energy industries continued to expand, the demand increased year by year, which promoted the research and production development of the extraction process of alfalfa. China established the metallurgical industry in the early 1960s.
First, resources
The physicochemical properties of lanthanum and cerium are similar, so they are symbiotic in minerals in nature. The classification of antimony or antimony ore is mainly based on the content of antimony and antimony in the mineral. The presence and chemical composition of niobium minerals are complex. In addition to niobium and tantalum, rare earth metals, titanium , zirconium , tungsten, uranium , thorium and tin are often included. The main mineral of tantalum are: iron ore of tantalum [(Fe, Mn) (Ta , Nb) 2 O 6], weight tantalite (FeTa 2 O 6), microlite [(Na, Ca) Ta 2 O 6 ( O, OH, F)] and black gold ore [(Y, Ca, Ce, U, Th) (Nb, Ta, Ti) 2 O 6 ] and the like. The slag of smelting tin contains strontium, which is also an important resource for cockroaches. It has been found that the world’s reserves (in sputum) are about 134,000 short tons, with Zaire taking the lead. In 1979, the world's production of antimony minerals (in sputum) was 788 short tons (1 short ton = 907.2 kg). China has made achievements in the process of extracting antimony from minerals with relatively low niobium.
Second, nature and use
The coefficient of linear expansion of 钽 is 6.5×10 -6 K-1 between 0 and 100 °C, the critical temperature of superconducting transition is 4.38 K, and the thermal neutron absorption cross section of atom is 21.3 target.
At temperatures below 150 ° C, hydrazine is one of the most chemically stable metals. Only the fluorine, hydrofluoric acid, fluoride-containing acidic solution and sulfur trioxide are reacted with ruthenium. It is reacted with a concentrated alkali solution at room temperature and dissolved in a molten alkali. The dense ruthenium begins to oxidize slightly at 200 ° C and oxidizes significantly at 280 ° C. Tantalum has a variety of oxides, the most stable of which is tantalum pentoxide (Ta 2 O 5 ). Niobium and hydrogen form brittle solid solutions and metal hydrides such as Ta 2 H, TaH, TaH 2 , TaH 3 at temperatures above 250 °C. At a vacuum of 800 to 1200 ° C, hydrogen is precipitated from the crucible, and the crucible returns to plasticity. Niobium and nitrogen begin to react at about 300 ° C to form solid solution and nitrogen compound; at higher than 2000 ° C and high vacuum, the absorbed nitrogen is precipitated from the crucible. Niobium and carbon exist in three phases above 2800 ° C: carbon niobium solid solution, low-cost carbide and high-valence carbide. Rhodium reacts with fluorine at room temperature and reacts with other halogens above 250 ° C to form halides.
é’½There is a stable anodized film formed in the acidic electrolyte. The electrolytic capacitor made of bismuth has the advantages of large capacity, small size and good reliability. The capacitor is the most important use of bismuth. The total dosage is 2/3 or more.é’½ is also the material for making electron emission tubes and high-power tube parts. Tanning anti-corrosion equipment is used in the production of chemical industries such as strong acid, bromine and ammonia. The metal crucible can be used as a structural material for the combustion chamber of an aircraft engine. Tungsten-tungsten, niobium-tungsten- rhenium and niobium alloys are used as heat-resistant and high-strength materials for rockets, missiles and jet engines, as well as parts for control and regulation equipment. Easy to process and form, support attachments, heat shields, heaters and heat sinks in high temperature vacuum furnaces.é’½ can be used as orthopedic and surgical materials. Tantalum carbide is used to make cemented carbide. Tantalum boron nitride, silicides and nitrides, and alloys used in the atomic energy industry and fuel element sheath liquid metal material. Cerium oxide is used in the manufacture of advanced optical glass and catalysts. In 1981, the proportion of consumption in various departments in the United States was about 73% for electronic components, 19% for machinery industry, 6% for transportation, and 2% for others.
Third, smelting
The antimony ore is often accompanied by a variety of metals. The main steps of smelting are to decompose the concentrate, purify and separate the strontium and barium, to prepare pure compounds of strontium and barium, and finally to obtain the metal.
The ore decomposition may be carried out by hydrofluoric acid decomposition, sodium hydroxide melting, and chlorination. The solvent separation method can be used for the separation of ruthenium [the commonly used extractants are methyl isobutyl copper (MIBK), tributyl phosphate (TBP), sec-octanol and acetamide, etc.), fractional crystallization and ion exchange.
Fourth, the separation of bismuth compounds
Firstly, the concentrate of the coltan is decomposed with hydrofluoric acid and sulfuric acid, and lanthanum and lanthanum are dissolved in the leaching solution, and the accompanying elements such as iron, manganese , titanium, tungsten and silicon are also dissolved in the leaching solution. Form a highly acidic solution with a very complex composition. The leaching solution is extracted with methyl isobutyl ketone, and the hydrazine is simultaneously extracted into the organic phase, and the trace impurities in the organic phase are washed with a sulfuric acid solution to obtain a pure cerium-containing organic phase, and the washing liquid and the raffinate are combined. It contains trace amounts of antimony and impurity elements and is a strong acidic solution that can be recovered comprehensively. The pure cerium-containing organic phase is back extracted with a dilute sulfuric acid solution to give a cerium-containing organic phase. The hydrazine and a small amount of hydrazine enter the aqueous phase, and then the hydrazine is extracted with methyl isobutyl ketone to obtain a pure cerium-containing solution. The pure hydrazine-containing organic phase is back-extracted with water to give a pure cerium-containing solution. The organic phase after back extraction of the ruthenium is returned to the extraction cycle. A pure fluoroantimonic acid solution or a pure fluoroantimonic acid solution is reacted with potassium fluoride or potassium chloride to form potassium fluoroantimonate (K 2 TaF 7 ) and potassium fluoroantimonate (K 2 NbF 7 ) crystals, respectively. Reaction with ammonium hydroxide to form barium hydroxide or barium hydroxide precipitate. The ruthenium or osmium hydroxide is calcined at 900 to 1000 ° C to form an oxide of ruthenium or osmium.
Fifth, the production of metal bismuth
1. Metal bismuth powder can be prepared by metal thermal reduction (sodium thermal reduction). Reduction of potassium fluoroantimonate with sodium metal under an inert atmosphere: K 2 TaF 7 +5Na-→Ta+5NaF+2KF. The reaction was carried out in a stainless steel tank, and the reaction was quickly completed when the temperature was heated to 900 °C. The powder prepared by this method has irregular grain shape and fine particle size, and is suitable for making tantalum capacitors. Metal bismuth powder can also be prepared by molten salt electrolysis: using a molten salt of a mixture of potassium fluoroantimonate, potassium fluoride and potassium chloride as an electrolyte, and dissolving tantalum pentoxide (Ta 2 O 5 ) therein at 750 ° C Electrolytic, a tantalum powder having a purity of 99.8% to 99.9% can be obtained.
2. Metal ruthenium can also be obtained by reduction of Ta 2 O 5 by carbothermal. The reduction is generally carried out in two steps: first, a certain mixture of Ta 2 O 5 and carbon is prepared in a hydrogen atmosphere at 1800 to 2000 ° C to form tantalum carbide (TaC), and then TaC and Ta 2 O 5 are fixed. The mixture is made into a mixture and vacuum-reduced into a metal crucible. The metal ruthenium can also be obtained by a method of thermally decomposing or hydrogen-reducing ruthenium chloride. The dense metal crucible can be prepared by vacuum arc, electron beam, plasma beam melting or powder metallurgy. The high-purity germanium single crystal is obtained by a flawless electron beam region melting method.
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