Performance comparison of titanium and tantalum metals

Titanium has great strength, and the tensile strength of pure titanium can reach 180kg/mm2. The strength of some steels is higher than that of titanium alloys, but the specific strength (the ratio of tensile strength to density) of titanium alloys is higher than that of high-quality steels. Titanium alloy has good thermal strength, low temperature toughness and fracture toughness, so it is often used as aircraft engine parts and rocket and missile structural parts. Titanium alloys can also be used as storage tanks and high-pressure vessels for fuels and oxidants. At present, titanium alloy has been used to manufacture automatic rifles, mortar bases and launch tubes of recoilless guns. In the petroleum industry, it is mainly used in various containers, reactors, heat exchangers, distillation columns, pipelines, pumps and valves. Titanium can be used as electrodes, power station condensers and environmental pollution control devices. Ti-Ni shape memory alloy has been widely used in instruments and meters. In medicine, titanium can be used as artificial bone and various instruments. Titanium is also a deoxidizer for steelmaking and a component of stainless steel and alloy steel. Titanium dioxide is a good raw material for pigments and paints. Titanium carbide and titanium carbide (hydrogen carbide) are new cemented carbide materials. Titanium nitride is close to gold in color and widely used for decoration.

Titanium and its alloys are widely used in aviation industry and are called "aerospace metals". In addition, it is also widely used in shipbuilding industry, chemical industry, manufacturing mechanical parts, telecommunications equipment, cemented carbide and so on.

In addition, titanium alloy has good compatibility with human body and can also be used as artificial bone.

Tantalum metal:

Used for metal alloys. Tantalum pentoxide is used in capacitors. Tantalum is also used in cutting tools, vacuum filaments and camera lenses.

Tantalum is very hard, and the hardness can reach 6-6.5. Its melting point is as high as 2996℃, second only to tungsten and rhenium, ranking third. Tantalum is malleable and can be drawn into a thin filament foil. Its coefficient of thermal expansion is very small, and it only expands by 6.6% when 1 degree Celsius is increased. In addition, its toughness is very strong, even better than copper.

Tantalum also has excellent chemical properties and extremely high corrosion resistance. It does not react with hydrochloric acid, concentrated nitric acid and aqua regia under cold or hot conditions. However, tantalum will be corroded in hot concentrated sulfuric acid. When it is lower than 150, it will not be corroded by concentrated sulfuric acid. Only above this temperature will there be a reaction. When it is immersed in concentrated sulfuric acid at 175℃ 1 year, the corrosion thickness is 0.0004 mm, and when it is immersed in sulfuric acid at 200℃ for one year, the surface layer will only be damaged by 0.006 mm. At 250℃, the corrosion rate will increase and the annual corrosion thickness will be 0.1/kloc-. At 300℃, the corrosion rate is faster. After soaking 1 year, the corrosion of surface 1.368mm .. in fuming sulfuric acid (containing 15% SO3) is more serious than that in concentrated sulfuric acid. After soaking at 130℃ for 1 year, the surface corrosion thickness is15.6 mm. Tantalum can also be corroded by phosphoric acid at high temperature, but the reaction usually occurs above 150℃. Immersed in 85% phosphoric acid at 250℃ for 1 year, the surface was corroded by 20 mm In addition, tantalum can be dissolved rapidly in the mixed acid of hydrofluoric acid and nitric acid, and also in hydrofluoric acid. But tantalum is more afraid of strong alkali. Tantalum will dissolve rapidly in 40% caustic soda solution with 1 10 degree, and it will dissolve rapidly in potassium hydroxide solution with the same concentration as long as 100 degree. In addition to the above, general inorganic salts generally cannot corrode tantalum below 150℃. Experiments show that tantalum has no effect on alkali liquor, chlorine gas, bromine water, dilute sulfuric acid and other chemicals at room temperature, but only reacts with hydrogen fluoride and hot concentrated sulfuric acid. This situation is rare in metals.

The oxide film on the surface of tantalum is destroyed at high temperature, so it can react with many substances, and tantalum can react with fluorine at room temperature. Tantalum is inert to chlorine, bromine and iodine at 150℃. At 250℃, tantalum still has dry chlorine corrosion resistance; It can still keep bright when heated to 400℃ in chlorine-containing steam; At 500℃, corrosion began; Tantalum reacts with bromine above 300℃, but tantalum is inert to iodine vapor before the temperature reaches red heat. Hydrogen chloride reacts with tantalum at 4 10℃ to produce carbon pentachloride, and hydrogen bromide reacts with tantalum at 375℃. When heated to 200 degrees or lower, S can react with Ta, and carbon and hydrocarbons can react with Ta at 800- 1 100 degrees.

Tantalum is widely used because of its characteristics. Tantalum can replace stainless steel in the equipment for preparing various inorganic acids, 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 needed precious metal platinum in the past, greatly reducing the cost. Tantalum is made into capacitors and equipped in military equipment. The United States has an extremely developed military industry and is the largest arms exporter in the world. Half of the world's tantalum production is used for the production of tantalum capacitors, and the logistics department of the US Department of Defense is the largest owner of tantalum metal, which once bought out one-third of the world's tantalum powder.