How is Tantalum Used in the Military Industry?

How is Tantalum Used in the Military Industry?

The inner covering of the gun body

When gunpowder is exploded, it produces a tail flame with a temperature of 2500 ~ 3500K and a pressure of 300 ~ 800MPa. The tail flame contains such corrosive components as H2S, CO, O2, H2, H2O, N2, and powder residue particles. Therefore, the gun barrel will undergo the physical and chemical effects of high-temperature and high-pressure gunpowder gas (the thermal effect of high-temperature gas, the scouring of high-speed airflow, the corrosion of gunpowder gas residue in the bore, and the wear of high-speed moving projectile on the inner wall) when the projectile is launched. Under this working condition, the gun barrel bore will be subjected to severe ablative erosion and wear, which will lead to the change in the geometry and size of the barrel bore, which will directly affect the firing accuracy of the gun and the life of the barrel.

military industry

Therefore, the research on ablative behavior and protection of gun barrels has received extensive attention. The main considerations of gun barrel material are thermal properties, including heat resistance, thermal expansion, thermal conductivity, and thermal shock resistance; mechanical properties, including elastic modulus, mechanical strength, and hardness; chemical stability, that is, the chemical stability of materials in high temperature and corrosive atmosphere.

Tantalum (Ta) has good physical and chemical properties. It is a high melting point (2996℃) refractory metal, with low thermal conductivity (57W/m℃), good chemical corrosion resistance (acid, salt, and organic chemical corrosion resistance at high temperature), and excellent ablative resistance, as well as good plastic and toughness. Tantalum or tantalum alloy coating is considered to be an ideal coating system to replace the electroplating Cr coating for ablative and scour resistance. If the tantalum layer is to be used in the gun barrel for the purpose of gas ablation of fire retardant for a long time, the sputtering Ta layer should be mainly composed of alpha-ta with a thickness of at least 75 microns. The coating should have enough binding force with the substrate in all directions to resist the thermal shock and high shear stress in the gun firing process.

The cylindrical magnetron sputtering tantalum technology was proposed by Benet Laboratories of the United States army for the dimension characteristics of the gun barrel; Also, the trial production of cylindrical magnetron sputtering deposition technology platform for 120mm, 155mm, and 105mm sputtering full-length large-caliber gun tubes were built in Waterfleet Arsenal, which was used for the magnetron sputtering full-bore tantalum plating for Abrams, Crusader, and future combat systems.

In the Bennett experiment of the US army, Vigilante et al. prepared pure tantalum ablative resistant layer in a 25mm rifled gun barrel and 120mm smooth rifled gun barrel bore by using explosive spraying technology. It was found that the bonding between the tantalum layer and the base metal was good, but the adiabatic shear band would appear in the base steel of the body tube and a Ta-Fe brittle intermetallic compound phase would be formed.

Armor-piercing projectile

In the 1980s, a new type of warhead, the explosively formed penetrator, was successfully developed, mainly using tantalum on the butterfly bushing next to the high explosive. When the explosive is detonated, the butterfly disc morphs into a long, steady, sliver of a penetrator, accelerating towards its target.

With the development of armor materials, modern anti-armor warhead has higher and higher requirements on the materials of explosive forming munition type hood. The formation of a longer and more stable jet requires high density, high sound velocity, good thermal conductivity, and high dynamic fracture elongation. In addition, it is required that the material has a fine grain, low recrystallization temperature, certain texture, and other microstructure.

Tantalum and depleted uranium have high density, high dynamic elongation, and arson. Especially, tantalum has a high density (16.6g/cm3) and good dynamic characteristics, which is a kind of material mainly used in the research of explosive forming ammunition types. As a material of explosively formed munitions, tantalum is widely used in TOW-2B, TOW-NG, and other U.S. missiles. Ballistic experiments show that tantalum’s affinity is 30%~35% higher than that of copper, and can reach 150mm.

At present, the research on using tantalum as the coating material mainly focuses on improving the processing technology and saving the cost. Among them, the United States Army Equipment Research and Development Center (ARDEC) uses the P/M method to develop explosively formed tantalum cartridge type housing; Two kinds of tantalum powders, PM2 and PM4, are pressed by static pressure, sintered, extruded, and processed into blank material, and then annealed and forged by rotary forging, tantalum cartridge prepared in this way can be successfully applied to a well-shaped explosive forming projectile; German Smart-155mm end-sensitive projectile is one of the most advanced end-sensitive projectiles in the world today. The missile is made of a thin-wall structure, and its sensitive device has high anti-interference ability, which can work normally in fog or a bad environment; The BONUS-155mm dexterous shell, jointly developed by the Swedish Bofors Company and the ground weapon group, has been mass-produced and is suitable for 45-caliber artillery.

High purity materials are required for the electrochemical cover of explosive forming. Trace elements have a great influence on the physical properties of the cover material, and ultimately affect the penetration depth of the projectile. The purity of tantalum has an influence on the strength, crystal structure, and length of the explosive forming projectile (EFP). Therefore, the purity of tantalum shall be strictly controlled in the preparation process.

Ultra-high vacuum aspirating material

Ultra-high vacuum aspirating material (tantalum alloy) is used in night vision equipment in conventional defense weapons. Using 15% tantalum as the framework and titanium as the adsorbent of hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, water vapor, methane, neon, and other gases can improve the service life of the inspiratory material. This material can be applied to the infrared camera tube in the active infrared night-vision instrument and the low-light tube in the passive low-light night vision instrument, to ensure the long-term high vacuum in the vacuum tube, so as to achieve the high efficiency, high-life span and improve the definition of the night vision instrument.

Stanford Advanced Materials supplies high-quality tantalum products to meet our customers’ R&D and production needs. Please visit https://www.samaterials.com for more information.

Protective Coatings Application of Tantalum Oxide

Protective Coatings Application of Tantalum Oxide

Tantalum oxide is shown to be chemically very robust. Reactively sputtered tantalum oxide thin films have been investigated as a protective coating for aggressive media exposed sensors.

The step coverage of the sputter-deposited amorphous tantalum oxide is reasonable, but metallization lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 pm thick films is below 3 cm.

tantalum oxide

Applying protective coatings as a solution to this sensor concept requires a number of properties for the coating to fulfill, a short list includes:

  1. Corrosion resistance: the maximum allowable thickness of the coating and minimum required lifetime sets the upper limit of the etch rate in the media of interest.
  2. Low residual stress in small thickness: to limit the reduction of sensitivity due to stiffness changes in the membrane.
  3. Step coverage: poor coverage over interconnects and contact windows are sites where degradation of the sensor will initiate.
  4. Pinhole density: usually no pinholes are allowed in the exposed area of the sensor. Etchants will penetrate the coating and degrade electrically active components or under etch, eventually resulting in an undesired lift-off of the coating. In case the pinholes are due to particulate contamination, the pinholes may be eliminated by growing thicker films.
  5. Electrical properties: a dielectric film is required to insulate electrical components on the sensor from electrically conducting media.
  6. Patternable: in many cases, it is desired to pattern the protective coating for access to bond pads. Patterning in a batch process, such as wet etching, is preferred.
  7. Double-sided deposition for protection of both sides of the differential pressure sensor.
  8. Coverage of sharp corners: a conformal coating is required.
  9. Coverage of deep cavities: a conformal coating is required down to the bottom of the cavity.

The use of tantalum, tantalum alloys, and tantalum oxide has already been suggested for sensor purposes. Besides, tantalum is used in chemical processing equipment because it is extremely stable. The reason for this is the formation of a thin amorphous tantalum oxide layer at the surface, which is chemically very inert.

Deposition of tantalum and its oxides and nitrides can be done by physical vapor deposition, chemical vapor deposition, or by thermal oxidation. This makes the use of these materials very flexible.

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Where Can We Find Tantalum Metal?

Where Can We Find Tantalum Metal?

Tantalum metal mainly exists in tantalite ore and is symbiotic with niobium. Tantalum is of moderate hardness and ductility and can be drawn into tantalum wire or tantalum foil. Tantalum has a wide range of applications due to its characteristics， and it widely exists in tantalite, tantalum alloy, tantalum powder, tantalum capacitors, etc.

tantalum alloy

Tantalum alloy is an alloy based on tantalum adding other elements. The tantalum anode oxide film is stable and corrosion-resistant. It has excellent dielectric properties and is suitable for making the electrolytic capacitor. Tantalum is highly resistant to chemical corrosion. Except for hydrogen fluoride, sulfur trioxide, hydrofluoric acid, hot concentrated sulfuric acid and alkali, tantalum can resist the corrosion of all organic and inorganic acids. Therefore, it can be used as corrosion resistant materials for chemical industry and medicine.

Tantalum alloy

As tantalum is similar to some rare elements such as uranium, thorium, rare earth, titanium, zirconium, tungsten, and common elements tin, calcium, iron, and manganese in crystalline chemistry, it is easy to have equivalence and heteromorphism.

The compact oxide film formed on the surface of metallic tantalum has the properties of valve metal of unidirectional conduction. The anodic film made of tantalum powder has chemical stability (especially in acidic electrolyte stability), high resistivity (7.5 x 1010 Ω, cm), dielectric constant (27.6) and small leakage current. Tantalum is not only the raw material for the production of pure metal tantalum but also used in the electronics industry. Lithium tantalate monocrystals and special optical glass with high refraction and low dispersion can be used as a catalyst in the chemical industry.

Tantalum oxide is a white powder insoluble in water and acids, but soluble in molten potassium bisulfate and hydrofluoric acid. The minerals containing tantalum and niobium are mainly iron tantalum and calcined greenstone. The ones containing more tantalum are called tantalite, while the ones containing more niobium are called niobite.

tantalum capacitor

The design of tantalum capacitors requires that the product performance parameters of tantalum capacitors can meet the circuit signal characteristics. However, it is often impossible to guarantee that the above two tasks are done well. Therefore, it is inevitable that failures of one kind or another will occur in the process of use. The solid tantalum capacitors were first developed in 1956 by Bell Laboratories in the United States. Tantalum capacitors can easily obtain large capacity, and there are few competitors in power filter, ac bypass, and other applications.

Stanford Advanced Materials supplies high-quality tantalum and related products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.

How do tantalum products work in modern industry?

How do tantalum products work in modern industry?

Capacitor tantalum powder

Tantalum electrolytic capacitor is an electronic device that takes tantalum as a metal anode and generates dielectric oxide film on the tantalum surface by anodic oxidation. The most important difference between tantalum capacitors and other types of capacitors is the quality of the tantalum oxide dielectric film, which has a high dielectric constant and breakdown voltage.

Generally speaking, the higher the purity of tantalum powder, the higher the breakdown voltage of the tantalum capacitor anode film. The tantalum powder has a high specific surface area, which can be remained even after compaction and sintering due to its special pore structure.

tantalum powder

Apart from the tantalum powder, tantalum foil is also used in foil capacitors, and tantalum wire is used as capacitor anode lead. In 2000, the annual output of tantalum capacitors reached 25 billion tons, requiring 800 tons of tantalum powder and nearly 150 tons of tantalum wire. Excellent performance such as high reliability and compactness, high efficiency, and long shelving time make tantalum capacitors be used in the instrument and control system of computers, communication systems, aircraft, missiles, ships, and weapon systems.

Tantalum and its alloys

The alloying of tantalum or tantalum-based alloy is usually carried out in the electron beam furnace. In order to obtain the ingot with uniform composition, vacuum arc remelting (VAR) is required after the smelting and purification in the electron beam furnace. All tantalum and tantalum alloy products are processed by electronic beam casting, and the use of vacuum arc remelting depends on the use of the product.

Tantalum alloy has the lowest ductile-brittle transition temperature, good low-temperature ductility, small work hardening coefficient, and excellent high-temperature strength, which is an ideal structural material for working under 1600-1800 ℃. At present, Ta-W and Ta-Nb alloy materials are mainly used in the manufacture of aerospace industry and space nuclear power system components.

Tantalum alloys

Other applications of tantalum

At present, the global annual consumption of tantalum is about 900 tons. The electronics industry is the largest and most promising application of tantalum, accounting for an estimated 66% of total consumption; the second application of tantalum is in the cutting tool industry, which accounts for 22 percent of total consumption; tantalum, as a superalloy high temperature strengthening additive, accounts for 6% of the total consumption; tantalum and tantalum alloy account for 3% of total consumption in valves, heat exchangers and plug-in heaters of chemical industries. As a biological material, tantalum is highly compatible with body fluids. In thoracic surgery, tantalum U nail is used to close vessels and arteries without an allergic reaction, and medical fields such as holes used to seal the skull during craniotomy account for about 1% of tantalum use. The other 2% of tantalum is used for military purposes.

Stanford Advanced Materials supplies high-quality tantalum products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.