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 of the geometry and size of the barrel bore, which will directly affect the firing accuracy of the gun and the life of the barrel.

Therefore, the research on ablative behavior and protection of gun barrel 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.

Gun-Barrel
Gun-barrel

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 25mm rifled gun barrel and 120mm smooth rifled gun barrel bore by using explosive spraying technology. It was found that the bonding between tantalum layer and the base metal was good, but the adiabatic shear band would appear in the base steel of the body tube and 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.

Armor-piercing-projectile
Armor-piercing-projectile

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 type. 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 of 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 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 thin-wall structure, and its sensitive device has high anti-interference ability, which can work normally in fog or the 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.

Tantalum-powder
Tantalum-powder

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 the 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.

A Brief History of Tantalum

In 1801, Charles Hatchett, a British chemist, analyzed a collection of minerals preserved in British museums and discovered a new element, Columbium (later renamed Columbium), in honor of Colombia, where the ore was made. In 1802, Anders Gustav Ekberg, a Swedish chemist, crystallized tantalum from niobium in Scandinavia.

Because tantalum and niobium have very similar properties and specific gravity, many scientists at the time mistakenly believed that the two elements were the same substance. In 1844, German chemist Rosser used chemical methods to prove that tantalum and niobium are two elements.

In 1903, pure tantalum was produced for the first time. Tantalum capacitors manufactured with tantalum, with high capacity, small size, and high reliability, are still irreplaceable components in the electronics industry.

With the continuous miniaturization and portability of global electronic products since 1990, tantalum capacitors have been widely used. Today, tantalum capacitors are shipped about 100 billion times a year.

tantalum-capacitors
Tantalum Capacitors

There are three major Tantalum companies operating in the world today: the US Cabot group, the German HCST group, and China Swing Orient Tantalum Industry Co., Ltd. These three companies produce more than 80 percent of the world’s tantalum products.

Tantalum used in electronics accounts for 60% of total production. But tantalum is not just used as a capacitor. Nickel-tantalum alloy is widely used in advanced aero-engine blades.

Before 2007, the world’s major sources of tantalum were Australia and Brazil. In 2000, the world’s major producing countries produced approximately 1,100 tons of tantalum concentrate, of which Australia accounted for 45%, mainly at Greenbush and Wodgina mines, while Brazil accounted for 17%, Rwanda 12%, and Congo 9%. At the time, Congo was in the midst of a second civil war, and large numbers of rebels smuggled Congolese tantalum mines into Rwanda for export under the Rwandan name.

In 2003, the Democratic Republic of Congo (DRC) signed a peace agreement with rebels in the east that ended a second civil war. But the rebels in eastern DRC have not really laid down their arms, and are no longer engaged in open, large-scale fighting with government forces. The rebels continue to splinter and regroup, with new rebels popping up every now and then. Congo and the surrounding great lakes countries are backward industrially, all guns and ammunition are imported, and any imports must be accompanied by foreign currency. Both the rebels and the great lakes countries are eyeing tantalum as a new source of revenue.

Tantalum has supported the fighting in eastern Congo. Subsequently, the world’s major tantalum deposits have undergone a stunning reversal. Cheap Labour in eastern Congo, using baskets and hammer-shovels, has been digging holes in droves, defeating Australian tantalum miners armed with big mining machines. Australia’s tantalum mines, unable to compete with a shoveled army of poor Congolese, went bust and quit altogether.

tantalum-mines
Tantalum-mines

In 2007, Rwanda and the Democratic Republic of Congo had the world’s largest and second-largest share of tantalum mines. On January 9, 2007, Apple’s Steve Jobs launched the first iPhone. In 2014, most of the world’s tantalum mines were exported by Rwanda and DRC, including 600 tons from Rwanda and 200 tons from DRC, accounting for more than 70% of the world’s tantalum output.

In 2010, the U.S. implemented the Dodd-Frank Wall Street reform and consumer protection act, which requires U.S. companies that purchase tantalum products and other materials to investigate their supply chains and determine that the materials are not sourced from conflict zones in the democratic republic of Congo. The United States describes minerals from the eastern DRC region that have been repeatedly contested by rebels and government forces as conflict minerals.

Rwanda, Tanzania, and Bolivia are investing in the construction of tantalum and niobium smelting plants due to the implementation of the Dodd-Frank Act in the US and the Conflict Minerals Regulation in the EU. It is expected that the supply of tantalum raw materials in the world, especially in Africa, will become more and tighter in the future.

Stanford Advanced Materials (SAM) is a trusted supplier of high-quality capacitor grade tantalum powdercapacitor grade tantalum wire and a wide variety of tantalum products. Please visit https://www.samaterials.com/ for more information.