With the advent of the era of big data, the storage of big data has become a matter of concern. Tantalum materials are developing at an amazing speed in today’s rapid development of the electronics industry.
Tantalum capacitors
Tantalum capacitors are one the indispensable electronic components for radar, aerospace aircraft, and missiles, and are widely used in civil applications, such as mobile communication, electronic equipment, instruments, and other aspects. On the contrary, the development of the electronic industry requires more and more stringent miniaturization and high reliability of tantalum capacitors.
Tantalum capacitors
Capacitor grade tantalum wire
Capacitor grade tantalum wire is used to make anode lead of tantalum electrolytic capacitor, and its advantages are high permittivity of the oxide film and high reliability. Compared with metallurgical tantalum wire, capacitor grade tantalum wire has high chemical purity, good surface finish, and anti-oxygen brittleness. Using tantalum powder as raw material, capacitor tantalum wire is made by powder metallurgy method after forming tantalum bar, and then through rolling, drawing, and other metal plastic processing. As a result, its surface is smooth and clean, and no grooves, burrs or other defects.
Capacitor grade tantalum wire
The important performance indexes of capacitor-grade tantalum wire include tensile strength, linearity, chemical composition, leakage current, etc. The diameter of the capacitor-grade tantalum is generally between Φ0.15 mm to Φ1.0 mm, and the tensile strength is between 400mpa and 1700mpa.
Tantalum target
The purity of the tantalum target is 99.95%, the surface is smooth, the grain diameter is less than 100μm, and the grain texture is mainly [111] type texture. Because of its high conductivity, high thermal stability, and barrier to foreign atoms, tantalum can be used as a barrier layer to prevent copper from diffusing into silicon. As electrode materials and surface engineering materials, tantalum target has been widely used in liquid crystal display (LCD) and heat-resistant, corrosion-resistant, and highly conductive coating industries.
Tantalum target
Tantalum sputtering target material has become a key raw material in the semiconductor industry, which is irreplaceable and has a broad application prospect. The tantalum sputtering target is completed by physical vapor deposition. The specific process includes high-pressure accelerated gaseous ions bombarding the tantalum target surface, enabling the atoms on the target surface to get enough energy and break free, sputtering on the silicon chip, and finally forming the precise wiring structure in the semiconductor chip with photolithography, corrosion, and other processes. Tantalum material can be used for various thin-film applications, as diffusion barrier material applied to memory devices, such as gate electrodes of MOSFET devices and protective coating on printing head devices.
Metal materials have excellent comprehensive mechanical properties and anti-fatigue properties and are especially suitable for bone replacement implantation of human-bearing parts. Therefore, many kinds of metal materials such as stainless steel, titanium alloy, and cobalt-base alloy have been widely used in the clinic as biomedical materials and have achieved a good therapeutic effect.
However, the complex human body environment will lead to corrosion of materials and the release of toxic elements, which will lead to the reduced biocompatibility of metal materials. In addition, the elastic modulus of the metal material is too different from human bone tissue, and it is easy to produce a stress shielding effect, which is not conducive to the growth and remodeling of new bone and even leads to secondary fracture.
At present, tantalum metal attracts the attention of medical workers and materials researchers with its unique advantages and is widely used in the following aspects.
Biomedical materials
Tantalum wire
Tantalum is so malleable that it can be made into even finer strands of hair. As a surgical suture, tantalum wire has the advantages of simple sterilization, less stimulation, and high tensile strength, but it also has the disadvantages of not easy knotting. Tantalum wire can be used to suture bone, tendon, and fascia, as well as reduce suture or internal dental fixation. It can also be used as a suture line for internal surgery or embedded in artificial eyeballs. Moreover, tantalum wire can even replace tendons and nerve fibers.
Tantalum sheet
Tantalum metal can be made into tantalum sheets of various shapes and sizes and implanted according to the needs of various parts of the human body, such as repairing and sealing the cracks and defects of broken skull bones and limbs fractures. An artificial ear made from tantalum sheets is attached to the head before the skin is transplanted. After a while, the new skin grew so well that it was barely visible as an artificial tantalum ear.
Tantalum stents
Tantalum wire can be used to weave the reticulocytes stent. Tantalum stent can be clearly seen under X-ray, which is very convenient for monitoring and follow-up, and there is no fracture and corrosion in the body for a long time. Tantalum has good flexibility, so the stents can better adapt to the normal pulse of arteries and can be released quickly and accurately.
Porous tantalum rod
Porous tantalum rod is a kind of honeycomb three-dimensional rod-shaped structure with characteristics of the human cancellous bone structure, with an average porosity of 430~m and a porosity of 75 ~ 80. The elastic modulus of the porous tantalum rod is about 3GPa, which is between the cancellous bone (about 1GPa) and cortical bone (about 15GPa), far lower than the commonly used titanium alloy implanted human material (about 11OGPa), thus avoiding the stress shielding effect.
Porous tantalum rod implantation is mainly used for the treatment of avascular necrosis of the femoral head in the early and middle stages. Femoral head necrosis is a kind of functional disease caused by the destruction of the blood circulation of the femoral head. It may affect the function at any age, but it usually occurs in young people. For the treatment of early femoral head necrosis, the main methods include reducing the internal pressure of the femoral head, increasing the blood supply of the femoral head, and preventing or slowing the deformation of the femoral head. The porous tantalum rod has a good supporting effect on the necrotic area of the femoral head, avoids the collapse of the femoral head, and has the potential for revascularization in the necrotic area of the femoral head.
Porous tantalum artificial joint
As an artificial joint material, the porous tantalum also has obvious advantages. The porous tantalum has a certain elasticity. When it interacts with the cortical bone with a relatively large elastic modulus, it will produce slight deformation in a certain range without fracture. This property allows the porous tantalum acetabular cover to better match the bone acetabular, improving the initial stability of the implant and reducing the possibility of acetabular fractures.
The results of the clinical experiment of total knee replacement with porous tantalum showed that the structure of porous tantalum provided sufficient support, and the patient’s bone healed well. In addition, the reduction of bone mineral salt density in patients using tantalum total knee replacement is smaller than that in patients using the cobalt-chromium alloy, but the long-term clinical effect remains to be further studied. Due to the inertia of tantalum itself and the appropriate mechanical properties and good biocompatibility of porous tantalum with the human body, porous tantalum will play a greater role in the field of artificial joints.
Porous tantalum artificial joint
Porous tantalum filler material
Porous tantalum can also be used as filling material for all parts of the human body, such as tissue reconstruction after tumor resection, dissolving filling of the neck and lumbar spine, and vertebral arch replacement. Because of the nearly perfect fusion of porous tantalum in mechanical properties, tissue growth, and processing properties, it provides a wide design space for the molding of porous tantalum.
Tantalum coating
Tantalum metal has been used for its excellent corrosion resistance, and it is coated on the surface of some medical metal materials to prevent the release of toxic elements and improve the biocompatibility of the metal materials, as well as the visibility of materials in the human body. In addition to metallic materials, tantalum can be coated on non-metallic materials such as carbon cage surface tantalum for spinal fusion, the tantalum coating increases the strength and toughness of the carbon cage to fit the spine and better meet the requirements of the surgical process. Tantalum can also be coated on the surface of materials with some polymer composites to improve the visibility and biocompatibility of materials.
Since the discovery of tantalum in 1802, the understanding and development of tantalum have had a long history. Tantalum metal is characterized by corrosion resistance, hard quality, high melting point, good thermal conductivity, good affinity with the human body, and easy processing, which is widely used in the fields of metallurgy, chemical industry, atomic energy, aerospace, electronics, and medical devices.
Biocompatibility test of tantalum metal
Biocompatibility refers to the concept of various biological, physical, and chemical reactions resulting from interactions between materials and organisms. Generally speaking, it is the degree of compatibility between the material and the human body after implantation, that is, whether it will cause a toxic effect on human tissue.
The principle of biosafety is to eliminate the destructive effect of biological materials on human organs, such as cytotoxicity and carcinogenicity. If biomaterials are to be successful, they must at least be accepted by the host without harmful effects. Therefore, biological safety evaluation, that is, biological evaluation, should be carried out on biological materials.
Insoluble tantalum salt is not absorbed by the human body through oral or local injection, and the absorption amount of soluble tantalum salt in the gastrointestinal tract is very small. Once tantalum enters the body, the main carrier responsible for the removal of tantalum is phagocytes. In the body, phagocytes can survive and have no cellular degeneration after 1h exposure to tantalum dust, with only a significant increase in glucose oxidation. Under the same conditions, silica dust can cause severe cytoplasmic degeneration and death of phagocytes, indicating that tantalum is non-cytotoxic.
Through abundant domestic and foreign materials, it is found that porous tantalum has the following advantages compared with titanium alloy.
The advantages of porous tantalum nails are one with the advantages of metal materials. After implantation, as the bone tissue grows, the fixation strength of porous tantalum nail will gradually increase. Meanwhile, as the bone tissue grows, blood circulation is also introduced into the nail body, which is conducive to preventing the occurrence of fracture nonunion and femoral head necrosis. The porous tantalum nail has excellent biocompatibility with bone. It does not need to be taken out after implantation, which can effectively prevent the risk of fracture after the removal of internal fixation. Therefore, porous tantalum nail has a good long-term effect in the treatment of femoral neck fracture and has a broad application prospect in other disciplines of orthopedics and medicine.
Application case of tantalum nail
Porous tantalum nail implantation is an ideal minimally invasive surgical treatment for the treatment of early Avascular Necrosis of Femur Head (ANFH) in adults. It has unique physical and biological advantages and is expected to achieve therapeutic effects that traditional therapies do not, as well as in line with the current concept of minimally invasive. For osteonecrosis in stage Ⅰ and Ⅱ young patients, it can relieve pain and minimize complications, at least slow down or even avoid the joint replacement, but the long-term curative effect is yet to be large sample especially central level and long-term follow-up.
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 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.
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.
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.
As a kind of biomedical material, the metal material is widely used in clinical medicine because of its high suitability for mechanical properties and fatigue resistance and is suitable for the implantation of bearing parts.
However, the development of metal materials in the medical field is limited by the corrosion of materials in the human body. In recent years, tantalum metal has attracted more and more attention from medical and materials workers due to its unique advantages such as excellent corrosion resistance and biocompatibility.
Many kinds of metal materials, such as stainless steel, titanium base, and cobalt base alloy, have been widely used in the clinic and have achieved a certain therapeutic effect. However, the complex human body environment may cause the corrosion of materials and lead to the release of toxic substances, which greatly reduces the biocompatibility of metal materials. In addition, the elastic modulus of some metal materials is too different from the human bone tissue, which is not conducive to the growth and remodeling of new bone and easy to leads to secondary fracture. These adverse conditions limit the application of metal materials as biomedical materials. Tantalum, also a metal material, is attracting more and more medical workers and materials researchers with its unique advantages.
Good corrosion resistance
At room temperature, tantalum does not react with hydrochloric acid, concentrated nitric acid, or even aqua regia, and ordinary inorganic salts cannot corrode it.
Good biocompatibility
Unlike conventional medical metal materials, biological tissue grows on tantalum after a period of implantation, just as it grows on real bones. Therefore, tantalum is also known as “Biophilic Metal”
Appropriate modulus of elasticity
The elastic modulus of tantalum with a special pore structure is between the human cancellous bone and cortical bone, which is especially suitable for bone replacement, joint replacement, and human tissue filling.
Tantalum metal is very safe, and insoluble tantalum salt is not absorbed by the human body through oral or local injection; soluble tantalum salt is also absorbed very little by the gastrointestinal tract. Once tantalum enters the body, the main carrier responsible for removing tantalum is the phagocyte. After the exposure to tantalum dust for 1 hour, all phagocytes in the body can survive and have no cellular degeneration, with the only significant increase in glucose oxidation. Under the same conditions, silica dust can cause severe cytoplasmic degeneration and death of phagocytes, indicating that tantalum is not cytotoxic.
In 1940, pure tantalum metal was first used in medical treatment, and most reports believe that tantalum as a human implant did not find any adverse reactions. The application of tantalum metal mainly focuses on the use of porous tantalum, which is a honeycomb three-dimensional structure with characteristics of the human cancellous bone structure, and the average pore size of which is 430 μm and the porosity is 75%~80%. Porous tantalum can be made into various specifications and shapes. For example, porous tantalum rods can be used for the treatment of early ischemic necrosis of the femoral head; the combination of porous tantalum and human bone is firm, so tantalum can also be used in the preparation of artificial joints; the porous tantalum can also be used as filling material for all parts of the human body, such as tissue reconstruction after tumor resection, dissolving and filling of the neck and lumbar, and vertebral arch replacement.
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.
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.
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.
Tantalum is a kind of refractory nonferrous metal with a hardness of 6-6.5. Its melting point can reach 2996 ℃, which is second only to tungsten and rhenium. Tantalum is malleable and can be drawn into thin foil, and it has a very small coefficient of thermal expansion, which is only 0.6 percent for every degree rise.
Tantalum also has excellent chemical properties and is highly resistant to corrosion. Tantalum does not react with hydrochloric acid, concentrated nitric acid, and aqua regia under both cold and hot conditions. The experiments showed that tantalum did not react with the alkali solution, chlorine gas, bromine water, dilute sulfuric acid, and many other agents at room temperature, but only with hydrofluoric acid and hot concentrated sulfuric acid, which is relatively rare in metals.
Tantalum has a wide range of applications due to its excellent performance. For example, tantalum can be used as a substitute for stainless steel in the production of various inorganic acids. Besides that, tantalum can replace tasks that used to be undertaken by precious metal platinum in chemical, electronic, electrical, and other industries, thus greatly reducing the cost. Tantalum is manufactured into capacitor equipment for military use, and half of the world’s production of tantalum is used in tantalum capacitors. America’s military industry is unusually advanced, and it is the world’s largest arms exporter. The Defense Logistics Agency, the largest owner of tantalum, once bought a third of the world’s tantalum powder.
Tantalum is a kind of stable anodic oxide film in the acidic electrolyte. The electrolytic capacitor made of tantalum has the advantages of large capacity, small volume, and good reliability. Capacitor making is the most important use of tantalum, and the consumption of tantalum accounts for more than 2/3 at the end of the 1970s. Tantalum is also used to make electronic transmitter tubes and high-power tube parts. Moreover, Tantalum metal can be used as the structure of the combustor of the aircraft engine.
Tantalum and its alloys are widely used in all walks of life. Tantalum and tantalum-hafnium alloys are often used as heat-resistant, high-strength materials for rockets, missiles, and jet engines, as well as components for control and adjustment equipment. Tantalum is easy to be processed and shaped, so it is used as supporting accessories, heat shield, heater, and radiator in the high-temperature vacuum furnace. Tantalum carbide is used to make cemented carbide.
Boride, silicified, and nitride alloys of tantalum are used as heat release elements and liquid metal sheathing materials in the nuclear industry. Tantalum oxide is used in the manufacture of advanced optical glass and catalysts. In 1981, tantalum was consumed by about 73% of electronic components, 19% of the machinery industry, 6% of transportation, and 2% of the rest.
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