زعيم المعادن التنتالوم المعادن الطبية الحيوية
Tantalum metal
The excellent mechanical properties, ease of processing and reliability of biomedical metal materials have been widely used in clinical medicine, and their importance keeps pace with biomedical polymer materials, each accounting for about 45% of the entire application of biomedical materials.
After clinical application of metal medical materials, the main problem is biocompatibility, which stems from metal corrosion and wear. Because metal materials contain more alloying elements, metal ions will dissolve due to corrosion and wear, which will trigger some biological reactions in cells and tissue fluids, such as tissue reactions, blood reactions and systemic reactions, manifested as edema, thromboembolism, infections and tumors.
01 The particularity of the human body environment
The body fluid of the human body is about 1% sodium chloride and a small amount of other salts and organic compounds. The local acidity and alkalinity often change slightly, and the temperature is kept at about 37°C.
This environment will corrode metal materials, and its corrosion products may be ions, oxides, chlorides, etc., which come into contact with adjacent tissues, and even penetrate into normal tissues or the entire biological system, affecting and stimulating normal tissues. Cause adverse biological reactions including abnormal tissue growth, distortion, allergy or inflammation, infection, and even induce cancer. Corrosion can attenuate the mechanical properties of the material at the same time, and these two processes usually cause the failure of the material alone or together. Therefore, as a biomedical metal material, two basic conditions must be met first: the first is non-toxic; the second is physiological corrosion resistance.
02 The performance of metal materials implanted in the human body
After biomedical metal materials are implanted into the human body, it is generally hoped that they can permanently or semi-permanently perform physiological functions in the body. The so-called semi-permanent metal artificial joints last at least 15 years. In such a long period of time, the metal surface is more or less Few ions or atoms will enter the surrounding biological tissues due to corrosion or wear. Therefore, whether the material is toxic to biological tissues becomes a necessary condition for material selection.
At present, medical metal materials commonly used in clinical applications mainly include stainless steel, cobalt alloys, titanium alloys, shape memory alloys, precious metals and pure metals such as tantalum, niobium, and zirconium. The properties of these materials during application are as follows.
stainless steel material
The biocompatibility and related issues of medical stainless steel mainly involve the tissue reaction caused by the dissolution of metal ions caused by corrosion or wear after stainless steel is implanted into the human body.
Corrosion will cause metal ions or other compounds to enter the surrounding tissue or the whole body, which can cause some adverse histological reactions in the body, such as edema, infection, tissue necrosis, etc., resulting in pain and allergic reactions. Especially severe lesions induced by the precipitation of nickel ions in stainless steel (commonly used austenitic medical stainless steel contains about 10% nickel).
cobalt alloy material
Cobalt alloys mostly maintain a passivation state in the human body, and corrosion is rare. Compared with stainless steel, its passivation film is more stable and its corrosion resistance is better. It is generally believed that there is no obvious histological reaction after implantation in the human body.
However, due to the high price of cobalt alloy, and the artificial hip joint made of cobalt alloy is caused by the dissolution of Co and Ni plasma due to metal wear and corrosion, the loosening rate in the body is high, and the precipitated Co and Ni elements have serious sensitization and other biological effects. Due to medical problems, it is easy to cause cell and tissue necrosis in the body, resulting in pain in patients and joint loosening and sinking, so the application is limited to a certain extent.
Titanium alloy material
The density of titanium and titanium alloys is about 4.5g/cm3, which is almost half of that of stainless steel and cobalt alloys. The density is close to that of human hard tissues, and its biocompatibility, corrosion resistance and fatigue resistance are better than stainless steel and cobalt alloys. , is currently the best metal medical material. The affinity of titanium and titanium alloys with the human body stems from the ability of the dense titanium oxide (TiO2) passivation film on its surface after implantation to induce the deposition of calcium and phosphorus ions in body fluids to form apatite, showing certain biological activity And osseointegration ability, especially suitable for intraosseous implantation.
The disadvantages of titanium and titanium alloys are low hardness and poor wear resistance. If wear occurs, it will first lead to the destruction of the oxide film, and then the corrosion products of the wear particles will enter the human tissue, especially the toxic vanadium (V) contained in the Ti-6A1-4V alloy can lead to the failure of the implant.
Shape Memory Alloys
The most widely used clinical shape memory alloys are nickel-titanium shape memory alloys. The shape memory recovery temperature of medical nickel-titanium shape memory alloy is 36±2°C, which is in line with human body temperature, and clinically shows biocompatibility comparable to that of titanium alloy.
However, since nickel-titanium memory alloy contains a large amount of nickel element, if the surface is not properly treated, the nickel ions may diffuse and penetrate into the surrounding tissue, causing cell and tissue necrosis.
Tantalum metal material
Tantalum will spontaneously oxidize in the air or during processing to form a dense Ta2O5 oxide layer. The oxide layer is non-conductive, so that the solubility of tantalum material is very low at all pH values and potentials, and it is not easy to be corroded in acid environment, thus showing very strong biological inertness, chemical stability and physiological corrosion resistance in vivo.
Therefore, compared with stainless steel, Co-Cr alloy, titanium alloy and other metal materials that are easy to corrode and produce metal ions or particles in the body fluid environment, the excellent corrosion resistance of tantalum makes it suitable as a biocompatible material. Bone implant material, used as bone plate, implant root, denture, cardiovascular stent and artificial heart, etc.
03 Tantalum Surface Alloy Technology
The advantages of tantalum metal in medical implant metals are needless to say, but as a rare metal, tantalum reserves in the earth are not much, which directly leads to the high price. Due to price constraints, the application of tantalum has been greatly restricted.
Zhuohangxin Metal Materials Co., Ltd. Tantalum Application Technology Co., Ltd. has been committed to the development of tantalum surface alloy technology for many years. By making tantalum alloys on the surface of ordinary materials, the equipment is endowed with high performance comparable to pure tantalum and niobium products. The emergence of this technology has perfectly solved the problem of the cost of tantalum metal, making the application of tantalum popular and widespread no longer a dream
1. Tantalum metal has 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 metal materials. At the same time, tantalum coating also improves the biocompatibility of materials in the human body. visibility.
2. Tantalum coating can improve the osseointegration performance of titanium metal, enhance the adhesion ability of cells, and promote the growth of cells.
3. The higher surface energy and better wettability of tantalum coatings improve the interaction between cells and implanted materials.
4. In addition to metal materials, tantalum can also be coated on the surface of some non-metallic materials, such as carbon cage surface coated with tantalum for spinal fusion, tantalum coating improves the strength and toughness of carbon cage to be suitable for spinal load and more well meet the requirements of the surgical procedure.
Chemical Properties of Tantalum
Tantalum also has very good chemical properties and is extremely resistant to corrosion. No matter in cold or hot conditions, it has no reaction to hydrochloric acid, concentrated nitric acid and "aqua regia". Soak tantalum in sulfuric acid at 200°C for one year, and the surface layer will only be damaged by 0.006mm. Experiments have proved that tantalum has no effect on alkaline solution, chlorine gas, bromine water, dilute sulfuric acid and many other agents under normal conditions, and only reacts under the action of hydrofluoric acid and hot concentrated sulfuric acid. Such cases are relatively rare in metals.
The use of metal tantalum
The characteristics of tantalum make its application field very broad. In the equipment for preparing various inorganic acids, tantalum can be used to replace stainless steel, and the service life can be dozens of times longer than stainless steel. In addition, in chemical, electronic, electrical and other industries, tantalum can replace the tasks that used to be undertaken by the precious metal platinum, which greatly reduces the required cost. In addition, tantalum is also an important element for refining super-strength steel, corrosion-resistant steel and heat-resistant steel alloy, which can provide special materials necessary for the development of rockets, spacecraft, jet aircraft and other space technologies. Non-magnetic alloys made of tantalum and tungsten are widely used in the electrical industry, especially tantalum carbide composed of tantalum and carbon, which has great hardness and is comparable to diamond even under high conditions. Turning tools made of it can cut many hard alloys at high speed; various drill bits made of it can replace the hardest alloy or diamond. Therefore, tantalum is also considered a "vitamin" in smelting. In modern medicine, tantalum can also play an important role. Studies have proved that tantalum is not only harmless to the human body, but also the muscles of the human body can grow on it, which is called biocompatibility in medicine. Doctors use this property of tantalum to repair and seal cracks and defects in broken skulls and limb fractures. At the same time, tantalum can also be made into filaments one-tenth thinner than hair, used as sutures for visceral surgery, or embedded in artificial eyeballs. This tantalum wire can even replace tendons and nerve fibers. Doctors use tantalum plates to make artificial ears, install them behind the head, and then transplant skin from the legs. After a period of time, the newly transplanted skin grows so well that it is almost impossible to see that it is an artificial tantalum ear.
Applications of Tantalum Products
(1) Tantalum is used to make tantalum capacitors: tantalum powder and tantalum wire are the key materials for making tantalum capacitors, and tantalum capacitors are the best capacitors. Niobium can also be used to make capacitors.
(2) Tantalum is used to make high-resistant tantalum products: tantalum has high resistance, good strength and rigidity, and is a high-quality material for making heating parts, heat insulating parts and charging vessels for vacuum blast furnaces.
(3) Tantalum and niobium are used to make corrosion-resistant tantalum and niobium products: tantalum and niobium are high-quality materials resistant to acid, alkali and liquid metal corrosion. They can be used in the chemical industry to make digesters, heaters, coolers, and various utensils.
(4) Application of tantalum and niobium in the aerospace industry: used to make engine components for aerospace aircraft, rockets, submarines, etc., such as combustion chambers, combustion ducts, turbo pumps, etc. For example, WC-103 Nb-Hf-Ti high-niobium-based alloy is a high-quality aerospace material, which is used as a rocket accelerator nozzle, a spacecraft propulsion booster and a nozzle valve.
(5) Tantalum is used to make linings for armor-piercing projectiles: this application is currently mainly in the United States, and it is a type of missile, such as the TOW2B missile
(6) Tantalum carbide as an additive to cemented carbide: cemented carbide is mainly used as knives, tools, molds and wear-resistant and corrosion-resistant structural components. Adding TaC can improve its hardness, strength, melting point and other properties. NbC can also be used in this way, and its performance is inferior to TaC.
(7) Niobium is the main additive of steel. Niobium-added micro-alloy steel can refine the steel grains and improve the strength and toughness of the steel. About 75% of niobium is used in this field.
1. Characteristics of tantalum
Tantalum is a bluish light gray metal with a hard texture, a density of 15g/cm3, a melting point of 3014°C, and an elastic modulus of 186-191GPa. After cold working, the tensile strength of tantalum is 200-300MPa, the elongation is 10-25%, and it has good ductility and toughness. Compared with other metal materials, tantalum has two obvious advantages:
(1) Excellent corrosion resistance. At room temperature, tantalum does not react chemically with hydrochloric acid, concentrated nitric acid or even "aqua regia", and general inorganic salts do not react with tantalum;
(2) Excellent biocompatibility. After tantalum is implanted in the body for a period of time, biological tissues are easy to grow on the surface of tantalum, so tantalum is also called "biophilic metal". These two advantages of tantalum have attracted the attention of the material science and medical circles, making metal tantalum a promising development direction in the field of biomedical materials.
2. The biological basis of tantalum
Insoluble tantalum salts will not be absorbed by the body through oral or local injection, and soluble tantalum salts will be absorbed very little from the gastrointestinal tract. After tantalum enters the human body, phagocytic cells in the body can survive and have no cell degeneration after 1 hour of contact with tantalum dust, only accompanied by a significant increase in glucose oxidation. Under the same conditions, silica dust can cause severe cytoplasmic degeneration and death of phagocytes, which shows that tantalum is non-cytotoxic. In 1940, tantalum metal was first used in orthopedic medicine, and most reports believed that no adverse reactions were found when tantalum was used as a human implant.
3. Application of tantalum as an implant
1) 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 cracks and defects of broken skulls and limb fractures. Someone once used tantalum sheets to make artificial ears and fixed them on the head, and then transplanted skin from the legs. After a period of time, the newly transplanted skin grew very well, and it was almost impossible to see that it was an artificial tantalum ear.
2) Porous tantalum rod
Porous tantalum rod is a honeycomb three-dimensional rod-shaped material with the characteristics of human cancellous bone structure, with an average pore size of 430µm and a porosity of 75-80%. Its elastic modulus can be adjusted between cancellous bone and cortical bone to avoid stress shielding effect. The implantation of porous tantalum rods is mainly used for the treatment of avascular necrosis of the femoral head in the early and middle stages. It has a good supporting effect on the necrotic area of the femoral head, can avoid the collapse of the femoral head, and has the potential to revascularize the avascular necrotic area of the femoral head. Porous tantalum can promote cell proliferation and improve the bone-building ability of osteoblasts.
3) Porous tantalum artificial joint
Porous tantalum has a certain degree of elasticity, so the porous tantalum joint can match well with human bone tissue, improve the initial stability of the implant, and reduce the possibility of acetabular fracture. In addition, the coefficient of friction of porous tantalum is larger than that of other porous materials, which is beneficial to the initial stability after implantation. At present, there have been related clinical research reports on hip joints, knee joints, femoral cones, and combined joints of tibia and patella [14-17] made of porous tantalum.
4) Porous tantalum filling material
Porous tantalum can also be used as a filling material for various parts of the human body, such as tissue reconstruction after tumor resection, cervical and lumbar dissolution and filling, and vertebral arch replacement. Due to the many advantages of porous tantalum in terms of mechanical properties, processing properties and biological properties, porous tantalum has broad development space as a filling material.
