Tantalum VS Niobium

Tantalum and niobium belong to one family in the periodic table. Due to their similar physical and chemical properties, as well as growing together in the same ore body, they are known as the twin of metals.

Tantalum and niobium were discovered in 1801 and 1802 by Charles Hatchett, a British chemist, and Ekberg, a Swedish chemist. Tantalum niobium ore is the main ore of tantalum and niobium, and a small amount of tantalum and niobium exist in tungsten and some rare earth ores.

ta-vs-nb

Properties

Tantalum and niobium are both high-melting metals with melting points of 2996℃ and 2468℃ respectively. Tantalum and niobium have very stable chemical properties, not only insoluble in nitric acid, hydrochloric acid, but also insoluble in aqua regia. Tantalum is malleable and can be pulled into strands thinner than a human hair or rolled into foil thinner than paper. Tantalum and niobium are both excellent superconducting materials with characteristics of compression and wear resistance.

Applications

Tantalum and niobium are widely used in various fields because of their excellent properties mentioned above.

1. Capacitor

Tantalum can form a compact and stable amorphous oxide film with high dielectric strength, so it is easy to control the anodic oxidation process of capacitor accurately and conveniently. Tantalum powder sintered blocks can obtain a large surface area in a small volume, so tantalum capacitors are the most excellent capacitors with small volume, large capacity, low leakage current, long service life, and excellent comprehensive performance. Under normal conditions, tantalum capacitors are smaller in size, higher in capacity and more stable in function than ceramic capacitors, aluminum capacitors, and thin film capacitors.

tantalum-vs-niobium

Tantalum capacitors have excellent characteristics that cannot be compared with many other capacitors. In the field of microelectronics science and surface mount technology, there is almost no other equivalent capacitor to compete with them. Therefore, 60~ 65% of tantalum is used in the manufacture of tantalum capacitors in the form of capacitor grade tantalum powder and tantalum wire.

Compared with tantalum, the main disadvantages of niobium capacitors are large leakage current (generally 5-10 times of tantalum), low breakdown voltage (< 10V) and low operating temperature (< 105℃), which are not suitable for capacitors with high-reliability requirements and high rated voltage. However, in the range of low voltage (< 10V) and large capacity (> 100muf), niobium capacitors may partially replace tantalum capacitors of the same level.

2. Metallurgical industry

In the metallurgical industry, niobium is mainly used to manufacture high-temperature resistant alloy steel and improve the strength of steel. In the smelting of carbon steel, the strength of the steel can be increased by more than one third by adding only a few parts per million of niobium. Superalloys made of niobium, tantalum, tungsten, aluminum, nickel, cobalt, vanadium and other metals are good structural materials for supersonic jet aircraft, rockets, and missiles.

superalloy

3. Mechanical industry

In the mechanical industry, the cutting tool made of carbides such as niobium carbide and tantalum carbide can withstand the high temperature of nearly 3000℃, and its hardness can be comparable with that of the diamond, the hardest substance in the world.

4. Biomedical industry

Tantalum is an ideal bio-adaptive material in medicine. When it comes in direct contact with human bones, muscle tissues, and fluids, it can adapt to biological cells and has an excellent affinity with almost no human stimulation and side effects. Tantalum can not only be used to make bone plates, screws and clamping rods for fracture treatment, but also can be directly used to repair bones with tantalum plates and pieces and replace broken bones due to trauma with tantalum strips. Tantalum wire and foil can be used to suture nerves, muscles and blood vessels above 1.5 mm, while the extremely thin tantalum wire can replace tendons and even nerve fibers.

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

Why Do Electrolytic Capacitors Explode?

If you want to know why the electrolytic capacitor explodes, first you have to know what the electrolytic capacitor is. An electrolytic capacitor is a kind of capacitance. The metal foil is the positive electrode (aluminum foil or tantalum foil), and the oxide film (aluminum oxide or tantalum oxide), which is closely attached to the metal, is the dielectric. The cathode consists of conductive material, electrolyte (which can be liquid or solid) and other materials. Because the electrolyte is the main part of the cathode, the electrolytic capacitor is hence named. At the same time, the capacitance of the electrolytic capacitor cannot be connected wrongly.

Capacitors-explode

Tantalum electrolytic capacitor mainly consists of sintering solid, foil winding solid, sintering liquid, and so on. The sintered solids account for more than 95% of the current production and are mainly composed of non-metallic sealed resin.

The aluminum electrolytic capacitor can be divided into four types: the lead type aluminum electrolytic capacitor; Horn type aluminum electrolytic capacitor; Bolted aluminum electrolytic capacitor; Solid aluminum electrolytic capacitor.

The possible reasons for the capacitor explosion are as follows:

  1. The breakdown of the internal components of the capacitor is mainly due to the poor manufacturing process.
  2. The capacitor is damaged by insulation to the shell. The high voltage side of the capacitor is made of a thin steel sheet. If the manufacturing process is poor, the edge is uneven with burr or serious bend. The tip is prone to corona, and the corona causes the breakdown of oil, the expansion of the case and the drop of oil. In addition, when the cover is closed, if the welding time is too long, the internal insulation burns and produces oil and gas, causing the voltage to drop greatly and damage.
  3. Poor sealing and oil leakage. The insulation resistance is reduced due to the poor sealing of the assembly casing. Or the oil spill caused the oil surface to drop, resulting in the extreme shell direction discharge or component breakdown.
  4. The belly and the inside dissociate. Due to the internal corona, breakdown discharge, and serious dissociation, under the action of overvoltage, the starting free voltage of the element is reduced to the working electric field intensity. This causes the physical, chemical and electrical effects to accelerate the aging and decomposition of the insulation, producing gas and forming a vicious circle, the pressure of the case is increased, causing the drum to explode
  5. A capacitor explodes with an electric charge. All capacitors with rated voltages are forbidden to be charged. Each time the capacitor bank recloses, the capacitor must be discharged for 3min after the switch is disconnected. Otherwise, the voltage polarity of the closing moment may be caused by the opposite polarity of the residual charge on the capacitor. For this purpose, a capacitor bank with a capacity of more than 160kvar is generally required, and automatic tripping device should be installed when there is no pressure. And the capacitor bank switches are not allowed to install automatic reclosing.

In addition, it may be caused by high temperature, poor ventilation, high operating voltage, excessive voltage harmonic component or operating overvoltage, etc.

Stanford Advanced Materials (SAM) is a leading supplier and manufacturer of high-quality capacitor grade tantalum powder and tantalum wire with competitive price and great delivery time. Please visit http://www.samaterials.com for more information.

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 underetch, 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, by chemical vapor deposition, or by thermal oxidation. This makes the use of these materials very flexible.

Please visit http://www.samaterials.com for more information.

How is the Tantalum Made?

Tantalum is a sensible choice whenever high corrosion resistance is required. This platinum-gray colored metal has a density of 16.6 g/cm3 which is twice as dense as steel. With its combination of specific physical and chemical properties, tantalum is an important product in many applications. Do you know how tantalum is made?

Tantalum
Tantalum

Tantalum smelting process

Tantalum niobium ore is the main raw material for the production of tantalum, but it is often associated with a variety of metal, so the main step is the decomposition of tantalum smelting concentrates, purification and separation of tantalum and niobium, produced the pure compound of tantalum and niobium, finally, we can produce metal.

To achieve ore–decomposition, we can use hydrofluoric acid decomposition method, sodium hydroxide melting method and chlorination. The method can be used in the separation of tantalum and niobium by solvent extraction, fractional crystallization, and ion exchange method.

Preparation of tantalum

The preparation of tantalum is the process of reducing pure tantalum compound to metal tantalum. The raw materials are five tantalum oxide, tantalum chloride, five tantalum fluoride and fluoride (such as K2TaF7,). The reducing agent is sodium, magnesium and other active metals and carbon and hydrogen. The melting point of tantalum is as high as 3669K, so it is a powder or spongy metal after reduction. It is necessary to further smelting or refining, in order to get dense metal.

The tantalum preparation methods are sodium thermal reduction, carbon thermal reduction, and molten salt electrolysis. Sodium thermal reduction of potassium tantalate is the most widely used method of tantalum production in the world.

tantanlum-powder
Tantalum-powder

The tantalum powder has a complex shape and large specific surface area. Carbon thermal reduction of five oxidation of tantalum has been an industrial method for the production of tantalum, but because the purity of the product is not high enough, is not as widely used as the sodium reduction method. Molten salt electrolysis method is divided into two ways: electrolyte electrolysis and oxygen free electrolyte electrolysis. Molten salt electrolysis can only produce metallurgical grade tantalum powder. Five hydrogen fluoride reduction is considered to be one of the most promising methods for tantalum production, but it has not been used in industrial production because of the high requirements of equipment material and environmental protection.

The majority of tantalum powder is directly used for tantalum capacitors in the electronic manufacturing industry, so the tantalum milling process, such as preparation of tantalum metal is also from tantalum and tantalum powder by vacuum heat treatment, capacitor grade tantalum powder hydrogenation method category.

Sodium thermal reduction process

Sodium metal thermal reduction method is an important method for the production of tantalum powder, is the main method of industrial production of tantalum powder (including metallurgical Ta powder), the metal tantalum powder particle shape is complex, large surface area, suitable for anode material for tantalum electrolytic capacitors, by electron beam melting, vacuum arc melting of tantalum or tantalum sintered in vacuum refining, made of high purity tantalum ingot or rod, and then processed into a variety of tantalum.

In order to obtain high purity tantalum powder, in addition to the main raw material, sodium and potassium fluorotantalate diluent (or NaCl+KCI), sodium chloride (argon or helium) must reach the required purity, must also be dehydration treated strictly at different temperatures in advance. It is also necessary to carry out the vacuum heat treatment at the temperature of 598 ~ 648K. After vacuum heat treatment, potassium fluorotantalate can remove the residual organic matter and hydrogen fluoride, and became the potassium fluorotantalate grain refinement, obtained fine tantalum powder in reduction.

Since the 1970s, it has been widely used to increase the specific capacitance of tantalum powder. The commonly used doping agent is phosphate, which can be mixed before or after crystallization of potassium fluoride and can be added before the vacuum heat treatment of tantalum powder. The doping can prevent the sintering of tantalum powder during sintering of tantalum anode block, thus avoiding the reduction of the specific surface area of tantalum anode block. We can remove oxides from metal sodium with the metal-ceramic filter or cold trap method.

The process of reduction of potassium and sodium fluoride in an inert atmosphere at 1153 ~ 1173K temperature and the reduction products are metal tantalum powder, potassium fluoride, sodium fluoride and diluent which is not involved in the reaction.

Before the 1950s, the solid metal sodium and potassium fluorotantalate layer placed in the reactor of bomb explosion reduction reaction, although the product of tantalum powder is fine particle size, large surface area, the oxygen, and carbon content is high, no practical value.

In this way, the reaction period is too long, the product size is coarse, and can only be used as 3000/uF.V/g low volume tantalum powder. After improvement by liquid-solid mixed loading reaction of sodium based reduction, the production cycle is shortened 3/4 than gas-liquid reaction, tantalum powder volume increased by more than 30%, but still not ideal will be phased out.

With tantalum capacitors are small and micro, the corresponding need to adopt more surface area tantalum powder, mainly used in the liquid reduction, mainly supplemented by mixing sodium, doping technology, the volume rate of tantalum powder increased to 1000uF-V yield every year.

Capacitor-Grade-Tantalum-Powder
Capacitor-Grade-Tantalum-Powder

The fluoride was removed by dipping, and then washed with HCl18% and HF1% solution at 1 2H for 363K, then washed with pure water and dried at 353K temperature. For the preparation of capacitor grade tantalum powder, tantalum powder should be the original size distribution, vacuum heat treatment (see tantalum powder vacuum heat treatment), crushing and screening and modulation post-processing, if necessary, will also increase the magnesium reduction deoxygenation, pickling, washing and plastic processing, in order to obtain high quality and low and high specific capacitance of capacitor grade tantalum powder.

It is expected that the continuous improvement and development of tantalum powder produced by sodium reduction is the result of the miniaturization, miniaturization and cost reduction of electronic products. Since the 1960s, the specific capacitance of tantalum powder has been increasing, and the capacitance ratio of tantalum powder has reached 22000~26000uF•V/g in the United States, Japan, Germany, and other countries.

Please visit http://www.samaterials.com for more information.