Lisa K.Ross – Page 3 – Zirconium Metal

4 Methods for Making Metal Zirconium

Zirconium and its alloys not only have good machinability, moderate mechanical strength, and high corrosion resistance, but also have a low neutron cross-section. In the nuclear energy industry, they are widely used as structural materials for water reactors. Zirconium widely exists in zircon, so most methods of preparing metal Zr use zircon as a raw material for extracting zircon. This article will mainly introduce four methods for purifying zirconium.

Metal Thermal Reduction Method

The reducing agents used in the thermal reduction method are mainly calcium and magnesium.

(1) Calcithermic reduction

Using ZrO2 as raw material and calcium as a reducing agent, the reduction reaction is carried out at 1273-1373K under vacuum. The reduction product is a powdery mixture of Zr, CaCl2, CaO, and Ca, which can be pickled, washed with water, filtered, dried, and sieved to obtain metal zirconium.

(2) Magnesium reduction method

The magnesium reduction method mainly includes steps such as the preparation of zirconium tetrachloride, purification, magnesium reduction, and vacuum distillation. Chloride zirconium dioxide or zircon sand to obtain zirconium tetrachloride, purify, remove impurities such as SiCl4, TiCl4, AlCl3, FeCl3, and then use molten magnesium to reduce ZrCl4 to obtain a mixture of metal zirconium, magnesium, and magnesium chloride, and finally, Zirconium metal is obtained by distillation and purification.

Hydrodehydrogenation

This method uses the reversible absorption characteristics of zirconium to hydrogen to prepare zirconium powder. At a certain temperature, zirconium and zirconium alloys absorb hydrogen to form hydrides or solid solutions. When reaching a certain level, the material will produce microcracks, become brittle, and contain a lot of hydrogen. Such powder is called zirconium hydride powder. Zirconium hydride powder is dehydrogenated under high temperature and vacuum conditions to obtain zirconium powder. After years of improvement and promotion, this method has become the main method for producing zirconium powder.

Molten Salt Electrolysis

Metals or alloys that are difficult to electrodeposit in an aqueous solution usually use molten salt electrodeposition. Insoluble anodes are usually used, stainless steel or other refractory metals are used as cathodes, and molten salts of electrodeposited metals and alkali metal chlorides or fluorides are used as electrolytes. During the electrolytic reduction process, they are decomposed by the electrolytic metal molten salts. and deposited at the cathode.

Direct Electro-Deoxidation Method

The direct electro-deoxidation method uses a single or mixed metal oxide as the raw material, presses it into a block as the cathode, removes the oxygen in the cathode by electrolytic deoxidation, and obtains a metal element or alloy with low impurity content in a high-temperature molten salt, also known as FFC Law. The metals successfully prepared by the FFC method include Zr, Hf, Be, Mg, Ca, Ba, V, Nb, W, Fe, and Cu.

Among the four methods, the magnesium reduction method and hydrogenation-dehydrogenation method are the main production methods in the industry.

For more information about zirconium materials, please visit https://www.samaterials.com/.

The Importance of Surface Coatings for Zirconium Alloy Cladding

Safety Issues in The Application of Zirconium Alloys

In the past few decades, zirconium alloy cladding has been successfully applied to light water reactors (LWR), and has shown good radiation resistance and corrosion resistance. However, a major problem in the application of zirconium alloys in stacks is that they react violently with water vapor at high temperatures, and when the temperature is greater than 1200 °C, a large amount of hydrogen and heat will be released. After the Fukushima nuclear power accident in Japan, the safety of nuclear power has once again been placed in front of all nuclear workers. How to further improve the safety and reliability of light water reactor nuclear fuel elements under accident conditions has become an urgent problem to be solved. Research and development directions include accident-resistant fuel cores and accident-resistant cladding materials.

Cladding Material for Zirconium

The accident-resistant cladding material has good thermodynamic properties, which can improve the reaction kinetics of zirconium and water vapor and reduce the hydrogen release rate. The development of this material is mainly reflected in two aspects: one is to improve the high-temperature oxidation resistance and strength of the zirconium alloy cladding; the other is to develop non-zirconium alloys with high strength and oxidation resistance. This paper discusses the research on the surface coating of zirconium alloy cladding for the former.

The main advantage of the application of coated zirconium cladding is economical. The technical challenge it faces is to meet various performance requirements of the fuel cladding and components without changing the size of the fuel cladding. During long-term operation, the coating should have certain stability under corrosion, creep, and abrasion conditions.

Research Status of Zirconium Alloy Cladding Surface Coating

The anti-oxidation coating technology on the surface of zirconium alloy is the main method to improve the anti-oxidation ability of the surface of zirconium cladding. The outer surface of the zirconium alloy is coated with a layer of material to enhance the wear resistance and high-temperature oxidation resistance of the cladding, thereby improving the accident resistance of the zirconium cladding under normal working conditions and accident conditions. At present, some preliminary screening results have been obtained in international research on the surface coating of zirconium alloy cladding, and the coating materials mainly involve MAX phase and metal Cr.

MAX-phase coating

A series of studies have shown that:

The essence of the MAX phase coating is the dressing effect, and the key to the problem is to solve the diffusion of oxygen atoms to the zirconium substrate.
No matter whether in a fast neutron reactor or thermal neutron reactor, under the three activation time conditions, the activity of MAX phase material is similar to that of SiC, but three orders of magnitude lower than that of 617 alloys.
The thickness of the MAX phase coating should be controlled at 10~30 μm to limit the loss of neutrons.
Ti3SiC2 shows better prospects than Ti2AlC as a candidate material for MAX-phase coatings for high-temperature nuclear energy applications.
At room temperature, the radiation resistance of Ti3AlC2 is better than that of Ti3SiC2, and the radiation stability of the two MAX phase materials at 600 ℃ is better than that at room temperature.

Metal Cr Coating

A series of studies have shown that:

The high-temperature oxidation resistance of the coated zirconium alloy is obviously better than that of the Zr-4 substrate.
The high-temperature oxidation resistance of the coated zirconium alloy is significantly stronger than that of the zirconium alloy substrate, and the Cr-coated zirconium cladding has better ductility.
The metal Cr coating has good high-temperature oxidation resistance and can be used as a candidate coating material for accident-resistant zirconium alloy cladding.

For more information about zirconium materials, please visit https://www.samaterials.com/70-zirconium.html.

If you are interested in coating materials, you can find more information at https://www.sputtertargets.net/.

3 Manufacturing Methods of Zirconium-containing Refractories

What is Zirconium-containing Refractory Material?

Zirconium-containing refractory materials are made of zirconia (ZrO2) and zircon (ZrSiO4) as raw materials. “Zirconium-containing” usually refers to materials containing the following zirconium products: zirconia, zircon, zirconium mullite and zirconium corundum. Zirconium-containing products have good corrosion resistance to various molten metals, acidic reagents and liquid glass.

Zirconium-containing refractory materials can be divided into the sintered, fused cast, and non-fired products based on different manufacturing methods.

What are the Different Manufacturing Methods?

Sintered Zr-Containing Refractory Product

The basic steps to manufacture zirconium-containing sintered bricks are to prepare raw materials, press green bodies, and sinter at high temperatures.

Another method is to obtain blanks by granulation, kneading, machine pressing or extrusion molding, and the clinker fired at high temperature is used as aggregate, and the clinker fine powder is used for batching, kneading, molding, drying, and sintering to finally obtain the finished product.

Cast Zr-Containing Refractory Product

1) Use zircon concentrate or industrial zirconia and industrial alumina powder as raw materials.

2) Add sodium oxide, calcium oxide, boron oxide and rare earth metal oxides as additives.

3) The powder is melted at a temperature above 2500°C by means of electric arc melting, cast in a mold, cooled, annealed, and machined.

Non-fired Zr-Containing Refractory Product

The manufacturing process of zirconium-containing refractory products without firing is simple, and the product qualification rate is high.

1) Use stabilized zirconia clinker or zircon as raw material.

2) Use water glass, phosphoric acid, phosphate, or sulfate as the cementing agent.

3) Mix the raw materials and cementing agents, and undergo high-pressure molding and low-temperature heat treatment to make zirconium-containing non-fired materials.

The heat treatment temperature varies with different binders. When aluminum dihydrogen phosphate is used as the cement, the heat treatment temperature is about 300°C; when phosphoric acid is used as the cement, the heat treatment is carried out at a temperature of about 600°C.

What Are These Products Used for?

Zirconium-containing refractory products can be widely used in metallurgy, building materials, the chemical industry, machinery and other professional fields due to their high refractoriness, mechanical strength and chemical stability.

Zirconia bricks can be used in thermal equipment in the building materials industry and metallurgical industry, such as billet continuous casting sizing nozzles, submerged nozzles and slag lines in long nozzles.
Zircon bricks are resistant to low-alkali glass corrosion. They can be used for the kiln wall of the glass melting furnace, as well as the arch feet of the upper structure of the glass melting furnace or the intermediate transition layer between silica bricks and corundum bricks.
Zirconia-mullite fused cast bricks can be used in heating furnaces, soaking furnaces in the metallurgical industry, glass melting furnaces in the building materials industry, etc.
Zirconium corundum bricks have good resistance to melt erosion. As a high-grade abrasive, it has a good grinding effect on steel, cast iron, heat-resistant steel, and various alloy materials.

If you want to know more about zirconium material, we would like to advise you to visit Stanford Advanced Materials (SAM) for more information.

10 Common Zirconium Products and Their Applications

1. Zirconium Silicate

Zirconium silicate is an important variety in traditional zirconium products. The product is made of zircon sand, which can be obtained after grinding, calcining and powdering. It is a high-quality and cheap opacifying agent for ceramic glazes.

Zirconium silicate is mainly used for color glazes of architectural ceramics, daily-use ceramics and electric porcelain. It is also widely used in high-grade refractory materials, precision casting, emulsified glass and other industries.

2. Zirconium Carbonate

Zirconium carbonate is a source of zirconium that is insoluble in water but is easily transformed into other zirconium compounds. It is mainly used as an additive for cosmetics, waterproofing agent, flame retardant, opacifying agent, and surface aid for fibers and paper, and can also be used to prepare zirconium-cerium composite catalytic materials. It is an important raw material in the textile, papermaking, paint, and cosmetic industries, and its consumption has been increasing in recent years.

3. Zirconium Oxychloride

Zirconium oxychloride is the main raw material for the production of other zirconium products such as zirconium dioxide, zirconium carbonate, zirconium sulfate, composite zirconium oxide, and the separation of zirconium and hafnium to prepare metal zirconium and hafnium. In addition, it can be used in textiles, leather, rubber additives, metal surface treatment agents, paint drying agents, refractory materials, ceramics, catalysts, fire retardants, and other products. The primary source material for zirconium oxychloride is zircon sand.

4. Fused Zirconia

Fused zirconia is mainly used in the production of glazes and refractory materials. Due to the high content of impurities in fused zirconium, its use is sometimes limited.

5. Zirconium Sulfate

Zirconium sulfate is an intermediate raw material for the production of zirconium chemicals and metal zirconium and hafnium. It is also an important raw material for the production of leather tanning agents, wool treatment agents and paint surface oxidants. Additionally, it can be used as a catalyst carrier, amino acid and protein, precipitant and deodorant.

Consumption Structure of Zirconium Products

6. Zirconium Dioxide

Zirconium dioxide, or zirconia, is a non-toxic, odorless white solid. It has sufficient stability in alkaline solutions and many acidic solutions. ZrO2 ceramic is suitable for precision ceramics, electronic ceramics, optical lenses, glass additives, electrolytic zirconia bricks, ceramic pigments, enamel, artificial gemstones, refractory materials, grinding and polishing and other industries and products.

7. Composite Zirconia

Composite zirconia, referring to stabilized zirconia, is a non-toxic, odorless white powder. It has stable chemical properties and controllable specific surface area. It is the basic raw material for the manufacture of various special ceramics, advanced refractory materials, optical communication devices, and new energy materials.

8. Nuclear Grade Zirconium

Nuclear-grade zirconium is mainly used as the structural material of nuclear-powered aircraft carriers, nuclear submarines, and civil power reactors, and the cladding of uranium fuel elements. It is an important strategic metal.

9. Industrial Grade Zirconium

Industrial-grade zirconium is mainly used in the production of chemical acid and alkali-resistant equipment, the military industry, the electronics industry, pipeline valve materials, special high-strength, and high-temperature alloy materials, and getters for electric vacuum and lighting bulb industries.

10. Metallurgical Grade Zirconium

Metallurgical grade zirconium is used as a firearms sponge zirconium combustion agent and is also suitable for alloy additives and metallurgical deoxidizers, the chemical industry, civilian flash fireworks, etc.

Comparison of zirconia ceramic teeth and metal ceramic teeth

Broken or missing teeth usually require fillings. The two conventional options are zirconia ceramic teeth and metal-ceramic teeth. This article will analyze the difference between the two and help those in need to choose the one that suits them.

Metal ceramic teeth

Metal-ceramic crowns are accepted by most patients because of their good strength, but they have many disadvantages. The metal substrate is easily oxidized to form gray oxides, which are scattered and deposited on the edge of the gums, causing the gums to turn gray and affecting the appearance; at the same time, metal porcelain teeth may have a strong stimulating effect on the gums, and even cause gum swelling, bleeding, allergies and other symptoms; the color of the metal-ceramic crown should be covered with opaque porcelain, so that the ceramic crown can block the light to a certain extent, thus affecting the aesthetics of the teeth.

Zirconia all-ceramic teeth

At present, there are many types of all-ceramic dental materials, such as leucite, lithium-based porcelain, alumina, zirconia, etc. There are also a variety of fabrication methods, such as infiltrated ceramics, hot pressure casting ceramics, porcelain deposition, computer-aided design, and computer-aided fabrication. In comparison, among all all-ceramic restoration materials, zirconia material has higher flexural strength, so it is accepted by more and more patients and doctors.

Zirconium dioxide all-ceramic crown has its own unique advantages. Since there is no metal bottom crown, its restoration has permeability and aesthetics, which provides a guarantee for aesthetic restoration. At the same time, zirconium dioxide has strong biocompatibility and is non-irritating to the gums. Most patients will not experience symptoms such as gum swelling, bleeding, and allergies, which meet the clinical requirements.

Advantages of zirconium dioxide

(1) Good mechanical properties: it has a flexural strength greater than 900MPa, so it can also be used for the repair of posterior teeth and porcelain bridges with more than 6 units.

(2) Good biocompatibility: The zirconia all-ceramic crown itself does not contain metal, which can exclude metal allergic reactions; zirconia also has good biocompatibility.

(3) No obstruction to X-rays: There is no need to remove the dentures when performing cranial X-rays, CT, and MRI examinations, because zirconia ceramic teeth have no obstruction to X-rays.

(4) Good strength and density: Zirconium dioxide is widely used, especially in high-precision instruments, such as aviation equipment. Because of its good crack resistance and tough curing after cracking, it can be made into a porcelain bridge with more than 6 units, and it can also solve the problem that the all-ceramic system cannot be used as a long bridge.

(5) The color is comparable to real teeth: the color of the base crown of the ceramic is white, so the neck of the porcelain tooth will not become black and darkened for a period of time after the porcelain tooth is inserted, thus avoiding the problem of discoloration of the metal porcelain crown.

(6) Healthy biological material: Zirconium dioxide is an excellent high-tech biological material with good biocompatibility, which is healthy and safe to use.

(7) High-tech quality: Zirconium dioxide ceramic teeth are made by good computer-aided design, laser scanning, and then controlled by computer-aided program grinding.

Hopefully, the above analysis will help you a lot in making your choice between metal ceramic teeth and ceramic teeth.

Purification of Zirconium by Vacuum Distillation

Vacuum distillation refers to the process of removing metal magnesium and MgCl2 in sponge zirconium by distillation under the condition of lower pressure than normal pressure. The zirconium sponge produced by distillation is then vacuum cast into metal or alloy, which is used in industrial sectors such as atomic energy, metallurgy, and chemistry.

Principle of Vacuum Distillation

The raw material of vacuum distillation is generally the product of the reduction of zirconium tetrachloride and magnesium, containing 55% to 60% of zirconium, 25% to 30% of magnesium, 10% to 15% of MgCl2 and a small amount of Zrcl3 and ZrCl2.

The vapor pressures of these components are different at a certain temperature and pressure. For example, in the standard state, the boiling point of magnesium is 1380K, MgCl2 is 1691K, and zirconium is 4673K; at normal pressure and 1173K temperature, the equilibrium vapor pressure of magnesium is 13332.2Pa, MgCl2 is 999.9Pa, and zirconium is less than 130μPa. Therefore, by controlling the appropriate distillation temperature and pressure, zirconium and other components can be separated.

In addition, under a 10Pa vacuum, the boiling points of magnesium and magnesium chloride dropped to 789K and 950K, respectively, and the volatilization rate was many times greater than that of atmospheric distillation. Therefore, the use of vacuum distillation can shorten the distillation time, reduce the distillation temperature, improve the separation effect, and avoid the formation of Zr–Fe alloys that contaminate the zirconium sponge and iron.

System for vacuum distillation

The vacuum distillation system is mainly composed of a distillation furnace, a distillation tank, a condensation sleeve, a condenser, a heat shield, and a vacuum system.

According to the installation position of the condenser, it can be divided into two types: upper cooling type and lower cooling type, and the structure of the two is basically the same. In industrial production, the distillation furnace and the reduction reactor are the same. Therefore, the structural design and material selection of the reduction reactor should take into account the requirements of the reduction and distillation processes.

The condenser is a hoistable bell-shaped cylindrical tank with a cooling water jacket. The condensing sleeve is cylindrical, and the condensing area is set according to the amount of condensate discharged by distillation. A heat shield is arranged between the distillation tank and the condenser, the function of which is to reduce the radiant heat from the heating area to the condenser, without hindering the passage of the airflow escaping from the distillation tank. In order to improve the thermal insulation effect, most of the heat shields are multi-layer structures.

The structure of the distillation furnace is the same as that of the reduction reactor, but the furnace shell of the former should be sealed and connected to a vacuum device. During operation, the furnace is in a low vacuum state to reduce the external pressure on the distillation tank and prevent the latter from deforming.

Process of vacuum distillation

The reducing crucible together with the reaction product is placed upside down in the distillation pot of the distillation furnace.
The distillation tank was evacuated to 13.3-1mPa, and then the distillation furnace was heated to a temperature of 573-673K and kept at a constant temperature for 1-4 hours to remove the crystal water adsorbed by MgCl2 during the assembly process of the distillation equipment.
Then the furnace temperature was raised to 1023-1073K. At this time, since the metal magnesium and MgCl2 begin to volatilize in large quantities, the vacuum degree drops sharply, and the heating rate needs to be controlled well.
After the distillation enters the constant temperature stage, the temperature should be controlled at 1223-1273K.
After 20-25 hours of constant temperature, when the vacuum in the distillation tank rises to less than 1Pa and tends to be stable for a certain period of time, the residual amount of volatiles is very small, and the distillation operation is over.

In the whole distillation process, process parameters such as distillation temperature, vacuum degree and distillation time should be well controlled. It takes about 50 to 60 hours to distill 700 to 800 kg of zirconium. The zirconium sponge produced by distillation is self-igniting. When the distillation tank is cooled to 323K temperature, a mixed gas consisting of 60% dry air and 40% indoor air should be slowly introduced to reduce the surface activity of the sponge zirconium and make it passivated before it is released.

Product handling after vacuum distillation

Zirconium sponge is a hard and tough metal. Usually, the zirconium lump is cut into pieces by a vertical hydraulic press equipped with a cutter, and then it is medium and finely crushed to make the particle size reach 5-25mm, and then sieved, classified, mixed in batches, and packed with argon. The typical impurity content (mass fraction ω/%) of sponge zirconium is Fe 0.08, Al 0.006, Mg 0.002-0.02, Cl 0.001-0.04, O 0.08-0.1, N 0.002-0.004.

Sponge zirconium taken out from the reduction crucible can be divided into four types: A, B, C, and D.

A type of zirconium sponge accounts for about 35% of the total and is a bulk dense metal that contains almost no metal magnesium and MgCl2.
B-type zirconium sponge accounts for about 20% of the total. It is the product formed in the initial stage of the reaction, which is plate-shaped and about 10mm thick. In addition to metal magnesium, it contains a lot of iron and nitrogen impurities.
C-type sponge zirconium accounts for about 35% of the total, is a light and porous sponge with the least impurities but contains a considerable amount of metal magnesium and chloride in the pores.
D-type zirconium sponge is a product that is close to the crucible wall and contains a lot of impurities. Generally, it is returned to the chlorination treatment to recover the zirconium in it.

For more information, please visit https://www.samaterials.com/70-zirconium.html.

Methods for Zircon Beneficiation

What is Zircon?

Zircon (also known as zircon) is zirconium orthosilicate with a chemical formula of ZrSiO4, which is the most common type of zirconium-containing mineral. Zircon is mainly used as a raw material for zirconate refractory bricks, and can also be used for precision casting sand and ceramic utensils.

What is Zircon Beneficiation?

Zircon beneficiation refers to the process of removing impurities in zircon ore and increasing the content of zircon. Most of the zircon deposits are coastal placers. In the heavy sand containing zircon, there are usually heavy minerals such as magnetite, ilmenite, rutile, and monazite. Generally, when zircon is selected, these heavy minerals are also recovered as target minerals.

What are Zircon Beneficiation Methods?

Zircon beneficiation methods mainly include gravity separation, magnetic separation, electrostatic separation, and flotation.

Gravity separation

Zircon mostly occurs in ilmenite and is often accompanied by heavy minerals such as hematite, chromite, and garnet. Therefore, in the initial stage of enriching zircon, gravity separation is often used, such as using a shaking table to separate heavy minerals from gangue (quartz, feldspar, biotite), etc., and then using other beneficiation methods to separate them from other heavy minerals.

Flotation

The commonly used collectors in this method are fatty acids (oleic acid, sodium oleate), etc.; the slurry conditioner is sodium carbonate; the inhibitor is sodium silicate; the activator is sodium sulfide and heavy metal salts (zirconium chloride, ferric chloride) ); this method also uses oxalic acid to adjust the pulp to acidity and uses amine collectors for flotation.

Electric selection

Conductive minerals such as ilmenite, hematite, chromite, cassiterite, and rutile are separated from non-conductive minerals such as zircon, monazite, garnet, and apatite by utilizing the difference in mineral conductivity. Desliming, grading, drying, and dosing should be done in advance before electrification.

Magnetic separation

Magnetic minerals in heavy minerals include ilmenite, hematite, chromite, garnet, biotite, monazite, etc. Zircon is a non-magnetic mineral or a weak magnetic mineral (the iron in zircon in some deposits is weak magnetic). Magnetic separation is divided into dry and wet. In dry magnetic separation, the selected materials need to be heated, dried, and classified before they can be sorted. The wet type strong magnetic field magnetic separator has a wide separation particle size, and the lower limit of particle size can reach 20um. Therefore, it is more appropriate to use a wet magnetic separator when the zircon particle size is fine.

Wrap up

Since there are many associated minerals in zircon ore, gravity separation, magnetic separation, flotation, electric separation, and other methods should be used in combination. For more information, please visit https://www.samaterials.com/70-zirconium.html.

What are Zirconium Containing Refractory Materials?

Description of zirconium-containing refractory products

Zirconium-containing refractory products refer to refractory products made of zirconia (ZrO2) and zircon (ZrSiO4) as raw materials, including zirconia products, zircon products, zirconium mullite, and zirconium corundum products. According to different production processes, zirconium-containing refractory products are divided into sintered products, fused cast products, and non-fired products. Zirconium-containing refractory products have the characteristics of high melting point, low thermal conductivity, and good chemical stability, especially good corrosion resistance to molten glass and liquid metal.

Properties of zirconium-containing refractory products

Dense, stabilized zirconia has a melting point of 2677°C and a service temperature of 2500°C. The bulk density fluctuates between 4.5 and 5.5 g/cm3 due to the purity of the raw materials and the different manufacturing methods. The bulk density of dense zirconia products can reach 5.75g/cm3. Sintered zirconia products do not chemically react with molten metal and liquid glass. Caustic alkali solutions, carbonate solutions, and acids (except concentrated H2SO4 and HF) do not chemically react to zirconia. When carbon reacts with sintered zirconia, zirconium carbide is formed only on the surface. Therefore, under the condition of oxidizing atmosphere, zirconia products can be used at high temperatures without chemical change.

The main component of zircon products is ZrO2•SiO. Zircon is decomposed into ZrO2 and SiO when heated at 1680℃. Quartz stone products have good corrosion resistance to various molten metals, acidic reagents, and liquid glass, but they are prone to erosion reactions when they come into contact with alkaline slag or alkaline refractory materials. Aluminum-zirconium-silicon (AZS) cast bricks and fired bricks have good resistance to glass liquid erosion, and can be used in the pool wall and upper structure of glass melting pool kilns.

$zirconium-containing refractory products$

Uses of zirconium-containing refractory products

Zirconium-containing refractory products have high refractoriness, mechanical strength, and chemical stability. It can be widely used in metallurgy, building materials, the chemical industry, machinery, and other professional fields.

Zircon bricks have good resistance to acid slag, small corrosion loss, and slight sticking of slag. They can be used in the slag line of the ladle and have a long service life. Zircon products can also be used as continuous-casting intermediate tank base bricks, cushion bricks, and nozzle bricks. Zircon bricks are corrosion-resistant to low alkali glass and can be used in the kiln walls of glass-melting furnaces. It can also be used for the arch foot of the upper structure of the glass melting furnace or the intermediate transition layer between the silica brick and the corundum brick and is also an important material for the comprehensive masonry bottom.

Zirconia bricks can be used in thermal equipment for the building materials industry and metallurgical industry, such as sizing nozzles for billet continuous casting, submerged nozzles, and slag lines in long nozzles.

Fused-cast bricks with a ZrO2 content of more than 90% can be used for side walls, partition walls and flow holes of borosilicate glass melting furnaces and aluminosilicate glass melting furnaces. AZS-fired bricks and fused cast bricks can be used in soda-lime glass melting kilns, such as flow holes and side walls. The use of this brick to build liquid flow holes and side walls can reduce the contamination of glass liquid by refractory materials. In addition, zirconium mullite fused cast bricks can be used in the metallurgical industry heating furnaces, soaking furnaces, glass melting furnaces in the building materials industry, etc.

For more information, please visit https://www.samaterials.com/.

How to Purify Zirconium Tetrachloride? – 3 Methods

The purification of zirconium tetrachloride is the process of removing the impurities of crude zirconium tetrachloride. Zirconium tetrachloride is generally prepared by chlorination of zirconium carbide, zircon, or zirconium dioxide. At this time, the finished product also contains a considerable amount of impurities such as FeCl3, AICl3, TiCl4, SiCl4, ZrOCl2, and carbon powder. To obtain high-purity zirconium tetrachloride, these impurities must be removed. The mainstream methods for purifying zirconium tetrachloride mainly include the hydrogen reduction method, the molten salt purification method.

Hydrogen Reduction

Principles

The basic principles on which this law is based are:

(1) Since Zrcl4 and TiCl4 and SiCI4 have different vapor pressure differences at the same temperature, by controlling a specific temperature, TiCl4, SiCl4 and H2O can be sublimated and removed;

(2) Since ferrous chloride or chromium chloride has a high boiling point (the former is 1303K, the latter is 1573K), trivalent iron and chromium can be reduced to divalent with hydrogen. At the sublimation temperature of ZrCl4 (723-933K), FeCl2, CrCl2 and ZrOCl2 do not sublime and remain in the residue and separate from zirconium.

Process

The purification furnace of the hydrogen reduction method consists of a sublimation furnace and a condenser. The sublimation furnace is a stainless steel container with a cylinder inside, and a multi-layer tray is placed in the cylinder. The zirconium tetrachloride is packed on the tray with an appropriate thickness, and the top of the sublimation furnace is sealed with the condenser to collect the purified ZrCl4.

The work is carried out in three steps.

Step 1

Evacuate the furnace and heat it to a temperature of 423-473K, while the pressure continued to rise. TiCl4, SiCl4, HCI, H2O and adsorbed chlorine gas are discharged out of the furnace by timing exhaust method.

Step 2

Evacuate the furnace and fill it with hydrogen, and raise the temperature to 573K. The iron and chromium in FeCl2 and CrCl2 are reduced to a low-price state.

Step 3

Gradually heat the furnace to 873-933K, and keep the temperature of the condenser at 523K. At this time, ZrCl4 continuously enters the condenser from the sublimation furnace and condenses into a solid, while FeCl3 and CrCl3 do not volatilize and remain in the slag.

Summary

The purification operation time depends on the physical state, impurity content and processing volume of the raw materials. 2.0～2.5t ZrCl4 generally needs to be purified for 100～120h, and the recovery rate of zirconium is 97%～98%. The main impurity content (mass fraction ω/%) of refined ZrCl4 is as follows:

Impurities	After purification (mass fraction ω/%)
Fe	0．001
Al	0．008
Ti	<0．003
Si	0．006

Molten Salt Purification

Principle

The basic principle on which this method is based is that zirconium, iron and aluminum form Na2ZrCl6, K2ZrCl6, NaFeCl4, KFeCl4, NaAlCl4 and KAlCl4 double salts in the NaCl-KCl molten salt system, respectively.

Zirconium double salt can be re-decomposed to ZrCl4 at the set temperature, while Na(K)FeCl4 and Na(K)AlCl4 are stable compounds with high boiling point. Due to the different partial pressures of zirconium salts and iron and aluminum salts at the same temperature, it can be separated from them by controlling a specific temperature to only volatilize ZrCl4. Crude ZrCl4 is purified by washing with molten salt and filtering.

Process

There are two methods of industrial production: intermittent operation and continuous operation.

Intermittent operation

First, make ZrCl4, NaCl, and KCl into molten salt in proportion, remove volatile components at a temperature of 573K, and then raise the temperature of the salt pool to a temperature of 773-873K, so that ZrCl4 is continuously volatilized to the condenser for collection.

Continuous operation

Add the crude ZrCl4 to the molten salt pool with a temperature of 623-723K by a screw feeder for washing and purification, and then transfer the ZrCl4 gas to a bubbling molten salt pool with a temperature of 773-873K for secondary purification. The gaseous product enters the baghouse and condenser for collection.

Summary

This method is suitable for processing raw materials with high iron and aluminum impurities. The main impurity content (mass fraction ω/%) of ZrCl4 product after purification is:

Impurities	After purification (mass fraction ω/%)
Fe	0．01～0．002
Al	0．003～0．008
Ti	0．002～0．009
Si	0．002～0．008。

Liquid Purification Method

In addition to the above two mainstream purification methods, there is also a liquid purification method. The process is to pass hydrogen and nitrogen mixed gas into the bottom of the purification furnace with a structure similar to that of the fluidized chlorination furnace, so that the coarse ZrCl4 powder in the furnace forms a fluidized layer, and trivalent chlorides such as iron and chromium are reduced to two due to reduction. The high boiling point chlorides remain in the slag and separate from ZrCl4. The refined ZrCI4 gas enters the condenser for cooling and collection after being filtered.

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Introduce Several Kinds of Zirconium Ores

Zirconium is abundant in the earth’s crust, and the natural silicate ores containing zirconium are called zircon or hyacinth. Since zirconium and hafnium have similar properties, zirconium and hafnium in nature always coexist, and the hafnium coexisting with zirconium generally only accounts for 1%-2% of the weight of zirconium and hafnium.

Zirconium metal and zirconium compounds

Zirconium metal has unique nuclear properties and is an important material for nuclear reactors. More than 90% of zirconium metal is used in nuclear reactions, as fuel tanks in nuclear power plants and as packaging materials for atomic fuel in nuclear-powered ships. In addition, zirconium metal has a series of properties, such as good heat resistance, plasticity, and corrosion resistance, and is widely used in electronics, chemistry, metallurgy, steel, defense, and other industries.

Zirconium compounds also have excellent physical and chemical properties and are widely used in ceramic knives, grinding media, precision machining and casting, optical glass, optical fibers, electronic ceramics, precision ceramics, petroleum cracking, jade processing, aerospace and other fields.

Major deposits of zirconium

1) Seaside placer type, such as mines on the east coast of Australia.

This type of deposit is often formed in the wave strike zone of the seashore, and is distributed in a narrow and long manner along the seashore, extending from several kilometers to more than 100 kilometers, and the thickness is generally tens of centimeters. Due to coastal changes, some deposits have become buried deposits. In addition to zircon, heavy minerals often contain ilmenite, rutile, monazite, etc., which can be comprehensively utilized.

2) Anisotropic nepheline-bearing syenite deposits, such as the Kola Peninsula Khibiny deposit in Russia, etc.

3) Zirconium-bearing albite alkaline rock deposits. Ore minerals are mainly spar, zircon, water zircon, etc., and other symbiotically available minerals.

Mineral composition of zirconium

Zirconium and zirconium-related products are almost entirely supplied by zircon and baddeleyite, with zircon being the main mineral. The color of zircon varies from colorless to a variety of colors including pale yellow, brownish yellow, orange-yellow, reddish brown, and brown, and some zircon form crystals with gemstone properties.

Physical and chemical properties of zircon

Zircon is zirconium orthosilicate and its molecular formula is ZrSiO4. Pure zircon is rare in nature, and most of them contain impurities such as iron, chromium, aluminum, and calcium.

Zircon has a Mohs hardness of 7-8, a tetragonal system, metallic luster or vitreous luster, and is generally transparent or opaque in brown, light gray, yellow, blue, etc. Weakly conductive, non-magnetic, or weakly magnetic. Zircon is generally insoluble in acids and alkalis.