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.

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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

Zirconium(IV) chloride

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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3 Types of Zirconium Based Getter Materials

Zirconium-based getter material refers to the alloy with high absorption active gas characteristics formed by adding other elements based on zirconium.

Before sealing in vacuum tubes and devices, the material must be heated and activated under vacuum conditions for fast and effective gettering. The function of activation is to remove the passivation film formed on the surface during the manufacturing and storage process to expose the fresh surface, which is conducive to the overall gettering, so as to achieve the purpose of absorbing a large amount of oxygen, nitrogen, hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, and water vapor.

Zirconium-aluminum alloy, zirconium-graphite, and zirconium-vanadium-iron alloy are widely used zirconium-based getter materials today.

Zirconium-aluminum alloy getter

Zirconium-aluminum alloy getter can be made into ring-shaped material and composite strip-shaped material.

(1) Ring-shaped material. The material has poor gettering performance at room temperature and is usually not used for gettering at room temperature. This material is commonly used in electronic tubes, various vacuum devices, special lamps, inert gas purification, zirconium-aluminum getter pumps, etc.

(2) Composite strip material. The advantage is that the amount of mercury can be accurately controlled, and it does not decompose or generate mercury vapor below 500°C, thereby greatly reducing environmental pollution, preventing workers from mercury poisoning, and improving lamp quality and life. It has been widely used in fluorescent lamps and energy-saving lamps.

ZR1422 Zirconium Aluminum Alloy, ZrAl Alloy
ZR1422 Zirconium Aluminum Alloy, ZrAl Alloy

Zirconium graphite getter

Zirconium graphite getter is often used in high-reliability and long-life vacuum tubes and devices for long-term operation and storage, such as traveling wave tubes, X-ray tubes, trigger tubes, ceramic tubes, and laser tubes.

Zirconium-vanadium-iron alloy getter

Zirconium-vanadium-iron alloy getter is a low-temperature activated getter material composed of zirconium, vanadium, and a small amount of iron. It is divided into two types:

(1) Zirconium vanadium ferroalloy getter material, smelted by 70%zr+24.6%V+5.4%Fe in electric arc furnace or medium frequency induction furnace under vacuum or filled with inert gas, then crushed, pulverized, and then pressed into getter elements.

(2) (Zirconium vanadium ferro)/zirconium getter material. It is made by adding the zirconium vanadium ferroalloy powder prepared in (1), adding zirconium powder in a certain proportion, mixing evenly, and then pressing, high temperature and high vacuum sintering and other processes. into a suction element. Product forms are powder, flakes, rings, and strips.

These two zirconium-vanadium-iron alloy getters are low-temperature activated getters, and the activation process is as follows: the temperature is 400-600°C, the vacuum degree is 10-2-10-4Pa, and the maintenance is 10-30min. The working temperature is from room temperature to 350℃.

Zirconium-vanadium-iron alloy getter is widely used in stainless steel vacuum insulated cups (bottles), solar vacuum water heaters, high-efficiency oil-insulated pipes, and vacuum tube containers that are only allowed to operate at 500°C.

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Zirconium Carbide and Its Composite Functional Materials

Introduction

Zirconium carbide, with the chemical formula ZrC, has a theoretical carbon content of 11.64%. It belongs to the typical NaCl type face-centered cubic structure. The atomic radius ratio of C atoms and Zr atoms is 0.481, which is less than 0.59, forming a simple interstitial phase. The Zr atoms form a compact cubic lattice, and the C atoms are located in the octahedral interstitial positions of the lattice.

The melting point of zirconium carbide is 3540℃, the theoretical density is 6.66g/cm3, and the thermal expansion coefficient is 6.7×10-6℃-1. It is insoluble in hydrochloric acid, but soluble in nitric acid. Zirconium carbide is a key material for the preparation of high-performance cemented carbide, aerospace, atomic energy, textiles, electronics, coatings, hard films and metallurgical automation and other high-tech fields.

ZR1394 Zirconium Carbide (ZrC) Powder

Advantages

Zirconium carbide has the advantages of high surface activity, high temperature resistance, oxidation resistance, high hardness, good thermal conductivity, good toughness, etc., and has the characteristics of efficient absorption of visible light, a reflection of infrared rays, and energy storage. It is an important high-temperature structural material.

Using ultra-high-purity zirconium dioxide and high-purity carbon black as raw materials, and applying core technology and alloying and sintering technology to prepare, can ensure the purity, low oxygen content, and low free carbon of zirconium carbide powder. The prepared ZrC powder has densified grains, stable phase composition, uniform particle size, and stable quality.

Application

1. Zirconium carbide is added to rubber, plastics, polyethylene, acrylonitrile-butadiene-styrene copolymer ABS plastics, transparent plastics, resins, polyurethane materials, and other materials for manufacturing related products. As an additive, zirconium carbide can greatly improve the strength, high-temperature resistance, and drop resistance of plastics and related materials.

2. Adding a certain proportion of zirconium carbide to Zr-Ti alloy, C/C-(Zr-Ti-C-B/SiC) composite material, and Zr-Ti-C-B ceramic material can be made into a ceramic coating resistant to 3000℃ ablation and its composite materials. The composite material made in this way exhibits superior ablation resistance and thermal shock resistance and is a new type of material for key components of hypersonic aircraft, which is now widely used in the military and aerospace fields.

3. Zirconium carbide has the characteristics of heat absorption and heat storage. Therefore, it can be used to manufacture solid propellants in rocket engines, to produce metal zirconium and zirconium tetrachloride, and as abrasive.

4. Zirconium carbide is used for U-shaped ZrC-graphite composite ceramic combined heating element. This heating element has high heating efficiency, good energy saving effect, small occupied volume, low cold end temperature, and stable electrical performance; under vacuum, neutral or reducing atmosphere, it can provide a high-temperature environment above 2000 ℃; it has good It has excellent thermal shock resistance, high thermal efficiency, and fast heating rate, and can be raised from room temperature to 2000 ° C in 120 minutes; it can be used for thermal shock resistance test of ultra-high temperature refractory materials.

5. Zirconium carbide is used for zirconium carbide composite ceramic sensors. This sensor has high mechanical strength, is not easy to deform and volatilize at high temperatures, and has stable electrical performance and long service life; in a vacuum or protective atmosphere, it can more accurately measure ultra-high temperature ambient temperature below 3000 °C; it is the temperature sensing element with the highest temperature measurable in the contact sensor.

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Zirconium – A Vacuum Material

Properties of Zirconium

Zirconium easily absorbs hydrogen, nitrogen, and oxygen; zirconium has a strong affinity for oxygen, and oxygen dissolved in zirconium at 1000°C can significantly increase its volume. The surface of zirconium is easy to form an oxide film with luster, so its appearance is similar to that of steel. Zirconium is resistant to corrosion but is soluble in hydrofluoric acid and aqua regia. At high temperatures, zirconium can react with non-metallic elements and many metal elements to form solid solutions. Zirconium has good plasticity and is easy to be processed into plates, wires, etc. Zirconium can absorb a large amount of oxygen, hydrogen, nitrogen, and other gases when heated, and can be used as a hydrogen storage material. The corrosion resistance of zirconium is better than that of titanium, and it is close to niobium and tantalum. Zirconium and hafnium are two metals with similar chemical properties that are symbiotic together and contain radioactive substances.

Applications of Zirconium

Like lithium and titanium, zirconium can strongly absorb nitrogen, hydrogen, oxygen, and other gases. When the temperature exceeds 900 degrees Celsius, zirconium can absorb nitrogen violently; under the condition of 200 degrees Celsius, 100 grams of metal zirconium can absorb 817 liters of hydrogen, which is equivalent to more than 800,000 times that of iron. This characteristic of zirconium makes it widely used in the electric vacuum industry. People use zirconium powder to coat the surface of the anode and other heated parts of electric vacuum components and instruments to absorb residual gas in vacuum tubes. The high vacuum tubes and other electric vacuum instruments made in this way have high quality and long service life.

high vacuum tubes

Zirconium has a small thermal neutron capture cross-section and has outstanding nuclear properties, so it is an indispensable material for the development of the atomic energy industry and can be used as a reactor core structural material. Zirconium powder is easy to burn in the air and can be used as a detonator and smokeless powder. Zirconium can be used as an additive for deoxidation and desulfurization of high-quality steel and is also a component of armor steel, cannon steel, stainless steel, and heat-resistant steel.

Zirconium can also be used as a “vitamin” in the metallurgical industry to exert its powerful deoxidation, nitrogen removal, and sulfur removal effects. Adding 1/1000 zirconium to steel will increase the hardness and strength amazingly; zirconium-containing armored steel, stainless steel, and heat-resistant steel are important materials for the manufacture of defense weapons such as armored vehicles, tanks, cannons, and bulletproof panels. When zirconium is mixed into copper and drawn into copper wire, the conductivity is not weakened, while the melting point is greatly improved, which is very suitable for high-voltage wires. Zirconium-containing zinc-magnesium alloy is light and resistant to high temperatures, and its strength is twice that of ordinary magnesium alloys. It can be used in the manufacture of jet engine components.

Zirconium powder is characterized by a low ignition point and fast burning speed and can be used as a primer for detonating detonators, which can explode even underwater. Zirconium powder plus oxidant is like adding fuel to the fire, it burns with strong light and dazzling, and it is a good material for making tracer and flare.

Zirconium alloys and their applications

Zirconium alloy is a non-ferrous alloy composed of zirconium as the matrix and other elements are added. The main alloying elements are tin, niobium, iron, and so on. Zirconium alloy has good corrosion resistance, moderate mechanical properties, low atomic thermal neutron absorption cross-section in high temperature and high-pressure water and steam at 300-400 °C, and has good compatibility with nuclear fuel. In addition, zirconium alloy has excellent corrosion resistance to various acids, alkalis, and salts, and has a strong affinity with oxygen, nitrogen, and other gases, so it is also used in the manufacture of corrosion-resistant parts and pharmaceutical machinery parts. For example, it is widely used as a non-evaporable getter in the electric vacuum and light bulb industries.

zirconium alloy

There are two types of zirconium alloys produced on an industrial scale: the zirconium-tin series and the zirconium-niobium series. The former alloy grades are Zr-2 and Zr-4, and the typical representative of the latter is Zr-2.5Nb. In zirconium-tin alloys, the alloying elements tin, iron, chromium, and nickel can improve the strength, corrosion resistance, and thermal conductivity of the corrosion-resistant film, and reduce the sensitivity of the surface state to corrosion. Usually, Zr-2 alloys are used in boiling water reactors, and Zr-4 alloys are used in pressurized water reactors. In zirconium-niobium-based alloys, the corrosion resistance of the alloy is the best when the addition amount of niobium reaches the solid solution limit of the crystal structure of zirconium at the service temperature. Zirconium alloy has isomorphous transformation, the crystal structure is body-centered cubic at high temperature, and hexagonal close-packed at low temperature. Zirconium alloy has good plasticity and can be made into pipes, plates, bars and wires by plastic processing; its weldability is also good and can be used for welding.

Other Zirconium Compounds

Zirconium dioxide and zircon are the most valuable compounds in refractory materials. Zirconium dioxide is the main material of new ceramics and cannot be used as a heating material that resists high-temperature oxidation. Zirconium dioxide can be used as an additive for acid-resistant enamel and glass, which can significantly improve the elasticity, chemical stability, and heat resistance of glass. Zircon has a strong light reflection performance and good thermal stability and can be used as sunscreen in ceramics and glass. Zirconium can absorb a large amount of oxygen, hydrogen, ammonia, and other gases when heated, and is an ideal getter. For example, zirconium powder is used as a degassing agent in electronic tubes, and zirconium wire and zirconium sheets are used as grid supports and anode supports.

Powdered iron mixed with zirconium nitrate can be used as glitter powder. Zirconium metal is used almost exclusively as the cladding for uranium fuel elements in nuclear reactors. It is also used to make photographic flashes, as well as corrosion-resistant containers and pipes, especially hydrochloric and sulfuric acids. Zirconium chemicals can be used as crosslinking agents for polymers.

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Applications of Zirconium Silicate Grinding Media

Zirconium Silicate is a high-quality and inexpensive opacifier with a high refractive index of 1.93-2.01 and chemical stability. It is widely used in the production of various ceramics. Besides, Zirconium Silicate has a high melting point, so it is also widely used in refractory materials, zirconium ramming materials for glass furnaces, casting materials, and spray coatings.

The zirconium silicate media ball is one of its kind, offering users the highest quality and superior grinding levels with improved abrasion resistance, better cost-effectiveness and lower overall contamination rates. Zirconium silicate beads are formulated in strict quality-controlled laboratory containers, in which they undergo specialized instillation techniques, followed by high-temperature sintering and final surface treatment. Compared to other alternative grinding media options such as glass beads or alumina, this ultra-hard media is an ideal solution for grinding special and complex products.

Zirconium Silicate Grinding Media
Zirconium Silicate Grinding Media

The basic characteristics of a good quality zirconium silicate grinding media are that they are high in density, shiny and smooth in appearance, and consist of a uniform solid spherical shape which in turn assures better efficiencies, decreased media wear, and a much longer life span respectively. Additional specialized techniques such as solidifying the media from surface to center result in further strengthening of the molecular structure of ZrSi beads. Zirconium silicate media balls exist in varying sizes and diameters in accordance with each buyer’s prerequisites.

ZrSi04 applications and uses are tremendous and widespread from everyday products such as paints and inks to ceramics, pharmaceuticals, and even in controlled quantities within edible food materials. Zirconium Silicate grinding media plays an integral role as an emulsion agent in order to achieve a ceramic glaze in refractory’s and on cutlery etc. Also being chemically inert and nonreactive allows ZiSi04 media to be used for grinding plastic on a mass level and at economical costs. Moreover, zirconium casting refractories of all kinds utilize this media for operational purposes within glass melting furnaces, cement production and heat/fire resistant porcelain among many others. On a generalized level, Zirconium Silicate grinding media performs numerous operations including mold cleaning of stainless steel, plastic as well as nonferrous materials, mechanical polishing, buffing and eventual after-cleaning processing.

On an overall rating scale, the benefits of this industrial product being extremely dense and strong results in creating an ideal surface roughness and metallic depth with a much lower breakage or contamination rate comparatively. These attributes in turn render Zirconium Silicate milling balls suitable for application on all types of materials and within both wet and dry environments easily.

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