October 2022 – Zirconium Metal

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.

For more information about zirconium tetrachloride or othe

zirconium products, please visit https://www.samaterials.com/.

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.

How to Prepare Zirconium Silicide Nanomaterials?

Introduction

Zirconium silicide is a steel gray orthorhombic shiny crystal. It is insoluble in water, mineral acids, and aqua regia, and soluble in hydrofluoric acid. Zirconium silicide is an excellent ceramic material with high hardness, high melting point, high electrical conductivity, high thermal conductivity, and excellent thermal shock resistance. Because of these advantages, it can be applied to structural materials or new engineering materials for high-temperature corrosive media.

Preparation

Zirconium silicide nanomaterial can be obtained by reacting a mixture of zirconium oxide powder, silicon powder and lithium in a proportioned amount at a high temperature in the absence of air. Specific steps are as follows:

(1) Add 5mmol zirconium dioxide, 5mmol silicon powder and 50mmol metallic lithium in a 20-milliliter stainless steel autoclave, then put the autoclave into an electric furnace.

2) Set the heating rate of the electric furnace to 10 °C per minute, and heat the electric furnace to 600 °C.

3) After the temperature was raised to 600°C, the temperature was maintained for 40 hours to ensure that the raw materials were fully reacted.

4) After the reaction was completed, naturally cool down the autoclave to room temperature, and then open the autoclave and take out the black deposit.

5) Wash the deposit with distilled water once, and then wash with dilute hydrochloric acid and absolute ethanol once respectively.

6) Filter the washed deposit, and then dry it in a vacuum drying oven at 60° C for 4 hours to obtain a zirconium silicide nanomaterial.

The above reaction process is represented by the following equation:

ZrO2+Si+4Li=ZrSi+2Li2O

According to the quality of the prepared zirconium silicide nanomaterials and the quality of the used raw material zirconium dioxide, the method obtains that the yield of zirconium silicide is 85%.

Application

Zirconium silicide nanomaterial can be used to prepare a high-density ceramic matrix composite material: zirconium diboride-zirconium disilicide-tungsten carbide ceramic matrix composite material. This material is prepared from zirconium diboride powder, zirconium disilicide and tungsten carbide (purity >98.0%) using a two-step hot pressing sintering process. Wherein, the mass fraction of zirconium diboride powder is 75-90%, the mass fraction of zirconium disilicide is 10-15%, and the mass fraction of tungsten carbide is 0-10%. Adding a higher content of zirconium diboride to the ceramic matrix composite material is beneficial to improve the physicochemical properties of the composite material; adding this appropriate amount of zirconium disilicide to the ceramic matrix composite material can significantly reduce the sintering temperature for material preparation; the added tungsten carbide can promote anisotropic growth of grains inside the material.

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