Zirconium oxide-based composite material for high-zirconium brick and preparation method thereof

Abstract

The invention belongs to the field of refractory materials, and particularly relates to a zirconia-based composite material for high-zirconium bricks and a preparation method of the zirconia-based composite material. Zircon sand is subjected to electrofusion desiliconization, and purifying agents scandium chloride and yttrium chloride are added in a molten state to react for a certain time; according to the method, silicon, aluminum, titanium and other impurities in the desiliconized zirconium oxide are converted into low-boiling-point gaseous compounds to be separated from a zirconium oxide melt, and scandium and yttrium elements are retained in a zirconium oxide material in the form of oxides, so that the purposes of impurity removal, zirconium oxide purification and doping modification are achieved; the desiliconized zirconium oxide and the carbon are simultaneously added in the desiliconizing process, the carbon serves as a reducing agent and wraps the surfaces of the desiliconized zirconium oxide particles in the mixing stage, a core-shell structure is formed, silicon volatilization is more thorough, and the content of residual silicon can be reduced to 0.08% or below.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of refractory materials, and particularly relates to a zirconia-based composite material for high-zirconia brick and a preparation method thereof. BACKGROUND

[0002] Zirconia is widely used in various glass furnaces as one of the key refractory materials that can be directly contacted with glass liquid due to its excellent properties such as high-temperature resistance, high mechanical strength, corrosion resistance and low pollution. The refractory material mainly composed of zirconia (ZrO2) exhibits excellent corrosion resistance to molten glass, and is therefore widely used in the inner wall part that is in contact with the molten glass of the glass melting furnace. Zirconite is one of the commonly used raw materials for high-zirconia castable bricks, and the main chemical component of zirconite is zirconium silicate (ZrSiO4), in which the content of ZrO2 is about 65% to 67%, and the content of SiO2 is about 32% to 34%. The core performance of high-zirconia brick depends on high-purity zirconia (ZrO2), for example, the content of ZrO2 is usually required to be more than 70% (or even higher) to achieve high-temperature resistance, corrosion resistance and other properties. Therefore, if zirconite is directly used as a raw material, SiO2 therein will exist as an impurity, which cannot meet the requirement of high-zirconia brick on the content of ZrO2. The methods for removing silicon from zirconite in the prior art mainly include chemical method and electric melting method. The chemical method has a high degree, but its process is complex and the production cost is high. The electric melting method has the advantages of stable quality and low production cost, and is widely used. For example, the prior art CN104445396A discloses a production method of high-purity electric melting zirconia, which uses low-grade zirconite or other zircon-containing raw materials as the main raw material, and obtains high-purity electric melting zirconia with a purity of more than 99.5% through the steps of electric melting desiliconization, impurity removal and separation. The production process provided by the invention is simple and low in cost, and realizes the technical effect of producing high-purity electric melting zirconia from low-grade zirconite or other zircon-containing raw materials. The prior art CN111057874A discloses a preparation method of electric melting zirconia for metal zircon parent material, which removes silicon from zirconite by electric melting, and adds a purifying agent magnesium halide and carbon in a molten state for a certain time, so that the silicon, aluminum, titanium and other impurities in the desiliconized zirconia are converted into low-boiling-point gaseous compounds and separated from the zirconia melt. The carbon reacts with magnesium oxide to generate carbon dioxide and metal magnesium, which escapes from the zirconia melt pool, so as to achieve the purpose of purifying zirconia by removing impurities, and high-purity low-aluminum low-titanium zirconia with a purity of more than 99.8% is prepared.

[0003] Although the prior art can obtain zirconia products with high purity, in the preparation process of fused cast high zirconia bricks, due to the reversible phase transition of ZrO2 (tetragonal phase-monoclinic phase), which shows the abnormal characteristics of volume shrinkage during phase transition when the temperature rises, and volume expansion when the temperature decreases, the t-ZrO2→m-ZrO2 phase transition from high temperature to room temperature is accompanied by a volume expansion of up to about 6.9%. It is usually necessary to dope and modify it to overcome the above problems, however, the prior art can only remove the related elements, and cannot achieve doping and modification while removing impurities, therefore, it is urgent to provide a zirconia-based composite material for high zirconia bricks and a preparation method thereof to overcome the above technical problems. SUMMARY

[0004] The purpose of the present application is to provide a zirconia-based composite material for high zirconia bricks and a preparation method thereof, by electrically melting and desiliconizing zircon sand, adding purifying agents scandium chloride and yttrium chloride in a molten state for a certain period of time, converting the silicon, aluminum, titanium and other impurities in the desiliconized zirconia into low-boiling-point gaseous compounds and separating them from the zirconia melt, and retaining the scandium and yttrium elements in the form of oxides in the zirconia material, so as to achieve the purpose of purifying zirconia by removing impurities while doping and modifying.

[0005] One purpose of the present application is to provide a preparation method of a zirconia-based composite material for high zirconia bricks, characterized by comprising the following steps:

[0006] S1: uniformly mixing scandium chloride and yttrium chloride and then pressing and forming to obtain a purifying agent;

[0007] S2: mixing zircon sand raw material, carbon source and desiliconized zirconia powder and then performing a desiliconization reaction in an electric arc furnace;

[0008] S3: after the desiliconization reaction in step S2 is completed, adding the purifying agent in step S1 into the melt after the desiliconization reaction, melting and discharging;

[0009] Further, the purifying agent in step S1 is a mixture of scandium chloride and yttrium chloride, and the mass ratio of scandium chloride to yttrium chloride is 1:0.5-1.

[0010] The reaction process of scandium chloride and related impurities in zircon sand in the present application is as follows:

[0011] Al2O3+2ScCl3→2AlCl3+Sc2O3;

[0012] 3TiO2+4ScCl3→3TiCl4+2Sc2O3;

[0013] 3SiO2+4ScCl3→3SiCl4+2Sc2O3;

[0014] The reaction process of yttrium chloride and the related impurities in zircon sand in the present application is as follows:

[0015] Al2O3+2YCl3→2AlCl3+Y2O3;

[0016] 3TiO2+4YCl3→3TiCl4+2Y2O3;

[0017] 3SiO2+4YCl3→3SiCl4+2Y2O3;

[0018] In the present application, scandium oxide is used to purify and modify zirconia, wherein Sc 3+ can form a solid solution by displacement solid solution reaction with Zr 4+ , change the lattice constant of zirconia, enhance the stability of tetragonal phase of zirconia, and inhibit the transformation of zirconia from tetragonal phase to monoclinic phase, thereby improving the phase transformation stability of zirconia under different temperature conditions. In addition, due to the better matching degree and lower lattice distortion of Sc 3+ , the zirconia doped with Sc 3+ has higher density and finer grains. In addition, Y 3+ is introduced in the present application for co-doping modification, Sc 3+ and Y 3+ are both trivalent cations, and they jointly replace Zr 4+ to generate more oxygen vacancies (one oxygen vacancy is generated for every two trivalent ions replacing two Zr 4+ to maintain charge balance. Higher oxygen vacancy concentration significantly enhances the lattice diffusion (bulk diffusion and grain boundary diffusion) rate. Due to the accelerated diffusion rate, Sc-Y co-doped zirconia can reach near theoretical density at a lower temperature than Y 3+ or pure Sc 3+ alone. This is very advantageous for reducing energy consumption, inhibiting excessive grain growth, and avoiding phase transformation or volatilization that may occur at high temperatures.

[0019] Further, the carbon source in step S2 is selected from one or more of graphite, petroleum coke and pitch coke, and the carbon content is ≥98.5wt%; the mass ratio of zircon sand to carbon source is 10-20:1; the voltage of the electric arc furnace is 110-270V, and the current is 5-16KA; the content of zirconia in the zircon sand is more than 60%; the desiliconization reaction time is 15-30min; and the mass ratio of the purifying agent to the desiliconized zirconia powder is 0.8-1:1.

[0020] Further, the mass ratio of the purifying agent to the carbon source in step S3 is 0.8-1:6-8; and the smelting time is 6-12min.

[0021] Another object of the present application is to provide a zirconia-based composite material for high-zircon bricks prepared by the above preparation method.

[0022] Beneficial effects:

[0023] This invention achieves purification by electro-melting zircon sand to remove silicon, then adding scandium chloride and yttrium chloride as purifying agents in the molten state and reacting for a certain period of time. This process converts impurities such as silicon, aluminum, and titanium in the desiliconized zircon oxide into low-boiling-point gaseous compounds that are separated from the molten zircon oxide, thereby achieving the purpose of impurity removal and purification.

[0024] This invention uses scandium chloride and yttrium chloride as purifying agents, which can remove silicon and related impurity elements from zircon sand while retaining scandium and yttrium elements in the zirconium oxide matrix, thereby achieving doping modification of zirconium oxide materials.

[0025] In this invention, scandium chloride and yttrium chloride are used as purifying agents, which can achieve relatively uniform doping modification of scandium and yttrium elements in zirconia materials. Compared with the existing post-doping method of cast high zirconium bricks, it can achieve uniform doping of zirconia, which is of great significance for improving the overall performance of cast high zirconium bricks.

[0026] This invention incorporates desilicationized zirconium oxide and carbon simultaneously during the desilication process. Carbon acts as a reducing agent, coating the surface of the desilicationized zirconium oxide particles during the mixing stage to form a "core-shell" structure. The active SiO2 generated from the decomposition of zircon sand directly contacts the carbon coating layer and is rapidly reduced to gaseous SiO / CO. The desilicationized zirconium oxide serves as the ZrO2 deposition substrate, preventing newly formed ZrO2 from encapsulating unreacted SiO2. Silicon volatilization is more thorough, and the residual silicon content can be reduced to <0.08%.

[0027] After adding yttrium oxide, yttrium chloride (YCl3) and scandium chloride (ScCl3) are mixed, Y... 3+ Ionic radius and Sc 3+ Due to their different ionic radii, they can enter the scandium chloride lattice to form a solid solution. This distorts the scandium chloride lattice, weakening its internal chemical bonds. Introducing "defects" into the crystal weakens the interatomic bonding forces, making them more prone to breakage upon heating, thereby lowering the decomposition temperature and improving the silicon removal effect. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the specific composition of the zircon sand used in the following embodiments and comparative examples is shown in the table below:

[0030] Ingredients ZrO2 + HfO2 SiO2 TiO2 MgO Al2O3 Fe2O3 Content (%) MgO Content (%) 64.62 33.14 0.14 0.71 0.36 0.03

[0031] Example 1

[0032] ScCl3 and YCl3 were mixed in a weight ratio of 1:1 and then briquetted to obtain a purifying agent; 600 g of zircon sand, 60 g of graphite electrode, and 10 g of desiliconized zirconia powder were mixed uniformly and then added into an electric arc furnace, the voltage of the electric arc furnace was controlled to be 110-270 V, the current was controlled to be 5-16 KA, and desiliconization was performed under the action of arc heat for 15 min. After the desiliconization was completed, 10 g of the purifying agent was added into the ZrO2 melt, and the ZrO2 melt was sufficiently melted for 12 min, and then poured out of the furnace. After the ZrO2 poured out of the furnace was cooled, crushing and finishing were performed.

[0033] Example 2

[0034] ScCl3 and YCl3 were mixed in a weight ratio of 1:0.5 and then briquetted to obtain a purifying agent; 800 g of zircon sand, 80 g of graphite electrode, and 10 g of desiliconized zirconia powder were mixed uniformly and then added into an electric arc furnace, the voltage of the electric arc furnace was controlled to be 110-270 V, the current was controlled to be 5-16 KA, and desiliconization was performed under the action of arc heat for 20 min. After the desiliconization was completed, 8 g of the purifying agent was added into the ZrO2 melt, and the ZrO2 melt was sufficiently melted for 10 min, and then poured out of the furnace. After the ZrO2 poured out of the furnace was cooled, crushing and finishing were performed.

[0035] Example 3

[0036] ScCl3 and YCl3 were mixed in a weight ratio of 1:0.8 and then briquetted to obtain a purifying agent; 1600 g of zircon sand, 80 g of graphite electrode, and 10 g of desiliconized zirconia powder were mixed uniformly and then added into an electric arc furnace, the voltage of the electric arc furnace was controlled to be 110-270 V, the current was controlled to be 5-16 KA, and desiliconization was performed under the action of arc heat for 25 min. After the desiliconization was completed, 9 g of the purifying agent was added into the ZrO2 melt, and the ZrO2 melt was sufficiently melted for 12 min, and then poured out of the furnace. After the ZrO2 poured out of the furnace was cooled, crushing and finishing were performed.

[0037] Example 4

[0038] ScCl3 and YCl3 were mixed in a weight ratio of 1:0.75 and then briquetted to obtain a purifying agent; 1000 g of zircon sand, 70 g of graphite electrode, and 10 g of desiliconized zirconia powder were mixed uniformly and then added into an electric arc furnace, the voltage of the electric arc furnace was controlled to be 110-270 V, the current was controlled to be 5-16 KA, and desiliconization was performed under the action of arc heat for 16 min. After the desiliconization was completed, 10 g of the purifying agent was added into the ZrO2 melt, and the ZrO2 melt was sufficiently melted for 8 min, and then poured out of the furnace. After the ZrO2 poured out of the furnace was cooled, crushing and finishing were performed.

[0039] Comparative Example 1

[0040] The scandium chloride powder is pressed into briquettes to obtain a purifying agent; 1600 g of raw material zircon sand is mixed with 80 g of graphite electrode and 10 g of desiliconized zirconia powder, and then added into an electric arc furnace, with the voltage of the electric arc furnace controlled at 110-270 V and the current controlled at 5-16 KA. The desiliconization reaction is carried out for 25 min under the action of arc heat. After the desiliconization is completed, 9 g of the purifying agent is added into the ZrO2 melt, and the melt is fully melted for 12 min, and then poured out of the furnace. After the ZrO2 poured out of the furnace is cooled, it is broken and finished.

[0041] Comparative Example 2

[0042] The scandium chloride and yttrium chloride are mixed at a weight ratio of 1:0.5, and then pressed into briquettes to obtain a purifying agent; 800 g of raw material zircon sand is mixed with 80 g of graphite electrode, and then added into an electric arc furnace, with the voltage of the electric arc furnace controlled at 110-270 V and the current controlled at 5-16 KA. The desiliconization reaction is carried out for 20 min under the action of arc heat. After the desiliconization is completed, 8 g of the purifying agent and 10 g of desiliconized zirconia powder are added into the ZrO2 melt, and the melt is fully melted for 10 min, and then poured out of the furnace. After the ZrO2 poured out of the furnace is cooled, it is broken and finished.

[0043] The component contents of the zircon sand in the examples and comparative examples are shown in the following table:

[0044] Table 1 Component contents of zircon sand in examples and comparative examples

[0045]

[0046] As can be seen from the data of Comparative Example 2 and Comparative Example 1, under the condition that the other conditions are basically the same, the addition of yttrium oxide and scandium oxide in the purifying agent can significantly improve the desiliconization effect. This is because the decomposition temperature of scandium chloride is relatively high when scandium chloride is added alone, which is not conducive to the removal of silicon. After the addition of yttrium oxide, the yttrium chloride (YCl3) and scandium chloride (ScCl3) are mixed, and Y 3+ The ionic radius of Y is smaller than that of Sc 3+ The ionic radius of Y is smaller than that of Sc, and it can enter the scandium chloride crystal lattice to form a solid solution. This will distort the scandium chloride crystal lattice and weaken the chemical bonds inside. The introduction of "defects" in the crystal makes the atomic interbonding force weaker, and it is easier to break under heat, thereby reducing the decomposition temperature and improving the desiliconization effect.

[0047] Comparing the experimental data from Example 2 and Comparative Example 2 in Table 1, it can be seen that in the desilication process of this invention, desilication-free zirconium oxide and carbon are added simultaneously. Carbon acts as a reducing agent, coating the surface of the desilication-free zirconium oxide particles during the mixing stage, forming a "core-shell" structure. The active SiO2 generated from the decomposition of zircon sand directly contacts the carbon coating layer and is rapidly reduced to gaseous SiO / CO. The desilication-free zirconium oxide serves as a ZrO2 deposition substrate, preventing newly formed ZrO2 from coating unreacted SiO2. Silicon volatilization is more thorough, and the residual silicon content can be reduced to <0.08%.

[0048] Furthermore, Y is introduced in this invention. 3+ Co-doping modification of it, Sc 3+ and Y 3+ They are all trivalent cations, jointly substituting Zr. 4+ More oxygen vacancies need to be generated (two Zr ions replace two Zr ions for every two trivalent ions). 4+ (This generates an oxygen vacancy) to maintain charge balance. Higher oxygen vacancy concentrations significantly enhance lattice diffusion (bulk diffusion and grain boundary diffusion) rates. Due to the accelerated diffusion rate, Sc-Y co-doped zirconia can achieve higher diffusion rates than Y alone. 3+ or pure Sc 3+ It achieves near-theoretical density at lower temperatures. This is highly advantageous for reducing energy consumption, suppressing excessive grain growth, and avoiding potential phase transitions or volatilization at high temperatures.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0050] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for producing a zirconia-based composite material for high zirconia bricks, characterized by, The method comprises the following steps: S1: uniformly mixing scandium chloride and yttrium chloride, and then pressing and forming to obtain a purifying agent; S2: mixing zircon sand raw material, a carbon source and desiliconized zirconia powder, and then carrying out a desiliconization reaction in an electric arc furnace; S3: after the desiliconization reaction gas in step S2 is volatilized, adding the purifying agent in step S1 into the solution after the desiliconization reaction, and then smelting and discharging.

2. The method of producing a zirconia-based composite material for high zirconia bricks according to claim 1, characterized by, The mass ratio of scandium chloride to yttrium chloride in step S1 is 1:0.5-1.

3. The method for preparing a zirconia-based composite material for high-zirconia bricks as described in claim 1, characterized in that, The carbon source in step S2 is selected from one or more of graphite, petroleum coke and pitch coke, and the carbon content is ≥98.5wt%.

4. The method of producing a zirconia-based composite material for high zirconia bricks according to claim 1, characterized by, The mass ratio of zircon sand to the carbon source in step S2 is 10-20:

1.

5. The method for preparing a zirconia-based composite material for high-zirconia bricks as described in claim 1, characterized in that, The voltage of the electric arc furnace in step S2 is 110-270V, and the current is 5-16KA.

6. The method for preparing a zirconia-based composite material for high-zirconia bricks as described in claim 1, characterized in that, The time of the desiliconization reaction in step S2 is 15-30min.

7. The method for preparing a zirconia-based composite material for high-zirconia bricks as described in claim 1, characterized in that, The mass ratio of the purifying agent to the desiliconized zirconia powder in step S3 is 0.8-1:

1.

8. The method for preparing a zirconia-based composite material for high-zirconia bricks as described in claim 1, characterized in that, The mass ratio of the purifying agent to the carbon source in step S3 is 0.8-1:6-8.

9. The method for preparing a zirconia-based composite material for high-zirconia bricks as described in claim 1, characterized in that, The smelting time in step S3 is 6-12min.

10. A zirconia-based composite material for high zirconia bricks, characterized by, The method is prepared by any one of claims 1-9.

Images