CN118326161B - Method for preparing Si-Ti alloy solder and simultaneously recovering tungsten and vanadium by utilizing waste SCR catalyst and crystalline silicon waste - Google Patents

Abstract

The present invention relates to a method for preparing Si-Ti alloy solder by using waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time, belonging to the technical field of solid waste resource utilization. The present invention uniformly mixes waste SCR catalyst, crystalline silicon waste and slag-making agent to obtain a mixed material; the mixed material is placed in an argon atmosphere, heated to 1773-1823K for reduction smelting, and slag-gold separation is performed to obtain Si-Ti alloy and residue containing tungsten and vanadium; the Si-Ti alloy containing tungsten and vanadium is placed in a vacuum or argon atmosphere and heated to a molten state and directional solidification separation and purification is performed to obtain (Ti, W, V) Si ₂ phase enrichment, V-containing eutectic Si-Ti alloy solder, and impurity enrichment in sequence; wherein the (Ti, W, V) Si ₂ phase enrichment can be used as a raw material for recovering tungsten and vanadium, and can also be used as a trace additive for V-containing eutectic Si-Ti alloy solder, and is melted at high temperature with V-containing eutectic Si-Ti alloy solder in a vacuum or argon atmosphere to form a composite Si-Ti alloy solder. V-containing eutectic Si‑Ti alloy solder and composite Si‑Ti alloy solder can be used for welding SiC-based ceramic materials.

Description

A method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and simultaneously recovering tungsten and vanadium

Technical Field

The invention relates to a method for preparing Si-Ti alloy solder by utilizing waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time, belonging to the technical field of solid waste resource utilization.

Background Art

Nitrogen oxides ( _NOx , x = 1, 2) emitted by coal-fired power plants are one of the main air pollutants. With the implementation of the latest _NOx emission reduction work, the selective catalytic reduction (SCR) method has been considered to be the most effective method for controlling _NOx emissions. SCR denitrification is the selective conversion of _NOx into _N2 and _H2O using ammonia ( _NH3 ) or other reducing agents under the action of a specific catalyst. At present, _{V2O5 - WO3} / _TiO2 catalyst is considered to be the most effective SCR catalyst for reducing _NOx emissions. It has the advantages of high _NOx conversion rate, poison resistance, sulfur resistance and good catalytic activity. However, due to the volatilization of active components, high-temperature sintering, pore blockage and alkaline earth metal poisoning, the activity of SCR catalyst is reduced, and the deactivated SCR catalyst eventually becomes a waste SCR catalyst. Typically, spent SCR catalyst contains 80-90 wt% TiO ₂ , 7-10 wt% WO ₃ and 0.5-1.5 wt% V ₂ O ₅ , and the total content of TiO ₂ , WO ₃ and V ₂ O ₅ is often higher than 90 wt%. Therefore, it is very necessary to recycle the secondary resources of Ti, W and V in spent SCR catalyst.

Crystalline silicon solar cells are devices that convert solar energy into electrical energy based on the photovoltaic effect. In the process of preparing silicon wafers, diamond wires are used to cut polycrystalline silicon or monocrystalline silicon ingots. During the cutting process, nearly 35%-40% of the crystalline silicon enters the cutting waste slurry in the form of silicon powder and is lost, resulting in a huge waste of silicon resources and serious environmental pollution. In addition, due to the extremely fine particle size of crystalline silicon waste, the oxidation and loss of silicon have become the biggest challenges restricting the recycling of crystalline silicon waste to prepare high-purity silicon and silicon alloys. The main and most difficult impurity to remove in crystalline silicon waste is O; therefore, how to remove O impurities in crystalline silicon waste and efficiently recover silicon resources is a problem currently faced.

In the process of preparing SiC ceramics to produce large-sized and complex-shaped devices, the wetting and bonding of the liquid solder alloy to SiC ceramics and the residual stress at the SiC ceramic/alloy interface are the key factors affecting SiC ceramic welding. Among the alloys for SiC ceramic welding, eutectic Si-Ti alloy is the most promising brazing alloy. This is mainly because Ti and Si elements have good wettability to SiC ceramics, eutectic Si-Ti alloy has ideal high-temperature microstructure and good fluidity at high temperatures, which is conducive to forming a dense and tight joint structure with SiC ceramics. However, the main method for preparing eutectic Si-Ti alloy solder is to use expensive high-purity silicon and high-purity titanium as raw materials, which is not conducive to resource sustainability and cost reduction. If the eutectic Si-Ti alloy solder can be directly prepared using waste SCR catalyst and crystalline silicon waste, the high cost problem of eutectic Si-Ti alloy solder preparation can be solved.

Summary of the invention

In view of the problems of difficulty in recycling Ti, W and V in the waste SCR catalyst in the prior art, difficulty in recycling Si in crystalline silicon waste, and high cost of preparing eutectic Si-Ti alloy solder, the present invention proposes a method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time, which can not only realize the clean recycling of the two industrial solid wastes, waste SCR catalyst and crystalline silicon waste, but also prepare Si-Ti alloy solder for welding SiC-based ceramic materials. It has obvious economic benefits and broad application prospects.

A method for preparing Si-Ti alloy solder by using waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time, the specific steps are as follows:

(1) Mixing the waste SCR catalyst, crystalline silicon waste and slag-forming agent uniformly to obtain a mixed material; placing the mixed material in an argon atmosphere, heating it to 1773-1823K for reduction smelting, and obtaining Si-Ti alloy containing tungsten and vanadium and harmless residue after slag and gold separation;

(2) placing the Si-Ti alloy containing tungsten and vanadium in step (1) in a vacuum or argon atmosphere, heating it to a molten state and subjecting it to directional solidification separation and purification, thereby obtaining in sequence a (Ti, W, V)Si ₂ phase enrichment, a V-containing eutectic Si-Ti alloy solder (>99.4%), and an impurity enrichment; the (Ti, W, V)Si ₂ phase enrichment can be used as a raw material for recovering tungsten and vanadium; the V-containing eutectic Si-Ti alloy solder can be directly used for brazing SiC ceramics;

(3) The enriched product of (Ti, W, V) _Si2 phase in step (2) is used as a trace additive and is melted at high temperature with the V-containing eutectic Si-Ti alloy solder obtained in step 2 in a vacuum or argon atmosphere to form a composite Si-Ti alloy solder; the composite Si-Ti alloy solder has the advantages of low preparation cost and fine eutectic structure compared with the eutectic Si-Ti alloy solder synthesized from pure raw materials.

The crystalline silicon waste in step (1) is crystalline silicon waste generated in the process of preparing silicon wafers by diamond wire cutting polycrystalline silicon or single crystal silicon ingots, and the waste SCR catalyst is _{V2O5 - WO3} / _TiO2 waste catalyst.

The slagging agent in step (1) is a mixture of CaO, _SiO2 and MgO, wherein the amount of CaO added is 15-30% of the waste SCR catalyst, the amount of _SiO2 added is 6-24% of the waste SCR catalyst, and the amount of MgO added is 15-30% of the waste SCR catalyst. The mass of the crystalline silicon waste is 1.48-1.52 times the total mass of the waste SCR catalyst and the slagging agent. The residue after smelting reduction is mainly composed of CaO, _SiO2 and MgO, and is harmless residue.

In step (2), the vacuum degree is less than 10Pa; the heating method is resistance heating or induction heating; the movement rate of the sample during directional solidification is not greater than 2 μm/s; due to the advantages of good alloy separation effect and fine eutectic structure, directional solidification separation and purification under induction heating is preferred.

In the step (3), the amount of the (Ti, W, V)Si ₂ phase enrichment added is 0.5-0.8% of the mass of the V-containing eutectic Si-Ti alloy solder; and the vacuum degree is <10Pa.

The O impurities in the crystalline silicon waste are removed by the slag during the smelting process. The TiO ₂ , WO ₃ and V ₂ O ₅ in the waste SCR catalyst are reduced by silicon and enter the silicon melt during the smelting process. After separation of slag and gold, Si-Ti alloy containing tungsten and vanadium and harmless residue mainly composed of CaO, SiO ₂ and MgO are obtained. After melting, the Si-Ti alloy containing tungsten and vanadium is separated and purified by directional solidification, and is successively separated into (Ti, W, V)Si ₂ phase enrichment, V-containing eutectic Si-Ti alloy solder, and impurity enrichment. The (Ti, W, V)Si ₂ phase enrichment can not only continue to recover tungsten and vanadium, but also be used as a trace additive for V-containing eutectic Si-Ti alloy solder, and form a composite Si-Ti alloy solder after melting with V-containing eutectic Si-Ti alloy solder. V-containing eutectic Si-Ti alloy solder and composite Si-Ti alloy solder can be used for welding SiC-based ceramic materials.

The beneficial effects of the present invention are:

(1) The present invention uses two solid wastes, crystalline silicon waste and waste SCR catalyst, as raw materials, and utilizes silicon in the crystalline silicon waste to extract Ti, W and V in the waste SCR catalyst, thereby obtaining a higher extraction rate of Ti, W and V. At the same time, the slag formed by the waste SCR catalyst and the slag-forming agent is utilized to remove the O impurity in the crystalline silicon waste, and a Si-Ti alloy containing tungsten and vanadium is obtained after reduction smelting; the Si-Ti alloy containing tungsten and vanadium is subjected to directional solidification separation and purification to obtain a eutectic Si-Ti alloy solder containing a small amount of V and a (Ti, W, V)Si ₂ phase enrichment containing W and V; the (Ti, W, V)Si ₂ phase enrichment can be used as a raw material for recovering tungsten and vanadium; the V-containing eutectic Si-Ti alloy solder can be directly used for brazing SiC ceramics;

(2) The present invention selects CaO, _SiO2 and MgO as slag-forming agents. The residue components after smelting reduction are mainly CaO, _SiO2 and MgO, which are harmless residues and will not cause secondary pollution to the environment; the slag-forming _agent does not contain _Al2O3 , avoiding the contamination of eutectic Si-Ti alloy solder by Al impurities;

(3) Compared with the traditional method of preparing eutectic Si-Ti alloy solder using high-purity silicon and high-purity titanium, the V-containing eutectic Si-Ti alloy solder and the composite Si-Ti alloy solder obtained by the present invention have the advantages of low preparation cost and fine eutectic structure; the enriched product of (Ti, W, V)Si ₂ phase can be used as a trace additive to effectively adjust the melting temperature and fluidity of the V-containing eutectic Si-Ti alloy solder;

(4) The present invention effectively realizes the recycling and reuse of waste SCR catalyst and crystalline silicon waste, and at the same time realizes the effective utilization of Ti, W, V and Si in these two wastes. It can not only alleviate the consumption of Ti, W and V metal resources and Si resources and protect the environment, but also generate good economic benefits and achieve the purpose of "solid waste resourceization" and "waste treatment with waste".

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a process flow chart of Examples 1 and 4;

Fig. 2 is a process flow chart of Examples 2 and 3;

FIG3 is a microstructure characterization diagram of the V-containing eutectic Si-Ti alloy solder of Example 1;

FIG4 is a structural representation diagram of SiC ceramic brazed with V-containing eutectic Si-Ti alloy in Example 1;

FIG5 is a microstructure characterization diagram of the composite Si-Ti alloy solder of Example 2;

FIG6 is a structural representation diagram of the composite Si-Ti alloy brazing SiC ceramic in Example 2;

FIG7 is a microstructure characterization diagram of the composite Si-Ti alloy solder of Example 3;

FIG8 is a structural representation diagram of the composite Si-Ti alloy brazing SiC ceramic in Example 3;

FIG9 is a microstructure characterization diagram of the V-containing eutectic Si-Ti alloy solder of Example 4;

FIG. 10 is a structural representation diagram of SiC ceramic brazed with V-containing eutectic Si-Ti alloy in Example 4.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

Example 1: The TiO ₂ content of the waste SCR catalyst (V ₂ O ₅ -WO ₃ /TiO ₂ waste catalyst) in this example is 84.9wt%, the WO ₃ content is 4.36wt%, the V ₂ O ₅ content is 0.64wt%, and the other main components are 1.31wt% CaO, 0.4wt% Fe ₂ O ₃ , 3.36wt% SiO ₂ and 0.72wt% Al ₂ O ₃ ; the Si content in the crystalline silicon waste is 86.9wt%, of which the contents of Fe, O and Al impurities are 0.4wt%, 5.2wt% and 0.87wt% respectively;

A method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and simultaneously recovering tungsten and vanadium (see FIG1 ), the specific steps are as follows:

(1) The waste SCR catalyst, crystalline silicon waste and slag-forming agent (CaO, _SiO2 and MgO) are mixed uniformly to obtain a mixed material; the mixed material is placed in an argon atmosphere, heated to a temperature of 1823K and reduced and smelted for 60 minutes, and the slag is separated to obtain a Si-Ti alloy containing tungsten and vanadium and a harmless residue (mainly composed of CaO, _SiO2 and MgO); the amount of CaO added is 30% of the waste SCR catalyst, the amount of _SiO2 added is 6% of the waste SCR catalyst, and the amount of MgO added is 30% of the waste SCR catalyst; the mass of the crystalline silicon waste is 1.50 times the total mass of the waste SCR catalyst and the slag-forming agent;

In the Si-Ti alloy containing tungsten and vanadium in this embodiment, the content of Ti is 24.5wt%, the content of tungsten is 1.63wt%, the content of vanadium is 0.23wt%, and the contents of impurities O, Fe, Ca, Mg and Al are 0.02wt%, 0.26wt%, 0.3wt%, 0.12wt% and 0.06wt% respectively;

(2) placing the Si-Ti alloy containing tungsten and vanadium in step (1) in a vacuum (vacuum degree <10 Pa), heating it to 1773K, keeping it in a molten state and keeping it warm for 1 hour, and directional solidification separation and purification under electromagnetic induction heating conditions (the sample moving downward at a rate of 1.5 μm/s during directional solidification) to obtain a (Ti, W, V)Si ₂ phase enrichment, a V-containing eutectic Si-Ti alloy solder, and an impurity enrichment in turn; the (Ti, W, V)Si ₂ phase enrichment can further recover tungsten and vanadium; the V-containing eutectic Si-Ti alloy solder can be directly used for brazing SiC ceramics;

In this embodiment, the enrichment of (Ti, W, V)Si ₂ phase has a tungsten content of 15.3wt%, and a vanadium content of 0.48wt%; the purity of the V-containing eutectic Si-Ti alloy solder is 99.6wt.%, and the V content is 0.1wt.%; the microstructure characterization diagram of the V-containing eutectic Si-Ti alloy solder is shown in FIG3 , wherein the Si phase (black phase) and the V-containing TiSi ₂ phase (white phase) are alternately distributed to form a uniform and dense eutectic structure, and the TiSi ₂ phase contains 0.38at% of V;

The V-containing eutectic Si-Ti alloy solder is directly used as a brazing alloy for welding SiC ceramics: the V-containing eutectic Si-Ti alloy solder is cut into alloy foil with a thickness of 300µm and placed in the middle of the SiC ceramic sheet to be brazed, and then high-temperature brazing is performed in an argon atmosphere at 1693K for 20 minutes. After the shear strength test, the brazed SiC ceramic has a shear strength of 86.5MPa; the structural characterization diagram of SiC ceramic brazed with the V-containing eutectic Si-Ti alloy is shown in Figure 4. The V-containing eutectic Si-Ti alloy and the SiC ceramic are well bonded and evenly distributed in the weld area.

Example 2: The waste SCR catalyst (V ₂ O ₅ -WO ₃ /TiO ₂ waste catalyst) and crystalline silicon waste in this example are the same as those in Example 1;

A method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time (see Figure 2), the specific steps are as follows:

(1) The waste SCR catalyst, crystalline silicon waste and slag-forming agent (CaO, _SiO2 and MgO) are mixed uniformly to obtain a mixed material; the mixed material is placed in an argon atmosphere, heated to a temperature of 1773K and reduced and smelted for 40 minutes, and the slag is separated to obtain a Si-Ti alloy containing tungsten and vanadium and a harmless residue (mainly composed of CaO, _SiO2 and MgO); the amount of CaO added is 25% of the waste SCR catalyst, the amount of _SiO2 added is 12% of the waste SCR catalyst, and the amount of MgO added is 25% of the waste SCR catalyst; the mass of the crystalline silicon waste is 1.51 times the total mass of the waste SCR catalyst and the slag-forming agent;

In the Si-Ti alloy containing tungsten and vanadium in this embodiment, the content of Ti is 24.3wt%, the content of tungsten is 1.56wt%, the content of vanadium is 0.21wt%, and the contents of impurities O, Fe, Ca, Mg and Al are 0.01wt%, 0.24wt%, 0.28wt%, 0.1wt% and 0.05wt% respectively;

(2) placing the Si-Ti alloy containing tungsten and vanadium in step (1) in an argon atmosphere, heating it to 1723K to keep it in a molten state and keeping it warm for 0.5h, and directional solidifying, separating and purifying it under electromagnetic induction heating conditions (the downward movement rate of the sample during the directional solidification process is 1.8μm/s), and obtaining a (Ti, W, V) _Si2 phase enrichment, a V-containing eutectic Si-Ti alloy solder, and an impurity enrichment in turn; the (Ti, W, V) _Si2 phase enrichment can continue to recover tungsten and vanadium;

In this embodiment, the tungsten content in the enriched material of (Ti, W, V)Si ₂ phase is 14.6wt%, and the vanadium content is 0.42wt%; the purity of the V-containing eutectic Si-Ti alloy solder is 99.7wt.%, and the V content is 0.09wt.%;

(3) The enriched product of (Ti, W, V)Si ₂ phase was added as an additive to the Si-Ti alloy containing tungsten and vanadium, and heated to 1823K in an argon atmosphere to make it melt at high temperature and kept warm for 0.5h to form a composite Si-Ti alloy solder; the amount of the enriched product of (Ti, W, V)Si ₂ phase added was 0.5% of the mass of the eutectic Si-Ti alloy solder containing V; the microstructure characterization diagram of the composite Si-Ti alloy solder is shown in Figure 5, in which the Si phase (black phase) and the TiSi ₂ phase (white phase) containing W and V are alternately distributed to form a uniform and dense eutectic structure, and the TiSi ₂ phase contains a small amount of V and W, whose contents are 3.13at% and 0.7at%, respectively;

Composite Si-Ti alloy solder is used as a brazing alloy for welding SiC ceramics: the composite Si-Ti alloy solder is cut into alloy foil with a thickness of 300µm and placed in the middle of the SiC ceramic sheet to be brazed, and then high-temperature brazing is performed in an argon atmosphere at 1723K for 20 minutes. After the shear strength test, the shear strength of the brazed SiC ceramic is 88.3MPa; the structural characterization diagram of the composite Si-Ti alloy brazing SiC ceramic is shown in Figure 6. The composite Si-Ti alloy and SiC ceramic are well bonded and evenly distributed in the weld area.

Example 3: The waste SCR catalyst (V ₂ O ₅ -WO ₃ /TiO ₂ waste catalyst) and crystalline silicon waste in this example are the same as those in Example 1;

A method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time (see Figure 2), the specific steps are as follows:

(1) The waste SCR catalyst, crystalline silicon waste and slag-forming agent (CaO, _SiO2 and MgO) are mixed uniformly to obtain a mixed material; the mixed material is placed in an argon atmosphere, heated to a temperature of 1823K and reduced and smelted for 80 minutes, and the slag is separated to obtain a Si-Ti alloy containing tungsten and vanadium and a harmless residue (mainly composed of CaO, _SiO2 and MgO); the amount of CaO added is 20% of the waste SCR catalyst, the amount of _SiO2 added is 18% of the waste SCR catalyst, and the amount of MgO added is 20% of the waste SCR catalyst; the mass of the crystalline silicon waste is 1.48 times the total mass of the waste SCR catalyst and the slag-forming agent;

In the Si-Ti alloy containing tungsten and vanadium in this embodiment, the content of Ti is 24.8wt%, the content of tungsten is 1.78wt%, the content of vanadium is 0.26wt%, and the contents of impurities O, Fe, Ca, Mg and Al are 0.02wt%, 0.29wt%, 0.34wt%, 0.16wt% and 0.07wt% respectively;

(2) placing the Si-Ti alloy containing tungsten and vanadium in step (1) in an argon atmosphere, heating it to 1723K to keep it in a molten state and keeping it warm for 0.5h, and directional solidifying, separating and purifying it under electromagnetic induction heating conditions (the downward movement rate of the sample during the directional solidification process is 1.0μm/s), and obtaining a (Ti, W, V) _Si2 phase enrichment, a V-containing eutectic Si-Ti alloy solder, and an impurity enrichment in sequence; the (Ti, W, V) _Si2 phase enrichment can continue to recover tungsten and vanadium;

In this embodiment, the tungsten content in the enriched product of (Ti, W, V)Si ₂ phase is 15.9wt%, and the vanadium content is 0.68wt%; the purity of the V-containing eutectic Si-Ti alloy solder is 99.7wt.%, and the V content is 0.11wt.%;

(3) The enriched product of (Ti, W, V)Si ₂ phase is added as an additive to the Si-Ti alloy containing tungsten and vanadium, and heated to 1773K under vacuum (vacuum degree <10 Pa) to make it melt at high temperature and keep it at this temperature for 1 hour to form a composite Si-Ti alloy solder. The amount of the enriched product of (Ti, W, V)Si ₂ phase added is 0.8% of the mass of the eutectic Si-Ti alloy solder containing V. The microstructure characterization diagram of the composite Si-Ti alloy solder is shown in Figure 7, in which the Si phase (black phase) and the TiSi ₂ phase (white phase) containing W and V are alternately distributed to form a uniform and dense eutectic structure. The TiSi ₂ phase contains a small amount of V and W, and the contents are 3.16at% and 0.73at%, respectively.

Composite Si-Ti alloy solder is used as a brazing alloy for welding SiC ceramics: the composite Si-Ti alloy solder is cut into alloy foil with a thickness of 300µm and placed in the middle of the SiC ceramic sheet to be brazed, and then high-temperature brazing is performed in an argon atmosphere at 1693K for 25 minutes. After the shear strength test, the shear strength of the brazed SiC ceramic is 87.9MPa; the structural characterization diagram of the composite Si-Ti alloy brazing SiC ceramic is shown in Figure 8. The composite Si-Ti alloy and SiC ceramic are well bonded and evenly distributed in the weld area.

Example 4: The waste SCR catalyst (V ₂ O ₅ -WO ₃ /TiO ₂ waste catalyst) and crystalline silicon waste in this example are the same as those in Example 1;

A method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and simultaneously recovering tungsten and vanadium (see FIG1 ), the specific steps are as follows:

(1) The waste SCR catalyst, crystalline silicon waste and slag-forming agent (CaO, _SiO2 and MgO) are mixed uniformly to obtain a mixed material; the mixed material is placed in an argon atmosphere, heated to a temperature of 1773K and reduced and smelted for 30 minutes, and the slag is separated to obtain a Si-Ti alloy containing tungsten and vanadium and a harmless residue (mainly composed of CaO, _SiO2 and MgO); the amount of CaO added is 25% of the waste SCR catalyst, the amount of _SiO2 added is 12% of the waste SCR catalyst, and the amount of MgO added is 25% of the waste SCR catalyst; the mass of the crystalline silicon waste is 1.52 times the total mass of the waste SCR catalyst and the slag-forming agent;

In the Si-Ti alloy containing tungsten and vanadium in this embodiment, the content of Ti is 24.1wt%, the content of tungsten is 1.52wt%, the content of vanadium is 0.19wt%, and the contents of impurities O, Fe, Ca, Mg and Al are 0.01wt%, 0.21wt%, 0.22wt%, 0.08wt% and 0.04wt% respectively;

(2) placing the Si-Ti alloy containing tungsten and vanadium in step (1) in a vacuum (vacuum degree <10 Pa), heating it to 1723K, keeping it in a molten state and keeping it warm for 0.5h, and directional solidification, separation and purification under electromagnetic induction heating conditions (the sample moving downward at a rate of 1.8μm/s during directional solidification) to obtain a (Ti, W, V)Si ₂ phase enrichment, a V-containing eutectic Si-Ti alloy solder, and an impurity enrichment in turn; the (Ti, W, V)Si ₂ phase enrichment can further recover tungsten and vanadium; the V-containing eutectic Si-Ti alloy solder can be directly used for brazing SiC ceramics;

In this embodiment, the tungsten content in the enriched product of (Ti, W, V)Si ₂ phase is 14.2wt%, and the vanadium content is 0.38wt%; the purity of the eutectic Si-Ti alloy solder containing V is 99.6wt.%, and the V content is 0.08wt.%; the microstructure characterization diagram of the eutectic Si-Ti alloy solder containing V is shown in FIG9 , wherein the Si phase (black phase) and the TiSi ₂ phase containing V (white phase) are alternately distributed to form a uniform and dense eutectic structure, and the TiSi ₂ phase contains 0.33at% of V;

The V-containing eutectic Si-Ti alloy solder is directly used as a brazing alloy for welding SiC ceramics: the V-containing eutectic Si-Ti alloy solder is cut into an alloy foil with a thickness of 300µm and placed in the middle of the SiC ceramic sheet to be brazed, and then high-temperature brazing is performed in an argon atmosphere at 1693K for 20 minutes. After the shear strength test, the brazed SiC ceramic has a shear strength of 87.0MPa; the structural characterization diagram of SiC ceramic brazed with the V-containing eutectic Si-Ti alloy is shown in Figure 10. The V-containing eutectic Si-Ti alloy and the SiC ceramic are well bonded and evenly distributed in the weld area.

The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims (5)

1. A method for preparing Si-Ti alloy solder using waste SCR catalyst and crystalline silicon waste and recovering tungsten and vanadium at the same time, characterized in that the specific steps are as follows: (1) Mixing waste SCR catalyst, crystalline silicon waste and slag-forming agent uniformly to obtain a mixed material; placing the mixed material in an argon atmosphere, heating it to 1773-1823K for reduction smelting, wherein the O impurities in the crystalline silicon waste are removed by slag during the smelting process, and _TiO2 , _{WO3 and V2O5} in the waste SCR catalyst are reduced by silicon in the crystalline silicon waste and enter into the silicon melt during the smelting process, and Si-Ti alloy containing _{tungsten and vanadium and harmless residue are obtained after slag-gold separation; the waste SCR catalyst is V2O5 - WO3} / _TiO2 waste catalyst; and the slag-forming agent is a mixture of CaO, _SiO2 and MgO; (2) placing the Si-Ti alloy containing tungsten and vanadium in step (1) in a vacuum or argon atmosphere, heating it to a molten state, and performing directional solidification separation and purification to obtain a (Ti, W, V) _Si2 phase enriched product, a V-containing eutectic Si-Ti alloy solder, and an impurity enriched product in sequence; (3) The enriched product of (Ti, W, V) _Si2 phase in step (2) is used as a trace additive and is melted at high temperature with the V-containing eutectic Si-Ti alloy solder obtained in step 2 in a vacuum or argon atmosphere to form a composite Si-Ti alloy solder. 2. The method for preparing Si-Ti alloy solder and recovering tungsten and vanadium by using waste SCR catalyst and crystalline silicon waste according to claim 1, characterized in that: the crystalline silicon waste in step (1) is crystalline silicon waste generated in the process of preparing silicon wafers by diamond wire cutting polycrystalline silicon or single crystal silicon ingots. 3. The method for preparing Si-Ti alloy solder and recovering tungsten and vanadium by using waste SCR catalyst and crystalline silicon waste according to claim 1, characterized in that: in step (1), the amount of CaO added is 15-30% of the waste SCR catalyst, the amount of _SiO2 added is 6-24% of the waste SCR catalyst, and the amount of MgO added is 15-30% of the waste SCR catalyst; the mass of the crystalline silicon waste is 1.48-1.52 times the total mass of the waste SCR catalyst and the slag-forming agent. 4. The method for preparing Si-Ti alloy solder and recovering tungsten and vanadium by using waste SCR catalyst and crystalline silicon waste according to claim 1, characterized in that: the vacuum degree in step (2) is <10Pa; the heating method is resistance heating or induction heating; and the movement rate of the sample during directional solidification is not greater than 2μm/s. 5. The method for preparing Si-Ti alloy solder and recovering tungsten and vanadium by using waste SCR catalyst and crystalline silicon waste according to claim 1, characterized in that: the amount of the enriched product of (Ti, W, V) _Si2 phase added in step (3) is 0.5-0.8% of the mass of the V-containing eutectic Si-Ti alloy solder; and the vacuum degree is <10Pa.