A method for designing and preparing silicon-based high entropy alloys using photovoltaic silicon waste by a compensation method

Abstract

The present invention discloses a method for preparing silicon-based high-entropy alloy by using photovoltaic silicon waste through a compensation method, which specifically includes the following steps: (1) pre-treating silicon wafer cutting slurry; (2) high-temperature refining and furnace cooling; (3) crushing and melting with solvent metal, and after the metal is completely melted, directionally solidifying and furnace cooling; (4) cutting and separating along the interface between the silicon-rich region and the silicon-based alloy to obtain the silicon-rich region; (5) preparing the target metal material according to the component ratio of the silicon-based high-entropy alloy; (6) melting the silicon-rich region and the target metal material, standing and keeping warm, pouring into a mold, and cooling with the furnace to obtain. The new idea of ​​the present invention to design and prepare silicon-based high-entropy alloy by using the "compensation method" can shorten the impurity removal process, and realize the preparation of high-quality high-entropy alloy materials through reasonable component allocation and organizational control.

Description

Technical Field

[0001] The present invention relates to the technical field of high-value recycling of secondary resources, and more specifically to a method for preparing a silicon-based high-entropy alloy by utilizing photovoltaic silicon waste through a compensation method. Background Art

[0002] The green renewable energy photovoltaic industry represented by solar energy is showing a rapid development momentum in China.

[0003] Silicon wafers are an important component of solar cells. At present, the production and cutting method is diamond wire cutting technology. This technology has the advantages of high production efficiency, high control precision, low environmental load in the production process, easy recycling of cutting waste, and shallow mechanical damage on the surface of silicon wafers. Since 2018, it has gradually become the mainstream technology and completely replaced the original mortar cutting technology in 2019. During the cutting process, the diameter of the diamond wire is 60~80 μm, while the thickness of the silicon wafer is generally 170~180 μm. The diamond wire needs to be embedded in the silicon ingot to be cut, and the two move relative to each other at the same time. Due to the gaps caused by cutting, about 35%~40% of the high-purity silicon will be lost, which will be mixed with the SiO2 oxide formed on the high-speed cutting surface, the carbon particles detached from the diamond wire, metal impurities and organic solvents to form diamond wire cutting silicon powder waste.

[0004] In the context of the increasing installed capacity of photovoltaic power generation, the output of silicon wafers is huge, and a large amount of silicon waste will be generated during its production process. The country strongly supports the research and development of solid waste resource utilization technology, so we should vigorously develop the secondary utilization of silicon resources, develop green, high-value and efficient silicon resource processing technology, and realize the cascade disposal and value-added utilization of silicon wafer cutting waste. This can not only reduce silicon resource consumption and carbon emissions, reduce environmental pollution, but also create huge economic benefits, reduce the production cost of the photovoltaic industry, and promote the sustainable development of the photovoltaic industry.

[0005] Since my country's diamond wire cutting technology has only achieved large-scale production in recent years, the recycling of silicon waste is still in its early stages. Domestic and foreign researchers have encountered the following difficulties in the research they have carried out: (1) Purification and recycling. Current research still has shortcomings such as the failure to achieve simultaneous control or removal of the oxide layer and impurities. (2) Preparation of catalytic materials. Complex processing steps are required to obtain suitable surface properties. (3) Preparation of lithium-ion battery materials. The synthesis cost of nano-silicon anodes is expensive and the actual energy density is low.

[0006] Therefore, how to recycle and reuse silicon waste is an urgent problem that technicians in this field need to solve. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a method for designing and preparing a silicon-based high-entropy alloy using photovoltaic silicon waste through a compensation method. Through the "compensation method", photovoltaic silicon waste is used to design and synthesize a silicon-based high-entropy alloy with uniform metallographic structure and no segregation at one time, so as to solve the problem in the prior art that the oxide layer on the surface of cut silicon waste is difficult to remove and the impurity elements are complex.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing a silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method, specifically comprising the following steps:

[0010] (1) pre-treating silicon wafer cutting slurry to obtain silicon wafer cutting waste;

[0011] (2) Refining the silicon wafer cutting waste at high temperature and cooling it in the furnace to obtain refined silicon ingots;

[0012] (3) crushing the refined silicon ingot and melting it with the solvent metal, and after the metal is completely melted, directionally solidifying it and cooling it in the furnace to obtain a silicon-based high entropy alloy precursor;

[0013] (4) cutting and separating the silicon-based high entropy alloy precursor along the interface between the silicon-rich region and the silicon-based alloy to obtain the silicon-rich region for later use;

[0014] (5) Preparing the target metal material according to the composition ratio of the silicon-based high entropy alloy;

[0015] (6) The silicon-rich region and the target metal material are melted, allowed to stand and heat-insulated, poured into a mold, and cooled in the furnace to obtain a silicon-based high-entropy alloy.

[0016] Furthermore, in the above step (1), the silicon wafer cutting slurry is the untreated silicon powder-containing cutting waste liquid generated during the production and cutting process of single crystal silicon rods and / or polycrystalline silicon rods.

[0017] Furthermore, in the above step (1), the pretreatment includes solid-liquid separation, dehydration and drying, and the conditions are oxygen-free or inert gas. Furthermore, the drying is vacuum drying, the temperature is 60-100°C, preferably 80°C, 85°C or 90°C; the pressure is not higher than -0.6Bar.

[0018] A further beneficial effect of the above method is that, through pretreatment, the oxide layer on the surface of the silicon wafer cutting waste can be reduced and oxidation can be prevented.

[0019] Furthermore, in the above step (2), the high temperature refining equipment is an induction furnace or an electric arc furnace; the temperature of the high temperature refining is not less than 1600°C, preferably 1650°C, 1800°C or 1850°C; the pressure of the high temperature refining is not higher than 50Pa or an inert gas is introduced under normal pressure; the time of the high temperature refining is 0.5-3h, preferably 0.5h or 1h.

[0020] A further beneficial effect of the above method is that volatile impurities such as oxygen (including O, P, Al, Ca, etc.) in silicon wafer cutting waste can be removed through high-temperature refining.

[0021] Furthermore, in the above step (3), the solvent metal is at least one of aluminum (Al), tin (Sn) and copper (Cu).

[0022] A further beneficial effect of the above method is that the solvent metal selected in the present invention has a certain adsorption effect on metal impurities in the refined silicon ingot.

[0023] Furthermore, in the above step (3), the equipment for molten material is a directional solidification resistance furnace or a directional solidification induction furnace; the temperature of the molten material is not less than 1450°C, preferably 1450°C or 1500°C; the pressure of the molten material is not higher than 50Pa or an inert gas is introduced under normal pressure; the time for directional solidification is 0.5-80h, preferably 6.5h, 10h or 18h.

[0024] A further beneficial effect of the above method is that, through melting and directional solidification, some metal impurities such as Fe, Ti, Ni can be removed without complete removal, and a certain amount of solvent metal can be introduced in a controllable manner. The residual metal impurities and the introduced solvent metal are the target metal materials required for the subsequent preparation of silicon-based high-entropy alloys, shortening the impurity removal process.

[0025] Furthermore, in the above step (5), the target metal material is at least four of chromium (Cr), aluminum (Al), iron (Fe), copper (Cu), tin (Sn), germanium (Ge), antimony (Sb), manganese (Mn), cobalt (Co), nickel (Ni), gallium (Ga) and niobium (Nb), preferably chromium, aluminum, iron and copper, or aluminum, tin, germanium, gallium and niobium, or iron, copper, tin, germanium and antimony.

[0026] Furthermore, in the above step (6), the smelting equipment is an induction furnace or an electric arc furnace; the smelting temperature is not less than 1450°C, preferably 1550°C, 1800°C or 2500°C; the smelting pressure is not higher than 50 Pa or an inert gas is introduced under normal pressure.

[0027] Furthermore, in the above step (6), the time of standing and keeping warm is 0.5-2.5h, preferably 0.5h.

[0028] Furthermore, in the above step (6), the silicon-based high entropy alloy is an Al-Cr-Cu-Fe-Si high entropy alloy, a Nb-Al-Ga-Ge-Si-Sn high entropy alloy or a Ge-Si-Sn-Cu-Fe-Sb high entropy alloy, the atomic mass percentage of each element is 5% to 35%, and the sum of the atomic mass percentages of all elements is 100%. Furthermore, the silicon-based high entropy alloy is an Al2CrCuFeSi high entropy alloy, a Nb3(Al 0.1 Ga 0.1 Ge 0.2 Si 0.3 Sn 0.3 ) High entropy alloy or Ge2Si2SnCu 0.5 Fe 0.5 Sb 0.5 High entropy alloy.

[0029] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The present invention starts from an interdisciplinary perspective, based on the unique physical and chemical properties of diamond wire-cut silicon waste in the photovoltaic industry and its natural "endowment" as a raw material for preparing silicon-based high-entropy alloys, and adopts vacuum refining and electromagnetic melting combined with the first proposed "compensation concept" to carry out the method and route of "vacuum refining combined with solvent refining to assist silicon waste purification-alloying design to prepare high-entropy alloy recycling", which has the advantages of short process, low cost, large-scale value-added utilization, environmental protection, pollution-free and sustainable development.

[0031] 2. The present invention adopts vacuum / inert gas atmosphere conditions to avoid secondary oxidation of raw materials, while improving the impurity removal effect, and has the advantages of high efficiency and energy saving.

[0032] 3. Since silicon waste itself contains metal impurities such as iron, nickel, aluminum, and copper, the present invention can omit the process of removing impurities from some metals, shorten the purification process, and directly prepare high entropy alloys by adding target elements to the resulting silicon-based alloy.

[0033] 4. The present invention utilizes electromagnetic metallurgy technology to controllably introduce a certain amount of solvent metals such as aluminum, tin and copper, thereby further removing non-target impurity elements in silicon waste while lowering the smelting temperature. The added solvent metals are used as raw materials for the subsequent preparation of silicon-based high-entropy alloys, thereby achieving the purpose of preparing silicon-based high-entropy alloy material precursors.

[0034] 5. The new idea of ​​the present invention to design and prepare silicon-based high-entropy alloys using the "compensation method" can shorten the impurity removal process and achieve the preparation of high-entropy alloy materials of high quality through reasonable composition blending and organizational control.

[0035] 6. The present invention is very suitable for preparing multi-component alloy materials (i.e., high entropy alloy materials) in view of the physicochemical characteristics of diamond wire cutting silicon waste, such as low silicon recovery rate and many impurity elements. It aims to make full use of the existing resource endowment of silicon waste and combine it with high entropy alloys to transform the waste into high-performance alloy materials and turn waste into treasure. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method specifically comprises the following steps:

[0039] (1) The untreated silicon powder-containing cutting waste liquid generated during the production and cutting process of the single crystal silicon rod is subjected to solid-liquid separation and dehydration in sequence under oxygen-isolating conditions, and is dried and dehydrated to a constant weight in a vacuum drying oven at a temperature of 85°C and a pressure not higher than -0.6 Bar to obtain silicon wafer cutting waste;

[0040] (2) placing the silicon wafer cutting waste in a graphite crucible, and then placing the graphite crucible in a vacuum induction furnace for high-temperature refining. The pressure in the furnace is not higher than 50 Pa. After heating for 0.5 hours, the temperature is kept at 1650°C for 1 hour, and the furnace is cooled to obtain a refined silicon ingot.

[0041] (3) The refined silicon ingot is crushed and placed in a vacuum directional solidification resistance furnace with the solvent metal aluminum for melting at a temperature of 1450°C and a pressure of no more than 50 Pa. After the metal is completely melted, the temperature is lowered to the liquidus temperature of the Si-Al system of 660°C, and the silicon-based high entropy alloy precursor is obtained by upward direction solidification at a rate of 1 μm / s for 18 hours and cooling with the furnace.

[0042] (4) cutting and separating the silicon-based high entropy alloy precursor along the interface between the silicon-rich region and the Si-Al alloy to obtain the silicon-rich region for later use;

[0043] (5) preparing the target metal materials chromium, aluminum, iron and copper according to the component ratio of Al2CrCuFeSi high entropy alloy;

[0044] (6) The silicon-rich zone and the target metal materials chromium, aluminum, iron and copper are placed in a vacuum induction furnace for smelting at a temperature of 1800°C and a pressure in the furnace of no more than 50 Pa. The mixture is kept at this temperature for 0.5 h and then poured into a mold and cooled with the furnace to obtain an Al2CrCuFeSi high entropy alloy.

[0045] Example 2

[0046] The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method specifically comprises the following steps:

[0047] (1) The untreated silicon powder-containing cutting waste liquid generated during the production and cutting process of the single crystal silicon rod is subjected to solid-liquid separation and dehydration in sequence under oxygen-isolating conditions, and is dried and dehydrated to a constant weight in a vacuum drying oven at a temperature of 80°C and a pressure not higher than -0.6 Bar to obtain silicon wafer cutting waste;

[0048] (2) placing the silicon wafer cutting waste in a graphite crucible, and then placing the graphite crucible in a vacuum induction furnace for high-temperature refining. The pressure in the furnace is not higher than 50 Pa. After heating for 0.5 hours, the temperature is kept at 1800°C for 1 hour, and the furnace is cooled to obtain a refined silicon ingot.

[0049] (3) The refined silicon ingot is crushed and placed in a vacuum directional solidification induction furnace with the solvent metal tin for melting at a temperature of 1500°C and a pressure of no more than 50 Pa. After the metal is completely melted, the temperature is lowered to the liquidus temperature of the Si-Sn system of 1332°C, and the silicon-based high entropy alloy precursor is obtained by downward directional solidification at a rate of 2 μm / s for 10 hours and cooling with the furnace.

[0050] (4) cutting and separating the silicon-based high entropy alloy precursor along the interface between the silicon-rich region and the Si-Sn alloy to obtain the silicon-rich region for later use;

[0051] (5) According to Nb3(Al 0.1 Ga 0.1 Ge 0.2 Si 0.3 Sn 0.3 ) The composition ratio of the high entropy alloy is to prepare the target metal materials of aluminum, tin, germanium, gallium and niobium;

[0052] (6) The silicon-rich region and the target metal materials aluminum, tin, germanium, gallium and niobium are placed in a vacuum induction furnace for smelting at a temperature of 2500°C and a pressure in the furnace of no more than 50 Pa. The mixture is kept at this temperature for 0.5 h and then poured into a mold and cooled with the furnace to obtain Nb3(Al 0.1 Ga 0.1 Ge 0.2 Si 0.3 Sn 0.3 )High entropy alloy.

[0053] Example 3

[0054] The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method specifically comprises the following steps:

[0055] (1) The untreated silicon powder-containing cutting waste liquid generated during the production and cutting process of polycrystalline silicon rods is subjected to solid-liquid separation and dehydration in sequence under oxygen-isolating conditions, and is dried and dehydrated to a constant weight in a vacuum drying oven at a temperature of 90°C and a pressure not higher than -0.6 Bar to obtain silicon wafer cutting waste;

[0056] (2) placing the silicon wafer cutting waste in a graphite crucible, and then placing the graphite crucible in a vacuum induction furnace for high-temperature refining. The pressure in the furnace is not higher than 50 Pa. After heating for 0.5 h, the temperature is kept at 1850 ° C for 0.5 h, and then cooled with the furnace to obtain a refined silicon ingot;

[0057] (3) The refined silicon ingot was crushed and placed in a directional solidification induction furnace with the solvent metal copper for melting at a temperature of 1450°C. Inert gas argon was introduced into the furnace. After the metal was completely melted, the temperature was lowered to the liquidus temperature of the Si-Cu system of 1075°C. The metal was directionally solidified downward at a rate of 3 μm / s for 6.5 hours. The metal was cooled in the furnace to obtain a silicon-based high entropy alloy precursor.

[0058] (4) cutting and separating the silicon-based high entropy alloy precursor along the interface between the silicon-rich region and the Si-Cu alloy to obtain the silicon-rich region for later use;

[0059] (5) According to Ge2Si2SnCu 0.5 Fe 0.5 Sb 0.5 The composition ratio of high entropy alloys, and the target metal materials iron, copper, tin, germanium and antimony;

[0060] (6) Place the silicon-rich region and the target metal materials iron, copper, tin, germanium and antimony in a vacuum arc furnace for smelting at a temperature of 1550°C and a pressure in the furnace of no more than 10Pa, heat to a molten state, and cool with the furnace to obtain Ge2Si2SnCu 0.5 Fe 0.5 Sb 0.5 High entropy alloy.

[0061] Performance Testing

[0062] 1. The Al2CrCuFeSi high entropy alloy prepared in Example 1 was measured to have a hardness of 782 HV under a load of 1 kg, which has great application potential in aerospace, automobile, shipbuilding, weapons and other fields that have high requirements on material density and hardness.

[0063] 2. Take the Nb3(Al 0.1 Ga 0.1 Ge 0.2 Si 0.3 Sn 0.3 ) high entropy alloy, and measured that its magnetization intensity and resistivity at 13 K changed with temperature and underwent a superconducting transition.

[0064] 3. Take the Ge2Si2SnCu obtained in Example 3 0.5 Fe 0.5 Sb 0.5 The high entropy alloy was crushed and ball-milled at 350 rpm for 3.5 h in an argon atmosphere. Then, a lithium-ion battery with the high entropy alloy as the negative electrode and a metal lithium sheet as the positive electrode was assembled. The electrochemical properties of the high entropy alloy were tested, and the results showed that its first discharge capacity was as high as 1528 mAh / g, the first charge capacity was 1425 mAh / g, and the first coulombic efficiency was as high as 93%. It has high reactivity and reversibility.

[0065] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing silicon-based high entropy alloys by using photovoltaic silicon waste through a compensation method, characterized in that: The specific steps include: (1) pre-treating silicon wafer cutting slurry to obtain silicon wafer cutting waste; (2) Refining the silicon wafer cutting waste at high temperature and cooling it in the furnace to obtain refined silicon ingots; (3) crushing the refined silicon ingot and melting it with the solvent metal, and after the metal is completely melted, directionally solidifying it and cooling it in the furnace to obtain a silicon-based high entropy alloy precursor; (4) cutting and separating the silicon-based high entropy alloy precursor along the interface between the silicon-rich region and the silicon-based alloy to obtain the silicon-rich region for later use; (5) Preparing the target metal material according to the composition ratio of the silicon-based high entropy alloy; (6) The silicon-rich region and the target metal material are melted, allowed to stand and kept warm, poured into a mold, and cooled along with the furnace to obtain the silicon-based high entropy alloy.

2. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (1), the silicon wafer cutting slurry is an untreated silicon powder-containing cutting waste liquid generated during the production and cutting process of single crystal silicon rods and / or polycrystalline silicon rods.

3. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (1), the pretreatment includes solid-liquid separation, dehydration and drying under the condition of oxygen exclusion or inert gas.

4. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (2), the high temperature refining equipment is an induction furnace or an electric arc furnace, the temperature is not less than 1600°C, the pressure is not higher than 50Pa or an inert gas is introduced under normal pressure for 0.5-3h.

5. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (3), the solvent metal is at least one of aluminum, tin and copper.

6. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (3), the equipment for the melt is a directional solidification resistance furnace or a directional solidification induction furnace, the temperature is not less than 1450°C, the pressure is not higher than 50Pa or an inert gas is introduced under normal pressure; the directional solidification time is 0.5-80h.

7. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (5), the target metal material is at least four of chromium, aluminum, iron, copper, tin, germanium, antimony, manganese, cobalt, nickel, gallium and niobium.

8. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (6), the smelting equipment is an induction furnace or an electric arc furnace, the temperature is not less than 1450°C, the pressure is not higher than 50 Pa or an inert gas is introduced under normal pressure.

9. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (6), the standing and heat preservation time is 0.5-2.5h.

10. The method for preparing silicon-based high entropy alloy by using photovoltaic silicon waste through a compensation method according to claim 1, characterized in that: In step (6), the silicon-based high entropy alloy is an Al-Cr-Cu-Fe-Si high entropy alloy, a Nb-Al-Ga-Ge-Si-Sn high entropy alloy or a Ge-Si-Sn-Cu-Fe-Sb high entropy alloy, the atomic mass percentage of each element is 5% to 35%, and the total atomic mass percentage of all elements is 100%.