Cobalt removal method for diamond compact

Abstract

The invention relates to the technical field of diamond compact treatment, and provides a diamond compact cobalt removal method which comprises the following steps: placing a diamond compact in a first cobalt removal solution, and carrying out first cobalt removal treatment under an ultrasonic-assisted condition; cleaning and drying the diamond compact subjected to the first cobalt removal treatment; the dried diamond compact serves as an anode, a stainless steel plate serves as a cathode, and the diamond compact and the stainless steel plate are placed in a second cobalt removal solution to be subjected to electrochemical cobalt removal treatment; and cleaning and drying the diamond compact subjected to the electrochemical cobalt removal treatment. According to the method, the cobalt removal efficiency is greatly improved by adopting a mode of combining ultrasonic-assisted chemical cobalt removal and electrochemical cobalt removal, and compared with a traditional single cobalt removal method, lower cobalt residual quantity can be realized within shorter time, damage to diamond can be reduced, and the structural integrity and performance stability of the diamond compact can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond composite sheet processing, and specifically to a method for cobalt removal from diamond composite sheets. Background Art

[0002] Diamond composite sheets (PDC) are sintered from diamond micropowders and cemented carbide substrates under ultra-high pressure and high temperature. They combine the high hardness and wear resistance of diamond with the impact toughness of cemented carbide, and play an important role in many fields such as oil drilling and machining. They are extremely important high-performance composite materials in modern industry. However, cobalt in diamond composite sheets, as a binder phase, needs to be removed in some application scenarios.

[0003] There are many problems with the existing cobalt removal methods. In traditional single chemical cobalt removal methods, such as using only solutions like nitric acid for cobalt removal, the cobalt removal efficiency is low, and it is difficult to deeply remove cobalt inside the composite sheet, resulting in a high cobalt residue content, which affects the product performance. Moreover, such methods often cause significant damage to the diamond surface, easily causing graphitization on the diamond surface and reducing the quality of diamond composite sheets. For some early electrochemical cobalt removal methods, due to unreasonable electrolyte formulations, such as the lack of components that can effectively reduce the interfacial tension, the current distribution is uneven during the cobalt removal process, the cobalt removal effect is poor, and the energy consumption is high. In addition, previous cobalt removal processes rarely consider improving the surface performance of diamond composite sheets after cobalt removal, resulting in difficulties in bonding the cobalt-removed composite sheets with other materials, which limits their further application. Summary of the Invention

[0004] In view of the deficiencies of the existing technology, the present invention provides a method for cobalt removal from diamond composite sheets, which solves the problem that the existing cobalt removal methods for diamond composite sheets have an adverse effect on product performance.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for cobalt removal from diamond composite sheets, comprising the following steps:

[0006] S1. Place the diamond composite sheet in a first cobalt removal solution and perform the first cobalt removal treatment under ultrasonic assistance. The first cobalt removal solution is a mixed solution containing nitric acid with a mass concentration of 5%-15% and hydrofluoric acid with a mass concentration of 3%-10%. The ultrasonic frequency is 20-40 kHz, the treatment temperature is 40-60°C, and the treatment time is 10-30 min;

[0007] S2. Clean and dry the diamond composite sheet after the first cobalt removal treatment;

[0008] S3. Use the dried diamond composite sheet as the anode and a stainless steel plate as the cathode, and place them in a second cobalt removal solution for electrochemical cobalt removal treatment. The second cobalt removal solution is an aqueous solution containing 0.1 - 0.5 mol / L of sodium sulfate and 0.05 - 0.2 mol / L of sodium dodecyl sulfate, and the current density is 0.5 - 2 A / cm 2 , and the treatment time is 15 - 40 min;

[0009] S4. Clean and dry the diamond composite sheet after the electrochemical cobalt removal treatment.

[0010] Preferably, in the mixed solution in S1, the volume ratio of nitric acid to hydrofluoric acid is (2 - 4):1.

[0011] Preferably, it also includes pre - treating the diamond composite sheet before S1. The pre - treatment steps are: ultrasonically clean the diamond composite sheet successively with acetone and deionized water, and the ultrasonic cleaning time is 5 - 15 min for both, and then dry it at 60 - 80 °C for 10 - 20 min.

[0012] Preferably, the pH value of the second cobalt removal solution is 6 - 8.

[0013] Preferably, during the electrochemical cobalt removal treatment, the second cobalt removal solution is magnetically stirred, and the stirring speed is 200 - 400 r / min.

[0014] Preferably, it also includes a step of surface modification treatment for the diamond composite sheet after S3. The surface modification treatment steps are: place the diamond composite sheet in an ethanol solution containing 2% - 5% by mass of a silane coupling agent, soak it at 30 - 50 °C for 10 - 20 min, and then clean and dry it with ethanol.

[0015] Preferably, in S1 and S3, the dosage of the cobalt removal solution is 5 - 10 mL per gram of the diamond composite sheet.

[0016] Preferably, the cleaning steps are all ultrasonically cleaned with deionized water, and the ultrasonic cleaning time is 5 - 10 min, and the drying steps are all dried to constant weight at 60 - 80 °C.

[0017] The present invention provides a method for removing cobalt from diamond composite sheets. It has the following beneficial effects:

[0018] 1. By combining chemical cobalt removal with ultrasonic assistance and electrochemical cobalt removal, the present invention can efficiently remove the cobalt on the surface and in the shallow layer of the composite sheet during the first cobalt removal treatment. Subsequently, the electrochemical cobalt removal treatment promotes the detachment of cobalt from the deep layer of the composite sheet, greatly improving the cobalt removal efficiency. Compared with the traditional single cobalt removal method, it can achieve a lower cobalt residue content in a shorter time, and the overall treatment time is relatively short.

[0019] 2. By using hydrofluoric acid in the first cobalt removal solution, the present invention can effectively inhibit the graphitization of the diamond surface while removing cobalt, reducing the damage to the diamond itself. At the same time, the parameters in the whole cobalt removal process are optimized to ensure the structural integrity and performance stability of the diamond composite sheet.

[0020] 3. By adding surface modification treatment after cobalt removal, the silane coupling agent can form chemical bonds with the diamond surface, significantly improving the surface performance of the composite sheet and enhancing its bonding force with other materials, enabling the cobalt-removed diamond composite sheet in subsequent application scenarios such as bonding with matrix materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Embodiment 1:

[0024] Please refer to the attached Figure 1 , the embodiment of the present invention provides a method for removing cobalt from a diamond composite sheet, including the following steps:

[0025] Pretreatment: Take a diamond composite sheet with a mass of 5 g, first put it into acetone for ultrasonic cleaning for 10 min, use the good solubility of acetone to remove the oil and some impurities on the surface of the composite sheet, then put it into deionized water for ultrasonic cleaning for 10 min to further remove the residual acetone and other water-soluble impurities, and finally dry it at 70 °C for 15 min to make the surface of the composite sheet dry and clean, preparing for the subsequent cobalt removal treatment;

[0026] The first cobalt removal treatment: Prepare 40 mL of the first cobalt removal solution, the mass concentration of nitric acid in this solution is 10%, the mass concentration of hydrofluoric acid is 6%, and the volume ratio of nitric acid to hydrofluoric acid is 3:1. Place the dried composite sheet in the solution and perform the first cobalt removal treatment for 20 min under the conditions of an ultrasonic frequency of 30 kHz and a treatment temperature of 50 °C. The cavitation effect of ultrasound can accelerate the reaction of nitric acid and hydrofluoric acid in the solution with cobalt. Nitric acid oxidizes cobalt to make it dissolve, and hydrofluoric acid inhibits the graphitization of the diamond surface. The two work together to efficiently remove the cobalt on the surface and in the shallow layer of the composite sheet;

[0027] First cleaning and drying: Ultrasonically clean the cobalt - removed composite sheet with deionized water for 8 min to remove the residual cobalt - removal solution and reaction products on the surface, and then dry it at 70 °C until constant weight to ensure that there is no water residue on the surface of the composite sheet, facilitating subsequent electrochemical cobalt removal;

[0028] Electrochemical cobalt removal treatment: Use a stainless - steel plate as the cathode and the composite sheet as the anode, and place them in 50 mL of a second cobalt - removal solution containing 0.3 mol / L sodium sulfate and 0.1 mol / L sodium dodecyl sulfate. Adjust the pH value of the solution to 7, and carry out electrochemical cobalt removal treatment at a current density of 1 A / cm 2 ² for 30 min. During this period, magnetically stir the solution at a speed of 300 r / min. Magnetic stirring makes the ions in the solution evenly distributed, ensuring the stability of the current density. Sodium sulfate in the second cobalt - removal solution provides conductive ions, and sodium dodecyl sulfate reduces the interfacial tension, promoting the detachment of cobalt from the deep layer of the composite sheet;

[0029] Second cleaning and drying: Ultrasonically clean the composite sheet with deionized water again for 8 min to remove the impurities generated during the electrochemical cobalt - removal process, and then dry it at 70 °C until constant weight. At this time, the cobalt content of the composite sheet is significantly reduced, the damage to the diamond surface is small, and the cobalt - removal efficiency is high;

[0030] Surface modification treatment: Place the composite sheet in an ethanol solution containing 3% (mass concentration) of silane coupling agent, and soak it at 40 °C for 15 min. The silane coupling agent can form chemical bonds with the diamond surface to improve the surface properties. Then wash and dry it with ethanol. After this treatment, the bonding force between the composite sheet and other materials is significantly enhanced.

[0031] Example 2:

[0032] The embodiment of the present invention provides a method for removing cobalt from a diamond composite sheet, including the following steps:

[0033] Pretreatment: Select a diamond composite sheet with a mass of 8 g, and ultrasonically clean it in acetone and deionized water in turn, with the time being 8 min for both. Through ultrasonic oscillation, acetone can quickly dissolve oil stains, and deionized water rinses off the residual impurities. Dry it at 65 °C for 12 min to ensure that there are no impurities and moisture on the surface of the composite sheet, creating good conditions for cobalt removal;

[0034] First cobalt - removal treatment: Prepare 80 mL of a first cobalt - removal solution with a nitric acid mass concentration of 8% and a hydrofluoric acid mass concentration of 5%, and the volume ratio is 2.5:1. Place the composite sheet in the solution and treat it at an ultrasonic frequency of 25 kHz and a temperature of 45 °C for 15 min. Under ultrasonic assistance, the cobalt - removal solution quickly reacts with cobalt, efficiently removing the cobalt on the surface and at a certain depth of the composite sheet. At the same time, hydrofluoric acid protects the diamond from excessive corrosion;

[0035] First cleaning and drying: Use deionized water to ultrasonically clean the composite sheet for 6 minutes to remove residual solution and reaction products, and then dry it at 65°C to constant weight to make the surface of the composite sheet clean and dry, which is conducive to subsequent operations;

[0036] Electrochemical decobaltization treatment: The stainless steel plate was used as cathode and the composite sheet was used as anode. The solution was placed in 80 mL of the second decobaltization solution containing 0.2 mol / L sodium sulfate and 0.08 mol / L sodium dodecyl sulfate. The pH value was adjusted to 6.5. The current density was 1.2 A / cm 2 The electrochemical decobaltization treatment was carried out for 35 minutes under the conditions of 400 °C. During the treatment, the solution was magnetically stirred at a speed of 250 r / min. The stirring promoted the full diffusion of ions in the solution, ensured the uniform decobaltization reaction, and further reduced the cobalt content in the composite sheet.

[0037] Second cleaning and drying: ultrasonic cleaning with deionized water for 8 minutes to remove impurities after electrochemical decobalting, and drying at 65°C to constant weight to obtain a decobalted composite sheet with good decobalting effect and stable surface quality;

[0038] Surface modification treatment: The composite sheet is immersed in an ethanol solution of silane coupling agent with a mass concentration of 2.5% at 45°C for 12 minutes, then washed with ethanol and dried. After modification, the surface properties of the composite sheet are optimized and the bond with the base material is more firmly established.

[0039] Embodiment three:

[0040] The embodiment of the present invention provides a method for removing cobalt from a diamond composite sheet, comprising the following steps:

[0041] Pretreatment: Take a diamond composite sheet with a mass of 3g, ultrasonically clean it in acetone for 12 minutes to dissolve organic impurities such as oil, then ultrasonically clean it in deionized water for 12 minutes to remove residual acetone and other impurities, and finally dry it at 75℃ for 18 minutes to make the surface of the composite sheet clean and dry;

[0042] First decobalting treatment: Prepare 30mL of the first decobalting solution, with a nitric acid mass concentration of 12% and a hydrofluoric acid mass concentration of 8%, with a volume ratio of 3.5:1, place the composite sheet in the solution, and treat it at an ultrasonic frequency of 35kHz and a temperature of 55°C for 25 minutes. The ultrasound and the decobalting solution work together to quickly and effectively remove the cobalt on the surface and shallow layer of the composite sheet, while protecting the diamond from serious damage;

[0043] First cleaning and drying: Use deionized water for ultrasonic cleaning for 10 minutes to completely remove the residual solution and reaction products, and then dry at 75°C to constant weight to ensure that the surface of the composite sheet is clean and free of moisture;

[0044] Electrochemical cobalt removal treatment: Using a stainless steel plate as the cathode and the composite sheet as the anode, place them in 30 mL of a second cobalt removal solution containing 0.4 mol / L sodium sulfate and 0.15 mol / L sodium dodecyl sulfate, adjust the pH value to 7.5, and perform electrochemical cobalt removal treatment for 25 min at a current density of 1.5 A / cm 2 while magnetically stirring the solution at a speed of 350 r / min. Stirring ensures uniform ion distribution in the solution, improves the cobalt removal efficiency, and further reduces the cobalt residue in the composite sheet;

[0045] Second cleaning and drying: Ultrasonically clean with deionized water for 10 min to remove impurities generated by electrochemical cobalt removal, and dry to constant weight at 75 °C to obtain a high-quality cobalt-removed composite sheet;

[0046] Surface modification treatment: Place the composite sheet in an ethanol solution of 4% mass concentration of silane coupling agent, soak it at 35 °C for 18 min, then wash and dry with ethanol. After surface modification, the hydrophilicity of the composite sheet surface and its bonding force with other materials are significantly improved, which is beneficial for subsequent applications.

[0047] Comparative example 1:

[0048] This comparative example provides a method for removing cobalt from diamond composite sheets, including the following steps:

[0049] Pretreatment: Take a diamond composite sheet with a mass of 5 g, first ultrasonically clean it in acetone for 10 min to remove oil stains and some impurities on the composite sheet surface using the good solubility of acetone, then ultrasonically clean it in deionized water for 10 min to further remove residual acetone and other water-soluble impurities, and finally dry it at 70 °C for 15 min to make the composite sheet surface dry and clean, preparing for subsequent cobalt removal treatment;

[0050] First cobalt removal treatment: Prepare 40 mL of the first cobalt removal solution, in which the mass concentration of nitric acid is 10% and the mass concentration of hydrofluoric acid is 6%, and the volume ratio of nitric acid to hydrofluoric acid is 3:1. Place the dried composite sheet in the solution and perform the first cobalt removal treatment for 20 min under the conditions of an ultrasonic frequency of 30 kHz and a treatment temperature of 50 °C. The cavitation effect of ultrasonic waves can accelerate the reaction of nitric acid and hydrofluoric acid with cobalt in the solution. Nitric acid oxidizes cobalt to make it dissolve, and hydrofluoric acid inhibits the graphitization of the diamond surface. The two work together to efficiently remove the cobalt on the surface and in the shallow layer of the composite sheet;

[0051] First cleaning and drying: Ultrasonically clean the cobalt-removed composite sheet with deionized water for 8 min to remove the residual cobalt removal solution and reaction products on the surface, and then dry it to constant weight at 70 °C to ensure no water residue on the composite sheet surface;

[0052] Second cleaning and drying: Ultrasonically clean the composite sheet with deionized water again for 8 min to remove impurities, and then dry it to a constant weight at 70 °C. At this time, the cobalt content of the composite sheet decreases somewhat. However, due to the lack of electrochemical decobalt treatment, the decobalt efficiency is not as good as that of the example.

[0053] Comparative Example 2:

[0054] This comparative example provides a method for decobalt of diamond composite sheets, which includes the following steps:

[0055] Pretreatment: Take a diamond composite sheet with a mass of 5 g, first ultrasonically clean it in acetone for 10 min to remove the oil stain and some impurities on the surface of the composite sheet by using the good solubility of acetone, then ultrasonically clean it in deionized water for 10 min to further remove the residual acetone and other water-soluble impurities, and finally dry it at 70 °C for 15 min to make the surface of the composite sheet dry and clean, preparing for the subsequent decobalt treatment;

[0056] First decobalt treatment: Prepare 40 mL of the first decobalt solution, in which the mass concentration of nitric acid is 10% and the mass concentration of hydrofluoric acid is 6%, and the volume ratio of nitric acid to hydrofluoric acid is 3:1. Place the dried composite sheet in the solution and carry out the first decobalt treatment for 20 min under the conditions of an ultrasonic frequency of 30 kHz and a treatment temperature of 50 °C. The cavitation effect of ultrasonic waves can accelerate the reaction of nitric acid and hydrofluoric acid with cobalt in the solution. Nitric acid oxidizes cobalt to dissolve it, and hydrofluoric acid inhibits the graphitization of the diamond surface. The two work together to efficiently remove the cobalt on the surface and in the shallow layer of the composite sheet;

[0057] First cleaning and drying: Ultrasonically clean the decobalt-treated composite sheet with deionized water for 8 min to remove the residual decobalt solution and reaction products on the surface, and then dry it to a constant weight at 70 °C to ensure that there is no water residue on the surface of the composite sheet, facilitating the subsequent electrochemical decobalt;

[0058] Electrochemical decobalt treatment: Use a stainless steel plate as the cathode and the composite sheet as the anode, and place them in 50 mL of the second decobalt solution containing 0.3 mol / L sodium sulfate and 0.1 mol / L sodium dodecyl sulfate. Adjust the pH value of the solution to 7, and carry out the electrochemical decobalt treatment for 30 min at a current density of 1 A / cm 2 ². During this period, magnetically stir the solution at a speed of 300 r / min. Magnetic stirring makes the ions in the solution evenly distributed, ensuring the stability of the current density. Sodium sulfate in the second decobalt solution provides conductive ions, and sodium dodecyl sulfate reduces the interfacial tension, promoting the detachment of cobalt from the deep layer of the composite sheet;

[0059] Second cleaning and drying: Ultrasonically clean the composite sheet with deionized water again for 8 min to remove the impurities generated during the electrochemical decobaltization process, and then dry it to a constant weight at 70 °C. At this time, the cobalt content of the composite sheet is significantly reduced, the damage to the diamond surface is small, and the decobaltization efficiency is high. However, due to the lack of surface modification treatment, the bonding strength with other materials is not as good as that of the examples.

[0060] In summary, in Examples 1 to 3, the composite sheets with different masses were first ultrasonically cleaned with acetone and deionized water and then dried for pretreatment; then, by preparing the first decobaltization solution with different components and volumes, the first decobaltization was carried out at a specific ultrasonic frequency, temperature, and time; subsequently, after being ultrasonically cleaned and dried with deionized water, with the stainless steel plate as the cathode and the composite sheet as the anode, in the second decobaltization solution containing a specific concentration of sodium sulfate and sodium dodecyl sulfate, the electrochemical decobaltization was carried out by adjusting different current densities, treatment times, stirring speeds, and solution pH values; then, it was ultrasonically cleaned and dried with deionized water again, and finally, the composite sheet was surface-modified with an ethanol solution of a silane coupling agent with different mass concentrations at a specific temperature and time, so as to achieve the effects of significantly reducing the cobalt content, reducing the damage to the diamond surface, improving the decobaltization efficiency, and enhancing the bonding strength with other materials. In Comparative Example 1, the electrochemical decobaltization treatment was missing, resulting in a lower decobaltization efficiency than that of the examples; in Comparative Example 2, the surface modification treatment was not carried out, making the bonding strength with other materials not as good as that of the examples.

[0061] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for cobalt removal from diamond composite sheets, characterized in that, It includes the following steps: S1. Place the diamond composite sheet in the first decobalt solution and perform the first decobalt treatment under ultrasonic assistance. The first decobalt solution is a mixed solution containing nitric acid with a mass concentration of 5%-15% and hydrofluoric acid with a mass concentration of 3%-10%. The ultrasonic frequency is 20-40 kHz, the treatment temperature is 40-60 °C, and the treatment time is 10-30 min; S2. Clean and dry the diamond composite sheet after the first decobalt treatment; S3. Use the dried diamond composite sheet as the anode and a stainless steel plate as the cathode, and place them in a second cobalt stripping solution for electrochemical cobalt stripping treatment. The second cobalt stripping solution is an aqueous solution containing 0.1 - 0.5 mol / L of sodium sulfate and 0.05 - 0.2 mol / L of sodium dodecyl sulfate, and the current density is 0.5 - 2 A / cm 2 , and the treatment time is 15 - 40 min; S4. Clean and dry the diamond composite sheet after the electrochemical decobalt treatment.

2. The method for cobalt removal of a diamond composite sheet according to claim 1, wherein In the mixed solution in S1, the volume ratio of nitric acid to hydrofluoric acid is (2-4):

1.

3. A method for cobalt removal of a diamond composite sheet according to claim 1, characterized in that, It also includes pre-treating the diamond composite sheet before S1. The pre-treatment steps are: ultrasonically clean the diamond composite sheet successively with acetone and deionized water, and the ultrasonic cleaning time is 5-15 min for both. Then dry it at 60-80 °C for 10-20 min.

4. A method for removing cobalt from a diamond composite sheet according to claim 1, characterized in that, The pH value of the second decobalt solution is 6-8.

5. A method for removing cobalt from a diamond composite sheet according to claim 1, characterized in that, During the electrochemical decobalt treatment process, magnetically stir the second decobalt solution, and the stirring speed is 200-400 r / min.

6. A method for cobalt removal from a diamond composite sheet according to claim 1, characterized in that, It also includes the step of surface modification treatment on the diamond composite sheet after S3. The surface modification treatment steps are: place the diamond composite sheet in an ethanol solution containing a silane coupling agent with a mass concentration of 2%-5%, soak it at 30-50 °C for 10-20 min, and then clean and dry it with ethanol.

7. A method for removing cobalt from a diamond composite sheet according to claim 1, characterized in that, In S1 and S3, the dosage of the decobalt solution is 5-10 mL per gram of diamond composite sheet.

8. A method for cobalt removal from a diamond composite sheet according to claim 1, characterized in that All the cleaning steps are carried out by ultrasonic cleaning with deionized water, and the ultrasonic cleaning time is 5-10 min. All the drying steps are carried out at 60-80 °C until constant weight.

Images