A method for decobaltizing a diamond compact

Abstract

The present application relates to the technical field of diamond compact processing, and provides a method for removing cobalt from a diamond compact, which comprises placing the diamond compact in a first cobalt-removing solution and performing first cobalt-removing treatment under the condition of ultrasonic assistance; cleaning and drying the diamond compact after the first cobalt-removing treatment; placing the dried diamond compact as an anode and a stainless steel plate as a cathode in a second cobalt-removing solution to perform electrochemical cobalt-removing treatment; and cleaning and drying the diamond compact after the electrochemical cobalt-removing treatment. By adopting the combination of chemical cobalt-removing under ultrasonic assistance and electrochemical cobalt-removing, the cobalt-removing efficiency is greatly improved, compared with the traditional single cobalt-removing method, the cobalt residual amount can be reduced in a shorter time, the damage to the diamond itself can be reduced, and the structural integrity and performance stability of the diamond compact are ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diamond compact processing, in particular to a method for removing cobalt from diamond compact. BACKGROUND

[0002] A diamond compact (PDC) is formed by sintering diamond powder and a hard alloy substrate under ultra-high pressure and high temperature, and has high hardness and wear resistance of diamond and impact toughness of hard alloy, and is widely used in oil drilling, mechanical processing and other fields. It is a very important high-performance composite material in modern industry. However, cobalt in the diamond compact needs to be removed in some application scenarios as a binder phase.

[0003] The existing cobalt removal method has many problems. The traditional single chemical cobalt removal method, such as using only nitric acid solution to remove cobalt, has low cobalt removal efficiency and cannot remove cobalt in the inner part of the compact, resulting in high cobalt residual amount and affecting product performance. Moreover, such method often causes great damage to the diamond surface, easily causes graphitization of the diamond surface, and reduces the quality of the diamond compact. Some early electrochemical cobalt removal methods have uneven current distribution and poor cobalt removal effect due to unreasonable electrolyte formula, such as lack of components to effectively reduce the interfacial tension, and high energy consumption. In addition, the previous cobalt removal process rarely considers the improvement of the surface performance of the diamond compact after cobalt removal, resulting in difficulty in combining the compact with other materials after cobalt removal and limiting its further application. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a method for removing cobalt from a diamond compact, which solves the problem that the existing cobalt removal method for diamond compact causes adverse effects on product performance.

[0005] To achieve the above purpose, the present application is implemented by the following technical scheme: a method for removing cobalt from a diamond compact, comprising the following steps:

[0006] S1. Placing the diamond compact in a first cobalt removal solution and performing first cobalt removal treatment under ultrasonic assistance, wherein the first cobalt removal solution is a mixed solution containing 5%-15% nitric acid and 3%-10% hydrofluoric acid, the ultrasonic frequency is 20-40 kHz, the treatment temperature is 40-60℃, and the treatment time is 10-30 min;

[0007] S2. Cleaning and drying the diamond compact after the first cobalt removal treatment;

[0008] S3. The dried diamond composite piece is taken as an anode, a stainless steel plate is taken as a cathode, and the diamond composite piece is placed in a second decobalt solution for electrochemical decobalt treatment, the second decobalt 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, the current density is 0.5-2 A / cm 2 , and the treatment time is 15-40 min.

[0009] S4. The diamond composite piece after the electrochemical decobalt treatment is cleaned and dried.

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

[0011] Preferably, the method further comprises a pretreatment step of the diamond composite piece before S1, and the pretreatment step is that the diamond composite piece is sequentially ultrasonically cleaned with acetone and deionized water, the ultrasonic cleaning time is 5-15 min, and then the diamond composite piece is dried at 60-80 ℃ for 10-20 min.

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

[0013] Preferably, the second decobalt solution is magnetically stirred at a stirring speed of 200-400 r / min during the electrochemical decobalt treatment.

[0014] Preferably, the method further comprises a surface modification treatment step of the diamond composite piece after S3, and the surface modification treatment step is that the diamond composite piece is placed in an ethanol solution containing 2%-5% of a silane coupling agent, and then the diamond composite piece is soaked at 30-50 ℃ for 10-20 min, cleaned with ethanol and dried.

[0015] Preferably, the amount of the decobalt solution used in S1 and S3 is 5-10 mL per gram of the diamond composite piece.

[0016] Preferably, the cleaning step is ultrasonic cleaning with deionized water, and the ultrasonic cleaning time is 5-10 min; and the drying step is drying at 60-80 ℃ until the weight is constant.

[0017] The present application provides a decobalt method for a diamond composite piece.

[0018] 1. The present application combines chemical decobalt treatment with ultrasonic assistance and electrochemical decobalt treatment, efficiently removes cobalt on the surface and in the shallow layer of the composite piece in the first decobalt treatment, promotes the separation of cobalt from the deep layer of the composite piece in the subsequent electrochemical decobalt treatment, greatly improves the decobalt efficiency, and realizes lower cobalt residue in a shorter time compared with the traditional single decobalt method, and the overall treatment time is relatively short.

[0019] 2、The present application can effectively inhibit graphitization of the diamond surface and reduce damage to the diamond itself by using hydrofluoric acid in the first decobalt solution during decobalt, and the parameters during the entire decobalt process are optimized to ensure the structural integrity and performance stability of the diamond composite sheet.

[0020] 3、The present application can significantly improve the surface performance of the composite sheet by increasing surface modification treatment after decobalt, and the silane coupling agent can form a chemical bond with the diamond surface, thereby enhancing the bonding force with other materials, so that the diamond composite sheet after decobalt can be used in subsequent applications such as bonding with a matrix material. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The present application is a method flowchart. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] Embodiment one:

[0024] Please refer to the accompanying Figure 1 The present application provides a decobalt method for a diamond composite sheet, which comprises the following steps:

[0025] Pretreatment: take a diamond composite sheet with a mass of 5g, first ultrasonic cleaning in acetone for 10min, use the good solubility of acetone to remove oil stains and part of impurities on the surface of the composite sheet, then ultrasonic cleaning in deionized water for 10min to further remove residual acetone and other water-soluble impurities, and finally dry at 70℃ for 15min to make the surface of the composite sheet dry and clean, preparing for subsequent decobalt treatment;

[0026] First decobalt treatment: configure 40mL of the first decobalt solution, the mass concentration of nitric acid in the 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 decobalt treatment under the conditions of ultrasonic frequency 30kHz and treatment temperature 50℃ for 20min, the cavitation effect of ultrasonic 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, and the two can effectively remove cobalt on the surface and in the shallow layer of the composite sheet;

[0027] First cleaning and drying: the composite sheet after decobalt is ultrasonically cleaned with deionized water for 8 min, the residual decobalt solution and reaction product on the surface are removed, then it is dried at 70 DEG C until constant weight, ensuring that the surface of the composite sheet is free of moisture, facilitating subsequent electrochemical decobalt;

[0028] Electrochemical decobalt treatment: with stainless steel plate as cathode, composite sheet as anode, put into 50mL of second decobalt solution containing 0.3mol / L sodium sulfate and 0.1mol / L sodium dodecyl sulfate, adjust the pH value of the solution to 7, carry out electrochemical decobalt treatment for 30min under the current density of 1A / cm 2 The solution is magnetically stirred at a speed of 300r / min during the electrochemical decobalt treatment, the magnetic stirring makes the ions in the solution uniformly distributed, ensures the stability of the current density, the sodium sulfate in the second decobalt solution provides conductive ions, and the sodium dodecyl sulfate reduces the interfacial tension, promotes the separation of cobalt from the deep layer of the composite sheet;

[0029] Second cleaning and drying: the composite sheet is ultrasonically cleaned with deionized water again for 8 min to remove impurities generated in the electrochemical decobalt process, and then dried at 70 DEG C until constant weight, at this time, the cobalt content of the composite sheet is significantly reduced, and the diamond surface damage is small, and the decobalt efficiency is high;

[0030] Surface modification treatment: the composite sheet is placed in an ethanol solution containing 3% silane coupling agent by mass concentration, and soaked at 40 DEG C for 15 min, the silane coupling agent can form a chemical bond with the diamond surface to improve the surface properties. Then clean and dry with ethanol, after this treatment, the bonding force between the composite sheet and other materials is significantly enhanced.

[0031] Example two:

[0032] The embodiment of the present application provides a kind of diamond composite sheet decobalt method, comprising the following steps:

[0033] Pretreatment: select the diamond composite sheet with a mass of 8g, ultrasonically clean in acetone and deionized water in turn, and the time is 8min, by ultrasonic vibration, acetone can quickly dissolve oil dirt, and deionized water can wash away residual impurities. Dry at 65 DEG C for 12 min to ensure that the surface of the composite sheet is free of impurities and moisture, creating good conditions for decobalt;

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

[0035] First cleaning and drying: ultrasonic cleaning the composite sheet in deionized water for 6 min to remove residual solution and reaction product, and then drying at 65 DEG C until constant weight to make the surface of the composite sheet clean and dry, which is beneficial to subsequent operation;

[0036] Electrochemical decobalt treatment: the stainless steel plate is used as cathode, and the composite sheet is used as anode, which is placed in the second decobalt solution 80 mL containing 0.2 mol / L sodium sulfate and 0.08 mol / L sodium dodecyl sulfate, and the pH value is adjusted to 6.5, and the current density is 1.2 A / cm 2 The electrochemical decobalt treatment is carried out for 35 min, and the solution is magnetically stirred at a speed of 250 r / min during the treatment, so that the ions in the solution are fully diffused, the decobalt reaction is uniformly carried out, and the content of cobalt in the composite sheet is further reduced;

[0037] Second cleaning and drying: ultrasonic cleaning in deionized water for 8 min to remove impurities after electrochemical decobalt, and then drying at 65 DEG C until constant weight to obtain the decobalt composite sheet, which has good decobalt effect and stable surface quality;

[0038] Surface modification treatment: the composite sheet is soaked in an ethanol solution of 2.5% silane coupling agent, and then soaked at 45 DEG C for 12 min, and then cleaned with ethanol and dried, after modification, the surface properties of the composite sheet are optimized, and the combination with the base material is more firm.

[0039] Example three:

[0040] The embodiment of the present application provides a kind of diamond composite sheet decobalt method, comprising the following steps:

[0041] Pretreatment: take 3g diamond composite sheet, ultrasonic cleaning in acetone for 12 min, dissolve organic impurities such as oil dirt, then ultrasonic cleaning in deionized water for 12 min, remove residual acetone and other impurities, and finally dry at 75 DEG C for 18 min to make the surface of the composite sheet clean and dry;

[0042] First decobalt treatment: configure 30 mL first decobalt solution, nitric acid mass concentration 12%, hydrofluoric acid mass concentration 8%, volume ratio 3.5:1, and put the composite sheet into the solution, and treat at ultrasonic frequency 35 kHz and temperature 55 DEG C for 25 min.Ultrasonic and decobalt solution act together, quickly and effectively remove cobalt on the surface and shallow layer of the composite sheet, while protecting diamond from serious damage;

[0043] First cleaning and drying: ultrasonic cleaning in deionized water for 10 min to completely remove residual solution and reaction product, and then drying at 75 DEG C until constant weight to ensure that the surface of the composite sheet is clean and free of moisture;

[0044] Electrochemical decobalt treatment: take a stainless steel plate as the cathode and the composite sheet as the anode, and put them into 30 mL of the second decobalt solution containing 0.4 mol / L sodium sulfate and 0.15 mol / L sodium dodecyl sulfate, and adjust the pH value to 7.5, and then perform 25 min of electrochemical decobalt treatment at a current density of 1.5 A / cm 2 The solution is magnetically stirred at a speed of 350 r / min to ensure uniform distribution of ions in the solution, improve the decobalt efficiency, and further reduce the residual amount of cobalt in the composite sheet;

[0045] Second washing and drying: ultrasonic cleaning with deionized water for 10 min to remove impurities generated by electrochemical decobalt, and drying at 75°C until constant weight to obtain high-quality decobalt composite sheet;

[0046] Surface modification treatment: put the composite sheet into an ethanol solution with a mass concentration of 4% silane coupling agent, soak at 35°C for 18 min, then clean with ethanol and dry. After surface modification, the hydrophilicity and adhesion of the composite sheet surface to other materials are significantly improved, which is beneficial to subsequent application.

[0047] Comparative Example 1

[0048] This comparative example provides a method for decobalt of diamond composite sheet, which comprises the following steps:

[0049] Pretreatment: take a diamond composite sheet with a mass of 5g, first ultrasonic cleaning in acetone for 10 min to remove oil stains and part of impurities on the surface of the composite sheet, then ultrasonic cleaning in deionized water for 10 min to further remove residual acetone and other water-soluble impurities, and finally drying at 70°C for 15 min to make the surface of the composite sheet dry and clean for subsequent decobalt treatment;

[0050] First decobalt treatment: configure 40 mL of the first decobalt solution, which contains 10% nitric acid and 6% hydrofluoric acid with a volume ratio of 3:1, and then put the dried composite sheet into the solution, and perform the first decobalt treatment under the conditions of ultrasonic frequency of 30 kHz and treatment temperature of 50°C for 20 min. The cavitation effect of ultrasonic can accelerate the reaction of nitric acid and hydrofluoric acid with cobalt in the solution, and the oxidation of cobalt by nitric acid can make it dissolve, and the inhibition of diamond surface graphitization by hydrofluoric acid can efficiently remove the cobalt on the surface and in the shallow layer of the composite sheet;

[0051] First washing and drying: ultrasonic cleaning with deionized water for 8 min to remove the residual decobalt solution and reaction products on the surface of the decobalted composite sheet, and then drying at 70°C until constant weight to ensure that there is no water residue on the surface of the composite sheet;

[0052] Second cleaning and drying: The composite wafer was cleaned with deionized water for 8 min again, and impurities were removed. Then, the composite wafer was dried at 70°C until the weight was constant. At this time, the cobalt content of the composite wafer was reduced, but the cobalt removal efficiency was not as good as that of the embodiment because there was no electrochemical cobalt removal treatment.

[0053] Comparative Example Two:

[0054] The present comparative example provides a method for removing cobalt from a diamond composite wafer, comprising the following steps:

[0055] Pre-treatment: A diamond composite wafer with a mass of 5 g was taken and first cleaned with acetone for 10 min. Acetone has good solubility and can remove oil stains and part of impurities on the surface of the composite wafer. Then, the composite wafer was cleaned with deionized water for 10 min to further remove residual acetone and other water-soluble impurities. Finally, the composite wafer was dried at 70°C for 15 min to make the surface dry and clean, preparing for the subsequent cobalt removal treatment.

[0056] First cobalt removal treatment: 40 mL of the first cobalt removal solution was prepared, in which the mass concentration of nitric acid was 10% and the mass concentration of hydrofluoric acid was 6%, and the volume ratio of nitric acid to hydrofluoric acid was 3:1. The dried composite wafer was placed in the solution and subjected to the first cobalt removal treatment for 20 min under the conditions of ultrasonic frequency of 30 kHz and treatment temperature of 50°C. The cavitation effect of ultrasonic 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 graphitization on the surface of diamond. The two work together to efficiently remove cobalt on the surface and in the shallow layer of the composite wafer.

[0057] First cleaning and drying: The composite wafer after cobalt removal was cleaned with deionized water for 8 min to remove the residual cobalt removal solution and reaction products on the surface. Then, the composite wafer was dried at 70°C until the weight was constant to ensure that there was no water residue on the surface of the composite wafer, facilitating the subsequent electrochemical cobalt removal treatment.

[0058] Electrochemical cobalt removal treatment: A stainless steel plate was used as the cathode, and the composite wafer was used as the anode. The composite wafer was placed in 50 mL of the second cobalt removal solution containing 0.3 mol / L of sodium sulfate and 0.1 mol / L of sodium dodecyl sulfate, and the pH value of the solution was adjusted to 7. The composite wafer was subjected to the electrochemical cobalt removal treatment for 30 min under the current density of 1 A / cm 2 During the treatment, the solution was magnetically stirred at a speed of 300 r / min. The magnetic stirring made the ions in the solution uniformly distributed, ensuring the stability of the current density. Sodium sulfate in the second cobalt removal solution provided conductive ions, and sodium dodecyl sulfate reduced the interfacial tension, promoting the detachment of cobalt from the deep layer of the composite wafer.

[0059] Second cleaning and drying: The composite sheet was cleaned again with deionized water for 8 min by ultrasonic, to remove the impurities produced in the process of electrochemical decobalt, and then dried at 70℃ until constant weight. At this time, the cobalt content of the composite sheet was significantly reduced, and the diamond surface damage was small, and the decobalt efficiency was high. However, since there was no surface modification treatment, the adhesion to other materials was not as good as that of the examples.

[0060] In summary, in examples one to three, the composite sheets of different qualities were first pretreated by ultrasonic cleaning and drying with acetone and deionized water. Then, the first decobalt solution with different components and volumes was configured, and the first decobalt was carried out at a specific ultrasonic frequency, temperature and time. After ultrasonic cleaning and drying with deionized water, the electrochemical decobalt was carried out in the second decobalt solution containing a specific concentration of sodium sulfate and sodium dodecyl sulfate, with a stainless steel plate as the cathode and the composite sheet as the anode, by adjusting different current densities, treatment times, stirring speeds and solution pH values. After ultrasonic cleaning and drying with deionized water, the surface modification treatment was carried out on the composite sheet with an ethanol solution of silane coupling agent of different mass concentrations at a specific temperature and time, so as to achieve the effects of significantly reducing the cobalt content, reducing the diamond surface damage, improving the decobalt efficiency and enhancing the adhesion to other materials. Comparative example one lacks electrochemical decobalt treatment, resulting in a decobalt efficiency lower than that of the examples. Comparative example two does not perform surface modification treatment, so that the adhesion to other materials is not as good as that of the examples.

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

Claims

1. A method for decobaltizing a diamond compact, comprising: The method comprises the following steps: S1. placing the diamond compact in a first decobalt solution for a first decobalt treatment under ultrasonic assistance, wherein the first decobalt solution is a mixed solution containing 5-15% nitric acid and 3-10% hydrofluoric acid by mass concentration, the ultrasonic frequency is 20-40 kHz, the treatment temperature is 40-60°C, and the treatment time is 10-30 min; S2. cleaning and drying the diamond compact after the first decobalt treatment; S3. The dried diamond compact is used as an anode, and a stainless steel plate is used as a cathode, and they are placed in a second decobalt solution for electrochemical decobalt treatment, the second decobalt 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, the current density is 0.5-2 A / cm 2 , and the treatment time is 15-40 min; S4. cleaning and drying the diamond compact after the electrochemical decobalt treatment.

2. The method according to claim 1, wherein, The volume ratio of nitric acid to hydrofluoric acid in the mixed solution in S1 is (2-4):

1.

3. The method according to claim 1, wherein the method is characterized by, Further comprising a pretreatment of the diamond compact before S1, wherein the pretreatment comprises sequentially ultrasonic cleaning the diamond compact with acetone and deionized water for 5-15 min, and then drying at 60-80°C for 10-20 min.

4. The method according to claim 1, wherein the method is characterized by, The pH value of the second decobalt solution is 6-8.

5. The method of claim 1, wherein the method further comprises: During the electrochemical decobalt treatment, the second decobalt solution is subjected to magnetic stirring at a stirring speed of 200-400 r / min.

6. The method of claim 1, wherein the method further comprises: Further comprising a surface modification treatment of the diamond compact after S3, wherein the surface modification treatment comprises placing the diamond compact in an ethanol solution containing 2-5% silane coupling agent by mass concentration, soaking at 30-50°C for 10-20 min, then cleaning with ethanol and drying.

7. The method according to claim 1, wherein the method is characterized by, In S1 and S3, the amount of the decobalt solution used is 5-10 mL per gram of the diamond compact.

8. The method of claim 1, wherein the method further comprises, In the cleaning steps, deionized water is used for ultrasonic cleaning for 5-10 min, and the drying steps are all performed at 60-80°C until constant weight.

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