Method for testing content of free carbon in boron carbide

Abstract

The invention discloses a method for testing the content of free carbon in boron carbide, which comprises the following steps: S1, weighing m g of a boron carbide sample containing free carbon, putting into a reaction device filled with a chromic sulfate iodic acid solution, and arranging a carbon dioxide detection device at the output end of the reaction device; s2, the reaction device is heated, the boron carbide sample and the chromic sulfate iodic acid solution react to generate carbon dioxide, the heating time is H, the heating temperature is T, and the detection device measures the content of carbon dioxide in the first reaction; s3, repeating the step S2 to obtain the content of carbon dioxide in the second reaction; and S4, subtracting the content of carbon dioxide obtained in the step S3 from the content of carbon dioxide obtained in the first reaction in the step S2 to obtain the content of carbon dioxide generated in the free carbon reaction, and obtaining the content of free carbon in the boron carbide sample through conversion. The content of carbon dioxide generated by the boron carbide reaction at the same temperature within the same time is the same, the content of carbon dioxide generated by free carbon can be obtained, and the error is small.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, in particular to a method for testing the free carbon content in boron carbide. Background Art

[0002] Boron carbide (B4C) is an important component of abrasives. It has high hardness (second only to diamond and cubic boron nitride), high elastic modulus, low density, low thermal expansion coefficient, high thermal conductivity, good thermal stability and other advantages. It is widely used in many fields such as grinding media, wear-resistant coatings, nuclear reactor control rods and shielding rods, lightweight armor, molten metal crucibles, etc. In particular, with the proposal of the "dual carbon" goal in recent years, the nuclear energy industry has developed vigorously, and boron carbide, as a core neutron absorption material, has become a hot spot in industry research.

[0003] In the process of producing and using boron carbide, the requirements for its quality standards are particularly stringent, especially for the content of free carbon in boron carbide (free carbon refers to free carbon in boron carbide material that is not combined with boron to form boron carbide compounds). Its presence may affect the performance of the material, such as reducing hardness and flexural strength, and reacting with the environment. Testing the free carbon content is an important step to ensure the quality of boron carbide products. Its content directly affects the performance and application areas of the material.

[0004] At present, domestic enterprises generally use the wet oxidation decomposition combined with gas absorption weight method in JB / T 7993-2012 "Chemical Analysis Method of Boron Carbide" to measure the content of free carbon, that is, the boron carbide sample is placed in a hot potassium dichromate-concentrated sulfuric acid solution, and high-temperature treatment is carried out in an environment of oxygen and water vapor to completely oxidize the free carbon into carbon dioxide, and then the released carbon dioxide is collected and measured by gas absorption weight method. In this method, the gas is absorbed by a U-shaped glass tube filled with soda lime, and the carbon dioxide content is calculated by measuring the weight gain of the U-shaped glass tube. However, the dead weight of the U-shaped glass tube is increased, and the weight gain is small, resulting in poor stability and large errors in the free carbon test.

[0005] Invention patent CN 110146405A is a device for determining free carbon in boron carbide. The boron carbide sample is heated (100-300°C) and oxygen is introduced for heating and primary oxidation to convert the free boron in the boron carbide into combined boron, and then heated in water, filtered, and dried to obtain a primary oxide; then heated again (650-900°C) and introduced into an oxygen environment, the free carbon reacts to generate carbon dioxide, and the free carbon is calculated by calculating the carbon dioxide content. The operation steps of this method involve low-temperature oxidation, heating water, filtering, drying, high-temperature oxidation, etc., which are cumbersome, complicated, and inefficient; and the use of high-purity oxygen heating oxidation has a high risk factor, and has high requirements and costs for various aspects such as device safety; and at high temperatures, if the temperature control accuracy is not enough, the combined carbon in the boron carbide will also participate in the reaction to generate carbon dioxide, affecting the test results, and the application and promotion have certain limitations.

[0006] In the invention patent CN106645559A, the device and method for determining the free carbon content in boron carbide react the boron carbide sample with potassium dichromate-concentrated sulfuric acid solution under heating conditions to generate carbon dioxide, and the carbon dioxide enters the multi-stage sodium hydroxide solution through the power gas nitrogen for absorption, and the molar amount of the sodium hydroxide solution remaining in the absorption bottle is calculated by hydrochloric acid calibration; the original sodium hydroxide solution minus the remaining sodium hydroxide solution is the molar amount of the reaction with the generated carbon dioxide, and the free carbon content is obtained by conversion. The boron carbide sample is placed in a potassium dichromate-concentrated sulfuric acid solution under heating conditions, and the free carbon in the sample and the combined carbon in the boron carbide will participate in the reaction to generate carbon dioxide, causing the result to be larger than the actual value; in addition, when measuring the remaining carbon dioxide content, it is necessary to concentrate the solutions in multiple solution bottles, introducing human errors; in addition, the molar amount of the remaining sodium hydroxide solution is determined by hydrochloric acid titration, and the human error is large, which requires high requirements for inspectors; the above reasons also limit the promotion and application of this method.

[0007] The present invention is based on the actual needs of downstream customers of boron carbide, and develops an accurate and simple testing method for free carbon in boron carbide, which helps boron carbide production enterprises to improve the process and quality, and provides a better selection basis for boron carbide users and traders. Summary of the invention

[0008] In view of the deficiencies in the above-mentioned background technology, the present invention proposes a method for testing the free carbon content in boron carbide, which solves the problems of poor stability and large error in the free carbon testing in boron carbide in the prior art.

[0009] The technical solution of the present invention is achieved in this way:

[0010] A method for testing the free carbon content in boron carbide comprises the following steps:

[0011] S1: Weigh m grams of boron carbide sample containing free carbon and put it into a reaction device filled with chromium sulfate iodic acid solution, and the output end of the reaction device is provided with a carbon dioxide detection device;

[0012] S2: heating the reaction device, the boron carbide sample reacts with the chromium sulfate iodic acid solution to produce carbon dioxide, wherein the heating time is H, the heating temperature is T, and the detection device measures the carbon dioxide content of the first reaction;

[0013] S3: Repeat step S2 to obtain the carbon dioxide content of the second reaction;

[0014] S4: The carbon dioxide content produced by the free carbon reaction is obtained by subtracting the carbon dioxide content obtained in the second reaction in step S3 from the carbon dioxide content obtained in the first reaction in step S2. The free carbon content in the boron carbide sample can be obtained by conversion.

[0015] Further preferably, the reaction device in step S1 comprises a reaction flask for containing chromium sulfate iodide solution, and a drying and filtering component is provided at a gas outlet of the reaction flask.

[0016] Further preferably, the dry filter assembly comprises a filter washing bottle and a dry washing bottle, the filter washing bottle is filled with one-half of silver metamanganate, and the dry washing bottle is filled with one-half of anhydrous calcium chloride.

[0017] Further preferably, the gas inlet end of the reaction flask is provided with nitrogen as a power gas source, and the nitrogen flow rate is 16-60 ml / min.

[0018] Further preferably, an anti-backflow empty bottle and a drying bottle filled with anhydrous calcium chloride are also provided between the reaction flask and the nitrogen source.

[0019] Further preferably, in step S2, nitrogen is first introduced into the reaction device, and then the nitrogen flows through the reaction device and enters the detection device. When the measurement data of the detection device no longer increases, the detection data of the detection device is cleared, and then heating is performed again.

[0020] Further preferably, in step S2, heating is performed using a heater, the heating time H is 15-30 min, and the heating temperature T is 150-300°C.

[0021] Further preferably, in step S2, after the detection time is reached, the reaction flask is removed from the heater and the content of carbon dioxide generated by the reaction is recorded.

[0022] Further preferably, in step S2, the device for detecting the carbon dioxide content is a non-dispersive infrared detector.

[0023] Further preferably, the free carbon content is 0.1-5wt%.

[0024] The beneficial effects of the present invention are as follows: the method is based on the fact that the carbon dioxide content produced by the boron carbide reaction at the same temperature and in the same time is the same, and thus the carbon dioxide content produced by the free carbon in the first reaction can be obtained. The free carbon content is calculated by the carbon dioxide content, and the calculation speed is fast. Moreover, the detection device is used to directly detect the measurement result, which is more accurate and has a small error. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0026] Figure 1 It is a structural schematic diagram of the present invention.

[0027] In the figure: 1. Power gas source, 2. Gas cylinder pressure gauge, 3. Rotor flowmeter, 4. Anhydrous calcium chloride drying bottle 1, 5. Water calcium chloride drying bottle 2, 6. Anti-backflow bottle, 7. Heating device, 8. Reaction container, 9. Condensation part, 10. Filter washing bottle, 11. Dry washing bottle, 12. Non-dispersive infrared detector. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown in Example 1, a method for testing the free carbon content in boron carbide comprises the following steps:

[0030] S1: Weigh m grams of boron carbide sample containing free carbon and put it into a reaction device filled with chromium sulfate iodic acid solution, and the output end of the reaction device is provided with a carbon dioxide detection device;

[0031] S2: heating the reaction device, the boron carbide sample reacts with the chromium sulfate iodic acid solution to produce carbon dioxide, wherein the heating time is H, the heating temperature is T, and the detection device measures the carbon dioxide content of the first reaction;

[0032] S3: Repeat step S2 to obtain the carbon dioxide content of the second reaction;

[0033] S4: The carbon dioxide content produced by the free carbon reaction is obtained by subtracting the carbon dioxide content obtained in the second reaction in step S3 from the carbon dioxide content obtained in the first reaction in step S2. The free carbon content in the boron carbide sample can be obtained by conversion.

[0034] The method is based on the fact that the carbon dioxide content produced by the boron carbide reaction at the same temperature and in the same time is the same, and thus the carbon dioxide content produced by the free carbon in the first reaction can be obtained. The free carbon content is calculated by the carbon dioxide content, and the calculation speed is fast. In addition, the detection device is used to directly detect the measurement result, which is more accurate and has a small error.

[0035] like Figure 1 As shown in Example 2, a method for testing the free carbon content in boron carbide,

[0036] S1: Weigh m grams of boron carbide sample containing free carbon and put it into a reaction device filled with chromium sulfate iodide acid solution, and the output end of the reaction device is provided with a carbon dioxide detection device; the reaction device includes a reaction flask for holding chromium sulfate iodide acid solution, and the gas outlet of the reaction flask is provided with a drying filter assembly. The drying filter assembly includes a filter washing bottle and a drying washing bottle, the filter washing bottle is filled with one-half silver metamanganate, and the drying washing bottle is filled with one-half anhydrous calcium chloride. The air inlet end of the reaction flask is installed with nitrogen as a power gas source, and the nitrogen flow rate is 16-60ml / min. An anti-backflow empty bottle and a drying bottle filled with anhydrous calcium chloride are also provided between the reaction flask and the nitrogen gas source. Before the experiment begins, the gas outlet of the flask containing chromium sulfate iodic acid solution needs to be connected to the filter washing bottle, dry washing bottle and carbon dioxide infrared detection device in sequence. The upper part of the flask is provided with a condenser tube with condensation function, and the air inlet pipe of the flask is connected to the anti-backflow empty bottle, two anhydrous calcium chloride drying bottles and nitrogen bottle in sequence. The nitrogen bottle is equipped with a gas cylinder pressure gauge and a rotor flowmeter.

[0037] S2: First, nitrogen is introduced into the reaction device. After the nitrogen flows through the reaction device, it enters the detection device. When the measurement data of the detection device is no longer increasing, the detection data of the detection device is cleared. The clearing process is used to remove the original air in the pipeline and remove interference. Then heat it again. The reaction device is heated, and the boron carbide sample reacts with the chromium sulfate iodic acid solution to produce carbon dioxide, wherein the heating time is H, the heating temperature is T, and the detection device measures the carbon dioxide content of the first reaction; the heating adopts a heater, the heating time H is 15-30min, and the heating temperature T is 150-300℃. In the step S2, after the detection time is reached, the reaction flask is removed from the heater, and the carbon dioxide content generated by the reaction is recorded. Removing the flask can terminate the reaction and make the measurement result more accurate. In the step S2, the equipment for detecting the carbon dioxide content is a non-dispersive infrared detector.

[0038] S3: Repeat step S2 to obtain the carbon dioxide content of the second reaction; specifically: nitrogen is introduced into the reaction device for the second time, and the nitrogen flows through the reaction device and enters the detection device. When the measurement data of the detection device is no longer increasing, the detection data of the detection device is cleared, and the clearing process is used to remove the original air in the pipeline and remove interference. Then heat it again. The reaction device is heated for the second time, and the boron carbide sample reacts with the chromium sulfate iodic acid solution to produce carbon dioxide, wherein the heating time is H, the heating temperature is T, and the detection device measures the carbon dioxide content of the first reaction; the heating adopts a heater, the heating time H is 15-30min, the heating temperature T is 150-300℃, and the time and temperature are the same as the first time. After the detection time is reached, the reaction flask is removed from the heater, and the carbon dioxide content generated by the reaction is recorded. Removing the flask can terminate the reaction and make the measurement result more accurate.

[0039] S4: Subtract the carbon dioxide content obtained in the second reaction in step S3 from the carbon dioxide content obtained in the first reaction in step S2 to obtain the carbon dioxide content produced by the free carbon reaction, and the free carbon content in the boron carbide sample can be obtained by conversion. The free carbon content is 0.1-5wt%.

[0040] Example 2

[0041] In a method for testing the free carbon content in boron carbide, 30 mL of chromium sulfate iodic acid solution is added to a reaction container 8, nitrogen is connected, the cylinder pressure gauge 2 shows greater than 0.1 bar, and the rotor flowmeter 3 is set to a flow rate of 20 ml / min; the heating device 7 is turned on, and the temperature is controlled to be set at 160±3° C.; the non-dispersive infrared detector is turned on to record, and when the non-dispersive infrared detector value is no longer increasing, click to clear the recorded value.

[0042] Weigh the boron carbide sample m, wrap the sample with aluminum foil, and put the sample into the reactor after the temperature of the heating device 7 reaches 160±3℃; the non-dispersive infrared detector starts to record the amount of carbon dioxide generated. Immediately after 30 minutes, cut off the nitrogen, move the reactor off the heating platform, and record the amount of carbon dioxide generated M1.

[0043] Reconnect nitrogen, the cylinder pressure gauge 2 shows more than 0.1 bar, and the rotor flowmeter 3 flow rate is set to 20 ml / min; turn on the non-dispersive infrared detector to record, when the non-dispersive infrared detector value is no longer increasing, click to clear the record value. Turn on the heating device 7 and control the temperature to 160 ± 3 ° C.

[0044] After the temperature of the heating device 7 reaches 160±3°C, the non-dispersive infrared detector starts to record the amount of carbon dioxide generated. After 30 minutes, the nitrogen is immediately cut off, the reactor is removed from the heating platform, and the amount of carbon dioxide generated M2 is recorded.

[0045]

[0046] Where: M1-mass of carbon dioxide produced in the first 30 minutes, g;

[0047] M2-mass of carbon dioxide produced in the second 30 minutes, g;

[0048] m - sample weight.

[0049] The above formula can quickly and accurately calculate the free carbon content in boron carbide.

[0050] Example 3

[0051] In a method for testing the free carbon content in boron carbide, the specific measurement process and calculation process are as follows:

[0052] 1. Add 30 mL of chromium sulfate iodide solution into the reaction vessel 8;

[0053] 2. Weigh 0.102g of boron carbide standard material and wrap it in aluminum foil. The standard material number is GBW06604, the nominal value of free carbon content is 0.436%, and the uncertainty is 0.035%.

[0054] 3. Connect nitrogen, adjust the pressure gauge 2 on the gas cylinder to about 0.1 bar, set the flow rate of the rotor flowmeter 3 to 20 ml / min, and observe bubbles continuously emerging from the reactor 8;

[0055] 4. Turn on the heating device 7 and control the temperature to be set at 200±3℃;

[0056] 5. Open the non-dispersive infrared detector record. When the non-dispersive infrared detector value is no longer increasing, click to clear the record value.

[0057] 6. After the temperature of the heating device 7 reaches 200±3°C, the sample is put into the reactor; the non-dispersive infrared detector starts to record the amount of carbon dioxide generated.

[0058] 7. After 30 minutes, the nitrogen gas was immediately cut off, the reactor was removed from the heating device 7, and the amount of carbon dioxide generated was recorded as 0.303 g.

[0059] 8. Reconnect the nitrogen, the cylinder pressure gauge 2 shows greater than 0.1 bar, and the rotor flow meter 3 flow rate is set to 20 ml / min

[0060] 9. Open the non-dispersive infrared detector record. When the non-dispersive infrared detector value is no longer increasing, click the record value to clear it.

[0061] 10. The reactor 8 was moved back to the heating device 7, and the non-dispersive infrared detector began to record the amount of carbon dioxide generated. After 30 minutes, the amount of carbon dioxide generated was recorded as 1.141 g.

[0062] 11. Immediately cut off the nitrogen and move the reactor off the heating platform. This reaction is over.

[0063]

[0064] 12. The results of multiple measurements are as follows

[0065]

[0066] Through multiple measurements, the average measurement result is 0.435% and the error is 0.026%, both of which are within the range of the standard value (nominal value 0.436%, uncertainty 0.035%). The test results are stable and accurate.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the free carbon content in boron carbide, characterized in that: The following steps are involved: S1: Weigh m grams of boron carbide sample containing free carbon and put it into a reaction device filled with chromium sulfate iodic acid solution, and the output end of the reaction device is provided with a carbon dioxide detection device; S2: heating the reaction device, the boron carbide sample reacts with the chromium sulfate iodic acid solution to produce carbon dioxide, wherein the heating time is H, the heating temperature is T, and the detection device measures the carbon dioxide content of the first reaction; S3: Repeat step S2 to obtain the carbon dioxide content of the second reaction; S4: The carbon dioxide content produced by the free carbon reaction is obtained by subtracting the carbon dioxide content obtained in the second reaction in step S3 from the carbon dioxide content obtained in the first reaction in step S2. The free carbon content in the boron carbide sample can be obtained by conversion.

2. The method for testing free carbon content in boron carbide according to claim 1, characterized in that: The reaction device in step S1 comprises a reaction flask for containing chromium sulfate iodide solution, and a drying and filtering component is provided at the gas outlet of the reaction flask.

3. The method for testing free carbon content in boron carbide according to claim 2, characterized in that: The dry filter component comprises a filter washing bottle and a dry washing bottle. The filter washing bottle is filled with one half of silver metamanganate, and the dry washing bottle is filled with one half of anhydrous calcium chloride.

4. The method for testing the free carbon content in boron carbide according to claim 3, characterized in that: The gas inlet end of the reaction flask is provided with nitrogen as a power gas source, and the nitrogen flow rate is 16-60 ml / min.

5. The method for testing the free carbon content in boron carbide according to claim 4, characterized in that: An anti-backflow empty bottle and a drying bottle filled with anhydrous calcium chloride are also arranged between the reaction flask and the nitrogen gas source.

6. The method for testing the free carbon content in boron carbide according to any one of claims 2 to 5, characterized in that: In the step S2, nitrogen is first introduced into the reaction device, and then flows through the reaction device and enters the detection device. When the measurement data of the detection device no longer increases, the detection data of the detection device is reset, and then heating is performed again.

7. The method for testing the free carbon content in boron carbide according to claim 6, characterized in that: In the step S2, heating is performed by a heater, the heating time H is 15-30 minutes, and the heating temperature T is 150-300°C.

8. The method for testing the free carbon content in boron carbide according to claim 7, characterized in that: In step S2, after the detection time is reached, the reaction flask is removed from the heater and the content of carbon dioxide generated by the reaction is recorded.

9. The method for testing the free carbon content in boron carbide according to claim 7 or 8, characterized in that: In step S2, the device for detecting the carbon dioxide content is a non-dispersive infrared detector.

10. The method for testing the free carbon content in boron carbide according to claim 9, characterized in that: The free carbon content is 0.1-5wt%.

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