Method for determining hafnium content in hafnium carbide

Abstract

The present application belongs to the technical field of analytical chemistry, and particularly relates to a method for determining the content of hafnium in hafnium carbide. The method comprises the steps of sample weighing, high-temperature melting, dissolution and leaching, primary precipitation separation, precipitation dissolution, secondary precipitation separation and constant weight calculation, and uses mandelic acid as a secondary precipitant and a mixture of alkali salt and boric acid as a high-temperature flux. The method provided by the present application is simple in equipment, scientific, fast, reasonable and reliable in determination, and effectively fills the gap in the field of chemical composition detection of internal hafnium carbide materials.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry technology, and specifically relates to a method for determining the hafnium content in hafnium carbide. Background Technology

[0002] Hafnium carbide possesses excellent physical and chemical properties, including high hardness, high melting point, and good thermal and electrical conductivity. It is a superior high-temperature refractory material widely used in aerospace, nuclear power, and other fields. Hafnium carbide has a very high Mohs hardness, second only to diamond, and is used in various saws and tools, as well as in cemented carbide, wear-resistant materials, and as an additive to other alloys to enhance their hardness and strength. For example, adding hafnium carbide to CC composites can improve various properties such as ablation resistance and thermal shock resistance, and it is used in engine throat liners. However, hafnium carbide is corrosion-resistant and does not melt at room temperature. Currently, there are few reports on the determination of elemental composition in hafnium carbide, both domestically and internationally. The hafnium content in hafnium carbide has a crucial impact on its performance, affecting the material's physical and chemical properties. Therefore, accurately determining the hafnium content in hafnium carbide is an urgent problem to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide a method for determining the hafnium content in hafnium carbide, the specific technical solution of which is as follows:

[0004] The first aspect of the present invention provides a method for determining the hafnium content in hafnium carbide, comprising the steps of sample weighing, high-temperature melting, dissolution and extraction, primary precipitation separation, precipitation dissolution, secondary precipitation separation, and constant weight calculation, using mandelic acid as a secondary precipitant and a mixture of alkali salt and boric acid as a high-temperature flux.

[0005] Furthermore, the mass fraction of hafnium in hafnium carbide is between 10% and 80%, and the water used in the test method is grade III or above water that meets the requirements of GB / T6682.

[0006] Furthermore, a mixture of anhydrous sodium carbonate and boric acid is used as a high-temperature flux; preferably, a mixture of anhydrous sodium carbonate and boric acid in a mass ratio of (2-4):1 is used as a high-temperature flux.

[0007] Preferably, the high-temperature melting temperature is 900–1050°C, and the time is 10–60 minutes;

[0008] And / or, the mass ratio of sample to flux is 0.2:(4-6); the sample is preferably completely isolated from the external atmosphere before high-temperature melting.

[0009] Furthermore, hydrochloric acid was used as the dissolving and extracting reagent, with a hydrochloric acid volume to flux mass ratio of (40-80) mL:(4-6) g.

[0010] Further, the extract obtained by heating and dissolving is added, and ammonia is added for a precipitation separation. The volume of ammonia added is 10 mL after a white precipitate appears.

[0011] Further, the precipitate obtained from the first precipitation separation was dissolved using hydrochloric acid and hydrogen peroxide, with the ratio of hydrochloric acid volume, hydrogen peroxide volume to sample mass being (10-15) mL: (2-5) mL: (0.1-0.5) g.

[0012] Furthermore, the concentration of mandelic acid is 300 g / L, and the added volume is 50–80 mL.

[0013] Furthermore, the primary and secondary precipitation separations are repeated multiple times until no precipitate appears; the precipitate from the primary precipitation separation is filtered using rapid quantitative filter paper, and the precipitate from the secondary precipitation separation is filtered using slow quantitative filter paper.

[0014] Further, the precipitate and filter paper were placed in a crucible, ashed, and then calcined in a furnace at 900°C until constant weight. The hafnium content w was calculated using the following formula (1):

[0015]

[0016] m = mass of the sample, in grams (g);

[0017] m1 = Mass of the empty crucible after constant weight, in grams (g);

[0018] m2 = the mass of the crucible and precipitate after constant weight, in grams (g).

[0019] The beneficial effects of this invention are as follows: The purpose of this invention is to provide an analytical method for hafnium content in hafnium carbide materials. This method is the first to achieve the dissolution of hafnium carbide samples and the quantitative analysis of hafnium. It has the advantages of simple operation and high accuracy. It can well meet the requirements for the determination of hafnium content in hafnium carbide. Detailed Implementation

[0020] This invention provides a method for determining the hafnium content in hafnium carbide. The invention will be further described below with reference to the embodiments.

[0021] The first aspect of the present invention provides a method for determining the hafnium content in hafnium carbide, comprising the steps of sample weighing, high-temperature melting, dissolution and extraction, primary precipitation separation, precipitation dissolution, secondary precipitation separation, and constant weight calculation, using mandelic acid as a secondary precipitant and a mixture of alkali salt and boric acid as a high-temperature flux.

[0022] For sample weighing, the present invention preferably uses a hafnium mass fraction in hafnium carbide between 10% and 80%, and the mass of the sample to be tested is 0.1 to 0.5 grams.

[0023] For high-temperature melting, a mixture of anhydrous sodium carbonate and boric acid is used as the high-temperature flux; preferably, a mixture of anhydrous sodium carbonate and boric acid in a mass ratio of (2-4):1 is used as the high-temperature flux.

[0024] Preferably, the high-temperature melting temperature is 900–1050°C, and the time is 10–60 minutes;

[0025] And / or, the mass ratio of sample to flux is 0.2:(4-6); the sample is preferably completely isolated from the external atmosphere before high-temperature melting.

[0026] For dissolution and extraction, hydrochloric acid is used as the dissolution and extraction reagent, and the volume ratio of hydrochloric acid to flux is (40-80) mL: (4-6) g.

[0027] For a single precipitation separation, the extract obtained by heating and dissolving is dissolved, and ammonia water is added for a single precipitation separation. The volume of ammonia water added is such that 10 mL is added after a white precipitate appears. Preferably, the container and precipitate are washed several times with ammonia water washing solution, and the precipitate and the precipitate are recovered together with filter paper. Preferably, the ammonia water concentration is 1 mL:(10-20) mL in volume ratio of ammonia water to water, and the number of washing times is 10-15.

[0028] For precipitate dissolution, hydrochloric acid and hydrogen peroxide are used to dissolve the precipitate obtained from the first precipitation separation. The ratio of hydrochloric acid volume, hydrogen peroxide volume to sample mass is (10-15) mL: (2-5) mL: (0.1-0.5) g.

[0029] For secondary precipitation separation, mandelic acid is added first for precipitation, followed by separation. The container and precipitate are then washed several times with mandelic acid washing solution. The concentration of mandelic acid is 300 g / L, and the added volume is 50–80 mL. The concentration of mandelic acid washing solution is 15–150 g / L, and the added volume is 50–80 mL. The washing is performed 10–15 times.

[0030] Furthermore, the primary and secondary precipitation separations described in this invention are repeated multiple times until no precipitate appears; the precipitate from the primary precipitation separation is filtered using rapid quantitative filter paper, and the precipitate from the secondary precipitation separation is filtered using slow quantitative filter paper.

[0031] For constant weight calculation, the precipitate and filter paper are placed in a crucible, ashed, and then ignited in a high-temperature furnace at 900℃ until constant weight. The hafnium content w is calculated according to the following formula (1):

[0032]

[0033] m = mass of the sample, in grams (g);

[0034] m1 = Mass of the empty crucible after constant weight, in grams (g);

[0035] m2 = the mass of the crucible and precipitate after constant weight, in grams (g).

[0036] The water used in the entire testing method is grade III or above water that meets the requirements of GB / T 6682.

[0037] To illustrate this more clearly, the first aspect of the present invention provides a method for determining the hafnium content in hafnium carbide, specifically comprising the following steps:

[0038] (1) Sample weighing

[0039] A mixture of anhydrous sodium carbonate and boric acid was used as a high-temperature flux. A hafnium carbide sample was weighed and placed in a platinum crucible with flux at the bottom. The flux was then spread on the sample and mixed thoroughly. The mass ratio of the sample to the flux was 0.2:(4-6).

[0040] (2) High-temperature melting

[0041] Place it in a high-temperature furnace for high-temperature melting at a temperature of 900–1050°C for 10–60 minutes;

[0042] (3) Dissolution and extraction

[0043] After melting and cooling, the molten material in the platinum crucible is extracted with hydrochloric acid in a glass beaker. After the molten material is completely extracted, it is washed out of the crucible. The volume ratio of hydrochloric acid to flux is (40-80) mL: (4-6) g.

[0044] (4) Primary precipitation separation

[0045] Heat the extract to a gentle boil, add ammonia, and continue heating to a boil for 5-6 minutes. Filter, and wash the beaker and precipitate several times with ammonia solution. Return the precipitate and filter paper to the original beaker. It is preferable to use rapid quantitative filter paper for filtration.

[0046] (5) Precipitation and dissolution

[0047] Add hydrochloric acid and hydrogen peroxide, heat until the filter paper is completely dissolved, then add deionized water and continue heating to boiling; wherein, the ratio of hydrochloric acid volume, hydrogen peroxide volume to sample mass is (10-15) mL: (2-5) mL: (0.1-0.5) g;

[0048] (6) Secondary precipitation separation

[0049] Slowly add the mandelic acid solution while it is still hot, keep it at 80℃ for 10-30 minutes while stirring constantly; remove it and let it stand at room temperature overnight or keep it at 80℃ for several hours, then filter; wash the beaker and precipitate several times with mandelic acid washing solution. Wipe the beaker wall with filter paper strips, and add the wiped paper strips into the precipitate;

[0050] (7) Constant weight calculation

[0051] The precipitate and filter paper were placed in a pre-weighed platinum crucible, dried and ashed with a graphite ring until no smoke was emitted, and then calcined in a 900℃ high-temperature furnace until constant weight was achieved; the hafnium content w was calculated according to formula (1):

[0052]

[0053] m = mass of the sample, in grams (g);

[0054] m1 = Mass of the empty crucible after constant weight, in grams (g);

[0055] m2 = the mass of the crucible and precipitate after constant weight, in grams (g).

[0056] Example

[0057] Weigh 0.10 g of the hafnium carbide sample to be tested and place it in a platinum crucible with 0.5 g of anhydrous sodium carbonate and sodium borate mixed flux (mass ratio = 2:1) at the bottom, accurate to 0.0001 g. Add 4 g of the mixed flux, mix well, and place in a high-temperature furnace at 950℃ for 0.5 hours to melt. Perform a blank test along with the sample. Cool to room temperature, remove and place in a 500 mL glass beaker. Add 40 mL of hydrochloric acid and heat to extract the melt completely. Wash the crucible and heat the extract to a gentle boil. Remove from heat and add concentrated ammonia while stirring until a white precipitate appears. Add another 10 mL of ammonia and continue heating to boiling for 5-6 minutes. Filter while hot using rapid quantitative filter paper. Titrate the beaker and precipitate 12 times with a 10% (v / v) ammonia solution. Return the precipitate and filter paper to the original beaker. Add 10 mL of hydrochloric acid and 2 mL of hydrogen peroxide, heat until the filter paper is completely dissolved, then add 100 mL of deionized water, continue heating to boiling, and remove from heat. While still hot, slowly add 50 mL of mandelic acid solution (concentration 300 g / L), stir continuously at 80°C for 15 minutes, remove from heat and let stand overnight. Filter with slow-speed quantitative filter paper, and wash the beaker and precipitate 10 times with 15 g / L mandelic acid washing solution. Wipe the beaker wall with filter paper strips, incorporating the paper strips into the precipitate. Place the precipitate and filter paper in a pre-weighed platinum crucible, dry and ashed with a graphite ring until no smoke is emitted, and then ignite in a 900°C furnace until constant weight.

[0058] The only difference between Examples 1 and 2 is the carbon content in the hafnium carbide samples being tested. The samples were purchased from Beijing Zhongjinyan New Materials Technology Co., Ltd. and GRINM Engineering Technology Research Institute Co., Ltd. The samples used in this invention are not limited to specific manufacturers, as long as the mass fraction of hafnium in the hafnium carbide is between 10% and 80%. The precision of the measurement results for Examples 1 and 2 is shown in Table 1. Each example was tested seven times using the same process.

[0059] Table 1 Precision test results

[0060]

[0061] As shown in Table 1, the RSD of hafnium content is 0.12% to 0.29%, indicating that the method has good precision and can meet the analytical requirements.

[0062] The Grubbs test was used to check for outliers in the precision test data of the above samples. The results are shown in Table 2.

[0063] Table 2. Results of outliers in precision experiment data.

[0064] Example Suspicious value / % s / ％ Gmax Test results Example 1 95.06 0.13 1.846 No outliers Example 2 53.79 0.11 1.727 No outliers

[0065] According to the table, the critical value of G(0.05,7) is 2.020. Therefore, the results of the seven independent measurements of the two hafnium carbide samples showed no outliers, indicating that the method has good precision.

[0066] Spike recovery experiments were performed on the samples according to the method described herein, and the results are shown in Table 3.

[0067] Table 3 Results of Spiked Recovery Test

[0068] Hafnium content in sample / mg Hafnium addition amount / mg Hafnium content measured / mg Recovery rate / % 55.2 20 75.3 100.5 50.1 50 100.2 100.2 50.1 70.2 120.4 100.1

[0069] As can be seen from the results in Table 3, the recovery rate of hafnium in hafnium carbide obtained by this experimental method is 100.1% to 100.5%, which is highly accurate and meets the analytical requirements.

[0070] Comparative Example

[0071] Comparative Example 1 used the same sample as Example 1, and Comparative Example 2 used the same sample as Example 2. The hafnium oxide determination method specified in YS / T568.1-2008 "Chemical Analysis Methods for Zirconia and Hafnium Oxide - Determination of the Combined Content of Zirconia and Hafnium Oxide - Gravimetric Method of Mandelic Acid" was used for comparative testing. The hafnium carbide was determined using this method, and the sample was not completely dissolved. The determination results are shown in Table 4.

[0072] Table 4 Precision Test Results

[0073] Comparative Example Hafnium content determination results / % average value / % Comparative Example 1 7.82，1.04，6.14，0.76，1.08，2.15，5.23 3.04 Comparative Example 2 3.89，0.79，1.75，3.69，0.71，5.74，6.98 3.36

[0074] Comparing the results in Tables 1 and 4, it can be seen that the hafnium carbide test results provided by this invention are accurate, while the test method specified in YS / T 568.1-2008 cannot be used to test the hafnium content in hafnium carbide and the results are significantly lower.

Claims

1. A method for determining the hafnium content of hafnium carbide, characterized by, The steps include sample weighing, high-temperature melting, dissolution leaching, primary precipitation separation, precipitation dissolution, secondary precipitation separation and constant weight calculation, and the steps specifically include the following steps. The steps specifically include the following steps. (1) Sample weighing The mixture of anhydrous sodium carbonate and boric acid is used as a high-temperature flux, and the hafnium carbide sample is weighed and placed in a platinum-gold crucible with the flux on the bottom. After the sample is evenly mixed with the flux, it is placed in a high-temperature furnace for high-temperature melting. (2) High-temperature melting The temperature for high-temperature melting is 900-1050℃, and the time is 10-60 minutes. (3) Dissolution leaching After cooling, the molten material in the platinum-gold crucible is leached with hydrochloric acid in a glass beaker. After the molten material is completely extracted, the crucible is washed out. The volume ratio of hydrochloric acid to the mass of the flux is (40-80) mL:(4-6) g. (4) Primary precipitation separation The extraction liquid is heated to a slight boil, and ammonia water is added. After boiling for 5-6 minutes, the filter paper is washed with ammonia water several times. The precipitate is placed back into the original beaker. (5) Precipitation dissolution Hydrochloric acid and hydrogen peroxide are added, and the filter paper is completely dissolved after heating. Then, deionized water is added, and the mixture is boiled. The volume ratio of hydrochloric acid, hydrogen peroxide and the sample is (10-15) mL:(2-5) mL:(0.1-0.5) g. (6) Secondary precipitation separation Hot mandelic acid solution is slowly added, and the mixture is kept at 80℃ for 10-30 minutes while being continuously stirred. After being taken out and placed at room temperature overnight or kept at 80℃ for several hours, the mixture is filtered. The beaker and the precipitate are washed with mandelic acid several times, and the filter paper is used to wipe the wall of the beaker. The filter paper is added to the precipitate. (7) Constant weight calculation The precipitate and the filter paper are placed in a constant weight platinum-gold crucible, which is dried and ashed with a graphite ring until no smoke is generated. Then, the mixture is placed in a 900℃ high-temperature furnace for calcination until the weight is constant. The hafnium content w is calculated according to the following formula (1): Formula (1) m=the mass of the sample, in grams (g); m1=the mass of the empty crucible after constant weight, in grams (g); m2=the mass of the crucible and the precipitate after constant weight, in grams (g).

2. The assay method according to claim 1, characterized by The concentration of mandelic acid is 300 g / L, and the volume of the added mandelic acid is 50-80 mL.

3. The assay method according to claim 1, characterized by, The primary precipitation separation and the secondary precipitation separation are repeated multiple times until no precipitate is generated. The precipitate of the primary precipitation separation is filtered with fast quantitative filter paper, and the precipitate of the secondary precipitation separation is filtered with slow quantitative filter paper.

4. The assay method according to claim 1, characterized by, The mass fraction of hafnium in the hafnium carbide is between 10% and 80%, and the water used in the test method is water of grade three or above according to GB / T 6682.

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