Microwave digestion method of CrSi alloy and application of microwave digestion method

Abstract

The invention provides a microwave digestion method of CrSi alloy and application of the microwave digestion method. The microwave digestion method comprises the following steps: mixing CrSi alloy and mixed acid, and then carrying out microwave digestion treatment to obtain a digestion solution; the mixed acid is a combination of hydrochloric acid and hydrofluoric acid. According to the microwave digestion method provided by the invention, the use of various acids is not needed, and the effect of fully dissolving the CrSi alloy can be realized only through a single mixed acid, so that the ICP-OES on-machine detection standard is achieved.

Description

Technical Field

[0001] This invention belongs to the field of element detection technology, specifically relating to a microwave digestion method for CrSi alloy and its application. Background Technology

[0002] In the field of materials analysis, inductively coupled plasma optical emission spectrometry (ICP-OES) is widely used to determine the elemental content in various samples due to its advantages such as wide detection range, high sensitivity, and good accuracy. The sample pretreatment process, especially the digestion step, is a crucial step in ensuring the reliability of ICP-OES detection results, directly affecting whether the target elements in the sample can be completely released and transformed into a form suitable for instrument detection.

[0003] Currently, acid dissolution is a commonly used method in ICP-OES testing for digesting metal and alloy samples. However, conventional acid dissolution methods often suffer from slow dissolution rates at room temperature, making them unsuitable for rapid detection. For specific samples such as chromium-silicon alloys (CrSi), the digestion process faces even more complex challenges.

[0004] Chromium (Cr), as an important component element in CrSi alloys, possesses certain unique chemical properties. Metallic chromium dissolves rapidly in dilute hydrochloric acid, producing hydrogen gas and Cr(H₂O)₆. 2+ Chromium(II) ions, existing in their complex ion form, also undergo a similar reaction in dilute sulfuric acid to produce chromium(II) ions and hydrogen gas. However, pure chromium does not react with strong oxidizing acids such as concentrated nitric acid. This is because chromium undergoes passivation in concentrated nitric acid, forming a protective oxide film on its surface, thus hindering further reaction.

[0005] Silicon (Si), another key element in CrSi alloys, also influences the digestion process due to its chemical properties. Silicon is relatively stable at room temperature, insoluble in water, nitric acid, and hydrochloric acid, but soluble only in hydrofluoric acid and alkaline solutions. However, in hydrofluoric acid, silicon is easily lost through volatilization, which can lead to lower-than-expected silicon content readings in the sample.

[0006] In the detection of CrSi alloys, conventional wet digestion methods have significant limitations. On the one hand, under these high silicon content conditions, chromium readily forms an oxide layer in the presence of hydrofluoric acid. This oxide layer encapsulates undissolved alloy particles, preventing the CrSi alloy from being completely dissolved and leading to lower chromium levels. On the other hand, as mentioned earlier, silicon is easily volatilized under the action of hydrofluoric acid, which can also cause inaccurate silicon level measurements.

[0007] Furthermore, current methods for detecting the main constituent elements (Cr and Si) in CrSi alloys are relatively scarce. While X-ray fluorescence spectrometry (XRF) has been applied, its accuracy is low, and the results are subject to significant bias, making it unsuitable for high-precision analysis. Therefore, developing a digestion method that can rapidly and completely dissolve CrSi alloys while effectively avoiding the loss of chromium and silicon, and suitable for ICP-OES detection, has become a pressing technical problem in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a microwave digestion method for CrSi alloys and its application. The microwave digestion method provided by this invention does not require the use of multiple acids; a single mixed acid is sufficient to achieve complete dissolution of the CrSi alloy, meeting the testing standards for ICP-OES.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a microwave digestion method for CrSi alloys, the microwave digestion method comprising the following steps:

[0011] A CrSi alloy and a mixed acid were mixed and then subjected to microwave digestion to obtain a digestion solution.

[0012] The mixed acid is a combination of hydrochloric acid and hydrofluoric acid.

[0013] This invention utilizes microwave digestion, employing only a mixed acid composed of hydrochloric acid and hydrofluoric acid, to achieve rapid dissolution of CrSi alloys. The microwave digestion method eliminates the need for multiple acids, achieving efficient microwave digestion of CrSi alloys with only a single mixed acid. This improves the convenience of ICP-OES sample preparation for CrSi alloys and enhances the accuracy of ICP-OES detection of the obtained samples.

[0014] As a preferred embodiment of the present invention, the Si content in the CrSi alloy is 48-52 wt%, for example, it can be 48 wt%, 48.5 wt%, 49 wt%, 49.5 wt%, 50 wt%, 50.5 wt%, 51 wt%, 51.5 wt%, or 52 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the particle size of the CrSi alloy is <2mm, for example, it can be 1.8mm, 1.7mm, 1.5mm, 1.2mm, 1.0mm or 0.5mm, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] In this invention, the CrSi alloy is in the form of small particles or powder. If the particle size of the CrSi alloy is too high, it will lead to incomplete dissolution of the CrSi alloy, thereby affecting the accuracy of alloy content detection.

[0017] As a preferred embodiment of the present invention, the volume ratio of hydrochloric acid to hydrofluoric acid is 3:6 to 8, for example, it can be 3:6, 3:6.4, 3:6.8, 3:7.2, 3:7.6 or 3:8, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the concentration of the hydrochloric acid is 35-38 wt%, for example, it can be 35 wt%, 35.5 wt%, 36 wt%, 36.5 wt%, 37 wt%, 37.5 wt%, or 38 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the concentration of the hydrofluoric acid is 38-42 wt%, for example, it can be 38 wt%, 39 wt%, 40 wt% or 42 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] As a preferred embodiment of the present invention, the solid-liquid ratio of the CrSi alloy and the mixed acid is 1g:9 to 11mL, for example, it can be 1g:9mL, 1g:9.4mL, 1g:9.8mL, 1g:10.2mL, 1g:10.6mL or 1g:11mL, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] As a preferred embodiment of the present invention, the microwave digestion process includes a first microwave digestion process with progressively increasing temperature, a second microwave digestion process, a third microwave digestion process, and a fourth microwave digestion process.

[0022] Preferably, the temperature of the first microwave digestion treatment is 75-85°C, for example, it can be 75°C, 77°C, 79°C, 81°C, 83°C or 85°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the time for the first microwave digestion treatment is 13 to 17 minutes, for example, 13 minutes, 14 minutes, 15 minutes, 16 minutes or 17 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the power of the first microwave digestion process is 280 to 320W, for example, it can be 280W, 290W, 300W, 310W or 320W, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0025] Preferably, the temperature of the second microwave digestion treatment is 115-125°C, for example, it can be 115°C, 117°C, 119°C, 121°C, 123°C or 125°C, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0026] Preferably, the second microwave digestion treatment time is 14 to 16 minutes, for example, it can be 14 minutes, 14.4 minutes, 14.8 minutes, 15.2 minutes, 15.6 minutes or 16 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the power of the second microwave digestion process is 320 to 380W, for example, it can be 320W, 330W, 340W, 350W, 360W, 370W or 380W, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0028] Preferably, the temperature of the third microwave digestion process is 155-165°C, for example, it can be 155°C, 157°C, 159°C, 161°C, 163°C or 165°C, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the time for the third microwave digestion process is 14 to 16 minutes, for example, it can be 14 minutes, 14.4 minutes, 14.8 minutes, 15.2 minutes, 15.6 minutes or 16 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the power of the third microwave digestion process is 320 to 380W, for example, it can be 320W, 330W, 340W, 350W, 360W, 370W or 380W, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the temperature of the fourth microwave digestion process is 195 to 205°C, for example, it can be 195°C, 197°C, 199°C, 201°C, 203°C or 205°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the time for the fourth microwave digestion process is 55 to 65 minutes, for example, 55 minutes, 57 minutes, 59 minutes, 61 minutes, 63 minutes, or 65 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the power of the fourth microwave digestion process is 320 to 380W, for example, it can be 320W, 330W, 340W, 350W, 360W, 370W or 380W, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0034] As a preferred embodiment of the present invention, the microwave digestion method for CrSi alloy provided in the first aspect of the present invention includes the following steps:

[0035] A CrSi alloy with a Si content of 48-52 wt% and a particle size of <2 mm was mixed with a mixed acid at a solid-liquid ratio of 1 g: 9-11 mL, and then microwave digestion was performed to obtain a dark green and clear digestion solution (transparent under light).

[0036] The mixed acid is a combination of hydrochloric acid and hydrofluoric acid in a volume ratio of 3:6 to 8; the concentration of the hydrochloric acid is 35 to 38 wt%, and the concentration of the hydrofluoric acid is 38 to 42 wt%.

[0037] The microwave digestion process includes a first microwave digestion process with progressively increasing temperature, a second microwave digestion process, a third microwave digestion process, and a fourth microwave digestion process.

[0038] The temperature of the first microwave digestion treatment is 75-85℃, the time is 13-17 min, and the power is 280-320W;

[0039] The second microwave digestion process is performed at a temperature of 115–125°C for 14–16 minutes and at a power of 320–380 W.

[0040] The third microwave digestion process is performed at a temperature of 155–165°C for 14–16 minutes and at a power of 320–380W.

[0041] The fourth microwave digestion process is performed at a temperature of 195–205°C for 55–65 minutes and at a power of 320–380 W.

[0042] Secondly, the present invention provides an application of the microwave digestion method as described in the first aspect in ICP-OES testing of CrSi alloys, wherein the specific steps of the application include:

[0043] After cooling the digestion solution, it was brought to a constant volume. The digestion solution was then placed in an ICP-OES instrument to simultaneously detect Cr and Si elements.

[0044] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The microwave digestion method provided by this invention does not require the use of multiple acids; a single mixed acid can be used to achieve the effect of fully dissolving CrSi alloys, thus meeting the testing standards for ICP-OES. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0048] Example 1

[0049] This embodiment provides a microwave digestion method for CrSi alloys, which includes the following steps:

[0050] Take 0.1g of CrSi alloy with a Si content of 50wt% and a particle size of 1.2mm, mix the CrSi alloy and mixed acid at a solid-liquid ratio of 1g:10mL, and then perform microwave digestion to obtain a digestion solution;

[0051] The mixed acid is a combination of hydrochloric acid and hydrofluoric acid in a volume ratio of 3:7; the concentration of the hydrochloric acid is 36 wt%, and the concentration of the hydrofluoric acid is 40 wt%.

[0052] The microwave digestion process includes a first microwave digestion process with progressively increasing temperature, a second microwave digestion process, a third microwave digestion process, and a fourth microwave digestion process.

[0053] The temperature of the first microwave digestion treatment was 80℃, the time was 15min, and the power was 300W;

[0054] The second microwave digestion process was performed at a temperature of 120°C for 15 minutes and a power of 350W.

[0055] The third microwave digestion process is performed at a temperature of 160°C for 15 minutes and a power of 350W.

[0056] The fourth microwave digestion process is performed at a temperature of 200°C for 60 minutes and a power of 350W.

[0057] Example 2

[0058] This embodiment provides a microwave digestion method for CrSi alloys, which includes the following steps:

[0059] Take 0.1g of CrSi alloy with a Si content of 52wt% and a particle size of 1.8mm, mix CrSi alloy and mixed acid at a solid-liquid ratio of 1g:9mL, and then perform microwave digestion treatment to obtain a digestion solution;

[0060] The mixed acid is a combination of hydrochloric acid and hydrofluoric acid in a volume ratio of 3:8; the concentration of the hydrochloric acid is wt%, and the concentration of the hydrofluoric acid is wt%.

[0061] The microwave digestion process includes a first microwave digestion process with progressively increasing temperature, a second microwave digestion process, a third microwave digestion process, and a fourth microwave digestion process.

[0062] The temperature of the first microwave digestion treatment was 75℃, the time was 17min, and the power was 280W;

[0063] The second microwave digestion process was performed at a temperature of 115°C for 16 minutes and a power of 320W.

[0064] The third microwave digestion process was performed at a temperature of 155°C for 16 minutes and a power of 320W.

[0065] The fourth microwave digestion process is performed at a temperature of 195°C for 65 minutes and a power of 320W.

[0066] Example 3

[0067] This embodiment provides a microwave digestion method for CrSi alloys, which includes the following steps:

[0068] Take 0.1g of CrSi alloy with a Si content of 48wt% and a particle size of 0.5mm, mix CrSi alloy and mixed acid at a solid-liquid ratio of 1g:11mL, and then perform microwave digestion treatment to obtain a digestion solution.

[0069] The mixed acid is a combination of hydrochloric acid and hydrofluoric acid in a volume ratio of 3:8; the concentration of the hydrochloric acid is wt%, and the concentration of the hydrofluoric acid is wt%.

[0070] The microwave digestion process includes a first microwave digestion process with progressively increasing temperature, a second microwave digestion process, a third microwave digestion process, and a fourth microwave digestion process.

[0071] The temperature of the first microwave digestion treatment was 85℃, the time was 13min, and the power was 320W;

[0072] The second microwave digestion process was performed at a temperature of 125°C for 14 minutes and a power of 380W.

[0073] The third microwave digestion process was performed at a temperature of 165°C for 14 minutes and a power of 380W.

[0074] The fourth microwave digestion process is performed at a temperature of 205°C for 55 minutes and a power of 380W.

[0075] Example 4

[0076] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0077] In this embodiment, the particle size of the CrSi alloy is adjusted to 3 mm.

[0078] Example 5

[0079] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0080] In this embodiment, the volume ratio of hydrochloric acid and hydrofluoric acid in the mixed acid is adjusted to 3:5.

[0081] Example 6

[0082] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0083] In this embodiment, the volume ratio of hydrochloric acid and hydrofluoric acid in the mixed acid is adjusted to 3:9.

[0084] Example 7

[0085] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0086] The first microwave digestion process is omitted in this embodiment.

[0087] Example 8

[0088] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0089] The second microwave digestion process is omitted in this embodiment.

[0090] Example 9

[0091] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0092] The third microwave digestion process is omitted in this embodiment.

[0093] Example 10

[0094] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0095] The fourth microwave digestion process is omitted in this embodiment.

[0096] Example 11

[0097] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0098] In this embodiment, the temperature of the first microwave digestion process is adjusted to 100°C.

[0099] Example 12

[0100] This embodiment provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and that of Embodiment 1 is:

[0101] In this embodiment, the temperature of the first microwave digestion process is adjusted to 70°C.

[0102] Comparative Example 1

[0103] This comparative example provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and Example 1 is that:

[0104] In this comparative example, the hydrochloric acid in the mixed acid is adjusted to an equal volume of sulfuric acid.

[0105] Comparative Example 2

[0106] This comparative example provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and Example 1 is that:

[0107] In this comparative example, the hydrofluoric acid in the mixed acid was adjusted to an equal volume of nitric acid.

[0108] Comparative Example 3

[0109] This comparative example provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and Example 1 is that:

[0110] In this comparative example, the mixed acid was adjusted to a volume ratio of hydrochloric acid, hydrofluoric acid, and nitric acid of 3:3:4.

[0111] Comparative Example 4

[0112] This comparative example provides a microwave digestion method for CrSi alloys, the only difference between this microwave digestion method and Example 1 is that:

[0113] In this comparative example, the microwave digestion process was adjusted to a stirring digestion process, and the stirring rates in the stirring digestion process were 200 rpm, 250 rpm, 250 rpm, and 250 rpm, respectively.

[0114] Performance testing:

[0115] The digestion solutions provided in the above examples and comparative examples were cooled and placed in volumetric flasks, diluted to 100 mL, then diluted 100 times, and then placed in an ICP-OES instrument to simultaneously detect Cr and Si elements. The detection results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] According to Table 1, the following information can be obtained:

[0120] (1) Comprehensive analysis of Examples 1-3 shows that the present invention, by using the specific combination of three acid solutions and microwave digestion, can directly dissolve CrSi alloy and achieve a full dissolution effect, thus meeting the detection standards of ICP-OES.

[0121] (2) Comprehensive analysis of Examples 1 and 4 shows that if the particle size of the CrSi alloy is too high, it will lead to a violent reaction during the digestion process, resulting in a large loss of Si element.

[0122] (3) Comprehensive analysis of Examples 1 and 5-6 shows that if the HF content in the mixed acid is too high, the reaction will be too fast and Si will be easily damaged; if the HF content is too low, Si will not react completely, resulting in a low content.

[0123] (4) Comprehensive analysis of Examples 1 and Examples 7-10 shows that omitting any one of the microwave digestion processes will result in incomplete dissolution and make it impossible to accurately measure the elemental composition content in the alloy.

[0124] (5) Comprehensive analysis of Examples 1 and 11-12 shows that if the temperature of the first microwave digestion treatment is too low, the Si content will be too low due to incomplete dissolution; if the temperature is too high, the reaction rate will be too fast and the Si content will be too low.

[0125] (6) Comprehensive analysis of Example 1 and Comparative Examples 1-3 shows that if the mixed acid used is adjusted to any one of the following: a mixture of sulfuric acid and hydrofluoric acid, a mixture of nitric acid and hydrofluoric acid, or a mixture of hydrochloric acid, hydrofluoric acid and nitric acid, the sample will not dissolve, thus making it impossible to detect the elemental composition in the CrSi alloy.

[0126] (7) Comprehensive analysis of Example 1 and Comparative Example 4 shows that if microwave digestion is changed to stirring digestion, it will lead to the loss of Si content.

[0127] In summary, the microwave digestion method provided by this invention does not require the use of multiple acids; it can achieve the effect of fully dissolving CrSi alloys using only a single mixed acid, thus meeting the testing standards for ICP-OES.

[0128] The applicant declares that the specific embodiments described above further illustrate the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above description is only a specific 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microwave digestion method for CrSi alloys, characterized in that, The microwave digestion method includes the following steps: A CrSi alloy and a mixed acid were mixed and then subjected to microwave digestion to obtain a digestion solution. The mixed acid is a combination of hydrochloric acid and hydrofluoric acid.

2. The microwave digestion method for CrSi alloy according to claim 1, characterized in that, The Si content in the CrSi alloy is 48–52 wt%. Preferably, the particle size of the CrSi alloy is <2 mm.

3. The microwave digestion method for CrSi alloy according to claim 1 or 2, characterized in that, The volume ratio of hydrochloric acid to hydrofluoric acid is 3:6 to 8; Preferably, the concentration of the hydrochloric acid is 35-38 wt%; Preferably, the concentration of the hydrofluoric acid is 38–42 wt%.

4. The microwave digestion method for CrSi alloy according to any one of claims 1-3, characterized in that, The solid-liquid ratio of the CrSi alloy and the mixed acid is 1g:9-11mL.

5. The microwave digestion method for CrSi alloy according to any one of claims 1-4, characterized in that, The microwave digestion process includes a first microwave digestion process with progressively increasing temperature, a second microwave digestion process, a third microwave digestion process, and a fourth microwave digestion process.

6. The microwave digestion method for CrSi alloy according to claim 5, characterized in that, The temperature of the first microwave digestion treatment is 75–85°C; Preferably, the time for the first microwave digestion treatment is 13 to 17 minutes; Preferably, the power of the first microwave digestion process is 280-320W.

7. The microwave digestion method for CrSi alloy according to claim 5, characterized in that, The temperature for the second microwave digestion process is 115–125°C; Preferably, the second microwave digestion process takes 14 to 16 minutes; Preferably, the power of the second microwave digestion process is 320-380W.

8. The microwave digestion method for CrSi alloy according to claim 5, characterized in that, The temperature of the third microwave digestion process is 155–165°C. Preferably, the third microwave digestion process takes 14 to 16 minutes; Preferably, the power of the third microwave digestion process is 320-380W.

9. The microwave digestion method for CrSi alloy according to claim 5, characterized in that, The temperature of the fourth microwave digestion process is 195–205°C. Preferably, the fourth microwave digestion process takes 55–65 minutes. Preferably, the power of the fourth microwave digestion process is 320-380W.

10. The application of the microwave digestion method as described in any one of claims 1-9 in ICP-OES testing of CrSi alloys, characterized in that, The specific steps of the application include: After cooling the digestion solution, it was brought to a constant volume. The digestion solution was then placed in an ICP-OES instrument to simultaneously detect Cr and Si elements.

Images