Solid hydrogen isotope calibration object and preparation method thereof

Abstract

The invention relates to the field of preparation of isotope calibration substances, in particular to a solid hydrogen isotope calibration substance and a preparation method thereof. On the basis of chemical reaction kinetics, substance thermal stability and element conservation, a certain amount of hydrogen isotope water is used for preparing the solid hydrogen isotope calibration substance, and the problems that isotope physical fractionation is caused by phase change of hydrogen isotope standard water, and the test result is further deviated are solved. Meanwhile, the solid calibration object is easy to store and transport, has certain thermal stability in vacuum, and is fixed in water content. The method can be used for equivalent replacement of water and ice in simulated water-containing lunar soil with extremely low water content, the equivalent water-containing simulated lunar soil, the water content and the isotope ratio are controllable, the method is easy to store and prepare, and solid powder can be uniformly distributed in the simulated lunar soil. And the method can also be used for calibration of high-precision spectrometers and mass spectrometers in a vacuum environment.

Description

Technical Field

[0001] The invention relates to the field of isotope calibration material preparation, in particular to a solid hydrogen isotope calibration material and a preparation method thereof. Background Art

[0002] In the existing technology, hydrogen isotope calibration materials mainly use liquid standard isotope water as a reference. However, this calibration material has significant technical defects in the process of storage and use. First, the storage requirements of liquid standard isotope water are strict, requiring specific containers and precise temperature and pressure control to prevent isotope fractionation and water vapor escape. Secondly, during phase change processes (such as from liquid to gas) and experiments under high vacuum conditions, the stability of liquid standard isotope water is insufficient and is easily affected by external environmental factors, resulting in measurement errors of isotope ratios.

[0003] At present, the preparation technology of solid hydrogen isotope markers has not been developed, and this field is still in a blank state. Solid hydrogen isotope markers are expected to have the following technical advantages: first, easier storage and transportation, without the need for complex temperature control systems; second, higher stability, reducing the impact of external environmental factors on isotope ratios, thereby improving the accuracy of experimental data.

[0004] In addition, there is no special technical research and product development for isotope calibration materials required for deep space exploration environments. Deep space exploration missions have more stringent requirements for isotope calibration materials, requiring them to remain stable in extreme temperature, pressure and radiation environments. Therefore, researching and developing isotope calibration technology suitable for deep space exploration is crucial to ensuring the accuracy and reliability of exploration data.

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide the following technical solutions: first, to develop a new method for preparing solid hydrogen isotope standards to meet the needs of different experimental environments; second, to study the stability of solid hydrogen isotope standards in extreme environments to provide a stable isotope calibration method for deep space exploration missions; third, to explore a new isotope calibration method suitable for deep space exploration to promote the development of deep space exploration technology. Through the implementation of the present invention, it is expected to fill the gap in the preparation technology of solid hydrogen isotope standards and provide important technical support for the field of deep space exploration. Summary of the invention

[0006] One of the purposes of the present invention is to solve the problems mentioned in the above-mentioned background technology, and proposes a method for preparing solid hydrogen isotope calibration materials based on chemical reaction kinetics, thermal stability of materials and conservation of elements. The method is mainly used in the field of deep space exploration engineering tests that require a fixed hydrogen isotope ratio for simulated water-containing lunar soil, and is used for equivalent experiments and ground or space calibration of deep space exploration payloads.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for preparing a solid hydrogen isotope marker, specifically comprising the following steps:

[0008] S1. In a glove box, high-purity anhydrous copper sulfate is dissolved in deionized water to a concentration of 0.1-0.3 mol / L, and then high-purity Na2O is added in small amounts and multiple times until no new precipitate is precipitated, to obtain a mixed reaction solution;

[0009] S2. Filter the mixed reaction solution in a glove box, wash the filter residue with anhydrous ethanol, dry it, and seal it for storage to obtain the calibration substance precipitate.

[0010] As a further improvement of the preparation method of solid hydrogen isotope standard:

[0011] Preferably, the high-purity Na2O contains 80wt% pure sodium oxide and 20wt% sodium peroxide, and the mass ratio of high-purity anhydrous copper sulfate to high-purity Na2O is (2-2.5):1.

[0012] Preferably, the purity of the high-purity anhydrous copper sulfate is analytically pure, and the high-purity anhydrous copper sulfate is dissolved in deionized water and stirred with a magnetic stirrer for 10-15 minutes.

[0013] Preferably, the high-purity Na2O, high-purity anhydrous copper sulfate, weighing device, dissolving device and filtering device used in steps S1 and S2 are placed in a transition chamber of a glove box for vacuum degassing before use.

[0014] Preferably, the heat-resistant devices are subjected to high-temperature vacuum degassing in the transition chamber of the glove box, and the non-heat-resistant devices are subjected to natural vacuum degassing.

[0015] Preferably, the temperature of high-temperature vacuum degassing is greater than 150-200°C, the degassing time is greater than 12-24h, the time of natural vacuum degassing is 1 to 2 days, and the temperature of natural vacuum degassing is 20-40°C.

[0016] Preferably, when high-purity Na2O and high-purity anhydrous copper sulfate are vacuum degassed in the transition chamber of the glove box, the mouth of the bottle containing the reagents is equipped with a stainless steel metal mesh to avoid contaminating the transition chamber of the glove box.

[0017] Preferably, the mixed reaction solution is filtered in step S2 by suction filtration, and precursor deionized water or anhydrous ethanol is used to assist the suction filtration during the suction filtration process.

[0018] Preferably, the calibration substance in step S2 is precipitated in an inert gas atmosphere in a glove box, bottled, and sealed for storage.

[0019] A second object of the present invention is to provide a solid hydrogen isotope marker prepared by the method for preparing the solid hydrogen isotope marker described in any one of the above.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The present invention provides a method for preparing a solid hydrogen isotope standard based on chemical reaction kinetics, thermal stability of substances and conservation of elements, and uses a simple synthesis route to prepare a solid hydrogen isotope standard with the same isotope ratio as isotope standard water. The synthesis principle mainly refers to the chemical formula:

[0022] CuSO4+2NaOH=Cu(OH)2↓+Na2SO4

[0023] During the synthesis process, the principle that the chemical reaction rate is much greater than the physical thermal fractionation is utilized and the source of the hydrogen element is strictly controlled by the law of conservation of elements. The copper source comes from anhydrous copper sulfate, the alkali source comes from high-purity sodium oxide, and all hydrogen sources come from liquid water. Physical water is converted into chemical water, and the thermal stability of the calibrant is improved through the action of chemical bonds. Finally, the hydrogen isotope solid calibrant is prepared.

[0024] In order to strictly control that all hydrogen elements come from the precursor deionized water, analytical pure anhydrous copper sulfate and high-purity sodium oxide (containing 20% ​​sodium peroxide impurities) were used as reactants. All experimental instruments were operated in an inert gas glove box, and the required chemicals were opened and used in the inert gas glove box. All equipment that may absorb water vapor in the air was degassed according to the requirements of the vacuum manual.

[0025] In the traditional industrial copper hydroxide preparation method, air is not isolated, the sources of hydrogen are diverse and cannot be traced, and the isotopes of the water produced by heating are uncertain, making it difficult to become a solid hydrogen isotope calibrator.

[0026] 2) According to the SEM electron microscope image, the solid hydrogen isotope calibration material prepared by the present invention mainly has a long strip crystal morphology. According to the XRD test, the main phase of the calibration material crystal is copper hydroxide, and the other miscellaneous peaks have no obvious component correspondence.

[0027] To ensure the high purity of the sample, an inert gas atmosphere is continuously maintained in the glove box, and sodium oxide is added in small amounts and multiple times. Adding sodium oxide too quickly will result in a high local pH value and reduce the concentration of the copper hydroxide product. Anhydrous ethanol is used to wash the filter residue to further reduce the exchange of product hydrogen isotopes and water hydrogen isotopes. Similarly, the sample is dried at low temperature in the glove box.

[0028] The water content of the calibration material is high (theoretical water content is 18% wt), XRD data show that it is high in purity, the sample crystal phase is mainly copper hydroxide, SEM photos show that the sample is well crystallized, and vacuum thermogravimetric analysis shows that the sample has good thermal stability. After being sealed for 7 days, the sample was used to measure the isotope value (4‰, -74‰, -24‰). The measurement results show that in the sealed state, the sample has not deteriorated and still has calibration capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is an X-ray diffraction (XRD) pattern of the solid hydrogen isotope calibration material prepared in Example 1 of the present invention;

[0030] Figure 2 is a scanning electron microscope (SEM) image of the solid hydrogen isotope calibration material prepared in Example 1 of the present invention;

[0031] Figure 3 is a vacuum thermogravimetric analysis (VTG) diagram of the solid hydrogen isotope calibration material prepared in Example 1 of the present invention;

[0032] Figure 4 1 is an isotope calibration result (after storage for 7 days) of the solid hydrogen isotope standard prepared in Example 1 of the present invention, wherein the upper and lower groups of graphs (a), (b), and (c) respectively represent the gas pressure value (upper graph) and isotope value (lower graph) of the solid standard prepared from precursor water with hydrogen isotope contents of 4‰, -74‰, and -24‰;

[0033] Figure 5 is a schematic diagram of the calibration spectrum equipment;

[0034] Figure 6 This is the isotope calibration result of commercial analytical grade copper hydroxide. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a method for preparing a solid hydrogen isotope standard, comprising the following steps:

[0038] S1. In a glove box, open the bottle mouths of high-purity Na2O (80% purity, containing 20% ​​sodium peroxide) and high-purity anhydrous copper sulfate (analytical grade), cover the bottle mouths with a layer of metal mesh (to prevent drug dust), and degas in a transition chamber of the glove box at 100°C for 8 hours under vacuum;

[0039] The weighing device, dissolving device and filtering device are placed in the transition chamber of the glove box for vacuum degassing before use; the heat-resistant device is subjected to high-temperature vacuum degassing (170°C, 12h degassing), and the non-heat-resistant device is subjected to natural vacuum degassing (1-2 days);

[0040] S2. In a glove box, 3.2 g of high-purity anhydrous copper sulfate was dissolved in 100 ml of deionized water to a concentration of 0.2 mol / L. The mixture was stirred magnetically for 10 min. High-purity Na2O was then added in small amounts and multiple times. The mass ratio of high-purity anhydrous copper sulfate to high-purity Na2O was 2.5:1. The addition was stopped until no new precipitate was precipitated to obtain a mixed reaction solution.

[0041] S2. Filter the mixed reaction solution in a glove box, wash the filtered material with anhydrous ethanol and then dry it, seal it with a stopper and place it on a semiconductor refrigeration chip for low-temperature storage, and obtain the calibration material precipitate 1 for standby use.

[0042] Example 2

[0043] This embodiment provides a method for preparing a solid hydrogen isotope marker. The specific steps are similar to those of Embodiment 1, except that, in step S2, 1.6 g of high-purity anhydrous copper sulfate is dissolved in 100 ml of deionized water at a concentration of 0.1 mol / L to obtain a marker precipitate 2 for standby use.

[0044] Example 3

[0045] This embodiment provides a method for preparing a solid hydrogen isotope standard. The specific steps are similar to those of Embodiment 1, except that in step S2, 4.8 g of high-purity anhydrous copper sulfate is dissolved in 100 ml of deionized water at a concentration of 0.3 mol / L to obtain a standard precipitate 3 for standby use.

[0046] Example 4

[0047] This embodiment provides a method for preparing a solid hydrogen isotope marker. The specific steps are similar to those of Embodiment 1, except that the mass ratio of high-purity anhydrous copper sulfate to high-purity Na2O is 2:1, and a marker precipitate 4 is prepared for use.

[0048] Figure 1 is the X-ray diffraction (XRD) pattern of the calibration material precipitate obtained in Example 1; Figure 1 The specific test steps are to use the calibration material precipitate prepared in Example 1, place it on the sample stage of the X-ray diffractometer, and scan at an angle of 20-80°. Figure 1 It can be seen that the main component of the calibration precipitate prepared in Example 1 is copper hydroxide, and it does not contain other obvious impurities. It should be noted that this substance is easily deteriorated by combining with carbon dioxide, and needs to be sealed and stored, and can be used immediately after opening.

[0049] Figure 2 This is a scanning electron microscope (SEM) image of the calibration material precipitate obtained in Example 1; Figure 2 The specific test steps are to spread the calibration material prepared in Example 1 on the weighing paper, dip it with an absorbent cotton swab, stick the conductive glue on the sample table, carefully remove the peeling paper, shake the sample on the cotton swab onto the conductive glue, and perform the scanning electron microscope test. Figure 2 It can be seen that the crystallization of the calibration material precipitate obtained in Example 1 is good, and it is almost uniformly long strip crystals. The calibration material obtained by this process has good crystal consistency.

[0050] Figure 3 This is a vacuum thermogravimetric analysis diagram of the calibration material precipitate obtained in Example 1; Figure 3 The specific test steps are as follows: the calibration material prepared in Example 1 is placed in the sample chamber, the gas in the sample chamber is evacuated by a vacuum pump, the temperature is raised at a rate of 1°C / min, and the temperature is maintained at 25, 50, and 70°C for 20 minutes each, and then heated to 150°C. Figure 3 It can be seen that the calibration material precipitate prepared in Example 1 has good thermal stability under vacuum, with a thermal decomposition temperature of about 100°C, and accelerated decomposition under high humidity conditions of about 140°C, indicating that the sample has vacuum thermal stability and can work in a vacuum environment, overcoming the shortcomings of traditional liquid calibration materials.

[0051] Figure 4 The isotope test results of the calibration material prepared in Example 1 after being precipitated and placed for 7 days; there are three groups of figures (a), (b), and (c), which represent the solid calibration materials prepared from precursor water with hydrogen isotope contents of 4‰, -74‰, and -24‰, respectively. The upper figure represents the pressure value and the lower figure represents the isotope value. Figure 4 The specific test steps are to place the sample in the calibration container, remove the gas, heat the calibration (greater than 100°C), start recording the spectrum data when the vacuum gauge reading reaches 150Pa, and end recording when the vacuum gauge reading reaches 250Pa. Figure 4 It can be seen that the calibration material prepared in Example 1 can be resealed and stored after being opened, and its isotope value will not change over time.

[0052] Isotope calibration:

[0053] The D / H value was tested using the calibration precipitate prepared in Example 1 and the deionized water sample, and the spectral equipment was calibrated as shown in the attached Figure 5 As shown, the calibration steps are as follows:

[0054] S1. Keep all valves closed, open valve 1 and valve 2, and exhaust the entire equipment at 35°C for 12 hours;

[0055] S2, close valve 1, and heat the gas calibration component containing the calibration object;

[0056] S3, start recording spectrum data when the vacuum gauge reading reaches 150Pa, and end recording when the reading reaches 250Pa;

[0057] S4. Analyze the gas isotope value to see if it is consistent with the water isotope of the synthetic calibration material. If it is consistent, it means that the chemical reaction kinetics and element conservation can be used to retain the water isotope in the solid calibration material before physical fractionation.

[0058] Similarly, use Figure 5 The above hydrogen isotope value test was performed on analytical pure copper hydroxide using a calibration spectrometer. Two samples were selected from a batch of analytical pure copper hydroxide. The test results are as follows: Figure 6 shown.

[0059] Similarly, use Figure 5 The solid hydrogen isotope calibration materials prepared in Example 2, Example 3 and Example 4 were subjected to the above hydrogen isotope value test using a calibration spectrum device.

[0060] Figure 5 It can be seen that the solid hydrogen isotope calibration material prepared by the present invention is consistent with the water isotope of the synthetic calibration material, indicating that the use of chemical reaction kinetics and element conservation can be used before physical fractionation to retain the isotope of water in the solid hydrogen isotope calibration material prepared in Example 1. The current liquid isotope tester is not suitable for solid calibration materials, and it is necessary to use the existing hydrogen isotope spectrum for calibration, and due to the concentration-dependent effect, the gas pressure should be maintained at about 200Pa. Compared with traditional liquid calibration materials, the solid hydrogen isotope calibration material prepared by the present invention can be resealed and stored after opening, and will not undergo phase change fractionation over time. The calibration process does not require complex quantitative sampling equipment, can withstand high vacuum environments, and does not require nitrogen blowing.

[0061] Figure 6 The hydrogen isotope composition of commercial analytical pure copper hydroxide is unknown while ensuring high purity. The hydrogen isotope difference of samples in the same batch is about 50‰, which cannot be used as a hydrogen isotope standard. This shows that when preparing copper hydroxide solid hydrogen isotope standard, it is necessary not only to ensure the high purity of the standard precipitation, but also to ensure the traceability of hydrogen isotopes.

[0062] When the solid hydrogen isotope standards prepared in Example 2, Example 3 and Example 4 were tested for hydrogen isotope values, the gas isotope values ​​were consistent with the water isotopes of the synthetic standards, indicating that the chemical reaction kinetics and element conservation can be used to retain the water isotopes in the solid hydrogen isotope standards prepared in Examples 2-4 before physical fractionation.

[0063] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a solid hydrogen isotope standard, characterized in that: The following steps are involved: S1. In a glove box, high-purity anhydrous copper sulfate is dissolved in deionized water to a concentration of 0.1-0.3 mol / L, and then high-purity Na2O is added in small amounts and multiple times until no new precipitate is precipitated, to obtain a mixed reaction solution; S2. Filter the mixed reaction solution in a glove box, wash the filter residue with anhydrous ethanol, dry it, and seal it for storage to obtain the calibration substance precipitate.

2. The method for preparing a solid hydrogen isotope standard according to claim 1, characterized in that: The high-purity Na2O contains 80wt% pure sodium oxide and 20wt% sodium peroxide, and the mass ratio of high-purity anhydrous copper sulfate to high-purity Na2O is (2-2.5):

1.

3. The method for preparing a solid hydrogen isotope standard according to claim 1 or 2, characterized in that: The purity of the high-purity anhydrous copper sulfate is analytically pure. The high-purity anhydrous copper sulfate is dissolved in deionized water and stirred with a magnetic stirrer for 10-15 minutes.

4. The method for preparing a solid hydrogen isotope standard according to claim 1, characterized in that: The high-purity Na2O, high-purity anhydrous copper sulfate, weighing device, dissolving device and filtering device used in steps S1 and S2 are placed in a transition chamber of the glove box for vacuum degassing before use.

5. The method for preparing a solid hydrogen isotope standard according to claim 4, characterized in that: In the glove box transition chamber, high-temperature vacuum degassing is performed on heat-resistant devices, and natural vacuum degassing is performed on non-heat-resistant devices.

6. The method for preparing a solid hydrogen isotope standard according to claim 5, characterized in that: The temperature of high-temperature vacuum degassing is greater than 150-200°C, the degassing time is greater than 12-24h, the time of natural vacuum degassing is 1-2 days, and the temperature of natural vacuum degassing is 20-40°C.

7. The method for preparing a solid hydrogen isotope standard according to claim 4, characterized in that: When high-purity Na2O and high-purity anhydrous copper sulfate are vacuum degassed in the glove box transition chamber, the bottle mouth containing the reagents is equipped with a stainless steel metal mesh to avoid contaminating the glove box transition chamber.

8. The method for preparing a solid hydrogen isotope standard according to claim 1, characterized in that: The mixed reaction solution is filtered in step S2 by suction filtration, and precursor deionized water or anhydrous ethanol is used to assist the suction filtration.

9. The method for preparing a solid hydrogen isotope standard according to claim 1, characterized in that: The calibration substance precipitated in step S2 is bottled and sealed for storage in an inert gas atmosphere in a glove box.

10. A solid hydrogen isotope standard obtained by the preparation method of a solid hydrogen isotope standard according to any one of claims 1 to 9.

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