A test method for detecting lead contamination in each processing flow of an extraterrestrial sample

Abstract

The application discloses a kind of detection method for detecting lead pollution of each process of extraterrestrial sample, comprising the following steps: preparation embedded in resin target inside polished standard sample and extraterrestrial sample;Raman spectrum is used to detect the structural change of standard sample and extraterrestrial sample after being polished without water in different time periods;The surface topography picture of standard sample and extraterrestrial sample is photographed after being treated using scanning electron microscope in different thickness polishing paste;The ratio and content of lead isotope of standard sample and extraterrestrial sample in different environments are detected using secondary ion mass spectrometry;The trace element content and lead isotope ratio of standard sample and extraterrestrial sample in different environments are tested using inductively coupled plasma mass spectrometry;The trace element content and lead isotope ratio of standard sample and extraterrestrial sample in different environments are tested using thermal ionization mass spectrometry.The absolute content of lead element in different processing processes can be detected according to the above standard sample micro area and chemical method experiment.

Description

Technical Field

[0001] This invention relates to the field of sample testing technology, and more specifically, to a test method for detecting lead contamination in various processing steps of off-site samples. Background Technology

[0002] Samples returned from extraterrestrial environments and meteorite samples from deep space exploration programs are important research subjects for understanding the evolution of the solar system.

[0003] Pb (lead) contains four stable isotopes. 204 Pb is formed from nuclear reactions. 206 Pb, 207 Pb and 208 Pb is respectively from 238 U(uranium), 235 U and 232 Thorium (Th) decays, and therefore lead isotopes can be used to calculate isotopic ages, making them an important tool for studying the age of extraterrestrial samples. Ideally, isotopic ages can be determined by the ratio of the daughter to the parent element (e.g.,...). 206 Pb / 238 U) is calculated using the decay coefficient, but natural sample systems are complex and can be contaminated at different stages. Therefore, measured Pb needs to be used for correction when calculating the age to deduct the contaminated portion. (e.g.) 206 Pb / 238 U middle 206 Pb contains the components of 238 U decays into 206 Pb and other contaminants were mixed in. 206 Pb, after deducting the contamination portion, is needed to calculate the true radioactive age.

[0004] Previous methods for correcting lead contamination in Earth samples used measured values. 204 The value of Pb, based on known modern Earth... 204 Pb, 206 Pb, 207 Pb and 208 The ratio of Pb is used to calculate the pollution level. 206 Pb, 207 Pb, 208 The value of Pb is thus corrected.

[0005] Extraterrestrial samples differ from terrestrial samples. They are not only contaminated with lead (Pb) from the surface of the celestial body itself, but also from the Earth itself during the collection, transport, and subsequent processing. Because the ratio of Earth's Pb evolution to that of celestial bodies varies significantly at different points in time, the inability to accurately assess the degree of lead contamination on Earth will directly affect the reliability of dating extraterrestrial samples.

[0006] Therefore, how to provide a test method that can effectively detect Pb in various processing steps of extraterrestrial samples has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a testing method for detecting lead contamination in various processing stages of extraterrestrial samples, in order to solve the problems mentioned in the background art.

[0008] According to one aspect of the present invention, a test method for detecting lead contamination in various processing stages of extraterrestrial samples is provided, comprising the following steps:

[0009] Step S1: Prepare polished standard samples and extraterrestrial samples embedded inside the resin target;

[0010] Step S2: Use Raman spectroscopy to detect the structural changes of standard samples and extraterrestrial samples after anhydrous polishing at different time periods;

[0011] Step S3: Use a scanning electron microscope to take images of the surface morphology of the standard sample and the extraterrestrial sample after treatment with polishing paste of different particle sizes;

[0012] Step S4: Use secondary ion mass spectrometry to detect the ratio and content of lead isotopes in standard samples and extraterrestrial samples under different environments;

[0013] Step S5: Use inductively coupled plasma mass spectrometry to test the trace element content and lead isotope ratio of standard samples and extraterrestrial samples under different environments;

[0014] Step S6: Use thermal ionization mass spectrometry to test the trace element content and lead isotope ratio of standard samples and extraterrestrial samples under different environments;

[0015] Step S7: By analyzing the changes in lead content and isotope ratios of standard samples under different processes, a correction index is provided for lead isotope dating of extraterrestrial samples.

[0016] Optionally, in the test method for detecting lead pollution in each processing step of an off-site sample according to the present invention, the specific time periods in step S2 are 2 hours, 6 hours, and 12 hours, respectively.

[0017] Optionally, in the test method for detecting lead contamination in each processing step of an off-site sample according to the present invention, in step S3, the specific thicknesses of the polishing paste are 3 micrometers, 0.5 micrometers, and 0.25 micrometers, respectively.

[0018] Optionally, in the test method for detecting lead contamination in each processing step of an off-site sample according to the present invention, in step S4, the environment to be tested includes surface roughness conditions such as 3 micrometers, 0.5 micrometers, and 0.25 micrometers.

[0019] Optionally, according to the test method for detecting lead contamination in each processing step of an off-site sample as described in the present invention, in step S4, the test environment further includes polishing time conditions such as 2 hours, 6 hours, and 12 hours.

[0020] Optionally, according to the test method for detecting lead contamination in each processing step of an off-site sample as described in the present invention, in step S4, the testing environment further includes ultrapure water cleaning and no cleaning conditions.

[0021] Optionally, according to the test method for detecting lead contamination in various processing steps of off-site samples as described in the present invention, the test environment also includes gold plating thickness conditions such as 40 nanometers and 20 nanometers.

[0022] Optionally, according to the test method for detecting lead pollution in various processing steps of off-site samples according to the present invention, in steps S5 and S6, the environment to be tested includes processing conditions such as agate grinding, crusher grinding, gold plating, and carbon spraying.

[0023] Optionally, according to the test method for detecting lead contamination in various processing steps of off-site samples according to the present invention, in steps S5 and S6, the environment to be detected also includes processing conditions such as coil cutting and wire saw cutting.

[0024] Optionally, according to the test method for detecting lead contamination in various processing steps of off-site samples according to the present invention, in steps S5 and S6, the detection environment further includes processing conditions such as resin preparation, metal target, dry polishing, oil polishing, and water polishing.

[0025] This invention provides a method for detecting Pb in various processing steps of extraterrestrial samples. It serves as a method to assess the degree of Pb contamination caused by differences in processing procedures and tools used in different laboratories. This method uses secondary ion mass spectrometry and thermal ionization mass spectrometry to test Pb isotope contamination during processes such as cutting, target preparation, thin section preparation, polishing, surface coating, and reagent cleaning, providing information on the Pb contamination status at each stage. Based on the aforementioned micro-area and chemical method experiments using standard samples, the absolute lead content in different processing steps can be detected. The difference between the measured lead content and the published lead content of the standard sample equals the increase in lead contamination during the processing. Subsequent lead isotope analysis of extraterrestrial samples processed using the same procedure should first subtract the increase in lead contamination during the processing before lead correction or lead isotope ratio calculation. This effectively solves the problem of lead contamination correction for multi-component Pb mixtures.

[0026] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0028] Figure 1 Raman spectra of standard sample BCR-2G after anhydrous polishing at different time periods;

[0029] Figure 2 Raman spectra of standard sample BHVO-2G after anhydrous polishing at different time periods;

[0030] Figure 3 Raman spectra of plagioclase from extraterrestrial sample NWA-11182 after anhydrous polishing at different time periods;

[0031] Figure 4 Raman spectra of olivine from extraterrestrial sample NWA-11182 after anhydrous polishing at different time periods;

[0032] Figure 5 Raman spectra of pyroxene from extraterrestrial sample NWA-11182 after anhydrous polishing at different time periods;

[0033] Figure 6 Images showing the surface morphology of standard samples BCR-2G and BHVO-2G after polishing at 0.25 micrometers;

[0034] Figure 7 Images showing the surface morphology of standard samples BCR-2G and BHVO-2G after polishing at 0.50 micrometers;

[0035] Figure 8 Images of the surface morphology of standard samples BCR-2G and BHVO-2G after polishing at 3 micrometers;

[0036] Figure 9 Secondary ion mass spectra of standard sample BCR-2G under different surface roughness conditions;

[0037] Figure 10 The secondary ion mass spectra of the standard sample BHVO-2G under different surface roughness conditions are shown.

[0038] Figure 11 Secondary ion mass spectra of standard sample BCR-2G under different surface cleaning conditions;

[0039] Figure 12 Secondary ion mass spectra of standard sample BHVO-2G under different surface cleaning conditions;

[0040] Figure 13 The secondary ion mass spectra of the standard sample BCR-2G under different gold plating thicknesses are shown.

[0041] Figure 14 The secondary ion mass spectra of the standard sample BHVO-2G under different gold plating thicknesses are shown.

[0042] Figure 15 Elemental analysis diagrams of extraterrestrial samples under different treatment conditions;

[0043] Figure 16 Elemental analysis charts of standard samples under different treatment conditions Detailed Implementation

[0044] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0045] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0046] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0047] In all ions shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other ions in the exemplary embodiments may have different values.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0049] according to Figures 1 to 16 As shown, this invention provides a test method for detecting lead contamination in various processing stages of extraterrestrial samples, comprising the following steps:

[0050] Step S1: Prepare polished standard samples (including standard minerals with known elemental content and age, rare earth glass, etc.) and extraterrestrial samples embedded inside the resin target;

[0051] Step S2: Use Raman spectroscopy to detect the structural changes of standard samples and extraterrestrial samples after anhydrous polishing at different time periods;

[0052] like Figure 1 and Figure 2As shown, Raman spectra of BCR-2G and BHVO-2G standard samples after anhydrous polishing for 2 hours, 6 hours, and 12 hours were analyzed using a Horiba LabRAM HR Evolution high-resolution Raman spectrometer under conditions of 100× / 0.90 objective lens, 532 nm wavelength, ~20 mW power, and 1 μm beam spot. The results indicate that no Raman peak shift occurred at different polishing times, and no structural changes were detected.

[0053] Then according to Figures 3 to 5 As shown, no Raman peak shift was observed in the NWA_11182 extraterrestrial meteorite sample under the same conditions. Plagioclase showed relatively consistent peak heights, while olivine and pyroxene peak heights varied. Energy dispersive spectroscopy / electron probe microanalysis revealed significant variations in the iron / magnesium content of olivine and pyroxene in this meteorite, which is the main reason for the different Raman peak heights.

[0054] Step S3: Use a scanning electron microscope to take images of the surface morphology of the standard sample and the extraterrestrial sample after treatment with polishing paste of different thicknesses;

[0055] according to Figures 6 to 8 As shown in the figure (STD represents the standard sample, BSE is the backscattered microscopy image, and SE is the secondary electron image), secondary electron and backscattered imaging analyses were performed on the standard sample and meteorite sample using field emission scanning electron microscopy at 15 kV and 4.0 nA. The results show that after polishing at 0.25 μm and 0.5 μm, BCR-2G and BHVO-2G samples exhibit only minute scratches under secondary electron imaging at 1000x magnification, and these scratches are almost invisible under backscattered signals. After polishing at 3 μm, however, obvious scratches are observed at 1000x magnification, and these scratches are still visible under backscattered signals.

[0056] Step S4: Use secondary ion mass spectrometry to detect the ratio and content of lead isotopes in standard samples and extraterrestrial samples under different environments;

[0057] according to Figure 9 and Figure 10The figure shows the lead content of the standard samples BCR-2G and BHVO-2G at different surface roughnesses using ion probes. BHVO-1 and BCR-1 are 0.25 μm polished surfaces; BHVO-2 and BCR-2 are 0.5 μm polished surfaces; BHVO-3 and BCR-3 are 3.0 μm polished surfaces. For BHVO-2G, the lead content on the 0.5 μm and 0.25 μm polished surfaces showed no significant difference, but was significantly lower than that on the 3 μm polished surface. The surface contamination signal disappeared on the 3 μm polished surface after the 45th data set, while it disappeared on the 0.5 μm and 0.25 μm surfaces after the 20th data set. For BCR-2G, the lead content on the 0.5 μm and 0.25 μm polished surfaces was slightly lower than that on the 3 μm polished surface, showing a smaller difference than that of the BHVO-2G sample. Therefore, surface roughness (after polishing with different particle sizes of polishing materials) greatly affects the lead content on the sample surface, and the impact is greater for samples with lower lead content.

[0058] Then according to Figure 11 and Figure 12 As shown, the lead element counts of ion probes for BCR-2G and BHVO-2G under different surface cleaning conditions are presented. STD-2 represents multiple surface cleanings with ultrapure water, and STD-3 represents surface wiping with alcohol. There were no significant differences between BHVO-2G and BCR-2G under different cleaning conditions.

[0059] Then according to Figure 13 and Figure 14 The figure shows the lead element counts of the ion probe for standard samples BCR-2G and BHVO-2G under different gold plating thicknesses. STD-BHVO-1 and STD-BCR-1 are under a 30 nm surface gold thickness condition, while STD-BHVO-2 and STD-BCR-2 are under a 15 nm surface gold thickness condition. The surface contamination signal disappeared after approximately 40 data sets for BHVO-2G and BCR-2G at a 30 nm gold film thickness, and after approximately 20 data sets at a 15 nm thickness. Therefore, it is necessary to strictly measure the coating thickness to adjust the surface ion cleaning time to eliminate surface contamination.

[0060] Step S5: Use inductively coupled plasma mass spectrometry to test the trace element content and lead isotope ratio of standard samples and extraterrestrial samples under different environments;

[0061] Step S6: Use thermal ionization mass spectrometry to test the trace element content and lead isotope ratio of standard samples and extraterrestrial samples under different environments;

[0062] Step S7: By analyzing the changes in lead content and isotope ratios of standard samples under different processes, a correction index is provided for lead isotope dating of extraterrestrial samples.

[0063] Then according to Figure 15 and Figure 16 The figures show elemental analysis diagrams of wet chemical chondrites under different treatment conditions and NIST 612 / 614 rare earth glass under different treatment conditions. The results indicate that various treatment methods are more likely to cause lead contamination during wet chemical elemental analysis. Furthermore, due to the more developed fractures in extraterrestrial samples (natural samples) and the differences in hardness and crystallinity among different minerals, lead contamination is more likely to occur compared to calibration rare earth glass samples. Iron, copper, and nickel also showed contamination during treatment, possibly due to surface conductivity treatment, high-temperature ion sputtering, or mechanical breakage during cutting.

[0064] Based on the above standard sample micro-area and chemical method experiments, the absolute content of lead in different treatment processes can be detected.

[0065] The measured lead content minus the published lead content of the standard sample equals the increase in lead pollution during the treatment process.

[0066] When performing lead isotope analysis on extraterrestrial samples processed using the same procedure, the data obtained should first be subtracted for the increase in lead pollution during the processing before lead correction or lead isotope ratio calculation.

[0067] By accurately testing the changes in Pb content and isotope ratios through different processes, a correction index is provided for Pb isotope dating of extraterrestrial samples.

[0068] While specific embodiments of the present invention have been described in detail using ion-based methods, those skilled in the art should understand that the above description is for illustrative purposes only and not intended to limit the scope of the invention. It should be understood that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A test method for detecting lead contamination in various processing stages of extraterrestrial samples, characterized in that, Includes the following steps: Step S1: Prepare polished standard samples and extraterrestrial samples embedded inside the resin target; Step S2: Use Raman spectroscopy to detect the structural changes of standard samples and extraterrestrial samples after anhydrous polishing at different time periods; Step S3: Use a scanning electron microscope to take images of the surface morphology of the standard sample and the extraterrestrial sample after treatment with polishing paste of different particle sizes; Step S4: Use secondary ion mass spectrometry to detect the ratio and content of lead isotopes in standard samples and extraterrestrial samples under different environments, wherein the environment in step S4 includes different surface roughness conditions. Step S5: Use inductively coupled plasma mass spectrometry to test the trace element content and lead isotope ratio of standard samples and extraterrestrial samples under different environments. The environment in step S5 includes the treatment conditions of agate grinding, crusher grinding, gold plating and carbon spraying. Step S6: Use thermal ionization mass spectrometry to test the trace element content and lead isotope ratio of standard samples and extraterrestrial samples under different environments. The environment in step S6 includes the treatment conditions of agate grinding, crusher grinding, gold plating and carbon spraying. Step S7: By analyzing the changes in lead content and isotope ratios of standard samples under different processes, a correction index is provided for lead isotope dating of extraterrestrial samples.

2. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 1, characterized in that, In step S2, the specific time periods are 2 hours, 6 hours, and 12 hours.

3. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 1, characterized in that, In step S3, the specific particle sizes of the polishing paste are 3 micrometers, 0.5 micrometers, and 0.25 micrometers.

4. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 1, characterized in that, In step S4, the environment includes surface roughness conditions of 3 micrometers, 0.5 micrometers, and 0.25 micrometers.

5. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 4, characterized in that, In step S4, the environment also includes polishing time conditions of 2 hours, 6 hours, and 12 hours.

6. The test method for detecting lead contamination in each processing step of an extraterrestrial sample according to claim 5, characterized in that, In step S4, the environment also includes ultrapure water rinsing and no rinsing conditions.

7. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 6, characterized in that, In step S4, the environment also includes gold plating with a thickness of 40 nanometers and 20 nanometers.

8. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 1, characterized in that, In steps S5 and S6, the environment also includes the processing conditions for coil cutting and wire saw cutting.

9. The test method for detecting lead contamination in each processing step of extraterrestrial samples according to claim 8, characterized in that, In steps S5 and S6, the environment also includes processing conditions such as resin preparation, metal target, dry polishing, oil polishing, and water polishing.

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