JP6540064B2 - Microparticle sampling method and microparticle analysis method - Google Patents

Description

  The present invention relates to a particulate sampling method and a particulate analysis method, and in particular, particulates (particulates in the atmosphere) that fly in the atmosphere using an electron beam, a focused ion beam or the like, in particular particulates from various emission sources including fixed emission sources. The present invention relates to a particulate sampling method and a particulate analysis method for measuring component information of each group of particles.

  Fine particles with a particle diameter of several microns or less represented by PM2.5 particles are required to develop accurate measurement techniques for the particle size distribution of the fine particles and their components due to high toxicity to the human body . In particular, PM2.5 from fixed sources has a large amount of emissions, so it has become necessary to conduct surveys. Here, “fact-finding” means the amount of emissions of substances emitted from each fixed source, such as primary particles of particulates such as PM 2.5 particles by type of each source such as industry, fuel, etc. It is to examine the discharge inventory of That is, by this "fact-finding", it is possible to specify the generation source of the fine particles and the scattering history of the fine particles, and it is possible to take efficient environmental measures.

For the actual condition survey, measurement of the amount of fine particles using a weight method, a method of examining average information of elements of fine particles using inductive coupling plasma mass spectrometry (ICP-MS method), etc. are known. (Non-Patent Document 1).
The average information of the elements of the particle group can clarify the average composition. However, when particles of composition elements that are completely different from the average composition are included in the particle group, there is a problem that the elemental composition of each particle can not be known. In particular, when a small but specific source contains characteristic particles, the origin of the particle can not be estimated from only the average information of the elements, and it has been difficult to identify the source.

  PM2.5 particles are likely to travel long distances as there is concern over transboundary effects of scattered particles from not only Japan but also from China and other continents, as has become a problem in recent years. Therefore, although it is necessary to consider a large number of sources of PM2.5 particles, efficient measures can not be taken if the contribution from the source can not be clarified. In particular, if fixed sources such as plant chimneys, mobile sources such as cars and ships, and transboundary influences can not be separated, it is impossible to take measures. And for the above-mentioned segmentation, only the average information of the elements of the particle group is insufficient, and the individual particles are analyzed, and the statistical particle group is clarified by cluster analysis based on the information. Is important. Therefore, single particle analysis technology for fine particles is important.

  Patent Document 1 discloses a micro site analysis apparatus using an electron beam and a focused ion beam in combination. In the technology described in Patent Document 1, it is possible to nondestructively identify a particle of interest with an electron beam, and perform component analysis of the particle with a focused ion beam.

  In addition, even with a scanning analysis electron microscope, it is possible to extract information on fine particles similar to that of Patent Document 1. However, many fine particles are hollow, and in order to determine the density thereof, a system provided with a focused ion beam that can separate and measure the internal structure of the fine particles from the outside is suitable.

  In Patent Document 2, fine particles are cut and processed by irradiating the fine particles on the collection substrate with the focused ion beam, and the sample table is rotated to emit secondary ions by irradiating the cut surface with the focused ion beam. There is disclosed a method of evaluating the components and voids inside the microparticles based on the results of detection of the secondary ions.

  When PM2.5 particles derived from a plurality of sources enter, it is not possible to know particle information from each source, and it is not possible to distinguish each source. In order to solve the problem, it is necessary to grasp a typical particle group contained in the collected PM 2.5 particles by performing elemental analysis for each particle. As one of the analysis methods of such PM2.5 particles, in Non-Patent Document 2, elemental information is acquired using a focused ion beam, and cluster analysis is performed to group PM 2.5 particles being collected. How to do it has been reported.

  Here, in order to conduct one-particle analysis of PM2.5 particles, particles with a diameter of more than 2.5 μm are separated with certainty, and further, there is no overlap between particles, and the PM2.5 particles are uniformly distributed on the substrate. Need to be collected.

  As a means for collecting fine particles, methods using various classification methods are known, but methods using impactors (hereinafter, also simply referred to as impactor methods), cyclone methods, methods using virtual impactors (hereinafter , Or simply called virtual impact method. These collection means depend on the difference in classification method.

  The impactor method is an inertial collision type, and has a structure including a jet nozzle of sample air directed vertically downward and a collision plate disposed at right angles to the nozzle. In this impactor method, when the airflow from the jet nozzle in the vertical direction bends in the horizontal direction by hitting the collision plate, it separates into coarse particles that collide with the collision plate by inertia force and small particles that bend in the horizontal direction on the airflow. How to

  The cyclone method is a method of centrifugal separation, which comprises a cylindrical portion, a conical portion, and a particle reservoir, and has a structure in which an air stream spirally swirls inside the main body. The cyclone method is a method of separating into coarse particles which are pressed against the wall surface by the centrifugal force of the swirling flow and collected in the particle reservoir and microparticles which pass through the air flow.

  On the other hand, the virtual impactor method is a method called virtual inertial collision type, in which the collision plate in the above-mentioned impactor type is removed and an opposing nozzle is provided instead. Among the particles accelerated from the jet nozzle, coarse particles are captured through the opposing nozzle and separated from the microparticles.

  Among the three collection means (classification methods), in the method using an impactor and the method using a cyclone method, the separation from coarse particles becomes insufficient at a location where the concentration of PM2.5 particles is high, and PM2. It is known that many particles having a particle size of 5 or more are sampled. For the above reasons, it is essential to use the virtual impactor method at locations where there is a large amount of dust such as fixed emission sources. Even in the JIS method, JIS Z 7152-2013 specifies that the virtual impactor be applied as a classification method in "PM10 / PM 2.5 mass concentration measurement method in exhaust gas by virtual impactor".

JP 2008-39521 A Unexamined-Japanese-Patent No. 2011-163872 Japanese Patent Application Publication No. 2003-225625

Ministry of the Environment Atmospheric particulate matter (PM2.5) component measurement manual in the atmosphere BUNSEKI KAGAKU Vol. 63, No. 4, pp. 317-322 (2014)

Here, the following sampling is important for single-particle analysis using a focused ion beam or the like at a location where there is a large amount of dust such as a fixed discharge source.
That is, it is important to accurately classify fine particles in dust and to place the classified fine particles uniformly on the smooth substrate so that there is no selectivity due to the dependence of the particles depending on the element and particle size. If the particles overlap when the classified particles are placed on a smooth substrate, individual particles can not be analyzed. Therefore, it is necessary for the particles to be sampled uniformly on the smooth substrate.
Further, when measurement is performed using a focused ion beam or the like, if the surface accuracy of the smooth substrate surface is low, the contrast with the fine particles can not be obtained, and there is a problem that particle measurement can not be performed. That is, high surface accuracy is required on the smooth substrate surface.
Further, the material of the smooth substrate does not deteriorate even under high temperature environment or corrosive gas in consideration of the environment of collection, and it is necessary to have conductivity enough not to charge up from the combination with the measurement method. It is disclosed that, for example, a silicon wafer is used as a substrate having such features (Patent Document 2).

  Here, as a method of collecting PM2.5 particles by a virtual impactor method, in a virtual impactor having a high removal rate of coarse particles, a silicon wafer is placed above a filter for collecting PM2.5 particles as a smooth substrate. Suction and collection of a sample for analysis of one particle of PM2.5 particles on a silicon wafer is generally considered as a collection method. However, although PM2.5 particles are collected by the surrounding filter, there is a problem that only a very small amount is collected on a silicon wafer.

  In addition, when component measurement of particles collected on a silicon wafer by the virtual impactor method described above is performed using a focused ion beam, the component analysis of the particles collected on a filter is an element whose component composition is completely different from the component analysis result by ICP-MS. Was found to be observed a lot. This indicates that the very small amount of particles collected on the silicon wafer by the virtual impactor method described above do not represent the PM2.5 particles sampled by the virtual impactor. That is, it is considered that PM2.5 particles are selectively collected on the silicon wafer by the specific gravity of the particles and the like.

  On the other hand, in the impactor method or the cyclone method in which the influence of coarse particles is large, sampling of fine particle groups is possible by installing a silicon wafer in the coarse particle removal portion. However, due to the structural problems, a large amount of oversized particles are mixed, the particles are overlapped and sampled, and it is difficult to distribute and collect the particles uniformly.

  The present invention has been made in view of the above problems in the prior art, and in order to measure component information of each particle of the particle group in the atmosphere, the particles are sufficiently separated from the coarse particles and smooth. It is an object of the present invention to provide a particulate sampling method and a particulate analysis method capable of collecting uniformly and uniformly on a substrate.

  The configuration of the present invention made to solve the above-mentioned problems is summarized below.

(1) A method of collecting particulates in the atmosphere on a smooth substrate, wherein the particulates in the atmosphere are classified by a virtual impact method to capture particulates having a particle diameter less than a specific particle diameter on a filter And collecting the fine particles on the smooth substrate by collecting and pressing the smooth substrate against the filter.
(2) When the fine particles are transferred onto the smooth substrate and collected, the smooth substrate is disposed so that the collection surface of the smooth substrate faces upward, and the filter surface is disposed from above the collection surface The particulate sampling method according to (1), wherein the filter and the smooth substrate are superposed with the particulate collection surface facing downward, and then the filter is transferred by pressing the filter against the smooth substrate.
( 3 ) The fine particle sampling method according to (1) or (2) , wherein the smooth substrate is a silicon wafer.
( 4 ) The particulate sampling method according to any one of (1) to ( 3 ), wherein the specific particle diameter is 2.5 μm.

( 5 ) A sample table on which a sample is placed, an electron beam irradiator for irradiating an electron beam, a detector for detecting electrons scattered by the irradiation of the sample to the electron beam, and a focused ion beam A particle analysis method using a device comprising: a focused ion beam irradiator; and an analyzer for detecting secondary ions emitted from the sample by irradiating the sample with the focused ion beam, the method comprising: (1) ( 4 ) The smooth substrate on which fine particles are attached on the surface by the fine particle sampling method according to any one of ( 4 ) to ( 6 ) is placed on the sample table, and the fine particles on the smooth substrate are irradiated with an electron beam; And detecting the electrons scattered by the irradiation by the detector, and based on the result of the detected electrons, identifying the particles, and irradiating the particles with a focused ion beam, A particle analysis method, comprising: detecting secondary ions emitted from the particles by irradiation of the focused ion beam; and analyzing a component of the particles based on the result of the detected secondary ions.
( 6 ) The sample is cut and processed using the focused ion beam, and the sample table is rotated so that the cut surface is substantially perpendicular to the focused ion beam, and the focused ion is cut on the cut surface of the fine particles The particle analysis according to ( 5 ), characterized in that a beam is irradiated to cause secondary particles to be emitted from the particles, and components and voids inside the particles are evaluated based on the results of the detected secondary ions. Method.

According to the present invention, even in the case where the fine particles are derived from a source having a large amount of dust such as a fixed discharge source, the fine particles in the atmosphere such as PM2.5 particles having a sufficient number to obtain representativeness are smoothed. It is possible to provide a sampling method for collecting uniformly and without overlapping on a substrate. In particular, according to the present invention, even on a smooth substrate for which conductivity has been secured, which is used in an analysis method using a focused ion beam, etc., uniform fine particles without selectivity can be captured regardless of the specific gravity and size of the particles. Enable collection.
Further, the particles sampled by the particle sampling method of the present invention should be subjected to measurement of elemental composition, evaluation of voids, and measurement of specific gravity therefrom for each particle by a particle analysis method using an electron beam or a focused ion beam. Is possible. As a result, it becomes possible to obtain source-specific information that can not be obtained from the average elemental composition from the obtained analysis results, and can provide powerful information for identifying the source, and the efficiency We can greatly contribute to good environmental measures.

FIG. 1 is a schematic diagram illustrating a method of sampling PM2.5 particles from a stationary source that is an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of each classifier for explaining the virtual impactor method. FIG. 3 is a schematic view of a SIMS apparatus using a focused ion beam. FIG. 4 (a) is a schematic view for explaining the entire configuration of an analyzer according to another aspect of the present embodiment, and FIG. 4 (b) is a sample of the analyzer shown in FIG. 4 (a). It is the schematic for demonstrating the state which rotated the stand 1 180 degree. FIG. 5 is an optical micrograph of the fine particles collected on the silicon wafer when transferred from the filter to the silicon wafer. FIG. 6 is a SIMS image ((a): K, (b): Na) obtained by measuring the fine particles collected on the silicon wafer when transferred from the filter to the silicon wafer using an FIB-TOF-SIMS apparatus. FIG. 7 is a schematic view (side view and top view) showing the state of collection of dust when collected by the impactor method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used in the following description, for the sake of easy understanding of the features of the present invention, the features that are the features may be enlarged and shown for convenience, and the dimensional ratio of each component is the same as the actual Not necessarily.
Also, in the following, among particulates in the atmosphere, sampling of PM2.5 particles will be described as an example.

(Particle sampling method)
FIG. 1 is a schematic diagram showing a method of collecting PM2.5 particles from a fixed discharge source, such as in a chimney.
Emissions of PM2.5 particles from fixed sources are usually emitted from chimneys in many cases. Therefore, the collection of PM2.5 particles from stationary sources is performed by introducing a sampler for classification in the flue. After the sampler has been introduced into the flue, it is common to start sampling after waiting for the temperature to equalize.
Therefore, in the present embodiment, as shown in FIG. 1, the virtual impactor 101 is put in the flue at the time of sampling in the flue.

The virtual impactor 101 generally comprises a final collecting portion 111 for collecting fine particles having a particle diameter of 2.5 μm or less, an intermediate collecting portion 108 for collecting particles larger than 2.5 μm and 10 μm or smaller, and coarse particles larger than that. And a rough collecting unit 105 for collecting the
Since it is necessary to adjust the suction amount of the suctioned gas in each collection section to a specified value, the final collection pump 104, the intermediate collection pump 103, and the rough collection pump 102 respectively suction independently.

The particles sampled from the flue at the dust collecting port 113 first enter the rough collecting unit 105, and the classifying unit 106 uses a virtual inertial collision type classification method (virtual impactor method) to measure particles having a particle diameter of 10 μm or more The particles having a diameter of 10 μm or less are classified, and those having a particle diameter of more than 10 μm are collected by a filter 107.
The particles having a particle diameter of 10 μm or less then enter the intermediate collecting portion 108 and are classified in the classifying portion 109 into particles having a particle diameter of more than 2.5 μm and particles having a particle diameter of 2.5 μm or less by virtual impactor method. Those larger than 5 μm are collected by the filter 110.
The particles having a particle diameter of 2.5 μm or less enter the final collecting unit 111, and the fine particles having a particle diameter of 2.5 μm or less, that is, PM 2.5 particles are collected by the filter 112.
In addition, as filter 112 which collects PM2.5 particle | grains, the thing made from quartz or Teflon (trademark) can be used.

FIG. 2 is a schematic cross-sectional view of the classifier 109. As shown in FIG. Hereinafter, a method of classifying particles by the virtual impactor method will be described with reference to FIG.
The classifier 109 is roughly composed of a circular nozzle 401 that ejects air and a circular opposing nozzle (air collecting portion) 403 having an axis that is the same as the axis of the nozzle 401. The nozzle 401 and the opposing nozzle 403 are opposed at an interval of a predetermined length. The classifier 106 also has substantially the same configuration.

  The opposing nozzle 403 is connected to the intermediate collection pump 103, and the air ejected from the nozzle 401 is at a predetermined ratio on the inner peripheral side of the opposing nozzle 403 and the outer periphery of the opposing nozzle 403 which does not pass inside the opposing nozzle 403. Distributed to the side, two air flows are formed. That is, since the air ejected from the nozzle 401 is diverted by the upper end of the opposing nozzle 403, a virtual collision surface (virtual collision surface 402) is present at the upper end when viewed from the particle group intruding from the nozzle 401. It can be said that it exists.

A particle (coarse particle) having a particle diameter of more than 2.5 μm which enters from the nozzle 401 travels straight as it is, and collides with the lower virtual collision surface 402 because the inertia force is large. Suctioned and collected at 110 (see FIG. 1).
On the other hand, fine particles (PM 2.5 particles) having a particle diameter of 2.5 μm or less have a small inertia force and are bent along the air flow flowing on the outer peripheral side of the opposing nozzle 403 and thus do not collide with the virtual collision surface 402 The suction pump 104 is configured to be sucked by the collection pump 104 and collected on the filter 112.
In the case of the classifier 106, coarse particles having a particle size of more than 10 μm are collected by the filter 107 shown in FIG. 1, and particles having a particle size of more than 2.5 μm and 10 μm or less are sent to the intermediate collection unit 108.

  The total weight of the PM 2.5 particles collected on the filter 112 is measured by a gravimetric method, and dissolved by an acid or the like, and analyzed by ICP-MS or the like to determine an average elemental composition. However, since only the average information of the elements of the particle group can be obtained by the above method, after being discharged from the fixed source and diffused, it mixes with particles from other sources, and the source and the observation point Can not understand the relationship between

In order to understand the relationship between the source and the observation point, not only the average information of the elements of the particle group but also the elemental composition of each particle is required. Furthermore, it is also possible to distinguish the influence of contamination, foreign matter contamination, and the like on particles by examining the element distribution by distinguishing individual particles from the surface and the inside of the particles.
As an example of the measurement of such individual particles, a method using a secondary ion mass spectrometry (SIMS) apparatus or the like using a focused ion beam or an evaluation method using an electron beam can be considered.
In order to measure PM 2.5 particles, statistical information is required, and at least about 1000 particles need to be measured individually. Therefore, PM2.5 particles to be introduced into the apparatus need to be collected in a dispersed state on the smooth substrate surface.

Since collection of particles by the virtual impact method is originally a method in which particles are uniformly collected on a filter, it is excellent to disperse and measure particles. However, when a smooth substrate is placed above this filter and sampling is performed, although it is collected by the filter around the smooth substrate, the amount of PM2.5 particles collected on the filter overwhelms the smooth substrate is overwhelming. The inventors found that only a small amount was collected.
This seems to be due to the virtual impactor method being a method of controlling the air flow as described above. That is, since the flow of gas in the virtual impactor method is slower than other classification methods, the use of a smooth substrate made of a non-windable material such as a silicon wafer will inhibit the flow of air flow, and the effect will cause adhesion to the substrate. It is considered that there is a possibility that fine particles may not get on the substrate. Therefore, it may be difficult to collect PM2.5 particles directly on the substrate where the gas flow is interrupted.

Therefore, it was conceived to transfer the fine particles collected by this virtual impactor method to a smooth substrate.
When transferring, place the filter so that the collection surface of the smooth substrate faces upwards, place the collection surface of PM2.5 particles of the filter downward from above the collection surface, overlay the filter and the smooth substrate, and then smooth the filter By pressing on the substrate, PM2.5 particles can be collected on the substrate having less element dependency and high smoothness.
In addition, transfer to the substrate is possible by using the method of placing the collection surface of the filter upward and pressing the smooth substrate from above, but when pressing with the same force as the former, the former with the smooth substrate down The collection efficiency of particles decreased by about 20% compared to the method of collection. Therefore, as for the efficient collection method, the method of pressing the filter from the top with the smooth substrate down is preferable.

When the fine particles are transferred from the filter, if the filter is pressed against the smooth substrate with a strong force, the material of the filter may be transferred to the smooth substrate. In particular, when the material of the filter is quartz, it is easy to peel off, so care must be taken when transferring.
As a method of transferring a sufficient number of fine particles on a smooth substrate surface with good reproducibility, an optional weight may be placed on a filter stacked on the smooth substrate and a pressure of 8 to 22 g / cm ² may be applied. I found it to be effective. This can be realized, for example, by mounting a weight of 100 g and a bottom area of about 37 cm ² . When the bottom area was 37 cm ² and a weight having a weight of 50 g was placed, fine particles were transferred only by about 1⁄5 as compared with the case of 100 g. On the other hand, in the case of the same bottom area and a weight of 300 g, the pressing force was too strong, and the fibers of the filter were transferred onto the smooth substrate, which was an obstacle to particle analysis.

  As the smooth substrate, it is preferable to use a substrate having a high surface accuracy, which does not deteriorate even in a high temperature environment or a corrosive gas, and which has a certain degree of conductivity. Preferably, it is a silicon wafer.

  Here, there is a dust removal method of the substrate or sheet in which the contaminant particles on the smooth substrate are positively charged, collected on the negatively charged roll, adsorbed and removed, and then transferred and removed to the adsorption roll. Patent document 3 (Unexamined-Japanese-Patent No. 2003-225625) is disclosed. However, Patent Document 3 does not disclose a method of transferring fine particles to the smooth substrate side, which is a feature of the present embodiment as described above. Transfer of fine particles onto a smooth substrate was achieved by devising to solve the unique problems found by the present inventors for the purpose of analyzing individual fine particles after classification with a virtual impactor. It is a thing.

(Particle analysis method)
Next, the particle analysis method according to the present embodiment will be described.
The particle analysis method according to the present embodiment includes a sample stage on which a sample is placed, an electron beam irradiator for irradiating an electron beam, and a detector for detecting electrons scattered by the irradiation of the sample with the electron beam. Particle analysis method using an apparatus comprising: a focused ion beam irradiator for irradiating a focused ion beam; and an analyzer for detecting secondary ions emitted from the sample by irradiating the sample with the focused ion beam The smooth substrate on which the fine particles are deposited on the surface by the fine particle sampling method described above is placed on the sample table, and the fine particles on the smooth substrate are irradiated with an electron beam and scattered by the irradiation of the electron beam. Detected electrons by the detector, and based on the result of the detected electrons, identify the particles, and irradiate the particles with a focused ion beam; Serial detecting secondary ions emitted from the fine particles by irradiation of the focused ion beam, based on the results of said detected secondary ions, characterized by analyzing the components of the fine particles.
Details will be described below with reference to the drawings.

FIG. 3 is a view showing an example of a schematic configuration of a SIMS apparatus using a focused ion beam, which is an apparatus used in the particle analysis method according to the present embodiment.
As shown, the particle analyzer mainly comprises the sample stage 1, focused ion beam irradiator 3, electron beam irradiator 4, mass spectrometer (analyzer) 5, and secondary electron detector (detector) And 6). The sample stage 1 is in a vacuum chamber.

In the smooth substrate 7, a plurality of PM2.5 particle groups 2 (in the following description, the plurality of PM2.5 particle groups 2 will be abbreviated as PM2.5 samples 2 in the following description) to be observed are transferred, It is installed in a state of being fixed on the sample table 1.
The smooth substrate 7 ideally has a flat (smooth) surface at the atomic level. For example, it is desirable to use a silicon wafer as the smooth substrate 7. Besides the silicon wafer, a substrate of SiC, GaAs, sapphire, glass or the like can be used as the smooth substrate 7.

  The focused ion beam irradiator 3 and the electron beam irradiator 4 are vertically elevated with respect to the sample stage 1 so that the beam is applied to the same point on the surface of the PM 2.5 sample 2 at an arbitrary height of the sample stage 1 It is installed in the position which becomes symmetrical relation on both sides of the mass spectrometer 5 installed in the direction. In the present embodiment, the focused ion beam irradiator 3 and the electron beam irradiator 4 irradiate the beam to the PM 2.5 sample 2 from the direction in which the inclining angle is 45 ° with respect to the sample table 1 installed horizontally. I have to.

The electron beam irradiator 4 is a device that irradiates the surface of the PM 2.5 sample 2 with a focused electron beam focused in the same manner as or more than a focused ion beam irradiator 3 described later.
Secondary electrons generated by irradiation while scanning the electron beam from the electron beam irradiator 4, that is, electrons scattered by the irradiation of the electron beam are detected by the secondary electron detector 6, and the detection result is Based on this, a secondary electron image of PM2.5 sample 2 can be observed.

  For the focused ion beam irradiator 3, generally available ones are available. For example, the ion beam is taken out from a liquid metal gallium ion source and focused on the surface of the PM 2.5 sample 2 to a level of several tens of nm It is a device that can In recent years, in addition to gallium ion sources, focused ion sources such as Bi and Au have also been developed, and it is also possible to use these focused ion sources. When a gallium ion source is used as a focused ion source of the focused ion beam irradiator 3, the pulsed Ga ion beam emitted from the focused ion beam irradiator 3 is a PM 2.5 sample on the surface of the PM 2.5 sample 2. The atoms constituting the surface of 2 are sputtered. As a result, secondary ions are generated from the PM2.5 sample 2. The secondary ions generated in this manner are detected by the mass spectrometer 5.

  The mass spectrometer 5 has a time-of-flight mass using a pulsed ion beam rather than a quadrupole mass spectrometer or a double focusing mass spectrometer that uses a direct current ion beam that causes damage to the sample because the particle size of the measurement is small. It is desirable to use a spectrometer for the mass spectrometer 5.

In this way, scanning the focused ion beam and irradiating the PM 2.5 sample 2 emits secondary ions from the PM 2.5 sample 2. The component of the PM2.5 sample 2 can be analyzed by detecting this secondary ion and analyzing the mass of the PM2.5 sample 2 with the mass spectrometer 5 based on the secondary ion image.
At this time, the secondary ion image is observed in the same field of view as when the secondary electron image obtained by detecting the electrons scattered by the irradiation of the electron beam by the electron beam irradiator 4 is observed. It is possible to use a highly focused gas ion source, a liquid metal ion source or the like instead of the above-described focused ion source.

There are also cases where it is desirable to remove the organic matter on the surface of the PM2.5 sample 2 and observe chemical reactions such as adhesion and oxidation of the PM2.5 sample 2 during scattering. In this case, 10 ² about ¹³ to 10 ¹⁶ ions / cm, a pulsed focused ion beam is irradiated from the focused ion beam irradiator 3 to PM2.5 Sample 2, with the surface of the PM2.5 samples 2 After removing the deposit, it is desirable to observe the secondary ion image as described above.

  As described above, in this embodiment, the components of the PM 2.5 sample 2 can be clarified while the PM 2.5 sample 2 is collected by the same apparatus.

In the particle analysis method of this embodiment, the sample (PM 2.5 sample 2) is cut and processed using a focused ion beam, and the sample stage 1 is rotated so that the cut surface is substantially perpendicular to the focused ion beam. And irradiate the focused ion beam to the cut surface of PM2.5 sample 2 to release the secondary ion from PM2.5 sample 2, and evaluate the component and the void inside the particle based on the result of the detected secondary ion You may
Hereinafter, although it demonstrates using FIG. 4, about the part same as FIG. 3, the detailed description is abbreviate | omitted by attaching the code | symbol same as the code | symbol attached | subjected to FIG.

FIG. 4A is a schematic conceptual view for explaining the entire configuration of an analysis apparatus which is another aspect of the analysis apparatus of the present embodiment shown in FIG. Although PM2.5 sample (sample particles) 2 in the figure is exaggerated and enlarged for convenience of explanation, the actual sample particles are fine and the magnitude relationship with the illustrated sample stand etc. Is not an accurate representation of
As shown in FIG. 4A, the analyzer according to another aspect of the present invention mainly comprises a sample stage 1, a focused ion beam irradiator 3, an electron beam irradiator 4, a rotation mechanism 8 and a mass spectrometer 5. The sample stage 1 is a stage on which the sample is placed, and is preferably kept horizontal.

  When information inside the PM2.5 sample 2 is to be extracted, the PM2.5 sample 2 is cut and processed by the focused ion beam irradiator 3 as described in Patent Document 1. In addition, a rotation mechanism capable of rotating the sample table 1 by 180 ° (with the vertical direction in FIG. 4 (a) as a rotation axis) centering on the eye position of the sample table 1 (the position where the particulate 2 to be measured exists). 8 (for example, a motor or the like) is attached to the sample table 1.

  It was impossible to determine the internal porosity of the PM2.5 sample 2 by the conventional electron beam excitation fluorescent X-ray analysis method. In the conventional electron beam excitation fluorescent X-ray analysis, the depth of information is about 1 μm, and it is impossible to extract the information of the void inside the fine particle having a particle diameter of submicron unit. The information depth on the surface of the secondary ion mass spectrometry used in the present embodiment is as shallow as several nm. For this reason, only the information on the pole surface of the PM2.5 sample 2 is detected. Therefore, by performing elemental mapping on the inside of the cut PM2.5 sample 2, information on the surface and the inside of the PM 2.5 sample 2 can be observed separately.

FIG. 4B shows a state in which the cross section of the sample particle 2 is directed toward the focused ion beam irradiator 2 in the analyzer shown in FIG. FIG.
As described above, by rotating the sample table 1 by the rotation mechanism 8, it becomes possible to irradiate the focused ion beam from the focused ion beam irradiator 3 to the cross section of the cut sample particle 2.

Specifically, while rotating the sample particle 2 cut as described above around the sample particle 2, the sample particle 2 is irradiated with the focused ion beam as described above, Get information inside 2 At this time, it is preferable that the electron beam and the focused ion beam be incident perpendicularly to the cutting plane.
Then, as described above, secondary ions emitted from the sample particle 2 by irradiation of the focused ion beam are detected, and component analysis of the inside of the sample particle 2 is performed based on the result of observing the secondary ion image. . Further, based on the observation result of the secondary ion image, the size (area) of the void inside the sample particle 2 is determined, and assuming that the sample particle 2 and the void are spheres, the volume of the void is calculated. The porosity of the sample particle 2 is determined by dividing by the volume of the sample particle 2.

  By doing as described above, the porosity of each of the fine particles can be clarified, and the density of the sample particles 2 can be determined.

  Each of the embodiments of the present invention described above is merely an example of implementation for carrying out the present invention, and the technical scope of the present invention should not be interpreted limitedly by these. It is a thing. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  Examples of each embodiment of the present invention will be described. The conditions of the examples are examples of the conditions adopted to confirm the feasibility and effects of the present invention, and the scope of application of the present invention is not limited to this one example of conditions. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the scope of the present invention.

(Example of the present invention)
From a flue containing a dust amount of about 20 mg / m ³ , sampling and classification were carried out for 10 minutes using a virtual impactor as shown in FIGS. 1 and 2 to collect PM 2.5 particles in the form of a quartz filter.
Next, the quartz filter from which PM2.5 particles were collected was taken out, and the microparticle collection surface of the quartz filter was directed downward, and the pressed PM2.5 particles were transferred onto the silicon wafer.
The result of observing the silicon wafer surface with an optical microscope is shown in FIG. From this photomicrograph, collection of about 400 PM2.5 particles was confirmed between 50 μm × 50 μm. Furthermore, when four field of view measurement was separately performed with a field of view different from the observed place and a total of five fields of view were measured, a total of about 2000 particles of PM2.5 particles were measured.

  Here, the PM2.5 particles on the quartz filter before transfer are subjected to decomposition treatment using nitric acid and hydrogen peroxide solution, and decomposition treatment is performed in a closed system using high frequency microwaves, and then ICP-MS method is performed. Of the main elements, K, Ca, Al, Mg, and Mn were calculated. Furthermore, when the abundance ratio of the particle group of the silicon wafer to which PM2.5 particles were transferred was similarly calculated, as shown in Table 1, it was observed at an abundance ratio equivalent to the fine particles collected on the filter. Moreover, it turned out that it exists in the equivalent amount also about trace elements other than that.

The results of K and Na measured by SIMS as shown in FIG. 2 for the transferred silicon wafer described above are shown in FIG. FIG. 6 (a) is a SIMS image of K, and FIG. 6 (b) is a SIMS image of Na.
Although each particle contained Na, K, and both Na and K, the ratio of the number of each particle became 4: 1 when the main components were respectively distinguished. That is, by measuring the individual particles transferred onto the silicon wafer, it was possible to distinguish particles having different compositions. This is information that could not be obtained by analysis by ICP-MS.

(Comparative example 1)
A silicon wafer was placed in advance on a quartz or Teflon (registered trademark) filter for collecting PM 2.5 particles by a virtual impact method, and the particles were sampled.
As a result, although the PM2.5 particles were uniformly collected on the filter as confirmed by an optical microscope, only a very small number of PM2.5 particles were collected on the silicon wafer as compared with the filter.
Moreover, when the silicon wafer sampled by the SIMS apparatus was confirmed, the result does not match the abundance ratio obtained from the elemental analysis value by ICP-MS method of the particles collected on the filter, and PM2 on the silicon wafer .5 It was confirmed that some of the five particle groups were selectively collected.

  Here, the elemental composition of the particles collected on the silicon wafer and the elemental composition of the particles collected by the filter were measured by the ICP-MS method. The results are shown in Table 2. This result also shows that the fine particles collected on the silicon wafer have sampling results that do not reflect the entire classified PM 2.5 particles.

(Comparative example 2)
A silicon wafer was adopted as a plate for collecting PM2.5 particles collected by an impactor method. As a result, classification ability is lowered and particles having a large size are mixed. In addition, even when the density of the particles to be introduced is lowered so that the classification ability does not decrease, the particles are collected in a mountain-like shape as shown in FIG. 7, and uniform sampling on a silicon wafer is impossible. there were.

1: Sample stand 2: PM 2.5 particle group (PM 2.5 sample, sample particle)
3: Focused ion beam irradiator 4: Electron beam irradiator 5: Mass spectrometer (analyzer)
6: Secondary electron detector (detector)
7: Smooth substrate 8: Rotation mechanism 101: Virtual impactor 102: Coarse collection pump 103: Intermediate collection pump 104: Final collection pump 105: Coarse collection part 106: Classification part 107: Filter 108: Intermediate collection part 109 Classification unit 110: Filter 111: Final collection unit 112: Filter 113: Dust collection port 401: Nozzle 402: Virtual collision surface 403: Opposing nozzle

Claims (6)

  A method of collecting particulates in the atmosphere on a smooth substrate, wherein the particulates in the atmosphere are classified by virtual impactor method, and particulates having a particle diameter less than a specific particle diameter are collected on a filter, A particulate sampling method, wherein the particulates are transferred and collected on the smooth substrate by pressing the smooth substrate against the filter.   When the fine particles are transferred onto the smooth substrate and collected, the smooth substrate is disposed so that the collection surface of the smooth substrate faces upward, and the fine particles of the filter are collected from above the collection surface 2. The particulate sampling method according to claim 1, wherein the filter and the smooth substrate are superimposed with the surface facing down, and then the filter is transferred by pressing the filter against the smooth substrate. Particulate sampling method according to claim 1 or 2, characterized in that said smooth support is a silicon wafer. The particulate sampling method according to any one of claims 1 to 3 , wherein the specific particle size is 2.5 μm. A sample stage on which a sample is placed, an electron beam irradiator for irradiating an electron beam, a detector for detecting electrons scattered by the irradiation of the sample to the electron beam, and a focused ion beam for irradiating a focused ion beam A particle analysis method using a device comprising: an irradiator; and an analyzer for detecting secondary ions emitted from the sample by irradiating the sample with the focused ion beam,
The smooth substrate on which fine particles are attached on the surface by the fine particle sampling method according to any one of claims 1 to 4 is placed on the sample table,
Irradiating the particles on the smooth substrate with an electron beam;
Detecting the electrons scattered by the irradiation of the electron beam by the detector;
Identifying the particles based on the result of the detected electrons;
Irradiating the particles with a focused ion beam;
Detecting secondary ions emitted from the particles by the irradiation of the focused ion beam;
A particulate analysis method, comprising analyzing the component of the particulate based on the result of the detected secondary ion. The sample is cut using the focused ion beam, and the sample table is rotated so that the cut surface is substantially perpendicular to the focused ion beam, and the cut ion of the particle is irradiated with the focused ion beam. The particulate analysis method according to claim 5 , wherein secondary particles are released from the particulates, and components and voids inside the particulates are evaluated based on the detected results of the secondary ions.