CN111879750B - 30-80 mesh NTO crystal defect rapid evaluation method for coating by supercritical method - Google Patents
30-80 mesh NTO crystal defect rapid evaluation method for coating by supercritical method Download PDFInfo
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Abstract
The invention discloses a method for quickly evaluating defects of 30-80-mesh NTO crystals for cladding by a supercritical method. Random testing of 10 NTO particles 1104cm by micro-Raman Spectroscopy ‑1 The half-height peak width of the characteristic peak is determined, the relative experiment standard deviation RSD is calculated, the influence of signal fluctuation of an instrument is eliminated, and the NTO crystal defect degree can be quantitatively evaluated. The PBX molding powder is prepared by coating the NTO crystal by a supercritical method, and when pressure is released finally, the 30-mesh NTO crystal with larger crystal defect is easy to break and the particle size is reduced, so that the proportion of NTO particle grading in the molding powder can be changed. The method can screen NTO crystals with less defects, is suitable for PBX molding powder coated by a supercritical method, and can press qualified PBX drug columns.
Description
Technical Field
The invention belongs to the field of detection and research of physical and chemical properties of explosive and powder samples, and mainly relates to characterization and research of NTO crystal quality, in particular to evaluation research of defects of a 30-mesh NTO crystal coated by a supercritical method.
Background
3-nitro-1, 2, 4-triazole-5-ketone (NTO for short) is a high-energy low-sensitivity elementary explosive with excellent comprehensive performance, the appearance of the elementary explosive is white or light yellow crystal particles, the thermal stability is better, the melting point is more than or equal to 260 ℃ (decomposition), the DSC decomposition peak temperature is more than or equal to 270 ℃, and the elementary explosive has certain acidity (pKa = 3.67). The NTO crude product is prepared by nitrifying 1,2, 4-triazole-5-ketone (TO for short), and then the NTO crude product can be applied only by improving the purity and the crystal form through technologies such as recrystallization and the like.
Various mixed explosive formulations based on NTO have been studied abroad and find application in some weapon systems. The research on the formula in China starts late.
Currently, the formula of NTO-based explosives mainly comprises 3 types: fusion cast explosives, plastic bonded explosives (PBX) and compression molded explosives. Dozens of NTO-based explosive formulations have been developed in Fahrenheit, american, english, etc. (see tables 1,2, 3, 4).
TABLE 1 US and Switzerland NTO-based fusion cast explosive formulations
| Name (R) | NTO | TNT | Additive agent | Adhesive agent |
| TNTO | 50 | 50 | — | — |
| TNTO/D2 | 52 | 42 | — | 6(D2) |
| TNTO/OD2 | 52 | 42 | — | 6(OD2) |
| TNTO 0 | 38 | 40 | 16 (aluminum) | 6(D2) |
| TNTO Ⅰ | 42 | 34 | 19 (aluminum) | 5(D2) |
| TNTO Ⅲ | 42 | 30 | 19 (aluminum) | 9(D2) |
| AFX-645 | 48 | 32 | 12 (aluminum) | 8(WP-660) |
| GD-1 | 65 | 35 | — | — |
| GD-2 | 35 | 35 | 30(HMX) | — |
TABLE 2 NTO-based PBX formulations in France and USA
| Name(s) | NTO | RDX | HMX | AP | Aluminium | Adhesive agent |
| B2214 | 72 | — | 12 | — | — | 16(HTPB) |
| B2245 | 8 | 12 | — | 43 | 25 | 12(HTPB) |
| B3017 | 74 | — | — | — | — | 26 (energy-containing adhesive) |
| PBXW-121 | 63 | 10 | — | — | 15 | 12(HTPB) |
| PBXW-121 | 47 | 5 | — | 20 | 15 | 13(HTPB) |
| PBXW-121 | 22 | 20 | — | 20 | 26 | 12(PU) |
TABLE 3 England, switzerland, germany and Canada NTO-based PBX formulations
| Name (R) | NTO | HMX | Additive agent | Energetic plasticizer | Adhesive agent |
| CPX 412 | 50 | 30 | — | 10(K10) | 10(PolyNIMMO) |
| CPX 450 | 40 | 20 | 20 (aluminum) | 10(K10) | 10(PolyNIMMO) |
| CPX 458 | 30 | 30 | 20 (aluminum) | 10(K10) | 10(PolyNIMMO) |
| GD-3 | 72 | 12 | — | — | 16(HTPB) |
| GD-5 | 40 | 43 | — | 10(BDNPA/F) | 7(PGA) |
| HX 310 | 25 | 47 | 10(NG) | — | 18(HTPB) |
| CHN-037 | 76 | — | — | — | 24(GAP) |
TABLE 4 NTO-based compression molded explosive formulations
| Name (R) | NTO | HMX | BDNPA/F | Adhesive agent |
| GD-9 | 47.5 | 47.5 | 2.5 | 2.5(Cariflex1101) |
| GD-11 | 48 | 48 | — | 4(Cariflex1101) |
| GD-13 | 48 | 48 | — | 2/2(Hy Temp/DOA) |
| France 1 | 55.5 | 37 | — | 7/0.5 (Kelf/graphite) |
The conventional explosive charging method comprises the following steps: tamping, injection, press, screw, and plastic loading. The coating of the NTO crystal refers to coating NTO (or multiple main high-energy explosives containing NTO) by using an adhesive to prepare molding powder, and pressing and assembling to prepare the PBX explosive column.
In the late stage of world war II, with the development of polymer materials and the requirements of missiles and nuclear weapons, people begin to research the formation of pressable shaped powder explosives by using plastics as a binder and a desensitizer, properly adding a plasticizer and high-energy explosive cyclonite (RDX) which is difficult to form independently. The shaped powder explosive not only maintains the explosive property of high-energy explosive, but also utilizes the advantage that high polymer materials are easy to form and process. In the 60-70 s, many polymer materials with special properties appeared, which can be used as explosive binders, such as rubber, polyester, polyamide, polyether, resin, polyvinyl alcohol derivatives, fluorine-containing polymers, organic silicon polymers, thermoplastic polymers, thermosetting polymers and the like, and various polymer bonded explosives, also called polymer bonded explosives, abbreviated as PBX explosives, also appeared.
The PBX explosives are various at present and can be divided into molding powder (pressed) explosives, cast thermosetting explosives, plastic explosives, flexible explosives and low-density explosives according to physical states and molding processes. More than 200 formulas of molding powder pressed explosive are known so far and are widely applied. The explosive can be used as the charge of the projectile of various weapons and the warhead of guided missiles, such as anti-tambourine ammunition and empty weapons, and can also be used for the charge of the initiation device of nuclear weapons and special devices for space navigation development.
The molding powder pressed explosive is generally called molding powder and belongs to high explosive. The composition of the explosive comprises high explosive, high molecular adhesive and plasticizer, and some formulations are added with desensitizer. The high-energy explosive is the most important component in the PBX explosive in the largest proportion, and determines the energy level and the detonation performance of the PBX explosive. The NTO-based PBX explosives in tables 2 and 3 contain a large amount of high-energy explosives such as NTO, HMX, RDX, etc.
The high-molecular adhesive can be used for adhering, coating and blunting the explosive with high sensitivity, and then the mixed explosive can be made into products with good forming performance and excellent physical and chemical properties by using the good mechanical properties of the high-molecular polymer through a proper forming and processing method, and can also be made into various physical states and specific shapes so as to meet various use requirements. Because of the good physical and mechanical properties of the high polymer, the compressibility, processability and compressive strength of the mixed explosive bonded by the high polymer are greatly improved.
At present, most of molding powder is manufactured by a solution-water suspension method process, and then is molded by a press-fitting process according to product requirements. The shaped product may be machined and bonded into the desired shape. The solution-water suspension method has simple operation, short production period and easy mass production. In the production process, water is used as a dispersion medium and a heat transfer medium, so that the production safety can be ensured. If the temperature, the vacuum degree and the stirring speed are well controlled, the particles with smooth and compact appearance and quite uniform size can be obtained.
However, due to the strong solubility of NTO in water, part of NTO is lost when the PBX molding powder explosive containing NTO base is prepared by the solution-water suspension method, and the loss amount is difficult to control. In addition, the process generates a large amount of organic solvent and NTO wastewater, is not easy to recycle and pollutes the environment.
The supercritical fluid coating (SCF) technology has been developed rapidly in recent years, and the main products include pharmaceuticals, foods, fertilizers and the like, so that the bad smell of the drugs can be covered or the stability of the products can be improved, and the products can be conveniently applied and stored. The SCF coating technique has the characteristics of high diffusion coefficient of the gas phase and strong solvency of the liquid phase. The PBX explosive is prepared by coating NTO crystals by adopting the technology, and due to supercritical CO 2 Has high-efficiency mass transfer and low surface tension, and can ensure that the adhesive polymer is uniformly coated on NTO particles.
Mixing NTO with ethyl acetate solution as binder at a certain proportion to form suspension, placing in high-pressure kettle heated in water bath, introducing CO from bottom of the kettle 2 Stirring the suspension until the temperature and pressure in the kettle reach a stable supercritical state (T) C ＝31℃，P C =7.39 MPa), then the upper valve of the kettle is partially opened, and the lower part is continuously filled with CO 2 Regulating upper valve to maintain constant pressure in reactor, supercritical CO 2 In the extraction suspensionThe residual solvent in the explosive can be taken away by the ethyl acetate, and finally, the final product can be obtained by quick release. By using supercritical CO 2 Because no water participates in the coating of NTO, the problems of the solution-water suspension method can be thoroughly solved (NTO loss is avoided, a large amount of waste water can not be generated), the processes of stirring, coating, drying and the like are completed at one time, time is saved, the efficiency is high, the safety is high, and the requirement of large-scale production can be met.
By using supercritical CO 2 When the prepared NTO molding powder is coated, high strain is generated due to pressurization to 7.39MPa and final quick release pressure relief to reduce the atmospheric pressure, more NTO with smaller granularity is possibly generated, and the phenomenon is more generated in NTO crystals with larger granularity. The analysis reason is that a part of NTO crystal quality originally has larger defects (the crystal quality refers to the neatness degree of the arrangement of crystal micro-regions, and the existence of structural defects such as microporosities, microcracks, crystal dislocation, twin crystals and the like in the crystal can reduce the crystal quality), and under the high strain rate generated by rapid pressure relief, the NTO crystal is broken into a plurality of particles from the defects.
The granularity ratio of the explosive in the molding powder has strict requirements, so that the energy and the density of a mixed explosive product can be improved, and the content of a main explosive can be improved as much as possible. In order to ensure that explosive particles are arranged as tightly as possible, the main explosive of the shaped explosive in foreign countries almost adopts the particle grading technology, namely the solid explosive particles are matched in size appropriately, so that small particles can be filled in gaps among large particles, the particles can be arranged more tightly, and the requirement of improving the filling density of the product is met. In order to meet the requirement of particle grading, the produced NTO particle products are classified according to particle size intervals, NTO with the particle size of 30-60 meshes (250 mu m-600 mu m) belongs to the I class, and NTO with the particle size of 60-80 meshes (180 mu m-250 mu m) belongs to the II class. When the particle size fraction is adopted, the large particles account for 3/4 and the small particles account for 1/4.
When the large-particle NTO is crushed into small particles after being coated by a supercritical method, the original proportion of particle gradation can be changed, and the compression density and the compression strength are influenced. At present, after NTO crystals are coated by a supercritical method, the crushing number of large-particle NTO crystals is represented by visual inspection of the NTO debonding condition or detection of the acidity of an aqueous solution, and thus, the proper NTO crystals are determined.
In summary, the project group finds that when coating NTO by supercritical method, NTO crystal with good crystal quality should be selected, but the problems existed at present are:
(1) There is no method for rapidly evaluating the quality of NTO crystals, and qualified NTO crystals cannot be selected in advance;
(2) Because there is no accurate quantitative method, it is not good for improving the technology of NTO production, recrystallization, etc.
Disclosure of Invention
The invention adopts the following technical scheme:
the method for rapidly evaluating the defects of the 30-80-mesh NTO crystal for cladding by the supercritical method is characterized by comprising the following steps of:
(1) Setting working parameters of the micro-Raman spectrometer: 50 times microscope, test micro area 0.8 μm, laser wavelength 785nm, laser energy 15-25 mW, and scanning range 2000cm -1 ～200cm -1 Exposure time of 1 second, resolution of 1cm -1 The number of scanning times is 2;
(2) Repeatedly testing the fixed point of the monocrystalline silicon piece 24 times according to 520cm -1 Results of the test at characteristic peaks Experimental relative Standard deviation RSD was calculated Si ；
(3) Placing the dried NTO recrystallized product in a laboratory dryer for 6-8 hours, uniformly mixing, then randomly selecting 10 NTO particles as test samples, and randomly selecting 2-3 points for testing each NTO particle by 1104cm -1 Calculating the relative standard deviation RSD of all the test results of 10 particles NTO ；
(4) Calculation magnification α = RSD NTO ÷RSD Si (ii) a When alpha is less than or equal to 3, the NTO crystal is evaluated to have no obvious defect and is suitable for being coated by a supercritical method; when alpha is more than 3 and less than or equal to 6, the NTO crystal is evaluated to have slight defects and is suitable for being coated by a supercritical method; when alpha is more than 6, NTO crystal is evaluated to have obvious defects and is not suitable for coating by a supercritical method.
The method for rapidly evaluating the NTO crystal defects for coating by the supercritical method is characterized in that the test interval time is 1-2 minutes when the single crystal silicon wafer or single NTO particle is repeatedly detected by Raman spectroscopy.
The NTO crystal defect rapid evaluation method for the coating by the supercritical method is characterized in that the purity of the monocrystalline silicon wafer is more than or equal to 99.9999 percent;
the method for rapidly evaluating the defects of the NTO crystal with the size of 30-80 meshes for coating by the supercritical method is characterized in that the particle size range of the NTO crystal to be evaluated is 30-60 meshes.
The method for rapidly evaluating the defects of the NTO crystal coated by the supercritical method with the size of 30-80 meshes is characterized in that the particle size range of the NTO crystal to be tested is NTO with the size of 60-80 meshes.
The method of the invention has the following advantages:
(1) A method for rapidly evaluating the quality of 30-80-mesh NTO crystals is established, the NTO crystals with better quality can be screened in advance and coated by a supercritical method, and large-particle NTO crystals in the coated molding powder are not crushed obviously;
(2) The characterization method can accurately quantify, has comparable data, and can be used for improving NTO production, recrystallization and other processes.
Drawings
Fig. 1 is a raman spectrum of an NTO sample.
The present invention will be described in further detail with reference to the following drawings and examples.
Detailed Description
Example 1
The invention adopts the micro-Raman spectroscopy technology to evaluate the NTO crystal defects. The micro-Raman spectrum is widely applied to the field of material analysis, and the characteristic Raman shift and the intensity characteristic of the material are closely related to the molecular structure, the molecular arrangement and the crystal arrangement.
In the embodiment, a rapid evaluation method is established through research works such as selecting a proper test condition, eliminating the influence of signal fluctuation of an instrument, selecting a characteristic peak, determining a judgment basis and the like, and is specifically described below.
1. Setting the working parameters of the micro-Raman spectrometer and reducing the influence on the detection result
The detection principle of the Raman spectrum is as follows: the micro-nano defects of the NTO crystal can widen the Raman spectrum peak (the peak area is larger), and the randomness of the defect distribution can increase the detection result of different particles relative to the experimental standard deviation RSD.
The experiment adopts an InVia type laser confocal micro-Raman spectrometer of the British RENISHAW company, and in order to improve the accuracy of a detection result, the following instruments are paid attention to when setting instrument parameters: firstly, obtain stronger spectral signal as far as possible, secondly prevent NTO from being heated up by laser stimulation and burning the pollution camera lens. The raman spectrometer operating parameter settings are shown in table 5.
TABLE 5 Raman spectrometer parameter settings
In addition, the thermal stress in the NTO particles to be tested sent from the outside of the laboratory affects the detection result of the sample particles, so the NTO particles to be tested should be placed in a dryer in the laboratory for 6-8 hours, and the detection is carried out after the temperature of the particles is consistent with the temperature of the environment in the laboratory. Similarly, when the monocrystalline silicon wafer or a certain NTO particle is repeatedly tested, the time interval between every two times of collection is 1-2 minutes in order to avoid the influence of heat accumulation on the detection result.
2. Selection of characteristic spectrum peak in NTO Raman spectrogram
Selecting a characteristic peak principle: (1) the difference of the peak heights of different crystal planes is not shown due to the anisotropy of the crystal; (2) in all characteristic spectral peaks, the spectral peak intensity belongs to a strong peak; (3) the selected spectral peak has good separation degree with adjacent spectral peaks. Comprehensive comparison, select 1104cm -1 The peak is a characteristic spectrum peak in an NTO Raman spectrum. In addition, the purity of the NTO recrystallization product is more than 99 percent, the crystal quality has certain defects, and in order to obtain a detection signal more accurately, the full width at half maximum is selected for quantification, but the peak area is not selected for quantification.
3. Obtaining relative experiment standard deviation generated by instrument signal fluctuation
Single crystal silicon is a form of elemental silicon. When the molten elemental silicon solidifies, the silicon atoms are arranged in a diamond lattice as a plurality of crystal nuclei, and if these crystal nuclei grow crystal grains having the same crystal plane orientation, these crystal grains are combined in parallel to crystallize as single crystal silicon having a crystal structure of a substantially complete lattice structure. Single crystal silicon is the purest material in the world. Currently, single crystal silicon having a purity of 12 pieces and 9 (12N) pieces has been manufactured. The monocrystalline silicon has high purity and high crystal quality, and when the temperature of the monocrystalline silicon crystal is kept consistent in the detection process by the Raman method, the monocrystalline silicon is tested repeatedly, and the experimental relative standard deviation RSD is obtained by calculation Si The influence of signal fluctuation of the instrument on test data can be reflected. RSD when any sample is tested by the Raman spectrometer Si It is equivalent to "instrumental noise". The very clear characteristic peak of single-crystal silicon is 520cm -1 Because of high purity and high crystal quality of the sample, the method can select the half-height peak width and the peak area quantification, and the RSD Si The calculation results are consistent.
Repeatedly testing the fixed point of the monocrystalline silicon wafer, and reading 520cm -1 The peak area of the characteristic peak is 5.451, 5.422, 5.457, 5.452, 5.454, 5.458, 5.469, 5.441, 5.445, 5.457, 5.464, 5.456, 5.448, 5.468, 5.451, 5.445, 5.438, 5.455, 5.462, 5.465, 5.446, 5.465 and 5.461, and the RSD is calculated Si ＝0.20％(n＝24)。
4. Determining the judgment basis
Taking dry (30-60) mesh NTO recrystallization products prepared under three different conditions, marking as No. 1, no. 2 and No. 3, and testing the quality of the NTO crystal by using the Raman spectroscopy of the patent. The test interval for the repeated testing of a single crystal is 1 minute. Test results and experimental relative standard deviation RSD of 1#, 2#, 3# NTO recrystallized products NTO And the magnification α is shown in table 6.
TABLE 6 (30-60) mesh NTO recrystallization product Raman test results
As can be seen from table 6: the alpha of the 1# NTO recrystallization product is 6.5, which is in the range of alpha > 6; the alpha of the 2# NTO recrystallization product is 1.6 and is in the range of alpha less than or equal to 3; the alpha of the 3# NTO recrystallization product is 3.2, and is in the range of more than 3 and less than or equal to 6.
Then, taking 1-2 kg of each of the three NTO recrystallization products, accurately weighing the products respectively, and simulating and coating the products by a supercritical method (without adding an adhesive): adding the NTO recrystallized product into ethyl acetate, mixing to form a suspension, and placing the suspension into a high-pressure kettle heated in a water bath at the temperature of 50-60 ℃; introducing CO from the bottom of the kettle 2 Gas, stirring the suspension until the temperature and pressure in the kettle reach supercritical state (T) C ＝31.1℃、P C =7.39 MPa), then the upper valve of the kettle is partially opened, and the lower part is continuously filled with CO 2 Gas, adjusting an upper valve to keep the pressure in the kettle constant, and stopping introducing CO after 1 hour 2 And (5) completely opening a valve at the upper part of the kettle by gas to finish the simulated coating.
And (3) sieving the simulated coated NTO recrystallization product through a 60-mesh sieve, counting the NTO amount passing through the sieve, and calculating the passing rate by combining the mass before coating, wherein the closer the passing rate is to 0%, the more the NTO crystal is not crushed in the supercritical pressure relief stage. The statistical results of the passing rates of 1#, 2#, 3# -NTO recrystallization products are respectively 11%, 1%, and 5%.
Then, another three (30-60 mesh) NTO recrystallization products are respectively coated by a supercritical heat preservation method to prepare three PBX molding powders: mixing the NTO recrystallization product with a certain batch (60-80 meshes) of NTO recrystallization product according to the mass ratio of 3; preparing an adhesive by using fluororubber F2641 and polyvinyl acetate according to the mass ratio of 3; adding the mixed particle size NTO recrystallized product into a binder solution according to the mass ratio of the mixed particle size NTO recrystallized product to the binder of 90g 10g to form a suspension, and placing the suspension into a high-pressure kettle heated by a water bath, wherein the water bath heating temperature is 50-60 ℃; introducing CO from the bottom of the kettle 2 Gas, stirring the suspension until the temperature in the kettle is reached,The pressure reaches a supercritical state, and the supercritical state is T C ＝31.1℃、P C After that, the upper valve of the kettle is partially opened, and CO is continuously introduced into the lower part of the kettle 2 Gas, adjusting an upper valve to keep the pressure in the kettle constant, and stopping introducing CO after 1 hour 2 Completely opening a valve at the upper part of the kettle by gas to obtain PBX modeling coarse powder; and (2) keeping the temperature of the PBX explosive modeling coarse powder at 70 ℃ for 1.5 hours, then heating to 120 ℃ at the heating rate of 20 ℃/hour, keeping the temperature for 2.0 hours, then cooling to 70 ℃ at the cooling rate of 20 ℃/hour, keeping the temperature for 1.5 hours, then naturally cooling to room temperature, and stirring the PBX modeling coarse powder every 0.5 hour in the whole temperature treatment process to obtain the PBX modeling powder. The corresponding molding powder prepared by the recrystallization products of No. 1 NTO, no. 2 NTO and No. 3 NTO is respectively marked as No. 1 PBX molding powder, no. 2 PBX molding powder and No. 3 PBX molding powder. Visual inspection of 3 PBX molding powders was performed without debonded NTO particles.
NTO has strong acidity, and after being coated by the adhesive, the aqueous solution of the molding powder becomes neutral along with the improvement of the coating quality. 1#, 2#, 3# PBX modeling powder are respectively prepared into water solution with the concentration of 0.1mol/L, the pH value is 4.67, 7.1, 7.2 at 20 ℃, which indicates that the coating quality of the 1# PBX modeling powder is not high, and partial NTO is exposed. This is because the 1# NTO crystal generates more crystal fragments in the process of coating by supercritical heat preservation, the surface area of the entire NTO crystal is increased, the coating capability of the adhesive is limited, and the effect of complete coating is difficult to achieve. When explosive columns are manufactured by subsequent press mounting, the debonded NTO crystals are in rigid contact under higher pressure, and are easy to become heat accumulation points due to friction, so that the debonded NTO crystals have higher potential safety hazards.
And (3) integrating the NTO passing rate and the detection result of the acidity of the PBX molding powder solution, and determining the corresponding criterion of the Raman detection result as follows: the NTO recrystallized product (1 #) with alpha more than 6 has obvious defects and is not suitable for being coated by a supercritical method; the NTO recrystallization product (2 #) crystal with alpha less than or equal to 3 has no obvious defect and is suitable for being coated by a supercritical method; and the NTO recrystallization product (3 #) with alpha more than 3 and less than or equal to 6 has certain defects and is suitable for being coated by a supercritical method.
Example 2
Prepared under three different conditionsThe dried NTO recrystallization products with (60-80) meshes are marked as No. 4, no. 5 and No. 6, and the quality, the test result and the RSD of the NTO crystal are tested by the Raman spectroscopy method of the patent NTO And the magnification α are shown in table 7.
TABLE 7 (60-80) mesh NTO recrystallization product Raman test results
As can be seen from table 7: the alpha of the 4# NTO recrystallization product is 2.4, which is in the range of alpha less than or equal to 3; the alpha of the 5# NTO recrystallization product is 2.8 and is in the range of alpha less than or equal to 3; the alpha of 6# NTO recrystallization product is 3.8, which is in the range of alpha more than 3 and less than or equal to 6.
The three NTO products are simulated and coated by a supercritical method (without adding an adhesive), the simulated and coated NTO recrystallization products are sieved by a 80-mesh sieve, and the NTO passing rates are calculated to be 2%, 2% and 4% respectively. And judging according to the passing rate: the 4# product with alpha less than or equal to 3 has no obvious defect and is suitable for being coated by a supercritical method; the 5# product crystal with alpha less than or equal to 3 has no obvious defect and is suitable for being coated by a supercritical method; the alpha is more than 3 and less than or equal to 6, and NTO crystal has certain defects and is suitable for being coated by a supercritical method.
Comparing the detection results of tables 6 and 7, it is common that the crystal form defects of the NTO of (60-80) purpose are smaller than those of the NTO of (30-60) purpose, and the analysis reason may be that the larger the particle, the more the internal defects are. From the practical viewpoint, it is considered that the (30 to 60) objective NTO crystal needs to be further evaluated for crystal defects before being coated by the supercritical method.
Claims (5)
1. The method for rapidly evaluating the defects of the 30-80-mesh NTO crystal for coating by the supercritical method is characterized by comprising the following steps of:
step one, setting working parameters of a micro-Raman spectrometer: 50 times microscope, test micro-area0.8 μm, laser wavelength of 785nm, laser energy of 15-25 mW, and scanning range of 2000cm -1 ～200cm -1 Exposure time of 1 second, resolution of 1cm -1 The number of scanning times is 2;
step two, repeatedly testing the fixed point of the monocrystalline silicon piece for 24 times according to the 520cm -1 Results of the test at characteristic peaks Experimental relative Standard deviation RSD was calculated Si ；
Step three, placing the dried NTO recrystallized product in a laboratory dryer for 6-8 hours, mixing uniformly, then randomly selecting 10 NTO particles as test samples, and randomly selecting 2-3 points for testing 1104cm for each NTO particle -1 Calculating the relative standard deviation RSD of all test results of 10 particles NTO ；
Step four, calculating multiplying power alpha = RSD NTO ÷RSD Si (ii) a When alpha is less than or equal to 3, the NTO crystal is evaluated to have no obvious defect and is suitable for being coated by a supercritical method; when alpha is more than 3 and less than or equal to 6, the NTO crystal is evaluated to have slight defects and is suitable for being coated by a supercritical method; when alpha is more than 6, the NTO crystal is evaluated to have obvious defects and is not suitable for being coated by a supercritical method.
2. The method for rapidly evaluating 30-80 mesh NTO crystal defects for coating by the supercritical method according to claim 1, wherein when a single crystal silicon wafer or a single NTO particle is repeatedly inspected by Raman spectroscopy, the test interval time is 1-2 minutes.
3. The method for rapidly evaluating 30-80 mesh NTO crystal defects for coating by the supercritical method as claimed in claim 1, wherein the purity of the single crystal silicon wafer is not less than 99.9999%.
4. The method for rapidly evaluating the defect of the NTO crystal with the size of 30-80 meshes for coating by the supercritical method as claimed in claim 1, wherein the particle size range of the NTO crystal to be tested is 30-60 meshes.
5. The method for rapidly evaluating defects of 30-80-mesh NTO crystals for coating by the supercritical method according to claim 1, wherein the particle size range of the NTO crystals to be evaluated is 60-80-mesh NTO.
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