Method for determining ash content of high purity graphite by using ceramic capsule

Abstract

The present application relates to high-purity graphite ash determination technical field, disclose a kind of method for determining high-purity graphite ash using ceramic square case, comprising the following steps: ceramic square case specification screening, ceramic square case grading washing, drying and pre-sintering, sample burning, cooling control, blank test, temperature and humidity correction, square case life management and wear correction and ash calculation.The detection result obtained by the present application is benchmarked with the result of national graphite detection center, realizes the detection of high-purity graphite using ceramic square case, and good precision and repeatability are obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-purity graphite ash content determination, in particular to a method for determining the ash content of high-purity graphite by using a ceramic canister. BACKGROUND

[0002] In recent years, high-purity graphite has been widely used in many high-tech and precision industrial fields, such as: 1. In the high-temperature heat treatment process such as chemical vapor deposition, high-purity graphite heaters can quickly and uniformly heat wafers and ensure that the semiconductor materials on the wafers maintain consistent performance during the heating process; 2. In the process of semiconductor epitaxial growth, high-purity graphite discs used as epitaxial pedestals provide a high-temperature stable support platform for wafer substrates, allowing the substrate surface to grow a high-quality epitaxial layer; 3. Plasma etching is a key step in forming fine patterns on wafers. High-purity graphite is used as an electrode material for plasma etching equipment due to its excellent corrosion resistance and high-temperature resistance, which can withstand the high-energy impact and chemical reaction of plasma, ensuring the stability and accuracy of the etching process; 4. In processes such as ion implantation, chemical vapor deposition, and physical vapor deposition that require high-temperature and high-vacuum environments, high-purity graphite is often used as a reaction container or lining material to protect the equipment from chemical reactions and prevent contamination of the wafer; Semiconductor equipment generates a large amount of heat during operation, and overheating can affect the performance and lifespan of the equipment. The high thermal conductivity of high-purity graphite makes it an important material in thermal management systems. By making high-purity graphite into a heat sink or heat exchanger, heat can be quickly removed from critical areas, protecting sensitive electronic components and improving the overall efficiency of the system.

[0003] The semiconductor industry requires high-purity graphite with a purity of ≤5ppm, and the purity difference between parallel samples during actual production should not exceed 1ppm.

[0004] Therefore, it is of great practical significance to provide a method for determining the ash content of high-purity graphite by using a ceramic canister. SUMMARY

[0005] In view of the above, the present application provides a method for determining the ash content of high-purity graphite by using a ceramic canister, which aims to solve at least one of the problems in the background art.

[0006] The present application provides a method for determining the ash content of high-purity graphite by using a ceramic canister, comprising the following steps:

[0007] Step one: ceramic ark specification screening, selecting 80x50x20mm or 110x50x20mm full-glazed ceramic arks, the full-glazed ceramic arks have an alumina content of ≥95%, a glaze layer thickness of 50-80μm, a surface roughness Ra≤0.2μm, a porosity of ≤0.5%, an appearance crack length of ≤0.5mm, a notch depth of ≤0.2mm, and a spot area of ≤1 ;

[0008] Step two: ceramic ark grading and cleaning, the screened ceramic arks are subjected to multi-stage cleaning, including: pure water pre-cleaning, nitric acid solution soaking, distilled water rinsing, ultrasonic cleaning, and ultrapure water final cleaning;

[0009] Step three: drying and pre-burning, the cleaned arks are dried in two stages using a vacuum drying oven, the first stage drying is performed at 60℃ for 1h, the second stage drying is performed at 110℃ for 1h, and the cooling rate is 5℃ / min; the pre-burning includes a first pre-burning stage and a second pre-burning stage, the temperature of the first pre-burning stage is 300℃, the heating rate is 10℃ / min, and the holding time is 30min; the temperature of the second pre-burning stage is 850℃, the heating rate is 5℃ / min, and the holding time is 12h, the mass deviation of the pre-burned ark is ≤0.00003g for three consecutive times, which is considered as constant weight, and the constant weight ark is obtained after the pre-burning is completed;

[0010] Step four: sample burning, 15.0000g of high-purity graphite sample sieved through a 0.28mm sieve and dried is placed in the constant weight ark, and placed in a muffle furnace, 50mL / min of high-purity oxygen is introduced, and the pre-burning process according to step three is performed to heat to 850℃ and hold for 20min, and the burning process is kept with the furnace door opened at a distance of 25mm;

[0011] Step five: cooling control, after the sample burning is completed, the ark is transferred to a constant temperature and humidity cooling cabin for cooling for 5min, and then transferred to a vacuum dryer for cooling for 120-125min to room temperature; the parameters of the constant temperature and humidity cooling cabin are: temperature 23±0.2℃, humidity 50±3%, and air flow speed 0.5m / s; the vacuum degree of the vacuum dryer is ≤ ;

[0012] Step six: blank test, three groups of blank arks are set for each furnace, and the sample arks are burned, cooled, and weighed synchronously, and the furnace blank average value and batch blank average value are calculated;

[0013] Step seven: temperature and humidity correction, the temperature and humidity during the cooling process are collected in real time through a sensor, and the mass deviation is calculated;

[0014] Step eight: Ark life management, monitor the ark quality change rate, glaze peeling area, size deformation, adhesion, weight loss stability, determine whether the ark is invalid;

[0015] Step nine: wear correction and ash calculation; according to the change of the mass of the blank ark before and after burning, the actual ash value of the detection sample is calculated after the weight loss correction of the ark.

[0016] Preferably, the ceramic ark in step one is obtained by isostatic pressing process, the forming pressure is greater than or equal to 20MPa, and the thermal expansion coefficient is less than or equal to .

[0017] Preferably, the screening in step one adopts a 2000 million pixel industrial CCD imaging system combined with AI recognition technology.

[0018] Preferably, the muffle furnace in step four adopts silicon molybdenum rod heating, the temperature control precision is ±1℃, and the temperature difference of 9 points in the furnace is less than or equal to 3℃.

[0019] Preferably, the blank test furnace blank average value in step six is the arithmetic average value of the mass change of 3 groups of blank arks in the same furnace, and the batch blank average value is the arithmetic average value of the mass change of 3 groups of blank arks in the first furnace of the day.

[0020] Preferably, the ark life monitoring in step eight adopts a laser diameter measuring instrument to detect size deformation, a tensile meter to test adhesion, and an industrial CCD imaging system to monitor the glaze state.

[0021] Preferably, the sample weighing in step nine adopts an analytical balance with a 0.01mg sensing amount and a 220g range, which needs to be preheated for 30min before weighing, and the environmental temperature and humidity is controlled at 23±0.5℃ and 50±5%.

[0022] Preferably, the standard for determining whether the ark is invalid is that the single burning change is greater than 0.0001g, the glaze peeling area is greater than 5 mm, the length-width-height deviation is greater than 0.3mm, the adhesion is greater than 5N, and the continuous three times of burning weight loss is greater than 0.00008g.

[0023] Preferably, the high-purity graphite is high-performance graphite for semiconductors, nuclear industry or aerospace.

[0024] Compared with the prior art, the beneficial effects of the present application are:

[0025] The application provides the method for determining ash content of the ultra-high purity graphite ceramic ware, and the method comprises the following steps: selecting, cleaning, drying and pre-burning the same specification ceramic square canister, repeatedly sintering, cooling and weighing, determining that the cooling time of the ceramic square canister in the air is 5-10 min, the cooling time in the dryer is 1.5-2 h, and the sintering service life of the square canister is 200-250 h. Meanwhile, the ceramic square canister and the platinum crucible are used to detect the ash content of the same sample, two parallel samples are arranged for each kind of ware, one blank ware is arranged for each furnace, the real-time temperature and humidity are monitored in the whole experimental process, the relationship between the temperature, humidity and the quality of the ceramic square canister is determined, the difference between the temperature and humidity ware correction and the blank correction is compared, the correction method is determined, the detection results of the experiment are compared with the results of the national graphite detection center, and finally the determination method of the ceramic square canister for detecting high-purity graphite is realized, and good precision and repeatability are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0026] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the application. Furthermore, like reference numerals are intended to represent the same components throughout the various drawings. In the drawings:

[0027] Figure 1 The application provides the method for determining ash content of the ultra-high purity graphite ceramic ware, and the method comprises the following steps: selecting, cleaning, drying and pre-burning the same specification ceramic square canister, repeatedly sintering, cooling and weighing, determining that the cooling time of the ceramic square canister in the air is 5-10 min, the cooling time in the dryer is 1.5-2 h, and the sintering service life of the square canister is 200-250 h. Meanwhile, the ceramic square canister and the platinum crucible are used to detect the ash content of the same sample, two parallel samples are arranged for each kind of ware, one blank ware is arranged for each furnace, the real-time temperature and humidity are monitored in the whole experimental process, the relationship between the temperature, humidity and the quality of the ceramic square canister is determined, the difference between the temperature and humidity ware correction and the blank correction is compared, the correction method is determined, the detection results of the experiment are compared with the results of the national graphite detection center, and finally the determination method of the ceramic square canister for detecting high-purity graphite is realized, and good precision and repeatability are obtained. DETAILED DESCRIPTION

[0028] The various illustrative embodiments of the application will now be described in detail in various examples, which should be considered to be illustrative of the application and not limiting. It should be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application.

[0029] Further, with respect to numerical ranges, it is to be understood that every intermediate value and sub-range between the upper and lower limits of the range is specifically contemplated herein. Any smaller range or sub-range within a larger range is also specifically contemplated. The upper and lower limits of these smaller ranges and sub-ranges can independently be included or excluded in the range.

[0030] Unless otherwise indicated, all technical and scientific terms have the same meaning as those one of ordinary skill in the art of the disclosure would understand. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. All documents mentioned herein are incorporated by reference to disclose and describe in further detail the methods and / or materials associated with the documents. In the case of conflict between any document incorporated by reference and the present disclosure, the present disclosure controls.

[0031] Many modifications and variations of the present disclosure described in the detailed description of the disclosure can be made by those of skill in the art without departing from the scope or spirit of the disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure. The specification and examples of the disclosure are illustrative only.

[0032] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more other elements can be added or otherwise included.

[0033] The present disclosure provides a method for determining the ash content of high-purity graphite using a ceramic capsule, comprising the following steps:

[0034] Step one: ceramic capsule specification screening, select 80x50x20mm or 110x50x20mm full-glazed ceramic capsules, the full-glazed ceramic capsules have an alumina content of ≥95%, a glaze layer thickness of 50-80μm, a surface roughness Ra≤0.2μm, a porosity of ≤0.5%, an appearance crack length of ≤0.5mm, a notch depth of ≤0.2mm, a spot area of ≤1 ;

[0035] Step two: ceramic capsule grading and cleaning, the screened ceramic capsules are subjected to multi-stage cleaning, which includes: pure water pre-cleaning, nitric acid solution soaking, distilled water rinsing, ultrasonic cleaning, and ultrapure water final cleaning;

[0036] Step three: drying and pre-burning, the dried capsules are dried in two stages using a vacuum drying oven, the first stage drying is performed at 60℃ for 1h, the second stage drying is performed at 110℃ for 1h, and the cooling rate is 5℃ / min; the pre-burning includes a first pre-burning stage and a second pre-burning stage, the temperature of the first pre-burning stage is 300℃, the heating rate is 10℃ / min, and the holding time is 30min; the temperature of the second pre-burning stage is 850℃, the heating rate is 5℃ / min, and the holding time is 12h, the mass deviation of the pre-burned capsules is ≤0.00003g for three consecutive times, which is considered as constant weight, and the constant weight capsules are obtained after the pre-burning is completed;

[0037] Step four: sample burning, 15.0000g of high-purity graphite sample which is sieved through 0.28mm sieve and dried is put into the constant weight capsule, and is placed in a muffle furnace, 50mL / min of high-purity oxygen is introduced, and after the pre-burning process as described in step three, the temperature is increased to 850℃ and is kept for 20min, and the burning process keeps the furnace door open at a distance of 25mm;

[0038] Step five: cooling control, after the sample burning is completed, the capsule is transferred to a constant temperature and humidity cooling cabin for cooling for 5min, and then is transferred into a vacuum dryer for cooling for 120-125min to room temperature; the parameters of the constant temperature and humidity cooling cabin are: temperature 23±0.2℃, humidity 50±3%, air flow speed 0.5m / s; the vacuum degree of the vacuum dryer is ≤ ;

[0039] Step six: blank test, 3 groups of blank capsules are set for each furnace, and are burned, cooled and weighed synchronously with the sample capsules, and the average value of the furnace blank and the average value of the batch blank are calculated;

[0040] Step seven: temperature and humidity correction, the temperature and humidity during the cooling process are collected in real time through a sensor, and the mass deviation is calculated;

[0041] Step eight: capsule service life management, the mass change rate, glaze peeling area, size deformation, adhesion force and weight loss stability of the capsule are monitored to determine whether the capsule is invalid;

[0042] Step nine: wear correction and ash content calculation; according to the mass change of the blank capsules before and after burning, the actual ash content value of the detected sample is calculated after the capsule weight loss correction.

[0043] Step one: ceramic capsule specification screening, 80x50x20mm or 110x50x20mm full-glazed ceramic capsules are selected, the full-glazed ceramic capsule has an alumina content of ≥95%, a glaze layer thickness of 50-80μm, a surface roughness Ra≤0.2μm, a porosity≤0.5%, an appearance crack length≤0.5mm, a notch depth≤0.2mm and a spot area≤1 ;

[0044] The application first screens the ceramic capsule specifications, selects ceramic capsules with low adsorption, low elution and high stability from the source, and avoids that the impurities (such as glaze layer peeling and pollutants adsorbed by pores) of the capsule are included in the graphite ash content, so that the detection result is high.

[0045] Meanwhile, the composition of the ceramic capsule is limited, and the high alumina content (≥95%): the alumina ceramic is resistant to high temperature (no softening at 850℃ burning), and has strong chemical stability, and will not react with the graphite combustion products (CO2, H2O, etc.) to form new substances, so that the ash content is not affected. ) or oxygen reaction, avoid introducing additional impurities; precise glaze parameters (thickness 50-80 pm, Ra≤0.2 pm): dense and smooth glaze, reduce the adsorption of graphite samples / ash on pores (coarse surface is easy to leave ash, leading to weighing deviation), while avoiding the peeling of over-thick glaze in burning; low porosity (≤0.5%) + strict appearance requirements (crack ≤0.5 mm, etc.): low porosity can reduce the adsorption of moisture / organic matter in the canister (if not completely removed during pre-burning, it will be misjudged as ash); appearance defect control can avoid the cracking of the canister during burning, preventing sample leakage or the mixing of external impurities.

[0046] Step two: multi-stage cleaning of the ceramic canister, the multi-stage cleaning of the screened ceramic canister comprises: pure water pre-cleaning, nitric acid solution soaking, distilled water rinsing, ultrasonic cleaning and ultrapure water final cleaning;

[0047] The present application performs multi-stage cleaning on the ceramic canister, completely removes the pollutants (such as production residual dust, grease, metal ions) on the surface and in the pores of the canister, and reduces the interference of “canister background impurities” on ash determination (if the cleaning is not thorough, the impurities will be counted as graphite ash after burning). Specifically: pure water pre-washing: quickly flush away the surface dust to avoid the reaction of impurities with acid to generate insoluble substances during subsequent nitric acid soaking; nitric acid soaking: dissolve metal ions (such as Fe, Cu, etc.) and organic matter by using the strong oxidizing property of acid; ultrasonic cleaning: strip the small impurities remaining in the pores (which cannot be reached by conventional rinsing) through high-frequency vibration; ultrapure water final washing: remove residual nitric acid and salt (avoid the formation of salt crystals after drying, which affects the constant weight measurement);

[0048] Preferably, the nitric acid used in the nitric acid soaking of the present application is 5% nitric acid solution, the soaking time is 10 minutes, the ultrasonic cleaning is performed at 300 W, 40 kHz, and the water temperature is 50°C for 18 minutes, and the parameters of other cleaning are not specially limited and can be limited in number and time according to the actual situation.

[0049] Step three: drying and pre-burning, the drying adopts a vacuum drying oven to dry the cleaned canister in two stages, the first stage drying adopts 60°C temperature drying for 1h, the second stage drying adopts 110°C temperature drying for 1h, and the cooling rate is 5°C / min; the pre-burning includes a first pre-burning stage and a second pre-burning stage, the temperature of the first pre-burning stage is 300°C, the heating rate is 10°C / min, and the holding time is 30min; the temperature of the second pre-burning stage is 850°C, the heating rate is 5°C / min, and the holding time is 12h, the mass deviation of the constant weight canister is ≤0.00003g after pre-burning for three times, and the pre-burning is ended;

[0050] In this way, the moisture adsorbed by the ark after cleaning is removed by drying (if the moisture remains, the weight loss will be misjudged as a decrease in ash content during pre-burning / calcination, resulting in a lower result); pre-burning: remove residual organic matter (such as oil stains that are not dry after cleaning) and trace impurities in the glaze layer, and at the same time, ensure stable ark mass (constant weight) through "continuous 3 times weighing deviation ≤0.00003g" to avoid the influence of ark weight loss on ash content calculation during subsequent sample calcination.

[0051] The benefits of vacuum drying + segmented temperature control method are: vacuum environment accelerates water evaporation, 60℃ removes surface water, 110℃ removes pore-bound water, avoids water damage to the glaze layer caused by direct high-temperature drying, and 5℃ / min cooling rate prevents ark cracking due to large temperature difference;

[0052] The benefits of two-stage pre-burning + constant weight determination are: 300℃ low-temperature pre-burning: slowly removes organic matter (avoids damage to the glaze layer caused by intense combustion of organic matter at high temperature); 850℃ high-temperature pre-burning: completely removes deep-layer impurities in the glaze layer, and is consistent with the subsequent sample calcination temperature (ensures that the ark has stable mass at the same temperature without additional weight loss); constant weight standard (deviation ≤0.00003g): meets the "microgram level" measurement accuracy of high-purity graphite ash (analytical balance sensitivity 0.01mg), and eliminates the error caused by the mass fluctuation of the ark itself.

[0053] Step four: sample calcination, place 15.0000g of high-purity graphite sample sieved through 0.28mm sieve and dried into the constant weight ark, place it in the muffle furnace, introduce 50mL / min of high-purity oxygen, heat to 850℃ according to the pre-burning process described in step three, and keep it at this temperature for 20min, and the calcination process keeps the furnace door open at a distance of 25mm;

[0054] The present application completely oxidizes carbon elements in the graphite sample to escape, leaving only non-combustible ash (such as , , etc.), preparing for subsequent ash weighing (ash mass / sample mass=ash content).

[0055] Step five: cooling control, after the sample calcination is completed, transfer the ark to the constant temperature and humidity cooling cabin for cooling for 5min, and then transfer it to the vacuum dryer for cooling for 120~125min to room temperature; the parameters of the constant temperature and humidity cooling cabin are: temperature 23±0.2℃, humidity 50±3%, air flow speed 0.5m / s; the vacuum degree of the vacuum dryer is ≤ ;

[0056] After the burning is finished, cooling is carried out, the temperature and humidity and the environment of the cooling process are controlled in the application, and the "moisture absorption" or "impurity pollution" in the cooling is avoided to cause the ash quality deviation (if the ark absorbs moisture during the cooling, the "ash + moisture" quality measured is too high; if the air dust is contacted, additional impurities are introduced). The constant temperature and humidity chamber is first rapidly cooled to be close to room temperature, and the stable temperature and humidity avoid the ark surface from being dewed (dewing can cause moisture absorption); the low air flow speed prevents the air dust from being blown in; the vacuum environment is isolated from the air, and the moisture absorption and dust pollution are completely avoided; the slow cooling to room temperature can prevent the ark from being cracked due to too large temperature difference, and at the same time, the ash temperature is consistent with the balance environment (the temperature difference can cause the buoyancy error of the balance measurement).

[0057] Step six: blank test, 3 groups of blank arks are set for each furnace, and the arks are synchronously burned, cooled and weighed with the sample arks, and the furnace blank average value and the batch blank average value are calculated;

[0058] The synchronous burning of the "blank ark" (without sample) is used for quantifying the "mass change of the ark in the burning-cooling process" (such as slight weight loss / weight gain), and the weighing result of the sample ash is corrected (to avoid misjudging the mass change of the ark as the sample ash change).

[0059] Step seven: temperature and humidity correction, the temperature and humidity in the cooling process are collected in real time through the sensor, and the mass deviation is calculated;

[0060] The slight fluctuation of the temperature and humidity in the cooling process (such as the parameter drift of the constant temperature and humidity chamber and the humidity rise caused by the poor sealing of the vacuum dryer) is monitored, and the influence of the fluctuation on the mass of the "ark + ash" is quantified (the change of the temperature and humidity can cause the change of the air density, and the buoyancy error of the balance measurement is caused; the humidity rise can cause the moisture absorption and weight gain of the ash).

[0061] In the application, the real-time monitoring and dynamic correction are used: the limitation of the "fixed temperature and humidity parameters" (such as the inaccuracy of the parameters caused by the equipment aging) is avoided, the deviation is calculated through the real-time data of the sensor (such as 0.00002g of weight gain of the ash per 5% of humidity rise), the weighing result is further corrected, and the precision is improved; the 0.00001g level deviation caused by the temperature and humidity accounts for 1%-10% of the ash mass, and the error can be greatly reduced after the correction.

[0062] Step eight: ark life management, the mass change rate, the glaze peeling area, the size deformation, the adhesion, the weight loss stability of the ark are monitored, and whether the ark is invalid is judged;

[0063] The application tracks the use state of the ceramic capsule, and timely eliminates the "performance degradation" capsule (such as glaze peeling, size deformation), to avoid the introduction of uncontrollable errors (such as glaze peeling being counted into ash, deformation leading to sample leakage) by the failed capsule. At the same time, the application adopts multi-dimensional monitoring to cover key failure points, specifically including:

[0064] Mass change rate: if the mass change of the capsule after single burning exceeds the threshold (such as > 0.00005g), it indicates that the glaze layer has been damaged and is easy to adsorb impurities;

[0065] Glaze peeling / size deformation: peeling will cause ash adhesion, and deformation will affect the sample holding volume (if the sample overflows, the mass reduction will cause the ash result to be low);

[0066] Adhesion: if the adhesion between graphite and glaze increases, the ash will remain on the surface of the capsule after burning, causing the weighing value to be low;

[0067] Avoiding the influence of "overuse" capsule on the test results, while optimizing the capsule replacement cycle through monitoring to reduce costs.

[0068] Step nine: wear correction and ash calculation; according to the mass change of the blank capsule before and after burning, the actual ash value of the test sample is calculated after capsule weight loss correction.

[0069] In the application, the ash calculation correction formula is as follows:

[0070]

[0071] The deviation value obtained by "blank test" and "temperature and humidity correction" is substituted into the calculation, and the mass change of the capsule itself (such as the weight loss of the blank capsule after burning 0.00002g, which needs to be added to the ash mass of the sample) is deducted from the "weighed ash mass" to obtain the "true ash mass" of the graphite sample.

[0072] The application covers "capsule weight loss / weight gain" (blank correction) and "temperature and humidity buoyancy / hydration" (temperature and humidity correction) at the same time, eliminating all quantifiable system errors; and the calculation formula defined in the application is fully adapted to the needs of micro-ash determination of high-purity graphite, ensuring that the results are true and reliable.

[0073] In the application, the ceramic capsule in step one is preferably obtained by isostatic pressing process, with a forming pressure ≥ 20MPa and a thermal expansion coefficient ≤ .

[0074] In the application, the screening in step one preferably uses a 2000 million pixel industrial CCD imaging system combined with AI recognition technology.

[0075] In the present application, the muffle furnace in step four preferably uses silicon molybdenum rod heating, the temperature control precision is ±1℃, and the temperature difference of 9 points in the furnace is ≤3℃.

[0076] In the present application, the average value of the blank test furnace in step six is preferably the arithmetic average of the mass changes of 3 groups of blank canisters in the same furnace, and the average value of the batch blank is the arithmetic average of the mass changes of 3 groups of blank canisters in the first furnace of the day.

[0077] In the present application, the canister life monitoring in step eight preferably uses a laser diameter gauge to detect size deformation, a tensile meter to test adhesion force, and an industrial CCD imaging system to monitor glaze state.

[0078] In the present application, the sample weighing in step nine preferably uses an analytical balance with a 0.01mg sensing weight and a 220g range, which needs to be preheated for 30min before weighing, and the environmental temperature and humidity are controlled at 23±0.5℃ and 50±5%.

[0079] In the present application, the criteria for determining whether the canister is invalid are preferably: single burning change >0.0001g, glaze peeling area >5mm², length-width-height deviation >0.3mm, adhesion force >5N, and continuous 3 times of burning weight loss >0.00008g.

[0080] In the present application, the high-purity graphite is preferably high-performance graphite for semiconductors, nuclear industry or aerospace.

[0081] Example 1

[0082] The specific test parameters and test results used in Example 1 are shown in Table 1

[0083] Table 1 Specific test parameters and test results of Example 1

[0084]

[0085] Example 2

[0086] The specific test parameters and test results used in Example 2 are shown in Table 2

[0087] Table 2 Specific test parameters and test results of Example 2

[0088]

[0089] Example 3

[0090] The specific test parameters and test results used in Example 3 are shown in Table 3

[0091] Table 3 Specific test parameters and test results of Example 3

[0092]

[0093] Example 4

[0094] The specific test parameters and test results used in Example 4 are shown in Table 4

[0095] Table 4 Specific test parameters and test results table of Example 4

[0096]

[0097] As shown in Examples 1, 2, and 3, the temperature and humidity were controlled simultaneously to test the effect of temperature and humidity on the ash content detection data. Each example was tested three times, and two parallel samples were taken for each test to verify the test results. Finally, through data analysis, the temperature and humidity control range of the ceramic capsule for determining the ash content of high-purity graphite was determined, thereby obtaining a stable detection method. When the humidity is > 50%, the ash content detection result is greater than the actual value, when the humidity is < 50%, the ash content detection result is less than the actual value, in the actual detection process, the humidity needs to be controlled at 50±2%, the ash content detection value can be stable within the range of actual value±0.3, which meets the purity requirements of the semiconductor industry for graphite; when the humidity is > 23℃, the ash content detection result is less than the actual value, when the temperature is < 23℃, the ash content detection result is greater than the actual value, in the actual detection process, the temperature needs to be controlled at 23±3℃, the ash content detection value can be stable within the range of actual value±0.3, which meets the purity requirements of the semiconductor industry for graphite. Based on this, the last verification test detection results are shown in Example 4 of Table 4, which is the best example detection data.

[0098] Effect test

[0099] The experimental precision and actual repeatability test data are shown in Table 5: In order to ensure the accuracy of the empty capsule and ash content data, the same graphite sample was tested six times, and two parallel samples were taken for each test. Finally, by comprehensively averaging the ash content and the reference results, it can be found that the fitting degree between the two data is ideal.

[0100] Table 5 Experimental precision and actual repeatability test data table

[0101]

[0102] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.

Claims

1. A method for determining the ash content of high-purity graphite using a ceramic boat, characterized in that, Includes the following steps: Step 1: Ceramic Ark Specification Screening. Select fully glazed ceramic arks of 80×50×20mm or 110×50×20mm. The fully glazed ceramic arks must have an alumina content ≥95%, a glaze thickness of 50-80μm, a surface roughness Ra ≤0.2μm, a porosity ≤0.5%, an external crack length ≤0.5mm, a notch depth ≤0.2mm, and a spot area ≤1. ; Step 2: Ceramic Ark Grading and Cleaning. The selected ceramic arks undergo multi-stage cleaning, which includes: pre-cleaning with pure water, soaking in nitric acid solution, rinsing with distilled water, ultrasonic cleaning, and final cleaning with ultrapure water. Step 3: Drying and Pre-firing. The drying process is carried out in two stages using a vacuum drying oven. The first stage of drying is carried out at 60℃ for 1 hour, and the second stage of drying is carried out at 110℃ for 1 hour, with a cooling rate of 5℃ / min. The pre-firing process includes a first pre-firing stage and a second pre-firing stage. The temperature of the first pre-firing stage is 300℃, the heating rate is 10℃ / min, and the holding time is 30 minutes. The temperature of the second pre-firing stage is 850℃, the heating rate is 5℃ / min, and the holding time is 12 hours. After pre-firing, the mass deviation is considered to be ≤0.00003g after three consecutive weighings, which is considered to be constant weight. After the pre-firing is completed, a constant weight boat is obtained. Step 4: Sample calcination. Place 15.0000g of high-purity graphite sample that has passed through a 0.28mm sieve and been dried into the constant weight boat, place it in a muffle furnace, introduce high-purity oxygen at 50mL / min, and calcinate it by raising the temperature to 850℃ and holding it at that temperature for 20min according to the pre-calcination process described in Step 3. During the calcination process, keep the furnace door open at a distance of 25mm. Step 5: Cooling Control. After the sample is ignited, the ark is transferred to a constant temperature and humidity cooling chamber for 5 minutes, and then transferred to a vacuum dryer for 120-125 minutes to room temperature. The parameters of the constant temperature and humidity cooling chamber are: temperature 23±0.2℃, humidity 50±3%, airflow velocity 0.5m / s; the vacuum degree of the vacuum dryer is ≤ ; Step 6: Blank test. Set up 3 blank boats for each furnace, and burn, cool and weigh them simultaneously with the sample boats. Calculate the average blank value of the furnace and the average blank value of the batch. Step 7: Temperature and humidity calibration. The temperature and humidity during the cooling process are collected in real time by sensors, and the quality deviation is calculated. Step 8: Ark life management, monitor the Ark mass change rate, glaze peeling area, dimensional deformation, adhesion force, and weightlessness stability to determine whether the Ark has failed; Step Nine: Wear Correction and Ash Content Calculation; Based on the change in mass of the blank ark before and after burning, perform ark weight loss correction and calculate the actual ash content of the test sample.

2. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, In step one, the ceramic boat is obtained using an isostatic pressing process with a molding pressure ≥20MPa and a thermal expansion coefficient ≤ .

3. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, In step one, the screening process uses a 20-megapixel industrial CCD imaging system combined with AI recognition technology.

4. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, In step four, the muffle furnace uses silicon molybdenum rods for heating, with a temperature control accuracy of ±1℃ and a temperature difference of ≤3℃ between 9 temperature measurement points inside the furnace.

5. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, In step six, the average blank value of the furnace test is the arithmetic mean of the mass changes of the three blank arks in the same furnace, and the average blank value of the batch is the arithmetic mean of the mass changes of the three blank arks in the first furnace of the day.

6. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, In step eight, the life monitoring of the ark uses a laser diameter gauge to detect dimensional deformation, a tensile tester to test adhesion force, and an industrial CCD imaging system to monitor the glaze condition.

7. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, In step nine, the sample is weighed using an analytical balance with a sensitivity of 0.01 mg and a range of 220 g. The balance must be preheated for 30 minutes before weighing, and the ambient temperature and humidity must be controlled at 23±0.5℃ and 50±5%, respectively.

8. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, The criteria for determining whether the ark has failed are: single burning change > 0.0001g, glaze peeling area > 5 Length, width and height deviation > 0.3mm, adhesion force > 5N, weight loss after three consecutive burns > 0.00008g.

9. The method for determining the ash content of high-purity graphite using a ceramic boat according to claim 1, characterized in that, The high-purity graphite is high-performance graphite used in semiconductors, nuclear industry, or aerospace.

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