Method for selecting raw material for preparing 6n ultra-high purity niobium
Patent Information
- Application Number
- CN202611102443.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-23
- Publication Date
- 2026-09-25
AI Technical Summary
上述杂质的去除难度和工艺路径各不相同，笼统的总量限值无法有效指导原料的筛选与工艺的适配
[0022]与现有技术相比，本发明提供的制备6N超高纯铌所用原料的选取方法，包括以下步骤，S1：选取主相纯度≥99.995%、有效铌含量≥79%的4N5级Nb2O5作为原料；S2：将选取的原料粉碎、过筛、干燥；S3：采用ICP-MS检测金属杂质、GDMS检测气体杂质与放射性杂质、XRD检测晶型，确保杂质达标；S4：根据6N铌制备工艺匹配原料特性；S5：选取100-200g的原料按量产工艺还原，成品经GDMS检测纯度≥99.9999%即为原料合格；若纯度为99.9995%-99.9999%，需将金属杂质限值再降低0.5ppm重新筛选；S6：每批次原料按500kg分组，随机抽取5个样品检测，确保杂质含量偏差≤5%、且判定整批合格。本发明通过建立靶向杂质控制体系，聚焦6N铌敏感杂质，较传统方法杂质管控精度提升10倍；通过明确工艺与晶型的适配关系，反应效率提升40%。小试验证环节将原料指标与成品纯度直接关联，使6N铌制备达标率从现有方法的65%提升至99%。通过精准筛选降低原料浪费率至5%以下，较国外技术生产成本降低。
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-purity metal material preparation technology, and in particular to a method for selecting raw materials for preparing 6N ultra-high purity niobium. Background Technology
[0002] High-purity niobium (≥99.99%) has been widely used in the manufacture of radio frequency superconducting accelerator cavities since the late 1960s due to its high superconducting critical transition temperature (Tc≈9.2 K), high critical magnetic field, and low surface resistivity. With the rapid development of high-energy physics, semiconductors, and quantum information, the purity requirements for niobium materials have increased from the conventional 4N grade (99.99%) to above 6N grade (99.9999%). The content of trace impurities in 6N grade ultra-high purity niobium needs to be controlled to the level of one part per million or even one part per billion to meet the stringent purity requirements of high-end applications such as the quality factor (Q value) of radio frequency superconducting cavities, the signal integrity of semiconductor devices, and superconducting quantum interference devices (SQUIDs).
[0003] Currently, the industrial production of 6N-grade ultra-high purity niobium typically employs a multi-stage combined process of "chemical purification—metalothermic reduction—vacuum refining." Starting with niobium pentoxide (Nb₂O₅), high-melting-point impurities such as Ta and W are removed through extraction and crystallization. Crude niobium is then obtained through aluminothermic or carbothermic reduction. Subsequently, electron beam melting is used to remove general metallic impurities and low-melting-point impurities, combined with ultra-high vacuum annealing to reduce the content of interstitial solid solution impurities (C, N, O, H) to extremely low levels. Electron beam melting usually requires at least three cycles to obtain high-purity niobium ingots that meet the RRR>300 standard. Alternatively, ultra-high purity niobium can also be prepared using the iodination method (Van Arkel-de Boer method). Thermal decomposition of niobium iodide yields high-purity niobium products with Ta ≤30 ppm and O, C, N, and H ≤10 ppm each.
[0004] However, existing raw material selection methods have significant shortcomings when preparing 6N-grade ultra-high purity niobium. Firstly, they lack a synergistic design concept encompassing "baseline purity – critical impurities – process adaptation." Currently, the industry's quality control of niobium pentoxide raw material is still based on general total purity indicators (such as 99.9% or 99.99%), failing to establish graded and itemized control standards for sensitive impurities in the finished 6N niobium product (such as radioactive impurities like U and Th, interstitial elements like O / N, and metallic impurities like Fe / Si). Studies have shown that alpha particles generated by the decay of radioactive impurities such as U and Th can trigger single-event effects in semiconductor devices, interfering with signal integrity; interstitial elements such as O and N easily form brittle compounds with the niobium matrix (such as NbO and NbN), which not only degrade the cold working performance of the material but also significantly reduce the superconducting critical transition temperature (each 1 at.% increase in interstitial oxygen can decrease Tc by approximately 0.93 K); metallic impurities such as Fe and Si can introduce local magnetic moments or scattering centers, reducing the superconducting bandgap and critical current density of niobium. The removal difficulty and process path of the above-mentioned impurities vary, and a general total limit cannot effectively guide the selection of raw materials and the adaptation of processes.
[0005] Secondly, the lack of small-scale testing verification leads to frequent instances of "qualified indicators but substandard finished products." The existing evaluation system relies excessively on the nominal purity of chemical elemental analysis, but the accuracy of chemical elemental analysis for high-purity niobium often cannot fully correspond to comprehensive quality indicators such as the residual resistivity ratio (RRR value). Trace impurities in raw materials may undergo complex physicochemical changes (such as segregation, volatilization, and secondary contamination) during subsequent reduction and vacuum refining processes, and some impurities are difficult to completely remove during the purification process. Due to the lack of an effective small-scale evaluation mechanism to verify the purification behavior of raw materials under actual process routes, the predicament of qualified raw materials but substandard performance of the finished 6N niobium frequently occurs in mass production, resulting in a raw material utilization rate of less than 70% and a waste rate exceeding 30%.
[0006] In summary, the existing technology lacks a precise and systematic method for screening and evaluating raw materials for 6N-grade ultra-high purity niobium, making it difficult to achieve predictable and controllable stable mass production from raw material quality to finished product performance. Summary of the Invention
[0007] In order to solve the technical problems existing in the above-mentioned technology, it is necessary to provide a method for selecting raw materials for preparing 6N ultra-high purity niobium.
[0008] A method for selecting raw materials for preparing 6N ultra-high purity niobium includes the following steps:
[0009] Step S1: Select 4N5 grade Nb2O5 with a main phase purity ≥99.995% and an effective niobium content ≥79% as raw material;
[0010] Step S2: Crush, sieve, and dry the selected raw materials;
[0011] Step S3: Use ICP-MS to detect metallic impurities, GDMS to detect gaseous and radioactive impurities, and XRD to detect crystal form to ensure that impurities meet the standards;
[0012] Step S4: Match raw material characteristics according to the 6N niobium preparation process;
[0013] Step S5: Select 100-200g of raw material and reduce it according to the mass production process. If the purity of the finished product is ≥99.9999% by GDMS testing, the raw material is qualified. If the purity is 99.9995%-99.9999%, the limit of metal impurities needs to be reduced by 0.5ppm and re-screened.
[0014] Step S6: Each batch of raw materials is divided into groups of 500kg, and 5 samples are randomly selected for testing to ensure that the impurity content deviation is ≤5% and the whole batch is deemed qualified.
[0015] Preferably, in step S3, the metallic impurities Fe≤3ppm, Si≤3ppm, and Ta≤2ppm.
[0016] Preferably, the total amount of metal impurities is ≤20ppm.
[0017] Preferably, in step S3, the gaseous impurities and radioactive impurities are U≤0.1ppm, Th≤0.08ppm, O≤5ppm, N≤3ppm, and C≤2ppm.
[0018] Preferably, in step S2, the raw material needs to be pulverized to 50-80μm and large particles are removed by passing it through a 200-mesh sieve.
[0019] Preferably, in step S2, the sieved raw material needs to be dried in a vacuum drying oven to reduce the adsorbed water content to ≤0.1%.
[0020] Preferably, vacuum drying requires drying at 80°C and 5Pa for 2 hours.
[0021] Preferably, in step S1, the particle size distribution deviation of the selected raw material is ≤10%.
[0022] Compared with the prior art, the method for selecting raw materials for preparing 6N ultra-high purity niobium provided by the present invention includes the following steps: S1: Select 4N5 grade Nb2O5 with a main phase purity ≥99.995% and an effective niobium content ≥79% as raw material; S2: Crush, sieve, and dry the selected raw material; S3: Use ICP-MS to detect metal impurities, GDMS to detect gaseous and radioactive impurities, and XRD to detect crystal form to ensure that impurities meet the standards; S4: Match the characteristics of the raw material according to the 6N niobium preparation process; S5: Select 100-200g of raw material and reduce it according to the mass production process. The finished product is considered qualified if the purity is ≥99.9999% after GDMS testing; if the purity is 99.9995%-99.9999%, the metal impurity limit needs to be reduced by 0.5ppm and re-screened; S6: Group each batch of raw material into 500kg groups, randomly select 5 samples for testing, ensure that the impurity content deviation is ≤5%, and determine that the whole batch is qualified. This invention establishes a targeted impurity control system, focusing on sensitive impurities in 6N niobium, achieving a 10-fold improvement in impurity control precision compared to traditional methods. By clarifying the compatibility between the process and crystal form, reaction efficiency is increased by 40%. The small-scale experimental verification directly links raw material indicators to finished product purity, raising the 6N niobium preparation compliance rate from 65% with existing methods to 99%. Precise screening reduces raw material waste to below 5%, lowering production costs compared to foreign technologies. Detailed Implementation
[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0024] This invention provides a method for selecting raw materials used in the preparation of 6N ultra-high purity niobium, the specific method being as follows:
[0025] Raw material baseline determination
[0026] Priority should be given to using 4N5 grade Nb2O5 purified by distillation, with a main phase purity of not less than 99.995%, an effective niobium content of not less than 79%, and a particle size distribution deviation of ≤10%. The high purity baseline is set to reduce the introduction of background impurities and alleviate the separation burden of subsequent purification processes from the source.
[0027] Pretreatment process
[0028] The raw materials were crushed to a particle size of 50–80 μm using an air jet mill, and coarse particles were removed by sieving through a 200-mesh standard sieve. Subsequently, the materials were dried in a vacuum drying oven at 80°C and 5 Pa for 2 hours to control the adsorbed water content to ≤0.1%, in order to avoid the formation of oxygen-containing impurities by reacting with the reducing agent during the subsequent reduction process.
[0029] Impurity and Crystal Form Detection
[0030] Metal impurities: ICP-MS was used for determination, with a focus on controlling Fe, Si and Ta. The individual limits were Fe≤3ppm, Si≤3ppm and Ta≤2ppm, respectively, and the total metal impurity content was ≤20ppm.
[0031] Gases and radioactive impurities: GDMS is used for detection, and the requirements are U≤0.1ppm, Th≤0.08ppm, O≤5ppm, N≤3ppm, and C≤2ppm.
[0032] Crystal form confirmation: XRD scanning at 2θ = 20 to 80° was performed, and the matching degree with the γ-Nb2O5 standard card (00-037-1492) must be ≥98% to confirm it as the target crystal phase.
[0033] Process adaptation requirements
[0034] For hydrogen reduction processes, γ-Nb2O5 crystal form must be selected, as its high specific surface activity can effectively shorten the reduction cycle; for electron beam melting processes, the raw materials need to be pressed into dense blanks and the porosity needs to be controlled to ≤0.05% in order to reduce splashing losses caused by gas release during the melting process.
[0035] Small batch verification
[0036] Take 100-200g of qualified raw materials and conduct a hydrogen reduction test according to the mass production process (850℃, hydrogen purity ≥99.999%, hold for 5h). The reduction product is tested by GDMS. If the purity is ≥99.9999%, the batch of raw materials is considered qualified; if the purity falls within the range of 99.9995% to 99.9999%, the limits for Fe and Si need to be tightened by 0.5ppm and the raw materials need to be re-screened.
[0037] Batch Sampling and Uniformity Control
[0038] Each batch of raw materials is divided into groups of 500 kg, and 5 samples are randomly selected for full testing. The relative deviation of each impurity content must be controlled within ≤5% to ensure consistent quality within the batch and avoid the impact of raw material fluctuations on the stability of the final product performance.
[0039] Example 1
[0040] 1. Raw materials: Select 4N5 grade Nb2O5, with main phase purity not less than 99.995%, effective niobium content not less than 79%, and particle size distribution deviation ≤10%;
[0041] 2. Pretreatment: Crush the raw material to 60-80μm and sieve it through a 200-mesh standard sieve. Dry it in a vacuum drying oven at 80℃ and 5Pa for 2 hours.
[0042] 3. Detection results: U=0.07ppm, Th=0.06ppm, O=4.2ppm, Fe=2.8ppm, Si=2.5ppm, XRD matching degree 98.5%;
[0043] 4. Small-scale test: Take 150g of qualified raw materials, and after hydrogen reduction, the purity of the finished product is 99.99993%, which is considered qualified;
[0044] 5. Batch selection: Three batches of raw materials were sampled and tested. The impurity deviation was ≤4%, and the whole batch was qualified.
[0045] Example 2
[0046] 1. Raw materials: Select 4N5 grade Nb2O5, with main phase purity not less than 99.995%, effective niobium content not less than 79%, and particle size distribution deviation ≤10%;
[0047] 2. Pretreatment: Crush the raw material to 60-80μm and sieve it through a 200-mesh standard sieve. Dry it in a vacuum drying oven at 80℃ and 5Pa for 2 hours.
[0048] 3. Detection results: U=0.06ppm, Th=0.06ppm, O=4.1ppm, Fe=2.8ppm, Si=2.5ppm, XRD matching degree 98.6%;
[0049] 4. Small-scale test: Take 100g of qualified raw materials, and after hydrogen reduction, the purity of the finished product is 99.99993%, which is considered qualified;
[0050] 5. Batch selection: Three batches of raw materials were sampled and tested. The impurity deviation was ≤4%, and the whole batch was qualified.
[0051] Example 3
[0052] 1. Raw materials: Select 4N5 grade Nb2O5, with main phase purity not less than 99.995%, effective niobium content not less than 79%, and particle size distribution deviation ≤10%;
[0053] 2. Pretreatment: Crush the raw material to 60-80μm and sieve it through a 200-mesh standard sieve. Dry it in a vacuum drying oven at 80℃ and 5Pa for 2 hours.
[0054] 3. Detection results: U=0.07ppm, Th=0.07ppm, O=4.2ppm, Fe=2.7ppm, Si=2.4ppm, XRD matching degree 98.5%;
[0055] 4. Small-scale test: Take 200g of qualified raw materials, and after hydrogen reduction, the purity of the finished product is 99.99993%, which is considered qualified;
[0056] 5. Batch selection: Three batches of raw materials were sampled and tested. The impurity deviation was ≤4%, and the whole batch was qualified.
[0057] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.
Claims
1. A method for selecting raw materials for preparing 6N ultra-high purity niobium, characterized in that: Includes the following steps, Step S1: Select 4N5 grade Nb2O5 with a main phase purity ≥99.995% and an effective niobium content ≥79% as raw material; Step S2: Crush, sieve, and dry the selected raw materials; Step S3: Use ICP-MS to detect metallic impurities, GDMS to detect gaseous and radioactive impurities, and XRD to detect crystal form to ensure that impurities meet the standards; Step S4: Match raw material characteristics according to the 6N niobium preparation process; Step S5: Select 100-200g of raw material and reduce it according to the mass production process. If the purity of the finished product is ≥99.9999% by GDMS testing, the raw material is qualified. If the purity is 99.9995%-99.9999%, the limit of metal impurities needs to be reduced by 0.5ppm and re-screened. Step S6: Each batch of raw materials is divided into groups of 500kg, and 5 samples are randomly selected for testing to ensure that the impurity content deviation is ≤5% and the whole batch is deemed qualified.
2. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 1, characterized in that: In step S3, the metallic impurities are Fe≤3ppm, Si≤3ppm, and Ta≤2ppm.
3. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 2, characterized in that: Total metallic impurities ≤20ppm.
4. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 2, characterized in that: In step S3, the gaseous impurities and radioactive impurities are U≤0.1ppm, Th≤0.08ppm, O≤5ppm, N≤3ppm, and C≤2ppm.
5. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 1, characterized in that: In step S2, the raw material needs to be crushed to 50-80μm and large particles are removed by passing it through a 200-mesh sieve.
6. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 5, characterized in that: In step S2, the sieved raw material needs to be dried in a vacuum drying oven to reduce the adsorbed water content to ≤0.1%.
7. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 6, characterized in that: Vacuum drying requires drying at 80℃ and 5Pa for 2 hours.
8. The method for selecting raw materials for preparing 6N ultra-high purity niobium according to claim 1, characterized in that: In step S1, the particle size distribution deviation of the selected raw material is ≤10%.