CN113683417A - Preparation method of nanocrystalline single-phase nickel niobate ceramic block - Google Patents
Preparation method of nanocrystalline single-phase nickel niobate ceramic block Download PDFInfo
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims abstract description 178
- 229910052759 nickel Inorganic materials 0.000 title claims abstract description 77
- 239000000919 ceramic Substances 0.000 title claims abstract description 33
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000005245 sintering Methods 0.000 claims abstract description 76
- 239000000843 powder Substances 0.000 claims abstract description 64
- 238000000034 method Methods 0.000 claims abstract description 22
- 239000012071 phase Substances 0.000 claims abstract description 21
- 239000011812 mixed powder Substances 0.000 claims abstract description 19
- 238000002156 mixing Methods 0.000 claims abstract description 17
- 239000011858 nanopowder Substances 0.000 claims abstract description 17
- 238000010532 solid phase synthesis reaction Methods 0.000 claims abstract description 12
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 11
- 238000001035 drying Methods 0.000 claims abstract description 9
- 238000000227 grinding Methods 0.000 claims abstract description 9
- 238000005303 weighing Methods 0.000 claims abstract description 6
- 238000007873 sieving Methods 0.000 claims abstract description 5
- 239000002159 nanocrystal Substances 0.000 claims abstract description 4
- 239000002994 raw material Substances 0.000 claims description 26
- 239000010955 niobium Substances 0.000 claims description 23
- 238000000498 ball milling Methods 0.000 claims description 14
- 239000011259 mixed solution Substances 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 6
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 6
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- 229910019804 NbCl5 Inorganic materials 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 238000002390 rotary evaporation Methods 0.000 claims description 4
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 claims description 3
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 claims description 3
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(II) nitrate Inorganic materials [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 claims description 3
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 abstract description 38
- 239000013078 crystal Substances 0.000 abstract description 15
- 229910052582 BN Inorganic materials 0.000 abstract description 9
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 abstract description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 8
- 229910052799 carbon Inorganic materials 0.000 abstract description 4
- 229910002804 graphite Inorganic materials 0.000 abstract description 4
- 239000010439 graphite Substances 0.000 abstract description 4
- 238000000137 annealing Methods 0.000 abstract description 3
- 238000005262 decarbonization Methods 0.000 abstract description 3
- 229910010293 ceramic material Inorganic materials 0.000 description 13
- 229910005805 NiNb Inorganic materials 0.000 description 8
- 238000000576 coating method Methods 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 235000019441 ethanol Nutrition 0.000 description 3
- 229910000484 niobium oxide Inorganic materials 0.000 description 3
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000013590 bulk material Substances 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 229910000480 nickel oxide Inorganic materials 0.000 description 2
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000001699 photocatalysis Effects 0.000 description 2
- 238000007750 plasma spraying Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000000930 thermomechanical effect Effects 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012776 electronic material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000012720 thermal barrier coating Substances 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention discloses a preparation method of a single-phase nickel niobate ceramic block with nano crystal grains, which is used for preparing nickel niobate nano powder by a solid phase method or a hydrothermal method; weighing nickel niobate nano powder and a sintering aid, mixing and grinding, and drying and sieving to obtain mixed powder C; performing pressure-maintaining sintering on the mixed powder C to obtain a single-phase nickel niobate block with purity of more than 99%, density of more than 99.5%, porosity of less than 0.5% and nanocrystalline grains; according to the invention, the sintering aid can promote the combination degree of powder during final sintering, so that the material can form crystal grains at a lower temperature, BN (boron nitride) is sprayed on the inner surface of the mold, carbon in the graphite mold is prevented from permeating into the material to cause pollution, and meanwhile, the annealing and decarbonization process after sintering is avoided, so that air holes and cracks are prevented from being introduced in the process to reduce the density of the material.
Description
Technical Field
The invention belongs to the technical field of ceramic material preparation, and particularly relates to a preparation method of a single-phase nickel niobate ceramic block with nano-crystalline grains.
Background
Microwave dielectric ceramics refer to ceramic materials which are used as dielectric materials in microwave frequency band circuits and can complete one or more functions. Microwave dielectric ceramics, as a new electronic material, are used as resonators, filters, dielectric substrates, dielectric antennas, dielectric guided wave circuits, etc. in modern communications, and are widely used in many fields of microwave technology, such as mobile phones, car phones, cordless phones, television satellite receivers, satellite broadcasting, radars, radio remote controls, etc.
Nickel niobate ceramic materials are generally studied and prepared as microwave ceramics due to their excellent electromagnetic properties. The conventional nickel niobate magnetocomposite material is prepared by a high-temperature solid phase method, but the nickel niobate ceramic prepared by the method has the defects of large crystal grains, more pores and cracks, low density of block materials and the like, thereby causing the problem of insufficient comprehensive mechanical properties of the materials.
Disclosure of Invention
The invention aims to provide a preparation method of a single-phase nickel niobate ceramic block with nano crystal grains so as to improve the comprehensive mechanical property of a nickel niobate ceramic material.
The invention adopts the following technical scheme: a preparation method of a single-phase nickel niobate ceramic block with nano-crystalline grains comprises the following steps:
preparing nickel niobate nano powder by a solid phase method or a hydrothermal method;
weighing nickel niobate nano powder and a sintering aid, mixing and grinding, and drying and sieving to obtain mixed powder C;
performing pressure-maintaining sintering on the mixed powder C, wherein the sintering temperature is 400-600 ℃, the heat preservation time is 10-180 min, and the sintering pressure is 200-300 MPa, so that a single-phase nickel niobate block which has the purity of more than 99%, the density of more than 99.5%, the porosity of less than 0.5% and nano-crystalline grains is obtained; wherein, the inner surface of the sintering grinding tool which is subjected to pressure-maintaining sintering is subjected to BN spraying treatment.
Further, the mass fraction of the sintering aid is 0.5-5%.
Further, the sintering aid is at least one of PVA, CMC and EPS.
Further, the preparation of the nickel niobate nano powder by using the solid phase method comprises the following steps:
sintered Ni (OH)2Obtaining NiO powder, wherein the sintering temperature is 400 ℃, and the sintering time is 3 h;
NiO powder and Nb2O5Ball-milling and mixing the powder to obtain mixed powder A; wherein NiO powder and Nb2O5The molar ratio of the powder is 1: 1;
and sintering the mixed powder A at 800 ℃, preserving heat for 1h, and cooling to obtain the nickel niobate nano powder.
Further, during ball milling and mixing, the rotating speed of the ball mill is 280r/min, and the ball milling time is 8 h.
Further, after ball milling and mixing, the method also comprises the following steps:
and (3) carrying out rotary evaporation drying on the mixed powder A at the rotating speed of 100r/h for 1 h.
Further, the preparation of the nickel niobate nano powder by a hydrothermal method comprises the following steps:
adding a first raw material and a second raw material into alcohol to obtain a mixed solution; wherein the first raw material is NiCl2、Ni(NO3)2、NiSO4The second raw material is NbCl5And Nb (NO)3)5At least one of nickel element in the first raw material and niobium element in the second raw material, wherein the molar ratio of the nickel element in the first raw material to the niobium element in the second raw material is 1:1, 3:2 or 2: 1;
heating and stirring the mixed solution, keeping the temperature at 135-220 ℃ for 5-8 h, and performing complete reaction to obtain powder in the mixed solution;
and preserving the heat of the powder to obtain the nano-grade nickel niobate powder.
The invention has the beneficial effects that: according to the invention, the sintering aid can promote the combination degree of powder during final sintering, so that the material can form crystal grains at a lower temperature, BN (boron nitride) is sprayed on the inner surface of the mold, carbon in the graphite mold is prevented from permeating into the material to cause pollution, and meanwhile, the annealing and decarbonization process after sintering is avoided, so that air holes and cracks are prevented from being introduced in the process to reduce the density of the material.
Drawings
FIG. 1 shows NiNb prepared in example 1 of the present invention2O6A real object diagram of (1);
FIG. 2 shows NiNb prepared in example 1 of the present invention2O6Comparing the XRD diffraction pattern with a standard card;
FIG. 3 shows NiNb prepared in example 1 of the present invention2O6A micro-topography of;
FIG. 4 shows NiNb prepared in example 1 of the present invention2O6Graph of thermal conductivity of bulk ceramic material as a function of temperature;
FIG. 5 is a graph of fracture toughness for different nickel niobate bulk ceramics prepared in accordance with the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
As for the problem of insufficient mechanical properties of the current nickel niobate ceramic material, analysis shows that the problem is caused by the difficulty in controlling the sintering process of the material in the traditional high-temperature sintering process. Usually, researchers estimate the final sintering temperature based on the melting point of the material, and then sinter the material to obtain a bulk material.
In the preparation process of the nickel niobate material, temperature, time and pressure all have great influence on the final appearance and performance of the material, so that the currently prepared bulk nickel niobate ceramic has difficult excellent mechanical properties. Furthermore, it is not possible to directly produce single-phase high-purity nickel niobate (Ni) using niobium oxide and nickel oxide as raw materials2Nb2O7、Ni3Nb2O8Or Ni4Nb2O9) Ceramic material (powder or block).
In the research process of the invention, the nickel niobate powder raw material at nanometer level is used, and the excessive growth of crystal grains can be effectively inhibited through the short-time sintering at ultralow temperature, and the crystal grains with nanometer size are obtained, so that the bulk nickel niobate ceramic has extremely high compactness, purity and excellent mechanical properties. Meanwhile, the phonon scattering strength of the material can be improved by utilizing the nano-sized crystal grains, so that the thermal conductivity of the nickel niobate ceramic is reduced, and the nickel niobate ceramic can be used as a high-temperature heat-insulation protective coating due to excellent comprehensive thermal-mechanical properties.
Aiming at the problems of low purity, more pores and cracks, low density and insufficient thermo-mechanical properties of the currently prepared nickel niobate ceramic material, the invention discloses a preparation method of a single-phase nickel niobate ceramic block with nano crystal grains, which comprises the following steps:
preparing nickel niobate nano powder by a solid phase method or a hydrothermal method; weighing nickel niobate nano powder and a sintering aid, mixing and grinding, and drying and sieving to obtain mixed powder C; performing pressure-maintaining sintering on the mixed powder C, wherein the sintering temperature is 400-600 ℃, the heat preservation time is 10-180 min, and the sintering pressure is 200-300 MPa, so that a single-phase nickel niobate block which has the purity of more than 99%, the density of more than 99.5%, the porosity of less than 0.5% and nano-crystalline grains is obtained; wherein, the inner surface of the sintering grinding tool which is subjected to pressure-maintaining sintering is subjected to BN spraying treatment.
According to the invention, the sintering aid can promote the combination degree of powder during final sintering, so that the material can form crystal grains at a lower temperature, BN (boron nitride) is sprayed on the inner surface of the mold, carbon in the graphite mold is prevented from permeating into the material to cause pollution, and meanwhile, the annealing and decarbonization process after sintering is avoided, so that air holes and cracks are prevented from being introduced in the process to reduce the density of the material.
In this embodiment, the mass fraction of the sintering aid is 0.5 to 5% (i.e., the mass fraction of the mixed powder C is 95 to 99.5%). The specific sintering aid is at least one of PVA, CMC, EPS and other low-melting-point organic aids, and the sintering aid can effectively promote the bonding degree between powders during final sintering, so that the material can form grains at lower temperature. A certain amount of organic sintering aid is added firstly to improve the density and the crystallinity of a final product, and low-melting-point organic matters as the sintering aid can automatically volatilize in the process of pressure sintering so as to effectively reduce the influence on the final purity of the material.
In one embodiment, the preparation of the nickel niobate nano powder by using the solid phase method comprises the following steps:
sintered Ni (OH)2Obtaining NiO powder, wherein the sintering temperature is 400 ℃, and the sintering time is 3 h; NiO powder and Nb2O5Ball-milling and mixing the powder to obtain mixed powder A; wherein NiO powder and Nb2O5The molar ratio of the powder is 1: 1; and sintering the mixed powder A at 800 ℃, preserving heat for 1h, and cooling to obtain the nickel niobate nano powder.
During ball milling and mixing, the rotating speed of the ball mill is 280r/min, and the ball milling time is 8 h. In addition, the ball-milling mixing device also comprises: and (3) carrying out rotary evaporation drying on the mixed powder A at the rotating speed of 100r/h for 1 h.
In the process of preparing the nickel niobate powder by the solid phase method, Ni (OH) is decomposed by heating2The method obtains the highly activated NiO powder, improves the reactivity of the nickel oxide and the niobium oxide, reduces the reaction temperature between the two kinds of powder and reduces the reaction time, thereby obtaining the nickel niobate powder through extremely low temperature and short heat preservation time during sintering, ensuring that the prepared powder has small enough grain diameter, and being beneficial to reducing the final sintering temperature and shortening the time.
In another embodiment of the present invention, the hydrothermal method for preparing nickel niobate nano-powder comprises:
adding a first raw material and a second raw material into alcohol to obtain a mixed solution; wherein the first raw material is NiCl2、Ni(NO3)2、NiSO4The second raw material is NbCl5And Nb (NO)3)5At least one of nickel element in the first raw material and niobium element in the second raw material, wherein the ratio of nickel element in the first raw material to niobium element in the second raw material is 1:1, 3:2 or 2: 1; heating and stirring the mixed solution, keeping the temperature at 135-220 ℃ for 5-8 h, and performing complete reaction to obtain powder in the mixed solution; and preserving the heat of the powder to obtain the nano-grade nickel niobate powder.
Preparation of nanoscale by hydrothermal methodThe nickel niobate powder, nanometer level nickel niobate powder, first guarantees the purity of the final block, and the smaller the particle size, the lower the temperature and time required for final sintering, thereby inhibiting the growth of the crystal grains and obtaining the crystal grains with nanometer size and high purity block. While Ni could not be obtained by ordinary high-temperature sintering2Nb2O7、Ni3Nb2O8And Ni4Nb2O9The high-purity material perfectly solves the problem by a hydrothermal method.
The micron nickel niobate powder prepared by the solid phase method can be directly used for preparing coating materials by atmospheric plasma spraying. The powder can be refined to a nanometer level (less than 100 nanometers) by high-energy grinding, the particle size of the powder prepared by a hydrothermal method is less than 100 nanometers, and the powder can be used for photocatalysis and the like. And the single-phase high-purity nickel niobate bulk ceramic of the nanocrystalline can be obtained after short-time, low-temperature and high-pressure sintering after the sintering aid is added.
The purity of the nickel niobate ceramic prepared by the invention is more than 99%, the compactness is more than 99.5%, the grain size is less than 100 nanometers, the mechanical properties (hardness, fracture toughness and Young modulus) of the material can be improved by utilizing grain refinement, the phonon scattering strength of the material is enhanced, and the thermal conductivity of the material is reduced, so that the nickel niobate ceramic can be used as structural ceramic at high temperature.
The density of the single-phase nickel niobate ceramic with nano-crystalline grains prepared by the method is more than 99.2%, the problem that the compact nickel niobate ceramic cannot be prepared by common high-temperature sintering is solved, the material has many pores and is not compact under the condition of low temperature in common sintering, and the material is melted due to overhigh temperature, so that the compact nickel niobate ceramic block cannot be obtained.
The nickel source used in the solid phase sintering is prepared by reacting Ni (OH) at medium temperature2Sintering and decomposing to obtain high-activity NiO powder, thereby effectively reducing the temperature and time required for preparing the nickel niobate powder by high-temperature sintering and finally obtaining the fine nickel niobate powder. The prepared ceramic material has nano-level crystal grains (less than 100 nanometers), and the mechanical property of the material is greatly improved, so that the material can be used as a structural material at high temperature, such as a thermal barrier coating and the environmentBarrier coatings and wear resistant coatings, and the like.
In the invention, the solid-phase method and the hydrothermal method are used for preparing nickel niobate powder comprising NiNb2O6、Ni2Nb2O7、Ni3Nb2O8Or Ni4Nb2O9. Solves the problem that the traditional high-temperature solid phase method can not prepare high-purity Ni all the time2Nb2O7、Ni3Nb2O8Or Ni4Nb2O9The problem of materials. Meanwhile, the prepared powder with the grain diameter less than 100 nanograms is used as a raw material of microwave ceramics and photocatalytic materials, and micron-sized powder prepared by high-temperature sintering can be directly used for preparing coatings by atmospheric plasma spraying.
The powder used in the final sintering of the invention is in a nanometer level, so that the final sintering temperature is effectively reduced, and the sintering time of less than 600 ℃ and less than 20 minutes can effectively inhibit the growth of crystal grains, thereby obtaining nanometer-level crystal grains, and finally playing the roles of improving the material compactness and optimizing the thermo-mechanical property. The nanometer powder is used as a raw material, the low-melting-point organic matter is used as a sintering aid, so that the sintering temperature and the heat preservation time are effectively reduced, and the BN is sprayed on the inner surface of the mold, so that carbon in the graphite mold is effectively prevented from permeating into the sample, and the high purity of the final product is ensured.
Example 1:
reacting Ni (OH)2Sintering the powder at 400 ℃ for 3 hours, and mixing the NiO powder with niobium oxide (Nb)2O5) Weighing the powder according to a molar ratio of 1:1, adding absolute ethyl alcohol, performing ball milling mixing (the rotating speed is 280r/min and the time is 8 hours), and performing rotary evaporation drying (the rotating speed is 100r/min and the time is 1 hour) to obtain mixed powder A. The powder A was sintered at 800 ℃ for 1 hour and then cooled to obtain a powder B.
Weighing PVA powder and powder B according to 1% of the mass fraction, grinding in a grinder (1000r/min, 10h), and sieving with 1000 mesh sieve to obtain powder C; 3g of powder C is weighed and placed in a die, and then discharge plasma sintering (480 ℃, and the temperature is kept for 10 minutes) is carried out to prepare the ceramic material with the density of more than 99.5 percent. FIG. 1 shows the NiNb prepared2O6As shown in the figure, the prepared material has a flat surface and no obvious cracks or pores, the measured compactness of the material is 99.9%, and the porosity is only 0.1%. FIG. 2 shows the NiNb prepared2O6The XRD diffraction result of the block ceramic material is compared with that of a standard PDF card 32-0694, and the result shows that the tested XRD diffraction peaks correspond to the peaks of the standard card one by one without the existence of other second-phase impurity peaks, so that the prepared material is proved to have extremely high purity. FIG. 3 shows the NiNb prepared2O6The observation of the condition of crystal grains on the surface of the block ceramic material shows that the crystal grain sizes are all in the nanometer level, and the crystal grain sizes are between 10 and 300 nanometers, thereby proving that the polycrystalline NiNb with the nanometer size is prepared2O6A bulk ceramic. FIG. 4 shows NiNb2O6The thermal conductivity of the bulk ceramic material changes along with the temperature, the thermal conductivity continuously decreases along with the increase of the temperature, the minimum value is about 1.2W/m/K, and the thermal conductivity is obviously lower than that of other materials at present, and the thermal insulation protective effect at high temperature can be provided. FIG. 5 shows the fracture toughness of different prepared nickel niobate bulk ceramics, and the values are 2.1-2.7 MPa.m1/2In between, the higher fracture toughness comes from the nano-scale grain size, which is beneficial for increasing grain boundary density deflection cracks.
Example 2:
according to the chemical formula Ni2Nb2O7、Ni3Nb2O8And Ni4Nb2O9The ratio of nickel to niobium is 1:1, 3:2 and 2:1, and NiCl is dropped into the alcohol solution2With NbCl5Solution, separately preparing Ni2Nb2O7、Ni3Nb2O8And Ni4Nb2O9The nanometer powder is dropped into a beaker in the process of being placed on a magnetic needle stirring heating table, the heating temperature is 135 ℃, 180 ℃ and 220 ℃, the heat preservation time is 5 hours, 7.5 hours and 8 hours, the stirring speed is 50, 35 and 60r/min, after the reaction is finished, deionized water is used for washing the obtained powder to keep the PH value of the powder to be 7, then the powder is placed in an alumina crucible and sintered at the high temperature of 500 ℃, 600 ℃ and 560 ℃, and the sintering temperature is 500 ℃, 600 ℃ and 560 ℃, the sintering is carried outThe time is 1, 3 and 1 hour, and the nickel niobate powder of nanometer level is obtained after cooling to the room temperature.
In this example, different target products were designed, different tests were performed, and different parameters in the preparation process were different according to different target products, and specific parameters corresponding to the products are shown in table 1.
TABLE 1
The nanocrystalline high-purity nickel niobate bulk material is prepared by directly preparing nano-grade nickel niobate powder by a hydrothermal method, mixing the ball-milling mixed material with a sintering aid, drying, and sintering by discharge plasma.
Claims (7)
1. A preparation method of a single-phase nickel niobate ceramic block with nano crystal grains is characterized by comprising the following steps:
preparing nickel niobate nano powder by a solid phase method or a hydrothermal method;
weighing the nickel niobate nano powder and a sintering aid, mixing and grinding, and drying and sieving to obtain mixed powder C;
performing pressure-maintaining sintering on the mixed powder C, wherein the sintering temperature is 400-600 ℃, the heat preservation time is 10-180 min, and the sintering pressure is 200-300 MPa, so that a single-phase nickel niobate block which has the purity of more than 99%, the density of more than 99.5%, the porosity of less than 0.5% and nano-crystalline grains is obtained; wherein, the inner surface of the sintering grinding tool which is subjected to pressure-maintaining sintering is subjected to BN spraying treatment.
2. The method for preparing the nanocrystalline single-phase nickel niobate ceramic block according to claim 1, wherein the mass fraction of the sintering aid is 0.5-5%.
3. The method of preparing a nanocrystalline single-phase nickel niobate ceramic block of claim 2, wherein the sintering aid is at least one of PVA, CMC, and EPS.
4. The method for preparing a nanocrystalline single-phase nickel niobate ceramic block according to any one of claims 1 to 3, wherein the preparation of the nickel niobate nanopowder by the solid phase method comprises:
sintered Ni (OH)2Obtaining NiO powder, wherein the sintering temperature is 400 ℃, and the sintering time is 3 h;
mixing the NiO powder and Nb2O5Ball-milling and mixing the powder to obtain mixed powder A; wherein the NiO powder and Nb2O5The molar ratio of the powder is 1: 1;
and sintering the mixed powder A at 800 ℃, preserving heat for 1h, and cooling to obtain the nickel niobate nano powder.
5. The method for preparing the single-phase nickel niobate ceramic block with nano-crystalline grains according to claim 4, wherein the ball milling and mixing are carried out at a ball mill rotation speed of 280r/min and a ball milling time of 8 h.
6. The method of preparing a nanocrystalline single-phase nickel niobate ceramic block of claim 5, further comprising, after the ball-milling and mixing:
and (3) carrying out rotary evaporation drying on the mixed powder A at the rotating speed of 100r/h for 1 h.
7. The method for preparing a nanocrystalline single-phase nickel niobate ceramic bulk according to any one of claims 1 to 3, wherein the hydrothermal method for preparing the nickel niobate nanopowder comprises:
adding a first raw material and a second raw material into alcohol to obtain a mixed solution; wherein the first raw material is NiCl2、Ni(NO3)2、NiSO4The second raw material is NbCl5And Nb (NO)3)5At least one of nickel element in the first raw material and niobium element in the second raw material in a molar ratio of 1:1, 3:2, or 2: 1;
heating and stirring the mixed solution, keeping the temperature at 135-220 ℃ for 5-8 h, and obtaining powder in the mixed solution after complete reaction;
and preserving the heat of the powder to obtain the nano-grade nickel niobate powder.
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