CN101559982B - Method of one-step synthesis of hexagonal barium ferrite nanometer crystal by microwave-assistant sol-gel spontaneous combustion - Google Patents
Method of one-step synthesis of hexagonal barium ferrite nanometer crystal by microwave-assistant sol-gel spontaneous combustion Download PDFInfo
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- CN101559982B CN101559982B CN2009100273192A CN200910027319A CN101559982B CN 101559982 B CN101559982 B CN 101559982B CN 2009100273192 A CN2009100273192 A CN 2009100273192A CN 200910027319 A CN200910027319 A CN 200910027319A CN 101559982 B CN101559982 B CN 101559982B
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- AJCDFVKYMIUXCR-UHFFFAOYSA-N oxobarium;oxo(oxoferriooxy)iron Chemical compound [Ba]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O AJCDFVKYMIUXCR-UHFFFAOYSA-N 0.000 title claims abstract description 53
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 52
- 239000013078 crystal Substances 0.000 title claims abstract description 40
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 19
- 238000003786 synthesis reaction Methods 0.000 title claims abstract description 18
- 230000002269 spontaneous effect Effects 0.000 title claims abstract description 17
- 238000000034 method Methods 0.000 title claims description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 23
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims abstract description 20
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 17
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 16
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000002360 preparation method Methods 0.000 claims abstract description 15
- 239000008139 complexing agent Substances 0.000 claims abstract description 12
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 10
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000002207 thermal evaporation Methods 0.000 claims abstract description 10
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 8
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 7
- 239000007788 liquid Substances 0.000 claims abstract description 7
- 239000010453 quartz Substances 0.000 claims abstract description 7
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000002994 raw material Substances 0.000 claims abstract description 6
- 238000001035 drying Methods 0.000 claims abstract description 5
- 239000004202 carbamide Substances 0.000 claims abstract description 4
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 3
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims abstract description 3
- 239000000908 ammonium hydroxide Substances 0.000 claims abstract description 3
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 3
- 238000007710 freezing Methods 0.000 claims abstract description 3
- 239000008103 glucose Substances 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 13
- 239000000843 powder Substances 0.000 claims description 11
- 239000003292 glue Substances 0.000 claims description 10
- 239000007864 aqueous solution Substances 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 238000010791 quenching Methods 0.000 claims description 4
- 230000005855 radiation Effects 0.000 claims description 4
- 239000003507 refrigerant Substances 0.000 claims description 4
- 238000007711 solidification Methods 0.000 claims description 4
- 230000008023 solidification Effects 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 230000000536 complexating effect Effects 0.000 claims description 3
- 238000000748 compression moulding Methods 0.000 claims description 2
- 230000008014 freezing Effects 0.000 claims description 2
- YPJKMVATUPSWOH-UHFFFAOYSA-N nitrooxidanyl Chemical compound [O][N+]([O-])=O YPJKMVATUPSWOH-UHFFFAOYSA-N 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 238000009827 uniform distribution Methods 0.000 claims description 2
- 229910000859 α-Fe Inorganic materials 0.000 abstract description 7
- 239000000446 fuel Substances 0.000 abstract description 5
- 150000001875 compounds Chemical class 0.000 abstract description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 3
- 238000010668 complexation reaction Methods 0.000 abstract description 2
- 229910002771 BaFe12O19 Inorganic materials 0.000 abstract 1
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Inorganic materials [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 abstract 1
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 abstract 1
- 229960001484 edetic acid Drugs 0.000 abstract 1
- 239000008187 granular material Substances 0.000 abstract 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 abstract 1
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(III) nitrate Inorganic materials [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 abstract 1
- 239000007800 oxidant agent Substances 0.000 abstract 1
- 230000009897 systematic effect Effects 0.000 abstract 1
- 239000000463 material Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 9
- 238000009767 auto-combustion synthesis reaction Methods 0.000 description 7
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 7
- 229910001864 baryta Inorganic materials 0.000 description 7
- 238000009841 combustion method Methods 0.000 description 7
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- PXRKCOCTEMYUEG-UHFFFAOYSA-N 5-aminoisoindole-1,3-dione Chemical compound NC1=CC=C2C(=O)NC(=O)C2=C1 PXRKCOCTEMYUEG-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 230000002459 sustained effect Effects 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
- -1 barium ferrite hydrocarbon Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000015895 biscuits Nutrition 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 238000012792 lyophilization process Methods 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000004530 micro-emulsion Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000006902 nitrogenation reaction Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 238000010671 solid-state reaction Methods 0.000 description 1
- 238000007704 wet chemistry method Methods 0.000 description 1
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Abstract
The present invention provides a preparation method of one-step synthesis of hexagonal barium ferrite (BaFe12O19) nanometer crystal by microwave-assistant sol-gel spontaneous combustion process. The technical scheme comprises the following steps: 1) nitrate Ba(NO3)2 and Fe(NO3)3 are taken as the raw materials; water solution with certain concentration is prepared according to barium ferrite chemometry; citric acid, ethylene diamine tetraacetic acid, urea, glucose and glycol and other organic reagents or compound thereof are taken as complexing agent of metal ion and hydrocarbon fuel required by sol-gel spontaneous combustion; ammonium nitrate and ammonium hydroxide are in addition added to adjust content of systematic oxidizer and PH value; even sol is formed by complexation. 2) xerogel which with desirable residual moisture content is prepared by using liquid nitrogen quick-freezing sol and vacuum condensation drying process. 3) the xerogel is compressed to form a block which is put into a quartz reaction chamber with microwave absorptive character; the xerogel is induced for spontaneous combustion in a microwave field, single-phase barium ferrite nanometer crystal is synthesized in one step which is precise in components and even in granule size; the invention can be used to prepare quasi-single crystal texture millimeter wave gyromagnetic ferrite.
Description
Technical field:
What the present invention relates to is the method for a kind of microwave-assisted colloidal sol-gel spontaneous combustion method one-step synthesis hexagonal barium ferrite nanometer crystal, belongs to the advanced function technical field of material.
Background technology:
M type hexagonal barium ferrite (BaFe with magnetoplumbite structure
12O
19, BaM) since nineteen fifty-two J.L.Went etc. is synthetic first, low and have than high magnetic accumulated energy and become one of oxide compound permanent magnet the most commonly used gradually because of its preparation cost.In recent years, people begin to pay close attention to the higher coercive field of M type hexagonal barium ferrite, saturation magnetization, magnetocrystalline anisotropy field and good characteristics such as chemical erosion resistance, extensively carry out as the synthetic preparation of material obsorbing radar waves, high performance vertical recording materials and millimetric wave device gyromagnetic material and the research of application facet.Especially on the millimeter wave gyromagnetic material, hexagonal barium ferrite polycrystalline Ferrite Material, realization device that preparation has accurate monocrystalline texture do not have the research focus that bias magnetic field has become this field.It is accurate to realize that this height-oriented structure depends on chemical constitution, the preparation of the single domain hexagonal barium ferrite nanometer crystal that particle size distribution is narrow.
According to open source literature report, the method that is used to prepare hexagonal barium ferrite nanometer crystal so far comprises reverse microemulsion process, coprecipitation method and sol-gel method etc.Their common feature is to be divided into for two steps: 1) make metal ion in the starting raw material reach the uniform mixing of atom or ion concentration by the wet-chemical process; 2) solid state reaction ℃ is carried out in mixture heating up to 800～1000, obtain target product.Even preparing in the research of hexagonal barium ferrite nanometer crystal with sol-gel auto-combustion method, the product that auto-combustion obtains does not carry out subsequent heat treatment exceptionally yet, to obtain single-phase hexagonal barium ferrite nanometer.Research practice shows that the subsequent heat treatment of comparatively high temps must cause the alligatoring of target product crystal grain and crystal grain is inter-adhesive and agglomeration, is difficult to satisfy the requirement of the accurate monocrystalline texture of preparation high quality hexagonal barium ferrite gyromagnetic ferrite material.
Be the single-phase hexagonal barium ferrite nanometer crystal of preparation high quality, patent applicant of the present invention research group has carried out system, deeply and careful research to sol-gel auto-combustion method, discovery utilizes sol-gel auto-combustion method can impel the Fe-Ba-O reaction in by the heat that the auto-combustion process produces fully, and a step forms single-phase hexagonal barium ferrite nanometer crystal.In the research in the past report, why failing one, go on foot successfully synthetic single-phase hexagonal barium ferrite nanometer crystal mainly be hydrocarbon content and the oxygenate content that acts as a fuel in the gel and their proportioning is improper, the distribution of metal ion and oxygenant fails to reach enough homogeneity and auto-combustion initiations and continue in the process due to the reasons such as the temperature of reaction system field is inhomogeneous.For this reason, we carry out appropriate design, further improve metal ion and the homogeneity of oxygenant distribution and the temperature field homogeneity of auto-combustion reaction system in the xerogel hydrocarbon content of auto-combustion system and oxygenate content, have realized the sol-gel auto-combustion method one-step synthesis of single-phase hexagonal barium ferrite nanometer crystal.Obviously, method of the present invention has the meaning of no less important for the synthetic and preparation of other functional complex oxide nanometer.
Summary of the invention:
The present invention need be under comparatively high temps carries out second heat treatment to products of combustion and the grain-size brought thus is wayward and problem such as crystal grain reunion adhesion, the method for a kind of microwave-assisted colloidal sol-gel spontaneous combustion one-step synthesis hexagonal barium ferrite nanometer crystal of proposition in order to solve existing common sol-when the gel spontaneous combustion method prepares the hexagonal barium ferrite powder.
Technical scheme of the present invention is: adopt the organism contain carboxyl and amido as complexing agent, when fully complexation of metal ions forms even colloidal sol, optimize required hydrocarbon fuel content of system auto-combustion and oxygenate content, guarantee that mol ratio is reasonable between them; Effectively improve the distributing homogeneity of metal ion and oxygenant in the gel by even colloidal sol liquid nitrogen flash freezer and vacuum condensation dry technology; The use of the silica glass auto-combustion reaction chamber by applying barium ferrite microwave absorbing film, be formed with the nearly adiabatic environment and the equally distributed temperature field that help the even initiation of xerogel spontaneous combustion and sustained combustion and the nanocrystalline formation of single-phase six side's barium ferrites, realized the auto-combustion one-step synthesis of hexagonal barium ferrite nanometer crystal.The present invention is by xerogel auto-combustion quick in situ chemical reaction process, six side's barium ferrites of one-step synthesis are nanocrystalline to have that chemical constitution is accurate, particle size evenly, characteristics such as good dispersity, need be under comparatively high temps when having avoided common sol-gel auto-combustion method to prepare the hexagonal barium ferrite powder to the second heat treatment of products of combustion and the grain-size brought thus is wayward and problem such as crystal grain reunion adhesion, for the preparation of the accurate monocrystalline texture of high-performance millimeter wave gyromagnetic ferrite provides the high quality material powder.
The introducing amount of hydrocarbon fuel and oxygenant in the choose reasonable of the present invention by complexing agent, the optimization system, adopt colloidal sol liquid nitrogen flash freezer and vacuum condensation dry technology to improve the homogeneity that metal ion and oxygenant distribute in xerogel and utilize technology such as microwave-assisted, realized the microwave-assisted colloidal sol-gel spontaneous combustion one-step synthesis of hexagonal barium ferrite nanometer crystal.
Concrete technical scheme of the present invention is: the method for a kind of microwave-assisted colloidal sol-gel spontaneous combustion one-step synthesis hexagonal barium ferrite nanometer crystal, and its concrete steps are as follows:
A. with solubility nitrate Ba (NO
3)
2And Fe (NO
3)
3Be raw material, press hexagonal barium ferrite (BaFe
12O
19) stoichiometry, accurately preparing metal ion volumetric molar concentration is the aqueous solution of 0.01～0.50M;
B. in the above-mentioned aqueous solution, by the ratio of metal ion molar weight in the molar weight of complexing agent and the aqueous solution is 1.0～3.0 to add complexing agents, and wherein complexing agent is at least any one in citric acid (CA), ethylenediamine tetraacetic acid (EDTA) (EDTA), urea (Ur) or the glucose (Glu); The mol ratio of adding and complexing agent is 0～2.0 organic reagent ethylene glycol (EG) again; Add ammonium hydroxide and ammonium nitrate simultaneously, adjustment and control system pH value reaches 6.0～8.0, oxidisability Q=0.5～1.5, and wherein oxidisability is the total oxygen demand of system nitrate radical introducing and the ratio of the required total oxygen demand of the hydrocarbon complete oxidation of system; Backflow stirring reaction 2～6 hours under 25 ℃～35 ℃ conditions forms and the uniform distribution of each component in structure to guarantee the abundant complexing of metal ion, system collosol structure again, obtains even colloidal sol;
C. the even colloidal sol of gained is poured the quartz curette that is dipped in the refrigerant into, forms the solid-state frozen glue that invests tube wall through quench solidification; Link to each other with vacuum condensing unit then and carry out the vacuum condensation drying, 10
-1～10
-3Collect the steam that from frozen glue, distils out by-40 ℃～-30 ℃ cold-traps under the vacuum tightness of Pa, until obtaining the suitable xerogel of residual water-content;
D. with xerogel compression moulding, place the silica glass burning chamber, carry out microwave in the immigration microwave oven and bring out auto-combustion, collect the auto-combustion product and promptly get the hexagonal barium ferrite nanometer crystal powder.
Wherein preferred steps C adopts liquid nitrogen as refrigerant, is frozen into colloidal sol solid-state rapidly.In the vacuum lyophilization process, can carry out infrared radiation heating or refrigerator freezing treatment to the solid-state frozen glue that invests tube wall, control its temperature in-20～-10 ℃ of intervals.Having formed residual water-content after 12～48 hours through vacuum lyophilization is 2～5% xerogel, and its chromaticness is vivid, even, and metal ion and oxygenant are evenly distributed in the gel, and ammonium nitrate grain is of a size of 30～150nm.
Wherein xerogel is pressed into disk among the preferred steps D, and pressure is at 1～5MPa, disk diameter 20～30mm, thickness 5～10mm.The frequency that adopts power to be output as 100～1000W microwave oven to provide is provided in the xerogel auto-combustion is that the microwave source even heating of 2.45GHz carries out.
Wherein xerogel piece auto-combustion reaction is placed in the cup-shaped silica glass chamber and carries out among the preferred steps D; This silica glass cavity wall is coated with the barium ferrite microwave absorbing film that thickness is 0.1～0.15mm, and area coverage is 40%-50%, and xerogel samples is placed in the support of silica glass, supports the barium ferrite microwave absorbing film that upper surface also applies same thickness.Cause in initial stage and the follow-up auto-combustion process at xerogel piece auto-combustion microwave, quartz glass reaction cavity wall temperature raises rapidly, and in the silica glass chamber, form a nearly adiabatic environment with respect to xerogel, make can be under the microwave even heating whole rapidly evenly ignition of xerogel, the heat accumulation that burning produces is set up a homogeneous temperature field that promotes that single-phase hexagonal barium ferrite nanometer crystal forms in reaction chamber.Silica glass auto-combustion reaction chamber structure and auto-combustion xerogel piece arrangement relation are as shown in Figure 1 in the microwave oven.
Beneficial effect:
The invention provides the technology of preparing of the single-phase hexagonal barium ferrite nanometer crystal of one-step synthesis, the gained hexagonal barium ferrite nanometer crystal has characteristics such as chemical constitution is accurate, grain morphology is regular, size is even, can be directly used in the height-oriented textured accurate monocrystalline hexagonal barium ferrite gyromagnetic material of preparation crystal grain.Compare with common sol-gel auto-combustion method, method thinking novelty provided by the invention, suitability are strong, have the quick in situ reaction, once synthetic and auto-combustion product need not advantages such as subsequent heat treatment, specifically comprises as follows:
1, realized xerogel auto-combustion process one-step synthesis hexagonal barium ferrite nanometer crystal, the auto-combustion product need not subsequent heat treatment, need be under comparatively high temps when having avoided common sol-gel auto-combustion method to prepare the hexagonal barium ferrite powder to the second heat treatment of products of combustion and the grain-size brought thus is wayward and problem such as crystal grain reunion adhesion.
2, prepared hexagonal barium ferrite nanometer crystal has one-domain structure, grain morphology rule, size evenly (～50nm), no particle is inter-adhesive.Loose powder can reach crystal grain along the orientations of field direction more than 90% in～250Oe magnetic field, under the 50MPa pressing under magnetic field condition in the biscuit preferable grain orientation degree can reach more than 50%, can be used as the preparation accurate monocrystalline hexagonal barium ferrite gyromagnetic ferrite material the high quality material powder.
3, adopt the compound complexing of metal ion, sol solutions chilled nitrogen and vacuum condensation dry technology to improve the homogeneity that metal ion and oxygenant distribute in the xerogel greatly in xerogel, for the related component reaction in form single-phase hexagonal barium ferrite and provide necessary and sufficient electrochemical conditions.By optimization and auto-combustion microwave-assisted quartz glass reaction chamber micro-wave energy ancillary technique xerogel is ignited and sustained combustion in nearly adiabatic environment, guaranteed the homogeneity of gel combustion system temperature field distribution and formed the required thermodynamic condition of hexagonal barium ferrite hydrocarbon fuel in the xerogel and oxygenate content.
4, the equipment that is adopted in the preparation process is simple, and is easy to operate, with low cost, is adapted to the nanocrystalline large-scale commercial applications production of hexagonal barium ferrite nanometer crystal and other functional complex oxide.
Description of drawings:
Fig. 1 is silica glass auto-combustion reaction chamber structure and an auto-combustion xerogel piece arrangement relation synoptic diagram in the microwave oven;
1-microwave radiation source wherein, 2-quartz glass reaction chamber, 3-sample holder, 4-xerogel sample, 5-microwave absorbing film.
The XRD figure spectrum of Fig. 2 microwave-assisted colloidal sol-gel spontaneous combustion method one-step synthesis M type hexagonal barium ferrite nanometer crystal;
The FE-SEM photo of Fig. 3 microwave-assisted colloidal sol-gel spontaneous combustion method one-step synthesis M type hexagonal barium ferrite powder;
The magnetic hysteresis loop of Fig. 4 microwave-assisted colloidal sol-gel spontaneous combustion one-step synthesis M type hexagonal barium ferrite nanometer crystal powder;
The XRD figure spectrum of Fig. 5 microwave-assisted colloidal sol-gel spontaneous combustion method one-step synthesis M type hexagonal barium ferrite nanometer crystal;
Embodiment:
Utilize microwave-assisted colloidal sol-gel spontaneous combustion method one-step synthesis hexagonal barium ferrite nanometer crystal
1) is raw material with analytical pure nitrate of baryta and iron nitrate, presses BaFe
12O
19Middle component chemical quantitative relation claims an amount of nitrate of baryta and iron nitrate to be dissolved in the proper amount of deionized water, obtains nitrate of baryta and iron nitrate solution, and their concentration is respectively: [Ba
2+]=0.02M, [Fe
3+]=0.24M;
2) add complexing agent ethylenediamine tetraacetic acid (EDTA) (EDTA), citric acid (CA) and ethylene glycol (EG) in above-mentioned solution, its dosage is by (M
EDTA+ M
CA)/M
Ba+Fe=1.5, M
EDTA/ M
CA=1/6 and M
EG/ (M
EDTA+ M
CACarry out)=1.2, is stirred to whole dissolvings then.And then add ammonium nitrate by oxidisability Q=0.8, and with the pH value to 7.0 of ammoniacal liquor regulator solution, the backflow stirring reaction is 2 hours under 25 ℃ of conditions, the even colloidal sol that must react completely;
3) above-mentioned colloidal sol rotation is flowed in the quartz curette that is dipped in the liquid nitrogen, form the solid-state frozen glue that invests wall of cup through quench solidification.Then quartz curette is linked to each other with the vacuum condensation moisture eliminator, 10
-2Collect the steam that distils out by-40 ℃ of cold-traps from frozen glue under the vacuum tightness of Pa, obtaining slightly red-brown, residual water-content through vacuum-drying in 18 hours is 2.1% xerogel, and wherein ammonium nitrate grain is of a size of 60～130nm.
The gained xerogel is pressed into diameter 25mm under the 1.5MPa condition, the disk of thick about 5mm places inwall to scribble the quartz glass reaction chamber of microwave absorbing film, brings out auto-combustion in power is made as the microwave oven of 250W.The auto-combustion microwave brings out about 10 seconds of time, continues internal combustion about 12 seconds of violent combustion time behind the xerogel ignition.Auto-combustion product X RD spectrum is single thing phase hexagonal barium ferrite as shown in Figure 2; Its SEM photo shows that hexagonal barium ferrite crystal grain is bordering on sphere as shown in Figure 3, and median size is～50nm; Its loose powder magnetzation curve can reach crystal grain as shown in Figure 4 along the orientations of field direction more than 90% under 250Oe magnetic field.
1) is raw material with analytical pure nitrate of baryta and iron nitrate, presses BaFe
12O
19Middle component chemical quantitative relation claims an amount of nitrate of baryta and iron nitrate and is dissolved in respectively in the proper amount of deionized water that obtain nitrate of baryta and iron nitrate solution, their concentration is respectively: [Ba
2+]=0.01M, [Fe
3+]=0.12M;
2) add ethylenediamine tetraacetic acid (EDTA) (EDTA) and urea (Ur) in solution in nitrate of baryta and iron nitrate solution, its dosage is pressed M
EDTA/ M
Ba+Fe=1.0, M
Ur/ M
Ba+FeMol ratios such as=1.0 are carried out.In solution, add ammonium nitrate by oxidisability Q=1.0, and be 6.5, and then at room temperature (20 ℃) stirring reaction guaranteed fully reaction, the even colloidal sol that must react completely in 2 hours with the pH value of strong aqua regulator solution;
3) above-mentioned colloidal sol is slowly poured in the quartz curette that is dipped in the liquid nitrogen, formed the solid-state frozen glue that invests wall of cup through quench solidification.Then quartz curette is linked to each other with the vacuum condensation moisture eliminator, 5 * 10
-2Collect the steam that distils out by-40 ℃ of cold-traps from frozen glue under the vacuum tightness of Pa, obtaining slightly red-brown, residual water-content through vacuum-drying in 24 hours is 2.3% xerogel, and wherein ammonium nitrate grain is of a size of 50～120nm.
4) the gained xerogel is pressed into diameter 25mm under the 1.0MPa condition, and the disk of thick about 10mm places inwall to scribble the quartz glass reaction chamber of barium ferrite microwave absorbing film, brings out auto-combustion in power is made as the microwave oven of 300W.The auto-combustion microwave brings out about 11 seconds of time, continues internal combustion about 13 seconds of violent combustion time behind the xerogel ignition.Auto-combustion product X RD spectrum is single thing phase hexagonal barium ferrite nanometer crystal as shown in Figure 5, and median size is～55nm.
Claims (4)
1. the method for microwave-assisted colloidal sol-gel spontaneous combustion one-step synthesis hexagonal barium ferrite nanometer crystal, its concrete steps are as follows:
A. with solubility nitrate Ba (NO
3)
2And Fe (NO
3)
3Be raw material, press hexagonal barium ferrite BaFe
12O
19Stoichiometry, accurately preparing metal ion volumetric molar concentration is the aqueous solution of 0.01～0.50M;
B. in the above-mentioned aqueous solution, be 1.0～3.0 to add complexing agents by the ratio of metal ion molar weight in the molar weight of complexing agent and the aqueous solution, wherein complexing agent is at least any one in citric acid, ethylenediamine tetraacetic acid (EDTA), urea or the glucose; The mol ratio of adding and complexing agent is 0～2.0 organic reagent ethylene glycol again; Add ammonium hydroxide and ammonium nitrate simultaneously, adjustment and control system pH value reaches 6.0～8.0, oxidisability Q=0.5～1.5, and wherein oxidisability is the total oxygen demand of system nitrate radical introducing and the ratio of the required total oxygen demand of the hydrocarbon complete oxidation of system; Backflow stirring reaction 2～6 hours under 25 ℃～35 ℃ conditions forms and the uniform distribution of each component in structure to guarantee the abundant complexing of metal ion, system collosol structure again, even colloidal sol;
C. the even colloidal sol of gained is poured the quartz curette that is dipped in the refrigerant into, forms the solid-state frozen glue that invests tube wall through quench solidification; Link to each other with vacuum condensing unit then and carry out the vacuum condensation drying, 10
-1～10
-3Collect the steam that from frozen glue, distils out by-40～-30 ℃ of cold-traps under the vacuum tightness of Pa, having formed residual water-content after 12～48 hours through the vacuum condensation drying is 2～5% xerogel, its chromaticness is vivid, even, metal ion and oxygenant are evenly distributed in the gel, and ammonium nitrate grain is of a size of 30～150nm;
D. with xerogel compression moulding, place the silica glass burning chamber, carry out microwave in the immigration microwave oven and bring out auto-combustion, collect the auto-combustion product and get the hexagonal barium ferrite nanometer crystal powder; Wherein this silica glass burning chamber is cup-shaped silica glass chamber, inwall is coated with the barium ferrite microwave absorbing film that thickness is 0.10～0.15mm, area coverage is 40%-50%, xerogel samples is placed in the support of silica glass, supports the barium ferrite microwave absorbing film that upper surface also applies same thickness.
2. preparation method according to claim 1 is characterized in that the refrigerant described in the step C is a liquid nitrogen; In the vacuum condensation drying process, the solid-state frozen glue that invests tube wall is carried out infrared radiation heating or refrigerator freezing treatment, control its temperature in-20～-10 ℃ of intervals.
3. preparation method according to claim 1 is characterized in that xerogel is pressed into disk among the step D, and pressure is at 1～5MPa, disk diameter 20～30mm, thickness 5～10mm.
4. preparation method according to claim 1 is characterized in that xerogel auto-combustion among the step D microwave radiation source even heating that adopts frequency to provide for 2.45GHz, power are output as 100～1000W microwave oven is provided carries out.
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| CN102408132B (en) * | 2011-08-12 | 2015-01-28 | 湖州师范学院 | Method for preparing nanometer lanthanum ferrite powder by using microwave process |
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| CN103570078B (en) * | 2013-11-01 | 2014-12-10 | 中北大学 | Preparation method of nanoscale ferrite |
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| CN107384507B (en) * | 2017-09-13 | 2019-04-05 | 新昌县群娇农业发展有限公司 | A kind of preparation method of oxygen carrier barium ferrite |
| CN109133182A (en) * | 2018-09-30 | 2019-01-04 | 江苏理工学院 | A kind of preparation method of macropore Manganese Ferrite |
| CN109231974B (en) * | 2018-10-19 | 2021-02-26 | 扬州大学 | Method for synthesizing epsilon-type iron oxide nano permanent magnet by sol-gel self-combustion |
| CN113979479B (en) * | 2021-09-26 | 2023-07-04 | 杭州电子科技大学 | Preparation method of graphene composite nano hexagonal barium ferrite wave-absorbing material |
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