CN105197952A - Preparation of nano single crystal lanthanum hexaboride and application of nano single crystal lanthanum hexaboride in electron microscope filament preparation - Google Patents
Preparation of nano single crystal lanthanum hexaboride and application of nano single crystal lanthanum hexaboride in electron microscope filament preparation Download PDFInfo
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- CN105197952A CN105197952A CN201510560436.0A CN201510560436A CN105197952A CN 105197952 A CN105197952 A CN 105197952A CN 201510560436 A CN201510560436 A CN 201510560436A CN 105197952 A CN105197952 A CN 105197952A
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Abstract
The invention relates to the field of field emission materials, and aims at providing the preparation of nano single crystal lanthanum hexaboride and the application of the nano single crystal lanthanum hexaboride in the electron microscope filament preparation. The preparation comprises the following steps: weighing lanthanum compounds and alkali metal boron hydride powder, and performing ball-milling to obtain a mechanical mixture; placing the mechanical mixture into a reactor, heating up to 300 to 700 DEG C from the room temperature at the heating rate of 2 DEG C per minute, then performing heat preservation for 2 hours and releasing hydrogen; then cooling, washing, separating and performing vacuum drying at the temperature of 80 DEG C to obtain the nano single crystal lanthanum hexaboride. According to the preparation, the synthesis temperature of lanthanum hexaboride is greatly decreased, the quality management during the industrial production of the lanthanum hexaboride is facilitated, the single crystal particle size consistency of the lanthanum hexaboride is improved, and the quality management of large-scale production is facilitated. The raw material cost is low, the energy consumption is low, and the preparation process is easy and simple. When the nano single crystal lanthanum hexaboride is used for preparing an electron microscope filament, low work function, low volatility and low resistance are realized; the mechanical strength is high, and the chemical stability is good, so that an electron microscope image is more clear, the cost is lower and the service life is prolonged greatly.
Description
Technical field
The invention relates to field emmision material field, relate to the preparation method of nano crystal lanthanum boride, the preparation method of the nano crystal lanthanum boride field emmision material low in particular to a kind of temperature of reaction, reaction conditions is gentle, energy consumption is little, effectively can improve Flied emission intensity and the life-span of lanthanum boride electro-mirror filament.
Background technology
Lanthanum boride is a kind of red-violet colour crystal, and fusing point is high, is 2715 DEG C, decomposes higher than fusing point lanthanum boride.Water insoluble and sour under normal temperature.Usually lanthanum sesquioxide and borax are dissolved in suitable fused salt, and at high temperature utilize graphite anode electrolysis, lanthanum hexaborane is deposited on the negative electrode of graphite or steel.Owing to having, fusing point is high, thermoelectronic emission performance is high, alternative refractory metal and alloy in fusion reactor, hot electron power generation etc.The purposes of lanthanum boride is very extensive, has been successfully applied to more than 20 military affairs such as radar aerospace, electronic industry, instrument, medicine equipment, family's electrometallurgy, environmental protection and high-tech area.Lanthanum hexaborane product mainly comprises amorphous, polycrystal, single crystal lanthanum hexaborane.Particularly lanthanum hexaborane monocrystalline is the best materials making high power valve, magnetic controller, electron beam, ionic fluid, accelerator negative electrode.Lanthanum hexaborane monocrystalline has good field emission characteristic, is the main raw making now high-resolution-ration transmission electric-lens filament, has low work function, low volatility, low resistance, high mechanical strength, the advantage of high chemical stability.
The preparation of metal boride has the synthetic methods such as hot pressed sintering, mechanical alloying, SHS process, electrolysis fused salt, solvent-thermal method, discharge plasma sintering.As mixed by a certain percentage with tungsten powder by boron powder, at high temperature synthesize tungsten boride powder, then as raw material adopt cold pressing and high temperature sintering prepared tungsten boride pottery; With ZrB
2as adulterating agent, prepare TiB by hot pressed sintering
2-ZrB
2solid solution composite ceramics, the shortcoming of hot pressed sintering is that process and equipment are complicated, and production control requires strict, and moulding stock requires high, and energy consumption is large, and production efficiency is lower, and production cost is high; Mechanical alloying is the non-equilibrium solid state reaction process under a normal temperature, and this reaction is also referred to as mechanico-chemical reaction, and its thermodynamics, kinetics are different from common solid state reaction, easily cause composition uneven, there is energy consumption equally large, production efficiency is lower, the shortcoming that production cost is high.
Self-propagating high-temperature synthesis (SHS), also combustion synthesis method is claimed, be the chemical reaction liberated heat utilized between material, make building-up reactions continue voluntarily to carry out until react end, thus synthesize a kind of novel method of material requested in a short period of time.SHS technology is because a kind of type material technology of preparing that resultant velocity is fast, temperature is high, speed of cooling is fast, equipment is simple, the feature of less investment, less energy consumption has become modern science and industrial technical field is extensively paid attention to.But SHS method can introduce " external " material (impurity) in the compound generated, and make the boron of the inertia high temperature participated in required for reaction can cause pollution from places such as reaction vessel (crucible), reactant (carbon, the metallic additions added as reductive agent) and reaction atmospheres (water and oxygen).Except the difficulty brought by inertia and the high temperature of boron, the instability problem of rich metallic boride in atmosphere or in wet environment also can not be ignored.
Boron trioxide (or borax) and metal oxide are dissolved in together in a kind of suitable fused salt (halogenide or fluoroborate as basic metal or alkaline-earth metal), anode is made with graphite at 700 ~ 1000 DEG C, negative electrode made by graphite or steel, carry out the easy control of reaction conditions of the fused salt electrolysis process of electrolysis, environmental facies, to close friend, are prepare one of up-and-coming method of metal boride.But the shortcoming existed also can not be ignored: (1) may generate the thing phase of several boride; (2) fused salt electrolysis process prepares boride not easily serialization, because electrolysate mostly is isolator, is attached near negative electrode, stops electrolysis to proceed.(3) shortcoming that fused salt electrolysis process ubiquity current efficiency is low, current efficiency is not higher than 50%.The insulating property of boride becomes the serious hindrance improving current efficiency.
Discharge plasma sintering (SPS), also pulse electric current sintering (pulsedelectriccurrentsintering is referred to as, and field assisted sintering (fieldassistedsinteringtechnique PECS), FAST), it be a kind of fast, low temperature, energy-saving and environmental protection material prepare New Machining Technology, not only can carry out the sintering of metal and stupalith, also can realize reaction in－situ sintering, thermograde sinters, and can also be used for material and connect.This technology directly passes into DC pulse electric energy between pressurization powder granule, the joule heating produced by granule interior causes granule interior to produce the temperature difference of hundreds of to thousands of degree with surface, thus the formation of realization sintering neck, expansion and densification, its electric energy consumed only has 1/5 ~ 1/3 of conventional sintering technique (pressureless sintering PLS, hot pressed sintering HP, hot isostatic pressing HIP).SPS technology has the advantages such as sintering is quick, sintering temperature is low, simple to operation, occupation area of equipment is little, level of automation is high, technical process is short, is widely used in recent years in the research and development of metal and alloy material, stupalith, matrix material, gradient material, nano material etc.Sinter synthesis by rare earth hydride powder and boron powder reaction in－situ, successfully preparing grain fineness number is 80 ~ 100nm, and density reaches the nanocrystalline rare-earth boride block materials of 99.2%, demonstrates excellent mechanical property and electron emission capability.But pulse electric current sintering also also exists, discharge uneven, production quality control difficulty, cannot the disadvantage such as mass industrialized production.
Summary of the invention
The technical problem to be solved in the present invention is, overcomes deficiency of the prior art, provides the monocrystalline lanthanum boride preparation method that a kind of temperature of reaction is low, reaction conditions is gentleer, energy consumption is little, and is provided in the application in electro-mirror filament preparation further.
For solving the problems of the technologies described above, solution of the present invention is:
The invention provides a kind of preparation method of nano crystal lanthanum boride, comprise the following steps:
Mol ratio by La: B is take lanthanum compound and alkali metal boronhydride powder at 1: 6, and add in ball grinder, under 400rpm rotating speed, ball milling is after 16 hours, obtains the mechanical mixture of lanthanum compound and alkali metal boronhydride; Mechanical mixture is placed in reactor, is incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, centrifugation after washing, vacuum-drying at 80 DEG C, obtains nano crystal lanthanum boride.
Further, the invention provides a kind of method preparing nano crystal lanthanum boride electro-mirror filament, comprise the following steps:
(1) be take lanthanum compound and alkali metal boronhydride powder at 1: 6 by the mol ratio of La: B, add in ball grinder, under 400rpm rotating speed, ball milling is after 16 hours, obtains the mechanical mixture of lanthanum compound and alkali metal boronhydride;
(2) above-mentioned mechanical mixture is imported in the groove of mould, at 1 ton/cm after filling up
2pressure real; Groove is broken line shape, and have 25 ° of acute angles, the length on acute angle both sides is 0.8cm; The cross section of groove is semicircle, and diameter is 1mm;
(3) the above-mentioned mould importing mechanical mixture is placed in reactor, is incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, vacuum-drying at 80 DEG C after washing, obtain nano crystal lanthanum boride electro-mirror filament.
Further, the invention provides a kind of preparation method of nano crystal lanthanum boride, comprise the following steps:
In ball grinder, be dissolved in by alkali metal boronhydride in solvents tetrahydrofurane (THF), every 100mL tetrahydrofuran (THF) containing 0.3 mole of alkali metal boronhydride, then is add lanthanum compound powder at 1: 6 by the mol ratio of La: B; Then ball milling 2 hours under 400rpm rotating speed, forms mashed prod; Mashed prod is placed in reactor, at 120 DEG C, evaporates tetrahydrofuran (THF), obtain the mechanical mixture of lanthanum compound and alkali metal boronhydride; Be incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min, discharge hydrogen; Then be cooled to room temperature, centrifugation after washing, vacuum-drying at 80 DEG C, obtains nano crystal lanthanum boride.
Further, the invention provides a kind of method preparing the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride, comprise the following steps:
(1) in ball grinder, be dissolved in by alkali metal boronhydride in solvents tetrahydrofurane (THF), every 100mL tetrahydrofuran (THF) containing 0.3 mole of alkali metal boronhydride, then is add lanthanum compound powder at 1: 6 by the mol ratio of La: B; Then ball milling 2 hours under 400rpm rotating speed, forms mashed prod;
(2) be the tungsten filament of 0.08 ~ 0.lmm by diameter, be placed on the acute angle shape soft foam rubber cushion curving 25 °, the length on acute angle both sides is 0.8cm; After tungsten filament is boiled 20 minutes with the potassium hydroxide of 50wt%, clean with distilled water flushing, dry;
(3) mashed prod that step (1) is obtained is coated on tungsten filament, coated weight is 10 ~ 30wt% of tungsten wire quality; Dry and be placed in reactor, be incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min, discharge hydrogen; Be cooled to room temperature, with vacuum-drying at 80 DEG C after water or washed with diethylether, obtain the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.
In the present invention, described lanthanum compound is lanthanum trioxide, lanthanum hydroxide, Phosbloc or lanthanum oxalate.
In the present invention, described alkali metal boronhydride is lithium borohydride, sodium borohydride or POTASSIUM BOROHYDRIDE.
Inventive principle describes:
In the present invention, at 300 ~ 700 DEG C, alkali metal boronhydride dehydrogenation forms highly active boride intermediate, and boride intermediate reacts with lanthanum compound and generates lanthanum boride, thus is obtained by reacting monocrystalline lanthanum boride at a lower temperature; The lanthanum boride obtained is water insoluble, and other by products are all water-soluble or can react with water and form water-soluble product, therefore can obtain highly purified lanthanum boride by simple washing.
The oxide compound of lanthanum or oxyhydroxide, the reaction of Phosbloc and lanthanum oxalate and alkali metal boronhydride thermodynamically can spontaneously be carried out, and by adjustment temperature of reaction, reduces the transformation efficiency that the means such as reactant granularity can improve reaction.
Illustrate:
During the source of lanthanum oxalate as lanthanoid metal, lanthanum oxalate and lithium borohydride react the solid product generated and only have lanthanum boride and lithium hydride,
La
2(C
2O
4)
3+12LiBH
4→2LaB
6+6CO
2+12LiH+18H
2
And lithium hydride is dissolved in ether, can reclaim.Therefore lanthanum oxalate and lithium borohydride discharge hydrogen and CO after reacting
2, add ether cleaning after being cooled to room temperature, lithium hydride is dissolved in ether, and after cleaning for several times, at 80 DEG C, vacuum-drying obtains nano crystal lanthanum boride.The diethyl ether solution of lithium hydride is evaporated solvent and obtains highly purified lithium hydride.
Compared with prior art, the invention has the beneficial effects as follows:
1, the present invention uses lanthanum compound and alkali metal boronhydride to be raw material, significantly reduce the synthesis temperature of lanthanum boride, be beneficial to qualitative control during lanthanum boride suitability for industrialized production, promote the monocrystalline granularity consistence of lanthanum boride, be conducive to the qualitative control of scale operation.
2, low raw-material cost, energy consumption is low, and preparation is simple.
When 3, using lanthanum oxalate as lanthanoid metal, obtain high-quality monocrystalline lanthanum boride and also may obtain highly purified lithium hydride simultaneously.And lithium hydride is in organic synthesis, as condensing agent, reductive agent, alkylating reagent, siccative, of many uses.The present invention has wide industrialization prospect.
4, nano crystal lanthanum boride electro-mirror filament has low work function, low volatility, low resistance, under equal conditions, uses nano crystal lanthanum boride electro-mirror filament that Electronic Speculum image can be made more clear compared with tungsten filament.
5, the electro-mirror filament of the coated tungsten of nano crystal lanthanum boride is compared with tungsten filament, and physical strength is high, and chemical stability is good, and make Electronic Speculum image more clear, cost is cheaper, and work-ing life is greatly improved.
Accompanying drawing explanation
Fig. 1 is the nano crystal lanthanum boride pattern obtained in embodiment 1.
Embodiment
Below in conjunction with embodiment, the present invention is described in further detail:
Embodiment 1: synthesize with the lanthanum boride that lanthanum trioxide and lithium borohydride are raw material
Be that 1:6 (La:B=1:6) takes lanthanum trioxide 0.001 mole (0.326g) and lithium borohydride 0.006 mole of (0.26g) powder adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of lanthanum trioxide and lithium borohydride after 16 hours, be placed in reactor, after temperature rise rate 2 DEG C/min is heated to 300 DEG C from room temperature, be incubated 2 hours.
La
2O
3+12LiBH
4→2LaB
6+3Li
2O+6LiH+21H
2
Discharge hydrogen, be cooled to room temperature after washing, during washing, LiH and water react and generate hydrogen and lithium hydroxide, and lithium hydroxide is water-soluble, centrifugation, and at 80 DEG C, vacuum-drying obtains nano crystal lanthanum boride.
Embodiment 2: synthesize with the lanthanum boride that lanthanum hydroxide and sodium borohydride are raw material
Be that 1:6 (La:B=1:6) takes lanthanum hydroxide 0.001 mole (0.19g) and sodium borohydride 0.006 mole of (0.227g) powder adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of lanthanum hydroxide and sodium borohydride after 2 hours, be placed in reactor, 2 hours are incubated after temperature rise rate 2 DEG C/min is heated to 500 DEG C
La(OH)
3+6NaBH
4→LaB
6+3Na
2O+13.5H
2
Discharge hydrogen, be cooled to room temperature after washing, be oxidized sodium and water reaction during washing and generate sodium hydroxide, sodium hydroxide is water-soluble, centrifugation, and at 80 DEG C, vacuum-drying obtains nano crystal lanthanum boride.
Embodiment 3: synthesize with the lanthanum boride that Phosbloc and POTASSIUM BOROHYDRIDE are raw material
Be that 1:6 (La:B=1:6) takes Phosbloc 0.01 mole (0.458g) and POTASSIUM BOROHYDRIDE 0.06 mole of (0.646g) powder adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of Phosbloc and POTASSIUM BOROHYDRIDE after 2 hours, be placed in reactor, 2 hours are incubated after temperature rise rate 2 DEG C/min is heated to 700 DEG C
La
2(CO
3)
3+12KBH
4→2LaB
6+3K
2CO
3+6KH+21H
2
Discharge hydrogen, be cooled to room temperature after washing, during washing, KH and water react and generate hydrogen and potassium hydroxide, and potassium hydroxide is water-soluble, centrifugation, and at 80 DEG C, vacuum-drying obtains nano crystal lanthanum boride.
Embodiment 4: prepared by lanthanum boride electro-mirror filament
Be that 1:6 (La:B=1:6) takes lanthanum trioxide 0.01 mole (3.26g) and lithium borohydride 0.06 mole of (2.6g) powder adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of lanthanum trioxide and lithium borohydride after 16 hours;
Above-mentioned mechanical mixture is imported and has in the mould of 25 ° of acute angle broken line shape grooves, fill up rear use 1 ton/cm
2pressure real, the length on groove acute angle both sides is 0.8cm; Cross section is semicircle, and diameter is 1mm;
Above-mentioned mould after the mechanical mixture importing lanthanum trioxide and lithium borohydride is placed in reactor, is incubated 2 hours after being heated to 300 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, vacuum-drying at 80 DEG C after washing, obtain nano crystal lanthanum boride electro-mirror filament.
Embodiment 5: prepared by the lanthanum boride filament being raw material with lanthanum hydroxide and sodium borohydride
Be that 1:6 (La:B=1:6) takes lanthanum hydroxide 0.01 mole (1.9g) and sodium borohydride 0.06 mole of (2.27g) powder adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of lanthanum hydroxide and sodium borohydride after 2 hours;
Above-mentioned mechanical mixture is imported and has in the mould of 25 ° of acute angle broken line shape grooves, fill up rear use 1 ton/cm
2pressure real, the length on groove acute angle both sides is 0.8cm; Cross section is semicircle, and diameter is 1mm;
Above-mentioned mould after the mechanical mixture importing lanthanum hydroxide and sodium borohydride is placed in reactor, is incubated 2 hours after being heated to 500 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, vacuum-drying at 80 DEG C after washing, obtain nano crystal lanthanum boride electro-mirror filament.
Embodiment 6: prepared by the lanthanum boride filament being raw material with Phosbloc and POTASSIUM BOROHYDRIDE
Be that 1:6 (La:B=1:6) takes Phosbloc 0.01 mole (4.58g) and POTASSIUM BOROHYDRIDE 0.06 mole of (6.46g) powder adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of Phosbloc and POTASSIUM BOROHYDRIDE after 2 hours;
Above-mentioned mechanical mixture is imported and has in the mould of 25 ° of acute angle broken line shape grooves, fill up rear use 1 ton/cm
2pressure real, the length on groove acute angle both sides is 0.8cm; Cross section is semicircle, and diameter is 1mm;
Above-mentioned mould after the mechanical mixture importing lanthanum hydroxide and sodium borohydride is placed in reactor, is incubated 2 hours after being heated to 700 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, vacuum-drying at 80 DEG C after washing, obtain nano crystal lanthanum boride electro-mirror filament.
Embodiment 7: the lanthanum boride Moist chemical synthesis being raw material with lanthanum hydroxide and sodium borohydride
In ball grinder, sodium borohydride 0.06 mole of (2.27g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes lanthanum hydroxide 0.01 mole (1.9g) and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours, be placed in reactor, the mechanical mixture that solvent THF obtains lanthanum hydroxide and sodium borohydride is evaporated at 120 DEG C, 2 hours are incubated after temperature rise rate 2 DEG C/min is heated to 500 DEG C
La(OH)
3+6NaBH
4→LaB
6+3Na
2O+13.5H
2
Discharge hydrogen, be cooled to room temperature after washing, be oxidized sodium and water reaction during washing and generate sodium hydroxide, sodium hydroxide is water-soluble, centrifugation, and at 80 DEG C, vacuum-drying obtains nano crystal lanthanum boride.
Embodiment 8: the lanthanum boride Moist chemical synthesis being raw material with Phosbloc and POTASSIUM BOROHYDRIDE
In ball grinder, POTASSIUM BOROHYDRIDE 0.06 mole of (6.46g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes Phosbloc 0.01 mole (4.58g) and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours; Mashed prod is placed in reactor, at 120 DEG C, evaporates tetrahydrofuran (THF), obtain the mechanical mixture of Phosbloc and POTASSIUM BOROHYDRIDE; Be incubated 2 hours after being heated to 300 DEG C with the temperature rise rate of 2 DEG C/min, discharge hydrogen; Then be cooled to room temperature, centrifugation after washing, vacuum-drying at 80 DEG C, obtains nano crystal lanthanum boride.
Embodiment 9: the lanthanum boride Moist chemical synthesis being raw material with lanthanum oxalate and lithium borohydride
In ball grinder, lithium borohydride 0.06 mole of (2.6g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes lanthanum oxalate 0.01 mole (3.15g) and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours; Mashed prod is placed in reactor, at 120 DEG C, evaporates tetrahydrofuran (THF), obtain the mechanical mixture of lanthanum oxalate and lithium borohydride; Be incubated 2 hours after being heated to 500 DEG C with the temperature rise rate of 2 DEG C/min, discharge hydrogen; Then be cooled to room temperature, centrifugation after washing, vacuum-drying at 80 DEG C, obtains nano crystal lanthanum boride.
Embodiment 10: the lanthanum boride Moist chemical synthesis being raw material with lanthanum trioxide and lithium borohydride
In ball grinder, lithium borohydride 0.06 mole of (2.6g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), be that 1:6 (La:B=1:6) takes lanthanum trioxide 0.01 mole of (3.26g) powder and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling obtains the mechanical mixture of lanthanum trioxide and lithium borohydride after 16 hours, be placed in reactor, after temperature rise rate 2 DEG C/min is heated to 700 DEG C from room temperature, be incubated 2 hours.Discharge hydrogen, be cooled to room temperature after washing, centrifugation, at 80 DEG C, vacuum-drying obtains nano crystal lanthanum boride.
Embodiment 11: prepared by electro-mirror filament
In ball grinder, POTASSIUM BOROHYDRIDE 0.06 mole (6.46g) is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes Phosbloc 0.01 mole of (4.58g) powder and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours; Be the tungsten filament of 0.08mm by diameter, be placed on the acute angle shape soft foam rubber cushion curving about 25 °, two edge lengths are respectively 0.8cm, boil 20 minutes with the potassium hydroxide of 50wt%, clean with distilled water flushing, dry; Above-mentioned mashed prod is coated on tungsten filament, dries and be placed in reactor, coated weight reaches the 30wt% of tungsten wire quality, is incubated 2 hours after temperature rise rate 2 DEG C/min is heated to 300 DEG C,
La
2(CO
3)
3+12KBH
4→2LaB
6+3K
2CO
3+6KH+21H
2
Discharge hydrogen, be cooled to room temperature after washing, during washing, KH and water react and generate hydrogen and potassium hydroxide, and potassium hydroxide is water-soluble, centrifugation, and at 80 DEG C, vacuum-drying obtains the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.
Embodiment 12: the electro-mirror filament performance of the coated tungsten of nano crystal lanthanum boride
In ball grinder, lithium borohydride 0.06 mole of (2.6g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes lanthanum oxalate 0.01 mole (3.15g) and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours; Be the tungsten filament of 0.lmm by diameter, be placed on the acute angle shape soft foam rubber cushion curving about 25 °, two edge lengths are 0.8cm, boil 20 minutes with the potassium hydroxide of 50wt%, clean with distilled water flushing, dry; Above-mentioned mashed prod is coated on tungsten filament, dries and be placed in reactor, coated weight reaches the 30wt% of tungsten wire quality, is incubated 2 hours after temperature rise rate 2 DEG C/min is heated to 300 DEG C,
La
2(C
2O
4)
3+12LiBH
4→2LaB
6+6CO
2+12LiH+18H
2
Discharge hydrogen and CO
2, add ether cleaning after being cooled to room temperature, lithium hydride is dissolved in ether, and after cleaning for several times, at 80 DEG C, vacuum-drying obtains the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.The diethyl ether solution of lithium hydride is evaporated solvent and obtains highly purified lithium hydride.
Embodiment 13: the electro-mirror filament performance of the coated tungsten of nano crystal lanthanum boride
In ball grinder, lithium borohydride 0.06 mole of (2.6g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes lanthanum oxalate 0.01 mole (3.15g) and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours; Be the tungsten filament of 0.lmm by diameter, be placed on the acute angle shape soft foam rubber cushion curving about 25 °, two edge lengths are 0.8cm, boil 20 minutes with the potassium hydroxide of 50wt%, clean with distilled water flushing, dry; Above-mentioned mashed prod is coated on tungsten filament, dries and be placed in reactor, coated weight reaches the 10wt% of tungsten wire quality, is incubated 2 hours after temperature rise rate 2 DEG C/min is heated to 500 DEG C,
La
2(C
2O
4)
3+12LiBH
4→2LaB
6+6CO
2+12LiH+18H
2
Discharge hydrogen and CO
2, be cooled to room temperature after washing, during washing, LiH and water react and generate hydrogen, and lithium hydroxide is water-soluble, clean vacuum-drying at latter 80 DEG C and obtain the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.Compared with only having 50 hours the work-ing life of former tungsten filament, the life-span of the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride that this example obtains reaches 150 hours, and work-ing life extends twice.
Also hydrogen and CO can discharged
2after, add ether cleaning after being cooled to room temperature, lithium hydride is dissolved in ether, and after cleaning for several times, at 80 DEG C, vacuum-drying obtains the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.The diethyl ether solution of lithium hydride is evaporated solvent and obtains highly purified lithium hydride.
Embodiment 14: lithium hydride reclaims
In ball grinder, lithium borohydride 0.06 mole of (2.6g) powder is dissolved in tetrahydrofuran (THF) (THF:20mL), then be that 1:6 (La:B=1:6) takes lanthanum oxalate 0.01 mole (3.15g) and adds ball grinder by the mol ratio of lanthanum and boron, under 400rpm rotating speed, ball milling formed mashed prod after 2 hours; Be the tungsten filament of 0.lmm by diameter, be placed on the acute angle shape soft foam rubber cushion curving about 25 °, two edge lengths are 0.8cm, boil 20 minutes with the potassium hydroxide of 50wt%, clean with distilled water flushing, dry; Above-mentioned mashed prod is coated on tungsten filament, dries and be placed in reactor, coated weight reaches the 20wt% of tungsten wire quality, is incubated 2 hours after temperature rise rate 2 DEG C/min is heated to 700 DEG C,
La
2(C
2O
4)
3+12LiBH
4→2LaB
6+6CO
2+12LiH+18H
2
Discharge hydrogen and CO
2, add ether cleaning after being cooled to room temperature, lithium hydride is dissolved in ether, and after cleaning for several times, at 80 DEG C, vacuum-drying obtains the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.The diethyl ether solution of lithium hydride is evaporated solvent and obtains highly purified lithium hydride.
If discharge hydrogen and CO
2after, wash with water after being cooled to room temperature, during washing, LiH and water react and generate hydrogen, and lithium hydroxide is water-soluble, although clean vacuum-drying at latter 80 DEG C to obtain the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride, can not reclaim lithium hydride.
Claims (6)
1. a preparation method for nano crystal lanthanum boride, is characterized in that, comprises the following steps:
Mol ratio by La: B is take lanthanum compound and alkali metal boronhydride powder at 1: 6, and add in ball grinder, under 400rpm rotating speed, ball milling is after 16 hours, obtains the mechanical mixture of lanthanum compound and alkali metal boronhydride; Mechanical mixture is placed in reactor, is incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, centrifugation after washing, vacuum-drying at 80 DEG C, obtains nano crystal lanthanum boride.
2. prepare a method for nano crystal lanthanum boride electro-mirror filament, it is characterized in that, comprise the following steps:
(1) be take lanthanum compound and alkali metal boronhydride powder at 1: 6 by the mol ratio of La: B, add in ball grinder, under 400rpm rotating speed, ball milling is after 16 hours, obtains the mechanical mixture of lanthanum compound and alkali metal boronhydride;
(2) above-mentioned mechanical mixture is imported in the groove of mould, at 1 ton/cm after filling up
2pressure real; Groove is broken line shape, and have 25 ° of acute angles, the length on acute angle both sides is 0.8cm; The cross section of groove is semicircle, and diameter is 1mm;
(3) the above-mentioned mould importing mechanical mixture is placed in reactor, is incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min from room temperature, discharges hydrogen; Then be cooled to room temperature, vacuum-drying at 80 DEG C after washing, obtain nano crystal lanthanum boride electro-mirror filament.
3. a preparation method for nano crystal lanthanum boride, is characterized in that, comprises the following steps:
In ball grinder, be dissolved in by alkali metal boronhydride in solvents tetrahydrofurane, every 100mL tetrahydrofuran (THF) containing 0.3 mole of alkali metal boronhydride, then is add lanthanum compound powder at 1: 6 by the mol ratio of La: B; Then ball milling 2 hours under 400rpm rotating speed, forms mashed prod; Mashed prod is placed in reactor, at 120 DEG C, evaporates tetrahydrofuran (THF), obtain the mechanical mixture of lanthanum compound and alkali metal boronhydride; Be incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min, discharge hydrogen; Then be cooled to room temperature, centrifugation after washing, vacuum-drying at 80 DEG C, obtains nano crystal lanthanum boride.
4. prepare a method for the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride, it is characterized in that, comprise the following steps:
(1) in ball grinder, be dissolved in by alkali metal boronhydride in solvents tetrahydrofurane, every 100mL tetrahydrofuran (THF) containing 0.3 mole of alkali metal boronhydride, then is add lanthanum compound powder at 1: 6 by the mol ratio of La: B; Then ball milling 2 hours under 400rpm rotating speed, forms mashed prod;
(2) be the tungsten filament of 0.08 ~ 0.lmm by diameter, be placed on the acute angle shape soft foam rubber cushion curving 25 °, the length on acute angle both sides is 0.8cm; After tungsten filament is boiled 20 minutes with the potassium hydroxide of 50wt%, clean with distilled water flushing, dry;
(3) mashed prod that step (1) is obtained is coated on tungsten filament, coated weight is 10 ~ 30wt% of tungsten wire quality; Dry and be placed in reactor, be incubated 2 hours after being heated to 300 ~ 700 DEG C with the temperature rise rate of 2 DEG C/min, discharge hydrogen; Be cooled to room temperature, with vacuum-drying at 80 DEG C after water or washed with diethylether, obtain the high-performance electro-mirror filament of the coated tungsten of nano crystal lanthanum boride.
5. according to the method described in Claims 1-4 any one, it is characterized in that, described lanthanum compound is lanthanum trioxide, lanthanum hydroxide, Phosbloc or lanthanum oxalate.
6. according to the method described in Claims 1-4 any one, it is characterized in that, described alkali metal boronhydride is lithium borohydride, sodium borohydride or POTASSIUM BOROHYDRIDE.
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