CN104831352B - A kind of high purity high dense（LaxSm1‑x）B6Polycrystalline cathode material and preparation method thereof - Google Patents
A kind of high purity high dense（LaxSm1‑x）B6Polycrystalline cathode material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a kind of high purity high dense（LaxSm1‑x）B6 polycrystalline cathode material and preparation method, belong to rare-earth boride cathode material technical field.The preparation method comprises the following steps：1) ball milling, by La2O3、Sm2O3Mixed with boron powder according to stoichiometric proportion, the ball milling under high-purity argon gas protection；2) shove charge, by ball-milled powder it is die-filling after be placed in hot-pressed sintering furnace；3) heating sintering, vacuum reaction sintering is carried out by powder；4) it is incubated, 1,700 1850 DEG C of 1.5 2h of insulation；5) cool, insulation terminates recession pressure, with the cold cooling of stove, obtains (LaxSm1‑x)B6Polycrystal, wherein 0≤x≤1.Powder synthesis and two processes of sintering densification are combined into one by the present invention, simplify preparation flow, improve purity and consistency, and reduce production cost, are adapted to industrial production and application.Polycrystal prepared by the present invention has the characteristics of single-phase, high-purity, high-compactness.
Description
Technical field
The invention belongs to rare-earth boride cathode material technical field, and in particular to a kind of high purity high dense multielement rare earth boron
Compound (LaxSm1-x)B6Cathode material and preparation method thereof.
Background technology
Rare-earth hexboride compound (REB6) especially lanthanum hexaboride (LaB6), due to possessing compared with low work function, high-melting-point, strong resistance to
The features such as Ions Bombardment and stable chemical property, it is good cathode material, there is excellent thermionic emission and Flied emission
Performance, it is civilian to be widely used in the sophisticated technology such as high power valve, plasma, Electronic Speculum department and automobile, electronics etc.
Industrial circle.In the recent period, domestic and foreign scholars accelerate the research to multicomponent rare earth boride.The discovery of applicant's early-stage Study,
(La0.6Sm0.4)B6With LaB6Compared to the hot-electron emission property with lower operating temperature and Geng Gao.This shows, appropriate Sm
Doping is expected to reduce LaB6Negative electrode operating temperature simultaneously greatly improves its hot-electron emission property.In addition, SmB6As radiation shield
With control rod materials application in neutron reactor, SmB6A kind of or excellent high temperature semiconductors material.It recent studies have shown that,
SmB6It is first topological Kondo insulator, possible application is spintronics material.Therefore, (LaxSm1-x)B6With wide
Application prospect.
At present, the preparation of rare-earth boride polycrystalline material generally requires in two steps, first prepares rare-earth boride powder, then adopt
With the method for cold-rolled sintered, hot pressed sintering or SPS discharge plasma sinterings to powder sintered densification, wherein SPS electric discharges etc. from
Sub- technology can also use reaction-sintered.Prepared by cold-rolled sintered and hot pressed sintering all has sintering temperature height (2000-2200 DEG C), system
The problems such as standby product consistency low (relative density is generally below 90%), mechanical property and emitting performance difference, cause product difficult
To apply in the industrial production.SPS discharge plasma sinterings are a kind of Fast Sintering technologies, but this method is to equipment requirement
Height, and yield is relatively low, is not suitable for the industrialization of product.
A kind of LaB is disclosed in the Chinese patent application of Publication No. 201310492257.96The preparation side of polycrystal
Method.This method comprises the following steps：Shove charge, LaB will be housed6The mould of powder is placed in sintering furnace；Heating, is divided into four-stage
Temperature is progressively increased to predetermined temperature from room temperature；Stop pressure and slow cooling, obtain LaB6Polycrystal.Wherein four temperature rise periods
Including：First temperature rise period：Room temperature is to 600-800 DEG C；Second temperature rise period：600-800 DEG C to 1600-1750 DEG C；3rd liter
Thermophase：1600-1750 DEG C to 1850-1900 DEG C；4th temperature rise period：1850-1900 DEG C to the predetermined temperature.Moreover,
3rd temperature rise period is to LaB6Powder applies the pressure less than 3Mpa；4th temperature rise period is to LaB6Powder applies 3-15Mpa's
Pressure.The soaking time of 3rd temperature rise period is 1-2 hours.To LaB6For prepared by polycrystalline bulk, this method does not include powder
Synthesis, be only the second step in conventional two-step, i.e., to raw material LaB6The process of powder sintered densification, therefore product is pure
Purity of the degree dependent on material powder.And sintering temperature is higher, the density of product is not high, relative density 92-96%.
One kind is disclosed in the Chinese patent application of Publication No. 200810225030.7 and utilizes discharge plasma sintering
It is quick to prepare LaB6The method of polycrystalline bulk cathode material, this method comprise the following steps：By LaB6Material powder loads graphite mo(u)ld
In tool, place into SPS sintering furnaces and be sintered after pressurization 10MPa compactings.Sintering process is：Axial compressive force 30-50MPa, gas
Atmosphere is the vacuum that high-purity argon gas or vacuum are higher than 5Pa, is heated up with 90-200 DEG C/min programming rate, and sintering temperature is
1400-1700 DEG C, soaking time 5-20min.Insulation terminate after with being furnace-cooled to room temperature.LaB prepared by this method6Product
Can be preferable, but it is high to equipment requirement, and yield is relatively low, is not suitable for the industrialization of product.In addition, this method is only powder sintered cause
Densification, the preparation not comprising material powder.The polycrystalline product purity of preparation depends on commercial raw material LaB6The purity of powder.
A kind of high purity high dense multielement rare earth boron is disclosed in the Chinese patent application of Publication No. 200810225029
Compound (LaxRE1-x)B6Cathode material and preparation method thereof, wherein RE are second of rare earth in addition to La in LREE
Element (i.e. RE is any one element in Ce, Pr, Nd, Sm, Eu and Gd).This method comprises the following steps：(1) respectively with
Simple substance rare earth lanthanum block and RE blocks are raw material, in hydrogen, argon atmospher, using DC arc-plasma evaporation condensation method, are prepared respectively
LaH2Nanometer powder and REH2Nanometer powder.(2) LaH that step (1) is prepared2Nanometer powder, REH2Nanometer powder with
Under hypoxemia ar gas environment, grinding is mixed and loads graphite jig raw material B nanometer powders, is placed in SPS sintering cavities, applies
50MPa axial compressive force, sintered under the vacuum condition of argon gas atmosphere or vacuum better than 8Pa, sintering temperature 1300-
1700 DEG C, room temperature is cooled to the furnace after being incubated 10min.This method prepares (LaxRE1-x)B6Polycrystalline needs two steps altogether：First
Rare earth nano powder is prepared using arc evaporation condensation method, polycrystalline bulk is then obtained using SPS sintering densifications.Preparation process
Relatively complicated, equipment is expensive, and raw material need to use high purity elemental rare earth metal, and cost is higher, and yield is relatively low unsuitable extensive raw
Production.
The content of the invention
In order to solve existing rare-earth boride polycrystalline preparation complex steps, cost is too high, product consistency is relatively low
The problems such as influenceing performance, the present invention provide a kind of high purity high dense multicomponent rare earth boride (LaxSm1-x)B6Polycrystalline cathode material and
Its preparation method.Rare-earth boride polycrystalline composition provided by the present invention is (LaxSm1-x)B6, wherein, 0≤x≤1.The present invention
The method provided is using RE oxide powder and boron powder as raw material, using vacuum hotpressing reaction-sintered.Powder is synthesized and burnt
Two processes of knot densification are combined into one, and simplify preparation flow, improve purity and consistency, and reduce production cost, are adapted to work
Industry produces and application.(the La obtained according to preparation method provided by the inventionxSm1-x)B6Polycrystal has single-phase, high-purity, height
The characteristics of consistency, be advantageous to expand the application of rare-earth boride polycrystalline material.
It is an aspect of the invention to provide one kind (LaxSm1-x)B6The preparation method of polycrystal.The preparation method is specific
Step is as follows：
1) ball milling, by La2O3、Sm2O3With boron powder according to reaction equation xLa2O3(s)+(1-x) Sm2O3(s)+15B(s)→2
(LaxSm1-x)B6(s)+3BO (g) stoichiometric proportion, i.e. mol ratio are x:(1-x):15 are mixed, and are subsequently placed in stainless steel
In grinding pot, φ 14mm, φ 12mm, φ 10mm, φ 8mm and φ 6mm stainless steel ball are selected as abrasive media, it is preferably stainless
Steel ball φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm mass ratio are 1： 1：3：2：1, ball and powder quality ratio are (10-
20)：1；It is oxidized to prevent from mixing the boron powder in powder, above operation is carried out in glove box.Ball grinder is placed in high energy
Ball milling is carried out in ball mill, sampling is preserved in glove box after rotating speed 500-700r/min, ball milling 1-2h；
2) shove charge, the La that step 1) ball milling is obtained2O3、Sm2O3Load graphite jig in glove box with boron powder, by stone
Black mould is placed in vacuum sintering funace；
3) heating sintering, the first temperature rise period：Room temperature is to 400-600 DEG C；Second temperature rise period：From the 400- of first stage
600 DEG C are warming up to 800-1000 DEG C；3rd temperature rise period：1200-1400 DEG C is warming up to from 800-1000 DEG C of second stage；The
Four temperature rise periods：1700-1850 DEG C is warming up to from 1200-1400 DEG C of the phase III；Wherein, the first temperature rise period is to the 4th liter
Thermophase is applied to applying axial compressive force, pressure limit 5-20MPa, the first temperature rise period and the second temperature rise period to powder to powder
Add identical axial compressive force, then the axial compressive force per the temperature rise period is stepped up；It is preferred that the first temperature rise period and the second heating
Stage applies 5Mpa axial compressive forces to powder, and the 3rd temperature rise period applied 10Mpa axial compressive forces to powder；4th temperature rise period
20Mpa axial compressive forces are applied to powder；
4) it is incubated, the 1700-1850 DEG C of temperature 1.5-2h after the heating of step 3) fourth stage；And it had been incubated
Journey applies 30-40Mpa axial compressive forces to powder；
5) cool, step 4) insulation terminates recession pressure, with the cold cooling of stove, obtains (the LaxSm1-x) B6Polycrystal.
Preferably, the raw material La described in step 1)2O3And Sm2O3Up to 99.99%, the purity of boron powder reaches the purity of powder
99%, and the particle size range of the material powder is 1-50 μm.But the present invention is not limited to above-mentioned raw materials, different-grain diameter
La2O3、Sm2O3It is applicable to the present invention with simple substance boron powder and other RE oxide powders.
Preferably, in step 1) and step 2), oxygen content and vapour content are equal in argon gas atmosphere in the glove box
≤5ppm。
Preferably, in step 2), the ball-milled powder is loaded before graphite jig with graphite paper coating mould
Wall, also need to cover graphite paper with powder upper and lower surface contact position.
Preferably, the heating rate of each temperature rise period described in step 3) is 5-15 DEG C/min, the first temperature rise period and
The heating rate of second temperature rise period is identical or different.
Preferably, before sintering in the step 3), forvacuum is to air pressure≤1 × 10 in the hot pressing furnace-2Pa。
It is another aspect of the invention to provide a kind of high purity high dense (LaxSm1-x)B6Polycrystal negative electrode, wherein, 0≤
x≤1.The negative electrode includes (La prepared by the above methodxSm1-x)B6Polycrystal, using (La obtained by the method for the present inventionxSm1-x)B6
Polycrystal relative density is 96.17-99.63%, by this (LaxSm1-x)B6Polycrystal processing can obtain required shape and chi
Very little negative electrode.
Method provided by the present invention is using RE oxide powder and boron powder as raw material, using vacuum hotpressing reaction-sintered.
Powder synthesis and two processes of sintering densification are combined into one, simplify preparation flow, improves purity and consistency, and reduce life
Cost is produced, is adapted to industrial production and application.(the La obtained according to preparation method provided by the inventionxSm1-x)B6Polycrystal has
The characteristics of single-phase, high-purity, high-compactness, be advantageous to expand the application of rare-earth boride polycrystalline material.
Compared with prior art, the present invention has advantages below：
1) the inventive method uses vacuum hotpressing reaction-sintered, and two processes of powder synthesis and sintering densification are closed into two is
One.Preparation flow is simplified, technique is simple, easy to operate.
2) La is used2O3、Sm2O3It is raw material with boron powder, reduces production cost, is adapted to industrial production and application, is advantageous to
Expand application field of the rare-earth boride in terms of cathode material.
3) (the La of synthesisxSm1-x)B6With high-purity and high-compactness.(the La preparedxSm1-x) B6Polycrystalline is through X ray
Diffraction is detected as single hexaboride phase, and relative density is up to 99.63%.
Brief description of the drawings
LaB prepared by Fig. 1, embodiment 16Polycrystalline X-ray spectrogram.
(La prepared by Fig. 2, embodiment 20.9Sm0.1)B6Polycrystalline X-ray spectrogram.
(La prepared by Fig. 3, embodiment 30.7Sm0.3)B6Polycrystalline X-ray spectrogram.
(La prepared by Fig. 4, embodiment 40.1Sm0.9)B6Polycrystalline X-ray spectrogram.
SmB prepared by Fig. 5, embodiment 56Polycrystalline X-ray spectrogram.
Embodiment
Below in conjunction with the drawings and specific embodiments, the invention will be further described, but protection scope of the present invention is unlimited
In following embodiments.The present invention is described in detail below with reference to accompanying drawing in conjunction with the embodiments, in the case where not conflicting, this Shen
Please in embodiment and embodiment in feature can be mutually combined.
Raw material La in the embodiment of the present invention2O3And Sm2O3The purity of powder is 99.99%, and boron powder purity is 99%, former
The particle size range at feed powder end is 1-50 μm.
Embodiment 1
1) ball milling.By La2O3With boron powder according to reaction equation La2O3(s)+15B(s)—— 2LaB6(s)+3BO (g) chemistry
Ratio is measured, i.e. mol ratio is 1:15 are mixed, and powder gross mass is 20g.It is subsequently placed in 250ml stainless-steel grinding tanks, selects
φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm stainless steel ball are selected as abrasive media, stainless steel ball φ 14mm, φ
12mm, φ 10mm, φ 8mm, φ 6mm mass ratio are 1：1：3：2：1, ball is 10 with powder quality ratio：1.To prevent from mixing powder
Boron powder in end is not oxidized, above operation oxygen content and vapour content≤5ppm argon gas atmosphere glove box in enter
OK.Ball grinder is placed in high energy ball mill and carries out ball milling, is sampled after rotating speed 500r/min, ball milling 2h in glove box.2)
Shove charge.The mixed-powder that ball milling is obtained loads φ 20mm graphite jigs in glove box, and mould is placed in into vacuum heating-press sintering
In stove.3) heating sintering.Air pressure 1 × 10 is evacuated in hot pressing furnace-2Pa, sintering process are：Pre-add 5Mpa axial compressive forces, with 5
DEG C/min heating rates rise to 400 DEG C from room temperature.Then 800 DEG C are risen to from 400 DEG C with 15 DEG C/min speed.Keep 10Mpa axles
To pressure, 1200 DEG C are risen to from 800 DEG C with 10 DEG C/min speed.Axial compressive force is forced into 20Mpa, with 10 DEG C/min speed from
1200 DEG C rise to 1750 DEG C.4) it is incubated.40Mpa is forced into when temperature reaches 1750 DEG C, is incubated 2h.5) cool.Insulation knot
Beam recession pressure, with the cold cooling of stove, obtains single-phase fine and close LaB6Polycrystal.
LaB6The X-ray spectrogram of polycrystal is as shown in figure 1, it can be seen that sample is LaB6Single-phase, diffraction peak intensity is high,
Well-crystallized.LaB is measured using electronics specific gravity balance6The relative density of polycrystal is 99.58%.
Embodiment 2
1) ball milling.By La2O3、Sm2O3With pure boron powder according to reaction equation 0.9La2O3(s)+0.1 Sm2O3(s)+15B
(s)——2(La0.9Sm0.1)B6(s)+3BO (g) stoichiometric proportion, i.e. mol ratio are 0.9:0.1:15 are mixed, powder
Gross mass is 30g.It is subsequently placed in 250ml stainless-steel grinding tanks, selects φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm
Stainless steel ball as abrasive media, stainless steel ball φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm mass ratio are 1：1：
3：2：1, ball is 10 with powder quality ratio：1.It is not oxidized to prevent from mixing the boron powder in powder, above operation in oxygen content and
Vapour content≤0.5ppm argon gas atmosphere glove box in carry out.Ball grinder is placed in high energy ball mill and carries out ball milling,
Rotating speed is 500r/min, is sampled after ball milling 2h in glove box.2) shove charge.The mixed-powder that ball milling is obtained fills in glove box
Enter φ 30mm graphite jigs, mould is placed in vacuum sintering funace.3) heating sintering.Air pressure 9 is evacuated in hot pressing furnace
×10-3Pa, sintering process are：Pre-add 5Mpa axial compressive forces, 500 DEG C are risen to from room temperature with 10 DEG C/min heating rates.Then with
15 DEG C/min speed rises to 900 DEG C from 500 DEG C.10Mpa axial compressive forces are kept, 1300 are risen to from 900 DEG C with 10 DEG C/min speed
℃.Axial compressive force is forced into 20Mpa, and 1800 DEG C are risen to from 1300 DEG C with 15 DEG C/min speed.4) it is incubated.When temperature reaches 1800
DEG C when be forced into 30Mpa, be incubated 2h.5) cool.Insulation terminates recession pressure, with the cold cooling of stove, obtains single-phase densification
(La0.9Sm0.1)B6Polycrystal.
(La0.9Sm0.1)B6The X-ray spectrogram of polycrystal is as shown in Fig. 2 it can be seen that sample is (La0.9Sm0.1)B6It is single
Phase, diffraction peak intensity is high, well-crystallized.(La is measured using electronics specific gravity balance0.9Sm0.1)B6The relative density of polycrystal is
96.57%.
Embodiment 3
1) ball milling.By La2O3、Sm2O3With pure boron powder according to reaction equation 0.7La2O3(s)+0.3 Sm2O3(s)+15B
(s)——2(La0.7Sm0.3)B6(s)+3BO (g) stoichiometric proportion, i.e. mol ratio are 0.7:0.3:15 are mixed, powder
Gross mass is 20g.It is subsequently placed in 250ml stainless-steel grinding tanks, selects φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm
Stainless steel ball as abrasive media, stainless steel ball φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm mass ratio are 1：1：
3：2：1, ball is 15 with powder quality ratio：1.More than operation be≤1ppm argon gas atmosphere hand in oxygen content and vapour content
Carried out in casing.Ball grinder is placed in high energy ball mill and carries out ball milling, after rotating speed 700r/min, ball milling 1h in glove box
Sampling.2) shove charge.The mixed-powder that ball milling is obtained loads φ 20mm graphite jigs in glove box, and mould is placed in into Vacuum Heat
Press in sintering furnace.3) heating sintering.Air pressure 8 × 10 is evacuated in hot pressing furnace-3Pa, sintering process are：Pre-add 5Mpa is axially pressed
Power, 600 DEG C are risen to from room temperature with 8 DEG C/min heating rates.Then 1000 DEG C are risen to from 600 DEG C with 15 DEG C/min speed.Keep
10Mpa axial compressive forces, 1400 DEG C are risen to from 1000 DEG C with 10 DEG C/min speed.Axial compressive force is forced into 20Mpa, with 10 DEG C/min
Speed rises to 1700 DEG C from 1400 DEG C.4) it is incubated.30Mpa is forced into when temperature reaches 1700 DEG C, is incubated 1.5h.5) cool.
Insulation terminates recession pressure, with the cold cooling of stove, obtains single-phase densification (La0.7Sm0.3)B6Polycrystal.
(La0.7Sm0.3)B6The X-ray spectrogram of polycrystal is as shown in figure 3, it can be seen that sample is (La0.7Sm0.3)B6It is single
Phase, diffraction peak intensity is high, well-crystallized.(La is measured using electronics specific gravity balance0.7Sm0.3)B6The relative density of polycrystal is
96.17%.
Embodiment 4
1) ball milling.By La2O3、Sm2O3With pure boron powder according to reaction equation 0.1La2O3(s)+0.9 Sm2O3(s)+15B
(s)——2(La0.1Sm0.9)B6(s)+3BO (g) stoichiometric proportion, i.e. mol ratio are 0.1:0.9:15 are mixed, powder
Gross mass is 20g.It is subsequently placed in 250ml stainless-steel grinding tanks, selects φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm
Stainless steel ball as abrasive media, stainless steel ball φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm mass ratio are 1：1：
3：2：1, ball is 20 with powder quality ratio：1.More than operation be≤5ppm argon gas atmosphere hand in oxygen content and vapour content
Carried out in casing.Ball grinder is placed in high energy ball mill and carries out ball milling, in glove box after rotating speed 600r/min, ball milling 1.5h
Middle sampling.2) shove charge.The mixed-powder that ball milling is obtained loads φ 20mm graphite jigs in glove box, and mould is placed in into vacuum
In hot-pressed sintering furnace.3) heating sintering.Air pressure 8.5 × 10 is evacuated in hot pressing furnace-3Pa, sintering process are：Pre-add 5Mpa axles
To pressure, 500 DEG C are risen to from room temperature with 6 DEG C/min heating rates.Then 900 DEG C are risen to from 500 DEG C with 15 DEG C/min speed.
10Mpa axial compressive forces are kept, 1300 DEG C are risen to from 900 DEG C with 10 DEG C/min speed.Axial compressive force is forced into 20Mpa, with 15 DEG C/
Min speed rises to 1800 DEG C from 1300 DEG C.4) it is incubated.40Mpa is forced into when temperature reaches 1800 DEG C, is incubated 1.5h.5) drop
Temperature.Insulation terminates recession pressure, with the cold cooling of stove, obtains single-phase densification (La0.1Sm0.9)B6Polycrystal.
(La0.1Sm0.9)B6The X-ray spectrogram of polycrystal is as shown in figure 4, it can be seen that sample is (La0.1Sm0.9)B6It is single
Phase, diffraction peak intensity is high, well-crystallized.(La is measured using electronics specific gravity balance0.1Sm0.9)B6The relative density of polycrystal is
99.33%.
Embodiment 5
1) ball milling.By Sm2O3With pure boron powder according to reaction equation Sm2O3(s)+15B(s)——2SmB6(s)+3BO (g)
Stoichiometric proportion, i.e. mol ratio are 1:15 are mixed, and powder gross mass is 20g.It is subsequently placed in 250ml stainless-steel grinding tanks
In, φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm stainless steel ball are selected as abrasive media, stainless steel ball φ 14mm,
φ 12mm, φ 10mm, φ 8mm, φ 6mm mass ratio are 1：1：3：2：1, ball is 10 with powder quality ratio：1.Operation exists above
Oxygen content and vapour content≤0.2ppm argon gas atmosphere glove box in carry out.Ball grinder is placed in high energy ball mill
Ball milling is carried out, is sampled after rotating speed 500r/min, ball milling 2h in glove box.2) shove charge.The mixed-powder that ball milling is obtained exists
Load φ 20mm graphite jigs in glove box, mould is placed in vacuum sintering funace.3) heating sintering.Taken out in hot pressing furnace true
It is empty to air pressure 1 × 10-2Pa, sintering process are：Pre-add 5Mpa axial compressive forces, 500 are risen to from room temperature with 6 DEG C/min heating rates
℃.Then 900 DEG C are risen to from 500 DEG C with 15 DEG C/min speed.10Mpa axial compressive forces are kept, with 10 DEG C/min speed from 900 DEG C
Rise to 1300 DEG C.Axial compressive force is forced into 20Mpa, and 1800 DEG C are risen to from 1300 DEG C with 15 DEG C/min speed.4) it is incubated.Work as temperature
Degree is forced into 40Mpa when reaching 1800 DEG C, be incubated 2h.5) cool.Insulation terminates recession pressure, with the cold cooling of stove, obtains single-phase cause
Close SmB6Polycrystal.
SmB6The X-ray spectrogram of polycrystal is as shown in figure 5, it can be seen that sample is SmB6Single-phase, diffraction peak intensity is high,
Well-crystallized.SmB is measured using electronics specific gravity balance6The relative density of polycrystal is 99.63%.
Claims (8)
1. one kind (LaxSm1-x)B6The preparation method of polycrystal, 0≤x≤1, the preparation method comprise the following steps that：
1) ball milling, by La2O3、Sm2O3With boron powder according to reaction equation xLa2O3(s)+(1-x)Sm2O3(s)+15B(s)→2
(LaxSm1-x)B6(s)+3BO (g) stoichiometric proportion, i.e. mol ratio are x:(1-x):15 are mixed, and are subsequently placed in stainless steel
In grinding pot, φ 14mm, φ 12mm, φ 10mm, φ 8mm and φ 6mm stainless steel ball are selected as abrasive media, ball and powder
Mass ratio is (10-20)：1；Operation is carried out in glove box above, and ball grinder is placed in high energy ball mill and carries out ball milling,
Rotating speed is 500-700r/min, and sampling is preserved in glove box after ball milling 1-2h；
2) shove charge, the La that step 1) ball milling is obtained2O3、Sm2O3Load graphite jig in glove box with boron powder, by graphite jig
It is placed in vacuum sintering funace；
3) heating sintering, the first temperature rise period：Room temperature is to 400-600 DEG C；Second temperature rise period：From the 400-600 of first stage
DEG C it is warming up to 800-1000 DEG C；3rd temperature rise period：1200-1400 DEG C is warming up to from 800-1000 DEG C of second stage；4th
Temperature rise period：1700-1850 DEG C is warming up to from 1200-1400 DEG C of the phase III；Wherein, the first temperature rise period to the 4th heating
Stage to powder to applying axial compressive force, pressure limit 5-20MPa；
4) it is incubated, the 1700-1850 DEG C of temperature 1.5-2h after the heating of step 3) fourth stage；And in insulating process to powder
End applies 30-40Mpa axial compressive forces；
5) cool, step 4) insulation terminates recession pressure, with the cold cooling of stove, obtains (the LaxSm1-x)B6Polycrystal.
2. according to the method for claim 1, it is characterised in that raw material La described in step 1)2O3And Sm2O3The purity of powder reaches
99.99%, the purity of boron powder is up to 99%, and the particle size range of the material powder is 1-50 μm；
In step 1) and step 2), in the glove box in argon gas atmosphere oxygen content and vapour content≤5ppm.
3. according to the method for claim 1, it is characterised in that in step 2), the ball-milled powder is loaded before graphite jig
With the inwall of graphite paper coating mould, also need to cover graphite paper with powder upper and lower surface contact position.
4. according to the method for claim 1, it is characterised in that stainless steel ball φ 14mm, φ 12mm, φ 10mm, φ 8mm, φ 6mm
Mass ratio be 1：1：3：2：1.
5. according to the method for claim 1, it is characterised in that the temperature rise period of step 3) first and the second temperature rise period apply to powder
Add identical axial compressive force, then the axial compressive force per the temperature rise period is stepped up.
6. according to the method for claim 1, it is characterised in that the temperature rise period of step 3) first and the second temperature rise period apply to powder
Add 5Mpa axial compressive forces, the 3rd temperature rise period applied 10Mpa axial compressive forces to powder；4th temperature rise period applied to powder
20Mpa axial compressive forces.
7. according to the method for claim 1, it is characterised in that the heating rate of each temperature rise period described in step 3) is 5-15
DEG C/mi n, the heating rate of the first temperature rise period and the second temperature rise period is identical or different.
8. according to the method for claim 1, it is characterised in that before being sintered in step 3), forvacuum in the hot pressing furnace
To air pressure≤1 × 10-2Pa。
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| CN111825463A (en) * | 2020-06-29 | 2020-10-27 | 井冈山大学 | LaB6-CrB2Composite cathode material and preparation method thereof |
| CN114920560A (en) * | 2022-05-05 | 2022-08-19 | 兰州理工大学 | LaB 6 Powder and method for producing sintered body thereof |
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