CN107500768A

CN107500768A - A kind of preparation method of boron carbide ceramics, boron carbide ceramics and its application

Info

Publication number: CN107500768A
Application number: CN201710607749.6A
Authority: CN
Inventors: 柯于斌; 曹磊; 陶举洲; 杜慧玲
Original assignee: Dongguan Neutron Science Center
Current assignee: Dongguan Neutron Science Center
Priority date: 2017-07-24
Filing date: 2017-07-24
Publication date: 2017-12-22

Abstract

This application discloses a kind of preparation method of boron carbide ceramics, boron carbide ceramics and its application.The boron carbide ceramics preparation method of the application includes (1) and mixes boron carbide powder and silicate glass powder, and compound is made；(2) the adding additives solution in compound, it is granulated；(3) granulated pellet is poured into mould, 5 30MPa compacting biscuits；(4) biscuit is dried, and less than 1000 DEG C sintering, are made boron carbide ceramics under inert atmosphere, reducing atmosphere or vacuum.The present processes, boron carbide ceramics low-temperature atmosphere-pressure sintering is realized, energy consumption is low, simple to operation, and cost is low；Silicate glass powder raw material is abundant, price is low, easy acquisition, reduce further cost；The boron carbide ceramics of preparation is not hydrogeneous, and neutron scattering back end can be greatly reduced, particularly suitable for making neutron-absorbing and shielding device around detector.The boron carbide ceramics material that it is good that the present processes are high-volume large-scale production neutron shield effect is laid a good foundation.

Description

A kind of preparation method of boron carbide ceramics, boron carbide ceramics and its application

Technical field

The application is related to boron carbide ceramics field, more particularly to a kind of preparation method of boron carbide ceramics, the carbon of preparation Change boron ceramics, and its application.

Background technology

Boron carbide, alias black diamond, usually grey black micro mist, is that a kind of hardness is only second to diamond and cubic boron nitride Material, Mohs' hardness 9.3, microhardness 55-67Gpa.The chemical stability of boron carbide is good, under normal temperature not with acid, alkali and big The reaction of most compounds, only has slow corrosion in the sulfuric acid of hydrofluoric acid one, the nitrate mixture of hydrofluoric acid one, be chemical property most One of stable compound.Meanwhile the small only 2.52g/cm of boron carbide density³, high temperature hardness it is high, also there is excellent slow neutron to inhale Receipts ability.Therefore, boron carbide is in wear-resisting, corrosion-resistant device, bullet resistant material, engine shower nozzle, blast nozzle, ceramic bearing, grinding The fields such as medium, nuclear energy and neutron shielding material suffer from important application.

Because boron carbide has excellent neutron absorption capability so that it has extremely importantly in nuclear industry field Position.The use of more neutron absorber material is exactly boron carbide in traditional nuclear industry field at present, that has announced in the world is anti- Answer in heap, significant fraction is often from boron carbide as the regulating rod of nuclear reactor, control rod, shielding rod and neutron shield material Material, wherein the importance of shielding rod is only second to fuel element.

C and B atomic radius is very close to the electronegativity of the two differs very little, forms very strong covalent bond, altogether in boron carbide Valence link ratio is up to 93.94%, causes the densification sintering of pure boron carbide extremely difficult.Common B₄C powder is at 2250-2300 DEG C The relative density of sintering acquisition finished product can only achieve 80%-87% under normal pressure, it usually needs using boron carbide superfines and adopt With hot pressed sintering, HIP sintering or discharge plasma sintering (abbreviation SPS) technology for growing up in recent years 2000 It is sintered more than DEG C；Even current its sintering temperature of addition sintering aid is also more than 1600 DEG C.Such as patent CN1541981A prepares lightweight boron carbide armor ceramic by 2200 DEG C -2300 DEG C of hot pressed sintering；Jiang Guoxin and Wang Shenghong exist Using boron carbide powder of the particle diameter less than 1 μm in the document report " low temperature and pressure of boron carbide " of nineteen ninety-five, Al is added₂O₃As burning Auxiliary agent is tied, boron carbide ceramics ceramics are prepared under 1750 DEG C, 35MPa hot pressing conditions.Due to the sintering of existing boron carbide ceramics It is complex process, high energy consumption, costly, its use is limited, is also not suitable for large-scale industrialized production.

Neutron is the powerful measure that the mankind explore material microcosmos, and neutron is not charged, has that magnetic moment, penetration power be strong, energy Light element, isotope and neighbour's element are differentiated, and to sample without destructiveness, therefore Neutron scattering technology is in biology, life, country The research field important role such as the energy, environment and new material.To adapt to the application requirement of different field, it is necessary to build all kinds of The neutron scattering spectrometer of different purposes.In the design-build of neutron scattering spectrometer, signal to noise ratio is to weigh all kinds of Spectrometer performances One common important indicator.In order to reduce the background of the spectrometer caused by stray neutron, it is necessary to around spectrometer bunch largely Use neutron absorber material.Especially around the bunch of neutron detector, it is desirable to which the neutron absorber material of use is as far as possible It is few containing being also easy to produce the larger member of the elements such as active element such as Ni, Co, Cu of spurious signal and inelastic neutron scattering section Element such as typical H element.And moderating effect of the existing neutron absorber material based on boron carbide for enhancing to high-energy neutron, mostly Contain more H element, such as Boron-containing-PE.Patent CN 104310400A prepare the carbon of shaping using colloid adhesive solidification Change boron-based neutron absorber, although reducing protium content, a certain amount of protium is still contained in the material, is unsuitable for As the neutron absorber material around detector.

The content of the invention

The purpose of the application is to provide a kind of preparation method of new boron carbide ceramics, the hydrogen-free boron carbide ceramics of preparation and It is applied.

The application employs following technical scheme：

The one side of the application discloses a kind of preparation method of boron carbide ceramics, comprises the following steps,

(1) boron carbide powder and silicate glass powder are well mixed by ball milling or ultrasonic disperse, compound is made；

(2) binder solution is added in the compound of step (1), is granulated；

(3) particle prepared by step (2) is poured into mould, biscuit is pressed under 5-30MPa pressure；

(4) biscuit of step (3) is dried, then sinters, be made under inert atmosphere, reducing atmosphere or vacuum condition Boron carbide ceramics, the temperature of sintering are less than 1000 DEG C.

Wherein, biscuit drying is generally dried to constant weight；Binder solution can use conventional binding agent.

It should be noted that the preparation method of the application, adds silicate glass powder, due to silicate in boron carbide powder The introducing of glass dust, reduces sintering temperature, realizes the sintering under the low temperature and normal pressure less than 1000 DEG C first and prepares carbonization Boron ceramics.Also, the preparation method of the application, is first dried to biscuit, wherein most distilled water and easily evaporation material are removed Material, is finally sintered, the oxidation for overcoming boron carbide in sintering process is asked under inert atmosphere, reducing atmosphere or vacuum condition Topic, so as to successfully solve sintered body water suction pulverizing problem, make the boron carbide ceramics of preparation there is excellent water resistance.This Outside, protium is free of in the boron carbide ceramics that prepared by the application, especially suitable for making neutron-absorbing and screen around detector Cover device.

Preferably, boron carbide powder accounts for the 50-90% of step (1) compound gross weight, and it is mixed that silicate glass powder accounts for step (1) The 10-50% of material gross weight is closed, the dosage of binder solution is the 1.5-22% of step (1) compound gross weight.

It should be noted that the addition of silicate glass powder can reduce sintering temperature, so as to realize low-temperature sintering, the application Low temperature refer to temperature less than 1000 DEG C, belong to low temperature for existing sintering method；It is appreciated that glassy silicate The amount that glass powder adds can directly affect low sintering temperature, and still, the amount of addition is bigger, can also influence the material of boron carbide in itself Expect performance, therefore, the dosage of boron carbide and silicate glass powder is defined in the preferred scheme of the application, it is low realizing While temperature sintering, the effective self performance for ensureing boron carbide material.It should be added that the application is to ensure carbon Change boron carbide and the silicate glass powder dosage that boron ceramic material limits as the angle of neutron-absorbing shielding material, if its Its purposes, such as wear resistant corrosion resistant device, bullet resistant material, engine shower nozzle, blast nozzle, ceramic bearing, abrasive media etc., carbonization Boron and silicate glass powder dosage can be adjusted voluntarily, as long as can realize that low-temperature sintering prepares boron carbide ceramics.

Preferably, the purity of boron carbide powder is more than 95wt.%, and the purity of silicate glass powder is more than 95wt.%, also, The particle diameter of boron carbide powder is less than 250 microns.

Preferably, protium is free of in silicate glass powder.

It should be noted that in the preparation method of the application or prepared boron carbide ceramics, can also contain other Additive, to improve the performance of boron carbide ceramics, as long as not hydrogeneous, without easily-activated element and inelastic neutron scattering section Larger element, other doped chemicals or additive, may be referred to existing preparation method and boron carbide ceramics, herein not It is specifically limited.

Preferably, binding agent is at least one of polyvinyl alcohol, phenolic resin, starch, carbohydrate, cellulose and dextrin.

Preferably, biscuit includes but are not limited to cylinder, strip or long plate shape.

It should be noted that biscuit can be prepared into according to use demand it is variously-shaped, wherein relatively common i.e. cylinder Shape, strip or long plate shape.

Preferably, the temperature of drying is less than 100 DEG C in step (4).

Preferably, in step (4), the temperature of sintering is 500 DEG C -765 DEG C, sintering time 0.5h-4h.

The another side of the application discloses boron carbide ceramics prepared by the preparation method of the application.

It should be noted that compared with existing boron carbide material, the boron carbide ceramics of the preparation method acquisition of the application, Without protium, especially suitable for the neutron-absorbing shielding around detector.

Application of the boron carbide ceramics for simultaneously disclosing the application again of the application in neutron-absorbing or neutron shield.

It should be noted that the boron carbide ceramics of the application is free of protium, especially suitable for the neutron around detector Absorb, therefore can apply to prepare equipment, parts of various neutron-absorbings or neutron shield etc..Likewise, the application Boron carbide ceramics, it is also applied for the application field of in general boron carbide material, such as wear resistant corrosion resistant device, bullet resistant material, hair Motivation shower nozzle, blast nozzle, ceramic bearing, abrasive media etc..

The beneficial effect of the application is：

The boron carbide ceramics preparation method of the application, the low-temperature atmosphere-pressure sintering of boron carbide ceramics is realized first, energy consumption is low, Preparation technology is simple, easy to operate, greatlys save preparation cost；Used silicate glass powder added material abundant raw material, It is cheap, be extremely readily available, reduce further the cost of raw material of boron carbide ceramics；Also, prepared boron carbide Ceramics are not hydrogeneous, especially suitable for the neutron shield absorbing material and device around detector.The preparation method of the application is big The boron carbide ceramics material that the large-scale production neutron shield of batch works well is laid a good foundation.

Brief description of the drawings

Fig. 1 is the X-ray diffraction analysis figure spectrum of the boron carbide ceramics prepared in the embodiment of the present application；

Fig. 2 is differential scanning calorimeter (abbreviation DSC) and the thermogravimetric (contracting of the boron carbide ceramics prepared in the embodiment of the present application Write TG) analysis collection of illustrative plates；

Fig. 3 is the scanning electron microscope diagram of the boron carbide ceramics prepared in the embodiment of the present application；

Fig. 4 is the EDS energy spectrum analysis figures and ingredient lists of the boron carbide ceramics prepared in the embodiment of the present application；

Fig. 5 is the EDS energy spectrum analysis figures and ingredient lists of the boron carbide ceramics prepared in the embodiment of the present application.

Embodiment

Existing neutron absorber material is mainly boron carbide, and still, boron carbide sintering process conditions are complicated, cost is high；And And still containing a certain amount of protium in existing boron carbide composite material, its stronger inelastic scattering effect is used in Scattering back end can be increased during sub- absorbing material.Therefore, the application has found by numerous studies and experiment, is added in boron carbide powder Silicate glass powder, sintering temperature can be effectively reduced, realize that low-temperature atmosphere-pressure sinters, greatly reduce sintering temperature, reduce Energy consumption.Also, the boron carbide ceramics obtained using the preparation method of application is not hydrogeneous, around detector Neutron shield absorbs.

The application is described in further detail below by specific embodiment.Following examples only are entered to advance to the application One step illustrates, should not be construed as the limitation to the application.

Embodiment one

This example prepares boron carbide ceramics using the boron carbide powder of parts by weight 70% and the silicate glass powder of parts by weight 30%, Binder solution uses concentration 5wt% poly-vinyl alcohol solution, and specific preparation method is as follows：

(1) it is 70g boron carbide powders and 30g silicate glass powder is uniform by ball milling mixing, compound is made；

(2) add 2g concentration 5wt% PVA solution in the compound of step (1) and appropriate distilled water, hand operated mixing are made Grain is into about 400 microns of particle；

(3) particle prepared by step (2) is poured into metal die, be pressed under 10MPa pressure a diameter of The a height of 4.8mm of 19.05mm or so cylindrical biscuit；

(4) biscuit of step (3) is dried to constant weight at 60 DEG C, is then placed in vacuum sintering furnace, vacuumizes and fill Enter nitrogen, in a nitrogen atmosphere, treat that vacuum drops to 1 × 10⁰After below Pa, 500 are warming up to 2 DEG C/min heating rate DEG C, 30min is incubated, with thorough venting organic matter binding agent, then with 4 DEG C/min heating rate is warming up to 765 DEG C, insulation 90min, then furnace cooling obtain the boron carbide ceramics of this example, and shape and biscuit are consistent substantially.

Embodiment two

This example prepares boron carbide ceramics using the boron carbide powder of parts by weight 60% and the silicate glass powder of parts by weight 40%, Binder solution uses concentration 5wt% poly-vinyl alcohol solution.Specifically, 60g boron carbide powders and 40g silicate glass powder are led to It is uniform to cross ball milling mixing, compound is made；Remaining is identical with embodiment one, is finally sintered in vacuum sintering furnace, furnace cooling, Obtain the boron carbide ceramics of this example.

Embodiment three

(2) 2g concentration 5wt% PVA solution and appropriate distilled water are added in the compound of step (1), is granulated；

(4) biscuit of step (3) is dried to constant weight at 60 DEG C, be then placed in nitrogen atmosphere sintering furnace, it is logical in advance Nitrogen 10min, nitrogen flow are arranged to 30mL/min, are then warming up to 500 DEG C with 2 DEG C/min heating rate, insulation 30min, then 765 DEG C are warming up to 4 DEG C/min heating rate, 90min is incubated, then furnace cooling, obtains the carbonization of this example Boron ceramics, shape and biscuit are consistent substantially.

Example IV

This example prepares boron carbide ceramics using the boron carbide powder of parts by weight 80% and the silicate glass powder of parts by weight 20%, Binder solution uses concentration 5wt% poly-vinyl alcohol solution.Specifically, 80g boron carbide powders and 20g silicate glass powder are led to It is uniform to cross ball milling mixing, compound is made；Remaining is identical with embodiment three, is finally sintered in nitrogen atmosphere sintering furnace, with stove Cooling, obtains the boron carbide ceramics of this example.

With reference to GB/T 6569-2006 and GB/T 3808-2002, the application four is determined respectively using three-point bending test Spent before the bending of boron carbide ceramics prepared by embodiment；Four embodiments of the application are determined using Charpy impact machine tester to prepare Boron carbide ceramics impact flexibility；Test result is as shown in table 1.

The density and apparent porosity of boron carbide ceramics prepared by four embodiments are determined using Archimede drainages, is surveyed Test result is as shown in table 1.

The boron carbide ceramics performance test of table 1

Embodiment	Density (g/cm³)	Apparent porosity (%)	Impact flexibility (kJ/m²)	Bending strength (MPa)
					1	1.622	22.93	2.36	28.89
2	1.701	19.19	2.84	36.28
					3	1.560	25.93	2.73	24.65
4	1.531	28.07	1.76	15.81

The result of table 1 is shown, as the raising of silicate glass composition, the mechanical property of boron carbide ceramics, i.e. bending are strong Degree and impact flexibility, and density is all as raising, the porosity decrease；And compared in nitrogen atmosphere with sintering in vacuum, Vacuum burns sintered density and bending strength is larger, and the apparent porosity and impact flexibility that are sintered in nitrogen atmosphere are relatively large.

The boron carbide ceramics material of different-thickness under different ratio is calculated to different ripples using international MCNPX softwares The transmitance of long neutron, different wave length neutron are the neutron of different-energy.Wherein, different ratio refers to, the weight of boron carbide powder Part is measured, such as boron carbide is 90wt.%, then silicate glass powder is 10wt.%, boron carbide 80wt.%, then silicate glass Powder is 20wt.%, boron carbide 70wt.%, then silicate glass powder is 30wt.%, boron carbide 60wt.%, then silicate Glass dust is 40wt.%.Calculating to different-thickness, specifically, this example calculates under each proportioning respectively, 1mm, 2mm, 3mm, Transmitance of the boron carbide ceramics thick 4mm and 5mm to the neutron of different-energy.This example specifically tests the (abbreviation of 1 angstrom of wavelength)、 The transmitance of 2 angstroms and 3 angstroms of neutron.Result of calculation is as shown in table 2.

The neutron transmitance of the boron carbide ceramics of table 2

The result of table 2 is shown, for same thickness, the transmitance of certain wavelength or energy neutron is with carbon in material mixture ratio The increase for changing boron reduces；And it is 60% to work as carbonization Boron contents, when thickness is 5mm, for wavelengthNeutron transmitance is only 4.62E-05, and wavelengthNeutron can then be absorbed completely.

The boron carbide ceramics prepared respectively to three embodiments using X-ray diffractometer is detected, and obtains diffraction pattern, portion Point result is as shown in figure 1, Fig. 1 is the analysis result figure of boron carbide ceramics prepared by embodiment one.X-ray diffraction analysis result shows Show, the diffraction peak intensity of boron carbide is obvious, due to containing 30% silicate glass, there is " steamed bun peak " at 10 ° to 30 °； And there is not the diffraction maximum of boron oxide, boric acid etc., as shown in figure 1, boron carbide ceramics prepared by explanation this method successfully solves Determine the problem of oxidation of boron carbide.

The boron carbide ceramics prepared respectively to four embodiments using means of differential scanning calorimetry synchronization thermogravimetric analyzer is examined Survey, obtain thermal analysis curue, partial results are as shown in Fig. 2 Fig. 2 is analysis knot of the biscuit of the preparation of embodiment three in nitrogen atmosphere Fruit is schemed.Poor simultaneous thermal analysis result shows there is an obvious exothermic peak, as moisture evaporation below 100 DEG C；100 DEG C- It is the volatilization process of organic matter at 550 DEG C；550 DEG C -765 DEG C are liquid sintering process.And 25 DEG C -1000 DEG C no obvious matter Amount increase, show that boron carbide is not oxidized, as shown in Figure 2.

Observe the microstructure of the section of boron carbide ceramics prepared by three embodiments respectively using SEM, Partial results are as shown in figure 3, Fig. 3 is the observation result figure of boron carbide ceramics section prepared by embodiment three.Scanning electron microscopy Sem observation result shows that the material is brittle fracture, and the silicate glass formation network structure of melting is simultaneously close by boron carbide Bond, as shown in Figure 3.

The boron carbide ceramics prepared respectively to four embodiments using EDS energy depressive spectroscopies is detected, and obtains analysis chart Spectrum, as shown in Figure 4 and Figure 5, Fig. 4 and Fig. 5 are the analysis collection of illustrative plates of boron carbide ceramics prepared by embodiment three to partial results, that is, are distinguished Analysis chart corresponding to spectrogram 1 and spectrogram 2 in Fig. 3.Four regions are have chosen, each region repeats at least 5 times, wherein the peak ignored For background peak.EDS collection of illustrative plates shows, boron carbide ceramics material prepared by four embodiments of the application all be free of protium, as Fig. 4 with Shown in Fig. 5.

Above content is to combine the further description that specific embodiment is made to the application, it is impossible to assert this Shen Specific implementation please is confined to these explanations.For the application person of an ordinary skill in the technical field, do not taking off On the premise of conceiving from the application, some simple deduction or replace can also be made, should all be considered as belonging to the protection of the application Scope.

Claims

A kind of 1. preparation method of boron carbide ceramics, it is characterised in that：Comprise the following steps,

(1) boron carbide powder and silicate glass powder are well mixed by ball milling or ultrasonic disperse, compound is made；

(2) binder solution is added in the compound of step (1), is granulated；

(3) particle prepared by step (2) is poured into mould, biscuit is pressed under 5-30MPa pressure；

(4) biscuit of step (3) is dried, is then sintered under inert atmosphere, reducing atmosphere or vacuum condition, carbonization is made Boron ceramics, the temperature of the sintering are less than 1000 DEG C.
2. preparation method according to claim 1, it is characterised in that：The boron carbide powder accounts for step (1) compound gross weight The 50-90% of amount, the silicate glass powder account for the 10-50% of step (1) compound gross weight, the use of the binder solution Measure as the 1.5-22% of step (1) compound gross weight.
3. preparation method according to claim 1, it is characterised in that：The purity of the boron carbide powder is more than 95wt.%, institute The purity for stating silicate glass powder is more than 95wt.%, also, the particle diameter of the boron carbide powder is less than 250 microns.
4. preparation method according to claim 1, it is characterised in that：Protium is not contained in the silicate glass powder.
5. preparation method according to claim 1, it is characterised in that：The binding agent is polyvinyl alcohol, phenolic resin, shallow lake At least one of powder, carbohydrate, cellulose and dextrin.
6. preparation method according to claim 1, it is characterised in that：The biscuit includes but are not limited to cylinder, length Bar shaped or long plate shape.
7. according to the preparation method described in claim any one of 1-6, it is characterised in that：The temperature of drying in the step (4) Less than 100 DEG C.
8. according to the preparation method described in claim any one of 1-6, it is characterised in that：In the step (4), the temperature of sintering For 500 DEG C -765 DEG C, sintering time 0.5h-4h.
9. boron carbide ceramics prepared by the preparation method according to claim any one of 1-8.
10. application of the boron carbide ceramics according to claim 9 in neutron-absorbing or neutron shield.