CN106430127B - A kind of preparation method of high alpha phase silicon nitride powders - Google Patents
A kind of preparation method of high alpha phase silicon nitride powders Download PDFInfo
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Abstract
The invention discloses a kind of preparation methods of high alpha phase silicon nitride powders, include the following steps：1) raw material is mixed in proportion to obtain reactant；Raw material is made of silica flour, diluent and accelerating agent three parts；By raw material ball milling 12 hours, to be uniformly mixed；2) charging and combustion synthesis reaction；3) collection of products and detection.The present invention starts with from optimization initial reaction condition, i.e. the composition of reactant, the structure of reactant, initial temperature and gas pressure, material type of cooling etc., on the basis of many experiments, by the optimum organization to above-mentioned technological parameter, the high alpha phase silicon nitride powders of enlarged conbustion synthesis are realized；The conbustion synthesis equipment of use further improves the single yield and alpha phase contents of reaction.
Description
Technical field
The present invention relates to nitride powder technical fields.More particularly, to a kind of system of high alpha phase silicon nitride powders
Preparation Method.
Background technology
Silicon nitride is typical covalent key compound, and there are two types of crystal forms, are α phase silicon nitrides and beta phase silicon nitride, α phases respectively
Silicon nitride is crystalline particulate body, belongs to low-temperature stabilization type；Beta phase silicon nitride is long rodlike crystalline solid, belongs to high-temperature stable.α
Phase silicon nitride free energy is higher than beta phase silicon nitride, therefore the sintering character of alpha silicon nitride powder is better than beta silicon nitride powder.In advanced pottery
In porcelain industry, alpha-phase silicon nitride powder is a kind of important basic material, can be not only used for sintering and prepares various silicon nitride ceramics
Product, it is also possible to make the releasing agent of casting polysilicon.
The production method of alpha-phase silicon nitride powder mainly has metallic silicon power direct nitridation method, ammonolysis process, titanium dioxide silicon-carbon heat
Reduction method, combustion synthesis method etc..
Metallic silicon power direct nitridation method is in the atmosphere of nitrogen or ammonia, and heating metallic silicon power is allowed to occur in electric furnace
Nitridation reaction, this method is simply direct, is the method for synthesis alpha silicon nitride powder commonly used in industry.But this method lacks
Point is that silica flour may melt in pyroreaction, causes reaction atmosphere diffusion difficult, and with the progress of reaction, coated Si
The silicon nitride layer of powder can prevent internal silica flour from further nitrogenizing.In addition, this method reaction time needs a couple of days, in reaction process
From beginning to end must stringent controlling reaction temperature, nitrogen partial pressure and gas flow, with ensure generate α phase silicon nitrides, this aspect need
Larger energy consumption is wanted, the equipment of complex and expensive is on the other hand needed, finally improves production cost.
Ammonolysis process is with SiCl4And NH3For raw material, Si (NH) is synthesized first with liquid phase reactor2, then pass through temperature control heat
Solution and Crystallizing treatment prepare the silicon nitride powder of high α phases content.Silicon nitride powder purity using ammonolysis process production is high, α phase contents
Height, granule-morphology is uniform, particle diameter distribution is narrow.The shortcoming of ammonolysis process is mainly that process route is long, and production procedure is complicated, equipment
Corrosion-resistant requirement is high, causes production cost higher.
Silica carbothermic method is to be sufficiently mixed SiO 2 powder and carbon dust, sharp under the nitrogen atmosphere of flowing
Reduction with carbon silica, the silicon being reduced out is reacted with nitrogen generates silicon nitride.The method has the nitrogen that cost of material is low, generates
SiClx powder has the characteristics that high α phases and is not necessarily to ball milling.But this method needs that excessive carbon is added to ensure that silica is complete
Full response, in addition SiO2-C-N2Reaction system reaction speed in low temperature is slow, can then generate silicon carbide at high temperature, directly affect
To the yield and purity of silicon nitride product.
Combustion synthesis method is a kind of method come synthetic material using exothermic heat of reaction between reactant, and reactant is once drawn
Combustion, will be from the regional spread that trend is not yet reacted, until the reaction is complete, and whole process provides energy with little need for the external world,
And be swift in response, generated time it is short.Compared with the method for three kinds of front, combustion synthesis method is with simple for process, the period is short, energy consumption
The features such as low, of low cost.
In terms of preparing beta-silicon nitride powder using burning synthesis method, have a large amount of patent and research paper report, this
A little disclosed results realize technological progress in one aspect, but also have shortcoming and defect.For example, the former Soviet Union
" a method of preparing alpha-phase silicon nitride " (the patent US5032370) of Merzhanov et al. inventions and " self- propagating prepares nitrogen
SiClx " (patent RU2257338) has successfully prepared α phase silicon nitride powders using burning synthesis method earlier, but use
Nitrogen pressure is higher (up to 30MPa), very high to equipment requirement, is unfavorable for amplification production, while using a large amount of ammonium halides
Salt will produce a large amount of hydrogen halide after reaction, both caused heavy corrosion to equipment, and also caused damages to operating personnel, such as
Fruit also pollutes the environment without processing direct emission.A kind of " stratiform cloth combustion of Ge Changchun of University of Science ＆ Technology, Beijing et al. inventions
Burnt together at isotropic silicon nitride powder method " (Chinese patent CN179995A), by stratiform cloth, synthesis has obtained homogeneous nitrogen
SiClx powder, but raw material ground and mixed and drying steps take cumbersome, and stratiform cloth is unfavorable for mass producing.The Chinese Academy of Sciences
" method that temperature control activates Self- propagating Sintering Synthetic α phase silicon nitride powders " of Lin Zhiming of physiochemical techniques research institute et al. inventions
(Chinese patent CN1673070A) has prepared alpha-phase silicon nitride powder by being activated to raw material under relatively low nitrogen pressure
Body, but because also need to use ammonium salt, therefore the problems such as there is also etching apparatuses.New et al. the inventions of Tsinghua University Chen Ke it is " a kind of
The method that low-pressure combustion synthesizes alpha-phase silicon nitride powder " (Chinese patent CN1362358A), using silica flour suspension Nitriding Technology,
Nitrogen pressure can be further decreased, realization is continuously synthesizing to, but process is more, the production cycle is longer, and energy consumption is also relatively large.
Currently, in preparing the existing equipment of alpha-phase silicon nitride powder using burning synthesis method, volume of equipment does not surpass
100L is crossed, the volume and synthesis scale of equipment are all smaller, and single synthesis amount is no more than 10kg, and overall production efficiency is relatively low, shadow
The performance of conbustion synthesis low-cost advantage is rung.Therefore, the enlargement of conbustion synthesis equipment and matching technological parameter
Optimization is the critical issue place of combustion synthesis technology industrialization, wherein the improvement to equipment is particularly difficult, combustion synthesis reaction
Generally carried out under the conditions of high temperature high pressure enclosed, the reaction chamber of equipment needs high temperature resistant, high pressure resistant, corrosion-resistant, and pressure and
The variation of temperature is violent, has higher requirement for thermal shock resistance, the compressive resistance mutability etc. of reaction chamber, in this case,
Blindly amplify conbustion synthesis equipment on the basis of not changing original structure design, is easy to cause amplified device temperature and pressure
Power operating mode changes, such as when the reaction that brings of volume increase that the promotion of reaction chamber cooling capacity is significantly smaller than reaction chamber is total
When the increase of heat, it can cause to maintain higher temperature inside reaction chamber, metal material used in reaction chamber is long in this case
Phase is in tolerance in high temperature and high pressure environment and declines, and is easy to cause safety accident.
Therefore, the present invention proposes a kind of preparation method of high alpha phase silicon nitride powders, from optimization initial reaction condition
Start with, i.e. the composition of reactant, the structure of reactant, initial temperature and gas pressure, material type of cooling etc., in many experiments
On the basis of, by the optimum organization to above-mentioned technological parameter, realize the high alpha phase silicon nitride powders of enlarged conbustion synthesis.
Invention content
It is an object of the present invention to provide a kind of preparation methods of high alpha phase silicon nitride powders.
Conbustion synthesis produces silicon nitride, and product quality is closely related with reaction temperature, and the key for controlling temperature is to adjust
Heat balance.Since conbustion synthesis is that violent, rapid self-sustaining reaction can not be implemented to intervene once reaction starts to it, because
This control to reaction process and product quality can only start with from optimization initial reaction condition, specifically include：The composition of reactant
(be formulated, such as diluent, reaction promoter type and content), the structure of reactant (such as raw material particle size distribution, granular-grade
Match, the shape of green body, size, porosity etc.), initial temperature and gas pressure, material type of cooling etc..The present invention is a large amount of real
On the basis of testing, by the optimum organization to above-mentioned technological parameter, the high alpha phase silicon nitrides powder of enlarged conbustion synthesis is realized
Body.
In order to achieve the above objectives, the present invention uses following technical proposals：
A kind of preparation method of high alpha phase silicon nitride powders, includes the following steps：
1) raw material is mixed in proportion to obtain reactant；
The raw material is made of silica flour, diluent and accelerating agent three parts；The weight percent of the reactant composition is：
Diluent 50-80wt%
Accelerating agent 0-20wt%
Silica flour surplus；
The diluent is varigrained beta-silicon nitride powder mixture；The granularity of beta-silicon nitride powder is in the diluent
0.1-0.5um, 0.5-1um and>1um, weight percent are：
0.1-0.5um 40-55wt%
0.5-1um 30-40wt%
>1um 5-30wt%；
The accelerating agent is by NH4Cl、NH4HCO3And NH4F is formed；The weight percent of the promoter component is：
NH4Cl 40-55wt%
NH4HCO330-40wt%
NH4F 5-30wt%；
By raw material ball milling 1-2 hours, to be uniformly mixed；
Reaction raw materials amount is increased in the present invention, improves the stability of burning.Specifically, it is increased ammonium in formula
The limit additive amount of salt.Its meaning has two：First, improving alpha phase contents in product, that is, improve product quality；Second is that reducing nitrogen
SiClx diluent dosage, improves net yield.
2) charging and combustion synthesis reaction
The reactant being uniformly mixed in step 1) is fitted into the reactor of conbustion synthesis equipment, reactant is in the reactor
Accumulation forms green body；Reactor is positioned in reaction chamber, chamber door is closed, vacuumizes, is then charged with high pure nitrogen, control starting
Temperature is lighted a fire in 20-700 DEG C of range, nitrogen pressure 0.3-5MPa using energization tungsten filament, by the way that temperature in the reactor chamber is arranged
Degree and pressure detecting element monitor in reaction chamber and reactor temperature；
There are the microstructure of the idiosome following characteristics, porosity 60-80% in pore-size distribution, to be not greater than 1mm
Hole,>Volume fraction shared by the hole of 500um<20%,>Volume fraction shared by the hole of 100um<50%；
3) collection of products and detection
Reaction finishes, and when environment temperature in reaction chamber is down to 40 DEG C or less, opens chamber door, takes out reaction product, will produce
Object cleaning is collected, is weighed, sampling observation, packing, storage.
Preferably, the single synthesis silicon nitride powder scale of construction>20kg, product yield>90%, alpha phase contents in product>
95%, the present invention increases substantially production efficiency, and the production cost of high alpha phase silicon nitride powders is made to be remarkably decreased.
Preferably, the conbustion synthesis equipment, including reaction cavity main body, reactor, hydraulic control system, temperature measure system
System, phase-change accumulation energy module control system, reaction chamber cooling system and pressure-measuring system；
The reaction cavity main body includes reaction chamber lid, reaction chamber, cooling chamber, relief valve, pressure measuring element, temperature measurement
Element, phase-change accumulation energy element and phase-change accumulation energy detection device；
The reaction chamber side is equipped with reaction chamber lid, and the other side is equipped with relief valve；The reaction chamber lid is connected by conducting wire
Hydraulic control system；
The reaction chamber is internally provided with reactor；
The inner wall of the reaction chamber is equipped with phase-change accumulation energy element；
The upper end of the reaction chamber is equipped with pressure measuring element, and lower end is equipped with temperature-measuring element and phase-change accumulation energy detection dress
It sets；The pressure measuring element connects pressure-measuring system by conducting wire, realizes the in due course acquisition and control of reaction cavity pressure；
The temperature-measuring element connects temperature measurement system by conducting wire, realizes the acquisition and detection of temperature；The phase-change accumulation energy inspection
The upper end for surveying device connects phase-change accumulation energy element, and lower end connects phase-change accumulation energy module control system by conducting wire, by phase-change accumulation energy
Control system is monitored and controlled the working condition of phase-change accumulation energy element；
The reaction chamber outer cover is equipped with cooling chamber；The cooling chamber is hollow structure, and cooling water can be flowed to from one end
The other end realizes cycle, takes away the partial heat of reaction chamber；The cooling chamber connects reaction chamber cooling system by conducting wire, passes through
Cooling system can realize accurately controlling for cooling velocity.
Preferably, the reaction chamber is in cylinder type, volume 0.2-20m3；
Preferably, it the movable connection of the phase-change accumulation energy element or fixed is connected on the inner wall of reaction chamber；The phase
Become energy-storage travelling wave tube as one group；
Preferably, the temperature-measuring element is at least two groups；
Preferably, the pressure measuring element is at least two groups；
Preferably, the reactor includes one layer or more of material boat, and more than two objects are equidistantly positioned on the material boat
Expect temperature measuring point, it is 5~10min, ignition position that the material boat, which uses separated ignition mode, the adjacent time interval lighted a fire twice,
It sets in one end of material boat；The temperature of charge measurement point connects temperature-measuring element by conducting wire, and reaction mass may be implemented
Temperature measures.
Preferably, the phase-changing energy storage material that the phase-change accumulation energy element uses is selected from Sodium acetate trihydrate, NH4Al(SO4)2·
6H2O、Mg(NO3)2·6H2O、KCl-ZnCl2、NaCl-MgCl2、NaF-KF-LiF-MgF2、Al-Si、Al-Cu-Si、Mg-Zn、
One or more of Al-Mg-Zn；The phase transition temperature interval of the phase-changing energy storage material is 300-600 DEG C, and latent heat of phase change is
400-1200kJ/kg；
Preferably, the structure of the phase-change accumulation energy element is bent-tube boiler, coiled or array tubular type, pipe interior sealing phase transformation storage
It can material；
Preferably, the structure of the phase-change accumulation energy element is circular or cylindric, annulus or cylinder interior sealing phase transformation storage
It can material.
The conbustion synthesis equipment realizes the enlargement production of high alpha phase silicon nitride powders, which closes burning
It is accurately controlled at total amount of heat in reaction chamber：First, reaction chamber cooling system accurately controls, by the cooling system come
Control the flow velocity and flow of cooling water in cooling chamber；Second is that phase-change accumulation energy element is set inside reaction chamber, it is anti-in conbustion synthesis
The leading portion answered and stage casing, during the temperature and pressure rapid growth of reaction chamber, phase-change accumulation energy element can absorb heat, directly
To phase transition temperature, slow down the reaction raised speed of cavity temperature, when entering posterior segment with combustion synthesis reaction, the temperature of reaction chamber
Degree starts gradually to decline, and when less than the phase transition temperature of phase-change accumulation energy element, phase-change accumulation energy element starts to discharge heat to reaction chamber
Can, to slow down the speed that reaction cavity temperature reduces, it can be seen that, phase-change accumulation energy element reduces in entire reaction process
The gradient of temperature ensures that combustion synthesis reaction is completed under a metastable environment temperature and pressure.
For high alpha phase silicon nitride powders, technical scheme of the present invention has extraordinary effect, not only ensures
High phase content, while single yield is improved, production cost is remarkably decreased.Certainly, technical scheme of the present invention is not limited to
In beta-silicon nitride powder, for a large amount of similar combustion synthesis reaction systems, especially those are needed to the temperature in reaction process
The reaction system accurately controlled with pressure, technical scheme of the present invention all have universal applicability.
Beneficial effects of the present invention are as follows：
(1) present invention starts with from optimization initial reaction condition, i.e. the composition of reactant, the structure of reactant, initial temperature
And gas pressure, material type of cooling etc., by the optimum organization to above-mentioned technological parameter, are realized on the basis of many experiments
Enlarged conbustion synthesis high alpha phase silicon nitride powders.
(2) limit additive amount that ammonium salt in formula is increased in the present invention, not only increases alpha phases content in product,
Product quality is improved, and reduces nitridation silicon diluent dosage, improves net yield.
(3) the conbustion synthesis equipment that the present invention uses realizes the enlargement production of high alpha phase silicon nitride powders, this sets
It is standby that combustion synthesis reaction intracavitary total amount of heat is accurately controlled：First, reaction chamber cooling system accurately controls, by described
Cooling system controls the flow velocity and flow of cooling water in cooling chamber；Second is that phase-change accumulation energy element is arranged inside reaction chamber, protect
Card combustion synthesis reaction is completed under a metastable environment temperature and pressure.
(4) for high alpha phase silicon nitride powders, technical scheme of the present invention process is few, production cycle section, energy consumption
Relatively low, single synthesis amount is more than 20kg, and product yield is more than 90%, and alpha phase contents are more than 95% in product, not only ensure that
High alpha phase contents, while single yield is improved, production cost is remarkably decreased.
Description of the drawings
Specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings.
Fig. 1 shows the schematic diagram of conbustion synthesis equipment in embodiment 1.
Fig. 2 shows the microscopic appearance photos of the raw material silica flour employed in embodiment 2.
Fig. 3 shows the testing graininess result of the raw material silica flour employed in embodiment 2.
Fig. 4 shows the XRD analysis collection of illustrative plates of combustion synthesized product in embodiment 2.
Specific implementation mode
In order to illustrate more clearly of the present invention, the present invention is done further with reference to preferred embodiments and drawings
It is bright.Similar component is indicated with identical reference numeral in attached drawing.It will be appreciated by those skilled in the art that institute is specific below
The content of description is illustrative and be not restrictive, and should not be limited the scope of the invention with this.
Embodiment 1
A kind of conbustion synthesis equipment, including reaction cavity main body, reactor 2, hydraulic control system, temperature measurement system, phase
Become energy-storage module control system, reaction chamber cooling system and pressure-measuring system；
It includes reaction chamber lid 1, reaction chamber 4, cooling chamber 5, relief valve 7, pressure measuring element 3, temperature survey to react cavity main body
Measure element 8, phase-change accumulation energy element 6 and phase-change accumulation energy detection device 9；Reaction chamber 4 is in cylinder type, volume 0.2-20m3；
4 side of reaction chamber is equipped with reaction chamber lid 1, and the other side is equipped with relief valve 7；Reaction chamber lid 1 connects hydraulic pressure by conducting wire
Control system；Reaction chamber 4 is internally provided with reactor 2；Reactor 2 includes one layer or more of material boat, expects to be equidistantly positioned two on boat
A above temperature of charge measurement point, temperature of charge measurement point connect temperature-measuring element by conducting wire, reactant may be implemented
The temperature of material measures；
The inner wall upper and lower ends of reaction chamber 4 are respectively equipped with one group of phase-change accumulation energy element 6；
The upper end of reaction chamber 4 is equipped with two groups of pressure measuring elements 3, and lower end is equipped with two groups of temperature-measuring elements 8 and phase transformation is stored up
It can detection device 9；The pressure measuring element 3 connects pressure-measuring system by conducting wire, realizes the in due course of reaction cavity pressure
Acquisition and control；The temperature-measuring element 8 connects temperature measurement system by conducting wire, realizes the acquisition and detection of temperature；Institute
The upper end connection phase-change accumulation energy element 6 of phase-change accumulation energy detection device 9 is stated, lower end connects phase-change accumulation energy module control system by conducting wire
System, the working condition of phase-change accumulation energy element is monitored and controlled by phase-change accumulation energy control system；
4 outer cover of reaction chamber is equipped with cooling chamber 5；Cooling chamber 5 is hollow structure, and cooling water can flow to the other end from one end
It realizes cycle, takes away the partial heat of reaction chamber；Cooling chamber 5 connects reaction chamber cooling system by conducting wire, passes through cooling system
Accurately controlling for cooling velocity can be achieved.
The movable connection of phase-change accumulation energy element 6 fixed is connected on the inner wall of reaction chamber；Phase-change accumulation energy element 6 is by normal
Phase-changing energy storage material is made, and the form of bend pipe, coil pipe or array tube, pipe interior sealing phase-changing energy storage material are taken in structure；
Circular or cylinder-like structure, annulus or cylinder interior sealing phase-changing energy storage material can also be taken.
Embodiment 2
Using equipment described in embodiment 1, high alpha phase silicon nitride powders are prepared, steps are as follows：
1) it is silica flour according to weight ratio by silica flour, diluent, accelerating agent：Diluent：Accelerating agent=40:55:5 ratio is equal
Even mixing；
The pattern of silica flour is as shown in Fig. 2, its size distribution is as described in Figure 3.Diluent be granularity be respectively 0.1-0.5um,
0.5-1um and>The beta-silicon nitride powder mixture of 1um；The weight percent of different grain size diluent is：
0.1-0.5um 40wt%
0.5-1um 35wt%
>1um 25wt%.
Accelerating agent is by NH4Cl、NH4HCO3And NH4F is formed, and weight percent is：
NH4Cl 50wt%
NH4HCO3 30wt%
NH4F 20wt%；
By the raw material ball milling 1 hour, to be uniformly mixed；
2) reaction mass after mixing is fitted into 3 identical cuboid moulding mixture boats, expects boat long 1m, wide 0.3m,
High 0.1m.Each material boat charge is 15kg.3 material boats are positioned in isosceles triangle lamination in reaction chamber.Reaction chamber is in cylinder
Type, internal diameter 1m, interior a length of 1.27m, volume 1m3。
There are the microstructure of material following characteristics, porosity 60-80% in pore-size distribution, to be not greater than the hole of 1mm
Hole,>Volume fraction shared by the hole of 500um<20%,>Volume fraction shared by the hole of 100um<50%；
Chamber door is closed, is vacuumized, control initial temperature is 20 DEG C, is then charged with high pure nitrogen to 4MPa.3 material boats use
Separated ignition mode, the adjacent time interval lighted a fire twice are 10min, the one end of ignition location in material boat along its length, point
Fire uses energization tungsten filament sparking mode.
Reaction chamber top is respectively equipped with temperature-measuring element, i.e. thermocouple all the way at chamber door 0.25m, 0.5m, 0.75m,
It is total to have No. three thermocouples.Positioned at intermediate thermocouple all the way, to monitor environment temperature in reaction chamber；Two-way positioned at both sides
Thermocouple, to monitor temperature of charge.
3) reaction finishes, and when intracavitary environment temperature is down to 40 DEG C or less, opens chamber door, takes out reaction product, combustion wave
Uniformly, illustrate that combustion synthesis reaction is stablized to complete, reaction is abundant.By product cleaning, collect, weigh, calculate after it is found that obtaining
The total weight of product powder is 51kg, product yield 93%.
Product is sampled and carries out XRD detections, as a result as described in Figure 4, XRD analysis shows that product is beta-silicon nitride powder, wherein
Alpha phase contents are 96%.
Embodiment 3
Prepare high alpha phase silicon nitride powders, method with embodiment 2, the difference is that：
Silica flour, diluent, accelerating agent are silica flour according to weight ratio in step 1)：Diluent：Accelerating agent=30:50:20
Ratio uniform mixes；
The composition weight percent of diluent is：
0.1-0.5um 55wt%
0.5-1um 40wt%
>1um 5wt%；
The composition weight percent of accelerating agent is：
NH4Cl 55wt%
NH4HCO340wt%
NH4F 5wt%.
Each expect that boat charge is 18kg in step 2), control initial temperature is 100 DEG C, is filled with high pure nitrogen to 3MPa；3
It is 5min that a material boat, which uses separated ignition mode, the adjacent time interval lighted a fire twice,.
The total weight of obtained product powder is 49kg, product yield 91%.Product is sampled and carries out XRD detections, XRD
Analysis shows product is beta-silicon nitride powder, wherein alpha phases content is 96%.
Embodiment 4
Prepare high alpha phase silicon nitride powders, method with embodiment 2, the difference is that：
Silica flour, diluent, accelerating agent are silica flour according to weight ratio in step 1)：Diluent：Accelerating agent=20:80:0 ratio
Example uniformly mixing；
The composition weight percent of diluent is：
0.1-0.5um 40wt%
0.5-1um 30wt%
>1um 30wt%；
Each expect that boat charge is 12kg in step 2), control initial temperature is 300 DEG C, is filled with high pure nitrogen to 2MPa；3
It is 8min that a material boat, which uses separated ignition mode, the adjacent time interval lighted a fire twice,.
The total weight of obtained product powder is 39kg, product yield 95%.Product is sampled and carries out XRD detections, XRD
Analysis shows product is beta-silicon nitride powder, wherein alpha phases content is 96%.
Embodiment 5
Prepare high alpha phase silicon nitride powders, method with embodiment 2, the difference is that：
Silica flour, diluent, accelerating agent are silica flour according to weight ratio in step 1)：Diluent：Accelerating agent=30:60:10
Ratio uniform mixes；
The composition weight percent of diluent is：
0.1-0.5um 45wt%
0.5-1um 40wt%
>1um 15wt%；
The composition weight percent of accelerating agent is：
NH4Cl 50wt%
NH4HCO340wt%
NH4F 10wt%.
Each expect that boat charge is 15kg in step 2), control initial temperature is 500 DEG C, is filled with high pure nitrogen to 3MPa；3
It is 6min that a material boat, which uses separated ignition mode, the adjacent time interval lighted a fire twice,.
The total weight of obtained product powder is 46kg, product yield 92%.Product is sampled and carries out XRD detections, XRD
Analysis shows product is beta-silicon nitride powder, wherein alpha phases content is 95%.
Embodiment 6
Prepare high alpha phase silicon nitride powders, method with embodiment 2, the difference is that：
Silica flour, diluent, accelerating agent are silica flour according to weight ratio in step 1)：Diluent：Accelerating agent=35:55:10
Ratio uniform mixes；
The composition weight percent of diluent is：
0.1-0.5um 40wt%
0.5-1um 30wt%
>1um 30wt%；
The composition weight percent of accelerating agent is：
NH4Cl 40wt%
NH4HCO330wt%
NH4F 30wt%.
Each expect that boat charge is 18kg in step 2), control initial temperature is 700 DEG C, is filled with high pure nitrogen to 3MPa；3
It is 10min that a material boat, which uses separated ignition mode, the adjacent time interval lighted a fire twice,.
The total weight of obtained product powder is 56kg, product yield 92%.Product is sampled and carries out XRD detections, XRD
Analysis shows product is beta-silicon nitride powder, wherein alpha phases content is 96%.
Comparative example 1
Prepare high alpha phase silicon nitride powders, method with embodiment 2, the difference is that：
The Small Combustion synthesis device that the equipment used is 40L for common volume, total charge are 1kg.
The total weight of obtained product powder is 0.92kg, product yield 73%.Product is sampled and carries out XRD detections,
XRD analysis shows that product is beta-silicon nitride powder, and wherein alpha phases content is 82%.
The above results show for same reactant, using common compact conbustion synthesis equipment, product yield and
Alpha phase contents are substantially reduced.
Obviously, the above embodiment of the present invention be only to clearly illustrate example of the present invention, and not be pair
The restriction of embodiments of the present invention may be used also on the basis of the above description for those of ordinary skill in the art
To make other variations or changes in different ways, all embodiments can not be exhaustive here, it is every to belong to this hair
Row of the obvious changes or variations that bright technical solution is extended out still in protection scope of the present invention.
Claims (7)
1. a kind of preparation method of high alpha phase silicon nitride powders, which is characterized in that include the following steps：
1）Raw material is mixed in proportion to obtain reactant；
The raw material is made of silica flour, diluent and accelerating agent three parts；The weight percent of the reactant composition is：
Diluent 50-80 wt%
Accelerating agent 0-20 wt%
Silica flour surplus；
The diluent is varigrained beta-silicon nitride powder mixture；The accelerating agent is by NH4Cl、NH4HCO3And NH4F is formed；
By raw material ball milling 1-2 hours, to be uniformly mixed；
2）Charging and combustion synthesis reaction
By step 1）In be uniformly mixed reactant be fitted into the reactor of conbustion synthesis equipment, reactant is accumulated in the reactor
Form green body；Reactor is positioned in reaction chamber, chamber door is closed, vacuumizes, be then charged with high pure nitrogen, using energization tungsten filament
Igniting, is monitored in reaction chamber by the way that temperature and pressure detecting element in the reactor chamber is arranged and reactor temperature；
3）Collection of products and detection
Reaction finishes, and when environment temperature in reaction chamber is down to 40 DEG C or less, opens chamber door, takes out reaction product, and product is clear
Reason is collected, is weighed, sampling observation, packing, storage；
Step 1）Described in conbustion synthesis equipment, including reaction cavity main body, reactor, hydraulic control system, temperature measurement system,
Phase-change accumulation energy module control system, reaction chamber cooling system and pressure-measuring system；The reactor is set in reaction cavity main body；
Hydraulic control system, temperature measurement system, phase-change accumulation energy module control system, reaction chamber cooling are connected on the reaction cavity main body
System and pressure-measuring system；
The reaction cavity main body includes reaction chamber lid, reaction chamber, cooling chamber, relief valve, pressure measuring element, temperature measurement member
Part, phase-change accumulation energy element and phase-change accumulation energy detection device；
The reaction chamber side is equipped with reaction chamber lid, and the other side is equipped with relief valve；The reaction chamber lid connects hydraulic pressure by conducting wire
Control system；
The reaction chamber is internally provided with reactor；
The inner wall of the reaction chamber is equipped with phase-change accumulation energy element；
The upper end of the reaction chamber is equipped with pressure measuring element, and lower end is equipped with temperature-measuring element and phase-change accumulation energy detection device；
The pressure measuring element connects pressure-measuring system by conducting wire；The temperature-measuring element connects temperature by conducting wire and measures
System；The upper end of the phase-change accumulation energy detection device connects phase-change accumulation energy element, and lower end connects phase-change accumulation energy module by conducting wire
Control system；
The reaction chamber outer cover is equipped with cooling chamber；The cooling chamber is hollow structure；The cooling chamber is connected anti-by conducting wire
Answer chamber cooling system；
The reaction chamber is in cylinder type, volume 0.2-20m3；The reactor includes one layer or more of material boat, and the material boat is adopted
With separated ignition mode, the adjacent time interval lighted a fire twice is 5 ~ 10 min, and ignition location is in one end of material boat；The material boat
On be equidistantly positioned more than two temperature of charge measurement points, the temperature of charge measurement point, which passes through conducting wire and connects temperature, measures member
Part；
Step 2）Middle initial temperature is 20-700 DEG C, and nitrogen pressure is 0.3-5 MPa.
2. a kind of preparation method of high alpha phase silicon nitride powders according to claim 1, which is characterized in that step 1）
Described in diluent the granularity of beta-silicon nitride powder be 0.1-0.5 um, 0.5-1um and>1um, weight percent are：
0.1-0.5 um 40-55 wt%
0.5-1um 30-40 wt%
>1um 5-30 wt%；
The weight percent of the promoter component is：
NH4Cl 40-55 wt%
NH4HCO3 30-40 wt%
NH4F 5-30 wt%。
3. a kind of preparation method of high alpha phase silicon nitride powders according to claim 1, which is characterized in that step 2）
Described in the microstructure of idiosome there are following characteristics, porosity 60-80% in pore-size distribution, to be not greater than the hole of 1mm,
>Volume fraction shared by the hole of 500um<20%,>Volume fraction shared by the hole of 100um<50%.
4. a kind of preparation method of high alpha phase silicon nitride powders according to claim 1, which is characterized in that the phase
Become the movable connection of energy-storage travelling wave tube or fixed is connected on the inner wall of reaction chamber；The phase-change accumulation energy element is one group；It is described
Temperature-measuring element is at least two groups；The pressure measuring element is at least two groups.
5. a kind of preparation method of high alpha phase silicon nitride powders according to claim 1, which is characterized in that the phase
Become the phase-changing energy storage material that energy-storage travelling wave tube uses and is selected from Sodium acetate trihydrate, NH4Al(SO4)2•6H2O、Mg(NO3)2•6H2O、KCl-
ZnCl2、NaCl-MgCl2、NaF-KF-LiF-MgF2, one or more of Al-Si, Al-Cu-Si, Mg-Zn, Al-Mg-Zn；
The phase transition temperature interval of the phase-changing energy storage material is 300-600 DEG C, and latent heat of phase change is 400-1200 kJ/kg.
6. a kind of preparation method of high alpha phase silicon nitride powders according to claim 1, which is characterized in that the phase
The structure of change energy-storage travelling wave tube is bent-tube boiler, coiled or array tubular type, pipe interior sealing phase-changing energy storage material.
7. a kind of preparation method of high alpha phase silicon nitride powders according to claim 1, which is characterized in that the phase
Become the structure of energy-storage travelling wave tube as circular or cylindrical shape, annulus or cylinder interior sealing phase-changing energy storage material.
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