CN116117173A - A kind of neutron-absorbing composite material preparation device and method based on screw extrusion - Google Patents

Abstract

The invention relates to a neutron-absorbing composite material preparation device and method based on screw extrusion. The preparation device includes a screw extrusion module, a material transportation module, a reaction module and a control device. The screw extrusion module is used for printing precursors, including extrusion The matrix material is used as the overall frame with pores, and the protective material is extruded into the pores of the overall frame; the material transportation module corresponds to the screw extrusion module and the reaction module respectively, and is used to transport the precursor printed by the screw extrusion module to the Reaction module; the reaction module is used to heat the precursor and feed the reaction gas and inert protective gas, so that the precursor undergoes a self-propagating reaction and sinters into a protective component; the control device is used to control the screw extrusion module, the material transportation module and the reaction module action. The invention combines multi-material screw extrusion and self-propagating reaction sintering to realize high-efficiency and high-quality forming of complex components of neutron protection materials.

Description

A kind of neutron-absorbing composite material preparation device and method based on screw extrusion

technical field

The invention belongs to the technical field of 3D printing, and in particular relates to a neutron-absorbing composite material preparation device and method based on screw extrusion.

Background technique

The increasing development of the atomic energy industry is accompanied by hidden safety hazards such as nuclear leakage and radiation. Among several types of nuclear radiation particles, neutrons and gamma rays are more difficult to shield. In particular, neutrons, as electrically neutral particles, are not affected by the Coulomb force, have strong penetrability, and will produce secondary gamma rays during the collision process, which is the research focus of modern nuclear radiation protection. Aluminum alloy is widely used in the field of nuclear protection because of its good machinability, corrosion resistance and nuclear radiation resistance. In order to further improve the nuclear shielding ability of components, some scholars add borides with neutron-absorbing ability to aluminum alloys to form aluminum-based composite protective materials. When boride is used as the second phase, B has a large thermal neutron absorption cross section, has a good shielding effect on neutrons, has strong corrosion resistance, and has good radiation resistance. Compared with traditional aluminum alloys, aluminum matrix composites have higher strength, wear resistance and neutron absorption effect, and have become a substitute material for traditional aluminum alloys. Radiation shielding and personal protection of production operators have been used.

Although aluminum matrix composites have excellent performance, there are many difficulties in the forming process of complex parts. Nowadays, there are two main methods of forming in-situ aluminum matrix composite parts: subtractive manufacturing and additive manufacturing. Since the machinability of in-situ aluminum matrix composites deteriorates with the decrease of plasticity and the increase of hardness, it is difficult to manufacture complex parts of in-situ aluminum matrix composites by traditional machining methods; in terms of additive manufacturing, aluminum matrix Composite parts are generally 3D printed using SLM laser selective melting technology. Although this technology can produce aluminum matrix composite parts, the mass fraction of borides that can be added is low. It is easy to cause the aluminum alloy matrix to fail to melt and form well due to excessive powder addition or uneven powder mixing, resulting in parts prone to deformation and cracking; and its printing efficiency is low, equipment and processing costs are high, which severely limits the original application of aluminum matrix composites.

Contents of the invention

In view of the technical problems existing in the prior art, one of the purposes of the present invention is to provide a neutron-absorbing composite material preparation device based on screw extrusion, which can prepare complex porous structures, improve the forming accuracy of parts, and ensure the performance of parts Excellent continuity and stability, low energy consumption and high printing efficiency.

The second object of the present invention is to provide a method for preparing neutron-absorbing composite materials based on screw extrusion.

The object of the invention is achieved through the following technical solutions:

A neutron-absorbing composite material preparation device based on screw extrusion, including a screw extrusion module, a material transportation module, a reaction module and a control device,

The screw extrusion module is used to print the precursor, including extruding the matrix material as the overall frame with pores, and extruding the protective material into the pores of the overall frame;

The material transportation module corresponds to the screw extrusion module and the reaction module respectively, and is used to transport the precursor printed by the screw extrusion module to the reaction module;

The reaction module is used to heat the precursor and pass in reaction gas and inert protective gas, so that the precursor undergoes a self-propagating reaction and is sintered into a protective component;

The control device is used to control the actions of the screw extruding module, the material transportation module and the reaction module.

Further, the screw extrusion module includes a sleeve, a base material extrusion assembly and a protective material extrusion assembly, the base material extrusion assembly and the protective material extrusion assembly are arranged in the sleeve and are respectively provided with feed ports, the bottom of the sleeve A nozzle is provided, and the material transportation module is arranged under the nozzle.

Further, a heating block is provided at the nozzle.

Further, the material transportation module includes a molding platform and a conveyor belt assembly. The molding platform is located under the screw extrusion module and is used to carry the precursor printed by the screw extrusion module; the conveyor belt assembly is connected to the molding platform to drive the molding platform to transport the precursor to the React module.

Further, the reaction module includes a metal cavity and a laser generator. The metal cavity is set above the forming platform and has an opening at the bottom to be fastened to the forming platform. The laser generator is used to emit a laser beam to the precursor in the metal cavity.

Further, grooves are provided on the forming platform, and the metal cavity is engaged and fixed on the forming platform through the grooves.

A method for preparing a neutron-absorbing composite material based on screw extrusion, using a neutron-absorbing composite material preparation device based on screw extrusion, comprising the following steps,

Control the screw extrusion module to extrude the matrix material as the overall frame with pores, and extrude the protective material into the pores of the overall frame to print the precursor;

The material transportation module transports the precursor printed by the screw extrusion module to the reaction module;

The reaction module heats the precursor and feeds in reaction gas and inert protective gas, so that the precursor undergoes a self-propagating reaction and is sintered into a protective component.

Further, the base material extruding assembly and the protective material extruding assembly can be selected to work independently or simultaneously as required, so as to extrude a single material or simultaneously extrude two materials.

Further, when the precursor is printed, the matrix material extrusion component is controlled to extrude the matrix material to form an overall frame with pores, and the protective material extrusion component extrudes the protective material into the pores of the overall frame, and in the transition area between the two , to print out the material transition area in such a way that the base material extrusion component extrudes the base material and the protective material extrusion component extrudes the protective material at the same time.

Further, by controlling the ratio of the matrix material to the protective material, and the molar ratio of the reactive gas to the inert protective gas, the reaction amount and reaction rate of the precursor are controlled, thereby realizing the regulation of the mechanical properties of the protective component.

Compared with the prior art, the present invention has the following beneficial effects:

1. Good molding quality of parts: There are three factors that affect the molding quality of parts. One is the cracking of parts: In the SLM3D printing process, excessive boride content will cause the aluminum alloy matrix to fail to melt and form well, resulting in cracking of parts. This limits the boride content, resulting in limited enhancement of the nuclear shielding capability of the part. The present invention can freely select two extrusion modes of single material extrusion and multi-material mixed extrusion to realize complementary advantages: single material adopts material separation and time-sharing extrusion, avoiding the mixing of matrix material and protective material, thereby reducing cracking of parts Possibility; Multi-material mixed extrusion realizes the smooth transition between matrix material and protective material, ensuring the continuity and stability of performance. The second is the deformation of the parts: the present invention adopts the feeding method of screw extrusion, which squeezes the material through the rotation of the screw, compacts the material and transports the material to the nozzle for extrusion. In addition, the screw extrusion assembly is equipped with a heating mechanism , to improve the fluidity of the material by increasing the transport temperature. In screw extrusion, after the material is compacted and heated, its solid content can be greatly improved, the deformation of heating can be reduced, and complex porous structures can be printed. The third is the molding accuracy of the parts: the two screw accommodation chambers of the present invention share the same sleeve and nozzle, which avoids repeated positioning of the screw extrusion assembly when extruding different materials in time, improves the positioning accuracy, and thus improves the molding accuracy of the parts .

2. Low energy consumption: In the commonly used SLM metal 3D printing process: continuous energy supply of laser is required for powder sintering, which will cause energy loss and increase cost. The present invention adopts a 3D printing method based on self-propagating reaction. During the printing process, it only needs to turn on the laser emitter for a short time to ignite the protective material precursor, and provide Initial energy, and then under the self-sustaining reaction of the precursor's own rapid automatic wave combustion, the desired composition and structure of the product can be obtained. The self-propagating reaction does not require additional heat sources other than laser ignition, and does not require continuous laser sintering. Compared with laser selective sintering, the cost is lower, the energy consumption is less, and the equipment is simple and easy to manufacture.

3. High printing efficiency: In the commonly used SLM metal 3D printing process, the powder needs to be mixed for a long time; in the printing process, it is formed point by point, and the forming efficiency is low. The invention adopts screw extrusion to realize high-efficiency extrusion molding of printing materials, and adopts self-propagating reaction 3D printing method, no preheating is required before printing, and integral self-propagating sintering is formed after printing, which has great advantages in printing complex composite materials. high efficiency.

Description of drawings

Fig. 1 is a schematic structural view of a neutron-absorbing composite material preparation device of the present invention.

Fig. 2 is a three-dimensional schematic diagram of the porous structure of the neutron absorbing composite material.

Fig. 3 is a schematic diagram of printing the porous structure of the neutron absorbing composite material.

In the picture:

1-first station, 2-X-axis moving platform, 3-installation bracket, 4-housing, 5-extrusion motor, 6-coupling, 7-sleeve, 8-Z-axis moving platform, 9-screw Extrusion module, 10-heating block, 11-nozzle, 12-laser generator, 13-protective mirror, 14-metal cavity, 15-second station, 16-air valve, 17-gas pipe, 18-inert protection Gas cylinder, 19-reactive gas cylinder, 20-vacuum air pump, 21-lifting module, 22-forming platform, 23-conveyor belt, 24-front and rear rollers, 25-matrix material, 26-transition area, 27-protection Material.

Detailed ways

The present invention will be described in further detail below.

A neutron-absorbing composite material preparation device based on screw extrusion, including a frame, a screw extrusion module 9, a material transportation module and a reaction module;

The frame is provided with two stations, the first station 1 and the second station 15, and the centers of the two stations are located on the same straight line. The first station 1 is equipped with a screw extrusion module 9 for the preparation of the precursor, and the second station 15 is equipped with a reaction module for reaction sintering of the protective material 27 . A material transport module is also installed on the frame, for transferring the precursor at the first station 1 to the second station 15 .

The screw extrusion module 9 includes a moving mechanism and more than two sets of screw extrusion components responsible for extruding printing materials. The moving mechanism is installed at the first station 1, and the moving mechanism is connected with the screw extrusion assembly and drives the screw extrusion assembly to move;

The reaction module includes a metal cavity 14, a vacuum pump 20, an inert protective gas cylinder 18, a reaction gas cylinder 19, a gas pipe 17, a gas valve 16, a laser generator 12 and a protective mirror 13. There are three gas valves at the bottom of the metal cavity 14 16. One end of the gas valve 16 is connected to the vacuum pump 20, the inert protective gas cylinder 18 and the reaction gas cylinder 19 respectively through the gas pipe 17; the protective mirror 13 and the laser generator 12 are installed on the top of the metal cavity 14, and the laser generator 12 Outside the metal cavity 14, the laser beam is directed to the precursor of the protective material 27 in the cavity through the protective mirror 13;

The material transportation module includes a forming platform 22 and a conveyor belt assembly. The conveyor belt assembly is installed on the frame of the two stations. The conveyor belt assembly connects with the forming platform 22 and drives the forming platform 22 to move horizontally.

The moving mechanism includes an X-axis mounting plate, a Y-axis mounting plate, an X-axis moving platform 2 that drives the extrusion component to translate along the X-axis, a Y-axis moving platform that drives the extrusion component to translate along the Y-axis, and drives the extrusion component to translate along the Z-axis The Z-axis mobile platform 8; the direction of the X-axis is set horizontally, the direction of the Y-axis is horizontal and perpendicular to the X-axis, and the direction of the Z-axis is vertical; the Z-axis mobile platform 8 is installed on the frame, and the X-axis mobile platform 2 passes through the X-axis. The shaft mounting plate is connected with the Y-axis mobile platform, so that the X-axis mobile platform 2 is driven by the Y-axis mobile platform to translate along the Y-axis, and the Y-axis mobile platform is connected with the Z-axis mobile platform 8 through the Y-axis mounting plate, so that the Y-axis mobile platform is driven by the Y-axis mobile platform. The Z-axis moving platform 8 is driven to translate along the Z-axis.

The screw extrusion assembly includes a mounting bracket 3, a casing 4, a motor 5, a coupling 6, a screw, a sleeve 7, a material guide pipe, a heating block 10, a nozzle 11 and a fan. The mounting bracket 3 is fixedly connected with the X-axis mobile platform 2, the casing 4 adopts an integrated structure, and is fixedly connected with the mounting bracket 3, the driving motor is installed on the casing 4, and the output shaft of the driving motor is connected with the screw through a coupling 6; the screw is formed by The sleeve 7 is wrapped, the middle part of the shell 4 is attached with the sleeve 7 mounting frame, the sleeve 7 is installed on the sleeve 7 mounting frame, the lower part of the shell 4 is attached with a fan frame, and the fan is installed on the fan frame facing the heat sink to accelerate cooling effect.

The forming platform 22 is located directly below the nozzle 11, and is used to carry the printed entity, and can be transported by the conveyor belt assembly to perform translational movement between the two stations.

According to the function, the screw extrusion assembly is divided into two parts: the base material 25 extrusion assembly and the protective material 27 extrusion assembly. Each of the two parts is equipped with a set of motor, coupling 6 and screw, which are used to extrude the base material 25 and protective material respectively. 27. The matrix material 25 extrusion assembly and the protective material 27 extrusion assembly are symmetrically distributed left and right on the same frame, and share the same sleeve 7 , heating block 10 and nozzle 11 . The sleeve 7 is an integrated structure, and the upper part of the sleeve 7 is two symmetrically distributed screw accommodation chambers independent of each other, which are respectively used to wrap the matrix material 25 extrusion screw and the protective material 27 extrusion screw, each screw accommodation chamber There is a feed port connected with it, the feed port is connected with the material guide pipe, the middle part of the sleeve 7 is equipped with cooling fins and installation holes, and the lower part is attached with a unique output port, and the two screw accommodation chambers are respectively connected with the output port, and the output The mouth is connected with the heating block 10 and the nozzle 11, which itself plays the role of heat conduction; the heating block 10 heats the high-solid content water-based particle material in the sleeve 7 through heat transfer, so that its viscosity is reduced and its fluidity is improved, and it cooperates with the screw Rotate and knead the granules into a paste and extrude from the nozzle 11.

When printing any layer, the two extrusion components can choose to work independently or simultaneously according to the printing characteristics; when one extrusion component works alone, the other extrusion component is in a static state, and a single material is extruded from the nozzle 11 Complete the printing of a single material feature; when working at the same time, the two extrusion components simultaneously extrude two materials from the nozzle 11 according to the output ratio to complete the printing of the transition area 26, so as to achieve a smooth transition between the base material 25 and the protective material 27. The conversion between the two modes is set by the path planning in the model slice information.

The conveyor belt assembly includes a motor, front and rear rollers 24, conveyor belts 23, etc. The front roller is fixed on the frame of the first station 1, the rear roller is fixed on the frame of the second station 15, and the conveyor belt 23 is wound on the front and rear rollers 24 and runs through the between two workstations. The front and rear rollers 24 are rotated by the motor, thereby driving the conveyor belt 23 to move in translation to convey the material; when the material is transported by the conveyor belt 23 to the second station 15, the feeding device assembly is responsible for feeding the metal cavity 14 and then fixing it on the forming platform 22 The molding platform 22 is provided with a groove, and the metal cavity 14 is engaged and fixed on the molding platform 22 through the groove; the delivery device assembly includes the metal cavity 14 and the lifting module 21; the lifting module 21 is fixed on the second frame. Position 15 is mechanically connected to the metal cavity 14, and the metal cavity 14 is raised and lowered by controlling the movement of the lifting module 21.

In the reaction module, the metal cavity 14 is a square container with one side open, and a plurality of gas valves 16 are installed, and are connected to different types of gas cylinders such as vacuum pump 20, inert protective gas cylinder, reaction gas cylinder 19, etc. through gas pipe 17. , different types of gases are transported into the metal cavity 14 through the air pipe 17, and the reaction products and reaction rates of the self-propagating reaction are controlled by regulating the amount of air intake; the upper part of the metal cavity 14 is equipped with a protective mirror 13 and a laser emitter for heating The precursor of the protective material 27 is to provide the initial energy required for self-propagation. Laser emitters can control the rate of self-propagating reactions by adjusting the probability of laser light. The protective mirror 13 is a circular sheet with the same size as the light outlet of the laser transmitter, embedded in the central groove on the inner side of the top of the metal cavity 14, and fixedly connected with the metal cavity 14 through the mounting hole.

Both the transmission motor of the conveyor belt assembly and the extrusion motor 5 of the screw extrusion assembly are preferably stepper motors. The X-axis mobile platform 2, the Y-axis mobile platform, the Z-axis mobile platform 8 and the lifting module 21 all adopt linear modules.

The nozzle 11 is a hollow funnel shape, the size of the inlet matches the outlet of the sleeve 7, and the outlet is smaller than the inlet, which can be adjusted according to requirements. Generally speaking, the smaller the size of the outlet, the higher the printing accuracy, but the lower the printing efficiency. The heating block 10 is a cuboid aluminum alloy heating block with a through hole in the middle, and the nozzle 11 is embedded in it for fixed connection. There are installation holes around the heating block 10 and is fixed at the output port of the sleeve 7 .

A method for preparing a neutron-absorbing composite material based on screw extrusion, using a neutron-absorbing composite material preparation device based on screw extrusion, comprising the following steps:

S1, this embodiment realizes the additive manufacturing of Al-AlB ₂ neutron absorbing porous structure composite material. Mix aluminum powder and water in proportion to form water-based paste-like aluminum powder, use water-based paste-like aluminum powder as base material 25, and water-based paste-like boron oxide powder as protective material 27 respectively add to the two reservoirs of the extrusion module In the barrel, and complete the printing platform leveling, gas cylinder connection and other preparations;

S2, importing the slice information of the printed model into the preparation device and starting the device;

S3, the screw extrusion module 9 extrudes the water-based pasty aluminum powder and the water-based pasty boron oxide powder at preset positions according to the path planning in the model slice information, and extrudes with two screws at the transfer of the two materials The components work at the same time to print out the material transition area 26, layer by layer until the precursor is printed;

S4, controlling the rotation of the front and rear rollers 24, thereby driving the forming platform 22 to move horizontally from the first station 1 to the second station 15;

S5, when the forming platform 22 reaches directly below the metal cavity 14, the lifting module 21 lowers the metal cavity 14 onto the forming platform 22, and the lower edge of the metal cavity 14 cooperates with the platform groove to realize gas sealing;

S6, the vacuum air pump 20 is turned on, and the air in the metal cavity 14 is drawn out to realize the vacuum in the metal cavity 14;

S7, the gas valve is opened, and a certain proportion of the inert protective gas argon and the reaction gas oxygen are transported into the inner space of the metal cavity 14 through different air pipes 17;

S8, the emitter emits a laser beam to heat the precursor so that it has the initial energy of the self-propagating reaction, and a self-propagating reaction occurs;

S9, the reaction is finished, and the lifting module 21 lifts up the metal cavity 14 .

In step S3, the preset position refers to the porous structure with the base material 25 water-based pasty aluminum powder as the overall frame, the protective material 27 water-based pasty boron oxide powder is filled in the pore position, and the transition between the two Area 26 uses mixed material printing to achieve material transitions. This method of multi-material printing in-situ synthesis improves the molding quality of porous materials and ensures the continuity and stability of the performance of neutron-absorbing composite parts. By controlling the ratio of water-based paste-like aluminum powder and water-based paste-like boron oxide powder during printing, it is also possible to control the composition of composite material components. In this self-propagating reaction, the products are mainly Al, AlB ₂ and Al ₂ O ₃ . Among them, Al and AlB ₂ are the expected ideal products, and Al ₂ O ₃ is the product of the heat-providing reaction. Excessive Al ₂ O ₃ will reduce the mechanical properties of components, and the amount of Al ₂ O ₃ is mainly related to the amount of boron oxide powder. By controlling the ratio of boron oxide powder to aluminum powder, the mechanical properties of protective components can be adjusted .

In step S7, by controlling the molar ratio of oxygen and argon, the self-propagating reaction amount and reaction rate can be controlled. The role of oxygen is mainly to react with aluminum powder in the initial stage of the self-propagating reaction under the ignition of the laser to supply energy for the aluminothermic reaction. Increasing the amount of oxygen can increase the rate of the self-propagating reaction, but excessive oxygen will cause excessive Too much Al ₂ O ₃ , thus affecting the mechanical properties of the protective components. The role of argon is to provide a suitable pressure for the self-propagating reaction. Generally speaking, the higher the pressure, the higher the rate of the self-propagating reaction.

In step S8, under laser irradiation, oxygen reacts with Al to generate the heat required for the initial reaction, and under the energy supply of the initial reaction heat, aluminum and boron oxide react to form aluminum oxide and boron. At the same time, relying on the large amount of heat generated by the aluminothermic reaction, the synthesis reaction of Al and B to generate AlB ₂ occurs, that is, the formation of AlB ₂ can only be realized by coupling with the aluminothermic reaction. The heat generated by the material reaction on the surface of the precursor further causes the material reaction inside the precursor, and finally realizes the overall self-propagating reaction of the precursor.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. The utility model provides a neutron absorption combined material preparation facilities based on screw extrusion which characterized in that: comprises a screw extrusion module, a material transportation module, a reaction module and a control device,

the screw extrusion module is used for printing a precursor and comprises extruding a matrix material as a whole frame containing pores, and extruding a protective material into the pores of the whole frame;

the material conveying module is respectively corresponding to the screw extrusion module and the reaction module and is used for conveying the precursor printed by the screw extrusion module to the reaction module;

the reaction module is used for heating the precursor, introducing reaction gas and inert protective gas to enable the precursor to perform self-propagating reaction and sinter into a protective component;

the control device is used for controlling the actions of the screw extrusion module, the material transportation module and the reaction module.

2. The apparatus for preparing a neutron absorbing composite material based on screw extrusion according to claim 1, wherein: the screw extrusion module comprises a sleeve, a base material extrusion assembly and a protective material extrusion assembly, wherein the base material extrusion assembly and the protective material extrusion assembly are uniformly distributed in the sleeve and are respectively provided with a feed inlet, a nozzle is arranged at the bottom of the sleeve, and the material transportation module is arranged below the nozzle.

3. A neutron absorbing composite preparation device based on screw extrusion as defined in claim 2, wherein: the nozzle is provided with a heating block.

4. The apparatus for preparing a neutron absorbing composite material based on screw extrusion according to claim 1, wherein: the material conveying module comprises a forming platform and a conveyor belt assembly, wherein the forming platform is positioned below the screw extrusion module and used for bearing the precursor printed by the screw extrusion module; the conveyor belt assembly is connected with the forming platform and is used for driving the forming platform to transport the precursor to the reaction module.

5. The apparatus for preparing a neutron absorbing composite material based on screw extrusion according to claim 1, wherein: the reaction module comprises a metal cavity and a laser generator, wherein the metal cavity is arranged above the forming platform, the bottom of the metal cavity is provided with an opening to be buckled on the forming platform, and the laser generator is used for emitting laser beams to precursors in the metal cavity.

6. The apparatus for producing a neutron absorbing composite material by screw extrusion according to claim 5, wherein: the forming platform is provided with a groove, and the metal cavity is meshed and fixed on the forming platform through the groove.

7. A method for preparing a neutron absorbing composite material based on screw extrusion, which adopts the neutron absorbing composite material preparation device based on screw extrusion as set forth in any one of claims 1-6, and is characterized in that: comprises the steps of,

controlling a screw extrusion module to extrude a matrix material to be used as an integral frame containing pores, and extruding a protective material into the pores of the integral frame so as to print out a precursor;

the material transporting module transports the precursor printed by the screw extrusion module to the reaction module;

the reaction module heats the precursor, and introduces the reaction gas and the inert shielding gas, so that the precursor is subjected to self-propagating reaction and sintered into the protective member.

8. The method for preparing the neutron absorbing composite material based on screw extrusion according to claim 7, wherein: the base material extrusion assembly and the protective material extrusion assembly may be operated individually or simultaneously as desired to extrude a single material or to extrude both materials simultaneously.

9. The method for preparing the neutron absorbing composite material based on screw extrusion according to claim 8, wherein: when the precursor is printed, the matrix material extrusion assembly is controlled to extrude the matrix material to form an integral frame with pores, the protective material extrusion assembly extrudes the protective material into the pores of the integral frame, and the material transition area is printed in a mode that the matrix material extrusion assembly extrudes the matrix material and the protective material extrusion assembly extrudes the protective material at the same time in a transition area between the matrix material extrusion assembly and the protective material extrusion assembly.

10. The method for preparing the neutron absorbing composite material based on screw extrusion according to claim 7, wherein: the reaction quantity and the reaction rate of the precursor are controlled by controlling the proportion of the matrix material to the protective material and the mole fraction proportion of the reaction gas to the inert protective gas, so that the regulation and control of the mechanical property of the protective member are realized.

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