Silicon nitride / polyether ether ketone composite powder, and method for producing and molding the same

Abstract

The application provides a silicon nitride / polyether ether ketone composite powder and a preparation method and a forming method thereof, and belongs to the field of laser selective sintering. The submicron polyether ether ketone can increase the surface energy to enhance the adhesion, so that the polyether ether ketone can be wrapped on the surface of the silicon nitride particles to act as a 'binder', and then the prepared silicon nitride / polyether ether ketone composite powder is easier to be sintered. Meanwhile, the solution blending evaporation method is adopted to uniformly mix the silicon nitride and the submicron polyether ether ketone together, and the high interfacial energy graphene oxide is added, so that the interfacial bonding force of the silicon nitride and the polyether ether ketone can be effectively enhanced, the problem of easy agglomeration of ordinary mechanical mixing is solved, the polyether ether ketone is more uniformly wrapped on the surface of the silicon nitride particles, and finally the prepared composite powder has good fluidity by adding a flow aid, so that the requirements of the laser selective sintering technology on the powder material can be met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of selective laser sintering, and more particularly relates to a silicon nitride / polyether ether ketone composite powder and a preparation method and forming method thereof. BACKGROUND

[0002] High-performance polymer polyether ether ketone (PEEK) has the advantages of light weight, high strength, corrosion resistance, etc., and is therefore widely used in key components of national strategic fields and pillar industries. For example, components such as airframe and pipeline, broadband wave-transparent radome, etc. Such components have gradually shown the development trend of functionalization (having a complex broadband wave-transparent functional structure), integration (antenna and support are integrally formed to avoid problems caused by block manufacturing), and light weight (honeycomb structure inside the part). They have asymmetric shape, irregular curved surface, and complex internal structure, and the forming difficulty gradually increases.

[0003] Selective laser sintering (SLS) is one of the widely used additive manufacturing (AM) technologies at present, which uses solid powder as raw material and directly forms a part entity from a three-dimensional model using the principle of layer-by-layer manufacturing, without the need for support. It has a significant advantage for once integrally forming complex structure parts. For PEEK material, its melting point is relatively high, close to 340℃. At the same time, the crystallization rate of PEEK material is very fast, more than twice that of SLS commercial nylon material processing temperature. Therefore, the temperature field requirement for SLS forming of PEEK material is very precise. A slight change in temperature field directly leads to rapid crystallization shrinkage in the sintering area with low temperature, and warping deformation of the part. How to slow down the crystallization rate of PEEK material is the key to reducing the SLS processing difficulty and promoting the application of PEEK material.

[0004] Silicon nitride (Si3N4) is an environmentally friendly ceramic material, which is an important structural ceramic material with high hardness, self-lubricating, wear resistance, corrosion resistance, and high temperature stability. More importantly, silicon nitride has a low thermal conductivity, which makes it easier to maintain the temperature field conditions of the high-temperature powder bed once heated to the powder bed processing temperature, and plays a key role in slowing down the crystallization rate of PEEK material. At the same time, the silicon nitride / PEEK composite material can further improve the direct strength and service temperature, and expand its application field. However, the existing preparation method of SLS composite powder material has the following problems: 1) the particle size of the commonly used micron-sized polyether ether ketone on the market is too large, and the surface energy is too low, so the adhesion with silicon nitride is not good; 2) the existing technology usually uses mechanical mixing method to mix the powder, which will cause uneven dispersion of the powder; 3) the interface adhesion between silicon nitride and PEEK is poor. SUMMARY

[0005] In view of the defects of the prior art, the present application aims to provide a silicon nitride / polyether ether ketone composite powder, a preparation method thereof and a forming method, and aims to solve the problems of uneven mixing, poor adhesion between silicon nitride and polyether ether ketone in the existing preparation method of the silicon nitride / polyether ether ketone composite powder.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present application, a preparation method of a silicon nitride / polyether ether ketone composite powder is provided, and the preparation method comprises the following steps:

[0007] S1 adding graphene oxide and a flow aid into an organic solvent aqueous solution to obtain a first suspension, adding silicon nitride into the organic solvent aqueous solution to obtain a second suspension, and adding sub-micron polyether ether ketone into the organic solvent aqueous solution to obtain a third suspension;

[0008] S2 mixing and stirring the first suspension, the second suspension and the third suspension to obtain a composite suspension, so that the polyether ether ketone is wrapped on the surface of the silicon nitride to act as a binder, and the graphene oxide is further used to improve the interfacial adhesion between the silicon nitride and the polyether ether ketone;

[0009] S3 heating the composite suspension to evaporate the organic solvent aqueous solution, so as to obtain the silicon nitride / polyether ether ketone composite powder.

[0010] As a further preferred, in step S1, the particle size of the silicon nitride is 10-100 μm, and the particle size of the sub-micron polyether ether ketone is less than 1 μm.

[0011] As a further preferred, in step S1, the concentration of the organic solvent aqueous solution is 20-95 vol%, and the organic solvent aqueous solution is a methanol aqueous solution, an ethanol aqueous solution, a propanol aqueous solution, a glycol aqueous solution or a butanol aqueous solution.

[0012] As a further preferred, in steps S1 and S2, the suspension is obtained by alternately using ultrasonic oscillation and physical stirring.

[0013] As a further preferred, in step S2, the mass ratio of the polyether ether ketone to the silicon nitride in the composite suspension is 1:4-4:1.

[0014] As a further preferred, in step S2, the ratio of the mass of the graphene oxide to the sum of the mass of the silicon nitride and the mass of the polyether ether ketone in the composite suspension is (0.1-2):100.

[0015] As a further preferred, in step S2, the ratio of the mass of the flow aid to the sum of the mass of the silicon nitride and the mass of the polyether ether ketone in the composite suspension is (0.1-0.5):100, and the flow aid is one or more of silicon dioxide, titanium dioxide and magnesium stearate.

[0016] According to another aspect of the present application, there is provided a silicon nitride / polyether ether ketone composite powder prepared by the above method.

[0017] According to still another aspect of the present application, there is provided a method of laser selective sintering forming using the above silicon nitride / polyether ether ketone composite powder.

[0018] As further preferred, the preheating temperature of the laser selective sintering is 298-328℃, the filling power is 15-25W, the layer thickness is 0.08-0.25mm, the filling interval is 0.1-0.3mm, the contour attack is 3-6W, and the spot offset is -0.1-0.1mm.

[0019] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0020] 1. The submicron polyether ether ketone used in the present application can increase its surface energy to enhance its adhesion, so that the polyether ether ketone can wrap around the surface of the silicon nitride particles to act as a "binder", thereby making the prepared silicon nitride / polyether ether ketone composite powder easier to sinter. Meanwhile, the solution blending evaporation method is used to uniformly mix the silicon nitride and submicron polyether ether ketone together, and the high interfacial energy graphene oxide is added, which can effectively enhance the interfacial bonding force between the silicon nitride and the polyether ether ketone, solve the problem of easy agglomeration of ordinary mechanical mixing, and make the polyether ether ketone more uniformly wrapped around the surface of the silicon nitride particles. Finally, the addition of the flow aid makes the prepared composite powder have good flowability, which can meet the requirements of the laser selective sintering technology for powder materials.

[0021] 2. Meanwhile, by optimizing the mass ratio of the polyether ether ketone to the silicon nitride, the present application can control the elastic modulus of the parts prepared by laser selective sintering to some extent, so that it can better fit the mechanical properties of different applications and different parts. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a preparation flowchart of the silicon nitride / polyether ether ketone composite powder provided by the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0024] As shown in Figure 1 the present application provides a preparation method of a silicon nitride / polyether ether ketone composite powder, which comprises the following steps:

[0025] S1 adds graphene oxide and a flow agent into an organic solvent aqueous solution to obtain a first suspension, adds silicon nitride with a particle size of 10-100 microns into the organic solvent aqueous solution to obtain a second suspension, and adds sub-micron polyether ether ketone into the organic solvent aqueous solution to obtain a third suspension, wherein the polyether ether ketone can be broken by ball milling to reduce the particle size, and then sub-micron polyether ether ketone with a particle size of less than 1 micron is screened out to increase the interfacial energy of the polyether ether ketone;

[0026] S2 mixes and stirs the first suspension, the second suspension and the third suspension to obtain a composite suspension, so that the polyether ether ketone is wrapped on the surface of the silicon nitride as a binder, and the interfacial bonding between the silicon nitride and the polyether ether ketone is further improved by using the graphene oxide, and the problem of easy agglomeration in ordinary mechanical mixing is solved.

[0027] S3 heats the composite suspension to evaporate the organic solvent aqueous solution, so as to obtain a silicon nitride / polyether ether ketone composite powder, in which the polyether ether ketone is uniformly wrapped on the surface of the silicon nitride, and the requirements of the powder material for the laser selective sintering technology are met.

[0028] The sub-micron polyether ether ketone can enhance the surface energy of the polyether ether ketone to enhance its adhesion, so that the polyether ether ketone can be wrapped on the surface of the silicon nitride particles as a "binder", and the silicon nitride / polyether ether ketone composite powder is easier to sinter. Meanwhile, the graphene oxide used as a nano material with high interfacial energy can further improve the interfacial bonding between the silicon nitride and the polyether ether ketone, thereby improving the toughness and mechanical properties of the silicon nitride / polyether ether ketone composite powder. In addition, the solution blending evaporation method is used in the present application, which avoids the agglomeration of the sub-micron polyether ether ketone compared with the ordinary mechanical mixing method, so that the sub-micron polyether ether ketone can be more uniformly wrapped on the silicon nitride particles, and the flowability of the prepared silicon nitride / polyether ether ketone composite powder is good, which is suitable for laser selective sintering, and the prepared parts have high precision and ideal mechanical properties.

[0029] Further, the specific process for preparing the sub-micron polyether ether ketone is as follows: the polyether ether ketone is put into a ball mill, and ball milling is performed at 400 rad / min for 8 h, and the mass ratio of the ball milling beads to the polyether ether ketone is 1:1.

[0030] Further, in step S1, the concentration of the organic solvent aqueous solution is 20-95 vol%, and the organic solvent aqueous solution is a methanol aqueous solution, an ethanol aqueous solution, a propanol aqueous solution, a glycol aqueous solution or a butanol aqueous solution. Preferably, the organic solvent aqueous solution is an ethanol aqueous solution, which has the advantage of environmental friendliness.

[0031] Further, in the step S1 and the step S2, the suspension is obtained by alternately using ultrasonic oscillation and physical stirring. In the step S1, ultrasonic oscillation is first used for 10 minutes under the condition of 250 W and 50 Hz, and then physical stirring is used for 10 minutes at the rotating speed of 350 r / min to 500 r / min, and the above process is repeated for 4 hours. In the step S2, ultrasonic oscillation is first used for 10 minutes under the condition of 250 W and 50 Hz, and then physical stirring is used for 10 minutes at the rotating speed of 350 r / min to 500 r / min, and the above process is repeated for 10 hours, and finally physical stirring is used for 2 hours at the rotating speed of 350 r / min to 500 r / min.

[0032] Further, in the step S2, the mass ratio of the polyether ether ketone to the silicon nitride is 1:4 to 4:1, and the content of the polyether ether ketone is adjusted to control the elastic modulus of the part prepared by the laser selective sintering to some extent, so that the part is more suitable for the mechanical properties of different parts in different application fields. The mass ratio of the polyether ether ketone to the silicon nitride directly affects the elastic modulus of the part prepared by the laser selective sintering, and therefore the mass ratio of the polyether ether ketone to the silicon nitride can be selected according to the requirement. When the mass ratio of the polyether ether ketone to the silicon nitride is 1:4, the elastic modulus of the prepared part is about 30 GPa, when the mass ratio of the polyether ether ketone to the silicon nitride is 1:2, the elastic modulus of the prepared part is about 15 GPa, when the mass ratio of the polyether ether ketone to the silicon nitride is 1:1, the elastic modulus of the prepared part is about 5.5 GPa, and when the mass ratio of the polyether ether ketone to the silicon nitride is 4:1, the elastic modulus of the prepared part is about 3.5 GPa.

[0033] Further, in the step S2, in order to fully play the role of enhancing the interface bonding between the reinforced silicon nitride and the polyether ether ketone, and at the same time avoid the agglomeration of the graphene oxide itself and affect the effect, the ratio of the mass of the graphene oxide to the sum of the mass of the silicon nitride and the mass of the polyether ether ketone in the composite suspension is preferably (0.1 to 2):100.

[0034] Further, in the step S2, the ratio of the mass of the flow aid to the sum of the mass of the silicon nitride and the mass of the polyether ether ketone in the composite suspension is (0.1 to 0.5):100, and the flow aid is one or more of silicon dioxide, titanium dioxide and magnesium stearate, so as to play the role of enhancing the flowability of the composite powder, and avoid the agglomeration of the flow aid itself and affect the effect.

[0035] According to another aspect of the present application, a silicon nitride / polyether ether ketone composite powder prepared by the above method is provided.

[0036] According to another aspect of the present invention, a method for selective laser sintering (SLS) using the aforementioned silicon nitride / polyetheretherketone (PEEK) composite powder is provided. The preheating temperature for SLS is 298°C to 328°C, the fill power is 15W to 25W, the fill rate is 2000mm / s, the layer thickness is 0.1mm, the fill spacing is 0.2mm, the contour sweeping power is 3W to 6W, the contour scanning rate is 4000mm / s, and the spot offset is 0mm. Excessive fill power can lead to degradation of the PEEK on the surface of the composite powder, and excessive fill power can also prevent the composite powder from being sintered.

[0037] The technical solution provided by the present invention will be further described below with reference to specific embodiments.

[0038] Example 1

[0039] S1. Graphene oxide and a flow aid are added to an aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a first suspension. Silicon nitride with a particle size of 10μm to 100μm is added to the aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a second suspension. Submicron-sized polyether ether ketone is added to the aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a third suspension. The aqueous organic solvent solution is an ethanol aqueous solution with a concentration of 20 vol%. The specific process of ultrasonic vibration and stirring is as follows: ultrasonication at 250W and 50Hz for 10 min, stirring at 350r / min for 10 min, and repeating this cycle for 4 h.

[0040] S2 mixes the first, second, and third suspensions, then ultrasonically vibrates and stirs to obtain a composite suspension. The mass ratio of graphene oxide to the sum of the masses of silicon nitride and polyetheretherketone (PEEK) in the composite suspension is 0.1:100, the mass ratio of the glidant to the sum of the masses of silicon nitride and PEEK is 0.1:100, and the mass ratio of PEEK to silicon nitride is 4. The specific process of ultrasonic vibration and stirring is as follows: ultrasonication at 250W and 50Hz for 10 minutes, followed by stirring at 350r / min for 10 minutes, repeated for 10 hours. Then, stirring at 350r / min for 2 hours.

[0041] S3 heats the composite suspension to evaporate the organic solvent aqueous solution, thereby obtaining silicon nitride / polyether ether ketone composite powder;

[0042] S4 uses selective laser sintering (SLS) technology to fabricate the prepared silicon nitride / polyetheretherketone (PEEK) composite powder into corresponding parts. The specific parameters are: preheating temperature of 298℃, fill power of 15W, fill rate of 2000mm / s, layer thickness of 0.1mm, fill spacing of 0.2mm, contour coverage of 3W, contour scanning rate of 4000mm / s, and spot offset of 0mm.

[0043] Example 2

[0044] S1. Graphene oxide and a flow aid are added to an aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a first suspension. Silicon nitride with a particle size of 10μm to 100μm is added to the aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a second suspension. Submicron-sized polyether ether ketone is added to the aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a third suspension. The aqueous organic solvent solution is an ethanol aqueous solution with a concentration of 95 vol%. The specific process of ultrasonic vibration and stirring is as follows: ultrasonication at 250W and 50Hz for 10 min, stirring at 500r / min for 10 min, and repeating this cycle for 4 h.

[0045] S2 mixes the first, second, and third suspensions, then ultrasonically vibrates and stirs to obtain a composite suspension. The mass ratio of graphene oxide to the sum of the masses of silicon nitride and polyetheretherketone (PEEK) in the composite suspension is 2:100, the mass ratio of the glidant to the sum of the masses of silicon nitride and PEEK is 0.5:100, and the mass ratio of PEEK to silicon nitride is 0.25. The specific process of ultrasonic vibration and stirring is as follows: ultrasonication at 250W and 50Hz for 10 minutes, followed by stirring at 500r / min for 10 minutes, repeated for 10 hours. Then, stirring at 500r / min for 2 hours.

[0046] S3 heats the composite suspension to evaporate the organic solvent aqueous solution, thereby obtaining silicon nitride / polyether ether ketone composite powder;

[0047] S4 uses selective laser sintering (SLS) technology to fabricate the prepared silicon nitride / polyether ether ketone (PEEK) composite powder into corresponding parts. The specific parameters are: preheating temperature of 328℃, fill power of 25W, fill rate of 2000mm / s, layer thickness of 0.1mm, fill spacing of 0.2mm, contour coverage of 6W, contour scanning rate of 4000mm / s, and spot offset of 0mm.

[0048] Example 3

[0049] S1. Graphene oxide and a flow aid are added to an aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a first suspension. Silicon nitride with a particle size of 10μm to 100μm is added to the aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a second suspension. Submicron-sized polyether ether ketone is added to the aqueous organic solvent solution and ultrasonically vibrated and stirred to obtain a third suspension. The aqueous organic solvent solution is an ethanol aqueous solution with a concentration of 65 vol%. The specific process of ultrasonic vibration and stirring is as follows: ultrasonication at 250W and 50Hz for 10 min, stirring at 400r / min for 10 min, and repeating this cycle for 4 h.

[0050] S2 mixes the first, second, and third suspensions, then ultrasonically vibrates and stirs to obtain a composite suspension. The mass ratio of graphene oxide to the sum of the masses of silicon nitride and polyetheretherketone (PEEK) in the composite suspension is 1:100, the mass ratio of the gliding agent to the sum of the masses of silicon nitride and PEEK is 0.2:100, and the mass ratio of PEEK to silicon nitride is 2. The specific process of ultrasonic vibration and stirring is as follows: ultrasonication at 250W and 50Hz for 10 minutes, followed by stirring at 400r / min for 10 minutes, repeated for 10 hours. Then, stirring at 400r / min for 2 hours.

[0051] S3 heats the composite suspension to evaporate the organic solvent aqueous solution, thereby obtaining silicon nitride / polyether ether ketone composite powder;

[0052] S4 uses selective laser sintering (SLS) technology to fabricate the prepared silicon nitride / polyetheretherketone (PEEK) composite powder into corresponding parts. The specific parameters are: preheating temperature of 298℃~328℃, fill power of 20W, fill rate of 2000mm / s, layer thickness of 0.1mm, fill spacing of 0.2mm, contour coverage of 5W, contour scanning rate of 4000mm / s, and spot offset of 0mm.

[0053] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing silicon nitride / polyetheretherketone composite powder, characterized in that, The preparation method includes the following steps: S1. Graphene oxide and a flow aid are added to an aqueous organic solvent to obtain a first suspension. Silicon nitride is added to an aqueous organic solvent to obtain a second suspension. Submicron-sized polyether ether ketone is added to an aqueous organic solvent to obtain a third suspension. The particle size of the silicon nitride is 10 μm to 100 μm, and the particle size of the submicron-sized polyether ether ketone is less than 1 μm. S2 mixes and stirs the first suspension, the second suspension and the third suspension to obtain a composite suspension, so that polyether ether ketone is coated on the surface of silicon nitride to act as a binder, and graphene oxide is used to further improve the interfacial bonding between silicon nitride and polyether ether ketone. S3 heats the composite suspension to evaporate the organic solvent aqueous solution, thereby obtaining silicon nitride / polyether ether ketone composite powder.

2. The method for preparing silicon nitride / polyetheretherketone composite powder as described in claim 1, characterized in that, In step S1, the concentration of the organic solvent aqueous solution is 20 vol% to 95 vol%, and the organic solvent aqueous solution is an aqueous solution of methanol, ethanol, propanol, ethylene glycol, or butanol.

3. The method for preparing silicon nitride / polyetheretherketone composite powder as described in claim 1, characterized in that, In steps S1 and S2, a suspension is obtained by alternating ultrasonic oscillation and physical stirring.

4. The method for preparing silicon nitride / polyetheretherketone composite powder as described in claim 1, characterized in that, In step S2, the mass ratio of polyetheretherketone to silicon nitride in the composite suspension is 1:4 to 4:

1.

5. The method for preparing silicon nitride / polyetheretherketone composite powder as described in claim 1, characterized in that, In step S2, the ratio of the mass of graphene oxide in the composite suspension to the sum of the masses of silicon nitride and polyether ether ketone is (0.1~2):

100.

6. The method for preparing silicon nitride / polyetheretherketone composite powder according to any one of claims 1 to 5, characterized in that, In step S2, the ratio of the mass of the flow aid in the composite suspension to the sum of the masses of silicon nitride and polyether ether ketone is (0.1~0.5):100, and the flow aid is one or more of silicon dioxide, titanium dioxide, and magnesium stearate.

7. Silicon nitride / polyether ether ketone composite powder prepared by the preparation method according to any one of claims 1 to 6.

8. A method for selective laser sintering using the silicon nitride / polyetheretherketone composite powder as described in claim 7.

9. The laser selective sintering method for silicon nitride / polyetheretherketone composite powder as described in claim 8, characterized in that, The preheating temperature for laser selective sintering is 298℃~328℃, the filling power is 15 W~25 W, the layer thickness is 0.08 mm~0.25 mm, the filling spacing is 0.1 mm~0.3 mm, the contouring is 3 W~6 W, and the spot offset is -0.1 mm~0.1 mm.

Images