Preparation method of nano-zinc oxide whisker reinforced zinc-based composite material

Abstract

The invention discloses a preparation method of a nano-zinc oxide whisker reinforced zinc-based composite material, and relates to the technical field of advanced non-ferrous metal materials, and the preparation method comprises the following steps: carrying out surface modification treatment on nano-zinc oxide whiskers by using a silane coupling agent, carrying out planetary ball-milling mixing on the nano-zinc oxide whiskers and zinc powder, carrying out compression molding, carrying out vacuum sintering, and carrying out hot extrusion treatment to obtain the nano-zinc oxide whisker reinforced zinc-based composite material. Through surface modification and reasonable process parameter control, uniform dispersion and good interface bonding of the nano-zinc oxide whiskers in a zinc matrix are realized, the prepared composite material has the characteristics of high strength, high hardness and high wear resistance, and compared with pure zinc, the tensile strength is improved by 40-60%, and the wear resistance is improved by 20-30%. The hardness is improved by 30-50%, the wear resistance is improved by 50-70%, and the method is simple in process and suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of advanced non-ferrous materials, in particular to a preparation method of zinc-based composite material reinforced by nano zinc oxide whiskers. BACKGROUND

[0002] Zinc and zinc alloys have good electrical conductivity, thermal conductivity, corrosion resistance and processing performance, and are widely used in electronic, chemical, construction, mechanical and other fields. However, pure zinc and traditional zinc alloys have low strength, poor wear resistance and insufficient high-temperature performance, which limits their application in structural materials and functional materials fields. In order to improve the comprehensive performance of zinc-based materials, researchers try to add various reinforcing phases to the zinc matrix to prepare zinc-based composite materials. Common reinforcing phases include ceramic particles, carbon materials, metal oxides, etc. Among them, zinc oxide whiskers are concerned due to their high strength, high modulus, good chemical stability and good chemical compatibility with zinc matrix. Nano-sized zinc oxide whiskers have larger specific surface area and better reinforcing effect. Currently, the preparation of zinc-based composite material reinforced by nano zinc oxide whiskers mainly faces the following technical problems: Nano zinc oxide whiskers have high surface energy and are easy to agglomerate, which is difficult to disperse uniformly in the zinc matrix. The interface bonding between nano zinc oxide whiskers and zinc matrix is weak, which affects the load transfer efficiency. Traditional melting and casting method has high preparation temperature, which easily leads to the growth, fracture of nano zinc oxide whiskers or adverse reaction with the matrix. During the preparation of powder metallurgy method, how to realize densification and maintain the integrity of nano reinforcing phase is a key problem. Therefore, it is necessary to develop a preparation method which can realize the uniform dispersion of nano zinc oxide whiskers in the zinc matrix, good interface bonding and maintaining the integrity of reinforcing phase. SUMMARY

[0003] The present application aims to provide a preparation method of zinc-based composite material reinforced by nano zinc oxide whiskers, to solve the problems of uneven dispersion of nano zinc oxide whiskers in the zinc matrix, weak interface bonding and poor reinforcing phase integrity in the prior art.

[0004] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A preparation method of zinc-based composite material reinforced by nano zinc oxide whiskers, comprising the following steps: S1: placing nano zinc oxide whiskers in a silane coupling agent solution for surface modification treatment, the mass concentration of silane coupling agent is 3-8%, the modification treatment temperature is 50-80℃, the treatment time is 1-3 hours, and modified nano zinc oxide whiskers are obtained; S2: mixing the modified nano zinc oxide whisker and zinc powder with a mass ratio of 2:98 to 8:92, using planetary ball milling during the mixing process, the ball milling speed is 200-400 rpm, and the ball milling time is 4-8 hours, to obtain a premixed powder; S3: loading the premixed powder into a graphite mold for pressing, the pressing pressure is 150-300 MPa, and the pressure holding time is 3-8 minutes, to obtain a green body; S4: sintering the green body in a vacuum sintering furnace, the sintering temperature is 350-420℃, the vacuum degree is 1×10 -3 Pa to 5×10 -3 Pa, and the sintering time is 2-4 hours, to obtain a sintered body; S5: hot extrusion treatment of the sintered body, the extrusion temperature is 280-350℃, the extrusion ratio is 8:1 to 15:1, and the extrusion speed is 1-3 mm / s, to obtain a zinc-based composite material reinforced by nano zinc oxide whiskers.

[0005] Preferably, in the step S1, the diameter of the nano zinc oxide whisker is 50-200 nm, the length is 2-10 μm, and the aspect ratio is 20:1 to 100:1.

[0006] Preferably, in the step S1, the silane coupling agent is one of γ-aminopropyl triethoxysilane, γ-glycidyl ether propyl trimethoxysilane, and vinyl triethoxysilane.

[0007] Preferably, in the step S1, after the surface modification treatment, the sample is washed with anhydrous ethanol for 3-5 times, and then vacuum dried at 60-80℃ for 2-4 hours.

[0008] Preferably, in the step S2, the purity of the zinc powder is above 99.5%, and the particle size is 10-50 μm.

[0009] Preferably, in the step S2, the ball-to-material ratio of the planetary ball milling is 5:1 to 10:1, and the ball milling medium is zirconia ball.

[0010] Preferably, in the step S4, the sintering process adopts a segmented heating method: increasing the temperature to 200-250℃ at a rate of 5-10℃ / min, holding for 30-60 minutes; then increasing the temperature to 350-420℃ at a rate of 3-5℃ / min, holding for 2-4 hours; and then cooling to room temperature with the furnace.

[0011] Preferably, in the step S5, the sintered body is preheated to the extrusion temperature before hot extrusion, and the preheating time is 20-40 minutes.

[0012] Preferably, after the step S5, the extruded material is subjected to aging treatment, the aging temperature is 100-150℃, and the aging time is 1-3 hours.

[0013] Compared with the prior art, the present application has the advantages that: 1. The surface of the nano zinc oxide whisker is modified by a silane coupling agent to form an organic-inorganic transition layer, thereby reducing the surface energy, effectively preventing agglomeration, and improving the interface bonding strength with the zinc matrix; 2. The modified nano zinc oxide whisker is uniformly dispersed in the zinc powder by mechanical force through a planetary ball milling mixing method, thereby avoiding local enrichment; 3. The nano zinc oxide whisker is prevented from growing and breaking and the integrity and nano size effect of the reinforcing phase are maintained by using a low-temperature vacuum sintering process; 4. The density and interface bonding quality of the material are further improved, and the mechanical properties are improved by heat extrusion treatment; 5. The zinc-based composite material prepared has the characteristics of uniform dispersion of nano zinc oxide whisker, good interface bonding, and dense structure, and compared with pure zinc, the tensile strength is increased by 40-60%, the hardness is increased by 30-50%, and the wear resistance is increased by 50-70%. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a process flow chart of the method of the present application; Figure 2 is a schematic diagram of surface modification treatment of the nano zinc oxide whisker; Figure 3 is a schematic diagram of powder mixing and pressing and sintering process; Figure 4 is a schematic diagram of heat extrusion treatment; Figure 5 is a process parameter comparison data table of the present application; Figure 6 is a performance test result comparison data table of the present application; Figure 7 is a schematic diagram of mechanical property comparison of the example and the comparative example; Figure 8 is a schematic diagram of wear resistance comparison of the example and the comparative example; Figure 9 is a schematic diagram of radar comparison of the comprehensive performance of the example and the comparative example. DETAILED DESCRIPTION

[0015] The present application will be further described in detail below with reference to the accompanying drawings and specific examples.

[0016] Example 1 According to the accompanying Figure 1 - the accompanying Figure 9 , a method for preparing a zinc-based composite material reinforced by nano zinc oxide whisker is shown, and the specific steps are as follows: S1: surface modification treatment Select the diameter of 100 nm, length of 5 μm, length-diameter ratio of 50:1 of nano zinc oxide whisker, 50 g of nano zinc oxide whisker is dispersed in 1000 ml of anhydrous ethanol, 5% mass concentration of γ-aminopropyl triethoxysilane is added, and stirring reaction is carried out at 65°C for 2 hours. During the reaction, the silanol groups of the hydrolyzed silane coupling agent and the hydroxyl groups on the surface of the nano zinc oxide whisker condense to form a chemical bonded organic-inorganic transition layer. After the reaction, the modified nano zinc oxide whisker is washed with anhydrous ethanol 4 times, and after each washing, it is separated by centrifugation (3000 rpm for 10 minutes). Finally, the modified nano zinc oxide whisker is vacuum dried at 70°C for 3 hours, with a vacuum degree of 100 Pa, to obtain the modified nano zinc oxide whisker.

[0017] S2: powder mixing The modified nano zinc oxide whisker and zinc powder with a purity of 99.8% and a particle size of 30 μm are mixed in a mass ratio of 5:95. The mixed powder is loaded into a stainless steel ball mill tank of a planetary ball mill, and zirconia balls are added as the ball milling medium. The ball-to-powder ratio is 8:1, and the ball milling is carried out at a speed of 300 rpm for 6 hours. The ball milling is stopped every 30 minutes for 10 minutes to prevent the temperature from being too high. During the ball milling, the nano zinc oxide whisker is uniformly dispersed in the zinc powder through the mechanical force of high-energy ball milling. After the ball milling, the pre-mixed powder is collected.

[0018] S3: pressing The pre-mixed powder is loaded into a graphite mold with a diameter of 30 mm, and pressed at a pressure of 200 MPa for 5 minutes to obtain a cylindrical compact. During the pressing process, a unidirectional pressing method is used, and the pressing speed is 10 mm / min.

[0019] S4: vacuum sintering The compact is placed in a vacuum sintering furnace for sintering, and the specific process parameters are as follows: First stage: increase the temperature from room temperature to 225°C at a rate of 8°C / min, and keep it for 45 minutes. The main purpose of this stage is to remove the gas and organic matter adsorbed on the surface of the powder particles; Second stage: increase the temperature from 225°C to 380°C at a rate of 4°C / min, and keep it for 3 hours. This stage is the main sintering stage, and the powder particles are combined through atomic diffusion in an environment with a vacuum degree of 3×10 -3 Pa; Third stage: cool down to room temperature at a rate of about 5°C / min.

[0020] During the sintering process, the temperature is lower than the melting point of zinc (419.5°C), which belongs to solid-phase sintering, and can effectively avoid the growth and fracture of the nano zinc oxide whisker.

[0021] S5: hot extrusion treatment The sintered compact is preheated at 300°C for 30 minutes, and then hot extruded, with the extrusion die preheated to 300°C, the extrusion ratio being 10:1 and the extrusion speed being 2 mm / s. During the extrusion, the material is subjected to strong plastic deformation, further eliminating pores and improving density, and improving the interface bonding between the nano zinc oxide whiskers and the zinc matrix.

[0022] S6: aging treatment The extruded material is aged at 120°C for 2 hours, and then air cooled to room temperature. The aging treatment can eliminate residual stress and stabilize the structure.

[0023] The final nano zinc oxide whisker reinforced zinc matrix composite material has a diameter of 9.5 mm (calculated from the initial diameter of 30 mm according to the extrusion ratio of 10:1) and a length of about 300 mm.

[0024] The prepared composite material is subjected to performance testing, and the results are as follows: Relative density: 98.5%; Tensile strength: 195 MPa (pure zinc about 130 MPa); Vickers hardness: 85 HV (pure zinc about 60 HV); Wear rate: 0.85 mg / 100m (pure zinc about 2.8 mg / 100m).

[0025] Example 2 The difference between this example and Example 1 is: In S1, 6% mass concentration of γ-glycidoxypropyltrimethoxysilane is used as the coupling agent, the treatment temperature is 75°C, and the treatment time is 1.5 hours.

[0026] In S2, the mass ratio of modified nano zinc oxide whiskers to zinc powder is 3:97, the ball milling speed is 250 rpm, and the ball milling time is 5 hours.

[0027] In S4, the sintering temperature is 360°C, and the holding time is 3.5 hours.

[0028] In S5, the extrusion temperature is 290°C, the extrusion ratio is 12:1, and the extrusion speed is 1.5 mm / s.

[0029] The other steps are the same as in Example 1.

[0030] The performance test results of the prepared composite material are as follows: Relative density: 98.2%; Tensile strength: 185 MPa; Vickers hardness: 80 HV; Wear rate: 1.0 mg / 100m.

[0031] Example 3 The difference between this example and Example 1 is: In S1, the diameter of the nano zinc oxide whisker is 150 nm, the length is 8 μm, the aspect ratio is 53:1, the mass concentration of the vinyl triethoxysilane used is 4%, the treatment temperature is 55℃, and the treatment time is 2.5 hours.

[0032] In S2, the mass ratio of the modified nano zinc oxide whisker to zinc powder is 7:93, the ball milling speed is 350 rpm, and the ball milling time is 7 hours.

[0033] In S3, the pressing pressure is 250 MPa, and the pressure holding time is 6 minutes.

[0034] In S4, the sintering temperature is 400℃, and the holding time is 2.5 hours.

[0035] In S5, the extrusion temperature is 320℃, the extrusion ratio is 9:1, and the extrusion speed is 2.5 mm / s.

[0036] In S6, the aging temperature is 135℃, and the aging time is 2.5 hours.

[0037] The other steps are the same as in Example 1.

[0038] The performance test results of the prepared composite material are as follows: Relative density: 98.8%; Tensile strength: 205 MPa; Vickers hardness: 88 HV; Wear rate: 0.75 mg / 100 m.

[0039] Comparative Example 1 The nano zinc oxide whisker that has not been surface modified is directly mixed with zinc powder, and the other process parameters are the same as in Example 1.

[0040] The performance test results of the prepared composite material are as follows: Relative density: 96.5%; Tensile strength: 160 MPa; Vickers hardness: 68 HV; Wear rate: 1.8 mg / 100 m.

[0041] As can be seen from Comparative Example 1, the nano zinc oxide whisker that has not been surface modified has poor dispersibility in the zinc matrix and weak interface bonding, and the comprehensive performance of the material is significantly lower than that of Examples 1-3.

[0042] Comparative Example 2 The conventional sintering temperature is 450℃ (450℃ is higher than the melting point of zinc (419.5℃), which is used to verify the damage of the whisker in the molten state), and other process parameters are the same as those in example 1.

[0043] During the sintering process, due to the excessively high temperature, it is found that part of the nano zinc oxide whiskers grow up, the aspect ratio is reduced to about 20:1, and part of the whiskers are broken, and the performance test results of the prepared composite material are as follows: Relative density: 98.0%; Tensile strength: 170 MPa; Vickers hardness: 72 HV; Wear rate: 1.5 mg / 100m.

[0044] As can be seen from the comparative example 2, high temperature sintering can damage the morphology and integrity of the nano zinc oxide whisker, and reduce the reinforcing effect.

[0045] Comparative example 3 No hot extrusion treatment is performed, and the sintering is directly aged, and other process parameters are the same as those in example 1.

[0046] The performance test results of the prepared composite material are as follows: Relative density: 96.8%; Tensile strength: 175 MPa; Vickers hardness: 75 HV; Wear rate: 1.3 mg / 100m.

[0047] As can be seen from the comparative example 3, the hot extrusion treatment plays an important role in improving the material density and improving the interface bonding.

[0048] In summary, by the process route of surface modification of nano zinc oxide whisker, planetary ball milling mixing, low temperature vacuum sintering and hot extrusion treatment, the zinc-based composite material with uniform dispersion of nano zinc oxide whisker, good interface bonding and excellent comprehensive performance is successfully prepared, compared with the prior art, the method has the advantages of simple process, moderate cost and suitable for industrial production.

[0049] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing zinc-based composite materials reinforced with nano-zinc oxide whiskers, comprising the preparation method, characterized in that: The preparation method includes the following steps: S1: Place the nano zinc oxide whiskers in a silane coupling agent solution for surface modification treatment. The mass concentration of the silane coupling agent is 3-8%, the modification treatment temperature is 50-80℃, and the treatment time is 1-3 hours to obtain modified nano zinc oxide whiskers. S2: Modified nano zinc oxide whiskers and zinc powder are mixed at a mass ratio of 2:98 to 8:

92. Planetary ball milling is used during the mixing process. The ball milling speed is 200-400 rpm and the ball milling time is 4-8 hours to obtain premixed powder. S3: The premixed powder is loaded into a graphite mold and pressed at a pressure of 150-300MPa for 3-8 minutes to obtain a pressed blank. S4: The pressed compact is sintered in a vacuum sintering furnace at a temperature of 350-420℃ and a vacuum degree of 1×10⁻⁶. -3 Pa to 5×10 -3 Pa, sintering time is 2-4 hours, to obtain sintered green body; S5: The sintered green body is subjected to hot extrusion treatment at an extrusion temperature of 280-350℃, an extrusion ratio of 8:1 to 15:1, and an extrusion speed of 1-3 mm / s to obtain a zinc-based composite material reinforced with nano zinc oxide whiskers.

2. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S1, the diameter of the nano zinc oxide whiskers is 50-200 nm, the length is 2-10 μm, and the aspect ratio is 20:1 to 100:

1.

3. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S1, the silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and vinyltriethoxysilane.

4. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S1, after surface modification treatment, the surface is washed with anhydrous ethanol 3-5 times, and then vacuum dried at 60-80℃ for 2-4 hours.

5. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S2, the zinc powder has a purity of 99.5% or higher and a particle size of 10-50 μm.

6. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S2, the ball-to-material ratio of the planetary ball mill is 5:1 to 10:1, and the milling medium is zirconia balls.

7. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S4, the sintering process adopts a segmented heating method: the temperature is raised to 200-250℃ at a heating rate of 5-10℃ / min and held for 30-60 minutes; then the temperature is raised to 350-420℃ at a heating rate of 3-5℃ / min and held for 2-4 hours; and then the furnace is cooled to room temperature.

8. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: In step S5, the sintered billet is preheated to the extrusion temperature before hot extrusion, and the preheating time is 20-40 minutes.

9. The method for preparing zinc-based composite material reinforced with nano-zinc oxide whiskers according to claim 1, characterized in that: After step S5, the extruded material is subjected to aging treatment at a temperature of 100-150℃ for 1-3 hours.

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