Multilayer composite metal fiber sintered felt and preparation process thereof

Abstract

The invention provides a multilayer composite metal fiber sintered felt and a preparation process thereof. The preparation process comprises the following steps: S1, preparing a coarse metal fiber sintered felt; s2, carbon nanotubes are deposited on the fine metal short fibers, and then a fine metal fiber sintered felt blank is prepared; s3, stacking and sintering the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt; s4, the face, away from the coarse metal fiber sintered felt, of the obtained multi-layer composite metal fiber sintered felt base body is coated with hydrophobic paint, standing is carried out, washing is carried out, and nitrogen is adopted for blow-drying; the hydrophobic coating is prepared from the following raw materials: nano silicon dioxide sol and octadecyl trimethoxy silane. And S5, repeating the step S4 for 2-3 times to obtain the multi-layer composite metal fiber sintered felt. The prepared multi-layer composite metal fiber sintered felt is excellent in mechanical property, the fine metal fiber sintered felt has an excellent hydrophobic surface, materials related to the hydrophobic layer are high in safety and environment friendliness, and oil-water separation is easy to achieve.

Description

Technical Field

[0001] The invention relates to the technical field of sintered felt, and in particular to a multi-layer composite metal fiber sintered felt and a preparation process thereof. Background Art

[0002] Metal fiber sintered felt is made of micron-sized metal fibers sintered at high temperature. It has the characteristics of high strength, high porosity, uniform pore size distribution, corrosion resistance, high temperature resistance, etc. These characteristics of metal fiber sintered felt make it widely used in fields such as filtration and separation.

[0003] At present, industries such as petrochemicals, mechanical processing, and food manufacturing will produce a large amount of oily wastewater, which has a great pollution to the environment, so it is necessary to effectively treat the oily wastewater. Among them, the metal fiber sintered felt after hydrophobic treatment can be used for oil-water separation, has a high pollution holding capacity, and can be reused after cleaning, which can effectively reduce the cost of use. Therefore, the metal fiber sintered felt after hydrophobic treatment is suitable for the treatment of oily wastewater.

[0004] For the hydrophobic modification of metal fiber sintered felt, fluorination treatment is currently mostly used to make the felt surface have hydrophobic and oleophilic properties, but many fluorine-containing compounds used in fluorination treatment are bioaccumulative and potentially toxic. Therefore, in order to improve the safety of oil-water separation, it is necessary to perform non-fluorinated hydrophobic treatment on metal fiber sintered felt, but the hydrophobic effect of general non-fluorinated hydrophobic treatment is not good enough. In addition, when using fine metal fiber sintered felt with high filtration accuracy for oily wastewater, if the flow rate of the oily wastewater is high, it will produce a large scouring force on the sintered felt, which may cause mechanical deformation of the fine metal fiber sintered felt. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-layer composite metal fiber sintered felt and a preparation process thereof, wherein the prepared multi-layer composite metal fiber sintered felt has excellent mechanical properties, wherein the fine metal fiber sintered felt has an excellent hydrophobic surface, the material obtained by the hydrophobic layer is highly safe and environmentally friendly, and it is easy to achieve oil-water separation.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A preparation process of a multi-layer composite metal fiber sintered felt comprises the following steps: S1. Using coarse metal short fibers with a diameter of 40 μm or more to prepare a coarse metal fiber sintered felt blank, and sintering to obtain a coarse metal fiber sintered felt; S2. Depositing carbon nanotubes on fine metal short fibers with a diameter of 5 to 10 μm by a vapor deposition method to obtain pretreated fine metal short fibers; and preparing fine metal fiber sintered felt blanks by using the pretreated fine metal short fibers; S3, stacking the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sintering them to obtain a multi-layer composite metal fiber sintered felt matrix; S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, standing for 2 to 4 minutes, washing with water and drying with nitrogen; the raw materials of the hydrophobic coating include nano-silica sol and octadecyltrimethoxysilane; S5. Repeat step S4 2-3 times to obtain the multi-layer composite metal fiber sintered felt.

[0007] Preferably, in step S2, the step of depositing carbon nanotubes on fine metal short fibers having a diameter of 5 to 10 μm by vapor deposition to obtain pretreated fine metal short fibers comprises the following steps: Place fine metal short fibers with a diameter of 5-10 μm in a vapor deposition furnace, evacuate the furnace, heat it to 670-720°C, introduce a mixed gas of hydrogen and inert gas, and then introduce ethylene and ferric chloride gas, keep warm for 20-25 minutes, and deposit carbon nanotubes on the fine metal short fibers; then stop heating, stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and inert gas until the vapor deposition furnace naturally cools to room temperature.

[0008] Preferably, the volume flow rate of the mixed gas is 300-400 sccm, the volume flow rate ratio of the hydrogen gas to the inert gas is 1:4-6; the volume flow rate of the ethylene is 30-50 sccm, and the volume flow rate of the ferric chloride gas is 200-300 sccm.

[0009] Preferably, the temperature is increased to 670-720° C. at a heating rate of 3-7° C. / min.

[0010] Preferably, in step S4, the hydrophobic coating comprises the following raw materials in weight percentage: 10-20% nano silica sol, 1-3% octadecyltrimethoxysilane, and the balance is ethanol; the solid content of the nano silica sol is 20-30%.

[0011] Preferably, the particle size of the nano-silica in the nano-silica sol is 120-160 nm; Each time the hydrophobic coating is applied, the coating amount of the hydrophobic coating is 50-75 g / m 2 .

[0012] Preferably, the coarse metal short fibers and the fine metal short fibers are both stainless steel fibers.

[0013] Preferably, in step S1, the sintering temperature is 1120-1200°C, the holding time is 1.5-2h, and the sintering is carried out in a mixed atmosphere of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is 1:8-9.

[0014] Preferably, in step S3, the sintering temperature is 950-1000° C., the holding time is 25-35 min, and the sintering is carried out in a mixed atmosphere of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is 1:8-9.

[0015] As a general inventive concept, the present invention provides a multi-layer composite metal fiber sintered felt prepared by the above-mentioned preparation process.

[0016] The beneficial effects of the present invention are: 1. The multi-layer composite metal fiber sintered felt of the present invention comprises a coarse metal fiber sintered felt and a fine metal fiber sintered felt fixed on the coarse metal fiber sintered felt. When preparing the fine metal fiber sintered felt, the present invention deposits carbon nanotubes on the fine metal short fibers used. The carbon nanotubes have excellent hydrophobicity, and the carbon nanotubes are loaded on the fine metal short fibers so that the surface of the fine metal short fibers has a higher roughness, thereby making the obtained pretreated fine metal short fibers have a higher hydrophobic property.

[0017] The pre-treated fine metal short fibers can be used to prepare hydrophobic fine metal fiber sintered felt. On this basis, the fine metal fiber sintered felt is further coated with the hydrophobic coating of the present invention, so that the part of the fine metal fiber sintered felt away from the coarse metal fiber sintered felt has better hydrophobic properties, and the farther away from the coarse metal fiber sintered felt, the stronger the hydrophobicity, while the coarse metal fiber sintered felt remains unmodified by hydrophobicity, so that the obtained multi-layer composite metal fiber sintered felt has excellent oil-water separation effect. In addition, when the present invention is hydrophobically modified, the material involved in the hydrophobic layer is highly safe and environmentally friendly, and the secondary pollution caused by the separated water and oil is very limited.

[0018] 2. In the multi-layer composite metal fiber sintered felt of the present invention, the coarse metal fiber sintered felt has high strength and can be used as a supporting layer of the sintered felt, making the sintered felt more impact-resistant and less prone to deformation. The deposition of carbon nanotubes on the fine metal short fibers can not only improve the hydrophobicity, but also improve the strength of the fine metal fiber sintered felt, so that the fine metal fiber sintered felt itself has higher mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The present invention is a process flow chart for preparing multi-layer composite metal fiber sintered felt. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the following examples and comparative examples, the coarse metal short fibers and the fine metal short fibers are all 316L stainless steel fibers.

[0023] Embodiment 1: A preparation process of a multi-layer composite metal fiber sintered felt comprises the following steps: S1. A coarse metal fiber sintered felt blank is prepared using coarse metal short fibers with a diameter of 50 μm, and the porosity of the coarse metal fiber sintered felt blank is 90%. The coarse metal fiber sintered felt blank is sintered to obtain a coarse metal fiber sintered felt, wherein the sintering temperature is 1150° C., the insulation time is 2 h, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:8.

[0024] S2. Place fine metal short fibers with a diameter of 6 μm in a vapor deposition furnace, then evacuate the furnace, and then heat the furnace to 700°C at a heating rate of 5°C / min, introduce a mixed gas of hydrogen and argon, the volume flow rate of the mixed gas is 400 sccm, and the volume flow rate ratio of hydrogen and argon is 1:5; then introduce ethylene and ferric chloride gas, the volume flow rate of ethylene is 40 sccm, and the volume flow rate of ferric chloride gas is 300 sccm; keep warm for 25 minutes to deposit carbon nanotubes on the fine metal short fibers; then stop heating, and stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and argon until the vapor deposition furnace naturally cools to room temperature to obtain pretreated fine metal short fibers.

[0025] The fine metal fiber sintered felt blank is prepared by pre-treating the fine metal short fibers; the porosity of the fine metal fiber sintered felt blank is 85%.

[0026] S3. Stack the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sinter them to obtain a multi-layer composite metal fiber sintered felt matrix; the sintering temperature is 980°C, the insulation time is 32 minutes, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:8.

[0027] S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, leaving it to stand for 3 minutes, washing it with water and drying it with nitrogen; The hydrophobic coating includes the following raw materials in weight percentage: 20% nano-silica sol, 2% octadecyltrimethoxysilane, and the balance is ethanol. The solid content of the nano-silica sol is 20%, and the particle size of the nano-silica in the nano-silica sol is 120~160nm; each time the hydrophobic coating is applied, the coating amount of the hydrophobic coating is 65g / m 2 .

[0028] S5. Repeat step S4 twice to obtain a multi-layer composite metal fiber sintered felt.

[0029] Embodiment 2: A preparation process of a multi-layer composite metal fiber sintered felt comprises the following steps: S1. A coarse metal fiber sintered felt blank is prepared using coarse metal short fibers with a diameter of 50 μm, and the porosity of the coarse metal fiber sintered felt blank is 90%. The coarse metal fiber sintered felt blank is sintered to obtain a coarse metal fiber sintered felt, wherein the sintering temperature is 1180°C, the insulation time is 1.5 h, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:8.

[0030] S2. Place fine metal short fibers with a diameter of 6 μm in a vapor deposition furnace, then evacuate the furnace, and then heat the furnace to 720°C at a heating rate of 7°C / min, introduce a mixed gas of hydrogen and argon, the volume flow rate of the mixed gas is 300 sccm, and the volume flow rate ratio of hydrogen and argon is 1:4; then introduce ethylene and ferric chloride gas, the volume flow rate of ethylene is 50 sccm, and the volume flow rate of ferric chloride gas is 200 sccm; keep warm for 25 minutes to deposit carbon nanotubes on the fine metal short fibers; then stop heating, and stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and argon until the vapor deposition furnace naturally cools to room temperature to obtain pretreated fine metal short fibers.

[0031] The fine metal fiber sintered felt blank is prepared by using pretreated fine metal short fibers; the porosity of the fine metal fiber sintered felt blank is 86%.

[0032] S3. Stack the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sinter them to obtain a multi-layer composite metal fiber sintered felt matrix; wherein the sintering temperature is 1000°C, the insulation time is 28 minutes, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:8.

[0033] S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, leaving it to stand for 2 minutes, washing it with water and drying it with nitrogen; The hydrophobic coating includes the following raw materials in weight percentage: 10% nano-silica sol, 1% octadecyltrimethoxysilane, and the balance is ethanol. The solid content of the nano-silica sol is 30%, and the particle size of the nano-silica in the nano-silica sol is 120~160nm; each time the hydrophobic coating is applied, the coating amount of the hydrophobic coating is 75g / m 2 .

[0034] S5. Repeat step S4 three times to obtain the multi-layer composite metal fiber sintered felt.

[0035] Embodiment 3: A preparation process of a multi-layer composite metal fiber sintered felt comprises the following steps: S1. A coarse metal fiber sintered felt blank is prepared using coarse metal short fibers with a diameter of 50 μm, and the porosity of the coarse metal fiber sintered felt blank is 90%. The coarse metal fiber sintered felt blank is sintered to obtain a coarse metal fiber sintered felt, wherein the sintering temperature is 1200°C, the insulation time is 1.5 h, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:9.

[0036] S2. Place fine metal short fibers with a diameter of 6 μm in a vapor deposition furnace, then evacuate the furnace, and then heat the temperature to 690°C at a heating rate of 3°C / min, introduce a mixed gas of hydrogen and argon, the volume flow rate of the mixed gas is 400sccm, and the volume flow rate ratio of hydrogen and argon is 1:5; then introduce ethylene and ferric chloride gas, the volume flow rate of ethylene is 40sccm, and the volume flow rate of ferric chloride gas is 300sccm; keep warm for 22 minutes to deposit carbon nanotubes on the fine metal short fibers; then stop heating, and stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and argon until the vapor deposition furnace naturally cools to room temperature to obtain pretreated fine metal short fibers.

[0037] The fine metal fiber sintered felt blank is prepared by pre-treating the fine metal short fibers; the porosity of the fine metal fiber sintered felt blank is 85%.

[0038] S3. Stack the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sinter them to obtain a multi-layer composite metal fiber sintered felt matrix; wherein the sintering temperature is 1000°C, the insulation time is 25 minutes, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:9.

[0039] S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, leaving it to stand for 2 minutes, washing it with water and drying it with nitrogen; The hydrophobic coating includes the following raw materials in weight percentage: 10% nano-silica sol, 2% octadecyltrimethoxysilane, and the balance is ethanol. The solid content of the nano-silica sol is 30%, and the particle size of the nano-silica in the nano-silica sol is 120~160nm; each time the hydrophobic coating is applied, the coating amount of the hydrophobic coating is 75g / m 2 .

[0040] S5. Repeat step S4 twice to obtain the multi-layer composite metal fiber sintered felt.

[0041] Embodiment 4: A preparation process of a multi-layer composite metal fiber sintered felt comprises the following steps: S1. A coarse metal fiber sintered felt blank is prepared using coarse metal short fibers with a diameter of 50 μm, and the porosity of the coarse metal fiber sintered felt blank is 90%. The coarse metal fiber sintered felt blank is sintered to obtain a coarse metal fiber sintered felt, wherein the sintering temperature is 1160° C., the insulation time is 1.5 h, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:9.

[0042] S2. Place fine metal short fibers with a diameter of 6 μm in a vapor deposition furnace, then evacuate the furnace, and then heat the temperature to 690°C at a heating rate of 3°C / min, introduce a mixed gas of hydrogen and argon, the volume flow rate of the mixed gas is 400sccm, and the volume flow rate ratio of hydrogen and argon is 1:5; then introduce ethylene and ferric chloride gas, the volume flow rate of ethylene is 40sccm, and the volume flow rate of ferric chloride gas is 300sccm; keep warm for 22 minutes to deposit carbon nanotubes on the fine metal short fibers; then stop heating, and stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and argon until the vapor deposition furnace naturally cools to room temperature to obtain pretreated fine metal short fibers.

[0043] The fine metal fiber sintered felt blank is prepared by pre-treating the fine metal short fibers; the porosity of the fine metal fiber sintered felt blank is 85%.

[0044] S3. Stacking the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sintering to obtain a multi-layer composite metal fiber sintered felt matrix; wherein the sintering temperature is 950° C., the insulation time is 35 min, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:9.

[0045] S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, leaving it to stand for 3 minutes, washing it with water and drying it with nitrogen; The hydrophobic coating includes the following raw materials in weight percentage: 15% nano-silica sol, 3% octadecyltrimethoxysilane, and the balance is ethanol. The solid content of the nano-silica sol is 20%, and the particle size of the nano-silica in the nano-silica sol is 120~160nm; each time the hydrophobic coating is applied, the amount of the hydrophobic coating is 55g / m 2 .

[0046] S5. Repeat step S4 twice to obtain the multi-layer composite metal fiber sintered felt.

[0047] Embodiment 5: A preparation process of a multi-layer composite metal fiber sintered felt comprises the following steps: S1. A coarse metal fiber sintered felt blank is prepared using coarse metal short fibers with a diameter of 50 μm, and the porosity of the coarse metal fiber sintered felt blank is 90%. The coarse metal fiber sintered felt blank is sintered to obtain a coarse metal fiber sintered felt, wherein the sintering temperature is 1120° C., the insulation time is 2 h, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:8.

[0048] S2. Place fine metal short fibers with a diameter of 6 μm in a vapor deposition furnace, then evacuate the furnace, and then heat the temperature to 690°C at a heating rate of 3°C / min, introduce a mixed gas of hydrogen and argon, the volume flow rate of the mixed gas is 400sccm, and the volume flow rate ratio of hydrogen and argon is 1:5; then introduce ethylene and ferric chloride gas, the volume flow rate of ethylene is 40sccm, and the volume flow rate of ferric chloride gas is 300sccm; keep warm for 22 minutes to deposit carbon nanotubes on the fine metal short fibers; then stop heating, and stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and argon until the vapor deposition furnace naturally cools to room temperature to obtain pretreated fine metal short fibers.

[0049] The fine metal fiber sintered felt blank is prepared by pre-treating the fine metal short fibers; the porosity of the fine metal fiber sintered felt blank is 85%.

[0050] S3. Stack the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sinter them to obtain a multi-layer composite metal fiber sintered felt matrix; the sintering temperature is 980°C, the insulation time is 30 minutes, and the sintering is carried out in a mixed atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1:8.

[0051] S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, leaving it to stand for 4 minutes, washing it with water and drying it with nitrogen; The hydrophobic coating includes the following raw materials in weight percentage: 20% nano-silica sol, 2% octadecyltrimethoxysilane, and the balance is ethanol. The solid content of the nano-silica sol is 20%, and the particle size of the nano-silica in the nano-silica sol is 120~160nm; each time the hydrophobic coating is applied, the amount of the hydrophobic coating is 50g / m 2 .

[0052] S5. Repeat step S4 three times to obtain the multi-layer composite metal fiber sintered felt.

[0053] Comparative Example 1: The difference from Example 1 is that the multi-layer composite metal fiber sintered felt matrix prepared in step S3 is used as the multi-layer composite metal fiber sintered felt.

[0054] Comparative Example 2: Different from the embodiment 1, in step S2, fine metal short fibers are directly used to prepare fine metal fiber sintered felt blanks.

[0055] Comparative Example 3: The difference from Example 1 is that the time for introducing ethylene and ferric chloride gas is 10 min.

[0056] Comparative Example 4: The difference from Example 1 is that the time for introducing ethylene and ferric chloride gas is 35 minutes.

[0057] Comparative Example 5: Different from Example 1, the particle size of the nano-silica in the nano-silica sol is 30-60 nm; Performance Test: In the multi-layer composite metal fiber sintered felt, the water contact angle of the coarse metal fiber sintered felt away from the fine metal fiber sintered felt (recorded as water contact angle 1) was tested, and the water contact angle of the fine metal fiber sintered felt away from the coarse metal fiber sintered felt (recorded as water contact angle 2) was tested. The specific test results are shown in Table 1.

[0058] Table 1: Water contact angle / (°) Water contact angle 2 / (°) Example 1 76 157 Example 2 74 159 Example 3 76 162 Example 4 75 160 Example 5 75 160 Comparative Example 1 76 125 Comparative Example 2 76 143 Comparative Example 3 76 150 Comparative Example 4 76 155 Comparative Example 5 76 152 It can be seen from Table 1 that in the multi-layer composite metal fiber sintered felt of Examples 1 to 5 of the present invention, the fine metal fiber sintered felt has excellent hydrophobic properties on the side away from the coarse metal fiber sintered felt, and the coarse metal fiber sintered felt maintains its original hydrophilic properties on the side away from the fine metal fiber sintered felt. This arrangement enables the multi-layer composite metal fiber sintered felt to have a good application effect in oil-water separation.

[0059] By comparing Example 1 with Comparative Example 1, it can be seen that the hydrophobic property of the fine metal fiber sintered felt surface is not coated with a hydrophobic coating, and the hydrophobic property is significantly reduced. By comparing Example 1 with Comparative Example 2, it can be seen that the hydrophobic property of the fine metal fiber sintered felt surface is significantly reduced by not depositing carbon nanotubes on the fine metal short fibers. Therefore, it can be seen that depositing carbon nanotubes on the fine metal short fibers and the hydrophobic coating can synergistically repel water.

[0060] From the comparison between Example 1 and Comparative Example 3, it can be seen that if the time for depositing carbon nanotubes is too short, the amount of carbon nanotubes deposited is insufficient, which has a certain impact on the hydrophobicity of the fine metal fiber sintered felt. From the comparison between Example 1 and Comparative Example 4, it can be seen that if the time for depositing carbon nanotubes is too long, the amount of carbon nanotubes deposited is large, and the hydrophobicity of the fine metal fiber sintered felt cannot be further improved, but rather reduced.

[0061] From the comparison between Example 1 and Comparative Example 5, it can be seen that if the particle size of the nano-silicon dioxide in the hydrophobic coating is reduced to 30-60 nm, the hydrophobicity of the fine metal fiber sintered felt will also be reduced.

[0062] 2. The fine metal fiber sintered felts in Examples 1-2 and Comparative Examples 2-4 were cut into test blocks of 8 cm×2 cm×0.5 mm, and then subjected to a tensile test at a tensile rate of 1.5 mm / min to test their breaking strength. The specific test results are shown in Table 2.

[0063] Table 2: Breaking strength / MPa Example 1 27.5 Example 2 28.0 Comparative Example 2 21.0 Comparative Example 3 24.7 Comparative Example 4 27.9 It can be seen from Table 2 that the fine metal fiber sintered felt in Examples 1 and 2 of the present invention has a relatively high fracture strength. It can be seen from the comparison between Example 1 and Comparative Example 2 that the deposition of carbon nanotubes on fine metal short fibers can significantly improve the fracture strength of the fine metal fiber sintered felt. It can be seen from the comparison between Example 1 and Comparative Example 3 that if the deposition time of carbon nanotubes is too short, resulting in insufficient deposition of carbon nanotubes, the fracture strength of the fine metal fiber sintered felt will be reduced. It can be seen from the comparison between Example 1 and Comparative Example 4 that if the deposition time of carbon nanotubes is too long, resulting in a large amount of carbon nanotubes deposited, the improvement in the fracture strength of the fine metal fiber sintered felt is less.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation process of a multi-layer composite metal fiber sintered felt, characterized in that: The following steps are involved: S1. Using coarse metal short fibers with a diameter of 40 μm or more to prepare a coarse metal fiber sintered felt blank, and sintering to obtain a coarse metal fiber sintered felt; S2, depositing carbon nanotubes on fine metal short fibers with a diameter of 5 to 10 μm by a vapor deposition method to obtain pretreated fine metal short fibers; Using the pretreated fine metal short fibers to prepare fine metal fiber sintered felt blanks; S3, stacking the fine metal fiber sintered felt blank and the coarse metal fiber sintered felt, and then sintering them to obtain a multi-layer composite metal fiber sintered felt matrix; S4, coating a hydrophobic coating on one side of the multi-layer composite metal fiber sintered felt substrate away from the coarse metal fiber sintered felt, standing for 2 to 4 minutes, washing with water and drying with nitrogen; the raw materials of the hydrophobic coating include nano-silica sol and octadecyltrimethoxysilane; S5. Repeat step S4 2-3 times to obtain the multi-layer composite metal fiber sintered felt.

2. The preparation process of the multi-layer composite metal fiber sintered felt according to claim 1, characterized in that: In step S2, the method of depositing carbon nanotubes on fine metal short fibers with a diameter of 5 to 10 μm by vapor deposition to obtain pretreated fine metal short fibers comprises the following steps: Place fine metal short fibers with a diameter of 5-10 μm in a vapor deposition furnace, evacuate the furnace, heat it to 670-720°C, introduce a mixed gas of hydrogen and inert gas, and then introduce ethylene and ferric chloride gas, keep warm for 20-25 minutes, and deposit carbon nanotubes on the fine metal short fibers; then stop heating, stop introducing ethylene and ferric chloride gas, and continue to introduce a mixed gas of hydrogen and inert gas until the vapor deposition furnace naturally cools to room temperature.

3. The preparation process of the multi-layer composite metal fiber sintered felt according to claim 2, characterized in that: The volume flow rate of the mixed gas is 300-400 sccm, the volume flow rate ratio of the hydrogen gas to the inert gas is 1:4-6; the volume flow rate of the ethylene gas is 30-50 sccm, and the volume flow rate of the ferric chloride gas is 200-300 sccm.

4. The preparation process of the multi-layer composite metal fiber sintered felt according to claim 2, characterized in that: The temperature was raised to 670-720°C at a heating rate of 3-7°C / min.

5. The preparation process of the multi-layer composite metal fiber sintered felt according to claim 1, characterized in that: In step S4, the hydrophobic coating comprises the following raw materials in weight percentage: 10-20% of nano silica sol, 1-3% of octadecyltrimethoxysilane, and the balance is ethanol; the solid content of the nano silica sol is 20-30%.

6. The preparation process of the multi-layer composite metal fiber sintered felt according to claim 1, characterized in that: The particle size of the nano-silica in the nano-silica sol is 120-160 nm; Each time the hydrophobic coating is applied, the coating amount of the hydrophobic coating is 50-75 g / m 2 .

7. The process for preparing the multi-layer composite metal fiber sintered felt according to claim 1, characterized in that: The coarse metal short fibers and the fine metal short fibers are both stainless steel fibers.

8. The process for preparing the multi-layer composite metal fiber sintered felt according to claim 7, characterized in that: In step S1, the sintering temperature is 1120-1200°C, the holding time is 1.5-2h, and the sintering is carried out in a mixed atmosphere of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is 1:8-9.

9. The process for preparing the multi-layer composite metal fiber sintered felt according to claim 7, characterized in that: In step S3, the sintering temperature is 950-1000°C, the holding time is 25-35 minutes, and the sintering is carried out in a mixed atmosphere of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is 1:8-9.

10. A multi-layer composite metal fiber sintered felt prepared by the preparation process according to any one of claims 1 to 9.

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