CN105669208A - Phenolic resin coated ceramic powder for laser 3D printing and preparation method thereof - Google Patents

Abstract

The invention provides a phenolic resin-coated ceramic powder for laser 3D printing. The stearic acid of 1.5wt%, the surplus is the ceramic powder of silane coupling agent surface modification, and its preparation method comprises a) modifying ceramic powder surface with dehydrated alcohol and silane coupling agent, b) surface modification The ceramic powder is reacted with phenolic resin, urotropine and stearic acid in a closed container to obtain aggregates, c) the aggregates are ball milled and sieved. The method removes impurities and modifies the surface of the ceramic powder, reduces its hydrophilicity, improves its wettability with the binder, and improves the efficiency of the binder and the strength of the initial parison; the absorption rate of the phenolic resin to the laser is relatively high. High, good bonding effect, which helps to improve the quality of ceramic parts; using urotropine as a curing agent and stearic acid as a lubricant can improve the strength and plasticity of the SLS body formed by phenolic resin coated ceramic powder.

Description

Phenolic resin coated ceramic powder for laser 3D printing and preparation method thereof

technical field

The invention relates to the technical field of laser 3D printing powder material preparation, in particular to a phenolic resin-coated ceramic powder for laser 3D printing and a preparation method thereof.

Background technique

Ceramic materials, especially high-performance ceramics, have many advantages such as high hardness, high temperature resistance, high strength, good insulation, and corrosion resistance, and have been widely used in aviation, aerospace, automobiles, electronics and other fields. However, ceramic materials are brittle and hard, and are prone to defects when formed by traditional machining methods. Ceramic parts with complex structures are more difficult to process. When forming ceramic parts by grouting, isostatic pressing, etc., the shape of the parts is still affected by the mold. limited, and the manufacturing cycle is long and the cost is high.

Selective Laser Sintering (SLS) is a 3D printing forming method based on the idea of discrete accumulation forming. This method breaks through the traditional thinking mode of equal volume forming and removal forming of materials. It can be generated by slicing the 3D CAD model along the z-axis. A series of two-dimensional planes, and then selectively layered and sintered powder materials under the action of lasers, layer by layer to form prototypes or parts of complex shapes. This kind of processing technology, which is not limited by the complexity of the shape of the formed part and does not require any tooling, is considered to be an important way to solve the difficult problem of forming and processing complex ceramic parts in the future.

There are usually two methods of SLS manufacturing parts: one is the direct laser melting method, that is, the powder material is melted and formed by the heat of the laser, which is suitable for polymer materials and metal materials with a low melting point; the other is the indirect laser sintering method , by melting the binder with a low melting point, using the binder to form a viscous flow or melting to achieve the bonding between the powders, and then through degreasing, sintering and other post-processing processes to obtain functional parts with a certain strength, suitable for high melting point refractory material. Ceramics have a relatively high melting point and are prone to cracks under direct high-power laser irradiation. Generally, they can only be formed by indirect laser sintering with low-power lasers.

The performance of ceramic composite powder materials for SLS is closely related to the type, content and introduction method of binder. The types of binders include metal binders, inorganic binders and organic binders. Metal binders are mainly used to form ceramic/metal composite parts, and require high-power lasers, which are slow in forming speed and high in cost; Inorganic binders have good thermal stability, and it is difficult to completely remove them in the post-processing process, which increases the production cost and manufacturing cycle; while organic binders require low laser power and are easy to control in forming, so they are suitable for SLS to manufacture ceramics pieces.

In order to improve the forming efficiency of the binder, the coating method is usually used, that is, under certain process conditions, the ceramic powder is tightly coated inside the organic binder as a crystal nucleus to form a coated ceramic composite powder. However, the film-coated ceramic powders suitable for SLS forming currently have disadvantages such as few types of organic binders, lack of preparation methods, and high cost.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, and to provide a phenolic resin coated ceramic powder for laser 3D printing and a preparation method thereof. With the characteristics of good bonding and small molding shrinkage, the phenolic resin coated ceramic powder with excellent comprehensive performance has been prepared.

Technical scheme of the present invention is as follows:

A phenolic resin coated ceramic powder for laser 3D printing, which is made from the following raw materials: ceramic powder, phenolic resin, hexamethamine, stearic acid, absolute ethanol and silane coupling agent.

The particle size of the phenolic resin coated ceramic powder is 10-50 μm.

In the phenolic resin-coated ceramic powder, phenolic resin accounts for 10-30wt%, methenamine accounts for 1-2.5wt%, stearic acid accounts for 0.5-1.5wt%, and the balance is surface-modified by silane coupling agent. For ceramic powder, the amount of silane coupling agent used for surface modification is 1-1.5% of the mass of ceramic powder, and the mass ratio of absolute ethanol to silane coupling agent is 3-5:1.

The ceramic powder is one of silicon carbide, titanium carbide, zirconium carbide, aluminum oxide, and zirconium oxide, and the silane coupling agent is one of vinyl silane, amino silane, and methacryloxy silane or Several kinds.

A kind of preparation method of the phenolic resin coating ceramic powder that is used for laser 3D printing described in the above scheme, comprises the following steps:

a) Preparation of surface-modified ceramic powder: wash a certain amount of ceramic powder with weak acid, weak base and water and then dry, mix the dried ceramic powder with absolute ethanol and silane coupling agent in a certain proportion and stir to carry out surface modification. Treatment, after the surface treatment is completed, the mixture is vacuum-dried, and the surface-modified ceramic powder is obtained through grading and sieving;

b) Preparation of phenolic resin-coated ceramic aggregates: the surface-modified ceramic powder and phenolic resin prepared in step a) are added in a certain proportion to a closed container filled with an organic solvent, and argon gas is fed into the closed container to reduce the temperature of the closed container. From room temperature to 65-75°C, add a certain amount of urotropine and stearic acid during the heating process and stir to dissolve it. After the heating is completed, keep it warm for a certain period of time, and then naturally cool to room temperature to obtain phenolic resin coated ceramics. body;

c) Pulverization and screening: the phenolic resin-coated ceramic aggregates prepared in step b) are taken out and dried, pulverized and passed through a grading sieve.

In step a), the ceramic powder is one of silicon carbide, titanium carbide, zirconium carbide, aluminum oxide, and zirconium oxide, the weak acid is one of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, and the weak base is dilute One of sodium hydroxide, dilute sodium carbonate, and dilute calcium sulfate, and the silane coupling agent is one or more of vinylsilane, aminosilane, and methacryloxysilane.

The dosage of the silane coupling agent in step a) is 1-1.5% of the mass of the ceramic powder, and the mass ratio of absolute ethanol to the silane coupling agent is 3-5:1.

The organic solvent in step b) is one of ethanol, carbon tetrachloride and tetrahydrofuran, the heating rate of the airtight container is 0.5-1°C/min, and the holding time is 1-2h.

The weight ratio of each component in step b) is based on the final product phenolic resin coated ceramic powder, phenolic resin is 10-30wt%, urotropine is 1-2.5wt%, stearic acid is 0.5-1.5wt% , and the balance is surface-modified ceramic powder.

Step a) and step c) select powders with a particle size of 10-50 μm after passing through the grading sieve.

The preparation method of the phenolic resin coated ceramic powder for laser 3D printing provided by the present invention has the following advantages:

1. The ceramic powder is treated with impurities removal and surface modification, which reduces the hydrophilicity of the ceramic, improves its wettability with the binder, and improves the efficiency of the binder and the strength of the initial parison.

2. Binder phenolic resin has a high absorption rate of laser light and good bonding effect. The carbon skeleton formed after pyrolysis is beneficial to the post-processing of carbide ceramics and improves the quality of ceramic parts.

3. The selected organic solvents such as ethanol, carbon tetrachloride, and tetrahydrofuran have good dissolving effect, low boiling point, and are easy to volatilize, which saves the process of vacuum distillation and saves costs.

4. Using urotropine as a curing agent and stearic acid as a lubricant can improve the strength and plasticity of the SLS body formed by phenolic resin coated ceramic powder.

Description of drawings

Fig. 1 is the flow chart of preparation of phenolic resin coated ceramic powder of the present invention;

Fig. 2 is a schematic diagram of the preparation and SLS molding principle of the phenolic resin coated ceramic powder of the present invention.

detailed description

In order to enable those skilled in the art to fully understand the technical solutions and beneficial effects of the present invention, the following will be further fully described in conjunction with the accompanying drawings and specific embodiments.

Example 1

A phenolic resin-coated silicon carbide ceramic powder comprises 20-30wt% phenolic resin, 1.5-2.5wt% urotropine, 1-1.5wt% stearic acid, and the balance is surface-modified silicon carbide. The preparation process and principle of the phenolic resin-coated silicon carbide ceramic powder are shown in Figure 1-2, which specifically includes the following steps:

(1) Preparation of surface-modified silicon carbide ceramic powder: 1000 g of silicon carbide ceramic powder was taken, washed with dilute hydrochloric acid, dilute sodium hydroxide and water, and put into a vacuum drying oven for drying. Then, the mixed solution of 30 g of absolute ethanol and 10 g of vinyl silane was uniformly mixed with the aforementioned silicon carbide ceramic powder, and at the same time, a stirring device was used to fully stir the mixture for surface modification treatment. After the reaction was completed, the mixture was vacuum-dried and sieved to obtain a surface-modified silicon carbide ceramic powder with a particle size of 10 microns.

(2) Preparation of phenolic resin-coated silicon carbide ceramic aggregates: add surface-modified silicon carbide ceramic powder and phenolic resin into a closed container filled with ethanol, and pass through argon gas for protection. Raise the temperature in the airtight container from room temperature to 65-75°C at a speed of 0.5-1°C/min. During the heating process, add urotropine and stearic acid, and stir with a stirring device to dissolve completely. The addition amount of each substance is as mentioned above. After the temperature rise is completed, it is kept for 1-2 hours under an argon atmosphere, and then naturally cooled to room temperature to obtain a phenolic resin-coated silicon carbide ceramic aggregate. Volatile solvents are recycled.

(3) Crushing and sieving: the prepared phenolic resin-coated silicon carbide ceramic aggregates are taken out from the airtight container, put into a vacuum drying oven for drying, and then ball milled and sieved to obtain a particle size of 10 microns The phenolic resin coated silicon carbide ceramic powder.

Example 2

A phenolic resin-coated titanium carbide ceramic powder comprises 15-25wt% phenolic resin, 1-2wt% urotropine, 0.5-1wt% stearic acid, and the balance is surface-modified titanium carbide. The preparation method of the phenolic resin coated titanium carbide ceramic powder is as follows:

(1) Preparation of surface-modified titanium carbide ceramic powder: 1000 g of titanium carbide ceramic powder was taken, washed with dilute sulfuric acid, dilute sodium carbonate and water respectively, and put into a vacuum drying oven for drying. Then, the mixed solution of 60 g of absolute ethanol and 15 g of aminosilane was uniformly mixed with the aforementioned titanium carbide ceramic powder, and at the same time, a stirring device was used to fully stir the mixture for surface modification treatment. After the reaction was completed, the mixture was vacuum-dried and sieved to obtain a surface-modified titanium carbide ceramic powder with a particle size of 30 microns.

(2) Preparation of phenolic resin-coated titanium carbide ceramic aggregates: add surface-modified titanium carbide ceramic powder and phenolic resin into a closed container filled with carbon tetrachloride, and pass in argon gas for protection. Raise the temperature in the airtight container from room temperature to 65-75°C at a speed of 0.5-1°C/min. During the heating process, add urotropine and stearic acid, and stir with a stirring device to dissolve completely. The addition amount of each substance is as mentioned above. After the temperature rise is completed, it is kept for 1-2 hours under an argon atmosphere, and then naturally cooled to room temperature to obtain a phenolic resin-coated titanium carbide ceramic aggregate. Volatile solvents are recycled.

(3) Crushing and sieving: the prepared phenolic resin-coated titanium carbide ceramic aggregates are taken out from the airtight container, put into a vacuum drying oven for drying, and then ball milled and sieved to obtain a particle size of 30 microns The phenolic resin coated titanium carbide ceramic powder.

Example 3

A phenolic resin-coated zirconia ceramic powder comprises 10-20wt% phenolic resin, 1-2wt% urotropine, 0.5-1wt% stearic acid, and the balance is surface-modified zirconia. The preparation method of the phenolic resin coated zirconia ceramic powder is as follows:

(1) Preparation of surface-modified zirconia ceramic powder: 1000 g of zirconia ceramic powder was taken, washed with dilute nitric acid, dilute calcium sulfate and water respectively, and put into a vacuum drying oven for drying. Then, a mixture of 50 g of absolute ethanol and 10 g of methacryloxysilane was uniformly mixed with the aforementioned zirconia ceramic powder, and at the same time, a stirring device was used to fully stir the mixture for surface modification treatment. After the reaction was completed, the mixture was vacuum-dried and sieved to obtain surface-modified zirconia ceramic powder with a particle size of 50 microns.

(2) Preparation of phenolic resin-coated zirconia ceramic aggregates: add surface-modified zirconia ceramic powder and phenolic resin into a closed container filled with tetrahydrofuran, and pass through argon for protection. Raise the temperature in the airtight container from room temperature to 65-75°C at a speed of 0.5-1°C/min. During the heating process, add urotropine and stearic acid, and stir with a stirring device to dissolve completely. The addition amount of each substance is as mentioned above. After the temperature rise is completed, it is kept under the protection of argon for 1-2 hours, and then naturally cooled to room temperature to obtain a zirconia ceramic aggregate coated with phenolic resin. Volatile solvents are recycled.

(3) Crushing and sieving: the prepared phenolic resin-coated zirconia ceramic aggregates are taken out from the airtight container, put into a vacuum drying oven for drying, and then ball milled and sieved to obtain a particle size of 50 microns Phenolic resin coated zirconia ceramic powder.

The phenolic resin coated ceramic powder prepared by the invention is used to obtain a molded blank through an SLS molding machine, and the obtained blank can be sintered at a high temperature after being completely degreased to obtain a ceramic part with better performance. As an adhesive, phenolic resin has the characteristics of high adhesive force and small molding shrinkage, and its SLS parison has strong subsequent self-reinforcing ability. Therefore, the selection of phenolic resin with better interface adhesion with ceramic powder and higher strength of SLS molded parts and some additives as adhesives is beneficial to improve the strength of the blank, reduce the content of polymer adhesives, and improve the precision of the parts. .

Claims (10)

1. A phenolic resin coated ceramic powder for laser 3D printing is characterized in that it is made of the following raw materials: ceramic powder, phenolic resin, urotropine, stearic acid, dehydrated alcohol and silane coupling agent. 2. The phenolic resin coated ceramic powder according to claim 1, characterized in that: the particle size of the phenolic resin coated ceramic powder is 10-50 μm. 3. phenolic resin coated ceramic powder as claimed in claim 1 is characterized in that: in described phenolic resin coated ceramic powder, phenolic resin accounts for 10-30wt%, urotropine accounts for 1-2.5wt%, stearin The acid accounts for 0.5-1.5 wt%, and the balance is the ceramic powder modified by the surface of the silane coupling agent. The amount of the silane coupling agent used for surface modification is 1-1.5% of the mass of the ceramic powder. The mass ratio is 3-5:1. 4. The phenolic resin coated ceramic powder as claimed in any one of claims 1-3, wherein the ceramic powder is one of silicon carbide, titanium carbide, zirconium carbide, aluminum oxide, zirconium oxide, and the The silane coupling agent is one or more of vinylsilane, aminosilane, and methacryloxysilane. 5. A method for preparing a phenolic resin-coated ceramic powder for laser 3D printing, characterized in that it comprises the following steps: a) preparing surface-modified ceramic powder: passing a certain amount of ceramic powder through weak acid, weak base and water respectively Drying after cleaning, mixing the dried ceramic powder with absolute ethanol and silane coupling agent in a certain proportion and stirring for surface treatment, after the surface treatment is completed, vacuum drying the mixture, and sieving the surface modified ceramic powder; b ) Preparation of phenolic resin-coated ceramic aggregates: the surface-modified ceramic powder and phenolic resin prepared in step a) are added in a certain proportion to an airtight container filled with an organic solvent, and argon gas is fed into the airtight container to increase the temperature of the airtight container from The room temperature is raised to 65-75°C. During the heating process, a certain amount of urotropine and stearic acid are added and stirred to dissolve them. After the heating is completed, the temperature is kept for a certain period of time, and then naturally cooled to room temperature to obtain a phenolic resin-coated ceramic aggregate. c) crushing and screening: take out the phenolic resin-coated ceramic aggregate prepared in step b), dry it, and pass it through a grading sieve after crushing. 6. the preparation method of phenolic resin coated ceramic powder as claimed in claim 5 is characterized in that: ceramic powder is the one in silicon carbide, titanium carbide, zirconium carbide, aluminum oxide, zirconium oxide in step a), so Described weak acid is a kind of in dilute hydrochloric acid, dilute sulfuric acid, dilute nitric acid, described weak base is a kind of in dilute sodium hydroxide, dilute sodium carbonate, dilute calcium sulfate, and described silane coupling agent is vinyl silane, amino One or more of silane and methacryloxysilane. 7. the preparation method of phenolic resin coated ceramic powder as claimed in claim 5 is characterized in that: step a) in the silane coupling agent consumption is the 1-1.5% of ceramic powder quality, dehydrated alcohol and silane coupling agent The mass ratio is 3-5:1. 8. the preparation method of phenolic resin coated ceramic powder as claimed in claim 5 is characterized in that: step b) described organic solvent is a kind of in ethanol, carbon tetrachloride, tetrahydrofuran, and airtight container heating rate is 0.5 -1°C/min, the holding time is 1-2h. 9. the preparation method of phenolic resin coated ceramic powder as claimed in claim 5 is characterized in that: the weight ratio of each component in step b) is based on final product phenolic resin coated ceramic powder, and phenolic resin is 10- 30 wt%, urotropine 1-2.5 wt%, stearic acid 0.5-1.5 wt%, and the rest is surface-modified ceramic powder. 10. The preparation method of phenolic resin coated ceramic powder as claimed in claim 5, characterized in that: step a) and step c) all select powders with a particle size of 10-50 μm after passing through a grading sieve.