CN103964887B - High mechanical strength foamed ceramic material and preparation method thereof - Google Patents

Abstract

The invention relates to the field of foamed ceramic materials, in particular to a high mechanical strength foamed ceramic material provided with a circular centre hole or a suborbicular centre hole and a preparation method of the high mechanical strength foamed ceramic material. The preparation method adopts a soluble high-molecular polymer cladding method to make a cross section shape of a rib body of the high-molecular foamed plastic transformed from a triangle to a circle; the circular high-molecular foamed plastic is taken as a precursor, and the foamed ceramic material obtained finally is provided with the circular centre hole or the suborbicular centre hole. The preparation method comprises the following steps: preparing an additional coating on the surface of the high-molecular foamed plastic; modifying the triangular rib of the high-molecular foamed plastic to be circular or suborbicular; utilizing the circular high-molecular foamed plastic as the precursor; adopting a cloning method to obtain the foamed ceramic material of which the centre hole is circular or suborbicular. Compared with the mechanical strength of the same material with a triangular centre hole, the mechanical strength of the foamed silicon carbide ceramic is obviously improved. Therefore, the service life of the material can be effectively prolonged.

Description

A kind of foam ceramic material with high mechanical strength and preparation method thereof

Technical field:

The invention relates to the field of foamed ceramic materials, in particular to a high-mechanical-strength foamed ceramic material with a circular or nearly circular central hole and a preparation method thereof.

Background technique:

Foamed silicon carbide ceramic materials not only have excellent material properties such as corrosion resistance, high temperature oxidation resistance, high thermal conductivity, low expansion, and chemical inertness, but also have structural characteristics such as three-dimensional connectivity and good heat and mass transfer performance, so they are ideal structural carrier material.

Among the current foamed silicon carbide production technologies, the most cost-effective and the most promising technology for large-scale industrial production is the replica molding method. The main technical feature of this method is to use the polymer foam material as the precursor, uniformly wrap a layer of slurry on the surface, and then remove the polymer foam through high temperature treatment, and then obtain the carbon foam with the same structure as the original polymer foam. Afterwards, under certain conditions, silicon and carbon foam can be reacted to obtain foamed silicon carbide. The foamed silicon carbide ceramic material prepared with the original foam as a template, in the replication molding process, due to the triangular tendon cross-section formed by the inherent preparation process of the polymer foam, determines the center of the polymer foam after the high temperature removal. The hole must be a sharp triangle center hole with the same shape as the polymer foam (see Figure 1a, Figure 2). When the central hole of this shape is subjected to internal stress or external force, it is easy to form a high stress concentration point at the top corner, etc., which will cause the material to break or break under a small pressure. The technical characteristics of the replication molding method determine the inevitability of the existence of the central hole. Then, to eliminate or reduce the negative impact of the central hole on the mechanical properties of the material, there are two methods: one method can consider filling the central hole in the subsequent steps in order to reduce or even eliminate the central hole, but the process is more complicated; the other is The law can consider changing the shape of the center hole to make it round or nearly round, and eliminate the sharp corner of the original center hole. According to the principle of mechanics, this treatment method can also reduce stress concentration and prolong the service life of the material. Purpose.

Invention content:

The purpose of the present invention is to provide a foamed ceramic material with high mechanical strength and its preparation method, which solves the problem that the triangular central hole of the existing foamed ceramic material is easy to form a high stress concentration point at the top corner under the condition of internal stress or external force. , which leads to problems such as fracture or shattering of the material under relatively small pressure.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A high mechanical strength foamed ceramic material, which uses a soluble polymer coating method to transform the cross-sectional shape of the ribs of the polymer foam from a triangle to a circle, and uses the rounded polymer foam as a precursor. The final ceramic foam material has a circular or nearly circular central cell.

The foamed ceramic material with high mechanical strength is an inorganic material such as silicon carbide, aluminum oxide, mullite or cordierite.

In the preparation method of the high mechanical strength ceramic foam material, an additional coating is prepared on the surface of the polymer foam, and the triangular ribs of the polymer foam are modified into a circle or a nearly circle, and the rounded polymer is used to The foamed plastic is used as the precursor, and the foamed ceramic material is obtained by the replication method, and its central hole is circular or nearly circular.

The preparation method of the high mechanical strength ceramic foam material specifically comprises the following steps:

(1) dissolving the soluble polymer resin in distilled water or an organic solvent to form a resin solution with a concentration of 10-100 g/L;

(2) Fully soak the polymer foam in the above solution to ensure that the resin solution and all areas of the polymer foam are fully infiltrated, take it out after soaking for 1 to 3 minutes, and blow off the excess liquid with compressed air;

(3) Dry the soaked polymer foam between 50°C and 100°C, so that a polymer resin coating can be obtained on the surface of the polymer foam. Due to the existence of the coating, the polymer foam The triangular ribs are initially rounded;

(4) Repeat above-mentioned 2), 3) step, until polymer resin coating reaches certain thickness, can meet the requirement to the rounding of triangular rib, until the increase of polymer foam plastic reaches 2～2～ of former polymer foam plastic weight 10 times;

(5) Using the polymer foam plastic obtained in step 4) as a precursor, prepare a foam ceramic material according to the content described in the Chinese patent: "a high-strength silicon carbide foam ceramic and its preparation method, patent number ZL00110479.9".

In the preparation method of the foamed ceramic material with high mechanical strength, if necessary, extrusion or kneading is adopted to achieve complete infiltration.

In the preparation method of the foamed ceramic material with high mechanical strength, the polymer foam is polyurethane foam or other organic foam with triangular tendon cross-section.

In the preparation method of the high mechanical strength ceramic foam material, the polymer resin is a soluble polymer polymer with decomposable and low carbon production rate such as polycarbonate, polyethylene resin, polystyrene resin, polyvinyl chloride resin or polyvinyl alcohol resin. thing.

In the preparation method of the foamed ceramic material with high mechanical strength, the organic solvent may be ethanol, propanol or butanol.

The method for preparing a foamed ceramic material with high mechanical strength is used to prepare a high-strength foamed ceramic material such as foamed silicon carbide, foamed alumina, foamed mullite or foamed cordierite.

Design idea of the present invention is as follows:

The present invention adopts the method of covering with soluble organic matter to transform the cross-sectional shape of the rib body of the polyurethane foam from triangle to circle, and finally close to circle. The rounded polyurethane foam is used as the precursor to prepare foamed ceramics, and the center hole of the obtained material is also circular. Compared with the same material with a triangular center hole, the mechanical strength of the foamed ceramic material is significantly improved, so it can be effectively extended. Material service life.

Compared with the method for preparing foam material with unrounded foamed plastics, the present invention has following beneficial effects:

1. After the foam plastic is modified by coating, the original triangular tendons become round or nearly round. The center hole of the foam prepared by using this as the precursor is the same circle as the foam plastic, eliminating the problem caused by the triangle center hole. Stress concentration reduces the probability of material damage and fracture, greatly improves the mechanical strength of the material, and prolongs the service life of the material.

2. The method for thickening and rounding foamed plastics adopted in the present invention can also be used in other fields where there is a demand for thickened foamed plastics.

Description of drawings

Fig. 1 is a schematic diagram of thickening and rounding of foamed plastics according to the present invention. In the figure, a, the cross section of the original foamed plastic tendon; b, the cross section of the foamed plastic tendon after the initial thickening; c, the cross section of the foamed plastic tendon after the final thickening.

Fig. 2 is a micrograph of the fracture of the silicon carbide foam used for comparison in the present invention (using the original foam plastic as a template).

Fig. 3 is a micrograph of the fracture of the foamed silicon carbide prepared by using the rounded thickened foam as the template according to the present invention.

Detailed ways

As shown in Fig. 1 and Fig. 3, the preparation method of the high mechanical strength ceramic foam material of the present invention prepares an additional coating on the surface of the polymer foam plastic, and the triangular tendon of the polymer foam plastic is modified into a circle or a near circle, and the This rounded polymer foam is used as a precursor, and the ceramic foam material is obtained by the replication method, and its central hole is circular or nearly circular. Compared with the ceramic foam material with a triangular central hole, the mechanical properties of the material The strength is significantly improved, specifically including the following steps:

(1) dissolving the soluble polymer resin in distilled water or an organic solvent to form a resin solution with a concentration of 10-100 g/L;

(2) Fully immerse the polymer foam in the above solution to ensure that the resin solution and all areas of the polymer foam are fully infiltrated. If necessary, extrusion and rubbing can be used. Take it out after soaking for 1-3 minutes, and blow off the excess liquid with compressed air;

(3) Dry the soaked polymer foam between 50°C and 100°C, so that a polymer resin coating can be obtained on the surface of the polymer foam. Due to the existence of the coating, the polymer foam The triangular ribs are initially rounded;

(4) Repeat above-mentioned 2), 3) step, until polymer resin coating reaches certain thickness, can meet the requirement to the rounding of triangular rib, until the increase of polymer foam plastic reaches 2～2～ of former polymer foam plastic weight 10 times;

(5) Using the polymer foam obtained in step 4) as a precursor, prepare a foam ceramic material according to the content described in the Chinese patent: "a high-strength silicon carbide foam ceramic and its preparation method (Patent No. ZL00110479.9)" .

Wherein, the polymer foam is polyurethane foam, and it can also be other organic foam with triangular rib cross-sectional shape; the polymer resin can be polycarbonate, polyethylene resin, polystyrene resin, polyvinyl chloride resin or polyethylene Alcohol resins and other soluble high molecular polymers that can be decomposed with low carbon yield rate; organic solvents can be ethanol, propanol or butanol, etc.; this method can also be used to prepare high-strength foamed ceramic materials such as foamed silicon carbide, foamed Other inorganic foam materials such as foamed mullite or foamed cordierite.

The present invention adopts the method of coating with soluble high molecular polymer to transform the cross-sectional shape of the rib body of the high molecular foam plastic from a triangle to a circle, and use this rounded high molecular foam plastic as the precursor, and finally obtain the foam The ceramic material has a circular or nearly circular central hole, while the same material obtained by conventional methods has a triangular central hole.

Example 1

The preparation process of the present embodiment to prepare high mechanical strength foamed silicon carbide is as follows:

1. Dissolve water-soluble polycarbonate in distilled water to obtain a resin solution with a concentration of 5 g/L;

2. Fully soak the polyurethane foam in the above solution, and squeeze the foam repeatedly to ensure that the resin solution is in full contact with all parts of the polyurethane foam. After soaking for 2 minutes, take out the polyurethane foam, and blow off the excess liquid with compressed air;

3. Dry the soaked polyurethane foam at 80°C, so that the resin is cured on the surface of the polyurethane foam to obtain a coating, and the triangular ribs of the polyurethane foam are initially rounded;

4. Weigh and record data;

5. Repeat steps 2 to 4 above until the weight gain of the polyurethane foam reaches twice the weight of the original polyurethane foam;

6. Using the polyurethane foam obtained in step 5 as a precursor, prepare a silicon carbide foam ceramic material according to the content described in Chinese patent ZL00110479.9.

As shown in Figure 1, the thickening and rounding process of the polymer foam by the method of the present invention is as follows: the cross section of the original foamed plastic tendon → the cross section of the foamed plastic tendon after the initial thickening → the cross section of the foamed plastic tendon after the final thickening.

As shown in Fig. 3, after adopting the method of the present invention to round the foamed silicon carbide section prepared as a template, the original triangular tendon becomes circular or nearly circular, and the central hole of the foamed silicon carbide prepared as a precursor The shape is the same as the foam plastic, which eliminates the stress concentration caused by the triangular center hole, reduces the probability of material damage and fracture, greatly improves the mechanical strength of the material, and prolongs the service life of the material.

Example 2

The difference from Example 1 is that the resin concentration is 10 g/L, and other conditions are the same.

Example 3

The difference from Example 1 is that the resin concentration is 50 g/L, and other conditions are the same.

Example 4

The difference from Example 1 is that the resin concentration is 100 g/L, and other conditions are the same.

Example 5

The difference from Example 1 is that the resin concentration is 200 g/L, and other conditions are the same.

Example 6

The difference from Example 1 is that the resin concentration is 500 g/L, and other conditions are the same.

Example 7

The difference from Example 4 is that the added amount of the resin is twice that of the original foamed plastic.

Example 8

The difference from Example 4 is that the amount of resin added is 4 times that of the original foam.

Example 9

The difference from Example 4 is that the increase of the resin is 6 times that of the original foam.

Example 10

The difference from Example 4 is that the added amount of the resin is 10 times that of the original foamed plastic.

Example 11

The difference from Example 9 is that the drying and curing temperature of the foamed plastic after soaking is 50°C.

Example 12

The difference from Example 9 is that the drying and curing temperature of the foamed plastic after soaking is 100°C.

Example 13

The difference from Example 9 is that the drying and curing temperature of the foamed plastic after soaking is 130°C.

It can be seen from the comparison of the examples that when the concentration of the resin solution is lower than 10 g/l, the foamed plastics gain weight is too slow and the efficiency is low; and when the concentration is higher than 200 g/l, the viscosity of the solution is too high and it is easy to block the pores, so it is suitable The concentration should be between 10 g/L and 200 g/L; the appropriate weight gain should be between 2 and 10 times that of the original foam; the appropriate curing temperature should be between 50°C and 100°C.

Under the same density conditions, the foamed silicon carbide prepared under the above conditions, compared with the foamed silicon carbide prepared by using the original foamed plastic as a template, its compressive strength is increased from 30MPa to 36MPa, and its performance is improved by 20%, which is an obvious improvement.

The results of the examples show that the present invention uses the method of soluble polymer coating to transform the cross-sectional shape of the ribs of the polymer foam from a triangle to a circle, so that the polymer foam remains behind after being removed at high temperature during the preparation of foamed silicon carbide. The lower central hole is circular or nearly circular, and then a foamed silicon carbide material with a circular central hole is obtained. Compared with foamed ceramic materials with triangular central holes, the mechanical strength of the material is significantly improved.

Claims (6)

1. a high mechanical strength foam ceramic material, it is characterized in that, adopt the method for soluble high-molecular resin-coated that the muscle body shape of cross section of polymeric foam plastics is transformed to circle by trilateral, do presoma with the polymeric foam plastics after sphering, the final foam ceramic material obtained has circular or rotund centre hole;

Additional coatings is prepared at polymeric foam frosting, the trilateral muscle of polymeric foam plastics is modified to circle or subcircular, presoma is done with this polymeric foam plastics after sphering, transfer printing is adopted to obtain foam ceramic material, its centre hole presents circle or subcircular, specifically comprises the steps:

(1) soluble high-molecular resin is dissolved in distilled water or organic solvent, forms the resin solution that concentration is 10 ~ 100 grams per liters;

(2) polymeric foam plastics are fully soaked in above-mentioned solution, guarantee that resin solution and each region of polymeric foam plastics all realize complete wetting, take out after soaking 1 ~ 3min, and blow away surplus liquid with pressurized air;

(3) dried between 50 DEG C ~ 100 DEG C by the polymeric foam plastics after immersion, obtain macromolecule resin coating at polymeric foam frosting like this, due to the existence of this coating, the trilateral muscle of polymeric foam plastics obtains preliminary sphering;

(4) repeat above-mentioned 2), 3) step, until macromolecule resin coating reaches certain thickness, can meet the demands to the sphering of triangle muscle, until the gain in weight of polymeric foam plastics reaches 2 ~ 10 times of former polymeric foam plastic weigh;

(5) the polymeric foam plastics obtained using step 4) as presoma, according to Chinese patent: the content described in " a kind of high-strength foam silicon carbide ceramics and preparation method thereof, patent No. ZL00110479.9 " prepares foam ceramic material.

2. according to high mechanical strength foam ceramic material according to claim 1, it is characterized in that, the mode adopting extruding or rub, to realize complete wetting.

3., according to high mechanical strength foam ceramic material according to claim 1, it is characterized in that, polymeric foam plastics be urethane foam or other there is the organic foam plastic of trilateral muscle cross-sectional shape.

4. according to high mechanical strength foam ceramic material according to claim 1, it is characterized in that, macromolecule resin is the soluble high molecular polymers of polycarbonate, polyvinyl resin, polystyrene resin, polyvinyl chloride (PVC) RESINS or polyvinyl alcohol resin decomposable asymmetric choice net, low yield carbon rate.

5. according to high mechanical strength foam ceramic material according to claim 1, it is characterized in that, organic solvent is ethanol, propyl alcohol or butanols.

6. according to high mechanical strength foam ceramic material according to claim 1, it is characterized in that, the method is foam silicon carbon, foamed alumina, foam mullite or foam trichroite for the preparation of the foam ceramic material of high strength.