LU501587B1

LU501587B1 - A Fly Ash-based Porous Geopolymer Thermal Insulation Material Filled with Potassium Titanate Whisker and Its Preparation Method and Application

Info

Publication number: LU501587B1
Application number: LU501587A
Authority: LU
Inventors: Yanguang Wu
Original assignee: Wuhan Inst Technology
Priority date: 2022-03-03
Filing date: 2022-03-03
Publication date: 2022-09-05

Abstract

The present invention relates to fly ash-based porous geopolymer thermal insulationmaterial filled with potassium titanate whisker and its preparation method and application. The material is made of fly ash, metakaolin, potassium titanate whisker, alkali activator, foaming agent and foam stabilizer. The slurry is obtained by powder mixing, solid-liquid mixing, and then it's molded, foamed and cured. The invention creatively introduces potassium titanate whisker into porous geopolymer. The resulting composite material has both mechanical properties and thermal insulation properties, and the compressive strength and thermal conductivity reach 6.32 MPa and 0.042 W/m·K respectively. The invention is helpful for the recycling and reuse of inorganic solid waste fly ash, and the whole preparation process is simple, without high temperature sintering and high temperature maintenance, the cost is low, and the harmful substances are not discharged in the production process, which has good environmental protection advantages. It is expected to be widely used as wall insulation materials, and further improve the energy saving and environmental protection level of buildings in China.

Description

DESCRIPTION LU501587 A Fly Ash-based Porous Geopolymer Thermal Insulation Material Filled with Potassium Titanate Whisker and Its Preparation Method and Application

TECHNICAL FIELD

[0001] The invention relates to the technical field of building materials, and specifically relates to a high-strength fly ash-based porous geopolymer thermal insulation material filled with potassium titanate whisker, its preparation method and application.

BACKGROUND TECHNOLOGY

[0002] With the increasing energy consumption and the increasingly serious environmental problems in the world, building energy conservation and environmental protection have gradually become the focus of attention of governments around the world. Studies have shown that building energy consumption accounts for about 30 % of the total social energy consumption. Effective realization of building energy efficiency is an important way to solve energy crisis and environmental problems. Therefore, the development and promotion of energy-saving and environmental protection building materials system is imperative.

[0003] Nowadays, the wall thermal insulation materials used at home and abroad mainly include two categories: traditional inorganic thermal insulation materials and organic synthetic thermal insulation materials. However, traditional inorganic insulation materials have some shortcomings in energy consumption, performance stability, process complexity and price. Organic synthetic insulation materials, such as polyurethane foam materials, polystyrene board materials, have certain advantages in thermal insulation effect compared with traditional inorganic materials, but the biggest disadvantage is the existence of fire safety hazards, which pose a greater threat to life, property and social economy. Therefore, the development of new building insulation materials with safety and environmental protection, green and energy saving, simple process and economic feasibility is a technical problem faced by scientific researchers.

[0004] Geopolymer is a new green gel material and its research began in the 1970s. Geopolymer refers to aluminosilicate mineral polymer formed by earth chemical 1

DESCRIPTION action or artificial imitation of geological polymerization. Its basic structure is a LUS01587 three-dimensional network gel polymer formed by the polymerization of aluminum oxide tetrahedron and silicon oxide tetrahedron, which has two characteristics of amorphous and semi-crystalline. Porous geopolymers have great potential applications in thermal insulation materials, noise reduction materials and filtration adsorption materials.

[0005] China patent CN107344863A discloses a geopolymer porous insulation material based on fly ash and its preparation method, which uses H20O2 as foaming agent. However, the resulting geopolymer porous insulation material has the disadvantages of uneven pore distribution and low strength. China patent CN107344863A publishes a method for the efficient preparation of porous geopolymers using vegetable oil. In this scheme, HO, which accounts for 0.2 % — % of the mass fraction of slurry, is used as foaming agent, and one or more 15 mixtures of vegetable oil such as rapeseed oil, soybean oil, coconut oil, flax oil, peanut oil, olive oil, flax oil and corn oil are added into the slurry of geopolymers as foam stabilizers. Although the porous geopolymers obtained by curing had uniform pore distribution and less pore defects, their thermal conductivity (0.093W/m-K) is high. China patent CN107344863A discloses a porous geopolymer/aerogel composite insulation material and its preparation method. By embedding SiO: aerogel into the matrix pores of porous geopolymer, porous geopolymer/aerogel composite insulation material is prepared. Although the material has good mechanical strength and high temperature resistance, the preparation process is complex and the cost is high.

[0006] In conclusion, the performance (especially thermal insulation) of existing geopolymer composites need to be improved, and there are still many problems in preparation methods.

THE CONTENT OF THE INVENTION

[0007] The purpose of the invention is to overcome the above-mentioned problems of the existing technology, and creatively introduce potassium titanate whisker into the preparation process of geopolymer. On the basis of recycling solid waste fly ash, an efficient thermal insulation geopolymer material with high compressive strength, low density and low thermal conductivity is successfully prepared. The material is prepared specifically as follows: the fly ash, metakaolin and potassium titanate whisker are mixed uniformly, and then the alkali activator and foaming agent are added to obtain the slurry. Finally, the slurry is injected, foamed and cured. 2

DESCRIPTION LU501587

[0008] Further, the mass ratio of fly ash, metakaolin and potassium titanate whisker is 5.0-7.0:3.0-5.0:0.1-2.0.

[0009] Further, the maximum particle size of the fly ash and metakaolin does not exceed 200 mesh.

[0010] Further, the potassium titanate whisker is selected from at least one of potassium tetratitanate whisker and potassium hexatitanate whisker, and a potassium hexantitanate whiskers is preferred.

[0011] Further, the diameter of potassium titanate whisker is 0.2-0.5 microns and the length is 8-100 microns. The fly ash, metakaolin and potassium titanate whisker with reasonable particle size can not only meet the grading requirements of mixing, but also have better compactness.

[0012] Further, the alkali activator is formed by mixing sodium hydroxide or potassium hydroxide with at least one of sodium silicate solution and potassium silicate solution and standing still. Its modulus is between 1.2 and 1.8.

[0013] Further, the mass ratio of fly ash, metakaolin, potassium titanate whisker to alkali activator is 1.0:0.5-0.9.

[0014] Further, the foaming agent is selected from at least one of HO», trimethylhexadyl ammonium bromide, sodium dodecyl sulfate, aluminum powder, sodium tetraborate and urea, and H>Oz is preferred.

[0015] Further, the mass fraction of the foaming agent in the slurry is 1.0 % -15 %.

[0016] Further, the foam stabilizer is added in the slurry. The foam stabilizer is selected from at least one of sodium dodecyl benzene sulfonate, stearic acid, olive oil, hydroxyethyl cellulose and sodium polyacrylate.

[0017] Further, the mass fraction of foam stabilizer in the slurry is 0.5 % — 10.0 %.

[0018] Further, the stirring speed is 200 — 800 rpm, and the stirring time is not more than 30 minutes. 3

DESCRIPTION

[0019] Further, the stirring is carried out in two times. The stirring is not more than LUS01587 20 minutes after adding alkali activator, and not more than 10 minutes after adding foaming agent and stabilizing agent.

[0020] Further, the curing conditions are as follows: curing in a constant temperature and humidity box with 25-40 °C and 95% humidity for 24-72 hours, and curing under the same conditions for 4-7 days after demolding.

[0021] Another purpose of the invention is to provide a high strength fly ash-based porous geopolymer insulation material filled with potassium titanate whisker prepared according to the above method. The compressive strength of the material is as high as 6.32 MPa and the thermal conductivity is as low as 0.042W/m-K.

[0022] The third purpose of the invention is to apply the high strength fly ash-based porous geopolymer insulation material filled with potassium titanate whisker as wall insulation material.

[0023] Fly ash is a by-product in the production process of coal-fired power plants or similar coal-fired equipment, and is one of the main solid wastes in China. The production of fly ash is increasing year by year. If it is not properly handled, it will have a significant impact on human health and natural environment. The invention takes fly ash as the main raw material. After the popularization and application of this technology, the demand for fly ash is relatively large, which is helpful for turning waste into treasure and recycling. And it is of great significance in environmental protection and solid waste disposal.

[0024] Potassium titanate whiskers have excellent mechanical and physical properties, stable chemical properties, excellent heat insulation and corrosion resistance. In addition, potassium titanate whiskers have low thermal conductivity (0.00534W/m-K) and high infrared reflectivity, which have important application value in thermal insulation materials. Before the existence of this application, potassium titanate whiskers are usually mixed with silica aerogel, yttrium oxide gel, nano silicon nitride and other materials to prepare high-temperature resistant coatings for fireproof building materials (such as China Patent CN107954745A). At present, no potassium titanate whiskers-based geopolymer thermal insulation material has been reported.

[0025] Compared with the existing technology, the invention has the following 4

DESCRIPTION unexpected beneficial effects : (1) The invention creatively introduces the LUS01587 reinforcing filler potassium titanate whisker with extremely low thermal conductivity into the porous geopolymer insulation material, taking into account the mechanical properties and thermal insulation properties of the material; (2) The porous geopolymer insulation material provided by the invention has higher mechanical strength than that of the polystyrene series organic insulation material, and its compressive strength can reach 6.32 MPa; (3) The porous geopolymer insulation material provided by the invention has low thermal conductivity (0.042W/m-K), and the insulation effect is very prominent. (4) In the present invention, the inorganic solid waste fly ash is used as the main matrix raw material. The target product has good fire resistance, simple preparation process, and no need for high-temperature sintering and high-temperature maintenance, so the production and use costs are low. In addition, no harmful substances are discharged in the production process, and it has good environmental protection advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Fig. 1 is a process flow chart of the method of the present invention.

[0027] Fig. 2 is the SEM figure of the obtained product of embodiment 1.

[0028] Fig. 3 is the SEM figure of the obtained product of embodiment 2.

[0029] Fig. 4 is the SEM figure of the obtained product of embodiment 3.

[0030] Fig. 5 is the SEM figure of the obtained product of embodiment 4.

SPECIFIC IMPLEMENTATION METHODS

[0031] In order to make the ordinary technical personnel in this field fully understand the technical scheme and beneficial effect of the invention, further descriptions are given below with reference to specific embodiments and attached drawings.

[0032] Embodiment 1

[0033] Step 1: Fly ash and metakaolin are sieved through 200-mesh sieves to obtain corresponding solid powder raw materials. Fly ash, metakaolin and potassium hexatitanate whiskers (0.2 microns in diameter and 20 microns in length) are weighed according to the mass ratio of 5.0:3.0:0.1, and added to a mechanical stirrer 5

DESCRIPTION for stirring for 15 minutes to obtain a mixture; LUS01587

[0034] Step 2: Sodium hydroxide solid powder is used to adjust the modulus of sodium silicate solution to 1.2, and alkali activator is obtained, which is kept for 24 h for further use.

[0035] Step 3: The alkali activator solution prepared in the second step and the mixture prepared in the first step are added into the mechanical agitator at the mass ratio of 0.5: 1.0, and stirred at 800 rpm for 5 mins to obtain the geopolymer slurry.

Then the foam stabilizer sodium dodecyl benzene sulfonate and foaming agent H:02 solution are added and stirred for 2 mins to obtain the mixed foaming slurry of geopolymer. The mass fractions of foam stabilizer and foaming agent in foaming slurry are 0.5 % and 1.0 % respectively.

[0036] Step 4: The foaming slurry of geopolymer prepared in step 3 is injected into 40 mm x 40 mm x 160 mm mold, and the mold is placed in a constant temperature and humidity box of 25°C and 95% respectively for 72h. After demolding, the mold is maintained for 4 days under the above conditions to obtain porous geopolymer insulation material products.

[0037] The preparation process of the porous geopolymer insulation material is shown in Fig. 1, and the microstructure of the final product is shown in Fig. 2. Fig. 2 shows that the geopolymer has evenly distributed pores and almost no cracks. The test results show that the compressive strength of the porous geopolymer insulation — material is 6.02 MPa, and the thermal conductivity is 0.045 W/m-K.

[0038] Embodiment 2

[0039] Step 1: Fly ash and metakaolin are sieved through 200-mesh sieves to obtain corresponding solid powder raw materials. Fly ash, metakaolin and potassium tetratitanate whisker (0.3 microns in diameter and 30 microns in length) are weighed according to the mass ratio of 6.0:4.0:0.5, and added to a mechanical stirrer for stirring for 15 minutes to obtain a mixture;

[0040] Step 2: The modulus of potassium silicate solution is adjusted to 1.4 by using potassium hydroxide solid powder to obtain alkali activator, which is kept for 24 h for further use.

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DESCRIPTION

[0041] Step 3: The alkali activator solution prepared in the second step and the LUS01587 mixture prepared in the first step are added into the mechanical agitator at the mass ratio of 0.7: 1.0, and stirred at 600 rpm for 10 mins to obtain the geopolymer slurry. Then compound bubble stabilizing agent sodium dodecyl phenylsulfonate/hydroxyethyl cellulose (mass ratio 1:1) and foaming agent H:O» solution are added and stirred for 5 mins to obtain the mixed foaming slurry of geopolymer. The mass fractions of foam stabilizer and foaming agent in foaming slurry are 2.0 % and 5.0 % respectively.

[0042] Step 4: The foaming slurry of geopolymer prepared in step 3 is injected into 40 mm x 40 mm x 160 mm mold, and the mold is placed in a constant temperature and humidity box of 30°C and 95% respectively for 48h. After demolding, the mold is maintained for 5 days under the above conditions to obtain porous geopolymer insulation material products.

[0043] The microstructure of the porous geopolymer insulation material is shown in Figure 3. Similarly, Figure 3 shows that geopolymer has evenly distributed pores and almost no cracks. The test results show that the compressive strength of the porous geopolymer insulation material is 6.11 MPa, and the thermal conductivity is 0.044 W/m-K.

[0044] Embodiment 3

[0045] Step 1: Fly ash and metakaolin are sieved through 200-mesh sieves to obtain corresponding solid powder raw materials. Fly ash, metakaolin and potassium hexatitanate whiskers (0.4 microns in diameter and 40 microns in length) are weighed according to the mass ratio of 6.5:4.5:1.0, and added to a mechanical stirrer for stirring for 15 minutes to obtain a mixture;

[0046] Step 2: Sodium hydroxide solid powder is used to adjust the modulus of sodium silicate solution to 1.6, and alkali activator is obtained, which is kept for 24 h for further use.

[0047] Step 3: The alkali activator solution prepared in the second step and the mixture prepared in the first step are added into the mechanical agitator at the mass ratio of 0.8: 1.0, and stirred at 400 rpm for 15 mins to obtain the geopolymer slurry. Then the foam stabilizer olive oil and foaming agent H2O: solution are added and stirred for 8 mins to obtain the mixed foaming slurry of geopolymer. The mass 7

DESCRIPTION . 1: . . . LU501587 fractions of foam stabilizer and foaming agent in foaming slurry are 5.0 % and 10.0 % respectively.

[0048] Step 4: The foaming slurry of geopolymer prepared in step 3 is injected into 40 mm x 40 mm x 160 mm mold, and the mold is placed in a constant temperature and humidity box of 30°C and 95% respectively for 48h. After demolding, the mold is maintained for 5 days under the above conditions to obtain porous geopolymer insulation material products.

[0049] The microstructure of the porous geopolymer insulation material is shown in Figure 4. Figure 4 shows that geopolymer has evenly distributed pores and no cracks. The test results show that the compressive strength of the porous geopolymer insulation material is 6.32 MPa, and the thermal conductivity is 0.042 W/m-K.

[0050] Embodiment 4

[0051] Step 1: Fly ash and metakaolin are sieved through 200-mesh sieves to obtain corresponding solid powder raw materials. Fly ash, metakaolin and potassium tetratitanate whisker (0.5 microns in diameter and 60 microns in length) are weighed according to the mass ratio of 7.0:5.0:1.5, and added to a mechanical stirrer for stirring for 15 minutes to obtain a mixture;

[0052] Step 2: The modulus of potassium silicate solution is adjusted to 1.8 by using potassium hydroxide solid powder to obtain alkali activator, which is kept for 24 h for further use.

[0053] Step 3: The alkali activator solution prepared in the second step and the mixture prepared in the first step are added into the mechanical agitator at the mass ratio of 0.9: 1.0, and stirred at 200 rpm for 15 mins to obtain the geopolymer slurry.

Then the foam stabilizer sodium polyacrylate and foaming agent HO: solution are added and stirred for 10 mins to obtain the mixed foaming slurry of geopolymer. The mass fractions of foam stabilizer and foaming agent in foaming slurry are 8.0 % and

15.0 % respectively.

[0054] Step 4: The foaming slurry of geopolymer prepared in step 3 is injected into 40 mm x 40 mm x 160 mm mold, and the mold is placed in a constant temperature and humidity box of 40°C and 95% respectively for 24h. After demolding, the mold is maintained for 4 days under the above conditions to obtain porous geopolymer 8

DESCRIPTION insulation material products. LUS01587

[0055] The microstructure of the porous geopolymer insulation material is shown in Figure 5. Figure 5 shows that geopolymer has evenly distributed pores and very few cracks. The test results show that the compressive strength of the porous geopolymer insulation material is 6.30 MPa, and the thermal conductivity is 0.042 W/m-K. The compressive strength and thermal conductivity of the samples prepared in the above embodiments are shown in Table 1. Table 1 Performance test results of samples of different embodiments Performance Embodiment Embodiment Embodiment Embodiment parameter 1 2 3 4 Compressive 02 11 .32 . strength / MPa 6.0 6 63 6.30 Thermal conductivity / 0.045 0.044 0.042 0.042 W/m-K 9

Claims

CLAIMS LU501587

1. A preparation method of fly ash-based porous geopolymer insulation material filled with potassium titanate whisker is characterized by the following steps: the fly ash, metakaolin and potassium titanate whisker are mixed uniformly, and then the alkali activator and foaming agent are added to obtain the slurry. Finally, the slurry is injected, foamed and cured.

2. As stated in claim 1, the characteristic of the preparation method is as follows: the mass ratio of fly ash, metakaolin and potassium titanate whisker is

5.0-7.0:3.0-5.0:0.1-2.0, and the maximum particle size of the fly ash and metakaolin does not exceed 200 mesh; the potassium titanate whisker is selected from at least one of potassium tetratitanate whisker and potassium hexatitanate whisker. The diameter of potassium titanate whisker is 0.2-0.5 microns and the length is 8-100 microns.

3. As stated in claim 1, the characteristic of the preparation method is that the alkali activator is formed by mixing sodium hydroxide or potassium hydroxide with at least one of sodium silicate solution and potassium silicate solution and standing still. Its modulus is between 1.2 and 1.8.

4. As stated in claim 1, the characteristic of the preparation method is that the mass ratio of fly ash, metakaolin, potassium titanate whisker to alkali activator is

1.0:0.5-0.9.

5. As stated in claim 1, the characteristic of the preparation method is that the foaming agent is selected from at least one of H2O», trimethylhexadyl ammonium bromide, sodium dodecyl sulfate, aluminum powder, sodium tetraborate and urea, and the mass fraction of the foaming agent in the slurry is 1.0 % -15.0 %.

6. As stated in claim 1, the characteristic of the preparation method is that the foam stabilizer is added i to the slurry. The foam stabilizer is selected from at least one of sodium dodecyl benzene sulfonate, stearic acid, olive oil, hydroxyethyl cellulose and sodium polyacrylate. The mass fraction of foam stabilizer in the slurry is 0.5 % — -10.0 %.

7. As stated in claim 1, the characteristic of the preparation method is as follows: the stirring speed is 200 — 800 rpm, and the stirring time is not more than 30 minutes; the curing conditions are as follows: curing in a constant temperature and humidity 10

CLAIMS . ° ° € . LU501587 box with 25-40 °C and 95% humidity for 24-72 hours, and curing under the same conditions for 4-7 days after demolding.

8. As stated in claim 1, the characteristic of the preparation method is: the stirring is carried out in two times. The stirring is not more than 20 minutes after adding alkali activator, and not more than 10 minutes after adding foaming agent and stabilizing agent.

9. The characteristic of a fly ash-based porous geopolymer insulation material filled with potassium titanate whisker is that the insulation material is prepared according to any method in claim 1 — 8.

10. As stated in claim 9, fly ash-based porous geopolymer insulation material filled with potassium titanate whisker is used as wall insulation material.

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