Thermal insulation material based on in-situ generated mullite whiskers and preparation method of thermal insulation material

Abstract

The invention belongs to the technical field of thermal insulation materials, and particularly relates to a thermal insulation material based on in-situ generation of mullite whiskers and a preparation method thereof, the material is composed of 65-85 parts of porous mullite particle aggregate subjected to hole sealing treatment, 15-35 parts of a floating bead and kyanite pretreatment mixture, and 2-5 wt% of water glass. The preparation method comprises the following steps: carrying out silicon-based modifier surface hole sealing treatment on the porous mullite aggregate to reduce open pores; floating beads and kyanite are pretreated with alumina sol, so that the bonding strength of mullite whiskers, aggregate and a matrix is improved; mixing the raw materials and adding a water glass binder; and carrying out hot-press molding, and keeping temperature and pressure. The aluminum sol and the silica sol react at high temperature, an interconnected mullite whisker reinforced network is generated in situ, and the high-temperature expansion effect of kyanite is combined, so that the lightweight, low heat conduction and high strength of the material are realized; the method is suitable for high-temperature scenes such as special steel cast ingot caps and has excellent high-temperature stability and industrial production potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal insulation materials, and particularly relates to a thermal insulation material based on in-situ generated mullite whiskers and a preparation method thereof. BACKGROUND

[0002] In the process of energy utilization, thermal insulation materials are one of the key technologies for improving energy efficiency and energy saving. As a widely used basic thermal insulation material, the thermal insulation plate plays an important role in the fields of metallurgy, building, aviation, automobile, etc. Especially in the special steel smelting industry, the thermal insulation plate used for the ingot cap needs to meet more stringent performance requirements, including resistance to high-temperature molten steel erosion, excellent heat preservation performance, and long service life. However, the traditional SiO2-Al2O3 system thermal insulation plate has inherent defects such as high density, high thermal conductivity, low strength, and short service life. Therefore, how to effectively improve the comprehensive performance of the thermal insulation plate of this system has become a research focus. Through retrieval:

[0003] The Chinese patent document with publication number CN114349521B discloses a high-strength nano thermal insulation plate and a preparation method thereof, which introduces nano silicon carbide particles and alumina reinforcing fibers to enhance the strength of the material. The Chinese patent document with publication number CN112341227A discloses a high-temperature-resistant nano thermal insulation material and a preparation method thereof, which uses ceramic additives, sunscreens, and nano mullite to generate fiber-reinforced mullite high-temperature-resistant nano thermal insulation materials in-situ under hot pressing conditions. Although these works have improved the performance of mullite thermal insulation plates to some extent, the external reinforcing bodies used are chemical raw materials, which not only have relatively high costs, but also have complex preparation processes, limiting the large-scale promotion and application of such high-performance thermal insulation materials. In addition, research has confirmed that the thermal conductivity of closed pores is significantly lower than that of open pores, which provides an important theoretical basis for the development of high-performance thermal insulation materials.

[0004] In view of the above challenges and opportunities, it is of great research value and application prospect to develop a lightweight, low thermal conductivity, and high-strength mullite thermal insulation plate suitable for the ingot cap of special steel smelting by fully utilizing porous mullite as the main raw material. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a thermal insulation material suitable for the ingot cap of the special steel smelting industry and a preparation method thereof. The material has the characteristics of lightweight, low thermal conductivity, and high strength, and the key is that it can generate mullite whiskers in-situ.

[0006] To achieve the above technical purposes and effects, the present application is realized by the following technical solutions:

[0007] The application provides a kind of in-situ generated mullite whisker based thermal insulation material, which is composed of the following raw materials by mass fraction: 65-85 parts of porous mullite aggregate with sealing treatment, 15-35 parts of pre-treated floating beads and kyanite matrix powder, and 2-5wt% of water glass based on the total mass of raw materials.

[0008] The application also provides a preparation method of the above thermal insulation material, comprising the following steps:

[0009] S1, sealing treatment of porous mullite aggregate:

[0010] Spray the silicon-based modifier solution on the surface of the porous mullite, and after drying, the mullite particle material with sealing treatment is obtained; the amount of silicon-based modifier is 10-15wt% of the mass of porous mullite; the silicon-based modifier is composed of silica sol and silane coupling agent, wherein the solid content of silica sol is 20-30wt%, and the average particle size is 15-40nm;

[0011] S2, pre-treatment of floating beads and kyanite matrix powder:

[0012] Mix 75-87:25-13 of floating beads and kyanite by mass fraction, and add 21-25wt% of aluminum sol by mass fraction, and mix uniformly;

[0013] S3, mixing:

[0014] Add the pre-treated matrix raw material obtained in step S2 to the sealed porous mullite particle material obtained in step S1, and stir uniformly; add water glass as a binder, and continue to stir uniformly to obtain a mixture;

[0015] S4, hot pressing:

[0016] Put the mixture obtained in step S3 into a forming mold and place it in a hot pressing furnace; heat to the reaction temperature, press after setting time, and continue to heat and press; cool to room temperature, demold, and obtain the in-situ generated mullite whisker based lightweight low thermal conductivity high strength thermal insulation material.

[0017] Further, in step S1, the porous mullite aggregate is composed of particles with particle sizes of 3-5mm, 1-3mm and 0-1mm, mixed in a mass ratio of 30:20:15.

[0018] Further, in step S1, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550), N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602) or N-β-aminoethyl-γ-aminopropyltrimethoxysilane (KH792).

[0019] Further, in step S1, the drying process is: placing at room temperature for 12-24h, and then placing at 80-110℃ for 5-12h.

[0020] Further, in step S2, the particle size of the floating beads and kyanite powder is 0.3-50μm.

[0021] Further, in step S2, the solid content of the aluminum sol is >40%, and the particle morphology is feather-like, and the average particle size is 15-60nm.

[0022] Further, in step S3, the water glass is sodium silicate water glass, and the modulus M is 3.5-4.0.

[0023] Further, in steps S1-S3, the mass ratio content of alumina and silicon oxide in the silicon-based modifier, the aluminum sol and the water glass is 71-80:29-20.

[0024] Further, in step S4, the reaction temperature is 850-1150℃, the initial holding time is 1-4h, the pressure is 0.5-2.5MPa, and the holding and pressure holding time is 1-4h.

[0025] The beneficial effects of the present application are:

[0026] 1. Light weight and low thermal conductivity: the light weight porous mullite is used as aggregate, and the hollow floating beads are used as matrix raw material, which endows the material with inherent light weight and low thermal conductivity; the sealing pretreatment of the porous mullite further significantly reduces the thermal conductivity of the material.

[0027] 2. High strength, high toughness and high temperature stability: the aluminum sol binder forms a coating layer on the surface of the floating beads and kyanite, which reacts with the silicon sol on the surface of the mullite at high temperature to form an interconnected mullite whisker network in situ, which effectively enhances the strength of the material; the network combines the high temperature volume expansion effect of kyanite to jointly ensure the high strength, high toughness and excellent high temperature volume stability of the material.

[0028] 3. Low cost and easy industrialization: the raw materials are cheap and easy to obtain, the preparation process is simple and efficient, and no complex equipment or tedious process is needed, which has significant advantages in large-scale production.

[0029] Of course, any product implementing the present application does not necessarily need to achieve all the above advantages at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating laborious work.

[0031] Figure 1 SEM image of the thermal insulation material prepared in Example 1;

[0032] Figure 2 SEM image of the thermal insulation material prepared in Example 2. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0034] The specific embodiments of the present application are as follows:

[0035] Example 1

[0036] The present embodiment provides a lightweight, low-thermal-conductivity and high-strength thermal insulation material based on in-situ generated mullite whiskers and a preparation method thereof, and the specific preparation steps are as follows:

[0037] First, the porous mullite is subjected to a pore sealing treatment: a mixed solution of silica sol and silane coupling agent KH550 is prepared in a mass ratio of 96:4, and is stirred uniformly to obtain a silicon-based modifier; 10wt% of the above-mentioned silicon-based modifier is sprayed on the surface of the porous mullite aggregate; after drying, a pore-sealed mullite granular material is obtained. Next, 75 parts of floating beads and 25 parts of kyanite are mixed uniformly; 25wt% of aluminum sol is added and mixed uniformly to obtain a pretreated floating bead and kyanite matrix powder. Then, 65 parts of the pore-sealed mullite aggregate and 35 parts of the pretreated floating bead and kyanite matrix powder are weighed and mixed uniformly; 2wt% of water glass is added and stirred uniformly to obtain a mixed material. Finally, the above-mentioned mixed material is loaded into a forming mold, placed in a hot pressing furnace, heated to 900℃, and kept for 4h; after the heat preservation is completed, a pressure of 2.0MPa is applied, and the temperature and pressure are kept for 3h; after cooling to room temperature, the mold is removed, and the lightweight, low-thermal-conductivity and high-strength thermal insulation material based on in-situ generated mullite whiskers is obtained.

[0038] Example 2

[0039] The present embodiment provides a lightweight, low-thermal-conductivity and high-strength thermal insulation material based on in-situ generated mullite whiskers and a preparation method thereof, and the specific preparation steps are as follows:

[0040] First, the porous mullite is sealed: a mixture solution of silica sol and silane coupling agent KH602 is configured in a mass ratio of 91:9, stirred uniformly, to obtain a silicon-based modifier; 10wt% of the above-mentioned silicon-based modifier is sprayed on the surface of the porous mullite; after drying, the sealed mullite aggregate is obtained. Then, 80 parts of floating beads and 20 parts of kyanite are mixed uniformly; 21wt% of aluminum sol is added and mixed uniformly to obtain a pretreated floating bead and kyanite matrix powder. Then, 60 parts of sealed mullite particles and 40 parts of pretreated floating bead and kyanite matrix powder are weighed and mixed uniformly; 3wt% of water glass is added to the total mixture, stirred uniformly, to obtain a mixture. Finally, the above-mentioned mixture is loaded into a molding mold, placed in a hot pressing furnace, heated to 1000℃, and kept for 3h; after the holding period ends, a pressure of 1.5MPa is applied, and the temperature and pressure are kept for 2h; after cooling to room temperature, the mold is removed, and the lightweight, low thermal conductivity and high strength insulation material with in-situ generated mullite whiskers is obtained.

[0041] Example 3

[0042] The present embodiment provides a lightweight, low thermal conductivity and high strength insulation material with in-situ generated mullite whiskers and a preparation method thereof, and the specific preparation steps are as follows:

[0043] First, the porous mullite is sealed: a mixture solution of silica sol and silane coupling agent KH602 is configured in a mass ratio of 91:9, stirred uniformly, to obtain a silicon-based modifier; 10wt% of the above-mentioned silicon-based modifier is sprayed on the surface of the porous mullite; after drying, the sealed mullite aggregate is obtained. Then, 80 parts of floating beads and 20 parts of kyanite are mixed uniformly; 21wt% of aluminum sol is added and mixed uniformly to obtain a pretreated floating bead and kyanite matrix powder. Then, 60 parts of sealed mullite particles and 40 parts of pretreated floating bead and kyanite matrix powder are weighed and mixed uniformly; 3wt% of water glass is added to the total mixture, stirred uniformly, to obtain a mixture. Finally, the above-mentioned mixture is loaded into a molding mold, placed in a hot pressing furnace, heated to 1000℃, and kept for 3h; after the holding period ends, a pressure of 1.5MPa is applied, and the temperature and pressure are kept for 2h; after cooling to room temperature, the mold is removed, and the lightweight, low thermal conductivity and high strength insulation material with in-situ generated mullite whiskers is obtained.

[0044] By reacting aluminum sol and silica sol at high temperature, an interconnected mullite whisker reinforcement network is generated in-situ, combined with the high-temperature expansion effect of kyanite, to achieve lightweight, low thermal conductivity and high strength. The present invention does not require additional chemical reinforcers, significantly reducing costs, and is suitable for high-temperature scenarios such as special steel ingot caps, with excellent high-temperature stability and industrial production potential.

[0045] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to provide the best illustration of the application and its practical application to those skilled in the art and to enable those skilled in the art to best utilize the application. The application is only limited by the claims as well as their full scope and equivalents.

Claims

1. A thermal insulating material based on in-situ generated mullite whiskers, characterized in that, The material is composed of 65-85 parts of porous mullite granular aggregate with sealing treatment, 15-35 parts of pre-treated floating beads and kyanite matrix powder, and 2-5wt% of water glass based on the total raw material mass.

2. The method of claim 1, wherein the method is performed at a temperature of 0°C or lower. The method comprises the following steps: S1, sealing treatment of porous mullite aggregate: Spray the silicon-based modifier solution on the surface of the porous mullite, and after drying, the mullite granular material with sealing treatment is obtained; wherein the amount of the silicon-based modifier is 10-15wt% of the mass of the porous mullite; the silicon-based modifier is composed of silica sol and silane coupling agent, wherein the solid content of the silica sol is 20-30wt%, and the average particle size is 15-40nm; S2, pre-treatment of floating beads and kyanite matrix powder: Mix 75-87:25-13 floating beads and kyanite in mass fraction, and add 21-25wt% of aluminum sol in mass fraction, and mix uniformly; S3, mixing: Add the pre-treated matrix raw material obtained in step S2 to the sealed porous mullite granular material obtained in step S1, and stir uniformly; add water glass as a binder, and continue to stir uniformly to obtain a mixture; S4, hot-pressing forming: Put the mixture obtained in step S3 into a forming mold, and place it in a hot-pressing furnace; heat to the reaction temperature, press after setting the holding time, and continue to hold and press; cool to room temperature, and demold to obtain the lightweight low-thermal-conductivity high-strength thermal insulation material with in-situ generated mullite whiskers.

3. The method of claim 2, wherein, In step S1, the porous mullite aggregate is composed of particles with particle sizes of 3-5mm, 1-3mm and 0-1mm, and the mass ratio is 30:20:

15.

4. The method of claim 1, wherein, In step S1, the silane coupling agent is γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane or N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

5. The preparation method according to claim 2, characterized in that, In step S1, the drying process is: placing at room temperature for 12-24h, and then placing at 80-110℃ for 5-12h.

6. The preparation method according to claim 2, characterized in that, In step S2, the particle size of the floating beads and kyanite powder is 0.3-50μm.

7. The preparation method according to claim 2, characterized in that, In step S2, the solid content of the aluminum sol is >40%, and the particle morphology is feather-like with an average particle size of 15-60nm.

8. The preparation method according to claim 2, characterized in that, In step S3, the water glass is sodium silicate water glass, and the modulus M is 3.5-4.

0.

9. The preparation method according to claim 2, characterized in that, In steps S1-S3, the mass ratio of aluminum oxide and silicon oxide in the silicon-based modifier, aluminum sol and water glass is 71-80:29-20.

10. The method of claim 2, wherein, In step S4, the reaction temperature is 850-1150℃, the initial holding time is 1-4h, the pressure is 0.5-2.5MPa, and the holding and pressing time is 1-4h.

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