A hollow / core-shell fiber-doped nanoporous composite material with high thermal stability and low thermal conductivity

Abstract

A kind of hollow / core-shell fiber doped nano-porous composite material with high thermal stability and low thermal conductivity, which is composed of several stacked hollow aerogel matrix units doped with metal oxides on the surface and several hollow / core-shell sub-micron fiber units oriented in the direction perpendicular to the heat flow direction and doped in the hollow aerogel matrix units.In high-temperature thermal environment, firstly, the hollow aerogel matrix can greatly reduce the solid-phase thermal conductivity of the material and improve the thermal stability of the composite material to a certain extent.At the same time, the core-shell structure and the metal oxides on the surface of the particles not only greatly reduce the radiation thermal conductivity, but also inhibit high-temperature sintering, further improve the thermal stability of the material.Secondly, the hollow / core-shell sub-micron fibers are oriented in the direction perpendicular to the heat flow direction, and the hollow / core-shell structure not only reduces the solid-phase thermal conductivity of the fibers, but also greatly inhibits high-temperature radiation, and improves the mechanical properties and high-temperature thermal stability of the composite material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nano-thermal insulation materials, and particularly relates to a hollow / core-shell fiber doped nano-porous composite material with high thermal stability and low thermal conductivity. BACKGROUND

[0002] With the continuous development of aerospace technology, the flight speed of aircraft is continuously improved, the flight environment is continuously deteriorated, and the requirement for thermal protection is also more and more demanding. Therefore, a light-weight high-thermal-stability low-thermal-conductivity thermal insulation material becomes one of the important links for high-speed flight thermal protection applications. Nano-porous aerogel is a product of the development of modern micro-nano science and preparation technology, has extremely low density and thermal conductivity, and extremely high porosity, and is widely used as a new type of high-efficiency nano-thermal insulation material. However, in a high-temperature thermal environment, the aerogel will have a serious sintering phenomenon, resulting in particle fusion, structure collapse, volume shrinkage, degradation of thermal insulation performance, and seriously limiting its application in the field of high-temperature thermal protection. Although increasing the particle size of the aerogel or doping high-temperature-resistant materials such as fibers and metal oxides can improve the thermal stability to a certain extent, the intrinsic thermal conductivity of the doped materials will inevitably reduce the temperature-resistant thermal insulation properties of the material. Therefore, according to the existing large-scale preparation technology, a hollow / core-shell aerogel large particle matrix combined with a hollow / core-shell sub-micron fiber is used as a new type of composite structure, the hollow degree of the large particle matrix and the sub-micron fiber and the core-shell structure of different materials are adjusted according to different thermal protection application requirements, and different densities, different thermal conductivities and different mechanical strengths of the composite material are realized. SUMMARY

[0003] The present application aims to provide a hollow / core-shell fiber doped nano-porous composite material with high thermal stability and low thermal conductivity, which can improve the thermal stability of the composite material in a high-temperature thermal environment, and the thermal insulation performance meets the requirements of aerospace, military materials and high-temperature thermal protection.

[0004] In order to achieve the above-mentioned purpose, the solution of the present application is: composed of a plurality of stacked hollow aerogel matrix units doped with metal oxides on the surface and a plurality of hollow / core-shell sub-micron fiber units doped in the hollow aerogel matrix units and arranged vertically to the heat flow direction.

[0005] The hollow / core-shell sub-micron fiber units are distributed in the hollow aerogel matrix units to form a composite structure, realizing the thermal protection effect, wherein the hollow structure can greatly reduce the density of the material, the hollow / core-shell sub-micron fiber can greatly improve the high-temperature light shielding performance of the aerogel composite material, and the hollow structure of the fiber can be adjusted according to different application environments to realize the adjustment of the thermal conductivity of the sub-micron fiber, and the heat flow direction is perpendicular to the heat flow direction, realizing the thermal protection effect.

[0006] The hollow aerogel matrix unit comprises a hollow / core-shell aerogel matrix and a metal oxide doped on the surface of the hollow / core-shell aerogel matrix.

[0007] The thermal conductivity of the aerogel large particle matrix in different application environments can be adjusted by adjusting the hollow structure of the hollow / core-shell aerogel matrix. According to the thermal protection application requirements of the application environment, the doping proportion of the metal oxide is adjusted to realize different thermal conductivities, different thermal stabilities and different densities of the composite material. The thermal stability of the material is further improved by doping the metal oxide. The equivalent thermal conductivity of the material after doping the metal oxide is established by non-equilibrium molecular dynamics to establish the relationship between the mass fraction of the doped metal oxide and the solid-phase thermal conductivity of the large particle matrix at different temperatures, and the equivalent thermal conductivity is calculated by combining the random thermal conduction model of the aerogel.

[0008] The hollow degree of the hollow / core-shell aerogel matrix hollow structure, that is, the ratio of the inner diameter of the hollow aerogel particle to the aerogel particle size, is greater than 0 and less than 1.

[0009] According to different application environments, the hollow degree of the hollow particle is adjusted to realize the adjustment of the different densities and thermal conductivities of the aerogel large particle matrix. The thermal conductivity of the hollow / core-shell aerogel large particle matrix at different temperatures is calculated by using the aerogel thermal conduction model according to different hollow degrees.

[0010] The hollow / core-shell aerogel matrix is composed of a hollow silica core and a carbon or carbon black shell wrapped on the surface of the silica core. The function of inhibiting radiation is realized.

[0011] The metal oxide is aluminum oxide or titanium oxide.

[0012] The hollow / core-shell sub-micron fiber unit is composed of a hollow aluminum oxide core, a carbon shell or a hollow carbon black core, and a titanium oxide shell.

[0013] Compared with the prior art, the present application has the following effective effects:

[0014] The hollow / core-shell aerogel matrix doped with metal oxide of the present application uses a hollow structure to reduce the influence of the particle size of the composite material on the thermal conductivity, and further inhibits high-temperature radiation by the hollow / core-shell structure. The doped metal oxide improves the thermal stability of the composite material. At the same time, by adjusting the different hollow degrees of the hollow structure and the different doping proportions of the metal oxide, the density, thermal conductivity and thermal stability of the composite material can be adjusted to meet the application requirements of different thermal protection.

[0015] The hollow / core-shell sub-micron fiber of the present application has a fiber size of sub-micron level, which can increase the attenuation performance of the composite material, and the hollow structure can reduce the density of the composite material, the solid phase thermal conductivity of the fiber, and the temperature-resistant and heat-insulating characteristics of the material.

[0016] The present application adopts a hollow / core-shell structure, such as aluminum oxide (core) / carbon (shell) or carbon black (core) / titanium oxide (shell) and the like, so that the composite material has strong light shielding characteristics and certain oxidation resistance. Meanwhile, the hollow / core-shell sub-micron fiber is arranged vertically to the heat flow direction. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural schematic diagram of the present application;

[0018] In the figure, 1 is a hollow core-shell aerogel matrix, 2 is a hollow / core-shell matrix framework, 4 is a metal oxide, 5 is a hollow core-shell hollow degree, 6 is a hollow aerogel matrix unit, 7 is a hollow / core-shell sub-micron fiber unit, 8 is a hollow aluminum oxide or hollow carbon black core, and 9 is a carbon shell or titanium oxide shell. DETAILED DESCRIPTION

[0019] The present application will be described in detail below in combination with the drawings.

[0020] Referring to Figure 1 The present application includes a plurality of stacked hollow aerogel matrix units 6 doped with metal oxide 4 on the surface to form a three-dimensional framework structure 2 and a plurality of hollow / core-shell sub-micron fiber units 7 doped in the hollow aerogel matrix units 6 and arranged vertically to the heat flow direction, wherein the hollow aerogel matrix unit 6 includes a hollow / core-shell aerogel matrix 1 and a metal oxide 4 doped on the surface of the hollow / core-shell aerogel matrix 1, and the metal oxide 4 is doped to improve the thermal stability. The matrix 1 is composed of a hollow silica core and a carbon or carbon black shell coated on the surface of the silica core to further reduce the thermal conductivity of the radiation. The metal oxide 4 is aluminum oxide or titanium oxide, and the hollow degree of the hollow structure of the hollow / core-shell aerogel matrix 1, i.e. the ratio of the inner diameter of the hollow aerogel particle to the aerogel particle size, is greater than 0 and less than 1. By adjusting the hollow / core-shell hollow degree 5, the density, thermal conductivity and thermal stability of the hollow / core-shell large particle matrix can be adjusted to meet the application requirements of different thermal protection.

[0021] The hollow / core-shell sub-micron fiber unit 7 of the present application is composed of a hollow aluminum oxide core 8, a carbon shell 9 or a hollow carbon black core 8, a titanium oxide shell 9; it is arranged vertically to the heat flow direction, and the fiber is selected to be a sub-micron scale fiber, which can greatly improve the high-temperature light shielding performance of the composite material. The hollow aluminum oxide core or the hollow carbon black core 8 greatly reduces the density of the composite material and the solid phase thermal conductivity of the fiber.

[0022] In a high-temperature thermal environment, firstly, the hollow / core-shell aerogel matrix 1 can greatly reduce the solid-phase thermal conductivity of the material, and the hollow / core-shell aerogel matrix 1 improves the thermal stability of the composite material to a certain extent. At the same time, the core-shell structure and the metal oxide on the surface of the particle not only greatly reduce the radiation thermal conductivity, but also inhibit high-temperature sintering, further improving the thermal stability of the material. Secondly, the hollow / core-shell sub-micron fibers are arranged in the vertical direction of the heat flow, and the hollow / core-shell structure greatly inhibits high-temperature radiation while reducing the solid-phase thermal conductivity of the fibers, and improves the mechanical properties and high-temperature thermal stability of the composite material. For the existing large-scale preparation technology, the hollow / core-shell structure is adopted to combine the silica aerogel large particle matrix with the sub-micron fiber, so as to achieve the purpose of reducing the thermal conductivity of the material and improving the thermal stability, and can meet the application requirements of aerospace, military materials and thermal protection under ultra-high temperature.

Claims

1. A hollow / shell fiber doped nanomporous composite material with high thermal stability, low thermal conductivity, characterized in that: The hollow aerogel matrix unit (6) is composed of a plurality of stacked surface-doped metal oxide (4) hollow aerogel matrix units (6) and a plurality of hollow / shell sub-micron fiber units (7) doped in the hollow aerogel matrix unit (6) and arranged vertically to the heat flow direction; The hollow aerogel matrix unit (6) comprises a hollow / shell aerogel matrix (1) and a metal oxide (4) doped on the surface of the hollow / shell aerogel matrix (1); The hollow / shell aerogel matrix (1) has a hollow structure, and the ratio of the inner diameter of the hollow aerogel particle to the aerogel particle size is greater than 0 and less than 1; The hollow / shell aerogel matrix (1) is composed of a hollow silica core and a carbon or carbon black shell wrapped on the surface of the silica core. The metal oxide (4) is aluminum oxide or titanium oxide.

2. The hollow / shell fiber doped nanoporous composite material with high thermal stability and low thermal conductivity according to claim 1, characterized in that: The hollow / shell sub-micron fiber unit (7) is composed of a hollow aluminum oxide core, a carbon shell, or a hollow carbon black core, a titanium oxide shell.

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