CN114134458A

CN114134458A - Periodic multilayer ultrathin heat insulation film with nano porous structure and preparation and application thereof

Info

Publication number: CN114134458A
Application number: CN202111490124.9A
Authority: CN
Inventors: 胡志宇; 张帅; 刘泽昆; 吴振华; 傅理夫
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2021-12-08
Filing date: 2021-12-08
Publication date: 2022-03-04

Abstract

The invention relates to a periodic multilayer ultrathin heat insulation film with a nano porous structure, and preparation and application thereof. Compared with the prior art, the preparation method has the advantages of simple preparation process, controllable conditions and low cost, and is expected to be popularized and applied in the fields of aerospace high-temperature heat insulation and civil heat insulation.

Description

Periodic multilayer ultrathin heat insulation film with nano porous structure and preparation and application thereof

Technical Field

The invention belongs to the technical field of heat insulation, and relates to a periodic multilayer ultrathin heat insulation film with a nano porous structure, and preparation and application thereof.

Background

The heat insulating material is a material with heat insulating performance and shielding effect on heat flow, and can effectively reduce heat transmission of the high-temperature surface of the material to the low-temperature surface. The insulation material should have a structure to block three modes of heat propagation: thermal conduction, thermal radiation and thermal convection.

The heat insulating material has important significance for relieving energy crisis, improving energy utilization efficiency, protecting instruments and equipment, prolonging service life and the like. In the fields of daily life, industrial and agricultural production, aviation and navigation and the like, heat-insulating materials are often required to have good heat-insulating performance and excellent mechanical properties, and the requirements on the weight reduction and safety of the heat-insulating materials are higher and higher.

In the industrial field, inorganic heat-insulating materials such as refractory bricks, refractory fibers, expanded perlite, porous calcium silicate and the like are widely applied to the thermal processing processes of metallurgy, chemical engineering, electromechanics, building materials and ceramics, and the materials are low in price but poor in heat-insulating effect, so that a large amount of energy loss is still caused. In the field of buildings, mineral wool, expanded perlite and foamed plastic are widely applied to heat preservation and insulation of buildings, but the materials are large in size and low in strength, and the overall attractiveness and safety performance of the buildings are affected. In the field of marine navigation, the temperature of a ship body is high due to the fact that the ship body is exposed to direct sunlight for a long time, normal life and work of crews in a cabin are influenced, and meanwhile normal operation of precise instruments, equipment and parts in the ship body is influenced, so that higher requirements are provided for the performance of heat insulation materials. However, the conventional heat insulating film has various defects in heat insulating performance, light weight, and the like, and the present invention has been proposed based on the defects.

Disclosure of Invention

The invention aims to provide a periodic multilayer ultrathin heat insulation film with a nano porous structure, and preparation and application thereof.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a periodic multilayer ultrathin heat insulation film with a nano porous structure, which comprises a substrate, a bonding layer deposited on the substrate, and a heat insulation layer and a reflecting layer which are periodically and sequentially compounded on the substrate. The reflective layer of this film can effectively reflect the infrared ray, reduces the film to the absorption of environment thermal radiation, and the insulating layer can reduce the heat conduction, and the tie coat can improve the holistic stability of film and fastness. By controlling the magnetron sputtering condition, the heat insulation layer has a porous structure with a nano scale, and the heat conduction path can be effectively prolonged.

Further, the substrate is one of a polymer film, glass, a silicon wafer, a metal and an oxide sheet thereof.

Furthermore, the bonding layer is a Cr layer, and the thickness of the bonding layer is preferably 1-1000 nm.

Further, the heat insulation layer is made of SiC and Si₃N₄、SiO₂、TiO₂、Al₂O₃Preferably, the thickness of the one or more of the above is 1 to 1000 nm.

Furthermore, when the heat insulation layer is a plurality of components, the different components are compounded in sequence. In addition, the thermal insulation layer has a nano-porous structure, and preferably, has a porous structure in a vertical type, a horizontal type and/or a disordered type, as shown in fig. 1.

Further, the reflective layer is one of W, Ag and Al, and preferably, the thickness ratio of the thermal insulation layer to the reflective layer is 1000: (1-1000).

Furthermore, the periodic number of the periodic composition of the heat insulation layer and the reflection layer is 1-100000.

The second technical scheme of the invention provides a preparation method of a periodic multilayer ultrathin heat insulation film with a nano porous structure, which comprises the following steps:

(1) placing a substrate on a magnetron sputtering platform, firstly depositing a binder layer on the substrate, and then periodically and sequentially depositing a heat insulation layer and a reflection layer to obtain a crude film;

(2) and annealing the crude film to obtain the target product.

Further, in the step (1), in the magnetron sputtering deposition process, the distance between the substrate and the target material is 50-1000 mm, the purity of the working gas is 98-99.9% of argon, and the vacuum degree is 0.1-10 x 10^-3pa, the sputtering working pressure is 0.1-10 pa, the substrate rotation speed is 2-40 r/min, the magnetron sputtering power is 20-250W, and the substrate temperature is 20-100 ℃.

Further, in the step (2), the annealing temperature is 200-1000 ℃, and the annealing time is 1-24 hours.

Further, the substrate is subjected to grinding and polishing treatment in advance.

The third technical scheme of the invention provides application of a periodic multilayer ultrathin heat insulation film with a nano porous structure, and the ultrathin heat insulation film is used in the fields of aviation and navigation equipment shells and civil heat insulation.

Compared with the prior art, the invention has the following advantages:

(1) the multilayer film deposited by the magnetron sputtering method has the potential of mass preparation and continuous production, and can realize micro-nano precise regulation, and the thickness and the weight of the prepared heat insulation film are far lower than those of heat insulation materials on the market.

(2) The combination and matching of the heat insulation layer and the reflecting layer can effectively weaken the absorption of the film on external heat radiation and reduce the self heat conduction; the bonding layer can improve the stability and reliability of the material;

(3) the heat-insulating layer with the nano-porous structure can effectively prolong a heat-conducting path, and the air in the porous structure enhances the heat-insulating effect of the whole material.

Drawings

FIG. 1 is a schematic diagram of a nanoporous structure of a thermal insulation layer provided by the present invention;

FIG. 2 is a periodic multilayer thermal film of a different construction provided by the present invention.

FIG. 3 is a heat flow profile of a multilayer thermal barrier film provided by the present invention.

FIG. 4 is a scanning electron microscope image of the cross section and surface of the multilayer thermal insulation film provided by the present invention.

The notation in the figure is:

1. a substrate; 2. a bonding layer; 3. a thermal insulation layer; 4. and a reflective layer.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.

Example 1:

quartz glass is placed on a sample stage of a magnetron sputtering cavity, and a SiC target material with the purity of 99.99 percent and Si are selected₃N₄Target material, Cr target material and Al target material, SiC target material and Si target material₃N₄The target material is placed in a radio frequency target, and the Cr target material and the Al target material are placed in a direct current target. The distance between the sample stage and the target is 100mm, the purity of the working gas is argon gas and the vacuum degree is 5 x 10^-3pa, the sputtering working pressure is 0.5pa, the substrate rotating speed is 10r/min, the radio frequency target power is 100W, the direct current target power is 50W, and the substrate temperature is 80 ℃;

firstly, 50nm Cr is deposited on a quartz glass substrate to be used as a bonding layer, and then 50nm SiC and 50nm Si are used₃N₄As a thermal barrier layer, 10nm Al was deposited as a reflective layer for 100 cycles. And annealing the film, wherein the working gas is argon, the annealing temperature is 500 ℃, and the annealing time is 4 hours.

The structure diagram is shown in fig. 2(b), which also comprises a substrate 1, an adhesive layer 2 deposited on the substrate 1, and a thermal insulating layer 3 and a reflective layer 4 deposited in sequence periodically, in particular of SiC — Si₃N₄Al is one period.

Example 2:

placing a silicon waferSelecting SiO with the purity of 99.99 percent on a sample table of a magnetron sputtering cavity₂Target material, TiO₂Target material, Cr target material and Al target material, SiO₂Target material and TiO₂The target material is placed in a radio frequency target, and the Cr target material and the Al target material are placed in a direct current target. The distance between the sample stage and the target is 150mm, the purity of the working gas is argon gas and the vacuum degree is 5 x 10^-3pa, the sputtering working pressure is 0.8pa, the substrate rotating speed is 10r/min, the radio frequency target power is 150W, the direct current target power is 100W, and the substrate temperature is 100 ℃;

firstly, 50nm Cr is deposited on a silicon wafer substrate as a bonding layer, and then 50nm SiO is sequentially deposited₂，10nm Al，50nm TiO₂And 10nm Al with a period of 50. And annealing the film, wherein the working gas is argon, the annealing temperature is 600 ℃, and the annealing time is 6 hours.

The structure diagram is shown in fig. 2(c), which also comprises a substrate 1, an adhesive layer 2 deposited on the substrate 1, and a thermal insulating layer 3 and a reflective layer 4 deposited in sequence periodically, in particular as SiO₂-Al-TiO₂Al is one period.

Example 3:

placing the aluminum oxide polished wafer on a sample table of a magnetron sputtering cavity, and selecting SiO with the purity of 99.99 percent₂Target material, Al₂O₃Target material, Cr target material and Al target material, SiO₂Target material and Al₂O₃The target material is placed in a radio frequency target, and the Cr target material and the Al target material are placed in a direct current target. The distance between the sample stage and the target is 150mm, the purity of the working gas is argon gas and the vacuum degree is 5 x 10^-3pa, sputtering working pressure is 1pa, substrate rotating speed is 10r/min, radio frequency target power is 200W, direct current target power is 100W, and substrate temperature is 100 ℃;

firstly, 50nm Cr is deposited on an alumina polishing sheet to be used as a bonding layer, and then 50nm SiO is sequentially deposited₂，10nm Al，50nm SiO₂，50nm Al₂O₃And 10nm Al with a period of 50. And annealing the film, wherein the working gas is argon, the annealing temperature is 700 ℃, and the annealing time is 8 h.

The structure is shown in FIG. 2(d), which also contains a substrate 1, a tie layer deposited on the substrate 12, and a thermal barrier layer 3 and a reflective layer 4, in particular of SiO, deposited periodically in succession₂-Al-SiO₂-Al₂O₃Al is one period.

Comparative example 1:

compared to example 1, most of them are the same except that in this example: omits a heat insulation layer component Si₃N₄And the thickness of SiC is 100 nm.

The structure diagram is shown in fig. 2(a), and comprises a substrate 1, an adhesive layer 2 deposited on the substrate 1, and a heat insulating layer 3 and a reflecting layer 4 which are periodically and sequentially deposited, specifically, taking SiC — Al as one period.

The data for the above examples and comparative examples are shown in the following table:

material	Thickness (nm)	Thermal conductivity (W.m)^-1·K^-1)
			Alumina (Al)₂O₃)	/	45
Silicon dioxide (SiO)₂)	/	7.6
			Silicon carbide (SiC)	/	490
Silicon nitride (Si)₃N₄)	/	200
			Titanium dioxide (TiO)₂)	/	10
Air (a)	/	0.01
			Example 1 (SiC/Si)₃N₄)	50nm/50nm	345
Example 2 (SiO)₂/TiO₂)	50nm/50nm	8.8
			Example 3 (SiO)₂/SiO₂/Al₂O₃)	50nm/50nm/50nm	20.01
COMPARATIVE EXAMPLE 1(SiC)	100nm	490

The same thickness of the thermal barrier layer can be found by comparing the theoretical thermal conductivities of example 1 and comparative example 1 without considering the multi-layer interface and the porous structure, but example 1 is SiC and Si₃N₄The combined multi-layer structure material has lower thermal conductivity. Due to the multilayer components SiC and Si₃N₄The thermal conductivity of the material is different, and when the thermoacoustic electrons and the thermal electrons are transmitted at the interface of the two materials, the thermoacoustic electrons and the thermal electrons are scattered, so that energy is consumed, and less energy is transmitted to the substrate, thereby achieving the thermal insulation effect.

As can be seen from the scanning electron microscope photos in FIG. 4(a-b), the cross section and the surface of the multilayer material prepared by the invention have obvious micro-nano scale pore structures. The multi-layer heat insulation material has a porous structure, and air has extremely low heat conductivity, so that on one hand, air holes can be used as a medium for heat insulation, and on the other hand, the air holes can form new interface heat insulation with a multi-layer material, so that the multi-layer material with the air hole structure has more excellent heat insulation effect.

By taking a magnetron sputtering method as an example, the formation of a loose porous structure is caused only when the Ar gas flow and the sputtering power selected for preparing the thermal insulation layer are larger. During operation, Ar gas is filled into the working cavity of the magnetron sputtering system, and Ar atoms are ionized into Ar in a strong electric field⁺And e^-. Accelerated in an electric field e^-Collide with Ar atoms, which are ionized to Ar under the impact of high-energy electrons⁺And e^-，e^-Moving towards the sample stage under the action of an electric field, and continuously colliding with Ar atoms in the moving process to generate more Ar⁺And e^-Until the energy of the electron is insufficient to ionize the Ar atom. Ar (Ar)⁺The target material moves in an accelerating way under the action of an electric field to bombard the surface of the target material, target atoms or molecules are sputtered from the surface of the target material, and the atoms or molecules are deposited on a substrate on a sample table to form a film. When the flow rate of Ar gas and the sputtering power are large, Ar⁺Nanoparticles are bombarded from the surface of the target material and are accumulated on the substrate to generate a porous structure. As can be seen from FIGS. 4(a-b), the interior and the surface of the multilayer structure have obvious granular feelings, and air media exist among the granules, so that the whole multilayer material has a porous structure. FIG. 4(c-d) is a cross section and a surface of a conventional multilayer thin film with low Ar gas flow and sputtering power, which has a dense structure without an obvious loose porous structure. In addition, in order to prevent the influence of the loose porous structure on the mechanical and thermal stability of the material, the porous structure can be adoptedAnd (4) eliminating local stress in a subsequent thermal annealing mode.

Comparative example 2:

compared to example 1, most of them are the same except that in this example: the deposition of the reflective layer is omitted.

Comparative example 3:

preparing a 500nm SiC compact film by a high-temperature hot pressing method.

The energy conversion process of different insulation materials was analyzed using solar radiation as an example of the heat source (fig. 3). For examples 1-3: heating of the substrate Q_{Heating of}＝Q_{Solar energy}-Q_Reflection-Q_{Air conduction}-Q_Conduction(Q_{Solar energy}Representing the radiant energy of the sun, Q_ConductionRepresenting the heat lost during heat conduction, Q_ReflectionRepresenting heat reflected by the reflective layer into the environment). Comparative example 1, which has a single-component, single-layer structure with a small heat-dissipating capacity and a small Q_ConductionTherefore, the heat insulation effect is not good. For comparative example 2, which lacks a reflective layer, the heated Q of the substrate_{Heating of}＝Q_{Solar energy}-Q_{Air conduction}-Q_ConductionThe greater part of the radiation energy is absorbed by the material, so the thermal insulation effect is not good. Comparative example 3, which is a dense film prepared by physical high temperature hot pressing, has no loose porous structure, lacks porous media and interfacial insulation, and has a substrate heated Q_{Heating of}＝Q_{Solar energy}-Q_ConductionThe heat insulation effect is not good.

Example 4:

the multilayer heat insulation film of the embodiment 3 is deposited on the surface of the wing of the aerospace plane, so that the influence of high temperature generated by friction between the wing and the atmosphere in the flying process of the aircraft on a precision instrument in a cavity of the aircraft can be effectively reduced.

Example 5:

the multilayer heat insulation film of the embodiment 3 is deposited on the surface of a water storage tank of a solar water heater to achieve the heat preservation effect.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A periodic multilayer ultrathin heat insulation film with a nano-porous structure is characterized by comprising a substrate, a bonding layer deposited on the substrate, and a heat insulation layer and a reflecting layer which are periodically and sequentially compounded on the substrate.

2. The periodic multilayer ultrathin thermal insulation film with the nano-porous structure as claimed in claim 1, wherein the substrate is one of a polymer film, glass, a silicon wafer, a metal and an oxide sheet thereof.

3. The periodic multilayer ultrathin heat insulation film with the nano-porous structure as claimed in claim 1, wherein the bonding layer is a Cr layer with a thickness of 1-1000 nm.

4. The periodic multilayer ultrathin thermal insulation film with the nano-porous structure as claimed in claim 1, wherein the thermal insulation layer is SiC or Si₃N₄、SiO₂、TiO₂、Al₂O₃One or more of them, the thickness of which is 1 to 1000 nm.

5. The periodic multilayer ultrathin thermal insulation film with the nano-porous structure as claimed in claim 4, characterized in that when the thermal insulation layer is a multi-component, different components are compounded in sequence.

6. The periodic multilayer ultrathin thermal insulation film with the nano-porous structure as claimed in claim 1, wherein the reflective layer is one of W, Ag and Al, and the thickness ratio of the thermal insulation layer to the reflective layer is 1000: (1-1000).

7. The periodic multilayer ultrathin heat insulation film with the nano-porous structure as claimed in claim 1, wherein the number of the periodic recombination cycles of the heat insulation layer and the reflection layer is 1-100000.

8. The method for preparing the periodic multilayer ultrathin thermal insulation film with the nano porous structure as claimed in any one of claims 1 to 7, characterized by comprising the following steps:

(2) and annealing the crude film to obtain the target product.

9. The method for preparing a periodic multilayer ultrathin heat insulation film with a nano-porous structure as claimed in claim 8, wherein in the step (1), in the magnetron sputtering deposition process, the distance between the substrate and the target is 50-1000 mm, the purity of the working gas is 98% -99.9% of argon, and the vacuum degree is 0.1-10 x 10^-3pa, the sputtering working pressure is 0.1-10 pa, the substrate rotating speed is 2-40 r/min, the magnetron sputtering power is 20-250W, and the substrate temperature is 20-100 ℃;

in the step (2), the annealing temperature is 200-1000 ℃, and the annealing time is 1-24 h.

10. The use of a periodic multilayer ultrathin thermal insulation film with a nanoporous structure as claimed in claim 1, wherein the ultrathin thermal insulation film is used in the fields of aerospace equipment housings and civil thermal insulation.