CN104697210A - In-situ self-assembly growth solar selective absorbing film and preparation method thereof - Google Patents

Abstract

The invention provides an in-situ self-assembly growth solar selective absorbing film and a preparation method thereof, and belongs to the technical field of preparation of solar selective absorbing films. The in-situ self-assembly growth solar selective absorbing film consists of a stainless steel metal substrate and an in-situ self-assembly growth foamed nano-structure absorbing film body on the stainless steel metal substrate, wherein the thickness of the absorbing film body is 1-3 micrometers; and uniform holes formed by accumulated Fe3-x-yCrxNiyO4 of a spinal-type structure are distributed in a film layer and on a film surface, x equals to 0.18-0.27, y equals to 0.25-0.35, the grain size of nanometer particle clusters is 20-60 nanometers, and the size of the holes is 20-80 nanometers. On the premise that the absorbing film has high solar absorptivity and low heat emissivity, the in-situ self-assembly growth solar selective absorbing film is simple in structure, the foamed nano-structure grows on the substrate in an in-situ manner and is combined to the substrate closely and firmly, and heat stability and the weather resistance are high. The in-situ self-assembly growth solar selective absorbing film can be used in the field of solar photo-thermal generation heat collecting tubes.

Description

Solar energy selective absorbing film of a kind of in-situ self-grown and preparation method thereof

Technical field

The invention belongs to solar energy selective absorbing film preparing technical field, high-selenium corn Low emissivity solar energy selective absorbing film being specifically related to a kind of foam-like nanostructured of in-situ self-grown and preparation method thereof.

Background technology

Solar energy thermal transition is that a kind of energy conversion efficiency and utilization rate are high and with low cost, the Solar use mode that can extensively promote in the whole society.Current solar thermal utilization enlivens, and forms industry.No matter be solar water heater or solar light-heat power-generation thermal-collecting tube, all will have a core apparatus being used for absorbing solar radiation, i.e. coating for selective absorption of sunlight spectrum.This coating needs has higher absorption rate at Visible-to-Near InfaRed wave band (0.3 ~ 2.5 μm), has comparatively low-launch-rate at infrared band (2.5 μm ~ 20 μm).And for the heated body in a practical application, its heat radiation concentration of energy is in the infrared range of spectrum that wavelength is 3.0 ~ 30.0 μm, in order to reduce heat loss, prevent the shortwave energy absorbed from falling with the radiation of long wave form again, alap heat emission ratio (usually representing with ε) will be kept in heat radiation wave band.In a word, to make sorbent surface exactly while absorbing solar radiation to greatest extent, reduce its radiation heat loss as far as possible.The material with this characteristic becomes the focus of current solar energy heat collection pipe and selective absorbing film area research.

The selective heat-absorbing film occurred in the market has black chromium, AIN/Al, NiCrN _xo _y, TiN _xo _ydeng.Chromium plating film, because of electroplate liquid contaminated environment, eliminates at present gradually; Although AIN/Al light thermal property is better, cannot work for a long time in high temperature air, so also reduce gradually; The NiCrN of current more use _xo _y, TiN _xo _ydeng absorption film, its manufacture craft is more complicated, needs the strict ratio controlling two kinds of gases simultaneously, also needs to use more accurate magnetic control sputtering device.NiCrN disclosed in China Patent Publication No. CNI584445A _xo _yabsorption film is after having done gradual change to NiCr tenor, and best absorptivity just reaches 92%, and minimum radiance is 0.1.TiN disclosed in China Patent Publication No. CN101240944A and CN201196495Y _xo _yfilm, its surface reloads one deck SiO ₂after antireflective film, absorptivity can reach 96%, and emissivity is lower than 4%, and above rete also needs the content more accurately controlling nitrogen and oxygen in the process of preparation., consider from extensive masking technique angle for this reason, need to introduce new technology, thus obtain cheap high performance selective absorbing film.

Summary of the invention

High-selenium corn Low emissivity solar spectrum selective absorbing film that the object of this invention is to provide a kind of foam-like nanostructured of in-situ self-grown and preparation method thereof.

The solar energy selective absorbing film of a kind of in-situ self-grown of the present invention, by stainless steel metal base substrate and in stainless steel metal base substrate the foam-like nanostructured absorbing membrane of in-situ self-grown form (as shown in Figure 1); The thickness of absorbing membrane is 1 ~ 3 μm, blocked uply can increase thermal emissivity, too thinly can affect absorptivity, and thicknesses of layers can be adjusted by the reaction time and control.In the rete of absorbing membrane and film surface distributed have more uniform from spinel-like structural (as Fig. 2 XRD scheme shown in) Fe _3-x-ycr _xni _yo ₄(x=0.18 ~ 0.27, y=0.25 ~ 0.35) nano particle group, particle diameter is 20 ~ 60nm, and the size of hole is 20 ~ 80nm (the SEM figure as Fig. 3 is known).The molar composition ratio of film element can be able to be obtained by electron spectroscopy data.

The preparation method of the solar energy selective absorbing film of a kind of in-situ self-grown of the present invention, its step is as follows:

1) alcohol swab wiping is used on stainless steel substrates surface, surface is polished and cleaning;

2) smooth surface and clean stainless steel substrates are put in the NaOH solution of 5M ~ 20M, then join together in reactor, under 100 ~ 250 degrees Celsius, react 6 ~ 40h;

3) room temperature is naturally cooled to after being taken out by reactor, then by ultrasonic for product 7 ~ 25h;

4) deionized water is spent after being taken out by stainless steel substrates, finally dry under 20 ~ 90 degrees Celsius, thus the solar energy selective absorbing film of in-situ self-grown is obtained on stainless steel substrates surface.

The feature of absorbing membrane of the present invention is that structure is simple, and preparation technology is simple, and environmental friendliness, film and substrate are connected firmly, Heat stability is good.There is high-absorbility, low-launch-rate simultaneously, and the excellent properties such as weatherability is strong, long service life.

Described stainless steel metal base substrate is the one in the stainless steels such as SS201, SS202, SS302, SS408, SS410, SS416, SS409, SS440, SS316L, SS304.In this stainless steel, by mass percentage, ≤ 2.00%), phosphorus (P :≤0.045%), (S :≤0.030%) etc., thickness is 0.2 ~ 2mm to sulphur containing chromium (Cr:16.00 ~ 18.00%), nickel (Ni:10.00 ~ 14.0%), manganese (Mn:.

The refractive index of absorbing membrane can realize by regulating the pore size in micro-texture on film surface, rete and distribution, the pore size on film surface and distribution etc., and then controls from film surface to the stainless steel-based end, from pottery to metallic transition.

Described foam-like nanostructured absorbing membrane, is connected firmly with substrate by hydro-thermal method growth in situ on the stainless steel-based end.Wherein the form of sunshine high-selenium corn material is the foamed nanostructured of being constructed by nano particle group, its size (20 ~ 60nm) is much smaller than infrared wavelength, and be distributed with comparatively concrete dynamic modulus in this micro-structural, sunshine can be caught better, reduce thermal emissivity, the selective absorbing to infrared light and visible ray can be realized.

Described radiation absorption film is based on the membrane structure of foam-like nanostructured, and the hole that its film distributes can carry out multiple reflections, scattering and absorption to the light of incidence.The local fields effect of combining nano particle greatly enhances the absorptivity of film simultaneously.This film can pass through adjusting reaction time, NaOH concentration, reaction temperature, product ultrasonic time, and then regulate number of apertures and size distribution etc. on the micro-structural on film surface and film, make the energy of visible and near-infrared sunshine spectral coverage by selective absorbing, the thermal emissivity on surface can be suppressed simultaneously, thus has good high-selenium corn and Low emissivity effect.

Absorbing membrane of the present invention has following advantage:

Owing to have employed foam-like nano-structure film as absorbed layer, surface pore size is much smaller than infrared light wavelength, absorbing membrane of the present invention is made can significantly to improve solar spectrum absorptivity on the one hand, significantly reduce whole film emissivity on the other hand, have the advantages that photo-thermal conversion efficiency is high, solar energy optical-thermal thermal-collecting tube can be widely used in.The advantages such as meanwhile, it is simple that this film has preparation method, and pre-treatment is convenient, environmental friendliness, energy one-step synthesis method.

Absorbing membrane of the present invention is under maintenance high solar absorption and low thermal emissivity prerequisite, there is structure simple, foam-like nanostructured growth in situ is in substrate, in conjunction with close and firm, heat endurance and weatherability are better, at 450 DEG C, process 24 hours, also do not occur that rete is chapped situation, foam nanostructured substantially goes up and can keep, and is that pore-size diminishes (15 ~ 45nm), nano particle granule footpath becomes about 45 ~ 80nm.This film can be used in solar light-heat power-generation thermal-collecting tube field.

Absorbing membrane of the present invention, the hydro-thermal method being applicable to cheap and simple is prepared, and does not need pre-treatment and the post-processing step of complexity and contaminated environment, to the development important in inhibiting in solar selectively photo-thermal film field.

Accompanying drawing explanation

Fig. 1: the section S EM figure of the foam-like nanostructured absorbing film of fabricated in situ, can find out that this film is foam-like porous nanostructured by figure, growth in situ is in stainless substrate, and the size of membrane pores is about 20 ~ 80nm.

Fig. 2: the surperficial SEM figure of the foam-like nanostructured absorbing film of fabricated in situ, can find out by figure, the nano particle group that film surface is is about 20 ~ 60nm by particle diameter is formed.

Fig. 3: the XRD figure of foam-like nanostructured absorbing film.Spectral line 2 shows, the foam-like nanostructured absorbing film of fabricated in situ is spinel structure, and peak is strong and crystallization is more weak; Spectral line 3 shows, the foam-like nanostructured absorbing film obtained after 24 hours through heat treatment in 450 DEG C of air is also Spinel, the strong and crystallization grow in peak.

Fig. 4: the electronic energy spectrum of synthesized foam-like nanostructured absorbing film, according to the integral area ratio at the peak of element each in spectrogram, can obtain the molar content ratio of each element on film.

Fig. 5: the reflection spectrum curve of foam-like nanostructured absorbing film; Curve 1 represents the reflection spectrum curve in 0.3 ~ 20 micron spectral interval of the foam-like nanostructured absorbing film of fabricated in situ.After curve 2 represents 450 DEG C of process, the reflection spectrum curve in 0.3 ~ 20 micron spectral interval of the foam-like nanostructured absorbing film of fabricated in situ.

Detailed description of the invention

Embodiment 1: stainless steel-based the end/preparation of foam-like nanostructured absorbing membrane

(1) first use alcohol swab wiping stainless steel substrates 12 times, stainless steel substrates surface is polished and cleaning, then stainless steel substrates is put in the NaOH solution of 16M, then pour into together in reactor;

(2) reactor is put into 200 degrees Celsius of baking ovens and react 22h, after then being taken out by reactor, naturally cool to room temperature, more ultrasonic process 7 hours; Spend deionized water, 90 DEG C of dryings after finally being taken out by stainless steel substrates, thus on stainless steel substrates, obtain the high-selenium corn Low emissivity solar spectrum selective absorbing film of the foam-like nanostructured of in-situ self-grown.Film thickness about 2.9 μm, in rete and film surface distributed have the more uniform nano particle by spinel-like structural to roll into a ball the hole piled up, the particle diameter of nano particle group is 20 ~ 56nm, and the size of hole is 20 ~ 77nm.The integral area ratio at the peak of each element in electronic energy spectrum by Fig. 4 .1, can obtain the molar content ratio of each element on film.The chemical formula that can obtain film is Fe _2.40cr _0.27ni _0.33o ₄.

In addition, this film is placed in high temperature furnace and heats up with 2 DEG C/min, in 450 DEG C of heat treatments Temperature fall after 24 hours, to check the heat endurance of this film.

$\mathrm{\α}=\frac{{\∫}_{0.3}^{2.5}[1-R\left(\mathrm{\λ}\right)]P_{\mathrm{sun}}\left(\mathrm{\λ}\right)\mathrm{d\λ}}{{\∫}_{0.3}^{2.5}{P}_{\mathrm{sun}}\left(\mathrm{\λ}\right)\mathrm{d\λ}}---\left(1\right)$

$\mathrm{\ϵ}=\frac{{\∫}_{2.5}^{20}[1-R\left(\mathrm{\λ}\right)]P_b\left(\mathrm{\λ}\right)\mathrm{d\λ}}{{\∫}_{2.5}^{20}{P}_b\left(\mathrm{\λ}\right)\mathrm{d\λ}}---\left(2\right)$

Film, in the absorptivity of 0.3 ~ 2.5 μm of spectrum range and the thermal emissivity at 2.5 ~ 20 μm of spectrum ranges, can calculate (as shown in Figure 5) according to above-mentioned formula (1), (2) and measured reflected spectrum data.In above formula, α and ε represents absorptivity and thermal emissivity respectively; R (λ) represents the reflectivity at λ wavelength place, obtains at 0.3 ~ 2.5 μm of available spectrophotometer measurement, obtains 2.5 ~ 20 μm of available Fourier infrared spectrograph measurements in place.P _sun(λ) represent the energy intensity of the solar radiation at λ wavelength place, adopt the normal data of ISO 9845-1 (1992) and AM1.5; P _b(λ) represent the blackbody radiation intensity at λ wavelength place, adopt the radiation value of absolute black body during 300K.

The main energetic of sunshine concentrates on 0.3 ~ 2.5 μm of interval, and a kind of outstanding solar energy selective absorbing film has very high absorptivity in this interval; Have very low thermal emissivity (namely showing very high infrared reflectivity at this spectrum range) in 2.5 ~ 20 μm of intervals simultaneously, suppress scattering and disappearing of the heat absorbed, thus realize the selective absorbing to sunshine.The film of the growth in situ that this experiment obtains has higher absorptivity that is 0.92 in 0.3 ~ 2.5 μm of interval, even if absorptivity also can reach 0.83 after 450 DEG C of heat treatment.Interval at the mid and far infrareds of 2.5 ~ 20 μm, the black body radiation choosing 300K does reference, and in conjunction with the reflectance spectrum in formula (2) and this interval, the thermal emissivity that can calculate this growth in situ film is be upgraded to 0.23 after 0.12,450 DEG C of heat treatments.To sum up, can say that the rete that this experiment growth in situ obtains can absorb sunshine preferably in solar spectrum interval, outwards launch lower heat radiation simultaneously; Though performance has small size decline after 450 DEG C of heat treatment.A kind of solar energy selective absorbing film preferably but this rete still be can yet be regarded as.

Embodiment 2: stainless steel-based the end/preparation of foam-like nanostructured absorbing membrane

(1) first 8 times surface is polished with alcohol swab wiping stainless steel substrates and clean, then put in the NaOH solution of 5M, then pour into together in reactor.

(2) 100 degrees Celsius of baking oven 6h put into by reactor, after take out reactor and naturally cool to room temperature, product carries out ultrasonic 7 hours, and deionized water is washed, 20 DEG C of dryings.Film thickness about 1 μm, in rete and film surface distributed have the more uniform nano particle by spinel-like structural to roll into a ball the hole piled up, the particle diameter of nano particle group is 35 ~ 59nm, and the size of hole is 49 ~ 80nm.The integral area ratio at the peak of each element in electronic energy spectrum by Fig. 4 .2, can obtain the molar content ratio of each element on film.The chemical formula that can obtain film is Fe _2.57cr _0.18ni _0.25o ₄.

Embodiment 3: stainless steel-based the end/preparation of foam-like nanostructured absorbing membrane

(1) first 20 times surface is polished with alcohol swab wiping stainless steel substrates and clean, then put in the NaOH solution of 20M, then pour into together in reactor.

(2) 250 degrees Celsius of baking oven 40h put into by reactor, after take out reactor and naturally cool to room temperature, product carries out ultrasonic 25 hours, and deionized water is washed, 90 DEG C of dryings.Film thickness about 3 μm, in rete and film surface distributed have the more uniform nano particle by spinel-like structural to roll into a ball the hole piled up, the particle diameter of nano particle group is 20 ~ 44nm, and the size of hole is 20 ~ 70nm.The integral area ratio at the peak of each element in electronic energy spectrum by Fig. 4 .3, can obtain the molar content ratio of each element on film.The chemical formula that can obtain film is Fe _2.45cr _0.20ni _0.35o ₄.

Claims (4)

1. the solar energy selective absorbing film of an in-situ self-grown, it is characterized in that: by stainless steel metal base substrate (1) and in stainless steel metal base substrate the foam-like nanostructured absorbing membrane (2) of in-situ self-grown form, the thickness of absorbing membrane is 1 ~ 3 μm, in rete and film surface distributed have the more uniform Fe by spinel-like structural _3-x-ycr _xni _yo ₄the hole that nano particle group piles up, the particle diameter of nano particle group is 20 ~ 60nm, and the size of hole is 20 ~ 80nm; Wherein, x=0.18 ~ 0.27, y=0.25 ~ 0.35.

2. the solar energy selective absorbing film of a kind of in-situ self-grown as claimed in claim 1, it is characterized in that: described stainless steel metal base substrate (1) by mass percentage, containing Mn :≤2.00%, S :≤0.030%, P :≤0.045%, Cr:16.00 ~ 18.00%, Ni:10.00 ~ 14.0%, thickness is 0.2 ~ 2mm.

3. the solar energy selective absorbing film of a kind of in-situ self-grown as claimed in claim 1 or 2, is characterized in that: stainless steel metal base substrate (1) is the one in stainless steel SS201, SS202, SS302, SS408, SS410, SS416, SS409, SS440, SS316L or SS304.

4. the preparation method of the solar energy selective absorbing film of a kind of in-situ self-grown described in claim 1,2 or 3, its step is as follows:

1) alcohol swab wiping is used on stainless steel substrates surface, surface is polished and cleaning;

2) smooth surface and clean stainless steel substrates are put in the NaOH solution of 5M ~ 20M, then join together in reactor, under 100 ~ 250 degrees Celsius, react 6 ~ 40h;

3) room temperature is naturally cooled to after being taken out by reactor, then by ultrasonic for product 7 ~ 25h;

4) deionized water is spent after being taken out by stainless steel substrates, finally dry under 20 ~ 90 degrees Celsius, thus the solar energy selective absorbing film of in-situ self-grown is obtained on stainless steel substrates surface.