CN106500374A - A kind of biphase composite solar absorber coatings and manufacture method - Google Patents

Abstract

The invention discloses a dual-phase nanocomposite solar energy absorbing coating and a manufacturing method thereof. The coating includes sequentially providing an infrared high reflection layer, a main absorbing layer, a secondary absorbing layer and an antireflection layer on a substrate, and cleaning the substrate by a chemical method. Put it in a vacuum furnace, then vacuumize it, feed high-flow nitrogen gas into the furnace, open the Ti target, and deposit a TiN infrared high-reflective layer on the substrate; then close the Ti target, open the AlTi alloy target, and feed low-flow oxygen and nitrogen, in a low-oxygen and low-nitrogen environment, deposit a dual-phase nanostructure primary absorption layer on the infrared high-reflection layer; increase the nitrogen flow rate, and deposit a single-phase nanostructure secondary absorption layer on the primary absorption layer in a low-oxygen and high-nitrogen environment layer; finally turn off the nitrogen, deposit the anti-reflection layer under high oxygen concentration conditions, turn off the heater, and naturally cool to obtain the Ti-Al-O-N dual-phase nanocomposite solar absorbing coating of the four-layer structure. The coating made by the present invention The absorption efficiency of the layer is good, the energy conversion efficiency is high, and it has great promotion and application value.

Description

A dual-phase nanocomposite solar absorbing coating and its manufacturing method

technical field

The invention relates to a solar light absorbing coating for seawater desalination and a preparation method thereof, in particular to a dual-phase nanocomposite solar absorbing coating and a manufacturing method, belonging to the field of thin film materials.

Background technique

In solar thermal utilization technology, the first step is to convert solar radiation into thermal energy. In this process, solar absorbing coatings are mainly used, which absorb most of the light waves in the ultraviolet to near-infrared range of the solar spectrum, and are transparent in the infrared band. Depositing the coating on a metal substrate can use Its highly infrared reflective properties reflect infrared waves away. The purpose of this design is to avoid as much as possible the high heat emissivity caused by the coating absorbing infrared light waves, resulting in heat energy loss, especially as the working temperature of the coating increases, this part of the heat loss becomes more serious. Therefore, the performance of the coating determines the efficiency of solar heat conversion.

In the field of solar absorbing coatings, cermet absorbing coatings are used the most. This coating is composed of nanoscale metal particles embedded in the matrix of metal oxide dielectric, which has a strong absorption effect on solar radiation; depositing a layer of anti-reflection coating on the coating can make its absorption ratio reach 0.9 above. For example, in domestic solar water heating systems, Al-AlN composite absorbing coatings are commonly used. Depositing this coating on a highly reflective substrate such as copper or aluminum can make the absorption rate as high as 0.95 and the surface emissivity as low as 0.05. However, due to the low melting point of aluminum, it is easy to diffuse at high temperatures, and it is easily corroded by water vapor, resulting in a decrease in its performance, which restricts the coating to be used only at low temperatures (100°C). In order to utilize solar energy in the medium and high temperature field, a series of new cermet solar absorbing coating materials have been developed, such as a solar medium and high temperature selective heat absorbing coating protected by the invention patent CN102734956A. In this technical scheme, a metal (CrAl, NiAl, SiAl) infrared reflective layer is first deposited on the base material of the heat collecting element, then a multi-layer cermet absorbing layer with a gradual composition is deposited in sequence, and finally an aluminum oxide anti-reflection layer is deposited. This coating has an absorptivity of 0.93-0.96 and an emissivity of 0.04-0.08, and has excellent light-to-heat conversion performance; after heat treatment in air at 400°C for 70 hours, the absorptivity decreases and the emission increases.

Cermet-type absorbing coatings are mostly prepared by magnetron sputtering technology. The thickness of the coating prepared by this technology can be controlled, and the coating can be prepared in combination with theoretical calculation results. Using effective medium theory and computer simulation technology, through numerical optimization, the optical parameters and thickness of the specific coating material to obtain the best selective absorption can be calculated, and then the coating can be prepared by taking advantage of the controllable thickness of this technology. The absorptivity of the coating prepared by the method is higher than 0.9, the emissivity is lower than 0.1, and has good thermal stability in vacuum; it has been commercially applied in solar water heating systems and other medium and low temperature solar energy utilization fields. However, due to the low ionization rate of sputtered metal atoms in this method, most of them are in the atomic state, and the energy carried by themselves is low, resulting in two obvious defects in the coating deposited by this method. One is the low binding force with the substrate. The sputtered target atoms themselves have no charge and are loosely combined with the substrate. Most of them are physically adhered, so the binding force is low. The second is that due to the low energy of atoms, cavities are easy to form during the coating growth process. These cavities can become oxygen diffusion channels, oxidize the metal components under high temperature conditions, and make the coating lose its absorption performance.

Especially in some new solar desalination systems. Due to the day and night run-off temperature cycles, high requirements are placed on the adhesion of the absorbent coating to the substrate. In addition, the system works in a high-temperature steam environment, and the absorbing coating must not only be resistant to high-temperature oxidation, but also be resistant to seawater corrosion for a long time. Arc ion plating technology is a physical vapor deposition technology. Due to its characteristics of no pollution, high ionization rate, fast deposition rate, high ion energy, and low cost, it is currently the main preparation technology for hard coatings. The ionization rate of metal atoms evaporated by the arc is over 90%, and dense coating materials can be prepared; at the same time, the chemical combination of the coating and the base material can be realized to improve the adhesion and meet the performance requirements of the seawater desalination system for the solar absorbing coating .

Contents of the invention

The invention aims to provide a high-efficiency solar light absorbing coating for seawater desalination and a preparation method thereof. A two-phase nanocomposite absorbing coating with a dense structure was prepared by utilizing the characteristics of high plasma ionization rate of high-power cathodic arc ion plating technology. And the coating has good oxidation resistance and seawater corrosion resistance, and can be well combined with the base material to meet the application conditions of solar seawater desalination. And the preparation method of the coating material is provided.

Absorption coating technical scheme provided by the present invention is:

A dual-phase nanocomposite solar absorbing coating, characterized in that: an infrared high reflective layer, a main absorbing layer, a secondary absorbing layer and an antireflection layer are successively arranged on a substrate, wherein the substrate adopts a hydrophilic and seawater corrosion-resistant porous The infrared high reflection layer is a transition metal nitride material that is resistant to seawater corrosion. The main absorption layer is composed of two metal nanoparticle materials with different optical properties embedded in the dielectric. The secondary absorption layer is composed of single-phase transition metal nitrogen. The anti-reflection layer is a low-refractive index material layer, and the gradient structure of the coating is beneficial to reduce the overall reflectivity of the coating and increase the absorption rate.

As an improvement, the porosity of the porous material made of the base is between 20-80%, the pore size is between 0.1-10 microns, and the thickness of the base is greater than or equal to 1 mm; the infrared high reflection layer is nitrogen of TiN or ZrN The compound material is embedded in the dielectric inner coating, and its thickness is 0.1-1 micron; the main absorption layer is composed of two kinds of transition metal nanoparticles and transition metal nitride nanomaterials with different optical properties embedded in the dielectric, in which the transition metal nanoparticles are The absorption peak of solar radiation is between 200-400 nanometers, the absorption peak of transition metal nitride nanomaterials is between 500-700 nanometers, the ratio of the nanocrystals of the two materials is adjustable between 0-1, and the nanocrystals of the two materials The particle size is 3-15 nanometers, the coating thickness of the main absorption layer is 30-100 nanometers; the single-phase transition metal nitride nanomaterial particle size of the secondary absorption layer is 3-10 nanometers, and the coating thickness is 30-100 nanometers; the anti-reflection layer The refractive index of the material is 1.8-2, and its thickness is 50-100 nm.

A method for manufacturing the above-mentioned dual-phase nanocomposite solar absorbing coating, characterized in that it comprises the following steps:

Step 1. Prepare the equipment for manufacturing the dual-phase nanocomposite solar absorbing coating. The equipment includes a vacuum furnace with a furnace door. A rotatable workpiece frame is arranged in the vacuum furnace. Two workpiece frames are arranged around the vacuum furnace. Symmetrically distributed heaters, AlTi alloy targets and Ti targets are respectively set on the left and right sides of the vacuum furnace;

Step 2. Cleaning of the substrate material. The porous material for the substrate is ultrasonically cleaned in acetone, alcohol and deionized water for 8-30 minutes, then placed in a desiccator for drying, and then loaded on the workpiece rack in the vacuum furnace, and the furnace is closed. Door;

Step 3, obtaining a vacuum environment, the vacuum furnace is evacuated into a vacuum environment through a vacuum pumping device;

Step 4. Start the equipment, let the workpiece holder rotate with the substrate, then open the Ti target, use high-power arc discharge technology to evaporate Ti ions from the Ti target with current, and pass high-flow nitrogen gas into the vacuum furnace. An infrared high reflective layer of TiN is formed on it;

Step 5. Close the Ti target, open the AlTi alloy target and adjust the current, pass low-flow oxygen into the vacuum furnace, and adjust the nitrogen to low flow. In a low-oxygen and low-nitrogen environment, deposit a dual-phase nanometer on the infrared high-reflection layer. Structural primary absorbent layer;

Step 6. Increase the flow rate of nitrogen gas in the vacuum furnace, and deposit a single-phase nanostructured secondary absorption layer on the main absorption layer under a low-oxygen and high-nitrogen environment;

Step 7, turn off the nitrogen flow meter, increase the oxygen flow rate into the vacuum furnace, and deposit the anti-reflection layer under the condition of high oxygen concentration;

Step 8: After the preparation is completed, the AlTi alloy target and the heater of the vacuum furnace are turned off, and then naturally cooled to below 100° C. to obtain a Ti-Al-O-N dual-phase nanocomposite solar absorbing coating with a four-layer structure.

As preferably, the vacuuming equipment of the vacuum furnace includes a mechanical pump and a molecular pump. When vacuuming in step 3, the mechanical pump is used to pump air. When the pressure in the vacuum furnace reaches below 2pa, the molecular pump is turned on to pump the air. Evacuate the vacuum furnace into a high vacuum system until the pressure is below 8×10 ^-4 Pa.

Preferably, in the step four, the arc discharge power of the Ti target is 0.2-0.5 kilowatts, the flow rate of nitrogen gas in the vacuum furnace is 200-500 SCCM, and the rotating speed of the workpiece holder is set at 3-5 rpm. The main purpose is to increase the energy of ions in the plasma, to form a chemical bond between the coating and the substrate, and to improve the bonding force.

As a preference, in the step five, the power of the AlTi alloy target is 0.1-0.3 kilowatts, the flow rate of oxygen into the vacuum furnace is 10-30 SCCM, and the flow rate of the adjusted low-flow nitrogen gas is 20-50 SCCM. The deposition time of the structural main absorption layer is 1-3min.

As a preference, in the sixth step, the power of the AlTi alloy target is 0.1-0.3 kilowatts, the nitrogen flow range after the increase is 60-100 SCCM, and the deposition time of the secondary absorption layer is 1-3 minutes.

Preferably, in the step seven, the power of the AlTi alloy target is 0.1-0.3 kilowatts, the increased oxygen flow rate is 200-500 SCCM, and the antireflection layer deposition time is 1-3 minutes.

The present invention is beneficial to:

1) The absorption coating containing dual-phase nanoparticles is used to effectively broaden the absorption spectrum width of the coating for solar radiation, increase the absorption rate of the coating, and then improve the light-to-heat conversion efficiency.

2) Cathodic arc ion plating technology is adopted, which has high plasma ionization rate and high ion energy, so that the coating is closely combined with the base material and is not easy to fall off; at the same time, high-energy ions have an impact on the coating, which can eliminate the coating The voids in the growth process can obtain a dense coating, which can effectively improve the oxidation resistance and seawater corrosion resistance of the coating.

3) The coating deposition rate of this technology is an order of magnitude faster than that of the magnetron sputtering technology, which saves time and reduces costs, and meets the requirements of non-blocking of micro-nanoporous substrates during the deposition process.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a dual-phase nanocomposite solar absorbing coating;

Fig. 2 is the schematic diagram of manufacturing dual-phase nanocomposite solar absorbing coating equipment;

Fig. 3 is the reflection spectrogram of dual-phase nanocomposite solar absorbing coating;

In the figure, 1-vacuum exhaust port, 2-workpiece holder, 3-Ti target, 4-heater, 5-furnace door, 6-AlTi alloy target, 7-vacuum chamber, 8-substrate, 9-infrared high reflective layer , 10-main absorption layer, 11-secondary absorption layer, 12-anti-reflection layer.

detailed description

Implement the device of the inventive method as shown in Figure 2, and device is the vacuum furnace that has furnace door 5, and vacuum furnace furnace wall surrounds vacuum chamber 7, and vacuum chamber 7 height is 0.5-1.5 meter, and volume is 50 * 50 * 50 cm. A furnace door 5 is arranged in front of the vacuum chamber 7 to facilitate the loading and unloading of the substrate material. The vacuum chamber 7 is provided with a vacuum pumping port 1. The vacuum pumping device of the vacuum furnace evacuates the vacuum chamber 7 through the vacuum pumping port 1. The vacuum pumping device is composed of a mechanical pump and a molecular pump, and the ultimate vacuum can reach 8×10 ^{- 4Pa} . The furnace walls on the left and right sides of the vacuum chamber 7 are equipped with AlTi alloy target 6 and high-purity Ti target 3 respectively. The AlTi atomic ratio of AlTi alloy target 6 is 67:33, and the target current of AlTi alloy target 6 and high-purity Ti target 3 are equal Adjustable within 20-170A. The vacuum furnace is equipped with two symmetrically distributed heaters 4 for heating the vacuum chamber 7 . The workpiece frame 2 can rotate counterclockwise, the rotating speed is adjustable within 1-5rpm, and is connected to the negative bias voltage. The furnace wall of the vacuum furnace is still equipped with a plurality of gas pipelines that can be fed into working gases such as oxygen, nitrogen and argon, and each gas pipeline is equipped with a mass flow meter to control the flow rate of the working gas.

As shown in Figure 1, it is a schematic diagram of the structure of the dual-phase nanocomposite solar absorbing coating of the present invention, including that an infrared high reflection layer 9, a main absorbing layer 10, a secondary absorbing layer 11 and an antireflection layer 12 are sequentially arranged on a substrate 8, wherein The substrate 8 is made of a porous material that is hydrophilic and resistant to seawater corrosion, the infrared high reflection layer 9 is made of a transition metal nitride material that is resistant to seawater corrosion, and the main absorption layer 10 is inlaid with two metal nanoparticle materials with different optical properties. Composed in the dielectric, the secondary absorption layer 11 is composed of a single-phase transition metal nitride nanomaterial embedded in the dielectric, and the anti-reflection layer 12 is a low-refractive index material layer. The gradient structure of the coating is conducive to reducing the overall reflectivity of the coating and improving the overall reflectivity of the coating. Absorption rate.

The porous material made of the base 8 has a porosity of 20-80%, a pore size of 0.1-10 microns, and a thickness of the base 8 greater than or equal to 1 mm;

The infrared high-reflection layer 9 is a nitride material of TiN or ZrN embedded in the dielectric inner coating, and its thickness is 0.1-1 micron. The infrared high-reflection layer 9 is slightly smaller than the material pore size of the substrate 8, so that it is not blocked during the deposition process. hole;

The main absorption layer 10 is composed of two kinds of transition metal nanoparticles and transition metal nitride nanomaterials with different optical properties embedded in the dielectric, that is, the absorption peak positions of the two kinds of nanoparticles are different, and both are within the range of 300-2500 nanometers of solar radiation , to broaden the absorption spectrum of the coating; wherein the absorption peak of transition metal nanoparticles to solar radiation is between 200-400 nanometers in the ultraviolet band of visible light, and the transition metal nitride nanomaterial is between 500-700 nanometers in the infrared band of visible light, The ratio of the nanocrystals of the two materials is adjustable between 0-1, the size of the nanoparticles of the two materials is 3-15 nanometers, and the coating thickness of the main absorption layer 10 is 30-100 nanometers;

The single-phase transition metal nitride nanomaterial particle size of the secondary absorption layer 11 is 3-10 nanometers, and the coating thickness is 30-100 nanometers. The nanoparticles are mainly transition metal nitride nanoparticles, which cooperate with the main absorption layer 10 to form a gradient structure;

The anti-reflection layer 12 is a low-refractive-index material, which can be selected according to the materials used in the main absorption layer 10 and the secondary absorption layer 11, and its thickness is controlled at 50-100 nanometers, which plays an anti-reflection role on the one hand and protects the primary and secondary absorption layers Not to be oxidized and corroded by seawater, the material of the anti-reflection layer 12 has a refractive index of 1.8-2.

A method for manufacturing the above-mentioned dual-phase nanocomposite solar absorbing coating, comprising the following steps:

Step 1, prepare the equipment for manufacturing the dual-phase nanocomposite solar absorbing coating, the equipment includes a vacuum furnace with a furnace door, a rotatable workpiece frame 2 is arranged in the vacuum furnace, and a workpiece frame 2 is arranged around the vacuum furnace. Two symmetrically distributed heaters 4, AlTi alloy targets 6 and Ti targets 3 are respectively arranged on the left and right sides of the vacuum furnace;

Step 2. Cleaning of the substrate material. The porous material for making the substrate 8 is ultrasonically cleaned in acetone, alcohol and deionized water for 8-30 minutes in turn, then placed in a desiccator for drying, and then loaded on the workpiece rack 2 in the vacuum furnace. Close the furnace door 5;

Step 3, obtaining the vacuum environment, the vacuum furnace is evacuated into a vacuum environment by the vacuum equipment, and the vacuum equipment of the vacuum furnace includes a mechanical pump and a molecular pump. After the pressure in the furnace reaches below 2pa, turn on the molecular pump to pump air, and pump the inside of the vacuum furnace into a high vacuum system until it is below 8×10 ^-4 Pa;

Step 4: Start the equipment, let the workpiece holder 2 rotate with the substrate 8, set the rotation speed of the workpiece holder 2 to 3-5rpm, then turn on the Ti target 3, and use high-power arc discharge technology to evaporate Ti ions from the Ti target with current out, the arc discharge power of the Ti target 3 is 0.2-0.5 kilowatts; the nitrogen gas with a flow rate of 200-500 SCCM (mass flow unit, standard state ml/min) is passed into the vacuum furnace, and the infrared high temperature of TiN is formed on the substrate. Reflective layer 9; the deposition time is 3-8 minutes;

Step 5, close the Ti target, open the AlTi alloy target 6 and adjust the current, adjust the power of the AlTi alloy target 6 to 0.1-0.3 kilowatts, feed oxygen with a flow rate of 10-30 SCCM into the vacuum furnace, and adjust the nitrogen to low Flow rate, the flow rate of low-flow nitrogen gas after adjustment is 20-50 SCCM, and in a low-oxygen and low-nitrogen environment, deposit a dual-phase nanostructure main absorption layer 10 on the infrared high-reflection layer 9, and the deposition time is 1-3min;

Step 6. Increase the nitrogen flow in the vacuum furnace to 60-100 SCCM, and deposit a single-phase nanostructure secondary absorption layer 11 on the main absorption layer 10 under a low-oxygen and high-nitrogen environment, and the deposition time is 1-3 minutes;

Step 7. Turn off the nitrogen gas flowmeter, set the flow rate of oxygen into the vacuum furnace to 200-500 SCCM, and deposit the anti-reflection layer 12 under the condition of high oxygen concentration, and the deposition time of the anti-reflection layer 12 is 1-3min;

Step 8: After the preparation is completed, the AlTi alloy target 6 and the heater 4 of the vacuum furnace are turned off, and then naturally cooled to below 100° C. to obtain a Ti-Al-O-N dual-phase nanocomposite solar absorbing coating with a four-layer structure.

During the preparation process of the main absorption layer 10 and the secondary absorption layer 11 , the flow rate of oxygen is kept constant, and the ratio of the two-phase nanoparticles is controlled by controlling the flow rate of nitrogen gas into the vacuum chamber 7 . During the deposition process, adjust the flow rate of oxygen into the vacuum chamber 7 to a certain value. Since Al ions are more likely to combine with O ions than Ti ions, most of the Al ions evaporated from the target participate in the reaction with O ions. , forming amorphous Al ₂ O ₃ . _{Amorphous Al2O3} is the dielectric. In the case of insufficient nitrogen, some Ti ions combine with N ions to form TiN nanoparticles, and some form Ti nanoparticles, which are embedded in amorphous alumina, and finally form a dual-phase nanocrystalline composite coating as the main absorption layer 10 . Under the condition of sufficient nitrogen, Ti ions combine with N ions to form TiN nanoparticles embedded in amorphous alumina, forming a single-phase nanocomposite coating as the secondary absorption layer 11 . Under the condition of sufficient oxygen flow rate, both Ti and Al ions are fully oxidized to form amorphous titanium aluminum oxide as the anti-reflection layer 12 .

When depositing the infrared high reflection layer 9 of TiN, high power is used mainly to increase the energy of the ions in the plasma, so as to form a chemical bond between the coating and the substrate 8 and improve the bonding force. By controlling the ratio of oxygen and nitrogen fed into the reaction chamber and adjusting the ratio of Ti and TiN nanocrystals, a dual-phase nanocrystal composite material is obtained, so that the coating has broad-spectrum absorption performance. A single-phase TiN nanocomposite absorbing material is obtained to form a graded structure with the main absorbing layer to reduce reflection and improve absorbing performance. Through excessive oxygen, fully oxidized amorphous titanium aluminum oxide is obtained, and its refractive index is about 1.8-2, which effectively reduces the reflection of the coating interface; at the same time, the oxide coating has a dense structure, no voids, and covers the main absorption The layer 10 and the secondary absorption layer 11 prevent the nanoparticles from contacting with high-temperature air and sea water, and improve the performance stability of the coating. The infrared high reflective layer of TiN will further illustrate the technical solution of the present invention in conjunction with specific examples below:

Under the vacuum degree of 10 ^-3 Pa, the rotation speed of the workpiece holder 2 is controlled to 5 rpm, and 300 SCCM nitrogen gas is introduced into the vacuum furnace, and the high-energy ions evaporated from the Ti target 3 are deposited on the cleaned stainless steel and porous capillary material substrate 8 Deposit the infrared high reflective layer 9 of TiN on the top, the power of the deposition source is 0.3 kilowatts, the bias voltage on the workpiece is -150V, the deposition time is 5 min, and the thickness of the infrared high reflective layer 9 is 200 nanometers; after the deposition is completed, close the Ti target 3, feed oxygen into the vacuum furnace with a flow rate of 20 SCCM, and adjust the flow rate of nitrogen gas to 20 SCCM, open the AlTi alloy target 6, adjust and set the current of the AlTi alloy target 6 to 65A, and the corresponding power is 0.2 kilowatts, Deposit the main absorption layer 10, the deposition time is 1.5 min, the thickness of the main absorption layer 10 is 60 nanometers; increase the nitrogen flow rate to 80 SCCM, deposit the sub-absorption layer 11, the deposition time is 1 min, the thickness of the sub-absorption layer 11 is 40 nanometers; turn off the nitrogen Flowmeter, continue to increase the flow rate of oxygen to 300 SCCM, deposit the anti-reflection layer 12 in a high oxygen environment, the deposition time is 2min, and the thickness is 60 nanometers; after the deposition is completed, it is naturally cooled, and the total thickness is 260 nanometers, and the solar light with a four-layer structure is obtained Absorbs coating. Its reflection spectrum in the range of 0.3-25 microns is shown in accompanying drawing 3, and the calculated coating absorptivity on the stainless steel substrate is 0.936, and the emissivity is 0.175; the absorptivity on the porous NiO substrate is 0.958, and the emissivity is 0.471.

Claims (8)

1. A two-phase nanocomposite solar absorbing coating, characterized in that: on the substrate, an infrared high reflection layer, a main absorbing layer, a secondary absorbing layer and an antireflection layer are successively arranged, wherein the substrate adopts hydrophilicity and seawater corrosion resistance The infrared high reflection layer is a transition metal nitride material resistant to seawater corrosion, the main absorption layer is composed of two nanoparticle materials with different optical properties embedded in the dielectric, and the secondary absorption layer is composed of single-phase transition metal nitrogen The anti-reflection layer is a low-refractive index material layer, and the gradient structure of the coating is beneficial to reduce the overall reflectivity of the coating and increase the absorption rate. 2. A kind of dual-phase nanocomposite solar absorbing coating according to claim 1, characterized in that: the porosity of the porous material made into the base is between 20-80%, and the pore size is 0.1-10 microns, and the base The thickness is greater than or equal to 1 mm; the infrared high reflective layer is TiN or ZrN nitride material embedded in the dielectric inner coating, and its thickness is 0.1-1 micron; the main absorption layer is composed of two transition metal nanoparticles with different optical properties and The transition metal nitride nanomaterial is embedded in the dielectric, and the absorption peak of the transition metal nanoparticle to solar radiation is between 200-400 nanometers, and the absorption peak of the transition metal nitride nanomaterial is between 500-700 nanometers. The ratio of material nanocrystals can be adjusted between 0-1, the size of the nanoparticles of the two materials is 3-15 nanometers, the coating thickness of the main absorption layer is 30-100 nanometers; the single-phase transition metal nitride nanomaterial of the secondary absorption layer The particle size is 3-10 nanometers, and the thickness of the coating is 30-100 nanometers; the refractive index of the material of the antireflection layer is 1.8-2, and the thickness is 50-100 nanometers. 3. A method for manufacturing the two-phase nanocomposite solar absorbing coating according to claim 2, characterized in that, comprising the following steps: Step 1. Prepare the equipment for manufacturing the dual-phase nanocomposite solar absorbing coating. The equipment includes a vacuum furnace with a furnace door. A rotatable workpiece frame is arranged in the vacuum furnace. Two workpiece frames are arranged around the vacuum furnace. Symmetrically distributed heaters, AlTi alloy targets and Ti targets are respectively set on the left and right sides of the vacuum furnace; Step 2. Cleaning of the substrate material. The porous material for the substrate is ultrasonically cleaned in acetone, alcohol and deionized water for 8-30 minutes, then placed in a desiccator for drying, and then loaded on the workpiece rack in the vacuum furnace, and the furnace is closed. Door; Step 3, obtaining a vacuum environment, the vacuum furnace is evacuated into a vacuum environment through a vacuum pumping device; Step 4. Start the equipment, let the workpiece holder rotate with the substrate, then open the Ti target, use high-power arc discharge technology to evaporate Ti ions from the Ti target with current, and pass high-flow nitrogen gas into the vacuum furnace. An infrared high reflective layer of TiN is formed on it; Step 5. Close the Ti target, open the AlTi alloy target and adjust the current, pass low-flow oxygen into the vacuum furnace, and adjust the nitrogen to low flow. In a low-oxygen and low-nitrogen environment, deposit a dual-phase nanometer on the infrared high-reflection layer. Structural primary absorbent layer; Step 6. Increase the flow rate of nitrogen gas in the vacuum furnace, and deposit a single-phase nanostructured secondary absorption layer on the main absorption layer under a low-oxygen and high-nitrogen environment; Step 7, turn off the nitrogen flow meter, increase the oxygen flow rate into the vacuum furnace, and deposit the anti-reflection layer under the condition of high oxygen concentration; Step 8: After the preparation is completed, the AlTi alloy target and the heater of the vacuum furnace are turned off, and then naturally cooled to below 100° C. to obtain a Ti-Al-O-N dual-phase nanocomposite solar absorbing coating with a four-layer structure. 4. A kind of method for manufacturing dual-phase nanocomposite solar energy absorbing coating as claimed in claim 3, is characterized in that: the vacuuming equipment of described vacuum furnace comprises mechanical pump and molecular pump, when vacuumizing in step 3, first pass through The mechanical pump pumps air. When the pressure in the vacuum furnace reaches below 2pa, turn on the molecular pump to pump air, and the vacuum furnace is pumped into a high vacuum system until it is below 8×10 ^-4 pa. 5. A kind of method for manufacturing dual-phase nanocomposite solar energy absorbing coating as claimed in claim 3, is characterized in that: in described step 4, the arc discharge power of Ti target is 0.2-0.5 kilowatts, passes into in the vacuum furnace The flow rate of nitrogen is 200-500SCCM, and the rotating speed of the workpiece holder is set at 3-5rpm. 6. A kind of method for manufacturing dual-phase nanocomposite solar energy absorbing coating as claimed in claim 3, is characterized in that: in described step 5, the power of AlTi alloy target is 0.1-0.3 kilowatts, and the flow rate that feeds oxygen in the vacuum furnace It is 10-30 SCCM, the flow rate of the adjusted low-flow nitrogen gas is 20-50 SCCM, and the deposition time of the dual-phase nanostructure main absorption layer is 1-3min. 7. A kind of method for manufacturing dual-phase nanocomposite solar energy absorbing coating as claimed in claim 3, is characterized in that: in described step 6, the power of AlTi alloy target is 0.1-0.3 kilowatts, and the nitrogen flow range after increasing is 60- 100 SCCM, the deposition time of the secondary absorbing layer is 1-3min. 8. A method for manufacturing a dual-phase nanocomposite solar absorbing coating as claimed in claim 3, characterized in that: in said step seven, the power of the AlTi alloy target is 0.1-0.3 kilowatts, and the increased oxygen flow rate is 200 -500 SCCM, the anti-reflection layer deposition time is 1-3min.