High-thermal-conductivity radiation refrigeration coating for 5G communication base station cabinet and preparation method thereof

Abstract

The application provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof, and belongs to the technical field of coatings. A SiC@BN / TiB2 three-phase fiber framework obtained through three-stage calcination is bonded with methylphenyl silicone resin through a silane coupling agent to form a longitudinal high-speed thermal conduction framework. Starburst calcium titanate and edge in-situ magnesium fluoride form a refractive index ladder and a rough multi-faceted structure, which not only reflects ultraviolet-near infrared light, but also endows weather resistance. Holmium / ytterbium co-doped calcium fluoride nanosheets are transversely overlapped to scatter near infrared light and convert the near infrared light into medium-far infrared radiation which can penetrate the atmospheric window, thereby further dissipating heat. Through mutual cooperation of a longitudinal continuous heat conduction path, a transverse heat dissipation network, optical multiple scattering and energy downshift radiation, stable chemical bond network support is achieved to realize high-efficiency, long-term reliable heat dissipation performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and relates to a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof. BACKGROUND

[0002] With the rapid expansion of 5G networks, macro base stations, micro base stations and even indoor distributed antenna systems are developing towards "high power, high integration and light weight". On the one hand, radio frequency power amplifiers, power modules and high-speed processing chips are compressed into smaller volumes, and the unit area power consumption increases exponentially; on the other hand, operators tend to directly hang the whole cabinet on the building outer wall or the horizontal arm of the tower to reduce construction costs, so that it is exposed to high temperature and other extreme climates for a long time. If the heat cannot be dissipated in time, the device will have performance drift, communication interruption and even irreversible failure.

[0003] The current passive heat dissipation coating generally follows two technical routes: one is to add high-thermal-conductivity insulating particles in the polymer matrix to increase the overall thermal diffusivity of the system by using the intrinsic thermal conductivity of the filler; the other is to introduce high-reflectivity or high-radiation components to achieve radiation refrigeration by enhancing the scattering of sunlight or mid-infrared emission. However, both types of coatings have disadvantages. For thermal conductive fillers, particles are in random point contact, and heat flow needs to "jump" between multiple interfaces to be transmitted, and interface phonon scattering and thermal resistance seriously weaken the improvement of macroscopic thermal conductivity; at the same time, high filler content leads to increased viscosity and enhanced brittleness of the coating, which is easy to crack and fall off in thermal cycling or mechanical vibration. For optical coatings, titanium dioxide can produce strong scattering in the visible light band, but its infrared emissivity is low, making it difficult to effectively dissipate heat in the atmospheric window; silicon dioxide is difficult to meet the dual requirements of solar reflection and infrared radiation. SUMMARY

[0004] To solve the above problems, the present application aims to provide a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof. The present application constructs a three-stage calcined SiC@BN / TiB2 continuous fiber as a longitudinal heat conduction skeleton, which is firmly connected with the resin by means of a silane coupling agent; uses star-shaped calcium titanate and the in-situ grown magnesium fluoride shell on the edges to strongly reflect in the ultraviolet to mid-infrared region and improve weather resistance through morphology multiple scattering and refractive index step interface; introduces holmium / ytterbium co-doped calcium fluoride nanosheets to supplement the heat conduction, enhance the near-infrared scattering, and at the same time convert the near-infrared heat into long-wave radiation that can be released through the atmospheric window; the whole filler system is uniformly dispersed in the methylphenyl silicone resin to form a micro-nano composite roughness under the synergistic effect of dispersants and leveling agents, and to construct a multi-level reflection / radiation interface of air sandwich-low refractive index particles. Through the mutual cooperation of longitudinal continuous heat conduction path, horizontal heat dissipation network, optical multiple scattering and energy downshift radiation, stable chemical bond network is supported to realize high-efficiency and long-term reliable heat dissipation performance.

[0005] To achieve the above object, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of high-thermal-conductivity radiation refrigeration paint for 5G communication base station cabinets, which comprises the following steps:

[0007] S1: Dissolve polycarbosilane, boric acid, isopropyl titanate and melamine in a mixed solvent, stir at room temperature to obtain a preliminary spinning solution, spin the solution after filtration to obtain a precursor fiber membrane, place the precursor fiber membrane in air, calcine and naturally cool to obtain a preliminary fiber skeleton; immerse the preliminary fiber skeleton in an ethanol aqueous solution of silane coupling agent, and dry to obtain a SiC@BN / TiB2 three-phase fiber skeleton;

[0008] S2: Prepare a calcium hydroxide dispersion liquid, add titanium chloride under ice bath and adjust pH with potassium hydroxide, and then perform hydrothermal reaction, centrifugation, water washing and vacuum drying to obtain star-shaped calcium titanate powder; disperse magnesium nitrate and ammonium fluoride in deionized water, add the calcium titanate powder to obtain a reaction liquid A, stir, filter, dry, crush and air calcine to obtain a calcium titanate / magnesium fluoride composite material;

[0009] S3: Disperse calcium nitrate, holmium nitrate and ytterbium nitrate in deionized water to obtain a mixed dispersion liquid, add sodium fluoride, stir, centrifuge, wash and dry to obtain a mixed precursor; place the mixed precursor in a quartz boat for crystallization, and naturally cool to obtain holmium / ytterbium co-doped calcium fluoride nanosheets;

[0010] S4: Place the SiC@BN / TiB2 three-phase fiber skeleton and methylphenyl silicone resin in a planetary vacuum stirred tank, stir to obtain a premix base liquid, add the calcium titanate / magnesium fluoride composite material and the holmium / ytterbium co-doped calcium fluoride nanosheets, uniformly disperse, supplement with methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate to obtain a pre-coating liquid, adjust the viscosity, vacuum degas, filter and obtain the high-thermal-conductivity radiation refrigeration paint for 5G communication base station cabinets.

[0011] As a preferred technical solution of the present application, in step S1, the mass ratio of polycarbosilane to boric acid is (17-19):(1.4-1.6), for example, it can be (17, 17.2, 17.4, 17.6, 17.8, 18, 18.2, 18.4, 18.6, 18.8 or 19):(1.4, 1.42, 1.44, 1.46, 1.48, 1.50, 1.52, 1.54, 1.56, 1.58 or 1.6), but is not limited to the listed values, and other values not listed in the range are also applicable.

[0012] In some alternative embodiments, the mass ratio of the polycarbosilane to the titanium isopropoxide is (17-19):(0.95-1.05), such as can be (17, 17.2, 17.4, 17.6, 17.8, 18, 18.2, 18.4, 18.6, 18.8, or 19):(0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, or 1.05), but is not limited to the listed values, as other unlisted values within the range are also applicable.

[0013] In some alternative embodiments, the mass ratio of the polycarbosilane to the melamine is (17-19):(0.75-0.85), such as can be (17, 17.2, 17.4, 17.6, 17.8, 18, 18.2, 18.4, 18.6, 18.8, or 19):(0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, or 0.85), but is not limited to the listed values, as other unlisted values within the range are also applicable.

[0014] In some alternative embodiments, the mass ratio of the DMF to the THF in the mixed solvent is 1:(1-1.2), such as can be 1:1.00, 1:1.02, 1:1.04, 1:1.06, 1:1.08, 1:1.10, 1:1.12, 1:1.14, 1:1.16, 1:1.18, or 1:1.20, but is not limited to the listed values, as other unlisted values within the range are also applicable.

[0015] In some alternative embodiments, the mass ratio of the polycarbosilane to the DMF is (17-19):(38-42), such as can be (17, 17.2, 17.4, 17.6, 17.8, 18, 18.2, 18.4, 18.6, 18.8, or 19):(38, 38.4, 38.8, 39.2, 39.6, 40, 40.4, 40.8, 41.2, 41.6, or 42), but is not limited to the listed values, as other unlisted values within the range are also applicable.

[0016] In some alternative embodiments, in step S1, the stirring speed is 350-450 rpm, such as can be 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, or 450 rpm, but is not limited to the listed values, as other unlisted values within the range are also applicable.

[0017] In some alternative embodiments, the stirring time in step S1 is 1.5-2.5h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0018] In some alternative embodiments, the air standing time of the precursor fiber membrane is 1.5-3h, for example, it can be 1.5h, 1.65h, 1.80h, 1.95h, 2.10h, 2.25h, 2.40h, 2.55h, 2.70h, 2.85h or 3.0h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0019] The first stage calcination atmosphere when calcining the precursor fiber membrane after standing in air is air.

[0020] In some alternative embodiments, the first stage heating rate is 1-3℃ / min, for example, it can be 1.0℃ / min, 1.2℃ / min, 1.4℃ / min, 1.6℃ / min, 1.8℃ / min, 2.0℃ / min, 2.2℃ / min, 2.4℃ / min, 2.6℃ / min, 2.8℃ / min or 3.0℃ / min, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0021] In some alternative embodiments, the first stage calcination temperature when calcining the precursor fiber membrane after standing in air is 240-260℃, for example, it can be 240℃, 242℃, 244℃, 246℃, 248℃, 250℃, 252℃, 254℃, 256℃, 258℃ or 260℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0022] In some alternative embodiments, the first stage calcination time when calcining the precursor fiber membrane after standing in air is 1.5-2.5h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0023] The second stage calcination atmosphere when calcining the precursor fiber membrane after standing in air is argon.

[0024] In some alternative embodiments, the precursor fiber membrane is calcined in air at a second stage argon flow rate of 180-220 mL / min, such as, for example, 180 mL / min, 184 mL / min, 188 mL / min, 192 mL / min, 196 mL / min, 200 mL / min, 204 mL / min, 208 mL / min, 212 mL / min, 216 mL / min, or 220 mL / min, although the application is not limited to the recited values, as other unrecited values within the range are also suitable.

[0025] In some alternative embodiments, the precursor fiber membrane is calcined in air at a second stage ramp rate of 4-6 °C / min, such as, for example, 4.0 °C / min, 4.2 °C / min, 4.4 °C / min, 4.6 °C / min, 4.8 °C / min, 5.0 °C / min, 5.2 °C / min, 5.4 °C / min, 5.6 °C / min, 5.8 °C / min, or 6.0 °C / min, although the application is not limited to the recited values, as other unrecited values within the range are also suitable.

[0026] In some alternative embodiments, the precursor fiber membrane is calcined in air at a second stage calcination temperature of 580-620 °C, such as, for example, 580 °C, 584 °C, 588 °C, 592 °C, 596 °C, 600 °C, 604 °C, 608 °C, 612 °C, 616 °C, or 620 °C, although the application is not limited to the recited values, as other unrecited values within the range are also suitable.

[0027] In some alternative embodiments, the precursor fiber membrane is calcined in air at a second stage calcination time of 0.4-0.6 h, such as, for example, 0.40 h, 0.42 h, 0.44 h, 0.46 h, 0.48 h, 0.50 h, 0.52 h, 0.54 h, 0.56 h, 0.58 h, or 0.60 h, although the application is not limited to the recited values, as other unrecited values within the range are also suitable.

[0028] In some alternative embodiments, the precursor fiber membrane is calcined in air at a third stage calcination atmosphere of a mixture of ammonia and argon, at a volume ratio of ammonia to argon of 1:4.

[0029] In some alternative embodiments, the third stage mixed gas flow rate during calcination of the precursor fiber membrane after air exposure is 450-550 mL / min, such as, for example, 450 mL / min, 460 mL / min, 470 mL / min, 480 mL / min, 490 mL / min, 500 mL / min, 510 mL / min, 520 mL / min, 530 mL / min, 540 mL / min, or 550 mL / min, but is not limited to the recited values, as other, non-recited values within the range are equally applicable.

[0030] In some alternative embodiments, the third stage temperature ramp during calcination of the precursor fiber membrane after air exposure is 8-12 °C / min, such as, for example, 8.0 °C / min, 8.4 °C / min, 8.8 °C / min, 9.2 °C / min, 9.6 °C / min, 10.0 °C / min, 10.4 °C / min, 10.8 °C / min, 11.2 °C / min, 11.6 °C / min, or 12.0 °C / min, but is not limited to the recited values, as other, non-recited values within the range are equally applicable.

[0031] In some alternative embodiments, the third stage calcination temperature during calcination of the precursor fiber membrane after air exposure is 1050-1150 °C, such as, for example, 1050 °C, 1060 °C, 1070 °C, 1080 °C, 1090 °C, 1100 °C, 1110 °C, 1120 °C, 1130 °C, 1140 °C, or 1150 °C, but is not limited to the recited values, as other, non-recited values within the range are equally applicable.

[0032] In some alternative embodiments, the third stage calcination time during calcination of the precursor fiber membrane after air exposure is 0.8-1.2 h, such as, for example, 0.80 h, 0.84 h, 0.88 h, 0.92 h, 0.96 h, 1.00 h, 1.04 h, 1.08 h, 1.12 h, 1.16 h, or 1.20 h, but is not limited to the recited values, as other, non-recited values within the range are equally applicable.

[0033] In some alternative embodiments, the silane coupling agent is KH-550, and the mass fraction of the silane coupling agent in the aqueous ethanol solution is 0.4-0.6 wt%, such as, for example, 0.40 wt%, 0.42 wt%, 0.44 wt%, 0.46 wt%, 0.48 wt%, 0.50 wt%, 0.52 wt%, 0.54 wt%, 0.56 wt%, 0.58 wt%, or 0.60 wt%, but is not limited to the recited values, as other, non-recited values within the range are equally applicable.

[0034] In some optional embodiments, the impregnation time is 25-35 min, for example, it can be 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min or 35 min, but not only limited to the listed values, other values not listed in the range are also applicable.

[0035] In some optional embodiments, in step S1, the drying temperature is 110-130℃, for example, it can be 110℃, 112℃, 114℃, 116℃, 118℃, 120℃, 122℃, 124℃, 126℃, 128℃ or 130℃, but not only limited to the listed values, other values not listed in the range are also applicable.

[0036] In some optional embodiments, in step S1, the drying time is 0.4-0.6h, for example, it can be 0.40h, 0.42h, 0.44h, 0.46h, 0.48h, 0.50h, 0.52h, 0.54h, 0.56h, 0.58h or 0.60h, but not only limited to the listed values, other values not listed in the range are also applicable.

[0037] As a preferred technical solution of the present application, in step S2, the mass ratio of calcium hydroxide to deionized water is (7-7.8):(190-210), for example, it can be (7, 7.08, 7.16, 7.24, 7.32, 7.40, 7.48, 7.56, 7.64, 7.72 or 7.80):(190, 192, 194, 196, 198, 200, 202, 204, 206, 208 or 210), but not only limited to the listed values, other values not listed in the range are also applicable.

[0038] In some optional embodiments, after the calcium hydroxide dispersion solution is added to titanium chloride, potassium hydroxide is used to adjust the pH to 10.5-11.5, for example, the pH can be 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, 11.2, 11.3, 11.4 or 11.5, but not only limited to the listed values, other values not listed in the range are also applicable.

[0039] In some alternative embodiments, the mass ratio of the titanium chloride to calcium hydroxide is (7-7.8):(9-10), for example, it can be (7, 7.08, 7.16, 7.24, 7.32, 7.40, 7.48, 7.56, 7.64, 7.72, or 7.80):(9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10.0), but is not limited to the listed values, other unlisted values within the range are also applicable.

[0040] In some alternative embodiments, the hydrothermal reaction temperature is 170-190°C, for example, it can be 170°C, 172°C, 174°C, 176°C, 178°C, 180°C, 182°C, 184°C, 186°C, 188°C, or 190°C, but is not limited to the listed values, other unlisted values within the range are also applicable.

[0041] In some alternative embodiments, the hydrothermal reaction time is 6-10h, for example, it can be 6.0h, 6.4h, 6.8h, 7.2h, 7.6h, 8.0h, 8.4h, 8.8h, 9.2h, 9.6h, or 10.0h, but is not limited to the listed values, other unlisted values within the range are also applicable.

[0042] In some alternative embodiments, the mass ratio of the magnesium nitrate, ammonium fluoride, and deionized water is (2.9-3.3):(1-1.2):(35-45), for example, it can be (2.90, 2.94, 2.98, 3.02, 3.06, 3.10, 3.14, 3.18, 3.22, 3.26, or 3.30):(1.00, 1.02, 1.04, 1.06, 1.08, 1.10, 1.12, 1.14, 1.16, 1.18, or 1.20):(35, 36, 37, 38, 39, 40, 41, 42, 43, 44, or 45), but is not limited to the listed values, other unlisted values within the range are also applicable.

[0043] In some alternative embodiments, the mass ratio of the calcium titanate powder to magnesium nitrate is (2.9-3.3):(9.5-10.5), for example, it can be (2.90, 2.94, 2.98, 3.02, 3.06, 3.10, 3.14, 3.18, 3.22, 3.26, or 3.30):(9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, or 10.5), but is not limited to the listed values, other unlisted values within the range are also applicable.

[0044] In some optional embodiments, in step S2, the stirring temperature is 65-75℃, for example, it can be 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃ or 75℃, but not only limited to the listed values, other values in the range of the values are also applicable.

[0045] In some optional embodiments, in step S2, the stirring time is 0.8-1.2h, for example, it can be 0.80h, 0.84h, 0.88h, 0.92h, 0.96h, 1.00h, 1.04h, 1.08h, 1.12h, 1.16h or 1.20h, but not only limited to the listed values, other values in the range of the values are also applicable.

[0046] In some optional embodiments, the air roasting temperature is 430-470℃, for example, it can be 430℃, 434℃, 438℃, 442℃, 446℃, 450℃, 454℃, 458℃, 462℃, 466℃ or 470℃, but not only limited to the listed values, other values in the range of the values are also applicable.

[0047] In some optional embodiments, the air roasting time is 0.8-1.2h, for example, it can be 0.80h, 0.84h, 0.88h, 0.92h, 0.96h, 1.00h, 1.04h, 1.08h, 1.12h, 1.16h or 1.20h, but not only limited to the listed values, other values in the range of the values are also applicable.

[0048] As a preferred technical solution of the present application, in step S3, the mass ratio of calcium nitrate, holmium nitrate, ytterbium nitrate and deionized water is (11.2-12.4):(0.26-0.30):(1.55-1.71):(90-110), for example, it can be (11.2, 11.32, 11.44, 11.56, 11.68, 11.80, 11.92, 12.04, 12.16, 12.28 or 12.4):(0.26, 0.264, 0.268, 0.272, 0.276, 0.280, 0.284, 0.288, 0.292, 0.296 or 0.30):(1.55, 1.566, 1.582, 1.598, 1.614, 1.630, 1.646, 1.662, 1.678, 1.694 or 1.710):(90, 92, 94, 96, 98, 100, 102, 104, 106, 108 or 110), but not only limited to the listed values, other values in the range of the values are also applicable.

[0049] In some optional embodiments, the mass ratio of calcium nitrate to sodium fluoride is (11.2-12.4):(11.5-13.5), for example, it can be (11.2, 11.32, 11.44, 11.56, 11.68, 11.80, 11.92, 12.04, 12.16, 12.28 or 12.4):(11.5, 11.7, 11.9, 12.1, 12.3, 12.5, 12.7, 12.9, 13.1, 13.3 or 13.5), but not limited to the listed values, other values not listed in the range are also applicable.

[0050] In some optional embodiments, the temperature when the mixed dispersion is added with sodium fluoride is 55-65℃, for example, it can be 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃ or 65℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0051] In some optional embodiments, in step S3, the stirring speed is 250-350 rpm, for example, it can be 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm or 350 rpm, but not limited to the listed values, other values not listed in the range are also applicable.

[0052] In some optional embodiments, in step S3, the stirring time is 1.5-2.5 h, for example, it can be 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, but not limited to the listed values, other values not listed in the range are also applicable.

[0053] The crystallization atmosphere is argon;

[0054] In some optional embodiments, the argon flow rate is 250-350 mL / min, for example, it can be 250 mL / min, 260 mL / min, 270 mL / min, 280 mL / min, 290 mL / min, 300 mL / min, 310 mL / min, 320 mL / min, 330 mL / min, 340 mL / min or 350 mL / min, but not limited to the listed values, other values not listed in the range are also applicable.

[0055] In some optional embodiments, the temperature rising rate during the crystallization is 4-6℃ / min, for example, it can be 4.0℃ / min, 4.2℃ / min, 4.4℃ / min, 4.6℃ / min, 4.8℃ / min, 5.0℃ / min, 5.2℃ / min, 5.4℃ / min, 5.6℃ / min, 5.8℃ / min or 6.0℃ / min, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0056] In some optional embodiments, the crystallization temperature is 330-370℃, for example, it can be 330℃, 334℃, 338℃, 342℃, 346℃, 350℃, 354℃, 358℃, 362℃, 366℃ or 370℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0057] In some optional embodiments, the crystallization time is 0.8-1.2h, for example, it can be 0.80h, 0.84h, 0.88h, 0.92h, 0.96h, 1.00h, 1.04h, 1.08h, 1.12h, 1.16h or 1.20h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0058] As a preferred technical solution of the present application, in step S4, the mass ratio of the SiC@BN / TiB2 three-phase fiber framework to the methylphenyl silicone resin is (28-32):(54-56), for example, it can be (28, 28.4, 28.8, 29.2, 29.6, 30, 30.4, 30.8, 31.2, 31.6 or 32):(54, 54.2, 54.4, 54.6, 54.8, 55.0, 55.2, 55.4, 55.6, 55.8 or 56), but is not limited to the listed values, and other values not listed in the range are also applicable.

[0059] In some optional embodiments, in step S4, the stirring speed is 450-550rpm, for example, it can be 450rpm, 460rpm, 470rpm, 480rpm, 490rpm, 500rpm, 510rpm, 520rpm, 530rpm, 540rpm or 550rpm, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0060] In some optional embodiments, in step S4, the stirring vacuum degree is -0.04 ~ -0.06 MPa, for example, it can be -0.060 MPa, -0.058 MPa, -0.056 MPa, -0.054 MPa, -0.052 MPa, -0.050 MPa, -0.048 MPa, -0.046 MPa, -0.044 MPa, -0.042 MPa or -0.040 MPa, but not only limited to the listed values, other values not listed in the range are also applicable.

[0061] In some optional embodiments, in step S4, the stirring time is 4-6 min, for example, it can be 4 min, 4.2 min, 4.4 min, 4.6 min, 4.8 min, 5.0 min, 5.2 min, 5.4 min, 5.6 min, 5.8 min or 6 min, but not only limited to the listed values, other values not listed in the range are also applicable.

[0062] In some optional embodiments, the mass ratio of the calcium titanate / magnesium fluoride composite material to the methylphenyl silicone resin is (23-27):(54-56), for example, it can be (23, 23.4, 23.8, 24.2, 24.6, 25.0, 25.4, 25.8, 26.2, 26.6 or 27):(54, 54.2, 54.4, 54.6, 54.8, 55.0, 55.2, 55.4, 55.6, 55.8 or 56), but not only limited to the listed values, other values not listed in the range are also applicable.

[0063] In some optional embodiments, the mass ratio of the holmium / ytterbium co-doped calcium fluoride nanosheet to the methylphenyl silicone resin is (7-9):(54-56), for example, it can be (7.0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8 or 9.0):(54, 54.2, 54.4, 54.6, 54.8, 55.0, 55.2, 55.4, 55.6, 55.8 or 56), but not only limited to the listed values, other values not listed in the range are also applicable.

[0064] In some optional embodiments, the mass ratio of the methylphenyl silicone resin, the additional methylphenyl silicone resin, the KH-550, the BYK-A530, the FC-4430 and the propylene glycol methyl ether acetate is (54-56):(17-21):(0.40-0.60):(0.15-0.25):(0.25-0.35):(8-12), for example, can be (54, 54.2, 54.4, 54.6, 54.8, 55.0, 55.2, 55.4, 55.6, 55.8 or 56):(17, 17.4, 17.8, 18.2, 18.6, 19.0, 19.4, 19.8, 20.2, 20.6 or 21):(0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58 or 0.60):(0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24 or 0.25):(0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34 or 0.35):(8.0, 8.4, 8.8, 9.2, 9.6, 10.0, 10.4, 10.8, 11.2, 11.6 or 12.0), but not only limited to the listed values, other values not listed in the range are also applicable.

[0065] In some optional embodiments, the viscosity is adjusted to 4-6 Pa·s, for example, can be 4.0 Pa·s, 4.2 Pa·s, 4.4 Pa·s, 4.6 Pa·s, 4.8 Pa·s, 5.0 Pa·s, 5.2 Pa·s, 5.4 Pa·s, 5.6 Pa·s, 5.8 Pa·s or 6.0 Pa·s, but not only limited to the listed values, other values not listed in the range are also applicable.

[0066] In the second aspect, the present application provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet.

[0067] In the present application, after the polycarbosilane is spun into continuous fibers, the fibers are calcined through three stages of pre-oxidation, inert pyrolysis, ammoniation and boronization, to sequentially complete crosslinking, amorphous silicon carbide formation, and silicon carbide crystallization, and simultaneously generate boron nitride and titanium diboride in situ, to form a three-phase fiber skeleton. The silicon carbide provides a main heat conduction channel, the layered boron nitride forms an additional in-plane phonon fast channel inside the fiber, and the dielectric constant of the whole is reduced; the lattice matching between titanium diboride and silicon carbide can form a phonon bridge between the two phases, further weakening the interface thermal resistance; after the fiber skeleton is impregnated with a silane coupling agent, the hydroxyl-siloxane network on the surface of the fiber skeleton can condense with the resin and filler, thereby enhancing the chemical bonding force between the skeleton and the matrix, and laying a foundation for the "heat conduction continuity" of the subsequent coating.

[0068] In the present application, calcium hydroxide and titanium chloride are reacted in an alkaline environment to form calcium titanate with multiple edges and hollow star-shaped structures, which can produce composite scattering in the ultraviolet-near infrared band, thereby efficiently reflecting solar energy; subsequently, a magnesium fluoride shell layer is generated in situ on the edges of the calcium titanate using fluorine ions and magnesium ions, forming a stepped interface with a refractive index mutation. The change in refractive index not only further enhances scattering, but also brings higher mid-infrared emissivity; and the magnesium fluoride itself has extremely low visible-near infrared absorption and excellent weather resistance, which can improve the durability of the coating.

[0069] In the present application, calcium fluoride crystals are introduced, which have a wide band gap and low phonon energy, making them ideal far-infrared radiation matrices. Through condition control, they are induced to grow into thin sheets along the layered orientation. The sheets can be stacked in-plane to supplement the lateral heat conduction channel and produce strong scattering of near-infrared light. After the ytterbium element absorbs common near-infrared thermal radiation, it transfers energy to the holmium element, which then radiates in the form of longer wavelengths (falling within the atmospheric transmission window). Through holmium and ytterbium co-doping, the near-infrared heat in the environment near the cabinet can also be "shifted down" and discharged.

[0070] In the present application, methylphenyl silicone resin is selected, and the three-phase fiber skeleton, calcium titanate / magnesium fluoride composite material, and holmium / ytterbium co-doped calcium fluoride nanosheet are uniformly dispersed in the matrix to avoid thermal resistance and optical defects caused by agglomeration. The dispersant BYK-A530 and the leveling agent FC-4430 further reduce the interfacial tension to ensure the lapping of the fillers in all directions. At the same time, the moderate viscosity of the system is beneficial to bubble removal and can also form a micron-nanometer level composite roughness during spraying. The roughness is constructed through the synergistic effect of "air sandwich-low refractive index particles" to build multi-level reflection / radiation interfaces.

[0071] There is also a synergistic effect in this application. In the longitudinal direction of the coating, the SiC@BN / TiB2 three-phase fiber skeleton is tightly coupled with the resin matrix to form a rapid heat conduction channel through the metal wall to the outer surface; in the transverse direction of the coating, the flaky calcium fluoride is interwoven with the calcium titanate / magnesium fluoride composite material to diffuse heat points and improve mechanical integrity; in terms of light management, the multi-level roughness-refractive index gradient improves solar light reflection, and the calcium fluoride and titanate together provide high radiation in the atmospheric window; the holmium / ytterbium energy level conversion further converts the ambient near-infrared heat and outputs it; in terms of interface, the coupling agent and the methylphenyl silicone resin form a stable chemical bond network to ensure the continuity of heat conduction and the integrity of the structure.

[0072] Compared with the prior art, the application has the following beneficial effects:

[0073] This application generates a continuous fiber skeleton containing silicon carbide, boron nitride and titanium diboride in one step by spinning polycarbosilane and three-stage calcination: silicon carbide undertakes the main heat conduction, layered boron nitride provides additional in-fiber phonon fast channel and reduces the dielectric constant, and titanium diboride matches the silicon carbide lattice to form a phonon bridge to reduce the interface thermal resistance; then the fiber surface is activated with a silane coupling agent to stabilize the combination of the inorganic skeleton and the organic matrix and ensure the continuity of the heat conduction network;

[0074] This application reacts calcium hydroxide and titanium chloride under alkaline conditions to generate hollow multi-angled star-shaped calcium titanate, which reflects ultraviolet to near-infrared light through the morphology-multiple scattering mechanism; then a magnesium fluoride shell layer is deposited in situ on the edges to form a refractive index step interface, further improving scattering and mid-infrared radiation, and improving the long-term stability of the coating due to the low light absorption and high weather resistance of magnesium fluoride;

[0075] This application uses calcium fluoride nanosheets with wide band gap and low phonon energy as a far-infrared radiation matrix, which can form a transverse heat conduction channel and strongly scatter near-infrared light; at the same time, ytterbium-holmium co-doping is used, ytterbium ions first absorb near-infrared energy and transfer it to holmium ions, and then holmium ions radiate and release it at a longer wavelength in the atmospheric window, realizing the downshift of ambient near-infrared heat and effective discharge;

[0076] This application uses methylphenyl silicone resin as polysiloxane, which has thermal stability, ultraviolet resistance and moisture resistance; with the help of a dispersing agent, the three-phase fiber skeleton, calcium titanate / magnesium fluoride composite material and holmium / ytterbium co-doped calcium fluoride nanosheet are uniformly distributed to eliminate the thermal resistance and optical defects caused by agglomeration; through viscosity control and flow leveling agent cooperation, a micro-nano composite rough surface is formed during spraying, and a multi-level reflection and radiation interface is constructed by air sandwich and low refractive index particles;

[0077] The SiC@BN / TiB2 three-phase fiber framework is coupled with the matrix to form a direct heat conduction path inside and outside; the flaky calcium fluoride and calcium titanate / magnesium fluoride are interwoven to disperse heat flow and enhance toughness; the micro-nano roughness and refractive index gradient improve solar light reflection, and the calcium fluoride and titanate jointly enhance the atmospheric window radiation; the holmium / ytterbium energy level conversion further outputs the environmental near-infrared heat, and the silane coupling agent and methylphenyl silicone resin construct a stable bond network to maintain the long-term integrity of the heat conduction network and structure, thereby realizing the synergistic enhancement of the overall heat dissipation performance. DETAILED DESCRIPTION

[0078] The technical solutions of the present application will be described in detail below in combination with specific examples. The examples described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; all the descriptions are explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the examples described herein, those skilled in the art can also employ other technical solutions based on the content disclosed in the claims and the specification of the present application, which include technical solutions employing any obvious substitutions and modifications to the examples described herein.

[0079] The chemical reagents used in the examples and comparative examples of the present application are commercially available and do not require further purification or treatment.

[0080] Example 1

[0081] The present embodiment provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof. The preparation method of the high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet specifically comprises the following steps:

[0082] S1: Polycarbosilane, boric acid, isopropyl titanate and melamine were dissolved in mixed solvents, wherein the mass ratio of polycarbosilane to boric acid was 18:1.4, the mass ratio of polycarbosilane to isopropyl titanate was 17.5:1.02, the mass ratio of polycarbosilane to melamine was 19:0.8, the mass ratio of DMF to THF was 1:1.15, the mass ratio of polycarbosilane to DMF was 41:18, and the initial spinning solution was obtained by stirring at a rotation speed of 420 rpm for 2.2 h at room temperature. The spinning solution was filtered and spun into a precursor fiber membrane. The precursor fiber membrane was placed in air for 2.5 h and then calcined, wherein the first stage of calcination was in air, the heating rate was 2.5 ℃ / min, the calcination temperature was 255 ℃, and the time was 2.2 h; the second stage was in argon atmosphere, the flow rate was 210 mL / min, the heating rate was 5.5 ℃ / min, the calcination temperature was 610 ℃, and the time was 0.55 h; the third stage was in ammonia and argon atmosphere, the volume ratio was 1:4, the flow rate was 520 mL / min, the heating rate was 11 ℃ / min, the calcination temperature was 1120 ℃, and the time was 1.1 h. The initial fiber skeleton was obtained by natural cooling; the initial fiber skeleton was immersed in an ethanol aqueous solution of silane coupling agent with a mass fraction of 0.55 wt% for 28 min, dried at 125 ℃ for 0.55 h to obtain a SiC@BN / TiB2 three-phase fiber skeleton;

[0083] S2: A calcium hydroxide dispersion liquid was prepared, wherein the mass ratio of calcium hydroxide to deionized water was 7.6:205. Titanium chloride was added under ice bath, and the pH was adjusted to 11.2 with potassium hydroxide, wherein the mass ratio of titanium chloride to calcium hydroxide was 7.5:9.8. The mixture was hydrothermally reacted at 185 ℃ for 9 h. After cooling, centrifugation, water washing and vacuum drying, star-shaped calcium titanate powder was obtained. Magnesium nitrate and ammonium fluoride were dispersed in deionized water, and the mass ratio of magnesium nitrate, ammonium fluoride and deionized water was 3.2:1.1:42. The calcium titanate powder was added to obtain a reaction liquid A, wherein the mass ratio of calcium titanate powder to magnesium nitrate was 3.2:10.2. The mixture was stirred at 72 ℃ for 1.1 h. After filtration, drying and crushing to 210 mesh, the mixture was calcined in air at 460 ℃ for 1.1 h to obtain a calcium titanate / magnesium fluoride composite material.

[0084] S3: Calcium nitrate, holmium nitrate and ytterbium nitrate were dispersed in deionized water to obtain a mixed dispersion liquid, wherein the mass ratio of calcium nitrate, holmium nitrate, ytterbium nitrate and deionized water was 12.0:0.29:1.65:105. Sodium fluoride was added at 62 ℃, wherein the mass ratio of calcium nitrate to sodium fluoride was 12.0:13.0. The mixture was stirred at 320 rpm for 2.2 h. After centrifugation, washing and drying, a mixed precursor was obtained. The mixed precursor was placed in a quartz boat for crystallization, wherein the crystallization atmosphere was argon atmosphere, the gas flow rate was 320 mL / min, the heating rate was 5.5 ℃ / min, the crystallization temperature was 360 ℃, and the time was 1.1 h. The holmium / ytterbium co-doped calcium fluoride nanosheet was obtained by natural cooling.

[0085] S4: the SiC@BN / TiB2 three-phase fiber framework and methylphenyl silicone resin were placed in a planetary vacuum stirred tank, the mass ratio of SiC@BN / TiB2 three-phase fiber framework to methylphenyl silicone resin was 31:55.5, stirring was carried out at a rotation speed of 520 rpm and a vacuum degree of-0.055 MPa for 5.5 min to obtain a premixed base liquid, calcium titanate / magnesium fluoride composite and holmium / ytterbium co-doped calcium fluoride nanosheet were added, the mass ratio of calcium titanate / magnesium fluoride composite to methylphenyl silicone resin was 26:55.5, the mass ratio of holmium / ytterbium co-doped calcium fluoride nanosheet to methylphenyl silicone resin was 8.5:55.5, after uniform dispersion, methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate were added to obtain a pre-coating liquid, the mass ratio of methylphenyl silicone resin, additional methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate was 55.5:20:0.55:0.22:0.32:11, the viscosity was adjusted to 5.5 Pa·s, vacuum degassing and filtration were carried out to obtain a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet.

[0086] Example 2

[0087] The embodiment provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof, and the preparation method of the high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet specifically comprises the following steps:

[0088] S1: polycarbosilane, boric acid, titanium isopropyl titanate and melamine were dissolved in a mixed solvent, the mass ratio of polycarbosilane to boric acid was 19:1.6, the mass ratio of polycarbosilane to titanium isopropyl titanate was 19:1.05, the mass ratio of polycarbosilane to melamine was 18:0.85, the mass ratio of DMF to THF was 1:1.2, the mass ratio of polycarbosilane to DMF was 38:19, the initial spinning solution was obtained by stirring at a rotation speed of 350 rpm at room temperature for 2.5 h, the precursor fiber membrane was obtained by spinning after filtration, and the precursor fiber membrane was placed in air for 3 h and then calcined, wherein the first stage of calcination was carried out in air, the heating rate was 3 ℃ / min, the calcination temperature was 260 ℃, and the time was 2.5 h, the second stage was carried out in argon atmosphere, the flow rate was 220 mL / min, the heating rate was 6 ℃ / min, the calcination temperature was 620 ℃, and the time was 0.6 h, the third stage was carried out in ammonia and argon atmosphere, the volume ratio was 1:4, the flow rate was 550 mL / min, the heating rate was 12 ℃ / min, the calcination temperature was 1150 ℃, and the time was 1.2 h, and the initial fiber framework was obtained by natural cooling; the initial fiber framework was immersed in a 0.6wt% silane coupling agent ethanol aqueous solution for 35 min and dried at 130 ℃ for 0.6 h to obtain a SiC@BN / TiB2 three-phase fiber framework;

[0089] S2: A calcium hydroxide dispersion liquid was configured, in which the mass ratio of calcium hydroxide to deionized water was 7:210, titanium chloride was added under ice bath, and potassium hydroxide was used to adjust the pH to 11.5, in which the mass ratio of titanium chloride to calcium hydroxide was 7.8:10, hydrothermal reaction was carried out at 190℃ for 10h, after cooling, centrifugation, water washing and vacuum drying, calcium titanate powder with star-shaped arms was obtained; magnesium nitrate and ammonium fluoride were dispersed in deionized water, the mass ratio of magnesium nitrate, ammonium fluoride and deionized water was 3.3:1.2:45, calcium titanate powder was added to obtain reaction liquid A, in which the mass ratio of calcium titanate powder to magnesium nitrate was 3.3:10.5, stirring was carried out at 75℃ for 1.2h, after filtration, drying and crushing to 220 mesh, calcium titanate / magnesium fluoride composite material was obtained by air calcination at 470℃ for 1.2h;

[0090] S3: Calcium nitrate, holmium nitrate and ytterbium nitrate were dispersed in deionized water to obtain a mixed dispersion liquid, in which the mass ratio of calcium nitrate, holmium nitrate, ytterbium nitrate and deionized water was 12.4:0.30:1.71:110, sodium fluoride was added at 65℃, in which the mass ratio of calcium nitrate to sodium fluoride was 12.4:13.5, stirring was carried out at 350rpm for 2.5h, and mixed precursor was obtained by centrifugation, washing and drying; the precursor was placed in a quartz boat for crystallization, in which the crystallization atmosphere was argon atmosphere, the gas flow rate was 350mL / min, the temperature rising rate was 6℃ / min, the crystallization temperature was 370℃, the time was 1.2h, and holmium / ytterbium co-doped calcium fluoride nanosheet was obtained by natural cooling;

[0091] S4: SiC@BN / TiB2 three-phase fiber framework and methylphenyl silicone resin were placed in a planetary vacuum stirred tank, the mass ratio of SiC@BN / TiB2 three-phase fiber framework to methylphenyl silicone resin was 32:56, pre-mixed base liquid was obtained by stirring at a rotation speed of 550rpm and a vacuum degree of-0.06MPa for 6min, calcium titanate / magnesium fluoride composite material and holmium / ytterbium co-doped calcium fluoride nanosheet were added, in which the mass ratio of calcium titanate / magnesium fluoride composite material to methylphenyl silicone resin was 27:56, and the mass ratio of holmium / ytterbium co-doped calcium fluoride nanosheet to methylphenyl silicone resin was 9:56, after uniform dispersion, methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate were added to obtain pre-coating liquid, the mass ratio of methylphenyl silicone resin, additional methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate was 56:21:0.6:0.25:0.35:12, the viscosity was adjusted to 6Pa·s, vacuum degassing and filtration were carried out to obtain high-thermal-conductivity radiation refrigeration coating for 5G communication base station cabinet.

[0092] Example 3

[0093] The embodiment provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof.

[0094] S1: polycarbosilane, boric acid, titanium isopropyl titanate and melamine are dissolved in a mixed solvent, wherein the mass ratio of polycarbosilane to boric acid is 17.5:1.55, the mass ratio of polycarbosilane to titanium isopropyl titanate is 18:1.0, the mass ratio of polycarbosilane to melamine is 17:0.75, the mass ratio of DMF to THF is 1:1.1, the mass ratio of polycarbosilane to DMF is 40:17, the initial spinning solution is obtained by stirring at a rotating speed of 400 rpm for 2.0 h at room temperature, the precursor fiber membrane is obtained by spinning after filtration, and the precursor fiber membrane is placed in air for 2.0 h and then calcined, wherein the first-stage calcination atmosphere is air, the heating rate is 2.0 ℃ / min, the calcination temperature is 250 ℃, and the time is 2.0 h, the second-stage calcination atmosphere is argon, the flow rate is 200 mL / min, the heating rate is 5.0 ℃ / min, the calcination temperature is 600 ℃, and the time is 0.5 h, the third-stage calcination atmosphere is ammonia and argon, the volume ratio is 1:4, the flow rate is 500 mL / min, the heating rate is 10 ℃ / min, the calcination temperature is 1100 ℃, and the time is 1.0 h, and the preliminary fiber skeleton is obtained by natural cooling;

[0095] S2: a calcium hydroxide dispersion liquid is configured, wherein the mass ratio of calcium hydroxide to deionized water is 7.5:200, titanium chloride is added under ice bath, and the pH is adjusted to 11.0 by potassium hydroxide, wherein the mass ratio of titanium chloride to calcium hydroxide is 7:9, the hydrothermal reaction is carried out at 180 ℃ for 8 h, and the star-shaped calcium titanate powder is obtained by centrifugation, water washing and vacuum drying after cooling; magnesium nitrate and ammonium fluoride are dispersed in deionized water, the mass ratio of magnesium nitrate, ammonium fluoride and deionized water is 3.1:1.15:40, the calcium titanate powder is added to obtain a reaction liquid A, wherein the mass ratio of calcium titanate powder to magnesium nitrate is 2.9:10.0, the stirring is carried out at 70 ℃ for 1.0 h, the calcium titanate / magnesium fluoride composite material is obtained by filtration, drying and crushing to 200 meshes, and air calcination at 450 ℃ for 1.0 h;

[0096] S3: dispersing calcium nitrate, holmium nitrate and ytterbium nitrate in deionized water to obtain a mixed dispersion liquid, wherein the mass ratio of calcium nitrate, holmium nitrate, ytterbium nitrate and deionized water is 11.8:0.28:1.60:100, adding sodium fluoride at 60°C, wherein the mass ratio of calcium nitrate to sodium fluoride is 11.8:12.0, stirring at 300 rpm for 2.0 h, centrifuging, washing and drying to obtain a mixed precursor; crystallizing it in a quartz boat, wherein the crystallization atmosphere is argon atmosphere, the gas flow rate is 300 mL / min, the heating rate is 5.0°C / min, the crystallization temperature is 350°C, the time is 1.0 h, and natural cooling obtains holmium / ytterbium co-doped calcium fluoride nanosheets;

[0097] S4: placing the SiC@BN / TiB2 three-phase fiber framework and methylphenyl silicone resin into a planetary vacuum stirred tank, the mass ratio of SiC@BN / TiB2 three-phase fiber framework to methylphenyl silicone resin is 30:55, stirring at a speed of 500 rpm and a vacuum degree of-0.05 MPa for 5 min to obtain a premixed base liquid, adding calcium titanate / magnesium fluoride composite and holmium / ytterbium co-doped calcium fluoride nanosheets, wherein the mass ratio of calcium titanate / magnesium fluoride composite to methylphenyl silicone resin is 25:55, and the mass ratio of holmium / ytterbium co-doped calcium fluoride nanosheets to methylphenyl silicone resin is 8:55, adding methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate to the premixed base liquid to obtain a pre-coating liquid, the mass ratio of methylphenyl silicone resin, additional methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate is 55:19:0.50:0.20:0.30:10, adjusting the viscosity to 5 Pa·s, vacuum degassing and filtering to obtain a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet.

[0098] Example 4

[0099] The embodiment provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet and a preparation method thereof, and the preparation method of the high-thermal-conductivity radiation refrigeration coating for the 5G communication base station cabinet specifically comprises the following steps:

[0100] S1: Polycarbosilane, boric acid, isopropyl titanate and melamine were dissolved in mixed solvents, wherein the mass ratio of polycarbosilane to boric acid was 17:1.55, the mass ratio of polycarbosilane to isopropyl titanate was 17:0.95, the mass ratio of polycarbosilane to melamine was 17.5:0.82, the mass ratio of DMF to THF was 1:1, the mass ratio of polycarbosilane to DMF was 17:38, and the initial spinning solution was obtained by stirring at a speed of 350 rpm for 1.5 h at room temperature. The precursor fiber membrane was obtained by spinning after filtration, and was placed in air for 1.5 h and then calcined, wherein the first stage of calcination was in air, the heating rate was 1 ℃ / min, the calcination temperature was 240 ℃, and the time was 1.5 h; the second stage was in argon atmosphere, the flow rate was 180 mL / min, the heating rate was 4 ℃ / min, the calcination temperature was 580 ℃, and the time was 0.4 h; the third stage was in ammonia and argon atmosphere, the volume ratio was 1:4, the flow rate was 450 mL / min, the heating rate was 8 ℃ / min, the calcination temperature was 1050 ℃, and the time was 0.8 h, and the preliminary fiber skeleton was obtained by natural cooling; the SiC@BN / TiB2 three-phase fiber skeleton was obtained by immersing the preliminary fiber skeleton in an ethanol aqueous solution of silane coupling agent with a mass fraction of 0.4 wt% for 25 min, drying at 110 ℃ for 0.4 h, and then cooling to room temperature;

[0101] S2: A calcium hydroxide dispersion liquid was prepared, wherein the mass ratio of calcium hydroxide to deionized water was 7:190, titanium chloride was added under ice bath, and the pH was adjusted to 10.5 with potassium hydroxide, wherein the mass ratio of titanium chloride to calcium hydroxide was 7:9, and the star-shaped calcium titanate powder was obtained by hydrothermal reaction at 170 ℃ for 6 h, centrifugation, water washing and vacuum drying after cooling; magnesium nitrate and ammonium fluoride were dispersed in deionized water, the mass ratio of magnesium nitrate, ammonium fluoride and deionized water was 2.9:1:35, and the calcium titanate powder was added to obtain a reaction liquid A, wherein the mass ratio of calcium titanate powder to magnesium nitrate was 2.9:9.5, and the calcium titanate / magnesium fluoride composite material was obtained by stirring at 65 ℃ for 0.8 h, filtering, drying and then crushing to 180 mesh, and then air calcining at 430 ℃ for 0.8 h;

[0102] S3: Calcium nitrate, holmium nitrate and ytterbium nitrate were dispersed in deionized water to obtain a mixed dispersion liquid, wherein the mass ratio of calcium nitrate, holmium nitrate, ytterbium nitrate and deionized water was 11.2:0.26:1.55:90, sodium fluoride was added at 55 ℃, wherein the mass ratio of calcium nitrate to sodium fluoride was 11.2:11.5, and the mixed precursor was obtained by stirring at 250 rpm for 1.5 h, centrifugation, washing and drying; the mixed precursor was placed in a quartz boat for crystallization, wherein the crystallization atmosphere was argon atmosphere, the gas flow rate was 250 mL / min, the heating rate was 4 ℃ / min, the crystallization temperature was 330 ℃, and the time was 0.8 h, and the holmium / ytterbium co-doped calcium fluoride nanosheet was obtained by natural cooling;

[0103] S4: The SiC@BN / TiB2 three-phase fiber framework and methylphenyl silicone resin were placed in a planetary vacuum stirred tank, the mass ratio of SiC@BN / TiB2 three-phase fiber framework to methylphenyl silicone resin was 28:54, stirring was carried out at a speed of 450 rpm and a vacuum degree of-0.04 MPa for 4 min to obtain a premixed base liquid, then calcium titanate / magnesium fluoride composite and holmium / ytterbium co-doped calcium fluoride nanosheet were added, the mass ratio of calcium titanate / magnesium fluoride composite to methylphenyl silicone resin was 23:54, the mass ratio of holmium / ytterbium co-doped calcium fluoride nanosheet to methylphenyl silicone resin was 7:54, after uniform dispersion, methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate were added to obtain a pre-coating liquid, the mass ratio of methylphenyl silicone resin, additional methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate was 54:17:0.40:0.15:0.25:8, the viscosity was adjusted to 4 Pa·s, vacuum degassing and filtration were carried out to obtain a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet.

[0104] Comparative Example 1

[0105] The present comparative example provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet, which is different from Example 1 in that, in S4, no SiC@BN / TiB2 three-phase fiber framework is added, and the other operation steps and process parameters are exactly the same as those of Example 1.

[0106] Comparative Example 2

[0107] The present comparative example provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet, which is different from Example 1 in that, in S4, no calcium titanate / magnesium fluoride composite is added, and the other operation steps and process parameters are exactly the same as those of Example 1.

[0108] Comparative Example 3

[0109] The present comparative example provides a high-thermal-conductivity radiation refrigeration coating for a 5G communication base station cabinet, which is different from Example 1 in that, in S4, no holmium / ytterbium co-doped calcium fluoride nanosheet is added, and the other operation steps and process parameters are exactly the same as those of Example 1.

[0110] The high-thermal-conductivity radiation refrigeration coatings for 5G communication base station cabinets of the above-mentioned Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the specific process was as follows:

[0111] The solar reflectance, near-infrared reflectance, hemispherical emissivity and thermal conductivity coefficient of the sample were tested according to GB / T 25261-2018;

[0112] The test results are shown in Table 1.

[0113] Table 1: Performance test results of high thermal conductivity radiation refrigeration coating for 5G communication base station cabinet

[0114] Solar reflectance Near infrared reflectance Hemispherical emittance Thermal conductivity (W / (m·K)) Example 1 0.93 0.89 0.92 2.4 Example 2 0.91 0.86 0.90 2.1 Example 3 0.89 0.87 0.91 2.0 Example 4 0.90 0.85 0.88 2.2 Comparative Example 1 0.86 0.82 0.85 1.2 Comparative Example 2 0.82 0.78 0.87 1.9 Comparative Example 3 0.84 0.81 0.87 1.8

[0115] From the test results of Example 1 and Comparative Example 1 in Table 1, without adding SiC@BN / TiB2 three-phase fiber framework, the vertical phonon high-speed channel of the coating from the metal wall surface to the surface is broken, the interface thermal resistance changes from the original chemical bond coupling surface to the "filler-resin-filler" multi-stage jump, and the vertical thermal conductivity decreases. At the same time, the loss of fiber roughness and its low refractive index "cavity" structure reduces the multi-stage scattering opportunities of light on the surface layer, and the solar reflectance and near-infrared reflectance decrease. Silicon carbide, boron nitride and titanium diboride have strong lattice radiation peaks in the atmospheric transmission window, and the mid-infrared radiation is also weakened after losing them, and the hemispherical emissivity decreases.

[0116] From the test results of Example 1 and Comparative Example 2, without adding calcium titanate / magnesium fluoride composite material, the corner multiple composite scattering and refractive index step interface are lost, the UV-near-infrared region diffuse reflection is weakened, resulting in a decrease in solar reflectance, and the near-infrared reflectance decreases due to the largest contribution of calcium titanate to the near-infrared region. The calcium titanate / magnesium fluoride composite material plays a "filling + bridging" role in the thermal conduction network, and the thermal conductivity decreases slightly after being lost; in the mid-infrared non-main emission phase, so the hemispherical emissivity decreases slightly.

[0117] From the test results of Example 1 and Comparative Example 3, without adding holmium / ytterbium co-doped calcium fluoride nanosheets, the in-plane heat dissipation and energy level downshift radiation double effects are weakened. After the interlayer stacking of the flaky calcium fluoride is evacuated, the lateral heat dissipation is reduced, and the thermal conductivity decreases. On the other hand, the energy transfer path between holmium and ytterbium elements disappears, and the near-infrared heat is no longer converted to the atmospheric window band and discharged in the form of radiation, so the near-infrared reflectance decreases, and the hemispherical emissivity also decreases due to the attenuation of the mid-infrared spontaneous radiation; the overall solar reflectance decreases.

[0118] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets, characterized in that, The preparation method includes: S1: Polycarbosilane, boric acid, isopropyl titanate and melamine are dissolved in a mixed solvent and stirred at room temperature to obtain a preliminary spinning solution. After filtration, a precursor fiber membrane is spun to obtain a precursor fiber membrane. The precursor fiber membrane is placed in air and then calcined and naturally cooled to obtain a preliminary fiber skeleton. The precursor fiber membrane is then impregnated in an ethanol-water solution of a silane coupling agent and dried to obtain a SiC@BN / TiB2 three-phase fiber skeleton. S2: Prepare calcium hydroxide dispersion, add titanium chloride under ice bath and adjust pH with potassium hydroxide, perform hydrothermal reaction, centrifuge after cooling, wash with water, and vacuum dry to obtain star-shaped calcium titanate powder; disperse magnesium nitrate and ammonium fluoride in deionized water, add calcium titanate powder to obtain reaction solution A, stir, filter, dry and pulverize, and air calcinate to obtain calcium titanate / magnesium fluoride composite material. S3: Calcium nitrate, holmium nitrate and ytterbium nitrate are dispersed in deionized water to obtain a mixed dispersion. Sodium fluoride is added, and the mixture is stirred to obtain a mixed precursor. The precursor is then placed in a quartz boat for crystallization and naturally cooled to obtain holmium / ytterbium co-doped calcium fluoride nanosheets. S4: SiC@BN / TiB2 three-phase fiber skeleton and methylphenyl silicone resin were placed in a planetary vacuum stirred tank and stirred to obtain a premixed base liquid. Calcium titanate / magnesium fluoride composite material and holmium / ytterbium co-doped calcium fluoride nanosheets were added and dispersed evenly. Then, methylphenyl silicone resin, KH-550, BYK-A530, FC-4430 and propylene glycol methyl ether acetate were added to obtain a pre-coating liquid. The viscosity was adjusted, vacuum degassing was performed, and filtration was carried out to obtain a high thermal conductivity radiation cooling coating for 5G communication base station cabinets.

2. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S1: The mass ratio of the polycarbosilane to boric acid is (17-19):(1.4-1.6); The mass ratio of the polycarbosilane to isopropyl titanate is (17-19):(0.95-1.05).

3. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S1: The mass ratio of polycarbosilane to melamine is (17-19):(0.75-0.85).

4. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S1: The mass ratio of DMF to THF in the mixed solvent is 1:(1-1.2); The mass ratio of the polycarbosilane to DMF is (17-19):(38-42).

5. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S2: The mass ratio of calcium hydroxide to deionized water in the calcium hydroxide dispersion is (7-7.8):(190-210); The mass ratio of titanium chloride to calcium hydroxide is (7-7.8):(9-10).

6. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S2: The mass ratio of magnesium nitrate, ammonium fluoride, and deionized water is (2.9-3.3):(1-1.2):(35-45); The mass ratio of calcium titanate powder to magnesium nitrate is (2.9-3.3):(9.5-10.5).

7. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S3: The mass ratio of calcium nitrate, holmium nitrate, ytterbium nitrate to deionized water is (11.2-12.4):(0.26-0.30):(1.55-1.71):(90-110).

8. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S3: The mass ratio of calcium nitrate to sodium fluoride is (11.2-12.4):(11.5-13.5).

9. The method for preparing a high thermal conductivity radiation cooling coating for 5G communication base station cabinets according to claim 1, characterized in that, In S4: The mass ratio of the SiC@BN / TiB2 three-phase fiber skeleton to methylphenyl silicone resin is (28-32):(54-56); The mass ratio of the calcium titanate / magnesium fluoride composite material to methylphenyl silicone resin is (23-27):(54-56); The mass ratio of the holmium / ytterbium co-doped calcium fluoride nanosheets to methylphenyl silicone resin is (7-9):(54-56); The mass ratio of the methyl phenyl silicone resin, the supplemented methyl phenyl silicone resin, KH-550, BYK-A530, FC-4430 to propylene glycol methyl ether acetate is (54-56):(17-21):(0.40-0.60):(0.15-0.25):(0.25-0.35):(8-12).

10. A high thermal conductivity radiation cooling coating for 5G communication base station cabinets prepared by the preparation method according to any one of claims 1-9.