Sunlight reflecting materials and methods of fabrication
Disclosed are nanostructured materials that reflect light in selected spectra incorporated in dark colored textiles or substrates. In one aspect, a light reflecting material includes a textile exhibiting a dark color and formed of a plurality of fibers, and nanostructures arranged on the fibers and formed of a plurality of nanoparticles, the nanostructures having a dimension size of substantially less than ½ of a visible light wavelength, in which the nanostructures reflect light from the textile or substrate in at least one of infrared, near-infrared, or red visible light spectra.
1. A light reflecting material, comprising:
a substrate; and
nanostructures arranged on or within the substrate and including a plurality of core-shell nanoparticles,
wherein the nanostructures are configured to reflect light from the substrate in a light spectral range,
wherein the nanostructures include metal nanoparticles having core-shell structures, each core-shell structure having a core metal material and a shell protective material, and
wherein the core metal material includes Ni, Co, Ti, Al, Mo, Zr, Ta, or W or a combination of any two or more of Ni, Co, Ti, Al, Mo, Zr, Ta, and W, and the shell protective material includes oxidation-resistant material including Cr2O3, Al2O3, ZrO2, HfO2, Ta2O5, Y2O3, ZnO, MgO, CaO, CrN, AlN, or ZrN or a combination of any two or more of Cr2O3, Al2O3, ZrO2, HfO2, Ta2O5, Y2O3, ZnO, MgO, CaO, CrN, AlN, and ZrN.
2. The material of claim 1 , wherein the light spectral range includes at least one of infrared, near-infrared, or red visible light.
3. The material of claim 1 , wherein the nanoparticles include metal nanoparticles including one or more of Ag, Au, or Pd.
4. The material of claim 1 , further comprising an adhesion enhancing material having a silane structure (Si(OEt)3).
5. The material of claim 1 , wherein the nanostructures configured to reflect light include a sunlight or infrared (IR) reflecting coating that exhibits a high durability of the nanoparticles adherence with one of at most 20% loss, at most 10% loss, or at most 5% loss of the adhered nanoparticles after repeated washing or repeated rubbing, with corresponding loss of superhydrophobic contact angle being one of at most 30 degrees, at most 15 degrees, or at most 5 degrees.
6. The material of claim 5 , wherein:
the at most 10% loss is more preferred than the at most 20% loss and the at most 5% loss is more preferred than the at most 10% loss; and
the at most 15 degrees contact angle is more preferred than the at most 30 degrees contact angle and the at most 5 degrees contact angle is more preferred than the at most 15 degrees contact angle.
7. The material of claim 1 , further comprising a thin film coating layer on an external surface of the substrate to enhance adhesion of the nanostructures on the substrate, the thin film coating layer including Ti, Cr, or adhesive material.
8. The material of claim 1 , wherein the substrate includes a textile substrate or solid substrate.
9. The material of claim 1 , wherein at least some of the nanoparticles are separated from one another with an average spacing of at least one half the average diameter of the particle.
10. The material of claim 1 , wherein the substrate includes at least a portion of an enclosure housing temperature sensitive components.
11. The material of claim 10 , wherein the enclosure includes metallic, ceramic, or polymer material and has a surface coated with a heat-insulating interfacial layer.
12. The material of claim 1 , wherein the nanostructures having a dimension size of substantially less than a half of a visible light wavelength, and an interparticle spacing of at least one half of an average nanoparticle diameter.
13. The material of claim 1 , wherein the nanostructures having a dimension size of substantially less than a half of a visible light wavelength, and an interparticle spacing of at least one half of an average nanoparticle diameter.
14. The material of claim 1 , wherein the core-shell nanoparticle structure is spherical or flaky in shape.
15. The material of claim 1 , wherein the shell thickness in the core-shell nanoparticle structure is in the range of 1-30 nm with the volume fraction of the shell material being less than 40%.