Heat-reflective dispersive light filter

 

(57) Abstract:

Heat-reflective dispersive light filter used for lighting, heating and protection against overheating of solar energy facilities, greenhouses, etc., the Filter includes a base, in which the dispersed filler is introduced particles of vanadium dioxide has a spherical shape with a diameter of 0.5 μm < d < 50 μm. 1 Il.

The invention relates to a reflective infrared radiation filters that are installed for lighting, heating and protection against overheating by solar energy facilities, greenhouses, etc.

Known dispersing the dispersion filter, which consists of linking the environment to put in her uniform particles used in the infrared spectral region in which the change in the spectral composition of the pass-through radiation occurs as a result of its scattering on inhomogeneities, the size of which is comparable with the radiation wavelength (K. R. Armstrong, F. J. Low, Far-Infrared Filters Utilizing Small Paaticle and Antireflection Coating, Applied Optics, vol. 13, N 2, - 1974. - P. 425-430).

However, the known filter is always opaque in the visible region of the spectrum and transmits only the far infrared region in a narrow spectral interval. The temperature has no effect on optionname, in which the dispersed filler is introduced particles of vanadium dioxide, and particles of vanadium dioxide have size d, not exceeding the wavelength of the filtered light (GB, application, 1265282, CL G 02 B 5/22, 1972). Filtering in this case is provided by the reflection due to Rayleigh scattering. However, the only conditions d < does not provide the maximum value of the reflection coefficient.

The basis of the invention is the task of creating a filter providing at certain temperatures, the maximum value of reflectance in a wide range of the infrared region of the spectrum (0.8 to 25 μm) and the transparency in the visible spectral range (0.3 to 0.8 μm) at any temperature.

The problem is solved due to the fact that in the known heat-reflecting dispersion optical filter, comprising a base, in which the dispersed filler is introduced particles of vanadium dioxide, they have a spherical shape with a diameter of 0.5 μm < d < 50 μm.

The technology of heat-reflective dispersive filter next. The filler is dispersed, is introduced into the binder medium (glass, polymer composition) and is moved until a uniform distribution is prehoda undergoing significant changes - increase by several orders of magnitude) the conductivity and the substance passes from a state of "dielectric" in the state of "metal". Because the substance is moved from the "dielectric" in the state of the metal, changing its optical properties. This leads to the fact that the filter with such a filler reflects infrared radiation (0.8 to 25 microns) and is transparent to visible radiation at temperatures higher than the temperature of the phase transition. At temperatures below the phase transition temperature, the filter is transparent in the whole spectral interval, since the filler - vanadium dioxide at these temperatures is in a state of "dielectric".

Were calculated reflectivity composite matrices (simulating filter) containing particles of vanadium dioxide of a certain size in the range of 0.1-50 microns with a volume concentration of up to 3%.

The drawing shows the results of calculations of the reflection coefficients of composite matrices containing particles of vanadium dioxide of a certain size range of 0.5 to 15 microns with a volume concentration of 0.1%, where curves 1 - 4 - the reflection coefficients for particles with a diameter of 0.5 μm (curve 1), 5 μm (curve 2), 10 μm (crooked estimated reflection coefficients for matrices with a particle diameter of 0.5 μm (curve 5), 5 μm (curve 6), 10 μm (curve 7), 15 μm (curve 8) at temperatures above the phase transition temperature of vanadium dioxide.

As can be seen from the graphs, the reflectivity of the composite matrix in the visible spectral range (0.3 to 0.8 μm) does not depend on temperature (curves 1 - 8) and in the infrared region of the spectrum of the phase state of the particles significantly affects the behavior of the reflectivity of the composite matrix. This composite matrix in the interaction with the incident radiation flux will work as follows. At temperatures below the transition temperature the dielectric-metal", reflectivity over the entire spectral range remains unchanged (curves 1 - 4), and its magnitude is not substantially greater than the magnitude of the reflectivity of the binder. At temperatures equal to or higher than the temperature of the phase transition, the reflectivity of the composite matrix is almost two times increase in the infrared region of the spectrum, in the visible region its value practically does not change (curves 5 - 8). The calculations also showed that the magnitude of the jump reflectivity of the phase transition depends on the size of the particles and their concentration in maddry transmission of samples in the region of 0.3-2.5 μm were obtained with a spectrophotometer SF-46, and in the area of 2.5-25 µm were obtained using IR-Specord. The analyzed samples were placed in a special heated module, the temperature of which was measured in the range of 20-100oC and was maintained at the specified level with accuracy of 0.1oC. Spectral characteristics of filters on the basis of PVC films in the interaction with a passing radiation in the table.

From the experimental data shown in the table, it follows that in the infrared region of the spectrum above the phase transition temperature observed decrease transmittance ability for all investigated samples. Fractional composition of the filler particles affects the degree of change in transmittance of the ability of the composite film after the phase transition. The biggest change is observed when selecting the particle size of the vanadium dioxide not exceeding 50 μm. Thus the attenuation of light transmission due to the reflection in the field 0,8025 μm and the preservation of constant transmittance in the visible region of 0.3-0.8 μm for temperatures exceeding the phase transition point, and the preservation of constant transmittance over the entire spectral interval at a temperature below a phase transition point, is achieved by using as filler h including base, in which the dispersed filler is introduced particles of vanadium dioxide, characterized in that the particles of vanadium dioxide have a spherical shape with a diameter of 0.5 < d < 50 μm.

 

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