435
in high-temperature applications, and serve a primarily insulating
function. Various other alumina/titania coatings also serve thermal
functions.
Many nanocoatings have been developed for light or optical
reasons. An interesting characteristic of nanoparticles is that their
size is smaller than the wavelength of visible light, which ranges
from 400 to 700 nm. Nanoparticles in coatings are much smaller,
around one tenth or so of the wavelength of visible light. When
dispersed in a transparent matrix, these nanoparticles are virtually transparent to the eye. Additionally, nanoparticles can now be
made wherein the refractive index of the particles can be matched
to those of a cured resin formulation. Translucent or optically transparent coatings can thus be made. Some nanocoatings have been
specifically developed to block ultraviolet light or to have particular
reflective properties.
A major application is for antireflection or brightness-enhancing
applications that are important in many areas of product design,
architecture, and industrial products. Most of these applications
consist of multiple layers of nanoscale materials built up sequentially. Antireflection films serve to either reduce troublesome
reflections (a typical architectural application or product design
application) or to enhance the light transmission efficiency of a
transparent material. As discussed in Section 9.5, light impinging
on a surface is reflected, transmitted, or absorbed. If less light is
reflected, more is transmitted. The brightness of a perceived image,
for example, can be improved. Contrast is normally improved as
well. Hence, many antireflection films are found in everything from
computer screens to telescopes.
Not only can high transmission be achieved in complex optical
devices, but troublesome ghosting effects can be reduced. Light
reflection on a surface is reduced via the use of multiple layers of
transparent materials that have different optical qualities, particularly their refractive indices. Depending on various layer thicknesses and the refractive indices present, different destructive and
constructive interferences are created that make the optical characteristics of the multilayer coating change with the wavelength of
the impinging light as well as its angle. Coatings can be designed
to respond to a wide range of infrared, visible, or ultraviolet wavelengths, depending on the needed application. Refractive indices
can be adjusted over a wide range by varying concentrations of
metal oxide nanoparticles in a polymer matrix. Optical coatings are
discussed in more detail in Section 9.5.
Nanoproduct Forms
in high-temperature applications, and serve a primarily insulating
function. Various other alumina/titania coatings also serve thermal
functions.
Many nanocoatings have been developed for light or optical
reasons. An interesting characteristic of nanoparticles is that their
size is smaller than the wavelength of visible light, which ranges
from 400 to 700 nm. Nanoparticles in coatings are much smaller,
around one tenth or so of the wavelength of visible light. When
dispersed in a transparent matrix, these nanoparticles are virtually transparent to the eye. Additionally, nanoparticles can now be
made wherein the refractive index of the particles can be matched
to those of a cured resin formulation. Translucent or optically transparent coatings can thus be made. Some nanocoatings have been
specifically developed to block ultraviolet light or to have particular
reflective properties.
A major application is for antireflection or brightness-enhancing
applications that are important in many areas of product design,
architecture, and industrial products. Most of these applications
consist of multiple layers of nanoscale materials built up sequentially. Antireflection films serve to either reduce troublesome
reflections (a typical architectural application or product design
application) or to enhance the light transmission efficiency of a
transparent material. As discussed in Section 9.5, light impinging
on a surface is reflected, transmitted, or absorbed. If less light is
reflected, more is transmitted. The brightness of a perceived image,
for example, can be improved. Contrast is normally improved as
well. Hence, many antireflection films are found in everything from
computer screens to telescopes.
Not only can high transmission be achieved in complex optical
devices, but troublesome ghosting effects can be reduced. Light
reflection on a surface is reduced via the use of multiple layers of
transparent materials that have different optical qualities, particularly their refractive indices. Depending on various layer thicknesses and the refractive indices present, different destructive and
constructive interferences are created that make the optical characteristics of the multilayer coating change with the wavelength of
the impinging light as well as its angle. Coatings can be designed
to respond to a wide range of infrared, visible, or ultraviolet wavelengths, depending on the needed application. Refractive indices
can be adjusted over a wide range by varying concentrations of
metal oxide nanoparticles in a polymer matrix. Optical coatings are
discussed in more detail in Section 9.5.
Nanoproduct Forms