X-MINING Heating White & Translucent Objects with Sunlight NIR Absorbing Materials

Black objects, such as asphalt, absorb light and convert the absorbed energy into heat.

However, colorless, transparent, white or fluorescent objects are considered to be very inefficient to heat with sunlight because they transmit or reflect light.

The sunlight contains not only visible light, but also invisible light like near-infrared light.

Accordingly, we thought that if we should use a material that absorbs only invisible near-infrared light and converts it into heat, we could heat even colorless, transparent, white, or fluorescent objects.

Fig. 1shows the change of the water temperature when a water dispersion liquid of each fine particle is heated by artificial sunlight.

Since Sumitomo Metal Mining’s CWO™ strongly absorbs the near-infrared rays in sunlight and convert them into heat, it shows a remarkable effect of water temperature rise even in the high transmittance range to warm up the transparent water.

In other words, CWO™ is not only near-infrared absorption materials but also excellent transparent photo-thermal conversion material.

Figure 1: Temperature rise of water dispersion liquids when they are heated by artificial sunlight.

(left: measuring method, right: result)

We prepared four kinds of water dispersion liquid in which different near-infrared absorption nano particles were dispersed. Then, we measured temperature rise of the water dispersion liquid when it was irradiated with artificial sunlight for 20 miniutes.　As the standard datum, we measured  temperature rise of pure water in the same condition.　At last, we calculated the contribution of each particle to temperature rise from the difference of temperature rise between water dispersion liquid and pure water.

(Cooperation: National Institute for Materials Science (NIMS))

These functions are expected to be applied to the local welding of transparent resin by laser, as shown in Figure 2.

And the functions are also expected to be applied to heating by halogen lamps (lamp heater).

Figure 3 shows the spectral intensity distribution of the radiator.

CWO™ is considered to be highly compatible with halogen lamps, because radiators at 3000K to 3300K which is equivalent to halogen lamps mainly emit near-infrared lights.

Halogen lamps have a conversion efficiency of around 90% for all electromagnetic waves, including infrared rays, and are a very efficient heating means, so they also contribute greatly to reducing the global environmental burden.

Functions of the light-absorbing and photo-thermal conversion realized by Sumitomo Metal Mining’s transparent materials can be applied to various fields.

Will you used them to achieve your imagination?

Figure 2 Laser spot welding of transparent resin

Figure 3 Spectral intensity distribution and radiant temperature versus wavelength