Photoacoustic response of coal
Journal Article
·
· Miner. Matters; (United States)
OSTI ID:6701898
In recent years the photoacoustic effect has evolved as an extremely powerful tool for probing either the thermal properties or the optical properties of solids. In a typical photoacoustic experiment, the sample under investigation is placed inside a closed cell containing a gas, such as air, and a sensitive microphone. A chopped light beam from an external lamp is transmitted through a window in the cell and focused on the sample. Upon absorbing the chopped light, the temperatures of both the sample and surrounding gas rise and fall with the same frequency as the modulated light. The resulting variations in the gas pressure are monitored by the microphone, the output voltage of which is called the photoacoustic signal. Although the basic principle of the photoacoustic effect has been known for many years, only since 1973 has it been seriously utilized for optical absorption measurements. The technique has emerged as an extremely useful and complementary method to the conventional optical transmission and reflection measurements, particularly on opaque samples. In fact, many solid materials are very opaque unless prepared extremely thin, and they exhibit reflectances of less than 10%. Coal is a prime example. In these cases the photoacoustic effect measures the remaining 90% of light energy absorbed. Today, the photoacoustic effect is widely used to study solid and liquid materials and its operation is well understood.
- Research Organization:
- Southern Illinois Univ., Carbondale
- OSTI ID:
- 6701898
- Journal Information:
- Miner. Matters; (United States), Journal Name: Miner. Matters; (United States) Vol. 3:4; ISSN MIMAE
- Country of Publication:
- United States
- Language:
- English
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