Reflection from Ceramic Surfaces

High reflectivity for glazes and enamels is also important, and can be achieved by using glass formulations with 

In some situations we do not want a high reflectivity. In fact, we want to minimize the reflectivity as far as possible. One very 

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Usually, particle size has relatively little effect on Raman line shapes unless the particles are extremely small, less than 100 nm. For this reason, high-quality Raman spectra can be obtained from powders and from polycrystalline bulk specimens like ceramics and rocks by simply reflecting the laser beam from the specimen surface. Solid samples can be measured in the 90° scattering geometry by mounting a slab of the solid sample, or a pressed pellet of a powder sample so that the beam reflects from the surface but not into the entrance slit (Figure 3). 

The final type of measurement that can be made with the microscope in its reflection mode is diffuse reflection (DR) spectroscopy. Today, very few appHca-tions of mid-lR microspectroscopy of neat samples are available, because for mid-IR DR spectrometry the samples should be diluted to a concentration of between 0.5 and 5% with a nonabsorbing diluent (e.g., KBr powder) to preclude band saturation and severe distortion by reflection from the front surface of the particles. However, this mode has substantial application for NIR measurements, where sample dilution is not needed. Because the absorption of NIR radiation by most samples is rather weak, they must either be at least 1 mm thick or be mounted on a reflective or diffusing substrate, such as a ceramic or Teflon disk. In the latter case, the spectrum is caused by a combination of diffuse reflection, transflection and front-surface reflection (hopefully with diffuse reflection being the dominant process). 

Often, the problem in optical examination of polycrystalline ceramics such as alumina is that light reflected from interior grain surfaces can interfere with observation of fracture surface features. One can suppress these internal reflections by coating the fracture surface with carbon or other opaque material. Alternatively, the surface can be replicated and analysis conducted on the replica. Replicas using a... 

Consider a ceramic specimen in the form of a plate that has front and back surfaces. For research purposes, a reflectance measurement would be made from a specimen in which the amount of fight reflected from the back surface, and lost from transmission through the specimen, is negligible compared to light scattered from the interior and the front surface. In other words, the specimen would appear infinitely thick to fight that penetrates the surface. With such a semiinfinite specimen, the total reflection coefficient (from the combined diffuse and specular components) is designated as. ... 

The reflectance of ceramic powders can be measured relatively easily. The large difference in index of refraction between powder particle, n s 1.5-2.5, and the space between the particles, n = 1.00, produces a large amount of light scattering. Hence, in general, only a thin layer of powder is necessary to achieve the condition of reflection from a semiinfinite surface. 

Powdered iron phosphates, 26 215 Powdered sugar, 23 482 Powdered surfaces, diffuse reflectance of radiation from, 24 110 Powder glass-ceramic processing,... 

Organic coated micro bubbles and inorganic silicon networks have been discussed. Another remarkable fmish is similar to these products evacuated micro bubbles from silicon compounds, fixed with an acrylate binder on the fibre surface provide new insulation textiles. The high insulation value of the vacuum and the reflectance of the ceramic bubbles of this so-called liquid ceramic fmish protects very effectively from heat and cold. ... 

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