Optically dense materials

Red-brown to optically dense material fiber-tracheid derived... 

High-absorptivity optically dense) materials with absorbances above 4-6 OD are difiicult to measure accurately without the use of doublemonochromator instruments with stray light specifications below 0.0001% T. Measurements can be made with extremely slow scanning speeds and by opening the slits during measurement. These measurements should be avoided by the novice unless high-performance instrumentation and technical support are available. 

Attenuated total reflectance infrared (ATR-IR) is used to study films, coatings, threads, powders, interfaces, and solutions. (It also serves as the basis for much of the communication systems based on fiber optics.) ATR occurs when radiation enters from a more-dense material (i.e., a material with a higher refractive index) into a material that is less dense (i.e., with a lower refractive index). The fraction of the incident radiation reflected increases when the angle of incidence increases. The incident radiation is reflected at the interface when the angle of incidence is greater than the critical angle. The radiation penetrates a short depth into the interface before complete reflection occurs. This penetration is called the evanescent wave. Its intensity is reduced by the sample which absorbs. 

The Kretchmann configuration illustrated in Figure 3.8 relies on the phenomenon of total internal reflection. This process occurs when light traveling through an optically dense medium, e.g. glass, reaches an interface with a material of lower optical density, e.g. air, and is reflected back into the dense medium. Although the... 

A few varieties of nonsilicate oxide ceramic powders synthesized through alkoxide processing are presented here. These oxide powders were developed for the use of electronic, optical, and high-temperature structural applications. For each material, we start with a brief description of the synthesis, which is followed by powder characteristics (e.g., particle sizes, morphologies, and size distributions) and densification behavior and some properties of dense material. 

Analysis of optically dense or high carbon-black content materials... 

Reflection occurs at any interface where the complex refractive index changes. We can define the medium with the lower refractive index as the optically rare medium and material with the higher refractive index as the optically dense medium. The optically dense medium will be designated by the subscript 2 and the optically rare medium will be designated by the subscript 1. We will just consider the case where the optically rare medium is a gas or a vacuum, so that the refractive index n 1 and the absorption index k 0. In this case, the reflectance at the interface depends on the optical constants of the optically dense medium, 2 and the angle... 

Cubic BC2N. Hetero-diamond B C—N compounds have recently received a great interest because of their possible applications as mechanical and optical devices. The similar properties and structures of carbon and boron nitrides (graphite and hexagonal BN, diamond, and cubic BN) suggested the possible synthesis of dense compounds with all the three elements. Such new materials are expected to combine the best properties of diamond (hardness) and of c-BN (thermal stability and chemical inertness). Several low-density hexagonal phases of B,C, and N have been synthesized [534] while with respect to the high-density phases, different authors report contradictory data [535-538], but the final products are probably solid mixtures of c-BN and dispersed diamonds [539]. 

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