Flame attenuation process

Flambant see coal grade (France), 6 713t Flame agents, 5 814, 824-825 Flame arrestors, for acetylene, 1 185 Flame attenuation process, 13 387 Flame detectors, 21 851 Flame heating, case hardening by, 16 199 Flame hydrolysis, in vitreous silica manufacture, 22 412, 413-414 Flame ionization detector (FID)... 

This CVD procedure is somewhat different from that used to deposit semiconductor layers. In the latter process, the primary reaction occurs on the substrate surface, following gas-phase decomposition (if necessary), transport, and adsorption. In the fiber optic process, the reaction takes place in the gas phase. As a result, the process is termed modified chemical vapor deposition (MCVD). The need for gas-phase particle synthesis is necessitated by the slow deposition rates of surface reactions. Early attempts to increase deposition rates of surface-controlled reactions resulted in gas-phase silica particles that acted as scattering centers in the deposited layers, leading to attenuation loss. With the MCVD process, the precursor gas flow rates are increased to nearly 10 times those used in traditional CVD processes, in order to produce Ge02-Si02 particles that collect on the tube wall and are vitrified (densified) by the torch flame. 

Figure 28-1 6 Block diagram of a single-beam atomic absorption spectrometer. Radiation from a line source is focused on the atomic vapor in a flame or an electrothermal atomizer. The attenuated source radiation then enters a monochromator, which isolates the line of interest. Next, the radiant power from the source, attenuated by absorption, is measured by the photomultiplier tube (PMT). The signal is then processed and directed to a computer system for output.

Atomic absorption The process by which unexcited atoms in a flame, furnace, or plasma absorb characteristic radiation from a source and attenuate the radiant power of the source. 

For decades, the majority of PCBs have been built with epoxy resins, dicy-cured, and with bromine flame retardant.The industry has developed around this paradigm. Drills and drilling, chemistry, lamination, and circuit card assembly are all well understood with reference to standard FR-4. Although there are fabricators with processes developed to manufacture PCBs using laminates other than standard FR-4, this knowledgebase is not distributed industrywide. Especially problematic is the intersection of requirements for HF and/or LFAC with high thermal resistance and improved electrical characteristics, such as low attenuation in the material. 

In this Chapter, thermal analysis of the decomposition process has been performed -hence, the flame retardancy and thermal stabihzation of halogenated and non-halogenated polyester resins by ZHS may be explained by the formation of smface-localized spherical barriers which are growing according to the nucleation growth mechanism and which attenuate the transfer of heat from the decomposition zone to the substrate. This effect was foimd as dominating in the flame-retardancy mode of action. 

---