Train sublimation

The most commonly used HTL materials are triarylamine compounds. These compounds were developed as HTMs for photoconductive applications such as xerography [69]. They naturally have been selected as HTMs for OLED applications largely because of their ready availability and their good electrochemical and thermal stabilities. The hole mobilities of these materials are also adequate for OLED applications. In addition, high purity, so as to ensure low hole-trap contamination, is believed necessary for long-lived OLED performance and such materials may often be train sublimed to very high purity. 

Besides chemical synthesis, purity of the employed chemicals is essential for the organic device performance desired. Small-molecule materials, which are only poorly soluble, are usually purified by repeated train sublimation, which results in substantial losses of material and additional purification costs. These material requirements are almost identical for OVPD and VTE. Because of the different deposition processes, the thermal stress on the organic materials is different in OVPD and in VTE. OVPD operates under steady-state temperature conditions without ramping of the evaporation temperature during processing, as is typically applied in VTE. Depending on the vapor pressure of the organic materials used and the... 

Loutfy et al. (1985a) have shown that the infrared absorption of CllnPc is unchanged upon purification by train sublimation or ball milling in halogenated solvents or tetrahydrofuran. The x-ray powder diffraction spectra likewise indicated that all these materials were the same polymorph. Dispersion generation layers showed both increased 830 nm sensitivity and increased dark... 

A combustion tube of either Jena hard glass or Corning 172 is constructed similar in design to that used for the preparation of rhenium pentachloride (synthesis 62). The pentachloride is prepared in the manner previously described and sublimed into the bulb D. The chlorine is then turned off, and the train swept out with nitrogen. When all chlorine has been displaced, the pentachloride is... 

Freeze-drying, a special application of the sublimation principle, uses apparatus of a different kind (Figure 6). The sample, usually a liquid at room temperature, is dispersed around the walls of a round-bottomed flask whilst it is frozen by immersion in a suitable freezing mixture, for example, dry ice/acetone. The flask is then attached to the evacuating system that usually comprises an oil vacuum pump protected from the ice sublimate by a train of... 

Because of the use of TATP by terrorists, a rehable and fast detection of this material is desirable. In addition to conventional analytical methods such as mass spectrometry and UV (ultra violet) spectroscopy specially trained explosive detection dogs (FDD) play an important role in the detection of organic peroxides. Although the high vapor pressure helps the dogs to detect the material, it is also a disadvantage because of the limited time-span in which the dog is able to find it (traces may sublime and disappear forever). Matrices in which the compounds can... 

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