Coating methods vapor-phase

Important processing methods vapor phase deposition, spin coating, injection molding, casting, ex-trusion, drawing of oriented films, compression molding, sintering... 

Other methods explored internally to alter the form of nicotine delivered included the use of base- or acid-coated filters. For example, researchers at RJR applied sodium hydroxide-coated filters to a cigarette yielding only 0.06 mg of nicotine in order to heighten sensory impact (Shannon et al. 1992). Alternately, a filter coated with an acid (lactic, levulinic, citric) was used to reduce the impact of a high nicotine sheet, either by trapping the nicotine or by changing the pH of the smoke so there is not as much lucotine in the vapor phase (Shannon et al. 1992). The researchers noted that ... 

In all vacuum coating methods layers are formed by deposition of material from the gas phase. The coating material may be formed by physical processes such as evaporation and sputtering, or by chemical reaction. Therefore, a distinction is made between physical and chemical vapor deposition ... 

Numerous methods have been described in the literature for depositing coatings onto piezoelectric acoustic sensors. They generally fall into three categories solvent casting techniques, vacuum deposition techniques, and vapor-phase deposition techniques. 

To reiterate, the choice of coating thickness is important in the analysis of organic analytes. For example, thick coatings (100 pm) are useful for volatile organic compounds because they have low values of K thus, more capacity is obtained for the isolation. An example method is EPA Method 624 for volatiles (Supelco). The sample may be analyzed either in the headspace or in the solution. When the headspace method is used, salt is added to the sample to the saturation point. This step helps to drive the compounds into the vapor phase. 

Another ammonia sensor speciHcally designed for use in bioliquids is based on the evanescent wave technique and can be applied to the vapor-phase determination of ammonia above blood and serum [136]. It utilizes the ninhydrin reaction occurring in the polymer coating of the fiber, and the resulting color change is monitored by total internal reflection. The probe is applicable to clinical determinations normally carried out in the vapor phase, but works irreversibly. A linear relationship exists between absorbance and ammonia concentration in the clinically useful range of 0-4.0 pg mL. Comparison with the reference method showed a correlation coefficient of 0.92. 

The CVD method involves a chemical reaction in a vapor phase which results in deposition of a solid on a heated surface. Various PVD processes such as ion plating, sputtering, molecular beam, evaporation, and epitaxy might be also included in CVD processes [112]. The various CVD methods are powerful processes used for the fabrications of a wide variety of thin-film materials including solar cell materials and semiconductor materials for electronic applications, as well as the manufacture of coatings, powders, fibers, and monolithic components. There are two types of CVD reactors, the differential reactor and the starved reactor, according to the value of the flow rate (F,) defined as... 

Physical Vapor Deposition (PVD) includes various methods for depositing thin films onto a substrate by the condensation of a desired vapor. For this process the coating material changes from the solid phase to the vapor phase and back to the solid phase (as it builds a film on the substrate). See Fig. 3 [12]. 

An additional type of coating method frequently used is vapor deposition. Generally, this method involves deposition of the coating onto a substrate from the vapor phase. Vapor deposition technologies can be categorized into chemical vapor deposition (CVD) and physical vapor deposition (PVD). The two methods are distinct. 

Other methods of preparation include chemical vapor deposition (CVD) and electrochemical methods. The latter are used to form thin films and protective coatings as well as battery electrodes. Since this is generally a low-temperature method, the structure can differ from that of the same material prepared at a higher temperature. It can be disordered or amorphous. Chemical vapor deposition involves vapor phase transport of volatile organometallics... 

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