Application method heat activation

CVD can also be classified using its activation methods. Thermal activated CVD processes are initiated only with the thermal energy of resistance heating, RF heating or by infrared radiation. They are widely used to manufacture the materials for high-temperature and hard-to-wear applications. In some cases enhanced CVD methods are employed, which includes plasma-enhanced CVD (PECVD), laser-induced CVD (LCVD), photo CVD (PCVD), catalysis-assisted CVD and so on. In a plasma-enhanced CVD process the plasma is used to activate the precursor gas, which significantly decreases the deposition temperature. 

Chemical vapour deposition (CVD) processes have become a very important group of film-formation methods. Basically CVD is a material synthesis in which constituents of the vapour phase react chemically to form thin solid films as a solid-phase reaction product which condenses on the substrate. The reaction should take place very near to or on the substrate surface (heterogeneous reactions) and not in the gas phase to avoid powdery deposits. Activation of the reaction can be performed by various means such as the application of heat, high-frequency electrical fields, light or X-ray radiation, electric arc, electron bombardment or catalytic action of the substrate surface. A marked influence of the process parameters such as sub-... 

There is a marked difference between the two inactive forms. Racemic acid may be separated into d- and Z-tartaric acid by the methods which have been described under i-lactic acid. Mesotartaric acid, not being a mixture of different kinds of molecules, can not be so separated. It is changed into the active form of tartaric acid only by the application of heat, when the molecule undergoes decomposition and a new arrangement of atoms is brought about. 

The binary sodium chloride-water system has been the object of many studies. As a result there is a wealth of published data for a wide range of temperatures. This data includes solubility, density, vapor pressure lowering and heat of solution measurements. Because of this availability of data and the straightforward strong electrolyte behavior of the system, sodium chloride has almost always been included as an example when illustrating activity coefficient modeling techniques. For this application, Meissner s method of activity coefficient calculation will be used. 

Enhancement techniques may be conveniently divided into two classes - passive methods and active techniques. Extended surfaces which require no direct application of external power fall within the passive category. Rotation (as used in the Rotex heat pump initially mentioned in Chapter 1) is an active technique, as obviously energy is needed to rotate the device. Additionally, each technique may be applicable to one or more modes of heat transfer (e.g. forced convection, boiling, condensation, etc.) and compound enhancement - the use of more than one technique on a single heat exchanger - is practised. 

Initiating systems which are effective at room temperature normally consist of mixtures of a peroxy compound and an activator ( accelerator ). In the presence of the accelerator, the peroxy compound rapidly decomposes without the application of heat into free radicals. The two most important peroxy materials now used for the cold curing of polyester resins are methyl ethyl ketone peroxide (MEKP) and cyclohexanone peroxide. These names are rather misleading in that neither of these materials is a single compound and both have a variable composition depending on their method of manufacture. The main... 

Dies, Hot Stamping n Method of depositing a decorative layer on the surface of a polymer, whereby a hot metal or rubber diem which bears the required design or lettering is placed in contact with the medium to be applied and the surface to be decorated. The application of heat melts the release coating and activates the adhesive. After a short contact, the die pressure is released and the film carrier separated from the plastic surface, leaving a decorative coating transferred in the area of the die. 

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