Low vacuum scanning electron microscope

Once a plasticizer has been identified, EDAX can be used to examine its distribution in the plastic matrix if the two components contain at least one element which is not common to both. Examination can be non-destructive if a low vacuum scanning electron microscope is used because the technique does not require the application of a conductive coating. The plastic surface is mapped for elements. 

Unless a microscopic technique can be used, which allows the sample to remain in the liquid state, for example, optical microscopy (OM), colloidal probes in AFM, environmental or low vacuum scanning electron microscopy (Uwins, 1994), the preparation and analysis of film forming dispersions present a number of problems, where the size, microstructure and composition shall remain imchanged throughout the treatment. The sample preparation is often tedious and difficult to perform but there are useful techniques that in most cases give reliable results (Shaffer etal, 1987). 

Penetration—Indentation. Penetration and indentation tests have long been used to characterize viscoelastic materials such as asphalt, mbber, plastics, and coatings. The basic test consists of pressing an indentor of prescribed geometry against the test surface. Most instmments have an indenting tip, eg, cone, needle, or hemisphere, attached to a short rod that is held vertically. The load is controlled at some constant value, and the time of indentation is specified the size or depth of the indentation is measured. Instmments have been built which allow loads as low as 10 N with penetration depths less than mm. The entire experiment is carried out in the vacuum chamber of a scanning electron microscope with which the penetration is monitored (248). 

Low energy transitions for elements up to phosphorus (Z = 15), require operating conditions in a vacuum. The resolution can be as low as a few electron-volts. There exists models of this type which are adapted for scanning electron microscopes. 

Scanning electron microscope (SEM) systems are ideal for a pictorial representation of morphological features of single layers of multilayered paint samples (particularly those not well contrasted by optical microscopy as the white ones) obtained by the contrast of secondary (SE) and backscattered electrons (BSE). An important advantage of SEM is the ability to analyze even the smallest smears for this purpose the smears are lifted from the underlying material using double-sided adhesive tape transferred to the sample holder (e.g., slide). Twenty micrometers microtome sections of paint cross-sections are recommended. In order to avoid electrical charging the samples have to be carbon coated or transferred into the chamber of a low vacuum system. 

Samples were investigated using a scanning electron microscope (FEI QUANTA 200 ESEM). Air dried samples were fixed onto aluminum stubs through carbon adhesive disks and their fractured surface was observed with a low-vacuum secondary electron detector using the accelerating voltage of 25.0 kV. The samples were analyzed at room temperature and at an internal pressure of 0.50 torr. 

The fibers morphology was evaluated in a scanning electron microscope JEOL JSM5310 with a tungsten filament operating at lOkV, employing low vacuum technique and secondary electron detector. Samples were dispersed on a brass support and fixed with a double face 3M tape. 

Scanning electron micrographs (SEM) were obtained using a JSM 5500 LV (Jeol, Japan) electron microscope. The observations were performed in a secondary electron (SE) and in a backscattering electron (BSE) mode at a low vacuum pressure of 12 kPa. 

Microscopic measurements were performed by using a Quanta 200 ESEM (environmental scanning electron microscopy) instrument (EEY Company), operating in low-vacuum mode, with an electron beam emitted at 25 or 30 kV under 1 Torr (133 Pa) pressiue. Solid-state backscatter detector (SSB) allowed collecting backscattered electrons emitted from the samples. 

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