Replica technique

Cationic quaternary ammonium compounds such as distearyldimethylammonium-chloride (DSDMAC) used as a softener and as an antistatic, form hydrated particles in a dispersed phase having a similar structure to that of the multilayered liposomes or vesicles of phospholipids 77,79). This liposome-like structure could be made visible by electron microscopy using the freeze-fracture replica technique as shown by Okumura et al. 79). The concentric circles observed should be bimolecular lamellar layers with the sandwiched parts being the entrapped water. In addition, the longest spacings of the small angle X-ray diffraction pattern can be attributed to the inter-lamellar distances. These liposome structures are formed by the hydrated detergent not only in the gel state but also at relatively low concentrations. 

Fig 1. Electron micrograph of a platinum/carbon replica prepared by the fast-freeze, deep-etch, rotary-shadow replica technique printed in reverse contrast. Cell walls of onion parenchyma have an elaborate structure with many thin fibres bridging between thicker cellulosic microfibrils. Scale bar represents 200nm. 

Werner, A. E., M. Bimson, and N. D. Meeks (1975), The use of replica techniques and the scanning electron microscope in the study of ancient glass, /. Glass Stud. 17, 158-160. 

Fig. 2. Using the carbon replica technique, this is an electron micrograph of cubic silver bromide grains in which the comers have been slightly rounded due to the presence of a silver complexing agent. (Photo by Dr. Donald h Black, Eastman Kodak Company)...

Several applications of scanning force microscopy (SFM) and related techniques in polymer science have been given in the above sections. The reviewed results were gathered from surfaces of cross-sectioned bulk polymers, polymer-matrix composites, and polymer blends as well as free surfaces of polymer samples such as films, or surfaces prepared by means of replica techniques. The materials contrasts reported on range from several mechanical ones via thermal to electrical ones. 

Preparation of Electron-micrographs. The polystyrene-rubber polyblend sample was etched by solvent according to the technique developed by Traylor. A double replica technique was used to prepare the sample. The first replica was methylcellulose, the second platinum and carbon, 800 A. thick. 

Figure 6.25 Structures of different Me deposits on GaAs (hk ) [6.181], (a) RHEED pattern of Ni deposit on GaAs (111) (b) TEM image (replica technique) of a Pt deposit on photo-etched GaAs (100) (c) TEM image of Ru deposit on photo-etched GaAs (100).

Several studies report the use of replica techniques to assess abrasion in situ [45, 48], This methodology has also been successfully applied in vivo (see previous section). In this case, the wear is assessed using optical or interference microscopy. A drawback of this approach is that the production of replicas and positive copies inevitably provides a source of error and reduces the ability to measure small changes in tooth surface profile. 

Several attempts to characterize quantitatively pore structures in ultrafiltration membranes have been described in the literature. Preusser(lJ analyzed surface porosities of Amicon membranes, using a carbon replica technique and a high-resolution transmission electron microscopy (TEM). A similar approach was... 

While small (ca. <100nm), particulate samples can be viewed direcdy after shadowcasting (pseudoreplicas), larger samples require that the biological material be stripped away to form a high resolution replica. Replica techniques are advantageous over other methods, here, in that thicker specimens can be used. With this approach, only the evaporator device dimensions limit primary sample size. 

An early investigation by Tess and Schmitz (29) on styrene-butadiene paints demonstrated that use of hexylene glycol improved tensile strength, elongation, leveling, and scrub resistance of latex paints. Electron micrographs of the films, obtained by a replica technique, showed that use of the coalescent resulted in... 

In 1941, the replica technique was introduced to simulate surfaces of materials normally opaque to electrons (38). Radiation damage to the specimen became recognized (39). and special techniques for viewing pigment powders were devised (40). 

Two examples of the characterization of IP stiffness profiles using FMM are given in Fig. 8.6. In both cases mixtures of epoxy resin with aliphatic/cycloaliphatic amines were cured in the presence of a Cu component. The investigated surface was prepared either by a replica technique similar to that described in Fig. 8.4, or by sectioning of a bulk sample (see Fig. 8.6a, b and Fig. 8.6c,d, respectively). 

S. S. Scherrer, J. B. Quinn, G. D. Quinn, FL W. A. Wiscott, Fractographic Ceramic Failure Analysis Using the Replica Technique Two Case Studies, Dental Materials, 23 (11), (2006) 1397-1404. 

The specimens are Si-SiC open-cell foams produced by Erbicol SA, Switzerland. Replica technique and Si infiltration have been used which consist of three steps ... 

Specimen preparation. The specimen preparation is always a very important problem in any method used in TEM. As stated by Steeds [25], for CBED the specimen preparation is more or less demanding depending in the considered objective. The crystallographic information is easily disturbed by artefacts, defects or interfaces with other phases. The carbon extraction replica technique has proved to be successful for CBED, in this sense this technique is good for examining powdered particles when they are separated from other phases. Another advantage of the extraction is that strain from the matrix is released. 

The extent of the probable damage and the remaining life time of the furnace tubes operating at the creep range may be assessed on the basis of material examinations, including replica techniques, and confirmed taking into account the service records and corrosion rates, according to Appendix E of the American Petroleum Institute s Reconunended Practice [8]. 

Surfaces can be investigated by TEM by the replica technique. Since it is difficult to remove a replica from a polymer surface, two-stage techniques are usually necessary. The gold decoration technique to mark surface structures [2] has been tested, but the difficulties of removing the replica films from the surfaces are too great for wide application. SEM has been increasingly used because it is a very easy way to investigate... 

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