Extraction replicas

The size of the nanoparticles was determined with TEM after the final ion bombardment on the same sample. The samples for TEM investigation were prepared by extraction replica method. The particles were stripped off the substrate surface by means of collodion which was covered by carbon film. The collodion was dissolved after carbon deposition. 

Yamaguchi M, Kondo I. Immunoelectron microscopy of Proteus vulgaris by the plasma polymerization metal-extraction replica method differential staining of flagellar (H) and somatic (0) antigens by colloidal golds. J Electron Microsc 1989 38 382-388. 

When higher spatial resolution examination of specimens is needed, transmission electron microscopy (TEM) is utilized. Here a specimen thin enough to transmit the electron beam is required. This can be achieved by thinning the specimen directly or mounting it and thinning a cross-section. If small precipitates are the feature of interest, they can sometimes be examined by preparing carbon extraction replicas from the specimen. 

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. 

TEM examinations of the carbon extraction replicas provided basic information on in-service degradation mechanism of the steel. TEM micrographs of the replicas taken from the as-received specimen and from the after-service specimen were compared. In the received specimen sound... 

Structural studies were conducted on PE and PTFE (polytetrafluoroethylene) fibrils extracted by coating with C-Pt and stripping with a backing layer. In this case [299, 300] the backing layer was 5% PAA in water. After dissolution of the PAA, fibrils were left for TEM observation. Thin shreds or layers of rubber were tom off blends of natural mbber, polyisoprene, SBR and neoprene using gelatin for the extraction replica [311]. 

Figure 5.7 A transmission electron micrograph of a Xi02 precipitate that has been removed from an internally oxidized Cu-Ti alloy in a carbon extraction replica.

The TEM micrographs presented in Figure 4.9 show typical results obtained by means of the freeze fracturing technique applied to overbased calcium alkyl benzene sulfonate (OCABS) dispersion in dodecane. The OCABS aggregates, clearly identified by X-ray analysis on the extractive replica, appear as approximately spherical particles dispersed in the apolar medium [4, 35]. 

Figure 4.9 TEM micrographs recorded on a platinum shadowed replica prepared by FFET. (a) Sample prepared on 5 % dispersion of overbased calcium didodecylbenzene sulfonate in dodecane. Spherical nanoparticles of 10 nm diameter are easily visible, (b) Extractive replica prepared on the same dispersion. (c) X-ray analysis of the selected area (black circle) reveals the composition of the particles (Ca, S, O) corresponding to the sulfonate. The presence of Pt is due to the shadowing layer and copper to the copper support grid, (d) Radial distribution functions (from EXAFS studies) uncorrected from phase shifts obtained on caldte, and two OCABS dispersions in oil. The presence of a single peak corresponding to the first Ca-0 distance points out the amorphous structure of the mineral part of the OCABS particles...

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