**2. Examination procedures and materials**

As the basis of the composite matrix, silicone low-molecular thermal shock resistant synthetic rubber CKTH brand A (silanol terminated polydimethylsiloxane, HO [–Si (CH<sup>3</sup> )2 O–] n H) was chosen. As a filler of CKTH-A rubber a natural schungit mineral was used (Zazhoginsky deposit, Carbon-Shungite Trade Ltd., Karelia, Russia) [3]. The rock is a natural composite, in the carbon matrix of which are distributed highly dispersed silicate particles and small amounts of other oxides. The chemical composition of schungit, according to [3], used in this work is shown in **Table 1**.

Fillers were both the original schungit from provider and the original schungit milled by us in a ball planetary mill PM100 (Retsch, Germany) under different environments. The fillers were added to the CKTN-A rubber according to the compositions given in **Table 2**, kneaded by hand, and then passed through rolls. The resulting mixtures were evacuated for 15 minutes; then, a catalyst No 68 was introduced with a certain concentration for each composition and again evacuated. The samples were placed in Teflon forms and cured [8]. **Table 2** shows the ingredients of the samples used and corresponding code of synthesized composites.

CKTN-A composites with silica fillers, precipitated silicon dioxide, and SIPERNAT 360 (Evonik Industries AG, Germany), were prepared analogues to composites with schungit. **Table 3** shows the ingredients of the samples studied.

The atomic-force microscope (AFM) easyScan (Nanosurf, Switzerland), operating in a contact mode at ambient conditions, using also the force modulation mode, or in the semi-contact mode with the phase contrast mode, was used. In a semi-contact mode, a SuperSharpSilicon probe (Nanosensors, Switzerland) with a tip radius of about 2 nm was


**Table 1.** Chemical composition of schungit (weight percentage).

mechanical strength. Reinforcement of these polymers is usually achieved with fillers. The nature of the interaction of matrix elastomers with fillers is determined by the chemical nature, dispersion, shape, activity of the filler particles, the possibility of chemical bonds between the components of composites, and the relationship between the processes of amplification and structuring. In the works of Mark and coworkers [1, 2], which generalize numerous studies, it is stated that the physical and mechanical properties of synthetic low-molecular-weight siloxane elastomers filled with silica are significantly enhanced. It is of great interest also for the search for new reinforcement fillers to PDMS. One of favorable proposals may be schungit [3]. In the development of advanced composites, it is advisable preliminary to perform the molecular computational modeling, which is an effective method of a virtual analysis of the structural, energetic, and micromechanical properties of micro- and nanomaterials. As reported in [4–6], the energetic and structural characteristics of elastomer complexes with silica or schungit have been calculated quantum chemically under developed NDDO/sp-spd semiempirical original program [7]. Numerical calculations on the supercomputer MBC-5000 in the Interdepartmental Supercomputer Center were performed. The microscopic characteristics of nanomechanical behavior, deformation, and strength characteristics of silica or schungit adsorbates with polydimethylsiloxane oligomer molecules during uniaxial tension based on this program in the cluster approximation were examined. It was deduced that one could expect a substantial reinforcement of physical-mechanical properties for such composites.

We used the conclusions of these calculations in the practical synthesis of siloxane composites with schungit and silica. The multistage physical-chemical modification technology for obtaining the active nanostructured schungit filler for rubbers, based on these quantum-

According to the results of [8], there is an increase in the tear resistance and in the specific work of the deformation during fracture, with preservation of the increased strength properties of synthetic thermally stable low-molecular-weight silicone elastomers based on CKTH-A, filled

To further elucidate the nature of the onset of strengthening effects, knowledge of the distribution of fillers in these elastomeric matrices is necessary. The surface structure of these composites, using atomic force and electron scanning microscopy, in the present chapter was

As the basis of the composite matrix, silicone low-molecular thermal shock resistant synthetic

was chosen. As a filler of CKTH-A rubber a natural schungit mineral was used (Zazhoginsky deposit, Carbon-Shungite Trade Ltd., Karelia, Russia) [3]. The rock is a natural composite, in the carbon matrix of which are distributed highly dispersed silicate particles and small amounts of other oxides. The chemical composition of schungit, according to [3], used in this

)2

O–] n H)

rubber CKTH brand A (silanol terminated polydimethylsiloxane, HO [–Si (CH<sup>3</sup>

chemical calculations, has also been developed.

16 Characterizations of Some Composite Materials

studied as extension of the studies [8–11].

work is shown in **Table 1**.

**2. Examination procedures and materials**

with micro- and nanoscale schungit and silica SIPERNAT 360.


**Table 2.** Ingredients of the synthesized composites with schungit filler.


**Table 3.** Ingredients of the synthesized composites with silica filler.

used. Image processing was performed using the SPIP™—advanced software package for processing and analyzing microscopy images at nano- and microscale (Image Metrology, Denmark). The scanning electron microscope (SEM) Merlin (Carl Zeiss, Germany) worked with an accelerating voltage of 5 kV and beam current of 300 pA. Investigations of the physical-mechanical properties of the composites were conducted on universal testing machine UTS-10 (Ulm, Germany), and nanoscale mechanical properties were studied with NanoTest 600 (MicroMaterials, UK) [8].

The AFM images data processing showed that the aggregate sizes of these nanostructured schungit fillers in composite C 308 are located in the range from 50 nm to 2 μm, and the near-

Atomic Force and Electron Scanning Microscopy of Silicone Composites

http://dx.doi.org/10.5772/intechopen.79537

19

Electron microscopic photographs of the C 308 composite are shown in **Figure 4a** and **b**. The SEM surface topography C 308 composite, prepared in the form of plate samples, is presented in **Figure 4a** and SEM images of its perpendicular cross section in **Figure 4b**. It is well known that the quality of many materials in particular of composites depends on a large extent on the homogeneity of the materials realized. Visualized by these methods

**Figure 3.** AFM surface images of C 308 composite. Scans 31.5 × 31.5 microns. Left—topography and right—phase contrast.

**Figure 2.** AFM images of the surface of the pure CKTH -A rubber C 300. Scans XY = 36.9 × 36.9 microns. Left—topography

est distance between them on average is 300 nm.

and right—phase contrast.
