# Synthesis of Si-Fe Chondrule-like Dust Analogues in RF Discharge Plasmas
## 4 Results and Discussion  
The results of the identification carried out using a scanning electron microscope (SEM) show that the obtained particles have mainly spherical shapes and they form non-uniform agglomerates. The surface of the agglomerates is heterogeneous and their sizes range up to 700 nm (Figure 2). The mainly spherical shape of particles without well-developed edges suggests that the particles' structures are amorphous. During the collection, the particles and agglomerated clusters settled on the substrate surface, forming a thin porous film. The simple visual analysis shows that the density of such agglomerated clusters is low for the samples collected at 30 W (Figure 2a,b) plasma power (in contrast to the 60 W, Figure 2c,d), indicating the higher production growth yield of nanoparticles. No other significant differences were found in the structure and morphology of nanoparticles synthesised at different RF discharge powers. Figure 2: SEM images (with different scales) of samples at 30 W (**a,b**) and 60 W (**c,d**). The morphology of the obtained structures was analysed by TEM. The samples were placed onto a copper mesh. Figure 3a,b shows bright-field TEM images of the sample at different magnifications and indicates that it is mainly composed of spherically shaped nanoparticles that form chain-like agglomerated structures. The mean diameter of a single nanoparticle is in the range of 20-30 nm. The same trends can be seen in Figure 3c,d for the particles obtained at 60 W. There is no significant difference between Figure 3a,b and Figure 3c,d. Figure 4 shows the signal intensities at certain energies of different chemical elements presented in the synthesised particles and deposited from the vapour in the plasma environment, in which a high percentage of carbon and oxygen elements were observed. Chemical analysis shows a high carbon content, \(36\pm 4\) wt. % (\(47\pm 5\) at. %), and the rest is oxygen, which either originates from the HMDSO (C\({}_{6}\)H\({}_{18}\)OSi\({}_{2}\)) structure or from moisture, which is usually present in the argon flow and difficult to avoid even in a vacuum system. Oxygen impurity has been found in different studies in the growth of plasma-polymerised films using a mixture and Ar in vacuum systems. Also, as expected, in the deposit structure, \(12\pm 2\) wt.% (\(6\pm 1\) at.%) silicon and \(5\pm 1\) wt.% (\(2\pm 1\) at.%) iron are present in the deposited structure. Figure 5 shows the XRD spectra of synthesised particles at 60 W (the same trend is observed at 30 W) both before and after irradiation in the plasma accelerator (see Table 1). The obtained signals are interpreted using the versatile PDXL2 software package (PDF2 Release 2016 RDB), which provides various analysis tools such as automatic phase identification, quantitative analysis, crystallite size analysis, lattice constant refinement, Rietveld analysis, ab initio structure determination, etc. (Rigaku). PDXL2 supports various diffraction databases such as ICDD PDF-2, PDF-4+, COD, and ICSD. In our case, XRD was used with the following parameters: scan rate/duration time--10.0000 deg/min, step width--0.0200\({}^{\circ}\), scan range--3-90\({}^{\circ}\), registration range--20. Figure 3: TEM images (with different scales) of samples synthesised with a power of 30 W (**a,b**) and 60 W (**c,d**). The diffraction pattern before irradiation indicates that the synthesised particles primarily exhibit an amorphous phase (the broad and diffuse peak between 2-25\({}^{\circ}\) 2-theta), with small and weak peaks. After irradiation, a significant transformation occurs: there is a marked increase in the intensity of several distinct peaks, and additional peaks emerge, corresponding to elements such as iron (PDF card No: 00-052-0513), silicon (PDF card No: 00-047-1187), and other unidentified phases. This alteration can be attributed to the interaction with high-energy plasma flux.