Miroslaw Bramowicz

Surface micromorphology and fractal geometry of Co/CP/X (X = Cu, Ti, SM and Ni) nanoflake electrocatalysts

This paper analyses the three-dimensional (3-D) surface texture of Co/CP/X (X = Cu, Ti, SM and Ni, CP: carbonaceous paste) nanoflakes prepared electrochemically using a conventional three electrode system. The surface chemical composition of the samples was investigated by X-ray photoelectron spectroscopy (XPS). Surface images were recorded using scanning electron microscopy (SEM) and analyzed by means of the fractal geometry. Statistical, fractal and functional surface properties of the prepared samples were computed. The statistical functions applied to the SEM data were employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The analysis of the 3-D surface texture of Co/CP/X nanoflakes is essential to control the surface topography and for the correct interpretation of surface topographic features as well as its functional role. It also provides a compact representation of complex micromorphology information.

Fractal features and surface micromorphology of diamond nanocrystals.

This paper analyses the three‐dimensional (3‐D) surface texture of growing diamond nanocrystals on Au thin films as catalyst on p‐type Si substrate using hot filament chemical vapour deposition (HFCVD). Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), Raman, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were applied also to characterize the 3‐D surface texture data in connection with the statistical, and fractal analyses. This type of 3‐D morphology allows a deeper understanding of structure/property relationships and surface defects in prepared samples. Our results indicate a promising way for preparing high‐quality diamond nanocrystals on Au thin films as catalyst on p‐type Si substrate via HFCVD method.

Effect of electric field direction and substrate roughness on three-dimensional self-assembly growth of copper oxide nanowires

This paper analyses the three-dimensional (3-D) surface texture of Copper oxide nanowires grown on different substrates and in an electric field. Atomic force microscopy, X-ray diffraction and field emission scanning electron microscopy analyses were applied also to characterize the 3-D surface texture data in connection with the statistical, and fractal analyses. This type of 3-D morphology allows a deeper understanding of structure/property relationships and studies the effect of micromorphology on CuO nanowires grown in electric field and the impact of growth direction on their properties. It also provides a compact representation of complex micromorphology information.

Fractal Analysis of AFM Data Characterizing Strongly Isotropic and Anisotropic Surface Topography

This study discusses changes in the value of fractal parameters determined based on functions of structure S(t), generated in different directions of anisotropy of the examined surfaces. The analyzed material consisted of AFM calibration standards TGT1, PG and TGZ1 which were used as models of strongly isotropic and anisotropic surfaces. The topography of the examined surfaces was imaged by atomic force microscopy. The obtained results indicate that all surfaces can be described mathematically to identify fractal parameters in any anisotropic direction.

Microstructure, morphology and electrochemical properties of Co nanoflake water oxidation electrocatalyst at micro- and nanoscale

Nowadays, fossil fuel limitations and environmental concerns push researchers to find clean and renewable energy resources. Solar hydrogen production via water splitting reactions in electrochemical and/or photo-electrochemical systems has been accepted as a promising route and efficient electrocatalysts are involved in both. Here, cobalt nanoflakes with an oxide/hydroxide surface and a conductive metallic core are grown on commercially available steel mesh modified with carbon based nanocomposites as a support layer. The portion of reduced graphene oxide sheets was changed from 0 to 100 wt% and the correlation of this concentration with the surface morphology and electro-catalytic activity of the final electrode was studied systematically for the first time. Obtained results revealed the least over potential (224.2 mV) for the sample with 50 wt% rGO in the water splitting reaction which is promising for use in alkaline electrolysis devices.

Microstructure and micromorphology of Cu/Co nanoparticles: Surface texture analysis

This paper analyses the three-dimensional (3-D) surface texture of Cu/Co thin films deposited by DC-Magnetron sputtering method on the silicon substrates. The prepared Cu/Co nanoparticles were used as research materials. Three groups of samples were deposited on silicon substrates in the argon atmosphere and gradually cooled down to room temperature. The crystalline structures and elemental compositions were analyzed by X-ray diffraction (XRD) spectrum with conventional Bragg-Brentano geometry. X-ray diffraction profile indicates that Co and Cu interpenetrating crystalline structures are formed in these films. The sample surface images were recorded using atomic force microscopy (AFM) and analyzed by means of the fractal geometry. Statistical, fractal and functional surface properties of prepared samples were computed to describe major characteristics of the spatial surface texture of Cu/Co nanoparticles. Presented deposition method is a versatile, costeffective, and simple method to synthesize nano- and microstructures of Cu/Co thin films. This type of 3-D morphology allows to understand the structure/property relationships and to investigate defect-related properties of Cu/Co nanoparticles. Presented results confirm the possibility of preparing high-quality Cu/Co nanoparticles via DC-Magnetron sputtering method on silicon substrates.

Fractal features of carbon–nickel composite thin films

This work analyses the three‐dimensional (3‐D) surface texture of carbon–nickel (C–Ni) films grown by radio frequency (RF) magnetron co‐sputtering on glass substrates. The C–Ni thin films were deposited under different deposition times, from 50 to 600 s, at room temperature. Atomic force microscopy was employed to characterize the 3‐D surface texture data in connection with the statistical, and fractal analyses. It has been found that up to 180 s the sputtering occurs in more metal content mode and in greater than 180 s it occurs in more non‐metal content mode. This behavior demonstrated a strong link between the structural and morphological properties of C–Ni composite films and facilitates a deeper understanding of structure/property relationships and surface defects in prepared samples. Furthermore, these findings can be applied to research on the mechanisms to prepare and control high‐quality C–Ni films.

Influence of the artificial saliva storage on 3-D surface texture characteristics of contemporary dental nanocomposites

The aim of this study was to analyse the influence of the artificial saliva on a three‐dimensional (3‐D) surface texture of contemporary dental composites. The representatives of four composites types were tested: nanofilled (Filtek Ultimate Body, FUB), nanohybrid (Filtek Z550, FZ550), microfilled (Gradia Direct, GD) and microhybrid (Filtek Z250, FZ250). The specimens were polymerised and polished by the multistep protocol (SuperSnap, Shofu). Their surface was examined, before and after 3 weeks’ exposure to artificial saliva storage. The surface texture was analysed using the atomic force microscope (AFM). The obtained images were processed to calculate the areal autocorrelation function (AACF), anisotropy ratio Str (texture aspect ratio), and structure function (SF). The log–log plots of SF were used to calculate fractal properties, such as fractal dimension D, and pseudo‐topothesy K. The analysis showed changes in surface anisotropy ratio Str values, which became higher, whereas the Sq roughness (root‐mean‐square) reduced after the artificial saliva storage. All the samples exhibited bifractal structure before the saliva treatment, but only half of them remained bifractal afterwards (GD, FZ250), whereas the other half turned into a monofractal (FUB, FZ550). The cube‐count fractal dimension Dcc was found to be material‐ and treatment‐insensitive.

Fractal Nature of Nanocomposite Thin Films with Co NPs in a-C:H Matrix

The aim of the present article is to investigate experimentally the fractal nature of the 3-D surface morphology of nanocomposite thin films consisting of partially oxidized cobalt nanoparticles with a face-centered-cubic (fcc) structure embedded in a hydrogenated amorphous carbon matrix. The samples were prepared by reactive magnetron sputtering using acetylene gas under gas pressures varying from 2.1 to 2.9 Pa. The characterization of the films surfaces was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the obtained AFM images were analyzed dividing them into motifs of significant peaks and pits using a segmentation algorithm. This analysis revealed that these nanocomposite thin films are well described as monofractal structures presenting only one scaling exponent whose value was found within the range from 2.4 to 2.7 for the different samples.

Evolution of rough-surface geometry and crystalline structures of aligned TiO 2 nanotubes for photoelectrochemical water splitting

Nowadays, increasing awareness of environment and fossil fuels protection stimulates intensive research on clean and renewable sources of energy. Production of hydrogen from water through solar-driven splitting reactions is one of the most promising approaches in the field of photoelectrochemistry (PEC). In this work we have fabricated well-aligned, highly-ordered, smooth-mouth TiO2 nanotube arrays (TNAs) in a two-step anodization process of titanium foil, which were then used as photoelectrodes for PEC water splitting. It demonstrates for the first time correspondence between non-linear component characteristics of multiscale rough surface and crystalline structure of annealed TNAs measured at various fabrication stages and their photoelectrochemical response. The as-anodized TNAs with isotropic surface (deduced from AFM and SEM images) and largest figure of merit (according to their PEC performance) were annealed at 450 °C in air. Scale-invariant descriptors of the surface structure of the deposits involved: fractal dimension, corner frequency, roughness, size of nanostructures and their dominant habits. Moreover, X-ray diffraction data processed using the Rietveld method confirmed co-existence of various oxides, for example: TiO2 in the form of anatase, TiO and Ti3O5 phases in the TNAs under study pointing that previous well-established mechanisms of the TNA growth were to certain degree incomplete.