Papers by Keyword: Atomic Force Microscopy (AFM)

Abstract: Catalytic reforming is one of the most significant processes in the field of petroleum refineries and catalysts as they are considered as the heart of these processes .this paper presents the utilization of Atomic scale microscopy (AFM) to investigate the morphological and the surface properties of two catalytic reforming catalysts that are used in Iraqi refineries (RG582 & PR9). This paper provides a new insight into the study of catalysts since reaction routs significantly rely upon the used catalysts and their basic properties such as morphology, topography, roughness, growth regime and grain size. Keywords: Atomic Force Microscopy (AFM), catalytic reforming catalysts (CRC), surface properties.

Abstract: Fe@Au is a type of nanoparticle that contains magnetic Fe NPs core with a fine layer of Au NPs synthesized using the Pulsed Laser Ablation in Liquid (PLAL) Method. These Fe@Au NPs characterized by Atomic Force Microscope (AFM), Field Emission Scanning Electron Microscopy (FESEM), and UV-Visible Spectrophotometer. The result was obtained at different laser fluences (1.9, 2.2, and 2.5) J/cm² with fixed pulse duration 5 ns, wavelength 532nm and number of pulse equal 100 pulsed. The obtained mean size of Fe@Au NPs at laser fluence (1.9, 2.2, and 2.5) J/cm² was (63.65, 32.47 and 31.18) nm respectively. UV-Visible Spectrophotometer carves was showed a redshift toward longer wavelength by increasing particle size. Obtained results exhibited that the laser fluence plays a key role in the size, and dispersity of Fe@Au NPs.

Abstract: The paper presents the results of mass spectrometric studies of laser-stimulated desorption from the surface of thin films based on organic copper phthalocyanine molecules with peripheral substituents on gallium arsenide substrates. Thin films (30-80 nm) of copper phthalocyanine with peripheral substituents in this regard are studied for the first time. The composition of particles desorbed from the surface of CuPc and CuPcF₁₆ films by laser radiation of various wavelengths of 532 nm and 1.06 μm with a pulse duration of 10 ns was studied. The identification of the main fragments of molecules present in the desorption stream was carried out. It was shown that under the action of laser radiation, the surface is leveled and the films are fragmented, followed by desorption of molecular fragments.

Abstract: During low-temperature annealing, the segregation of the alloying element leads to a strong enrichment of the surface layer, causing a rearrangement of the surface electron structure. This change in the electron structure is manifested in the characteristic energy loss spectra. Annealing of single crystals at 400–500 K leads to an increase in the density of surface electron states. As shown by the calculations of the surface potential using experimental data on the temperature dependence of the surface concentration, dopant segregation causes a linear increase in the surface potential.

Abstract: The aim of this work was an attempt to verify two concepts of cathode modules, and the qualification of structure analysis of nitride coatings with the addition of silicon. The analysis covered one of the most commonly used in industrial conditions AlCrSiN coatings manufactured by the planar ARC and rotating (LARC^®) technology, which have recently gained more and more recognition in the production of coatings by physical vapour deposition (PVD) technique. Their microstructure was examined using transmission electron microscope (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Their mechanical and tribological properties were compared in terms of their application in the field of surface engineering. Tribological tests were performed in sliding friction conditions using the ball-on-disc method, where a ceramic Al₂O₃ ball was used as the counterpart. Presented research results allow to determine the relationship between the structure, wear resistance, and the specific module responsible for the number, type and position of cathodes used in the constitution of the tested coatings. This study complements and contributes to the knowledge on the direct influence of the chemical composition of the coating and the method of its production on the quality and structure of the coated element for wear-resistant coatings produced by PVD in the arc evaporation method (AE).

Abstract: Low friction thin layers are an excellent alternative for conventional coatings. They provide increased life of the elements, to which they were applied, due to enhancing the hardness or chemical and electrochemical resistance. They help to avoid the cracks, oxidation, as well as possible structural changes during the element's work. However, they primarily improve tribological properties by increasing wear resistance and reducing the friction. This also applies to components operating under variable conditions such as load, speed, temperature. The presented article analyzes the properties of various low-friction thin layers deposited by vacuum methods on the steel substrates. DLC, TiC, MoS2, CrCN thin layers were chosen, as they achieve the lowest possible coefficient of friction. In the framework of this work the measurements of adhesion of the investigated layers to the substrate as well as the friction coefficient, chemical analysis, microstructure and topographic analysis of the low-friction layers were carried out.

Abstract: In this paper, nanosteps were fabricated by a new method. This method used the energy of focus imaging of focused ion beam to peel the material surface for fabricating the nanosteps. By changing the number of focus imaging can get different deepness nanosingle-steps. Changing the magnification, the second-step can be fabricated on nanosingle-step. An atomic force microscopy was used to measure the 3D morphology of nanosteps. When the magnification was 25000, the deepness of nanosingle-step was 65.34±3.00 nm and the deepness of the first step of nanodual-step was 56.03 nm. When the magnification was 50000, the deepness of nanosingle-step was 142.28±3.54 nm and the deepness of the second step of nanodual-step was 178.68nm. This means that the redeposition made the deepness of the first step become bigger, that of the second step becomes smaller. Based on comparison and analysis, the relation of the depth, the magnification and the number of the focus imaging were obtained.

Abstract: Due to their specific properties magnesium and magnesium alloys find huge application possibilities mainly in automotive, engineering, transport and space industry. Important properties of magnesium alloys for engineering applications are high specific strength and high internal dumping values, while biocompatibility, biotoxicity and biodegradability open them the possibility to be used for biomedical applications. Development of new biodegradable magnesium alloys, investigation of new production and processing technologies on their properties and evaluation of corrosion degradation in simulated body fluids solutions are the main topics of the last decades.The paper offers a method simulating in-vivo tests for description of the corrosion process of potential biomedical materials in time using atomic force microscopy (AFM). To prove the proposed methodology detailed analysis of the corrosion degradation of AZ31 cast magnesium alloy in flowing Hanks’ balanced salt solution (HBSS) was performed. Corrosion degradation process of the examined alloy was influenced by different microstructural features and their interfaces. Results of the created corrosion galvanic cells and the corrosion attack evolution on the interface of the present intermetallic phases and the matrix led to profile changes detected by AFM.

Abstract: The Oliver–Pharr method has extensively been adopted for measuring hardness and Young’s modulus by indentation techniques. However, the method assumes that the contact periphery sinks in, which limits the applicability to the materials pile-up [1]. In this work, we characterize the pile-up (shape and height) in steel sheets with different mechanical properties and propose an improved methodology to calculate the real mechanical characteristics of steel sheets with significant pile-up. Pile-up correction of mechanical characteristics is based on ratio of pile-up height and contact depth. Pile-up height was measured by atomic force microscopy (AFM).

Abstract: Natural biodegradable and biocompatible polysaccharides chitosan, pectin, carrageenan and heparin were used to form thin nanostructured films. In this study using atomic force microscopy (AFM) and force spectroscopy the special characteristics of formation and structure of thin coatings were investigated, three models of the polymers interaction were proposed. Different mechanisms of polymers influence on each other in the bilayers formation were shown, coatings with different surface structure and mechanical properties were formed. The obtained data can be used for the preparation of nanostructured coatings with desired surface parameters.