In this work, w e are studying about a special oscillator system, which consists of one spring and a magnet-mass. The system is placed in nonlinear magnetic field, produced by two other permanent magnets, which are oriented for attraction, where can appear different types of oscillations. The magnetbody is simultaneously the subject of the linear field of spring and also of the nonlinear magnetic field of permanent magnets which has inverse quadratic dependence on distance. We are studying the ideal case, without friction, where the oscillations are produced wi th energy conservation, the oscillator system is started by applying the initial impulse and we consider the hypothesis that magnetic field produced by the permanent magnets is conservative and there is no loss of en ergy in the magnetic interactions. We are going to find the law of motion for the general case of study and a typically numerical application will be done.

The aim of this paper was the fabrication of Ni-Co and Ni-Co/barium ferrite (BaFe) nanowires in sulfamate electrolyte by using anodic aluminum oxide (AAO) as template. Self-ordered porous AAO membranes have been fabricated and used as templates in order to produce Ni-Co/BaFe nanowires. Morphological and structural studies of nanowires have been performed by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD), respectively. Energy Dispersive X-Ray Analysis (EDAX) was used for determination of the chemical composition. The nucleation process of nanowires was monitored by galvanostatic analysis. Our investigations showed the formation of the Ni-Co and Ni-Co/BaFe nanowires by incorporating nanoparticles during electrodeposition process. The magnetic investigations have been performed by using Superconducting Quantum Interference Device (SQUID) and the influence of the BaFe particles embedded in Ni-Co wires was revealed.

Pulsed laser deposition (PLD) proves to be successful for the preparation of bismuth oxide films, by using pure bismuth targets and oxygen atmosphere inside the ablation chamber. This paper proves that the wavelength and the number of laser pulses strongly influence the structure, morphology and optical properties of the films.

Electrodeposition can be used in order to prepare nanocomposite coatings made of nanoparticles dispersed into a metallic matrix, onto a metallic substrate. These kinds of coatings can combine the properties of the matrix and of the dispersed nanoparticles, which can lead to some interesting properties of the mixture. Including diamond nanoparticles into a metallic matrix can take advantage of the diamond properties, especially of its hardness and inertness in many chemical media. Still, the proper control of the electrodeposition parameters is a must in order to obtain the best microhardness and corrosion behavior of such nanocomposite coating. This paper proposes the comparative analysis between Ni/diamond nanocomposite coatings, prepared by electrodeposition, by varying several deposition parameters and the corresponding pure nickel coatings onto the same type of substrate, namely copper. Microstructural and morphological analysis of the two kinds of coatings are also performed and studied, along with microhardness measurements and corrosion resistance tests. It is concluded that specific electrodeposition technique and corresponding parameters must be used in order to prepare those Ni/diamond nanocomposite coatings with the best microhardness and best corrosion resistance.

Bismuth oxide thin films are investigated. Two oxidation methods are compared: thermal oxidation in air and pulsed laser ablation (PLD) in oxygen atmosphere of bismuth targets, respectively. It is found that PLD-prepared films have simpler structure, more uniform morphology and slightly lower refractive index than those prepared by thermal oxidation.

SnO2 nanostructures thin films with thickness of 500 nm were prepared by electron beam-physical vapor deposition on glass substrate at temperature of 300, 373, 443, and 583 K. Structural and morphological properties of these nanostructured thin films were studied by Scanning and Transmission Electron Microscopy (SEM, TEM) and Atomic Force Microscope (AFM) methods. The changes in structural and morphological properties are found at different temperatures. Increase temperature causes important change of the structural and morphological properties. The sample prepared at 300 K has crystalline structure and the sample prepared at 583 K has amorphous structure. Roughness parameters have low values at 300, 373, 443 K as opposed to the values obtained at 583 K. This different behavior may be due to the amorphous structure of the sample that was observed in the TEM analysis.

Tin oxide (SnO) thin films were prepared onto glass substrates by thermal evaporation under vacuum. The substrate temperature was kept constant at 300 K during the film growth. The structural studies using transmission electron microscopy (TEM) analysis showed that the SnO thin films have a polycrystalline and tetragonal crystal structure with preferential orientation of (110) planes parallel to the substrate. Optical transmission and reflection spectra, at normal incidence, in the spectral range 300-1100 nm, are investigated. The optical properties of SnO thin films were determined. The optical energy band gap, Eg, has been estimated from the absorption coefficient values using Tauc’s procedure. It is found that the SnO thin films exhibit direct band gap.

The paper presents experimental results of the mechanical tests (alternating plane bending and Charpy impact) performed on samples obtained from X 65 PSL 2 steel slabs. Samples were taken from different batches, cast at the same continuous casting machine. Since metallographic analyses indicates a heterogeneous micro and macrostructure, the samples were collected from different areas of the slabs (surface and middle). In order to highlight the influence of hydrogen embrittlement on mechanical characteristics of steel, some specimens were hydrogenated into hydrogen sulphide environment, for different periods of time. There were calculated the hydrogen embrittlement degree and the structural heterogeneity degree of the slabs structure with data from the two types of the mentioned tests. It is found that the hydrogen embrittlement mainly influences the fatigue characteristics. The structural differences between surface and middle of the slabs are mainly highlighted by the impact tests.

The goal of this study was to obtain an alumina template (AAO) by one-step anodization method and to evaluate its optical properties correlated with the annealing temperature. AAO was obtained from two different media: sulphuric acid (1.5 M H2SO4) and oxalic acid (0.4 M H2C2O4) at a potential of 15 V and 40 V, respectively. AAO morphology and chemical composition had been investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The average pore diameters such as 20 nm for AAO obtained from H2SO4 and 40 nm from H2C2O4 were measured. The crystalline structures of AAO samples annealed at three different temperatures of 150 ºC, 300 ºC and 350 ºC were studied by Xray diffractometry (XRD). The effect of annealing temperature on the optical properties of AAO was studied by UV-VIS spectrophotometry.

Copper plating was performed on nickel substrate by means of the potentiostatic electrodeposition method from a sulphate electrolyte solution. The copper coatings morphology was studied by means of the optical and electronic scanning microscopy techniques. The uniform electrodeposited films have a thickness of about 15 µm measured in cross-section. The corrosion behaviours of nickel substrate and copper films in different corrosive environments were studied. The corrosion study was performed by means of the linear polarisation method in four acid environments: 0.5 M H2SO4, HCl, HNO3 and glacial CH3COOH. From the recorded Tafel curves it was possible to obtain some information about the corrosion rate and the polarization resistance. In order to confirm these results, the gravimetric parameter was calculated by means of the “mass loss” method. By means of the X-ray diffraction analysis, the crystallographic structure of the specimens before and after corrosion was revealed. By means of the spectrophotometer device, the optical properties of the specimens were analysed.

This paper deals with the preparation and characterization of thin Ni layers. The electrodeposition was carried out galvanostatically from a Watts bath at different current densities in the range from 1 to 10 A dm−2 and for deposition times between 900 and 7200 s. The structure and the morphology of the nickel coatings were investigated by SEM and XRD techniques. The microhardness of deposited layers, the electrochemical behavior and the corrosion properties of the deposits were investigated by means of Vickers microhardness, polarization measurements, and electrochemical impedance spectroscopy (EIS). The uniform deposits showed fine grains and good protection against corrosion.

The way to characterize the behaviour of a naval steel grade E36 subjected to the corrosive fatigue process is investigated. The tests were carried out by bending fatigue of plate specimens with thickness of 10 mm in the corrosive environment consisting of an aqueous solution of 3.5% of NaCl which is similar to seawater. Experimental results show that the principal mechanism of degradation of the superficial layer is based on the pit evolution,evidenced by electrochemical,micro and macro structural timely changes such as evolution of electrode potential,evolution of current density,polarization resistance,anodic and cathodic parameters,and dislocation density evolution.

Synthesis and characterisation of nanocomposite coatings consisting of Ag doped TiO2 nanocrystals at different concentrations have been carried out. Composites were obtained by electrochemical deposition using a slightly alkaline cyanide free electrolyte containing AgNO3 as Ag precursors. Morphology and crystalline structure of the Ag/TiO2 hybrid materials with up to 8.5 vol.-%TiO2 were compared with those of pure Ag coatings. The presence of TiO2 nanoparticles in the bath led to an increase in the degree of orientation of crystallites on [111] and [311] crystallographic directions. During the electrodeposition, the presence of TiO2 particles at the electrode/electrolyte interface retards the crystal growth, and hence, the composites possess smaller grain sizes. The surface morphology observations show that TiO2 nanocrystals were attached within the metallic matrix surface, and the appearance of the surface indicates a porous structure with different geometrically shaped grains; this is also confirmed by atomic force microscopy measurements.

Measuring the thickness of steel plates during the hot rolling process is crucial for getting the necessary feedback to obtain the desired values at room temperature. The dilatation and the phase transformations of steel occur during heating and subsequent cooling and rolling strongly influences the results of thickness measurements. The radiometric method provides the necessary means for making real-time and fully automatized measurements of steel thickness during rolling, if only the temperature correction is precisely known and taken into consideration. This article proves that the experimental results concerning the relative variation of steel thickness and corresponding mass-thickness variation can be correctly explained by means of the theory of metal dilatation correlated with the theory of nuclear radiation absorption when passing through a metal or metallic alloy, such as steel.

It is well known that during cold plastic deformation of metals at high pressure, some important mechanical and electrical properties of the deformed material are modified as well as structural changes typical to nanomaterials take place. X-ray diffraction was used to investigate texture, internal stresses, grain size and dislocation density in Al 99,5 % and CuE, subjected to hydrostatic extrusion. Evidence of favourable influence of the hydrostatic pressure on the material properties is presented.

The aim of this paper is to study the corrosion behaviour of AISI 316L Stainless Steel (SS) in various solutions with nanoparticle suspensions by electrochemical testing. It is very important to determine the chemical reactivity of AISI 316L SS in the presence of some aqueous solutions in order to characterize the biocompatibility with the human body. The tested corrosive environments are: demineralised and deionised water at different immersion times, aqueous solution of 0.1 or 0.2 g/l TiO2 as well as aqueous solution of 0.1 or 0.2 g/l Al2O3. The measurements at room temperature were made in a conventional three-electrodes chemical cell, using a platinum electrode, a calomel and an AISI 316 SS as working electrode. The corrosion process was examined by linear polarization (LP) using a Bio-Logic potentiostate. For the LP measurements the potential ranged between -1.15+1.13 V vs. SCE. The immersion time before each measurement was 60 sec. to assess an equilibrium open potential. From the LP curves, the corrosion potential and parameters such as corrosion current, the polarisation resistance and corrosion rate are determined. Under certain circumstances, the results show that the nanoparticle suspensions act as a protective layer on the AISI 316L SS sample surface.

The aim of this study was to synthesize titanium dioxide (TiO2) thin films coated on 316L stainless steel (316L SS) and to characterize hydroxyapatite (HAp) growing onto TiO2 layer coated on the metallic substrate. These films were obtained by the electrophoretic synthesis (EPS) method using an acidic electrolyte containing H2SO4 and TiO2 nanoparticles. The growth of HAp on TiO2 thin films was achieved by immersion in simulated body fluid (SBF) during different periods of time in order to evaluate the bioactivity of structure in vitro study. The obtained coatings were characterized by XRD, SEM, AFM and EDX measurements. The XRD results reveal a crystalline phase (anatase) of TiO2 nanoparticles. The presence of TiO2 nanoparticles in the bath led to the preferential orientation of TiO2 crystallites after [101] crystallographic direction. During the coating EPS process, the presence of TiO2 provides more nucleation sites which are favourable to the adherence of nanoparticles on the metallic substrate. The surface morphology observed by SEEM analysis showed that TiO2 nanocrystals were attached on metallic surface. The appearance of the surface indicates porous structure and island-like cracked morphology with polygonal shapes. The roughness of the coating is in good agreement with standards for biomaterials which is proved by AFM measurements. The EDX spectra also confirm the presence of the Ca2+ and PO43- ions in the structure obtained by EPS method.

Electrodeposition processes using direct current (DC) require the use of additives to control deposit structure and properties as well as current distribution. This work presents a study on the influence of electrodeposited nickel prepared from a Watts bath at different current density ranging from 1 Adm(-2) to 10 Adm(-2) at pH = 4. The structure of the nickel layers was investigated by scanning electron microscopy (SEM). Vickers hardness of deposited layers was also investigated. The electrochemical behaviour of the nickel layers was investigated by polarization potentiodynamic and electrochemical impedance spectroscopy methods. Protection level against corrosion was evaluated by polarization curves and Electrochemical Impedance Spectroscopy (EIS). Important results include the formation of uniform deposits showing fine grain and excellent protection against corrosion.