Analysis of Al2O3 Nanostructure Using Scanning Microscopy

It has been reported that the size and shape of the pores depend on the structure of the base metal, the type of electrolyte, and the conditions of the anodizing process. The paper presents thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of EN AW-5251 aluminum alloy. The oxidation of the ceramic layer was carried out for 40–80 minutes in a three-component SAS electrolyte (aqueous solution of acids: sulphuric 33ml/l, adipic 67 g/l, and oxalic 30 g/l) at a temperature of 293–313K, and the current density was 200–400 A/m2. Presented images were taken by a scanning microscope. A computer analysis of the binary images of layers showed different shapes of pores. The structure of ceramic Al2O3 layers is one of the main factors determining mechanical properties.The resistance to wear of specimen-oxide coating layer depends on porosity, morphology, and roughness of the ceramic layer surface.A3D oxide coatingmodel, based on the computer analysis of images froma scanning electron microscope (Philips XL 30 ESEM/EDAX), was proposed

Properties of composite alluminium oxide-graphite layers obtained by an electrolytic method

The paper presents the mechanical properties of composite aluminium oxide-graphite surface layers. The layers were obtained by an electrolytic method, on a EN AW-5251 aluminium alloy substrate, in electrolytes with different graphite concentrations. The layers produced were subjected to tests with use of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results of tests concerning the microstructure, thickness and microhardness of the layers are presented. aluminium-grafit. Warstwy otrzymano metodą elektrolityczną na podłożu stopu aluminium EN AW-5251, w elektrolitach o różnym stężeniu grafitu. Wytworzone warstwy poddano badaniom przy zastosowaniu elektronowej mikroskopii skaningowej (SEM) oraz spektrometrii fotoelektronów (XPS). Przedstawiono wyniki badań mikrostruktury i morfologii powierzchni oraz grubości i mikrotwardości warstw

The finite element method in tribological studies of polymer materials in tribo-pair with oxcide layer

We present an approach to the analysis of mechanisms of the tribological contact of a thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of the aluminium alloy EN AW-5251. The oxidation of the 50-μm ceramic layer was carried out for 60 min in a three-component electrolyte (SAS), a three-component electrolyte consisting of adipic, sulphuric and oxalic acid, at a temperature of 298.15 K and a current density of 3 A/dm2. A three-dimensional oxide coating model, based on the computer analysis of images from a scanning electron microscope, is proposed. Tribological tests of stresses, strains and dislocations formed in the oxide layer and in the sample material (a block) were conducted. Modified polytetrafluoroethylene (TG15, TGK20/5, TMP12) and polyetheretherketone with carbon fibre and graphite were used as samples for tests in the tribological couple rider-plate of a linear reciprocating friction tester. A tribological couple modelled in the Solid Edge CAD programme was subjected to numerical analyses using the finite element method in the Autodesk Simulation Multiphysics programme under conditions consistent with actual conditions for contact pressures of 0.25, 0.50, and 1.0 MPa

The Effect of Production Parameters of Oxide Layers on Their Nanostructure, Nanomorphology, and Surface Free Energy

Nanotechnology is currently a very promising field of materials science. One of the most recent directions of research in this field is the nanotechnology of the upper layers for applications in engineering kinematic systems. The paper presents the influence of the production parameters of Al2O3 oxide layers on an EN AW-5251 aluminum alloy substrate on the nanostructure, nanomorphology of these layers, and their energy condition. The energy level was determined on the basis of Surface-Free Energy (SFE), determined from wettability (contact) angle measurements using the Owens-Wendt method. Using systematic scanning, the geometric structure of the surface (SGS) was determined for the produced layers. By means of a scanning electron microscope (SEM), the surface morphology and structure, and the chemical composition of the layers (EDS) were analyzed. Computer analysis of the surface nanoporosity was performed by means of the ImageJ 1.50i program. It was noted in the investigations that the oxide layer production parameters induce changes in the surface free energy of the layers. Changes in the nanomorphology of the upper layers were also observed, depending on the anodizing parameters

Influence of Anodizing Parameters on Surface Morphology and Surface-Free Energy of Al2O3 Layers Produced on EN AW-5251 Alloy

The paper presents the influence of the surface anodizing parameters of the aluminum alloy EN AW-5251 on the physicochemical properties of the oxide layers produced on it. Micrographs of the surface of the oxide layers were taken using a scanning electron microscope (SEM). The chemical composition of cross-sections from the oxide layers was studied using energy dispersive spectroscopy (EDS). The phase structure of the Al2O3 layers was determined by the pattern method using X-ray diffractometry (XRD). The nanomorphology of the oxide layers were analyzed based on microscopic photographs using the ImageJ 1.50i program. The energetic state of the layers was based on the surface-free energy (SFE), calculated from measurements of contact angles using the Owens-Wendt method. The highest surface-free energy value (49.12 mJ/m2) was recorded for the sample produced at 293 K, 3 A/dm2, in 60 min. The lowest surface-free energy value (31.36 mJ/m2) was recorded for the sample produced at 283 K, 1 A/dm2, in 20 min (the only hydrophobic layer). The highest average value nanopore area (2358.7 nm2) was recorded for the sample produced at 303 K, 4 A/dm2, in 45 min. The lowest average value nanopore area (183 nm2) was recorded for the sample produced at 313 K, 1 A/dm2, in 20 min

Tribological properties of Al2O3 layers after thermo-chemical treatment

The article presents the influence of the thermo-chemical treatment of Al2O3 layers on their tribological properties. The Al2O3 layers were produced on the EN AW-5251 aluminium alloy by means of direct current anodizing in a three-component electrolyte. For the sake of comparison, some of the samples were thermochemically treated in three liquids (sodium sulphate solution, sodium dichromate solution, distilled water). The parameters of the production and thermo-chemical treatment were selected on the basis of two Hartley's plans. The tribological properties were determined on the basis of a tribological test carried out for a pin-on-disc friction pair on a T-17 tester in reciprocating motion. The tests were carried out in conditions of technically dry friction. Thanks to the tests, coefficient of friction µ and the mass wear, together with the intensity of the material wear were determined. The use of thermo-chemical treatment in the sodium dichromate solution contributed to an increase in coefficient of friction μ and a reduction in the wear intensity of the polymer from 36 μg/km (layer without thermo-chemical treatment) to 21.33 μg/km (layer after thermo-chemical treatment in the sodium dichromate solution).The conducted stereometric tests before and after the tribological test for selected samples allow the authors to state that the thermo-chemical treatment in the sodium dichromate solution increases the amplitude parameters of surface roughness. The study of the surface morphology of the layer with the lowest mass wear showed the formation of an additional sub-layer as a result of thermo-chemical treatment carried out in the sodium dichromate solution

Oxidative stress triggers aggregation of GFP-tagged Hsp31p, the budding yeast environmental stress response chaperone, and glyoxalase III

The Saccharomyces cerevisiae Hsp31p protein belongs to the ubiquitous DJ-1/ThiJ/PfpI family. The most prominent member of this family is human DJ-1; defects of this protein are associated with Parkinson's disease pathogenesis. Numerous recent findings reported by our group and others have revealed the importance of Hsp31p for survival in the post-diauxic phase of cell growth and under diverse environmental stresses. Hsp31p was shown to possess glutathione-independent glyoxalase III activity and to function as a protein chaperone, suggesting that it has multiple cellular roles. Our previous work also revealed that HSP31 gene expression was controlled by multiple stress-related transcription factors, which mediated HSP31 promoter responses to oxidative, osmotic, and thermal stresses, toxic products of glycolysis, and the diauxic shift. Nevertheless, the exact role of Hsp31p within budding yeast cells remains elusive. Here, we aimed to obtain insights into the function of Hsp31p based on its intracellular localization. We have demonstrated that the Hsp31p-GFP fusion protein is localized to the cytosol under most environmental conditions and that it becomes particulate in response to oxidative stress. However, the particles do not colocalize with other granular subcellular structures present in budding yeast cells. The observed particulate localization does not seem to be important for Hsp31p functionality. Instead, it is likely the result of oxidative damage, as the particle abundance increases when Hsp31p is nonfunctional, when the cellular oxidative stress response is affected, or when cellular maintenance systems that optimize the state of the proteome are compromised

Tribological properties of ceramic-carbon surface layers obtained in electrolytes with a different graphite content

W pracy przedstawiono tribologiczne właściwości kompozytowych warstw powierzchniowych tlenek glinu-grafit. Warstwy otrzymano metodą elektrolityczną, w elektrolitach o różnym stężeniu grafitu. Wytworzone warstwy skojarzono z tworzywem PEEK/BG w ruchu posuwisto-zwrotnym, w warunkach tarcia bezsmarowego. Przedstawiono rezultaty badań współczynnika tarcia pary ślizgowej i zużycia masowego tworzywa. Celem określenia mikrogeometrii powierzchni warstw tlenku glinu oraz warstw tlenek glinu-grafit przeprowadzono badania struktury geometrycznej powierzchni za pomocą profilografometru stykowego, przed i po teście tribologicznym. Zaprezentowano również obrazy struktury i morfologii powierzchni warstw tlenek glinu-grafit oraz tworzywa PEEK/BG wykonane przy zastosowaniu elektronowej mikroskopii skaningowej

The influence of anodic alumina coating nanostructure produced on EN AW-5251 alloy on type of tribological wear process

The article presents the influence of the anodic alumina coating nanostructure produced on aluminum alloy EN AW-5251 on the type of tribological wear process of the coating. Oxide coatings were produced electrochemically in a ternary electrolyte by the DC method. Analysis of the nanostructure of the coating was performed using ImageJ 1.50i software on micrographs taken with a scanning electron microscope (SEM). Scratch tests of the coatings were carried out using a Micron-Gamma microhardness tester. The scratch marks were subjected to surface geometric structure studies with a Form TalySurf 2 50i contact profiler. Based on the studies, it was found that changes in the manufacturing process conditions (current density, electrolyte temperature) affect changes in the coating thickness and changes in the anodic alumina coating nanostructure (quantity and diameter of nanofibers), which in turn has a significant impact on the type of tribological wear. An increase in the density of the anodizing current from 1 to 4 A/dm2 causes an increase in the diameter of the nanofibers from 75.99 ± 7.7 to 124.59 ± 6.53 nm while reducing amount of fibers from 6.6 ± 0.61 to 3.8 ± 0.48 on length 1 × 103 nm. This affects on a change in the type of tribological wear from grooving to micro-cutting

Wpływ swobodnej energii powierzchniowej na właściwości tribologiczne warstw tlenkowych wytwarzanych na stopie aluminium EN AW-5251

W artykule przedstawiono wpływ parametrów wytwarzania warstw tlenkowych na swobodną energię powierzchniową oraz właściwości tribologiczne tych warstw. Warstwy zostały wytworzone na stopie aluminium EN AW-5251 metodą elektrochemiczną, przy zmiennych wartościach temperatury elektrolitu oraz gęstości prądowej. Do wytwarzania warstw tlenkowych zastosowano elektrolit trójskładnikowy. Swobodna energia powierzchniowa wyznaczona została metodą osadzonej kropli poprzez pomiar kątów zwilżania, natomiast do obliczeń zastosowano metodę van Ossa-Chaunhury’ego-Gooda. Testy tribologiczne przeprowadzono na testerze tribologicznym T-17 w warunkach tarcia technicznie suchego dla ruchu posuwisto-zwrotnego. W testach tribologicznych jako próbki użyto kompozytu T7W