Papers by Keyword: Surface

Abstract: The article deals with the corrosive effects of acids on the selected surface layers of concrete with/ without an epoxy coating. Concrete sample was placed in extreme environments, which represented the 40% sulphuric acid solution. In addition to measuring surface degradation of concrete, this work focused on the depth of acid penetration into the sample. It can be concluded that the long-term effects of aggressive environments severely degrades the concrete surface on the samples causing corrosion of Type II.

Abstract: The incorporation of biomaterials in human tissue requires methods to study the interface of the implant with the biological setting. We set out to study whether Photoacoustic spectroscopy with a higher level of sensitivity from the cantilever detector could simultaneously detect amorphous calcium phosphate and the bacteria. The calcium phosphate was synthesized, pressed into tablets, and then immersed in a solution containing S.epidermidis bacteria. Spectra were recorded after 1, 2, 3, 4 and 5 days. Deconvolution of the spectra at different time periods was able to separate bands belonging to the bacteria and carbonate bands arising from the calcium phosphate. This allowed the simultaneous identification of the biomaterial and bacteria. It was found that the PAS spectra could not identify the bacterial adhesion process due to the low concentration, but the amide peaks at 3 days inferred colonization of bacteria. This was confirmed by SEM that shoed an increase in the bacteria concentration. This is the first step in showing the simultaneous detection of calcium phosphate and bacteria by Photoacoustic spectroscopy, a method that required more research to show changes on the surface of the implant.

Abstract: Residual stress measurements were successfully performed on the representative IN718 fatigue specimens by X-Ray Diffraction. All surface residual stresses were found to be compressive. A stress gradient normal to the surface was observed on all specimens. The residual stresses tended to become less compressive with increasing depth into the parts. Residual stress measurement is the special requirement for NADCAP CRITERIA AC 7101/7. In this paper, residual stress measurements were successfully performed on two IN718 low cycle fatigue test specimens.

Abstract: In this paper, the durability of fabric formwork-based concrete made from supersulfated cement was studied. The study involved comparison of chloride and carbonation resistance, pH values, and water absorption between of surfaces of SSC, the one being cast and the other cast in fabric formwork. It was shown that the use of fabric formwork minimized the pore volume near the surface, maintained the pH values at higher profile depths and showed improved durability when compared to the mould-cast surface. Carbonation depths were reduced by approximately 35% and calculated ab sorption rates were found to be approximately 40% lower at the fabric cast surface, indicating that fabric formwork is a promising aspect towards promoting the comeback of SSC in construction.

Abstract: Copper indium gallium selenide/sulfide (CIGS) and copper zinc tin selenide/sulfide (CZTS) are two thin film photovoltaic materials with many similar properties. Therefore, three new processing steps – which are well-known to be beneficial for CIGS solar cell processing – are developed, optimized and implemented in CZTS solar cells. For all these novel processing steps an increase in minority carrier lifetime and cell conversion efficiency is measured, as compared to standard CZTS processing. The scientific explanation of these effects is very similar to its CIGS equivalent: the incorporation of alkali metals, ammonium sulfide surface cleaning, and Al₂O₃ surface passivation leads to electrical enhancement of the CZTS bulk, front surface and reduced front interface recombination, respectively.

Abstract: The research presents the capabilities of the method of plasma-electrolytic treatment of metal surface that define it as an innovative and resource-saving technology. It is characterized by the synergetic effect of the plasma-electrolytic technology on the surface being treated. The paper shows the effect of different plasma-electrolytic treatment conditions on change of metal physico-chemical and structural-energy properties.

Abstract: The specific features of atmospheric nitrogen surface nitriding of cold-rolled foils (the value of the coherent-scattering region is 10 nm) from stainless maraging steels after hardening in a confined space containing air are considered. Thermodynamic evaluation of the probability of influence caused by the confined space air on the phase transformations and solubility of the atmospheric nitrogen shows that the surface modification takes place in two stages: at the first stage, oxidation dominates; and at the second stage, predominantly the nitrogen absorption by the surface takes place. While changing, the nitrogen solubility reaches the maximum in the range of 10 – 22 % of Cr and has the largest values at the air pressure in the range of 0.001 – 0.04 MPa. Based on the nitrogen solubility diagrams, optimal conditions for the nitrogen austenite formation without the formation of nitrides are established. The developed method for nitriding allows the formation of nitrogen austenite layer of about 20 μm in thickness in the surface of nanostructured maraging steels without deteriorating the surface electrochemical properties.

Abstract: This paper contains the continuation of basic research from 2012 - the molar ratio influence to water glass coatings basic properties (adhesion, diffusion properties, surface quality) was expanded with basic resistance (combination of sun, UV light and rain). Most silicate coatings for concrete protection are currently based on potassium water glass. Water glass matrix itself is, however, insufficient for coatings matrix and often is modified by polymer substances for the coating purpose. Combinations of water glass basic matrix (Sodium, Potassium, Lithium, Sodium - Lithium and Potassium - Lithium) with the appropriate polymer modifiers is also content of the presented paper. Polymer dispersions modification effect to basic properties and resistance to developed silicate coating binder is also part of paper.

Abstract: In this work we accomplished a study concerning the surface state of acrylic prosthetic biomaterials both optimized and non-optimized and we studied their compatibility on test animals. Various methods are seeking to improve the quality of implants and minimally invasive devices for body analysis, the increase of biocompatibility and resistance to corrosion of materials intended to come into contact with biological tissues. Poly (methyl methacrylate) is used in a wide range of applications and offers increased resistance and color stability over time and it can be relatively easy to smooth and polish. The morphology and roughness of the surfaces in case of acrylic prosthetic biomaterials were analyzed by atomic force microscopy that provides qualitative information regarding the chemical uniformity from phase.

Abstract: It can be stated that over the last ten years in the European Union, the number of bone fractures caused by osteoarthritis has increased twofold. More than 100,000 hip or knee joints in total were implanted in Germany during one year. Within ten years, 5% of them have failed by aseptic loosening.The non-invasive determination of friction forces and control of their values during lubrication of cartilage cells on the superficial layer of human joint surfaces before implantation has a significant but not sufficient impact on the observation of the early abrasive wear of the cartilage joint and development of osteoporosis. From this fact was drawn the inspiration for the performed investigations related to the endoprosthesis surface parameters because knowledge of the roughness of prosthesis surfaces and friction forces and their control methods permits provision of a necessary standard deviation of the gap height and finally information about the implantation possibility. This paper has been prepared based on the objective of European Project UE Grant IRSES,612593, 2013-2016 to represent the methodology and goal of the idea described in and make a wider discussion possible on this subject for further developments during the realization.