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In recent years, on the basis of FSP/FSW technologies, a number of new solutions, methods and variants have been developed, constituting not only proof of the continuous evolution of FSP/FSW technologies, but also of the huge scientific and application potential hidden in these methods [...]

The current COVID-19 pandemic situation and the associated restrictions have increased the amount of generated waste. It results from the necessity to wear personal protective equipment. Thus, the disposal of masks and gloves is a topical issue and requires immediate investigation. The main aims of this work are management and environmental studies of municipal solid wastes (MSW), which have been generated during the COVID-19 pandemic time. Effective waste management in relation to a circular economy is presented. A sample of refuse derived fuel (RDF) with a high content of plastics was used for the experimental and calculation studies. Pyrolysis was selected as the best thermal decomposition process for this kind of wastes. Proximate and ultimate analyses were performed for RDF and its products. Pyrolysis was carried out using a pilot-scale reactor with a continuous flow of 250 kg/h at 900 °C. Thermogravimetric analysis was applied during the pyrolysis investigation and showed that the main decomposition of RDF took place in the temperature range of 250-500 °C. The pyrolysis gas contained combustible compounds like CO (19.8%), H

Friction stir processing (FSP) was used to modify the surface layer of the AZ91 magnesium alloy. The treatment was carried out using a jet cooling nozzle, generating a stream of cold air and enabling intensive cooling of the friction stir processed (FSPed) zone. Single-pass FSP was carried out using a tool rotational speed of 500 rpm and travel speed of 30 mm/min. The treatment was conducted using a truncated cone-shaped tool with a threaded side surface. Strong grain refinement and microstructural changes typical for FSP were found in all the samples. Very fine, equiaxed recrystallized grains dominated in the stirring zone. In the samples modified with the jet cooling nozzle, greater grain refinement was obtained than in the case of naturally-cooled material. The average grain size in the surface part of the stirring zone was 1.4 µm and 9 µm in the samples with air cooling and with natural cooling, respectively. Both the naturally-cooled specimen and air-cooled specimen were characterized by a distinctly higher hardness than the base material. The average Vickers hardness in the stirring zone was 91 HV0.1 in the FSPed sample with the air-cooling system and 85.5 HV0.1 with natural cooling, respectively. The average Vickers hardness of the as-cast alloy was 64 HV0.1. Slightly higher wear resistance of the FSPed samples using a jet cooling nozzle was found in relation to the naturally-cooled sample. Based on the conducted research, high efficiency of the jet cooling nozzle in cooling the modified zone during friction stir processing was found.

A rolled plate of 7075 aluminum alloy was friction-stir-processed (FSP) with simultaneous cooling by an air stream cooled to −11 °C with a jet cooling nozzle. Two variants of air blowing were used: at an angle of 45° to the sample surface and at an angle of 90°. The reference material was a sample subjected to analogous treatment but naturally cooled in still air. The microstructural tests revealed strong grain refinement in all the samples, with higher grain refinement obtained in the air-cooled friction-stir-processed samples. For the naturally cooled samples, the average grain size in the near-surface area was 7.6 µm, while for the air-cooled sample, it was 1.4 µm for the 45° airflow variant and 3.2 µm for the 90° airflow variant. A consequence of the greater grain refinement was that the hardness of the air-cooled friction-stir-processed samples was higher than that of the naturally cooled samples. The improvement in abrasive wear resistance was achieved only in the case of the friction-stir-processed specimens with air cooling. It was found that the change in the air blowing angle affects not only the degree of grain refinement in the stirring zone, but also the geometrical structure of the surface. In all the samples, FSP caused redistribution of the intermetallic precipitates combined with their partial dissolution in the matrix.

The main goal of the work was to evaluate the vitrification process of asbestos-cement waste (ACW). A mixture of 50 wt% ACW and 50 wt% glass cullet was melted in an electric furnace at 1400 °C for 90 min and then cast into a steel mold. The vitrified product was subjected to annealing. Optical microscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to evaluate the effects of the vitrification. The chemical constitution of the material before and after the vitrification process was also analyzed. It was found that the vitrified product has an amorphous structure in which the components of asbestos-cement waste are incorporated. MIR spectroscopy showed that the absorption bands of chrysotile completely disappeared after the vitrification process. The results of the spectroscopic studies were confirmed by X-ray studies - no diffraction reflections from the chrysotile crystallographic planes were observed. As a result of the treatment, the fibrous asbestos construction, the main cause of its pathogenic properties, completely disappeared. The vitrified material was characterized by higher resistance to ion leaching in an aquatic environment than ACW and a smaller volume of nearly 72% in relation to the apparent volume of the substrates. The research has confirmed the high effectiveness of vitrification in neutralizing hazardous waste containing asbestos and the FT-IR spectroscopy was found to be useful to identify asbestos varieties and visualizing changes caused by the vitrification process. The work also presents the current situation regarding the utilization of asbestos-containing products.

Asbestos-Containing Waste (ACW) in the form of a fragment from an asbestos-cement board was subjected to high-energy milling in a planetary mill at a constant rotational speed of 650 rpm and for variable milling times: 1, 2, and 3 h. The initial and the milled materials were subjected to infrared spectroscopic examination to identify the asbestos variety and to evaluate changes in the structure caused by high-energy milling. FT-IR (Fourier Transform Infrared Spectroscopy) examinations followed optical microscopy and SEM (Scanning Electron Microscopy) studies as well as X-ray analysis of the phase composition. It was found that the asbestos fibres present in the asbestos-cement board were respirable fibres with pathogenic properties. Identifying asbestos using the spectroscopic method showed that chrysotile asbestos was present in the as-received ACW while no characteristics of absorption bands from crocidolite or amosite were found. The results of the spectroscopic examinations were confirmed by the X-ray phase analysis. During SEM investigations of the milled ACW, complete loss of the fibrous structure of chrysotile was observed. The FT-IR examinations of the milled material showed that with an increased milling time, the characteristic absorption bands characteristic for chrysotile diminished and already after 2 h of milling their almost complete decay was observed. Thereby, it was confirmed that high-energy milling results in destruction of the crystalline structure of the asbestos phase. The conducted studies have shown that the treatment of asbestos-cement materials using high-energy milling is an effective method for asbestos disposal, capable of competing with other technologies and solutions. Moreover, FT-IR spectroscopy was found to be useful to identify asbestos phases and to assess changes caused by high-energy milling.

FSP (friction stir processing) technology is a modern grain refinement method that is setting new trends in surface engineering. This technology is used not only to modify the microstructure of the surface layer of engineering materials, but increasingly more often also to produce surface composites. The application potential of FSP technology lies in its simplicity and speed of processing and in the wide range of materials that can be used as reinforcement in the composite. There are a number of solutions enabling the effective and controlled introduction of the reinforcing phase into the plasticized matrix and the production of the composite microstructure in it. The most important of them are the groove and hole methods, as well as direct friction stir processing. This review article discusses the main and less frequently used methods of producing surface composites using friction stir processing, indicates the main advantages, disadvantages and application limitations of the individual solutions, in addition to potential difficulties in effective processing. This information can be helpful in choosing a solution for a specific application.

The study assessed the possibility of using waste glass cullet from the screen part of CRTs (cathode ray tube) in the vitrification of asbestos-cement materials (ACM). The composition consisting of 50% by mass ACM and 50% by mass cullet was subjected to vitrification. The research material before and after vitrification was subjected to comparative analysis. As a result of vitrification, a transparent amorphous material was produced with a hardness about 7% higher than that of CRT glass and lower ion leachability in an aqueous environment compared to ACM. X-ray and spectroscopic examinations did not reveal the presence of chrysotile, i.e. a type of asbestos found in ACM. This fact proves that during vitrification the asbestos decomposed and formed a lattice of glass composed of the products of this decomposition. Moreover, the presence of heavy metals in the vitrified product was found, including Ba and Sr, the source of which was the CRT cullet. The obtained research results prove that ACM vitrification with CRT cullet leads to the effective utilization of both types of waste during one technological process. Therefore, the vitrification of ACM can be successfully carried out using waste CRT glass, and the harmless product obtained in the vitrification process can be used in practice. The use of CRT cullet in the vitrification of asbestos-cement materials will also have a positive impact on the environment as it will reduce the amount of electronic waste deposited in landfills.

In this study, surface remelting treatment of the AZ91 magnesium alloy by means of welding using a non-consumable electrode in an inert gas shield was carried out. Three variants of surface treatment were used, i.e. the single torch variant with a single heat source without cooling down the samples, the single torch variant with a single heat source and a cooling system with liquid nitrogen, and the double welding torch variant with a double heat source in the torches operating in a tandem configuration. Experimental verification of the applied apparatus solutions was based on both macro- and microstructural assessment of the obtained effects. Comparative analysis of the variants used and the obtained microstructural results allowed the authors to indicate the deficiencies and limitations of particular solutions and to single out the best solution that would be useful for modifying the surface layers of magnesium alloys, as well as other materials having a strong oxygen affinity.

The main objective of the study was the modification of the surface layer of magnesium alloy by the CO2 laser. The studied material was the commercial AZ91 magnesium alloy. The effectiveness of the alternations caused by the remelting process was verified on the basis of microscopic observation and corrosion investigations, i e, recording of potentiodynamic polarization curves, electrochemical noise measurements and hydrogen evolution rate measurements. For the adopted range of the treatment parameters, favourable changes were observed in the surface layer such as the refinement of structure and more uniform arrangement of individual phases. As a consequence of those favourable structural changes the improvement of the corrosion resistance of the alloy was achieved in comparison to its non-remelted equivalent. For the treated material corrosion rates expressed as corrosion current densities were at least three times lower than the appropriate values for the untreated alloy comparing them for the same period of samples immersion in the test solution. The obtained results have confirmed the effectiveness of the applied surface treatment resulting in favourable changes in the structure and corrosion properties of the AZ91 magnesium alloy.

The samples of the as-cast AM60 magnesium alloy were subjected to Friction Stir Processing (FSP). The effect of FSP on the microstructure of AM60 magnesium alloy was analyzed using optical microscopy and X-ray analysis. Besides, the investigation of selected properties, i.e. hardness and resistance to abrasion wear, were carried out. The carried out investigations showed that FSP leads to more homogeneous microstructure and significant grain refinement. The average grain size in the stirred zone (SZ) was about 6-9 μm. in the thermomechanically affected zone (TMAZ), the elongated and deformed grains distributed along flow line were observed. The structural changes caused by FSP lead to an increase in microhardness and wear resistance of AM60 alloy in comparison to their non-treated equivalents. Preliminary results show that friction stir processing is a promising and an effective grain refinement technique.

In the study, samples of AZ91 magnesium alloy were subjected to a surface remelting treatment by means of a continuous wave (cw) CO2 laser. The scope of the investigation included both macro- and microstructural examination, hardness measurements, and wear resistance tests. The investigation has shown that remelting treatment leads to a strong refinement of structure in the surface layer and a more even distribution of phases. Fine α-phase dendrites have been observed to dominate in the remelting zone. The dendritic arm spacing in the laser treated surface was in the range of 1–2.5 μm. The structural changes triggered by remelting have contributed to an increase in the hardness and the wear resistance of AZ91 alloy. The microhardness of the remelted zone has increased to 71–93 HV0.05 for single-strip remelting and to 84–107 HV0.05 for multi-strip remelting in comparison with about ~60 HV0.05 for untreated alloy. The friction coefficient has decreased from 0.375 for material w/o treatment to 0.311 for remelted material. SEM investigations of samples after tribological tests have revealed the presence of parallel grooves proving the occurrence of microploughing and micro cutting of the material during the tribological testing. The results of the conducted investigation have indicated a beneficial influence of the cw-CO2 laser remelting treatment on the structure and properties of AZ91 alloy.

In this study, modification of the AZ91 magnesium alloy surface layer with a CO2 continuous wave operation laser has been taken on. The extent and character of structural changes generated in the surface layer of the material was being assessed on the basis of both macro- and microscopy investigations, and the EDX analysis. Considerable changes in the structure of the AZ91 alloy surface layer and the morphology of phases have been found. The remelting processing was accompanied by a strong refinement of the structure and a more uniform distribution of individual phases. The conducted investigations showed that the remelting zone dimensions are a result of the process parameters, and that they can be controlled by an appropriate combination of basic remelting parameters, i.e. the laser power, the distance from the sample surface, and the scanning rate. The investigations and the obtained results revealed the possibility of an effective modification of the AZ91 magnesium alloy surface layer in the process of remelting carried out with a CO2 laser beam.

The paper evaluates the possibility of efficiently processing waste generated in the process of biomass torrefaction into a non-toxic material, suitable for practical reuse. The water was evaporated from the liquid fraction resulting from the torrefaction of Virginia mallow, after which the resulting sludge was subjected to vitrification. The vitrification process was carried out at 1450 °C using tempered glass cullet, which constituted 85% by weight of the total processed material. The obtained product was subjected to the following analyses: microstructural characterization, X-ray diffraction, energy dispersive spectroscopy, spectroscopic tests, as well as measurements of hardness and ion leachability in an aqueous medium. It was found that vitrification of the sludge obtained from the waste liquid fraction leads to incorporation of the inorganic components of the waste into the glass structure, and in the case of organic components, causes their thermal decomposition. As a result of vitrification, a product was obtained that has no toxic properties and is characterized by favorable utility properties, i.e. low ion leachability and high hardness, higher than the hardness of the glass used in the vitrification process. The conducted research showed that vitrification is an effective method to recycle waste generated in the production process of treated biomass, and the product of the vitrification process can be used, for example, in the production of glassy building materials.

In work, the modelling of a three-dimensional temperature field during surface modification of AlZn5.5MgCu aluminum alloy using GTAW (Gas Tungsten Arc Welding) technology is presented. GTAW is widely used for making welded joints using additional material (filler material). In the analyzed process, no additional material was used, and the effect of heat treatment was obtained by directly applying the electric arc to the surface of the material. The calculations were performed using Finite Element Method. The Goldak’s double ellipsoidal heat source model has been used in modelling. The thermal-mechanical properties of the material were assumed to depend on the temperature. The Workbench, DesignModeler, Mechanical, Fluent and CFD-Post modules of the ANSYS program were used for numerical simulations. In the description of the geometry of element heat treated, cube type elements were used, with density of grid in the heat affected zone. The temperature distributions in cross-sections of heated element as well as welding thermal cycles at selected points were analyzed. The results of numerical simulations were verified experimentally. Comparison of calculated and obtained in the experiment the fusion lines showed satisfactory compatibility.

7075 aluminum alloy in the T6 state was subjected to surface remelting treatment using Gas Tungsten Arc Welding (GTAW). The changes in the material microstructure were examined by means of light microscopy, scanning electron microscopy and EDS. Moreover, profilometric tests and comparative measurements of material hardness in the state before and after the treatment were conducted. In the remelted layer strong microstructure refinement and the disappearance of microstructure banding were found. A fine dendritic microstructure was dominant in the remelted zone. Use of the GTAW method reduced the number of intermetallic precipitates in the surface layer. A consequence of dissolving the precipitates was a decrease in the hardness of the material in relation to the hardness before the modification. All the samples were characterized by the presence of a remelted zone, a narrow partially remelted zone and a wide heat affected zone. With an increase in the heat source travel speed, and consequently less heat entering the remelted material, the dimensions of the individual zones decreased. The conducted research showed that GTAW technology can be used in the surface remelting treatment of aluminum alloys and can be a competitive solution in comparison to other technologies.

The main purpose of the study was to modify the surface layer of the AZ91 magnesium alloys with the use of the GTAW (Gas Tungsten Arc Welding) method. The remelting process was conducted with the use of an AC current with the concurrent cooling of the magnesium alloy in the liquid nitrogen bath. The assessment of the effectiveness of the treatment carried out with the use of the GTAW method was based on the analysis of the surface layer structure, and the investigation of hardness and the resistance to abrasion wear. Besides, the investigations of the corrosion resistance were carried out. The analysis of the treatment parameters combined with a macroscopic assessment and the structural changes in the surface layers allowed to distinguish some correlations attesting to the possibility of the remelting zone geometry shaping. The found structural effects of treatment such as significant refinement of the structure and its homogenization, as well as the positive results of corrosion investigations and mechanical tests proved that it is possible to achieve the intended research objectives and effectively modify magnesium alloys by the welding method.

The main aim of the study was the evaluation of magnesium alloy surface treatment effectiveness using high-energy heat sources, i.e. a Yb-YAG Disk Laser and the GTAW method. The AZ91 and AM60 commercial magnesium alloys were subject to surface layer modification. Because of the physicochemical properties of the materials studied in case of the GTAW method, it was necessary to provide the welding stand with additional equipment. A novel two-torch set with torches operating in tandem was developed within the experiment. The effectiveness of specimen remelting using a laser and the GTAW method was verified based on macro- and microscopic examinations as well as in X-ray phase analysis and hardness measurements. In addition, the remelting parameters were optimised. The proposed treatment methodology enabled the achieving of the intended result and effective modification of a magnesium alloy surface layer.

The primary objective of the study was to adapt the GTAW (Gas Tungsten Arc Welding) technique for the purposes of the surface remelting processing of non-conductive plasma sprayed coatings. Modification concerned the surface layer of complex oxide compositions based on ZrO2 and Al2O3, which had been applied onto a steel substrate using the plasma spraying technique. In the course of research it was demonstrated that the process of surface remelting of non-conductive oxide coatings may be successfully conducted using welding sources of heat provided that the standard welding station is previously redesigned and additionally equipped. The methodological and apparatus-related work undertaken led to the development and construction of a welding set with a free independent arc, in which the active participation of the oxide coating in the creation of the electric arc and its stabilisation has been eliminated. The effects of the remelting treatment on the structure of the plasma sprayed coatings have been investigated. The microstructures of both the as-deposited and the remelted coatings were observed by optical microscope and scanning electron microscope (SEM). Observation of the remelted coating structure allowed to distinguish areas with characteristic structural and morphological effects and changes in the structure thereof. On the basis of regularities noted and observations made, a zonal model of the remelted coating structure was put forward and elaborated.

Background: People with rheumatoid arthritis (RA) often have comorbidities with associated disability and complex medication regimens. Little published evidence exists about why people with RA require so many medications, although it is logical to hypothesize that this may relate to older age, longer duration of RA, more active RA, worse functional disability and a greater number of comorbidities. Objectives: We set out to quantify polypharmacy in RA and identify its predictors in an observational cohort. Methods: The case notes of 348 people receiving secondary care for RA were reviewed to record polypharmacy. The 28-joint Disease Activity Score (DAS28) was calculated and the Health Assessment Questionnaire (HAQ) and the Self-administered Comorbidity Questionnaire (SCQ) were completed. Results: The mean total number of medications was 5.39, with a maximum of 16; of these, a mean of 2.41 medications were directly for RA. A mediational relationship was identified: older age and longer RA duration were significant predictors of a greater total number of medications, but these relationships were explained by the greater number of comorbidities in older participants and those with longer RA duration. Polypharmacy was not related to RA activity or functional disability. Conclusions: Polypharmacy is common among people with RA and associates with older age and longer RA duration through a greater number of comorbidities. Regular review of the full treatment plan of individuals with RA by pharmacists and other health professionals specializing in rheumatology, to weigh the benefits and risks of each medication and their interactions in light of RA activity and comorbidities, is advocated. Copyright © 2007 John Wiley & Sons, Ltd.

Oxide Al2O3 + 13 wt.% TiO2 coatings, formed by means of plasma spraying on steel surfaces, were remelted using high-energy heat sources, i.e., the welding TIG (Tungsten Inert Gas) method and a cw-CO2 laser. The treated and untreated samples were subjected to comparative structural examination using both optical and scanning electron microscopes. For quantitative investigation of porosity, a computer image analyser was used. To analyse the phase transformations in oxide coatings, the X-ray diffraction method was utilised. Due to the polymorphic nature of Al2O3, the phase transformation of the Al2O3 + 13% TiO2 coating material was investigated at every stage of the performed modifications following the scheme: powder → sprayed coating → remelted coating. Additionally, the effect of the remelting treatment on the wear resistance and hardness of plasma-sprayed coatings was studied. The microstructural examination of the remelted coatings revealed numerous structurally positive and technologically beneficial changes such as reduction in porosity, chemical composition homogenisation, surface smoothing and increase in the structure dispersion. Further investigations provided evidence that the coatings improved by remelting possess enhanced mechanical properties. Also, the investigations confirmed the possibility of replacing laser techniques by the TIG method with a guarantee of obtaining similar results.

Carbide layers applied on the steel substrate by the plasma spraying method were remelted using high-energy heat sources. A diverse methodology of coating treatment was used: ranging from a single and multiple treatment with a continuous micro-plasma arc, through the treatment by the TIG (tungsten inert gas) welding method, to CO2 laser remelting. The quality of the remelted layers was evaluated based on macro- and microscopic structural examinations, x-ray phase analysis, tribological tests, and hardness measurements. The results of the investigations carried out confirmed the possibility of remelting sprayed coatings and obtaining layers free from faults and imperfections typical of plasma spraying. The micro- and x-ray structural examinations revealed, among other things, a significant reduction of porosity (both open and closed ones), homogenization of the chemical composition, smoothing of the surface, and the improvement of coating adhesion to the substrate. The present study is a continuation of th...