Tadeusz Knych

Characterization of Nanocarbon Copper Composites Manufactured in Metallurgical Synthesis Process

Currently, there is a worldwide search for new forms of materials with properties that are significantly improved in comparison to materials currently in use. One promising research direction lies in the synthesis of metals containing modern carbon materials (e.g., graphene, nanotubes). In this article, the research results of metallurgical synthesis of a mixture of copper and two different kinds of carbon (activated carbon and multiwall carbon nanotubes) are shown. Samples of copper–carbon nanocomposite were synthesized by simultaneously exposing molten copper to an electrical current while vigorously stirring and adding carbon while under an inert gas atmosphere. The article contains research results of density, hardness, electrical conductivity, structure (TEM), and carbon decomposition (SIMS method) for the obtained materials.

Antibiotic resistance, ability to form biofilm and susceptibility to copper alloys of selected staphylococcal strains isolated from touch surfaces in Polish hospital wards

BackgroundDespite the employment of sanitary regimes, contact transmission of the aetiological agents of hospital infections is still exceedingly common. The issue of microbe transmission becomes particularly important when facing multidrug-resistant microorganisms such as methicillin-resistant staphylococci. In the case of deficiencies in cleaning and disinfection procedures, hospital equipment made of copper alloys can play an important role, complementing traditional hospital hygiene procedures.The objective of this study was to characterize staphylococcal strains isolated from touch surfaces in Polish hospital wards in terms of their drug resistance, ability to form biofilm and susceptibility to antimicrobial activity of copper alloys.MethodsThe materials for the study were 95 staphylococcal strains isolated from touch surfaces in 13 different hospital wards from Małopolska province (the south of Poland). Phenotypic and genotypic antibiotic resistance were checked for erythromycin, clindamycin, gentamycin, ciprofloxacin, trimethoprim/sulfamethoxazole and mupirocin. Biofilm formation ability for the tested strains was checked with the use of culture on Congo red agar. Susceptibility to copper, tin bronze, brass and new silver was tested using a modification of the Japanese standard.ResultsOver 67% of the analysed staphylococcal strains were methicillin-resistant (MR). Four strains were resistant to all of the tested antibiotics, and 14 were resistant to all except mupirocin. Strains classified as MR had significantly increased resistance to the remaining antibiotic groups. About one-third of the analysed strains revealed biofilm-forming ability. Among the majority of species, biofilm-forming and non-biofilm-forming strains were distributed evenly; in the case of S. haemolyticus only, negative strains accounted for 92.8%. Susceptibility to copper alloys was different between strains and rather lower than in the case of the SA strain selected for comparison.ConclusionsCoagulase-negative staphylococci, the most commonly isolated in Polish hospital wards, should not be neglected as an infection risk factor due their high antibiotic resistance. Our experiments confirmed that touch surfaces made of copper alloys may play an important role in eliminating bacteria from the hospital environment.

The Influence of Heat Treatment Parameters on the Electrical Conductivity of AlSi7Mg and AlSi10Mg Aluminum Cast Alloys

Aluminum alloy casts are widely used in industry as elements for heat exchangers. In this case, the main requirements are the thermal conductivity and the mechanical properties of the alloy. According to the Wiedemann-Franz law, the thermal conductivity of the alloy can be expressed by its electrical conductivity. The paper presents the results of the research on the effect of the heat treatment parameters on the electrical conductivity of cast aluminum alloys, type AlSi7Mg and AlSi10Mg. The aim of the work is to determine the possibilities of obtaining the electrical conductivity of an alloy, while maintaining the required level of mechanical properties. The tests include the Brinell hardness measurements and the electrical conductivity evaluation by means of the eddy current method, on samples after artificial ageing. On the basis of the studies determining a range of heat treatments, it is possible to obtain 23.5 MS/m, in the case of AlSi10Mg, and 27 MS/m, in the case of AlSi7Mg.

Impact of the Direct Ageing Procedure on the Age Hardening Response of Al-Mg-Si 6101 Alloy

Al-Mg-Si alloys are used not only as construction material, but also as a material for electrical conductors. For this application, it is crucial for the alloy to achieve a balance between strength and electrical properties. This is achieved in practice by a combination of strain and precipitation hardening. The current paper focuses on a heat treatment procedure in which the EN AW 6101 alloy is cooled by a flowing air stream from the solutionizing temperature down to the artificial ageing temperature. The proposed procedure, unlike the common heat treatment leading to the T6 temper, allowed for the precipitation of the coarser β” phase with the presence of relatively wide precipitate-free zones. The age hardening response was investigated by Brinell hardness measurements, eddy current testing and microstructural observations using transmission electron microscopy (TEM). The applied heat treatment resulted in slightly lower strength (compared to the T6 temper), but improved electrical performance of the alloy.

Antimicrobial Properties of Selected Copper Alloys on Staphylococcus aureus and Escherichia coli in Different Simulations of Environmental Conditions: With vs. without Organic Contamination

Background: Hospital equipment made from copper alloys can play an important role in complementing traditional methods of disinfection. Aims of the study: The aim of this study was to assess the dynamics of the antimicrobial properties of selected copper alloys in different simulations of environmental conditions (with organic contamination vs. without organic contamination), and to test alternatives to the currently used testing methods. Materials and Methods: A modification of Japanese standard JIS Z 2801 as well as Staphylococcus aureus (SA) and Escherichia coli (EC) suspended in NaCl vs. tryptic soy broth (TSB) were used in tests performed on seven commonly used copper alloys, copper, and stainless steel. Results: A much faster reduction of the bacterial suspension was observed for the inoculum prepared in NaCl than in TSB. A faster reduction for EC than for SA was observed in the inoculum prepared in NaCl. The opposite results were found for the inoculum based on TSB. A significant correlation between the copper concentration in the copper alloys and the time and degree of bacterial suspension reduction was only observed in the case of EC. Conclusions: This study confirmed the antimicrobial properties of copper alloys, and additionally showed that Staphylococcus aureus was more resistant than Escherichia coli in the variant of the experiment without organic contamination. However, even for SA, a total reduction of the bacterial inoculum’s density took no longer than 2 h. Under conditions simulating organic contamination, all of the tested alloys were shown to have bactericidal or bacteriostatic properties, which was contrary to the results from stainless steel.

Research of the Laboratory Wire Drawing Process of Zinc

The paper present results of the research on the laboratory drawing process of zinc obtained in industrial conditions in the CCR by Properzi method. The force drawing, mechanical properties before and after process was measured and formability limit in drawing process was specified. Because the wire drawing process was on hot (above the recrystallization temperature) the material didn’t work hardening as a function of strain which reduces the ductility and breaking just after the die. The microscopic images of microstructure reveal the presence of large twins recrystallization reflecting the dynamic renewal structure.

Research into the Aluminum-Zirconium Alloys Dedicated for Electirical Purposes

The discussed subject matter concerns the influence of two kinds of Al-Zr alloy production technologies on the properties of the wires dedicated for electrical purposes. The paper presents research and the analysis of the research into the influence of the production technology and the processing technology on the ingot wires made from the heat resistant Al-Zr alloys as well as on the characteristics of the properties of the examined materials with the focus on the electrical and mechanical properties and their microstructure analysis. The materials subject to the mechanical and physicochemical research were materials manufactured in industrial and laboratory conditions in the form of the wire rod and cast bars as well as wires of various diameters drawn from them. The research concerned six Al-Zr alloys with the zirconium content from 0.05 to 0.32% of the mass.

Effect of Selected Alloying Elements on Aluminium Physical Properties and its Effect on Homogenization after Casting

Modern technology for near net shape aluminium alloy flat rolled products includes twin roll casting, cold rolling and heat treatment. The technology is most common for 1XXX, 3XXX and 8XXX aluminium alloys. In fact, this technology of cold forming is applied to materials with as cast structure which may in some cases limit formability during rolling. As a consequence, the fundamental operation for high quality products is a well chosen homogenization process of material after casting. During the homogenization of 8XXX alloys after twin roll casting, important changes in electrical conductivity of the material have been reported in the literature. Possibly, the observed effects are connected with the migration of alloying element atoms in the microstructure. This study presents the influence of selected alloying elements on the electrical conductivity and mechanical properties of aluminium. On this basis, it is possible to analyse the effect and level of diffusion of alloying elements from particles to matrix and from matrix to particles during homogenization of 8XXX alloys in as cast temper. Additional comparison of experimental results with theoretical considerations via Nordheim’s rule was also analyzed in this study.

A Study of the Influence of Strain Hardening and Precipitation Hardening Sequence on Mechanical Properties of AlMgSi Conductor Alloys

Precipitation-hardenable AlMgSi alloys grade 6101 of 0.5% Mg and 0.5% Si contents, are used for the construction of homogenous wires in overhead power lines. The dominating group of alloys with increased electrical conductivity is the AlMgSi alloy group, these are HC, EHC and EEHC type materials with tensile strength at approximately 300 MPa and electrical conductivity lower than conventional wires (56,5 – 54,3 %IACS). The study presents the results of the research of AlMgSi wires heat treatment in compliance with the PN-EN 50183 standard. The shaping of heat treatable AlMgSi alloy rods and wires properties is possible through an appropriate sequence of a precipitation hardening (during ageing) and strain hardening (during drawing processes). This paper is a comprehensive analysis of the technologies for the production of wires from AlMgSi alloys.

Effect of Iron Addition to Aluminium on the Structure and Properties of Wires Used for Electrical Purposes

Eight hypoeutectic aluminium alloys with iron content within the range of 0.07-1.09% by weight, were examined. The structure, the mechanical and electrical properties of wires used for electrical purposes were studied. The batch material for the drawing process was wire rod obtained from the continuous casting and rolling line by Continuus-Properzi method. It has shown a linear relationship between mechanical properties of wire rod, a higher plasticity of wire after drawing process and an increase in thermal resistance of the material with increasing iron content. The findings enable to draw conclusions of basic and application characteristics, pointing to the possibility of using aluminium with higher iron content in the wire drawing process of small diameter and microwires for the production of automotive bundles, accumulator cables and winding wires.