Search

Purpose The purpose of this paper is to present the possibility of technology of chemical metallization for the production of electrodes and resistors based on Ni–P alloy on silicon (Si), alundum (Al2O3) and low temperature cofired ceramic (LTCC) substrates. The developed technology provides low cost in any form. Design/methodology/approach During the study monocrystalline Si plates and Al2O3 and LTCC substrates were used. On the surface of the substrates, the electrodes (resistors) by the electroless metallization were made. Subsequently, the electrical parameters of obtained structures were measured. Afterwards, trial soldering was made to demonstrate that the layer is fully soldered. Findings Optimal parameters of the metallization bath were specified. As a result of the research conducted, it has been stated that the most appropriate way leading to the production of soldered metal layers with good adhesion to the portion of selectively activated Si plate and Al2O3 and LTCC substrates comprises the following technology: masking, selective activation, nickel-plating of activated plate. Such obtained metal layers have a great variety of application; in particular they can be used for the preparation of electric contacts in Si solar cells, production of electrodes and resistors and production of electrodes in thermoelectric structures. Originality/value The paper presents a new, unpublished method of manufacturing electrodes (resistors) on Si plate and Al2O3 and LTCC substrates.

The purpose of the paper is to investigate X73MnSiAlNbTi25-1-3 high manganese austenitic steel containing 0.73% C to determine structural mechanisms decisive for increasing a reserve of cold deformation energy of such steel. The influence of a strain rate on the structure of the investigated steels and on the structural mechanisms decisive for their properties was analysed. Specialist research instrumentation was used for this purpose such as Scanning Transmission Microscopy (including EBSD examinations), conventional and high-resolution transmission electron microscopy together with diffraction examinations and metallographic examinations. It was found that the principal cause of an increased reserve of cold deformation energy of the investigated steels in dynamic conditions is the activation of mechanical twinning in the mutually intersecting systems in austenite grains and annealing twins, which are densifying when a cold deformation rate is growing, thereby confirming the basic mechanism of TWIP (TWinning Induced Plasticity).

The purpose of this paper is to determine the influence of high strain rates on the structure and mechanical properties of high-Mn austenitic TWIP steel. Low and high strain deformation rates in the range of 0.001 s–1 to 1000 s–1 have a significant effect on the forming of the structure and mechanical properties of high-manganese austenitic steel. Also, the strain energy per unit volume of advanced high-Mn TWIP steel containing Mn, Al and SI, with Nb and Ti microadditions, increases considerably in dynamic conditions. This group of steels not only shows excellent strength, but also excellent formability due to twinning, thereby leading to a unique combination of strength, ductility and formability when compared with conventional dual phase steels or transformation induced plasticity TRIP steels. The microstructure of the investigated steel was determined in metallographic investigations using scanning and high-resolution transmission electron microscopies (HRTEM). Results obtained in static and dynamic conditions for new developed high-manganese austenitic steel indicate their possible employment for the constructional elements of vehicles, especially passenger cars, to take advantage of the significant growth of their strain energy per unit volume. This guarantees a reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from the activation of twinning induced by cold working, which may lead to a significant growth of the passive safety of these vehicles' passengers.

Purpose – This paper aims to present the results of measurements of the photovoltaic structures made by electroless selective metallization technology. The developed technology provides low-cost contacts in any form, and parameters of photovoltaic cells made in this technology provide reliable results, comparable with those usually used. Design/methodology/approach – In this paper, photovoltaic cells with contacts based on Nip and NiCuP alloy were performed. As a substrate, mono- and multicristaline silicon was used. After photovoltaic cells have been prepared, sheet resistance of the contact layers and electrical parameters were measured. Composition and structure of contact layers were also measured. Findings – Obtained results of sheet resistance and contact layers are repeatable and comparable with previously published results. Electrical parameters of the photovoltaic cells made are comparable with used substrate and technologies. The authors have also noticed that the costs of the electroless metallization which is used to make contact layers is lower than metallization made by thick film or vacuum deposition technologies. Originality/value – The paper presents new, unpublished results of electrical parameters of photovoltaic cells with contact layers made by electroless metallization. The original idea is the usage of metallization in an acidic solution (pH = 2). In this proposed technology, photovoltaic cells on mono- and multicrystalline silicon plates were performed.

The aim of this paper is to determine the high-manganese austenite propensity to twinning induced by the cold working and its effect on structure and mechanical properties, and especially the strain energy per unit volume of new-developed high-manganese Fe – Mn – (Al, Si) investigated steel, containing about 24,5 % of manganese, 1% of silicon, 3 % of aluminium and microadditions Nb and Ti with various structures after their heat- and thermo-mechanical treatments. The new-developed high-manganese Fe – Mn – (Al, Si) steel provide an extensive potential for automotive industries through exhibiting the twinning induced plasticity (TWIP) mechanisms. TWIP steel not only show excellent strength, but also have excellent formability due to twinning, thereby leading to excellent combination of strength, ductility, and formability over conventional dual phase steels or transformation induced plasticity (TRIP) steels. Results obtained for high-manganese austenitic steel with the properly formed structure and properties in the thermo-mechanical processes indicate the possibility and purposefulness of their employment for constructional elements of vehicles, especially of the passenger cars to take advantage of the significant growth of their strain energy per unit volume which guarantee reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from activation of twinning induced by the cold working as the fracture counteraction factor, which may result in significant growth of the passive safety of these vehicles' passengers.

Purpose – This paper aims to present the possibility of the technology of chemical metallization for the production of contact of photovoltaic cells. The developed technology allows you to perform low-cost contacts in any form. Design/methodology/approach – The study used a multi- and monocrystalline silicon plates. On the surface of the plates, the contact by the electroless metallization was made. After metallization stage, annealing process in a temperature range of 100-700°C was conducted to obtain ohmic contact in a semiconductor material. Subsequently, the electrical parameters of obtained structures were measured. Therefore, trial soldering was made, which demonstrated that the layer is fully soldered. Findings – Optimal parameters of the metallization bath was specified. The equations RS = f (metallization time), RS = f (temperature of annealing) and C-V characteristics were determined. As a result of conducted research, it has been stated that the most appropriate way leading to the production of soldered metal layers with good adhesion to the portion of selectively activated silicon plate is technology presented below in the following steps: masking, selective activation and nickel-plating of activated plate. Such obtained metal layers have great variety in application and, in particular, can be used for the preparation of electric terminals in silicon solar cell. Originality/value – The paper presents a new, unpublished method of manufacturing contacts in the structure of the photovoltaic cell.

This paper presents of the results on the heat treatment parameters influence on the structure of the newly developed complex hot-work tool steel 47CrMoWVTiCeZr16-26-8 in relation to standard hot-work tool steel X40CrMoV5-1. After soft annealing the examined steels indicate the alloy ferrite structure with the great number of the carbides of the type of M 6 C and MC (nearing VC, (Ti,V)C and ZrC) as well as M 2 C 3 (nearing Ce 2 C 3 ) in the 47CrMoWVTiCeZr16-26-8 steel and with the carbides of the type of M 6 C, MC, M 23 C 6 as well as M 7 C 3 in the X40CrMoV5-1 steel. The volume fraction of carbides in the 47CrMoWVTiCeZr16-26-8 steel amounts to 8.2% and is higher then in the X40CrMoV5-1 steel. After hardening from temperature of 970–1180 °C the 47CrMoWVTiCeZr16-26-8 and X40CrMoV5-1 steels obtain the lath martensitic structure, partially twinned with a small fraction of retained austenite and the carbides partially undissolved in solid solution of the type of MC (TiC and ZrC) as well as M 2 C 3 in the 47CrMoWVTiCeZr16-26-8 steel and of the type of MC (VC) in the X40CrMoV5-1 steel. The 47CrMoWVTiCeZr16-26-8 steel characterises itself by the greater fraction of carbides partially undissolved in solid solution during austenitizing as well as by the greater resistance to the growth of primary austenite grains then the X40CrMoV5-1 steel. Tempering the examined steels within the range of temperatures between 450 and 540 °C results in starting the precipitation processes in martensite and the secondary hardness effect after tempering from temperature of 540 °C in the 47CrMoWVTiCeZr16-26-8 steel and from temperature of 510 °C for the X40CrMoV5-1 steel, which is caused by the carbides M 4 C 3 and M 7 C 3 in the 47CrMoWVTiCeZr16-26-8 steel and M 7 C 3 in the X40CrMoV5-1 steel.

The electrochemical performance of polyaniline thin films on platinum electrode substrates has been investigated using cyclic voltammetry in two aprotic ionic liquid electrolyte systems, 1-butyl-3-methyl imidazolium hexafluorophosphate (BMI PF6−) or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfon)imide (EMI TFSI). Enhanced redox stability of the polyaniline was observed in both electrolyte systems. Initial redox cycles in both ILs exhibited increasing current responses, over the first 10–20 cycles, which was attributed to the electrochemically induced ion exchange processes occurring within polyaniline film. Extended cycling after the redoping process was observed to result in a stable and reversible electrochemistry.

Solid complexes of apple pectin with egg albumin could be prepared from their aqueous solutions in the 12V gradient of potential on the stainless steel electrodes. The complexes were separated as a gel on anode. The composition of the complexes was dependent on the component ratio in solution and practically independent of pH of solution which varied from 4 to 11.6 within 90 min process. Elektrochemische Synthese von Polysaccharid-Protein-Komplexen. Teil 1: Vorlaufige Untersuchungen an Apfelpektin-Albumin-Komplexen. Feste Komplexe von Apfelpektin mit Eialbumin konnten aus ihren wasrigen Losungen im 12V-Potentialgradienten der Rostfrei-Stahlelektroden dargestellt werden. Die Komplexe waren als Gel an der Anode abgetrennt. Die Zusammensetzung der Komplexe war abhangig von dem Verhaltnis der Komponenten in Losung und praktisch unabhangig vom pH-Wert der Losung, der im 90min Prozes zwischen 4 und 11,6 variierte.

AIMS--To investigate the effect of pregnancy on serum concentrations of lipids, lipoproteins, and apolipoproteins. METHODS--Fasting serum concentrations of total cholesterol, triglyceride, low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), apolipoproteins AI, AII, and B, and lipoprotein (a) were measured in 178 women with normal glucose tolerance in the second and third trimesters of pregnancy and in a control group of 58 non-pregnant women of similar age. Data were analysed using the unpaired t test and by one-way analysis of variance. RESULTS--The pregnant women had significantly higher concentrations of total cholesterol, triglyceride, LDL cholesterol, HDL cholesterol, and apolipoproteins AI and B (p < 0.001) and apolipoprotein AII (p = 0.003) than the control women. The ratio of apolipoprotein B:apolipoprotein AI was significantly higher in the pregnant women than in the controls (p < 0.001), but the total cholesterol:HDL cholesterol ratio was not significantly different. No significant difference was found in the concentration of lipoprotein (a). CONCLUSIONS--Hyperlipidaemia is common in the second half of pregnancy. This may be a purely physiological response to pregnancy or it may be indicative of pathology in some women. These results warrant a follow up study to investigate whether the hyperlipidaemic response to pregnancy is variable and if so, whether it can predict future hyperlipidaemia in a manner analogous to that of impaired glucose tolerance during pregnancy, predicting non-insulin dependent diabetes in later life.

AIMS--To investigate differences in serum lipid, lipoprotein and apolipoprotein concentrations in pregnant women of different ethnic origin. METHODS--Serum lipid, lipoprotein and apolipoprotein concentrations were measured in 232 women (114 Caucasians, 118 Africans/Afro-Caribbeans), who presented consecutively for screening for gestational diabetes in the third trimester of pregnancy. RESULTS--African/Afro-Caribbean pregnant women had lower serum concentrations of total cholesterol, low density lipoprotein cholesterol, triglycerides, and apolipoprotein B and higher high density lipoprotein cholesterol and Lp(a) lipoprotein concentrations compared with Caucasian women. Apolipoprotein A1 concentrations were similar in the two groups. The differences were not attributable to differences in weight, age, parity, or postload plasma glucose levels. CONCLUSION--Ethnic origin is an important determinant of serum lipid, lipoprotein and apolipoprotein concentrations during pregnancy.

The Cholestech L-D-X lipid analyser (LDX) is one of the first fully automated desktop analysers to determine serum high-density-lipoprotein cholesterol (HDL-C) concentration, an important measurement for assessing dyslipidaemia, particularly in patients with non-insulin-dependent diabetes mellitus. We compared results of total cholesterol (TC), triglyceride (TG) and HDL-C concentrations measured by the LDX and by a standard (DAX) laboratory analyser from serum obtained from 40 patients in our diabetic clinic. The mean differences between the concentrations measured were not statistically significant, there being a very close correlation between methods (TC: LDX = 0.98. DAX + 0.06, r = 0.98, p