Mechanisms and morphologies of cavitation damage of NN 70 steel

Broken test tubes for low-cycle fatigue testing of Nionicral 70 (NN-70) parent material (PM) steel and simulated heat-affected zones (SHAZ) were used to produce samples for cavitation resistance testing. Ultrasonic vibrational cavitation method (stationary sample method) was applied for testing in laboratory conditions. The test conditions and procedure, sample preparation and interpretation of results are defined by ASTM G32. The surfaces of the NN-70 PM and SHAZ steel samples were exposed to cavitation and damage monitoring over time. Measuring the weight loss of samples on the analytical balance after a certain time allowed us to determine the cavitation velocity as a measure of the material's resistance to the effect of cavitation. Scanning electron microscopy (SEM) was applied to monitor variations in surface morphology with changing test time. On the basis of the results of the cavitation resistance test, the morphologies of the surface damage for different exposure times of the cavitation of PM and SHAZ steel NN-70 samples were analyzed, as well as the mechanisms that led to the damage of the sample surfaces.

A review of fungal influenced corrosion of metals

The growth of fungi on the surface of metals has great influence on their structural integrity and failure. Their growth on metal surfaces is determined by their secreted metabolites which enable them to adapt to new environmental and nourishment conditions. Although information on the capacity of fungi to adapt to metal surfaces is scarce, most fungi growing on metal surfaces alter the composition of the metals involving it in the process of functional growth and metabolism. Changes in the composition and colour of the metals are some of the evidences confirming that fungus has penetrated the metal surfaces and use it to satisfy its nutritional need with resultant corrosion. In this work we tried to explain different mechanisms of fungal influenced corrosion from different perspectives ranging from the role of biofilms, corrosive media generation by fungal metabolism processes to electrochemical processes generated by fungal growth on metal surfaces. Finally, no single mechanism can conclusively explain all forms of fungal influenced corrosion because every mechanism is unique and applies to individual fungus, its metabolic biproducts or the growth pattern.

Comparison of theoretical and experimental investigation of protonation process of some thiones in acid media

PM3 semiempirical method was used for quantum chemical investigation in order to investigate the electronic properties and to determine the protonation centre in 1,2,4-triazoline-3-thione molecule. Confirmation of protonation center in acid media of investigated compounds was made using the values of atomic charges, as well as, proton affinity values. The results from semiempirical calculations indicated that the protonation center in the thione molecule was the sulphur atom. The behavior of thiones was investigated in mineral acid media using UV spectroscopy. The influence of the strength of the acid and its anion on the protonation process was discussed using three different mineral acids (perchloric, hydrochloric and phosphoric acid) for protonation. The protonation process in perchloric and hydrochloric acid took place in one step, while in phosphoric acid was not finished even when its concentration was to the highest degree. The dissociation constants of protonated forms (pKBH + ) and the solvation parameter m* values were calculated in accordance with "excess acidity" function method (Cox and Yates) using the absorbance data from the experimental and reconstructed spectra (Characteristic Vector Analysis (CVA)). The determined pKBH + values in hydrochloric acid had more negative value than those obtained in perchloric acid media. The pKBH + values were in agreement with the literature data for this class of compounds.

Detailed characterization of the Ti-O based thin films obtained by cathodic arc evaporation

Physicochemical properties of thin films on the base of titanium oxides, obtained by a cathodic arc evaporation on the surface of glass substrate are analysed in details. The analysis of these films was made by using XRD, FTIR, SEM, XPS analysis and ellipsometry. On the basis of these analyses, particularly analysis obtained by XPS, the oxidative state Ti and corresponding phases are determined through various film layers from the surface to the substrate. The depth of the various levels and their extinction coefficients and refractory indexes are estimated by ellipsometry.

Sample analysis of organically produced honey and conventionally produced honey in Western Serbia

Conventional method of honey production is widely spread in the area of western Serbia. Despite the advantages of honey production in an organic manner, beekeepers are still hesitant to take this step, regardless of the difficulties with placement of such honey on the foreign market, so their products are mainly sold on the domestic market. Besides the undeniable nutritional value, honey produced in the conventional way with proper use of agro technical measures and implementation of the wide range of products in the treatment of bee diseases, in its composition very often contain residues of hazardous chemical compounds, pesticides, antibiotics. Research on four qualitative differences of the content of certain substances between the conventional and organic honey producers has been conducted in western Serbia. The research obtained five manufacturers, out of which two were engaged in organic manner of production, while the remaining three dealt with the conventional honey production. After examining the area and the apiaries in question, interviews with honeybee producers, the sampling of honey took place. Upon performed analysis, it was concluded that one conventionally produced sample of honey was not safe for human consumption, due to presence of pesticides.

Thermal behavior and biological activity of [Co2(Cl)2 tpmc](BF4)2 complex

A large number of interesting Co (II) complexes with macrocyclicligands have been synthesized and the recognition of its complexes as important bioactive compounds in vitro and in vivo has aroused growing interest in these agents as potential drugs for therapeutic use in various diseases. Numerous available information on their bioinorganic properties and mode of action in several biological systems, combined with the new possibilities imposed by the development of medical chemistry, opens space for the development of a new generation of highly active drugs with minimized side effects which could add significantly to the current clinical research and practice. In this paper we attempt to present some properties of the earlier isolated the first Co(II)tpmc complex for which crystal structure confirmed chair conformation of macrocycle. Complex with formula (Co2(Cl)2tpmc)(BF4)2 (tpmc = N,N`,N``,N```tetrakis(2-pyridylmethyl)-1,4,8,11 - tetraazacyclotetradecane), was studied on thermal behaviour and biological activity. TG-DTA analysis indicates that complex decomposition in a single step in the range of 365 -435 °C. Investigated cytotoxic activity against two human cancer cell lines: HeLa (human cervix adenocarcinoma) and K562 (human myelogenous leukaemia). Complex was also preliminary assayed in vitro toward bacteria, fungi and mould together with the starting material for the synthesis (ligands, simple salts and solvents) as test substances. Investigated complex showed a moderate activity against strains of bacteria and were inactive against the tested fungi and mould. Minimal inhibitory concentration suppressing the visible growth of bacteria was determined. Biological investigations show the complex has significant cytotoxic potential.

Vitrification as a method of soil remediation

Various types of contaminated soil and hazardous waste that have a negative impact on the environment and human health can be treated with the vitrification process. This process is based on thermal treatment of contaminated soil or waste at high temperatures, with the addition of additives, whereby the soil/waste melts and a stable glass is formed. The resulting glass and glass-ceramic products have good mechanical resistance, chemically are resistant and immobilize contaminants, thus preventing their further negative impact on the environment. This paper presents a literature review of the vitrification process of different types of contaminated soil and hazardous waste.

Influence of digene tablet juice orally taken in on the corrosion resistance of orthodontic wire made of SS 18/8 in presence of artificial saliva

Dentists make use of orthodontic wires such as SS 18/8, SS 316, Ni-Cr etc., to regulate the growth of teeth. In the saliva environment these wires undergo corrosion. Aside from this, they undergo corrosion by the food items, juices and Tablets orally in taken. Corrosion resistance of SS 18/8 alloy in artificial saliva (AS) , in the absence and presence of Digene Tablet juice, has been investigated by polarization and AC impendance techniques. It is inferred that corrosion resistance of SS 18/8 alloy in artificial saliva decreases in presence of Digene Tablet. This is exposed by decrease in Linear Polarization Resistance (LPR) value, Charge transfer resistance (Rt) value, in impedance value, and increase in corrosion current and double layer capacitance value(Cdl). In presence of Digene Tablet, the LPR value decreases from 3488228 to 1629535 Ohmcm2. The corrosion current value increases from 1.447 x10-8 to 2.637x10-8A/cm2 . The Charge transfer resistance (Rt) value decreases from 37796 to 10481Ohmcm2 . The double layer capacitance value increases from 1.349x10-10 F/cm2 to 4.866x10-10F/cm2. The impedance value decreases from 4.857 to 4.428. Hence it implies that people with orthodontic wire made of SS 18/8 alloy should avoid taking Digene Tablet juice orally.

Influence of non-metallic inclusions on the destruction of mechanically loaded steel products

The paper describes in detail the reasons for the cracking of steel products, despite the fact that all the conditions of mechanical loading were met - the working stresses were much less than the maximum tensile stress of the applied type of steel. Deep metallographic analysis, as well as stress analysis show that the main cause is the formation of non-metallic inclusions in the material of the product, which essentially change its mechanical characteristic.

Candesartan: A pharmaceutical product as effective corrosion inhibitor for aluminum in acidic solution

The corrosion performance of aluminum in 1 M hydrochloric acid solution in the existence and absence of Candesartan drug was examined utilizing, potentiodynamic polarization (PDP) and AC impedance (EIS) tests. It was found that the inhibition efficacy (%IE) of Candesartan drug was influenced by its doses and temperature and reached to 92.9% at 40x10-6 M, 30oC. The adsorption isotherm agreed with Langmuir model. From Tafel data the investigated Candesartan drug acts as mixed kind inhibitor. The influence of temperature on the rate of dissolution and the thermodynamic parameters in the existence and absence of Candesartan drug were also, studied and explained. All tests gave similar results.