The influence of corrosion on the microstructure of thermally treated ZA27/SiCp composites

The influence of corrosion on the microstructure of ZA27/SiCp composites was examined. The composites were produced by compo casting technique and then subjected to the thermal treatment (T4 regime). Microstructural examinations were performed after 30-day exposure of thermally treated composites in the sodium-chloride solution. Corrosion processes have occurred in the composite matrix. Corrosion did not affect SiC particles in the composites. The local progress of corrosion in depth of the composite matrix was noticed in micro-cracks. Corrosion resistance of ZA27/SiCp composites was evaluated based on the mass loss of composite samples during the immersion test. It was found that corrosion resistance of the composites decreased with increase in content of SiC particles. The applied thermal treatment had a negative influence on the corrosion resistance of ZA27/SiCp composites

Corrosion behavior of compocasted ZA27/SiCp composites in sodium chloride solution

The corrosion behavior of particulate ZA27/SiCp composites in an aerated sodium chloride solution was studied. The composites were synthesized via compocasting with addition of 1, 3 and 5 wt.% SiC particles in the matrix alloy. Composite samples were immersed for 30 days in the 3.5 wt.% NaCl solution open to the atmospheric air. Surface appearance and microstructure of the composites were examined by means of optical microscopy and scanning electron microscopy, while corrosion rates of the composites were determined using the weight loss method. It was revealed that SiC particles were not influenced by corrosion. General uniform corrosion occurred in the composite matrices, mainly in the region of the η phase. Local corrosion was noticed in micro-cracks and near clusters of particulate reinforcements. Results of microstructural examinations and immersion test indicate a slightly lower corrosion resistance of the ZA27/SiCp composites compared to that of the matrix alloy

Corrosion behavior of compocasted ZA27/SiCp composites in sodium chloride solution

The corrosion behavior of particulate ZA27/SiCp composites in an aerated sodium chloride solution was studied. The composites were synthesized via compocasting with addition of 1, 3 and 5 wt.% SiC particles in the matrix alloy. Composite samples were immersed for 30 days in the 3.5 wt.% NaCl solution open to the atmospheric air. Surface appearance and microstructure of the composites were examined by means of optical microscopy and scanning electron microscopy, while corrosion rates of the composites were determined using the weight loss method. It was revealed that SiC particles were not influenced by corrosion. General uniform corrosion occurred in the composite matrices, mainly in the region of the η phase. Local corrosion was noticed in micro-cracks and near clusters of particulate reinforcements. Results of microstructural examinations and immersion test indicate a slightly lower corrosion resistance of the ZA27/SiCp composites compared to that of the matrix alloy

The Difference in Complex Psychomotor Reaction Time Between Patients With and Without Signs of Cerebral Circulatory Disorders

On a sample of 65 subjects rheoencephalography (REG) – the electrical impedance plethysmographic method for assessment of cerebral circulation was applied, as well as an electronic psychodiagnostic instrument Complex Reactionmeter Drenovac (CRD) constructed for assessment of complex psychomotor reactions. The aim of this study was to evaluate the potential differences between subjects with and without signs of cerebral circulatory disorders with regard to speed, stability and accuracy of complex psychomotor reaction. The results revealed that variable »maximal speed« on CRD showed significant difference between the groups, in favor of the control group

Determination of susceptibility to intergranular corrosion of stainless steels type X5CrNi18-10 in field

In this paper, the DL EPR method (electrochemical potentiokinetic reactivation with double loop) was modified and used to study the susceptibility to intergranular corrosion and stress corrosion cracking of a stainless steel type X5CrNi18-10. The tests were performed in a special electrochemical cell, with the electrolyte in the gel form. Modified DL EPR method is characterized by simple and high accuracy measurements as well as repeatability of the test results. The indicator of susceptibility to intergranular corrosion (Qr/Qp)GBA obtained by modified DL EPR method is in a very good agreement with the same indicator obtained by standard DL EPR method. The modified DL EPR method is quantitative and highly selective method. Small differences in the susceptibility of the stainless steel type CrNi18-10 to intergranular corrosion and stress corrosion cracking can be determined. Test results can be obtained in a short time. The cost of tests performed by modified DL EPR method is much lower than the cost of tests by conventional chemical methods. Modified DL EPR method can be applied in the field on the stainless steels constructions

The Difference in Complex Psychomotor Reaction Time Between Patients With and Without Signs of Cerebral Circulatory Disorders

On a sample of 65 subjects rheoencephalography (REG) – the electrical impedance plethysmographic method for assessment of cerebral circulation was applied, as well as an electronic psychodiagnostic instrument Complex Reactionmeter Drenovac (CRD) constructed for assessment of complex psychomotor reactions. The aim of this study was to evaluate the potential differences between subjects with and without signs of cerebral circulatory disorders with regard to speed, stability and accuracy of complex psychomotor reaction. The results revealed that variable »maximal speed« on CRD showed significant difference between the groups, in favor of the control group

A mathematical model for determining elliptical volumes of fluid contents by means of ultrasound

Predložena je formula za izračunavanje elipsoidnih volumena tekućeg sadržaja pomoću ultrazvuka kojim su izmjereni potrebni elementi za proračun. Predložena formula glasi: V = ABCπ/6. Model je ispitan na aparatu koji je za ovu priliku posebno konstruiran. Zbog tehničkih karakteristika aparature područje mjerenja bilo je ograničeno na volumene od 50 do 112 ml. Rezultati 32-ju mjerenja na modelu pokazali su veoma visoku povezanost između proračunatih i pravih vrijednosti koja je iznosila r = 0,979 i veoma točnu procjenu (najmanja razlika između proračunatih i pravih vrijednosti iznosila je 0,1 ml, a najveća 10,0 ml), pa se otvara mogućnost primjene ovog modela u medicinskoj dijagnostičkoj praksi.A mathematical model for calculating elliptical volumes of fluid contents by means of ultrasound is described. The suggested formula is: V = ABCπ/6. The model was investigated on the apparatus which was especially constructed for the purpose. Because of the technical characteristics of the apparatus the measuring range was limited to the volumes from 50 to 112 ml. The results of 32 measurements on the model showed a very high correlation between the calculated and real values (r = 0.979), and a high accuracy of evaluation (the lowest difference between the calculated and real values was 0.1 and the highest 10.0 ml). This opens a possibility of applying the model in medical diagnostic practice

Examination of the Corrosion Process Impact on the Microstructure and Mechanical Properties of Zn27Al1.5Cu0.02Mg Alloy Castings Reinforced with Silicon Carbide Particles

Na osnovu izvršenih istraživanja ustanovljeno je da postoji međusobna povezanost mikrostrukture, mehaničkih svojstava i korozionog ponašanja čestičnih ZA27/SiC kompozita. Livena ZA27 legura predstavlja metalnu osnovu za dobijanje kompozita. Struktura legure je tipična dendritna. Trajna transformacija dendritne u ne-dendritnu strukturu izvršena je tiksoformiranjem, dok je poluočvrsli rastop legure bio izložen dejstvu sila smicanja. Kompoziti su dobijeni kompokasting postupkom, uz infiltraciju 1, 3 i 5 mas.% SiC čestica u metalnu osnovu. Otpornost prema koroziji matrične legure i ZA27/SiC kompozita određena je na osnovu vrednosti za brzinu korozije u rastvoru NaCl (pH=6,7). Određivanje brzine opšte korozije izvršeno je metodom gubitka mase i elektrohemijskim metodama. Otpornost matrične legure prema koroziji veća je od otpornosti kompozita. Uticaj korozije na mikrostrukturu ispitan je primenom svetlosne i skenirajuće elektronske mikroskopije. Posle izlaganja uzoraka u rastvoru NaCl, promena granice tečenja (pri ispitivanju pritiskivanjem), uzeta je kao pokazatelj uticaja korozije na mehanička svojstva matrične legure i kompozita. U matričnoj leguri procesi korozije zahvataju oblast η faze i oblast smeše faza α+η, a koroziona razaranja su površinskog karaktera. Zapaženo je da je u kompozitima sa većim sadržajem infiltriranih SiC čestica (3 i 5 mas.%) došlo do stvaranja nakupina SiC čestica, što je dovelo do obrazovanja mikroprslina i mikropora. Na ovim mestima proces korozije napreduje u dubinu materijala, što se negativno odrazilo na otpornost prema koroziji i mehanička svojstva čestičnih ZA27/SiC kompozita.On the basis of examination carried out, the mutual dependence of the microstructure, mechanical properties and corrosion behaviour of particulate ZA27/SiC composites was established. As-cast ZA27 alloy was the metal matrix for producing composites. The structure of as-cast ZA27 alloy is typically dendritic. A permanent transformation of the dendritic structure into nondendritic one was achieved through thixoforming during exposure of ZA27 alloy semi-solid melt to the influence of shear forces. Composites were obtained by compocasting process, through infiltration of 1, 3 and 5 wt.% SiC particles into the metal matrix. Corrosion resistance of the metal matrix and ZA27/SiC composites was evaluated on the basis of corrosion rate in NaCl solution (pH=6.7). Mass loss method and electrochemical polarization measurements were used to determine rate of general corrosion. Matrix alloy resistance to corrosion is higher than the resistance of the composites. The influence of corrosion on the microstructure was examined using light and scanning electron microscopy. After exposure of samples in NaCl slution, compressive yield strength was taken as an indicator of corrosion impact on the mechanical properties of the matrix alloy and the composites. Corrosion process in the matrix alloy takes place through η phase (interdendritic phase rich in zinc) and α+η phase mixture, while corrosion damage is limited to the surface of samples. Agglomeration of reinforcing particles was noticed within composites with higher content of SiC particles (3 and 5 mas.% SiC) which resulted in formation of microvoids and microcracks. These were places where progress of corrosion processes in the depth of material was observed, which had a negative impact on the corrosion resistance and mechanical properties of particulate ZA27/SiC composites

Barium titanate thick films prepared by screen printing technique

The barium titanate (BaTiO3) thick films were prepared by screen printing technique using powders obtained by soft chemical route, modified Pechini process. Three different barium titanate powders were prepared: i) pure, ii) doped with lanthanum and iii) doped with antimony. Pastes for screen printing were prepared using previously obtained powders. The thick films were deposited onto Al2O3 substrates and fired at 850°C together with electrode material (silver/palladium) in the moving belt furnace in the air atmosphere. Measurements of thickness and roughness of barium titanate thick films were performed. The electrical properties of thick films such as dielectric constant, dielectric losses, Curie temperature, hysteresis loop were reported. The influence of different factors on electrical properties values was analyzed

Reconciling independence and accountability at the European Central Bank: the false promise of proceduralism

This article revisits the balancing act between independence and accountability at the European Central Bank (ECB). It contrasts procedural and substantive concepts of accountability, and challenges the mainstream idea that independence and accountability can be reconciled through narrow mandates, the indiscriminate increase of transparency, the creation of multiple channels of accountability, and the active use of judicial review. These assumptions form the pillars of a procedural type of accountability that promises to resolve the independence/accountability dilemma but fails to do so in practice. The article brings evidence to show how ECB accountability has become a complex administrative exercise that focuses on the procedural steps leading up to monetary and supervisory decisions while simultaneously limiting substantive accountability. The failure to acknowledge the trade-off between independence and accountability (said to be ‘two sides of the same coin’) has resulted in a tendency to privilege the former over the latter.Horizon 2020(H2020)716923Institutions, Decisions and Collective Behaviou