Thermal Stability and Phase Transformations of Multicomponent Iron-Based Amorphous Alloys

Due to their excellent functional properties enabling their applicability in different fields of modern technology, amorphous alloys (metallic glasses) based on iron have been attracting attention of many scientists. In this chapter, the results of multidisciplinary research of five multicomponent iron-based amorphous alloys with different chemical composition, Fe81Si4B13C2, Fe79.8Ni1.5Si5.2B13C0.5, Fe75Ni2Si8B13C2, Fe73.5Cu1Nb3Si15.5B7, and Fe40Ni40P14B6, are summarized in order to study the influence of chemical composition on their physicochemical properties and functionality. The research involved thermal stability, mechanism, thermodynamics, and kinetics of microstructural transformations induced by thermal treatment and their influence on functional properties. Determination of crystallization kinetic triplets of individual phases formed in the alloys is also included. The results obtained for different alloys are compared, correlated, and discussed in terms of the alloy composition and microstructure

Simply Prepared Magnesium Vanadium Oxides as Cathode Materials for Rechargeable Aqueous Magnesium Ion Batteries

Vanadium-oxide-based materials exist with various vanadium oxidation states having rich chemistry and ability to form layered structures. These properties make them suitable for different applications, including energy conversion and storage. Magnesium vanadium oxide materials obtained using simple preparation route were studied as potential cathodes for rechargeable aqueous magnesium ion batteries. Structural characterization of the synthesized materials was performed using XRD and vibrational spectroscopy techniques (FTIR and Raman spectroscopy). Electrochemical behavior of the materials, observed by cyclic voltammetry, was further explained by BVS calculations. Sluggish Mg2+ ion kinetics in MgV2O6 was shown as a result of poor electronic and ionic wiring. Complex redox behavior of the studied materials is dependent on phase composition and metal ion inserted/deinserted into/from the material. Among the studied magnesium vanadium oxides, the multiphase oxide systems exhibited better Mg2+ insertion/deinsertion performances than the single-phase ones. Carbon addition was found to be an effective dual strategy for enhancing the charge storage behavior of MgV2O6. © 2022 by the authors

Simply prepared Mg-V-O as potential cathode material for rechargeable aqueous magnesium ion batteries

Although today widely used in electronic devices and electric vehicles, lithium ion batteries encounter problem of future application, resulting from limited Li resources, relatively high costs and operational safety problems. Rechargeable magnesium batteries as a potential alternative to the Li-ion ones stand out because of their high theoretical specific capacity, high abundance of Mg resources, atmospheric stability, safety of handling, eco friendliness and low cost. Layered materials including oxides, sulphides and selenides are promising candidates for host materials for Mg2+ storage in rechargeable magnesium batteries. Slow migration of Mg2+ in the layered oxides, ascribed to the strong interaction between Mg and neighbouring O atoms, inspires researchers to look for the ways of improving their electrochemical performance. In this work, Mg-V-O material was synthesized by simple precipitation method, followed by thermal annealing. The obtained material is single-phase material consisted of MgV2O6 phase, according to the results of XRD, FTIR and Raman spectroscopy. Electrochemical test by cyclic voltammetry in aqueous solution revealed redox peaks corresponding to the insertion/deinsertion of Mg2+ ions into/from the material, but with poor current densities. In order to improve the electrochemical performance of the simply prepared Mg-V-O material, carbon was integrated with the Mg-V-O by sucrose-assisted thermal treatment. Although composed of several phases, the obtained Mg-V-O/C material exhibited around 40 times higher maximal specific current values of Mg2+ insertion/deinsertion than the Mg-V-O. Also, the electrochemical performance of the Mg-VO/ C for the insertion/deinsertion of Mg2+ ions was better than those of Al3+ and Li+ ions

Microstructure and crystal growth in thermally treated Fe73,5Cu1Nb3Si15,5B7 alloy

Thermal treatment of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy induces structural changes, including crystallization of several different phases and subsequent crystal growth. X-ray diffraction combined with differential scanning calorimetry were used to investigate these, to determine kinetic parameters and mechanism of individual steps, and the dimensionality of crystal growth using Matusita-Sakka method and texture analysis. It was found that after the alloy becomes fully crystalline, crystal growth of individual phases is, in general, impeded, leading to decreased dimensionality of growth. However, this does not impact the texture, due to lack of preferred direction of crystal growth.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

XRD and FTIR investigation of the structural and phase transformations of the composite material containing α-Fe2O3/CuFe2O4 phases in silica matrix

Military stuff handling the missile systems and radars can be exposed to pronounced microwave radiation, which is resulting in the serious impairment of employee health. Since hematite/silica and copper ferrite/silica composite materials are recognized in literature as suitable materials for microwave absorption, better insight in the properties of nanocomposites based on hematite and copper ferrite phases is of high importance for improvement of microwave absorption properties of mentioned materials. For this reason, composite material containing hematite and copper ferrite in silica matrix is prepared by sol-gel method. XRD and FTIR investigation are performed to study the structural and phase transformations of the examined material under thermal treatment. The obtained results are discussed in terms of temperature gradient, which is acting on the samples during the thermal treatment.9th International Scientific Conference on Defensive Technologies : Oct 15-16, Belgrade

NiA and NiX zeolites as bifunctional electrocatalysts for water splitting in alkaline media

NiA and NiX zeolites were prepared and characterised using XRD, FTIR and SEM, and subsequently tested as electrodes for hydrogen (HER) and oxygen (OER) evolution reactions in alkaline media. Linear sweep voltammetry and chronoamperometry techniques showed that NiA has higher catalytic activity for these two reactions, as evidenced by higher current densities, which can be correlated with a higher weight fraction of Ni in this electrocatalyst than in the NiX and with its higher conductivity. HER and OER kinetic parameters, including Tafel slope, exchange current density and apparent activation energy were evaluated. Electrochemical impedance spectroscopy analysis yielded values of the resistance of the solution, charge transfer and mass transfer, as well as double layer capacitance and pseudo-capacitance of the working electrode, at different potentials and temperatures. Unlike the HER, during which the mass transfer resistance of the adsorbed intermediate is dominant in the case of NiA, the OER impedance response is controlled by the charge transfer process itself at the potentials of interest for these process. The overall resistance related to the HER is lower for NiA than for NiX. © 2018 Hydrogen Energy Publications LL

Thermal stability and mechanism of thermally induced crystallization of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy

Investigation of thermal stability of the alloy revealed stepwise crystallization process, manifested by two distinct complex exothermic peaks in differential scanning calorimetry curves. Kinetic parameters of individual crystallization steps were found using the Kissinger and Vyazovkin methods. Structural characterization of thermally treated samples showed formation of different iron-based phases including α-Fe(Si), Fe2B, Fe16Nb6Si7 and Fe2Si and some metastable intermediary species. Morphology characterization of the surface and cross-section of the thermally treated samples showed granulated structure composed of several different phases and indicated occurrence of impingement effects during crystal growth. Value of estimated lifetime suggested very high stability against crystallization at room temperature and abrupt decrease of lifetime with temperature increase

Multivariate analysis of the contents of metals in urban snow near traffic lanes in Novi Sad, Serbia

During December 2009, snow was collected at twenty two locations across the urban area of Novi Sad, directly from roads and from traffic islands near crossroads. The total metal concentration was determined for each of ten metals (Al, Ca, Cu, Fe, K, Mn, Na, Ni, Pb and Zn) using the ICP-OES analytical technique. Ni was found to have the lowest concentration (0.0265 mg dm(-3)). Na was the metal with the highest concentration (10786 mg dm(-3)), which was the consequence of sodium chloride being used as a de-icing salt on the roads. The metal with the second highest concentration at all locations was Ca; this was most likely the result of soil dust. The Spearman rank correlation coefficients between analyzed metals were calculated to determine how the concentrations of the metals were related. Cluster analysis was performed on the obtained data sets, using both the hierarchical and partitioning methods in order to identify associations among metals and/or locations. It was shown that traffic density was not the most important factor that caused the differences between the concentrations of the metals in the samples

Ocena stopnia zaawansowania miażdżycy u dzieci i młodzieży z cukrzycą typu 1

Introduction: To evaluate the degree of atherosclerosis in children and adolescents with type 1 diabetes and its correlation with risk factors, traditional and other, such as anti-oxidative capacity of circulating blood and level of lipid peroxidation. Material and methods: Forty children and adolescents with type 1 diabetes with mean age 13.7 years were compared with 20 age- and sex-matched healthy control subjects. Association of carotid artery intima-media thickness (cIMT) with different risk factors measured in children with type 1 diabetes was evaluated. Results: Mean carotid IMT was higher in subjects with diabetes (p < 0.01) and was strongly associated with total cholesterol with an odds ratio of 4.08 (p = 0.016), LDL-cholesterol with an odds ratio of 2.78 (p = 0.037), length of disease with an odds ratio of 1.87 (p = 0.007) and positive family history (first- and second-degree relatives) of diabetes and early CVD (heart attack and/or stroke before the age of 60 years) with an odds ratio of 6.8 (p = 0.007). Conclusions: We found significantly increased cIMT in the diabetic patients compared to the healthy control subjects. Risk factors for the development of atherosclerosis included higher total and LDL-cholesterol, higher systolic blood pressure, positive family history of diabetes and early CVD and longer diabetes duration. In spite of the documented increased oxidative stress, we failed to establish a correlation between the oxidative stress parameters and cIMT values. (Endokrynol Pol 2012; 63 (6): 414&#8211;419)Wstęp: Ocena stopnia zaawansowania miażdżycy u dzieci i młodzieży z cukrzycą typu 1 oraz jego korelacja z czynnikami ryzyka, tradycyjnymi i innymi, na przykład potencjałem antyoksydacyjnym krwi krążącej i poziomem peroksydacji lipidów. Materiał i metody: Porównano 40 dzieci i nastolatków z cukrzycą typu 1, średnia wieku 13,7 roku, z 20 zdrowymi osobnikami stanowiącymi grupę kontrolną odpowiednio dobranymi pod względem wieku i płci. Oceniano związek pomiędzy grubością kompleksu błony wewnętrznej i środkowej tętnic szyjnych (cIMT) a różnymi czynnikami ryzyka ocenianymi ilościowo u dzieci z cukrzycą typu 1. Wyniki: Średnia wartość cIMT była większa u pacjentów z cukrzycą (p < 0,01) i wykazywała silny związek ze stężeniem cholesterolu całkowitego [iloraz szans (OR) 4,08; p = 0,016], cholesterolem frakcji LDL (OR 2,77; p = 0,037), czasem trwania choroby (OR 1,87; p = 0,007) i dodatnim wywiadem rodzinnym (krewni pierwszego i drugiego stopnia) w kierunku cukrzycy i wczesnego występowania chorób układu krążenia (zawału serca i/lub udaru mózgu przed 60. rokiem życia) (OR 6,8; p = 0,007). Wnioski: Stwierdzono znamiennie podwyższoną wartość cIMT u pacjentów z cukrzycą w porównaniu ze zdrowymi osobnikami z grupy kontrolnej. Czynniki ryzyka rozwoju miażdżycy obejmowały podwyższone stężenie cholesterolu całkowitego i cholesterolu frakcji LDL, podwyższone skurczowe ciśnienie tętnicze, dodatni wywiad rodzinny w kierunku cukrzycy i wczesnego występowania chorób układu krążenia oraz dłuższy czas trwania cukrzycy. Pomimo udokumentowanego wzmożenia stresu oksydacyjnego nie udało się ustalić korelacji pomiędzy parametrami stresu oksydacyjnego a wartościami cIMT. (Endokrynol Pol 2012; 63 (6): 414&#8211;419