Aluminium Underpotential Deposition from AlCl3+NaCl Melts and Alloy Formation with Vanadium Substrate

Aim of this work was to study underpotential deposition of aluminium onto polycrystalline vanadium electrode from equimolar AlCl3+NaCl melt at 473, 523 and 573 K. It was found that aluminium was deposited and incorporated into polycrystalline vanadium electrode at potentials more positive than the Al reverse potential. Applied electrochemical techniques: linear sweep voltammetry and potentiostatic deposition/ galvanostatic striping, showed clear evidence of formation of three intermetallic compounds whose presence depends on temperature and applied deposition time. Deposits were studied via scanning electron microscopy (SEM), energy dispersive spectrometry and X-ray spectroscopy (EDS and EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD)

Content and distribution of iron in river sediments at borehole site Rb-6/P-5d in area of Belgrade water supply

The current problem of water supplying systems for large cities with quality drinking water be‐ comes more and more complex every day. Consumption is growing rapidly due to an increase in the number of inhabitants, an increase in per capita consumption, and a number of large water consumers, such as industry and agriculture. For many cities, including Belgrade, the main source of drinking water is groundwater. The captured groundwater of Belgrade water source is formed in alluvial deposits of the Sava River and layers of Pleistocene age, previously formed from torrential flows of melted glaciers. Beside the limiting factor of the "capacity of the site", during the exploitation of the wells, due to the rapid ageing of wells, reducing of the capacity of the well and screen is observed (Dimkić, 2017). Reducing of the capacity of the well and screen happens due to hydrogeological, hydrological, hydraulic factors, as well as geochemical, mechanical and biological processes that take place in the collector of groundwater. Interaction of these factors leads to the formation of "deposits" (e.g. Majkić‐Dursun et al., 2015), which causes clogging the perforations on well screen structures and thus reduces the capacity of wells. Preliminary studies of water supply wells of the Belgrade groundwater source indicated to the increased content of iron in the deposits which causes clogging the filter perforations. The aim of this research is to determine the content of iron in individual lithological layers, as well as the distribution of iron content along the stratigraphic column, particularly in the aquifer, as a potential source of iron and the causative agent for the formation of the deposits on the well screen. These studies are part of the activities on the definition of the mechanism of transport of iron from the primary lithological setting, as well as on elucidation of the mechanism responsible for the precipitation of iron‐bearing deposits (i.e. iron minerals) on the well screen

Thermal resistance testing of standard and protective filtering military garment on the burning napalm mixture

Fires are an accompanying manifestation in modern weaponry use and in various accidents in peacetime. The standard military uniform is a primary barrier in protection of a soldier's body from all external influences, including the thermal ones which can cause burns. The minimum thermal resistance to the effect of burning napalm mixture (BNM) in individual uniform garment materials was determined, and found to be higher for simultaneous use of more materials one over another (the so called sandwich materials), where the best thermal protection was exhibited by sandwich materials with an air interspace. The requirement for the thermal resistance of the material of the filtrating protective suit (FPS) to the effect of BNM (≥ 15 s) was fully met. The highest thermal resistance was demonstrated by the FPS whose inner layer was made of polyurethane foam with active carbon. The FPS thermal resistance to the effect of BNM was found to be proportional to water vapor permeability through this garment mean, and inversely proportional to air permeability.Požari su prateća manifestacija kod upotrebe naoružanja u savremenom ratu i u slučajevima nastanka različitih akcidenata u mirnodopskim uslovima. Standardna vojnička uniforma predstavlja primarnu prepreku u zaštiti tela vojnika od svih spoljnih uticaja, uključujući i termičke koji mogu da izazovu opekotine. Cilj ovog rada je da utvrdi koja vrsta standardne vojničke odeće i odela filtrirajućeg zaštitnog (OFZ) kao predstavnika zaštitne RHB odeće filtracionog tipa će u sebi najbolje da objedini prihvatljivi nivo efikasne termičke zaštite od goruće napalm smeše (GNS) uz istovremeno obezbeđenje zadovoljavajućih funkcionalnih karakteristika tj. adekvatnog fiziološkog odgovora organizma čoveka. Sve ove aktivnosti su sprovedene uz poštovanje relevantnih zahteva na polju standardizacije uslova ispitivanja. Utvrđena je najmanja termička otpornost na delovanje GNS kod pojedinačnih odevnih materijala uniforme, veća kod istovremenog korišćenja više materijala jednih preko drugih (tzv. sendvič materijala), a najbolju termičku zaštitu pružaju sendvič materijali sa vazdušnim međuprostorom (VP). Taktičko-tehnički zahtev za termičku otpornost materijala OFZ na dejstvo GNS (≥ 15s) kod sva tri ispitivana modela u potpunosti je ispunjen. Najveću termičku otpornost je pokazao OFZ-M2PUR koji je urađen na bazi poliuretanske pene i aktivnog uglja, zatim OFZ-M00 na bazi tkane tkanine i sferičnog ugljeničnog adsorbenta i konačno OFZ-M2 na bazi tkane tkanine i sferičnog ugljeničnog adsorbenta. Utvrđena je proporcionalna zavisnost između termičke otpornosti OFZ na dejstvo GNS i propustljivosti vodene pare kroz ovo odevno sredstvo, a obrnuta u odnosu na propustljivost vazduha

Synthesis and sintering of Cu-Al2O3 nanocomposite powders produced by a thermochemical route

By hydrometallurgy and powder metallurgy along with prognosis of physical-chemical properties, a synthesis of new improved materials can be successfully performed with in advance pre-set properties which is conditioned by a quality of starting powders i.e. by improving their structure. In accordance with that, this paper presents synthesis of the nanocomposite Cu-Al2O3 powder by thermochemical method and sintering with a comparative analysis of the mechanical and electrical properties of obtained solid samples. Nanocrystaline Cu-Al2O3 powders were produced by thermochemical method through following stages: spray-drying, oxidation of precursor powder, reduction by hydrogen and homogenisation. Characterization of powders included differential-thermal and thermo-gravimetric analysis (DTA-TGA), X-ray-diffraction (XRD) and analytical electron microscopy (AEM) coupled with energetic dispersive spectroscopy (EDS). Size of produced powders was 20-50nm with noticeable presence of agglomerates. Composite powders are characterized with A12O3 homogenous distribution in copper matrix. Powders were cold pressed with pressure of 500 MPa and sintered. Sintering of the obtained samples was performed in the hydrogen atmosphere in isothermal conditions at temperature range from 800 to 900°C and time up to 120 minutes. Characterization of Cu-Al2O3 sintered system included examination of density, relative volume change, electrical and mechanical properties, examination of microstructure by SEM analysis, as well as by EDS. The obtained nanocomposite, which structure is with certain changes preserved in final structure, has provided sintered material with homogenous distribution of dispersive in copper matrix, with exceptional effects of reinforcing and excellent combination of mechanical and electrical properties