Zaštita materijala 1. 2018

Ispitivanje uticaja tretmana i mineraloškog sastava na tačku nultog naelektrisanja crvenog mulja

Izvod

Crveni mulj predstavlja jalovinu koja zaostaje nakon prerade boksita u glinicu po Bayer-ovom postupku. Svi elementi prisutni u crvenom mulju se nalaze u formi različitih minerala. Ovi minerali ne egzistiraju kao individualne čestice, nego su povezani sa drugim mineralima u agregate koji predstavljaju čestice crvenog mulja. Površinsko naelektrisanje predstavalja svojstvo crvenog mulja, koje utiče na niz njegovih karakteristika. Površinsko naelektrisanje se može razmatrati preko tačke nultog naelektrisanja. U ovom radu određena je tačka nultog naelektrisanja originalnog crvenog mulja i pojedinih tretiranih uroraka. Primenjeni tretmani imali su različit uticaj na pomeranje PZC i pufer područja. Originalni uzorak crvenog mulja odlikovao se visokom vrednošću pH_PZC (9,7±0,2). Delimično ispiranje nije uticalo na promenu PZC, što sugeriše na veliku količinu zaostale baze iz proseca luženja. Termički tretman crvenog mulja nije bitno uticao na promenu finalne pH vrednosti pri kojoj se uočava plato (pH_PZC = 9,4-9,9), dok je kiselinski tretman imao izraženiji uticaj (pH_PZC = 6,2-7,9). Vrednosti PZC za kiselinski tretirane uzorke dobijene u inertnom elektrolitu, bile su niže od onih dobijenih u destilovanoj vodi. Svi razmatrani uzorci imali su izražen puferski region u kojem su finalne pH vrednosti bile nezavisne od inicijalnih. Delimično ispiranje i termički tretman nisu značajnije uticali na promenu pufer područja, dok je kiselinski tretman izazivao suženje pufer oblasti sa povećanjem koncentracije kiseline. Za pomeranje PZC tretiranih muljeva najodgovornije su fazne promene koje nastaju pri tretmanu, neutralizacija zaostale baze i alkalnih anjona u rastvoru, te promena kristaličnosti i rastvorljivosti minerala u mulju. Pravilnim izborom tretmana može se uticati na naelektrisanje površine mulja.

Ključne reči: crveni mulj, tačka nultog naelktrisanja, mineraloški sastav, tretman, fazne transformacije, pufer područje.

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EXAMINATION OF THE INFLUENCE OF TREATMENTS AND MINERAL COMPOSITION ON THE POINT OF ZERO CHARGE OF RED MUD

Abstract

Red mud represents tailings which remains after the processing of bauxite into alumina by Bayer’s proceedings. All the elements are present in the red mud are found in the form of different minerals. These minerals do not exist as individual particles, but are associated with other minerals in aggregates which represent particles of red mud. Surface charge is an important property of the red mud, which affects a number of its characteristics. Surface charge can be considered through the zero charge point. In this paper, the point of zero charge of the original red mud and certain treated samples is determined. Incomplete washing, thermal and acid treatment were used as treatments. The applied treatments had a different effect on the movement of the PZC and buffer region. The red mud sample was distinguished by a high value of pH_PZC (9.7 ± 0.2). Incomplete washing did not affect the change in PZC, while thoroughly rinsing caused a significant movement of PZC to a lower pH. This suggests to a large amount of residual base from the leaching process. Thermal treatment of red mud did not significantly affect the change in the final pH at which plateau was observed (pH_PZC 9.4-9.9), while acid treatment had a more pronounced effect (pH_PZC 6.2-7.9). PZC values for acid-treated samples obtained in an inert electrolyte were lower than those obtained in distilled water, at least for one pH unit. All the analysed samples had a pronounced buffer region in which the final pH values were independent of the initial ones. Partial rinsing and thermal treatment did not significantly affect the change in buffer region, while acid treatment caused the narrowing of the buffer region with increasing acid concentration, but the samples continued to retain significant neutralization capacity.

For the move of the PZC treated muds, major responsibility have phase changes that occur in the treatment, neutralization of the residual base and the anions in the solution, and changing the crystallinity and the solubility of minerlas in the mud. Applying the appropriate treatment can affect the change in the mineral composition and, consequently, the changes in the charge of the surface.

Keywords: red mud, point of zero charge, mineral composition, phase transformation, treatment, buffer region.

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Hibridni metod za detekciju ivica na TEM slikama nanočestica

Izvod

Opšta primena fundamentalnih delova digitalne obrade slike nalazi sve širu primenu u različitim oblastima nauke. Sa ubrzanim razvojem tehnologije mikroskopskih slikanja, potreba za robusnom segmentacijom nanočestica značajno se povećava. Zbog velike različitosti u broju i obliku nanočestica na TEM slikama većina postojećih metoda samo je sposobna da segmentira određene vrste nanočestica. Uzimajući u obzir karakteristike nanočestičnih materijala, ovaj rad daje predlog novog algoritma detekcije ivica. Kao ocena podobnosti predloženog algoritma u radu, analiza je izvršena kako kroz prostornu, tako i kroz amplitudsku rezoluciju digitalne slike. U cilju dodatne preciznosti rezultata, analiza je vršena kroz slike nanočestica različitog stepena uvećanja. Slike tog tipa daju i različit stepen šumova u digitalnoj slici, pa je krajnja analiza dala ocenu stepena otpornosti na predloženi algoritmi detekcije ivica na šumove koji se javljaju u slikama nanočestica. Svi dobijeni rezultati ukazuju na visok stepen korisnosti obrađenih TEM slika, kako u prostornom tako i u amplitudskom domenu.

Ključne reči: digitalna obrada slike, detekcija ivica, hibridni metod, TEM slike, nanočestice.

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HYBRID EDGE DETECTION METHOD ON TEM IMAGES OF NANOPARTICLES

General application of the fundamental part of digital image processing is widely used in various fields of science. With the rapid development of microscopic imaging technology, the need for the robust segmentation of nanoparticles increased significantly. Due to large differences in the number and form of nanoparticles in TEM images, most of the existing methods are only capable of segmenting certain types of nanoparticles. Taking into account the characteristics of nanoparticle materials, this paper gives some suggestions for a new edge detection algorithm. As an assessment of similarity of the proposed algorithm in the paper, the analysis was carried out both through the spatial and through the amplitude resolution of the digital image. With the aim of obtaining additional accurate results, the analysis was conducted through images of nanoparticles of different degrees of magnification. Images of this type provide different levels of noise in digital image, therefore the final analysis gave an assessment of the degree of resistance to the proposed edge detection algorithm for noise occurring in nanoparticle images. All the obtained results indicate a high degree of utility of the processed TEM images, both in spatial and amplitude domain.

Keywords: digital image processing, edge detection, hybrid method, TEM images, nanoparticles.

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Darko Manjenčić¹*, Suzana Cakić², Branka Pilić¹, Vojislav Aleksić³, Jaroslava Budinski-Simendić¹, Sanja Rackov¹,Ivan Ristić^1
1Univerzitet u Novom Sadu, Tehnološki fakultet, Novi Sad, ²Univerzitet u Nišu, Tehnološki fakultet Leskovac, Leskovac, Srbija, ³Univerzitet u Istočnom Sarajevu, Tehnološki fakultet, Zvornik, R. Srpska

Naučni rad
ISSN 0351-9465, E-ISSN 2466-2585
UDC:504.064:800.6
doi: 10.5937/ZasMat1704421V

Zastita Materijala 59 (1)
31 – 38  (2018)

THE INFLUENCE OF NANOFILLER ON THE  PROPERTIES OF BIOCOMPATIBLE SILICONE BASED ON DIFFERENT NETWORK PRECURSORS 

Abstract

The choice of starting network precursors for elastomeric material preparation is highly important in order to obtain materials for specific application. During the cross linking of macromolecules, with the choice of type and quantity of the components, it is possible to fine tuning material flexibility, mechanical and chemical characteristics. Silicones, more precisly polysiloxanes, are for sure one of most interested class of elastomeric materials.  For decades silicones are under huge interest of academical and industrial researches so the fields of their potentially usages are broad (electronics, personal care products, structural engineering and textiles, medicine, sports equipment…). Silicones, because of their extraordinary properties are predestined for biomedical purposes because they are bioinert, transparent and they have excellent oxygen permeability. Great biocompatibility is partly because of its low chemical reactivity, low surface energy and hydrofobicity of polydimethylsiloxane. The purpose of this work was to determine branched structures and charachteristics of noanocomposite organofunctionals siloxanes.  For synthesis were used vinyl-functionalized siloxanes and also polysiloxanes with adding of nanofillers. Cross linking of materials based on polydemitylsiloxanes and this compound was performed on 80˚C in vacuum. The chemical structure of the obtained materials was confirmed on the basis of the FTIR analysis, which confirmed the assumed mechanism of crosslinking of used silicone precursors. The influence of nanofillers on the mechanical and thermal properties of the obtained silicon is studied in detail, wherein was present a clear trend of improvement of mechanical properties of the silicone with the addition of nanofillers.  Influence of nanofillers on the thermal properties of the silicone is confirmed based on DSC results. From this group of linear organic functional siloxanes, difunctional α and ω – siloxanes are more in focus of science and economy in recent times, as they are reactive agens for synthesis of organic polymers. Three cooperative influences are their inner flexibility, characteristic of lateral packing of individual macromolecules and presence of intermolecular attraction represent sensitive system of factors which have to be observed in order to acquire defined properties.

Keywords: nanocomposites, elastomers, silicones, silica.

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MINERALOGICAL, PHYSICO-CHEMICAL AND CERAMIC PROPERTIES OF BREZACI CLAY

Abstract

The Podrinje-Kolubara region, from the point of non-metallic mineral raw materials, is characterized not only by numerous mineral types, but the quality of mineral resources as well as, being one of few mineral regions in that part of Serbia. Deposits of clay and ceramic clay in the Tamnava basin have been industrially the most important deposits up to now.

This paper presents some results of mineralogical, physico-chemical and ceramical-technological analyses of ceramic clay Brezaci-Donje Crniljevo. Based on the obtained experimental results, it can be concluded that clay Brezaci-Donje Crniljevo belongs to the kaolinite-illite  clay with traces of quartz, feldspar and mica. The findings from this study indicate that the examined clay has significant potential as a material raw component for numerous ceramic products.

Keywords: clay, clay minerals, mineralogical composition, ceramic properties.

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Elemental composition and nutritional value of three edible mushrooms from Serbia

Abstract

Nutrition value, as well as macro- and microconstituents of three edible mushrooms (Pleurotus ostreatus, Lentinula edodes, Macrolepiota procera) collected in Serbia were tested. It has been determined that all three mushroom samples were low in energy, fat and carbohydrates, but rich in β-glucans content. The most abundant elements in these three mushrooms were essential marcroelements Ca, K and P, but also there is a significant amount of Li, Se and Zn. On the other hand, toxic elements, such as Pb, As and Cd were also detected in level higher than allowed.

Keywords: Pleurotus ostreatus, Lentinula edodes, Macrolepiota procera, nutrition value, elemental analysis.

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SASTAV MIKRO I MAKROELEMENATA I NUTRITIVNA VREDNOST U TRI JESTIVE PEČURKE IZ SRBIJE

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Nutritivna vrednost, kao i sadržaj makro- i mikroelemenata testirana je u uzorcima tri jestive pečurke, sakupljene u Srbiji (Pleurotus ostreatus, Lentinula edodes, Macrolepiota procera). Pokazano je da su sve tri gljive bile siromašne energijom, mastima i ugljenimhidratima, ali bogate β-glukanima. Najzastupljeniji elementi u sva tri uzorka bili su esencijalni makroelementi Ca, K i P, ali je takođe je detektovana značajna količina Li, Se i Zn. Sa druge strane, koncentracija toksičnih metala, Pb, As i Cd, bila je iznad dozvoljenih granica.

Ključne reči: Pleurotus ostreatus, Lentinula edodes, Macrolepiota procera, nutritivna vrednost, analiza hemijskih elemenata.

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NOVI MEŠOVITO-LIGANDNI KOMPLEKSI Co (II)- SINTEZA, KARAKTERIZACIJA I ANTIMIKROBNA AKTIVNOST

Izvod

Pripremlljena  su  dva nova kompleksa opšte formule [Co₂(X)₂tpmc](BF₄)₂·Y (X= F^–, Y=CH₃CN; X= Br^–, Y= H₂O; tpmc = N,N’,N”,N”’- tetrakis(2-piridilmetil)-1,4,8,11-tetraazaciklotetradekan), čiji su sastav, neke fizičke i hemijske osobine kao i približne geometrije  određene na osnovu  elementalne analize (C, H, N), konduktometrijskih i magnetnih merenja i spektroskopskih podataka (UV/Vis, IR). Podaci su upoređeni sa ranije sintetisanim i opisanim hloro analogom. Oba nova kompleksa Co(II) su dinuklearna sa pretpostavljenom egzo koordinacijom makrocikla u konformaciji  stolice. Kompleksi su preliminarno testirani na neke Gram (+), Gram (-) bakterije,  plesni i kvasce zajedno sa startnim supstancama za sintezu (ligandima, prostim solima i rastvaračima) koje su služile kao test supstance. Određivana je minimalna inhibitorna koncentracija koja sprečava rast bakterija. U nekim slučajevima je nađena izvesna antimikrobna  aktivnost. Oba kompleksa su pokazala aktivnost prema bakterijama ali su inaktivni prema gljivicama i kvascima dok je pod istim uslovima i istim primenjenim koncentracijama  kontrolna grupa bila neaktivna.

Ključne reči: antimikrobna aktivnost, Co(II) kompleksi, pendantni oktaazamakrocikli.

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BIOMETRIJSKE TEHNIKE ZA OCENU STEPENA USVAJANJA TOKSIČNIH I ESENCIJALNIH ELEMENATA

Izvod

Fokus ove studije je na biometrijsku klasifikaciju biljaka, biljnih organa, lokaliteta i vremena uzorkovanja, u smislu praćenja stepena usvajanja toksičanih (As, Cd, Hg i Pb) i esencijalnih elemenata (Cu i Zn), i mogućnost primene u fito-remedijaciji. Stepen usvajanja elemenata zavisi od biljne vrste i njenih morfoloških i fizioloških osobina. Usvajanje toksičnih i esencijalnih elemenata u ovom radu je praćeno kod tri vrste biljaka (podbel, maslačak i kopriva). Uzorkovanje biljaka i zemljišta je vršeno u priobalnom regionu Kriveljske reke, Srbija. Analiza glavnih komponenti i analiza varijanse su korišćene za procenu efekasnosti usvajanja toksičnih i esencijalnih elemenata kod pomenutih biljnih vrsta, biljnih organa (korena, stabla i lišća), lokaliteta i vremena uzorkovanja (april, maj, jun). Dobijeni rezultati su pokazali da je razlika u usvajanju toksičnih i esencijalnih elemenata najviše zavisi od sorte i tipova biljnih organa. Biometrijske tehnike pružaju mogućnost za bolje razumevanje ponašanja biljaka i dobijanja mnogo korisnih informacija iz izvornih podataka.

Ključne reči: podbel, maslačak, kopriva, toksični elementi, esencijalni elementi, biometrijski monitoring.

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HEMP FIBERS  (Cannabis Sativa)  IMPREGNATED BY Ca-ALGINATE GEL AS A NOVEL BIOSORBENT FOR THE REMOVAL OF  Pb(II) and Zn(II) IONS

Abstract

In this paper the possibility of implementing the new biosorbent composed of chemically modified short hemp fibers impregnated with alginate gel for adsorption of lead(II) and zinc (II) ions was investigated. Waste hemp fibers, alkaly treated, were used as an alginate carrier in order to improve the mechanical stability of alginate. Morphological characteristics of obtained alginate-hemp composite were investigated by scanning electron microscopy (SEM), while the Fourier transform infrared spectroscopy (FT-IR) was used for examination of surface chemistry. Alginate immobilization on the hemp fibers surface leads to the morphological changes, by decreasing the roughness of short hemp fibers. FT-IR analysis showed that surface chemistry was changed after alginate immobilization, primarily by increasing the amount of carboxyl groups. The presence of surface groups characteristic for hemp fibers, on the surface of biocomposite, indicate that the surface of hemp fibers is not completely covered by alginate. Adsorption characteristics of alginate-hemp biosorbent were examined through the adsorption of lead and zinc ions, and compared with the adsorption characteristics of alkali treated hemp fibers. Biosorption of lead and zinc ions onto both hemp fibers and alginate-hemp composite, represent fast process since 80 % of initial ions amount were adsorbed in first five minutes. Obtained adsorption data were analyzed by Lagergren pseudo-first and pseudo-second order kinetic models, as well as intraparticle diffusion model. It was found that biosorption of lead and zinc ions on alkali treated hemp fibers and alginate-hemp composite obey the pseudo-second order adsorption kinetics, indicating that adsorption/binding of ions is mediated by chemical forces rather than physical forces of attraction. This observation was confirmed by results of FT-IR analysis of alginate composite surface before and after ions adsorption. It was found that lead and zinc ions predominantly bind on carboxyl and hydroxyl groups through the ion-exchange and surface complexation. New biosorbent demonstrated effective removal of the ions, with the possibility of further process optimization in order to increase the adsorption capacity and rate of metal ions removal.

Keywords: biosorption, alginate, hemp fibers, biocomposite, Pb(II),  Zn(II).

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Determination of Au and Ag from iron ores combining FA and ICP/AES methods

Abstract

In this paper, the combination of FA (Flame Analysis of Noble Metals – Cupellation) and ICP/AES (Atomic Emission Spectrometry with Induction Coupled Plasma) methods for determination of Au and Ag in geological samples of iron ore-magnetite was presented.Au and Ag were concentrated with Pb from PbO after desulphurisation and melting process (Pb²⁺→Pb). Regulus (Pb with noble metals) is then cupellated. The resulting bead-pril after cupellation was dissolved in HNO₃ and then in HCl (imperial water: 2HNO₃ and 6HCl). After the preparation of standard solutions and a blank test, the ICP/AES recording is performed. The obtained results werecompared with those obtained by the classical method of cupellation. The advantages of ICP/AES are excellent detection limits and linear dynamic range as well as a stable and repeating signal which is particularly important for samples of iron tested due to the low content of noble metals.

Keywords: geological samples, FA, ICP / AES,noble metals.

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ODREĐIVANJE Au I Ag IZ RUDE GVOŽĐA KOMBINOVANJEM FA I ICP/AES METODA

Izvod

U ovom radu je prikazana kombinacija FA (plamena analiza plemenitih metala-kupelacija) i ICP/AES (atomska emisiona spektrometrija sa indukovanom kuplovanom plazmom) metoda za određivanje Au i Ag u geološkim uzorcima rude gvožđa-magnetit. Au i Agse koncentišu sa Pb iz PbOnakon procesa odsumporavanja i topljenja (Pb²⁺→Pb).Regulus (Pb sa Au i Ag)se kupelira. Dobijena perla-pril nakon kupelacije se rastvara u HNO₃ a zatim u HCl(carska voda 2HNO₃ : 6HCl). Nakon pripreme standardnih rastvora i blank probe vrši se snimanje na ICP/AES. Dobijeni rezultati su poređeni sa rezultatima dobijenim klasičnom metodom kupelacije. Prednosti ICP/AES su odlične granice detekcije i linearni dinamički opseg kao i stabilan i ponovljiv signal što je posebno bitno za uzorke ispitivane rude gvožđa zbog malog sadržaja plemenitih metala.

Ključne riječi: geološki uzorci, FA, ICP/AES, plemeniti metali

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Karakterizacija otpadnog mulja sa jalovišta tretiranog letećim pepelom i crvenim muljem u cilju solidifikacije/stabilizacije

Izvod

U radu je prikazana problematika otpadnog mulja sa jalovišta rudnika ”Sase” zagađenog toksičnim metalima, kao i tretman jalovine postupkom solidifikacije/stabilizacije (S/S). Kao imobilizacioni agensi korišćeni su leteći pepeo i crveni mulj koji predstavljaju sporedan industrijski otpad, te je njihovom primenom u ovom tretmanu ujedno ostvarena imobilizacija dve vrste otpada.  Tokom poslednjih nekoliko godina termin “zeleni” koncept u upravljanju opasnim otpadom dobija sve veći značaj, i odnosi se na procese i aktivnosti koje imaju mali ili zanemarljiv uticaj na životnu sredinu. Za procenu potencijalne mobilnosti metala u netretiranim i tretiranim uzorcima jalovine korišćena je modifikovana sekvencijalna ekstrakcija. Rezultati sekvencijalne ekstrakcione procedure S/S smeša ukazali su na to da su metali u smešama skoro potpuno imobilisani i ne predstavljaju rizik za životnu sredinu, naročito u smeši jalovine sa crvenim muljem. Glavni cilj ovog rada je karakterizacija tretiranih uzoraka primenom skenirajuće elektronske mikroskopije sa elementarnom analizom (SEM-EDS) i rendgenske difrakcije (XRD), koje su pružile dokaze o formiranju kompaktnog matriksa i pozolaničkih produkata.  Dobijeni rezultati pokazuju da je crveni mulj efikasniji za imobilizaciji metala u odnosu na leteći pepeo.

Ključne riječi: jalovina, crveni mulj, leteći pepeo, SEM-EDS, XRD, modifikovana sekvencijalna ekstrakcija.

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CHARACTERIZATION OF SLUDGE FROM THE TAILINGS WITH FLY ASH AND RED MUD AFTER THE PROCESS OF SOLIDIFICATION/STABILIZATION

Abstract

The paper presents the problem of waste sludge from mine tailing ”Sasa” contaminated with toxic metals, as well as the treatment of process solidification/stabilization. As a stabilizing agent fly ash and red mud were used.  Fly ash and red mud represent a secondary industrial waste, and its application in the treatment immobilized two types of waste. Over the past few years, the term “green” concept of hazardous waste management has gained increasing importance, and refers to processes and activities that have a small or negligible impact on the environment. A modified sequential extraction was used to estimate potential metal mobility in untreated and treated mine tailings samples. The results of the sequential extraction procedure of the S/S mixture indicate that the metals in the mixtures are almost completely immobilized and do not pose a risk to the environment, especially in the red sludge mixture. The main objective of this paper is to characterize the treated samples using a scanning electron microscopy with elemental analysis (SEM-EDS) and X-ray diffraction (XRD). This  analysis  confirmed  the formation of compact matrices and pozzolanic products. Obtained results indicated that red mud and fly ash effectively perform the immobilization of metals in the mine tailing.

Keywords: mine tailing, red mud, fly ash, SEM-EDS, XRD

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FORMATION AND GROWTH OF PITS ON X5CrNi18-10 AUSTENITIC STAINLESS STEEL IN PRESENCE OF CHLORIDES AND SULPHATES

Abstract

The resistance of X5CrNi18-10 stainless steel to pitting corrosion in a solution containing chlorides and sulphates was tested using the potentiodynamic polarization method. The obtained results show that the stainless steel is significantly resistant to pit formation, but it is susceptible to pit growth and crevice corrosion. Pits formed at the corrosion potential grow continuously. Statistical analysis of the results obtained during pitting corrosion testing was performed. It can be assumed with a probability of 95% that values of indicators of resistance to pit formation (the pitting potential E_pit, the metastable pitting potential E_mpit and the difference E_pit-E_kor) will be within the range of several percents. Values of indicators of resistance to pit growth (the amount of charge required for the pit growth q, the protective potential E_prot and the difference E_pit-E_prot) will be within the broader range. In addition, the appearance of pits on the surface of the stainless steel, as well as the appearance of the pits bottom, were analyzed. It was shown that the structure of the stainless steel tested was not sensitized to pitting and intergranular corrosion, which means that the stainless steel was not previously thermally treated.

Keywords: stainless steels, pitting corrosion, potentiodynamic polarization method, statistical analysis.

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VALORIZACIJA MOLIBDENA IZ OTPADNOG MOLIBDENSKOG RASTVORA ZA LEGIRANJE SIVOG LIVA

Izvod

U istraživačkom radu opisan je komercializovan reciklažni proces prerade otpadnog rastvora iz postrojenja za proizvodnju sijaličnih vlakana od volframa radi izdvajanja molibden (VI)-oksida i njegovom daljem iskorišćavanju kao legirajućeg agensa sivog liva. U prvom delu izvršena je neutralizacija utrošene kiseline, koja u sebi sadrži izvesne količine molibdena, uz pomoć rastvora amonijaka, a potom kristalizacija i filtracija amonijum-molibdata, njegovo sušenje i prženje u cilju dobijanja praha molibdentrioksida tehničke čistoće (maseni udeo molibdena 59,2 mas%). U drugom delu izvršeno je legiranje sivog liva uz pomoć MoO₃ u indukcionoj peći. Finalni proizvod je legura železa sa povećanom tvrdoćom uz postignut visok stepen usvajanja molibdena u leguri (čak do 86%).

Ključne reči: otpadni rastvor, neutralizacija amonijakom, molibdentrioksid, legiranje, sivi liv.

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ISPITIVANJE  EFEKATA Na₂MoO₄ KAO INHIBITORA NA ELEKTROHEMIJSKO KOROZIONO PONAŠANJE NERĐAJUĆEG ČELIKA 316L U RASTVORU LiBr

Izvod

Uticaj natrijum-molibdata (Na₂MoO₄) kao inhibitora pri njegovim različitim koncentracijama 50, 100 i 200 ppm na elektrohemijsko korozijsko ponašanje nerđajućeg čelika 316L u LiBr rastvoru na 60°C ispitani su polarizacionim krivinama, metodama elektrohemijske impedansne spektroskopije (EIS) i elektronske mikroskopije. Otpornost na koroziju uzorka nerđajućeg čelika 316L povećava se sa koncentracijom inhibitora do 200ppm. Povećanjem koncentracije inhibitora od 50ppm do 200ppm smanjuje se gustina korozivne struje. Ovi rezultati su potvrđeni daljom analizom koristeći skenirajući elektronski mikroskop.

Ključne reči: natrijum molibdat, korozija, nerđajući čelik 316L, litijum bromid.

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Solvatochromism of 5-(4-substituted arylazo) -4-phenyl-6-methyl-3-cyano-2-pyridones

Abstract

Eight 5-(4-substituted arylazo)-4-phenyl-6-methyl-3-cyano-2-pyridones were synthesized by reaction of benzoylacetone and arendiazonium salt, followed by condensation with cyanoacetamide. Absorption spectra of all azo pyridone dyes were recorded in twelve protic and aprotic solvents in the range of 200-600 nm. A simple Hammett equation was used to study the effect of the substituents on the absorption spectra of these azo dyes. The solute-solvent interactions were clarified on the basis of linear solvation energy relationships concept proposed by Kamlet and Taft. The results showed that the solvent effects on the absorption spectra of the investigated azo dyes were very complex and strongly dependent on the nature of the substituents on the phenylazo group.

Keywords: Arylazo pyridone dyes, solvent effects, substituent effects, absorption spectra.

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SOLVATOHROMIZAM   5-(4-supstituisanih arilazo) -4-fenil-6-metil-3-cijano-2-piridona

Izvod

Osam 5-(4-supstituisanih arilazo)-4-fenil-6-metil-3-cijano-2-piridona je sintetizovano reakcijom benzoilacetona i arendiazonijumove soli, i kondenzacijom nastalog proizvoda sa cijano­acetamidom. Apsorpcioni spektri dobijenih arilazo piridonskih boja su snimljeni u dvanaest protičnih i aprotičnih rastvarača u opsegu od 200-600 nm. za proučavanje uticaja supstituenata na apsorpcione spektre ispitivanih azo boja korišćena je prosta Hametova jednačina. Interakcije rastvorak-rastvarač su razjašnjene na osnovu koncepta linearne korelacije energije solvatacije, koji su predložili Kamlet i Taft. Rezultati pokazuju da su efekti rastvarača na apsorpcione spektre istraženih azo boja veoma kompleksni i jako zavise od prirode supstituenata na fenilazo grupi.

Ključne reči: arilazo piridonske boje, uticaj rastvarača, uticaj supstituenata, apsorpcioni spektri.

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Egy- dronate drug as promising corrosion inhibitor of C – steel in aqueous medium

Abstract

The effect of Egy – dronate as the corrosion inhibition of Carbon steel (CS) in 1 M HCl was studied by weight loss (WL), hydrogen evaluation (HE), Open circuit potential (E_OCP), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), electron frequency modulation (EFM) and surface examination of the specimens by atomic force microscopy (AFM), energy dispersion spectroscopy (EDS) and scanning electron microscopy (SEM). The results of the inhibition efficiency (IE %)   with increasing the concentration of inhibitor but decreases with raising the temperature. The adsorption of Egy – dronate on the C – steel surface obeys with Langmuir adsorption isotherm. The adsorption process is spontaneous, endothermic and physical adsorption.  . The results obtained from chemical and electrochemical techniques are a good agreement quality and gives the same behavior of the adsorption of Egy-dronate drug. All techniques have proved the thin film   formation adsorbed on the metal surface as a protective coated to prevent the dissolution metal in the corrosive medium, due to electrostatic attraction between unshared electrons of inhibitor molecules and the positive sites on the metal surface.

Keywords: corrosion inhibition, HCl, CS, adsorption, SEM, EDX, AFM.

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EGI-DRONAT KAO PERSPEKTIVNI INHIBITOR KOROZIJE UGLENIČNOG ČELIKA U VODENIM RASTVORIMA

Izvod

Uticaj Egi-dronata kao inhibitora korozije ugljeničnog čelika u 1M HCl proučavan je gubitkom težine, procenom vodonika, potencijalom otvorenog kola, potentiodinamičkom polarizacijom, elektrohemijskom spektroskopskom impedancijom, modulacijom elektronske frekvencije i ispitivanjem površina uzoraka atomskom mikroskopijom (AFM), spektroskopijom disperzije energije (EDS) i skenirajućom elektronskom mikroskopijom (SEM). Rezultati efikasnosti inhibicije (IE%) povećavaju se s povećanjem koncentracije inhibitora, ali se smanjuju sa podizanjem temperature. Adsorpcija Egi-dronata na ugljeničnoj – čeličnoj površini podudara se sa Langmuirovom adsorpcionom izotermom. Proces adsorpcije je spontana, endotermna i fizička adsorpcija. Polarizacijske krive pokazuju da je Egi-dronat mešoviti inhibitor koji ima tendenciju anodnom tipu. Rezultati dobijeni hemijskim i elektrohemijskim tehnikama su dobar kvalitet odogovora i daju isto ponašanje adsorpcije Egi-dronata. Sve tehnike su dokazale formiranje tankog filma na površini metala kao zaštitnu oblogu, kako bi se sprečio metal da se razlaže u korozivnom medijumu, zbog elektrostatičke privlačnosti između nerastvornih elektrona molekula inhibitora i pozitivnih mesta na površini metala.

Ključne reči: inhibicija korozije, HCl, ugljenični čelik, adsorpcija, SEM, EDKS, AFM.

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