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Zaštita materijala 2. 2017

 

Abd El-Aziz S.Fouda1*, Ayman Y. El-Khateeb2, Nabila M. Elbahrawi1

1El-Mansoura University, Department of Chemistry, Faculty of Science, El-Mansoura, Egypt, 2Mansoura University, Department
of Agric. Chemistry, Faculty of Agriculture, Mansoura, Egypt

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:620.193.3:669.15-194
doi:10.5937/ZasMat1702131F

Zastita Materijala 58 (2)
131 – 143  (2017)

Cupressus sempervirens extract as green inhibitor for corrosion of carbon steel in hydrochloric acid solutions

Abstract

The effect of an aqueous extract of Cupressus sempervirens on the corrosion manner of carbon steel in 1M hydrochloric acid solution has been measured by mass reduction, hydrogen evolution, electrochemical frequency modulation (EFM), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods The efficiency of Cupressus sempervirens extract was examined with increasing dose of the extract and the temperature.The parameters of thermodynamic of corrosion and adsorption processes were measured and discussed. The extract was adsorbed on surface of metal chemically and was obtain obey Temkin isotherm. The potentiodynamic polarization resulted lead to the extract is mixed inhibitor type. The results given from the various methods were in best agreement.

Keywords: cupressus sempervirens, corrosion inhibition, carbon steel, adsorption, HCl.

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EKSTRAKT Cupressus sempervirens KAO ZELENI INHIBITOR ZA KOROZIJU UGLJENIČNOG ČELIKA U RASTVORU HLOROVODONIČNE KISELINE

Izvod

Efekat vodenog ekstrakta Cupressus sempervirens na način korozije ugljeničnog čelika u rastvoru 1M hlorovodonične kiseline je određivana promenom mase pri redukciji, izdvajanjem vodonika i metodama – elektrohemijskom frekvencijskom modulacijom (EFM), potentiodinamičkom polari­zacijom i merenjem impedanse (EIS). Efikasnost ekstrakta Cupressus sempervirens je ispitivana sa povećanjem doze ekstrakta i temperature. Termodinamički parametri procesa korozije i adsor­pcije su mereni i diskutovani. Ekstrakt Cupressus se adsorbuje na površini metala hemijski i prati Temkinovu izotermu. Rezultat potentiodinamičke polarizacije je doveo do zaključka da ekstrakt pripada mešovitom tipu inhibitora. Navedeni rezultati dobijeni pri različitim metodama ispitivanja bili su u najboljoj korelaciji.

Ključne reči: cupressus sempervirens, zeleni inhibitor, ugljenični čelik, adsorpcija, HCl.

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Aleksandar Todić1, Dejan Čikara1, Branko Pejović1*, Tomislav Todić1, Ivica Čamagić1, Vladan Mićić2, Suzana Yusup3

1University of Pristina, Faculty of Technical Sciences, Kosovska Mitrovica, Serbia, 2University of East Sarajevo, Faculty of Technology Zvornik, Zvornik, Republic of Srpska, Bosnia and Herzegovina, 3University Teknologi Petronas, Chemical Engineering Department, Bandar Sei Iskandar, Tronoh, Malaysia

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:669.15`26`28-194.3
doi: 10.5937/ZasMat1702145T

Zastita Materijala 58 (2)
145 – 150  (2017)

The influence of the vanadium content on the toughness and hardness of high-alloyed Cr-Mo steel

Abstract

Characteristics of air hardening steel are high hardness and low impact toughness. In order to increase the impact toughness while retaining replace with the high hardness value numerous research added. One of the ways to achieve this is the alloying of specified steel with vanadium and application of appropriate heat treatment. Vanadium affects the solidification process of these alloys by narrowing of the temperature interval of crystallization. In addition, vanadium formed V6C5 carbides that block the growth of austenitic dendrites and structure makes fine-grained. Vanadium which forms V6C5 carbides is partly distributed between present phases in the steel, carbide (Cr,Fe)7C3 and austenite. Also, the presence of vanadium can enable the formation of (Cr,Fe)23C6 carbide and its precipitation in austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite. In other words vanadium reduces the amount of remained austenite and so improves hardenbility of the steel. In this way, better technical characteristics of these steels are obtained.

Key words: vanadium, impact toughness, hardness, microstructure.

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UTICAJ  SADRŽAJA VANADIJUMA NA ŽILAVOST I TVRDOĆU VISOKO LEGIRANIH Cr-Mo ČELIKA

 

Karakteristike kaljenih čelika na vazduhu su visoka tvrdoća i mala udarna žilavost. U pokušaju da se poveća udarna žilavost uz zadržavanje visoke tvrdoće brojna istraživanja su izvršena. Jedan od načina da se postigne ovaj cilj je legiranje specifičnih čelika sa vanadijumom i primena odgovarajuće toplotne obrade.  Vanadijum utiče na proces očvršćavanja ovih legiranih čelika u uskom temperaturnom intervalu kristalizacije. Dodavanjem vanadijuma nastaju V6C5 karbidi koji sprečavaju rast austenitnih dendrita i strukturu čine sitnozrnastom. Vanadijum koji formira V6C5 karbide je delimično raspodeljen između prisutnih faza u čeliku, karbidne (Cr,Fe)7C3 i austenitne. Takođe, prisustvo vanadijuma može omogućiti formiranje (Cr,Fe)23C6 karbida i njegovo taloženje u austenite tokom procesa hlađenja.  U području oko čestica finih karbida, austenite se transformiše u martenzit. Drugačije rečeno vanadijum redukuje količinu zaostalog austenite i na taj način unapređuje sposobnost čelika za kaljenje. Ovim postupkom dobijaju se povoljnije karakteristike ovih čelika.

Ključne reči: vanadijum,  udarna žilavost, tvrdoća, mikrostruktura

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Snežana Dević1* , Mira Cocić2

1Institut IMS a.d, Beograd, Srbija,  2Univerzitet u Beogradu,
Tehnički fakultet u Boru, Bor, Srbija

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:669.141.25-147
doi: 10.5937/ZasMat1702151D

Zastita Materijala 58 (2)
151 – 157  (2017)

Submerge entry Nozzles based on alumo-graphite refractory material in the process of continuous steel casting

ABSTRACT

Submerge entry Nozzles are parts made of refractory material and are utilized for steel casting in the continuous casting process. Steel is cast from the tundish into the crystallizer through the Submerge entry Nozzle (SEN). The role of the SEN is to protect steel from oxidation and to provide a uniform flow of steel during casting[1][2]. SEN are manufactured from refractory material with diverse composition. At the beginning of application of SEN, when introducing the continuous casting process, white SEN, based on melted quartz, were utilized.White SEN were utilized primarily for casting one steel grade.

 Alumo-graphite SEN are another type of SEN that are utilized for casting all steel grades. They are sensitive to thermal shocks, so before use they must be heated in special heating facilities at the temperature ranging from 1000°C-1100°C. Alumo-graphite SEN are manufactured by special isostatic pressing process. These are used successfully today. During casting, the SEN are in contact with steel on the internal side of the wall, and on the external side of the wall with casting powder and slag formed in the crystallizer. Internal erosion sometimes appears at the contact with steel on the internal side of the wall of alumo-graphite SEN, but build-up is formed more often. The SEN erosion occurs on the external side of the SEN wall, which originated due to the effect of casting powder and slag. All three phenomena affect SEN durability. External erosion reduces the thickness of SEN wall and causes SEN cracking. On the other hand, the formed build-up reduces the diameter of SEN orifice (aperture) leading to reduction of steel flow and excluding the SEN from the exploitation process. Depending on the steel grade being cast, mineralogical composition of casting powder, quality of alumo-graphite SEN, SEN design, technological parameters and technological process itself, the internal, external erosion or build-up will appear on the internal wall of the alumo-graphite SEN. Each of enumerated phenomena affects the lifetime of the alumo-graphite SEN.This scientific paper aimed at presenting and explaining the phenomena and causes of reduced lifetime of the alumo-graphite SEN on a few characteristic examples.

Keywords: SEN (Submerge entry nozzle), alumo-graphite material, erosion, build-up.

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IZLIVNICI NA BAZI ALUMO-GRAFITNOG VATROSTALNOG MATERIJALA U PROCESU KONTINUIRANOG LIVENJA ČELIKA

Izvod

Izlivnici su oblikovani delovi od vatrostalnog materijala i koriste se za livenje čelika u procesu kontinuiranog livenja. Čelik se lije iz međulonca u kristalizator kroz izlivnik.Uloga izlivnika je da štiti čelik od oksidacije i da obezbedi ravnomeran protok čelika pri livenju. Izlivnici se proizvode od vatrostalnog materijala različitog sastava.U početku primene izlivnika pri uvođenju postupka kontinuiranog livenja, korišćeni su beli izlivnici na bazi stopljenog kvarca. Beli izlivnici su korišćeni prvenstveno za livenje jedne vrste čelika.  Alumo-grafitni izlivnici su druga vrsta izlivnika koji se koriste za livenje svih vrsta čelika. Osetljivi su na termošokove, pa se pre upotrebe moraju zagrevati u posebnim uređajima za zagrevanje na temperaturi od 1000°C-1100°C. Alumo-grafitni izlivnici se proizvode posebnim postupkom izostatičkog presovanje. Ovi izlivnici se uspešno koriste i danas. Izlivnici su pri livenju u kontaktu sa čelikom s unutrašnje strane zida, a sa spoljašnje strane zida sa livnim prahom i troskom formiranom u kristalizatoru. Na kontaktu sa čelikom na unutrašnjoj strani zida alumo-grafitnog izlivnika ponekad se javlja unutrašnja erozija, ali se češće formira nalep. Na spoljašnoj strani zida izlivnika javlja se erozija izlivnika nastala usled dejstva livnog praha i troske. Sve tri pojave utiču na izdržljivost izlivnika. Spoljašnja erozija smanjuje debljinu zida izlivnika i izaziva pucanje izlivnika. Sa druge strane formirani nalep smanjuje prečnik otvora izlivnika što dovodi do smanjenja protoka čelika i izbacivanja izlivnika iz procesa eksploatacije.U zavisnosti od vrste čelika koji se lije, mineralnog sastava livnog praha, kvaliteta alumo-grafitnog izlivnika, dizajna izlivnika, tehnoloških parametara i samog tehnološkog procesa  pojaviće se unutrašnja, spoljašna erozija ili nalep na unutrašnjem zidu izlivnika. Svaka od nabrojanih pojava utiče na vek trajanja alumo-grafitnog izlivnika.Rad je imao za cilj da prikaže i objasni na nekoliko karakterističnih primera pojave i uzroke smanjenog veka trajanja alumo-grafitnog izlivnika.

Ključne reči: izlivnici, alumo-grafitni materijal, erozija, nalep.

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Zoran M. Karastojković1*, Suzana R. Polić2, Milesa Ž. Srećković3, Nataša A. Ilić2, Zoran V. Janjušević4

1Technical college, Novi Beograd, Serbia, 2Central institute for conservation, Belgrade, Serbia, 3University of Belgrade, Faculty
of electrical engineering, Belgrade, Serbia, 4Institute for technology of nuclear and other mineral raw materials, Belgrade, Serbia

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:620.152.1:620.183.4/.6
doi:10.5937/ZasMat1702158K

Zastita Materijala 58 (2)
158 – 162  (2017)

X-ray transparent testing of leaves from an artistic desk lamp

ABSTRACT

For investigation of artistic components, generaly, there are many developed methods, but a lot of them still are not fully reliable or standardized. One of the available method for such investigation is radiographic testing, when the thickness of testing components does not represents a problem, whatever if the great or small thickness exists. Here is tested an artefact in the shape of desk lamp. The chemical composition of the body is analysed by using XRF spectrography while the radiographic transparent testing is applied through the whole body of the lamp.

The body of this desk lamp is produced by casting, using the precise casting method, while other decorative ornaments were shaped by hammering. The fastening of those components is provided by brazing or mechanically. The plastic deformation is designated as method for shaping of thin elements – here leaves. The radiographic testing has revealed the existence of some indications only at leaves produced by hammering. The indications usualy mean discontinuity in material homogenity. Registration of indications and their locations are necessary steps in every further approach for removing such discontinuities. Chossing the repair method always is particular problem, however in entire technique, especially in sensitive artistic component(s). Every action in repairing or restauration may led to more or less visible traces. Unadequate actions may permanently change the appearance or usage of treated artefact.

Keywords: artistic castings, radiographic testing, indications at leaves.

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RENDGENSKO ISPITIVANJE PROZRAČIVANJEM LISTOVA SA JEDNE UMETNIČKI OBLIKOVANE STOLNE LAMPE

Izvod

Za ispitivanje umetničkih predmeta, uopšte, razvijene su brojne metode ali sve te metode još uvek nisu potpuno pouzdane ili standardizovane. Jedna od primenljivih metoda za ovakva ispitivanje je radiografsko ispitivanje, kada debljina ispitivanih delova ne predstavlja problem, bilo da se radi o velikoj ili maloj debljini. Ovde je ispitivan jedan umetnički predmet u obliku stolne lampe. Hemijski sastav tela je analiziran korišćenjem rendgenske spektrografske analize (XRF) dok je rendgensko prozračivanje upotrebljeno za snimanje celog tela lampe.

Telo lampe je proizvedeno livenjem, korišćenjem metode preciznog liva, dok su ostali dekorativni ornamenti oblikovani kovanjem. Pričvršćivanje ostalih komponenti je izvedeno lemljenjem ili mehanički. Plastično deformisanje je označeno kao metoda oblikovanja tankih elemenata – ovde su to listovi. Radiografsko ispitivanje je otkrilo prisustvo izvesnih indikacija samo na listovima izrađenih kovanjem. Indikacije obično označavaju prekid u homogenosti materijala.  Registrovanje indikacija i njihovo lociranje su neophodni koraci u svakom daljem pristupu u cilju uklanjanja takvih diskontinuiteta. Izbor metode repariranja uvek je poseban problem, dakako u celoj tehnici a posebno pri ispitivanju umetničkih komponenti. Svaka akcija u reparaciji ili restauraciji može dovesti do manje ili više vidljivih tragova. Neadekvatne akcije mogu za stalno da promene izgled ili upotrebu tretiranog artefakta.

Ključne reči: umetnički odlivak, radiografsko ispitivanje, indikacije na listovima.

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Nataša Šetrajčić1, Stevo K. Jaćimovski2, Jovan P. Šetrajčić3*

1Univerzitet u Novom Sadu, Fakultet tehničkih nauka, Departman
za građevinu i geodeziju, Novi Sad,  Srbija,  2Kriminalističko-policijska akademija, Zemun – Beograd, Srbija, 3Univerzitet u Novom Sadu, Prirodno-matematički fakultet, Departman za fiziku, Novi Sad,  Srbija

Naučni rad
ISSN 0351-9465, E-ISSN 2466-2585
UDC:536.241:692.241.3
doi:10.5937/ZasMat1702163S

Zastita Materijala 58 (2)
163 – 170  (2017)

Razmena toplote kroz kompozitne zidove

IZVOD

U radu je razmatrano provođenje toplote kroz različite kompozitne zidove i toplotni bilans – termalna efikasnost sa obe strane zidova. Navedene su prednosti i neophodnost postavljanja termoizolacije i dati su i analizirani primeri više kombinacija za dva načina pasivne izolacije. Predstavljeni su brojni termoizolacioni materijali i izračunata je vrednost ukupnog koeficijenta prolaza za razne kombinacije. Konstatovano je da je kod konstrukcije zidova bolje koristiti šuplju opeku od pune i da je efikasnije postaviti termoizolaciju na spoljašnjoj strani zida, jer samo tada može ostvariti neprekinut izolacioni omotač.

Ključne reči: Provođenje toplote, termalna efikasnost, kompozitni zidovi, pasivna izolacija.

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HEAT EXCHANGE THROUGH COMPOSITE WALLS

Abstract

We investigated the heat conduction through different composite walls and analysed heat balance – thermal efficiency on both sides of the walls. Advantages are commented and the necessity of thermal isolation is emphasized. Examples of several combinations for two ways of passive isolation are analysed. Numerous materials for thermal isolation are presented and value of the overall coefficient of transmission is calculated for different combinations. It is concluded that for construction of walls it is better to use shallow brick rather than full and that it is more efficient to place thermal isolation on the exterior side of wall because only in that case continual isolating layer can be realized.

Keywords: heat conduction, thermal efficiency, composite walls, passive isolation.

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Miloš B. Rajković1*, Mirjana Stojanović2, Gordana Pantelić3, Maja Eremić-Savković4

1Univerzitet u Beogradu, Poljoprivredni fakultet, Institut za prehrambenu tehnologiju i biohemiju, Beograd, Srbija, 2Institut za tehnologiju nuklearnih i drugih mineralnih sirovina (ITNMS), Beograd,Srbija, 3Institut za nuklearne nauke „Vinča”, Laboratorija za zaštitu od zračenja i zaštitu životne sredine, Beograd, Srbija, 4Agencija za zaštitu od jonizujućih zračenja i nuklearnu sigurnost, Beograd, Srbija

Naučni rad
ISSN 0351-9465, E-ISSN 2466-2585
UDC:628.191/.196(497.11)
doi: 10.5937/ZasMat1702171R

Zastita Materijala 58 (2)
171 – 187  (2017)

Analiza sadržaja makro i mikroelemenata u vodi za piće iz beogradskog vodovoda (pogon Bežanija) tokom perioda 2008-2015. godine

IZVOD

Indirektna metoda određivanja sadržaja metala u vodi za piće bazirana na ispitivanju kamenca pokazala je preciznost, pouzdanost i reproduktivnost dobijenih rezultata.

Rezultati ispitivanja potvrdili su da je kvalitet vode, baziran na sadržaju metala u vodi, konstantan i da se metali nalaze u koncentraciji koja je dozvoljena pravilnikom. Utvrđen je porast urana u vodi za piće (uglavnom izotopa 238U), a na osnovu rezultata frakcione ekstrakcije dokazano je njegovo antropogeno poreklo.

Na osnovu sadržaja makro- i mikroelemenata utvrđeno je da je ispitivani tip vode HCO3-Ca-Mg.

U ispitivanom periodu koncentracija makro- i mikroelemenata bila je ispod MDK (Maksimalno dozvoljena koncentracija) vrednosti.

Odnos Ca/Mg po pravilniku treba da iznosi između 3 i 4, dok je u ovom periodu varirao u opsegu 10,67-16,76, što znači da je sadržaj Mg u vodi jako nizak.

Unos teških metala preko vode za piće u periodu od 2011-2015. godine značajno je povećan (čak 10 puta) u odnosu na period od 2008-2011. godine. Ovako visok porast teških metala posledica je povećane koncentracije Fe i Zn.

Proračunati podaci ukazuju da rizik od unošenja mikroelemenata: Al, Fe i Pb, koji se u ispitivanim vodama nalaze u vrednosti višoj od one dozvoljene pravilnikom, ni za jedan metal ne pokazuju kratkoročni zdravstveni rizik po zdravlje ljudi.

Analiza podataka o dugoročnom zdravstvenom riziku ukazuje da jedina realna opasnost postoji od prisustva Pb u vodi za piće. Rizik od pojave kancera prisutan je kod 23-58 stanovnika od 1000 stanovnika koji koriste ovu vodu za piće.

Ključne reči: voda za piće, kamenac, teški metali, kratkoročni i dugoročni zdravstveni rizik.

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CONTENT ANALYSIS OF MACRO- AND MICRO-ELEMENTS IN WATER FROM BELGRADE PLUMBING (PURIFIED IN BEŽANIJA TREATMENT PLANT) DURING THE PERIOD OF 2008-2015

ABSTRACT

An indirect method of metal content determination in drinking water based on a study of scale, showed precision, reliability and reproducibility of the obtained results.

Results showed that the water quality, based on the metal content in the water, is quite constant and metals are in a concentration allowed by the Regulations. An increase of Uranium in drinking water (mainly the isotope 238U) was determined and its anthropogenic origin is proven based on the results of fractional extraction.

Based on the content of macro- and microelements it is determined type of tested water as HCO3-Ca-Mg.

In the examined period the concentration of macro- and microelements was below the MAC (Maximum Allowable Concentration) values.

Ratio of Ca/Mg according to the Regulations should be between 3 and 4, while in the period of examination was varied in the range of 10.67 to 16.76, which means that the content of Mg in water is very low.

Regarding to the period of 2011-2015 the input of heavy metals via drinking water was significantly increased (even 10 times) in comparison to the period of 2008-2011. As result of increased concentrations of Fe and Zn is a high growth of heavy metals.

Calculated data showed that the risk of input microelements: Al, Fe and Pb, which are in studied water much higher than allowed by the Regulations, is not having any short-term risk to human health.

Data analysis of the risk on the long-term health showed that the only real danger is the presence of Pb in drinking water. The risk of cancer is present in 23-58 population of 1000 people who are using this water for drinking.

Keywords: drinking water, scale, heavy metals, short-term and long-term human health risk.

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Jelena Rusmirović1, Dragana Milošević2, Zorica Veličić2, Milica Karanac1, Mustafa Kalifa3, Jovana Nikolić2, Aleksandar Marinković3*

1University of Belgrade, Innovation Center of Faculty of Technology and Metallurgy, Belgrade, Serbia, 2University of Belgrade, Institute for Chemistry, Technology and Metallurgy, Belgrade, Serbia, 3University of Belgrade, Faculty of Techology and Metallurgy, Belgrade, Serbia

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:678.46.004.8
doi: 10.5937/ZasMat1702189R

Zastita Materijala 58 (2)
189 – 197 (2017)

Production of rubber plasticizers based on waste PET: techno-economical aspect

ABSTRACT

Production of rubber plasticizers, based on waste poly(ethylene terephthalate) (PET), and economic effectiveness of developed technologies are presented and discussed. Waste PET glycolyzates, named diisononyl terephthalate(DINTP), didecyl terephthalate (DDTP), dibenzyl terephthalate(DBTP) and diglyceryl terephthalate(DGTP), were obtained by catalytic depolymerization of PET with isononyl alcohol, decyl alcohol, benzyl alcohol and glycerol. The structural analysis of the synthesized plasticizers was done using elemental, FTIR and NMR spectral analysis. Physical-mechanical properties of the rubber products composed of 100 phr of 28 % nitrile butadiene caoutchouc (NBR) and 20.7 phr of plasticizer were investigated. Influence of the synthesized plasticizers on Shore hardness, breaking strength and elongation at break was investigated. Obtained results were compared with ones obtained for commercial plasticizer dioctyl phthatale (DOP). Evaluation of economic potential of new technology for plasticizers production, i.e. results of techno-economic analysis, was presented. Benefits of the presented technology was based on the use of waste PET which is related to both environmental protection and profitability aspects.

Keywords: waste PET glycolysis, plasticizers, rubber, PET recycling.

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SINTEZA PLASTIFIKATORA IZ OTPADNOG PET-a ZA PRIMENU U GUMENIM PROIZVODIMA: TEHNO-EKONOMSKA ANALIZA

Izvod

U radu je predstavljen postupak sinteze plastifikatora na bazi otpadnog poli(etilen tereftalata) (PET-a), kao i ekonomičnost razvijene tehnologije. Plastifikatori na bazi otpadnog PET-a: diizononil-tereftalat (DINTP), didecil-tereftalat (DDTP), dibenzil-tereftalat (DBTP) i digliceril-tereftalat (DGTP) dobijeni su katalitičkom depolimerizacijom PET-a monohidroksilnim alkoholima (izononil, decil i benzil alkoholi) i trohidroksilnim alkoholom (glicerinom). Struktura sintetisanih plastifikatora potvrđena je primenom elementalne, FT-IR i NMR analize. Proučavane su fizičko-mehaničke karakteristike (tvrdoća po Šoru, prekidna jačina i prekidno istezanje) proizvoda od gume, koje se sastoje od 100 phr-a 28%-nog nitril butadien kaučuka (NBR) i 20,7 phr-a plastifikatora na bazi otpadnog PET-a. Dobijeni rezultati su upoređeni sa fizičko-mehaničkim karakteristikama proizvoda dobijenim korišćenjem komercijalnog plastifikatora dioktil-ftalata (DOP-a). Procena ekonomskog potnecijala prikazane tehnologije za proizvodnju plastifikatora na bazi otpadnog PET-a izvršena je izradom detaljne tehno-ekonomske analize. Na osnovu određene tačke rentabiliteta doređena je minimalna cena koštanja jedinice proizvoda koja je, uz evidentno smanjen uticaj na životnu sredinu, konkurentna komercijalnom DOP-u.

Ključne reči: glikolizati otpadnog PET-a, tehnologija plasticizera, tehnologija gume, reciklaža PET-a.

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Milorad V. Tomić1*, Milica Gvozdenović2, Marija G.Riđošić1,Jelena B. Bajat2

1University of Eastern Sarajevo, Faculty of Technology Zvornik, Zvornik, Republic of Srpska, 2University of Belgrade,
Faculty of Technology and Metallurgy, Belgrade, Serbia

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:620.193.94:669.55`24`25
doi: 10.5937/ZasMat1702198T

Zastita Materijala 58 (2)
198 – 203  (2017)

The comparative study of the corrosion stability of Zn-Ni-Co alloy coatings deposited from chloride and sulphate baths

Abstract

The ternary Zn–Ni–Co alloy coatings were electrodeposited on steel from chloride and sulphate baths. The deposition was carried out galvanostatically at different current densities at ambient temperatures from additives free baths with different ratios of Ni and Co. Corrosion behaviour of these coatings was evaluated from polarization measurements in 3% NaCl.

The deposition current density exhibited small influence on the corrosion potential and corrosion current density of alloys obtained from both chloride and sulfate baths. On the other hand, [Co2+]/Ni2+] ion ratio showed a significant influence on corrosion behaviour of ternary alloy coatings, and this influence was more pronounced with alloys deposited from chloride baths. It was shown that increased corrosion protection of steel can be achieved by electrochemical deposition of ternary alloys that contained lower amount off the alloying elements, while the composition of the ternary alloy can be optimized by proper choice of the type and composition of the deposition bath.

Keywords: electrochemical deposition, Zn-Ni-Co alloys, coatings, corrosion stability, polarization measurements.

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Uporedna analiza korozione stabilnosti prevlaka Zn-Ni-Co legura elektrohemijski taloženih iz hloridnih i sulfatnih rastvora

Izvod

Trojne Zn-Ni-Co legure su elektrohemijski taložene na čeliku iz hloridnih i sulfatnih rastvora na 25 °C. Legure su taložene galvanostatski, različitim gustinama struje iz rastvora bez dodataka i sa različitim odnosom jona legirajućih elemenata, Ni i Co. Koroziona stabilnost dobijenih prevlaka je ispitivana polarizacionim merenjima u 3 % NaCl.

Gustina struje taloženja ima mali uticaj na korozioni potencijal i gustinu struje korozije prevlaka dobijenih i iz hloridih i slufatnih rastvora. Veći uticaj pokazuje odnos jona legirajućih elemenata ([Co2+]/Ni2+]), pri čemu je ovaj uticaj više izražen kod prevlaka dobijenih elektrohemijskim taloženjem iz hloridnih rastvora. Pokazano je da se koroziona stabilnost čelika može produžiti elektrohemijskim taloženjem prevlaka trojnih Zn-Ni-Co legura koje sadrže malu količinu legirajućih elemenata, i da se sastav trojnih legura može optimizovati pogodnim odabirom vrste i sastava rastvora za taloženje.

Ključne reči: elektrohemijsko taloženje, Zn-Ni-Co legure, koroziona stabilnost, polarizaciona merenja.

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Milan Milivojević1*, Marija Jocić1, Zorica Lopičić2, Jelena Petrović2, Mirjana Stojanović2

1Univerzitet u Beogradu, Tehnološko metalurški fakultet, Beograd, Srbija, 2Institut za tehnologiju nuklearnih i drugih mineralnih sirovina, Beograd, Srbija

Naučni rad
ISSN 0351-9465, E-ISSN 2466-2585
UDC:546.161.128:661.482
doi: 10.5937/ZasMat1702204M

Zastita Materijala 58 (2)
204 – 211  (2017)

Adsorpcija fluoridnih jona na Al-alginatnim česticama

Izvod

Antropogeni faktor uslovio je sve veće prisustvo fluoridnih jona u podzemnim vodama. Sa druge strane, povećana svest o štetnosti visokih koncentracija ovog polutanta u pijaćoj vodi, dovela je do strožijih standarda kada su ovi joni u pitanju. Zato se poslednje decenije vrše intenzivna ispitivanja novih metoda za uklanjanje fluoridnih jona iz otpadnih i pijaćih voda. U ovom radu je ispitana mogućnost upotrebe aluminijum alginatnih čestica, jeftinog i efikasnog adsorbenta, za uklanjanje fluoridnih jona. Detaljna karakterizacija primenjenog adsorbenta urađena je pre i nakon adsorpcije primenom FT-IR tehnike. Eksperimenti su izvedeni u šaržnom sistemu sa mešanjem, pri različitim polaznim koncentracijama adsorbenta i adsorbata. Dobijen rezultat od 11,40 mg F/g Al-alginata ukazuje na visok kapacitet adsorbenta, a kinetički parametri pokazuju brzu kinetiku uklanjanja ispitivanog polutanta.

Ključne reči: adsorpcija, fluoridni joni, aluminijum-alginat, FT-IR.

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Fluoride ion adsorption onto Al-alginate particles

Abstract

Fluoride ions are increasingly present in the groundwater mainly due to the anthropogenic activity. On the other hand, increased awareness of harmful effects caused by high concentrations of Fin drinking water, leads to severe standards of water quality. Because of this, intensive researches of new methods for fluoride removal from water streams have been made in last decade. This paper examines the potential of aluminum alginate particles as a cheap and efficient biosorbent for F removal. The adsorbent characterization before and after Fadsorption was performed using FT-IR technique. Adsorption experiments were conducted in a stirring batch mode, varying both concentration of adsorbate and adsorbent dose. Obtained result of 11,40 mg F/g Al-alginate indicates a high adsorption capacity, while the kinetic parameters show fast removal kinetics.

Keywords: adsorption, fluoride, aluminum alginate, FT-IR.

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Aurel Nuro1*, Elda Marku1, Bledar Murtaj1, Valbona Plaku2

1Tirana University, Faculty of Natural Sciences, Chemistry Department, Tirana, Albania, 2Tirana Polytechnic University, General and Inorganic Chemistry Department,Tirana, Albania

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:628.191/.196(497.5)
doi: 10.5937/ZasMat1702212N

Zastita Materijala 58 (2)
212 – 221  (2017)

Determination of some organic pollutants in waters rivers of Tirana city

Abstract

This study presented data about concentrations of some organic pollutants in two main rivers of Tirana city: Lana River that crosses through the city and Tirana River that lies in northeast of the city. Twenty stations were analyzed in this study. Sampling of water was realized in July 2016. These rivers present important aquatic areas of Tirana region in Albania. For both water river samples were analyzed organochlorine pesticides (OCPs), their degradation products, polychlorinated biphenyls (PCBs), BTEX (benzene, toluene, ethylbenzene and o-, m-, p-xylenes) and polyromantic hydrocarbons (PAH). For extraction of OCPs and PCBs by water samples were used liquid-liquid (LLE) extraction and n-Hexane as extracting solvent. After clean-up and concentration procedures for all samples were performed gas chromatographic analyzes using Rtx-5 capillary column (30 m x 0.33 mm x 0.25 um) and electron capture detector (GC/ECD). Headspace solid phase micro extraction (HS-SPME) technique was used to trace BTEX in water samples. For isolation of PAH, LLE extraction assisted with Dichloromethane as extraction solvent were used. The extracts were concentrated and then were injected in gas chromatograph. The analysis of BTEX and PAH in water samples was performed by gas chromatography technique using flame ionization detector (GC/FID). Injections of BTEX were done directly by using Head-Space mode of Polydimethyl Siloxane fiber. VF-1ms capillary column (30 m x 0.33 mm x 0.25 um) was used for separation of BTEX and PAH compounds.

The higher concentrations of organochlorine pesticides and PCBs were found for water samples of Tirana River because of their previous use, in the agricultural areas near the basin of this river. The higher concentrations were for volatile PCBs because of their atmospheric deposition in Albanian territory. Relatively high concentrations of BTEX and more volatile PAH compounds were detected in water samples of Lana River. The presence of volatile organic pollutants could be mostly of automobilist transport near the stations, discharging of wastes from some gas stations or some mechanical industries neat the river.

Keywords: Tirana River; Lana River; OCP; PCB; BTEX; PAH; LLE; HS-SPME; GC/ECD; GC/FID.

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Određivanje nekih organskih zagađivača u vodama reka grada Tirana

Izvod

Ova rad prikazuje podatke o koncentraciji nekih organskih zagađivača u dve glavne reke u gradu Tirani: reke Lana, koja prolazi kroz grad, i reke Tirana, koja se nalazi na severoistoku grada. Izvršeno je uzorkovanje i analiza na dvadeset tačaka na navedenim rekama. Uzorkovanje vode ostvareno je u julu 2016. Ove reke predstavljaju važne vodene površine grada Tirane i šireg regiona u Albaniji. Na uzorcima iz reka su analizirani organohlorni pesticidi (organohlorirani pesticidi), njihovi produkti razgradnje, polihlorovani bisfenoli (PCBs), BTEX (benzen, toluen, etilbenzol i o-, m-, p-ksilen) i poliromantični ugljovodonici (PAH). Za određivanje organohloriranih pesticida (OCPs) i polihlorovanih bisfenola PCBs) iz uzoraka vode, korišćena je tečno-tečno (LLE) ekstrakcija i n-heksan kao ehstrahujući rastvarač. Nakon čišćenja i koncentracije, procedure za sve uzorke su bile da je izvršena analiza korišćenjem gasne hromatografije sa kapilarnom kolonom Rtx-5  (30m x 0.33 mm x 0.25 μm) i korišćenjem elektronskog detektor (GC / ECD). Mikro ekstrakciona tehnika (HS-SPME) je korišćen da se prate BTEX u uzorcima vode. Za izolaciju PAO, korišćena je LLE ekstrakcija sa dihlorometanom kao ekstrakcijskim rastvaračem. Ekstrakti su koncentrovani, a zatim su injektirani u gasni hromatograf. Analiza BTEX i PAH u uzorcima vode izvedena je tehnikom gasnom hromatografijom  uz korišćenje plameno jonizujućeg detektora (GC / FID). Injektovanje BTEX je izvedeno direktno koristeći Ofis-Space režima sa polidimetilsiloksan vlakna. VF-1ms capillare  (30m x 0.33 mm x 0.25 um) su korišćene za odvajanje BTEX i PAH jedinjenja.

Povećane koncentracije organohloriranih pesticida i PCBs pronađeni su u uzorcima vode iz reke Tirana zbog njihove upotrebe u poljoprivrednim područjima u blizini sliva ove reke. Povećanje koncentracije isparljive supstance PCBs je zbog njihovog prisustva u atmosfiri na albanskoj teritoriji. Relativno visoke koncentracije BTEX i više isparljivih PAH jedinjenja su detektovani u uzorcima vode reke Lana. Prisustvo isparljivih organskih zagađivača može biti uglavnom zbog auto prevoza u blizini stanice, ispuštanje otpada iz nekih benzinskih pumpi ili neke mašinske industrije u vodotokove ovih reka.

Ključne reči: reka Tirana; reka Lana; OCP; PCB; BTEX; PAH; LLE; HS-SPME; GC/ECD; GC/FID

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Kreshnik Hakrama1*, Genti Guxho2, Eldi Liço3

1Metrology, Kashar, Albania, 2Polytechnic University of Tirana, Mechanical Engineering Faculty, Tirana, Albania, 3University of Tirana, Natural Sciences Faculty, Tirana, Albania

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:620.187
doi: 10.5937/ZasMat1702222H

Zastita Materijala 58 (2)
222 – 227  (2017)

Morphological and chemical study of recycled synthetic rubber tire crumbs by using scanning electron microscopy and energy dispersive analysis

Abstract

The present paper aims to investigate the structure and chemistry of recycled synthetic rubber tire crumbs. It comprises the microscopic structure description of rubbers, separation of component phases and determination of chemical elements of additives that we use. For this purpose we have used scanning electronic microscope (SEM) JEOL6380LV equipped with the system of dispersive of energy spectroscopy (EDS). The rubber samples were collected from different mini soccer fields in Albania that use synthetic grass, where the rubber is used as filler increasing the stability and the elastic properties of the synthetic grass. The samples were analyzed as crumbs, as taken from the fields. Crumb metal infill a sustainable metal free and should not contain liberated fibers in an amount that exceed 0.01% of the total weight f crumb rubber. So far, we have studied 7 different crumbs of recycled synthetic rubber tire. Through the images provided by SEM we could study the microstructure of our samples. Also, after conducting an EDX spectrum analysis, we observed additives in the recyclable materials.

Keywords: recycled rubber, SEM, EDS, synthetic a artificial grass, EDX, additives.

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Morfološka i hemijska studija recikliranih opiljaka sintetičke gume pomoću SEM i EDX

Izvod

Ovaj rad ima za cilj da istraži strukturu i hemiju recikliranih opiljaka sintetičkih guma. Sastoji se od mikroskopske strukture gume, razdvajanja faza komponenti i određivanja hemijskih elemenata aditiva koji su korišćeni. Za tu svrhu korišćen je skenirajući elektronski mikroskop (SEM), tip JEOL6380LV, opremljen sistemom EDS. Uzorci gume su sakupljani na različitim mini fudbalskim terenima u Albaniji, koji koriste sintetičku veštačku travu i gde se guma koristi kao punioc, povećavajući stabilnost i elastične osobine sintetičke trave. Uzorci gume su analizirani kao mrvice, dobijene u polju. Crumb metal ispuna je održiva bez metala i ne sme da sadrži oslobođena vlakna u količini koja prevazilaze 0,01% od ukupne težine f crumb gume. Proučavano je sedam različitih uzoraka mrvica reciklirane sintetičke gume. Pomoću slika koje pruža SEM proučavana je mikrostruktura ispitivanih uzoraka. Takođe, nakon analize EDX spektara, uočeni su aditivi u materijalima koji su reciklirani.

Ključne reči: reciklirana guma, SEM, EDS, sintetička veštačka trava, EDX, aditivi.

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Milovan Jotanović, Vladan Mićić*, Stefan Pavlović

Univerzitet u Istočnom Sarajevu, Tehnološki fakultet Zvornik, Zvornik, BiH

Pregledni rad
ISSN 0351-9465, E-ISSN 2466-2585
UDC:661.96:628.042
doi:10.5937/ZasMat1702228J

Zastita Materijala 58 (2)
228 – 234  (2017)

Proizvodnja vodonika gasifikacijom biomase

Izvod

Vodonik bi u narednom periodu mogao postati značajan izvor energije jer su njegova proizvodnja, transport i skladištenje uglavnom riješeni. U ovom radu se daje pregled proizvodnje vodonika iz lignoceluloznih obnovljivih izvora. Proces je obrađen u svim njegovim fazama i alternativnim rješe­njima. Tako su obrađene dva različita, alternativna, procesa gasifikacije biomase – direktna i indi­rektna i dva različita, alternativna, reforming modela – parcijalna oksidacija i reformiranje vodenom parom. Prečišćavanje gasa je, takođe, dato sa dvije različite, alternativne, koncepcije – hladno i toplo prečišćavanje gasa. Konverzija radnog gasa i razdvajanje vodonika od CO2 i drugih primjesa se danas radi u membranskom cijevnom reaktoru – sve na jednom mjestu što je znatno smanjilo cijenu koštanja 1 kg vodonika. U svim ovim procesima je posebno vođeno računa o integraciji energije u procesu što je takođe znatno doprinijelo ekonomski povoljnijoj cijeni vodonika.

Ključne reči: vodonik, gasifikacija, biomasa, energija.

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HYDROGEN PRODUCTION BY BIOMASS GASIFICATION

Abstract

Hydrogen could be the important energy sources of the next period provided that its production, transportation, and storage are solved. In this paper review of the production of hydrogen from lignocellulosic feedstock is given. The process is analyzed in all its phases and alternative solutions. Two different, alternative biomass gasification process – direct and indirect, and two different, alternative reforming model – partial oxidation and steam reforming are described. Gas cleaning is also provided with two different, alternative concepts – cold and hot cleaning. Conversion of the working gas and the separation of hydrogen from CO2 and other impurities are still used as a method in the tubular membrane reactor – all in one place which significantly reduced the cost of 1 kg of hydrogen. In all these processes is especially taken into consideration on the integration of energy in the process, which is also significantly contributed to the better price of hydrogen.

Keywords: hydrogen, gasification, biomass, energy.

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Ljiljana M. Babincev1*, Ivana Sredović Ignjatović2, Dragan M. Stević1

1University of Priština, Faculty of Technical Sciences, Kosovska Mitrovica, Serbia,  2University of Belgrade, Faculty of Agriculture, Belgrade, Serbia

Scientific paper
ISSN 0351-9465, E-ISSN 2466-2585
UDC:631.428:546.8
doi:10.5937/ZasMat1702235B

Zastita Materijala 58 (2)
235 – 242  (2017)

Determination of heavy metals in soil and biomass by the application of potentiometric stripping analysis

Abstract

In this paper the determination of lead, cadmium and zinc in soil and biomass was performed using potentiometric stripping analysis (PSA). In order to establish the optimal experimental conditions for PSA of Pb, Cd and Zn, the influence of pH value, time of metals extraction, stirring rate of the solution and the thickness of the mercury layer, as the working electrode, was investigated. The influence of mentioned parameters was tested for individual and simultaneous metals determination. The achieved limits of determination of single ions were for: lead 22.5 μg dm-3, cadmium 16.2 μg dm-3 and zinc 18.8 μg dm-3. The obtained results deviated from the expected for 1.1%, 1.9% and 1.8%, for lead, cadmium and zinc, respectively.

For simultaneous determination, the method is tested using the ions contents as follows: 45.0 μg dm-3 for lead, 32.5 μg dm-3 for cadmium and 37.5 μg dm-3 for zinc. The relative errors for simultaneous determination were: 4.6% for lead, 1.9% for cadmium and 1.9% for zinc. For the established optimal conditions, except for lead, deviations did not exceed ±2%. It is shown that potentiometric stripping analysis is usable for individual and simultaneous determination of lead, cadmium and zinc in soil and biomass.

Key words: lead, cadmium, zinc, potentiometric stripping analysis, soil, biomass.

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ODREĐIVANJE TEŠKIH METALA U ZEMLJIŠTU I BIOMASI PRIMENOM POTENCIOMETRIJSKE STRIPING ANALIZE

Izvod

U ovom radu je opisana primena potenciometrijske striping analize (PSA) za određivanje olova, kadmijuma i cinka u uzorcima zemljišta i biomase. U cilju utvrđivanja optimalnih eksperimentalnih uslova ispitivan je uticaj pH vrednosti rastvora, vremena izdvajanja metala iz rastvora, brzine mešanja rastvora i debljine filma žive, kao radne elektrode. Uticaj ovih parametara je ispitan za pojedinačno i istovremeno određivanje analiziranih metala. Postignute granice kvantifikacije pojedinačnih određivanja su za: olovo 22.5 μg dm-3, kadmijum 16.2 μg dm-3 i cink 18.8 μg dm-3. Dobiveni rezultati odstupaju od očekivanih vrednosti 1.1%, 1.9% i 1.8%, za olovo, kadmijum i cink, respektivno. Pri istovremenom određivanju sva tri ispitivana jona, metoda je testirana pri sledećim koncentracijama: 45.0 μg dm3 za olovo, 32.5 μg dm3 za kadmijum i 37.5 μg dm3 za cink. Relativne greške simultanog određivanja su bile: 4.6% za olovo, 1.9% za kadmijum i 1.9% za cink. Obzirom da greške određivanja ne prelaze ±2%, osim za olovo, dobijeni rezultati ukazuju da se PSA može primeniti i za istovremeno određivanje sadržaja olova, kadmijuma i cinka u zemljištu i biomasi.

Ključne reči: olovo, kadmijum, cink, potenciometrijska striping analiza, zemljište, biomasa.

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Bosiljka Stojanović1*, Jovan Đuković2, Miladin Drobnjak3

1RiTE Ugljevik, Ugljevik,BiH, 2Univerzitet u Istočnom Sarajevu,
Tehnološki fakultet Zvornik, Zvornik, BiH, 3Patenting, Beograd, Srbija

Naučni rad
ISSN 0351-9465, E-ISSN 2466-2585
UDC:620.196:621.182.44
doi: 10.5937/ZasMat1702243S

Zastita Materijala 58 (2)
243 – 248  (2017)

Procjena sklonosti rashladne vode prema koroziji ili stvaranju inkrustacija u termoenergetskim postrojenjima

Izvod

Sklonost rashladne vode ka koroziji ili stvaranju inkrustacija se procjenjuje prema izračunatim indeksima: Langelier Saturation Index, Ryznar Stability Index, Larson-Skold Index i drugi. U ovom radu je dat osvrt na tendenciju rashladne vode u TE Ugljevik u kratkim intervalima tokom 2015. i 2016. godine.

Ključne riječi: tendecija, indeks, vrijednost, korozija, prekrivenost.

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Assessment preferences cooling water to the corrosion or making incrustation in TPP

Abstract

The tendency of cooling water to the corrosion or inlay is estimated by the calculated index Langelier Saturation Index, Ryznar Stability Index, Larson-Skold Index and others. This paper gives an overview of the tendency of cooling water in TPP Ugljevik in short intervals during 2015. and 2016.

Keywords: tendency, index, value, corrosion, incrustation.

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