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Zaštita materijala 3. 2013

ZORAN GRDIĆ, GORDANA TOPLIČIĆ ĆURČIĆ,                                    Review paper
NENAD RISTIĆ, DUŠAN GRDIĆ                                                         UDC:631.811.85

Nondestructive methods for determination of reinforcement steel corrosion in concrete

Corrosion is the result of the reaction between a material and its environment. Corrosion of the rebar steel may occur under certain conditions in the reinforced concrete structures. The combination of concrete and reinforcement steel was considered optimal, but the practice has revealed the insufficient durability of these structures, the main factor of structural deterioration being the corrosion of reinforcement in concrete. The maintenance and repair of bridges and buildings for their safety requires effective inspection and monitoring techniques for assessing the reinforcement corrosion. Providing of structural safety, that is, regular maintenances and timely repairs require application of efficient techniques of monitoring and control of corrosion of reinforcement in concrete. These methods should enable identification of the degree of damage, and thus indicate the severity of the problem at the moment of inspection. This paper deals with implementation of various non-destructive methods of detection and monitoring of progress of reinforcement corrosion process in concrete, with the emphasis on the method used by CANIN (Corrosion Analyzing Instrument) apparatus. The principle of the method is based on the measuring of the electric potential which is detected on the surface of concrete and which is generated as a result of the electro-chemical corrosion process of the reinforcement.  Key words: reinforcement corrosion, determination, monitoring, nondestructive methods, CANIN        More >>>

 

NEDESTRUKTIVNE METODE ZA UTVRĐIVANJE KOROZIJE ARMATURE U BETONIMA

Korozija je rezultat reakcije između materijala i njegove okoline. Korozija armaturnih čelika može se pojaviti pod određenim uslovima u armirano betonskim konstrukcijama. Kombinacija betona i armature smatra se optimalnom, ali praksa je pokazala na nedovoljnu trajnost tih struktura. Često je glavni činilac nedovoljne trajnosti armirano betonskih struktura korozija armature u betonu. Obezbeđivanje sigurnosti konstrukcije, to jest, redovno održavanje i blagovremene popravke zahtevaju primenu efikasnih tehnika za praćenje i kontrolu korozije armature u betonu. Ove metode treba da omoguće identifikaciju stepena oštećenja i na taj način ukažu na ozbiljnost problema u trenutku inspekcije. Ovaj rad daje prikaz različitih nedestruktivnih metoda detekcije i praćenja napretka procesa korozije armature u betonu, s naglaskom na metode koje koriste Canin aparata. Princip metode se zasniva na merenju električnog potencijala koji se detektuje na površini betona, a koji je nastao kao rezultat elektro-hemijskog procesa korozije armature.
Ključne reči: korozija armature, monitoring, metode bez razaranja, CANIN  Dalje >>>


MIRJANA STOJANOVIĆ1, MARIJA MIHAJLOVIĆ1, ZORICA                       Review paper
LOPIČIĆ1, MARIJA PETROVIĆ1, JELENA MILOJKOVIĆ1,                      UDC:631.811.85
ČASLAV LAČNJEVAC2, DRAGAN RADULOVIĆ1

Raw phosphate composite as a natural fertilizer and soil remediation amendment

Our investigation is focused on the design of novel multifunctional material based on the synergistic conjunction of raw phosphate, zeolites modified with ammonium ions and waste biomass, in support to increase phospho-mobilization in various soil types and wider pH range. The results of the vegetation experiment in semi-controlled conditions with maize on soil type distric cambisol indicates that the addition of modified zeolite and ash pit cherries to the rock phosphate favors the growth of the culture and its yield. Released phosphate ions have a dual role as donor of nutrients, and soil remediation amendment through phosphate-induced stabilization of heavy metals. The field vegetation experiment with maize on soil type leached chernozem showed that NH4+-zeolite/raw phosphate composite has multifunctional properties applicable in sustainable agriculture.
Key words: modified zeolite, phosphate rock, ash pit cherries, nature mineral fertilizers, soil remediation amendment.              More >>>

 

KOMPIZITI NA BAZI SIROVOG FOSFATA KAO PRIRODNA DJUBRIVA I  REMEDIJACIONI AGENSI

Naša istraživanja su bila usmerena ka dizajniranju novog multifunkcionalnog materijala na bazi sinergističkog dejstva sirovog fosfata i modifikovanog zeolita amonijum jonima i otpadne biomase, u cilјu povećanja fosfo-mobilizacije u različitim tipovima zemlјišta i širokom opsegu pH vrednosti Efikasnost je ispitana na vegetacionom ogledu sa biljkama kukuruza u polukontrolisanim uslovima , na tipu zemljišta, distrični kambisol. Rezultati ukazuju da dodavanje modifikovanog zeolita i pepela koštica višnji, prirodnom fosfatu, doprinosi rastu, razvoju i povečanju prinosa ispitivane kulture. Otpušteni fosfatni joni imali su dvostruku ulogu kao donor hranlјivih materija i remedijacioni agens mehanizmom fosfatno -indukovane stabilizacije teških metala. Rezultati ukazuju da kompozit NH4+ -zeolit/prirodni fosfat ima multifunkcionalna svojstva pogodna za u održivoj polјoprivredi.
Ključne reči: modifikovan zeolite, sirovi fosfat, pepeo koštica višnji, prirodna djubriva, remedijacioni agens.                  Dalje >>>


RADU CLAUDIU FIERASCU1,                                                                   Scientific paper
RODICA MARIANA ION1, IRINA FIERASCU2                                        UDC:620.193.91

Remediation of biodegradation using synthesized nano – and micromaterials

The artefacts in general are subject to degradation processes that require physical intervention techniques and/or chemicals to minimize destructive effects. One of the most sensitive types of artefacts are the painting (both mural or on conventional support). The methods used for the prevention/removal of biodegradation must be able to prevent microbial contamination, or remove microorganisms already developed. The most common contaminant fungi (moulds) are Aspergillus sp. and Penicillium sp., species that shows a greater tolerance to environmental factors. They are versatile species, which requires relatively little moisture, compared with bacteria. To obtain remediation of the biodegradation of simulated artefacts presented in the study, we used a mixture of hydroxyapatite – nano-shaped barium hydroxide dispersed in isopropyl alcohol.    Key words: artefacts, restoration, conservation, nanomaterials, biodegradation.        More >>>

 

REMEDIJACIJA BIORAZGRADNJOM KORIŠĆENJEM SINTETIZOVANIH NANO I MIKROMATERIJALA

Predmeti u celini podležu procesima degradacije koje zahtevaju fizičke interventne tehnike i / ili hemikalije da bi  se smanjili destruktivni efekti. Metode koje se koriste za sprečavanje/uklanjanje biorazgradnje moraju biti u stanju da spreči mikrobiološku kontaminaciju, ili uklanjanje mikroorganizama koji su već razvijeni. Najčešći zagađiva­či među gljivicama (plesni) su Aspergillus sp. i Penicillium sp., vrste koje pokazuje veću toleranciju na faktore sredine. Oni predstavljaju raznovrsne vrste i zahtevaju relativno malo vlage, u poređenju sa bakterijam. Da bi se dobila remedijacija biorazgradljivošću korišćenih predmeta , data u radu, korišćena je mešavina hidroksiapatita – nano u obliku barijum hidroksid dispergovanog u izopropil alkoholu. Ključne reči: predmeti, restauracije, konzervacije, nanomaterijali, biodegradacija.      Dalje >>>


 

DRAGICA CHAMOVSKA1, ALEKSANDRA                                                Scientific paper
PORJAZOSKA KUJUNDZISKI2, TOMA GRCHEV1                                UDC :620.197.6

Polypyrrole coatings for corrosion protection of stainless steel

Electrochemical synthesis of PPy films with different thicknesses, using stainless steel electrode (18% Cr, 10% Ni) as a substrate (A=1.27 cm2), was performed at constant current (5 mA) under controlled polymerization time from a solution of 0.5M H2SO4 containing 0.1M Py (E = 0.95 ¸ 1.05 V/SHE). The electrochemical characteristics of the synthesized PPy-films on stainless steel electrode were determined using cyclic voltammetry in the potential range from 0.95 to -0.6 V/SHE, and sweep rate of 10 mVs-1 in 0.5M H2SO4 solution, while their anticorrosion features were studied by polarization current-potential measurements in 0.5, 1.0 and 1.5M solutions of H2SO4, and electrochemical impedance spectroscopy (EIS) performed in the solution of 1M H2SO4, in the frequency range from 100 kHz to 10 mHz at a corrosion potential of -0.1 V/SHE (a.c. signal of 5 mV). The parameters of the R(QR) equivalent electric circuit (EEC) for the best fit of the experimentally obtained data, where: R1 is the ohmic resistance of the electrolyte; the element Q(with n), represents the double layer capacitance Cdl at the polymer/solution interface; the element R2 is the charge transfer resistance, were obtained using the software developed by Boukamp. Key words: polypyrrole (PPy), stainless steel, corrosion protection, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), electrical equivalent circuits (EEC).     More >>>

Koroziona zaŠtita nerđajućeg čelika polipirolnim prevlakama

Elektroprovodljivi PPy-filmovi različitih debljina su elektrohemijski sintetizovani konstantnom anod­nom strujom (5 mA; E = 0.95 ¸ 1.05 V/ZVE) na elektrodi od nerđajućeg čelika (18% Cr, 10% Ni; A = 1.27 cm2) iz rastvora 0.5 M H2SO4 koji sadrži 0.1 M Py. Elektrohemijske i koroziono zaštitne karakteristike sintetizovanih PPy-filmova bili su određivani pomoću ciklične voltametrije, polariza­cijskih struja-potencijal zavisnosti, kao i elektrohemijskom impedansnom spektroskopijom, u vodenim rastvorima sulfurne kiseline. Koristeći softver Boukamp dobijeni su parametri R(QR)-ekvivalentnog električnog kola (EEK), za najbolje fitovanje eksperimentalno dobijenih podataka.   Ključne reči: polipirol (PPy), nerđajući čelik, ciklična voltametrija (CV), elektrohemijska ipedansna spektroskopija (EIS), ekvivalentno električno kolo (EEK).        Dalje >>>


DRITAN PRIFTI1,                                                                                         Scientific paper
MARJOLA PRIFTI2                                                                  UDC:541.123.1.012.001.53

Laboratory trials of liquid chromium reducing agents Tecno Ts (Tecnochem) and Synchro 205 (Grace)

There are certain advantages associated with the use of liquid Cr6+ reducing agents. Two liquid Cr reducing agents both based on tin sulphate solutions have been laboratory tested namely Tecno Chrored TS supplied by Tecnochem and Synchro 205 supplied by Grace. Based on the properties of laboratory cements and indicative cost it was observed that the reducing efficiency of Tecno TS is limited and given its high cost it is not recommended for use. Synchro 205 would require a dosage approx. 67 grams/ton of cement/ppm of Cr6+, to reduce Cr6+ to the desirable levels. An industrial trial of Synchro 205 is recommended for finally assessing its chromium reducing capacity. Despite, being clearly a more expensive solution at first liquid additives could be beneficial in plants that haven’t already invested in FeSO4 storage and handling equipment and plan to export within EU, or face clogging caused by FeSO4 inherent stickiness.  Key words: reducing agents, additives, cement.      More >>>

 

Laboratorijska ispitivanja tečnog hroma redukcijom agenasa Tecno TS (Tecnochem) i Sinchro 205 (Grace)

Postoje određene prednosti povezane sa korišćenjem tečnih Cr6+ redukcionih sredstava. Dva tečna Cr redukciona sredstva, na bazi sulfatnih rastvora, su laboratorijski testirana pod nazivom Tecno Chrored TS a isporučena su kao Tecnochem i Sinchro 205 (Grace). Na osnovu svojstava laboratorijskih cementa i indikativnih troškova uočeno je smanjenje efikasnost i ograničenost Tecno TS i ima svoju visoku cenu, pa se ne preporučuje za upotrebu. Sincro 205 bi zahtevao doziranje od oko 67 grama / tona cementa / ppm Cr6+, da se smanji Cr6+ do željenog nivoa. Industrijska ispitivanja Sinchro 205 se preporučuju za konačno ocenjivanje njegove hrom kapacitivnosti. Uprkos tome, što je očigledno skuplje rešenje , prvi tečni aditivi mogu biti od koristi u biljkama koje nisu već investirale FeSO4.    Ključne reči: redukciona sredstva, aditivi, cement.         Dalje >>>


JADRANKA MALINA, NATALIJA DOLIC,                                           Originalni naučni rad
FARUK UNKIC                                                                                         UDC:620.194.4

Mikrostrukturni aspekti lokalne korozije Al-slitina u lijevanom stanju

U ovom je radu proučavan utjecaj mikrostrukture na mehanička svojstva i lokalnu koroziju dviju komercijalnih aluminijevih slitina u lijevanom stanju. Eksperimenti su provedeni s uzorcima gnječive Al-Mg slitine povišenog sadržaja magnezija (EN AW-5083) i ljevačke Al-Si slitine eutektičkog sastava (EN AC-44200). Primjenom potenciodinamičke cikličke polarizacije određen je za svaku slitinu karakteristični piting potencijal Ebd, kod kojeg počinje lokalna korozija u otopini 0.01 mol/L NaCl. Nakon toga su uzorci Al-slitina bili izloženi djelovanju istog medija pri anodnom potencijalu višem od Ebd, sa ciljem da se optičkim mikroskopom prati nastajanje pitova i njihov rast tijekom određenog vremena. Vlačnim ispitivanjima ustanovljeno je da Al-Mg slitina ima bolja mehanička svojstva od Al-Si slitine, ali elektrokemijski parametri sugeriraju da je njena otpornost jamičastoj koroziji manja. Na osnovi metalografskih analiza, takvo se ponašanje može pripisati činjenici da mikrostrukturni konstituenti koji poboljšavaju mehanička svojstva Al-Mg slitine, tvore na njenoj površini lokalne galvanske članke na kojima počinje piting zbog otapanja aluminijeve osnove.
Ključne riječi: Al- slitine, lijevano stanje, kloridni medij, piting.        Dalje >>>

 

MICROSTRUCTURAL ASPECTS OF PITTING IN COMMERCIAL Al- ALLOYS IN AS-CAST CONDITION

In this work mechanical properties and local corrosion of two commercial aluminium alloys were studied in as-cast condition. Experiments were performed on the wrought Al-Mg alloy with high Mg content (EN AW-5083) and eutectic Al-Si alloy (EN AC-44200). Using potentiodynamic cyclic polarization, characteristic pitting potentials Ebd of alloys were determined at which local corrosion in 0.01 M NaCl solution starts. Afterwards, specimens of Al-alloys were polarized at an anodic potential 50 mV higher than Ebd in order to follow formation of pits and their evolution during the time. Mechanical testing has shown that Al-Mg alloy is characterized by higher mechanical properties than Al-Si alloy, while electrochemical parameters suggest the lower resistance to local corrosion. On the basis of metallographic analyses, such behavior can be ascribed to the fact that micro-constituents contributing to better mechanical performances of Al-Mg alloy, form local galvanic couples on its surface, where pitting starts by dissolution of aluminium matrix.
Key words: Al alloys, as-cast condition, chloride medium, pitting.   More >>>


MAGDALENA JAROSZ1, AGNIESZKA BRZÓZKA2,                              Scientific paper

MARIAN JASKULA1                                                                                 UDC:681.17.085

New H2O2 sensors based on silver nanowire arrays

Owing to its strong oxidizing properties, hydrogen peroxide (H2O2) has a wide range of applications. It is a key component for many industrial applications, such as pharmaceutical and cosmetic production or sterilization. Moreover, H2O2 is produced in the human body by immune system cells and is a product of glucose oxidation. Therefore, creating an effective and selective method of H2O2 detection has been of great importance. A novel glucose sensor, based on silver nanowires deposited into nanoporous anodic aluminum oxide (AAO) templates has been proposed. AAO templates has been prepared via anodization of Al in three electrolytes: oxalic, sulphuric and phosphoric acids. Silver nanowires has been created by deposition of silver in AAO templates. Electrodes based on silver nanowires were then investigated for electrocatalytical properties. H2O2 reduction on silver nanowires was tested using cyclic voltammetry (CV) and chronoamperometry (ChA). An influence of interfering substances like ascorbic acid was also examined.
Key words: sensors, hydrogen peroxide, silver nanowires, electrocatalytical properties.         More >>>

 

NOVI H2O2 SENZORI NA BAZI NIZOVA SREBRO NANOŽICA

Zahvaljujući svojim jakim oksidacionim svojstvima , vodonik peroksid (H2O2 ) ima širok spektar primene. To je ključna komponenta za mnoge industrijske aplikacije, kao što su farmaceutski i kozmetički proizvodi ili sterilizacija. Šta više, H2O2 se proizvodi u ljudskom telu u ćelijama imunog sistema i predstavlja proizvod oksidacije glukoze. Dakle, stvaranje efikasnog i selektivnog načina H2O2 detekcije je bilo od velikog značaja. Novi senzor glukoze, na osnovu srebro nanožica deponovanih u nanoporozni anodni aluminijum-oksida (AAO) je predložen. AAO šabloni su pripremljeni preko anodne oksidacije aluminijuma u tri elektrolita: oksalne, sumporne i fosforne kiseline. Srebro nanožice stvorene su taloženjem srebra u AAO šablone. Elektrode na osnovu srebro nanožica su zatim ispitivane na elektrokatalitička svojstva . Redukcija H2O2 na srebrnim nanožicama je testirana primenom ciklične voltametrije (CV) i hronoamperometrije (CHA ). Uticaj smeša supstanci, kao što su askorbinska kiselina, je takođe ispitivan. Ključne reči: senzori, vodonikperodsid, srebro nanožice, elektrokatalitička svojstva.     Dalje >>>


ZVONKO GULIŠIJA, ALEKSANDRA PATARIĆ,                                 Originalni naučni rad
MARIJA MIHAILOVIĆ, ZORAN JANJUŠEVIĆ                                          UDC:620.179.12

Mehanička svojstva otkovaka od legure Al EN AW 7075 dobijene elektromagnetnim livenjem

U radu su prikazani osnovi elektromagnetnog postupka livenja aluminijumske legure EN AW 7075 kao i rezultati mehaničke karakterizacije otkovka od ove legure koja je dobijena livenjem klasičnim polukontinualnim postupkom livenja i livenjem pod dejstvom elektromagnetnog polja sa dve različite frekvence. Rezultati pokazuju da uzorci otkovaka dobijeni od legure koja je livena u elektromagnetnom polju imaju zadovoljavajuće vrednosti mehaničkih svojstava i da se pravilnim izborom radnih parametara livenja mogu stvoriti uslovi za skraćenje tehnološkog postupka prerade ove legure. Ključne reči: Al legura, elektromagnetno livenje, otkovak.      Dalje >>>

 

MECHANICAL PROPERTIES OF forgings obtained from 7075 Al-alloy casted under electromegnetic field influence

The electromagnetic casting process fundamentals of EN AW 7075 Al-alloy casting, as well as the mechanical characterization results of this alloy forgings are presented in this paper. Forgings are obtained from the alloy casted by classical semi-continuous casting process and by electromagnetic casting process using two different frequencies. Results reveal that forgings obtained from the alloy casted by electromagnetic casting process have adequate values of mechanical properties and that proper choice of operating parameters can lead to shortening of this alloy processing. Key words: Al-alloy, electromagnetic casting, forging.      More >>>


SLAVICA S. RISTIC1, MARINA M. KUTIN1,                                                Scientific paper
MIRJANA A. PUHARIC2                                                                              UDC:620.179.13

Comparative testing of metal and welded joints by thermography and classical methods

The paper shows the results obtained in the simultaneously testing of steel spaceman’s and welded joints using conventional methods and thermography.  The main aim of testing was to relate the temperature changes of the specimen, continuously recorded by thermography, with stress – extension diagram. It is shown that the temperature changes on the specimen surface provide possibility to predict the critical stresses and to define the criteria for allowed maximum specimen temperature changes during elastic and elastoplastic strains, important for material caracterisation, diagnosis and monitoring of complex metal structures with welded joints by thermography. Key words:  thermography, welded joints, tension, material caracterization.          More >>>

 

UPOREDNO ISPITIVANJE METALNIH UZORAKA I ZAVARENIH SPOJEVA TERMOGRAFIJOM I KLASIČNIM METODAMA

U radu su prikazani rezultati dobijeni simultanim ispitivanjem čeličnih uzoraka i zavarenih spojeva standardnim metodama i termografijom. Glavni cilj istraživanja je bio da se povežu temperaturne promene uzorka, snimljene termografijom, sa parametrima dijagrama napon – izduženje. Dobijeni rezultati su pokazali da temperaturne promene na površini uzorka, snimljene termografijom, omo-gučavaju da se predvidi kritični napon i da se definiše kriterijum maksimalno dozvoljene temperaturne promene tokom elastičnih i elastoplastičnih naprezanja, što je veoma značajno za karakterizaciju materijala, dijagnostiku i monitoring složenih metalnih konstrukcija sa zavarenim spojevima. Ključne reći: termografija, zavareni spojevi, naprezanje, karakterizacija materijala.              Dalje >>>


SNEŽANA DEVIĆ1 ,MIRA COCIĆ2,                                                              Scientific paper
MIHOVIL LOGAR3                                                                                             UDC:620.186

Optical microscopy and its contribution to the control of applied submerged entry nozzle (SEN) in continuous casting of steel

The aim of this paper is to represent results of optical microscopy in control of Submerged Entry Nozzle (SEN) that will show the contribution of this method in the process of continuous casting of steel. A large number of SEN have been monitored and tested in the long period. This paper shows the most interesting results. SEN are formed parts of refractory materials based on alumina-graphite. They are produced with isostatic pressing process and used in all kinds of steel casting. A polarizing microscope Neophot 32 was used for examination with optical microscopy (reflected light) method. In the process of continuous casting of steel, SEN is in contact with steel and casting powder that can act destructively on SEN. Thus, SEN erosion is the result of that destruction. Steel effects on the inner wall of SEN, while casting powder effects on the outside of the wall. The destructive effect of steel and casting powder reduces the durability and resistance of SEN. Micrographs in this paper present the appearance and structure formed at the contact of steel – wall of SEN and casting powder – wall of SEN. Appearance, structure and minerals as a result of optical microscopy examination indicate the influence of various factors on the process of continuous steel casting. These factors are the quality of casting powder, the quality of SEN, technological parameters (speed of steel casting, casting temperature, composition of the steel) and others. Depending on the obtained SEN results, if necessary, the correction of technology parameters and other influencing factors could be performed. The correction depends on the causes for SEN resistance reduction. Thus, if external SEN erosion is large, a less aggressive casting powder will be used in the process.The results of optical micrscopy in control SEN indirectly contribute to improving processes, increasing quality of the final products and reduce costs. Key words: optical microscopy, SEN, casting powder,steel, continuous casting.         More >>>

 

OPTIČKA MIKROSKOPIJA I NJEN DOPRINOS KOD KONTROLE IZLIVNIKA PRIMENJENIH U PROCESU KONTINUIRANOG LIVENJA ČELIKA

Cilj rada je da prikaže pojedine rezultate primene Optičke mikroskopije u kontroli uronjavajucih izlivnika (SEN). Istovremeno da ukaže na doprinos ove metode u procesu kontinuiranog livenja čelika. U dužem vremenskom periodu praćen je i ispitan veliki broj izlivnika. U radu su prikazani najinteresantniji rezultati. Ispitani SEN su oblikovani delovi od vatrostalnog materijali na bazi alumografita (Al2O3-C) proizvedeni izostatičkim presovanjem. Primenjuju se pri livenju svih vrsta čelika. Za ispitivanja metodom Optičke mikroskopije korišćen je polarizacioni mikroskop Neophot 32 i odbijena svetlost. SEN u toku odvijanja procesa kontinuiranog livenja delom je uronjen u čelik koji se nalazi u kristalizatoru. U kristalizatoru SEN je u kontaktu sa čelikom, ali i sa livnim prahom koji je posut po čeliku radi zaštite čelika od oksidacije. I čelik i livni prah destruktivno dejstvuju na SEN, te dolazi do pojave erozije zida SEN. Čelik dejstvuje na unutrašnju stranu zida SEN, dok livni prah na spoljašnju stranu zida. Destruktivno dejstvo čelika i livnog praha smanjuje vek trajanja SEN, to jest njegovu izdržljivost. U ovom radu prikazane su mikrofotografije izgleda i strukture nastale na kontaktu čelik – zid SEN i kontaktu livni prah – zid SEN. Izgled, struktura i minerali kao rezultat ispitivanja optičkom mikroskopijom ukazuju na uticaje pojedinih faktora na proces kontinuiranog livenja čelika. Ti faktori se odnose na kvalitet livnog praha, kvalitet SEN, prvilno odabrane tehnološke parametre kao što su brzina livenja, temperatura livenja, odgovarajući sastav čelika i dr. Na osnovu dobijenih rezultata ispitivanja SEN, ako je potrebno može se vršiti korekcija u vodjenju procesa. Ta korekcija se vrši i zavisi od uzroka smanjenja veka trajanja SEN. Tako ako je velika spoljašnja erozija SEN pristupa se uvodjenju u proces manje agresivanog livnog preha. Rezultati optičke mikroskopije pri kontroli SEN indirektno doprinose poboljšanju procesa, povećanju kvaliteta finalnog prozvoda i smanjenju troškova.    Ključne reči: optička mikroskopija,uronjavajući izlivnik,livni prah,čelik, kontinuirano livenje.             Dalje >>>


NOVICA ĐORĐEVIĆ1, MIODRAG ŠMELCEROVIĆ1,                               Scientific paper

DRAGAN ĐORĐEVIĆ1, MILENA MILJKOVIĆ2                                          UDC:620.191.7

Thermodynamics of reactive dye adsorption on the bottom ashes

This paper describes the adsorption thermodynamics of textile reactive dye from aqueous solution on the bottom waste ashes formed by burning brown coal at the local city heating station. Reactive dyes are identified as problematic agents in the waste waters because they are water-soluble. In the waste-water, they are found in larger quantities than the other kinds of dyes and mainly in the hydrolyzed form, so they cannot be so easily removed by the systems of the conventional treatments. The values of thermodynamic parameters are the actual indicators for practical application in the adsorption process. Based on characteristic diagrams are determined the thermodynamic parameters, enthalpy and entropy of adsorption, and based on those determined the Gibbs’s free energy changes. In all cases, there is a negative sign of the thermodynamic parameters. Based on the results, it can be concluded that absolutely dominates the physical dye adsorption. Certain anomalies (several cases) in some indicators may indicate an error and the existence of, for example, chemical interactions in the system.
Key words: adsorption, ash, reactive dye, entropy, enthalpy, free energy.     More >>>

 

TERMODINAMIKA ADSORPCIJE REAKTIVNE BOJE NA KOTLOVSKI PEPEO

Ovaj rad opisuje termodinamiku adsorpcije tekstilne reaktivne boje iz vodenog rastvora na kotlovski otpadni pepeo nastao posle sagorevanja mrkog uglja u gradskoj toplani. Reaktivne boje su identifikovani kao problematični agensi u otpadnim vodama, jer su rastvorljive u vodi. U otpadnoj vodi se nalaze u većim količinama nego druge vrste boja i uglavnom u hidrolizovanom obliku, tako da se ne mogu tako lako ukloniti sistemima konvencionalnih tretmana prečišćavanja. Vrednosti termodinamičkih parametara u adsorpcionim procesima su stvarni pokazatelji za praktičnu primenu. Na osnovu karakterističnih dijagrama se određuju termodinamički parametri, entalpija i entropija adsorpcije, a na osnovu njih promena Gibbs-ove slobodne energije. U svim slučajevima, postoji negativan predznak termodinamičkih parametara. Na osnovu rezultata, može se zaključiti da dominira fizička adsorpcije boje. Određene anomalije (nekoliko slučajeva) kod nekih pokazatelja mogu ukazivati na greške i postojanje, na primer, izvesne hemijske interakcije u sistemu.   Ključne reči: adsorpcija, pepeo, reaktivna boja, entropija, entalpija, slobodna energija.      Dalje >>>


KOSTA VELIMIROVIĆ1, LJILJANA GAJIĆ-KRSTAJIĆ2,                 Originalni naučni rad
NEMANJA VELIMIROVIĆ3                                                      UDC:621.355.5:629.7.035.7

Propulzija električne bespilotne letelice – poređenje Li-jon kobalt i Li-jon čelik fosfat akumulatora

Bespilotna letelica je daljinski komandovan leteći robot sa automatskim upravljanjem koji se koristi kao platforma za nošenje specifičnog korisnog tereta kao što su kamere, senzori, komunikaciona ili neka druga oprema i naoružanje. Bespilotne letelice se sve više primenjuju na ekološkim zadacima civilnog sektora kao što su: osmatranja i kontrola saobraćaja, cevovoda, dalekovoda, zaštita od šumskih požara, zaštita od zagađivanja, očuvanja i istraživanja prirodne sredine, merenja radijacije itd. U radu su prikazane neke mogućnosti poboljšanja letnih performansi bespilotne električne letelice srednjeg dometa koja za propulziju i pogon opreme koristi hibridnu kombinaciju vodoničnih gorivih ćelija i litijum-jon kobalt akumulatora u prvom slučaju i vodoničnih gorivih ćelija i litijum-jon čelik-fosfat akumulatora u drugom slučaju. Razmatran je i ekološki aspekt obe hibridne kombinacije.
Ključne reči: ekologija, bespilotna letelica, gorive ćelije, performanse, litijum-jon-kobalt akumulatori, litijum-jon-čelik-fosfat akumulatori, performance.    Dalje >>>

PROPULSION OF UNMANNED AERIAL VEHICLES – COMPARISON OF LITHIUM – ION COBALT AND LITHIUM – ION IRON PHOSPHATE BATTERIES

Unmanned aerial vehicles are remotely commanded flying robots with automatic control. They are used as platforms for carrying specific payload, such as cameras, sensors, communication equipment and weapons. Unmanned aerial vehicles, in addition to military applications, are increasingly being applied to environmental civil society tasks, such as surveillance and control of traffic, pipelines, power lines,forest fires protection, protection from pollution, conservation and research of environment, etc. This paper presents some possibilities to improve flight performances of unmanned aerial vehicles with electric propulsion. The unmanned aerial vehicle uses a hybrid combination of hydrogen fuel cells and lithium – ion – cobalt battery or lithium – ion – iron phosphate battery. The environmental aspect of both hybrids combinations was also considered.   Key words: Ecology, Unmanned aerial vehicles, Fuel cell, Lithium-ion-cobalt batteries, Lithium-ion-iron phosphate batteries, Performances.        More >>>


ANDREJ ČEŠNOVAR                                                                        Professional paper

UDC:620.193.4:665.66

PROPULSION OF UNMANNED AERIAL VEHICLES – COMPARISON OF LITHIUM – ION COBALT AND LITHIUM – ION IRON PHOSPHATE BATTERIES

Unmanned aerial vehicles are remotely commanded flying robots with automatic control. They are used as platforms for carrying specific payload, such as cameras, sensors, communication equipment and weapons. Unmanned aerial vehicles, in addition to military applications, are increasingly being applied to environmental civil society tasks, such as surveillance and control of traffic, pipelines, power lines,forest fires protection, protection from pollution, conservation and research of environment, etc. This paper presents some possibilities to improve flight performances of unmanned aerial vehicles with electric propulsion. The unmanned aerial vehicle uses a hybrid combination of hydrogen fuel cells and lithium – ion – cobalt battery or lithium – ion – iron phosphate battery. The environmental aspect of both hybrids combinations was also considered.  Key words: Ecology, Unmanned aerial vehicles, Fuel cell, Lithium-ion-cobalt batteries, Lithium-ion-iron phosphate batteries, Performances.      More >>>

Inspekcija i upravljanje korozijom u rafineriji nafte OKTA

Pojava korozije predstavlja veliki problem u naftenoj industriji. Oštećenja usled korozije su glavni razlog za pojavu defekata opreme i cevovoda, što utiče na smanjenje efikasnosti procesa i značajno uvećava troškove. Takođe, defekti prouzrokovani korozijom predstavljaju opasnost za zaposlene, kao i za okolinu. Zbog ovoga, inspekcija i upravljanje korozijom pretstavljaju ključni aspekat menadžmenta svake rafinerije nafte. Tema ovog rada je analiza glavnih uzroka i najčešćih tipova korozije koji se sreću u rafineriji OKTA, kao i upravljanje korozijom. Detekcija korozije se uglavnom obavlja putem vizuelne kontrole. Stanje materijala se ispituje ultrazvučnim merenjem debljine i defektoskopijom kao i merenjem tvrdoće, dok se oprema podložena visokotemperaturnim uslovima ispituje infracrvenom kamerom. Inspekcijski izveštaji se koriste za određivanje brzine korozije, proračune preostalog vremena upotrebe opreme i ispitivanje pogodnosti za korišćenje.
Ključne reči: rafinerija, korozija, inspekcija, upravljanje korozijom.     Dalje >>>


BORISLAV MALINOVIĆ1, JOVO MANDIĆ1,                                                   Stručni rad
SLOBODAN BUNIĆ2                                                                                  UDC:620.197.2

Hemijsko taloženje kalaja na aluminijumu i njegovim legurama 

Klipovi za motorne pile, mopede, motokultivatore i  sl. izrađuju se od aluminijumskih legura i zaštićuju se prevlakama kalaja. Pošto je kalaj prema elektrohemijskom potencijalu plemenitiji od aluminijuma, nanosi se u odgovarajućim kupatilima hemijskim putem. Na ovaj način na pripremljenoj površini mogu se dobiti slojevi debljine do 0,003 mm. Ova prevlaka, uprkos svojoj maloj debljini ima odlične klizne i zaštitne osobine. Kalajna prevlaka na površini klipa pomaže i ubrzava uhodavanje novog klipa u cilindru i sprečava zaribavanje pri preopterećenju. Naročito je povoljan uticaj prevlake kod startovanja motora, kad klipovi rade u uslovima suvog i polusuvog trenja. Razvili smo florboratno kupatilo za hemijsko kalajisanje dijelova od aluminijuma i njegovih legura sa redukcionim sredstvom. Potencijal redukcionog sredstva je negativniji od potencijala aluminijuma, s tim da razlika nije suviše velika. U kupatilo smo dodali dodatke za sjaj koji značajno poboljšavaju izgled prevlake.
Ključne riječi: prevlaka kalaja, aluminijum, kalaisanje, klip.       Dalje >>>

 

CHEMICAL DEPOSITION OF TIN COATINGS ON ALUMINUM AND ITS ALLOYS

Pistons for chainsaws, mopeds, motor-cultivators, etc. are made of aluminum alloys and protected with a coating of tin. Since the electrochemical potential of tin more noble than aluminum, is applied by electroless plating. In this way, on a prepared surface can be obtained from thick layers up to 0.003 mm. This coating, in spite of its small thickness has excellent sliding and protective properties. Tin coating on the surface of the piston helps to speed up running a new piston in the cylinder and prevents the seizure of the overload. In particular, the beneficial effect of tin coating in starting the engine, when the pistons are working in conditions of dry and semi-dry friction. We have developed boron-fluoride bath for electroless tin plating parts of aluminum and its alloys with a reducing agent. Potential of reducing agent is more negative potentials than aluminum, but the difference is not too great. In the plating bath we add additive for the glow that greatly improves the appearance of the coating.    Key words: coating of tin, aluminum, tinning, piston.      More >>>


VIŠA TASIĆ,                                                                                                          Stručni rad
SILVANA DIMITRIJEVIĆ                                                                           UDC:665.66:681.17

Kontrolni sistem postrojenja za elektrolitičku rafinaciju

Pri rekonstrukciji postrojenja za elektrolitičku rafinaciju u Institutu za rudarstvo i metalurgiju Bor, uveden je i novi kontrolni sistem zasnovan na mikrokontroleru i personalnom računaru. Ovim sistemom omogućen je pravovremeni prenos informacija o stanju svih važnih parametara procesa do tehnologa. Nadzor rada ovog postrojenja može se vršiti i sa udaljenih lokacija posredstvom lokalne računarske mreže ili putem Interneta. Kontrolni sistem omogućuje automatsko praćenje i beleženje napona na svakoj ćeliji, temperature elektrolita, indikaciju rada i automatsko uključenje i isključenje grejača, kao i alarmiranje u slučaju prekoračenja ili podkoračenja zadatih graničnih uslova rada. Primenom kontrolnog sistema postignut je pouzdaniji rad i bolji uvid u tok procesa elektrolitičke rafinacije.
Ključne reči: elektrolitička rafinacija, kontrolni sistem, računarska mreža, temperatura, nadzor.          Dalje >>>

 

Control system for the electrolytic refining plant

As a part of reconstruction of the equipment for electrolytic refining in Mining and Metallurgy Institute Bor, a new control system was introduced. The system is based on microcontroller and PC. This system proviedes automatic control and timely transfer of informations about the status of all important process parameters to process operators. Supervision of the process can be performed localy, or from a remote location through a local area network or over the Internet. The control system provides automatic monitoring and recording of cell voltages, electrolyte temperatures, and automatic control of the heaters. In case of exceeding the given boundary conditions system generates alarm messages. Now, after application of the control sistem, the reliability of electrolitic refining process is improved and insight into the status of process parameters is better.   Key words: electrolytic refining, control system, network, temperature, monitoring.     More >>>


MILOŠ PETROVIĆ                                                                                                  Stručni rad
UDC:666.982.022.1

Polimerni betoni

Razvoj novih materijala je oblast u koju se danas najviše ulaže. Kompozitni materijali postoje i koriste se već hiljadama godina. Poboljšane osobine kompozitnih materijala pružaju mogućnost njihove široke primene. Jedan od najpoznatijih i najčešće korišćenih kompozita je beton sa česticama peska i šljunka povezanih cementom. Modifikacija betona pomoću polimera jedan od mogućih pravaca dobijanja materijala sa zadovoljavajućim mehaničkim karakteristikama, sa poboljšanom trajnošću u različitim sredinama i sa visokim estetskim vrednostima. Sve veća potrošnja agregata i ograničenja u eksploataciji prirodnih sirovina za proizvodnju agregata, dovela su do primene alternativnih materijala. Ovi materijali su najčešće industrijski sekundarni proizvodi ili građevinski otpad, čije deponovanje predstavlja veliki ekološki problem. Sve kompozite karakterišu neke zajedničke odlike koje ih čine posebnim i izdvajaju od drugih materijala: velika jačina i krutost – mogu biti jači od čelika, mala gustina i masa, otpornost na koroziju i visoke temperature, hemijska inertnost, mogućnost obrade i oblikovanja u raznovrsne oblike, izdržljivost i postojanost.    Ključne reči: beton, impregnacija, polimeri, modifikovacija, monomeri, kompoziti…          Dalje >>>

Polymer concrete

Development of new materials is an area that is today the most invested. Composite materials are also used for thousands of years. Improved properties of composite materials offer the possibility of their wide range of applications. One of the most commonly used composite the concrete with sand and gravel particles associated with cement. Modification polymer concrete using one of the possible routes to obtain materials with satisfactory mechanical properties, with improved durability in different environments and with high aesthetic values. The increasing aggregate consumption and limits the exploitation of natural resources for production units, led to the use of alternative materials. These materials are usually secondary products or industrial construction waste, whose disposal represents a major environmental problem. All composites are characterized by some common features that make them special and apart from other materials: high strength and stiffness-can be stronger steel, low density and weight, corrosion resistance and high temperature, chemical inertness, the possibility of processing and shaping the various forms, stamina and endurance.      Key words: concrete, impregnation, polymerization, modified, monomers, composites…        More >>>


LJILJANA RAŠKOVIĆ[1], DUŠICA SAMARDŽIĆ[2], BRATISLAV MILOŠEVIĆ²

Vodorazrediva dvokomponentna epoksi osnovna boja za zaštitu od korozije vojne opreme i naoružanja

 

Korozivno delovanje na vojnoj opremi i naoružanju je jedan od ključnih faktora u pogledu sigurnosti, ekonomije i ekologije. Korozivno delovanje može se zaustaviti ili sprečiti nanošenjem antikorozivnih premaza i formiranjem prevlaka, koje u prvom redu stvaraju barijeru prema korozivnoj sredini. Većina antikorozivnih premaza, koji se danas koriste nisu ekološki prihvatljivi zbog povećane emisije organskih rastvarača u okolinu sredine. Jedan od smerova za razvoj ekološki prihvatljivih antikorozivnih premaza su vodorazredivi premazi. U ovom radu razvijena je nova formulacija Vodorazredive dvokomponentne epoksi osnovne boje za zaštitu gotovo u svim korozivnim sredinama. Izbor epoksi veziva za optimalno formiranje filma, usledio je nakon praćenja procesa umrežavanja odabrane disperzije čvrste epoksi smole i umreživača alifatičnog poliaminadukta, metodom IR spektroskopije i merenjem tvrdoće formiranog filma u periodu umrežavanja. Ekološki prihvatljiv antikorozivni premaz, razvijen po novoj tehnologiji, ispitan je po standardu odbrane SORS 1549/05. Pored standardnog ispitivanja, izvršeno je i ispitivanje zaštitnih sistema: sa čisto vodorazredivim bojama i kombinovanog sistema sa vodorazredivom i bojom na bazi organskih rastvarača.

Dobijeni rezultati ukazuju da je novorazvijena ekološki prihvatljiva antikorozivna Vodorazrediva dvokomponentna epoksi osnovna boja zadovoljila sve zahteve kvaliteta za osnovnu boju po standardu odbrane SORS 1549/05. Ova boja takođe poseduje dobra zaštitna svojstva u sistemimu sa vodorazredivim poliuretanskim bojama i u sistemu sa poliuretanskim bojama na bazi organskih rastvarača.
Ključne reči: vodorazredivi antikorozivni premazi, epoksi vezivo, netoksični pigmenti.       Dalje>>>



[1] Adresa autora: ¹Niš, Nikole Pašića 65/14,

[2] Vojno-tehnički institut, Beograd, Ratka Resanovića 1

Waterborne two-pack epoxy base paint for anticorrosion protection of weapon and military equipment

Effects of corrosion on military equipment and weapons is one of the key factors in the terms of safety, economy and ecology. Corrosion activity can be stopped or prevented by applying anti-corrosion coatings and coating formation, which primarily creates a barrier to the corrosive environment. Most of the anticorrosion coatings, that are used today, are environmentally unfriendly due to increased emissions of organic solvents to the environment. One of the directions for the development of environmentally friendly anticorrosion coatings are waterborne coatings. In this paper the new formulation of waterborne two-pack epoxy coatings for basic protection in almost all corrosive environments is developed. Epoxy binder for optimum film formation, has been selected by monitoring the cross-linking of specific solid dispersion of epoxy resin and aliphatic polyamine adduct cross-linker, performed by IR spectroscopy and by measuring the hardness of the film formed during the cross-linking. Environmentally friendly anticorrosive coating, developed by new technology, has been tested according to the military standard SORS 1549/05. Besides that, a few more testing (by using the clean waterborne paints and by using the combined system with waterborne paints and paints based on organic solvents) of protective systems are performed.

The final results indicate that the newly developed, environmentally acceptable, anticorrosive paint, Waterborne two-pack epoxy base paint, meet all the quality requirements according to the military standard SORS 1549/05, to be used as the basic paint color.This paint also has a good protective properties in the system with waterborne polyurethane coatings and in the system with polyurethane paints based on organic solvents.  Keywords: waterborne anticorrosion coatings, epoxy binder, non-toxic pigments.      More >>>