BROJ 1
M. M. ANTONIJEVIĆ, M. RADOVANOVIĆ
Pregledni rad [PDF]
UDC:620.193.4:669.018=861
Uloga legirajućih elementa i nekih organskih inhibitora na koroziju mesinga
U radu su prikazani uticaji legirajućih elemenata (arsen, aluminijum, kalaj, fosfor, olovo, antimon, bor), koji se dodaju u mesing u malim količinama, na koroziju te legure. Pored toga, uticaj nekih organskih jedinjenja, prvenstveno azola i peptida, na brzinu i mehanizam korozije mesinga je analizirano.
INFLUENCE OF ALLOY ELEMENTS AND SOME ORGANIC INHIBITORS ON BRASS CORROSION
In the review paper, influence of alloy elements (arsenic, aluminium, tin, phosphorus, lead, antimony, boron) on brass corrosion is presented. Influence of some organic compunds, primarily azoles and peptides, on brass corrosin rate and mechanisam of dissoulution of the alloy is presented, too.
ŽELJKA JOVANOVIĆ, VESNA B. MIŠKOVIĆ-STANKOVIĆ, JELENA B. BAJAT
Originalni naučni rad [PDF]
UDC:620.4.5.197.6:667.637.2.4-036.8=861
Elektrohemijske i sorpcione karakteristike prevlaka metakriloksipropiltrimetoksisilana
Cilj ovog rada je ispitivanje uticaja parametara taloženja prevlake (koncentracija rastvora silana, vreme taloženja i vreme pečenja) na elektrohemijske i sorpcione karakteristike prevlaka metakriloksipropiltrimetoksisilana (MAPT) na aluminijumu.
Elektrohemijske i sorpcione karakteristike prevlaka metakriloksipropiltrimetoksisilana na aluminijumu su ispitivane u 3 mas. % rastvoru NaCl primenom spektroskopije elektro-hemijske impedancije (SEI), metode potencijal-vreme, gravimetrijske metode određivanja sorpcionih karakteristika i određivanjem adhezije. Pokazano je da veću korozionu stabilnost imaju prevlake metakriloksipropiltrimetoksisilana taložene iz rastvora koncentracije 5 vol. %, a da vreme taloženja i vreme pečenja prevlaka nemaju uticaja na njihova zaštitna svojstva.
Ključne reči: Prevlake, metakriloksipropiltrimetoksisilan, korozija, spektroskopija elektro-hemijske impedancije
ELECTROCHEMICAL AND SORPTION CHARACTERISTICS OF METACRYLOXYPROPYLTRIMETHOXYSILANE COATINGS
The aim of this work was to investigate the influence of deposition parameters (silane
solution concentration, deposition time, curing time) on electrochemical and sorption
characteristics of metacryloxypropyltrimethoxysilane (MAPT) coatings on aluminum.
The electrochemical and sorption characteristics of metacryloxypropyltrimethoxysilane coatings on aluminum were investigated during exposure to 3 wt. % NaCl solution using electrochemical impedance spectroscopy (EIS), potential-time measurements, gravimetric liquid sorption measurements and adhesion measurements. The coatings deposited from 5 vol. % solution exhibited better corrosion stability, while the deposition time and curing time have no influence on protective properties of MAPT coatings.
Key words: Coatings, metacryloxypropyltrimethoxysilane, corrosion, electrochemical
impedance spectroscopy
ŽELJKA JOVANOVIĆ, VESNA B. MIŠKOVIĆ-STANKOVIĆ, JELENA B. BAJAT
Originalni naučni rad [PDF]
UDC:620.193.197.6;667.637.2.4-036.8=861
Koroziona stabilnost prevlaka viniltrietoksisilana
U radu je ispitivan uticaj uslova taloženja prevlake,tj. koncentracije rastvora silana, vre-mena taloženja i vremena pečenja na korozionu stabilnost prevlaka viniltrietoksisilana (VTES) na aluminijumu.
Zaštitna svojstva prevlaka viniltrietoksisilana na aluminijumu su ispitivana u 3 mas. % ras-tvoru NaCl primenom spektroskopije elektrohemijske impedancije (SEI), metode potencijal – vreme, gravimetrijske metode određivanja sorpcionih karakteristika i određivanjem adhe-zije. Pokazano je da ve ću korozionu stabilnost imaju prevlake viniltrietoksisilana taložene iz rastvora koncentracije 5 vol. %, a da vreme taloženja i vreme pečenja prevlaka nemaju uticaja na njihova zaštitna svojstva.
Ključne reči: Prevlake, viniltrietoksisilan, korozija, spektroskopija elektrohemijske im-pedancije
CORROSION PROTECTION OF ALUMINUM BY VINYLTRIETHOXYSILANE COATINGS
In this work the influence of the deposition parameters, i.e. silane solution concentration, deposition time and curing time on the corrosion stability of vinyltriethoxysilane (VTES) coatings on aluminum was investigated.
The protective properties of vinyltriethoxysilane coatings on aluminum were investigated during exposure to 3 wt. % NaCl solution using electrochemical impedance spectroscopy (EIS), potential-time measurements, gravimetric liquid sorption measurements and adhesion measurements. It was shown that films deposited from 5 vol. % solution exhibited better corrosion stability, while the deposition time and curing time have no influence on corrosion resistance of VTES coatings.
Key words : Coatings, vinyltriethoxysilane, corrosion, electrochemical impedance spectroscopy
M. M. ANTONIJEVIĆ, M. RADOVANOVIĆ, M. PETROVIĆ, Z. LJUBOMIROVIĆ
Originalni naučni radrad [PDF]
UDC:669.35.5:621.315.5=861
Elektrohemijsko ponašanje mesinga u rastvoru boraksa u prisustvu 1-fenil-5-merkaptotetrazola
U ovom radu ispitivani su uticaji 1-fenil-5merkapto tetrazola (PMT) i hloridnih jona na elektrohemijsko ponašanje mesinga u rastvorima boraksa. Polarizaciona merenja vršena su u 0,1M rastvoru boraksa koji sadrži različite koncentracije (1,7·10-6 M – 8,5·10-3M) inhibitora PMT, kao i nakon izlaganja (5, 15, 60 min) elektrode u rastvoru PMT. Takođe, polariza-ciona merenja su vršena u rastvoru boraksa sa dodatkom različitih koncentracija (1·10-4M – 1·10-1M) hlorida, sa i bez prethodnog stajanja (15 minuta) elektrode u rastvoru PMT. Stepen pokrivenosti elektrode inhibitorom raste sa porastom koncentracije inhibitora i vremenom izlaganja elektrode inhibitoru PMT. Stepen pokrivenosti je veći pri prethodnom stajanju elektrode u rastvoru PMT nego pri dodavanju PMT u rastvor boraksa. Visoke vrednosti stepena pokrivenosti postignute sa i bez prisustva hloridnih jona ukazuju na to da je PMT dobar inhibitor mesinga u alkalnoj sredini. Adsorpcija inhibitora na površini mesinga odvija se prema Lengmirovoj adsorpcionoj izotermi.
Ključne reči: mesing, 1-fenil-5-merkapto tetrazol, hloridni joni, boraks
The effect of 1-phenyl-5-mercapto tetrazole (PMT) and chloride ions on electrochemical behavior of brass in borax solutions was investigated. The polarization measurements were conducted in 0.1M borax solution containing various concentrations (1,7·10-6M – 8,5·10– 3M) of PMT, as well as after electrode exposure (5, 15, 60 min) in PMT solution. Also, the polarization measurements were performed in borax solution containing various concentrations (1·10-4M – 1·10-1 M) of chloride ions, with and without previous immersion of electrode in PMT solution. The electrode surface coverage degree increases with inhibitor concentration and exposure time in PMT. The better effect was accomplished when brass electrode was previosly exposed to PMT solution, than when PMT was added to the borax solution. The high values of surface coverage degree recorded with and without the presence of chloride ions indicate that PMT is good brass corrosion inhibitor in alkaline media. The adsorption of PMT on the brass surface obays the Langmuir’s adsorption isotherm.
Key words: brass, 1-phenyl-5-mercapto tetrazole, chloride ions, borax.
1UROŠ LAČNJEVAC, 1VLADIMIR D. JOVIĆ, 1BORKA M. JOVIĆ, 1ZVEZDANA BAŠČAREVIĆ, 2MIOMIR G. PAVLOVIĆ
Originalni naučni rad [PDF]
UDC:669.245’28’787.419-492.2:620.18=861
Morfologija prahova Ni-Mo-O legura istaloženih elektrohemijskim postupkom iz rastvora amonijum sulfata
Elektrohemijsko taloženje prahova Ni-Mo-O legura ispitivano je snimanjem polarizacionih dijagrama u sulfatno-amonijačnim elektrolitima pri različitim odnosima Ni/Mo. Sve polarizacione krive okarakterisane su prisustvom dve prelomne tačke (A i B) na dijagramu. Tačka A odgovara početku taloženja Ni-Mo-O legure, dok tačka B reflektuje momenat kada je ukupna elektrohemijska reakcija kontrolisana brzinom formiranja mehurova gasovitog vodonika pri čemu se sa povećanjem koncentracije MoO42- jona u elektrolitu potencijal početka taloženja (tačka A) pomera ka negativnijim vrednostima. Morfologija čestica prahova ispitivana je skenirajućom elektronskom mikroskopijom (SEM). Prahovi istaloženi na staklastom ugljeniku iz elektrolita sa Ni/Mo ≥ 1/1 okarakterisani su prisustvom dve vrste čestica: sunđeraste čestice veličine 100 – 200 µm relativno glatkih površina sa jasno izraženim rupama i aglomerati sličnih veličina na kojima su prisutne jasno izražene naprsline i rupe, čija površina nije glatka i pokriveni su novo stvorenim grozdovima dendritičnog taloga. Za čestice praha istaloženog iz elektrolita koji sadrži odnos jona Ni/Mo = 1/3 karakteristično je da je udeo kompaktnog taloga značajan u poređenju sa ostalim prahovima, na kome se mogu registrovati dva tipa loptastih izraslina: manje kompaktne izrasline sa jasno definisanim dendritima i znatno kompaktnije izrasline. Kod prahova istaloženih na elektrodi od Ni, pored vrsta čestica koje su registrovane pri taloženju prahova na elektrodi od staklastog ugljenika, može se videti da se deo kompaktnog taloga praktično sastoji iz slojevitih struktura koje su posledica favorizovanog epitaksijalnog rasta taloga na srodnim podlogama.
MORPHOLOGY OF NI-MO-O ALLOY POWDERS ELECTRODEPOSITED FROM AMMONIUM SULFATE SOLUTIONS
The electrodeposition of the Ni-Mo-O alloy powders from ammonium sulfate containing electrolytes of different Ni/Mo ions concentration ratios was investigated by the polarization measurements. In all electrolytes similar polarization curves were obtained, characterized by two inflection points: Point A, the beginning of the electrodeposition process and point B, a moment when the powder electrodeposition is controlled by the hydrogen bubbles formation. The morphology of the electrodeposited Ni -Mo-O alloy powders was investigated using SEM. At Ni/Mo ratios higher or equal to 1/1 two types of particles were detected in the powder deposits: spongy-type particles (100 – 200 µm) with flat nodular surface and presence of cavities and agglomerates of similar dimensions characterized by the presence of cracks and cavities, with the nodular surface that is not flat, but is covered by the freshly formed dendrites. At Ni/Mo ratios of 1/3 the contribution of the amorphous-compact deposit is significant, while on top of this deposit rounded dendritic and compact outgrowths were detected.
LJUBICA IVANIĆ
Originalni naučni rad [PDF]
UDC:669.332.11.094.2=861
Praćenje kinetike prenosa kiseonika u rastopu bakra
U radu su dati rezultati ispitivanja uticaja dovođenja gasnog reagensa u kontakt sa rastopom na kinetiku prenosa kiseonika u tečan bakar. Kinetika prenosa je iskazana preko zavisnosti stepena usvajanja kiseonika od vremena tretiranja rastopa i brzine usvajanja od vremena tretiranja. Na osnovu rezultata opita vidi se da kinetika prenosa kiseonika u rastop zavisi od načina dovođenja gasa u kontakt sa rastopom, kao i od koncentracije kiseonika u struji gasa.
Ključne reči: bakar, kiseonik, kinetika prenosa
ABSTRACT
In this paper the results of investigation the influence of input mode the gas reagent ineraction with liquid copper to transfer kinetics of oxygen in to liquid copper, has been presented. Reaction kinetics has been shown trough oxygen inlet degree depending of time. According to results of investigation, transfer kinetics of oxygen in to liquid depends of the gas input mode to interaction with the liquid, and of oxygen concentration gas flow.
Key words: copper, oxygen, transfer kinetics
DARKO VUKSANOVIĆ1, DRAGAN, RADONJIĆ1, DUŠAN BORIČIĆ1, ZORICA CVIJOVIĆ2 , LJUBICA PAVLOVIĆ3
Originalni naučni rad [PDF]
UDC:620.193:669.715’3′:621.745=861
Ispitivanje korozione stabilnosti livenih legura aluminijuma sistema Al-Mg-Cu u livenom i termički obrađenom stanju
Poznato je da legure sistema Al-Mg imaju visoku korozionu stabilnost u rastvorima hlorida, koja je uslovljena obrazovanjem sloja koji otežava korozioni proces.
U ovom radu praćena su ispitivanja ponašanja livenih legura aluminijuma u rastvorima NaCl različite koncentracije sa ciljem praćenja njihovog ponašanja pri različitom sadržaju pojedinih legirajućih elemenata, prvenstveno Cu i Mg. Vršeno je i određivanje kvantitativnog udjela intermetalnih faza čije je učešće u strukturi legure u određenoj mjeri utiče na njene korozione karakteristike.
U radu su osim strukturnih vršena su ispitivanja hemijskog sastava, mehaničkih osobina i koroziona ispitivanja koja su obuhvatila tri metode: promjenu korozionog potencijala sa vremenom, metodu polarizacionog otpora i potenciodinamičku metodu.
INVESTIGATION OF CORROSION STABILITY OF CASTED ALUMINUM ALLOYS BASED ON SYSTEM Al-Mg-Cu IN CAST AND THERMALLY TREATED STATE
It is known that Al-Mg system alloys have high corrosion stability in chloride solutions that is caused by forming of layer that makes corrosion rate decreased.
In this work examination of casted Al-alloys behaviour in NaCl solutions of different concentration were followed with the purpose of following of their behaviour at different contents of alloying elements, first of all Cu and Mg. There was carried out determination of quantitative impact of intermetallic phases whose involvement in structure of alloy in certain measure influences on corrosion characteristics.
During examination apart of structure there were determined chemical contents, mechanical characteristics and corrosion characteristics that included three methods: corrosion potential versus time, polarization resistance method and potentiodynamic method.
BROJ 2
S. A. ABD EL–MAKSOUD
Review paper [PDF]
UDC:620.193.4:669.35=20
Electrochemical behaviour of copper corrosion and its inhibition in acidic media. A review
The literature dealing with the electrochemical behavior and corrosion characteristics of copper in acidic media was studied. Factors affect the inhibition efficiency of the organic compounds in acidic media were discussed. The dissolution of copper in different acids and the adsorption mechanisms of the compounds were discussed. The effect of temperature and synergistic inhibition were identified.
Key words: copper, corrosion, inhibition, behaviour, acid.
JOVAN P.POPIĆ1, BORE JEGDIĆ2
Originalni naučni rad [PDF]
UDC:620.193.4:669.131.2=861
Korozija visokohromnog belog gvožđa u kiseloj sredini
U ovom radu proučavano je elektrohemijsko ponašanje visokohromnog belog gvožđa u dearisanim rastvorima sumporne kiseline u oblasti pH 1-3. Provedena su merenja kon-centracije rastvorenog gvožđa i hroma u rastvoru, kao i zapremine izdvojenog vodonika. Po-ređenjem rezultata konstatovano je da pored elektohemijske korozije jednovremeno teče i drugi hemijski proces koji se odigrava na površini metala u kontaktu sa molekulima vode ili vodoničnim jonima uz izdvajanje vodonika. Ovi rezultati ukazuju da se uobičajene metode elektrohemijskog određivanja brzine korozije metala moraju primenjivati vrlo kritički, uz prethodno dokazivanje da su ovakvi hemijski procesi u odnosu na elektohemijske na ispitivanom metalu relativno zanemarljivi.
COOROSION OF CHROMIUM WHITE CAST IRON IN ACIDIC MEDIUM
In this work we studied the electrochemical behaviour of chromium white cast irons in deaerated aqueous sulphuric acid solutions of the pH 1-3. The measurements of concentrations of dissolved iron and chromium in the solution, as well as the volume of hydrogen evolved were carried out. By comparing the results, it was found that besides the electrochemical corrosion, another, chemical, process occurs at the same time. This process takes place at the surface of the metal, in the contact with the water molecules or hydrogen ions, and produces hydrogen evolution. These results show, that the usual electrochemical determination of the metal corrosion rate must be very critically applied.
JASMINA STEVANOVIĆ1, BRANIMIR JUGOVIĆ2, JOVAN POPIĆ1, JASNA STAJIĆ-TROŠIĆ3, NADA TALIJAN3
Originalni naučni rad [PDF]
UDC:669.25.24.28.787.012.37-492.2=861
Elektrohemijsko dobijanje prahova legure Co-Ni-Mo-O
Alkalni, amonijačni elektrolit je koričćen za dobijanje prahova Co-Ni-Mo-O legure. Prahovi su taloženi pri konstantnoj gustini struje, kao sporedna reakcija pri reakciji intenzivnog izdvajanja vodonika. Metali grupe gvožđa, Co i Ni indukuju taloženje Mo, koji sam ne može da se taloži iz vodenih elektrolita. Dobijeni prahovi su ispitani EDX, X-ray i SEM analizom i na osnovu dobijenih rezultata može se zaključiti da se promenom odnosa koncentracija soli u elektrolitu za taloženje, kao i gustinom struje taloženja može uticati na hemijski sastav i veličinu čestica prahova Co-Ni-Mo- O legure. Rezultati rendgenske analize ukazuju na amorfnu strukturu dobijenih prahova.
Ključne reči: prah Co-Ni-Mo-O, indukovano taloženje
ELECTROCHEMICAL DEPOSITION OF POWDER
ALLOY Co-Ni-Mo-O
The electrodeposition of the Co-Ni-Mo-O alloy powders from alkaline ammonium electrolytes and at constant current density was investigated. Metals of iron group, Co and Ni induce deposition of Mo, which alone can not be deposited from water electrolytes. Electrodeposited powders were investigated by SEM analysis where it is possible to determine the particle size, as well as the morphology of powders. The quantitative mass and chemical composition of Co-Ni-Mo-O alloy powders was determined by EDX analysis.
Key words: powder Co-Ni-Mo-O
SVETLANA NESTOROVIĆ, IVANA RANGELOV, DESIMIR MARKOVIĆ
Orginalni naučni rad [PDF]
UDC:669.35’18.046.44=861
Poboljšanje svojstava sinterovanih bakarnih legura termomehaničkom obradom
U ovom radu su dati rezultati ispitivanja sinterovanog bakra i legura na bazi bakra sistema Cu-Ag sa 4at.% srebra, odnosno legura sistema Cu-Au-Ni sa 2at.% Ni i 1at.% Au. Svi uzorci su podvrgnuti istoj termomehaničkoj obradi, koja je obuhvatala hladno valjanje sa različitim stepenima deformacije i izohrono i izotermalno žarenje do temperature rekristalizacije. DTA analiza je urađena na uzorcima koji su prethodno deformisani najvećim stepenom deformacije. Ovo istraživanje je pokazalo da žarenjem hladno deformisane Cu-4 at.% Ag legure dolazi do porasta mehaničkih osobina i električne provodnosti, kao posledica pojave efekta ojačavanja žarenjem.
Ključne reči: bakar, bakarne legure, ojačavanje,, električna provodnost
IMPROVEMENT THE PROPERTIES OF SINTERED COPPER ALLOYS BY THERMOMECHANICAL TREATMENT
This paper reports results of investigation carried out on sintered pure copper, copper-silver alloys containing 4at% Ag and copper-gold-nickel alloys containing 2at% Ni and 1at% Au. All samples were subjected to the same thermomechanical treatment, which included cold rolling with a different final reduction and isochronal and isothermal annealing up to the recrystallization temperature. DTA analysis was performed for the samples deformed with the highest deformation degree. This investigation shows that annealing treatment of cold deformed Cu-4 at% Ag alloy increased the strength and electrical conductivity, due to anneal hardening effect.
Key words: copper, copper alloys, strengthening, electrical conductivity
З. КАРАСТОЈКОВИЋа, З. КОВАЧЕВИЋб , З. ЈАЊУШЕВИЋв, С. ЈАКОВЉЕВИЋг
Оригинални научни рад [PDF]
UDC:620.193.92:669.131.6-462=861
Графитна корозија по ободу цеви од сивог лива за водоснабдевање потпомогнута утицајем тла
Сиви лив поседује добру корозиону отпорност и то му омогућује прилично велику употребу. Осим уобичајеног типа оксидације и грађења хидроксида железа, у сивом ливу је могућ још један облик корозије – у питању је тзв. графитна корозија. Још је специфичније када такав облик корозије настаје под утицајем тла. У питању је насута земља преко водоводних цеви. Графитна корозија обично се јавља после више година експлоатације , овде је забележена после око 15 година рада водоводних цеви од сивог лива у једном великом граду.
Компактан графит се јавио местимично у слојевима по ободу водоводних цеви, и такви слојеви никако не потичу из стадијума ливења. Графитизација као корозиони процес ће изазвати крти лом, а то даље за последицу има хаварију целог водовода. Почетне вредности тврдоће су биле у распону од 220-390 HV док су те вредности у кородираним деловима биле чак испод 40 HV, што је типична вредност тврдоће за овакав тип графитног слоја. Микроструктурна испитивања су, такође, потврдила да је графитна корозија настала и то након не тако дугог периода у експлоатацији, што је објашњиво утицајем тла.
Појава графитизације још увек није довољно третирана у нашој литератури и захтева даље разјашњење, како не би настале још веће забуне и/или заблуде код произвођача, корисника или оних који пројектују овакве системе.
Кључне речи: графитна корозија, сиви лив, водоводне цеви, насута земља
GRAPHITE CORROSION АROUND OF THE WATER-SUPPLYING PIPES MADE FROM GRAY IRON ASSISTED BY OF SOIL ATACK
Gray iron castings usually posses a better corrosion resistance than almost low alloyed steels, and this is one reason for their wide application. Besides an ordinary type of oxidation an iron-hydroxide formation, in gray iron is possible to found out an onother type of corrosion – it′s graphitic corrosion. The more specific is fact that such type of corrosion is related to soil atack on metal surface. That soil is dumped over these water pipes. The graphitic corrosion is discovered only after a years in service, here is registered after about 15 years in service in one great water supplying system.
The compact graphite has appeared partially in layers around the outer diameter of these pipes, but their appearance could not be related to the casting periode into the foundry. the hardness values in regions without graphitization were in range of 220-390 HV while in graphitized layer only about 40 HV, or less- which are typical values for such kind of layer. Microstructural investigations have prooved that that graphitic corrosion is made after not so long periode of service time, which could be explained by additional soil atack.
The graphitization phenomenon is not still well treated in our literature and it needs further explanations, for preventing the more confusions and mistakes, both to producer and users, or projectants.
Key words: graphite corrosion, gray cast iron, water-pipes, soil damped
MILOŠ B. RAJKOVIĆ1, UROŠ Č. LAČNJEVAC2 ZVEZDANA BAŠČAREVIĆ2,, TEODORA M. RAJKOVIĆ3, DRAGAN V. TOŠKOVIĆ4, DUŠAN D. STANOJEVIĆ4
Originalni naučni rad [PDF]
UDC:546.264-41:620.183=861
Određivanje kristalne strukture kalcijum-karbonata dobijenog iz vode za piće
Ispitivan je uzorak kamenca koji je uzet sa kućnog bojlera nastao zagrevanjem vode za piće koja se nalazi u vodovodnoj mreži grada Beograda – Novi Beograd (blokovi).
Ispitivanja na atomskom apsorpcionom spektrofotometru ukazala su da se nalazi domi-nantno kalcijum, kao CaO i to 48,90%, što preračunato na sadržaj CaCO3 iznosi 87,32%. Snimanja na difraktometru ukazala su da se kamenac sastoji od CaCO3 (85,25%), MgCO3 (11,05%), FeCO3 (1,90%) i MnCO3 (1,80%). Takođe je dokazano da je kamenac mešavina koja se sastoji od 66,92 % kalcita i 33,07% aragonita. Ovakav sastav posledica je činjenice da su kalcit i aragonit nastali u mirnijim uslovima sedimentacije u poluzatvorenoj plitkovodnoj sredini na temperaturi između 60 i 100°C (najbliže oko 80°C) i pri niskom pritisku.
Ključne reči: voda za pi će, kamenac, skenirajući elektronski mikroskop, rendgenska difrakciona analiza, atomski apsorpcioni spektrofotometar (AAS)
DETERMINATION OF CRYSTALLINE STRUCTURE OF CALCIUM CARBONATE OBTAINED FROM DRINKING WATER
Sample of scale which taken from house boiler is examined. This scale is made by warming drinking water from water-supply system of the -city of Belgrade – New Belgrade. Examinations on atomic absorption spectrophotometer (AAS) showed that there was mostly calcium, like CaO, for 48.90 % of mass which means calculated on contents CaCO3 takes 87.32 % of mass. Research on difraction meter showed that scale is composed of CaCO3 (in % of mass): (85.25%), MgCO3 (11.05%), FeCO3 (1.90%) and MnCO3 (1.80%). It was also proved that scale is mixture of 66.92 % Mg kalcite and 33.07 % aragonite. Zhis structure is result of fact that Mg calcite and aragonite are become in quiet conditions of sendimentation of half shut skin-deep water surrounding on temperature between 60 and 100°C (nearest about 80°C) and low pressure.
Key words: drinking water, scale, scaning electron microscope (SEM), X-ray diffraction analysis, atomic absorption spectrophotometer (AAS)
З. КАРАСТОЈКОВИЋа, Р. ПЕРИЋб, М. СРЕЋКОВИЋв, З. ЈАЊУШЕВИЋг, С. ЈАКОВЉЕВИЋд , З. КОВАЧЕВИће
Стручни рад [PDF]
UDC:669.215.018.11:620.192.4=861
Корозиони лом у легури злата 585 услед фазних трансформација
Корозиони процеси су увек прилично сложени по својој природи. Свакако најзаступљенији вид корозије је корозија настала услед оксидације, било железних или обојених метала. Већину племенитих метала одликује изванредно добра корозиона постојаност, са изузетнком бакра и делимично сребра. За злато се нипошто не би могло рећи да је кородиван метал. Исто би се могло рећи и за велику већину легура злата. Легирање се врши ради повећања чврстоће, али тада корозиона отпорност опада. Па ипак, у неким легурама злата присутан је један специфичан начин деградације особина, а механизам такве деградације наравно да није везан за оксидацију или деловање хлора, односно сулфида већ за структурне трансформације и проблеме који притом настају. Механизми корозионог пропадања, уопште, мало се изучавају код легура племенитих метала, што се објашњава тајношћу златарског заната а делом и високом ценом узорака. Овде се износе резултати испитивања промене микротврдоће и микроструктуре након заваривања, у циљу откривања разлога појаве лома у легури злата комерцијалне ознаке 585. Настали лом се никако не може везати за оксидацију или неки сличан уобичајени корозиони процес , већ искључиво за настале фазне трансформације. Нова фаза је регистрована преко знатног повећања тврдоће , што у материјалу изазива велике напоне, чак толике да настаје лом. У овом раду је посвећена пажња структурним трансформацијама и деградацији особина.
Кључне речи: легура злата 585, корозиони лом, фазне трансформације
CORROSION DAMAGE OF GOLD 585 ALLOY AS A RESULT OF PHASE TRANSFORMATIONS
The corrosion processes always are pretty complex in their nature. One of the most common type of corrosion is the oxidation, either the ferrous or non-ferrous metals. Almost of noble metals have an excellent good corrosion resistance with exception of copper and partially silver. For gold it could not be said to be a corrodive metal.
Eventhough in few gold alloys is present one specific type of degradation of the properties and this mechanism however is not related to the oxidation, chlorine or sulphide atack, but problems arising when some slow cooling structural transformations took place. The mechanisms of corrodive degradation generally are not well established into the noble metal alloys which could be partially explained by existing the secret of state of the art and also by a high price of specimen. Here are reported the results of microhardness and microstructural testing after welding for discovering the reason(s) for damage of treated commercial gold alloy 585. The examined damage could not be anyway related to the oxidation or similar corrodive process, but only according to the phase transformations. The new phase is registered through the very high values of hardness, which also have produced a high level of stress, to such level which is enough to causes a damage. In this paper is shown an example of damage in gold alloy 585 after welding and slow cooling.
Key words: graphite corrosion, gray cast iron, water-pipes, soil damped
JASMINA LILIĆ1, VESNA FILIPOVIĆ1, MIROSLAV GRUJIĆ1, MIODRAG ŽIKIĆ2, SAŠA STOJADINOVIĆ2
Stručni rad [PDF]
UDC:622.763’17:502.37(497.11)0861
Rekultivacija brane 3A flotacijskog jalovišta Veliki Krivelj
Prilikom flotiranja rude bakra u okviru rudnika Veliki Krivelj, kod Bora, stvara se nus proizvod koji se zove flotacijska jalovina i ona se kao otpadni materijal iz flotacije odlaže na posebno za to određeno mesto u industrijskom krugu. Tako je nastalo flotacijsko jalovište Veliki Krivelj, koje je i danas u funkciji. Područja koja su degradirana flotacijskom jalovinom nekada su bila očuvana u neporemećenom ekosistemu. Sada se ova podru čja moraju rekultivisati, što je dugotrajan i skup proces, jer podležu zakonskoj regulativi iz oblasti rekultivacije degradiranih površina iz Zakona o rudarstvu. Odlaganjem flotacijske jalovine u dolini Kriveljske reke, degradirano je 395 ha plodne zemlje opštine Bor.
Ključne reči: flotacijska jalovina, degradirana površina, rekultivacija, životna sredina.
ABSTRACT
Byproduct of the copper ore flotation within the processing plant at Veliki Krivelj open pit mine are the tailings. Tailings are disposed on a special place near the processing plant. This disposal created the tailings waste dump Veliki Krivelj, which is used up to date. The area degraded by tailings disposal once had preserved and undisturbed ecosystems. Today these areas must be rehabilitated which is long and expensive process regulated by the Serbian mining law.The disposal of tailings degraded 395 ha of fertile soil in the municipality Bor.
Key words: tailings, degraded area, rehabilitation, environment.
BROJ 3
HA-WON SONG, CHANG-HONG LEE, KEWN CHU LEE and V. SARASWATHY*
Scientific paper [PDF]
UDC:666.981/982.004.69=20
Rehabilitation of reinforced concrete by electro deposition and physicochemical process – a Review
Cracks in concrete can be caused by various factors, such as bleeding, shrinkage, faulty construction methods, poor construction practices, thermal gradients, settlement, corrosion of reinforcement, weathering (freeze-thaw) and alkaliaggregate reaction [1]. Micro cracks in concrete can also be induced by external loadings or as a result of the interaction of the concrete with the environment.
These cracks play a major role on important parameters like permeability, rate of chloride ingress, compressive strength etc., and thus affects the reinforcement corrosion protection. Normally smaller cracks are harmless according to the durability point of view than larger cracks[2].
M. ABDALLAH, A. S. FOUDA* S. M. EL-ASHREY
Scientific paper [PDF]
UDC:620.193.197.6:669.14.018.8=20
Corrosion inhibiting properties of some crown ethers on corrosion of stainless steel (types 304 and 316) in hydrochloric acid
Crown ethers as macrocyclic compounds constitute a potential class of corrosion inhibitors. The effect of some types of crown ethers on the corrosion behavior of stainless steels of types 304 and 316 in 2M HCl at different temperatures was investigated. Loss in mass and galvanostatic polarization techniques were used to achieve this purpose. In addition surface examinations and morphological studies were applied using scanning electron microscope (SEM) and emission dispersive X-ray analysis (EDX) to study the nature of the protective film formed in absence and presence of these compounds. The inhibition efficiency of these compounds was found to increase with concentration and decrease with rising temperature. The adsorption of these compounds was found to obey Temkin’s adsorption isotherms. The values of activation energy and free energy of adsorption indicated physical adsorption of these compounds on the surface. Galvanostatic polarization studies showed that crown ethers act as mixed type inhibitors and retard the dissolution of stainless steels. All the results achieved were compared and discussed and the investigated crown ethers were arranged depending on their effectiveness as corrosion inhibitors of types 304SS and 316SS.
Keywords: stainless steel, 304SS, 316SS, crown ethers, corrosion inhibitors.
E.H. EL-MOSSALAMY
Scientific paper [PDF]
UDC:665.652.2.09:678.65=20
Synthesis and thermal kinetic studies of quinazolin polymer complexes
Polymer of 2-acrolyl-quinazolin-carboxyl and homopolymer (PAQNH) complexes with Mn2+, Uo22+, Zr4+ and Nb 5+ metals have been synthesized and characterized using different spectroscopic techniques (1H- NMR, IR and Uv-Vis) and magnetic measurements. The results obtained suggest that the metal ions dopping in dimer monomer forming octahedral complexes. The thermal stabilities of dopping polymer complexes of AQNH with metal chlorides were studied thermally, The rates of polymerization of quinazoline acrolyl (PAQNH) in the absent and in presence of metal ions were studied. The activation parameters of the degradation of doping were discussed and calculated.
Key words: Quinazoline; Dopping, polymer complexes; IR, UV VIS 1H-NMR, (TGA, DTA).Activation parameters.
A. M. BADIEA* , K. N. MOHANA
Scientific paper [PDF]
UDC:620.197.3.001.572.575=20
New study of passivation as an isotherm on metals surface: theoretical and experimental approach
Most of the studies on metals surfaces paid attention to adsorption isotherm. The present study focuses on passivation as an isotherm and its relation to Gibbs free energy and other thermodynamic parameters. Based on the equilibrium and dynamics of the processes that occur at the interface between the solid (surface) and reaction products, passivation isotherm model was created. The mode of relationship among the reaction products, metals surfaces and the inhibitor was also obtained. New expressions for passivation processes were introduced and new mathematical models for passivation as an isotherm were created.
Key words: Passivity, Oxidation, Weigh loss, Passive film
VLADIMIR CVETKOVSKI1, VESNA CONIĆ1, MILENA CVETKOVSKA2
Naučni rad [PDF]
UDC:669.354.76(497.11)=861
Prečišćavanje otpadnih kiselih rastvora iz elektrolitičke rafinacije bakra Bor postupkom flokulacije
U radu se prezentira izdvajanje suspendovanih materija iz otpadnih kiselih rastvora elektro-litičke rafinacije bakra u Boru. Ispitivanja su izvedena taloženjem suspendovanih materija prirodnim putem kao i taloženje uz pomoć flokulanta FN-001 (poliakrilamid proizvod Hemijske industrije ″Župa″ Kruševac). Prirodno taloženje je praktično završeno posle trećeg sata, a istalo-žilo se 95 % čvrste faze sadržane u kiselom rastvoru. Taloženje uz pomoć flokulanta praktično je završeno posle petog minuta, a istaložilo se takođ e 95 % čvrste faze. To ukazuje da je brzina taloženja uz pomoć flokulanta bila 40 puta veća od brzine taloženja prirodnim putem. Na osnovu ovih razultata moguće je projektovanje taložnika manjih dimenzija. Koloidni disperzni sistemi su vrlo stabilni, tako da se obično ne mogu prirodnim putem istaložiti. U cilju pre čišćavanja otpadnih rastvora koji sadrže grubo dispergovane ili koloidne čestice najčešće se primenjuje postupak flokulacije, tj. taloženje suspendovanih materija pod dejstvom hemijskih reagenasa-flokulanata.
Ključne reči: kiseli otpadni rastvori, suspendovane čvrste čestice, flokulanti
PURIFICATION OF ACIDIC WASTEWATER FROM ELECTROLYTIC RAFINATION OF COPPER BY SETTLING
In this work is presented the separation of suspended solids from the Bor tank house acid solutions. Investigation was performed by settling the suspended particles on natural way as well as by settling with help of flocculant FN-001 (polyacrylamide, product of Chemical industry ″Župa″ Kruševac). Natural settling was practically completed after three hours, and on this way was settled 95 % of the suspended particles. Settling with help of flocculant was practically completed after five minutes, and, also was settled 95 % of the suspended particles. It was pointed that settling rate using flocculant is 40 time faster than natural settling rate. On the base of these results, it is possible to designs the settler with smaller dimensions.
Key words: acid solutions, suspended solids, flocculant
VELJKO ĐUKIĆ
Stručni rad[PDF]
UDC:666.002.68.004.69(497.15)=861
Uloga cementne industrije BiH u sistemu upravljanja otpadom
U ovom radu su prikazani: pregled industrije cementa , stanje upravljanja otpadom i strategija snabdjevanja energijom u BiH, svjetska iskustva u primjeni alternativnih energenata u proizvodnji cementa i tehnički uslovi za njihovo korištenje, uticaj na tehnološki proces i svojstva primarnog proizvoda, uticaj na okolinu i mjere zaštite, važeći svjetski propisi, te prijedlog uputstva za rad komisije za procjenu uticaja na okolinu za zahvate uvođenja otpada kao goriva u našoj cementnoj industriji.
Ključne riječi: cementna industrija, energija, zaštita životne sredine
THE ROLE OF BOSNIA AND HERZEGOVINA CEMENT INDUSTRY IN THE SYSTEM OF WASTE MANAGMENT
In the paper are presented: experiences in recycling of waste materials in the cement industry, features of cement industry related to this subject and technical conditions for these activities, influence on cemnt production process and properties of cement as well as onto the environment and finally existing European and world regulations for such waste recycling.
Key words: cement industry, energy, environment protection
STEVA BOŽIĆ, RADE RADOJEVIĆ
Stručni rad [PDF]
UDC:620.193.194:631.3=861
Korozija sredstava mehanizacije u poljoprivredi
Poljopruvreda Srbije raspolaže sa oko 5.000.000 jedinica sredstava mehanizacije. Ta sredstva su svakodnevno, bilo da su u procesu rada ili van njega, izložena dejstvu nekih sredina koje na njih deluju korozivno. Štete koje pri tome mogu nastati, kao i troškovi koje je potrebno činiti da bi se štete umanjile ili sprečile vrlo su veliki. Štete i troškovi su u uzajamnoj vezi koja funkcioniše po principu spojenih sudova. Iz tog razloga je želja da se ukaže na značaj izučavanja korozije u oblasti sredstava poljoprivredne tehnike.
Ključne reči: korozija, poljoprivreda, mehanizacija.
CORROSION OF AGRICURTULAR MACHINERY
The agriculture of Serbia has approx. 5 million units of agricultural machinery and equipment at its disposal exposed daily to unfavourable environmental and weather conditions with corroding impacts. Damages are enormous as well as costs needed to decrease or even eliminate the undesirable effects. Damages and costs are closely linked and the aim was to point to the importance of focusing attention on corrosion in the field of agricultural machinery.
Key words: corrosion, agriculture, machinery
S. DRAGULOVIĆ, V. GARDIĆ, S. DIMITRIJEVIĆ, A. IVANOVIĆ, Z. STANOJEVIĆ-ŠIMŠIĆ
Stručni rad [PDF]
UDC:620.193.194:631.3=861
Reciklaža srebra iz srebrnih kontakata hemijskim postupkom
Cilj rada je bio da se iz srebrnih kontakata valorizuje srebro, a da se legirajući elementi odvoje u obliku nerastvornog taloga. Srebrni kontakti, pored srebra sadrže veliki procenat bakra, koji u postupku prerade prelazi u hidroksid bakra koji se može dalje preraditi procesom topljenja u korisnu komponentu.
Ključne reči: srebrni kontakti, valorizacija, srebro
RECYCLING OF SILVER FROM SILVER CONTACTS USING CHEMICAL TREATMENT
The aim of this paper is silver recycling from silver contacts , and precipitation alloing element like sludge. Silver contacts consist large percent of copper, and in processing copper conversion to copper hydroxyde. Copper hydroxyde convert in usefull componente in melting process.
Key words: silver contact, valorization, silver
BROJ 4
S. MURALIDHARAN, A.K.PARANDE*, V.SARASWATHY, K.KUMAR, and N.PALANISWAMY
Scientific paper [PDF]
UDC:620.193-4:666.942.6=20
Effect of silica fume on the corrosion performance of reinforcements in concrete
The influence of silica fume on the corrosion resistance and strength of concrete was studied. The aim of this investigation mainly focused on how the silica fume was involved in the strength of concrete and also in the corrosion property of steel rebar embedded in mortar and concrete. Compressive strength measurements were made on various silica fume addition for the different curing period. Potential-time behavior studies were carried out to determine the status of rebars inside the mortar. Weight loss measurements were adopted to quantify the corrosion of rebars embedded in silica fume admixed concrete. Anodic polarisation studies were carried out to understand the optimum level of silica fume with better corrosion resistant properties. Alkalinity and free chloride contents were analysed at the initial and final exposure periods. All these studies showed that additions of silica fume up to 8 percent by weight of Ordinary Portland cement (OPC) improved the corrosion resistance properties of steel in mortar and concrete. Silica-fume has both positive and negative effects on the different factors governing the steel reinforcement corrosion. However, the positive factors by far dominate over the negative factors. Silica fume has a positive effect on the risk of corrosion and rate of corrosion, provided that normal good workmanship is carried out and that silica fume is not used in very low-quality concrete to reduce the cement content.
Key words: Corrosion; Reinforcements; Mortar; Concrete; Silica fume
A. H. ABBAR1*, A. H. SULAYMON2 and M. G. JALHOOM3
Scientifica paper [PDF]
UDC:661.717.3:621.357.3=20
A Novel, Pilot Scale Electrolysis System for Production of P-Aminophenol using Parallel Screen Electrode
The present research investigates the nitrobenzene reduction to p-aminophenol by using a novel pilot scale electrolysis system consisting of parallel amalgamated copper screens electrode followed by direct acetylating to paracetamol. The preparative electrolysis of nitrobenzene was carried out using supporting electrolytes consisting of (2M) H2SO4 in a solution of 50% 2-propanol/50%water (v/v) and two modes of operation galvanostatic (controlled current) and potentiostatic (controlled potential). A Factorial experimental design was adopted for studying the effect of electrode potential, nitrobenzene concentration, flow rate, and number of screens in the electrode on the yield of p-aminophenol.
The results indicated that yield of p -aminophenol increases with cathode potential more positive than (-400mV vs. SCE), increasing flow rate, decreasing nitrobenzene concentration, and num-ber of screens. The best results were obtained at cathode potential (-375mVvs.SCE), catholyte flow rate (111cm 3s- 1) ,nitrobenzene concentration (0.1gcm-3) and number of screens not grater than five in which p-aminophenol yield was (80%) ,with maximum conversion (83%) of p-aminophenol to paracetamol.
Key words: Nitrobenzene, P-aminophenol, electrochemical reduction, Preparative electrolysis, Screens electrode.
S. RAJENDRAN1*, M. KANAGAMANI1, M. SIVAKALAIVANI1, J. JEYASUNDARI2, B. NARAYANASAMY3 and K. RAJAM4
Scientific paper [PDF]
UDC:620.193.4:669.14.018.841=20
Corrosion behaviour of carbon steel in presence of Cu2+ ions and citrate ions
Corrosion behaviour of carbon steel in the presence of Cu2+ ions and citrate ions has been investigated by electrochemical studies such as polarization, AC impedance and cyclic voltammetry. It was found that as the concentration of Cu2+ ions increased, the corrosion rate of carbon steel citrate also increased. When citrate was added in the presence of Cu2+, corrosion rate decreased. As the concentration of increased, the corrosion rate decreased. The protective film consisted of Fe2+ – citrate complex formed on the anodic sites of the metal surface. In the presence of Cu2+ ion and citrate ion, two semicircles were observed in the AC impedance spectra.
Key words: Corrosion of carbon steel, pitting corrosion, copper ion, citrate ion, rain water(RW)
D. STANOJEVIĆ1, J. PJEŠČIĆ2, M. V. TOMIĆ1, M. G. PAVLOVIĆ1
Scientific paper [PDF]
UDC:669.25.5.73.054.6=20
Evaluation of cobalt from zinc and cadmium
This work deals with testing the possibilities for enriching with cobalt the waste sludge from the production of electrolytic zinc and cadmium. Cobalt is present in zinc concentrates, as accompanying metal, in low concentrations (0,001-0,005%). During certain stages of hydrometallurgical zinc and cadmium production, cobalt is, however, concentrated up to commercially important values. In the cadmium production process, which is technologically connected with zinc production, the so called “cobalt purification cake” precipitate presents such a resource of cobalt. This precipitate contains 0,6-1% Co, 2-6% Cd, 40-55% Zn, 0,1-0,6% Ni, 0,1-0,7% Cu, 30-35% H2O, etc. The metals present are leached from the fresh cobalt purification cake by a sulphuric acid solution (150g/dm3), with strict pH control of the reaction pulp, and as a result of this, a precipitate with a cobalt concentration of 6-12%, is obtained. Sulphates of the leached metals go back to the process, while precipitate with higher cobalt content (“cobalt-concentrate”) can be used for various purposes. Starting from cobalt concentrate, CoO(OH), Co2O3, CoSO4⋅7H 2O, ceramic pigments, etc, have been obtained.
Key words: production of electrolytic zinc and cadmium, cadmium production, zinc production, „cobalt purification cake“
DOBIJANJE KOBALTA IZ MEĐUPRODUKATA PROIZVODNJE ELEKTROLITIČKOG CINKA I KADMIJUMA
Predmet ovog rada je ispitivanje mogućnosti za oboga ćivanje kobaltom otpadnog mulja iz proizvodnje elektrolitnog cinka i kadmijuma. Kobalt je u koncentratima cinka, kao prateći metal, prisutan u malim količinama (0.001 – 0.005%). U pojedinim fazama hidrometalurške proizvodnje cinka i kadmijuma, kobalt se, međutim, koncentriše do komercijalno značajnih vrednosti. U procesu proizvodnje kadmijuma, koja je tehnološki vezana za proizvodnju cinka, tzv. “talog od prečišćavanja kobalta” predstavlja takav resurs kobalta. Ovaj talog sadrži 0.6-1% Co, 2-6% Cd, 40-50% Zn, 0.1-0.6 % Ni, 0.1-0.7% Cu i td. Iz svežeg taloga od prečićavanja kobalta rastvorom sumporne kiseline (150 g/dm3), uz striktnu kontrolu pH vrednosti reakcione pulpe, izlužuju se prisutni metali, a kao rezultat luženja dobija se isprani talog u kome se koncentriše kobalt (6-11%). Sulfati izluženih metala se vra ćaju u proces, dok se talog sa povišenim sadržajem kobalta može koristiti u različite svrhe. Polazeći od ovog taloga u laboratoriji su dobijeni: Co3O4, CoSO4⋅7H2O, keramički pigmenti i td.
Ključne reči: elektrolitička proizvodnja cinka i kadmijuma, proizvodnja kadmijuma, proizvodnja cinka, „talog od prečišćavanja kobalta“
S. M. MILIĆ, M. M. ANTONIJEVIĆ
Originalni naučni rad [PDF]
UDC:669.33.053.4=861
Elektrohemijsko ponašanje bakra u alkalnom rastvoru u prisustvu benzotriazola i hloridnih jona
U ovom radu je ispitivano elektrohemijsko ponašanje bakra u rastvoru natrijum-tetraborata (boraksa) u prisustvu i odsustvu hloridnih jona. Takođe, ispitivan je i uticaj benzotriazola (BTA) na anodno ponašanje bakra. Nađeno je da se na bakru grade oksidi Cu2O i CuO i da se potencijal pikova pomera u pozitivnu stranu sa vremenom stajanja u rastvoru boraksa. Stajanjem Cu elektrode od 1 h u rastvoru boraksa koji sadrži različite koncentracije hloridnih jona (0,001; 0,010; 0,050 i 0,100 mol/dm3 Cl–) ispoljava se aktivatorsko dejstvo tih jona, dok stajanjem bakra u vremenu od 6 h u navedenim rastvorima, hloridni joni su imali, pored aktivacionog, i pasivacioni efekat. Prilikom ispitivanja uticaja benzotriazola, nađeno je da BTA ispoljava inhibitorski efekat i u slučaju različitih vremena ekspozicije, kao i pri različitim koncentracijama BTA. Na osnovu Langmuir-ove adsorpcione izoterme, nađena je vrednost za adsorpcionu slobodnu energiju ∆G = – 35,4 kJ/mol.
Ključne reči: elektrohemijsko ponašanje, bakar, benzotriazol, hloridni joni, Langmuir-ova adsorpciona izoterma
ELECTROCHEMICAL BEHAVIOUR OF COPPER IN PRESENCE OF BENZOTRIAZOLE AND CHLORIDE IONS IN ALKALINE SOLUTION
In this paper, electrochemical behavior of copper in presence of benzotriazole and chloride ions in alkaline solution are presented. Influence of concentration of benzotriazole, concentration of chloride ions, immersion time on copper corrosion are investigated. It was found that Cu2O and CuO were formed on copper during anodic polarization. The activation effect of Cl– ions was found. The investigation of the effect of benzotriazole led to a conclusion that BTA has an inhibiting effect with increasing immersion times. Based on the Langmuir adsorption isotherm, the value of the standard free energy adsorption was found to be ∆G0 = −35.4 kJ/mol.
Key words: electrochemical behavior of copper, benzotriazole, copper, chloride ions Lengmuir adsorption isotherm
MILOŠ B. RAJKOVIĆ1, MIRJANA D. STOJANOVIĆ 2, ČASLAV M. LAČNJEVAC1, DRAGAN V. TOŠKOVIĆ3, DUŠAN D. STANOJEVIĆ3
Originalni naučni rad [PDF]
UDC:628.161.2:546.79=861
Određivanje tragova radioaktivnih supstanci u vodi za piće
Od radioaktivnih elemenata u kamencu, koji je dobijen na grejaču kućnog bojlera iz vode za piće, nađeni su stroncijum i uran u koncentracijama koje nisu zanemarljive, 00,5% i 1,38 ppm, respektivno. Za razliku od stroncijuma čije prisustvo nije alarmantno niti se nalazi u takvim količinama u kojima može dovesti do značajnog pogoršanja konzumenata vode za piće (a uz to je i β-emiter), uran je značajno opasniji i zbog svoje hemijske toksi čnosti i zbog radioaktivnosti. Glavna meta napada urana u čovekovom organizmu je bubreg, a dejstvo lagano i dugotrajno, tako da i 75% funkcije bubrega može uništeno da bi se tek tada pokazali prvi pravi klinički simptomi. Iako se najveći deo rastvornog urana u čovekovom organizmu (67%) izluči tokom prvih 24 h, ostatak urana ostaje u organizmu i, u zavisnosti od njene količine, može delovati sa većim ili manjim intenzitetom, ali uglavnom nepovoljno po zdravlje. Treba istaći da se u vodi za piće može naći i prirodni uran ali i uran koji je u biološki ciklus ishrane došao antropogenim putem (npr. osiromašeni uranijum koji se mogao naći u vodi za piće usled NATO bombar-dovanja tokom 1999.god.). Iako se radi o različitoj toksičnosti ova dva oblika urana a, takođe, nisu ni precizni podaci o prisutnosti osiromašenog uranijuma na prostorima Srbije, efekat njegovog prisustva je u suštini isti – opasnost po zdravlje ljudi.
Ključne reči: voda za piće, dugoživeći radionuklidi, uran, stroncijum, kamenac, nisko jonizujuće zračenje, bubrezi, hemijska toksičnost
DETERMINATION OF TRACES OF RADIOACTIVE ELEMENTS IN A DRINKING WATER
Of radioactive elements, strontium and uranium have been found in the fur at concentrations that are not negligible, 0.05 wt.% and 1.38 ppm, respectively. Contrary to strontium the quantity of which is not alarming and is not such that it may lead to significant spoiling of drinking water (beside Sr being a β-emitter), uranium is significantly more dangerous both due to its chemical toxicity and its radioactivity. The main target of uranium in human organism is kidney, and the action is slow and prolonged, inducing thus a 75% destruction of kidney function before first actual clinical symptoms become apparent. Although the greatest part of dissolved uranium in human organism (67%) is excreted during the first 24 h, the rest remains in the organism and, in dependence of the quantity, may act more or less severely, but generaly unfavourably for human health. It should be mentioned that although natural uranium may be found in drinking water there also depleted uranium may be encountered which was present in the drinking water due to NATO bombing campaigne during 1999. Although these two forms of uranium exert different levels of toxicity, data on the presence of depleted uranium are not precise, and the effect of its presence is in essence the same – danger for human health.
Key words: drinking water, long lived radionuclides, uranium, strontium, scale, low-level ionizing radiation, kidney, chemical toxicity
BOŽIDARKA ARSENOVIĆ1, ZORANA ŽIVIĆ1, BOŠKO IVANOVIĆ1, MIRKO SARIĆ1, JELENA PJEŠČIĆ2
Originalni naučni rad [PDF]
UDC:669.248.6;620.18=861
Ispitivanje mehaničkih i strukturno-morfoloških karakteristika prevlaka sulfamatnog nikla
Uzorci za ispitivanje kvaliteta prevlaka nanešenih iz nikal-sulfamatnog rastvora su ravne epruvete i originalni deo komponente noge stajnog trapa aviona “Boeing”. Ispitivanja su vršena u skladu sa Boeing-ovim standardima BAC 5746 i BSS 7235. U radu su prikazani rezultati ispitivanja mikrotvrdoće HV 0,3; adhezije prevlake sa osnovnim materijalom,, mikrografije metalografskih snimaka pomoću kojih se dao odgovor na pitanje veze između osnovnog materijala i nanešene prevlake, kao i poroznosti i debljine prevlake snimljenih na tri poprečna preseka ispitivanih uzoraka. Potvrđeno je postizanje zadovoljavajućih mehaničkih i strukturno-morfoloških karakteristika, kako na prevlaci nanešenoj na ispitivane epruvete tako i na originalnom upotrebljenom delu noge stajnog trapa aviona “Boeing”.
INVESTIGATION OF MECHANICAL AND STURUCTURALLY-MORPHOLOGICAL CHARACTERISTICS OF THE SULPHAMATE NICKEL COATINGS
The samples for investigating the quality of coatings from sulphamate-nickel solution are flat test tubes and original part of the leg componente of the landing gear of the “Boeing”airplane. The researches are done according to Boeing standards BAC 5746 and BSS 7235. The paper shows the results of the examination of microhardness HV 0.3; adhesion of the coating with base material, microphotographs of the melatographic photographs which give the answer to the question of bonding between base material and the coating, as well as porosity and thickness of the coating on three cross-cuts of the examined samples. The achievement of satisfying mechanical and structural morphological characteristics has been confirmed, both on coating deposited on test tubes and on the original used part of the leg of the landing gear of the airplane.
RANKO GRUJIĆ, VASO NOVAKOVIĆ, MILADIN GLIGORIĆ
Stručni rad [PDF]
UDC:628.112.033:624.157=861
Izbor vrste materijala za izradu bunara u zavisnosti od hidrohemijskih karakteristika podzemne vode i namjene bunara
Istraživači su u svojoj stručnoj praksi uočili da izbor materijal za izradu bunara zavisi od hidrohemijskih karakteristika podzemne vode i od njene namjene. U radu su obuhvaćeni različiti materijali za izradu bunara, njihove karakteristike i dato relativno vrednovanje za pojedine namjene, a u zavisnosti od hidrohemijskih uslova, vrijedosti pH, mineralizacije, sadržaja gvožđa, mangana, gasova i drugih faktora. Obrađeni parametri omogućavaju pravilan izbor materijala za izradu bunara sa stanovišta izrade, korištenja i vijaka trajanja bunarske konstrukcije.
Ključne riječi: voda, bunarska konstrukcija, mineralizacija, korozija.
SELECTION OF THE TYPE OF MATERIAL FOR THE CONSTRUCTION OF WELLS DEPENDING ON HYDROCHEMICAL PROPERTIES OF UNDERGROUND WATER AND THE PURPOSE OF THE WELL
Researches have noticed in their professional work that the type of material to be used in the construction of wells depends on hydrochemical properties of underground waters as well as on their purpose.The work includes different materials for the construction of wells, their properties and it gives relative evaluation for particular purposes depending on hydrochemical conditions, pH value, mineralization, the content of iron, manganese, gases and other factors. The parameters investigated enable a fair choice of material for the construction of wells from the aspect of constructing, using and duration period of the well construction.
Key words: water, well construction, mineralization, corrosion.
