DUMITRU TSIULYANU, OLGA MOCREAC
Scientific paper UDC:620.197.5
Hydrogen sensing behavior of tellurium thin films studied by A.C. measurements
For the first time it is pointed out that tellurium films exhibit sensitivity to H2 at room temperature along with sensitivity to NO2. The hydrogen gas sensing performance of tellurium thin films was investigated by method of impedance spectroscopy. The impedance spectra are strongly influenced by gaseous environment but the effect of target gas is mainly due to variation of resistance of the film. It is assumed that the sensitivity of tellurium films to H2 arises because – of reducing effect of oxygen priory absorbed on the surface of the film from carrier (dry air) gas. The high concentration of oxygen in carrier gas promotes the formation of a catalytic gate, which can be removed by other gases including hydrogen. Removing of the priory-adsorbed oxygen results in decreasing of both, hole concentration and conductivity of the surface and intragrain regions of tellurium film. Due to impedance change in different direction, reducing H2 may be distinguished from oxidizing NO2, hence the effective, operating at room temperature H2 sensors can be manufactured using tellurium-based films. Key words: Gas sensing, Tellurium, Hydrogen, A.C. measurements More>>>
PROUČAVANJE PONAŠANJA VODONIKA NA OSETLJIVIM TANKIM FILMOVIMA OD TELURA POMOĆU AC MERENJA
Po prvi put je pokazano da su Telurovi tanki filmovi osetljivost na H2 na sobnoj temperaturi uz osetljivost na NO2. Reagovanje vodonika na Telurove tanke filmove ispitan je metodom spektroskopske impedanse. Spektri impedanse su pod jakim uticajem gasovitog okruženju, ali je efekat ciljanog gasa uglavnom zbog varijacija otpora filma. Pretpostavlja se da osetljivost Telurovih tankih filmova za H2 nastaje zato – da se smanji dejstvo kiseonika apsorbovanog na površini filma od provodnog gasa (suv vazduh). Visoka koncentracija kiseonika u nosećem gasu podstiče formiranje katalitičkog kapije, koja može ukloniti druge gasove, uključujući i vodonik.
Uklanjanje apriori apsorbovanog kiseonika smanjenjuje koncentracije i provodljivosti na površinskim i intrgranularnim regionima Telurovih tankih filmova. Zbog promene impedanse u drugom pravcu, redukcija H2 može se razlikovati od oksidacije NO2, stoga efikasno, rad na sobnoj temperaturi H2 senzora mogu biti proizvedeni pomoću telur osnovnih filmova. Ključne reči: vodonik, osetljivi tanki filmovi, telur, AC merenja Dalje>>>
IRINA FIERASCU1 , RADU CLAUDIU FIERASCU2
Scientific paper UDC:620.183.19
Research on the degraded artifacts for the development of new protection methods
The history of metals and metal artefacts is closely related to the history of mankind. The discovery of metals and metalworking are important factors that led to the development of human civilization. Even though the metals are considered stable materials, once in contact with the environment, they gradually deteriorate and the deterioration rate depends on every metal/alloys characteristic. That is why the restorer/conservator of metallic artefacts should have knowledge from diverse areas (metalworking techniques, history of metalwork, history of art, archaeology, corrosion of metals, scientific research methods and others). The paper presents some aspects regarding the steps involved in the restoration and conservation of some selected artifacts, from the point of view of researchers in the field of materials science and chemistry.
Key words: archaeometallurgy, artefacts, protection methods. More >>>
ANJA TERZIĆ1, LJUBICA PAVLOVIĆ2,LJILJANA MILIČIĆ1
Scientific paper UDC:620.111.168
Prevention of electrofilter ash toxic leaching by embbeding in composite materials
Disposal of the fly ash may pose a significant risk to the environment due to the leaching of hazardous pollutants. The only sustainable solution for the pollution-prevention is the reapplication of fly ash as one of the components in construction material composites. There is a risk of leaching even when fly ash is built-in the construction composites and the goal of this investigation was to prove that leaching concentrations of toxic elements is in range assigned by actual regulations. Fly ash was applied in several composits: mortar, concrete and asphalt. The leachability of the potentially toxic elements from the fly ash based products was investigated. The leaching behavior and potential environmental impact of the 11 potentially hazardous elements was tracked: Pb, Cd, Zn, Cu, Ni, Cr, Hg, As, Ba, Sb and Se. A detailed study of physico-chemical characteristics of the fly ash is included. The overall results showed that most of the elements are more readily leachable from the fly ash in comparison with the fly ash based composites. Key words: leaching, toxic elements fly ash, reapplication, construction composites. More >>>
PREVENCIJA TOKSIČNOG LUŽENJA ELEKTROFILTERSKOG PEPELA UGRAĐIVANJEM U KOMPOZITNE MATERIJALE
Skladištenje letećeg pepela može prouzrokovati značajno zagađenje životne sredine zbog opasnosti od luženja opasnih elemenata. Jedino održivo rešenje za prevenciju zagađenja je ponovna upotreba pepela kao komponente u kompozitima, tj. konstrukcionim materijalima. Postoji rizik od luženja čak i kada je leteći pepeo ugrađen u konstrukcioni kompozit, pa je cilj ovog istraživanja da se dokaže da su koncentracije toksičnih elemenata u izluževini u granicama propisanim standardima i direktivama. Leteći pepeo je primenjen u nekoliko kompozita: malter, beton i asphalt. Mogućnost luženje potencijalno toksičnih elemenata iz kompozita na bazi letećeg pepela je ispitivana. Luženje i potencijalni uticaj na životnu sredinu 11 potencijalno opasnih elemenata je praćen: Pb, Cd, Zn, Cu, Ni, Cr, Hg, As, Ba, Sb i Se. Detaljna studija fizičko-hemijskih svojstava je sprovedena. Konačni rezultati su pokazali da najveći broj elemenata se lakše izlužuje iz letećeg pepela nego iz kompozita na bazi pepela. Ključne reči: luženje, toksični elementi, leteći pepeo, ponovna upotreba, konstukcioni kompoziti. Dalje>>>
JELENA PJEŠČIĆ1, DARKO VUKSANOVIĆ1, Originalni naučni rad
DRAGAN RADONJIĆ1, VESELINKA GRUDIĆ1, UDC:620.197.3 :669.15’74
REFIK ZEJNILOVIĆ2
Ispitivanje efekta inhibitora na koroziono ponašanje austenitnog manganskog čeličnog liva u vodenim rastvorima
Za izradu rezervnih djelova mlinova i drobilica kao nezamjenljiv materijal koristi se austenitni manganski čelični liv. U toku rada ovaj materijal je izložen abrazivnom habanju i udarnom opterećenju. Osim ove primjene austenitno manganski čelici mogu biti korišćeni i kao materijali u uslovima vodene korozione sredine. Abrazivno habanje je često uvećano prisustvom korozionih materijala, među kojima se može ubrajati i voda, obzirom da je djelovanje korozije znatno izraženije mehaničkim odnošenjem materijala. Najčešće proizvodi korozije imaju malu otpornost na habanje. Iz prakse je poznato da je brzina habanja obloga kod mlinova za mokro mljevenje cementa mnogo veća u odnosu na brzinu habanja obloga kod suvog mljevenja. Cilj ovog rada je da pokaže uticaj različitih inhibitora na koroziono ponašanje austenitnog manganskog čeličnog liva, koji u svom sastavu ima različit odnos aluminijuma i molibdena. Dobijeni rezultati će pokazati efekat korišćenih inhibitora. Ključne reči: inhibitori, korozija, austenitni manganski čelični liv, vodeni rastvori. Dalje >>>
INVESTIGATION OF THE INHIBITORS EFFECT ON THE CORROSION BEHAVIOR OF AUSTENITIC MANGANESE STEEL CASTINGS IN AQUEOUS SOLUTIONS
Production of spare parts for mills and crushers as an indispensable material is austenitic manganese steel casting. In the course of this material is subjected to abrasive wear and impact load. In addition to the application of austenitic manganese steels can be used as materials in aqueous corrosive environment conditions. Abrasive wear is often increased by the presence of corrosive materials, among which counts water, since the corrosion effects are much more pronounced mechanical removal of material. Corrosion products usually have a low resistance to abrasion. Practice has shown that the wear rate of coating mills for wet grinding of cement is much higher compared to the rate of wear of lining dry milling. The aim of this paper was to investigate the influence of different inhibitors on the corrosion behavior of austenitic manganese steel, which is composed of different relationships aluminum and molybdenum. The results will show the effect of the used inhibitors.
Key words: inhibitors, corrosion, austenitic manganese steel castings, aqueous solutions. More >>>
JADRANKA MALINA1 Scientific paper
ANITA BEGIĆ HADŽIPAŠIĆ1 UDC:620.193.7:669.14
ŠTEFAN NIŽNIK2
Electrochemical corrosion and hydrogen diffusivity in dual phase steel
Due to application in automotive industry, dual phase (DP) steels have received enormous attention over the last three decades. They show superior mechanical properties when compared to conventional high strength low alloyed (HSLA) steels, but their susceptibility to hydrogen embrittlement need to be explored in a greater extent. Therefore, in this study diffusion properties of hydrogen absorbed in steel were investigated in order to quantify the parameters of H-migration through complex microstructure of DP. Electrochemical experiments have shown that exposure of DP steel in 2M H2SO4 under free corrosion potential at room temperature led to the evolution of hydrogen atoms in amount high enough for diffusion through the metal. The values obtained for diffusivity and solubility of atomic hydrogen in DP steel suggest that permeability depends primarily on fine-grained microstructure of ferrite and martensite. Such heterogeneous polymorphic structure enables a high solubility of hydrogen within a network of numerous grain boundaries which act as reversible hydrogen traps. At ambient temperatures, these traps cannot retain hydrogen permanently and therefore the net result of trapping is low diffusion rate of hydrogen.
Key words: DP steel, electrochemical corrosion, hydrogen diffusivity, ferrite, martensite More >>>
ELEKTROHEMIJSKA KOROZIJA I DIFUZIJA VODONIKA U DVOJNOJ FAZI ČELIKA
Zbog primjene u automobilskoj industriji, dvofazni čelici (DP) pobudili su tijekom protekle tri dekade izuzetno zanimanje. U usporedbi s konvencionalnim visokočvrstim niskolegiranim čelicima (HSLA) imaju superiorna mehanička svojstva, ali njihovu sklonost krhkosti potaknutoj vodikom (HE) treba posebno ispitati. Stoga su u ovom radu proučavana difuzijska svojstva vodika apsorbiranog u čeliku, s ciljem da se odrede parametri karakteristični za H- migraciju kroz kompleksnu mikrostrukturu DP-a.Elektrokemijski eksperimenti pokazali su da tijekom kontakta DP čelika s otopinom 2M H2SO4 u uvjetima spontane korozije pri sobnoj temperaturi nastaju vodikovi atomi u količini koja je dovoljna za difuziju u metalu.Vrijednosti izračunate za topljivost i difuziju atomarnog vodika u DP čeliku sugeriraju da permeabilnost prvenstveno ovisi o izrazito sitnozrnatoj mikrostrukturi ferita i martenzita. Takva heterogena polimorfna struktura omogućava dobru topljivost vodika zahvaljujući brojnim granicama zrna koje djeluju kao reverzibilne zamke za vodik. Pri sobnim temperaturama ovakve zamke ne mogu vodik trajno zadržati, ali ga usporavaju tako da je brzina difuzije smanjena.
Ključne riječi: DP-čelik, elektrokemijska korozija, difuzija vodika, ferit, martenzit Dalje >>>
ANDREJ ČEŠNOVAR1, Scientific paper
MARTINA SALOVA2 UDC :629.193.7:663.4
Appearance, management and prevention of corrosion in the brewing industry
In the food industry, the brewing sector is one of the most severely affected by corrosion. The process uses large quantities of water for beer production, bottling, storage and cleaning. The beer itself is acidic and aggressive to low carbon steel. Furthermore, it contains live microorganisms, which can cause biocorrosion. The cleaning agents used in the plant are also known to cause corrosion problems. Corrosion causes significant expenses, in terms of equipment damage. Moreover, corrosion products dissolved in the beer can cause impairment of its quality.
This paper deals with the appearance of corrosion in different stages of the brewing process, as well as with the methods of management and prevention of corrosion. Different types of materials used in breweries are analyzed, regarding their corrosion resistance. Also, the conditions of the process which may cause corrosion are considered. The corrosion control and prevention are reviewed through controlling the process parameters and selection of improved materials.
Key words: brewing industry, corrosion, causes and solutions. More >>>
POJAVA, UPRAVLJANJE I PREVENCIJA KOROZIJE U INDUSTRIJI PIVA
U prehrambenoj industriji, sektor proizvodnje piva je jedan od najteže pogođenih korozijom. U samom procesu se koriste velike količine vode za proizvodnju piva, flaširanje, skladiranje i čiščenje. Samo po sebi, pivo je kiselo i agresivno u odnosu na niskolegirani ugljenični čelik. Osim toga, pivo sadrži žive mikroorganizme koji mogu da izazovu biokoroziju. Sredstva koja se koriste za čiščenje postrojenja isto tako mogu da prouzrokuju probleme sa korozijom. Korozija izaziva velike troškove, u smislu oštećenja opreme. Povrh toga, korozioni produkti rastvoreni u pivu mogu da umanje kvalitet finalnog proizvoda. Ovaj rad se bavi pojavom korozije u različitim fazama procesa proizvodnje piva, kao i proučavanjem metoda upravljanja i prevencije korozije. Analizirani su različiti tipovi materijala koji se koriste u pivarama, sa aspekta njihove korozione otpornosti. Takođe, razgledani su uslovi procesa koji mogu da izazovu koroziju. Takođe su razgledani upravljanje i prevencija korozije putem kontrolisanja procesnih parametara i selekcije poboljšanih materijala.
Ključne reči: industrija proizvodnje piva, korozija, uzroci i rešenja. Dalje >>>
VERA OBRADOVIĆ, DUŠICA B. STOJANOVIĆ Scientific paper
IRENA ŽIVKOVIĆ, PETAR S. USKOKOVIĆ, UDC:620.193.7:66.095.115
RADOSLAV ALEKSIĆ
Dynamic mechanical properties of aramid fabrics impregnated with multiwalled carbon nanotubes
Carbon nanotubes (CNT) represent allotropes of carbon with a cylindrical nanostructure. In multiwalled carbon nanotubes (MWCNT), graphitic layers make up concentric tubes. The multiwalled nanotubes length in our research is from 3 μm to 30 μm and their outer diameter is from 13 nm to 18 nm. Their purity is greater than 99 wt.%. The carbon nanotubes possess extraordinary physical properties, great electrical and thermal conductivity. The addition of carbon nanotubes as the reinforcement in polymer composites can significantly improve the composite mechanical properties. In the study, the pristine multiwalled carbon nanotubes (MWCNT) were introduced in order to additionally enhance mechanical properties of materials for ballistic protection.
Keywords: multiwalled carbon nanotubes, p-aramid fabrics, AMEO silane, mechanical properties. More >>>
DINAMIČKO MEHANIČKA SVOJSTVA ARAMIDNIH LAMINA IMPREGNISANIH SA VIŠESLOJNIM UGLJENIČNIM NANOCEVIMA
Ugljenične nanocevi (carbon nanotubes, CNT) predstavljaju alotropsku modifikaciju ugljenika cilindrične nanostrukture. Kod višeslojnih ugljeničnih nanocevi (multiwalled carbon nanotubes, MWCNT), grafitni slojevi obrazuju koncentrične cevi. U našem istraživanju dužina višeslojnih nanocevi iznosi od 3 µm do 30 µm i njihov spoljašnji prečnik je od 13 nm do 18 nm. Njihova čistoća je veća od 99 mas.%. Ugljenične nanocevi imaju izvanredna fizička svojstva, veliku električnu i toplotnu provodljivost. Njihovim dodatkom u vidu ojačanja u polimernim kompozitima se mogu značajno poboljšati mehanička svojstva kompozita. U ovom radu su čiste višeslojne ugljenične nanocevi bile korišćene sa ciljem da se poboljšaju mehanička svojstva materijala za zaštitu u balistici. Ključne reči: višeslojne ugljenične nanocevi, p-aramidne lamine, AMEO silan, mehanička svojstva. Dalje >>>
STEVAN STOJADINOVIĆ1, JELENA BAJAT2, Originalni naučni rad
RASTKO VASILIĆ3, VESNA MIŠKOVIĆ -STANKOVIĆ2 UDC:620.197.5669.7
Karakterizacija oksidnih slojeva dobijenih plazma elektrolitičkom oksidacijom aluminijuma u natrijum volframatu
U radu su prikazana ispitivanja morfologije i faznog sastava površina oksidnih slojeva dobijenih metodom plazma elektrolitičke oksidacije aluminijuma u 0.1 M vodenom rastvoru natrijum volframatu pri stalnoj gustini struje od 15 mA/cm2, kao i njihova koroziona stabilnost. Pokazano je da hrapavost dobijenih slojeva raste sa vremenom trajanja procesa, dok mikro tvrdoća uzoraka dostiže maksimalnu vrednost posle 5 minuta od početka procesa i posle tog vremena opada. Osidni slojevi su delimično kristalizovane i uglavnom se sastoje od γ-Al2O3, α-Al2O3 i WO3, a sadržaj γ-Al2O3 raste sa trajanjem PEO procesa. Dobijeni oksidni slojevi imaju veću impedansu od čistog aluminijuma, pri čemu dužem vremenu PEO procesa ne odgovara i najveća impedansa. Najveću korozionu stabilnost su pokazali oksidni slojevi dobijeni posle 7.5 minuta od početka anodizacije. Ključne reči: aluminijum, plazma elektrolitička oksidacija, mikro tvrdoća, SEI, korozija. Dalje >>>
Characterization of oxide coatings formed by plasma electrolytic oxidation of aluminum in sodium tungstate
This paper presents our recent research on morphology and phase composition of oxide coatings formed by plasma electrolytic oxidation of aluminum in 0.1 M sodium tungstate at constant current density of 15 mA/cm2 and corrosion stability of such coatings. Roughness of obtained oxide coatings increases with prolonged process time, while their microhardness reaches maximal value after about 5 minutes from the onset of the process and then decreases. Oxide coatings are partly crystallized and mainly consist of γ-Al2O3, α-Al2O3 i WO3, with γ-Al2O3 content increasing with prolonged PEO time. All obtained oxide coatings have higher impedance than pure aluminum and no relationship between PEO time and impedance is found. The evolution of impedance spectra shows that samples obtained after 7.5 minutes of PEO time have most efficient corrosion protection of aluminum substrate.
Key words: aluminum, plasma electrolytic oxidation, microhardness, SEI, corrosion
More >>>
DIANA KIRIN1, BOYAN BOYANOV2, Scientific paper
NIKOLINA ILIEVA1 UDC:504.45.7.054
Biodiversity and heavy metal pollutions in freshwater ecosistems in border areas from Tunja river
The purpose of the carried out examinations is to investigate heavy metal pollutions and the biological variety of the freshwater ecosystems of the Tunja River, Bulgaria, and to make an ecological evaluation of their condition. The Tunja River is related to the Aegean water collecting region. Basic abiotic (temperature, pH, conductivity μS/sm, COD, BOD5, ionic groups – PO4 mg/l, N-NO3 mg/l, N-NO2 mg/l and heavy metals – Pb, Zn, Cd and Cu, structure of the river bed, dominant tree vegetation, etc.) and biotic characteristics (total number of specimens, prevalence, mean intensity, etc.) were determined. The bioindicative macrozoobenthos was characterized for assessment of the ecological status of the examined freshwater ecosystem. Helminths communities of Squalius orpheus and heavy metal contaminations in fish tissues, organs and chub parasite Acanthocephalus anquillae were determined. The present studies are connected with applying of the new approach for integrated environmental assessment of the freshwater ecosystem based on the living communities and fish parasite communities.
Key words: bioindication, heavy metals, macrozoobenthos, chub parasite communities, Tunja River. More >>>
BIODIVERZITET I ZAGAĐENJA TEŠKIM METALIMA U SLATKOVODNOM EKOSISTEMU U POGRANIČNIM ZONAMA REKE TUNJA
Cilj ispitivanja je da se ispita sadržaj teških metala i zagađenja na biološku raznovrsnost slatkovodnih ekosistema reke Tunja, Bugarska, i da se da ekološka procena njihovog stanja. Reka Tunja sakuplja vode Egejskog regiona. Izvršeno je određivanje osnovnih abiotičkih (temperatura, pH, provodljivost i μs/sm, HPK, BPK5, jonske grupe – PO4 mg/l, N-NO3 mg / l, N-NO2 mg / l, i teški metali – Pb, Zn, Cd i Cu, struktura rečnog korita, dominantno drvo vegetacija, itd) i biotičkih karakteristika (ukupan broj uzoraka, učestalost, intenzitet, itd. Bioindikativna makrozobentoza je karakteristična za procenu ekološkog statusa ispitivanog slatkovodnog sistema. Određivani su mikroorganizmi Helminths of Squalius orpheus, paraziti Acanthocephalus anquillae i teški metali u tkivima i organima riba. Sadanje studije su povezani sa primenom novog pristupa za intregisanu ocenu životne sredine slatkovodnih ekosistema na osnovu životnih zajednica i zajednica parazita riba.
Ključne reči: bioindikacija, teški metali, makrozoobentosa, parazitske zajednice, reka Tunja. Dalje >>>
VESNA DIMOVA Scientific paper
UDC :545
A quantum chemical investigation of tautomerion forms of 4-phenyl-5-(4- hydroxyphenyl)-1,2,4-triazoline-3-thione
4-phenyl-5-(4-hydroxyphenyl)-1,2,4-triazoline-3-thione (TT) was obtained by the oxidative cyclization of the appropriate 4-hydroxybenzoyl phenylthiosemicarbazide. From the obtained spectral analysis it is possible to consider that the 1,2,4-triazoline-3-thiones may exist in thion-thiol tautomeric forms. The molecular conformations and electronic properties of TT containing various reaction centers were investigated by the AM1 semiempirical method. The total energies, heat of formation, dipole moments, geometric parameters, ionization potential, full atomic charges, EHOMO and ELUMO (energies of frontier molecular orbital) and their electron densities were calculated. Ionization constants and protonation site in TT molecule were obtained experimentally. The proton affinities for the different atoms (nitrogen, oxygen and sulfur) of the investigated triazole molecule were calculated using AM1 method, and possible protonation sites were discussed. The quantum chemical investigations of tautomerion froms of TT were in accordance with our previously experimental investigation for protonation/deprotonation process of TT: PA of TT calculated for S atom form C=S group was higher than the other atoms, meaning that the electrophilic attack of the proton on this atom is easier than the other; the most acidic hydrogen atoms were N-H/S-H (first deprotonation process) and OH (second deprotonation process). Key words: 1,2,4-Triazolin-3-thion, AM1, Total Energies, Heats of Formation. More >>>
KVANTNO-HEMIJSKA ISPITIVANJA TAUTOMERNIH FORMI 4-FENIL-5-(4-HIDROKSIFENIL) -1,2,4-TRIAZOLIN-3-TIONA
4-Fenil-5-(4-hidroksifenil) -1,2,4-triazoline-3-tion (TT) dobijen je oksidativnom ciklizacijom odgovarajućeg 4-hidroksibenzoilfeniltiosemicarbazida. Spektralne analize ukazuju na postojanje tion-tiolnih tautomernih formi, 1,2,4-triazolin-3-tiona. Molekularne konformacije i elektronska svojstva TT ispitivane su AM1 semiempirijskom metodom. Ukupna energija, toplota formiranja, dipolni momenat, energija jonizacije, atomske polneze EHOMO i ELUMO i elektronske gustine, su izračunate. Jonizacione konstante i protonaciona mesta u TT, dobijena su eksperimentalno. Protonski afiniteti (PA) za različite atome (azot, kiseonik i sumpor) izračunati su AM1 metodom. Kvantno-hemijska ispitivanja tautomernih formi TT u skladu su sa eksperimentalnim istraživanjima: PA za S atoma iz C = S grupe je veći od ostalih atoma, što ukazuje na lakši elektrofilni napad na ovaj atom. Ključne reči: 1,2,4-triazolin-3-tion, AM1, ukupna energija, toplota formiranja. Dalje >>>
VINETA SREBRENKOSKA1, Scientific paper
EMILIJA FIDANCEVSKA2 UDC:502.34/.35
Environmental issues in materials science and engineering
Тhe industrial engineering consumes of materials and is dependent on a continuous supply of them. Increasing population and living standards cause the consumption rate to grow – something it cannot do forever. Finding ways to use materials more efficiently is a prerequisite for a sustainable future. Recent global attention to the issues and challenges of sustainable development is forcing industries to conduct self-assessments to identify where they stand within the framework for sustainability, and more importantly, to identify opportunities, strategies and technologies that support achieving this goal. Design for environmental sustainability is the long-term view: that of adaptation to a lifestyle that meets present needs without compromising the needs of future generations. The composite material is a group of materials which they have not yet gained the same amount of utilisation as metallic materials. Since the composites consist of a mixture of several types of materials on macro level they cannot be regarded as homogenous as the steel materials. Both these circumstances complicate the possibilities to form a well-organised system for waste handling. The increased use of composites in industry will create continuously more waste to be handled in the future. Also for this type of materials several regulations put pressure on producers to consider the waste treatment. Examples are prohibition against landfill, producer responsibility for specific groups of products and eventually taxes on waste incineration. All these regulations are aiming for material recycling, due to decreased environmental impact. A common opinion is that recycling composite materials will be especially difficult or not even possible. The main alternative used today for handling composite waste is landfill but also waste incineration is an alternative. To respond to environmental awareness in society and to regulations, companies require new methods for waste disposal. Key words: environmental effects, eco-design, composites, waste. More >>>
Питања заштите животне средине у материјалима наукa и инжењерство
Индустријски инжењеринг троши материјале и зависи од сталног снабдевања. Повећање броја становника и животног стандарда проузрокује да потрошња расте – нешто што се не може заувек уради. Проналажење начина да се користе материјали ефикасније је предуслов за одрживу будућност. Недавна глобална пажња о питањима и изазовима одрживог развоја присиљава индустрије да спроведе самопроцене и да идентификују где они стоје у оквиру одрживости, и што је још важније, да се идентификују могућности, стратегије и технологије које подржавају постизање овог циља. Дизајн за одрживост животне средине је дугорочан и окренут на поглед адаптације на живот који задовољава садашње потребе без угрожавања потреба будућих генерација. Композитни материјал је група материјала који још нису стекли исту количину коришћења као метални материјали. Пошто се композити састоје од мешавине неколико врста материјала на макро нивоу, они се не могу сматрати хомогеним као челични материјали. Обе ове околности компликују могућности да формирају добро организован систем за отпадом. Повећано коришћење композита у индустрији ће створити континуирано више отпада који ће се руковати у будућности. Такође, за ову врсту материјала, неколико прописа врше притисак на произвођаче да размотре третман отпада. Примери су забрана бацања на депоније, одговорности произвођача за специфичне групе производа и напослетку порези на спаљивање отпада. Сви ови прописи имају за циљ материјалну рециклажу, због смањеног утицаја на животну средину. Заједничко мишљење је да ће рециклажа композитних материјала бити посебно тешка или чак и не могућа. Главна алтернатива данас за руковање отпадом композитних материјала је депонија, али и спаљивање отпада је алтернатива. Да би се одговорило на еколошке свести у друштву и прописима, компаније захтевају нове методе за одлагање отпада. Кључне речи: еколошки ефекти, еко-дизајн, композити, отпада. Dalje >>>
SNEŽANA AKSENTIJEVIC1, JELENA KIURSKI2, Originalni naučni rad
ZAGORKA AĆIMOVIĆ PAVLOVIĆ3 UDC:628.358.043.045
Olovo u otpadnim vodama metaloprerađivačke industrije Zapadne Srbije
Regioni u Republici Srbiji u kojima je razvijena metalska, metaloprerađivačka industrija su lokaliteteti gde se detektuje prisustvo teških metala u zemljištu, vodi, a posebno u sedimentu koji se ponaša kao sedište i potencijalni izvor metala u akvatičnoj sredini. U frekvenciji vremena koncentracija metala se povećava iznad dozvoljenih granica, a preko lanca ishrane može imati negativan uticaj i na čoveka. Cilj rad se odredi koncentracija teškog metala olova u vodi i sedimentu u Zapadnoj Srbiji, Sevojnu, gde posluju dva velika proizvođača poluproizvoda od bakra i aluminijuma. Programski paket MAT LAB korišćen je za definisanje distribucije olova između čvrste i tečne faze u funkciji rastojanja od mesta izlivanja industrijskih otpadnih voda. Ključne reči: teški metali, olovo, voda, sediment. Dalje>>>
LEAD IN WASTEWATER METAL PROCESSING INDUSTRY WESTERN SERBIAN
In The Republic of Serbia which has been developed metallurgy, metal industry of the site where they detect the presence of heavy metals in soil, water, and especially in the sediment, which acts as a seat and a potential source of metals in the aquatic environment. The frequency of time metal concentrations increase above the allowable limits, and through the food chain may have a negative impact on humans. This paper aims to determine the concentration of heavy metals such as lead in water and sediments in western Serbia, Sevojno, which operate two large producers of semi-finished copper and aluminum. MAT LAB software package was used to define the distribution of lead between the solid and liquid phases in function of the distance from the spill of industrial waste water. Key words: heavy metals, lead, water, sediment More >>>
RADOJKA JONOVIĆ1, LJILJANA AVRAMOVIĆ1 Originalni naučni rad
MILE BUGARIN1, RADMILA MARKOVIĆ1 UDC:669.35:622.772.002.84
ZORAN STEVANOVIC1, MARKO JONOVIĆ2
Proces luženja bakra iz rudarskog otpada sa otpadnim vodama
Rudarstvo je, kao glavna industrijska grana u Boru, tokom proteklih sto godina, imalo ogroman uticaj na životnu okolinu samog grada, ali i šireg regiona. Kao posledica rudarenja nastaju kisele rudničke otpadne voda koje se generišu iz kopovskih raskrivki i flotacijskih jalovišta. Ove kisele rudničke vode slivaju se ka akumulaciji „Robule“ i Borskoj reci, koja pripada slivu reke Timok, i zajedno sa čvrstim otpadom predstavljaju opasnost po životnu okolinu regiona, dok raskrivka i jalovište predstavljaju “rudnik na otvorenom” u kome se nalazi oko 148.000 t bakra. Tema ovog rada je mogućnost integralnog tretmana otpadnih rudničkih voda i vanbilansnih delova ležišta. Urađena je detaljna fizičko-hemijska karakterizacija rudničkih otpadnih voda iz akumulacije „Robule“, karakterizacija raskrivke deponovane na „Oštreljskom“ planiru kao i karakterizacija flotacijskog jalovišta. Izvršena su ispitivanja procesa luženja bakra iz uzorka raskrivke sa kiselim otpadnim vodama i postignut stepen izluženja od 67 % bakra, kao i luženja bakra iz uzoraka jalovine sa stepenom izluženja bakra od 76 %. Ključne riječi: bakar, luženje, rudarski otpad,otpadne vode Dalje>>>
COPPER LEACHING PROCESS FROM THE OVERBURDEN MATERIALS WITH WASTE WATER
Mining, as a major industry in Bor, over the past hundred years, had an enormous impact on the environment of the city itself, but also for the region. Arise as a result of mining acid mine waste water that is generated from flotation tailings and overburden. These acidic mine waters flowing toward the accumulation of “Robule” and the Bor river, which belongs to the Timok River, and along with solid waste pose a threat to the environment of the region, while the overburden and tailings are “open mine” which is about 148,000 t copper. The theme of this work is the possibility of an integrated waste treatment of mine waters and off parts of the deposit. Underwent detailed physical and chemical characterization of mining waste water from reservoirs “Robule,” characterization of overburden deposited in “Oštrelj“ plans and characterization of flotation tailings. The studies of leaching of copper from overburden samples with acidic waste water and reached the level of 67% leaching of copper and copper leaching from overburden samples with levels of copper leaching by 76%.
Key words: copper, leacning, overburden materiaals, waste water. More >>>
ŽELJKO STOJANOVIĆ Originalni naučni rad
SANJA STANISAVLJEV UDC:620.197.5:669.15.292
SNEŽANA RADOSAVLJEVIĆ
Primena postupka vanadiranja u funkciji produženja radnog veka delova
U radu je dat pregled literaturnih podataka o istraživanju uticaja sloja vanadijum karbida, formiranog termo-reaktivnom difuzijom na površini alatnih čelika i kalupa za livenje i kovanje. U zapadnoj naučno-stručnoj literaturi (USA i Japan) postoji dosta informacija o vanadiranim slojevima dobijenim na alatnim čelicima i kalupima, dok je u našim naučno-stručnim krugovima, i pored superiornih osobina koje sloj pruža u procesu eksploatacije, postupak ostao gotovo nepoznat. Kako je postupak vanadiranja još uvek uglavnom nepoznat našoj široj naučno-stručnoj javnosti, u radu su sistematizovana znanja i opisane osnovne zakonitosti, prednosti i nedostaci postupka vanadiranja, sa osvrtom na karakteristične primere njegove primene na sadašnjem nivou znanja. S obzirom da ekstremno tvrdi sloj formiran postupkom vanadiranja poseduje odlične osobine, od kojih treba izdvojiti: veoma visoku otpornost prema mehanizmu abrazije i athezije, dobre tribo-hemijske osobine i vrlo nizak koeficijent trenja, autori smatraju da će podaci u ovom radu poslužiti kao korisna referenca za proširenje primene ovog postupka i u našim proizvodnim pogonima, kao uobičajenog postupka obrade. Ključne reči: vanadiranje, abrazija, athezija, tribo-korozija, alatni čelici, kalupi Dalje >>>
APPLICATION PROCESS OF VANADIZING IN THE FUNCTION OF EXTENSION WORKING LIFE OF PARTS
This paper gives review of literature data about the research influence of vanadium carbide layer formed by thermal-reactive diffusion on the surface of the tool steel and die for casting and forging. In western scientific and professional literature (USA and Japan) exists a lot of information about the vanadized layers obtained on tool steel and dies, while in our scientific and professional circles, and beside of the superior qualities whose layer provides in the process of exploitation, the process remained almost unknown. As the procedure of vanadizing still largely unknown our broader scientific and professional public, therefore, in the paper are systematized knowledge and described the basic principles, advantages and disadvantages of the procedure of vanadizing, with emphasis on specific examples of its application on current level of knowledge. Considering that the extremely hard layer formed by procedure of vanadizing possesses excellent properties, of which should be singled out: very high resistance to the abrasion and adhesion mechanism, good tribo-chemical properties and very low coefficient of friction, the authors belive that the data in this paper serve as a useful reference for the expansion of application this procedure in our manufacturing facilities, as the usual treatment process.Key words: vanadizing, abrasion, adhesion, tribo-corrosion, tool steel, dies. More >>>
PETRONIJA J. JEVTIC Scientific paper
UDC :620.197.6 :674.5
Quality of wood surface finished with polyurethane coating
Comparative analysis of some properties of various wood coatings is performed in this paper. A special attention is paid to polyurethane coating and several different types were taken into consideration. Their properties are compared with those of nitrocellulose and acid curing coatings. Resistance to liquids, heat resistance and scratch resistance were examined. Key words: wood coatings, polyurethane coatings, resistance to liquids, heat resistance, scratch resistance. More >>>
KVALITET POVRŠINE DRVETA OBRAĐENOG POLIURETANSKIM PREMAZOM
U ovom radu ispitivana je otpornost na tečnosti – alkohol, aceton, vodu, kafu, Coca Colu; otpornost na toplotu i otpornost na grebanje. Komparativno su ispitivani različiti tipovi poliuretanskih premaza, a zatim su rezultati upoređeni sa rezultatima dobijenim za nitroceluloze i kiselinski-očvršćavajuće premaze – druga dva tipa najčešće korišćenih klasičnih premaza. Na ovaj način je ispitana mogućnost primene ovih materijala u različitim oblastima eksploatacije. Nitrocelulozni premazi pokazali su najniže vrednosti, dok su kiselinski-očvršćavajući i poliuretanski premazi pokazali zadovoljavajuća svojstva za upotrebu za obradu nameštaja. Ključne reči: premazi za drvo, poliuretanski premazi, otpornost na tečnosti, otpornost na toplotu, otpornost na grebanje. Dalje >>>
DRAGAN UGRINOV Stručni rad
ALEKSANDER STOJANOV UDC:628.046:351.773/.776
Zakonodavni okvir i nadležnosti u oblasti upravljanja medicinskim otpadom
Medicinski otpad u zdravstvenim ustanovama u Republici Srbiji se stvara u neravnomernim količinama, u zavisnosti od tipa ustanove, broja kreveta, vrste i prirode oboljelja i stanja koje se zbrinjavaju, kao i vrste i kvaliteta usluga koje se u ustanovama pružaju. Medicinski otpad se smatra potencijalno opasnim otpadom za ljudsko zdravlje i upravljanje otpadom se razlikuje od zemlje do zemlje, zavisno do stepena razvijenosti, geografskih uslova i kulture. Svaka zemlja može imati svoje Pravilnike i vodiče za upravljanje medicinskim otpadom, ali se većina zasniva na dokumentima koja je dala Svetska zdravstvena organizacija (SZO). U poslednjoj deceniji se intenzivno radi na rešavanju ovog problema u svetu. Ključne reči : medicinski otpad, zakon, pravilnik, upravljanje. Dalje >>>
Legislation framework and responsibilities in medical waste management
Medical waste in hospitals and appropriate institutions in Serbia is generated in huge amounts, in dependence of the type of institution, number of beds, type and nature of diseases and conditions to be treated, as well as kind and quality of services provided. Medical waste is treated as potentially harmful for human health and waste management is different from country to country, depending on development level, geographic conditions and culture. Each country could have appropriate Regulations and manuals for medical waste management, but majority of them is based on documents issued by World Health Organization (WHO). During the last decade, work on solving the problem is intensive throughout the world.
Key words: medical waste, law, regulation, management. More >>>
