Zaštita materijala 4. 2017

 

Zagađivanje jezika kao dela životne sredine

Izvod

Jezik i reči koje ga čine su deo životne sredine i deo našeg dnevnog života. Jezik je, takođe, jedan od ključnih karakteristika odgovarajuće nacije. Razvoj nauke i kulture dovodi do nastajanja novih reči. To je povećanje rečnika. Ali zamena reči svoga jezika sa reči iz drugog jezika je zagađenje jezika. Takođe, korišćenje konstrukcije rečenice iz drugog jezika u svom jeziku je, takođe, zagađivanje jezika. To je posledica niskog nivoa kulture i niskog nivoa znanja, nedovoljno kvalifikovanih.

Ključne reči: zagađenje jezika, jezik, nove reči.

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POLLUTION OF LANGUAGE AS A PART OF THE ENVIRONMENT

Abstract

Language, and words which make it, is a part of the environment and a part of our daily lives.  Language is also the essential characteristic of the corresponding nation. Development of the science and culture drive to the formation of new words. That is the increase of vocabulary. But the echange a word of one’s own language with a word of another language is pollution of language. Also the using of sentence construction from forein language in one’s own language is also language pollution. This is a consequence of the low culture level and the low knoweledge level of individues with a half qualification.

Keywords: language pollution, language, new words.

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Influence of the test emulsion on filtration efficiency and pressure drop of mist Separators for cooling lubricants

Abstract

This work deals with standardized filter tests of mist separators for cooling lubricants aerosols. The Austrian standard ÖNORM Z1263 describes a filter test rig and test procedure for standardized comparable filter tests and futher for a classificiation.

Following this guideline six industiral used filter elements with different designs and materials were tested to determine filtration specific parameters like the pressure drop, total liquid holdup, oil holdup and separation efficiency. Finally, filter elements will be classified by their separation efficiency into a filter-class from 1 to 10.

The ÖNORM Z1263 does not give any specific test substance, so there is an interest to study the influence of various coolant oils as used in industry.

Therefore for the filter test, three different coolant oils were used as test substance: mineral oil, semi-synthetic oil and full-synthetic oil. The six filter elements have been tested according to the guideline to reach a steady-state liquid equilibrium within 2-4 hours.

Comparing the results of the steady-state pressure drop, total holdup and oil holdup as well as the separation efficiency in four particle size ranges there was no significant influence of the test oil base found. The achieved filter-class numbers differ only by one number.

Keywords: Coolant oil, emulsion, filter elements, separation efficiency, pressure drop, filter testing.

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UTICAJ TEST EMULZIJENA EFIKASNOST FILTRACIJE I PAD PRITISKA KOD FILTERA ZA UKLANJANJE AEROSOLA FORMIRANOG OD SHP SREDSTAVA

Izvod

Ovaj rad se bavi standardizacijom procedure za ispitivanje filtera za separaciju tečnog aerosola formiranog od SHP sredstava u radnoj sredini mašina alatki. Austrijski standard  ÖNORM Z1263 opisuje opremu za ispitivanje aerosol filtera, postupak njihovog ispitivanja,  kao i način njihove klasifikacije. Prateći ove smernice šest filtera različite konsutrukcije i materijala, koji se primenjuju u industriji testirani su u cilju određivanja filtracionih parametara, kao što su: pad pritiska, ukupno zadržavanje tečnosti u filteru, zadržavanje ulja u filteru i efikasnost separacije. Na osnovu efikasnosti separacije testirani filteri će se klasifikovati u određenu klasu filtera od 1 do 10.

Standard ÖNORM Z1263 ne definiše test supstancu, tako da postoji interes za proučavanje uticaja različitih test supstanci. Kao test supstance ispitivana su tri ulja koja se koriste u  industriji: mineralno ulje, polusintetičko i sintetičko ulje. Ova ulja se primenjuju kao emulzije, i spadaju u grupu SHP sredstava. Šest filtera je testirano po ÖNORM Z1263 standardu. Upoređivanjem dobijenih rezultata primenom različitih test ulja, odnosno njihovih emulzija uočava se se da ne postoji značajan uticaj ulja na klasifikaciju filtera. Postignuta klasa filtera se samo u pojedinim slučajevima razlikovala za jednu klasu, što je zanemarljivo sa obzirom na usku granicu među klasama.

Ključne reči: sredstva za hlađenje i podmazivanje (SHP), emulzija, aerosol filteri, efikasnost separacije, pad pritiska, testiranje filtera.

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The influence of synthesis parameters on swelling behaviour of pH-sensitive acrylate based hydrogels

Abstract

In this work poly(acrylamide-co-acrylic acid) based hydrogels were prepared using the two types of initiators – potassium persulfate (KPS) and ammonium persulfate (APS) and accelerator N,N,N’,N’-tetramethylethylenediamine (TEMED). N,N’-methylenebis(acrylamide) (MBAM) was used as crosslinking agent (1 and 3% per total weight of monomers). For the synthesis of hydrogels, acrylic acid (Aac) and acrylamide (Aam) were used in the following mass ratios: 30:70, 50:50, 70:30 and 0:100% Aac/Aam. The swelling behaviour of cross-linked copolymers was characterized in acidic (pH=4.5) and alkaline (pH=10) medium at constant temperature of 37 °C. Lower amount of crosslinking agent has given the hydrogels with greater water absorption capacity. The forming of polymer network has been confirmed by FT-IR method. Thermal properties of obtained hydrogels were analyzed by differential scanning calorimetry (DSC). Obtained results have showed the strong correlation between hydrogels composition and their swelling and thermal properties.

Keywords: hydrogel, swelling ratio, acrylic acid, acrylamide, monomer ratio.

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UTICAJ PARAMETARA SINTEZE NA BUBRENJE pH OSETLJIVIH AKRILATNIH HIDROGELOVA

U ovom radu su sintetisani hidrogelovi na osnovu poli(akrilamid-ko-akrilne kiseline) primenom dva tipa inicijatora – kalijum persulfata (KPS) i amonijum persulfata (APS) i akceleratora N,N,N’,N’-tetrametil etilen diamina (TEMED). Umrežavanje je vršeno posredstvom N,N’-metilen bisakrilamida (MBAM) koji je korišćen u udelima 1 i 3% u odnosu na ukupnu masu monomera. Pripremljeni su hidrogelovi sa sledećim masenim odnosima monomera akrilne kiseline i akrilamida: 70:30, 50:50, 30:70 i 0:100%. Svojstva bubrenja sintetisanih gelova ispitana su u kiseloj (pH=4.5) i alkalnoj sredini (pH=10) na konstantnoj temperaturi od 37 °C. Niži udeo umreživača dao je hidrogelove sa većom sposobnošću bubrenja. Struktura hidrogelova potvrđena je FT-IR metodom. Toplotna svojstva su ispitana diferencijalnom skenirajućom kalorimetrijom (DSC). Dobijeni rezultati pokazali su postojanje izražene korelacije između sastava hidrogela i njegovih toplotnih svojstava i svojstava bubrenja.

Ključne reči: hidrogel, stepen bubrenja, akrilna kiselina, akrilamid, odnos monomera.

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Prirodno prečišćavanje podzemnih voda zagađenih naftnim ugljovodonicima: mehanizam, koncepcija istraživanja, primena u praksi

Izvod

Prirodno prečišćavanje objedinjuje niz procesa koji dovode do smanjenja zagađenja podzemnih voda naftnim ugljovodonicima. Biodegradacija često ima glavnu ulogu među ovim procesima, pošto mikroorgranizmi koriste naftne ugljovodonike kao izvor energije i ugljenika. Primena prirodnog prečišćavanja kao remedijacionog tretmana podrazumeva detaljnu hidrogeološku karakterizaciju zagađene lokacije i osmatranje procesa kojim dolazi do smanjenja zagađenja. U radu su prikazani rezultati osmatranja prirodnog prečišćavanja na lokaciji istorijskog zagađenja kerozinom kod Kraljeva. U cilju osmatranja efekata biodegradacije, u podzemnim vodama su vršena merenja sledećih parametara: ukupnih naftnih ugljovodonika (TPH), elektron akceptora (O₂, NO₃^–, SO₄^2-), metaboličkih produkata biodegradacije (Mn, Fe) i redoks potencijala (Eh). Dobijeni rezultati i metodološki pristup mogu se smatrati korisnim kod koncipiranja budućih istraživanja ovog tipa.

Ključne reči: podzemne vode, naftni ugljovodonici, prirodno prečišćavanje, biodegradacija.

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NATURAL ATTENUATION OF GROUNDWATER  CONTAMINATED BY PETROEUM HYDROCARBONS: MECHANISM, RESEARCH CONCEPT, PRACTICAL APPLICATION

Natural attenuation includes a number of processes that cause the reduction of groundwater contamination by petroleum hydrocarbons. Among these processes biodegradation often plays a major role, since microorganisms use petroleum hydrocarbons as the source of energy and carbon. Application of natural attenuation as a remediation approach requires detailed hydrogeological characterization of the contaminated site and monitoring of attenuation processes. This paper presents the results of monitored natural attenuation at the site of historical contamination by kerosene near Kraljevo. In order to demonstrate effects of biodegradation, following parameters in groundwater were measured: total petroleum hydrocarbons (TPH), electron acceptors (O₂, NO_3, SO₄^2-), metabolic products of biodegradation (Mn, Fe), and redox potential (Eh). Obtained results and methodological approach can be considered useful in conceptualizing future studies of this type.

Keywords: groundwater, petroleum hydrocarbons, natural attenuation, biodegradation.

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Biological hard materials

Abstract

Using only precursors commonly available in the environment at ambient temperatures evolution has developed materials with complexity and properties which today‘s engineers can only dream of producing. When examining biological hard materials the inclination is to compare the mechanical properties of biological materials with man made materials and to say man made materials are superior in some ways they are. Biology has never come up with materials as hard as silicon carbide, or as strong as steel, but to make these comparisons is to severely misunderstand the materials present in the natural world. The hard materials biology has produced, each of which while not hard by engineering standards, is incredibly complex and performs its role within the organism better than any synthetic material ever could.

Keywords: biological hard materials, mechanical properties, synthetic materials, engineering standards.

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BIOLOŠKI TVRDI MATERIJALI

Koristeći samo prekursore koji su uobičajeno dostupni u okruženju na temperaturama okoline, razvili su se materijali sa složenošću i svojstvima o kojima današnji inženjeri mogu samo sanjati u proizvodnji. Prilikom ispitivanja bioloških tvrdih materijala vršeno je upoređivanje mehaničkih osobina bioloških materijala sa materijalima izrađenim od strane čoveka i može se reći da su materijali izrađeni od strane čoveka na neki način superiorniji. Biologija nikada nije došla do materijala čvrstog kao silicijum karbida, ili jake kao čelik, ali da bi se napravila ova poređenja moraju se ozbiljno shvatati materijali prisutni u prirodnom svetu.

Biologija čvrstih materijala je izuzetno kompleksna, nije teška po inženjerskim standardima, i svoju ulogu bolje organizuje u organizmu nego bilo koji sintetički materijali.

Ključne reči: biološki tvrdi materijali, mehaničke osobine, sintetički materijali, inženjerski standardi.

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Analysis of the effects of butt welded joints on a carrying capacity of a structure tank

Abstract

In the present paper, after calculation using the Finite Element Method (FEM), stress distribution on the model of a part of the pressure-tank mantle without welded joints (WJ), with transversal WJ, longitudinal WJ and cross point location of WJ is analyzed. Also, FEM calculation and comparative analysis of the effects of WJ on the stress distribution have been conducted using the tank for liquid carbon dioxide as an example, on which, in addition to the mantle sheet-metal and bottom with necessary openings and elements such as saddles with supports and hangers, transversal and longitudinal butt WJ, have been modelled.

Keywords: Finite Element Method, tank, stress distribution on the model, welded joints.

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ANALIZA UTICAJA SUČEONO ZAVARENIH SPOJEVA NA NOSIVOST KONSTRUKCIJE REZERVOARA

Izvod

U radu je posle proračuna metodom konačnih elemenata (MKE) analizirana raspodela napona na modelu dela oplate rezervoara pod pritiskom bez zavarenih spojeva (ZS), sa obimnim ZS, podužnim ZS i ukrsnim mestom ZS. Takođe, u radu je na primeru rezervoara za tečni ugljen-dioksid, na kome su pored limova oplate i danaca sa potrebnim otvorima i elementima kao što su sedla sa osloncima i uške modelirani obimni i podužni sučeoni ZS, urađen proračun MKE i uporedna analiza uticaja ZS na raspodelu napona.

Ključne reči: Metoda Konačnih Elemenata, rezervoar, raspodela napona na modelu, zavareni spojevi.

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Corrosion resistance of Ni-Ti alloy, SS18/8 alloy and thermoactive alloy in artificial saliva in the absence and presence of tea

Abstract

Corrosion resistance of Ni-Ti alloy, SS18/8 alloy and thermoactive alloy in artificial saliva (AS) in the absence and presence of tea has been evaluated by such as polarization study. For  Ni-Ti alloy, SS18/8 alloy and thermoactive alloy, polarization study lead to the conclusion that corrosion resistance of Ni-Ti alloy and thermoactive alloy decreases in the order

AS + Tea > Tea > AS

Hence, people implanted with orthodontic wire, made of Ni-Ti alloy and thermoactive alloy can take tea orally without any hesitation.

For SS18/8 alloy, polarization study lead to the conclusion that corrosion resistance of SS18/8 alloy decreases in the order

AS > AS + Tea >Tea

So, people implanted with orthodontic wire, made of SS18/8 alloy should avoid taking tea.

Keywords: corrosion resistance, orthodontic wires, artificial saliva, extract tea, Ni-Ti alloy, SS18/8 alloy,  thermoactive alloy, polarization study.

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OTPORNOST NA KOROZIJU LEGURE  Ni-Ti, LEGURE SS18 / 8 I TERMOAKTIVNE LEGURE U VEŠTAČKOJ PLJUVAČCI U ODSUSTVU I PRISUSTVU ČAJA

Izvod

Otpornost na koroziju legure Ni-Ti, legure SS18 / 8 i termoaktivne legure u veštačkoj pljuvačci (AS) u odsustvu i prisustvu čaja procenjena je polarizacijom. Za legure Ni-Ti, legure SS18 / 8 i termoaktivne legure, polarizaciono ispitivanje dovodi do zaključka da se otpornost na koroziju legure Ni-Ti i  termoaktivne legure smanjuje u redosledu

AS + Tea > Tea > AS

Stoga, ljudi implantirani sa ortodontskom žicom, napravljenom od legure Ni-Ti legure i termoaktivne legure mogu uzimati čaj oralno bez ikakvih oklevanja.

Za leguru SS18/8, studija polarizacije dovodi do zaključka da se otpornost na koroziju legure SS18 / 8 smanjuje u redosledu

AS > AS + Tea >Tea

Dakle, ljudi implantirani sa ortodontskom žicom, napravljenom od legure SS18/8 trebalo bi izbegavati uzimanje čaja.

Ključne reči: otpornost na koroziju, ortodontska žica, veštačka pljuva, ekstrakt čaja, Ni-Ti legura, legura SS18/8, termoaktivna legura, polarizacija.

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Ekstrakt žalfije kao inhibitor korozije čelika i bakra

Izvod

Zaštita od korozije čelika i bakra vršena je obradom korozione sredine primenom ekstrakta žalfije različitih koncentracija (0.5, 1 i 1.5 g/dm³), kao zelenog inhibitora, u rastvorima  3% NaCl i 4% HCl. Brzina korozije čelika i bakra u pripremljenim rastvorima merena je gravimetrijskom metodom i elektrohemijskim metodama (Tafelovom metodom ekstrapolacije i spektroskopijom elektrohemijske impedanse).

Najveći stepen zaštite  čelika u 3% NaCl je pri koncentraciji žalfije 1.5 g/dm³ u vremenskom intervalu od 6h i iznosi z= 97.5%. Koncentracije žalfije 1.0 i 1.5 g/dm³ u 3% NaCl pokazuju veoma dobro inhibitorsko dejstvo, jer je srednji zaštitni faktor 78.5% odnosno 95.3%.  Ovi rezultati preporučuju žalfiju kao mogući inhibitor pri zaštiti čelika u rastvorima 3% NaCl. Zaštita čelika u 4% HCl je znatno manja i stepen zaštite se kreće do 64,5%, što žalfiju može preporučiti kao zeleni inhibitor korozije za neki kraći period.

Najveći stepen zaštite  bakra u 3% NaCl je pri koncentraciji žalfije 1 g/dm³  i iznosi 60,04%, dok pri koncentraciji ekstrakta žalfije 1,5 g/dm³ z=53% u vremenskom intervalu od 6 sati. Međutim, isti rastvori u vremenskom intervalu od 4 i 24 h deluju katalitički na proces korozije bakra, te se ekstrakt žalfije ne može preporučiti kao inhibitor korozije bakra u 3% NaCl. Najveća dostignuta vrednost zaštitnog faktora ekstrakta žalfije na koroziju bakra u 4% HCl je 59,96% u rastvoru koji sadrži 1 g/dm³ ekstrakta žalfije. Ostvarena vrednost zaštitnog faktora nije dovoljna da se ekstrakt žalfije preporuči kao inhibitor korozije bakra u 4% HCl.

Rezultati dobijeni elektrohemijskim merenjima su u skladu sa rezultatima dobijenim gravimet­rijskom metodom, te se mogu preporučiti kao brze metode za pouzdana koroziona ispitivanja.

Ključne reči: zeleni inhibitori, korozija čelika i bakra, ekstrakt žalfije, spektroskopija elektrohemijske impedanse, Tafelovi polarizacioni dijagrami.

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SAGE EXTRACT AS AN INHIBITOR OF STEEL AND COPPER CORROSION

Abstract

Protection of steel and copper from corrosion was caried out by processing corrosive environment using different concentrations of sage extract (0.5 g/dm³, 1 g/dm³ and 1.5 g/ dm³) as a green inhibitor in 3% NaCl and  4% HCl solutions. The rates of  steel and copper corrosion in the solutions prepared were measured using gravimetric analysis and electrochemical methods (the Tafel extrapolation method and electrochemical impedance spectroscopy).

The highest level of steel protection (z= 97.5%) in the 3% NaCl solution occurs with the concentartion of sage of 1.5 g/dm³ for a six-hour time interval. Sage concentrations of 1.0 g/dm³ and 1.5 g/dm³ in the 3% NaCl solution exhibit a very good inhibitory action, since the average protction factors are 78.5% and 95.3% respectively.  These results prove that sage can be used as a potential inhibitor of steel corrosion  in the 3% NaCl solutions. Corrosion protection for steel in the 4% HCl is considerably lower, not more than 64.5%, which means that sage can only be used as a green inhibitor for a shorter period of time.

The highest level of copper protection (z=60,04%) in the 3% NaCl is for the sage concentration of 1 g/dm³, whereas for the concentration of 1.5 g/dm³ it is 53%  for a six-hour time interval. However, the same solutions for the time intervals of  4 and 24 h have a catalytic action in the process of copper corrosion, so it is not recommended to use sage extract as a green inhibitor for copper in the 3% NaCl. The highest protection factor achieved in the 4% HCl  is 59.96% in the solution which contains 1 g/dm³ of sage extract. This value is not sufficent to recommend sage extract as an inhibitor of copper corrosion in the  4% HCl.

The results obtained from electrochemical measurements confirm the results obtained by gravimetric analysis, which makes them, therefore, recommendable as fast and relibale methods in corrosion testing.

Keywords: green inhibitors, corrosion of steel and copper, sage extract, electrochemical impedance spectroscopy, Tafel extrapolation method.

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Efikasnost zeolita i apatita na mobilnost teških metala u zemljištima praćena preko test kulture Sinapis Alba

Izvod

Zaštita i unapređenje životne sredine, posebno očuvanje i zaštita zemlјišta, postao je danas jedan od najznačajnijih problema savremenog sveta. Istraživanja u ovom radu imaju za cilј ispitivanje efikasnosti dva tipa mineralnih sirovina, zeolita i apatita na imobilzaciju teških metala i sprečavanja njihovog uključenja u lanac ishrane.   Ispitivani su Pb, Cd, Zn i radionuklid (U), u dozama 10 mg kg^-1 Cd, 500 mg kg^-1 Pb, 300 mg kg^-1 Zn i 300 mg kg^-1 U na zemlјištima različitih fizičko-hemijskih karakteristika (peskoviti černozem i pseudoglej). Efikasnost mineralnih sirovina kroz procese adsorpcije/precipitacije polutanata u zemlјištima ispitivana je preko vegetacionih ogleda sa test kulturom-bilјke slačice, Sinapis Alba, preko sadržaja Pb, Cd, Zn i U u korenu i nadzemnoj masi. Rezultati ukazuju da su i zeolit i apatit, domačeg porekla, u dozi 20 g kg^-1 zemljišta, doprineli imobilizaciji ispitivanih polutanata, da njihova efikasnost zavisi od fizičko hemijskih osobina polutanta i kiselosti zemljišta, tako da njihovo korišćenje opravdava primenu u tehnologijama remedijacije kontaminiranih zemljišta a u funkciji održivosti poljoprivredne proizvodnje i proizvodnji zdravstveno bezbedne hrane.

Ključne reči: apatit, zeolit, teški metali Pb, Cd, Zn, U, zemljište, slačica, imobilizacija.

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EFFICIENCY OF ZEOLITE AND APATITE ON THE MOBILITY OF HEAVY METALS IN THE SOIL THROUGH THE Sinapis Alba AS TEST CULTURE

Abstract

Protection and improvement of the environment, especially preservation and protection of the land, has become one of the most important problems of the modern world today. The research in this paper aims at examining the efficiency of two types of mineral raw materials, zeolites and apatites on the immobilization of heavy metals and preventing their inclusion in the food chain. Pb, Cd, Zn and radionuclides (U) were tested. In doses 10 mg kg^-1Cd, 500 mg kg^-1 Pb,  300 mg kg^-1Zn i 300 mg kg^-1U. On soil with various physico-chemical properties (sandy chernozem and pseudocley). The efficiency of mineral resources through the adsorption / precipitation of pollutants in the soil was investigated through vegetation experiments with the test culture-plant, Sinapis Alba, through the contents of Pb, Cd, Zn and U in the root and overgrowth mass. The results indicate that both, zeolite and apatite in dosage 20 g kg^-1 soils, have contributed to the immobilization of the investigated pollutants, that their effectiveness depends of soils  type and their acidity, kinds of pollutant, so their use is justified in the application of technologies for the remediation of contaminated soils in the function of sustainability of agricultural production and the production of healthy food.

Keywords: apatite, zeolite, heavy metals Pb, Cd, Zn, U, soil, slag, immobilization.

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Warm upsetting tests with cylindrical molybdenum and wolfram samples

Abstract

The resistance of a modern ceramic material – silicon nitride – was examined by cyclical high temperature and compressive loads by the use of warm upsetting tests at cylindrical molybdenum and wolfram samples. Furthermore, flow curves of these samples were determined for different temperatures.

Keywords: upsetting test, silicon nitride, molybdenum, wolfram, flow curves

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TESTOVI ZA POBUĐIVANJE TOPLOTE SA CILINDRIČNIM MOLIBDENOM I VOLFRAM UZORCIMA

Izvod

Otpor savremenog keramičkog materijala – silicijum nitrida – ispitivan je cikličnim visokim temperaturama i pritiscima na korišćenje testova toplog uzbuđenja na cilindričnom molibdenu i uzorcima volframa. Pored toga, krive protoka ovih uzoraka su određene za različite temperature.

Ključne reči: test pobude, silicijum nitrid, molibden, volfram, krive protoka

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Optička molekularna anizotropija materijala i Rayleighevo rasejanje

Izvod

Rayleighevo rasejanje izraženo formalizmom depolarizovanih i polarizovanih komponenti pruža mogućnosti za analizu optičke molekularne anizotropije za tečne materijale (čiste, razblažene rastvore sa velikim i malim molekulima). Postoje razni uređaji za merenje rasejanja, ali se i sa aparaturama sa statičkim rasejanjem dobija dosta podataka. Primenom He Ne lasera na osnovnom prelazu 632,8nm na uređaju laboratorijskog tipa, mereno je rasejanje organskih rastvarača karakterističnih za etaloniranje. Ova merenja su poslužila i za poređenje karakteristika materijala dobijenih sa spontanim izvorima i kvantnim generatorima–laserima. Na osnovu potvrde, ocenjena su i merenja manje poznatih materijala i od interesa za biološke procese (fitola i srodnih jedinjenja za sticanja uvida u ponašanje fitil grupe).

Ključne riječi: laser, rasejanje, molekularna anizotropija, rastvori, biomaterijali.

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OPTICAL MOLECULAR ANISOTROPY OF MATERIALS AND RAYLEIGH SCATTERING

Abstract

Rayleigh scattering expressed with formalism of depolarized and polarized components offers possibilites for analysis of optical molecular anisotropy for liquid materials (pure, diluted solutions with large and small molecules). Various devices exist for measuring scattering, but with laser systems for static scattering enough data is collected. With the use of laboratory type He Ne lasers with basic transition at 632.8nm, scattering of organic solvents was measured, characteristic for calibration. These measurements served for materials feature comparison acquired with spontaneous sources and quantum generators – lasers. Based on assessment, the measurements of less known materials were evaluated which are of interest for biological processes (phytol and related compounds) for gaining in site into behaviour of phytil group).

Keywords: laser, scattering, molecular anisotropy, solvents, biomaterials

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Karakterizacija plazma sprej bioinertne kompozitne prevlake Al₂O₃25tež.%(ZrO₂8%Y₂O₃)

Izvod

Kompoziti Al₂O₃ZrO₂ i ZrO₂Al₂O₃ su inertni perspektivni biomaterijali za primenu na implantatima zbog biokompatibilnosti i mehaničkih svojstava koja kombinuju visoku čvrstoću savijanja sa visokom žilavosti. Keramika Al₂O₃ ima odličnu biokompatibilnost i otpornost na habanje. Međutim, ova keramika ima malu čvrstoću savijanja i žilavost.

U cilju povećanja mehaničkih karakteristika keramici Al₂O₃ se dodaje oksidna keramika ZrO₂. Oksid ZrO₂ je inertan u fiziološkom okruženju i pokazuje veću otpornost na savijanje, veću žilavost loma i manji Joungov modul u poređenju sa čistim oksidom Al₂O₃. Keramike Al₂O₃ i ZrO₂ se intezivno primenjuju za proizvodnju proteza kuka. Sa mešavinom oba materijala mogu se povećati mehanička čvrstoća. Takođe, mešavina keramičkih materijala Al₂O₃ i ZrO₂ ima bolju otpornost protiv neravnina i oštećenja pod opterećenjem površine tokom testa iščašenja u poređenju sa čistom keramikom Al₂O₃.

Cilj ovog rada je da se analiziraju mehaničke osobine (miktotvrdoća HV_0.1 i čvrstoća spoja) i mikrostruktura kompozitne prevlake APS-Al₂O₃(ZrO₂8%Y₂O₃) sa sadržajem od 25tež.% ZrO₂8%Y₂O₃ na optičkom mikroskopu (OM) i skening elektronskom mikroskopu (SEM). Rezultati ispitivanja mehaničkih i strukturnih karakteristika pokazuju da se slojevi keramičke prevlake Al₂O₃ZrO₂ mogu uspešno primeniti u ortopediji na implantima.

Ključne reči: APS, Al₂O₃25tež.%(ZrO₂8%Y₂O₃), implanti, mikrostruktura, mikrotvrdoća, čvrstoća spoja

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CHARACTERIZATION OF COMPOSITE BIO INERT APS-Al₂O₃25wt.%(ZrO₂8%Y₂O₃) COATING

Abstract

Composites Al₂O₃ZrO₂ and ZrO₂Al₂O₃ are inert perspective biomaterials for use in implants due to their biocompatibility and mechanical properties that combine high flexural strength with high toughness. Ceramics Al₂O₃ has excellent biocompatibility and wear resistance, however, this ceramics has low flexural strength and toughness.

In order to increase the mechanical properties of Al₂O₃ ceramics oxide ceramics ZrO₂ is added to it. Oxide ZrO₂ is inert in a physiological environment and has higher flexural strength, higher fracture toughness, and lower Young’s modulus, compared with pure oxide Al₂O₃. Ceramics Al₂O₃ and ZrO₂ are extensively used for the production of hip prosthesis. By mixing both materials the mechanical strength can be increased. Also, the mix of ceramic materials Al₂O₃ and ZrO₂ has a better resistance against uneven surfaces and damage under load during a luxation test compared to the pure ceramics Al₂O₃.

The aim of this study was to analyze the mechanical characteristics (microhardness HV_0.1 and bond strength) and microstructure of the composite coating APS-Al₂O₃(ZrO₂8%Y₂O₃) with a content of 25wt.%ZrO₂8%Y₂O₃ on an optical microscope (OM) and scanning electron microscope (SEM). Results of testing mechanical and structural characteristics indicate that the layers of ceramic coating Al₂O₃ZrO₂ can be successfully applied in orthopedic implants.

Keywords: APS, Al₂O₃25wt.%(ZrO₂8%Y₂O₃), implants, microstructure, microhardness, bond strength

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Uticaj hemijskog i mineraloškog sastava crvenog mulja na parametre alkaliteta

Izvod

Crveni mulj je visokoalkalna koloidna suspenzija, zaostala nakon prerade boksita u glinicu po Bayer-ovom postupku. Uprkos višestrukom ispiranju crveni mulj zadžava snažan alkalitet, usled prisustva zaostale baze i čitavog niza alkalnih minerala. U ovom radu se razmatraju aspekti Bayer-ovog procesa koji utiču na alkalitet mulja, mehanizmi i hemizmi koji ga uslovljavaju, te parametri koji služe za njegovo kvantifikovanje.

U crvenom mulju pojavljuje se veliki broj minerala. Deo minerala vodi poreklo iz boksita, a ostali minerali su sintetisani usled delovanja procesnih uslova na boksit. Ovi novonastali minerali značajno doprinose alkalitetu crvenog mulja, a posebno desilikacioni produkti. Alkalitet crvenog mulja najlakše je posmatrati preko pH vrednosti. pH crvenog mulja je uglavnom u rasponu 10.5 – 12.5, i snažno je puferovana zbog prisustva više alkalnih minerala (hidroksidi, karbonati, aluminati i aluminosilikati) i njihovog dugoročnog rastvaranja. Prisustvo više puferujućih materija u mulju, izaziva kompleksno ponašanje mulja pri neutralizaciji kiselinama. Pored rastvaranja minerala nosioca alkalnih anjona, alkalitetu doprinose i reakcije izmene alkalnih anjona koje se dešavaju na površini metalnih oksida. Alkalni minerali uglavnom su nerastvorni ili slabo rastvorni u vodi, a rastvaraju se u mineralnim kiselinama. Zbog toga je alkalitet iz crvenog mulja vrlo teško ukloniti ispiranjem vodom. Tretman mulja mineralnim kiselinama, CO₂, i gipsom, kao i odležavanje mulja na jalovištimima dovode do sniženja alkaliteta.

Konačno, alkalitet crvenog mulja predstavlja nepoželjno svojstvo sa širokim spektrom uticaja i potrebno ga je otkloni. Poznavanje mehanizama neutralizacije i rastvaranja, može doprineti efikasnosti neutralizacije i pronalaženju novih postupaka, kao i različitih primena neutralisanog mulja.

Ključne riječi: crveni mulj, alkalitet, hemijski i mineraloški sastav, desilikacioni produkti, pH, neutralizacioni kapacitet, natrijum, puferovanje, rastvaranje.

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THE EFFECT OF CHEMICAL AND MINERALOGICAL COMPOSITION OF RED MUD ON ALKALINITY PARAMETERS

Abstract

Red mud is highly alkaline colloidal suspension, which remains after processing bauxite into alumina by Bayer’s proceedings. Despite repeated washing red mud keep strong alkalinity, due to the presence of residual base and a number of alkaline minerals. This paper examines aspects of Bayer’s processes that affect the formation of alkalinity in the mud, and chemical reactions are considered significant for neutralization. Chemical and mineralogical content of red mud varies over a wide range. In the red mud appears a large number of minerals. Part of minerals that occur in the red mud originates from bauxite (insoluble minerals during leaching), and other minerals were synthesized due to the effect of process conditions on bauxite. These newly created minerals contribute significantly to the alkalinity of the red mud. Alkalinity of the red mud is most easily considered through the pH value. The pH of the solid phase of sludge is generally in the range from 10.5 to 12.5, and it is strongly buffered due to the presence of more alkaline minerals (hydroxides, carbonates, aluminates, and aluminosilicates). The presence of more buffering substances in the mud, causing a complex behavior of mud in the neutralization of acids. On neutralization curves are observed inflection points that are not typical of the pure substance. In addition to dissolving minerals holder alkaline anion, when considering the alkalinity should be considered alkaline anion exchange reactions occurring on the surface of metal oxides. Alkaline minerals are generally insoluble or poorly soluble in water, and dissolved in mineral acids. Therefore, the alkalinity of the red mud is very difficult to remove by washing with water. Treatment of mud with mineral acids, CO₂, and gypsum causes a decrease of alkalinity. Aged sludge tailings also contributes to lowering the alkalinity. Finally, the alkalinity of the red mud is necessary to remove, as it is the undesirable property with a wide range of negative impacts. Knowledge of the neutralization mechanisms and dissolution, can contribute to the efficiency of the neutralization and finding new procedures, as well as different applications of neutralized red mud.

Keywords: red mud, alkalinity, chemical-minerological composition, desilification products, pH, acid neutralizing capacity, sodium, buffering, dissolution.

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Sorpcija nitrata pomoću modifikovane biomase Lagenaria vulgaris: kinetička i ravnotežna ispitivanja

Izvod

U cilju prevencije pojave eutrofikacije analizirana je efikasnost novog alternativnog sorbenta na bazi hemijski modifikovane kore Lagenaria vulgaris za uklanjanje nitrata iz vodenih rastvora. Sorpcioni eksperimenti su vršeni iz vodenih rastvora različitih početnih koncentracija nitrata (2 – 100 mg N dm^-3), sa dozom sorbenta od 2 g dm^-3, pri optimalno utvrđenim uslovima. Za predviđanje mehanizma sorpcije nitrata i procenu karakterističnih sorpcionih parametara primenjena su kinetička i ravnotežna ispitivanja. Modelovanje eksperimentalno dobijenih rezultata u ravnoteži vršeno je pomoću sorpcionih izotermi, tipičnih za definisanje ravnoteže sorpcije u sistemu tečno-čvrsto (Langmuir-ova, Freundlich-ova i Temkin-ova izoterma). Najbolje slaganje podataka postignuto je pomoću Langmuir-ovog modela (R² = 0,994), koji predviđa maksimalni sorpcioni kapacitet sorbenta od 16,67 mg N g^-1. Za kinetička ispitivanja procesa sorpcije primenjeni su Lagergren-ov model pseudo-prvog reda, Ho-ov model pseudo-drugog reda i Weber-Morris-ov model unutarčestične difuzije. Proces sorpcije nitrata pomoću modifikovane biomase Lagenaria vulgaris najbolje opisuje kinetički model pseudo-drugog reda. Multilinearan Weber-Morris-ov model sugeriše da mehanizam površinske fizisorpcije, pored unutarčestične difuzije, kontroliše ukupnu brzinu procesa.

Ključne reči: lagenaria vulgaris, biomasa, sorpcija, nitrati, kinetika, ravnoteža

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NITRATE SORPTION BY MODIFIED Lagenaria vulgaris  BIOMASS: KINETIC AND EQUILIBRIUM STUDIES

In order to prevent the occurrence of eutrophication, the efficiency of a new alternative sorbent based on a chemically modified Lagenaria vulgaris shell for nitrates removal from aqueous solution was analyzed in batch conditions. The sorption experiments were performed from aqueous solutions of different initial nitrate concentrations (2 – 100 mg N dm^-3), with a sorbent dose of 2 g dm^-3 at optimal conditions. Kinetic and equilibrium studies to predict the nitrate sorption mechanism and to evaluate characteristic sorption parameters were applied. Modeling the equilibrium data was performed using the typical sorption isotherms: Langmuir, Freundlich and Temkin, by a linear regression method. The nitrate sorption followed the Langmuir isotherm model (R² 0,994) with the maximum sorption capacity of 16,67 mg N g^-1. For the kinetic studies, pseudo-first order and pseudo-second order equatios, as well as the Weber-Morris model of intra-particle diffusion were applied. The sorption process was found to be best fitted by the pseudo-second order kinetic model. The multilinear Weber-Morris model suggests that the surface physisorption mechanism, in addition to intra-particle diffusion, controls the total process rate.

Keywords: lagenaria vulgaris, biomass, sorption, nitrates, kinetics, equilibrium.

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Calotropis procera plant extract as green corrosion inhibitor for 304 stainless steel in hydrochloric acid solution

Abstract

The effect of Calotropis Procera (CP) extract on the corrosion inhibition of 304 stainless steel (SS) in 2 M HCl was studied using electrochemical (electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and electrochemical frequency modulation (EFM) and chemical weight loss (WL) methods at 25ºC. The adsorption of the extract on 304 SS surface is consistent with Langmuir adsorption isotherm. The polarization plots revealed that the addition of extract shifts the cathodic and anodic branches towards lower currents. Such shifts indicate that CP extract acts as a mixed-type inhibitor. The thermodynamic parameters of activation and adsorption processes were calculated and discussed. The surface morphology of the 304 SS specimens was evaluating using different techniques.

Keywords: Corrosion inhibition, 304 SS, HCl, WL, PP, EIS, EFM.

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EKSTRAKT BILJKE Calotropis Procera KAO ZELENI INHIBITOR KOROZIJE ZA NERĐAJUĆI ČELIK No-304 U RASTVORU HLOROVODONIČNE KISELINE

Izvod

Uticaj ekstrakta Calotropis Procera (CP) kao inhibitora na koroziju nerđajućeg čelika No-304 (SS) u 2M HCl proučavan je pomoću metoda: elektrohemijske impedansne spektroskopije (EIS), potentiodinamičke polarizacije (PP) i elektrohemijske frekventne modulacije (EFM)) i hemijskog gubitka težine (GL) na 25ºC. Adsorpcija ekstrakta na površini nerđajućeg čelika No-304 SS je u skladu sa Langmirovom izotermom adsorpcije. Polarizacijske parcele otkrile su da dodavanje ekstrakta pomera katodnu i anodnu granu prema nižim strujama. Takvi pomaci ukazuju da CP ekstrakt deluje kao mešoviti inhibitor. Izračunati su i razmatrani termodinamički parametri procesa aktivacije i adsorpcije. Površinska morfologija uzorka nerđajućeg čelika No-304 SS ocenjena je korišćenjem različitih tehnika.

Ključne reči: inhibicija korozije, nerđajući čelik No-304 SS, hlorovodonična kiselina, GL, PP, EIS, EFM.

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Long-term performance of stabilised/solidified polluted sediment in terms of metal leachability and matrix characterization

Abstract

Sustainable and economically feasible polluted sediment treatment is gaining more and more importance. Stabilization/solidification (S/S) technologies are widely used for treatment of sediment and possibilities of using low-cost and readily available materials and binders are increasingly being examined. This work is concerned with aquairing more data about long-term performance of this kind of treatment in therms of metal leaching and microstructural cnaracterization when treating sediment with fly ash and lime. Extraction potential of metals and the effectiveness of the S/S treatment applied, together with compliance with national legislative, were performed by using Toxicity Characteristic Leaching Procedure – TCLP and The German standard leaching test – DIN 3841-4 S4. Leaching test results showed that the applied S/S treatment was effective in immobilizing metals even after seven years of aging. Scanning electron microscope (SEM) and X-ray diffraction analysis confirmed that pozzolanic reactions took place during 28 days and continued along S/S mixture maturation. Compressive strength measurement further proved the treatment efficacy in terms of obtained matrix stability, which enables their subsequent use. It can be concluded that the S/S technique, with the usage abundant materials has a significant potential for treatment of metal polluted sediment.

Keywords: sediment, fly ash, leaching, stabilization/solidification, matrix characterization.

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DUGOROČNE PERFORMANSE STABILIZIRANOG/SOLIDIFIKOVANOG SEDIMENTA U POGLEDU IZLUŽIVANJA METALA I KARAKTERIZACIJE MATRIKSA

Izvod

Održivi i ekonomski izvodljivi tretmani zagađenog sedimenta postaju sve važniji. Tehnologija stabilizacije/solidifikacije (S/S) ima široku primenu u tretmanu sedimenta i mogućnosti korišćenja jeftinih i lako dostupnih materijala, a vezivni materijali se sve više ispituju. Ovaj rad se bavi praćenjem dugoročnih performansi u tretmanu izluživanja metala i mikrostrukturne karakterizacije pri tretiranju sedimenta sa letećim pepelom i krečom. Ekstrakcioni potencijal metala i efektivnost korišćenja S/S tretmana, izvršeni su korišćenjem TCLP testa izluživanja i standardnim nemačkim testom izluživanja (DIN 38414-4). Rezultati izluženih koncentracija metala pokazali su da je primenjeni S/S tretman bio efikasan u imobilizaciji metala čak i posle sedam godina starenja. Skenirajuća elektronska mikroskopija (SEM) i x-ray difrakciona analiza potvrdili su da se pozolanske reakcije dešavaju tokom 28 dana, kao i tokom sazrevanja S/S smeša. Merenje pritisne čvrstoće dodatno je dokazalo efikasnost tretmana u smislu dobijenih stabilnih matriksa, što omogućava njegovu kasniju upotrebu. Može se zaključiti da S/S tehnika, uz korištenje letećeg pepela i kreča, ima značajan potencijal za tretman sedimenta zagađenog metalima.

Ključne reči: sediment, leteći pepeo, izluživanje,stabilizacija/solidifikacija, karakterizacija matriksa.

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Influence of crystalization temperature on morphological properties of dibutylphtalate alumosilicate adsorbents

Abstract

Alumosilicates have advantages over other adosrbents because they have high adsorption capacity and high selectivity. Due to this fact, the paper investigates the synthesis and characterization of the aluminosilicate materialused as a potential adsorbent of dibutyl phthalate (DBP)  The following analyses were conducted on the samples synthesized at various crystallization temperatures (70, 80 and 90° C): the adsorption of DBP, crystallinity (XRD), medium particle diameter (Ds50%)  and scanning electron microscopy (SEM) It has been found that the aluminosilicate species obtained at temperatures of 80 and 90 C have good adsorbent properties for DBP The medium particle diameter varied depending on the crystallization temperature according to the principles of autocatalytic nucleation and the “memory effect” of the gel. At the temperature of 90°C, crystallinity decreases significantly (37.87%) whereas dibutylphthalate adsorption increases  due to the increase in the content of other nonzeolite species.

Keywords: morphological properties, aluminosilicates, adsorption, dibutyl phthalate.

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UTICAJ TEMPERATURE KRISTALIZACIJE NA MORFOLOŠKE KARAKTERISTIKE ALUMOSILIKATNIH ADSORBENASA DIBUTILFTALATA

Izvod

Alumosilikati imaju prednosti u odnosu na druga adsorpciona sredstva jer pokazuju visok adsorpcioni kapacitet i visoku selektivnost. Zbog ove činjenice, izvršena je sinteza i karakterizacija alumosilikatnog materijala koji se može koristiti kao potencijalni adsorbens dibutilftalata (DBF). Ispitana je adsorpcija DBF-a na alumosilikatu sintetisanom pri različitim temperaturama kristalizacije (70, 80 i 90°C), praćena je njegova kristaličnost (XRD), srednji prečnik čestica (D_s50%), a urađena je i skenirajuća elektronska mikroskopija (SEM) sintetisanih uzoraka. Utvrđeno je da na temperaturama od 80 i 90°C  dobijamo alumosilikatne vrste koje po svojim osobinama mogu poslužiti kao dobri adsorbensi DBF-a. Srednji prečnik čestica kretao se zavisno od temperature kristalizacije u skladu sa principima autokatalitičke nukleacije i „efekta pamćenja“ gela. Na temperaturi kristalizacije od 90°C kristaličnost znatno pada i iznosi 37,87% dok adsorpcija dibutilftalata raste na račun povećanja udjela drugih nezeolitnih vrsta.

Ključne reči: morfološke osobine, alumosilikati, adsorpcija, dibutilftalat.

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Tensile strength properties of hybrid magnetic composite materials

Abstract

The Nd-Fe-B-barium ferrite hybrid composite materials with epoxy matrix presented in this paper cover maximum energy product from 1 to 13 MGOe. Mixture of magnetic particles is responsible for high magnetic quality, while the thermosetting resin plays a role in mechanical properties. Samples with various ratio of Nd-Fe-B to barium ferrite in constant weight of epoxy resin are examined by tensile strength measurements. Magnetic measurements carried out by using vibrating sample magnetometer (VSM) show typical hysteresis loop. A structural analysis of composite surface is conducted by scanning electron microscope (SEM). Uniform particle distribution of plate shape Nd-Fe-B particles and spherical barium ferrite agglomerates is essential for both, mechanical and magnetic properties of composite materials. Fine particles are incorporated in-between larger particles in epoxy bulk which lead to improving the properties.

Keywords: Nd-Fe-B, ferrite, bonded magnets, composite, tensile strength.

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ZATEZNA ČVRSTOĆA HIBRIDNIH MAGNETNIH KOMPOZITNIH MATERIJALA

Izvod

U ovom radu proučavani su hibridni Nd-Fe-B-barijum ferit kompozitni materijali sa epoksi matricom čiji se maksimani energetski proizvod kreće od 1 do 13 MGOe. Odlična magnetna svojstva kompozita potiču od smeše magnetnih čestica, dok termoočvršćavajući polimer ima uticaj na mehanička svojstva. Uzorci sa različitim odnosom udela Nd-Fe-B i barijum ferita u konstantnoj masi epoksi veziva su ispitivani na zateznu čvrstoću. Magnetna merenja vršena pomoću vibracionog magnetometra (VSM) pokazuju karakteristučnu histerezisnu petlju. Strukturnu analizu na površini kompozita sprovedena pomoću skenirajuće elektronske mikroskopije (SEM). Uniformna raspodela pločastih Nd-Fe-B čestica i sferičnih aglomerata barijum ferita je veoma značajna i za mehanička i za magnetna svojstva kompozitnih materijala. Sitne čestice su inkorporirane između velikih čestica u masi epoksida što dovodi do poboljšanja svojstava.

Ključne reči: Nd-Fe-B, feriti, bonded magneti, kompoziti, zatezna čvrstoća.

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