Zaštita Materijala 3. 2020

Sub-monolayers of iridium electrodeposited on Ti₂AlC substrate as catalysts for hydrogen evolution reaction in sulfuric acid solution

Abstract

The hydrogen evolution reaction (HER) was investigated at sub-monolayers of iridium electrodeposited on Ti₂AlC substrate. The lowest amount of electrodeposited iridium was 3 close-packed (111) monolayers (3 ML), while the highest one was 22 ML (3, 5, 10, 15 and 22 ML). The lowest and the highest amounts of iridium were electrodeposited by linear sweep voltammetry (LSV), while the other three samples were electrodeposited by controlled potential coulometry, from the solution containing 1 mM, or 3 mM K₃IrCl₆ + 0.5 M Na₂SO₄ (pH 6.2) at 70 ^oC. The HER was investigated by polarization and electrochemical impedance spectroscopy (EIS) measurements. Polarization curves for iridium sub-monolayers equal, or higher than 6 ML showed low Tafel slope of -14 to -16 mV dec^-1 up to about -0.1 A cm^-2, while at higher current densities the Tafel slopes increased, varying between -40 and -72 mV dec^-1. The highest value of exchange current density (j_o) was obtained for 6 ML of electrodeposited iridium, being -27.89 A g^-1. The overpotential at j = -0.3 A cm^-2 could be determined for samples containing 15 ML and 22 ML of iridium, being 82 mV.

Keywords: Sub-monolayer, iridium electrodeposition, hydrogen evolution, sulfuric acid

More >>>

Nekoliko monoslojeva elektrohemijski istaloženog iridijuma na podlozi od  Ti₂AlC kao katalizatori za izdvajanje vodonika u rastvoru sumporne kiseline

Izvod

Izdvajanje vodonika ispitivano je u rastvoru sumporne kiseline na elektrohemijski istaloženim slojevima (od 3 monosloja do 22 monosloja) iridijuma na podlozi od Ti₂AlC. Najmanja i najveća količina iridijuma (3 i 22 monosloja) elektrohemijski su istaložene metodom linearne voltametrije, dok su preostala tri uzorka (6, 10  i 15 monoslojeva) elektrohemijski istaložena pri konstantnom potencijalu do potrebne količine naelektrisanja iz rastvora 1 mM, ili 3 mM K₃IrCl₆ + 0.5 M Na₂SO₄ (pH 6.2) na temperaturi rastvora od 70 ^oC. Reakcija izdvajanja vodonika ispitivana je na svim elektrodama snimanjem polarizacionih krivih. Za uzorak sa 22 monosloja Ir primenjena je i metoda impedanse. Polarizacione krive za uzorke sa 6, 10, 15 i 22 monosloja Ir bile su okarakterisane malom vrednošću Tafel-ovog nagiba od -14 to -16 mV dek^-1 u oblasti gustina struja do -0.1 A cm^-2, dok se Tafel-ov nagib povećavao pri većim gustinama struja varirajući od -40 do -72 mV dek^-1. Najveća vrednost specifične gustine struje izmene (j_o) dobijena je kod uzorka sa 6 monoslojeva Ir i iznosila je  – 27.89 A g^-1. Za uzorke sa 15 i 22 monosloja  Ir vrednost prenapetosti pri gustini struje j = -0.3 A cm^-2 (uslovi industrijske proizvodnje vodonika) iznosila je 82 mV.

Ključne reči: izdvajanje vodonika, elektrohemijsko taloženje Ir (3 do 22 monosloja), sumporna kiselina.

Dalje >>>

Expired nizatidine drug as eco-friendly corrosion Inhibitor for α-brass alloy in aqueous solutions

Abstract

Expired nizatidine drug (END) was studied as inhibitor for α-brass in 1M HCl utilizing weight loss (WL), and electrochemical methods namely, AC impedance (EIS), Potentiodynamic polarization (PP), and electrochemical frequency modulation (EFM) tests. The protection efficiency (%IE) was improved with raising in the dose of the expired nizatidine and decreases with raising the temperature. The (%IE) reaching maximum value 95 % at higher dose of expired nizatidine drug at 25^oC. PP data indicated that nizatidine drug behaves like a mixed kind drug. The protection of α-brass corrosion by nizatidine can fit to the adsorption ability of nizatidine drug molecules onto the reactive sites of the α-brass surface. The adsorption of the drug follows Langmuir adsorption isotherm. The surface morphology of α-brass was investigated. The results obtained from different methods are in excellent agreement.

Keywords: Acidic inhibition, α-brass, Nizatidine, EFM, EIS, AFM, FTIR

More >>>

Nizatidin lek kao ekološki inhibitor korozije za legure  α-mesinga u vodenim rastvorima

Izvod

Istekli lek nizatidine (END) proučavan je kao inhibitor α-mesinga u 1M HCl korišćenjem gubitka težine (WL) i elektrohemijskim metodama, naime, AC impedancijom (EIS), potenciodinamičkom polarizacijom (PP) i testovima elektrohemijske frekventne modulacije (EFM). Efikasnost zaštite (% IE) poboljšana je povećanjem doze isteklog leka nizatidina i smanjuje se s povećanjem temperature. Efikasnost zaštite (% IE) dostiže maksimalnu vrednost  95% pri većoj dozi istrošenog leka nizatidina na 25⁰C. Podaci PP pokazali su da se lek nizatidin ponaša kao lek mešovite vrste. Zaštita od korozije α -mesinga od strane leka nizatidina može da se uklapa u adsorpcionu sposobnost molekula leka nizatidina na reaktivna mesta α-mesingove površine. Adsorpcija leka sledi Langmuirovu izotermu adsorpcije. Ispitivana je površinska morfologija α-mesinga. Rezultati dobijeni različitim metodama se odlično slažu.

Ključne reči: Inhibicija kiseline, α-mesing, Nizatidin, EFM, EIS, AFM, FTIR.

Dalje >>>

Possibility of applying pyrophylite as filler in refractory coatings

Abstract

The paper investigates the procedures for the preparation of fillers based on pyrophyllite for obtaining refractory coatings with controlled rheological properties. Starting samples of pyrophyllite were obtained from the Parsović-B&H deposit. The influence of the micronizing ginding process on the change in the properties of the refractory filler, the change in the size and shape of filler grain, the dispersion and stability of the coating suspension was investigation. To characterize the obtained fillers XRD, SEM and optical microscopy were used. In the second phase of the research, the fillers were subjected to the process of micronizing grinding in the mill with ceramic balls. The upper limit of the size of the input material was 100% -2,00 mm. Micronizing grinding time (min): 15; 20; 25. The aim was to optimize the properties of fillers based on pyrophyllite, to define the composition of coatings and the procedures for their production. The quality of the obtained coatings was controlled in accordance with the standard for this type of refractory products.

Keywords: pyrophyllite, filler preparation, micronizing grinding, refractory coating, sedimentation stability of suspension.

More >>>

Mogućnost primene pirofilita kao punioca u vatrostalnim premazima

Izvod

U radu su istraživani postupci pripreme punioca na bazi pirofilita za dobijanje vatrostalnih premaza sa kontrolisanim reološkim svojstvima. Polazni uzorci pirofilita dobijeni su iz ležišta Parsović-BiH. Istraživan je uticaj procesa mikronizirajućeg mlevenja na promenu svojstava vatrostalnog punioca, promenu veličine i oblika zrna punioca, disperznost i stabilnost suspenzije premaza. Za karakterizaciju dobijenih punioca korišćene su metode XRD, SEM i optička mikroskopija. U drugoj fazi istraživanja punioci su podvrgnuti procesu mikronizirajućeg mlevenja u mlinu sa keramičkim kuglama. Gornja granica krupnoće ulaznog materijala bila je 100% -2,00 mm. Vremena mikronizirajućeg mlevenja (min): 15; 20;25. Cilj je bio optimizacija svojstava punioca na bazi pirofilita, definisanje sastava premaza i postupaka njihove izrade. Kvalitet dobijenih premaza kontrolisan je u skladu sa standardom za ovu vrstu vatrostalnih proizvoda.

Ključne reči: pirofilit, priprema punioca, mikronizirajuće mlevenje, vatrostalni premaz, sedimentaciona stabilnost suspenzije.

Dalje >>>

Characterization and corrosion behaviours of AISI 316 in hydrochloric environment at various concentrations

Abstract

Characterization and corrosion behaviours of austenitic stainless steel (AISI 316) types at various concentrations of hydrochloric acid solutions were investigated in relation to its pitting corrosion resistance. Both gravimetric-weight loss and potentiodynamic polarization were used for the investigations. The AISI 316 was characterized by X-ray fluorescent (XRF). The characterization of the coupon before and after the corrosion test in various concentrations was done using scanning electron microscopy (SEM). The temperature, acid concentration and time were varied in the range of 30-60°C at 10°C interval, 0.5-2M at 0.5M interval and 1 to 6 day at 1day interval, respectively. The XRF revealed some important elements in the AISI 316 such as (Cr, Ni, Mn, Si, C, S, P etc) which confirmed the materials to AISI 316. The weight loss results revealed that the corrosion rate decreased with increase in exposure time from day 1 to day 6. The corrosion rate of the AISI 316 increased with increase in temperature, severe to pits formation and growths with increase in concentration of acid from 0.5 – 2M. The corrosion rate of AISI 316 increases with increase in acid concentrations. The Tafel results also revealed that both anodic and cathodic sites were shifted with the lowest corrosion resistance occurring at 0.5M of HCl. The SEM of the coupons in the presence of acid revealed pits formation, growths and pitted AISI 316 surfaces. The results obtained from the weight loss, Tafel and characterization were also in good agreement.

Keywords: Austenitic AISI 316, Characterization, Corrosion Behavior, Pitting, Resistance, HCl solution, Tafel.

More >>>

Karakterizacija i korozijsko ponašanje AlSl 316 u hidrohlornoj okolini pri različitim koncentracijama

Izvod

Ispitivane su karakteristike i korozijsko ponašanje vrsta austenitnog nerđajućeg čelika (AISI 316) u različitim koncentracijama rastvora hlorovodonične kiseline u odnosu na njegovu korozijsku otpornost. Za istraživanje su korišćeni gravimetrijski gubitak težine i potenciodinamička polarizacija. AISI 316 je okarakterisan pomoću rendgenski fluorescentnog analizatora (KSRF). Karakterizacija uzoraka pre i posle korozijskog testa u različitim koncentracijama izvršena je pomoću skenirajuće elektronske mikroskopije (SEM). Temperatura, koncentracija kiseline i vreme varirali su u rasponu od 30-60°C u intervalu od 10°C, 0,5-2M na intervalu 0,5M i 1 do 6 dana u intervalu od jednog dana, respektivno. Pomoću KSRF otkriveni su neki važni elementi u AISI 316, kao što su (Cr, Ni, Mn, Si, C, S, P itd) koji su potvrdili tačnost materijala AISI 316. Rezultati gubitka težine otkrili su da se stopa korozije smanjivala s povećanjem vremena izlaganja od jedan do šestog dana. Brzina korozije AISI 316 povećavala se sa porastom temperature, teškim za formiranje rupa, i rasla je sa povećanjem koncentracije kiseline od 0,5 – 2M. Brzina korozije AISI 316 raste sa povećanjem koncentracije kiseline. Rezultati Tafelih krivi, takođe, su otkrili da su i anodna i katodna mesta pomerena sa najmanjom otpornošću na koroziju koja se pojavljuje pri 0,5M HCl. SEM uzorka u prisustvu kiseline otkrio je formiranje jama i narasle površine AISI 316. Rezultati dobijeni merenjem gubitka težine, Tafel-om i karakterizacijom su se takođe dobro slagali.

Ključne reči: Austenitni AISI 316, karakterizacija, ponašanje korozije, pitting, otpornost, rastvor HCl, Tafel.

Dalje >>>

Circular economy in food industry

Abstract

The concept of the circular economy goes beyond the outdated idea of the linear economy, which involves the uncontrolled exploitation of natural resources, and the material flows from the factory through the user to the landfill. In the circular economy, the circle product – waste – product is closed. It is expected from the industry to function as a natural eco-system, and waste from one industry becomes a raw material to another industry, i.e. to stimulate circulation, from which the term circular originates. The circular economy is a general term that encompasses all activities that reduce, reuse, and recycle materials in the processes of production, distribution, and consumption. Taking into account the projections for population growth on Earth, the food industry is expected to increase production, which inevitably carries an increase in the amount of generated waste. Organic components of vegetable waste are of interest for further use because they contain large quantities of highly valuable molecules. This paper aimed to show that waste from the food industry is not waste but a raw material that can be incorporated into other processes, which are the basic principles of circular economy – regeneration and circulation. The wine industry, as a major industry for the grape as raw material, creates large quantities of such waste. In the literature review are provided various innovative solutions that show what to do next with wine by-products, especially grape hush. Besides using in the industry of strong drinks, through composting or as a forage supplement, new solutions are presented. They are: the hush as a significant bioenergy source; the use of the most important substances from the hush, such as polyphenolic compounds, dietary fiber, tartaric acid, oils; the hush as a raw material for the production of biofuels, enzymes, biosurfactants, etc.

Keywords: Circular economy; food industry; wine industry; pomace.

More >>>

Cirkularna ekonomija u prehrambenoj industriji

Izvod

Koncept cirkularne ekonomije prevazilazi zastareli koncept linearne ekonomije, koji podrazumeva nekontrolisanu eksploataciju prirodnih resursa i protok materijala od fabrike preko korisnika do deponije. U cirkularnoj ekonomiji dolazi do zatvaranja kruga: proizvod – otpad – proizvod. Od industrije se očekuje da funkcioniše kao prirodni eko-sistem i da otpad iz jedne industrije postaje sirovina u drugoj tj. da podražava kruženje, odakle potiče naziv cirkularna. Generalno, cirkularna ekonomija je opšti pojam koji obuhvata sve aktivnosti koje smanjuju, ponovo koriste i recikliraju materijale u procesima proizvodnje, distribucije i potrošnje. Uzimajući u obzir predviđanja o rastu populacije na Zemlji, od industrije hrane se očekuje porast proizvodnje, koji neminovno sa sobom nosi i povećanje količine generisanog otpada. Organske komponente otpada biljnog porekla interesantne su za dalje iskorišćenje, jer sadrže velike količine visoko vrednih molekula. Cilj rada bio je da se pokaže kako otpad iz prehrambene industrije nije otpad već sirovina koja se može uključiti u druge procese, osnovni principi cirkularne ekonomije – regenerativnost i kruženje. Vinska industrija, kao glavna industrija kada se radi o grožđu kao sirovini, stvara velike količine ovakvog otpada. U ovom pregledu literature data su razna inovativna rešenja koja pokazuju šta dalje raditi sa nus-proizvodima dobijanja vina, pre svega komine grožđa. Osim iskorišćenja u industriji jakih pića, putem kompostiranja ili kao dodataka stočnoj hrani, prikazana su nova rešenja – komina kao značajan bioenergetski izvor, iskorišćenje najvažnijih supstanci iz komine, kao što su polifenolna jedinjenja, dijetetska vlakna, vinska kiselina, ulja, zatim osvrt na kominu kao sirovinu za dobijanje biogoriva, enzima, biosurfaktanata, itd.

Ključne reči: cirkularna ekonomija, prehrambena industrija, vinska industrija, komina.

Dalje >>>

Corrosion resistance of orthodontic wire made of SS 316L alloy in artificial saliva in the presence of amlodipine tablet by electrochemical studies

Abstract

The corrosion resistance of SS 316L alloy in artificial saliva, in the absence and presence of Amlodiphine-2.5 mg has been evaluated by polarization study and AC impedance spectra. Polarisation study reveals that in the presence of Amlodipine-2.5 mg, LPR value increases and corrosion current decreases. In presence of Amlodipine-2.5 mg mg, the corrosion resistance of SS 316L alloy in artificial saliva increases. AC impedance study reveals that in the presence of Amlodipine-2.5 mg, R_t value increases and C_dl decreases. In the presence of Amlodipine-2.5 mg the corrosion resistance of SS 316L alloy in AS increases. From the present study it is concluded that people clipped with orthodontic wire made of SS 316L alloy need not hesitate to take Amlodipine-2.5 mg  orally.

Keywords: SS 316L alloy, Amlodipine-2.5 mg, electrochemical studies, artificial saliva

More >>>

Elektrohemijska ispitivanja otpornosti na koroziju ortodontske žice izrađene od legure SS 316L u veštačkoj slini u prisustvu amlodipinske tablete

Izvod

Otpornost na koroziju legure SS 316L u veštačkoj slini, u odsustvu i prisustvu Amlodifina-2,5 mg, procenjena je polarizacijskim istraživanjem i spektrima AC impedance. Polarizaciona studija otkriva da se u prisustvu Amlodipina-2,5mg povećava LPR vrednost i smanjuje se struja korozije. U prisustvu Amlodipina-2,5mg povećava se korozijska otpornost legure SS 316L u veštačkoj slini. Ispitivanje AC impedance pokazuje se da u prisustvu Amlodipina-2,5mg Rt vrednost raste i Cdl opada. U prisustvu Amlodipina-2,5mg povećava se korozijska otpornost legure SS 316L u AS. Iz ove studije je zaključeno da ljudi koji su vezani za ortodontsku žicu izrađenu od legura SS 316L ne moraju se ustručavati da uzimaju Amlodipin-2,5mg oralno.

Ključne reči: SS 316L legura, Amlodipin-2,5mg, elektrohemijska ispitivanja, veštačka pljuvačka

Dalje >>>