Zaštita Materijala 1. 2021

Study of antioxidant activity of selected monocarbohydrazone derivatives

Abstract

Many of carbohydrazone derivatives have shown a wide range of biological activities. In previous studies, these compounds have proven to be excellent anti-cancer, antitumor, antibacterial, antimicrobial and antioxidant agents. Monocarbohydrazones, as one of the carbohydrazone derivatives, have been slightly explored. Due to that reason, in this study, eight newly synthesized monocarbohydrazones were subjected to examinations by the use of three antioxidant tests. To determine the effectiveness of monocarbohydrazone as potential radical scavengers, DPPH (2,2-Diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and FRAP (Ferric Reducing Antioxidant Power) assays were used. The obtained results could open the door for further studies of these compounds as biologically active substances.

Keywords: antioxidant, ABTS, biological activity, DPPH, FRAP, monocarbohydrazones

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Proučavanje antioksidativne aktivnosti odabranih derivata monokarbohidrazona

Izvod

Mnogi derivati karbohidrazona pokazali su širok spektar bioloških aktivnosti. U prethodnim studijama ova jedinjenja su se pokazala kao odlični antikancerogeni, antitumorski, antibakterijski, antimikrobni i antioksidantni agensi. Monokarbohidrazoni, kao jedni od derivata karbohidrazona, su do sada malo istraženi. Iz tog razloga, u ovoj studiji, osam novosintetisanih monokarbohidrazona podvrgnuto je ispitivanju njihove antioksidativne aktivnosti primenom različitih testova. Da bi se utvrdila efikasnost monokarbohidrazona kao potencijalnih agenasa za uklanjanje radikala, korišćeni su DPPH, ABTS i FRAP testovi. Dobijeni rezultati predstavljaju osnovu za dalja ispitivanja ovih jedinjenja kao biološki aktivnih supstanci.

Ključne reči: antioksidant, ABTS, biološka aktivnost, DPPH, FRAP, monokarbohidrazoni

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Comparison of theoretical and experimental investigation of protonation process of some thiones in acid media

Abstract

PM3 semiempirical method was used for quantum chemical investigation in order to investigate the electronic properties and to determine the protonation centre in 1,2,4-triazoline-3-thione molecule. Confirmation of protonation center in acid media of investigated compounds was made using the values of atomic charges, as well as, proton affinity values. The results from semiempirical calculations indicated that the protonation center in the thione molecule was the sulphur atom. The behavior of thiones was investigated in mineral acid media using UV spectroscopy. The influence of the strength of the acid and its anion on the protonation process was discussed using three different mineral acids (perchloric, hydrochloric and phosphoric acid) for protonation. The protonation process in perchloric and hydrochloric acid took place in one step, while in phosphoric acid was not finished even when its concentration was to the highest degree. The dissociation constants of protonated forms (pK_BH⁺) and the solvation parameter m^* values were calculated in accordance with „excess acidity” function method (Cox and Yates) using the absorbance data from the experimental and reconstructed spectra (Characteristic Vector Analysis (CVA)). The determined pK_BH⁺ values in hydrochloric acid had more negative value than those obtained in perchloric acid media. The pK_BH⁺ values were in agreement with the literature data for this class of compounds.

Keywords: 1,2,4-triazoline-3-thiones, protonation, dissociation constants, proton affinity, UVspectrophotometry, PM3 semiempirical method

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Poređenje teorijskog i eksperimentalnog ispitivanja procesa protonacije nekih tionova u kiselim medijima

Izvod

PM3 poluempirijska metoda korišćena je za kvantno-hemijsko istraživanje kako bi se istražila elektronska svojstva i odredio centar za protonaciju u 1,2,4-triazolin-3-tionu. Potvrda centra za protonaciju u kiselom mediju ispitivanih jedinjenja izvršena je korišćenjem vrednosti atomskog naboja, kao i vrednosti protonskog afiniteta. Rezultati poluempirijskih izračunavanja pokazali su da je centar za protonaciju u molekulu tiona bio atom sumpora. Ponašanje tiona ispitivano je u mineralnom kiselinskom medijumu pomoću UV spektroskopije. Uticaj snage kiseline i priroda njenog aniona na proces protonacije diskutovana je korišćenjem tri različite mineralne kiseline za protonaciju (perhlorna, hlorovodonična i fosforna kiselina). Proces protonacije u perhlornoj i hlorovodoničnoj kiselini odvijao se u jednom koraku, dok u fosfornoj kiselini nije završen ni kada je koncentracija imala maksimalnu vrednost. Vrednosti konstante disocijacije protoniranih oblika (pKBH+) i parametar solvatacije m* izračunate su u skladu sa metodom funkcije „višak kiselosti“ (Cox and Yates) koristeći podatke apsorpcije iz eksperimentalnih i rekonstruisanih spektra (Karakteristična VektorskaAnaliza – CVA). Određene vrednosti pKBH+ u hlorovodoničnoj kiselini imale su više negativne vrednosti od onih dobijenih u medijumu perhlorne kiseline. Vrednosti pKBH+  bile su u saglasnosti sa literaturnim podacima za ovu klasu jedinjenja.

Ključne reči: 1,2,4-triazolin-3-tioni, protonacija, konstante disocijacije, afinitet protona, UVspektrofotometrija, PM3 poluempirijska metoda

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Sample analysis of organically produced honey and conventionally produced honey in western Serbia

Abstract

Conventional method of honey production is widely spread in the area of western Serbia. Despite the advantages of honey production in an organic manner, beekeepers are still hesitant to take this step, regardless of the difficulties with placement of such honey on the foreign market, so their products are mainly sold on the domestic market. Besides the undeniable nutritional value, honey produced in the conventional way with proper use of agro technical measures and implementation of the wide range of products in the treatment of bee diseases, in its composition very often contain residues of hazardous chemical compounds, pesticides, antibiotics. Research on four qualitative differences of the content of certain substances between the conventional and organic honey producers has been conducted in western Serbia. The research obtained five manufacturers, out of which two were engaged in organic manner of production, while the remaining three dealt with the conventional honey production. After examining the area and the apiaries in question, interviews with honeybee producers, the sampling of honey took place. Upon performed analysis, it was concluded that one conventionally produced sample of honey was not safe for human consumption, due to presence of pesticides.

Keywords: beekeeping, honey, organic beekeeping, residues, pesticides, amitraz

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Analiza uzoraka organski proizvedenog meda i meda proizvedenog na konvencionalni način na području Zapadne Srbije

Izvod

Na području Zapadne Srbije izuzetno je zastupljena proizvodnja meda na konvencionalni način. Uprkos prednostima koje donosi organska proizvodnja meda, pčelari se ipak, ne odlučuju na taj korak, bez obzira na teškoće sa plasmanom na inostrano tržište. Osim neospornih nutritivnih vrednosti, med proizveden na konvencionalni način, uz upotrebu agrotehničkih mera i primenu široke palete proizvoda za tretiranje bolesti pčela, u svom sastavu vrlo često sadrži i ostatke opasnih hemijskih jedinjenja, pesticida i antibiotika. Istraživanje je vršeno na području Zapadne Srbije. Obuhvaćeno je pet proizvođača meda, dva koja proizvodnju vrše na organski način i tri sa konvencionalnim načinom rada. Nakon osmatranja terena i pčelinjaka, intervjuisanja proizvođača, uzeti su uzorci meda. Po izvršenim analizama, konstantovano je da je jedan uzorak iz konvencionalne proizvodnje nebezbedan za ljudsku upotrebu, jer sadrži ostatke pesticida – amitraza.

Ključne reči: pčelarstvo, med, organsko pčelarenje, ostaci, pesticidi, amitraz

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Characterization of deposited plasma spray NiCrAlCoY₂O₃ coating layers on AlMg1 alloy substrates

Abstract

In this paper, analyzed are the effects of the plasma spray distance on the microstructure and mechanical properties of the NiCrAlCoY₂O₃ coating layers deposited at atmospheric pressure. The microstructure and mechanical properties of the coating layers are under the influence of the interaction of plasma particles (ions and electrons) with powder particles, providing the transfer of velocity and temperature of the plasma particles onto the powder particles. The effect of the interaction is directly dependent on the time the powder particles were present in the plasma which is defined by distance of the plasma gun from the substrate, depending on the granulation of the powder, the melting point and specific gravity. In order to obtain homogeneous and denser coating layers with high adhesion, in the experiment three distances from the substrate were used: 95 mm, 105 mm and 115 mm. The layers were deposited on thin sheets of AlMg1 aluminum thickness of 0.6 mm. Evaluation of mechanical properties of the layers was carried out by examining microhardness using the HV_0.1 method and the bond strength by tensile testing. The morphology of the powder particles was examined on the SEM, while the microstructure of the layers was evaluated under a light microscope in accordance with the Pratt Whitney standard.

The results of the experiment showed that the distance from the substrate substantially influenced the structure and mechanical properties of the coating layers. The best deposited layers were examined in the system with the ZrO₂24%MgO ceramic coating, which have proved to be reliable protectionfrom high temperature and abrasive rocket jet fuel.

Keywords: atmospheric plasma spray (APS), microstructure, microhardness, bond strength

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Karakterizacija deponovanih slojeva plazma sprej prevlake NiCrAlCoY₂O₃  na podlogama od legure AlMg1

Izvod

U ovome radu analiziran je uticaj plazma sprej odstojanja na mikrostrukturu i mehaničke karakteristike slojeva NiCrAlCoY₂O₃ prevlake deponovane na atmosferskom pritisku. Mikrostruktura i mehanička svojstva slojeva prevlake pod uticajem su interakcije čestica plazme (jona i elektrona) sa česticama praha, pri čemu nastaje transfer brzine i temperature čestica plazme na čestice praha. Efekat interakcije je u direktnoj zavisnosti od vremena boravka čestica praha u plazmi koji je definisan odstojanjem plazma pištolja od podloge zavisno od granulacije praha, temperature topljenja i specifične težine. U cilju dobijanja homogenih i gušćih slojeva prevlake visoke adhezije, u eksperimentu su korišćenja tri odstojanja od podloga: 95 mm, 105 mm i 115 mm. Slojevi su deponovani na tankim limovima od legure AlMg1 debljine 0,6 mm. Procena mehaničkih osobina slojeva je sprovedena ispitivanjem mikrotvrdoće metodom HV_0.1 i čvrstoće spoja ispitivanjem na zatezanje. Morfologija čestica praha je ispitana na SEM-u, dok su mikrostrukture slojeva procenjene na svetlosnom mikroskopu u skladu sa standardom Pratt-Whitney. Rezultati eksperimenta su pokazali da odstojanje podloga bitno utiče na strukturu i mehaničke karakteristike slojeva prevlaka. Najbolji deponovani slojevi su ispitani u sistemu sa keramičkom prevlakom ZrO₂24%MgO, koji su se pokazali kao pouzdana zaštuta  od visokotemperaturnog i abrazivnog raketnog mlaza.

Ključne reči: atmosferski plazma sprej (APS), mikrostruktura, mikrotvrdoća, čvrstoća spoja.

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Detailed characterization of the Ti-O based thin films obtained by cathodic arc evaporation

Abstract

Physicochemical properties of thin films on the base of titanium oxides, obtained by a cathodic arc evaporation on the surface of glass substrate are analysed in details. The analysis of these films was made by using XRD, FTIR, SEM, XPS analysis and ellipsometry. On the basis of these analyses, particularly analysis obtained by XPS, the oxidative state Ti and corresponding phases are determined through various film layers from the surface to the substrate. The depth of the various levels and their extinction coefficients and refractory indexes are estimated by ellipsometry.

Keywords: titanium oxide thin films; XRD; FTIR; SEM; XPS; ellipsometry

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Detaljna karakterizacija tankih filmova na bazi Ti-O dobijenih katodno lučnim isparavanjem

Izvod

Detaljno su analizirana fizičko-hemijska svojstva tankih filmova na bazi titan-oksida, dobijenih katodno-lučnim isparavanjem na površini staklene podloge. Analiza ovih filmova napravljena je primenom XRD, FTIR, SEM, XPS analize i elipsometrije. Na osnovu ovih analiza, posebno analiza koje su dobijene primenom XPS, određena su oksidaciona stanja Ti i identifikovane odgovarajuće faze koje se formiraju unutar različitih slojeve filma od gornje površine do podloge. Dubina različitih faznih slojeva, i njihovi ekstinkcioni koeficijenti  i indeksi prelamanja procenjeni su pomoću elipsometrije.

Ključne reči: titanium oksidni tanki filmovi; XRD; FTIR; SEM; XPS; elipsometrija

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Investigation of fractures mechanisms of railway axles

The paper gives a systematic overview of literature sources who consider impacts critical damage of mechanical, corrosive and thermal nature which may occur on railway axles during operation and which may be the causes of their fracture. The results of the research of the mechanisms that cause cracks, crack propagation and final fracture of the railway vehicle axle, such as material fatigue and the appearance of localized notches caused by paint (coating) separation, damage from ballast impact and pitting corrosion are presented. The influence of high temperatures and overheating on the axles was analyzed and an excerpt from the research published in one research report was given. Some significant suggestions for optimizing the design of the axles are highlighted which would take into account the analysis of time-varying axle stresses, stress spectrum in operation, axle tolerance to damage and the existence of residual surface stresses. The reliefs of the fracture surfaces of the axle after the railway incidents and the derailment of the rail vehicle from the rails are presented and explained.

Keywords: axle, railway vehicle, material fatigue, railway incidents, corrosion

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Istraživanje mehanizama loma železničkih osovina

Izvod

U radu je dat sistematizovan pregled literaturnih izvora koji razmatraju uticaje kritičnih oštećenja mehaničke, korozivne i termičke prirode koja se mogu pojaviti na železničkim osovinama u toku eksploatacije i koja mogu biti uzročnici njihovog loma. Predstavljeni su rezultati istraživanja mehanizama koji svojom pojavom i delovanjem uzrokuju nastajanje pukotina, širenje pukotina i konačni prelom osovine železničkog vozila, kao što su zamor materijala i pojava lokalizovanih zareza nastalih odvajanjem farbe (premaza), oštećenjima od udara balasta i piting korozijom. Analiziran je uticaj visokih temperatura i pregrevanja na osovine i dat je izvod iz istraživanja objavljen u okviru jednog istraživačkog izveštaja. Istaknuti su neki značajni predlozi za optimizaciju konstrukcije osovina koji bi uzimali u obzir analizu vremenski promenljivih naprezanja osovine, spektar naprezanja u eksploataciji, toleranciju osovine na oštećenja i postojanje zaostalih površinskih naprezanja. Prikazani su i objašnjeni reljefi prelomnih površina osovine nakon železničkih incidenata i iskliznuća šinskog vozila iz šina.

Ključne reči: osovina, železničko vozilo, zamor materijala, železnički incidenti, korozija

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