Synthesis and characterization of CeO2-Bi2O3 solid solution

Nanoprahovi kristalnih faza iz serije čvrstih rastvora u pseudo-binarnom sistemuCeO2-Bi2O3 sintetisani su primenom jednostavne i ekonomične samopropagirajućemetode na sobnoj temperaturi korišćenjem nitrata metala i natrijum-hidroksida kaopolaznih supstanci. Osim krajnjih članova niza, CeO2 i niskotemperaturne polimorfnemodifikacije α-Bi2O3, sintetisani su i čvrsti rastvori nominalnog sastava Ce1-xBixO2-δ,gde je x = 0,1; 0,2; 0,3; 0,4; 0,5; 0,6; 0,7; 0,8; 0,9. Rezultati proučavanja metodomrendgenske difraktometrije na polikristalnom materijalu i ramanske spektroskopskeanalize pokazali su da su sintetisani prahovi sa nižim sadržajem bizmuta (x = 0,1 – 0,5)monofazna jedinjenja koja kristališu teseralno sa fluoritskim tipom strukture, kakvuimaju CeO2 i visokotemperaturna polimorfna modifikacija, δ-Bi2O3. Utvrđeno je dagranica rastvorljivosti jona Bi3+ u strukturi CeO2 iznosi 50 at.% Bi i da sa povećavanjemsadržaja Bi iznad 50 at.% dolazi do izdvajanja sekundarne faze, α-Bi2O3. Veličinekristalita za sva sintetisana jedinjenja su nanodimenzione sa prosečnom veličinommanjom od 5 nm, izuzev u slučaju α-Bi2O3, čija veličina kristalita iznosi 541 nm.Iz Ritveldove analize difrakcionih podataka dobijenih na polikristalnimuzorcima koji sadrže do 50 at.% Bi, proizilazi da se sa porastom koncentracije Bi iugradnjom većeg jona Bi3+ na mesto manjeg Ce4+, povećavaju parametri a jediničnihćelija dok rezultati analize difrakcionih profila pokazuju porast mikrostrukturnihnaprezanja. Hemijski sastav sintetisanih čvrstih rastvora, koji je određen pomoćuskenirajuće elektronske mikroskopije u kombinaciji sa EDS analizom, približno jejednak željenom, tj. nominalnom sastavu. Sintetisani prahovi pokazuju strukturuneuniformno raspoređenih rastresitih aglomerata sa srednjom veličinom čestica od 0,1do 0,4 μm.Optička svojstva proučavana su metodom spektroskopske elipsometrije, pričemu je utvrđeno da dopiranje niževalentnim jonima Bi3+ dovodi do pomakaenergijskog procepa ka nižim energijama, tj. apsorpciona granicaCe1-xBixO2-δ pomera se ka vidljivom delu spektra, u odnosu na nedopiran CeO2, kodkojeg se apsorpciona granica nalazi u UV oblasti...A series of nanocrystalline powders of solid solutions in pseudo-binaryCeO2-Bi2O3 system has been prepared from metal nitrates and sodium hydroxide usingthe simple and cost effective self-propagating room temperature reaction. Besides theend-members of the sequence, CeO2 and low-temperature polymorphic modification,α-Bi2O3, solid solutions with nominal composition Ce1-xBixO2-δ, x = 0.1, 0.2, 0.3, 0.4,0.5, 0.6, 0.7, 0.8, 0.9, were also synthesized. The results of the study by X-ray powderdiffraction and Raman spectroscopic analyses showed that the synthesized powders withlower bismuth contents (x = 0.1 – 0.5) are monophased samples which have the bodycenteredcubic fluorite-type structure like CeO2 and high-temperature polymorphicmodification, δ-Bi2O3. The experimentally determined solubility limit of Bi3+ in thecrystal structure of CeO2 is 50 at.% of Bi3+ ions. The increase of Bi quantity above50 at.% causes the formation of the α-Bi2O3 as a secondary phase. Crystallite size of allsynthesized powders is in the nanometric range with an average less than 5 nm in size,except in the case of α-Bi2O3 where the crystallite size is 541 nm.The Rietveld and diffraction profile analysis of samples containing up to 50 at.%Bi showed that the unit cell parameter a and microstrains increase with the increasing ofbismuth amount and the entrance of the larger Bi3+ ion at the Ce4+ position. Thechemical composition of the synthesized solid solutions, which was determined byscanning electron microscopy coupled with EDS analysis, is very close to the desirednominal one. The synthesized powders have the structure of non-uniform spread of looseagglomerates with average particle sizes ranging from 0.1 to 0.4 μm.The optical properties were studied using spectroscopic ellipsometry. It wasshown that the incorporation of Bi3+ ions of lower oxidation state than Ce4+ in CeO2leads to a shift of the energy gap to lower energies. This is associated with the shift ofthe absorption limit of Ce1-xBixO2-δ solid solutions toward the visible spectrumcompared to the undoped CeO2 in which the absorption limit is in the UV range..

Biohemijski i antropometrijski monitoring rasta prevremeno rođene dece

Enriched human milk may stimulate gain weight in preterm infants during neonatal period. Aim is biochemical assessment of preterm infants, feed by mother's milk fortificated with special domestic formula preImpamil during the first month of life. 80 preterm infants (45 male and 35 female), up to 36 weeks of gestation. BW less than 2500 g, which started enteral intake in the first three day of life. Total volume intake was in range from 70 ml/kg first day, to 170-200 ml/kg, after 10th day of life. Mother's milk fortification was prepared as 5% mixture solution of preImpamil. The dynamics of biochemical analyses started on the first day of study and was repeated once weekly. We analyzed levels of: total protein, albumin, prealbumin, transferin, urea, Ca ionised, P and alkaline phosphatase using standard biochemical methods. Statistical analyses completed by ANOVA test, one factorial analyses of variance. During monitoring total protein level increased in the second week of life (p lt 0,03), as well as albumin (p lt 0,03). Prealbumin level increased, as well as transferin (p-NS). Initial level of ionised fraction of Ca was significantly lower (p lt 0,03) at the beginning of the study, compared to the rest. Serum level of P increased, as well as level of alkaline phosphatase at the end of first and second week (p lt 0,01). Conclusion is that biochemical parameters as level of protein and albumin are important at the assessment growth in preterm infants on special feeding regimes.Obogaćeno humano mleko može da stimuliše napredovanje u telesnoj masi prevremeno rođene dece za vreme neonatalnog perioda. U radu su praćeni i procenjivani biohemijski parametri iz seruma ovih beba hranjenih majčinim mlekom obogaćenim specijalnom domaćom formulom preImpamil, za vreme prvog meseca života. Kod 80 prevremeno rođenih beba (45 dečaka i 35 devojčica) ispod 36 gestacionih nedelja, TM ispod 2500 g je počet enteralni unos u prva tri dana života. Ukupni volumni unos je bio u rasponu od 70 ml/kg prvog dana, do 170-200 ml/kg posle 10. dana života. Majčino mleko je pripremano kao mešavina sa 5% preImpamil-a. Biohemijski parametri su određivani 1. dana studije i ponavljani jednom nedeljno. Određivani su: totalni proteini, albumini, prealbumin, transferin, ureja, jonizovani kalcijum, fosfor i alkalna fosfataza korišćenjem standardnih biohemijskih metoda. Od statističkih metoda primenili smo ANOVA test jednofaktorske analize varijanse. U praćenom periodu do 4. nedelje nivo proteina i albumina pokazuje najveći skok u 2. nedeljni života (p lt 0,03). Nivoi prealbumina i transferina su viši (p- NS). Inicijalni nivo jonizovanog kalcijuma je signifikantno niži (p lt 0,03) u odnosu na kasniji period. Nivoi serumskog fosfora kao i alkalne fosfataze su značajno viši na kraju prve i druge nedelje (p lt 0,01). Dobijeni rezultati ukazuju da su praćeni biohemijski parametri, a naročito proteini i albumini važni u procesu napredovanja prevremeno rođene dece na specijalnim režimima ishrane što dokazuje i paralelno praćenje antropometrijskih parametara

High-density ceramics obtained by andesite basalt sintering

In the present study, andesite basalt originated from the deposit site “Donje Jarinje”, Serbia, was examined as a potential raw material for high-density ceramics production. The production of high-density ceramics included dry milling, homogenization, cold isostatic pressing and sintering in the air. To determine the optimal processing parameters the sintering was conducted at 1040, 1050, 1060, 1070 and 1080°C, and afterwards the sintering duration was varied from 30 to 240min at the optimal sintering temperature of 1060°C. Characterization of the starting and sintered materials included the estimation of particle size distribution, density, hardness and fracture toughness complemented with X-ray diffraction, optical light microscopy, scanning electron microscopy and energy dispersive spectroscopy analysis. Phase transformations did not occur during processing in the investigated temperature range from 1040 to 1080°C. The obtained research results showed that 99.5% of relative density and the highest hardness and fracture toughness values of 6.7GPa and 2.2MPa•m1/2, respectively, were achieved for the andesite basalt sintered at 1060°C for 60min in the air. The results of the present study confirmed that the sintered andesite basalt can be used as a high-density ceramic material for various industrial applications

Combined magnetic and structural characterization of hidrothermal bismuth ferrite (BiFeO3) nanoparticles

Bismuth ferrite (BiFeO3) was synthesized by hydrothermal method. The crystal and magnetic structures of BiFeO3 have been studied by means of X-ray diffraction and neutron powder diffraction at ambient temperature. Microstructure was analysed by scanning electron microscopy. Quantitative phase analysis by the Rietveld method was conducted and crystallite sizes of 27 nm were determined from the XRD line broadening. The magnetic structure of BiFeO3 is described by the G-type antiferromagnetic order with magnetic peak located at 4.6 Å and a noticeable magnetic contribution to a reflection located at 2.4 Å in the diffraction pattern. The values of the ordered magnetic moment of Fe ions μFe=3.8(1) μB, obtained at ambient conditions, are consistent with those determined earlier. The magnetic moments in the crystal plane z = const are arranged in parallel, changing the direction from [100] to [ 110 ] when moving from one to the other z = const plane. © 2018 Authors. Published by the International Institute for the Science of Sintering

Synthesis and characterization of BiFeO3 nanopowder

Well-crystallized single-crystal BiFeO3 (BFO) nanopowder has been successfully synthesized by the hydrothermal and solid state synthesis methods. We analyzed the particles size using granulometric analysis and scanning electron microscopy (SEM). The phase composition of the sintered samples was determined by x-ray diffraction (XRD) analysis. It revealed that synthesized material crystallize in space group R3c with cell parameters a = b = 5.5780(10) Å and c = 13,863(3) Å. The powders behavior was characterized by TG/DTA and Heating stage microscope. The magnetic behavior of synthesized material is done by means of SQUID device and using a vibrating sample magnetometer (VSM).Program and the book of abstracts available at: [https://dais.sanu.ac.rs/handle/123456789/175

Metal-Like Thermal Conductivity Possessed By Atmosphere Assisted Synthesis Of Spark Plasma Sintered Mayenite (Ca12Al14O33)

Mayenite (Ca12Al14O33) samples have been synthesized in ambient air, argon, and nitrogen atmospheres to vary the defect chemistry and to investigate its role in thermal conductivity. Highly dense sintered pellets (SEM) were obtained through spark plasma sintering and the X-ray diffractograms revealed predominantly mayenite phase with the presence of a minor amount of secondary phases. Thermal conductivity was measured for the sintered samples and it was observed that mayenite synthesized in nitrogen atmosphere exhibited a colossal value of 579 Wm-1K-1 at room temperature close to that of cubic-BN, comparable with that of metals.Supplementary material: [https://vinar.vin.bg.ac.rs/handle/123456789/9937

Metal-Like Thermal Conductivity Possessed By Atmosphere Assisted Synthesis Of Spark Plasma Sintered Mayenite (Ca12Al14O33): Supporting Information

Supporting information of the article Metal-Like Thermal Conductivity Possessed By Atmosphere Assisted Synthesis Of Spark Plasma Sintered Mayenite (Ca12Al14O33).Supplementary material for: [https://vinar.vin.bg.ac.rs/handle/123456789/9936

Hydrothermal synthesis and characterization of BiFeO3

With Bi(NO3)3 ⋅ 5H2O and Fe(NO3)3 ⋅ 9H2O as starting material and 8 M KOH as mineralizer, the pure-phase BiFeO3 (BFO) powders were synthesized by hydrothermal method at 200 °C. The microstructure, morphology and chemical analysis of the powders were analyzed using Scanning Electron Microscopy (SEM) combined with X-ray microanalysis (by Energy Dispersive Spectrometer – EDS). The phase composition of obtained samples was determined by X-ray diffraction (XRD) analysis. It revealed that synthesized material crystallize in space group R3c with cell parameters a = b = 5.5780(10) Å and c = 13,863(3) Å. The particle size and distribution was determined by small – angle X-ray scattering (SAXS). The magnetic behavior of synthesized material is done by means of SQUID devic

Mleko u ljudskoj ishrani - poređenje profila masnih kiselina

Milk and milk products are very important in human nutrition. Fatty acids (FA), which are the major component of milk lipids, have different effects on human health. The aim of this study was to determine and compare fatty acid composition of human milk, infant formula and cow's milk most often consumed in Serbian population. Samples were analyzed by gas chromatography. Our results showed that saturated FA were predominant in all types of milk, particularly in cow's milk with more than 70%. Monounsaturated oleic acid was significantly higher in human milk (36%) than in infants formula (30%) and cow's milk (26%). Although polyunsaturated FA content of cow's milk was very low (3.6%) compared with infant formula (15%) and human milk (19%), cow's milk had the most desirable n6/n3 ratio, and content of n-3 precursor α-linolenic acid. Low content of n-3 FA may be due to a relatively low consumption of marine foods in Serbian population. Long chain polyunsaturated fatty acids, which are important in infant development and maintenance of overall human health, were detected only in human milk. These results suggest that human milk is the most desirable food in infants' nutrition, but low content of n-3 FA indicates that supplementation of lactating women with n-3 FA is highly recommendable.Mleko i mlečni proizvodi su od velikog značaja za ljudsku ishranu. Masne kiseline (MK), koje su glavna komponenta lipida mleka, imaju različite efekte na zdravlje. Iz tog razloga, cilj ove studije je bio da se odredi i uporedi sastav masnih kiselina u humanom mleku, formuli za ishranu novorođenčadi i kravljem mleku, koji se uobičajeno konzumiraju u Srbiji. Uzorci su analizirani gasnom hromatografijom. Naši rezultati su ukazali da su zasićene MK najzastupljenije u svim tipovima mleka, posebno u kravljem, gde čine više od 70% ukupnih MK. Mononezasićena oleinska kiselina bila je značajno zastupljenija u humanom mleku (36%) nego u formuli (30%) i kravljem mleku (26%). Mada su polinezasićene MK u kravljem mleku zastupljene u vrlo niskom procentu (3.6%) u poređenju sa formulom (15%) i humanim mlekom (19%), kravlje mleko je imalo najpoželjniji odnos n6/n3 MK, i sadržaj n-3 prekursora α-linoleinske kiseline. Nizak sadržaj n-3 MK u humanom mleku je posledica slabe zastupljenosti morskih plodova u ishrani u Srbiji. Dugolančane polinezasićene MK, koje su od izuzetnog značaja za razvoj novorođenčadi i očuvanje zdravlja uopšte, detektovane su samo u humanom mleku. Ovi rezultati ukazuju da je humano mleko najpoželjnija hrana za novorođenčad, ali nizak sadržaj n-3 MK ukazuje da je suplementacija dojilja preparatima n-3 MK veoma preporučljiva