Synthesis, optical and magnetic properties studies of multiferroic BiFeO3

Nanosized bismuth ferrite powder has a potential application in the production of lead free piezoelectric materials for actuators as well as magnetoelectric sensors. The simple, low-costing and energy-saving hydrothermal method has advantages over the conventional methods. BiFeO3 powders were made using Bi(NO3)35H2O and Fe(NO3)3 9H2O as starting material and 8 M KOH as mineralizer. The particle size and morphology were analyzed using scanning electron microscopy (SEM). 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. IR and Raman spectroscopy have been performed on the synthesized bismuth ferrite (BFO) powders in order to confirm the formation of pure and well-crystallized BFO nanocrystallites. 57Fe Mössbauer spectroscopy was performed in order to provide information on Fe cation arrangement in the BiFeO3 phase. The magnetic and optical properties of properties of BFO samples were characterized by SQUID magnetometry, and ultraviolet–visible spectroscopy. Temperature dependence of magnetization shows antiferromagnetic-paramagnetic phase transition at TN = 220 K, while below this temperature weak ferromagnetic ordering is detected

Mikromorfološke karakteristike ahenije populacija divljih, jednogodišnjih vrsta suncokreta

The aim of this research is to characterize wild annual sunflowers on the basis of achene micro-morphology. Plant material was grown up on an experimental field of the Institute of Field and Vegetable Crops in Novi Sad during 2015. Achene samples were hand-collected at the time of physiological maturity. Morphological measurements of achenes were performed using stereoscopic microscope Leica MZ16 with Leica DFC 320 Camera. The micro-morphological diversity of achenes was assessed using scanning electron microscopy (SEM). Obtained results indicated the presence of some quantitative and qualitative differences in achene characteristics among analyzed species, such as in their size, color, carpopodium and stylopodium shape, and distribution of trichomes on the achene surface. The carpopodium of examined species was asymmetrical at the maturity. Differences in the cuticle and wax ornamentation in different parts of the achenes, on the anticlinal walls of epidermal cells, were identified. The SEM analysis revealed the presence of non-glandular, multicellular bi-seriate trichomes (twin hairs) on the achene surface. This trichome type consisted of two elongated, parallel cells of different length. Considering the distribution of trichomes among the apical, median and basal regions of the fruit, most of the species demonstrated greater trichome density in the apical part.Cilj istraživanja u ovom radu je karakterizacija jednogodišnjih vrsta suncokreta na osnovu mikromorfoloških parametara ahenije. Biljni materijal uzgajan je na eksperimentalnom polju Instituta za ratarstvo i povrtarstvo u Novom Sadu. Uzorci ahenija sakupljani su ručno tokom 2015. godine, u vreme fiziološke zrelosti. Morfološka merenja izvršena su primenom stereoskopskog mikroskopa Leica MZ16 sa Leica DFC 320 kamerom. Mikromorfološke karakteristike analizirane su pomoću skening elektronskog mikroskopa (SEM). Dobijeni rezultati ukazuju na prisustvo kvalitativnih i kvantitaivnih razlika između analiziranih vrsta, u parametrima kao što su veličina i boja ahenije, karakteristike karpopodijuma i stilopodijuma, kao i distribucija trihoma. Pronađena je razlika u ornamentici kutikule i voska antiklinih zidova epidermalnih ćelija na različitim delovima ahenije. SEM analiza ukazala je na prisustvo nežlezdanih, višećelijskih, biserijatnih trihoma (twin hairs). Navedeni tip trihoma sastoji se od dve izdužene, paralelne ćelije različite dužine. Imajući u vidu različitu raspodelu trihoma na apikalnom, medijalnom i bazalnom delu, većina vrsta se karakteriše najvećom gustinom trihoma u apikalnom delu ahenije

The Process of Making Flooring Elements for Interior and Exterior Paving and a Flooring Element

Postupak izrade elemenata podnih obloga za unutrašnje i spoljašnje popločavanje i element podne obloge, pripada oblasti hemije, obrade materijala i građevinarstva, u širem smislu, a odnosi se na završne radove i oblikovane keramičke proizvode karakteristične po svom sastavu i svojstvima u užem smislu. Uz pravilnu tehnološku proceduru, koju čine: mlevenje, mešanje, presovanje i sinterovanje materijala, nastaje element (5) željenih mehaničkih svojstava, koj može biti u obliku cigle ili ploče različitih geometrijskih oblika u osnovi. Za izradu elemenata (5) koristi se mleveni bazaltni prah (2.2) u koji se kao vezivno sredstvo dodaje paraplast, čijim mešanjem se dobije smeša (S). Radi poboljšanja mehaničkih svojstava elemenata (5), u smešu (S) se dodaju čelična vlakna (2.1) kako bi se formirala mešavina (M). Element (5) se sastoji od jezgra (J), koje je izrađeno od mešavine smeše (S) i čeličnih vlakana (2.1) i omotača (4) koji je izrađen od smeše (S) koju čini bazaltni prah (2.2) i paraplast. Element (5) se potom može brusiti i polirati u cilju dobijanja željenih tolerancija i kvaliteta površine za finalnu industrijsku primenu.Registarski broj: 63186Broj i datum rešenja o priznanju prava: 2022/4928, 17.05.2022.Podaci o nosiocu prava: INSTITUT ZA NUKLEARNE NAUKE „VINČA“ – INSTITUT OD NACIONALNOG ZNAČAJA ZA REPUBLIKU SRBIJU, UNIVERZITETA U BEOGRADU (CENTAR ZA SINTEZU, PROCESIRANJE I KARAKTERIZACIJU MATERIJALA ZA PRIMENU U EKSTREMNIM USLOVIMA-CEXTREME LAB), Mike Petrovića Alasa 12-14, 11351 Beograd-Vinča, RSPriznati datum podnošenja prijave: 07.05.202

Synthesis of silver doped hydroxyapatite nanospheres using Ouzo effect

Nanoemulsion technique, based on Ouzo effect, was applied for synthesis of the pure and silver doped (2.5 and 5 mol%) calcium hydroxyapatite (HAp). After calcination at 500 degrees C fully crystallized powders were obtained. X-ray powder diffraction analysis accompanied with Rietveld refinement revealed that the synthesized powders were single-phase hydroxyapatite. Raman spectroscopy also confirmed that the synthesized powders were single-phase. The obtained HAp particles were spherical in shape and their sizes were in the nanometer range which was revealed by field emission scanning electron microscopy analysis (FESEM). The successful synthesis of the single-phase Ag doped HAp showed that nanoemulsion method is a simple technique for obtaining pure and doped hydroxyapatite nanospheres

Oxidation and erosion behaviour of SiC-HfC multilayered composite

The fabrication of SiC-HfC ceramic composite via self-propagating high-temperature synthesis and simultaneous consolidation was investigated. Dense composite consisting of alternating layers of SiC and HfC was obtained by spark plasma sintering of stack of SiC cloths covered by electrophoretically deposited HfO2. The deposited HfO2 was converted into HfC during sintering. The obtained ceramics was characterized in terms of microstructure, cavitation resistance and oxidation resistance. It was shown that spark plasma sintering is effective way to preserve fibre-like mikrostructure of SiC. The obtained material showed good erosion resistance. The surface layer of HfC transformed to HfO2 during oxidation of samples and protected SiC from further oxidation

Luminescence Properties Of Eu3+ Doped Mayenite Under High Pressure

Europium doped mayenite (C12A7) powders of different concentrations (0.5, 1.0, 1.5, and 2.0 at.%) have been synthesized by a modified glycine/nitrate procedure - MGNP). Obtained samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE- SEM), and steady-state photoluminescence spectroscopy. The effect of doping concentration on photoluminescence properties of Eu3+ doped mayenite was studied and discussed. With the increasing of Eu3+ doping concentration, the red-emitting intensity exhibited behavior that increased firstly and then decreased. The optimal Eu3+ ion concentration is found to be 1.5%. High-pressure luminescence was measured in a Betsa high-pressure membrane diamond anvil cell up to 23 GPa

Comprehensive Characterization of Multiferroic BiFeO3 Powder Fabricated by the Hydrothermal Procedure

Bismuth ferrite (BiFeO3) has recently drawn attention due to its outstanding multifunctional properties, as well as for being a lead-free ceramic material. In the current study, BiFeO3 nanoparticles were synthesized by strictly controlled hydrothermal process. High geometric molded particles of a small size and with high degree of purity (99.74 %) were obtained. We used nitrates of bismuth and iron as well as 8M potassium hydroxide as a basis for synthesis. The results of the X-ray diffraction study of the obtained polycrystalline material show single-phase bismuth ferrite that crystallizes with a rhombohedral lattice. Using the Rietveld method it has been determined that the particles of the synthesized powder are in a nanometric range with a particle size of about 30 nm. It was found that all reflec-tions of the obtained bismuth ferrite belong to the rhombohedral α-BiFeO3 phase which crystallizes in the space group R3c (No. 161). In addition, electronic and magnetic properties of BiFeO3 were investigated using combination of experimental and theoretical methods. HRTEM analysis confirmed existence of twin stacking faults, which are responsible for enhanced magnetic properties. EPR measurements suggested existence of electrons trapped by vacancies or defects. It has been pro-posed that Fe3+−OV defect complex could be created at elevated temperatures fol-lowed by formation of trivalent Fe ions, which intensely provide local 3d moments. The magnetic behavior of the synthesized material was studied by means of SQUID device and using a vibrating sample magnetometer (VSM). The temperature dependence of the magnetization shows the antiferomagnetic-paramagnetic phase transition at the temperature of TN = 220K, while below this temperature weak ferro-magnetic behavior has been detected. Theoretical studies were performed using a full potential linearized augmented plane-waves plus local orbital (FP(L)APW+lo) method, based on the density functional theory (DFT). In addition, a structure prediction has been performed and 11 additional BiFeO3 modifications have been pro-posed. In the next stage, an ab initio optimization of predicted structures has been performed and the structure of the γ-phase has been elucidated

Influence of Mg doping on structural, optical and photocatalytic performances of ceria nanopowders

Nanosized Mg-doped ceria powders were obtained by self-propagating room temperature reaction without using surfactants or templates. X-ray diffraction analysis and field emission scanning microscopy results showed that the doped samples are solid solutions with fluorite-type structure and spherical morphology. Raman spectra revealed an increase in the amount of oxygen vacancies with the increase of Mg concentration. This increasing results in a narrowing of the bandgap of CeO2. The photocatalytic performances of the Mg-doped ceria solid solutions were evaluated by decomposing an organic dye, crystal violet under UV irradiation. The Mg-doped ceria solid solutions exhibit significantly better photocatalytic activity than the pure CeO2 and commercial TiO2. The higher first rate constant of the Mg-doped samples demonstrated that they are much more efficient than TiO2 and CeO2 under UV light. Mg2+ dopant ions and oxygen vacancies play a significant role in the enhancement of photocatalytic performances of the Mg-doped ceria

Crystalline WO3 nanoparticles for No2 sensing

This study shows excellent NO2-sensing properties of tungsten oxide nanoparticles, prepared using a facile procedure which includes dissolution of metallic tungsten in hydrogen peroxide with subsequent low-temperature (400 °C) heating. We also conducted a thorough literature survey on sensor properties of tungsten oxide prepared by various means and found that the sensor response towards NO2 registered in this work achieved the highest level. The most intriguing feature of the material obtained was a highly reproducible sensor signal at room temperature which was more than 100 times higher than any reported previously for WO3. The probable reason for such high sensor response was the presence of two WO3 polymorphs (-WO3 and h-WO3) in the material synthesized using a peroxide-assisted route. In order to further investigate synthesizedWO3 materials, sophisticated experimental (XRD, SEM, TEM, BET) and theoretical (B3LYP, HSE) methods have been used, as well as resistance and sensor response measurements at various temperatures