Study of Barium Bismuth Titanate Prepared by Mechanochemical Synthesis

Barium-bismuth titanate, BaBi4Ti4O15 (BBT), a member of Aurivillius bismuth-based layer-structure perovskites, was prepared from stoichiometric amounts of barium titanate and bismuth titanate obtained via mechanochemical synthesis. Mechanochemical synthesis was performed in air atmosphere in a planetary ball mill. The reaction mechanism of BaBi4Ti4O15 and the preparation and characteristics of BBT ceramic powders were studied using XRD, Raman spectroscopy, particle analysis and SEM. The Bi-layered perovskite structure Of BaBi4Ti4O15 ceramic forms at 1100 degrees C for 4 h without a pre-calcination step. The microstructure of BaBi4Ti4O15 exhibits plate-like grains typical for the Bi-layered structured material and spherical and polygonal grains. The Ba2+ addition leads to changes in the microstructure development, particularly in the change of the average grain size

Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy

Barium titanate, BaTiO3 ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and TiO2 was treated in a planetary ball mill in an air atmosphere for Lip to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min BaTiO3 phase was formed. In both ways BaTiO3 ceramics were sintered after 2 h on 1300 degrees C without pre-calcinations step. The heating rate was 10 degrees C min(-1). The formation of phase and crystal structure of BaTiO3 was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials

Kарактеризација наночестица кобалт ферита добијених различитим методама синтезе и поређење са Рамановим спектрима других ферита и неких кубичних оксидних спинела

ingle phase cobalt ferrite (CoFe2O4) with nanoparticles of similar sizes (15.7-19 nm) was obtained by different synthesis methods: coprecipitation, ultrasonically assisted coprecipitation, coprecipitation followed by mechanochemical treatment, microemulsion and microwave assisted hydrothermal synthesis. The obtained CoFe2O4 samples have been studied using a variety of characterization techniques: X-ray diffraction (XRD), Raman spectroscopy, far infrared (FIR) reflectivity and attenuated total reflectance (ATR) in combination with Fourier-transform infrared (FTIR) spectroscopy in mid IR spectra. Different methods of synthesis produced nanoparticles with different lattice constants, internal stresses and different cation inversion values. This is confirmed in the subtle changes in the Raman and IR spectra of different CoFe2O4 nano-powders. The Raman spectra of CoFe2O4 were compared with the spectra of other ferrites and some cubic oxide spinels in an attempt to evaluate the contribution of tetrahedral and octahedral oscillations in certain Raman modes.Монофазни кобалт ферит са наночестицама сличних величина (15,7-19 нанометара) добијен је различитим методама синтезе: копреципитацијом, ултразвучно потпомогнутом копреципитацијом, копреципитацијом праћеном механохемијском синтезом, микроемулзијом и микроталасном хидротермалном синтезом. Добијени узорци кобалт ферита су проучавани коришћењем различитих техника карактеризације: дифракцијом рендгенских зрака на праху, Раман спектроскопијом, рефлексијом у далекој инфра-црвеној области (ИЦ) и методом апсорпције при вишеструкој тоталној рефлексији у комбинацији са инфра-црвеном спектроскопијом (АТР-ИЦ) у средњој инфра црвеној области. Различитим методама синтезе добијене су наночестице са различитим константама решетке, унутрашњим напрезањима и различитим вредностима инверзије катјона. Ово је потврђено у суптилним променама у Раман и ИЦ спектрима различитих нано-прахова кобалт ферита. Раман спектри кобалт ферита упоређени су са спектрима других ферита и неких кубних оксидних спинела у покушају да се процени утицај удела тетраедарских и октаедарских осцилација у одређеним Раман модовима

Determination of the lipophilicity of 2҆'-Hydroxychalcones by RP-HPLC method [Određivanje lipofilnosti 2'-hidroksihalkona primenom RP-HPLC metode]

Lipophilicity of twelve synthesized chalcones, whose ring B is a ortho, meta or para monosubstituted with alkyl, oxyalkyl groups or halogens was determined by reverse phase liquid chromatography, using octadecyl-functionalized (RP-18) silica gel as a stationary phase and two-component mixture of methanol/water as a mobile phase. Linear dependence of log k' values of the volume fraction of methanol in the mobile phase was determined for all analyzed compounds, with high coefficient of correlation (r > 0.99). Extrapolation of the line to 0% methanol concentration resulted in the capacity factor of chromatographic system where water is the mobile phase (log k(w)). For five standard substances, chemically similar to chalcones, log kw values were determined under experimental conditions and they were correlated with logP values of those compounds available in the literature. log P-EXP values of synthesized chalcones were calculated on the basis of the created standard curve. In order to estimate the relevance of the experimentally obtained log P values for chalcones, correlation of log P-EXP values with the log P values obtained through various computational procedures was performed using linear regression analysis. Statistical parameters of dependence showed that the best matching of the results had been achieved with ChemOffice program, suggesting that this program is suitable for calculating logP values of newly-synthesized chalcones, as well as of compounds structurally similar to chalcones

THE IMPACT OF THE COVID-19 PANDEMIC ON PEDIATRIC APPENDICITIS MANAGEMENT AND OUTCOMES

The pandemic caused by the SARS-CoV-2 virus had a significant impact on providing health services the world over and is reflected in pediatric surgery also. The aim of this study was to determine the differences in the prevalence of forms of appendicitis among children during and prior to the pandemic, and to compare the demographic characteristics. A retrospective study which covered a period from September 1, 2018 until September 1, 2021 and all the patients who underwent surgery for acute appendicitis was carried out. Demographic and clinical data were collected and analysed. The study included a total of 267 patients. Prior to the pandemic a total of 160 children underwent surgical treatment, 61.9% boys and 38.1% girls, while during the pandemic a total of 107 underwent surgical treatment, mostly boys 68,2%, and to a lesser extent, girls 31.8%. The average age of the patients was 11.0±3.9 years. Even though there is a difference in the number of children who underwent surgical treatment for perforated appendicitis prior to and during the Covid-19 pandemic, 54:44 or 33.8:41.1%, the difference is not statistically significant. During the pandemic, two patients who tested positive for the SARS-CoV-2 virus received surgical treatment for a perforated appendicitis. The Covid-19 pandemic had an impact on the healthcare system worldwide. In most centers for pediatric surgery, there was an increased incidence of perforated appendicitis without significant deviations in the demographic characteristics, which correlates with the results of this stud

RAMAN SPECROSCOPY STUDY OF ANODIC FILM ON Ag43Cu37Zn20 ALLOY

The aim of the present work is characterization of electrochemically treated Ag43-Cu37-Zn20 alloy in near neutral chloride solutions by the X-ray diffraction and Raman spectroscopy. At potential of +0.25 V, a complex multilayer film is formed. XRD shows that it consists of CuCl and zinc hydroxichlorides with small amount of Cu2O, probably formed in the film pores. It can be concluded that the Raman spectroscopy is observed almost all the modes that are registered with the XRD analysis

Yttrium Orthoferrite Powder Obtained by the Mechanochemical Synthesis

Yttrium orthoferrite (YFeO3) powder was prepared by a mechanochemical synthesis from a mixture of Y2O3 and alpha-Fe2O3 powders in a planetary ball mill for 2.5 h. The obtained YFeO3 powder sample was characterized by X-ray diffraction (XRD), Raman and infrared spectroscopy. The average crystallite size calculated by the Scherrer equation was 12 nm. The Mossbauer spectroscopy at room temperature confirms the superparamagnetic character of YFeO3 orthoferrite sample

Supplementary data for the article: Dordević, T.; Kašanin-Grubin, M.; Gajica, G.; Popović, Z.; Matić, R.; Josić, L.; Milenković, M.; Lazarević, A.; Jovaněićević, B. Fruška Gora Mountainous Environments - Assessing the Impact of Geological Setting and Land Use on Soil Properties. Journal of the Serbian Chemical Society 2016, 81 (4), 459–468. https://doi.org/10.2298/JSC151014001D

Supplementary material for: [https://doi.org/10.2298/JSC151014001D]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1938

Vibrational and magnetic properties of nano-sized CoFe2O4 obtained by various synthesis techniques: a comparative study

Nanocrystalline CoFe2O4 has been synthesized by various synthesis methods. The obtained monodomain nanoparticles are similar in sizes (15.8-19 nm), but with different internal stresses, size distributions and cation inversion coefficients (0.51 - 0.90) due to different synthesis routes. The structure and cation distribution are investigated by XRD diffraction analysis, Raman and FIR spectroscopy. Measurement of magnetization, i.e. coercivity, enable the calculation of the anisotropy coefficient K1 = (3.6-5.12)·105 J cm-3, which is very high in cobalt ferrite. The anisotropy coefficient directly depends on the nanoparticle size. It has been shown that magnetization linearly depends on the cation inversion, except in the sample with the largest nanoparticles (19 nm), where the more regular crystal structure prevails and higher values of magnetization were obtained. The average magnetic moments at 300 K are: μFe = 3.6μB and μCo = 2.5μB. It is obvious that with small adjustments in the synthesis, desirable nanoparticle properties can be obtained

Formation of Self-Organized Mn3O4 Nanoinclusions in LaMnO3 Films

We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn3O4) in a pristine perovskite matrix (LaMnO3) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO3 stoichiometric target by Pulsed Laser Deposition, the most favorable mechanism to accommodate Mn2+ cations is the spontaneous segregation of self-assembled wedge-like Mn3O4 ferrimagnetic inclusions inside a LaMnO3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behavior. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn3O4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight (~9°) c-axis tilting. Furthermore, a Ruddlesden-Popper La2MnO4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn3O4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions