Space Group Fm3m Research Articles

Nanoceria and hybrid silver–ceria nanoparticles fabricated by liquid-mediated laser ablation as antimicrobial agents

In this study, cerium oxide and hybrid silver–ceria nanoparticles (NPs) have been fabricated, characterized and tested for antimicrobial efficacy for applications in the fields of biotechnology and environmental object disinfection/protection. For the preparation of CeO2 and the hybrid silver–ceria NPs, two approaches based on an eco-friendly laser ablation in solution method have been developed. Ceria NPs were synthesized by pulsed laser ablation of a ceria pressed tablet in distilled water. The size distribution of the formed NPs was bimodal, with average diameters of 2.5 and 7.6 nm. The cubic crystalline structure of the NPs (space group Fm-3 m) was confirmed by X-ray diffraction data, as well as Raman and optical absorption spectroscopy. The sequential laser ablation of silver and ceria targets in water allows for the preparation of hybrid CeO2–Ag NPs having a core–shell, decorated and Janus-like structure. Laser ablation of Ag in a CeO2 colloidal solution offers new opportunities to tune the structure and morphology, and to enhance the antimicrobial properties of the resulting NPs. The interaction of ceria and silver in a composite resulted in an improved antimicrobial activity, as tested towards Escherichia coli, Staphylococcus aureus bacteria and Candida albicans fungi, demonstrating the great potential of the hybrid silver–ceria NPs in biocatalytic and antimicrobial applications.

Green synthesis of magnesium oxide nanoparticles by chitosan polymer and assessment of their photocatalytic activity and cytotoxicity influences

The present study for the first time describes a synthesizing route for Magnesium Oxide nanoparticles (MgO-NPs) through a green chemistry method by the exertion of chitosan polymer as the stabilizer and reducing agent. The prepared MgO-NPs were described by the outcomes of TGA/DTA, FTIR, UV–Vis, XRD, and FESEM/EDX/PSA methods. FTIR spectra confirmed the presence of some essential functional groups throughout the synthesized MgO-NPs. Additionally, as the seen peak at 358 nm in the UV–Vis corroborated the formation of NPs, their pure cubic crystallinity framework with an Fm-3m space group was exhibited by the XRD pattern as well. The FESEM images were indicative of achieving a spherical morphology, while the EDX analysis approved the presence of Mg and O elements throughout our product. Also, for the first time, the cytotoxic effects of MgO-NPs were measured on Huh-7 cancer cell lines, and the IC50 value was reported as 54 μg/mL. Also, the photocatalytic activity of these NPs in the degradation process of methylene blue (MB) pigment was studied and the results showed the high ability of these NPs in pigment degradation.

Structural and photoluminescence properties of Dy-doped nanocrystalline ZrO2 for optoelectronics application

Nanocrystalline Dy3+ doped ZrO2 sample has been synthesized using sol-gel wet chemical method. The sample has been investigated for structural, thermal, and photoluminescence properties employing X-ray Diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetric analysis, Transmission Electron Microscopy, UV–visible spectroscopy, and Photo-Luminescence characterization techniques, respectively. The Rietveld refinement of XRD data reveals cubic phase (lattice constant = 5.138 Å) of doped-ZrO2 nano-crystals with space group Fm-3m. The average crystallite size and micro-strain are estimated as 46.21 nm and 0.0047, respectively, from Williamson-hall (W–H) plot analysis. FT-IR spectroscopy confirms the existence of Zr–O vibration modes of ZrO2 phase. The optical band gap of Dy-doped ZrO2 sample is found as 5.3 eV which is analogous to other reports. Photo-Luminescence result shows that the Dy doped-zirconia contains three significant characteristic peaks at 484, 583 and 678 nm under the excitation of a wavelength of 350 nm. Those peaks attribute to the electronic transition of Dy ions. The obtained CIE chromaticity coordinate of doped ZrO2 is (0.337, 0.335) representing neutral white light. The findings of this work implies application of doped zirconia in the area of optoelectronic devices.

High-pressure high-temperature preparation of CeGe3

Abstract The metastable compound CeGe3 was obtained by high-pressure high-temperature synthesis from pre-reacted Ce and Ge at 3 GPa of pressure and 1873 K, with subsequent annealing over several hours at 1173 K. The product crystallises in a 2 × 2 × 2 superstructure of the cubic Cu3Au-type structure with space group F m 3 ‾ m $Fm\overline{3}m$ and a = 8.6970(2) Å. CeGe3 decomposes at 520(10) K into CeGe2−x and elemental Ge.

Growth and scintillation properties of Cs2LiLa0·1Y0·9Cl6:Ce crystal

Cs2LiLa0·1Y0·9Cl6:Ce crystals with the dopant concentration from 0.2 to 5 mol% have been successfully grown by the vertical Bridgman method to optimize the scintillation properties for thermal neutron detection. The effects of Ce3+ concentration on the crystal structure, luminescence and scintillation properties were systematically investigated. The PXRD patterns verified the purity of phase and the cubic crystal system with the space group of Fm࠘3m. The Cs2LiLa0·1Y0·9Cl6 crystals doped with low Ce3+ concentration can achieve more than 60% transmittance. In this paper, we introduce successful efforts to grow crack-free single crystals with the size up to ⌀1″ × 5″. The large-size single crystal obtained a decent energy resolution of 5.3% at 662 keV. The figure of merit (FOM) for this scintillator under 252Cf reached 1.82, indicating a good discrimination between neutron and gamma.

Cyclo-hexane plastic phase I: single-crystal diffraction images and new structural model.

The plastic phase of cyclohexane (polymorph I) was studied by Kahn and co-workers, without achieving a satisfactory determination of the atomic coord-inates [Kahn et al. (1973). Acta Cryst. B29, 131-138]. The positions of the C atoms cannot be determined directly as a consequence of the disorder in a high-symmetry space group, an inherent feature of plastic materials. Given this situation, the building of a polyhedron describing the disorder was the main tool for determining the molecular structure in the present work. Based on the shape of reflections {111}, {200} and {113} in space group Fm 3 m, we assumed that cyclohexane is disordered through the action of rotation group 432. The polyhedral cluster of disordered molecules is then a rhombic dodecahedron centred on the nodes of an fcc Bravais lattice. The vertices of this polyhedron are the positions of C atoms for the cyclohexane molecule, which is disordered over 24 positions. With such a model, the asymmetric unit is reduced to two C atoms placed on special positions, and an acceptable fit between the observed and calculated structure factors is obtained.

The Effect of Nickel Content on Phase Transition Characteristics of Ni-rich Fe-Ni Elastocaloric Refrigeration Alloys

In order to examine the impact of Ni content on the phase transition properties of Ni-rich Fe-Ni elastocaloric refrigeration alloys, the mechanical alloying (AM) and powder metallurgy (PM) technologies were used to create the Fe-Ni alloys.The results show that similar to the Ni-lacked Fe-Ni alloys, the phase transition characteristics varied with the different of Ni content and displayed various trends. Besides, it was found that the phase change enthalpy reached 44.43J/g when the Ni content was 50% (at%), which was about 1.3 times of Ni-lacked Fe14.6Ni (at%) alloy. In addition, different from the BCC structure with crystal space group of IM-3M (225) of Ni-lacked Fe-Ni alloy, Ni-rich Fe-Ni elastocaloric refrigeration alloys presented the FCC structure with crystal space group of FM-3M (225). This study provides an experimental reference for the preparation and application of Ni-rich Fe-Ni elastocaloric refrigeration content.

Hydrometallurgy two stage process for preparation of (Nd, La, Ce)2O3 from end-of-life NiMH batteries

The present work aims to investigate the recovery of light rare earth elements (LREEs) oxides from end-of-life NiMH batteries using a hydrometallurgical process followed by effective precipitation. The operational leaching parameters such as phosphoric acid concentration, temperature, and the solid–liquid ratio were first optimized by Box-Behnken design. The results reveal that under optimum conditions ([H3PO4] = 2 mol/L, T = 80 °C, and S/L = 1: 10 g/mL) the leaching efficiencies of Ni, Co reach 98.1% and 99.3%. While La, Ce, and Nd elements remain in the leaching residue as (La, Ce, Nd)PO4 with yields of 98.2%, 98.6%, and 99.6% for La, Ce, and Nd, respectively. Afterward, the (La, Ce, Nd)PO4 is leached with HCl acid, then the rare earth oxalate was precipitated using oxalic acid at a pH of 1.8 and then the product was calcined at 800 °C for 2 h in order to synthesize the (Nd, La, Ce)2O3. The analysis using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) confirms the homogeneity of (Nd, La, Ce)2O3 particles that have two morphologies, i.e., flower and sticks with a particle size between 3 and 6 μm. The unit cell parameters of (Nd, La, Ce)2O3 were calculated after Rietveld refinement of the XRD patterns, in the space group of Fm-3m are a = b = c = 0.57921 nm and the volume equal to 0.194322 nm3.

Multi-functional lead-free Ba2XSbO6 (X = Al, Ga) double perovskites with direct bandgaps for photocatalytic and thermoelectric applications: A first principles study

In this paper, the structural formability, electronic, optical, and thermoelectric properties of Ba2XSbO6 (X = Al, Ga) double perovskite oxides are investigated with density functional theory (DFT). Based on our calculations, by considering dynamic stability, energetic stability, the (τ)-tolerance and the (μ)-octahedral factors, both Ba2AlSbO6 and Ba2GaSbO6 double perovskites show perfectly cubic structures with space group Fm-3 m (space group no: 225). Our calculations revealed that Ba2AlSbO6 and Ba2GaSbO6 are semiconductors with direct bandgaps of about 2.87 and 1.86 eV. As a direct bandgap semiconductor with tunable electronic and optical properties, it has been found that these materials are promising candidates for use in water splitting. Furthermore, optical properties investigation has represented remarkable optical properties as they exhibit good absorption coefficients in the visible region of the spectrum. Moreover, we investigated the effect of hydrostatic pressure in the 0–8 GPa range on the compounds' electronic properties and discovered that stress increases the bandgap of the materials while their band gaps remain direct. Finally, our study on the thermoelectric characteristics of Ba2AlSbO6 and Ba2GaSbO6 indicates that they have good Seebeck coefficients and thermoelectric power factors, making them promising thermoelectric materials. The obtained tunable moderate bandgaps, good optical absorption in the visible light region, and high power factors suggest the double perovskite materials for use in different electronic, optical and thermoelectric applications, especially in new energy production applications.

Thermochemical Investigations of Bismuth, Dysprosium, Samarium, and Niobium Oxide Compounds

Ceramic Bi1.4Dy0.6O3 and Bi3Nb0.2Sm0.8O6.2 samples were prepared by solid-phase synthesis. The compounds have cubic structures (space group Fm3m). Their standard enthalpies of formation were determined by solution calorimetry, and their lattice enthalpies were calculated. The lattice enthalpies of Bi3Nb0.2R0.8O6.2 compounds decrease in magnitude when erbium is replaced by samarium, due to the lanthanide radius increasing from erbium to samarium. The lattice enthalpy of Bi1.4Dy0.6O3 has a greater magnitude than the lattice enthalpy of Bi1.2Gd0.8O3.

Fluorine doping as a feasible method to enhancing functional properties of Ce0.8Sm0.2O1.9 electrolyte

In this work, materials with a fluorite structure of the Ce0.8Sm0.2O1.9-(3х)/2F3х series are obtained and studied for the first time. The synthesis method has been developed based on the solid-phase interaction of SmF3 with a highly dispersed precursor obtained in reactions of solution combustion synthesis (SCS) of cerium and samarium nitrates with a mixture of glycine and citric acid. The materials in the range of 0.01 = x ≤ 0.1 possess a cubic structure (Fm-3m space group), the unit cell parameter decreases according to the size factor. The Raman spectra study shows that for Ce0.8Sm0.2O1.9 the main Raman peak is described by the sum of two components with maxima at 460.5 cm−1, FWHM = 28.1 cm−1 and at 484.5 cm−1, FWHM = 18.3 cm−1. After the introduction of fluorine, the third component appears at ∼461.2 cm−1 with a much smaller FWHM equal to12.1 cm−1. Thus, the Raman spectra analysis allows the presence of fluorine in the fluorite-like materials including sintered ceramics to be identified. The conductivity maximum (3.7 mS cm−1 at 600 °C, Ea = 0.95 eV) and the maximal electrolyte domain boundary value (1.58 × 10−22 atm) is reached at x = 0.10 of fluorine content, which generally determines the prospects for the fluorine-doped material application in the SOFC technology.

Structure and opto-electronic properties of MgO nanocrystals calculated by GGA approximation

This study uses the CASTEP code and the density functional theory (DFT) to look into the structure, electrical properties, and optical properties of MgO. The generalised gradient approximation (GGA-PW91 approximation) was used to measure both the energy of the band gap and the energy of the exchange-correlation. This computation was done based on the cubic MgO crystal structure, which has a space group of Fm-3m and a 3x3x3 supercell. In structural optimization, the results that are expected for the lattice constant and the bulk modulus elastic constant are very close to known experiments and theories. The anticipated direct band gap of 4.283eV at the G point is in excellent agreement with the results of the tests. Also, the total (DOS) and partial (PDOS) densities of states have been measured, and the results of the absorption coefficient have been looked at in terms of the different energies of the phonons that hit the material.

Efficiently enhanced deep-red emission of Ba3WO6:Mn4+ oxide phosphor via the Gd3+ incorporation

At present, it is highly desirable to seek the inorganic phosphors with deep-red emission for the plant cultivation lighting. In this paper, the lanthanide Gd 3+ -incorporated Ba 3 WO 6 :Mn 4+ oxide phosphors were successfully prepared by the conventional high-temperature solid state reaction. The oxide phosphors were confirmed to crystallize into the double-perovskite structure corresponding to the cubic system with space group Fm-3m. Under the excitation with ultraviolet light 365 nm, all the phosphor samples displayed the deep-red emission band from 650 to 750 nm with the peaks around 678 and 692 nm, which was attributed to the intrinsic 2 E g → 4 A 2g transition of activator Mn 4+ . It was observed that the luminescence of Ba 3 WO 6 :Mn 4+ material was almost ignorable due to the low quantum yield (less than 2%). After the introduction of certain amount of Gd 3+ ions to substitute the octahedral Ba 2+ site, the double-perovskite structure of the phosphor was hardly changed, but the deep-red emission intensity of Mn 4+ was efficiently enhanced and the quantum yield reached 30.4% through the optimization to the Gd 3+ and Mn 4+ doping concentration. The optimal composition was Ba 2.1 Gd 0.9 WO 6 :0.3%Mn 4+ and the Commission International de L'Eclairage (CIE) color coordinate was (0.731, 0.269), which located at the deep-red spectral region. The mechanism for the enhanced deep-red luminescence after Gd 3+ incorporation was discussed. Owing to the highly suited to the phytochrome absorption wavelength, the optimized oxide phosphor with bright deep-red emission in the 650–750 nm range is a potential candidate for the plant cultivation lighting.

Synthesis, characterisation and optical studies of CdO-NiO NCs for comparative dye degradation study between two hazardous dyes Congo red and Rose Bengal

In this study, CdO-NiO nano composites (NCs), CdO NPs, NiO NPs were synthesized by the help of chemical co precipitation method and investigated by XRD, SEM, UV–vis, PL and FTIR. Face centered cubic structure having Fm3m space group were observed by the help of XRD for both metal oxides CdO and NiO, their corresponding crystallite size obtained from WH plot are 73 nm and 16 nm presents in CdO-NiO NCs. Similarly we have observed FCC cubic structure for CdO and NiO which are synthesized separately. EDX reveals the elements present with their atomic percentage. Band gap for the NCs was calculated using tauc plot which is around 2.89 eV, 2.74 eV and 4 eV for CdO-NiO NCs, CdO NPs and NiO NPs respectively confirming their semi conducting nature. The presence of bonds Cd-O and Ni-O were confirmed using FTIR. An enhanced comparative photo catalytic activity in the presence of UV light for 140 min was also done for the two hazardous dyes Congo red with 90.18 % degradation [K = 0.0155 min−1, T50 = 45 min] and Rose bengal with 83.53 % degradation [K = 0.0126 min−1, T50 = 55 min] for CdO-NiO NCs. By similar observation for separately synthesized CdO NPs and NiO NPs, the corresponding values obtained are Congo red with 88.86 % degradation [K = 0.0165 min−1, T50 = 42 min], Rose bengal with 79.71 % degradation [K = 0.0117 min−1, T50 = 59.23 min] and Congo red with 87.81 % degradation [K = 0.0164 min−1, T50 = 42.25 min], Rose bengal with 82.68 % degradation [K = 0.0131 min−1, T50 = 52.90 min] respectively.

Comparative study between degradation of dyes (MB, MO) in monotonous and binary solution employing synthesized bimetallic (Fe-CdO) NPs having antioxidant property

Herein, we compare the degradation of the binary dye mixture containing methyl orange (MO) and methylene blue (MB)in respect to them separately in presence of newly synthesized (chemical co-precipitation method) bimetallic optical material Fe-CdO NPs with greater surface area. NPs were characterized via XRD, SEM, EDX, FTIR, UV visible and PL. XRD patterns indicate that NPs have FCC structure, Fm3m space group with lattice constant value 4.6900A0. Absorption spectra were studied in the UV visible region. EDX signify the elemental composition and its percentage value. FTIR helps to understand the occurrence of functional groups and chemical bonding. After irradiation with UV light for 130 min in presence of NPs we observed 90.78 % degradation [K = 0.0161 min−1, T50 = 43.04 min] for only MB dye and 87.28 % degradation [K = 0.0135 min−1, T50 = 51.33 min] for MB in binary dye mixture. Similarly, we noticed 93.44 % degradation [K = 0.0188 min−1, T50 = 36.86 min] for only MO dye and 88.29 % degradation [K = 0.0142 min−1, T50 = 48.80 min] for MO in binary dye mixture. We have also observed that NPs exhibited effective antioxidant activity in scavenging in vitro DPPH (removal percentages of 50.41 %) assay. Based on the obtained findings, bimetallic Fe-CdO NPs could act as a promising material for drug development and to deliver low-cost, clean drinking water without toxic dyes.

Chemical Deposition of CdxPb1 – xS/CdyS Thin-Film Composite Structures

Thin films of CdxPb1 – xS (0 ≤ x ≤ 0.094) substitutional solid solutions of cubic structure B1 (space group Fm) were prepared by chemical deposition and characterized by X-ray diffraction, scanning electron microscopy, EDX elemental analysis, and Raman spectroscopy. Once the cadmium sulfate concentration in the batch reached some critical value (0.1 mol/L), the films formed involved two autonomous phases: CdxPb1 – xS substitutional solid solutions and hexagonal cadmium sulfide CdyS of structure В4 (space group P63mc). The method and its parameters as proposed are efficient for manufacturing heterostructures in the CdS–PbS system in one-pot deposition.

Воздействие слабого импульсного магнитного поля на ионную проводимость суперионного проводника Pb-=SUB=-0.67-=/SUB=-Cd-=SUB=-0.33-=/SUB=-F-=SUB=-2-=/SUB=-

A magnetoconductometric effect was found under pulsed magnetic action (B = 0.1–1 T) on a single crystal of the superionic conductor Pb0.67Cd0.33F2 (cubic symmetry, space group Fm¯3m, unit cell parameter a = 5.7575 A). The static electrical conductivity σdc was determined from impedance spectra in the frequency range (5–5)×105 Hz. In the absence of magnetic influence (B = 0) the ionic conductivity of a superionic crystal is σdc = 1.4×10–4 S/cm. When applying a magnetic field (B = (0.1−1) T) it increases, reaching σdc = 9.5 10−4 S/cm and σdc(B)/σdc(0) = 6.8 at B = 1 T. The nature of the magnetoconductometric effect in the superionic Pb0.67Cd0.33F2 is discussed in connection with the features its atomic structure.

Structural Evolution from Neutron Powder Diffraction of Nanostructured SnTe Obtained by Arc Melting

Among chalcogenide thermoelectric materials, SnTe is an excellent candidate for intermediate temperature applications, in replacement of toxic PbTe. We have prepared pure polycrystalline SnTe by arc melting, and investigated the structural evolution by temperature-dependent neutron powder diffraction (NPD) from room temperature up to 973 K. In this temperature range, the sample is cubic (space group Fm-3m) and shows considerably larger displacement parameters for Te than for Sn. The structural analysis allowed the determination of the Debye model parameters and provided information on the Sn–Te chemical bonds. SEM images show a conspicuous nanostructuration in layers below 30 nm thick, which contributes to the reduction of the thermal conductivity down to 2.5 W/m·K at 800 K. The SPS treatment seems to reduce the number of Sn vacancies, thus diminishing the carrier density and increasing the Seebeck coefficient, which reaches 60 μV K−1 at 700 K, as well as the weighted mobility, almost doubled compared with that of the as-grown sample.

Synthesis and characterization of Bi17Ba0,45V2,1-xPxO31,2 composite and their application as heterogeneous catalysts in biscoumarins derivatives synthesis

New Bi17Ba0,45V2,1-xPxO31,2 composites have been synthesized using an easy process according to a solid-state method from vanadium oxide (V2O5), barium carbonate (BaCO3), bismuth oxide (Bi2O3) and ammonium hydrogen phosphate ((NH4)2HPO4). Their characterization was carried out by spectroscopic and microscopic analyzes methods, namely diffraction RDX, FT-IR, and SEM coupled to the EDX. They crystallize in the cubic system with Fm3m space group. The cell parameters are a = 5.5465(1), 5.5445(4), 5.5430(3), and 5.5418 (3) Å which correspond respectively to fraction x of P2O5 0, 0.15, 0.3, and 0.45. Consequently, the new composites belong to δ-variety of solid-state. Besides, the valorization of the prepared composites was performed by using them as a heterogeneous catalyst in the biscoumarinderivatives synthesis. They show a high catalytic efficiency because of the excellent yields and short reaction times for biscoumarins derivatives synthesis.

HRPD and TEM Study of P/M 58Fe17Cr25Ni Austenitic Stainless Steel Synthesized by Spark Plasma Sintering

58Fe17Cr25Ni austenite stainless steel has been fabricated using metal powder through sintering with a spark plasma at temperatures of 900 and 950°C for 5 minutes. High purity Fe, Ni and Cr powders were used as materials for this steel. Before sintering, the powder was mixed in a milling equipment which was processed for 5 hours, then it is formed into a coin by pressing it under a load of 25 tons. High resolution powder neutron diffractometer was used for identifying the crystal structure in the 58Fe17Cr25Ni austenitic stainless steel. The sintering process at temperatures of 900C and 950°C generally forms microstructure having matrix of equiaxed austenite grains, with a crystal structure of face-centered cubic which included in the Fm3m space group. Some particles with high Cr content, a'-Cr, are distributed in all austenite grains. The austenite grains seen in the 58Fe17Cr25Niaustenitic stainless steel sintered at 900°C are twin grains. Dislocations, slip planes and bands are also existed in those grains. These defects are expected to decrease with increasing sintering temperatures up to 950° C. This change was followed by the appearance of air bubbles and sub-grains as the dominant sub-structures in the 58Fe17Cr25Ni austenitic stainless steel sintered at 950°C.