Oxide Samples Research Articles

Morphology mediated photocatalysis and room temperature ferromagnetism in cerium oxide

Present work is focused on fine-tuning of magnetic and photocatalytic properties of three samples of cerium oxide nano/micro-sized particles synthesized via different chemical routes. X-ray diffraction measurement infers the growth of single phase cubic fluorite structure of pure CeO2 with a space group of Fm3‾m. The route of synthesis significantly altered the morphology and particle size as evident from high resolution transmission electron microscopy. Raman spectra and XPS confirmed the existence of oxygen vacancies defects in CeO2 matrix. In this article, investigations of magnetic properties and photocatalytic activity of rose Bengal dye in the presence of UV light have been carried out. For SG, CO, and HB samples, room temperature ferromagnetism was observed with small magnetizations of 2.21, 16.8, and 3.58 emu/g × 10−4 respectively. The photocatalytic efficiency of CO sample was 76.3% for degradation of rose Bengal dye on UV illumination for 140 min. Thus, morphology dependent enhanced ferromagnetic and superior photocatalytic behavior of CeO2 make it a multifunctional material for its use as a photocatalyst for organic dye decomposition and in spintronics devices.

The effect of Y, Er co-doped on the sintering and electrical properties of Mo0.05 Bi1.95O3 electrolyte materials for solid oxide fuel cells

Bismuth oxide-based electrolyte materials co-doped with yttrium and erbium were synthesized by nitrate combustion method. The crystal structure was analyzed by X-ray diffraction. The data on electrical conductivity were carried out using AC impedance spectroscopy. The results suggested that all of the co-doped bismuth oxide samples obtained [Formula: see text]-phase with cubic fluorite structure. The conductivity of (YO[Formula: see text])[Formula: see text](MoO3)[Formula: see text](ErO[Formula: see text])[Formula: see text](BiO[Formula: see text])[Formula: see text] ceramic electrolyte sintered at 925[Formula: see text]C for 10 h reached 12.26 × 10[Formula: see text] S cm[Formula: see text] at 700[Formula: see text]C. It has good thermal stability and is a promising electrolyte material for SOFC.

Trace Actinide Signatures of a Bulk Neptunium Sample.

In nuclear forensic analyses, measurements of actinide elements in a sample can assist with identifying interdicted or unknown materials. While these radiochemical signatures have been extensively investigated in uranium materials, less is known about bulk neptunium samples. This paper describes the measurement of trace actinide concentrations and isotopic profiles in a 237Np oxide sample. Uranium, plutonium, americium, and curium concentrations and isotopic profiles in the sample were determined and deemed potentially useful for distinguishing different sources of 237Np. Several different potential radiochronometry systems were also investigated; discordant results indicate that the Np sample was never completely purified of other actinide elements, or that subsequent contamination of the sample occurred. Few prior studies of neptunium materials have been reported, and these data suggest that trace actinide constituents could provide unique signatures to identify material out of regulatory control.

From AuPd Nanoparticle Alloys towards Core‐Shell Motifs with Enhanced Alcohol Oxidation Activity

AbstractThe best activity of bimetallic AuPd nanoparticles for alcohol oxidation reaction is usually achieved by adjusting the Au/Pd molar ratio. Herein, alloy AuPd nanoparticles of ∼2.5–3.5 nm, ranging from Au‐rich to Pd‐rich compositions, were synthesized through a sol‐immobilization method. A calcination step under air conditions caused an increase in size up to 5.5 nm, but also driven the segregation of Pd to the surface, which generated an Au rich core with Pd on the shell. At high Pd content, the shell structure is formed by PdO. The catalytic activity of Pd‐rich samples (1 : 1, 1 : 2 and 1 : 4 Au : Pd) for benzyl alcohol oxidation increased ∼4‐fold after calcination. Upon reduction with H2, surface PdO motifs are reduced to Pd that did not dissolve back into the AuPd alloy core, maintaining the metallic Pd shell. The catalytic activity decreased. Therefore, restructuring alloyed AuPd nanoparticles into core‐shell like structures with PdO in the shell is beneficial to the catalytic activity, but reduction of PdO layer was detrimental. These results provide new insights on the optimization of AuPd catalysts, considering not only the Au/Pd molar ratio, but also the importance of PdO, which was not anticipated in the previous literature.

Graphene oxide saturable absorber for a [formula omitted] passively Q-switched single crystal fiber pulsed laser

In this work, the graphene oxide (GO) samples of different oxidation degree prepared by modified Hummers method were drop-coated on sapphire substrates as saturable absorber (SA). On this basis, this work innovatively combines GO, the excellent SA, with single crystal fiber (SCF), the outstanding laser gain medium, for the first time to achieve 1.03μm passively Q-switched pulsed laser output with the maximum average power of 2.183 W and the repetition frequency of 317.42 kHz, which is, to our knowledge, the largest average power of passively Q-switched SCF pulsed laser output reported so far.

Signal-Decay Based Approach for Visualization of Buried Defects in 3-D Printed Ceramic Components Imaged with Help of Optical Coherence Tomography.

We propose the use of Optical Coherence Tomography (OCT) as a tool for the quality control of 3-D-printed ceramics. Test samples with premeditated defects, namely single- and two-component samples of zirconia, titania, and titanium suboxides, were printed by stereolithography-based DLP (Digital Light Processing) processes. The OCT tomograms obtained on the green samples showed the capability of the method to visualize variations in the layered structure of the samples as well as the presence of cracks and inclusions at depths up to 130 µm, as validated by SEM images. The structural information was visible in cross-sectional images as well as in plan-view images. The optical signal measured from the printed zirconia oxide and titanium oxide samples showed strong attenuation with depth and could be fit with an exponential decay curve. The variations of the decay parameter correlated very well with the presence of defects and material variation. When used as an imaging quantity, the decay parameter projects the position of the defects into 2-D (X,Y) coordinates. This procedure can be used in real time, it reduces the data volume up to 1000 times, and allows for faster subsequent data analysis and transfer. Tomograms were also obtained on sintered samples. The results showed that the method can detect changes in the optical properties of the green ceramics caused by sintering. Specifically, the zirconium oxide samples became more transparent to the light used, whereas the titanium suboxide samples became entirely opaque. In addition, the optical response of the sintered zirconium oxide showed variations within the imaged volume, indicating material density variations. The results presented in this study show that OCT provides sufficient structural information on 3-D-printed ceramics and can be used as an in-line tool for quality control.

A von Hámos spectrometer for diamond anvil cell experiments at the High Energy Density Instrument of the European X-ray Free-Electron Laser.

A von Hámos spectrometer has been implemented in the vacuum interaction chamber 1 of the High Energy Density instrument at the European X-ray Free-Electron Laser facility. This setup is dedicated, but not necessarily limited, to X-ray spectroscopy measurements of samples exposed to static compression using a diamond anvil cell. Si and Ge analyser crystals with different orientations are available for this setup, covering the hard X-ray energy regime with a sub-eV energy resolution. The setup was commissioned by measuring various emission spectra of free-standing metal foils and oxide samples in the energy range between 6 and 11 keV as well as low momentum-transfer inelastic X-ray scattering from a diamond sample. Its capabilities to study samples at extreme pressures and temperatures have been demonstrated by measuring the electronic spin-state changes of (Fe0.5Mg0.5)O, contained in a diamond anvil cell and pressurized to 100 GPa, via monitoring the Fe Kβ fluorescence with a set of four Si(531) analyser crystals at close to melting temperatures. The efficiency and signal-to-noise ratio of the spectrometer enables valence-to-core emission signals to be studied and single pulse X-ray emission from samples in a diamond anvil cell to be measured, opening new perspectives for spectroscopy in extreme conditions research.

Heat capacity of microgram oxide samples by fast scanning calorimetry.

Quantitative scanning calorimetry on microgram-sized samples opens a broad, new range of opportunities for studying the thermodynamic properties of quantity-limited materials, including those produced under extreme conditions or found as rare accessory minerals in nature. We calibrated the Mettler Toledo Flash DSC 2+ calorimeter to obtain quantitative heat capacities in the range 200-350 °C, using samples weighing between 2 and 11.5 μg. Our technique is applied to a new set of oxide materials to which it has never been used before, without the need for melting, glass transitions, or phase transformations. Heat capacity data were obtained for silica in the high pressure stishovite (rutile) structure, dense post-stishovite glass, standard fused quartz, and for TiO2 rutile. These heat capacities agree within 5%-15% with the literature values reported for rutile, stishovite, and fused SiO2 glass. The heat capacity of post-stishovite glass, made by heating stishovite to 1000 °C, is a newly reported value. After accurate calibrations, measured heat capacities were then used to calculate masses for samples in the microgram range, a substantial improvement over measurement in conventional microbalances, which have uncertainties approaching 50%-100% for such small samples. Since the typical uncertainty of heat capacities measured on 10-100 mg samples in conventional differential scanning calorimetry is typically 7% (1%-5% with careful work), flash differential scanning calorimetry, using samples a factor of 1000 smaller, increases the uncertainty of heat capacity measurements by a factor of <3, opening the door for meaningful measurements on ultra-small, high-pressure samples and other quantity-limited materials.

Comparative Investigation of XPS Spectra of Oxidated Carbon Nanotubes and Graphene

X-ray photoelectron emission spectra of thermally reduced graphene oxide samples and carbon nanotubes (CNTs) with various oxidation degrees are presented in this paper. A method for the reconstruction of differential electron inelastic scattering cross sections from the energy loss spectra of photoelectrons is described and discussed. The analysis of the part of the characteristic photoelectron energy loss spectrum adjacent to the C1 peak indicated a considerable influence of the thermal reduction of graphene oxide on the electron properties of the samples obtained. On the contrary, the oxidation of CNTs by refluxing in a concentrated HNO3 solution does not change the free electron excitation spectrum.

Rational fabrication of low carbon foot-print electrode materials for lithium-ion batteries from electric arc furnace dust via integrated hydrometallurgical process

Transforming industrial waste into high-value-added products represents a new avenue in the field of material science. This paper puts forward a comprehensive example for future works which target fabricating low-carbon footprint electrodes for rechargeable batteries. Within this scope, first time in the open literature, an integrated hydrometallurgical process has been designed to fabricate metal oxide powders of different properties from electric arc furnace (EAF) dust. Leaching, cementation, distillation, chemical precipitation, and calcination are used to produce powders rich in zinc oxide (Sample 1), ferrite (Sample 2), and nanocomposite (Sample 3) from the electric arc furnace flue dust.While sample 1 (zinc oxide with 97.8% purity) may be used in optics and other engineering applications, sample 2 (rich in zinc ferrite) and sample 3 (made of nanocomposites) that are recovered from the EAF dust may be utilized as electrode active material in lithium-ion batteries: Sample 2 and Sample 3 retain 43% and 50% of their capacities after 125th cycle, respectively. To further improve the cycle performance of Sample 2, the powder rich in ferrite is mixed with nickel salt, then heat treated. The latter performs 65% capacity retention after 125th cycle. The fact that every fabricated electrode achieves 125 cycles with success demonstrates the viability of the proposed technique; thus, various procedures may be developed to further elaborate the use of various industrial wastes in electrode fabrication.

Group Extraction of the Rare-Earth Elements by Alkyl Phosphine Oxides of the Hexyl–Octyl Series

Samples of monoalkyl and mixed-alkyl phosphine oxides of the hexyl–octyl series were synthesized previously by the Grignard method. Here, the group extraction of rare-earth metals contained simultaneously in their nitrate solutions has been studied using then-synthesized alkyl phosphine oxides. Extraction isotherms for the recovery of the total of lanthanides, scandium, and thorium from nitrate solutions have been obtained. Trihexyl phosphine oxide (THPO) exhibits the highest efficiency under these conditions. Trioctyl phosphine oxide (TOPO) exhibits the best selectivity to heavy-group lanthanides, which makes it useful for the recovery of the heavy-group lanthanide fraction. In addition, scandium and thorium were extracted completely, which in turn indicates the usefulness of phosphine oxides for their extraction. The separation factors have been determined for the entire lanthanides series.

Hydrothermal-assisted synthesis and characterization of MWCNT/copper oxide nanocomposite for the photodegradation of methyl orange under direct sunlight

In this study, we report synthesis of a novel MWCNT/copper oxide hybrid nanocomposite and pristine copper oxide using hydrothermal techniques and employed them as a sunlight-driven photocatalyst for the degradation of methyl orange organic (MO) pollutant. The prepared specimens were evaluated using various characterization techniques to analyze the crystallographic, optical, and nanoscale characteristics and the results revealed that the incorporation of MWCNTs significantly altered the crystalline phase, lattice parameters, particle size, shape, and optical band gap when compared with pure copper oxide sample. Pure copper oxide, MWCNT/copper oxide nanocomposite and MWCNT exhibited band gaps of 1.43 eV, 1.90 eV, and 3.8 eV, respectively. After 6 h of exposure to sunlight, pure copper oxide and MWCNT/copper oxide hybrid nanocomposite photodegraded 85 % and 92 % of the MO dye, with pseudo-first-order kinetics and high recyclability up to 5 cycles. The proposed composite shows higher solar radiation-induced photodegradation than pure copper oxide owing to its hybrid heterostructure, making it a promising photocatalyst for wastewater treatment.

RP-HPLC hyphenated with ESI -Q-TOF –MS for the detection of potential degradants in dolutegravir

Dolutegravir is an antiviral agent, a second-generation HIV integrase strand transfer inhibitor (INSTI). A precise liquid chromatography-tandem mass spectrometry method has been developed and validated for the detection of potential degradants in Dolutegravir. The goal of this study was to detect major and minor potential degradants that can develop during the various stages of the drug molecule, start from acquiring of raw material for the synthesis, manufacturing, formulation and storage of the final product. With this objective in mind preparative scale HPLC was used to detect possible oxidative degradants in Dolutegravir. The oxidative degradation sample was isolated using Prominence preparative high performance liquid chromatograph equipped with a reverse phase C18 Inertsil ODS (300mm×19mm ×7µ) column. Mobile phase was 0.1% trifluoro acetic acid in water (A) and acetonitrile (B) (50:50). Ethyl acetate was used for the extraction of aqueous layer and the same was distilled and the collected fractions were evaporated to dryness for LCMS studies. To detect the degradation products mass spectra of the drug was established by direct infusion of degradant into mass spectrometry systems. The LC-MS spectrum of Dolutegravir was recorded by Shimadzu LCMS spectrometer in the electron spray ionization mode. The outcome was intense protonated molecular ion peak at m/z 304.27 and 249.06 in the positive ionization mode, scan range 120–560 amu and the other possible degradant structures with m/z 320.32, m/z 207.18, m/z 185.17, m/z 385.41, m/z 155.14. The information obtained from degradation behaviour of dolutegravir by stress degradation studies, under peroxide oxidation and the degradation products formed were identified by HPLC, LCMS analytical techniques are useful information regarding manufacturing, formulation and storage of the drug.

The transformation of amorphous aluminum oxide during the catalytic dehydration of aromatic alcohol

A wide application of aluminum oxides in the synthesis of heterogeneous catalysts for petrochemistry and oil refining makes it necessary to reveal factors determining the efficiency of the catalytic systems. However, the literature provides no data concerning the effect produced by the amorphous phase in aluminum oxide catalysts on characteristics of the catalytic reaction. Usually the content of amorphous phase is not categorized; however, its presence may significantly deteriorate the catalyst efficiency. X-ray diffraction analysis, low-temperature nitrogen adsorption, electron microscopy and temperature-programmed desorption of ammonia were used in this work to examine samples of the amorphous aluminum oxide obtained from two different precursors. Catalytic properties of the samples were investigated during the vaporphase dehydration of 1-phenylethanol to styrene. It was shown for the first time that the transformation of amorphous aluminum oxide in the catalytic reaction decreased the conversion of alcohol from 84 (for the fresh catalyst) to 64 % (for the regenerated sample). Crystallization of amorphous aluminum oxide by the high-temperature treatment enhanced the catalytic performance, but it did not reach the desired values due to a considerable deterioration of the textural characteristics and acidic properties of the aluminum oxide surface.

Removal of imipramine using advanced oxidation processes: Degradation products and toxicity evolution

Pharmaceuticals are frequently detected in natural and wastewater bodies, and are very important in environmental toxicology because of their stable nature. Advanced oxidation methods used to remove contaminants are of great benefit, especially removing pharmaceuticals unsuitable for biodegradation. In this study, imipramine was degraded by anodic oxidation and subcritical water oxidation, which are advanced oxidation methods. The determination of degradation products was performed by Q-TOF LC/MS analysis. The genotoxicity and cytotoxicity of the degradation samples were determined by the in vivo Allium Cepa method. Among the anodic oxidation samples, the lowest cytotoxicity was obtained after using 400 mA current, and 420 min of degradation time. No cytotoxic effect was observed in any subcritical water oxidation sample. However, when 10 mM hydrogen peroxide as an oxidant was used at 150 °C and the reaction time was 90 min, the subcritical water oxidation sample showed a genotoxic effect. The results of the study showed that it is crucial to evaluate the toxicity levels of the degradation products and which advanced oxidation methods are preferred for removing imipramine. The optimum conditions determined for both oxidation methods can be used as a preliminary step for biological oxidation methods in the degradation of imipramine.

Debugging periodate oxidation of cellulose: Why following the common protocol of quenching excess periodate with glycol is a bad idea

Periodate oxidation of cellulose to produce “dialdehyde cellulose” (DAC) has lately received increasing attention in sustainable materials development. Despite the longstanding research interest and numerous reported studies, there is still an enormous variation in the proposed preparation and work-up protocols. This apparently reduces comparability and causes reproducibility problems in DAC research. Two simple but prevalent work-up protocols, namely glycol quenching and filtration/washing, were critically examined and compared, resulting in this cautionary note. Various analytical techniques were applied to quantify residual iodine species and organic contaminations from quenching side reactions. The commonly practiced glycol addition cannot remove all oxidising iodine compounds. Both glycol and the formed formaldehyde are incorporated into DAC's polymeric structure. Quenching of excess periodate with glycol can thus clearly be discouraged. Instead, simple washing protocols are recommended which do not bear the risk of side reactions with organic contaminants. While simple washing was sufficient for mildly oxidised celluloses, higher oxidised samples were more likely to trap residual (per)iodate, as determined by thiosulfate titration. For work-up, simple washing with water is proposed while determining potential iodine contaminations after washing with a simple colorimetric test and, if needed, removal of residual periodate by washing with an aqueous sodium thiosulfate solution.

Increasing the Strain Resistance of Si/SiO2 Interfaces for Flexible Electronics.

Understanding the changes that occur in the micro-mechanical properties of semiconductor materials is of utmost importance for the design of new flexible electronic devices, especially to control the properties of newly designed materials. In this work, we present the design, fabrication, and application of a novel tensile-testing device coupled to FTIR measurements that enables in situ atomic investigations of samples under uniaxial tensile load. The device allows for mechanical studies of rectangular samples with dimensions of 30 mm × 10 mm × 0.5 mm. By recording the alternation in dipole moments, the investigation of fracture mechanisms becomes feasible. Our results show that thermally treated SiO2 on silicon wafers has a higher strain resistance and breaking force than the SiO2 native oxide. The FTIR spectra of the samples during the unloading step indicate that for the native oxide sample, the fracture happened following the propagation of cracks from the surface into the silicon wafer. On the contrary, for the thermally treated samples, the crack growth starts from the deepest region of the oxide and propagates along the interface due to the change in the interface properties and redistribution of the applied stress. Finally, density functional theory calculations of model surfaces were conducted in order to unravel the differences in optic and electronic properties of the interfaces with and without applied stress.

Fabrication & characterizations of reduced graphene oxide via low potential electrochemical exfoliation followed by thermal treatment

In the present work few layered graphene (FLG) was synthesized via low potential (DC power) electrochemical method followed by thermal treatment. During the synthesis of rGO, a 12 V of potentials has been applied in an aqueous solution of the 1.5 M of the H2SO4. In order to obtain FLG, previously oxidised graphite oxide was put through a heat treatment at a temperature of 600 °C for a period of 45 min. The obtained compound has been identified to be rGO based on the material's dark balck colour, which was produced throughout the synthesis process. The experiments reveals that the concentration of acid as well as applied voltage impact the microstructure and physical as well as morphologicalproperties of synthesized graphene. The microstructure, surface texture, surface topography, crystallinity, and thermal stability has been investigated via scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) analysis. SEM analysis indicates that the gap between the carbon layers get increased as the thermal stress inceases in periodic manner as a overall result obtained enlargement in the volume of graphene oxide sample very soon. AFM analysis indicates that the roughness height of the rGO sheet reached a maximum of 1.58 nm at its highest point.The AFM results dictate surface roughness of reduced graphene oxide decrease surprisingly under cyclic thermal stress.The XRD sharp peak detected around 2θ = 26.42°, which corresponds interlayer spacing (dhkl) of 0.326 nm.

Efficient Propylene Carbonate Synthesis from Urea and Propylene Glycol over Calcium Oxide-Magnesium Oxide Catalysts.

A series of calcium oxide-magnesium oxide (CaO-MgO) catalysts were prepared under the effects of different precipitating agents and using varied Mg/Ca ratios. The physiochemical characteristics of the prepared catalysts were analyzed using XRD, FE-SEM, BET, FTIR, and TG/DTA techniques. Quantification of basic active sites present on the surface of the CaO-MgO catalysts was carried out using the Hammett indicator method. The as-prepared mixed oxide samples were tested for propylene carbonate (PC) synthesis through the alcoholysis of urea with propylene glycol (PG). The effects of the catalyst composition, catalyst dose, reaction temperature, and contact time on the PC yield and selectivity were investigated. The maximum PC yield of 96%, with high PC selectivity of 99% and a urea conversion rate of 96%, was attained at 160 °C using CaO-MgO catalysts prepared using a Mg/Ca ratio of 1 and Na2CO3 as a precipitating agent. The best-performing catalysts also exhibited good reusability without any significant loss in PC selectivity. It is expected that the present study will provide useful information on the suitability of different precipitating agents with respect to the catalytic properties of the oxides of Ca and Mg and their application in the synthesis of organic carbonates.

Oxidation behavior of Cr-coated Zr-4 alloy prepared by multi-arc ion plating at 1000-1200°C

The oxidation behavior of Cr-coated Zr-4 alloy is studied in air environment at temperatures ranging from 1000 °C to 1200 °C and for oxidation times ranging from 1 h up to 4 h. The oxidation weight gain, sample appearance, surface and cross-sectional microstructure, Cr-Zr diffusion and phase at different oxidation times for the three temperatures were analyzed in detail. The results reveal that the oxidation weight gain is parabola with oxidation time, and the parabolic rate constant increases with the increase of oxidation temperature. At 1000 °C and 1100 °C, the Cr coating can provide oxidation protection for the internal Zr-4 alloy after 4 h of oxidation. While at 1200 °C, Cr coating can only provide effective oxidation protection for the internal Zr-4 alloy for 1 h. At 1000 °C and 1100 °C, the thickness of the Cr-Zr diffusion layer increases linearly with the oxidation time, while at 1200 °C, the thickness of the Cr-Zr diffusion layer increases linearly with the oxidation time after 1–3 h of oxidation, and after 4 h of oxidation, it suddenly increases sharply. And the XRD results imply that the preferred orientation of Cr2O3 grains is related to the oxidation temperature.