Solvothermal synthesis and characterization of α-Fe2O3 nanodiscs and Mn3O4 nanoparticles with 1,10-phenanthroline

α-Fe₂O₃ nanodiscs and Mn₃O₄ nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectra. The average diameter of α-Fe₂O₃ nanodiscs is of 2 μm. In the case of Mn₃O₄ sample, the Mn₃O₄ crystallites are nanoparticles with an average size of 34 nm. A formation mechanism for the α-Fe₂O₃ and Mn₃O₄ nanomaterials was proposed.     

Spectroscopic characterization of Yb:Sc2O3 transparent ceramics

Yb：Sc2O3 transparent ceramics are fabricated by a conventional ceramic process and sintering in H2 atmosphere. The room-temperature spectroscopic properties are investigated, and the Raman spectrum shows an obvious vibration characteristic band centred at 415 cm-1. There are three broad absorption bands around 891, 937, and 971 nm, respectively. The strongest emission peak is centred at 1.04 μm with a broad bandwidth （11 nm） and an emission cross-section of 1.8×10^-20 cm^2. The gain coefficient implies a possible laser ability in a range from 990 nm to 1425 nm. The energy-level structure shows that Yb：Sc2O3 ceramics have large Stark splitting at the ground state level due to their strong crystal field. All the results show that Yb：Sc2O3 transparent ceramics are a promising material for short pulse lasers.     

Chemical bath deposition of hausmannite Mn3O4 thin films

A low-temperature chemical bath deposition (CBD) technique has been used for the preparation of Mn₃O₄ thin films onto glass substrates. The kinetic behavior and the formation mechanism of the solid thin films from the aqueous solution have been investigated. Structure (X-ray diffraction and Raman), morphological (atom force microscope), and optical (UV-vis-NIR) characterizations of the deposited films are presented. The results indicated that the deposited Mn₃O₄ thin films of smooth surface with nanosized grains were well crystalline and the optical bandgap of the film was estimated to be 2.54 eV.     

High temperature and low current density synthesis of Mn3O4 porous nano spheres: Characterization and electrochemical properties

Uniform and single-crystalline Mn₃O₄ nano-spheres were synthesized by cathodic electrodeposition at high temperature (80 °C) and low current density (0.25 mA cm⁻¹) on steel electrode. Further the annealed samples were characterized for their structural and morphological properties by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) studies. TEM and SEM images showed that particles have spherical shapes and the average diameter size was about 50 nm. Formation of Mn₃O₄ compound was confirmed from FTIR studies. The XRD pattern showed that the Mn₃O₄ exhibit tetragonal hausmannite structure. The results of N₂ adsorption-desorption analysis indicated that Mn₃O₄ nano-sphere has BET surface area of about 177.6 m² g⁻¹ and average pore diameters of 3 and 4 nm. The possible formation mechanism of Mn₃O₄ nanostructures has been discussed. The supercapacitive properties of Mn₃O₄ sample in 0.5 M Na₂SO₄ electrolyte showed maximum supercapacitance of 235.4 Fg⁻¹ at scan rate 10 mV s⁻¹. Coulumbic efficiency could be kept about 90% during 1000 cycles at 10 mV s⁻¹.     

A Study on the Rheological and Magnetic Properties of Polymer-Bonded Magnets Using Polycarbonate as the Bonding Material

The effect of three metal oxides on the magnetic properties of polymer bonded magnets (PBMs) was studied. The three PBMs, using polycarbonate (PC) as binder and 5 wt% of Fe₃O₄, Fe₂O₃, or CuO nanoparticles, were prepared by melt extrusion in a twin screw extruder followed by compression molding. Transmission electron microscopic (TEM) images showed a better dispersion for the PC/Fe₃O₄ nanocomposite compared with that of the other nanocomposites. The dynamic intersection frequency (ω_c), which is related to the crossing of the G′ and G^″ curves, showed that there was more homogeneity in the PC/Fe₃O₄ and PC/Fe₂O₃ nanocomposites. The curves of saturation magnetization for the three nanocomposites showed that there was a relationship between the magnetic properties and the homogeneity of the nanoparticles studied by rheometry. Because the magnetic strength of PC/Fe₃O₄ was greater than that of the other nanocomposites, it was concluded that not only the intrinsic magnetic property of the filler was an important factor to increase the magnetic property, but also the homogeneity of the filler within the matrix had an important role.     

Nickel-induced magnetic behaviour of nano-structured α-Fe2O3, synthesised by facile wet chemical route

We report the synthesis of pristine and nickel containing iron oxide (α-Fe₂O₃) nanocrystallites by facile environmentally benign wet chemical process. The magnetic behaviour of the samples has been found to change progressively with nickel content. The Mössbauer spectra revealed the precipitation of secondary phase of nickel ferrite (NiFe₂O₄) at ～2?wt% nickel contents. The transmission electron micrographs together with asymmetric magnetic hysteresis loop have confirmed the formation of core–shell structure. The Morin temperature of nanostructured α-Fe₂O₃ as estimated by superconducting quantum interference device has been found to be 257, 245, 247 and 242?K at nickel content of 0, 1, 2 and 4?wt%, respectively. The similar trends of increase/decrease in Morin temperature have been noticed by Mössbauer analysis. Furthermore, below Morin temperature, the temperature range of coexisted antiferromagnetic and ferromagnetic states has been found to increase with increase in nickel content.     

Electrochemical characterization of Mn: Co3O4 thin films prepared by spray pyrolysis via aqueous route

Present investigation reports, spray pyrolytic deposition of Mn: Co₃O₄ thin films onto the stainless steel by spray pyrolysis, at the deposition temperature 573 ± 2 K via aqueous route. Prepared electrodes were characterized structurally and morphologically by means of XRD and SEM. Also optical and electrochemical characterizations were carried out in depth. Structural characterization confirms face centered cubic and tetragonal body centered crystal structures for Co₃O₄ and Mn₃O₄ respectively. The rough granular morphology is observed form SEM. Electrochemical study reveals the pseudo capacitive as well as double layer behavior with optimum specific capacitance 485.29 F/g at the scan rate 1 mV/s in 1 M KOH electrolyte. Specific energy, specific power and columbic efficiency were calculated using chronopotentiometric technique. Electrochemical impedance spectroscopy was carried out in the frequency range 1 mHz–1 MHz. Randles equivalent circuit parameters associated with the operative cell are reported.     

Spectroscopic Investigation of Tungsten Ions in Lead Scandium Phosphate Glass System

Lead scandium phosphate glasses (PbO-Sc₂O₃-P₂O₅) containing different concentrations of tungsten oxide (WO₃) ranging from 0 to 5 mol% were prepared. A number of studies, viz. differential thermal analysis (DTA), infrared spectra, optical absorption, and electron spin resonance (ESR) spectra, have been carried out. The results of DTA indicated the highest glass forming ability for the glass containing 5 mol% of WO₃. The results of spectroscopic studies have been analyzed in light of different oxidation states of tungsten ions.     

Vibrational Spectroscopic Studies of Molybdena Dispersed on Ceria Support

Abstract

Diffuse Reflectance Infrared Fourier Transform (DRIFT) and FT-Raman spectra have been used to investigate the interactions between molybdena and ceria in MoO₃/CeO₂ samples with different Mo loadings. The spectra exhibit a weak Mo=O broad band of surface species at ca. 920–970 cm^?1, which reveals that the interaction between dispersed molybdena and ceria could be mainly ionic in nature. With the increasing of Mo loadings, the observed Mo=O band broadening and frequency shifting are due to the overlapping and condensation of different hydrated surface species. On the basis of the measured surface dispersion capacity of morybdena and the structure of the preferentially exposed (111) plane of ceria, it is reasonable to suggest that the Mo⁶⁺ cations and the accompanying O²- anions are incorporated into the surface available vacant sites of CeO₂, accordingly the dispersed molybdena species are interacted electrostatically with the support instead of only physically dispersed on the surface of it.     

Fourier Transform Infrared Study of A C18 Modified Quartz Surface

In reversed-phase liquid chromatography the separation mechanism depends on the solute-stationary phase and solute-solvent interactions. These interactions can be studied under near-normal chromatographic conditions by total internal reflection fluorescence (TIRF) spectroscopy. Quartz crystals chemically modified with n-octadecyl-substituted-silanes, which are common derivatizing reagents used to modify chromatographic surfaces, can be used as a model stationary phase in TIRF studies. To facilitate study of the separation mechanisms using TIRF, surfaces of quartz crystals were chemically modified with silylating reagents and characterized by Fourier Transform Infrared Spectroscopy (FT-IR). Susceptibility tests of the modified surfaces were performed using protic and aprotic solvents. Siloxane bonds were formed, between the reagent and the quartz surface, at high reaction temperature in the absence of any solvent. Siloxane bond formation in the presence of organic solvent at room temperature was observed only when the crystal was previously dehydrated at high temperature.     

Study of electrical conductivity changes and phase transitions in Co3O4 doped ZrO2

The electrical conductivity of ZrO₂ doped with Co₃O₄ has been measured at various temperatures for different molar ratios. The conductivity increases due to the migration of vacancies created by doping. The conductivity is also found to increase with rise in temperature up to 120°C, and after attaining a maximum the conductivity decreases due to a collapse of the lattice framework. A second rise in conductivity around 460°C in all the compositions confirms the phase transition in ZrO₂ from monoclinic to tetragonal symmetry. X-ray powder diffraction and DTA studies were carried out for confirming the doping effects and the transition in ZrO₂.     

Effects of RE2O3 (RE = Tm, Sc, Yb) addition on the superconducting properties of ErBa2Cu3Oy

We investigated the effects of added Tm₂O₃, Sc₂O₃, and Yb₂O₃ on the superconducting properties of sintered Er123 samples. Tm₂O₃ addition caused the least T_c degradation, exhibiting a T_c above 90 K even for 17 vol% addition. Samples with added Sc₂O₃ maintained a T_c at above 90 K up to an addition of 7.2 vol%, while Yb₂O₃-containing samples showed a monotonic decrease in T_c with increased vol% of added Yb₂O₃. Tm₂O₃-containing samples exhibited a slight increase in J_c(0.1 T)/J_c(0) and had constant J_c values even for 17 vol% addition. XRD and SEM results indicate that the Tm₂O₃ is very stable in the superconducting matrix.     

Thermally stimulated luminescence from alkaline earth borates

The thermally stimulated luminescence from XB₂O₄ (X=Ca,Sr,Ba) has been investigated. The results on CaB₂O₄ and SrB₂O₄ are being reported here for the first time. In both cases, the emission is found to be quite intense, contrary to the case with BaB₂O₄. The presence of two peaks in the glow curves is noted over the temperature range of 300-570 K. The emission spectra corresponding to both the peaks have been observed to be identical, consisting of two broad emissions, one in the UV and other in the blue-green regions. The emission is apparently quite different from that of BaB₂O₄ in which case only very weak emission spreading over a broad wavelength range around 410 nm is observed. This result has been understood in terms of the overlap between the excitation and the emission spectra.     

CH3OH/TiO2(110)界面的光电子能谱研究

Methanol/TiO₂(110) is a model system in the surface science study of photocatalysis where methanol is taken as a hole capture. However, the highest occupied molecular orbital of adsorbed methanol lies below the valence band maximum of TiO₂, preventing the hole transfer. To study the level alignment of this system, electronic structure of methanol covered TiO₂(110) surface has been measured by ultraviolet photoelectron spectroscopy and the molecular orbitals of adsorbed methanol have been clearly identified. The results indicate the weak interaction between methanol and TiO₂ substrate. The static electronic structure also suggests the mismatch of the energy levels. These static experiments have been performed without band gap excitation which is the prerequisite of a photocatalytic process. Future study of the transient electronic structure using time-resolved UPS has also been discussed.     

The nature of antimony-enriched surface layer of Fe-Sb mixed oxides

Antimony segregation is a common feature in Fe-Sb mixed oxides, which have been widely applied as catalysts in selective oxidation and ammoxidation reactions. This paper attempts to shed a light on the cause of such a common feature and on the nature of the antimony-enriched surface layer over FeSbO₄ by means of XPS surface analysis. Single-phase FeSbO₄ samples prepared by different methods were studied, and the antimony in their surface layer is a mixture of both Sb⁵⁺ and Sb³⁺ rather than single Sb⁵⁺. Their surface composition is close to FeSb₂O₆, which could be described as (FeSbO₄)(Sb₂O₄)_δ, δ = 0.5, and it is not “Fe(II)Sb(V)₂O₆” as suggested in literature. Fe-Sb mixed oxides with Sb/Fe > 1 (mol/mol) are mixtures of FeSbO₄ and Sb₂O₄, and the surface of FeSbO₄ grains would be a layer of (FeSbO₄)(Sb₂O₄)_δ, δ ≥ 0.5. Fe-Sb mixed oxides with Sb/Fe < 1 are mixtures of FeSbO₄ and Fe₂O₃, and the surface of FeSbO₄ grains would be a layer of (FeSbO₄)(Sb₂O₄)_δ, δ ≤ 0.5, but the remaining Fe₂O₃ would be encapsulated by a layer of FeSbO₄.     

Group Classification of Biological Tissues by Infrared Spectroscopy

Infrared spectra of rat tissues, RNA tumor virus (Rauschler) and pure RNA and DNA are examined by the technique of frustrated multiple internal reflection (FMIR). An attempt has been made to characterize biologically important tissue components on the basis of infrared spectral analysis and published literature on the subject.

Under the conditions described, rat tissues may be grouped according to their infrared spectra. The spectral differences in vivo between normal and N-nitroso-dimethylamine (DMN)-injected rat liver have been presented to show the usefulness of the FMIR technique for rapid detection of induced changes in the tissue composition.     

The structure and luminescence properties of a novel orange emitting phosphor Y3MnxAl5−2xSixO12

A series of phosphors with the composition Y₃Mn_xAl_5−2xSi_xO₁₂ (x=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6) was prepared through solid state reactions. X-ray powder diffraction analysis of samples shows that when co-doping content does not exceed 16% of Al³⁺, equimolar co-doping of Mn²⁺ and Si⁴⁺ does not change the garnet structure of phosphors, but makes the interplanar distance to decrease a certain extent. However, if the co-doping content exceeds 16%, new phases will form in the samples. The excitation and emission spectra of samples show that Mn²⁺ in Y₃Mn_xAl_5−2xSi_xO₁₂ emits broadband orange light (peak wavelength varies from 586 to 593 nm). With an increment in co-doping content, the emission intensity of the phosphors increases when the value of x is lower than 0.1 while it decreases when it is higher than 0.1 and the emission peak moves to a longer wavelength.     

A new high-pressure polymorph of Ti2O3: implication for high-pressure phase transition in sesquioxides

The post-corundum phase transition has been investigated in Ti₂O₃ on the basis of synchrotron X-ray diffraction in a diamond anvil cell and transmission electron microscopy. The new polymorph of Ti₂O₃ was found at about 19 GPa and 1850 K, and this phase was stable even at about 40 GPa. A new polymorph of Ti₂O₃ can be indexed on a Pnma orthorhombic cell, and the unit-cell parameters are a=7.6965 (19) Å, b=2.8009 (9) Å, c=7.9300 (23) Å, V=170.95 (15) Å³ at 19 GPa, and a=7.8240 (2) Å, b=2.8502 (1) Å, c=8.1209 (3) Å, V=181.10 (1) Å³ at ambient conditions. The Birch–Murnaghan equation of state yields K ₀=206 (3) GPa and K′₀=4 (fixed) for corundum phase, and K ₀=296 (4) GPa and K′₀=4 (fixed) for the post-corundum phase. The molar volume decreases by 12% across the phase transition at around 20 GPa. The structural identification was carried out on a recovered sample by the Rietveld method, and a new polymorph of Ti₂O₃ can be identified as Th₂S₃-type rather than U₂S₃-type structure. The transition from corundum-type to Th₂S₃-type structure accompanies the drastic change of the form of polyhedron: from TiO₆ octahedron in the corundum-type to TiO₇ polyhedron in the Th₂S₃-type structures.     

Constituted oxides/nitrides on nitriding 304, 430 and 17-4 PH stainless steel in salt baths over the temperature range 723 to 923 K

The progressively developed oxides and nitrides that form on nitriding 304, 430 and 17-4 PH stainless steel are analysed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) in this study. The experimental results show that the Cr contents and matrix structures (ferrite, austenite and martensite) play an important role in forming FeCr₂O₄, Cr₂O₃ and Fe₂O₃ oxides as well as nitrides. After a short immersion time, oxides of Cr₂O₃ and FeCr₂O₄ form in nitride films on 304 stainless steel samples. Fe₂O₃ oxide will subsequently form following an increasing immersion time. For the 430 stainless steel, Cr₂O₃ predominately forms after a short dipping time which hinders the growth of the nitride layer. As a result, this sample had the thinnest nitride film of the three for a given immersion time. After the formation of oxides, both CrN and Cr₂N were detected near the surface of the nitride films of three samples while Cr₂N phases formed in the deeper zone. The greatest amount of Fe₂O₃ oxide among the three samples was obtained on the nitriding 17-4 PH stainless steel which also had a high intensity count of N 1s.     

Free Surface and Interface Thermodynamics of Liquid Nickel in Contact with Alumina

Sessile drop experiments of Ni and Ni(2at.%Al) were conducted under controlled working conditions, at 1500°C, P(O₂) 10^–9 Torr. It is shown that Al and oxygen atoms engaged in the capillary driven mass transport at the interface have a significant impact on the surface/interface thermodynamics. The surface energy of liquid Ni determined from experiments in which Ni comes into contact with Al₂O₃ is significantly lower than that of high purity Ni, due to the segregation of Al. The free energy of segregation of Al to the free surface of Ni ( G _S) was found to range from –164 to –152 kJ/mol, indicating a relatively strong tendency for segregation of Al to the free surface of Ni(Al). It is proposed that an Al(O)-rich liquid layer forms adjacent to the Ni-Al₂O₃ interface, which improves interfacial adhesion. In the Ni(Al)-Al₂O₃ system, an increase in the Al content of the alloy leads to the improvement of both wetting and adhesion of the alloy on the ceramic, correlating with the improvement in the interface strength after solidification.