Different Degrees Of Order Research Articles

DETERMINATION OF THE PHASE COMPOSITION OF INTERMEDIATE AND FINAL PRODUCTS OF SYNTHESIS OF SPINEL TYPE CATALYSTS Cu1Cr2O4 AND Cu1Fe2O4 BY DIFFERENTIATING DISSOLUTION METHOD

Traditionally, the X-ray analysis (XRD) method is used to study the phase composition of a solid. But phases with structural defects, poorly crystallized (with disordered structure and amorphous), microphases, phases of variable composition, surface phases and phases, distributed in various ways throughout the entire volume of the sample, often turn out to be X-ray amorphous. In these situations, the stochiographic DR method proves to be more effective, since it allows qualitatively and quantitatively to detect both the crystalline and X-ray amorphous phases listed above. The phase compositions of the spinel type catalysts Cu 1 Cr 2 O 4 and Cu 1 Fe 2 O 4 were studied by the stoichiographic method of differentiating dissolution (DR). It is established that the nature of the element and temperature influence the formation of the spinel structure, creating new shapes. The paper describes phase transformations occurring in the synthesis of catalysts, which was carried out by coprecipitation from a mixture of solutions of nitrate salts. It was found that the temperature of 85°C forms various stoichiometric formations, which are precursors of spinels. The 600°C temperature in the case of copper-chromium systems forms stoichiometric compounds of the spinel composition Cu 1 2+ Cr 2 3+ O 4 and structures with different degree of ordering. In the case of copper-iron systems at 600 °C, stoichiometric compounds of the Cu 1-x 2+ Fe 2 3+ O 4 spinel composition and structure are defective in copper. The 900°C temperature pro­vides the formation of compounds of a given spinel composition Me 1 2+ Me 2 3+ O 4 and structures in both systems. The results by the DR method were compared with the results of the XRD method. A comparative analysis has shown that the ordered or crystallized forms of spinels and oxides are detected by both methods, while disordered and defective forms of spinels, the shapes of disordered solid solutions, and also small amounts of oxides show only the DR method.

The effect of diffusive re-equilibration time on trace element partitioning between alkali feldspar and trachytic melts

We present new experimental data on major and trace element partition coefficients between alkali feldspar and trachytic melt. Experiments were conducted at 500 MPa, 870–890 °C to investigate through short disequilibrium and long near-equilibrium experiments the influence of diffusive re-equilibration on trace element partitioning during crystallization. Our data show that Ba and Sr behave compatibly, and their partition coefficients are influenced by re-equilibration time, orthoclase (Or) content, growth rate and cation order-disorder. High field strength elements (HFSE) and rare earth elements (except Eu) are strongly incompatible, but alkali feldspar efficiently fractionates light (LREE) from heavy rare earth elements (HREE).Our crystallization experiments reveal a strong influence of disequilibrium crystal growth on the partitioning of Ba and Sr. In particular, short-duration experiments show that rapid alkali feldspar crystal growth after nucleation, promotes disordered growth and less selectivity in the partitioning of compatible trace elements that easily enter the crystal lattice (e.g., Ba and Sr). This produces partition coefficients of compatible elements higher than those obtained through long-duration experiments, in which growth is slower and more selective. On approach to equilibrium, decreasing growth rate and timescales of diffusive re-equilibration facilitates the incorporation of compatible elements within the crystal lattice (through ordered growth), on the basis of the charge and size of the octahedral site, resulting in lower partition coefficients of Ba and Sr. Therefore, our results indicate that besides crystal-chemical effects, i.e. lattice strain, the substitution mechanisms during growth (with different degrees of ordering) of Ba and Sr in alkali feldspar are strongly influenced by diffusive re-equilibration and crystal growth kinetics. This implies that partition coefficients of Ba and Sr can be used to establish timescales of crystallization processes under pre- and syn-eruptive conditions. The application of our results to alkali feldspar in rocks from Campi Flegrei, constrain the magma residence time at subliquidus conditions in a reservoir to a maximum of 6 days under disequilibrium conditions and to a minimum of 9 days upon approaching near-equilibrium conditions.

Controlling the Hierarchical Assembly of π-Conjugated Oligoelectrolytes.

Here, a means of controlling the assembly pathways of p-conjugated oligoelectrolytes into supramolecular fibers and microtubes is presented, and it is shown how the addition of small end-caps to well-defined and pH-responsive conjugated oligomers can alter the balance between repulsive and attractive supramolecular forces and enables control of the morphology of the hierarchical assembly process. The assembly stages from nuclei to protofibers are evidenced and a hypothesis on the mechanism of microtubes formation using a combination of analytical methods is provided, revealing different degrees of order at different scales along the structural hierarchy.

Ordnung muss sein: heteroelement order and disorder in polyoxovanadates

The first mixed antimonato-germanato polyoxovanadates were synthesized using two different strategies, highlighting the critical role of the precursors. Following the traditional route using multiple single sources as precursors the polyanions [V15Sb2Ge4O42(OH)4(H2O)]6- (1) and [V15Sb3Ge3O42(OH)3(H2O)]6- (2) are obtained, which display disorder of their Sb/Ge positions, indicating that clusters of different compositions are in equilibrium in solution. In contrast, if the water-soluble single-source precursor {Ni(en)3}3[V15Sb6O42(H2O)]·ca. 15H2O is reacted with GeO2, {Ni(en)3}3[V15Sb3Ge3O42(OH)3(H2O)]·≈9H2O (3) forms, in which Sb and Ge occupy distinct positions that might have been formed via partial substitution reactions in the {V15Sb6} precursor.

Optical analysis of nanoparticle packing after drying in microdroplets

The optical spectra of nanostructured patterns with different degrees of order, obtained by dehydration self-assembly of nanoparticles in solution microdroplets placed on a planar substrate, have been analyzed. The reflectance spectrum of the best-ordered pattern contains a characteristic peak, the position of which is determined by the average lattice period in the layer. It is shown that the height of this peak depends on the degree of order of the pattern structure. Patterns with different degrees of order have been simulated using a software for modeling the self-assembly process, which takes into account the properties of particles, substrate, and solvent, as well as the contact line dynamics during solvent evaporation. A peak occurs in the reflectance spectrum due to the resonance Rayleigh scattering in the ordered layer. The described technique for optical diagnostics can be used to analyze the degree of particle order in a pattern.

Effect of magnetic field pulses on the structure and properties of magnetite

The effect of weak pulsed magnetic fields on the structure and properties of magnetite is analyzed. It is found that different degrees of ordering of cations and vacancies and, consequently, iron ions facilitate the formation of its polymorphic modifications.

Memory effect on the crystallization behavior of poly(lactic acid) probed by infrared spectroscopy

The influence of crystalline memory effect on poly(lactic acid) (PLA) crystallization was probed by time-resolved Fourier transform infrared spectroscopy (FTIR). The melt with different degrees of order was prepared by melting at various temperatures. The vibrational changes associated with inter- and intra-chain interactions during crystallization were monitored. In the initial period of crystallization, the order of intensity changes is as follows: 1458cm−1>1210cm−1≫921cm−1, 1458cm−1>1210cm−1>921cm−1, and 1458cm−1>1210cm−1∼921cm−1 for PLA melted at 190, 170, and 168°C, respectively. With increasing the degree of order, both the formation of skeletal conformational-ordered structure and, especially, the 103 helix structure are accelerated. The influence of memory effect on the crystallization kinetics was also discussed based on the Avrami model.

Open‐Circuit Voltage in Organic Solar Cells: The Impacts of Donor Semicrystallinity and Coexistence of Multiple Interfacial Charge‐Transfer Bands

In organic solar cells (OSCs), the energy of the charge‐transfer (CT) complexes at the donor–acceptor interface, E CT, determines the maximum open‐circuit voltage (V OC). The coexistence of phases with different degrees of order in the donor or the acceptor, as in blends of semi‐crystalline donors and fullerenes in bulk heterojunction layers, influences the distribution of CT states and the V OC enormously. Yet, the question of how structural heterogeneities alter CT states and the V OC is seldom addressed systematically. In this work, we combine experimental measurements of vacuum‐deposited rubrene/C60 bilayer OSCs, with varying microstructure and texture, with density functional theory calculations to determine how relative molecular orientations and extents of structural order influence E CT and V OC. We find that varying the microstructure of rubrene gives rise to CT bands with varying energies. The CT band that originates from crystalline rubrene lies up to ≈0.4 eV lower in energy compared to the one that arises from amorphous rubrene. These low‐lying CT states contribute strongly to V OC losses and result mainly from hole delocalization in aggregated rubrene. This work points to the importance of realizing interfacial structural control that prevents the formation of low E CT configurations and maximizes V OC.

Electroencephalogram Signal Classification for Automated Epileptic Seizure Detection Using Genetic Algorithm.

Background:Epilepsy causes when the repeated seizure occurs in the brain. Electroencephalogram (EEG) test provides valuable information about the brain functions and can be useful to detect brain disorder, especially for epilepsy. In this study, application for an automated seizure detection model has been introduced successfully.Materials and Methods:The EEG signals are decomposed into sub-bands by discrete wavelet transform using db2 (daubechies) wavelet. The eight statistical features, the four gray level co-occurrence matrix and Renyi entropy estimation with four different degrees of order, are extracted from the raw EEG and its sub-bands. Genetic algorithm (GA) is used to select eight relevant features from the 16 dimension features. The model has been trained and tested using support vector machine (SVM) classifier successfully for EEG signals. The performance of the SVM classifier is evaluated for two different databases.Results:The study has been experimented through two different analyses and achieved satisfactory performance for automated seizure detection using relevant features as the input to the SVM classifier.Conclusion:Relevant features using GA give better accuracy performance for seizure detection.

The Roles of Structural Order and Intermolecular Interactions in Determining Ionization Energies and Charge‐Transfer State Energies in Organic Semiconductors

The energy landscape in organic semiconducting materials greatly influences charge and exciton behavior, which are both critical to the operation of organic electronic devices. These energy landscapes can change dramatically depending on the phases of material present, including pure phases of one molecule or polymer and mixed phases exhibiting different degrees of order and composition. In this work, ultraviolet photoelectron spectroscopy measurements of ionization energies (IEs) and external quantum efficiency measurements of charge‐transfer (CT) state energies (ECT) are applied to molecular photovoltaic material systems to characterize energy landscapes. The results show that IEs and ECT values are highly dependent on structural order and phase composition. In the sexithiophene:C60 system both the IEs of sexithiophene and C60 shift by over 0.4 eV while ECT shifts by 0.5 eV depending on molecular composition. By contrast, in the rubrene:C60 system the IE of rubrene and C60 vary by ≤0.11 eV and ECT varies by ≤0.04 eV as the material composition varies. These results suggest that energy landscapes can exist whereby the binding energies of the CT states are overcome by energy offsets between charges in CT states in mixed regions and free charges in pure phases.

Synthesis, X-ray structure analysis, and Raman spectroscopy of R2TiO5-based (R = Sc, Y) solid solutions

Order–disorder transitions in xR2O3 · (1 − x)TiO2 (R = Sc, 0.4 ≤ x ≤ 0.5; R = Y, 0.5 ≤ x ≤ 0.6) solid solutions with highly imperfect fluorite-derived structures have been studied using monochromatic synchrotron X-ray diffraction and Raman spectroscopy. The results demonstrate that the synthesis process leads to the formation of a fluorite-like (Fm3m) disordered phase and a nanoscale (~10–100 nm) pyrochlore-like (Fd3m) ordered phase of the same composition, coherent with the disordered phase. We have determined their lattice parameters. The Raman spectra of Sc2TiO5 (Y2TiO5) contain broad lines in low- and high-frequency regions: at 190, 350, and 775 (134, 188, 365, 404, and 727) cm−1. These lines are characteristic of a pyrochlore-like phase with a varying degree of order and a disordered fluorite-like phase, respectively. The pyrochlore-like phase Y2Ti2O7 has two strong Raman peaks in the low-frequency region: at 312 and 527 cm−1. The formation of nanodomains with different degrees of order is caused by the internal stress that arises from the high density of structural defects in the unit cells of the solid solutions.

Hydrocarbon alteration in the bituminous salt of the Kłodawa Salt Dome (Central Poland)

The so called bituminous salts occurring in the Kłodawa dome, located in Central Poland, differ from the surrounding salts by their colour change from light to dark brown. This colour is associated with an extremely large amount of hydrocarbon, mainly located in the inclusions. The presence of numerous fluid inclusions has been documented in previous petrologic studies, distinguishing seven main types of fluid inclusion assemblages (FIA) in terms of size, shape as well as the ratio of filling material. However, four types of inclusions were selected in the current investigations according to their unusual optical behaviour. Raman micro-spectroscopy a modern, non-destructive method was used for investigating a single inclusion being a part of FIA. Presented in this paper Raman spectra revealed a unique pattern of bands characterizing the content of the inclusions. The hydrocarbons show a very complex character reflected in the appearance of a strong fluorescence background. A well-marked heterogeneity characterized the inclusions, by diversity in the intensity of the background and in the pattern of the bands characterizing the presence of certain components. One can distinguish the presence of carbonaceous matter showing the different degrees of order. The depth profile and the analysis of the various points of the inclusions indicate that the carbonaceous matter is not evenly distributed in the inclusions but forms a thin, disorganized film on their walls. This film was also found in sites where the inclusions are filled with brine. The certain characteristics associated with the presence of the incipient phase transformation of the organic matter, or slightly transformed organic matter and the lack of light hydrocarbons as well as a number of petrologic features of inclusions indicate that these salt rocks have been subdivided into thermal transformations, accompanied by the recrystallization of the halite and the escape of the more volatile compounds such as methane, ethane, etc.

Anisotropy of spin–spin and spin–lattice relaxation times in liquids entrapped in nanocavities: Application to MRI study of biological systems

Spin–spin and spin–lattice relaxations in liquid or gas entrapped in nanosized ellipsoidal cavities with different orientation ordering are theoretically investigated. The model is flexible in order to be applied to explain experimental results in cavities with various forms, from very prolate up to oblate ones, and different degree of ordering of nanocavities.In the framework of the considered model, the dipole–dipole interaction is determined by a single coupling constant, which depends on the form, size, and orientation of the cavity and number of nuclear spins in the cavity. It was shown that the transverse and longitudinal relaxation rates differently depend on the angle between the external magnetic field and cavity main axis.The calculation results for the local dipolar field, transverse and longitudinal relaxation times explain the angular dependencies observed in MRI experiments with biological objects: cartilage and tendon. Microstructure of these tissues can be characterized by the standard deviation of the Gaussian distribution of fibril orientations. The comparison of the theoretical and experimental results shows that the value of the standard deviation obtained at the matching of the calculation to experimental results can be used as a parameter characterizing the disorder in the biological sample.

On a combined approach to studying the correlation parameters of self-organizing structures

The correlation parameters of self-organizing structures are investigated using a combined approach, a combination of 2D detrended fluctuation analysis and the average-mutual-information method. The self-organizing structures to be investigated are model surfaces with different degrees of ordering (ordered, disordered, and mixed) and amorphous hydrogenated silicon and tetrahedral carbon films. It is demonstrated using test structures that the correlation vectors determined by kinks on the scale dependence of the fluctuation function with the use of the 2D detrended fluctuation analysis coincide with sufficient accuracy with specified periods of surface harmonic components. It is more expedient to study disordered structures using the average-mutual-information method. The physical meaning of maximum mutual information is shown to characterize the information capacity of a system. The combined approach allows the correlation parameters of combined systems to be investigated most comprehensively.

Peculiarities of the initial stages of carbonization processes in polyimide-based nanocomposite films containing carbon nanoparticles

AbstractCarbonization of the polyimide-based composite films containing carbon nanoparticles, namely nanofibers and nanocones/disks, in the temperature range 500–550°C was studied and the kinetics of the initial stage of carbonization and the effect of the filler on the mechanical properties of the carbonized films were evaluated. Two polyimides (PIs) characterized by different macrochains’ rigidity and different degrees of ordering of the intermolecular structure were used. The character of the nanofiller’s action on the kinetics of the carbonization process depends on the heating rate. In this work, the intensity of the destruction of the PI matrix of the composite films was shown to be slightly higher than that of films of the same polymers with no filler. The introduction of the carbon nanoparticles into both PIs provokes the increase in the ultimate deformation values of the partially carbonized films, while the carbonization of the unfilled PI films yields the brittle materials. The Young’s modulus ...

Implications of Metal-Site Vacancies on Li-Ni-Mn-Co Based Positive Electrode Materials

One of the key issues with Li-excess positive electrode materials is their high irreversible capacity loss (IRC), which is usually ~ 20 % of their first charge capacity. Li-excess materials with IRC as low as 4% have been recently reported by us1. Those materials were intentionally synthesized with less Li than the stoichiometric amount, based on oxidation state rules, and as a result, metal-site vacancies were found in their single-phase, layered, pristine structures. With metal-site vacancies, the structure can be written as Li[ΔqM(1-q)]O2, where Δ is a metal site vacancy and the transition metal layer has no Li atoms. An elemental analysis of metals only on such materials would conclude they were Li rich because when q > 0, the number of moles of Li is greater than the number of moles of transition metal atoms, even though there are no Li atoms in the transition metal layer. The small IRC was found to be related to the presence of metal site vacancies. Following that work, a comprehensive search for materials that contain metal-site vacancies was performed in the Li-Ni-Mn-Co pseudo-ternary system. An array of materials with deliberate Li-deficiency and a wide-range of Ni, Mn, and Co compositions was synthesized and their properties were investigated. It was found that, in the Li-Ni-Mn-Co pseudo-ternary system, materials with metal-site vacancies can be synthesized at many Ni-Mn-Co combinations by forcing Li deficiency. Most of the materials were layered single-phase materials but increasing Li deficiency eventually caused the evolution of a spinel phase. The presence of metal-site vacancies were verified by density measurements made with a He-pycnometer. Figure 1 shows the XRD patterns of several single-phase materials (a to f), which have considerable amount of metal-site vacancies, in the range of 20° to 34° representing superlattice ordering between TM ions and vacancies in the TM layer similar to that reported by McCalla et al2. The relative intensity of superlattice peaks varied with overall metal composition (not shown here) suggesting different degrees of ordering. For example, the absence of superlattice peaks in samples e and f suggests that only a negligible amount of vacancies reside in the TM layer whereas the prominent superlattice peaks in samples a and b suggests a significant amount of vacancies in the TM layer. Thus the nature and the relative intensity of the superlattice peaks can be used as a first approximation to predict the location and distribution of vacancies between TM and Li layers. Detailed results on the implications of metal-site vacancies on the properties of Li-Ni-Mn-Co based positive electrode materials will be presented.

Spectroscopic Signature of Two Distinct H-Aggregate Species in Poly(3-hexylthiophene)

In an endeavor to correlate the optoelectronic properties of π-conjugated polymers with their structural properties, we investigated the aggregation of P3HT in THF solution within a temperature range from 300 to 5 K. By detailed steady-state, site-selective, and time-resolved fluorescence spectroscopy combined with Franck–Condon analyses, we show that below a certain transition temperature (265 K) aggregates are formed that prevail in different polymorphs. At 5 K, we can spectroscopically identify two H-type aggregates with planar polymer backbones yet different degree of order regarding their side chains. Upon heating, the H-character of the aggregates becomes gradually eroded, until just below the transition temperature the prevailing “aggregate” structure is that of still phase-separated, yet disordered main and side chains. These conclusions are derived by analyzing the vibrational structure of the spectra and from comparing the solution spectra with those obtained from thin films that were cooled slo...

Defect structure of xSc2O3 · (1 − x)TiO2 (x = 0.4–0.5) solid solutions

X-ray diffraction characterization with monochromatic synchrotron X-rays has demonstrated that xSc2O3 · (1 − x)TiO2 (x = 0.4–0.5) solid solutions consist of a fluorite-like (Fm3m) disordered phase and a nanoscale (≃ 10–50 nm) pyrochlore-like (Fd3m) ordered phase of the same composition, coherent with the disordered phase. We have determined their lattice parameters. The formation of nanodomains with different degrees of order is shown to be caused by the internal strain due to the high density of structural defects in their unit cells. The materials obtained in this study possess enhanced sorption capacity and can be used as catalysts, catalyst supports, gas sensors, etc.

Nano-beam X-ray microscopy of dried colloidal films.

We report on a nano-beam small angle X-ray scattering study on densely-packed, dried binary films made out of spherical silica particles with radii of 11.2 and 19.3 nm. For these three-dimensional thin films prepared by drop casting, only a finite number of colloidal particles contributes to the scattering signal due to the small beam size of 400 × 400 nm(2). By scanning the samples, the structure and composition of the silica particle films are determined spatially resolved revealing spatial heterogeneities in the films. Three different types of domains were identified: regions containing mainly large particles, regions containing mainly small particles, and regions where both particle species are mixed. Using the new angular X-ray cross-correlations analysis (XCCA) approach, spatial maps of the local type and degree of orientational order within the silica particle films are obtained. Whereas the mixed regions have dominant two-fold order, weaker four-fold and marginal six-fold order, regions made out of large particles are characterized by an overall reduced orientational order. Regions of small particles are highly ordered showing actually crystalline order. Distinct differences in the local particle order are observed by analyzing sections through the intensity and XCCA maps. The different degree of order can be understood by the different particle size polydispersities. Moreover, we show that preferential orientations of the particle domains can be studied by cross-correlation analysis yielding information on particle film formation. We find patches of preferential order with an average size of 8-10 μm. Thus, by this combined X-ray cross-correlation microscopy (XCCM) approach the structure and orientational order of films made out of nanometer sized colloids can be determined. This method will allow to reveal the local structure and order of self-assembled structures with different degree of order in general.

Glucose oxidase adsorption performance of carbonaceous mesocellular foams prepared with different carbon sources

Several carbonaceous mesocellular foams (C-MCFs) were prepared with MCF-silica as template using the carbon precursors of sucrose, furfuryl alcohol and lab-made phenolic resin, and the corresponding C-MCFs were named as C-MCF-Suc, C-MCF-FA and C-MCF-PR, respectively. The results of SEM, transmission electron microscopy, N2 adsorption-desorption and energy-dispersive X-ray measurements indicated that the C-MCFs prepared from different carbon source appeared morphologically with different degree of order and different pore distribution. The C-MCF-FA exhibited the highest ordered structure and the smallest pore distribution among the foams. The optimum conditions for adsorption of C-MCFs on glucose oxidase (GOD) were also studied, and the maximum adsorbance was determined. The adsorption of GOD on C-MCF-FA was performed at different pH with different GOD concentrations. The maximum adsorption (423.3 mg g(-1)) was observed near the isoelectric point of the GOD (pI ≈ 5.0) with a GOD concentration of 6.0 mg mL(-1), suggesting that the GOD adsorption on C-MCFs might be affected strongly by the electric repulsion between the GOD molecules. Moreover, GOD adsorption performances on different C-MCFs revealed that both the pore size and the pore volume played important roles in the adsorption process, and the window size of C-MCFs dominated the residual immobilized amounts of GOD. Compared to the other two C-MCFs, the C-MCF-FA with a smaller window pore (10 nm) and higher volume (1.40 cm(3) g(-1)) exhibited the highest GOD adsorption and catalytic activity. Furthermore, the immobilized GOD exhibited improved thermal and storable stabilities. Thus the C-MCF-FA could be served as the prospective GOD carrier material used in enzymatic fuel cells.