Different Degrees Of Order Research Articles

IR Magnetotransmission in Double Manganite NdBaMn2O6 with Different Degrees of Order in A-Position

IR Magnetotransmission in Double Manganite NdBaMn2O6 with Different Degrees of Order in A-Position

Flow Pattern Study and Pressure Drop Prediction of Two-Phase Boiling Process in Different Surface Wettability Microchannel.

An experimental study of two-phase flow pressure drop using R-134a is conducted on three types of different surface wettability microchannels with superhydrophilic (contact angle of 0°), hydrophilic (contact angle of 43°) and common (contact angle of 70°, unmodified) surfaces, all with a hydraulic diameter of 0.805 mm. Experiments were conducted using a mass flux of 713-1629 kg/m2s and a heat flux of 7.0-35.1 kW/m2. Firstly, the bubble behavior during the two-phase boiling process in the superhydrophilic and common surface microchannel is studied. Through a large number of flow pattern diagrams under different working conditions, it is found that the bubble behavior shows different degrees of order in microchannels with different surface wettability. The experimental results show that the hydrophilic surface modification of microchannel is an effective method to enhance heat transfer and reduce friction pressure drop. Through the data analysis of friction pressure drop and C parameter, it is found that the three most important parameters affecting the two-phase friction pressure drop are mass flux, vapor quality, and surface wettability. Based on flow patterns and pressure drop characteristics obtained from the experiments, a new parameter, named flow order degree, is proposed to account for the overall effects of mass flux, vapor quality, and surface wettability on two-phase frictional pressure drop in microchannels, and a newly developed correlation based on the separated flow model is presented. In the superhydrophilic microchannel, the mean absolute error of the new correlation is 19.8%, which is considerably less than the error of the previous models.

Study of solid state transformations and their effect on mechanical response in the stoichiometric Ni2Cr using in-situ synchrotron radiation diffraction experiments

A complete microstructural characterization of the stoichiometric Ni2Cr alloy after different ageing times in which different degrees of order are attained has been carried out. The study of order-disorder transformation has been done using synchrotron radiation diffraction monitoring eventual changes in high-energy X-ray diffraction (HEXRD) patterns every six seconds in the course of differential scanning calorimetry DSC experiments. According to acquired data, the onset of the order-disorder transformation occurs at 630 °C, temperature higher than that reported in previous works. In addition, the appearance of fine carbide precipitation has also been found inside the grains and at grain boundaries. Both ordering of the stoichiometric Ni2Cr and carbide precipitation seems to be responsible for the strengthening of the alloy.

Forces Controlling the Assembly of Particles at Fluid Interfaces.

The interaction of particles with fluid interfaces is ubiquitous in synthetic and natural work, involving two types of interactions: particle-interface interactions (trapping energy) and interparticle interactions. Therefore, it is urgent to gain a deep understanding of the main forces controlling the trapping of particles at fluid interfaces, and their assembly to generate a broad range of structures characterized by different degrees of order. This Perspective tries to provide an overview of the main contributions to the energetic landscape controlling the assembly of particles at fluid interfaces, which is essential for exploiting this type of interfacial systems as platforms for the fabrication of interface-based soft materials with technological interest.

Moving smectic phase and transverse mode locking in driven vortex matter

Out-of-equilibrium systems exhibit various dynamic phases with different degrees of order. A moving smectic phase with transverse periodicity is one of the ordered states, which is theoretically expected to be generic to driven two-dimensional systems. However, a comprehensive dynamic phase diagram, including the moving smectic phase, has not been obtained because of lack of suitable experimental methods. Here we study dynamic phases of driven vortex matter in an amorphous ${\mathrm{Mo}}_{x}{\mathrm{Ge}}_{1\ensuremath{-}x}$ film by using two-step measurements of transient voltage in response to mutually perpendicular driving currents. We find dynamic orderings from the plastic flow to the anisotropic smectic flow and from the anisotropic smectic flow to the isotropic moving Bragg glass as a function of the current. Convincing evidence of the moving smectic phase is obtained from the first transverse mode locking (ML) with signals larger than those of longitudinal ML, indicating the higher transverse order than the longitudinal one. Transverse ML developed here is useful to detect the anisotropic periodicity in driven media.

Effect of Pressure on the Temperature Dependence of the Effective Thermal Conductivity of Gallium Antimonide with Different Degrees of Ordering

Effect of Pressure on the Temperature Dependence of the Effective Thermal Conductivity of Gallium Antimonide with Different Degrees of Ordering

Formation of metastable aluminum silicide as intermediate stage of Al-Si alloy crystallization

The mechanism of Al-Si alloy crystallization from an amorphous state is still unclear. Despite the absence of equilibrium compounds for this binary system, there are several experimental evidences confirming the formation of metastable silicide at annealing of amorphous Si mixed with Al. Classification of this metastable structure is a missing puzzle piece in the description of Al-Si alloy crystallization kinetics. Here, we considered the properties of aluminum silicide Al2Si structure, which is a probable candidate for the role of the observed metastable compound. Our investigation was based on the atomistic simulations with the interatomic potential developed recently and DFT approach. All used methods revealed that there are several crystal structures of Al2Si with close geometry and relatively low formation energies. The chemical ordering in such structures is similar to the one in Si-Al melt. We also showed that the combination of these structures allows to form a crystal with different degree of ordering.

Ordering mechanism and kinetics in Ni2Mn1−xCuxGa ferromagnetic shape memory alloys

The effect of atomic order on the martensitic and magnetic transformations undergone by Ni2Mn1−xCuxGa ferromagnetic shape memory alloys has been investigated. Different degrees of order have been induced by performing selected thermal treatments, and it has been found that, although both the structural (martensitic) and magnetic transformation temperatures increase with the improvement of the atomic order, each of these temperatures evolve with different kinetics. Reinforcing this result, during post–quench heating of Ni2Mn1−xCuxGa alloys two consecutive DSC exothermic peaks are observed, while the ternary Ni–Mn–Ga, Co–doped Ni–Mn–Ga and even Cu–doped Ni–Mn–Ga alloy when Cu replaces Ni show a single peak. The kinetics of the post–quench ordering processes have been studied using the Kissinger’s method, and two different activation energies have been obtained: 1.16 eV for the process that is common to all alloys and 1.35 eV for the one that is only observed in Ni2Mn1−xCuxGa alloys. The former, responsible for the change in Curie temperature, is attributed to the improvement of L21 order mainly due to Mn diffusion; for the second, which underlies the rise of martensitic transformation temperatures, diffusion of Cu atoms, misplaced in the Ni sublattice after quench, towards their most favourable sites in the Mn sublattice is proposed as the responsible mechanism.

Structures of dipotassium rubidium citrate monohydrate, K2RbC6H5O7(H2O), and potassium dirubidium citrate monohydrate, KRb2C6H5O7(H2O), from laboratory X-ray powder diffraction data and DFT calculations.

The crystal structures of the isostructural compounds dipotassium rubidium citrate monohydrate, K2RbC6H5O7(H2O), and potassium dirubidium citrate monohydrate, KRb2C6H5O7(H2O), have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The compounds are isostructural to K3C6H5O7(H2O) and Rb3C6H5O7(H2O), but exhibit different degrees of ordering of the K and Rb cations over the three metal-ion sites. The K and Rb site occupancies correlate well to both the bond-valence sums and the DFT energies of ordered cation systems. The MO6 and MO7 coordination polyhedra share edges to form a three-dimensional framework. The water mol-ecule acts as a donor in two strong charge-assisted O-H⋯O hydrogen bonds to carboxyl-ate groups. The hydroxyl group of the citrate anion forms an intra-molecular hydrogen bond to one of the central carboxyl-ate oxygen atoms.

Liquid Crystal Coacervates Composed of Short Double-Stranded DNA and Cationic Peptides.

Phase separation of nucleic acids and proteins is a ubiquitous phenomenon regulating subcellular compartment structure and function. While complex coacervation of flexible single-stranded nucleic acids is broadly investigated, coacervation of double-stranded DNA (dsDNA) is less studied because of its propensity to generate solid precipitates. Here, we reverse this perspective by showing that short dsDNA and poly-l-lysine coacervates can escape precipitation while displaying a surprisingly complex phase diagram, including the full set of liquid crystal (LC) mesophases observed to date in bulk dsDNA. Short dsDNA supramolecular aggregation and packing in the dense coacervate phase are the main parameters regulating the global LC-coacervate phase behavior. LC-coacervate structure was characterized upon variations in temperature and monovalent salt, DNA, and peptide concentrations, which allow continuous reversible transitions between all accessible phases. A deeper understanding of LC-coacervates can gain insights to decipher structures and phase transition mechanisms within biomolecular condensates, to design stimuli-responsive multiphase synthetic compartments with different degrees of order and to exploit self-assembly driven cooperative prebiotic evolution of nucleic acids and peptides.

Gemini Surfactant-Directed Facile Pillaring of Two-Dimensional Zeolites with Enhanced Catalytic Activity in Friedel–Crafts Alkylation

We report an efficient procedure for the synthesis of pillared MWW zeolites (MCM-36) via integrating intercalation and hydrolysis of tetraethyl orthosilicate (TEOS) into one step. Specifically, two specially selected surfactants with more hydrophilicity instead of the conventional swelling agent cetyltrimethylammonium bromide (CTAB) were employed to increase the interlayer wetting ability and water content. The resultant intercalation and hydrolysis of TEOS occur concurrently in a confined interlayer microenvironment with enriched interlayer water and basic hexamethyleneimine (HMI). It is found that the wetting ability of swelling surfactants has a profound effect on pillarization efficiency, resulting in the different degrees of order of the layered structure, pore-size distribution, and accessibility of the acid sites of MCM-36. MCM-36 prepared using a gemini-type surfactant as a swelling agent shows a highly long-range ordered structure and enhanced catalytic activity for alkylation of benzene with benzyl alcohol compared to the one produced using conventional CTAB as a swelling agent.

Inhomogeneity of a one-dimensional Yukawa system in a trap

A system of like charges interacting with a weak repulsive Yukawa potential and confined in a one-dimensional parabolic electrostatic trap is under consideration. It is shown that inter-particle distance in this system grows from the center of the structure to its periphery. The same effect takes place for the mean square displacement of particles from their equilibrium positions, which corresponds to the amplitude of thermal oscillations, and for the value of Lindemann parameter. This leads to different degrees of order for particles located at different distances from the center of the structure. This result might be important for the study of phase transitions in dusty, colloidal and one-component plasmas.

Di-urea cross-linked siloxane hybrid materials incorporating oligo(oxypropylene) and oligo(oxyethylene) chains

Novel bridged silsesquioxanes (BSs) incorporating short oligo(oxypropylene) or oligo(oxyethylene) chains bonded to a siliceous network via urea cross-links were synthesized by the sol–gel process from the organosilane precursors (CH3CH2O)3-Si-(CH2)3-NHC(=O)NH-R-NH(O=C)NH-(CH2)3-Si-(OCH2CH3)3, with R≡-[CH(CH3)CH2O]xCH2CH(CH3)- (x∼2.5 and 6.1) or R≡-(CH2)2O(CH2)2O(CH2)2-, respectively. The new BSs were identified by the notations d-U′(Y′) with Y′ = 400 and 230, and d-U(Y) with Y = 148, where d stands for di, and U/U′ denote the urea group. The hybrid materials were produced as transparent, amorphous, homogeneous, and soft monoliths, although d-U(148) presented some rigidity. In the three samples the siliceous framework is mainly composed of [–(CH2)Si(OSi)3] and [–(CH2)Si(OSi)2(OH)] substructures. The highest polycondensation degree of the siloxane network was found in the case of d-U′(400), pointing out the formation of a three dimensional framework. In the three materials the urea groups are extensively involved in the formation of strong ordered urea-urea hydrogen-bonded aggregates of different degree of order. The d-U′(230) BS is a promising candidate as mold material for micropatterning applications aiming the fabrication of smart coatings. The prospects for these materials in flexible electrochromic devices for smart windows, where they can act as outermost substrates, are also excellent.

Order–Disorder Structural Transformations in Highly Imperfect Fluorite-Derived R2TiO5-Based (R = Tm, Er) Solid Solutions

Order–disorder structural transformations in xR2O3 ∙ (1 – х)TiO2 (R = Tm, Er; х = 0.5−0.6) solid solutions with a highly imperfect fluorite-derived structure at 1600°C have been studied using monochromatic synchrotron X-ray diffraction and Raman spectroscopy. The results demonstrate that the synthesis process leads to the formation of two cubic phases identical in composition: a disordered fluorite-like (F) phase (Fm3m) and an ordered pyrochlore-like (P) phase (Fd3m), which is coherent with the disordered phase and consists of nanoscale (<100 A) and nanocrystalline domains. The lattice parameters of these phases have been determined. In the stability range of the solid solutions ((0.5 ≤ x ≤ 0.6)), the lattice parameter of the fluorite-like phases follows Vegard’s law. The Raman spectra of the R2TiO5-based (R = Tm, Er) solid solutions contain broad bands at low and high frequencies, with peaks at 100, 171, 291, 355, 385, and 723 cm–1 for R = Tm and at 100, 169, 292, 355, 390, and 720 cm–1 for R = Er, which correspond to the P- and F-phases, respectively. The formation of pyrochlore-like phases with different degrees of order in a fluorite matrix is due to the internal stress induced by the high density of structural defects in their unit cells. The materials obtained in this study have a large specific surface area and can be used as catalysts and catalyst supports.

Dendritic polymer spherulites: birefringence correlating with lamellae assembly and origins of superimposed ring bands

Dendritic spherulites are one type of diversified ways of crystal aggregations into micrometer-size consortia by kinetics-driven assembly from nanometer-size crystal plates (i.e., lamellae or single crystals). Crystallized polymers can exist in states of different degrees of order, which lead to the resulting assembled morphologies are of non-equilibrium supramolecular hierarchical patterns of crystal structures. Diffusion-controlled growth patterns emerge, which change the details of dendritic morphology depending on Tc (degree of super-cooling), polymer-diluent interactions, confinement. Investigation to the diversified patterns of lamellar assembly into polymer dendritic spherulites has come to several key conclusions. This article reviews and summarizes the top-surface-relief morphology and interior dissections of polymer dendritic spherulites, where the dendrites may be composed of ringed stripes or fibrous cilia crystals. The results yield interesting consistency for constructing workable mechanisms to account for each type of morphologies with respect to their molecular weights and crystallization kinetics conditions (i.e., Tc, space confinements, film thickness, blend interaction, as well as blend composition).

Effect of pressure on the order-disorder phase transitions of B cations in AB'1/2B''1/2O3 perovskites.

Perovskite-like oxides AB'1/2B''1/2O3 may experience different degrees of ordering of the B cations that can be varied by suitable synthesis conditions or post-synthesis treatment. In this work the earlier proposed statistical model of order-disorder phase transitions of B cations is extended to account for the effect of pressure. Depending on the composition, pressure is found to either increase or decrease the order-disorder phase transition temperature. The change in transition temperature due to pressure in many cases reaches several hundred kelvin at pressures accessible in the laboratory, which may significantly change the degree of atomic ordering. The work is intended to help in determining how pressure influences the degree of atomic ordering and to stimulate research into the effect of pressure on atomic order-disorder phase transitions in perovskites.

Gum-like mechanical behavior of a partially ordered Al5Nb24Ti40V5Zr26 high entropy alloy

Microstructure and mechanical behavior of a new bcc Al5Nb24Ti40V5Zr26 high-entropy alloy in the as-cast, cold-rolled and recrystallized conditions were studied. In the as-cast condition, the Al5Nb24Ti40V5Zr26 alloy had a single bcc phase coarse-grained (~80 μm) structure. After cold rolling to a total thickness strain 80% the alloy demonstrated typical of deformed metals tensile behavior with a short hardening stage and early necking. Annealing at 800 °C resulted in recrystallization of the matrix and formation of a small fraction of C14 type Laves phase particles. After annealing at 1100 °C, a partial B2 ordering of the matrix phase was found. In the annealed condition, the alloy showed some typical of gum metals features associated with low work hardening and large elongation. The manifestation of a gum-like behavior can be ascribed to the formation of dislocation channels due to the local disordering of the bcc matrix in shear planes. In addition, an unusual (inverse) dependence of yield strength on the recrystallized grain size was observed, most possibly due to a different degree of ordering of the matrix phase.

Phase Composition and Microstructure of UHPHT Vein Glass from Giant Diamondiferous Kara Impact Crater by Raman Mapping

2D and 3D Raman mapping allows to observe “in situ” distribution of phases and relationship of minerals in rock samples, different mineral aggregates, mineral inclusions within crystals and other quantitative spectroscopic studies of mineral substances and materials. The method is realized in accumulating and processing of big data array of Raman spectra (RS) from selected areas of a studied sample with subsequent visualization in XY plane at 2D mapping or in the form of 3D experimental models with XYZ coordinates in a case of 3D Raman mapping. During the mapping different analytical data can be visualized as maps such as spatial distribution of mineral phases, degrees of their crystallinity, orientation of crystallites and their size, residual tension in minerals and inclusions and many other parameters. As 3D Raman mapping demands higher requirements to quality of samples, takes significantly long time expenditure and big data for processing, 2D Raman mapping looks to be the most effective for different mineralogical applications. In this work we demonstrate advantages of 2D Raman mapping on the example of studying of the impact ultrahigh-pressure high-temperature (UHPHT) vein glasses with melt-crystallized ultrahigh-pressure silica phase – coesite, for the first time found within diamondiferous impactites of the giant Kara meteorite crater. The mapping was produced with processing of typical spectra ranges of recognized mineral phases met in analyzed areas. As a result of the conducted studies it has been established what according to spectroscopic data coesite hangs to central parts of UHPHT silica glass located in general matrix of aluminosilicate glass. The sites of silicate glass are characterized by fully amorphous state that is obviously shown in its typical ranges. The areas with a high luminescence correspond to inclusions of smectite micro-drops in UHPHT silica glass isolations that has been confirmed with the accompanying study with use of electron probe microanalysis (EPMA), energy dispersive spectroscopy (EDS) and electron diffraction (ED). The used 2D Raman mapping to the impact vein glasses of the Kara meteorite crater allowed to reveal distribution of mineral phases in UHPHT glass, showing distribution of amorphous and crystalline phases that is undoubted advantage of the Raman spectroscopy. In full text of the paper technical features of Raman 2D mapping are shown that can be useful for similar mineral objects and materials with complex phase structure and different degree of ordering.

Deformation twinning characteristics in hot-rolled Fe-6.5wt%Si alloy with different degree of order

Tensile deformation behavior of the Fe-6.5 wt%Si alloy with different degree of order at intermediate temperatures (200-500 °C) was investigated. Deformation twinning was observed in this body centered cubic A2 phase together with ordered structures. It is found that the ductility of the quenched samples with low degree of order is higher than that of the furnace cooled samples with high degree of order. Deformation twinning occurred in the quenched samples after dislocation slip during deformation at 200-300 °C, while no deformation twins were observed in the furnace cooled samples. The results indicate that the low degree of order is an essential precondition for the deformation twinning, which can also enhance dislocation slip. The <001> orientation along the rolling direction and large grain size can reduce the critical twinning stress. High strain rate and low deformation temperature can further promote the formation of the twinning by dislocations pile-up and high work hardening rate. Our work provides new insights into the deformation mechanism in the Fe-6.5 wt%Si alloy.

Molecular order and dynamics of water in hybrid cellulose acetate–silica asymmetric membranes

ABSTRACTIn this work 2H NMR spectroscopy and 1H NMR relaxometry and diffusometry were used to characterise water order and dynamics in cellulose acetate/silica asymmetric membranes. Two hydrated membranes were characterised allowing the identification of extra ordering of the water molecules and the presence in each membrane of up to two spectral components with different degrees of order and different values. The mechanism behind this order increase was ascribed to the rapid exchange of the water molecules between the pore walls and its interior. relaxometry dispersions allowed for the identification of the relevant mechanisms of pore-confined water motion, with rotations mediated by translational displacements (RMTD) as the dominant mechanism in the low frequency region. Using the RMTD low cut off frequency along with the in situ directly measured diffusion constant it was possible do determine characteristic lengths of correlated water motion in both membranes studied, which fall in ranges compatible with typical pore dimensions in similar membranes.