Line Broadening and Enthalpy: Some Empirical Calibrations of Solid Solution Behaviour from IR Spectra

Following recent developments in the application of autocorrelation analysis of line broadening in powder absorption IR spectra, the possibility that elastic strain heterogeneities are responsible both for such broadening and for enthalpy variations in solid solutions has been explored systematically. Recent data for five silicate solid solutions, augite-jadeite, almandine-grossular, albite-anorthite, anthophyllite-grunerite and clinoenstatite-clinoferrosilite, are reviewed. Variations in the autocorrelation parameter for line broadening, j corr, scale linearly with calorimetric data for enthalpy variations, j H , associated with cation substitutions and ordering in these systems. It is proposed that, while there may not be a universal calibration of j H in terms of j corr for all structures, it should be possible to produce empirical calibrations for groups of solid solutions with the same basic structure. Variations in j corr at different phonon frequency ranges provide additional insights into the structural mechanisms by which ordering, mixing, displacive and reconstructive processes occur in silicate solid solutions.     

Interrelation between optical, refractometric, and lattice parameters of Cu6P(S1−x Sex)5I crystals

The influence of the compositional disordering on the energy of the fundamental absorption edge and the refractive index dispersion of the crystalline solid solutions Cu₆P(S_1?x Se_x)₅I is studied. It is shown that the concentration dependences of the optical pseudogap width, the refractive index, and the lattice parameter in these crystalline solid solutions are interrelated.     

Coexistence of the chiral superconductivity and noncollinear magnetic order in the ensemble of Hubbard fermions on a triangular lattice

For the system of strongly correlated electrons on a triangular lattice, the possibility of coexisting superconductivity with the chiral order parameter and the 120°-type noncollinear spin ordering is demonstrated. The integral self-consistency equation for the superconducting order parameter is derived using the diagram technique for Hubbard operators taking into account the spin structure, exchange interaction within two coordination spheres, and intersite Coulomb repulsion.     

Über die Interpretation der Röntgenbeugungsdiagramme von mehrkomponentigen Schmelzen

The final results of x-ray diffraction experiments in molten alloys are electron distribution curves. These are used to get a decision between statistical distribution of the atoms of different kinds in the melt, between ordering of the atoms or between segregation. The according equations are deduced and finally a simple graphical method for the evaluation of the results is given. Important fact for the evaluation of molten alloys with a great difference between the atomic numbers of the two components is the number of scattering electrons in the first coordination sphere. With molten alloys which show little difference between the atomic numbers of the components the radius of the first coordination sphere is deciding. Finally it is shown, that the short range order parameter, which until now only was used in regard to the ordering in solid solutions, also can be used to get valuable results of the degree of ordering in molten alloys.     

预处理对垃圾焚烧飞灰玻璃化的影响

在垃圾焚烧飞灰进行熔融玻璃化之前,先用磷酸盐或绿矾溶液对飞灰进行洗涤,研究这种化学稳定化预处理对飞灰玻璃固化效果的影响。结果表明当使用磷酸盐溶液或磷酸盐与绿矾(FeSO4·7H2O)溶液一起对飞灰进行预处理、并且磷酸盐用量达2g磷/kg干灰时,对飞灰的熔融玻璃化有良好的促进效果,经过预处理后的飞灰通过玻璃化过程可实现对所检测的Pb、Hg、As、Cd、Cr五种重金属的全部稳定化,并且在熔融过程中烟尘的产生和重金属的挥发得到有效抑制。     

Free energy of semiflexible polymers and structure of interfaces

The free energy of semiflexible polymers is calculated as a functional of the compositional scalar order parameter and the orientational order parameter of second-rank tensor S_ij on the basis of a microscopic model of wormlike chains with variable segment lengths. We use a density functional theory and a gradient expansion to evaluate the entropic part of the free energy, which is given in a power series of .The interaction term of the free energy is derived with a random phase approximation. For the rigid rod limit, the nematic-isotropic transition point is given by , N and w being the degree of polymerization and the anisotropic interaction parameter, respectively, and the degree of ordering at the transition point is 0.33448. We also find that the contour length of polymer chains becomes larger in a nematic phase than in an isotropic phase. Interface profiles are obtained numerically for some typical cases. In the neighborhood of isotropic-isotropic interfaces, polymer chains tend to align parallel to the interface on the polymer-rich side and perpendicular on the poor side. When an isotropic region and a nematic region coexist, orientational order parallel to the interface is preferred in the nematic region. Received: 28 May 1998 / Revised: 12 August 1998 / Accepted: 8 September 1998     

The solubility of substitutional atoms in ordered substitutional-intrestitial solid solutions

The solubility of substitutional impurities in ordered bcc A–B–(C) solid solutions has been calculated in a static approximation. The effect of the energy splitting of geometrically equivalent interstitial sites into interstitial sites of two types during ordering was taken into account. The solubility has been determined as a function of temperature, alloy composition, and long-range order parameter.     

Cryopreservation of mango (Mangifera indica L.) embryogenic cultures

Three techniques were compared for cryopreserving embryogenic masses (EMs) sampled from mango (Mangifera indica L.) cv. Zihua embryogenic cultures: (i) encapsulation/dehydration; (ii) pregrowth/dehydration; and (iii) vitrification. In all experiments, EMs were sampled from embryogenic cultures during their exponential growth phase and pretreated for 24 h on solid medium containing 0.5 M sucrose before freezing. No recovery was achieved after cryopreservation using the encapsulation/dehydration technique, whatever the moisture content (fresh weight basis) of EMs, which ranged from 78.3% without dehydration to 40.8% after 6 h dehydration. With the pregrowth plus dehydration technique, limited recovery (8.3%) was achieved after desiccation of EMs for 1 h, to 58.5% MC. Using the vitrification technique, recovery ranged from 94.3% after treatment of EMs with the PVS3 vitrification solution for 20 min (EM moisture content of 34.7%) to 10.9% after a 120 min treatment with the vitrification solution (EM moisture content of 26.0%).     

First-principles investigations of ordering in binary α-Ti solid solutions

The ordering tendency in binary f-Ti solid solution containing 3sp or 4sp simple-metal (SM) or 3d transition-metal (TM) solute is investigated systematically by the linear muffin-tin orbital (LMTO) method within the atomic sphere approximation (ASA). We demonstrated that the effective pairwise interaction (EPI) energy in a solid solution is equal to half the solute-solute interaction energies and can be evaluated by a supercell total energy approach. The calculations of EPI energy both with and without volume relaxation of the supercells and local density of states (LDOS) show that the EPI energies of Ti-SM and Ti-TM solutions are dominated by different factors. For Ti-SM solutions, the EPI energies are of large absolute values with a negative sign, indicating strong ordering tendency in these solutions. The volume relaxation does not alter the EPI energy substantially. The calculated LDOS shows that the ordering tendency in Ti-SM solutions may be related to the hybridization between the electrons of the SM atoms when they are close to each other. For most Ti-TM solutions, if calculated without relaxation, the absolute EPI energies are very small; however, if calculated with relaxation, they are of relatively large positive values, indicating a clustering tendency in these solutions. By combining the calculated EPI energy and Flinn's model for short-range order (SRO) strengthening, the increase in critical shear stress sro due to SRO is estimated for Ti-SM alloys, and the results qualitatively agree with experiment.     

Ising-Nakano model for an amorphous alloy

A lattice model, taking into account the possibility of an atom being pinned at a site upon vitrification, has been developed for binary alloys. The Hamiltonian found for the problem is used in the average-field approximation to obtain equations for the parameters of atom pinning and long-range compositional order. The conditions under which mixing of the components promotes vitrification are analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 89–93, December, 1991.     

Compositional fluctuations in isotopic solid solutions

The effect of compositional fluctuations in isotopic solid solutions on the frequency shift and broadening of Raman lines is investigated. The broadening of the optical phonon line depends on the composition throughout the concentration range of the binary solid solution. It is shown that the line broadening is caused by elastic phonon scattering from compositional fluctuations. The type, size, and number of fluctuations responsible for the scattering are determined, and the dependences of these quantities on the concentration of solid solution components are established.     

Theory of improper decay of binary solid solutions

A phenomenological theory of improper decay of solid solutions has been developed for the first time. This theory differs from the previous versions by consideration of three- and four-particle interactions. One of possible two-dimensional cross sections of the complete phase diagram is presented, which includes all possible versions of improper decay at the one-component order parameter, describing the proper ordering that leads to decay. This cross section makes it possible to understand the dissolution of ordered nanoregions in PbMg _1/3Nb_2/3O₃ with a decrease in temperature.     

Cryopreservation of Citrus madurensis embryonic axes by vitrification: importance of loading and treatment with vitrification solution

This paper investigates the importance of loading and treatment with a vitrification solution on the survival of Citrus madurensis embryonic axes cryopreserved using a vitrification protocol. Among the seven different loading solutions tested, the solution containing 2 M glycerol + 0.4 M sucrose was the most efficient. Of the six vitrification solutions tested, the PVS2 vitrification solution, applied for 20 min at 25 degree C or for 60 min at 0 degree C, ensured the highest survival. A three-step vitrification protocol, involving the treatment of embryonic axes at 0 degree C with half strength PVS2 solution for 20 min then with full strength PVS2 for an additional 40 min was more efficient than a two-step protocol that involved treatment of axes directly with full strength PVS2 solution for 60 min. After rapid immersion in liquid nitrogen, rapid rewarming, unloading in a 1.2 M sucrose solution for 20 min, culture on solid medium with 0.3 M sucrose for 1 day and growth recovery for 4 weeks on standard medium, survival of C. madurensis embryonic axes reached 85 % following the three-step process, compared with 70 % for the two-step process.     

Vitrification, encapsulation-vitrification and droplet-vitrification: a review

This paper discusses the importance of the successive steps of the vitrification technique and reviews the current development and use of vitrification and of the two derived protocols, encapsulation-vitrification and droplet-vitrification. Vitrification refers to the physical process by which a highly concentrated cryoprotective solution supercools to very low temperatures and finally solidifies into a metastable glass, without undergoing crystallization at a practical cooling rate. Samples are thus cryopreserved without detrimental intracellular ice formation. In a standard vitrification protocol, excised explants are precultured on medium enriched with sucrose, treated (loaded) with a loading solution composed of 2 M glycerol + 0.4 M sucrose, dehydrated with a highly concentrated vitrification solution [e.g. the PVS2 vitrification solution, which contains 30 percent (w/v) glycerol, 15 percent (w/v) ethylene glycol and 15 percent (w/v) DMSO and 0.4 M sucrose], frozen and rewarmed rapidly, unloaded with basal culture medium supplemented with 1.2 M sucrose, and then transferred to standard culture conditions. In the encapsulation-vitrification technique, the explants are encapsulated in alginate beads, loaded and dehydrated with a vitrification solution before rapid immersion in liquid nitrogen. In the droplet-freezing technique, excised explants are loaded, treated with the vitrification solution and frozen in individual microdroplets of vitrification solution placed on aluminium foils, which are immersed rapidly in liquid nitrogen. These three techniques have been applied to different tissues of over 100 plant species from temperate and tropical origins and the number of cases where they are being tested on a large scale or applied routinely is increasing.     

Resistometric and anelastic approaches to the determination of the mobility of vacancies and self-interstitials in concentrated alloys

Analysis of the kinetics for local ordering to probe the atomic mobility in concentrated alloys is considered. Some recent applications in -AgZn solid solutions are reported to show the potentials and limitations of this method for the investigation of point defect properties. They are based on the use of mechanical after-effect and resistivity measurements to monitor the ordering rates in conditions of permanent irradiation or after quenching.     

Pressure-induced ferroelectric-antiferroelectric phase transitions in lead zirconate-tatanate-based solid solutions

The ferroelectric-antiferroelectric phase transitions induced by hydrostatic pressure in solid solutions based on lead zirconate-titanate (PZT) with introducing 20 at % tin into B sites and composites based on these ceramics have been studied. In the composites with the same composition of solid solution, the transition pressure can be varied within wide ranges depending on the type of binders. The latter is due to the vitrification of the binder and, consequently, the formation of a rigid framework preventing the transmission of pressure to the ceramic matrix.     

Nonmonotonic TC trends in bi-based ferroelectric perovskite solid solutions

We use first-principles density functional theory calculations to investigate the strongly nonlinear compositional trends in ferroelectric BiBO3-PbTiO3 solid solutions for a variety of cations on the perovskite B site. We demonstrate that previously tabulated crystal chemical parameters (extracted from other Pb-based perovskite alloys [Grinberg et al., J. Appl. Phys. 98, 094111 (2005)]) permit accurate prediction of cation displacements in these new Bi-Pb alloys. We find that observed transition temperatures in these materials are well correlated with computed polarization magnitudes. The presented model for coupling between compositional variation and cation displacements explains the highly nonlinear and often nonmonotonic dependence of the Curie temperature (T(C)) on composition observed in these solid solutions.     

Solid/liquid interfacial free energies in binary systems

The interfacial segregation and the free energy of segregation for solid/liquid interfaces between binary solutions are computed for the (111) boundary of face-centered-cubic crystals. A lattice-liquid interfacial model and pair-bonded regular solution model are employed in the treatment with an accommodation for liquid interfacial entropy. It is concluded that the zone of compositional transition across the interface is generally a few atomic layers in width and is moderately narrower for ideal solutions. The free energy of the segregated interface depends primarily upon the solid composition and the heats of fusion of the component atoms, the composition difference of the solutions, and the difference of the heats of mixing of the solutions. Master plots are presented for predicting the segregation and interfacial free energies in general binary systems.     

Simulation of pair and three-particle correlations in a binary solid solution with a hexagonal lattice

The correlations revealed in an A _y B _{1 ?y} disordered solid solution in which atoms occupy sites in the planar hexagonal lattice are investigated. It is demonstrated that pair correlations in the first coordination shell necessarily result in the appearance of pair correlations in the second and subsequent coordination shells. These induced pair correlations decay to the tenth coordination shell. The atomic ordering in solid solutions of all compositions is studied using the computer simulation. It is shown that, within the limits of computational error, the functional dependence between the pair correlation parameter of the first coordination shell and the parameters of the induced pair correlations in the second to ninth coordination shells is described by a third-degree polynomial. The results of the computer simulation of three-particle correlations are in agreement with the analytical solution for the corresponding correlations in the first coordination shell of the hexagonal lattice.     

Elastoacoustic model with uncertain mechanical properties for ultrasonic wave velocity prediction: application to cortical bone evaluation

The axial transmission technique can measure the longitudinal wave velocity of an immersed solid. An elementary model of the technique is developed with a set of source and receivers placed in a semi-infinite fluid coupled at a plane interface with a semi-infinite solid. The acoustic fluid is homogeneous. The solid is homogeneous, isotropic, and linearly elastic. The work is focused on the prediction of the measured velocity (apparent velocity) when the solid is considered to have random material properties. The probability density functions of the random variables modeling each mechanical parameter of the solid are derived following the maximum entropy principle. Specific attention is paid to the modeling of Poisson's ratio so that the second-order moments of the velocities remain finite. The stochastic solver is based on a Monte Carlo numerical simulation and uses an exact semianalytic expression of the acoustic response derived with the Cagniard-de Hoop method. Results are presented for a solid with the material properties of cortical bone. The estimated mean values and confidence regions of the apparent velocity are presented for various dispersion levels of the random parameters. A sensibility analysis with respect to the source and receivers locations is presented.