СЕРООЧИСТКА ДыМОВыХ ГАЗОВ ДЛЯ ТЕПЛОВыХ ЭЛЕКТРОСТАНЦИЙ РОССИИ

Розглянуто методи діагностики та управління показниками якості палива у вигляді суміші вугілля і газу (або топкового мазуту) на теплових електростанціях. Результати досліджень можна використа- ти для автоматизації процесу оптимізації якості суміші цих палив методом математичного лінійного програмування. Рассмотрены методы диагностики и управления показателями качества топлива в виде смеси углей и га- за (или топочного мазута) на тепловых электростанциях. Результаты исследований предложено ис- пользовать для автоматизации процесса оптимизации качества смеси этих топлив методом матема- тического линейного программирования

Turn-key module for neutron scattering with sub-micro-eV resolution

We report the development of a compact turn-key module that boosts the resolution in quasi-elastic neutron scattering by several orders of magnitude down to the low sub-micro-eV range. It is based on a pair of neutron resonance spin flippers that generate a well defined temporal intensity modulation, also known as MIEZE (Modulation of IntEnsity by Zero Effort). The module may be used under versatile conditions, in particular in applied magnetic fields and for depolarising and incoherently scattering samples. We demonstrate the power of MIEZE in studies of the helimagnetic order in MnSi under applied magnetic fields

Self-Assembly of Coil/Liquid-Crystalline Diblock Copolymers in a Liquid Crystal Solvent

Diblock copolymers having a random-coil polymer block (polystyrene, PS) connected to a side-group liquid crystal polymer (SGLCP) self-assemble in a nematic liquid crystal (LC), 4-pentyl-4′-cyanobiphenyl, into micelles with PS-rich cores and SGLCP-rich coronas. The morphologies of block copolymers with varying PS content are characterized as a function of temperature and concentration using small-angle neutron scattering, rheometry, and transmission electron microscopy. Unlike conventional solvents, the nematic LC can undergo a first-order transition between distinct fluid phases, accessing the regimes of both strong and slight selectivity in a single polymer/solvent pair. Micelles dissolve away above a microphase separation temperature (MST) that is often equal to the solution’s isotropization point, TNI. However, increasing or decreasing the polymer’s PS content can shift the MST to be above or below TNI, respectively, and in the former case, micelles abruptly swell with solvent at TNI. Comparable effects can be achieved by modulating the overall polymer concentration

The curvature changes induced by grafted polymers in microemulsions

The results on Winsor phases, droplet and bicontinous microemulsions phases with polymer-grafted lipids studied by Small Angle Neutron Scattering (SANS) are reported below, together with the contrast variation techniques used to characterize the average curvature in the system. We have clearly shown that polymer-grafted lipids change the interaction between microemulsion droplets --it need not be just repulsive but could also be attractive. They induce structural changes or bring about complete phase changes as observed visually in the Winsor phases when added in sufficient amounts. In the bicontinous microemulsion phases, the polymer-grafted lipids decrease the persistence length, hence the bending rigidity, increase the apparent average thickness of the film, and cause a complex deformation of the film which brings about a negative curvature change at a semi-local scale. Contrary to the naive prediction that the polymer-grafted lipids should increase membrane rigidity our experiments show a decrease. This is a subtle effect caused by perhaps an indirect coupling between film curvature and concentration fluctuations

Perturbations of microemulsion droplets by confinement and adsorption of polymer

We perturb the structure of dilute microemulsion droplets by confining polymer chains inside the droplets and by adsorbing polymer on the surfactant shells from the outer phase. We observe the local structure changes by small-angle neutron scattering. The curvature fluctuations and the size distribution of the droplets increase in both cases by different possible mechanisms, an induced size polydispersity minimizing osmotic stresses in the first case, a lowering of the film rigidity in the second one. The polymer adsorption is observed by measuring the polymer-droplet cross-structure factor

Structure of Polymer Chains Confined in Vycor

We observe by Small Angle Neutron Scattering the structure of polystyrene chains in semi-dilute solutions confined in a model porous medium, Vycor. The size of the free chains in solution is always larger than the pore diameter, 70 Å. The use of a suitable mixture of hydrogenated and deuterated solvents and polymers enables us to measure directly the form factor of one single chain among the others. The penetration of the chains in the porous medium is almost complete for the concentration ($\Phi$ = 20%) and the range of molecular weight ($35\,000 < M_{\rm w} < 800\,000$) used. The radius of gyration of the confined chains is always smaller than the radius of gyration of the free chains in the equivalent bulk solution. Our measurements are in agreement with the theoretical predictions established by Daoud and de Gennes for chains confined in a cylindrical pore when the chains are entangled and laterally squeezed but remain ideal at large scale along the cylinder axis because of the screening of the excluded volume interactions (so-called regime of “semi-dilute cigars”). The values of the partition coefficient of the chains between the porous medium and the free solution and the asymptotic behavior of the structure factors indicate that polystyrene adsorbs onto the bare surface of Vycor. We show that silanizing Vycor suppresses this adsorption.Nous observons par diffusion de neutrons aux petits angles la structure de chaînes de polystyrène en solution semi-diluée confinées dans un milieu poreux modèle, le Vycor. La taille des chaînes en solution à l'état libre est toujours supérieure au diamètre des pores, 70 Å. L'utilisation d'un mélange adéquat de solvants et de polymères hydrogénés et deutérés nous permet de mesurer directement le facteur de forme d'une seule chaîne au milieu des autres. La pénétration des chaînes dans le milieu poreux est presque totale pour la concentration ($\Phi$ = 20%) et la gamme de poids moléculaire ($35\,000 < M_{\rm w} < 800\,000$) utilisées. Le rayon de gyration des chaînes confinées est toujours inférieur au rayon de gyration des chaînes libres dans la solution équivalente. Nos mesures sont en accord avec les prédictions théoriques établies par Daoud et de Gennes pour des chaînes confinées dans un pore cylindrique quand les chaînes sont enchevêtrées et comprimées transversalement mais restent idéales à grande échelle dans la direction du cylindre à cause de l'écrantage du volume exclus (régime dit “de cigares semi-dilués”). Les valeurs des coefficients de partage des chaînes entre le milieu poreux et la solution libre ainsi que le comportement asymptotique des facteurs de structure montrent que le polystyrène s'adsorbe sur la surface nue du Vycor. Nous montrons que la silanisation du Vycor supprime cette adsorption

Using the “Switchable” Quality of Liquid Crystal Solvents To Mediate Segregation between Coil and Liquid Crystalline Polymers

The discontinuous change in solvent quality of a liquid crystal (LC) solvent, 5CB, at the nematic−isotropic phase transition produces abrupt changes in the phase behavior of solutions of coil and LC polymers and in the self-assembly of coil−LC block copolymers. Nematic 5CB is strongly selective for a side-group liquid crystal polymer (SGLCP), and isotropic 5CB is a good solvent for both SGLCP and a random coil (polystyrene, PS). In nematic 5CB, unfavorable LC−PS interactions drive phase separation in SGLCP−PS−LC ternary solutions and drive micellization of PS−SGLCP diblocks. In isotropic 5CB, rich phase behavior occurs in both ternary solutions and block copolymer solutions. Despite the fact that isotropic 5CB is a good solvent for both SGLCP and PS, segregation can occur due to the asymmetric solvent effect (i.e., the preference of the solvent for the SGLCP). In concentrated isotropic solutions, unfavorable SGLCP−PS interactions become dominant

Chain Anisotropy of Side-Group Liquid Crystalline Polymers in Nematic Solvents

We demonstrate a method for measuring the anisotropy of a side group liquid crystalline polymer (SGLCP) in a perdeuterated nematic solvent using small-angle neutron scattering. In this system scattering originates from both the polymer backbone and the large pendant side groups, causing the measured anisotropy to vary with molecular weight. Since it is the backbone anisotropy that is of interest, we show how to mathematically account for scattering due to the side groups. Using a molecular weight series of SGLCPs that have an oblate conformation, this method yields a constant ratio of the backbone radii independent of molecular weight and spacer length