Energetics of Ce and Pu incorporation into zirconolite waste-forms

The General Utility Lattice Program (GULP) has been used to model the zirconolite lattice, calculate the energies of substituting Ce(3+), Ce(4+), Pu(3+), Pu(4+) and Fe(3+) into the lattice both as single and multi-defect systems and model the formation of Ce(3+), Ce(4+), Pu(3+) and Pu(4+) doped zirconolite lattices. These results have been compared against experimental observations, with particular emphasis on those Ce containing solid solutions that exhibit Ce(3+)/Ce(4+) mixed valence characteristics. It is found that the Ce(3+)/Ce(4+) mixed valence is as a result of reduction within the lattice, with the Ce(3+) being stabilised on the Ca site, and that this behaviour would not be expected for the corresponding Pu solid solutions.     

Phase and aggregation behaviour of alkylglycosides

Alkylmonoglucopyranosides are the main compounds of technical alkylpoyglucosides. New contributions to crystallisation and thermotropic properties, phase and aggregation behaviour are presented because of their central interest for understanding the technical products. Synchrotron and neutron scattering give a detailed insight into the micelle formation of pure compounds and to the sphere–rod transition as a function of added long chain alcohols. The phase behaviour of the surfactant systems and microemulsions is heavily influenced by traces of ionic surfactants.     

共沉淀-流变相法制备YAG:Ce

分别用共沉淀和共沉淀-流变相法合成了YAG:Ce荧光粉.采用红外、热分析、X射线衍射仪、扫描电子显微镜、荧光光谱仪对合成的荧光粉进行了表征.SEM图和光谱分析表明,用共沉淀-流变相法所制备的YAG:Ce荧光粉粒度更细、分布更均匀,具有更高的发光强度.     

Polarographic reduction behaviour of clay minerals

Suspensions of the clay minerals bentonite, kaolinite illite and chlorite have been examined polarographically and reduction waves found. The differences in their behaviour, with and without the addition of surface active reagents, are reported.     

Phase behaviour of amphiphilic side-chain polymers

The present study describes the phase behaviour of a low-molar-mass 1,3-diol with a linear alkyl chain in aqueous solution. From the combined results of differential scanning calorimetry and optical polarizing microscopy a phase diagram was constructed. The low-molar-mass diol forms a lamellar mesophase only in the presence of water. The influence of the linkage of the amphiphilic molecule to different polymer backbones on the stability of the mesophase was investigated. It is evident that amphiphilic side-chain polymers show a distinct stabilization of the mesophase. Moreover, comparison between the polyacrylate, polymethacrylate and polysiloxane indicates a strong influence of the main-chain flexibility on the stability of the liquid-crystalline phase. The type of the liquid-crystalline phase of the side-chain polyacrylate in the water-saturated state was identified by X-ray investigations as lamellar. The hydration behaviour of the polymers was investigated by ²H-N.M.R. and isopiestic measurements.     

Phase behaviour of ordered polymer solutions

Rules for equilibrium phase behaviour, laid down long ago on the basis of the two laws of thermodynamics, appear to be valid also for many polymer systems in which aggregates of various topology occur. The phase rule offers a useful tool for the construction and understanding of phase diagrams for systems in which order of some kind is prevalent in certain ranges in the diagram. ‘Double sickle’ type phase diagrams, found for surfactant solutions, microemulsions as well as block-copolymer solutions can be traced back to the considerable loss of translational entropy which accompanies aggregation.     

Phase behaviour of amphiphilic side-chain polymers

The present study describes the phase behaviour of a low-molar-mass 1,3-diol with a linear alkyl chain in aqueous solution. From the combined results of differential scanning calorimetry and optical polarizing microscopy a phase diagram was constructed. The low-molar-mass diol forms a lamellar mesophase only in the presence of water. The influence of the linkage of the amphiphilic molecule to different polymer backbones on the stability of the mesophase was investigated. It is evident that amphiphilic side-chain polymers show a distinct stabilization of the mesophase. Moreover, comparison between the polyacrylate, polymethacrylate and polysiloxane indicates a strong influence of the main-chain flexibility on the stability of the liquid-crystalline phase. The type of the liquid-crystalline phase of the side-chain polyacrylate in the water-saturated state was identified by X-ray investigations as lamellar. The hydration behaviour of the polymers was investigated by ²H-N.M.R. and isopiestic measurements.     

The phase behaviour and optical properties of a nematic/chiral dopant liquid crystalline mixture system

The phase behaviour and aggregation states of a binary mixture of a nematic liquid crystal and a chiral dopant have been investigated. The nematic liquid crystal E7 was miscible with the chiral dopant S811 over their entire concentration range. Binary E7/S811 mixtures formed the N* phase for S811 contents under 20%, and the SmA* phase for S811 contents between 40% and 90%. BP and TGBA* frustrated phases were found during cooling, for S811 contents between 25% and 35%. The helical pitches of the binary mixtures decreased with increasing chiral dopant content. From XRD profiles, the orientational ordering of the binary composites was found to increase with increasing chiral dopant content.     

Phase behaviour and conductivity study of electrolytes in supercritical hydrofluorocarbons

The purpose of this work was to characterise supercritical hydrofluorocarbons (HFC) that can be used as solvents for electrodeposition. The phase behaviour of CHF(3), CH(2)F(2), and CH(2)FCF(3) containing [NBu(n)(4)][BF(4)], [NBu(n)(4)][B{3,5-C(6)H(3)(CF(3))(2)}(4)] and Na[B{3,5-C(6)H(3)(CF(3))(2)}(4)] was studied and the conditions for forming a single supercritical phase established. Although all three HFCs are good solvents for [NBu(n)(4)][BF(4)] the results show that the CH(2)F(2) system has the lowest p(r) for dissolving a given amount of [NBu(n)(4)][BF(4)]. The solubility of Na[B{3,5-C(6)H(3)(CF(3))(2)}(4)] in CH(2)F(2) was found to be unexpectedly high. Studies of the phase behaviour of CH(2)F(2) containing [NBu(n)(4)][BF(4)] and [Cu(CH(3)CN)(4)][BF(4)] showed that the copper complex was unstable in the absence of CH(3)CN. For CHF(3), [Cu(hfac)(2)] was more soluble and more stable than [Cu(CH(3)CN)(4)][BF(4)] and only increased the phase-separation pressure by a moderate amount. Studies of the conductivity of [NBu(n)(4)][B(C(6)F(5))(4)], [NBu(n)(4)][B{3,5-C(6)H(3)(CF(3))(2)}(4)], [NR(f)Bu(n)(3)][B{3,5-C(6)H(3)(CF(3))(2)}(4)] (R(f) = (CH(2))(3)C(7)F(15)), and Na[B{3,5-C(6)H(3)(CF(3))(2)}(4)] were carried out in scCH(2)F(2). The results show that these salts are more conducting than [NBu(n)(4)][BF(4)] under the same conditions although the increase is much less significant than that reported in previous work in supercritical CO(2) + CH(3)CN. Consequently, either [NBu(n)(4)][BF(4)] or the corresponding BARF salts would be suitable background electrolytes for electrodeposition from scCH(2)F(2).     

Phase behaviour of blends with mesophase components

Temperature transitions and structural transformations were studied for blends of two thermotropic mesophase cyclolinear polymethylsiloxanes with linear PDMS of various molecular weights by means of DSC, optical polarizing microscopy, and optical interferometry. Compatibility of the components which depends on the chemical structure of cyclolinear polymethylsiloxanes, molecular weight of PDMS, composition, and temperature affect formation of mesophase in cyclolinear polymethylsiloxanes. The most interesting aspect of the phase behaviour consists in the fact that it is possible to reach compatibility of the components in the mesomorphic state for the blends of two cyclolinear polymethylsiloxanens due to various annealing regimes in one‐phase molten state.     

Phase behaviour of the dioctadecyldimethylammonium bromide-water system

The phase behaviour of the twin-tailed surfactant dioctadecyldimethylammonium bromide with water was studied by DSC, FT-IR, X-ray and polarizing microscope. The phase diagram of DODAB-water system is very similar to that of DODAC-water. The dihydrate is in equilibrium with isotropic solution below 55°C. Above this temperature there is a lamellar liquid crystalline region, in equilibrium with isotropic liquid and solid crystals of DODAB·2H₂O, up to 69°C. From 69 to 86°C, the lamellar mesophase is in equilibrium with ‘waxy’ anhydrous DODAB. From 86 to 116°C and very high DODAB content, there is a very narrow region of existence of inverse hexagonal mesophase, in equilibrium via a narrow biphase region with lamellar mesophase. AtT > 116°C an isotropic liquid appears. There seems to exist two different lamellar mesophases, one of them between 10 and 40 wt.% DODAB and the other between 60 and about 97 wt.% DODAB, with a biphase zone between them.     

Phase behaviour and morphology from a current viewpoint

The presentation is to give an overview of polymer morphology from the standpoint of recent developments with emphasis on the underlying phase transformations. In the latter context it is essential to recognize that with the exception of special systems having complex equilibrium surfaces, the conventionally considered morphology represents a non-equilibrium state, hence a metastable state of matter arising from phase transformation having been arrested at some stage before the transformation was complete. In respect to the term ‘complete’ distinction needs to be made between completeness of material conversion and attainment of the equilibrium phase size and shape, a distinction which acquires special significance in polymeric systems as will be illustrated and discussed.     

Branched chain discotics Phase structure and orientation behaviour

Studies show that branching the side chains of hexakis(acoyloxy)-benzenes (HAB) and -cyclohexanes (HAChx) does not modify the structure of the discotic mesophase formed. Shear fields appear to act on entire columns, not on individual discs, thereby causing alignment of columns in the shear direction. X-ray diffraction patterns of samples at temperatures between 30°C and 40°C above the clearing temperature provide evidence for the presence of mesophase order.     

Phase behaviour and microstructures of microemulsions (I)

By the orthogonal design, the optimal formation conditions for the middle-phase microemulsions in the system dioctadecyldimethylammonium chloride (DODMAC)/ sodium dodecyl sulfate (SDS)/n-butanol/n-hep-tane/brine were obtained as follows: W_DODMAC: W_SDS = 1:4-1:5,C _π-butanol (%) = 11.0-12.0, andC _NaCl (%) = 3.25 Investigations have been made on the effects of the concentrations of NaCl and n-butanol (l.0%-14.0%), the ratios ofWDODMAC: to W_SDS, and the kinds of alcohols (n-propanol, n-butanol, and n-pentanol) on the formation, the phase behaviour, the ultralow interfacial tensions, the optimal salinity (S^*), and the length of salinity (δS). Some rules and data were worked out about the formation and characteristics of the middle-phase microemulsions. The mi-crostructures of the middle-phase microemulsions were also studied by using FT-IR, ESR, and freeze fracture electron microscopy techniques. The results from the three methods show that the microstructures of the middlephase mi-croemulsions undergo the change from O/W to bicontinuous (B.C.) and to W/O. The distribution rule of the orga-nized molecule assemblies in the middle-phase microemulsions is conducible to constructing the model of microemulsion systems, to recognizing the microstructures of the middle-phase microemulsions, and to setting forth the relationship between the microstructures and macro-properties of rnicroemulsions. Project supported by the Niltional Natural Science Foundation of China and the Chinese Postdoctoral Science Foundation.     

Phase behaviour and structure of a non-ionic discoidal amphiphile in water

The phase behaviour and structure of mixtures of a novel non-ionic discoidal amphiphile, 2,3.6,7,10,11-hexa-(1,4,7-trioxaoctyl)-triphenylene, and water have been investigated using deuterium NMR spectroscopy and X-ray diffraction. The feature of special interest is the occurrence of a nematic phase, intermediate to an isotropic micellar solution at higher temperatures and a columnar hexagonal phase at lower temperatures. This nematic phase exists over wide concentration (0.1 to 0.5 volume fraction of amphiphile) and temperature intervals. The molecules are stacked in columnar (rod-shaped) aggregates. In the isotropic micellar solution and nematic phase the length of the micelle is of the order of the centre-to-centre separation.     

Phase behaviour of binary systems of lactones in carbon dioxide

Experimental phase equilibrium data for binary systems involving ε-caprolactone, δ-hexalactone, and γ-caprolactone with carbon dioxide have been measured applying the synthetic method using a high-pressure, variable-volume view cell over the temperature range of (303 to 343) K and pressures up to 21 MPa. For the systems investigated, (vapour + liquid) (VLE), (liquid + liquid) (LLE), and (vapour + liquid + liquid) (VLLE) equilibrium were visually recorded. It was observed that an increase in temperature or in carbon dioxide concentration led to a pronounced raise in transition pressure values. The experimental results were modelled using the Peng–Robinson equation of state with the conventional quadratic mixing rule, affording a satisfactory representation of the experimental values.     

Phase behaviour of lithium and sodium salts of phenylstearic acid

Phenylstearic acid, prepared from oleic acid and benzene, using the Friedel-Crafts reaction, has been confirmed to be a reproducible mixture of twelve positional isomers. Lithium and sodium salts of this acid are semi-crystalline solids which behave in many ways like pure single substances. The thermotropic polymorphism of these soaps has been studied using DSC and polarizing microscopy (as well as X-ray diffraction and ⁷Li NMR spectroscopy for the former soap). Both soaps exhibit characteristic stepwise melting behaviour and form stable reversed hexagonal mesophases at elevated temperatures, in contrast to the lamellar phases exhibited by the unsubstituted soaps.