bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanostructure and properties of ZnO films produced by the pyrosol process
Authors: Hammer Peter , Tokumoto Miriam S. , Santilli Celso V. , Pulcinelli Sandra H. , Craievich Aldo F. , Smith A.
Published: April 2003

Indium doped ZnO films were deposited by the pyrosol process on glass substrates at different temperatures from solutions containing In/Zn molar ratios up to 10%. The nanostructure of the films was investigated using grazing-incidence small-angle X-ray scattering (GISAXS). The mass density was determined by X-ray reflectivity and the composition by X-ray photoelectron spectroscopy. The GISAXS measurements revealed an anisotropic pattern for films deposited at 573 and 623 K and a isotropic one for those deposited at higher temperatures. The anisotropic patterns indicate the presence of elongated nanopores with their long axes perpendicular to the film surface. In contrast, the isotropic nature of GISAXS patterns of films grown at high temperatures (673 and 723 K) suggests the presence of spherical voids. The pore size distribution function determined from the isotropic patterns indicates a multimodal size distribution. On the other hand, the measured mass density of the doped films with isotropic nanotexture is higher than that of the anisotropic films while the electric resistivity is significantly lower. This is in agreement with the detected strong reduction of the void density and specific surface area at approximately constant pore size.
Small-angle X-ray and nuclear-magnetic resonance study of siloxane-PMMA hybrids prepared by the sol-gel process
Authors: Sarmento V. H. V. , Dahmouche K. , Santilli C. V. , Pulcinelli S. H. , Craievich A. F.
Published: April 2003

Transparent siloxane-polymethylmethacrylate (PMMA) hybrids were synthesized by the sol-gel process through hydrolysis of methacryloxyproyltrimethoxysilane (TMSM), tetramethoxysilane (TMOS) and polymerization of methylmethacrylate (MMA) using benzol peroxide (BPO) as catalyst. These composites have a good chemical stability due to the presence of covalent bonds between the inorganic (siloxane) and organic (PMMA) phases. The effects of siloxane content, pH of the initial sol and BPO content on the structure of the dried gels were analyzed by small-angle X-ray scattering (SAXS). SAXS results revealed the presence of an interference (or correlation) peak at medium q-range for all compositions, suggesting that siloxane groups located at the ends of PMMA chains form isolated clusters that are spatially correlated. The average intercluster distance - estimated from the q-value corresponding to the maximum in SAXS spectra - decreases for samples prepared with increasing amount of TMSM-TMOS. This effect was assigned to the expected increase in the number density of siloxane groups for progressively higher siloxane content. The increase of BPO content promotes a more efficient polymerization of MMA monomers but has no noticeable effect on the average intercluster distance. High pH favors polycondensation reactions between silicon species of both TMOS and TMSM silicon alcoxides, leading to a structure in which all siloxane clusters are bonded to PMMA chains. This effect was confirmed by 29Si nuclear-magnetic resonance (NMR) measurements.
Ion beam synthesis of buried Zn-VI quantum dots in SiO2 – grazing incidence small-angle X-ray scattering studies
Authors: Desnica-Frankovic I.D. , Desnica U.V. , Dubček P. , Buljan M. , Bernstorff S. , Karl H. , Grosshans I. , Stritzker B.
Published: April 2003

Grazing incidence small-angle X-ray scattering was used to study ion-beam synthesized Zn-VI compound-semiconductor quantum dots (QDs), buried in a SiO2 matrix. The ZnTe and ZnS QDs were formed by successive ion implantation of constituent atoms, at high ion doses and subsequent annealing at different temperatures in the 1070–1370 K range. In Zn and Te implanted SiO2, small nano-crystals were formed at higher annealing-temperatures, a bimodal size distribution of nano-particles was observed for both materials, which could be explained by an interplay of Ostwald ripening and enhanced diffusion in the irradiation-damaged region.
Small-angle X-ray scattering and X-ray absorption near-edge structure study of iron-doped siloxane-polyoxyethylene nanocomposites
Authors: Chiavacci L.A , Dahmouche K , Santilli C.V , de Zea Bermudez V , Carlos L.D , Briois V , Craievich A.F
Published: April 2003

The local and medium-range structures of siloxane-POE hybrids doped with Fe(III) ions and prepared by the sol-gel process were investigated by X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS), respectively. The experimental results show that the structure of these composites depends on the doping level. EXAFS data reveal that, for low doping levels ([O]/[Fe] > 40, oxygens being of the ether-type of the POE chains), Fe(III) ions are surrounded essentially by a shell of chlorine atoms, suggesting the formation of FeCl4
- anions. At high doping levels ([O]/[Fe] < 20), Fe(III) ions interacts mainly with oxygen atoms and form FeOx species. The relative proportion of FeOx species increases with iron concentration, this result being consistent with the results of SAXS measurements showing that increasing iron doping induces the formation of iron-rich nanodomains embedded in the polymer matrix.
Grazing incidence small-angle X-ray scattering studies of the synthesis and growth of CdS quantum dots from constituent atoms in SiO2 matrix
Authors: Desnica U.V. , Dubček P. , Desnica-Frankovic I.D. , Buljan M. , Bernstorff S. , White C.W.
Published: April 2003

Grazing incidence small angle X-ray scattering was applied to study the synthesis and growth of CdS quantum dots (QDs) from Cd and S atoms implanted in SiO2. For a dose of 1017/cm2, the partial synthesis of CdS QDs occurred already during implantation, with only moderate size increase upon subsequent annealing up to T
a=1073 K. The dynamics of QD synthesis and growth were considerably different for just two times lower dose, where synthesis started only if the implanted samples were annealed at T
a = 773 K or higher, with a strong increase of the size of QDs upon annealing at higher T
a. The results suggest that high-dose implantation followed by low-temperature annealing could lead to better defined sizes and narrower size distributions of QDs.
Small-angle X-ray scattering of extended defects in diamonds
Authors: Shiryaev A. , Dembo K. , Klyuev Yu. , Naletov A. , Feigelson B.
Published: April 2003

Results of the small-angle X-ray scattering (SAXS) of diamonds with different concentrations and types of optically-active defects are reviewed. It is shown that nitrogen-free (IIA) diamonds and diamonds with a low degree of nitrogen aggregation have no SAXS. Annealing of diamonds leads to the formation of three-dimensional clusters of defects with sizes in the range from ~8 to 60 nm. There is no correlation between nitrogen concentration and the existence or the size of the clusters, however, the clusters are related to the degree of diamond annealing. The presence of the clusters is unrelated to 'platelets' and they contain little, if any, nitrogen. With annealing, the size of the clusters decreases and the contrast of electronic density with the matrix increases.
Anomalous small-angle X-ray scattering in materials science
Authors: Goerigk Günter , Haubold Heinz-Günter , Lyon Olivier , Simon Jean-Paul
Published: April 2003

After the exploratory studies of the 1980s, anomalous small-angle X-ray scattering (ASAXS) is now a mature technique to disentangle complex subjects in materials science: this is illustrated through selected examples.
Two-dimensional camera for millisecond range time-resolved small- and wide-angle X-ray scattering
Authors: Urban Volker , Panine Pierre , Ponchut Cyril , Boesecke Peter , Narayanan Theyencheri
Published: April 2003

A combined small-angle and wide-angle X-ray scattering (SAXS/WAXS) camera has been implemented using area detectors suitable for real time experiments down to millisecond time range. The design is based on the existing high brilliance SAXS camera with a sample-to-detector distance variable from 1 m to 10 m and to which a two-dimensional WAXS detector is coupled. Two independent image intensified CCD detectors allow simultaneous real-time SAXS/WAXS experiments on oriented samples down to the millisecond time range. A wide scattering vector range spanning from 0.001 Å-1 to 6 Å-1 is covered by this combined setup. Both detectors have single photon sensitivity and the spatial resolution is about 200 μm. The WAXS detector is mounted at an angle inclined to the primary beam and the process of image transformation into non-arbitrary scattering vector coordinates is demonstrated for a standard p-bromobenzoic acid sample.
Pole figure analysis of mineral nanoparticle orientation in individual trabecula of human vertebral bone
Authors: Jaschouz Daniel , Paris Oskar , Roschger Paul , Hwang Hae-Sook , Fratzl Peter
Published: April 2003

The spongious interior of human vertebral bone consists of interconnected trabecula with a thickness of about 0.2 mm. The texture of the bone material, a collagen-mineral nanocomposite, was studied within single trabecula by collecting two-dimensional small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD) data exactly at the same specimen positions with an X-ray beam of 0.2 mm diameter. Three-dimensional information was reconstructed by combining measurements with different specimen orientations. The XRD data, and for the first time also the SAXS data, were subjected to a pole figure analysis. The method provides a quantitative description of the crystallographic orientation distribution as well as the morphological orientation distribution of the plate shaped nanoparticles, both with respect to the orientation of the investigated trabecula. As a main result it could be shown that a fibre-texture exists in the trabecula, and that the plate shaped nanoparticles are aligned with the lamellae within the trabecula.
Self-assembled structures of hydrophobins HFBI and HFBII
Authors: Ritva Serimaa , Torkkeli Mika , Paananen Arja , Linder Markus , Kisko Kaisa , Knaapila Matti , Ikkala Olli , Vuorimaa Elina , Lemmetyinen Helge , Seeck Oliver
Published: April 2003

Hydrophobins are small proteins that function in the growth and development of fungi. The structures of class II hydrophobins HFBI and HFBII from Trichoderma reesei were studied using grazing incidence X-ray diffraction. HFBI was weakly ordered but HFBII formed a highly crystalline coating on water surface. Change from monoclinic to hexagonal structure was observed as the sample dried. The three-dimensional structures differed from the oblique two-dimensional structures observed in Langmuir-Blodgett monolayers of both HFBI and HFBII by atomic force microscopy.
Right- / left-circular orientation of biological macromolecules under magnetic field gradient
Authors: Hirai Mitsuhiro , Koizumi Masaharu , Han Ru , Hayakawa Tomohiro , Sano You
Published: April 2003

In spite of many studies on phase behaviors and orientational phenomena of biological marcomolecular suspensions under magnetic field, a translational force from magnetic field gradient was paid less attention. We have developed a high-performance compact magnetic circuit that can apply both periodic magnetic field strength and gradient to samples. Owing to the periodicity of the magnetic field strength and gradient, macromolecules are subject to both rotational and translational forces from magnetic field. By using this magnet, we have carried out time-resolved small-angle X-ray scattering measurements on an orientational behavior of a biological supermolecular suspension under periodic magnetic field and gradient. The sample was tobacco mosaic virus (TMV) which is one of rod-shaped plant viruses. The time courses of the orientational processes of TMV were monitored by a two-dimensional CCD detector. We have found that right-circular or left-circular orientation of TMV appears depending on a combination of magnetic field and gradient directions. Such a translational force from magnetic field gradient is able to cause various interesting phenomena of macromolecular systems, which would be applicable to a control of nano-scale assembling processes of macromolecules.
New methods for domain structure determination of proteins from solution scattering data
Authors: Petoukhov Maxim V. , Svergun Dmitri I.
Published: April 2003

New approaches for domain structure determination of macromolecules from X-ray solution scattering are presented. An ab initio method for building structural models of proteins from the scattering data implemented in the computer program GASBOR employs simulated annealing to find a chain-like spatial distribution of dummy residues (DR), which fits the experimental scattering pattern up to a resolution of 0.5 nm. This method substantially improves the resolution and reliability of models derived from the scattering data. A modification of GASBOR fitting distance distribution data in real space substantially (by a factor of 3 to 7) speeds up the calculation of DR models. The DR approach is further extended to reconstruct missing domains in multisubunit proteins and fusion proteins and to find probable configurations of missing loops in crystallographic models. Four computer programs have been written to provide appropriate tools for different situations in which a high or low resolution structural model lacks a loop or domain. These methods permit solution scattering analysis to usefully complement the results obtained by high-resolution methods like X-ray crystallography and nuclear magnetic resonance spectroscopy. The efficiency of the presented approaches is illustrated by their application for structure analysis of several proteins, with known and unknown crystal structure, from experimental scattering data.
Structure and intermicellar interactions in block polyelectrolyte assemblies
Authors: Crichton Mark , Bhatia Surita
Published: April 2003

Amphiphilic diblock polyelectrolytes are becoming popular in industrial applications due to their versatility, ranging from usage in pharmaceuticals to personal care products. Many of these systems also exhibit interesting rheological and morphological behavior. Our system is based on a polystyrene-poly(ethyl acrylate) diblock. The properties can be tuned by utilizing a simple hydrolysis reaction, converting poly(ethyl acrylate) (PEA) to poly(acrylic acid) (PAA). We study the effect of this hydrolysis reaction on the interaction between micelles of polystyrene-poly(acrylic acid) in water using small-angle and ultra-small-angle neutron scattering. We see that as more PEA is converted to PAA, the aggregation number and polystyrene core size decrease. We also studied the effect of cationic (DTAB) and anionic surfactant (SDS) on the PS-PAA diblocks using small-angle neutron scattering. We see that as SDS is added, there are no significant changes in the micellar structure. However, on the addition of DTAB past the CMC, we observe changes in the spectra that may correspond to complexation between the PS-PAA micelles and DTAB aggregates.
An in situ cell for small-angle scattering experiments on nano-structured catalysts
Authors: Andreasen Jens Wenzel , Rasmussen Ove , Feidenhans'l Robert , Berg Rasmussen Frank , Christensen Robin , Molenbroek Alfons M. , Goerigk Guenter
Published: April 2003

The design, construction and operation of an in situ cell covering the temperature range from room temperature to 870 K with the sample in a controlled gas flow is demonstrated. The setup is designed specifically for acquiring small angle X-ray scattering data at the JUSIFA beam line at the Hamburger Synchrotronstrahlungslabor although it can be employed at other beam lines with only slight modifications. The cell is used for studying dynamic changes in size and morphology of nano structured catalyst particles.
Segmental contrast of dendrimers: a small-angle neutron scattering study including contrast variation
Authors: Dingenouts N. , Rosenfeldt S. , Werner N. , Vögtle F. , Lindner P. , Roulamo A. , Rissanen K. , Ballauff M.
Published: April 2003

We present an analysis of the distribution of endgroups within a urea-functionalized poly(propyleneamine)-dendrimer of 4th generation by small-angle neutron scattering (SANS). The contrast between the solute and the solvent is varied in a systematic fashion (contrast variation). The analysis of the scattering intensity corrected for incoherent contributions gives three partial scattering functions that depend differently on contrast. It is demonstrated that difference in contrast of the different segments of the molecules give an additional scattering contribution not related to the overall structure. From these data the scattering length density distribution within the dendritic structure can be derived. All results obtained for the fully protonated dendrimer under consideration here agree with the deductions obtained previously for a partially deuterated dendrimer having the same chemical structure.
Temperature-dependent three-dimensional small-angle scattering in semicrystalline polymers
Authors: Barnes John D. , Bras Wim
Published: April 2003

Processes for forming products from synthetic polymers often yield materials whose morphology is of low (orthorhombic, monoclinic, etc) symmetry. Characterizing such morphology by means of small-angle scattering (SAS) requires the mapping of the full three-dimensional scattering pattern from such materials. This requires special protocols in SAXS (small-angle X-ray scattering) or SANS (small-angle neutron scattering) experiments. SAS patterns from such experiments usually contain contributions from more than one scattering mechanism. In the case of semicrystalline polymers we have found that recording SAS patterns as a function of temperature allows the analyst to separate contributions arising from the two-phase morphology from those attributable to other effects such as voids and long-range molecular correlations. The synchrotron SAXS observations presented here extend our previous analysis of temperature-induced contrast variation in two-dimensional SAS patterns to two interesting three-dimensional cases.
Ultra-small-angle X-ray diffraction and scattering experiments using medium-length beamlines at SPring-8
Authors: Yagi Naoto , Inoue Katsuaki
Published: April 2003

Ultra-small-angle X-ray diffraction experiments were made at the two so-called medium-length beamlines at SPring-8. One is a bending magnet beamline (BL20B2) and the other an undulator beamline (BL20XU). Both have two experimental stations separated by 140–150 m. Specimens were placed in the first hutch and the diffraction or scattering patterns were recorded in the second hutch with an X-ray image intensifier or an imaging plate. At an X-ray energy of 12–21 keV, a small-angle resolution of 2 µm was achieved. The exposure time required to record sarcomere diffraction from frog skeletal muscle was 10 min at BL20B2 and 2 s at BL20XU. These results demonstrate the capability of these beamlines in ultra-small angle diffraction/scattering experiments.
Small-angle neutron scattering measurements with polarised neutrons on Fe–Ag magnetic granular systems
Authors: Spizzo F. , Angeli E. , Bisero D. , Da Re A. , Ronconi F. , Vavassori P. , Bergenti I. , Deriu A. , Hoell A.
Published: April 2003

Different Fe-Ag magnetic granular samples have been prepared by changing the relative Fe volume concentration. The evolution of their morphology with iron concentration has been studied by small angle scattering measurements performed with polarised neutrons. The particles average size determined from nuclear scattering data is about 7 Å and it does not change with varying Fe content. On the other hand, the shapes of nuclear and magnetic scattering curves are different in the range of sizes corresponding to magnetic particles, indicating that similar structures display different magnetic behaviours. Finally, the analysis of polarised neutron data suggests the existence of Fe rich regions with negligible magnetisation.
Fullerene - polymer complexes: fractal crossover in solutions
Authors: Lebedev Vassily , Török Gyula , Cser László , Len Adél , Orlova Diana , Zgonnik Vladimir , Melenevskaya Elena , Vinogradova Ludmilla , Treimer Wolfgang
Published: April 2003

Poly(vinylpyrrolidone)(PVP)-tetraphenylporphyrin(TPP)-C60-complexes in heavy water at concentration C
P=1 wt.% have been studied at 293 K. Starting from PVP+TPP-complex and doping it with C60 up to C~6 wt.%, we recognised complexes' structural evolution. We observed the changes from mass fractals with dimension D
M~2.3 at C=0 wt.% to surface fractals, having dimension D
S ~2.8 at C~2 wt.%. Then the system returns to mass fractals, D
M(C)~2.9-2.8 at C~5-6 wt.%. These structural peculiarities we explain as a result of cross linking action of fullerene, forming a microgel above a critical concentration C*~1 wt.%. Meanwhile, the network of over-doped complex (C~5 wt.%) is degraded, indicating a strong influence of fullerene on the water structure.
New high-flux small-angle neutron scattering instrumentation and the Center for Structural and Molecular Biology at Oak Ridge National Laboratory
Authors: Lynn G.W. , Buchanan M.V. , Butler P.D. , Magid L. J. , Wignall G.D.
Published: April 2003

A number of upgrades are currently being undertaken at the High Flux Isotope Reactor (HFIR), including the installation of a supercritical hydrogen moderator (T ~ 20 K) that will be one of the "brightest" cold sources currently available. It will feed four cold neutron guides (CG1-4), each with new instrumentation. CG2 and CG3 are reserved for two new small-angle neutron scattering (SANS) instruments. A 40 m SANS instrument (SANS1), funded by the Department of Energy (DOE) Office of Basic Energy Sciences and the University of Tennessee, Knoxville is designed for CG2. Our 35 m small-angle neutron scattering facility (SANS2 on CG3) is optimized for the study of biological systems as part of a Center for Structural and Molecular Biology (CSMB), funded by the DOE Office of Biological and Environmental Research. In addition to the new SANS facilities, there will be suite of instruments including a reflectometer and a cold triple-axis spectrometer. Both SANS facilities will have variable wavelength and large area (1m2) high count-rate detectors that can translate 45 cm off axis to increase the dynamic Q-range (< 0.001-1 Å-1 overall). As the HFIR is one of only two reactors with a core flux > 1015 neutrons/s/cm2, the beam intensities (up to 107/s/cm2) will be comparable to the best facilities worldwide and this will enhance our ability to collect data from synthetic and biological macromolecules more quickly and study smaller sample quantities.
Evaluation of anisotropic small-angle neutron scattering data; a faster approach
Authors: Strunz Pavel , Gilles Ralph , Mukherji Debashis , Wiedenmann Albrecht
Published: April 2003

An improvement of the anisotropic small-angle neutron scattering (SANS) data evaluation program is presented. The program is particularly suited for treatment of data from dense precipitate systems like those appearing in single crystal Ni-base superalloys. A new model of the precipitate microstructure was implemented allowing for a significant shortening of the evaluation time which is necessary mainly for in-situ studies. The change concerns the mode in which the size distribution is calculated. The local random smearing of the size as well as the distance of particles was introduced, too, which leads to a more realistic look of the microstructure model. The form of individual cuboidal particle was changed as well. The characteristics of the new microstructure model with respect to the SANS data modeling are tested on several measured as well as simulated data.
Small-angle scattering curves of densely packed particulate solids obtained by nucleation and growth kinetics
Authors: Garrido Victor , Pineda Eloi , Crespo Daniel
Published: April 2003

The computation of small-angle scattering (SAS) curves is still an open problem in densely packed systems. This fact reduces the applicability of SAS largely, in particular to solid-state densely packed systems. Solid-state transformations often follow nucleation and growth kinetics. In this case, even for isotropic growth the spherical symmetry of the precipitates is broken due to impingement, and their actual shape becomes unknown. However, in these systems the developed microstructure is given by the transformation kinetics. Because the SAS curve is given by the microstructure, the SAS curve should also be determined by the nucleation and growth protocol. In this work this link is revealed and the kinetics of the system is connected with the average radial density function. Statistical considerations allow us to determine the adequate inter-particle correlation function, enabling the computation of the SAS curve along the transformation. The formalism is applied to a system where grains appear randomly at initial time and grow with a constant growth rate (p-cell system). The resulting SAS curve at different times are computed and compared to Monte Carlo simulations, showing quantitative agreement for transformed fractions up to 95%.
Effect of drying on the structure and dispersion of precipitated silica
Authors: Suryawanshi C. N. , Pakdel P. , Schaefer Dale W.
Published: April 2003

We use a combination of light scattering and ultra-small-angle X-ray scattering (USAXS) to establish the effect of drying on the structure of reinforcing silica. The data show that drying substantially changes the morphology on two different length-scales corresponding to aggregates and agglomerates. The rather gentle process of oven drying leads to deeply interpenetrated aggregates that are clustered into agglomerates that exceed 100 µm in radius of gyration. Spray drying, on the other hand, produces agglomerates in the 20 µm range, made up of aggregates that are weakly interpenetrated. On incorporation in organic rubber, the fillers look structurally identical as far as aggregate morphology is concerned. These results, along with light scattering data on sonicated samples, show that oven-dried powders are made up of robust agglomerates. Spray-dried agglomerates are less interpenetrated and substantially more fragile, making them easier to disperse in rubber by mechanical means. This observation was confirmed by the measuring the modulus and elongation at break measurements of silica filled rubber.
Ultra-small-angle X-ray scattering studies of attractive colloidal glass transition
Authors: Pontoni D. , Narayanan T.
Published: April 2003

The microstructure of a colloidal system with short-ranged inter-particle interactions is studied by ultra-small-angle X-ray scattering (USAXS). A gas-liquid type transition can be induced when the short-ranged attractive interactions attain sufficient magnitude. The static structure factor revealed a systematic development of attractive interactions prior to the appearance of the liquid-like structure. The interparticle interaction in the close vicinity of the transition can be approximately described by a square-well potential with a hard-sphere repulsion. The colloid-rich phase is structurally similar to a liquid, but dynamically it shows extreme non-ergodic behaviour with a complete kinetic arrest. Furthermore, the USAXS intensity from the colloid-rich phase shows Porod behaviour indicating that the colloidal clusters have non-fractal morphology. The attractive term disappears when the domains develop towards their final size suggesting that particles within the clusters interact like hard spheres.
Solvent dependent arrangement of shell molecules in ferrofluids studied by small-angle scattering with polarized neutrons
Authors: Hoell Armin , Kammel Martin , Heinemann André , Wiedenmann Albrecht
Published: April 2003

Ferrofluids are stable dispersions of nano-sized magnetic particles coated by organic surfactants to prevent them from aggregation. For advanced medical applications, surfactants are chosen based on their ability to form complex bonding with immunoassays. We report on structural investigations of two identical Magnetite-ferrofluids with oleoylsarkosine as surfactant, which are stabilized in different solutions in water or in toluene. Combining contrast variation using polarized neutrons (SANSPOL) in combination with H/D isotope variation of solvents allows different magnetic and non-magnetic structural units of ferrofluids to be identified by small angle neutron scattering. Three structural parts, core-shell particles, aggregates and excess surfactants were found in both ferrofluids. Their size distributions and volume fractions were derived. As a main result the shell thickness of the surfactant, oleoylsarcosine, is found to be clearly different in water (2.3 nm ± 0.1 nm) and toluene (1.9 nm ± 0.1 nm) based ferrofluids. From that we conclude to have a bilayer formation in water and a monolayer in toluene. This indicates that bonding of the surfactants to the magnetic core is mediated via the hydrophilic acid group.
Nucleation and growth of CaCO3 minerals on biomimetic templates studied by small-angle scattering
Authors: Schwahn D. , Balz M. , Bartz M. , Fomenko A. , Tremel W.
Published: April 2003

The process of mineralization of CaCO3 on surfaces built up with DMAP (4-dimethylamino-pyridine) molecules was explored by time resolved SANS experiments. In most samples the DMAP molecules were attached to colloidal gold representing a model system of biomimetic template structures. The small-angle neutron scattering (SANS) data, however, show that DMAP forms in water a more complex structure built up of large (>1000 Å) and small aggregates of about 20 Å radius. The process of CaCO3 mineralization in a 0.1 M aqueous solution of CaCl2 was initiated by thermal decomposition of solid (NH4)2CO3 in a closed vessel. This process was followed in-situ by SANS over a time period of about 12 h. Experiments were performed with colloids plus DMAP concentrations between 0 and 49 mg/cm3 and at two temperatures. A further set of experiments was performed in solution containing a DMAP concentration of 15 mg/cm3 without colloidal gold. The process of mineralization could be characterized by the time evolution of size and number density of the mineralized particles as will be presented and discussed in this paper.
An analysis of a polymer additive for calcium carbonate crystallization - a small-angle neutron scattering investigation by applying contrast variation
Authors: Endo Hitoshi , Cölfen Helmut , Schwahn Dietmar
Published: April 2003

The role of the double-hydrophilic block copolymers (poly(ethylene glycol)-block-poly(methacrylic acid)) on the morphogenesis of calcium carbonate (CaCO3) was studied by applying contrast variation small-angle neutron scattering (SANS). The scattering function for ternary systems can be expressed by only partial scattering functions of the single species, as derived on the assumption of incompressibility. We demonstrate the feasibility of this formula by means of contrast variation SANS, and the decomposed partial scattering functions give their detailed information. Especially the partial scattering function of polymer shows a Q
−2.7 monotonic slope at low Q (0.002 Å < Q < 0.02 Å; Q is the modulus of the scattering vector), which is a clear evidence that the distribution of the polymer in CaCO3 has a mass fractal dimension. This result is confirmed by time-resolved SANS experiments with CaCO3 contrast, where a Q
−2.5 slope was observed at the early stage of the reaction in the same Q range.
Pore characteristics and water absorption in a synthetic smectite clay
Authors: Knudsen Kenneth D. , Fossum Jon Otto , Helgesen Geir , Bergaplass Vegard
Published: April 2003

Information on size and shape of pores in layered silicates can be obtained via analysis of the relative scattered intensity for different scattering vectors. In this study the small-angle neutron scattering technique was used to investigate the synthetic clay Na-fluorohectorite. The anisotropically shaped pores showed an average correlation length ratio of about 1:2 between the direction of sedimentation and the direction perpendicular to this. The absorption of water, which can be controlled via the temperature and humidity of the surrounding air, consists both in the intercalation of water molecules between the clay platelets and the filling of the mesopores between the platelet stacks.
Separation of scattering contributions from carbides and γ' precipitates in Nimonic 80a by combining small-angle X-ray and neutron scattering
Authors: Zickler Gerald Andreas , Tian Baohui , Lind Christoph , Paris Oskar
Published: April 2003

If small-angle scattering investigations are performed on aged Nimonic 80a, the signal consists of scattering contributions from carbides and γ' precipitates. The carbides account for a considerable amount of the scattering signal because of their high scattering contrast, although their volume fraction is much smaller than that of γ'. By combining small-angle X-ray and neutron scattering on the same samples, a simple model is developed to describe the scattering profiles. The model allows a separation of the contributions from carbides and γ' precipitates and shows good agreement with observations from transmission electron microscopy. By analysing the kinetics of γ' coarsening for different ageing temperatures, an estimate for the specific interfacial energy of γ' is obtained.
Characterization of heterogeneities in new-generation synthetic quartz crystals by small-angle X-ray scattering
Authors: Guzzo P. L. , Shinohara A. H. , Pasquali M. A. , Gusken E. , Suzuki C.K. , Azevedo W. M. , Mikawa Y.
Published: April 2003

Small-angle X-ray scattering was employed to investigate heterogeneities in growth sectors of a large Z-bar synthetic quartz. The measurements were performed in as-grown and heat-treated samples. As a result, X-ray scattering was observed in all samples. The Guinier approximation revealed a polydispersive distribution of heterogeneities in as-grown samples with a radius of gyration ranging from 80 to 250 Å. Infrared spectroscopy and X-ray fluorescence analysis were used to elucidate the nature of these heterogeneities. Considerable variations in the intensity of scattered X-rays due to heat treatments were only noticed in growth sectors with high OH-content. The results suggest that tiny aggregates of molecular water are the main reason for the scattering patterns observed in the range 0.006 < q < 0.1 Å-1.
A high sensitivity pinhole camera for soft condensed matter
Authors: Zemb Thomas , Tache Olivier , Né Frédéric , Spalla Olivier
Published: April 2003

A significant improvement in the sensitivity of a Huxley-Holmes design for a small angle X-ray scattering camera is obtained by separating the mirror and the monochromator. The "separated optics" camera described in this paper involves a long X-ray mirror close to a point X-ray source associated with a curved focusing crystal located close to the sample. The sample area is located at half the distance between the source and detector planes. Diffuse scattering produced by the mirror is not incident on the focusing crystal, thus reducing the background signal. Complete elimination of hard X-rays allows precise calibration and hence absolute determination of sample cross-section by means of a semi-transparent beam-stop. In pinhole geometry, the flux corresponds to a ca. 107 photons/s through the sample, collimated to q=10-2 Å-1 in scattering vector range. This allows determination of scattered intensities of the order of 10-3 cm-1, corresponding to the scattering related to isothermal compressibility of less than 0.1 mm of pure water. Values of absolute intensities for water as well as convenient widespread buffer solutions are shown, in order to be usable for calibration as secondary standards. As solid reference sample, the widely studied Lupolentm – a semi-crystalline polymer- is calibrated. The high-q limit (q ≃ 4.5 nm–1 ) of a porous calcite sample can be used as a secondary standard for specific area determination of solid/solid or solid-liquid dispersions.
Comparative study of porosity in 3Y-TZP superplastic ceramics by ultra-small-angle neutron scattering and scanning electron microscopy image analysis
Authors: Ryukhtin Vasyl , Šaroun Jan , Harjo Stefanus , Motohashi Yoshinobu , Baron Matthias , Loidl Rudolph
Published: April 2003

Recent measurements of cavitation in superplastically strained 3Y-TZP ceramics by scanning electron microscopy and ultra small-angle neutron scattering (USANS) led to systematic differences in volume fractions of cavities determined by both methods. We show that the scattering curves measured by double crystal USANS diffractometers can be calculated directly from scanning electron micrographs taken from a single section of the material, without any assumptions of cavity shape or distribution. This technique was used to compare the USANS measurements with electron micrographs and showed that the calculated and measured curves agree well for medium scattering vectors. This result confirms that the electron micrographs represent well the microstructure of small cavities up to about 0.6 μm in radius. On the contrary, the calculations resulted in systematically larger intensities for small scattering vectors. This indicates that large cavities are responsible for the observed differences in volume fraction for the samples with nominal strain above 100%. An explanation by an inhomogeneous distribution of large cavities generated at high strains in the bulk of the tensile specimen and/or by surface artifacts is suggested.
Polarised neutron investigation of iron composite nanoparticles
Authors: Bergenti I. , Deriu A. , Savini L. , Bonetti E. , Hoell A.
Published: April 2003

Iron nanoparticles obtained by the inert-gas condensation technique have been analysed by small-angle polarised neutron scattering. The use of polarised neutrons allows a more precise determination of the magnetic scattering length profile inside each particle giving information about the magnetic order. In iron nanoparticles surrounded by an oxide layer (core-shell structure), the magnetic scattering length profile indicates that the oxide layer is weakly magnetised. In the case of intermixing with copper nanoparticles, the nuclear contributions are well described by a bimodal size distribution.
Small-angle X-ray scattering study of the growth kinetics of CuCl nanocrystals in NaCl
Authors: Kranold R. , Kriesen S. , Haselhoff M. , Weber H.-J. , Goerigk G.
Published: April 2003

The precipitation of CuCl nanocrystals in a NaCl matrix has been studied by time-resolved small-angle X-ray scattering. The experimental results suggest that the nucleation process is accelerated by lattice defects of the matrix remaining in the NaCl lattice after the dissolution of previous nanocrystals at high temperature. The evolution of structural parameters calculated from the scattering curves, such as volume fraction, mean radius and particle number density of the nanocrystals, is discussed in terms of a classical phase separation process but with specific concern for the effect of elastic strains. It was found that Ostwald ripening is effective during the whole period of observation. The effect of elastic strains results in an increase of the critical radius and a decrease of the coarsening rate. The results of the scattering experiments confirm the miscibility gap data determined by exciton spectroscopy.
Direct observation of the crystallization of fat in a Drosophila fly body by small- and wide-angle X-ray scattering
Authors: Takahashi Hiroshi , Ueno Satoru , Katagiri Chihiro
Published: April 2003

Many overwintering livings accumulate fat (triacylglycerol) before winter and use it for basal metabolism. However, triacylglycerol in solid state is not digested by lipase. Therefore, it is expected that livings using fat during overwintering have some special strategies to avoid crystallization of fat at low temperatures. In order to clarify the strategies, Ohtsu et al. have studied the phase behavior of fat extracted from the cold-adapted Drosophila flies [Ohtsu, T., Katagiri, C., Kimura, M. T. & Hori, S. H. (1993). J. Biol. Chem. 268, 1830-1834]. It is, however, uncertain that the results obtained from the extracted fat can reflect the in vivo phenomena. In the present study, we investigated the crystallization of fat in a fly body with small- and wide-angle X-ray scattering, and detected the Bragg diffraction peaks that can be assigned to those originated from the solid triacylglycerol crystallized in the fly body below 253 K (– 20 oC).
Locating the minor components of double-stranded RNA bacteriophage φ6 by neutron scattering
Authors: Ikonen Teemu , Kainov Denis , Timmins Peter , Serimaa Ritva , Tuma Roman
Published: April 2003

The polymerase core of double-stranded (ds) RNA virus provides the molecular machinery for RNA packaging and replication. Procapsid of bacteriophage φ6 constitutes the best studied model of such dsRNA-processing machine. A total of 120 copies of protein P1 form the procapsid framework to which other proteins are attached. Due to their low abundance minor procapsid constituents, P2 (RNA polymerase) and P7 (packaging factor), have not up to now been localized. We have applied small-angle neutron scattering (SANS) and contrast variation in order to localize the two proteins. Procapsids containing deuterated P2 or P7 were produced in vitro and SANS was collected at several contrast levels. Radial positions of labeled proteins were obtained and modeled within the electron density of the procapsid. P2 monomers reside at each five-fold vertex just under the RNA packaging complex. P7 was detected at a distance of 160 Å from the procapsid center indicating localization on the inner surface of P1 framework.
Modeling of protein solution structures
Authors: Zipper Peter , Durchschlag Helmut
Published: April 2003

Reconstructions of low-resolution three-dimensional solution structures of proteins from one-dimensional small-angle X-ray scattering (SAXS) data can be achieved by trial-and-error or ab initio approaches. It is demonstrated that all tested advanced approaches (GA, DAMMIN, SAXS3D) reproduce the shape of three selected test proteins (malate synthase, cellobiose dehydrogenase, extracellular hemoglobin). The agreement between SAXS profiles and functions derived from beaded model structures and experimental data, however, varies with respect to the angular range covered; the same holds true for the accuracy of the molecular parameters calculated from the respective patterns. The uniqueness of the structures obtained is crucial and may be increased by combined use of different approaches. The obtained models can be used for predicting both structural and hydrodynamic data with a high degree of probability.
Characterization of materials of industrial importance using small-angle scattering techniques
Authors: Thiyagarajan P.
Published: April 2003

Small angle scattering (SAS) techniques using either X-rays or neutrons are versatile tools for deriving information on the size, morphology and dispersion of colloidal systems in complex materials of industrial importance. The processes such as self-assembly, aggregation, crystallization and phase separation can be studied using SAS techniques at relevant conditions. The difference in the interaction of X-rays and neutrons with matter enables complementary contrast variation studies using SANS and anomalous SAXS (in the presence of metals) on multi-component materials with hierarchical structures. In this paper we present results from small angle scattering studies on a number of systems of industrial importance including, temperature/pressure/shear dependent phase behaviour of pluronics in aqueous media, solution structures of aggregates/polymers of metal-extractant complexes, third phase formation of metal-extractant complexes in organic phase, encapsulation of lanthanides and actinides in porous silica and phase separation and nanocrystallization in bulk metallic glasses.
Characterization of the porosity developed in a new titania-alumina catalyst support prepared by the sol gel route
Authors: Kaneko E.Y. , Pulcinelli S.H. , Santilli Celso V. , Craievich Aldo F. , Chiaro S.S.X.
Published: April 2003

Titanium oxide (TiO2) is a good candidate for support of hydrotreating catalysts but has the disadvantage of presenting a low surface area and a poor thermal stability when compared with Al2O3. A mixed TiO2-Al2O3 support was proposed as an alternative that is expected to be free from these drawbacks. The variation during firing of the nanoporous texture of supports composed of TiO2-Al2O3, TiO2 and Al2O3 was studied by small-angle X-ray scattering (SAXS). The supports were prepared by the sol-gel route using Ti and Al isopropoxides. We have particularly analyzed the effects of acid and basic hydrolysis on the nanostructural features of catalyst supports fired at different temperatures. The nanopore radius distribution functions were determined from SAXS results assuming a simple model of spherical nanopores embedded in a homogeneous solid matrix. The modal pore radius in both pure TiO2 and pure Al2O3 supports grows from 1.3 to 2.2 nm as the firing temperature increases from 673 to 973 K. On the other hand, the modal pore radius in the mixed TiO2-Al2O3 support remains below 1.2 nm over the same range of firing temperatures. These results demonstrate the good thermal stability of the nanoporous texture of mixed TiO2-Al2O3 supports.
Displacement measurements from nanoprecipitates in alloyed Cu single crystals using anomalous small- and wide-angle X-ray scattering
Authors: Guillon I. , Lyon O. , Servant C.
Published: April 2003

Single crystals of Cu-3Ti, Cu-41.5Ni-16Fe and Cu-23Ni-7Fe (at. %) were studied by anomalous small-angle and wide-angle X-ray scattering in order to determine the displacements induced by the precipitates (ordered Cu4Ti rods in the first case or (Ni,Fe) discs in the other cases) as a function of ageing time and temperature. The small-angle scattering patterns give information on the size and arrangement of the precipitates, while the scattering around the Bragg peak allows the elastic lattice distortions around these precipitates to be determined. The precipitates formed in these three alloys are elastically contracted while the matrix enriched in Cu atoms is dilated. This succession of compressed and dilated regions is responsible for the alignment of the precipitates along the elastically soft directions <100>.
Essential role of w/o microemulsion structure on catalytic activity of entrapped proteins studied by small-angle X-ray scattering and circular dichroism
Authors: Kawai-Hirai Rika , Hirai Mitsuhiro
Published: April 2003

For understanding the mechanism of enhancement of catalytic activity of proteins in w/o microemulsions, it is very important to clarify a relation between structural characteristics of w/o microemulsion and occluded protein. We have studied the structure and catalytic activity of two different types of bovine serum albumins occluded in biological solvent / sodium bis(2-ethylhexyl)sulfosuccinate (AOT) / 2,2,4-trimethylpentane (isooctane) microemulsions. The secondary structures of the albumins both in AOT w/o microemulsions and in aqueous buffer solvents containing AOT have been measured by using circular dichroism. The structures of AOT microemulsions occluding the proteins have been studied by using synchrotron radiation small-angle X-ray scattering. We will show the detailed relation between the microemulsion structure and the catalytic activity of the proteins.