共查询到20条相似文献,搜索用时 21 毫秒
1.
应用中子小角散射技术研究了水溶液中富勒烯-PVP聚合物的链团结构及其大小以及它们在不 同富勒烯含量下的变化.结果表明:当加入富勒烯后,不论是PVP单体分子链还是大分子链团 ,其相关长度与纯PVP溶液相比均变小,且大分子链团的变化更为明显;在不同富勒烯含量 情况下,高富勒烯含量的富勒烯-PVP分子链团的体积更小.
关键词:
中子小角散射
富勒烯
PVP聚合物 相似文献
2.
N. O. Elyutin D. V. L’vov E. V. Rakshun A. N. Tyulyusov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(3):585-590
A procedure for studying multiple small-angle neutron scattering using a double-crystal spectrometer is presented. It is based on measuring the linear coefficient of beam attenuation caused by smallangle scattering. The method has been substantiated theoretically, and the range of its applicability has been determined. 相似文献
3.
Lautrup B Appali R Jackson AD Heimburg T 《The European physical journal. E, Soft matter》2011,34(6):1-9
Internal structures of agar-gelatin co-hydrogels were investigated as a function of their volumetric mixing ratio, $\ensuremath r=[\mathrm{AG}]:[\mathrm{Ge}]=0.5Internal structures of agar-gelatin co-hydrogels were investigated as a function of their volumetric mixing ratio, [Formula: see text] , 1.0 and 2.0 using dynamic light scattering (DLS), small-angle neutron scattering (SANS) and rheology. The degree of non-ergodicity ( X = 0.2 ± 0.02) , which was extracted as a heterodyne contribution from the measured dynamic structure factor data remained less than that of homogeneous solutions where ergodicity is expected (X = 10. The static structure factor, I(q) , results obtained from SANS were interpreted in the Guinier regime (low-q , which implied the existence of ≈ 250 nm long rod-like structures (double-helix bundles), and the power law (intermediate-q regions) yielded I (q) ~ q(?α) with α = 2.3 , 1.8 and 1.6 for r = 0.5 , 1.0 and 2.0. This is indicative of the presence of Gaussian chains at low r , while at r = 2 there was a propensity of rod-shaped structures. The gel strength and transition temperatures measured from frequency sweep and temperature ramp studies were suggestive of the presence of a stronger association between the two biopolymer networks at higher r . The results indicate that the internal structures of agar-gelatin co-hydrogels were highly dependent on the volumetric mixing ratio. 相似文献
4.
The dependence of the spectra of small-angle multiple neutron scattering on the volume fraction occupied by scattering grains is considered. The concentration expansion is used to develop scattering theory in the eikonal approximation. The leading term of the expansion reproduces the standard low-concentration theory (Mollier). Some properties of the first correction term are analyzed, and it is shown that the angular distribution narrows with an increase in concentration, in qualitative agreement with the experimental data. 相似文献
5.
D.?Honecker A.?Ferdinand F.?D?brich C. D.?Dewhurst A.?Wiedenmann C.?Gómez-Polo K.?Suzuki A.?Michels 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(2):209-213
Due to recent progress in the development of 3He spin filters, it has only now become possible to perform routinely longitudinal (one-dimensional) neutron-spin analysis
(POLARIS) in small-angle neutron scattering (SANS) experiments. It is the purpose of this article to provide a brief introduction
into the technique and to discuss first experimental data. In particular, for the most common scattering geometry where the
applied magnetic (guide) field is perpendicular to the incident neutron beam, we write down the equations for the non-spin-flip
and spin-flip SANS cross sections of a bulk ferromagnet, and we discuss the various angular anisotropies and asymmetries along
with some selected experimental results on an FeCr based soft magnetic nanocrystalline alloy. In particular, we show that
the analysis of the spin-flip data allows one to obtain the magnitude-squares of the three vector (Fourier) components of
the magnetization. 相似文献
6.
Morten Ring Eskildsen 《Frontiers of Physics》2011,6(4):398-409
Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba(Fe0.93Co0.07)2As2. 相似文献
7.
Yu. G. Abov D. S. Denisov N. O. Elyutin S. K. Matveev Yu. I. Smirnov A. O. Éidlin F. S. Dzheparov D. V. L’vov 《Journal of Experimental and Theoretical Physics》1998,87(6):1195-1200
The asymptotic behavior of the spectra for large values of the scattering vector for the case of elastic multiple small-angle
neutron scattering (SANS) is investigated theoretically and experimentally. An expansion of the spectrum in terms of the reciprocal
of the magnitude of the momentum transfer is obtained taking account of the influence of the instrumental line. It is shown
that, to within some factor, the leading term of the expansion is identical to the differential single-scattering cross section
averaged over a statistical ensemble of particles; several subsequent terms in the expansion are calculated and the range
of applicability of the resulting expressions is determined. The asymptotic behavior of the multiple SANS spectrum is measured,
using a two-crystal neutron spectrometer, for samples of an HTSC ceramic, the alloy Fe-Ni, and Al powder. The agreement between
the experimental results and the theoretical predictions is analyzed.
Zh. éksp. Teor. Fiz. 114, 2194–2203 (December 1998) 相似文献
8.
Pencer J Mills T Anghel V Krueger S Epand RM Katsaras J 《The European physical journal. E, Soft matter》2005,18(4):447-458
Using coarse grained models of heterogeneous vesicles we
demonstrate the potential for small-angle neutron scattering
(SANS) to detect and distinguish between two different categories
of lateral segregation: 1) unilamellar vesicles (ULV) containing a
single domain and 2) the formation of several small domains or
“clusters” (~10 nm in radius) on a ULV. Exploiting the
unique sensitivity of neutron scattering to differences between
hydrogen and deuterium, we show that the liquid ordered (lo)
DPPC-rich phase can be selectively labeled using chain deuterated
dipalymitoyl phosphatidylcholine (dDPPC), which greatly
facilitates the use of SANS to detect membrane domains. SANS
experiments are then performed in order to detect and
characterize, on nanometer length scales, lateral heterogeneities,
or so-called “rafts”, in ~30 nm radius low polydispersity
ULV made up of ternary mixtures of phospholipids and cholesterol.
For 1:1:1 DOPC:DPPC:cholesterol (DDC) ULV we find evidence for the
formation of lateral heterogeneities on cooling below 30 °C. These heterogeneities do not appear when DOPC is
replaced by SOPC. Fits to the experimental data using coarse
grained models show that, at room temperature, DDC ULV each
exhibit approximately 30 domains with average radii of ~10 nm. 相似文献
9.
《Comptes Rendus Physique》2012,13(3):246-256
Small-angle scattering enables the extraction of precise, quantitative information about nano-scale precipitate microstructures. It can be used with X-rays (SAXS) or neutrons (SANS). This paper presents simple methods for extracting information on the precipitate size and volume fraction from SAS spectra. The various possibilities for obtaining precipitate size are reviewed, and the meaning of their differences is discussed. Examples of applications for complex precipitate microstructure measurements are given in the following areas: kinetic in-situ measurements in Fe–Cu and Fe–Nb–C alloys, non-stoichiometric precipitation in an Al–Zn–Mg–Cu alloy studied by anomalous SAXS (ASAXS), and precipitation mapping in weld cross-sections. 相似文献
10.
Yu. V. Kul’velis S. V. Kononova K. A. Romashkova V. T. Lebedev 《Physics of the Solid State》2014,56(1):86-90
The structure of gradient-porous (asymmetric) membranes based on polyamide imide at different conditions of their formation has been investigated using small-angle neutron scattering. It has been shown that the membranes consist of rigid porous networks with well-defined interfaces between the polymer and the pores. It has been found that there are differences in the packings of structural elements of porous membranes-spherical pores with radii from 4 to 100 nm—depending on the membrane preformation time, drying regime, and the presence of fullerene C60 for modifying the mechanical and selective properties of membranes. The membranes also contain larger pores of micrometer sizes. Differences in the rates of saturation of membranes with water and their limiting swelling ratios are found, which can be explained by the structure of the dense layers of membranes (skin layer) and their different hydrophilities (depending on the fullerene content). 相似文献
11.
12.
T. Striffler U. Stuhr H. Wipf H. Hahn S. Egelhaaf 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):245-251
By means of small-angle neutron scattering the microstructure of two nanocrystalline Pd samples (prepared by inert gas condensation)
has been studied at room temperature in a Q-range from [0pt] to [0pt] . An additional subsequent doping of the two samples with H as well as with D (concentrations < 4 at%) caused contrast variations
that provided more detailed structural information. The measured scattering intensity was modeled by a Porod contribution
from large heterogenities (e.g. pores) and a contribution from spherical grains with a log-normal distribution of their radii. To account for the presence
of grain boundaries, the grains were considered to be surrounded by a shell with a reduced Pd density and a thickness half
as large as the thickness of the grain boundaries. For the above model, the data of the H-doped, D-doped and undoped sample
were simultaneously fitted with one single set of adjustable parameters. The fits yielded for the two samples volume-weighted
mean grain radii of 10 nm and 13 nm. The values for the grain boundary thickness lie between 0.2 and 0.8 nm. Almost all of
the H- and D-atoms are, at low hydrogen concentrations, located in the grain boundaries.
Received 1 May 2000 相似文献
13.
Small angle neutron scattering (SANS) and its contrast-matching variant are employed in order to determine structural properties (inter-pillar distances and mass/surface fractal dimensions of the clay layers and pillars) of a series of smectite natural clays (montmorillonite, beidellite, and bentonite) and their pillared and pillared/ion-exchanged analogues. Moreover, a comparative analysis with the adsorption data is carried out on the basis of a systematic study of the structural changes induced by a particular treatment or modification (e.g. pillaring) of the clay systems. 相似文献
14.
V. V. Isaev-Ivanov D. V. Lebedev H. Lauter R. A. Pantina A. I. Kuklin A. Kh. Islamov M. V. Filatov 《Physics of the Solid State》2010,52(5):1063-1073
The nucleosome structure in native nuclei of normal (chicken erythrocyte and rat leukocyte nuclei) and anomalously proliferating
(the human cervical adenocarcinoma cell line HeLa and the Chinese hamster fibroblast cell line A238) cells has been investigated
using small-angle neutron scattering. The experimental results obtained allow one to make the inference that the parameters
of the nucleosome structure for the chicken erythrocyte and rat leukocyte nuclei (on average over the nucleus) are close to
the universally accepted values and that the distance distribution function is bimodal. The bimodality of the distance distribution
function reflects a narrow distribution of distances between nucleosomes (on average over the nucleus) at the fibril level
of the chromatin organization. The histone core of the nucleosome structure in the nuclei of the HeLa and A238 cells (on average
over the nucleus) is considerably less compact than that in the chicken erythrocyte and rat leukocyte nuclei, and the distance
distribution function does not exhibit indications of the bimodality. 相似文献
15.
The analysis of the spatial structure of a rigid polyphenylene dendrimer G4-M of fourth generation by small-angle neutron scattering (SANS) is presented. This dendrimer is composed of phenyl units and is therefore devoid of any flexible unit. The scattering intensity of dilute solutions of the dendrimer was measured by SANS at different contrast which was adjusted by mixtures of protonated and deuterated toluene. Hence, the method of contrast variation could be applied and the data yield the scattering function extrapolated to infinite contrast. The comparison of this data with simulations demonstrates that the scaffold of the dendrimer is rigid as expected from its chemical structure. The positions of the various units setting up consecutive shells of the dendrimer are relatively well localized and the entire structure cannot be modeled in terms of spherically symmetric models. No backfolding of the terminal groups can occur and the model calculations demonstrate that higher generations of this dendritic scaffold must exhibit a dense shell and a congestion of the terminal groups. This finding is directly corroborated by recent solid-state NMR data. All results show that the rigid dendrimer investigated here presents the first example for a dendritic structure whose segment density does not have its maximum at the center. Rigid scaffolds are therefore the only way to achieve the goal of a “dense-shell” dendrimer whereas flexible scaffolds leads invariably to the “dense-core” case. 相似文献
16.
V. I. Petrenko V. L. Aksenov M. V. Avdeev L. A. Bulavin L. Rosta L. Vekas V. M. Garamus R. Willumeit 《Physics of the Solid State》2010,52(5):974-978
The structures of several aqueous magnetic fluids stabilized by different combinations of surfactants have been compared using small-angle neutron scattering. The size distribution functions of colloidal particles in water have been determined. The degree of clustering of magnetic nanoparticles has been obtained from comparison with electron microscopy data. The combinations of surfactants that lead to a minimum clustering have been revealed. 相似文献
17.
18.
A. V. Nagornyi V. I. Petrenko M. V. Avdeev L. A. Bulavin V. L. Aksenov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(6):976-981
The possibility to conduct the experiment on small-angle neutron scattering on very dilute magnetic fluids (the volume fraction
of magnetite is ∼0.1%) is discussed. The aim of these experiments is to determine the structural parameters of these fluids
using the Guinier approximation. Primary attention is concentrated on the experimental observation of a nonmagnetic layer
on the surfaces of magnetic nanoparticles dispersed in a liquid carrier. Significant parameters are determined, and conditions
for the experiment on the contrast variation are chosen in model calculations. 相似文献
19.
Pautrat A Goupil C Simon Ch Charalambous D Forgan EM Lazard G Mathieu P Brûlet A 《Physical review letters》2003,90(8):087002
We report small-angle neutron scattering measurements on the vortex lattice in a PbIn polycrystal in the presence of an applied current. Using the rocking curves as a probe of the distribution of current in the sample, we observe that vortex pinning is due to the surface roughness. This leads to a surface current that persists in the flux-flow region. We show the influence of surface treatments on the distribution of this current. 相似文献
20.
V. M. Lebedev V. T. Lebedev V. V. Runov O. P. Smirnov B. Z. Margolin A. M. Morozov N. E. Pirogova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2016,10(6):1154-1160
The results of neutron studies of the metal nanostructure of anticorrosive cladding for vessels of WWER -1000 nuclear reactors under different conditions of additional tempering are presented. In the anticorrosive-cladding material, small structural components (inhomogeneities) with a correlation radius of 2–3 nm are observed which form fractal structures with a scale of more than 100 nm. It is shown that at different annealing temperature, these small objects create new structures at crystal boundaries in the form of defect surfaces with the fractal dimension D s = 2.4–2.6. In samples of anticorrosive cladding, nonmagnetic austenitic γ-phase iron (γ-Fe) and magnetic δ-ferrite (α-Fe) are observed. The alloy is found to be magnetically hard. 相似文献