排序方式: 共有47条查询结果,搜索用时 15 毫秒
1.
M. Balasoiu M. L. Craus E. M. Anitas I. Bica J. Plestil A. I. Kuklin 《Physics of the Solid State》2010,52(5):917-921
Stomaflex elastomers filled with two types of magnetic particles (nano- and micro-sized) were investigated. It was observed
that doping with Fe3O4 nanoparticles and applying a magnetic field during the polymerisation process led to a significant change in the local structure
of the elastomer. Decreases in the quasi-crystalline phase concentration, in the average size of the crystalline blocks, and
in the ordering distance were observed after doping the elastomer with magnetite nanoparticles. After filling the polymer
with Fe3O4 nanoparticles, yet the elastomer fractal dimension changes. For the elastomer filled with a large amount of Fe microparticles
(75% particle concentration) a texture effect is observed, and this effect is larger for the samples polymerised in a magnetic
field. At all microparticle concentrations, these elastomers exhibit surface fractal structure. 相似文献
2.
Elisabeth-Jeanne Popovici Mihail Nazarov Laura Muresan Do Young Noh Marius Morar Ecaterina Bica Emil Indrea 《Radiation measurements》2010,45(3-6):300-303
Terbium activated yttrium niobium tantalate phosphors were prepared by solid-state reaction and were characterized by photoluminescence measurements, X-ray diffraction and scanning electron microscopy. Photoluminescence (PL) of Y0.95Tb0.05Ta1?xNbxO4 phosphors (x = 0–1) are influenced by the host-lattice composition, degree of crystalline order and particle morphology and size. The effect of the morpho-structural properties on PL characteristics of Y(Ta,Nb)O4:Tb powders is reported. 相似文献
3.
Nicolae Aldea Rodica Turcu Alexandrina Nan Izabella Craciunescu Ovidiu Pana Xie Yaning Zhonghua Wu Doina Bica Ladislau Vekas Florica Matei 《Journal of nanoparticle research》2009,11(6):1429-1439
In this article, we focus on the structural peculiarities of nanosized Fe3O4 in the core-shell nanocomposites obtained by polymerization of conducting polypyrrole shell around Fe3O4 nanoparticles. The local structure of Fe atoms was determined from the Extended X-ray Absorption Fine Structure analysis
using our own package computer programs. An X-ray diffraction method that is capable to determine average particle size, microstrains,
as the particle size distribution of Fe3O4 nanoparticles is presented. The method is based on the Fourier analysis of a single X-ray diffraction profile using a new
fitting method based on the generalized Fermi function facilities. The crystallites size obtained by X-ray diffraction spectra
analysis was estimated between 3.2 and 10.3 nm. Significant changes in the first and the second Fe coordination shell in comparison
with standard bulk were observed. The global and local structure of the nanosized Fe3O4 are correlated with the synthesis conditions of the core-shell polypyrrole nanocomposites. 相似文献
4.
Ioan Bica 《Journal of magnetism and magnetic materials》2004,270(3):321-326
The magnetorheological suspension (MRS) brake is of the monoblock type. The main part of the electromagnetic brake is an electromagnet, between whose poles two MRS disks are placed. For distances between disks of 0.65×10−3 m±10%, revolutions of the electric motor, coupled to the electromagnetic brake, ranging between 200 and 1600 rev/min and braking powers of up to 85 W, there are no differences in revolutions between the disks of the electromagnetic brake. For fixed revolutions of the electric motor, the revolution of the parallel disk can be modified continuously by means of the intensity of the magnetic field. In all cases, the quantity of MRS is of 0.35×10−3 kg. 相似文献
5.
Ioan Bica 《Plasma Chemistry and Plasma Processing》2003,23(1):175-182
A chamotte rod is transformed in vapors through chemical reactions, at temperatures exceeding 5000 K. SiO2 micro-tubes formation is determined by a low vapor concentration and a stable vapor flow, along the streamlines of the plasma jet, and, respectively, by the difusion processes, in non-stationary regime, inside the liquid membrane. A mass of SiO2 vapor, in the range of 0.5×10–8 kg–10×10–8 kg, allows one to obtain micro-tubes with the outer diameter between 6.2 and 28.8 m and the inner diameter between 3.8 and 12.2 m. 相似文献
6.
A. V. Feoktystov M. V. Avdeev V. L. Aksenov L. A. Bulavin D. Bica L. Vekas V. M. Garamus R. Willumeit 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(1):1-4
A magnetic fluid with magnetite dispersed in D-benzene and stabilized by myristic acid is investigated using the contrast variation technique in small-angle neutron scattering. The results obtained are interpreted within a new approach to the basic functions for polydisperse multicomponent and superparamagnetic systems. Myristic acid is considered an alternative to oleic acid, which is commonly used in these fluids. The parameters characterizing the particle size distribution function and the thickness of the myristic acid layer are determined. The data obtained are in good agreement with the results derived from previous investigations with the use of polarized neutrons. 相似文献
7.
Mendonça CR Bica CI Piatnicki CM Simó-Alfonso EF Ramis-Ramos G 《Electrophoresis》2005,26(17):3307-3314
The separation of hydroxyaromatic compounds in vegetable oils, including synthetic antioxidants (3-tert-butyl-4-hydroxyanisol and 2,6-di-tert-butyl-4-hydroxytoluene), E-vitamers and other natural oil components, by nonaqueous capillary electrophoresis in an oil-miscible background electrolyte (BGE) was investigated. The BGE contained 40 mM KOH in a methanol/1-propanol (PrOH) mixture (15:85 v/v). The oil samples were 1:1 diluted with PrOH and directly injected in the capillary. Under negative polarity (cathode at the injection end), the anionic solutes moved faster than the electroosmotic flow, being well-resolved among them and from the triacylglycerols. Using virgin palm, extra virgin olive, wheat germ, virgin soybean and other oils, the capability of the procedure to quickly yield a characteristic profile of the biophenols present in the sample was demonstrated. The alpha-, (beta + gamma)- (as unresolved pair) and delta-tocopherols of a soybean oil sample were quantified. 相似文献
8.
Steven F. Durrant Mrio A. Bica De Moraes 《Journal of Polymer Science.Polymer Physics》1998,36(11):1881-1888
An actinometric optical emission spectroscopy (AOES) study of the trends in the concentrations of the plasma species H, CH, CO, OH, and CN in film-producing glow discharges of mixtures of isopropanol and nitrogen was undertaken. Conventional AOES was used to obtain the trends in the plasma concentrations of these species as a function of the proportion of nitrogen in the feed, Rn. A dynamic variant of actinometry in which trends in the concentrations of plasma species are measured as a function of time following the cutting of one of the principal gas flows was also employed to investigate the relative importance of gas phase and plasma/polymer–surface interactions in the production of the species of interest. Each of the above-mentioned species is produced, to some degree, by plasma/polymer–surface reactions. As revealed by transmission infrared spectroscopy, the films deposited contain C H, CO, and O H groups. For Rn > 0, the films become nitrogenated, with both N H and CN groups being present. As revealed by transmission ultraviolet-visible spectroscopy, both the optical gap and the refractive index of the deposited films decrease as Rn is increased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1881–1888, 1998 相似文献
9.
Doina Bica Ladislau Vékás Mikhail V. Avdeev Oana Marinică Vlad Socoliuc Maria Bălăsoiu Vasil M. Garamus 《Journal of magnetism and magnetic materials》2007
Magnetic fluids (MFs), prepared by chemical co-precipitation followed by double layer steric and electrostatic (combined) stabilization of magnetite nanoparticles dispersed in water, are presented. Several combinations of surfactants with different chain lengths (lauric acid (LA), myristic acid (MA), oleic acid (OA) and dodecyl-benzene-sulphonic acid (DBS)) were used, such as LA+LA, MA+MA, LA+DBS, MA+DBS, OA+DBS, OA+OA and DBS+DBS. Static light scattering, transmission electron microscopy, small angle neutron scattering, magnetic and magneto-rheological measurements revealed that MFs with MA+MA or LA+LA biocompatible double layer covered magnetite nanoparticles are the most stable colloidal systems among the investigated samples, and thus suitable for biomedical applications. 相似文献
10.
Noor Rehman Maria Inez G. de Miranda Simone M. L. Rosa Clara I. D. Bica 《高分子科学》2016,34(11):1301-1310
Hydroxypropylcellulose (HPC) films were prepared by casting with cellulose nanocrystals in the presence of anionic surfactant sodium dodecylsulphate (SDS) and cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB). The cellulose nanocrystals were isolated from maize straw, a biomass source produced in huge quantities as an agrowaste in Brazil. These bionanocomposite films had good transparency and their surface hydrophilic character was evidenced by static contact angle measurements. Thermogravimetry (TGA) measurement revealed that nanocrystals and surfactants changed the thermal stability of the HPC films. Dynamic mechanical analysis (DMA) showed that the tensile storage and loss moduli of the HPC films increased by increasing the contents of cellulose nanocrystals and surfactants, especially in the case of CTAB. This good reinforcing effect of HPC matrix can be explained as due to electrostatic attractive interactions brought about by the presence of CTAB and the nanocrystals. 相似文献