共查询到20条相似文献,搜索用时 15 毫秒
1.
K. Bruer H.-H. Hrhold E. Klemm S. Krah G. Rudakoff W. Vogelsberger 《Crystal Research and Technology》1988,23(9):1145-1151
Spherical mixed silica/titania particles are prepared from silica/titania sol by an ultrasonic vibrator. The titania content of the samples varies from pure silica to a titania mole fraction of 0.31. Narrow size distributions with most frequent particle diameter of about 1 μm are obtained. Specific surface area and pore volume, mean pore radius as well as the meso pore size distribution are influenced by titania content. The spheres are composed of both silica and titania homogeneous distributed as it is indicated by scanning electron microscopy. X-ray diffraction studies show that the particles must be considered amorphous. Structural modifications of the framework are detected. Samples with varying refractive index may be prepared. 相似文献
2.
L. V. Lutsenko L. P. Oleksenko O. P. Ripko G. V. Fedorenko 《Molecular Crystals and Liquid Crystals》2020,699(1):63-70
AbstractEffect of composition and morphology on the catalytic activity in CO oxidation of Co-, Cu-, Ce-containing oxide materials prepared by citrate method has been studied. It was shown that composites consist of well-dispersed oxides Со3O4, CuO and CeO2 with average crystallite sizes 13–24?nm, 14–26?nm and 3–7?nm, respectively. It was established that Co-, Cu-, Ce-oxide nanocomposites demonstrated higher catalytic activity in CO oxidation in comparison with individual oxides. The ternary oxide system Со3O4–CuO–СеO2 (Со:Cu:Се=10:1:1) was found to possess the highest catalytic activity due to formation finely dispersed particles of CuO and СеO2 oxides simultaneously with nanosized Со3O4 species and formation of large quantity of mobile oxygen at the interfaces between the oxide nanoparticles. 相似文献
3.
N. V. Matsyuk V. S. Dutka O. I. Aksimentyeva P. Yu. Demchenko 《Molecular Crystals and Liquid Crystals》2017,642(1):99-105
Composites based on polyaniline and nanostructured zinc oxide were synthesized by mechanical mixing and the method of in situ polymerization and their physicochemical properties were studied. The electrical conductivity, surface structure and morphology of composites have been investigated. It is shown that the method of synthesis and quantity of filler affects the morphology and physicochemical properties of composite materials. An addition of various quantities of mineral filler to composite allows controlling conductivity of obtained materials. XRD-analysis of composite materials synthesized by in situ polymerization confirms the interaction of the components of the composite. 相似文献
4.
Effects of boron addition on the glass forming characteristics, structure and properties of iron phosphate glasses with nominal compositions of xB2O3-(40−x)Fe2O3-60P2O5 (x = 2-20, mol%) and xB2O3-(100−x)[Fe2O3-60P2O5] (x = 2-20, mol%) have been investigated by DTA, XRD, IR and Mössbauer spectroscopy. Although there were some weak local surface crystallizations on especially most of the glasses in group B, all of the compositions formed glass. DTA spectra showed two exothermic peaks corresponding to crystallizations along with an endothermic glass transition peak. Tg increased with increasing B2O3 content for the glasses in the first series which indicates that the addition of B2O3 increases the thermal stability of glasses in this series while the opposite is observed in the second series. The dissolution rates of boron containing bulk glasses were found to be around 10−9 gr/cm2 min which are comparable to that of the base iron phosphate glass. When the B2O3 content was above 14%, new bands related to BO4 tetrahedral groups have been observed in the IR spectra. The Mössbauer isomer shift values of boron doped glasses were found to be a little lower than that of base glass but both iron ions had distorted octahedral coordination in all glasses. The fraction of Fe2+ ions in glasses (Fe2+/∑(Fe2+ + Fe3+)) was found to be 23% for the base glass while it was 10-22% for the boron doped glasses. 相似文献
5.
The relation between ionic conductivity, glass transition temperature and structure has been investigated in silver-metaphosphate, AgPO3, glasses synthesized under varying conditions. The key finding of this work concerns the AgPO3 doping with up to 3 mol.% Al2O3 when melting is done in alumina crucibles, a practice used widely for the synthesis of fast ion conducting glasses. Vibrational spectroscopy showed that Al2O3-doping increases the phosphate network connectivity by P-O-Al-O-P cross-links. This effect causes a drastic enhancement in ionic conductivity and glass transition temperature relative to Al2O3-free AgPO3 glasses obtained by melting in Pt crucibles. 相似文献
6.
Lingcui Zhang Yongfeng Ruan Yali Liu Ying Zhai 《Crystal Research and Technology》2013,48(11):996-1002
ZnO nanorod arrays have been successfully prepared on ITO substrate by a chemical‐bath deposition method at different growth temperatures. The influence of the growth temperature on the morphology and microstructure of the ZnO nanorods was investigated by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The results showed that the diameter of the ZnO nanorods decreased and the size of the nanocrystals increased with increasing growth temperature. Optical absorption measurements showed the absorption band edge has shifted to a lower‐energy region due to the quantum size effect. Green emission and UV emission bands were observed and they are found to be temperature dependent, which indicates that the deep‐level emission and band‐edge emission of ZnO nanorods is closely related to the rod diameter, and the related mechanism is discussed. 相似文献
7.
V. A. Trounov V. T. Lebedev A. E. Sokolov Yu. S. Grushko Gy. Török J. C. van den Heuvel É. Batyrev T. M. Yurieva L. M. Plyasova 《Crystallography Reports》2007,52(3):474-478
The composites ZnOCuH(D) saturated with hydrogen (deuterium) to a content of ~1 wt % are investigated by the neutron scattering methods. Upon cooling of the samples (the ZnO matrix containing Cu crystals ~10 nm in size) from 300 to 4 K, hydrogen (deuterium) is condensed on the cluster surface and penetrates inside the clusters in which the atomic hydrogen content with respect to copper can be as high as 30% at 20 K. Simultaneously, hydrogen fills nanopores of the ZnO matrix. It is revealed that, at temperatures of 90–300 K, approximately one-third of the hydrogen amount participates in the fast diffusion (the diffusion constant is approximately equal to 8 × 10?5 cm2/s) and the other two-thirds are immobilized. At 20 K, the fraction of mobile hydrogen decreases to ~10%. An analysis of the results obtained demonstrates that the energy barriers retaining hydrogen in defect regions are relatively low. 相似文献
8.
F. Shahri 《Journal of Non》2008,354(14):1487-1493
In this work an attempt is made to study the effect of super-heat temperature and quenching wheel speed on the structure and magnetic properties of the Al/Ge substituted FINEMET alloy. In this respect, various as-spun ribbons were prepared at two different super-heat temperatures (150 and 250 °C) and various quenching wheel speeds (20, 30 and 40 m/s). Based on the results obtained, it was shown that both the super-heat temperature and wheel speed play an important role in the control of the level of amorphicity and of magnetic properties of the as-spun ribbons. Further, it was seen that the higher was the super-heat temperature/quenching wheel speed the higher was the degree of amorphicity giving rise to a lower magnetic saturation induction/magnetic permeability and higher coercivity for the ribbons prepared. 相似文献
9.
V. A. Petrova A. S. Orekhov D. D. Chernyakov Yu. G. Baklagina D. P. Romanov S. V. Kononova A. V. Volod’ko I. M. Ermak V. V. Klechkovskaya Yu. A. Skorik 《Crystallography Reports》2016,61(6):945-953
A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs. 相似文献
10.
Strontium ions can promote bone growth and enhance bioactivity in bioactive glasses that find critical biomedical applications. In this paper, the effect of SrO/CaO substitution on the structure, ionic diffusion, and dynamic properties of 45S5 bioactive glasses has been studied using constant pressure molecular dynamics simulations with a set of effective partial charge potentials. The simulated structure models were validated by comparing with experimental neutron diffraction results. It was found that the SrO/CaO substitution leads to an increase of glass density and decrease of oxygen density, a measure of compactness of the glass, in excellent agreement with available experimental data. On the other hand, the substitution does not significantly change of the medium range glass structures as characterized by silicon and phosphorous Qn distributions, network connectivity, and ring size distributions. The diffusion and dynamic behavior of these glasses and their melts were also determined by calculating the mean square displacements and velocity autocorrelation functions. It was found that the diffusion energy barriers of sodium, calcium and strontium ions remain nearly constant with respect to the level of substitution. However, strontium ions do influence the diffusion behaviors of calcium and sodium ions at high temperature, as evidenced from their velocity autocorrelation functions. Like calcium and sodium, strontium ions only contribute to the lower frequency (around 100 cm? 1) of the vibrational spectra the substitution has little effect on high frequency features and the general shape of the vibrational density of states. These results suggest that the increase of the dissolution rate in strontium containing glasses are mainly due to the increase of free volume and the non-local effect that weakens the silicon-oxygen network due to strontium ions. 相似文献
11.
Jian Min Liu Yi Ben Xia Lin Jun Wang Qing Feng Su Wei Min Shi 《Journal of Crystal Growth》2007,300(2):353-357
Highly c-axis-oriented ZnO films were successfully deposited on the nucleation sides of freestanding diamond films by RF reactive magnetron sputtering. I–V characteristics of ultraviolet (UV) photodetectors with ZnO/diamond structure were studied and a significant photoresponse was observed under UV light illumination. The dark-current and the photocurrent of the ZnO photodetectors were relative to the grain size and the quality of ZnO films. For the photodetector with a bigger grain size, a weaker dark current and a stronger photocurrent were obtained under 10 V bias voltage. The photocurrent rise and decay process confirmed the carrier-trapping effect. 相似文献
12.
In the framework of the model of a piezoelectrically active ferroelectric crystal-ceramic composite of the 0–3 type, the concentration dependences of the effective piezoelectric properties of this composite are determined. Two examples of such composites are discussed: the single-domain PbTiO3 crystal (Pb1 ? xCa itx)TiO3 ceramic and the polydomain PbTiO3 crystal (Pb1 ? xCax)TiO3 ceramic. Based on these examples, we analyzed the effect of the 90° domain structure, the form of crystalline inclusions, the remanent polarization of the ceramics, molar Ca concentration (x), and other factors of the effective piezoelectric coefficients e 3j * and d 3j * and and their anisotropy. The relation between the piezoelectric polarization of the composite to single-domain inclusions and the anisotropy of its piezoelectric coefficients is also studied. 相似文献
13.
M. V. Golubkov J. I. Gorina G. A. Kaljuzhnaia V. V. Rodin T. A. Romanova N. N. Sentjurina S. G. Chernook 《Crystallography Reports》2014,59(5):753-757
Single crystals of topological insulators—bismuth chalcogenides Bi2Te3, Bi2 ? x Sn x Te3, Bi2Se3, and Bi2 ? x Cu x Se3 with different charge-carrier densities—are grown by the modified Bridgman method. Their composition and structure are investigated and temperature dependences of the electric resistance and magnetic field dependences of the Hall voltage are obtained. 相似文献
14.
《Journal of Non》2006,352(42-49):4495-4499
We studied a set of float glass samples prepared with different fictive temperatures by previous annealing around the glass transition temperature. We compared the results to previous measurements on a series of amorphous silica samples, also prepared with different fictive temperatures. We showed that the modifications on the structure at a local scale are very small, the changes of physical properties are moderate but the changes on density fluctuations at a nanometer scale are rather large: 12% and 20% in float glass and silica, for relative changes of fictive temperature equal to 13% and 25% respectively. Local order and mechanical properties of silica vary in the opposite way compared to float glass (anomalous behavior) but the density fluctuations in both glasses increase with temperature and fictive temperature. 相似文献
15.
16.
《Journal of Non》2006,352(32-35):3697-3704
This work reports the investigation of the characteristics of catalysts produced by the sol gel process. Our analysis focuses on the properties related to heterogeneous catalysis, such as methane steam reforming, dry reforming, hydrogenation of organic compositions. Alumina, silica and titania based materials doped with Ni were synthesized. The characterization techniques used were: temperature programmed reduction, thermogravimetric analysis, specific surface area and X-ray powder diffraction. The specific surface area values obey the following sequence: Ni–SiO2 > Ni–Al2O3 > Ni–TiO2. The temperature programmed reduction indicated that in the Ni–SiO2 sample, the nickel oxide is present in two different forms on the surface; the Ni–Al2O3 material presented one peak at high temperature, suggesting the presence of a nickel aluminate form. However, Ni–TiO2 did not present reduction peaks. The thermogravimetric analysis, which was performed under inert atmosphere, showed the decomposition of the organic residues adsorbed on surface. The X-ray powder diffraction patterns of calcined materials showed two crystalline forms for TiO2 in Ni–TiO2 rutile and anatase. In Ni–Al2O3, crystalline areas composed of α-Al2O3, γ-Al2O3 and NiO were observed and finally for Ni–SiO2, amorphous areas and NiO were found. 相似文献
17.
Elaine Kikuti Adriana P. Ibaldo Livia M. C. Sousa 《Molecular Crystals and Liquid Crystals》2016,625(1):165-172
Poly(3-methylthiophene/overoxidized pyrrole) (PMT/OPPy) composites were electrochemically prepared by simultaneous polymerization of 3-methylthiophene and pyrrole, which were added together at a 10:1 concentration ratio into a non-aqueous medium (acetonitrile). The films were characterized by cyclic voltammetry, spectroscopic (FTIR, UV-VIS, and photocurrent) and current-voltage measurements, and with atomic force microscopy (AFM). The PMT/OPPy films exhibited intermediate characteristics than those seen for the homopolymers, OPPy and PMT, but with PMT as the predominant element of the PMT/OPPy composition. Optical, morphological, and electrical properties of the OPPy, PMT, and PMT/OPPy films were compared aiming toward application in optoelectronic devices and sensors. 相似文献
18.
Gel silica glass prepared by the sol-gel process can be modified by incorporating an organic phase into the intrinsically porous inorganic gel matrix, which results in a composite material with much improved mechanical and optical properties. Characterisation of PMMA modified gel silica glass prepared by the in situ polymerisation method using FT-Raman spectroscopy, gel permeation chromatography and the nitrogen adsorption technique are reported. Some essential problems encountered in the preparation are discussed. 相似文献
19.
Ahmed Bachar Cyrille Mercier Arnaud Tricoteaux Anne Leriche Claudine Follet Mohamed Saadi Stuart Hampshire 《Journal of Non》2012,358(3):693-701
Bioglasses have been developed for use in surgery because of their ability to form a hydroxy-carbonate apatite (HCA) layer on their surface which facilitates bonding to natural bone. However, they do not have sufficient strength for use in load-bearing situations and therefore improving their mechanical properties would allow their use in more robust applications. The purpose of this work was to study the effects of nitrogen addition on the physical and mechanical properties and the structure of oxynitride bioglasses based on the system Na2O–CaO–SiO2–Si3N4. The density, glass transition temperature, hardness and elastic modulus were measured and observed to increase linearly with nitrogen content. These increases are consistent with the incorporation of N into the glass structure in three-fold coordination with silicon which results in extra cross-linking of the glass network. The characterization of these oxynitride bioglasses using solid state nuclear magnetic resonance 29Si MAS NMR and infrared spectroscopy have shown firstly that all the N atoms are bonded to Si atoms and secondly that this increase in rigidity of the glass network can be explained by the formation of SiO3N, SiO2N2 tetrahedra and Q4 units with extra bridging anions at the expense of Q3 units. The oxynitride bioglasses in simulated body fluid form a hydroxy-carbonate apatite (HCA) layer on their surfaces showing that bioactivity is retained. 相似文献
20.
This letter describes the effects that the surfactant, sodium dodecylbenzene sulfonate (SDBS), has on the structure and electrical properties of monolithic carbon aerogels (CA). Using organic sol-gel chemistry, a series of novel CA materials prepared with different concentrations of SDBS were characterized to evaluate the influence the surfactant had on the network structure of the resultant material. Addition of the SDBS surfactant to the sol-gel reaction mixture was shown to generate CA structures that had different pore sizes, higher densities and improved electrical conductivity than those prepared without the surfactant. These results are discussed in comparison with relevant sol-gel literature and theory. 相似文献