排序方式: 共有18条查询结果,搜索用时 15 毫秒
1.
Laxman Singh Ravikant Sharma Narayan Singh Atendra Kumar Dev K Mahato Youngil Lee Mikhael Bechelany KD Mandal 《Progress in Crystal Growth and Characterization of Materials》2021,67(4):100542
This review paper covers the low temperature wet growth of nano-engineered particles of ZnO-based mixed metal oxides, their growth mechanism, and characterization using X-ray diffraction, SEM, TEM and IR, UV–visible, and XPS spectral techniques. Main focus of this article is centered on low temperature semi-wet methods of synthesis that are suitable for large scale production of zinc oxide-based systems mixed with iron oxide, copper oxide, nickel oxide and cobalt oxide. These mixed metal oxides have broad industrial applications as catalyst, semiconductors, adsorbents, superconductors, electro-ceramics, and antifungal agents in addition to extensive applications in medicines. This paper discusses the low-cost and environment friendly synthesis of these mixed metal oxides, measurement of properties and applicability of these materials systems. 相似文献
2.
Study of negative thermal expansion and shift in phase transition temperature in Ti4+- and Sn4+-substituted ZrW2O8 materials 总被引:1,自引:0,他引:1
Buysser KD Driessche IV Putte BV Vanhee P Schaubroeck J Hoste S 《Inorganic chemistry》2008,47(2):736-741
The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism. 相似文献
3.
We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the
central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density
distribution. 相似文献
4.
Nadine S Simons-Weidenmaier Maruschka Weber Claudia F Plappert Peter KD Pilz Susanne Schmid 《BMC neuroscience》2006,7(1):38
Background
Short-term habituation of the startle response represents an elementary form of learning in mammals. The underlying mechanism is located within the primary startle pathway, presumably at sensory synapses on giant neurons in the caudal pontine reticular nucleus (PnC). Short trains of action potentials in sensory afferent fibers induce depression of synaptic responses in PnC giant neurons, a phenomenon that has been proposed to be the cellular correlate for short-term habituation. We address here the question whether both this synaptic depression and the short-term habituation of the startle response are localized at the presynaptic terminals of sensory afferents. If this is confirmed, it would imply that these processes take place prior to multimodal signal integration, rather than occurring at postsynaptic sites on PnC giant neurons that directly drive motor neurons. 相似文献5.
Klaartje De Buysser Isabel Van Driessche Joseph Schaubroeck 《Journal of solid state chemistry》2007,180(8):2310-2315
Powder XRD-analysis and thermo-mechanical analysis on sintered TiO2-WO3-ZrO2 mixtures revealed the formation of Zr1−xTixW2O8 solid solutions. A noticeable decrease in unit cell parameter ‘a’ and in the order-disorder transition temperature could be seen in the case of Zr1−xTixW2O8 solid solutions.Studies performed on other ZrW2O8 solid solutions have attributed an increase in phase transition temperature to a decrease in free lattice volume, whereas a decrease in phase transition temperature was suggested to be due to the presence of a more disordered state. Our studies indicate that the phase transition temperature in our materials is strongly influenced by the bond dissociation energy of the substituting ion-oxygen bond. A decrease in bond strength may compensate for the effect of a decrease in lattice free volume, lowering the phase transition temperature as the degree of substitution by Ti4+ increases. This hypothesis is proved by differential scanning calorimetry. 相似文献
6.
M. Arin J. Watté G. Pollefeyt K. De Buysser I. Van Driessche P. Lommens 《Journal of Sol-Gel Science and Technology》2013,66(1):100-111
In this paper, we present a microwave-assisted, hydrothermal method for the synthesis of TiO2 suspensions. These were obtained from Ti4+ aqueous precursor solutions using titanium-isopropoxide with EDTA and triethanolamine or tetraethylammonium hydroxide by applying a microwave treatment at temperatures between 100 and 140 °C. The influence of the ligands, pH, reaction temperature and time on the particle size and crystallinity was investigated and discussed. A selection of the TiO2 suspensions was deposited on glass substrates using piezoelectric driven ink-jet printing. The rheological properties of the suspensions were evaluated against the relevant criteria for ink-jet printing and their jetting behavior was analyzed. The ink-jet printed layers were heated at temperatures between 150 and 500 °C to create transparent titanium oxide layers. The photocatalytic activity of the finally obtained layers was analyzed by following the decomposition of a methylene blue solution under UV illumination. The presence of preformed titania nanoparticles makes it possible to obtain photocatalytic active coatings at reduced heating temperatures. This can widen the application range of these functional layers to heat-sensitive substrates such as polymers. The influence of the heat treatment temperature on the film roughness, thickness and photocatalytic activity was also studied. 相似文献
7.
Vyshnavi Narayanan Petra Lommens Klaartje De Buysser Ruben Hühne Isabel Van Driessche 《Journal of solid state chemistry》2011,184(11):2887-2896
In this work, water-based precursor solutions suitable for dip-coating of thick La2Zr2O7 (LZO) buffer layers for coated conductors on Ni-5%W substrates were developed. The solutions were prepared based on chelate chemistry using water as the main solvent. The effect of polymer addition on the maximum crack-free thickness of the deposited films was investigated. This novel solution preparation method revealed the possibility to grow single, crack-free layers with thicknesses ranging 100–280 nm with good crystallinity and an in-plane grain misalignment with average FWHM of 6.55°. TEM studies illustrated the presence of nanovoids, typical for CSD–LZO films annealed under Ar-5%H2 gas flow. The appropriate buffer layer action of the film in preventing the Ni diffusion was studied using XPS. It was found that the Ni diffusion was restricted to the first 30 nm of a 140 nm thick film. The surface texture of the film was improved using a seed layer. 相似文献
8.
Jozefien Geltmeyer Lien Van der Schueren Frederik Goethals Klaartje De Buysser Karen De Clerck 《Journal of Sol-Gel Science and Technology》2013,67(1):188-195
Silica nanofibres have, due to their excellent properties, promising characteristics for multiple applications such as filtration, composites, catalysis, etc. Silica nanofibres can be obtained by combining electrospinning and the sol–gel process. To produce silica nanofibres most of the time organic solutions are applied containing a carrying polymer, which is afterwards removed by a thermal treatment to form pure ceramic nanofibres. Although electrospinning of the pure silica precursors without carrying polymer is preferred, the parameters influencing the stability of the electrospinning process are however largely unknown. In addition, this knowledge is essential for potential upscaling of the process. In this study, the optimum viscosity to electrospin in a stable manner is determined and the way to obtain this viscosity is evaluated. Sols with a viscosity between 120 and 200 mPa.s could be electrospun in a stable way, resulting in uniform and beadless nanofibres. Furthermore, this viscosity region corresponded with nanofibres having the lowest mean nanofibre diameters. Electrospinning with diluted sols was possible as well, but electrospinning of the fresh sols was more stable. These results illustrate the importance of the viscosity and degree of crosslinking of the sol for the stable electrospinning of silica nanofibres and demonstrate that upscaling of the electrospinning process of silica nanofibres is feasible. 相似文献
9.
S. Abdul Sattar B. Seetharami Reddy V. Koteswara Rao K. Ramnarayana G. J. Naga Raju S. Bhuloka Reddy T. KD. Phanisree P. V. Madhusudhana Rao 《X射线光谱测定》2012,41(2):111-116
A trace elemental analysis was carried out in various parts of 12 anticancer medicinal plants, using the PIXE (particle‐induced X‐ray emission) technique. A 3‐MeV proton beam was used to excite the samples, and spectra were recorded using a Si (Li) detector. Data analysis was done using the GUPIX software. The elements Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified, and their concentrations estimated. The results of the present study provide justification for the usage of these medicinal plants in the development of anticancer drugs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
In search of analogs of 1α,25-dihydroxyvitamin D3 featuring a dissociation of calcemic and other activities, a series of stereoisomeric 19-nor-22-oxa derivatives, characterized by a spiro[4.5]decane cyclic system instead of the classical CD-ring system, have been synthesized in an enantioselective way. 相似文献