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The effect of vibration grinding on the DTA curves of montmorillonite isolated from the most important locality of bentonite in the Slovak Republic (Jel?ovy potok, Middle Slovakia) was studied in the temperature range 20–1500°C. Interpretation is offered for 6 endothermic and 3 exothermic peaks. vibration grinding modified the course of dehydration of the mineral, suppresses the “dehydroxylation’ peak at 700°C, enables the crystallization of high-temperature quartz, cristobalite and cordierite at lower temperatures in comparison with unground natural montmorillonite. Vibration griding slows down the crystallization of mullite which—unlike quartz, cristobalite and cordierite—does not belong to high-temperature phases of Cheto-montmorillonite. The order in which these high-temperature phases occur is not influenced by vibration grinding. 相似文献
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Jesenák K. Kuchta L'. Hudec P. Fajnor V. Š. 《Journal of Thermal Analysis and Calorimetry》1999,55(3):773-777
Differences in mass loss occurring in the course of dynamic and isothermal heating of SiO2-aerogel and changes of specific surface and hydrophylicity during calcination were studied by thermal analysis. SiO2-aerogel was prepared from tetramethoxysilane (TMOS) hydrolyzed by ammonia solution at 0°C with molar ratio TMOS: H2O:NH4OH 4:1:0.01. Differences are caused mainly by oxidation of organic matter and by diffusion of products of the oxidation. Heat
transfer has none or little effect on the differences. Samples calcined at temperatures about 300°C reach maximum hydrophilicity
though they still contain small amounts of residual organic matter.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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EP Sheretov VS Gurov MV Dubkov OV Korneeva 《Rapid communications in mass spectrometry : RCM》1999,13(16):1699-1702
In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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The discovery of neutron rich isotopes of the lightest elements on the neutron drip line exhibiting a halo structure has opened
up new vistas in research activities. The novel structural features associated with the halo phenomena have been the subject
for extensive theoretical and experimental investigations in recent times. In this talk, I propose to present a broad overview
of the recent developments in this field, bringing out the striking features which show that a large number oflight nuclei
near the neutron drip line are characterized by a clear separation between a ‘normal’ core nucleus and a loosely bound low
density veil of neutrons. Specifically, the two neutron halos offer a natural premises, from a theoretical standpoint, to
employ three body techniques for studying their detailed structural properties. A considerable part of the talk will be devoted
to report and highlight the results on a number of light halo nuclei such as 11Li, 11Be, 19B and 22C on which we have been carrying out investigations employing a simple but realistic three body model. These three body systems
which have been termed as ‘Borromean’ (i.e while three body systems are bound, the corresponding binary subsystems on the
other hand are unbound) are characterized by large spacial extension and very low separation energy of the neutron. They are,
therefore, ideally suited for exploring the possibility of the existence of Efimov states in two neutron halo nuclei. We have
recently carried out the three body analyses to predict the possibility of the occurrence of such states on which experimental
work at various laboratories is underway. 相似文献
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The comparison of thermal stabilities of different organoclay intercalation complexes is presented in this work. Montmorillonite/monomer and montmorillonite/polymer intercalation complexes with similar basal spacings show a pronounced difference in changes of d
001 values after 30 min heating. The hydrophilic and/or organophilic surface modification of the starting montmorillonite is an important factor affecting the intercalated amount of organic material and thus the expansion of the sheet silicate structure.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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Synthetic zeolite ZSM5 and its copper forms containing N,N-dimethylethylenediamine (dmen) have been investigated by CHN, energy dispersive spectroscopy (EDS) analysis, X-ray powder diffractometry, X-ray photoelectron spectroscopy and continuous waves hydrogen nuclear magnetic resonance (CW 1H NMR) spectroscopy. Thermal properties have been studied by methods of thermal analysis—TG, DTA and DTG in the temperature range 20-1000 °C in air atmosphere. Mass spectroscopy method was used for the study of the released gas products of thermal decomposition.The results of thermal analyses of two zeolitic samples Cu-ZSM5 and Cu(dmen)xZSM5 (x depends on the mode of preparation) demonstrated their different thermal properties. The main part of the decomposition process of the samples Cu(dmen)xZSM5 occurs at considerably higher temperatures than the boiling point of dimethylethylenediamine, proving strong bond and irreversibility of dmen-zeolite interaction. According to the results of mass spectroscopy the decomposition process in inert atmosphere is characterized by the development of a large spectrum of products with atomic mass from 18 to 447 atomic mass units as a consequence of the catalytic effect of the silicate surface. 相似文献
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NL Asfandiarov AI Fokin VG Lukin EP Nafikova GS Lomakin VS Fal'ko YV Chizhov 《Rapid communications in mass spectrometry : RCM》1999,13(12):1116-1123
A series of anthraquinone (C(14)O(2)H(8)) derivatives has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), photoelectron spectroscopy (PES), and AM1 quantum chemical calculations. Mean lifetimes of molecular negative ions M(-.) (MNI) have been measured. The mechanism of long-lived MNI formation in the epithermal energy region of incident electrons has been investigated. A simple model of a molecule (a spherical potential well with the repulsive centrifugal term) has been applied for the analysis of the energy dependence of cross sections at the first stage of the electron capture process. It has been shown that a temporary resonance of MNI at the energy approximately 0.5 eV corresponds to a shape resonance with lifetime 1-2.10(-13) s in the f-partial wave (l = 3) of the incident electron. The next resonant state of MNI at the energy approximately 1.7 eV has been associated with the electron excited Feshbach resonance (whose parent state is a triplet npi* transition). In all cases the initial electron state of the MNI relaxes into the ground state by means of a radiationless transition, and the final state of the MNI is a nuclear excited resonance with a lifetime measurable on the mass spectrometry timescale. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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J. Masár Ľ. Kuchta H. Gerthofferová V. Š. Fajnor 《Journal of Thermal Analysis and Calorimetry》1982,24(1):43-50
The thermal behaviour of synthetic montmorillonite of relatively simple chemical composition has been studied and interpreted. Montmorillonite was prepared by hydrothermal synthesis at 300° and 8.8 MPa during 165 hours. With the methods of DTA, DTG, TG, X-ray diffraction analysis, infrared spectroscopy and electron microscopy it was proved that the synthetic montmorillonite is a monomineral sample and no differences from natural montmorillonite were observed.
Zusammenfassung Das thermische Verhalten synthetischer Montmorillonite verhältnismässig einfacher chemischer Zusammensetzung wurde untersucht und gedeutet. Montmorillonit wurde durch hydrothermische Synthese bei 300°C und 8.8 MPa in 165 Stunden hergestellt. Durch die Methoden der DTA, DTG, TG, Röntgendiffraktionsanalyse, Infrarotspektroskopie und Elektronenmikroskopie wurde erwiesen, daß synthetische Montmorillonit eine monominerale Probe ist und keine Abweichungen von natürlichem Montmorillonit beobachtet werden konnten.
. 165 300° 8.8 . , , , , , .相似文献
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