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1.
Thermal behaviour and biochemical activity of potassium-silicate-phosphate glasses modified by addition of Ca, Mg, acting
as ecological fertilisers of controlled release rate of the nutrients for plants were studied. It has been found that the
biochemical activity of silicate-phosphate glasses depends on the nature and the number of components forming the glassy framework
and is related to the thermal stability of glass demonstrated by the formation of new compounds during the process of crystallisation.
It is proved that these seemingly different properties are determined by the same parameters which are the strengths bonds
of glass network-formers and modifiers as well as their chemical affinity.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Gravimetric measurements of thermodesorption of n-hexane and n-heptane were performed under quasi-equilibrium conditions. Differential thermodesorption profiles for ZSM-5 and ZSM-11 showed two peaks, but for Y zeolites, only one thermodesorption peak was observed. A model function, derived from the Langmiur adsorption model, was fitted to the experimental data, and the model parameters (the adsorption entropy and enthalpy) were estimated. The two-step desorption profiles observed for ZSM-5 and ZSM-11 were attributed to the commensurate freezing effect, i.e. a transition in the adsorbed phase resulting in ordering of the adsorbed molecules in the zeolite channels. The results observed for ZSM-11 indicate that the zigzag channels typical for ZSM-5 micropore system are not necessary for this transition to occur. 相似文献
3.
The DTA method was used to determine the phase diagram of the NaCl-CaSO4 system over the range 0.55 wt.% of CaSO4 in air atmosphere. The effects of SiO2, CaCO3 and Fe2O3 on the melting temperatures of pure NaCl and the eutectic were determined. On the basis of the above temperatures, a method of quantitative determination of the anhydrite content in rock salts has been developed.
Zusammenfassung DTA wurde benutzt, um in Luft im Bereich 0 bis 55,0 Gew.% CaSO4 das Phasendiagramm des Systemes NaCl-CaSO4 zu bestimmen. Es wurde auch der Einfluß von SiO2, CaCO3 und Fe2O3 auf die Schmelztemperatur von reinem NaCl bzw. des Eutektikums bestimmt. Auf der Grundlage obiger Temperaturen wurde eine Methode zur quantitativen Bestimmung des Anhydritgehaltes in Steinsalzen entwickelt.
- 0–55,0 . , . , ( ) .相似文献
4.
Krzysztof Maruszewski Marek Jasiorski Witold Wacławek Wiesław Stręk Marek Lisowski 《Journal of Sol-Gel Science and Technology》1998,13(1-3):585-586
A series of silicate xerogels with entrapped chiral amino acids have been obtained via sol-gel technology. The transparent, glassy samples obtained exhibit chirality in the bulk due to the presence of the entrapped asymmetric molecules. Measurements of the optical activity of the doped xerogel samples revealed that the entrapment did not significantly influence the optical activity observed for liquid solutions of the amino acids. Thus, the sol-gel method enables the preparation of amorphous optical materials exhibiting properties of strictly spatially defined molecular systems. Apart from the obvious optical applications, such porous materials with asymmetric centers might find interesting applications in chiral chemical syntheses and separations. 相似文献
5.
Quasi-isothermal-isobaric analysis was applied as a main method for investigation of thermal decomposition of borates. The
structural mechanism of the dehydration and dehydroxylation of selected borates is considered. It has been found that they
consist of two independent stages: formation of gaseous water molecules localized into the structural framework and their
release. The internal pressure of gaseous water molecules is the factor influencing the course of these processes. The strengths
of the chemical bonds of the components and the freedom of their displacement also determine thermal stability of hydrated
borates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Thermal
and structural properties of model silicate-phosphate glasses containing the
different amounts of the glass network modifiers, i.e. Mg2+
and Ca2+ were studied. To explain the changes of
the parameters characterizing the glass transition effect (Tg, Δcp) and the crystallization
process (Tc, ΔH) depending on the cations modifiers additions,
analysis of the bonds and chemical interactions of atoms in the structure
of glasses was used.
31P
MAS-NMR spectra of SiO2–P2O5–MgO(CaO)–K2O glasses show that the phosphate complexes are mono- and diphosphate. It
has been found that increasing amounts of Mg2+
or Ca2+ cations in the structure of glasses causes
the reduction of the degree of polymerization of the phosphate framework (Q1→Q0).
The influence of increasing of modifiers in the structure of silicate- phosphate
glasses on the number of non-bridging oxygens per SiO4
tetrahedron and density of glasses was presented. 相似文献
7.
Dorota Majda Wac?aw Makowski Maria Mańko 《Journal of Thermal Analysis and Calorimetry》2012,109(2):663-669
Thermoporosimetry, i.e., DSC measurements of melting point depression of water and heptane confined in mesopores, has been used for determination the pore size distribution of several mesoporous silicas synthesized with the use of micelle templates. Porosity of these materials was additionally characterized by low-temperature nitrogen adsorption and quasi-equilibrated thermodesorption of nonane. The pore size distributions obtained using the water thermoporosimetry were similar to those determined using the other methods, but the pore size values found for the narrow pore materials were underestimated by ca 1?nm. Too large pore sizes obtained for the wide pore silica from heptane thermoporosimetry were attributed to nonlinear dependence of the melting point depression on the reciprocal of the pore size. 相似文献
8.
Densities for DMSO solutions of iron(III), aluminium(III), beryllium(II) and magnesium(II) perchlorates and silver nitrate are reported. Densities for DMSO solutions of tetraethylammonium perchlorate and nitrate and tetrabutylammonium perchlorate and tetraphenylborate are also presented. The partial molar volumes of the DMSO-solvated cations are derived and discussed in terms of variation with the charge number. 相似文献
9.
In 1974 Michael Shub asked the following question [29]: When is the topological entropy of a continuous mapping of a compact manifold into itself is estimated from below by the logarithm of the spectral radius of the linear mapping induced in the cohomologies with real coefficients? This estimate has been called the Entropy Conjecture (EC). In 1977 the second author and Micha? Misiurewicz proved [23] that EC holds for all continuous mappings of tori. Here we prove EC for all continuous mappings of compact nilmanifolds. Also generalizations for maps of some solvmanifolds and another proof via Lefschetz and Nielsen numbers, under the assumption the map is not homotopic to a fixed points free map, are provided. 相似文献
10.
I. Wacławska 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1337-1345
The properties and course of phase transition of amorphous borates obtained by solid-state thermal and mechanical treatment of hydrated borates and melt quenched glasses with the compositions of these borates were studied. Processes of structural relaxation and crystallization were considered.It was found that different methods of preparation of amorphous borates and the differences in their structural ordering resulting from these methods affect the rate and the mechanism of transformations occurring during their heating.Support for this work was provided by the Polish Committee of Scientific Research (KBN) — grant No. 3 P407 034 06. 相似文献