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  • Author or Editor: P. Staszczuk x
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Abstract  

The paper presents evaluation of energy distribution of n-octane and pore-size distribution functions on the alumina oxide surface (e.g. total heterogeneity) of on the basis one experimental run. the Q-TG mass loss and derivative Q-DTG mass loss curves of n-octane thermodesorption from the alumina oxide sample were made using a hungarian derivatograph with an analyser equipped with an automatic ultraslow procedure and a special crucible of maintaining the quasi-isothermal heating procedure to increase the resolution of thermal analysis. a new theoretical and experimental procedure was developed for evaluation of distribution functions of liquid preadsorbed on the mesoporous surface from special thermogravimetry. An example of the approach to quantitative description of the energetic and structural heterogeneities of alumina oxide surface is given.

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Abstract  

Energetic heterogeneity of adsorbents is conditioned by the differences in topology of adsorption centres, dispersion of pore sizes and other factors. This paper describes theoretical and experimental studies that demonstrate a method for estimation of the energetic heterogeneity of adsorbents by making use of the results from single thermogravimetry Q-TG and Q-DTG curves, recorded under quasi-equilibrium conditions, for preadsorbed liquid on a porous solid surface.

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Abstract  

Modified carbon multiwall nanotubes were prepared via the oxidation process by means of 65% nitric acid or ferric nitrate dissolved with 65% nitric acid. Using special thermogravimetry and sorptometry methods physicochemical properties of pure and modified nanotube surfaces were investigated. A numerical and analytical procedure for the evaluation of total heterogeneous properties on the basis of liquid thermodesorption from the sample surfaces under the quasi-equilibrium conditions are presented. The calculations of the fractal dimensions of carbon nanotubes using the sorptometry and thermogravimetry data is presented.

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Abstract  

In this paper the theoretical approach and applications of Cahn ultramicrobalance to kinetic study on the thermal decomposition of the high-temperature Y1Ba2Cu3O7-x superconductor are presented. Thermogravimetric in situ measurements of oxygen loss from Y1Ba2Cu3O6 samples heated isothermally in a relatively high dynamic vacuum were performed with a Cahn RG electrobalance. Single-phase orthorhombic samples of composition Y1Ba2Cu3O7-x (highest oxygen content) were synthesized from stoichiometric (1:2:3) mixtures of high-purity Y2O3, BaCO3 and CuO. The original 1:2:3 mixture was prepared by the two-stage procedure described earlier. The crystal structure of the sample in the original orthorhombic phase was controlled by the X-ray powder method (CuKα radiation) using a Stadi P Stoe diffractometer with a position-sensitive detector. Activation energy is estimated from appropriate Arrhenius plots.

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Abstract  

The gravimetric measurement of the moisture content of solids is discussed in comparison to other usual methods. Results of measurements of silica gel are reported. Furthermore, we inform on standardisation work.

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Abstract  

Using thermo-analytical and sorptometric methods physicochemical properties and especially surface heterogeneity of HgBa2Ca2Cu3O8+, (Hg-1223) was investigated. The desorption energy distribution was derived from mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption in quasi-isothermal conditions of pre-adsorbed n-octane and water vapour. It is shown that the superconducting Hg-1223 phase is highly sensitive to water vapours. The mechanism of water adsorption depends largely on the activation time. By water vapour saturation in a period of 90 min, physisorption takes place. Prolonged periods result in a chemical decomposition. From nitrogen ad- and desorption isotherms the fractal dimension of superconductors were calculated. A new approach is proposed to calculate fractal dimension from Q-TG curves.

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Abstract  

The Q-TG mass loss and first derivative Q-DTG mass loss accompanying benzene thermodesorption from silica gel samples under quasi-isothermal conditions were studied with a Derivatograph Q-1500 D (MOM, Hungary). The isotherms of adsorption-desorption of benzene vapour on different porous silica gels were measured gravimetrically by using a McBain balance. The benzene mass loss in the adsorption region, obtained from the Q-TG curves, and the adsorption capacity, established gravimetrically, exhibited a satisfactory correlation.

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Abstract  

The new method of diffusion coefficient calculations from thermogravimetry Q-TG data has been presented. Programmed thermodesorption of polar and apolar liquids from aluminium oxide and montmorillonite-Na and -La samples in quasi-isothermal conditions has been made. The result from above method was compared with literature data and good correlation were obtained.

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Abstract  

Complex studies of physicochemical properties of pure and modified of aluminia oxides samples are presented. The presence of Mn2+ and Ni2+ modifiers on the aluminium oxide surface causes increase in water adsorption capacity and decrease in benzene and n-octane adsorption. This is due to decrease of specific surface area, volume and radius of pores as a result of surface impregnation and microcrystal formation during modification with manganese and nickel chlorides. Microcrystal formation on the surface and porosity decrease as confirmed by AFM, EDX and powder diffraction studies using automated diffractometer by step scanning. From the Q-TG and Q-DTG data, the energies of liquid desorption from the surface of the samples and the functions of desorption, energy distribution were calculated. High degree of nonlinearity of the functions resulting from great heterogeneity of the studied surface was found. Adsorption of cations creates more homogeneous surface in aluminium oxide, and it is responsible for the change in adsorbate molecule interaction energy and changes mechanism of adsorption and desorption as well as thickness and structure of the adsorbed film. From the experimental data some parameters characterizing adsorption properties and porosity of the studied samples were determined using the complex measuring methods (thermal analysis, sorptometry, porosimetry, AFM and EDX).

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Abstract  

Jntti published in 1970 a method to obtain values of the sorption parameters at an early stage of gravimetric sorption measurements. In the present paper we apply that method to volumetric sorption measurements to discuss its applicability. A method is presented to cope with inaccuracies when using Jntti’s method. This will be of special importance for volumetric measurements where accuracy plays a major part. In the paper a second order regression method is used. We use a computer simulation as well as experimental data on desorption of nitrogen from a silica aerogel at 77 K.

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