排序方式: 共有51条查询结果,搜索用时 15 毫秒
1.
Summary Packings containing chemically bonded C18 groups with different coverage density were prepared using monochlorooctadecylsilane. The method permitting the determination of the free surface energy on the basis of adsorption measurements of two different liquids, noctane and water, was utilized to evaluate the coverage homogeneity of the silica gel surface by the alkylsilyl ligands. It was found that the packing is characterized by a coverage greater than 3.8 mol/m2, it is homogenous and the support surface is fully screened. 相似文献
2.
P. Staszczuk J. C. Bazan M. Błachnio D. Sternik N. J. Garcia 《Journal of Thermal Analysis and Calorimetry》2006,86(1):57-68
This paper presents possible applications of thermal analysis, sorptometry
and porosimetry to study physico-chemical properties of Na- and La-montmorillonite
samples, especially for determination of total surface heterogeneity. The
quasi-isothermal thermogravimetric (Q-TG) mass loss and its first derivative
(Q-DTG) curves with respect to temperature and time obtained during programmed
liquid thermodesorption under quasi-isothermal conditions have been used to
study adsorbed layers and heterogeneous properties of the Na- and La-montmorillonites.
Calculations of the desorption energy distribution functions by analytical
procedure using mass loss Q-TG and differential mass loss Q-DTG curves of
thermodesorption under quasi-isothermal conditions of polar and non-polar
liquid vapours preadsorbed on a material surface are presented. Parameters
relating to porosity of samples were determined by sorptometry, mercury porosimetry
and atomic force microscopy (AFM). From nitrogen sorption isotherms from sorptometry
and porosimetry methods, the fractal dimensions of montmorillonites have been
calculated. Moreover, a new approach is proposed to calculate fractal dimensions
of materials obtained from Q-TG curve; this is compared with values obtained
by the above methods. The total heterogeneous properties (energy distribution
function and pore-size distribution functions) of samples studied were estimated.
The radius and pore volume of the tested samples calculated on the basis of
thermogravimetry, sorptometry and porosimetry techniques were compared and
good correlations obtained. 相似文献
3.
D. Sternik P. Staszczuk M. Majdan A. Gładysz-Płaska E. Dąbrowska K. Bigda 《Journal of Thermal Analysis and Calorimetry》2006,86(1):69-75
The paper presents physico-chemical properties
of mixed adsorbents in the clinoptylolite (mordenite)/SiO2
system containing 30, 50, 80 mass% zeolite. Adsorption capacity towards polar
(water, butanol) and non-polar (n-octane)
substances as well as total surface heterogeneity (energetic and geometrical)
were determined. Desorption energy distribution functions as well as fractal
dimensions were also determined and compared with the low-temperature nitrogen
adsorption data. Irregular shapes of the curves q=f(E
d)
as well as large values of volumetric fractal dimensions (D
f~2.6)
revealed heterogeneous properties of the zeolite/SiO2 system surfaces. Addition
of zeolite increases total heterogeneity of the material. 相似文献
4.
Staszczuk P. Sternik D. Chądzyński G. W. 《Journal of Thermal Analysis and Calorimetry》2003,71(1):173-182
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.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
5.
P. Staszczuk 《Journal of Thermal Analysis and Calorimetry》1986,31(5):1055-1061
This paper presents a method for calculation of the adsorption and immersion heats of water on a silica gel surface from the DTA curve obtained with a modified derivatograph. The adsorption and desorption heats have also been determined. The relationship between the adsorption heat and the amount of water adsorbed is presented.
Zusammenfassung Eine Methode zur Berechnung der Adsorptions- und Immersionswärmen von Wasser an Silikagel aus den mit einem modifizierten Derivatographen gemessenen DTA-Kurven wird beschrieben. Adsorptions- und Desorptionswärmen wurden bestimmt. Die Beziehung zwischen der Adsorptionswärme und der Menge des adsorbierten Wassers wird angegeben.
, , . . .相似文献
6.
The Studies of the Heterogeneous Properties of Solid Surfaces by Means of the Derivatograph Q-1500 D
A simple method has been adopted to obtain an important information on the heterogeneous properties of materials studied,
adsorbed liquid films and liquid-solid interactions. The method utilizes Q-TG mass loss and the first derivative Q-DTG mass
loss curves with respect to temperature and time obtained during programmed liquid thermodesorption in quasi-isothermal conditions.
The values of the adsorption capacity, total porosity of material, the value of active centers, desorption energy distribution
and mesopore-size distribution functions obtained by this method are in good agreement with those estimated on the basis of
independent methods. The theoretical and experimental results provided novel and unique data on the heterogeneity of solid
surfaces, properties of liquid adsorbed films and thermal stability of the liquid/solid interfaces.
This paper presents the more important results obtained so far in the studies the liquid/solid systems by means of the Paulik's
classical and quasi-isothermal techniques.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
D. Sternik P. Staszczuk J. Pękalska G. Grodzicka B. Gawdzik J. Osypiuk-Tomasik P. Witer 《Journal of Thermal Analysis and Calorimetry》2006,86(1):85-91
The adsorption of a polar (water)
and a non-polar (n-octane) liquid on silica
gels, modified by adsorption of proteins, has been studied by thermal analysis.
Silica gels with physically adsorbed BSA and ovalbumin layers were used. Thermodesorption
energies were determined from Q-TG and Q-DTG curves recorded under quasi-equilibrium
conditions. Significant differences in liquid desorption were observed from
the surfaces due to heterogeneous changes (energetic and geometrical) as a
result of modification. These results are compared with those obtained for
the samples heated at 160°C for 1 h. 相似文献
8.
P. Staszczuk D. Sternik G. W. Chądzyński E. Robens M. Błachnio 《Journal of Thermal Analysis and Calorimetry》2006,86(1):133-136
Nitrogen
adsorption measured at 77 K was used to characterize the surface heterogeneity
of high-temperature superconductor surfaces. Properties relating to adsorption
and porosity of the solids (adsorption capacity, specific surface area, radii
and volume of the pores, pore-size distribution function) were determined
from nitrogen adsorption–desorption isotherms and atomic force microscopy
(AFM) for a series of oxide superconductors. It is shown that the adsorption
isotherms of all samples are S-shaped and belong to type II according to the
IUPAC classification. On the basis of the nitrogen adsorption isotherms and
AFM data, fractal dimensions were determined and correlations found with adsorption
and porosity parameters. 相似文献
9.
Piotr Staszczuk Dagmara Zimmerman-Rysz 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1101-1110
The paper presents the physicochemical (adsorption and porosity) properties of closed carbon nanotubes, opened through the action of an oxidizing acid and modified with metal ions of nickel, cobalt, and iron/cobalt. The carbon nanotubes were prepared via the oxidation process by means of 65 % nitric acid and/or nickel and cobalt nitrates dissolved with 65 % nitric acid. Using special thermogravimetry Q-TG and sorptometry methods physicochemical properties of pure and modified nanotube surfaces were investigated. A numerical and analytical procedure for the evaluation of heterogeneous properties (adsorption capacity, statistical number of adsorbed liquid layers, desorption energy distribution functions) on the basis of liquid thermodesorption Q-TG from the sample surfaces under the quasi-equilibrium conditions are presented. The calculations of the specific surface areas, pore size and volume, and fractal dimensions of carbon nanotubes were made from sorptometry data. 相似文献
10.
P. Staszczuk 《Chromatographia》1985,20(12):724-728
Summary Investigation of water adsorption by the step profile method (Glueckauf method) was carried out with the help of a modified gas chromatography equipped with thermal-conductivity detector. On the basis of the adsorption isotherm obtained, the water film pressure and the polar component of the surface free energy of quartz were calculated. The calculated value of the polar component of the surface free energy of quartz agrees with analogous values obtained by other methods. 相似文献