Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (23)
- Posterpräsentation (11)
- Vortrag (10)
- Beitrag zu einem Sammelband (4)
- Forschungsbericht (3)
- Buchkapitel (2)
- Beitrag zu einem Tagungsband (1)
- Sonstiges (1)
Sprache
- Englisch (38)
- Deutsch (16)
- Mehrsprachig (1)
Schlagworte
- Gasadsorption (4)
- Specific surface area (4)
- Gas adsorption (3)
- Porosity (3)
- Poröse Materialien (3)
- Computertomographie (2)
- Hg-Porosimetrie (2)
- Mechanochemistry (2)
- Metal-organic frameworks (2)
- Pore size distribution (2)
- Porous materials (2)
- Referenzmaterialien (2)
- SAXS (2)
- Adsorption isotherm (1)
- Aerogels (1)
- Al2O3 ceramics (1)
- Allermöhe (1)
- Alumina (1)
- Anhydritzement (1)
- Atomic mass (1)
- Average pore size (1)
- Bootstrap confidence bands (1)
- Bootstrap prediction bands (1)
- C-14-PMMA impregnation (1)
- C14-PMMA-Imprägnations-Radiographie (1)
- Capillary condensation (1)
- Cellulose (1)
- Certified pressure (1)
- Certified reference material (1)
- Certified reference materials (1)
- Density (1)
- Diffusion (1)
- Disperse Feststoffe (1)
- Dispersed solids (1)
- Dynamic mechanical analysis (1)
- ESW (1)
- Electron volt (1)
- Flammability (1)
- Gel (1)
- Geothermie (1)
- Green-chemistry synthesis (1)
- He-Diffusion (1)
- Hg porosimetry (1)
- IUPAC physical and biophysical chemistry division (1)
- Image analysis (1)
- Internal surface density (1)
- Liquid intrusion (1)
- MMA-Diffusion (1)
- MOF-14 (1)
- Macroporous materials (1)
- Mass (1)
- Mercury intrusion (1)
- Mercury intrusion porosimetry (1)
- Mercury porosimetry (1)
- Mercury prorsimetry (1)
- Mesopores (1)
- Micropores (1)
- Mikroporenbestimmung (1)
- N2 sorption (1)
- Nanocomposite (1)
- Nanoporous solids (1)
- Niobium and tantalum carbides (1)
- Normen (1)
- Normung (1)
- Nuclear waste disposal (1)
- Oberfläche (1)
- Optische Mikroskopie (1)
- Particle (1)
- Partikel (1)
- Permeation (1)
- Phase transitions (1)
- Polyurethane (1)
- Pore (1)
- Pore radius (1)
- Pore size (1)
- Pore size characterization (1)
- Pore structure (1)
- Poren (1)
- Porenradius (1)
- Porosimetry (1)
- Porosity fluctuation (1)
- Porous ceramics (1)
- Quecksilberporosimetrie (1)
- Reference material (1)
- Reference porous materials (1)
- Relative (1)
- Rhätsandstein (1)
- Rock porosity (1)
- SEM (1)
- Silica (1)
- Small-angle X-ray scattering (1)
- Sol-gel processing (1)
- Specific (1)
- Specific pore volume (1)
- Spezifische Oberfläche (1)
- Spezifisches Porenvolumen (1)
- Standardization (1)
- Statistical reconstruction of porous solids (1)
- Stimulation (1)
- Strength (1)
- Surface (1)
- Thermal analysis (1)
- Thermal conductivity (1)
- Volume curve (1)
- Wassersättigung (1)
- Weight (1)
- X-ray refraction topography (1)
- X-ray refractometry (1)
- ZRM-Entwicklung (1)
- Zertifizierte Referenzmaterialien (1)
Eingeladener Vortrag
- nein (10)
Aiming at ceramic materials of low thermal radiation emittance titania yttrium oxide ceramics have been prepared by sintering in air at 1,100 and 1,400 °C, respectively, and characterised. Due to its high infrared refractive index, average pore sizes up to 1 µm for optimal Mie scattering cross sections and over 35% porosity the material is a promising candidate for elevated temperature insulations. The essentially in large pore growth is achieved by graphitic nano and micro particle additives.
The microstructure parameters of porosity, specific surface area, median and average pore sizes are determined by mercury intrusion porosimetry. Beyond this classical technique supplementary measurements by X-ray Absorption and X-ray refractometry reveal considerably larger average pore sizes due to closed pores not accessible for mercury. An additional advantage of the X-ray techniques is their non-destructive application, which allows other treatments afterwards. The combined application of both methods provides additional information and reliability in case of complex ceramic microstructures and may serve for improved developments of porous ceramics with optimised thermal scattering for energy savings in high temperature applications.
The analysis of the porosity of materials is an important and challenging field in analytical chemistry. The gas adsorption and mercury intrusion methods are the most established techniques for quantification of specific surface areas, but unfortunately, dry materials are mandatory for their applicability. All porous materials that contain water and other solvents in their functional state must be dried before analysis. In this process, care has to be taken since the removal of solvent bears the risk of an incalculable alteration of the pore structure, especially for soft materials. In the present paper, we report on the use of small-angle X-ray scattering (SAXS) as an alternative analysis method for the investigation of the micro and mesopores within cellulose beads in their native, i.e., water-swollen state; in this context, they represent a typical soft material. We show that even gentle removal of the bound water reduces the specific surface area dramatically from 161 to 109 m² g-1 in cellulose bead sample type MT50 and from 417 to 220 m² g-1 in MT100. Simulation of the SAXS curves with a bimodal pore size distribution model reveals that the smallest pores with radii up to 10 nm are greatly affected by drying, whereas pores with sizes in the range of 10 to 70 nm are barely affected. The SAXS results were compared with Brunauer–Emmett–Teller results from nitrogen sorption measurements and with mercury intrusion experiments.
Characterization of organic aerogels as model materials for thermal conductivity measurements
(2008)
The pore size analysis of solids is widely applied in chemical industries, materials engineering, ceramic production, environmental engineering, catalysis, chromatography, nanotechnology, and many other fields. In spite of several new methods used for determining the pore size distribution of meso- and macropores [see IUPAC Recommendations of 1994], mercury porosimetry has remained one of the most popular methods employed for the characterisation of porous materials. In this paper, a new way is described for the estimation of certified pressure-volume curves from experimental curves measured by different laboratories in connection with the certification of new reference materials for a comparatively low-pressure range of mercury intrusion (<2 MPa). Simultaneous confidence and prediction bands for the certified pressure-volume curves are constructed by bootstrapping.
Abstract Porous and finely dispersed certified reference materials (CRM) were certified using the gas adsorption method. The special certification procedure for IUPAC isotherm classification types I, II, and IV is presented for meso- and macroporous materials with special emphasis on specific surface area, specific pore volume and pore width according to standards DIN 66 131, 66 134, and 66 135. Four CRMs (SiO2, f-Al2O3, two transition aluminas) with a macro- and mesopore range are presented. Certification was made on the basis of BCR guidelines in connection with interlaboratory tests (altogether 38 participating laboratories, 44 various gas adsorption apparatus).
This document deals with the characterization of porous materials having pore widths in the macropore range of 50 nm to 500 µm. In recent years, the development of advanced adsorbents and catalysts (e.g., monoliths having hierarchical pore networks) has brought about a renewed interest in macropore structures. Mercury intrusionextrusion porosimetry is a well-established method, which is at present the most widely used for determining the macropore size distribution. However, because of the reservations raised by the use of mercury, it is now evident that the principles involved in the application of mercury porosimetry require reappraisal and that alternative methods are worth being listed and evaluated. The reliability of mercury porosimetry is discussed in the first part of the report along with the conditions required for its safe use. Other procedures for macropore size analysis, which are critically examined, include the intrusion of other non-wetting liquids and certain wetting liquids, capillary condensation, liquid permeation, imaging, and image analysis. The statistical reconstruction of porous materials and the use of macroporous reference materials (RMs) are also examined. Finally, the future of macropore analysis is discussed.
Under environmental conditions water exists in all three classical States of matter: solid, liquid and gas. The water molecule is non-linear and therefore polar. In comparison with other liquids water has anomalous features; about 63 exceptional properties are recorded. This article starts with reviewing properties of water, typical occurrences and definitions such as relative and absolute humidity and moisture content.
Water is present everywhere in nature and engineering; it may be helpful or harmful. The survey concerns both: atmospheric hygrometry and usual measuring methods of the moisture content of solids and liquids as well as water Sorption. The determination of the atmospheric humidity is among the more difficult problems in metrology. In contrast, humidity determination of materials is simple; however the definition of the dry state is difficult. Because water is bound at and in solids and liquids in many different ways it tums out that the humidity content of materials is difficult to define and to measure accurately. We provide a survey on the measuring methods, describe the most important ones and discuss advantages and accuracy.
In the search for extraterrestrial water special remote measuring methods have been developed analysing the spectrum of electromagnetic radiation either of natural sources or produced by a probe and reflected. Spacious deposits have been detected photographically. In situ investigations are made using conventional methods.
With regard to the problems of measurements, Standardisation of measuring methods and procedures is required. There exist many institutions, which are engaged in investigating the use of water and standardising measuring methods. In tabular form, we give a survey on existing Standards.