Tag Archives: absorption

1548-1561 I. Černá, J. Pecen, T. Ivanova and Z. Piksa
The dependence of the durability of digestate briquettes and sorption properties on represented particle sizes
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The dependence of the durability of digestate briquettes and sorption properties on represented particle sizes

I. Černá, J. Pecen, T. Ivanova* and Z. Piksa

Czech University of Life Sciences Prague, Faculty of Tropical AgriSciences, Department of Sustainable Technologies, Kamýcká 129, CZ 16521 Prague 6, Czech Republic
*Correspondence: ivanova@ftz.czu.cz

Abstract:

Digestate, a product of the anaerobic digestion process, is traditionally used as liquid fertiliser. Besides agriculture use, it became possible to dry its separated solid part and compress it into briquette or pellet form. In the context of the characterisation of briquettes, the description here largely covers the mechanical properties of texture components and the distribution of particles within the briquette space. In order to define these properties and understand the relations between the mechanical part and any influencing factors, researchers started to identify the relationship between particles size distribution in briquettes and sorption properties and therefore mechanical properties. The objective of the present research was to compare size distribution in particles in different digestate samples and to study the connection to water sorption by briquettes and the durability of briquettes that have been made from two kinds of digestate material. For a comparison, two types of digestate were used, for which particles were split into a few size files according to the sieve size. By using digital image analysis, the dimensions of particles were specified and compared with values that were measured by means of a calliper. Sorption properties were defined through experimentation: exposing briquettes to a water source with water adsorption being determined via moisture content. Other mechanical properties were represented by toughness and the rate of abrasion. As result, digestate is an appropriate sorption matter which can multiply its initial mass by a factor of five if the water supply is sufficient. In the case of a dimension measurement of particles, digestate texture is represented by particles with one prevalent dimension, in most cases this being length. The length of particles was between approximately 1mm to 9mm. The digestate has been proven to be a good water sorbent material and can be applied in various sectors of agriculture.

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1015–1022 T. Koppel, A. Shiskin, I. Hussainova, H. Haldre and P. Tint
Electromagnetic shielding properties of ceramic spheres coated with paramagnetic metal
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Electromagnetic shielding properties of ceramic spheres coated with paramagnetic metal

T. Koppel¹*, A. Shiskin², I. Hussainova¹, H. Haldre³ and P. Tint¹

¹Tallinn University of Technology, Ehitajate 5, EE 12616 Tallinn, Estonia
²Faculty of Material Science and Applied Chemistry, Riga Technical University, 3 Paula Valdena str, LV-1048 Riga, Latvia
³Institute of Environmental Health and Safety, Jaam 14, EE 11615 Tallinn, Estonia
*Correspondence: tarmo.koppel@ttu.ee

Abstract:

 This study utilized a setup of radiofrequency generating and metering instruments to measure the reflective and pass-through properties of the innovative material of paramagnetic metal coated ceramic hollow spheres (MCS). The dimensions of the spherical articles reside around 50–250 μm, the thickness of metal (Cu) coating is 0.5–1.3 μm. The radiofrequency field was of 2.4 GigaHertz (GHz) frequency and radiated towards the material via a waveguide-horn antenna at 100 mWt power output. Two additional waveguide-horn antennas connected to a radiofrequency analyzer measured the reflection and pass-through characteristics of the material. Reflection and pass-through coefficients (from 0 to 1) were calculated to each tested sample. The material was tested at different thicknesses: from single – to multi (up to 5) mono-layers and 5 mm layer in bulk condition of MCS.
The measurement results show insignificant shielding characteristics for 1 to 5 layer thickness samples: pass-through coefficient from 0.96 to 0.92. Noteworthy shielding characteristics were starting to show in case of MCS mixed with graphite emulsion: transmission coefficient dropped to 0.16.
The latter sample demonstrates the prospective shielding characteristics of the material, since most of the radiofrequency radiation was not allowed to pass through the material neither to be reflected, but absorbed within the structure of the material.

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