Porous ceramics from capillary suspension for soil moisture measurement
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Porous ceramics are used to measure the soil water tension. The soil water tension correlates with the free moisture in a soil and thus provides information about the irrigation requirements of plants growing in it. Knowledge of the soil water tension is therefore essential for the selection of a suitable irrigation concept.
Several challenges are placed on a porous ceramic, which can serve as the core element of a new type of moisture sensor: the realization of a high porosity with sufficient mechanical stability at the same time, as well as a pore size distribution suitable for the respective soil, depending on the application. Macro-porous inorganic sintered bodies with high porosity and small pore size in the micrometer range (0.5 – 50 mm) can be manufactured using capillary suspensions as precursors. In this project this method is used to develop ceramic elements with a wide pore size distribution, which serve as a measuring medium for dielectric measurements to characterize soil moisture. In order to achieve this, a suitable main and secondary liquid have to be determined, Al2O3 particle sizes will be adjusted and the volume fractions of the three phases will varied with respect to an optimized performance in humidity sensing.
These ceramic discs are to be used in depth-resolving soil water tension sensors for simultaneous measurement in different soil layers. Porosity and pore sizes must be adjusted so that the sensors can be used in a variety of soils and provide good measurement accuracy.
The project is carried out in cooperation with Truebner GmbH and funded by the KMU innovative initiative.