The paper deals with physical mechanisms of disintegration of solid particles in new device called WJM-“Water Jet Mill” and a global description of the said system includes internal milling cycles and particle size separators of a liquid suspension. A disintegration agent here is a high energy liquid jet influence with outlet velocity about 660 m∙s-1 and high level of cavitation in disintegration zones. Dominate disintegration mechanism affected by cavitation bubble implosions direct on a particle surface inside a liquid suspension brings about a particle refinement to the level under 100 nm followed with a small mechanical damage of ar impact target. in the paper, results of aggregates morphology of silicon nanoparticles prepared using disintegrator WJM have been presented via separated chapter of Atomic Force Microscopy AFM, Scanning Electronic Microscopy SEM, confocal optical microscopy, and laser diffraction. and Práce prezentuje fyzikální mechanismy desintegrace pevných částic v novém zařízení, pracovně nazývaném WJM (Water Jet Mill) a globální popis uvedeného systému včetně interních mlecích cyklů a rozměrových separátorů partikulární kapalinové suspenze. Desintegračním činitelem je zde působení vysokoenergetického kapalinového paprsku s výtokovou rychlostí cca 660 m∙s-1 a vysokou mírou kavitace v desintegračních zónách. Z dosahované míry zdrobnění až do oblasti pod 100 nm a z malého mechanického poškození impaktního terče vyplývá dominantní mechanismus dezintegrace implozí kavitačních bublin přímo na povrchu částic uvnitř kapalinové suspenze. V samostatných oddílech mikroskopie atomárních sil AFM, skenující elektronové mikroskopie SEM, konfokální optické mikroskopie a laserové difrakce jsou následně prezentovány výsledky analýzy morfologie agregátů nanočástic křemíku připravených v desintegrátoru WJM.
This study explored the effect of soil water repellency (SWR) on soil hydrophysical properties with depth. Soils were sampled from two distinctly wettable and water repellent soil profiles at depth increments from 0–60 cm. The soils were selected because they appeared to either wet readily (wettable) or remain dry (water repellent) under field conditions. Basic soil properties (MWD, SOM, θ v) were compared to hydrophysical properties (Ks, Sw, Se, Sww, Swh, WDPT, RIc, RIm and WRCT) that characterise or are affected by water repellency. Our results showed both soil and depth affected basic and hydrophysical properties of the soils (p<0.001). Soil organic matter (SOM) was the major property responsible for water repellency at the selected depths (0–60). Water repellency changes affected moisture distribution and resulted in the upper layer (0–40 cm) of the repellent soil to be considerably drier compared to the wettable soil. The water repellent soil also had greater MWDdry and Ks over the entire 0–60 cm depth compared to the wettable soil. Various measures of sorptivity, Sw, Se, Sww, Swh, were greater through the wettable than water repellent soil profile, which was also reflected in field and dry WDPT measurements. However, the wettable soil had subcritical water repellency, so the range of data was used to compare indices of water repellency. WRCT and RIm had less variation compared to WDPT and RIc. Estimating water repellency using WRCT and RIm indicated that these indices can detect the degree of SWR and are able to better classify SWR degree of the subcritical-repellent soil from the wettable soil.
The aim of this study was to determine the potential development of water sorptivity of soil aggregates by heating. Soil aggregates were sampled from arable layer of 5 Polish soils: Haplic Luvisol 1 from Czesławice, Haplic Luvisol 2 from Wierzchucinek, Haplic Cambisol from Felin, Gleyic Mollic Cambisol from Chylice, and Haplic Phaeozem from Grabiec. Three aggregates of each soil type with minimum diameter between 4 and 10 mm were heated in the oven for at least 3 hours at temperatures 20, 100, 200, 250, and 360ºC. After each temperature treatment the soil aggregates were conditioned at the room temperature for 16 hours. Laboratory measurements of water sorptivity of soil aggregates were performed under a negative tension h0 = -2 cm using tension infiltrometer. It was found that the exposure to temperatures between 100 and 200°C tends to decrease water sorptivity of aggregates from all the studied soils but one (Haplic Luvisol 1), followed by about two- to four-fold increase in water sorptivity for exposure to temperatures of 250°C (in Haplic Luvisol 1, Haplic Luvisol 2, and Haplic Phaeozem) or 360°C (in Haplic Cambisol and Gleyic Mollic Cambisol).
Reduced soil tillage practices are claimed to improve soil health, fertility and productivity through improved soil structure and higher soil organic matter contents. This study compares soil structure stability of soil aggregates under three different tillage practices: conventional, reduced and no tillage. The erosive strength of soil aggregates has been determined using the abrasion technique with the soil aggregate erosion chambers (SAE). During abrasion soil aggregates have been separated into the exterior, transitional and interior regions. The forces needed to remove the material from the aggregate were calculated as erosive strength and compared with the tensile strength of the aggregates derived from crushing tests. The relationship between aggregate strength and other soil properties such as organic carbon and hydrophobic groups’ content has also been identified. The results show that erosive and tensile strength of soil aggregates is very low in topsoil under conventional and reduced tillage comparing with the subsoil horizons. Negative correlation was found between the content of organic carbon, hydrophobic compounds and erosive aggregate strength which suggests that the stabilising effect of soils organic carbon may be lost with drying. The positive relationship between the tensile strength and erosive strength for aggregates of 8–5 mm size suggests that the total strength of these aggregates is controlled by the sum of strength of all concentric layers.