The Influence of Relative Humidity on Particle Adhesion – a                    Review of Previous Work and the Anomalous Behaviour of Soda-lime                    Glass

Cleaver, J.A.S.; Tyrrell, James W. G.

doi:10.14356/kona.2004008

Cited by 43 publications

(18 citation statements)

References 41 publications

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“…Water films resulting from molecular adsorption appear only on particles of the clay size, which are attached to the outside of the sand grains and form a large surface for evaporation. The importance of air humidity on cohesion forces of particles in the dust fraction above a relative humidity of 50 per cent as reported by Zimon (1982), Harnby et al (1996) and Cleaver and Tyrell (2004) is proven by these findings. Generally, silt and clay soils possess more stable micro-aggregates which can retain more water internally and do not react so sensitively to such small changes of water content.…”

Section: Wind-tunnel Investigationssupporting

confidence: 66%

Effect of moisture on fine dust emission from tillage operations on agricultural soils

Funk

Reuter

Hoffmann

et al. 2008

Earth Surf Processes Landf

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Tillage is an important cause of release of particulate matter (PM) from soils. Measurements in Europe indicate that emission of dust by tillage operations is many times higher than by natural wind erosion. In Europe there are two periods when most tillage operations are carried out -in spring and in late summer. These operations are carried out under different soil moisture conditions. In spring soil moisture is close to field capacity and the surface soil dries mainly by evaporation. At this surface a dry layer is established, which is only few centimetres thick and impedes further evaporation. A different situation occurs in late summer, when the crops have depleted the soil water in the root zone. In this case the soils are dried-up to a depth of some decametres. Tillage operations differ in depth and intensity, ranging from few centimetres of mixing at seedbed preparations to a few decametres of turning by ploughing. Hence, tillage-related emissions are the combined result of vertical soil moisture distribution and depth and intensity of tillage operations.The objective of our study is to determine the influence of soil moisture on the particulate matter emission of soils subjected to mechanical disturbance, particularly tillage. Because the emission is a result of many variables that cannot be controlled in field experiments, we followed a stepwise analysis of the main influencing factors. First, we used a wind tunnel as a cross-flow gravitational separator to investigate the relation between soil type, soil moisture and fine dust emission. Twelve soils of different texture were investigated with regard to their water content within a range from 0 to 40 per cent mass. The results show that soils can emit dust over a certain range of moisture, but even a small increase in soil moisture causes a distinct reduction of dust emission. The threshold water content for fine dust emission of soils was between 2 and 5 per cent mass for sandy soils, 5-10 per cent mass for silty soils, about 30 per cent mass for the clayey soils and 25-45 per cent mass for organic soils.The wind-tunnel results were used to calculate the PM 10 emission potential of a sandy soil in spring and late summer for a tillage depth of 20 cm by taking the measured vertical soil moisture profiles at these times into consideration. In spring only the upper 2·5 cm was dry enough to emit PM 10 , whereas in summer the soil was desiccated to the entire tillage depth. The calculated PM 10 emission potential resulted in 13·4 g m Our results show the importance of the vertical soil moisture profile on the PM emission of soils. Therefore, the emission factors resulting from field operations should preferably be related to the affected amount/volume of a soil that is dry enough to emit PM rather than to the affected area. This is confirmed by the good correlation between the proportions of affected soil to the measured emissions. Our findings show that the differences between results obtained from laboratory methods and field measurements need furth...

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Section: Wind-tunnel Investigationssupporting

confidence: 66%

Effect of moisture on fine dust emission from tillage operations on agricultural soils

Funk

Reuter

Hoffmann

et al. 2008

Earth Surf Processes Landf

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“…The influence of relative humidity (RH) on adhesion force is discussed by Harriman and Simkins [185] and Bracken [42,44,46,48,[186][187][188]. The significance of air humidity in powder processing is stressed by Harnby et al [189].…”

Section: Influence Of Humidity On Adhesionmentioning

confidence: 99%

“…It is well known that humidity influences the cohesion in powders and the adhesion of particles to surfaces [44][45][46][47][48]. One reason is certainly the meniscus force.…”

Section: Introductionmentioning

confidence: 99%

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

et al. 2006

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To optimize the handling of fine powders in industrial applications, understanding the interaction forces between single powder particles is fundamental. The forces between colloidal particles dominate the behavior of a great variety of materials, including paints, paper, soil, and many industrial processes. With the invention of the atomic force microscope (AFM), the direct measurement of the interaction between single micron-sized particles became possible. The adhesional contact between a particle and a substrate is a parameter for analyzing pull-off force data generated by AFM. The aim of this study was to understand surface interactions between fine particles. I measured the adhesion forces between AFM tips or particles attached to AFM cantilevers and different solid samples. Smooth and homogeneous surfaces such as silicon wafer, mica, or highly oriented pyrolytic graphite (HOPG), and more rough and heterogeneous surfaces such as iron particles or patterns of TiO 2 nanoparticles on silicon wafer were used. First, I addressed to the wellknown issue that AFM adhesion experiment results show wide distributions of adhesion forces rather than a single value. My experimental results show that variations in adhesion forces comprise fast (i.e., from one force curves to the next) random fluctuations and slower fluctuations, which occur over tens or hundreds of consecutive measurements. Slow fluctuations are not likely to be the result of variations in external factors such as lateral position, temperature, humidity, and so forth because those were kept constant. Even if two solid bodies are brought into contact under precisely the same conditions (same place, load, direction, etc.) the result of such a measurement will often not be the same as for the previous contact. The measurement itself will induce structural changes in the contact region which can change the value for the next adhesion force measurement.In the second part I studied the influence of humidity on the adhesion of nanocontacts. Humidity was adjusted relatively fast to minimize tip wear during one experiment. For hydrophobic surfaces, no signification change of adhesion force with humidity was observed. Adhesion force-versus-humidity curves recorded with hydrophilic surfaces either showed a maximum or continuously increased. I demonstrate that the results can be interpreted with simple continuum theory of the meniscus force. The meniscus force is calculated based on a model that includes surface roughness and takes into account different AFM tip (or particle) shapes by a two-sphere-model.Experimental and theoretical results show that the precise contact geometry has a critical influence on the humidity dependence of the adhesion force.Changes of tip geometry on the sub-10-nm length scale can completely change adhesion force-versus-humidity curves. Our model can also explain the differences between earlier AFM studies, where different dependencies of the adhesion force on humidity were observed.Keywords: Atomic force microscopy (AFM), cantile...

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“…For SFA the two mica surfaces are molecularly smooth, and thus the measurements are reliable and consistent with the results using other methods. However, for AFM poor reproducibility in pull-off force measurements have been reported [62][63][64][65][66]. It appears that the results from AFM measurements are qualitative rather than quantitative.…”

Section: Verification Of Young-laplace Equationmentioning

confidence: 99%

On the modified Tabor parameter for the JKR–DMT transition in the presence of a liquid meniscus

Liechti

Ravi‐Chandar

2007

Journal of Colloid and Interface Science

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The Influence of Relative Humidity on Particle Adhesion – a Review of Previous Work and the Anomalous Behaviour of Soda-lime Glass

Abstract: The adhesion of fine particles plays a significant role in the performance of particulate processes and in the quality of particulate products.

Cited by 43 publications

References 41 publications

Effect of moisture on fine dust emission from tillage operations on agricultural soils

Effect of moisture on fine dust emission from tillage operations on agricultural soils

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

On the modified Tabor parameter for the JKR–DMT transition in the presence of a liquid meniscus

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