In ceramic processing, the study of the different phases of the drying stage considers the material at a macroscopic scale. Very often, the various parameters (among which the temperature and the relative humidity) ar...In ceramic processing, the study of the different phases of the drying stage considers the material at a macroscopic scale. Very often, the various parameters (among which the temperature and the relative humidity) are chosen in an empirical way, mostly through visual observations. This stage is governed by capillary phenomena which take place within the material, responsible for both the shrinkage and the risk of cracks which can damage the final piece. As part of a better understanding of the local mechanisms during drying, liquids contained in the pores have been reproduced in an ideal case. Drying kinetics and parameter measurements from 303 to 343 K of deionized water liquid bridges between two plates of silicon wafers are presented. Experimental work was carried out using specific device to create liquid bridges, coupled with image analysis and within an adapted instrumented climatic chamber. While the volume and the exchange surface of liquid bridges decrease regularly throughout the drying process, contact angles only diminish at the end. One of the four contact angles may have a different variation, which results in a pinned contact line in its area and reveals a local change of the surface state. From these measurements and observations, the liquid bridge break is proposed as a cracking criterion of porous materials during drying. Indeed, the challenge is to limit the risk of cracking and damaging pieces during this crucial step in material processing.展开更多
Cemented paste backfill(CPB)is largely used in underground mine stopes worldwide.When a CPB is placed in a stope,an important task is to estimate the settlement associated with the shrinkage and selfweight consolidati...Cemented paste backfill(CPB)is largely used in underground mine stopes worldwide.When a CPB is placed in a stope,an important task is to estimate the settlement associated with the shrinkage and selfweight consolidation of the CPB.This is closely related to the volume management to ensure the stability of barricades and tight contacts between the backfill and stope roof.Over the years,shrinkage studies were mostly performed on fine-grained soils(silts and clays),with only a few publications on the shrinkage behavior of uncemented tailings.No study has been published on the shrinkage behavior of CPB.To fill this gap,a series of shrinkage tests has been conducted on CPB with different cement contents,including zero cement content(uncemented paste backfill,uCPB).The results show that the shrinkage response of CPB is very different from that of uCPB.At a given initial water content,CPB exhibits a shorter normal shrinkage stage than uCPB.The unsaturation onset water content and void ratio,shrinkage limit and final void ratio of CPB are generally higher than those of uCPB.At a given cement content,the shrinkage behaviors of CPB and uCPB are significantly influenced by the initial water content.展开更多
The evaporation of sessile water droplets on hydrophobic surfaces is a topic which led to numerous investigations. However, how does the liquid behave when the evaporation occurs between two of these particular substr...The evaporation of sessile water droplets on hydrophobic surfaces is a topic which led to numerous investigations. However, how does the liquid behave when the evaporation occurs between two of these particular substrates? The drying stage is governed by capillary phenomena which takes place in a confined space. In the field of material shaping, it is also possible that some regions of a green body exhibit hydrophobic properties. As part of a better understanding of the local mechanisms during drying, liquid bridges have been reproduced in an ideal case. Drying kinetics and parameters measurements from 303 to 343 K (relative humidity of 55%) of deionized water liquid bridges between two plates of hydrophobic substrates are presented. Experimental work was carried out using a specific device to create liquid bridges, coupled with image analysis within an adapted instrumented climatic chamber. While the volume and the exchange surface of liquid bridges decrease regularly throughout the process, contact angles constantly diminish and more significantly at the end. This is different from the evaporation between two hydrophilic plates. From these measurements, the change of curvature of the liquid bridges during evaporation is highlighted.展开更多
文摘In ceramic processing, the study of the different phases of the drying stage considers the material at a macroscopic scale. Very often, the various parameters (among which the temperature and the relative humidity) are chosen in an empirical way, mostly through visual observations. This stage is governed by capillary phenomena which take place within the material, responsible for both the shrinkage and the risk of cracks which can damage the final piece. As part of a better understanding of the local mechanisms during drying, liquids contained in the pores have been reproduced in an ideal case. Drying kinetics and parameter measurements from 303 to 343 K of deionized water liquid bridges between two plates of silicon wafers are presented. Experimental work was carried out using specific device to create liquid bridges, coupled with image analysis and within an adapted instrumented climatic chamber. While the volume and the exchange surface of liquid bridges decrease regularly throughout the drying process, contact angles only diminish at the end. One of the four contact angles may have a different variation, which results in a pinned contact line in its area and reveals a local change of the surface state. From these measurements and observations, the liquid bridge break is proposed as a cracking criterion of porous materials during drying. Indeed, the challenge is to limit the risk of cracking and damaging pieces during this crucial step in material processing.
基金The authors would like to acknowledge the financial support from the Natural Sciences and Engineering Research Council of Canada(Grant No.NSERC 402318)Fonds de recherche du Québec-Nature et Technologies(Grant No.FRQNT 2015-MI-191676)+1 种基金Mitacs Elevate Postdoctoral Fellowship(Grant No.IT12573)industrial partners of the Research Institute on Mines and the Environment(RIME UQAT-Polytechnique).
文摘Cemented paste backfill(CPB)is largely used in underground mine stopes worldwide.When a CPB is placed in a stope,an important task is to estimate the settlement associated with the shrinkage and selfweight consolidation of the CPB.This is closely related to the volume management to ensure the stability of barricades and tight contacts between the backfill and stope roof.Over the years,shrinkage studies were mostly performed on fine-grained soils(silts and clays),with only a few publications on the shrinkage behavior of uncemented tailings.No study has been published on the shrinkage behavior of CPB.To fill this gap,a series of shrinkage tests has been conducted on CPB with different cement contents,including zero cement content(uncemented paste backfill,uCPB).The results show that the shrinkage response of CPB is very different from that of uCPB.At a given initial water content,CPB exhibits a shorter normal shrinkage stage than uCPB.The unsaturation onset water content and void ratio,shrinkage limit and final void ratio of CPB are generally higher than those of uCPB.At a given cement content,the shrinkage behaviors of CPB and uCPB are significantly influenced by the initial water content.
文摘The evaporation of sessile water droplets on hydrophobic surfaces is a topic which led to numerous investigations. However, how does the liquid behave when the evaporation occurs between two of these particular substrates? The drying stage is governed by capillary phenomena which takes place in a confined space. In the field of material shaping, it is also possible that some regions of a green body exhibit hydrophobic properties. As part of a better understanding of the local mechanisms during drying, liquid bridges have been reproduced in an ideal case. Drying kinetics and parameters measurements from 303 to 343 K (relative humidity of 55%) of deionized water liquid bridges between two plates of hydrophobic substrates are presented. Experimental work was carried out using a specific device to create liquid bridges, coupled with image analysis within an adapted instrumented climatic chamber. While the volume and the exchange surface of liquid bridges decrease regularly throughout the process, contact angles constantly diminish and more significantly at the end. This is different from the evaporation between two hydrophilic plates. From these measurements, the change of curvature of the liquid bridges during evaporation is highlighted.
