Theoretical study of reactive melt infiltration to fabricate Co-Si/C composites
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Abstract:
Cobalt-silicon based carbon composites (Co–Si/C) have established a noteworthy consideration in recent years as a replacement for conventional materials in the automotive and aerospace industries. To achieve the composite, a reactive melt infiltration process (RMI) is used, in which a melt impregnates a porous preform by capillary force. This method promises a high-volume fraction of reinforcement and can be steered in such a way to get the good “near-net” shaped components. A mathematical model is developed using reaction-formed Co–Si alloy/C composite as a prototype system for this process. The wetting behavior and contact angle are discussed; surface tension and viscosity are calculated by Wang’s and Egry’s equations, respectively. Pore radii of 5 μm and 10 μm are set as a reference on highly oriented pyrolytic graphite. The graphs are plotted using the model, to study some aspects of the infiltration dynamics. This highlights the possible connections among the various processes. In this attempt, the Co–Si (62.5 at.% silicon) alloy’s maximum infiltration at 5 μm and 10 μm radii are found as 0.05668 m at 125 s and 0.22674 m at 250 s, respectively.Keywords:
Pyrolytic carbon
Infiltration (HVAC)
Chemical vapor infiltration
Volume fraction
Chemical vapor infiltration
Carbon fibers
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An experimental measurement of dynamic contact angles of droplets and capillary bridges is presented. The hysteresis of water retention in unsaturated granular materials during wetting and drainage cycles has been numerically found to arise from the dynamics of solid-liquid contact angles as a function of local liquid volume. The system established here aims to experimentally investigate the correlation between contact angle dynamics and liquid volume in both droplets and capillary bridges on different surfaces through the following scenarios: wetting and drainage of droplets and capillary bridges; surface tension and capillary force variation; and spontaneous contact angles and liquid volume arising from the evaporation of droplets and capillary bridges.
Hysteresis
Capillary length
Capillary surface
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Summary Contact angle measurements play an important role in determination of liquid wettability and hence, recovery from hydrocarbon reservoirs. When a liquid sessile drop is placed on a surface the balance of dominant forces affects its spreading rate and the equilibrium state for the shape of the liquid drop. On a porous surface, the capillary forces of the pores play an important role on the droplet equilibrium state. In this study, the impact of the capillary-driven imbibition on air-liquid contact angle data has been investigated. In each test, contact angle, droplet volume, droplet height and base diameter have been measured versus time for various liquids using a well-equipped automatic drop shape analyzer. The experimental results show that the rate of imbibition depends on the properties of fluids (i.e. surface tension and viscosity) and porous rock (i.e. permeability and wetting tendency). Based on the experimental observations, a conceptual model has been proposed to describe the free imbibition rate into the porous substrate when the spreading rate of the liquid drop on the surface is negligible.
Imbibition
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Pyrolytic carbon
Chemical vapor infiltration
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The role of surface tension and wettability in the dynamics of air-liquid interfaces during immiscible fluid displacement flows in capillary tube driven by pressure has been investigated. The contact angle and capillary number drive the force wetting processes which is controlled by the balance between the capillary and the viscous lubrication forces. The dynamic wetting condition with the critical capillary number is studied analytically and validated experimentally, which demonstrates that the critical capillary number is associated with the contact angle, slip length and capillary radius.
Capillary pressure
Capillary length
Capillary surface
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2D C/SiC composites were fabricated by chemical vapor infiltration(CVI)combining with slurry infiltration(SI)process.Effects of content of SI-SiC particles on the microstructure and mechanical performances were investigated.The particles can be infiltrated into inter-bundle pores of fiber preform after CVI SiC for 80h.The density and mechanical strength of the as-fabricated composites increase not only with increasing the CVI SiC time before SI process,but also with decreasing content of the particles.The SI process greatly reduces the interlaminar shear strength,and has little influence on the tensile strength.
Chemical vapor infiltration
Infiltration (HVAC)
Shear Strength
Mechanical strength
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Volume fraction
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Multiphase flow
Capillary pressure
Wetting transition
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Introduction: Wettability and fluid absorption are two important bone scaffold characteristics that determine proper cell attachment and flow of nutrition and oxygen. To imitate the human bone structure, the current study was carried to investigate the effect of the porosity of bone scaffold and contact angle of the fluid by evaluating the height of capillary rise. Methods: The structure was simplified based on the circle and square pattern and evaluated using Computational Fluid Dynamic (CFD). Porosity and contact angle were varied from 50% to 80%, while the contact angle ranged from 0 degrees to 60 degrees. The result was evaluated further using statistical analysis. Results: The CFD result was in agreement with Jurin’s law (9% error). The height of capillary rise was found to be excellent for the square pattern, while the circle was found to work across all the investigated parameters better. The porosity was correlated with the height of capillary rise (r = -0.549). The strongest correlation happened to contact angle (r =-0.781). Conclusion: The study concludes that water absorption and wettability can be altered and improved based on porosity. Meanwhile, the height of capillary rise depends strongly on the contact angle.
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Meniscus
Crystal (programming language)
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