Aggregation and chimney formation during the solidification of ammonium chloride.
نویسندگان
چکیده
Experiments study large-scale pattern formation during the growth of ammonium chloride (NH4Cl) from solution in a thin (Hele-Shaw) geometry. In particular a solid-liquid mixture ("mushy layer") forms in which growing solid NH4Cl crystals form a solid network interspersed with liquid. There are different ways that the mushy layer can be formed, however. If the cell is heated from below and cooled from above, thermal convection generates large-scale recirculating flows that carry seed crystals from the upper (cold) boundary to the (warmer) side and bottom boundaries. Ballistic deposition of these seed crystals leads to aggregation patterns with significant voids (filled with liquid) with a wide range of length scales. If the cell is cooled from below with a warm environment, the solid NH4Cl grows dendritically without deposition, resulting in a compact mushy layer. Plume convection within this mushy layer produces one or two well-defined "chimneys." If the environment is cool (comparable to the liquidus temperature of the solution), the mushy layer forms by a combination of dendritic growth and ballistic deposition, resulting in a more permeable mushy layer and enhanced chimney formation. The effects of ballistic deposition are enhanced if the cell is tipped, in which case the voids reappear. Plume convection and chimney formation are dramatically enhanced in this case. Additional experiments are done in which fluid flows in the system are enhanced artificially to verify that enhancements in chimney formation are due primarily to the aggregation process, and not to the increases in fluid flows due to thermal and compositional convection.
منابع مشابه
Competitive particle growth at different conditions of oligo-micelle formation in hydro-alcoholic solution of anionic double-chain emulsifier via batch emulsion polymerization of vinyl chloride
The condition of oligo-micelle formation of sodium di-isodecyl sulfosuccinate (SDIDS) emulsifier in hydroalcoholic solutions is used to study particle formation of vinyl chloride emulsion polymerization in a batch reactor. The change on micellization behavior was investigated by critical micelle concentration (CMC) and zeta potential parameters. To detect the occurrence of secondary nucleation ...
متن کاملMultifractal patterns formed by laser irradiation in GeAl thin multilayer films.
Fractal ' growth processes have been the subject of extensive experimental, numerical and theoretical studies in the last decade. Processes that give rise to the formation of very complex structures include, for example, dendritic solidification in an undercooled medium, viscous fingering, or electrochemical deposition. Fractal dimensions have been widely employed in an attempt to relate the ge...
متن کاملHOT CRACK FORMATION IN PURE CU AND CU-30%ZN ALLOY DURING IN SITU SOLIDIFICATION
The hot cracking susceptibility can be determined by establishing the transition temperature between brittle and ductile fracture at high temperature tensile testing of in situ solidified samples. High temperature tensile properties were determined for commercial cathodic pure Cu and Cu- 30%Zn alloy. The transition temperatures for pure Cu and Cu-30%Zn were evaluated from ultimate tensile stres...
متن کاملAssessment of the formation of inorganic oxidation by-products during the electrocatalytic treatment of ammonium from landfill leachates.
This work investigates the formation of oxidation by-products during the electrochemical removal of ammonium using BDD electrodes from wastewaters containing chlorides. The influence of the initial chloride concentration has been experimentally analyzed first, working with model solutions with variable ammonium concentration and second, with municipal landfill leachates. Two different levels of...
متن کاملEffect of Prunus Mahaleb L. Seed Extract on Ethylene glycol- and Ammonium Chloride-Induced Urolithiasis in BALB/c Mice
Background: Kidney stone disease can be quite painful, recurrent, and affects many people. Despite advances in drug therapy, there is still a need to find effective drugs with fewer complications for long-term treatment of kidney stones and to prevent its recurrence. The present study aimed to evaluate the effect of Prunus mahaleb L. seed extract on ethylene glycol- and ammonium chloride-induce...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
دوره 60 3 شماره
صفحات -
تاریخ انتشار 1999