Chirality of electrodeposits grown in a magnetic field.
نویسندگان
چکیده
Electrodeposits grown around a point cathode in a flat, horizontal electrochemical cell have fractal form. When grown in the presence of a perpendicular applied magnetic field, the deposits develop a spiral structure with chirality which reverses on switching the field direction. These structures are modeled numerically using biased variants of the diffusion limited aggregation (DLA) model. The effects of electric and magnetic fields are modeled successfully by varying the probabilities that a random walker will move in a given direction as a result of a Coulomb force and the Lorentz force-induced flow of electrolyte past the deposit surface. By contrast, a numerical model which considers only the effect of the Lorentz force on individual ions, without reference to the surface of the growing deposit, produces spiral structures with incorrect chirality. The modified DLA model is related to the differential equations for diffusion, migration, and convection. Length scales in the problem are understood by associating the step length of the random walker with the diffusion layer thickness, the lookup radius with the hydrodynamic boundary layer thickness and a point on the numerical deposit with a nucleation center for growth of a crystallite.
منابع مشابه
Magnetic fields in electrochemistry: The Lorentz force. A mini-review
Some recent work on the flow induced by uniform or non-uniform magnetic fields acting on currents in an electrochemical cell is reviewed. The effects include modifying the structure and texture of electrodeposits including their chirality, controlling hydrogen bubble release, inducing microfluidic flow and influencing nucleation. Much of this depends on micro-magnetohydrodynamic flow, on a scal...
متن کاملخواص مغناطیسی نانو ذرات FeCo برای ذخیره سازی اطلاعات
Submicron FeCo magnetic grains with different percents of cobalt were grown in the presence of magnetic field. After omitting the excess ions and oxygen, heat treatment was performed and some samples were oriented in a polymer background in the presence of a magnetic field. The results of SEM, XRD, and magnetic measurements confirm the existence of induced magnetic anisotropy. As the strength...
متن کاملPatterning metallic electrodeposits with magnet arrays
The influence of a pattern of a magnetic field on the structure of metal deposits at the cathode of a small electrochemical cell is investigated for cobalt, nickel, copper, and zinc. The different magnetic properties of the ions in their oxidized and reduced states, together with the influence on the patterned electrodeposits of variables, including the structure of the array of small magnets u...
متن کاملOptical Chirality Enhancement in Twisted Arrays of Plasmonic Nano-rods
An important property of electromagnetic fields, which arises from the interaction between fields and chiral molecules, is called optical chirality. By enhancing this field property, while maintaining constant input power, we are able to increase absorption of circularly polarized light by chiral molecules of a certain handedness. This enhancement is achieved through the use of achiral plasmoni...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Physical review. E, Statistical, nonlinear, and soft matter physics
دوره 69 6 Pt 1 شماره
صفحات -
تاریخ انتشار 2004