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Surface conductivity is an additional electric conductivity of fluid in the vicinity of the charged surface. Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an Electric current. FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code Fluid conductivity is associated with ions motion in electric field. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can Concentration of ions is higher close to the charged surfaces. They are attracted there by electrostatic forces induced by the surface charge. Surface charge is the Electric charge present at an interface, for instance on the Surface of a Semiconductor material or for example on the This layer with higher ions concentration is a part of the interfacial Double Layer. Higher concentration of ions in this layer leads to higher conductivity.

Smoluchowski was the first one who recognized importance of the surface conductivity at the beginning of the 20th century [1]. Marian Smoluchowski ( Marian Ritter von Smolan Smoluchowski, 28 may 1872 in Vorderbrühl near Vienna - 5 September

There is detail description of the surface conductivity by Lyklema in "Fundamentals of Interface and Colloid Science" [2]

Double Layer has two regions, according to well established Gouy-Chapmann-Stern model, Ref. 2. The upper level, which is in contact with fluid bulk is diffuse layer. Double Layer (interfacial (DL also called electrical double layer EDL is a structure that appears on the surface of an object when it is placed into a Liquid Interior part, that is in contact with interface is Stern layer. Double Layer (interfacial (DL also called electrical double layer EDL is a structure that appears on the surface of an object when it is placed into a Liquid

It is possible that lateral ions motion in both part of the DL contributes to the surface conductivity.

Contribution of the Stern layer is less known. It is often called "additional surface conductivity" [3].

Theory of the surface conductivity over diffuse part of the DL has been developed by Bikerman [4]. He derived a simple equation that links surface conductivity κσ with properties of ions and interface. For symmetrical electrolyte and assuming indentical ions diffusion coefficients D+=D-=D it is given in the Ref. 2:

{\kappa}^{\sigma} = \frac{4F^2Cz^2D(1+3m/z^2)}{RT\kappa}(cosh\frac{zF\zeta}{2RT}-1)

where

F is Faraday constant
T is absolute temperature
R is gas constant
C is ions concentration in bulk
z is ion valency
ζ is electrokinetic potential

Parameter m characyterizes contribution of electro-osmosis into motion of ions within DL:

m = \frac{2\varepsilon_0\varepsilon_m R^2T^2}{3\eta F^2 D}

There is dimensionless parameter Dukhin number that characterizes contribution of the surface conductivity to variety of electrokinetic phenomena, such as electrophoresis, and electroacoustic phenomena. In Physics and Chemistry, the Faraday constant (named after Michael Faraday) is the magnitude of Electric charge per mole of Thermodynamic temperature is the absolute measure of Temperature and is one of the principal parameters of Thermodynamics. Relationship with the Boltzmann constant The Boltzmann constant kB (often abbreviated k) may be used in place of the gas constant by working An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge In Chemistry, valence, also known as valency or valency number, is a measure of the number of Chemical bonds formed by the Atoms Double Layer (interfacial (DL also called electrical double layer EDL is a structure that appears on the surface of an object when it is placed into a Liquid In Electrochemistry, Physics and Vascular plant biology, electro-osmosis, also called electroendosmosis, is the motion of polar Dukhin number is dimensionless quantity that characterizes contribution of the Surface conductivity to various Electrokinetic and Electroacoustic effects Electrokinetic phenomena is a family of several different effects that occur in Heterogeneous Fluids or in porous bodies filled with fluid Electrophoresis is the most well-known electrokinetic phenomenon. Electroacoustic phenomena arises when Ultrasound propagates through a Fluid containing Ions.

See also

References

  1. ^ M. Interface and colloid science is a branch of Chemistry dealing with Colloids Heterogeneous systems consisting of a mechanical mixture of particles between von Smoluchowski, Physik, Z. , 6, 529 (1905)
  2. ^ Lyklema, J. "Fundamentals of Interface and Colloid Science", vol. 2, Academic Press, 1995
  3. ^ Dukhin, S. S. and Derjaguin, B. V. "Electrokinetic Phenomena", John Wiley and Sons, NY (1974)
  4. ^ Bikerman, J. J. Z. Physik. Chem. A163, 378, 1933

External links

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