Shear moduli in bcc-fcc structure transition of colloidal crystals

Abstract

Effective charges along the melting line of colloidal crystals J. Chem. Phys. 125, 194714 (2006) Shear moduli variation in the metastable-stable structure transition of charged colloidal crystals was investigated by the combination techniques of torsional resonance spectroscopy and reflection spectrometer. Modulus of the system increases with the proceeding of the transition process and it finally reaches the maximum value at the end of the transition. For colloidal crystals in stable state, the experimental moduli show good consistence with theoretical expectations. However, in the transition process, the moduli are much smaller than theoretical ones and this can be chalked up to crystalline imperfection in the transition state. C 2015 AIP Publishing LLC. [http://dx

Microliter viscometry using a bright-field microscope: η-DDM

“…In concentrated solutions, the viscosity also reflects the interactions between the macromolecules and can indicate, e.g., structural changes or aggregation. [5][6][7][8] Conventional viscometry, e.g. using a falling ball viscometer or Ostwald viscometer tube, has successfully been used to measure shear viscosity.…”

Determination of Bulk Modulus for a Colloidal Crystal with Highly Charged Particles by DC Electric Field

“…Here, the effective mobility charge, Z*, is measured from the fitting of the conductivity versus number density curve, 48,49 while the effective elasticity charge, Z*′, is determined from the fitting of shear modulus versus number density curve. 50,51 The difference of these two kinds of effective charges has been discussed thoroughly. 52,53 In this paper, the effective mobility charge, Z*, is used to calculate the conductivity of suspension when the crystal structure is formed in the experimental method since it is directly measured from conductivity.…”

Effect of void structures in crystalline structure on the shear moduli of charged colloidal crystals

“…Its theoretical limits are f A = 0.4 for homogeneously distributed strains and f A = 0.6 for homogeneously distributed stresses, respectively [26,27]. For polycrystalline samples a value of f A = 0.5 is encountered in most cases [16,28] and will also be used in this work. The Yukawa potential V Yukawa (r) which considers Coulomb repulsions only was usually used for V (r) in this shear modulus-potential model before [11,29,30].…”

“…This situation corresponds to harmonic lattice vibrations on the colloidal level which can be visible as shifts of the Bragg-peaks or distortions of the first structure factor peak. These standing waves are detected and frequency analyzed by time resolved static light scattering in combination with lock-in technique [16,21,54]. Resonance frequencies are observed at [15,21]: Fig.…”

“…In this respect the elasticity of the colloidal crystals has been studied in recent years both experimentally and theoretically [10][11][12][13][14]. Experimentally, shear elastic moduli of the colloidal crystals are usually measured through the method of torsional resonance spectroscopy (TRS) in which standing waves are excited when rotary oscillations are imposed on the colloidal crystals [15][16][17]. In the aspect of theoretical studies, general equations between two-body interatomic potentials in a lattice model and elastic constants were derived for monoatomic solids [18][19][20].…”