A device for measuring the viscosity and density of liquids is presented. It is a Couette-type viscometer that uses a submerged rotor to measure the viscosity without errors originating in the contact of the rotor with the sample/air boundary. The inner cylinder is a glass rotor suspended in the liquid, and the outer cylinder is also made of glass. The rotor is stabilized on the axis of the outer cylinder by an electromagnetic force controlled by feedback from the rotor's vertical position. In the lower part of the rotor is an aluminum cylinder located in a magnetic field generated by rotating permanent magnets. The interaction of this rotating magnetic field with eddy currents generated in the aluminum cylinder causes rotation of the rotor. This rotation is optically detected, and viscosity is calculated from the measured angular velocity of rotor. The density of the liquid is calculated from the applied vertical equilibrating force. A computer controls the whole measurement. The device works at constant temperature or while scanning temperature. The sample volume is 1.6 ml, and the accuracy of measurement of both viscosity and density is ϳ0.1%. The range of measured densities is ͑0.7-1.4͒ g/ml, and viscosity can be measured in the range (3ϫ10 Ϫ4 -0.3) Pa s. The shear rate of the viscosity measurement varies in the range ͑20-300͒ s Ϫ1 . The accuracy of the temperature measurement is 0.02 K.
A novel rotary viscometer--developed for the determination of rheologic properties of liquid/air interface layers--is presented. The instrument can be used to measure the shear viscosity and the shear elasticity of liquid surfaces. It contains a rotor floating on the liquid surface which is rotated by means of an electromagnetic torque. A torsion filament is used to calibrate the applied torque. The viscosity data are obtained on the basis of the Navier-Stokes equation solved for the rotation of a cylinder touching the surface of water and submerged into the water. The time behavior of the surface viscosity of films gradually formed from solutions of some proteins as well as their activation energy is presented.
A composite material of graphite/polystyrene sulfonate was prepared by solvothermal method. The dissolution of polystyrene sulfonate in water ensures homogeneous distributions of graphite and creates composition material at room temperatures. Water removing by the drying, permit to prepare films. Structure of the film was analyzed by scanning electron microscopy. The influence of different ratio between graphite and polystyrene sulfonate is discussed.
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