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Accueil > Colloïdes, Verres et Nanomatériaux > Services et Plateformes > Conception d’instruments

Strain-controlled Rheometer, ARES-RFS

par Dominique CARON, Klaus STEUCKARDT - publié le

Table of Content

Short introduction to the instrument

Figure 1 : DSCN1582 © LCVN

  • A rheometer is a mechanical spectrometer that is capable of subjecting a sample to either a dynamic or a steady shear strain and do measure the resultant torque exerted by the sample in response to the shear strain.
  • Shear strain is applied by the motor ; torque is measured by the transducer.
  • Rheological experiments in the Charles Coulomb laboratory involve complex fluids (oil-water-surfactant systems) and composite fluids (fluids filled with nanoparticles). Linear and non linear rheology are investigated.

Instrument Specifications :

  • menu-driven software (Orchestrator Software)
  • viscosity range : 10-3 to 104 Pa.s
  • steady rates from 10-3 to 102 rad/s
  • dynamic rates from 10-5 to 102 rad/s
  • torques from 2x10-7 to 102 mN.m
Instrument :Strain-controlled Rheometer
Make :TA instruments
Model :ARES-RFS (Rheometrics Fluid Spectrometer)
Manufactured :2007
Update :
Localization :Building : 11, Floor : 1, Room : 137
Phone :(33) 4 67 14 35 88
Status :L2C , Dpt. CVN, soft matter group. Scientific collaborations involving the device are possible.
Scientific Responsible :Serge Mora
Technical Responsible :Jean Marc Fromental

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Detailed Features

This strain-controlled rheometer can be used to test samples for both oscillatory (dynamic mode) and steady (steady mode) shear measurements in three test fixture geometries : parallel plate, cone and plate and concentric cylinders (Couette). Concentric cylinders are especially useful for very low viscosity fluids, dispersions of limited stability, and for applications where fluid/solvent evaporation may be a concern.

Deformation : In the dynamic mode, the motor begins all tests at the motor zero position, and drives symmetrically about motor zero to the strain commanded by the software. The maximum angular deflection of the motor is 0.5 rad. The minimum deflection is 5 μrad. The angular frequency ranges from 10-5 to 200 rad/s.
In the steady mode, the motor can begin a test from any position, rotating clockwise or counterclockwise as specified by the software. The angular speed ranges from 10-3 to 100 rad/s.

Torque measurement : The rheometer is equipped with a torque captor from 0.2 μN.m to 100 N.m, and with a normal force sensor from 0,01 to 20 N.

Geometries : This apparatus is fitted with steel, titanium or plexiglass geometries, smooth or rough :

  • Couette : bob diameter is 32 mm, cup diameter is 34 mm, bob length is 33.2 mm.
  • Cone/plate : two diameters are available at the L2C : diameter 50 mm, cone angle : 0.02 radians (minimum sample volume : 0.65 cm3) or diameter 30 mm, cone angle : 0.02 radians.
  • Plate/plate : diameter is 50 mm, thickness between 0.5 to 2 mm.

Temperature control : Sample temperature can be controlled within a large range :

  • A fluid bath can be used with parallel plate, cone and plate, as well as with concentric cylinder geometries. The temperature range is -10 to 150 ºC.
  • A Peltier plate temperature control can be used with parallel plate and cone and plate geometries, with a temperature range of -30 to 150 °C. A platinum resistance thermometer sensor is positioned in the middle of the lower sample plate and ensures accurate measurement and control of sample temperature. Maximum heating rate is 30 °C/min with a temperature accuracy of +/- 0.1 °C.

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Further information

The ARES-RFS provides rapid response and extremely accurate strain resolution. These are essential for accurate determination of critical strains in structured fluids, stress relaxation studies, and the characterization of non linear rheological behaviour. The ARES-RFS air-lubricated, Force Rebalance Transducer combines high linearity, sensitivity, and stability with a five-decade range. This allows you to characterize materials over a broad viscosity range without having to change transducers. The ARES-RFS is also ideal for testing lower viscosity materials ; even materials with viscosities comparable to water.

(Optical) diagram (s) (to be completed)

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Miscellaneous – related instruments

  • The laboratory also possesses two other rheometers :
    An other strain controlled rheometer : a Rheometrics Fluid Spectrometer RFS 2 (1992). Although the main characteristics of this device are similar to that of the ARES-RFS, the ranges of the torque captor, of the frequency, the strain and the shear rate are more limited.
  • A stress control rheometer : Physica UDS 200 (1995). This device is appropriate for characterizing a wide variety of materials (broad spectrum of medium to high viscosity fluids). Shear rate range:10-2 to 103 s-1. Viscosity range:10-1 to 104 Pa.s. Temperature range : 0 to 50°C (Recirculating bath temperature control).

Figure 2 : Rheometrics Fluid Spectrometer RFS 2 © LCVN Figure 3 : Physica UDS 200 © LCVN

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Sample and Sample-Environment

Geometry
ApplicationsFluids, melts, Medium or high viscosity samplesFluids, melts
Medium or high viscosity samples
Fluids, melts
Medium or low viscosity samples
Sample volume (cm3)0.14 or 0.65variable8
Min/Max strain (%)0.25 / 2500-0.088 / 875
Min/Max shear rate (s-1)0.05 / 50000.0175 / 1750
Min/Max stress (Pa)0.004/95000.004/95000.004/2000
Temperature controlFluid bath or Peltier plate -30°C /150°CFluid bath or Peltier plate -30°C /150°CFluid bath -10°C /150°C
Advantages* Homogeneous shear
* Small sample volume
* Normal force measurements
* Easy handling
* Variable sample thickness
* Shear rate limits adjustable by changing gap
* Easy handling
* Large surface area
* High shear rate available
Disadvantages* Highly sensitive to correct positioning (gap) of cone and plate
* Sample preparation for high viscosity samples difficult
* Shear rate not constant* Large sample volume
* Possible shear history effects from loading

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To learn more about the instrument

http://www.tainstruments.com

Macosko, C.W. Rheology : principles , measurements and application, Weley-vch, 1994.

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