Facilities & Laboratories
Multiphase Fluids Characterization Laboratory
The Radiological Materials and Technology Development uses the Multiphase Fluids Laboratory for both research and implementation.
Instrumentation
1. Rheometer (APEL)
Rheological characterization is the most critical step to understand suspensions and slurries. Anton Paar MCR 301 can measure rheological properties of various slurries and colloidal suspensions such as viscosity, yield stress, shear strength, and storage and loss modulus via steady and oscillatory setups at different temperatures. Two different geometries, bob-in-cup and vane-in-cup, are available depending on conditions of sample. The picture below shows a setup with the bob-in-cup geometry which is typically used to perform a flow curve (shear stress vs. shear rate) experiment for slurries. A maximum torque allowed is 200mN·m and the measuring temperature can be varied from -10°C to 150°C in case water is used as a circulating medium.
Left:A rheogram for a waste simulant slurry sample. Right: A typical setup for Anton Paar MCR 301 with bob-in-cup geometry
.2. Zeta potential meter (APEL)
Zeta potential of particles in suspensions and slurries is one of the critical parameters to show the electrostatic interaction between suspended particles which influences rheological properties of suspensions and slurries. A zeta potential meter, DT-310 (Horiba), is based on electroacoustic method. A laser light scattering technique to measure zeta potential utilizes the motion of suspended particles so that high ionic concentration and high particle concentration environments typically create problems due to very slow mobility and hindered motion of suspended particles respectively. DT-310 can resolve these problems, especially for high particle concentration without dilution of a sample (without disturbing ionic concentration of a sample). This nature would be very valuable for many nuclear waste slurries. The range of the particle size is limited to only up to 2-3 microns for a laser light scattering technique but it can be up to 100 micron for DT-310 which covers a wide range of particle sizes. Furthermore, a titration burretts/pump system enables us to easily measure an isoelectric point of suspended particles in slurry.
3. Particle size analyzer
The size distribution of suspended particles significantly has been known to influence rheological properties of suspensions and slurries. Mastersizer 2000 (Malvern) measures the particle size distribution of various suspensions and slurries via the laser diffraction. The instrument uses a focused laser beam (He-Ne laser and solid-state light source) and subsequent scattering light by motion of particles. The angular intensity of the scattered light is then measured by a series of photosensitive detectors. When coupled with the Hydro G wet dispersion accessory, the Mastersizer can measure the size of particles ranging from 0.02 to 2000 µm. However, the actual range is dependent on the accessory used as well as the properties of the suspended particles being analyzed.
Mastersizer particle size distribution analyzer
An example of particle size distribution from the Mastersizer
4. Moisture analyzer
One of the fundamental parameters to characterize suspensions and slurries is a total solids content. Mettler Toledo Halogen Moisture Analyzer (Model HR83) provides this property. A small sample (~5 g) is heated in the moisture analyzer to 95°C and held at that temperature for 30 minutes to remove the free water; the temperature was then ramped up to 105°C and held at that final temperature until the mass decreased by less than 0.001 grams over 140 seconds. The mass of the dried sample divided by the mass of the initial sample is the total solids fraction. In addition, wt% of dissolved solid can be analyzed to identify the amount of dissolved solids of suspension/slurry from supernatant liquid of suspension/slurry. Combining the total solids content with wt% of dissolved solid, undissolved solids content (i.e., content of suspended particles) can be obtained.
Mettler Toledo Halogen Moisture Analyzer (Model HR83)
5. High Temperature Viscometer (APEL)
Viscosity is important not only for slurry but also for glass melt processing under very high temperature; its evaluation directly influences the designs of glass melter and processing conditions. The Brookfield DV-II+ viscometer measures shear stress and viscosity at given shear rates. The viscometer uses a spindle immersed in the sample fluid. The viscous drag of the fluid against the spindle is measured by the spring deflection and detected by rotary transducer. Especially, combined with furnace and a special spindle (see the picture below), the viscosity of glass melts can be measured at different high temperature ranges (typically 1100-1200°C).
Brookfield DV-II+ viscometer with a special spindle for glass melts
Research
One of the many topics the IS&R group focuses on is effective rheological modifiers, which:- Reduce the yield stress of solid suspensions in liquid
- Improve processing, e.g., handling characteristics
- Increase solids loading and process efficiency
Graphic of how shear motion can reduce flocculant behaviors in a network
Before and after of a clay with an added deflocculant (also known as a dispersant)