Materials - General
Click on the thumbnails below to enlarge images.
Stable emulsion of a hydrophobic polymer
This image illustrates a stable emulsion of a synthetic liquid polymer dispersed in an aqueous continuous phase. Low-temperature SEM allows observations of dispersion phase droplet size in relation to emulsifier concentration, and at higher magnification provides information about the interface between the two phases.
Bar: 10um
Unstable emulsion of hydrophobic polymer
This is similar to the liquid polymer in that it is again dispersed in an aqueous continuous phase. Emulsifiers are absent, however, and within a short time after dispersion, coalescence or droplets within the dispersion phase starts to occur.
Bar: 10um
Wax crystals in gas oil
When cooled to a temperature below about 2°C, the waxes in fuel oils such as this tend to crystallise out. Wax crystal size and shape can be varied by altering the rate at which the oil is cooled.
This image illustrates the appearance of the crystals within the cooled oil. By filtering out the oil, structural information about the crystals themselves can be demonstrated.
Bar: 10um
Frozen fractured liquid laundry detergent
Laundry detergents are liquid complex emulsion/suspensions. In this particular example a liquid polymer is distributed in an aqueous matrix. Additives include surface active agents, anti-redeposition agents such as carboxymethyl cellulose and a foam-controlling agent. In addition, a water softener (sodium tripolyphosphate) is added. The phosphate is obvious as large crystals.
Bar: 1um
Dendritic ice crystals
If it is cooled slowly, water forms dendritic ice crystals. These can have a variety of branching patterns - the complexity of which depends upon cooling rate. Arms extend from the main body of the crystal at an angle of 60°. Some, such as the one illustrated, resemble the arms of a snowflake.
Bar: 2um
Hexagonal ice
Water crystallises in the hexagonal system. The typical representative of that type is illustrated here as ice crystals in the form of hexagonal prisms.
Bar: 200um (inset: 100um)
Rubber particles in natural latex after freezing
Natural latex consists of a suspension of rubber particles of approximately 0.1-1um in diameter, suspended in a buffered aqueous medium. One method for the manufacture of rubber - the Talalay process - includes a stage in which the latex is cooled to a temperature of -30°C. As a result of the crystallization of water, the rubber particles are forced into a boundary around the ice, where partial coalescence occurs. Low-temperature techniques such as LTSEM are ideal for monitoring this process.
Chalk rock saturated with brine and oil
In the first image, the dark grey bubbles are dried oil droplets in brine-filled cracks. The second image is an x-ray analysis of fluids - green is oxygen, red is carbon.
Images courtesy of Ola Risvik, University of Stavanger, Norway.