Blog – Page 6

A research team from Aarhus University, Denmark, has measured and explained the exceptionally low thermal conductivity of the crystalline material AgGaGe₃Se₈. Despite its ordered structure, the material behaves like a glass in terms of heat transport—making it one of the least heat-conductive crystalline solids known to date.

At room temperature, AgGaGe₃Se₈ exhibits a thermal conductivity of just 0.2 watts per meter-Kelvin—which is three times lower than water and five times lower than typical silica glass. The material is composed of silver (Ag), gallium (Ga), germanium (Ge), and selenium (Se), and has previously been studied for its optical properties.

Now, for the first time, researchers from iMAT—the Aarhus University Center for Integrated Materials Research—have measured its thermal transport properties and identified the structural origin of its unusually low thermal conductivity.

If your hand lotion is a bit runnier than usual coming out of the bottle, it might have something to do with the goop’s “mechanical memory.”

Soft gels and lotions are made by mixing ingredients until they form a stable and uniform substance. But even after a gel has set, it can hold onto “memories,” or residual stress, from the mixing process. Over time, the material can give in to these embedded stresses and slide back into its former, premixed state. Mechanical memory is, in part, why hand lotion separates and gets runny over time.

Now, an MIT engineer has devised a simple way to measure the degree of residual stress in soft materials after they have been mixed, and found that common products like hair gel and shaving cream have longer mechanical memories, holding onto residual stresses for longer periods of time than manufacturers might have assumed.