Selecting the correct instrument to characterize your powders and porous ceramics can be a daunting task. This article serves to make selection easier and decision making more streamlined. The focus of this article is on those physical properties whose measurement is often overlooked, but that are no less important than e.g. particle size!
Sometimes different techniques can do (at least at first glance) much the same thing. See Pore Size Analyzers (below) for example; in this case you will be guided primarily by the range of pore sizes of interest.
Surface Area Analyzers
If you want to minimize footprint and conserve bench space, it should have on-board degassing (preparation) station(s). Helium-free operation simplifies setup and reduces operating costs. It is usually possible to analyse with N2 as low as 1m2 available area. Less than that might require krypton capability. If it does, demand an oil-free vacuum system (and for degassing too).
True (solid) density is measured by gas pycnometry. Multiple station pycnometers are available, complete with balance interface, printer port and PC data archiving, plus optional temperature control. You'll need a different (mechanical) device for tapped powder bulk density; easily automated, even on two samples at one time.
The same tap density analysers can even measure geometric (envelope) density, at remarkably low cost.
Pore Size Analyzers
Micropores require gas sorption technology: look for analyzers with advanced techniques like CO2 and argon adsorption combined with state-of-the-art DFT (Density Functional Theory) calculation models.
Most mesoporous materials can be analyzed by either gas sorption or mercury porosimetry. The latter offers much more rapid analysis however. The most up-todate porosimeters have automatic purging of the hydraulic system, and vapor traps. Macropore sizes extend well above the upper limit of gas sorption and so must be measured by mercury intrusion. On the right instrument it is possible to measure, as a standard feature, up to 900 μm pore diameter.
Speed, automation and robustness are offered in manometric (volumetric) systems. It is now possible to measure complete moisture uptake isotherms at temperatures from 12°C to 85°C.