TABLE 2

Advanced analytical techniques used to determine the physicochemical characteristics of aggregatesa

MethodSample sizeResolutionLimitationsInformation collectedReference(s)
SANS150-μm-thick sections1 nm to 0.8 μmTechnique relies on the contrasting agent (D2O/H2O), diffusion of contrasting agent to estimate pore connectivity, requires a long time to collect data, and pore geometry is assumed for when analyzing natural samplesParticle size distribution, pore vol, surface roughness, surface area, and interconnected porosity143
USANS150-μm-thick sections60 nm to 20 μm
FIB-T10 μm310 nm to 0.1 μmSmall sample volume used in analysis, and the technique is destructive, which limits reproducibilityPore vol, porosity, pore size statistics, and connected and unconnected pore network; also, data can be correlated to elemental composition using EDS144, 145
ET100-nm needle<1 nm to 0.05 μmSmall sample volume, fixed-needle geometry, and technique relies on image analysis and 3D reconstructionPore geometry and connectivity; pore data can be cross-correlated with elemental composition using EDS146
BSEMThin sections100 nm to ∼500 μm2D analysis of a 3D geometry requires sample prep, and technique relies on image analysis to distinguish intra- and intergrain porosityPore geometry and connectivity; pore data can be cross-correlated with elemental composition using EDS145
XCT1 mm by 5-mm cylinders to 10-cm-diam cores300 nm to 100 μmbTechnique relies on image analysis and 3D reconstructionResults allow for full reconstruction of pore network147
MIP3.38 cm32 nm to 500 μmTechnique only measures connected porosity and assumes pore geometryResults provide details on pore vol, pore size distribution, and surface area148
PGAPowder samples0.5 nm to 0.2 μmTechnique only measures connected porosity and assumes pore geometryResults provide details on pore vol, pore size distribution, and surface area149
  • a SANS, small-angle neutron scattering; USANS, ultrasmall-angle neutron scattering; FIB-T, focused ion beam tomography; ET, electron tomography; BSEM, backscattered scanning electron microscopy; XCT, X-ray computed tomography; MIP, mercury intrusion porosimetry; PGA, physical gas adsorption; EDS, energy dispersive spectroscopy. Table adapted from Zachara et al. (89).

  • b Actual detectable pore size resolution will vary depending upon X-ray source, optics, and material.