Understanding Material Characteristics through Signature Traits from Helium Pycnometry
| Autor: | Matthew Bleakney, Jarod C. Horn, Daniel W. Siderius, Laura Espinal, Huong Giang T. Nguyen |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Analytical chemistry chemistry.chemical_element 02 engineering and technology Surfaces and Interfaces 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Residual 01 natural sciences Article 0104 chemical sciences chemistry Volume (thermodynamics) Gas pycnometer Electrochemistry General Materials Science 0210 nano-technology Porous medium Porosity Carbon Spectroscopy Helium Water vapor |
| Zdroj: | Langmuir : the ACS journal of surfaces and colloids. 35(6) |
| ISSN: | 1520-5827 |
| Popis: | Although helium pycnometry is generally the method of choice for skeletal density measurements of porous materials, few studies have provided a wide range of case studies that demonstrate how to best interpret raw data and perform measurements using it. The examination of several different classes of materials yielded signature traits from helium pycnometry data that are highlighted. Experimental parameters important in obtaining the most precise and accurate value of skeletal density from the helium pycnometer are as high as possible percent fill volume and good thermostability. The degree of sample activation is demonstrated to affect the measured skeletal density of porous zeolitic, carbon, and hybrid inorganic-organic materials. In the presence of a significant amount of physisorbed contaminants (water vapor, atmospheric gases, residual solvents, etc.), which was the case for ZSM-5, MIL-53, and F400, but not ZIF-8, the skeletal density tended to be overestimated in the low percent volume region. In addition, the kinetic data (i.e., skeletal density vs measurement cycle) reveals distinctive traits for a properly activated vs a nonactivated sample for all examined samples: activated samples with a significant amount of mass loss show a curved down plot that eventually reaches the equilibrium value, whereas nonactivated, nonporous, or extremely hydrophobic samples exhibit a flat line. This work illustrates how helium pycnometry can provide information about the structure of a material, and that, conversely, when the structure of the material and its percent mass loss after activation (amount of physisorbed contaminants) are known, the behavior of activated and nonactivated samples in terms of skeletal density, percent fill volume, and measurement cycle can be predicted. |
| Databáze: | OpenAIRE |
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