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Search Publications by: Christopher Stafford (Fed)

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Displaying 1 - 25 of 197

Assessing Composite Structure in Metal-Organic Framework-Polymer Mixed-Matrix Membranes

March 15, 2024
Avery Baumann, Peter Beaucage, Richard Vallery, David Gidley, Ryan Nieuwendaal, Chad R. Snyder, Jan Ilavsky, Fu Chen, Christopher Stafford, Christopher Soles
Metal-organic frameworks (MOFs) are renowned for their tunable structure, porosity, and internal chemistry with demonstrated applications in molecular separations, storage, and conversion. While they are widely usable, the powdery characteristics of MOF

Correlating the Diffusion of Water in Model Polyamides with Controlled Crosslink Densities to the Performance in Reverse Osmosis Membranes for Desalination

April 18, 2023
Velencia Witherspoon, Kanae Ito, Chad R. Snyder, Madhusudan (Madhu) Tyagi, Tyler Martin, Peter Beaucage, Ryan Nieuwendaal, Richard Vallery, David Gidley, Jeffrey Wilbur, Dean Welsh, Christopher Stafford, Christopher Soles
To elucidate robust design cues for improving the active polyamide (PA) filtration layers in reverse osmosis (RO) membrane for desalination, we systematically reduce the cross-link density of a PA network based on m-phenylene diamine by substituting a

Solvent Transport Model for Polyamide Nanofilm Membranes Based on Accurate Hansen Solubility Parameters

February 21, 2023
Min Gyu Shin, Wansuk Choi, June Huh, William Mulhearn, Jung Sun Hwang, Christopher Stafford, Jeong F Kim, Jung Hyun Lee
Polyamide (PA) nanofilm membranes for solvent filtration are widely used in various industries. However, reliable models that can describe solvent transport in PA membranes have yet to be developed owing to measurement challenges associated with the highly

Reproducible Sorbent Materials Foundry for Carbon Capture at Scale

September 22, 2022
Austin McDannald, Howie Joress, Brian DeCost, Avery Baumann, A. Gilad Kusne, Kamal Choudhary, Taner N. Yildirim, Daniel Siderius, Winnie Wong-Ng, Andrew J. Allen, Christopher Stafford, Diana Ortiz-Montalvo
We envision an autonomous sorbent materials foundry (SMF) for rapidly evaluating materials for direct air capture of carbon dioxide ( CO2), specifically targeting novel metal organic framework materials. Our proposed SMF is hierarchical, simultaneously

Specification for Interoperability Testing of Contactless Fingerprint Acquisition Devices

June 8, 2022
John M. Libert, Shahram Orandi, Bruce Bandini, Kenneth Ko, Craig I. Watson, Christopher Stafford, Matthew E. Staymates, John Grantham
This guidance specifies a protocol and associated metrics for the evaluation of contactless fingerprint acquisition device, and their interoperability with legacy devices. This protocol enables contactless fingerprint developers seeking certification of

A method to quantify composition, purity, and cross-link density of the polyamide active layer in reverse osmosis composite membranes using 13C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy

February 12, 2022
Ryan Nieuwendaal, Christopher Stafford, Jeff Wilbur
A method for harvesting and purifying the thin polyamide (PA) active layer from thin-film composite (TFC) reverse osmosis (RO) membranes was developed, enabling quantitative nuclear magnetic resonance (NMR) measurements of the composition and cross-linking

Orientation of Thin Polyamide Layer-by-Layer Films on Non-Porous Substrates

December 16, 2021
Tawanda J. Zimudzi, Sarah E. Sheffield, Kathleen E. Feldman, Peter Beaucage, Dean DeLongchamp, Douglas I. Kushner, Christopher Stafford, Michael A. Hickner
The orientation of polyamide thin films on non-porous substrates was investigated using Fourier transform infrared (FTIR) spectroscopy and corroborated by near edge X-ray absorption fine structure (NEXAFS) measurements. Polyamide films comprised of m

Thickness-Dependent Permeability of Molecular Layer-By-Layer Polyamide Membranes

August 28, 2020
William D. Mulhearn, Vladimir Oleshko, Christopher Stafford
We present the thickness-dependent permeability of highly crosslinked polyamide (PA) membranes formed by a molecular layer-by-layer (mLbL) deposition process. The deposition allows for the synthesis of extremely smooth, uniform PA films of tunable

X-ray Scattering Studies of Reverse Osmosis Materials

August 25, 2020
Qinyi Fu, Nisha Verma, Benjamin S. Hsiao, Francisco J. Medellin-Rodriguez, Peter Beaucage, Christopher Stafford, Benjamin M. Ocko
Scarcity of freshwater is becoming a world crisis. In a recent annual risk report, the World Economic Forum lists it in their greatest global risk category. Currently, about four billion people live under conditions of severe water scarcity for at least

Water-Polyamide Chemical Interplay in Desalination Membranes explored by Ambient Pressure X-ray Photoelectron Spectroscopy

June 24, 2020
Sabrina Gericke, William D. Mulhearn, Dana E. Goodacre, Joseph Raso, Daniel J. Miller, Lauryn Carver, Slavomir Nemsak, Osman Karslioglu, Lena Trotochaud, Hendrik Bluhm, Christopher Stafford, Christin Buechner
Reverse osmosis using aromatic polyamide membranes is currently the most important technology for seawater desalination. The performance of reverse osmosis membranes is highly dependent on the interplay of their surface chemical groups with water and water

Quantifying Strain via Buckling Instabilities in Surface Modified Polymer Brushes

May 21, 2020
Cassandra M. Reese, Wei Guo, Brittany J. Thompson, Phillip K. Logan, Christopher Stafford, Derek L. Patton
We present a quantitative method of measuring the compressive strain of wrinkled polymer films and coatings with knowledge of the "skin" thickness, wrinkle wavelength, and wrinkle amplitude. The derived analytical expression is validated with a well

Nanoscale Pattern Decay Monitored via in-situ Heated Atomic Force Microscopy

March 12, 2020
Sonal Bhadauriya, Jianan Zhang, Jaejun Lee, Michael R. Bockstaller, Alamgir Karim, Richard J. Sheridan, Christopher Stafford
We combine in-situ heated atomic force microscopy (AFM) with automated line-by-line spectral analysis to quantify the relaxation or decay of nanopatterned polymer films at temperatures above the glass transition. This approach enables assessment of pattern

Insights into the Water Transport Mechanism in Polymeric Membranes from Neutron Scattering

February 5, 2020
Edwin P. Chan, Bradley R. Frieberg, Jacob Daniel Tarver, Madhusudan Tyagi, WenXu Zhnag, Bryan Coughlin, Christopher M. Stafford, Abhishek Roy, Steve Rosenberg, Christopher L. Soles
Polymeric membranes are ubiquitous in a number of transport ap- plications including gas separation, water desalination, solid state batteries and fuel cells. The permeability and selectivity of these membranes are intimately linked to the structure and

Reduced Holey Graphene Oxide Membranes for Desalination with Improved Water Permeance

December 13, 2019
Xiaoyi Chen, Zhihao Feng, Janavi Gohil, Christopher Stafford, Ning Dai, Liang Huang, Haiqing Lin
Reduced-graphene oxide (r-GO) membranes with narrow channels exhibit salt rejections comparable to conventional nanofiltration (NF) membranes. However, their water permeances are much lower because of the high tortuosity for water permeation. Herein we