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Search Publications by: Jan Obrzut (Fed)

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Displaying 1 - 25 of 150

A Spatially-Resolved Evaluation of Accelerated Environmental Aging on Emerging Polypropylene-based Photovoltaic Backsheets using Raman Spectroscopy

March 13, 2025
Author(s)
Ashlee Aiello, Stefan Mitterhofer, Jan Obrzut, Karissa Jensen, Patryk Wasik, Chiara Barretta, Gernot Oreski, Stephanie Watson, Li Piin Sung, Xiaohong Gu
Accelerated aging was used to assess environmental degradation in emerging co-extruded polypropylene (PP)-based backsheets under three different environmental conditions (65 °C/20 % relative humidity (RH), 75 °C/20 % RH, and 75 °C/50 % RH). Although

Effect of Cosolvents on the Phase Separation of Polyelectrolyte Complexes

September 13, 2024
Author(s)
Yuanchi Ma, Robert Ivancic, Jan Obrzut, Debra Audus, Vivek Prabhu
Evidence is shown that cosolvent mixtures control the coacervation of mixtures of oppositely charged polyelectrolytes. Binary and ternary solvent mixtures lead to non-monotonic solubility as a function of measured average dielectric constants of the

Dielectric Characterization of H2O and CO2 Uptake by Polyethylenimine Films

April 10, 2024
Author(s)
Jan Obrzut, Jennifer Clark, Avery Baumann, Jack F. Douglas
This study investigates the dielectric properties of branched polyethylenimine (PEI) films in relation to their interaction with moisture and CO2. The dielectric measurements were carried out using a non-contact resonant microwave cavity testing method

Evaluation of Microstructure of BaTiO 3 -Polymer Composites by Confocal Microscopy

October 12, 2021
Author(s)
C. K. Chiang, Li Piin Sung, R Popielarz, Jan Obrzut
Laser scanning confocal microscopy has been applied to examine the distribution of BaTiO3 particles in ceramic-polymer composite films. The thin-slice images of the thickness of the order of one micron allowed us to visualize the micron-size particles and

Microwave characterization of graphene inks

October 11, 2021
Author(s)
Jan Obrzut, Ana C. M. Moraes
Systematic charge transport characterization of solution-processed graphene inks using ethyl cellulose polymer as a binder/stabilizer, showed graphene patterns with high mobility ( 160 cm2 V-1 s-1), low energy gap, thermally activated charge transport and

Fluorescence Microscopy Reveals Structure-Property Relationships and Polymer Dynamics in Biocomposites

July 21, 2021
Author(s)
Quinn Easter, Shawn Chen, Jeremiah Woodcock, Amanda Souna, Sindhu Seethamraju, Jan Obrzut, Douglas M. Fox, Stephan J. Stranick, Jeffrey Gilman
OBJECTIVES: Developing the next generation of materials for use in restorative work requires a multifaceted approach. While mimicking the properties of the tooth, currently available dental composites and porcelains eventually fail and require replacement

Elucidating Charge Transport Mechanisms in Graphene Inks

August 7, 2020
Author(s)
Ana C. de Moraes1, Jan Obrzut, Vinod K. Sangwan, Julia R. Downing, Lindsay E. Chaney, Dinesh K. Patel, Randolph Elmquist, Mark C. Hersam
Solution-processed graphene inks using ethyl cellulose polymer as a binder/stabilizer were blade-coated into large area films. Systematic charge transport characterization showed graphene patterns with high mobility ( 160 cm2 V-1 s-1), low energy gap

Contactless Resonant Cavity Dielectric Spectroscopic Studies of Recycled Office Papers

November 5, 2019
Author(s)
Mary Kombolias, Jan Obrzut, Michael T. Postek, Dianne L. Poster, Yaw S. Obeng
Current product composition and quality test methods for the paper and pulp industry are rooted in wet-bench chemistry techniques which are highly subjective. These techniques have rather limited utility and cannot be used to distinguish between virgin and

Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper Aging

August 28, 2019
Author(s)
Mary Kombolias, Jan Obrzut, Michael T. Postek, Dianne L. Poster, Yaw S. Obeng
The current analytical techniques for characterizing printing and graphic arts substrates, particularly those used to date and to authenticate provenance, are largely ex situ and destructive. This limits the amount of data that can be captured from an

Characterization of graphene conductance using a microwave cavity

January 9, 2019
Author(s)
Jan Obrzut, Keith White, Yanfei Yang, Randolph Elmquist
Surface conductance of graphene films is investigated in a non-contact microwave cavity operating at 7.4543 GHz. This cavity technique characterizes specimens with high accuracy, without disruption of morphological integrity and without the processing

Hierarchical Cellulose Nanocrystal Blends for Bioinspired Damage Tolerant Photonic Films

May 4, 2018
Author(s)
Bharath NMN Natarajan, Ajay Krishnamurthy, Caglar Dogu Emiroglu, Amanda L. Forster, E. J. Foster, Christoph Weder, Douglas M. Fox, Jan Obrzut, Jeffrey W. Gilman
Attempts to emulate strong and tough natural composites using wood cellulose nanocrystals (CNCs) fall short in mechanical performance due to the low shear transfer ability of CNC interfaces in their helicoidal ensembles. This shortcoming is ascribed to the

Examining epitaxial graphene surface conductivity and quantum Hall device stability with Parylene passivation

March 20, 2018
Author(s)
Albert F. Rigosi, Chieh-I Liu, Bi Y. Wu, Hsin Y. Lee, Mattias Kruskopf, Yanfei Yang, Heather M. Hill, Jiuning Hu, Emily G. Bittle, Jan Obrzut, Angela R. Hight Walker, Randolph E. Elmquist, David B. Newell
When it comes to the advancement of quantized Hall resistance (QHR) standards, homogeneous, single-crystal, monolayer epitaxial graphene (EG) is the most promising candidate. EG-based quantum Hall devices, though emerging as a useful tool for metrology

Moisture Uptake Characterization in Nanocellulose Using Microwave Cavity

August 17, 2017
Author(s)
Caglar Emiroglu, Bharath N. Natarajan, Jeffrey W. Gilman, James Alexander Liddle, Jan Obrzut
Cellulose nanocrystal films with different helical modulation lengths are characterized. Films are obtained by tuning the rate of evaporation and surface functionalization. Dielectric constant measurements are performed and the water confinement is

Preservation of surface conductivity and dielectric loss tangent in large-scale, encapsulated epitaxial graphene measured by non-contact microwave cavity perturbations

May 19, 2017
Author(s)
Albert F. Rigosi, Nicholas R. Glavin, Chieh-I Liu, Yanfei Yang, Jan Obrzut, Heather M. Hill, Jiuning Hu, Hsin Y. Lee, Angela R. Hight Walker, Curt A. Richter, Randolph E. Elmquist, David B. Newell
Regarding the improvement of current quantized Hall resistance (QHR) standards, one promising avenue is the growth of homogeneous monolayer epitaxial graphene (EG). A clean and simple process was used to produce large, precise areas of EG. Properties like

Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films

April 10, 2017
Author(s)
Bharath N. Natarajan, Caglar Emiroglu, Jan Obrzut, Douglas M. Fox, Beatriz Pazmino, Jack F. Douglas, Jeffrey W. Gilman
A known deterrent to a large scale development and use of cellulose nanocrystals (CNCs) is their affinity for moisture, which has a profound effect on dispersion, wetting, interfacial adhesion, matrix crystallization and water uptake. To quantify the

Relationship Between Quantitative Dispersion and Physical Properties of PMMA/SWNT Nanocomposites

February 19, 2017
Author(s)
Takashi Kashiwagi, Jeffrey Fagan, Keith Yamamoto, A N. Heckert, Stefan D. Leigh, Jan Obrzut, F Du, Sheng Lin-Gibson, Minfang Mu, K Winey, R Haggenmueller, Jack F. Douglas
Six PMMA/SWNT(0.5 wt%) nanocomposite samples intended to have different dispersion levels were prepared by the coagulation method using six different concentrations of SWNTs in DMF from 0.05 mg/ml to 1.2 mg/ml. The morphology of the samples was determined

Non-contact Surface Conductance Measurement of Graphene using Resonant Cavity

October 10, 2016
Author(s)
Jan Obrzut, Oleg A. Kirillov
The measurement of conductance by a resonant cavity involves monitoring the resonant frequency shift and change in the quality factor before and after insertion of the specimen into the cavity. The method is applicable to carbon Vapor deposited (CVD)