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Search Publications by: Jan Obrzut (Fed)

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Displaying 26 - 50 of 226

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)

A Q-band free-space characterization of carbon nanotube composites

September 19, 2016
Author(s)
Ahmed M. Hassan, Jan Obrzut, Edward Garboczi
We present a free-space measurement technique for non-destructive non-contact electrical and dielectric characterization of nano-carbon composites in the Q-band frequency range of 30 GHz to 50 GHz. The experimental system and error correction model