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Search Publications by: John H. Lehman (Fed)

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Displaying 76 - 100 of 154

Evaluating the characteristics of multiwall carbon nanotubes

July 1, 2011
Author(s)
John H. Lehman, M. Terrones, Elisabeth Mansfield, Katie Hurst, Vincent Muenier
During the past 20 years, multiwall carbon nanotubes (MWCNTs) have become an important industrial material. Hundreds of tons are produced each year. This review is a survey of the scientific literature, motivated by industrial requirements and guidelines

Optical fiber power meter comparison between NIST and NIM

November 1, 2010
Author(s)
Igor Vayshenker, Jian Li, L. M. Xiong, Z. X. Zhang, David J. Livigni, Xiaoyu X. Li, John H. Lehman
We describe the results of a comparison of reference standards between the National Institute of Standards and Technology (NIST-USA) and National Institute of Metrology (NIM-China). We report optical fiber-based power measurements at nominal wavelengths of

Quartz crystal microbalance for in-situ monitoring of laser cleaning of carbon nanotubes

August 1, 2010
Author(s)
Katie Hurst, Abram Van Der Geest, Mark T. Lusk, Elisabeth Mansfield, John H. Lehman
Photochemical changes of single-walled carbon nanotubes (SWCNTs), graphite and amorphous carbon have been investigated with a quartz crystal microbalance (QCM). The method of in-situ measurements reduces our uncertainty that is attributable to

Method to determine the absorbance of thin films for photovoltaic technology

June 20, 2010
Author(s)
Nathan A. Tomlin, John H. Lehman, Katherine E. Hurst, D. B. Tanner, K. Kamaras, Aron Pekker
We have demonstrated a novel method to determine optical properties of opaque or semi-transparent films for photovoltaic (PV) applications. Such films may be the basis of transparent conductors or photoconductive material. As an example, we measure the

Core-shell composite of SiCN and multiwalled carbon nanotubes from Toluene dispersion

May 21, 2010
Author(s)
John H. Lehman, Katherine E. Hurst, Gurpreet Singh, Elisabeth Mansfield, John D. Perkins, Christopher L. Cromer
Carbon nanotubes are known to have high thermal conductivity, and in bulk form, a topology that could constitute the matrix of an inhomogeneous solid. Among the promised applications of carbon nanotubes is a composite material that is practical for thermal

Excimer laser-based purification of single-walled carbon nanotubes

April 1, 2010
Author(s)
Katie Hurst, Elisabeth Mansfield, Anne Dillon, John H. Lehman
Bulk purified carbon nanotube (CNT) material is essential for the realization of CNT applications including incorporating them into various composite materials. We have developed a laser-based purification technique for bulk single-walled carbon nanotubes

Improving carbon nanotube transparent conductor performance by UV laser irradiation

April 1, 2010
Author(s)
Katie Hurst, Jeffrey Blackburn, Larsen A. Brian, John H. Lehman
We discuss the photochemical treatment of transparent conducting (TC) films made from single-walled carbon nanotubes (SWCNTs).(1) The treatment process is comparable to that described previously, whereby unwanted amorphous carbon is removed from bulk

Multiwalled carbon nanotubes coated with silicon carbonitride (SiCN)

April 1, 2010
Author(s)
Katie Hurst, Christopher L. Cromer, Elisabeth Mansfield, Roop Mahajan, John H. Lehman, Gurpreet Singh
We describe the development of two next-generation optical coatings; amorphous polymer-derived silicon carbonitride (SiCN) particles and a composite consisting of SiCN surrounding a multiwalled carbon nanotube (MWCNT) core. Laser-induced damage testing of

Reflective attenuators for high energy laser measurements

March 14, 2010
Author(s)
John H. Lehman, David J. Livigni, Christopher L. Cromer, Xiaoyu X. Li, Marla L. Dowell
A high-energy laser attenuator in the range of 250 mJ (20 nsec pulse width, 10 Hz repetition rate, 1064 nm, 1574 nm wavelengths) is described. The optical elements that constitute the attenuator are mirrors with relatively low reflectance, oriented at 45°

Uncertainty calculation for spectral-responsivity measurements

September 1, 2009
Author(s)
John H. Lehman, Chih-Ming Wang, Marla L. Dowell, Joshua A. Hadler
This paper discusses a procedure for measuring the absolute spectral responsivity of optical-fiber power meters and computation of the calibration uncertainty. The procedure reconciles measurement results associated with a monochromator-based measurement

International comparisons of optical fiber power measurements

October 1, 2008
Author(s)
Igor Vayshenker, David J. Livigni, Xiaoyu X. Li, John H. Lehman
We discuss the results of optical fiber power meter (OFPM) measurements at 1302 and 1546 nm made by NIST and six national measurement institutes (NMIs). We also describe transfer standards and the associated uncertainties. The comparisons show a reasonably

High power laser calibrations at NIST

September 1, 2008
Author(s)
Xiaoyu X. Li, Joshua A. Hadler, Christopher L. Cromer, John H. Lehman, Marla L. Dowell
This document describes the calibration service for the responsivity of laser power meters and detectors used with continuous wave high power lasers at laser wavelengths of 1.06 and 10.6 micrometers. An overview of the calibration procedures, measurement

Inverted spectra of single-wall carbon nanotube films

July 10, 2008
Author(s)
John H. Lehman, Katie Hurst, Lara Roberson, K. Nield, J. D. Hamlin
We present absolute measurements of reflectance and absorbance for a purified single wall carbon nanotube (SWCNT) film. The absorbance spectrum of a SWCNT-laminated pyroelectric detector for wavelengths 0.6 - 2 υm is inverted when compared to absorbance

Bilateral optical power meter comparison between NIST and CENAM

July 1, 2008
Author(s)
Igor Vayshenker, J. Bermudez, J. Molina, Z. Ruiz, David J. Livigni, Xiaoyu X. Li, John H. Lehman
We describe the results of a comparison of reference standards between the National Institute of Standards and Technology (NIST-USA) and Centro Nacional De Metrologia (CENAM-Mexico). Open beam (free field) and optical-fiber-based measurements at

Reflective attenuator for high energy laser measurements

June 20, 2008
Author(s)
John H. Lehman, David J. Livigni, Xiaoyu X. Li, Christopher L. Cromer, Marla L. Dowell
A high-energy laser attenuator in the range of 250 mJ (20 nsec pulse width, 10 Hz repetition rate, 1064 nm wavelength) is described. The optical elements which constitute the attenuator are mirrors with relatively low reflectance, oriented at 45° angle of

High-performance carbon nanotube coatings for high-power laser radiometry

January 3, 2008
Author(s)
Krishna Ramadurai, Christopher L. Cromer, Laurence A. Lewis, Katie Hurst, Anne Dillon, Roop Mahajan, John H. Lehman
Radiometry for the next generation of high-efficiency, high-power industrial lasers requires thermal management at optical power levels exceeding 10 kW. Laser damage and thermal transport present fundamental challenges for laser radiometry in support of

Foam-based optical absorber for high-power laser radiometry

December 1, 2007
Author(s)
Krishna Ramadurai, Christopher L. Cromer, Xiaoyu X. Li, Roop Mahajan, John H. Lehman
We report damage threshold measurement results for novel absorbers comprised of either liquid-cooled silicon carbide or vitreous carbon foams. The measurements demonstrate damage thresholds up to 1.6×10^+4 W/cm 2 at an incident circular spot size of 2 mm

Photoconductive lifetimes of carbon nanotubes films

November 29, 2007
Author(s)
Katie Hurst, Richard K. Ahrenkiel, Steve W. Johnston, Anne Dillon, Lara Roberson, John H. Lehman
The photoconductive recombination lifetimes of carbon nanotube (CNT) thin films as a function of wavelength are measured by resonant-coupled photoconductive decay (RCPCD) method (1). The carrier recombination lifetime is a fundamental property of carbon