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in creator/contributor: "Holt, J K"

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Direct Laser Ablation and Ionization of Solids for Chemical Analysis by Mass Spectrometry

A laser ablation/ionization mass spectrometer system is described for the direct chemical analysis of solids. An Nd:YAG laser is used for ablation and ionization of the sample in a quadrupole ion trap operated in an ion-storage (IS) mode that is coupled with a reflectron time-of-flight mass spectrometer (TOF-MS). Single pulse experiments have demonstrated simultaneous detection of up to 14 elements present in glasses in the ppm range. However, detection of the components has produced non-stoich… more

Date: September 2, 2005

Creator: Holt, J K; Nelson, E J & Klunder, G L

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A High-Flux, Flexible Membrane with Parylene-encapsulated Carbon Nanotubes

We present fabrication and characterization of a membrane based on carbon nanotubes (CNTs) and parylene. Carbon nanotubes have shown orders of magnitude enhancement in gas and water permeability compared to estimates generated by conventional theories [1, 2]. Large area membranes that exhibit flux enhancement characteristics of carbon nanotubes may provide an economical solution to a variety of technologies including water desalination [3] and gas sequestration [4]. We report a novel method of … more

Date: March 14, 2008

Creator: Park, H. G.; In, J.; Kim, S.; Fornasiero, F.; Holt, J. K.; Grigoropoulos, C. P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ion Exclusion by Sub 2-nm Carbon Nanotube Pores

Carbon nanotubes offer an outstanding platform for studying molecular transport at nanoscale, and have become promising materials for nanofluidics and membrane technology due to their unique combination of physical, chemical, mechanical, and electronic properties. In particular, both simulations and experiments have proved that fluid flow through carbon nanotubes of nanometer size diameter is exceptionally fast compared to what continuum hydrodynamic theories would predict when applied on this … more

Date: April 9, 2008

Creator: Fornasiero, F; Park, H G; Holt, J K; Stadermann, M; Grigoropoulos, C P; Noy, A et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nanofiltration of Electrolyte Solutions by Sub-2nm Carbon Nanotube Membranes

Both MD simulations and experimental studies have shown that liquid and gas flow through carbon nanotubes with nanometer size diameter is exceptionally fast. For applications in separation technology, selectivity is required together with fast flow. In this work, we use pressure-driven filtration experiments to study ion exclusion in silicon nitride/sub-2-nm CNT composite membranes as a function of solution ionic strength, pH, and ion valence. We show that carbon nanotube membranes exhibit sign… more

Date: March 13, 2008

Creator: Fornasiero, F.; Park, H. G.; Holt, J. K.; Stadermann, M.; Kim, S.; In, J. B. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development of a particle monitor for the CFFF

To evaluate and improve the performance of particulate control devices (dry electrostatic precipitator or DESP, wet electrostatic precipitator or WESP, Baghouse or BH), the entering particle loading, and size distribution if measurable, is needed. Standard extraction methods provide this data but we labor intensive and thus can not provide this data on-line in near-real-time as needed to determine best particulate device settings for changing operating conditions. Furthermore, the extreme parti… more

Date: June 1, 1993

Creator: Parker, J. L.; Giel, T. V.; Winkleman, B. C.; Hodges, M. E.; Holt, J. K. & Douglas, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Carbon Nanotube-Based Permeable Membranes: A Platform for Studying Nanofluidics

A membrane of multiwalled carbon nanotubes embedded in a silicon nitride matrix was fabricated for use in studying fluid mechanics on the nanometer scale. Characterization by fluorescent tracer diffusion and scanning electron microscopy suggests that the membrane is void-free near the silicon substrate on which it rests, implying that the hollow core of the nanotube is the only conduction path for molecular transport. Nitrogen flow measurements of a nanoporous silicon nitride membrane, fabricat… more

Date: May 25, 2004

Creator: Holt, J K; Park, H G; Noy, A; Huser, T; Eaglesham, D & Bakajin, O

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fabrication of a Carbon Nanotube-Embedded Silicon Nitride Membrane for Studies of Nanometer-Scale Mass Transport

A membrane consisting of multiwall carbon nanotubes embedded in a silicon nitride matrix was fabricated for fluid mechanics studies on the nanometer scale. Characterization by tracer diffusion and scanning electron microscopy suggests that the membrane is free of large voids. An upper limit to the diffusive flux of D{sub 2}O of 2.4x10-{sup 8} mole/m{sup 2}-s was determined, indicating extremely slow transport. By contrast, hydrodynamic calculations of water flow across a nanotube membrane of si… more

Date: August 25, 2004

Creator: Holt, J K; Noy, A; Huser, T; Eaglesham, D & Bakajin, O

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Carbon Nanotube-Based Permeable Membranes

A membrane of multiwalled carbon nanotubes embedded in a silicon nitride matrix was fabricated for use in studying fluid mechanics on the nanometer scale. Characterization by fluorescent tracer diffusion and scanning electron microscopy suggests that the membrane is void-free near the silicon substrate on which it rests, implying that the hollow core of the nanotube is the only conduction path for molecular transport. Assuming Knudsen diffusion through this nanotube membrane, a maximum helium t… more

Date: April 6, 2004

Creator: Holt, J K; Park, H G; Bakajin, O; Noy, A; Huser, T & Eaglesham, D

Item Type: Article

Partner: UNT Libraries Government Documents Department