Fabian Naab
University of Michigan
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Featured researches published by Fabian Naab.
American Mineralogist | 2011
Karen L. Wang; Youxue Zhang; Fabian Naab
Abstract In this work, we have calibrated the infrared (IR) method for determining OH concentrations in apatite with absolute concentrations obtained through elastic recoil detection (ERD) analysis. IR spectra were collected on oriented, single-crystal apatite samples using polarized transmission infrared spectroscopy. The weight percent H2O is 0.001199 ± 0.000029 (the error is given at 1σ level hereafter) times A/d, where A is the linear absorbance peak height measured using polarized IR when the light vector E is parallel to the c-axis of the apatite crystal, and d is the sample thickness in centimeters. This corresponds to a linear molar absorptivity, ε = 470 ± 11 L/mol/cm-1. The calibration using linear absorbance can be applied when there is only one dominant peak at 3540 cm-1. If other peaks are significant, then the integrated molar absorptivity, ε = (2.31 ± 0.06) ×104 L/mol/cm2, should be used. The detection limit of H2O concentration in apatite by IR approaches parts per million level for wafers of 0.1 mm thickness. The accuracy based on our calibration is 5-10% relative.
21st International Conference on Application of Accelerators in Research and Industry, CAARI 2010 | 2011
Fabian Naab; E. A. West; Ovidiu Toader; G. S. Was
A firm understanding of the effect of radiation on materials is required to develop predictive models of materials behavior in‐reactor and provide a foundation for creating new, more radiation‐tolerant materials. Ion irradiation can serve this purpose for nuclear reactor components and is becoming a key element of materials development for advanced nuclear reactors. Ion irradiations can be conducted quickly, at low cost, and with precise control over irradiation temperature, temperature uniformity, dose rate, dose uniformity and total dose. During proton irradiations the 2σ (twice the standard deviation) of the sample temperature is generally below ∼7 °C, the dose rate variation ∼3%, the dose uncertainty ∼3%, and there is an excellent temperature and dose uniformity across the irradiated area. In this article, we describe the experimental setup and irradiation procedure used to conduct well‐controlled ion irradiations at the University of Michigan.A firm understanding of the effect of radiation on materials is required to develop predictive models of materials behavior in‐reactor and provide a foundation for creating new, more radiation‐tolerant materials. Ion irradiation can serve this purpose for nuclear reactor components and is becoming a key element of materials development for advanced nuclear reactors. Ion irradiations can be conducted quickly, at low cost, and with precise control over irradiation temperature, temperature uniformity, dose rate, dose uniformity and total dose. During proton irradiations the 2σ (twice the standard deviation) of the sample temperature is generally below ∼7 °C, the dose rate variation ∼3%, the dose uncertainty ∼3%, and there is an excellent temperature and dose uniformity across the irradiated area. In this article, we describe the experimental setup and irradiation procedure used to conduct well‐controlled ion irradiations at the University of Michigan.
American Mineralogist | 2016
Kathryn Clark; Youxue Zhang; Fabian Naab
Abstract We have calibrated the infrared (IR) method for determining CO2 concentrations in apatite with absolute concentrations obtained through nuclear reaction analysis (NRA). IR data were obtained on double-polished apatite wafers using polarized transmission IR spectroscopy. Due to the various sites and orientations of CO2-3 in apatite, the IR spectra are complicated and do not have the same shape in different apatite samples. Hence, simple peak heights are not used to characterize CO2 concentrations in apatite. The total absorbance (Atotal) was derived using the integrated area under the curves in a given polarized spectral region. Then Atot!ll is calculated as AE//c + 2AE±c. The calibration has been carried out for two wavenumber regions, one with high sensitivity and the other applicable to apatite with high CO2 concentrations. The first calibration is for the fundamental asymmetric CO32−
Nature Communications | 2017
Pratyasha Mohapatra; Santosh Shaw; Deyny Mendivelso-Perez; Jonathan M. Bobbitt; Tiago F. Silva; Fabian Naab; Bin Yuan; Xinchun Tian; Emily A. Smith; Ludovico Cademartiri
\rm CO^{2-}_3
Materials Science-poland | 2016
Riffat Sagheer; M. S. Rafique; Farhat Saleemi; Shafaq Arif; Fabian Naab; Ovidiu Toader; Arshad Mahmood; R. Rashid; I. Hussain
stretching at wavenumbers of 1600-1300 cm-1, and the CO2 concentration in parts per million can be obtained as (0.0756 ± 0.0036) Atotal/d where d is sample thickness in centimeters. The fundamental stretching bands are strong and hence sensitive for measuring low CO2 concentrations in apatite, down to parts per million level. The second calibration is for the CO32−
IEEE Transactions on Nuclear Science | 2016
Prabir K. Roy; S. Taller; Ovidiu Toader; Fabian Naab; Shyam Dwaraknath; Gary S. Was
\rm CO^{2-}_3
22nd International Conference on the Application of Accelerators in Research and Industry, CAARI 2012 | 2013
Fabian Naab; Ovidiu Toader; G. S. Was
bands at wavenumbers of2650-2350 cm-1, and the CO2 concentration in parts per million is (9.3 ± 0.6) Atotal/d where d is sample thickness in centimeters. These bands are weak and hence are useful for measuring high CO2 concentrations in apatite without preparation of super-thin wafers. The anisotropy is significant. The difference between AE//c and AE±c can reach a factor of 2.73. Hence, for high accuracy, it is best to use polarized IR to determine CO2 concentrations in apatite. For rough estimation, unpolarized IR spectra may be used by estimating Atotal = 3Aunpol, where Aunpol is the integrated absorbance from unpolarized spectra.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 2015
Shafaq Arif; M. Shahid Rafique; Farhat Saleemi; Riffat Sagheer; Fabian Naab; Ovidiu Toader; Arshad Mahmood; Rashad Rashid; Mazhar Mahmood
Removing organics from hybrid nanostructures is a crucial step in many bottom-up materials fabrication approaches. It is usually assumed that calcination is an effective solution to this problem, especially for thin films. This assumption has led to its application in thousands of papers. We here show that this general assumption is incorrect by using a relevant and highly controlled model system consisting of thin films of ligand-capped ZrO2 nanocrystals. After calcination at 800 °C for 12 h, while Raman spectroscopy fails to detect the ligands after calcination, elastic backscattering spectrometry characterization demonstrates that ~18% of the original carbon atoms are still present in the film. By comparison plasma processing successfully removes the ligands. Our growth kinetic analysis shows that the calcined materials have significantly different interfacial properties than the plasma-processed counterparts. Calcination is not a reliable strategy for the production of single-phase all-inorganic materials from colloidal nanoparticles.Synthesis of all-inorganic nanomaterials often relies on organic templates, which are assumed to then be fully removed by calcination. Here, the authors use elastic backscattering spectroscopy to challenge this assumption, finding that calcination leaves behind considerable carbon content that can severely affect material function.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 2011
Alejandro G. Perez-Bergquist; Fabian Naab; Yanwen Zhang; L.M. Wang
Abstract Ion implantation has a potential to modify the surface properties and to produce thin conductive layers in insulating polymers. For this purpose, poly-allyl-diglycol-carbonate (CR-39) was implanted by 400 keV Au+ ions with ion fluences ranging from 5 × 1013 ions/cm2 to 5 × 1015 ions/cm2. The chemical, morphological and optical properties of implanted CR-39 were analyzed using Raman, Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM) and UV-Vis spectroscopy. The electrical conductivity of implanted samples was determined through four-point probe technique. Raman spectroscopy revealed the formation of carbonaceous structures in the implanted layer of CR-39. From FT-IR spectroscopy analysis, changes in functional groups of CR-39 after ion implantation were observed. AFM studies revealed that morphology and surface roughness of implanted samples depend on the fluence of Au ions. The optical band gap of implanted samples decreased from 3.15 eV (for pristine) to 1.05 eV (for sample implanted at 5 × 1015 ions/cm2). The electrical conductivity was observed to increase with the ion fluence. It is suggested that due to an increase in ion fluence, the carbonaceous structures formed in the implanted region are responsible for the increase in electrical conductivity.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 2016
Shafaq Arif; M. Shahid Rafique; Farhat Saleemi; Fabian Naab; Ovidiu Toader; Riffat Sagheer; Shazia Bashir; Rehana Zia; K. Siraj; Saman Iqbal
A new multi-pinhole Faraday cup (MPFC) device was designed, fabricated and tested to measure ion beam uniformity over a range of centimeters. There are 32 collectors within the device, and each of those is used as an individual Faraday cup to measure a fraction of the beam current. Experimental data show that the device is capable of measuring a charged particles distribution - either in the form of a raster scanned focused beam or a defocused beam.