N. Teslich

Publications (20)34.21 Total impact

• Article: Characterization of Pd Impurities and Finite-Sized Defects in Detector Grade CdZnTe

  M.C. Duff, J.P. Bradley, Z.R. Dai, N. Teslich, A. Burger, M. Groza, V. Buliga
  [show abstract] [hide abstract]
  ABSTRACT: Synthetic CdZnTe or “CZT” crystals are highly suitable for γ-spectrometers operating at the room temperature. Secondary phases (SP) in CZT are known to inhibit detector performance, particularly when they are present in large numbers or dimensions. These SP may exist as voids or composites of non-cubic phase metallic Te layers with bodies of polycrystalline and amorphous CZT material and voids. Defects associated with crystal twining may also influence detector performance in CZT. Using transmission electron microscopy, we identify two types of defects that are on the nano scale. The first defect consists of 40 nm diameter metallic Pd/Te bodies on the grain boundaries of Te-rich composites. Although the nano-Pd/Te bodies around these composites may be unique to the growth source of this CZT material, noble metal impurities like these may contribute to SP formation in CZT. The second defect type consists of atom-scale grain boundary dislocations. Specifically, these involve inclined “finite-sized” planar defects or interfaces between layers of atoms that are associated with twins. Finite-sized twins may be responsible for the subtle but observable striations that can be seen with optical birefringence imaging and synchrotron X-ray topographic imaging.
  MRS Proceedings. 12/2010; 1341.
• Article: Survivability of Cometary Phyllosilicates in Stardust Collections and Implications for the Nature of Comets

  P. J. Wozniakiewicz, H. A. Ishii, A. T. Kearsley, M. J. Burchell, J. P. Bradley, N. Teslich, M. J. Cole
  [show abstract] [hide abstract]
  ABSTRACT: In response to the recent report of phyllosilicates in comet 9P/Tempel 1, we explored survivability and alteration of phyllosilicates under Stardust hypervelocity collection conditions for comet 81P/Wild 2 dust and discuss the implications.
  02/2010; 41:2357.
• Source

  Available from: Kevin Mckeegan

  Article: Constraints on the formation age of cometary material from the NASA Stardust mission.

  J E P Matzel, H A Ishii, D Joswiak, I D Hutcheon, J P Bradley, D Brownlee, P K Weber, N Teslich, G Matrajt, K D McKeegan, G J MacPherson
  [show abstract] [hide abstract]
  ABSTRACT: We measured the 26Al-26Mg isotope systematics of a approximately 5-micrometer refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic 26Mg and define an upper limit to the abundance of 26Al at the time of particle formation: 26Al/27Al < 1 x 10(-5). The absence of 26Al indicates that Coki formed >1.7 million years after the oldest solids in the solar system, calcium- and aluminum-rich inclusions (CAIs). The data suggest that high-temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and was incorporated into comets several million years after CAI formation.
  Science 02/2010; 328(5977):483-6. · 31.20 Impact Factor
• Article: Focused ion beam recovery of hypervelocity impact residue in experimental craters on metallic foils

  G. A. Graham, N. Teslich, Z. R. Dai, J. P. Bradley, A. T. Kearsley, F. Hörz
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— The Stardust sample return capsule returned to Earth in January 2006 with primitive debris collected from comet 81P/Wild-2 during the flyby encounter in 2004. In addition to the cometary particles embedded in low-density silica aerogel, there are microcraters preserved in the aluminum foils (1100 series; 100 μm thick) that are wrapped around the sample tray assembly. Soda lime spheres (˜49 μm in diameter) have been accelerated with a light gas gun into flight-grade aluminum foils at 6.35 km s−1 to simulate the capture of cometary debris. The experimental craters have been analyzed using scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDX) to locate and characterize remants of the projectile material remaining within the craters. In addition, ion beam-induced secondary electron imaging has proven particularly useful in identifying areas within the craters that contain residue material. Finally, high-precision focused ion beam (FIB) milling has been used to isolate and then extract an individual melt residue droplet from the interior wall of an impact. This has enabled further detailed elemental characterization that is free from the background contamination of the aluminum foil substrate. The ability to recover “pure” melt residues using FIB will significantly extend the interpretations of the residue chemistry preserved in the aluminum foils returned by Stardust.
  Meteoritics & Planetary Science. 01/2010; 41(2):159 - 165.
• Article: Interpretation of Wild 2 dust fine structure: Comparison of Stardust aluminum foil craters to the three‐dimensional shape of experimental impacts by artificial aggregate particles and meteorite powders

  A. T. Kearsley, M. J. Burchell, M. C. Price, G. A. Graham, P. J. Wozniakiewicz, M. J. Cole, N. J. Foster, N. Teslich
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— New experimental results show that Stardust crater morphology is consistent with interpretation of many larger Wild 2 dust grains being aggregates, albeit most of low porosity and therefore relatively high density. The majority of large Stardust grains (i.e. those carrying most of the cometary dust mass) probably had density of 2.4 g cm−3 (similar to soda-lime glass used in earlier calibration experiments) or greater, and porosity of 25% or less, akin to consolidated carbonaceous chondrite meteorites, and much lower than the 80% suggested for fractal dust aggregates. Although better size calibration is required for interpretation of the very smallest impacting grains, we suggest that aggregates could have dense components dominated by μm-scale and smaller sub-grains. If porosity of the Wild 2 nucleus is high, with similar bulk density to other comets, much of the pore space may be at a scale of tens of micrometers, between coarser, denser grains.Successful demonstration of aggregate projectile impacts in the laboratory now opens the possibility of experiments to further constrain the conditions for creation of bulbous (Type C) tracks in aerogel, which we have observed in recent shots. We are also using mixed mineral aggregates to document differential survival of pristine composition and crystalline structure in diverse finegrained components of aggregate cometary dust analogues, impacted onto both foil and aerogel under Stardust encounter conditions.
  Meteoritics & Planetary Science. 09/2009; 44(10):1489 - 1509.
• Article: Characterization of heterogeneities in detector-grade CdZnTe crystals

  M.C. Duff, D.B. Hunter, A. Burger, M. Groza, V. Buliga, J.P. Bradley, G. Graham, Z.R. Dai, N. Teslich, D.R. Black, A. Lanzirotti
  [show abstract] [hide abstract]
  ABSTRACT: Synthetic Cd1–x Zn x Te or “CZT” crystals are highly suitable for γ-spectrometers operating at room temperature. Secondary phases (SP) within CZT, presumed to be Te metal, have detrimental impacts on the charge collection efficiency of fabricated device. Using analytical techniques rather than arbitrary theoretical definitions, we identify two SP morphologies: (i) many void, 20-μm “negative” crystals with 65-nm nanoparticle residues of Si, Cd, Zn, and Te and (ii) 20-μm hexagonal-shaped bodies, which are composites of metallic Te layers with cores of amorphous and polycrystalline CZT material that surround the voids.
  Journal of Materials Research. 03/2009; 24(04):1361 - 1367.
• Article: Dust from comet Wild 2: Interpreting particle size, shape, structure, and composition from impact features on the Stardust aluminum foils

  A. T. Kearsley, J. Borg, G. A. Graham, M. J. Burchell, M. J. Cole, H. Leroux, J. C. Bridges, F. Hörz, P. J. Wozniakiewicz, P. A. Bland, [......], N. Teslich, T. See, P. Hoppe, P. R. Heck, J. Huth, F. J. Stadermann, C. Floss, K. Marhas, T. Stephan, J. Leitner
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— Aluminum foils of the Stardust cometary dust collector are peppered with impact features of a wide range of sizes and shapes. By comparison to laboratory shots of known particle dimensions and density, using the same velocity and incidence geometry as the Stardust Wild 2 encounter, we can derive size and mass of the cometary dust grains. Using scanning electron microscopy (SEM) of foil samples (both flown on the mission and impacted in the laboratory) we have recognized a range of impact feature shapes from which we interpret particle density and internal structure. We have documented composition of crater residues, including stoichiometric material in 3 of 7 larger craters, by energy dispersive X-ray microanalysis. Wild 2 dust grains include coarse (>10 μm) mafic silicate grains, some dominated by a single mineral species of density around 3–4 g cm−3 (such as olivine). Other grains were porous, low-density aggregates from a few nanometers to 100 μm, with an overall density that may be lower than 1 g cm−3, containing mixtures of silicates and sulfides and possibly both alkali-rich and mafic glass. The mineral assemblage is very similar to the most common species reported from aerogel tracks. In one large aggregate crater, the combined diverse residue composition is similar to CI chondrites. The foils are a unique collecting substrate, revealing that the most abundant Wild 2 dust grains were of sub-micrometer size and of complex internal structure. Impact residues in Stardust foil craters will be a valuable resource for future analyses of cometary dust.
  Meteoritics & Planetary Science. 01/2008; 43(1‐2):41 - 73.
• Source

  Available from: arxiv.org

  Article: Analytical scanning and transmission electron microscopy of laboratory impacts on Stardust aluminum foils: interpreting impact crater morphology and the composition of impact residues

  A. T. Kearsley, G. A. Graham, M. J. Burchell, M. J. Cole, Z. R. Dai, N. Teslich, J. P. Bradley, R. Chater, P. A. Wozniakiewicz, J. Spratt, G. Jones
  [show abstract] [hide abstract]
  ABSTRACT: The known encounter velocity (6.1kms-1) and particle incidence angle (perpendicular) between the Stardust spacecraft and the dust emanating from the nucleus of comet Wild 2 fall within a range that allows simulation in laboratory light gas gun experiments designed to validate analytical methods for the interpretation of dust impacts on the aluminum foil components of the Stardust collector. Buckshot of a wide size, shape and density range of mineral, glass, polymer and metal grains, have been fired to impact perpendicularly upon samples of Stardust Al1100 foil, tightly wrapped onto aluminium alloy plate as an analogue of foil on the spacecraft collector. We have not yet been able to produce laboratory impacts by projectiles with weak and porous aggregate structure, as may occur in some cometary dust grains. In this report we present information on crater gross morphology and its dependence on particle size and density, the pre-existing major and trace element composition of the foil, geometrical issues for energy dispersive X-ray analysis of the impact residues in scanning electron microscopes, and the modification of dust chemical composition during creation of impact craters as revealed by analytical transmission electron microscopy. Together, these observations help to underpin the interpretation of size, density and composition for particles impacted upon the Stardust aluminum foils.
  01/2007;
• Article: Mineralogy and Petrology of Comet Wild 2 Nucleus Samples.

  M. E. Zolensky, T. J. Zega, H Yano, S. Wirick, A. J. Westphal, M. K. Weisberg, I. Weber, J. L. Warren, M. A. Velbel, A. Tsuchiyama, [......], M. Chi, A. L. Butterworth, D. E. Brownlee, John C. Bridges, S Brennan, A. Brearley, J. P. Bradley, P. Bleuet, P. A. Bland, R. Bastien
  [show abstract] [hide abstract]
  ABSTRACT: The bulk of the Wild 2 samples appear to be weakly-constructed mixtures of nanometerscale grains with occasional much larger (>1{micro}m) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in Wild 2 require a wide range of formation conditions, probably reflecting different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and absence of hydrous phases indicate that Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require large-scale radial transport in the early protoplanetary disk. The nature of cometary solids is of fundamental importance to our understanding of the early solar nebula and protoplanetary history. Until now we have had to study comets from afar using spectroscopy, or settle for analyses of interplanetary dust particles (IDPs) of uncertain provenance. We report here mineralogical and petrographic analyses of particles derived directly from Comet Wild 2. All of the Wild 2 particles we have thus far examined have been modified in various ways by the capture process. All particles that may have been loose aggregates, ''traveling sand piles'', disaggregated into individual components with the larger, denser components penetrating more deeply into the aerogel. Individual grains experienced a wide range of heating effects that range from excellent preservation to melting (Fig. 1); such behavior was expected (1, 2 ,3). What is remarkable is the extreme variability of these modifications and the fact that severely modified and unmodified materials can be found within a micrometer of each other, requiring tremendous local temperature gradients. Fortunately, we have an internal gauge of impact collection heating. Fe-Ni sulfides are ubiquitous in the Wild 2 samples, are very sensitive indicators of heating, and accurate chemical analyses can reveal which have lost S, and which have not (and are therefore stoichiometric) (Fig. 2). Our surveys show that crystalline grains are found along the entire lengths of tracks, not just at track termini.
  10/2006;
• Article: Elemental Compositions of Comet 81P/Wild 2 Samples Collected by Stardust

  Flynn, G.~J, P. Bleuet, J. Borg, Bradley, J.~P, Brenker, F.~E, S. Brennan, J. Bridges, [......], B. Vekemans, Vicenzi, E.~P, L. Vincze, Westphal, A.~J, P. Wozniakiewicz, E. Zinner, Zolensky, M.~E
  Science. 01/2006; 314:1731-.
• Article: High Resolution Phase Contrast X-ray Imaging of Cosmic Dust Captured in Aerogel

  J  Sheffield-Parker , G A  Graham , S C  Mayo , N  Teslich , P G  Grant , C  Snead , A J  Westphal 
  Microscopy and Microanalysis 07/2005; 11:1396 - 1397. · 3.01 Impact Factor
• Article: Electron Beam Analysis of Micrometeoroids Captured in Aerogel as Stardust Analogues

  G. A. Graham, J. Sheffield-Parker, P. Bradley, A. T. Kearsley, Z. R. Dai, S. C. Mayo, N. Teslich, C. Snead, A. J. Westphal, H Ishii
  [show abstract] [hide abstract]
  ABSTRACT: In January 2004, NASA s Stardust spacecraft passed through the tail of Comet 81P/Wild-2. The on-board dust flux monitor instrument indicated that numerous micro- and nano-meter sized cometary dust particles were captured by the dedicated silica aerogel capture cell. The collected cometary particles will be returned to Earth in January 2006. Current Stardust analogues are: (i) Light-gas-gun accelerated individual mineral grains and carbonaceous meteoritic material in aerogels at the Stardust encounter velocity ca.approximately 6 kilometers per second. (ii) Aerogels exposed in low-Earth orbit (LEO) containing preserved cosmic dust grains. Studies of these impacts offer insight into the potential state of the captured cometary dust by Stardust and the suitability of various analytical techniques. A number of papers have discussed the application of sophisticated synchrotron analytical techniques to analyze Stardust particles. Yet much of the understanding gained on the composition and mineralogy of interplanetary dust particles (IDPs) has come from electron microscopy studies. Here we discuss the application of scanning electron microscopy (SEM) for Stardust during the preliminary phase of post-return investigations.
  02/2005;
• Source

  Available from: caltech.edu

  Article: The formation of boundary clinopyroxenes and associated glass veins in type B1 CAIs

  J. M. Paque, J. R. Beckett, H. A. Ishii, A. Aléon-Toppani, D. S. Burnett, N. Teslich, Z. R. Dai, J. P. Bradley
  [show abstract] [hide abstract]
  ABSTRACT: We used focused ion beam thin section preparation and scanning transmission electron microscopy (FIB/STEM) to examine the interfacial region between spinel and host melilite for spinel grains in type B1 inclusions from the Allende and Leoville carbonaceous chondrites. Boundary clinopyroxenes decorating spinel surfaces have compositions similar to those of coarser clinopyroxenes from the same region of the inclusion, suggesting little movement after formation. Host melilite displays no anomalous compositions near the interface and late-stage minerals are not observed, suggesting that boundary pyroxenes did not form by crystallization of residual liquid. Allende spinels display either direct spinel-melilite contact or an intervening boundary clinopyroxene between the two phases. Spinel-melilite interfacial regions in a Leoville B1 are more complex, with boundary clinopyroxene, as observed in Allende, but also variable amounts of glass, secondary calcite, perovskite, and an Mg-, Al-, OH-rich and Ca-, Si-poor crystalline phase that may be a layered double hydrate. One possible scenario of formation for the glass veins is that open system alteration of melilite produced a porous, hydrated aggregate of Mg-carpholite or sudoite + aluminous diopside that was shock melted and quenched to a glass. The hydrated crystalline phase we observed may have been a shocked remnant of the precursor phase assemblage, but is more likely to have formed later by alteration of the glass. In the mantle, boundary clinopyroxenes may have been crystallized from Ti-rich liquids formed by the direct dissolution of perovskite and an associated Sc-Zr-rich phase or as a reaction product between dissolving perovskite and liquid. In the core, any perovskite and associated Ti-enriched liquids that may have originally been present disappeared before the growth of boundary clinopyroxene, and the observed boundary clinopyroxene may have nucleated and grown from the liquid, along with the larger core clinopyroxene.
• Article: SEM-EDS analyses of small craters in Stardust aluminum foils: Implications for the Wild-2 dust distribution

  J. Borg, F. Hörz, J. C. Bridges, M. J. Burchell, Z. Djouadi, C. Floss, G. A. Graham, S. F. Green, P. R. Heck, P. Hoppe, J. Huth, A. Kearsley, H. Leroux, K. Marhas, F. J. Stadermann, N. Teslich
  Lunar and Planetary Science XXXVIII, Lunar and Planetary Institute (2007).
• Source

  Available from: open.ac.uk

  Article: SEM-EDS analyses of small craters in stardust aluminium foils: implications for the Wild-2 dust distribution

  J. Borg, F. Hörz, J. C. Bridges, M. J. Burchell, Z. Djouadi, C. Floss, G. A. Graham, S. F. Green, P. R. Heck, P. Hoppe, J. Huth, A. Kearsley, H. Leroux, K. Marhas, F. J. Stadermann, N. Teslich
  [show abstract] [hide abstract]
  ABSTRACT: Implications for the Wild-2 dust distribution of the statistical results obtained by SEM-EDS from nearly 300 impact craters on aluminium foils of the Stardust sample tray assembly.
• Article: Report - Mineralogy and petrology of comet 81P/Wild 2 nucleus samples

  M. E. Zolensky, T. J. Zega, H Yano, S. Wirick, A. J. Westphal, M. K. Weisberg, I. Weber, J. L. Warren, M. A. Velbel, A. Tsuchiyama, [......], M. F. Chi, A. L. Butterworth, D. E. Brownlee, J. C. Bridges, S Brennan, A. Brearley, J. P. Bradley, P. Bleuet, P. A. Bland, R. Bastien
  [show abstract] [hide abstract]
  ABSTRACT: The bulk of the comet 81P/Wild 2 ( hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger ( over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.
• Article: Research article - Comet 81P/Wild 2 under a microscope

  D. Brownlee, P. Tsou, J. Aleon, C. M. O. Alexander, T Araki, S. Bajt, G. A. Baratta, R. Bastien, P. Bland, P. Bleuet, [......], I. Wright, H. Yabuta, H Yano, E. D. Young, R N Zare, T. Zega, K. Ziegler, L. Zimmerman, E. Zinner, M. Zolensky
  Science, v.314, 1711-1716 (2006).
• Article: Comet 81P/Wild 2 under a microscope

  D. Brownlee, P. Tsou, J. Aleon, C. M. O. Alexander, T Araki, S. Bajt, G. A. Baratta, R. Bastien, P. Bland, P. Bleuet, [......], I. Wright, H. Yabuta, H Yano, E. D. Young, R N Zare, T. Zega, K. Ziegler, L. Zimmerman, E. Zinner, M. Zolensky
  Science, v.314, 1711-1716 (2006).
• Source

  Available from: Phil A. Bland

  Article: Dust from comet Wild 2: Interpreting particle size, shape, structure, and composition from impact features on the Stardust aluminum foils

  A. T. Kearsley, J. Borg, G. A. Graham, M. J. Burchell, M. J. Cole, H. Leroux, J. C. Bridges, F. Horz, P. J. Wozniakiewicz, P. A. Bland, [......], N. Teslich, T. See, P. Hoppe, P. R. Heck, J. Huth, F. J. Stadermann, C. Floss, K. Marhas, T. Stephan, J. Leitner
  Meteoritics & Planetary Science, v.43, 41-73 (2008).
• Source

  Available from: open.ac.uk

  Article: Microcraters in aluminum foils exposed by Stardust

  F. Hörz, J. Borg, J. P. Bradley, John Bridges, D. E. Brownlee, M. J. Burchell, M. J. Cole, Z. R. Dai, Z. Djouadi, C. Floss, [......], N. Teslich, K. K. Marhas, C. S. Schwandt, T. H. See, F. J. Stadermann, T. Stephan, D. Troadec, P. Tsou, M. E. Zolensky, The Stardust Cratering Team
  [show abstract] [hide abstract]
  ABSTRACT: We will present preliminary results on the nature and size frequency distribution of microcraters that formed in aluminum foils during the flyby of comet Wild 2 by the Stardust spacecraft.