scholarly journals Surface Persistence of Trace Level Deposits of Highly Energetic Materials

2019 ◽  
Author(s):  
Leonardo C. Pacheco-Londoño ◽  
Jose L. Ruiz-Caballero ◽  
Michael L. Ramirez-Cedeño ◽  
Ricardo Infante-Castillo ◽  
Nataly J. Galan-Freyle ◽  
...  
Keyword(s):  
Energetic Materials ◽  
Grazing Angle ◽  
Surface Concentration ◽  
Beta Phase ◽  
Alpha Phase ◽  
Triacetone Triperoxide ◽  
Ftir Microscopy ◽  
Different Temperatures ◽  
Highly Energetic Materials ◽  
Ss Substrates

The sublimation enthalpies of four highly energetic materials (HEMs): triacetone triperoxide (TATP), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrohexahydro-s-triazine (RDX) deposited on stainless steel (SS) substrates were determined by optical fibre coupled-grazing angle probe (GAP) FTIR spectroscopy and thermogravimetric analysis (TGA) for bulk crystaline HEMs samples. The desorption energy of RDX on SS was also studied using grazing angle FTIR microscopy. Metastable phases of 2,4-DNT and TNT were observed when deposited on SS, and their sublimation enthalpies values were obtained by GAP measurements and compared with those for the crystalline phases. The sublimation enthalpies for the alpha phase RDX was also determined by TGA measurements. A layer of crystalline beta phase RDX was observed on SS, and it's sublimation enthalpies was determinate by GAP. PLS calibration curves for the surface concentrations of RDX on SS were generated using GAP to determinate the surface concentration with time at different temperatures.

scholarly journals Surface Persistence of Trace Level Deposits of Highly Energetic Materials

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3494 ◽  
Author(s):  
Leonardo C. Pacheco-Londoño ◽  
José L. Ruiz-Caballero ◽  
Michael L. Ramírez-Cedeño ◽  
Ricardo Infante-Castillo ◽  
Nataly J. Gálan-Freyle ◽  
...  
Keyword(s):  
Energetic Materials ◽  
Metastable Phase ◽  
Grazing Angle ◽  
Sublimation Enthalpy ◽  
Gravimetric Analysis ◽  
Ftir Microscopy ◽  
Linear Behavior ◽  
Highly Energetic Materials ◽  
Ss Substrates ◽  
Enthalpies Of Sublimation

In the fields of Security and Defense, explosive traces must be analyzed at the sites of the terrorist events. The persistence on surfaces of these traces depends on the sublimation processes and the interactions with the surfaces. This study presents evidence that the sublimation process of these traces on stainless steel (SS) surfaces is very different than in bulk quantities. The enthalpies of sublimation of traces of four highly energetic materials: triacetone triperoxide (TATP), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and 1,3,5- trinitrohexahydro-s-triazine (RDX) deposited on SS substrates were determined by optical fiber coupled-grazing angle probe Fourier Transform Infrared (FTIR) Spectroscopy. These were compared with enthalpies of sublimation determined by thermal gravimetric analysis for bulk amounts and differences between them were found. The sublimation enthalpy of RDX was very different for traces than for bulk quantities, attributed to two main factors. First, the beta-RDX phase was present at trace levels, unlike the case of bulk amounts which consisted only of the alpha-RDX phase. Second, an interaction between the RDX and SS was found. This interaction energy was determined using grazing angle FTIR microscopy. In the case of DNT and TNT, bulk and traces enthalpies were statistically similar, but it is evidenced that at the level of traces a metastable phase was observed. Finally, for TATP the enthalpies were statistically identical, but a non-linear behavior and a change of heat capacity values different from zero was found for both trace and bulk phases.

scholarly journals Detection of Nitroaromatic and Peroxide Explosives in Air Using Infrared Spectroscopy: QCL and FTIR

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Leonardo C. Pacheco-Londoño ◽  
John R. Castro-Suarez ◽  
Samuel P. Hernández-Rivera
Keyword(s):  
Pattern Recognition ◽  
Infrared Spectroscopy ◽  
Gas Phase ◽  
Energetic Materials ◽  
Organic Peroxide ◽  
Triacetone Triperoxide ◽  
Quantum Cascade ◽  
Spectroscopic Information ◽  
Ft Ir ◽  
Highly Energetic Materials

A methodology for processing spectroscopic information using a chemometrics-based analysis was designed and implemented in the detection of highly energetic materials (HEMs) in the gas phase at trace levels. The presence of the nitroaromatic HEM 2,4-dinitrotoluene (2,4-DNT) and the cyclic organic peroxide triacetone triperoxide (TATP) in air was detected by chemometrics-enhanced vibrational spectroscopy. Several infrared experimental setups were tested using traditional heated sources (globar), modulated and nonmodulated FT-IR, and quantum cascade laser- (QCL-) based dispersive IR spectroscopy. The data obtained from the gas phase absorption experiments in the midinfrared (MIR) region were used for building the chemometrics models. Partial least-squares discriminant analysis (PLS-DA) was used to generate pattern recognition schemes for trace amounts of explosives in air. The QCL-based methodology exhibited a better capacity of discrimination for the detected presence of HEM in air compared to other methodologies.

scholarly journals Tensile Flow Behaviour and Fracture Studies of Beta Titanium Alloys at Elevated Temperatures

2021 ◽  
pp. 1-6
Author(s):  
Saurabh Rai ◽  
◽  
Kalyani Panigrahi ◽  
Keyword(s):  
Elevated Temperatures ◽  
Beta Phase ◽  
Alpha Phase ◽  
Beta Titanium ◽  
Beta Alloy ◽  
Wide Range ◽  
Different Temperatures ◽  
Single Sheet ◽  
Processing Techniques ◽  
Metastable Beta

Tensile testing on metastable beta alloy with various microstructures was carried out in this study. Beta 21S is a metastable alloy that exhibits a wide range of material characteristics depending on the processing techniques used. Three different sheets that have been used in this paper which has the same substance but three different microstructures. At a strain rate of 0.001/s, the tensile test was done on a single sheet at five different temperatures. The sheet has developed varied microstructures, the tensile nature of the material varies the alloy’s characteristics. Mechanical characteristics for 400°C, 500°C, 600°C, and 7000°C are described for 21S sheets. The alpha phase sheet elongated at room temperature by 1-3 %, whereas the pure beta phase sheet elongated by 22-24 %. There is a significant improvement in the extension of the sheet with the variation in temperature for the alpha phase. The elongation of the pure beta phase does not alter as the temperature rises. The fracture surface was tested at all temperatures and the optimal temperature for forming the sheet has been determined

scholarly journals PVDF Membrane Morphology - Influence of Polymer Molecular Weight and Preparation Temperature

2017 ◽  
Author(s):  
Monika Haponska ◽  
Anna Trojanowska ◽  
Adrianna Nogalska ◽  
Renata Jastrzab ◽  
Tania Gumi ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Beta Phase ◽  
Alpha Phase ◽  
Membrane Properties ◽  
Precipitation Method ◽  
Coagulation Bath ◽  
Environmental Scanning ◽  
Polymer Molecular Weight ◽  
Preparation Temperature ◽  
Different Temperatures

The global polyvinyldene flouride market is estimated to reach $937,278.5 thousand by 2019, therefore to develop new membranes and gain pioneering ideas, which could create innovative business opportunities, a fundamental knowledge about membrane properties fabricated from recent commercially available PVDF polymers is highly mandatory. In this study, we successfully prepared nine non-woven supported PVDF membranes using a phase inversion precipitation method starting from a 15 wt% PVDF solution in N-methyl-2-pyrrolidone. Various membrane morphologies were obtained by using (1) PVDF polymers with diverse molecular weight in a range from 300.000 Da to 700.000 Da and (2) different temperatures of the coagulation bath (20, 40, and 60 ±2°C) used for the films precipitation. Environmental Scanning Electron Microscope (ESEM) was used for surface and cross-section morphologies characterization.  Atomic Force Microscope (AFM) was employed to investigate surface roughness, while Contact Angle (CA) instrument was used for membranes wettability studies. Fourier Transform Infrared Spectroscopy (FTIR) results show that the fabricated membranes are formed by a mixture of TGTG’ chains in α phase crystalline domains and all-TTTT trans planar zigzag chains characteristic to β phase. Moreover, generated results indicate that the phases content and membrane morphologies depend on the polymer molecular weight and conditions used for the membranes preparation. The diversity of fabricated membranes could be applied by the End User Industries for different applications.

scholarly journals Structural Factors Inducing Cracking of Brass Fittings

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3255
Author(s):  
Lenka Kunčická ◽  
Michal Jambor ◽  
Adam Weiser ◽  
Jiří Dvořák
Keyword(s):  
Chemical Composition ◽  
Plastic Flow ◽  
Beta Phase ◽  
Alpha Phase ◽  
Structural Factors ◽  
Transmission Electron ◽  
Medical Gas ◽  
Hot Die Forging ◽  
Multiple Step

Cu–Zn–Pb brasses are popular materials, from which numerous industrially and commercially used components are fabricated. These alloys are typically subjected to multiple-step processing—involving casting, extrusion, hot forming, and machining—which can introduce various defects to the final product. The present study focuses on the detailed characterization of the structure of a brass fitting—i.e., a pre-shaped medical gas valve, produced by hot die forging—and attempts to assess the factors beyond local cracking occurring during processing. The analyses involved characterization of plastic flow via optical microscopy, and investigations of the phenomena in the vicinity of the crack, for which we used scanning and transmission electron microscopy. Numerical simulation was implemented not only to characterize the plastic flow more in detail, but primarily to investigate the probability of the occurrence of cracking based on the presence of stress. Last, but not least, microhardness in specific locations of the fitting were examined. The results reveal that the cracking occurring in the location with the highest probability of the occurrence of defects was most likely induced by differences in the chemical composition; the location the crack in which developed exhibited local changes not only in chemical composition—which manifested as the presence of brittle precipitates—but also in beta phase depletion. Moreover, as a result of the presence of oxidic precipitates and the hard and brittle alpha phase, the vicinity of the crack exhibited an increase in microhardness, which contributed to local brittleness.

scholarly journals Active Mode Remote Infrared Spectroscopy Detection of TNT and PETN on Aluminum Substrates

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
John R. Castro-Suarez ◽  
Leonardo C. Pacheco-Londoño ◽  
Joaquín Aparicio-Bolaño ◽  
Samuel P. Hernández-Rivera
Keyword(s):  
Infrared Spectroscopy ◽  
Energetic Materials ◽  
Angle Of Incidence ◽  
Least Squares Regression ◽  
Active Mode ◽  
Infrared Telescope ◽  
Infrared Spectrometer ◽  
Highly Energetic Materials ◽  
Aluminum Plates ◽  
Aluminum Substrates

Two standoff detection systems were assembled using an infrared telescope coupled to a Fourier transform infrared spectrometer, a cryocooled mercury-cadmium telluride detector, and a telescope-coupled midinfrared excitation source. Samples of the highly energetic materials (HEMs) 2,4,6-trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) were deposited on aluminum plates and detected at several source-target distances by carrying out remote infrared spectroscopy (RIRS) measurements on the aluminum substrates in active mode. The samples tested were placed at 1–30 m for the RIRS detection experiments. The effect of the angle of incidence/collection of the IR beams on the vibrational band intensities and the signal-to-noise ratios (S/N) were investigated. Experiments were performed at ambient temperature. Surface concentrations from 50 to 400 μg/cm2 were studied. Partial least squares regression analysis was applied to the spectra obtained. Overall, RIRS detection in active mode was useful for quantifying the HEMs deposited on the aluminum plates with a high confidence level up to the target-collector distances of 1–25 m.

scholarly journals Phase and power modulations on the amplitude of TMS-induced motor evoked potentials

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0255815
Author(s):  
Lukas Schilberg ◽  
Sanne Ten Oever ◽  
Teresa Schuhmann ◽  
Alexander T. Sack
Keyword(s):  
Evoked Potentials ◽  
Diagnostic Tool ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Single Pulse ◽  
Beta Phase ◽  
Alpha Phase ◽  
Individual Variability ◽  
Oscillatory Activity ◽  
Alpha Power

The evaluation of transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs) promises valuable information about fundamental brain related mechanisms and may serve as a diagnostic tool for clinical monitoring of therapeutic progress or surgery procedures. However, reports about spontaneous fluctuations of MEP amplitudes causing high intra-individual variability have led to increased concerns about the reliability of this measure. One possible cause for high variability of MEPs could be neuronal oscillatory activity, which reflects fluctuations of membrane potentials that systematically increase and decrease the excitability of neuronal networks. Here, we investigate the dependence of MEP amplitude on oscillation power and phase by combining the application of single pulse TMS over the primary motor cortex with concurrent recordings of electromyography and electroencephalography. Our results show that MEP amplitude is correlated to alpha phase, alpha power as well as beta phase. These findings may help explain corticospinal excitability fluctuations by highlighting the modulatory effect of alpha and beta phase on MEPs. In the future, controlling for such a causal relationship may allow for the development of new protocols, improve this method as a (diagnostic) tool and increase the specificity and efficacy of general TMS applications.

Mechanical behavior of fine-grained Mg-6.5Li at elevated temperature

1994 ◽  
Vol 9 (6) ◽  
pp. 1392-1396 ◽  
Author(s):  
Eric M. Taleff ◽  
Oleg D. Sherby
Keyword(s):  
Stress Exponent ◽  
Solute Drag ◽  
Beta Phase ◽  
Alpha Phase ◽  
Dislocation Creep ◽  
Creep Process ◽  
Strain Rate Change ◽  
Fine Grained ◽  
Diffusion Controlled ◽  
Average Grain Size

A Mg-6.5 wt. % Li alloy containing 80% hep alpha phase and 20% bcc beta phase was processed to achieve an average grain size of 5.9 μm. Strain-rate-change tests were performed in the temperature range from 398 K to 573 K. Two types of creep behavior were observed. A stress exponent of five, obtained at low temperatures and high stresses, is attributed to a diffusion-controlled dislocation creep process in the alpha matrix. A stress exponent of three, obtained at high temperatures and low stresses, is attributed to a solute-drag controlled dislocation creep process in the alpha matrix.

Crystal Engineering for Creating Low Sensitivity and Highly Energetic Materials

2018 ◽  
Vol 18 (10) ◽  
pp. 5713-5726 ◽  
Author(s):  
Chaoyang Zhang ◽  
Fangbao Jiao ◽  
Hongzhen Li
Keyword(s):  
Crystal Engineering ◽  
Energetic Materials ◽  
Highly Energetic Materials ◽  
Low Sensitivity

Effect of Deposition Conditions on Intrinsic Stress, Phase Transformation and Stress Relaxation in Tantalum Thin Films

1991 ◽  
Vol 239 ◽  
Author(s):  
A. Mutscheller ◽  
L. A. Clevenger ◽  
J.M.E. Harper ◽  
C. Cabrai ◽  
K. Barmakt
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Phase Transformation ◽  
Stress Relaxation ◽  
Compressive Stress ◽  
Stress Relief ◽  
Beta Phase ◽  
Alpha Phase ◽  
Intrinsic Stress

AbstractWe demonstrate that the high temperature polymorphic tantalum phase transition from the tetragonal beta phase to the cubic alpha phase causes complete stress relaxation and a large decrease in the resistance of tantalum thin films. 100 nm beta tantalum thin films were deposited onto thermally oxidized <100> silicon wafers by dc magnetron sputtering with argon. In situ stress and resistance at temperature were measured during temperature-ramped annealing in purified He. Upon heating, films that were initially compressively stressed showed increasing compressive stress due to thermo-elastic deformation from 25 to 550°C, slight stress relief due to plastic deformation from 550 to 700°C and complete stress relief due to the beta to alpha phase transformation at approximately 700–800°C. Incomplete compressive stress relaxation was observed at high temperatures if the film was initially deposited in the alpha phase or if the beta phase did not completely transform into alpha by 800°C. This incomplete beta to alpha phase transition was most commonly observed on samples that had radio frequency substrate bias greater than -100 V. We conclude that the main stress relief mechanism for tantalum thin films is the beta to alpha phase transformation that occurs at 700 to 800°C.

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