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51	Hydration and ion pair formation in common aqueous La(III) salt solutions: a Raman scattering and DFT study Rudolph, Wolfram W., Irmer, Gert 19 December 2019 (has links) Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121–3.050 mol Lˉ¹) range at room temperature (23 °C). A very weak mode at 343 cmˉ¹ with a full width at half height at 49 cmˉ¹ in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol Lˉ¹) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La³⁺ nona-hydrate was also detected in a 1.2 mol Lˉ¹ La(CF₃SO₃)₃(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5–3.050 mol Lˉ¹. The chloro-complexes in LaCl₃(aq) are fairly weak and disappear with dilution. At a concentration <0.1 mol Lˉ¹ almost all complexes disappeared. In LaCl₃ solutions, with additional HCl, a series of chloro-complexes of the type [La(OH₂)₉₋nCln]⁺³⁻ⁿ (n = 1–3) were formed. The La(NO₃)₃(aq) spectra were compared with a spectrum of a 0.409 mol Lˉ¹ NaNO₃(aq) and it was concluded that in La(NO₃)₃(aq) over the concentration range from 0.121–1.844 mol Lˉ¹, nitrato-complexes, [La(OH₂)₉₋n-(NO₃)n]⁺³⁻ⁿ (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution <0.01 mol Lˉ¹. DFT geometry optimizations and frequency calculations are reported for a lanthanumnona-hydrate with a polarizable dielectric continuum in order to take the solvent into account. The bond distances and angles for the cluster geometry of [La(OH₂)₉]³⁺ with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La–O stretching mode at 328.2 cmˉ¹, is only slightly smaller than the experimental one. info:eu-repo/classification/ddc/540 ddc:540
52	Formation and preservation of abiotic organic signatures vs. lipid biomarkers—experimental studies in preparation for the ExoMars 2020 mission Mißbach, Helge 30 May 2018 (has links) No description available. 910 550 geobiology astrobiology biogeochemistry biomarker ratios closed system pyrolysis gas chromatography–mass spectrometry Green River Shale maturity indicators vitrinite reflectance thermal degradation Fischer–Tropsch-type synthesis abiotic synthesis lipids experimental maturation Dresser Formation Archean kerogen ExoMars Planetary instrumentation thermochemolysis perchlorate Mars Organic Molecule Analyzer life detection
53	IMPACT BEHAVIOR OF AMMONIUM PERCHLORATE (AP) - HYDROXYL-TERMINATED POLYBUTADIENE (HTPB) COMPOSITE MATERIAL Saranya Ravva (15353902) 25 April 2023 (has links) <p>This work investigated the effects of varying the crystal sizes of ammonium perchlorate (AP) when embedded with a polymeric binder, hydroxyl-terminated polybutadiene (HTPB) on impact-induced temperature behavior. AP and HTPB are the most used oxidizers and fuel binders in the aerospace solid rocket design industry. In this study, samples of 200 µm and 400µm coarse AP crystals in HTPB were constructed using a conventional hand-mixing method. Using a parametric optimization technique such as the Taguchi method, direct-ink-writing as the additive manufacturing process was used for achieving the required shape fidelity in printing HTPB and by introducing ultraviolet polymers to decrease the curing time.</p> <p>A drop hammer experiment in conjunction with an infrared camera was used to study the impact-induced behavior in the conventionally made AP-HTPB samples. The thermal images obtained from the camera at millisecond resolution are invaluable and provide information about distribution across the sample surface, and the evolution of temperature rise observed in the samples which are complex and not easily understood otherwise and therefore help in improving and attaining desired propellant performance. A two-sample t-Test has been utilized to infer the results and statistical nonsignificance has been observed in the highest temperature rises among 200 µm and 400 µm AP-HTPB sample conditions but a difference in temperature distribution has been observed. A much uniform distribution of temperature over the sample surface on impact is observed in thermal images of 200 µm AP-HTPB sample condition compared to 400 µm AP-HTPB sample condition.</p> Aerospace materials Aerospace structures Additive manufacturing Composite and hybrid materials Ammonium Perchlorate (AP) Hydroxyl-Terminated Polybutadiene (HTPB) Impact Testing Aerospace Engineering Additive Manufacturing Direct Ink Writing Parametric Optimization Taguchi Method Drop Hammer Impact IR camera Solid Rocket Propellant APCP T-test p-value Aerospace Materials
54	<b>Closed Vessel Burning Rate Measurements of Composite Propellants Using Microwave Interferometry</b> Shane A Oatman (18396357) 17 April 2024 (has links) <p dir="ltr">Burning rate as a function of pressure is one of the primary evaluation metrics of solid propellants. Most solid propellant burning rate measurements are made at a nearly constant pressure using a variety of measurement approaches. This type of burning rate data is highly discretized and requires many tests to accurately determine the burning rate response to pressure. It would be moreefficient to measure burning rate dynamically as pressures are varied. Techniques used to make transient burning rate measurements are reviewed briefly and initial results using a microwave interferometry (MI) technique are presented. The MI method used in tandem with a closed bomb enables nearly continuous measurement of burning rates for self-pressurizing burns, capturing burning rate data over a wide range of pressures. This approach is especially useful for characterization of propellants with complex burning behaviors (e.g., slope breaks or mesa burning). The burning rates of three research propellants were characterized over a pressure range of 0.101-24.14 MPa (14-3500 psi). One research propellant exhibited a slope break at a pressure of 6.63 MPa (960 psi). Using MI in a closed pressure vessel, 14 propellant strand burns resulted in a nearly continuous burning rate curve over a pressure range of 0.41-24.13MPa (60-3500psi) that reasonably matched conventional burning rate measurements. The development of this technique provides an opportunity to quickly characterize the burning rate curve of solid propellants with greater fidelity and efficiency than traditional quasi-static pressure testing techniques.</p> microwave interferometry burning rate Burning rate interferometry Spatially Composite propellants slope break exponent break lab scale propellant testing crawford bomb closed bomb pressure vessel

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