Propellant Chemistry Research Articles

Characterization of water propellant in an electron cyclotron resonance thruster

A coaxial electron cyclotron resonance thruster operating on water vapor propellant is investigated to determine the influence of molecular propellant chemistry on thruster performance. The performance is characterized at different mass flow rates (0.1–0.4 mg/s) and powers (20–200 W) using a thrust stand, ion energy analyzer, and spectrometer. Experimental data are compared to the results from a theoretical model that includes non-equilibrium chemical kinetics. The thruster is observed to transition from a state where power deposition favors propellant dissociation and ionization into a state where it favors electron heating and ion acceleration. The results suggest that the majority of plasma heating occurs in a core region that surrounds the thruster antenna and that propellant flow outside this region is not efficiently utilized for propulsion.

Dielectric and structural properties of polyaniline-tungsten trioxide nanocomposites: For the packing of nano-electronic devices and EMI shielding

Polymer nanocomposites (PNCs) have showed the significant applications in the fields of packing, energy, safety, defense, sensors, EMI shielding, optoelectronics etc. Tungsten trioxide nanoparticles (NPs) were prepared by propellant chemistry technique using Azadirachta indica extracts as a fuel/surfactant. Conducting polyaniline (PANI) was prepared using aniline monomer and suitable polymerizing agents. Ex-situ nanocomposites were prepared by mixing the different weight percentage of NPs into PANI matrix. For the better dispersion of NPs in to the matrix, solvents like Dodesyl benzene sulphonic acid (DBSA) and Camphor sulphonic acid (CSA) were used. Crystal structure, morphological features and their dielectric response at room temperature were reported. Electromagnetic Shielding (EMI) studies were compared between the PANI-WO3 composites prepared by CSA and DBSA solvents. Composites showed worthy shielding response of 80 dB with CSA and 38 dB with DBSA. Here, the protonation of the solvent and the dispersion of NPs with the polymer matrix matters for the shielding efficiency. Hence, prepared materials are suitable for packing of electronic devices which provides the better EMI shielding and also suppress the heat through effective absorption of EM waves of X-Band.

Canister valve and actuator deposition in metered dose inhalers formulated with low-GWP propellants

A challenge in pressurised metered-dose inhaler (pMDI) formulation design is management of adhesion of the drug to the canister wall, valve and actuator internal components and surfaces. Wall-material interactions differ between transparent vials used for visual inspection and metal canister pMDI systems. This is of particular concern for low greenhouse warming potential (GWP) formulations where propellant chemistry and solubility with many drugs are not well understood. In this study, we demonstrate a novel application of X-ray fluorescence spectroscopy using synchrotron radiation to assay the contents of surrogate solution and suspension pMDI formulations of potassium iodide and barium sulphate in propellants HFA134a, HFA152a and HFO1234ze(E) using aluminium canisters and standard components. Preliminary results indicate that through unit life drug distribution in the canister valve closure region and actuator can vary significantly with new propellants. For solution formulations HFO1234ze(E) propellant shows the greatest increase in local deposition inside the canister valve closure region as compared to HFA134a and HFA152a, with correspondingly reduced actuator deposition. This is likely driven by chemistry changes. For suspension formulations HFA152a shows the greatest differences, due to its low specific gravity. These changes must be taken into consideration in the development of products utilising low-GWP propellants.

Synthesis of plutonium dioxide by citric acid-assisted solution combustion synthesis

Plutonium dioxide synthesis is an essential step in fuel reprocessing, solution combustion synthesis method (SCS) can offer advantages on fuel preparation. This study reports for the first time the synthesis of PuO2 by SCS with citric acid. It allowed to determine an optimal ratio for citric acid over plutonium ratio (CA/Pu=1.1) for PuO2 synthesis, which is consistent with the propellant chemistry theory, leading to oxides with SCS's characteristic morphologies.

Sm-SrAl2O4 Nanomaterial: Intensive Orange-red component for white LED, Latent finger Print, and anti-counterfeiting applications

Sm3+ (1.0 –11.0 mol %) doped SrAl2O4 nanopowders were synthesized by ultrasonication followed by propellant chemistry technique using Aloe Vera (A.V.) extract as a surfactant/fuel. The prepared sample's average crystallite size of ∼ 30.0–32.0 nm was estimated. The surface morphology of the samples showed better porosity with nanorods networked to obtain superstructures. Diffused reflection spectral analysis showed that the prepared samples have an optical energy band gap of 5.22 to 5.6 eV, where the increased concentration of Sm3+ decreased the Eg value of the SrAl2O4: Sm3+ (1.0 – 11.0 mol%). Samples showed intense orange-red emission upon excited with 372 nm. Thereafter CIE and CCT values explain that the prepared nanophosphors (NPs) are highly advantageous for the production of red or excited with 372 nm orange emitting diodes in optoelectronics for display devices and WLED applications. SrAl2O4: Sm3+ (5.0 mol %) NPs were considered to study the LFPs. Hence, the synthesized NPs will give an efficient outlook to visualize ridge patterns in LFPs investigations and anti-counterfeiting applications, which were studied by considering different material surfaces.

Novel Segregated Solid Propulsion System with Separately Stored Fuel and Oxidizer

The development and experimentation of a solid propulsion concept consisting of separate hydrogen-rich solid propellant and solid oxidizer grains is presented. This system consists of an extremely fuel-rich solid propellant, which, once ignited, undergoes a self-sustaining decomposition to release fuel-rich product gases, which are particularly rich in hydrogen gas. These relatively high-temperature gases subsequently react with a solid oxidizer grain stored downstream. Progress in high-nitrogen materials has allowed for the synthesis of fuel-rich compounds that can store significant amounts of hydrogen, with little or no bound oxygen. With these new developments in propellant chemistry, a unique segregated propulsion system has been developed, creating an all-solid propulsion system that combusts analogously to a reverse hybrid rocket system. Because of the physical separation of fuel and oxidizer, a higher level of safety is achieved which concurrently allows for the utilization of higher energy ingredients without the penalty of higher sensitivity. Theoretical performance calculations and experimental data have shown the potential for this system to compete with existing composite rocket propellants while having significant benefits in terms of safety, toxicity, and mission space. This paper presents a detailed overview of the conception, development, and testing of this propulsion system.

Role of pH on the Structural and Infrared Properties of Nickel Ferrite Nanoparticles Prepared via Sol-Gel Auto Combustion Method

Wet chemical methods in particular sol-gel auto combustion method play a vital role in governing the size and the shape of the particles. In the present communication, nickel ferrite nanoparticles were prepared by sol-gel auto combustion technique using citric acid as a fuel. The metal nitrate to fuel ratio was chosen as 1:3 using propellant chemistry approach. The nanopowder of the nickel ferrite was prepared at various pH viz. 2, 5, 7 and 9. The obtained nanopowder was annealed at 600°C for 4 h and used for further characterizations. All the samples were structurally characterized by X-ray diffraction and infrared spectroscopy technique. The room temperature XRD pattern reveals the formation of single-phase cubic spinel structure. The lattice constant calculated from XRD data shows dependence of pH values. The Fourier transform infrared spectra show two absorption bands in all the four samples near 400 cm-1 and 600 cm-1. However, a slight variation in the absorption band is observed for different pH.

Sol-gel auto-combustion, structural and morphological properties of Co60 γ-ray irradiated ZnFe2O4 NPs

In this study, we used the sol-gel auto-combustion method to make zinc ferrite nanoparticles (ZnFe2O4 NPs) utilizing glycine as a fuel to boost the chemical reaction in the right direction, following the propellant chemistry protocols. The influence of preparation conditions and sintering temperature kept during the synthesis were investigated using a controlled reaction and ionic exchange. In a gamma chamber, the produced zinc ferrite nanoparticles were irradiated with a total dose of 5 Mrad by Co60-γirradiation. The morphological and topographical character of ZnFe2O4 NPs were studied, as well as the thermal analysis and physico-chemical parameters; TGA exothermic ranged from 220 °C to 660 °C, and TGA endothermic at 660 °C. The phase purity and existence of Bragg's reflections belonging to the space group Fd3m-1; a normal type cubic spinel structure of ZnFe2O4 NPs were shown by the XRD pattern. The lattice constant (a), unit cell volume (V), X-ray density (dx), and other microstructural parameters have been determined using Debye-formula Scherrer's crystallite size (D = 40.164 nm). To support the phase formation investigation, the Raman spectra were examined for the active mode A1g. The UV–Vis spectral absorption of ZnFe2O4 NPs was reported at ∼ 258.03 Å. The optical bandgap was estimated by using a Tauc’s plot; Kubelka-Munk function F(R); which was reported to be 3.69 eV.

Functionalized surfaces created by perturbation in luminescent polymer nanocomposites: Materials for forensic and security ink applications

Europium ions doped pearl white dispersed effectively in PVA binder using Bovine Serum Albumin (BSA) as a stabilizer. Nano-powders (NPs) were synthesized by using propellant chemistry approach. Further, these NPs were incorporated into the polymer binder matrix by solvent casting approach to obtain nanocomposites (NCs). BSA stabilizer made any avenue for the perturbation to the secondary protein chains leading to functionalized surfaces. This helped in obtaining the uniform dispersion of the filler added. Different proportions of (2–10 wt%) functionalized BiOCl-Y2O3:Eu3+ NPs were loaded into PVA matrix. X-ray diffraction profile shows the effective incorporation of the NPs into the polymer. Upon exciting at 398 nm near UV light, the NC shows strong red emission at 612 nm along with other three peaks were due to the transition from 5D0 to 7Fj (j = 1, 2, 3 and 4). The highest PL intensity was registered for 8 wt% NPs in PVA matrix. The optimized NCPs were further utilized for various technological applications namely solid-state lighting, forensic and security ink preparation. The latent fingerprints developed on commonly encountered objects were investigated from the functionalized BiOCl-Y2O3:Eu3+ NCPs by powder dusting method. The results undoubtedly revealed all the Type – I – III ridge details irrespective of surfaces. Anti – counterfeiting ink has been developed and testified on various surfaces. The overall results clearly revealed that surface functionalized NCs were quite suitable for multifunctional applications.

Sub‐Thermionic Negative Capacitance Field Effect Transistors with Solution Combustion‐Derived Hf0.5Zr0.5O2

AbstractThe fabrication of Hf0.5Zr0.5O2‐ferroelectric negative capacitor using solution combustion is presented for the first time. The starting materials used for the solution combustion to form equimolar Hf0.5Zr0.5O2 are to act as both combustible elements and cation sources. Jain's method, which is used for estimating the stoichiometric quantities of precursors in propellant chemistry, has also been modified and applied. The conventional assumption for this method that molecular oxygen does not take part in the reaction is refuted and stoichiometric combustion in the presence of molecular oxygen is proposed. This reaction is followed by post‐rapid thermal processing to stabilize the metastable, non‐centrosymmetric orthorhombic phase. The thin film stacks, Hf0.5Zr0.5O2/HfO2, are used to achieve sub‐thermionic swing (forward sweep: 25.42 ± 8.05 mV dec−1, reverse sweep: 42.56 ± 4.87 mV dec−1) in MoS2 negative capacitance field effect transistors with a hysteresis of ≈40 mV at 1 nA, resulting in ultra‐low‐power operation.

Modeling thermodynamic trends of rotating detonation engines

The formation of a number of co- and counter-rotating coherent combustion wave fronts is the hallmark feature of the Rotating Detonation Engine (RDE). The engineering implications of wave topology are not well understood nor quantified, especially with respect to parametric changes in combustor geometry, propellant chemistry, and injection and mixing schemes. In this article, a modeling framework that relates the time and spatial scales of the RDE to engineering performance metrics is developed and presented. The model is built under assumptions of backpressure-insensitivity and nominally choked gaseous propellant injection. The Euler equations of inviscid, compressible fluid flow in one dimension are adapted to model the combustion wave dynamics along the circumference of an annular-type RDE. These adaptations provide the necessary mass and energy input and output channels to shape the traveling wave fronts and decaying tails. The associated unit processes of injection, mixing, combustion, and exhaust are all assigned representative time scales necessary for successful wave propagation. We find that the separation, or lack, of these time scales is responsible for the behavior of the system, including wave co- and counter-propagation and bifurcations between these regimes and wave counts. Furthermore, as there is no imposition of wave topology, the model output is used to estimate the net available mechanical work output and thermodynamic efficiency from the closed trajectories through pressure–volume and temperature–entropy spaces. These metrics are investigated with respect to variation in the characteristic scales for the RDE unit physical processes.

Disaccharide assisted LaAlO3:Ce3+ perovskite: Structural and optical studies suitable for display devices

Sucrose mediated LaAlO3: Ce3+ nanopowders were prepared by propellant chemistry technique. The preliminary characterizations were carried out using Powder X-Ray Diffraction (PXRD), Fourier Transform InfraRed spectra (FTIR), Scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM) to analyse the structure and morphology of the prepared nanophosphors. PXRD studies showed pure rhombohedral single phase with average crystallite size of the order of 45–62 nm. SEM micrographs confirmed nanoparticles formation and the crystallite size agrees well with the TEM image. The optical band gap of LaAlO3: Ce3+ (1–2 mol%) nanophosphors was found to be in the range 4.5–4.93 eV. PL spectra showed broad intense band at 449 nm and 541 nm up on 330 nm excitation. Chromaticity studies exhibit the blue green color emission of the prepared phosphors. The intensity and color of Ce3+ doped LaAlO3 nanophosphors confirm that these phosphors can be a potential material for display and optical devices.

Mixed Mg–Co spinel ferrites: Structure, morphology, magnetic and photocatalytic properties

CoxMg1-xFe2O4 (where x was 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) spinel ferrites were synthesized by the sol-gel combustion method using citric acid as fuel, following the rules of propellant chemistry. Amorphous powders were then calcined at 700 °C for 3 h. Structural analysis by X-Ray diffraction (XRD), FTIR and Raman spectroscopy confirmed the formation of a cubic spinel structure where the cation distribution and inversion degree depended on the Co2+ and Mg2+ ion content. Accordingly, the lattice parameter varied between 8.3703 Å (MgFe2O4) and 8.3919 Å (Co0.9Mg0.1Fe2O4) as did the crystallite size, from 34 nm (Co0.1Mg0.9Fe2O4) to 48 nm (Co0.9Mg0.1Fe2O4). Scanning electron microscopy (SEM) showed the formation of multigrain agglomerates. Determined values of the maximal and remanent magnetization, as well as coercive field, depended on the Co2+ and Mg2+ ion content and increased with substitution of diamagnetic Mg2+ ions with magnetic Co2+ ions. Most impressive is the increase of the coercive field from 74 Oe for MgFe2O4 to 1000 Oe for CoFe2O4, as well as an increase of magnetization in the field of 10 kOe from 27.4 emu g−1 to 75.7 emu g−1. The determined optical band gaps from UV/Vis DRS measurements showed a strong dependence on cation content, morphology, and crystallite size, decreasing from 2.09 eV for MgFe2O4 to 1.42 eV for CoFe2O4. The photocatalytic efficiency of as-synthesized ferrites was investigated by monitoring photocatalytic degradation of Methylene Blue (MB) under natural sunlight, and artificial light source emitting visible light. Different conditions of MB degradation such as photocatalyst loading, molar concentration of MB, and pH values were investigated. Results have shown that under both visible light and natural sunlight, excessive amounts of cobalt retarded the photocatalytic process. Co0.9Mg0.1Fe2O4 showed considerable activity (74.5% after 4 h) that is unexpected but possibly connected to structural anomalies. The best photocatalytic activity under natural sunlight was achieved by MgFe2O4 (82% after 4 h), while the best photocatalytic activity under visible light was achieved by Co0.1Mg0.9Fe2O4 (79% after 4 h).

David A. Flanigan

David A. Flanigan, 83, died on June 21 in Athens, Alabama. “Dr. Dave had a keen mind and wit. His work covered four decades of research into solid rocket propellant chemistry with a focus on the co...

Synthesis and characterization of advanced functional dysprosium doped Sr2MgSi2O7 nanopowders for white LED application

Dy3+ doped Sr2MgSi2O7 (0–11 mol%) nanopowders were prepared by low-temperature solution combustion technique which is based on the propellant chemistry concepts. Powder X-ray diffraction study confirms the crystalline nature with a crystallite size of about 30 nm and single-phase formation with space group P4̅21m. The optical band gap and refractive indices were estimated by diffused reflectance spectroscopy. Purity of the samples and the molecular bonding strengths were identified through Fourier-transform infrared spectroscopy. Transmission electron microscopic images shows the rod-like shape with polycrystalline nature. Scanning electron microscope indicates the non-uniform and irregular shaped particles. Photoluminescence studies exhibited emission peaks at 479 nm (blue), 575 nm (yellow) and 668 nm (red) for the excitation wavelength at 348 nm attributes to white light-emission. The intensity parameters and various radiative properties were estimated using the Judd- Ofelt theory to support the optical transitions. AC Conductivity, dielectric constant studies were studied in the range of 100 Hz to 1 MHz and DC conductivity behaviors were also reported. Prepared samples showed the high dielectric constant with low dielectric loss. Hence, these silicate samples are useful for white LED components and as an electrical insulation material in nanopacking applications.

Cinnamomum verum Bark Extract Mediated Green Synthesis of ZnO Nanoparticles and Their Antibacterial Potentiality.

Cinnamomum verum plant extract mediated propellant chemistry route was used for the green synthesis of zinc oxide nanoparticles. Prepared samples were confirmed for their nano regime using advanced characterization techniques such as powder X-ray diffraction and microscopic techniques such as scanning electron microscopy and transmission electron microscopy. The energy band gap of the green synthesized zinc oxide (ZnO)-nanoparticles (NPs) were found between 3.25–3.28 eV. Fourier transmission infrared spectroscopy shows the presence of Zn-O bond within the wave number of 500 cm−1. SEM images show the specific agglomeration of particles which was also confirmed by TEM studies. The green synthesized ZnO-NPs inhibited the growth of Escherichia coli and Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 125 µg mL−1 and 62.5 µg mL−1, respectively. The results indicate the prepared ZnO-NPs can be used as a potential antimicrobial agent against harmful pathogens.

Podcast: When rocket chemistry blasted off and came back to Earth

Rocket propellant research had its heyday in the mid-20th century, when the space race and the Cold War meant chemists had plenty of money and long leashes. Only a few of their most interesting ideas ended up in working rockets, but they charted new areas of chemical space, some of which, like boron chemistry, have proved useful in other fields. Geopolitical shifts, along with a growing emphasis on health, safety, and the environment, put a damper on propellant chemistry in the last decades of the 1900s. But the need for high-performance propellants hasn’t gone away, and neither has chemists’ interest in pushing the envelope. In this episode of Stereo Chemistry, we hear from chemists who lived through the heady days of the ’50s and ’60s and the ones carrying rocket chemistry’s torch today. Listen at cenm.ag/rocketfuel.

Phase evolution and magnetic properties of Dy3Fe5+xO12−x nanocrystalline powders: A choice of fuel approach

Garnet based Dy3Fe5O12 nanostructured materials have gained considerable attention in recent years due to their potential technological applications. Garnet type structured Dy3Fe5+xO12−x nanocrystalline powders were synthesized via propellant chemistry route. Single and mixed-fuel approaches were employed in the solution combustion process. Annealing the combusted powders at 1000 °C for 6 h resulted in nanocrystalline powders which are about 95% by weight garnet type and 5% orthorhombic DyFeO3. This was confirmed from powder X-ray diffraction studies through Rietveld analysis. The solution combustion mechanisms involved in the formation of Dy3Fe5+xO12−x nanocrystalline powders are briefly discussed. Scanning electron microscopy and energy dispersive X-ray spectroscopy studies revealed that the choice of fuel approach in the synthesis process affected the morphology and elemental composition. Raman spectroscopic studies revealed the existence of two magnon and two phonon scattering peaks rarely observed for garnet based Dy3Fe5O12. The synthesized Dy3Fe5+xO12−x nanocrystalline powders displayed ferromagnetic behavior. The saturation and remanent magnetization varied between 2.67-8.29 and 1.08–2.64 emu/g respectively, while the corecivities were in the order of few hundreds oersteds, characteristic of a soft ferromagnetic material. It is suggested that Dy3Fe5+xO12−x nanocrystalline powders with different magnetic properties could be tailored for different requirements.

A novel approach for solution combustion synthesis of tungsten oxide nanoparticles for photocatalytic and electrochromic applications

Tungsten oxide (WO3) and tungsten oxide hydrate (WO3.H2O) nanoparticles were synthesized via a novel solution combustion synthesis (SCS) method. Various organic fuels (i.e. oxalic acid, glycine, and citric acid) and heat sources were used to obtain different morphologies of nanoparticles. Combustion thermodynamic relations were explained based on propellant chemistry. Adiabatic temperature (Tad) and specific impulse (Isp) were also obtained. The synthesized nanoparticles were investigated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and UV–Visible spectrophotometer. XRD patterns indicated that the structures were transformed from orthorhombic and amorphous structures to monoclinic and tetragonal ones, respectively, upon combustion on the hot plate. Fourier-transform infrared (FTIR) spectra provided evidence of WO6 octahedral. SEM images showed different microstructures from sponge or rock-like to fine spherical particles with up to 100 nm size. The obtained band gap of all samples was higher than 2.6 eV which is the band gap of bulk tungsten oxide. The synthesized WO3 nanoparticles showed over 50% photocatalytic efficiency for the degradation of azo dye. The results exhibited that the nanoparticles can be used to make the electroactive layer for electrochromic applications.

Synthesis of YBCO superconductor by the method of combustion reaction in solution

Solutions of metallic nitrate were prepared to obtain the Y1Ba2Cu3O7−δand Y3Ba5Cu8O18−δphases in different mixtures of urea and glycine balanced stoichiometrically according to the principle of propellant chemistry to be synthesized by the method of combustion reaction in solution using a thermal blanket type furnace. The obtained powders required a post-reaction heat treatment at 920° C for 2h in air. The X-ray diffraction (XRD) characterization showed that the synthesized powders have a predominant superconducting Y1Ba2Cu3O7−δ phase with an orthorhombic crystal structure and a complementary phase Y3Ba8Cu5O18−δ. The Y3Ba5Cu8O18−δ phase was not found in any of the cases. The results of the transition electron microscopy (TEM) showed most grains with an average size of 300 nm and confirmed the Y123 phase. In addition, it was observed grains with an average diametrer of 1.6 µm. The measurement of electrical transport gave a Tc ∼ 91 K by the 4-probe method and by SQUID magnetometry it was obtained a Tc ∼ 92 K for zero field cooled (ZFC) and field cooled (FC) magnetizations.