Unsymmetrical Dimethylhydrazine Research Articles

Ppb-level unsymmetrical dimethylhydrazine detection based on In2O3 hollow microspheres with Nd doping

As one of main high-energy fuels for rocket launching, unsymmetrical dimethylhydrazine (UDMH) and its decomposition products do harm to environment and human health. It is significant to develop a device to monitor its leakage. In this work, a UDMH gas sensor based on In2O3 hollow microspheres with Nd dopant was fabricated. The pure, 1.0mol%, 3.0mol% and 5.0mol% Nd doped In2O3 were synthesized via one-step solvothermal method. Among them, 3.0% Nd-In2O3 based sensor exhibits the highest response toward UDMH vapor. Its response value to 100 ppm UDMH is 183.3 at optimal working temperature of 250°C, 6.8 times higher than that of pure In2O3 (26.8). Besides high response to UDMH, the 3% Nd-In2O3 based sensor represents excellent selectivity, rapid response speed (2s) and ultra-low theoretical LOD to UDMH (0.28 ppb). The improved gas sensing performance via Nd doping could be attributed to the enhanced specific surface area, increased concentration of adsorbed oxygen and improved adsorption capacity for UDMH molecular on the surface. The excellent sensing performance of Nd doped In2O3 hollow microspheres makes it a promising candidate for real-time UDMH detection. Environmental ImplicationUnsymmetrical dimethylhydrazine (1,1-dimethylhydrazine, UDMH) is a colorless, highly toxic compound. It has been classified as 2B human carcinogen by the International Agency for Research on Cancer (IARC). The National Institute for Occupational Safety and Health (SLOSH) also regulates the UDMH concentration limitation of 0.06 ppm in workplace. Therefore, it is urgent to fabricate a device for detecting the UDMH leakage timely during its storage and transport. In our work, Nd doped In2O3 hollow microspheres based chemiresistive gas sensor for the monitoring of UDMH was developed, which will promote the practical applications for gas sensor.

Experimental Study of the Effect of the Initial Droplet Diameter on the Evaporation Characteristics of Unsymmetrical Dimethylhydrazine Droplets in a Subcritical Environment

The evaporation characteristics of unsymmetrical dimethylhydrazine droplets with different initial diameters in a subcritical environment were experimentally investigated with the temperature–pressure separation technique. The evaporation processes of unsymmetrical dimethylhydrazine droplets with different initial diameters in this environment have the same general pattern. All the studied droplets exhibit a short transient heating phase and a steady-state evaporation phase obeying d2. Notably, the expansion of the transient heating phase gradually increases with increasing ambient pressure. The change in diameter squared ∆d2max increases from 1.03% at 1 MPa to 12.48% at 5 MPa. Under subcritical conditions, the evaporation rate decreases linearly with decreasing droplet diameter, and the droplet evaporation lifetime increases linearly. Changes in the initial droplet diameter may still have a large effect on droplets smaller than those studied here. When the ambient pressure is not greater than 3 MPa, the change in the steady-state evaporation time for both medium- and large-diameter droplets accounts for more than 70% of the variation in the droplet evaporation lifetime. As the ambient pressure increases to 4 MPa and 5 MPa, the percentage of the change in the transient heating time contributing to the variation in the droplet evaporation lifetime gradually increases to more than 45%.

Zn2SnO4@Ti ceramic film anode preparation by microarc oxidation for 2e– WOR degradation of unsymmetrical dimethylhydrazine (UDMH)

The main challenge facing the anodic electro-Fenton through the 2e– water oxidation reaction (WOR) for toxics degradation lies in the electrode's stability, because the anodic oxygen evolution (OER) generated O2 will inevitably exfoliate the electro-active components loaded on the electrode substrate. To address this point, two aspects need attention: 1) Identifying a catalyst that exhibits both excellent electrocatalytic activity and selectivity can improve the faradaic efficiency of hydrogen peroxide (H2O2); 2) Employing novel methods for fabricating highly stable electrodes, where active sites can be firmly coated. Consequently, this study utilized microarc oxidation (MAO) to prepare a ceramic film electrode Zn2SnO4@Ti at 300 V. Zn2SnO4 acts as an WOR electrocatalyst and further improved the generation of H2O2 for treating real wastewater containing Unsymmetrical Dimethylhydrazine (UDMH). From the perspective of characterization of electrode structure, Zn2SnO4@Ti forms a stable active coating, the electrochemical yield of H2O2 is high up to 78.4 μmol h−1 cm−2, and the selectivity of H2O2 is over 80% at 3.3 V vs. RHE, which can be fully applied to scenarios where it is inconvenient to transport H2O2 and need in-situ safe production. Additionally, the prepared electrodes exhibit significant stability, suitable for various applications, providing insightful preparation strategies and experiences for constructing highly stable anodes.

Effect of subchronic use of unsymmetrical dimethylhydrazine on contractile activity of isolated lymphatic vessels

Introduction. Unsymmetric dimethylhydrazine (UDMH, heptyl) is widely used as a rocket fuel. Heptyl belongs to especially dangerous substances (hazard class I). UDMH with chronic intragastric administration has a cardiotropic effect, which served as the basis for studying its effect on the contractile activity of lymphatic vessels, since they are part of the vascular system. In addition, lymphatic vessels are considered as objects similar in terms of parameters of phase contractile activity with the heart and having a certain commonality of regulatory mechanisms of cardiomyocytes and smooth muscle cells of lymphangions.
 Materials and methods. The toxic effect of UDMH was evaluated on a model of isolated rat lymphatic vessels with subchronic intragastric administration of heptyl for 28 days at doses of 0.02; 0.2; and 2 mg/kg.
 Results. The use of UDMH in all studied doses led to a decrease in the contractile activity of lymphatic vessels, which manifested itself in the suppression of the frequency and amplitude of contractions and, as a consequence, the integral indicator – minute productivity. At the same time, the tonic voltage increased dose-dependent. When assessing the state of the endothelium of lymphatic vessels using acetylcholine, a decrease (inversion) of the response of lymphangions to the vasodilator was revealed.
 Limitations of the study. The study was performed on male white rats and does not take into account gender differences in the effect of NDMG on lymphatic vessels. 
 Conclusion. As a result of the study, it was found that UDMH in doses of 0.02; 0.2; and 2 mg/kg causes inhibition of the pumping function of lymphatic vessels, due to a violation of the processes of both excitation and contraction in smooth muscle cells of lymphangions.

Experimental study of the evaporation characteristics of unsymmetrical dimethylhydrazine in a sub-supercritical environment

In this study, the temperature–pressure separation technique was used to successfully obtain the process of the unsymmetrical dimethylhydrazine droplet diameter variation with time during evaporation in subcritical, supercritical, and far-supercritical environments at temperatures and pressures of 473–773 K and 1–9 MPa, respectively. The results show that unsymmetrical dimethylhydrazine droplet evaporation has two characteristic stages, transient heating and steady-state evaporation, under low-pressure and low-temperature environments; the steady-state evaporation stage influences droplet evaporation life more than the transient heating stage. Under high-pressure and high-temperature environments, droplet evaporation shows only a single feature of steady-state evaporation, and the droplet expansion process in the transient heating stage disappears. The normalized droplet lifetime decreased exponentially with temperature and decreased linearly and monotonically with pressure. The evaporation rate constant increases linearly and monotonically with temperature and exponentially with pressure.

Effects of transition-metal ions on the reduction of N-nitrosodimethylamine in water by zinc

The influencing factors, products and mechanism of N-nitrosodimethylamine (NDMA) reduction by zinc (Zn) in the presence of transition-metal ions (Mn2+, Co2+ and Ni2+), were investigated. The NDMA removal by Zn was significantly improved by them, and the promoting effect of Co2+ and Ni2+ were better than Mn2+. With the decrease of pH values and dissolved oxygen concentrations, the removals of NDMA were enhanced in all reaction systems. NDMA was mainly reduced to unsymmetrical dimethylhydrazine (UDMH) in Zn and Zn/Mn2+ systems. It was mainly reduced to dimethylamine (DMA) and ammonium (NH4+) in Zn/Co2+ and Zn/Ni2+ systems. There were undetected products in all reaction systems. Catalytic hydrogenation was the main mechanism, and active hydrogen atom was the main active species. The presence of Mn2+, Co2+ and Ni2+ promoted the corrosion of Zn and changed the surface morphology of Zn. The formation of type I film on Zn surface was promoted in the presence of Co2+ and Ni2+, which was conducive to the continuous corrosion of Zn and hydrogen generation. While type II film which would inhibit the corrosion of Zn formed on Zn surface in the presence of Mn2+. MnO2, Co3O4 and Ni(OH)2 were formed in Zn/Mn2+, Zn/Co2+ and Zn/Ni2+ systems, respectively. They would facilitate more generation of active hydrogen atoms.

Unsymmetrical dimethylhydrazine (UDMH) exposure to zebrafish embryos causes lethal and severe teratogenic effects

The assessment of lethal and teratogenic effects of unsymmetrical dimethylhydrazine (UDMH) using zebrafish embryo toxicity test for 72 h was performed. Following UDMH concentrations were studied for embryotoxic effects: 0.64M, 0.13M, 0.06M, 0.04M, 5x10-3M and 1,7x10-3M after 3 h embryo exposure to UDMH at 7-10 hpf. It was shown that high UDMH concentrations (0,64М, 0,13М, and 0,06М) possess significant embryotoxic action to D.rerio embryos followed by concentration-dependent embryo lysis. 0.04M UDMH and vapors caused severe teratogenic effects and growth retardation prior to hatching resulted in embryo mortality to 48 hpf and 72 hpf, respectively. Zebrafish embryos exposure to low UDMH concentrations of 5x10-3M and 1,7x10-3M caused no significant lethal, but pronounced teratogenic effect (in latter case accumulated from 24 to 72 hpf), with observed malformations of spinal cord and tail tip, yolk sac and pericardial edemas, hypopigmentation. Thus short term 3 h. exposure of D.rerio embryos to UDMH at gastrulation stage induces alterations that further revealed themselves throughout embryonic development causing dose-dependent lethal and teratogenic effects.

Direct quantification of 1,1-dimethylhydrazine transformation products in sandy soil by thermal desorption gas chromatography – Tandem mass spectrometry

The use of rocket propellants based on unsymmetrical dimethylhydrazine (UDMH) in launch vehicles and boosters poses a threat to the environment due to the release of UDMH into soils and its subsequent transformation into a variety of nitrogen-containing compounds, including toxic and carcinogenic ones. The present proof-of-concept study proposes a novel approach to screening and simultaneous determination of a wide range of nitrogen-containing UDMH transformation products in soils, based on direct thermal desorption (TD) as a solvent-free sample extraction technique coupled with GC–MS/MS analysis.Optimal TD conditions consisting of the incubation of 5 mg sample at 300 °C for 30 min, allowed attaining high recoveries (80–100 %) for the most tested compounds and developing the method for quantification of fifteen acyclic and heterocyclic UDMH transformation products in sandy soil with LODs of 0.3–7.8 µg kg−1. The matrix matched calibration and introduction of the internal standard (pyridine‑d5) ensured high accuracy (75–100 %) and precision (RSD < 15 %) of the analysis. Along with high sensitivity and accuracy, the main advantages of the developed method are exceptional simplicity of sample preparation, low amount of toxic sample, high automation degree, and environmental friendliness.The developed method was successfully tested in the analysis of seven real soil samples taken from the Baikonur cosmodrome operational zone (Kazakhstan). The use of TD-GC–MS analysis in full spectrum scanning mode allowed for tentative identification of 62 UDMH transformation products including several compounds not yet described in the literature.

К вопросам транспортировки гептила железнодорожным транспортом

Purpose: To estimate the properties of heptyl and its effect on the human body and the environment. To provide an overview of the sphere of heptyl application and the features of its transportation by rail. To consider the structural features of the model 15-629 tank car and to perform a calculation to select the optimal crosssectional area for the inlet opening of the relief valve to enhance safety during the transportation of heptyl by the model 15-629 tank car. Methods: To calculate the inner and outer surface areas of the tank shell using the technical characteristics of the six-axis multi-unit tank-car of model 15-629. Next, we will calculate the mass air flow rate through the inlet relief valve and determine the heat transfer occurring due to the external heat dissipation from the tank shell into the surrounding environment. These data are necessary to estimate the equivalent diameter of the inlet relief valve orifice. Results: Thanks to the calculations performed, a more suitable diameter of the inlet safety valve orifice has been determined. This will ensure a safer transportation of highly toxic liquid rocket fuel components used in both Russian launch vehicles (“Kosmos”, “Cyclone”, “Proton”) and international ones (such as American “Titan” rockets, French launch vehicles of the “Ariane”, Chinese rockets of the “Long March” family, and others). Practical significance: Hydrazine-based propellants are more energy-efficient compared to hydrocarbon-based propellants, which has led to an increased usage of Unsymmetrical Dimethylhydrazine (UDMH) in recent years. Due to the rapid growth of space industry, the volume of heptyl transportation by railway has been increasing. In order to prevent technological disasters, calculations have been conducted to determine the diameter of the inlet relief valve to minimize depressurization of the tank car, regardless of temperature conditions.

Study of Hedge Ignition and Flame Propagation Characteristics of Unsymmetrical Dimethylhydrazine and Its Metamorphosed Mixtures in a Nitrogen Tetroxide Atmosphere

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant widely used in rocket engines and other applications. The safety of UDMH in service is affected by its slow oxidation during long-term storage to form impurities such as dimethylamine (DMA) and formaldehyde dimethylhydrazone (FDH). How these impurities affect combustion performance is not known, and in order to assess these effects, the present experiments investigated the combustion characteristics of self-igniting fuels and carried out ignition delay time measurements and flame propagation velocity measurements of pure UDMH and its denatured mixtures in a nitrogen tetroxide (NTO) atmosphere. This experiment was carried out to measure the delay time of hedge ignition of pure UDMH and qualitative analysis of its flame propagation properties under vacuum conditions at room temperature (T = 293 K). Ignition delay time measurements and flame propagation characterization were performed under the same experimental conditions for UDMH mixed with 1%, 5% and 10% FDH, UDMH mixed with 1%, 5% and 10% H2O, UDMH mixed with 1%, 5% and 10% DMA, as well as for UDMH mixed with the same proportions of the three substances (1%, 5% and 10%). The flame propagation characteristics were analyzed. The results showed that the incorporation of DMA, H2O and FDH in different proportions could inhibit the combustion of UDMH to varying degrees and prolong its ignition delay time. It is worth noting that the introduction of FDH had the least effect on it, and the least effect was observed at a concentration of 1%. In contrast, the effect of DMA on UDMH is more obvious, and the addition of H2O has the largest increase in the ignition delay time of UDMH. In the flame propagation experiment, the flame of the experimental group adding H2O can no longer fill the whole experimental window, while the other experimental groups can still make the window full of flame. Combined with the measurements of the ignition delay time, it can be seen that the moisture content has the greatest effect on the combustion characteristics.

A wide ranging experimental and kinetic modeling study of TMEDA pyrolysis and oxidation

Traditional liquid propellants like unsymmetrical dimethylhydrazine include several issues, such as toxicity, short storage time and preservation difficulty at low temperatures. For this reason, exploring green and stable propellant fuels is imperative in the development of propellants. Tetramethyl ethylenediamine (TMEDA) is considered to be a promising green propellant fuel with high specific impulse, non-toxicity, and long-term storage stability. Thus, investigating the combustion characteristics of TMEDA and constructing a detailed chemical kinetic mechanism are of fundamental importance in describing its combustion in computational fluid simulation. For this work, ignition delay times of TMEDA were measured in a shock tube at equivalent ratios of 0.5, 1.0 and 2.0, at pressures of 2, 10, and 20 bar, and in the temperature range of 870–1500 K with fixed fuel concentration at 2 %. After the reflected shock at 990–1500 K, the pyrolysis products of 2000 and 5000 ppm TMEDA in Argon were also measured at 5 and 10 bar conditions in a single pulse shock tube. In addition, laminar flame speeds of TMEDA were measured at initial pressures of 1 bar, initial temperatures of 333 and 353 K, and equivalence ratios ranging from 0.8 to 1.5 in a constant volume reactor. The experimental results were simulated using a detailed TMEDA kinetic mechanism. Reaction path analysis and sensitivity analysis were provided to clarify the chemical kinetics of TMEDA oxidation and pyrolysis. The current work provides new experimental data and fundamental analyses for understanding the oxidation and pyrolysis characteristics of TMEDA, and sheds light on optimal directions for future models.

Influence of Composition of Shungite on Its Reaction with Unsymmetrical Dimethylhydrazine

Influence of Composition of Shungite on Its Reaction with Unsymmetrical Dimethylhydrazine

Influence of Composition of Shungite on Its Reaction with Unsymmetrical Dimethylhydrazine

Influence of Composition of Shungite on Its Reaction with Unsymmetrical Dimethylhydrazine

ZIF-8-derived magnetic FCZ@C-600 composite for efficient adsorptive removal of unsymmetrical dimethylhydrazine from wastewater

Efficient and convenient removal of hazardous unsymmetrical dimethylhydrazine (UDMH) remains challenging for ecological security and human health. In this work, ZIF-8-derived magnetic porous carbons (FCZ@Cs) were synthesized via layer-by-layer self-assembly and pyrolysis using chitosan as an external carbon source. The optimal pyrolysis temperature of FCZ@Cs is 600 °C and the maximum adsorption capacity of FCZ@C-600 for UDMH is 185.70 mg/g at 298 K. Moreover, FCZ@C-600 has wide pH adaptability and good resistance to acid, natural organic matter, and interfering ions. UDMH adsorption onto FCZ@C-600 and ZIF-8-600 conforms to pseudo-second-order and Langmuir models. Thermodynamic studies demonstrate that the adsorption performance is endothermic and favorable. Mechanisms investigations further identify electrostatic interactions, diffusion, and hydrogen/coordination bonds as the greatest contributors to UDMH adsorption. Notably, magnetic FCZ@C-600 can be readily separated by a magnet and exhibits high stability with an adsorption capacity of 42.05 mg/g after six cycles. Furthermore, the leaching concentration of Fe and Zn can be as low as 0.3 mg/L and 1.0 mg/L (pH ≥ 4), respectively. UDMH wastewater after adsorption also shows good biosafety. This work provides insights into the development of emerging metal-organic framework-derived adsorbents with multifunctionality and good sustainability for efficient wastewater treatment.

Preparation of mesoporous TiO2 nanomaterials doped with rare earth ions (La3+, Sm3+, Nd3+, Gd3+) and its application in the photodegradation of unsymmetrical dimethylhydrazine

&lt;p&gt;Methyldimethylhydrazine and its by-products cause serious damage to human health. In this paper, Re3+-doped mesoporous TiO2 were synthesized for the photodegradation of UDMH. The structure, morphology and optical properties of photocatalyst were extensively characterized. The photocatalytic degradation was significantly enhanced, and 2%Nd-TiO2 showed the most excellent photocatalytic degradation performance with 93.3% degradation rate of UDMH. NDMA and FDMH were gradually and completely degraded. .O2- and·OH played an important role in the photocatalytic degradation of UDMH. The possible degradation pathways of UDMH analyzed by GC-MS. The work provided an effective method for the degradation of UDMH wastewater.&lt;/p&gt;&#x0D;

Insights into the Reaction Kinetics of Hydrazine-Based Fuels: A Comprehensive Review of Theoretical and Experimental Methods

While researchers have extensively studied the initial decomposition mechanism of Monomethylhydrazine (MMH, CH3NHNH2) in the MMH/dinitrogen tetroxide (NTO) system, the investigation of Unsymmetrical Dimethylhydrazine (UDMH, (CH3)2NNH2) has been limited due to its high toxicity, corrosiveness, and deterioration rate. Hence, the effects of UDMH’s deterioration products on combustion performance and gas-phase combustion reaction mechanisms remain unclear. This comprehensive review examines the existing research on the reaction kinetics of the three widely used hydrazine-based self-ignition propellants: Hydrazine (HZ, N2H4): MMH: and UDMH, emphasizing the necessity for further investigation into the reaction kinetics and mechanisms of UDMH. It also discusses the implications of these findings for developing safer and more efficient rocket propulsion systems. Additionally, this review underscores the importance of utilizing computational chemistry theory to analyze hydrazine-based fuels’ combustion and decomposition properties, constructing detailed pyrolysis and combustion reaction mechanisms to optimize rocket engine fuel performance and environmental concerns.

Pd NPs/MGO[sbnd]COOH based electrochemical sensor for detection of unsymmetrical dimethylhydrazine

Unsymmetrical dimethylhydrazine (UDMH) was used as hydrazine fuels in the aerospace field because of its high specific impulse and advantageous storage properties. In the development of the defense industry, large quantities of wastewater-containing UDMH, a carcinogenic chemical, are often released into the environment. In fact, accumulation of low concentrations of UDMH over a long period of time can also be hazardous to the human health and the environment. Therefore, rapid and accurate detection methods of UDMH at low concentrations are urgently needed in the defense industry sector in order to protect water resources and the environment. Herein, a carboxy-functional group ligand was constructed to act synergistically with metal nanoparticles for the detection of UDMH in wastewater. An in situ electrochemical deposition method was used to synthesize Pd NPs/monolayer carboxylated graphene oxide (MGOCOOH) which was employed, for the first time, as a high-efficient electrode to detect UDMH in aqueous medium. The experimental findings showed the linear range of Pd NPs/MGOCOOH electrode detection of UDMH ranging from 0.1 to 0.9 μg.L−1 and the limit of detection (LOD) was 0.012 μg.L−1 (S/N = 3). The Pd NPs/MGOCOOH electrode was employed for sensing of UDMH in water from the tap with good recovery rate. To define the possible structure of UDMH during detection process, Gaussian software was utilized to calculate the possible structure intermediates of UDMH at the B3LYP-D3BJ/def2tzvp level. Finally, the possible mechanisms are discussed. These findings show that the obtained Pd NPs/MGOCOOH composite electrode can serve as a prospective sensing composite for the detection of industrial contaminants in wastewater.

Escape inhibition of unsymmetrical dimethylhydrazine in aqueous solution by carboxyl-rich graphene oxide loaded with Fe3O4

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant. In order to reduce the losses caused by propellant leakage accidents, water spraying devices have been widely applied in UDMH storage sites. However, the UDMH pools are formed in the storage facilities due to this emergency measure, resulting in the generation of toxic UDMH gas. To solve this practical problem, a magnetically recoverable sorbent for UDMH leakage is designed and prepared in this work. The microstructure characteristics of the green recoverable inhibitor which meet the theoretical design requirements are verified, so environmental protection and recyclability can be achieved. The dynamic spray experiments under different leakage conditions show that the treatment of UDMH leakage accidents with this green recoverable agent helps reduce the maximum leakage of UDMH gas, saving valuable time for subsequent emergency rescue. Additionally, the environmental pollution caused by leakage accidents can be greatly reduced.

Activated Persulfate by Dielectric Barrier Discharge Plasma for the Degradation of Unsymmetrical Dimethyl Hydrazine as Wastewater Pollutants

Activated Persulfate by Dielectric Barrier Discharge Plasma for the Degradation of Unsymmetrical Dimethyl Hydrazine as Wastewater Pollutants

A Coupled Heat Transfer Calculation Strategy for Composite Cooling Liquid Rocket Engine

To better understand the characteristics of coupled heat transfer in liquid rocket engines, a calculation scheme is proposed in this paper. This scheme can simulate the coupled heat transfer processes, including combustion and flow in the thrust chamber, radiation heat transfer, heat conduction in the wall, heat transfer of coolant flow in the cooling channel, and gas film cooling in the thrust chamber wall. The numerical method used in each physical area, the data transfer method between each computing module, the strategy of data transfer on the coupling interface, the calculation process, and the convergence criterion are all introduced in detail. The calculation scheme was verified by analyzing a water-cooled nozzle. Then, the coupled heat transfer calculation was carried out for a liquid rocket engine using a propellant composed of unsymmetrical dimethylhydrazine and dinitrogen tetroxide. Two working conditions were analyzed: whether the gas film cooling was performed or not. The results showed that the algorithm successfully indicated the protective effect of the gas film on the wall surface, and the calculation results were reasonable. It played a guiding role for the coupled heat transfer of the liquid rocket engine using a composite cooling method.