This paper applies cumulative and aggregate risk methods and weight of evidence determination to re-analysis of epidemiological and clinical studies of exposure to perchlorates. The implications of cumulative and aggr...This paper applies cumulative and aggregate risk methods and weight of evidence determination to re-analysis of epidemiological and clinical studies of exposure to perchlorates. The implications of cumulative and aggregate risk are considered for 28 epidemiological studies on IUI, serum thyroid hormone levels and clinical indicators. Consideration is given to simultaneous exposures to perchlorates, nitrates, thiocyanates and organohalogens in the study populations. The elevation of effects by perchlorates alone is found only in the studies that use urinary perchlorate as the metric of exposure. These studies are beset by a problem with use of urinary perchlorate concentration in that there is large inter-subject variability in the relationship between intake and urinary concentration due to differences in metabolism and disposition of the compounds following ingestion. As a result, an individual placed into the “high urinary concentration” group may be there due to high values of exposure, to long biological clearance halflives, or due to high transfer fractions from the serum into the urine. The influence could be removed by correcting urinary levels by measured clearance half-times for individuals in a study, but that has not been done in the case of the studies examined here. It is of interest therefore that the studies that use direct measures of intake of perchlorates rather than urine concentration fail to display the hormone effects. The current study uses a “weight of evidence” approach for perchlorates, employing all 28 studies. The result is a slope of the exposure response curve (percentage change in hormone effect per unit exposure) of 0.3% per μg/kg-day, with 95% confidence interval of (?0.05%, 1%). This confidence interval for the slope encompasses 0, indicating no statistically significant slope when all data are combined in a weight of evidence determination. This is consistent with the conclusions of the USEPA and EFSA that the epidemiological studies do not provide compelling evidence for a causal association between exposures to perchlorates and either hormone effects or clinically adverse effects. The conclusions are 1) that current epidemiological results do not provide evidence of effects induced by perchlorates apart from the IUI effects, 2) that the same results provide evidence that the IUI effects induced at environmental levels of exposure are associated with down-stream adverse effects and 3) that effective risk management requires the cumulative and aggregate risk framework adopted here, suggesting a need for risk assessors to return to the original studies and provide separate estimates of exposure response relationships for all four compounds or at the least to control for exposures to nitrates, thiocyanates and organohalogens.展开更多
Perchlorate(ClO_(4)^(−))is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility,poor degradability,and widespread distribution.However,the impacts of perch...Perchlorate(ClO_(4)^(−))is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility,poor degradability,and widespread distribution.However,the impacts of perchlorate on aquatic autotrophs such cyanobacterium are still unclear.Herein,Synechocystis sp.PCC6803(Synechocystis)was used to investigate the response mechanisms of perchlorate on cyanobacterium by integrating physiological and transcriptome analyses.Physiological results showed that perchlorate mainly damaged the photosystem of Synechocystis,and the inhibition degree of photosystem II(PSII)was severer than that of photosystem I(PSI).When the exposed cells were moved to a clean medium,the photosynthetic activities were slightly repaired but still lower than in the control group,indicating irreversible damage.Furthermore,perchlorate also destroyed the cellular ultrastructure and induced oxidative stress in Synechocystis.The antioxidant glutathione(GSH)content and the superoxide dismutase(SOD)enzyme activity were enhanced to scavenge harmful reactive oxygen(ROS)in Synechocystis.Transcriptome analysis revealed that the genes associated with“photosynthesis”and“electron transport”were significantly regulated.For instance,most genes related to PSI(e.g.,psaf,psaJ)and the“electron transport chain”were upregulated,whereas most genes related to PSII(e.g.,psbA3,psbD1,psbB,and psbC)were downregulated.Additionally,perchlorate also induced the expression of genes related to the antioxidant system(sod2,gpx,gst,katG,and gshB)to reduce oxidative damage.Overall,this study is the first to investigate the impacts andmechanisms of cyanobacterium under perchlorate stress,which is conducive to assessing the risk of perchlorate in aquatic environments.展开更多
Selective perchlorate(ClO_(4)^(−))removal from surface water is a pressing need due to the stringent perchlorate drinking water limits around the world.Herein,we anchored N^(+)–C–H hydrogen bond donors in hydrophobi...Selective perchlorate(ClO_(4)^(−))removal from surface water is a pressing need due to the stringent perchlorate drinking water limits around the world.Herein,we anchored N^(+)–C–H hydrogen bond donors in hydrophobic cavities via interactions of cationic surfactants with montmorillonite to prioritize perchlorate bonding.The prepared adsorbent exhibited high selectivity over commonly occurring competing anions,including SO_(4)^(2−),NO_(3)^(−),PO_(4)^(3−),HCO_(3)^(−),and halide anions.High adsorption capacity,fast adsorption kinetics,and excellent regeneration ability(removal efficiency≥80%after 20 cycles)were confirmed via batch experiments.Unconventional CH···O hydrogen bonding was verified as the primary driving force for perchlorate adsorption,which relies on the higher bond energy(∼80 kcal·mol−1)than conventional bonding.The removal efficiency of anions followed the order of the Hofmeister Series,demonstrating the importance of hydrophobic cavities formed by the tail groups of cationic surfactants.The hydrophobic cavities sheltered the C–H bonds from interacting with anions of low hydration energy(e.g.,perchlorate).Furthermore,a fixed-bed column test demonstrated that about 2900 bed volumes of the feeding streams(∼500μg·L^(−1))can be treated to≤70μg·L^(−1),with an enrichment factor of 10.3.Overall,on the basis of the hydrophobicity-induced hydrogen bonding mechanism,a series of low-cost adsorbents can be synthesized and applied for specific perchlorate removal.展开更多
Nitrates,thiocyanates,and perchlorates are ubiquitous in the environment and can be introduced to the public through various dietary and environmental sources.Nitrates,thiocyanates,and perchlorates mainly affect healt...Nitrates,thiocyanates,and perchlorates are ubiquitous in the environment and can be introduced to the public through various dietary and environmental sources.Nitrates,thiocyanates,and perchlorates mainly affect health via the same mechanism.These toxins may act as endocrine disrupters and can result in decreased levels of thyroid hormones^([1]).展开更多
A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energ...A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.展开更多
Perchlorate and chlorate are ubiquitous pollutants that can adversely affect the thyroid function in humans.This study assessed the potential health risks associated with the dietary exposure of infants and young chil...Perchlorate and chlorate are ubiquitous pollutants that can adversely affect the thyroid function in humans.This study assessed the potential health risks associated with the dietary exposure of infants and young children to perchlorate and chlorate present in infant formulas available in Shanghai.The assessment was based on risk monitoring data from 150 samples of infant formulas in Shanghai between 2020 and 2022,along with the dietary consumption data of infants and young children.The detection rates of perchlorate and chlorate in infant formulas were 46.0%and 98.7%,with mean contents of 9.98μg/kg and 112.01μg/kg,and the maximum values of 151.00μg/kg and 1475.00μg/kg,respectively.The mean and 95th percentile(P95)values of daily perchlorate exposure of 0-36-month-old infant and young children via infant formulas were 0.07 and 0.17μg/kg body weight(bw)per day,respectively,which were lower than the tolerable daily intake(TDI)of perchlorate(0.3μg/kg bw per day).The mean and P95 values of chlorate exposure via infant formulas in 0-36-month-old infants and young children were 0.83 and 1.89μg/kg bw per day,which were lower than the TDI of chlorate(3μg/kg bw per day).The P95 exposure of different age groups(0-6 months,7-12 months and 13-36 months)of infants and young children to perchlorate and chlorate in infant formulas was below the TDI.Therefore,the risk associated with the exposure of 0-36-month-old infants and young children to perchlorate and chlorate from infant formulas in Shanghai is considered acceptable.Prioritizing environmental pollution control efforts to reduce the levels of perchlorate and chlorate in food products is important to safeguard the health of the infants and children under the One Health concept.展开更多
Perchlorate and chlorate are present in various extraterrestrial celestial bodies throughout the solar system,such as Mars,the moon,and asteroids.To date,the origin mechanisms of perchlorate and chlorate on the Martia...Perchlorate and chlorate are present in various extraterrestrial celestial bodies throughout the solar system,such as Mars,the moon,and asteroids.To date,the origin mechanisms of perchlorate and chlorate on the Martian surface have been well-established;however,relatively little attention has been cast to airless bodies.Here,we experimentally investigated the potential oxidation mechanisms of chloride to chlorate and perchlorate,such as ultraviolet irradiation under H_(2)O-and O_(2)-free conditions and mechanical pulverization processes.Individual minerals,olivine,pyroxene,ilmenite,magnetite,TiO_(2)and anhydrous ferric sulfate,and lunar regolith simulants(low Ti,CLRS-1;high-Ti,CLRS-2)and their metallic iron(Fe^( 0))bearing counterparts were examined.We found that pulverization of dry matrix material-halite mixtures,even in the presence of O_(2),does not necessarily lead to perchlorate and chlorate formation without involving water.Under photocatalytic and H_(2)O and O_(2)-free conditions,olivine and pyroxene can produce oxychlorine(ClO_(x)^(−))species,although the yields were orders of magnitude lower than those under Martian-relevant conditions.Nanophase-Fe^(0)particles in the lunar regolith and the common photocatalyst TiO_(2)can facilitate the ClO_(x)^(−)formation,but their yields were lower than those with olivine.The oxides ilmenite and magnetite did not efficiently contribute to ClO_(x)^(−)production.Our results highlight the critical role of H_(2)O in the oxidation chloride to chlorate and perchlorate,and provide essential insights into the environmental influence on the formation of oxychlorine species on different celestial bodies.展开更多
Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a c...Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a catalytic center point.The carbon aerogel(C(CS)/g-C_(3)N_(4)/Co)with a three-dimensional network-like structure was prepared by assembling the three materials through experimental operations such as freeze-drying and high-temperature carbonization.It was demonstrated by scanning and transmission characterization that the CS in the carbon aerogel could provide more active sites for the cobalt nanoparticles,and the doping of graphite-phase carbon nitride as a template dispersed the cobalt nanoparticles and changed the conductivity of the CS.To investigate the catalytic effect of carbon aerogel on ammonium perchlorate(AP),it was investigated by differential thermal analyzer and TG thermal analysis.This carbon aerogel was very effective in catalyzing AP,and the 10 wt% content of the catalyst reduced the AP pyrolysis peak from 703.9 to 595.5 K.And to further investigate the synergistic effect of the three materials,further carbon aerogels such as C(CS)/Co,g-C_(3)N_(4)/Co were prepared and applied to catalyze AP,and the same ratio reduced the AP pyrolysis peak by 98.1℃ and 97.7℃.This result indicates a synergistic effect of the assembly of the three materials.展开更多
To investigate the process optimizationof Cu-en/AP composite microspheres preparation via electrostatic spraying,and to reveal the effects of droplet properties and flow rate variations on the experimental results dur...To investigate the process optimizationof Cu-en/AP composite microspheres preparation via electrostatic spraying,and to reveal the effects of droplet properties and flow rate variations on the experimental results during the electrostatic spraying process,the prepared process parameters of Cu-en/AP composite microspheres by electrostatic spray method under the orthogonal experimental design simulated by ANSYS(Fluent).The influence of flow rate,solvent ratio,and solid mass on the experimental results is examined using a controlled variable method.The results indicate that under the conditions of a flow rate of 2.67×10^(-3)kg/s an acetone-to-deionized water ratio of 1.5∶1.0,and a solid mass of 200 mg,the theoretical particle size of the composite microspheres can reach e nanoscale.Droplet trajectories in the electric field remain stable without significant deviation.The simulation results show that particle diameter decreases with increasing flow rate,with the trend leveling off around a flow rate of 1×10^(-3)kg/s.As the solvent ratio increases(with higher acetone content),particle diameter initially decreases,reaching a minimum around a ratio of 1.5∶1.0 before gradually increasing.Increasing the solid mass also reduces the particle diameter,with a linear increase in diameter observed at around 220 mg.Cu-en/AP composite microspheres with nanoscale dimensions were confirmed under these conditions by the final SEM images.展开更多
Several mixtures,based on urea derivatives and some inorganic oxidants,including also alumina,were studied by means of ballistic mortar techniques with TNT as the reference standard.The detonation pressure(P),detonati...Several mixtures,based on urea derivatives and some inorganic oxidants,including also alumina,were studied by means of ballistic mortar techniques with TNT as the reference standard.The detonation pressure(P),detonation velocity(D),detonation energy(Q),and volume of gaseous product at standard temperature and pressure(STP),V,were calculated using EXPLO5V6.3 thermochemical code.The performance of the mixtures studied was discussed in relation to their thermal reactivity,determined by means of differential thermal analysis(DTA).It is shown that the presence of hydrogen peroxide in the form of its complex with urea(i.e.as UHP)has a positive influence on the explosive strength of the corresponding mixtures which is linked to the hydroxy-radical formation in the mixtures during their initiation reaction.These radicals might initiate(at least partially)powdered aluminum into oxidation in the CJ plane of the detonation wave.Mixtures containing UHP and magnesium are dangerous because of potential auto-ignition.展开更多
The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were char...The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy （TEM）, BET equation, X-ray diffraction （XRD）, and the corresponding selected area electron diffraction （SAED）. The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate （AP） was investigated by differential thermal analyzer （DTA）. Compared with the thermal decomposition of pure AP, the addition of Co nanoparticles （2%-10%, by mass） decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nano-particles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparficles in the AP-based propellant.展开更多
To investigate the effects of exogenous lanthanum （La） on Alternanthera philoxeroides （Mart.） Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution cultu...To investigate the effects of exogenous lanthanum （La） on Alternanthera philoxeroides （Mart.） Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution culture experiments under controlled condi- tions. Different concentrations of La （NO3）3 were used in our study. It was shown that 0. 1 and 0.5 mg/L La3＋ alleviated the inhibition effect of perchlorate on A. philoxeroides, including relative growth yield, dry weight of different organs, leaf area and root activity. And La3＋ prevented decline in the relative chlorophyll content and chlorophyll fluorescence parameters including Fv/Fm, Fv＇/Frn＇, φPSll and ETR induced by perchlorate stress. Moreover, 0.5 mg/L La3＋ showed an optimal mitigative effect, while excess La3＋ （5.0 mg/L） led to synergistic effect on stress. Correlation analysis revealed a significant positive relationship between growth indexes and the chlorophyll fluorescence parameters, root activity and relative chlorophyll content （p〈0.05）. The results suggested that appropriate concentration of La3＋ could effectively alleviate growth inhibition and injury ofA. philoxeroides caused by perchlorate stress, and the mitigative effect of La3＋ might be achieved by improving root activity, maintaining chlorophyll content and promoting photochemical efficiency of photosystem II ofA. philoxeroides under perchlorate stress.展开更多
Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination te...Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate （AP） decomposition was investigated by differential scanning calorimetry （DSC）. The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 - 350 ℃ and 400 - 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g^- 1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7℃ by reduction of 114.6℃ and increases the apparent decomposition heat from 515 to 1240 J·g^-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.展开更多
Synthesis and use of the iron compounds supported on granular activated carbon （ICs/GAC） have shown significant environmental implications for perchlorate （ClO4^- ） removal. ICs/GAC was synthesized via hydrolyzing...Synthesis and use of the iron compounds supported on granular activated carbon （ICs/GAC） have shown significant environmental implications for perchlorate （ClO4^- ） removal. ICs/GAC was synthesized via hydrolyzing FeSO 4 ·7H2O on GAC, reduced by NaBH 4 solution in polyethylene glycol 6000 and ethanol solution, dried in vacuum condition and exposed to air. Synthesized ICs/GAC was characterized using transmission electron micrograph （TEM）, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy （XPS）. ICs/GAC was determined to be containing a large amount of FeOHSO 4 , Fe2O3 and a small amount of zero-valent iron （ZVI） nanoparticles according to TEM and XPS measurements. Batch static kinetic tests showed that 97% of ClO4^- was removed within 10 hr at 90°C and 86% of ClO4^- was removed within 12 hr at 25°C, at ICs/GAC dosage of 20 g/L. The experimental results also showed that FeOHSO 4 and Fe 2 O 3 nanoparticles have the function of perchlorate adsorption and play important roles in ClO4^- removal. The activation energy （E a ） was determined to be 9.56 kJ/mol.展开更多
The catalytic proficiency of three MONs for AP thermal decomposition was studied in this work.A chemical co-precipitation method was used for synthesis of MONs(CuZnO,CoZnO,and NiZnO)and their characterization carried ...The catalytic proficiency of three MONs for AP thermal decomposition was studied in this work.A chemical co-precipitation method was used for synthesis of MONs(CuZnO,CoZnO,and NiZnO)and their characterization carried out by utilizing XRD,FTIR,and SEM.The TGA/DSC technique was employed for the investigation of the catalytic proficiency of MONs on the AP.The DSC data were used for measuring activation energy of catalyzed AP by using Ozawa,Kissinger,and Starink method.The MONs were much sensitive for AP decomposition,and the performance of AP decomposition was further improved.Among all the MONs,the CuZnO exhibits higher catalytic action than others and decomposition temperature of AP is descending around 117℃ by CuZnO.The reduction in the activation energy was noticed after the incorporation of MONs in AP.展开更多
Two cells consisting of a chloride-selective electrode and a nitrate-selective electrode or of a chloride-selective electrode and a perchlorate-selective electrode were directly put in the soil suspension to determine...Two cells consisting of a chloride-selective electrode and a nitrate-selective electrode or of a chloride-selective electrode and a perchlorate-selective electrode were directly put in the soil suspension to determine the concentration ratios Cl-/ NO3- or Cl-/ ClO4- for studying the adsorption of the three anions by variable charge soils. It was found that all the concentration ratios CCl- / CNO3- and CCl- / CClO4- in suspension were smaller than unity when soil samples were in equilibrium with mixed KCl and KNO3 or KCl and KClO4 solutions of equal concentration. The order of the amount of chloride, nitrate and perchlorate adsorbed by variable charge soils was Cl-> NO3-> ClO4- when the soils adsorbed these anions from the solution containing equal concentrations of Cl-, NO3- and ClO4-. Such factors as the pH of the suspension, the iron oxide content of the soil etc. could affect the amounts and the ratios of anions adsorbed. The adsorption was chiefly caused by coulombic attraction, but a covalent force between the anion and the metal atom on the surface of soil particles may also be involved, at least for Cl- ions, even for NO3- ions.展开更多
To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum （Co-B/M） nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of amm...To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum （Co-B/M） nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of ammonium perchlorate （AP） and AP-based solid state propellants. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, inductive coupled plasma emission spectrometry （ICP）, differential scanning calorimetry （DSC） as well as strand burner method were employed to characterize the crystal phase, morphologies, chemical composition, and catalytic activity of the as-synthesized material. The results show that a continuous layer of about 100 nm amorphous Co72.6B27.4 covers the surfaces of M particles. Addition of the as-synthesized Co-B/A1 nanocomposites as catalysts promotes AP decomposition, enhances the burning rate, and lowers the pressure exponent of the AP-based propellants considerably.展开更多
Ammonium perchlorate(APC)is the most common oxidizer in use for solid rocket propulsion systems.However its initial thermal decomposition is an endothermic process that requires 102.5 J·g^-1.This manner involves ...Ammonium perchlorate(APC)is the most common oxidizer in use for solid rocket propulsion systems.However its initial thermal decomposition is an endothermic process that requires 102.5 J·g^-1.This manner involves high activation energy and could render high burning rate regime.This study reports on the sustainable fabrication of CuO nanoparticles as a novel catalyzing agent for APC oxidizer.Colloidal CuO nanoparticles with consistent product quality were fabricated by using hydrothermal processing.TEM micrographs demonstrated mono-dispersed particles of 15 nm particle size.XRD diffractogram demonstrated highly crystalline material.The synthesized colloidal CuO particles were effectively coated with APC particles via co-precipitation by using fast-crash solvent-antisolvent technique.The impact of copper oxide particles on APC thermal behavior has been investigated using DSC and TGA techniques.APC demonstrated an initial endothermic decomposition stage at 242℃ with subsequent two exothermic decomposition stages at 297,8℃ and 452.8℃ respectively.At 1 wt%,copper oxide offered decrease in initial endothermic decomposition stage by 30%.The main outcome of this study is that the two main exothermic decomposition peaks were merged into one single peak with an increase in total heat release by 53%.These novel features can inherit copper oxide particles unique catalyzing ability for advanced highly energetic systems.展开更多
In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other ca...In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other catalytic applications. Initially, SrTiO3 was characterized for particle size, morphology and material/ phase identification (using XRD). By varying SrTiO3 content in a standard composite propellant, different compositions were prepared and their performance and processing parameters like the end of mix (EOM) viscosity, mechanical properties, density, burning rate, pressure exponent (n-value), etc. were measured. The results reveal that 2% SrTiO3 causes more than 12% enhancement in propellant burning rate (at 70 ksc pressure) in comparison to the standard propellant composition. The pressure exponent also increases to 0.46, whereas the standard composition was having its value as 0.35.展开更多
文摘This paper applies cumulative and aggregate risk methods and weight of evidence determination to re-analysis of epidemiological and clinical studies of exposure to perchlorates. The implications of cumulative and aggregate risk are considered for 28 epidemiological studies on IUI, serum thyroid hormone levels and clinical indicators. Consideration is given to simultaneous exposures to perchlorates, nitrates, thiocyanates and organohalogens in the study populations. The elevation of effects by perchlorates alone is found only in the studies that use urinary perchlorate as the metric of exposure. These studies are beset by a problem with use of urinary perchlorate concentration in that there is large inter-subject variability in the relationship between intake and urinary concentration due to differences in metabolism and disposition of the compounds following ingestion. As a result, an individual placed into the “high urinary concentration” group may be there due to high values of exposure, to long biological clearance halflives, or due to high transfer fractions from the serum into the urine. The influence could be removed by correcting urinary levels by measured clearance half-times for individuals in a study, but that has not been done in the case of the studies examined here. It is of interest therefore that the studies that use direct measures of intake of perchlorates rather than urine concentration fail to display the hormone effects. The current study uses a “weight of evidence” approach for perchlorates, employing all 28 studies. The result is a slope of the exposure response curve (percentage change in hormone effect per unit exposure) of 0.3% per μg/kg-day, with 95% confidence interval of (?0.05%, 1%). This confidence interval for the slope encompasses 0, indicating no statistically significant slope when all data are combined in a weight of evidence determination. This is consistent with the conclusions of the USEPA and EFSA that the epidemiological studies do not provide compelling evidence for a causal association between exposures to perchlorates and either hormone effects or clinically adverse effects. The conclusions are 1) that current epidemiological results do not provide evidence of effects induced by perchlorates apart from the IUI effects, 2) that the same results provide evidence that the IUI effects induced at environmental levels of exposure are associated with down-stream adverse effects and 3) that effective risk management requires the cumulative and aggregate risk framework adopted here, suggesting a need for risk assessors to return to the original studies and provide separate estimates of exposure response relationships for all four compounds or at the least to control for exposures to nitrates, thiocyanates and organohalogens.
基金supported by the Project of Chinese Manned Spaceflight(No.YYWT-0801-EXP-09)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA17010502)Jiangsu Province Ecological Environment Scientific Research Project(No.2022008).
文摘Perchlorate(ClO_(4)^(−))is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility,poor degradability,and widespread distribution.However,the impacts of perchlorate on aquatic autotrophs such cyanobacterium are still unclear.Herein,Synechocystis sp.PCC6803(Synechocystis)was used to investigate the response mechanisms of perchlorate on cyanobacterium by integrating physiological and transcriptome analyses.Physiological results showed that perchlorate mainly damaged the photosystem of Synechocystis,and the inhibition degree of photosystem II(PSII)was severer than that of photosystem I(PSI).When the exposed cells were moved to a clean medium,the photosynthetic activities were slightly repaired but still lower than in the control group,indicating irreversible damage.Furthermore,perchlorate also destroyed the cellular ultrastructure and induced oxidative stress in Synechocystis.The antioxidant glutathione(GSH)content and the superoxide dismutase(SOD)enzyme activity were enhanced to scavenge harmful reactive oxygen(ROS)in Synechocystis.Transcriptome analysis revealed that the genes associated with“photosynthesis”and“electron transport”were significantly regulated.For instance,most genes related to PSI(e.g.,psaf,psaJ)and the“electron transport chain”were upregulated,whereas most genes related to PSII(e.g.,psbA3,psbD1,psbB,and psbC)were downregulated.Additionally,perchlorate also induced the expression of genes related to the antioxidant system(sod2,gpx,gst,katG,and gshB)to reduce oxidative damage.Overall,this study is the first to investigate the impacts andmechanisms of cyanobacterium under perchlorate stress,which is conducive to assessing the risk of perchlorate in aquatic environments.
基金supported by the National Key Research and Development Program of China(2023YFC3207904).
文摘Selective perchlorate(ClO_(4)^(−))removal from surface water is a pressing need due to the stringent perchlorate drinking water limits around the world.Herein,we anchored N^(+)–C–H hydrogen bond donors in hydrophobic cavities via interactions of cationic surfactants with montmorillonite to prioritize perchlorate bonding.The prepared adsorbent exhibited high selectivity over commonly occurring competing anions,including SO_(4)^(2−),NO_(3)^(−),PO_(4)^(3−),HCO_(3)^(−),and halide anions.High adsorption capacity,fast adsorption kinetics,and excellent regeneration ability(removal efficiency≥80%after 20 cycles)were confirmed via batch experiments.Unconventional CH···O hydrogen bonding was verified as the primary driving force for perchlorate adsorption,which relies on the higher bond energy(∼80 kcal·mol−1)than conventional bonding.The removal efficiency of anions followed the order of the Hofmeister Series,demonstrating the importance of hydrophobic cavities formed by the tail groups of cationic surfactants.The hydrophobic cavities sheltered the C–H bonds from interacting with anions of low hydration energy(e.g.,perchlorate).Furthermore,a fixed-bed column test demonstrated that about 2900 bed volumes of the feeding streams(∼500μg·L^(−1))can be treated to≤70μg·L^(−1),with an enrichment factor of 10.3.Overall,on the basis of the hydrophobicity-induced hydrogen bonding mechanism,a series of low-cost adsorbents can be synthesized and applied for specific perchlorate removal.
文摘Nitrates,thiocyanates,and perchlorates are ubiquitous in the environment and can be introduced to the public through various dietary and environmental sources.Nitrates,thiocyanates,and perchlorates mainly affect health via the same mechanism.These toxins may act as endocrine disrupters and can result in decreased levels of thyroid hormones^([1]).
基金supported by the National Natural Science Foundation of China,China(Grant Nos.U20B2018,U21B2086,11972087)。
文摘A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.
基金supported by Science and Technology Project of Shanghai Municipal Administration for Market Regulation in 2022(No.2022-67).
文摘Perchlorate and chlorate are ubiquitous pollutants that can adversely affect the thyroid function in humans.This study assessed the potential health risks associated with the dietary exposure of infants and young children to perchlorate and chlorate present in infant formulas available in Shanghai.The assessment was based on risk monitoring data from 150 samples of infant formulas in Shanghai between 2020 and 2022,along with the dietary consumption data of infants and young children.The detection rates of perchlorate and chlorate in infant formulas were 46.0%and 98.7%,with mean contents of 9.98μg/kg and 112.01μg/kg,and the maximum values of 151.00μg/kg and 1475.00μg/kg,respectively.The mean and 95th percentile(P95)values of daily perchlorate exposure of 0-36-month-old infant and young children via infant formulas were 0.07 and 0.17μg/kg body weight(bw)per day,respectively,which were lower than the tolerable daily intake(TDI)of perchlorate(0.3μg/kg bw per day).The mean and P95 values of chlorate exposure via infant formulas in 0-36-month-old infants and young children were 0.83 and 1.89μg/kg bw per day,which were lower than the TDI of chlorate(3μg/kg bw per day).The P95 exposure of different age groups(0-6 months,7-12 months and 13-36 months)of infants and young children to perchlorate and chlorate in infant formulas was below the TDI.Therefore,the risk associated with the exposure of 0-36-month-old infants and young children to perchlorate and chlorate from infant formulas in Shanghai is considered acceptable.Prioritizing environmental pollution control efforts to reduce the levels of perchlorate and chlorate in food products is important to safeguard the health of the infants and children under the One Health concept.
基金supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(XDB41000000)the National Natural Science Foundation of China(42373042)+3 种基金the National Key Scientifi c Instrument and Equipment Development Project(2012YQ090229)the Scientifi c Instrument Upgrading Project of Shandong Province(2012SGGZ18)the Key Research Program of the Chinese Academy of Sciences(ZDBS-SSWTLC001)the Program of the Institute of Geology&Geophysics CAS(IGGCAS-201905).
文摘Perchlorate and chlorate are present in various extraterrestrial celestial bodies throughout the solar system,such as Mars,the moon,and asteroids.To date,the origin mechanisms of perchlorate and chlorate on the Martian surface have been well-established;however,relatively little attention has been cast to airless bodies.Here,we experimentally investigated the potential oxidation mechanisms of chloride to chlorate and perchlorate,such as ultraviolet irradiation under H_(2)O-and O_(2)-free conditions and mechanical pulverization processes.Individual minerals,olivine,pyroxene,ilmenite,magnetite,TiO_(2)and anhydrous ferric sulfate,and lunar regolith simulants(low Ti,CLRS-1;high-Ti,CLRS-2)and their metallic iron(Fe^( 0))bearing counterparts were examined.We found that pulverization of dry matrix material-halite mixtures,even in the presence of O_(2),does not necessarily lead to perchlorate and chlorate formation without involving water.Under photocatalytic and H_(2)O and O_(2)-free conditions,olivine and pyroxene can produce oxychlorine(ClO_(x)^(−))species,although the yields were orders of magnitude lower than those under Martian-relevant conditions.Nanophase-Fe^(0)particles in the lunar regolith and the common photocatalyst TiO_(2)can facilitate the ClO_(x)^(−)formation,but their yields were lower than those with olivine.The oxides ilmenite and magnetite did not efficiently contribute to ClO_(x)^(−)production.Our results highlight the critical role of H_(2)O in the oxidation chloride to chlorate and perchlorate,and provide essential insights into the environmental influence on the formation of oxychlorine species on different celestial bodies.
基金the financial support received from the Natural Science Foundation of China(21875192)Outstanding Youth Science and Technology Talents Program of Sichuan(no.19JCQN0085)Open Project of State Key Laboratory of Environment-friendly Energy Materials(Southwest University of Science and Technology,No.22fksy18)。
文摘Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a catalytic center point.The carbon aerogel(C(CS)/g-C_(3)N_(4)/Co)with a three-dimensional network-like structure was prepared by assembling the three materials through experimental operations such as freeze-drying and high-temperature carbonization.It was demonstrated by scanning and transmission characterization that the CS in the carbon aerogel could provide more active sites for the cobalt nanoparticles,and the doping of graphite-phase carbon nitride as a template dispersed the cobalt nanoparticles and changed the conductivity of the CS.To investigate the catalytic effect of carbon aerogel on ammonium perchlorate(AP),it was investigated by differential thermal analyzer and TG thermal analysis.This carbon aerogel was very effective in catalyzing AP,and the 10 wt% content of the catalyst reduced the AP pyrolysis peak from 703.9 to 595.5 K.And to further investigate the synergistic effect of the three materials,further carbon aerogels such as C(CS)/Co,g-C_(3)N_(4)/Co were prepared and applied to catalyze AP,and the same ratio reduced the AP pyrolysis peak by 98.1℃ and 97.7℃.This result indicates a synergistic effect of the assembly of the three materials.
基金National Natural Science Foundation of China(No.2275150)。
文摘To investigate the process optimizationof Cu-en/AP composite microspheres preparation via electrostatic spraying,and to reveal the effects of droplet properties and flow rate variations on the experimental results during the electrostatic spraying process,the prepared process parameters of Cu-en/AP composite microspheres by electrostatic spray method under the orthogonal experimental design simulated by ANSYS(Fluent).The influence of flow rate,solvent ratio,and solid mass on the experimental results is examined using a controlled variable method.The results indicate that under the conditions of a flow rate of 2.67×10^(-3)kg/s an acetone-to-deionized water ratio of 1.5∶1.0,and a solid mass of 200 mg,the theoretical particle size of the composite microspheres can reach e nanoscale.Droplet trajectories in the electric field remain stable without significant deviation.The simulation results show that particle diameter decreases with increasing flow rate,with the trend leveling off around a flow rate of 1×10^(-3)kg/s.As the solvent ratio increases(with higher acetone content),particle diameter initially decreases,reaching a minimum around a ratio of 1.5∶1.0 before gradually increasing.Increasing the solid mass also reduces the particle diameter,with a linear increase in diameter observed at around 220 mg.Cu-en/AP composite microspheres with nanoscale dimensions were confirmed under these conditions by the final SEM images.
基金supported by means of the financial resources of Students Grant Projects No.SGSFCHT_2016002 of the Faculty of Chemical Technology at the University of Pardubice
文摘Several mixtures,based on urea derivatives and some inorganic oxidants,including also alumina,were studied by means of ballistic mortar techniques with TNT as the reference standard.The detonation pressure(P),detonation velocity(D),detonation energy(Q),and volume of gaseous product at standard temperature and pressure(STP),V,were calculated using EXPLO5V6.3 thermochemical code.The performance of the mixtures studied was discussed in relation to their thermal reactivity,determined by means of differential thermal analysis(DTA).It is shown that the presence of hydrogen peroxide in the form of its complex with urea(i.e.as UHP)has a positive influence on the explosive strength of the corresponding mixtures which is linked to the hydroxy-radical formation in the mixtures during their initiation reaction.These radicals might initiate(at least partially)powdered aluminum into oxidation in the CJ plane of the detonation wave.Mixtures containing UHP and magnesium are dangerous because of potential auto-ignition.
基金Supported by the National Natural Science Foundation of China （50306008, 50602024）.
文摘The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy （TEM）, BET equation, X-ray diffraction （XRD）, and the corresponding selected area electron diffraction （SAED）. The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate （AP） was investigated by differential thermal analyzer （DTA）. Compared with the thermal decomposition of pure AP, the addition of Co nanoparticles （2%-10%, by mass） decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nano-particles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparficles in the AP-based propellant.
基金Foundation item： Project supported by Priority Academic Program Development of Jiangsu Higher Education Institutions （PAPD） and National Basic Research Program of China （2006CB403301）
文摘To investigate the effects of exogenous lanthanum （La） on Alternanthera philoxeroides （Mart.） Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution culture experiments under controlled condi- tions. Different concentrations of La （NO3）3 were used in our study. It was shown that 0. 1 and 0.5 mg/L La3＋ alleviated the inhibition effect of perchlorate on A. philoxeroides, including relative growth yield, dry weight of different organs, leaf area and root activity. And La3＋ prevented decline in the relative chlorophyll content and chlorophyll fluorescence parameters including Fv/Fm, Fv＇/Frn＇, φPSll and ETR induced by perchlorate stress. Moreover, 0.5 mg/L La3＋ showed an optimal mitigative effect, while excess La3＋ （5.0 mg/L） led to synergistic effect on stress. Correlation analysis revealed a significant positive relationship between growth indexes and the chlorophyll fluorescence parameters, root activity and relative chlorophyll content （p〈0.05）. The results suggested that appropriate concentration of La3＋ could effectively alleviate growth inhibition and injury ofA. philoxeroides caused by perchlorate stress, and the mitigative effect of La3＋ might be achieved by improving root activity, maintaining chlorophyll content and promoting photochemical efficiency of photosystem II ofA. philoxeroides under perchlorate stress.
基金Project supported by the National Natural Science Foundation of China (50306008)Advance Research Foundation forGeneral Equipment Department (41328030507)
文摘Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate （AP） decomposition was investigated by differential scanning calorimetry （DSC）. The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 - 350 ℃ and 400 - 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g^- 1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7℃ by reduction of 114.6℃ and increases the apparent decomposition heat from 515 to 1240 J·g^-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.
基金supported by the National Natural Science Foundation of China(No.5087816350708067)+1 种基金the National Major Project of Science&Technology Ministry of China(No.2008ZX07421-002)the Research and Development Project of Ministry of Housing and Urban-Rural Development(No.2009K7-4)
文摘Synthesis and use of the iron compounds supported on granular activated carbon （ICs/GAC） have shown significant environmental implications for perchlorate （ClO4^- ） removal. ICs/GAC was synthesized via hydrolyzing FeSO 4 ·7H2O on GAC, reduced by NaBH 4 solution in polyethylene glycol 6000 and ethanol solution, dried in vacuum condition and exposed to air. Synthesized ICs/GAC was characterized using transmission electron micrograph （TEM）, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy （XPS）. ICs/GAC was determined to be containing a large amount of FeOHSO 4 , Fe2O3 and a small amount of zero-valent iron （ZVI） nanoparticles according to TEM and XPS measurements. Batch static kinetic tests showed that 97% of ClO4^- was removed within 10 hr at 90°C and 86% of ClO4^- was removed within 12 hr at 25°C, at ICs/GAC dosage of 20 g/L. The experimental results also showed that FeOHSO 4 and Fe 2 O 3 nanoparticles have the function of perchlorate adsorption and play important roles in ClO4^- removal. The activation energy （E a ） was determined to be 9.56 kJ/mol.
文摘The catalytic proficiency of three MONs for AP thermal decomposition was studied in this work.A chemical co-precipitation method was used for synthesis of MONs(CuZnO,CoZnO,and NiZnO)and their characterization carried out by utilizing XRD,FTIR,and SEM.The TGA/DSC technique was employed for the investigation of the catalytic proficiency of MONs on the AP.The DSC data were used for measuring activation energy of catalyzed AP by using Ozawa,Kissinger,and Starink method.The MONs were much sensitive for AP decomposition,and the performance of AP decomposition was further improved.Among all the MONs,the CuZnO exhibits higher catalytic action than others and decomposition temperature of AP is descending around 117℃ by CuZnO.The reduction in the activation energy was noticed after the incorporation of MONs in AP.
文摘Two cells consisting of a chloride-selective electrode and a nitrate-selective electrode or of a chloride-selective electrode and a perchlorate-selective electrode were directly put in the soil suspension to determine the concentration ratios Cl-/ NO3- or Cl-/ ClO4- for studying the adsorption of the three anions by variable charge soils. It was found that all the concentration ratios CCl- / CNO3- and CCl- / CClO4- in suspension were smaller than unity when soil samples were in equilibrium with mixed KCl and KNO3 or KCl and KClO4 solutions of equal concentration. The order of the amount of chloride, nitrate and perchlorate adsorbed by variable charge soils was Cl-> NO3-> ClO4- when the soils adsorbed these anions from the solution containing equal concentrations of Cl-, NO3- and ClO4-. Such factors as the pH of the suspension, the iron oxide content of the soil etc. could affect the amounts and the ratios of anions adsorbed. The adsorption was chiefly caused by coulombic attraction, but a covalent force between the anion and the metal atom on the surface of soil particles may also be involved, at least for Cl- ions, even for NO3- ions.
基金supported by the National Natural Science Foundation of China (No. 50876046)
文摘To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum （Co-B/M） nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of ammonium perchlorate （AP） and AP-based solid state propellants. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, inductive coupled plasma emission spectrometry （ICP）, differential scanning calorimetry （DSC） as well as strand burner method were employed to characterize the crystal phase, morphologies, chemical composition, and catalytic activity of the as-synthesized material. The results show that a continuous layer of about 100 nm amorphous Co72.6B27.4 covers the surfaces of M particles. Addition of the as-synthesized Co-B/A1 nanocomposites as catalysts promotes AP decomposition, enhances the burning rate, and lowers the pressure exponent of the AP-based propellants considerably.
文摘Ammonium perchlorate(APC)is the most common oxidizer in use for solid rocket propulsion systems.However its initial thermal decomposition is an endothermic process that requires 102.5 J·g^-1.This manner involves high activation energy and could render high burning rate regime.This study reports on the sustainable fabrication of CuO nanoparticles as a novel catalyzing agent for APC oxidizer.Colloidal CuO nanoparticles with consistent product quality were fabricated by using hydrothermal processing.TEM micrographs demonstrated mono-dispersed particles of 15 nm particle size.XRD diffractogram demonstrated highly crystalline material.The synthesized colloidal CuO particles were effectively coated with APC particles via co-precipitation by using fast-crash solvent-antisolvent technique.The impact of copper oxide particles on APC thermal behavior has been investigated using DSC and TGA techniques.APC demonstrated an initial endothermic decomposition stage at 242℃ with subsequent two exothermic decomposition stages at 297,8℃ and 452.8℃ respectively.At 1 wt%,copper oxide offered decrease in initial endothermic decomposition stage by 30%.The main outcome of this study is that the two main exothermic decomposition peaks were merged into one single peak with an increase in total heat release by 53%.These novel features can inherit copper oxide particles unique catalyzing ability for advanced highly energetic systems.
文摘In a quest of search for a new burning rate modifier for composite propellant, strontium titanate (SrTiO3), a perovskite oxide has been chosen for evaluation in a composite propellant formulation based on its other catalytic applications. Initially, SrTiO3 was characterized for particle size, morphology and material/ phase identification (using XRD). By varying SrTiO3 content in a standard composite propellant, different compositions were prepared and their performance and processing parameters like the end of mix (EOM) viscosity, mechanical properties, density, burning rate, pressure exponent (n-value), etc. were measured. The results reveal that 2% SrTiO3 causes more than 12% enhancement in propellant burning rate (at 70 ksc pressure) in comparison to the standard propellant composition. The pressure exponent also increases to 0.46, whereas the standard composition was having its value as 0.35.
