No abstract available

No abstract available

[en] By reacting 3-formylchromone [bpa] and hydrated terbium (III) perchlorate in isopropanol, 3-hydroxymethylchromone [icm], bis(3-chromonyl)methanol [dcm] and the novel complex Tb(imc)₃(ClO₄)₃.5H₂O are obtained. Neither icm nor dcm can be obtained by reacting bpa with Lewis acids other than lanthanide(III) salts. By studying the mechanisms of icm and dcm formation, it was demonstrated that: (i) the two processes are independent; (ii) icm is formed through a Meerwein-Pondorf-Verley like reaction, with in situ isopropanol deprotonation; (iii) dcm is formed by interaction between a bpa molecule and a bpa-hemiacetal one, followed by a decarbonylation

[en] The propellant composition is one of several parameter that influencing the temperature sensitivity of composite propellant. In this paper, experimental investigation of temperature sensitivity in burning rate of composite propellant was conducted. Four sets of different propellant compositions had been prepared with the combination of ammonium perchlorate (AP) as an oxidizer, aluminum (Al) as fuel and hydroxy-terminated polybutadiene (HTPB) as fuel and binder. For each mixture, HTPB binder was fixed at 15% and cured with isophorone diisocyanate (IPDI). By varying AP and Al, the effect of oxidizer- fuel mixture ratio (O/F) on the whole propellant can be determined. The propellant strands were manufactured using compression molded method and burnt in a strand burner using wire technique over a range of pressure from 1 atm to 31 atm. The results obtained shows that the temperature sensitivity, a, increases with increasing O/F. Propellant p80 which has O/F ratio of 80/20 gives the highest value of temperature sensitivity which is 1.687. The results shows that the propellant composition has significant effect on the temperature sensitivity of composite propellant

[en] A facile electrochemical method for modification of the 5-position in N-acryloyl-proline methyl ester (N-Acr-Pro-OMe), followed by post-functionalization at the N-terminus by conjugate addition, was developed using anodic modification in a LiClO_4-MeNO_2 system. Anodic insertion of carbon and sulfur nucleophiles at the 5-position of N-Acr-Pro-OMe was carried out, with the N-acryloyl group remaining intact. Furthermore, a retained N-acryloyl group in the 5-modified proline was transformed by subsequent conjugate addition using thiols, which allowed the introduction of distinct functional groups between the 5-position and the N-terminus.

[en] The densities of ammonium perchlorate, tetraalkylammonium perchlorates, R₄NClO₄ (R=methyl, ethyl, propyl, and butyl) and tetrabutylammonium tetraphenylborate solutions in N,N-dimethylformamide have been measured over the whole composition range at the temperatures from 283.15 K to 333.15 K. From these densities apparent and limiting partial molar volumes of the electrolytes have been evaluated and split into respective ionic contributions. The partial molar volume for the ClO₄^- anion in N,N-dimethylformamide is reported for temperatures (283.15, 293.15, 298.15, 303.15, 313.15, 323.15, and 333.15) K. The effects related to length of alkyl chain and temperature are described and discussed in terms of solvent penetration. The volume expansibilities are calculated for T=298.15 K and discussed

[en] The pressure of water vapor has been measured by a static method, the temperature limits of existence has been determined, and parameters of the equation lgp(Torr) = b - a/T have been calculated for the crystal hydrates Cd(ClO₄)₂ · 6H₂O (25-58.2 degC, a = 3143.7, b = 9.356), Cd(ClO₄)₂ · 2H₂O (90-144.8 degC, a = 3823.3, 9.472) and some others. A metastable hydrate Cd(ClO₄)₂ · 4H₂O with phase transition at 30.9 degC (20-30.9 degC, a = 3669.5, b = 11.343 and 30.9-63.7 degC, a = 3058.6, b = 9.339) hitherto unknown has been detected

No abstract available

[en] The Closed vessel (CV) is an equipment used to study the ballistic parameters by recording burning time history, pressure buildup during the process and vivacity of the propellants. It is an apparatus which consists of strong pressure vessel, piezo-electric pressure transducers, sensors and dedicated software. To save time and resources this method is employed instead of dynamic firing while doing research and development of propellants. A measured amount of propellant charge is loaded in the vessel and fired remotely. Ignition is provided by the filament which ignites the black powder charge. In this study, we have used Closed Vessel Tests (CVT) for the first time for recording the ballistic parameters of slow burning composite rocket propellant. We developed a set of composite solid propellant samples containing a mixture of bimodal Ammonium Perchlorate (AP) as an oxidizer, Hydroxy-terminated Polybutadiene (HTPB) as a binder as well as fuel, Dioctyl Sebacate (DOS) as plasticizer, 1-(2-methyl) Aziridinyl Phosphine Oxide (MAPO) as bonding agent and Toluene Diisocyanate (TDI) as curator. Samples were developed by changing the solid loading percentage of bimodal AP particles. By increasing the percentage of AP, the oxidizer-fuel ratio (O/F) increases which effects the ballistic parameters. It is observed that maximum pressure and vivacity increases with increase in solid filler in the propellants. As quantity of AP increases, rate of rise of pressure also increases. CVT firing of each sample was done three times to obtain average burning time and pressure buildup history to evaluate the effect of oxidizer loadings on ballistic parameters of the composite propellant. (author)

[en] Chlorate and perchlorate of strontium are prepared by electrolysis employing noble metal oxide coated and platinum anodes respectively with a rotating stainless steel cathode. The effects of electrolyte concentration, pH, temperature, cathode current density and cathode rotation on current efficiency for the preparation of strontium chlorate and perchlorate were studied. Maximum current efficiencies of 55-64% and 40-45% were achieved in the case of chlorate and perchlorate of strontium respectively. (author). 13 refs., 5 figs