Friction Sensitivity of Nitramines. Part Ⅱ: Comparison with Thermal Reactivity（英）

The friction sensitivity (FS) of five linear and eight cyclic nitramines has been determined.Arrhenius parameters of non-autocatalyzed thermal decomposition of these nitramines were used for comparison...     

Friction Sensitivity of Nitramines. Part Ⅲ: Comparison with Detonation Performance（英）

The friction sensitivities (FS) of five linear and eight cyclic nitramines have been determined.These FS values were compared with the respective detonation velocities,D,and with the dimensionless ratio created by relating the heat of explosion,Qreal,to the activation energy,Ea,of non-autocatalyzed thermal decomposition of the explosives concerned.For the nitramaines studied,these comparisons show a general trend of FS decreasing with increasing energy content.     

1,3,3-trinitroazetidine (TNAZ). Study of thermal behaviour. Part II

Abstract

Thermal behavior of TNAZ (1,3,3 - trinitroazetidine) was studied by using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetryc analysis (TGA).

It was found out that TNAZ is thermally more stable than RDX, but less stable than HMX and TNT. The reaction of intensive thermal decomposition starts at 183–230 °C, depending on heating rate, while the first exothermic reaction was observed at 178 °C at the heating rate of 1 °C/min.

By applying multiple heating rate DSC measurements and Ozawa's method the activation energy of 161.3 kJ/mol and pre-exponential factor of 8.27·10¹³ 1/s were calculated from DSC peak maximum temperature-heating rate relationship. By the same method the activation energy of 157.5 kJ/mol and pre-exponential factor of 4.55·10¹³ 1/s were calculated from DTA peak maximum temperature.

By applying Flynn-Wall isoconversional method it was calculated from DSC measurements that the activation energy equals between 140 and 155.6 kJ/mol at degrees of conversion ranging between 0.3 and 0.7, while pre-exponential factor ranges between 7.8·10¹² and 1.92·10¹³ 1/s.     

cis-1,3,4,6-Tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), its properties and initiation reactivity

Pre-treatment of simulated industrial wastewaters (SIM1, SIM2 and SIM3) containing organic and inorganic compounds (1,2-dichloroethane, sodium formate, sodium hydrogen carbonate, sodium carbonate and sodium chloride) by oxidative degradation using homogeneous Fenton type processes (Fe²⁺/H₂O₂ and Fe³⁺/H₂O₂) has been evaluated. The effects of initial Fe²⁺ and Fe³⁺ concentrations, [Fe^2+/3+], type of iron salt (ferrous sulfate vs. ferric chloride), initial hydrogen peroxide concentration, [H₂O₂], on mineralization extent, i.e., total organic content (TOC) removal, were studied. Response surface methodology (RSM), particularly Box–Behnken design (BBD) was used as modelling tool, and obtained predictive function was used to optimize the overall process by the means of desirability function approach (DFA). Up to 94% of initial TOC was removed after 120 min. Ferrous sulfate was found to be the most appropriate reagent, and the optimal doses of Fe²⁺ and H₂O₂ for reducing the pollutant content, in terms of final TOC and sludge production were assessed.     

Reliability-based code calibration applied to thin elements made of UHPFRC

A semi-probabilistic approach used in current design codes requires calibrated partial factors to secure safety of structures and people. The current code calibration procedure has an inefficient and imprecise iterative loop and it also neglects economical aspects which should be an integral part of any code calibration. This paper suggests a modified approach to the reliability-based code calibration which eliminates disadvantages of the original procedure and it is defined in a way to take advantage of the current computation means such as parallel and cloud computing. The modified approach was used to calibrate the partial factors for the structural verification of UHPFRC thin elements predominantly loaded in bending. The described example proves efficiency of the modified approach and it illustrates the advantages of the reliability-based code calibration. Indeed, the design method of UHPFRC with the calibrated partial factors allows better exploitation of the material without compromising the safety requirements. Because of the straightforward procedure, independent reliability and design computations, and selection of the ideal partial factors at the end of the calibration procedure, the modified approach is an ideal option for various code calibrations. It is worth noting that the modified approach can “grow” with development of material, knowledge, applications, and safety requirements due its simple updating which was not possible before. Moreover, the removal of the iterative loop allows using Monte Carlo methods (among other options) which are normally time-consuming and impractical for code calibration.     

On the mechanical stability of mesoporous silica SBA-15

Mesoporous silica SBA-15 was synthesised at 80 °C. The calcined solids were exposed to a unilateral external pressure in the range 16–191 MPa in order to monitor the impact of the mechanical pressure on the properties of SBA-15. N₂ adsorption–desorption measurements, XRD and UV-Raman spectroscopy was used in order to evaluate the changes occurring in the SBA-15. For the XRD measurement, an internal Si standard was used to correct the position of the SBA-15 patterns. It appeared that the elevated pressure has no influence on the hexagonal cell parameter a. Through the N₂ sorption measurements the fraction of the preserved mesoporous structure was estimated to be 60% when the highest pressure has been used. As the remaining part of the material is irreversibly disintegrated into small particles, the pressed sample is considered to be heterogeneous. However, the preserved fraction is slightly modified, showing a smaller pore width and plugs located within the mesopores. The plugs most likely originate from a disintegrated fraction of the SBA-15. UV-Raman spectroscopy shows that the relative intensity of the band associated with the siliceous network (ω₁) has decreased on the pressed samples resulting in a less ordered material possessing an enhanced population of silanols as compared to parent SBA-15. We propose that the disorder introduced by pressing is responsible for the observed expansion of the SBA-15 walls, which is detected for the samples treated at higher pressures (112, 191 MPa).     

Decomposition of some polynitro arenes initiated by heat and shock Part I. 2,4,6-Trinitrotoluene

Samples of 2,4,6-trinitrotoluene (TNT) exposed to heat or to shock and residues after their detonation have been analyzed chromatographically (LC-UV and LC/MS). It was found that the main identified decomposition intermediates are identical in all the three cases. 4,6-Dinitro-2,1-benzoisoxazole and 2,4,6-trinitrobenzaldehyde are the most reactive from them. It has been stated that the chemical micro-mechanism of the primary fragmentations of shock-exposed TNT molecules and/or its detonation transformation should be the same as in the case of its low-temperature thermal decomposition.     

Decomposition of some polynitro arenes initiated by heat and shock Part II: Several N-(2,4,6-trinitrophenyl)-substituted amino derivatives

Samples of 2,4,6-trinitroaniline (PAM), 2,4,6-trinitro-N-(2,4,6-trinitrophenyl)aniline (DPA), N,N'-bis(2,4,6-trinitrophenyl)-3,5-dinitropyridine-2,6-diamine (PYX) and N,N',N'-tris(2,4,6-trinitrophenyl)-1,3,5-triazine-2,4,6-triamine (TPM) were exposed to heat or to shock and then analysed chromatographically (LC-UV and LC/MS). It was found that the main identified decomposition products of these two incomplete initiations are identical for each of the compounds studied. It has been stated that the chemical micro-mechanism of the primary fragmentations of their low-temperature decomposition should be the same as in the case of their initiation by shock, including fragmentation during their detonation transformation.     

Vergleichende wärmetechnische Bewertung von Brennstoffen für Industrieöfen

Graphische Darstellung der thermodynamischen Grundlagen der Brennstoffbewertung durch Enthalpie-Volumen- und Temperatur-Wärmekapazität-Schaubilder. Überprüfung der bisherigen Bewertungsverfahren. Untersuchung des Einflusses des Luftüberschusses, der Verbrennungsluft- und Brennstoffvorwärmung, der Anfangstemperatur der Wärmgase, der Abgastemperatur und des Verbrennungsablaufs auf die Bewertungsrechnung.     

New Aspects of the Impact Reactivity of Nitramines

The impact reactivity (“the first reaction”) of 16 nitramines was determined as the drop energy E_d, required for 50% initiation probability. Relationships have been found between the E_d values, on the one hand, and heats of fusion, ¹⁵N NMR chemical shifts of aza atoms in reaction centers, parameters of low‐temperature thermolysis, and oxygen balances of nitramines studied, on the other. Taking these relationships the E_d values were predicted for four nitramines, from which three have not been synthesized yet. On the basis of the said relationships it was stated that the impact reactivity of nitramine molecules depends on the electronic configuration within their reaction centers and on their conformational stability and intensity of their intermolecular interactions. The reaction centers here are the same as in the case of initiation of the nitramines by shock. It is found that ϵ‐HNIW possesses higher thermal and impact reactivities in comparing with those of β‐modification.