Design and characterization of new advanced energetic biopolymers based on surface functionalized cellulosic materials

A new class of energetic biopolymers, which contain nitrate ester (O-NO₂) and nitramine (N-NO₂) as explosophoric groups, was successfully synthesized by surface modification of renewable pristine cellulose (PC) and microcrystalline cellulose (MCC) via epichlorohydrin-mediated amination followed by nitration process to produce new promising energetic aminated and nitrated cellulose and microcrystalline cellulose (APCN and AMCCN). Their structural, thermal, crystallinity and morphological features were examined and compared to those of the common cellulose nitrate. Furthermore, their energetic performances were evaluated by EXPLO5 V6.04 software. Experimental results confirm the successful chemical functionalization process to develop insensitive APCN and AMCCN with outstanding features such as nitrogen content of 15.01% and 15.39%, density of 1.692 g/cm³ and 1.708 g/cm³, and detonation velocity of 7526 m/s and 7752 m/s, respectively, which are significantly higher than those of the nitrated unmodified cellulosic biopolymers. The present investigation provides a suitable pathway to design new insensitive and energy-rich dense cellulosic biopolymers for potential application in high-performance solid propellants and composite explosives.

     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

Experimental validation of the largest calculated isospin-symmetry-breaking effect in a superallowed Fermi decay

A precision measurement of the γ yields following the β decay of (32)Cl has determined its isobaric-analogue branch to be (22.47(-0.18)(+0.21))%. Since it is an almost pure-Fermi decay, we can also determine the amount of isospin-symmetry breaking in this superallowed transition. We find a very large value, δ(C) = 5.3(9)%, in agreement with a shell-model calculation. This result sets a benchmark for isospin-symmetry-breaking calculations and lends support for similarly calculated, yet smaller, corrections that are currently applied to 0+ → 0 + transitions for tests of the standard model.     

Spectral Investigation of an a. c. Plasma Display

The work presents the spectral investigations on an a.c. plasma display, in order of a better understanding of the physical phenomena taking place in such a device. The spectral characteristics of the panel filled with a Penning mixture Ne + 0.1% Ar are presented and the influence of the nitrogen addition on these characteristics was evidentiated. The presence of the trace of nitrogen in the device may be used in order to evidentiated. The presence of the trace of nitrogen in the device may be used in order to evidentiate small leaks or imperfections in pumping and outgasing processing of the display.     

Excited levels in the neutron deficient nucleus111Sb

The level scheme of the neutron deficient isotope¹¹¹Sb up to about 3.7 MeV is established from in-beam gamma-ray spectroscopy experiments. The identification of the reaction channel using cross bombardments:⁹⁵Mo+¹⁹F (56–68 MeV),¹⁰⁶Cd+⁷Li (20–30 MeV),¹⁰²Pd+¹¹B (45 MeV), charged partice-γ and neutron-γ coincidences is discussed.     

Comments on “An experimental investigation on heating rate effect in the thermal behavior of perhydrous bituminous coal during pyrolysis”

This paper has the intension of discussing about the published paper by Wu et al. (J Therm Anal Calorim 119:2195–2203, 2015). The original paper has shown some errors in quoting and using the Coats–Redfern integral kinetic equation. This discussion is focused on the employment of this model, and some arguments and clarifications are also given.     

Asymptotic normalization coefficients and astrophysical direct capture rates

Peripheral transfer reactions can be used to determine asymptotic normalization coefficients (ANCs). These coefficients, which specify the normalization of the tail of the nuclear overlap function, determine S-factors for direct capture reactions at astrophysical energies. A variety of proton transfer reactions involving both stable and radioactive beams have been used to measure ANCs. Tests have demonstrated that ANCs determined from proton transfer reactions can be used to calculate astrophysical direct capture rates to within 9%. The ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the ANC appropriate for determining the ⁷Be(p,γ)⁸B rate, and the ¹⁴N(¹¹C, ¹²N)¹³C reaction has been used to measure the ANC required to calculate the ¹¹C(p,γ)¹²N rate. Received: 1 May 2001 / Accepted: 4 December 2001     

Enhanced production of neutron-rich rare isotopes in peripheral collisions at Fermi energies

A large enhancement in the production of neutron-rich projectile residues is observed in the reactions of a 25 MeV/nucleon 86Kr beam with the neutron-rich 124Sn and 64Ni targets relative to the predictions of the EPAX parametrization of high-energy fragmentation, as well as relative to the reaction with the less neutron-rich 112Sn target. A hybrid model based on a deep-inelastic transfer (DIT) code followed by a statistical deexcitation code accounts for part of the observed large cross sections. The DIT simulation indicates that the production of neutron-rich nuclides in these reactions is associated with peripheral nucleon exchange in which the neutron skins of the neutron-rich 124Sn and 64Ni target nuclei may play an important role. From a practical viewpoint, such reactions offer a novel synthetic avenue to access extremely neutron-rich rare isotopes towards the neutron-drip line.     

Study on the influence of ageing on chemical and mechanical properties of N,N′-dimethyl-N,N′-diphenylcarbamide stabilized propellants

Double-base propellants undergo chemical, physical and mechanical changes upon ageing, leading to changes in ballistic performance and presenting explosive hazards. This report studies the variation of chemical and mechanical properties of aged N,N′-dimethyl-N,N′-diphenylcarbamide (methyl centralite) stabilized propellants in order to simulate and evaluate the natural ageing throughout the artificial one. Therefore, a comparative study of stabilizer depletion, plasticizers content, heat of combustion and mechanical properties such as storage modulus, loss modulus and damping of naturally and artificially aged propellants has been carried out by the following techniques: high-performance liquid chromatography (HPLC), thermogravimetric analyzer (TG), calorimeter of combustion and dynamic mechanical analyzer (DMA), respectively. The results obtained show that all properties are closely connected. In addition, the determination of stabilizer depletion, plasticizers evaporation, decrease of heat of combustion and mechanical properties are very useful for a better understanding of the decomposition and ageing behaviour of propellants. The HPLC investigation of stabilizer has shown good stability of the propellants. The results obtained for DMA have shown that some considerable changes of the mechanical and viscoelastic properties of the propellants occurred during ageing. These results confirm the results obtained by TG for the reduction of the nitroglycerine amount and the decrease of the heat of combustion.