A Thermodynamic Proposal for the Exposition of Critically and other Subtle Features in Self-Deflagrating Ammonium Perchlorate Systems

A first comprehensive investigation on the deflagration of ammonium perchlorate (AP) in the subcritical regime, below the low pressure deflagration limit (LPL, 2.03 MPa) christened as regime I$^{\prime}$, is discussed by using an elegant thermodynamic approach. In this regime, deflagration was effected by augmenting the initial temperature (T$_{0}$) of the AP strand and by adding fuels like aliphatic dicarboxylic acids or polymers like carboxy terminated polybutadiene (CTPB). From this thermodynamic model, considering the dependence of burning rate ($\dot{r}$) on pressure (P) and T$_{0}$, the true condensed (E$_{\text{s,c}}$) and gas phase (E$_{\text{s,g}}$) activation energies, just below and above the surface respectively, have been obtained and the data clearly distinguishes the deflagration mechanisms in regime I$^{\prime}$ and I (2.03-6.08 MPa). Substantial reduction in the E$_{\text{s,c}}$ of regime I$^{\prime}$, compared to that of regime I, is attributed to HClO$_{4}$ catalysed decomposition of AP. HClO$_{4}$ formation, which occurs only in regime I$^{\prime}$, promotes dent formation on the surface as revealed by the reflectance photomicrographs, in contrast to the smooth surface in regime I. The HClO$_{4}$ vapours, in regime I$^{\prime}$, also catalyse the gas phase reactions and thus bring down the E$_{\text{s,g}}$ too. The excess heat transferred on to the surface from the gas phase is used to melt AP and hence E$_{\text{s,c}}$, in regime I, corresponds to the melt AP decomposition. It is consistent with the similar variation observed for both the melt layer thickness and $\dot{r}$ as a function of P. Thermochemical calculations of the surface heat release support the thermodynamic model and reveal that the AP sublimation reduces the required critical exothermicity of 1108.8 kJ kg$^{-1}$ at the surface. It accounts for the AP not sustaining combustion in the subcritical regime I$^{\prime}$. Further support for the model comes from the temperature-time profiles of the combustion train of AP. The gas and condensed phase enthalpies, derived from the profile, give excellent agreement with those computed thermochemically. The $\sigma _{\text{p}}$ expressions derived from this model establish the mechanistic distinction of regime I$^{\prime}$ and I and thus lend support to the thermodynamic model. On comparing the deflagration of strand against powder AP, the proposed thermodynamic model correctly predicts that the total enthalpy of the condensed and gas phases remains unaltered. However, 16% of AP particles undergo buoyant lifting into the gas phase in the `free board region' (FBR) and this renders the demarcation of the true surface difficult. It is found that T$_{\text{s}}$ lies in the FBR and due to this, in regime I$^{\prime}$, the E$_{\text{s,c}}$ of powder AP matches with the E$_{\text{s,g}}$ of the pellet. The model was extended to AP/dicarboxylic acids and AP/CTPB mixture. The condensed ($\Delta $H$_{1}$) and gas phase ($\Delta $H$_{2}$) enthalpies were obtained from the temperature profile analyses which fit well with those computed thermochemically. The $\Delta $H$_{1}$ of the AP/succinic acid mixture was found just at the threshold of sustaining combustion. Indeed the lower homologue malonic acid, as predicted, does not sustain combustion. In vaporizable fuels like sebacic acid the E$_{\text{s,c}}$ in regime I$^{\prime}$, understandably, conforms to the AP decomposition. However, the E$_{\text{s,c}}$ in AP/CTPB system corresponds to the softening of the polymer which covers AP particles to promote extensive condensed phase reactions. The proposed thermodynamic model also satisfactorily explains certain unique features like intermittent, plateau and flameless combustion in AP/ polymeric fuel systems.

Facial Coordination in BIS[BIS(Benzimidazol-2-Ylmethyl)Amine]Copper(II) Perchlorate Dihydrate - Synthesis, Structure, Spectra and Redox Behavior

The 1:1 and 1:2 cooper(II) complexes with the tridentate compound bis(benzimidazol-2-ylmethyl)amine (L(1)) and its benzimidazole (L(2)) and amine (L(3)) N-methyl-substituted derivatives have been prepared and their spectroscopic properties studied. While the 1:1 complexes are of the type CuLX(2) nH(2)O (X = C/O-4(-), NO3-, Cl- or Br-), the 1:2 complexes are of the type CuL(2) (ClO4)(2) nH(2)O (L = L(1) or L(3), n = 0-4). In all these complexes L acts as a tridentate ligand with the amine nitrogen and both the benzimidazole nitrogens co-ordinating to Cu-II. The complex [CuL(2)(1)][ClO4](2) 2H(2)O crystallises in the monoclinic space group P2(1)/c with a = 9.828(2), b = 9.546(2) and c = 19.906(2) Angstrom and beta = 95.71(1)degrees, for Z = 2. The R value is 0.0635 for 2180 significant reflections. The copper(II) ion has an elongated octahedral geometry with four equatorial benzimidazole and two long-distance axial amine N donors. The Cu-N-bzim and Cu-N-amine distances are 2.011(4) and 2.597(6) Angstrom respectively. Factors favouring facial co-ordination to tridentate ligands are discussed. The 1:1 complexes involve meridonal co-ordination of the ligands, with square-based geometry as revealed by ligand-field and EPR spectral properties. The NMe substitution as in CuL(3)(ClO4)(2) confers low V ($) over tilde$$(max) and high E(1/2) for the cu(II)-Cu-I couple. Most of the 1:1 complexes are less reversible but exhibit E(1/2) values more positive than those of the corresponding 1:2 complexes.

Preparation of a thermally sensitive ammonium perchlorate

The effect of ultrasound on the thermal decomposition behaviour of ammonium perchlorate (AP) has been investigated. It was observed that significant changes in the thermal behaviour of A-P, followed using differential thermal analysis and thermogravimetry, was observed when AP was subjected to power ultrasound in water saturated with oxygen-nitrogen mixture. The decomposition temperature of AP was found to have been lowered by nearly 25degreesC. A similar thermal sensitization was observed in AP when subjected to sonication in the presence of transition metal oxides. Kinetic parameters were calculated for AP, modified AP and catalyzed AP decomposition using non-isothermal kinetics. The activation energy for the decomposition of the sonicated AP samples were found to be lower than normal AP.

Exceptional activity of mesoporous beta-MnO2 in the catalytic thermal sensitization of ammonium perchlorate

Mesoporous beta-MnO2 has been prepared, characterized and demonstrated to possess excellent catalytic activity in the thermal decomposition of ammonium perchlorate. The observed unprecedentedly low decomposition temperatures, fast reaction rates and enhanced heat releases in the catalysed formulations make mesoporous beta-MnO2 promising as a high-performing ballistic modifier in AP-based composite solid rocket propellants.

Crystal Coulomb energies: I. Organic donor-acceptor complexes--a review. II. Classical Ewald calculations of the Coulomb binding energy of four donor-acceptor crystals and Wurster's blue perchlorate. III. A rapid-convergence quantum-mechanical formalism for crystal electronic energies

Chapter I

Theories for organic donor-acceptor (DA) complexes in solution and in the solid state are reviewed, and compared with the available experimental data. As shown by McConnell et al. (Proc. Natl. Acad. Sci. U.S., 53, 46-50 (1965)), the DA crystals fall into two classes, the holoionic class with a fully or almost fully ionic ground state, and the nonionic class with little or no ionic character. If the total lattice binding energy 2ε₁ (per DA pair) gained in ionizing a DA lattice exceeds the cost 2ε_o of ionizing each DA pair, ε₁ + ε_o less than 0, then the lattice is holoionic. The charge-transfer (CT) band in crystals and in solution can be explained, following Mulliken, by a second-order mixing of states, or by any theory that makes the CT transition strongly allowed, and yet due to a small change in the ground state of the non-interacting components D and A (or D⁺ and A^-). The magnetic properties of the DA crystals are discussed.

Chapter II

A computer program, EWALD, was written to calculate by the Ewald fast-convergence method the crystal Coulomb binding energy E_C due to classical monopole-monopole interactions for crystals of any symmetry. The precision of E_C values obtained is high: the uncertainties, estimated by the effect on E_C of changing the Ewald convergence parameter η, ranged from ± 0.00002 eV to ± 0.01 eV in the worst case. The charge distribution for organic ions was idealized as fractional point charges localized at the crystallographic atomic positions: these charges were chosen from available theoretical and experimental estimates. The uncertainty in E_C due to different charge distribution models is typically ± 0.1 eV (± 3%): thus, even the simple Hückel model can give decent results.

E_C for Wurster's Blue Perchl orate is -4.1 eV/molecule: the crystal is stable under the binding provided by direct Coulomb interactions. E_C for N-Methylphenazinium Tetracyanoquino- dimethanide is 0.1 eV: exchange Coulomb interactions, which cannot be estimated classically, must provide the necessary binding.

EWALD was also used to test the McConnell classification of DA crystals. For the holoionic (1:1)-(N,N,N',N'-Tetramethyl-para- phenylenediamine: 7,7,8,8-Tetracyanoquinodimethan) E_C = -4.0 eV while 2ε_o = 4.6₅ eV: clearly, exchange forces must provide the balance. For the holoionic (1:1)-(N,N,N',N'-Tetramethyl-para- phenylenediamine:para-Chloranil) E_C = -4.4 eV, while 2ε_o = 5.0 eV: again EC falls short of 2ε₁. As a Gedankenexperiment, two nonionic crystals were assumed to be ionized: for (1:1)-(Hexamethyl- benzene:para-Chloranil) E_C = -4.5 eV, 2ε_o = 6.6 eV; for (1:1)- (Napthalene:Tetracyanoethylene) E_C = -4.3 eV, 2ε_o = 6.5 eV. Thus, exchange energies in these nonionic crystals must not exceed 1 eV.

Chapter III

A rapid-convergence quantum-mechanical formalism is derived to calculate the electronic energy of an arbitrary molecular (or molecular-ion) crystal: this provides estimates of crystal binding energies which include the exchange Coulomb inter- actions. Previously obtained LCAO-MO wavefunctions for the isolated molecule(s) ("unit cell spin-orbitals") provide the starting-point. Bloch's theorem is used to construct "crystal spin-orbitals". Overlap between the unit cell orbitals localized in different unit cells is neglected, or is eliminated by Löwdin orthogonalization. Then simple formulas for the total kinetic energy Q^(XT)_λ, nuclear attraction [λ/λ]^XT, direct Coulomb [λλ/λ'λ']^XT and exchange Coulomb [λλ'/λ'λ]^XT integrals are obtained, and direct-space brute-force expansions in atomic wavefunctions are given. Fourier series are obtained for [λ/λ]^XT, [λλ/λ'λ']^XT, and [λλ/λ'λ]^XT with the help of the convolution theorem; the Fourier coefficients require the evaluation of Silverstone's two-center Fourier transform integrals. If the short-range interactions are calculated by brute-force integrations in direct space, and the long-range effects are summed in Fourier space, then rapid convergence is possible for [λ/λ]^XT, [λλ/λ'λ']^XT and [λλ'/λ'λ]^XT. This is achieved, as in the Ewald method, by modifying each atomic wavefunction by a "Gaussian convergence acceleration factor", and evaluating separately in direct and in Fourier space appropriate portions of [λ/λ]^XT, etc., where some of the portions contain the Gaussian factor.

Studies of perchlorate triggered ion-gate behavior of sBLM by electrochemiluminescence and its application to a sensor for perchlorate

Ru(bpy)(3)(2+) electrochemiluminescence (ECL) method and electrocatalysis method were first used to study the ion-gate behavior of supported lipid bilayer membrane (sBLM). We found that sBLM, made of dimethyldioctadecylammonium bromide (a kind of synthetic lipid), showed ion-gate behavior for the permeation of Ru(bpy)(3)(2+) in the presence of perchlorate anion. There existed a threshold concentration (0.1 muM) of perchlorate anion for ion-gate opening. Below the threshold the ion-gate was closed. Above the threshold, the number of opened ion-gate sites increased with the increase of perchlorate anion concentration and leveled off at concentrations higher than 1200 muM. Based on it, a new sensor for perchlorate was developed. Furthermore, the opening and closing of the ion-gate behavior was reversible, which means the sensor can repeatedly be used.

Electrochemiluminescent determination of perchlorate by solvent extraction in the presence of Ru(bpy)(3)(2+)

A novel method for the highly sensitive determination of perchlorate was proposed. It was based on solvent extraction in the presence of Ru(bpy)(3)(2+) followed by Ru(bpy)(3)(2+) electrochemiluminescent determination. A linear calibration was obtained over the range of 0.1 to 10 mu mol l(-1) with a correlation coefficient of 0.998. The detection limit (S/N = 3) was 5.0 x 10(-8) mol l(-1). The relative standard deviation for 10 replicates of 1 mu mol l(-1) perchlorate was 1.6%. Interference studies suggest that this method is selective for the determination of perchlorate. Application of this method to the highly sensitive determination of other anions is suggested. (C) 1999 Elsevier Science S.A. All rights reserved.

Study on diffusion of electroactive species in polyelectrolyte polyethylene glycol lithium perchlorate by chronoamperometry at a microdisk electrode

The mass transport dynamics of Ferrocene in polyelectrolyte polyethylene glycol lithium perchlorate (PEG . LiClO4) was studied by using chronoamperometry at a microdisk electrode. Chronoamperometry is a powerful method for the study of mass transport in polyelectrolyte, it has many advantages over the conventional methods at a microelectrode and the steady-state method at an ultramicroelectrode. By using this method the apparent diffusion coefficient D-app and concentration C-a of the electroactive species, can be estimated from a single experiment without previous knowledge of either one. We have estimated D-app and C-a of ferrocene in PEG . LiClO4 polyelectrolyte from 25 degrees C to 75 degrees C. The dependence on the concentration of electroactive species was observed. The diffusion coefficients decrease with increasing ferrocene concentration and decreasing temperature. The mass transport mechanism is explained, by using a free volume model.

LANTHANIDE PERCHLORATE COMPLEXES OF 1,4-BIS(PHENYLSULFINYL)BUTANE

Seven trivalent lanthanide perchlorate complexes of the types [Ln(bphab)(4)ClO4] (ClO4)2 (where La = La(III), Pr(III), Nd(III) and Eu(III)) and [Ln(bphab)(3)ClO4] (ClO4)(2) (where Ln = Ho(III), Er(III) and Lu(III), and bphab = 1,4-bis(phenylsulfinyl)butane) have been synthesized by the reaction of bphsb with lanthanide(III) perchlorate in methanol-chloroform mixture. The complexes have been characterized by elemental analyses, molar conductance, electronic and infrared spectral techniques. Several bonding parameters have been calculated from the absorption spectra of the Pr(III), Nd(III), Ho(III) and Er(III) complexes. Infrared spectral data suggest that bphsb acts as bidentate ligand coordinating through the oxygen atoms of the S=O moieties.

ELECTROCHEMICAL AND IN-SITU SPECTROELECTROCHEMICAL STUDY OF (TETRAPHENYLPORPHINATO)MANGANESE(III) PERCHLORATE IN THE PRESENCE OF CHLORIDE ANIONS .2. OXIDATION PROCESSES

An investigation of electrode oxidation processes of (tetra-phenylporphinato) manganese (III) Perchlorate, (TPS)Mn(III)ClO4, was carried out during the titration of chloride anions by conventional cyclic voltammetry, thin-layer cyclic voltammetry and spectroelectrochemistry. It was demonstrated that in the presence of one equivalent amount of Cl-, the first one electron oxidation reaction corresponds to the Mn(III)I cation radical oxidation, and the second one electron oxidation corresponds to the cation radical/dication generation followed by an iso-porphyrin formation reaction, however in the presence of two equivalent amount of Cl-, the first one electron oxidation of Mn(III) gives Mn(IV) porphyrin and the second one electron oxidation generates cation radicals of Mn(IV) followed by an iso-porphyrin formation reactions. Mechanisms of these redox processes are postulated.

ELECTROCHEMICAL AND INSITU SPECTROELECTROCHEMICAL STUDY OF (TETRAPHENYLPORPHINATO)MANGANESE (III) PERCHLORATE IN THE PRESENCE OF CHLORIDE ANIONS .1. REDUCTION PROCESSES

The mechanism of electrochemical redox reactions of (tetra-phenylporphinato) managanese(III) perchlorate, (TPP)Mn(III)ClO4, was studied In the presence of chloride anions in dichloroethane solution. It was demonstrated that Mn(II) or Mn (III) centre can be coordinated with only one chloride anion, this result makes an about 100 mV negative shift of half-wave potential of Mn (III)/Mn (II) reduction. An equilibrium constant of 2.2 x 10(4) was determined for the complexation reaction of Cl- and Mn(III) centre.