Improving safety performance of lactose-fueled binary pyrotechnic systems of smoke dyes

The lactose/KClO₃ is a widely used pyrotechnic mixture to vaporize organic materials, such as smoke dyes. However, because of low ignition temperature of this mixture, serious precaution should be taken into account to prevent its accidental self-ignition. In order to find a safe and efficient alternative of this conventional mixture, KClO₃ has been replaced by common oxidizing agents including KMnO₄, KNO₃, KClO₄, Ba(NO₃)₂, PbO₂ and NH₄ClO₄. TG and DTA analysis have been used to obtain thermal characteristic of the mixtures. Based on ignition temperature of the pyrotechnic mixtures we can divide them into four categories as follows: (1) the mixture igniting at low temperature, i.e., at about 200 °C. (2) Moderate temperature igniting mixture, in which ignition occurs at 300–400 °C. (3) High temperature igniting mixture with ignition temperature higher than 400 °C .(4) Not igniting mixtures. Also, the apparent activation energy (E), ΔG ^#, ΔH ^#, ΔS ^# and critical ignition temperature (T _b ) of the ignition processes of low and moderate temperature igniting mixtures were obtained from the DSC experiments. Finally, among the investigated mixtures, lactose/KNO₃ can be considered as a safe and efficient pyrotechnic composition for vaporization of organic materials, such as smoke dyes, due to its moderate safe ignition temperature.     

Thermodynamic properties of crystalline magnesium zirconium phosphate

Heat capacity $ C_{\text{p}}^{^\circ } $ (T) of crystalline magnesium zirconium phosphate was measured between 6 and 815 K. The experimental data obtained were used to calculate the standard thermodynamic functions $ C_{\text{p}}^{^\circ } $ (T), H°(T) ? H°(0), S°(T), G°(T) ? H°(0) over the temperature ranging from T → 0 to 810 K and standard entropy of formation at 298.15 K. The fractal dimension of Mg_0.5Zr₂(PO₄)₃ was calculated from experimental data on the low-temperature (6 ≤ T/K ≤ 50) heat capacity, and the topology of the phosphate’s structure was estimated. Thermodynamic properties of structurally related phosphates M_0.5Zr₂(PO₄)₃ (M = Mg, Ca, Sr, Ba, Ni) were compared.     

A novel pycnometer for density measurements of liquids at elevated temperatures

A novel pycnometer has been designed for density measurements at elevated temperatures (up to T=473.15 K). The pycnometer consists of a stainless steel cell connected to a small-bore tube. The main feature of the design includes a bored-through expansion fitting, which allows the overflow due to thermal expansion from the cell (via the small-bore tube) to collect in a pressurized line. Densities were measured for pure 1-butanol, pure n-heptane, and for mixtures {x_bCH₃(CH₂)₃OH + (1−x_b)CH₃(CH₂)₅CH₃}, from T=316.85 K to T=458.15 K, at a pressure of 4.93 MPa. Excess volumes were calculated and reported for these mixtures.     

Molar heat capacity and thermodynamic properties of Lu(C5H9NO4)(C3H4N2)6(ClO4)3·5HClO4·10H2O

A complex of Lutetium perchloric acid coordinated with l-glutaminic acid (C₅H₉NO₄) and imidazole (C₃H₄N₂), Lu(C₅H₉NO₄)(C₃H₄N₂)₆(ClO₄)₃·5HClO₄·10H₂O was synthesized and characterized. Thermodynamic properties of the complex were studied with an adiabatic calorimeter (AC) from 80 to 390 K and differential scanning calorimetry (DSC) from 100 to 300 K. Two thermal abnormalities were discovered at 220.34 and 248.47 K, which were deduced to be phase transitions. One was interpreted as a freezing-in phenomenon of the reorientational motion of ClO₄ ^? ions and the other was attributed to the orientational order/disorder process of ClO₄ ^? ions. The low-temperature molar heat capacities were measured by AC and the thermodynamic functions [H _T  ? H _298.15] and [S _T  ? S _298.15] were derived in the temperature range from 80 to 390 K with temperature interval of 5 K. Thermal decomposition behavior of the complex was studied by thermogravimetric analysis and DSC.     

Characterization of the aluminum/potassium chlorate mixtures by simultaneous TG-DTA

Thermogravimetry (TG) and differential thermal analysis (DTA) in the non-isothermal mode have been used to examine the thermal behaviour of the micron sized aluminum (Al) powder/potassium chlorate pyrotechnic systems in air, in relation to the behaviour of the individual constituents. The effects of different parameters of Al powder, such as particle size and its content in the mixtures, on their thermal property were investigated. The results showed that, the reactivity of Al powder in air increases as the particle size decreases. Also, it was found that neat Al with 5 μm particle sizes (Al₅) has a fusion temperature of about 647°C, that for 18 μm powder (Al₁₈) is 660°C. Pure potassium chlorate has a fusion temperature around 356°C and decomposes at 472°C. DTA curves for Al₅/KClO₃ (30:70) mixture showed a maximum peak temperature for the ignition of mixture at 485°C. Also, by increasing the particle size of Al powder, the ignition temperature of the mixture increased. On the other hand, the oxidation temperature increased by enhancing the Al content of the mixtures. In this particular study, we observed that the width of reaction peak for the mixtures corresponds to their Al contents of samples.     

Thermoanalytical investigation of relative reactivity of some nitrate oxidants in tin-fueled pyrotechnic systems

In order to investigate relative reactivity of different oxidants in solid-state reactions of pyrotechnic mixtures, thermal properties of Sn + Sr(NO₃)₂, Sn + Ba(NO₃)₂, and Sn + KNO₃ pyrotechnic systems have been studied by means of TG, DTA, and DSC methods and the results compared with those of pure oxidants. The apparent activation energy (E), ΔG ^#, ΔH ^#, and ΔS ^# of the combustion processes were obtained from the DSC experiments. The results showed that the nature of oxidant has a significant effect on ignition temperature, and the kinetic of the pyrotechnic mixtures’ reactions, and the relative reactivity of these mixtures was found to obey in the following order: Sn + Sr(NO₃)₂ > Sn + Ba(NO₃)₂ > Sn + KNO₃.     

Thermodynamic properties of crystalline phosphate Ba0.5Zr2(PO4)3 over the temperature range from T → 0 to 610 K

The temperature dependence of the heat capacity of crystalline barium zirconium phosphate C _p ^o  = f(T) was measured over the temperature range 6–612 K. The experimental data obtained were used to calculate the standard thermodynamic functions C _p ^o (T), H°(T) ? H°(0), S°(T), G°(T) ? H°(0) over the temperature range from T → 0 to 610 K and standard entropy of formation at 298.15 K. The data on the low-temperature (6 ≤ T/K ≤ 50) heat capacity were used to determine the fractal dimension of Ba_0.5Zr₂(PO₄)₃. Conclusions concerning the topology of the structure of phosphate were drawn. Thermodynamic properties of M_0.5Zr₂(PO₄)₃ (M = Ca, Sr, Ba) were compared.     

A three-parameter cubic equation of state for asymmetric mixture density calculations

A new three-parameter cubic equation of state of the van der Waals type with one parameter temperature dependent, P = RT/(V − b) − a(T)/[V(V + c) + b(3V + c)], has been developed for representation of liquid volumes (or densities) for asymmetric mixtures such as CO₂C₁₉ and C₁C₁₀. The calculated results are better than those obtained from the two-parameter Peng—Robinson equation, the three parameter Schmidt—Wenzel equation, the volume-translated Soave—Redlich—Kwong equation proposed by Peneloux et al., and the volume-translated Peng—Robinson equation developed in this work. The parameters of the new equation have been generalized in terms of the acentric factor ω and reduced temperature T_r.     

Thermophysical studies on uranyl nitrate hexahydrate–Iron (III) nitrate nonahydrate system

Individual nitrates, UO₂(NO₃)₂·6H₂O and Fe(NO₃)₃·9H₂O as well as their binary mixtures in various mol ratios have been studied using simultaneous thermal techniques and X-ray powder diffraction measurements. Nature and stoichiometry of hydroxynitrates of iron and uranium were altered by changing the heating rates for the equal mass of binary nitrate mixtures under identical gas flow conditions. Evolved gas analysis and thermogravimetric measurements indicated the absence of direct interaction between two nitrates in the binary nitrate mixtures. Both the nitrates decomposed independently in the mixtures to their respective oxides. These results have been supported by X-ray powder diffraction measurements. Phase diagram of UO₂(NO₃)₂·6H₂O–Fe(NO₃)₃·9H₂O system containing 0–100 mol% of UO₂(NO₃)₂·6H₂O was constructed using differential thermal analysis technique. The formation of the eutectic at 33 °C for 50 mol% uranyl nitrate hexahydrate–50 mol% iron (III) nitrate nonahydrate mixture has been observed for the first time.     

Determination of thermodynamic properties of aqueous mixtures of MgCl2 and Mg(NO3)2 by the potentiometric method at T = 298.15

In this research, thermodynamic properties of the ternary electrolyte system (MgCl₂ + Mg(NO₃)₂ + H₂O) were investigated using a potentiometric method. The galvanic cell used had no liquid junction of type: Mg-ISE|MgCl₂ (m_A), Mg(NO₃)₂ (m_B), H₂O|Ag/AgCl. The measurements were performed at T = 298.15 K and at total ionic strengths from 0.001 to 8.000 mol/kg for different series of salt ratios r=mMgCl₂/mMg₂(NO₃) =1.00, 2.50, 5.00, 7.50, 10.00 and 15.00. The PVC based magnesium ion-selective electrode (Mg-ISE) and the Ag/AgCl electrode used in this work were prepared in our laboratory and showed a reasonably good Nernst response. The Pitzer ion interaction model and Harned rule were used to illustrate the ternary electrolyte system investigated. The experimental results showed that both Pitzer model and Harned rule were suitable to be used satisfactorily to describe this ternary system.     

Miniaturization of GPS patch antennas based on novel dielectric ceramics Zn(1−x)MgxAl2O4 by sol–gel method

The need for miniaturization and weight reduction of GPS patch antennas has prompted the search for new microwave dielectric materials. In this study, a sol–gel method was used to prepare Zn_(1?x)Mg_xAl₂O₄ thin films and fabricate GPS patch antennas at a low annealing temperature (700 °C). X-ray diffraction (XRD) patterns, field emission scanning electron microscopy images, Fourier transform infrared spectra, and optical band gap analyses confirmed the nanostructure of (Mg/Zn)Al₂O₄. The XRD patterns displayed the characteristic peaks of (Mg/Zn)Al₂O₄ with a face-centered cubic structure. Mg addition decreased the crystallite size, surface morphology, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (? _r ). Based on the material investigated and microwave antenna theory, GPS patch antennas were fabricated using Zn_(1?x)Mg_xAl₂O₄ and then studied using a PNA series network analyzer. The fabricated patch antennas with different ? _r ceramics decreased in size from 12.5 to 10.8 cm². The patch antennas resonated at a frequency of 1.570 GHz and provided a return loss bandwidth between ?16.6 and ?20.0 dB; their bandwidth also improved from 90 to 255 MHz. The GPS patch antenna fabricated from Zn_0.70Mg_0.30Al₂O₄ showed an excellent combination of return loss (?20.0 dB), small size (10.8 cm²), and wide bandwidth (255 MHz). Therefore, addition of Mg improves antenna performance and decreases the dimensions of the device.     

Kinetic parameters for thermal decomposition of hydrazine

The propulsion of most of the operating satellites comprises monopropellant (hydrazine––N₂H₄) or bipropellant (monometilydrazine—MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of N₂H₄. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela–Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 °C min^?1, kinetic parameters could be determined in nitrogen (E = 47.3 ± 3.1 kJ mol^?1, lnA = 14.2 ± 0.9 and T _b = 69 °C) and oxygen (E = 64.9 ± 8.6 kJ mol^?1, lnA = 20.7 ± 3.1 and T _b = 75 °C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f(α)g(α) master-plot curves were closed to F _1/3 model.     

Kinetics of non-isothermal crystallization in Cu50Zr43Al7 and (Cu50Zr43Al7)95Be5 metallic glasses

The crystallization kinetics of Cu₅₀Zr₄₃Al₇ and (Cu₅₀Zr₄₃Al₇)₉₅Be₅ metallic glasses was studied using differential scanning calorimetry (DSC) at four different heating rates under non-isothermal condition. The glass transition temperature T _g, the onset temperature of crystallization T _x, and the peak temperature of crystallization T _p of the two metallic glasses were determined from DSC curves. The values of various kinetic parameters such as the activation energy of glass transition E _g, activation energy of crystallization E _p, Avrami exponent n and dimensionality of growth m were evaluated from the dependence of T _g and T _p on the heating rate. The values of E _g and E _p, calculated from many different models, are found to be in good agreement with each other. The average values of the Avrami exponent n are (2.8 ± 0.4) for Cu₅₀Zr₄₃Al₇ metallic glass and (4.2 ± 0.3) for (Cu₅₀Zr₄₃Al₇)₉₅Be₅ metallic glass, which are consistent with the mechanism of two-dimensional growth and three-dimensional growth, respectively. Finally, the parameter H _r, S, and crystallization enthalpy ΔH _c are introduced to estimate the glass-forming ability and thermal stability of metallic glasses. The result shows that the addition of Be improves the glass-forming ability and thermal stability of Cu₅₀Zr₄₃Al₇ metallic glass.     

Lanthanoid metal nitrates with hydrogen bonded hexamethylenetetramine

Cerium, praseodymium, and neodymium nitrate complexes with hydrogen bonded hexamethylenetetramine (HMTA) of the formula [Ce(NO₃)₂(H₂O)₅](HMTA)₂(NO₃)(H₂O)₃, [Pr(NO₃)₂(H₂O)₆]₂[Pr(H₂O)₉](HMTA)₆(NO₃)₆(H₂O)₄ and [Nd(NO₃)₂(H₂O)₅](HMTA)₂(NO₃)(H₂O)₃ have been prepared and characterized by X-ray crystallography. All the complexes belong to monoclinic crystal system. Ce and Nd complexes have P21/n space group, whereas Pr complex has C2/c. Thermal analyses of these complexes were carried out using TG, DSC, which showed their multi-step decomposition. Kinetics of thermolysis has been done by applying model fitting as well as model free isoconversional method. In order to see the response of rapid heating, ignition delay measurements were carried out. The thermal decomposition pathways have also been demonstrated. On the basis of thermal studies the thermal stability of the complexes was found in the order; Pr > Ce > Nd. In order to identify the end products of thermolyses, X-ray diffraction patterns of end product were carried out which showed the formation of corresponding metal oxides.     

A Non-Hydrolytic Sol-Gel Approach for the Preparation of Mg x Al2(1−x)Ti(1+x)O5 Powders

The study of non-hydrolytic reactions for the synthesis of Mg _x Al_2(1?x)Ti_(1+x)O₅ solid solution with x = 0.6 is reported. The reagents chosen were Al(OsBu)₃, Ti(OiPr)₄, TiCl₄ and Mg(NO₃)₂·6H₂O in toluene. The reactions were followed using ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy. Sol-gel synthesized powders were calcined in air at 300, 500, 1000, and 1200°C for 1 h. The powders were analysed by X-Ray Diffraction (XRD) demonstrating the formation of a Mg_0.6Al_0.8Ti_1.6O₅ phase in samples treated at the higher calcination temperature.     

Thermal stability and sensitivity of RDX-based aluminized explosives

The thermal decomposition characteristics and thermal sensitivity are key indicators for reflecting the thermal stability of explosives in storage and application. The thermal decompositions in different degrees are used to determine the dominant factor which controls the thermal stability of composite explosive. Four kinds of RDX-based aluminized explosives are marked as RA1, RA2, RA3, and RA4 with the Al content increasing from 10 to 40 mass%. The initial thermal decomposition behaviors were studied by DPTA and the complete thermal decompositions were studied by DSC and TG. The thermal sensitivities were characterized by 5-s explosion point. The effects of micron-sized Al particles and their contents on thermal decomposition were investigated. The evolved gas amount (V _i) from DPTA test follows RA3 < RA4 < RA2 < RA1, indicating that RA3 has the best thermal stability at ambient storage conditions. However, according to TG and DSC tests, the characteristic temperatures of thermal decomposition (T _p, T _b, and T _SADT), the thermodynamic parameters (?H _e, ?S ^≠, and ?H ^≠), the kinetic parameters (E _a and A), and the 5-s explosion points all follow RA4 < RA3 < RA2 < RA1. The results indicate that the Al particles play different roles in the different degrees of thermal decomposition. In the initial decomposition, the Al particles have not been activated and are considered as inert materials that hinder the decomposition of explosive. In the complete decomposition, the Al particles catalyze the thermal decomposition, and such catalysis becomes more obvious as the Al content increases to a certain degree.     

Indium-containing catalysts for oxidative dehydrogenation of organic compounds

For the first time, a method was developed for introducing indium into Mg-Al hydrotalcites—precursors of oxide catalysts for oxidative dehydrogenation of alkanes. Samples of oxide catalysts were synthesized that contained indium oxide and also oxides of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. The catalytic properties of the produced catalysts were studied in the oxidative dehydrogenation of ethane, propane, and isobutane. It was established that the introduction of indium into catalysts increases the selectivity and the yields of desired products. New hydroxo salts with a layered structure of the hydrotalcite type were synthesized: [Al_{1 ? n} In _n Mg _m (OH)_{3 + 2m ? 1}][(NO₃) · nH₂O] and quaternary magnesium indium chromium aluminum hydroxonitrate of the composition [Al_0.5In_0.5Cr_0.5Mg_2.5(OH)_8.5][(NO₃) · nH₂O]; these salts were found to be isostructural. The obtained compounds were studied as catalyst precursors.     

Synthesis, crystal structures and photoluminescence properties of new oxyborates, Mg5NbO3(BO3)3 and Mg5TaO3(BO3)3, with novel warwickite-type superstructures

Single crystals of new oxyborates, Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃, were prepared at 1370 °C in air using B₂O₃ as a flux. They were colorless and transparent with block shapes. X-ray diffraction analysis of the single crystals revealed Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ to be isostructural. The X-ray diffraction reflections were indexed to the orthorhombic Pnma (No. 62) system with a=9.3682(3) Å, b=9.4344(2) Å, c=9.3379(3) Å and Z=4 for Mg₅NbO₃(BO₃)₃ and a=9.3702(3) Å, b=9.4415(3) Å, c=9.3301(2) Å and Z=4 for Mg₅TaO₃(BO₃)₃. The crystal structures of Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ are novel warwickite-type superstructures having ordered arrangements of Mg and Nb/Ta atoms. Polycrystals of Mg₅NbO₃(BO₃)₃ prepared by solid state reaction at 1200 °C in air showed broad blue-to-green emission with a peak wavelength of 470 nm under 270 nm ultraviolet excitation at room temperature.     

Synergistic use of Knudsen effusion quadrupole mass spectrometry, solid-state galvanic cell and differential scanning calorimetry for thermodynamic studies on lithium aluminates

Three ternary oxides LiAl₅O₈(s), LiAlO₂(s) and Li₅AlO₄(s) in the system Li-Al-O were prepared by solid-state reaction route and characterized by X-ray powder diffraction method. Equilibrium partial pressure of CO₂(g) over the three-phase mixtures {LiAl₅O₈(s)+Li₂CO₃(s)+5Al₂O₃(s)}, {LiAl₅O₈(s)+5LiAlO₂(s)+2Li₂CO₃(s)} and {LiAlO₂(s)+Li₅AlO₄(s)+2Li₂CO₃(s)} were measured using Knudsen effusion quadrupole mass spectrometry (KEQMS). Solid-state galvanic cell technique based on calcium fluoride electrolyte was used to determine the standard molar Gibbs energies of formations of these aluminates. The standard molar Gibbs energies of formation of these three aluminates calculated from KEQMS and galvanic cell measurements were in good agreement. Heat capacities of individual ternary oxides were measured from 127 to 868 K using differential scanning calorimetry. Thermodynamic tables representing the values of Δ_fH⁰(298.15 K), S⁰(298.15 K) S⁰(T), C_p⁰(T), H⁰(T), {H⁰(T)-H⁰(298.15 K)}, G⁰(T), Δ_fH⁰(T), Δ_fG⁰(T) and free energy function (fef) were constructed using second law analysis and FACTSAGE thermo-chemical database software.