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 In order to find a safe and efficient alternative of this conventional mixture, KClO₃ has been replaced by common oxidizing agents including KMnO₄, KNO₃, KClO₄, Ba(NO₃)₂, PbO₂ and NH₄ClO₄.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.     

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.     

Heating effect on the DSC melting curve of flaxseed oil

Flaxseed oil is rich in the alpha-linolenic acid. The effect of heating on the thermal properties of flaxseed oil extracted from flax seeds has been investigated. The flaxseed oils were heated at a certain temperature (75, 105, and 135 °C, respectively) for 48 h. The melting curve (from ?75 to 100 °C) of flaxseed oil was determined by differential scanning calorimetry (DSC) at intervals of 4 h. Three DSC parameters of exothermic event and endothermic event, namely, peak temperature (T _peak), enthalpy, and temperature range were determined. The initial flaxseed oil exhibited an exothermic peak, two endothermic peaks, and two endothermic shoulders between ?68 and ?5 °C in the melting profile. Heating temperature had a significant influence on the oxidative deterioration of flaxseed oil. The melting curve and parameters of flaxseed oil were almost not changed when flaxseed oil was heated at 75 °C. However, the endothermic peaks of melting curve decreased dramatically with the increasing of heating time when heating temperature was above 105 °C. There is almost no change of melting heat flow of flaxseed oil when heating time exceeded 32 h at 135 °C. The preliminary results suggest that the DSC melting profile can be used as a fast and direct way to assess the deterioration degree of flaxseed oil.     

DTA study of the chlorination of fly ash and bauxite in the presence of carbon

The chlorination processes of fly ash and bauxite in the presence of carbon were studied by means of a gas-flow type DTA, X-ray analysis and SEM observation, and the reactivity of Al-compounds as their constituents was compared. In the case of fly ash, the exothermic peak due to the formation of AlCl₃ (mainly) and FeCl₃ appeared at about 790–920°C. The reactivity of Al estimated from the DTA peak temperature depended on the particle size, carbon content and preparation temperature of fly ash, and was much lower than that of bauxite. Fractional conversion of Al was about 60–70%, when fly ash (?300 mesh) was heated up to 900°C in Cl₂ at 5°C min^?1 of heating rate. In the case of bauxite, two exothermic peaks due to the chlorination of Fe and Al appeared at about 270 and 490°C, respectively. The chlorination of Al was completed at 550°C under the above conditions.     

Investigation on the reaction of iron powder mixture as a portable heat source for thermoelectric power generators

This paper reports our investigation on the thermal behavior and ignition characteristics of iron powder and mixtures of iron with other materials such as activated carbon and sodium chloride in which iron is the main ingredient used as fuel. Thermal analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis were used to characterize the materials and for further understanding of reaction kinetics of the pyrophoric iron mixtures. The experimental results demonstrated that iron micron particles react exothermically to the oxygen in atmosphere and produced iron oxide with ignition temperature of 427.87 °C and heat generation of 4,844 J g^?1. However, in this study, the pyrophoric iron mixture acts as a heat source for the thermoelectric power generators, the final mixture composition is determined to compose of iron powder, activated carbon, and sodium chloride with the mass ratio of approximately 5/1/1. The mixture generated two exothermic peaks DSC curves that showed ignition temperature of 431.53 and 554.85 °C and with a higher heat generation of 9,366 J g^?1 at higher temperature. The effects of test pan materials and heating rate on the ignition were also examined by DSC method. Kinetic data such as the activation energy (E _a), the entropy of activation (ΔS ^# ), enthalpy of activation (ΔH ^# ), and Gibbs energy of activation (ΔG ^# ) on the ignition processes was also derived from the DSC analysis. From the ignition temperature, heat generation, and kinetics test data, the mass ratio of 5/1/1 proved to generate the most amount of heat with high temperatures for the standalone thermoelectric power generators.     

Thermal behaviour and firing characteristics of Zr/KClO4 primer mixture containing CuO

The effect of CuO on the thermal behaviour of Zr/KClO₄ primer mixtures was studied by thermoanalytical techniques, and the Bruceton method and its related calculation. It was found that the CuO catalytically promoted the decomposition of Zr/KClO₄ primer mixtures and shifted the exothermic peak of DSC curves to lower temperatures. In addition, the Zr/KClO₄ primer mixture containing CuO had a significant effect on the firing characteristics of electro-explosive devices.     

Characterization of fatty acid methyl esters by thermal analysis

The thermal stability of selected straight-chain (C₆-C₁₄) esters of fatty acids has been studied by TG-DTG and DTA analysis. In DTG, a peak is detected between 84° and 125° C followed by a main effect in the range 105°–215°C, whereas in DTA only an exothermic peak appears in the range of 126.5° to 187°C (onset temperatures). The temperatures of these effects have been related with ignition points, molecular weights and boiling points. The characteristics of melting and recrystallization of the above fatty acid methyl esters and those with carbon numbers between C₁₄ and C₂₄ have been established by DSC along the melting range between ?83° and 50°C. Polymorphism appears in caproic, heptanoic, palmitic and stearic acid methyl esters.     

Tailoring of morphology and crystal structure of nanomaterials in MgO–TiO2 system by controlling Mg:Ti molar ratio

The morphological manipulation and structural characterisation of TiO₂?CMgO binary system by an aqueous particulate sol?Cgel route were reported. Different crystal structures including pure MgTiO₃, mixtures of MgTiO₃ and TiO₂ and mixtures of MgTiO₃ and Mg₂TiO₄ were tailored by controlling Mg:Ti molar ratio and annealing temperatures as the processing parameters. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that all compounds crystallised at the low temperature of 500?°C. Furthermore, it was found that the average crystallite size of the compounds depends upon the Mg:Ti molar ratio as well as the annealing temperature, being in the range 3?C5?nm at 500?°C and around 6?nm at 700?°C. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had nanocrystalline structure with the average grain size of 25?C30?nm at 500?°C depending upon the Mg:Ti molar ratio. Moreover, atomic force microscope (AFM) images presented that the thin films had a hill-valley like morphology made up of small grains.     

Effect of LiPF<Subscript>6</Subscript> on the thermal behaviors of four organic solvents for lithium ion batteries

The thermal behaviors of four organic solvents with/without LiPF₆ were measured by C80 microcalorimeter at a 0.2°C min⁻¹ heating rate. With the addition of 1 M LiPF₆, the ethylene carbonate (EC) and propylene carbonate (PC) show the exothermic peaks at elevated temperature, which lessen their stabilities. The exothermic peak temperatures of EC and PC based LiPF₆ solutions are at 212 and 223°C, respectively, in argon filled vessel. However, two endothermic peak temperatures were detected in diethyl carbonate (DEC) based LiPF₆ solution at 182 and 252.5°C, respectively, in argon filled vessel. Dimethyl carbonate (DMC) based LiPF₆ solution shows two endothermic peak temperatures at 68.5 and 187°C in argon filled vessel at elevated temperature. Consequently, it is concluded that LiPF₆ play a key role in the thermal behavior of its organic solution.     

The differential thermal analysis behavior of lead zirconate titanate materials

Differential thermal analysis has been used to examine the reactions involved in the formation of lead zirconate titanate and related materials. The reaction of PbO and TiO₂ produced an exothermic peak near 600°C, while mixtures of PbO and ZrO₂ gave endothermic peak at 760°C. Lead titanate and lead zirconate mixtures showed no evidence of reaction below 900°C. Evidence is presented which suggests that PbO and PbTiO₃ react in the vicinity of 750°C. For ternary mixtures of PbO, titanate, the thermograms indicate a complicated behavior between 600–800°C, depending on the ratios of the reactant materials. The results suggest that the calcination reaction to form lead zirconate titanate is a more complex process than has been recognized. Data on the various phase transitions for the lead zirconate titanate materials are also presented.     

Thermal hazard investigation of cumene hydroperoxide in the first oxidation tower

This article studies the thermokinetics and safety parameters of cumene hydroperoxide (CHP) manufactured in the first oxidation tower. Vent sizing package 2 (VSP2), an adiabatic calorimeter, was employed to determine reaction kinetics, the exothermic onset temperature (T ₀), reaction order (n), ignition runaway temperature (T _{C, I}), etc. The n value and activation energy (E _a) of 15?mass% CHP were calculated to be 0.5 and 120.2?kJ?mol^?1, respectively. The heat generation rate (Q _g) of 15?mass% CHP compared with hS (cooling rate)?=?6.7?J?min^?1?K^?1 of heat balance, the T _S,E and the critical extinction temperature (T _{C, E}) under 110?°C of ambient temperature (T _a) were calculated 111 and 207?°C, respectively. The Q _g of 15?mass% CHP compared with hS?=?0.3?J?min^?1?K^?1 of heat balance was applied to determine the T _{C, I} that was evaluated to be 116?°C. This article describes the best operating conditions when handling CHP, starting from the first oxidation tower.     

Ignition limits of hydrogen–methane–air mixtures over metallic Rh at a pressure of 1–2 atm

The ignition temperatures and effective activation energies of the ignition limits of mixtures (40–70% H₂ + 60–30% CH₄)_stoich + air over Rh were experimentally determined at a pressure of 1 atm in the temperature range 20–300 °C. Over an ignition-treated Rh surface, the ignition temperature of a mixture of 70% H₂ + 30% methane + air is 62 °C. This indicates the potential of using Rh to markedly lower the ignition temperature of fuels based on hydrogen–methane mixtures.     

Anwendung der Differential-Thermoanalyse zur Bestimmung der Zündtemperatur von Schwel- und Hochtemperaturkoks

The application of differential thermal analysis to the determination of the ignition temperature of coke from low-temperature and high-temperature carbonization is treated. The sample mixed with NaNO₂ was heated at a rate of 10?/min, using kaolin as inert substance. As ignition temperature, that of the high exothermic peak on the DTA curve was taken. It has been stated that the ignition temperature of the untreated coal increases from 310 to 365? as the degree of carbonization increases. The ignition temperature of coke from low-temperature carbonization was found to vary between 350 and 370?, and that of coke from high-temperature carbonization between 380 and 400?.     

Thermal and stability study of tetracene using differential scanning calorimetry

A thermal analysis study was made of tetracene using differential scanning calorimetry (DSC). The effect of different scan speeds was investigated. At scan speeds of 0.625 to 10°C min^?1 two large rounded exothermic peaks were produced. The peaks occurred at an increasingly high temperature as the scan speed increased (for example, the peaks occurred at 128 and 130°C at a scan speed of 0.625°C min^?1 and at 148 and 150°C at a scan speed of 10°C min^?1. When tetracene was heated at a scan speed of 80°C min^?1 only one large sharp exothermic peak was produced. It is believed that the two peaks obtained at scan speeds of 0.625 to 10°C min^?1 represent decomposition of the tetracene in two successive stages, while the one peak obtained at 80°C min^?1 represents an explosion. A stability test for tetracene is proposed that involves heating of the tetracene in aluminum pans from the DSC apparatus in ovens at 100, 75, and 60°C, removing the pans and samples at intervals of 30 min, 24 h, and 7 days, respectively, subjecting the samples to DSC at 1.25°C min^?1, and noting the time interval in the oven that produces a DSC curve that shows obliteration of the second peak. Two lots of tetracene made by different processes showed marked differences in stability characteristics.     

Synthesis and phosphorescence properties of Dy3+ and (Pr3+–Dy3+) in MgTiO3

Using tetra-n-butyl titanate and magnesium nitrate as raw materials, Dy³⁺ and Pr³⁺ ions in the matrix of magnesium titanate (MgTiO₃) was successfully synthesized by a modified solid-state reaction. The mixtures to achieve a solid-state reaction were heated in porcelain crucibles at 600?°C for 2?h, 900?°C for 6?h, and 1000.0?°C for 2?h. The reaction products obtained in an air atmosphere were characterized by X-ray powder diffractions. The optimization of reaction conditions were carried out by thermal gravimetry and differential thermal analysis methods. Surface and elemental analyses were performed by using on SEM instrument. The excitation and emission spectra were recorded by photoluminescence spectrophotometer.     

Isothermal differential scanning calorimetry on an exothermic phenomenon during thermal decomposition of hydromagnesite 4 MgCO3 · Mg(OH)2 · 4 H2O

An exothermic phenomenon and a simultaneous rapid evolution of a small amount of carbon dioxide at ?500°C during thermal decomposition of hydromagnesite 4 MgCO₃ · Mg(OH)₂ · 4 H₂O was studied by isothermal DSCTG in a carbon dioxide atmosphere. It was quantitatively confirmed that the exothermic phenomenon was due to crystallization of MgCO₃ from the amorphous phase and that the evolution of carbon dioxide was due to decomposition of the MgCO₃ by the heat of crystallization (?3.4 kcal mole^?1.     

Thermal behaviour of lignins extracted from different raw materials

The thermal degradation of lignins extracted from bagasse, rice straw, corn stalk and cotton stalk, have been investigated using the techniques of thermogravimetric analysis (TG) and differential thermal analysis (DTA), between room temperature and 600°C. The actual pyrolysis of all samples starts above 200°C and is slow. The results calculated from TG curves indicated that the activation energy, Efor thermal degradation for different lignins lies in the range 7.949–8.087 kJ mol^?1. The DTA of all studied lignins showed an endothermic tendency around 100°C. In the active pyrolysis temperature range, thermal degradation occurred via two exothermic process at about 320 and 480°C, and a large endothermic pyrolysis region between 375 and 450°C. The first exothermic peak represents the main oxidation and decomposition reaction, the endothermic effect represents completion of the decomposition and the final exothermic peak represents charring.     

Evolved gas analyses on a mixed valence copper(I,II) complex salt with thiosulfate and ammonia by in situ TG-EGA-FTIR and TG/DTA-EGA-MS

Thermal decomposition of a mixed valence copper salt, Na₄[Cu(NH₃)₄][Cu(S₂O₃)₂]₂·0.5NH₃ (1) prepared from pentahydrates of sodium thiosulfate and copper sulphate of various molar ratios in 1:1 v/v aqueous ammonia solution, has been studied up to 1,000 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR), in comparison. Compound 1 releases first but very slowly some of the included ammonia till 170 °C, then simultaneously ammonia (NH₃) and sulphur dioxide (SO₂) from 175 to 225 °C, whilst the evolution of SO₂ from thiosulfate ligands continues in several overlapping stages until 410 °C, and is escorted by explicit exothermic heat effects at around 237, 260, 358 and 410 °C. The former two exothermic DTA-peaks correspond to the simultaneous degradation and air oxidation processes of excess thiosulfate anions not reacted by formation of copper sulfides (both digenite, Cu_1.8S and covellite, CuS, checked by XRD) and sodium sulfate, while the last two exothermic peaks are accompanied also by considerable mass gains, as the result of two-step oxidation of copper sulfides into various oxosulfates. The mass increase continues further on until 580 °C, when the sample mass begins to decrease slowly, as a continuous decomposition of the intermediate copper oxosulfates, indicated also by re-evolution of SO₂. At 1,000 °C, a residual mass value of 64.3% represents a stoichiometric formation of Cu^IIO and anhydrous Na₂SO₄.     

Evolved gas analysis of amorphous precursors for S-doped TiO2 by TG-FTIR and TG/DTA-MS

Thermal decomposition of an amorphous precursor for S-doped titania (TiO₂) nanopowders, prepared by controlled sol–gel hydrolysis–condensation of titanium(IV) tetraethoxide and thiourea in aqueous ethanol, has been studied up to 800 °C in flowing air. Simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) have been applied for analysis of released gases (EGA) and their evolution dynamics in order to explore and simulate thermal annealing processes of fabrication techniques of the aimed S:TiO₂ photocatalysts with photocatalytic activities under visible light. The precursor sample prepared with thiourea, released first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 240 °C in two stages, ammonia (NH₃) from 170 to 350 °C in three steps, and organic mater (probably ether and ethylene) between 140 and 230 °C. The evolution of CO₂, H₂O and SO₂, as oxidation products, occurs between 180 and 240 °C, accompanied by exothermic DTA peaks at 190 and 235 °C. Some small mass gain occurs before the following exothermic heat effect at 500 °C, which is probably due to the simultaneous burning out of residual carbonaceous and sulphureous species, and transformation of amorphous titania into anatase. The oxidative process is accompanied by evolution of CO₂ and SO₂. Anatase, which formed also in the exothermic peak at 500 °C, mainly keeps its structure, since only 10% of rutile formation is detected below or at 800 °C by XRD. Meanwhile, from 500 °C, a final burning off organics is also indicated by continuous CO₂ evolution and small exothermic effects.     

Crystallization of Anodic Alumina Membranes Studied by Simultaneous TG-DTA/FTIR

The thermal change of anodic alumina (AA), particularly the exothermic peak followed by the endothermic peak at ca 950°C was studied in detail by mainly using simultaneous TG-DTA/FTIR. The gradual loss of mass up to ca 910°C is attributed to dehydration. When heated at a constant rate by using TG-DTA, an exothermic peak with subsequent endothermic peak is observed at ca 950°C, but the exothermic peak becomes less distinct with decreasing heating rate. It has been found that gaseous SO₂ accompanying a small amount of CO₂ is mainly discharged at this stage. The reaction in this stage can be considered roughly in two schemes. The first scheme can be said collectively as crystallization, in which the migration of S or C trapped inside the crystal lattice of the polycrystalline phase (γ-, δ-, and θ-Al₂O₃, which presumably accompanies a large amount of amorphous or disordered phase) occurs. In the second scheme, the initial polycrystalline (+amorphous) phase crystallizes into a quasi-crystallineγ-Al₂O₃-like metastable phase after amorphization. Conclusively,after the distinct exo- and endothermic reactions, the amorphous phase crystallizes intoγ-Al₂O₃, presumably accompanying small amount of δ-Al₂O₃. It is also found that, when maintained isothermally, the metastable phases undergo transformation into the stable α-Al₂O₃ at 912°C. This revised version was published online in July 2006 with corrections to the Cover Date.