Adiabatic calorimetric decomposition studies of 50 wt.% hydroxylamine/water

Calorimetric data can provide a basis for determining potential hazards in reactions, storage, and transportation of process chemicals. This work provides calorimetric data for the thermal decomposition behavior in air of 50wt.% hydroxylamine/water (HA), both with and without added stabilizers, which was measured in closed cells with an automatic pressure tracking adiabatic calorimeter (APTAC). Among the data provided are onset temperatures, reaction order, activation energies, pressures of noncondensable products, thermal stability at 100 degrees C, and the effect of HA storage time. Discussed also are the catalytic effects of carbon steel, stainless steel, stainless steel with silica coating, inconel, titanium, and titanium with silica coating on the reaction self-heat rates and onset temperatures. In borosilicate glass cells, HA was relatively stable at temperatures up to 133 degrees C, where the HA decomposition self-heat rate reached 0.05 degrees C/min. The added stabilizers appeared to reduce HA decomposition rates in glass cells and at ambient temperatures. The tested metals and metal surfaces coated with silica acted as catalysts to lower the onset temperatures and increase the self-heat rates.     

Thermal decomposition hazard evaluation of hydroxylamine nitrate

Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family and it is a liquid propellant when combined with alkylammonium nitrate fuel in an aqueous solution. Low concentrations of HAN are used primarily in the nuclear industry as a reductant in nuclear material processing and for decontamination of equipment. Also, HAN has been involved in several incidents because of its instability and autocatalytic decomposition behavior. This paper presents calorimetric measurement for the thermal decomposition of 24 mass% HAN/water. Gas phase enthalpy of formation of HAN is calculated using both semi-empirical methods with MOPAC and high-level quantum chemical methods of Gaussian 03. CHETAH is used to estimate the energy release potential of HAN. A Reactive System Screening Tool (RSST) and an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC) are used to characterize thermal decomposition of HAN and to provide guidance about safe conditions for handling and storing of HAN.     

聚丙烯的热分解与超临界水分解对比实验研究

为了寻求一种更为有效的聚合物分解回收方法，采用热分解和超临界水分解方式对聚丙烯(PP)的分解行为和分解产物进行了对比实验研究，并利用红外光谱、热分析仪等分析手段对反应残留物进行分析，用气相色谱和质谱对液相成分进行表征．结果表明：在反应温度为420℃的条件下，PP经热分解全部转化成液体油状物，而超临界水分解只有63％的分解率，反应较热分解进程缓慢；超临界水分解时，压力越高，PP分解率越低；压力的存在对于某些小分子分解产物的生成有一定的抑制作用。     

Effect of the partial pressure of water vapour on the thermal decomposition of γ-FeOOH and on the dispersity of the solid decomposition products

The thermal decomposition of pureγ-FeOOH in air flow has been studied at a water vapour partial pressure of 1 X 10⁻³ to 20 mm Hg. The specific surface areas of the decomposition products (γ-Fe₂O₃ andα-Fe₂O₃) have been found to decrease with increasing partial pressure. It has been also established that the increase in partial pressure of the water vapour accelerates the transformation ofγ-Fe₂O₃ intoα-Fe₂O₃.     

Decomposition of hydroxylamine/water solution with added iron ion

Decomposition hazards of hydroxylamine (HA)/water solution with and without the addition of iron ion were studied in this paper. Tests were conducted to obtain information about decomposition hazards of HA/water solution following the United Nations recommendations on the transport of dangerous goods.When the heat accumulation storage test was conducted using HA50 wt.%/water solution without the addition of iron ion, the self-accelerating decomposition temperature (SADT) was 80 degrees C. Therefore, HA50 wt.%/water solution was not classified with self-reactive substances following the United Nations recommendations on the transport of dangerous goods. Decomposition hazards of HA50 wt.%/water solution with added iron ion were investigated. The concentration of iron ion in sample of HA50 wt.%/water solution without the addition of iron ion was below 1.0 ppm. The range of the concentration of iron ion in sample of HA50 wt.%/water solution with added iron ion was between 1.0 and 5.4 ppm. The thermal stability of HA50 wt.%/water solution decreased by the addition of iron ion in the heat accumulation storage test. HA50 wt.%/water solution with the addition of iron ion was classified with self-reactive substances following the United Nations recommendations on the transport of dangerous goods. The intensity of the thermal decomposition of HA50 wt.%/water solution increased by the addition of iron ion in the Koenen test.     

Calorimetric study on the decomposition of hydroxylamine in the presence of transition metals

Hydroxylamine (HA), hydroxylamine chloride (HAC1), and hydroxylamine nitrate (HAN) were each mixed with aqueous solutions of Cr3+, Cr6+, Mn7+, Co2+, Co3+, and Cu2+, and their heat flow profiles were monitored by a small-scaled reaction calorimeter, SuperCRC. These mixing tests demonstrated that HA was less reactive than HACl and HAN with Mn7+ and Cr6+. Their UV-vis spectra confirmed that the substrates reacted when Mn7+ and Cr6+ were reduced. HA was more reactive with Cu2+ than HAC1 and HAN and exhibited the highest reactivity among the three substrates with regard to metals in the intermediate oxidation states: Cr3+, Co3+, and Co2+. During the reaction of HA and Co3+, an induction period was observed. All exothermic reactions were accompanied by precipitation or a change in the UV-vis spectra.     

Effect of high heating rate on thermal decomposition behaviour of titanium hydride (TiH2) powder in air

DTA and TGA curves of titanium hydride powder were determined in air at different heating rates. Also the thermal decomposition behaviour of the aforementioned powder at high heating rates was taken into consideration. A great breakthrough of the practical interest in the research was the depiction of the P _H2-time curves of TiH ₂ powder at various temperatures in air. In accordance with the results, an increase in heating rate to higher degrees does not change the process of releasing hydrogen from titanium hydride powder, while switching it from internal diffusion to chemical reaction. At temperatures lower than 600 °C, following the diffusion of hydrogen and oxygen atoms in titanium lattice, thin layers TiH _x phase and oxides form on the powder surface, controlling the process. On the contrary, from 700 °C later on, the process is controlled by oxidation of titanium hydride powder. In fact, the powder oxidation starts around 650 °C and may escalate following an increase in the heating rate too.     

Effect of nitrate content on thermal decomposition of nitrocellulose

Data on the thermal stability of energetic materials such as nitrocellulose was required in order to obtain safety information for handling, storage and use. In the present study, the thermal stability of four nitrocellulose samples containing various amount of nitrate groups was determined by differential scanning calorimetery (DSC) and simultaneous thermogravimetery-differential thermal analysis (TG-DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the nitrocellulose occurs in the temperature ranges of 192-209 degrees C. On the other hand, the TG-DTA analysis of compounds indicates that nitrate content of nitrocellulose could has affect on its thermal stability and its decomposition temperature decrease by increasing its nitrogen percent. The influence of the heating rate (5, 10, 15 and 20 degrees C/min) on the DSC behaviour of the nitrocellulose was verified. The results showed that, as the heating rate was increased, decomposition temperature of the compound was increased. Also, the kinetic parameters such as activation energy and frequency factor for the compound was obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa.     

树枝状纳米钴微晶对高氯酸铵热分解的影响

采用化学还原法制备了纳米钴微晶,并对产物进行了XRD、SEM、TEM和EDAX表征,结果表明,纳米钴微晶呈树枝状、结晶度高、颗粒尺寸均匀;运用DTA分析研究了纳米钴微晶对AP分解的催化性能,结果显示AP的高低温放热峰相连且合并成一个高而大的放热峰,峰温最大幅度降低了180℃,表观分解热显著增大.表明纳米钴微晶对AP热分解有着极强的催化活性.     

On the thermal decomposition of acrylic copolymer/ nitric acid liquors

The hazards of the ASAHI process for the wet-spinning of an acrylic copolymer (90% by weight polyacrylonitrile and 10% by weight methylacrylate) by watThe experimental program has been performed using a Sikarex-3 adiabatic calorimeter, for initial temperatures up to 50°C and acrylic copolymer concenThe experiments have shown that, at the highest PAN concentrations, self-heating of the liquors occurs even when starting from ambient temperature, proA two step reaction mechanism has been tentatively proposed. During the first step, reactive intermediates are formed through a slightly exothermic rea     

Effect of nonequilibrium decomposition on the thermal regime of composite ablative coatings

The decomposition of an ablative material under a refractory facing forward reaction: is examined for an arbitrary reaction regime. It is shown that the decomposition rate can be calculated from well-established equilibrium parameters.     

Effect of pulsed magnetic field on the thermal decomposition of zirconium hydroxide

An applied magnetic field was found to raise the rate and reduce the temperature of the dehydration, dehydroxylation, and crystallization of zirconium hydroxide. The role of water in the crystallization and aggregation of zirconium hydroxide was examined.     

Comparative analysis of polychlorinated biphenyl decomposition processes in air or argon (+oxygen) thermal plasma

Thermal plasmas may solve one of the biggest toxic waste disposal problems. The disposal of polychlorinated biphenyls (PCBs) is a long standing problem which will get worse in the coming years, when 180000 tons of PCB-containing wastes are expected to accumulate in Europe (Hot ions break down toxic chemicals, New Scientist, 16 April 1987, p. 24.). The combustion of PCBs in ordinary incinerators (at temperature T approximately 1100 K, as measured near the inner wall of the combustion chamber (European Parliament and Council Directive on Incineration of Waste (COM/99/330), Europe energy, 543, Sept. 17, 1999, 1-23.)) can cause more problems than it solves, because highly toxic dioxins and dibenzofurans are formed if the combustion temperature is too low (T<1400 K). The paper presents a thermodynamic consideration and comparative analysis of PCB decomposition processes in air or argon (+oxygen) thermal plasmas.     

硝酸异丙酯对双基推进剂的热分解性能影响研究

为研究云爆剂中硝酸异丙酯渗露对双基推进剂的热分解性能影响,采用加速量热仪(ARC)对双基推进剂在加入硝酸异丙酯环境下的热分解情况进行测试,得到其绝热分解的温度、压力时间曲线,利用速率常数法计算出样品的活化能和指前因子等动力学参数。研究发现在加入硝酸异丙酯后,双基推进剂的起始热分解温度升高,表观活化能变大,表明硝酸异丙酯会提高双基推进剂的热稳定性。     

Effect of compaction on the kinetics of thermal decomposition of dolomite under non-isothermal condition

Many workers [1–9] studied the kinetics of dolomite decomposition to study the effects of different parameters like, gas (CO₂, N₂ etc.) pressures, water vapor, presence of other impurities, particle size and grain size of the dolomite samples, crystallinity etc. on the decomposition kinetics of dolomite using different tools like, thermal analysis, thermo-gravimetric analyses, XRD technique etc. and different values of the activation energies for the decomposition reaction, order of reactions have been reported. It has been observed that pure dolomite decomposed in only two steps. The first stage of the thermal decomposition of dolomite resulted in the formation of Mg-calcite [(CaMg)CO₃] and periclase (MgO), with the liberation of CO₂. It was further observed that under CO₂, dolomite decomposed directly to CaCO₃, accompanied by the formation of MgO between 550 and 765^∘C. Calcite decomposed to CaO between 900 and 960^∘C and under air, simultaneous formation of CaCO₃, CaO and MgO accompanied dolomite decomposition between 700 and 740–750∘C. At the latter temperature, the calcite began to decompose even though a significant amount of dolomite was still present and simultaneous decomposition of the two carbonates was terminated at 780^∘C. Also, changes in decomposition rates of the various phases correlated with changes in the rate of weight loss determined by derivative thermo-gravimetric analysis.     

空气/水界面上的棕榈酰胺单分子膜

天空了棕榈酰胺单分子膜在空气／水界面上的性质，及其在抑制水面蒸发方面的作用，研究表明，在曙下棕榈酰 单个膜呈液态凝聚膜状态，能够显著降水的蒸发速率，棕榈酰胺阻止水蒸发的能力比相同碳锭长的直链脂肪酸，醇要强。     

Collapse in binary phospholipid monolayers at the air/water interface

The behavior in the stochastic collapse of lipid monolayers of a 7:3 mixture of DPPC (dipalmitoylphosphatidylcholine) and POPG (palmitoyloleoylphosphatidylglycerol), a model system of pulmonary surfactant assembly, was studied using Langmuir isotherms, fluorescence microscopy, and atomic force microscopy. The monolayers at the air-water interface appeared to be phase separated under compression and retained the continuous liquid-expanded phase network surrounding islands of condensed phase even at a surface pressure approaching 70 mN/m. When the two-dimensional monolayers were compressed beyond the equilibrium surface pressure, they collapsed and assumed a three-dimensional formation. Collapse events involved folding of the monolayer on a micron scale, and each event produced a macroscopic jerk of the layer. The distribution of waiting times between events was estimated to be an exponential function, indicating that the events were independent. Folded regions coexisted with the flat monolayer, remained attached to the interface, and reversibly reincorporated into the monolayer upon expansion.     

纳米MgO对六氟丙烷热分解性能影响及机理研究

研究了纳米MgO在管式反应器中对六氟丙烷热分解性能的影响,用在线气相色谱（GC）、气相色谱-质谱（GC-MS）、离子色谱仪（IC）对热分解气体进行分析,采用X射线衍射仪（XRD）及X射线光电子能谱仪（XPS）对作用前后的纳米MgO晶型和组成进行表征。研究表明,六氟丙烷高温热分解时主要发生脱氟化氢（HF）的反应。在空管中随着反应温度的增加,六氟丙烷的分解率提高,而加入纳米MgO后六氟丙烷分解率均增大,在700℃时,六氟丙烷的分解率由空管时的23.9%增加到100.0%,同时热分解气体中HF的含量比空管时降低了42.4%。XRD及XPS结果表明,作用后的纳米MgO是MgO和MgF2的混合物。分析作用机理认为是部分纳米MgO与六氟丙烷热分解产生的HF进行反应生成MgF2,MgF2催化六氟丙烷发生脱HF反应。     

Low-cost thermal /spl Sigma/-/spl Delta/ air flow sensor

This paper describes the design and optimization of a hot-wire air flowmeter. A low-cost design of the packaging allows good thermal contact with the airflow, as well as good thermal isolation between the hot and cold points. It is a compact solution which allows easy PCB mounting and adaptation to standard-size small air pipes. The design has been optimized for low-cost applications. The sensor is read out by a thermal sigma-delta modulator. The dynamic range of this modulator has been extended by adding a constant power offset to its output. The fractal nature of the modulator response at low-clock frequencies is also experimentally shown.     

The thermal decomposition of dimethoate.

The thermal decomposition of dimethoate, an organophosphorus pesticide, has been studied with the aim at assessing the reaction kinetics, the energy released during the process and the decomposition products. Dimethoate shows a marked tendency to undergo thermal decomposition at temperature higher than 369 K. A moderate pressure increase has been recorded at the end of all runs. Many thiophosphoric compounds have been identified among the decomposition products.