Effects of heating rate, temperature and iron catalysis on the thermal behaviour and decomposition of 2-nitrobenzoyl chloride

Runaway reactions arising from the decomposition of thermally unstable materials are a concern in industry due to the potentially devastating effects that they yield. Studies into the occurrence of thermal runaway incidents have shown the most likely cause to be a result of an inadequate investigation of the process prior to its operation on a large-scale. The chlorination of ortho-nitrated carboxylic acids is an industrially important reaction in the fine and agrochemical industries. The products of these reactions, ortho-nitrated acid chlorides, have been involved in runaway incidents that have resulted in violent explosions; hence, their thermal stability must be studied. Previous studies [S.D. Lever, M. Papadaki, Study of condition-dependent decomposition reactions: the thermal behaviour and decomposition of 2-nitrobenzoyl chloride, Part I, J. Hazard. Mater. 115 (2004) 91-100] showed that the decomposition of the parent molecule, 2-nitrobenzoyl chloride, is highly condition-dependent with the sample heating rate and temperature of decomposition playing a preponderant role in the course of the decomposition. Here, we present the results of studies of the decomposition of 2-nitrobenzoyl chloride, when the sample is subjected to various heating treatments, temperatures and in the presence of iron. As the temperature of decomposition was increased from 150 to 162 degrees C, the heat of decomposition was reduced from -215 to -90 kJ/mol. As the heat up rate applied in bringing the sample to the decomposition temperature increased, the heat of decomposition also increased. An increase in the heat up rate from 2 to 7.5 degrees C/min resulted in an increase in the heat of decomposition from -90 to -215 kJ/mol. The presence of iron and silver was observed to lower the heat of decomposition from -185 to -160 and -110 kJ/mol, respectively. Under most conditions investigated, the temperature at which gas flow was initiated was 147-150 degrees C. The presence of iron reduced this temperature to 140 degrees C. Decomposition was observed to take place over two stages, where the sample was heated directly from 40 degrees C at the required heat up rate. Where the sample was heated in stages and where calibrations had been carried out preceding decomposition, the decomposition took place in one stage alone.     

The relationship between thermal decomposition properties of titanium hydride and the Al alloy melt foaming process

Using a new temperature programmed decomposition (TPD) theory and related experimental technique, a set of thermal decomposition kinetics equations of titanium hydride can be acquired by separating and simulating its TPD spectrum. According to these equations, the relation curve of decomposition quantity and time for titanium hydride at temperature of 940 K is obtained and the result coincides well with the Al alloy melt foaming process, which provides a scientific basis for controlling the Al alloy melt foam and then the Al alloy foams with different pore structure are successfully prepared.     

氧化处理对Ti2分解特性及组织结构的影响

针对制备泡沫铝异型件的熔体路径发泡先驱体二次发泡工艺,对TiH2的氧化处理、变温分解特性、等温分解特性、组织结构进行了研究.研究表明:氧化处理可有效提高发泡剂的开始分解温度,随氧化处理温度的提高,开始分解温度提高;氧化处理后发泡剂的等温分解曲线由低分解平台、快速分解阶段和稳定分解阶段3部分组成,低分解平台随氧化处理温度的提高而延长;400℃/6h+500℃/1h+620℃/30s的处理,可使TiH2的分解量较400℃/6h+500℃/1h处理时有所提高;TiH2氧化处理后在其表面生成了厚约1.1~1.5μm的TixOy致密氧化层,TiH2在300~550℃氧化,其物相依次变化为:TiH1.97—TiH1.97+TiO2—TiH+TiO+TO—TiH+TiO+TO+TiH.     

Effect of TiH2 particle size distribution on aluminum foaming using the powder metallurgy method

TiH₂ decomposes over a range of temperatures strongly influenced by diverse factors including particle size. In the present research, a systematic study of the dehydrogenation behavior of TiH₂ powder of different particle size distribution was undertaken with the aid of thermogravimetric analysis. The effect of this parameter on aluminum foaming was evaluated. It was found that when TiH₂ exceeds a critical particle size (around 50 μm), dehydrogenation occurs as a single desorption event with onset temperatures around 500 °C. The reduction of particle size, besides reducing the onset of hydrogen release, decreases the dehydrogenation rate. As a result, the first dehydrogenation event gets sharper and tends to overlap with the second with increasing particle size. The use of selected powders on foaming showed that the final foam expansion and porosity features, such as pore size, pore density, and homogeneity are largely influenced by the particle size distribution of the foaming powder. TiH₂ of the largest particle size was the most suitable for foaming pure aluminum.     

Effect of heating rate on porous TiAl-based intermetallics synthesized by thermal explosion

TiAl-based porous materials were synthesized by a novel process of thermal explosion (TE) reaction. The effects of heating rate on the expansion behavior of powder assemblies, phase compositions, and pore structures were investigated. Results showed that the actual temperature of specimen increased rapidly from 655 to 661°C (furnace temperature) to 1018–1136°C (combustion temperature) in a short time interval of 25–55?s, indicating that an obvious TE reaction occurred at different heating rates (1, 2, 5, and 10°C min^?1). TE reaction in Ti/Al powder assemblies resulted in the formation of open-celled TiAl-based intermetallics. When the heating rate was set at 5°C min^?1, the maximum open porosity of 59% was obtained in Ti-Al bodies, which experienced the highest combustion temperature (1136°C) and underwent maximum volume expansion (48%). The pore size distribution was uniform and pores were interconnected in TE products.     

Effect of air in the thermal decomposition of 50 mass% hydroxylamine/water

This paper presents experimental measurements of 50 mass% hydroxylamine (HA)/water thermal decomposition in air and vacuum environments using an automatic pressure tracking adiabatic calorimeter (APTAC). Overall kinetics, onset temperatures, non-condensable pressures, times to maximum rate, heat and pressure rates versus temperature, and mixture vapor pressures for the experiments in vacuum were similar when compared to the corresponding data for HA decomposition in air. Determined was an overall activation energy of 119+/-8 kJ/mol (29+/-2 kcal/mol), which is low compared to 257 kJ/mol (61.3 kcal/mol) required to break the H(2)N-OH bond reported in the literature. The availability of oxygen from air did not affect detected runaway decomposition products, which were H(2), N(2), N(2)O, NO, and NH(3), for samples run in vacuum or with air above the sample. A delta H(rxn) of -117 kJ/mol (28 kcal/mol) was estimated for the HA decomposition reaction under runaway conditions.     

Effect of heating temperature and magnesium content on the thermal cyclic failure behaviour of ductile irons

Abstract

This study elucidates the effect of residual magnesium content and heating temperature on the thermal cyclic failure behaviour of ductile irons by applying repeated heating and cooling cycles. Five irons with different residual magnesium contents ranging from 0.038 to 0.066 wt-% were obtained by controlling the amount of nodulariser additions. The thermal fatigue cracking behaviour was investigated during thermal cycling from 25°C to 650, 700, 750, and 800°C, respectively. Experimental results indicate that the thermal fatigue cracking resistance of ductile iron decreases with increasing residual magnesium content. The maximum heating temperatures of 700°C and 750°C led to the most severe thermal fatigue cracking in the specimens containing 0.054 wt-% and 0.060 wt-% residual magnesium content. Recrystallisation of ferrite grain occurred when the thermal cycles exceeded a certain number after testing at 800°C, which deferred the initiation of thermal fatigue cracking.     

Study of condition-dependent decomposition reactions; Part I. The thermal behaviour and decomposition of 2-nitrobenzoyl chloride

The risks associated with batch processing in the manufacture of chemicals and pharmaceuticals via highly exothermic reactions are of special interest due to the possibility of runaway reactions. o-Nitrated benzoyl chlorides are intermediates in the production of agrochemicals and are produced via the reaction of o-nitrated carboxylic acids with thionyl chloride in a solvent mixture. ortho-Nitrated acyl chlorides have exploded violently on attempted distillation on numerous occasions. An inadequate investigation of the process prior to large-scale operation is the most likely cause. Here we present preliminary results of studies on the decomposition of 2-nitrobenzoyl chloride. This study has revealed that the decomposition reaction is strongly condition dependent. The heating rate of the sample plays a preponderant role in the course of the decomposition reaction. That renders the interpretation of differential scanning calorimetry (DSC) or adiabatic calorimetry measurements, which are routinely used to assess the thermochemistry and safety of the large-scale reactions, problematic. Following this on-going study, we report here key features of the system that have been identified.     

Scalable preparation of carbon nanotubes by thermal decomposition of phenol with high carbon utilizing rate

Practical application of carbon nanotube would have to be determined by a matter of its economical and large-scale preparation. In this study, phenol was used as carbon resource to fabricate carbon nanotubes with large scale in home-made chemical vapor deposition setup. The as-prepared carbon nanotubes are of multi-walls with bamboo compartments, and of having a limited distribution in diameter of 10-15 nm and length of several decades μm. In particular, in this preparation the carbon transformation rate from the carbon content in used phenol to carbon nanotubes is 75%, much higher than the previous reports. Hence this work would be of significance for the industrial preparation of carbon nanotubes even their practical applications.     

Effects of nano-Fe2O3 powder on thermal emission property of microarc oxidation coating on titanium alloy

Abstract

A ceramic coating was formed on the titanium alloy by microarc oxidation in an electrolyte containing nano-Fe₂O₃, emulsifier OP-10 and sodium phosphate. The composition, surface and cross-sectional morphology and the element compositions of the coatings were characterised by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis system. The spectral emissivity of the coatings was measured by a Fourier transform spectrometer apparatus. The bonding strength between the coating and the titanium alloy was studied by tensile strength test. The thermal shock resistance of the coatings was also evaluated. The results showed that nano-Fe₂O₃ was incorporated into the coating, and the coating had high emission at the wavelength range of 3–20 μm. The bonding strength was 33·2 MPa, and after being subjected to severe thermal shocking for 50 cycles, little peeling-off of the coating occurred.     

高能球磨对碱式碳酸锌热分解活化能的影响

采用行星式球磨机对碱式碳酸锌进行湿法研磨,研究不同球磨工艺条件下,碱式碳酸锌颗粒形态、大小及分解活化能的变化;产物采用SEM、XRD、TG和DSC等进行分析表征。结果表明:球磨时间对碱式碳酸锌的颗粒大小形态及热分解活化能影响显著,球料比为10∶1(质量比),转速为200r/min,占物料质量64%的乙醇控制剂作用下,高能球磨6 h后,颗粒形态大小由粒径为50μm的片状变为粒径为50nm的等轴状,球磨至24h时,颗粒形态大小并没有进一步缩小;热分解活化能在球磨24h后由138.0 kJ·mol-1减少到112.4 kJ·mol-1,热分解的温度前推了14.8℃。     

Effect of thermal oxidation on titanium oxides' characteristics

Nanocrystalline TiO₂, in the form of anatase or rutile, is one of the most important and used photocatalysts because of its excellent conversion efficiencies and its chemical stability. TiO₂ layers can be grown on titanium by means of anodising processes: the so-obtained oxides present either amorphous or semicrystalline structure, depending on process parameters. When a homogeneous oxide with maximum thickness of the order of hundreds of nanometres is formed, a wide range of interference colours appear on the oxide surface, showing different hues and saturations. Similar effects are obtained when the oxidation process consists of a thermal treatment. This work is aimed at the exploration of the parameters involved in thermal oxidation and of their influence on the growing oxide characteristics, with particular reference to its thickness and the contingent generation of crystal phases (anatase and rutile) responsible for photoinduced properties. Oxide characteristics are investigated by means of reflectometry and X-ray diffraction. Thermal treatments proved to be an efficient way to tune oxide thickness and structure, in order to achieve the formation of oxides showing photoactivated properties both in the UV and in the visible light range, as well as to tune their chromatic properties.     

Effects of aluminium powder content and cold rolling on foaming behaviour of xAlp/Al5Si4Cu4Mg/0.8TiH2 composites

Abstract

Aluminium foams were produced by applying powder metallurgy technology. The process began by making aluminium powder and mixing it with alloy powder (Al5Si4Cu4Mg) and foaming agent (TiH₂). The mix was compacted to the form of a billet by cold pressing and then it was hot extruded to a dense foamable strip, which was cold rolled to give 40% thickness reduction. The resulting precursor composites of both the extruded strip and the extruded plus rolled strip were then freely foamed without a mould at a constant temperature of 700°C for different foaming times. The effects of aluminium powder content and cold rolling on the foaming characteristics of the foamable composite strip were studied. It is noted that aluminium powder fibre in the extruded composite strip acts as a barrier to pore initiation and evolution due to the higher melting point of pure aluminium fibre than that of the alloy matrix. Cold rolling promotes foaming of the composite strip due to the TiH₂ cracking and debonding between TiH₂ particles and metal matrix. The morphological and microstructural evolution of composite foams was also investigated. The foaming mechanism can be described by the following sequence: cracklike pore nucleation between elongated powder fibres; ellipsoidal, spherical, and polygonal pore growth; and the collapse of pores as a result of coalescence.     

升温速率和烧结温度对纳米晶MnZn粉体直接制备功率铁氧体性能的影响

采用纳米晶粉体直接造粒压制成块材烧结的方法制备MnZn铁氧体,研究了不同的升温速率和烧结温度对样品微观结构、磁性能的影响。研究表明,与传统的制备方法相比,直接烧结纳米晶MnZn铁氧体粉体,可以降低烧结温度。采用低的升温速率有利于提高样品的密度和初始磁导率,降低比损耗因子,并且低温烧结可以形成良好的微观结构和磁性能。