Explosive vaporization in microenclosures

The explosive vaporization of a liquid above planar microheaters induces a fast increase of pressure that is exploited in many thermally driven actuators in MEMS components such as ink jet printer cartridges, pumps, valves and optical switches. Some of these components need to enclose the working fluid as it is the case of valves in which the heated liquid is separated from the flow that it regulates by a flexible membrane. To achieve a better insight into the thermodynamic processes involved, the present work investigates experimentally an enclosed microsystem designed and fabricated for this purpose, composed of a small liquid volume (8 nL) heated by a electric pulse for 2 μs supplied to a planar microfabricated heater. During the heating, the temperature-induced change in resistance can be determined by imposing a defined current and measuring the voltage drop over the heater. While the chip is based on a silicon substrate with integrated platinum heaters and sensors, the structure enclosing the fluid (cavity and fluidic access to it) is made of a silicone elastomer, poly(dimethylsiloxane) (PDMS). This transparent material is widely used in microfluidics and allows for flexible and transparent walls that can be deflected by increasing the pressure inside the cavity. To seal the system the inlet and the outlet were closed by blocking them with a metallic stab. In the present work we visualize vaporization of isopropanol in contact with a suddenly heated planar resistor for two different cavity heights, 150 μm and 16 μm. The rate of temperature rise of the thin liquid layer in contact with the heater is of the order of 10⁷ K s⁻¹ for a pulse duration of 2 μs. We compare bubble growth and collapse for the open and closed systems. Compared to the open system, the bubble growth in the closed system is considerably damped.     

Detection of explosives in traces by laser induced breakdown spectroscopy: Differences from organic interferents and conditions for a correct classification

With the aim to study and to improve LIBS capability for detecting residues of energetic compounds in air surrounding, nine types of explosives and some potential interferents, placed in small quantities on a metallic support, were interrogated by a laser. Shot-to-shot behavior of the line intensities relative to the sample constituents was studied. The detected plasma was not stoichiometric and the line intensities, as well as their ratios, were changing even for an order of magnitude from one sampling point to another, particularly in the case of aromatic compounds. We explained some sources of such LIBS signal's behavior and this allowed us to establish a data processing procedure, which leads to a good linearization among the data sets. In this way, it was possible to determine some real differences between the LIBS spectra from explosives and interferents, and to correlate them with molecular formulas, with some known pathways for the molecule's decomposition and with successive chemical reactions in the plasma. Number spectral parameters, which distinguish the each studied explosive from other organic materials, were also determined and compared with previously published results relative to percentages of correct classifications for the same explosives. Experimental conditions for reliable recognition of the explosives by LIBS in air are also suggested, together with the parameters that should be considered or discarded from the classification procedure.     

Determination of explosives based on novel type of sensor using porphyrin functionalized carbon nanotubes

The hydroxide of meso-tetraphenylporphyrin derivatives functionalized carbon nanotubes (CNTs) was fabricated in our research to explore the interaction between porphyrin and explosive. It was turned out that in the formation of grid porphyrin film, carbon nanotubes as a cruciul base materials promoted the electron transfer rate. Most of important, the results also showed that the electrochemical response was enhanced through increasing the number of -OH substitution in porphyrin. Such information provides the platform for a practical strategy for rational design of the sensor of explosives.     

Analytical techniques in the study of highly-nitrated nitrocellulose

This work presents an updated overview of the analytical techniques used to study highly-nitrated nitrocellulose, which is used in explosives and is of forensic interest. Most articles published in the past decade were designed:(1) to investigate polymeric parameters of nitrocellulose (e.g., molar mass distribution, viscosity and specific refractive index) by size-exclusion chromatography;(2) to determine the morphological and thermal characteristics of nitrocellulose using thermal and spectroscopic techniques; and,(3) to study the thermal, biological and mechanical degradation of nitrocellulose by thermal, spectroscopic, and mass spectrometric (MS) techniques, alone or coupled to gas chromatography.However, the few papers that focused on the determination of nitrocellulose used in explosives employed analytical techniques [e.g., vibrational techniques (infrared and Raman spectroscopy), MS and ion-mobility spectrometry (IMS) and liquid chromatography (LC) (high-performance LC and ion chromatography)]. Most of the information reported by these techniques has been qualitative. Only quantitative determination of nitrocellulose or its nitrogen content has been performed by measuring the nitrite and/or nitrate ions released from its basic hydrolysis.     

炸药爆轰瞬态温度的光谱法测定

在双谱线原子发射光谱测温原理的基础上,设计了对炸药爆轰的瞬态温度进行实时测量的光纤光谱测试系统,利用光学纤维将炸药爆轰的光谱信号传入测光系统,用多通道数据采集器处理数据,系统的时间分辨率可高达0.1μs,所选择的两条谱线的波长分别为CuI 510.5和CuI 521.8nm,为炸药爆温的测量提供了一种简单有效的方法。利用该测温系统,通过对炸药爆轰光谱的测量,获得了实时瞬态爆轰温度-时间分布曲线。     

炸药爆温的光纤测温法测量

本文阐述了光纤测温技术依据的原理，给出了多通道瞬时光纤测温装置的构成利用该装置对液体炸药硝基甲烷的实际爆轰温度及其光谱发射率进行了实验测量，结果分别为３７００±１００（Ｋ）和０７１±０１５     

Selected Nitrocarbamates of Glycerine & Co. and the First Acetylene Derivative

A simple two step synthesis route for the preparation of several energetic multivalent nitrocarbamates of easily available alcohols is presented. The carbamates were obtained by the reaction of the alcohols and the reactive reagent chlorosulfonyl isocyanate (CSI) with subsequent aqueous work‐up. The nitration of the carbamates was performed with mixed acid (nitric and sulfuric acid). The thermal stabilities were explored by using differential scanning calorimetry and the energies of formation were calculated on the CBS‐4M level of theory, as well as several detonation and propulsion parameters for the application as energetic materials. All compounds were fully characterized and discussed in addition with single X‐ray diffraction.     

多波段微量TNT成像探测的数值分析和实验研究

建立了CO2激光器辐照微量爆炸物温升分布三维模型,对激光辐照过程和冷却过程中8~14μm和3~5μm波段内的目标表面辐射温度变化特性分别进行分析.利用设计的探测系统对目标进行初步探测,用8~14μm和3~5μm热像设备对目标进行观察分析.研究表明:在10.6μm激光照射过程中,8~14μm波段内沾有TNT目标的辐射温度分别由TNT、基底在8~14μm波段的发射率和对激光辐照的反射率共同决定;在3~5μm内目标辐射温度主要由TNT、基底在3~5μm波段的自身发射率决定.在探测过程中,8~14μm波段内沾染TNT区域的辐射温度明显高于周围区域,而在3~5μm波段内,目标表面辐射温度整体下降,并且沾染区域的辐射温度变得低于周围.     

直接紫外光度法测定炸药废水中TNT含量

炸药废水中的主要成分是 2 ,4 ,6 -三硝基甲苯 (TNT) ,组成比较单一 ,不含有其他有机物。 TNT水溶液在紫外区有特征吸收 (2 30 nm) ,可用分光光度法直接测定。不引入其他试剂 ,无引入误差 ,与国标方法(GB/ T1 390 5 - 92 )比较 ,有良好的准确度 ,方法操作简单易行。但本法不适宜组成复杂的有机废水测定