MHz-rate laser absorption spectroscopy for temperature and N2O concentration measurements in laser-induced ADN propellant decomposition

Thermal and photoinduced decomposition of W(CO) 6 on W(110)

The decomposition of ethylene by pulsed, unfocussed CO2-laser radiation has been studied at pressures from 500 to 3000 Torr, using the P(14) line of the 10.6μm band (v=949.48cm−1) at incident fluences from about 0.1 to 1.0J/cm2. Major products in order of decreasing importance were 1,3-butadiene, acetylene, ethane, propane, 1-butene and methane. These are known products of the thermal free-radical chain decomposition, and it is concluded that the laser-induced decomposition under our conditions is a transient bulk thermal reaction occurring in a thin disc of heated gas close to the entrance window of the reaction vessel at temperatures ranging from about 1000 to 1500K. As in the thermal decomposition, cyclobutane was observed to be a minor product, which in a sequence of laser pulses approached a final constant concentration. The possibility that this corresponded to an equilibrium concentration at some “effective” reaction temperature was explored. Computer simulation was used to model the accumulation of cyclobutane in the system, both in a single pulse and in a sequence of pulses, and predictions of this model were compared with experiment. It was concluded that cyclobutane could be used in this way as an approximate internal thermometer, within certain limits. Mechanisms of formation of the free-radical chain products are discussed. It is concluded that the chains are initiated by the bimolecular disproportionation reaction, 2C2H4 → C2H3+C2H5, and that secondary initiation by dissociation of the product, 1-butene, becomes increasingly important as the reaction proceeds, leading to autocatalysis. It is further concluded that the radical chain decomposition in this system is a transient process occurring in a brief time interval following the short laser pulse (FWHM=110ns), and is far from steady-state conditions.

Laser skin treatment using micro-lens arrays (MLA) and diffractive optical elements (DOE) have clinically been applied to treat pigmented lesions [1,2]. However, DOE hardly has a deep penetration depth and MLA shows a non-uniform distribution of lesions, making it difficult to target lesions deeply located in the dermis [2]. The purpose of this study is to investigate the feasibility of diffractive lens arrays (DLA, combination of MLA and DOE) to treat the pigmented skin via laser-induced thermal decomposition at various tissue depth. Porcine skin tissue and one farm pig were used to compare spatial distributions of the laser-induced damage after irradiation with DOE, MLA, and DLA. 1064 nm picosecond Nd:YAG laser light was irradiated on a target tissue at 3.0 ~ 6.0 J/cm² under DOE, MLA, and DLA conditions. According to ex vivo tests, DOE generated laser-induced vacuoles near the basal membrane (208 ± 80 μm), and MLA distributed vacuoles more deeply located in dermis than DOE (382 ± 147 μm). On the other hand, DLA created laser-induced thermal decomposition deeply positioned in dermis (548 ± 137 μm). In vivo tests demonstrated that DOE generated the vacuolization in epidermis and dermis (235 ± 82 μm). On the other hand, DLA generated the deep laser-induced thermal decomposition in dermis (1057 ± 286 μm). The current study demonstrated that the picosecond laser irradiation with DLA could create the thermal decomposition in the deep dermis. Therefore, the DLA-assisted laser application may help to achieve selective skin treatment for deeply located pigments.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFlow pyrolysis and direct and silicon tetrafluoride-sensitized laser-induced decomposition of tetralin. Identification of retro-[2 + 4] cleavage as the primary homogeneous thermal decomposition channelMichael R. Berman, Paul B. Comita, C. Bradley Moore, and Robert G. BergmanCite this: J. Am. Chem. Soc. 1980, 102, 17, 5692–5694Publication Date (Print):August 1, 1980Publication History Published online1 May 2002Published inissue 1 August 1980https://doi.org/10.1021/ja00537a055RIGHTS & PERMISSIONSArticle Views64Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (432 KB) Get e-Alerts Get e-Alerts

The objective of this work was to study the near-surface phenomena of an energetic binder, butanetriol trinitrate/ glycidyl azide polymer, during thermal decomposition and combustion. A triple quadrupole mass spectrometer with microprobe sampling was used to obtain gas-phase quantitative species from CO 2 laser-induced decomposition and laser-assisted combustion of the butanetriol trinitrate/glycidyl azide polymer sample. To get the species profile as a function of height from the surface, a linear positioner was used to move the sample towards the microprobe during sampling. Fine-wire thermocouples were used to get the surface temperature and gas-phase temperature profile in the primary flame zone. The experiments were conducted at a laser heat flux of 35 W/cm 2 and in both argon environment and ambient air conditions with varying pressures from 1.0 to 4.0 atm. The flame structure and burning event were recorded using a digital camcorder so that the burning rates at these pressures can also be determined.

Nanoscale lead zirconate (PbZrO3) was prepared by using co-precipitation method, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The catalytic performances of PbZrO3 on the decomposition of ammonium perchlorate (AP), cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX) were examined by differential scanning calorimetry (DSC). The thermal behaviors, nonisothermal decomposition kinetics of nitroglycerin/nitrocotton (NG/NC) double-base propellant with nano PbZrO3 (PbZrO3-DB) were also studied. The results show that PbZrO3 presents a typical perovskite structure. Nano PbZrO3 can remarkably reduce the thermal decomposition temperature and apparent activation energy of decomposition process(reduced by 21, 7.4 and 15 kJ/mol respectively). The thermal decomposition of PbZrO3-DB propellant is heterogeneous. Thermal decomposition mechanism of PbZrO3-DB propellant is a contracting cylinder with phase boundary reaction, and the kinetic equation is: $ \frac{{{\rm{d}}\alpha }}{{{\rm{d}}t}} = \frac{{{{10}^{16.7}}}}{\beta }2{\left( {1-\alpha } \right)^{1/2}}\exp \left( {-1.696 \times {{10}^5}/RT} \right)$ .Used as a combustion catalyst of NG/NC solid propellant, nano PbZrO3 can obviously increase the burning rate and decrease the pressure exponent (0.37-0.39) in the pressure range of 2-14 MPa. The catalytic combustion action of nano PbZrO3 is much better than that of PbO.

Simultaneous temperature and species measurements of the glycidyl azide polymer (GAP) propellant during laser-induced decomposition

Effects of magnesium-based hydrogen storage materials on the thermal decomposition, burning rate, and explosive heat of ammonium perchlorate-based composite solid propellant

Thermal stability and lifetime estimates of a high temperature epoxy by Tg reduction

Thermal and oxidative degradation of PE-EPDM blends vulcanized differently using sulfur accelerator systems

Sand casting, currently the most popular approach to the casting production, has wide adaptability and low cost. The thermal decomposition characteristics of foundry sand for cast iron were determined for the first time in this study. Thermogravimetry was monitored by simultaneous thermal analyser to find that no obvious oxidation or combustion reaction in the foundry sand; the thermal decomposition degree increased as the heating rate increased. There was an obvious endothermic peak at about 846 K due to the transition of quartz from β to α phase. A novel technique was established to calculate the starting temperature of volatile emission in determining the volatile release parameter of foundry sand for cast iron. Foundry sand does not readily evaporate because its volatile content is only about 2.68 wt% and its main components have high-temperature stability. The thermal decomposition kinetics parameters of foundry sand, namely activation energy and pre-exponential factor , were obtained under kinetics theory. The activation energy of foundry sand for cast iron was small, mainly due to the wide temperature range of thermal decomposition in the foundry sand.

Transition metal oxide (MO) can obviously influence the thermal decomposition process of ammonium polyphosphate (APP) to improve the flame retardant efficiency of intumescent flame retardant composites based on APP in polymer. ZnO, Fe2O3 and TiO2, in same amount were added into APP to study the influence of MO on thermal decomposition behavior of APP, and to analyze the evolution of chemical state of metallic atoms and phosphorus atom and crystal structure in the interaction processes by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) respectively. TGA and XPS spectra showed that MO could catalyze the releasing of NH3 and H2O of APP in the earlier period, and increase the high temperature residue in the later period due to the formation of metallic phosphate. The sequence of catalytic activity for the process of releasing of NH3 and H2O was as follows: ZnO>Fe2O3>TiO2, and that of cross-linking ability for thermal decomposition product P-O of APP was as follows: Fe2O3>ZnO>TiO2. XRD showed that APP could react with ZnO, Fe2O3 and TiO2 to produce Zn(PO3)(2), Fe-4(P2O7)(3) and TiP2O7, respectively, at high temperature.

Time resolved 2D concentration and temperature measurement using CT tunable laser absorption spectroscopy

Considering the fact that the GaAs has the characteristics of thermal decomposition, the thermal decomposition damage to GaAs surface, induced by a 532 nm wavelength long pulse laser with a millisecond pulse width is studied by the heat conduction theoretical and semi-analytical method. First, the calculation models of two-dimensional axisymmetric transient temperature field and the surface thermal decomposition damage threshold for long pulse laser irradiation of GaAs are established, and the transient temperature fields and the thermal decomposition damage thresholds in GaAs with different absorption rates are simulated. The results show that the higher absorption rate causes the higher temperature rise on the surface of material, but the required decomposition damage energy density is lower. With the increase of laser energy density, the decomposition damage occurs more early. This paper has guiding significance and practical value for investigating the interaction between long pulse laser and GaAs and its damage mechanism.

Laser-induced direct writing of silver lines on a ferrite surface from a silver acetate (CH3COOAg) thin layer has been investigated. The deposition is a thermochemical process and the threshold temperature for thermal decomposition of CH3COOAg is about 380° C. About 100% of Ag in the deposited lines has been achieved. The width of the deposited Ag-lines increased with the increase in laser power, and it can be accurately estimated by the temperature profile induced by laser irradiation within the power region below the melting point of ferrite. A line thickness of micron order can be formed both on a ferrite surface and on a deposited SiO2 surface, whereas the line width decreased with the increase in beam dwell time due to the vaporization of both CH3COOAg precursor and deposited Ag material.