High Temperature Molecules Research Articles

Analysis of the fire-extinguishing effect and the weakening of flame intensification of nonionic liquid water mist*

ABSTRACTThe determination of a water mist additive is important to weaken the flame enhanced by water mist, which affects the safety and applicability of the water mist fire-fighting technology to a certain extent. Based on the theory of physical chemistry, in this study, a water mist additive, that is, a nonionic liquid alkyl phenol epoxide (APE) condensate to weaken the flame intensification and systematically perform an experimental study on extinguishing the fire in oil pool with nonionic liquid water mist. The results show that the nonionic liquid water mist has better atomization parameters. The extinguishing time and the maximum temperature are all decreased with the increase of nonionic liquid mass fraction under the action of nonionic liquid water mist. The maximum CO volume fraction and the time to maintain a high CO volume fraction in fire flue gas decreases with the increasing nonionic liquid mass fraction. The minimum O2 volume fraction and the recovery rate from this minimum value to the normal value increases with increasing nonionic liquid mass fraction. The nonionic liquid water mist can weaken the flame intensification and extinguish the oil pool fire better than pure water mist. This is because the suspended air and water bubbles formed after the spraying of the nonionic liquid water mist can block heat radiation, cutting off the oxygen supply and isolating the contact of combustibles with oxygen. In addition, owing to high temperature, surfactant and water molecules linked by hydrogen bond ether group rupture, resulting in reduced HLB, thus enhancing the ability to trap hydrocarbon molecules and capture H• and OH• radicals in the chain reaction.

Magnesium(I) Halide versus Magnesium Metal: Differences in Reaction Energy and Reactivity Monitored in Reduction Processes of P−Cl Bonds

AbstractMagnesium(I) halides (MgIX; X=Cl, Br, I), as high temperature molecules, are trapped and finally stored at −80 °C in toluene/donor solutions. These solutions provide insights into the fundamental mechanism of reduction reactions using activated magnesium metal as a prototype for every base metal. The most important example of such a reaction is the preparation of Grignard reagents (RMgX). The details of this highly complex mechanism especially of intermediates between Mg metal and MgII (RMgX) remain unknown until today. The same is true for the reaction of bulk magnesium with Group 15 halide compounds that give biradicaloid species. We investigate the reduction of P−Cl bonds with solutions of [MgIBr(NnBu3)]2 (1). The phosphanes [ClP(μ‐NTer)]2 (2) and (Me3Si)2N‐PCl2 (3), were chosen as they had successfully been reduced by Mg metal before. Furthermore, reactions of both 1 and Mg metal are compared with an MgI chelate complex L1Mg−MgL1 containing a strong Mg−Mg σ‐bond.

Magnesium(I) Halide versus Magnesium Metal: Differences in Reaction Energy and Reactivity Monitored in Reduction Processes of P-Cl Bonds.

Magnesium(I) halides (MgI X; X=Cl, Br, I), as high temperature molecules, are trapped and finally stored at -80 °C in toluene/donor solutions. These solutions provide insights into the fundamental mechanism of reduction reactions using activated magnesium metal as a prototype for every base metal. The most important example of such a reaction is the preparation of Grignard reagents (RMgX). The details of this highly complex mechanism especially of intermediates between Mg metal and MgII (RMgX) remain unknown until today. The same is true for the reaction of bulk magnesium with Group 15 halide compounds that give biradicaloid species. We investigate the reduction of P-Cl bonds with solutions of [MgI Br(Nn Bu3 )]2 (1). The phosphanes [ClP(μ-NTer)]2 (2) and (Me3 Si)2 N-PCl2 (3), were chosen as they had successfully been reduced by Mg metal before. Furthermore, reactions of both 1 and Mg metal are compared with an MgI chelate complex L1 Mg-MgL1 containing a strong Mg-Mg σ-bond.

Interfacial Reaction Mechanisms in Al2O3/Ge Structure by Oxygen Radical Process

We have investigated the impacts of the oxygen radical process on the interfacial structures and electrical properties of Al2O3/Ge structures to clarify the interfacial reaction mechanisms. At a low process temperature, the oxygen radical process can introduce oxygen atoms to the Al2O3/Ge interface without a thermally activated process in spite of the high barrier property of the oxygen diffusion for the Al2O3 layers. In addition, the oxygen radical process at a low process temperature can relatively suppress the diffusion of Ge atoms from the Ge substrate or GeO molecules from the Al2O3/Ge interface to the surface of the Al2O3 layer. However, at a high process temperature, Ge atoms and/or GeO molecules actively diffuse into the Al2O3 layer during the oxygen radical process as well as the O2 thermal annealing, and the diffusion changes the depth distribution of Ge oxides in the Al2O3/Ge structure. From the analysis of the electrical properties of MOS capacitors, the interface state density (Dit) of the Al2O3/Ge structure decreases not with increasing thickness of the Ge oxide interlayer but with the amount of Ge oxide near the Al2O3/Ge interface. The increase in the amount of the Ge oxide distributed in the Al2O3 layer induces the increase in the capacitance equivalent thickness (CET). The diffusion of Ge into the Al2O3 layer with a high process temperature causes the unexpected increase in CET. Therefore, the oxygen radical process at low temperature effectively decreases Dit of Al/Al2O3/Ge MOS capacitors without increasing CET.

Hunting for the Magnesium(I) Species: Formation, Structure, and Reactivity of some Donor‐Free Grignard Compounds

Magnesium bromide radicals have to be prepared as high-temperature molecules and trapped as a metastable solution because a seemingly simple reduction of donor-free Grignard compounds failed. However, the essential role of magnesium(I) species during the formation of Grignard compounds could be demonstrated experimentally.

Overexpression of a multiple stress-responsive gene, ZmMPK4, enhances tolerance to low temperature in transgenic tobacco

Mitogen-activated protein kinase (MAPK) cascades play important roles in mediating biotic and abiotic stress responses. In this study, we found that ZmMPK4 protein was predominantly localized in the nucleus. Semi-quantitative RT-PCR analysis revealed that the ZmMPK4 transcription in maize leaves was up-regulated by low temperature, high temperature and exogenous signaling molecules such as hydrogen peroxide, methyl jasmonate and ethephon. Hydrogen peroxide acted as second messenger to mediate 4°C-induced up-regulation of ZmMPK4 mRNA. Transgenic tobacco of overexpressing ZmMPK4 accumulated less reactive oxygen species (ROS), more peroxidase and catalase activities, more proline and soluble sugar contents, and more stress-responsive genes expression, leading to enhancing low temperature stress tolerance compared to the control plants. Taken together, these results strongly suggest that ZmMPK4 positively regulates low temperature stress tolerance in plants.

Effect of framework flexibility on diffusion of short alkanes in metal-organic framework

Molecular dynamics simulations is performed to study the diffusion of several short alkanes in a flexible and rigid metal-organic framework, IRMOF-1. The results show that the self-diffusivities of alkanes in the flexible framework are larger than in a rigid framework and the activation energies in the flexible framework are less than in the rigid framework. The effect of framework flexibility on the self-diffusiviy increases with temperature inereasing and loading or chain length decreasing. Therefore, in the study of the diffusion behavior of alkanes in the metal-organic framework materials using molecular simulation method, especially for the case of the high temperature and shorter alkane molecules, flexible force field may give more reasonable results.

Electronic energy exchange in high-temperature air

Kinetic processes with the participation of electronic states of atoms and molecules in air behind the shock wave front were analyzed. All metastable levels of molecular and atomic oxygen and nitrogen and nitrogen oxide molecules situated below the dissociation energy were analyzed. In high-temperature air, atom and molecule electronic states are formed in dissociation and recombination, electronic energy exchange in collisions of particles, and chemical exchange reactions. The formation of excited electronic states in the recombination of atoms and isoenergy vibrational energy transfer from highly excited vibrational levels into electronic energy is the fastest process. The quenching of metastable particles occurs in collisions between particles, dissociation and recombination, and chemical exchange reactions. A database on electronic energy exchange rate constants in high-temperature air is presented.

Formation, structure and bonding of metalloid Al and Ga clusters. A challenge for chemical efforts in nanosciences

The renaissance of Al and Ga cluster chemistry is presented in three steps: on the grounds of boron hydride chemistry and the Wade concept, the first step starts in the early nineties of the last century with the formation of single Al-Al and Ga-Ga bonds in molecular entities, obtained by different synthetic approaches. The special method via reaction of high-temperature molecules like AlCl and its disproportionation to Al metal and AlX(3) leads to the second step which started about 10 years ago: the formation of nanoscaled metalloid Al and Ga clusters as intermediates on the way to the metal. Based on the structure of several recent examples, bonding is discussed with respect to the structure of the elements and the generation of naked metal atom clusters. After discussion of the individual metalloid clusters including experiments of the gaseous species and discussion about the jellium model, the third step and main part of this review starts only a few years ago. This latest period hardly can be called a renaissance period as, so far, interactions of nanoscaled metal atom clusters in a perfect 1-, 2- or 3-dimensional arrangement of a crystal have never been investigated before. The most remarkable result in this perspective is the superconducting behaviour of a Ga(84) cluster compound in the crystalline state which had never been observed in metal atom clusters before. However, these experiments show that superconductivity is only observed if the clusters in the crystal are perfectly orientated: as a cluster arrangement of this type can hardly be fabricated by physical methods, these results, which have been predicted by theory, may be called a disillusionment for nanosciences; for chemistry, however, these conclusions pose a challenge.

Chemistry in Low‐Temperature Matrices

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

{Ge10Si [Si(SiMe3)3] 4(SiMe3)2Me}‐: A Ge10Si Framework Reveals a Structural Transition onto Elemental Germanium.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Chemistry in low-temperature matrices

This is the fifth report in this series on Matrix Isolation; the previous reports appeared in the 1985, 1991, 1997 and 2001 volumes of Annual Reports on the Progress of Chemistry, Section C. The report is divided into sections: weak adducts and conformational isomers; reactions of atoms; high-temperature molecules; photochemistry; biological molecules; astrochemistry. The last two sections reflect the fact that matrix isolation now extends into areas outside the traditional mainstream disciplines of chemistry. There are a number of areas where substantial progress has been made during the period of this report. First, the routine use of laser-ablation to generate atoms and to initiate atomic reactions in matrices has increased the scope of matrix isolation to synthesise many new molecular species in inorganic chemistry. Laser-ablation allows ground state atoms to be more easily studied than is the case when atoms are produced by thermal methods. Moreover, this procedure allows atoms to be generated from materials where thermal production is difficult. Secondly, the manufacture of more efficient closed-cycle helium refrigerators allows hydrogen matrices to be deposited readily. A significant body of work therefore has focussed upon metal hydrides, dihydrogen complexes and other hydrogen species in matrices. Underpinning all of this experimental work are theoretical calculations, without which the correct identification of most matrix isolation molecules would remain dangerously ambiguous. Infrared spectroscopy remains—as it has for the past 50 years—the workhorse of matrix isolation studies. It does seem that this situation will not change—it is impossible to conceive of another spectroscopic method that combines the necessary sensitivity to study molecules at very low dilution with the structural information required to make a reasonably certain identification.

{Ge10Si[Si(SiMe3)3]4(SiMe3)2Me}−: A Ge10Si framework reveals a structural transition onto elemental germanium

The reaction of the metastable high temperature molecule GeCl synthesized via a co-condensation technique with LiSi(SiMe(3))3 leads to a metalloid Ge(10)Si cluster compound, in which the arrangement of the germanium atoms can be seen as a cutout from the structure of elemental germanium.

Catalysed self-cleaning of air on the earth's surface

Generally, it is assumed that UV-light, high temperature or reactive molecules like O3 and OH are needed to activate gas reactions in air. In consequence, the catalytic activity on natural materials such as sand and soil on the earth's surface is assumed to be insignificant. We have measured O2-dissociation rates on natural quartz sand at 40˚C and compared these with O2-dissociation rates near 500˚C on materials with well-known catalytic activity. In terms of probabilities for dissociation of impinging O2-molecules the measured rates are in the 10−12–10−4 range. We have also measured dissociation rates of H2 and N2, water-formation from H2 and O2 mixtures, exchange of N between N2, NOx and a breakdown of HNO3, NO2 and CH4 on natural quartz sand at 40˚C. The measured rates together with an effective global land area have been used to estimate the impact of thermodynamically driven reactions on the earth's surface on the global atmospheric budgets of H2, NO2 and CH4. The experimental data on natural quartz sand together with data from equilibrium calculations of air suggest that an expected increase in anthropogenic supply of air pollutants, such as NOx or other “reactive” nitrogen compounds, hydrogen and methane, will be counter-acted by catalysis on the earth's surface. On the other hand, at Polar Regions and boreal forests where the “reactive” nitrogen concentration is below equilibrium, the same catalytic effect activates formation of bio-available nitrogen compounds from N2, O2 and H2O.

Infrared diode laser spectroscopy of the △ ν = 2 band of AlF

A vibrational–rotational spectrum of the △ ν = 2 transitions of a high-temperature molecule AlF was observed between 1490 and 1586 cm −1 with a diode laser spectrometer. Measurements were made on the ν = 3–1, 4–2, 5–3 and 8–6 bands at a temperature of 900 °C. Measured spectral lines were fitted to effective band constants ν 0, B ν and D ν for each band. Present measurements were made with only one Pb-salt laser diode. Physical significance of the effective band constants is discussed.

Symmetry-Resolved Absorption Spectra of Vibrationally ExcitedCO2Molecules

Symmetry-resolved x-ray absorption spectroscopy has been first carried out on high-temperature molecules. From the angle-resolved ion yield spectra of CO2 both at room temperature and at 430 degrees C, symmetry-resolved absorption profiles of the C 1s(-1) 2pi(u) and O 1s(-1) 2pi(u) resonances have been extracted for the vibrational ground state molecules and bending-vibration excited ones. The profiles change dramatically between them, and the Renner-Teller effect becomes more evident for the vibrationally excited molecules. The effects of the multimode vibronic coupling are suggested for the O 1s(-1) 2pi(u) and O 1s(-1) 3s sigma(g) resonances.

Mass spectrometric determination of the ionisation cross-sections of BaO, Ba, BaF 2 and BaI 2 by electron impact

A Nier-type mass spectrometer coupled with a Knudsen cell was used for the ionisation cross-section measurements of Ba, BaO, BaF 2 and BaI 2, using appropriate internal standards with known ionisation cross-sections. The vapour pressure ratio of standard to investigated compound, needed for calculation was obtained via the chemical analysis of the effusate. The use of this approach eliminated several sources of uncertainties. The problems concerning the preferential loss of fragment ions was also discussed and partly eliminated. The results obtained were compared with predictions, usually used in the field of high temperature mass spectrometry and a more recent approach using a model for ionisation cross-sections of high temperature molecules (MCM).

Synthesis and Structure of a Neutral SiAl14 Cluster

A metastable AlCl solution obtained by co-condensation of the high-temperature molecule AlCl and a mixture of toluene/diethyl ether reacted with SiCp*2 or SiCl4/AlCp*, giving a unique SiAl14 cluster species that bears six Cp* ligands protecting the compound from disproportionation and formation of the bulk material (elemental Al or an Si/Al alloy). The structure of the SiAl14 core represents a section of the body-centered packing where a Si atom resides in the center of an Al cube. Each of the six faces of the cube is capped by an additional Al(η5 Cp*) moiety. This cluster compound was investigated by mass spectrometry, X-ray diffraction, 27Al NMR spectroscopy, and ab initio theory. The solid-state structure contains minor amounts of molecules with additional Cl atoms bonded to the Al atoms at the corners of the cube, and the presence of Cl-containing molecules in the crystal is rationalized on basis of the suggested reaction path.

Matrix isolation and spectroscopic characterization of a linear AlOSi radical

In the past, matrix isolation technique proved to be a proper method to generate new species by oxidation and reduction of the high-temperature molecule SiO. In each case the variation of the SiO multiple bonding was of central interest. During the reduction of SiO with different metal atoms M, different MSiO intermediates result. The co-condensation of Al atoms with SiO ends up with a linear AlOSi radical, which represents the first example of a metal coordination via the O atom of SiO. The structural data based on IR- and Raman spectra are confirmed by quantum chemical calculations. Bonding of AlOSi is similar to that of the high-temperature molecule AlOAl; however, an additional electron is present in the lowest antibonding Π-orbital.

Infrared diode laser spectroscopy of a high-temperature molecule GeS using spectrum processing by fourier transformation

The vibrational-rotational spectrum of GeS has been observed using a diode laser spectrometer equipped with a heatpipe high-temperature cell of a White cell type. Fringes due to optical reflections inside the high-temperature White cell were inherent in the observation of the spectra. However, they were eliminated, as were high-frequency noises, by Fourier manipulation of the observed diode laser spectrum. About 620 spectral lines for the Δv = 1 band sequences of the eight isotopomers, 74Ge 32S, 72Ge 32S, 70Ge 32S, 73Ge 32S, 76Ge 32S, 74Ge 34S, 72Ge 34S and 70Ge 34S have been assigned between 522 and 593 cm −1. These infrared data combined with 91 microwave data from the literature have been analyzed with a least-squares fit to a Dunham potential function with only 11 parameters which included three Watson type Δ correction terms. The Dunham Y ij coefficients have been derived for each of the eight isotopomers. The equilibrium vibrational frequency ω e of 74Ge 32S is 574.269 313(271) cm −1.