Kinetic Model and Experiment for Self-Ignition of Triethylaluminum and Triethylborane Droplets in Air.

Triethylaluminum Al(C2H5)3, TEA, and triethylborane, B(C2H5)3, TEB, are transparent, colorless, pyrophoric liquids with boiling points of approximately 190 °C and 95 °C, respectively. Upon contact with ambient air, TEA, TEB, as well as their mixtures and solutions, in hydrocarbon solvents, ignite. They can also violently react with water. TEA and TEB can be used as hypergolic rocket propellants and incendiary compositions. In this manuscript, a novel scheme of the heterogeneous interaction of gaseous oxygen with liquid TEA/TEB microdroplets accompanied by the release of light hydrocarbon radicals into the gas phase is used for calculating the self-ignition of a spatially homogeneous mixture of fuel microdroplets in ambient air at normal pressure and temperature (NPT) conditions. In the primary initiation step, TEA and TEB react with oxygen, producing an ethyl radical, which can initiate an autoxidation chain. The ignition delay is shown to decrease with the decrease in the droplet size. Preliminary experiments on the self-ignition of pulsed and continuous TEA-TEB sprays in ambient air at NPT conditions are used for estimating the Arrhenius parameters of the rate-limiting reaction. Experiments confirm that the self-ignition delay of TEA-TEB sprays decreases with the injection pressure and provide the data for estimating the activation energy of the rate-limiting reaction, which appears to be close to 2 kcal/mol.

Diffraction on periodic surface microrelief grating with positive or negative optical anisotropy.

Diffraction optical elements (DOE) are important elements of systems for images displaying and processing. The DOE materials with both positive and negative birefringence enhance performances and functionality of such systems. We have calculated the diffraction of rays passing through optically anisotropic grating with surface microrelief by using our original Exedeep software. At the first time the diffraction parameters for both transmitted and reflected TE- and TM-waves are calculated for materials with both positive and negative optical anisotropy. The simulation results are to be used to create DOE for the visible, UV, IR and THz ranges.

Alkynyl triphosphine copper complexes: synthesis and photophysical studies.

A rigid triphosphine PPh2C6H4-PPh-C6H4PPh2 () reacted with Cu(+) and a stoichiometric amount of terminal alkyne under basic conditions to give a family of copper(i) alkynyl compounds [Cu()C[triple bond, length as m-dash]CR]. The number of terminal -C[triple bond, length as m-dash]CH groups in the starting ligand determines the nuclearity of the resulting complexes giving mono- (, R = Ph; , R = C6H4OMe; , R = C6H4NO2; , R = C6H4CF3; , R = 2-pyridyl), di- (R = -(C6H4)n-, n = 1 (), n = 2, (), n = 3 ()) and trinuclear complexes (, R = 1,3,5-(C6H4)3-C6H3; , R = 1,3,5-(C6H4-4-C2C6H4)3-C6H3). In all the complexes the Cu(i) centers are found in a distorted tetrahedral environment that is achieved by tridentate coordination of the ligand and σ-bonding to the alkynyl function. The crystal structures of , and were estimated by single crystal X-ray diffraction analysis. The (31)P, (1)H and (1)H-(1)H COSY NMR spectroscopy confirms that all the molecules remain intact in solution. The photophysical studies carried out in the solid state at 298 and 77 K revealed moderate to weak orange luminescence (Φem up to 19%), tentatively assigned to thermally activated delayed fluorescence for the mononuclear complexes. The quantum yields of emission of demonstrated strong dependence on the nature of the alkynyl ligand, the role of which in the electronic transitions was elucidated by TD-DFT computational studies.