SYNTHESIS AND THERMAL INTERCONVERSION OF 5-FLUOROACENAPHTHYLENE BY FLASH VACUUM THERMOLYSIS

Abstract

The utility of high-temperature gas-phase cyclisation reactions for the synthesis of fluorosubstituted cyclopenta-fused polycyclic aromatic hydrocarbons (PAHs) was illustrated by the synthesis of 5-fluoroacenaphthylene by flash vacuum thermolysis (FVT) of 1-ethynyl-5-fluoronaphthalene.

The experimental results suggest that monofluorinated PAHs can be used as model compounds to study thermal interconversion of their parent PAHs since, with fluorine as a label; ¹⁹ F-NMR is a valuable tool to characterize complex mixtures.     

Digital Signal Processing for Optical Particle Counters in Order to Improve the Signal-to-Noise Ratio

ABSTRACT

Especially In clean technology optical particle counters with high flow rates, low detection limits with respect to particle size and a low false count rate are needed. The lower detection limit and the false count rate can be reduced if the SNR can be increased. In this paper, we present a method to increase the SNR for any given optical particle counter using electronics means. First, the process of signal formation is investigated and the quantities determining the signal are described. The task is then to extract the particle pulses from the mixture of signals. Current methods for signal detection are briefly described. Using the signal theory, a correlation receiver is designed which provides a maximum SNR at the filter exit. This receiver has built-in digital technology. It offers the possibility of on-line filtering of particle signals. The results show a distinct improvement of the SNR. The actual value is different for each individual optical particle counter. In the case of the clean room optical particle counter (TSI LPC 3751), the SNR increased by a factor of 2.06. This means that the lower detection limit can be reduced from 500 to 420 nm or that, without lowering of the detection limit, the security of false counting can be improved to greater than 6σ.     

Selbstansaugende rotierende Sonde zur Entnahme von partikelfreien Gasproben aus Prozessgasen

A filtration system for keeping the analytics free of particles is usually required for inline characterization of particle‐laden process gasses. Additionally gas pumps may be needed for overcoming the pressure drop of filter element and filter cake. Consecutive reactions of process gas and filter cake may be disadvantageous for the quality of the gas analysis. A new probing apparatus is presented for extraction of particle‐free gas samples from particle‐laden process gasses. The probe combines the functionalities of a gas pump and a particle separator. While the gas is transported from process to analysis, particles are separated according to the principle of air classification.     

Effects of Tm3+ Additions on the Crystallization of LaF3 Nanocrystals in Oxyfluoride Glasses: Optical Characterization and Up‐Conversion

The influence of the addition of 1 mol% Tm₂O₃ on the nanocrystallization of LaF₃ in a glass of composition 55SiO₂–20Al₂O₃–15Na₂O–10LaF₃ (mol%) has been studied. Tm₂O₃ affects the phase separation in the glass and delays the onset of crystallization with respect to the undoped glass. Additionally, the maximum LaF₃ crystal size is slightly greater than that in the undoped glass–ceramics. The microstructural and compositional changes in the glass matrix have been studied using several techniques, including viscosity, dilatometry, X‐ray and neutron diffraction (XRD, ND), quantitative Rietveld refinement, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Raman spectroscopy. Photoluminescence measurements indicate that the Tm³⁺ ions are distributed between the glassy matrix and LaF₃ crystals. Eu₂O₃ has been used as structure probe and part of the Eu³⁺ ions are reduced to Eu²⁺ when incorporated in the LaF₃ nano‐crystals. Up‐conversion spectra under IR‐excitation show a higher intensity of the blue emission in the Tm‐doped glass–ceramic compared with that in the glass.     

Interfacial Chemistry of Langmuir-Blodgett Deposited Polyimide Films on Si (100)

Using the Langmuir-Blodgett (LB) technique, ultrathin films of the octadecylammonium salt of polyamic acid (PACS) on (100) oriented silicon wafers with one, three and five monolayers were prepared. The imidization of the films was investigated with x-ray photoelectron spectroscopy (XPS) during a stepwise heating procedure in vacuum. Significant differences in the XPS spectra indicate an incomplete polymerization of the films as a function of film thickness. It is believed that the chemical interaction at the interface between Si substrate and PACS is responsible for the incomplete polymerization of the LB film in direct contact with the substrate. From ellipsometric measurements the absolute thickness of a PACS and a polyimide layer has been determined to be 1.7 nm and 0.6nm, respectively. These measurements allow us to determine the electron mean free path for the Si2p electrons (E_k=1153 eV) of λ = 4.2±0.1 nm through these films.     

Effect of PLA crystallization on the structure of biomimetic composites of PLA and clay

Composites of poly(lactic acid) (PLA) and organoclays with clay loadings of up to 80% were prepared as self‐supporting films using a doctor‐blading approach. Depending on the properties of the used organoclay, either intercalated nanocomposites or conventional composites were obtained. The incorporation of such high amounts of clay resulted in up to 10‐fold decrease in the water vapor transmission rate when compared to the pristine polymer. The effect of clay platelets on the crystallization of PLA chains was also studied; it was found that high amounts of clay hinder only the melt crystallization of the polymer, whereas cold crystallization proceeds as usual. On the other hand, the crystallization of PLA also influenced the composite structure by increasing the extent of intercalation of polymer between clay layers. This study thus shows that the change in the extent of clay‐polymer interactions is also an important factor in controlling nanocomposite structure, especially for high loading. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reduction of a single granule drying model: An essential step in preparation of a population balance model with a continuous growth term

The development of a Population Balance Model (PBM) for a pharmaceutical granule drying process requires a continuous growth term; the latter actually represents the drying process as the moisture content is the internal coordinate of the PBM. To establish such a PBM, a complex drying model for a single granule needs reduction in complexity. The starting point is a detailed model that describes the drying behavior of single pharmaceutical granules. A Global Sensitivity Analysis (GSA) was performed to detect the most sensitive degrees of freedom in the model as these need to be retained in the reduced model. Simulations of the complex drying model were, in a next phase, used to develop the reduced model, which describes the decrease of the moisture content in function of the gas temperature. The developed reduced model was then included in a Population Balance Equation (PBE) to describe the drying behavior of a population of granules. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1127–1138, 2013     

Integrated DeNO x –DeSoot Catalytic Systems with Improved Low-Temperature Performance

Performance of the combined catalysts [CeO₂–ZrO₂ + FeBETA] and [Mn/CeO₂–ZrO₂ + FeBETA], prepared by mechanical mixing of the component powders, was studied in soot oxidation and NH₃-SCR. [CeO₂–ZrO₂ + FeBETA] catalyst (with component volumetric ratio of 3/1) demonstrated efficient soot oxidation at 400–450 °C and DeNO _x performance similar to that of FeBETA catalyst, despite the fact that the amount of zeolite was reduced by four times indicating a strong synergistic effect between the components. Low-temperature DeNO _x performance of the [CeO₂–ZrO₂ + FeBETA] system can be additionally enhanced by doping the CeO₂–ZrO₂ with Mn. It was found that NO _x conversion over [Mn/CeO₂–ZrO₂ + FeBETA] at 150–250 °C was steadily improved by increasing the Mn loading, and [5.4 % Mn/CeO₂–ZrO₂ + FeBETA] attained NO _x conversion above 90 % at T_react ~190 °C. Comparative studies of soot oxidation and NH₃-SCR over combined catalysts and individual components indicated that the soot oxidation activity is assigned to the soot oxidation over ceria–zirconia component, while enhanced low-temperature SCR performance is a result of a “bi-functional” SCR mechanism comprising NO oxidation to NO₂ over CeO₂–ZrO₂ component followed by fast-SCR over FeBETA.     

Stress redistributions in adhesively bonded double-lap joints, with elastic–perfectly plastic adhesive behavior, subjected to axial lap-shear cyclic loading

A shear-lag model is developed in order to evaluate stress redistributions in double-lap joints under axial (tensile) lap-shear cyclic loading. The adherend materials exhibit linear elastic behavior, whereas the material of the adhesive layer satisfies the elastic–perfectly plastic shear stress–strain constitutive relation. The reference state (from which the stresses are redistributed) is based on the standard elastic–perfectly plastic shear-lag analysis for double-lap joints. The main conclusion of the current analysis is that, during unloading, shear stresses of opposite sign may develop in the plastic zones of the adhesive layer, at the ends of the overlap, without reversing the direction of the applied load. A simple model for evaluating the variation of the maximum peel stress in the adhesive layer, based on the variation of the peak shear stress, demonstrates that the sign of peel stresses may alternate, as well. Under cyclic (fatigue) loading, the range of the peak stresses in the adhesive layer is the basic parameter for the evaluation of the variation of the energy release rate and the associated crack growth rate in the overlap. In this framework, the current simplified analysis may provide a reference model for comparisons with experimental data or with results which are based on more complex numerical models. The current model can be readily extended to cover the cases of development of plastic zones in the adhesive layer with shear stresses and plastic strains of opposite sign (during unloading or during load direction change).