Grinding-induced equimolar complex formation between thiourea and ethenzamide.
We prepared and characterized a grinding-induced equimolar complex of thiourea with ethenzamide. When thiourea and ethenzamide were co-ground at a molar ratio of 3 : 1, new powder X-ray diffraction (PXRD) peaks were observed in addition to PXRD peaks of thiourea crystals. The optimum stoichiometry of the new structure was confirmed as 1 : 1 mol/mol. Effect of grinding time on the thiourea-ethenzamide equimolar complex formation was investigated by using PXRD, differential scanning calorimetry and Fourier transform infrared spectroscopy. The equimolar crystal structure was confirmed by X-ray diffraction measurements of the single crystal which was recrystallized from ethanol. It was found that the intermolecular hydrogen bond formations between thiourea and ethenzamide molecules contributed to the equimolar complex formation. The complex formation was not observed in the cases where benzamide, salicylamide or 3-ethoxybenzamide was co-ground with thiourea. 2-Alcoxyl benzamide structures should be required for the grinding-induced equimolar complex formation with thiourea.
Structural investigations of the poly(ε-caprolactam)–urea inclusion compound
Abstract An interesting inclusion compound (IC) between guest poly(e-caprolactam) (PeCL) and host urea was successfully obtained, for the first time, by co-crystallization from their common solution. X-ray diffraction, infrared spectroscopy and differential scanning calorimetry have been utilized for a detailed structural investigation of PeCL–urea IC (U IC) crystals. The results were compared with those obtained for well-known structures of the hexagonal polyethylene–U IC, the trigonal polyethylene oxide–U IC and the ‘large tetragonal’ poly(propylene)–U IC. The structure of PeCL–U IC reconfirms that the urea host molecules may crystallize, even in the presence of a rather slim polymer guest, into an IC with a lattice channel diameter of more than 5.25 A.
Spectroscopy of high rate events during active interrogation
Abstract Pulsed accelerators are being used for radiographic inspections in homeland security applications. Adding spectroscopic detection capability enables additional information to be extracted but challenges signal processing hardware. This work compares two approaches to cost-effective digital spectroscopy systems designed to handle these high rate scenarios. In the first system, the signal from a PMT is directly digitized and then deconvolved on a PC using standard techniques. Bypassing the preamplifier, this system can handle high count rates (>10 6  cps) from an LaCl 3 detector with no dead time and an energy resolution of 5% at 1.33 MeV. Spectra acquired from fission product gamma rays between interrogation pulses are shown. At higher rates, this approach is limited by the DAQ transfer rate to the PC. Instead, we tested a fast ADC (125 MSPS) and an FPGA that performed onboard, real-time digital signal processing (DSP). The energy spectrum is generated on the FPGA board during the measurement and transferred later. This system was tested in nuclear resonance fluorescence (NRF) experiments. Resonance peaks from NRF reactions are shown.