Weathering investigation of PVC coatings on iron sheets by the NMR MOUSE

Abstract

Communications amined, only one gave diffraction of sufficient intensity to permit the hope of a structure determination. Data were collected up to 45" 20 in three shells, with variable scan speeds giving up to 10 min measuring time per reflection. Even so, the mean value of I/o(Z) for the entire data set was 2.7, and only 39 % of the measurements had I > 2u(I), indicative of the weakness of the scattering. The high least-squares residuals, a relatively poor data-to-parameter ratio (6.81), and high standard deviations are representative of the problems encountered. Still, the determination permits the observation of the connectivity, the packing pattern, the spatial relationship between the organic and inorganic components of the crystal, and coarse values for anion-anion and anion-cation separation, the features most related to the interpretation of the magnetic and electrical properties. We do not attempt to derive conclusions based on the exact bond distance or angle values from these structural results. The unit cell of the Fe derivative has been measured on a single crystal. The resulting parameters are a = 7.726(8)A,b = 6 . 2 7 0 ( 3 )~,~= 3 0 . 4 ( 1 )~, c c = 8 7 . 9 ( 1 ) " ,~= 8 8 . 9 ( 2 ) " , y = 88.09(5)"; V = 1470(6)A3. These are very close to those obtained in the Ga derivative, which support the isostructurality of the two salts.[12] The contribution coming from the organic sublattice was obtained from the magnetic measurements performed on the Ga derivative thatshow an almost constant value of the magnetic susceptibility of (2.4-2.6) x 10~3emumol-' in the temperature range 300-20 K. Below this temperature increases, reaching a value of 3.8 x 10" emu mol-' at

Nuclear Magnetic Resonance in Inhomogeneous Magnetic Fields

“…Carr-Purcell-like pulse sequences (18 -22) represent an important NMR technique for obtaining relaxation information and have been applied in connection with the NMR-MOUSE (12)(13)(14)(15)(16). Therefore understanding the spin response for such a pulse sequence is of importance.…”

“…7 were recorded on a silicone rubber sample using the NMR-MOUSE probe (12)(13)(14)(15)(16) driven by a Bruker Minispec whose characteristics were employed in the calculations of B 0 and b 1n . The amplitude of the simulated echo was scaled to the experimental one by a factor that was the same for Figs.…”

“…Thus NMR devices for spatially resolved material characterization can be constructed with inhomogeneous magnetic fields, without the need for the superconducting magnet, the most expensive component in commercial imaging equipment. Based on these considerations, the NMR-MOUSE (mobile universal surface explorer) has been developed (12)(13)(14)(15)(16). It has been shown that relaxation measurements by the NMR-MOUSE are useful in nondestructive, in situ characterization of polymers (12)(13)(14)(15).…”

“…Based on these considerations, the NMR-MOUSE (mobile universal surface explorer) has been developed (12)(13)(14)(15)(16). It has been shown that relaxation measurements by the NMR-MOUSE are useful in nondestructive, in situ characterization of polymers (12)(13)(14)(15).…”

Mobile single-sided NMR

“…Short interecho times of 20 ls can be achieved with the bar-magnet NMR-MOUSE (Fig. 6c), so that semi-crystalline and other hard polymers can be studied [42,46,184,241,275,301,[481][482][483]566,579] including glass-fiber reinforced epoxy [42,481,482]. Carbon-fiber reinforced material is hard to measure as it is conducting and shields rf, and the sensitivity of the NMR-MOUSE in the T 1q measurements needed for identification of thermal damage is too low [315,580].…”