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Lubricating greases are an important class of lubricants to reduce wear and friction in moving components. SP [ sp [[1]] SP ] sp Greases consist of a thickener network which includes base oil and additives of typically low molecular weight. As expected, signals from base oil molecules, thickeners and the alkyl chains of additives were clearly detected in the SP 1 sp H-NMR spectra at 80 MHz. This reveals that additives have a strong influence on the interaction of base oil and thickener and might also affect the thickener and its structure. [Extracted from the article]

Sedimentation of opaque suspensions of carbon black and lithium-iron-phosphate was investigated by spin-echo-based magnetic resonance imaging. Optical methods are usually applied to determine settling velocities, but are limited with respect to high concentrations and optical transparency. The presented method uses intensity data from the noninvasively measured magnetic resonance signal of the sample. The settling velocity is obtained from the evolution of the signal intensity profiles based on the contrast in 1H magnetic resonance imaging between particles and liquid. New insights into the sedimentation in opaque suspensions are provided, since the 1H images uncover the spatial distribution of the particles and its agglomerates, as well as the shape of the settling front. Additionally, the sedimentation was experimentally studied using a sedimentation balance, which gravimetrically measures the increase in mass fraction over time due to the settling of particles. By parallel usage of these two methods, the sedimentation processes of opaque suspensions of lithium-ion-battery electrode materials were investigated. The sedimentation balance covers high, technically relevant concentrations. Limiting factors of the methods are discussed, which are mainly signal intensity in the magnetic resonance imaging and the increasing viscosity of highly concentrated suspensions. [ABSTRACT FROM AUTHOR]

Ultrafiltration with ceramic hollow fiber membranes was investigated by compressed sensing rapid acquisition relaxation enhancement (CS‐RARE) magnetic resonance imaging (MRI) to characterize filtration mechanisms. Sodium alginate was used as a model substance for extracellular polymeric substances. Dependent on the concentration of divalent ions like Ca2+ in an aqueous alginate solution, the characteristics of the filtration change from concentration polarization to a gel layer. The fouling inside the membrane lumen could be measured by MRI with a CS‐RARE pulse sequence. Contrast agents have been used to get an appropriate contrast between deposit and feed. The lumen was analyzed quantitatively by exploring the membrane's radial symmetry, and the resulting intensity could be modeled. Thus, different fouling mechanisms could be distinguished. CS‐RARE‐MRI was proven to be an appropriate in situ tool to quantitatively characterize the deposit formation during in‐out filtration processes. The results were underlined by flux interruption experiments and length dependent studies, which make it possible to differentiate between gel layer or cake filtration and concentration polarization filtration processes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4039–4046, 2018 [ABSTRACT FROM AUTHOR]

Ceramic hollow fiber membranes are investigated with respect to the fouling behavior. Constant pressure dead-end filtration experiments have been performed using alginate as model substance for extracellular polymeric substances. In addition to the evaluation of the filtration data using conventional cake filtration model, nuclear magnetic resonance imaging (MRI) was used to elucidate the influence of Ca2+ on the fouling layer structure for alginate filtration within ceramic hollow fiber membranes. To visualize the alginate layers inside the opaque ceramic hollow fiber membranes by means of MRI, specific contrast agents were applied. Supplementary to multi slice multi echo imaging, flow velocity measurements were performed to gain more insight into the hydrodynamics in the fouled membranes. MRI reveals the structure of the alginate layers with the finding that the addition of Ca2+ to the alginate feed solution promotes the formation of a dense alginate gel layer on the membrane's surface. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2459-2467, 2016 [ABSTRACT FROM AUTHOR]

The dynamic nuclear polarization effect between the nitroxide radical TEMPO and the 1H protons of water solution was investigated at an electron pumping frequency of 9.7 GHz for different experimental conditions. In particular, we compared 14N-4-hydroxy-TEMPO (TEMPOL) with 4-oxo-TEMPO and evaluated the effect of 2H and 15N isotope labelling. Furthermore, we tested the effect of concomitant irradiation on both electron paramagnetic resonance (EPR) lines with the 15N-labelled compound. Our results show that the reduction in the EPR line width given by the 2H and 15N labelling and the collapse in the number of hyperfine lines due to 15N substitution leads to the highest enhancement of ε = −140 ever reported in the literature. Concomitant pumping on two hyperfine lines does not give higher enhancements at our experimental conditions. [ABSTRACT FROM AUTHOR]