A robust Freeman-Hill-inspired pulse protocol for ringdown-free T1 relaxation measurements

Mayes, Zachary G.; Rice, William H.; Chi, Lingyu; Woelk, Klaus

doi:10.1016/j.jmr.2023.107490

Cited by 5 publications

References 19 publications

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Nuclear spin relaxation

Tayler

2024

Nuclear Magnetic Resonance

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This chapter explores current theoretical and experimental trends in nuclear spin relaxation, providing a digest of around 100 research papers published between 2022 and mid 2023. As is customary, this deliberately excludes the latest literature to capture trends and insights that have developed after publication. Throughout, emphasis is placed on a few topics: (1) relaxation in systems that exhibit enhanced nuclear spin polarization, through techniques like dynamic nuclear polarization and parahydrogen-induced polarization that have revolutionized signal-to-noise ratios in NMR and MRI; (2) relaxation in liquids at low and ultralow magnetic fields, where interest is drawn towards new mechanisms and applications in biomolecular systems; (3) long-lived spin states, a relaxation methodology that is complementary to the usual T1 and T2 approaches, which always seems to be applied in molecules with increasing complexity and relevance to biochemistry. Conventional study areas are also reviewed, grouped by phase of matter (solid, liquid, gas, mixtures) and technique (theory/modeling, experiment: solvent-relaxation, co-solute relaxation, relaxation-dispersion mapping, and fast-field cycling).

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Nuclear spin relaxation

Tayler

2024

Nuclear Magnetic Resonance

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Physical and Chemical Methods to Assess Performance of TPO-Modified Asphalt Binder

Herndon,

Balasubramanian,

Woelk

et al. 2024

Applied Sciences

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The demand for effective asphalt additives is growing as road infrastructure ages and more sustainable pavement solutions are needed. Tire pyrolysis oil (TPO) is an example material that has been gaining attention as a potential asphalt additive. While physical performance grade (PG) temperatures are the predominant performance requirements for asphalt binders, chemical properties are also significant in the evaluation of asphalt performance. There is a need to chemically characterize the aging of asphalt binders modified with TPO and link chemical changes in binder components to binder performance. This study compares 2%, 4%, and 8% TPO and asphalt binder blends via dynamic shear rheometry (DSR), Fourier-transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) relaxometry. The variability in the modified blends was seen by both physical and chemical testing during four different blending times (1, 60, 120, and 240 min). After blending, high and intermediate PGs were determined by physical testing. The 8% TPO blend reduced the high PG of the binder from 64 °C to 58 °C. This effect was confirmed by chemical testing through changes in carbonyl indices and NMR relaxation times. With more oil present in the binder matrix, the binder’s resistance to rutting was reduced. While the high PG was hindered, the intermediate PG remained unchanged for all TPO blends. This physical similarity was mirrored in chemical testing. The chemical and physical variability along with the hindrance of the high PG temperature indicate that more treatment may be needed before TPO can be effectively applied to asphalt binders. This study suggests a correlation between physical performance and key chemical indicators.

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Asphalt-Binder Mixtures Evaluated by T1 NMR Relaxometry

Herndon,

Balasubramanian,

Abdelrahman

et al. 2024

Physchem

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Asphalt pavements make up a majority of the essential transportation systems in the US. Asphalt mixtures age and degrade over time, reducing the pavement performance. Pavement performance critically depends on the aging of asphalt binder. The aging of asphalt binder during construction is traditionally modeled by rolling thin film oven (RTFO) testing, while aging during service life is modeled by pressure aging vessel (PAV) testing. Comparing these models to the aging of binders in actual pavements is limited because, to be used for current testing, binders must be separated from the pavement’s aggregate by solvent extraction. Solvent extraction will, at least in part, compromise the structural integrity of asphalt binder samples. Spin-lattice NMR relaxometry has been shown to nondestructively evaluate asphalt properties in situ through the analysis of hydrogen environments. The molecular mobility of hydrogen environments and with it the stiffness of asphalt binder samples can be determined by characteristic T1 relaxation times, indicating the complexity of asphalt-binder aging. In this study, two laboratory-generated asphalt mixtures, a failed field sample, and several laboratory-aged binder samples are compared by NMR relaxometry. NMR relaxometry was found to be able to differentiate between asphalt samples based on their binder percentage. According to the relaxometry findings, the RTFO binder aging compared favorably to the 6% laboratory-mixed sample. The PAV aging, however, did not compare well to the relaxometry results found for the field-aged sample. The amount of aggregate was found to have an influence on the relaxation times of the binder in the mixed samples and an inverse proportionality of the binder content to the primary NMR relaxation time was detected. It is concluded that molecular water present in the pores of the aggregate material gives rise to such a relationship. The findings of this study lay the foundation for nondestructive asphalt performance evaluation by NMR relaxometry.

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A robust Freeman-Hill-inspired pulse protocol for ringdown-free T1 relaxation measurements

Cited by 5 publications

References 19 publications

Nuclear spin relaxation

Nuclear spin relaxation

Physical and Chemical Methods to Assess Performance of TPO-Modified Asphalt Binder

Asphalt-Binder Mixtures Evaluated by T1 NMR Relaxometry

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