Nuclear Magnetic Resonance Technology Research Articles

Study on mechanical properties and damage characteristics of acid corrosion in granite based on NMR technology

In acidic environments, rock masses are frequently subjected to severe chemical corrosion, resulting in the initiation of numerous geological engineering disasters. This study aimed to collect physical and mechanical parameters of granite exposed to prolonged acid corrosion and analyze fracture characteristics using acoustic emission (AE) techniques. Additionally, it examined the evolution of pore structure and damage mechanisms through the use of low-field nuclear magnetic resonance (NMR) and fractal theory. The results demonstrate a monotonic decrease in mass, volume, density, P-wave velocity, and S-wave velocity of granite with increasing corrosion time. Particularly notable is the phased reduction observed in uniaxial compressive strength and elastic modulus. The transition from brittle to ductile failure in corroded granite is accompanied by a gradual decrease in internal fracture strength. The trend in the correlation dimension reveals the relationship between the formation time of the main fracture surface and the pore structure. Additionally, total porosity and macropores (D, Da) exhibit significant fractal characteristics. The fractal dimension correlates positively with the damage variable and inversely with uniaxial compressive strength and elastic modulus. This indicates that more severe pore structure damage leads to a higher fractal dimension and lower mechanical performance. Among these, Da demonstrates higher sensitivity in characterizing rock mechanical properties. These findings provide important basis for evaluating the stability of granite geotechnical engineering in acidic environments.

Non-destructive inspection method for egg freshness evaluation via low-field nuclear magnetic resonance technology

Non-destructive inspection method for egg freshness evaluation via low-field nuclear magnetic resonance technology

Research on influence laws of aggregate sizes on pore structures and mechanical characteristics of cement mortar

Aggregate plays an important role in cement-based materials. Evaluating the impact of aggregate gradation on pore structure and mechanical properties will help to optimize the mortar ratio and improve its durability. In this study, artificial sand with 5 different particle sizes was used as aggregate, and the synthetic gradation formed by their coupling was compared. The pore structure distribution of mortar was quantitatively characterized by nuclear magnetic resonance (NMR) technology. Surface-to-volume ratio (SVR) and ρd (aggregate packing density) were used to characterize the aggregate grading characteristics. The correlation between aggregate gradation characteristics and mortar parameters, such as porosity, pore structure fractal dimension, permeability coefficient, and mechanical strength, was analyzed, and a compressive modulus of mortar was established. The results indicate that the pore structure characteristics, K (permeability), and mechanical characteristics of mortar are all influenced by both SVR and ρd. The predominant pores in the mortar are micropores and movable fluid pores, and the addition of 0.1–0.5 mm aggregates reduces the formation of micropores, mesopores, macropores, and movable fluid pores in the mortar. As the number of pores increases, the complexity of the pore structure decreases, leading to higher homogeneity. Moreover, the K shows a strong power function relationship with the total porosity and the total porosity fractal. The compressive strength and Ec (compression modulus) of GM1–6 are significantly higher than those of GM7–9, correlating with the minimum aggregate size and the inherent strength of the aggregates. The regression results of the strength correlation model are significant, and the strength model established based on the porosity of micropores and Ec can accurately predict the compressive strength of mortar.

Study on early hydration and pore structure evolution of cement paste containing graphene oxide

Graphene oxide (GO) significantly enhances cement hydration. This study investigates the effects of GO on the early hydration and pore structure evolution of cement paste by examining its impact on the setting time and mechanical properties of cement-based materials. In situ monitoring of the hydration process and microstructural changes was conducted using low-field nuclear magnetic resonance technology. The findings reveal that GO's nucleation effect accelerates cement hydration, reducing the setting time and increasing both the hydration rate and degree. Moreover, hydration products utilize GO as a template, leading to adjusted morphologies and enhanced interlinking of C–S–H gels. This results in a marked reduction in porosity and a denser microstructure within the cement paste. Consequently, the early mechanical properties of the cement paste are improved, with a significant increase in flexural strength observed at 72 hours. These results suggest that GO, which is cost-effective, size-controllable and suitable for mass production, holds great potential for applications in cement-based materials.

Evolution of Pore Structure and Fractal Characteristics in Red Sandstone under Cyclic Impact Loading

Fatigue damage can occur in surface rock engineering due to various factors, including earthquakes, blasting, and impacts. The underlying cause for the variations in physical and mechanical properties of the rock resulting from impact loading is the alteration in the internal pore structure. To investigate the evolution characteristics of the pore structure under impact fatigue damage, red sandstone subjected to cyclic impact compression by split Hopkinson pressure bar (SHPB) was analyzed using nuclear magnetic resonance (NMR) technology. The parameters describing the evolution of pore structure were obtained and quantified using fractal methods. The development of the pore structure in rocks subjected to cyclic impact was quantitatively analyzed, and two fractal evolution models based on pore size and pore connectivity were constructed. The results indicate that with an increasing number of impact loading cycles, the porosity of the red sandstone gradually increases, the T2 cutoff (T2c) value decreases, the most probable gray value of magnetic resonance imaging (MRI) increases, the pores’ connectivity is enhanced, and the fractal dimension decreases gradually. Moreover, the pore distribution space tends to transition from three-dimensional to two-dimensional, suggesting the expansion of dominant pores into clusters, forming microfractures or even macroscopic fissures. The findings provide valuable insights into the impact fatigue characteristics of rocks from a microscopic perspective and contribute to the evaluation of time-varying stability and the assessment of progressive damage in rock engineering.

Damage regularity and multifractal analysis of sol-gel reflection coating of KDP crystal under low UV irradiation flux.

This study employed multifractal analysis to investigate the changes in surface morphology of SiO2 anti-reflective coatings prepared on KDP substrates using the sol-gel method, under various conditions of ultraviolet (UV) irradiance. The coatings were successfully fabricated, and the chemical structure of the SiO2 sol was comprehensively characterized using Solid-State Nuclear Magnetic Resonance (SSNMR) technology. Under low UV irradiance (4 J/cm2), repeated experiments revealed a crack-induced mechanism of surface fatigue damage. Utilizing Scanning Electron Microscopy (SEM), the study discovered the induction effect of initial crack defects in UV-damaged coatings and established a damage model. Furthermore, Atomic Force Microscopy (AFM) was used to acquire images of the coatings' surface morphology at different damage levels, which were analyzed using the multifractal spectrum f(α). This analysis confirmed the multifractal nature of the coatings both before and after damage. This study identified significant effects of UV irradiation on the width of the multifractal spectrum and Δf, indicating that the SiO2 anti-reflective coatings exhibit multifractal characteristics under various damage states. The coatings displayed a pattern of decreasing and then increasing singularity spectrum width, height distribution unevenness, and surface roughness with increasing damage. This study demonstrates that multifractal analysis is an effective tool for describing the complexity of the surface morphology of sol-gel-derived anti-reflective coatings for the first time and for validating their multifractal properties across different stages of UV damage. HIGHLIGHTS: Damage dynamic process of KDP crystal sol-gel coating was described by SEM&AFM; The crack propagation mechanism of sol-gel coating under UV radiation is proposed; The damage evolution of sol-gel coating was described by multifractal analysis.

Experimental and numerical simulation study on enhanced oil recovery by N2-Assisted water huff-n-puff in a tight oil reservoir

The water huff-n-puff (WHP) method is widely used for improving oil recovery in tight reservoirs. However, the poor flow conductivity and low sweep efficiency of the matrix restrict the oil recovery performance of this method. Herein, N2-assisted water huff-n-puff (NAWHP) was proposed to improve oil recovery under reservoir conditions. First, the feasibility of NAWHP for tight reservoirs was investigated by comparing the enhanced oil recovery (EOR) performance with that of WHP and N2 huff-n-puff (NHP). The core flooding experimental results revealed that NAWHP facilitated oil recovery improvement, outperforming the existing practice of water or N2 huff-n-puff injection. Thereafter, with the aid of nuclear magnetic resonance (NMR) technology, the application of NAWHP could significantly enhance oil recovery in fractured tight cores, which mainly increased oil recovery from micro- and nanopores in the matrix. Specifically, for submicron pores and micropores, after three cycles of NAWHP, the recovery efficiency increased by 21.35% and 36.19%, respectively, while the recovery only increased by 14.34% and 24.8%, respectively, during WHP. For nanopores and micro/nanopores, the use of WHP increased the total oil recovery by only 4.71%, while the use of NAWHP increased the total oil recovery threefold. Finally, a series of numerical simulations were conducted to explore the effects of different parameters on oil recovery by NAWHP. The results illustrated that a high N2–water ratio (NWR) positively affected the overall oil recovery, but the higher the NWR was, the more difficult to extract the oil below the injection layer. By injecting 13,000 m3 of N2, the maximum swept volume was achieved for the matrix, and water filled the major fractures after injecting 11,000 m3, effectively accomplishing this task. Increasing the soaking time positively influenced oil recovery, N2 diffusion within the matrix led to an even distribution over 50 days, and water imbibition caused a significant increase in the oil saturation in hydraulic fractures within 30 days. The application of NAWHP increased the number of huff-n-puff cycles of water from a maximum of 3–5.

Evaluation of pore characteristics evolution and damage mechanism of granite under thermal-cooling cycle based on nuclear magnetic resonance technology

During the development process of deep geothermal energy (Hot dry rock, HDR), the high-temperature granite matrix in the wellbore needs to withstand thermal-cooling cycles, easily leading to wellbore instability and collapse. Considering the actual drilling engineering using different types of drilling fluid, thermal-cooling cycle experiments (cycles of 1, 2, 4, 8, 12 times) of granite were conducted using natural, water, and liquid nitrogen (LN2) cooling methods. Based on the low-field nuclear magnetic resonance measurement, the development and evolution of pore size, quantity, and distribution under different cooling ways and thermal cycles were studied, and the changes in rock mechanical parameters under different cooling methods and thermal cycling conditions were quantified. Then, the rock damage coefficients based on the variation patterns of different types of pores were calculated, and a quantitative relationship was established among T2 spectrum, pore, and mechanical damage. Finally, the proton weighting method was used to analyze the changes in the internal bearing area of rocks, revealing the deterioration mechanism of rock mechanical properties under different cooling ways and thermal cycling conditions. The results showed that the porosity increased with thermal cycles during the thermal-cooling cycle treatment, and the growth rate was first fast and then slow. Under the same number of thermal cycles, the groundwater cooling porosity was the highest, followed by LN2 and natural cooling. The relationship between T2 spectral area and rock damage was established on this basis, and the rock damage value increased with thermal cycles in an exponential function, and the proportion of large pores significantly affected the pore damage. A relationship (positively proportional linear) between pore damage and the mechanical degradation coefficient of high-temperature cooling cycle granite and a method for predicting rock degradation through pore damage were established, the deterioration mechanism of rock mechanical properties under thermal cycle treatment was revealed.

Study on the damage mechanism and evolution model of preloaded sandstone subjected to freezing–thawing action based on the NMR technology

Abstract Investigating the damage degradation of rock during the freezing and thawing process is more consistent with the actual engineering environment, considering its internal initial damage. In this study, the effects of initial damage from preloading and subzero-temperature freezing–thawing on microscopic and macroscopic mechanical properties of sandstone were studied based on the nuclear magnetic resonance (NMR) technique. The results show that the P-wave velocity of the sample decreased, while the porosity increased as the initial damage level increased. The distribution of T2 signal intensity exposed to the low-temperature freezing–thawing–saturation treatment was rather larger than that under normal temperature conditions for samples with different levels of initial damage from preloading, indicating that the low-temperature freezing–thawing condition would promote the porosity and have an obvious increase in damage. A continuum damage model considering subzero-temperature freezing–thawing damage from different pore sizes was finally introduced to describe the damage evolution mechanism of sandstone. The research results can be used to quantitatively evaluate the damage evolution mechanism of sandstone treated by subzero-temperature freezing–thawing without mechanical tests. Furthermore, the analysis and research results show that the damage variables of sandstone obtained by the NMR theory were lower than those of classical rock mechanics theory.

Experimental investigation of the roughness, freezing temperature and normal stress on the shear mechanical action of frozen saturated clay-rock interface

Recently, with the increase in global temperature, the permafrost degradation trend has intensified, and the soil-rock binary slope in permafrost regions has become more unstable. Therefore, this paper focuses on the shear strength of the clay-rock interface in the binary slope. The three-dimensional roughness, freezing temperature, and normal stress are key factors affecting the shear strength of the clay-rock interface. The influence of freezing temperature can be further quantified by using the unfrozen water content (UWC), which was measured by nuclear magnetic resonance (NMR) technology. By analyzing experimental results, it can be concluded that the three-dimensional roughness can effectively improve the shear strength of the clay-rock interface under freezing conditions, and the shear strength increases with the growth of the climbing angle (ic). The influence of temperature can be attributed to the effect of UWC on the internal friction angle and cohesion of saturated clay. Compared with the internal friction angle, the cohesion of saturated clay decreases faster with the increase of UWC. In addition, the shear strength of the clay-rock interface rises linearly as the normal stress increases, therefore the Mohr-Coulomb criterion also can be used to characterize the shear strength of the clay-rock interface. An interesting finding is that significant tensile cracks will appear in the clay part around the large bulge under low normal stress and high roughness. It further confirmed the contribution of large bulges to the prevention of shear slides of soft clay. The quantification understanding of the shear mechanical action of the clay-rock interface can provide a reference for scientific disaster reduction in cold regions.

Investigation on the influences of CaO on tar of biomass model compounds by Boltzmann-Monte Carlo-Percolation (BMCP) model

CaO have been widely used in biomass thermal conversion processes to deal with tar of biomass. The influences of the CaO on the function groups or intermediates of the bio tars are crucial because strategies on refining bio tars can be determined. The pyrolysis experiments of three typical model compounds, lignin, cellulose, hemicellulose, are carried out in a multi-stage tube followed by a cold trap. The influence of CaO can be analyzing the products distribution and components obtained from Nuclear Magnetic Resonance and Gas Chromatography-Mass Spectrometry technologies with and without CaO-loaded honeycombs. As the adsorbed matters on CaO-loaded honeycombs are hardly to be analyzed, the Boltzmann-Monte Carlo-Percolation model is introduced to make further investigations on the possible influence of CaO. The experimental results suggest that generations of unsaturated structures are inhibited by CaO, and the comparison of simulation and experimental results suggest that aliphatic carbon-centered radicals rather than oxygen-centered radicals are adsorbed and stabilized by CaO.

Long-term durability investigation of basalt fiber-reinforced geopolymer concrete in marine environment

The long-term durability of basalt fiber-reinforced geopolymer concrete (BFRGC) in marine environments is importance for the development of sustainable construction practices. This study examines the long-term durability of basalt fiber-reinforced geopolymer concrete exposed to dry-wet cycles and immersion treatment in marine conditions. A geopolymer concrete with 1% fiber content was prepared and subjected to dry-wet cycles and immersion treatments in a 5% sulfate solution (Tehmina et al., 2014; Nasir et al., 2016; John et al., 2016) [1-3]. Density measurements, ultrasonic pulse velocity tests, and uniaxial compression tests were conducted on the BFRGC after various treatment durations. The mechanical properties of BFRGC were compared with geopolymer concrete without fibers in marine environments. Additionally, the changes in compressive strength of geopolymer concrete with and without fibers in different immersion environments were further discussed. Using low-field nuclear magnetic resonance (LF-NMR) technology, the variations in pore structure were also analyzed. The results show that the mechanical property loss from dry-wet cycles was greater than from immersion treatment. In BFRGC, strength decreased by 10.1% after 192 days of dry-wet cycles, compared to a smaller decrease of 5.6% in immersion environments. The inclusion of basalt fibers effectively enhances stability. When in dry-wet cycle tests, BFRGC strength decreased from 49.6 MPa to 44.6 MPa, a reduction of 10.1%. Conversely, geopolymer concrete without fibers dropped from 49.7 MPa to 42.1 MPa, a reduction of 15.5%. LF-NMR test results show that the porosity of geopolymer concrete without fibers increased by 21.6% and 17.5% in dry-wet cycles and immersion environments, respectively. In contrast, the porosity of BFRGC increased by 16.1% and 12.7%.

Water-bearing properties of high rank coal reservoir and the effect on multiphase methane

Coal reservoirs commonly exhibit the coexistence of gas and water, wherein the distribution of water plays a crucial role in influencing methane storage and transportation. The presence of water affects methane adsorption, and models predicting adsorbed methane that do not account for water conditions can introduce errors, posing challenges in meeting practical production needs. In this study, through a series of centrifugation experiments and nuclear magnetic resonance (NMR) adsorption experiments, the distribution characteristics of bound water and movable water in reservoirs and their influence on multiphase methane were assessed. The results indicate that under water-bearing conditions, there exists specific methane in the adsorption space, exhibiting properties similar to free methane. In terms of the relaxation characteristics, the presence of water affects both the peak area and morphology of the T2 spectra of multiphase methane. Based on the NMR response characteristics of adsorbed methane at different water saturations, we proposed and established a theoretical model for predicting the content and density of adsorbed methane under varying water saturations. Additionally, utilizing two-dimensional NMR technology, a simple identification spectrum for multiphase methane was established. The study suggests that the presence of water delays the time of adsorption equilibrium for methane. At low water saturations, water primarily inhibits the adsorption rate of methane. However, with increasing pressure and water saturation, water predominantly suppresses the adsorption capacity of methane. At low water saturations, the bound water has a significant effect on adsorbed methane. Conversely, as water saturations increase, movable water gradually occupies adsorption sites with weaker adsorption potential. It is worth noting that with an increase in water saturation, the content of adsorbed methane decreases, but the adsorption phase density may not necessarily decrease. These research findings provide new insights into the interaction mechanisms between water and methane in water-bearing coal reservoirs.

Dynamic NMR methodology for kinetic studies

NMR (Nuclear magnetic resonance) is a popular tool used to characterize the structure of molecules, which is widely used for its high precision and accurate results. Due to these advantages, the NMR technique has been developed for monitoring the changes in the components during a reaction. This is called dynamic NMR technology. The kinetic measuring of a reaction is an important application of dynamic NMR, and the unique design of the methodology allows the NMR technique to be used for the determination of kinetic data such as reaction rates. In addition, dynamic NMR has also been used to monitor the reaction process and determine the reaction mechanism. Dynamic NMR techniques have developed rapidly in recent decades and have led to new research ideas and tools in chemistry and other related fields. In this paper, some examples of kinetic properties of reactions studied by dynamic NMR methods are introduced, including a summary of their development and prospects.

Investigation of carbon-based nanofluid imbibition processes in low-permeability reservoirs using nuclear magnetic resonance

Spontaneous imbibition has been demonstrated to be an important approach to enhance the oil recovery of unconventional reservoirs after hydraulic fracturing. Adding chemical agents to modulate the properties of the oil-water and oil-rock interfaces is a common method to enhance imbibition. Carbon-based nanofluid showed excellent ability to reduce interfacial tension and alter wettability due to their distinct surface properties and ultra-small particle size. However, there are few systemic studies on the imbibition process of carbon-based nanofluid and the unclear mechanism of the enhanced oil recovery (EOR) restricts their oilfield application. In this study, the carbon-based nanofluid was prepared by dispersing carbon nitride quantum dots (CNQDs) of 2.34 ± 0.34 nm synthesized by citric acid and urea in deionized water. The spontaneous imbibition process of nanofluids was monitored by nuclear magnetic resonance (NMR) technology. The T2 relaxation distribution results suggested that the oil recovery of CNQDS nanofluid by spontaneous imbibition was 24.6%, which was 5% higher than that of nano-SiO2 nanofluid. Moreover, the variations of oil saturation profiles analyzed based on NMR data indicated that the maximum imbibition distance of the carbon-based nanofluid was about 20.34 mm which is also larger than that of the nano-SiO2 nanofluid of 16.02 mm. The oil saturation variations of saturated oil cores imbibed in carbon-based nanofluid was also significantly improved compared with nano-SiO2 nanofluid. This finding was attributed to the fact that compared with nano-SiO2 nanofluid, the CNQDs nanofluid can not only promote the fluid to enter deeper matrix, but also effectively reduce the residual oil saturation in the area that the nanofluid accesses to. The interfacial tension and contact angle measurements were conducted to reveal the underlying EOR mechanisms of CNQDs nanofluid. This study provides vital insights into the prospective application of carbon-based nanofluid in low-permeability reservoirs.

Low-density lipoprotein particle profiles compared with standard lipids measurements in the association with asymptomatic intracranial artery stenosis

The Shiga Epidemiological Study of Subclinical Atherosclerosis was conducted in Kusatsu City, Shiga, Japan, from 2006 to 2008. Participants were measured for LDL-p through nuclear magnetic resonance technology. 740 men participated in follow-up and underwent 1.5 T brain magnetic resonance angiography from 2012 to 2015. Participants were categorized as no-ICAS, and ICAS consisted of mild-ICAS (1 to < 50%) and severe-ICAS (≥ 50%) in any of the arteries examined. After exclusion criteria, 711 men left for analysis, we used multiple logistic regression to examine the association between lipid profiles and ICAS prevalence. Among the study participants, 205 individuals (28.8%) had ICAS, while 144 individuals (20.3%) demonstrated discordance between LDL-c and LDL-p levels. The discordance “low LDL-c–high LDL-p” group had the highest ICAS risk with an adjusted OR (95% CI) of 2.78 (1.55–5.00) in the reference of the concordance “low LDL-c–low LDL-p” group. This was followed by the concordance “high LDL-c–high LDL-p” group of 2.56 (1.69–3.85) and the discordance “high LDL-c–low LDL-p” group of 2.40 (1.29–4.46). These findings suggest that evaluating LDL-p levels alongside LDL-c may aid in identifying adults at a higher risk for ICAS.

Pore fractal characteristics and ANN model of polyacrylonitrile fiber reinforced concrete under the synergistic effects of freeze-thaw and erosion

The degradation of the concrete pore structure is a major concern among scholars due to its negative impact on durability. This study conducted a salt freezing test on polyacrylonitrile fiber concrete (PANFRC) using a composite freeze-thaw medium consisting of Na2SO4, MgSO4, and NaCl (5 % + 5% + 3.5 %). The pore volume fractal dimension was determined by analyzing the T2 spectrum obtained through nuclear magnetic resonance technology. The study explored the influence of different types of pores on frost resistance and developed an artificial neural network-based machine learning model to predict macroscopic frost resistance using the pore volume fractal dimension. The experimental findings indicate that plain concrete exhibits a density loss of 4.67 % upon failure, whereas the density loss in PANFRC is reduced to less than 3 %. The frost resistance durability index is observed to improve as the fiber mass fraction increases within specific ranges. Notably, when the fiber content surpasses 1.2 kg/m³, the durability factor (DF) can be effectively doubled. Drawing from the concept of freeze-thaw cycles, a novel frost-thaw erosion damage model was developed, which incorporates the influence of fiber content under the combined action of freeze-thaw cycles and erosion. The analysis of pore dimensions reveals that the fractal characteristics become more pronounced with the increase in pore size, although this does not extend to the micro-pore range (i.e., those smaller than 0.1 μm). In comparison to other machine learning algorithms, the ANN demonstrates its superiority by establishing a meso-macro transfer prediction model with enhanced generalization capabilities.

Experimental study on the influence of external fluids on the pore structure of carbonaceous shale

Shale reservoirs have complex mineral compositions and are rich in micro-scale pores. It is of great scientific and engineering significance to explore the mechanism of external fluids on the pore throat structure of shale. In this paper, pure carbonaceous shale is taken as the research object, and the mechanism of the influence of slip water and reflux fluid on the pore throat structure is analyzed by using nuclear magnetic resonance (NMR) technology. Then, the sensitivity of different types of shale to external fluids is comparatively analyzed and summarized. The results show that (1) the oil slick has a certain effect on the total porosity of different types of shale. The rate of change is shown as carbonaceous shale (− 7.1%) > pure shale (− 1.6%). (b) For slickwater, the average reduction of macro- and micro/nanopores in carbonaceous shale is 90.0% and 5.0%, respectively, while the average reduction of macro- and mesopores in pure shale is 17.7% and 6.8%, respectively. (c) Total porosity of different shale types is insensitive to refluxing fluids. The average increase in macro-, meso-, and small pores of carbonaceous shale is 31.8%, 23.6%, and 20.2%, respectively; the average increase in macro- and small pores of pure shale is 17.1%.

SEI/dead Li-turning capacity loss for high-performance anode-free solid-state lithium batteries

Anode-free solid-state lithium metal batteries (AF-SSLBs) have the potential to deliver higher energy density and improved safety beyond lithium-metal batteries. However, the unclear mechanism for the fast capacity decay in AF-SSLBs, either determined by dead Li or solid electrolyte interface (SEI), limits the proposal of effective strategies to prolong cycling life. To clarify the underlying mechanism, herein, the evolution of SEI and dead Li is quantitatively analyzed by a solid-state nuclear magnetic resonance (ss-NMR) technology in a typical LiPF6-based polymer electrolyte. The results show that the initial capacity loss is attributed to the formation of SEI, while the dead Li dominates the following capacity loss and the growth rate is 0.141 mA h cm−2 cycle−1. To reduce the active Li loss, the combination of inorganic-rich SEI and self-healing electrostatic shield effect is proposed to improve the reversibility of Li deposition/dissolution behavior, which reduces the capacity loss rate for the initial SEI and following dead Li generation by 2.3 and 20.1 folds, respectively. As a result, the initial Coulombic efficiency (ICE) and stable CE increase by 15.1% and 15.3% in Li-Cu cells, which guides the rational design of high-performance AF-SSLBs.

Spontaneous increasing of sensitivity and resolution in parahydrogen-induced hyperpolarization by RASER

Enhancing the sensitivity of nuclear magnetic resonance (NMR) technology has been the focus of NMR research for decades, which offers the potential to significantly expand its applications in chemistry, biology, and medical imaging. Parahydrogen-induced polarization (PHIP) emerges as a cost-effective approach to substantially enhance the sensitivity of NMR. Nevertheless, the amplification of the 1H signal in PHIP is susceptible to interference from the thermal polarization state 1H NMR signal. Employing RASER (radiofrequency amplification by stimulated emission of radiation) proves effective in mitigating such interference, which can reduce the linewidth and increase the sensitivity at the same time. In this work, we utilized PHIP and RASER to enhance the signal-to-noise ratio (SNR) of a series of biocompatible alkynyl organic acid molecules. The alkynyl acid with the highest enhancement factor was first identified through PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) experiments. Subsequently, RASER experiments were carried out through hyperpolarization of 5-hexynoic acid, exploring its signal characteristics under varying flow rates and pressures. The SNR of proton signals of 5-hexynoic acid surpassed 150,000, an 18.62-fold improvement compared with traditional hyperpolarized signals in PASADENA, and a markedly narrowed linewidth of 0.06 Hz.