Characteristic Relaxation Research Articles

Cation-Cation, Cation-Anion, and Anion-Anion Translation Diffusion in Ionic Liquids─Insight from NMR Relaxometry.

1H and 19F spin-lattice relaxation experiments have been performed for a series of ionic liquids: [HMIM][TFSI], [OMIM][TFSI], and [DMIM][TFSI] including the same anion and cations with progressively longer alkyl chains. The experiments were performed in a wide frequency range from 10 kHz to 10 MHz (referring to the 1H resonance frequency) versus temperature. This extensive data set has been analyzed in terms of a theoretical model including all relevant homonuclear (1H-1H and 19F-19F) and heteronuclear (1H-19F) relaxation pathways and linking the relaxation features to the relative translational diffusion between the ion pairs (cation-cation, cation-anion, and anion-anion). In addition to the comprehensive theoretical approach, closed-form expressions have been provided and applied to determine the diffusion coefficients from the slopes of the linear dependences of the relaxation rates on the square root of the resonance frequency. The combined experimental and theoretical studies have led to the determination of the complete set of diffusion coefficients, forming a consistent picture of the dynamical scenario. In addition to revealing the dynamical properties of the liquids and the influence of the subtle changes in the cation structure on the movement of both cations and anions, the theoretical means for exploiting Nuclear Magnetic Resonance relaxometry for ionic liquids have been provided.

Dynamic NMR Relaxometry as a Straightforward Measurement of Concentration Variations in Colloidal Gels.

We show that dynamic NMR relaxometry allows one to probe the particle size or the concentration evolution over time in homogeneous colloidal suspensions or the concentration in different regions of heterogeneous suspensions, up to large volume fractions. We first demonstrate that the NMR transverse relaxation time is independent of the gel structure at the particle scale so that it only slightly varies during the gelation of a colloidal suspension. The evolution over time of the NMR transverse relaxation time during gel drying and its analysis with the help of the fast-exchange assumption extended to a partially saturated medium then allowed us to identify three successive regimes: homogeneous shrinkage, desaturation, and molecular film regime. A detailed analysis of the NMR relaxation characteristics provides information on the distribution of the fluid along the solid structure at the particle scale in the two last (partially desaturated) regimes. This in particular shows that, thanks to such analysis of their temporal evolution, such simple, nondestructive, time-resolved, global measurements can be used to follow precisely the solid volume fraction of the system and its state of saturation up to full drying, independently of the exact solid structure.

Dynamic reaction of slag-based geopolymer with brick powder: insights from acoustic emission, heat flow, and relaxation characteristics

Fractal dimension, heat, and NMR relaxation characterizations were employed to monitor the dynamic geopolymerization process of slag-based geopolymer (SBG) with brick powder (BP) in this research. Introducing 30% BP to SBG resulted in a delay of 6minutes in the occurrence of polymerization peak, with a 24.12% decrease in heat peak value. Furthermore, during the rapid polymerization phase, the time of the gel formation in SBG containing 30% BP was reduced by 34.18%, accompanied by a 20.91% decrease in gel water content. The sequence of AE parameters associated with early-age geopolymerization reaction has good fractal characteristics, with fitting coefficient greater than 0.95. Importantly, the heat flow curve, water evolution, and corresponding fractal dimension curves have good correspondence at 0-3h. Especially, the dissolution peak and polymerization peak of the heat flow curve basically coincide with the fractal dimension curve. The fractal dimension not only serves as an effective indicator for evaluating the geopolymerization process but also compensates for the limitations of calorimetry in characterizing reaction processes with relatively small particle migration and local heat release.

Bearing capacity of constrained grouting expansion bored pile based on CPTU and expansion tests

Bored Pile of Constrained Grouting Expansion (BPCGE) is a new type of pile that combines grouting, compression, and expansion technologies. However, there is still insufficient understanding of its bearing characteristics and strength degradation, especially when the surrounding mass is located in soft cohesive soil layers. To address the issues mentioned above, analysis of bearing capacity and strength assessment of BPCGE based on piezocone penetration test (CPTU) and expansion tests are taken into account. Firstly, based on the similarity between the pile prototypes and models, constrained grouting expansion tests are conducted to study the borehole expansion and soil consolidation effects, and analyze the influence on effective stress of soil around the pile and stress relaxation characteristics of cohesive soil. Secondly, CPTU tests and numerical simulations were carried out to investigate the size effect of BPCGE, and a conversion relationship between lateral friction resistance of pile and CPTU friction resistance was established. Finally, the ultimate bearing capacity of BPCGE is proposed. In an application of a high-rise residential project, the calculation method based on CPTU data can effectively predict the ultimate bearing capacity of BPCGE, saving 262 ordinary piles.

Ohmic Resistance Response of a Practical Protonic Ceramic Fuel Cell upon Hydration/Dehydration

Protonic Ceramic Fuel Cells (PCFCs) can show high performance, power density and efficiency at an intermediate temperature range from 400°C to 600°C. Proton-conducting ceramics is reported to have multiple mobile defects such as proton, hole, and oxygen vacancy. Conductivity of those defect species depends on the concentration of the atmosphere gas such as hydrogen, oxygen and water vapor. To date, the effect of hydration/dehydration on the proton conductivity as a single electrolyte material has been studied1,2. However, as a whole cell assembled with electrolyte and electrode, there are few reports on that effect. When using such a whole cell to measure the hydration/dehydration effect, practical gas for a real operation can be supplied. This study focuses on the transition characteristics with hydration/dehydration in practical gas condition by using a BaZrO3-based perovskite cell.Firstly, to assess the time delay of hydration/dehydration reactions at the electrolyte-electrode interface, experiments were conducted using the cells with different electrolyte thicknesses, 6μm, 13μm and 24μm at open-circuit voltage. Figure1(a) shows the results. Time constant increased with thicker electrolyte. Despite the difference in electrolyte thicknesses, almost the same Fourier numbers were calculated by using each of the response time point crossing 63% from one steady state to another. This result suggests that the reaction rate at the interface was fast enough compared to the transport rate within the bulk of electrolyte.Secondly, transport within the electrolyte was considered. Incorporation of water vapor into the electrolyte is considered to follow next equilibrium:H2O+Vo ··+OO ×⇔OHO · (1)When the water vapor concentration in supplied gas is switched, a pair of proton and oxygen, described as OHO · in equation (1), is generated into the electrolyte. Protons detached from OHO · can be transported by hopping to the neighboring oxygen atom1. Protons could be also transported via vehicle mechanism, as a pair of proton and oxygen. Diffusion coefficient for the measured curve was determined from the solid curve in Figure1(a), which was fitted by using Fick's law. Fitted diffusion coefficient was 4.5×10-13 m2/s at 600 °C. This diffusion coefficient is significantly smaller than reported diffusion coefficients of proton and hole3. In this cited paper, those diffusion coefficients are determined through conductivity measurement. Protons could mainly be transported via hopping mechanism in a fixed atmosphere gas, suggesting that the reported value for proton was related to hopping mechanism. Holes are considered to be similar with electrons, suggesting high diffusivity. Therefore, the fitted value in our research could be for the transport via vehicle mechanism, potentially influencing the determination of the relaxation time by limiting the proton transport. For further investigation of the relaxation characteristics, experiments will be conducted at different external current densities providing varying potential gradients within the electrolyte. Acknowledgements This presentation is the result of the research and development of ultra-efficient proton-conducting ceramic fuel cell devices, JPNP20003, funded by the New Energy and Industrial Technology Development Organization (NEDO), Japan. We would like to express our gratitude to all parties involved. Reference Rongzheng R., et al., ACS Appl. Energy Mater., 3(5), 4914 (2020)Han-Ill Y., et al., Solid State Ion, 180(28), 1443(2009)Kwati L., et al., J Mater Chem A, 6 (39) (2018) Figure 1

Predicting Cycle Life of Lithium Metal Batteries Using Discharge/Charge Capacity and Voltage Relaxation Features Via Machine Learning

Introduction Precise estimation of battery cycle life is crucial for assessing quality and planning long-term battery management systems. Given the nonlinear nature of battery degradation, early and accurate cycle life prediction amid minimal degradation is exceptionally difficult. Machine learning (ML) methods, independent of specific mechanisms, can offer promising alternatives for predicting battery lifespan1. Li metal anode battery (LMB) is a promising next-generation battery because of the high energy density, whereas the safety concern with complex degradation mechanisms is still a crucial issue. For such challenge, ML-based cycle life prediction may play a role, though the LMB data are still limited. Here, we report our study on lifespan prediction of lithium metal-based batteries with high mass loading Ni-rich NMC electrode (NMC811/Li) by ML method through more battery features from various processes in the experimental charge/discharge cycles. We also explore the most crucial feature of NMC811/Li metal anode batteries' cycle life prediction with the feature importance analysis. Methodology In our project, 48 batteries are used to build ML model, 35 features are generated from the processes during cycle test, which are divided into discharge, charge, and voltage relaxation related features. The whole dataset is regarded as the training dataset, the testing datasets are generated by 4-fold cross validation of the whole dataset. ElasticNet and XGBoost ML methods are used in our study to predict the cycle life. Pearson’s correlation coefficient is used to define the relationship between features and cycle life. Feature importance analysis is done by XGBoost ML model under exhaustive feature selection method. Results and Discussion Firstly, we use discharge related features, charge capacity related features, and voltage relaxation features to predict the battery cycle life separately by ElasticNet linear regression model. We then find that discharge-related features give us the best prediction result compared to the other two feature sets. However, the prediction result is still not satisfactory. Hence, by calculating Pearson’s correlation coefficient we selected 12 features out of the 35 features which have strong or moderate correlation to cycle life. Through exhaustive feature selection, we generated totally 4095 feature subsets from the 12 features. We implement advanced XGBoost ML model on all the possible feature subsets to predict the cycle life. The result shows that XGBoost ML model has a significant increase of the prediction performance and there is one case which contains 6 features out of the 12 features can give us the best prediction result (Fig. (a)) which decrease the RMSE to 8.29, MAE to 6.45 and increase R2 to 0.89. In addition, we find logarithm of the minimum value of discharge capacity difference between 100 cycle and 10 cycle (Log(|min(100-10(V))|)) is the most important feature ranking for the 6 features in lifetime prediction (Fig. (b)). It contributes more than 44% for lifetime prediction. Finallly, we provide our model with 8 new NMC811/Li metal batteries as unseen data to test the prediction performance, The prediction result is shown in Fig. (c), the MAE and RMSE of the testing data are relatively small and the test error (Mean Absolute Percentage Error) equals to 6.6%, which suggests the model provides predictions with reasonable accuracy. This study underscores the successful application of ML in predicting cycle life for LMBs with high energy density design, paving the way for enhanced battery performance and longevity in practical applications. References Severson, Kristen A., et al. Nature Energy4(5) (2019): 383-391. Figure 1

Compression stress relaxation characteristics and failure mechanism of silicone rubber for high voltage cable accessories

Sufficient interfacial pressure between silicone rubber (SIR) insulation and cross-linked polyethylene (XLPE) in high-voltage cable accessories is the basic condition to ensure the normal operation of cable accessories. However, in the actual operation of cables and accessories, high-temperature aging and mechanical aging can cause the mechanical properties of SIR materials to decline, thus affecting the size of the insulation interface pressure. Firstly, the relaxation law of compressive stress of SIR material is obtained by measuring the compressive stress under force-thermal synergistic aging. Secondly, the time-temperature equivalent model is established according to the measured data to evaluate the service life of the cable accessories. Thirdly, the physical and chemical properties of SIR with different aging times are tested to analyze the change in its mechanical properties. Finally, the effect of temperature on the stress relaxation characteristics of SIR is calculated from the microscopic level by molecular simulation. The experimental results show that the compressive stress of SIR decreases first and then becomes stable with the increase of aging time due to the movement of molecular chains and chemical reactions in SIR. In addition, the compression stress relaxation rate of SIR increases with temperature. The aging life prediction model shows that when the relaxation coefficient of compressive stress drops to 50% of the initial value at the end of cable life, the service life of cable accessories at 70°C is about 24 years. The molecular simulation shows that the relaxation of the molecular chain of SIR is accelerated with the increase in temperature, and the stress relaxation of SIR material is accelerated on a macroscopic level. This research can provide a theoretical basis for the design and operation reliability of cable accessories.

Paramagnetic salt and agarose recipes for phantoms with desired T1 and T2 values for low-field MRI.

Tissue-mimicking reference phantoms are indispensable for the development and optimization of magnetic resonance (MR) measurement sequences. Phantoms have greatest utility when they mimic the MR signals arising from tissue physiology; however, many of the properties underlying these signals, including tissue relaxation characteristics, can vary as a function of magnetic field strength. There has been renewed interest in magnetic resonance imaging (MRI) at field strengths less than 1 T, and phantoms developed for higher field strengths may not be physiologically relevant at these lower fields. This work focuses on developing materials with specific relaxation properties for lower magnetic field strengths. Specifically, we developed recipes that can be used to create synthetic samples for target nuclear magnetic resonance relaxation values for fields between 0.0065 and 0.55 T. and mixing models for agarose-based gels doped with a paramagnetic salt (one of CuSO4, GdCl3, MnCl2, or NiCl2) were created using relaxation measurements of synthetic gel samples at 0.0065, 0.064, and 0.55 T. Measurements were evaluated for variability with respect to measurement repeatability and changing synthesis protocol or laboratory temperature. The mixing models were used to identify formulations of agarose and salt composition to approximately mimic the relaxation times of five neurological tissues (blood, cerebrospinal fluid, fat, gray matter, and white matter) at 0.0065, 0.0475, 0.05, 0.064, and 0.55 T. These mimic sample formulations were measured at each field strength. Of these samples, the GdCl3 and NiCl2 measurements were closest to the target tissue relaxation times. The GdCl3 or NiCl2 mixing model recipes are recommended for creating target relaxation samples below 0.55 T. This work can help development of MRI methods and applications for low-field systems and applications.

Dinuclear Dysprosium Compounds: The Importance of Rigid Bridges.

We report the synthesis, structures and magnetic behaviour of two isostructural dinuclear Dy3+ complexes where the metal ions of a previously reported monomeric building block are connected by a peroxide (O2 2-) or a pair of fluoride (2×F-) bridges. The nature of the bridge determines the distance between the metal ion dipoles leading to a dipolar coupling in the peroxido bridged compound of only ca. 70 % of that in the bis-fluorido bridged dimer. The sign of the overall coupling between the metals is antiferromagnetic for the peroxido bridged compound and ferromagnetic for the bis-fluorido bridged complex. This in turn influences the magnetisation dynamics. We compare the relaxation characteristics of the dimers with those of the previously reported monomeric building block. The relaxation dynamics for the bis-fluorido system are very fast. On the other hand, comparing the properties of the monomer, the peroxido bridged sample and the corresponding Y-doped sample show that the relaxation properties via a Raman process have very similar parameters. We show that a second dysprosium is important for either tuning or detuning the Single Molecule Magnet (SMM) properties of a system.

Intrinsic 77 K Phosphorescence Characteristics and Computational Modeling of Ru(II)-(Bidentate Cyclometalated-Aromatic Ligand) Chromophores: Their Relatively Low Nonradiative Rate Constants Originating from Low Spin-Orbit Coupling Driven Vibronic Coupling Amplitudes between Emitting and Ground States.

We investigated the photoinduced relaxation of Kasha-type emitting ruthenium-(bidentate cyclometalated aromatic ligand), Ru-CM, chromophores of [Ru(pzpy)2(CM)]+ ions (CM = 1-phenylisoquinoline, 2,3-diphenylpyrazine, and 1,4-diazatriphenylene and pzpy = 2-pyrazol-1-yl-pyridine). This is the first report of the phosphorescence behavior of pure Ru-(bidentate CM) chromophores. The 77 K photoinduced relaxation characteristics of phosphorescence chromophores showed emission quantum yields higher than those of reference Ru-bpy (bpy = 2,2'-bipyridine) chromophores in the emission region of 670-900 nm. This phenomenon of the Ru-CM chromophores could be attributed to their unusually low magnitudes for 77 K nonradiative rate constants (kNRD), although their radiative rate-constants (kRAD) are not remarkable. In order to examine the 77 K photoinduced behavioral relaxation difference between Ru-CM and Ru-bpy chromophores, we used computational simulation, applying the fundamental formalism of kRAD and temperature-independent kNRD equations, which included calculated spin-orbit coupling values.

Radiation-Induced Paramagnetic Centers in Meso- and Macroporous Synthetic Opals from EPR and ENDOR Data

The paramagnetic defects and radiation-induced paramagnetic centers (PCs) in silica opals can play a crucial role in determining the magnetic and electronic behavior of materials and serve as local probes of their electronic structure. Systematic investigations of paramagnetic defects are essential for advancing both theoretical and practical aspects of material science. A series of silica opal samples with different geometrical parameters were synthesized and radiation-induced PCs were investigated by means of the conventional and pulsed X- and W-band electron paramagnetic resonance, and 1H/2H Mims electron-nuclear double resonance. Two groups of PCs were distinguished based on their spectroscopic parameters, electron relaxation characteristics, temperature and time stability, localization relative to the surface of silica spheres, and their origin. The obtained data demonstrate that stable radiation-induced E’ PCs can be used as sensitive probes for the hydrogen-containing fillers of the opal pores, for the development of compact radiation monitoring equipment, and for quantum technologies.

Markers of low field NMR relaxation features of tissues

This work presents an approach to exploiting Nuclear Magnetic Resonance (NMR) relaxometry data (1H spin-lattice relaxation rates covering the frequency range from below 1 kHz to 10 MHz) for the purpose of differentiating between pathological and reference tissues. Characteristic quantities (markers) that can be obtained in a straightforward manner, not resorting to an advanced analysis of 1H spin-lattice relaxation data, have been identified and compared for pathological and reference colon tissues. Moreover, the relaxation data have been parametrised in terms of Lorentzian spectral densities and the possibility of using the obtained dipolar relaxation constants and correlation times as biomarkers to assess the state of tissues has been discussed. It has also been demonstrated that the relaxation data for the reference and the pathological tissues can be attributed to two groups (for each case). The studies are a step towards exploiting the potential of NMR relaxometry for characterisation of pathological changes in tissues.

Composition analysis of β-(In x Ga1-x )2O3 thin films coherently grown on (010) β-Ga2O3 via mist CVD

ABSTRACT This study investigates the compositional analysis and growth of β-(In x Ga1-x )2O3 thin films on (010) β-Ga2O3 substrates using mist chemical vapor deposition (CVD), including the effects of the growth temperature. We investigated the correlation between In composition and b-axis length in coherently grown films, vital for developing high-electron-mobility transistors and other devices based on β-(In x Ga1-x )2O3. Analytical techniques, including X-ray diffraction (XRD), reciprocal space mapping, and atomic force microscopy, were employed to evaluate crystal structure, strain relaxation, and surface morphology. The study identified a linear relationship between In composition and b-axis length in coherently grown films, facilitating accurate composition determination from XRD peak positions. The films demonstrated high surface flatness with root-mean-square roughness below 0.6 nm, though minor relaxation and granular features emerged at higher In compositions (x = 0.083) at the growth temperature of 750°C. XRD results revealed that lattice relaxation were observed at a growth temperature of 700°C despite low In composition. In contrast, at 800°C, the In composition was higher than at 750°C, and coherent growth was achieved. The surface morphology was the flattest at 750°C. These findings indicate that the growth temperature plays a crucial role in the mist CVD growth of β-(In x Ga1-x )2O3 thin films. This study offers insights into the relationship between In composition and lattice parameters in coherently grown β-(In x Ga1-x )2O3 films, as well as the effect of growth conditions, contributing to the advancement of ultra-wide bandgap semiconductor device development.

Analysis of relaxation characteristics of multi-bolted connections under the transverse cyclic load

A modeling method under lateral cyclic loading is proposed for the complex multi-bolt connection loosening problem. Firstly, the thread stress surface is divided into n small sectors, and the self-relaxation mechanical model of multi-bolt connection is established considering the interaction between bolts. Secondly, the self-relaxation model is solved by MATLAB software and compared with Nassar model to verify the correctness of the model. Finally, considering the influence of different bolt number, hole clearance and connection spacing, the relaxation characteristics of multi-bolt connection are studied. The results show that during the loosening process, the bolt head undergoes a bending-sliding-bending cycle process, and the bolt tension shows a wave downward trend. When multiple bolts are connected, the number of loosening cycles decreases linearly with the increase of hole clearance. With the equidistant increase of bolt connection spacing, the number of bolt loosening cycles shows a decreasing trend. Compared with the number of bolts, the change of bolt hole clearance and connection spacing is more likely to affect bolt loosening.

Nonlinear dielectric response and conductivity characteristics of epoxy resin in high voltage AC electric field

Abstract High-voltage dielectric and AC conduction behaviors of epoxy resin (EP) insulation are beneficial for the design and application of solid-state power electronic devices. This study investigates the nonlinear dielectric response and AC conduction characteristics of EP. The dielectric relaxation characteristics, including permittivity and AC conductivity of the EP samples, were investigated using high-voltage dielectric spectroscopy and the ionic polarization model. The results demonstrate a nonlinear increase in the relative permittivity and AC conductivity concerning the AC electric field. The increase in AC conduction under a high-frequency electric field is attributed to the reduction in the threshold field for charge injection caused by elevated temperatures. Considering the dielectric response and carrier hopping, it is evident that the nonlinear dielectric response of EP primarily originates from the ionic process under high electric fields. Ionic polarization, in conjunction with ion-hopping conduction, enhances the dielectric loss at high frequencies and electric fields, thereby facilitating the nonlinear conversion of AC conduction. The equivalent free volume is likely to increase in high-frequency fields. This phenomenon leads to an increase in AC conduction and even dielectric breakdown. This study offers a pivotal theoretical framework for the design and application of high-frequency insulation.

Dielectric analysis of unpolymerized and photopolymerized NOA65 in a parallel-plate cell

The flourishing development of liquid crystal research in recent decades has highlighted the importance of polymer materials in enhancing liquid–crystal material and device properties, demonstrating tremendous potential in a wide range of industries. One of the polymer materials widely used in polymer-dispersed liquid crystal is Norland UV-curable optical adhesive (NOA65). This study focuses on the dielectric behavior of the optical adhesive in a parallel-plate cell. Given the broadness and asymmetry of the dielectric dispersion curve, the two-relaxation Havriliak–Negami model was employed to analyze the complex dielectric spectra of NOA65 before and after photocuring. Experimental results indicate that as temperature rises, the dielectric relaxation of NOA65 undergoes a blue shift, leading to an eventual overlap with pseudo-dielectric relaxation at a higher frequency. This brings about an increase in the obtained signal in the dielectric loss spectrum, implying that the observed feature of pseudo-dielectric relaxation is actually superposed or contributed by the intrinsic relaxation signal. Furthermore, as temperature continues to rise, the intrinsic dielectric loss signal of NOA65 becomes untraceable beyond the frequency span within which the pseudo-dielectric relaxation signal lies.

Time-dependent relaxation dynamics of remanent strain in textured PMN–PZ–PT and PMN–PIN–PT piezoceramics

Crystallographically textured lead-based piezoceramics, particularly Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 (PMN–PZ–PT) and Pb(Mg1/3Nb2/3)O3–Pb(In1/2Nb1/2)O3–PbTiO3 (PMN–PIN–PT), play a pivotal role in electromechanical applications due to their enhanced field-induced strain responses. However, challenges in precision positioning arise from heightened remanent strain (Sr) caused by embedded templates in the textured grains, impacting strain cycle consistency due to increased time delay for Sr relaxation. This study investigates the time-dependent relaxation dynamics of Sr in textured PMN–PZ–PT and PMN–PIN–PT piezoceramics, focusing on experimentally determining relaxation time between cycles required for complete Sr relaxation. Our findings reveal that the relaxation time in textured piezoceramics is notably longer than that in their non-textured counterparts, primarily due to pinning of domain walls by embedded templates. This work provides insights into the strain relaxation characteristics of piezoceramics and underscores the importance of time delay in designing precision positioning systems for improved reliability.

Optimized energy storage performances via high-entropy design in KNN-based relaxor ferroelectric ceramics

Dielectric capacitors play an irreplaceable role in complex and integrated electronic systems. However, attaining ultrahigh recoverable energy storage density (Wrec) alongside energy storage efficiency (η) poses a formidable challenge, impeding the advance towards the miniaturization and integration of cutting-edge energy storage devices. In this work, a high-entropy strategy with a viscous polymer process is adopted, bringing about ultrafine grains and polar nanoregions (PNRs) accompanied by enhanced electrical homogeneity and polarization relaxation characteristics. As a result, an ultrahigh Wrec ∼ 7.51 J/cm3 is achieved in a high-entropy KNN-based energy storage ceramic with a high η ∼ 88.4% at 750 kV/cm. Moreover, the ceramic capacitor exhibits a colossal power density reaching approximately 420 MW/cm3 and a discharge energy density of approximately 4.85 J/cm3 at 160 ℃. Impressively, it maintains low variation rates of less than 4% across a broad temperature range from 20 ℃ to 160 ℃. The new approach opens avenues for the design and development of superior dielectric materials used in next-generation high-power pulse devices.

Experimental study on the macroscopic and mesoscopic mechanical characteristics of deep damaged and fractured rock

Most of the rock surrounding deep roadways is in a fractured state; fractured rock has significant rheological properties, and the time-dependent mechanical properties of fractured rock affect excavation construction, support design, and long-term stability of deep roadways. Triaxial compression and mercury intrusion tests are conducted on the bearing characteristics of severely damaged and fractured rock samples, indicating the strength degradation properties of these samples. The evolution of the internal pore structure in damaged and fractured rock samples is analyzed in relation to changes in unloading points (pre-peak stage, peak point, and post-peak stage), leading to the establishment of a quantitative evaluation index for rock damage based on the porosity evolution. Short-term rheological testing is performed on rock samples with varying degrees of damage and fracture, demonstrating the evolution of creep and stress relaxation characteristics. The findings contribute to a deeper theoretical understanding of the post-peak mechanical properties of coal and rock masses, which hold significant theoretical implications and can inform research on long-term stability in underground engineering applications, such as deeply buried roadways, tunnels, and chambers.

Exploring the Impact of Ring Mobility on the Macroscopic Properties of Doubly Threaded Slide-Ring Gel Networks.

The integration of mechanically interlocked molecules (MIMs) into polymeric materials has led to the development of mechanically interlocked polymers (MIPs). One class of MIPs that have gained attention in recent years are slide-ring gels (SRGs), which are generally accessed by crosslinking rings on a main-chain polyrotaxane. The mobility of the interlocked crosslinking moieties along the polymer backbone imparts enhanced properties onto these networks. An alternative synthetic approach to SRGs is to use a doubly threaded ring as the crosslinking moiety, yielding doubly threaded slide-ring gel networks (dt-SRGs). In this study, a photo-curable ligand-containing thread was used to assemble a series of metal-templated pseudo[3]rotaxane crosslinkers that allow access to polymer networks that contain doubly threaded interlocked rings. The physicochemical and mechanical properties of these dt-SRGs with varying size of the ring crosslinking moieties were investigated and compared to an entangled gel (EG) prepared by polymerizing the metal complex of the photo-curable ligand-containing thread, and a corresponding covalent gel (CG). Relative to the EG and CG, the dt-SRGs exhibit enhanced swelling behavior, viscoelastic properties, and stress relaxation characteristics. In addition, the macroscopic properties of dt-SRGs could be altered by "locking" ring mobility in the structure through remetalation, highlighting the impact of the mobility of the crosslinks.