Nanoscale Level Research Articles

Nanoscale single-vesicle analysis: High-throughput approaches through AI-enhanced super-resolution image analysis

The analysis of membrane vesicles at the nanoscale level is crucial for advancing the understanding of intercellular communication and its implications for health and disease. Despite their significance, the nanoscale analysis of vesicles at the single particle level faces challenges owing to their small size and the complexity of biological fluids. This new vesicle analysis tool leverages the single-molecule sensitivity of super-resolution microscopy (SRM) and the high-throughput analysis capability of deep-learning algorithms. By comparing classical clustering methods (k-means, DBSCAN, and SR-Tesseler) with deep-learning-based approaches (YOLO, DETR, Deformable DETR, and Faster R–CNN) for the analysis of super-resolution fluorescence images of exosomes, we identified the deep-learning algorithm, Deformable DETR, as the most effective. It showed superior accuracy and a reduced processing time for detecting individual vesicles from SRM images. Our findings demonstrate that image-based deep-learning-enhanced methods from SRM images significantly outperform traditional coordinate-based clustering techniques in identifying individual vesicles and resolving the challenges related to misidentification and computational demands. Moreover, the application of the combined Deformable DETR and ConvNeXt-S algorithms to differently labeled exosomes revealed its capability to differentiate between them, indicating its potential to dissect the heterogeneity of vesicle populations. This breakthrough in vesicle analysis suggests a paradigm shift towards the integration of AI into super-resolution imaging, which is promising for unlocking new frontiers in vesicle biology, disease diagnostics, and the development of vesicle-based therapeutics.

Silver nanoparticles (AGNPs): A review on properties and behavior of silver at the nanoscale level

Silver nanoparticles (AgNPs) have garnered significant interest due to their unique and enhanced properties compared to bulk silver. These nanoparticles exhibit remarkable chemical, physical, and biological characteristics, primarily attributed to their high surface area-to-volume ratio and nanoscale dimensions. Key properties include superior antibacterial, antiviral, and antifungal activities, potent catalytic capabilities, and distinctive optical properties, such as localized surface plasmon resonance (LSPR). These enhanced properties stem from the increased surface reactivity and quantum effects at the nanoscale. AgNPs are extensively applied across various fields. In medicine, they are utilized for their antimicrobial properties in wound dressings, coatings for medical devices, and as components in drug delivery systems. In environmental science, they serve as effective agents in water treatment processes due to their potent antimicrobial action. Additionally, AgNPs are employed in electronics for conductive inks, in catalysis for chemical reactions, and in textiles for producing antibacterial fabrics. The improved properties of silver nanoparticles over bulk silver are mainly due to the increased proportion of surface atoms, which leads to higher surface energy and reactivity. Furthermore, the nanoscale dimensions allow for quantum confinement effects, enhancing their optical and electronic properties. These unique characteristics enable AgNPs to perform more effectively and efficiently in various applications, making them a vital component in advancing technology and healthcare solutions.

Nanotechnology applications in breast implant manufacturing for improved durability and functionality

Breast implants are often used in restorative and cosmetic surgeries. However, the materials used for implants today could be better regarding biocompatibility and mechanical strength. It is possible to make composite biomaterials out of nanomaterials with better mechanical qualities than common implant materials like silicone elastomers and saline-filled shells. Researchers have found that adding carbon nanotubes, graphene, and hydroxyapatite nanoparticles to the shells of metal and silicone implants makes them much stronger, more flexible, and less likely to break. Researchers are also looking into polymer nanocomposites made of polycaprolactone and polylactic acid to see if they can break down better and integrate better with tissues. Changing the surface of implants at the nanoscale level can make them more biocompatible by controlling how proteins stick to the material and how cells interact with it. Animal tests with nanocoatings of polyacrylate, chitosan, and hyaluronic acid showed that they lowered the formation of capsules and inflammation. Antimicrobial nanoparticles, such as silver, zinc oxide, and antibiotics, are attached to the surfaces of implants to protect against infections and release drugs locally. Nanocontrast agents are used in high-resolution MRI and ultrasound images of implant shell integrity to get new imaging and diagnosis tools. By tracking biomarkers, nanostructured sensors could be used to find seromas, ruptures, and device failures with little to no damage. Much work has been done to show that different nanotechnologies can help breast implants in a pre-clinical setting. However, problems with regulation and standardization still need to be fixed before the implants can be used in people and made in large quantities. The process needs to be improved even more to make a lot of nanocomposite and etched surfaces. To make sure patients are safe, it is also important to do long-term biocompatibility and nanotoxicology tests. Nanotechnology has a lot of promise to change the way breast implants are made so that they look better and improve people's quality of life. This review examines nanotechnology's emerging applications for enhancing breast implants' durability and performance.

Optical axis-driven field enhancement in a hyperbolic medium.

Field enhancement of applied electric field is the foundation for the variety of applied domains at a nanoscale level. Traditionally, efforts to achieve field enhancement have required the use of complicated metamaterial-based structures with a transition behavior. Here, the electromagnetic field solution of the TM-polarized wave that interacts with an optical-axis-driven hyperbolic medium with a transition behavior is established. Detailed calculations reveal that such field enhancement can be achieved over a broad range of incident angles (i.e., near critical angle). Definitely, such flexibility of the incident angle for achieving the field enhancement enriches the understanding and provides novel prospective toward its practical realization.

Stereocilia fusion pathology in the cochlear outer hair cells at the nanoscale level.

The hair bundle of cochlear hair cells comprises specialized microvilli, the stereocilia, which fulfil the role of mechanotransduction. Genetic defects and environmental noise challenge the maintenance of hair bundle structure, critically contributing to age-related hearing loss. Stereocilia fusion is a major component of the hair bundle pathology in mature hair cells, but its role in hearing loss and its molecular basis are poorly understood. Here, we utilized super-resolution expansion microscopy to examine the molecular anatomy of outer hair cell stereocilia fusion in mouse models of age-related hearing loss, heightened endoplasmic reticulum stress and prolonged noise exposure. Prominent stereocilia fusion in our model of heightened endoplasmic reticulum stress, Manf (Mesencephalic astrocyte-derived neurotrophic factor)-inactivated mice in a background with Cadherin 23missense mutation, impaired mechanotransduction and calcium balance in stereocilia. This was indicated by reduced FM1-43 dye uptake through the mechanotransduction channels, reduced neuroplastin/PMCA2 expression and increased expression of the calcium buffer oncomodulin inside stereocilia. Sparse BAIAP2L2 and myosin 7a expression was retained in the fused stereocilia but mislocalized away from their functional sites at the tips. These hair bundle abnormalities preceded cell soma degeneration, suggesting a sequela from stereociliary molecular perturbations to cell death signalling. In the age-related hearing loss and noise-exposure models, stereocilia fusion was more restricted within the bundles, yet both models exhibited oncomodulin upregulation at the fusion sites, implying perturbed calcium homeostasis. We conclude that stereocilia fusion is linked with the failure to maintain cellular proteostasis and with disturbances in stereociliary calcium balance. KEY POINTS: Stereocilia fusion is a hair cell pathology causing hearing loss. Inactivation of Manf, a component of the endoplasmic reticulum proteostasis machinery, has a cell-intrinsic mode of action in triggering outer hair cell stereocilia fusion and the death of these cells. The genetic background with Cadherin 23missense mutation contributes to the high susceptibility of outer hair cells to stereocilia fusion, evidenced in Manf-inactivated mice and in the mouse models of early-onset hearing loss and noise exposure. Endoplasmic reticulum stress feeds to outer hair cell stereocilia bundle pathology and impairs the molecular anatomy of calcium regulation. The maintenance of the outer hair cell stereocilia bundle cohesion is challenged by intrinsic and extrinsic stressors, and understanding the underlying mechanisms will probably benefit the development of interventions to promote hearing health.

Quantifying and Modeling the Crystallinity of Polymers Confined in Nanopores.

We propose a methodology to characterize the crystalline content of interfacial polymer layers in systems confined at the nanoscale level in a 2D geometry. Based on the crystallinity data of a set of polymers, we introduce a simple model to describe the gradient in crystallinity introduced by confining polymer chains in nanopores. Our model underscores the pivotal role that interfaces play in crystallization and unequivocally contradicts the existence of interfacial "dead" layers where crystallization cannot take place. Further, we verified that the organization of crystals near the pore walls resembles the macromolecular architecture of adsorbed layers, hinting at a strong interplay between crystallization and adsorption.

Enhanced figure of merit in two-dimensional ZrNiSn nanosheets for thermoelectric applications

A novel two-dimensional (2D) half-Heusler ZrNiSn nanosheet for thermoelectric applications was designed from bulk half-Heusler ZrNiSn through first-principles calculation. Investigation of bulk half-Heusler and 2D nanosheet ZrNiSn was performed with the Quantum Espresso code based on a density functional theory plane wave basis set. Electronic band structure and density of states calculations were used to study the confinement effects. On moving from bulk to 2D a change of structure is observed from face-centered cubic to trigonal due to confinement effects. The semiconducting nature of bulk ZrNiSn is undisturbed while moving to a 2D nanosheet; however, the band gap is widened from 0.46 to 1.3 eV due to the restricted motion of electrons in one direction. Compared with bulk ZrNiSn, 2D nanosheets were found to have a higher Seebeck coefficient a lower thermal conductivity and higher figure of merit, which makes 2D ZrNiSn nanosheets suitable for thermoelectric applications. Atomically thin 2D structures with a flat surface have the potential to form van der Waals heterojunctions, paving the way for device fabrication at the nanoscale level.

Efficiently high energy storage density in Ba2+ ion modified K0·5Na0·5NbO3 (KNN) ferroelectric ceramics for super capacitors

In the present work, Perovskites BaxK0.5-xNa0.5NbO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) were synthesized via solid-state synthesis technique. XRD analysis confirmed the successful phase formation of the synthesized perovskites. Further, Rietveld refinement revealed the presence of coexisting orthorhombic and tetragonal phases. High-resolution transmission electron microscopy (HRTEM) was employed to explore the lattice fringes and SAED patterns at nano scale level of prepared samples. The morphology was investigated using a field emission scanning electron microscope (FESEM). Dielectric measurements indicated that both the dielectric constant (ε′) and loss tangent (tan δ) exhibited significant dispersion at low frequencies and high temperatures. Notably, the Ba-doped perovskite samples demonstrated enhanced dielectric properties compared to the undoped KNN sample, with Ba0·1K0·4Na0·5NbO3 (x = 0.10) showing optimal dielectric performance, characterized by a dielectric constant (ɛ՛⁓4000) and a tanẟ ⁓7.23 at 100 Hz frequency and room temperature.AC conductivity is observed to increase with increasing both frequency and temperature. DC conductivity exhibited positive temperature coefficient indicating the semiconductor-like behavior of the prepared samples. The ferroelectric behavior was confirmed through P-E hysteresis curves and Ba0·1K0·4Na0·5NbO3 sample revealed the highest energy storage density among all prepared samples making it a suitable candidate for energy storage applications.

Graph Theoretical Description of Phase Transitions in Complex Multiscale Phases with Supramolecular Assemblies.

Phase transitions are typically quantified using order parameters, such as crystal lattice distances and radial distribution functions, which can identify subtle changes in crystalline materials or high-contrast phases with large structural differences. However, the identification of phases with high complexity, multiscale organization and of complex patterns during the structural fluctuations preceding phase transitions, which are essential for understanding the system pathways between phases, is challenging for those traditional analyses. Here, it is shown that for two model systems- thermotropic liquid crystals and a lyotropic water/surfactant mixtures-graph theoretical (GT) descriptors can successfully identify complex phases combining molecular and nanoscale levels of organization that are hard to characterize with traditional methodologies. Furthermore, the GT descriptors also reveal the pathways between the different phases. Specifically, centrality parameters and node-based fractal dimension quantify the system behavior preceding the transitions, capturing fluctuation-induced breakup of aggregates and their long-range cooperative interactions. GT parameterization can be generalized for a wide range of chemical systems and be instrumental for the growth mechanisms of complex nanostructures.

Synergistic effect of carbonation and dry–wet cycles on the adhesion, elastic modulus, and dimensional stability of rendering mortars – A multiscale approach

This study explored the combined effects of drying and wetting cycles with carbonation aging on rendering mortars and investigated mechanical properties, bond strength, dimensional stability, and durability at the macro and nanoscale levels. The rendered mortars were evaluated individually and applied to a ceramic substrate. The prepared samples were cured for 150 days, carbonated (5 % CO2 and an RH of 60 %), and underwent 20 drying–wetting cycles. Carbonation shrinks the mortar, which can be completely reversed after the first drying–wetting cycle. Exposing the mortar to drying–wetting cycles suppresses the improvements in the bond strength and modulus of elasticity attributed to carbonation. The nanoscale tests confirmed the results measured in the macroscale. In conclusion, this paper showed that changes in the render caused by carbonation may be reversed after wetting and drying cycles.

Understanding of Lanthanide-Doped Core-Shell Structure at the Nanoscale Level.

The groundbreaking development of lanthanide-doped core-shell nanostructures have successfully achieved precise optical tuning of rare-earth nanocrystals, leading to significant improvements in energy transfer efficiency and facilitating multifunctional integration. Exploring the atomic-level structural, physical, and optical properties of rare-earth core-shell nanocrystals is essential for advancing our understanding of their fundamental principles and driving the development of emerging applications. However, our knowledge of the atomic-level structural details of rare-earth nanocrystal core-shell structures remains limited. This review provides a comprehensive discussion of synthesis strategies, characterization techniques, interfacial ion-mixing phenomena, strain effects, and spectral modulation in core-shell structures of rare-earth-doped nanocrystals. Additionally, we prospectively discuss the challenges encountered in studying the fine structures of rare-earth-doped core-shell nanocrystals, particularly the increasing demand for researchers to integrate interdisciplinary knowledge and utilize high-end precision instruments.

Nanoengineering of Cathode Catalysts for Li-O2 Batteries.

Lithium-oxygen (Li-O2) batteries have obtained widespread attention as next-generation energy storage systems due to their extremely high energy density. However, the high charge overpotential, attributed to the insulating property of Li2O2, significantly limits the energy efficiency and triggers solvent degradation. The high electrochemical activities of oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) on the cathode are crucial for alleviating the high charging polarizations and enhancing the lifetime of Li-O2 batteries, which are also top challenges of state-of-art research. In this review, the scientific challenges and the proposed solutions in the development of cathode catalysts have been summarized. The recent research advancements on the nanoengineering of cathode catalysts for Li-O2 batteries have been comprehensively discussed, and the perspectives on the structure optimization are presented. Meanwhile, we have elucidated the structure-performance relationship between the electronic state and performance of the cathode catalysts at the nanoscale level. This review intends to provide guidelines for the design and construction of cathode catalysts in advanced Li-O2 batteries.

Room temperature thermal rectification in suspended asymmetric graphene ribbon

Thermal rectifiers are essential in optimizing heat dissipation in solid-state devices to enhance energy efficiency, reliability, and overall performance. In this study, we experimentally investigate the thermal rectification phenomenon in suspended asymmetric graphene ribbons (GRs). The asymmetry within the graphene is introduced by incorporating periodic parallel nanoribbons on one side of the GR while maintaining the other side in a pristine form. Our findings reveal a substantial thermal rectification effect in these asymmetric graphene devices, reaching up to 45% at room temperature and increasing further at lower environmental temperatures. This effect is attributed to a significant thermal conductivity contrast between pristine graphene and nanoribbon graphene within the asymmetric structure. We observe that the incorporation of nanoribbons leads to a notable reduction in thermal conductivity, primarily due to phonon scattering and bottleneck effects near the nanoribbon edges. These findings suggest that graphene structures exhibiting asymmetry, facilitated by parallel nanoribbons, hold promise for effective heat management at the nanoscale level and the development of practical phononic devices.

AI analysis of super-resolution microscopy: Biological discovery in the absence of ground truth.

Super-resolution microscopy, or nanoscopy, enables the use of fluorescent-based molecular localization tools to study molecular structure at the nanoscale level in the intact cell, bridging the mesoscale gap to classical structural biology methodologies. Analysis of super-resolution data by artificial intelligence (AI), such as machine learning, offers tremendous potential for the discovery of new biology, that, by definition, is not known and lacks ground truth. Herein, we describe the application of weakly supervised paradigms to super-resolution microscopy and its potential to enable the accelerated exploration of the nanoscale architecture of subcellular macromolecules and organelles.

ExSeq: Expansion Sequencing for Single-Cell Spatial Transcriptomics

The innovation of spatial transcriptomics allows for the study of gene expression while preserving spatial information on the detected transcripts. Expansion Sequencing (ExSeq) is an advanced spatial transcriptomic method combining in situ sequencing with expansion microscopy, thus enablingthe sequencing of RNAs in a physically enlarged tissue. The experiment involves the steps of tissue expansion, RNA library preparation and multiplexed sequencing by rounds of fluorescent dye addition, imaging and fluorescent dye removal. ExSeq significantly enhances resolution capacity of RNA transcripts up to the nanoscale level, thus identifying subcellular location of RNAs. The method is applicable to exploring cellular RNA in an untargeted approach, as well as to specifically detecting certain RNA types in a targeted approach, thus making the method suitable for a variety of research questions. However, limitations to the method include referring to the readout length of transcripts obtainable during sequencing and the availability of the method. ExSeq has the potential to be used in multiple tissues to allow for new insights into cellular identity, heterogeneity, interactions and implications in diseases and could possibly be adapted to inquire other cellular molecules, such as DNA or proteins on a nanoscale level.

Strength Indicators of Fiber Reinforced Concrete with Carbon Nanomaterials

Concrete composites with low defects, dense and homogeneous, with a high degree of adhesion between the cement matrix and aggregates, as well as a high ratio between static tensile and compressive strengths and plasticity have the best crack resistance characteristics. This ratio increases in the case of the use of fiber-reinforced concrete. Modern research in nanotechnology focuses on the management of matter at the nanoscale level, which makes it possible to create materials with new properties. Due to the high aspect ratio, flexibility, high strength and rigidity, carbon nanotubes (CNTs) exhibit reinforcing properties. Due to their nanoscale features, CNTs interact with a complex network of calcium-silicate-hydrate binder (C – S – H), contribute to a decrease in porosity and compaction of the cement stone structure, increase the shear forces of matrix adhesion in the contact zone. Thus, there are all prerequisites to assert that fiber concrete with a cement matrix modified with carbon nanotubes will have the required high strength characteristics and crack resistance due to multilevel dispersed reinforcement and the efficient operation of fiber in a nanomodified concrete matrix. This article presents the results of testing samples made of cement stone, concrete and fiber concrete with carbon nanotubes. The presence of carbon nanotubes in cement stone contributes to an increase in compressive strength by 11 %, tensile strength during bending by 20 %. The test results of samples made of reinforced fiber concrete modified with nanocarbon materials have shown an increase in tensile strength during bending up to 109 %, tensile strength during splitting up to 82 %, axial tensile strength up to 78 %.

A broad-band investigation of ferromagnetic resonance in exchange coupled permalloy/phthalocyanine bilayer heterostructures at room temperature

The phenomenon of ferromagnet/molecule interfacial electronic hybridization enables the possibility of modifying magnetic characteristics of downscaled systems for spintronic applications. Ferromagnetic resonance (FMR) at the nanoscale level through a coplanar waveguide (CPW) over a wide frequency range is a remarkably reliable technique for investigation of the magnetic heterostructure’s interfacial properties and their feasibility in applications as spintronic devices. Here, magnetron sputtering and organic molecular beam epitaxy methods are used to fabricate the following nanoscale heterostructures: permalloy (Py)/Fe phthalocyanine (Pc), Py/ZnPc, and Py/Cr. Magnetization dynamics of the bilayer heterostructures is investigated in a CPW by studying frequency dependence (5–50 GHz) of the resonance field and linewidth with parallel and perpendicular geometries of the static applied magnetic field, thereby providing insights into possible intrinsic and extrinsic sources of FMR damping. Planar Pc molecules at the Py layer interface are found to have the potential to contribute to magnetic stabilization based on calculated magnetic parameters. This is evidenced by the larger results of surface anisotropy of the Py/MPc bilayer heterostructures induced by exchange coupling interaction at room temperature as well as the lower values of damping constant.

Mechanical-scan-free multicolor super-resolution imaging with diffractive spot array illumination.

Point-scanning microscopy approaches are transforming super-resolution imaging. Despite achieving parallel high-speed imaging using multifocal techniques, efficient multicolor imaging methods with high-quality illumination are currently lacking. In this paper, we present for the first time Mechanical-scan-free multiColor Super-resolution Microscopy (MCoSM) with spot array illumination, which enables mechanical-scan-free super-resolution imaging with adjustable resolution and a good effective field-of-view based on spatial light modulators. Through 100-2,500 s super-resolution spot illumination with different effective fields of view for imaging, we demonstrate the adjustable capacity of MCoSM. MCoSM extends existing spectral imaging capabilities through a time-sharing process involving different color illumination with phase-shift scanning while retaining the spatial flexibility of super-resolution imaging with diffractive spot array illumination. To demonstrate the prospects of MCoSM, we perform four-color imaging of fluorescent beads at high resolution. MCoSM provides a versatile platform for studying molecular interactions in complex samples at the nanoscale level.

Cadmium oxide nanoparticles from new organometallic Cd(II)-Schiff base complex and in vitro biological potentials: dual S. aureus and E. coli DNA gyrase inhibition by the precursors via in silico binding modes’ study

At the nanoscale level, several biological processes take place, owing to the potential that engineered nanomaterials might interrelate with bio-molecules and cellular procedures. This study aimed to synthesize cadmium oxide nanoparticles via a one-step calcination process of tetradentate Schiff base-Cd(II) complex at different temperature ranges. The as-synthesized compounds were carried out via a viz UV–visible, elemental analysis, 1H NMR, molar conductivity, transmission electron microscopy (TEM), FT-IR spectroscopy, and X-ray diffraction (PXRD). The band gap energy and average particle sizes of the CdO particles are respectively (2.69 eV, 3.54 eV), 26.88 nm for CdO@250, and (3.20 eV, 3.57 eV), 25.67 nm for CdO@300, while CdO@350 exhibited the 3.78 eV and 28.42 nm values. The antioxidant accomplishments of the test samples through the scavenging activity of DPPH radicals showed CdO@300 to possess (IC50 = 5.18 ± 0.56 µg/mL). Similarly, the as-synthesized CdO nanoparticles exhibited higher antibacterial activities against S. aureus and E. coli as compared to the corresponding Cd-HMB and ligand (HMB), while ciprofloxacin acted as a standard antibiotic. Furthermore, HMB and its complex Cd-HMB were docked against the DNA gyrase enzymes of S. aureus (PDB IDs: 5CDQ) and E. coli (PDB IDs: 6F86) as receptors. The binding sites docking results showed that the binding energies of HMB and Cd-HMB to 5CDQ ranged from − 3.44 to − 4.99 kcal/mol and from − 6.45 to − 6.64 kcal/mol, while the binding energies related to the target 6F86 are in the ranges of (− 3.64, − 4.76) kcal/mol and (− 6.08, − 6.09) kcal/mol respectively. Therefore, the significant antioxidant and antibacterial activities of the ligand (HMB), Cd-HMB, and CdO NPs review the broad application prospects of these compounds as therapeutic agents for wide-ranging biomedical applications.

Fabrication, sintering behavior, and strength of tritium breeding ceramic pebbles with Pb addition

Lithium ceramics are regarded as potential candidates for tritium breeding in fusion reactors. Lead (Pb) was added to the ceramic to improve the strength and tritium release properties. The Li2TiO3-0.5Li4SiO4–Pb ceramic powders with the Pb contents of 5 wt% and 20 wt% were prepared by microwave-induced solution combustion synthesis. It was confirmed that the Pb was in the form of the Li2PbO3 phase in the powders. The Li2TiO3, Li4SiO4, and Li2PbO3 crystallites were composited at nanoscale level, which was confirmed by the transmission electron microscopy (TEM). During high-temperature sintering, the Li2PbO3 was transformed into PbO, which facilitated the densification process at low temperatures. The chemical state in the sintered body was characterized by X-ray photoelectron spectroscopy (XPS) with 3 keV Ar+ sputtering. The binding energies for Pb were 137.2 and 142.2 eV. There was almost no change in peak position during Ar+ sputtering, showing that Pb was firmly adherent with oxygen atoms. Besides, the as-synthesized powders were used for the pebble fabrication. The average crush load of Li2TiO3-0.5Li4SiO4–20%Pb pebbles sintered at 1223 K was 124 N, which was much higher than that without Pb addition. It was proved that the crush load increased almost linearly with the increase in the size of the pebbles. Thus, the bending strength of the sintered ceramic body was used to evaluate the mechanical properties. Further, the grain growth kinetics was studied. It was confirmed that the Pb addition reduced the activation energy of grain growth, which realized the densification of the ceramic pebbles at low temperatures.