First-principles calculation of self-interstitial atom-impurity atom interactions in ferritic steel.

In this study, the interactions between self-interstitial atoms (SIA) and impurity atoms (Cu and P) in the body-centered cubic (bcc)-Fe matrix have been investigated using the first principles approach. The results show that Cu and P atoms are more prone to segregation on perpendicular and parallel surfaces containing dumbbell atoms, respectively. Next, by combining the charge density difference and considering the electronic structure and lattice distortion, the origin of the binding energy of complexes formed between SIA and impurity atoms was discussed. The results show that as the number of impurity atoms increases, the atomic bonds formed by the interactions between the impurity atoms decrease the binding energy between single impurity atoms and the matrix and reduce the strain field around them, resulting in an increase in the stability of the complexes. Comparison with previous experimental results revealed the reasons for the changes in atomic occupancy during the segregation of Cu and P atoms. The results provide insights into the behavior of impurity atoms in irradiated materials and provide a deeper understanding of the electron level of impurity atomization.

Defect properties of a body-centered cubic equiatomic TiVZrTa high-entropy alloy from atomistic simulations.

TiVZrTa high-entropy alloys (HEAs) have been experimentally proven to exhibit excellent irradiation tolerance. In this work, defect energies and evolution were studied to reveal the underlying mechanisms of the excellent irradiation tolerance in TiVZrTa HEA via molecular statics calculations and molecular dynamics simulations. The atomic size mismatch of TiVZrTa is ∼6%, suggesting a larger lattice distortion compared to most face-centered cubic and body-centered cubic M/HEAs. Compared to pure Ta and V, smaller vacancy formation and migration energies with large energy spreads lead to higher equilibrium vacancy concentration and faster vacancy diffusion via low-energy migration paths. Vacancies in TiVZrTa have weaker abilities to form large vacancy clusters and prefer to form small clusters, indicating excellent resistance to radiation swelling. The formation energies of different types of dumbbells in TiVZrTa show significant differences and have large energy spreads. The binding abilities of interstitials in TiVZrTa are weaker compared to that in pure Ta and V. In TiVZrTa, fast vacancy diffusion and slow interstitial diffusion result in closer mobilities of vacancies and interstitials, significantly promoting point defect recombination. We further studied the effects of short-range ordered structures (SROs) on defect diffusion and evolution. SROs in TiVZrTa can effectively lead to higher fractions of defect recombination and fewer surviving defects. Our findings provide a comprehensive understanding of the underlying mechanisms of the high irradiation tolerance in body-centered cubic HEAs with large lattice distortion and suggest SROs are beneficial microstructures for enhancing irradiation tolerance.

Defect Filling Method of Sensor Encapsulation Based on Micro-Nano Composite Structure with Parylene Coating.

The demand for waterproofing of polymer (parylene) coating encapsulation has increased in a wide variety of applications, especially in the waterproof protection of electronic devices. However, parylene coatings often produce pinholes and cracks, which will reduce the waterproof effect as a protective barrier. This characteristic has a more significant influence on sensors and actuators with movable parts. Thus, a defect filling method of micro-nano composite structure is proposed to improve the waterproof ability of parylene coatings. The defect filling method is composed of a nano layer of Al2O3 molecules and a micro layer of parylene polymer. Based on the diffusion mechanism of water molecules in the polymer membrane, defects on the surface of polymer encapsulation will be filled and decomposed into smaller areas by Al2O3 nanoparticles to delay or hinder the penetration of water molecules. Accordingly, the dense Al2O3 nanoparticles are utilized to fill and repair the surface of the organic polymer by low-rate atomic layer deposition. This paper takes the pressure sensor as an example to carry out the corresponding research. Experimental results show that the proposed method is very effective and the encapsulated sensors work properly in a saline solution after a period of time equivalent to 153.9 days in body temperature, maintaining their accuracy and precision of 2 mmHg. Moreover, the sensors could improve accuracy by about 43% after the proposed encapsulation. Therefore, the water molecule anti-permeability encapsulation would have broad application prospects in micro/nano-device protection.

Ultrathin and Robust Micro-Nano Composite Coating for Implantable Pressure Sensor Encapsulation.

Implantable pressure sensors enable more accurate disease diagnosis and real-time monitoring. Their widescale usage is dependent on a reliable encapsulation to protect them from corrosion of body fluids, yet not increasing their sizes or impairing their sensing functions during their lifespans. To realize the above requirements, an ultrathin, flexible, waterproof while robust micro-nano composite coating for encapsulation of an implantable pressure sensor is designed. The composite coating is composed of a nanolayer of silane-coupled molecules and a microlayer of parylene polymers. The mechanism and principle of the composite encapsulation coating with high adhesion are elucidated. Experimental results show that the error of the sensors after encapsulation is less than 2 mmHg, after working continuously for equivalently over 434 days in a simulated body fluid environment. The effects of the coating thickness on the waterproof time and the error of the sensor are also studied. The encapsulated sensor is implanted in an isolated porcine eye and a living rabbit eye, exhibiting excellent performances. Therefore, the micro-nano composite encapsulation coating would have an appealing application in micro-nano-device protections, especially for implantable biomedical devices.

Regulating Surface and Grain-Boundary Structures of Ni-Rich Layered Cathodes for Ultrahigh Cycle Stability.

The wide applications of Ni-rich LiNi1- x-y Cox Mny O2 cathodes are severely limited by capacity fading and voltage fading during the cycling process resulting from the pulverization of particles, interfacial side reactions, and phase transformation. The canonical surface modification approach can improve the stability to a certain extent; however, it fails to resolve the key bottlenecks. The preparation of Li(Ni0.4 Co0.2 Mn0.4 )1- x Tix O2 on the surface of LiNi0.8 Co0.1 Mn0.1 O2 particles with a coprecipitation method is reported. After sintering, Ti diffuses into the interior and mainly distributes along surface and grain boundaries. A strong surface and grain boundary strengthening are simultaneously achieved. The pristine particles are fully pulverized into first particles due to mechanical instability and high strains, which results in serious capacity fading. In contrast, the strong surface and the grain boundary strengthening can maintain the structural integrity, and therefore significantly improve the cycle stability. A general and simple strategy for the design of high-performance Ni-rich LiNi1- x - y Cox Mny O2 cathode is provided and is applicable to surface modification and grain-boundary regulation of other advanced cathodes for batteries.

A Simple, Low-Cost Micro-Coating Method for Accuracy Improvement and Its Application in Pressure Sensors.

The demand for high-accuracy pressure sensors has increased with the advancement of technology in a wide variety of applications. However, it is generally difficult and expensive to improve the accuracy of the pressure sensor because it usually depends on the sensing principle and the internal physical structure of the pressure sensor, varying with its material and production process. Thus, a simple, low-cost, and generally applied post-processing method is proposed to improve the accuracy of pressure sensors. In this method, a micro-coating is cladded on the surface of the sensor, which effectively isolates the adverse effect of the external environment, similar to applying a "micro-protective clothing" on the pressure sensor. Experiments on seven pressure sensors are conducted, in which the micron-thin parylene polymer is utilized as the surface-deposited coating layer to demonstrate the improvement of accuracy. Results show that the accuracy was improved, with an average increase of approximately 62.54% than before cladding, while the sensitivity was almost unchanged. The principle of improving the accuracy of this method was also analyzed. The proposed simple, efficient, and low-cost method of cladding micro-coating for enhancing the accuracy of sensors can be widely applied in various fields of industrial automatic control.

Fabrication and Microstructure of Laminated HAP⁻45S5 Bioglass Ceramics by Spark Plasma Sintering.

Hydroxyapatite (HAP) has excellent biocompatibility with living bone tissue and does not cause defensive body reactions, therefore, it has become one of the most widely used calcium phosphate materials in dental and medical fields. However, its poor mechanical properties have been a substantial challenge in the application of HAP for the replacement of load-bearing or large bone defects. Laminated HAP⁻45S5 bioglass ceramics composites were prepared by the spark plasma sintering (SPS) technique. The interface structures between the HAP and 45S5 bioglass layers and the mechanical properties of the laminated composites were investigated. It was demonstrated that there was mutual transfer and exchange of Ca and Na atoms at the interface between 45S5 bioglass/HAP laminated layers, which contributed considerably to the interfacial bonding. Due from the laminated structure and strong interface bonding, laminated HAP⁻45S5 bioglass is recommended for structural applications.