Memristive devices that integrate gas sensing with neuromorphic functionality have been identified as a promising route to compact, low-power, and multifunctional artificial olfaction. Herein, we presented a chemically gated memristive device based on a V2CTx MXene/PANI:PSS nanocomposite. A dense, strongly bonded heterostructure was constructed via HF etching followed by in situ oxidative polymerisation, enabling molecular interactions to directly modulate device conductance and thus realise gas-electrical co-operative synaptic operation. As a gas sensor, the device shows a 31.8% response to 5 ppm NH3, with response/recovery times of 26 s/52 s and >95% signal retention over 15 days at room temperature. As a memristor, it exhibits stable bipolar resistive switching (ON/OFF > 102) with a switching time of ∼10 ms; under preset gaseous atmospheres and pre-synaptic electrical pulses, EPSC/IPSC and PPD-type temporal plasticity are elicited. Mechanistically, protonation/deprotonation of PANI sets the chemical working point, while interfacial trap charging and barrier modulation at the V2CTx/PANI interface enable reversible conductance updates, mapping molecular events into time-amplitude fingerprints. At the array level, a 2 × 2 crossbar with a multi-task neural network enables parallel identification of gas type and concentration, achieving 96.2% and 94.1% accuracy, respectively. This strategy enables an end-to-end chain-from molecular transduction through synaptic modulation to algorithmic inference-within a single device, providing a scalable path to compact, low-power artificial olfaction hardware.

MAX phases are promising materials for nuclear reactor components and advanced nuclear energy systems due to their tolerance of irradiation and capability of working under extreme conditions. When exploring the damage mechanism of the MAX phase under irradiation using molecular dynamics simulations, the reliability of the results largely depends on the accuracy of the interatomic potential. While the conventional Tersoff potential is capable of studying the equilibrium state properties of covalently bonded systems, its description of short-range atomic interactions often leads to biased results. In this study, we introduce a modified interatomic potential model that accurately captures short-range interactions for the Ti3AlC2 MAX phase. This model couples the Ziegler-Biersack-Littmark potential with the potential function from first-principles calculations at the repulsive region and the Tersoff potential at the equilibrium region. It is then employed in collision simulations of Ti3AlC2 under irradiative environment. It is found that the modified potential can well reproduce recently reported stress-strain relationship of Ti3AlC2 nanowires under tension. The calculated phonon dispersion relationship and kinetic energy transfer during collision are all consistent with first-principles calculations. A large Ti3AlC2 model containing 22 968 atoms is also constructed to investigate the structural reconstruction under irradiation. The results demonstrate good capability of our modified model in studying Ti3AlC2 under extreme conditions.

Reversible protonic ceramic cells (RePCC) have attracted significant research attention. We report a novel positive electrode, BaCo0.4Fe0.4Ce0.1Gd0.1O3-s (BCFCeGd), for RePCC applications in this study. Experimental results show the introduction of Ce and Gd in the B site of ABO3 perovskite increases the capacity for oxygen vacancy formation. DFT calculations support these findings by confirming that the substitution of Ce and Gd lowers the oxygen vacancy formation energy. The measured total conductivity of BCFCeGd is1.91 S cm-1, which is slightly higher than the widely recognized BaCo0.4Fe0.4Zr0.1Y0.1O3-s (BCFZY) electrode of 1.70 S cm-1 at 650 degrees C. In terms of symmetrical cell test, the polarization resistance of BCFZY is about 30 % higher than the proposed BCFCeGd electrode under similar testing conditions. Moreover, a tested RePCC full cell with BCFCeGd electrode demonstrates a relatively low polarization resistance of 0.08 Omega cm2 at 650 degrees C, thus enabling a peak power density of 935 mW cm-2 in fuel cell mode. Short-term fuel cell stability test and a 95-cycle test under +/- 360 mA cm-2 reversible operation both demonstrate high stability. The combined insights from experimental data and theoretical modeling suggest that BCFCeGd is a highly promising positive electrode for RePCC applications.

In this study, we introduce an innovative post-processing, i.e., ultrasonic surface rolling process (USRP) to create a grain-size gradient structure in electron beam melting (EBM) fabricated Ti6Al4V alloy. The microstructural evolution mechanisms are revealed through detailed transmission electron microscope (TEM) and highresolution TEM analyses. Notably, deformation twinning is observed to occur in alpha phase with hexagonal close-packed (HCP) structure of EBM-Ti6Al4V alloy, which is associated with the dislocation structure at alpha/(3 boundary and the morphology of (3 phase. Both dislocation motion and deformation twinning contribute to the initial subdivision of the coarse HCP-alpha phase. With plastic deformation accumulated, the dislocation activities will dominate the further refinement of nano-scale HCP-alpha phase and (3 phase with body-centered cubic. Additionally, USRP treatment results in the formation of nano-scale titanium oxide and amorphous structure in the surface of EBM-Ti6Al4V alloy due to the presence of pores, high-density dislocations and boundaries. Our findings offer a theoretical framework for enhancing the mechanical properties to use metal additively manufactured components for aerospace applications via developing a gradient microstructural strategy.

Understanding the graphitization behavior of diamond is crucial for improving its conductivity and advancing all-carbon diamond-based electronic devices. Using nickel (Ni) as catalyst combining with annealing treatment provides a simple method to achieve the graphitization of diamond. However, investigations of the Ni-catalyzed diamond-to-graphite transformation at the atomic level are limited and its underlying mechanisms remain unclear. In this study, atomic insights into the graphitization transformation behavior of Ni-catalyzed diamond were investigated in detail through rapid annealing at different temperatures and in situ heating observations using the transmission electron microscope. The results revealed that Ni recrystallized first as the temperature increased. Then, C atoms in the diamond gradually diffused and migrated into the Ni layer, leading to the formation of a metastable C-Ni compound. As the temperature-induced migration of C atoms continued, the C concentration in the C-Ni compound became supersaturated, resulting in ordered precipitation and forming the graphite layer on the diamond surface. In addition, graphite layers with excellent conductivity and controllable thickness were also achieved at elevating temperatures, demonstrating its potential advantageous of diamond graphitization by Ni catalysis. The results of this work support the development of diamond-based all-carbon devices incorporating high-quality graphite or graphene.

Metal halide perovskites are highly favorable materials for efficient photovoltaic and optoelectronic applications. Understanding the origin of their intrinsic instability under extreme environments is indispensable for their advancement in practical applications. In this work, advanced focused ion beam (FIB)/transmission electron microscope (TEM) characterization techniques were used to investigate the atomic-scale structural evolution of FA-based and MA-based perovskites-specifically, MAPbI3 and FA0.85MA0.1Cs0.05Pb(I2.75Br0.25)3-under diverse extreme conditions, including Ga ion irradiation, thermal cycling, and ultraviolet (UV) exposure. This study revealed that both types of films underwent varying degrees of phase transition and degradation under above extreme environments. Notably, a Pb-rich surface region appeared on perovskite films after the thermal cycling with thickness of approximately 100 nm for the FA-based film and approximately 150 nm for the MA-based film, respectively. In addition, Moire fringes and grain refinement were observed on the surface of the FA-based film following UV exposure. Photoluminescence (PL) mapping was utilized to assess the optoelectronic properties of films before and after exposure to thermal and UV stress. Spectral analysis further illustrated varying degrees of degradation and phase separation induced by these treatments. The visualization of atomic-scale structure evolution under such extreme environments provides critical insights into the stability mechanism of perovskite photovoltaics.

Additively manufactured alloys have a great potential in engineering field, but there still have many issues to be addressed, i.e., the reliability, strength-ductility trade-off of manufactured parts. In this study, a treatment called ultrasonic surface rolling process (USRP) was utilized to achieve superior strength and ductility in the Ti6Al4V alloy prepared via electron beam melting (EBM). The treated additive-manufactured alloy obtained various gradient microstructures and excellent surface quality, as well as its mechanical properties were significantly improved. Especially, the USRP-3 specimen exhibited a high elongation of 17.1 +/- 0.9 % and a good ultimate tensile strength of 1043 +/- 5.0 MPa, which were both higher than those of untreated specimen; the fine laminated structure with a preferred orientation of (1010) direction and gradient structure promoted the hardening capacity and provided the rich dislocations sources, taking a better strength-ductility combination. In addition, the surface microhardness of the multi-pass processed specimen was markedly enhanced. However, excessive USRP treatment would induce micro-cracks in the nano-composite layer, resulting in a significant reduction in ductility. Therefore, appropriate USRP treatment is expected to expand the application range of additive- manufactured metallic materials.

Microstructure can play a vital role in defining mechanical properties of metallic materials. To elucidate this correlation in the case of Ti-15Mo-3Nb-3Al-0.2Si (TB8) alloy, herein, we designed various microstructures via heat treatment exploring the effects of grain size, precipitates and segregation on crack initiation behavior during tensile tests in metastable beta-Ti alloy. After solution treatment at 830 degrees C, the TB8 alloy with equiaxed beta grain displayed a good fracture elongation of 30.2 +/- 0.63%. The adiabatic shearing band and beta ->alpha phase transformation were activated to increase the compatible deformation capability during tensile testing; however, the phase transformation caused the stress concentration in the boundary, resulting in crack initiation. For the samples prepared using solution and low aging at 440 degrees C, large grain, elements segregation at grain boundary and incomplete precipitates induced a slight reduction in ultimate tensile strength and elongation. After solution and aging at 520 degrees C, the short-rod or/and lamellar alpha phase precipitated in beta grain effectively enhancing ultimate tensile strength (1398.71 +/- 15.6 MPa). The increased boundaries provided the interface or precipitation strengthening effect, but high-density dislocations were also accumulated at the beta/alpha interface, causing unstable deformation and crack initiation. These findings advance our understanding of the correlation between microstructure and crack initiation, and provide a basis for designing and customizing the mechanical properties of metastable beta-Ti alloy.

MAX phases have attracted considerable interest due to their structural diversities and potential applications. More than 150 MAX phases have been synthesized, especially expanding the range of A-site atoms from traditional main group elements to subgroup elements with outer layer d electronic structure. However, the functional applications for MAX phases remain somewhat limited. The A-site elements in MAX phases can amplify their inherent properties, transforming primary structural materials into multifunctional materials. As highly catalytic elements, introducing cobalt into the A-site of MAX phases can reveal surprising catalytic activities. Hence, the MAX phase with single-atom-thick cobalt layers was synthesized via an A-site alloying strategy in this work. The obtained V-2(Sn2/3Co1/3)C MAX phase demonstrates efficient electrocatalysis in 5-hydroxymethylfurfural (HMF) oxidation reaction along with hydrogen evolution reaction (HER). In-situ electrochemical studies discover that HMF can prevent the self-reconstruction of MAX phase and oxygen evolution reaction (OER). The overall reaction reaches 94.4% yield to 2,5-furandicarboxylic acid (FDCA) at 1.60 V. Density functional theory calculations suggest that the Co-Sn bimetallic synergy in the A-site promotes the reaction. This groundbreaking investigation into using MAX phases for biomass upgrading highlights their potential in green chemistry and beyond.

Despite extensive efforts devoted to developing self-healing materials in the past half-century, very limited successes are reported for ceramics or metals. Reported self-healing materials usually have low healing strength (megapascal) and long healing time (hours), and the healing of ceramics or metals normally requires external stimuli. Here, we report on intrinsic, highly efficient self-healing phenomena in Ti3AlC2 MAX phase nanowires at room temperature, which exhibit both ceramic and metallic properties. In situ transmission electron microscopy tensile testing reveals that the fracture strength of 2.1 GPa is achieved on the fractured Ti3AlC2 nanowire after self-healing for 5 min, corresponding to the self-healing efficiency of 36.2%, and the smaller the diameter, the higher the self-healing efficiency. The underlying mechanisms are uncovered by atomic-resolution characterizations combined with atomic simulations. The highly efficient self-healing of Ti3AlC2 is attributed to the cleavage behavior, atomic migrations, and rebonding on fracture surfaces. Al atoms trapped between partially filled Al layers on both fracture surfaces act as obstacles for the Ti-Al rebonding and are responsible for the size effect. These findings provide new insights into developing high-performance micro- or nano-devices, especially those that require high security and long service lifetime.

Wide-bandgap semiconductors with high carrier mobility are in great demand for high-power radio-frequency applications. In the past decades, extensive efforts have been devoted to investigating the carrier transport properties of hydrogen-terminated diamond (H-diamond), however, achieving its high hole mobility remains a challenge, thereby limiting the development of diamond electronic devices. Herein, we propose a novel strategy to increase the hole mobility of H-diamond by boron nitride (BN) clusters modifications. Amorphous BN clusters were deposited on high-quality H-diamond surfaces using magnetron sputtering. The modified H-diamond exhibits an ultrahigh hole mobility of 1100 cm2 V-1 s-1, over 10-fold higher than that of H-diamond prior to BN modification. Moreover, the BN-modified H-diamond also exhibits outstanding high-temperature tolerance and excellent thermal stability benefitting from the passivation effect of BN. At 380 K, it still maintains a hole mobility of 385 cm2 V-1 s-1. Even after annealing at 350 K for over 8 h, there are no noticeable variations in its carrier transport properties. The hole mobility enhancing mechanism and the factors influencing carrier transport properties of the BN-modified H-diamond are discussed using first principles calculations analysis. The developed BN-modified H-diamond opens up new possibilities for diamond-based radio-frequency electronic devices operating in challenging temperature environments.

Finding water resources is a crucial objective of lunar missions. However, both hydroxyl (OH) and natural water (H2O) have been reported to be scarce on the Moon. We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith (LR), specifically through the reaction FeO/Fe2O3 + H -> Fe + H2O. This process is demonstrated using LR samples brought back by the Chang'E-5 mission. FeO and Fe2O3 are lunar minerals containing Fe oxides. Hydrogen (H) retained in lunar minerals from the solar wind can be used to produce water. The results of this study reveal that 51-76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K. This amount is similar to 10,000 times the naturally occurring OH and H2O on the Moon. Among the five primary minerals in LR returned by the Chang'E-5 mission, FeTiO3 ilmenite contains the highest amount of H, owing to its unique lattice structure with sub-nanometer tunnels. For the first time, in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles. Electron irradiation promotes the endogenous redox reaction, which is helpful for understanding the distribution of OH on the Moon. Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon, which is helpful for establishing a scientific research station on the Moon.

As a third-generation semiconductor material, chemical vapor deposition (CVD) diamond single crystals find crucial applications in electronic devices. While focused ion beam (FIB) milling which is a commonly employed method for processing micro/nano electronic devices, it inevitably results in the implantation of ion source materials and the formation of tens of nanometers of damaged layer, which is typically excessively thick for modern micro/nano electron devices. This study systematically explores the damaged layer induced by Ga ions during FIB diamond processing. The research revealed that damaged layer on the diamond surface measures 43 nm under 30 kV. The structure and electronic properties of the damaged layer were analyzed using high spatial resolution transmission electron microscopy (TEM) and high energy resolution electron energy loss spectroscopy (EELS) techniques. The findings indicate that the damaged layer consists of a double -layer structure, identified as an a -C I layer mainly composed of sp 2 hybridized carbon atoms and an a -C II layer primarily composed of sp 3 hybridized carbon atoms. Through the integration of results from energy -dispersive X-ray spectroscopy (EDS), EELS, and stopping and range of ions in matter (SRIM) simulations, it was determined that the a -C I layer is predominantly caused by the direct implantation of Ga ions, whereas the a -C II layer is primarily influenced by carbon recoil atoms. Remarkably, a 4.0 eV bandgap was deduced from the EELS spectrum of the a -C II layer. This semiconducting amorphous carbon layer (a -C II) and the diamond substrate together form an all-carbon heterostructure, suggesting potential applications in field-effect transistors.

Rechargeable lithium-oxygen (Li-O-2) batteries are known for their ultrahigh theoretical energy density among chemical batteries. However, the low catalytic activity and poor stability of the cathode catalyst are the root issues limiting their practical applications. In this work, a design strategy to enhance the catalytic activity of the TiC material was devised by C surface modification. The carbon-coated core-shell TiC@C nanomaterial was designed, which combined the good electrical conductivity and low density of carbon materials with the excellent catalysis of TiC. The calculated catalytic activities of TiC (100) with and without C coating were compared by first-principles calculations, showing that the TiC (100)@C surface has a lower ORR/OER overpotential. The C layer enhances the conductivity of the TiC (100) surface significantly. This work fully demonstrates the synergistic catalysis of TiC material and C coating, which not only effectively accelerates the practical process by improving the charging and discharging kinetic rate of Li-O-2 batteries but also provides an efficient catalyst design strategy for other energy-catalytic industries.

Tree-like α-Si3N4 dendrites and [001]-oriented unbranched α-Si3N4 whiskers are fabricated using electron irradiation technology.

Diamond is considered the most promising next-generation semiconductor material due to its excellent physical characteristics. It has been more than three decades since the discovery of a special structure named n-diamond. However, despite extensive efforts, its crystallographic structure and properties are still unclear. Here, we show that subdisordered structures in diamond provide an explanation for the structural feature of n-diamond. Monocrystalline diamond with subdisordered structures is synthesized via the chemical vapor deposition method. Atomic-resolution scanning transmission electron microscopy characterizations combined with the picometer-precision peak finder technology and diffraction simulations reveal that picometer-scale shifts of atoms within cells of diamond govern the subdisordered structures. First-principles calculations indicate that the bandgap of diamond decreases rapidly with increasing shifting distance, in accordance with experimental results. These findings clarify the crystallographic structure and electronic properties of n-diamond and provide new insights into the bandgap adjustment in diamond.

Gallium oxide (Ga2O3) usually fractures in the brittle form, and achieving large plastic deformability to avoid catastrophic failure is in high demand. Here, ε-Ga2O3 thin films with columnar crystals and partial unoccupied Ga sites are synthesized, and it is demonstrated that the ε-Ga2O3 at the submicron scale can be compressed to an ultra-large plastic strain of 48.5% without cracking. The compressive behavior and related mechanisms are investigated by in situ transmission electron microscope nanomechanical testing combined with atomic-resolution characterizations. The serrated plastic flow and large strain burst are two major deformation forms of ε-Ga2O3 during compression, which are attributed to the dislocation nucleation and avalanches, formation of new grains, and amorphization. The ultra-large compressive plasticity of ε-Ga2O3 thin films at the submicron scale can inspire new applications of Ga2O3 in micro- or nano- electronic and optoelectronic devices, especially those that require impact resistance during processing or service.

Self-healing materials are highly desirable in the nuclear industry to ensure nuclear security. Although extensive efforts have been devoted to developing self-healing materials in the past half century, very limited successes have been reported for ceramics or metals. Here, we report an intrinsic self-healing material of Ti3AlC2 MAX phase, which exhibits both ceramic and metallic properties, and a strategy for further enhancing the self-healing via irradiation is proposed. Quantitative in situ transmission electron microscopy tensile testing reveals that the fracture strength of 1.58 GPa is achieved on thoroughly fractured Ti3AlC2, corresponding to the self-healing efficiency of 19.8%, which is increased to 28.1% after irradiation. In situ irradiation experiments, atomic-resolution characterizations, and molecular dynamics simulations reveal that spontaneous rebonding of partial atoms on fracture surfaces is responsible for the self-healing, and irradiation-enhanced atomic migration, interplanar spacing increment, and gap-filling contribute to the self-healing enhancement.

The self-healing capability is highly desirable in semiconductors to develop advanced devices with improved stability and longevity. In this study, the automatic self-healing in silicon nanowires is reported, which are one of the most important building blocks for high-performance semiconductor nanodevices. A recovery of fracture strength (10.1%) on fractured silicon nanowires is achieved, which is demonstrated by in situ transmission electron microscopy tensile tests. The self-healing mechanism and factors governing the self-healing efficiency are revealed by a combination of atomic-resolution characterizations and atomistic simulations. Spontaneous rebonding, atomic rearrangement, and van der Waals attraction are responsible for the self-healing in silicon nanowires. Additionally, the self-healing efficiency is affected by the fracture surface roughness, the nanowire size, the nanowire orientation, and the passivation of dangling bonds on fracture surfaces. These new findings shed light on the self-healing mechanism of silicon nanowires and provide new insights into developing high-lifetime and high-security semiconductor devices.

In recent years, diamond has shown great potential in solar-blind ultraviolet (UV) photodetection due to its ultrawide bandgap (∼ 5.5 eV) and other superior semiconductor properties. However, the response region of diamond photodetector is usually smaller than 230 nm, which cannot cover the whole solar-blind region from 200 to 280 nm. In this work, an ε-Ga2O3/diamond photodetector with wide spectra responsivity from 210 (or even lower) to 260 nm was fabricated. High-quality ε-Ga2O3 film with columnar crystal was epitaxially grown on single crystalline CVD diamond substrate by pulse laser deposition (PLD). TEM characterization revealed that the ε-Ga2O3 film grew along the <001> orientation on diamond (100) substrate. The deep ultraviolet (DUV) photodetector based on the ε-Ga2O3/diamond structure showed a high light-to-dark ratio over 5.7 × 104 and good linear response to the incident light power density from 10 to 400 mW/cm2. Moreover, compared to other photodetectors, the fabricated ε-Ga2O3/diamond photodetector achieved high responsivity and wide spectra response region from 210 to 260 nm, with high solar-blind rejection ratio of 104 (R240/R280) and 165 (R210/R280), respectively. The extension of spectra region with high responsivity of the ε-Ga2O3/diamond photodetector can be attributed to the thin thickness of ε-Ga2O3 film (around 200 nm) and parts of the DUV light were absorbed by diamond. The high responsivity and wide spectra response region indicate the fabricated ε-Ga2O3/diamond photodetector can be used for the detection of ultraviolet in the most of the DUV region.