Crystal Boundaries Research Articles

A Thermal‐Pressed Strategy for Crystal Growth and Boundaries Self‐Fusion of Mixed‐Halide Perovskite Films against Halide Phase Segregation

AbstractAll‐inorganic mixed‐halide perovskite CsPbI3−xBrx materials have attracted extensive attention in optoelectronics due to upgraded stability and tuned bandgap. Unfortunately, undesired halide phase segregation by ion migration under illumination deteriorates photoelectrical performance and long‐term stability of devices. The severity of phase segregation is prone to occur at grain boundaries and relies on surface/interface defects. Herein, a thermal‐pressed (TP) crystal‐growth strategy is proposed to realize sufficient grain growth and boundary fusion simultaneously in a series of CsPbI3−xBrx films. The large‐sized crystals (20–40 µm), self‐fused boundaries, and single‐crystal‐like surface effectively block photoinduced ion migration. The TP‐based CsPbI3−xBrx films maintain excellent long‐life photostability over one year and exhibit markedly suppressed halide phase segregation under continuous laser illumination. Consequently, the TP‐based photodetector devices exhibit superior long‐term stability under laser illumination with different wavelengths.

Building a stable artificial solid electrolyte interphase on lithium metal anodes toward long-life Li–O2 batteries

Rechargeable Li–O2 batteries (LOBs) are considered as a promising battery technology due to their high energy density. The performance of the batteries, however, is limited by inevitable chemical/electrochemical corrosion and uncontrollable Li dendrite growth. Here, a uniform and dense LiF artificial solid electrolyte interphase (SEI) is introduced to address these issues. This LiF layer with rich and uniform crystal boundary can homogenize the Li-ion flux on Li metal anodes (LMAs) surface and thus accomplish planar Li deposition under the LiF layer, improving the interfacial stability of LMAs. In addition, the dense LiF layer enables high corrosion resistance against the electrolyte and air. As a result, the symmetric cells with LiF layer coated Li anodes (LiF@Li) show stable polarization voltage and long cycle life up to 1000 h. Moreover, the Li–O2 battery with LiF@Li shows excellent cycle stability up to 150 cycles at an ultrahigh current density of 4.50 mA cm−2. This work illustrates a promising way for the unfettered development of advanced LOBs.

Effect of Water Vapor on the Microstructure of Al2O3 on the Free-Standing MCrAlY Alloy at 1100 °C

The oxidation resistance of the MCrAlY binding coat is due to the formation of protective Al2O3 oxide scale at high temperature. The oxidation behavior of NiCrAlYHf alloy in 1100 °C air and air-water vapor atmosphere was studied. The effect of water vapor on the microstructure and distribution of reactive elements was discussed. The results showed that the oxide scale in air has a double layer structure composed of columnar and equiaxed crystals, while the oxide scale in water vapor contains fine alumina grains, which provides more channels for the diffusion of reactive elements. In addition, The Cr element in the oxide scale is mainly concentrated in the outer equiaxed crystal zone, and the Hf oxide is mainly concentrated in the columnar crystal boundary. In air-water vapor atmosphere, the Cr element is uniformly distributed in the oxide scale.

Numerical Analysis Nucleation and Growth Conditions of Single-Crystallinity Control during Laser Surface Modification of Ni-Based Single-Crystal Superalloy Part I: Thermal and Chemical Determinants

Nucleation and growth conditions of single-crystallinity control are convincingly elaborated by multi-scale mathematical modeling of heat and mass transport to totally abate undesirable weld defects, e.g. disoriented crystal and hot cracking inside molten pool of nonequilibrium crystallization, in order to illustrate the usefulness of predictive capability through theory and experiment procedures. Crystal growth is complicated by crystallinity-dependent thermal and chemical driving forces in front of dendrite tip during viable laser surface modification of Ni-based single-crystal superalloy. These two thermal metallurgical determinants play crucial role in crack-insusceptible columnar crystal growth, which is favorably oriented throughout weld depth. There is particular challenge in complete elimination of disoriented crystal, i.e. stray grain formation, for acceptable surface quality. Conservative (001)/[100] crystalline orientation is desired to diminish Al concentration and supersaturation, and morphologically satisfy epitaxial growth kinetics to successfully lessen central cracking with satisfactory variability of laser power and welding speed. Comparatively, (001)/[110] crystalline orientation is disadvantageous to asymmetrically augment Al concentration and supersaturation and aggressively increase interface instability, microstructure heterogeneity and hot cracking vulnerability along disoriented crystal boundaries. Disoriented crystal is increasingly withstood if the Al concentration and supersaturation in front of dendrite tip are low enough and crack-unsusceptible part is relatively large enough in case of attractive (001)/[100] crystalline orientation with optimal range of heat input to ameliorate microstructure homogeneity. Crystalline orientation region varies with diverse welding configurations, and epitaxy across solid/liquid interface is also sensitive to heat input of laser processing, which necessitate high efficient welding conditions optimization. Considerable effort is made to distinguish diffusion-driven crystal growth between a series of combinations of multiple welding conditions, such as critical welding configuration and heat input. Metallographically, the morphologies of crystal growth and hot cracking are experimentally observed to consistently support kinetics calculation result and well explain correlation between solidification behavior and crystal growth.

DMF-Based Large-Grain Spanning Cu2 ZnSn(Sx ,Se1- x )4 Device with a PCE of 11.76.

A main concern of the promising DMF‐based Cu2ZnSn(S x ,Se1‐ x )4 (CZTSSe) solar cells lies in the absence of a large‐grain spanning structure, which is a key factor for high open‐circuit voltage (V oc) and power conversion efficiency (PCE). A new strategy to achieve CZTSSe large‐grain spanning monolayer is proposed, by taking advantage of the synergistic optimization with a Cu2+ plus Sn2+ redox system and pre‐annealing temperatures. A series of structural, morphological, electrical, and photoelectric characterizations are employed to study the effects of the pre‐annealing temperatures on absorber qualities, and an optimized temperature of 430 ℃ is determined. The growth mechanism of the large‐grain spanning monolayer and the effect of redox reaction rate are carefully investigated. Three types of absorber growth mechanisms and a concept of critical temperature are proposed. The devices based on this large‐grain spanning monolayer suppress the recombination of carriers at crystal boundaries and interfaces. The champion device exhibits a high V oc (>500 mV) and PCE of 11.76%, which are both the maximum values among DMF‐based solar cells at the current stage.

Rational Design on Chemical Regulation of Interfacial Microstress Engineering by Matching Young's Modulus in a CsPbBr3 Perovskite Film with Mechanical Compatibility toward Enhanced Photoelectric Conversion Efficiency.

Thermodynamically induced tensile stress in the perovskite film will lead to the formation of atomic vacancies, seriously destroying the photovoltaic efficiency stability of the perovskite solar cells (PSCs). Among them, cations and halide anions vacancies are unavoidable; these point vacancies are considered to be a major source of the ionic migration and perovskite degradation at the crystal boundary and surface of the perovskite films. Here, we use choline bromide to modify the perovskite film by occupying the atomic defects in the CsPbBr3 perovskite film. The results show that the zwitterion quaternary ammonium ions and bromide ions in choline bromide can simultaneously occupy the Cs+ cation and Br- anions vacancies in the perovskite film by the ionic bonding effect, for which the defect-state density on the surface of the perovskite film can be significantly reduced, leading to the effective enhancement of carrier lifetime. In addition, the residual stress at the crystal boundary can be effectively reduced by lowering the Young's modulus in the CsPbBr3 perovskite film. As a result, the optimized device achieves a photoelectric conversion efficiency (PCE) of 9.06% with an increase of 41.1% compared to the control device with a PCE of 6.42%. Most importantly, the newborn thermal stress due to thermal expansion during heat working conditions can be transferred from the polycrystalline perovskite to the carbon layer by the matched Young's modulus, thus resulting in improved stability perovskite film under environmental conditions. The work provides new insights for preparing high-quality perovskite films with low defect-state density and residual stress.

Manipulate organic crystal morphology and charge transport

Organic electronics has become one of the fastest developing fields with exciting advances in discovering novel organic semiconductors, enhancing charge carrier mobility, and exploring high-performance electronic device applications. Nevertheless, the solution-induced growth of small molecular organic semiconductors provokes predominant crystal misorientation, thermal cracks and grain boundary, which poses a tough challenge to maneuver the crystal alignment towards device fabrication. In this article, we conduct an in-depth review of external force-based, additive-based, and binary solvent-based techniques to effectively control the organic semiconductor crystallization, thin-film morphology, and crystal orientations. We first introduce the recent progress and the various challenges of flexible electronics, and discuss how these issues are correlated to charge carrier mobility variations. Next, we discuss the miscellaneous external force alignment methods based on the categories of slot-die coating, blade coating, substrate patterning, and air flow. Furthermore, we investigate the additive-based methods for controlling crystal growth and orientations, including polymeric additives, small molecular additives, and nanostructured additives. Finally, we discuss the binary solvent-based methods to control the crystal morphology and dimensionality. By correlating the charge transport characteristics with the intrinsic merits of those unique methods, this article shares a useful insight into maximizing the performance of organic semiconductors from a new perspective.

Homogeneous hybridization of NASICON-type cathode for enhanced sodium-ion storage

Na3V2(PO4)3 has attracted intensive interest as cathode materials of sodium-ion batteries (SIBs), whereas, its performance is hindered by the sluggish Na-ion diffusion. Herein, with delicate reaction-component regulation and ideal paired Na7V4(P2O7)4PO4, homogeneous hybridized Na3V2(PO4)3-based cathode (denoted as HNVP) is designed to fully unleash the biphase synergy and trigger the ultra-fast kinetics in the SIBs. The dynamics of HNVP can be largely motivated by the intimate interaction via homogeneous hybridized Na3V2(PO4)3 and Na7V4(P2O7)4PO4, the intermediate state of Na7V4(P2O7)4PO4 and the in-situ constructed expressway of amorphous crystal boundaries, all of which enable ultra-high rate capability up to 50C and applicable area loading of 48.85 mg cm−2; while the reinforced structural of HNVP enables record-low capacity decay of 0.0051% per cycle over 2100 cycles. Moreover, under the guidance of phase diagrams, the homogeneous hybridization strategy can be further promoted to various types of advanced composite cathodes for intrinsic innovations.

Dynamic Reconfiguration of Compressed 2D Nanoparticle Monolayers.

A Gibbs monolayer of jammed, or nearly jammed, spherical nanoparticles was imaged at a liquid surface in real time by in-situ scanning electron microscopy performed at the single-particle level. At nanoparticle areal fractions above that for the onset of two-dimensional crystallization, structural reorganizations of the mobile polymer-coated particles were visualized after a stepwise areal compression. When the compression was small, slow shearing near dislocations and reconfigured nanoparticle bonding were observed at crystal grain boundaries. At larger scales, domains grew as they rotated into registry by correlated but highly intermittent motions. Simultaneously, the areal density in the middle of the monolayer increased. When the compression was large, the jammed monolayers exhibited out-of-plane deformations such as wrinkles and bumps. Due to their large interfacial binding energy, few (if any) of the two-dimensionally mobile nanoparticles returned to the liquid subphase. Compressed long enough (several hours or more), monolayers transformed into solid nanoparticle films, as evidenced by their cracking and localized rupturing upon subsequent areal expansion. These observations provide mechanistic insights into the dynamics of a simple model system that undergoes jamming/unjamming in response to mechanical stress.

Energy Transfer Assisted Fast X-ray Detection in Direct/Indirect Hybrid Perovskite Wafer.

Metal halide perovskite scintillators encounter unprecedented opportunities in indirect ionizing radiation detection due to their high quantum yields. However, the long scintillation lifetime of microseconds upon irradiation, known as the afterglow phenomenon, obviously limits their fast development. Here, a new type of hybrid X‐ray detector wafer combining direct methylamine lead iodide (MAPbI3) semiconductor and indirect zero‐dimensional cesium copper iodide (Cs3Cu2I5) scintillator through low‐cost fast tableting processes is reported. Due to the fast energy transfer from Cs3Cu2I5 to MAPbI3, the device response time to X‐rays is dramatically reduced by nearly 30 times to 36.6 ns, which enables fast X‐ray detection capability by a large area detector arrays within 1 s. Moreover, Cs3Cu2I5 exists at the grain boundaries of MAPbI3 crystals, and blocks the paths of mobile ions of perovskite, leading to the lowest detectable dose rate of hybrid X‐ray detector is thus reduced by 1.5 times compared with control MAPbI3 direct‐type semiconductor, and 10 times compared with the Cs3Cu2I5 indirect‐type scintillator. The direct/indirect hybrid wafer also exhibits improved operation stability at ambient conditions without any encapsulation. This new kind of hybrid X‐ray detectors provides strong competitiveness by combining the advantages of both direct perovskite semiconductors and indirect perovskite scintillators for next‐generation products.

Correlating dislocation structures to basal and prismatic slip bands near grain boundaries in tensile-tested Mg–4Al using a multiscale electron microscopy approach

Dislocation structures where basal and prismatic slip bands meet grain boundaries in tensile-tested Mg with 4 wt% Al (Mg–4Al) were studied using a multiscale electron microscopy approach to explore the assumptions made for the dislocation pileup theory: a) slip bands consist of dislocation arrays piling up near grain boundaries, and b) stress concentration in the adjacent grain is solely caused by dislocation pileup. After post-testing electron backscatter diffraction (EBSD) scans, focused-ion-beam (FIB) lift-out specimens were prepared from regions of interest so that the specimen plane is parallel to the bulk sample surface to allow for direct correlation between mesoscale and microscale characterization. High dislocation density and the dislocation arrays in the slip bands corroborated with the first assumption. Evidence of plastic deformation in all grains, however, showed that the second assumption was false. In addition, dislocation structures including crystal rotation boundaries and <c+a> dislocations dissociating to the basal plane provide additional stress relief mechanisms near grain boundaries that are not accounted for in many crystal plasticity models, which requires auxiliary models to more accurately predict the stress and strain distribution in a microstructure.

High-Resolution Topographic and Chemical Surface Imaging of Chalk for Oil Recovery Improvement Applications

Chalk is a very fine-grained carbonate and can accommodate high porosity which is a key characteristic for high-quality hydrocarbon reservoirs. A standard procedure within Improved Oil Recovery (IOR) is seawater-injection which repressurizes the reservoir pore pressure. Long-term seawater-injection will influence mineralogical processes as dissolution and precipitation of secondary minerals. These secondary minerals (&lt;1 micrometer) precipitate during flooding experiments mimicking reservoir conditions. Due to their small sizes, analysis from traditional scanning electron microscopy combined with energy dispersive X-ray spectroscopy is not conclusive because of insufficient spatial resolution and detection limit. Therefore, chalk was analyzed with high-resolution imaging by helium ion microscopy (HIM) combined with secondary ion mass spectrometry (SIMS) for the first time. Our aim was to identify mineral phases at sub-micrometer scale and identify locations of brine–rock interactions. In addition, we wanted to test if current understanding of these alteration processes can be improved with the combination of complementary imaging techniques and give new insights to IOR. The HIM-SIMS imaging revealed well-defined crystal boundaries and provided images of excellent lateral resolution, allowing for identification of specific mineral phases. Using this new methodology, we developed chemical identification of clay minerals and could define their exact location on micron-sized coccolith grains. This shows that it is essential to study mineralogical processes at nanometer scale in general, specifically in the research field of applied petroleum geology within IOR.

Physicochemical Aspects of Oxidative Consolidation Behavior of Manganese Ore Powders with Various Mn/Fe Mass Ratios for Pellet Preparation.

With the depletion of rich manganese ore resources, plentiful manganese ore powders with various Mn/Fe mass ratios are produced. The physicochemical aspects of oxidative consolidation behavior of manganese ores with various Mn/Fe mass ratios were investigated in this work to determine whether manganese ore powders with high iron content (Fe-Mn ore) can be prepared as high-quality pellets. Physicochemical properties of the pellets were investigated, including cold compression strength (CCS), phase transformation, microstructural evolution, Vickers hardness (HV), porosity, and lattice parameter. CCS testing indicated that the strength of roasted Fe-Mn ore pellets was observably lower than that of pure hematite or manganese ore pellets. Phase and morphology results showed that in Fe-Mn ore pellets, an Mn ferrite phase was generated between hematite and pyrolusite particles. However, newborn Mn ferrites and hematite had an obvious crystal boundary in the crystallographic particles. Moreover, poorly crystallized Mn ferrite particles were evident, along with Mn and Fe element concentration gradients, due to the inadequate diffusion of metal ions. This resulted in poor mechanical properties of the Fe-Mn ore pellets. A temperature over 1275 °C and a roasting time of 15 min is required for the oxidative consolidation of Fe-Mn ores. In such optimized cases, Mn, Fe, O, and Al elements were uniformly distributed in the well-crystallized Mn ferrite grains, which provided favorable mineralogy for the consolidation of Fe-Mn ore powders.

Frequency regulation in alternating current transportation properties for electron correlated rare-earth nickelates heterostructures

Although the rare-earth nickelate (ReNiO3) based heterostructures exhibit promising applications in logical devices based on the metal to insulator transition property that regulates abruptly their direct current transportations, their alternating current (ac) properties have not been fully studied. Herein, we demonstrate the frequency manipulation in the ac properties of various SmNiO3-based heterostructures as grown by pulsed laser deposition including SmNiO3/SrRuO3/SrTiO3, SmNiO3/SrRuO3/LaAlO3, and SmNiO3/SrRuO3/quartz. The activation energies as calculated from the dielectric relaxation process of the SmNiO3 heterostructure from the ac aspect are in consistence with the ones obtained from their direct current (dc) conduction. Assisted by the complex impedance equivalent circuit fitting, we further distinguished the dominance in carrier transportations associated with the intrinsic SmNiO3 crystal (SmNiO3/SrRuO3/SrTiO3), interfacial defects (SmNiO3/SrRuO3/LaAlO3), or grain boundaries (SmNiO3/SrRuO3/quartz). Owing to the strong Coulomb interaction between the electron carrier and NiO6 octahedron within the electron correlated insulating phase of SmNiO3, the temperature dependence in their real part impedance cross-linked at characteristic ranges of temperature and frequency. As a result, their electronic transportations gradually transit from the negative temperature coefficient resistance thermistor toward delta-tendency via elevating the input ac-frequency. This functionality is expected to enrich potential applications of SmNiO3-based correlated electronic devices in temperature sensing and control.

Laboratory evaluation of modified cashew nut shell liquid as oilfield wax inhibitors and flow improvers for waxy crude oils

• Pour point depressants were derived from natural cashew nut shell liquid and alcoholamines. • Wax crystal morphology was modified in oil doped with the CNSL derivatives as crystal average Feret diameter, aspect ratio and boundary fractal dimension were reduced. • Wax area fraction decreased by 65%. • Pour point, viscosity and shear stress of crude oil was reduced by -18 °C, 49% and 45%, respectively. Biobased wax inhibitors and flow improvers have become attractive due to the need to cut production cost and migrate towards more eco-friendly oilfield chemicals. Natural cashew nut shell liquid (CNSL) extracted from shells of Anacardium occidentale was chemically modified using diethanolamine and ethanolamine. Pour point of doped oil was reduced by -18 °C. Cross-polarized micrographs of crude oils analyzed using Image J software showed reduction in crystal size, aspect ratio and boundary fractal dimension. Wax area fraction decreased by 65% indicative of wax inhibition as smooth, rounded, morphologically uniform crystals formed. Shear stress and viscosity decreased by 45% and 49%, respectively.

Nitrogen, sulfur Co-doped carbon nanosheets embedded with CoS/Co9S8 composite for high-stability lithium storage

Metal sulfides have emerged as eminent candidates for anodes in lithium-ion batteries because of their low cost and high theoretical capacity. Nevertheless, their Li storage performance is hindered by their inherent low conductivity and dramatic volume changes. To exceed this limitation, in this study, we synthesized a composite material comprising heterostructured CoS/Co 9 S 8 grains incorporated into N, S co-doped carbon (labeled as CSCS-C-800) through a solid-state pyrolysis reaction. The N, S co-doped carbon matrix could boost electrical conductivity and protect cobalt sulfides from volume changes. Furthermore, the heterostructured CoS/Co 9 S 8 possesses abundant electrochemical active sites owing to its ubiquitous crystal boundary between the CoS and Co 9 S 8 grains. Benefiting from the synergy of the two components, CSCS-C-800 displayed a satisfactory cycling lifespan, achieving remarkable capacity retention of 90% and low capacity fading per cycle of 0.025% during 400 successive cycles at 0.5 A g −1 . We believe that these outcomes obtained herein will be helpful in obtaining advanced metal sulfide-based materials for applications in electrochemical charge storage systems.

Bernal Boron Nitride Crystals Identified by Deep-Ultraviolet Cryomicroscopy.

The presence of metastable Bernal stacking boron nitride is verified by combining second harmonic generation (SHG) and photoluminescence (PL) spectroscopy. The scanning confocal cryomicroscope, operating in the deep-ultraviolet range, shows a one-to-one correlation between inversion symmetry breaking probed by SHG and the detection of an intense PL line at ∼6.035 eV, the specific signature of the noncentrosymmetric Bernal stacking. The coherent character of the Bernal phase in boron nitride crystals is demonstrated by two-photon excitation spectroscopy. Direct and indirect excitons are simultaneously detected in the emission spectrum; they are quasi-degenerate, in agreement with theoretical predictions for Bernal boron nitride. The transition from AA' to AB stacking is characterized by an intense emission from stacking faults at the grain boundaries of hexagonal and Bernal boron nitride crystals.

Design and investigation on the reliability of a ceramic power package

The popularity of electronic devices used in a wide range of applications has significantly increased over recent years. As a result, more and more power packages are needed. Plastic packages have many problems in preserving and long-time employing. Unlike conventional power package, a ceramic power package is designed and investigated in this paper. Finite element simulation is applied to help package design. On the basis of high temperature co-fired ceramic technique, packages are fabricated. Several kinds of reliability test are carried out. Moreover, the mechanism of crack initiation and propagation in the outer leads of invalid sample are also discussed. Experiment results showed that cracks on the surfaces of standard outer leads were initiated under stress, and propagated along the direction of crystal boundaries. After optimizing the structure of outer leads, all packages have passed reliability test successfully. This investigation would enlarge the way for power package in application by improving its reliability in harsh environment.

Hetero‐Lattice Intergrown and Robust MOF Membranes for Polyol Upgrading

AbstractMetal–organic framework membranes are frequently used in gas separations, but rare in pervaporation for liquid chemical upgrading, especially for separating water from polyols, due to lack of highly compact and robust micro‐architecture. Here, we report hetero‐lattice intergrown membranes in which amino‐MIL‐101 (Cr) particles embedded into the micro‐gaps of MIL‐53 (Al) rod arrays after secondary growth. By means of high‐resolution TEM and two‐dimensional topologic simulation, the connection between these two distinct MOF lattices at the molecular‐level and their crystallographic geometry harmony is identified, which leads to a close‐knit structure at the crystal boundaries of membranes. Typically, the membrane shows a separation factor as high as 13 000 for a 90/10 ethanediol/water solution in pervaporation, yields polymer‐grade ethanediol, and saves ca. 32 % of energy consumption vs. vacuum distillation. It has a highly robust micro‐architecture, with great tolerance to high pressure, durability against ultrasonic therapy and long‐term separation stability over 600 h.

Hetero-Lattice Intergrown and Robust MOF Membranes for Polyol Upgrading.

Metal-organic framework membranes are frequently used in gas separations, but rare in pervaporation for liquid chemical upgrading, especially for separating water from polyols, due to lack of highly compact and robust micro-architecture. Here, we report hetero-lattice intergrown membranes in which amino-MIL-101 (Cr) particles embedded into the micro-gaps of MIL-53 (Al) rod arrays after secondary growth. By means of high-resolution TEM and two-dimensional topologic simulation, the connection between these two distinct MOF lattices at the molecular-level and their crystallographic geometry harmony is identified, which leads to a close-knit structure at the crystal boundaries of membranes. Typically, the membrane shows a separation factor as high as 13 000 for a 90/10 ethanediol/water solution in pervaporation, yields polymer-grade ethanediol, and saves ca. 32 % of energy consumption vs. vacuum distillation. It has a highly robust micro-architecture, with great tolerance to high pressure, durability against ultrasonic therapy and long-term separation stability over 600 h.