Showing papers on "Grain boundary published in 2022"
TL;DR: In this article , the authors proposed a method for the optimization of thermoelectric properties by introducing strong grain boundary scattering of low-frequency phonons in bulk nanostructures.
Abstract: Bulk nanostructuring has been one of the leading strategies employed in the past decade for the optimization of thermoelectric properties by introducing strong grain boundary scattering of low-frequency phonons. However,...
82 citations
TL;DR: In this article , a near-atomic scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al-alloy was performed to guide atomistic ab-initio calculations which showed that the co-segregation of alloying elements and H favours grain boundary decohesion, while the strong partitioning of H into the second-phases removes solute H from the matrix, hence preventing H-embrittlement.
Abstract: Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles. High-strength Al-alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation. Hydrogen (H) "embrittlement" is often pointed as the main culprit, however, the mechanisms underpinning failure are elusive: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the materials' durability. Here we successfully performed near-atomic scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al-alloy. We used these observations to guide atomistic ab-initio calculations which show that the co-segregation of alloying elements and H favours grain boundary decohesion, while the strong partitioning of H into the second-phases removes solute H from the matrix, hence preventing H-embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al-alloys, emphasizing the role of H-traps in retarding cracking and guiding new alloy design.
77 citations
TL;DR: Lihua et al. as mentioned in this paper conducted an in situ atomic-resolution study to reveal how sliding-dominant deformation is accomplished at general tilt GBs in platinum bicrystals.
Abstract: Grain boundaries (GBs) play an important role in the mechanical behavior of polycrystalline materials. Despite decades of investigation, the atomic-scale dynamic processes of GB deformation remain elusive, particularly for the GBs in polycrystals, which are commonly of the asymmetric and general type. We conducted an in situ atomic-resolution study to reveal how sliding-dominant deformation is accomplished at general tilt GBs in platinum bicrystals. We observed either direct atomic-scale sliding along the GB or sliding with atom transfer across the boundary plane. The latter sliding process was mediated by movements of disconnections that enabled the transport of GB atoms, leading to a previously unrecognized mode of coupled GB sliding and atomic plane transfer. These results enable an atomic-scale understanding of how general GBs slide in polycrystalline materials. Description Pushing the grain boundaries The behavior of grain boundaries in metals during deformation is important because it can dictate the macroscopic behavior. Lihua et al. used aberration-corrected in situ electron microscopy observation of platinum grain boundaries during straining to detail how they evolve. The authors observed grain boundary sliding, which is a well-known and expected mechanism. However, the authors also observed a unexpected mechanism that involves the removal of lattice planes at the grain boundaries. Their observations show the importance of using very-high-resolution microscopy to understand the role of grain boundaries during deformation. —BG Electron microscopy shows that platinum grain boundaries evolve in unexpected ways during straining.
76 citations
TL;DR: In this paper , a metal Cu0 predominated absorber (Cu-NC (N-doped carbon)-10) exhibits an ultra-width effective absorption band of 8.28 GHz (9.72-18.00 GHz) at a thickness of 2.47mm and the minimum reflection loss (RL) value of -63.8
Abstract: High density and skin effect restrict the research progress of metal predominated electromagnetic wave absorbing (EMA) materials. Although some works try to solve it, they do not focus on the metal itself and do not involve the optimization of the active site of the inherent defects of the metal. In this work, the modulation of morphology, composition, interface, defects, and conductivity is achieved by adjusting the ratio of copper salt to reducing agent chitosan. Uniquely, the appearance of twin boundaries (TBs) accelerates the ability of the homogeneous interfaces to transfer charges, resists the oxidation of metal Cu0 , keeps the high electric conductivity of Cu0 nanoparticles, and enhances the conduction loss, which provides a boost for electromagnetic wave dissipation. As a result, the metal Cu0 predominated absorber (Cu-NC (N-doped carbon)-10,) exhibits an ultra-width effective absorption band of 8.28 GHz (9.72-18.00 GHz) at a thickness of 2.47 mm and the minimum reflection loss (RL) value of -63.8 dB with a thickness of 2.01 mm. In short, this work explores the EM regulation mechanism of TBs compared with grain boundaries (GBs), which provides a new insight for the rational design of metal predominated EMA materials.
65 citations
TL;DR: In this article , a low-alloyed Mg-2Sm-0.8Mn- 0.5Zn alloy is prepared by low-temperature and low-speed extrusion, which exhibits an excellent combination of high-strength and high-ductility.
61 citations
TL;DR: In this article, a low-alloyed Mg-2Sm-0.8Mn- 0.5Zn alloy was developed by low-temperature and low-speed extrusion.
61 citations
TL;DR: In this article , 2D/3D perovskite films were modulated with 2PbI4 and 1Naphthalenemethylammonium iodide (NpMAI) to reduce the grain boundary defects, improve the charge carrier lifetime and hinders ionic diffusion.
Abstract: Reducing the electronic defects in perovskite films has become a substantial challenge to further boost the photovoltaic performance of perovskite solar cells. Here, 2D (NpMA)2PbI4 perovskite and 1‐naphthalenemethylammonium iodide (NpMAI) are separately introduced into the PbI2 precursor solutions to regulate the crystal growth in a 2D/3D perovskite film using a two‐step deposition method. The (NpMA)2PbI4 modulated perovskite film shows a significantly improved film quality with enlarged grain size from ≈500 nm to over 1000 nm, which greatly reduces the grain‐boundary defects, improves the charge carrier lifetime, and hinders ionic diffusion. As a result, the best‐performing device shows a high power conversion efficiency (PCE) of 24.37% for a small‐area (0.10 cm−2) device and a superior PCE of 22.26% for a large‐area (1.01 cm−2) device. Importantly, the unencapsulated device shows a dramatically improved operational stability with maintains over 98% of its initial efficiency after 1500 h by maximum power point (MPP) tracking under continuous light irradiation.
57 citations
TL;DR: In this paper , a low concentration of novel ionic liquid is reported as being promising for managing defects in CsPbI3 films, interfacial energy alignment, and device stability of solar cells fabricated via ambient blade-coating.
Abstract: All-inorganic cesium lead triiodide (CsPbI3 ) perovskite is well known for its unparalleled stability at high temperatures up to 500 °C and under oxidative chemical stresses. However, upscaling solar cells via ambient printing suffers from imperfect crystal quality and defects caused by uncontrollable crystallization. Here, the incorporation of a low concentration of novel ionic liquid is reported as being promising for managing defects in CsPbI3 films, interfacial energy alignment, and device stability of solar cells fabricated via ambient blade-coating. Both theoretical simulations and experimental measurements reveal that the ionic liquid successfully regulates the perovskite thin-film growth to decrease perovskite grain boundaries, strongly coordinates with the undercoordinated Pb2+ to passivate iodide vacancy defects, aligns the interface to decrease the energy barrier at the electron-transporting layer, and relaxes the lattice strain to promote phase stability. Consequently, ambient printed CsPbI3 solar cells with power conversion efficiency as high as 20.01% under 1 sun illumination (100 mW cm-2 ) and 37.24% under indoor light illumination (1000 lux, 365 µW cm-2 ) are achieved; both are the highest for printed all-inorganic cells for corresponding applications. Furthermore, the bare cells show an impressive long-term ambient stability with only ≈5% PCE degradation after 1000 h aging under ambient conditions.
56 citations
TL;DR: In this paper , the influence of Y2O3 on forming quality and microstructure of composite coatings was investigated systematically and the cracks were eliminated completely and the number of pores was drastically minimised when 2 wt% Y 2O3 was added.
49 citations
TL;DR: In this paper , a grain boundary engineering with the addition of either metalloid B or C was proposed to solve the room-temperature brittleness of Refractory High-entropy Alloys (RHEAs).
48 citations
TL;DR: In this paper, the authors summarized the development of grain boundary modification techniques with emphasis on their recent work using cost-effective non-rare earth (non-RE) sources for GBD.
TL;DR: In this article, the macromorphology, microhardness and corrosion resistance of FeCoNiCrMo coating with rare earth oxides CeO2 were characterized in detail.
TL;DR: In this article , a dynamic healing interface (DHI) is presented by incorporating a low-melting point small molecule onto perovskite film surface for highly efficient and stable PSCs.
Abstract: Healing charge‐selective contact interfaces in perovskite solar cells (PSCs) highly determines the power conversion efficiency (PCE) and stability. However, the state‐of‐the‐art strategies are often static by one‐off formation of a functional interlayer, which delivers fixed interfacial properties during the subsequent operation. As a result, defects formed in‐service will gradually deteriorate the photovoltaic performances. Herein, a dynamic healing interface (DHI) is presented by incorporating a low‐melting‐point small molecule onto perovskite film surface for highly efficient and stable PSCs. Arising from the reduced non‐radiative recombination, the DHI boosts the PCE to 12.05% for an all‐inorganic CsPbIBr2 solar cell and 14.14% for a CsPbI2Br cell, as well as 23.37% for an FA0.92MA0.08PbI3 (FA = formamidinium, MA = methylammonium) cell. The solid‐to‐liquid phase conversion of DHI at elevated temperature causes a longitudinal infiltration into the bulk perovskite film to maximize the charge extraction, passivate defects at grain boundaries, and suppress ion migration. Furthermore, the stability is remarkably enhanced under air, heat, and persistent light‐irradiation conditions, paving a universal strategy for advanced perovskite‐based optoelectronics.
TL;DR: In this paper, a new method for the development of high-performance CrMnFeCoNi high-entropy alloys (HEAs) at cryogenic temperatures by jointly utilizing additive manufacturing and the addition of interstitial atoms was introduced.
TL;DR: In this paper , the effects of T4, T5, and T6 treatment on the microstructure and mechanical properties of the extruded Mg-4.3Gd-3.2Y-1.5Zr alloy with a relatively low RE content (7.5 wt.%) were investigated.
TL;DR: In this article , Ge incorporation is found to be able to modify crystallization growth of CsPb1−xGexI3 films and reduce annealing temperature and treatment time by lowering C sPbI3 formation energy.
Abstract: Aiming at stable CsPbI3 perovskite solar cells, Ge incorporated for the first time into DMAPbI3‐based precursor systems. Ge incorporation is found to be able to modify crystallization growth of CsPb1−xGexI3 films and reduce annealing temperature and treatment time by lowering CsPbI3 formation energy. The champion power conversion efficiency (PCE) of 19.52% is achieved with a certified PCE of 18.8%, which is the highest performance of CsPbI3 PSCs with alien element‐doping. In addition, in situ formation of GeO2 can passivate the grain boundary and surface defects, thus significantly improving the moisture resistance of the perovskite film and related devices. Excellent operational stability is achieved with no PCE degradation over 3000 h at a fixed bias voltage of 0.85 V under continuous white LED (6500 K) illumination and a nitrogen atmosphere. This work demonstrates that Ge‐incorporation is a promising way to stabilize CsPbI3 perovskite solar cells by simultaneously improving perovskite crystallinity and passivating the grain boundary and interfacial defects.
TL;DR: In this article , a review of the state-of-the-art solid-state electrolyte (SSE) systems is presented, with a focus on the performance degradation of the SSE.
TL;DR: In this paper , a fast isostatic hot pressing method was proposed for the formation of W-Cu composites in comparison to the traditional ones, and the influence of both the high temperature and pressure conditions on the microstructure, structure, chemical composition, and density values were observed.
Abstract: The W–Cu composites with nanosized grain boundaries and high effective density were fabricated using a new fast isostatic hot pressing method. A significantly faster method was proposed for the formation of W–Cu composites in comparison to the traditional ones. The influence of both the high temperature and pressure conditions on the microstructure, structure, chemical composition, and density values were observed. It has been shown that W–Cu samples have a polycrystalline well-packed microstructure. The copper performs the function of a matrix that surrounds the tungsten grains. The W–Cu composites have mixed bcc-W (sp. gr. Im 3¯ m) and fcc-Cu (sp. gr. Fm 3¯ m) phases. The W crystallite sizes vary from 107 to 175 nm depending on the sintering conditions. The optimal sintering regimes of the W–Cu composites with the highest density value of 16.37 g/cm3 were determined. Tungsten–copper composites with thicknesses of 0.06–0.27 cm have been fabricated for the radiation protection efficiency investigation against gamma rays. It has been shown that W–Cu samples have a high shielding efficiency from gamma radiation in the 0.276–1.25 MeV range of energies, which makes them excellent candidates as materials for radiation protection.
TL;DR: In this paper , a 3D crosslinking agent named borax is selected to carry out grain boundary penetration treatment on perovskite film to realize full-dimensional stress release.
Abstract: Perovskite photovoltaics are strong potential candidates to drive low‐power off‐grid electronics for indoor applications. Compared with rigid devices, flexible perovskite devices can provide a more suitable surface for indoor small electronic devices, enabling them have a broader indoor application prospect. However, the mechanical stability of flexible perovskite photovoltaics is an urgent issue solved. Herein, a kind of 3D crosslinking agent named borax is selected to carry out grain boundary penetration treatment on perovskite film to realize full‐dimensional stress release. This strategy improves the mechanical and phase stabilities of perovskite films subjected to external forces or large temperature changes. The fabricated perovskite photovoltaics deliver a champion power conversion efficiency (PCE) of 21.63% under AM 1.5G illumination, which is the highest one to date. The merit of low trap states under weak light makes the devices present a superior indoor PCE of 31.85% under 1062 lux (LED, 2956 K), which is currently the best flexible perovskite indoor photovoltaic device. This work provides a full‐dimensional grain boundary stress release strategy for highly stable flexible perovskite indoor photovoltaics.
TL;DR: In this paper , a nanostructured Al-5Mg alloy with a high proportion of low angle grain boundary equiaxed grains were generated by dynamic plastic deformation and appropriate annealing treatment.
TL;DR: In this paper , the effect of nitrogen addition on the microstructural evolution and mechanical properties of the alloys at 298 K and 77 K was investigated, and it was shown that the nitrogen-doped CoCrFeMnNi alloy exhibits excellent ultimate tensile strength with substantial strain hardening.
TL;DR: In this paper , a hybrid additive manufacturing (LAHAM) method was proposed to balance the element vaporization, microstructure uniformity, and mechanical properties of the Al-Zn-Mg-Cu alloy.
Abstract: A novel additive manufacturing followed by a hybrid process involving pulsed laser and tungsten inert gas (TIG) arc was proposed to balance the element vaporization, microstructure uniformity, and mechanical properties of the Al-Zn-Mg-Cu alloy. The amount of vaporized Zn in the laser-arc hybrid additive manufacturing (LAHAM) reduced by merely 2.5%, whereas the Zn vaporization loss of the WAAM specimens reached up to 8.3%. Compared with the grain sizes of specimen obtained via WAAM, those obtained via LAHAM decreased by approximately two times. The < 100 > texture in the LAHAM specimen was decreased significantly, due to the appearance of equiaxed grains and grain refinement. Furthermore, in contrast to WAAM specimen, the eutectics contained Al, Zn, Mg and Cu were evenly distributed in the LAHAM specimen, resulting in uniform element distribution. Nano-precipitates were dispersedly distributed within the grains in the LAHAM specimen, whereas they merely appeared around the grain boundaries in the WAAM specimen. Owing to microstructure changes, LAHAM improved the ultimate tensile strength and yield strength by up to 11.4% and 29.9%, as compared with WAAM. The substantial improvement in yield strength was primarily attributed to precipitation strengthening, instead of grain boundary strengthening or solid solution strengthening.
TL;DR: In this article, five layers of NiTi alloy with dimensions of 80 × 12 × 15 mm were deposited by the cold metal transfer (CMT) welding based WAAM process and the macroscopic morphology, microstructure evolution, phase transformation and mechanical properties of each layer were investigated and compared with each other.
01 Jan 2022
TL;DR: In this paper , the authors summarized the development of grain boundary modification techniques with emphasis on their recent work using cost-effective non-rare earth (non-RE) sources for GBD.
Abstract: The magnetic performance of Nd-Fe-B magnets depends on their grain boundary structure. Intergranular addition and grain boundary diffusion (GBD) process are effective approaches for enhancing coercivity with low material cost. This review summarizes the development of grain boundary modification techniques with emphasis on our recent work using cost-effective non-rare earth (non-RE) sources for GBD. Up to now, heavy rare earth (HRE) based compounds, metals and light rare earth (LRE) based alloys have been successfully employed as the diffusion sources for coercivity enhancement. Inspired from the previous investigations on the intergranular addition of non-RE compounds and alloys for Nd-Fe-B magnets, in 2015, we firstly proposed a novel GBD process based on diffusion source of MgO. After that, various non-RE diffusion sources have been developed. The fundamentals of non-RE additives and non-RE diffusion sources for hard magnetic properties enhancement of Nd-Fe-B magnets are summarized here based on both the experimental and computational results. In particular, the properties-microstructure relationships of non-RE GBD modified magnets are discussed. The non-RE alloys or compounds modify the composition and structure of the grain boundary by diffusing into the intergranular regions, resulting in enhanced coercivity and corrosion resistance. Recently, we used Al-Cr coatings for both coercivity enhancement and surface protection, which shortens the production process and makes non-RE diffusion sources more competitive. The opportunity and future directions for non-RE GBD are also discussed in this review.
TL;DR: In this paper , a controllable synthesis of 1D grain boundary-rich Pt nanowires strongly coupled with ultrathin Ti3C2Tx MXene nanosheets (Pt NWs/MX) is presented.
TL;DR: A new organic chemical reduction method was successfully used to synthesize magnesium-coated graphene (GNPs), and xGNPs/AZ91 nanocomposites with different contents were fabricated by vacuum hot-pressing sintering as mentioned in this paper .
TL;DR: Li et al. as mentioned in this paper proposed an effective method to regulate Li2S deposition to avoid the catalyst surface passivation by introducing grain boundaries (GBs) in the catalyst, which can act as two-dimensional nucleation sites, guiding the fast nucleation and three-dimensional deposition of Li 2S around them.
TL;DR: In this article , the macromorphology, microhardness and corrosion resistance of FeCoNiCrMo coating with rare earth oxides CeO2 were characterized in detail.
TL;DR: Li et al. as mentioned in this paper proposed an effective method to regulate Li2S deposition to avoid the catalyst surface passivation by introducing grain boundaries (GBs) in the catalyst, which can act as two-dimensional nucleation sites, guiding the fast nucleation and three-dimensional deposition of Li 2S around them.
TL;DR: In this paper, the first prominent crystallographic texture of tungsten using laser powder bed fusion (LPBF) was formed to reduce the crystal misorientation at the melt pool center, at which the solidification fronts from the right and left halves of the encounter.