Uniform Phase Distribution Research Articles

Effect of TiN Coating on the Structure, Mechanical Properties and Fracture of the Mg-Ca-Zn Alloy

This paper establishes the optimal thickness of TiN ceramic coating on the surface of Mg-Ca-Zn alloy using optical and scanning microscopy methods. X-ray diffraction analysis and tests on its mechanical properties showed that deposition of coating with a thickness of not less than 1 μm on the alloy causes a uniform distribution of the TiN phase over the magnesium alloy surface. The TiN coating also contributes to simultaneous increases in the yield strength, tensile strength, ductility and microhardness of the Mg-Ca-Zn alloy.

Influence of pre-stretching on the tensile strength, fatigue properties and the in-plane anisotropy in Al-Cu-Li alloy AA2099

The influence of pre-stretching prior to artificial aging on microstructure, tensile properties, and fatigue behavior of AA2099-T8 sheets was investigated. The results showed that increased pre-strain level from 1% to 6% resulted in a more uniform distribution and increasing density of the T1 phase. The localized plastic deformation during pre-stretching led to the formation of dense precipitation bands (DPBs) and precipitation free bands (T1-PFBs) in the sheets with the 1% pre-strain. The non-uniform distribution of the T1 phase with T1-PFBs and DPBs resulted in a decrement in elongation and a strong in-plane anisotropy of tensile properties. An appropriate level of pre-strain should be executed aiming to improve elongation and reduce the tensile anisotropy by promoting a uniform distribution of the T1 phase. In-plane anisotropy of yield strength due to the presence of DPBs and T1-PFBs was quantitatively analyzed by the modified Hall-Petch formula. The results of the calculation for the modified model showed good agreement with the experiment. In addition, resistances of fatigue crack propagation (FCP) in the same orientation were gradually decreased with the increment of pre-strain due to the increment in yield strength and more uniform distribution of the T1 phase. For the in-plane anisotropy of FCP resistance, the main reasons were the development of rough fracture surfaces and the transgranular fracture modes in L-T orientation.

High Gain Monopulse Variable Inclination Continuous Transverse Stub Antenna for Satellite-Aided Vehicular Communications

This article presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band high gain monopulse variable inclination continuous transverse stub (VICTS) antenna for satellite-aided vehicular communications. The radiating part is divided into four regions and fed by an air-filled single-layer E-plane waveguide comparator cascaded with two groups of mirror-symmetric multiple-port excited linear source generators (LSGs). Two waveguide delay lines are carefully designed to compensate the phase difference between the adjacent radiating regions in the desired frequency band. Combined with the nonuniform slow-wave structure underneath the radiating slots, excitation signal with uniform phase distribution can be obtained, and then, the sum and difference patterns can be produced by using the comparator. For verification, a prototype operating at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band is designed and demonstrated. The experimental results show that the reflection coefficients for the sum and difference patterns are all lower than −10 dB within the frequency range of 19–21 GHz. The gain drop of the sum pattern is less than 5.7 dB within the beam scanning range of −1° to −62° at 21 GHz, while the amplitude imbalance and null depth of difference patterns are less than 4.5 and −20.6 dB, respectively. The proposed antenna can be a potential candidate for the future Internet of Vehicles.

The structure and properties of laser-cladded Inconel 625/TiC composite coatings

Abstract The article presents the research in the field of production of metal–matrix composite coatings using laser cladding technology. The general purpose of producing composite coatings is the improvement of wear resistance of the material surface. In this research, Inconel 625 was used as a matrix material. Nickel-based superalloys are used in several industries for unique applications because they possess a number of beneficial properties including high tensile and fatigue strengths and resistance to high-temperature corrosion in aggressive environments. However, for some applications, this alloy shows insufficient wear resistance of the surface; therefore, for the tests, Inconel 625-based composite coatings were produced with the addition of 10 vol.%, 20 vol.%, and 40 vol.% of titanium carbide (TiC) particles as reinforcement. In general, the addition of TiC particles had a positive effect on the erosion resistance of the surface. The aim of the current research was to test the influence of TiC particle reinforcement of Inconel 625 laser-cladded coatings on corrosion resistance of the surface. For the tests, the laser-cladded composite coatings with uniform phase distribution were produced. The proceeded tests included penetrant tests, macrostructure and microstructure analysis, X-ray diffraction (XRD), and microhardness and corrosion resistance tests. The results showed that using laser cladding, TiC-reinforced Inconel 625 uniform composite coatings may be produced. The addition of TiC particles caused microstructure changes in the Inconel 625 matrix and an increase in hardness. The addition of TiC particles had a negative influence on Inconel 625 corrosion resistance, but with the increased composite coating homogeneity, the corrosion resistance improved.

Preparation of NiCrBSi-WC/Co coatings by stable magnetic field assisted supersonic plasma spraying and its wear resistance mechanism

To enhance the wear resistance resistance of Ni-based coatings, Ni-based coatings were prepared using NiCrBSi (80 wt%) and WC/Co powders (20 wt%) as raw materials with a stable magnetic field assisted supersonic plasma spraying device at four magnetic field strength gradients. The microstructures, grain orientations and sizes of the four coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) techniques. The mechanical and tribological properties of the four coatings were also investigated. The results show that the average grain size of the coating increases from 0.92 μm decreases to 0.55 μm. The composition distribution of hard phase is more uniform, and the defects such as internal pores are significantly reduced. The maximum wear loss of the coating was reduced by 66.1% after applying a stable magnetic field. The main wear mechanisms are adhesive wear and abrasive wear. This is because the steady magnetic field induces thermoelectric magnetic force (TEMF) and thermoelectric magnetic convection (TEMC) in the deposition process of the coating, resulting in uniform distribution of hard phase and fine grain. And the coating exhibits excellent wear resistance. This process provides new possibilities and methods for processing and molding of materials assisted by a steady magnetic field. • A steady magnetic field assisted supersonic plasma spraying technique was innovatively used to prepare nickel-based coatings. • The effect of magnetic field on coating properties is proved by the improvement of stable magnetic field. • The wear resistance mechanism of NiCrBSi-WC/Co coating assisted by supersonic plasma spraying with steady magnetic field was studied. • The research results not only provide new ideas for improving the defects of coatings prepared by thermal spraying technology, but also provide references for further exploration by colleagues.

Mechanism of magnetite iron ore concentrate morphology affecting the pellet induration process

The effect and mechanism of magnetite concentrate morphology on the quality of indurated pellets were investigated. Concentrates with different morphologies were prepared using high-pressure grinding rolls (HPGR) and ball mill (BM) grinding techniques. Then pelletizing and induration process is done in the temperature range of 800 to 1300 °C. With similar specific surface area for both BM and HPGR concentrates, the morphology of HPGR concentrate had a broad particle size distribution with a high aspect ratio for particles. Results showed that the porosity and FeO content of indurated HPGR and BM pellets decreased with increasing temperature while their cold compressive strength (CCS) increased. However, the porosity and FeO content of HPGR pellets were lower than BM pellets. Also, the CCS of indurated HPGR pellets at temperatures above 1100 °C was significantly higher than BM pellets. Microstructural analysis was performed on concentrate powder, fracture surface, and cross-section of pellets to analyze the mechanism of morphological influences. It was found that the irregular shape and broad particle size distribution of HPGR particles improved the CCS of HPGR pellets due to the improved sintering, increased interlocking force, longer crack propagation path, formation of the uniform liquid phase distribution, and decreased the pellet porosity.

Processing, Mechanical Characterization, and Electric Discharge Machining of Stir Cast and Spray Forming-Based Al-Si Alloy Reinforced with ZrO2 Particulate Composites

High performance lightweight structures made of metal matrix composites (MMCs) are in demand for application in variety of industries such as aircraft, spacecraft, automobile, marine, sports equipment, etc. However, uniform distribution of the reinforcement phase to improve the mechanical properties and quality of MMCs has been the challenge for the manufacturing industries. Hence, researchers are focusing on the development of traditional low-cost method of producing metal matrix composites. In the view of above facts, an attempt is made to study the processing and characterization of Si-Al alloy reinforced with zirconium dioxide particulate composites in this paper. Hence, this paper concentrates on experimentally identifying the effect of stir cast and spray forming processing techniques followed by hot pressing on micro hardness, compressive strength, and tensile strength using Taguchi’s design of experiments for aluminum silicon matrix alloy reinforced with zirconium dioxide particulates. From the extensive experimentation on aluminum and silicon reinforced with the ZrO2 powder particulates, it was observed that there was an improvement in selected mechanical properties as the percentage of ZrO2 increased with 13 wt.% of silicon under spray forming processing technique compared to stir cast composites. This may be due to uniform distribution homogenous dispersion, larger work hardening rate, and structure of dislocation tangles around the ZrO2 particulates that occurred during spray forming processing technique. Further, results obtained from the interaction plot, contour plot, main effects plot, and analysis of variance (ANOVA) proved to be successful for identifying the optimum processing parameters for Si-Al alloy reinforced with zirconium dioxide particulate composites. Further, this paper also discusses wear study using pin on disc wear testing apparatus on spray forming processed aluminum and silicon (13.0 wt.%) alloy reinforced with the ZrO2 powder particulates based on Taguchi’s design of experiments followed by second order model generation for wear using response surface methodology. Finally, electrode wear study of spray forming processed aluminum and silicon alloy reinforced with the ZrO2 powder particulates using electric discharge machining by varying peak current (A), pulse on time (μs), and pulse off time (μs) using brass, copper, and graphite as electrode material based on L27orthogonal array. The understanding gained from the design of experiments in this paper can be used to develop future guidelines for processing and characterization of Si-Al alloy reinforced with zirconium dioxide particulate composites.

A Magnetic Yagi-Uda Antenna With Vertically Polarized Endfire Radiation in Millimeter-Wave Band Applying Higher Order Mode

A magnetic Yagi-Uda antenna applying higher order mode in millimeter-wave (mm-Wave) band with vertically polarized endfire radiation is proposed in this article. Surface wave mode analysis is applied to spot TE mode for magnetic Yagi-Uda antenna in contrast to TM mode for electric Yagi-Uda antenna. A modified structure evolved from conventional U-shaped cavity is used to address the reversed current issue for higher order mode, which exhibits a more uniform phase distribution at the Yagi-Uda array end. Then, a composite end-feeding structure with reflector integrated is further introduced to minimize its parasitic effects for practical antenna design in mm-Wave band. To validate the design, a prototype with a size of 2.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathbf {0}}\times1.25\lambda _{\mathbf {0}}\times0.088\lambda _{\mathbf {0}}$ </tex-math></inline-formula> is fabricated and tested. It can achieve anendfiregain of 8–11 dBi within 24–26 GHz with –10 dB impedance band covering an even wider frequency range. The measured front-to-back ratio (FBR) is larger than 16.1 dB. Vertically polarized radiation is realized with cross-polarization level lower than –20 dB atendfiredirection.

Preparation and mechanical properties of (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4)-Co high-entropy cermets

A novel (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 )-Co high-entropy cermets were prepared by two-steps method and the microstructure and mechanical properties were investigated. The single-phase high-entropy carbonitride (HECN) (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 ) powders were synthesized at 1600 °C. Subsequently, the HECN-Co cermets were successfully fabricated by the pressureless sintering technique. The results revealed that HECN powders (grain size ~0.79 μm) with uniform composition could be prepared at a lower temperature (1600 °C) by using oxide and carbon powders as raw materials. This preparation method also maintained the oxygen content and free carbon at low levels of 0.13 wt% and 0.03 wt%, respectively. The HECN-Co high-entropy cermets sintered at 1500 °C showed uniform distribution of the metal phase along the ceramic phase and good denseness (apparent porosity of only 0.08%). In addition, the samples possessed excellent mechanical properties, with hardness and fracture toughness of 15.72 GPa and 12.9 MPa·m 1/2 . Because of the unique features of high-entropy ceramics and the effective combination of ceramic and metal phases, HECN-based high-entropy cermets offer excellent overall properties. • A novel (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 )-Co high-entropy cermets were designed and prepared. • (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 ) powders were synthesized at 1600 °C with the O 0.13 wt% and C f 0.03 wt%. • (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 )-Co cermets were fabricated at 1500 °C with H V 15.72 GPa and K IC 12.9 MPa·m 1/2 . • The synthesis of (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 ) powders and its densification behavior were discussed.

Structural phase stability and homogeneity enhancement of electrochemically synthesized Mn2V2O7 by nanocarbon networks

Structural phase stability and homogeneity of the electrochemically synthesized Mn 2 V 2 O 7 (MVO) on nanocarbon network structures are investigated. The cup-stacked multi-walled carbon nanotubes (CNTs) and electrolytic graphene oxide (eGO) are the networks exploited in present work. It is shown that co-electrodeposition of carbonaceous network and V 2 O 5 .nH 2 O followed by electro-insertion of Mn 2 + cations results in the formation of intermixed β -Mn 2 V 2 O 7 nano-structures. The morphology and surface chemistry of the synthesized nano-structures is studied via high-resolution electron transmission and scanning X-ray photo-emission microscopies as well as Raman spectroscopy. The synthesized MVO on carbon fiber surface in the absence of the nanocarbon network shows a non-uniform phase formation and uneven coating distribution. The nanocarbon networks assisted MVO demonstrate uniform phase formation and distribution. The dominant MVO structural phase product present in these samples differs with different type of carbonaceous networks. The possible effect of the catalytic activity of the carbonaceous network as well as their hydrophilicity on the final structural and phase formation is discussed. The present study establishes new possibilities on catalytic assisted metal alloy oxide deposition for advanced applications.

Microstructure, mechanical and thermal properties of titanium matrix composites with different reinforcements

In this study, three titanium matrix composites (TMCs) reinforced with graphite, graphene, and boron carbide (B4C) were fabricated through powder metallurgical techniques. The morphologies of grains and secondary phases of these TMCs were observed through Optical Micrograph (OM) and Scanning Electron Microscopy (SEM). The results of the mechanical properties of the TMCs showed that B4C was the most effective in increasing the strength and hardness, while the strengthening effect was comparable between graphite and graphene. The plasticity of the graphene reinforced TMC decreased sharply because of the formation of strip-like agglomerations. The small size, large volume fraction, and uniform distribution of the secondary phases contributed to the enhancement of strength and hardness in boron carbide reinforced TMC. Although the thermal properties of the TMCs were lower than pure titanium in the temperature range of 25 ∼ 300 °C, the thermal conductivities of the TMCs were all above 15.6W m−1·K.

Development of a novel high strength and toughness Al–Cu–Li alloy casting billet with a new process

In this study, a novel Al–5Cu-0.6Li-0.5Mn-0.3Mg-0.15Ti alloy was developed, in which Li is as low as 0.6 wt% and Ti is added, no Ag, Zn, Zr, RE, etc., and high-performance Al–Cu–Li alloy casting billets were prepared by squeeze casting (SC) with ultrasonic treatment (UT). The results show that compared with traditional gravity casting (GC), the porosity and compositional segregation in the SC billets are significantly reduced, and the grain size is also reduced from 80 μm to 38 μm, especially the microstructure of UT + SC billets is further optimized. After UT + SC, the ultimate tensile strength (UTS), yield strength (YS) and elongation of Al–Cu–Li alloy billets are 300 MPa, 190 MPa and 16.5%, which are 27.1%, 35.7% and 230% higher than those of the GC billets, and these as-cast properties are increased by 13.2%, 15.2% and 37.5%, compared with Li-free Al–5Cu-0.5Mn-0.3Mg-0.15Ti alloy billet prepared by UT + SC, respectively. The improvement of the strength and elongation of Al–Cu–Li alloy billet prepared by UT + SC is attributed to the reduction of porosity, grain refinement and uniform distribution of second phases.

Longitudinally Miniaturized H-Plane Horn Antenna With −30 dB Sidelobes Realized by Simple Blocks Redistributing the Aperture Field

A longitudinally miniaturized H-plane horn antenna with suppressed sidelobes by redistributing the field on the radiating aperture is proposed by loading a few rectangular blocks. The substantial longitudinal length reduction (around 50% of an optimal horn) will cause a nonuniform phase and nontapering magnitude distributions of the electric fields on the horn aperture, resulting in high sidelobes and decreased gain. Four pairs of rectangular blocks perturbing the fields are loaded near the radiating aperture, realizing a field redistribution for a tapered magnitude distribution and relatively uniform phase distribution on the aperture. Thus, the sidelobes are noticeably reduced to lower than −30 dB, and 10.6 dBi average gain in the frequency band of 10.5–15 GHz is achieved. A prototype of the proposed miniaturized H-plane horn antenna is manufactured and measured, and good agreements between the measured and simulated results are obtained. The proposed miniaturized H-plane horn has two advantages over other reported miniaturized horn antennas: 1) simple geometry resulting in easy fabrication and low cost and 2) −30 dB ultralow sidelobe level (SLL).

Ablation behaviors of SiC nanowire-reinforced ZrC-SiC coating-matrix integrated C/C composites with different ratios of precursors

A novel method to prepare a coating on the C/C composite is discussed. The precursor infiltration pyrolysis method is usually applied to prepare interior ceramic matrix, thus SiC nanowires that can absorb the surficial precursor are added to prepare surficial ceramics. The method accomplishes the integration of the coating and the matrix so that no coating peels off after ablation. Moreover, the material with a ZrC/SiC precursor ratio of 5:1 (Z5S1), whose mass and linear rates are 0.47 mg/s and 0.95 µm/s, exhibits the highest overall resistance to ablation. The results demonstrate that higher ZrC content and more uniform phase distribution are beneficial to keep ZrO2 in solid and form a denser and firmer oxide layer, which is more effective in improving the ablation resistance of the C/C composite.

FUNCTIONAL AND TECHNOLOGICAL PROPERTIES OF OAT BETA-GLUCAN IN ACIDOPHILIC-WHEY ICE CREAM

The purpose of the work is to study the functional and technological properties of oat beta-glucan both individually and as part of acidophilic-whey ice cream. The research methods, that were used, are well known and have relevant references in the work. At the first stage of the experiment, the functional and technological properties of oat beta-glucan from two manufacturers were studied: «AMULYN» (China) and «DANSON» (China). According to the results of sensory evaluation, beta-glucan «DANSON» received 8.75 points, and «AMULYN» - 10 points. It was found that the water holding capacity of beta-glucan «AMULYN» is 15.45 % higher than with beta-glucan «DANSON», and fat binding capacity is higher by 8.61 %, which is probably due to the different degree of purification of these additives. Therefore, a more effective beta-glucan «AMULAN» was chosen for further use in acidophilic-whey low-fat ice cream. At the second stage of scientific work the influence of oat beta-glucan «AMULYN» on the quality of acidophilic-whey low-fat ice cream was studied. It was found that beta-glucan in the amount of 0.75 % increases the indicator of overrun more than twice compared to the control sample without beta-glucan. Beta-glucan in a certain amount also significantly improves the organoleptic characteristics of ice cream, increases resistance to melting and ensures uniform distribution of the air phase throughout the volume of the product, as evidenced by microstructural analysis of its samples. A significant effect of beta-glucan on the dynamic viscosity coefficient of ice cream mixes has been established. The detected effect allows to reduce the ripening process of ice cream mixtures with beta-glucan in the amount of 0.75 % by 2 hours, provided that the recommended viscosity of these systems is achieved. Thus, the expediency of using oat beta-glucan as an effective functional and technological ingredient in acidophilic-whey ice cream is scientifically substantiated.

In-situ TEM study of Kr ion irradiation tolerance of SiFeOC nanocomposite

In this work, ion irradiation of polymer derived SiFeOC nanocomposite was carried out using 1.2 MeV Kr ions at room temperature and 600°C. The starting composite was composed of Fe3Si, SiC, SiOC, SiO2, and graphitic C. In-situ TEM investigations show uniform distribution of nano-crystalline Fe3Si and SiC phases in the amorphous SiOC matrix. During ion irradiation, the SiOC bulk microstructure and interfaces between Fe3Si or SiC crystallites and the SiOC matrix remain defect-free and demonstrate outstanding ion irradiation resistance. At room temperature, the crystalline domains are stable up to 2 dpa. At 600°C, Fe3Si crystallites are more stable than SiC; SiC crystallites are stable up to 4 dpa while the Fe3Si crystallites are stable up to 10 dpa. These crystallites also coalescence and amorphize simultaneously during ion irradiation. The exceptional tolerance to defect formation and irradiation of the SiFeOC nanocomposite provides important guidance to developing irradiation resistant fuels for advanced gas cooled reactors.

Generating high-energy densities by sidelobe suppression in the far-field of phase-locked lasers

Laser beams with high-energy densities are desired for both fundamental research and applied applications. We present a numerical study on the generation of high-energy densities by sidelobe suppression in the far-field intensity distribution of phase-locked lasers. The method relies on modifying the combined field distribution of phase-locked lasers to obtain uniform amplitude and phase distributions in a near-field plane, which enables the formation of a high-energy density main central lobe (zeroth order) in the far field. The method is applied to various one-dimensional (1D) and two-dimensional (2D) array geometries, such as square, triangular, Kagome, random, and 1D ring. The results show that for in-phase-locked lasers in 2D array geometries, the diffraction efficiency of the high-energy density region (zeroth-order lobe) can be increased in the range of 90%–95%. For in-phase-locked lasers in a 1D ring array, the maximum diffraction is found to be ∼ 75 % . Further, the effects of the range of phase locking, system size, as well as topological defects are examined on diffraction efficiency. The method is also applied to an out-of-phase-locked laser in the square array, and a high-energy density output beam is obtained.

Deep‐Red Perovskite Light‐Emitting Diodes with External Quantum Efficiency Exceeding 21% Enabled by Ligand‐Modulated Dimensionality Control

AbstractQuasi‐2D perovskites show great promise for light‐emitting diodes owing to suppressed non‐radiative losses enabled by the energy funneling/cascading nanostructures. However, for red emission quasi‐2D perovskites, these ideal energy landscapes for efficient perovskite light‐emitting diodes (PeLEDs) can rarely be achieved due to detrimental aggregation of the low‐dimensional ligands in perovskite precursors, leading to poor device efficiency and stability. Here, a ligand‐modulated dimensionality control strategy is explored to achieve uniform phase distribution and reduce defect density for efficient light emission. In contrast to the model phenethylammonium iodide 2D ligand, the formation of small‐n phases can be inhibited by a structurally similar phenoxyethylammonium iodide ligand owing to the weakened aromatic stacking between ligands. Besides, the oxygen atoms can interact with the uncoordinated Pb2+ ions and promote the NI coordination in the perovskites, which greatly reduces the non‐radiative recombination defects in the ionic lattice. With this simple and effective approach, deep‐red quasi‐2D PeLEDs with record‐high external quantum efficiency of 21.6% and decent operational stability are achieved without the need for additional additives. These results highlight the potential of ligand‐modulated dimensionality control to achieve highly efficient and stable PeLEDs with a facile fabrication process.

Inkjet Printing of Quasi‐2D Perovskite Layers with Optimized Drying Protocol for Efficient Solar Cells

AbstractMetal halide perovskites of reduced dimensionality constitute an interesting subcategory of the perovskite semiconductor family, which attract a lot of attention, primarily due to their excellent moisture resistance and peculiar optoelectronic properties. Specifically, quasi‐2D materials of the Ruddlesden–Popper (RP) type, are intensely investigated as photoactive layers in perovskite solar cells. Here, a scalable deposition of quasi‐2D perovskite thin films, with a nominal composition of 4F‐PEA2MA4Pb5I16 (4‐FPEA+‐4‐fluoro‐phenethylammonium, applied as a spacer cation), using an inkjet printing technique, is developed. An optimized precursor formulation, and appropriate post‐printing treatment, which enable good control over nucleation and crystal growth steps, result in highly crystalline and uniform perovskite layers. Particularly, vacuum with nitrogen flushing provides an optimal drying treatment, which produces a more uniform distribution of low dimensional phases, and a high level of vertical (out‐of‐plane) alignment, which is beneficial for charge carrier transport. Solar cells reaching 13% of power conversion efficiency for the rigid, and 10.6% for the flexible, large area (1 cm2) devices are presented.

Generation of hollow Gaussian beams by restoring structured light with meta-optics

Hollow Gaussian beams (HGBs) with annular intensity distributions but uniform phase and polarization distributions have aroused enormous interest due to their advantages in optical trapping, optical limiting, etc. Although extensive HGB generation methods have been performed previously, there are still existing limitations in polarization independence and broadband response, which hinder the application of HGBs. Here, we propose and experimentally demonstrate an HGB generation method by restoring structured light with a pair of cascaded dielectric metasurface q-plates. The metasurface q-plates are based on Pancharatnam-Berry (PB) phase and work as elements of optical spin-to-orbital angular momentum conversion. The first metasurface q-plate is used to introduce orbital angular momentum to an incident circularly polarized beam, and the output light field possesses both annular intensity distribution and spiral phase with reversed circular polarization. Since the phase retardation of the metasurface q-plates isπ, the reversed circularly polarized beam output from the first metasurface q-plate will obtain opposite spiral phase after the second metasurface q-plate. Then, the spiral phase of the output light field is counteracted, but its annular intensity distribution is retained as a new HGB. Arbitrarily polarized Gaussian beams are available for incident beams because they can be decomposed into orthogonal circularly polarized components. Furthermore, this method is applicable to a broad spectrum of visible light owing to the dispersion-free characteristic of the PB phase. This work suggests a polarization-independent and broadband HGB generation method, which may benefit HGB-based fundamental research.